Identification and localization of estrogen receptor alpha- and beta-positive cells in adult male and female mouse intestine at various estrogen levels

Uterine Uptake of Estrogen and Progestogen-Based Radiotracers in Rhesus Macaques with Endometriosis

PURPOSE

Endometriosis is an estrogen-dependent disorder of menstruating primates where tissues similar to the inner lining of the uterus exist "ectopically" outside of the uterus. The ectopic endometrium, like the endometrium within the uterus, expresses estrogen receptors (ER) and progesterone receptors (PR) and undergoes hormone-dependent cell proliferation and bleeding each menstrual cycle. The goal of this study was to conduct abdominopelvic positron emission tomography (PET) scans with computed tomography (CT) imaging of rhesus macaques (Macaca mulatta) using radiotracers that target ER and PR [16α-[18F]fluoroestradiol (FES) and 12-[18F]fluoro-furanyl-nor-progesterone (FFNP)] in individuals with and without endometriosis. We also aimed to determine if menstrual cycle phase and/or the presence of endometriosis affected the uptake of these radiotracers.

PROCEDURES

Rhesus macaques with either clinically diagnosed endometriosis (n = 6) or no endometriosis (n = 4) underwent PET/CT scans with FES. A subset of the animals also underwent PET/CT scans with FFNP. Standard uptake values corrected for body weight (SUVs) were obtained for each radiotracer in target and background tissues (e.g., intestinal). We performed repeated measure analysis of variance tests to determine how uterine and background uptake differed with scan time, phase of the menstrual cycle, and disease state.

RESULTS

Abdominopelvic PET/CT could not resolve small, individual endometriotic lesions. However, macaques with endometriosis displayed higher uterine uptake compared to those without the disorder. Radiotracer uptake differed by menstrual cycle phase with increased uterine uptake of both radiotracers in the proliferative phase of the menstrual cycle. Background intestinal uptake of FFNP increased over time after infusion, but only during the proliferative phase.

CONCLUSIONS

PET/CT with FES and FFNP support the concept that ER and PR levels are altered in individuals with endometriosis. This highlights the impact of the disease on typical reproductive tract function and may provide a novel pathway for the identification of individuals with endometriosis.

Plasticity of colonic enteric nervous system following spinal cord injury in male and female rats

BACKGROUND

Neurogenic bowel is a dysmotility disorder following spinal cord injury (SCI) that negatively impacts quality of life, social integration, and physical health. Colonic transit is directly modulated by the enteric nervous system. Interstitial Cells of Cajal (ICC) distributed throughout the small intestine and colon serve as specialized pacemaker cells, generating rhythmic electrical slow waves within intestinal smooth muscle, or serve as an interface between smooth muscle cells and enteric motor neurons of the myenteric plexus. Interstitial Cells of Cajal loss has been reported for other preclinical models of dysmotility, and our previous experimental SCI study provided evidence of reduced excitatory and inhibitory enteric neuronal count and smooth muscle neural control.

METHODS

Immunohistochemistry for the ICC-specific marker c-Kit was utilized to examine neuromuscular remodeling of the distal colon in male and female rats with experimental SCI.

KEY RESULTS

Myenteric plexus ICC (ICC-MP) exhibited increased cell counts 3 days following SCI in male rats, but did not significantly increase in females until 3 weeks after SCI. On average, ICC-MP total primary arborization length increased significantly in male rats at 3-day, 3-week, and 6-week time points, whereas in females, this increase occurred most frequently at 6 weeks post-SCI. Conversely, circular muscle ICC (ICC-CM) did not demonstrate post-SCI changes.

CONCLUSIONS AND INFERENCES

These data demonstrate resiliency of the ICC-MP in neurogenic bowel following SCI, unlike seen in other related disease states. This plasticity underscores the need to further understand neuromuscular changes driving colonic dysmotility after SCI in order to advance therapeutic targets for neurogenic bowel treatment.

Uterine uptake of estrogen and progestogen-based radiotracers in rhesus macaques with endometriosis

Purpose

Few investigations have examined the uptake of radiotracers that target the prominent sex-steroid receptors in the uterus across the menstrual cycle and with disease state. We aimed to determine if uptake of the radiotracers that target estrogen and progesterone receptors (ER and PR) differ with the presence of endometriosis and/or across the menstrual cycle. We performed PET and computed tomography (CT) imaging procedures on rhesus macaques (Macaca mulatta) using 16α-[18F]fluoroestradiol (FES) and 21-[18F]fluoro-furanyl-nor-progesterone (FFNP) in individuals with and without endometriosis in the proliferative and secretory phases of the menstrual cycle.

Procedures

Macaques with either clinically diagnosed endometriosis (n = 6) or no endometriosis (n = 4) underwent abdominopelvic PET/CT scans with FES. A subset of these animals also underwent PET/CT scans with FFNP. Standard uptake values corrected for body weight (SUVbw) were obtained for each radiotracer in target and background tissues (i.e., intestinal and muscle). We performed repeated measure analysis of variance tests to determine how uterine and background uptake differed with scan time, phase of the menstrual cycle, and disease state.

Results

PET/CT could not resolve small, individual endometriotic lesions. However, uterine uptake of both radiotracers was elevated in the proliferative phase compared to the secretory phase of the menstrual cycle. Intestinal uptake exhibited greater variation during the proliferative phase compared to the secretory phase. Further, intestinal uptake of FFNP increases as the scan progresses, but only during the proliferative phase. Muscle uptake did not differ with menstrual phase or radiotracer type. Lastly, macaques with endometriosis displayed higher uterine uptake of FES compared to those without endometriosis.

Conclusions

PET/CT with FES and FFNP support the concept that ER and PR levels are altered in individuals with endometriosis. This highlights the impact of the disease on typical reproductive tract function and may provide a novel pathway for the identification of individuals with endometriosis.

Zearalenone Exposure Affects the Keap1-Nrf2 Signaling Pathway and Glucose Nutrient Absorption Related Genes of Porcine Jejunal Epithelial Cells

This study aims to examine the impact of zearalenone (ZEA) on glucose nutrient absorption and the role of the Kelch-like erythroid cell-derived protein with CNC homology-associated protein 1 (Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway in zearalenone-induced oxidative stress of porcine jejunal epithelial cells (IPEC-J2). For 24 and 36 h, the IPEC-J2 cells were exposed to ZEA at concentrations of 0, 10, 20, and 40 (Control, ZEA10, ZEA20, ZEA40) mol/L. With the increase of ZEA concentration and prolongation of the action time, the apoptosis rate and malondialdehyde level and relative expression of sodium-dependent glucose co-transporter 1 (Sglt1), glucose transporter 2 (Glut2), Nrf2, quinone oxidoreductase 1 (Nqo1), and hemeoxygenase 1 (Ho1) at mRNA and protein level, fluorescence intensity of Nrf2 and reactive oxygen species increased significantly (p < 0.05), total superoxide dismutase and glutathione peroxidase activities and relative expression of Keap1 at mRNA and protein level, fluorescence intensity of Sglt1 around the cytoplasm and the cell membrane of IPEC-J2 reduced significantly (p < 0.05). In conclusion, ZEA can impact glucose absorption by affecting the expression of Sglt1 and Glut2, and ZEA can activate the Keap1-Nrf2 signaling pathway by enhancing Nrf2, Nqo1, and Ho1 expression of IPEC-J2.

Maternal adaptations to food intake across pregnancy: Central and peripheral mechanisms

A sufficient and balanced maternal diet is critical to meet the nutritional demands of the developing fetus and to facilitate deposition of fat reserves for lactation. Multiple adaptations occur to meet these energy requirements, including reductions in energy expenditure and increases in maternal food intake. The central nervous system plays a vital role in the regulation of food intake and energy homeostasis and responds to multiple metabolic and nutrient cues, including those arising from the gastrointestinal tract. This review describes the nutrient requirements of pregnancy and the impact of over- and undernutrition on the risk of pregnancy complications and adult disease in progeny. The central and peripheral regulation of food intake is then discussed, with particular emphasis on the adaptations that occur during pregnancy and the mechanisms that drive these changes, including the possible role of the pregnancy-associated hormones progesterone, estrogen, prolactin, and growth hormone. We identify the need for deeper mechanistic understanding of maternal adaptations, in particular, changes in gut-brain axis satiety signaling. Improved understanding of food intake regulation during pregnancy will provide a basis to inform strategies that prevent maternal under- or overnutrition, improve fetal health, and reduce the long-term health and economic burden for mothers and offspring.

