nystatin-a1 and 1-2-oleoylphosphatidylcholine

The polyene antifungal antibiotic nystatin confers its biological activity by forming pores in the membranes of target cells. Exposure of only one side of the membrane to nystatin is more relevant than two-side exposure because in vivo antibiotic molecules initially interact with cell membrane from the exterior side. The effect of flavonoids and styryl dyes on the steady-state conductance induced by a cis-side addition of nystatin was investigated by using electrophysiological measurements on artificial membranes. The assessment of changes in membrane dipole potential by dipole modifiers was carried out by their influence on K(+)-nonactin (K(+)-valinomycin) current. The alterations of the phase segregation scenario induced by nystatin and flavonoids were observed via confocal fluorescence microscopy. The introduction of phloretin, phlorizin, biochanin A, myricetin, quercetin, taxifolin, genistin, genistein, and RH 421 leads to a significant increase in the nystatin-induced steady-state transmembrane current through membranes composed of a mixture of DOPC, cholesterol and sphingomyelin (57:33:10 mol%). Conversely, daidzein, catechin, trihydroxyacetophenone, and RH 237 do not affect the transmembrane current. Three possible mechanisms that explain the observed results are discussed: changes in the membrane dipole potential, alterations of the phase separation within the lipid bilayer, and influences of the dipole modifiers on the formation of the lipid mouth of the polyene pore. Most likely, changes in the monolayer curvature in the vicinity of trans-mouth of a nystatin single-length channel prevail over alterations of dipole potential of membrane and the phase segregation scenarios induced by dipole modifiers.

Topics: Antifungal Agents; Cell Membrane; Cholesterol; Flavonoids; Genistein; Isoflavones; Lipid Bilayers; Membrane Lipids; Membrane Potentials; Microscopy, Confocal; Microscopy, Fluorescence; Molecular Structure; Nystatin; Phlorhizin; Phosphatidylcholines; Pyridinium Compounds; Quercetin; Sphingomyelins; Styrenes

This work presents the investigations of the interactions between nystatin, a polyene antibiotic, and phospholipids with various head groups (phosphatidylcholine and phosphatidylethanolamine) and acyl chains of different length and saturation degree. The experiments were performed with the Langmuir monolayer technique. Among phosphatidylethanolamines, DMPE, DPPE and DSPE were studied, while phosphatidylcholines were represented by DSPC and DOPC. The influence of the antibiotic on the molecular organization of the phospholipid monolayer was analysed with the compression modulus values, while the strength of nystatin/phospholipid interactions and the stability of the mixed monolayers were examined on the basis of the excess free energy of mixing values. The results obtained proved a high affinity of nystatin towards phospholipids. Nystatin was found to interact more strongly with phosphatidylcholines than with phosphatidylethanolamines. The most negative values of the excess free energy of mixing observed for the antibiotic and DOPC mixtures prove that nystatin favors the phospholipid with two unsaturated acyl chains. The results imply that nystatin/phospholipid interactions compete in the natural membrane with nystatin/sterol interactions, thereby affecting the antifungal activity of nystatin and its toxicity towards mammalian cells.

Topics: Antifungal Agents; Membranes; Models, Chemical; Models, Statistical; Nystatin; Phosphatidylcholines; Phosphatidylethanolamines; Phospholipids; Polyenes; Pressure; Surface Properties; Thermodynamics

It has generally been assumed that the polyene antibiotics Nystatin and Amphotericin B cause membrane damage by the same mechanism. However, using kinetic fluorescence methods we have found that AmB and Nystatin have very different activities on sterol-free dioleoyl phosphatidylcholine and egg phosphatidylcholine small unilamellar vesicles. At very low AmB concentrations (less than 1/1000 lipids in egg phosphatidylcholine) significant K+ permeability enhancement is observed. However, even at very high Nystatin to lipid ratios (1/100) very little K+ current is induced, particularly in dioleoyl phosphatidylcholine vesicles. The novel technique described here uses a K+/H+ exchange mechanism to detect minute transmembrane K+ currents by monitoring internal membrane vesicle pH changes with pyranine.

Topics: Amphotericin B; Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; Hydrogen-Ion Concentration; Kinetics; Liposomes; Models, Biological; Nystatin; Permeability; Phosphatidylcholines; Potassium