Chronic stress induces mast cell-dependent bacterial adherence and initiates mucosal inflammation in rat intestine

Astaxanthin (ATX) enhances the intestinal mucosal functions in immunodeficient mice

Increasing pressure of life may bring some disease risks and stress injuries, which may destroy the immune system and result in intestinal mucosal immune disorders. In this study, the effects of different doses of ATX (30 mg per kg b.w., 60 mg per kg b.w. and 120 mg per kg b.w.) on intestinal mucosal functions were explored in cyclophosphamide (Cy)-induced immunodeficient mice. The results showed that continuous intraperitoneal injection of 100 mg per kg b.w. Cy for three days led to a persistent decrease of body weight and a range of abnormalities in the intestine of C57BL/6 mice. However, administration of ATX at 60 and 120 mg per kg b.w. could effectively prevent intestinal mucosa from this damage, including reduced levels of oxidative stress (MDA, GSH and GSH-PX), increased intestinal morphological structural integrity, stimulative growth of goblet cells and mucous secretion, decreased development of Paneth cells and expression levels of antimicrobial peptides (AMPs) (Reg-3γ and lysozyme), increased IgA secretion, ameliorative main gut flora (especially total bacteria, Lactobacillus and Enterobacteriaceae spp. ) and its metabolites (acetic acid, propionic acid and butyric acid). These protective effects of ATX were better than those of control-β-carotene in general. Our results may provide a new protective measure to keep intestinal mucosal barriers, which is of great significance for maintaining immune function in the body.

GPER-mediated, oestrogen-dependent visceral hypersensitivity in stressed rats is associated with mast cell tryptase and histamine expression

Visceral hypersensitivity (VH) is common in irritable bowel syndrome (IBS), and female patients are more likely to seek healthcare services for IBS-related abdominal pain. Oestrogen has been reported to mediate pain modulation via its receptor, and mast cells are known to participate in the development of visceral hypersensitivity. Our previous studies showed that the G-protein-coupled oestrogen receptor (GPER, also known as GPR30) was expressed by mast cells in human colonic tissues and was associated with IBS type and severity of visceral pain. However, whether GPER is involved in oestrogen-dependent visceral hypersensitivity via mast cell degranulation is still unknown. Rats were subjected to wrap partial restraint stress to induce visceral hypersensitivity and were ovariectomized (OVX) to eliminate the effects of oestrogen on visceral hypersensitivity. OVX rats were treated with oestrogen, an oestrogen receptor α and β antagonist (ICI 182.780), a GPER antagonist (G15) or a GPER agonist (G1), to evaluate the effects of oestrogen via its receptor. The colorectal distention test was performed to assess visceral sensitivity. Immunofluorescence studies were performed to evaluate GPER and mast cell tryptase co-expression. Mast cell number with degranulation was detected by specific staining. Mast cell tryptase expression in rat colon was also investigated by Western blot and immunohistochemistry. Substance P and histamine expression were examined by ELISA. GPER was expressed by the majority of tryptase-positive mast cells in the colonic mucosa. Stressed rats showed increased visceral sensitivity, increased mast cell degranulation, mast cell tryptase expression, and increased colon histamine levels. Ovariectomy reduced stress-induced VH in female rats and decreased mast cell degranulation, mast cell tryptase expression, and histamine levels, whereas oestrogen replacement reversed these effects. In OVX rats, the GPER antagonist G15 counteracted the enhancing effects of oestrogen on stress-induced VH, mast cell degranulation, mast cell tryptase, and histamine expression, whereas VH was preserved after treatment with ICI 182.780. On the other hand, pretreatment with the selective GPER agonist G1 at doses between 1 and 20 μg/kg significantly increased VH, mast cell tryptase, and histamine expression in OVX-stressed rats, mimicking the effects of oestrogen. GPER plays a pivotal role in the regulation of mast cell degranulation, mast cell tryptase expression, and histamine levels and contributes to the development of colonic hypersensitivity in a female rat model of IBS.

Gut Microbiome and Modulation of CNS Function

Preclinical evidence strongly suggests a role for the gut microbiome in modulating the host central nervous system function and behavior. Several communication channels have been identified that enable microbial signals to reach the brain and that enable the brain to influence gut microbial composition and function. In rodent models, endocrine, neural, and inflammatory signals generated by gut microbes can alter brain structure and function, while autonomic nervous system activity can affect the microbiome by modulating the intestinal environment and by directly regulating microbial behavior. The amount of information that reaches the brain is dynamically regulated by the blood-brain barrier and the intestinal barrier. In humans, associations between gut microbial composition and function and several brain disorders have been reported, and fecal microbial transplants from patient populations into gnotobiotic mice have resulted in the reproduction of homologous features in the recipient mice. However, in contrast to preclinical findings, there is little information about a causal role of the gut microbiome in modulating human central nervous system function and behavior. Longitudinal studies in large patient populations with therapeutic interventions are required to demonstrate such causality, which will provide the basis for future clinical trials. © 2020 American Physiological Society. Compr Physiol 10:57-72, 2020.

Mast cells are increased in the small intestinal mucosa of patients with irritable bowel syndrome: A systematic review and meta-analysis

BACKGROUND

Colonic mast cells have been proposed to be related to the pathophysiology of irritable bowel syndrome (IBS). Whether mast cell counts are altered in the small intestine, a less-explored region in patients with IBS is not completely clear.

METHODS

PubMed and EMBASE were searched for case-control studies on mast cell count/density in the small intestine of patients with IBS vs controls through February 2019. Mast cell counts were separately analyzed in the duodenum, jejunum, and ileum. Data were pooled using the standardized mean difference (SMD) method. When zero was not within the 95% confidence interval (CI), the SMD was considered significant.

KEY RESULTS

Data from 344 patients with IBS and 229 healthy controls from three studies in the duodenum, six in the jejunum, and five in the ileum were pooled in this meta-analysis. The number of mast cells was significantly higher in the ileum (SMD: 1.78 [95% CI: 0.89, 2.66]) of patients with IBS. Mast cell counts were not significantly different in the duodenum (SMD: 0.81 [-0.06, 1.67]) or the jejunum (SMD: 0.58 [-0.03, 1.19]) of patients with IBS vs healthy controls.

CONCLUSIONS AND INFERENCES

Mast cells are increased in the small intestine of IBS vs controls, mainly in the ileum. Future studies should address whether such findings are IBS subtype or gender-dependent. Methodological variations, single-center bias, and the limited number of studies included in this meta-analysis may affect the final results.

