title: Effect of thyroid hormone on mitochondrial properties and oxidative stress in cells from patients with mtDNA defects.
abstract: Mitochondrial (mt)DNA mutations contribute to various disease states characterized by low ATP production. In contrast, thyroid hormone [3,3',5-triiodothyronine (T(3))] induces mitochondrial biogenesis and enhances ATP generation within cells. To evaluate the role of T(3)-mediated mitochondrial biogenesis in patients with mtDNA mutations, three fibroblast cell lines with mtDNA mutations were evaluated, including two patients with Leigh's syndrome and one with hypertrophic cardiomyopathy. Compared with control cells, patient fibroblasts displayed similar levels of mitochondrial mass, peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha), mitochondrial transcription factor A (Tfam), and uncoupling protein 2 (UCP2) protein expression. However, patient cells exhibited a 1.6-fold elevation in ROS production, a 1.7-fold elevation in cytoplasmic Ca2+ levels, a 1.2-fold elevation in mitochondrial membrane potential, and 30% less complex V activity compared with control cells. Patient cells also displayed 20-25% reductions in both cytochrome c oxidase (COX) activity and MnSOD protein levels compared with control cells. After T(3) treatment of patient cells, ROS production was decreased by 40%, cytoplasmic Ca2+ was reduced by 20%, COX activity was increased by 1.3-fold, and ATP levels were elevated by 1.6-fold, despite the absence of a change in mitochondrial mass. There were no significant alterations in the protein expression of PGC-1alpha, Tfam, or UCP2 in either T(3)-treated patient or control cells. However, T(3) restored the mitochondrial membrane potential, complex V activity, and levels of MnSOD to normal values in patient cells and elevated MnSOD levels by 21% in control cells. These results suggest that T(3) acts to reduce cellular oxidative stress, which may help attenuate ROS-mediated damage, along with improving mitochondrial function and energy status in cells with mtDNA defects.
authors.affiliation: School of Kinesiology and Health Science, Farqhuarson Life Science Bldg., Rm. 302, York Univ., Toronto, ON M3JIP3, Canada.
authors.forename: Keir J
authors.initials: KJ
authors.lastname: Menzies
authors.forename: Brian H
authors.initials: BH
authors.lastname: Robinson
authors.forename: David A
authors.initials: DA
authors.lastname: Hood
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002312:Cardiomyopathy, Hypertrophic / Q000235:genetics / Q000378:metabolism; D016022:Case-Control Studies; D045744:Cell Line, Tumor; D004272:DNA, Mitochondrial; D004268:DNA-Binding Proteins / Q000378:metabolism; D042967:Electron Transport Complex I / Q000235:genetics / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D005347:Fibroblasts / Q000201:enzymology / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D007473:Ion Channels / Q000378:metabolism; D007888:Leigh Disease / Q000235:genetics / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D025261:Mitochondrial Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D018384:Oxidative Stress; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D012356:RNA, Transfer, Leu / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism; D037021:Thyroid Hormone Receptors alpha / Q000378:metabolism; D037042:Thyroid Hormone Receptors beta / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014284:Triiodothyronine / Q000378:metabolism*; D000071246:Uncoupling Protein 2
chemical_list: D004272:DNA, Mitochondrial; D004268:DNA-Binding Proteins; D006360:Heat-Shock Proteins; D007473:Ion Channels; C501005:MT-ATP6 protein, human; D024101:Mitochondrial Proteins; C486497:PPARGC1A protein, human; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D012356:RNA, Transfer, Leu; D017382:Reactive Oxygen Species; C499631:TFAM protein, human; D037021:Thyroid Hormone Receptors alpha; D037042:Thyroid Hormone Receptors beta; D014157:Transcription Factors; C000604389:UCP2 protein, human; D000071246:Uncoupling Protein 2; C021983:complex V (mitochondrial oxidative phosphorylation system); D014284:Triiodothyronine; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D013482:Superoxide Dismutase; C481838:MT-ND5 protein, human; D003576:Electron Transport Complex IV; D025261:Mitochondrial Proton-Translocating ATPases; D042967:Electron Transport Complex I; D002118:Calcium