Psychophysiological stress-regulated gene expression in mice

Comparative Expression Analysis of Stress-Inducible Genes in Murine Immune Cells

Background: Psychological stress affects the immune system. Upon stress occurrence, glucocorticoid is released that binds to the glucocorticoid receptor and regulates gene expression. Thus, we aimed to examine the stress-induced immunomodulatory mechanisms by investigating the expression patterns of stress-inducible genes in murine immune cells. Methods: BALB/c, C57BL/6, glucocorticoid-receptor congenic mice, and corticotropin-releasing hormone (CRH)-deficient mice were exposed to synthetic glucocorticoid, dexamethasone, or placed under a restraint condition. The expression level of stress-related genes, such as Rtp801, Gilz, Mkp-1, Bnip3, and Trp53inp1 was measured in the immune cells in these mice. Results: Short restraint stress induced Rtp801 and Gilz expressions that were higher in the spleen of BALB/c mice than those in C57BL/6 mice. Mkp-1 expression increased equally in these two strains, despite the difference in the glucocorticoid level. These three genes induced by short restraint stress were not induced in the CRH-deficient mice. In contrast, Bnip3 and Trp53inp1 were only upregulated upon longer restraint events. In the thymus, Trp53inp1 expression was induced upon short restraint stress, whereas Gilz expression constantly increased upon short and repetitive restraint stresses. Conclusion: These results suggest that singular and repetitive bouts of stress lead to differential gene expression in mice and stress-induced gene expression in thymocytes is distinct from that observed in splenocytes. Gilz, Rtp801, and Mkp-1 genes induced by short restraint stress are dependent on CRH in the spleen.

The reduced bactericidal activity of neutrophils as an incisive indicator of water-immersion restraint stress and impaired exercise performance in mice

The incisive evaluation of psychological stress may be required to determine the exercise performance of stressed hosts. We investigated objective markers of psychological stress that reflect exercise performance, focusing on the neutrophil function. We used murine water-immersion restraint (WIR) stress for our assessments. After receiving WIR for 1 or 2 h, mice were exercised on an airtight treadmill that monitors their respiratory exchange ratio. The neutrophil function was analyzed after WIR stress. Although the control mice (without WIR) showed good combustion of both carbohydrates and lipids as energy sources during treadmill exercise, mice that underwent 2-h WIR did not combust carbohydrates or lipids effectively, drastically reducing their performance. In contrast, the 1-h WIR mice showed carbohydrate combustion (albeit a slow response) but did not use lipids for energy, thereby running longer than the 2-h WIR mice but shorter than the control mice. The bactericidal activity of neutrophils, but not their superoxide production or microsphere-phagocytic activity, was significantly reduced by 1-h WIR and further reduced by 2-h WIR, indicating a significant association between WIR stress and exercise performance. The neutrophil bactericidal activity may be a good indicator of psychological stress and a useful tool for precisely assessing exercise performance.

Dynamic glucocorticoid-dependent regulation of Sgk1 expression in oligodendrocytes of adult male rat brain by acute stress and time of day

Recent studies support plasticity in adult brain white matter structure and myelination in response to various experiential factors. One possible contributor to this plasticity may be activity-dependent modulation of serum- and glucocorticoid-inducible kinase 1 (Sgk1) expression in oligodendrocytes. We examined whether Sgk1 expression in adult rat brain white matter is increased by acute stress-induced elevations in endogenous corticosterone and whether it fluctuates with diurnal variations in corticosterone. We observed rapid increases (within 30 min) in Sgk1 mRNA in the corpus callosum in response to acute stress, as well as large increases at the beginning of the rat's active period (the time of peak corticosterone secretion). These increases were absent in adrenalectomized rats. Corticosterone treatment of adrenalectomized rats also rapidly increased corpus callosum Sgk1 mRNA. The majority of Sgk1 mRNA in corpus callosum was co-localized with myelin basic protein mRNA, suggesting that mature oligodendrocytes respond dynamically to acute stress and circadian rhythms. The regulation of Sgk1 expression by acute stress and time of day was selective for white matter, with limited alteration of Sgk1 expression by these factors in hippocampus and somatosensory cortex. These results indicate a unique sensitivity of oligodendrocyte Sgk1 expression to activity-dependent fluctuations in corticosterone hormone secretion, and raises the prospect that hypothalamic-pituitary-adrenal axis dysregulation or glucocorticoid pharmacotherapy may compromise the normal activity-dependent interactions between oligodendrocytes and neurons.

