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Arginine and Citrulline and the Immune Response in Sepsis

Karolina Wijnands, Tessy Castermans, Merel Hommen and 2 more

Nutrients · 2015 · Review

doi:10.3390/nu7031426

Abstract

Arginine, a semi-essential amino acid is an important initiator of the immune response. Arginine serves as a precursor in several metabolic pathways in different organs. In the immune response, arginine metabolism and availability is determined by the nitric oxide synthases and the arginase enzymes, which convert arginine into nitric oxide (NO) and ornithine, respectively. Limitations in arginine availability during inflammatory conditions regulate macrophages and T-lymfocyte activation. Furthermore, over the past years more evidence has been gathered which showed that arginine and citrulline deficiencies may underlie the detrimental outcome of inflammatory conditions, such as sepsis and endotoxemia. Not only does the immune response contribute to the arginine deficiency, also the impaired arginine de novo synthesis in the kidney has a key role in the eventual observed arginine deficiency. The complex interplay between the immune response and the arginine-NO metabolism is further underscored by recent data of our group. In this review we give an overview of physiological arginine and citrulline metabolism and we address the experimental and clinical studies in which the arginine-citrulline NO pathway plays an essential role in the immune response, as initiator and therapeutic target.

Full text

From PubMed Central, U.S. National Library of Medicine, as current on Oct 22, 2026. Paragraph numbers are ours, so an answer can point at one.

1. Introduction

Sepsis and associated inflammatory conditions, such as bacteremia and endotoxemia; a condition with increased presence of lipopolysaccharide (LPS), the essential component of the outer membrane of Gram-negative bacteria, are associated with arginine deficiency. This arginine deficiency is suggested to be the result of a decreased arginine uptake and an impaired arginine de novo synthesis from citrulline, in combination with an enhanced arginine catabolism by the upregulation of arginase and the inflammatory nitric oxide synthase (iNOS; NOS2) in the immune response. As a result, strategies to improve the arginine availability during inflammatory conditions have gathered widespread attention over the past decades. However, this does not necessary mean that arginine deficiency occurs universally in all inflammation or sepsis related illnesses. It is beyond the purpose of this review to determine whether arginine deficiency is present in all these conditions. The purpose of this review is to provide an overview of the recent literature that discusses the presence of arginine deficiency during sepsis and endotoxemia, and to discuss the recent studies on improving the arginine and citrulline availability in relation to the immune response. The focus of this review is on the role of the arginine-citrulline nitric oxide (NO) metabolism during these inflammatory conditions, such as endotoxemia and sepsis. In addition, strategies to influence the arginine and citrulline availability in endotoxemia will be discussed. Furthermore, to understand the role of arginine and citrulline and the immune response during inflammatory conditions such as sepsis, insight in the normal physiological processes of arginine and citrulline and the relevant enzymes that maintain this metabolism is essential. Therefore, the important relevant metabolic pathways of arginine in health will be highlighted.

2. Arginine during Physiological Conditions

Arginine is an amino acid that can be derived from dietary intake (approximately 4–6 g of arginine per day), from de novo synthesis from citrulline (10%–15% of the total arginine production) and through protein breakdown (approximately 80%). Arginine is poorly absorbed in the intestine, with the jejunum as major absorption site, and exhibits a significant liver uptake. The synthesized arginine from citrulline accounts for 60% of the de novo whole-body arginine synthesis, however this only represents 5%–15% of the total circulating arginine. This indicates that most of the plasma arginine is derived from proteolysis and food intake.

Arginine plays a key role in several metabolic pathways; however it is beyond the purpose of this review to discuss all the pathways of arginine during physiological conditions (see references for reviews). In this review only the arginine de novo synthesis-regulated anabolic and the arginase and the NOS enzymes-regulated catabolic pathways of arginine will be discussed (Figure 1), since these pathways play an essential role during inflammatory conditions.

2.1. Arginine de novo Synthesis; Conversion of Citrulline into Arginine by Argininosuccinate Synthetase and Argininosuccinate Lyase

Arginine can be produced from the conversion of citrulline by the combined action of the cytosolic enzymes argininosuccinate synthetase (ASS) and argininosuccinate lyase (ASL). Citrulline, the limiting factor in the arginine de novo synthesis, exhibits a low dietary intake (approximately 13% of total arginine). However, the main precursor of citrulline is glutamine, which is converted in the enterocytes of the proximal small bowel, accounting for 60%–80% of the total citrulline. The small intestine releases the produced citrulline into the circulation, of which approximately 80% is taken up by the proximal tubular cells of the kidney for the arginine de novo synthesis. This is also known as the intestinal-renal axis. The balance between gut synthesis and kidney degradation determines the plasma citrulline concentration. Since the intestine is the main site of citrulline production, plasma citrulline concentration has been suggested as a biomarker of the functionality of the small bowel enterocyte mass, although the plasma concentration does not provide exact information concerning the balance between production and disposal. For example, renal failure is associated with an impairment of citrulline metabolism, because the kidney is the main organ that metabolizes citrulline into arginine.

In addition, citrulline can also be derived from the conversion of ornithine by ornithine transcarbamylase, which is present in the enterocytes and hepatocytes. This produced citrulline is also exported and enters the portal circulation to bypass the liver and serve as arginine precursor. Furthermore, the dietary intake of arginine account for 40% of the circulating citrulline.

In the arginine de novo synthesis, ASS catalyzes the condensation of citrulline and aspartate to form argininosuccinate, the immediate precursor for arginine. The produced argininosuccinate is split by ASL to release fumarate and arginine. ASS and ASL are the rate-limiting enzymes for the intracellular arginine regeneration form citrulline.

The arginine de novo synthesis is not limited to the kidneys, although the kidney is the only organ that significantly releases newly synthesized arginine into the plasma in an amount to sustain whole-body arginine requirements. The citrulline, not used in the kidneys, is transported via the systemic circulation for intracellular arginine de novo synthesis in several different cell types, such as macrophages, aortic smooth muscle cells, neural cells and endothelial cells.

In the endothelial cells, ASS and ASL located in the caveola are part of the NOS3 complex, and their activity is essential for maintenance of a functional NOS3 complex, to maintain sufficient NO production (Wijnands et al., unpublished data).

The intracellular arginine de novo synthesis in macrophages does not play a role during physiological conditions, however in case of arginine starvation in inflammatory conditions this pathway may becomes essential, which will be discussed in more detail later in this review.

2.2. Arginine and Citrulline Transport Systems

The produced arginine is transported by specific arginine transport systems into the cells, to provide in the arginine demand of cells. The most important arginine transporter is y+ (for recent review), which consists of four different types of cationic amino acids transporters (CATs); CAT-1, CAT-2a and CAT-2b, CAT-3 and CAT-4. Since CAT-2a, CAT-3 and CAT-4 have a very low affinity for cationic amino acids arginine and citrulline, only CAT-1 and CAT-2b will be discussed in this review.

CAT-1 is expressed in almost all adult cells, such as endothelial cells and epithelial cells. In endothelial cells, CAT-1 is co-localized with NOS3 in the plasma membrane caveolae which facilitates specifically arginine channeling for the endothelial NO production. This co-localization results in exclusive arginine availability for NOS3, preventing mixture of arginine in the intracellular pool. CAT-2b is only expressed after induction with cytokines or lipopolysaccharide (LPS) treatment in inflammatory cells and is highly associated with NOS2 expression and will be discussed in more detail in the next section of this review.

In basal conditions, arginine transport across the cell membrane of human monocytes and murine bone marrow-derived macrophages is mainly mediated through y+ associated with CAT-1, while after activation of the immune response, the increase in transport is due to CAT-2.

Uptake from food-derived citrulline in the enterocytes of the small bowel is regulated by different transport systems, such as B0,+, L, and b0,+ systems. Presence of system L in the cell membrane of intestinal epithelial cells allows passage of citrulline in both directions depending on the concentration gradient. Similar to system L, transporter systems b0,+ and B0,+ are also localized in the cell membrane regulating citrulline uptake. Also the main glutamine transporter in the intestine belongs to transport system B0, the SLC6A19 or B0AT1 transporter, which is located in the epithelial cell layer of the intestinal microvilli.

2.3. Catabolic Pathways of Arginine during Basal Conditions

Besides its dietary intake and endogenous production, arginine availability is also influenced by arginine clearance. Arginine catabolism can be catalyzed by five different group of enzymes; arginases (arginase-I and arginase-II) as part of the urea cycle, nitric oxide synthases (NOSs for the NO production), arginine decarboxylase (ADC) and arginine:glycine amidinotransferase. Through these pathways arginine gives rise to ornithine, urea, polyamines, proline, NO and citrulline, proteins, glutamate, agmatine and finally creatine. In this review only the arginase and NOS pathways during basal and inflammatory conditions such as sepsis will be discussed (see for additional reviews on these pathways).

2.4. Arginase Pathway: Synthesis of Urea, Ornithine, Polyamine and Proline

Approximately 15%–20% of arginine enters the urea cycle where the enzyme arginase converts arginine into urea and ornithine. There are two different isotypes of arginase; arginase-I and arginase-II. The cytosolic arginase-I is highly expressed constitutively in the liver, which accounts for 20% of the whole body conversion of arginine into ornithine. Furthermore, arginase-I is also expressed in macrophages and endothelial cells. Mitochondrial arginase-II is expressed in low concentrations in extrahepatic tissue, such as kidney, brain, small intestine, mammary gland and macrophages. Type II arginase is mainly involved in the syntheses of ornithine as precursor for proline and polyamines synthesis, such as spermine, spermidine, and putrescine.

In endothelial cells, both arginase isoforms are expressed constitutively, although the expression of the specific isoforms differs between the species. Arginase activity can consequently regulate NO synthesis, promote the production of glutamate and proline due to expression of ornithine aminotransferase and enhance cellular polyamine levels. In the presence of arginase-I overexpression in the small intestine, as present in transgenic mice, an impaired growth and development was observed as a result of a decreased arginine availability.

2.5. NOS Pathway (NOS1, NOS2, NOS3); Synthesis of Citrulline and NO

The nitric oxide synthase (NOS) enzymes convert arginine into NO and citrulline. The total production of NO depends on the activity of these NOS enzymes. Three isoforms of NOS exist: neuronal NOS (NOS1 or nNOS), inducible NOS (NOS2 or iNOS) and endothelial NOS (NOS3 or eNOS). Generally, NOS1 and NOS3 are constitutive Ca2+ dependent enzymes that are expressed at low levels in various cell types. The function of the NOS2 enzyme is not calcium-dependent and is mainly expressed in macrophages and tissues in response to (pro)inflammatory mediators, this will be discussed in more detail in the next section of this review.

NOS1 is expressed in central and peripheral neurons and other tissues and cell types such as the adrenal glands, the kidney, epithelial cells, smooth muscle cells and pancreatic cells. The function of NOS1 includes synaptic plasticity in the central nervous system, central regulation of blood pressure, smooth muscle relaxation, and vasodilatation via peripheral nitrergic nerves; nerves in which transmission is regulated by NO.

NOS3 is expressed in endothelial cells and regulates vascular tone and exhibits vasoprotective effects such as preventing vasoconstriction, leucocyte adhesion and platelet aggregation (see for a recent review). Based on these vasoprotective effects and the regulation of vascular tone NOS3 is therefore considered as the main source of NO during basal conditions and endotoxemic conditions in the microcirculation. As described above, NOS3 is co-localized with ASS and ASL in the caveola of endothelial cells and regulates the endothelial derived NO production via this pathway. However, in the presence of a dysfunctional NOS3 complex, by tissue-specific ablation of the Ass gene, no alterations in blood pressure or vasomotor responses were observed in arteries of healthy mice, although the intracellular regeneration of arginine was diminished. This indicates that arginine resynthesis is not rate-limiting for the NO production in the endothelium of healthy arteries, and only becomes important in case of a disease state or in case of a diminished availability of arginine.

The NOS enzymes require several cofactors for NO synthesis, of which tetrahydrobiopterin (BH4) is the most important one. BH4 stabilizes the NOS structure and enhances the binding of l-arginine to NOS (see recent review). Therefore, diminished availability or presence of BH4 results in NOS uncoupling, and results in superoxide production.

3. Arginine-NO Metabolism during Sepsis and Inflammatory Conditions

Sepsis and inflammatory conditions are characterized by organ dysfunction, as a result of a misdistribution of blood flow and low peripheral vascular resistance especially at the microcirculatory level which in turn results from the inflammation and endotoxemia. Furthermore, sepsis is considered to be an arginine deficient state with arginine becoming a semi-essential amino acid during stressed conditions such as sepsis (see Figure 2). Although more arginine is being released from protein breakdown, it is also accompanied by an enhanced consumption of arginine, an impaired arginine de novo synthesis and a decreased supply of arginine, as observed in septic patients compared with healthy adults and with non-septic intensive care unit patients, leading to an impaired availability. However, this does not necessarily mean that arginine deficiency occurs universally in all septic or inflammatory conditions. It is beyond the purpose of this review to determine whether arginine deficiency is present in all these conditions. Therefore, we focus on the available literature on arginine deficiency in human sepsis and animal models, using prolonged endotoxemia to mimic the arginine deficient state as observed in human septic patients. We previously observed decreased arginine concentrations in murine endotoxemia and in septic ICU patients. During murine endotoxemia, arginine deficiency was present accompanied by a decreased NO production in the jejunal tissue of these animals. As a result, an impaired microcirculation in the jejunal villi was observed. In the septic ICU patients, the decreased arginine concentrations were present independent of the cause of sepsis.

Several causes may be responsible for this impaired arginine production or the enhanced catabolism of arginine. The impaired arginine production can be the result of limited citrulline availability for arginine de novo synthesis, which may result from decreased nutritional intake in the critically ill patient, decreased uptake of protein by intestinal failure or an impaired glutamine-to-citrulline conversion despite adequate splanchnic glutamine uptake. Furthermore, renal failure can limit arginine de novo production from citrulline.

