title: Overexpression of Nrf2 protects against microcystin-induced hepatotoxicity in mice.
abstract: Oxidative stress and glutathione (GSH) depletion are implicated in mycocystin hepatotoxicity. To investigate the role of nuclear factor erythroid 2-related factor 2 (Nrf2) in microcystin-induced liver injury, Nrf2-null, wild-type, and Keap1-hepatocyte knockout (Keap1-HKO) mice were treated with microcystin (50 μg/kg, i.p.). Blood and liver samples were collected 8 h thereafter. Microcystin increased serum alanine aminotransferase and aspartate aminotransferase activities, and caused extensive inflammation and necrosis in Nrf2-null and wild-type mice, but not in Keap1-HKO mice. Oxidative stress and inflammation are implicated in microcystin-induced hepatotoxicity, as evidenced by increased lipid peroxidation and increased expression of pro-inflammatory genes, such as neutrophil-specific chemokines mKC and MIP-2, and pro-inflammatory cytokines IL-1β and IL-6. The increased expression of these pro-inflammatory genes was attenuated in Keap1-HKO mice. Nrf2 and Nqo1 mRNA and protein were higher in Keap1-HKO mice at constitutive levels and after microcystin. To further investigate the mechanism of the protection, hepatic GSH and the mRNA of GSH-related enzymes were determined. Microcystin markedly depleted liver GSH by 60-70% in Nrf2 and WT mice but only 35% in Keap1-HKO mice. The mRNAs of GSH conjugation and peroxide reduction enzymes, such as Gstα1, Gstα4, Gstμ, and Gpx2 were higher in livers of Keap1-HKO mice, together with higher expression of the rate-limiting enzyme for GSH synthesis (Gclc). Organic anion transport polypeptides were increased by microcystin with the most increase in Keap1-HKO mice. In conclusion, this study demonstrates that higher basal levels of Nrf2 and GSH-related genes in Keap1-HKO mice prevented microcystin-induced oxidative stress and liver injury.
authors.affiliation: University of Kansas Medical Center, Kansas City, Kansas, United States of America; Key Lab for Basic Pharmacology of Ministry of Education, Zunyi Medical College, Zunyi, China.
authors.forename: Yuan-Fu
authors.initials: YF
authors.lastname: Lu
authors.affiliation: University of Kansas Medical Center, Kansas City, Kansas, United States of America; Key Lab for Basic Pharmacology of Ministry of Education, Zunyi Medical College, Zunyi, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Liu
authors.affiliation: University of Kansas Medical Center, Kansas City, Kansas, United States of America.
authors.forename: Kai Connie
authors.initials: KC
authors.lastname: Wu
authors.affiliation: University of Kansas Medical Center, Kansas City, Kansas, United States of America.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Qu
authors.affiliation: Cytopathology, University of Kansas Medical Center, Kansas City, Kansas, United States of America.
authors.forename: Fang
authors.initials: F
authors.lastname: Fan
authors.affiliation: University of Kansas Medical Center, Kansas City, Kansas, United States of America.
authors.forename: Curtis D
authors.initials: CD
authors.lastname: Klaassen
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D056486:Chemical and Drug Induced Liver Injury / Q000235:genetics* / Q000378:metabolism / Q000517:prevention & control*; D018925:Chemokines / Q000235:genetics; D005978:Glutathione / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D051379:Mice; D052998:Microcystins / Q000378:metabolism / Q000633:toxicity*; D051267:NF-E2-Related Factor 2 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism
chemical_list: D018925:Chemokines; D052998:Microcystins; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; D017392:Thiobarbituric Acid Reactive Substances; C078588:microcystin; D005978:Glutathione