Bothrops asper and Bothrops jararaca snake venoms trigger microbicidal functions of peritoneal leukocytes in vivo

Venoms from snakes of the genus Bothrops cause pronounced local effects in the victims. These alterations result not only from the direct toxic action of venom components, but also from the prominent inflammatory reaction ass ociated with these envenomations. In this study we investigated the ability of Bothrops asper (BaV) and Bothrops jararaca (BjV) venoms to induce cellu lar influx and microbicidal functions in leukocytes. BaV and BjV (5 mug/ani mal) caused a long lasting infiltration of leukocytes (3-48 h) when injecte d into mouse peritoneal cavity. Both venoms increased phagocytosis and prod uction of hydrogen peroxide (H2O2) by polymorphonuclear (PMN) and mononucle ar (MN) peritoneal leukocytes. In addition, nitric oxide (NO) production by macrophages was also enhanced after the venom injections. This effect was inhibited by treating animals with L-NAME and aminoguanidine, thus suggesti ng the induction of iNOS synthesis by the venoms. Western blot analysis con firmed the expression of iNOS in macrophages. BaV and BjV injection led to increased levels of IFN-gamma at the site of inflammation. Since IFN-gamma is an effective inducer of iNOS expression, an indirect action of the venom s on iNOS expression can be proposed. A marked formation of nitrotyrosine-c ontaining proteins was also observed in macrophage homogenates. Based on th ese results, we suggest that reactive oxygen and nitrogen-derived species a re involved in the pathogenesis of the local tissue damage characteristic o f Bothrops sp envenomations. (C) 2001 Elsevier Science Ltd. All rights rese rved.