Aldehyde Dehydrogenase 2 Protects Against Acute Kidney Injury by Regulating Autophagy via PI3KC3/Beclin-1 Pathway

Background: Recent studies have called into question the effectiveness of the widely used intravenous saline, sodium bicarbonate and oral acetylcysteine for the treatment of Acute kidney injury (AKI). To investigate the pathogenesis of AKI and develop new treatment and prevention protocols, the present study explored the effect and mechanisms of aldehyde dehydrogenase 2 (ALDH2) on AKI. Method: Wild-type, ALDH2 overexpression or knockout mice were tested in radiocontrast agent Iohexol or renal ischemia/reperfusion induced acute kidney injury models. Autophagy, cell apoptosis and reactive oxygen species were detected by western blot, immunohistochemistry, immunofluorescence and transmission electron microscopy. Autophagy flux was measured using mRFP-GFP-LC3 adenovirus transfection in HK-2 cells. Finding: ALDH2 knockout mice were at significantly greater risk for developing AKI. Activated ALDH2 significantly protected from AKI by attenuating ROS level, tubular damage, renal tissue apoptosis and cleaved caspase-3 expression. mRNA-Seq revealed a positive connection between ALDH2 activation and autophagy regulator BECN1. Transmission electron microscopy images shown a significantly increase of autophagic vacuoles and autolysosomes in ALDH2 activation mice epithelial kidney tubule cells. Western blot, immunohistochemistry and immunofluorescence analysis showed the expression of PI3KC3, Beclin1 and LC3BII/LC3BI were notably increased in vivo and vitro with overexpression or activation of ALDH2. 3-Methyladenine, an inhibitor of autophagy via its inhibitory effect on PI3KC3, mitigated ALDH2-induced protection against renal injury and increased generation of ROS and cell apoptosis in vivo and vitro. Interpretation: Activation of ALDH2 protected against AKI by promoting autophagic activation in close association with the PI3KC3/Beclin-1 pathway. These findings raise a significant concern regarding the therapeutic approaches that rely on activation of ALDH2 pathway for the management of AKI. Greater attention to AKI might have to be paid in the setting of ALDH2 gene mutation (present in almost 8% of the global population). Funding Statement: This work was supported by National Natural Science Foundation of China [81873950,81571934, 81570401, 81671952, 81601717, 81772036, 81873953], National Key R&D Program of China [2017YFC0908700, 2017YFC0908703], National S&T Fundamental Resources Investigation Project [2018FY100600, 2018FY100602], Taishan Young Scholar Program of Shandong Province [tsqn20161065, tsqn201812129], Taishan Scholar Climbing Program of Shandong Province [tspd20181220], The Key R&D Program of Shandong Province [2016ZDJS07A14, 2016GSF201235, 2017G006013, 2018GSF118003, 2018GSF118122], and Fundamental Research Funds of Shandong University [2018JC011]. Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: All animal procedures performed conform to the guidelines from directive 2010/63/EU of the European Parliament on the protection of animals used for scientific purposes and were approved by the Animal Use and Care Committee of Shandong University.