PKC∈ activation augments cardiac mitochondrial respiratory post-anoxic reserve -: a putative mechanism in PKC∈ cardioprotection

Modest cardiac-overexpression of constitutively active PKC epsilon (aPKC epsilon) in transgenic mice evokes cardioprotection against ischemia. As aPKC epsilon interacts with mitochondrial respiratory-chain proteins we hypothesized that aPKC epsilon Modulates respiration to induce cardioprotection. Using isolated cardiac mitochondria wild-type and aPKC epsilon mice display similar basal mitochondrial respiration, rate of ATP synthesis and adenosine nucleotide translocase (ANT) functional content. Conversely, the aPKC epsilon mitochondria exhibit modest hyperpolarization of their inner mitochondrial membrane potential (Delta Psi(m)) compared to wild-type mitochondrial by flow cytometry. To assess whether this hyperpolarization engenders resilience to simulated ischemia, anoxia-reoxygenation experiments were per-formed. Mitochondria were exposed to 45 min anoxia followed by reoxygenation. At reoxygenation, aPKC epsilon 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 aPKC epsilon mitochondria vs. WT control (P < 0.0001)], retention of mitochondrial cytochrome c and conservation of Delta Psi(m). These data demonstrate that mitochondria from PKC epsilon 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 PKC epsilon activation augmented mitochondrial respiratory capacity in response to anoxia-reoxygenation may contribute to the PKC epsilon cardioprotective program. (c) 2005 Elsevier Ltd. All rights reserved.