Single GUV Method Reveals Interaction of Tea Catechin (−)-Epigallocatechin Gallate with Lipid Membranes

Abstract

Tea catechins, which are flavonoids and the main components of green tea extracts, are thought to have antibacterial and antioxidant activity. Several studies indicate that lipid membranes are one of the targets of the antibacterial activity of catechins. Studies using a suspension of large unilamellar vesicles (LUVs) indicate that catechin causes gradual leakage of internal contents from LUVs. However, the detailed characteristics of the interaction of catechins with lipid membranes remain unclear. In this study, we investigated the interaction of (-)-epigallocatechin gallate (EGCg), a major catechin in tea extract, with single giant unilamellar vesicles (GUVs) of egg phosphatidylcholine (egg PC) using phase-contrast fluorescence microscopy and the single GUV method. We prepared GUVs of lipid membranes of egg PC in a physiological ion concentration ( approximately 150 mM NaCl) using the polyethylene glycol-lipid method. Low concentrations of EGCg at and above 30 muM induced rapid leakage of a fluorescent probe, calcein, from the inside of single egg PC-GUVs; after the leakage, the GUVs changed into small lumps of lipid membranes. On the other hand, phase-contrast microscopic images revealed the detailed process of the EGCg-induced burst of GUVs, the decrease in their diameter, and their transformation into small lumps. The dependence of the fraction of burst GUVs on EGCg concentration was almost the same as that of the fraction of leaked GUV. This correlation strongly indicates that the leakage of calcein from the inside to the outside of the GUV occurred as a result of the burst of the GUV. The fraction of completely leaked GUV and the fraction of the burst GUV increased with time and also increased with increasing EGCg concentration. We compared the EGCg-induced leakage from single GUVs with EGCg-induced leakage from a LUV suspension. The analysis of the EGCg-induced shape changes shows that the binding of EGCg to the external monolayer of the GUV increases its membrane area, inducing an increase in its surface pressure. Small angle x-ray scattering experiments indicate that the intermembrane distance of multilamellar vesicles of PC membrane greatly decreased at EGCg concentrations above the threshold, suggesting that neighboring membranes came in close contact with each other. On the basis of these results, we discuss the mechanism of the EGCg-induced bursting of vesicles.

Genistein derivatives decrease liposome membrane integrity — Calcein release and molecular modeling study

“…This method was also applied to monitor the effects exerted by different flavonoids on vesicle [18] and giant unilamellar liposome membranes [19]. In the present paper the calcein leakage assay was used to study the impact of a group of newly synthesized genistein derivatives on the liposome membrane permeability.…”

Quercetin and epigallocatechin gallate effects on the cell membranes biophysical properties correlate with their antioxidant potential

“…Several studies investigated the interaction between the two polyphenols and the cell membrane using both artificial membranes (Kajiya et al 2002;Kumazawa et al 2004;Tamba et al 2007;Kamihara et al 2008;Iftime et al 2010) and cell lines (Kanupriya et al 2006;Verstraeten et al 2008) and the results showed that flavonoids induced changes at the cell membrane level that lead to an increased protection against oxidative stress.…”

Epigallocatechin Gallate Induces Upregulation of the Two-Component VraSR System by Evoking a Cell Wall Stress Response in Staphylococcus aureus

“…Epigallocatechin gallate (EGCG), the major polyphenol component of green tea extract, has been shown to possess several antibacterial activities, such as partitioning the lipid bilayer of the bacterial cytoplasmic membrane (7,19,37,38) and specifically inhibiting the activities of bacterial FabG and FabI reductases (key enzymes in fatty acid synthesis) (42), DNA gyrase (16), and gelatinase (5). Moreover, EGCG has been shown to interfere with the integrity of the cell wall through direct binding to peptidoglycan (43).…”