Abstract 13994: Single-Dose Intervention With Rapamycin at Reperfusion Preserves Cardiac Function Through Attenuation of Inflammation and Increased Cardiomyocyte Proliferation in Diabetic Rabbit- Role of Hippo Pathway

Abstract

Background: Rapamycin (RAPA, mTOR inhibitor) given at reperfusion protects diabetic rabbit hearts against ischemia/reperfusion (I/R) injury by reducing infarct size and apoptosis. We hypothesized that RAPA administration may preserve post-ischemic cardiac function through decreased inflammation and increased cardiomyocyte proliferation with regulation of YAP- the effector of Hippo pathway). Methods and Results: Diabetes (DM) was induced by administration of alloxan monohydrate (125 mg/kg, i.v.) in New Zealand rabbits (n=12; body weight≈3 kg, 4-month-old). Four weeks after alloxan treatments, conscious diabetic rabbits (maintaining blood glucose>250 mg/dL) were subjected to 45 min of ischemia and 10 days of reperfusion (R) by inflating/deflating previously implanted hydraulic balloon occluder. RAPA (0.25 mg/kg, i.v.) or DMSO (vehicle) was infused 5 min before onset of R. Post-I/R cardiac function in diabetic rabbit, assessed by echocardiography, showed significant improvement of ejection fraction (EF, Fig. A ). Left ventricular fibrosis ( Fig. B , evaluated by picrosirius red staining) was attenuated following treatment of RAPA in diabetic rabbits. Immunofluorescence staining revealed the attenuation of post-I/R inflammasome formation with RAPA treatment as shown by reduced ASC aggregation (apoptosis speck-like protein with a caspase recruitment domain) in cardiomyocytes ( Fig. C ). RAPA suppressed the phosphorylation of YAP in cytosol of cardiomyocytes ( Fig. D ). Proliferation markers, Ki-67 positive and phospho-Aurora B Kinase positive cells indicated cardiomyocytes were in G2-M phase in RAPA-treated diabetic rabbits after I/R injury ( Fig. E ). Conclusion: RAPA treatment at reperfusion preserves cardiac function and improves cardiomyocyte proliferation with attenuation of inflammation and possibly regulation of Hippo pathway following I/R injury in diabetes.