Antinociceptive effect of isoorientin against neuropathic pain induced by the chronic constriction injury of the sciatic nerve in mice.

Neuropathic pain is a widespread and debilitating chronic pain and the treatment remains a clinical challenge. Isoorientin (3',4',5,7-tetrahydroxy-6-C-glucopyranosyl flavone) is a natural flavonoid-like compound that exhibits antioxidant and anti-inflammatory activities; however, its effect on neuropathic pain remains unclear. Our study aimed to evaluate the antinociceptive effect of isoorientin in neuropathic pain mouse models induced by chronic constriction injury (CCI). In our study, the mice with CCI were administered with 7.5, 15, and, 30 mg/kg isoorientin for 8 consecutive days. Behavioral parameters were assayed on days 0, 7, 8, 10, 12, and 14 post-CCI surgery. Electrophysiological, histopathological, and biochemical indices were analyzed on day 14. Immunofluorescence was utilized to examine matrix metalloproteinase-9 (MMP-9) and glial cell activation, and proinflammatory cytokine expression levels were detected via Western blot. It is obvious that the treatment of Isoorientin remarkably ameliorated hyperalgesia and allodynia, increased sensory nerve conduction velocities, and restored CCI-induced sciatic nerve damage in mice. Isoorientin treatment significantly increased the total antioxidant capacity (T-AOC), total superoxide dismutase (T-SOD) and catalase (CAT) levels, and decreased the malondialdehyde (MDA) concentrations. Isoorientin also suppressed MMP-9 and glial cell activation, and downregulated tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) expression levels. Therefore, this study provided a novel approach for neuropathic pain treatment and new insights into the pharmacological action of isoorientin.