Effects of two serine proteases from Bothrops pirajai snake venom on the complement system and the inflammatory response

The present study aimed to evaluate the effects of two serine proteases from Bothrops pirajai snake venom, named BpirSP27 and BpirSP41, on the complement system and the inflammatory response. The effects of these enzymes on the human complement system were assessed by kinetic hemolytic assays, evaluating the hemolysis promoted by the classical/lectin (CP/LP) and alternative (AP) pathways after incubation of normal human serum with the serine proteases. The results suggested that these enzymes were able to induce modulation of CP/LP and AP at different levels: BpirSP41 showed higher inhibitory effects on the hemolytic activity of CP/LP than BpirSP27, with inhibition values close to 40% and 20%, respectively, for the highest concentration assayed. Regarding AP, both enzymes showed percentages of inhibition of the hemolytic activity around 20% for the highest concentrations tested, indicating similar effects on this complement pathway. The proinflammatory effects of B. pirajai serine proteases were evaluated regarding their ability to induce paw edema, variations in the pain threshold and leukocyte recruitment at the site of injection. Both showed mild effects on these inflammatory processes, leading to low levels of increase of paw volumes and decrease in pain thresholds in rats up to 6 h after injection, and inducing neutrophil recruitment without significant increases in the total number of leukocytes in the inflammatory exudates after 6 and 24 h of administration into mice peritoneal cavity. These results suggest that serine proteases must present a minor role in the inflammation caused by B. pirajai snake venom.