Abstract 671: High Density Lipoprotein Restores Impaired Re-Endothelialization Capacity of Endothelial Progenitor Cells from Patients with Metabolic Syndrome via Lysophospholipid Receptor S1P3-mediated NAD(P)H Oxidase Inhibition
Introduction: Recent studies suggest that endothelial injury in the absence of sufficient endothelial progenitor cells (EPCs) promotes progression of vascular disease. High density lipoprotein (HDL) is thought to mediate vasoprotection, however, the underlying mechanisms remain to be characterized.
Hypothesis: The present study examines the effect of HDL from healthy subjects (HS) and patients with metabolic syndrome (MetS) on in vivo re-endothelialization capacity of EPCs and characterizes underlying mechanisms.
Methods: In vivo endothelial regeneration capacity of EPCs from HS and patients with MetS was determined by transplantation of EPCs (5x105 cells) into nude mice using a carotid endothelial injury model. Re-endothelialized area (REA) was assessed after 3 days. The effect of HDL isolated by ultracentrifugation from HS and MetS patients on re-endothelialization capacity of EPCs was determined. NAD(P)H oxidase activity, superoxide (O2.−) and nitric oxide (NO) production were analyzed by ESR spectroscopy. siRNA transfection for scavenger receptor-BI (SR-BI) and lysophospholipid receptor S1P3 of EPCs was used to determine the receptor responsible for HDL effects.
Results: Re-endothelialization capacity of EPCs from MetS patients was markedly impaired (REA HS vs. MetS: 37±10 vs. 7±3 %; P<0.001). HDL from HS, but not from MetS patients, restored re-endothelialization capacity of EPCs from MetS patients (REA 32±11%; P<0.001 vs. no HDL). HDL from HS, but not from MetS patients, reduced NAD(P)H oxidase activity and O2.− production and increased NO availability of EPCs from patients with MetS. Knockdown of S1P3, but not SR-BI, abolished the effect of HDL on NAD(P)H oxidase in EPCs. siRNA inhibition of p47phox, a critical NAD(P)H oxidase component, restored re-endothelialization capacity of EPCs from patients with MetS.
Conclusions: HDL from healthy subjects restores in vivo re-endothelialization capacity of EPCs from patients with MetS, at least in part by NAD(P)H oxidase inhibition via lysophospholipid receptor S1P3. HDL from MetS patients has a markedly reduced effect on EPC re-endothelialization capacity as compared to HDL from healthy subjects, suggesting a loss of important vasoprotective properties of HDL in metabolic syndrome.