Abstract 1617: Epsilon Protein Kinase C Improves Cytochrome c Oxidase (CO) Activity and Preserves CO Subunits in Adult Rat Cardiac Ischemic Preconditioning (PC)
Diminished cytochrome c oxidase (CO) activity can decrease cellular ATP and elevate ROS via electron leak from electron transport chain complexes I and III. Our previous work in neonatal cardiac myocytes suggests ϵPKC enhances CO activity in PC to improve energetics, decrease ROS and preserve the # IV subunit of CO (COIV). We therefore, tested these hypotheses in an in vivo tetrazolium staining-based infarct model. In S-D rats given two cycles of PC (one cycle =5 minutes of coronary ligation followed by 5 minutes of reperfusion) ϵPKC translocated to a gradient-purified mitochondrial (MITO) fraction in samples taken from the cardiac left ventricular region at risk (RaR) for ischemic damage. Mitochondria from the ventricular region not at risk showed no ϵPKC accumulation. We found no change in MITO δPKC levels in the RaR following PC alone and an 84 ± 6 % decrease in MITO δPKC levels in the RaR of animals exposed to PC prior to 30 minutes ischemia / 2 hr reperfusion (I/R). ϵPKC co-immunoprecipitated with COIV in mitochondria isolated from PC alone or PC + I/R groups. This colocalization correlated with 2-fold increases in CO activity. I/R alone decreased ϵPKC-COIV interactions, CO activity and the levels of COI (by 85 ± 7%) and COIV (by 37 ± 5%) in RaR mitochondria. COI and COIV decreases were reduced to 47 ± 7 and 7 ± 4 %, respectively when PC was induced prior to I/R. PC alone had no effect on MITO CO subunit levels. All results were statistically significant at the p ≤ 0.05 level and equal concentrations of viable mitochondria were used for each treatment group. Our work suggests:1) ϵPKC elevates CO activity early in PC via covalent modification or binding to COIV, 2) the augmentation of CO activity following PC + I/R is associated with protection of COI and COIV and 3) δPKC has been implicated by others in I/R injury. We propose that PC may reduce I/R injury by decreasing MITO δPKC levels.