title: The effect of small molecules on nuclear-encoded translation diseases.
abstract: The five complexes of the mitochondrial respiratory chain (MRC) supply most organs and tissues with ATP produced by oxidative phosphorylation (OXPHOS). Inherited mitochondrial diseases affecting OXPHOS dysfunction are heterogeneous; symptoms may present at any age and may affect a wide range of tissues, with many diseases giving rise to devastating multisystemic disorders resulting in neonatal death. Combined respiratory chain deficiency with normal complex II accounts for a third of all respiratory deficiencies; mutations in nuclear-encoded components of the mitochondrial translation machinery account for many cases. Although mutations have been identified in over 20 such genes and our understanding of the mitochondrial translation apparatus is increasing, to date no definitive cure for these disorders exists. We evaluated the effect of seven small molecules with reported therapeutic potential in fibroblasts of four patients with combined respiratory complex disorders, each harboring a known mutation in a different nuclear-encoded component of the mitochondrial translation machinery: EFTs, GFM1, MRPS22 and TRMU. Six mitochondrial parameters were screened as follows; growth in glucose-free medium, reactive oxygen species (ROS) production, ATP content, mitochondrial content, mitochondrial membrane potential and complex IV activity. It was clearly evident that each patient displayed an individual response and there was no universally beneficial compound. AICAR increased complex IV activity in GFM1 cells and increased ATP content in MRPS22 fibroblasts but was detrimental to TRMU, who benefitted from bezafibrate. Two antioxidants, ascorbate and N-acetylcysteine (NAC), significantly improved cell growth, ATP content and mitochondrial membrane potential and decreased levels of intracellular reactive oxygen species (ROS) in EFTs fibroblasts. This study presents an expanded repertoire of assays that can be performed using the microtiter screening system with a small number of patients' fibroblasts and highlights some therapeutic options while providing additional evidence for the importance of personalized medicine in mitochondrial disorders.
authors.affiliation: Monique and Jacques Roboh Department of Genetic Research, Hadassah-Hebrew University Medical Center, Jerusalem, Israel; Department of Genetics and Metabolic Diseases, Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
authors.forename: Devorah
authors.initials: D
authors.lastname: Soiferman
authors.affiliation: Department of Genetics and Metabolic Diseases, Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
authors.forename: Oshrat
authors.initials: O
authors.lastname: Ayalon
authors.affiliation: Department of Genetics and Metabolic Diseases, Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
authors.forename: Sarah
authors.initials: S
authors.lastname: Weissman
authors.affiliation: Monique and Jacques Roboh Department of Genetic Research, Hadassah-Hebrew University Medical Center, Jerusalem, Israel; Department of Genetics and Metabolic Diseases, Hadassah-Hebrew University Medical Center, Jerusalem, Israel. Electronic address: annsr@hadassah.org.il.
authors.forename: Ann
authors.initials: A
authors.lastname: Saada
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D001629:Bezafibrate / Q000494:pharmacology; D030401:Cytochrome-c Oxidase Deficiency / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D004272:DNA, Mitochondrial / Q000235:genetics / Q000378:metabolism; D004579:Electron Transport / Q000187:drug effects / Q000235:genetics; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D017240:Mitochondrial Myopathies / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010085:Oxidative Phosphorylation / Q000187:drug effects; D020653:Peptide Elongation Factor G / Q000235:genetics / Q000378:metabolism; D061251:Primary Cell Culture; D014176:Protein Biosynthesis / Q000187:drug effects*; D017382:Reactive Oxygen Species / Q000378:metabolism; D012265:Ribonucleotides / Q000494:pharmacology; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism; D054852:Small Molecule Libraries / Q000494:pharmacology*; D012359:tRNA Methyltransferases / Q000235:genetics / Q000378:metabolism
chemical_list: D004272:DNA, Mitochondrial; C441680:GFM1 protein, human; C526186:MRPS22 protein, human; D024101:Mitochondrial Proteins; D020653:Peptide Elongation Factor G; D017382:Reactive Oxygen Species; D012265:Ribonucleotides; D012269:Ribosomal Proteins; D054852:Small Molecule Libraries; D000620:Aminoimidazole Carboxamide; D003576:Electron Transport Complex IV; D012359:tRNA Methyltransferases; C496706:TRMU protein, human; C031143:AICA ribonucleotide; D000111:Acetylcysteine; D001629:Bezafibrate
keywords: Mitochondrial disease; OXPHOS; Personalized medicine; Respiratory chain; Translation