Cerebral vessels express interleukin 1 β after focal cerebral ischemia

Abstract

Rapid and marked increased levels of expression of interleukin 1 β (IL-1 β) mRNA have been detected in animal models of cerebral ischemia. However, the protein production of IL-1 β and the cellular sources of IL-1 β are largely undefined after cerebral ischemia. In the present study, we have measured the cellular localization of IL-1 β protein in brain tissue from non-ischemic and ischemic mice using immunohistochemistry. Male C57B/6J ( n=45) mice were subjected to middle cerebral artery (MCA) occlusion by a clot or a suture. The mice were sacrificed at time points spanning the period from 15 min to 24 h after onset of the MCA occlusion. Non-operated and sham-operated mice were used as control groups. A monoclonal anti-IL-1 β antibody was used to detect IL-1 β. In the non-operated and sham-operated mice, a few IL-1 β immunoreactive cells were detected scattered throughout both hemispheres. IL-1 β immunoreactive cells increased in the ischemic lesion as early as 15 min and peaked at 1 h to 2 h after MCA occlusion. IL-1 β immunoreactivity was detected in the cortex of the contralateral hemisphere 1 h after ischemia. By 24 h after onset of ischemia, IL-1 β immunoreactivity was mainly present adjacent to the ischemic lesion and in the non-ischemic cortex. IL-1 β immunoreactivity was found on endothelial cells and microglia. This study demonstrates an early bilateral expression of IL-1 β on endothelium after MCA occlusion in mice.