Early NFκB activation is inhibited during focal cerebral ischemia in interleukin-1β-converting enzyme deficient mice

Abstract

Our previous study demonstrated that the inhibition of interleukin-1β (IL-1β) reduces ischemic brain injury; however, the molecular mechanism of the action of IL-1 in cerebral ischemia is unclear. We are investigating currently the role of NFκB during focal cerebral ischemia, using mutant mice deficient in the interleukin-1 converting enzyme gene (ICE KO) in a middle cerebral artery occlusion (MCAO) model. Adult male ICE KO and wild-type mice (n = 120) underwent up to 24 hr of permanent MCAO. Cytoplasmic phospho-NFκ B/p65 expression in ischemic brain was examined using Western blot analysis and immunohistochemistry. NFκB DNA-binding activity was detected using electrophoretic mobility shift assay (EMSA). Furthermore, ICAM-1 expression was examined in both the ICE KO and wild-type mice (WT). Western blot analysis and immunostaining showed that the level of cytosolic phosphorylated NFκB/p65 increased after 2 and 4 hr of MCAO in WT mice; however, NFκB/p65 was significantly reduced after MCAO in the ICE KO mice (P < 0.05). EMSA showed that NFκB DNA-binding activity increased after MCAO in WT mice; but this effect was reduced in the ICE KO mice. The number of ICAM-1-positive vessels in the ischemic hemisphere was greatly attenuated in the ICE KO mice (P < 0.05), which paralleled the results of immunohistochemistry. Our results demonstrate that NFκB phosphorylation is reduced in ICE KO mice, suggesting that ICE or IL-1 are involved in early NFκB phosphorylation. Because cerebral ischemia induced infarction is significantly reduced in ICE KO mice, we conclude that early NFκB phosphorylation plays a disruptive role in the ischemic process. © 2003 Wiley-Liss, Inc.