Histone deacetylase 9 is an epigenetic suppressor of intrarenal angiotensinogen, serving as a key mechanism in angiotensinogen augmentation in hypertension

组蛋白脱乙酰酶 9 是肾内血管紧张素原的表观遗传抑制因子，是高血压血管紧张素原增加的关键机制

• 批准号: 9008798
• 负责人: Ryosuke Sato
• 金额: $ 27.09万
• 依托单位: TULANE UNIVERSITY OF LOUISIANA
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-12-01 至 2020-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9008798
• 关键词: Address; Aldosterone; Angiotensinogen; Animal Model; Attenuated; Binding Sites; Cell model; Cells; Chronic; Clinical; Complex; Development; Disease; Dose; Down-Regulation; Enzymes; Epigenetic Process; Exhibits; Female; Gender; Genes; Genetic Transcription; Glucose; Goals; HDAC9 gene; Histone Deacetylase; Histone Deacetylation; Human; Hypertension; Immune; Infection; Infiltration; Injury; Interleukin-6; Kidney; Knockout Mice; Liver; Mediating; Morbidity - disease rate; Mus; Outcome; Plasma; Process; Rattus; Regulation; Renin; Renin-Angiotensin System; Rodent; Role; Small Interfering RNA; Specificity; Stimulus; System; Tissues; Transfection; Transgenic Mice; Tubular formation; Up-Regulation; activating transcription factor; cell type; cytokine; extracellular; gender difference; gender disparity; genetically modified cells; in vivo; inhibitor/antagonist; kidney cell; knock-down; male; mortality; nephrogenesis; novel; overexpression; promoter; public health relevance; research study; response; treatment duration

 DESCRIPTION (provided by applicant): Augmented intrarenal angiotensinogen (AGT) is a critical contributor to the activation of intrarenal renin- angiotensin system (RAS) which leads to the development of hypertension and associated tissue injury. Therefore, elucidating mechanisms underlying AGT upregulation is essential for the development of strategies to treat these diseases. Chronic Ang II elevation induces increased immune cell infiltration in the kidneys contributing to increase in intrarenal cytokine levels specifically interleukin 6 (IL-6). Notably, IL-6 is required for Ang II-induced AGT augmentation in renal proximal tubular cells (PTC). However, the cellular mechanisms underlying these complex interactions leading to AGT augmentation have not been delineated. Renal cortical AGT levels are lower in female rodents than in males under normal conditions; however, plasma and liver AGT levels do not exhibit this gender disparity, suggesting that kidneys have a unique mechanism inherent to establishing basal AGT levels. Our preliminary studies demonstrated that histone deacetylase 9 (HDAC9) levels are higher in the kidneys of female rats than those of male rats and that HDAC9 inhibitions by siRNA and an inhibitor resulted in augmentation of AGT levels in PTC. These results indicate that HDAC9 is a suppressor of intrarenal AGT expression. Since HDACs suppress gene transcription by histone-deacetylation, changes in HDAC levels alter accessibility of activated transcription factors to their binding sites on gene promoters. The preliminary study showed that HDAC9 levels are decreased by Ang II in PTC. Accordingly, we hypothesize that downregulation of HDAC9 by Ang II reduces the suppressive effects of HDAC9 on AGT expression. This allows other transcription factors activated by pathological stimuli, in particula IL-6, to augment AGT expression, thus leading to the progression of hypertension and associated tissue injury in Ang II-dependent hypertension. To address this hypothesis, we will establish that Ang II suppresses intrarenal HDAC9 levels during the development of Ang II-dependent hypertension using unique PTC and Ang II- dependent hypertensive animal models (Specific Aim 1). In addition, the proposed studies will demonstrate that Ang II-induced intrarenal HDAC9 downregulation is required for intrarenal AGT augmentation by synergistic effects of Ang II and IL-6 and consequent development of hypertension (Specific Aim 2). In these experiments, HDAC9 knockdown by siRNA and overexpression via AAV2 infection will be used to show that the HDAC9 knockdown and IL-6 synergistically augment AGT expression in PTC and that kidney-specific HDAC9 overexpression attenuates intrarenal AGT elevation facilitating consequent the development of kidney injury in Ang II-dependent hypertension. Gender differences of intrarenal HDAC9 regulation and its contribution to AGT regulation in hypertension will also be investigated in the projects. The results will establish the cardinal rol of intrarenal HDAC9 in the regulation of intrarenal AGT in Ang II-dependent hypertension and provide a mechanistic rationale for targeting HDAC9 to treat hypertension and RAS associated tissue injury.

 描述（由申请方提供）：增强的肾内血管紧张素原（AGT）是肾内肾素-血管紧张素系统（RAS）激活的关键因素，导致 高血压和相关组织损伤的发展。因此，阐明AGT上调的潜在机制对于制定治疗这些疾病的策略至关重要。慢性血管紧张素II升高诱导肾脏中免疫细胞浸润增加，导致肾内细胞因子水平增加，特别是白细胞介素6（IL-6）。值得注意的是，在肾近端小管细胞（PTC）中，Ang II诱导的AGT增强需要IL-6。然而，这些复杂的相互作用，导致AGT增强的细胞机制尚未划定。在正常条件下，雌性啮齿动物的肾皮质AGT水平低于雄性;然而，血浆和肝脏AGT水平未表现出这种性别差异，表明肾脏具有建立基础AGT水平的独特机制。我们的初步研究表明，组蛋白去乙酰化酶9（HDAC 9）的水平在雌性大鼠的肾脏高于雄性大鼠，HDAC 9抑制siRNA和抑制剂导致AGT水平的增加在PTC。这些结果表明HDAC 9是肾内AGT表达的抑制剂。由于HDAC通过组蛋白去乙酰化抑制基因转录，HDAC水平的变化改变了激活的转录因子对其在基因启动子上的结合位点的可及性。初步研究表明，HDAC 9水平降低，血管紧张素II在PTC。因此，我们推测，血管紧张素II下调HDAC 9降低了HDAC 9对AGT表达的抑制作用。这使得由病理刺激激活的其他转录因子，特别是IL-6，增加AGT表达，从而导致高血压的进展和Ang II依赖性高血压中相关的组织损伤。为了解决这一假设，我们将使用独特的PTC和Ang II依赖性高血压动物模型（具体目的1）确定在Ang II依赖性高血压的发展期间Ang II抑制肾内HDAC 9水平。此外，所提出的研究将证明，Ang II诱导的肾内HDAC 9下调是通过Ang II和IL-6的协同作用以及随后的高血压发展而导致的肾内AGT增强所必需的（具体目的2）。在这些实验中，通过siRNA的HDAC 9敲低和通过AAV 2感染的过表达将用于显示HDAC 9敲低和IL-6协同增加PTC中的AGT表达，并且肾特异性HDAC 9过表达减弱肾内AGT升高，从而促进Ang II依赖性高血压中肾损伤的发展。本项目还将研究肾内HDAC 9调节的性别差异及其对高血压AGT调节的贡献。这些结果将确立肾内HDAC 9在Ang II依赖性高血压中调节肾内AGT的主要作用，并为靶向HDAC 9治疗高血压和RAS相关组织损伤提供机制依据。