Increase of Oxidative Stress by Deficiency of The ALDH2/UCP2/Nrf2 Axis Exacerbates Cardiac Dysfunction in Chronic Kidney Disease

Background: Both epidemiologic and experimental studies have evidenced that chronic kidney disease (CKD) could increase the incidence and risk of cardiac dysfunction, especially in aging patients. However, the underlying mechanisms are still not fully understood. Methods: In this study, we used 8 weeks old male wild-type (WT) C57BL/6 mice and ALDH2 knockout (ALDH2-/-) mice with C57BL/6 background. Here the 5/6 nephrectomy (NX) mouse model was constructed to study how CKD affects cardiac function and explored the related role of aldehyde dehydrogenase 2 (ALDH2), a well-established cardioprotective factor, in this process. Results: Compensatory cardiac hypertrophy was found in wild type (WT) mice 12 weeks post 5/6 NX as shown by increased left ventricular wall thickness (LVWD), cross-sectional area (CSA) of cardiomyocytes, and preserved left ventricular ejection fraction (EF) and fractional shorten (FS). Deficiency of ALDH2 (ALDH2-/-) significantly reduced EF and FS as compared with WT mice 12 weeks post 5/6 NX, while left ventricular hypertrophy was similar between the two NX groups. ALDH2-/- CKD groups showed more severe nephritic damages and increased fibrosis deposition in hearts. Besides, levels of reactive oxygen species (ROS) and apoptosis were also significantly upregulated in hearts of ALDH2-/- NX mice. The above changes were related with decreased expressions of uncoupling protein 2 (UCP2) and nuclear factor like 2 (Nrf2), as well as the downstream effectors of Nrf2 (heme oxygenase-1, HO-1 and superoxide dismutase 2, SOD2). Conclusions: Our data indicated that ALDH2 deficiency did not affect NX-induced left ventricular hypertrophy, but could increase oxidative stress and exacerbate CKD-induced cardiac dysfunction, partly via downregulation of UCP2 and Nrf2/ARE (antioxidant response element) pathways.