Genetic Evidence of an Evolutionarily Conserved Role for Nrf2 in the Protection against Oxidative Stress

Abstract

Transcription factor Nrf2 is considered a master regulator of antioxidant defense in mammals. However, it is unclear whether this concept is applicable to nonmammalian vertebrates, because no animal model other than Nrf2 knockout mice has been generated to examine the effects of Nrf2 deficiency. Here, we characterized a recessive loss-of-function mutant of Nrf2 (nrf2^fh318) in a lower vertebrate, the zebrafish (Danio rerio). In keeping with the findings in the mouse model, nrf2^fh318 mutants exhibited reduced induction of the Nrf2 target genes in response to oxidative stress and electrophiles but were viable and fertile, and their embryos developed normally. The nrf2^fh318 larvae displayed enhanced sensitivity to oxidative stress and electrophiles, especially peroxides, and pretreatment with an Nrf2-activating compound, sulforaphane, decreased peroxide-induced lethality in the wild type but not nrf2^fh318 mutants, indicating that resistance to oxidative stress is highly dependent on Nrf2 functions. These results reveal an evolutionarily conserved role of vertebrate Nrf2 in protection against oxidative stress. Interestingly, there were no significant differences between wild-type and nrf2^fh318 larvae with regard to their sensitivity to superoxide and singlet oxygen generators, suggesting that the importance of Nrf2 in oxidative stress protection varies based on the type of reactive oxygen species (ROS).

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.00481-12.

ACKNOWLEDGMENTS

We thank the TILLING consortium (http://webapps.fhcrc.org/science/tilling/index.php) for the mutant screen, T. Kinoshita, T. Hayashi, S. Hosoyamada, R. Sakurazawa, M. Takeuchi, and N. Tsuruta for help in fish maintenance, and E. Warabi for helpful discussion and comments.

This work was supported by Grants-in-Aid for Scientific Research (20059004, 21026003, 21659043, 24116504, and 24590340) from the Ministry of Education, Culture, Sports, Science and Technology and the Japan Society for the Promotion of Science (to M.K.). The generation of the nrf2 mutant zebrafish by TILLING was carried out with the support of NIH grant HG002995 to Cecilia Moens in the Fred Hutchinson Cancer Research Center.