Endothelium-protective sphingosine-1-phosphate provided by HDL-associated apolipoprotein M
Protection of the endothelium is provided by circulating sphingosine-1-phosphate(S1P), which maintains vascular integrity. We show that HDL-associated S1P is bound specifically to both human and murine apolipoprotein M (apoM). Thus, isolated human ApoM(+) HDL contained S1P, whereas ApoM(-) HDL did not. Moreover, HDL in Apom(-/-) mice contains no S1P, whereas HDL in transgenic mice overexpressing h
