HIF-1α triggers long-lasting glutamate excitotoxicity via system xc−in cerebral ischaemia-reperfusion

Hypoxia-inducible factor 1α (HIF-1α) controls many genes involved in physiological and pathological processes. However, its roles in glutamatergic transmission and excitotoxicity are unclear. Here, we proposed that HIF-1α might contribute to glutamate-mediated excitotoxicity during cerebral ischaemia–reperfusion (CIR) and investigated its molecular mechanism. We showed that an HIF-1α conditional knockout mouse displayed an inhibition in CIR-induced elevation of extracellular glutamate and N-methyl-d-aspartate receptor (NMDAR) activation. By gene screening for glutamate transporters in cortical cells, we found that HIF-1α mainly regulates the cystine–glutamate transporter (system xc−) subunit xCT by directly binding to its promoter; xCT and its function are up-regulated in the ischaemic brains of rodents and humans, and the effects lasted for several days. Genetic deletion of xCT in cortical cells of mice inhibits either oxygen glucose deprivation/reoxygenation (OGDR) or CIR-mediated glutamate excitotoxicity in vitro and in vivo. Pharmaceutical inhibition of system xc− by a clinically approved anti-cancer drug, sorafenib, improves infarct volume and functional outcome in rodents with CIR and its therapeutic window is at least 3 days. Taken together, these findings reveal that HIF-1α plays a role in CIR-induced glutamate excitotoxicity via the long-lasting activation of system xc−-dependent glutamate outflow and suggest that system xc− is a promising therapeutic target with an extended therapeutic window in stroke. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.