title: Ethylmalonic acid induces permeability transition in isolated brain mitochondria.
abstract: Predominant accumulation of ethylmalonic acid (EMA) in tissues and biological fluids is a characteristic of patients affected by short chain acyl-CoA dehydrogenase deficiency and ethylmalonic encephalopathy. Neurological abnormalities are frequently found in these disorders, but the mechanisms underlying the brain injury are still obscure. Since hyperlacticacidemia is also found in many affected patients indicating a mitochondrial dysfunction; in the present work, we evaluated the in vitro and ex vivo effects of EMA plus Ca(2+) on mitochondrial integrity and redox balance in succinate-supported brain organelles. We verified that the evaluated parameters were disturbed only when EMA was associated with exogenous micromolar Ca(2+) concentrations. Thus, we found that this short chain organic acid plus Ca(2+) dissipated the membrane potential and provoked mitochondrial swelling, as well as impaired the mitochondrial Ca(2+) retention capacity, resulting in a rapid Ca(2+) release and decreased NAD(P)H matrix content. In contrast, EMA was not able to stimulate mitochondrial hydrogen peroxide generation. We also observed that all these effects were prevented by the mitochondrial Ca(2+) uptake inhibitor ruthenium red and the mitochondrial permeability transition (MPT) inhibitors cyclosporin A (CsA) and ADP. Furthermore, mitochondria isolated from rat brains after in vivo intrastriatal administration of EMA was more susceptible to Ca(2+)-induced swelling, which was fully prevented by CsA and ADP. Finally, EMA significantly decreased striatal slice viability, which was attenuated by CsA. The data strongly indicate that EMA reduced the mitochondrial threshold for Ca(2+)-induced MPT reinforcing the role of this cation in EMA-induced disruption of mitochondrial bioenergetics. It is, therefore, presumed that EMA acting synergistically with Ca(2+) compromises mitochondrial energy homeostasis in the central nervous system that may explain at least in part the neurologic alterations presented by patients with abnormal levels of this organic acid.
authors.affiliation: Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal de Rio Grande do Sul, Rua Ramiro Barcelos, 2600-Anexo, Porto Alegre, RS, 90035-003, Brazil.
authors.forename: Cristiane
authors.initials: C
authors.lastname: Cecatto
authors.forename: Alexandre Umpierrez
authors.initials: AU
authors.lastname: Amaral
authors.forename: Guilhian
authors.initials: G
authors.lastname: Leipnitz
authors.forename: Roger Frigério
authors.initials: RF
authors.lastname: Castilho
authors.forename: Moacir
authors.initials: M
authors.lastname: Wajner
mesh_terms: D000818:Animals; D001921:Brain / Q000187:drug effects / Q000503:physiopathology*; D002118:Calcium / Q000378:metabolism; D002491:Central Nervous System Agents / Q000494:pharmacology; D003342:Corpus Striatum / Q000187:drug effects / Q000503:physiopathology; D006861:Hydrogen Peroxide / Q000378:metabolism; D008297:Male; D008314:Malonates / Q000378:metabolism*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects / Q000502:physiology*; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology*; D008933:Mitochondrial Swelling / Q000187:drug effects / Q000502:physiology*; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D010539:Permeability / Q000187:drug effects; D017208:Rats, Wistar; D019802:Succinic Acid / Q000494:pharmacology; D046509:Tissue Culture Techniques
chemical_list: D002491:Central Nervous System Agents; D008314:Malonates; C038080:ethylmalonic acid; D009249:NADP; D019802:Succinic Acid; D006861:Hydrogen Peroxide; D002118:Calcium