Venom from Loxosceles Spiders Collected in Southeastern and Northeastern Brazilian Regions Cause Hemotoxic Effects on Human Blood Components

Spiders of the genus <i>Loxosceles</i> 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 <i>Loxosceles</i> accidents, the venom of some species has not yet been properly characterized considering these hemotoxic effects, such as that of <i>Loxosceles amazonica</i>, <i>Loxosceles aff. Variegata</i>, and <i>Loxosceles similis</i>. To better understand their toxic potential, this study aimed to characterize the hematotoxic properties of these <i>Loxosceles</i> venoms. The crude venom was obtained from specimens of <i>L. amazonica</i>, <i>L. aff. Variegata</i>, and <i>L. similis</i> available from Funed's arachnidary. In washed platelets, <i>L. aff. variegata</i> inhibited platelet aggregation induced by collagen and convulxin, whereas <i>L. amazonica</i> and <i>L. similis</i> 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 <i>Loxosceles</i> 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 <i>Loxosceles</i> venoms in blood.