Signaling pathways involved in zymosan phagocytosis induced by two secreted phospholipases A isolated from Bothrops asper snake venom in macrophages.

Phagocytosis, a process involved in host defense, requires coordination of a variety of signaling reactions. MT-II, a catalytically-inactive Lys49-PLA¸ and MT-III, an active Asp49-PLA isolated from Bothrops asper snake venom, activate phagocytosis in macrophages. In this study the signal pathways mediating zymosan phagocytosis, focusing in lipidic second messengers, were investigated. Macrophages collected from male Swiss mouse peritoneum were obtained 96h after i.p. injection of thioglycollate. Phagocytosis was evaluated with non-opsonized zymosan in the presence or absence of specific inhibitors. Data showed that both venom PLAs increased phagocytosis. Zileuton, Etoricoxib, PACOCF (5-LO, COX-2 and iPLA inhibitors, respectively), as well as WEB2170 (PAF receptor antagonist) significantly reduced phagocytosis induced by both venom PLAs. However, Indomethacin (COX-1/COX-2 inhibitor) and Montelukast (CysL receptor antagonist) did not affect the toxins-induced phagocytosis. Moreover, while PACOCF3 (iPLA inhibitor), reduced the phagocytosis induced by MT-II and MT-III, AACOCF (cPLA inhibitor) significantly reduced the MT-II, but not MT-III-induced phagocytosis. These data suggest the effect of both sPLAs depends on iPLA and that the effect of MT-II depends on activation of cPLA. COX-2 and 5-LO-derived metabolites as well as PAF are involved in the signaling events required for phagocytosis induced by both venom sPLAs.