脊髓内质网应激在长期饮酒致术后疼痛慢性化中的作用及其机制

Previous studies have demonstrated that chronic alcohol consumption is associated with postsurgical pain chronification, but the underlying mechanisms remain unclear. The endoplasmic reticulum (ER) stress receptor inositol requiring enzyme 1 (IRE1α) and toll-like receptor 4 (TLR4) in microglia can increase the production of proinflammatory cytokine tumor necrosis factor-α (TNFα) and then promote the switch of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors from Ca2+ impermeable to Ca2+ permeable receptors, thereby regulating neuronal excitability and enhancing central sensitization in the spinal cord, which is beneficial to the development of chronic pain. In addition, previous studies have shown that TLR4 can activate IRE1α and its downstream target X box-binding protein (XBP-1). Our preliminary data showed that chronic alcohol consumption prolonged postsurgical pain, increased the spinal expression of IRE1α and enhanced the phosphorylation of eukaryotic initiation factor 2 subunit alpha (eIF2α) in the spinal cord, which is the downstream molecule of another ER stress receptor protein kinase RNA-like ER kinase (PERK). Meanwhile, we observed that chronic alcohol consumption activated microglia in the spinal dorsal horn and increased the expression of TLR4. Therefore, we hypothesize that by regulating spinal ER stress and TNFα-AMPA receptor signaling pathway-mediated microglia-neuron crosstalk, chronic alcohol consumption promotes postsurgical pain chronification. To address this hypothesis, we will use Cre-LoxP system-based cell-specific gene knockout (KO) mice combined with pain behavioral testing, spinal slice recording, in vivo Ca2+ imaging to investigate the effect of spinal endoplasmic reticulum stress on chronic alcohol consumption-induced pain chronification after surgery and its underlying mechanisms. The present study will provide new thoughts for the treatment of chronic postsurgical pain in alcoholics.

长期饮酒可致术后疼痛慢性化，但机制未明。脊髓内质网应激受体IRE1α和小胶质细胞表达的TLR4可通过调控TNFα而促进AMPA受体从Ca2+不通透型转换为Ca2+通透型、调节神经元兴奋性、增强脊髓中枢敏化以利于慢性痛发生。另外，TLR4可激活IRE1α及其下游靶点XBP-1。我们预实验观察到长期饮酒导致术后疼痛时间延长、上调脊髓背角IRE1α表达并增强另一内质网应激受体PERK下游分子eIF2α的磷酸化、激活脊髓背角小胶质细胞并上调TLR4的表达。因此我们推测：长期饮酒通过调控脊髓内质网应激、增强TNFα-AMPA受体信号通路介导的小胶质细胞与神经元之间的对话，以促进术后疼痛慢性化。我们将用基于Cre-LoxP构建的基因敲除小鼠，结合行为学测试、脊髓片电生理记录和在体钙成像技术，探讨脊髓内质网应激在长期饮酒所致的术后疼痛慢性化中的作用及其机制，以期为治疗酒精成瘾患者术后慢性疼痛提供新思路。

研究表明疼痛慢性化的一个重要影响因素是长期饮酒。本研究中，我们利用基于Cre/LoxP系统构建的小胶质细胞特异性Inositol requiring enzyme 1（IRE1α），Protein kinase RNA-like ER kinase （PERK）和Toll-like receptor 4（TLR4）基因敲除小鼠以及小胶质细胞特异性TNFα过表达小鼠，通过疼痛行为学测试，脊髓片电生理记录，在体钙离子成像，以及生化和药理分析等，观察了脊髓内质网应激在长期饮酒导致的术后疼痛慢性化中的作用。我们的研究结果显示长期饮酒导致术后疼痛时间延长。另外我们发现，长期饮酒使脊髓内质网应激受体IRE1α表达增多，以及另一内质网应激受体PERK的下游分子eIF2α磷酸化增强。此外，长期饮酒使脊髓背角小胶质细胞被激活从而导致TLR4表达增多。通过转基因小鼠和野生型小鼠的应用，我们还发现IRE1α-TNFα-AMPA受体信号通路参与了酒精致术后疼痛慢性化，并且胶质细胞与神经元之间存在对话机制，进一步导致了长期饮酒导致的术后疼痛慢性化。