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

摘要 外周的获得性免疫细胞(T和B细胞)和脑内的先天免疫细胞(小胶质细胞) 与健康和疾病中的大脑动态平衡有关。利用免疫缺陷小鼠进行啮齿动物研究 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， 焦虑样行为，社交能力受损。然而，尚不清楚获得性免疫细胞如何 与小胶质细胞沟通，影响大脑发育和功能。我们的长期目标是了解 获得性免疫细胞和免疫细胞间通讯的分子和细胞机制 大脑发育和成年期的脑细胞。我们的初步研究显示Rag1-/-和[Rag2- /-小鼠]，缺乏T和B细胞，表现出社会行为受损。在Rag1-/-小鼠中，c-Fos增加 观察内侧前额叶皮质(MPFC)的表达和小胶质细胞表型的改变。这是 与之前的报告一致，即mPFC功能障碍与社会行为有关。[值得注意的是，领养 野生型(WT)脾细胞(包括T和B细胞)的转移挽救了Rag1-/-社会行为缺陷。 此外，注射WT血清外切体挽救了相同的表型。社会行为缺陷是 在Rag2-/-小鼠中也观察到了这一现象，尽管WT大脑中通常不存在Rag2。加在一起，这些 研究结果表明，T和B细胞通过外体对社会行为做出贡献。]事实上，我们观察到 Rag1-/-小鼠血清外体缺乏T、B细胞标志和多种microRNAs的表达 (MiRNAs)可能来源于T和B细胞。这些病毒预测靶基因(S)的表达 在Rag1-/-小鼠的PFC中，miRNAs如Ski被增强。相反，WT血清外切体减少 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 提示适应性免疫细胞-小胶质细胞通过外切体沟通不足会损害社会行为 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 细胞衍生的外切体及其miRNAs通过改变小胶质细胞对 前额叶内侧的神经元功能。我们将首先验证和扩展我们在血清外切体和 Rag1-/-小鼠的mPFC神经元，并通过以下方式确定缺乏适应性免疫细胞的原因 用过继转移技术将它们恢复到Rag1-/-小鼠体内(目标1)。我们还将审查直接 适应性免疫细胞外切小体释放和miRNA合成受损对小胶质细胞和 用遗传学方法研究mPFC中的神经元和社会行为(目标2)。[此外，我们将解决 中脑皮质锥体神经元和小胶质细胞在受损社会行为中的作用(目标3)。]本研究 将揭示适应性免疫细胞衍生的外切体影响大脑功能和 并可能最终导致精神障碍的新治疗策略。

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.