Hippocampal gene expression induced by cold swim stress depends on sex and handling

Stress-related disorders such as PTSD and depression are more prevalent in women than men. One reason for such discordance may be that brain regions involved in stress responses are more sensitive to stress in females. Here, we compared the effects of acute stress on gene transcription in the hippocampus of female and male mice, and also examined the involvement of two key stress-related hormones, corticosterone and corticotropin releasing hormone (Crh). Using quantitative reverse transcription polymerase chain reaction (RT-qPCR), we measured gene expression of Fos, Per1 and Sgk1 45 min after exposure to brief cold swim stress. Stress induced a stronger increase in Fos and Per1 expression in females than males. The handling control procedure increased Fos in both sexes, but occluded the effects of stress in males. Further, handling increased Per1 only in males. Sgk1 was insensitive to handling, and increased in response to stress similarly in males and females. The transcriptional changes observed after swim stress were not mimicked by corticosterone injections, and the stress-induced increase in Fos, Per1 and Sgk1 could neither be prevented by pharmacologically blocking glucocorticoid receptor (GR) nor by blocking Crh receptor 1 (Crhr1) before stress exposure. Finally, we demonstrate that the effects are stressor-specific, as the expression of target genes could not be increased by brief restraint stress in either sex. In summary, we find strong effects of acute swim stress on hippocampal gene expression, complex interactions between handling and sex, and a remarkably unique response pattern for each gene. Overall, females respond to a cold swim challenge with stronger hippocampal gene transcription than males, independent of two classic mediators of the stress response, corticosterone and Crh. These findings may have important implications for understanding the higher vulnerability of women to certain stress-related neuropsychiatric diseases.

Social overcrowding as a chronic stress model that increases adiposity in mice

Stress is a widely recognized risk factor for psychiatric and metabolic disorders. A number of animal models utilizing various stressors have been developed to facilitate our understanding in the pathophysiology of stress-related dysfunctions. The most commonly used chronic stress paradigms include the unpredictable chronic mild stress paradigm, the social defeat paradigm and the social deprivation paradigm. Here we assess the potential of social crowding as an alternative chronic stress model to study the effects on affective behaviors and metabolic disturbances. Ten-week-old male C57BL/6 mice were housed in groups of four (control) or eight (social crowding; SC) in standard cage for 9 weeks. Exploration, anxiety- and depressive-like behaviors were assessed in the open field test, the elevated T-maze, the novelty-suppressed feeding test and the forced swim test. SC mice exhibited a modest anxiety-like phenotype without change in depressive-like behaviors. Nine weeks of social crowding did not affect the body weight, but robustly increased adiposity as determined by increased mass of fat depots. Consistent with the increased fat content, serum leptin was markedly elevated in the SC mice. Specific changes in gene expression were also observed in the hypothalamus and the white adipose tissue following SC housing. Our study demonstrates the potential of social crowding as an alternative model for the study of stress-related metabolic and behavioral dysfunctions.

Astrocytes are a neural target of morphine action via glucocorticoid receptor-dependent signaling

Chronic opioid use leads to the structural reorganization of neuronal networks, involving genetic reprogramming in neurons and glial cells. Our previous in vivo studies have revealed that a significant fraction of the morphine-induced alterations to the striatal transcriptome included glucocorticoid (GC) receptor (GR)-dependent genes. Additional analyses suggested glial cells to be the locus of these changes. In the current study, we aimed to differentiate the direct transcriptional effects of morphine and a GR agonist on primary striatal neurons and astrocytes. Whole-genome transcriptional profiling revealed that while morphine had no significant effect on gene expression in both cell types, dexamethasone significantly altered the transcriptional profile in astrocytes but not neurons. We obtained a complete dataset of genes undergoing the regulation, which includes genes related to glucose metabolism (Pdk4), circadian activity (Per1) and cell differentiation (Sox2). There was also an overlap between morphine-induced transcripts in striatum and GR-dependent transcripts in cultured astrocytes. We further analyzed the regulation of expression of one gene belonging to both groups, serum and GC regulated kinase 1 (Sgk1). We identified two transcriptional variants of Sgk1 that displayed selective GR-dependent upregulation in cultured astrocytes but not neurons. Moreover, these variants were the only two that were found to be upregulated in vivo by morphine in a GR-dependent fashion. Our data suggest that the morphine-induced, GR-dependent component of transcriptome alterations in the striatum is confined to astrocytes. Identification of this mechanism opens new directions for research on the role of astrocytes in the central effects of opioids.

