Rats chirp with their mouth full: During an experimental meal, adult male Wistar rats emitted flat ultrasonic vocalisations upon feeding

Rats produce ultrasonic vocalisation (USVs) that are classified into different types, based on their average frequency. In pups 40 kHz USVs are produced upon social isolation, and in adults USVs can be associated with affective states and specific behavioural patterns (i.e., appetitive 50 kHz vocalisations of frequency range 30-100 kHz, or aversive 20 kHz vocalisations of frequency range 18-30 kHz). Generally, USVs of frequency around 50 kHz are linked to activation of brain reward pathways, during anticipation or experience of rewarding stimuli. Previous studies have described several subtypes of 50 kHz USVs, according to their acoustic properties. We asked whether USV production might be relevant to feeding behaviour. We recorded USVs from 14-week old adult rats during the satisfaction of a physiological need: refeeding following mild food deprivation (17 h overnight fast). We analysed a 10 min consummatory phase, preceded by a 10 min anticipatory phase, as a control for the experimental meal. Following identification of USV subtypes, we applied frequentist and Bayesian (Monte Carlo shuffling) statistical analyses to investigate the relationship between USV emission and rat behaviour. We found that it was not total USV quantity that varied in response to food consumption, but the subtype of USV produced. Most importantly we found that rats who feed tend to produce flat USVs of a frequency around 40 kHz. Beyond the previous reports of circumstantial association feeding-flat USVs, our observation directly correlate vocalisation and ingestive behaviour. Our study highlights that, in addition to quantification of the production rate, study of USV subtypes might inform us further on rat consummatory behaviour. Since this vocalisation behaviour can have a communicative purpose, those findings also illustrate nutrition studies might benefit from considering the possible social dimension of feeding behaviour.

Stage 1 Registered Report: Refinement of tickling protocols to improve positive animal welfare in laboratory rats

Rat tickling is a heterospecific interaction for experimenters to mimic the interactions of rat play, where they produce 50 kHz ultrasonic vocalisations (USV), symptoms of positive affect; tickling can improve laboratory rat welfare. The standard rat tickling protocol involves gently pinning the rat in a supine position. However, individual response to this protocol varies. This suggests there is a risk that some rats may perceive tickling as only a neutral experience, while others as a positive one, depending on how tickling is performed. Based on our research experiences of the standard tickling protocol we have developed a playful handling (PH) protocol, with reduced emphasis on pinning, intended to mimic more closely the dynamic nature of play. We will test whether our PH protocol gives rise to more uniform increases in positive affect across individuals relative to protocols involving pinning. We will compare the response of juvenile male and female Wistar rats as: Control (hand remains still against the side of the test arena), P0 (PH with no pinning), P1 (PH with one pin), P4 (PH with four pins). P1 and P4 consist of a background of PH, with treatments involving administration of an increasing dosage of pinning per PH session. We hypothesise that rats exposed to handling protocols that maximise playful interactions (where pinning number per session decreases) will show an overall increase in total 50 kHz USV as an indicator of positive affect, with less variability. We will explore whether behavioural and physiological changes associated with alterations in PH experience are less variable. We propose that maximising the numbers of rats experiencing tickling as a positive experience will reduce the variation in response variables affected by tickling and increase the repeatability of research where tickling is applied either as a social enrichment or as a treatment.

