Estudo das interações da miltefosina com membranas de L. (Leishmania) amazonensis e macrófagos peritoneais

• Autor(a) principal: Fernandes, Kelly de Souza
• Data de Publicação: 2016
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/5684
• topic: Miltefosina; L. (L.) amazonensis; Macrófagos peritoneais; RPE; Marcador de spin; Miltefosine; L. (L.) amazonensis; Peritoneal macrophages; EPR; Spin label; FISICA::FISICA GERAL

Miltefosine (MT) is a alkylphospholipid originally developed for treatment of breast cancer and other solid tumors. It is currently used in the treatment of leishmaniasis, an infectious parasitic disease caused by protozoa of the genus Leishmania, being the first oral drug adopted for this purpose. However, its mechanism of action remains unclear. Electron paramagnetic resonance (EPR) spectroscopy of a spin-labeled lipid (5-DOXIL stearate) and a thiol-specific spin label (4-maleimido-TEMPO) in the membrane of axenic amastigotes of L.(Leishmania) amazonensis and peritoneal macrophages from Balb/c mice showed that MT causes significant increase in membrane dynamics at similar concentrations that inhibit parasite growth or are cytotoxic to macrophage. Although these alterations can be detected using a spin-labeled lipid, our experimental results indicated that MT interacts predominantly with the protein component of the membrane. Using a method for the rapid incorporation of MT into the membrane, these effects were measured immediately after treatment. Cytotoxicity, estimated via microscopic counting of living and dead cells, indicated ~80% parasites and macrophages death at the concentration of MT at which EPR spectroscopy detected a significant change in membrane dynamics. Cell viability, analyzed using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide tetrazolium) reduction assay, showed that 50% inhibitory concentration (IC50) of MT depends on the cell concentration used in the assay. This dependence was analyzed using a theoretical equation involving biophysical parameters such as the partition coefficient of watermembrane and MT concentrations on the membrane and in the aqueous medium. The data showed that cells more sensitive to MT are respectively: erythrocytes, Leishmania promastigotes and Leishmania amastigotes and macrophage. The IC50 value of MT for 4 x 107 parasites/mL was 24,35 M. For the same cell concentration, a significant alteration was detected in the membrane lipid fluidity of parasites to 15 M of MT. The EPR spectra of spinlabeled membrane-bound proteins were consistent with more expanded and solvent exposed protein conformations, suggesting a detergent-like action, with a possible formation of micelle-like structures around polypeptide chains.