Protein Kinase C Beta II Peptide Inhibitor Elicits Robust Effects on Attenuating Myocardial Ischemia/Reperfusion Injury
Authors: Metellus Daphne , Lipscombe Christina , Ebo Chinyere , Nair Arjun , Patel Harsh , Humayun Annam , Michaels Megan , Dang Jennifer , Finnegan Matthew , Checchio Lucy , Muftau‐Lediju Faosat , Martorana Rose M , Chen Qian , Barsotti Robert , Young Lindon 
Published: June 2021

Reperfusion injury is known to augment myocardial tissue injury following a heart attack partly due to the generation of reactive oxygen species (ROS) upon cardio‐angioplasty. Inhibition of protein kinase C beta II (PKCβII) during reperfusion with peptide inhibitor (N‐myr‐SLNPEWNET; PKCβ−) has been associated with decreased ROS release and leukocyte infiltration in rat hind‐limb and myocardial ischemia/reperfusion (I/R) studies, respectively. However, the role of activating PKCβII during the early reperfusion phase following myocardial ischemia is not known. It is thought that PKCβII activation augments tissue NADPH oxidase (NOX‐2) to enhance ROS release and exacerbate myocardial I/R (MI/R) injury. We were interested in studying the effects of myristoylated (myr‐) PKCβII peptide activator (N‐myr‐SVEIWD; myr‐PKCβ+) and myr‐PKCβ− in a rat MI/R model. Myristoylation of PKCβII peptides facilitate their entry into the cell in order to affect PKCβII activity by either augmenting or attenuating its translocation to cell membrane proteins, such as NOX‐2, via its selective receptor for activated C kinase domain. In this study, we hypothesize that myr‐PKCβ− will decrease infarct size and improve post‐reperfused cardiac function compared to non‐drug treated controls, whereas myr‐PKCβ+ treated hearts will not improve these parameters. Male Sprague‐Dawley rats (~300g) were anesthetized with an IP injection of pentobarbital (60mg/kg) and anticoagulated with 1000U of heparin. The heart was then removed and placed on the perfusion needle of the Langendorff heart apparatus and a pressure transducer was placed into the left ventricle to measure cardiac function. After establishing baseline for 15min, the heart was subjected to global MI(30min)/R(50min). Thereafter, 20μM of myr‐PKCβ + (n=6), 20 μM myr‐PKCβ− (n=6) or plasma without myr‐PKCβ+/− (control; n=8) was infused into the heart during the first 5min of reperfusion. Following reperfusion, all hearts were frozen at −20°C for 30min, sectioned into 2mm slices and incubated at 37°C in 1% triphenyltetrazolium chloride. The ratio of dead heart tissue (unstained) weight to total heart tissue weight was calculated for infarct size. Myr‐PKCβ− hearts significantly restored post‐reperfused left ventricular developed pressure by 68±11% of initial baseline values compared to control (32±5%, p<0.01) and myr‐PKCβ+ (49±8%, p<0.05) hearts. Additionally, myr‐PKCβ− significantly reduced infarct size to 16±3% compared to control (30±4%, p<0.05) hearts. Myr‐PKCβ+ hearts (infarct size of 26±4%) were not different from control hearts, suggesting that it would not be effective to attenuate MI/R injury. The data indicate that myr‐PKCβ− would be an effective treatment to reduce myocardial reperfusion injury when given to heart attack patients during cardio‐angioplasty.Support or Funding InformationThis research was supported by the Department of Bio‐Medical Sciences and the Division of Research at Philadelphia College of Osteopathic Medicine (PCOM) and by Young Therapeutics, LLC. 4170 City Avenue, Philadelphia, PA 19131This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.