Nitric Oxide Regulates Estrus Cycle Dependent Colonic Motility in Mice

Women are more susceptible to functional bowel disorders than men and the severity of their symptoms such as diarrhea, constipation, abdominal pain and bloating changes over the menstrual cycle, suggesting a role for sex hormones in gastrointestinal function. Nitric oxide (NO) is a major inhibitory neurotransmitter in the gut and blockade of nitric oxide synthase (NOS; responsible for NO synthesis) increases colonic motility in male mice ex vivo. We assessed the effects of NOS inhibition on colonic motility in female mice using video imaging analysis of colonic motor complexes (CMCs). To understand interactions between NO and estrogen in the gut, we also quantified neuronal NOS and estrogen receptor alpha (ERα)-expressing myenteric neurons in estrus and proestrus female mice using immunofluorescence. Mice in estrus had fewer CMCs under control conditions (6 ± 1 per 15 min, n = 22) compared to proestrus (8 ± 1 per 15 min, n = 22, One-way ANOVA, p = 0.041). During proestrus, the NOS antagonist N-nitro-L-arginine (NOLA) increased CMC numbers compared to controls (189 ± 46%). In contrast, NOLA had no significant effect on CMC numbers during estrus. During estrus, we observed more NOS-expressing myenteric neurons (48 ± 2%) than during proestrus (39 ± 1%, n = 3, p = 0.035). Increased nuclear expression of ERα was observed in estrus which coincided with an altered motility response to NOLA in contrast with proestrus when ERα was largely cytoplasmic. In conclusion, we confirm a cyclic and sexually dimorphic effect of NOS activity in female mouse colon, which could be due to genomic effects of estrogens via ERα.

Sex differences feed into nuclear receptor signaling along the digestive tract

Sex differences in physiology are noted in clinical and animal studies. However, mechanisms underlying these observed differences between males and females remain elusive. Nuclear receptors control a wide range of physiological pathways and are expressed in the gastrointestinal tract, including the mouth, stomach, liver and intestine. We investigated the literature pertaining to ER, AR, FXR, and PPAR regulation and highlight the sex differences in nutrient metabolism along the digestive system. We chose these nuclear receptors based on their metabolic functions, and hormonal actions. Intriguingly, we noted an overlap in target genes of ER and FXR that modulate mucosal integrity and GLP-1 secretion, whereas overlap in target genes of PPARα with ER and AR modulate lipid metabolism. Sex differences were seen not only in the basal expression of nuclear receptors, but also in activation as their endogenous ligand concentrations fluctuate depending on nutrient availability. Finally, in this review, we speculate that interactions between the nuclear receptors may influence overall metabolic decisions in the gastrointestinal tract in a sex-specific manner.

The Endocrine Disruptor Bisphenol A (BPA) Affects the Enteric Neurons Immunoreactive to Neuregulin 1 (NRG1) in the Enteric Nervous System of the Porcine Large Intestine

The enteric nervous system (ENS), located in the wall of the gastrointestinal (GI) tract, is characterized by complex organization and a high degree of neurochemical diversity of neurons. One of the less known active neuronal substances found in the enteric neurons is neuregulin 1 (NRG1), a factor known to be involved in the assurance of normal development of the nervous system. During the study, made up using the double immunofluorescence technique, the presence of NRG1 in the ENS of the selected segment of porcine large intestine (caecum, ascending and descending colon) was observed in physiological conditions, as well as under the impact of low and high doses of bisphenol A (BPA) which is commonly used in the production of plastics. In control animals in all types of the enteric plexuses, the percentage of NRG1-positive neurons oscillated around 20% of all neurons. The administration of BPA caused an increase in the number of NRG1-positive neurons in all types of the enteric plexuses and in all segments of the large intestine studied. The most visible changes were noted in the inner submucous plexus of the ascending colon, where in animals treated with high doses of BPA, the percentage of NRG1-positive neurons amounted to above 45% of all neuronal cells. The mechanisms of observed changes are not entirely clear, but probably result from neurotoxic, neurodegenerative and/or proinflammatory activity of BPA and are protective and adaptive in nature.

Diminished enteric neuromuscular transmission in the distal colon following experimental spinal cord injury

Neurogenic bowel following spinal cord injury (SCI) leads to decreased colonic motility, remodeling of the neuromuscular compartment and results in chronic evacuation difficulties. The distal colon of the rat serves a dual role for fluid absorption and storage that is homologous to the descending colon of humans. Dysmotility of the descending colon is one component of neurogenic bowel. We investigated the integrity of the enteric neuromuscular transmission responsible for the generation of excitatory and inhibitory junction potentials (EJPs and IJPs, respectively) in the distal colon of rats. We previously demonstrated a chronic reduction in colonic enteric neurons from rats with acute and chronic high-thoracic (T3) SCI and hypothesized that neurogenic bowel following T3-SCI results from diminished enteric neuromuscular transmission. Immunohistochemical labeling for myenteric neuronal nitric oxide synthase (nNOS) and choline acetyltransferase (ChAT) neurons demonstrated a significant loss of presumptive nitric oxide (NO) and acetylcholine (ACh) immunoreactive neurons in both 3-day and 3-week injured animals. Colonic neuromuscular transmission in response to transmural electrical stimulation of the colon was significantly reduced 3-days and 3-weeks following SCI in male rats. Specifically, cholinergic-mediated excitatory junction potentials (EJPs) and nitrergic-mediated slow inhibitory junction potentials (IJPs) were significantly reduced while ATP-mediated fast IJPs remained unaffected. We conclude that a reduction in excitatory and inhibitory enteric neuromuscular transmission contributes to neurogenic bowel observed following SCI, and that these loss-of-function changes involve enteric-mediated cholinergic and nitrergic pathways.

The Role of Sex and Sex Hormones in Neurodegenerative Diseases

Neurodegenerative diseases (NDs) are a wide class of disorders of the central nervous system (CNS) with unknown etiology. Several factors were hypothesized to be involved in the pathogenesis of these diseases, including genetic and environmental factors. Many of these diseases show a sex prevalence and sex steroids were shown to have a role in the progression of specific forms of neurodegeneration. Estrogens were reported to be neuroprotective through their action on cognate nuclear and membrane receptors, while adverse effects of male hormones have been described on neuronal cells, although some data also suggest neuroprotective activities. The response of the CNS to sex steroids is a complex and integrated process that depends on (i) the type and amount of the cognate steroid receptor and (ii) the target cell type-either neurons, glia, or microglia. Moreover, the levels of sex steroids in the CNS fluctuate due to gonadal activities and to local metabolism and synthesis. Importantly, biochemical processes involved in the pathogenesis of NDs are increasingly being recognized as different between the two sexes and as influenced by sex steroids. The aim of this review is to present current state-of-the-art understanding on the potential role of sex steroids and their receptors on the onset and progression of major neurodegenerative disorders, namely, Alzheimer's disease, Parkinson's diseases, amyotrophic lateral sclerosis, and the peculiar motoneuron disease spinal and bulbar muscular atrophy, in which hormonal therapy is potentially useful as disease modifier.

Activation of the p38/MAPK pathway regulates autophagy in response to the CYPOR-dependent oxidative stress induced by zearalenone in porcine intestinal epithelial cells

Zearalenone (ZEA) can widely contaminate crops and agricultural products. The ingestion of ZEA-contaminated food or feed affects the integrity and functions of the intestines. In this study, we aimed to find the potential protective mechanism against ZEA ingestion. We found that ZEA induced cell death in IPEC-J2 cells. Meanwhile, the cytoprotective autophagy was activated in ZEA-treated cells. Further studies demonstrated that a p38/MAPK inhibitor down-regulated autophagy and increased cell death compared to those of the controls. Furthermore, ZEA could induce the accumulation of ROS, and eliminating ROS with NAC resulted in a decline in cell death, p38/MAPK phosphorylation, and the expression of LC3-II compared to those of ZEA-group. In addition, cytochrome P450 reductase (CYPOR) was significantly increased in ZEA-treated cells compared to that in the controls, and an inhibitor of CYPOR decreased ROS levels and mitigated cell death compared to those of the ZEA-group. More importantly, we found that blocking both p38/MAPK signalling and autophagy could enhance CYPOR expression and elevate ROS levels. Overall, our study indicated that the p38/MAPK pathway could activate protective autophagy in response to the CYPOR-dependent oxidative stress that was induced by ZEA in IPEC-J2 cells.

