Neonatal maternal separation of rat pups results in abnormal cholinergic regulation of epithelial permeability

Early life adversity in piglets induces long-term upregulation of the enteric cholinergic nervous system and heightened, sex-specific secretomotor neuron responses

BACKGROUND

Early life adversity (ELA) is a risk factor for the later-life onset of gastrointestinal (GI) diseases such as irritable bowel syndrome (IBS); however, the mechanisms are poorly understood. Here, we utilized a porcine model of ELA, early weaning stress (EWS), to investigate the influence of ELA on the development and function of the enteric nervous system (ENS).

METHODS

Female and castrated male (Male-C) piglets were weaned from their sow either at 15 days of age (EWS) or 28 days of age (late weaning control, LWC). At 60 and 170 days of age, ileal mucosa-submucosa preparations were mounted in Ussing chambers and veratridine- and corticotropin releasing factor (CRF)-releasing factor-evoked short circuit current (Isc ) responses were recorded as indices of secretomotor neuron function. Enteric neuron numbers and the expression of select neurotransmitters and their receptors were also measured.

KEY RESULTS

Compared with LWC pigs, female, but not Male-C EWS, pigs exhibited heightened veratridine-induced Isc responses at 60 and 170 days of age that were inhibited with tetrodotoxin and atropine. Ileum from EWS pigs had higher numbers of enteric neurons that were choline acetyltransferase positive. Markers of increased cholinergic signaling (increased acetylcholinesterase) and downregulated mucosal muscarinic receptor 3 gene expression were also observed in EWS pigs.

CONCLUSIONS & INFERENCES

This study demonstrated that EWS in pigs induces lasting and sex-specific hypersensitivity of secretomotor neuron function and upregulation of the cholinergic ENS. These findings may represent a mechanistic link between ELA and lifelong susceptibility to GI diseases such as IBS.

Disturbance in the Mucosa-Associated Commensal Bacteria Is Associated with the Exacerbation of Chronic Colitis by Repeated Psychological Stress; Is That the New Target of Probiotics?

Psychological stress can exacerbate inflammatory bowel disease. However, the mechanisms underlying how psychological stress affects gut inflammation remain unclear. Here, we focused on the relationship between changes in the microbial community of mucosa-associated commensal bacteria (MACB) and mucosal immune responses induced by chronic psychological stress in a murine model of ulcerative colitis. Furthermore, we examined the effect of probiotic treatment on exacerbated colitis and MACB composition changes induced by chronic psychological stress. Repeated water avoidance stress (rWAS) in B6-Tcra-/- mice severely exacerbated colitis, which was evaluated by both colorectal tissue weight and histological score of colitis. rWAS treatment increased mRNA expression of UCN2 and IFN-γ in large intestinal lamina propria mononuclear cells (LI-LPMC). Interestingly, exacerbated colitis was associated with changes in the microbial community of MACB, specifically loss of bacterial species diversity and an increase in the component ratio of Clostridium, revealed by 16S rRNA gene amplicon analysis. Finally, the oral administration of a probiotic Lactobacillus strain was protective against the exacerbation of colitis and was associated with a change in the bacterial community of MACB in rWAS-exposed Tcra-/- mice. Taken together, these results suggested that loss of species diversity in MACB might play a key role in exacerbated colitis induced by chronic psychological stress. In addition, probiotic treatment may be used as a tool to preserve the diversity of bacterial species in MACB and alleviate gut inflammation induced by psychological stress.

Sex-related differences in pain behaviors following three early life stress paradigms

Background

Early life stress (ELS) serves as a risk factor for the development of functional pain disorders such as irritable bowel syndrome (IBS) in adults. Although rodent models have been developed to mimic different forms of ELS experience, the use of predominantly male animals across various rodent strains has led to a paucity of information regarding sex-related differences in the persistent effects of ELS on pain behaviors in adulthood. We hypothesized that the context or nature of ELS experience may interact with sex differences to influence the development of chronic pain.

Methods

We employed three rodent models mimicking different facets of early life adversity to investigate the effects of ELS on pain perception in adulthood. To eliminate strain differences, all experiments were carried out using Long Evans rats. As neonates, male and female rat pups were exposed to maternal separation (MS), limited nesting (LN), or odor attachment learning (OAL). In adulthood, visceral sensitivity and somatic sensitivity were assessed at ~postnatal day 90 via quantification of visceromotor responses to colorectal distension and von Frey probing, respectively.

Results

Following exposure to MS or LN, male rats developed visceral and somatic hypersensitivity compared to controls, whereas females subjected to the same paradigms were normosensitive. In the OAL model, females exposed to unpredictable ELS exhibited visceral but not somatic hypersensitivity. There were no observed differences in visceral or somatic sensitivity in male animals following OAL exposure.

Conclusions

In summary, our data confirms that early adverse experiences in the form of MS, LN, and OAL contribute to the long-term development of heightened pain responsiveness in adulthood. Furthermore, this study indicates that sex-related vulnerability or resilience for the development of heightened pain perception is directly associated with the context or nature of the ELS experienced.

Fecal Incontinence in Adolescents Is Associated With Child Abuse, Somatization, and Poor Health-related Quality of Life

BACKGROUND

The aim of this study was to evaluate the association between fecal incontinence (FI), child abuse, somatization, and health-related quality of life (HRQoL) in adolescents.

METHODS

Adolescents (ages 13-18 years) were selected from 4 semi-urban schools in the Gampaha district, Sri Lanka. A validated, self-administered questionnaire was used for data collection. FI was defined as at least 1 episode of leakage of feces per month.

RESULTS

A total of 1807 adolescents were analyzed (boys 973 [53.8%], mean age 14.4 years, standard deviation [SD] 1.4 years). A total of 47 (2.6%) had FI. Prevalence of sexual abuse (17% vs 2.3% in controls, P < 0.0001), emotional abuse (40.4% vs 22.7%, P < 0.0001), and physical abuse (51% vs 24.3%, P < 0.0001) was significantly higher in children with FI. Adolescents with FI had higher mean somatization scores [mean 20.1, (SD 14.5) vs mean 9.3, (SD 9.2)] compared with those without FI (P < 0.0001). Those with FI also had lower HRQoL scores for physical functioning, social functioning, emotional functioning domains, and performances at school, together with a lower overall HRQoL score compared with those without FI (74.6 vs 87.1, P < 0.0001).

CONCLUSIONS

There is a significant association between FI and physical, sexual, and emotional abuse. They also have a higher somatization score and a poor HRQoL score in physical, emotional, social, and school functioning domains compared with those without FI.

Stress and the Microbiota-Gut-Brain Axis in Visceral Pain: Relevance to Irritable Bowel Syndrome

Visceral pain is a global term used to describe pain originating from the internal organs of the body, which affects a significant proportion of the population and is a common feature of functional gastrointestinal disorders (FGIDs) such as irritable bowel syndrome (IBS). While IBS is multifactorial, with no single etiology to completely explain the disorder, many patients also experience comorbid behavioral disorders, such as anxiety or depression; thus, IBS is described as a disorder of the gut-brain axis. Stress is implicated in the development and exacerbation of visceral pain disorders. Chronic stress can modify central pain circuitry, as well as change motility and permeability throughout the gastrointestinal (GI) tract. More recently, the role of the gut microbiota in the bidirectional communication along the gut-brain axis, and subsequent changes in behavior, has emerged. Thus, stress and the gut microbiota can interact through complementary or opposing factors to influence visceral nociceptive behaviors. This review will highlight the evidence by which stress and the gut microbiota interact in the regulation of visceral nociception. We will focus on the influence of stress on the microbiota and the mechanisms by which microbiota can affect the stress response and behavioral outcomes with an emphasis on visceral pain.

Gut microbiota regulates key modulators of social behavior

Social behavior plays a pivotal role in the mental well-being of an individual. Continuous efforts in the past have led to advancements in the area of how the brain regulates emotion and cognition, while the understanding of human social behavior still remains eluded. A major breakthrough in understanding the etiology of neurological disorders is the recent insight on the role of the gut microbiota (GM). Human GM also referred to as the "forgotten organ" is home to 10(13-14) microorganisms, which is 10 times the number of cells present in the human body. In addition, the gut microbiome (total genome of GM) is 150 times greater as compared to the human genome. An emerging concept gaining worldwide focus and acceptance is that, this much big genome can potentially control human behavior and other biological functions. Herein we hypothesize on the basis of GM's ability to modify brain and behavior and that it can directly or indirectly control social behavior. This review focuses on the association of GM with various domains of social behavior like stress, cognition and anxiety.

