Epigallocatechin-3-gallate, a green-tea polyphenol, suppresses Rho signaling in TWNT-4 human hepatic stellate cells

• Published in: The Journal of laboratory and clinical medicine 2005-06, Vol.145 (6), p.316-322
• Main Authors: Higashi, Nobuhiko, Kohjima, Motoyuki, Fukushima, Marie, Ohta, Satoshi, Kotoh, Kazuhiro, Enjoji, Munechika, Kobayashi, Naoya, Nakamuta, Makoto
• Format: Article
• Language: English
• Subjects: Actins - metabolism; Anticarcinogenic Agents - pharmacology; Apoptosis - drug effects; Biological and medical sciences; Catechin - analogs & derivatives; Catechin - pharmacology; Cell Division - drug effects; Cell Line; Flavonoids - pharmacology; Focal Adhesion Kinase 1; Focal Adhesion Protein-Tyrosine Kinases; General aspects; Hepatocytes - cytology; Hepatocytes - drug effects; Hepatocytes - metabolism; Humans; In Vitro Techniques; Investigative techniques, diagnostic techniques (general aspects); JNK Mitogen-Activated Protein Kinases - metabolism; Liver Cirrhosis - drug therapy; Liver Cirrhosis - metabolism; MAP Kinase Signaling System - drug effects; Medical sciences; Mitogen-Activated Protein Kinase 1 - metabolism; Mitogen-Activated Protein Kinase 3 - metabolism; p38 Mitogen-Activated Protein Kinases - metabolism; Phenols - pharmacology; Phosphorylation - drug effects; Polyphenols; Protein-Tyrosine Kinases - metabolism; rho GTP-Binding Proteins - metabolism; Stress Fibers - drug effects; Tea
• ISSN: 0022-2143; 1532-6543
• DOI: 10.1016/j.lab.2005.03.017

Epigallocatechin-3-gallate (EGCG), a major constituent of the polyphenoids in green tea, has been reported to possess a wide range of biologic activities, including antifibrogenesis. Activated hepatic stellate cells (HSCs) are central to hepatic fibrosis, and Rho (a small GTPase)-signaling pathways have been implicated in the activation and proliferation of HSCs. In this study, we investigated the effect of EGCG on Rho-signaling pathways in activated human HSC-derived TWNT-4 cells. EGCG inhibited stress-fiber formation, an indicator of Rho activation, and changed the distribution of α-smooth-muscle actin. These inhibitory effects of EGCG were restored by overexpression of constitutively active Rho. A pull-down assay revealed that activated Rho (GTP-bound state) was strongly inhibited by ECGC and accompanied by suppressed phosphorylation of focal adhesion kinase, which is a regulator of Rho-signaling pathways. 5-Bromo-2′-deoxy-uridine incorporation demonstrated that ECGC (100 μmol/L suppressed cell growth by 80%, and terminal deoxynucleotidyl transferase viotin-deoxyruidine triphosphate nick end-labeling revealed that EGCG (100 μmol/L) caused apoptosis in half of the total cells. EGCG also strongly inhibited lysophoaphatidic acid (an activator of Rho) and induced phosphorylation of mitogen-activated protein kinases (Erk1/2, c-jun kinase, and p38). These findings demonstrate that EGCG regulates the structure and growth of HSCs by way of Rho-signaling pathways and suggest that EGCG has therapeutic potential in the setting of liver fibrosis.