Targeting Tiam1-mediated synaptic plasticity for the relief of opioid tolerance

项目总结/摘要 该建议的主要目的是确定Tiam 1介导的突触可塑性作为分子机制 潜在的阿片类药物耐受性，并验证Tiam 1作为缓解耐受性的有前途的治疗靶点。阿片 止痛药仍然是治疗中度至重度围手术期和慢性疼痛的金标准。 痛苦然而，随着时间的推移，阿片类药物的使用可能导致耐受性，这是阿片类药物滥用的主要驱动因素， 过量用药直接导致发病率和死亡率增加。阿片类药物对μ阿片受体（MORs）的作用 伤害感受器表达的谷氨酸不仅能急性抑制伤害性感受的传递，而且能诱导谷氨酸的释放 和脑源性神经营养因子（BDNF）在脊髓背角的释放，启动下游事件 触发分子、突触和网络水平的适应，从而驱动耐受性。其中，Synaptic 可塑性被认为是阿片耐受性的关键决定因素。然而，分子机制， 触发突触可塑性仍不清楚。Rho GTP酶，由鸟嘌呤核苷酸交换因子激活 在树突棘的形成过程中，GTF（GEFs）起重要作用，并被GTP酶激活蛋白（GAP）抑制 通过控制肌动蛋白细胞骨架的重塑， 线索我们和其他人先前确定Rac 1-GEF Tiam 1是树突、棘和树突形成的关键调节因子。 突触发育，其偶联突触N-甲基-D-天冬氨酸受体（NMDAR）和TrkB受体 Rac 1信号介导的肌动蛋白细胞骨架重塑在大脑发育过程中。在初步研究中，我们 发现Tiam 1在脊髓背角对慢性吗啡治疗的反应中被激活， 通过促进慢性吗啡诱导的肌动蛋白聚合和突触NMDAR进行突触重塑 表情Tiam 1的遗传缺失，脊髓背角神经元Tiam 1的缺失，或药理学 阻断Tiam 1信号传导可防止吗啡耐受性的发展。此外，吗啡 和Tiam 1抑制剂治疗减少完全弗氏佐剂（CFA）炎性疼痛中的吗啡耐受 管理在本提案中，我们将使用多学科方法来检验我们的中心假设，即Tiam 1 将阿片类药物诱导的突触NMDAR和/或TrkB受体激活与脊髓背角Rac 1信号传导联系起来 角神经元，通过肌动蛋白细胞骨架重组导致突触结构和功能可塑性， NMDAR稳定，共同构成阿片类药物耐受的基础。此外，我们将确定是否阻止 Tiam 1抑制剂或反义寡核苷酸（ASO）的Tiam 1介导的突触可塑性产生长- 持久缓解阿片类药物耐受性。这项研究的贡献是重大的，因为它将揭示 一种以前未知的机制，是阿片类药物耐受的基础，并将提供一个有希望的治疗靶点 用于长期缓解阿片类药物耐受性。

PROJECT SUMMARY/ABSTRACT The major objective of this proposal is to identify Tiam1-mediated synaptic plasticity as the molecular mechanism underlying opioid tolerance and validate Tiam1 as a promising therapeutic target in the relief of tolerance. Opioid pain medications remain the gold standard for the treatment of moderate to severe perioperative and chronic pain. However, over time, opioid use can result in tolerance, which is a primary driver for opioid misuse and overdose that directly contribute to increased morbidity and mortality. Opioid action at µ opioid receptors (MORs) expressed by nociceptors not only acutely depresses nociceptive transmission, but can induce glutamate release and brain-derived neurotrophic factor (BDNF) release in the spinal dorsal horn, which initiate downstream events that trigger the molecular, synaptic, and network-level adaptations that drive tolerance. Among these, synaptic plasticity is assumed to be the key determinant in opioid tolerance. However, the molecular mechanisms that trigger synaptic plasticity remain unclear. Rho GTPases, activated by guanine nucleotide exchange factors (GEFs) and inhibited by GTPase-activating proteins (GAPs), play important roles in dendritic spine morphogenesis and synaptic plasticity by controlling actin cytoskeleton remodeling in response to extracellular cues. We and others previously identified the Rac1-GEF Tiam1 as a critical regulator of dendrite, spine, and synapse development, which couples synaptic N-methyl-D-aspartate receptors (NMDARs) and TrkB receptors to Rac1 signaling-mediated actin cytoskeleton remodeling during brain development. In preliminary studies, we found that Tiam1 is activated in the spinal dorsal horn in response to chronic morphine treatment and it modulates synaptic remodeling by promoting chronic morphine-induced actin polymerization and synaptic NMDAR expression. Genetic deletion of Tiam1, deletion of Tiam1 from spinal dorsal horn neurons, or pharmacological blockade of Tiam1 signaling prevents the development of morphine tolerance. Moreover, combination morphine and Tiam1 inhibitor therapy reduce morphine tolerance in completer Freund’s adjuvant (CFA) inflammatory pain management. In this proposal, we will use a multidisciplinary approach to test our central hypothesis that Tiam1 links opioid-induced activation of synaptic NMDARs and/or TrkB receptors to Rac1 signaling in spinal dorsal horn neurons, resulting in synaptic structural and functional plasticity via actin cytoskeleton reorganization and NMDAR stabilization, which together underlies opioid tolerance. Moreover, we will determine whether blocking Tiam1-mediated synaptic plasticity with Tiam1 inhibitor or antisense oligonucleotides (ASOs) produces the long- lasting relief of opioid tolerance. The contribution of this proposed research is significant because it will uncover a previously unknown mechanism that underlies opioid tolerance and will provide a promising therapeutic target for the long-lasting relief of opioid tolerance.