Endothelial HIF-2 mediates protection and recovery from ischemic kidney injury.

The hypoxia-inducible transcription factors HIP-1 and HIF-2 mediate key cellular adaptions to hypoxia and contribute to renal homeostasis and pathophysiology; however, little is known about the cell type-specific functions of HIP-1 and HIF-2 in response to ischemic kidney injury. Here, we used a genetic approach to specifically dissect the roles of endothelial HIP-1 and HIF-2 in murine models of hypoxic kidney injury induced by ischemia reperfusion or ureteral obstruction. In both models, inactivation of endothelial HIP increased injury-associated renal inflammation and fibrosis. Specifically, inactivation of endothelial HIF-2 alpha, but not endothelial HIF-1 alpha, resulted in increased expression of renal injury markers and inflammatory cell infiltration in the postischemic kidney, which was reversed by blockade of vascular cell adhesion molecule-1 (VCAM1) and very late antigen-4 (VLA4) using monoclonal antibodies. In contrast, pharmacologic or genetic activation of HIP via HIP prolyl-hydroxylase inhibition protected wild-type animals from ischemic kidney injury and inflammation; however, these same protective effects were not observed in HIP prolyl-hydroxylase inhibitor-treated animals lacking endothelial HIF-2. Taken together, our data indicate that endothelial HIF-2 protects from hypoxia-induced renal damage and represents a potential therapeutic target for renoprotection and prevention of fibrosis following acute ischemic injury.