Abstract 496: Inhibition of the Rna Binding Protein Hur Protects Against Cardiac Ischemia/reperfusion Injury by Reducing Inflammatory Gene Expression

Despite medical advances, cardiac ischemia/reperfusion (I/R) injury remains a leading cause of morbidity and a huge economic burden in the United States. RNA binding proteins are becoming recognized as potential mediators of cardiac physiology and pathology, but the role of HuR, an RNA binding protein highly expressed in myocytes, in acute cardiac I/R injury is unknown. HuR has been shown in other tissues to be a critical post-transcriptional mediator of pro-inflammatory chemokine and cytokine gene expression, and we have shown HuR to be activated (nuclear-to-cytoplasmic translocation) in cardiomyocytes 2 hours post-ischemia/reperfusion injury. To address the functional role of HuR in I/R, cardiomyocyte-specific HuR deletion mice (iCM-HuR -/- ) were subjected to 30 minutes of LAD (left anterior descending) coronary artery ligation followed by 24 hours of reperfusion. In parallel, a separate group of wild-type mice were subjected to 30 minutes ischemia with a pharmacological inhibitor of HuR given just prior to reperfusion. Analysis of infarct size showed a smaller infarct with both HuR genetic deletion (~10% decrease in infarct size compared to control, N=3, P<0.05) and pharmacological inhibition (~11% decrease in infarct size compared to vehicle, N=4, P=0.069). Similarly, HuR inhibition significantly reduced cell death, caspase-3 activity, and inflammatory gene expression in an in vitro model of simulated I/R using neonatal rat ventricular myocytes. HuR inhibition results in a significant blunting of IL-6 and TNF-alpha gene expression two hours post-reperfusion in vivo , suggesting that HuR activity is necessary for the early induction of inflammatory gene expression networks. In addition, it appears that HuR inhibition attenuates macrophage infiltration following ischemia/reperfusion injury. In conclusion, our results suggest that inhibition of HuR is protective against cardiac I/R injury through a reduction in inflammatory gene expression.