自噬调控DNA损伤诱导的G2/M停滞在急性肾损伤向慢性化转归中的作用及机制

Autophagy and G2/M arrest could be induced by DNA damage in renal tubular epithelial cells. However the relationship between autophagy and G2/M arrest, the regulatory mechanism of autophagy, and their role in the evolution of chronic kidney disease (CKD) from acute kidney injury (AKI) remains unclear. Our previous studies showed that autophagy occurred earlier than apoptosis during aristolochic acid (AAІ)-induced tubular epithelial cell injury. Autophagy could attenuate apoptosis, but excess autophagy increased non-apoptotic cell death and impaired cell regeneration. These results indicate that autophagy is associated with DNA repair. Persisted G2/M arrest-induced maladaptive repair is the initiation of tissue fibrosis. The objectives of this study are to investigate the role of autophagy in G2/M arrest in tubular epithelial cell, and its effect on the progression of AKI to CKD in AA-induced AKI model in vivo and vitro. Autophagy will be regulated by rapamycin (upregulation) and Atg7 gene knockout (downregulation). Furthermore, autophagy regulatory mechanism for G2/M arrest through DNA-damage checkpoint signaling pathway ATM/ATR-Chk1/Chk2 will also be examined. This study will likely reveal the relationship between autophagy and DNA repair as well as autophagy’s regulatory mechanism, which will provide experimental evidence for AKI to CKD progression mechanism and novel targets for its intervention.

肾小管上皮细胞DNA损伤可触发自噬及细胞周期G2/M期停滞。但自噬与G2/M期停滞的关系、调控机制及在急性肾损伤(AKI)慢性转归中的作用尚不清楚。我们以往研究报道，在马兜铃酸（AA）诱导的AKI中，肾小管上皮细胞自噬早于细胞凋亡发生，适度自噬抑制细胞凋亡；过量自噬则增加细胞非凋亡性死亡且细胞再生障碍。提示自噬与细胞DNA损伤修复相关。G2/M期持续停滞导致细胞修复不良是组织纤维化的始动环节。本项目以AA为损伤因子建立AKI小鼠和细胞模型，通过雷帕霉素上调自噬活性及特异性敲除Atg7致自噬缺陷，明确自噬在AKI肾小管上皮细胞G2/M期停滞中的作用及对AKI慢性化转归的影响；并从细胞DNA损伤检测点信号通路ATM/ATR-Chk1/Chk2不同级联探讨自噬调控G2/M期停滞的机制。本研究有助于揭示自噬与细胞DNA损伤修复的关系及调控机制，为AKI向CKD进展机制的阐明提供实验依据及干预靶点。

本项目已完成研究。我们的研究结果发现：1、AAI 10mg/kg单次腹腔注射C57BL/6小鼠可建立马兜铃酸肾病小鼠模型。随着AA作用时间进展，分别表现为急性损伤及慢性化转变的肾脏组织学特征性改变。AAN小鼠肾组织自噬出现在肾组织急性损伤期，早于肾组织G2/M检测点关键激酶（Chk1）活化及纤维化。2、中药关木通浸膏间断灌胃的方法可成功制备慢性AAN模型；AAN肾小管上皮细胞线粒体损伤随病程进展加重，12周时损伤最为严重；3、AA-I诱导HK-2发生自噬、DNA损伤、G2/M停滞及胶原分泌增多。沉默自噬相关基因ATG5上调G2/M停滞比例和G2/M检测点激酶Chk1（s345）磷酸化水平。提示抑制自噬通过促进Chk1活化而增加G2/M停滞，可能在AAN急性肾损伤慢性化病变中发挥作用。4、Nrf2活化受损是AA诱导肾小管上皮细胞损伤的机制之一，激活Nrf2信号通路可能通过其抗氧化应激效应而发挥细胞保护作用。综上所述，本研究自噬调控G2/M停滞在AA诱导急性肾损伤慢性化转归中的作用及机制；揭示自噬调控G2/M停滞的机制通过活化G2/M检测点关键激酶Chk1实现，而Nrf2 可通过其抗氧化应激效应发挥细胞保护作用。.本项目目前已发表论著2篇，均为SCI收录论文；综述2篇。2篇摘要参加美国肾脏病学会（ASN）进行壁报交流； 3篇摘要参加中国中西医结合学会肾脏疾病年会。2篇论文正在整理并撰写。