Effect of antimicrobial peptides from Galleria mellonella on molecular models of Leishmania membrane. Thermotropic and fluorescence anisotropy study

Antimicrobial peptides are molecules of natural origin, produced by organisms such as insects, which have focused attention as potential antiparasitic agents. They can cause the death of parasites such Leishmania by interacting with their membrane. In this study, additional information was obtained on how the anionic peptide 2 and cecropin D-like peptide derived from Galleria mellonella interact with liposomes that mimic the composition of the Leishmania membrane. In order to do this, lipid bilayers consisting of dipalmitoylphosphatidylcholine, dipalmitoylphosphatidylethanolamine, dimyristoylphosphatidylserine, and dimyristoylphosphatidylglycerol were constructed. The effect of the peptides on these membranes was evaluated using calorimetry analysis and fluorescence spectroscopy. The results obtained using differential scanning calorimetry indicated a concentration-dependent effect on membranes composed of phosphatidylserine and phosphatidylglycerol, showing a preference of both peptides for anionic lipids. The binding of the peptides drastically reduced the transition enthalpy in the phosphatidylserine and phosphatidylglycerol liposomes. The results suggest that the mode of action of anionic peptide 2 and cecropin D-like peptide is different, with a higher effect of cecropin D-like on the anionic lipids, which led to changes in the main transition temperature and a complete solubilization of the vesicles. Interactions between peptides and phosphatidylcholine, which is the most abundant lipid on the surface of Leishmania cells, were evaluated using isothermal titration calorimetry and the anisotropy of fluorescence of DPH. The peptides had a slight effect on the gel phase of the phosphatidylcholine, with changes in the anisotropy correlated with that observed by DSC. The results showed a selectivity of these peptides toward some lipids, which will direct the study of the development of new drugs.