title: mtDNA T8993G mutation-induced F1F0-ATP synthase defect augments mitochondrial dysfunction associated with hypoxia/reoxygenation: the protective role of melatonin.
abstract: BACKGROUND
  F1F0-ATP synthase (F1F0-ATPase) plays important roles in regulating mitochondrial function during hypoxia, but the effect of F1F0-ATPase defect on hypoxia/reoxygenation (H/RO) is unknown. The aim of this study was to investigate how mtDNA T8993G mutation (NARP)-induced inhibition of F1F0-ATPase modulates the H/RO-induced mitochondrial dysfunction. In addition, the potential for melatonin, a potent antioxidant with multiple mitochondrial protective properties, to protect NARP cells exposed to H/RO was assessed.
  
  
  RESULTS
  NARP cybrids harboring 98% of mtDNA T8993G genes were established as an in vitro model for cells with F1F0-ATPase defect; their parental osteosarcoma 143B cells were studied for comparison. Treating the cells with H/RO using a hypoxic chamber resembles ischemia/reperfusion in vivo. NARP significantly enhanced apoptotic death upon H/RO detected by MTT assay and the trypan blue exclusion test of cell viability. Based on fluorescence probe-coupled laser scanning imaging microscopy, NARP significantly enhanced mitochondrial reactive oxygen species (mROS) formation and mitochondrial Ca(2+) (mCa(2+)) accumulation in response to H/RO, which augmented the depletion of cardiolipin, resulting in the retardation of mitochondrial movement. With stronger H/RO stress (either with longer reoxygenation duration, longer hypoxia duration, or administrating secondary oxidative stress following H/RO), NARP augmented H/RO-induced mROS formation to significantly depolarize mitochondrial membrane potential (ΔΨm), and enhance mCa(2+) accumulation and nitric oxide formation. Also, NARP augmented H/RO-induced mROS oxidized and depleted cardiolipin, thereby promoting permanent mitochondrial permeability transition, retarded mitochondrial movement, and enhanced apoptosis. Melatonin markedly reduced NARP-augmented H/RO-induced mROS formation and therefore significantly reduced mROS-mediated depolarization of ΔΨm and accumulation of mCa(2+), stabilized cardiolipin, and then improved mitochondrial movement and cell survival.
  
  
  CONCLUSIONS
  NARP-induced inhibition of F1F0-ATPase enhances mROS formation upon H/RO, which augments the depletion of cardiolipin and retardation of mitochondrial movement. Melatonin may have the potential to rescue patients with ischemia/reperfusion insults, even those associated with NARP symptoms.
authors: Graduate Institute of Clinical Medical Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan ; Department of Neurology, Chang-Gung Memorial Hospital, Keelung Branch, Taiwan.
authors: Wen-Yi
authors: WY
authors: Huang
authors: Mei-Jie
authors: MJ
authors: Jou
authors: Tsung-I
authors: TI
authors: Peng
authors: I Peng
authors: IP
authors: Tsung
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D002118:Calcium / Q000378:metabolism; D002308:Cardiolipins / Q000378:metabolism; D015687:Cell Hypoxia / Q000187:drug effects; D045744:Cell Line, Tumor; D004272:DNA, Mitochondrial / Q000235:genetics*; D006801:Humans; D008550:Melatonin / Q000494:pharmacology*; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism*; D025261:Mitochondrial Proton-Translocating ATPases / Q000235:genetics*; D009154:Mutation; D018696:Neuroprotective Agents / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D002308:Cardiolipins; D004272:DNA, Mitochondrial; D018696:Neuroprotective Agents; D017382:Reactive Oxygen Species; C474451:F1F0-ATP synthase; D025261:Mitochondrial Proton-Translocating ATPases; D008550:Melatonin; D010100:Oxygen; D002118:Calcium