Protein Kinase C Beta II Inhibitor Conjugated with Myristic Acid and Trans-Activator of Transcription improves intracellular delivery and cardiovascular protection in porcine myocardial ischemia/reperfusion injury
Authors: Melnik Juliet , Ramsarran James , Clair Logan , Boakye Tanoh Desmond , Dang Jennifer , Le Mai An , Harrell Kayla 
Published: May 2024

Introduction: While timely reperfusion of oxygenated blood is critical during resuscitation of ischemic myocardium, oxidative stress during reperfusion still leads to ischemia/reperfusion (I/R) injury and ultimately, cardiomyocyte death. The major sources of oxidative stress targeted in this study are NADPH oxidase (NOX-2) and mitochondria, which are both activated by protein kinase C beta II (PKCβII). In previous studies with an ex-vivo rat heart I/R model, Myristic Acid (Myr) and Trans-Activator Transcription (Tat; YGRKKRRQRRR) conjugated PKCβII inhibitor (Myr-Tat-PKCβII-; N-Myr-Tat-CC-SLNPEWNET) showed cardioprotective effects and decreased infarct size. In this study, we hypothesized that Myr-Tat-PKCβII- will offer cardioprotective effects in comparison with a scrambled peptide control (Myr-Tat-PKCβII-scram; N-Myr-Tat-CC-WNPESLNTE) in an in-vivo porcine myocardial I/R model. Methods: Regional I(1 hour)/R(3 hours) was induced in Male Yorkshire pigs (38-50kg) by inflating a balloon to occlude the Left Anterior Descending Artery (LAD) at the level of the second diagonal branch (supplies 40% of anterior left ventricle) and then deflating it to allow for reperfusion. Then, a bolus of either Myr-Tat-PKCβII- or Myr-Tat-PKCβII-scram (20ng/kg; ~100pmol in blood) was immediately administered into the LAD. Cardiac function and injury were measured by monitoring changes in ejection fraction (EF) and through routine measurements of serum creatine phosphokinase (CPK), troponin I, and myoglobin, respectively. After I/R, the hearts were stained with 1% Evans Blue dye to identify the area at risk (AR) and 1% triphenyltetrazolium chloride to determine the area of necrosis (AN). Infarct size was then quantified (AN/AR) and all data was analyzed via Student’s t-test. Results: Analysis showed that Myr-Tat-PKCβII- significantly restored EF to within 1.40.7% of baseline compared to controls which only restored EF to within 6.42.1% (p<0.05) of baseline EF. Myr-Tat-PKCβII- showed a significant increase in serum myoglobin levels at 1 hr of reperfusion (1362.1 83.4 μg/mL, n=4) compared to scrambled control (202.1197.3 μg/mL, n=3 p<0.05). Myr-Tat-PKCβII- reduced infarct size to 10.0±2.8%; n=4; compared to scrambled control hearts (28.5±8.3%; n=6; p<0.05). CPK and Troponin I levels were comparable in both groups. These results suggest that Myr-Tat-PKCβII- can help prevent cardiac injury when given immediately after an ischemic event. Conclusions: Data from ex-vivo rat heart I/R model, coupled with data from this in-vivo porcine myocardial I/R model indicate the effcacy of Myr-Tat-PKCβII- in preventing oxidative stress-induced myocardial I/R injury when given at the beginning of reperfusion. These findings suggest that Myr-Tat-PKCβII- could be useful in the clinical setting when administered immediately after cardiac resuscitation. Future studies include the treatment of rat cardiomyocyte cells with Myr-Tat-PKCβII- prior to 24 hr hypoxia/24 hr reoxygenation, followed by cell viability assays compared to untreated control. This additional data can help determine the optimal dose to use in a 12 week survival study using the same porcine myocardial I/R protocol.

Funding: This study was funded by the Philadelphia College of Osteopathic Medicine, Department of Biomedical Sciences, Division of Research, and the Center for Chronic Diseases of Aging, the National Heart, Lung & Blood Institute at NIH (grant # 1R43HL160338-01) and Young Therapeutics, LLC.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.