Abstract 442: Intralipid Protects the Heart in Late Pregnancy Against Ischemia/Reperfusion Injury by Reducing Cardiomyocyte Apoptosis via Mir122 Induction

Abstract

The prevalence of coronary artery disease in late pregnancy (LP) has increased recently due to significant changes in women’s lifestyle patterns (age, stress, smoking, diabetes and chronic hypertension). Myocardial infarction during LP and the peripartum is associated with significant maternal mortality and morbidity compared to non pregnant women for unclear reasons. We have recently demonstrated that cardiac vulnerability to I/R injury drastically increases in LP rodents, leading to myocardial infarct size ~4 fold greater than in non-pregnant controls. We also discovered that administration of intralipid (an emulsion of soy bean oil, egg yolk phospholipids and glycerol) at reperfusion resulted in ~60% reduction in infarct size of the heart in LP rat subjected to I/R injury. However, the molecular mechanisms underlying intralipid-induced cardioprotection in late pregnancy is not clear. Here we hypothesized that intralipid protects the heart in late pregnancy by regulating the levels of specific microRNAs. The left anterior descending coronary artery was occluded in LP rats (21-22 days of pregnancy) for 45 min followed by 3 hr of reperfusion. One single bolus of PBS (control group) or 20% intralipid (intralipid group) was applied through the femoral vein 5 min before the reperfusion. The hearts of control and intralipid groups were used for microRNA microarray analysis (Ocean Ridge Biosciences). MicroRNA-microarray analysis identified MiR122 as a novel micro-RNA which its expression was strikingly upregulated more than 10 fold in the heart of LP rats in intralipid group compared to control group. miR122 regulates apoptosis in cardiomyocytes subjected to hypoxia/reoxygenation since miR122-overexpression resulted in reduced apoptosis, whereas knockdown of miR122 enhanced apoptosis. Pyruvate kinase isoform M2 (PKM2), which is known to regulate cell apoptosis in the liver, is a direct target of miR122. Our data show that PKM2 and caspase 3 are two targets of miR122 since the expression of PKM2 and capase-3 in the heats subjected to I/R was significantly lower in intralipid group compared to control group in LP. In conclusion intralipid protects the heart in late pregnancy against ischemia/reperfusion injury via inducing miR122 by targeting PKM2.