SEX-DEPENDENT IMPACT OF MICROBIOTA STATUS ON CEREBRAL μ -OPIOID RECEPTOR DENSITY IN FISCHER RATS

μ‐opioid receptors (MOPr) play a critical role in social play, reward and pain, in a sex‐ and age‐dependent manner. There is evidence to suggest that sex and age differences in brain MOPr density may be responsible for this variability; however, little is known about the factors driving these differences in cerebral MOPr density. Emerging evidence highlights gut microbiota's critical influence and its bidirectional interaction with the brain on neurodevelopment. Therefore, we aimed to determine the impact of gut microbiota on MOPr density in male and female brains at different developmental stages. Quantitative [³H]DAMGO autoradiographic binding was carried out in the forebrain of male and female conventional (CON) and germ‐free (GF) rats at postnatal days (PND) 8, 22 and 116–150. Significant ‘microbiota status X sex’, ‘age X brain region’ interactions and microbiota status‐ and age‐dependent effects on MOPr binding were uncovered. Microbiota status influenced MOPr levels in males but not females, with higher MOPr levels observed in GF versus CON rats overall regions and age groups. In contrast, no overall sex differences were observed in GF or CON rats. Interestingly, within‐age planned comparison analysis conducted in frontal cortical and brain regions associated with reward revealed that this microbiota effect was restricted only to PND22 rats. Thus, this pilot study uncovers the critical sex‐dependent role of gut microbiota in regulating cerebral MOPr density, which is restricted to the sensitive developmental period of weaning. This may have implications in understanding the importance of microbiota during early development on opioid signalling and associated behaviours.

Targeted Suppression of Lipoprotein Receptor LSR in Astrocytes Leads to Olfactory and Memory Deficits in Mice

Perturbations of cholesterol metabolism have been linked to neurodegenerative diseases. Glia–neuron crosstalk is essential to achieve a tight regulation of brain cholesterol trafficking. Adequate cholesterol supply from glia via apolipoprotein E-containing lipoproteins ensures neuronal development and function. The lipolysis-stimulated lipoprotein receptor (LSR), plays an important role in brain cholesterol homeostasis. Aged heterozygote Lsr+/− mice show altered brain cholesterol distribution and increased susceptibility to amyloid stress. Since LSR expression is higher in astroglia as compared to neurons, we sought to determine if astroglial LSR deficiency could lead to cognitive defects similar to those of Alzheimer’s disease (AD). Cre recombinase was activated in adult Glast-CreERT/lsrfl/fl mice by tamoxifen to induce astroglial Lsr deletion. Behavioral phenotyping of young and old astroglial Lsr KO animals revealed hyperactivity during the nocturnal period, deficits in olfactory function affecting social memory and causing possible apathy, as well as visual memory and short-term working memory problems, and deficits similar to those reported in neurodegenerative diseases, such as AD. Furthermore, GFAP staining revealed astroglial activation in the olfactory bulb. Therefore, astroglial LSR is important for working, spatial, and social memory related to sensory input, and represents a novel pathway for the study of brain aging and neurodegeneration.

Diet Protein Content and Individual Phenotype Affect Food Intake and Protein Appetence in Rats

BACKGROUND

A low-protein diet can induce compensatory intake of excess energy. This must be better evaluated to anticipate the obesogenic risk that may result from the dietary recommendations for reducing animal protein consumption.

OBJECTIVES

We aimed to further characterize the behavioral and physiological responses to a reduction in dietary protein and to identify the determinants of protein appetite.

METHODS

Thirty-two male Wistar rats [4 wk old, (mean ± SEM) 135 ± 32 g body weight] were fed a low-protein (LP; 6% energy value) or normal-protein (NP; 20%) diet for 8 wk. Food intake and body mass were measured during the entire intervention. During self-selection sessions after 4 wk of experimental diets, we evaluated rat food preference between LP, NP, or high-protein (HP; 55%) pellets. At the end of the experiment, we assessed their hedonic response [ultrasonic vocalizations (USVs)] and c-Fos neuronal activation in the olfactory tubercle and nucleus accumbens (NAcc) associated with an LP or HP meal.

RESULTS

Rats fed an LP diet had greater food intake (24%), body weight (5%), and visceral adiposity (30%) than NP rats. All LP rats and half of the NP rats showed a nearly exclusive preference for HP pellets during self-selection sessions, whereas the other half of the NP rats showed no preference. This suggests that the appetite for proteins is driven not only by a low protein status but also by individual traits in NP rats. LP or HP meal induced similar USV emission and similar neuronal activation in the NAcc in feed-deprived LP and NP rats, showing no specific response linked to protein appetite.

CONCLUSIONS

Protein appetite in rats is driven by low protein status or individual preferences in rats receiving adequate protein amounts. This must be considered and further analyzed, in the context of current recommendations for protein intake reduction.

