Protection by vascular prostaglandin E2 signaling in hypoxic-ischemic encephalopathy

Hypoxic-ischemic encephalopathy (HIE) in neonates is a leading cause of neurological impairment. Significant progress has been achieved investigating the pathologic contributions of excitotoxicity, oxidative stress, and neuroinflammation to cerebral injury in HIE. Less extensively investigated has been the contribution of vascular dysfunction, and whether modulation of cerebral perfusion may improve HIE outcome. Here, we investigated the function of the prostaglandin E2 (PGE2) EP4 receptor, a vasoactive Gαs-protein coupled receptor (GPCR), in rodent models of neonatal HIE. The function of PGE2 signaling through the EP4 receptor was investigated using pharmacological and conditional knockout genetic strategies in vivo in rodent models of HIE. Pharmacologic activation of the EP4 receptor with a selective agonist was significantly cerebroprotective both acutely and after 7 days. Measurement of cerebral perfusion during and after hypoxia-ischemia demonstrated that EP4 receptor activation improved cerebral perfusion in both the contralateral and ipsilateral hypoxic-ischemic hemispheres. To test whether vascular EP4 signaling exerted a critical function in HIE injury, cell specific conditional knockout mouse pups were generated in which endothelial EP4 receptor was selectively deleted postnatally. VE-Cadherin Cre-ERT2;EP4lox/lox pups demonstrated significant increases in cerebral injury as compared to VE-Cadherin Cre-ERT2;EP4+/+ control littermates, indicating that endothelial EP4 signaling is protective in HIE. Our findings identify vascular PGE2 signaling through its EP4 receptor as protective in HIE. Given the pharmacologic accessibility of endothelial EP4 GPCRs, these data support further investigation into novel approaches to target cerebral perfusion in neonatal HIE.