IS THE PHOSPHOLIPASE A₂ (PLA₂) ACTIVITY OF THE MT-II AND MT-III ISOLATED FROM Bothrops asper VENOM IMPORTANT FOR MACROPHAGES FUNCTIONS ?

ZULIANI, J.P.(1), SAMPAIO, S.C.(2), GUTIERREZ, J.M.(3), TEIXEIRA, C.F.P.(1)

(1)Laboratory of Pharmacology and (2)Laboratory of Pathophysiology, Butantan Institute, SP, Brazil, (3)Clodomiro Picado Institute, San José, Costa Rica.

Introduction and goals: MT-III is a PLA₂-Asp49 with high enzymatic activity and MT-II, a PLA₂-Lys49, devoid of catalytic activity. However both are myotoxic. In the present work we have investigated the ability of these myotoxins to induce activation of macrophages (phagocytosis, H₂O₂, NO and cytokines liberation) and the participation of PLA₂-activity in these effects. Methods and Results: Macrophages were obtained from Swiss mice peritoneal cavity 96 hours after intraperitoneal injection of thioglicolate (3%). Cell viability was measured by Trypan blue exclusion test. Phagocytosis via C3b receptor, via Fcgreceptor and via mannose receptor were studied with opsonized zymosan, opsonized sheep red blood cells and Candida albicans, respectively. Release of H₂O₂ and NO was measured by Phenol red and Griess reaction, respectively. Myotoxins (1 mg/kg) or saline were injected in the peritoneal cavity. At selected time, peritoneal washes were colected and concentrations of IL-1, IL-6 and TNF-awere measured by ELISA and L929 cytotoxicity, respectively. Both myotoxins are cytotoxic for macrophages only at high concentrations (50-200 mg/mL). MT-II affected phagocytosis via C3b, Fcgand mannose receptors (p<0,05). On the other hand, MT-III affected only phagocytosis via mannose receptor (p<0,05). Both myotoxins induced a significant release of H₂O₂ and NO (p<0,05) from isolated macrophages as well as an increase in concentrations of IL-1, IL-6 and TNF-a(p<0,05) in the peritoneal washes. Conclusion: These data suggest that myotoxins are able to stimulate microbicidal functions of macrophages and the release of cytokines. These do not appear to be connected with PLA₂ activity. Therefore, distinct domains in the molecule of the myotoxins are important for activation of the macrophage functions.

Financial Support: FAPESP.

CORRESPONDENCE TO:

JULIANA PAVAN ZULIANI, Rua Coronel Quirino,137 Apto. 64, Campinas, SP, CEP: 13025000, Brasil, Email: jzuliani@usp.br