Region-specific sex modulation of central oxytocin receptor by gut microbiota: An ontogenic study

Oxytocin (OT) is a developmentally important neuropeptide recognized to play a dominant role in social functioning and stress-related behaviors, in a sex-dependent manner. Nonetheless, the underlining factors driving OT and OT receptor (OTR) early brain development remain unclear. Recent evidence highlight the critical influence of gut microbiota and its bidirectional interaction with the brain on neurodevelopment via the gut microbiota-brain axis. Therefore, we aimed to determine the impact of gut microbiota on the OTR system of the rat brain at different developmental stages in a pilot study. Quantitative OTR [¹²⁵ I]-OVTA autoradiographic binding was carried out in the forebrain of male and female conventional (CON) and germ-free (GF) rats at postnatal days (PND) 8, 22, and 116-150. OTR binding was also assessed in the eyes of PND 1 and PND 4 GF female rats. Significant "microbiota × sex × region" interaction and age-dependent effects on OTR binding were demonstrated. Microbiota status influenced OTR levels in males but not females with higher levels of OTR observed in GF versus CON rats in the cingulate, prelimbic, and lateral/medial/ventral orbital cortex, and septum across all age groups, while sex differences were observed in GF, but not in CON rats. Interestingly, OTRs present in the eyes of CON rats were abolished in GF rats. This is the first study to uncover a sex-specific role of gut microbiota on the central OTR system, which may have implications in understanding the developmental neuroadaptations critical for behavioral regulation and the etiology of certain neurodevelopmental disorders.

Effect of environmental exposure to a maternally-learned odorant on anxiety-like behaviors at weaning in mice

Early sensory experience, such as exposure to maternal or other environmental factors, is considered to influence neurocognitive development and behaviors. In many species, exposure to odorants during pregnancy or lactation impacts the morpho-functional development of the olfactory circuitry with changes in olfactory sensitivity, feeding behavior and food preferences at birth or later. However, few studies have investigated the impact of a perinatal exposure to odorants on the anxiety-like behavior of animals to stressfull stimuli. Here, we exposed mice to heptaldehyde (HEP) during pregnancy and lactation and measured the anxiety-like behavior of their offspring to stress-inducing novel stimuli at weaning in presence or absence of odorants. We applied a combined social and maternal separation as a stressor and measured the anxiety-like behavior in an open field (OF) in presence of two odorants, HEP or α-pinene (AP) as a control odorant. Although the presence of the odorant during the social separation did not influence anxiety-like behavior, we found that, if mice born to non-odorized mothers exhibited a decreased exploratory behavior in the presence of both odorants, the effect was restricted to AP for the mice perinatally exposed to HEP. These results show that anxiety-like behaviors during a stress-inducing event could be reduced by the presence of a familiar odorant. We propose that the recall of an early olfactory experience could contribute to the improvement of animal welfare in various situations associated with husbandry practices.

The olfactory mucosa, first actor of olfactory detection, is sensitive to glucocorticoid hormone

The olfactory mucosa (OM) is the primary site of odorant detection, and its axonal projections relay information to brain structures for signal processing. We have previously observed that olfactory function can be affected during a prolonged stress challenge in Wistar rats. The stress response is a neuroendocrine retro-controlled loop allowing pleiotropic adaptive tissue alterations, which are partly mediated through the release of glucocorticoid hormones. We hypothesised that, as part of their wide-ranging pleiotropic effects, glucocorticoids might affect the first step of olfactory detection. To study this, we used a number of approaches ranging from the molecular detection and functional characterisation of glucocorticoid receptors (GRs) in OM cells, to the study of GR acute activation in vivo at the molecular, electrophysiological and behavioural levels. In contrast to previous reports, where GR was reported to be exclusive in olfactory sensory neurones, we located functional GR expression mostly in olfactory ensheathing cells. Dexamethasone (2 mg/kg) was injected intraperitoneally to activate GR in vivo, and this led to functional odorant electrophysiological response (electro-olfactogram) and OM gene expression changes. In a habituation/cross-habituation test of olfactory sensitivity, we observed that DEX-treated rats exhibited higher responsiveness to a complex odorant mixture. These findings support the idea that olfactory perception is altered in stressed animals, as glucocorticoids might enhance odour detection, starting at the first step of detection.

