Abstracts

Experimentally induced epileptogenesis elicits profound changes in early response gene (ERG) expression in the mammalian brain. In these studies we analyzed early (0-6 hr), medium (1-7 da) and long term (2-8 wk) changes in the DNA-binding of transcription factors (TFs) AP1, AP2, Egr1, HIF-1, STAT1, NF-kB, NFIL-6, SP1 and TFIID to target DNA sequences in adult rat hippocampus after a single kainic acid (KA) injection. These TFs are enriched in the immediate promoters of the cFOS and cyclooxygenase-2 (COX-2) ERGs., To trigger epileptogenesis, male albino Wistar rats were injected i.p. with 10mg/kg KA using saline as a vehicle. At indicated time points (0, 1, 3, 6 hr; 1, 3, 7 da and 2, 4, 8 wk) rats were sacrificed and hippocampal and cortical cellular and nuclear proteins and total RNA were co-isolated from the same samples. TF-DNA binding was studied using gel shift and super-shift assay; RNA message levels were determined using DNA array analysis, RT-PCR and Northern blots. cFOS and COX-2 protein levels were quantified using Western immunochemistry., Of the TFs examined, AP1, HIF-1, NF-kB and STAT1 binding were found to display oscillatory DNA binding profiles over the short, medium and long term. AP1-DNA binding kinetics strongly correlated with COX-2 gene activation over the short term while NF-kB-DNA binding paralleled COX-2 gene expression at longer time points. Sustained increases in TFIID-DNA binding suggested prolonged [italic]de novo[/italic] induction of transcription from TATA-containing rat hippocampal genes., Taken together, these results suggest that induction of the pro-inflammatory and pro-apoptotic TFs AP1, HIF-1, NF-kB and STAT1, and their binding to specific target DNAs in ERG promoters, drives inflammatory and apoptotic gene expression in a phasic fashion. These data also support the notion of a global re-programming of hippocampal gene expression patterns long after a single KA-induced triggering of epileptogenic events., (Supported by NIH AG18031 and NIH NS23002.)