Homocysteine induces epithelial‐to‐mesenchymal transition of podocytes through the activation of NADPH oxidase

Abstract

Our previous studies have demonstrated that hyperhomocyteinemia (hHcys) induced glomerulosclerosis through the activation of NADPH oxidase (Nox). However, it remains unknown how homocysteine (Hcys) produces detrimental effects on podocytes. The present study tested the hypothesis that Hcys may induce epithelial‐to‐mesenchymal transition (EMT) in podocytes through the activation of Nox. Mouse podocytes were incubated with L‐Hcys, a pathogenic isoform of Hcys. It was found that L‐Hcys (80 μM) induced a dramatic increase in the expression of Nox subunits and subsequent superoxide (O2.‐) production (2.9 folds vs. control), which was accompanied by significantly decreased expression of slit diaphragm‐associated protein, P‐cadherin and zonula occludens‐1, a change consistent with loss of the epithelial feature. Meanwhile, L‐Hcys induced the expression of mesenchymal markers, fibroblast‐specific protein‐1 and α‐smooth muscle actin. Nox inhibitors significantly reversed these Hcys‐induced changes in podocytes. In functional studies, L‐Hcys was found to increase dextran permeability across podocyte monolayers by 1.9 folds, which was inhibited by Nox inhibitors. These results suggest that an EMT occurs in podocytes due to cellular oxidative stress during hHcys and that enhanced EMT may result in podocyte dysfunction leading to glomerulosclerosis (supported by NIH grants DK54927 and HL075316).