It's what's on the inside that counts: stress physiology and the bacterial microbiome of a wild urban mammal

The microbiome's capacity to shape the host phenotype and its mutability underlie theorization that the microbiome might facilitate host acclimation to rapid environmental change. However, when environmental change occurs, it is unclear whether resultant microbiome restructuring is proximately driven by this changing external environment or by the host's physiological response to this change. We leveraged urbanization to compare the ability of host environment (urban or forest) versus multi-scale biological measures of host hypothalamic-pituitary-adrenal (HPA) axis physiology (neutrophil : lymphocyte ratio, faecal glucocorticoid metabolites, hair cortisol) to explain variation in the eastern grey squirrel (Sciurus carolinensis) faecal microbiome. Urban and forest squirrels differed across all three of the interpretations of HPA axis activity we measured. Direct consideration of these physiological measures better explained greater phylogenetic turnover between squirrels than environment. This pattern was strongly driven by trade-offs between bacteria which specialize on metabolizing digesta versus host-derived nutrient sources. Drawing on ecological theory to explain patterns in intestinal bacterial communities, we conclude that although environmental change can affect the microbiome, it might primarily do so indirectly by altering host physiology. We demonstrate that the inclusion and careful consideration of dynamic, rather than fixed (e.g. sex), dimensions of host physiology are essential for the study of host-microbe symbioses at the micro-evolutionary scale.

Chronic Stress, Inflammation, and Colon Cancer: A CRH System-Driven Molecular Crosstalk

Chronic stress is thought to be involved in the occurrence and progression of multiple diseases, via mechanisms that still remain largely unknown. Interestingly, key regulators of the stress response, such as members of the corticotropin-releasing-hormone (CRH) family of neuropeptides and receptors, are now known to be implicated in the regulation of chronic inflammation, one of the predisposing factors for oncogenesis and disease progression. However, an interrelationship between stress, inflammation, and malignancy, at least at the molecular level, still remains unclear. Here, we attempt to summarize the current knowledge that supports the inseparable link between chronic stress, inflammation, and colorectal cancer (CRC), by modulation of a cascade of molecular signaling pathways, which are under the regulation of CRH-family members expressed in the brain and periphery. The understanding of the molecular basis of the link among these processes may provide a step forward towards personalized medicine in terms of CRC diagnosis, prognosis and therapeutic targeting.

Chronic Unpredictable Mild Stress in Rats Induces Colonic Inflammation

Chronic psychological stress is associated with an increased risk for relapse of inflammatory bowel diseases (IBD) and impedes the treatment of this condition. However, the impact of stress on the risk of IBD onset remains unclear. The goal of the present study was to examine whether chronic unpredictable mild stress (CUMS) could initiate or aggravate the onset of colon inflammation in rats which, in turn, would be capable of triggering bowel disease. We found that CUMS exposure increased infiltration of CD-45 positive cells and MPO activity, as well as augmented the expression of the inflammatory cytokines, IFN-γ and IL-6 within the colon of these rats. In addition, CUMS treatment changed the composition and diversity of gut microbiota and enhanced intestinal epithelial permeability, indicating the presence of a defect in the intestinal barrier. This CUMS-induced disruption of mucosal barrier integrity was associated with a reduction in expression of the tight junction protein, occludin 1, and an inhibition in mucosal layer functioning via reductions in goblet cells. Results from bacterial cultures revealed an increased presence of bacterial invasion after CUMS treatment as compared with that observed in controls. Thus, our data indicate that CUMS treatment induces alterations of the fecal microbiome and intestinal barrier defects, which facilitates bacterial invasion into colonic mucosa and further exacerbates inflammatory reactions within the colon. Accordingly, chronic stress may predispose patients to gastrointestinal infection and increase the risk of inflammation-related gut diseases.

Mode of Action of Dietary Dexamethasone May Not Be Dependent Upon Microbial Mechanisms in Broilers

Dexamethasone (Dex), a synthetic glucocorticoid (GC), in feed has been shown to increase gut permeability via stress-mediated mechanisms, but the exact mode of action on gut barrier function is not fully understood. Stress has been reported to alter the profile and virulence of intestinal flora predisposing for opportunistic disease. This study aimed to evaluate the relationship between dietary Dex and recoverable intestinal microbial profile in broilers to better understand mode of action and refine future uses of the model. Three experiments were conducted that administered Dex-treated feed for one week in conjunction with the antibiotics BMD (bacitracin methylene disalicylate) or Baytril^® (enrofloxacin) to evaluate if enteric microbial mechanisms were important in Dex-induced permeability. Serum fluorescein isothiocyanate-dextran (FITC-d) and bacterial translocation (BT) have been reported to increase after Dex treatment and were used to assess gut epithelial leakage. Shifts in bacterial profiles were also measured on selective agar. Combining Dex with BMD or Baytril resulted in increased (P < 0.05) serum FITC-d versus Dex-only. Additionally, Baytril did not reduce aerobic BT and bacterial profiles remained similar after Dex. These results suggest a minimal role of intestinal microbes in Dex-induced changes to intestinal barrier function.

Small Intestine Protection of Mica Against Non-Steroidal Anti-Inflammatory Drugs-Injury Through ERK1/2 Signal Pathway in Rats

Objective: The impact of non-steroidal anti-inflammatory drugs (NSAIDs) to damage the small intestine has been well known. Mica, one kind of natural clay, has been widely marketed in China for the treatment of gastric diseases. However, the role and mechanism of mica in small intestinal injure is still unknown. The study was designed to declare the effects of mica on intestinal injury induced by diclofenac in rats.

Methods: Rats were randomly divided into control, model, PAR-2 agonist group (SLIGRL-NH2group), control peptide group (LRGILS-NH2 group), and ERK blocker group (eight mice per group). Morphological changes of mucous membrane of small intestine were observed, and the expression of tryptase, PAR-2, and p-ERK1/2 was measured by immunohistochemistry and western blot. PAR-2 mRNA was tested by qRT-PCR. Rats were also randomly divided into control, model, and mica group (eight mice per group). Morphological changes of mucous membrane were observed. The expression of tryptase, PAR-2, and p-ERK1/2 was measured by immunohistochemistry.

Results: The expression of trypsin, PAR-2, and p-ERK1/2 was increased in model group compared with control. The expression of PAR-2 and p-ERK1/2 was increased in SLIGRL-NH2 group compared with model, but not LRGILS-NH2 group. The expression of PAR-2 was down-regulated in ERK blocker group compared with SLIGRL-NH2 group. Macroscopically visible lesions of mucous membrane were positively correlated with the expression of PAR-2 and p-ERK1/2. Furthermore, we also found that mica could inhibit small intestinal injure, as evidenced by the improvement of macroscopic damage. Tryptase, PAR-2, and p-ERK1/2 expression was down-regulated in mica group compared with model group.

Conclusion: Mica inhibit small intestinal injury induced by NSAIDs via ERK signaling pathway.

