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. (C) 2004 Elsevier Inc. All rights reserved.