肾纤维化是慢性肾脏疾病（CKD）的常见组织病理特征，越来越多的证据表明，在肾纤维化的发生和进展中涉及到表观遗传调控。N-myc下游调控基因2（NDRG2）在肾纤维化中明显下调，其机制仍不清楚。以前的研究证实，抑制肿瘤细胞中NDRG2的表达与高甲基化有关，主要由DNA甲基转移酶（DNMTS）调节。因此，我们探讨了肾纤维化中NDRG2的表达及其表观遗传调控机制。结果显示，在体内和体外，NDRG2的表达显着受到抑制，而NDRG2的过表达有效缓解了肾纤维化。同时，我们发现，DNA甲基转移酶1/3A/3B的表达在低氧诱导的HK2细胞和单侧输尿管梗阻（UUO）小鼠中显着增加，而NDGR2启动子的高甲基化伴随着这种现象。甲基转移酶抑制剂（5-AZA-dC）矫正了DNMT1/3A/3B的异常表达，降低了NDRG2启动子的甲基化水平，并恢复了NDRG2的表达。我们进一步探讨了介导NDRG2甲基化变化的上游事件。反应性氧化物（ROS）是重要的表观遗传调节因子，已被证明在多种原因引起的肾损伤中起关键作用。因此，我们进一步探讨ROS是否能诱导NDRG2表达的DNA表观遗传变化，并参与肾纤维化的发展。结果表明，靶向线粒体的抗氧化剂（Mito-TEMPO）可以在敏感于DNMT的方式下，逆转NDRG2的表观遗传抑制，表现出强大的DNA去甲基化能力，展现了类似于5-AZA-dC的表观遗传调节和抗纤维化效果。更重要的是，5-AZA-dC和Mito-TEMPO的抗纤维化效果在具有NDRG2沉默的HK2细胞中被消除。这些发现凸显了靶向ROS介导的NDRG2启动子高甲基化是肾纤维化潜在有效的治疗策略，为CKD的治疗提供了新的见解。版权所有©2023 Elsevier B.V.，本文使用许可已获授权。

Renal fibrosis is the common histopathological feature of chronic kidney diseases (CKD), and there is increasing evidence that epigenetic regulation is involved in the occurrence and progression of renal fibrosis. N-myc downstream-regulated gene 2 (NDRG2) is significantly down-regulated in renal fibrosis, the mechanism of which remains unclear. Previous studies have confirmed that the inhibition of NDRG2 expression in tumor cells is related to hyper-methylation, mainly regulated by DNA methyltransferases (DNMTS). Herein, we explored the expression of NDRG2 and its epigenetic regulatory mechanism in renal fibrosis. The results showed that the expression of NDRG2 was significantly inhibited in vivo and in vitro, while the overexpression of NDRG2 effectively alleviated renal fibrosis. Meanwhile, we found that the expression of DNMT1/3A/3B was significantly increased in hypoxia-induced HK2 cells and Unilateral Ureteral Obstruction (UUO) mice accompanied by hyper-methylation of the NDGR2 promoter. Methyltransferase inhibitor (5-AZA-dC) corrected the abnormal expression of DNMT1/3A/3B, reduced the methylation level of NDRG2 promoter and restored the expression of NDRG2. The upstream events that mediate changes in NDRG2 methylation were further explored. Reactive oxygen species (ROS) are important epigenetic regulators and have been shown to play a key role in renal injury due to various causes. Accordingly, we further explored whether ROS could induce DNA-epigenetic changes of the expression of NDRG2 and then participated in the development of renal fibrosis. Our results showed that mitochondria-targeted antioxidants (Mito-TEMPO) could reverse the epigenetic inhibition of NDRG2 in a DNMT-sensitive manner, showing strong ability of DNA demethylation, exhibiting epigenetic regulation and anti-fibrosis effects similar to 5-AZA-dC. More importantly, the anti-fibrotic effects of 5-AZA-dC and Mito-TEMPO were eliminated in HK2 cells with NDRG2 knockdown. These findings highlight that targeting ROS-mediated hyper-methylation of NDRG2 promoter is a potentially effective therapeutic strategy for renal fibrosis, which will provide new insights into the treatment of CKD.Copyright © 2023. Published by Elsevier B.V.