Glutathione adducts induced by ischemia and deletion of glutaredoxin-1 stabilize HIF-1α and improve limb revascularization

Reactive oxygen species (ROS) are increased in ischemic tissues and necessary for revascularization; however, the mechanism remains unclear. Exposure of cysteine residues to ROS in the presence of glutathione (GSH) generates GSH-protein adducts that are specifically reversed by the cytosolic thioltransferase, glutaredoxin-1 (Glrx). Here, we show that a key angiogenic transcriptional factor hypoxia-inducible factor (HIF)-1 alpha is stabilized by GSH adducts, and the genetic deletion of Glrx improves ischemic revascularization. In mouse muscle C2C12 cells, HIF-1 alpha protein levels are increased by increasing GSH adducts with cell-permeable oxidized GSH (GSSG-ethyl ester) or 2-acetylamino-3-[4-(2-acetylamino-2-carboxyethylsulfanyl thiocarbonylamino) phenylthiocarbamoylsulfanyl] propionic acid (2-AAPA), an inhibitor of glutathione reductase. A biotin switch assay shows that GSSG-ester-induced HIF-1 alpha contains reversibly modified thiols, and MS confirms GSH adducts on Cys(520) (mouse Cys(533)). In addition, an HIF-1 alpha Cys520 serine mutant is resistant to 2-AAPA-induced HIF-1 alpha stabilization. Furthermore, Glrx overexpression prevents HIF-1 alpha stabilization, whereas Glrx ablation by siRNA increases HIF-1 alpha protein and expression of downstream angiogenic genes. Blood flow recovery after femoral artery ligation is significantly improved in Glrx KO mice, associated with increased levels of GSH-protein adducts, capillary density, vascular endothelial growth factor (VEGF)-A, and HIF1 alpha in the ischemic muscles. Therefore, Glrx ablation stabilizes HIF-1 alpha by increasing GSH adducts on Cys(520) promoting in vivo HIF-1 alpha stabilization, VEGF-A production, and revascularization in the ischemic muscles.