Daily oscillation of odorant detection in rat olfactory epithelium

Most of biological variables follow a daily rhythm. It holds true as well for sensory capacities as two decades of research have demonstrated that the odorant induced activity in the olfactory bulbs oscillates during the day. Olfactory bulbs are the first central nervous system structures, which receive inputs from the olfactory neurons located in the nose olfactory epithelium in vertebrates. So far, data on variation in odorant detection in the olfactory epithelium throughout the day are missing. Using electroolfactogram recordings in rats housed under daily light and dark cycles, we found that the olfactory epithelium responsiveness varies during the day with a maximum in the beginning of the light phase. This fluctuation was consistent with cycling of transduction pathway gene expression in the olfactory epithelium examined by qPCR. It was also consistent with the levels of two transduction pathway proteins (olfactory-type G protein and adenylyl cyclase III) examined by western blot. Daily variations were also observed at the level of olfactory sensory neurons responses recorded by patch-clamp. To rule out a potential effect of the feeding status of the animal, we examined the variation in odorant response in starved animals during the day. We observed a similar pattern to ad libidum fed animals. Taken together, our results reveal that the olfactory epithelium sensitivity varies during the day in part due to modulation of the very first step of odorant detection.

Fetal brain 11β-hydroxysteroid dehydrogenase type 2 selectively determines programming of adult depressive-like behaviors and cognitive function, but not anxiety behaviors in male mice

Stress or elevated glucocorticoids during sensitive windows of fetal development increase the risk of neuropsychiatric disorders in adult rodents and humans, a phenomenon known as glucocorticoid programming. 11β-Hydroxysteroid dehydrogenase type 2 (11β-HSD2), which catalyses rapid inactivation of glucocorticoids in the placenta, controls access of maternal glucocorticoids to the fetal compartment, placing it in a key position to modulate glucocorticoid programming of behavior. However, the importance of the high expression of 11β-HSD2 within the midgestational fetal brain is unknown. To examine this, a brain-specific knockout of 11β-HSD2 (HSD2BKO) was generated and compared to wild-type littermates. HSD2BKO have markedly diminished fetal brain 11β-HSD2, but intact fetal body and placental 11β-HSD2 and normal fetal and placental growth. Despite normal fetal plasma corticosterone, HSD2BKO exhibit elevated fetal brain corticosterone levels at midgestation. As adults, HSD2BKO show depressive-like behavior and have cognitive impairments. However, unlike complete feto-placental deficiency, HSD2BKO show no anxiety-like behavioral deficits. The clear mechanistic separation of the programmed components of depression and cognition from anxiety implies distinct mechanisms of pathogenesis, affording potential opportunities for stratified interventions.

Behavioral responses to odors from other species: introducing a complementary model of allelochemics involving vertebrates

It has long been known that the behavior of an animal can be affected by odors from another species. Such interspecific effects of odorous compounds (allelochemics) are usually characterized according to who benefits (emitter, receiver, or both) and the odors categorized accordingly (allomones, kairomones, and synomones, respectively), which has its origin in the definition of pheromones, i.e., intraspecific communication via volatile compounds. When considering vertebrates, however, interspecific odor-based effects exist which do not fit well in this paradigm. Three aspects in particular do not encompass all interspecific semiochemical effects: one relates to the innateness of the behavioral response, another to the origin of the odor, and the third to the intent of the message. In this review we focus on vertebrates, and present examples of behavioral responses of animals to odors from other species with specific reference to these three aspects. Searching for a more useful classification of allelochemical effects we examine the relationship between the valence of odors (attractive through to aversive), and the relative contributions of learned and unconditioned (innate) behavioral responses to odors from other species. We propose that these two factors (odor valence and learning) may offer an alternative way to describe the nature of interspecific olfactory effects involving vertebrates compared to the current focus on who benefits.

