Action of two phospholipases A2 purified from Bothrops alternatus snake venom on macrophages

Abstract

The in vitro effects of BaltTX-I, a catalytically inactive Lys49 variant of phospholipase A2 (PLA2), and BaltTX-II, an Asp49 catalytically active PLA2 isolated from Bothrops alternatus snake venom, on thioglycollate-elicited macrophages (TG-macrophages) were investigated. At non-cytotoxic concentrations, the secretory PLA2 BaltTX-I but not BaltTX-II stimulated complement receptor-mediated phagocytosis. Pharmacological treatment of TG-macrophages with staurosporine, a protein kinase C (PKC) inhibitor, showed that this kinase is involved in the increase of serum-opsonized zymosan phagocytosis induced by BaltTX-I but not BaltTX-II secretory PLA2, suggesting that PKC may be involved in the stimulatory effect of this toxin in serum-opsonized zymosan phagocytosis. Moreover, BaltTX-I and -II induced superoxide production by TG-macrophages. This superoxide production stimulated by both PLA2s was abolished after treatment of cells with staurosporine, indicating that PKC is an important signaling pathway for the production of this radical. Our experiments showed that, at non-cytotoxic concentrations, BaltTX-I may upregulate phagocytosis via complement receptors, and that both toxins upregulated the respiratory burst in TG-macrophages.

Activation of J77A.1 Macrophages by Three Phospholipases A2Isolated fromBothrops atroxSnake Venom

“…The authors showed that MT-II, a Lys-49 isolated from the venom of Bothrops asper , also considerably increases phagocytosis via the complement receptor, while MT-III, an Asp-49, only stimulates phagocytosis via mannose receptors. Similar results were obtained by Setúbal et al [19]. These authors showed that BaltTX-I, a Lys49, but not BaltTX-II, an Asp-49 enzyme, is able to directly stimulate phagocytosis via the complement receptor.…”

“…Thus, for the realization of the other proposed experiments, the highest concentration, 6  μ g/mL, was chosen. It is noteworthy that the same concentration was used in the study of macrophage activation by Zuliani et al [12] and Setúbal et al [19]. The three PLA 2 s used had the same effect on macrophages.…”

“…The study also showed that the enzymatically active toxin MT-III (Asp-49) is more toxic than the enzymatically inactive toxin MT-II (Lys-49). In addition, Setúbal et al [19] examined the effects of BaltTX-I and BaltTX-II on thioglycollate elicited murine peritoneal macrophage viability. These two basic PLA 2 did not affect macrophage viability, indicating their low toxicity on this cell type.…”

“…In addition, among the pro inflammatory activities, it was shown that various venom PLA 2 s are able to stimulate neutrophil chemotaxis, degranulate mast cells in vitro , induce prostaglandin production in peritoneal leukocytes, and activate macrophage functions [12, 15–19]. …”

Lemnitoxin, the major component of Micrurus lemniscatus coral snake venom, is a myotoxic and pro-inflammatory phospholipase A2

“…The release of histamine from mast cells has been proposed to be a mechanism of snake venom PLA2-induced local inflammation (Cirino et al, 1989;Teng, 1990, Landucci et al, 1998). Some group II snake venom PLA2 are able to recruit and activate leukocytes (Zuliani et al, 2005b, Moreira et al, 2011, Setúbal et al, 2013, Furtado et al, 2014, but there are only few reports on the action of group I snake venom PLA2. Naja m. mocambique PLA2 induced dose-and time-dependent cellular infiltration into the rat pleural cavity (Weichman et al, 1989).…”