Department of Biochemistry, School of Life Sciences, University of Hyderabad, Hyderabad, India.
Nephrology (Carlton). 2023 Jan;28(1):60-71. doi: 10.1111/nep.14121. Epub 2022 Oct 17.
Podocytes, a vital component of the glomerular filtration barrier, are vulnerable to various noxious stimuli, including Hypoxic. HIF1α that transduces hypoxic adaptations induces Transglutaminase 2 (TG2), which catalyses cross-linking of extracellular matrix proteins. In this study, we investigated the mechanism of regulation of TG2 by HIF1α.
HIF1α was induced in podocytes by treating with FG4592 (Roxadustat) or hypoxia (1% oxygen) and in mice by treating with FG4592. Gene expression and protein analysis of ZEB2, TRPC6 and TG2 were performed in both experimental models. Histological and kidney function analyses were performed in mice.
Data mining revealed co-expression of HIF1α, ZEB2, TRPC6 and TG2 in the chronic kidney diseases (CKD)-validated dataset. We observed elevated expression of ZEB2, TRPC6 and TG2 in FG4592-treated podocytes. Ectopic expression of ZEB2 resulted in high TRPC6 expression, elevated intracellular calcium levels and increased TG2 activity. Blocking the TRPC6 channel or inhibiting its expression partially attenuated FG4592-induced TG2 activity, whereas suppression of ZEB2 expression significantly abolished TG2 activity. Furthermore, we noticed the induction of the ZEB2/TRPC6/TG2 axis in podocytes in mice administered with FG-4592. Metformin ameliorated the HIF1α-induced podocyte injury and proteinuria in mice administered with FG-4592.
This study demonstrates that HIF1α stimulates both TG2 expression and activity via ZEB2/TRPC6 axis, whereas abrogation of HIF1α by metformin prevented hypoxia-induced glomerular injury. Metformin could be explored to treat proteinuric diseases such as CKD, sleep apnea and renal Ischemia-reperfusion-injury, where hypoxia is considered a risk factor.
足细胞是肾小球滤过屏障的重要组成部分，容易受到各种有害刺激的影响，包括缺氧。缺氧诱导因子 1α（HIF1α）介导缺氧适应，诱导转谷氨酰胺酶 2（TG2），后者催化细胞外基质蛋白的交联。在这项研究中，我们研究了 HIF1α 调节 TG2 的机制。
用 FG4592（罗沙司他）或缺氧（1%氧气）处理足细胞诱导 HIF1α，用 FG4592 处理小鼠诱导 HIF1α。在两种实验模型中均进行 ZEB2、TRPC6 和 TG2 的基因表达和蛋白分析。对小鼠进行组织学和肾功能分析。
数据挖掘显示，HIF1α、ZEB2、TRPC6 和 TG2 在经 CKD 验证的数据集中共表达。我们观察到在 FG4592 处理的足细胞中 ZEB2、TRPC6 和 TG2 的表达水平升高。ZEB2 的异位表达导致 TRPC6 表达升高、细胞内钙离子水平升高和 TG2 活性增加。阻断 TRPC6 通道或抑制其表达部分减弱 FG4592 诱导的 TG2 活性，而抑制 ZEB2 表达则显著消除 TG2 活性。此外，我们注意到在给予 FG-4592 的小鼠的足细胞中诱导了 ZEB2/TRPC6/TG2 轴。二甲双胍改善了给予 FG-4592 的小鼠的 HIF1α 诱导的足细胞损伤和蛋白尿。
本研究表明，HIF1α 通过 ZEB2/TRPC6 轴刺激 TG2 的表达和活性，而二甲双胍通过阻断 HIF1α 可预防缺氧诱导的肾小球损伤。二甲双胍可用于治疗 CKD、睡眠呼吸暂停和肾缺血再灌注损伤等蛋白尿疾病，这些疾病中缺氧被认为是一个危险因素。