The microgenderome revealed: sex differences in bidirectional interactions between the microbiota, hormones, immunity and disease susceptibility

Sex differences in immunity are well described in the literature and thought to be mainly driven by sex hormones and sex-linked immune response genes. The gastrointestinal tract (GIT) is one of the largest immune organs in the body and contains multiple immune cells in the GIT-associated lymphoid tissue, Peyer's patches and elsewhere, which together have profound effects on local and systemic inflammation. The GIT is colonised with microbial communities composed of bacteria, fungi and viruses, collectively known as the GIT microbiota. The GIT microbiota drives multiple interactions locally with immune cells that regulate the homeostatic environment and systemically in diverse tissues. It is becoming evident that the microbiota differs between the sexes, both in animal models and in humans, and these sex differences often lead to sex-dependent changes in local GIT inflammation, systemic immunity and susceptibility to a range of inflammatory diseases. The sexually dimorphic microbiome has been termed the 'microgenderome'. Herein, we review the evidence for the microgenderome and contemplate the role it plays in driving sex differences in immunity and disease susceptibility. We further consider the impact that biological sex might play in the response to treatments aimed at manipulating the GIT microbiota, such as prebiotics, live biotherapeutics, (probiotics, synbiotics and bacteriotherapies) and faecal microbial transplant. These alternative therapies hold potential in the treatment of both psychological (e.g., anxiety, depression) and physiological (e.g., irritable bowel disease) disorders differentially affecting males and females.

Localization of estrogen receptor ERα, ERβ and GPR30 on myenteric neurons of the gastrointestinal tract and their role in motility

Estrogen is well known to have a modulatory role on gastrointestinal tract, particularly through its interaction with nuclear estrogen receptors (ERs), alpha and beta (ERα/β). Recent functional studies also indicate that estrogen can activate a G-protein coupled estrogen receptor, GPR30, or GPER1. The present study was designed to identify either the presence or absence of nuclear ERs and GPR30 in the myenteric plexus of the stomach, duodenum, jejunum, ileum and colon of female and male mice. Immunofluorescence staining revealed a high expression of GPR30 in the cytoplasm but not within the nucleus of enteric neurons in female and male mice. ERβ localization was similar to GPR30, where it was expressed in cytoplasm of enteric neurons, but was absent from nuclei, opening up the possibility that ERβ and GPR30 might work together to manifest estrogenic effects. Comparatively, ERα was mainly located in the nuclei of enteric neurons. ERα, ERβ and GPR30 were also expressed in the cytoplasm of glial cells in the stomach and small intestine, but levels were lower in the colon. The expression nuclear:cytoplasm ratio of ERα was higher in male than female mice, which might relate to sex-dependent translocation of ERα from cytoplasm to nucleus in response to known plasma levels of estrogen. A functional study using isolated ileal segments showed that ERα, ERβ and GPR30 are involved in the neuronal-mediated contractions in female tissues, but only ERα was involved in male tissues. This may indicate although expression level was similar between males and females, the downstream mechanisms of ERβ and GPR30 could be different between sexes. The present study provides a rationale for the action of estrogen to modulate gastrointestinal function in health and disease in different sexes.

Intestinal macrophages in mucosal immunity and their role in systemic lupus erythematosus disease

Monocytes play an important role in inducing host systemic immunity against invading pathogens and inflammatory responses. After activation, monocytes migrate to tissue sites, where they initiate both innate and adaptive immune responses, and become macrophages. Although mucosal macrophages produce inflammatory cytokines in response to pathogens, the perturbations in innate immune signaling pathway have been implicated in autoimmune diseases such as systemic lupus erythematosus (SLE). In this review, we focus on the role of human macrophages in intestinal innate immune responses, homeostasis, and SLE disease. We further discuss sex differences in the intestinal macrophages and their role in the physiology and pathogenesis of SLE.

Potential Mechanisms of Age Acceleration Caused by Estrogen Deprivation: Do Endocrine Therapies Carry the Same Risks?

Longer duration of endocrine therapy decreases breast cancer recurrence and mortality, but these benefits need to be weighed against potential risks to overall health. Notable side effects of endocrine therapy include cataracts, uterine cancer, thromboembolic events, osteoporosis and fracture risk, chronic musculoskeletal complaints, as well as vaginal dryness and discharge, and vasomotor symptoms. Estrogen deprivation in healthy women younger than 50 years undergoing bilateral oophorectomy has been shown to accelerate the development of diseases related to aging, including coronary artery disease, cardiac arrhythmias, stroke, dementia, and osteoporosis, raising concern that even less dramatic modulation of estrogen homeostasis may adversely affect health outcomes. Diminished available estrogen at the cellular and molecular level may facilitate mechanisms that underlie the aging process, often termed the hallmarks of aging. In this review, we describe estrogen's role in normal physiology across tissues, review the effects of estrogen deprivation on health outcomes in the setting of both surgical and natural menopause, and examine the hallmarks of aging with attention to the effects of estrogen and estrogen blockade on each molecular mechanism underlying the aging process.

Sexual dimorphism of cardiometabolic dysfunction: Gut microbiome in the play?

BACKGROUND

Sex is one of the most powerful modifiers of disease development. Clear sexual dimorphism exists in cardiometabolic health susceptibility, likely due to differences in sex steroid hormones. Changes in the gut microbiome have been linked with the development of obesity, type 2 diabetes, and atherosclerosis; however, the impact of microbes in sex-biased cardiometabolic disorders remains unclear. The gut microbiome is critical for maintaining a normal estrous cycle, testosterone levels, and reproductive function. Gut microbes modulate the enterohepatic recirculation of estrogens and androgens, affecting local and systemic levels of sex steroid hormones. Gut bacteria can also generate androgens from glucocorticoids.

SCOPE OF REVIEW

This review summarizes current knowledge of the complex interplay between sexual dimorphism in cardiometabolic disease and the gut microbiome.

MAJOR CONCLUSIONS

Emerging evidence suggests the role of gut microbiome as a modifier of disease susceptibility due to sex; however, the impact on cardiometabolic disease in this complex interplay is lacking. Elucidating the role of gut microbiome on sex-biased susceptibility in cardiometabolic disease is of high relevance to public health given its high prevalence and significant financial burden.

Estrogen receptor β controls proliferation of enteric glia and differentiation of neurons in the myenteric plexus after damage

Injury to the enteric nervous system (ENS) can cause several gastrointestinal (GI) disorders including achalasia, irritable bowel syndrome, and gastroparesis. Recently, a subpopulation of enteric glial cells with neuronal stem/progenitor properties (ENSCs) has been identified in the adult ENS. ENSCs have the ability of reconstituting the enteric neuronal pool after damage of the myenteric plexus. Since the estrogen receptor β (ERβ) is expressed in enteric glial cells and neurons, we investigated whether a selective ERβ agonist, LY3201, can influence neuronal and glial cell differentiation. Myenteric ganglia from the murine muscularis externa were isolated and cultured in either glial cell medium or neuronal medium. In glial cell medium, the number of glial progenitor cells (Sox10⁺) was increased by fourfold in the presence of LY3201. In the neuronal medium supplemented with an antimitotic agent to block glial cell proliferation, LY3201 elicited a 2.7-fold increase in the number of neurons (neurofilament⁺ or HuC/D⁺). In addition, the effect of LY3201 was evaluated in vivo in two murine models of enteric neuronal damage and loss, namely, high-fat diet and topical application of the cationic detergent benzalkonium chloride (BAC) on the intestinal serosa, respectively. In both models, treatment with LY3201 significantly increased the recovery of neurons after damage. Thus, LY3201 was able to stimulate glial-to-neuron cell differentiation in vitro and promoted neurogenesis in the damaged myenteric plexus in vivo. Overall, our study suggests that selective ERβ agonists may represent a therapeutic tool to treat patients suffering from GI disorders, caused by excessive neuronal/glial cell damage.

G protein-coupled estrogen receptor and estrogen receptor ligands regulate colonic motility and visceral pain

BACKGROUND

Diarrhea-predominant irritable bowel syndrome (IBS-D) is a functional gastrointestinal (GI) disorder, which occurs more frequently in women than men. The aim of our study was to determine the role of activation of classical estrogen receptors (ER) and novel membrane receptor, G protein-coupled estrogen receptor (GPER) in human and mouse tissue and to assess the possible cross talk between these receptors in the GI tract.

