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      Oxr1 Is Essential for Protection against Oxidative Stress-Induced Neurodegeneration

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          Abstract

          Oxidative stress is a common etiological feature of neurological disorders, although the pathways that govern defence against reactive oxygen species (ROS) in neurodegeneration remain unclear. We have identified the role of oxidation resistance 1 (Oxr1) as a vital protein that controls the sensitivity of neuronal cells to oxidative stress; mice lacking Oxr1 display cerebellar neurodegeneration, and neurons are less susceptible to exogenous stress when the gene is over-expressed. A conserved short isoform of Oxr1 is also sufficient to confer this neuroprotective property both in vitro and in vivo. In addition, biochemical assays indicate that Oxr1 itself is susceptible to cysteine-mediated oxidation. Finally we show up-regulation of Oxr1 in both human and pre-symptomatic mouse models of amyotrophic lateral sclerosis, indicating that Oxr1 is potentially a novel neuroprotective factor in neurodegenerative disease.

          Author Summary

          Oxygen is vital for life, but it can also cause damage to cells. Consequently, protective proteins (antioxidants) are utilised to maintain the fine balance between oxygen metabolism and the production of potentially toxic reactive oxygen species (ROS). If this balance is not maintained, oxidative stress occurs and excess ROS are generated, causing damage to DNA, proteins, and lipids. The brain is particularly susceptible to oxidative stress, and ROS–induced damage is a common feature of all major neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD). However, the molecular mechanisms of ROS defence in neurons are still under investigation. Here we describe the characterisation of oxidation resistance 1 ( Oxr1), a gene previously shown to be induced under oxidative stress. We show both in mice and in cells that loss of Oxr1 causes cell death and that increasing protein levels can protect against ROS. In addition, Oxr1 is over-expressed in the spinal cord in ALS patients, as well as in a pre-symptomatic ALS mouse model. These data demonstrate for the first time that Oxr1 is vital for the protection of neuronal cells against oxidative stress and that induction of Oxr1 may be relevant to neurodegenerative pathways in disease.

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          Most cited references41

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          Neurodegeneration, myocardial injury, and perinatal death in mitochondrial superoxide dismutase-deficient mice.

          Manganese superoxide dismutase (SOD2) converts superoxide to oxygen plus hydrogen peroxide and serves as the primary defense against mitochondrial superoxide. Impaired SOD2 activity in humans has been associated with several chronic diseases, including ovarian cancer and type I diabetes, and SOD2 overexpression appears to suppress malignancy in cultured cells. We have produced a line of SOD2 knockout mice (SOD2m1BCM/SOD2m1BCM) that survive up to 3 weeks of age and exhibit several novel pathologic phenotypes including severe anemia, degeneration of neurons in the basal ganglia and brainstem, and progressive motor disturbances characterized by weakness, rapid fatigue, and circling behavior. In addition, SOD2m1BCM/SOD2m1BCM mice older than 7 days exhibit extensive mitochondrial injury within degenerating neurons and cardiac myocytes. Approximately 10% of SOD2m1BCM/SOD2m1BCM mice exhibit markedly enlarged and dilated hearts. These observations indicate that SOD2 deficiency causes increased susceptibility to oxidative mitochondrial injury in central nervous system neurons, cardiac myocytes, and other metabolically active tissues after postnatal exposure to ambient oxygen concentrations. Our SOD2-deficient mice differ from a recently described model in which homozygotes die within the first 5 days of life with severe cardiomyopathy and do not exhibit motor disturbances, central nervous system injury, or ultrastructural evidence of mitochondrial injury.
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            The selenoprotein GPX4 is essential for mouse development and protects from radiation and oxidative damage insults.

