Overexpression of TFAM or twinkle increases mtDNA copy number and facilitates cardioprotection associated with limited mitochondrial oxidative stress

PLoS One. 2015 Mar 30;10(3):e0119687. doi: 10.1371/journal.pone.0119687. eCollection 2015.

Abstract

Background: Mitochondrial DNA (mtDNA) copy number decreases in animal and human heart failure (HF), yet its role in cardiomyocytes remains to be elucidated. Thus, we investigated the cardioprotective function of increased mtDNA copy number resulting from the overexpression of human transcription factor A of mitochondria (TFAM) or Twinkle helicase in volume overload (VO)-induced HF.

Methods and results: Two strains of transgenic (TG) mice, one overexpressing TFAM and the other overexpressing Twinkle helicase, exhibit an approximately 2-fold equivalent increase in mtDNA copy number in heart. These TG mice display similar attenuations in eccentric hypertrophy and improved cardiac function compared to wild-type (WT) mice without any deterioration of mitochondrial enzymatic activities in response to VO, which was accompanied by a reduction in matrix-metalloproteinase (MMP) activity and reactive oxygen species after 8 weeks of VO. Moreover, acute VO-induced MMP-2 and MMP-9 upregulation was also suppressed at 24 h in both TG mice. In isolated rat cardiomyocytes, mitochondrial reactive oxygen species (mitoROS) upregulated MMP-2 and MMP-9 expression, and human TFAM (hTFAM) overexpression suppressed mitoROS and their upregulation. Additionally, mitoROS were equally suppressed in H9c2 rat cardiomyoblasts that overexpress hTFAM or rat Twinkle, both of which exhibit increased mtDNA copy number. Furthermore, mitoROS and mitochondrial protein oxidation from both TG mice were suppressed compared to WT mice.

Conclusions: The overexpression of TFAM or Twinkle results in increased mtDNA copy number and facilitates cardioprotection associated with limited mitochondrial oxidative stress. Our findings suggest that increasing mtDNA copy number could be a useful therapeutic strategy to target mitoROS in HF.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • DNA Helicases / genetics
  • DNA Helicases / metabolism*
  • DNA, Mitochondrial / genetics*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Gene Dosage*
  • Heart Failure / metabolism*
  • Humans
  • Matrix Metalloproteinases / genetics
  • Matrix Metalloproteinases / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mitochondria / metabolism
  • Mitochondrial Proteins / genetics
  • Mitochondrial Proteins / metabolism*
  • Myocytes, Cardiac / metabolism
  • Oxidative Stress*
  • Rats
  • Reactive Oxygen Species / metabolism
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*

Substances

  • DNA, Mitochondrial
  • DNA-Binding Proteins
  • Mitochondrial Proteins
  • Reactive Oxygen Species
  • TFAM protein, human
  • Transcription Factors
  • Matrix Metalloproteinases
  • Twnk protein, mouse
  • DNA Helicases

Grant support

This work was supported by JSPS KAKENHI Grant Number 23220013, 23591084, 50163043, and the Strategic Funds for the Promotion of Science and Technology from Ministry of Culture, Sports, Sciences and Technology. This work was also supported by Grants-in-Aid for Scientific Research from the Ministry of Health, Labour, and Welfare of Japan. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.