Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0004134 (ataxia)
 15,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ataxia-telangiectasia (A-T) is an autosomal recessive disorder caused by mutations in the ATM gene. A-T children demonstrate sensitivity to ionizing radiation, predisposition to hematological malignancies, and telangiectasias. However, the hallmark of A-T is fulminant degeneration of cerebellar Purkinje cells accompanied by a progressive ataxia with features of both cerebellar and basal ganglia dysfunction. Although the ATM gene product (ATM) is known to be involved in DNA repair, the mechanisms that link loss of ATM with neurodegeneration remain unknown. Recently, it has been suggested that abnormalities in redox status contribute to the A-T phenotype. To address this question in the nervous system, we measured reactive oxygen species (ROS) in brain regions and specific neuronal populations in ATM-/- mice. We found increased ROS levels in cerebellum and striatum but not cortex of ATM-/- mice compared to ATM+/+ mice. Confocal microscopic examination revealed elevated superoxide levels in cerebellar Purkinje cells and nigral dopaminergic neurons but not cortical neurons, thus mapping increased superoxide levels onto the neuronal populations selectively affected in A-T. These data are the first demonstration of elevated levels of ROS in neurons at risk in any genetic neurodegenerative disorder and, furthermore, suggest that ATM acts as a pro-survival signal in post-mitotic Purkinje cells and dopaminergic neurons by modifying superoxide radical handling in these selectively vulnerable neurons.
 ...
PMID:Superoxide stress identifies neurons at risk in a model of ataxia-telangiectasia. 1135 53

Vitamin E is the major lipid-soluble chain-breaking antioxidant in mammals and plays an important role in normal development and physiology. Deficiency (whether dietary or genetic) results in primarily nervous system pathology, including cerebellar neurodegeneration and progressive ataxia (abnormal gait). However, despite the widely acknowledged antioxidant properties of vitamin E, only a few studies have directly correlated levels of reactive oxygen species with vitamin E availability in animal models. We explored the relationship between vitamin E and reactive oxygen species in two mouse models of vitamin E deficiency: dietary deficiency and a genetic model (tocopherol transfer protein, Ttp-/- mice). Both groups of mice developed nearly complete depletion of alpha-tocopherol (the major tocopherol in vitamin E) in most organs, but not in the brain, which was relatively resistant to loss of alpha-tocopherol. F4-neuroprostanes, an index of lipid peroxidation, were unexpectedly lower in brains of deficient mice compared with controls. In vivo oxidation of dihydroethidium by superoxide radical was also significantly lower in brains of deficient animals. Superoxide production by brain mitochondria isolated from vitamin E-deficient and Ttp-/- mice, measured by electron paramagnetic resonance spectroscopy, demonstrated a biphasic dependence on exogenously added alpha-tocopherol. At low concentrations, alpha-tocopherol enhanced superoxide flux from mitochondria, a response that was reversed at higher concentrations. Here we propose a mechanism, supported by molecular modeling, to explain decreased superoxide production during alpha-tocopherol deficiency and speculate that this could be a beneficial response under conditions of alpha-tocopherol deficiency.
 ...
PMID:Prolonged alpha-tocopherol deficiency decreases oxidative stress and unmasks alpha-tocopherol-dependent regulation of mitochondrial function in the brain. 1818 Mar 6