Abstract

Protein Kinase C epsilon (PKCε) signaling is known to mediate superoxide production from mitochondrial and uncoupled endothelial nitric oxide synthase sources in myocardial ischemia-reperfusion (I/R) injury. Previously, PKCε peptide inhibitor conjugated with myristic acid and trans-activator of transcription (N-Myr-Tat-CC-EAVSLKPT [PKCε-]; Myr-Tat-PKCε-) exhibited profound reduction in infarct size compared to Myr-PKCε- or Tat-PKCε- in ex vivo rat hearts♰. This study aims to evaluate the effects of Myr-Tat-PKCε- in porcine myocardial I/R in vivo compared to a scrambled control peptide.

Male Yorkshire castrated pigs (38-54kg) were subjected to regional I(1hr)/R(3hrs) via catheter-balloon in the left anterior descending coronary artery (LAD) at the location of the second LAD branch. Myr-Tat-PKCε- or Myr-Tat-PKCε-scrambled control peptide (N-Myr-Tat-CC-LSETKPAV [PKCε-scram]; Myr-Tat-PKCε-scram) bolus (0.2 mg/kg) was administered into the LAD at reperfusion. Echocardiography was used to determine ejection fraction (EF). Following reperfusion, hearts were excised and stained. The area at risk (AR) and area of necrosis (AN) were identified with 1% Evans Blue dye and 1% triphenyltetrazolium chloride respectively. Infarct size (AN/AR) and EF were analyzed with unpaired Student’s t-test.

Myr-Tat-PKCε-scram exhibited a reduced final EF compared to baseline (551 vs 621%, n=3). Myr-Tat-PKCε- significantly increased final EF back to baseline (591 vs 591%, n=5; p<0.05). Myr-Tat-PKCε- exhibited a reduction in infarct size (102%, n=4; p<0.01) compared to Myr-Tat-PKCε-scram (297%, n=3). Results suggest that Myr-Tat-PKCε- mitigates myocardial I/R injury when administered during reperfusion. Future studies will test the effects of Myr-Tat-PKCε- in an 8-week porcine myocardial I/R survival study to determine its therapeutic potential for heart attack patients.