Lipid-Raft Redox Signaling Platform And Apoptosis Of Podocytes Upon Homocysteine Stimulation

Lipid raft (LR) redox signaling platform associated with NADPH oxidase (NOX) was reported to mediate the actions of death receptor activation in different cells. It is interesting to know whether this LR redox signaling platform is also involved in podocytes injury during hyperhomocysteinemia. The present study first characterized the presence of the NOX membrane subunit‐gp91 phox and it LR clusters in podocytes, and then tested whether this redox signaling platform contributes to homocysteine (Hcys)‐induced podocytes apoptosis. It was found that Hcys markedly increased the expression of gp91 phox and stimulated NOX‐dependent superoxide (O 2 .− ) production in a concentration‐dependent manner, as measured by electronic spin resonance (ESR). Using confocal microscopy, gp91 phox was found to aggregate in LR clusters upon Hcys stimulation, which was inhibited by lipid‐raft disruptors, methyl‐β ‐cyclodextrin (MCD) and filipin. Functionally, increased O 2 .− production associated with these LR‐gp91 phox platform was also blocked by MCD or filipin. Flow cytometry showed that Hcys induced podocytes apoptosis, which could be attenuated by gp91 phox siRNA or LR disruptors. Our results indicate that the formation of gp91 phox ‐associated LR redox signaling platform importantly contributes to podocytes injury during exposure to high Hcys levels (supported by NIH grants DK54927, HL075316, and HL57244).