Effects of thermized donkey milk with lysozyme activity on altered gut barrier in mice exposed to water-avoidance stress

Nutrition plays a crucial role in human gut health through the improvement of gut barrier functionality. Donkey milk represents an interesting source of natural antimicrobial factors such as lysozyme. Recently, anti-inflammatory properties of donkey milk lysozyme activity were described in a mouse model of ileitis. The current increase of donkey milk consumption highlights the necessity to propose a healthy milk compliant with microbiological standards. This study aims to define a heat treatment of donkey milk, retaining its high lysozyme activity, and to evaluate its beneficial effects on a gut barrier impairment model due to chronic stress in mice. To perform this experiment, samples of raw donkey milk were collected in 15 distinct French farms. Microbiological analysis and lysozyme content and activity were evaluated for each sample. Then, several heat treatments were carried out to define a time and temperature combination that allowed for both a reduction in the number of total micro-organisms, increasing the shelf-life of the product, and preservation of lysozyme activity. The beneficial effect of heated donkey milk on the gut barrier of mice was evaluated and compared with raw donkey milk. We found that samples of raw donkey milk showed low total mesophilic microbial counts, and no pathogens were detected. Among the different heat-treatment procedures tested, a 2-min, 72°C combination was determined to be the most optimal time and temperature combination to preserve lysozyme activity and increase the shelf-life of donkey milk. Oral administration of this heat-treated donkey milk in mice counteracted chronic stress-induced intestinal damage, illustrated by gut hyper-permeability and low-grade inflammation, similar to raw donkey milk. We have demonstrated for the first time that oral intervention with donkey milk, optimally heat-treated to retain enzymatic lysozyme activity, improves intestinal barrier damage linked to psychological stress in mice.

Gene-environment interactions in primary atopic disorders

Environmental factors modify disease presentation and severity in allergic disorders. Primary atopic disorders (PADs) are a heterogenous group of single gene disorders that lead to significant atopic and allergic disease manifestations. However, a number of these monogenic diseases have variable penetrance suggesting that gene-gene and/or gene-environment interactions could modulate the clinical phenotype. Environmental factors such as diet, the microbiome at the epithelial-environment interface, the presence and/or extent of infection, and psychologic stress can alter disease phenotypic expression of allergic diseases, and PADs provide discrete contexts in which to understand these influences. We outline how gene-environment interactions likely contribute to a variable penetrance and expressivity in PADs. Dietary modifications of both macronutrients and/or micronutrients alter T-cell metabolism and may influence effector T-cell function. The mucosal microbiome may affect local inflammation and may remotely influence regulatory elements, while psychologic stress can affect mast cell and other allergic effector cell function. Understanding gene-environment interactions in PADs can hopefully provide a foundation for interrogating gene-environment interactions to common allergic disorders, and also present opportunities for personalized interventions based on the altered pathways and environmental influences in affected individuals.

Yeast fermentate prebiotic improves intestinal barrier integrity during heat stress by modulation of the gut microbiota in rats

Aims

To evaluate efficacy of Saccharomyces cerevisiae fermentate prebiotic (EH) in protection of intestinal barrier integrity in rats during heat stress, to analyze the impact of heat stress and preventive treatment with EH on the structure of the gut microbiota.

Methods and Results

Two groups of rats were treated orally with EH or phosphate‐buffered saline for 14 days. On day 15, half of the rats in each group were exposed to heat stress conditions, while control animals were kept at room temperature. Histological and Western blot analyses of the intestine, culture‐based microbiological analysis and high‐throughput 16S rRNA sequencing for the gut microbiota were performed for each rat. Exposure of animals to heat stress conditions resulted in inhibition of tight junction (TJ) proteins expression, decrease of Paneth and goblet cells, decrease of beneficial and increase of pathogenic bacteria. Oral treatment of rats with EH before stress significantly prevents these adverse effects by elevation of the gut beneficial bacteria, particularly butyrate‐producing bacteria.

Conclusions

Essential effect of EH in protection of intestinal barrier integrity during heat stress is connected with beneficial modulation of the gut microbiota.

Significance and Impact of the Study

Our results will contribute to the development of new approaches to prevention of heat stress‐related complications.

Inflammatory Bowel Disease: A Stressed "Gut/Feeling"

Inflammatory bowel disease (IBD) is a chronic and relapsing intestinal inflammatory condition, hallmarked by a disturbance in the bidirectional interaction between gut and brain. In general, the gut/brain axis involves direct and/or indirect communication via the central and enteric nervous system, host innate immune system, and particularly the gut microbiota. This complex interaction implies that IBD is a complex multifactorial disease. There is increasing evidence that stress adversely affects the gut/microbiota/brain axis by altering intestinal mucosa permeability and cytokine secretion, thereby influencing the relapse risk and disease severity of IBD. Given the recurrent nature, therapeutic strategies particularly aim at achieving and maintaining remission of the disease. Alternatively, these strategies focus on preventing permanent bowel damage and concomitant long-term complications. In this review, we discuss the gut/microbiota/brain interplay with respect to chronic inflammation of the gastrointestinal tract and particularly shed light on the role of stress. Hence, we evaluated the therapeutic impact of stress management in IBD.

Impact of chronic immobilization stress on parameters of colonic homeostasis in BALB/c mice

The intestinal epithelium is a monolayer of cells arranged side‑by‑side and connected by tight junction (TJ) proteins expressed at the apical extreme of the paracellular membrane. This layer prevents stress‑induced inflammatory responses, thus helping to maintain gut barrier function and gut homeostasis. The aim of the present study was to evaluate the effects of chronic immobilization stress on the colonic expression of various parameters of homeostasis. A total of two groups of female BALB/c mice (n=6) were included: A stressed group (short‑term immobilization for 2 h/day for 4 consecutive days) and an unstressed (control) group. Colon samples were obtained to detect neutrophils and goblet cells by optical microscopy, TJ protein expression (occludin, and claudin ‑2, ‑4, ‑7, ‑12 and ‑15) by western blotting, mRNA levels of TJ genes and proinflammatory cytokines [tumor necrosis factor (TNF)‑α, interleukin (IL)‑1β, ‑6 and ‑8] by reverse transcription‑quantitative PCR, fecal lactoferrin by ELISA and the number of colony‑forming units of aerobic bacteria. Compared with goblet cells in control mice, goblet cells were enlarged and reduced in number in stressed mice, whereas neutrophil cellularity was unaltered. Stressed mice exhibited reduced mRNA expression for all evaluated TJ mRNAs, with the exception of claudin‑7, which was upregulated. Protein levels of occludin and all claudins (with the exception of claudin‑12) were decreased in stressed mice. Fecal lactoferrin, proinflammatory cytokine mRNA levels and aerobic bacterial counts were all increased in the stressed group. These results indicated that immobilization stress induced proinflammatory and potential remodeling effects in the colon by decreasing TJ protein expression. The present study may be a useful reference for therapies aiming to regulate the effects of stress on intestinal inflammatory dysfunction.

Lactobacillus paracasei PS23 reduced early-life stress abnormalities in maternal separation mouse model

Maternal separation (MS) has been developed as a model for inducing stress and depression in studies using rodents. The concept of the gut-brain axis suggests that gut health is essential for brain health. Here, we present the effects of administration of a probiotic, Lactobacillus paracasei PS23 (PS23), to MS mice against psychological traits including anxiety and depression. The administration of live and heat-killed PS23 cells showed positive behavioural effects on MS animals, where exploratory tendencies and mobility were increased in behavioural tests, indicating reduced anxiety and depression compared to the negative control mice (P<0.05). Mice administered with both live and heat-killed PS23 cells also showed lower serum corticosterone levels accompanied by higher serum anti-inflammatory interleukin 10 (IL-10) levels, compared to MS separated mice (P<0.05), indicating a stress-elicited response affiliated with increased immunomodulatory properties. Assessment of neurotransmitters in the brain hippocampal region revealed that PS23 affected the concentrations of dopaminergic metabolites differently than the control, suggesting that PS23 may have improved MS-induced stress levels via neurotransmitter pathways, such as dopamine or other mechanisms not addressed in the current study. Our study illustrates the potential of a probiotic in reversing abnormalities induced by early life stress and could be an alternative for brain health along the gut-brain axis.

