Epigallocatechin-3-gallate, a green-tea polyphenol, suppresses Rho signaling in TWNT-4 human hepatic stellate cells.
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 alpha-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 micromol/L suppressed cell growth by 80%, and terminal deoxynucleotidyl transferase viotin-deoxyruidine triphosphate nick end-labeling revealed that EGCG (100 micromol/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.
Higashi
Nobuhiko
N
Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, Japan.
Kohjima
Motoyuki
M
Fukushima
Marie
M
Ohta
Satoshi
S
Kotoh
Kazuhiro
K
Enjoji
Munechika
M
Kobayashi
Naoya
N
Nakamuta
Makoto
M
D000199:Actins / Q000378:metabolism; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D005419:Flavonoids / Q000494:pharmacology; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008103:Liver Cirrhosis / Q000188:drug therapy / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010636:Phenols / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D059808:Polyphenols; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D022502:Stress Fibers / Q000187:drug effects; D013662:Tea; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
D000199:Actins; D016588:Anticarcinogenic Agents; D005419:Flavonoids; D010636:Phenols; D059808:Polyphenols; D013662:Tea; D002392:Catechin; C045651:epigallocatechin gallate; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D020741:rho GTP-Binding Proteins