title: Mitochondrial oxidative stress corrupts coronary collateral growth by activating adenosine monophosphate activated kinase-α signaling.
abstract: OBJECTIVE
  Our goal was to determine the mechanism by which mitochondrial oxidative stress impairs collateral growth in the heart.
  
  
  RESULTS
  Rats were treated with rotenone (mitochondrial complex I inhibitor that increases reactive oxygen species production) or sham-treated with vehicle and subjected to repetitive ischemia protocol for 10 days to induce coronary collateral growth. In control rats, repetitive ischemia increased flow to the collateral-dependent zone; however, rotenone treatment prevented this increase suggesting that mitochondrial oxidative stress compromises coronary collateral growth. In addition, rotenone also attenuated mitochondrial complex I activity and led to excessive mitochondrial aggregation. To further understand the mechanistic pathway(s) involved, human coronary artery endothelial cells were treated with 50 ng/mL vascular endothelial growth factor, 1 µmol/L rotenone, and rotenone/vascular endothelial growth factor for 48 hours. Vascular endothelial growth factor induced robust tube formation; however, rotenone completely inhibited this effect (P<0.05 rotenone versus vascular endothelial growth factor treatment). Inhibition of tube formation by rotenone was also associated with significant increase in mitochondrial superoxide generation. Immunoblot analyses of human coronary artery endothelial cells with rotenone treatment showed significant activation of adenosine monophosphate activated kinase (AMPK)-α and inhibition of mammalian target of rapamycin and p70 ribosomal S6 kinase. Activation of AMPK-α suggested impairments in energy production, which was reflected by decrease in O2 consumption and bioenergetic reserve capacity of cultured cells. Knockdown of AMPK-α (siRNA) also preserved tube formation during rotenone, suggesting the negative effects were mediated by the activation of AMPK-α. Conversely, expression of a constitutively active AMPK-α blocked tube formation.
  
  
  CONCLUSIONS
  We conclude that activation of AMPK-α during mitochondrial oxidative stress inhibits mammalian target of rapamycin signaling, which impairs phenotypic switching necessary for the growth of blood vessels.
authors.affiliation: Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, OH 44272, USA.
authors.forename: Yuh Fen
authors.initials: YF
authors.lastname: Pung
authors.forename: Wai Johnn
authors.initials: WJ
authors.lastname: Sam
authors.forename: Kelly
authors.initials: K
authors.lastname: Stevanov
authors.forename: Molly
authors.initials: M
authors.lastname: Enrick
authors.forename: Chwen-Lih
authors.initials: CL
authors.lastname: Chen
authors.forename: Christopher
authors.initials: C
authors.lastname: Kolz
authors.forename: Prashanth
authors.initials: P
authors.lastname: Thakker
authors.forename: James P
authors.initials: JP
authors.lastname: Hardwick
authors.forename: Yeong-Renn
authors.initials: YR
authors.lastname: Chen
authors.forename: Jason R B
authors.initials: JR
authors.lastname: Dyck
authors.forename: Liya
authors.initials: L
authors.lastname: Yin
authors.forename: William M
authors.initials: WM
authors.lastname: Chilian
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000818:Animals; D001835:Body Weight / Q000502:physiology; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000166:cytology / Q000201:enzymology*; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000166:cytology / Q000201:enzymology*; D006801:Humans; D007511:Ischemia / Q000378:metabolism / Q000473:pathology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D009206:Myocardium / Q000201:enzymology / Q000473:pathology; D018384:Oxidative Stress / Q000502:physiology*; D051381:Rats; D011921:Rats, Inbred WKY; D012402:Rotenone / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology*; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D014475:Uncoupling Agents / Q000494:pharmacology
chemical_list: D014475:Uncoupling Agents; D012402:Rotenone; C546845:mTOR protein, rat; D058570:TOR Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; C568305:Prkaa1 protein, rat
keywords: collateral circulation; coronary circulation; mitochondria; reactive oxygen species