Early-life stress origins of gastrointestinal disease: animal models, intestinal pathophysiology, and translational implications

Early-life stress and adversity are major risk factors in the onset and severity of gastrointestinal (GI) disease in humans later in life. The mechanisms by which early-life stress leads to increased GI disease susceptibility in adult life remain poorly understood. Animal models of early-life stress have provided a foundation from which to gain a more fundamental understanding of this important GI disease paradigm. This review focuses on animal models of early-life stress-induced GI disease, with a specific emphasis on translational aspects of each model to specific human GI disease states. Early postnatal development of major GI systems and the consequences of stress on their development are discussed in detail. Relevant translational differences between species and models are highlighted.

Gut Microbiome: What We Do and Don't Know

Within the last decade, research regarding the human gut microbiome has exploded. While the gastrointestinal tract was once regarded simply as a digestive organ, new technologies have led the science world to wonder about the impact that the gut microbiota may have on human health and disease. The gut microbiome is now becoming known for its role in metabolism, immune defense, and behavior. From in utero variations to those that rapidly occur post partum, our gut microbiome changes with age, environment, stress, diet, and health status as well as medication exposure. This article reviews what is currently known regarding various influences on the gut microbiome and is meant to encourage the reader to further explore the unknown.

Childhood abuse history is associated with the development of dyspepsia: a population-based survey in Japan

BACKGROUND

Functional dyspepsia (FD) is a heterogeneous disorder, and it is not clear whether childhood abuse influences the severity of dyspeptic symptoms and the type of dyspepsia. Accordingly, we administered a questionnaire survey to evaluate the association of abuse history in the development of dyspepsia.

METHODS

Study subjects were selected from among a panel of volunteers, to make equal distribution of age, sex, and residential area. A Web-based questionnaire was administered to uninvestigated dyspepsia subjects who had obtained a consultation at a medical institute, dyspepsia subjects who had not, and healthy control subjects. Dyspepsia was categorized into epigastric pain syndrome (EPS) and postprandial distress syndrome (PDS) using the Rome III adult FGID questionnaire. Physical, sexual, and psychological abuse history and severity of dyspeptic symptoms were assessed by a questionnaire.

RESULTS

Each type of abuse was significantly prevalent in uninvestigated dyspepsia subjects. Childhood abuse history was significantly prevalent in dyspepsia. However, these abuse histories were not associated with consultation behavior. Childhood abuse was more prevalent in subjects with dyspepsia and in females. Severity of dyspeptic symptoms was significantly greater in dyspepsia subjects with a history of abuse. Childhood abuse was more prevalent in dyspepsia subjects with the overlap of EPS and PDS and in those who also had irritable bowel syndrome (IBS).

CONCLUSIONS

Childhood abuse history was associated with the development of dyspepsia especially in the overlapping diagnoses of EPS and PDS, and overlapping with IBS but not with consultation behavior. Abuse history should be assessed in the care of patients with dyspepsia.

Inhibitory effect of TongXie-YaoFang formula on colonic contraction in rats

AIM: To investigate the pharmacological effect of TongXie-YaoFang (TXYF) formula and its underlying mechanisms.

METHODS: A neonatal maternal separation plus restraint stress (NMS + RS) model of diarrhea-predominant irritable bowel syndrome was developed by subjecting male Sprague-Dawley rats to daily maternal separation from postnatal days 2 to 21 plus restraint stress from days 50 to 59. Rats were randomly divided into two groups (NMS + RS and TXYF formula), and rats with no handling or separation were used as normal controls. Starting from postnatal day 60, rats were administered TXYF formula (9.84 g/100 g body weight) orally twice daily for 14 consecutive days, while the normal and NMS + RS groups were given distilled water. The distinctions of movement index (MI, area under the curve of contraction intensity/min, mg/min) and contraction frequency (CF, number of contractions/min, times/min) of isolated colonic longitudinal smooth muscle strips (CLSMs) in the three groups before and after treatment were observed with a Power Lab system. Different inhibitors were applied, and then 10^-4 mol/L acetylcholine chloride (Ach) was added to CLSMs to induce muscle contraction.

RESULTS: Before treatment, the MI of CLSMs in the NMS + RS and TXYF formula groups was similar and both higher than that in the normal group (545.49 ± 73.66 mg/min vs 245.76 ± 34.44 mg/min and 551.09 ± 54.29 mg/min vs 245.76 ± 34.44 mg/min, P < 0.01, respectively). After treatment, the MI in the TXYF formula group was lower than that in the NMS + RS group (261.39 ± 38.59 mg/min vs 533.9 ± 61.63 mg/min, P < 0.01). In the same way, the CF of CLSMs in the NMS + RS and TXYF formula groups was similar and both higher than that in the normal group (3.42 ± 0.25 times/min and 3.31 ± 0.21 vs 1.1 ± 0.17 times/min, P < 0.01) before treatment. After treatment, the CF in the TXYF formula group was lower than that in the NMS + RS group (1.42 ± 0.87 times/min vs 3.11 ± 0.82 times/min, P < 0.01) and similar to that in the normal group (1.42 ± 0.87 times/min vs 1.09 ± 0.13 times/min). When 8-(N,N-diethylamino)octyl 3,4,5-trimethoxybenzoate hydrochloride and 4-aminopyridine were added to the bath and equilibrated for 30 min, respectively, and 10^-4 mol/L Ach was added to CLSMs to induce muscle contraction, MI of the CLSMs in the TXYF formula group was lower than that in the normal group (666 ± 36.32 mg/min vs 747.77 ± 49.47 mg/min, and 686.53 ± 39.17 mg/min vs 750.45 ± 29.39 mg/min; P < 0.01, respectively). The MI of CLSMs in the TXYF formula group was lower than that in the normal group after treatment with nifedipine (689.48 ± 30.84 mg/min vs 741.65 ± 32.41 mg/min; P < 0.05).

CONCLUSION: TXYF formula inhibits colon contraction in rats. This may be related to activation of specific potassium channels and inhibition of extracellular calcium internal flow.

Childhood functional abdominal pain: mechanisms and management

Chronic abdominal pain is one of the most common clinical syndromes encountered in day to day clinical paediatric practice. Although common, its definition is confusing, predisposing factors are poorly understood and the pathophysiological mechanisms are not clear. The prevailing viewpoint in the pathogenesis involves the inter-relationship between changes in hypersensitivity and altered motility, to which several risk factors have been linked. Making a diagnosis of functional abdominal pain can be a challenge, as it is unclear which further diagnostic tests are necessary to exclude an organic cause. Moreover, large, well-performed, high-quality clinical trials for effective agents are lacking, which undermines evidence-based treatment. This Review summarizes current knowledge regarding the epidemiology, pathophysiology, risk factors and diagnostic work-up of functional abdominal pain. Finally, management options for children with functional abdominal pain are discussed including medications, dietary interventions, probiotics and psychological and complementary therapies, to improve understanding and to maximize the quality of care for children with this condition.

Role of Corticotropin-releasing Factor in Gastrointestinal Permeability

The interface between the intestinal lumen and the mucosa is the location where the majority of ingested immunogenic particles face the scrutiny of the vast gastrointestinal immune system. Upon regular physiological conditions, the intestinal micro-flora and the epithelial barrier are well prepared to process daily a huge amount of food-derived antigens and non-immunogenic particles. Similarly, they are ready to prevent environmental toxins and microbial antigens to penetrate further and interact with the mucosal-associated immune system. These functions promote the development of proper immune responses and oral tolerance and prevent disease and inflammation. Brain-gut axis structures participate in the processing and execution of response signals to external and internal stimuli. The brain-gut axis integrates local and distant regulatory networks and super-systems that serve key housekeeping physiological functions including the balanced functioning of the intestinal barrier. Disturbance of the brain-gut axis may induce intestinal barrier dysfunction, increasing the risk of uncontrolled immunological reactions, which may indeed trigger transient mucosal inflammation and gut disease. There is a large body of evidence indicating that stress, through the brain-gut axis, may cause intestinal barrier dysfunction, mainly via the systemic and peripheral release of corticotropin-releasing factor. In this review, we describe the role of stress and corticotropin-releasing factor in the regulation of gastrointestinal permeability, and discuss the link to both health and pathological conditions.