METHODS

Immunohistochemistry was used to determine the expression of GPER in human and mouse intestines. The effect of G-1, a GPER selective agonist, and estradiol, a non-selective ER agonist, on muscle contractility was characterized in isolated preparations of the human and mouse colon. To characterize the effect of G-1 and estradiol in vivo, colonic bead expulsion test was performed. G-1 and estradiol activity on the visceral pain signaling was assessed in the mustard oil-induced abdominal pain model.

KEY RESULTS

GPER is expressed in the human colon and in the mouse colon and ileum. G-1 and estradiol inhibited muscle contractility in vitro in human and mouse colon. G-1 or estradiol administered intravenously at the dose of 20 mg/kg significantly prolonged the time to bead expulsion in females. Moreover, G-1 prolonged the time to bead expulsion and inhibited GI hypermotility in both genders. The injection of G-1 or estradiol resulted in a significant reduction in the number of pain-induced behaviors in mice.

CONCLUSIONS AND INFERENCES

GPER and ER receptors are involved in the regulation of GI motility and visceral pain. Both may thus constitute an important pharmacological target in the IBS-D therapy.

Stress, sex, and the enteric nervous system

Made up of millions of enteric neurons and glial cells, the enteric nervous system (ENS) is in a key position to modulate the secretomotor function and visceral pain of the gastrointestinal tract. The early life developmental period, through which most of the ENS development occurs, is highly susceptible to microenvironmental perturbation. Over the past decade, accumulating evidence has shown the impact of stress and early life adversity (ELA) on host gastrointestinal pathophysiology. While most of the focus has been on alterations in brain structure and function, limited experimental work in rodents suggest that the enteric nervous system can also be directly affected, as shown by changes in the number, phenotype, and reactivity of enteric nerves. The work of Medland et al. in the current issue of this journal demonstrates that such alterations also occur in pigs, a larger mammalian species with high translational value to human. This work also highlights a sex-differential susceptibility of the ENS to the effect of ELA, which could contribute to the higher prevalence of GI disorders in women. In this mini-review, we will discuss the development and composition of the ENS and related gastrointestinal sensory motor and secretory functions. We will then focus on the influence of stress on the enteric nervous system, with a particular emphasis on neurodevelopmental changes. Finally, we will discuss the influence of sex on those parameters.

The joint power of sex and stress to modulate brain-gut-microbiota axis and intestinal barrier homeostasis: implications for irritable bowel syndrome

BACKGROUND

Intestinal homeostasis is a dynamic process that takes place at the interface between the lumen and the mucosa of the gastrointestinal tract, where a constant scrutiny for antigens and toxins derived from food and microorganisms is carried out by the vast gut-associated immune system. Intestinal homeostasis is preserved by the ability of the mucus layer and the mucosal barrier to keep the passage of small-sized and antigenic molecules across the epithelium highly selective. When combined and preserved, immune surveillance and barrier's selective permeability, the host capacity of preventing the development of intestinal inflammation is optimized, and viceversa. In addition, the brain-gut-microbiome axis, a multidirectional communication system that integrates distant and local regulatory networks through neural, immunological, metabolic, and hormonal signaling pathways, also regulates intestinal function. Dysfunction of the brain-gut-microbiome axis may induce the loss of gut mucosal homeostasis, leading to uncontrolled permeation of toxins and immunogenic particles, increasing the risk of appearance of intestinal inflammation, mucosal damage, and gut disorders. Irritable bowel syndrome is prevalent stress-sensitive gastrointestinal disorder that shows a female predominance. Interestingly, the role of stress, sex and gonadal hormones in the regulation of intestinal mucosal and the brain-gut-microbiome axis functioning is being increasingly recognized.

PURPOSE

We aim to critically review the evidence linking sex, and stress to intestinal barrier and brain-gut-microbiome axis dysfunction and the implications for irritable bowel syndrome.

G protein-coupled estrogen receptor is involved in modulating colonic motor function via nitric oxide release in C57BL/6 female mice

BACKGROUND

Estrogen may regulate gastrointestinal motor functions, but the mechanism(s) is not totally understood. Here, we investigated whether G protein-coupled estrogen receptor (GPER/GPR30) was involved in regulating colonic motor functions and explored the underlying physiological mechanisms.

METHODS

Adult female C57BL/6 mice were used. The expression and localization of GPER were examined by RT-PCR, western blot, and immuno-labeling. The role of GPER in modulating colonic motor functions was assessed by the bead propulsion test in vivo and organ bath experiments in vitro.

KEY RESULTS

GPER was expressed in colonic myenteric neurons. The colonic transit time (CTT) in proestrus and estrus was significantly longer than that in diestrus. In vivo treatment with the selective GPER blocker G15 significantly shortened CTT in proestrus and estrus. In ovariectomized mice, acute estrogen supplementation increased CTT, which could be abolished by G15 co-administration. The GPER agonist G-1 caused a concentration-dependent inhibition of carbachol -induced circular muscle strips contraction, which was abolished by tetrodotoxin and the neuronal nitric oxide synthase (nNOS) inhibitor N-propyl-l-arginine. G-1 stimulated NO production in isolated longitudinal muscle myenteric plexus and cultured myenteric neurons, which was dependent on nNOS. Immunofluorescence labeling showed co-localization of GPER with nNOS in the myenteric plexus.

CONCLUSIONS & INFERENCES

We suggest that activation of GPER exerts an inhibitory effect on colonic motility by promoting NO release from myenteric nitrergic nerves. These results raise a possibility that GPER may be involved in mediating the inhibitory effect of estrogen on colonic motor functions, via a non-genomic, neurogenic mechanism.

Generation of an estrogen receptor beta-iCre knock-in mouse

A novel knock-in mouse that expresses codon-improved Cre recombinase (iCre) under regulation of the estrogen receptor beta (Esr2) promoter was developed for conditional deletion of genes and for the spatial and/or temporal localization of Esr2 expression. ESR2 is one of two classical nuclear estrogen receptors and displays a spatiotemporal expression pattern and functions that are different from the other estrogen receptor, ESR1. A cassette was constructed that contained iCre, a polyadenylation sequence, and a neomycin selection marker. This construct was used to insert iCre in front of the endogenous start codon of the Esr2 gene of a C57BL/6J embryonic stem cell line via homologous recombination. Resulting Esr2-iCre mice were bred with ROSA26-lacZ and Ai9-RFP reporter mice to visualize cells of functional iCre expression. Strong expression was observed in the ovary, the pituitary, the interstitium of the testes, the head and tail but not body of the epididymis, skeletal muscle, the coagulation gland (anterior prostate), the lung, and the preputial gland. Additional diffuse or patchy expression was observed in the cerebrum, the hypothalamus, the heart, the adrenal gland, the colon, the bladder, and the pads of the paws. Overall, Esr2-iCre mice will serve as a novel line for conditionally ablating genes in Esr2-expressing tissues, identifying novel Esr2-expressing cells, and differentiating the functions of ESR2 and ESR1.

Ontogenetic changes in the expression of estrogen receptor β in mouse duodenal epithelium

Estrogen is considered to be involved in duodenal function; however, the details of its receptor expression are largely unknown. The purpose of this study was to determine the expression and localization of estrogen receptors (ERs) in mouse duodenum. Male and female C57BL/6J mouse intestinal tissues were used to investigate the expression of ERα and ERβ by RT-PCR, western blotting, immunohistochemistry, and Southwestern histochemistry. ERβ, but not ERα, was expressed in proximal duodenal epithelium, but not in jejunum and ileum. The expression of ERβ mRNA and protein were confirmed by RT-PCR and western blotting, respectively. At postnatal day 20, the transit period of suckling to weaning, the distribution of ERβ-positive cells was changed in the crypt-villus axis, and cytoplasm/nuclear staining changed to only nuclear staining. Moreover, Southwestern histochemistry was used to detect estrogen response element (ERE)-binding proteins, and their expression pattern was highly similar to that of ERβ. These results suggested that ERβ is the predominant ER type in mouse small intestine, and the highly similar co-localization of ERE-binding proteins reveals that ERβ is functionally active in mouse duodenum. The ERβ expression changes during postnatal development indicate that ERβ may be involved in the differentiation of duodenal epithelium.

