Linearized esculentin-2EM shows pH dependent antibacterial activity with an alkaline optimum

Here the hypothesis that linearized esculentin 2EM (E2EM-lin) from Glandirana emeljanovi possesses pH dependent activity is investigated. The peptide showed weak activity against Gram-negative bacteria (MLCs ≥ 75.0 μM) but potent efficacy towards Gram-positive bacteria (MLCs ≤ 6.25 μM). E2EM-lin adopted an α-helical structure in the presence of bacterial membranes that increased as pH was increased from 6 to 8 (↑ 15.5 to 26.9 %), while similar increases in pH enhanced the ability of the peptide to penetrate (↑ 2.3 to 5.1 mN m-1) and lyse (↑ 15.1 to 32.5%) these membranes. Theoretical analysis predicted that this membranolytic mechanism involved a tilted segment, that increased along the α-helical long axis of E2EM-lin (1-23) in the N → C direction, with - increasing overall from circa - 0.8 to - 0.3. In combination, these data showed that E2EM-lin killed bacteria via novel mechanisms that were enhanced by alkaline conditions and involved the formation of tilted and membranolytic, α-helical structure. The preference of E2EM-lin for Gram-positive bacteria over Gram-negative organisms was primarily driven by the superior ability of phosphatidylglycerol to induce α-helical structure in the peptide as compared to phosphatidylethanolamine. These data were used to generate a novel pore-forming model for the membranolytic activity of E2EM-lin, which would appear to be the first, major reported instance of pH dependent AMPs with alkaline optima using tilted structure to drive a pore-forming process. It is proposed that E2EM-lin has the potential for development to serve purposes ranging from therapeutic usage, such as chronic wound disinfection, to food preservation by killing food spoilage organisms

Mitochondrial Alterations and Oxidative Stress in Cystic Fibrosis

Cystic fibrosis (CF) is the most frequent autosomal recessive disease and is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Since the discovery of the deletion in the phenylalanine 508 site (ΔF508) of the CFTR gene, the study of its function as chloride channel occupied most investigations. Now, we know that CFTR is also involved in the GSH and HCO3− transport, and its function could regulate the mitochondrial function and ROS production. In this way, the notion of the CFTR as a simple chloride channel has begun to change toward a more complex function as molecular hub that integrates different cellular signals. There is a growing body of evidence that shows mitochondrial dysfunctions and increased oxidative stress in CF. Here, we review the mitochondrial defects induced by the altered function of the CFTR in CF, focusing on oxidative stress and inflammation as targets for therapy.Fil: Valdivieso, Ángel Gabriel. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires". Instituto de Investigaciones Biomédicas. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas; Argentin