Activation of the KEAP1-NRF2-ARE signaling pathway reduces oxidative stress in Hep2 cells

At present there are no studies investigating the effects of the kelch-like ECH-associated protein 1 (KEAP1)-nuclear factor erythroid 2-related factor 2 (NRF2)-antioxidant response element (ARE) signaling pathway on Hep2 cell line. The present study aimed to investigate this topic through knockdown of the KEAP1 gene. A stable Hep2 cell line specifically silencing the human KEAP1 gene was initially constructed. Hydrogen peroxide (H(2)O(2)) was added to the culture medium at various concentrations for various durations to interact with the short hairpin (sh)KEAP1-transfected Hep2 cells. Subsequently, the gene and protein expression levels of KEAP1, NRF2, NAD(P)H quinone oxidoreductase1 (NQO1) and heme oxygenase 1 (HO1) in experimental and control cells were measured by reverse transcription-quantitative polymerase chain reaction and western blotting, respectively. Furthermore, the viability and apoptotic rate of the shKEAP1-transfected Hep2 cells were detected by a Cell Counting-Kit 8 assay and flow cytometry, respectively. In the shKEAP1 Hep2 cell line, the mRNA and protein expression levels of NRF2, NQO1 and HO1 were markedly higher compared with the scramble control-transfected Hep2 and parent Hep2 cell lines. Immunofluorescence staining indicated that NRF2 was primarily located in the cytoplasm of scHep2 and parent Hep2 cell lines, but was present in the nuclei and cytoplasm of the shKEAP1 Hep2 cell line, where it translocates into the nuclei in response to H(2)O(2). Following knockdown of the KEAP1 gene Hep2 cells, the apoptosis rates were 31.8 and 45.3% in scHep2 cells at 0.1 and 0.25 mmol/l H(2)O(2) respectively and 14.1 and 27.9% in shKEAP1 cells. The present study indicated that the KEAP1-NRF2-ARE signaling pathway may exhibit an antioxidative effect within Hep2 cells and may be used for clinical treatment of cancer.