Peroxiredoxin III and sulfiredoxin together protect mice from pyrazole-induced oxidative liver injury

Aims: To define the mechanisms underlying pyrazole-induced oxidative stress and the protective role of peroxiredoxins (Prxs) and sulfiredoxin (Srx) against such stress. Results: Pyrazole increased Srx expression in the liver of mice in a nuclear factor erythroid 2-related factor 2 (Nrf₂)-dependent manner and induced Srx translocation from the cytosol to the endoplasmic reticulum (ER) and mitochondria. Pyrazole also induced the expression of CYP2E1, a primary reactive oxygen species (ROS) source for ethanol-induced liver injury, in ER and mitochondria. However, increased CYP2E1 levels only partially accounted for the pyrazole-mediated induction of Srx, prompting the investigation of CYP2E1-independent ROS generation downstream of pyrazole. Indeed, pyrazole increased ER stress, which is known to elevate mitochondrial ROS. In addition, pyrazole upregulated CYP2E1 to a greater extent in mitochondria than in ER. Accordingly, among Prxs I to IV, PrxIII, which is localized to mitochondria, was preferentially hyperoxidized in the liver of pyrazole-treated mice. Pyrazoleinduced oxidative damage to the liver was greater in PrxIII ^-/- mice than in wild-type mice. Such damage was also increased in Srx ^-/- mice treated with pyrazole, underscoring the role of Srx as the guardian of PrxIII. Innovation: The roles of Prxs, Srx, and ER stress have not been previously studied in relation to pyrazole toxicity. Conclusion: The concerted action of PrxIII and Srx is important for protection against pyrazole-induced oxidative stress arising from the convergent induction of CYP2E1-derived and ER stress-derived ROS in mitochondria.