            Lipid peroxidation has been implicated in a variety of pathophysiological processes, including inflammation, atherogenesis, neurodegeneration, and the ageing process. Phospholipid hydroperoxide glutathione peroxidase (GPX4) is the only major antioxidant enzyme known to directly reduce phospholipid hydroperoxides within membranes and lipoproteins, acting in conjunction with alpha tocopherol (vitamin E) to inhibit lipid peroxidation. Here we describe the generation and characterization of GPX4-deficient mice by targeted disruption of the murine Gpx4 locus through homologous recombination in embryonic stem cells. Gpx4(-/-) embryos die in utero by midgestation (E7.5) and are associated with a lack of normal structural compartmentalization. Gpx4(+/-) mice display reduced levels of Gpx4 mRNA and protein in various tissues. Interestingly, cell lines derived from Gpx4(+/-) mice are markedly sensitive to inducers of oxidative stress, including gamma-irradiation, paraquat, tert-butylhydroperoxide, and hydrogen peroxide, as compared to cell lines derived from wild-type control littermates. Gpx4(+/-) mice also display reduced survival in response to gamma-irradiation. Our observations establish GPX4 as an essential antioxidant enzyme in mice and suggest that it performs broad functions as a component of the mammalian antioxidant network.
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              DJ-1 gene deletion reveals that DJ-1 is an atypical peroxiredoxin-like peroxidase.

              Parkinson's disease (PD) is a common neurodegenerative movement disorder. Whereas the majority of PD cases are sporadic, rare genetic defects have been linked to this prevalent movement disorder. Mutations in DJ-1 are associated with autosomal recessive early-onset PD. The exact biochemical function of DJ-1 has remained elusive. Here we report the generation of DJ-1 knockout (KO) mice by targeted deletion of exon 2 and exon 3. There is no observable degeneration of the central dopaminergic pathways, and the mice are anatomically and behaviorally similar to WT mice. Fluorescent Amplex red measurements of H(2)O(2) indicate that isolated mitochondria from young and old DJ-1 KO mice have a 2-fold increase in H(2)O(2). DJ-1 KO mice of 2-3 months of age have a 60% reduction in mitochondrial aconitase activity without compromising other mitochondrial processes. At an early age there are no differences in antioxidant enzymes, but in older mice there is an up-regulation of mitochondrial manganese superoxide dismutase and glutathione peroxidase and a 2-fold increase in mitochondrial glutathione peroxidase activity. Mutational analysis and mass spectrometry reveal that DJ-1 is an atypical peroxiredoxin-like peroxidase that scavenges H(2)O(2) through oxidation of Cys-106. In vivo there is an increase of DJ-1 oxidized at Cys-106 after 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine intoxication of WT mice. Taken together these data indicate that the DJ-1 KO mice have a deficit in scavenging mitochondrial H(2)O(2) due to the physiological function of DJ-1 as an atypical peroxiredoxin-like peroxidase.
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                Author and article information

                Contributors
                Role: Editor
                Journal
                PLoS Genet
                plos
                plosgen
                PLoS Genetics
                Public Library of Science (San Francisco, USA )
                1553-7390
                1553-7404
                October 2011
                October 2011
                20 October 2011
                : 7
                : 10
                : e1002338
                Affiliations
                [1 ]Medical Research Council Functional Genomics Unit, Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford, United Kingdom
                [2 ]Medical Research Council Harwell, Harwell, United Kingdom
                [3 ]Wellcome Trust Centre for Human Genetics, Oxford, United Kingdom
                University of Minnesota, United States of America
                Author notes

                Conceived and designed the experiments: PLO MJF EB EBEB BD KED. Performed the experiments: PLO MJF BE EB DLB MTC BD. Analyzed the data: PLO MJF BE. Contributed reagents/materials/analysis tools: BD. Wrote the paper: PLO MJF KED.

                Article
                PGENETICS-D-11-01031
                10.1371/journal.pgen.1002338
                3197693
                22028674
                c69ee133-e4d4-4465-b7bb-39314448d636
                Oliver et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
                History
                : 18 May 2011
                : 24 August 2011
                Page count
                Pages: 13
                Categories
                Research Article
                Biology
                Model Organisms
                Animal Models
                Neuroscience
                Neurobiology of Disease and Regeneration
                Medicine
                Neurology
                Cerebellar Disorders
                Neurodegenerative Diseases

                Genetics
                Genetics

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