Heminecrolysin, the first hemolytic dermonecrotic toxin purified from scorpion venom.

Envenomation caused by Hemiscorpius (H.) lepturus from Liochlidae family presents clinical features that have not been previously described for the Buthidae family scorpions. The most significant manifestations of H. lepturus envenomation are hemolysis and dermonecrosis which could lead in severe cases to renal, cardio-respiratory failure, and death. In this study, we aimed to identify and characterize the protein(s) causing these effects. We have purified a 33 kDa protein from the venom of H. lepturus and named it Heminecrolysin. Tryptic digestion and MS/MS analysis of obtained peptides showed homology with previously described brown spider sphingomyelinases D. Functional characterization of Heminecrolysin indicated a sphingomyelinase D, a complement-dependent hemolysis properties and a dermonecrosis activity. Heminecrolysin displayed higher hemolytic activity to human erythrocytes (ED50 of 0.025 μg/ml), a stronger inflammatory and dermonecrotic effects when injected intra-dermally to rabbit skins, while its efficiency to hydrolyze sphingomyelin seems weaker than other known spider dermonecrotic SMasesD (149 ± 32.5 nmol/mg). Step of sensitization of human erythrocytes by Heminecrolysin was shown to be Mg²⁺ and Ca²⁺-independent while hemolysis step in the presence of complement required both bivalent ions. Heminecrolysin is the first hemolytic dermonecrotic toxin identified in venom other than spiders. Except in spider Loxosceles genus and some pathogenic strains of Corynebacteria, sphingomyelinase D activity is unknown in the animal kingdom.