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 (NFκB) during liver regeneration induces hepatocyte apoptosis associated with normal DNA synthesis but decreased mitosis, suggesting that inhibition of NFκB impairs progression from S-phase through the G₂/M phase of the cell cycle. Our aim was to determine if inhibition of NFκB alters cell cycle characteristics in hepatocytes treated with tumor necrosis factor alpha (TNFα). Methods Primary hepatocytes from BALB/c mice were infected with adenoviruses expressing luciferase (control; AdLuc) or the IκB super-repressor (AdIκB) and treated with or without TNFα (30 ng/ml). Flow cytometry was performed (0 to 40 hours) to determine apoptosis and cell cycle progression. Reverse transcriptase-polymerase chain reaction and immunoblots assessed changes in cell cycle mediators and antiapoptotic factors. Results Primary hepatocytes treated with AdIκB and TNFα demonstrated significantly more S-phase cells (14% ± 3% vs 6% ± 2%, P<.05) at 14 hours compared with controls. Inhibition of NFκB with or without TNFα was associated with decreased expression of stem loop bind protein, a marker of cell cycle progression through S-phase. The NFκB-induced antiapoptotic proteins, iNOS and TRAF2, had decreased message at 9 and 12 hours, respectively, in TNFα- and AdIκB-treated cells. Conclusion Inhibition of NFκB in TNFα-treated primary mouse hepatocytes is associated with increased S-phase cell cycle retention and decreased stem loop bind protein.