TLR4介导腹侧被盖区（VTA）小胶质细胞参与吗啡成瘾的作用及机制

Recent evidence showed that microglia plays an important role in morphine addiction. However, the underlying mechanism remains largely unknown. We recently found that morphine addiction resulted in the upregulation of TLR4 in the activated microglia in the ventral tegmenta area (VTA) and intra-VTA injection of TLR4 antagonist significantly inhibited the acquisition of morphine-induced conditioned place preference (CPP) and the increase in the magnitude and frequency of miniature excitatory postsynaptic currents (mEPSCs). Further investigation indicated that TLR4 agonist LPS induced the upregulation of CXCL12 in the purified VTA microglia. These prior experiment suggested that TLR4 in the VTA microglia might modulate the expression of CXCL12 thereby promoting the sensitivity of dopaminergic neurons and contribute to morphine addiction. Using behavior testing, electrical physiological and molecular biological methods, the present project focuses on TLR4 and explores the role of VTA microglia in morphine CPP, investigate the modulation mechanisms of CXCL12 by TLR4 during the development of morphine addiction. Finally, to examine the mechanisms that TLR4 mediates morphine addiction, the CXCL12 signaling is interrupted. Our project will provide novel theraputic target for morphine addiction.

近年来研究显示小胶质细胞在吗啡成瘾中发挥了重要作用，但机制不清。我们最近发现，吗啡成瘾大鼠腹侧背盖区（VTA）小胶质细胞显著激活，且其表达的TLR4上调；而VTA内分别微量注射两种TLR4拮抗剂能够显著抑制吗啡诱导的条件性位置偏爱（CPP）的获得和多巴胺能神经元自发性微小突触后电流（mEPSCs）幅度与频率增大；进一步研究显示TLR4激动剂LPS明显上调培养纯化的VTA小胶质细胞CXCL12的表达。以上预实验提示VTA小胶质细胞TLR4可能通过上调CXCL12增强多巴胺能神经元兴奋性参与吗啡成瘾。因此本项目拟以TLR4为切入点，结合行为学，电生理及分子生物学技术，明确VTA小胶质细胞TLR4在吗啡CPP获得中的作用，阐明TLR4在吗啡诱导CXCL12表达中的调控机制。并通过进一步干预CXCL12的信号通路，揭示TLR4介导吗啡成瘾的分子机制。本项目为防治吗啡成瘾提供新颖的作用靶点。

在该基金的支持下，我们发现：.1：腹侧背盖区（VTA）多巴胺神经元的持续兴奋是耦联环境的吗啡成瘾的关键因素，且该持续性兴奋主要受海马神经元的活性影响。该内容发表于2016年物质依赖一区的神经科学优秀期刊《Addiction biology》。.2：下丘脑释放的食欲素通过影响海马神经元的功能介导吗啡成瘾，该内容发表2015年于物质依赖一区的神经科学优秀期刊《Addiction biology》。.3：众所周知，吗啡是治疗疼痛的金标准，而病理性疼痛的是困扰临床的重要问题，目前机制不清。我们发现：脊髓背角miRNA500介导的GABA神经递质合成和释放的减少在神经损伤及化疗药诱导的病理性疼痛中起重要作用。该部分内容发表在医学一区杂志《J Neuronsci》。.4：脊髓背角和背根神经节NF-Kb激活介导趋化因子CX3CL1的上调在化疗药诱导的急性和慢性疼痛中起关键作用，该部分内容发表在麻醉学一区杂志《Anesthesiology》和《Brain, behavior, and immunity》。.5：AMPK下调脊髓背角和背根神经节细胞因子的上调在多种化疗药，如硼替佐米、泰素和奥沙利铂等，诱导的持续疼痛中起重要作用。.总之，在该项目及相关项目的支持下，我们详细探讨吗啡成瘾的机制，以及病理性疼痛的的分子机制，共发表SCI论文10篇。.6：我们还发现，TLR4可能通过上调CXCL12介导VTA多巴胺神经元兴奋性的持续增加，参与耦联环境的吗啡成瘾，相关内容正在整理中，待发表。