title: Antioxidant dysfunction: potential risk for neurotoxicity in ethylmalonic aciduria.
abstract: Mitochondrial dysfunction and oxidative stress are central to the molecular basis of several human diseases associated with neuromuscular disabilities. We hypothesize that mitochondrial dysfunction also contributes to the neuromuscular symptoms observed in patients with ethylmalonic aciduria and homozygosity for ACADS c.625G>A-a common variant of the short-chain acyl-coenzyme A (CoA) dehydrogenase (SCAD) enzyme in the mitochondrial fatty acid oxidation pathway. This study sought to identify the specific factors that initiate cell dysfunction in these patients. We investigated fibroblast cultures from 10 patients with neuromuscular disabilities, elevated levels of ethylmalonic acid (EMA) (>50 mmol/mol creatinine), and ACADS c.625G>A homozygosity. Functional analyses, i.e., ACADS gene and protein expression as well as SCAD enzyme activity measurements, were performed together with a global nano liquid chromatography tandem mass spectroscopy (nano-LC-MS/MS)-based screening of the mitochondrial proteome in patient fibroblasts. Moreover, cell viability of patient fibroblasts exposed to menadione-induced oxidative stress was evaluated. Loss of SCAD function was detected in the patient group, most likely due to decreased ACADS gene expression and/or elimination of misfolded SCAD protein. Analysis of the mitochondrial proteome in patient fibroblasts identified a number of differentially expressed protein candidates, including reduced expression of the antioxidant superoxide dismutase 2 (SOD2). Additionally, patient fibroblasts demonstrated significantly higher sensitivity to oxidative stress than control fibroblasts. We propose that reduced mitochondrial antioxidant capacity is a potential risk factor for ACADS c.625G>A-associated ethylmalonic aciduria and that mitochondrial dysfunction contributes to the neurotoxicity observed in patients.
authors.affiliation: Research Unit for Molecular Medicine, Aarhus University Hospital, Skejby, Brendstrupgaardsvej 100, Aarhus N, Denmark. cbak@ki.au.dk
authors.forename: Christina B
authors.initials: CB
authors.lastname: Pedersen
authors.forename: Zarazuela
authors.initials: Z
authors.lastname: Zolkipli
authors.forename: Søren
authors.initials: S
authors.lastname: Vang
authors.forename: Johan
authors.initials: J
authors.lastname: Palmfeldt
authors.forename: Margrethe
authors.initials: M
authors.lastname: Kjeldsen
authors.forename: Vibeke
authors.initials: V
authors.lastname: Stenbroen
authors.forename: Stinne P
authors.initials: SP
authors.lastname: Schmidt
authors.forename: Ronald J A
authors.initials: RJ
authors.lastname: Wanders
authors.forename: Jos P N
authors.initials: JP
authors.lastname: Ruiter
authors.forename: Flemming
authors.initials: F
authors.lastname: Wibrand
authors.forename: Ingrid
authors.initials: I
authors.lastname: Tein
authors.forename: Niels
authors.initials: N
authors.lastname: Gregersen
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D044926:Butyryl-CoA Dehydrogenase / Q000235:genetics; D002470:Cell Survival; D002675:Child, Preschool; D002853:Chromatography, Liquid / Q000379:methods; D005347:Fibroblasts / Q000378:metabolism; D006720:Homozygote; D006801:Humans; D008314:Malonates / Q000652:urine*; D013058:Mass Spectrometry / Q000379:methods; D008661:Metabolism, Inborn Errors / Q000175:diagnosis* / Q000235:genetics; D008928:Mitochondria / Q000378:metabolism; D008957:Models, Genetic; D018384:Oxidative Stress; D040901:Proteomics / Q000379:methods; D012307:Risk Factors
chemical_list: D000975:Antioxidants; D008314:Malonates; C038080:ethylmalonic acid; D044926:Butyryl-CoA Dehydrogenase