Selectivity, cocrystal structures, and neuroprotective properties of leucettines, a family of protein kinase inhibitors derived from the marine sponge alkaloid leucettamine B

DYRKs (dual specificity, tyrosine phosphorylation regulated kinases) and CLKs (cdc2-like kinases) are implicated in the onset and development of Alzheimer's disease and Down syndrome. The marine sponge alkaloid leucettamine B was recently identified as an inhibitor of DYRKs/CLKs. Synthesis of analogues (leucettines) led to an optimized product, leucettine L41. Leucettines were cocrystallized with DYRK1A, DYRK2, CLK3, PIM1, and GSK-3β. The selectivity of L41 was studied by activity and interaction assays of recombinant kinases and affinity chromatography and competition affinity assays. These approaches revealed unexpected potential secondary targets such as CK2, SLK, and the lipid kinase PIKfyve/Vac14/Fig4. L41 displayed neuroprotective effects on glutamate-induced HT22 cell death. L41 also reduced amyloid precursor protein-induced cell death in cultured rat brain slices. The unusual multitarget selectivity of leucettines may account for their neuroprotective effects. This family of kinase inhibitors deserves further optimization as potential therapeutics against neurodegenerative diseases such as Alzheimer's disease.

Mating alters gene expression patterns in Drosophila melanogaster male heads

Background

Behavior is a complex process resulting from the integration of genetic and environmental information. Drosophila melanogaster rely on multiple sensory modalities for reproductive success, and mating causes physiological changes in both sexes that affect reproductive output or behavior. Some of these effects are likely mediated by changes in gene expression. Courtship and mating alter female transcript profiles, but it is not known how mating affects male gene expression.

Results

We used Drosophila genome arrays to identify changes in gene expression profiles that occur in mated male heads. Forty-seven genes differed between mated and control heads 2 hrs post mating. Many mating-responsive genes are highly expressed in non-neural head tissues, including an adipose tissue called the fat body. One fat body-enriched gene, female-specific independent of transformer (fit), is a downstream target of the somatic sex-determination hierarchy, a genetic pathway that regulates Drosophila reproductive behaviors as well as expression of some fat-expressed genes; three other mating-responsive loci are also downstream components of this pathway. Another mating-responsive gene expressed in fat, Juvenile hormone esterase (Jhe), is necessary for robust male courtship behavior and mating success.

Conclusions

Our study demonstrates that mating causes changes in male head gene expression profiles and supports an increasing body of work implicating adipose signaling in behavior modulation. Since several mating-induced genes are sex-determination hierarchy target genes, additional mating-responsive loci may be downstream components of this pathway as well.

Corticotropin-releasing hormone stimulates SGK-1 kinase expression in cultured hippocampal neurons via CRH-R1

Corticotropin-releasing hormone (CRH) has been shown to exhibit various functions in hippocampus. In the present study, we examined the effect of CRH on the expression of serum/glucocorticoid-inducible protein kinase-1 (SGK-1), a novel protein kinase, in primary cultured hippocampal neurons. A dose-dependent increase in mRNA and protein levels of SGK-1 as well as frequency of SGK-1-positive neurons occurred upon exposure to CRH (1 pmol/l to 10 nmol/l). These effects can be reversed by the specific CRH-R1 antagonist antalarmin but not by the CRH-R2 antagonist astressin 2B. Blocking adenylate cyclase (AC) activity with SQ22536 and PKA with H89 completely prevented CRH-induced mRNA and protein expression of SGK-1. Blockage of PLC or PKC did not block CRH-induced SGK-1 expression. Our results suggest that CRH act on CRH-R1 to stimulate SGK-1 mRNA and protein expression in cultured hippocampal neurons via a mechanism that is involved in AC/PKA signaling pathways.

