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

项目摘要/摘要 这一建议的主要目的是确定Tiam1介导的突触可塑性是分子机制 基础阿片耐受性，并验证Tiam1作为缓解耐受性的有前景的治疗靶点。阿片类药物 止痛药仍然是治疗中重度围手术期和慢性疼痛的金标准 疼痛。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和 服药过量直接导致发病率和死亡率增加。阿片受体(MORS)的阿片作用 由伤害性感受器表达的蛋白不仅能强烈抑制伤害性信息的传递，还能诱导谷氨酸的释放 和脑源性神经营养因子(BDNF)在脊髓背角释放，启动下游事件 这会触发分子、突触和网络层面的适应，从而驱动耐受性。其中，突触 可塑性被认为是阿片类药物耐受性的关键决定因素。然而，分子机制是 触发突触的可塑性仍不清楚。鸟嘌呤核苷酸交换因子激活的Rho GTP酶 (GEF)和被GTP酶激活蛋白(GAP)抑制，在树突棘中发挥重要作用 细胞外调控肌动蛋白细胞骨架重构的形态发生和突触可塑性 暗示。我们和其他人之前发现rac1-gef Tiam1是树突、棘突和 突触发育，连接突触N-甲基-D-天冬氨酸受体(NMDAR)和TrkB受体 至脑发育过程中rac1信号介导的肌动蛋白细胞骨架重塑。在初步研究中，我们 研究发现，慢性吗啡治疗后，脊髓背角中Tiam1被激活，并调节 促进慢性吗啡诱导的肌动蛋白聚合和突触NMDAR的突触重塑 表情。Tiam1的遗传缺失、脊髓背角神经元的Tiam1缺失或药理学 阻断Tiam1信号通路可阻止吗啡耐受的形成。此外，复合吗啡 Tiam1抑制剂治疗降低完全弗氏佐剂(CFA)炎性疼痛患者对吗啡的耐受性 管理层。在这个提案中，我们将使用多学科方法来测试我们的中心假设Tiam1 阿片类药物激活突触NMDAR和/或TrkB受体与脊髓背侧的rac1信号联系 角神经元，导致突触结构和功能可塑性通过肌动蛋白细胞骨架重组和 NMDAR稳定，这共同奠定了阿片类药物耐受性的基础。此外，我们将确定是否阻止 Tiam1介导的突触与Tiam1抑制剂或反义寡核苷酸(ASOS)的突触可塑性产生长- 持久缓解阿片类药物耐受性。这项拟议的研究的贡献是重大的，因为它将揭示 一种以前不为人知的机制，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 对阿片类药物耐受性的持久缓解。

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.