ACTION OF GD+3 AND ZN+2 IONS ON THE DERMONECROTIC ACTIVITY OF THE SMASES D FROM Loxosceles SPIDER VENOMS

FERNANDES-PEDROSA M. F. (1, 2), ANDRADE S. A. (1), TAMBOURGI D. V. (1)

(1) Laboratório de Imunoquímica, Instituto Butantan, SP, Brazil; (2) Departamento de Farmácia, Universidade Federal do Rio Grande do Norte, RN, Brazil.

Bites by Loxosceles spiders can produce severe clinical symptoms, including dermonecrosis, thrombosis, vascular leakage, hemolysis, and persistent inflammation. The causative factor is a sphingomyelinase D (SMaseD) that cleaves sphingomyelin into choline and ceramide 1-phosphate and has intrinsic lysophospholipase D activity toward LPC. We have cloned and expressed the fully active recombinant sphingomyelinases from L. laeta (SMase I) and Loxosceles intermedia (SMases P1 and P2). The recombinant toxins were endowed with all biological properties ascribed for the whole venoms, including dermonecrotic and complement-dependent haemolytic activities and the ability of hydrolysing sphingomyelin. The aim of this study was to investigate the effect of Gd+3 and Zn+2 ions on the dermonecrotic inducing activity of the Loxosceles SMases D. Samples of the SMases I, P1 and P2 were incubated with increased concentrations of Gd+3 and Zn+2 ions (10mM, 20mM, 40mM) for 30 min at 37°C and then tested for dermonecrotic activity on rabbit model. Data obtained showed that both ions were able to neutralise the necrotic reaction induced by SMase I fromL. laeta and SMases P1 and P2 from L. intermedia. These data suggest that Gd+3 and Zn+2 ions can compete with Mg+2 present in the active site of the SMases D blocking their toxic activity.

KEY WORDS: Loxosceles spiders venoms, sphingomyelinase D, dermonecrosis, Gd+3 and Zn+2 ions.

FINANCIAL SUPPORT: FAPESP, CNPq.

CORRESPONDENCE TO: DENISE VILARINHO TAMBOURGI, Laboratório de Imunoquímica, Instituto Butantan, SP, Brazil. Phone: + 55 11 3726-7222, 2231, Fax: + 55 11 3726-7222, 1505. E-mail: dvtambourgi@butantan.gov.br.