Phosphatidylserine is a Key Component of High-density Lipoproteins (HDLs) Determining their Atheroprotective Functions
Anatol Kontush,1 Laurent Camont,1 Marie Lhomme,1 Fabiana Rached,1,2 Wilfried Le Goff,1 Carolane Dauteuille,1 Isabelle Guillas-Baudouin,1 Anne Nègre-Salvayre,3 Robert Salvayre,3 Catherine Calzada,4 Michel Lagarde,4 Kerry-Anne Rye,5 M. John Chapman1
1 UMR INSERM-UPMC 1166 ICAN; University of Pierre and Marie Curie – Paris 6; AP-HP, Groupe Hospitalier Pitié Salpétrière; ICAN, Paris, France; 2 Heart Institute-InCor, University of Sao Paulo Medical School Hospital, Sao Paulo, Brazil; 3 INSERM UMR-1048; Faculty of Medicine, Department of Biochemistry, University of Toulouse, Toulouse, France; 4 INSERM UMR-1060, Université de Lyon, Cardiovasculaire, Métabolisme, Diabétologie, et Nutrition (CarMeN), INSA-Lyon, IMBL, Lyon, France
5 Centre for Vascular Research, University of New South Wales, Sydney, Australia

HDL displays multiple atheroprotective activities and is heterogeneous in structure, composition and function; the molecular determinants of HDL functions are incompletely understood. As phospholipids represent principal HDL components, we characterised the phosphosphingolipidome of five major normolipidemic HDL subpopulations and related it to HDL function. Using LC-MS/MS methodology, 162 individual molecular lipid species were quantified across the nine lipid subclasses, in the order of decreasing abundance, phosphatidylcholine > sphingomyelin (SM) > lysophosphatidylcholine (LPC) > phosphatidylethanolamine > phosphatidylinositol > ceramide > phosphatidylserine (PS) > phosphatidylglycerol > phosphatidic acid (PA). When data were expressed relative to total lipid, the contents of LPC, PS and PA increased progressively with increase in hydrated density of HDL, whereas the proportions of SM and ceramide decreased. Key biological activities of HDL subpopulations, notably cholesterol efflux capacity from human THP-1 macrophages, antioxidative activity towards low-density lipoprotein oxidation, anti-thrombotic activity in human platelets, cell-free anti-inflammatory activity and anti-apoptotic activity in endothelial cells, were predominantly associated with small, dense, protein-rich HDL3. The biological activities of HDL particles exhibited significant correlations with multiple components of the HDL phosphosphingolipidome. Intriguingly, the content of PS revealed positive correlations with all metrics of HDL function. When PS was included into reconstituted phosphatidylcholine-based HDLs (rHDLs), their biological activities were significantly enhanced. Most strikingly, PS-containing rHDLs fully inhibited proinflammatory activation of human macrophages, indicative of their strong anti-inflammatory potential. Inclusion of PS into rHDL also improved cholesterol efflux capacity together with antioxidative, anti-thrombotic and anti-apoptotic activities of HDL. These data identify PS as a key component of HDL determining its biological function.