Effect of various Viperidae and Crotalidae snake venoms on endothelial cells in vitro

The effect of various crotalid and viperid venoms at 10, 50 and 100 μg/ml was examined on bovine and murine endothelial cells in vitro. The venoms caused the cells to lose their processes, leading to the appearance of spaces which were gradually enlarged between clusters of cells. The cells became round and finally detached from the substrate. This effect was more pronounced on bovine normal cells than on murine transformed cells. Most of the venoms did not affect the viability of the cells even after 24 hr of incubation, as determined by the trypan blue dye exclusion procedure. Moreover, after the cells were washed from the venoms and transferred into fresh medium, they regained their original morphology after spreading on the substrate and they then proliferated normally. This reversible effect shows that most of the crotalid and viperid venoms examined were not directly cytotoxic to the endothelial cells at the concentrations tested./[DHR-5544-6-00-1064-00]/AID/UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto Clodomiro Picado (ICP

Cancer cell injury by cytotoxins from cobra venom is mediated through lysosomal damage

Cytotoxins from cobra venom are known to manifest cytotoxicity in various cell types. It is widely accepted that the plasma membrane is a target of cytotoxins, but the mechanism of their action remains obscure. Using the confocal spectral imaging technique, we show for the first time that cytotoxins from cobra venom penetrate readily into living cancer cells and accumulate markedly in lysosomes. Cytotoxins CT1 and CT2 from Naja oxiana, CT3 from Naja kaouthia and CT1 from Naja haje are demonstrated to possess this property with respect to human lung adenocarcinoma A549 and promyelocytic leukaemia HL60 cells. Immobilized plasma membrane binding accompanies the internalization of CT3 from Naja kaouthia in the HL60 cells, but it is very weak for other cytotoxins. Detectable membrane binding is not a property of any of the cytotoxins tested in A549 cells. The kinetics and concentration-dependence of cytotoxin accumulation in lysosomes correlate well with their cytotoxic effects. On the basis of the results obtained, we propose that lysosomes are a primary target of the lytic action of cytotoxins. Plasma membrane permeabilization seems to be a downstream event relative to lysosome rupture. Direct damage to the plasma membrane may be a complementary mechanism, but its relative contribution to the cytotoxic action depends on the cytotoxin structure and cell type