Chemotherapy

Abstract

Miltefosine, initially developed as an anti-tumor agent, is the newest drug for the treatment of visceral leishmaniasis. Several laboratories have shown that this ether-lipid analogue is also toxic against different forms of T. cruzi, but its mechanism(s) of action is(are) still unclear. In leukemic cells, Miltefosine seems to interfere with cellular signal transduction pathways by inhibition of protein kinase C (PKC) and Na + , K + -ATPase. In order to verify if Miltefosine is able to act in a similar way on T. cruzi, we initially tested its effects against on the ouabain-insensitive and furosemide-sensitive Na + -ATPase activities of the parasites (1).The Na + -ATPase activitiy was measured as described previously (1-2) using an enriched plasma membrane fraction from epimastigotes obtained after subcellular fractionation by differential centrifugation in sucrose-containing buffer. The addition of increasing amounts of Miltefosine (0,003-0,3 mg/mL) resulted in a dose-dependent inhibition of the Na + -ATPase activity. In a second stage, the inhibition of the Na + -ATPase by Miltefosine was confirmed by performing activity measurements in the presence of increasing amounts of NaCl, containing or not 0,015mg/mL of Miltefosine. As expected, there was a Na + -dependent increase of the Na + -ATPase activity, with a K 0.5 and V max of 13.7±1.9 mM Na + and 11.4±0.5 nmol Pi x mg -1 x min 1 , respectively. In the presence of Miltefosine there was a change in the kinetic parameters, with the K 0.5 for Na + raising to 28.5±5.3 mM and the V max dropping to 7.6±0.5 nmol Pi x mg -1 x min 1 . When the membrane fractions were pre-incubated with Miltefosine (0,015 mg/mL) and diluted to a condition containing four times less drug before performing the assay, no inhibition was observed when compared to controls. Taken together, the results suggest that Miltefosine act as a reversible inhibitor of the T. cruzi Na + -ATPase.Supported by: CNPq, FAPERJ, TWAS and IFS.References 1 -Caruso- Neves et al.,1999, Z. Naturforsch. 54c, 100-104. 2 -Grubmeyer and Penefsky, 1981, J. Biol. Chem. 256, 3718-3727. QT2 -ATIVIDADE ANTIPARASITÁRIA DA HEMOLINFA DE DUAS ESPÉCIES NATIVAS DE MOLUSCOS BIVALVESLöfgren, S.E. 1 ; Steindel, M. 2 ; Barracco, M.A. 1 1 Depto de Biologia Celular, Embriologia e Genética -CCB -UFSCFlorianópolis, SC. 2 Depto de Microbiologia e Parasitologia -CCB -UFSCFlorianópolis, SC Peptídios ou proteínas antimicrobianas (PAM) são componentes do sistema imune inato, presentes na maioria dos seres vivos, que podem apresentar uma atividade microbicida potente contra um amplo espectro de microrganismos. Entretanto, dos PAM conhecidos atualmente, muito poucos têm sido avaliados quanto a sua atividade antiparasitária contra protozoários. Neste trabalho foi investigada a atividade antiparasitária da hemolinfa de duas espécies nativas de moluscos, o mexilhão Perna perna e a ostra do mangue Crassostrea rhizophorae, contra formas promastigotas de Leishmania (V.) braziliensis e formas epimastigotas de Trypanosoma cruzi. Foram utilizadas a...