Minimizing myocardial damage

This project investigates a cell-permeable peptide inhibitor of Protein Kinase C epsilon (PKCε) designed to minimize myocardial ischemia–reperfusion (MIR) injury and thereby reduce myocardial damage after acute myocardial infarction (MI). The work builds on prior observations that PKCε activation contributes to reactive oxygen species (ROS) production during reperfusion through interactions with mitochondrial ATP-sensitive K+ channels and uncoupled endothelial nitric oxide synthase (eNOS). The investigational agent, a dual-conjugated peptide denoted N-Myr-Tat-PKCε (YT-002), is derived from a previously studied myristic acid–conjugated PKCε inhibitor (YT-001).

YT-002 combines myristic acid and a transactivator of transcription (Tat) sequence to enhance cell permeability and tissue delivery, and it is administered at reperfusion onset to target the acute phase of reperfusion-mediated injury. The study employs both ex vivo rat hearts and an in vivo porcine model to evaluate cardioprotective efficacy. In the ex vivo model, rat hearts subjected to 30 minutes of global ischemia followed by 50 minutes of reperfusion were treated with YT-002 at 100 nM. Treatment produced a marked reduction in infarct size to 9.3 ± 1.8% (n = 5), indicating substantial preservation of viable myocardium compared with control conditions. In the in vivo porcine model, a clinically relevant scenario of 1 hour of regional ischemia followed by 3 hours of reperfusion was used. YT-002 was delivered at 0.2 mg/kg at reperfusion onset. Functional assessment at the end of reperfusion showed restoration of ejection fraction to baseline (59.4 ± 1.2% at end of reperfusion versus baseline 59.4 ± 0.8%, n = 3), and infarct size was reduced to 10.0 ± 2% (n = 4) compared with 29 ± 9% (n = 3) for a scrambled peptide control.

These results demonstrate that YT-002 can both reduce the extent of necrotic myocardium and preserve cardiac function when administered at the time of reperfusion. Mechanistically, the project emphasizes PKCε as a strategic therapeutic target for limiting ROS-mediated reperfusion injury. Restoration of blood flow rapidly induces signaling cascades involving tumor necrosis factor-alpha, diacylglycerol, and calcium that activate PKC isoforms, including PKCε. PKCε translocation via RACK1 to mitochondria and uncoupled eNOS amplifies ROS generation, which drives lipid peroxidation, protein modification, mitochondrial permeability transition pore opening, and inflammatory leukocyte recruitment. By inhibiting PKCε activity at reperfusion, YT-002 aims to interrupt these pathways, reduce ROS production, prevent eNOS uncoupling–driven superoxide generation, and blunt inflammatory cell infiltration. Collectively, the preclinical data indicates that YT-002 is a promising cardioprotective agent that mitigates reperfusion-associated myocardial damage and preserves ventricular function. Given the relationship between infarct size and subsequent heart failure risk, these findings suggest potential for reducing post-MI morbidity. The translational approach—validating effects in both small and large animal models and administering therapy at reperfusion onset—supports further development toward clinical application for minimizing myocardial damage in patients undergoing reperfusion therapy.