The Multifactorial Etiopathogeneses Interplay of Inflammatory Bowel Disease: An Overview

The gastrointestinal system where inflammatory bowel disease occurs is central to the immune system where the innate and the adaptive/acquired immune systems are balanced in interactions with gut microbes under homeostasis conditions. This article overviews the high-throughput research screening on multifactorial interplay between genetic risk factors, the intestinal microbiota, urbanization, modernization, Westernization, the environmental influences and immune responses in the etiopathogenesis of inflammatory bowel disease in humans. Inflammatory bowel disease is an expensive multifactorial debilitating disease that affects thousands new people annually worldwide with no known etiology or cure. The conservative therapeutics focus on the established pathology where the immune dysfunction and gut injury have already happened but do not preclude or delay the progression. Inflammatory bowel disease is evolving globally and has become a global emergence disease. It is largely known to be a disease in industrial-urbanized societies attributed to modernization and Westernized lifestyle associated with environmental factors to genetically susceptible individuals with determined failure to process certain commensal antigens. In the developing nations, increasing incidence and prevalence of inflammatory bowel disease (IBD) has been associated with rapid urbanization, modernization and Westernization of the population. In summary, there are identified multiple associations to host exposures potentiating the landscape risk hazards of inflammatory bowel disease trigger, that include: Western life-style and diet, host genetics, altered innate and/or acquired/adaptive host immune responses, early-life microbiota exposure, change in microbiome symbiotic relationship (dysbiosis/dysbacteriosis), pollution, changing hygiene status, socioeconomic status and several other environmental factors have long-standing effects/influence tolerance. The ongoing multipronged robotic studies on gut microbiota composition disparate patterns between the rural vs. urban locations may help elucidate and better understand the contribution of microbiome disciplines/ecology and evolutionary biology in potentially protecting against the development of inflammatory bowel disease.

Gut permeability and depressive symptom severity in unmedicated adolescents

OBJECTIVE

This study examined gut permeability in unmedicated adolescents with and without major depressive disorder.

METHOD

Medically healthy, non-medicated, 12-17 year-old females in a major depressive episode (MDE) or healthy controls, without any psychiatric condition, were enrolled. They completed the Children's Depression Rating Scale-Revised (CDRS-R) and underwent a clinical interview. Preejection period (PEP) and respiratory sinus arrhythmia (RSA) data were collected to measure autonomic nervous system activity. Following an overnight fast, participants ingested lactulose and mannitol and collected urine for 4 hours while still fasting, to examine gut permeability. Plasma cytokines (interleukin 1β, interleukin 6, and tumor necrosis factor α) were measured. Correlational analyses were used to examine the associations between relevant variables.

RESULTS

41 female participants (age: 14.8 ± 1.6 years, n = 25 with MDE) were enrolled. PEP, but not RSA, was inversely associated with neurovegetative symptom severity on the CDRS-R (r = -0.31, p < 0.06). In the 30 participants with gut permeability data, the lactulose to mannitol ratio (LMR) was significantly positively associated with depression severity, particularly neurovegetative symptom severity (r = 0.37, p < 0.05). Notably, the association between neurovegetative symptom severity and PEP was substantially reduced after adjusting for LMR. Additionally, depression severity was significantly associated with circulating cytokines.

CONCLUSIONS

This is the first study to examine gut permeability in unmedicated adolescents, offering preliminary support for a mechanistic pathway linking sympathetic nervous system activation to increased gut permeability and activation of the innate immune system, likely contributing to the emergence of neurovegetative symptoms of depression.

Antioxidant Capacity and Behavioral Relevance of a Polyphenolic Extract of Chrysanthellum americanum in a Rat Model of Irritable Bowel Syndrome

Chrysanthellum americanum L. (Vatke) is a medicinal plant from the Compositae family used in west-African traditional medicine, known for its flavonoid and saponin richness and for its strong antioxidant potential. In the present study, we assessed the effects of Chrysanthellum americanum polyphenolic extract in the psychological stress-induced rat model of irritable bowel syndrome (IBS), a chronic functional digestive tract disorder marked by immune and inflammatory-related disturbances of central nervous and peripheral intestinal systems, which is often associated with mood disorders including depression and anxiety. Consequently, memory impairment, anxiety and depression behavioral indicators, and cerebral oxidative stress biomarker dynamics were evaluated in a multifactorial heterotypic stress-exposed IBS rats after 6-day gavage with polyphenolic C. americanum extract (100 mg/kg body weight). Y-maze, elevated plus maze, and forced swimming tests were used for assessing behavioral responses. Administration of the extract exhibited significant anxiolytic and antidepressant-like effects coupled with significantly increased temporal lobe antioxidant enzyme specific activity (superoxide dismutase and glutathione peroxidase) and decreased malondialdehyde levels, a well-known lipid peroxidation marker. Furthermore, linear regression statistical analyses showed significant correlations between the oxidative stress parameters and behavioral tests. In conclusion, our results suggest that the administration of Chrysanthellum americanum polyphenolic extract could ameliorate mood and cognitive disturbances related to stress-induced in an IBS rat model. This could be also related to cerebral oxidative stress status attenuation.

Stress Triggers Flare of Inflammatory Bowel Disease in Children and Adults

Inflammatory bowel disease (IBD) is an idiopathic inflammatory disease characterized by chronic and relapsing manifestations. It is noteworthy that the prevalence of IBD is gradually increasing in both children and adults. Currently, the pathogenesis of IBD remains to be completely elucidated. IBD is believed to occur through interactions among genetics, environmental factors, and the gut microbiota. However, the relapsing and remitting course of IBD underlines the importance of other modifiers, such as psychological stress. Growing evidence from clinical and experimental studies suggests that stress acts as a promoting or relapsing factor for IBD. Importantly, recent studies have reported an increasing incidence of anxiety or depression in both children and adults with IBD. In this article, we review the mechanisms by which stress affects IBD, such as via impaired intestinal barrier function, disturbance of the gut microbiota, intestinal dysmotility, and immune and neuroendocrine dysfunction. With regard to both children and adults, we provide recent evidence to describe how stress can affect IBD at various stages. Furthermore, we emphasize the importance of mental healing and discuss the value of approaches targeting stress in clinical management to develop enhanced strategies for the prevention and treatment of IBD.

