胶质细胞TSPO抗神经病理性疼痛的机制研究

Proinflammatory cytokines released from glial cells in the spinal dorsal horn play an important role in the maintenance of neuropathic pain. Our recent studies showed that the immunoreactivity (IR) of TSPO was increased in astrocytes and microglia in the L5 spinal dorsal horn following L5 spinal nerve ligation (L5 SNL) and that intrathecal injection of a specific TSPO agonist 7 days after L5 SNL could reverse the established mechanical allodynia. In vitro, TSPO agonist substantially attenuated TNFα release from cultured astrocytes. These results suggest that TSPO could reverse neuropathic pain, which is related to glia cells, but the exact mechanism is still unclear. In the present study, we will examine whether TSPO agonist and SiRNA influence the expression and release of proinflammatory cytokines in glia cells, and examine whether MAPK,NF-kB is involved in this process. Meanwhile we will examine whether TSPO in glia cells affect the excitatory transmission to Substantia Gelatinosa (SG） neurons in the spinal dorsal horn. Thus we will elucidate the mechanisms that TSPO inhibit neuropathic pain, and serve to develop new analgesics.

脊髓背角胶质细胞通过分泌致炎细胞因子在神经病理性疼痛的维持中起关键作用。我们最近研究发现，腰5脊神经结扎（L5 SNL）引起脊髓背角星形、小胶质细胞TSPO表达上调，同时L5 SNL后7d 鞘内注射TSPO激动剂可抑制触诱发痛。体外实验研究发现，TSPO激动剂抑制培养的星形胶质细胞释放TNF-α，提示TSPO可能有抑制神经病理性疼痛发展的作用，并与胶质细胞活动有关，但其确切的作用机制尚不清楚。本项目拟用分子生物学，电生理等多种方法，观察TSPO激动剂、基因沉默对脊髓背角胶质细胞致炎细胞因子表达、释放的影响并进一步探讨MAPK、NF-kB通路在其中的作用，同时研究胶质细胞TSPO是否通过抑制致炎细胞因子的表达而影响背角神经元信息传递的效能，以期阐明TSPO抗神经病理性疼痛的作用机制，为研发新型镇痛药物提供实验证据。

研究报道转位蛋白18 kDa（Translocator protein 18 kDa,TSPO）激动剂可抑制完全氟氏佐剂引起的炎性痛，但TSPO是否参与损伤所导致的神经病理性疼痛尚不不清。本项目发现腰5脊神经结扎（L5 SNL）引起脊髓背角星形、小胶质细胞TSPO表达上调。TSPO的表达与痛敏行为具有较高相关性。单次鞘内或腹腔注射TSPO特异性激动剂激动剂Ro5-4864或FGIN1-27或非特异性激动剂diazepam均可翻转神经损伤引起的机械性触诱发和痛热痛觉过敏。Ro5-4864鞘内注射后7d，脊髓背角TSPO、星形胶质细胞标记物GFAP及致炎细胞因子的表达均显著降低，但小胶质细胞的激活标记物OX-42的表达不受影响。体外实验研究发现，TSPO激动剂抑制混合培养的星形胶质细胞和小胶质细胞释放TNF-α，Ro5-4864的上述作用可被腹腔注射神经甾体合成阻断剂所阻断。本项目还发现TSPO上调由TLR4激活介导。这些结果提示外周神经损伤后，损伤神经所释放的物质可能激活了TLR4, 从而导致神经病理性疼痛和脊髓背角TSPO的上调，而上调的TSPO可能通过上调神经甾体的合成进而降低TNF-α在星形胶质细胞内的合成和释放而起抗神经病理性疼痛的作用。 该研究为临床开发镇痛药物提供了一定的实验室依据。