Beacon-like/ubiquitin-5-like immunoreactivity is highly expressed in human hypothalamus and increased in haloperidol-treated schizophrenics and a rat model of schizophrenia

The beacon gene is involved in the regulation of energy metabolism, food intake, and obesity. We localized its gene product, beacon-/ubiquitin 5-like immunoreactivity in brains of normal-weight, non-psychotic individuals, adipose (BMI over 32), non-psychotic individuals, and haloperidol-treated schizophrenics. The protein was found to be highly expressed in many neurons of the paraventricular and supraoptic hypothalamic nuclei. Besides, it was detected in neurons of other hypothalamic areas (suprachiasmatic, arcuate, and ventromedial nuclei) as well as outside the hypothalamus (Nuc. basalis Meynert, thalamus, hippocampus, and some neocortical areas). A morphometric analysis of beacon-immunoreactive hypothalamic and neocortical neurons revealed that compared to normal-weight controls in haloperidol-treated schizophrenics, there was a significant increase of protein-expressing supraoptic, paraventricular, and orbitofrontal neurons. However, a significant increase in beacon-expressing supraoptic neurons was also seen in adipose, non-psychotic individuals in comparison with normal-weight controls. Haloperidol at different doses has no effect on beacon expression in SHSY5Y neuroblastoma cells, which makes the assumption unlikely that haloperidol per se is responsible for the increased neuronal expression of the peptide in schizophrenics. In rats with a neonatal lesion of the ventral hippocampus (a widely used animal model of schizophrenia), we found an increased neuronal expression of beacon in the paraventricular and supraoptic nuclei. We suppose that elevated hypothalamic expression of beacon-like protein in non-obese schizophrenics is not primarily related to metabolic alterations, but to a certain role in schizophrenia, which is possibly unrelated to aspects of weight gain and obesity. The latter assumption finds some support by data obtained in rats with ventral hippocampus lesion.

Phenomic, convergent functional genomic, and biomarker studies in a stress-reactive genetic animal model of bipolar disorder and co-morbid alcoholism

We had previously identified the clock gene D-box binding protein (Dbp) as a potential candidate gene for bipolar disorder and for alcoholism, using a Convergent Functional Genomics (CFG) approach. Here we report that mice with a homozygous deletion of DBP have lower locomotor activity, blunted responses to stimulants, and gain less weight over time. In response to a chronic stress paradigm, these mice exhibit a diametric switch in these phenotypes. DBP knockout mice are also activated by sleep deprivation, similar to bipolar patients, and that activation is prevented by treatment with the mood stabilizer drug valproate. Moreover, these mice show increased alcohol intake following exposure to stress. Microarray studies of brain and blood reveal a pattern of gene expression changes that may explain the observed phenotypes. CFG analysis of the gene expression changes identified a series of novel candidate genes and blood biomarkers for bipolar disorder, alcoholism, and stress reactivity.

Toki-to protects dopaminergic neurons in the substantia nigra from neurotoxicity of MPTP in mice

Parkinson's disease (PD) is a neurodegenerative disease of the brain characterized by the progressive loss of dopaminergic neurons in the substantia nigra (SN). No clinically proven drugs that may halt or retard the progression of PD have been reported. This study examined the anti-PD effect of a traditional Japanese/Chinese herbal remedy Toki-to (TKT) using mice treated with a neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydroxypyridine (MPTP). TKT showed improvement of MPTP-induced PD-like symptoms (bradykinesia) in a behavioral test (pole test). Histological studies of SNs from these mice demonstrated that TKT had a protective effect on dopaminergic neurons against MPTP neurotoxicity. Real-time RT-PCR analyses of mRNA from SNs demonstrated that expression of tyrosine hydroxylase (TH) and dopamine transporter (DAT) genes were decreased by MPTP treatment and that these decreases were reversed by TKT administration prior to MPTP treatment. DNA microarray analyses indicated that TKT per se suppressed gene expression of serum- and glucocorticoid regulated kinase (SGK) that is believed to be a molecule that drives the pathogenesis of PD. Hence, it is suggested that TKT may inhibit the activation of SGK at the transcriptional level and thusmay participate in halting the progression of MPTP-induced neurotoxicity.

