FOXO1 inhibition potentiates endothelial angiogenic functions in diabetes via suppression of ROCK1/Drp1-mediated mitochondrial fission

Diabetes-induced endothelial cell (EC) dysfunction and neovascularization impairment constitute vascular complications with limited treatment regimens. Transcription factor FOXO1 is a key angiogenic regulator and plays a pathologic role in progression of diabetes. The present study was designed to determine the involvement of FOXO1 in impaired EC function and post-ischemic neovascularization in diabetes and investigate underlying mechanisms. We found that FOXO1-selective inhibitor AS1842856 improved blood flow recovery and capillary density in ischemic hindlimb, and rescued the delay of wound closure with a concomitant augmentation of mean perfusion rate in diabetic mice. In vitro, treatment with AS1842856 or FOXO1 siRNA abrogated high glucose-induced apoptosis and ameliorated capillary tube formation in human umbilical vein endothelial cells (HUVECs). FOXO1 inhibition relieved alterations in mitochondrial networks and significantly suppressed the overproduction of mitochondrial reactive oxygen species (mtROS) induced by high glucose in ECs. Expression of dynamin-related protein-1 (Drp1) and phosphorylation at Ser616, a protein required for mitochondrial fission, were enhanced by hyperglycemia, which could be neutralized by FOXO1 inhibition. Moreover, the transcription of Rho-associated coiled-coil containing protein kinase 1 (ROCK1), which phosphorylates Drp1 at Ser616, was shown by luciferase assay to be directly regulated by FOXO1. These findings suggested that FOXO1 is critical to preserve mitochondrial quantity and function in ECs, and FOXO1 may serve as a therapeutic target for microvascular complications of diabetes.