Arginine utilization is enhanced by the catabolic activity of arginase and NOS2 or by an increased protein synthesis during inflammatory conditions. In the past, an enhanced NO synthesis during the initial phase of sepsis was suggested. This was considered as observed by enhanced plasma concentrations of nitrate/nitrite (NOx). Based on these increased plasma nitrite and nitrate levels in septic patients, and on the fact that cytokine-induced NOS2 expression releases more NO during experimental conditions compared to the other NOS enzymes, a key role for NOS2 in the hemodynamic changes of sepsis was expected. More recent studies indicate that the role of NOS2 expression rates and excessive NO production in causing hypotension is overrated, which will be discussed in more detail in Section 3.4. To estimate the NO production in septic patients, measurement of NOx levels was frequently used. As recently observed, increased plasma levels of NOx were observed in septic ICU patients compared to control patients. These concentrations were even significantly increased in septic patients with hemodynamic failure or fatal outcome. However, this enhanced nitrate/nitrite levels do not necessarily reflect an increased NO production during sepsis or endotoxemia, as several causes may result in these elevated plasma concentrations. At first, a possible slower turnover of NOx in the plasma during sepsis may result in the increased concentrations of NOx, as observed in hypotensive septic patient. A second contributor to higher plasma NOx concentrations may be the impaired renal excretion of NOx, as a result of renal failure as present in sepsis. Another important explanation may be the discrepancy in time-specific changes, per hour and day, in the NOS enzyme activity during the course of endotoxemia and sepsis, which may result in an increased plasma nitrate concentrations as result of the delay in conversion into nitrate and the renal excretion. Thus, the above-mentioned explanation has to be kept in mind when interpreting studies using NOx concentrations as marker for NO production.

Another method used to determine the NO production in sepsis is by using stable isotopes. In recent years a number of research groups used this method to measure the in vivo whole-body NO production. Data from these studies indicate that the whole-body NO production was significantly reduced in sepsis compared to critically ill control patients and healthy subjects. However, the possible compartmentalization of arginine, intracellular or within organs, may influence the NO production measurements with stable isotopes, as this is not used in the calculation of whole-body NO production. As observed, this may also contribute to differences measured in NO concentration with NOx or total body NO production. Furthermore, the location of the expressed NOS-isoforms within the organs may influence the measurement of the NO production. As described by Cauwels et al., non-hematopoietic cells are essential for the systemic NO production during inflammation, such as the intestinal enterocytes, the Paneth cells or hepatocytes. Therefore, these different expression sites, which may be differently affected by inflammation and sepsis, can also lead to unparalleled concentrations of NO production. For example, nasal NO measurements is a good sensitive and specific biomarker for nosocomial infection acquisition in the upper airway and respiratory tract. In patients with maxillary sinusitis and sepsis, nasal NO production was significantly reduced in the sinus epithelium compared to control patients, suggested to be the result of reduced NOS2 mRNA expression. Also in patients with acute respiratory distress syndrome (ARDS) low NO levels were measured, which as suggested by the authors may be the result of the rapid reaction of NO with other molecular species, and therefore of less value to measure pulmonary inflammation. As for patients with pneumonia on mechanical ventilation, the NO levels were significantly increased, although basal concentrations were significantly lower compared to other studies. In line, in acute lung injury patients increased urine NO was measured, which was associated with a better outcome, which may reflect more perfused lung beds and associated decreased organ failure.

Another suggestion is the time point at which the NO production is measured which may influence the differences in NO production and outcome of the abovementioned studies. This time-point is influenced by the expression of the enzymes, the possible plateau phase of NOS expression or the maximum NO production. This plateau phase of NO production further depends on sufficient substrate availability, in other words arginine availability and its co-factors. As described in the clinical sepsis studies and experimental studies with endotoxemia, arginine deficiency is related to sepsis and also to a decreased NO production. All the abovementioned factors may lead to the discrepancy between the low NO production measured in tissue or plasma during sepsis and the increase in nitrite/nitrate plasma or urine concentrations as measured in experimental and human sepsis. Thus, measurements of total NO production during sepsis and endotoxemia may only be an estimation of the total production or presence of NO in the tissues during sepsis and endotoxemia.

On the other hand, the production of NO by NOS3, especially for the endothelial cell, is decreased during sepsis and prolonged endotoxemia. Decreased arginine availability is suggested to play a role in this downregulation of NOS3 and thereby in the decreased bioavailability of NO. This reduced NO results in endothelial dysfunction.

The immune response also contributes to the arginine depletion. During infection and inflammation, macrophages become active in response to a range of stimuli including damaged cells, pathogens and inflammatory cytokines such as TNF-α. Non-activated macrophages exhibit minimal utilization of arginine and do not express NOS2 or arginase activity. Macrophages are classified based on their two main functions resulting in 2 phenotypes; the M1 macrophages which “fight and kill” and the M2 macrophages which “restore and heal tissue”. As part of the immune response, M1 and M2 macrophages stimulate T-lymphocytes to produce Th1 or Th2 cytokines to maintain the predominant type of immune phenotype. Upon activation by the immune response, M1-macrophages actively import extracellular arginine to synthesize NO by NOS2. This enhanced NOS2 induced NO production in peripheral blood mononuclear cells is likely to be associated with an increased arginine transport across the cell membrane. Hypothetically, decreasing the arginine availability during sepsis may, therefore function as a protective mechanism to decrease excessive NO production by NOS2 and to regulate excessive adaptive (T-lymphocyte) immune responses, preventing possible excessive inflammation during sepsis. Arginase, expressed by M2-macrophages, which is part of the anti-inflammatory response, competes with NOS2 for arginine and therefore contributes to arginine deficiency for M1/Th1-type macrophages (see for an excellent review on the competing arginine pathways in macrophages). However, this not only results in less NO production by M1 macrophages, but also in an impaired T-cell function, which is not beneficial during sepsis. The capacity of intracellular arginine de novo synthesis in M1 macrophages partly preserves the arginine availability for NO synthesis, and as will be discussed in more detail below, also presences NOS2 derived NO synthesis, which is essential in the immune response as part of the host defense. As for the T cell function, arginase-induced arginine depletion results in suppression of T-cell activation, proliferation and differentiation in vitro and in vivo. However, in human T-cells, this arginine depletion does not seem to impair the important aspects of T-cell function such as chemotaxis and cytotoxicity. Therefore, these findings, strengthen the believe that a decreased arginine availability may not be beneficial in sepsis, although a more balanced arginine availability may be essential, which preserves arginine for both pathways in the immune response, and so maintains the balance between NOS2 and arginase in inflammatory conditions.

As observed by our group, in tissue-specific arginase deficient mice, lacking arginase in hematopoietic cells, NOS2 produced significantly more NO during endotoxemia in the tissues and in macrophages compared to control. However, this was not accompanied with an improved microcirculation in these animals, which may suggest the importance of compartmentalization of arginine. Based on the different expression levels and tissues in which the expressed NOS isoforms exist, this may lead to tissue specific differences in arginine and NO production, and therefore a disbalance in the local (micro)circulation and immune response. Thus, we believe sepsis and endotoxemia are not characterized by too much NO, but by a maldistribution of the produced NO, leading to perfusion differences and eventually organ dysfunction as a result of the impaired microcirculation.

3.1. Alterations in the Arginine and Citrulline Transport Systems in Sepsis

During sepsis or endotoxemia a shift in the expression of CAT transporters is observed as the increased cytokine production and bacterial endotoxins result in a downregulation of CAT-1 transporters and upregulation of CAT-2, mainly CAT-2b. The upregulated CAT-2 is the main arginine transporter for activated macrophages, which import large amounts of extracellular arginine for NOS2-derived NO synthesis. CAT-2 is co-induced with NOS2 in these macrophages, which results in shifting arginine towards NOS2 instead of NOS3, to maintain the required arginine availability for NOS2-derived NO production. This shift in arginine transport is suggested to be a part of the immune host response to produce increased amounts of NO, as a response to endotoxemia and the bacterial load, to control pathogens. In addition, LPS-induced macrophages produce the cytokine TNF-α during infection or septicaemia, which is capable of activation of other macrophages to participate in the host defence system.

3.2. Decreased Citrulline Availability as Cause for Diminished Arginine de novo Synthesis in Sepsis/Infection

Besides the observed decreased arginine concentration in sepsis and endotoxemia, endotoxemia and inflammatory conditions are characterized by a reduced citrulline production and bioavailability. This reduced citrulline production and bioavailability may contribute to the decreased arginine de novo synthesis during sepsis and endotoxemia. These low citrulline concentrations have been associated with higher mortality rates in this patient population. Furthermore, lower citrulline concentrations are associated with decreased NO production. Indeed, supplementation of citrulline during endotoxemia led to an enhanced NO production in tissues of these animals.

A number of mechanisms can be responsible for this reduced citrulline production. At first, a decreased nutritional intake may contribute to the observed low citrulline and arginine levels in the critically ill. Moreover, a reduced uptake of glutamine by the enterocyte as part of the intestinal failure is suggested to contribute to the decreased citrulline synthesis, although normal levels of glutamine and ornithine have also been reported in these patients. Impaired absorption of citrulline, arginine and glutamine as a result from a decreased blood flow in the intestinal villi may be a factor in this reduced uptake by the enterocyte. Also an impaired glutamine-to-citrulline conversion plays a role in this citrulline deficiency.

As a compensation, ornithine transcarbamylase (OTC) may help to restore the citrulline availability during conditions with low protein intake, such as sepsis and endotoxemia. OTC converts ornithine into citrulline, which can freely pass the liver to serve as a substrate for the arginine de novo synthesis in the kidney. Also a reduction of protein synthesis and ureagenesis may aid in restoring the citrulline and arginine metabolism during these conditions.

3.3. Decreased Arginine Availability by Enhanced Arginase Activity in Sepsis

During inflammatory conditions, both arginase-I activity and arginase-II activity are induced by specific cytokines in macrophages and neutrophils (see Figure 2). The cytokines that induce arginase activity are T-helper II produced cytokines, such as interleukins 4, 10 and 13, which preferentially induce the expression of arginase-I.

The expression of arginase occurs at different time points during the course of endotoxemia. As observed in an LPS-induced murine-endotoxemia model, arginase-I, already present in low levels before LPS induction, was upregulated in activated murine peritoneal macrophages at 12 h after the onset of endotoxemia. Arginase-I remained present during the total time course of the experiment with a peak expression at 36 h after the onset. On the contrary, arginase-II exhibited an increase in expression after 3 h of LPS stimulation with a peak expression at 6 h after induction and slowly decreased afterwards.

As described above, arginase-I and NOS2 compete for the same substrate, which may suggest that the late onset of arginase-I expression is suggested to prevent the toxic effects of NOS2-induced overproduction of NO. Indeed, the different time points of peak expression of NOS2 and arginase in murine endotoxemia models, after, respectively, 20 min, 4–6 h and 12 h for NOS2 and 12–36 h for arginase may indicate this inhibitory effect. Furthermore, the increased circulating neutrophils, with arginase containing granules which are capable of releasing arginase in the extracellular space in case of cell damage or phagocytosis, further contribute to the depletion of extracellular arginine availability for NO synthesis during endotoxemia.

In endothelial cells both arginase-I and arginase-II are expressed during inflammatory conditions, which compete with NOS3 for arginine, resulting in an impaired NOS3-derived NO production and endothelial dysfunction. We recently demonstrated that tissue-specific absence of arginase-I, in endothelial cells and macrophages, resulted in increased arginine availability. However, due to the increased NOS2 induced NO production this did not result in beneficial effects upon the microcirculation during endotoxemia. In addition, an increased arginase-II activity in endothelial cells also resulted in enhanced arginine utilization. This led to limited substrate availability for NOS3; resulting in NOS3 uncoupling accompanied by a reduced NO production and augmented superoxide anions production.

3.4. Regulation of NOS2 during Sepsis/Inflammation

Historically, cytokine-induced NOS2 expression and consequential enhanced NO production were suggested to be key factors in the development of sepsis-induced acute hemodynamic changes and end-organ damage. The impact of NOS2 derived NO production was recently re-evaluated in an experimental LPS endotoxemia model indicating no association between NOS2 derived NO production and hypotension.

LPS and T-helper I cytokines, such as interleukin-1, 6 and 8, TNF and interferon-γ, can induce NOS2 expression as part of the cellular immune response. On cellular level, sepsis results in a cytokine-mediated induction of NOS2 in almost any cell type, but especially in macrophages. Other cell types, including hepatocytes, aortic smooth muscle cells, vascular smooth muscle cells, Paneth cells and enterocytes of the jejunum also participate. As mentioned above, the non-hematopoietic cells contribute to the systemic NO production, and not the hematopoietic cells such as macrophages or endothelial cells.

This enhanced NOS2 expression plays a major role in the host defense mechanisms against various intracellular pathogens, and represents a major cytotoxic principle by accomplishing successful clearance and control of these intracellular pathogens. Therefore, maintenance of NOS2 derived NO is essential during sepsis and endotoxemia as part of the host defense mechanism, as inhibition results in detrimental outcome, which will be discussed in Section 4.1.

3.5. Regulation and Expression of Constitutive NOS during Infection/Sepsis

During inflammatory conditions and especially during sepsis, NOS1 exhibits an important immunoregulatory role, involving both pro-inflammatory and anti-inflammatory pathways. As part of the pro-inflammatory pathway, NOS1-induced NO production is suggested to act as a free radical and is prone to be converted into more reactive nitrogen species. Endothelial cells express both NOS1 and NOS3, with NOS1 localized in the nucleus and NOS3 in the cytosol. Previous studies already indicated an important role for NOS1 in the maintenance of the microvascularisation. Furthermore, NOS1 localized in nucleus of endothelial cells, exhibits an anti-inflammatory role by preventing cytokine production after TNF stimulation in cultured endothelial cells.

As for NOS3, inflammatory conditions and the decreased arginine availability result in NOS3 uncoupling, endothelial dysfunction, with an increased superoxide production and disturbed microcirculatory flow as a result.

Another important contributor to NOS3 uncoupling is the induction of asymmetric dimethylarginine (ADMA). ADMA and NG-methyl-l-arginine (l-NMMA) are the most powerful endogenous non-selective NOS inhibitors. ADMA competes with l-arginine for the active site of NOS and for y+-mediated uptake into cells (see for recent review). These methylarginines are eliminated from the body by enzymatic degradation by dimethylaminohydrolase (DDAH) and renal excretion. Along with arginine availability, endogenous inhibitors of NOS, including ADMA, may affect NO synthesis. During sepsis increased ADMA levels have been observed which inhibit NOS derived NO production resulting in an impaired microcirculation. Furthermore, increased mortality in critically ill patients has also been related to elevated ADMA levels. The correlation between arginine and ADMA, defined as the l-arginine/ADMA ratio, is decreased in adult sepsis patients indicating a role of ADMA in the modulation of NOS-regulated microcirculation.

