Antiproliferative Effects Associated with Membrane Lipid Interaction of Green Tea Catechins

Abstract

In the light of a novel mode of action, the antiproliferative effects of green tea catechins were studied with relating to their membrane lipid interactions. Mouse myeloma cells and liposomes consisting of phospholipids and cholesterol were treated with structurally-different catechins of 10 and 100µ Mf or 0.5–48 hr. The induced changes in membrane fluidity were comparatively determined by measuring fluorescence polarization with different probes to characterize the membrane-acting sites. (–)-Epicatechin3-gallate (ECG) and (–)-epigallocatechin-3-gallate (EGCG) showed the growth-inhibitory effects on tumor cells with the potency increasing in this order, but neither (–)-epicatechin (EC) nor (+)-catechin (C). Simultaneously with inhibiting the cell growth, both catechin gallates rigidified tumor cell membranes by acting on their hydrophilic and hydrophobic regions. The most antiproliferative EGCG predominantly affected the centers of cell membranes and its acting site was deeper with increasing the culture time. Correlating to the comparative effects on tumor cells, EGCG reduced the fluidity of liposomal membranes more intensively than ECG, whereas EC and Cw ere essentially ineffective. The antiproliferative effects of green tea catechin sa re associated with their structure-dependent interactions with lipid bilayers to modify cell membrane fluidity.