Thrombomodulin-dependent effect of factor V Leiden mutation on the cross-linking of α2-plasmin inhibitor to fibrin and its consequences on fibrinolysis

Abstract Introduction It has been shown that thrombomodulin (TM) considerably delays factor XIII (FXIII) activation and this effect is abrogated by Factor V Leiden (FV Leiden ) mutation. The aim of the study was to explore the effect of TM on the cross-linking of α 2 -plasmin inhibitor (α 2 -PI) to fibrin in plasma samples of different FV genotypes and how this effect is related to the impaired fibrinolysis of FV Leiden carriers. Methods In the plasma samples of fifteen individuals with different FV genotypes and in FV deficient plasma supplemented with wild type FV or FV Leiden coagulation was initiated by recombinant human tissue factor and phospholipids with or without recombinant human TM (rhTM). In the recovered clots the extent of α 2 -PI-fibrin cross-linking was evaluated by Western blotting and quantitative densitometry. The effect of rhTM on tissue plasminogen activator (tPA) induced clot lysis was measured by turbidimetric method. Results rhTM significantly delayed the formation of α 2 -PI-fibrin α-chain heterodimers/oligomers in plasma samples containing wild type FV. This effect of rhTM was impaired in the presence of FV Leiden . rhTM delayed tPA-induced clot lysis and this effect of rhTM was more pronounced in plasma containing FV Leiden . When TAFIa was inhibited by potato carboxypeptidase inhibitor, rhTM accelerated clot lysis in the presence of wild type FV, which is explained by the delayed α 2 -PI-fibrin cross-linking. This effect of rhTM did not prevail in the presence of FV Leiden . Conclusion FV Leiden abrogates the delaying effect of rhTM on α 2 -PI-fibrin cross-linking, which contributes to the impaired fibrinolysis observed in FV Leiden carriers.