[Abstract Title]. - Society for Neuroscience

Topic: C.06.h. In vivo mechanisms
Title: Selective suppression of neuronal NF-θB signaling: effect on intensity of kainic acid
induced seizures and hippocampal neurodegeneration
Authors: *P. RATHORE 1 , S. J. LISTWAK 2 , M. HERKENHAM 2 ;
1 Section of Functnl Neuroanatom, NIMH , NIH, Bethesda, MD; 2 Section of Functional
Neuroanatomy, Natl. Inst. of Mental Health, NIH, Bethesda, MD
Abstract: Nuclear Factor-kappaB (NF-kB) is a transcription factor activated in response to
inflammation and injury. In brain, NF-kB has a role in cell survival and also in synaptic
plasticity, learning, and memory consolidation. It is reported that kainic acid (KA)-induced
excitotoxic seizures activate NF-kB in brain, but the consequences of such activation are not
known in part because the role played by NF-kB in neurons versus glia may be different. The
present study uses tetracycline-inducible NSE-tTA + tet-IKK2-DN double transgenic mice to
investigate the role of NF-kB activation in neurons following KA injection (30 mg/kg). In these
mice, the tetracycline-regulated IkB kinase2-dominant negative (tet-IKK2-DN) construct is
under control of neuron-specific enolase (NSE-tTA) promoter. This allows suppression of NFkB
signaling in neurons upon removal of doxycycline (Dox Off) from the diet. KA-treated mice
were scored for seizure intensity using the Racine scale. Changes in body and brain weight
following seizures were measured. We found that Dox-Off NSE-IKK2-DN mice and C57BL/6
wildtype (WT) mice exhibited very severe KA-induced seizures in contrast to relatively milder
seizures seen in Dox-On NSE-IKK2-DN mice. Alterations in body and brain weight correlated
with the intensity of seizures. Fluorojade B staining at 3 days revealed that WT and Dox-Off
NSE-IKK2-DN mice showed neurodegeneration in the CA3 region of hippocampus in contrast
to no degeneration detected in Dox-On NSE-IKK2-DN mice. qRT-PCR analysis showed
manifold increase in expression of cytokines like MCP-1, GRO-alpha, TIMP-1, and IL-6 in the
cortex from WT and Dox-Off NSE-IKK2-DN mice. In Dox-Off NSE-IKK2-DN mice, the
increased expression of genes was blunted relative to WT. DNA binding assays (EMSAs) and
Western blot analysis in nuclear extracts from cortex showed involvement of p50 and p65 NF-kB
subunits. Neuroanatomical localization of the up-regulated genes following seizures is being
detected using in situ hybridization technique. The study so far suggests a pivotal role for
neuronal NF-kB in transcriptional regulation of cytokines and chemokines in brain, which may
be dictating the fate of neurons during seizures. We will explore further why in comparing Dox-
On and Dox-Off animals, neuronal NF-kB expression appears to be neuroprotective, whereas in
comparing Dox-Off with WT, it appears to be deleterious.
Disclosures: P. Rathore, None; S.J. Listwak, None; M. Herkenham, None.
Poster
250. Epilepsy: Networks