Nitric oxide and TGF-beta1 inhibit HNF-4alpha function in HEPG2 cells.
This study analyzes if the profibrogenic factors nitric oxide and transforming growth factor-beta1 (TGF-beta1) affect hepatocyte nuclear factor-4alpha (HNF-4alpha) function. For this purpose, HepG2 cells were treated with TGF-beta1 or with a nitric oxide donor to determine mRNA levels of coagulation factor VII and HNF-4alpha. Treatment effect on factor VII gene promoter was assessed by chloramphenicol acetyl-transferase assays in cells transfected with the pFVII-CAT plasmid. HNF-4alpha binding and protein levels were determined by gel shift assays and Western blot. TGF-beta1 and nitric oxide downregulated factor VII mRNA levels by inhibiting its gene promoter activity. This inhibition is caused by a decrease in the DNA binding of HNF-4alpha. TGF-beta1 induces degradation of HNF-4alpha in the proteasome while nitric oxide provokes nitrosylation of cysteine residues in this factor. TGF-beta1 and nitric oxide inhibit HNF-4alpha activity. These findings may explain the loss of liver functions that occurs during fibrosis progression.
de Lucas
Susana
S
Fundación para el Estudio de las Hepatitis Virales, Madrid, Spain.
López-Alcorocho
Juan Manuel
JM
Bartolomé
Javier
J
Carreño
Vicente
V
D045744:Cell Line, Tumor; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005167:Factor VII / Q000235:genetics / Q000378:metabolism; D005355:Fibrosis / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation; D051557:Hepatocyte Nuclear Factor 4; D006801:Humans; D008099:Liver / Q000473:pathology / Q000502:physiology; D009097:Multienzyme Complexes / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D026423:S-Nitroso-N-Acetylpenicillamine / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D053773:Transforming Growth Factor beta1
D004268:DNA-Binding Proteins; C496592:HNF4A protein, human; D051557:Hepatocyte Nuclear Factor 4; D009097:Multienzyme Complexes; D010750:Phosphoproteins; D012333:RNA, Messenger; C508960:TGFB1 protein, human; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D009569:Nitric Oxide; D026423:S-Nitroso-N-Acetylpenicillamine; D005167:Factor VII; D004247:DNA; D015500:Chloramphenicol O-Acetyltransferase; D017868:Cyclic AMP-Dependent Protein Kinases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex