HDL₃-Mediated Inhibition of Thrombin-Induced Platelet Aggregation and Fibrinogen Binding Occurs via Decreased Production of Phosphoinositide-Derived Second Messengers 1,2-Diacylglycerol and Inositol 1,4,5-tris-Phosphate

Abstract

Abstract-We demonstrate that physiological concentrations of HDL 3 inhibit the thrombin-induced platelet fibrinogen binding and aggregation in a time-and concentration-dependent fashion. The underlying mechanism includes HDL 3 -mediated inhibition of phosphatidylinositol 4,5-bis-phosphate turnover, 1,2-diacylglycerol and inositol 1,4,5-tris-phosphate formation, and intracellular calcium mobilization. The inhibitory effects of HDL 3 on inositol 1,4,5-tris-phosphate formation and intracellular calcium mobilization were abolished after covalent modification of HDL 3 with dimethylsuberimidate. Furthermore, they could be blocked by calphostin C and bis-indolylmaleimide, 2 highly selective and structurally unrelated protein kinase C inhibitors. However, the inhibitory effects of HDL 3 were not blocked by H89, a protein kinase A inhibitor. In addition, HDL 3 failed to induce cAMP formation but stimulated the phosphorylation of the protein kinase C 40-to 47-kD major protein substrate. We observed a close temporal relationship between the HDL 3 -mediated inhibition of thrombininduced inositol 1,4,5-tris-phosphate formation, intracellular calcium mobilization, and fibrinogen binding and the phosphorylation of the protein kinase C 40-to 47-kD major protein substrate. Taken together, these findings indicate that the HDL 3 -mediated inhibition of thrombin-induced fibrinogen binding and aggregation occurs via inhibition of phosphatidylinositol 4,5-bis-phosphate turnover and formation of 1,2-diacylglycerol and inositol 1,4,5-tris-phosphate. Protein kinase C may be involved in this process. (Arterioscler Thromb Vasc Biol. 1998;18:861-869.)Key Words: high-density lipoprotein Ⅲ protein kinase C Ⅲ signal transduction Ⅲ platelet aggregation Ⅲ fibrinogen B oth HDL and platelets are intimately involved in the pathogenesis of atherosclerosis, thrombosis, and coronary heart disease.1-3 Numerous observations demonstrated a direct effect of HDL on platelet functions.4 Platelet hyperreactivity was noted in subjects with hypoalphalipoproteinemia.5 Decreased activation of platelets by strong agonists such as thrombin and collagen has been reported in the presence of physiological concentrations of HDL.6-8 Furthermore, HDL inhibited thromboxane A 2 liberation, and addition of HDL to clotting blood diminished platelet thromboxane A 2 formation capacity. 9,10The mechanism underlying the effects of HDL on platelet function is little understood. HDL 3 , the major HDL subfraction in blood, is known to interact with specific binding sites on platelets that appear to be identical with GP IIb/IIIa. [11][12][13][14] In human platelets, HDL 3 was also shown to activate cellular phospholipases, resulting in the formation of DAG.15-18 The involvement of both phosphatidylcholine-specific phospholipase C and phosphatidylcholine-specific phospholipase D was postulated. 16 -18 Recently, the PKC-dependent enhancement of the Na ϩ /H ϩ antiport in the presence of HDL 3 has been reported. 19Both HDL 3 -induced DAG formation and Na ϩ /H ϩ exchange stimulation w...

HDL and Atherothrombotic Vascular Disease

“…A similar decrease in the aggregation of platelets was observed when isolated human platelets were incubated with rHDLs or native HDLs in vitro (Calkin et al 2009;Nofer et al 1998;Badrnya et al 2013). Native HDLs and rHDLs not only modulate platelet aggregation but also prevent platelet degranulation and spreading as well as adhesion of platelets to fibrinogen (Calkin et al 2009;Nofer et al 1998;Badrnya et al 2013). In addition, rHDLs limited the incorporation of platelets in growing thrombi under flow conditions in vitro (Calkin et al 2009).…”

“…Study results established that a 40 % increase in HDL cholesterol levels in patients with type 2 diabetes mellitus was associated with a 50-75 % reduction in platelet aggregation (Calkin et al 2009). A similar decrease in the aggregation of platelets was observed when isolated human platelets were incubated with rHDLs or native HDLs in vitro (Calkin et al 2009;Nofer et al 1998;Badrnya et al 2013). Native HDLs and rHDLs not only modulate platelet aggregation but also prevent platelet degranulation and spreading as well as adhesion of platelets to fibrinogen (Calkin et al 2009;Nofer et al 1998;Badrnya et al 2013).…”

Advanced glycation of apolipoprotein A-I impairs its anti-atherogenic properties

“…Bar=10 μm modification [40]. In addition to their role in RCT, apoA-I and HDL have other anti-atherogenic functions, including anti-inflammatory [32], antioxidant [41] and antithrombotic actions [42]. Hence, AGE modification of apoA-I may have wide-ranging implications for the development of atherosclerosis, particularly in the setting of diabetes.…”

Relationship Between Adiponectin and Glycemic Control, Blood Lipids, and Inflammatory Markers in Men With Type 2 Diabetes

“…Hyperglycemia acutely increases circulating cytokine concentrations (38,39). HDL cholesterol downregulates expression of adhesive molecules on the surface of vascular endothelium (40) and inhibits platelet aggregation (41) and thus has anti-inflammatory and antithrombotic properties. However, adjustment for HDL cholesterol and HbA 1c in our study only slightly attenuated the association between adiponectin and CRP and fibrinogen.…”