Endothelial progenitor cells (EPCs) play an essential role in angiogenesis but are functionally impaired in diabetes. We recently reported that decreased expression of
manganese superoxide dismutase (MnSOD) critically contributes to diabetic
EPC dysfunction.
AMP-activated protein kinase (AMPK) activation has been shown to induce MnSOD and suppress
hyperglycemia-induced mitochondrial ROS production in endothelial cells. However, whether AMPK protects EPCs from oxidative stress in diabetes is unknown. We tested the hypothesis that AMPK activation rescues impaired
EPC functions through MnSOD induction in
type 1 diabetes. Bone marrow-derived EPCs from adult male
streptozotocin-induced diabetic mice and normal controls were used. AMPK activity was decreased in diabetic EPCs, indicated by reduced AMPK and
acetyl-CoA carboxylase phosphorylation. AMPK activation by treating diabetic EPCs with its selective agonist
AICAR rescued their in vitro functions, including
Matrigel tube formation, adhesion, and migration. Furthermore,
AICAR restored the decreased MnSOD
protein and enzymatic activity and suppressed the mitochondrial
superoxide level in diabetic EPCs, indicated by
MitoSOX flow cytometry. These beneficial effects of
AICAR on MnSOD and
EPC functions were significantly attenuated by silencing MnSOD or AMPK antagonist compound C pretreatment. Finally, the expression of
protein phosphatase 2A, a key
enzyme for AMPK dephosphorylation and inactivation, was increased in diabetic EPCs, and its inhibition by
siRNA or
okadaic acid reversed the deficient AMPK activation and MnSOD level in diabetic EPCs. These findings demonstrate for the first time that AMPK activation rescues impaired
EPC functions and suppresses mitochondrial
superoxide by inducing MnSOD in
type 1 diabetes.