Atividades biológicas do veneno de serpentes Bothrops atrox capturadas na Floresta Nacional do Tapajós, Oeste do Pará

Abstract

Bothrops atrox (Ba) snake is responsible for most of the snakebites in Brazilian Amazon region and its venom induces a variety of local and systemic effects. However, this venom is not included in the pool of immunization used to produce Bothrops antivenom. It is known that the composition of snake venoms and their biological activities can vary not only among species but also within the same species. This variation can be influenced by snake ontogenetic stage, sex or geographical origin. In this work we characterize the electrophoretic profile and coagulant, phospholipase, fibrino(geno)lytic, platelet aggregation, desfibrinogenanting, edematogenic and hemorrhagic activities of Ba venom. We also evaluated the cellular migration induced by this venom and verified the capability of Bothrops antivenom to neutralize the coagulant and desfibrinogenanting activities. Thus, we used the lyophilized crude venom from adult, males (3) and females (3) Ba snakes (n=6), captured at Floresta Nacional do Tapajós (FLONA), Santarém region (Belterra), Pará. Adult B. jararaca (Bj) venom from Instituto Butantan was used in order to compare the results obtained in vitro assays. The Ba and Bj venoms showed differences in the number and intensity of protein bands under reducing or nonreducing conditions. The values of minimum coagulant dose of Ba and Bj venoms, respectively, on bovine plasma (10.87 ± 0.42 and 35.89 ± 0.22 µg/mL) and fibrinogen (17.68 ± 1.67 and 68.25 ± 0.64 µg/mL) indicated that Ba venom was more coagulant. In relation to the activation of procoagulant factors by Ba venom, we found higher activity on factor II (636.71 ± 25.76 µmol p-nitroaniline/min/mg venom) in comparison to factor X (182.15 ± 4.87 µmol p-nitroaniline/min/mg venom). Ba and Bj venoms were able to hydrolyze phospholipids and directly degrade fibrin on dose-dependent, but with different intensities. Both venoms induced a quick degradation of human fibrinogen Aα chain, a slow hydrolysis of the Bβ chain and no degradation of the γ chain, but the Bj venom hydrolyzed the Bβ chain more slowly than Ba venom. Unlike the verified Bj venom, the Ba venom did not induce platelet aggregation. We also observed that Ba venom showed desfibrinogenanting, edematogenic and hemorrhagic activities and induced cellular migration. Interestingly, Bothrops antivenom neutralized the coagulant and desfibrinogenanting activities of Ba venom. Our data indicate variability between the biological activities of Ba venom from FLONA and Bj venom from Instituto Butantan, as well as those of Ba from other geographical origins. This variability may influence on the severity of clinical manifestations observed on victims of snake bites and the necessity or not of more effective antivenoms.