Oxysophocarpine Ameliorates Carrageenan-induced Inflammatory Pain Via Inhibiting ERK1/2-COX-2-PGE₂ Pathway In Mice

Objectives In this study we investigated the analgesic effect of oxysophocarpine(OSC) on carrageenan-induced inflammatory pain in mice and to explore its possible mechanism.Methods Mouse ear swelling test and carrageenan-induced paw edema were used to investigate the effects of OSC(10, 40 and 80 mg/kg) on inflammatory pain in mice. The mechanical hyperalgesia and allodynia were measured by von Frey filaments. Paw edema was assessed by toe volumetric measuring instrument. Morphological changes on inflamed paw sections were performed for hematoxylin-eosin(HE) staining. The m RNA and protein expression of ERK1/2, p-ERK1/2, COX-2, TNF-α, IL-1β, IL-6 and PGE2 were investigated by Quantitative real-time PCR, immunohistochemistry, western-blot and ELISA kit.Results OSC showed a significant anti-inflammatory effect in the mouse ear swelling test. OSC(10, 40 and 80 mg/kg) also significantly reduced the paw edema volume and improved mechanical allodynia threshold value on carrageenan-induced inflammatory pain, as well as relieved paw tissues inflammatory damage and reduced the numbers of neutrophils in mice. OSC significantly suppressed over-expression of COX-2, TNF-α, IL-1β, IL-6 and PGE2, and inhibited the over-phosphorylation of ERK1/2 at the dose of 80 mg/kg.Conclusion Based on these findings we propose that OSC attenuates inflammatory pain by suppressing the ERK1/2 COX-2 PGE2 signalling pathway.