Hana Satonaka1, Kumiki Ishida1, Miho Takai1, Ryoji Koide1, Ryota Shigemasa1, Jun Ueyama1, Tetsuya Ishikawa1, Kazuhiko Hayashi2, Hidemi Goto2, Shinya Wakusawa3. 1. Division of Medical Laboratory Sciences, Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya, Japan. 2. Division of Gastroenterology, Department of Internal Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan. 3. Division of Medical Laboratory Sciences, Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya, Japan wakusawa@met.nagoya-u.ac.jp.
Abstract
BACKGROUND/AIM: (-)-Epigallocatechin-3-gallate (EGCG) has been indicated to regulate the function of P-glycoprotein (P-gp), which is a drug transporter encoded by the MDR1 (ABCB1) gene. P-gp expression is induced by doxorubicin (DOX). We aimed to clarify the mechanisms and inhibitory effects of EGCG on DOX-induced P-gp expression in HepG2 cells. MATERIALS AND METHODS: Rhodamine 123 (Rho123) was used for P-gp substrate. Western blotting and polymerase chain reactions (PCRs) were conducted using specific antibodies and primer sets. RESULTS: The DOX-pretreated cells accumulated a significantly decreased amount of Rho123), than control cells; however, the cells pretreated with EGCG and DOX, in combination, accumulated Rho123 more than DOX-pretreated cells. DOX induced the overexpression of MDR1 mRNA and increased the phosphorylation of Akt, ERK1/2, p38 MAPK and JNK. EGCG significantly inhibited the phosphorylation of Akt and ERK. The DOX-induced P-gp overexpression was partially suppressed by an inhibitor of MEK1/2 (U0126), but not by a PI3K inhibitor (LY294002). Interestingly, the expression of P-gp was synergistically inhibited by combined treatment of U0126 with LY294002 and also inhibited by an mTORC1 inhibitor, rapamycin. CONCLUSION: EGCG inhibited DOX-induced overexpression of P-gp through the coordinate inhibitory action on MEK/ERK and PI3K/Akt signaling pathways. Copyright
BACKGROUND/AIM: (-)-Epigallocatechin-3-gallate (EGCG) has been indicated to regulate the function of P-glycoprotein (P-gp), which is a drug transporter encoded by the MDR1 (ABCB1) gene. P-gp expression is induced by doxorubicin (DOX). We aimed to clarify the mechanisms and inhibitory effects of EGCG on DOX-induced P-gp expression in HepG2 cells. MATERIALS AND METHODS:Rhodamine 123 (Rho123) was used for P-gp substrate. Western blotting and polymerase chain reactions (PCRs) were conducted using specific antibodies and primer sets. RESULTS: The DOX-pretreated cells accumulated a significantly decreased amount of Rho123), than control cells; however, the cells pretreated with EGCG and DOX, in combination, accumulated Rho123 more than DOX-pretreated cells. DOX induced the overexpression of MDR1 mRNA and increased the phosphorylation of Akt, ERK1/2, p38MAPK and JNK. EGCG significantly inhibited the phosphorylation of Akt and ERK. The DOX-induced P-gp overexpression was partially suppressed by an inhibitor of MEK1/2 (U0126), but not by a PI3K inhibitor (LY294002). Interestingly, the expression of P-gp was synergistically inhibited by combined treatment of U0126 with LY294002 and also inhibited by an mTORC1 inhibitor, rapamycin. CONCLUSION:EGCG inhibited DOX-induced overexpression of P-gp through the coordinate inhibitory action on MEK/ERK and PI3K/Akt signaling pathways. Copyright