title: Glutamate and glutathione interplay in a motor neuronal model of amyotrophic lateral sclerosis reveals altered energy metabolism.
abstract: Impairment of mitochondrial function might contribute to oxidative stress associated with neurodegeneration in amyotrophic lateral sclerosis (ALS). Glutamate levels in tissues of ALS patients are sometimes altered. In neurons, mitochondrial metabolism of exogenous glutamine is mainly responsible for the net synthesis of glutamate, which is a neurotransmitter, but it is also necessary for the synthesis of glutathione, the main endogenous antioxidant. We investigated glutathione synthesis and glutamine/glutamate metabolism in a motor neuronal model of familial ALS. In standard culture conditions (with glutamine) or restricting glutamine or cystine, the level of glutathione was always lower in the cell line expressing the mutant (G93A) human Cu, Zn superoxide dismutase (G93ASOD1) than in the line expressing wild-type SOD1. With glutamine the difference in glutathione was associated with a lower glutamate and impairment of the glutamine/glutamate metabolism as evidenced by lower glutaminase and cytosolic malate dehydrogenase activity. d-β-hydroxybutyrate, as an alternative to glutamine as energy substrate in addition to glucose, reversed the decreases of cytosolic malate dehydrogenase activity and glutamate and glutathione. However, in the G93ASOD1 cell line, in all culture conditions the expression of pyruvate dehydrogenase kinase l protein, which down-regulates pyruvate dehydrogenase activity, was induced, together with an increase in lactate release in the medium. These findings suggest that the glutathione decrease associated with mutant SOD1 expression is due to mitochondrial dysfunction caused by the reduction of the flow of glucose-derived pyruvate through the TCA cycle; it implies altered glutamate metabolism and depends on the different mitochondrial energy substrates.
authors.affiliation: Laboratory of Molecular Pathology, Department of Molecular Biochemistry and Pharmacology, Istituto di Ricerche Farmacologiche Mario Negri, Via La Masa 19, 20156 Milan, Italy.
authors.forename: Giuseppina
authors.initials: G
authors.lastname: D'Alessandro
authors.forename: Eleonora
authors.initials: E
authors.lastname: Calcagno
authors.forename: Silvia
authors.initials: S
authors.lastname: Tartari
authors.forename: Milena
authors.initials: M
authors.lastname: Rizzardini
authors.forename: Roberto William
authors.initials: RW
authors.lastname: Invernizzi
authors.forename: Lavinia
authors.initials: L
authors.lastname: Cantoni
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D002450:Cell Communication / Q000502:physiology*; D002460:Cell Line; D004195:Disease Models, Animal; D004734:Energy Metabolism / Q000502:physiology*; D018698:Glutamic Acid / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D028361:Mitochondrial Diseases / Q000378:metabolism / Q000473:pathology; D008959:Models, Neurological; D009046:Motor Neurons / Q000378:metabolism* / Q000473:pathology
chemical_list: D018698:Glutamic Acid; D005978:Glutathione