O. Yu. Borikov

Background. The use of antimicrobial peptides is one of the possible ways to overcome the threatening rapid growth of resistance of microorganisms to traditional antibiotics. Of the particular role in this context is gramicidin S (GS), which is used for topical medical applications for over 70 years. An acute hemolytic side effect of GS on human cells prevents its systemic use. Understanding the molecular mechanisms of interaction of GS with biological membranes will enhance its bactericidal effect on the one hand, and reduce the negative side effects on human cells and thus expand the range of antibacterial peptides to combat infectious diseases caused by resistant microorganisms. Objectives. Study of the effect of different doses of the antimicrobial oligopeptide antibiotic GS on the morphological and electrophysical characteristics of human erythrocytes during in vitro incubation. Materials and methods. Morphological changes of erythrocytes of healthy donors after preliminary incubation with GS at concentrations 5–40 μg/ml were studied by flow cytometry using resistance pulse spectroscopy. Single-cell volume, erythrocyte volume distribution in the population was measured, and the electrical breakdown potential of the human erythrocyte plasma membrane was determined. Results. Incubation of human erythrocytes with sub-lytic concentrations of GS is accompanied by a redistribution of erythrocytes in this population by volume with an increased number of smaller erythrocytes with less resistance of the membrane to electrical breakdown. However, increasing the concentration of GS to 40 μg/ml leads to an increase in the proportion of cells of increased volume with increased resistance to electrical breakdown of the membrane. Possible mechanisms of morphological changes of erythrocytes under the action of GS are discussed. Conclusions. Incubation of erythrocytes with GS at concentrations 5–40 μg/ml is accompanied by a redistribution of cells by volume and changes in the resistance of their plasma membrane to electrical breakdown due to destabilizing membrane-tropic action of the peptide, microsimulation, or cytoskeleton rearrangement.