3.6. ASS during Sepsis/Inflammation

Inflammation results in an upregulation of ASS expression, especially in macrophages and vascular smooth muscle cells. This may indicate stimulation of the intracellular arginine de novo synthesis to maintain the NOS2-derived NO production. During the early phase of inflammation and sepsis, with still sufficient extracellular arginine available, macrophages export approximately >98% of the intracellular produced citrulline into the plasma. The intracellular regeneration of citrulline, therefore, only becomes important in case of arginine deficiency. During arginine deficiency, NO synthesis in macrophages depends on the import of citrulline to maintain the NOS2-induced NO production. Since intracellular accumulation of citrulline is thought to facilitate excessive arginine de novo synthesis, which results in abundant amounts of NO, exporting citrulline is suggested to regulate the NO production in macrophages. Another important role of ASS as part of the innate immune system’s defensive role, is the clearance and detoxification of LPS by binding to the active portion of LPS, lipid A, which result in inactivation of LPS. In addition, ASS released from the liver into the systemic circulation neutralizes the extracellular LPS-induced cytotoxicity in response to inflammation.

Until know, no studies on ASL function during endotoxemia or inflammatory conditions have been conducted.

4.1. Modulation of NOS

Historically, excessive NO production by NOS2 was suggested to play an important role in the development of the key features of sepsis and endotoxemia, the systemic hypotension and vascular hyporeactivity to vasopressor agents. The inhibition of the excess NO formation by inhibiting NOS2 activity was therefore proposed as a treatment for endotoxic shock or sepsis in the past. Over the past years multiple studies, in vitro and in vivo, have been conducted to investigate the role of selective NOS2 inhibition or deficiency, all using different sepsis or endotoxemia models with different selective inhibitors, which resulted in inconclusive results as discussed in brief below.

Supplementation of the selective NOS2 inhibitor N-(3-(Aminomethyl)benzyl)acetamidine (1400W), did not affect systemic hemodynamic parameters during prolonged hyperdynamic porcine endotoxemia, however was capable of attenuating the impaired intestinal oxygenation and energy state. In another porcine endotoxemia model, the supplementation of the selective NOS2 inhibitor mercaptoethylguanadine (MEG) prevented hypotension and was capable of decreasing the amount of expired NO, however this did not result in an improved hepatosplanchnic metabolism.

Nω-nitro-l-arginine methyl ester (l-NAME) supplementation during porcine endotoxemia exhibited detrimental effects on the liver perfusion, as it reduced the flow even further during endotoxemia, while aminoethyl-isothiourea (AE-ITU) administration resulted in an improved liver blood flow.

Diminishing the arginine uptake for NOS2 in CAT-2 knock-out mice resulted in a reduced macrophage NOS2 activity compared to healthy control mice. Furthermore, genetic ablation of NOS2 in mice exhibited a decrease mortality and enhanced microvasculature responsiveness in a cecal ligation and puncture induced sepsis model. In addition, in the absence of NOS2 a decreased defense against bacterial inoculation was observed, which underlines that NOS2 also exhibits a protective role during endotoxemia. In vitro studies in rat macrophages and lung cells pre-treated with selective inhibition of NOS2, with AE-ITU and aminoguanidine (AG), resulted in significantly decreased NOS2 mRNA and protein expression. The supplementation of the selective NOS2 inhibitor ONO-1714 in a septic lung injury model induced by cecal ligation and puncture in rats lead to a decreased NOS2 activity and improved survival. However, this beneficial effect was only present when ONO-1714 was administered 12 h after the onset of sepsis.

In an ovine acute long injury model, representing sepsis, which was induced by inhalation of Pseudomonas aeruginosa bacteria administration in the lungs, specific inhibition of NOS2 with AG did not prevent the characteristic hypotension during endotoxemia, and still exhibited a significant increase in nitrite production. Also the investigation of a BBS-2, a more potent selective NOS2 inhibitor, was not capable of reversing the sepsis induced vasodilatation, which may indicate that NOS2 may not or only partially be involved in the vasodilatation during sepsis and inflammation. As recently observed in an experimental sepsis model with LPS, excessive NOS2-derived NO production may not be accompanied by hypotension or morbidity during inflammation. This resulted in the usage of non-selective NOS-inhibitors, to determine the role of the other NOS enzymes in sepsis.

Supplementation of the non-selective NOS inhibitor l-NAME in an experimental hyperdynamic sepsis model in ewes lead to a normalized renal blood flow, indicating an important contribution of the local NOS1 and NOS3 derived NO production in the hypotension. In a rat endotoxemia model, the beneficial and adverse effects of the selective NOS2 inhibitor AE-ITU and the non-selective NOS-inhibitor l-NMMA were studied to determine the influence on organ failure as caused by endotoxemia. Both AE-ITU and l-NMMA resulted in NOS2 inhibition and attenuated the liver dysfunction and circulatory failure in the liver as caused by endotoxemia.

However, non-selective NOS inhibition also exhibited unfavorable side effects, such as a decreased regional blood flow and accompanied decreased cardiac output as observed after the administration of l-NMMA or l-NAME. Also a higher vascular resistance and increased mortality in LPS treated dogs was demonstrated after administration of the non-selective NOS inhibitor N omega-amino-l-arginine. In line, prolonged inhibition of NOS by l-NAME, in patients with severe shock, exhibited an increased blood pressure and vascular resistance during the course of supplementation. However, the effect of l-NAME tended to decrease during the course of infusion, which led to the conclusion that l-NAME supplementation only exhibited minor effects on the enhanced mortality in the patients studied.

Furthermore, inhibition of NOS activity in patients suffering from sepsis using the non-specific NOS inhibitor l-NG-methylarginine-hydrocholine was associated with an increased mortality rate. Patients supplemented with another non-selective NOS inhibitor, 546C88, exhibited a significantly higher mortality rate, as a result of increased cardiovascular deaths compared to placebo treated patients within the seven days follow-up. In search of an explanation why this increased mortality was found, attention focused on the function of the constitutive expression NOS3 and NOS1. The NO that is produced under physiological conditions by these NOS isoforms regulates blood-flow distribution in organs. During inflammation and sepsis, this NOS1 and NOS3-mediated NO production is reduced, reducing blood flow to the individual organs, thereby compromising its function. Indeed, experimental evidence indicates that inhibition of NOS1 and NOS3 activity during sepsis increases hepatic and splanchnic damage. Therefore, it is suggested that the upregulation of NOS2 during sepsis may compensate for the downregulation of NOS1 and NOS3 with respect to organ perfusion. However, as observed in previous studies untimely or uncontrolled inhibition of non-selective NOS or selective NOS2 during septic shock may induce splanchnic ischemia seen in some experiments. Indeed, early inhibition of NOS2 resulted in a trend toward decreased survival, whereas early inhibition of NOS1, by 7-nitroindazole infusion, exhibited an improved survival in a murine pulmonary sepsis model. On the contrary, NOS1 inhibition during the early time course of this model, combined with a late NOS2 inhibition, exhibited potential beneficial effects by decreasing the oxidative stress. Therefore, we believe that modulations in NOS enzymes activity during human sepsis need to be performed with great precautions based on the diverse outcome of the several experimental models and the previous detrimental outcome in human sepsis with NOS2 inhibition. The place at which and the time when the NO is produced may be the key to better outcome in sepsis and endotoxemia. Thus, maintenance of good NOS isoforms function, such as NOS3 in the microcirculation for tissue perfusion and NOS2 in the initial phase to fight the pathogens may be essential. However, this complex regulation mechanism of the arginine-NO metabolism remains to be investigated in future studies.

4.2. Modulation of Arginase during Inflammatory Conditions

Several methods are used to study inhibition of arginase activity, such as therapeutic intervention with the non-specific arginase inhibitors l-valine or l-norvaline, or by the usage of (tissue-specific) arginase deficient mice models. Supplementation of l-valine or l-norvaline resulted in arginase inhibition in vitro, which led to an increased NO production in bovine pulmonary cells treated with LPS. This enhanced NO production was also observed after specific knock-down of arginase in an in vitro experiment in thoracic aortas of rats. Since arginase competes with NOS for the same substrate, inhibition of arginase directly influences the NO production. We recently demonstrated that tissue specific arginase-I deficiency in macrophages and endothelial cells exhibit an increased NOS2 mediated NO production in a prolonged murine endotoxemic model, which was abolished by NOS2 inhibition.

Arginase upregulation, as competitor for the substrate arginine, also contributes to endothelial dysfunction, by NOS3 uncoupling resulting in a decreased NO production. As previous observed in vivo chronic inhibition of arginase by administration of 2(S)-amino-6-boronohexanoicacid restored the endothelial function in the vessels of the rats supplemented with the arginase inhibitor compared to control.

4.3. Modulation of ASS in Sepsis

Absence or reduction of ASS is detrimental due to a decreased NO production. In conditions in which extracellular arginine is depleted from the environment, activated macrophages of ASS-deficient mice were not able to maintain its function as a fail-safe system to sustain NOS2-derived NO production. Also in endothelial cells ASS exhibits an essential role as selective reduction of ASS protein levels by siRNA demonstrated a decreased cell viability and was accompanied by a 80% decrease in NO production in endothelial cells. ASS deficient mice, as developed by Patejunas et al. in 1994, resulted in animals with high levels of plasma citrulline, accompanied by hyperammonemia, which eventually lead to early dead within 24–48 h after birth. Injection of a recombinant adenovirus carrying human Ass cDNA in these ASS deficient mice ameliorated this neonatal crisis, and resulted in an expanded life span of approximately 16 days.

In heterozygotic ASS deficient mice, ASS+/− mice, significantly increased plasma citrulline and decreased tissue arginine concentrations were observed. Furthermore, these results were accompanied by a decreased inflammatory response upon liver injury by pyrazole, as demonstrated by a decreased nitrosative stress, decreased TNF-α production, impaired apoptosis, and diminished neutrophil infiltration, which may be related to the role of ASS as part of the innate immune systems in the clearance and detoxification of LPS. In our developed tissue-specific ASS deficient mice, with ASS deficiency in endothelial cells and macrophages, we observed similar results during prolonged endotoxemia in macrophages (Wijnands et al., unpublished data). ASS deficient macrophages exhibited a significant decreased nitrite production upon LPS stimulation compared to littermates and also a decreased inflammatory response with decreased TNF-α production.

4.4. Modulation of ASL in Sepsis

The role of ASL modulations in sepsis has not been investigated thus far. However, recently ASL deficiency was studied in necrotizing enterocolitis, for which a enterocyte-specific heterozygotic deletion of ASL mouse model was developed (Aslflox/flox; VillinCretg/+ or CKO). This study showed that in the absence of ASL in the enterocytes an increased pro-inflammatory state and enhanced apoptosis occurred in these animals. Another recent study, investigating ASL−/− mice, showed early mortality within 48 h after birth in all homozygotes as a result of elevated plasma ammonia, argininosuccinic acid, glutamine, and citrulline concentrations to toxic concentrations. In addition, significantly lower concentrations of arginine and nitrite production were observed in the ASL deficient animals, accompanied by an incompetent NOS3 complex formation, indicating the importance of intracellular regeneration of citrulline into arginine.

5.1. Arginine Supplementation during Inflammatory Conditions

Over the past decades, supplementation of l-arginine was considered a logical therapeutic option to restore the decreased arginine levels in septic and critical ill patients, as increased arginine concentrations may restore the important physiologic processes, including organ perfusion, immune function, protein synthesis and wound healing. Several studies have evaluated the effects of l-arginine supplementation in a variety of conditions, at first in healthy controls. Arginine supplemented in a dosage of three to eight grams a day, rarely resulted in unwanted side effects, suggesting the supplementation of arginine to be safe. However, given in a higher dosage, exceeding nine grams, human subjects experience gastro-intestinal discomfort, vomiting and diarrhea. The severity of these side effects seem to be dosage dependent.

Previous meta-analysis and systematic reviews evaluated the value of enhanced nutrition as a possible additional treatment in surgical patients and critically ill patients. Most studies using arginine as supplement investigated a combination of different nutrition compounds, such as omega-3-fatty-acids, glutamine, or nucleotides, unfortunately all with different results. A prospective, randomized, double-blind, placebo-controlled study in ICU patients, used oral arginine supplementation added to the enteral nutrition which resulted in enhanced arginine and ornithine concentrations, possibly by an increased arginase activity in this patient population without an enhancement of the NO production. As for the clinical outcome, in a randomized control trial enteral formula enriched with arginine, and other select nutrients, showed no differences in hospital mortality, infectious complications or ICU length of stay between the arginine supplemented group and the placebo treated ICU patients. In line, in another study in critically ill trauma patients, no differences in the arginine supplemented versus placebo treated group on clinical outcomes were observed. However, a study in severe sepsis patients has proven otherwise as a significantly higher mortality was observed in the enteral supplemented patients with arginine containing diets. Although all studies agree that enhancing the metabolic response in patients and especially the critical ill is necessary to improve outcome and to reduce mortality and complications, the different results of these studies led to the questionability of the effectiveness of supplementation, and in this case also of arginine supplementation. Therefore, experts in the field suggested not to use arginine supplementation in critical ill patients, as this may result in an enhanced mortality rate. However, this questionability and the assumption of an increased mortality especially after arginine supplementation in sepsis and critical ill patients may be confounded by grouping different formulas and different types of patients together. As previously observed in elective surgical patients, a significant reduction in infectious complications and a trend towards improved mortality in patients supplemented with nutrition containing high arginine concentrations was present, suggesting these negative results of arginine to be patient population and interventional driven. Therefore, good-quality studies examining l-arginine monotherapy are essential to define the clinical usage of l-arginine in the critical ill patients.

