INTRODUCTION: Acute kidney injury (AKI) due to ischemia-reperfusion (I/R) insult involves oxidative stress and inflammation leading to rapid renal decline. In this study, we test a novel myristoylated protein kinase C beta II peptide inhibitor (N-myr-SLNPEWNET; myr-PKCβII-), known to attenuate ex vivo rat myocardial I/R injury in a murine model of renal ischemia. We aim to demonstrate the attenuation of renal I/R injury by myr-PKCβII- in comparison to scrambled control peptide (N-myr-WNPESLNTE; myr-PKCβII-scram) by quantifying serum creatinine (Cr) and glomerular filtration rate (GFR).

METHODS: Renal pedicles of anesthetized male C57BL/6J mice were clamped bilaterally for 20-min or 19-min. Five minutes before unclamping, 2.0 mg/kg (20 µM serum) myr-PKCβII- or myr-PKCβII-scram were given IV into the tail vein. Cr was measured at baseline, 24h, 72h, and 96h post-injury. GFR was determined with fluorescein-isothiocyanate (FITC)-Sinistrin renal clearance. Data were evaluated by unpaired Student’s t-test.

RESULTS: Following 20-min renal ischemia, Myr-PKCβII- (n=9) significantly reduced Cr at 24h and 72h post-injury compared to myr-PKCβII-scram (n=8; p<0.05). Three unexpected fatalities followed 20-min ischemia, but not 19-min ischemia. Serum Cr levels modestly increased following 19-min renal I/R and were similar for Myr-PKCβII-scram control and Myr-PKCβII- treated groups. Compared to myr-PKCβII-scram control, Myr-PKCβII- demonstrated a trend towards improved GFR at 72hr (130 ± 28 vs 96 ± 44 µl/ml; p=0.065) and 96 hr (133 ± 33 vs 113 ± 50 µl/ml; p=0.095) post-I/R injury.

DISCUSSION: Results suggest 20-min renal ischemia was more severe, indicated by a 5-fold increase in Cr at 72h post-injury compared to 19-min ischemia and unanticipated fatalities of three mice. Myr-PKCβII- attenuated renal injury following 20-min renal ischemia, but not after 19-min in which Cr levels were too low to detect therapeutic benefit. The difference in injury severity between 20-min and 19-min renal ischemia emphasizes the temporal relationship between renal function and ischemic duration.