Adriana Silva Pontes

Activation of J77A.1 Macrophages by Three Phospholipases A2 Isolated from Bothrops atrox Snake Venom

In the present study, we investigated the in vitro effects of two basic myotoxic phospholipases A2 (PLA2), BaTX-I, a catalytically inactive Lys-49 variant, and BaTX-II, a catalytically active Asp-49, and of one acidic myotoxic PLA2, BaPLA2, a catalytically active Asp-49, isolated from Bothrops atrox snake venom, on the activation of J774A.1 macrophages. At noncytotoxic concentrations, the toxins did not affect the adhesion of the macrophages, nor their ability to detach. The data obtained showed that only BaTX-I stimulated complement receptor-mediated phagocytosis. However, BaTX-I, BaTX-II, and BaPLA2 induced the release of the superoxide anion by J774A.1 macrophages. Additionally, only BaTX-I raised the lysosomal volume of macrophages after 15 min of incubation. After 30 min, all the phospholipases increased this parameter, which was not observed within 60 min. Moreover, BaTX-I, BaTX-II, and BaPLA2 increased the number of lipid bodies on macrophages submitted to phagocytosis and not submitted to phagocytosis. However, BaTX-II and BaPLA2 induced the release of TNF-α by J774A.1 macrophages. Taken together, the data show that, despite differences in enzymatic activity, the three toxins induced inflammatory events and whether the enzyme is acidic or basic does not seem to contribute to these effects.

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

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.

Effect of Bothrops alternatus snake venom on macrophage phagocytosis and superoxide production: participation of protein kinase C

Envenomations caused by different species of Bothrops snakes result in severe local tissue damage, hemorrhage, pain, myonecrosis, and inflammation with a significant leukocyte accumulation at the bite site. However, the activation state of leukocytes is still unclear. According to clinical cases and experimental work, the local effects observed in envenenomation by Bothrops alternatus are mainly the appearance of edema, hemorrhage, and necrosis. In this study we investigated the ability of Bothrops alternatus crude venom to induce macrophage activation. At 6 to 100 ¼g/mL, BaV is not toxic to thioglycollate-elicited macrophages; at 3 and 6 ¼g/mL, it did not interfere in macrophage adhesion or detachment. Moreover, at concentrations of 1.5, 3, and 6 ¼g/mL the venom induced an increase in phagocytosis via complement receptor one hour after incubation. Pharmacological treatment of thioglycollate-elicited macrophages with staurosporine, a protein kinase (PKC) inhibitor, abolished phagocytosis, suggesting that PKC may be involved in the increase of serum-opsonized zymosan phagocytosis induced by BaV. Moreover, BaV also induced the production of anion superoxide (O2_) by thioglycollate-elicited macrophages. This BaV stimulated superoxide production was abolished after treating the cells with staurosporine, indicating that PKC is an important signaling pathway for the production of this radical. Based on these results, we suggest that phagocytosis and reactive oxygen species are involved in the pathogenesis of local tissue damage characteristic of Bothrops spp. envenomations.

p38 MAPK is involved in human neutrophil chemotaxis induced by L-amino acid oxidase from Calloselasma rhodosthoma

The action of LAAO, an L-amino acid oxidase isolated from Calloselasma rhodosthoma snake venom, on isolated human neutrophil function was investigated. Cr-LAAO showed no toxicity on neutrophils. Cr-LAAO in its native form induced the neutrophil chemotaxis, suggesting that its primary structure is essential for stimulation the cell. p38 MAPK and PI3K have a role as signaling pathways of CR-LAAO induced chemotaxis. This toxin also induced the production of hydrogen peroxide and stimulated phagocytosis in neutrophils. Furthermore, Cr-LAAO was able to stimulate neutrophils to release IL-6, IL-8, MPO, LTB4 and PGE2. Together, the data showed that the Cr-LAAO triggers relevant proinflammatory events.

Effect of BjcuL, a lectin isolated from Bothrops jararacussu, on human peripheral blood mononuclear cells

BjcuL is a C-type lectin with specificity for the binding of β-d-galactose units isolated from Bothrops jararacussu venom. It triggers cellular infiltration in post capillary venules, increases edema and vascular permeability in murine models, contributes to in vitro neutrophil activation and modulates macrophage functional activation towards an M1 state. The purpose of this study was to investigate the effect of BjcuL on human peripheral blood mononuclear cells (PBMCs) activation with a focus on PBMCs proliferation and inflammatory mediators release. Results showed that BjcuL is not toxic to PBMCs, that BjcuL inhibits PBMCs proliferation and that it stimulates PBMCs to produce superoxide anion and hydrogen peroxide, primarily via lymphocyte stimulation, but does not stimulate the production of nitric oxide and PGE2. These results demonstrate that BjcuL has an immunomodulatory effect on PBMCs. Further studies are needed to confirm the immunomodulatory effect of BjcuL, to elucidate the molecular mechanisms of action responsible for its effects and to determine its potential application as an immunopharmacological and biotechnological tool.

Role of l -amino acid oxidase isolated from Calloselasma rhodostoma venom on neutrophil NADPH oxidase complex activation

ABSTRACT The action of Cr‐LAAO, an l‐amino acid oxidase isolated from Calloselasma rhodosthoma snake venom, on NADPH oxidase activation in isolated human neutrophil function was investigated. This enzyme has an intrinsic activity of hydrogen peroxide production. Cr‐LAAO, in its native form, induces the ROS production in neutrophil and migration of cytosolic NADPH oxidase components p40phox, p47phox and p67phox to the membrane, and Rac, a GTPase protein member, with the involvement of intracellular signaling mediated by phospho PKC‐&agr;. In its inactive form, iCr‐LAAO does not induce NADPH oxidase activation in neutrophil showing that the intrinsic enzymatic activity does not have a role in this process, suggesting that its primary structure is essential for the cells stimulation. Accordingly, the data showed for the first time that the Cr‐LAAO has a role in NADPH oxidase complex activation triggering relevant proinflammatory events in human neutrophils. Graphical abstract Figure. No Caption available. HighlightsCr‐LAAO induced NADPH oxidase activation in neutrophils.Cr‐LAAO induced migration of p40phox, p47phox and p67phox and Rac to the membrane.Cr‐LAAO induced PKC‐&agr; phosphorylation.Cr‐LAAO induces the ROS production in neutrophil.