Prior to the usage of l-arginine monotherapy in critical ill patients, our research group tested l-arginine monotherapy in experimental sepsis/endotoxemia models. l-arginine supplementation exhibited beneficial effects on the arginine concentrations without deleterious side effects in an endotoxemia model in pigs. Furthermore, in this model, pre-treatment with arginine prior to endotoxemia induction resulted in an increased hepatosplanchnic perfusion and enhanced NO production compared to untreated endotoxemic animals. In addition, l-arginine supplementation not only enhances the immune response, but also the protein turnover in endotoxemic pigs and resulted in elevated whole-body NO synthesis without adverse effects. In line, in a murine endotoxemia model, l-arginine supplementation, starting during arginine deficiency, resulted in increased arginine plasma concentrations and an enhanced jejunal NO production without negative side effects. These positive effects of l-arginine supplementation in experimental models led to the start of a new study of l-arginine supplementation in septic ICU patients.

The recent dose-titration study with l-arginine from our group showed increased plasma arginine concentrations, combined with an enhanced arginine de novo synthesis and increased NO production. More importantly, this did not result in negative alterations in hemodynamic parameters. The absence of clinically adverse effects was also described in a previous conducted pilot study with l-arginine monotherapy in non-surgical critical ill patients. In this study, l-arginine supplementation was associated with an increased ornithine synthesis, suggesting a preferential usage of the available arginine by arginase, with only a minimal enhancement of the citrulline/NO synthesis. In line, the results from our endotoxemia murine model support this clinical observation, as the enhanced arginine plasma concentrations were not accompanied by enhanced intracellular arginine concentrations, but only with increased ornithine concentrations. Thus, l-arginine monotherapy in septic patients seems to result in enhanced arginine concentrations and also increased NO production without adverse events. Therefore, based on beneficial effects without an adverse outcome, the issue of l-arginine supplementation during sepsis remains an actual point of discussion and to our opinion needs to be revisited.

5.2. Citrulline Supplementation during Inflammatory Conditions

Since reduced citrulline bioavailability in sepsis and endotoxemia, resulting in low plasma arginine is associated with higher mortality rates, the supplementation of citrulline could be another therapeutic intervention restoring the balance between arginine production and metabolism as well as improving NO production and related functions. During endotoxemia and inflammatory conditions, supplementation of l-citrulline enhances plasma citrulline and arginine concentrations. Oral supplementation of l-citrulline in endotoxemic rats resulted in higher plasma arginine concentrations compared to l-arginine supplementation, making l-citrulline a more efficient supplement than l-arginine during inflammation. We previously showed that l-citrulline supplementation resulted in an enhanced NO concentration and improved microcirculation during endotoxemia in the jejunal villi, which was not observed following l-arginine supplementation.

Study of Qualls and colleagues showed no enhancement of NO synthesis under arginine overflowing conditions in LPS + IFN-γ stimulated rat fetal liver-derived macrophages after addition of citrulline. However, under conditions of arginine scarcity, addition of citrulline contributed to an enhanced NO production in that same model. Interestingly, the effect of citrulline supplementation on increased NO production was only seen in arginine depleted macrophages, suggesting citrulline metabolism contributes to macrophage arginine biosynthesis and NO production only under conditions of arginine scarcity.

However, citrulline supplementation requires a functional NOS3 complex, and thus also a functional intracellular ASS-ASL complex. As previously demonstrated, in tissue specific arginase-deficient mice, an enhanced NOS2 pathway was present due to the absence of the inhibitory effects of arginase in the macrophage. Citrulline supplementation in these animals did not lead to an improved outcome, based on the absence of a functional NOS3 complex.

6. Modulations in the Arginine-NO Metabolism

To illustrate the complexity and outcome of modulations in the arginine pathway, we added a table with an overview of our findings in murine endotoxemia, which underscores this complexity (see Table 1). As demonstrated, murine endotoxemia is characterized with arginine deficiency and also a decreased NO production in jejunal tissue of these animals. Furthermore, the microcirculation was also significantly decreased in these animals. Since arginase-I and NOS2 compete for the same substrate, arginine, we developed a tissue-specific arginase-I deficient mouse model, to determine whether the absence of arginase-I in endothelial cells and macrophages would exhibit beneficial effects on the arginine concentration and NO production during endotoxemia. The absence of arginase-I was accompanied by an increased inflammatory response and an enhanced NOS2 derived NO production. This increased NOS2 activity is suggested to contribute to the decreased NOS3 derived NO production and the depressed microcirculatory flow during endotoxemia. In addition, ADMA concentrations were significantly increased after prolonged endotoxemia in both mouse strains, which led to a significant decreased arginine/ADMA ratio. Since citrulline supplementation is suggested to be a more preferential substrate for NOS3, to result in an enhanced arginine availability, we supplemented citrulline in control and tissue specific arginase-I-deficient mice during prolonged endotoxemia.

As expected, citrulline supplementation resulted in increased plasma arginine concentrations in control mice during endotoxemia. However, as for the arginase-I tissue specific deficient mice, arginine concentrations did not significantly increase compared to LPS-treated animals alone. Citrulline supplementation enhanced the NO production in jejunal tissue and the microcirculation in the jejunal villi. These results were not present in the arginase-I deficient mice, as the NO production and microcirculation in jejunal tissue did not improve after citrulline supplementation during endotoxemia. Furthermore, citrulline supplementation did not influence the ADMA concentrations in control or arginase-I deficient mice. However, the arginine/ADMA ratios were significantly improved in both mouse strains based on the effects on the arginine concentration during LPS and citrulline supplementation.

Based on these results, in arginase-I deficient mice, citrulline supplementation is not used as a source for NOS2 derived NO production, which may indicate that arginase-I deficient mice exhibit a dysfunctional NOS3-derived NO production.

These findings underscore the complexity of the interaction between substrate metabolism and the functional enzyme complex. Future research is essential in this field to unravel the complexity of the arginine-NO metabolism during endotoxemia and sepsis and most importantly to prevent arginine deficiency. At this moment, we are conducting a clinical study in septic ICU patients with citrulline supplementation to investigate whether citrulline is capable of enhancing the arginine availability and the microcirculation during sepsis in these patients.

7. Conclusions

In conclusion, arginine and its precursor citrulline play an important role in the immune response during inflammation and sepsis. Maintaining the arginine availability during inflammatory conditions is of crucial importance, probably best by enhancing the citrulline concentration, preventing NOS uncoupling and maintaining adequate enzyme function during these conditions. Future studies are warranted to determine the presence of arginine deficiency in other inflammatory conditions, the safety of supplementation and also to find the best supplement to enhance the arginine-NO pathway in these situations.

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  45. 45.

    Ratner S., Anslow W.P., Petrack B. Biosynthesis of urea. VI. Enzymatic cleavage of argininosuccinic acid to arginine and fumaric acid. J. Biol. Chem. 1953;204:115-125.

    Not in our library

  46. 46.

    Goodwin B.L., Solomonson L.P., Eichler D.C. Argininosuccinate synthase expression is required to maintain nitric oxide production and cell viability in aortic endothelial cells. J. Biol. Chem. 2004;279:18353-18360.

    Not in our library10.1074/jbc.m308160200

  47. 47.

    Nussler A.K., Billiar T.R., Liu Z.Z., Morris S.M. Coinduction of nitric oxide synthase and argininosuccinate synthetase in a murine macrophage cell line. Implications for regulation of nitric oxide production. J. Biol. Chem. 1994;269:1257-1261.

    Not in our library

  48. 48.

    Erez A., Nagamani S.C., Shchelochkov O.A., Premkumar M.H., Campeau P.M., Chen Y., Garg H.K., Li L., Mian A., Bertin T.K., et al. Requirement of argininosuccinate lyase for systemic nitric oxide production. Nat. Med. 2011;17:1619-1626.

    Not in our library10.1038/nm.2544

  49. 49.

    Cao M., George T.J., Prima V., Nelson D., Svetlov S. Argininosuccinate synthase as a novel biomarker for inflammatory conditions. Biomarkers. 2013;18:242-249.

    Not in our library10.3109/1354750x.2013.773080

  50. 50.

    Qualls J.E., Subramanian C., Rafi W., Smith A.M., Balouzian L., DeFreitas A.A., Shirey K.A., Reutterer B., Kernbauer E., Stockinger S., et al. Sustained generation of nitric oxide and control of mycobacterial infection requires argininosuccinate synthase 1. Cell Host Microbe. 2012;12:313-323.

    Not in our library10.1016/j.chom.2012.07.012

  51. 51.

    Wileman S.M., Mann G.E., Pearson J.D., Baydoun A.R. Role of l-citrulline transport in nitric oxide synthesis in rat aortic smooth muscle cells activated with LPS and interferon-gamma. Br. J. Pharmacol. 2003;140:179-185.

    Not in our library10.1038/sj.bjp.0705407

  52. 52.

    Schmidlin A., Fischer S., Wiesinger H. Transport of l-citrulline in neural cell cultures. Dev. Neurosci. 2000;22:393-398.

    Not in our library10.1159/000017468

  53. 53.

    Hilderman R.H., Casey T.E., Pojoga L.H. P(1),P(4)-Diadenosine 5′-tetraphosphate modulates l-arginine and l-citrulline uptake by bovine aortic endothelial cells. Arch. Biochem. Biophys. 2000;375:124-130.

    Not in our library10.1006/abbi.1999.1643

  54. 54.

    Flam B.R., Eichler D.C., Solomonson L.P. Endothelial nitric oxide production is tightly coupled to the citrulline-no cycle. Nitric Oxide. 2007;17:115-121.

    Not in our library10.1016/j.niox.2007.07.001

  55. 55.

    Hattori Y., Campbell E.B., Gross S.S. Argininosuccinate synthetase mrna and activity are induced by immunostimulants in vascular smooth muscle. Role in the regeneration or arginine for nitric oxide synthesis. J. Biol. Chem. 1994;269:9405-9408.

    Not in our library

  56. 56.

    Schwartz D., Schwartz I.F., Gnessin E., Wollman Y., Chernichovsky T., Blum M., Iaina A. Differential regulation of glomerular arginine transporters (CAT-1 and CAT-2) in lipopolysaccharide-treated rats. Am. J. Physiol. Renal. Physiol. 2003;284:F788-F795.

    Not in our library10.1152/ajprenal.00221.2002

  57. 57.

    Closs E.I., Boissel J.P., Habermeier A., Rotmann A. Structure and function of cationic amino acid transporters (CATs). J. Membr. Biol. 2006;213:67-77.

    Not in our library10.1007/s00232-006-0875-7

  58. 58.

    Fotiadis D., Kanai Y., Palacin M. The SLC3 and SLC7 families of amino acid transporters. Mol. Aspects Med. 2013;34:139-158.

    Not in our library10.1016/j.mam.2012.10.007

  59. 59.

    Verrey F., Closs E.I., Wagner C.A., Palacin M., Endou H., Kanai Y. CATs and HATs: The SLC7 family of amino acid transporters. Pflugers Arch. 2004;447:532-542.

    Not in our library10.1007/s00424-003-1086-z

  60. 60.

    Cynober L.A. Plasma amino acid levels with a note on membrane transport: Characteristics, regulation, and metabolic significance. Nutrition. 2002;18:761-766.

    Not in our library10.1016/s0899-9007(02)00780-3

  61. 61.

    Shen L.J., Beloussow K., Shen W.C. Accessibility of endothelial and inducible nitric oxide synthase to the intracellular citrulline-arginine regeneration pathway. Biochem. Pharmacol. 2005;69:97-104.

    Not in our library10.1016/j.bcp.2004.09.003

  62. 62.

    McDonald K.K., Zharikov S., Block E.R., Kilberg M.S. A caveolar complex between the cationic amino acid transporter 1 and endothelial nitric-oxide synthase may explain the “Arginine paradox”. J. Biol. Chem. 1997;272:31213-31216.

    Not in our library10.1074/jbc.272.50.31213

  63. 63.

    Yeramian A., Martin L., Serrat N., Arpa L., Soler C., Bertran J., McLeod C., Palacin M., Modolell M., Lloberas J., et al. Arginine transport via cationic amino acid transporter 2 plays a critical regulatory role in classical or alternative activation of macrophages. J. Immunol. 2006;176:5918-5924.

    Not in our library10.4049/jimmunol.176.10.5918

  64. 64.

    Rotoli B.M., Bussolati O., Sala R., Barilli A., Talarico E., Gazzola G.C., Dall’Asta V. Infgamma stimulates arginine transport through system y+L in human monocytes. FEBS Lett. 2004;571:177-181.

    Not in our library10.1016/j.febslet.2004.06.086

  65. 65.

    Yeramian A., Martin L., Arpa L., Bertran J., Soler C., McLeod C., Modolell M., Palacin M., Lloberas J., Celada A. Macrophages require distinct arginine catabolism and transport systems for proliferation and for activation. Eur. J. Immunol. 2006;36:1516-1526.

    Not in our library10.1002/eji.200535694

  66. 66.

    Vadgama J.V., Evered D.F. Characteristics of l-citrulline transport across rat small intestine in vitro. Pediatr. Res. 1992;32:472-478.

    Not in our library10.1203/00006450-199210000-00019

  67. 67.

    Bahri S., Curis E., el Wafi F.Z., Aussel C., Chaumeil J.C., Cynober L., Zerrouk N. Mechanisms and kinetics of citrulline uptake in a model of human intestinal epithelial cells. Clin. Nutr. 2008;27:872-880.

    Not in our library10.1016/j.clnu.2008.08.003

  68. 68.

    Chen J., Zhu Y., Hu M. Mechanisms and kinetics of uptake and efflux of l-methionine in an intestinal epithelial model (Caco-2). J. Nutr. 1994;124:1907-1916.

    Not in our library10.1093/jn/124.10.1907

  69. 69.
  70. 70.

    Nagata N., Endo F., Matsuda I. Ornithine carbamoyltransferase (OCT) in the jejunal mucosa, as a reference of the liver oct. Clin. Chim. Acta. 1983;134:155-166.

    Not in our library10.1016/0009-8981(83)90193-6

  71. 71.

    Luiking Y.C., ten Have G.A., Wolfe R.R., Deutz N.E. Arginine de novo and nitric oxide production in disease states. Am. J. Physiol. Endocrinol. Metab. 2012;303:E1177-E1189.

    Not in our library10.1152/ajpendo.00284.2012

  72. 72.

