Abstract
We have revealed that a novel stress-inducible protein, Sestrin2, declines in the heart with aging. Moreover, there is an interaction between Sestrin2 and energy sensor AMPK in the heart in response to ischemic stress. The objective of this study is to determine whether Sestrin2-AMPK complex modulates PGC-1α in the heart and protects the heart from ischemic insults. In order to characterize the role of cardiac Sestrin2-AMPK signaling cascade in aging, C57BL/6 wild type young mice (3-4months), aged mice (24-26months) and young Sestrin2 KO mice were subjected to left anterior descending coronary artery occlusion for in vivo regional ischemia. Intriguingly, ischemic AMPK activation was blunted in aged WT and young Sesn2 KO hearts as compared with young WT hearts. In addition, the AMPK downstream PGC-1α was down-regulated in the aged and Sestrin2 KO hearts during post myocardial infarction. To further determine the regulation of AMPK on mitochondrial functions in aging, the downstream of mitochondrial biogenesis PGC-1α transcriptional factor were measured. The results demonstrated that the PGC-1α downstream effectors TFAM and UCP2 were impaired in the aged and Sestrin2 KO post-MI hearts as compared to the young hearts. While the apoptotic flux markers such as AIF, Bax/Bcl-2 were up-regulated in both aged and Sestrin2 KO hearts versus young hearts. Furthermore, both Sestrin2 KO and aged hearts demonstrated more susceptible to ischemic insults as compared to young hearts. Additionally, the adeno-associated virus (AAV9)-Sestrin2 delivered to the aged hearts via a coronary delivery approach significantly rescued the ischemic tolerance of aged hearts. Taken together, the decreased Sestrin2 levels in aging lead to an impaired AMPK/PGC-1α signaling cascade and an increased sensitivity to ischemic insults.