Ethanol induces transforming growth factor-alpha expression in hepatocytes, leading to stimulation of collagen synthesis by hepatic stellate cells.
BACKGROUND
Liver fibrosis often develops in alcoholic liver diseases without accompanying inflammation; however, the underlying mechanism is unclear. Using ethanol-exposed human HepG2 hepatoblastoma cells as a model for alcoholic liver diseases, we previously found that ethanol exposure causes HepG2 cells to secrete an approximately 6,000 Da nonheparin-binding polypeptide that stimulates collagen synthesis in human IMR-90 fibroblasts. The aim of the current study was to characterize and identify this factor.


METHODS
Concentration of type I procollagen peptide and transforming growth factor (TGF)-alpha was assessed by enzyme-linked immunosorbent assay. TGF-alpha protein expression was examined by Western blot. Type I collagen messenger RNA expression in rat hepatic stellate cells was assessed by reverse transcription-polymerase chain reaction.


RESULTS
The collagen-stimulating activity in conditioned media from ethanol-exposed HepG2 cells to stimulate type I procollagen peptide synthesis of IMR-90 cells was specifically inhibited by addition of anti-TGF-alpha antibodies. Western blot analysis showed increased TGF-alpha protein expression in ethanol-treated HepG2 cells. TGF-alpha in conditioned medium from ethanol-exposed HepG2 cells stimulated type-I collagen messenger RNA expression in rat hepatic stellate cells.


CONCLUSIONS
These results suggest that TGF-alpha derived from ethanol-exposed hepatocytes may contribute to the development of hepatic fibrosis in alcoholic liver diseases.
Kato
Junji
J
Fourth Department of Internal Medicine, Sapporo Medical University School of Medicine, Sapporo, Japan. jkato@sapmed.ac.jp
Sato
Yasuhiro
Y
Inui
Noriaki
N
Nakano
Yoichiro
Y
Takimoto
Rishu
R
Takada
Kohich
K
Kobune
Masayoshi
M
Kuroiwa
Ganji
G
Miyake
Sachie
S
Kohgo
Yutaka
Y
Niitsu
Yoshiro
Y
D015153:Blotting, Western; D003094:Collagen / Q000096:biosynthesis*; D024042:Collagen Type I / Q000235:genetics*; D017077:Culture Media, Conditioned; D000431:Ethanol / Q000633:toxicity*; D015870:Gene Expression / Q000502:physiology; D018197:Hepatoblastoma; D022781:Hepatocytes / Q000187:drug effects*; D006801:Humans; D008104:Liver Cirrhosis, Alcoholic / Q000235:genetics / Q000473:pathology; D008113:Liver Neoplasms; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016211:Transforming Growth Factor alpha / Q000235:genetics*; D014407:Tumor Cells, Cultured / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects
D024042:Collagen Type I; D017077:Culture Media, Conditioned; D012333:RNA, Messenger; D016211:Transforming Growth Factor alpha; D000431:Ethanol; D003094:Collagen