Participação dos mastócitos e histamina no edema induzido pelo veneno da lacraia Scolopdendra viridicornis em modelo murino

Abstract

Bites caused by centipede Scolopendra viridicornis are mainly characterized by burning pain, paresthesia and edema. The aim of this work was to verify the involvement of mast cells and histamine in inflammatory events induced by Scolopendra viridicornis (Sv) centipede venom. Two lots of Sv venom were used (lot 1 and lot 2). Edema was measured by plethysmometer at different times after injection Sv venom (lot 1 -15 µg) or PBS in the footpad of the right hind paw in mice pretreated with cromoglycate (mast cell degranulation inhibitor) and antagonists of histamine such as promethazine (H1R), cimetidine (H2R) and thioperamide (H3/H4R). The peak of edema was observed 15 min after injection of Sv venom, returning to baseline levels after 24 h. Cromoglycate treatment significantly inhibited edema at all times analysed (38 - 58 %). It was also observed reduction of edema in the animals pre-treated with antagonists of histamine: promethazine 50 - 59 % (15 min to 6 h) and thioperamide about 30 % (4 to 24 h). On the other hand, treatment with cimetidine did not cause any change in edema in the evaluation period. To view the histological changes, the animals were injected with the Sv venom (lot 1 - 15 µg) or PBS in the footpad of the right hind paw, and 30 min after injection the animals were euthanized and the tissue was processed. The Sv venom induced edema, leukocyte recruitment and degranulation of mast cells at the lesion site. To investigate whether Sv venom had direct action on mast cells, PT-18 line (mouse mast cell) and RBL-2H3 cells (rat mast cells) were incubated with the venom (lot 1 and lot 2) at different concentrations and time periods. It was found that in larger doses, the venom was highly cytotoxic, especially in lot 2 for the two cells lineages. This effect was also observed by morphological analysis by scanning. The two lots of the venom induced degranulation in cells lines. To evaluate some inflammatory mediators that may be involved in the activation of mast cells in vitro, the supernatants from PT-18 and RBL2H3 cells stimulated with venom (lot 2) were dosed. The Sv venom induced 12 production of MCP-1 and IL-6. However, there was only release of PGD2 in the RBL2H3 line. Moreover, it was not detected the release of IL1-β and TNF-α in mast cells cultures. Our results showed that there was variability in toxicity of Sv venom between lots 1 and 2, as observed in the degranulation and cytotoxicity assays, and this difference was also observed in the electrophoretic profile. In conclusion, mast cells and histamine participate in the inflammation induced by Sv venom, however, other factors may be involved in this process.