SGLT2 Mediates Glucose-Induced Angiotensinogen Synthesis in Proximal Tubule Cells

 描述（由申请方提供）：肾内肾素-血管紧张素系统（RAS）与高血压的发生和糖尿病导致的肾损伤进展有关。RAS阻断是预防糖尿病肾病和糖尿病高血压的有效策略。在高糖条件下，肾近端小管细胞中血管紧张素原（AGT）的产生上调。这一过程部分由葡萄糖代谢和线粒体呼吸导致的活性氧（ROS）的形成介导。AGT形成血管紧张素II（Ang II），其通过激活Ang II 1型受体（AT 1 R）引起氧化应激。AT 1 R活化也是近端肾小管细胞中ROS产生的主要来源。本研究的总体目标是阐明糖尿病和慢性高血糖时近端小管AGT上调的机制。钠-葡萄糖协同转运蛋白2（SGLT 2）是肾脏重吸收滤过葡萄糖的主要机制。尚不清楚SGLT 2介导的葡萄糖重吸收是否是糖尿病期间报告的小管内AGT表达增加的原因。因此，我们的总体假设是，高糖条件下近端肾小管细胞中AGT表达的增加是通过SGLT 2增加葡萄糖进入介导的，SGLT 2与AT 1 R激活的作用协同作用。这将为深入了解糖尿病早期肾脏中发生的分子机制提供帮助。为了验证这一假设，我们将确定在高糖条件下培养的近端肾小管细胞中ROS蓄积和AGT表达增加，并且这种上调依赖于通过SGLT 2进入葡萄糖。我们将证明，葡萄糖进入和线粒体呼吸增加血管紧张素II通过AT 1 R激活。此外，我们将表明，AT 1 R激活协同作用的影响，高葡萄糖增加AGT的表达。实验设计将利用来源于野生型和AT 1 R敲除小鼠的永生化近端肾小管细胞系。卡格列净是一种高选择性的SGLT 2药物阻断剂，将用于证明高糖条件下SGLT 2对AGT产生的作用，并解决总体假设。

 DESCRIPTION (provided by applicant): The intra-renal renin-angiotensin system (RAS) has been implicated in the development of hypertension and the progression of kidney injury that results from diabetes mellitus. RAS blockade is an effective strategy in preventing diabetic nephropathy and hypertension during diabetes. The production of angiotensinogen (AGT) is upregulated in the renal proximal tubular cells under high glucose conditions. This process is partially mediated by the formation of reactive oxygen species (ROS) as a result of glucose metabolism and mitochondrial respiration. AGT forms angiotensin II (Ang II) which causes oxidative stress by activating the Ang II Type 1 Receptor (AT1R). AT1R activation is also a major source of ROS generation in proximal tubular cells. The overall aim of this proposal is to elucidate the mechanisms underlying the up-regulation of AGT in the proximal tubule during diabetes and chronic hyperglycemia. The sodium-glucose cotransporter 2 (SGLT2) is the primary mechanism responsible for reabsorbing filtered glucose in the kidney. It is not known if SGLT2- mediated glucose reabsorption is responsible for the increased intratubular AGT expression reported during diabetes. Therefore, our overall hypothesis is that the increase in AGT expression in proximal tubular cells under high glucose conditions is mediated by increased glucose entry via SGLT2 which synergizes with the effects of AT1R activation. This will provide insight into the molecular mechanisms that occur in the kidney in the early stages of diabetes. To test this hypothesis, we will establish an increase in ROS accumulation and AGT expression in proximal tubular cells cultured in high glucose conditions and that this upregulation is dependent on glucose entry via SGLT2. We will demonstrate that glucose entry and mitochondrial respiration are increased by Ang II through AT1R activation. In addition, we will show that AT1R activation synergizes with the effects of high glucose to augment AGT expression. The experimental design will utilize immortalized proximal tubular cell lines derived from the wild type and AT1R knockout mice. Canagliflozin, a highly selective pharmaceutical blocker of SGLT2, will be used to demonstrate the role of SGLT2 on the production of AGT during high glucose conditions and address the overall hypothesis.