电针刺激对神经病理性疼痛大鼠脊髓星形胶质细胞自噬的影响及其机制的研究

Neuropathic pain may be caused by peripheral nerve injury. The mechanisms of neuropathic pain involve an activation of astrocytes in the spinal cord, which are hypertrophic in the maintenance period of neuropathic pain. It was shown that electro-acupuncture (EA) induces pain relief partially through inhibiting spinal astrocytes activation. Recent study in a rat model of neuropathic pain showed a change in the expression of autophagy associtated proteins in the spinal dorsal horn, indicating an impaired autophagy flux. Intrathecal injection of autophagy blocker cloroquine in naïve mice induced significant mechanical hypersensitivity, and autopahgy inducer rapamycin could ameliorate neuropathic pain by activating autophagy in the spinal cord, suggesting that neuropathic pain may be attributable to autophagy impairment. In a mouse model of spinal cord injury, autophagy inducer rapamycin inhibited astrocyte proliferation and reduced the number of GFAP expressing cells at the lesion site. The modulation of autophagy is mainly through AMPK/mTOR pathway. It was shown that AMPK activation achieves analgesic effects largely through inhibition mTOR signaling, and hypothalamic AMPK expression determines the individual differences in the sensitivity to EA incuced analgesia. Based on aforementioned scientific premise, we hypothesize that EA may activate the AMPK/mTOR pathway and restore normal autophagy progress in spinal astrocytes, which attenuates their activation and hypertrophic activity to inhibit neuropathic pain. In rats subjected to spinal nerve ligation, we will examine the effects of EA on autophagy and AMPK/mTOR activation in spinal astrocytes. Findings from current study will provide new viewpoints for the mechanisms of neuropathic pain inhibition by EA, and reveal new targets for pain treatment in the future.

外周神经损伤常导致神经病理性疼痛的发生，前期研究发现其机制与脊髓背角星形胶质细胞激活有关，维持期可见其胞体肥大增生。电针可通过抑制星形胶质细胞激活而减轻疼痛。研究发现外周神经损伤大鼠脊髓背角自噬相关蛋白表达的变化提示自噬受阻。正常小鼠鞘内注射自噬抑制剂可导致机械痛敏，而自噬诱导剂可减轻神经病理性疼痛，并抑制脊髓损伤模型损伤部位星形胶质细胞增生，提示自噬障碍可能参与神经病理性疼痛。自噬调控主要通过AMPK/mTOR通路，研究发现激活AMPK可通过抑制mTOR信号通路减轻慢性疼痛，降低感觉神经元兴奋性，且下丘脑AMPK的表达与电针镇痛效果相关。由此假设：电针通过激活脊髓星形胶质细胞自噬AMPK/mTOR通路，抑制其激活及增生，从而减轻神经病理性疼痛。拟观察电针对脊神经结扎模型脊髓背角星形胶质细胞自噬及AMPK/mTOR通路的影响。本研究从新视角探讨电针治疗神经病理性疼痛机制，并提供新治疗靶点。

中枢或外周神经损伤常导致神经病理性疼痛的发生，主要表现为痛觉高敏、自发性疼痛和痛觉异常。近期神经病理性疼痛的治疗受到广泛关注。有研究发现镇痛机制可能涉及到胶质细胞中自噬过程的激活。本研究发现电针可减轻大鼠坐骨神经部分损伤（SNI）模型神经病理性疼痛。在大鼠接受坐骨神经部分损伤手术后7天，分别接受足三里和环跳穴位的电针或手针治疗。电针减轻了机械痛敏。脊髓免疫荧光结果发现SNI组损伤侧脊髓背角小胶质细胞标志CD11b与自噬标志p62有共定位，而星形胶质细胞标志或神经元标志NeuN与p62无共定位，损伤侧L4-L6背根神经节(DRG)中巨噬细胞标志CD11b与自噬标志p62有共定位，而卫星胶质细胞标志GFAP或神经元标志NeuN与p62无共定位。Western blot结果提示：对比对照组，坐骨神经部分损伤组的脊髓和DRG中p62、 Beclin-1、 LC3-II/LC3-I表达均升高。电针治疗后，p62表达降低，而Beclin-1、 LC3-II/LC3-I表达均升高。电镜结果提示：对比对照组，坐骨神经部分损伤组的脊髓小胶质细胞和背根神经节中自噬体明显增多，电针治疗后自噬体进一步增多。通过使用AMPK抑制剂C物质，我们研究了电针镇痛与小胶质细胞和巨噬细胞中自噬水平增高之间可能的关联，结果发现电针可能通过激活脊髓背角小胶质细胞和背根神经节巨噬细胞自噬AMPK/mTOR通路，从而减轻神经病理性疼痛。本研究从新视角探讨电针治疗神经病理性疼痛机制，并提供新治疗靶点。