Interleukin-1α expression precedes IL-1β after ischemic brain injury and is localised to areas of focal neuronal loss and penumbral tissues

Background: cerebral ischemia is a devastating condition in which the outcome is heavily influenced by inflammatory processes,which can augment primary injury caused by reduced blood supply. the cytokines interleukin-1α (il-1α) and il-1β are key contributors to ischemic brain injury. however,there is very little evidence that il-1 expression occurs at the protein level early enough (within hours) to influence brain damage after stroke. in order to determine this we investigated the temporal and spatial profiles of il-1α and il-1β expression after cerebral ischemia.findings: we report here that in mice,as early as 4 h after reperfusion following ischemia induced by occlusion of the middle cerebral artery,il-1α,but not il-1β,is expressed by microglia-like cells in the ischemic hemisphere,which parallels an upregulation of il-1α mrna. 24 h after ischemia il-1α expression is closely associated with areas of focal blood brain barrier breakdown and neuronal death,mostly near the penumbra surrounding the infarct. the sub-cellular distribution of il-1α in injured areas is not uniform suggesting that it is regulated.conclusions: the early expression of il-1α in areas of focal neuronal injury suggests that it is the major form of il-1 contributing to inflammation early after cerebral ischemia. this adds to the growing body of evidence that il-1α is a key mediator of the sterile inflammatory response. © 2011 luheshi et al; licensee biomed central ltd.