Poovitha Sundar, Khan Abrar A, Arkat Silpa, Vijayakumar Anupama, Natarajan Bhargavi, Barthwal Manoj K, Mahapatra Nitish R
Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, 600036, India.
Pharmacology Division, CSIR-Central Drug Research Institute, Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India.
Cell Mol Life Sci. 2025 Jun 4;82(1):222. doi: 10.1007/s00018-025-05736-3.
Hypercholesterolemia is a leading cause of various cardiovascular diseases (CVDs). 3-hydroxy-3-methylglutaryl-Coenzyme A reductase (Hmgcr) is the rate-limiting enzyme in the cholesterol biosynthesis pathway. Previous studies investigated the regulation of Hmgcr expression under various pathophysiological conditions. However, its expression under hypoxia, an important player in the pathogenesis of CVD, is poorly understood. The present study investigated the hepatic expression of Hmgcr and Hif-1α in Spontaneously hypertensive rats [SHR] and its normotensive control, Wistar Kyoto [WKY] rats. Interestingly, hepatic Hmgcr expression was diminished while Hif-1α expression was elevated in SHR. In cultured rat liver cells, the Hmgcr promoter activity/transcript/protein and intracellular cholesterol levels were diminished after hypoxia treatment. Further, while Hif-1α /Runx3 transcript and protein levels were enhanced, Srebf levels decreased upon hypoxia. Knock-down of Hif-1α abrogated the hypoxia-mediated effect on Hmgcr, intracellular cholesterol levels, and the expression of Srebf and Runx3. Chromatin immunoprecipitation (ChIP) assays showed binding of Hif-1α to both endogenous SHR- and WKY-Hmgcr/Srebf/Runx3 domains with similar promoter occupancies. However, differential binding of Hif-1α to Srebf and Runx3 promoter domains were observed from ChIP assay. While HIF-1α showed a negative correlation with HMGCR/SREBF transcript levels, it correlated positively with RUNX3. Additionally, ChIP assays demonstrated differential binding of Srebf and Runx3 to SHR/WKY-Hmgcr promoter domains upon hypoxic stress. Taken together, this study elucidates the regulatory role of Hif-1α in modulating Hmgcr expression and intracellular cholesterol levels via Srebf and Runx3 under hypoxic stress. These findings provide new mechanistic insights underlying cholesterol homeostasis under hypoxia.
高胆固醇血症是各种心血管疾病（CVD）的主要病因。3-羟基-3-甲基戊二酰辅酶A还原酶（Hmgcr）是胆固醇生物合成途径中的限速酶。以往的研究调查了Hmgcr在各种病理生理条件下的表达调控。然而，在缺氧（CVD发病机制中的一个重要因素）条件下其表达情况却知之甚少。本研究调查了自发性高血压大鼠（SHR）及其血压正常的对照Wistar Kyoto（WKY）大鼠肝脏中Hmgcr和Hif-1α的表达。有趣的是，SHR肝脏中Hmgcr表达降低，而Hif-1α表达升高。在培养的大鼠肝细胞中，缺氧处理后Hmgcr启动子活性/转录本/蛋白及细胞内胆固醇水平降低。此外，缺氧时Hif-1α /Runx3转录本和蛋白水平升高，而Srebf水平降低。敲低Hif-1α可消除缺氧对Hmgcr、细胞内胆固醇水平以及Srebf和Runx3表达的影响。染色质免疫沉淀（ChIP）分析显示，Hif-1α与内源性SHR-和WKY-Hmgcr/Srebf/Runx3结构域结合，启动子占有率相似。然而，ChIP分析观察到Hif-1α与Srebf和Runx3启动子结构域的结合存在差异。虽然HIF-1α与HMGCR/SREBF转录本水平呈负相关，但与RUNX3呈正相关。此外，ChIP分析表明，缺氧应激时Srebf和Runx3与SHR/WKY-Hmgcr启动子结构域的结合存在差异。综上所述，本研究阐明了缺氧应激下Hif-1α通过Srebf和Runx3调节Hmgcr表达和细胞内胆固醇水平的调控作用。这些发现为缺氧状态下胆固醇稳态的潜在机制提供了新的见解。
