Contribution of crotoxin for the inhibitory effect of Crotalus durissus terrificus snake venom on macrophage function S.C. Sampaio a , P. Brigatte a , M.C.C. Sousa-e-Silva a , E.C. dos-Santos b , A.C. Rangel-Santos b , R. Curi c , Y. Cury a, * a Laboratory of Pathophysiology, Butantan Institute, Av Vital Brazil, 1500, 05503-900, Sa ˜o Paulo, Brazil b Laboratory of Immunopathology, Butantan Institute, Av Vital Brazil, 1500, 05503-900, Sa ˜o Paulo, Brazil c Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sa ˜o Paulo, Av. Prof. Lineu Prestes, 1524, 05508-900, Sa ˜o Paulo, Brazil Received 25 July 2002; accepted 26 February 2003 Abstract Previous work of our group demonstrated that Crotalus durissus terrificus venom has a dual effect on macrophage function: it inhibits spreading and phagocytosis and stimulates hydrogen peroxide and nitric oxide production, antimicrobial activity and glucose and glutamine metabolism of these cells. Crotalid venom also induces analgesia and this effect is mediated by opioid receptors. The involvement of opioidergic mechanism and the determination of the active component responsible for the inhibitory effect of crotalid venom on macrophage function were investigated. The venom reduced the spreading and phagocytic activities of peritoneal macrophages. This effect was observed in vitro, 2 h after incubation of resident peritoneal macrophages with the venom, and in vivo, 2 h after subcutaneous injection of the venom. The inhibition of phagocytosis was not modified by naloxone, an antagonist of opioid receptors. Venom neutralization with crotalid antivenom abolished the inhibitory effect of the venom, indicating that venom toxins are involved in this effect. Crotoxin, the main toxin of crotalid venom, s.c. injected to rats or added to the medium of peritoneal cell incubation, inhibited macrophage function in a similar manner to that observed for crude venom. The present results suggest that crotoxin causes a direct inhibition of macrophage spreading and phagocytic activities and may contribute to the inhibitory effect of crotalid venom on macrophage function. q 2003 Elsevier Science Ltd. All rights reserved. Keywords: Crotoxin; Macrophage; Spreading; Phagocytosis; Crotalus durissus terrificus venom 1. Introduction The Crotalus durissus terrificus snake venom (CdtV) inhibits the immune and inflammatory responses and causes antinociception (Giorgi et al., 1993; Landucci et al., 1995; Sousa-e-Silva et al., 1996; Cardoso and Mota, 1997; Picolo et al., 2000; Cardoso et al., 2001). Recent work has shown that the crotalid venom has a dual effect on macrophage function. It inhibits spreading and phagocytosis and stimulates hydrogen peroxide and nitric oxide production, antimicrobial activity and glucose and glutamine metab- olism of these cells (Sampaio et al., 2001). These effects on macrophage function are not dependent on the cell activation state, since they were observed in resident, elicited, and activated cells (Sampaio et al., 2001). Resident macrophages occur in specific sites in normal, non-inflamed tissue; elicited macrophages are cells attracted to a given site because of a particle stimulus, independent of the developmental stage or functional state of the cells; activated macrophage are cells with increased or new 0041-0101/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0041-0101(03)00069-2 Toxicon 41 (2003) 899–907 www.elsevier.com/locate/toxicon * Corresponding author. Tel.: þ55-11-3726-7222; fax: þ 55-11- 3726-1505. E-mail address: yarac@attglobal.net (Y. Cury).