Early-life stress selectively affects gastrointestinal but not behavioral responses in a genetic model of brain-gut axis dysfunction

BACKGROUND

Early-life stress and a genetic predisposition to display an anxiety- and depressive-like phenotype are associated with behavioral and gastrointestinal (GI) dysfunction. Animals exposed to early-life stress, and those genetically predisposed to display anxiety or depressive behaviors, have proven useful tools in which to study stress-related GI disorders, such as irritable bowel syndrome (IBS). IBS is a heterogeneous disorder, and likely a consequence of both genetic and environmental factors. However, the combined effects of early-life stress and a genetic predisposition to display anxiety- and depression-like behaviors on GI function have not been investigated.

METHODS

We assessed the effect of maternal separation (MS) on behavioral and GI responses in WKY animals relative to a normo-anxious reference strain.

KEY RESULTS

Both non-separated (NS) WKY and WKY-MS animals displayed anxiety-like responses in the open-field test and depressive-like behaviors in the forced swim test relative to Sprague-Dawley rats. However, MS had no further influence on anxiety- and depressive-like behaviors exhibited by this stress-prone rat strain. Similarly, corticosterone levels measured after the OFT were insensitive to MS in WKY animals. However, WKY-MS displayed significantly increased colonic visceral hypersensitivity, fecal output, and altered colonic cholinergic sensitivity.

CONCLUSIONS & INFERENCES

Our data suggest that early-life stress, on the background of a genetic predisposition to display an anxiety- and depressive-like phenotype, selectively influences GI function rather than stress-related behaviors. Thus, our findings highlight the importance of genetic predisposition on the outcome of early-life adversity on GI function.

Cigarette smoking is associated with intestinal barrier dysfunction in the small intestine but not in the large intestine of mice

AIMS

To observe the effect of cigarette smoke (CS) on the small bowel and colon in mice and to attempt to explain the potential mechanisms that account for these effects.

METHODS

Male BALB/c mice age 6-8 weeks were randomly divided into a CS group and a control group (n=10 per group). CS mice were exposed to CS (five cigarettes each time, four times a day for 5 days a week using Hamburg II smoking machine and CS was diluted with air at a ratio of 1:6) for 10 weeks, and control mice were exposed to room air. After 10 weeks, mice were sacrificed for analysis (colon and small bowel).

RESULTS

CS exposure impaired the intestinal barrier of the small bowel, based on evidence that CS mice exhibited increased intestinal permeability, bacterial translocation, intestinal villi atrophy, damaged tight junctions and abnormal tight junction proteins. These changes were partly mediated through the activated NF-κB (p65) signalling pathway. However, no obvious changes associated with the intestinal barrier were identified in the small bowel of control mice or the colons of control or CS mice.

CONCLUSIONS

CS is associated with intestinal barrier dysfunction in the small intestine but not in the large intestine of mice.

Early maternal separation induces alterations of colonic epithelial permeability and morphology

BACKGROUND

Early maternal separation could lead to significant intestinal barrier and epithelial dysfunction. However, the exact mechanism remains to be elucidated and need to be investigated.

METHODS

Neonatal C57BL/6 mice were subjected to maternal separation: Maternal separation (MS) daily 3 h between postnatal day (PND) 5-9, single separation (SS) 3 h on PND 9 and no separation (NS). Colon and ileum permeability was measured by Ussing chamber. Severity of morphological changes in the colon was evaluated by blinded grading of histological stained sections.

RESULTS

Trans-epithelial resistance of colon and ileum did not change indicating that the tissues remained intact during the course of the experiment. Permeability of trans-cellular tracer Horseradish peroxidase (HRP) was significantly increased in the colon of MS compared to SS and NS (p < 0.05 for SS and p < 0.001 for NS), but there was no difference in para-cellular permeability of fluorescein isothiocyanate-conjugated dextran (FD4). However, there was no change in permeability of both HRP and FD4 in the ileum. MS and SS groups had marked intestinal epithelium morphology changes in comparison to controls (p < 0.05).

CONCLUSION

These preliminary observations indicate that neonatal maternal separation increases colonic trans-cellular permeability. This increase may be caused by the change of the transmural colonic morphology. The underlying mechanism is unknown and further investigation is necessary as it is of relevance to the development of early intestinal diseases such as necrotizing enterocolitis.

The microbiota-gut-brain axis in gastrointestinal disorders: stressed bugs, stressed brain or both?

The gut-brain axis is the bidirectional communication between the gut and the brain, which occurs through multiple pathways that include hormonal, neural and immune mediators. The signals along this axis can originate in the gut, the brain or both, with the objective of maintaining normal gut function and appropriate behaviour. In recent years, the study of gut microbiota has become one of the most important areas in biomedical research. Attention has focused on the role of gut microbiota in determining normal gut physiology and immunity and, more recently, on its role as modulator of host behaviour ('microbiota-gut-brain axis'). We therefore review the literature on the role of gut microbiota in gut homeostasis and link it with mechanisms that could influence behaviour. We discuss the association of dysbiosis with disease, with particular focus on functional bowel disorders and their relationship to psychological stress. This is of particular interest because exposure to stressors has long been known to increase susceptibility to and severity of gastrointestinal diseases.

Glutamine and intestinal barrier function

The intestinal barrier integrity is essential for the absorption of nutrients and health in humans and animals. Dysfunction of the mucosal barrier is associated with increased gut permeability and development of multiple gastrointestinal diseases. Recent studies highlighted a critical role for glutamine, which had been traditionally considered as a nutritionally non-essential amino acid, in activating the mammalian target of rapamycin cell signaling in enterocytes. In addition, glutamine has been reported to enhance intestinal and whole-body growth, to promote enterocyte proliferation and survival, and to regulate intestinal barrier function in injury, infection, weaning stress, and other catabolic conditions. Mechanistically, these effects were mediated by maintaining the intracellular redox status and regulating expression of genes associated with various signaling pathways. Furthermore, glutamine stimulates growth of the small intestinal mucosa in young animals and also enhances ion transport by the gut in neonates and adults. Growing evidence supports the notion that glutamine is a nutritionally essential amino acid for neonates and a conditionally essential amino acid for adults. Thus, as a functional amino acid with multiple key physiological roles, glutamine holds great promise in protecting the gut from atrophy and injury under various stress conditions in mammals and other animals.

Spinal toll-like receptor 4-mediated signalling pathway contributes to visceral hypersensitivity induced by neonatal colonic irritation in rats

BACKGROUND

Although visceral hypersensitivity is a major pathophysiological feature of irritable bowel syndrome (IBS), its underlying mechanisms remain elusive. Toll-like receptor 4 (TLR4) is a critical pattern recognition molecule of the innate immune system. In this study, we investigated whether the TLR4/myeloid differentiation factor 88 (MyD88)/nuclear factor-kappa B (NF-κB) signalling pathway in the spinal cord contributed to the visceral hypersensitivity induced by neonatal colonic irritation (CI) in rats.

METHODS

The Sprague-Dawley rat model of IBS was induced by colon irritation on post-natal day (PND) 8, PND10 and PND12. Experiments were conducted in adult rats. TLR4 mRNA and protein, and its downstream signalling molecules, MyD88, inhibitory nuclear factor-kappa B (IκB) and NF-κB protein expressions in L2-S4 spinal segments were detected by quantitative real-time reverse transcription-polymerase chain reaction as well as Western blotting. TLR4 co-localization was determined by immunohistochemistry. Levels of tumour necrosis factor-alpha (TNF-α) and interleukin 1β (IL-1β) were measured with enzyme-linked immunosorbent assay.

