Establishment of chronic hepatitis C virus infection: Translational evasion of oxidative defence

Figure 4 Oxidant and anti-oxidant systems. During active respiration in the mitochondria, electron leaked from the respiratory chain reacts with oxygen (O₂) to form reactive oxygen species (ROS) superoxide anion O₂^.- and pro-oxidant-hydrogen peroxide (H₂O₂). O₂^.- is quickly dismuted to H₂O₂ in a reaction catalyzed by superoxide dismutase. Non-mitochondrial sources of O₂^.- and H₂O₂ include cytosolic xanthine oxidase and plasma membrane nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. H₂O₂ is decomposed by iron in the Fenton reaction to yield the highly oxidizing hydroxyl radical .OH, causing macromolecule damage, DNA damage and lipid peroxidation. H₂O₂ can be reduced to water (H₂O) by catalase, glutathione peroxidases and peroxiredoxins.