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Background-Current treatment for acute myocardial infarction (AMI) focuses on reestablishing blood flow (reperfusion).Paradoxically, reperfusion itself may cause additional injury to the heart. We previously found that ␦-protein kinase C (␦PKC) inhibition during simulated ischemia/reperfusion in isolated rat hearts is cardioprotective. We focus here on the role for ␦PKC during reperfusion only, using an in vivo porcine model of AMI. Methods and Results-An intracoronary application of a selective ␦PKC inhibitor to the heart at the time of reperfusion reduced infarct size, improved cardiac function, inhibited troponin T release, and reduced apoptosis. Using 31 P NMR in isolated perfused mouse hearts, we found a faster recovery of ATP levels in hearts treated with the ␦PKC inhibitor during reperfusion only. Conclusions-Reperfusion injury after cardiac ischemia is mediated, at least in part, by ␦PKC activation. This study suggests that including a ␦PKC inhibitor at reperfusion may improve the outcome for patients with AMI. (Circulation. 2003;108:2304-2307.)Key Words: reperfusion Ⅲ cardioprotection Ⅲ kinases C urrent treatment for acute myocardial infarction (AMI) is aimed at limiting the duration of the ischemic period by disrupting the occlusion in the coronary artery. However, no therapeutic treatment is available to prevent reperfusion injury, which occurs after these interventions. 1,2 We previously developed several isozyme-selective inhibitor and activator peptides of protein kinase C (PKC). 3 Recently, we found that treatment with a ␦PKC-selective inhibitor during ischemia/reperfusion reduced cardiac damage in isolated perfused rat hearts. 3,4 Here, we show that the ␦PKC inhibitor prevented reperfusion injury in an in vivo porcine model of AMI. Methods Peptide SynthesisThe ␦PKC inhibitor peptide ␦V1-1 was synthesized and conjugated to Tat-derived peptide 5 via a cysteine S-S bond as described. 3 In Vivo Local Occlusion, Peptide Delivery, and Pathological AssessmentWe applied a balloon catheter into the mid left anterior descending coronary artery of female juvenile Yorkshire pigs (35 to 40 kg) under anesthesia (1% isoflurane) and inflated the balloon to produce a total occlusion for 30 minutes. The guide wire was removed, and Tat alone (Tat) or Tat-␦V1-1 conjugate (␦V1-1) was infused via the lumen of the balloon catheter only for the last 1 minute of ischemia (250 ng/kg, 1 mL/min). Left ventriculograms were performed to determine cardiac function. Hearts were harvested 4 hours or 5 days after ischemia. Double staining with Evans blue dye and TTC marked areas at risk for ischemia and infarcted areas, respectively, as described previously. 6 Troponin T levels in blood, as an indicator of cardiac cytolysis, were also determined after 24 hours of reperfusion.Wedge biopsies of liver, spleen, lung and kidney were fixed in 10% buffered neutral formalin and embedded in paraffin, and 8-m-thick sections were stained with hematoxylin and eosin for pathological examination. Biochemical Analysis of Porcine Cardiac TissueH...

Background-Protein kinase C (PKC) plays a major role in cardioprotection from ischemia/reperfusion injury. Using an HIV-1 Tat protein-derived peptide to mediate rapid and efficient transmembrane delivery of peptide regulators of PKC translocation and function, we examined the cardioprotective effect of selective ␦-PKC inhibitor (␦V1-1) and ⑀-PKC activator (⑀RACK) peptides for ischemia/reperfusion damage in isolated perfused rat hearts. Furthermore, we examined the protective effects of these PKC isozymes in isolated perfused hearts subjected to ischemia/reperfusion damage using transgenic mice expressing these peptides specifically in their cardiomyocytes. Methods and Results-In isolated perfused rat hearts, administration of ␦V1-1 but not ⑀RACK during reperfusion improved cardiac function and decreased creatine phosphokinase release. In contrast, pretreatment with ⑀RACK but not ␦V1-1, followed by a 10-minute washout before ischemia/reperfusion, also improved cardiac function and decreased creatine phosphokinase release. Furthermore, administration of ⑀RACK before ischemia followed by ␦V1-1 during reperfusion only conferred greater cardioprotective effects than that obtained by each peptide treatment alone. Both the ␦-PKC inhibitor and ⑀-PKC activator conferred cardioprotection against ischemia/reperfusion injury in transgenic mice expressing these peptides in the heart, and coexpression of both peptides conferred greater cardioprotective effects than that obtained by the expression of each peptide alone. Conclusions-␦-PKC inhibitor prevents reperfusion injury, and ⑀-PKC activator mimics ischemic preconditioning. Furthermore, treatment with both peptides confers additive cardioprotective effects. Therefore, these peptides mediate cardioprotection by regulating ischemia/reperfusion damage at distinct time points. (Circulation. 2003;108:869-875.)