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

摘要 外周的适应性免疫细胞（T 细胞和 B 细胞）和大脑中的先天免疫细胞（小胶质细胞） 与健康和疾病中的大脑稳态有关。使用免疫缺陷小鼠进行啮齿动物研究 研究表明，适应性免疫细胞（T 细胞和 B 细胞）的丧失会导致学习和记忆受损， 焦虑样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 适应性免疫细胞和免疫细胞之间通讯的分子和细胞机制 大脑发育和成年期间的脑细胞。我们的初步研究表明 Rag1-/- 和 [Rag2- /-小鼠]缺乏T细胞和B细胞，表现出社交行为受损。在 Rag1-/- 小鼠中，c-Fos 增加 观察到内侧前额皮质（mPFC）中的表达和小胶质细胞表型的改变。这是 与之前的报道一致，mPFC 功能障碍与社会行为有关。 [值得注意的是，收养 野生型 (WT) 脾细胞（包含 T 细胞和 B 细胞）的转移挽救了 Rag1-/- 社会行为缺陷。 此外，注射 WT 血清外泌体可挽救相同的表型。社会行为缺陷是 尽管 Rag2 通常在 WT 大脑中不存在，但也在 Rag2-/- 小鼠中观察到。在一起，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 Rag1-/- 小鼠血清中的外泌体缺乏 T 细胞和 B 细胞标记以及多种 microRNA 的表达 (miRNA) 大概源自 T 细胞和 B 细胞。这些的预测目标基因的表达 miRNA，例如 Ski，在 Rag1-/- 小鼠的 PFC 中得到增强。相反，WT 血清外泌体减少 小胶质细胞中的 Ski 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 表明通过外泌体的适应性免疫细胞-小胶质细胞通讯缺陷会损害社会行为 通过改变 mPFC 功能。因此，在这项研究中，我们将检验我们的假设，即缺乏适应性免疫 细胞源性外泌体及其 miRNA 通过改变小胶质细胞控制而导致社会行为受损 内侧 PFC 的神经元功能。我们将首先验证并扩展我们关于血清外泌体和 Rag1-/- 小鼠的 mPFC 神经元，并通过以下方法确定适应性免疫细胞缺乏的因果作用 通过过继转移技术将它们恢复为 Rag1-/- 小鼠（目标 1）。我们还将检查直接 适应性免疫细胞中外泌体释放和 miRNA 生成受损对小胶质细胞和 通过遗传方法研究 mPFC 中的神经元和社会行为（目标 2）。 [此外，我们将解决 mPFC 中锥体神经元和小胶质细胞对社会行为受损的贡献（目标 3）。] 这项研究 将揭示适应性免疫细胞衍生的外泌体影响大脑功能的新机制 行为，并可能最终导致精神疾病的新治疗策略。

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.