Abstract
Proinflammatory mediators trigger intensive postischemic inflammatory remodeling of the blood-brain barrier (BBB) including extensive brain endothelial cell surface and junctional complex changes. Junctional adhesion molecule-A (JAM-A) is a component of the brain endothelial junctional complex with dual roles: paracellular route occlusion and regulating leukocyte docking and migration. The current study examined the contribution of JAM-A to the regulation of leukocyte (neutrophils and monocytes/macrophages) infiltration and the postischemic inflammatory response in brain ischemia/reperfusion (I/R injury). Brain I/R injury was induced by transient middle cerebral artery occlusion (MCAO) for 30min in mice followed by reperfusion for 0-5days, during which time JAM-A antagonist peptide (JAM-Ap) was administered. The peptide, which inhibits JAM-A/leukocyte interaction by blocking the interaction of the C2 domain of JAM-A with LFA on neutrophils and monocytes/macrophages, attenuated I/R-induced neutrophil and monocyte infiltration into brain parenchyma. Consequently, mice treated with JAM-A peptide during reperfusion had reduced expression (~3-fold) of inflammatory mediators in the ischemic penumbra, reduced infarct size (94±39 vs 211±38mm3) and significantly improved neurological score. BBB hyperpermeability was also reduced. Collectively, these results indicate that JAM-A has a prominent role in regulating leukocyte infiltration after brain I/R injury and could be a new target in limiting post-ischemic inflammation.