Abstract 13199: Novel Insights of the Role of miR-181 in Cardiac Dysfunction, through Mitochondrial Gene Regulation
Recently, we have demonstrated that microRNAs (miRs) not only target nuclear genes, but they also can regulate mitochondrial genes in the heart. Specifically, miR-181 family is encoded in the nucleus, processed in the cytosol, and translocated into the mitochondria, where it ultimately regulates mitochondrial gene expression. In an in-vitro neonatal cardiomyocyte model, we have shown that overexpressing miR-181c can modulate mitochondrial bioenergetics by complex IV remodeling, by targeting the 3’-end of mt-COX1 (cytochrome c oxidase subunit I). Here we report that in-vivo administration of miR-181c in rats leads to cardiac dysfunction. We cloned miR-181c, expressing it in an expression vector, and packaged this construct into lipid-based cationic nanoparticles for systemic delivery. The nanovector is approximately 100 nm in diameter and shows no apparent histopathologic or biochemical evidence of toxicity when administered by tail vein injection. We delivered a 4 mg/kg dose of plasmid, which increases miR-181c levels in heart tissue almost 1.5 fold with 6 injections over 3 weeks. We find that rats that overexpress miR-181c become fatigued during a forced swimming test compared to the empty expression vector control group. Using 2D, M-mode, and Doppler echocardiography, we observe that miR-181c overexpression causes a significant decrease in left ventricular ejection fraction. qPCR data reveal that mRNA levels of mitochondrial complex IV genes, like mt-COX1, mt-COX2 and mt-COX3, but not any other mitochondrial genes, are significantly altered with miR-181c overexpression, suggesting mitochondrial complex IV remodeling due to miR-181c targeting mt-COX1. Protein levels of mt-COX1 and mt-COX2 are also markedly lower in the hearts of animals with miR-181c overexpression. Isolated heart mitochondrial studies showed significantly altered O2 consumption, ROS production, matrix calcium retention capacity, and mitochondrial membrane potential in miR-181c overexpressor animals. Taken together, this study shows, for the first time, that miRNAs can be delivered to the heart by nanovector delivery and that overexpression of miR-181c can lead to cardiac dysfunction in vivo by regulating mitochondrial genes.
- Oxidative stress
- Mitochondrial energetics, heart failure, arrhythmias
- © 2013 by American Heart Association, Inc.