PKCε activation augments cardiac mitochondrial respiratory post-anoxic reserve—a putative mechanism in PKCε cardioprotection

Modest cardiac-overexpression of constitutively active PKCε (aPKCε) in transgenic mice evokes cardioprotection against ischemia. As aPKCε interacts with mitochondrial respiratory-chain proteins we hypothesized that aPKCε modulates respiration to induce cardioprotection. Using isolated cardiac mitochondria wild-type and aPKCε mice display similar basal mitochondrial respiration, rate of ATP synthesis and adenosine nucleotide translocase (ANT) functional content. Conversely, the aPKCε mitochondria exhibit modest hyperpolarization of their inner mitochondrial membrane potential (ΔΨm) compared to wild-type mitochondrial by flow cytometry. To assess whether this hyperpolarization engenders resilience to simulated ischemia, anoxia-reoxygenation experiments were performed. Mitochondria were exposed to 45 min anoxia followed by reoxygenation. At reoxygenation, aPKCε mitochondria recovered ADP-dependent respiration to 44 ± 3% of baseline compared to 28 ± 2% in WT controls (P = 0.03) in parallel with enhanced ATP synthesis. This preservation in oxidative phosphorylation is coupled to greater ANT functional content [42% > concentration of atractyloside for inhibition in the aPKCε mitochondria vs. WT control (P < 0.0001)], retention of mitochondrial cytochrome c and conservation of ΔΨm. These data demonstrate that mitochondria from PKCε activated mice are intrinsically resilient to anoxia-reoxygenation compared to WT controls. This resilience is in part due to enhanced recovery of oxidative phosphorylation coupled to maintained ANT activity. As maintenance of ATP is a prerequisite for cellular viability we conclude that PKCε activation augmented mitochondrial respiratory capacity in response to anoxia-reoxygenation may contribute to the PKCε cardioprotective program.