Intratubular Angiotensin II and AT1a Receptors in The Proximal Tubules: Roles in Hypertension and Kidney Injury

高血压是心血管疾病、中风和终末期肾衰竭的最重要危险因素。在联合 在美国，近46%的成年人患有高血压，并将在其一生中接受降压药物治疗。只 50%的高血压患者对目前的降压药物有反应，而1/3的高血压患者对目前的降压药物有反应。 病人会出现心血管，中风及肾脏并发症。负责发展的机制 心血管和肾脏损伤以及目前抗高血压治疗反应差的原因仍然存在， 不完全理解。因此，有必要进行进一步的研究，以发现新的机制、途径和 治疗靶点不受控制的高血压和靶器官损伤。在初步研究中，我们使用了最先进的技术 SGLT 2-Cre/LoxP方法删除血管紧张素II（ANG II）AT1a受体、Na +/H+交换器3（NHE 3）或关键 线粒体蛋白sirtuin 3（SIRT3）选择性地在S1和S2段的近端小管在肾脏。我们 有证据表明，近端小管特异性缺失AT1a或NHE3降低基础血压，增加 压力钠尿反应，并减弱ANG II诱导的高血压，以及近端小管特异性缺失 AT1a受体的表达显著减弱，而SIRT3的近端小管特异性缺失显著降低 肾缺血再灌注损伤加重。这些初步研究强烈表明，小管内ANG 近端小管II及其AT1a受体和SIRT3在高血压的发生发展中起重要作用， 肾I/R损伤在这个提议中，我们将检验以下假设： 肾脏近端小管是ANG II诱导的高血压和肾I/R发展所必需的 损伤和近端小管中选择性AT 1a受体或血管紧张素原（AGT）缺失将 减轻ANG II诱导的高血压和肾I/R损伤的两个特定目的。具体目标1将测试 假设近端小管内ANG II和AT 1a受体在维持基础血液中起关键作用 通过激活Na +/H+逆向转运蛋白，压力稳态和ANG II诱导的高血压的发展 （NHE 3）、Na+和葡萄糖协同转运蛋白2（sglt2）以及压力性尿钠排泄反应的调节。具体目标2 将检验近端小管中的AT 1a受体在肾I/R损伤的发病机制中起关键作用的假设， 由小管内和细胞内ANG II激活，上调Toll样受体4（TLR-4），下调 线粒体SIRT3表达，并损害近端小管中的线粒体功能。这些假设将 使用高度创新的小鼠模型进行测试，所述小鼠模型具有a）AT 1a的全局和近端小管特异性敲除 受体; B）血管紧张素原; c）NHE 3; d）SGLT 2; e）TLR 4;或f）SIRT 3。ANG II依赖性高血压， 肾I/R损伤将通过以下方式诱导：a）输注天然ANG II; B）2肾1夹肾性高血压; c）遗传性 编码的循环弹性蛋白样多肽-ANG II（ELP-ANG II）;或 特异性，靶向细胞内ECFP/ANG II。遥测血压，压力尿钠排泄 反应，无创性肾小球滤过率，活体双光子成像和XFe 24细胞外通量分析仪， 测量线粒体功能，电子显微镜和免疫组织化学成像，以及Western印迹分析 促炎、促纤维化和信号蛋白的研究。研究建议高度 重要的和临床相关的，新的知识将导致一个范式的转变，对理解 高血压和肾I/R损伤的发病机制，并有助于开发近端小管靶向药物治疗不良 控制高血压和肾I/R损伤。

Hypertension is the most important risk factor for cardiovascular diseases, stroke, and end-stage kidney failure. In the United States, nearly 46% of adults develop hypertension and will be treated with antihypertensive drugs in their lifetime. Only 50% of hypertensive patients are responsive to current antihypertensive drugs, whereas 1/3 of remaining hypertensive patients will develop cardiovascular, stroke and renal complications. The mechanisms responsible for the development of cardiovascular and kidney injury and the reasons for poor responses to current antihypertensive therapies remain incompletely understood. Thus, further studies are necessary in order to uncover new mechanisms, pathways, and therapeutic targets of uncontrolled hypertension and target organ injury. In preliminary studies, we used the state of the art SGLT2-Cre/LoxP approach to delete angiotensin II (ANG II) AT1a receptors, the Na+/H+ exchanger 3 (NHE3), or a key mitochondrial protein sirtuin 3 (SIRT3) selectively in the S1 and S2 segments of the proximal tubules in the kidney. We have evidence that proximal tubule-specific deletion of AT1a or NHE3 decreases basal blood pressure, augments the pressure natriuresis response, and attenuates ANG II-induced hypertension, and that proximal tubule-specific deletion of AT1a receptors significantly attenuated, whereas proximal tubule-specific deletion of SIRT3 significantly worsened renal ischemia and reperfusion (I/R) injury. These preliminary studies strongly suggest that intratubular ANG II and its AT1a receptors and SIRT3 in the proximal tubules play an important role in the development of hypertension and renal I/R injury. In this proposal, we will test the hypotheses that intratubular ANG II and AT1a receptors in the proximal tubules of the kidney are required for the development of ANG II-induced hypertension and renal I/R injury, and that deletion of AT1a receptors or angiotensinogen (AGT) selectively in the proximal tubules will attenuate ANG II-induced hypertension and renal I/R injury in two specific aims. Specific Aim 1 will test the hypothesis that intratubular ANG II and AT1a receptors in the proximal tubules play a key role in maintaining basal blood pressure homeostasis and the development of ANG II-induced hypertension, via the activation of the Na+/H+ antiporter (NHE3), Na+ and glucose cotransporter 2 (sglt2), and the regulation of the pressure natriuresis response. Specific Aim 2 will test the hypothesis that AT1a receptors in the proximal tubules play a key role in the pathogenesis of renal I/R injury, activated by intratubular and intracellular ANG II to upregulate Toll-Like receptor 4 (TLR-4), downregulate mitochondrial SIRT3 expression, and impair mitochondrial function in the proximal tubules. These hypotheses will be tested using highly innovative mouse models with global and proximal tubule-specific knockout of a) AT1a receptors; b) angiotensinogen; c) NHE3; d) SGLT2; e) TLR4; or f) SIRT3. ANG II-dependent hypertension and renal I/R injury will be induced by a) infusing a native ANG II; b) 2-kidney, 1-clip renal hypertension; c) a genetically encoded circulating Elastin-Like Polypeptide-ANG II (ELP-ANG II); or d) overexpressing a proximal tubule- specific, mitochondria-targeting intracellular ECFP/ANG II. Telemetry blood pressure, the pressure natriuresis response, noninvasive glomerular filtration rate, intravital two-photon imaging and XFe24 Extracellular Flux Analyzer to measure mitochondrial function, electron microscopic and immunohistochemical imaging, and Western blot analyses of proinflammatory, profibrotic and signaling proteins will be studied. The proposed studies are highly significant and clinically relevant, and the new knowledge will lead to a paradigm shift on understanding the pathogenesis of hypertension and renal I/R injury, and help develop proximal tubule-targeting drugs to treat poorly controlled hypertension and renal I/R injury.