    Morris S.M. Recent advances in arginine metabolism: Roles and regulation of the arginases. Br. J. Pharmacol. 2009;157:922-930.

    Not in our library10.1111/j.1476-5381.2009.00278.x

  73. 73.

    Curis E., Nicolis I., Moinard C., Osowska S., Zerrouk N., Benazeth S., Cynober L. Almost all about citrulline in mammals. Amino Acids. 2005;29:177-205.

    Not in our library10.1007/s00726-005-0235-4

  74. 74.

    Yu H., Yoo P.K., Aguirre C.C., Tsoa R.W., Kern R.M., Grody W.W., Cederbaum S.D., Iyer R.K. Widespread expression of arginase I in mouse tissues. Biochemical and physiological implications. J. Histochem. Cytochem. 2003;51:1151-1160.

    Not in our library10.1177/002215540305100905

  75. 75.

    Poeze M., Bruins M.J., Kessels F., Luiking Y.C., Lamers W.H., Deutz N.E. Effects of l-arginine pretreatment on nitric oxide metabolism and hepatosplanchnic perfusion during porcine endotoxemia. Am. J. Clin. Nutr. 2011;93:1237-1247.

    Not in our library10.3945/ajcn.110.007237

  76. 76.

    Wijnands K.A., Hoeksema M.A., Meesters D.M., van den Akker N.M., Molin D.G., Briede J.J., Ghosh M., Kohler S.E., van Zandvoort M.A., de Winther M.P., et al. Arginase-1 deficiency regulates arginine concentrations and NOS2-mediated no production during endotoxemia. PLoS One. 2014;9:e86135.

    Not in our library10.1371/journal.pone.0086135

  77. 77.

    Louis C.A., Mody V., Henry W.L., Reichner J.S., Albina J.E. Regulation of arginase isoforms I and II by IL-4 in cultured murine peritoneal macrophages. Am. J. Physiol. 1999;276:R237-R242.

    Not in our library10.1152/ajpregu.1999.276.1.r237

  78. 78.

    Berkowitz D.E., White R., Li D., Minhas K.M., Cernetich A., Kim S., Burke S., Shoukas A.A., Nyhan D., Champion H.C., et al. Arginase reciprocally regulates nitric oxide synthase activity and contributes to endothelial dysfunction in aging blood vessels. Circulation. 2003;108:2000-2006.

    Not in our library10.1161/01.cir.0000092948.04444.c7

  79. 79.

    Chicoine L.G., Paffett M.L., Young T.L., Nelin L.D. Arginase inhibition increases nitric oxide production in bovine pulmonary arterial endothelial cells. Am. J. Physiol. Lung Cell Mol. Physiol. 2004;287:L60-L68.

    Not in our library10.1152/ajplung.00194.2003

  80. 80.

    Kim J.H., Bugaj L.J., Oh Y.J., Bivalacqua T.J., Ryoo S., Soucy K.G., Santhanam L., Webb A., Camara A., Sikka G., et al. Arginase inhibition restores NOS coupling and reverses endothelial dysfunction and vascular stiffness in old rats. J. Appl. Physiol. 2009;107:1249-1257.

    Not in our library10.1152/japplphysiol.91393.2008

  81. 81.

    Li H., Meininger C.J., Hawker J.R., Haynes T.E., Kepka-Lenhart D., Mistry S.K., Morris S.M., Wu G. Regulatory role of arginase I and II in nitric oxide, polyamine, and proline syntheses in endothelial cells. Am. J. Physiol. Endocrinol. Metab. 2001;280:E75-E82.

    Not in our library10.1152/ajpendo.2001.280.1.e75

  82. 82.

    Ozaki M., Gotoh T., Nagasaki A., Miyanaka K., Takeya M., Fujiyama S., Tomita K., Mori M. Expression of arginase II and related enzymes in the rat small intestine and kidney. J. Biochem. 1999;125:586-593.

    Not in our library10.1093/oxfordjournals.jbchem.a022324

  83. 83.

    Mori M. Regulation of nitric oxide synthesis and apoptosis by arginase and arginine recycling. J. Nutr. 2007;137:1616S-1620S.

    Not in our library10.1093/jn/137.6.1616s

  84. 84.

    Morris S.M., Bhamidipati D., Kepka-Lenhart D. Human type II arginase: Sequence analysis and tissue-specific expression. Gene. 1997;193:157-161.

    Not in our library10.1016/s0378-1119(97)00099-1

  85. 85.

    Gotoh T., Sonoki T., Nagasaki A., Terada K., Takiguchi M., Mori M. Molecular cloning of cdna for nonhepatic mitochondrial arginase (arginase II) and comparison of its induction with nitric oxide synthase in a murine macrophage-like cell line. FEBS Lett. 1996;395:119-122.

    Not in our library10.1016/0014-5793(96)01015-0

  86. 86.

    Vockley J.G., Jenkinson C.P., Shukla H., Kern R.M., Grody W.W., Cederbaum S.D. Cloning and characterization of the human type II arginase gene. Genomics. 1996;38:118-123.

    Not in our library10.1006/geno.1996.0606

  87. 87.

    Buga G.M., Singh R., Pervin S., Rogers N.E., Schmitz D.A., Jenkinson C.P., Cederbaum S.D., Ignarro L.J. Arginase activity in endothelial cells: Inhibition by NG-hydroxy-l-arginine during high-output NO production. Am. J. Physiol. 1996;271:H1988-H1998.

    Not in our library10.1152/ajpheart.1996.271.5.h1988

  88. 88.

    De Jonge W.J., Hallemeesch M.M., Kwikkers K.L., Ruijter J.M., de Gier-de Vries C., van Roon M.A., Meijer A.J., Marescau B., de Deyn P.P., Deutz N.E., et al. Overexpression of arginase I in enterocytes of transgenic mice elicits a selective arginine deficiency and affects skin, muscle, and lymphoid development. Am. J. Clin. Nutr. 2002;76:128-140.

    Not in our library10.1093/ajcn/76.1.128

  89. 89.

    Mayer B., John M., Bohme E. Purification of a Ca2+/calmodulin-dependent nitric oxide synthase from porcine cerebellum. Cofactor-role of tetrahydrobiopterin. FEBS Lett. 1990;277:215-219.

    Not in our library10.1016/0014-5793(90)80848-d

  90. 90.

    Schmidt H.H., Pollock J.S., Nakane M., Gorsky L.D., Forstermann U., Murad F. Purification of a soluble isoform of guanylyl cyclase-activating-factor synthase. Proc. Natl. Acad. Sci. USA. 1991;88:365-369.

    Not in our library10.1073/pnas.88.2.365

  91. 91.

    Forstermann U., Pollock J.S., Schmidt H.H., Heller M., Murad F. Calmodulin-dependent endothelium-derived relaxing factor/nitric oxide synthase activity is present in the particulate and cytosolic fractions of bovine aortic endothelial cells. Proc. Natl. Acad. Sci. USA. 1991;88:1788-1792.

    Not in our library10.1073/pnas.88.5.1788

  92. 92.

    Stuehr D.J., Gross S.S., Sakuma I., Levi R., Nathan C.F. Activated murine macrophages secrete a metabolite of arginine with the bioactivity of endothelium-derived relaxing factor and the chemical reactivity of nitric oxide. J. Exp. Med. 1989;169:1011-1020.

    Not in our library10.1084/jem.169.3.1011

  93. 93.

    Knowles R.G., Moncada S. Nitric oxide synthases in mammals. Biochem. J. 1994;298:249-258.

    Not in our library10.1042/bj2980249

  94. 94.

    Bredt D.S., Snyder S.H. Isolation of nitric oxide synthetase, a calmodulin-requiring enzyme. Proc. Natl. Acad. Sci. USA. 1990;87:682-685.

    Not in our library10.1073/pnas.87.2.682

  95. 95.

    Moncada S., Higgs A. The l-arginine-nitric oxide pathway. N. Engl. J. Med. 1993;329:2002-2012.

    Not in our library10.1056/nejm199312303292706

  96. 96.

    Mulsch A., Bassenge E., Busse R. Nitric oxide synthesis in endothelial cytosol: Evidence for a calcium-dependent and a calcium-independent mechanism. Naunyn. Schmiedebergs Arch. Pharmacol. 1989;340:767-770.

    Not in our library10.1007/bf00169688

  97. 97.

    Hibbs J.B., Taintor R.R., Vavrin Z., Rachlin E.M. Nitric oxide: A cytotoxic activated macrophage effector molecule. Biochem. Biophys. Res. Commun. 1988;157:87-94.

    Not in our library10.1016/s0006-291x(88)80015-9

  98. 98.

    Hibbs J.B., Taintor R.R., Vavrin Z. Macrophage cytotoxicity: Role for l-arginine deiminase and imino nitrogen oxidation to nitrite. Science. 1987;235:473-476.

    Not in our library10.1126/science.2432665

  99. 99.

    Downen M., Zhao M.L., Lee P., Weidenheim K.M., Dickson D.W., Lee S.C. Neuronal nitric oxide synthase expression in developing and adult human CNS. J. Neuropathol. Exp. Neurol. 1999;58:12-21.

    Not in our library10.1097/00005072-199901000-00002

  100. 100.

    Dun N.J., Dun S.L., Wu S.Y., Forstermann U. Nitric oxide synthase immunoreactivity in rat superior cervical ganglia and adrenal glands. Neurosci. Lett. 1993;158:51-54.

    Not in our library10.1016/0304-3940(93)90610-w

  101. 101.

    Schmidt H.H., Gagne G.D., Nakane M., Pollock J.S., Miller M.F., Murad F. Mapping of neural nitric oxide synthase in the rat suggests frequent co-localization with nadph diaphorase but not with soluble guanylyl cyclase, and novel paraneural functions for nitrinergic signal transduction. J. Histochem. Cytochem. 1992;40:1439-1456.

    Not in our library10.1177/40.10.1382087

  102. 102.

    Kavdia M., Popel A.S. Contribution of nNOS- and eNOS-derived NO to microvascular smooth muscle no exposure. J. Appl. Physiol. 2004;97:293-301.

    Not in our library10.1152/japplphysiol.00049.2004

  103. 103.

    Toda N., Okamura T. The pharmacology of nitric oxide in the peripheral nervous system of blood vessels. Pharmacol. Rev. 2003;55:271-324.

    Not in our library10.1124/pr.55.2.3

  104. 104.

    Schmidt H.H., Warner T.D., Ishii K., Sheng H., Murad F. Insulin secretion from pancreatic B cells caused by l-arginine-derived nitrogen oxides. Science. 1992;255:721-723.

    Not in our library10.1126/science.1371193

  105. 105.

    Han G., Ma H., Chintala R., Miyake K., Fulton D.J., Barman S.A., White R.E. Nongenomic, endothelium-independent effects of estrogen on human coronary smooth muscle are mediated by type I (neuronal) NOS and PI3-kinase-Akt signaling. Am. J. Physiol. Heart Circ. Physiol. 2007;293:H314-H321.

    Not in our library10.1152/ajpheart.01342.2006

  106. 106.

    Seddon M.D., Chowienczyk P.J., Brett S.E., Casadei B., Shah A.M. Neuronal nitric oxide synthase regulates basal microvascular tone in humans in vivo. Circulation. 2008;117:1991-1996.

    Not in our library10.1161/circulationaha.107.744540

  107. 107.

    Förstermann U., Closs E.I., Pollock J.S., Nakane M., Schwarz P., Gath I., Kleinert H. Nitric oxide synthase isozymes. Characterization, purification, molecular cloning, and functions. Hypertension. 1994;23:1121-1131.

    Not in our library10.1161/01.hyp.23.6.1121

  108. 108.

    Förstermann U., Sessa W.C. Nitric oxide synthases: Regulation and function. Eur. Heart J. 2012;33:829-837d.

    Not in our library10.1093/eurheartj/ehr304

  109. 109.

    Bohme G.A., Bon C., Stutzmann J.M., Doble A., Blanchard J.C. Possible involvement of nitric oxide in long-term potentiation. Eur. J. Pharmacol. 1991;199:379-381.

    Not in our library10.1016/0014-2999(91)90505-k

  110. 110.

    Togashi H., Sakuma I., Yoshioka M., Kobayashi T., Yasuda H., Kitabatake A., Saito H., Gross S.S., Levi R. A central nervous system action of nitric oxide in blood pressure regulation. J. Pharmacol. Exp. Ther. 1992;262:343-347.

    Not in our library

  111. 111.

    Bult H., Boeckxstaens G.E., Pelckmans P.A., Jordaens F.H., van Maercke Y.M., Herman A.G. Nitric oxide as an inhibitory non-adrenergic non-cholinergic neurotransmitter. Nature. 1990;345:346-347.

    Not in our library10.1038/345346a0

  112. 112.

    Stone J.R., Marletta M.A. Spectral and kinetic studies on the activation of soluble guanylate cyclase by nitric oxide. Biochemistry. 1996;35:1093-1099.

    Not in our library10.1021/bi9519718

  113. 113.

    Rapoport R.M., Draznin M.B., Murad F. Endothelium-dependent relaxation in rat aorta may be mediated through cyclic GMP-dependent protein phosphorylation. Nature. 1983;306:174-176.

    Not in our library10.1038/306174a0

  114. 114.

    Forstermann U., Mulsch A., Bohme E., Busse R. Stimulation of soluble guanylate cyclase by an acetylcholine-induced endothelium-derived factor from rabbit and canine arteries. Circ. Res. 1986;58:531-538.

    Not in our library10.1161/01.res.58.4.531

  115. 115.

    Shesely E.G., Maeda N., Kim H.S., Desai K.M., Krege J.H., Laubach V.E., Sherman P.A., Sessa W.C., Smithies O. Elevated blood pressures in mice lacking endothelial nitric oxide synthase. Proc. Natl. Acad. Sci. USA. 1996;93:13176-13181.

    Not in our library10.1073/pnas.93.23.13176

  116. 116.

    Huang P.L., Huang Z., Mashimo H., Bloch K.D., Moskowitz M.A., Bevan J.A., Fishman M.C. Hypertension in mice lacking the gene for endothelial nitric oxide synthase. Nature. 1995;377:239-242.

    Not in our library10.1038/377239a0

  117. 117.

