Chronic Intermittent Hypoxia: Common PVN Adaptations Contribute to Neurogenic Hypertension and Ischemic Neuroprotection

项目摘要 睡眠呼吸暂停（SA）影响约15%的美国人口。大多数SA患者会发展为神经源性高血压 (HTN)与交感神经活动（SNA）升高有关。在上一个融资周期，我们 通过将大鼠暴露于慢性间歇性缺氧（CIH）来模拟SA HTN。我们确定HTN由 7天的CIH由过度的NMDA驱动的交感神经前PVN神经元放电维持 受体（NMDAR）张力。重要的是，我们发现CIH激活PVN涉及局部适应性 响应（即，可塑性），其中神经元NMDAR亚基（GluN 1和GluN 2B）的表达降低， 神经胶质L-谷氨酸（L-Glu）转运体EEAT 2的表达增加。这些反应反映了 我们假设，对夸大的神经元能输入的自我平衡适应至少部分来自于 中脑NTS（项目1）和前脑MnPO（项目2）。CIH还降低了PVN的表达， 与NMDA受体GluN 2B亚基和神经元硝酸盐形成三元复合物的接头蛋白PSD 95 一氧化氮合酶（nNOS）。该复合物将NMDAR Ca 2+内流与NO的产生偶联。 假设这些适应CIH有两个抵消作用。(1)NMDAR降低， EAAT 2表达减弱了神经元能PVN的激活，从而缓冲了HTN的发展。(2)减少 PSD 95减弱NMDAR驱动的NO产生，并减少其对GABA释放的紧张性促进作用。这会解除 PVN，从而支持HTN的发展。这些相反的适应的净效应是HTN 由CIH诱导的不太明显，因为它会在他们的缺席。除了HTN，SA还增加了风险 缺血性中风的发病率降低了4倍。参与HTN开发的相同PVN对SA/CIH的适应 假设通过限制细胞外L-Glu的升高和减少 本修订提案中的研究将使大鼠暴露于CIH 7天和28天， 与高碳酸血症（CIHHC），以更密切地模拟人类SA。我们的具体目标是：（1）确定 CIH & CIHHC对神经源性HTN、PVN突触/兴奋毒性信号蛋白和PVN表达的影响 局部缺血后的神经元/组织存活。(2)确定CIH/CIHHC适应对PVN控制的影响 SNA/MAP和神经元对局部缺血的脆弱性的机制。(3)使用病毒介导的基因 转移/shRNA敲低，以模拟和拯救特定的PVN适应，并确定它们对 CIH和CIHHC的高血压和神经保护作用。

Project Summary Sleep apnea (SA) affects ~15% of the US population. Most people with SA develop neurogenic hypertension (HTN) associated with elevated sympathetic nerve activity (SNA). During the previous funding cycle, we modeled SA HTN by exposing rats to chronic intermittent hypoxia (CIH). We determined that HTN induced by 7 days of CIH is maintained by pre-sympathetic PVN neuronal discharge driven by exaggerated NMDA receptor (NMDAR) tone. Importantly, we discovered that PVN activation by CIH involves local adaptive responses (i.e., plasticity) wherein expression of neuronal NMDAR subunits (GluN1 & GluN2B) is reduced and expression of the glial L-glutamate (L-Glu) transporter EEAT2 is increased. These responses reflect homeostatic adaptations to exaggerated glutamatergic input, which we postulate arises, at least in part, from the hindbrain NTS (Project 1) and the forebrain MnPO (Project 2). CIH also decreased PVN expression of the adaptor protein PSD95 that forms a ternary complex with the NMDAR GluN2B subunit and neuronal nitric oxide (NO) synthase (nNOS). This complex couples NMDAR Ca2+ influx with production of NO. We hypothesize that these adaptations to CIH have two offsetting actions. (1) Reduced NMDAR and increased EAAT2 expression blunt glutamatergic PVN activation and thereby buffer development of HTN. (2) Reduced PSD95 blunts NMDAR-driven NO production and lessens its tonic facilitation of GABA release. This disinhibits the PVN and thereby supports development of HTN. The net effect of these opposing adaptations is that HTN induced by CIH is less pronounced than it would be in their absence. In addition to HTN, SA increases the risk of ischemic stroke by ~4 fold. The same PVN adaptations to SA/CIH that participate in development of HTN are hypothesized to reduce ischemic injury by limiting the rise of extracellular L-Glu and reducing the production of neurotoxic NO. Studies in this revised proposal will expose rats to 7 and 28 days of CIH and CIH with hypercapnia (CIHHC) to more closely model human SA. Our specific aims will: (1) Determine effects of CIH & CIHHC on neurogenic HTN, PVN expression of synaptic/excitotoxic signaling proteins and PVN neuronal/tissue survival after local ischemia. (2) Determine effects of CIH/CIHHC adaptations on PVN control of SNA/MAP and mechanisms of neuronal vulnerability to local ischemia. (3) Use viral-mediated gene transfer/shRNA knockdown to mimic and rescue specific PVN adaptations and determine their contributions to hypertensive and neuroprotective effects of CIH & CIHHC.