Nuclear Factor-κB and Cell Death After Experimental Intracerebral Hemorrhage in Rats

Abstract

Background and Purpose —Nuclear factor-κB (NF-κB) is a ubiquitous transcription factor that, when activated, translocates to the nucleus, binds to DNA, and promotes transcription of many target genes. Its activation has been demonstrated in chronic inflammatory conditions, cerebral ischemia, and apoptotic cell death. The present study evaluated the presence and activation of NF-κB in relation to cell death surrounding intracerebral hemorrhage (ICH). Methods —Striatal ICH was induced in rats by the double blood injection method. Animals were killed 2, 8, and 24 hours and 4 days after ICH. To examine changes in NF-κB protein, Western blot was performed on brain extract. We determined NF-κB activity using electrophoretic mobility shift assay (EMSA) and immunohistochemistry, using an antibody that only recognizes active NF-κB. DNA fragmentation was detected with terminal deoxynucleotidyl transferase–mediated uridine 5′-triphosphate-biotin nick end-labeling (TUNEL) staining. Results —Western blot analysis of the NF-κB p65 subunit showed that there was no difference in p65 protein levels in the control, 2-hour, 8-hour, or 24-hour groups. However, ipsilateral perilesional samples from the 4-day group revealed a 1.8- to 2.5-fold increase compared with the contralateral hemisphere. Western blotting showed no differences in the inhibitor of NF-κB, IκBα, in any group. EMSA showed 1.3-, 2.1-, and 3.6-fold increased NF-κB activation in the ipsilateral striatum from the 8-hour, 24-hour, and 4-day groups, respectively, compared with the contralateral hemisphere. Immunohistochemistry, in which an activation-dependent anti–NF-κB antibody was used, demonstrated perivascular NF-κB activation as early as 2 hours after ICH with more generalized activation at 8 hours, in agreement with the EMSA results. NF-κB activation colocalized to cells containing fragmented DNA measured by TUNEL. Conclusions —The present study suggests a relationship between NF-κB and the pathobiology of perilesional cell death after ICH.