    Radomski M.W., Palmer R.M., Moncada S. The anti-aggregating properties of vascular endothelium: Interactions between prostacyclin and nitric oxide. Br. J. Pharmacol. 1987;92:639-646.

    Not in our library10.1111/j.1476-5381.1987.tb11367.x

  118. 118.

    Murohara T., Asahara T., Silver M., Bauters C., Masuda H., Kalka C., Kearney M., Chen D., Symes J.F., Fishman M.C., et al. Nitric oxide synthase modulates angiogenesis in response to tissue ischemia. J. Clin. Investig. 1998;101:2567-2578.

    Not in our library10.1172/jci1560

  119. 119.

    Kietadisorn R., Juni R.P., Moens A.L. Tackling endothelial dysfunction by modulating NOS uncoupling: New insights into its pathogenesis and therapeutic possibilities. Am. J. Physiol. Endocrinol. Metab. 2012;302:E481-E495.

    Not in our library10.1152/ajpendo.00540.2011

  120. 120.

    Chennupati R., Meens M.J., Marion V., Janssen B.J., Lamers W.H., de Mey J.G., Kohler S.E. Endothelial arginine resynthesis contributes to the maintenance of vasomotor function in male diabetic mice. PLoS One. 2014;9:e102264.

    Not in our library10.1371/journal.pone.0102264

  121. 121.

    Chatterjee A., Black S.M., Catravas J.D. Endothelial nitric oxide (NO) and its pathophysiologic regulation. Vascul. Pharmacol. 2008;49:134-140.

    Not in our library10.1016/j.vph.2008.06.008

  122. 122.

    Crabtree M.J., Channon K.M. Synthesis and recycling of tetrahydrobiopterin in endothelial function and vascular disease. Nitric Oxide. 2011;25:81-88.

    Not in our library10.1016/j.niox.2011.04.004

  123. 123.

    Stroes E., Hijmering M., van Zandvoort M., Wever R., Rabelink T.J., van Faassen E.E. Origin of superoxide production by endothelial nitric oxide synthase. FEBS Lett. 1998;438:161-164.

    Not in our library10.1016/s0014-5793(98)01292-7

  124. 124.

    Vincent J.L. Clinical sepsis and septic shock—Definition, diagnosis and management principles. Langenbecks Arch. Surg. 2008;393:817-824.

    Not in our library10.1007/s00423-008-0343-1

  125. 125.

    Levy M.M., Fink M.P., Marshall J.C., Abraham E., Angus D., Cook D., Cohen J., Opal S.M., Vincent J.L., Ramsay G., et al. 2001 SCCM/ESICM/ACCP/ATS/SIS international sepsis definitions conference. Crit. Care Med. 2003;31:1250-1256.

    Not in our library10.1097/01.ccm.0000050454.01978.3b

  126. 126.

    McCuskey R.S. Hepatic and splanchnic microvascular responses to inflammation and shock. Hepatogastroenterology. 1999;46:1464-1467.

    Not in our library

  127. 127.

    Ince C. The microcirculation is the motor of sepsis. Crit. Care. 2005;9:S13-S19.

    Not in our library10.1186/cc3753

  128. 128.

    Schmidt H., Secchi A., Wellmann R., Bach A., Bohrer H., Gebhard M.M., Martin E. Effect of endotoxemia on intestinal villus microcirculation in rats. J. Surg. Res. 1996;61:521-526.

    Not in our library10.1006/jsre.1996.0157

  129. 129.

    Tadie J.M., Cynober L., Peigne V., Caumont-Prim A., Neveux N., Gey A., Guerot E., Diehl J.L., Fagon J.Y., Tartour E., et al. Arginine administration to critically ill patients with a low nitric oxide fraction in the airways: A pilot study. Intensive Care Med. 2013;39:1663-1665.

    Not in our library10.1007/s00134-013-2984-y

  130. 130.

    Freund H., Atamian S., Holroyde J., Fischer J.E. Plasma amino acids as predictors of the severity and outcome of sepsis. Ann. Surg. 1979;190:571-576.

    Not in our library10.1097/00000658-197911000-00003

  131. 131.

    Kao C.C., Bandi V., Guntupalli K.K., Wu M., Castillo L., Jahoor F. Arginine, citrulline and nitric oxide metabolism in sepsis. Clin. Sci. 2009;117:23-30.

    Not in our library10.1042/cs20080444

  132. 132.

    Wijnands K.A.P., Poeze M., Luiking Y.C., Breedveld P., Dejong C.H.C., Ramsay G., Deutz N.E.P. Reduced arginine production and arginase activity are independent of the cause of sepsis. proceedings of the 21st ESICM Annual Congress.

    Not in our library

  133. 133.

    Bansal V., Ochoa J.B. Arginine availability, arginase, and the immune response. Curr. Opin. Clin. Nutr. Metab. Care. 2003;6:223-228.

    Not in our library10.1097/00075197-200303000-00012

  134. 134.

    Calder P.C. Immunonutrition in surgical and critically ill patients. Br. J. Nutr. 2007;98:S133-S139.

    Not in our library10.1017/s0007114507832909

  135. 135.

    Galban C., Montejo J.C., Mesejo A., Marco P., Celaya S., Sanchez-Segura J.M., Farre M., Bryg D.J. An immune-enhancing enteral diet reduces mortality rate and episodes of bacteremia in septic intensive care unit patients. Crit. Care Med. 2000;28:643-648.

    Not in our library10.1097/00003246-200003000-00007

  136. 136.

    Ware L.B., Magarik J.A., Wickersham N., Cunningham G., Rice T.W., Christman B.W., Wheeler A.P., Bernard G.R., Summar M.L. Low plasma citrulline levels are associated with acute respiratory distress syndrome in patients with severe sepsis. Crit. Care. 2013;17:R10.

    Not in our library10.1186/cc11934

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    Kao C., Hsu J., Bandi V., Jahoor F. Alterations in glutamine metabolism and its conversion to citrulline in sepsis. Am. J. Physiol. Endocrinol. Metab. 2013;304:E1359-E1364.

    Not in our library10.1152/ajpendo.00628.2012

  138. 138.

    Tizianello A., de Ferrari G., Garibotto G., Gurreri G., Robaudo C. Renal metabolism of amino acids and ammonia in subjects with normal renal function and in patients with chronic renal insufficiency. J. Clin. Investig. 1980;65:1162-1173.

    Not in our library10.1172/jci109771

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    Durante W., Johnson F.K., Johnson R.A. Arginase: A critical regulator of nitric oxide synthesis and vascular function. Clin. Exp. Pharmacol. Physiol. 2007;34:906-911.

    Not in our library10.1111/j.1440-1681.2007.04638.x

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    Ochoa J.B., Udekwu A.O., Billiar T.R., Curran R.D., Cerra F.B., Simmons R.L., Peitzman A.B. Nitrogen oxide levels in patients after trauma and during sepsis. Ann. Surg. 1991;214:621-626.

    Not in our library10.1097/00000658-199111000-00013

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    Bruins M.J., Soeters P.B., Deutz N.E. Endotoxemia affects organ protein metabolism differently during prolonged feeding in pigs. J. Nutr. 2000;130:3003-3013.

    Not in our library10.1093/jn/130.12.3003

  142. 142.

    Salimuddin, Nagasaki A., Gotoh T., Isobe H., Mori M. Regulation of the genes for arginase isoforms and related enzymes in mouse macrophages by lipopolysaccharide. Am. J. Physiol. 1999;277:E110-E117.

    Not in our library10.1152/ajpendo.1999.277.1.e110

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    Darcy C.J., Woodberry T., Davis J.S., Piera K.A., McNeil Y.R., Chen Y., Yeo T.W., Weinberg J.B., Anstey N.M. Increased plasma arginase activity in human sepsis: Association with increased circulating neutrophils. Clin. Chem. Lab. Med. 2014;52:573-581.

    Not in our library10.1515/cclm-2013-0698

  144. 144.

    Luiking Y.C., Engelen M.P., Deutz N.E. Regulation of nitric oxide production in health and disease. Curr. Opin. Clin. Nutr. Metab. Care. 2010;13:97-104.

    Not in our library10.1097/mco.0b013e328332f99d

  145. 145.

    Gomez-Jimenez J., Salgado A., Mourelle M., Martin M.C., Segura R.M., Peracaula R., Moncada S. l-arginine: Nitric oxide pathway in endotoxemia and human septic shock. Crit. Care Med. 1995;23:253-258.

    Not in our library10.1097/00003246-199502000-00009

  146. 146.

    Martin G., Asensi V., Montes A.H., Collazos J., Alvarez V., Perez-Is L., Carton J.A., Taboada F., Valle-Garay E. Endothelial (NOS3 E298D) and inducible (NOS2 exon 22) nitric oxide synthase polymorphisms, as well as plasma NOX, influence sepsis development. Nitric Oxide. 2014;42:79-86.

    Not in our library10.1016/j.niox.2014.09.004

  147. 147.

    Groeneveld A.B., Hartemink K.J., de Groot M.C., Visser J., Thijs L.G. Circulating endothelin and nitrate-nitrite relate to hemodynamic and metabolic variables in human septic shock. Shock. 1999;11:160-166.

    Not in our library10.1097/00024382-199903000-00002

  148. 148.

    Cauwels A., Bultinck J., de Zwaef R., Vandendriessche B., Magez S., Brouckaert P. Nitric oxide production by endotoxin preparations in TLR4-deficient mice. Nitric Oxide. 2014;36:36-43.

    Not in our library10.1016/j.niox.2013.11.001

  149. 149.

    Bultinck J., Sips P., Vakaet L., Brouckaert P., Cauwels A. Systemic no production during (septic) shock depends on parenchymal and not on hematopoietic cells: In vivo inos expression pattern in (septic) shock. Faseb. J. 2006;20:2363-2365.

    Not in our library10.1096/fj.06-5798fje

  150. 150.

    Villalpando S., Gopal J., Balasubramanyam A., Bandi V.P., Guntupalli K., Jahoor F. In vivo arginine production and intravascular nitric oxide synthesis in hypotensive sepsis. Am. J. Clin. Nutr. 2006;84:197-203.

    Not in our library10.1093/ajcn/84.1.197

  151. 151.

    Adrie C., Monchi M., Dinh-Xuan A.T., Dall’Ava-Santucci J., Dhainaut J.F., Pinsky M.R. Exhaled and nasal nitric oxide as a marker of pneumonia in ventilated patients. Am. J. Respir. Crit. Care Med. 2001;163:1143-1149.

    Not in our library10.1164/ajrccm.163.5.9906049

  152. 152.

    Luiking Y.C., Deutz N.E. Isotopic investigation of nitric oxide metabolism in disease. Curr. Opin. Clin. Nutr. Metab. Care. 2003;6:103-108.

    Not in our library10.1097/00075197-200301000-00015

  153. 153.

    Braulio V.B., Ten Have G.A., Vissers Y.L., Deutz N.E. Time course of nitric oxide production after endotoxin challenge in mice. Am. J. Physiol. Endocrinol. Metab. 2004;287:E912-E918.

    Not in our library10.1152/ajpendo.00540.2003

  154. 154.

    Hallemeesch M.M., Janssen B.J., de Jonge W.J., Soeters P.B., Lamers W.H., Deutz N.E. NO production by cNOS and iNOS reflects blood pressure changes in LPS-challenged mice. Am. J. Physiol. Endocrinol. Metab. 2003;285:E871-E875.

    Not in our library10.1152/ajpendo.00004.2002

  155. 155.

    Van Eijk H.M., Luiking Y.C., Deutz N.E. Methods using stable isotopes to measure nitric oxide (NO) synthesis in the l-arginine/NO pathway in health and disease. J. Chromatogr. B Anal. Technol. Biomed. Life Sci. 2007;851:172-185.

    Not in our library10.1016/j.jchromb.2006.08.054

  156. 156.

    Tadie J.M., Trinquart L., Janniere-Nartey C., Guerot E., Louis B., Fagon J.Y., Diehl J.L., Delclaux C. Prediction of nosocomial infection acquisition in ventilated patients by nasal nitric oxide: Proof-of-concept study. Shock. 2010;34:217-221.

    Not in our library10.1097/shk.0b013e3181d67494

  157. 157.

    Deja M., Busch T., Bachmann S., Riskowski K., Campean V., Wiedmann B., Schwabe M., Hell B., Pfeilschifter J., Falke K.J., et al. Reduced nitric oxide in sinus epithelium of patients with radiologic maxillary sinusitis and sepsis. Am. J. Respir. Crit. Care Med. 2003;168:281-286.

    Not in our library10.1164/rccm.200207-640oc

  158. 158.

    Lundberg J.O., Farkas-Szallasi T., Weitzberg E., Rinder J., Lidholm J., Anggaard A., Hokfelt T., Lundberg J.M., Alving K. High nitric oxide production in human paranasal sinuses. Nat. Med. 1995;1:370-373.

    Not in our library10.1038/nm0495-370

  159. 159.

    Brett S.J., Evans T.W. Measurement of endogenous nitric oxide in the lungs of patients with the acute respiratory distress syndrome. Am. J. Respir. Crit. Care Med. 1998;157:993-997.

    Not in our library10.1164/ajrccm.157.3.9705060

  160. 160.

    McClintock D.E., Ware L.B., Eisner M.D., Wickersham N., Thompson B.T., Matthay M.A. Higher urine nitric oxide is associated with improved outcomes in patients with acute lung injury. Am. J. Respir. Crit. Care Med. 2007;175:256-262.

    Not in our library10.1164/rccm.200607-947oc

  161. 161.

    Mori M., Gotoh T. Regulation of nitric oxide production by arginine metabolic enzymes. Biochem. Biophys. Res. Commun. 2000;275:715-719.

    Not in our library10.1006/bbrc.2000.3169

  162. 162.

    Siegemund M., van Bommel J., Schwarte L.A., Studer W., Girard T., Marsch S., Radermacher P., Ince C. Inducible nitric oxide synthase inhibition improves intestinal microcirculatory oxygenation and CO2 balance during endotoxemia in pigs. Intensive Care Med. 2005;31:985-992.

    Not in our library10.1007/s00134-005-2664-7

  163. 163.

