Contribution of Lysosomal Vesicles to the Formation of Lipid Raft Redox Signaling Platforms in Endothelial Cells

We have demonstrated that the formation of lipid raft (LR)-redox signaling platforms membrane is associated with activation of acid sphingomyelinase (ASMase) in coronary arterial endothelial cells (CAECs). Given that the trafficking of lysosomal vesicles might play an essential role in ASMase activation, the present study tested whether lysosomal vesicles contribute to the formation of LR redox signaling platforms. By confocal microscopy, we found that Fas ligand (FasL) induced the formation of LR clusters in the plasma membrane of CAECs, accompanied by aggregation of NAD(P)H oxidase subunits, gp91 ^phox and p47 ^phox , and ROS production. When the cells were pretreated with two structurally different lysosomal vesicle function inhibitors, bafilomycin A1 (Baf) and glycyl-L-phenylalanine-β-naphthylamide (GPN), the FasL-induced LRs clustering was substantially blocked, and corresponding ROS production significantly decreased. By confocal microscopic observations in living CAECs by using LysoTracker, a colocalization of LRs and lysosomal vesicles was found around the cell membrane, which was abolished by Baf or GPN. Functionally, FasL-induced inhibition of endothelium-dependent vasorelaxation was also reduced by both inhibitors of lysosome function. These results suggest that lysosomal vesicles importantly contribute to the formation of LR-redox signaling platforms and thereby participate in the oxidative injury of endothelial function during activation of death receptor-Fas in coronary arteries.