Neurovascular signaling and associated forebrain circuits in PTSD

创伤后应激障碍(PTSD)是一种致残性精神疾病，在 退伍军人。只有一小部分接触创伤的人会患上创伤后应激障碍，这表明 神经生物学因素导致易感性/风险。目前，特定的分子/电路水平的机制 导致创伤后应激障碍风险的因素没有明确的定义。大量信息支持先前存在的功能障碍 在恐惧中，回路可能会增加创伤后应激障碍的易感性，然而，有助于创伤前个体的机制 恐惧监管方面的差异尚不清楚。到目前为止，我们目前对恐惧的大多数理解都是基于 对外部威胁的防御性反应。而“身体到大脑”的信号在情绪调节中的重要性 早就被认识到，体内平衡威胁在形成恐惧和创伤后应激障碍风险方面的个体差异中所起的作用 还没有被调查。以前的研究报告了患有创伤后应激障碍的退伍军人对碳的敏感性增加 二氧化碳(CO2)，一种会产生强烈恐惧的动态平衡威胁。重要的是，部署前的二氧化碳敏感性 与后来的创伤后应激障碍症状发展有关，这表明二氧化碳敏感性和相关 机制可以提供有关创伤后应激障碍风险的有价值的信息。 PI实验室以前的工作报告了白细胞介素1受体(IL-1R1)信号在体内的独特作用 血脑屏障(BBB)损害CO_2诱发的感觉脑室周区、穹隆下器(SFO) 恐惧反应。在二氧化碳敏感性-创伤后应激障碍的小鼠模型中，我们观察到延迟的恐惧消退缺陷和 增强二氧化碳敏感小鼠的惊厥，这种反应可被SFO中的IL-1R1拮抗剂减弱。我们的分子 研究揭示IL-1R1在SFO内皮细胞的定位及其与肾素血管紧张素系统(RAS)的相互作用 靶区，以及前脑区边缘下皮质和终纹床核(BNST)，也与 创伤后应激障碍。总而言之，我们的数据支持一种独特的神经血管信号传递机制 可能调节前脑恐惧回路的区域(SFO)，导致创伤后应激障碍风险增加。拟议的研究将 研究SFO内的神经血管机制如何调节恐惧回路并促进创伤后应激障碍- 相关行为。我们将使用基于细胞电路的转基因、电生理和化学遗传方法。 在雄性和雌性小鼠身上。我们的假说，SFO神经血管IL-1R1-RAS与前脑回路相互作用 促进二氧化碳敏感性和创伤后应激障碍的相关行为将在三个目标下进行测试。目标1将测试 假设二氧化碳相关的创伤后应激障碍相关行为依赖于SFO内皮细胞IL-1R1和RAS 延迟恐惧条件化、消退和惊吓(与创伤后应激障碍相关的行为)将在暴露在空气/二氧化碳中进行测量。 SFO靶向RAS治疗野生型或内皮特异性缺失IL-1R1(Tie-2Cre：IL1R1fl/fl)小鼠 调制器。目的2将验证这样的假设，即二氧化碳诱发的SFO投射神经元的激活是依赖的 关于内皮细胞IL-1R1和AT1R信号的功能，将使用Patch评估IL-1R1-RAS的相关性 野生型Tie-2Cre：IL1R1fl/fl和AT1R-td番茄SFO切片的钳夹电生理和药理学 记者老鼠。目标3将检验假设，即sfo►IL和sfo►bnst投射调节创伤后应激障碍相关 行为。利用逆转录Cre依赖的化学发生策略，我们将调控sFo►IL和sfo►Bnst 二氧化碳挑战期间的预测，并测量与创伤后应激障碍相关的延迟恐惧和惊吓行为 相关性：我们的数据将揭示创伤后应激障碍背后独特的神经血管核心机制和新的电路 风险。除了二氧化碳，这种机制还与潜在的神经免疫、RAS和神经血管异常有关 据报道，患有创伤后应激障碍的退伍军人的长期目标是确定预测性风险因素和治疗目标 在退伍军人群体中管理创伤后应激障碍。

Posttraumatic Stress Disorder (PTSD) is a disabling psychiatric condition that is highly prevalent in combat veterans. Only a fraction of trauma-exposed individuals develop PTSD, suggesting that pre-existing neurobiological factors contribute to susceptibility/ risk. Currently, specific molecular/ circuit-level mechanisms that contribute to PTSD risk are not well-defined. Substantial information supports that pre-existing dysfunction in fear circuits may promote vulnerability to PTSD, however mechanisms contributing to pre-trauma individual differences in fear regulation are unclear. To date, most of our current understanding of fear is based on defensive reactions to external threats. While the importance of “body-to-brain” signaling in emotional regulation has long been recognized, the role of homeostatic threats in shaping individual differences in fear and PTSD risk has not been investigated. Previous studies reported increased sensitivity in veterans with PTSD to carbon dioxide (CO2), a homeostatic threat producing intense fear. Importantly, pre-deployment CO2 sensitivity associates with later development of PTSD symptoms, suggesting that CO2 sensitivity and associated mechanisms