interleukin-8 and dihydroceramide

The sphingolipid ceramide mediates a variety of stress responses, including vascular inflammation and thrombosis. Activated endothelial cells release Weibel-Palade bodies, granules containing von Willebrand factor (vWF) and P-selectin, which induce leukocyte rolling and platelet adhesion and aggregation. We hypothesized that ceramide induces vascular inflammation and thrombosis in part by triggering Weibel-Palade body exocytosis. We added ceramide to human aortic endothelial cells and assayed Weibel-Palade body exocytosis by measuring the concentration of vWF released into the media. Exogenous ceramide induces vWF release from endothelial cells in a dose-dependent manner. Activators of endogenous ceramide production, neutral sphingomyelinase, or tumor necrosis factor-alpha also induce Weibel-Palade body exocytosis. We next studied NO effects on ceramide-induced Weibel-Palade body exocytosis because NO can inhibit vascular inflammation. The NO donor S-nitroso-N-acetylpenicillamine decreases ceramide-induced vWF release in a dose-dependent manner, whereas the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester increases ceramide-induced vWF release. In summary, our findings show that endogenous ceramide triggers Weibel-Palade body exocytosis, and that endogenous NO inhibits ceramide-induced exocytosis. These data suggest a novel mechanism by which ceramide induces vascular inflammation and thrombosis.

Topics: Aorta; Cells, Cultured; Ceramides; Desipramine; Dose-Response Relationship, Drug; Egtazic Acid; Endothelial Cells; Endothelium, Vascular; Enzyme Inhibitors; Exocytosis; Humans; Interleukin-8; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Sphingomyelin Phosphodiesterase; Tumor Necrosis Factor-alpha; Weibel-Palade Bodies