title: Loxosceles intermedia spider envenomation induces activation of an endogenous metalloproteinase, resulting in cleavage of glycophorins from the erythrocyte surface and facilitating complement-mediated lysis.
abstract: Loxosceles is the most venomous spider in Brazil, and envenomation causes dermonecrosis and complement (C)-dependent intravascular hemolysis. The authors studied the mechanism of induction of C-induced hemolysis. Purified Loxosceles toxins rendered human erythrocytes susceptible to lysis by human C but did not have an effect on the E-bound C-regulators DAF, CR1, or CD59. However, incubation with venom toxins caused cleavage of glycophorin from the erythrocyte (E) surface, facilitating C activation and hemolysis. The results suggest that glycophorin is an important factor in the protection of E against homologous C. Cleavage of glycophorin (GP) A, GPB, and GPC occurred at sites close to the membrane but could not be accomplished using purified GPA and purified toxins, demonstrating that cleavage was not an effect of a direct proteolytic action of the Loxosceles toxins on the glycophorins. Inhibition of the cleavage of glycophorins induced by Loxosceles venom was achieved with 1,10-phenanthroline. The authors propose that the sphingomyelinase activity of the toxins induces activation of an endogenous metalloproteinase, which then cleaves glycophorins. They observed the transfer of C-dependent hemolysis to other cells, suggesting that the Loxosceles toxins can act on multiple cells. This observation can explain the extent of hemolysis observed in patients after envenomation. Identification of the mechanism of induction of susceptibility to C-mediated lysis after Loxosceles envenomation opens up the possibility of the development of an effective therapeutic strategy. (Blood. 2000;95:683-691)
authors.affiliation: Laboratório de Imunoquímica, Instituto Butantan, São Paulo, Brazil. butlim@eu.ansp.br
authors.forename: D V
authors.initials: DV
authors.lastname: Tambourgi
authors.forename: B P
authors.initials: BP
authors.lastname: Morgan
authors.forename: R M
authors.initials: RM
authors.lastname: de Andrade
authors.forename: F C
authors.initials: FC
authors.lastname: Magnoli
authors.forename: C W
authors.initials: CW
authors.lastname: van Den Berg
mesh_terms: D000818:Animals; D003165:Complement System Proteins / Q000502:physiology*; D004789:Enzyme Activation; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000502:physiology*; D004912:Erythrocytes / Q000187:drug effects / Q000502:physiology*; D006021:Glycophorins / Q000187:drug effects* / Q000378:metabolism; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D019169:Jurkat Cells; D020014:K562 Cells; D008666:Metalloendopeptidases / Q000097:blood* / Q000187:drug effects; D009439:Neuraminidase / Q000494:pharmacology; D010727:Phosphoric Diester Hydrolases / Q000302:isolation & purification / Q000494:pharmacology*; D011480:Protease Inhibitors / Q000494:pharmacology; D013111:Spider Venoms / Q000302:isolation & purification / Q000494:pharmacology*; D013112:Spiders; D020298:U937 Cells
chemical_list: D006021:Glycophorins; D011480:Protease Inhibitors; D013111:Spider Venoms; C055161:loxosceles venom; D003165:Complement System Proteins; D010727:Phosphoric Diester Hydrolases; D009439:Neuraminidase; D008666:Metalloendopeptidases