Type-I interferon signalling through IFNAR1 plays a deleterious role in the outcome after stroke

Neuroinflammation contributes significantly to the pathophysiology of stroke. Here we test the hypothesis that the type I interferon receptor (IFNAR1) plays a critical role in neural injury after stroke by regulating the resultant pro-inflammatory environment. Wild-type and IFNAR1^-/- primary murine neurons and glia were exposed to oxygen glucose deprivation (OGD) and cell viability was assessed. Transient cerebral ischemia/reperfusion injury was induced by mid-cerebral artery occlusion (MCAO) in wild-type and IFNAR1^-/- and IFNAR2^-/- mice in vivo, and infarct size, and molecular parameters measured. To block IFNAR1 signalling, wild-type mice were treated with a blocking monoclonal antibody directed to IFNAR1 (MAR-1) and MCAO was performed. Quantitative PCR confirmed MCAO in wild-type mice induced a robust type-I interferon gene regulatory signature. Primary cultured IFNAR1-deficient neurons were found to be protected from cell death when exposed to OGD in contrast to primary cultured IFNAR1-deficient glial cells. IFNAR1^-/- mice demonstrated a decreased infarct size (24.9 ± 7.1 mm³ n = 8) compared to wild-type controls (65.1 ± 4.8 mm³ n = 8). Western blot and immunohistochemistry showed alterations in Akt and Stat-3 phosphorylation profiles in the IFNAR1^-/- brain. MAR-1 injection into WT mice (i.v. 0.5 mg 60 min prior to MCAO) resulted in a 60% decrease in infarct size when compared to the IgG control. IFNAR2^-/- mice failed to display the neuroprotective phenotype seen in IFNAR1^-/- mice after MCAO. Our data proposes that central nervous system signalling through IFNAR1 is a previously unrecognised factor that is critical to neural injury after stroke.