Objective To investigate whether polypeptide cSN50,as a transmembrane peptides,can inhibit NF-κB nuclear translocation and its downstream gene expression to play a role to protect cells by blocking the combination of NF-κB with the importinα3 during the alcohol and endotoxin-induced inflammation and apoptosis.Methods Flow cytometry method was used to observe the apoptosis rate of HepG2 by different concentration of alcohol and/or endotoxin.Spectrophotometer method was used to detect Caspase-3 activity.TNF- α in cell culture supernatant was detected by ELISA assay.p50,importinα3,and IκBαunder the stimulation of alcohol and/or endotoxin at selected optimal concentration were detected by Western blot.Indirect immunofluorescence assay was used to measure the activation of p50,IκBα,and importinα3.Results The change of TNF-α and Caspase-3 in the dose-effect course,compared with control group,was significant (P ＜0.05 ).p50 was increased in the nucleus ( P ＜ 0.05 ),and IκBα was decreased in the cytoplasm ( P ＜ 0.05 ).cSN50( 100 μmol/L) partially blocked nuclear translocation of p50 and its downstream factor( P ＜ 0.05 ).Conclusion NF-κB nuclear translocation may play an important role in acute alcoholic liver injury.cSN50 can effectively inhibit NF-κB activity and its downstream gene expression in HepG2 cells.