Connexin-43 induces chemokine release from spinal cord astrocytes to maintain late-phase neuropathic pain in mice
Connexin-43 induces chemokine release from spinal cord astrocytes to maintain late-phase neuropathic pain in mice
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DOI：
10.1093/brain/awu140
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发表时间：
2014-08-01
期刊：
影响因子：
14.5
通讯作者：
Ji, Ru-Rong
中科院分区：
文献类型：
--
作者：
Chen, Gang;Park, Chul-Kyu;Ji, Ru-Rong
越来越多的证据表明，脊髓星形胶质细胞维持神经性疼痛敏感，但确切地说，它们是如何做到这一点尚不清楚。Chen等人利用小鼠神经性疼痛模型证明，神经损伤后星形胶质细胞中的半通道连接蛋白-43上调，并通过诱导趋化因子释放维持晚期神经性疼痛。越来越多的证据表明，脊髓星形胶质细胞通过释放星形胶质细胞介质（如细胞因子、趋化因子和生长因子）在神经性疼痛致敏中发挥重要作用。然而，目前尚不清楚星形胶质细胞如何控制星形胶质细胞介质的释放并维持晚期神经性疼痛。星形胶质细胞连接蛋白-43（现在被称为GJ1）分别参与间隙连接和细胞质内容物通过胶质合胞体和细胞外空间的半通道通信。Connexin-43在促进神经性疼痛的发展中也起着重要作用，但其作用机制尚不清楚。在这项研究中，我们研究了神经损伤是否可以通过释放趋化因子从脊髓星形胶质细胞上调连接蛋白43来维持晚期神经性疼痛。慢性收缩损伤引起脊髓星形胶质细胞中连接蛋白43的持续上调，持续bbbb3周。脊髓（鞘内）注射卡贝诺洛酮（一种非选择性半通道阻滞剂）和选择性连接蛋白-43阻滞剂（连接蛋白-43模拟肽（43）Gap26和（37,43）Gap27），以及星形胶质细胞毒素，而不是小胶质细胞抑制剂，在神经损伤后3周给予，有效减轻机械异常性痛，这是晚期神经性疼痛的主要特征。在培养的星形胶质细胞中，tnf - α诱导趋化因子CXCL1的显著释放，并被卡贝诺酮、Gap26/Gap27和连接蛋白43小干扰RNA阻断。tnf - α也增加了连接蛋白43的表达和半通道活性，但在皮层和脊髓制备的星形胶质细胞培养中没有增加间隙连接的通讯。脊髓注射tnf - α激活的星形胶质细胞足以诱导持续的机械异位痛，并且这种异位痛可以通过CXCL1中和、CXCL1受体（CXCR2）拮抗剂和连接蛋白-43小干扰RNA预处理星形胶质细胞来抑制。此外，神经损伤持续增加脊髓板ii期伤害性突触的兴奋性突触传递（自发兴奋性突触后电流），这种增加被卡贝诺洛酮和Gap27抑制，并被CXCL1再现。总之，我们的研究结果证明了星形细胞连接蛋白43通过释放趋化因子增强脊髓突触传递和维持晚期神经性疼痛的新机制。
Increasing evidence suggests that spinal cord astrocytes maintain neuropathic pain sensitization, but precisely how they do this is unclear. Using a mouse model of neuropathic pain, Chen et al. demonstrate that the hemichannel connexin-43 is upregulated in astrocytes after nerve injury, and maintains late-phase neuropathic pain by inducing chemokine release.Accumulating evidence suggests that spinal cord astrocytes play an important role in neuropathic pain sensitization by releasing astrocytic mediators (e.g. cytokines, chemokines and growth factors). However, it remains unclear how astrocytes control the release of astrocytic mediators and sustain late-phase neuropathic pain. Astrocytic connexin-43 (now known as GJ1) has been implicated in gap junction and hemichannel communication of cytosolic contents through the glial syncytia and to the extracellular space, respectively. Connexin-43 also plays an essential role in facilitating the development of neuropathic pain, yet the mechanism for this contribution remains unknown. In this study, we investigated whether nerve injury could upregulate connexin-43 to sustain late-phase neuropathic pain by releasing chemokine from spinal astrocytes. Chronic constriction injury elicited a persistent upregulation of connexin-43 in spinal astrocytes for > 3 weeks. Spinal (intrathecal) injection of carbenoxolone (a non-selective hemichannel blocker) and selective connexin-43 blockers (connexin-43 mimetic peptides (43)Gap26 and (37,43)Gap27), as well as astroglial toxin but not microglial inhibitors, given 3 weeks after nerve injury, effectively reduced mechanical allodynia, a cardinal feature of late-phase neuropathic pain. In cultured astrocytes, TNF-alpha elicited marked release of the chemokine CXCL1, and the release was blocked by carbenoxolone, Gap26/Gap27, and connexin-43 small interfering RNA. TNF-alpha also increased connexin-43 expression and hemichannel activity, but not gap junction communication in astrocyte cultures prepared from cortices and spinal cords. Spinal injection of TNF-alpha-activated astrocytes was sufficient to induce persistent mechanical allodynia, and this allodynia was suppressed by CXCL1 neutralization, CXCL1 receptor (CXCR2) antagonist, and pretreatment of astrocytes with connexin-43 small interfering RNA. Furthermore, nerve injury persistently increased excitatory synaptic transmission (spontaneous excitatory postsynaptic currents) in spinal lamina IIo nociceptive synapses in the late phase, and this increase was suppressed by carbenoxolone and Gap27, and recapitulated by CXCL1. Together, our findings demonstrate a novel mechanism of astrocytic connexin-43 to enhance spinal cord synaptic transmission and maintain neuropathic pain in the late-phase via releasing chemokines.