Chronic variable stress exposure in male Wistar rats affects the first step of olfactory detection

For most animal species, olfaction plays a paramount role in their perception of the environment. Odours are initially detected in neurons located in the olfactory mucosa. This tissue is regulated by several physiological signals and can be altered in pathology. A number of clinical studies suggest an association between depressive disorders and olfactory sensory loss. In rodents, depressive-like states can be observed in models of chronic stress. We tested the hypothesis that olfactory function might be altered in a rat model of depression, induced by chronic variable stress (CVS). While CVS rats exhibited several symptoms consistent with chronic stress exposure and depressive-like states (increased sucrose intake in sucrose preference test, increased immobility in forced swim test, hyperlocomotion), their odorant responses recorded at the olfactory mucosa level by electro-olfactogram were decreased. In addition we observed increased apoptosis markers in the olfactory mucosa using Western Blot. Our data are consistent with reduced olfactory capacities in a laboratory rat model of chronic stress and depression, in agreement with human clinical data; this warrants further mechanistic studies. Furthermore, this works raises the possibility that altered olfactory function might be a confounding factor in the behavioural testing of chronically stressed or depressed rats.

Prevention of 5-hydroxytryptamine2C receptor RNA editing and alternate splicing in C57BL/6 mice activates the hypothalamic-pituitary-adrenal axis and alters mood

The 5-hydroxytryptamine2C (5-HT)2C receptor is widely implicated in the aetiology of affective and eating disorders as well as regulation of the hypothalamo-pituitary-adrenal axis. Signalling through this receptor is regulated by A-to-I RNA editing, affecting three amino acids in the protein sequence, with unedited transcripts encoding a receptor (INI) that, in vitro, is hyperactive compared with edited isoforms. Targeted alteration (knock-in) of the Htr2c gene to generate 'INI' mice with no alternate splicing, solely expressing the full-length unedited isoform, did not produce an overt metabolic phenotype or altered anxiety behaviour, but did display reduced depressive-like and fear-associated behaviours. INI mice exhibited a hyperactive hypothalamo-pituitary-adrenal axis, with increased nadir plasma corticosterone and corticotrophin-releasing hormone expression in the hypothalamus but responded normally to chronic stress and showed normal circadian activity and activity in a novel environment. The circadian patterns of 5-HT2C receptor mRNA and mbii52, a snoRNA known to regulate RNA editing and RNA splicing of 5-HT2C receptor pre-mRNA, were altered in INI mice compared with wild-type control mice. Moreover, levels of 5-HT1A receptor mRNA were increased in the hippocampus of INI mice. These gene expression changes may underpin the neuroendocrine and behavioural changes observed in INI mice. However, the phenotype of INI mice was not consistent with a globally hyperactive INI receptor encoded by the unedited transcript in the absence of alternate splicing. Hence, the in vivo outcome of RNA editing may be neuronal cell type specific.

IUPHAR-DB: updated database content and new features

The International Union of Basic and Clinical Pharmacology (IUPHAR) database, IUPHAR-DB (http://www.iuphar-db.org) is an open access, online database providing detailed, expert-driven annotation of the primary literature on human and rodent receptors and other drug targets, together with the substances that act on them. The present release includes information on the products of 646 genes from four major protein classes (G protein-coupled receptors, nuclear hormone receptors, voltage- and ligand-gated ion channels) and ∼3180 bioactive molecules (endogenous ligands, licensed drugs and key pharmacological tools) that interact with them. We have described previously the classification and curation of data for small molecule ligands in the database; in this update we have annotated 366 endogenous peptide ligands with their amino acid sequences, post-translational modifications, links to precursor genes, species differences and relationships with other molecules in the database (e.g. those derived from the same precursor). We have also matched targets with their endogenous ligands (peptides and small molecules), with particular attention paid to identifying bioactive peptide ligands generated by post-translational modification of precursor proteins. Other improvements to the database include enhanced information on the clinical relevance of targets and ligands in the database, more extensive links to other databases and a pilot project for the curation of enzymes as drug targets.

A Role for the orphan nuclear receptor estrogen-related receptor alpha in endometrial stromal cell decidualization and expression of genes implicated in energy metabolism

CONTEXT

Differentiation (decidualization) of endometrial stromal cells (ESC) is an essential prerequisite for successful implantation and establishment of pregnancy.

OBJECTIVE

The aim was to determine whether the orphan nuclear receptor estrogen-related receptor α (ERRα, NR3B1), and its target genes, medium chain specific acyl-CoA dehydrogenase (MCAD, ACADM), pyruvate dehydrogenase kinase 4 (PDK4), and phosphoenolpyruvate carboxykinase 2 (PEPCK, PCK2), play a role in the decidualization process.