RESULTS

We found that neonatal CI treatment induced long-lasting visceral hypersensitivity without identifiable structural abnormalities in descending colons of adult rats. Neonatal CI treatment evoked a significant up-regulation of the expressions of TLR4 in glia, MyD88, p-IκB-α and NF-κB in adult rats. Neonatal CI treatment also increased the levels of its downstream inflammatory agents TNF-α and IL-1β in the L2-S4 regions of the spinal cord of adult rats.

CONCLUSIONS

These results suggest that neonatal CI stimulates the production of IL-1β and TNF-α through the TLR4/MyD88/NF-κB signalling pathway in the spinal cord, which contributed to visceral hypersensitivity induced by neonatal CI in rats.

The microbiota-gut-brain axis in functional gastrointestinal disorders

Functional gastrointestinal disorders (FGIDs) are highly prevalent and pose a significant burden on health care and society, and impact patients' quality of life. FGIDs comprise a heterogeneous group of disorders, with unclear underlying pathophysiology. They are considered to result from the interaction of altered gut physiology and psychological factors via the gut-brain axis, where brain and gut symptoms are reciprocally influencing each other's expression. Intestinal microbiota, as a part of the gut-brain axis, plays a central role in FGIDs. Patients with Irritable Bowel Syndrome, a prototype of FGIDs, display altered composition of the gut microbiota compared with healthy controls and benefit, at the gastrointestinal and psychological levels, from the use of probiotics and antibiotics. This review aims to recapitulate the available literature on FGIDs and microbiota-gut-brain axis.

Characterisation of faecal protease activity in irritable bowel syndrome with diarrhoea: origin and effect of gut transit

OBJECTIVES

Faecal serine proteases (FSPs) may play a role in irritable bowel syndrome with diarrhoea (IBS-D), but their origin is unclear. We aimed to structurally characterise them and define the impact of colonic cleansing and transit time.

DESIGN

Faecal samples were obtained from 30 healthy volunteers (HV) and 79 patients with IBS-D participating in a trial of ondansetron versus placebo. Colonic transit was measured using radio-opaque markers. Samples were also obtained from 24 HV before and after colonic cleansing with the osmotic laxative MoviPrep. FSPs were purified from faecal extracts using benzamidine-Sepharose affinity chromatography. SDS-PAGE profiled components were identified using trypsinolysis and tandem mass spectrometry. Functional protease activity in faecal extracts was measured using a colorimetric assay based on the proteolysis of azo-casein.

RESULTS

Protein analysis identified the most abundant FSPs as being of human origin and probably derived from pancreatic juice. Functional assays showed increased faecal protease (FP) and amylase in patients with IBS-D compared with HV. Those with higher amylase had significantly higher FP and greater anxiety. FP activity correlated negatively with whole gut transit in patients with IBS-D (Spearman r=-0.32, p=0.005) and HV (r=-0.55, p=0.014). Colon cleansing caused a significant rise in FP activity in HV from a baseline of median (IQR) 253 (140-426) to 1031 (435-2296), levels similar to those seen in patients with IBS-D. FSP activity correlated positively with days/week with urgency.

CONCLUSIONS

The most abundant FSPs are of human origin. Rapid transit through the colon and/or decreased (possibly bacterial) proteolytic degradation increases their faecal concentration and could contribute to visceral hypersensitivity in patients with IBS-D.

CLINICALTRIALSGOV

NCT00745004.

Association between child maltreatment and constipation: a school-based survey using Rome III criteria

OBJECTIVE

Child abuse leads to multiple physical and psychosomatic sequelae. The aim of the present study was to evaluate the association between child abuse and constipation among schoolchildren.

METHODS

Children 13 to 18 years of age were selected from 4 semiurban schools in Gampaha District, Sri Lanka. A self-administered questionnaire was used for data collection. Information regarding sociodemographic factors and gastrointestinal symptoms, child abuse, and somatisation were collected. Constipation was diagnosed using Rome III criteria.

RESULTS

A total of 1792 children were included in the analysis (boys 975 [54.4%], mean age 14.4 years, standard deviation [SD] 1.3 years). One hundred thirty-eight (7.7%) fulfilled Rome III criteria for constipation. The number of children exposed to physical, emotional, and sexual abuse were, respectively, 438 (24.4%), 396 (22.1%), and 51 (2.8%). The prevalence of constipation was significantly higher in those exposed to sexual (5.8% vs 2.6% P = 0.03), emotional (40.9% vs 20.8%, P < 0.0001), and physical abuse (41.6% vs 23.2%, P < 0.0001). Mean somatisation score was higher in the total group of abused children with constipation (mean 18.6, SD 12.5) compared with those without (mean 13.9, SD 12.3; P = 0.027). Children with a history of abuse did not seek health care more often than children without this history. Patient-perceived severity of bowel symptoms was higher in children with physical abuse (23.7 vs 19.7 P = 0.001) and emotional abuse (25.4 vs 19.3 P < 0.0001).

CONCLUSIONS

Childhood constipation shows a significant association with physical, sexual, and emotional abuse. Children with constipation complain of more somatic symptoms and bowel symptoms when they are exposed to abuse.

Reprint of: Role of enteric neurotransmission in host defense and protection of the gastrointestinal tract

Host defense is a vital role played by the gastrointestinal tract. As host to an enormous and diverse microbiome, the gut has evolved an elaborate array of chemical and physicals barriers that allow the digestion and absorption of nutrients without compromising the mammalian host. The control of such barrier functions requires the integration of neural, humoral, paracrine and immune signaling, involving redundant and overlapping mechanisms to ensure, under most circumstances, the integrity of the gastrointestinal epithelial barrier. Here we focus on selected recent developments in the autonomic neural control of host defense functions used in the protection of the gut from luminal agents, and discuss how the microbiota may potentially play a role in enteric neurotransmission. Key recent findings include: the important role played by subepithelial enteric glia in modulating intestinal barrier function, identification of stress-induced mechanisms evoking barrier breakdown, neural regulation of epithelial cell proliferation, the role of afferent and efferent vagal pathways in regulating barrier function, direct evidence for bacterial communication to the enteric nervous system, and microbial sources of enteric neurotransmitters. We discuss these new and interesting developments in our understanding of the role of the autonomic nervous system in gastrointestinal host defense.

Differential activation of the prefrontal cortex and amygdala following psychological stress and colorectal distension in the maternally separated rat

Visceral hypersensitivity is a hallmark of many clinical conditions and remains an ongoing medical challenge. Although the central neural mechanisms that regulate visceral hypersensitivity are incompletely understood, it has been suggested that stress and anxiety often act as initiating or exacerbating factors. Dysfunctional corticolimbic structures have been implicated in disorders of visceral hypersensitivity such as irritable bowel syndrome (IBS). Moreover, the pattern of altered physiological responses to psychological and visceral stressors reported in IBS patients is also observed in the maternally separated (MS) rat model of IBS. However, the relative contribution of various divisions within the cortex to the altered stress responsivity of MS rats remains unknown. The aim of this study was to analyze the cellular activation pattern of the prefrontal cortex and amygdala in response to an acute psychological stressor (open field) and colorectal distension (CRD) using c-fos immunohistochemistry. Several corticoamygdalar structures were analyzed for the presence of c-fos-positive immunoreactivity including the prelimbic cortex, infralimbic cortex, the anterior cingulate cortex (both rostral and caudal) and the amygdala. Our data demonstrate distinct activation patterns within these corticoamygdalar regions including differential activation in basolateral versus central amygdala following exposure to CRD but not the open field stress. The identification of this neuronal activation pattern may provide further insight into the neurochemical pathways through which therapeutic strategies for IBS could be derived.

Role of enteric neurotransmission in host defense and protection of the gastrointestinal tract

Host defense is a vital role played by the gastrointestinal tract. As host to an enormous and diverse microbiome, the gut has evolved an elaborate array of chemical and physicals barriers that allow the digestion and absorption of nutrients without compromising the mammalian host. The control of such barrier functions requires the integration of neural, humoral, paracrine and immune signaling, involving redundant and overlapping mechanisms to ensure, under most circumstances, the integrity of the gastrointestinal epithelial barrier. Here we focus on selected recent developments in the autonomic neural control of host defense functions used in the protection of the gut from luminal agents, and discuss how the microbiota may potentially play a role in enteric neurotransmission. Key recent findings include: the important role played by subepithelial enteric glia in modulating intestinal barrier function, identification of stress-induced mechanisms evoking barrier breakdown, neural regulation of epithelial cell proliferation, the role of afferent and efferent vagal pathways in regulating barrier function, direct evidence for bacterial communication to the enteric nervous system, and microbial sources of enteric neurotransmitters. We discuss these new and interesting developments in our understanding of the role of the autonomic nervous system in gastrointestinal host defense.

