Oct-1－MUTYH通路介导的足细胞线粒体功能障碍：肾小球硬化干预的新靶标

Glomerulosclerosis is one of the common pathophysiology pathways of various chronic renal diseases that contribute to end-stage renal disease. Understanding the mechanisms of glomerulosclerosis is essential in establishing novel therapeutic strategies for the prevention or arrest of progressive kidney diseases. Among the renal residential cells, podocytes are the principal effectors initiating and mediating glomerulosclerosis. Our previous study showed that mitochondrial dysfunction was the early event and the initial step in podocyte injury, whereas the relevant mechanism remains unclear. It has been reported that oxidative stress-induced mitochondrial DNA injury (mutation and copy number decrease) initiates mitochondrial dysfunction. MUTYH (MutY homologue), a DNA glycosylase, plays a key role in the elimination of DNA lesions and therefore helps maintain the integrity of the cell genome. Our preliminary data showed that MUTYH is required to maintain normal mitochondrial function in podocyte and the downregulation of MUTYH expression in mitochondria is associated with the progression of glomerulosclerosis. Transcription factor Oct-1, acting as a transcriptional repressor for MUTYH, inhibites the expression of MUTYH in podocytes. Therefore, we hypothesize that Oct-1－MUTYH signaling dysregulation induces mitochondrial dysfunction, which plays an important role in the progression of glomerulosclerosis. In the current study, we will take advantange of a podocyte conditional knockout mouse model, in vitro podocyte culture system, and kidney tissues from patients with FSGS, to investigate the temporal and spatial expression pattern of Oct-1 and MUTYH in glomerulosclerosis. We will also determine the effet of Oct-1 on the transcriptional regulation of MUTYH, and define the roles of Oct-1－MUTYH signaling in maintaining mitochondrial function, blocking podocyte injury, and inhibiting glomerulosclerosis. Through the study, we will not only elucidate the mechanism of mitochondrial dysfunction involved in the development of glomerulosclerosis, but also provide new therapeutic targets for the intervention of glomerulosclerosis.

肾小球硬化是CKD进展到ESRD的共同病生理改变之一，足细胞损伤是肾小球硬化启动和进展的关键环节。我们前期揭示线粒体功能障碍是足细胞损伤的早期事件和起始步骤，深入探讨该机制有望为干预肾小球硬化提供新的靶标。氧化应激介导的线粒体DNA损伤是线粒体功能障碍的始发环节，MUTYH是DNA氧化损伤修复系统的重要组分。预实验发现MUTYH参与维持足细胞线粒体功能，其表达下降与肾小球硬化进展密切相关，转录因子Oct-1参与足细胞MUTYH表达调控。由此设想，Oct-1－MUTYH通路失调引发线粒体功能障碍是肾小球硬化发生与进展的重要机制。本研究拟利用足细胞条件性基因敲除小鼠和细胞模型并结合临床病例，明确MUTYH和Oct-1在肾小球硬化中表达的时空规律以及Oct-1对MUTYH的表达调控在维持线粒体功能和阻断足细胞损伤中的作用机制。本研究不仅阐明肾小球硬化发生的线粒体机制，还为其早期干预提供新的靶标。

MUTYH是一种参与DNA修复的糖基化酶，在人体细胞中存在两种类型的蛋白变体，1型MUTYH定位于线粒体并参与线粒体DNA的修复以及定位于细胞核的2型MUTYH，MUTYH在碱基错配切除修复（BER）中起关键作用。尽管如此，MUTYH在肾脏病中的作用尚不清楚。我们的研究发现了MUTYH在慢性肾脏病CKD表达显著下调，MUTYH敲除加剧了CKD的进展；进一步的，我们还研究了MUTYH在急性肾损伤（AKI）中的作用和机制，叶酸诱导的AKI和AKI患者的肾脏中，MUTYH的蛋白水平显着下调。 MUTYH敲除加重了顺铂或叶酸诱导的肾功能不全，与野生型小鼠相比，敲除小鼠血清肌酐和血尿素氮水平更高。此外，在MUTYH敲除小鼠中，KIM-1和NGAL等肾小管损伤标记物表达增强。顺铂或叶酸诱导的MUTYH敲除小鼠肾脏中TUNEL阳性细胞数量显著高于WT小鼠。此外，MUTYH缺失导致8-oxoG的累积（表明更严重的氧化性DNA损伤）和线粒体功能障碍的加重。另外，2型MUTYH的过表达显着改善了顺铂诱导的细胞凋亡和氧化应激，而1型MUTYH的过表达在体内和体外显示出对顺铂诱导的细胞损伤的微弱作用。我们的结果还表明，E3连接酶HUWE1的上调可能介导了AKI肾脏中MUTYH的下调。综上所述，所有这些结果表明，泛素E3连接酶HUWE1介导的MUTYH泛素降解显著加重了DNA损伤和线粒体功能障碍，导致AKI的进展。我们的结果为AKI防治提供了潜在靶点。. 此外，我们也进行了AKI防治相关药物的探索研究，我们的研究发现，海藻糖显著改善双侧I/R诱导AKI，具备临床治疗AKI的潜能。