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: 9187452
• 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/9187452
• 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; Female; Gender; Genes; Genetic Transcription; Glucose; Goals; HDAC9 gene; Histone Deacetylase; Histone Deacetylation; Human; Hypertension; Immune; Infection; Infiltration; Injury; Interleukin-2; Interleukin-6; Kidney; Knockout Mice; Liver; Mediating; Morbidity - disease rate; Mus; Outcome; Pathologic; Plasma; Process; Rattus; Regulation; Renin; Renin-Angiotensin System; Rodent; Role; Small Interfering RNA; Specificity; Stimulus; System; Tissues; Transfection; Transgenic Mice; Tubular formation; Up-Regulation; cell type; cytokine; experimental study; extracellular; gender difference; gender disparity; genetically modified cells; in vivo; inhibitor/antagonist; knock-down; male; mortality; nephrogenesis; novel; overexpression; promoter; public health relevance; response; transcription factor; 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（由申请人提供）：增强的肾内血管紧张素原（AGT）是激活肾内肾素-血管紧张素系统（RAS）的关键因素，从而导致 高血压和相关组织损伤的发展。因此，阐明 AGT 上调的机制对于制定治疗这些疾病的策略至关重要。慢性 Ang II 升高会导致肾脏中免疫细胞浸润增加，从而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，IL-6 是 Ang II 诱导的肾近端肾小管细胞 (PTC) 中 AGT 增强所必需的。然而，导致 AGT 增强的这些复杂相互作用背后的细胞机制尚未阐明。正常情况下，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 水平并未表现出这种性别差异，这表明肾脏具有确定基础 AGT 水平的独特机制。我们的初步研究表明，雌性大鼠肾脏中的组蛋白脱乙酰酶 9 (HDAC9) 水平高于雄性大鼠，并且 siRNA 和抑制剂对 HDAC9 的抑制导致 PTC 中 AGT 水平升高。这些结果表明 HDAC9 是肾内 AGT 表达的抑制因子。由于 HDAC 通过组蛋白脱乙酰化抑制基因转录，因此 HDAC 水平的变化会改变激活的转录因子与其在基因启动子上的结合位点的可及性。初步研究表明，Ang II 可以降低 PTC 中的 HDAC9 水平。因此，我们假设 Ang II 下调 HDAC9 会降低 HDAC9 对 AGT 表达的抑制作用。这使得病理刺激激活的其他转录因子，特别是 IL-6，增强 AGT 表达，从而导致高血压的进展以及 Ang II 依赖性高血压中的相关组织损伤。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确定 Ang II 在 Ang II 依赖性高血压发生过程中抑制肾内 HDAC9 水平（具体目标 1）。此外，拟议的研究将证明，Ang II 诱导的肾内 HDAC9 下调是通过 Ang II 和 IL-6 的协同作用增强肾内 AGT 以及随后发生高血压所必需的（具体目标 2）。在这些实验中，通过siRNA敲低HDAC9和通过AAV2感染过表达将用于表明HDAC9敲低和IL-6协同增强PTC中的AGT表达，并且肾脏特异性HDAC9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。该项目还将研究肾内 HDAC9 调节的性别差异及其对高血压 AGT 调节的贡献。这些结果将确定肾内 HDAC9 在 Ang II 依赖性高血压中肾内 AGT 调节中的主要作用，并为靶向 HDAC9 治疗高血压和 RAS 相关组织损伤提供机制原理。