Impacts of β-estradiol on intestinal injury in newborn rats

OBJECTIVE

Necrotizing enterocolitis has been investigated and debated extensively in recent years; however, there is still no effective treatment. The aim of this study was thus to examine the effects of β-estradiol on intestinal injury in rats.

METHODS

Twenty-four newborn female rat pups were divided into three groups. In group 1 (sham), hypoxia-re-oxygenation was not performed. In group 2 (saline), the rats were injected with saline after hypoxia-re-oxygenation, and the process was repeated for 5 d. In group 3 (β-estradiol treatment), the rats were subjected to hypoxia-re-oxygenation and then given β-estradiol intraperitoneally once a day for 5 d. After these procedures, the terminal ileum was removed for analysis.

RESULTS

Statistically significant differences in histological grades were found between groups 1 and 2 (p = 0.000), groups 1 and 3 (p = 0.028), and groups 2 and 3 (p = 0.021). There were also differences in TNF-α and IL-6 levels between groups 2 and 3 (p = 0.000 and p = 0.038, respectively) and between groups 1 and 2 (p = 0.000 and p = 0.000); there was no difference between groups 1 and 3 (p = 0.574 and p = 0.195, respectively). Electron microscopy examination revealed a decrease in lipid droplets at the apical cytoplasm of the columnar cells in group 2; in group 3, the absorption of the lipids as lipid droplets was similar to that of group 1.

CONCLUSION

In this study, β-estradiol was found to decrease the intensity of intestinal injury significantly by inhibiting TNF-α and IL-6.

Host responses to the pathogen Mycobacterium avium subsp. paratuberculosis and beneficial microbes exhibit host sex specificity

Differences between microbial pathogenesis in male and female hosts are well characterized in disease conditions connected to sexual transmission. However, limited biological insight is available on variances attributed to sex specificity in host-microbe interactions, and it is most often a minimized variable outside these transmission events. In this work, we studied two gut microbes-a pathogen, Mycobacterium avium subsp. paratuberculosis, and a probiotic, Lactobacillus animalis NP-51-and the interaction between each agent and the male and female gastrointestinal systems. This trial was conducted in BALB/c mice (n=5 per experimental group and per sex at a given time point), with analysis at four time points over 180 days. Host responses to M.avium subsp. paratuberculosis and L. animalis were sensitive to sex. Cytokines that were significantly different (P ≤ 0.05) betweenthe sexes included interleukin-1α/β (IL-1α/β), IL-17, IL-6, IL-10, IL-12, and gamma interferon (IFN-) and were dependent on experimental conditions. However, granulocyte-macrophage colony-stimulating factor (GM-CSF), vascular endothelial growth factor (VEGF), and IL-13/23 showed no sex specificity. A metabolomics study indicated a 0.5- to 2.0-fold (log2 scale) increase in short-chain fatty acids (butyrate and acetate) in males and greater increases in o-phosphocholine or histidine from female colon tissues; variances distinct to each sex were observed with age or long-term probiotic consumption. Two genera, Staphylococcus and Roseburia, were consistently overrepresented in females compared to males; other species were specific to one sex but fluctuated depending on experimental conditions. The differences observed suggest that male and female gut tissues and microbiota respond to newly introduced microorganisms differently and that gut-associated microorganisms with host immune system responses and metabolic activity are supported by biology distinct to the host sex.

Gender-related differences in irritable bowel syndrome: Potential mechanisms of sex hormones

According to epidemiological studies, twice as many women as men are affected by irritable bowel syndrome (IBS) in western countries, suggesting a role for sex hormones in IBS pathophysiology. Despite growing evidence about the implications of sex hormones in IBS symptom modulation, data on mechanisms by which they influence disease development are sparse. This review aims to determine the state of knowledge about the role of sex hormones in sensorimotor dysfunctions and to address the possible interplay of sex hormones with common risk factors associated with IBS. The scientific bibliography was searched using the following keywords: irritable bowel syndrome, sex, gender, ovarian hormone, estradiol, progesterone, testosterone, symptoms, pain, sensitivity, motility, permeability, stress, immune system, brain activity, spinal, supraspinal, imaging. Ovarian hormones variations along the menstrual cycle affect sensorimotor gastrointestinal function in both healthy and IBS populations. They can modulate pain processing by interacting with neuromodulator systems and the emotional system responsible for visceral pain perception. These hormones can also modulate the susceptibility to stress, which is a pivotal factor in IBS occurrence and symptom severity. For instance, estrogen-dependent hyper-responsiveness to stress can promote immune activation or impairments of gut barrier function. In conclusion, whereas it is important to keep in mind that ovarian hormones cannot be considered as a causal factor of IBS, they arguably modulate IBS onset and symptomatology. However, our understanding of the underlying mechanisms remains limited and studies assessing the link between IBS symptoms and ovarian hormone levels are needed to improve our knowledge of the disease evolution with regard to gender. Further studies assessing the role of male hormones are also needed to understand fully the role of sex hormones in IBS. Finally, investigation of brain-gut interactions is critical to decipher how stress, ovarian hormones, and female brain processing of pain can translate into gut dysfunctions.

Xenoestrogens challenge 17β-estradiol protective effects in colon cancer

Several epidemiological, cellular, and molecular studies demonstrate the role of environmental chemicals with endocrine disrupting activities, typical of Westernized societies, in the pathogenesis of numerous diseases including cancer. Nonetheless this information, the design and execution of studies on endocrine disruptors are not yet cognizant that the specific actions of individual hormones often change with development and ageing, they may be different in males and females and may be mediated by different receptors isoforms expressed in different tissues or at different life stages. These statements are particularly true when assessing the hazard of endocrine disruptors against 17β-estradiol (E2) actions in that this hormone is crucial determinant of sex-related differences in anatomical, physiological, and behavioral traits which characterize male and female physiology. Moreover, E2 is also involved in carcinogenesis. The oncogenic effects of E2 have been investigated extensively in breast and ovarian cancers where hormone-receptor modulators are now an integral part of targeted treatment. Little is known about the E2 preventive signalling in colorectal cancer, although this disease is more common in men than women, the difference being more striking amongst pre-menopausal women and age-matched men. This review aims to dissect the role and action mechanisms of E2 in colorectal cancer evaluating the ability of estrogen disruptors (i.e., xenoestrogens) in impair these E2 actions. Data discussed here lead to define the possible role of xenoestrogens in the impairment and/or activation of E2 signals important for colorectal cancer prevention.

Estrogen receptor beta: tissue distribution and the still largely enigmatic physiological function

In 1996, the molecular biology of E2 had to be reevaluated: in an effort to identify novel nuclear receptors or unknown isoforms of existing receptors Kuiper and colleague described the expression of a novel subtype of the estrogen receptor (ER) in rat prostate and ovary. Upon this pioneering discovery the already known ER was renamed ERα while the newly described ER was termed ERβ. In this review an attempt is made to summarize the current knowledge regarding the expression and function of ERβ in selected reproductive and non-reproductive organs under physiological conditions. The data suggest that ERβ may be considered as a dominant-negative regulator of ERα modulating transcriptional responses to estrogens. The ratio of ER α vs. β. within a cell may determine the cell sensitivity to estrogens and its biological responses to the hormone.

CONCLUSION

It is not the ligand, it is the multiplicity of receptors which determines the plethora of estrogen actions. This article is part of a Special Issue entitled 'Phytoestrogens'.

The effect of female sexual hormones on the intestinal and serum cytokine response after traumatic brain injury: different roles for estrogen receptor subtypes

The purpose of this study was to evaluate the effect of female sexual hormones on intestinal and serum cytokines following traumatic brain injury (TBI). Adult female rats were ovariectomized and distributed among the following 9 groups: (i) sham trauma, (ii) TBI (Marmarou's method), (iii) vehicle (dimethylsulfoxide) treated, (iv) estrogen (E2) treated, (v) progesterone (P) treated, (vi) treated with E2+P, (vii) propylpyrazole triol (PPT) treated, (viii) diarylpropionitrile (DPN) treated, and (ix) control. PPT and DPN are estrogen receptor αand β agonists, respectively. Serum and intestinal levels of interleukin (IL)-1β were increased by TBI (P < 0.001). The level of intestinal IL-1β was increased in the group treated with E2 (P < 0.001). There was a reduction in serum IL-1β (P < 0.01) and an increase in intestinal IL-1β level (P < 0.001) in the PPT-treated group compared with the vehicle-treated group. TBI reduced serum IL-6 (P < 0.01) and increased intestinal IL-6 (P < 0.001). Serum IL-6 was increased in the group treated with E2 (P < 0.001), P (P < 0.001), E2+P (P < 0.01), and DPN (P < 0.001) after TBI; however, intestinal IL-6 was higher in the E2-treated group compared with the vehicle-treated group (P < 0.01). Intestinal tumor necrosis factor α (TNF-α) was increased by TBI (P < 0.001). Progesterone decreased serum TNF-α (P < 0.01). Intestinal TNF-α in the E2 (P < 0.01), E2+P (P < 0.001), and PPT (P < 0.001) treatment groups was less than in the vehicle-treated group. In conclusion, estrogen influences the intestinal levels of proinflammatory cytokines, in particular TNF-α, mediated through estrogen receptor α.

