肉毒毒素A对神经病理性疼痛小鼠施旺细胞髓鞘形成的影响

THE ROLE OF BOTULINUM NEUROTOXIN TYPE A IN SCHWANN CELL MYELINATION IN A MOUSE MODEL OF NEUROPATHIC PAIN

目的:观察不同给药途径的肉毒毒素A(Botulinum neurotoxin type A,Bo NT/A)对慢性坐骨神经缩窄性损伤(Chronic constriction injury,CCI)疼痛模型小鼠的镇痛效果;研究Bo NT/A对施旺细胞髓鞘标志蛋白以及调控髓鞘形成的转录因子表达的影响。方法:通过CCI建立神经病理性疼痛模型小鼠,并随机平均分成4组:生理盐水皮下注射(intraplantar injection,i.pl.)组、Bo NT/A皮下注射组、生理盐水神经旁注射(peripheral nerve injection,i.pn.)组、Bo NT/A神经旁注射组,此外设置未造模的空白对照组。在造模后第5天给药,测量不同时间点各组小鼠机械缩足阈值和热缩足潜伏期的变化。在术后14天和28天分别对Bo NT/A皮下注射组、生理盐水皮下注射组及空白对照组小鼠进行坐骨神经采样,应用蛋白印迹检测坐骨神经髓鞘相关蛋白MBP、P0、Krox-20及C-jun表达量的变化,应用免疫荧光技术检测坐骨神经P0的表达情况。结果:皮下注射或神经旁注射Bo NT/A均可增加神经病理性疼痛模型小鼠的机械缩足阈值和热缩足潜伏期(P<0.05)。Bo NT/A皮下注射组坐骨神经MBP、P0、Krox-20及C-jun表达量与生理盐水皮下注射组对比无显著性差异。结论:皮下注射和神经旁注射Bo NT/A均可改善神经病理性疼痛小鼠的机械痛敏和热痛敏,但皮下注射Bo NT/A不能促进神经病理性疼痛小鼠坐骨神经施旺细胞髓鞘的形成,提示Bo NT/A并不是通过促进髓鞘形成这一机制来促进运动功能恢复以及缓解神经病理性疼痛。

Objective： This study aimed to test the analgesic effects of botulinum neurotoxin type A （BoNT/ A） with intraplantar （i.pl.） or peripheral nerve injection （i.pn.）, and also to evaluate expression of major myelin proteins and their relevant regulators in the sciatic nerves in a mouse model of neuropathic pain induced by chronic constriction injury （CCI）. Methods： The animal model of neuropathic pain was induced by CCI in adult, male C57BL mice. A single BoNT/A （i.pl. or i.pn.） or saline （i.pl. or i.pn.） was administrated 5 days after CCI. Behavioral tests, including mechanical withdrawal threshold and thermal withdrawal latency, were performed at predefined postoperative days. The expression of MBP, P0, Krox-20 and C-jun in the sciatic nerve was detected by Western blotting and the expression of P0 was by immunofluorescence at postoperative days 14 and 28. Results： Both i.pl. and i.pn. BoNT/A administration significantly reduced the mechanical allodynia and thermal hyperalgesia in CCI mice. However, BoNT/A and saline treatment, at days 14 or 28 via i.pl. administration, did not produce any different effects on expression ofMBP, P0, Krox- 20 and C-jun. Conclusion： Diverse administrations of BoNT/A cause anti-allodynia and anti-hyperalgesia effects in neuropathic mice, but BoNT/A fails to promote the injured nerve remyelination which involved in counteracting pain and nerve regenerative processes.