Astrocyte-derived signals for neuronal and behavioral modulation and its implications in mental illness.

项目摘要/摘要： 严重抑郁障碍(MDD)是一种常见但严重的精神疾病，会对情绪产生负面影响， 认知、体力活动和增加死亡率。一般来说，抑郁症的表现被认为是 由于大脑中神经递质的失衡。这些神经递质包括谷氨酸、GABA和 尤指一类单胺，如5-羟色胺、多巴胺和去甲肾上腺素。最近的许多研究 已经证明了多巴胺的动态平衡和动态对奖励和动机的重要性 尤其是在长期承受压力之后。我们之前的研究已经确定了一种新的星形胶质细胞依赖 多巴胺系统的调节机制，其中激素胰岛素调节ATP的释放 星形胶质细胞，这反过来有助于调节多巴胺释放和抑郁样行为 老鼠。这些令人兴奋的发现为该病的病因学提供了新的和潜在的重要的分子基础。 抑郁症，考虑到糖尿病和严重抑郁症之间的流行病学联系。胰岛素是如何 尽管分泌型溶酶体的胞吐作用已经影响了星形胶质细胞的三磷酸腺苷的释放，但其机制尚不清楚。 被认为是星形胶质细胞释放ATP的主要途径。因此，在拟议的研究中，我们的目标是 进一步研究星形胶质细胞胰岛素作用与三磷酸腺苷的分子机制及功能相关性 慢性应激下多巴胺能信号的释放。我们假设胰岛素调节胞吐作用。 星形胶质细胞分泌溶酶体中的三磷酸腺苷对多巴胺释放的贡献及其损害 星形胶质细胞启动的通路将对小鼠的多巴胺释放产生负面影响，并加剧奖赏缺陷 暴露在长期的压力之下。为了验证这一中心假设，我们开发了一种新的遗传小鼠模型，在 我们可以特别删除所需的星形细胞囊泡核苷酸转运体(VNUT) 将三磷酸腺苷装载到分泌型溶酶体内。与我们最初的发现一致，初步分析表明 星形胶质细胞特异的VNUTKO小鼠表现出抑郁样行为增加和激活减少 伏隔核中有中等刺状神经元，表明多巴胺信号减弱。搬家 接下来，在目标1中，我们将继续使用星形胶质细胞特异性的VNUTKO小鼠来确定ATP的作用 星形胶质细胞的胞吐作用对多巴胺信号和奖赏的影响 慢性轻度应激(CMS)和慢性社会失败应激(CSDS)。在目标2中，利用高度 灵敏的基于荧光素酶的三磷酸腺苷定量和纳米成像仪S的超分辨率活体成像，我们将 量化胰岛素诱导的星形胶质细胞的溶酶体转运和胞吐作用。进一步的体外试验 以及体内应用药物抑制剂和病毒表达突变的关键信号 分子将剖析胰岛素刺激星形胶质细胞释放ATP的分子机制。一起， 这项拟议的研究将扩大我们对抑郁障碍病因学的理解 展望胰岛素在星形胶质细胞中的作用，并可能揭示抑郁症的新治疗方法。

Project Summary/Abstract: Major depressive disorder (MDD) is a common but serious mental illness that negatively affects emotion, cognition, physical activity, and increases mortality. In general, the manifestation of depression is thought to be due to the imbalance of neurotransmitters in the brain. These neurotransmitters include glutamate, GABA, and especially a class of monoamines, such as serotonin, dopamine, and norepinephrine. Many recent studies have demonstrated the importance of dopamine homeostasis and dynamics on reward and motivation especially after exposure to chronic stress. Our previous studies have identified a novel astrocyte-dependent modulatory mechanism for the dopamine system, in which the hormone insulin regulates ATP release in astrocytes, which in turn contributes to the modulation of dopamine release and depressive-like behavior in mice. These exciting findings provide a novel and potentially important molecular basis for the etiology of depressive disorders, given the epidemiological link between diabetes and major depression. How insulin mediates astrocytic ATP release has yet to be elucidated, although exocytosis from secretory lysosomes has been suggested as a major route of ATP release by astrocytes. Therefore, in the proposed research, we aim to further investigate the molecular mechanism and functional relevance of the astrocytic insulin action and ATP release on dopaminergic signaling under chronic stress. We hypothesize that insulin regulates the exocytosis of ATP from secretory lysosomes in astrocytes to contribute to dopamine release, and impairment of this astrocyte-initiated pathway will negatively impact dopamine release and exacerbate deficits in reward in mice exposed to chronic stress. To test this central hypothesis, we have developed a new genetic mouse model, in which we can specifically delete astrocytic vesicular nucleotide transporters (VNUTs) that are required for loading ATP into secretory lysosomes. Consistent with our original findings, preliminary analyses show that astrocyte-specific VNUTKO mice display increased depressive-like behavior and decreased activation of medium spiny neurons in the nucleus accumbens, indicating decreased dopamine signaling. Moving forward, in Aim 1, we will continue to use astrocyte-specific VNUTKO mice to determine the role of ATP exocytosis by astrocyte on dopamine signaling and reward in these mice after exposure to both unpredictable chronic mild stress (CMS) and chronic social defeat stress (CSDS). In Aim 2, taking advantage of the highly sensitive luciferase-based ATP quantification and the super-resolution living imaging by Nanoimager S, we will quantify the insulin-induced lysosomal trafficking and exocytosis of ATP in cultured astrocytes. Further in vitro and in vivo applications of pharmacological inhibitors and viral expression of mutations of key signaling molecules will dissect the molecular mechanisms of insulin-stimulated ATP release by astrocytes. Together, the proposed research will expand our understanding of the etiology of depressive disorders from a novel perspective of insulin action in astrocytes and may reveal new therapeutic approaches for depression.