Stress and food allergy: mechanistic considerations

Recent years have seen a marked increase in food allergy prevalence among children, particularly in Western countries, that cannot be explained by genetic factors alone. This has resulted in an increased effort to identify environmental risk factors underlying food allergies and to understand how these factors may be modified through interventions. Food allergy is an immune-mediated adverse reaction to food. Consequently, considerations of candidate risk factors have begun to focus on environmental influences that perturb the healthy development of the emerging immune system during critical periods of development (eg, prenatally and during early childhood), particularly in the gut. Given that psychosocial stress is known to play an important role in other allergic and inflammatory diseases, such as asthma, its potential role in food allergy is a growing area of research. However, research to date has largely focused on animal studies. This review synthesizes relevant animal research and epidemiological data, providing proof of concept for moderating influences of psychological stress on food allergy outcomes in humans. Pathways that may underlie associations between psychosocial stress and the expression of food allergy are discussed.

Prenatal intestinal obstruction affects the myenteric plexus and causes functional bowel impairment in fetal rat experimental model of intestinal atresia

Background

Intestinal atresia is a rare congenital disorder with an incidence of 3/10 000 birth. About one-third of patients have severe intestinal dysfunction after surgical repair. We examined whether prenatal gastrointestinal obstruction might effect on the myenteric plexus and account for subsequent functional disorders.

Methodology/Principal Findings

We studied a rat model of surgically induced antenatal atresia, comparing intestinal samples from both sides of the obstruction and with healthy rat pups controls. Whole-mount preparations of the myenteric plexus were stained for choline acetyltransferase (ChAT) and nitric oxide synthase (nNOS). Quantitative reverse transcription PCR was used to analyze mRNAs for inflammatory markers. Functional motility and permeability analyses were performed in vitro. Phenotypic studies were also performed in 8 newborns with intestinal atresia. In the experimental model, the proportion of nNOS-immunoreactive neurons was similar in proximal and distal segments (6.7±4.6% vs 5.6±4.2%, p = 0.25), but proximal segments contained a higher proportion of ChAT-immunoreactive neurons (13.2±6.2% vs 7.5±4.3%, p = 0.005). Phenotypic changes were associated with a 100-fold lower concentration-dependent contractile response to carbachol and a 1.6-fold higher EFS-induced contractile response in proximal compared to distal segments. Transcellular (p = 0.002) but not paracellular permeability was increased. Comparison with controls showed that modifications involved not only proximal but also distal segments. Phenotypic studies in human atresia confirmed the changes in ChAT expression.

Conclusion

Experimental atresia in fetal rat induces differential myenteric plexus phenotypical as well as functional changes (motility and permeability) between the two sides of the obstruction. Delineating these changes might help to identify markers predictive of motility dysfunction and to define guidelines for post-surgical care.

Early weaning stress in pigs impairs innate mucosal immune responses to enterotoxigenic E. coli challenge and exacerbates intestinal injury and clinical disease

Background and Aims

The clinical onset and severity of intestinal disorders in humans and animals can be profoundly impacted by early life stress. Here we investigated the impact of early weaning stress in pigs on intestinal physiology, clinical disease, and immune response to subsequent challenge with enterotoxigenic F18 E. coli (ETEC).

Methodology

Pigs weaned from their dam at 16 d, 18 d, and 20 d of age were given a direct oral challenge of F18 ETEC at 26 d of age. Pigs were monitored from days 0 to 4 post-infection for clinical signs of disease. On Day 4 post-ETEC challenge, ileal barrier function, histopathologic and inflammatory cytokine analysis were performed on ileal mucosa.

Results

Early weaned pigs (16 d and 18 d weaning age) exhibited a more rapid onset and severity of diarrhea and reductions in weight gain in response to ETEC challenge compared with late weaned pigs (20 d weaning age). ETEC challenge induced intestinal barrier injury in early weaned pigs, indicated by reductions in ileal transepithelial electrical resistance (TER) and elevated FD4 flux rates, in early weaned pig ileum but not in late weaned pigs. ETEC-induced marked elevations in IL-6 and IL-8, neutrophil recruitment, and mast cell activation in late-weaned pigs; these responses were attenuated in early weaned pigs. TNF levels elevated in ETEC challenged ileal mucosa from early weaned pigs but not in other weaning age groups.

Conclusions

These data demonstrate the early weaning stress can profoundly alter subsequent immune and physiology responses and clinical outcomes to subsequent infectious pathogen challenge. Given the link between early life stress and gastrointestinal diseases of animals and humans, a more fundamental understanding of the mechanisms by which early life stress impacts subsequent pathophysiologic intestinal responses has implications for the prevention and management of important GI disorders in humans and animals.

5-Hydroxytryptamine (serotonin) in the gastrointestinal tract

PURPOSE OF REVIEW

Although the gut contains most of the body's 5-hydroxytryptamine (5-HT), many of its most important functions have recently been discovered. This review summarizes and directs attention to this new burst of knowledge.

RECENT FINDINGS

Enteroendocrine cells have classically been regarded as pressure sensors, which secrete 5-HT to initiate peristaltic reflexes; nevertheless, recent data obtained from studies of mice that selectively lack 5-HT either in enterochromaffin cells (deletion of tryptophan hydroxylase 1 knockout; TPH1KO) or neurons (TPH2KO) imply that neuronal 5-HT is more important for constitutive gastrointestinal transit than that of enteroendocrine cells. The enteric nervous system of TPH2KO mice, however, also lacks a full complement of neurons; therefore, it is not clear whether slow transit in TPH2KO animals is due to their neuronal deficiency or absence of serotonergic neurotransmission. Neuronal 5-HT promotes the growth/maintenance of the mucosa as well as neurogenesis. Enteroendocrine cell derived 5-HT is an essential component of the gastrointestinal inflammatory response; thus, deletion of the serotonin transporter increases, whereas TPH1KO decreases the severity of intestinal inflammation. Enteroendocrine cell derived 5-HT, moreover, is also a hormone, which inhibits osteoblast proliferation and promotes hepatic regeneration.

SUMMARY

New studies show that enteric 5-HT is a polyfunctional signalling molecule, acting both in developing and mature animals as a neurotransmitter paracrine factor, endocrine hormone and growth factor.

The digestive neuronal-glial-epithelial unit: a new actor in gut health and disease

The monolayer of columnar epithelial cells lining the gastrointestinal tract--the intestinal epithelial barrier (IEB)--is the largest exchange surface between the body and the external environment. The permeability of the IEB has a central role in the regulation of fluid and nutrient intake as well as in the control of the passage of pathogens. The functions of the IEB are highly regulated by luminal as well as internal components, such as bacteria or immune cells, respectively. Evidence indicates that two cell types of the enteric nervous system (ENS), namely enteric neurons and enteric glial cells, are potent modulators of IEB functions, giving rise to the novel concept of a digestive 'neuronal-glial-epithelial unit' akin to the neuronal-glial-endothelial unit in the brain. In this Review, we summarize findings demonstrating that the ENS is a key regulator of IEB function and is actively involved in pathologies associated with altered barrier function.

A new soy germ fermented ingredient displays estrogenic and protease inhibitor activities able to prevent irritable bowel syndrome-like symptoms in stressed female rats

BACKGROUND & AIMS

Irritable bowel syndrome (IBS) often associated with psychological distress, is characterized by increased gut permeability and visceral sensitivity. In animals, stress increases intestinal paracellular permeability (IPP), visceral sensitivity and colonic proteolytic activity. Estradiol reduces IPP and affects visceral sensitivity in non-stressed ovariectomized rats, but whether estrogens affect stress-induced hyperpermeability and hypersensitivity in cyclic females remains unclear. We aimed to evaluate (i) the effects of a phytoestrogen-rich soy germ fermented ingredient (SG) on visceral hypersensitivity, hyperpermeability and other symptoms in stressed intact female rats, (ii) the mechanisms of action involved on the basis of both estrogenic and protease inhibitor activities of SG.

