Ischemic preconditioning exaggerates cardiac damage in PKC-δ null mice

Abstract

Ischemic preconditioning confers cardiac protection during subsequent ischemia-reperfusion, in which protein kinase C (PKC) is believed to play an essential role, but controversial data exist concerning the PKC-delta isoform. In an accompanying study (26), we described metabolic changes in PKC-delta knockout mice. We now wanted to explore their effect on early preconditioning. Both PKC-delta(-/-) and PKC-delta(+/+) mice underwent three cycles of 5-min left descending artery occlusion/5-min reperfusion, followed by 30-min occlusion and 2-h reperfusion. Unexpectedly, preconditioning exaggerated ischemia-reperfusion injury in PKC-delta(-/-) mice. Whereas ischemic preconditioning increased superoxide anion production in PKC-delta(+/+) hearts, no increase in reactive oxygen species was observed in PKC-delta(-/-) hearts. Proteomic analysis of preconditioned PKC-delta(+/+) hearts revealed profound changes in enzymes related to energy metabolism, e.g., NADH dehydrogenase and ATP synthase, with partial fragmentation of these mitochondrial enzymes and of the E(2) component of the pyruvate dehydrogenase complex. Interestingly, fragmentation of mitochondrial enzymes was not observed in PKC-delta(-/-) hearts. High-resolution NMR analysis of cardiac metabolites demonstrated a similar rise of phosphocreatine in PKC-delta(+/+) and PKC-delta(-/-) hearts, but the preconditioning-induced increase in phosphocholine, alanine, carnitine, and glycine was restricted to PKC-delta(+/+) hearts, whereas lactate concentrations were higher in PKC-delta(-/-) hearts. Taken together, our results suggest that reactive oxygen species generated during ischemic preconditioning might alter mitochondrial metabolism by oxidizing key mitochondrial enzymes and that metabolic adaptation to preconditioning is impaired in PKC-delta(-/-) hearts.

Letter by Metzler et al Regarding Article, “Intracoronary KAI-9803 as an Adjunct to Primary Coronary Intervention for Acute ST-Segment Elevation Myocardial Infarction”

“…We have previously demonstrated in an in vivo mouse model of myocardial infarction, that PKC␦ deficiency (PKC␦ Ϫ/Ϫ ) is associated with a reduction of infarct size. 2 Consistent with the findings described in the DELTA MI trial, this difference failed to reach statistical significance. However, we also observed that ischemic preconditioning before index ischemia resulted in exaggerated myocardial injury in PKC␦ Ϫ/Ϫ hearts as shown by biomarker measurements (creatine kinase MB, troponin T, and lactate dehydrogenase isoenzyme 1) and triphenyltetrazolium chloride delineation of infarction.…”

Molecular Basis of Cardioprotection

“…184 PKCε is also translocated to the sarcoplasmic reticulum where it reduces calcium content. 185 The role of the PKCδ isoform in IPC is more controversial, and both protection 186 and injury 187 through PKCδ activation were reported. This controversy continued into a recent clinical trial, in which-after promising preliminary datathe PKCδ inhibitor delcasertib, when given before reperfusion, failed to protect patients with reperfused AMI in terms of IS reduction, as reflected by creatine kinase-muscle band release.…”

Protein kinase cascades in the regulation of cardiac hypertrophy

“…Instead, the phenotypes have been endocrine, immunological, and neural (reviewed in ref. 58), and only under physiological stress such as ischemia-reperfusion or pressure overload have subtle cardiac phenotypes been provoked (54,59,60). Does the absence of a cardiac phenotype associated with PKC isoform gene ablation indicate that the postulated roles for these kinases, based upon their activation in heart disease and their effects on hypertrophy of cultured cardiomyocytes, were incorrect?…”

“…Although it has long been recognized as being activated in myocardial ischemia, relatively little is known about this PKC isoform in cardiac hypertrophy. A cardiac PKCδ-transgenic mouse model has not been described, and PKCδ-knockout mice have no basal cardiac phenotype (56,60). Translocation modification has confirmed that PKCδ is a critical mediator of postischemic cardiomyocyte necrosis and contractile dysfunction in mice, rats, and pigs (71,72).…”