title: Evidence that 3-hydroxy-3-methylglutaric acid promotes lipid and protein oxidative damage and reduces the nonenzymatic antioxidant defenses in rat cerebral cortex.
abstract: In the present work we investigated the in vitro effect of 3-hydroxy-3-methylglutarate (HMG) that accumulates in 3-hydroxy-3-methylglutaryl-CoA lyase deficiency (HMGLD) on important parameters of oxidative stress in rat cerebral cortex. It was observed that HMG induced lipid peroxidation by significantly increasing chemiluminescence and levels of thiobarbituric acid-reactive substances (TBA-RS). This effect was prevented by the antioxidants alpha-tocopherol, melatonin, N-acetylcysteine, and superoxide dismutase plus catalase, suggesting that free radicals were involved in the lipid oxidative damage. On the other hand, HMG did not change TBA-RS levels in intact or disrupted mitochondrial preparations, indicating that generation of oxidants by this organic acid was dependent on cytosolic mechanisms. HMG also induced protein oxidative damage in cortical supernatants, which was reflected by increased carbonyl content and sulfhydryl oxidation. Furthermore, HMG significantly reduced the nonenzymatic antioxidant defenses total-radical trapping antioxidant potential, total antioxidant reactivity, and reduced glutathione (GSH) levels in rat cerebral cortex. HMG-induced GSH reduction was totally blocked by melatonin pretreatment. We also verified that the decrease of GSH levels provoked by HMG in cortical supernatants was not due to a direct oxidative effect of this organic acid, because exposition of commercial GSH and purified membrane protein-bound thiol groups to HMG in the absence of cortical supernatants did not decrease the reduced sulfhydryl groups. Finally, the activities of the main antioxidant enzymes were not altered by HMG exposure. Our data indicate that oxidative stress elicited in vitro by HMG may possibly contribute at least in part to the pathophysiology of the brain injury in HMGLD.
authors.affiliation: Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal de Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Guilhian
authors.initials: G
authors.lastname: Leipnitz
authors.forename: Bianca
authors.initials: B
authors.lastname: Seminotti
authors.forename: Josué
authors.initials: J
authors.lastname: Haubrich
authors.forename: Manuela B
authors.initials: MB
authors.lastname: Dalcin
authors.forename: Karina B
authors.initials: KB
authors.lastname: Dalcin
authors.forename: Alexandre
authors.initials: A
authors.lastname: Solano
authors.forename: Giorgia
authors.initials: G
authors.lastname: de Bortoli
authors.forename: Rafael B
authors.initials: RB
authors.lastname: Rosa
authors.forename: Alexandre U
authors.initials: AU
authors.lastname: Amaral
authors.forename: Carlos S
authors.initials: CS
authors.lastname: Dutra-Filho
authors.forename: Alexandra
authors.initials: A
authors.lastname: Latini
authors.forename: Moacir
authors.initials: M
authors.lastname: Wajner
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D002540:Cerebral Cortex / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D015536:Down-Regulation; D005978:Glutathione / Q000037:antagonists & inhibitors; D066298:In Vitro Techniques; D015227:Lipid Peroxidation / Q000187:drug effects*; D015093:Meglutol / Q000494:pharmacology*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D010088:Oxidoreductases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013481:Superoxides / Q000378:metabolism
chemical_list: D000975:Antioxidants; D009419:Nerve Tissue Proteins; D013481:Superoxides; D015093:Meglutol; D010088:Oxidoreductases; D005978:Glutathione