Prevention of tobacco carcinogen-induced lung cancer in female mice using antiestrogens

Increasing evidence shows that estrogens are involved in lung cancer proliferation and progression, and most human lung tumors express estrogen receptor β (ERβ) as well as aromatase. To determine if the aromatase inhibitor anastrozole prevents development of lung tumors induced by a tobacco carcinogen, alone or in combination with the ER antagonist fulvestrant, ovariectomized female mice received treatments with the tobacco carcinogen 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanone (NNK) along with daily supplements of androstenedione, the substrate for aromatase. Placebo, anastrozole and/or fulvestrant were administered in both an initiation and a promotion protocol of lung tumorigenesis. The combination of fulvestrant and anastrozole given during NNK exposure resulted in significantly fewer NNK-induced lung tumors (mean = 0.5) compared with placebo (mean = 4.6, P < 0.001), fulvestrant alone (mean = 3.4, P < 0.001) or anastrozole alone (mean = 2.8, P = 0.002). A significantly lower Ki67 cell proliferation index was also observed compared with single agent and control treatment groups. Beginning antiestrogen treatment after NNK exposure, when preneoplastic lesions had already formed, also yielded maximum antitumor effects with the combination. Aromatase expression was found mainly in macrophages infiltrating preneoplastic and tumorous areas of the lungs, whereas ERβ was found in both macrophages and tumor cells. Antiestrogens, especially in combination, effectively inhibited tobacco carcinogen-induced murine lung tumorigenesis and may have application for lung cancer prevention. An important source of estrogen synthesis may be inflammatory cells that infiltrate the lungs in response to carcinogens, beginning early in the carcinogenesis process. ERβ expressed by inflammatory and neoplastic epithelial cells in the lung may signal in response to local estrogen production.

Estradiol receptors agonists induced effects in rat intestinal microcirculation during sepsis

The steroid hormone estradiol is suggested to play a protective role in intestinal injury during systemic inflammation (sepsis). Our aim was to determine the effects of specific estradiol receptor (ER-α and ER-ß) agonists on the intestinal microcirculation during experimental sepsis. Male and sham ovariectomized female rats were subjected to sham colon ascendens stent peritonitis (CASP), and they were compared to male and ovariectomized female rats underwent CASP and either estradiol receptor α (ER-α) agonist propyl pyrazole triol (PPT), estradiol receptor ß (ER-ß) agonist diarylpropiolnitrile (DPN), or vehicle treatment. Intravital microscopy was performed, which is sufficiently sensitive to measure changes in the functional capillary density (FCD) as well as the major steps in leukocyte recruitment (rolling and adhesion). The leukocyte extravasations were also quantified by using histological paraffin sections of formalin fixed intestine. We found that either DPN (ER-β) or PPT (ER-α) significantly reduced (P<0.05) sepsis-induced leukocyte-endothelial interaction (rolling, adherent leukocytes and neutrophil extravasations) and improved the intestinal muscular FCD. [PPT: Female; Leukocyte rolling (n/min): V(3) 3.7±0.7 vs 0.8±0.2, Leukocyte adhesion(n/mm(2)): V(3) 131.3±22.6 vs 57.2±13.5, Neutrophil extravasations (n/10000 μm(2)): 3.1±0.7 vs 6 ±1. Male; Leukocyte adhesion (n/mm(2)): V(1) 154.8±19.2 vs 81.3±11.2, V(3) 115.5±23.1 vs 37.8±12]. [DPN: Female; neutrophil extravasations (n/10000 μm(2)) 3.8±0.6 vs 6 ±1. Male; Leukocyte adhesion (n/mm(2)) V(1) 154.8±19.2 vs 70±10.5, V(3) 115.5±23.1 vs 52.8±9.6].Those results suggest that the observed effects of estradiol receptors on different phases of leukocytes recruitment with the improvement of the functional capillary density could partially explain the previous demonstrated salutary effects of estradiol on the intestinal microcirculation during sepsis. The observed activity of this class of compounds could open up a new avenue of research into the potential treatment of sepsis.

An assessment of enteric nervous system and estroprogestinic receptors in obstructed defecation associated with rectal intussusception

BACKGROUND

The pathophysiological basis of obstructed defecation (OD) is still incompletely understood. In particular, few or no data are available concerning the enteric nervous system (ENS) in this condition. We investigated ENS abnormalities in patients with OD, undergoing surgery, together with the presence of estrogen (α and β) and progesterone receptors, and compare the results with those obtained in controls.

METHODS

Full-thickness rectal samples were obtained from 17 patients undergoing stapled transanal rectal resection for OD associated with rectal intussusception. Samples were analyzed by immunohistochemistry for enteric neurons, enteric glial cells, interstitial cells of Cajal (ICC), and for estrogen and progesterone receptors. Data were compared with those obtained in 10 controls.

KEY RESULTS

No differences between patients and controls were found for enteric neurons, whereas (compared with controls) OD patients displayed a significant decrease of enteric glial cells in both the submucous (P = 0.0006) and the myenteric (P < 0.0001) plexus. ICC were significantly increased in patients in the submucosal surface (P < 0.0001) and the myenteric area (P < 0.0001). Concerning estroprogestinic receptors, both were present on ICC in patients and controls. Estrogen receptors α and progesterone receptors were absent on enteric neurons and enteric glial cells in patients and controls, whereas estrogen receptors β were present in all controls and in 69% of patients' enteric neurons (P = 0.18) and in 12% of patients' glial cells (P = 0.0001).

CONCLUSIONS & INFERENCES

Patients with OD associated to rectal intussusception display abnormalities of the ENS and of estrogen receptors β.

Estrogen-dependent regulation of sodium/hydrogen exchanger-3 (NHE3) expression via estrogen receptor β in proximal colon of pregnant mice

Although constipation is very common during pregnancy, the exact mechanism is unknown. We hypothesized that the involvement of estrogen receptor (ER) in the regulation of electrolyte transporter in the colon leads to constipation. In this study, the intestines of normal female ICR mouse and pregnant mice were examined for the expression of ERα and ERβ by immunohistochemistry and in situ hybridization. ERβ, but not ERα, was expressed in surface epithelial cells of the proximal, but not distal, colon on pregnancy days 10, 15, and 18, but not day 5, and the number of ERβ-positive cells increased significantly during pregnancy. Expression of NHE3, the gene that harbors estrogen response element, examined by immunohistochemistry and western blotting, was localized in the surface epithelial cells of the proximal colon and increased in parallel with ERβ expression. In ovariectomized mice, NHE3 expression was only marginal and was up-regulated after treatment with 17β-estradiol (E(2)), but not E(2) + ICI 182,780 (estrogen receptor antagonist). Moreover, knock-down of ERβ expression by electroporetically transfected siRNA resulted in a significant reduction of NHE3 expression. These results indicate that ERβ regulates the expression of NHE3 in the proximal colon of pregnant mice through estrogen action, suggesting the involvement of increased sodium absorption by up-regulated NHE3 in constipation during pregnancy.

Estrogen regulation of duodenal bicarbonate secretion and sex-specific protection of human duodenum

BACKGROUND & AIMS

The reason that women have a lower prevalence of duodenal ulcer is not clear. We investigated whether estrogen regulates human duodenal bicarbonate secretion (DBS) and whether this process accounts for sex differences in the prevalence of duodenal ulcer.

METHODS

We performed an epidemiologic study to correlate duodenal ulcer prevalence with sex and age. Proximal DBS was measured from healthy subjects. Estrogen-receptor expression was examined in human duodenal mucosa by immunoblot and immunohistochemical analyses.

