Zhang Xiaobo, Zhu Ying, Zhou Ying, Fei Bingru
Department of Nephrology, The Affiliated Huaian No. 1 People's Hospital of Nanjing Medical University, Huaian, Jiangsu, China (mainland).
Med Sci Monit. 2020 Sep 15;26:e922979. doi: 10.12659/MSM.922979.
BACKGROUND Diabetic nephropathy (DN), the formation of albuminuria, is one of the most important complications seen in diabetic patients. IL-37, an inhibitor of congenital inflammation and immune response, plays an important role in the occurrence and development of diabetes, but its study in DN has not been previously reported. MATERIAL AND METHODS Podocyte transfection techniques were used to overexpress STAT3 and cyclophilin A (CypA). The expression of IL-37, STAT3, and CypA was detected by RT-qPCR and western blot. Cell survival was detected by CCK-8. The expression of inflammatory factors and molecules related to oxidative stress was detected by ELISA and western blot, and cell apoptosis was detected by flow cytometry and western blot. RESULTS The expression of IL-37 was significantly decreased in high glucose-treated podocytes. IL-37 improved the survival rate of podocytes suffering from high glucose-induced apoptosis. It inhibited the expression of the inflammation-related factors tumor necrosis factor alpha (TNF-alpha), IL-1ß, IL-6, malondialdehyde (MDA), and lactate dehydrogenase (LDH), and promoted the expression of superoxide dismutase (SOD) in high glucose-treated podocytes. In addition, IL-37 inhibited the expression of the inflammation-related proteins MCP-1, NLRP3, ASC, and caspase-1. IL-37 also inhibited high glucose-induced apoptosis of podocytes by inhibiting the expression of the apoptosis-related proteins Bax and cleaved caspase-3/6/9, and by promoting the expression of Bcl-2. At the same time, we found that the STAT3/CypA signaling pathway was activated after induction by high glucose, while it was inhibited after treatment with IL-37. Overexpression of STAT3 and CypA inhibited the effects of IL-37 on the alleviation of inflammation and oxidative stress and on the reduction of apoptosis of high glucose-treated podocytes. CONCLUSIONS IL-37 can significantly reduce podocyte inflammation, oxidative stress, and apoptosis induced by high glucose, and can inhibit the STAT3-CypA signaling pathway. Upregulation of the STAT3-CypA signaling pathway can inhibit the protective effect of IL-37 against podocyte injury induced by high glucose.
背景 糖尿病肾病（DN），即蛋白尿的形成，是糖尿病患者中最常见的重要并发症之一。白细胞介素-37（IL-37）是先天性炎症和免疫反应的抑制剂，在糖尿病的发生和发展中起重要作用，但此前尚未见其在DN中的研究报道。
材料与方法 采用足细胞转染技术过表达信号转导和转录激活因子3（STAT3）和亲环素A（CypA）。通过逆转录定量聚合酶链反应（RT-qPCR）和蛋白质免疫印迹法检测IL-37、STAT3和CypA的表达。采用细胞计数试剂盒-8（CCK-8）检测细胞存活率。通过酶联免疫吸附测定（ELISA）和蛋白质免疫印迹法检测炎症因子和氧化应激相关分子的表达，采用流式细胞术和蛋白质免疫印迹法检测细胞凋亡。
结果 在高糖处理的足细胞中，IL-37的表达显著降低。IL-37提高了高糖诱导凋亡的足细胞的存活率。它抑制了高糖处理的足细胞中炎症相关因子肿瘤坏死因子-α（TNF-α）、白细胞介素-1β（IL-1β）、白细胞介素-6（IL-6）、丙二醛（MDA）和乳酸脱氢酶（LDH）的表达，并促进了超氧化物歧化酶（SOD）的表达。此外，IL-37抑制了炎症相关蛋白单核细胞趋化蛋白-1（MCP-1）、NLR家族含pyrin结构域蛋白3（NLRP3）、凋亡相关斑点样蛋白（ASC）和半胱天冬酶-1（caspase-1）的表达。IL-37还通过抑制凋亡相关蛋白Bax和裂解的半胱天冬酶-3/6/9的表达，并促进B细胞淋巴瘤-2（Bcl-2）的表达，抑制了高糖诱导的足细胞凋亡。同时，我们发现高糖诱导后STAT3/CypA信号通路被激活，而IL-37处理后该信号通路被抑制。STAT3和CypA的过表达抑制了IL-37对高糖处理的足细胞炎症和氧化应激的减轻作用以及对细胞凋亡的减少作用。
结论 IL-37可显著减轻高糖诱导的足细胞炎症、氧化应激和凋亡，并可抑制STAT3-CypA信号通路。STAT3-CypA信号通路的上调可抑制IL-37对高糖诱导的足细胞损伤的保护作用。
