Transcription factor gene expression profiling after acute intermittent nicotine treatment in the rat cerebral cortex

Abstract

Several studies in different in vitro and in vivo models have demonstrated neuroprotective effects of nicotinic receptor agonists and indirect trophic actions of nicotine on brain are suggested from observations describing nicotine as a cognitive enhancer by increasing vigilance and improving learning and memory. While an increasing number of studies have given evidence of neuroprotective and neurotrophic effects of nicotine treatment, the molecular mechanism mediating the neurotrophic effects of nicotine are not fully understood. Previously in an analysis of several neurotrophic factors as possible mediators of nicotine-induced neuroprotection and/or neurotrophic effects we could reveal that an acute intermittent nicotine treatment increases fibroblast growth factor-2 mRNA and protein in several brain regions of rat brain. Even if other studies have demonstrated in different paradigms that nicotine administration modulates expression level of a variety of genes, there is still a lack of indication which candidate genes, involved in neuroprotective responses are modulated by nicotine. In the present work we have used a microarray assay to further find and characterize new genes responsive to acute intermittent nicotine treatment and linked to neuroprotection. Therefore, we used Rat Genome U34A Affymetrix GeneChip arrays containing about 8800 probe sets to characterize transcriptional responses in the rat parietal cortex after acute intermittent nicotine treatment. We focused our attention to expression of transcription factors and several of them were up- or down-regulated by nicotine, among these Nr4a1 (Nurr77), Egr-1 and Egr-2. In situ hybridization was used to corroborate the microarray data and to reveal further spatial and temporal patterns of these nicotine induced genes. Taken together the present results identified several novel candidate genes modified by acute intermittent nicotine exposure and as such potentially involved in neuroprotective-neurotrophic actions.