Vulnerability to Oxidative Stress <em>In Vitro</em> in Pathophysiology of Mitochondrial Short-Chain Acyl-CoA Dehydrogenase Deficiency: Response to Antioxidants

ObjectiveTo elucidate the pathophysiology of SCAD deficient patients who have aunique neurological phenotype, among fatty acid oxidation disorders, withearly developmental delay, CNS malformations, intractable seizures, myopathyand clinical signs suggesting oxidative stress. MethodsWe studied skin fibroblast cultures from patients homozygous for ACADScommon variant c.625G>A (n = 10), compound heterozygousfor c.625G>A/c.319C>T (n = 3) or homozygous forpathogenic c.319C>T (n = 2) and c.1138C>T (n = 2)mutations compared to fibroblasts from patients with carnitine palmitoyltransferase2 (CPT2) (n = 5), mitochondrial trifunctional protein(MTP)/long-chain L-3-hydroxyacyl-CoA dehydrogenase (LCHAD) (n = 7),and medium-chain acyl-CoA dehydrogenase (MCAD) deficiencies (n = 4)and normal controls (n = 9). All were exposed to 50 µMmenadione at 37°C. Additonal conditions included exposure to 39°Cand/or hypoglycemia. Time to 100% cell death was confirmed with trypanblue dye exclusion. Experiments were repeated with antioxidants (VitaminsC and E or N-acetylcysteine), Bezafibrate or glucose and temperature rescue. ResultsThe most significant risk factor for vulnerability to menadione-inducedoxidative stress was the presence of a FAO defect. SCADD fibroblasts werethe most vulnerable compared to other FAO disorders and controls, and weresimilarly affected, independent of genotype. Cell death was exacerbated byhyperthermia and/or hypoglycemia. Hyperthermia was a more significant independentrisk factor than hypoglycemia. Rescue significantly prolonged survival. Incubationwith antioxidants and Bezafibrate significantly increased viability of SCADDfibroblasts. InterpretationVulnerability to oxidative stress likely contributes to neurotoxicity ofSCADD regardless of ACADS genotype and is significantly exacerbatedby hyperthermia. We recommend rigorous temperature control in SCADD patientsduring acute illness. Antioxidants and Bezafibrate may also prove instrumentalin their management.