Department of Nephrology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong, China.
Research Center of Medical Sciences, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong, China.
Kidney Int. 2021 Aug;100(2):377-390. doi: 10.1016/j.kint.2021.04.036. Epub 2021 May 27.
Receptor activator of NF-κB (RANK) expression is increased in podocytes of patients with diabetic nephropathy. However, the relevance of RANK to diabetic nephropathy pathobiology remains unclear. Here, to evaluate the role of podocyte RANK in the development of diabetic nephropathy, we generated a mouse model of podocyte-specific RANK depletion (RANKCre T), and a model of podocyte-specific RANK overexpression (RANK TG), and induced diabetes in these mice with streptozotocin. We found that podocyte RANK depletion alleviated albuminuria, mesangial matrix expansion, and basement membrane thickening, while RANK overexpression aggravated these indices in streptozotocin-treated mice. Moreover, streptozotocin-triggered oxidative stress was increased in RANK overexpression but decreased in the RANK depleted mice. Particularly, the expression of NADPH oxidase 4, and its obligate partner, P22phox, were enhanced in RANK overexpression, but reduced in RANK depleted mice. In parallel, the transcription factor p65 was increased in the podocyte nuclei of RANK overexpressing mice but decreased in the RANK depleted mice. The relevant findings were largely replicated with high glucose-treated podocytes in vitro. Mechanistically, p65 could bind to the promoter regions of NADPH oxidase 4 and P22phox, and increased their respective gene promoter activity in podocytes, dependent on the levels of RANK. Taken together, these findings suggested that high glucose induced RANK in podocytes and caused the increase of NADPH oxidase 4 and P22phox via p65, possibly together with the cytokines TNF- α, MAC-2 and IL-1 β, resulting in podocyte injury. Thus, we found that podocyte RANK was induced in the diabetic milieu and RANK mediated the development of diabetic nephropathy, likely by promoting glomerular oxidative stress and proinflammatory cytokine production.
核因子-κB 受体激活剂（RANK）在糖尿病肾病患者的足细胞中表达增加。然而，RANK 与糖尿病肾病发病机制的相关性尚不清楚。在此，我们构建了 RANK 敲除（RANKCre T）和 RANK 过表达（RANK TG）的足细胞特异性小鼠模型，并诱导这些小鼠发生链脲佐菌素（streptozotocin）诱导的糖尿病，以评估足细胞 RANK 在糖尿病肾病发生发展中的作用。我们发现，足细胞 RANK 缺失减轻了白蛋白尿、系膜基质扩张和基底膜增厚，而 RANK 过表达则加重了链脲佐菌素处理的小鼠的这些指标。此外，在 RANK 过表达的小鼠中，链脲佐菌素触发的氧化应激增加，而在 RANK 缺失的小鼠中则减少。特别是，NADPH 氧化酶 4 及其必需伴侣 P22phox 的表达在 RANK 过表达的小鼠中增强，而在 RANK 缺失的小鼠中减少。同时，p65 转录因子在 RANK 过表达的小鼠足细胞核中增加，而在 RANK 缺失的小鼠中减少。相关发现与体外高糖处理的足细胞基本一致。在机制上，p65 可以结合 NADPH 氧化酶 4 和 P22phox 的启动子区域，并依赖于 RANK 的水平增加它们各自的基因启动子活性。综上所述，这些发现表明，高糖诱导了足细胞中的 RANK，并通过 p65 引起 NADPH 氧化酶 4 和 P22phox 的增加，可能与细胞因子 TNF-α、MAC-2 和 IL-1β一起，导致足细胞损伤。因此，我们发现，在糖尿病环境中诱导了足细胞中的 RANK，并且 RANK 通过促进肾小球氧化应激和促炎细胞因子的产生介导了糖尿病肾病的发生。
