Novel odors affect gene expression for cytokines and proteinases in the rat amygdala and hippocampus.

Olfaction in rodents provides an excellent modality for the study of cellular mechanisms of information processing and storage, since a single occurrence of precisely timed stimuli has high survival value. We have followed up preliminary evidence of cytokine and proteinase involvement in normal (as opposed to pathologically-induced) brain plasticity by surveying for the presence of these factors in the olfactory circuitry of the rat. Genes for 25-30 common cytokines and their receptors, and over 30 cell matrix and adhesion molecules were found to be expressed across the olfactory bulb, insular cortex, amygdala, and dorsal hippocampus. We then measured by real-time PCR the transcriptional expression of seven of these genes following a one-time exposure to the novel odor of blueberry bars or cornnuts, in contrast to presentation of the familiar odor of lab chow. In the amygdala significant up-regulation of interleukin-1 receptor 1 (IL1r1), interleukin-4 receptor (IL4r), fibroblast growth factor 13 (FGF13), and cathepsin-H (CtsH) was observed in males in response to the odor of cornnuts only. Changes were less consistent and widespread in the hippocampus, but were again sex specific for three genes: cathepsin-L (CtsL), matrix metalloproteinase-14 (MMP-14) and MMP-16. Our results show that transcription for several specific cytokines, growth factors, and proteinases responds to a one-time exposure to a novel odor, in a manner that tends to be region- and sex-specific. This suggests considerable variation in the way that olfactory information is processed at the cellular level in different brain regions and by the two sexes.

Disialogangliosides and TNFα alter gene expression for cytokines and chemokines in primary brain cell cultures.

Gangliosides have long been implicated in multiple pathologies affecting the central nervous system. Empirical studies have suggested the possibility that gangliosides, particularly GD3, work in tandem with pro-inflammatory cytokines, especially tumor necrosis factor alpha (TNFα), to initiate or facilitate cell death in the CNS. As a step toward unraveling the metabolic pathways activated in the pathogenesis of brain cell death, we have surveyed gene expression for a host of cytokines and chemokines in primary brain cell cultures exposed to GD3, GD1b, and TNFα for 24 h. An initial screen of 98 genes on a focused mini-array revealed the expression of at least 28 genes related to cell growth, death, or inflammation in our system of mixed cells cultured from neonatal rat brains. Clear evidence of a differential response to the gangliosides or TNFα was seen in 12 genes. Quantitative PCR was used to validate the response of six of these genes. We found that both GD3 and GD1b, but not TNFα, up-regulated expression of macrophage inflammatory protein 3 (MIP3A) and interleukin-1 receptor 1 (IL1R1), but down-regulated fibroblast growth factor 13 (FGF13). The expression of FGF receptor activating protein 1 (FRAG1) and interleukin-3 receptor alpha (IL3RA) was down-regulated by GD3. Exposure to TNFα resulted in a dramatic up-regulation of IL3RA and chemokine ligand 2 (CCL2), both of which have been implicated in multiple sclerosis. Our results provide strong evidence that the expression of these genes might be critical links in the metabolic cascades leading to cell degeneration and death in the brain.

Sex and diet affect the behavioral response of rats to chronic mild stressors.

To investigate the interaction between sex, stressors, and dietary choice in rats, a preferred diet under the influence of chronic mild stressors was empirically determined to consist of soybeans and cookies in addition to lab chow. This preferred mixed diet was then tested for its influence on several behavioral tests at the end of prolonged exposure to the potential stressors. Rats of both sexes decreased their frequency of rearing but increased their attention to novelty in response to stressors. In the elevated plus maze, diet interacted with exposure to stressors to influence time spent in the open arm in females but not males. In the forced swim test, females but not males fed the mixed diet showed increased immobility, whether exposed to stressors or not. Finally, females but not males showed a differential effect of diet under stressors on the sucrose preference test, but this result was confounded by estrus cycling, demonstrating the importance of this factor in analyzing behavior in females. These results suggest that male and female rats differ in their susceptibility to the behavioral-modifying influences of stressors. And to the extent that diet serves as a coping mechanism, it does so differently in males and females.

Chronic mild stressors and diet affect gene expression differently in male and female rats.

