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

项目概要/摘要： 重度抑郁症（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，并增加死亡率。一般来说，抑郁症的表现被认为是 因为大脑中神经递质的失衡这些神经递质包括谷氨酸、GABA和 特别是一类单胺类，如血清素、多巴胺和去甲肾上腺素。最近许多研究 已经证明了多巴胺稳态和动态对奖励和动机的重要性 尤其是在长期压力下。我们以前的研究已经发现了一种新的星形胶质细胞依赖性 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，这反过来又有助于调节多巴胺的释放和抑郁样行为， 小鼠这些令人兴奋的发现为研究脑梗死的病因学提供了一个新的和潜在的重要分子基础。 考虑到糖尿病和重度抑郁症之间的流行病学联系，胰岛素如何 介导的星形胶质细胞ATP释放尚未阐明，虽然分泌溶酶体的胞吐作用已经 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和ATP的分子机制和功能相关性， 在慢性应激下释放多巴胺能信号。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ATP的释放有助于多巴胺的释放， 星形胶质细胞启动的通路将对多巴胺释放产生负面影响，并加剧小鼠的奖励缺陷 长期承受压力为了验证这一核心假设，我们开发了一种新的遗传小鼠模型， 我们可以特异性地删除星形胶质细胞囊泡核苷酸转运蛋白（VNUTs）， 将ATP装入分泌性溶酶体。与我们最初的发现一致，初步分析表明， 星形胶质细胞特异性VNUTKO小鼠表现出增加的抑郁样行为和减少的 中脑核中的中等多刺神经元，表明多巴胺信号减少。移动 在目标1中，我们将继续使用星形胶质细胞特异性VNUTKO小鼠来确定ATP的作用。 在这些小鼠中，在暴露于不可预测的 慢性轻度应激（CMS）和慢性社会失败应激（CSDS）。在目标2中，利用 灵敏的基于ATP酶的ATP定量和Nanoimager S的超分辨率活体成像，我们将 定量培养的星形胶质细胞中胰岛素诱导的溶酶体运输和ATP胞吐。进一步的体外 以及在体内应用药理学抑制剂和病毒表达突变的关键信号传导 分子将剖析胰岛素刺激的星形胶质细胞释放ATP的分子机制。在一起， 这项拟议中的研究将扩大我们对抑郁症病因的理解， 胰岛素在星形胶质细胞中的作用，并可能揭示新的治疗抑郁症的方法。

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.