    Lu J.L., Schmiege L.M., Kuo L., Liao J.C. Downregulation of endothelial constitutive nitric oxide synthase expression by lipopolysaccharide. Biochem. Biophys. Res. Commun. 1996;225:1-5.

    Not in our library10.1006/bbrc.1996.1121

  164. 164.

    Soeters P.B., Hallemeesch M.M., Bruins M.J., van Eijk H.M., Deutz N.E. Quantitative in vivo assessment of arginine utilization and nitric oxide production in endotoxemia. Am. J. Surg. 2002;183:480-488.

    Not in our library10.1016/s0002-9610(02)00847-4

  165. 165.

    Xaus J., Comalada M., Valledor A.F., Lloberas J., Lopez-Soriano F., Argiles J.M., Bogdan C., Celada A. LPS induces apoptosis in macrophages mostly through the autocrine production of TNF-alpha. Blood. 2000;95:3823-3831.

    Not in our library

  166. 166.

    Mills C.D. M1 and M2 macrophages: Oracles of health and disease. Crit. Rev. Immunol. 2012;32:463-488.

    Not in our library10.1615/critrevimmunol.v32.i6.10

  167. 167.

    Reade M.C., Clark M.F., Young J.D., Boyd C.A. Increased cationic amino acid flux through a newly expressed transporter in cells overproducing nitric oxide from patients with septic shock. Clin. Sci. (Lond.). 2002;102:645-650.

    Not in our library10.1042/cs20010329

  168. 168.

    Munder M. Arginase: An emerging key player in the mammalian immune system. Br. J. Pharmacol. 2009;158:638-651.

    Not in our library10.1111/j.1476-5381.2009.00291.x

  169. 169.

    Munder M., Engelhardt M., Knies D., Medenhoff S., Wabnitz G., Luckner-Minden C., Feldmeyer N., Voss R.H., Kropf P., Muller I., et al. Cytotoxicity of tumor antigen specific human T cells is unimpaired by arginine depletion. PLoS One. 2013;8:e63521.

    Not in our library10.1371/journal.pone.0063521

  170. 170.
  171. 171.

    Baydoun A.R., Bogle R.G., Pearson J.D., Mann G.E. Discrimination between citrulline and arginine transport in activated murine macrophages: Inefficient synthesis of no from recycling of citrulline to arginine. Br. J. Pharmacol. 1994;112:487-492.

    Not in our library10.1111/j.1476-5381.1994.tb13099.x

  172. 172.

    Munder M., Choi B.S., Rogers M., Kropf P. l-arginine deprivation impairs leishmania major-specific T-cell responses. Eur. J. Immunol. 2009;39:2161-2172.

    Not in our library10.1002/eji.200839041

  173. 173.

    Feldmeyer N., Wabnitz G., Leicht S., Luckner-Minden C., Schiller M., Franz T., Conradi R., Kropf P., Muller I., Ho A.D., et al. Arginine deficiency leads to impaired cofilin dephosphorylation in activated human T lymphocytes. Int. Immunol. 2012;24:303-313.

    Not in our library10.1093/intimm/dxs004

  174. 174.

    Modolell M., Choi B.S., Ryan R.O., Hancock M., Titus R.G., Abebe T., Hailu A., Muller I., Rogers M.E., Bangham C.R., et al. Local suppression of T cell responses by arginase-induced l-arginine depletion in nonhealing leishmaniasis. PLoS Negl. Trop. Dis. 2009;3:e480.

    Not in our library10.1371/journal.pntd.0000480

  175. 175.

    Herbert D.R., Orekov T., Roloson A., Ilies M., Perkins C., OʼBrien W., Cederbaum S., Christianson D.W., Zimmermann N., Rothenberg M.E., et al. Arginase I suppresses IL-12/IL-23p40-driven intestinal inflammation during acute schistosomiasis. J. Immunol. 2010;184:6438-6446.

    Not in our library10.4049/jimmunol.0902009

  176. 176.

    Lewis N.D., Asim M., Barry D.P., de Sablet T., Singh K., Piazuelo M.B., Gobert A.P., Chaturvedi R., Wilson K.T. Immune evasion by helicobacter pylori is mediated by induction of macrophage arginase II. J. Immunol. 2011;186:3632-3641.

    Not in our library10.4049/jimmunol.1003431

  177. 177.

    Kakuda D.K., Sweet M.J., Mac Leod C.L., Hume D.A., Markovich D. CAT2-mediated l-arginine transport and nitric oxide production in activated macrophages. Biochem. J. 1999;340:549-553.

    Not in our library10.1042/0264-6021:3400549

  178. 178.

    Nicholson B., Manner C.K., Kleeman J., MacLeod C.L. Sustained nitric oxide production in macrophages requires the arginine transporter CAT2. J. Biol. Chem. 2001;276:15881-15885.

    Not in our library10.1074/jbc.m010030200

  179. 179.

    Luiking Y.C., Poeze M., Dejong C.H., Ramsay G., Deutz N.E. Sepsis: An arginine deficiency state? Crit. Care Med. 2004;32:2135-2145.

    Not in our library10.1097/01.ccm.0000142939.81045.a0

  180. 180.

    Luiking Y.C., Poeze M., Deutz N.E. Arginine infusion in patients with septic shock increases nitric oxide production without haemodynamic instability. Clin. Sci. (Lond.). 2015;128:57-67.

    Not in our library10.1042/cs20140343

  181. 181.

    Crenn P., Neveux N., Chevret S., Jaffray P., Cynober L., Melchior J.C., Annane D., COIITSS Study Group. Plasma l-citrulline concentrations and its relationship with inflammation at the onset of septic shock: A pilot study. J. Crit. Care. 2014;29:315.e1-315.e6.

    Not in our library10.1016/j.jcrc.2013.11.015

  182. 182.

    Elwafi F., Curis E., Zerrouk N., Neveux N., Chaumeil J.C., Arnaud P., Cynober L., Moinard C. Endotoxemia affects citrulline, arginine and glutamine bioavailability. Eur. J. Clin. Investig. 2012;42:282-289.

    Not in our library10.1111/j.1365-2362.2011.02581.x

  183. 183.

    Cynober L. Citrulline: Just a biomarker or a conditionally essential amino acid and a pharmaconutrient in critically ill patients? Crit. Care. 2013;17:122.

    Not in our library10.1186/cc12534

  184. 184.

    Piton G., Manzon C., Cypriani B., Carbonnel F., Capellier G. Acute intestinal failure in critically ill patients: Is plasma citrulline the right marker? Intensive Care Med. 2011;37:911-917.

    Not in our library10.1007/s00134-011-2172-x

  185. 185.

    Bruins M.J., Luiking Y.C., Soeters P.B., Akkermans L.M., Deutz N.E. Effect of prolonged hyperdynamic endotoxemia on jejunal motility in fasted and enterally fed pigs. Ann. Surg. 2003;237:44-51.

    Not in our library10.1097/00000658-200301000-00007

  186. 186.

    Cynober L., Moinard C., de Bandt J.P. The 2009 ESPEN sir david cuthbertson. Citrulline: A new major signaling molecule or just another player in the pharmaconutrition game? Clin. Nutr. 2010;29:545-551.

    Not in our library10.1016/j.clnu.2010.07.006

  187. 187.

    Moinard C., Cynober L. Citrulline: A new player in the control of nitrogen homeostasis. J. Nutr. 2007;137:1621S-1625S.

    Not in our library10.1093/jn/137.6.1621s

  188. 188.

    Morris S.M., Kepka-Lenhart D., Chen L.C. Differential regulation of arginases and inducible nitric oxide synthase in murine macrophage cells. Am. J. Physiol. 1998;275:E740-E747.

    Not in our library10.1152/ajpendo.1998.275.5.e740

  189. 189.

    Tabuchi S., Gotoh T., Miyanaka K., Tomita K., Mori M. Regulation of genes for inducible nitric oxide synthase and urea cycle enzymes in rat liver in endotoxin shock. Biochem. Biophys. Res. Commun. 2000;268:221-224.

    Not in our library10.1006/bbrc.2000.2105

  190. 190.

    Corraliza I.M., Soler G., Eichmann K., Modolell M. Arginase induction by suppressors of nitric oxide synthesis (IL-4, IL-10 and PGE2) in murine bone-marrow-derived macrophages. Biochem. Biophys. Res. Commun. 1995;206:667-673.

    Not in our library10.1006/bbrc.1995.1094

  191. 191.

    Modolell M., Corraliza I.M., Link F., Soler G., Eichmann K. Reciprocal regulation of the nitric oxide synthase/arginase balance in mouse bone marrow-derived macrophages by Th1 and Th2 cytokines. Eur. J. Immunol. 1995;25:1101-1104.

    Not in our library10.1002/eji.1830250436

  192. 192.

    Hey C., Boucher J.L., Vadon-Le Goff S., Ketterer G., Wessler I., Racke K. Inhibition of arginase in rat and rabbit alveolar macrophages by N omega-hydroxy-d,l-indospicine, effects on l-arginine utilization by nitric oxide synthase. Br. J. Pharmacol. 1997;121:395-400.

    Not in our library10.1038/sj.bjp.0701143

  193. 193.

    Hecker M., Nematollahi H., Hey C., Busse R., Racke K. Inhibition of arginase by NG-hydroxy-l-arginine in alveolar macrophages: Implications for the utilization of l-arginine for nitric oxide synthesis. FEBS Lett. 1995;359:251-254.

    Not in our library10.1016/0014-5793(95)00039-c

  194. 194.

    Chang C.I., Liao J.C., Kuo L. Arginase modulates nitric oxide production in activated macrophages. Am. J. Physiol. 1998;274:H342-H348.

    Not in our library10.1152/ajpheart.1998.274.1.h342

  195. 195.

    Bivalacqua T.J., Hellstrom W.J., Kadowitz P.J., Champion H.C. Increased expression of arginase II in human diabetic corpus cavernosum: In diabetic-associated erectile dysfunction. Biochem. Biophys. Res. Commun. 2001;283:923-927.

    Not in our library10.1006/bbrc.2001.4874

  196. 196.

    White A.R., Ryoo S., Li D., Champion H.C., Steppan J., Wang D., Nyhan D., Shoukas A.A., Hare J.M., Berkowitz D.E. Knockdown of arginase I restores NO signaling in the vasculature of old rats. Hypertension. 2006;47:245-251.

    Not in our library10.1161/01.hyp.0000198543.34502.d7

  197. 197.

    Tumer C., Bilgin H.M., Obay B.D., Diken H., Atmaca M., Kelle M. Effect of nitric oxide on phagocytic activity of lipopolysaccharide-induced macrophages: Possible role of exogenous l-arginine. Cell Biol. Int. 2007;31:565-569.

    Not in our library10.1016/j.cellbi.2006.11.029

  198. 198.

    Rafiee P., Ogawa H., Heidemann J., Li M.S., Lamirand T.H., Fisher P.J., Graewin S.J., Dwinell M.B., Johnson C.P., Shaker R., et al. Isolation and characterization of human esophageal microvascular endothelial cells: Mechanisms of inflammatory activation. Am. J. Physiol. Gastrointest. Liver Physiol. 2003;285:G1277-G1292.

    Not in our library10.1152/ajpgi.00484.2002

  199. 199.

    Hollenberg S.M., Broussard M., Osman J., Parrillo J.E. Increased microvascular reactivity and improved mortality in septic mice lacking inducible nitric oxide synthase. Circ. Res. 2000;86:774-778.

    Not in our library10.1161/01.res.86.7.774

  200. 200.

    Kubes P., McCafferty D.M. Nitric oxide and intestinal inflammation. Am. J. Med. 2000;109:150-158.

    Not in our library10.1016/s0002-9343(00)00480-0

  201. 201.

    Cobb J.P., Hotchkiss R.S., Swanson P.E., Chang K., Qiu Y., Laubach V.E., Karl I.E., Buchman T.G. Inducible nitric oxide synthase (iNOS) gene deficiency increases the mortality of sepsis in mice. Surgery. 1999;126:438-442.

    Not in our library10.1016/s0039-6060(99)70189-3

  202. 202.

    Groeneveld P.H., Kwappenberg K.M., Langermans J.A., Nibbering P.H., Curtis L. Relation between pro- and anti-inflammatory cytokines and the production of nitric oxide (NO) in severe sepsis. Cytokine. 1997;9:138-142.

    Not in our library10.1006/cyto.1996.0147

  203. 203.

    Hesse M., Modolell M., la Flamme A.C., Schito M., Fuentes J.M., Cheever A.W., Pearce E.J., Wynn T.A. Differential regulation of nitric oxide synthase-2 and arginase-1 by type 1/type 2 cytokines in vivo: Granulomatous pathology is shaped by the pattern of l-arginine metabolism. J. Immunol. 2001;167:6533-6544.

    Not in our library10.4049/jimmunol.167.11.6533

  204. 204.

    Pinsky M.R., Vincent J.L., Deviere J., Alegre M., Kahn R.J., Dupont E. Serum cytokine levels in human septic shock. Relation to multiple-system organ failure and mortality. Chest. 1993;103:565-575.

    Not in our library10.1378/chest.103.2.565

  205. 205.

    Bruins M.J., Lamers W.H., Meijer A.J., Soeters P.B., Deutz N.E. In vivo measurement of nitric oxide production in porcine gut, liver and muscle during hyperdynamic endotoxaemia. Br. J. Pharmacol. 2002;137:1225-1236.

    Not in our library10.1038/sj.bjp.0704993

  206. 206.

    Xie L., Gross S.S. Argininosuccinate synthetase overexpression in vascular smooth muscle cells potentiates immunostimulant-induced no production. J. Biol. Chem. 1997;272:16624-16630.

    Not in our library10.1074/jbc.272.26.16624

  207. 207.

    Enkhbaatar P., Murakami K., Traber L.D., Cox R., Parkinson J.F., Westphal M., Esechie A., Morita N., Maybauer M.O., Maybauer D.M., et al. The inhibition of inducible nitric oxide synthase in ovine sepsis model. Shock. 2006;25:522-527.

    Not in our library10.1097/01.shk.0000209525.50990.28

  208. 208.

