Atherosclerotic and thrombotic disorders like CAD, MI, and hypercoagulability are associated with hypertriglyceridemia (HTG) by unknown mechanisms. Our goal is to test the hypothesis that the abnormal triglyceride-rich lipoproteins (TGRLP) in HTG subjects are mechanistically linked to both atherosclerosis and thrombosis. Basic studies address the hypothesis that HTG-TGRLP are thrombogenic by binding prothrombin, FX(FXa), and providing phospholipid for thrombin generation. Basic molecular interactions of coagulation factors(CF) with purified subspecies of native normal(N), and HTG-TGRLP, CF activation and its effects on apoprotein structure and cellular interactions will be characterized. Because of the complex and subtle structure of native TcRLP, model LP will then be used to pinpoint structural determinants of cF/TcRLP interaction. Cellular studies using native and model TcRLP subspecies test the hypotheses that HTG- TGRLP are: (1) atherogenic due to abnormal binding to the LDL receptor and/or a distinct macrophage receptor, converting macrophages into foam cells (this is exacerbated by thrombin cleavage of TGRLP). (2) Thrombogenic by promoting endothelial cell (EC) procoagulant activity (increase tissue factor (TF), decrease thrombomodulin (TM) activity) and by inhibiting the net activators (PA); stimulate synthesis and (inhibit release and synthesis of plasminogen release of PA inhibitors (PAI)). Clinical studies test the hypothesis that TGRLP from subjects with documented MI show increased proteolysis of apoproteins due to associated activated CFs such TGRLP are more atherogenic and/or thrombogenic than TGRLP from subjects with similar TG levels but no evidence of MI/CAD. Methods include binding studies of radiolabeled CFs with model TGRLP of defined lipid, apoprotein, and factor content and native N- and HTG-TGRLP subspecies isolated by ultracentrifugation and affinity chromatography; assays for CF activation; cell studies in fibroblasts, P388D1 and THP-l macrophages, and porcine aortic and human umbilical vein ECs; binding of TGRLP plus/minus CFs to LDL and macrophage receptors in cells and in ligand blots; TG,C macrophage loading; cellular clotting assays for TF activity/antigen and TM; SDS PAGE 125I-fibrin well assays for t- PA, u-PA, and PAI activity/antigen; cDNA probes mRNA levels for synthesis of TF, TM, t-PA, u-PA, and PAI. These studies should provide insights into the basic molecular and cellular causes of atherosclerosis and thrombosis in HTG.
| Bradley, W A; Gianturco, S H (1994) Triglyceride-rich lipoproteins and atherosclerosis: pathophysiological considerations. J Intern Med Suppl 736:33-9 |
