Reversal by high-density lipoprotein of the effect of oxidized low-density lipoprotein on nitric oxide synthase protein expression in human platelets.
Oxidized low-density lipoproteins (ox-LDLs) induce vasoconstriction and platelet activation, and high-density lipoproteins (HDLs) reverse these effects of ox-LDL. To determine the involvement of the L-arginine-nitric oxide (NO) pathway in the effects of lipoproteins on platelets, washed human platelets were incubated with native-LDL, ox-LDL, or HDL plus ox-LDL, but not native LDL, potentiated thrombin-induced platelet aggregation and carbon 14-labeled serotonin release, and these effects of ox-LDL were blocked by pretreatment of platelets with HDL. Incubation of ox-LDL with platelets resulted in reduction in the uptake of tritiated L-arginine by intact platelets and in NO synthase activity in platelet lysate. These effects of ox-LDL on platelet NO synthase activity were also reversed by pretreatment of platelets with HDL. Western blot analysis demonstrated about a 50% reduction in the expression of NO synthase protein in platelets treated with ox-LDL. Whereas HDL alone had no effect on NO synthase protein expression, it blocked the decrease in NO synthase expression caused by ox-LDL. Thus ox-LDL stimulates platelet function primarily by diminishing NO synthase expression, and this effect of ox-LDL can be blocked by pretreatment of platelets with HDL.
Mehta
J L
JL
Department of Medicine, Colege of Medicine, University of Florida, Gainesville 32610-0277, USA.
Chen
L Y
LY
D001120:Arginine / Q000493:pharmacokinetics; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism*; D002784:Cholesterol / Q000097:blood; D006801:Humans; D008074:Lipoproteins / Q000097:blood; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000097:blood*; D010974:Platelet Aggregation; D012701:Serotonin / Q000378:metabolism
D008074:Lipoproteins; D008077:Lipoproteins, LDL; C099252:oxidized low density lipoprotein; D012701:Serotonin; D001120:Arginine; D002784:Cholesterol; D019001:Nitric Oxide Synthase