Spiders of the genus Loxosceles represent a public health problem in Brazil due to the severity of the cutaneous and systemic effects that may result from their bite. In the systemic form of loxoscelism, hemolytic anemia, thrombocytopenia, and disseminated intravascular coagulation can occur. Despite the seriousness of Loxosceles accidents, the venom of some species has not yet been properly characterized considering these hemotoxic effects, such as that of Loxosceles amazonica, Loxosceles aff. Variegata, and Loxosceles similis. To better understand their toxic potential, this study aimed to characterize the hematotoxic properties of these Loxosceles venoms. The crude venom was obtained from specimens of L. amazonica, L. aff. Variegata, and L. similis available from Funed's arachnidary. In washed platelets, L. aff. variegata inhibited platelet aggregation induced by collagen and convulxin, whereas L. amazonica and L. similis venoms were able to induce platelet aggregation. In the in vitro hemolysis assays, all venoms experimentally induced direct hemolysis of human erythrocytes in a concentration-dependent manner, with different intensities. Furthermore, evidence suggest that the ABO and Rh systems may influence hemolytic activity. Finally, the studied Loxosceles venoms degraded fibrinogen, suggesting possible alterations in the coagulation cascade. Based in the here-presented preliminary study, in vivo assays in model animals are needed to verify the real toxic potential of these species' venom, building up knowledge to elucidate the action of Loxosceles venoms in blood.
Keywords: Loxosceles; fibrinogenolysis; hemolysis; platelet aggregation; spider venom.