蓝斑核-脊髓背角NE能通路缓解神经病理性疼痛的胶质细胞机制研究

The pathogenesis of neuropathic pain (NP) is complicated. Present clinical strategies are not satisfactory. The pontospinal descending pathways from noradrenergic nuclei in pons relieve NP, but the specific target cells and receptors of NE in spinal dorsal horn (DH) are not fully understood. By using one of the chemogenetics methods that was termed as Designer Receptors Exclusively Activated by Designer Drugs (DREADD), we specificly activated the noradrenergic locus coeruleus (LC) neurons. LC activation was accompanied by the reduction of NP pain, the increase of norepinephrine and the decrease of the activation of astrocytes and microglias in DH. So we come to the hypothesis that besides binding with NE receptors on neurons, DH NE from the pontospinal descending pain inhibition pathway also binds to NE receptors on astrocytes and microglias, then releases NP by reducing their inflammation. The respective anti-neuropathic pain effects of microglia and astrocyte will be assayed by inhibiting them with DREADD. In addition, the specific NE receptors that contributed to NP alleviation will be studied both in vivo and in vitro. The clarification of anti-neuropathic pain effects of astrocyte and microglia will be helpful for the development of strategies targeting NE receptors or glia cells.

神经病理性疼痛（NP）发病机制复杂，目前仍缺乏有效的治疗手段。脑桥-脊髓背根（DH）去甲肾上腺素（NE）能脊髓下行通路能减缓NP，但NE在DH的细胞和分子机制不清。前期利用化学遗传学（DREADD）技术特异激活蓝斑核（LC）NE能神经元能有效缓解大鼠NP。进一步发现LC激活后DH NE增加，星形胶质细胞和小胶质细胞激活减少，且DH炎症因子的产生减少。故提出脑干-DH下行疼痛抑制通路来源NE除作用于神经元上的NE受体外，还作用于DH星形胶质细胞和/或小胶质细胞NE受体，抑制胶质炎症，缓解NP这一假说。后续拟用DREADD法分别抑制DH两类胶质细胞，观察抑制前后NE抗NP效果变化，明确抗NP的胶质细胞；利用在体和细胞模型探讨胶质细胞上介导抗炎作用的NE受体类型。该项目重点研究NE在DH的抗NP机制。阐明DH两类胶质细胞在NE抗NP中的作用，将有助于开发以NE受体和胶质细胞为靶点的镇痛策略。

蓝斑核（locus coeruleus）去甲肾上腺素能神经元投射下行纤维到达脊髓背角（spinal dorsal horn），释放去甲肾上腺素（Norepinephrine，NE）抑制疼痛上传。该通路对生理痛觉抑制作用不明显，但在病理情况下，其释放到脊髓背角的NE有所增加，能明显抑制病理性疼痛的传递。然而，该下行通路在脊髓背角通过NE抑制病理性疼痛的具体机制不清。本研究旨在探索蓝斑-脊髓背角NE能通路对神经病理性疼痛（neuropathic pain，NP）及脊髓胶质细胞的影响。通过该项目研究发现：1. 激活蓝斑-脊髓背角NE能通路增加NE缓解CCI小鼠机械痛和热痛。2. 脊髓背角NE增加可减少CCI小鼠脊髓背角TNF-α、IL-1β、IL-6、INOS、CD11b、CD68等促炎因子的表达，促进CCI小鼠脊髓背角Arg1、IL-4、IL-10、CD206等抗炎因子的表达。3. 特异性激活蓝斑-脊髓背角下行通路可抑制脊髓背角小胶质细胞及星形胶质细胞的激活。4. 脊髓背角的NE通过抑制背角WDR神经元的放电抑制疼痛的上传。这些结果提示LC去甲肾上腺素能脊髓下行通路能缓解神经病理性疼痛，但蓝斑核来源的NE在脊髓背角的效应细胞和具体分子机制仍有待阐明。脊髓背角星形胶质细胞和小胶质细胞可能在NE抗神经病理性疼痛效应中发挥着重要作用，并影响脊髓层面的中枢敏化。该方向研究将有助于开发以NE受体和胶质细胞为靶点的镇痛策略。