Mast cells at the crossroads of microbiota and IBD

The human gut harbors a wide range of microorganisms that play a fundamental role in the well-being of their host. A dysregulation of the microbial composition can lead to the development or exacerbation of gastrointestinal (GI) disorders. Emerging evidence supports the hypothesis that mast cells (MCs) play a role in host-microbiota communication, modulating the mutual influence between the host and its microbiota through changes in their activation state. The ability of some bacteria to specifically affect MC functions and activation has been extensively studied, with different and sometimes conflicting results, while only little is known about MC-fungi interactions. In this review, the most recent advances in the field of MC-bacteria and MC-fungi interactions will be discussed, with a particular focus on the role of these interactions in the onset of GI disorders such as inflammatory bowel diseases (IBD). Moreover, the connection between some MC-targeting drugs and IBD was discussed, suggesting probiotics as reasonable and promising therapy in the management of IBD patients.

Mast cell corticotropin-releasing factor subtype 2 suppresses mast cell degranulation and limits the severity of anaphylaxis and stress-induced intestinal permeability

BACKGROUND

Psychological stress and heightened mast cell (MC) activation are linked with important immunologic disorders, including allergy, anaphylaxis, asthma, and functional bowel diseases, but the mechanisms remain poorly defined. We have previously demonstrated that activation of the corticotropin-releasing factor (CRF) system potentiates MC degranulation responses during IgE-mediated anaphylaxis and psychological stress through corticotropin-releasing factor receptor subtype 1 (CRF₁) expressed on MCs.

OBJECTIVE

In this study we investigated the role of corticotropin-releasing factor receptor subtype 2 (CRF₂) as a modulator of stress-induced MC degranulation and associated disease pathophysiology.

METHODS

In vitro MC degranulation assays were performed with bone marrow-derived mast cells (BMMCs) derived from wild-type (WT) and CRF₂-deficient (CRF₂^-/-) mice and RBL-2H3 MCs transfected with CRF₂-overexpressing plasmid or CRF₂ small interfering RNA. In vivo MC responses and associated pathophysiology in IgE-mediated passive systemic anaphylaxis and acute psychological restraint stress were measured in WT, CRF₂^-/-, and MC-deficient Kit^W-sh/W-sh knock-in mice.

RESULTS

Compared with WT mice, CRF₂^-/- mice exhibited greater serum histamine levels and exacerbated IgE-mediated anaphylaxis and colonic permeability. In addition, CRF₂^-/- mice exhibited increased serum histamine levels and colonic permeability after acute restraint stress. Experiments with BMMCs and RBL-2H3 MCs demonstrated that CRF₂ expressed on MCs suppresses store-operated Ca²⁺ entry signaling and MC degranulation induced by diverse MC stimuli. Experiments with MC-deficient Kit^W-sh/W-sh mice systemically engrafted with WT and CRF₂^-/- BMMCs demonstrated the functional importance of MC CRF₂ in modulating stress-induced pathophysiology.

CONCLUSIONS

MC CRF₂ is a negative global modulator of stimuli-induced MC degranulation and limits the severity of IgE-mediated anaphylaxis and stress-related disease pathogenesis.

Chronic dexamethasone exposure retards growth without altering the digestive tract microbiota composition in goats

Background

Dexamethasone (Dex), an artificially synthetic cortisol substitute, is commonly used as an anti-inflammatory drug, and is also employed to mimic the stress state experimentally. It is well known that chronic stress disturbs the gut microbiota community and digestive functions. However, no relevant studies have been conducted in ruminants.

Results

In this study, a low dosage of Dex (0.2 mg/kg body weight, Dex group, n = 5) was consecutively injected intramuscularly for 21 days to simulate chronic stress in growing goats. Goats were injected with saline (0.2 mg/kg body weight) as the control group (Con, n = 5). Dex-treated goats showed a higher number of white blood cells and blood glucose levels (p < 0.01), but lower dry matter intake (DMI) and body weight (p < 0.01) than those of saline-injected goats. Plasma cortisol concentration decreased significantly in response to the Dex injection compared to the control (p < 0.05). The Dex treatment did not change most ruminal volatile fatty acid (VFAs) concentrations before the morning feeding after 1–21 days of treatment (p > 0.05); however, ruminal VFA concentrations decreased dramatically 2, 4, 6, and 8 h after the morning feeding on day 21 of the Dex injections. In this study, chronic Dex exposure did not alter the community structure of microbes or methanogenes in the rumen, caecum, or colonic digesta. Only Prevotella increased on days 7 and 14 of Dex treatment, but decreased on day 21, and Methanosphaera was the only genus of methanogene that decreased.

Conclusions

Our results suggest that chronic Dex exposure retards growth by decreasing DMI, which may be mediated by higher levels of blood glucose and lower ruminal VFA production. Microbiota in the digestive tract was highly resistant to chronic Dex exposure.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1253-1) contains supplementary material, which is available to authorized users.

Chronic stress-associated visceral hyperalgesia correlates with severity of intestinal barrier dysfunction

In humans, chronic psychological stress is associated with increased intestinal paracellular permeability and visceral hyperalgesia, which is recapitulated in the chronic intermittent water avoidance stress (WAS) rat model. However, it is unknown whether enhanced visceral pain and permeability are intrinsically linked and correlate. Treatment of rats with lubiprostone during WAS significantly reduced WAS-induced changes in intestinal epithelial paracellular permeability and visceral hyperalgesia in a subpopulation of rats. Lubiprostone also prevented WAS-induced decreases in the epithelial tight junction protein, occludin (Ocln). To address the question of whether the magnitude of visceral pain correlates with the extent of altered intestinal permeability, we measured both end points in the same animal because of well-described individual differences in pain response. Our studies demonstrate that visceral pain and increased colon permeability positively correlate (0.6008, P = 0.0084). Finally, exposure of the distal colon in control animals to Ocln siRNA in vivo revealed that knockdown of Ocln protein inversely correlated with increased paracellular permeability and enhanced visceral pain similar to the levels observed in WAS-responsive rats. These data support that Ocln plays a potentially significant role in the development of stress-induced increased colon permeability. We believe this is the first demonstration that the level of chronic stress-associated visceral hyperalgesia directly correlates with the magnitude of altered colon epithelial paracellular permeability.

Effects of coeliacomesenteric blood flow reduction on intestinal barrier function in rainbow trout Oncorhynchus mykiss

The aim of the current work was to elucidate if there is a connection between stress-induced decrease in coeliacomesenteric artery blood flow (i.e. gastrointestinal blood flow; GBF) and disruption of the intestinal primary barrier in rainbow trout Oncorhynchus mykiss. Upon initiation of a 15 min acute chasing stress, the GBF decreased instantly by c. 92%. The GBF then slowly increased and reached c. 28% of resting values at the end of the stress protocol. After the stress was ceased, the GBF slowly increased and returned to resting values within c. 45 min. Intestinal permeability assessment in an Ussing-chambers set-up revealed impaired intestinal barrier function 24 h after stress. When the stress-induced GBF reduction was mimicked by an experimental occlusion of the coeliacomesenteric artery for 15 min followed by 24 h recovery, no effect on intestinal barrier function was observed. These results suggest that no direct causal relationship can be found between the GBF reduction and development of intestinal barrier dysfunction following periods of acute stress in this species of fish.

