JararhaginPromotes ActinPolymerization And Increases Leukocyte Adhesion To ExtracellularMatrix And Endothelial Cells. 

Costa;E.P. & Santos, M.F. 

Dept. of Histology and Embriology, ICB/USP, 05508-000. 

Objectives: The snake venom metalloproteinase-disintegrin Jararhagin (JG) has no chemotactic activity but stimulates the migration of epithelial cells in vitro and neutrophils in vivo, through a mechanism still unclear. In this study we analyzed the effects of JG on leukocyte adhesion to several substrata, as well as their filamentous actin (F-actin) organization.

Methods and results: Blood samples were collected from Wistar rats and the leukocytes were isolated using a discontinuous gradient of Percoll^®. Neutrophils-enriched fractions (98%) were treated with different concentrations of JG (0,31 to 10mg/ml) and submitted to adhesion assays using treated dishes, basement membrane extract (Matrigel^®) and non-stimulated murine endothelial cells (tEND) as substrata. Controls consisted of unstimulated cells and cells treated with 1 mM fMLP. The number of adherent cells was evaluated through myeloperoxidase activity, whereas rodhamine-phalloidin was used for F-actin staining. The toxin increased cellular adhesion to treated dishes and tEND in concentrations above 0,31mg/ml after 30 and 90 minutes, respectively, but not in a concentration-related manner. Adhesion to Matrigel was increased after treatment with 2,5mg/ml JG during 30 minutes. Under the same conditions, JG clearly stimulated cortical actin polymerization in adherent neutrophils.

Conclusions: JG promotes actin polymerization and stimulates the adhesion of neutrophils to different substrata.

Financial support: FAPESP, CNPq.

Correspondence to: epcosta@usp.br or mfsantos@usp.br