SETTING

We conducted the study at a University Research Institute.

PATIENTS AND METHODS

Endometrial tissues were collected from women with regular menstrual cycles; tissues were used for recovery of primary ESC or RNA extraction or were fixed for immunohistochemistry. Primary ESC were decidualized in vitro; some cells were treated with XCT790 (ERRα inverse agonist).

RESULTS

Decidualization of ESC in vitro was associated with a significant increase in expression of transcripts encoding ERRα and its coactivator peroxisome proliferator-activated receptor γ coactivator-1 α. Expression of ERRα target genes was altered with increased expression of MCAD and PDK4 and reduced expression of PEPCK. Incubation of decidualized ESC with XCT790 reduced expression of ERRα and markers of decidualization such as IGFBP-1.

CONCLUSION

Increased expression of ERRα may play a role in altering the bioenergetics of decidualized ESC in preparation for implantation of the embryo and successful establishment of early pregnancy.

Modulation of ER alpha transcriptional activity by the orphan nuclear receptor ERR beta and evidence for differential effects of long- and short-form splice variants

Oestrogen receptor related proteins (ERRs) affect target gene expression without binding oestradiol. We investigated the functional activity of two splice variant isoforms of ERR beta (ERR beta S [short], ERR beta L [long]) expressed in human endometrium, where they are coexpressed with the oestrogen receptor alpha (ER alpha). Over-expression of ERRbetaL enhanced ER alpha-dependent ligand-induced activation of an ERE-luciferase reporter construct, altered the induction of c-myc mRNA and increased proliferation of Ishikawa cells whereas ERR beta S was found to reduce these endpoints. Fluorescent recovery after photobleaching (FRAP) revealed that intra-nuclear mobility of YFP-ERR beta S was more rapid than YFP-ERR beta L. Fluorescence resonance energy transfer (FRET) assays revealed a close association between ERR beta L and ER alpha following addition of ligand. We speculate that ERR beta L may alter ER alpha-dependent gene activation by enhancing the recruitment of co-activators. In conclusion, variant isoforms of ERR beta have differential effects on ER alpha-dependent gene expression and this has implications for human endometrial cell function.

Expression of oestrogen receptors, ERalpha, ERbeta, and ERbeta variants, in endometrial cancers and evidence that prostaglandin F may play a role in regulating expression of ERalpha

Background

Endometrial cancer is the most common gynaecological malignancy; risk factors include exposure to oestrogens and high body mass index. Expression of enzymes involved in biosynthesis of oestrogens and prostaglandins (PG) is often higher in endometrial cancers when compared with levels detected in normal endometrium. Oestrogens bind one of two receptors (ERα and ERβ) encoded by separate genes. The full-length receptors function as ligand-activated transcription factors; splice variant isoforms of ERβ lacking a ligand-binding domain have also been described. PGs act in an autocrine or paracrine manner by binding to specific G-protein coupled receptors.

Methods

We compared expression of ERs, progesterone receptor (PR) and cyclooxygenase-2 (COX-2) in stage 1 endometrial adenocarcinomas graded as well (G1), moderately (G2) or poorly (G3) differentiated (n ≥ 10 each group) using qRTPCR, single and double immunohistochemistry. We used endometrial adenocarcinoma cell lines to investigate the impact of PGF2α on expression of ERs and PR.

Results

Full length ERβ (ERβ1) and two ERβ variants (ERβ2, ERβ5) were expressed in endometrial cancers regardless of grade and the proteins were immunolocalised to the nuclei of cells in both epithelial and stromal compartments. Immunoexpression of COX-2 was most intense in cells that were ERα^neg/low. Expression of PR in endometrial adenocarcinoma (Ishikawa) cell lines and tissues broadly paralleled that of ERα. Treatment of adenocarcinoma cells with PGF2α reduced expression of ERα but had no impact on ERβ1. Cells incubated with PGF2α were unable to increase expression of PR mRNA when they were incubated with E2.

Conclusion

We have demonstrated that ERβ5 protein is expressed in stage 1 endometrial adenocarcinomas. Expression of three ERβ variants, including the full-length protein is not grade-dependent and most cells in poorly differentiated cancers are ERβ^pos/ERα^neg. We found evidence of a link between COX-2, its product PGF2α, and expression of ERα and PR that sheds new light on the cross talk between steroid and PG signalling pathways in this disease.