Neural, Hormonal, and Cognitive Correlates of Metabolic Dysfunction and Emotional Reactivity

OBJECTIVE

Prediabetes and type 2 diabetes (i.e., hyperglycemia) are characterized by insulin resistance. These problems with energy metabolism may exacerbate emotional reactivity to negatively valenced stimuli and related phenomena such as predisposition toward negative affect, as well as cognitive deficits. Higher emotional reactivity is seen with hyperglycemia and insulin resistance. However, it is largely unknown how metabolic dysfunction correlates with related neural, hormonal, and cognitive outcomes.

METHODS

Among 331 adults from the Midlife in the United States study, eye-blink response (EBR) we cross sectionally examined to gauge reactivity to negative, positive, or neutrally valenced pictures from international affect picture system stimuli proximal to an acoustic startle probe. Increased EBR to negative stimuli was considered an index of stress reactivity. Frontal alpha asymmetry, a biomarker of negative affect predisposition, was determined using resting electroencephalography. Baseline urinary cortisol output was collected. Cognitive performance was gauged using the Brief Test of Adult Cognition by telephone. Fasting glucose and insulin characterized hyperglycemia or the homeostatic model assessment of insulin resistance.

RESULTS

Higher homeostatic model assessment of insulin resistance corresponded to an increased startle response, measured by EBR magnitude, for negative versus positive stimuli (R = 0.218, F(1,457) = 5.48, p = .020, euglycemia: M(SD) = .092(.776), hyperglycemia: M(SD) = .120(.881)). Participants with hyperglycemia versus euglycemia showed greater right frontal alpha asymmetry (F(1,307) = 6.62, p = .011, euglycemia: M(SD) = .018(.167), hyperglycemia: M(SD) = -.029(.160)), and worse Brief Test of Adult Cognition by telephone arithmetic performance (F(1,284) = 4.25, p = .040, euglycemia: M(SD) = 2.390(1.526), hyperglycemia: M(SD) = 1.920(1.462)). Baseline urinary cortisol (log10 μg/12 hours) was also dysregulated in individuals with hyperglycemia (F(1,324) = 5.09, p = .025, euglycemia: M(SD) = 1.052 ± .332, hyperglycemia: M(SD) = .961 (.362)).

CONCLUSIONS

These results suggest that dysmetabolism is associated with increased emotional reactivity, predisposition toward negative affect, and specific cognitive deficits.

Infliximab restores colonic barrier to adherent-invasive E. coli in Crohn's disease via effects on epithelial lipid rafts

OBJECTIVE

Infliximab is important in the therapeutic arsenal of Crohn's disease (CD). However, its effect on mucosal barrier function is not fully understood. Adherent-invasive Escherichia coli (AIEC) are important in CD pathophysiology, but the transmucosal uptake routes are partly unknown. We investigated effects of infliximab on uptake of colon-specific AIEC HM427 across CD colonic mucosa.

MATERIALS AND METHODS

Endoscopic biopsies from non-inflamed colon of seven patients with CD, before and after two infliximab infusions, and eight non-inflammation controls, were mounted in Ussing chambers. Paracellular permeability (⁵¹Cr-EDTA) and transmucosal passage of GFP-expressing HM427 were studied. Mechanisms of HM427 transepithelial transport were investigated in Caco-2 monolayers treated with TNF, in the presence of infliximab and/or endocytosis inhibitors.

RESULTS

Before infliximab treatment, colonic passage of HM427 [CD: 2475 CFU (450-3000); controls 1163(225-1950)] and ⁵¹Cr-EDTA permeability were increased in CD (p < .05), but were restored to control levels by infliximab (CD: 150 (18.8-1069)). In TNF-exposed Caco-2 monolayers HM427 transport and lipid rafts/HM427 co-localization was decreased by infliximab. The lipid raft inhibitor methyl-β-cyclodextrin decreased HM427 transport.

CONCLUSION

Infliximab restored the colonic barrier to AIEC in CD; an effect partially mediated by blocking lipid rafts in epithelial cells. This ability likely contributes to infliximab's clinical efficacy in colonic CD.

The Brain-Gut-Microbiome Axis

Preclinical and clinical studies have shown bidirectional interactions within the brain-gut-microbiome axis. Gut microbes communicate to the central nervous system through at least 3 parallel and interacting channels involving nervous, endocrine, and immune signaling mechanisms. The brain can affect the community structure and function of the gut microbiota through the autonomic nervous system, by modulating regional gut motility, intestinal transit and secretion, and gut permeability, and potentially through the luminal secretion of hormones that directly modulate microbial gene expression. A systems biological model is proposed that posits circular communication loops amid the brain, gut, and gut microbiome, and in which perturbation at any level can propagate dysregulation throughout the circuit. A series of largely preclinical observations implicates alterations in brain-gut-microbiome communication in the pathogenesis and pathophysiology of irritable bowel syndrome, obesity, and several psychiatric and neurologic disorders. Continued research holds the promise of identifying novel therapeutic targets and developing treatment strategies to address some of the most debilitating, costly, and poorly understood diseases.

Psychoneuroimmunology: The Experiential Dimension

Accumulating evidence has made clear that experience-the knowledge an individual acquires during a lifetime of sensing and acting-is of fundamental biological relevance. Experience makes an impact on all adaptive systems, including the endocrine, immune, and nerve systems, and is of the essence, not only for the unfolding of an organisms' healthy status, but also for the development of malfunctional traits. Nevertheless, experience is often excluded from empirical approaches. A variety of complex interactions that influence life histories are thereby neglected. Such ignorance is especially detrimental for psychoneuroimmunology, the science that seeks to understand how the exquisite and dynamic interplay between mind, body, and environment relates to behavioral characteristics. This chapter reviews claims for incorporating experience as a member of good explanatory standing in biology and medicine, and more specifically claims that experiential knowledge is required to enable meaningful and relevant explanations and predictions in the psychoneuroimmunological realm.

Repeated water avoidance stress induces visceral hypersensitivity: Role of interleukin-1, interleukin-6, and peripheral corticotropin-releasing factor

BACKGROUND AND AIM

Repeated water avoidance stress (WAS) induces visceral hypersensitivity. Additionally, it is also known to activate corticotropin-releasing factor (CRF), mast cells, and pro-inflammatory cytokines systems, but their precise roles on visceral sensation have not been determined definitely. The aim of the study was to explore this issue.

METHODS

Abdominal muscle contractions induced by colonic balloon distention, that is, visceromotor response (VMR) was detected electrophysiologically in conscious rats. WAS or sham stress as control for 1 h daily was loaded, and the threshold of VMR was determined before and at 24 h after the stress.

