title: Increase of mitochondria and mitochondrial DNA in response to oxidative stress in human cells.
abstract: Mitochondrial respiratory function is impaired in the target tissues of patients with mitochondrial diseases and declines with age in various human tissues. It is generally accepted that respiratory-chain defects result in enhanced production of reactive oxygen species and free radicals in mitochondria. Recently, we have demonstrated that the copy number of mitochondrial DNA (mtDNA) is increased in the lung tissues of elderly human subjects. The mtDNA copy number was suggested to be increased by a feedback mechanism that compensates for defects in mitochondria harbouring mutated mtDNA and a defective respiratory system. However, the detailed mechanism remains unclear. In this study, we treated a human lung fibroblast cell line, MRC-5, with H(2)O(2) at concentrations of 90-360 microM. After the treatment for 24-72 h, we found that cells were arrested at G(0) and G(1) phases but that mitochondrial mass and mtDNA content were significantly increased in a concentration- and time-dependent manner. Moreover, the oxidative stress induced by buthionine sulphoximine was also found to cause an increase in mitochondrial mass of the treated cells. Increased uptake of a vital mitochondrial dye Rhodamine 123 and enhanced tetrazolium [MTT, 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide] reduction revealed that the mitochondria increased by H(2)O(2) treatment were functional. In addition, the increase in the mitochondrial mass was also observed in cell-cycle-arrested cells induced by mimosine, lovastatin and genistein. Taken together, these findings suggest that the increase in mitochondrial mass and mtDNA content are the early molecular events of human cells in response to endogenous or exogenous oxidative stress through cell-cycle arrest.
authors.affiliation: Department of Biochemistry and Center for Cellular and Molecular Biology, National Yang-Ming University, Taipei, Taiwan 112, Republic of China.
authors.forename: H C
authors.initials: HC
authors.lastname: Lee
authors.forename: P H
authors.initials: PH
authors.lastname: Yin
authors.forename: C Y
authors.initials: CY
authors.lastname: Lu
authors.forename: C W
authors.initials: CW
authors.lastname: Chi
authors.forename: Y H
authors.initials: YH
authors.lastname: Wei
mesh_terms: D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004272:DNA, Mitochondrial / Q000187:drug effects / Q000378:metabolism*; D005347:Fibroblasts; D019833:Genistein / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008148:Lovastatin / Q000494:pharmacology; D008168:Lung; D008898:Mimosine / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D018384:Oxidative Stress / Q000502:physiology*; D020112:Rhodamine 123 / Q000493:pharmacokinetics; D013778:Tetrazolium Salts / Q000493:pharmacokinetics
chemical_list: D004272:DNA, Mitochondrial; D013778:Tetrazolium Salts; D020112:Rhodamine 123; D008898:Mimosine; D008148:Lovastatin; D006861:Hydrogen Peroxide; D019833:Genistein