Roles of spinal astrocyte in the induction and maintenance of chronic pain

我们研究了脊髓星形胶质细胞在慢性疼痛中的作用。大鼠鞘内注射ATP可产生短时间的痛觉过敏（<20 min）和长时间的触诱发痛，后者在5 min内出现，15 ~ 30 min达到平台，持续3-4周。在脊髓中，鞘内ATP给药在1天内引起小胶质细胞活化（诱导期），随后引起星形胶质细胞活化，其在1-3天达到峰值（过渡期和早期维持期）。结合使用小胶质细胞和星形胶质细胞活化抑制剂和MAPK抑制剂的进一步行为研究，表明早期小胶质细胞活化有助于慢性疼痛的初始诱导，并进而沉淀随后的和持续的星形胶质细胞活化，其与持续性疼痛状态的转变和维持有关。（角叉菜胶/高岭土）和神经性疼痛（部分坐骨神经结扎（pSNL）） ...更多信息 在大鼠模型中，主要在星形胶质细胞中表达的神经胶质谷氨酸转运体GLT-1在脊髓中的总表达或膜定位降低。通过重组腺病毒将GLT-1基因转移到脊髓中减少了炎性机械性痛觉过敏和pSNL诱导的异常性疼痛（神经性疼痛）的诱导，尽管它对急性机械性疼痛和热疼痛没有影响。这些结果表明，GLT-1的功能障碍，减少表达的细胞内运输的星形胶质细胞有助于诱导慢性pain.Finally，阐明GLT-1贩运星形胶质细胞的分子机制，我们构建了一个重组腺病毒表达EGFP标记的GLT-1和分析的时间推移成像GLT-1的动态活星形胶质细胞。在大鼠星形胶质细胞-神经元混合培养物中，用谷氨酸处理快速诱导簇的形成和通过内吞途径的GLT-1的细胞内运输。此外，我们的研究结果表明，与通过GLT-1的底物转运相关的Na^+内流，而不是谷氨酸受体和细胞内Ca^<2+>信号的刺激，触发了GLT-1的聚集。少

We have investigated the roles of spinal astrocytes in chronic pain. Intrathecal administration of ATP to rats produced short-lasting hyperalgesia (<20 min) and subsequently long-lasting allodynia, which appeared within 5 min, reached a plateau between 15 and 30min and lasted fm 3-4 weeks. In the spinal cord, intrathecal ATP administration caused microglia activation within 1 day (induction phase) and subsequently astrocytic activation, which peaked at 1-3 days (transition and early maintenance phase). Taken together with further behavioral studies using inhibitors for microglial and astrocytic activation, and MAPK inhibitors, it is suggested that early microglia activation contributes to the initial induction of chronic pain and precipitates, in turn, the subsequent and sustained astrocytic activation, which is implicated in the transition and maintenance of the persistent pain state.In the inflammatory (carrageenan/kaolin) and neuropathic pain (partial sciatic nerve ligation (pSNL)) … More rat models, the total expression or membrane localization of a glial glutamate transporter GLT-1, which is mainly expressed in astrocytes, in the spinal cord was decreased. Gene transfer of GLT-1 into the spinal cord by the recombinant adenoviruses reduced the induction of inflammatory mechanical hyperalgesia and pSNL-induced allodynia (neuropathic pain), although it had no effect in acute mechanical and thermal pain. These results suggest that dysfunction of GLT-1 by decreased expression of intracellular trafficking in astrocytes contributes to the induction of chronic pain.Finally, to elucidate the molecular mechanisms underlying GLT-1 trafficking in astrocyte, we constructed a recombinant adenovirus expressing EGFP-tagged GLT-1 and analyzed time-lapse imaging of GLT-1 dynamics in live astrocytes. In rat astroglia-neuronal mixed cultures, treatment with glutamate rapidly induced formation of clusters and intracellular trafficking of GLT-1 via endocytotic pathways. Furthermore, our results suggest that Na^+ influx associated with substrate-transport via GLT-1, but not stimulation of glutamate receptors and intracellular Ca^<2+> signaling, triggers the GLT-1 clustering. Less