Abstract 11431: Critical Role of miR-181 Family During Oxidative Stress in Heart
The role of oxidative stress in cardiac injury has been extensively studied. Mitochondria are the major source of ROS and a target for ROS damage. Recently, we have identified a mi(cro)RNA, miR-181c, which localizes to heart-mitochondria and regulates ROS production by targeting a mitochondrial gene, mt-COX1. To investigate the mechanism(s), we designed miR-181-sponges, RNA molecules with ten repeated complimentary miR-181 “seed” sequences, and generated a set of stable H9c2 cell lines by transfecting either scramble- or miR-181-sponge-sequences. We found a significant decrease in ROS production and reduced basal mitochondrial respiration with sponge group.But unlike our miR-181c overexpression study, here we observed a significant increase in all of the mitochondrial genes, coding for subunits of different respiratory complexes, ND2 (complex I) and ATPase 8 (complex V), as well as complex IV subunits. This occurs because the miR-181-sponge lowers the expression level of the entire miR-181 family (a, b, c and d). We find that the sponge decreases PI3K signaling because miR-181a/b target PTEN. Using siRNA specific to PTEN, we found Sponge-expressed cells with lower PTEN expression offered a significantly higher level of protection against oxidative stress compared to scramble as well as Sponge-expressed without PTEN siRNA. In-vitro data suggests that miR-181a/b targets PTEN in the cytosol and miR-181c/d targets mt-COX1 in the mitochondria. To extend this finding, we have used two sets of knock-out mice (miR-181a/b-/- and miR-181c/d-/-), and subjected them to ischemia-reperfusion injury. miR-181c/d-/- show a significant decrease, while miR-181a/b-/-show a significant increase in infarct size compared to WT-animals. Taken together, the miR-181 family plays an important role in important signaling pathways in oxidative stress, notably with protection by targeting mt-COX1 (miR-181c) or with detrimental results by targeting PTEN (miR-181a/b).
Author Disclosures: S. Das: None. M. Kohr: None. B. Dunkerly: None. O.A. Kent: None. A.K. Leung: None. J. Henao-Mejia: None. R.A. Flavell: None. C. Steenbergen: None.
This research has received full or partial funding support from the American Heart Association.
- © 2014 by American Heart Association, Inc.