RESULTS

Repeated WAS for three consecutive days reduced the threshold of VMR, but sham stress did not induce any change. Astressin, a CRF receptor antagonist (50 μg/kg) intraperitoneally (ip) at 10 min before each WAS session, prevented the visceral allodynia, but the antagonist (200 μg/kg) ip at 30 min and 15 h before measurement of the threshold after completing 3-day stress session did not modify the response. Ketotifen, a mast cell stabilizer (3 mg/kg), anakinra, an interleukin (IL)-1 receptor antagonist (20 mg/kg) or IL-6 antibody (16.6 μg/kg) ip for two times before the measurement abolished the response.

CONCLUSIONS

Repeated WAS for three consecutive days induced visceral allodynia, which was mediated through mast cells, IL-1, and IL-6 pathways. Inhibition of peripheral CRF signaling prevented but did not reverse this response, suggesting that peripheral CRF may be an essential trigger but may not contribute to the maintenance of repeated WAS-induced visceral allodynia.

FODMAP diet modulates visceral nociception by lipopolysaccharide-mediated intestinal inflammation and barrier dysfunction

Foods high in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) exacerbate symptoms of irritable bowel syndrome (IBS); however, their mechanism of action is unknown. We hypothesized that a high-FODMAP (HFM) diet increases visceral nociception by inducing dysbiosis and that the FODMAP-altered gut microbial community leads to intestinal pathology. We fed rats an HFM and showed that HFM increases rat fecal Gram-negative bacteria, elevates lipopolysaccharides (LPS), and induces intestinal pathology, as indicated by inflammation, barrier dysfunction, and visceral hypersensitivity (VH). These manifestations were prevented by antibiotics and reversed by low-FODMAP (LFM) diet. Additionally, intracolonic administration of LPS or fecal supernatant (FS) from HFM-fed rats caused intestinal barrier dysfunction and VH, which were blocked by the LPS antagonist LPS-RS or by TLR4 knockdown. Fecal LPS was higher in IBS patients than in healthy subjects (HS), and IBS patients on a 4-week LFM diet had improved IBS symptoms and reduced fecal LPS levels. Intracolonic administration of FS from IBS patients, but not FS from HS or LFM-treated IBS patients, induced VH in rats, which was ameliorated by LPS-RS. Our findings indicate that HFM-associated gut dysbiosis and elevated fecal LPS levels induce intestinal pathology, thereby modulating visceral nociception and IBS symptomatology, and might provide an explanation for the success of LFM diet in IBS patients.

Exhaled nitric oxide and vascular endothelial growth factor as predictors of cold symptoms after stress

OBJECTIVE

Prior research has demonstrated that psychosocial stress is associated with respiratory infections. Immunologic, endocrine, and cardiovascular predictors of such infections have been explored with varying success. We therefore sought to study the unexplored role of airway mucosal immunity factors, nitric oxide (NO) and vascular endothelial growth factor (VEGF). NO is secreted by airway epithelial cells as part of the first line of defense against bacteria, viruses, and fungi. VEGF is expressed by mast cells in respiratory infections and recruits immune cells to infected sites, but in excess lead to vulnerability of the airway epithelium.

METHODS

In this proof-of-concept study we measured exhaled NO, exhaled breath condensate (EBC) VEGF, salivary VEGF, and salivary cortisol in 36 students undergoing final academic examinations at three occasions: a low-stress baseline during the term, an early phase of finals, and a late phase of finals. Participants also reported on cold symptoms at these time points and approximately 5 and 10days after their last academic examination.

RESULTS

Higher baseline NO was associated with fewer cold symptoms after stress, whereas higher baseline VEGF in EBC and saliva were associated with more cold symptoms after stress. Perceived stress at baseline as well as salivary VEGF and cortisol late in the finals also contributed to the prediction of later cold symptoms.

CONCLUSION

Basal levels of NO and VEGF may inform about mucosal immunocompetence and add to preventative treatments against airway infections from periods of stress in daily life.

Frontline Science: Corticotropin-releasing factor receptor subtype 1 is a critical modulator of mast cell degranulation and stress-induced pathophysiology

Life stress is a major risk factor in the onset and exacerbation of mast cell-associated diseases, including allergy/anaphylaxis, asthma, and irritable bowel syndrome. Although it is known that mast cells are highly activated upon stressful events, the mechanisms by which stress modulates mast cell function and disease pathophysiology remains poorly understood. Here, we investigated the role of corticotropin-releasing factor receptor subtype 1 (CRF₁) in mast cell degranulation and associated disease pathophysiology. In a mast cell-dependent model of IgE-mediated passive systemic anaphylaxis (PSA), prophylactic administration of the CRF₁-antagonist antalarmin attenuated mast cell degranulation and hypothermia. Mast cell-deficient Kit^W-sh/W-sh mice engrafted with CRF₁^-/- bone marrow-derived mast cells (BMMCs) exhibited attenuated PSA-induced serum histamine, hypothermia, and clinical scores compared with wild-type BMMC-engrafted Kit^W-sh/W-sh mice. Kit^W-sh/W-sh mice engrafted with CRF₁^-/- BMMCs also exhibited suppressed in vivo mast cell degranulation and intestinal permeability in response to acute restraint stress. Genetic and pharmacologic experiments with murine BMMCs, rat RBL-2H3, and human LAD2 mast cells demonstrated that although CRF₁ activation did not directly induce MC degranulation, CRF₁ signaling potentiated the degranulation responses triggered by diverse mast cell stimuli and was associated with enhanced release of Ca²⁺ from intracellular stores. Taken together, our results revealed a prominent role for CRF₁ signaling in mast cells as a positive modulator of stimuli-induced degranulation and in vivo pathophysiologic responses to immunologic and psychologic stress.

Psychological stress-induced colonic barrier dysfunction: Role of immune-mediated mechanisms

BACKGROUND

Evidence suggests that patients with irritable bowel syndrome (IBS) exhibit increases in gut permeability and alterations in tight junction (TJ) protein expression. Although psychological stress worsens IBS symptoms, the mechanisms by which stress enhances gut permeability and affects TJ protein expression remain to be determined. Here, we test the hypothesis that chronic intermittent psychological stress activates the release of proinflammatory cytokines to alter TJ proteins and promotes increased gut permeability.

METHODS

Male Fischer-344 rats were subjected to 1 hour of water avoidance stress (WAS) or SHAM stress per day for 7 days. Following the stress protocol, colonic permeability was measured via transepithelial electrical resistance (TEER) and macromolecular flux of horseradish peroxidase (HRP). In tissue isolated from rats exposed to the WAS or SHAM stress, TJ proteins claudin-2, junctional adhesion molecule-A (JAM-A) and zonula occluden-1 (ZO-1) were measured via Western blotting, histological appearance of the colonic segments was assessed via hematoxylin and eosin staining, and an inflammatory cytokine panel was quantified via quantitative reverse transcription-polymerase chain reaction.

KEY RESULTS

Repetitive daily exposure to WAS decreased the TEER, increased the macromolecular flux of HRP, and altered the expression of claudin-2, JAM-A and ZO-1 proteins within colonic tissue compared to SHAM controls. In the absence of a histologically defined inflammation, the cytokine profiles of WAS-treated animals revealed an increase in interleukin-1β and tumor necrosis factor (TNF)-α. Subsequent analysis revealed a significant positive correlation between TNF-α and expression of TJ protein claudin-2.