can provide valuable information on PTSD risk. Previous work from the PI’s lab reported a unique role of interleukin 1 receptor (IL-1R1) signaling within blood-brain-barrier (BBB) compromised sensory circumventricular area, subfornical organ (SFO) in CO2-evoked fear responses. In a mouse model of CO2 sensitivity-PTSD, we observed delayed fear extinction deficits and enhanced startle in CO2-sensitive mice, a response attenuated by IL-1R1 antagonism in SFO. Our molecular studies reveal IL-1R1 localization on SFO endothelial cells and interaction with renin angiotensin system (RAS) targets, and forebrain regions infralimbic cortex and bed nucleus of stria terminalis (BNST), also implicated in PTSD. Collectively, our data support a unique neurovascular signaling mechanism in an interoceptive brain region (SFO) that may regulate forebrain fear circuits contributing to increased PTSD risk. Proposed studies will investigate how neurovascular mechanisms within the SFO regulate fear circuits and contribute to PTSD- relevant behaviors. We will use cell-circuit based transgenic, electrophysiological and chemogenetic approaches in male and female mice. Our hypothesis that, SFO neurovascular IL-1R1-RAS interactions with forebrain circuits promote CO2-sensitivity and PTSD relevant behaviors will be tested under three aims. Aim 1 will test the hypothesis that CO2-associated PTSD relevant behaviors are dependent on SFO endothelial IL-1R1 and RAS Delayed fear conditioning, extinction, and startle (PTSD-relevant behaviors) will be measured in air/CO2 exposed wild type or endothelial-specific deletion of IL-1R1 (Tie-2Cre:IL1R1fl/fl) mice treated with SFO-targeted RAS modulators. Aim 2 will test the hypothesis that CO2-evoked activation of SFO projection neurons is dependent on endothelial IL-1R1 and AT1R signaling Functional IL-1R1-RAS associations will be assessed using patch clamp electrophysiology and pharmacology in SFO slices from wild type, Tie-2Cre:IL1R1fl/fl or AT1R-tdtomato reporter mice. Aim 3 will test the hypothesis that SFO►IL and SFO►BNST projections regulate PTSD relevant behaviors. Using a retroCre-dependent chemogenetic strategy we will modulate SFO ►IL and SFO►BNST projections during the CO2 challenge and measure delayed PTSD-relevant fear and startle behaviors Relevance: Our data will reveal a unique neurovascular core mechanism and novel circuit underlying PTSD risk. Beyond CO2, this mechanism is relevant to underlying neuroimmune, RAS and neurovascular abnormalities reported in veterans with PTSD The long-term goal is to identify predictive risk factors and therapeutic targets for management of PTSD in the veteran population.