Lower activity of CCAAT/enhancer-binding protein and expression of cyclin E, but not cyclin D1, activating protein-1 and p21^WAF1, after partial hepatectomy in obstructive jaundice

CCAAT/enhancer-binding protein (C/EBP)-α stabilizes p21^WAF1, whereas activating protein-1 (AP-1) and C/EBP-β enhance cyclin D1 and cyclin E expression, respectively, during the progress of liver regeneration. In this study, we investigated the differences in the transcription factors and cell cycle regulators between obstructive jaundiced and control rats before and after hepatectomy accompanied with a release of biliary obstruction by internal biliary drainage. The expressions and activities of C/EBP-α and -β were significantly decreased in the jaundiced group concomitant with the significantly lower cyclin E expression after hepatectomy than in the controls. The activities of AP-1, cyclin D1 and p21^WAF1 were not significantly different between the two groups. These results suggest that obstructive jaundice inhibits hepatic expression and activity of C/EBP, resulting in the impaired cyclin E expression that is partly responsible for the cell cycle dysfunction after hepatectomy.