Homocysteine-thiolactone induces caspase-independent vascular endothelial cell death with apoptotic features

Objective. Cell death is generally classified into two large categories: ap optosis, which represents active, physiological programmed cell death, and necrosis, which represents passive cell death without underlying regulatory mechanisms. Apoptosis plays an important role in tissue homeostasis and it s role in endothelium integrity can be influenced by the functional status of endothelial cells. Homocysteine, a sulfated amino-acid product of methio nine demethylation, is an independent risk factor for vascular disease (art erial and venous thombosis). Our goal was to investigate the thiol-derivati ves effect on the endothelial cell apoptosis. Methods. Three parameters wer e measured: mitochondrial membrane potential using DiOC(6)(3) as the probe, DEVDase activation, and phosphatidylserine exposure on the cell surface wi th fluorosceinated annexin V labeling which allows apoptosis to be distingu ished from necrosis. Results. Homocysteine-thiolactone induced endothelial cell apoptosis in a concentration-dependent manner (range: 50-200 muM), ind ependently of the caspase pathway. Only homocysteine-thiolactone, among the thiol derivatives tested, induced apoptosis. Apoptosis was not influenced by the serum concentration in culture medium, suggesting that the observed apoptotic process could occur in vivo. None of the inhibitors used (e.g., l eupeptin, fumosinin Bl, catalase, or z-VAD-fmk) was able to prevent homocys teine-induced apoptosis of vascular endothelial cells. Conclusion. The apop tosis of vascular endothelial cells induced by high concentration of homocy steine-thiolactone might be one step atherosclerotic cardiovascular disease , and contribute to its complication.