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-1beta (IL-1beta) 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 NFkappaB 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-NFkappaB/p65 expression in ischemic brain was examined using Western blot analysis and immunohistochemistry. NFkappaB 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 NFkappaB/p65 increased after 2 and 4 hr of MCAO in WT mice; however, NFkappaB/p65 was significantly reduced after MCAO in the ICE KO mice (P < 0.05). EMSA showed that NFkappaB 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 NFkappaB phosphorylation is reduced in ICE KO mice, suggesting that ICE or IL-1 are involved in early NFkappaB phosphorylation. Because cerebral ischemia induced infarction is significantly reduced in ICE KO mice, we conclude that early NFkappaB phosphorylation plays a disruptive role in the ischemic process.

Caspases as Drug Targets in Ischemic Organ Injury

“…Interestingly, TNF-α did not change in caspase-1 -/-mice although ICAM-1 expression (by immunoblotting and immunohistochemistry) was reduced at all time points. NFκB, a transcription factor known to regulate numerous proinflammatory target genes, was reduced in the caspase-1 -/-mice at 2 and 4 hours, but not at later time points; ICAM-1 expression was also reduced in this study [77]. Neither of these studies assessed parameters of protection such as infarct size or neurological score.…”

NF-κB signaling in cerebral ischemia

“…Mice deficient in IL-1RA show increased ischemic brain damage, further supporting the notion that IL-1 plays a detrimental role in the pathophysiology of stroke (Allan et al, 2005). Furthermore, mice lacking interleukin-1␤-converting enzyme (ICE), also known as caspase-1, showed less ischemic brain injury, edema formation, and inflammatory responses (Huang et al, 2003). Interestingly, this was paralleled by reduced activation of NF-B in electrophoretic mobility shift assays and a significant reduction in the phosphorylation of the RelA subunit.…”

Activation of nuclear factor‐κB signaling pathway by interleukin‐1 after hypoxia/ischemia in neonatal rat hippocampus and cortex

“…2004). Huang et al . (2003) documented that decreased NF‐κB activity was observed in ischemic ICE null adult mice and suggested that IL‐1 signaling contributes to NF‐κB activation and subsequent ischemic damage.…”