title: Nrf2 activation in the liver of rats subjected to a preconditioning sub-chronic iron protocol.
abstract: Sub-chronic iron (Fe) administration induces liver oxidative stress upregulating cytoprotective mechanisms that may involve redox-sensitive nuclear factor erythroid 2-related factor 2 (Nrf2). We aimed to investigate whether Fe activates Nrf2, in relation to its negative regulator Kelch-like ECH associated protein 1 (Keap1), with consequent antioxidant enzyme induction. Sprague-Dawley rats received six Fe doses (50 mg kg(-1)) on alternate days or saline (controls), a protocol that abrogates ischemia-reperfusion liver injury. Liver reduced glutathione (GSH) content and Nrf2 (Western blot) were measured 24 h after each Fe dose. Increased hepatic Fe deposition (Perls staining) was paralleled by reversible GSH depletion and enhancements in nuclear Nrf2 content and in nuclear/cytosolic Nrf2 ratios. A similar profile was observed for heme oxygenase-1 (HO-1) and NADPH-quinone oxidoreductase 1 (NQO-1) contents, antioxidant enzymes that significantly correlated with nuclear/cytosolic Nrf2 ratios. Normalization of Fe-induced oxidative stress status occurred concomitantly with that of Nrf2 and with the Nrf2-dependent HO-1 and NQO-1 expression, which are associated with delayed enhancement in cytosolic Keap1 levels. This is in agreement with the significant inverse correlation of nuclear/cytosolic Nrf2 ratios with those of nuclear Keap1/Nrf2, suggesting a negative feed-back mechanism normalizing Nrf2 signaling. In conclusion, sub-chronic Fe administration leads to transient liver oxidative stress development and Nrf2 activation, as evidenced by early GSH depletion, enhanced nuclear Nrf2 protein levels, and HO-1 and NQO-1 induction, with late normalization of these changes being related to Keap1 upregulation.
authors.affiliation: Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, Santiago, Chile. vfernand@med.uchile.cl.
authors.forename: Paula
authors.initials: P
authors.lastname: Morales
authors.forename: Romina
authors.initials: R
authors.lastname: Vargas
authors.forename: Luis A
authors.initials: LA
authors.lastname: Videla
authors.forename: Virginia
authors.initials: V
authors.lastname: Fernández
mesh_terms: D000818:Animals; D005978:Glutathione / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D000072019:Kelch-Like ECH-Associated Protein 1; D008099:Liver / Q000378:metabolism*; D008297:Male; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D018384:Oxidative Stress; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; C486610:KEAP1 protein, rat; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2; D007501:Iron; D005978:Glutathione