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

Abstract

Abstract. Quercetin and epigallocatechin gallate are two of the most abundant polyphenols in dietary plants, including apples, onions, red wine and green tea. The bioactivity of polyphenols is linked to their ability to interact with cell membranes without being internalized. The aim of the present study was to assess the short-time effect of these polyphenols on membrane anisotropy and transmembrane potential of U937 monocytes and Jurkat T lymphoblasts. Results showed that quercetin and epigallocatechin gallate induced, after 20 minutes cell exposure, a dose-dependent increase of membrane anisotropy and polarization. Anisotropy increase was correlated with the reduction of lipid peroxidation. Our results could indicate that the antioxidant capacity of the tested polyphenols is due to their stabilizing effect on the cell membranes, thus contributing to cell protection in various pathologies and as adjuvant therapy in highly toxic treatment regimens.

In vitro effects of prolonged exposure to quercetin and epigallocatechin gallate of the peripheral blood mononuclear cell membrane

“…Many studies were devoted to the effect of flavonoids on the cell membrane, using different methods to assess membrane fluidity [10,21,47,48]. Steadystate fluorescence polarization of TMA-DPH bound to the cell membrane was used in this study, as the dye displays in isotropic media-specific fluorescence anisotropy properties, which are changed if the free orientation of the probe is restricted by the local microenvironment: membrane fluidity is proportional to the inverse of squared anisotropy [19,30,31]. Polyphenols could affect cell function by modifying plasma membrane structure and physical characteristics, such as fluidity and electrical properties [19,24,25,43,[47][48][49][50][51][52].…”

“…One cell aliquot constituted the control, the second was cultivated in presence of 10 µM quercetin, and the third was cultivated in the presence of 10 µM EGCG. Previous experiments showed that the small amount of DMSO in which quercetin was dissolved did not affect any of the investigated parameters [19].…”

“…DPPP (code D7894, Life Technologies Inc., Molecular Probes) was dissolved in dimethylsulfoxide (DMSO) at a concentration of 5 mM. Previous experiments showed that DMSO (present at less than 1% in the biological samples) did not influence the measurements [19]. After the addition of DPPP at a final concentration of 5 μM, the biological samples were incubated for 20 min at room temperature, in the dark, then DPPP-labeled samples were treated with 10 µM cumene hydroxiperoxide (code 247502, technical grade, from Aldrich) to induce DPPP-oxide formation.…”

“…We previously studied the effects induced by two polyphenol compoundsquercetin and epigallocatechin gallate (EGCG) -in different models of natural and artificial membranes. We demonstrated that the antioxidant effects of quercetin and EGCG correlate with their ability to modulate membrane anisotropy in a dose-dependent manner [19]. The study was performed on constitutively proliferating human cell lines (Jurkat T lymphoblasts and U937 monocytic cells), corresponding to peripheral leukocytes, in order to further translate the effects to in vivo human studies.…”

“…The ability of polyphenols to enter membrane lipid bilayers is critical in explaining their antioxidant and cardio-protective effects. For instance, compounds that can locate to the non-polar region of the bilayer inhibit lipid oxidation either by intercepting intra-membrane radicals or by changing membrane fluidity, disorganizing lipid chains and hindering free radical propagation [9,[19][20][21]. The enhanced generation and accumulation of advanced glycation end products (AGEs) is known to contribute to various disorders, increasing the risk for macrovascular and microvascular complications associated with diabetes mellitus, aging and neurodegenerative diseases [22,23].…”