Elevated levels of lipoprotein(a) (Lp[a]) are a causal risk factor for atherosclerotic cardiovascular disease. Similarities between the apolipoprotein(a) (apo[a]) component of Lp(a) and plasminogen su Show more
Elevated levels of lipoprotein(a) (Lp[a]) are a causal risk factor for atherosclerotic cardiovascular disease. Similarities between the apolipoprotein(a) (apo[a]) component of Lp(a) and plasminogen suggest that antifibrinolytic properties may account for the pathological effects of Lp(a). However, the antifibrinolytic effects of apo(a) do not appear to be retained by the complete Lp(a) particle. We evaluated the effects of Lp(a), apo(a), and various apo(a) variants on clot formation and lysis times, thrombin generation, plasminogen activation, and fibrin architectures in ex vivo plasma clots. We also constructed predictive protein models to gain insight into the apo(a)-plasminogen interaction. Apo(a) strongly inhibited fibrinolysis, an effect dependent on the presence of the apo(a) protease domain and mediated by Lys216 in this domain. Modeling of apo(a) suggests that Lys216 is blocked from binding to plasminogen in the Lp(a) particle by the presence of the apoB-containing lipoprotein. Lp(a) and apo(a) shortened plasma clot formation times, and accounting for this revealed a small but significant prolongation of fibrinolysis by Lp(a). The procoagulant effects involved the development of lysis-resistant clot architectures and were mediated through the strong lysine-binding site in apo(a) kringle IV type 10. In addition, Lp(a) (but not apo[a]) accelerated thrombin generation. The strong antifibrinolytic effects of apo(a) do not appear to be retained in the complete Lp(a) particle. However, Lp(a) and apo(a) displayed procoagulant effects, in part dependent on the kringle 4-like lysine-binding site. Further analysis is required to determine whether these reported procoagulant effects of Lp(a) impact thrombosis in vivo. Show less