To find out whether increased mitochondrial stress and ER stress led to changes in antioxidant profiles, western blot analyses were carried out to determine the protein levels of CuZnSOD, MnSOD, peroxiredoxin 1 (PRDX1), peroxiredoxin 3 (PRDX3), thioredoxin 1 (TRX1), and thioredoxin 2 (TRX2). Among them, CuZnSOD, PRDX1, and TRX1 are cytosolic proteins, and MnSOD, PRDX3, and TRX2 are mitochondrial proteins. The sulfonylated peroxiredoxins (PRDX-SO3), which are the end products of irreversible oxidation of the active site cysteine in peroxiredoxins, were also monitored and served as indicators for the redox state in HCV protein-expressing cells ( Figure S5C ). Significant increases in the protein levels of CuZnSOD, MnSOD, PRDX1, PRDX3, TRX1, and TRX2 were consistently observed in the subgenomic replicon cells, and the extent of increase ranges from 1.5-to 4.9-fold ( Figure 5 ). The genome-length replicon cells showed a modest (1.8-fold) but significant increase in TRX2, and a marginal decrease in CuZnSOD (p = 0.0734) and PRDX3 (p = 0.0739) ( Figure 5 ). No remarkable changes were observed between Core-on and Core-off cells. The ratios of PRDX1-SO3/ PRDX1 and PRDX3-SO3/PRDX3 were also used to gauge the redox state in the cytosol and the mitochondria, respectively, and no significant changes were observed across all cell lines analyzed ( Figure S5A and S5B).