While depression is reportedly more prevalent in women than men, a neurobiological basis for this difference has not been documented. Chronic mild stress (CMS) is a widely recognized animal model, which uses mild and unpredictable environmental stressors to induce depression. Studies of chronic stress, mainly in males, have reported an increase in the relative intake of "comfort food" as a means of counteracting the effects of stress. This study was designed to test the hypothesis that genes for certain neurotrophic factors, stress markers, and appetite regulators would be expressed differentially in male and female rats exposed to chronic, mild stressors with access to a preferred diet. Gene expression for neuropeptide Y was upregulated in females purely in response to stressors, whereas that for the epidermal growth factor receptor (EGFR) and arginine vasopressin (AVP) in males and fatty acid synthase (FASN) in females responded primarily to diet. Genes for brain-derived neurotrophic factor (BDNF), AVP, and the cocaine-amphetamine regulator of transcription (CART) in males, and leptin in females, showed a significant response to the interaction between stressors and diet. Every affected gene showed a different pattern of expression in males and females. This study confirms the intimate relationship between dietary intake and response to stress at the molecular level, and emphasizes the sex- and gene-specific nature of those interactions. Therefore, it supports a neurobiological basis for differences in the affective state response to stress in males and females.

Prenatal exposure to the acetylcholinesterase inhibitor methanesulfonyl fluoride alters forebrain morphology and gene expression.

Methanesulfonyl fluoride (MSF) is a CNS-selective acetylcholinesterase (AChE) inhibitor, currently being developed and tested for the treatment of symptoms of Alzheimer's disease. We have previously confirmed that a single in utero exposure to MSF at clinically appropriate doses inhibits AChE activity in fetal rat brain by 20%, and when administered throughout gestation, MSF achieves a 40% level of inhibition. Here, we show that rats chronically exposed in utero to MSF display marked sex-specific differences in morphological development of the cerebral cortical layers compared with controls at 7 days of age. Forebrain size and cortical thickness were increased in females and decreased in males. An analysis of gene expression in neonate brain on the day of birth revealed sex-specific differential expression of over 25 genes, including choline acetyltransferase (ChAT), which were affected by prenatal MSF exposure. Many of these genes are associated with sexual differentiation and brain development, while others are involved in more generalized cellular and metabolic processes. The changes observed in cortical morphology and gene expression suggest a critical developmental role for AChE in the fetal nervous system, most likely through its effect on cholinergic neurotransmission.

Gene expression following traumatic brain injury in humans: analysis by microarray.

Global changes in gene expression were analyzed in pericontusional tissue taken during surgery from 4 patients with traumatic brain injury (TBI), in cerebral infarction tissue from a patient with vasculitis and in normal brain tissue resected during craniotomy for meningioma. Of approximately 1,200 genes showing some level of expression by cDNA microarray hybridization, 104 ( approximately 8%) showed differential expression in traumatized tissue. Genes controlling transcriptional regulation, intermediary and energy metabolism, signal transduction, and intercellular adhesion and recognition were differentially affected most often. Four genes previously shown to be associated with TBI (c-Fos, Jun B, HSP70, and Zif/268) were all found to be up-regulated in at least one TBI patient. Thus, the robust response to TBI of several immediate early genes is confirmed, and a longer list of candidate genes from other functional categories is suggested for further studies aimed at understanding the molecular and cellular consequences of TBI.

Ganglioside patterns mature at different rates in functionally related subregions of the rat pons.

Gangliosides are known to be developmentally regulated and regionally variable, but these variations have not been shown to occur among precisely defined nuclei of the brain in relation to either aging or function. We have sought to correlate changes in ganglioside distribution with age-related changes in highly specific brain regions known to control a common function, the regulation of rapid eye movement sleep architecture. Gangliosides were extracted and quantified from micropunched regions of the locus coeruleus, dorsal raphe, laterodorsal tegmentum, pedunculopontine tegmentum and the general region of the pons containing these nuclei in young adult (3 months), adult (12 months), and aged (24 months) rats. The ganglioside distribution patterns were generally characteristic of the pons as a whole, but showed a high level of differentiation in time course at specific anatomical sites.