Impact of immune cell-derived exosomes and miRNAs on brain function and behavior

摘要 外周中的适应性免疫细胞（T和B细胞）和脑中的先天性免疫细胞（小胶质细胞）具有 与健康和疾病中的大脑稳态有关。使用免疫缺陷小鼠的啮齿动物研究 已经揭示了适应性免疫细胞（T和B细胞）的丧失导致学习和记忆受损， 类似焦虑的行为和社交能力受损然而，目前尚不清楚适应性免疫细胞如何 与小胶质细胞沟通并影响大脑发育和功能。我们的长期目标是了解 适应性免疫细胞之间沟通的分子和细胞机制， 大脑发育和成年期的脑细胞。我们的初步研究表明，Rag 1-/-和[Rag 2-] /-小鼠]，缺乏T和B细胞，表现出受损的社会行为。在Rag 1-/-小鼠中，增加的c-Fos 观察内侧前额叶皮质（mPFC）中的表达和改变的小胶质细胞表型。这是 这与先前的报道一致，即mPFC功能障碍与社会行为有关。（注：adoptive 野生型（WT）脾细胞（含有T和B细胞）的转移挽救了Rag 1-/-社会行为缺陷。 此外，注射WT血清外来体挽救了相同的表型。社会行为缺陷是 在Rag 2-/-小鼠中也观察到，尽管Rag 2在WT脑中通常不存在。所有这些 研究结果表明T细胞和B细胞通过外泌体促进社会行为。]事实上，我们观察到， 来自Rag 1-/-小鼠血清的外泌体缺乏T和B细胞标志物以及多种microRNA的表达 （miRNAs）推测来源于T和B细胞。这些基因的预测靶基因的表达 miRNA，如Ski，在Rag 1-/-小鼠的PFC中增强。相反，WT血清外泌体减少， Ski在小胶质细胞中的表达。最近的研究表明，小胶质细胞控制神经元突触。因此，我们的数据 这表明缺乏适应性免疫细胞-小胶质细胞通过外泌体的通讯会损害社会行为 通过改变mPFC功能。因此，在这项研究中，我们将测试我们的假设，即缺乏适应性免疫， 细胞来源的外泌体及其miRNA通过改变小胶质细胞对 我们将首先验证和扩展我们对血清外泌体和中膜PFC的研究结果。 Rag 1-/-小鼠的mPFC神经元，并通过以下方法确定缺乏适应性免疫细胞的因果关系： 采用过继转移技术将其恢复到Rag 1-/-小鼠中（Aim 1）。我们还将研究直接 适应性免疫细胞中受损外泌体释放和miRNA产生对小胶质细胞和 神经元在mPFC和社会行为的遗传方法（目的2）。[In此外，我们会处理 mPFC中锥体神经元和小胶质细胞对受损社会行为的贡献（目的3）。本研究 将揭示适应性免疫细胞来源的外泌体影响脑功能的新机制， 行为，并可能最终导致新的治疗策略，在精神疾病。

ABSTRACT Adaptive immune cells in the periphery (T and B cells) and innate immune cells in the brain (microglia) have been implicated in the brain homeostasis in health and disease. Rodent studies using immunodeficient mice have revealed that the loss of adaptive immune cells (T and B cells) led to impaired learning and memory, anxiety-like behaviors, and impaired sociability. Nevertheless, it is not clear how adaptive immune cells communicate with microglia and affect brain development and function. Our long-term goal is to understand the molecular and cellular mechanisms underlying the communication between adaptive immune cells and brain cells during brain development and in adulthood. Our preliminary studies revealed that Rag1-/- and [Rag2- /-mice], lacking both T and B cells, exhibited impaired social behaviors. In Rag1-/- mice, increased c-Fos expression and altered microglial phenotypes in the medial prefrontal cortex (mPFC) were observed. This is consistent with previous reports that mPFC dysfunction is involved in social behaviors. [Notably, adoptive transfer of wild-type (WT) splenocytes (containing T and B cells) rescued Rag1-/- social behavioral deficits. Further, injection of WT serum exosomes rescued the same phenotype. The social behavioral deficits were also observed in Rag2-/- mice despite the fact that Rag2 is normally absent in the WT brain. Together, these findings suggest that T and B cells contribute to social behaviors via exosomes.] Indeed, we observed that exosomes from the sera of Rag1-/- mice lacked the expression of T and B cell markers and multiple microRNAs (miRNAs) presumably derived from T and B cells. The expression of predicted target gene(s) of these miRNAs, such as Ski, was enhanced in the PFC of Rag1-/- mice. In contrast, WT serum exosomes decreased Ski expression in microglia. Recent studies showed that microglia control neuronal synapses. Thus, our data suggest that deficient adaptive immune cell-microglia communication via exosomes impairs social behaviors by altering mPFC function. Hence, in this study, we will test our hypothesis that the lack of adaptive immune cell-derived exosomes and their miRNAs results in impaired social behaviors via altered microglial control of neuronal function in the medial PFC. We will first validate and extend our findings on serum exosomes and the mPFC neurons in Rag1-/- mice, and determine the causal role for the lack of adaptive immune cells by restoring them back into Rag1-/- mice with adoptive transfer technique (Aim 1). We will also examine the direct impact of impaired exosome release and miRNA production in adaptive immune cells on microglia and neurons in the mPFC and social behaviors by genetic approaches (Aim 2). [In addition, we will address the contribution of pyramidal neurons and microglia in the mPFC to impaired social behaviors (Aim 3).] This study will reveal novel mechanisms whereby adaptive immune cell-derived exosomes influence brain function and behavior and may eventually lead to novel therapeutic strategies in psychiatric disorders.