RESULTS

Among women, the prevalence of duodenal ulcer was significantly lower than among men. The reduced prevalence was greatest among premenopausal women (20-49 y), who were 3.91- to 5.09-fold less likely to develop duodenal ulcers than age-matched men; the difference was reduced to 1.32-fold or less among subjects aged 60 years or older. Premenopausal (20-29 y), but not postmenopausal (60-69 y), women had significantly higher basal and acid-stimulated DBS than the age-matched men. Basal and acid-stimulated DBS in premenopausal women (20-29 y) were significantly higher than in postmenopausal women (60-69 y), whereas there were no significant differences in basal or acid-stimulated DBS between men who were aged 20-29 years or 60-69 years. Serum levels of estradiol changed in parallel with basal and acid-stimulated DBS during the physiological menstrual cycle in premenopausal women. 17β-estradiol-stimulated DBS was independent of age or sex. Estrogen receptors α and β were detected on plasma membranes and in the cytosol of human duodenal epithelial cells.

CONCLUSIONS

Estrogen regulates human DBS, which could reduce the risk for duodenal ulcer in women and contribute to sex differences in the prevalence of duodenal ulcer.

Normal vitamin D and low free estradiol levels in women on enzyme-inducing antiepileptic drugs

Relationships between reproductive hormone levels, bone turnover marker levels, bone mineral density, and rates of bone loss were evaluated in premenopausal women with epilepsy taking enzyme-inducing antiepileptic drugs (EIAEDs: phenytoin or carbamazepine) or lamotrigine. Calciotropic and reproductive hormone levels, bone turnover marker levels, and bone mineral density were measured at baseline and 1 year. Bone mineral density did not differ between groups. Serum calcium (P<0.001) and estrone (P<0.001) levels were lower in the EIAED group. Sex hormone-binding globulin levels were higher (P<0.001) and percentage free estradiol levels were lower (P<0.001) in the EIAED group. We detected no relationship between bone mineral density change and calciotropic hormone or bone turnover marker levels. Women with higher sex hormone-binding globulin and lower free estradiol levels sustained more bone loss at the total hip (P=0.04 and P=0.02) and a trend toward more bone loss at the lumbar spine (P=0.07 and P=0.08). These findings suggest that lower estrogen levels may contribute to bone loss in premenopausal women with epilepsy.

Potential of an in vitro toolbox combined with exposure data as a first step for the risk assessment of dietary chemical contaminants

In vitro risk assessment of dietary contaminants has become a priority in human food safety. This paper proposes an in vitro approach associating different complementary tools in an original toolbox and aims to improve the assessment of the toxicological impact of dietary contaminants at realistic human exposure levels, with a special focus on the intestinal compartment. The system is based on the use of four complementary cellular tools, namely stress gene induction in transgenic strains of Escherichia coli, modulation of the activity of key biotransformation enzymes (cytochrome P-450 (CYP) 1A1 and 3A4) in a human intestinal cell line, and activation of aryl hydrocarbon receptor (AhR) and oestrogenic receptor (ER)-dependent genes in agonistic and antagonistic assays with luciferase reporter cells. It was applied to four chosen model molecules: ochratoxin A (OTA) and deoxynivalenol (DON), two common food-borne mycotoxins, and imazalil (IMA) and benomyl (BEN), two fungicides widely occurring in foodstuffs. All these assays were performed at or around a realistic intestinal concentration, determined through a deterministic approach based on the calculation of a theoretical maximum daily intake (TMDI). Using the four model molecules, it is clearly highlighted that induction of CYP1A1 activity and inhibition of CYP3A4 activity occurred in Caco-2 cells at a realistic intestinal concentration of IMA. Furthermore, some bacterial stress genes were induced in a range of realistic concentrations, following exposure to DON and IMA. In addition, BEN clearly provoked an ER agonistic activity in a human oestrogen sensitive reporter cell line. All these results are in accordance with the literature, suggesting that the in vitro toolbox constitutes an interesting approach in order to obtain a first 'fingerprint' of dietary contaminants at realistic human exposure for further risk assessment.

Estradiol-17beta and linseed meal interact to alter visceral organ mass and hormone concentrations from ovariectomized ewes

To evaluate the estrogenic potential of secoisolariciresinol diglycoside (SDG) found in linseed meal (LSM) on visceral organ mass, IGF-I, and thyroid hormone (T(3) and T(4)) concentrations, 48 multiparous, ovariectomized ewes (54.6 +/- 1.1 kg) were used in a 3 x 4 factorial arrangement. Main effects were length of LSM feeding (0, 1, 7, or 14 d) and length of exposure to estradiol-17beta (E(2)) implant (0, 6, or 24 h prior to tissue collection). Implanting ewes with E(2) for 24h increased liver mass relative to empty body weight (EBW; g/kg EBW) compared with ewes implanted for 0 or 6 h (P <or= 0.03), whereas feeding LSM for 14 d decreased liver mass compared with ewes fed LSM for 1 or 7 d (P <or= 0.02). There was an LSM x E(2) interaction (P = 0.01) for duodenal mass (g/kg EBW), LSM, and E(2) tended (P = 0.07) to influence the stomach complex mass; however, ileal mass was not affected. Neither LSM nor E(2) affected (P >or= 0.12) CYP2C or CYP3A mRNA expression or cellularity of the liver. Exogenous E(2) influenced circulating concentrations of IGF-I, T(3), and T(4). The estrogenic or anti-estrogenic potential of LSM is dependent upon the tissue, exposure to E(2), and the duration of LSM feeding. Feeding LSM during gestation, lactation, or during the grow-finish phase warrants further investigation.

Oestradiol decreases colonic permeability through oestrogen receptor beta-mediated up-regulation of occludin and junctional adhesion molecule-A in epithelial cells

Oestradiol modulates paracellular permeability and tight junction (TJ) function in endothelia and reproductive tissues, but whether the ovarian hormones and cycle affect the paracellular pathway in the intestinal epithelium remains unclear. Oestrogen receptors (ERs) are expressed in intestinal epithelial cells, and oestradiol regulates epithelium formation. We examined the effects of oestrous cycle stage, oestradiol benzoate (EB), and progesterone (P) on colonic paracellular permeability (CPP) in the female rat, and whether EB affects expression of the TJ proteins in the rat colon and the human colon cell line Caco-2. In cyclic rats, CPP was determined through lumen-to-blood (51)Cr-labelled EDTA clearance, and in Ussing chambers for dextran permeability. CPP was also examined in ovariectomized (OVX) rats treated with P or EB, with and without the ER antagonist ICI 182,780, or with the selective agonists for ER beta (propyl pyrazole triol; PPT) or ER beta (diarylpropionitrile; DPN). In oestrus rats, CPP was reduced (P < 0.01) relative to dioestrus. In OVX rats, EB dose-dependently decreased CPP, an effect mimicked by DPN and blocked by ICI 182,780, whereas P had no effect. Oestradiol increased occludin mRNA and protein in the colon (P < 0.05), but not zona occludens (ZO)-1. Further, EB and DPN enhanced occludin and junctional adhesion molecule (JAM)-A expression in Caco-2 cells without change in ZO-1, an effect blocked by ICI 182,780. These data show that oestrogen reinforces intestinal epithelial barrier through ER beta-mediated up-regulation of the transmembrane proteins occludin and JAM-A determining paracellular spaces. These findings highlight the importance of the ER beta pathway in the control of colonic paracellular transport and mucosal homeostasis.

(Xeno)estrogen regulation of food allergy

Food allergy and other types of allergies are becoming epidemic in both the developed and developing countries. A large amount of information is available in literature that (xeno)estrogens can regulate the immune response in general, and the development of allergy in particular; however, the effect of (xeno)estrogens on food allergy is basically unknown. With increasing use of xenobiotics worldwide, chemicals with estrogenic activity have been accumulating in our environment. This review has summarized the current literature relating to the topic (xeno)estrogen regulation of food allergy. The effect of (xeno)estrogens on enterocytes, proteases for protein hydrolysis, dendritic cells and T-regulatory cells in the gastrointestinal tract has been discussed. Finally, considering the current confusion in literature regarding the effect of phytoestrogen genistein on the immune system, a brief discussion has been included for its effect on T(H)1-T(H)2 polarization, and possibly food allergy in its relation to windows of exposure. Sufficient evidences exist to support the notion that (xeno)estrogens can regulate food allergy, with the developmental periods more sensitive. Further clinical and animal studies are needed to determine the causal relationship between the exposure of (xeno)estrogens and incidence of food allergy, and the underlying mechanisms.

