Abstract 20182: MicroRNA Let-7f Alleviates Mitochondrial Superoxide Production and Improves Angiogenic Functions of Endothelial Progenitor Cells through AMPK-Dependent MnSOD Induction in Type 1 Diabetes
Background: Endothelial progenitor cells (EPCs) play a key role in postnatal neovascularization, which is impaired in diabetes due to excessive oxidative stress. MicroRNA let-7f has been found to promote angiogenesis in endothelial cells. However, the role of let-7f in EPC-mediated angiogenesis is unknown. We hypothesized that let-7f alleviates mitochondrial superoxide level and improves EPC functions via AMPK-dependent MnSOD induction in diabetes.
Methods and Results: Bone marrow-derived EPCs from adult male streptozotocin (STZ)-induced type 1 diabetic mice were used (glucose 456.0±24.46 vs. 165.3±7.35 mg/dl, n=36, p<0.01). First, endogenous let-7f expression was decreased by 65% in diabetic vs. normal EPCs (real-time PCR, n=6, p<0.01). Transfection of diabetic EPCs with let-7f mimic resulted in an improvement of their angiogenic (1.8 fold by Matrigel tube formation), adhesion (1.5 fold) and migration (1.3 fold) functions (n=4, p<0.05 vs. scramble). Conversely, let-7f inhibitor transfection significantly impaired normal EPC angiogenic and adhesion functions (n=5, p<0.05 vs. scramble). Second, elevated mitochondrial ROS level in diabetic EPCs was reduced by let-7f mimic (MitoSOX Red, n=5, p<0.05 vs. scramble). Let-7f mimic restored decreased MnSOD protein and activity (1.4 fold, n=4–5, p<0.05 vs. scramble) in diabetic EPCs, but had no effect on Cu/ZnSOD and mitochondrial thioredoxin 2. Third, AMPK activity was decreased in diabetic EPCs. Treatment with the selective AMPK agonist AICAR increased AMPK activity, and restored MnSOD protein and activity (∼1.3 fold, n=5, p<0.05 vs. vehicle). Let-7f mimic transfection also increased AMPK activity (1.3 fold, n=5, p<0.05 vs. scramble) and the selective AMPK inhibitor compound C pretreatment retarded the effects of let-7f on MnSOD induction, ROS suppression and EPC function. Finally, protein phosphatase 2A (PP2A), an endogenous AMPK inactivator, was increased in diabetic EPCs, which was reduced by let-7f mimic (n=5, p<0.05 vs. scramble).
Conclusions: MicroRNA let-7f alleviates mitochondrial superoxide production and improves EPC functions via AMPK-dependent MnSOD induction in type 1 diabetes. These findings may provide a mechanistic basis for targeting let-7f to augment EPC angiogenesis.
- © 2010 by American Heart Association, Inc.