    Okamoto I., Abe M., Shibata K., Shimizu N., Sakata N., Katsuragi T., Tanaka K. Evaluating the role of inducible nitric oxide synthase using a novel and selective inducible nitric oxide synthase inhibitor in septic lung injury produced by cecal ligation and puncture. Am. J. Respir. Crit. Care Med. 2000;162:716-722.

    Not in our library10.1164/ajrccm.162.2.9907039

  209. 209.

    Enkhbaatar P., Lange M., Nakano Y., Hamahata A., Jonkam C., Wang J., Jaroch S., Traber L., Herndon D., Traber D. Role of neuronal nitric oxide synthase in ovine sepsis model. Shock. 2009;32:253-257.

    Not in our library10.1097/shk.0b013e318193e2ba

  210. 210.

    Gocan N.C., Scott J.A., Tyml K. Nitric oxide produced via neuronal nos may impair vasodilatation in septic rat skeletal muscle. Am. J. Physiol. Heart Circ. Physiol. 2000;278:H1480-H1489.

    Not in our library10.1152/ajpheart.2000.278.5.h1480

  211. 211.

    Ortiz F., Garcia J.A., Acuna-Castroviejo D., Doerrier C., Lopez A., Venegas C., Volt H., Luna-Sanchez M., Lopez L.C., Escames G. The beneficial effects of melatonin against heart mitochondrial impairment during sepsis: Inhibition of inos and preservation of nnos. J. Pineal. Res. 2014;56:71-81.

    Not in our library10.1111/jpi.12099

  212. 212.

    Miller M.J., Sandoval M. Nitric oxide. III. A molecular prelude to intestinal inflammation. Am. J. Physiol. 1999;276:G795-G799.

    Not in our library10.1152/ajpgi.1999.276.4.g795

  213. 213.

    Beck P.L., Xavier R., Wong J., Ezedi I., Mashimo H., Mizoguchi A., Mizoguchi E., Bhan A.K., Podolsky D.K. Paradoxical roles of different nitric oxide synthase isoforms in colonic injury. Am. J. Physiol. Gastrointest Liver Physiol. 2004;286:G137-G147.

    Not in our library10.1152/ajpgi.00309.2003

  214. 214.

    Qu X.W., Thaete L.G., Rozenfeld R.A., Zhu Y., de Plaen I.G., Caplan M.S., Hsueh W. Tetrahydrobiopterin prevents platelet-activating factor-induced intestinal hypoperfusion and necrosis: Role of neuronal nitric oxide synthase. Crit. Care Med. 2005;33:1050-1056.

    Not in our library10.1097/01.ccm.0000162908.14887.36

  215. 215.

    Chakrabarti S., Chan C.K., Jiang Y., Davidge S.T. Neuronal nitric oxide synthase regulates endothelial inflammation. J. Leukoc. Biol. 2012;91:947-956.

    Not in our library10.1189/jlb.1011513

  216. 216.

    Bachetti T., Comini L., Curello S., Bastianon D., Palmieri M., Bresciani G., Callea F., Ferrari R. Co-expression and modulation of neuronal and endothelial nitric oxide synthase in human endothelial cells. J. Mol. Cell Cardiol. 2004;37:939-945.

    Not in our library10.1016/j.yjmcc.2004.07.006

  217. 217.

    Domenico R. Pharmacology of nitric oxide: Molecular mechanisms and therapeutic strategies. Curr. Pharm. Des. 2004;10:1667-1676.

    Not in our library10.2174/1381612043384709

  218. 218.

    Forstermann U., Li H. Therapeutic effect of enhancing endothelial nitric oxide synthase (eNOS) expression and preventing eNOS uncoupling. Br. J. Pharmacol. 2011;164:213-223.

    Not in our library10.1111/j.1476-5381.2010.01196.x

  219. 219.

    Venugopal S.K., Devaraj S., Yuhanna I., Shaul P., Jialal I. Demonstration that C-reactive protein decreases enos expression and bioactivity in human aortic endothelial cells. Circulation. 2002;106:1439-1441.

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    Mori M., Gotoh T., Nagasaki A., Takiguchi M., Sonoki T. Regulation of the urea cycle enzyme genes in nitric oxide synthesis. J. Inherit. Metab. Dis. 1998;21:59-71.

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    Wei X.Q., Charles I.G., Smith A., Ure J., Feng G.J., Huang F.P., Xu D., Muller W., Moncada S., Liew F.Y. Altered immune responses in mice lacking inducible nitric oxide synthase. Nature. 1995;375:408-411.

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    MacMicking J.D., Nathan C., Hom G., Chartrain N., Fletcher D.S., Trumbauer M., Stevens K., Xie Q.W., Sokol K., Hutchinson N., et al. Altered responses to bacterial infection and endotoxic shock in mice lacking inducible nitric oxide synthase. Cell. 1995;81:641-650.

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    Southan G.J., Szabo C., Thiemermann C. Isothioureas: Potent inhibitors of nitric oxide synthases with variable isoform selectivity. Br. J. Pharmacol. 1995;114:510-516.

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    Misko T.P., Moore W.M., Kasten T.P., Nickols G.A., Corbett J.A., Tilton R.G., McDaniel M.L., Williamson J.R., Currie M.G. Selective inhibition of the inducible nitric oxide synthase by aminoguanidine. Eur. J. Pharmacol. 1993;233:119-125.

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    Murakami K., McGuire R., Jodoin J., Katahira J., Schmalstieg F.C., Traber L.D., Traber D.L. Aminoguanidine did not attenuate septic changes and acute lung injury in sheep. proceedings of the 7th World Congress for Microcirculation. 465-469.

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    Ishikawa K., Calzavacca P., Bellomo R., Bailey M., May C.N. Effect of selective inhibition of renal inducible nitric oxide synthase on renal blood flow and function in experimental hyperdynamic sepsis. Crit. Care Med. 2012;40:2368-2375.

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    Thiemermann C., Ruetten H., Wu C.C., Vane J.R. The multiple organ dysfunction syndrome caused by endotoxin in the rat: Attenuation of liver dysfunction by inhibitors of nitric oxide synthase. Br. J. Pharmacol. 1995;116:2845-2851.

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    Bone H.G., Waurick R., van Aken H., Booke M., Prien T., Meyer J. Comparison of the haemodynamic effects of nitric oxide synthase inhibition and nitric oxide scavenging in endotoxaemic sheep. Intensive Care Med. 1998;24:48-54.

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    Zhang H., Rogiers P., Smail N., Cabral A., Preiser J.C., Peny M.O., Vincent J.L. Effects of nitric oxide on blood flow distribution and O2 extraction capabilities during endotoxic shock. J. Appl. Physiol. 1997;83:1164-1173.

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    Cobb J.P., Natanson C., Hoffman W.D., Lodato R.F., Banks S., Koev C.A., Solomon M.A., Elin R.J., Hosseini J.M., Danner R.L. N omega-amino-l-arginine, an inhibitor of nitric oxide synthase, raises vascular resistance but increases mortality rates in awake canines challenged with endotoxin. J. Exp. Med. 1992;176:1175-1182.

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    Avontuur J.A., Tutein Nolthenius R.P., van Bodegom J.W., Bruining H.A. Prolonged inhibition of nitric oxide synthesis in severe septic shock: A clinical study. Crit. Care Med. 1998;26:660-667.

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    Lopez A., Lorente J.A., Steingrub J., Bakker J., McLuckie A., Willatts S., Brockway M., Anzueto A., Holzapfel L., Breen D., et al. Multiple-center, randomized, placebo-controlled, double-blind study of the nitric oxide synthase inhibitor 546c88: Effect on survival in patients with septic shock. Crit. Care Med. 2004;32:21-30.

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    Scott J.A., Mehta S., Duggan M., Bihari A., McCormack D.G. Functional inhibition of constitutive nitric oxide synthase in a rat model of sepsis. Am. J. Respir. Crit. Care Med. 2002;165:1426-1432.

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    Kilbourn R.G., Szabo C., Traber D.L. Beneficial versus detrimental effects of nitric oxide synthase inhibitors in circulatory shock: Lessons learned from experimental and clinical studies. Shock. 1997;7:235-246.

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    Saetre T., Smiseth O.A., Scholz T., Carlsen H., Nordsletten L., Fahlstrom E., Aasen A.O. Nitric oxide synthase inhibition reduces venous return in porcine endotoxemia. Am. J. Physiol. 1996;271:H1325-H1332.

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    Lange M., Hamahata A., Traber D.L., Nakano Y., Traber L.D., Enkhbaatar P. Specific inhibition of nitric oxide synthases at different time points in a murine model of pulmonary sepsis. Biochem. Biophys. Res. Commun. 2011;404:877-881.

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    Lange M., Connelly R., Traber D.L., Hamahata A., Cox R.A., Nakano Y., Bansal K., Esechie A., von Borzyskowski S., Jonkam C., et al. Combined neuronal and inducible nitric oxide synthase inhibition in ovine acute lung injury. Crit. Care Med. 2009;37:223-229.

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    Vanhoutte P.M. Arginine and arginase: Endothelial no synthase double crossed? Circ. Res. 2008;102:866-868.

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    Ye X., Whiteman B., Jerebtsova M., Batshaw M.L. Correction of argininosuccinate synthetase (AS) deficiency in a murine model of citrullinemia with recombinant adenovirus carrying human AS cDNA. Gene Ther. 2000;7:1777-1782.

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    Lu Y., Leung T.M., Ward S.C., Nieto N. Partial deletion of argininosuccinate synthase protects from pyrazole plus lipopolysaccharide-induced liver injury by decreasing nitrosative stress. Am. J. Physiol. Gastrointest Liver Physiol. 2012;302:G287-G295.

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    Premkumar M.H., Sule G., Nagamani S.C., Chakkalakal S., Nordin A., Jain M., Ruan M.Z., Bertin T., Dawson B.C., Zhang J., et al. Argininosuccinate lyase in enterocytes protects from development of necrotizing enterocolitis. Am. J. Physiol. Gastrointest Liver Physiol. 2014;307:G347-G354.

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    Barbul A., Lazarou S.A., Efron D.T., Wasserkrug H.L., Efron G. Arginine enhances wound healing and lymphocyte immune responses in humans. Surgery. 1990;108:331-336.

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    Boger R.H. The pharmacodynamics of l-arginine. Altern. Ther. Health Med. 2014;20:48-54.

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    Vissers Y.L., Debats I.B., Luiking Y.C., Jalan R., van der Hulst R.R., Dejong C.H., Deutz N.E. Pros and cons of l-arginine supplementation in disease. Nutr. Res. Rev. 2004;17:193-210.

    Not in our library10.1079/nrr200490

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    Bode-Boger S.M., Boger R.H., Galland A., Tsikas D., Frolich J.C. l-arginine-induced vasodilation in healthy humans: Pharmacokinetic-pharmacodynamic relationship. Br. J. Clin. Pharmacol. 1998;46:489-497.

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    Bertolini G., Luciani D., Biolo G. Immunonutrition in septic patients: A philosophical view of the current situation. Clin. Nutr. 2007;26:25-29.

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    Deutz N.E. The 2007 ESPEN Sir David Cuthbertson lecture: Amino acids between and within organs. The glutamate-glutamine-citrulline-arginine pathway. Clin. Nutr. 2008;27:321-327.

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    Grover Z., Tubman R., McGuire W. Glutamine supplementation for young infants with severe gastrointestinal disease. Cochrane Database Syst. Rev. 2007;CD005947.

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    Preiser J.C., Berre P.J., van Gossum A., Cynober L., Vray B., Carpentier Y., Vincent J.L. Metabolic effects of arginine addition to the enteral feeding of critically ill patients. JPEN J. Parenter Enteral. Nutr. 2001;25:182-187.

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    Kieft H., Roos A.N., van Drunen J.D., Bindels A.J., Bindels J.G., Hofman Z. Clinical outcome of immunonutrition in a heterogeneous intensive care population. Intensive Care Med. 2005;31:524-532.

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    Tsuei B.J., Bernard A.C., Barksdale A.R., Rockich A.K., Meier C.F., Kearney P.A. Supplemental enteral arginine is metabolized to ornithine in injured patients. J. Surg. Res. 2005;123:17-24.

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    Bertolini G., Iapichino G., Radrizzani D., Facchini R., Simini B., Bruzzone P., Zanforlin G., Tognoni G. Early enteral immunonutrition in patients with severe sepsis: Results of an interim analysis of a randomized multicentre clinical trial. Intensive Care Med. 2003;29:834-840.

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    Zheng Y.M., Li F., Zhang M.M., Wu X.T. Glutamine dipeptide for parenteral nutrition in abdominal surgery: A meta-analysis of randomized controlled trials. World J. Gastroenterol. 2006;12:7537-7541.

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    Heyland D.K., Novak F., Drover J.W., Jain M., Su X., Suchner U. Should immunonutrition become routine in critically ill patients? A systematic review of the evidence. JAMA. 2001;286:944-953.

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    Cynober L. Can arginine and ornithine support gut functions? Gut. 1994;35:S42-S45.

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    Stechmiller J.K., Treloar D., Allen N. Gut dysfunction in critically ill patients: A review of the literature. Am. J. Crit. Care. 1997;6:204-209.

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    Heyland D.K., Dhaliwal R., Drover J.W., Gramlich L., Dodek P. Canadian clinical practice guidelines for nutrition support in mechanically ventilated, critically ill adult patients. JPEN J. Parenter Enteral. Nutr. 2003;27:355-373.

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    Dhaliwal R., Cahill N., Lemieux M., Heyland D.K. The canadian critical care nutrition guidelines in 2013: An update on current recommendations and implementation strategies. Nutr. Clin. Pract. 2014;29:29-43.

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    Bruins M.J., Soeters P.B., Lamers W.H., Deutz N.E. l-arginine supplementation in pigs decreases liver protein turnover and increases hindquarter protein turnover both during and after endotoxemia. Am. J. Clin. Nutr. 2002;75:1031-1044.

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    Schwedhelm E., Maas R., Freese R., Jung D., Lukacs Z., Jambrecina A., Spickler W., Schulze F., Boger R.H. Pharmacokinetic and pharmacodynamic properties of oral l-citrulline and l-arginine: Impact on nitric oxide metabolism. Br. J. Clin. Pharmacol. 2008;65:51-59.

    Not in our library10.1111/j.1365-2125.2007.02990.x

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