Inactivation of endothelial adenosine A_2A receptors protects mice from cerebral ischaemia-induced brain injury

Background and Purpose: Inactivation of the gene for adenosine A_2A receptors (ADORA2A for humans and Adora2a for rodents) protects against brain injury in experimental stroke. However, the cell-specific pathogenic effects of A_2A receptors in thromboembolic stroke and the underlying mechanisms remain undefined. Here, we tested the hypothesis that inhibition of endothelial A_2A receptors after thromboembolic stroke improves post-stroke outcomes via down-regulation of inflammation. Experimental Approach: Thromboembolic stroke was induced by embolic middle cerebral artery occlusion in mice. Post-stroke outcomes were determined with neurological deficit scoring, infarct volume, inflammatory marker expression, brain leukocyte infiltration, blood–brain barrier (BBB) leakage, and oedema assessment. Anti-inflammatory effects of silencing the gene for A_2A receptors or pharmacological antagonism of these receptors were assessed in vitro. Key Results: Thromboembolic stroke induced Adora2a expression in the brain. Mice globally deficient in Adora2a (Adora2a^−/−) were resistant to stroke injury. Mice specifically deficient in endothelial Adora2a (Adora2a^ΔVEC) showed reduced leukocyte infiltration, BBB leakage, and oedema after stroke, along with attenuated downstream proinflammatory markers, both in vivo and in vitro. The A_2A receptor antagonist, KW 6002, also reduced brain injury and inflammation after stroke. Inactivation of ADORA2A inhibited endothelial inflammation via suppression of the NLRP3 inflammasome, down-regulating cleaved caspase 1 and IL-1β expression. Conclusions and Implications: Specific inactivation of endothelial A_2A receptors mitigated ischaemic brain injury and improved post-stroke outcomes, at least partly, through anti-inflammatory effects via blockade of NLRP3 inflammasome activity. Our findings may open new approaches to vascular protection after ischaemic stroke.