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The participation of phospholipids in the interaction of leucocidin and the cell membrane of the polymorphonuclear leucocyte.

ABSTRACT: 1. The interaction of the two components of leucocidin with various lipids has been studied by sedimentation, flotation, light-scattering and changes in the biological activity of leucocidin. 2. Phosphatidylserine, phosphatidylcholine, diphosphoinositide, triphosphoinositide and phosphatidic acid, but not phosphatidylethanolamine, lysophosphatidylcholine, cerebrosides, gangliosides or tristearin, induce aggregation of the F component of leucocidin. 3. The S component of leucocidin does not interact directly with these phospholipids, but interacts with the F component of leucocidin after its modification by lipids. 4. The increased sedimentation or light-scattering induced by low phospholipid concentrations is reversed at higher phospholipid concentrations. 6. The aggregates formed by phospholipids and leucocidin are due, not to adsorption of leucocidin alone, but also to the formation of leucocidin polymers. 7. It is concluded that the aggregation is due to the interaction of the F component with the fatty acid side chains in the lipid micelle. 8. The S component of leucocidin is inactivated by triphosphoinositide at physiological ionic strength; the F component of leucocidin is inactivated at low ionic strength by triphosphoinositide and remains inactive when the ionic strength is increased. 9. It is suggested that in the leucocyte cell membrane the S component of leucocidin interacts with the polar hydrophilic groups of triphosphoinositide and that the F component of leucocidin interacts with the hydrophobic parts of triphosphoinositide.

SUBMITTER: Woodin AM

PROVIDER: S-EPMC1198422 | biostudies-other | 1967 Dec

REPOSITORIES: biostudies-other

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Project description:BackgroundCarvacrol, a mono-terpenoid phenol found in herbs, such as oregano and thyme, has excellent antibacterial properties against Streptococcus pyogenes. However, its mechanism of bactericidal activity on S. pyogenes has not been elucidated.ObjectivesThis study investigated the bactericidal mechanism of carvacrol using three strains of S. pyogenes.MethodsFlow cytometry (FCM) experiments were conducted to determine carvacrol's membrane permeabilization and cytoplasmic membrane depolarization activities. Protoplasts of S. pyogenes were used to investigate carvacrol's effects on the membrane, followed by gel electrophoresis. The carvacrol-treated protoplasts were examined by transmission electron microscopy (TEM) to observe ultrastructural morphological changes. The fluidity of the cell membrane was measured by steady-state fluorescence anisotropy. Thin-layer chromatographic (TLC) profiling was conducted to study the affinity of carvacrol for membrane phospholipids.ResultsIncreased membrane permeability and decreased membrane potential from FCM and electron microscopy observations revealed that carvacrol killed the bacteria primarily by disrupting membrane integrity, leading to whole-cell lysis. Ultra-structural morphological changes in the membrane induced by carvacrol over a short period were confirmed using the S. pyogenes protoplast and membrane isolate models in vitro. In addition, changes in the other biophysical properties of the bacterial membrane, including concentration- and time-dependent increased fluidity, were observed. TLC experiments showed that carvacrol preferentially interacts with membrane phosphatidylglycerol (P.G.), phosphatidylethanolamine (P.E.), and cardiolipins (CL).ConclusionsCarvacrol exhibited rapid bactericidal action against S. pyogenes by disrupting the bacterial membrane and increasing permeability, possibly due to affinity with specific membrane phospholipids, such as P.E., P.G., and CL. Therefore, the bactericidal concentration of carvacrol (250 µg/mL) could be used to develop safe and efficacious natural health products for managing streptococcal pharyngitis or therapeutic applications.

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The participation of phospholipids in the interaction of leucocidin and the cell membrane of the polymorphonuclear leucocyte.

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