Estrogen receptor related beta is expressed in human endometrium throughout the normal menstrual cycle

BACKGROUND

Estrogen receptor related beta (ERRbeta, ESRRB/NR3B2) is an orphan receptor that shares significant sequence homology with estrogen receptors ERalpha and ERbeta. ERR family members are reported to exhibit constitutive transcriptional activity; however, little is known about the biological function of ERRbeta. In an attempt to delineate its role, we examined expression of ERRbeta in normal human endometrium, a tissue that undergoes cyclic remodelling under the influence of estrogen and progesterone.

METHODS

Well-characterized endometrial tissue (n = 31), including full-thickness biopsies, was obtained from women with regular menstrual cycles. RT-PCR was used to measure mRNA encoding ERRbeta, the peroxisome proliferator activated receptor gamma coactivators (PGC)-1alpha and beta and to determine whether ERRbeta splice variant mRNAs were expressed. ERRbeta was immunolocalized using both single and double antibody immunohistochemistry.

RESULTS

Total ERRbeta mRNA appeared higher in proliferative phase samples but results did not reach significance. Transcripts corresponding to the long- and short-splice variants of ERRbeta as well as PGC1alpha and beta were detected but ERRbetaDelta10 was absent. ERRbeta protein was localized to cell nuclei within multiple endometrial cell types including the glands, stroma, endothelium and immune cells, including uterine natural killer (uNK) cells and macrophages. Fluorescent immunohistochemistry revealed that some cells co-expressed ERRbeta and ERalpha or ERbeta, for example, endothelial and uNK cells were ERRbeta+/ERbeta+.

CONCLUSIONS

ERRbeta mRNA and protein are expressed in healthy human endometrium. Further studies are warranted to characterize the functional impact of ERRbeta on endometrial biology.

Transcriptional regulation of cytochrome P4503A4 gene expression: effects of inherited mutations in the 5′-flanking region

1. Understanding the genetic basis of interindividual variability in drug disposition and response is a fundamental focus for rational and individualized drug treatment. Cytochrome P4503A4 (CYP3A4) has a central role in human drug metabolism and polymorphic variation has been reported in this gene. 2. This study reports the in vitro functional analysis of inherited mutations in the 5' flanking region of the CYP3A4 gene using reporter constructs in which the 1141 bp proximal promoter region from the mutant alleles was inserted between a single copy of the CYP3A4 300 bp core distal enhancer (XREM) sequence and the cDNA for human secretory alkaline phosphatase. 3. Reporter constructs were co-transfected with an hPXR expression vector into human liver and intestinal cells in culture and xenobiotic modulation of CYP3A4 promoter activity determined by chemiluminescent secretory alkaline phosphatase assay. DNA-protein interactions were next examined using electrophoretic mobility shift assays. 4. The results demonstrated that inherited mutations in the CYP3A4 gene proximal promoter region could cause significant up-regulation of in vitro transcriptional activation by CYP3A4 xenobiotic inducers. In addition, the magnitude of the effect appeared to be dependent on the cell type used in the functional assays, possibly due to the differing availability of specific intracellular transcription factors or their activating ligands.