Involvement of ribonucleotide reductase M1 subunit overexpression in gemcitabine resistance of human pancreatic cancer

Pancreatic cancer is the most lethal of all solid tumors partially because of its chemoresistance. Although gemcitabine is widely used as a first selected agent for the treatment of this disease despite low response rate, molecular mechanisms of gemcitabine resistance in pancreatic cancer still remain obscure. The aim of this study is to elucidate the mechanisms of gemcitabine resistance. The 81-fold gemcitabine resistant variant MiaPaCa2-RG was selected from pancreatic cancer cell line MiaPaCa2. By microarray analysis between MiaPaCa2 and MiaPaCa2-RG, 43 genes (0.04%) were altered expression of more than 2-fold. The most upregulated gene in MiaPaCa2-RG was ribonucleotide reductase M1 subunit (RRM1) with 4.5-fold up-regulation. Transfection with RRM1-specific RNAi suppressed more than 90% of RRM1 mRNA and protein expression. After RRM1-specific RNAi transfection, gemcitabine chemoresistance of MiaPaCa2-RG was reduced to the same level of MiaPaCa2. The 18 recurrent pancreatic cancer patients treated by gemcitabine were divided into 2 groups by RRM1 levels. There was a significant association between gemcitabine response and RRM1 expression (p = 0.018). Patients with high RRM1 levels had poor survival after gemcitabine treatment than those with low RRM1 levels (p = 0.016). RRM1 should be a key molecule in gemcitabine resistance in human pancreatic cancer through both in vitro and clinical models. RRM1 may have the potential as predictor and modulator of gemcitabine treatment.

Region-specific transcriptional changes following the three antidepressant treatments electro convulsive therapy, sleep deprivation and fluoxetine

The significant proportion of depressed patients that are resistant to monoaminergic drug therapy and the slow onset of therapeutic effects of the selective serotonin reuptake inhibitors (SSRIs)/serotonin/noradrenaline reuptake inhibitors (SNRIs) are two major reasons for the sustained search for new antidepressants. In an attempt to identify common underlying mechanisms for fast- and slow-acting antidepressant modalities, we have examined the transcriptional changes in seven different brain regions of the rat brain induced by three clinically effective antidepressant treatments: electro convulsive therapy (ECT), sleep deprivation (SD), and fluoxetine (FLX), the most commonly used slow-onset antidepressant. Each of these antidepressant treatments was applied with the same regimen known to have clinical efficacy: 2 days of ECT (four sessions per day), 24 h of SD, and 14 days of daily treatment of FLX, respectively. Transcriptional changes were evaluated on RNA extracted from seven different brain regions using the Affymetrix rat genome microarray 230 2.0. The gene chip data were validated using in situ hybridization or autoradiography for selected genes. The major findings of the study are: 1. The transcriptional changes induced by SD, ECT and SSRI display a regionally specific distribution distinct to each treatment. 2. The fast-onset, short-lived antidepressant treatments ECT and SD evoked transcriptional changes primarily in the catecholaminergic system, whereas the slow-onset antidepressant FLX treatment evoked transcriptional changes in the serotonergic system. 3. ECT and SD affect in a similar manner the same brain regions, primarily the locus coeruleus, whereas the effects of FLX were primarily in the dorsal raphe and hypothalamus, suggesting that both different regions and pathways account for fast onset but short lasting effects as compared to slow-onset but long-lasting effects. However, the similarity between effects of ECT and SD is somewhat confounded by the fact that the two treatments appear to regulate a number of transcripts in an opposite manner. 4. Multiple transcripts (e.g. brain-derived neurotrophic factor (BDNF), serum/glucocorticoid-regulated kinase (Sgk1)), whose level was reported to be affected by antidepressants or behavioral manipulations, were also found to be regulated by the treatments used in the present study. Several novel findings of transcriptional regulation upon one, two or all three treatments were made, for the latter we highlight homer, erg2, HSP27, the proto oncogene ret, sulfotransferase family 1A (Sult1a1), glycerol 3-phosphate dehydrogenase (GPD3), the orphan receptor G protein-coupled receptor 88 (GPR88) and a large number of expressed sequence tags (ESTs). 5. Transcripts encoding proteins involved in synaptic plasticity in the hippocampus were strongly affected by ECT and SD, but not by FLX. The novel transcripts, concomitantly regulated by several antidepressant treatments, may represent novel targets for fast onset, long-duration antidepressants.

