Fig. 4. Hepatic mRNA expression of antioxidant signaling pathway related genes including nuclear factor erythroid 2-related factor 2 (Nrf2) (A) and Kelch-like ECH-associated protein-1 (Keap1) (B) in HepG2 cells pretreated with different concentrations of PHP, and each mRNA was normalized to ribosomal protein GAPDH and is expressed relative to the control level. Hepatic protein expression of oxidative stress metabolism-related protein and antioxidant signaling pathway related protein (C and D) in HepG2 cells, pretreated with different concentrations of PHP, and each protein expression was normalized to ribosomal protein GAPDH and is expressed relative to the control level. Data are expressed as the mean ± SD. Different letters indicate significant difference at P < 0.05.