title: Differential loss of cytochrome-c oxidase subunits in ischemia-reperfusion injury: exacerbation of COI subunit loss by PKC-epsilon inhibition.
abstract: We have previously described a PKC-epsilon interaction with cytochrome oxidase subunit IV (COIV) that correlates with enhanced CO activity and cardiac ischemic preconditioning (PC). We therefore investigated the effects of PC and ischemia-reperfusion (I/R) injury on CO subunit levels in an anesthetized rat coronary ligation model. Homogenates prepared from the left ventricular regions at risk (RAR) and not at risk (RNAR) for I/R injury were fractionated into cell-soluble (S), 600 g low-speed centrifugation (L), gradient-purified mitochondrial (M), and 100,000 g particulate (P) fractions. In RAR tissue, PC (2 cycles of 5-min ischemia and 5-min reperfusion) decreased the COI in the P fraction ( approximately 29% of total cellular COI), suggesting changes in interfibrillar mitochondria. After 30 min of ischemia and 120 min of reperfusion, total COI levels decreased in the RAR by 72%. Subunit Va was also downregulated by 42% following prolonged I/R in the RAR. PC administered before I/R reduced the loss of COI in the M and P fractions approximately 30% and prevented COVa losses completely. We observed no losses in subunits Vb and VIIa following I/R alone; however, significant losses occurred when PC was administered before prolonged I/R. Delivery of a cell-permeable PKC-epsilon translocation inhibitor (epsilonV1-2) to isolated rat hearts before prolonged I/R dramatically increased COI loss, suggesting that PKC-epsilon protects COI levels. We propose that additional measures to protect CO subunits when coadministered with PC may improve its cardioprotection against I/R injury.
authors.affiliation: Department of Pharmacology and Toxicology, School of Medicine, Medical College of Georgia, Augusta, Georgia, USA.
authors.forename: Qilin
authors.initials: Q
authors.lastname: Yu
authors.forename: Tiffany
authors.initials: T
authors.lastname: Nguyen
authors.forename: Mourad
authors.initials: M
authors.lastname: Ogbi
authors.forename: Robert W
authors.initials: RW
authors.lastname: Caldwell
authors.forename: John A
authors.initials: JA
authors.lastname: Johnson
mesh_terms: D000818:Animals; D002458:Cell Fractionation; D003331:Coronary Vessels / Q000601:surgery; D004195:Disease Models, Animal; D015536:Down-Regulation; D003576:Electron Transport Complex IV / Q000378:metabolism*; D006352:Heart Ventricles / Q000201:enzymology; D006439:Hemodynamics; D019157:Ischemic Preconditioning, Myocardial; D008026:Ligation; D008929:Mitochondria, Heart / Q000201:enzymology; D009206:Myocardium / Q000201:enzymology* / Q000473:pathology; D010446:Peptide Fragments / Q000494:pharmacology; D051744:Protein Kinase C-epsilon / Q000037:antagonists & inhibitors* / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D021122:Protein Subunits; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000201:enzymology* / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control; D013997:Time Factors; D019210:Troponin I / Q000097:blood; D014357:Trypsin / Q000378:metabolism
chemical_list: D010446:Peptide Fragments; D047428:Protein Kinase Inhibitors; D021122:Protein Subunits; D019210:Troponin I; C448318:epsilonV1-2 peptide; D003576:Electron Transport Complex IV; D051744:Protein Kinase C-epsilon; D014357:Trypsin