METHODS

Female rats received orally for 15-d either SG, 17β-estradiol benzoate (EB), or vehicles, with or without the estrogen receptor (ER) antagonist ICI182.780 before stress. Visceral sensitivity, IPP, faecal proteolytic activity, plasma corticosterone, rat mast cell protease II immunostaining, and occludin expression were assessed.

RESULTS

Stress increased IPP (concomitantly to a drop in occludin expression), visceral sensitivity, faecal proteolytic activity and plasma corticosterone. Similarly to EB, SG prevented the stress-induced hyperpermeability, and hypersensitivity, without changes in plasma corticosterone. SG inhibited the increase in faecal proteolytic activity, enhanced occludin expression, and reduced the colonic mast cell density. All SG effects, except decrease on faecal proteolytic activity, were blocked by ICI182.780.

CONCLUSION

A 2-wk oral treatment with SG prevented the stress-induced hyperpermeability and visceral hypersensitivity in cyclic rats through ER activation, and blocked the increase in colonic proteolytic activity, suggesting that SG can be promising in IBS management.

Early weaning increases intestinal permeability, alters expression of cytokine and tight junction proteins, and activates mitogen-activated protein kinases in pigs

Although weaning stress has been reported to impair intestinal barrier function, the mechanisms have not yet been elucidated. In the present study, the intestinal morphology and permeability and mRNA expressions of tight junction proteins and cytokines in the intestine of piglets during the 2 wk after weaning were assessed. The phosphorylated (activated) ratios of p38, c-Jun NH(2)-terminal kinase (JNK), and extracellular regulated kinases (ERK1/2) were determined to investigate whether mitogen-activated protein kinase (MAPK) signaling pathways are involved in the early weaning process. A shorter villus and deeper crypt were observed on d 3 and 7 postweaning. Although damaged intestinal morphology recovered to preweaning values on d 14 postweaning, the intestinal mucosal barrier, which was reflected by transepithelial electrical resistance (TER) and paracellular flux of dextran (4 kDa) in the Ussing chamber and tight junction protein expression, was not recovered. Compared with the preweaning stage (d 0), jejunal TER and mRNA expressions of occludin and claudin-1 on d 3, 7, and 14 postweaning and Zonula occludens-1 (ZO-1) mRNA on d 3 and 7 postweaning were reduced, and paracellular flux of dextran on d 3, 7, and 14 postweaning was increased. An increase (P < 0.05) of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) mRNA on d 3 and d 7 postweaning and an increase (P < 0.05) of interferon-γ (IFN-γ) mRNA on d 3 postweaning were observed compared with d 0. No significant increase of transforming growth factor β1 (TGF-β1) and interleukin-10 (IL-10) mRNA after weaning was observed. The phosphorylated (activated) ratios of JNK and p38 on d 3 and 7 postweaning and the phosphorylated ratio of ERK1/2 on d 3 postweaning were increased (P < 0.05) compared with d 0. The results indicated that early weaning induced sustained impairment in the intestinal barrier, decreased mRNA expression of tight junction proteins, and upregulated the expression of proinflammatory cytokines, but anti-inflammatory cytokines were not affected in the intestine of piglets. The recovery of the intestinal barrier function was slower than that of the intestinal mucosal morphology. The weaning stress activated MAPK signaling pathways in the intestine, which may be an important mechanism of weaning-associated enteric disorders of piglets.

Effect of maternal probiotic intervention on HPA axis, immunity and gut microbiota in a rat model of irritable bowel syndrome

OBJECTIVE

To examine whether maternal probiotic intervention influences the alterations in the brain-immune-gut axis induced by neonatal maternal separation (MS) and/or restraint stress in adulthood (AS) in Wistar rats.

DESIGN

Dams had free access to drinking water supplemented with Bifidobacterium animalis subsp lactis BB-12® (3 × 10(9) CFU/mL) and Propionibacterium jensenii 702 (8.0 × 10(8) CFU/mL) from 10 days before conception until postnatal day (PND) 22 (weaning day), or to control ad lib water. Offspring were subjected to MS from PND 2 to 14 or left undisturbed. From PND 83 to 85, animals underwent 30 min/day AS, or were left undisturbed as controls. On PND 24 and 86, blood samples were collected for corticosterone, ACTH and IgA measurement. Colonic contents were analysed for the composition of microflora and luminal IgA levels.

RESULTS

Exposure to MS significantly increased ACTH levels and neonatal fecal counts of aerobic and anaerobic bacteria, E. coli, enterococci and clostridia, but reduced plasma IgA levels compared with non-MS animals. Animals exposed to AS exhibited significantly increased ACTH and corticosterone levels, decreased aerobic bacteria and bifidobacteria, and increased Bacteroides and E. coli counts compared to non-AS animals. MS coupled with AS induced significantly decreased anaerobes and clostridia compared with the non-stress adult controls. Maternal probiotic intervention significantly increased neonatal corticosterone levels which persisted until at least week 12 in females only, and also resulted in elevated adult ACTH levels and altered neonatal microflora comparable to that of MS. However, it improved plasma IgA responses, increased enterococci and clostridia in MS adults, increased luminal IgA levels, and restored anaerobes, bifidobacteria and E. coli to normal in adults.

CONCLUSION

Maternal probiotic intervention induced activation of neonatal stress pathways and an imbalance in gut microflora. Importantly however, it improved the immune environment of stressed animals and protected, in part, against stress-induced disturbances in adult gut microflora.

Irritable bowel syndrome: methods, mechanisms, and pathophysiology. The confluence of increased permeability, inflammation, and pain in irritable bowel syndrome

Irritable bowel syndrome (IBS) is one of the most common gastrointestinal ailments among those seeking health care for gastrointestinal disorders. Despite its prevalence, IBS pathophysiology is still not completely understood. Continued elucidation of IBS etiological mechanisms will lead to a greater appreciation of possible therapeutic targets. In the past decade, there has been increasing focus on the possible connection between increased intestinal mucosal permeability, inflammation, and visceral hypersensitivity. Increased permeability in subsets of IBS patients has been observed and the possible mechanisms underlying this defect are just beginning to be understood. The objectives of this review are to summarize the role of the healthy intestinal epithelium as a barrier between the lumen and the rest of the body with a focus on tight junctions; to examine the lines of evidence that suggest that different triggers lead to increased intestinal mucosal permeability and disruption of tight junctions in IBS patients; and to explore how this increased permeability may elicit immune responses that affect afferent nerves, resulting in the pain associated with IBS.

CRF induces intestinal epithelial barrier injury via the release of mast cell proteases and TNF-α

BACKGROUND AND AIMS

Psychological stress is a predisposing factor in the onset and exacerbation of important gastrointestinal diseases including irritable bowel syndrome (IBS) and the inflammatory bowel diseases (IBD). The pathophysiology of stress-induced intestinal disturbances is known to be mediated by corticotropin releasing factor (CRF) but the precise signaling pathways remain poorly understood. Utilizing a porcine ex vivo intestinal model, the aim of this study was to investigate the mechanisms by which CRF mediates intestinal epithelial barrier disturbances.

METHODOLOGY

Ileum was harvested from 6-8 week-old pigs, mounted on Ussing Chambers, and exposed to CRF in the presence or absence of various pharmacologic inhibitors of CRF-mediated signaling pathways. Mucosal-to-serosal flux of 4 kDa-FITC dextran (FD4) and transepithelial electrical resistance (TER) were recorded as indices of intestinal epithelial barrier function.

RESULTS

Exposure of porcine ileum to 0.05-0.5 µM CRF increased (p<0.05) paracellular flux compared with vehicle controls. CRF treatment had no deleterious effects on ileal TER. The effects of CRF on FD4 flux were inhibited with pre-treatment of tissue with the non-selective CRF(1/2) receptor antagonist Astressin B and the mast cell stabilizer sodium cromolyn (10(-4) M). Furthermore, anti-TNF-α neutralizing antibody (p<0.01), protease inhibitors (p<0.01) and the neural blocker tetrodotoxin (TTX) inhibited CRF-mediated intestinal barrier dysfunction.

