AGE receptor 1 silencing enhances advanced oxidative protein product-induced epithelial-to-mesenchymal transition of human kidney proximal tubular epithelial cells via RAGE activation

Abstract

Advanced oxidative protein products (AOPPs) are novel uremic toxins whose concentrations continuously increases in patients with chronic kidney disease (CKD). Epithelial-to-mesenchymal transition (EMT) of tubular cells is the main mechanism underlying CKD pathogenesis. Studies have shown that AOPPs can induce EMT and promote renal fibrosis. However, the mechanism through which AOPPs induce tubular cell-EMT is poorly understood. In this study, we aimed to clarify the mechanisms underlying AOPP-induced EMT in human kidney proximal tubular (HKC-8) epithelial cells. Small molecule inhibitor, CRISPR-Cas9 knockout technology, siRNA knockdown technology, western blot, and reverse transcription-quantitative polymerase chain reaction were applied to investigate the mechanisms underlying AOPP-induced EMT in HKC-8 cells. AOPP treatment was found to significantly induce EMT, as evidenced by increased α-smooth muscle actin (α-SMA) and decreased E-cadherin levels, and upregulated Wnt1, β-catenin, Tcf4, and Gsk-3β expression. Conversely, blockade of Wnt/β-catenin signaling using small molecule inhibitor ICG-001 hindered AOPP-induced EMT. Moreover, knockout of receptor of advanced glycation end-products (RAGE) reversed these aforementioned effects, whereas AGE receptor 1 (AGER1)-specific siRNA transfection enhanced them. Taken together, these data suggested that AOPPs could induce HKC-8 cell EMT by activating the RAGE/Wnt/β-catenin signaling pathway and AGER1 could restore EMT by antagonizing the role of RAGE. These results may provide a new theoretical basis for EMT and help identify new therapeutic targets for suppressing CKD progression.