Effect of Loxosceles gaucho venom on cell morphology and behaviour in vitro in the presence and absence of sphingomyelin

This study was performed to investigate whether the toxic effects of Loxosceles gaucho venom on cells might be exerted via stimulators of TNF-α release generated by sphingomyelinase D—a major component of the venom. It was demonstrated that L. gaucho venom alone is unable to induce TNF-α release by J774A.1 cells, while in the presence of exogenous sphingomyelin it induces a high level of TNF-α release which is significantly increased by incubation with non-inactivated serum. Ceramide phosphate also induces TNF-α release in J774A.1 cells, but (unlike sphingomyelin/sphingomyelinase) the level of release is not influenced by the presence or otherwise of non-inactivated serum. L. gaucho venom does not induce proliferation of J774A.1 cells and even at high concentrations it does not affect their viability. J774A.1 cells, which prior to venom treatment were elongated and clumped, round up after venom treatment, but, revert to their original morphology after incubation with fresh medium. TNF-α resistant MRC-5 cells and TNF-α sensitive MCF-7 cells are susceptible to the toxic effect of both L. gaucho venom and ceramide phosphate. The results obtained in this study demonstrate that exogenous sphingomyelin can modulate, in vitro, the release of TNF-α induced by L. gaucho venom in mouse macrophages. In addition, the results also indicate that ceramide phosphate and L. gaucho venom are toxic to several different cell types, via a variety of mechanisms, some, but not all, of which may involve TNF-α as an intermediary. [Copyright &y& Elsevier]