ROLE OF Sp1, C/EBPα, HNF3, AND PXR IN THE BASAL- AND XENOBIOTIC-MEDIATED REGULATION OF THECYP3A4GENE

Cytochrome P450 3A4 (CYP3A4) is the major cytochrome P450 present in adult human liver and is involved in the metabolism of over 50% of therapeutic compounds currently in use. Since expression levels of CYP3A4 are regulated by many of these compounds, this raises the potential for drug-drug interactions and subsequent altered efficacy or toxicity of the individual compounds at the dose prescribed. Hence, understanding the molecular mechanisms of CYP3A4 regulation is of key importance in predicting and understanding such interactions. To examine this we have used DNase I footprinting and bioinformatic analysis to identify putative transcription factor binding sites within the 250 base pairs of promoter proximal to the transcription start site. We identified several protected fragments within this region that corresponded to putative binding sites for Sp1, AP2, CCAAT/enhancer binding protein (C/EBPalpha), and hepatic nuclear factor-3 (HNF3), as well as confirming previously identified C/EBPalpha, pregnane X receptor (PXR), and HNF3 binding sites. Sequential site-directed mutagenesis of C/EBPalpha, Sp1, HNF3, and PXR binding sites was next used to examine the role of these sites in basal CYP3A4 expression. Disruption of the C/EBPalpha, HNF3, and PXR binding sites all affected basal expression. Finally, the role of these sites was examined in activation of CYP3A4 expression by rifampicin, metyrapone, clotrimazole, and phenobarbital. Disruption of any of these sites either led to an altered pattern of activation by the xenobiotic, as altered maximal activation, or altered the EC(50) value of activation. Such effects were xenobiotic-specific, with each disrupted site playing a role in the activation of some of the xenobiotics.

Perturbation of epigenetic status by toxicants

It is becoming increasingly apparent that toxicant-induced changes in epigenetic status, particularly DNA methylation patterns, may play a role in some mechanisms of toxicity. Here, we discuss briefly the evidence that alterations in DNA methylation accompany, and may even promote, carcinogenesis induced by non-genotoxic chemicals. We also address recent findings indicating that the availability of dietary methyl donors can modulate DNA methylation levels and precipitate adverse effects.

Glucocorticoid-mediated induction of CYP3A4 is decreased by disruption of a protein: DNA interaction distinct from the pregnane X receptor response element

CYP3A4 is the most abundant cytochrome P450 (P450) in human liver, comprising approximately 30% of the total liver P450 content. This enzyme has an important role in steroid catabolism and metabolism of foreign compounds, with the majority of pharmaceutical compounds being substrates for CYP3A4. The molecular mechanisms that underlie transcriptional activation of CYP3A4 are complex with many steroid hormone nuclear receptors, including glucocorticoid receptor, pregnane X receptor (PXR), vitamin D receptor, and constitutive androstane receptor, playing roles. Nowhere is this more evident than in the induction of CYP3A4 gene expression by glucocorticoids. CYP3A genes lack a consensus glucocorticoid receptor response element and yet are highly induced by classical glucocorticoids such as hydrocortisone and dexamethasone. Recent evidence has demonstrated that glucocorticoids are ligands for the orphan nuclear receptor PXR, and induction of CYP3A genes by glucocorticoids may occur primarily through PXR interactions. In this paper, we present a mutant that disrupts a hepatocyte-nuclear-factor-3/CCAAT-enhancer binding protein alpha binding site in the CYP3A4 proximal promoter. This mutation disrupts induction of a reporter gene construct by the glucocorticoids dexamethasone and hydrocortisone; yet induction by the potent PXR ligand rifampicin is unaffected. Such data provides strong evidence that glucocorticoids induce CYP3A4 gene expression both through the established PXR-dependent pathway but also through a PXR-independent pathway.

Application of the comet and micronucleus assays to butterfish (Pholis gunnellus) erythrocytes from the Firth of Forth, Scotland

This report describes an investigation of genotoxic effects in an inter-tidal fish species sampled along a pollution gradient in the Firth of Forth, Scotland, UK. The comet assay is an electrophoretic technique for measuring DNA breakage in nuclei from individual cells and has only recently been applied to field investigations of genotoxicity. The measurement of nuclear anomalies (NA), such as the presence of micronuclei (MN) and 'lobes', has been successfully utilised in many field studies of genotoxic effects of contaminated sediments. These two techniques were applied to nucleated red blood cells (RBC) from the butterfish, Pholis gunnellus. The comet assay was adapted and validated for use in this species. Fish were sampled from the inner Firth of Forth, which has a legacy of industrial contamination and the outer Firth of Forth which is comparatively clean. The analysis of DNA strand breakage using this technique did not reveal any significant differences between animals sampled from inner and outer zones of the Firth. In contrast, MN and NA frequencies were elevated in the inner polluted zone of the Firth compared to the outer zone. This study suggests: (1) there are genotoxic effects associated with contaminants in the inner Firth of Forth, and (2) the comet assay may not be a suitable genotoxicity biomarker in fish.