Protective effect of HIF-1alpha-dependent HO-1 overexpression on hypoxic human hepatoma cells in vitro

Abstract

To investigate the protective effect of overexpressed heme oxygenase-1 (HO-1) in hypoxia and the correlation between HO-1 overexpressoin and hypoxia inducible factor-1alpha (HIF-1alpha) in human hepatoma HepG2 cells. The expressions of HO-1 and HIF-1alpha mRNA as well as the protein were detected by RT-PCR and Western blotting, respectively. MTT assay was used to examine the relative cell survival rate. The total superoxide dismutase (SOD) activity was examined with a SOD kit. Hypoxia induced overexpression of HO-1 gene in HepG2 cells at transcriptional and translational levels. The relative survival rate of HepG2 cells under hypoxia was significantly decreased after the HO-1 protein overexpression was inhibited by ZnPPIX (P < 0.01). The total SOD activity of cells was significantly increased after cells were treated by hypoxia for 16 hours (P < 0.05), while decreased significantly by HO-1 inhibitor ZnPPIX treatment (P < 0.01). HIF-1alpha was upregulated under hypoxia. In addition, the HO-1 overexpression under hypoxia was decreased by HIF-1alpha inhibitor, while the HIF-1alpha expression level under hypoxia was not significantly changed after HO-1 expression was inhibited by ZnPPIX. The overexpression of HO-1 in hypoxic HepG2 cells is HIF-1alpha-dependent or at least partly HIF-1alpha-dependent. The relative survival rate of hypoxic hepatoma cells was significantly decreased by HO-1 inhibitor treatment. The results of this study may offer new thought and drug target for the therapy of human hepatoma in the future.