Small, dense HDL3 particles attenuates apoptosis in endothelial cells: Pivotal role of apolipoprotein A-I

International audience; Abstract Plasma high-density lipoprotein (HDL) protect endothelial cells against apoptosis induced by oxidatively modified low-density lipoprotein (oxLDL). The specific component(s) of HDL implicated in such cytoprotection remain(s) to be identified. Human microvascular endothelial cells (HMEC-1) were incubated with mildly oxLDL in the presence or absence of each of five physicochemically-distinct HDL subpopulations fractionated from normolipidemic human plasma (n=7) by isopycnic density gradient ultracentrifugation. All HDL subfractions protected HMEC-1 against oxLDL-induced primary apoptosis as revealed by nucleic acid staining, annexin V binding, quantitative DNA fragmentation, inhibition of caspase-3 activity, and reduction of cytoplasmic release of cytochrome c and apoptosis-inducing factor. Small, dense HDL3c displayed twofold superior intrinsic cytoprotective activity (as determined by mitochondrial dehydrogenase activity) relative to large, light HDL2b on a per particle basis (p