Gender-specific protection of estrogen against gastric acid-induced duodenal injury: stimulation of duodenal mucosal bicarbonate secretion

Because human duodenal mucosal bicarbonate secretion (DMBS) protects duodenum against acid-peptic injury, we hypothesize that estrogen stimulates DMBS, thereby attributing to the clinically observed lower incidence of duodenal ulcer in premenopausal women than the age-matched men. We found that basal and acid-stimulated DMBS responses were 1.5 and 2.4-fold higher in female than male mice in vivo, respectively. Acid-stimulated DMBS in both genders was abolished by ICI 182,780 and tamoxifen. Estradiol-17beta (E2) and the selective estrogen receptor (ER) agonists of ERalpha [1,3,5-Tris(4-hydroxyphenyl)-4-propyl-1H-pyrazole] and ERbeta [2,3-bis(4-hydroxyphenyl) propionitrile], but not progesterone, rapidly stimulated ER-dependent murine DMBS in vivo. E2 dose dependently stimulated murine DMBS, which was attenuated by a Cl(-)/HCO3(-) anion exchanger inhibitor 4,4'-didsothio- cyanostilbene-2, 2'-disulfonic acid, removal of extracellular Cl(-), and in cystic fibrosis transmembrane conductance regulator knockout female mice. E2 stimulated murine DMBS in vitro in both genders with significantly greater response in female than male mice (female to male ratio = 4.3). ERalpha and ERbeta mRNAs and proteins were detected in murine duodenal epithelium of both genders; however, neither ERalpha nor ERbeta mRNA and protein expression levels differed according to gender. E2 rapidly mobilized intracellular calcium in a duodenal epithelial SCBN cell line that expresses ERalpha and ERbeta, whereas BAPTA-AM abolished E2-stimulated murine DMBS. Thus, our data show that E2 stimulates DMBS via ER dependent mechanisms linked to intracellular calcium, cystic fibrosis transmembrane conductance regulator, and Cl(-)/HCO3(-) anion exchanger. Gender-associated differences in basal, acid- and E2-stimulated DMBS may have offered a reasonable explanation for the clinically observed lower incidence of duodenal ulcer in premenopausal women than age-matched men.

Circulating hormones and estrous stage predict cellular and stromal remodeling in murine uterus

The understanding of how estrogen and progesterone (P4) drive uterine remodeling in rodents has largely been based on studies involving administration of exogenous hormones, using steroid receptor-deficient mice, or relying on vaginal smears. In all these cases, the actual serum levels of 17β-estradiol (E2) and P4are not directly measured, and the relationship between physiological levels of female sex hormones and uterine remodeling in cycling mice has not been fully explored. Here, we measured the circulating levels of E2and P4in cycling mice and performed correlation analysis between hormone levels and epithelial and stromal uterine parameters, irrespective of the estrous stage. In parallel, these parameters were analyzed in relation to the more conventional method of vaginal smear classification of estrous stage. We found that circulating P4inversely correlated with uterine width, luminal epithelial proliferation, stromal apoptosis, and degradation of luminal epithelial basement membrane collagen type-IV. Circulating E2positively correlated with uterine width, stromal cell proliferation, and collagen type-I content, while it negatively correlated with glandular epithelial proliferation, loss of collagen type-IV surrounding glandular epithelium, and apoptosis in luminal, glandular, and stromal compartments. Our findings indicate that measuring P4or E2levels can predict many concurrent cellular and stromal events in the mouse uterus, suggesting that in naturally cycling mice cellular responses to hormone changes are not delayed, but occur very rapidly.

Diethylstilbestrol increases the density of prolactin cells in male mouse pituitary by inducing proliferation of prolactin cells and transdifferentiation of gonadotropic cells

Diethylstilbestrol (DES) has been implicated in mammalian abnormalities. We examined the effects of DES on follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL) cells in the pituitaries of male mice treated with various doses of DES for 20 days. DES reduced the density of FSH and LH cells in a dose-dependent manner, but increased that of PRL cells. When the expression of estrogen receptor (ER) alpha and beta was assessed, an induction of ERbeta by DES was found predominantly in PRL cells. However, since these effects were abolished in ERalpha knockout mice, DES appears to act primarily through ERalpha. When the expression of Ki-67 and Pit-1 in PRL cells was examined at various time-points after DES treatment, some PRL cells became Ki-67 positive at 10-15 days, and Pit-1-positive cells were increased at 5-15 days. Furthermore, some FSH and LH cells became Pit-1 positive, and co-localized with PRL at 5-10 days. Our results indicate that DES increases PRL cells by inducing proliferation of PRL cells and transdifferentiation of FSH/LH cells to PRL cells.

Molecular Characterization of Estrogen Receptors 1, 2a, and 2b and Their Tissue and Ontogenic Expression Profiles in Fathead Minnow (Pimephales promelas)1

There are two estrogen receptor (ER) subtypes in fish, Esr1 and Esr2 (formerly ERalpha and ERbeta), and in some species the Esr2 subtype has two forms, Esr2b (formerly ERbeta1) and Esr2a (formerly ERbeta2 or ERgamma). There is little information, however, on the different characteristics and functional significance of the two receptor subtypes in fish, and this is especially relevant for understanding the disruption of ER signaling by chemicals with estrogenic activity. In this study, the full-length cDNAs for esr1 (3167 base pairs [bp]) and esr2b (2318 bp), and a partial-length (267 bp) cDNA for esr2a, were cloned and characterized in fathead minnow (fhm; Pimephales promelas), and their patterns of expression established during development and in adults. Real-time polymerase chain reaction revealed some clear distinctions in the ontogenic and tissue expression of fhm esr1, esr2b, and esr2a, suggesting different functions for each ER subtype. Fhm ERs were expressed in brain, pituitary, liver, gonad, intestine, and gill of male and female fish, esr2b and esr2a were also expressed in muscle. Fhm esr1 and esr2b were expressed predominantly in the liver, whereas fhm esr2a was expressed predominantly in intestine and was lowest expressed in liver. Responses of the different hepatic ERs in male fathead minnow exposed to 100 ng estradiol/L differed, with a significant induction (5-fold) of fhm esr1 but no effect on esr2b or esr2a expression, suggesting different mechanisms of regulation for the different ERs. The detailed characterization of ERs in fathead minnow provides the foundation for understanding the molecular basis of estrogenic disruption in fish.

Induction of cell death in rat small intestine by ischemia reperfusion: differential roles of Fas/Fas ligand and Bcl-2/Bax systems depending upon cell types

Although ischemia reperfusion (I/R) induces apoptotic damage of mammalian small intestine, the molecular mechanism is largely unknown. We investigated the appearance of apoptosis at various time-points (0-24 h) of reperfusion after 1-h ischemia and the expression of various apoptosis-related proteins, such as Bcl-2, Bax, Fas, Fas ligand (FasL), activated caspase-3, and cytochrome c, immunohistochemically in rat small intestine. As assessed by TUNEL and electron microscopy, apoptotic cells were increased at 3 h of reperfusion in all intestinal parts (villous epithelium, crypt epithelium, and stroma of intestine). Moreover, the TUNEL-positive cells in the stroma were later identified as T cells. The expression of Fas and FasL as well as activated caspase-3 was markedly increased at 3 h of reperfusion in the stroma. In the villous epithelium, a transient decrease in Bcl-2 expression was found while in the crypt epithelium, Fas expression was induced. Finally, intraperitoneal injection of leupeptin (an SH-protease inhibitor) after I/R resulted in a significant inhibition of the induction of apoptosis in the stroma and crypt epithelium. Our results indicate that the triggering molecules of apoptosis in the I/R rat small intestine may vary depending on cell type and that the use of a broad-spectrum protease inhibitor may reduce intestinal damage.

News and views in Histochemistry and Cell Biology

Advances in histochemical methodology and ingenious applications of novel and improved methods continue to confirm the standing of morphological means and approaches in research efforts, and contribute significantly to increasing our knowledge about structures and functions in all areas of the life sciences from cell biology to pathology. Reports published during recent months documenting this progress are summarized in the present review.