Effect of brief corticosterone administration on SGK1 and RGS4 mRNA expression in rat hippocampus

Acute stress and corticosterone enhance 5-HT1A receptor-mediated responses in rat hippocampal CA1 cells within 1-2 h, through a process involving transcriptional regulation of unknown genes. Earlier studies showed that regulation of the 5-HT1A receptor gene cannot explain the functional effects. We here tested the hypothesis that corticosterone targets genes encoding RGS4 or SGK1, which can both affect the 5-HT1A receptor associated Kir channel, thus affecting 5-HT1A receptor function. To this end, the effect of a single corticosterone injection on hippocampal expression of RGS4 and SGK1 mRNAs, measured by in situ hybridization, was studied. Expression of RGS4 or SGK1 mRNA was not affected by the corticosterone injection, neither in the CA1 area nor in other hippocampal subregions. Strikingly, SGK1 mRNA expression was strongly up-regulated in the corpus callosum. We reject, however, the hypothesis that the effect of corticosterone on 5-HT1A responsiveness is mediated via altered RGS4 or SGK1 mRNA expression.

Sgk kinases and their role in epithelial transport

The serum/glucocorticoid-induced kinase Sgk1 plays an important role in the regulation of epithelial ion transport. This kinase is very rapidly regulated at the transcriptional level as well as via posttranslational modifications involving phosphorylation by the MAP or PI-3 kinase pathways and/or ubiquitylation. Although Sgk1 is a cell survival kinase, its primary role likely concerns the regulation of epithelial ion transport, as suggested by the phenotype of Sgk1-null mice, which display a defect in Na( homeostasis owing to disturbed renal tubular Na+ handling. In this review we first discuss the molecular, cellular, and regulatory aspects of Sgk1 and its paralogs. We then discuss its roles in the physiology and pathophysiology of epithelial ion transport.

No effect of prolonged corticosterone over-exposure on NCAM, SGK1, and RGS4 mRNA expression in rat hippocampus

Prolonged over-exposure of rats to corticosterone attenuates 5-HT(1A)-receptor-mediated responses in hippocampal CA1 cells through an unknown mechanism, not involving downregulation of 5-HT(1A) receptor expression. We here tested if corticosterone changes 5-HT(1A) receptor function indirectly, by altering hippocampal mRNA expression of NCAM, SGK1, or RGS4, which all modulate 5-HT(1A) receptor function. We found that the expression of none of these candidates was affected by corticosterone treatment.

Induction of hypothalamic serum- and glucocorticoid-induced protein kinase-1 gene expression and its relation to plasma des-acyl ghrelin in energy homeostasis in mice

Serum- and glucocorticoid-induced protein kinase (SGK) is a serine/threonine-specific protein kinase that is transcriptionally regulated by serum, glucocorticoids, and mineral corticoids. Here, we report that fasting or obesity with hyperphagia increased hypothalamic SGK-1 gene expression. Hypothalamic SGK-1 mRNA levels were proportional to daily food intake and body weights in C57BL6J mice, KK mice, and KKA(y) mice matched for age. Plasma des-acyl ghrelin, but not active ghrelin, levels were inversely proportional to daily food intake and body weights among these animals. The increases in hypothalamic SGK-1 gene expression in these animals were not accompanied by increases in plasma corticosterone levels. Under conditions of increased energy usage such as fasting, hypothalamic SGK-1 gene expression and plasma des-acyl ghrelin levels were positively correlated while during conditions of increased energy storage, they were negatively correlated. These results suggest that hypothalamic SGK-1 gene is a novel candidate gene involving in energy homeostasis in mice.