Isorhamnetin plays an analgesic role by regulating NF-κB pathway

Objective To investigate the analgesic effect of isorhamnetin and its underlying mechanisms. Methods The analgesic effect of isorhamnetin was measured by hot plate pain model and acetic acid torsion pain model in mice. Fifty SPF Kunming mice were selected in each model and then were randomly divided into 5 groups according to their body weight: blank control group, positive control indomethacin group, and isorhamnetin high, middle and low dose groups, and the analgesic effect of isorhamnetin was observed and recorded. In addition, the effects of isorhamnetin on the expression levels of pain-inducing factors and inflammatory factors were examined. The contents of NO and TNF-α in mouse macrophage RAW264.7 cells were detected by Griess assay and ELISA assay, respectively, and the mRNA levels of IL-1β and IL-6 in RAW264.7 cells were determined using RT-PCR. Finally, the activation of NF-κB pathway in LPS-induced RAW264.7 was determined by Western blotting. Results In vivo experiments showed that isorhamnetin (25, 50 and 100 mg/kg) dose-dependently increased the pain threshold of mice induced by hot plate test (P < 0.05), and significantly reduced the acetic acid-induced writhing response in mice (P < 0.05). In vitro cell experiments suggested that isorhamnetin (5, 10, 20 μmol/L) greatly inhibited the up-regulation of NO and TNF-α induced by LPS (P < 0.05), decreased the mRNA levels of IL-1β and IL-6, and blocked the activation of NF-κB signaling pathway in RAW264.7 cells. Pre-administration of the inhibitor of NF-κB pathway synergically enhanced the inhibitory effect of isorhamnetin on NO level in RAW264.7 cells. Conclusion Isorhamnetin has certain analgesic effect, and its mechanism may be associated with the suppression of NF-κB pathway and the subsequent reductions in expression, syntheses and releases of NO, TNF-α, IL-1β and IL-6.

Abstract licence: CC BY

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