Glycated high-density lipoprotein induces apoptosis of endothelial cells via a mitochondrial dysfunction

Glycation of plasma proteins may contribute to an excess risk of developing atherosclerosis in patients with diabetes mellitus. Although it is believe d that high-density lipoprotein (HDL) is nonenzymatically glycosylated at a n increased level in diabetic individuals, little is known about a possible linkage between glycated HDL and endothelium. dysfunction in diabetes. Thi s study set out to clarify whether glucose-modified HDL affects the functio n of endothelial cells by examining the apoptosis of cultured human aortic endothelial cells (HAECs) exposed to a glycated-oxidized HDL (gly-ox-HDL) p repared in vitro. Incubation of HAECs with 100 mug/ml of gly-ox-HDL for 48 h showed apoptotic features, such as cell shrinkage, membrane blebbing, and concentration and fragmentation of the nucleus, and the degree of apoptosi s was dose-dependent on the glucose used in the preparation of gly-ox-HDL. Stimulation of HAECs with gly-ox-HDL elicited a marked increase in caspase 3 activity and the expressions of active caspase 3 and caspase 9, whereas c oncomitant treatment with a caspase 3 inhibitor significantly blocked gly-o x-HDL-induced apoptosis of HAECs. The release of cytochrome c into cytosols markedly increased in HAECs during the treatment with gly-ox-HDL. The incr eased expressions of Bax and Bad were detected in HAECs incubated for 24 h with gly-ox-HDL, but gly-ox-HDL failed to interfere with the expression of Bcl-2 and Bcl-x. Moreover, in vitro experiments with HDL (gly-HDL) glycated in the presence of 2 mM EDTA and Cu2+-oxidized HDL suggested that the apop totic effect of gly-ox-HDL on endothelial cells might be due to an addition al oxidative modification of gly-HDL. Taken altogether, additional oxidatio n of HDL under hyperglycemic conditions may induce endothelial apoptosis th rough a mitochondrial dysfunction, following the deterioration of vascular function. (C) 2001 Academic Press.