CONCLUSION

These data demonstrate that CRF triggers increases in intestinal paracellular permeability via mast cell dependent release of TNF-α and proteases. Furthermore, CRF-mast cell signaling pathways and increases in intestinal permeability require critical input from the enteric nervous system. Therefore, blocking the deleterious effects of CRF may address the enteric signaling of mast cell degranulation, TNFα release, and protease secretion, hallmarks of IBS and IBD.

Association between early adverse life events and irritable bowel syndrome

BACKGROUND & AIMS

Although childhood and adult abuse are more prevalent among patients with irritable bowel syndrome (IBS) than healthy individuals (controls), other types of early adverse life events (EALs) have not been well characterized. We investigated whether different types of EALs, before age 18 years, are more prevalent among patients with IBS, and the effects of sex and nongastrointestinal symptoms on the relationship between EALs and IBS.

METHODS

EALs were evaluated in 294 IBS patients (79% women) and 435 controls (77% women) using the Early Trauma Inventory Self-Report Form, which delineates subcategories of general trauma and physical, emotional, and sexual abuse. Validated questionnaires assessed gastrointestinal, psychological, and somatic symptoms.

RESULTS

Compared with controls, IBS patients reported a higher prevalence of general trauma (78.5% vs 62.3%), physical punishment (60.6% vs 49.2%), emotional abuse (54.9% vs 27.0%), and sexual events (31.2% vs 17.9%) (all P < .001). These significant differences were observed mainly in women. Of the EAL domains, emotional abuse was the strongest predictor of IBS (P < .001). Eight of the 27 EAL items were significant (P < .001) and increased the odds of having IBS by 108% to 305%. Although EALs and psychological variables were related, EALs had an independent association with IBS (P = .04).

CONCLUSIONS

Various types of EALs are associated with the development of IBS-particularly among women. Psychological distress and somatic symptoms might contribute to this relationship. When appropriate, EALs and nongastrointestinal symptoms should be assessed in IBS patients.

The intestinal microbiota are necessary for stressor-induced enhancement of splenic macrophage microbicidal activity

The indigenous microbiota impact mucosal, as well as systemic, immune responses, but whether the microbiota are involved in stressor-induced immunomodulation has not been thoroughly tested. A well characterized murine stressor, called social disruption (SDR), was used to study whether the microbiota are involved in stressor-induced enhancement of macrophage reactivity. Exposure to the SDR Stressor enhanced the ability of splenic macrophages to produce microbicidal mediators (e.g., inducible nitric oxide synthase (iNOS), superoxide anion, and peroxynitrite) and to kill target Escherichia coli. Exposure to the SDR Stressor also increased cytokine production by LPS-stimulated splenic macrophages. These effects, however, were impacted by the microbiota. Microbicidal activity and cytokine mRNA in splenic macrophages from Swiss Webster germfree mice that lack any commensal microbiota were not enhanced by exposure to the SDR Stressor. However, when germfree mice were conventionalized by colonizing them with microbiota from CD1 conventional donor mice, exposure to the SDR Stressor again increased microbicidal activity and cytokine mRNA. In follow-up experiments, immunocompetent conventional CD1 mice were treated with a cocktail of antibiotics to disrupt the intestinal microbiota. While exposure to the SDR Stressor-enhanced splenic macrophage microbicidal activity and cytokine production in vehicle-treated mice, treatment with antibiotics attenuated the SDR Stressor-induced increases in splenic macrophage reactivity. Treatment with antibiotics also prevented the stressor-induced increase in circulating levels of bacterial peptidoglycan, suggesting that translocation of microbiota-derived peptidoglycan into the body primes the innate immune system for enhanced activity. This study demonstrates that the microbiota play a crucial role in stressor-induced immunoenhancement.

Cytokines and irritable bowel syndrome: where do we stand?

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder, which presents with one or more gastrointestinal symptoms without any structural or organic abnormality. The etiology and pathophysiological mechanisms of IBS remain uncertain. Residual or reactivated inflammation at the molecular level is considered the underlying mechanism of post-infectious IBS. On the other hand, genetic variations in the immunological components of the body, including cytokine gene polymorphisms, are proposed as a potential mechanism of IBS even in patients without previous gastrointestinal infection. Several studies have suggested imbalanced cytokine signaling as an etiology for IBS. In this review, recent findings on cytokine profiles and cytokine gene polymorphisms in patients with IBS are described and the role of cytokines in animal models of IBS is discussed.

Anti-inflammatory effects of nicotine in obesity and ulcerative colitis

Cigarette smoke is a major risk factor for a number of diseases including lung cancer and respiratory infections. Paradoxically, it also contains nicotine, an anti-inflammatory alkaloid. There is increasing evidence that smokers have a lower incidence of some inflammatory diseases, including ulcerative colitis, and the protective effect involves the activation of a cholinergic anti-inflammatory pathway that requires the α7 nicotinic acetylcholine receptor (α7nAChR) on immune cells. Obesity is characterized by chronic low-grade inflammation, which contributes to insulin resistance. Nicotine significantly improves glucose homeostasis and insulin sensitivity in genetically obese and diet-induced obese mice, which is associated with suppressed adipose tissue inflammation. Inflammation that results in disruption of the epithelial barrier is a hallmark of inflammatory bowel disease, and nicotine is protective in ulcerative colitis. This article summarizes current evidence for the anti-inflammatory effects of nicotine in obesity and ulcerative colitis. Selective agonists for the α7nAChR could represent a promising pharmacological strategy for the treatment of inflammation in obesity and ulcerative colitis. Nevertheless, we should keep in mind that the anti-inflammatory effects of nicotine could be mediated via the expression of several nAChRs on a particular target cell.

Need for a comprehensive medical approach to the neuro-immuno-gastroenterology of irritable bowel syndrome

Irritable bowel syndrome (IBS) is defined by the Rome III criteria as symptoms of recurrent abdominal pain or discomfort with the onset of a marked change in bowel habits with no evidence of an inflammatory, anatomic, metabolic, or neoplastic process. As such, many clinicians regard IBS as a central nervous system problem of altered pain perception. Here, we review the recent literature and discuss the evidence that supports an organic based model, which views IBS as a complex, heterogeneous, inter-dependent, and multi-variable inflammatory process along the neuronal-gut axis. We delineate the organic pathophysiology of IBS, demonstrate the role of inflammation in IBS, review the possible differences between adult and pediatric IBS, discuss the merits of a comprehensive treatment model as taught by the Institute of Functional Medicine, and describe the potential for future research for this syndrome.

Role of intestinal circadian genes in alcohol-induced gut leakiness

BACKGROUND

Several studies have indicated that endotoxemia is the required co-factor for alcoholic steatohepatitis (ASH) that is seen in only about 30% of alcoholics. Recent studies have shown that gut leakiness that occurs in a subset of alcoholics is the primary cause of endotoxemia in ASH. The reasons for this differential susceptibility are not known. Since disruption of circadian rhythms occurs in some alcoholics and circadian genes control the expression of several genes that are involved in regulation of intestinal permeability, we hypothesized that alcohol induces intestinal hyperpermeability by stimulating expression of circadian clock gene proteins in the intestinal epithelial cells.

METHODS

We used Caco-2 monolayers grown on culture inserts as an in vitro model of intestinal permeability and performed Western blotting, permeability, and siRNA inhibition studies to examine the role of Clock and Per2 circadian genes in alcohol-induced hyperpermeability. We also measured PER2 protein levels in intestinal mucosa of alcohol-fed rats with intestinal hyperpermeability.

RESULTS

Alcohol, as low as 0.2%, induced time dependent increases in both Caco-2 cell monolayer permeability and in CLOCK and PER2 proteins. SiRNA specific inhibition of either Clock or Per2 significantly inhibited alcohol-induced monolayer hyperpermeability. Alcohol-fed rats with increased total gut permeability, assessed by urinary sucralose, also had significantly higher levels of PER2 protein in their duodenum and proximal colon than control rats.

