Bothrops erythromelas and Bothrops leucurus venoms exhibit distinct coagulotoxic profiles with differential effects on coagulation and platelets

Investigations conducted in the present study explore the haemostatic disturbances induced by Bothrops erythromelas and Bothrops leucurus venoms, two medically important species not included in the immunizing venom pool for bothropic antivenom production in Brazil. Both venoms trigger human platelet activation and aggregation sensitive to snake venom metalloproteases (SVMPs) inhibitors, potentially through protease-activated receptor 1 (PAR-1) activation; however, B. erythromelas exhibits significantly higher potency. Conversely, B . leucurus -induced platelet aggregation also displays sensitivity to snake venom serine proteases (SVSPs) inhibitors. Within the coagulation cascade, B. erythromelas shows higher Factor XII and Factor X activation attributed to SVMPs, whereas B. leucurus features prominent kallikrein-like and thrombin-like enzyme (TLE) activities driven by SVSPs. Mechanistically, results suggest that B. erythromelas processes prothrombin to yield cleavage products with apparent molecular masses corresponding to prethrombin-1 and thrombin, while B. leucurus produces an ~ 45 kDa fragment consistent with meizothrombin molecular mass. B. erythromelas and B. leucurus venoms display fibrinogenolytic action, driving a pseudo-procoagulant consumption profile and unstable clot formation. In vitro assays demonstrated limited efficacy of Bothropic Anti-venom (BAV) in neutralizing platelet aggregation and procoagulant mechanisms at the tested BAV-to-venom ratios, though BAV remains the clinically essential specific treatment. Interestingly, the small-molecule metalloproteinase inhibitor marimastat drastically reduced platelet aggregation and clotting cascade activation across both species. Furthermore, combining marimastat with BAV improved neutralization compared to antivenom alone, suggesting its high potential as an adjuvant therapeutic strategy for managing bothropic envenomation. Altogether, we show distinct mechanisms through which B. erythromelas and B. leucurus induce platelet aggregation and coagulotoxicity.