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Protein kinase C beta II (PKCβII) activates polymorphonuclear leukocyte (PMN) superoxide (SO) production via NADPH oxidase (NOX-2) phosphorylation to exacerbate myocardial ischemia/reperfusion (I/R) injury. In prior studies, myristoylation (myr) of PKCβII peptide inhibitor (N-myr-SLNPEWNET; myr-PKCβII-), which disrupts PKCβII translocation/phosphorylation of NOX-2, was shown to dose-dependently attenuate PMN SO release induced by phorbol 12-myristate 13-acetate (PMA), a broad-spectrum PKC agonist. However, the role of myr on the inhibitory effects of myr-PKCβII- has yet to be elucidated. We hypothesized that myr-PKCβII peptide activator (N-myr-SVEIWD; myr-PKCβII+) would augment, myr-PKCβII- would attenuate, and scrambled myr-PKCβII- (N-myr-WNPESLNTE; myr-PKCβII-scram), a control for myr, would not affect PMA-induced PMN SO release compared to unconjugated peptides and nontreated controls. Rat PMNs (5х10 6 ) were incubated for 15 min at 37 o C in the presence/absence of SO dismutase (SOD; 10 μg/mL), unconjugated PKCβII+/-, myr-PKCβII+/-, or myr-PKCβII-scram (all 20 μM). SO release was measured by the change in absorbance at 550 nm via ferricytochrome c reduction after PMA (100 nM) stimulation for 390 sec. Data were analyzed by ANOVA using Student-Newman-Keuls post hoc analysis. Myr-PKCβII- significantly attenuated SO release (0.30±0.02; n=27; p2 O 2 , significantly reduced absorbance by 94±7%, indicating that absorbance increased mainly due to PMA stimulation. Cell viability (trypan blue exclusion) was similar in all groups (94±2%). Unexpectedly, myr-PKCβII-scram significantly stimulated the highest increase in absorbance compared to all groups (p

Reactive oxygen species (ROS) induced ischemia-reperfusion (I/R) injury is a phenomenon causing paradoxical myocardial damage after cardio-angioplasty, coronary bypass and organ transplantation. Previous studies show that a cell-permeable myristic acid (myr-) conjugated PKCβII peptide inhibitor given at reperfusion prevents PKCβII translocation (N - myr-SLNPEWNET; myr-PKCβII-) and significantly attenuates ROS mediated I/R injury. We included a scrambled myr-PKCβII- (N-myr-WNPESLNTE; myr-PKCβII-scram) to examine the effects of myr separately. We hypothesize that myr-PKCβII- will improve and myr-PKCβII activator peptide (N-myr-SVEIWD; myr-PKCβII+) will exacerbate infarct size and post-reperfused cardiac function compared to myr-PKCβII-scram and untreated controls. Hearts isolated from male Sprague-Dawley rats (~300g) were perfused with Krebs’ buffer at a constant pressure of 80mmHg and subjected to 30 min of global ischemia and 50 min reperfusion. Myr-PKCβII-, myr-PKCβII+, myr-PKCβII-scram (all 20μM), or untreated control were given during the first five minutes of reperfusion. Left ventricular (LV) dP/dt max and dP/dt min (mmHg/s) were measured using a pressure transducer, and infarct size was determined using 1% triphenyltetrazolium chloride staining comparing infarcted tissue vs. total tissue weight. Data were evaluated using ANOVA with Student-Newman-Keuls post-hoc analysis. Myr-PKCβII- (n=17) significantly improved LV dP/dt max and dP/dt min to 1535±107 and 1063±83 at 50 min post-reperfusion compared to untreated control (815±107 and 722±89; n=15); myr-PKCβII-scram (513±78 and 433±66; n=12), and myr-PKCβII+ (860±118 and 694±81; n=14) (all pmax and LV dP/dt min compared to untreated control and other treated groups (p