CONCLUSIONS

Our studies: (i) demonstrate a novel mechanism for alcohol-induced intestinal hyperpermeability through stimulation of intestinal circadian clock gene expression, and (ii) provide direct evidence for a central role of circadian genes in regulation of intestinal permeability.

The role of stress on physiologic responses and clinical symptoms in irritable bowel syndrome

Studies support the concept that irritable bowel syndrome (IBS) is a biopsychosocial disorder that can be explained by a neurobiological model which postulates stress-induced alterations in central stress and arousal circuits and activation of parallel motor outputs from brain regions that can affect bodily function and behavior. Sustained stress can result in chronic overactivity or underactivity of allostatic (or adaptive) systems, including the hypothalamic-pituitary-adrenal (HPA) axis, autonomic nervous system, metabolic, and immune systems, can occur. Animal and human studies have demonstrated that chronic or sustained stress is associated with the onset and exacerbation of symptoms of IBS. Chronic stress is also an independent predictor of developing post-infectious IBS. IBS patients specifically show stress-induced alterations in gastrointestinal motility, rectal perception, autonomic tone and HPA axis responses, although these findings are not entirely consistent among studies. This can be in part due to differences in study methodology or to various factors that can affect these physiologic responses. A greater recognition and understanding of the effects of stress in IBS may help identify targets for future drug development and also help guide more effective management of IBS symptoms.

Maternal separation as a model of brain-gut axis dysfunction

RATIONALE

Early life stress has been implicated in many psychiatric disorders ranging from depression to anxiety. Maternal separation in rodents is a well-studied model of early life stress. However, stress during this critical period also induces alterations in many systems throughout the body. Thus, a variety of other disorders that are associated with adverse early life events are often comorbid with psychiatric illnesses, suggesting a common underlying aetiology. Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder that is thought to involve a dysfunctional interaction between the brain and the gut. Essential aspects of the brain-gut axis include spinal pathways, the hypothalamic pituitary adrenal axis, the immune system, as well as the enteric microbiota. Accumulating evidence suggest that stress, especially in early life, is a predisposing factor to IBS.

OBJECTIVE

The objective of this review was to assess and compile the most relevant data on early life stress and alterations at all levels of the brain gut axis.

RESULTS

In this review, we describe the components of the brain-gut axis individually and how they are altered by maternal separation. The separated phenotype is characterised by alterations of the intestinal barrier function, altered balance in enteric microflora, exaggerated stress response and visceral hypersensitivity, which are all evident in IBS.

CONCLUSION

Thus, maternally separated animals are an excellent model of brain-gut axis dysfunction for the study of disorders such as IBS and for the development of novel therapeutic interventions.

Non-neuronal release of ACh plays a key role in secretory response to luminal propionate in rat colon

Colonic chloride secretion is induced by chemical stimuli via the enteric nervous reflex. We have previously demonstrated that propionate stimulates chloride secretion via sensory and cholinergic systems of the mucosa in rat distal colon. In this study, we demonstrate non-neuronal release of ACh in the secretory response to propionate using an Ussing chamber. Mucosa preparations from the colon, not including the myenteric and submucosal plexuses, were used. Luminal addition of propionate and serosal addition of ACh caused biphasic changes in short-circuit current (Isc). TTX (1 μm) had no effects, while atropine (10 μm) significantly inhibited the Isc response to propionate and abolished that to ACh. In response to luminal propionate stimulation, ACh was released into the serosal fluid. A linear relationship was observed between the maximal increase in Isc and the amounts of ACh released 5 min after propionate stimulation. This ACh release induced by propionate was not affected by atropine and bumetanide, although both drugs significantly reduced the Isc responses to propionate. Luminal addition of 3-chloropropionate, an inactive analogue of propionate, abolished both ACh release and Isc response produced by propionate. RT-PCR analysis indicated that isolated crypt cells from the distal colon expressed an enzyme of ACh synthesis (ChAT) and transporters of organic cation (OCTs), but not neuronal CHT1 and VAChT. The isolated crypt cells contained comparable amounts of ACh to the residual muscle tissues including nerve plexuses. In conclusion, the non-neuronal release of ACh from colonocytes coupled with propionate stimulation plays a key role in chloride secretion, via the paracrine action of ACh on muscarinic receptors of colonocytes.

Stress at the intestinal surface: catecholamines and mucosa-bacteria interactions

Psychological stress has profound effects on gastrointestinal function, and investigations over the past few decades have examined the mechanisms by which neural and hormonal stress mediators act to modulate gut motility, epithelial barrier function and inflammatory states. With its cellular diversity and large commensal bacterial population, the intestinal mucosa and its overlying mucous environment constitute a highly interactive environment for eukaryotic host cells and prokaryotic bacteria. The elaboration of stress mediators, particularly norepinephrine, at this interface influences host cells engaged in mucosal protection and the bacteria which populate the mucosal surface and gut lumen. This review will address growing evidence that norepinephrine and, in some cases, other mediators of the adaptation to stress modulate mucosal interactions with enteric bacteria. Stress-mediated changes in this delicate interplay may shift the microbial colonization patterns on the mucosal surface and alter the susceptibility of the host to infection. Moreover, changes in host-microbe interactions in the digestive tract may also influence ongoing neural activity in stress-responsive brain areas.

The intestinal barrier and its regulation by neuroimmune factors

BACKGROUND

The ability to control uptake across the mucosa and protect from damage of harmful substances from the lumen is defined as intestinal barrier function. A disturbed barrier dysfunction has been described in many human diseases and animal models, for example, inflammatory bowel disease, irritable bowel syndrome, and intestinal hypersensitivity. In most diseases and models, alterations are seen both of the paracellular pathway, via the tight junctions, and of the transcellular routes, via different types of endocytosis. Recent studies of pathogenic mechanisms have demonstrated the important role of neuroimmune interaction with the epithelial cells in the regulation of barrier function. Neural impulses from extrinsic vagal and/or sympathetic efferent fibers or intrinsic enteric nerves influence mucosal barrier function via direct effects on epithelial cells or via interaction with immune cells. For example, by nerve-mediated activation by corticotropin-releasing hormone or cholinergic pathways, mucosal mast cells release a range of mediators with effects on transcellular, and/or paracellular permeability (for example, tryptase, TNF-alpha, nerve growth factor, and interleukins).

PURPOSE

In this review, we discuss current physiological and pathophysiological aspects of the intestinal barrier and, in particular, its regulation by neuroimmune factors.

Increased colonic motility in a rat model of irritable bowel syndrome is associated with up-regulation of L-type calcium channels in colonic smooth muscle cells

OBJECTIVE

This paper aimed to investigate the relationship between up-regulation of L-type calcium channels and altered motility disorder in a rat model of irritable bowel syndrome (IBS).

METHODS

Male Sprague-Dawley rats were subjected to neonatal maternal separation (NMS) from postnatal day 2-14 or normal handling (NH), and used when weighted 250-300 g. Colonic smooth muscle contractions was studied in an organ bath system. L-type Ca(2+) channel alpha(1c) subunit expression in smooth muscles from rat colon were studied by immunofluorescence and Western blotting analysis. The intracellular calcium concentration ([Ca(2+)](i)) of enzymatically isolated single colonic smooth muscle cell was studied with laser confocal fluorescent microscopy.

RESULTS

The fecal pellets during 1 h water avoidance stress (WAS) were significantly increased; the amplitude of spontaneous contractions and contractions induced by Bay K 8644 (10 nM-1 microM), KCl (10-60 mM) and ACh (100 nM-10 microM) were significantly increased in NMS rats, when comparing with that of NH rats. [Ca(2+)]i induced by Bay K 8644 (1 microM), KCl (40 mM), and ACh (10 microM) significantly increased in muscle cells of NMS rats than NH rats. Further, alpha(1c) protein expression was significantly up-regulated in colonic smooth muscle of NMS rats than NH rats.

CONCLUSION

These results suggest that NMS lead to up-regulation of L-type Ca(2+) channels expression in the colon, which contributes to the colonic motility disorder. Our findings provide direct evidence to help understanding the underlying mechanism of chronic stress-induced colonic motility disorder in IBS.