- Email: [email protected]
Loxosceles intermedia spider venom sphingomyelinases are responsible for both dermonecrosis and complement-dependent haemolysis
Abstracts/Toxlcot~ 38 (2000) 487-595
501
particularly in species of Rana, Bombina, Xenopus, and Phy/lomedusa. Examples of these peptides included: bombinins, magainins, dermaseptin, brevinins, xenoxins, gaegurins, temporins, and esculentin. Among Caudata amphibians, particularly in Salamandridae and Plethodontidae families, occur cytotoxic proteins, TTX, and alkaloids, such as samandarin which holds a strong neurotoxic activity. Unlike Anura and Caudata species, few works were done with the skin secretion of caecilian species. A cardiotoxic compound was described m Siphonops anmdatus (Caeciliidae). However, in the skin secretion of S. paulensis, this cardiotoxicity was demonstrated to be indirect, as a consequence of an hemolytic activity. The skin secretion of the aquatic caecilian Typhlonectes compressicauda was shown to be toxic to fish.
Loxosceles intermedia spider venom sphingomyelinases are responsible for both dermonecrosis and complement-dependent haemolysis. D.V. Tambourgi ~, B.P. Morgan b, F.C. Magnoli a, Gon~alves de Andrade RM a, C.W. van den Berg b (~Laborat6rio de Imunoquimica, Instituto Butantan, S8o Paulo, Brazil; bDepartment of Pharmacology and Department of Medical Biochemistry, University of Wales, College of Medicine, Cardiff, UK). Loxosceles spiders are ubiquitous in South and North America and Europe. The bite of the spider induces dermonecrosis and in extreme cases haemolysis and thrombosis. We have previously showed that a 35 kDa protein, named F35, purified from Loxosceles intermedia venom renders erythrocytes susceptible to lysis by autologous complement (Tambourgi et al. 1995, J. Immunol. 155, 4459). We showed that by incorporation of the F35 molecule into the cell membrane, activation of the alternative pathway of complement is facilitated leading to haemolysis. We have further purified the active components in the F35 fraction to homogeneity and two proteins (P1 and P2) were shown to be able to induce both dermonecrosis and complement-dependent haemolysis (Tambourgi et al., submitted).The mechanisms of these apparently separate events are still largely unresolved. We are currently studying the mechanism by which venom proteins induce lysis of human red blood cells. Erythrocytes treated with toxins were examined for the expression of Complement-Regulatory (C-R) molecules DAF, CD59 or CR1. No change in expression was observed eliminating the possibility that the C-susceptibility was induced by removal of these C-R by the spider toxins. Preliminary results indicate that the spider proteins Pl and P2 induce the removal of glycophorin from the red blood cells making them susceptible to complement attack. The toxins have sphingomyelinase activity but no proteolytic action. Our hypothesis is that removal of glycophorin is probably an indirect effect of activation of a yet unidentified membrane bound protease. It is quite possible that dermonecrosis is also a secondary effect of the sphingomyelinase activity of the toxins. Acknowledgements: Supported by CNPq and FAPESP.
Bioinsecticidal plant proteins." Canatoxin in the spot. C~lia R. Carlini (Department
501
particularly in species of Rana, Bombina, Xenopus, and Phy/lomedusa. Examples of these peptides included: bombinins, magainins, dermaseptin, brevinins, xenoxins, gaegurins, temporins, and esculentin. Among Caudata amphibians, particularly in Salamandridae and Plethodontidae families, occur cytotoxic proteins, TTX, and alkaloids, such as samandarin which holds a strong neurotoxic activity. Unlike Anura and Caudata species, few works were done with the skin secretion of caecilian species. A cardiotoxic compound was described m Siphonops anmdatus (Caeciliidae). However, in the skin secretion of S. paulensis, this cardiotoxicity was demonstrated to be indirect, as a consequence of an hemolytic activity. The skin secretion of the aquatic caecilian Typhlonectes compressicauda was shown to be toxic to fish.
Loxosceles intermedia spider venom sphingomyelinases are responsible for both dermonecrosis and complement-dependent haemolysis. D.V. Tambourgi ~, B.P. Morgan b, F.C. Magnoli a, Gon~alves de Andrade RM a, C.W. van den Berg b (~Laborat6rio de Imunoquimica, Instituto Butantan, S8o Paulo, Brazil; bDepartment of Pharmacology and Department of Medical Biochemistry, University of Wales, College of Medicine, Cardiff, UK). Loxosceles spiders are ubiquitous in South and North America and Europe. The bite of the spider induces dermonecrosis and in extreme cases haemolysis and thrombosis. We have previously showed that a 35 kDa protein, named F35, purified from Loxosceles intermedia venom renders erythrocytes susceptible to lysis by autologous complement (Tambourgi et al. 1995, J. Immunol. 155, 4459). We showed that by incorporation of the F35 molecule into the cell membrane, activation of the alternative pathway of complement is facilitated leading to haemolysis. We have further purified the active components in the F35 fraction to homogeneity and two proteins (P1 and P2) were shown to be able to induce both dermonecrosis and complement-dependent haemolysis (Tambourgi et al., submitted).The mechanisms of these apparently separate events are still largely unresolved. We are currently studying the mechanism by which venom proteins induce lysis of human red blood cells. Erythrocytes treated with toxins were examined for the expression of Complement-Regulatory (C-R) molecules DAF, CD59 or CR1. No change in expression was observed eliminating the possibility that the C-susceptibility was induced by removal of these C-R by the spider toxins. Preliminary results indicate that the spider proteins Pl and P2 induce the removal of glycophorin from the red blood cells making them susceptible to complement attack. The toxins have sphingomyelinase activity but no proteolytic action. Our hypothesis is that removal of glycophorin is probably an indirect effect of activation of a yet unidentified membrane bound protease. It is quite possible that dermonecrosis is also a secondary effect of the sphingomyelinase activity of the toxins. Acknowledgements: Supported by CNPq and FAPESP.
Bioinsecticidal plant proteins." Canatoxin in the spot. C~lia R. Carlini (Department