Nicotine exerts neuroprotective effects by attenuating local inflammatory cytokine production following crush injury to rat sciatic nerves

Recent studies have demonstrated that nicotine exhibited anti-inflammatory and neuroprotective properties by interacting with the alpha 7 nicotinic acetylcholine receptor (α7nAChR). However, the role of nicotine in regeneration during peripheral nerve injury has not been elucidated. The aim of this study was to investigate whether nicotine down-regulated production of proinflammatory cytokines and promoted peripheral nerve regeneration in rats. Rats challenged with sciatic nerve crush injury were treated with nicotine (1.5 mg/kg), three times per day. The expression of the proinflammatory cytokines tumor necrosis factor alpha (TNF-α) and interleukin (IL-1β), pinch test results, growth-associated protein 43 (GAP-43) expression, morphometric analyses, and the sciatic functional indexes were determined in sciatic nerves. Treatment with nicotine decreased local levels of TNF-α and IL-1β, and increased the expression of GAP-43. Nicotine also improved nerve regeneration and functional recovery. The overall protective effects of nicotine were reversed by concomitant treatment with α7nACHR antagonist methyllycaconitine, indicating that nicotine exerted its specific anti-inflammatory and neuroprotective effects through the α7nAChR. These findings show that nicotine administration can provide a potential therapeutic pathway for the treatment of peripheral nerve injury, by a direct protective effect through the α7nAChR-mediated cholinergic anti-inflammatory pathway.