Navegando por Palavras-chave "Membrane permeabilization"

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    Characterization of dual effects induced by antimicrobial peptides: Regulated cell death or membrane disruption
    (Elsevier B.V., 2012-07-01) Paredes-Gamero, Edgar Julian [UNIFESP]; Martins, Marta Natividade Crizol [UNIFESP]; Cappabianco, Fabio Augusto Menocci [UNIFESP]; Ide, Jaime Shinsuke [UNIFESP]; Miranda, Antonio [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    Background: Some reports describe lysis mechanisms by antimicrobial peptides (AMPs), while others describe the activation of regulated cell death. in this study, we compare the cell death-inducing activities of four beta-hairpin AMPs (gomesin, protegrin, tachyplesin and polyphemusin II) along with their linear analogs in the human erythroleukemia K562 cell line to investigate the relationship between their structure and activity.Methods: K562 cells were exposed to AMPs. Morphological and biochemistry alterations were evaluated using light microscopy, confocal microscopy and flow cytometry.Results: Gomesin and protegrin displayed cytotoxic properties that their linear counterparts did not. Tachyplesin and polyphemusin II and also their linear analogs induced cell death. We were able to distinguish two ways in which these AMPs induced cell death. Lower concentrations of AMPs induced controlled cell death mechanisms. Gomesin, tachyplesin and linear-tachyplesin promoted apoptosis that was characterized by annexin labeling, sensitivity to Z-VAD, and caspase-3 activation, but was also inhibited by necrostatin-1. Gomesin and protegrin induced cell death was dependent on intracellular Ca2+ mechanisms and the participation of free radicals was observed in protegrin induced cell death. Polyphemusin II and its linear analog mainly induced necrosis. Conversely, treatment with higher concentrations of AMPs primarily resulted in cell membrane disruption, but with clearly different patterns of action for each AMP tested.Conclusion: Different actions by beta-hairpin AMPs were observed at low concentrations and at higher concentrations despite the structure similarity.General significance: Controlled intracellular mechanism and direct membrane disruption were clearly distinguished helping to understand the real action of AMPs in mammalian cells. (C) 2012 Elsevier B.V. All rights reserved.
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    Membrane permeabilization induced by Triton X-100: The role of membrane phase state and edge tension
    (Elsevier Ireland Ltd, 2017) Mattei, Bruno [UNIFESP]; Lira, Rafael Bezerra de [UNIFESP]; Perez, Katia Regina [UNIFESP]; Riske, Karin do Amaral [UNIFESP]
    Detergents are widely used to solubilize and separate biomembrane components. It is therefore relevant to study and understand the mechanistic details underlying detergent-lipid interactions using biomimetic systems. Here, we have investigated in detail the process of membrane permeabilization and the nature of pores induced by sub-solubilizing concentrations of the detergent Triton X-100 (TX-100) in bilayers composed of palmitoyl oleoyl phosphatidylcholine (POPC), sphingomyelin (SM) and binary mixtures of these phospholipids with 30 mol% cholesterol (chol). A fluorescence quenching assay was used to evaluate the permeability of large unilamellar vesicles (LUVs) in the presence of increasing concentrations of TX-100. Confocal microscopy was employed to visualize and quantify the permeability of giant unilamellar vesicles (GUVs) to two fluorescent dyes of different sizes in the presence of TX-100. Both methods showed that POPC, POPC/chol and SM membranes become fully permeable at a specific TX-100 concentration, followed by complete (POPC and SM) and partial (POPC/chol) solubilization at a higher detergent concentration. The confocal microscopy experiments revealed that opening of pores occurs as a well-defined event and that for POPC and POPC/chol the pores were initially selective to the small probe and then grew and allowed passage of the larger dye as well. On the other hand, the insoluble SM/chol membranes exhibited only a mild TX-100-induced permeabilization. The membrane edge tension of the liquid phases was measured from the closure rate of macropores induced by electric pulses in GUVs. Membrane edge tension was shown to be sensitive to membrane composition and to decrease in the presence of TX-100. We propose that extensive permeabilization occurs below a critical membrane edge tension, which is eventually reached in the partially and fully soluble compositions, but not in the insoluble mixture. (C) 2016 Elsevier Ireland Ltd. All rights reserved.