Hepatitis C virus F protein inhibits cell apoptosis by activation of intracellular NF-κB pathway

Aim:  To observe the influence of HCV F protein on apoptosis of HepG2 cells, and explore the association between F protein and NF-κB signal pathway.
Methods:  HCV 1b F gene containing HepG2-F cells and HCV 1b C gene containing HepG2-C cells were treated with 100 IU/mL TNF-α, and analyzed by flow cytometry, Western blotting, and dual luciferase reporter assay. Empty plasmid pcDNA3.1⁺ containing HepG2-3.1 cells were used as control.
Results:  (i) With the treatment of TNF-α for 18 h, the apoptosis rates (AR) of HepG2-F and HepG2-3.1 cells were 0.41% (± 0.11%) and 37.43% (± 2.03%) respectively, while that of HepG2-C was 4.07% (± 0.18%). At 36 h after TNF-α treatment, the AR of HepG2-F and HepG2-3.1 cells were 10.03% (± 0.41%) and 44.63% (± 3.37%), and that of HepG2-C was 14.95% (± 0.85%). (ii) After the treatment of TNF-α for 0.5–18 h, the p65 contents in the whole cells of HepG2-F and HepG2-3.1 showed no significant difference ( P  = 0.34, t  = 1.08), while the p65 contents in the nucleus of HepG2-F and HepG2-3.1 cells were 3.8–1.9 times and 1.8–1.0 times higher than that in the non-treated cells ( P  = 0.013, t  = 4.25). (iii) The relative luciferase unit (RLU) of the HepG2 cells, co-transfected with pcDNA3.1-F and pNF-κB-luc, and then treated with TNF-α (100 IU/mL) for 18 h, showed a pcDNA3.1-F dose-dependent increase.
Conclusion:  HCV F protein can over-activate NF-κB signal pathway, which makes HepG2-F cells able to resist TNF-α induced apoptosis.