TNFα-induced hepatocyte apoptosis is associated with alterations of the cell cycle and decreased stem loop binding protein

Background. Inhibition of nuclear factor kappa B (NFkappaB) during liver regeneration induces hepatocyte apoptosis associated with normal DNA synthesis but decreased mitosis, suggesting that inhibition of NFkappaB impairs progression from S-phase through the G(2)/M phase of the cell cycle. Our aim was to determine if inhibition of NFkappaB alters cell cycle characteristics in hepatocytes treated with tumor necrosis factor alpha (TNFalpha). Methods. Primary hepatocytes from BALB/c mice were infected with adenoviruses expressing luciferase (control; AdLuc) or the IkappaB super-repressor (AdIkappaB) and treated with or without TNFalpha (30 ng/ml). Flow cytometry was performed (0 to 40 hours) to determine apoplosis and cell cycle progression. Reverse transcriptase-polymerase chain reaction and immunoblots assessed changes in cell cycle mediators and antiopoptotic factors. Results. Primary hepatocytes treated with AdIkappaB and TNFalpha demonstrated significantly more S-phase cells (14% +/- 3% vs 6% +/- 2%, P < .05) at 14 hours compared with controls. Inhibition of NFkappaB with or without TNFalpha was associated with decreased expression of stem loop bind protein, a marker of cell cycle progression through S-phase. The NFkappaB-induced antiapoptotic proteins, iNOS and TRAF2, had decreased message at 9 and 12 hours, respectively, in TNFalpha- and AdIkappaB-treated cells. Conclusion. Inhibition of NFkappaB in TNFalpha-treated primary mouse hepatocytes is associated with increased S-phase cell cycle retention and decreased stem loop bind protein.