title: Myocardial ischemic reperfusion induces de novo Nrf2 protein translation.
abstract: Nrf2 is a bZIP transcription factor regulating the expression of antioxidant and detoxification genes. We have found that Nrf2 knockout mice have an increased infarction size in response to regional ischemic reperfusion and have a reduced degree of cardiac protection by means of ischemic preconditioning. With cycles of brief ischemia and reperfusion (5'I/5'R) that induce cardiac protection in wild type mice, an elevated Nrf2 protein was observed without prior increases of Nrf2 mRNA. When an mRNA species is being translated into a protein, it is occupied by multiple ribosomes. The level of ribosome-associated Nrf2 mRNA increased following cycles of 5'I/5'R, supporting de novo Nrf2 protein translation. A dicistronic reporter assay indicated a role of the 5' untranslated region (5' UTR) of Nrf2 mRNA in oxidative stress induced Nrf2 protein translation in isolated cardiomyocytes. Western blot analyses after isolation of proteins binding to biotinylated Nrf2 5' UTR from the myocardium or cultured cardiomyocytes demonstrated that cycles of 5'I/5'R or oxidants caused an increased association of La protein with Nrf2 5' UTR. Ribonucleoprotein complex immunoprecipitation assays confirmed such association indeed occurring in vivo. Knocking down La using siRNA was able to prevent Nrf2 protein elevation by oxidants in cultured cardiomyocytes and by cycles of 5'I/5'R in the myocardium. Our data point out a novel mechanism of cardiac protection by de novo Nrf2 protein translation involving interaction of La protein with 5' UTR of Nrf2 mRNA in cardiomyocytes.
authors.affiliation: Department of Pharmacology, College of Medicine, University of Arizona, 1501 N. Campbell Ave, Tucson, AZ 85724, USA.
authors.forename: Beibei
authors.initials: B
authors.lastname: Xu
authors.affiliation: Department of Pharmacology, College of Medicine, University of Arizona, 1501 N. Campbell Ave, Tucson, AZ 85724, USA.
authors.forename: Jack
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Pharmacology, College of Medicine, University of Arizona, 1501 N. Campbell Ave, Tucson, AZ 85724, USA.
authors.forename: Joshua
authors.initials: J
authors.lastname: Strom
authors.affiliation: Department of Pharmacology, College of Medicine, University of Arizona, 1501 N. Campbell Ave, Tucson, AZ 85724, USA.
authors.forename: Sang
authors.initials: S
authors.lastname: Lee
authors.affiliation: Department of Pharmacology, College of Medicine, University of Arizona, 1501 N. Campbell Ave, Tucson, AZ 85724, USA. Electronic address: qchen@email.arizona.edu.
authors.forename: Qin M
authors.initials: QM
authors.lastname: Chen
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D017202:Myocardial Ischemia / Q000209:etiology / Q000378:metabolism / Q000473:pathology*; D015425:Myocardial Reperfusion; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D051267:NF-E2-Related Factor 2 / Q000502:physiology*; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress; D046188:Protein Modification, Translational; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D016601:RNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012270:Ribosomes / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: C522787:La protein, rat; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; D016877:Oxidants; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D006861:Hydrogen Peroxide
keywords: Cardiac protection; Ischemic stress; Protein translation; RNA binding