CONCLUSIONS & INFERENCES

Our findings suggest that chronic stress increases colonic permeability via sub-inflammatory cytokine-mediated remodeling of TJ protein expression.

Effects of dietary L-tryptophan supplementation on intestinal response to chronic unpredictable stress in broilers

Stress has been recognized as a critical risk factor for gastrointestinal diseases in both humans and animals. However, nutritional strategies to attenuate stress-induced intestinal barrier function and underlying mechanisms remain largely unknown. This study tested the hypothesis that L-tryptophan enhanced intestinal barrier function by regulating mucosal serotonin metabolism in chronic unpredictable stress-exposed broilers. One-day-old male broilers (Arbor Acres) were fed a basal diet supplemented with or without L-tryptophan in the absence or presence of chronic unpredictable stress. Feed intake, body weight gain, plasma corticosterone and 5-hydroxytryptamine (5-HT), intestinal permeability, mucosal secretory IgA (sIgA), and mRNA levels for tryptophan hydroxylase 1 (TPH1), IL-1β, IL-6, TNF-α, IL-10, protein abundance for claudin-1, occludin, and ZO-1 were determined. Stress exposure led to elevated plasma corticosterone (P < 0.05), increased intestinal permeability (P < 0.05), reduced growth performance (P < 0.05), and decreased sIgA secretion compared with the controls. These effects were largely reversed (P < 0.05) by L-tryptophan supplementation. Western blot analysis showed that stress exposure resulted in decreased protein abundance for occludin, claudin-1, and ZO-1, which was attenuated by L-tryptophan. mRNA levels for IL-1β, IL-6, and TNF-α were increased, but those for IL-10 were decreased, in the jejunal tissue of broilers subjected to stress. This effect of stress on cytokine expression was abolished by L-tryptophan treatment. The effects of stress were associated with decreased plasma concentration of 5-HT (P < 0.05), and reduced (P < 0.05) mRNA levels for TPH1. L-Tryptophan supplementation markedly attenuated stress-induced alterations in 5-HT and TPH1 mRNA level in jejunal tissues of broilers. Collectively, these results indicate that L-tryptophan supplementation alleviates chronic unpredictable stress-induced intestinal barrier dysfunction by regulating 5-HT metabolism in broilers.

The role of the commensal microbiota in adaptive and maladaptive stressor-induced immunomodulation

Over the past decade, it has become increasingly evident that there are extensive bidirectional interactions between the body and its microbiota. These interactions are evident during stressful periods, where it is recognized that commensal microbiota community structure is significantly changed. Many different stressors, ranging from early life stressors to stressors administered during adulthood, lead to significant, community-wide differences in the microbiota. The mechanisms through which this occurs are not yet known, but it is known that commensal microbes can recognize, and respond to, mammalian hormones and neurotransmitters, including those that are involved with the physiological response to stressful stimuli. In addition, the physiological stress response also changes many aspects of gastrointestinal physiology that can impact microbial community composition. Thus, there are many routes through which microbial community composition might be disrupted during stressful periods. The implications of these disruptions in commensal microbial communities for host health are still not well understood, but the commensal microbiota have been linked to stressor-induced immunopotentiation. The role of the microbiota in stressor-induced immunopotentiation can be adaptive, such as when these microbes stimulate innate defenses against bacterial infection. However, the commensal microbiota can also lead to maladaptive immune responses during stressor-exposure. This is evident in animal models of colonic inflammation where stressor exposure increases the inflammation through mechanisms involving the microbiota. It is likely that during stressor exposure, immune cell functioning is regulated by combined effects of both neurotransmitters/hormones and commensal microbes. Defining this regulation should be a focus of future studies.

Prevalence and Determinants of Job Stress in Patients with Inflammatory Bowel Disease

BACKGROUND

Psychosocial factors have been shown to predict a poor disease course in patients with inflammatory bowel disease (IBD), but whether this applies to job stress is currently unknown. We assessed the prevalence of job stress and its correlates in a large cohort of patients with IBD.

METHODS

We included all adult, professionally active patients enrolled between 2006 and 2015 in the Swiss IBD Cohort. Job stress was measured through the self-report effort-reward imbalance ratio and overcommitment (OC) to work questionnaires. We used multiple linear regressions to assess association with sociodemographic, lifestyle, psychosocial, and disease-related factors.

RESULTS

Altogether 1656 patients completed the questionnaires (905 Crohn's disease and 751 ulcerative colitis/IBD unclassified). Only 91 (5.7%) of patients had an effort-reward imbalance ratio >1. Effort-reward imbalance and OC scores were higher in full-time versus part-time employees (coef = 0.050, P = 0.002; coef = 0.906, P < 0.001) and among those absent from the workplace in the previous 3 months (coef = 0.049, P = 0.010; coef = 1.062, P < 0.001). Higher OC scores were associated with sex (women vs. men: coef = 0.568, P = 0.014), being in a relationship (coef = 0.805, P = 0.001), higher level of occupation (director vs. trainee: coef = 1.447, P < 0.001), and extraintestinal manifestations (coef = 0.623, P = 0.005). Patients hospitalized in the previous 12 months had lower OC scores (coef = 0.560, P = 0.038).

CONCLUSIONS

The average level of job stress seems to be remarkably low in patients with IBD from Switzerland. The clinician should turn attention especially to women, full-time employees with a high level of education, and patients with extraintestinal manifestations to identify those with the most vulnerability to suffer from job stress.

Pathogenesis, Experimental Models and Contemporary Pharmacotherapy of Irritable Bowel Syndrome: Story About the Brain-Gut Axis

Background

Although the precise pathophysiology of irritable bowel syndrome (IBS) remains unknown, it is generally considered to be a disorder of the brain-gut axis, representing the disruption of communication between the brain and the digestive system. The present review describes advances in understanding the pathophysiology and experimental approaches in studying IBS, as well as providing an update of the therapies targeting brain-gut axis in the treatment of the disease.

Methods

Causal factors of IBS are reviewed. Following this, the preclinical experimental models of IBS will be introduced. Besides, both current and future therapeutic approaches of IBS will be discussed.

Results

When signal of the brain-gut axis becomes misinterpreted, it may lead to dysregulation of both central and enteric nervous systems, altered intestinal motility, increased visceral sensitivity and consequently contributing to the development of IBS. Interference of the brain-gut axis can be modulated by various psychological and environmental factors. Although there is no existing animal experiment that can represent this complex multifactorial disease, these in vivo models are clinically relevant readouts of gastrointestinal functions being essential to the identification of effective treatments of IBS symptoms as well as their molecular targets. Understanding the brain-gut axis is essential in developing the effective therapy for IBS. Therapies include improvement of GI motor functions, relief of visceral hypersensitivity and pain, attenuation of autonomic dysfunctions and suppression of mucosal immune activation.

Conclusion

Target-oriented therapies that provide symptomatic, psychological and physiological benefits could surely help to improve the quality of life of IBS patients.

Antibiotics Suppress Activation of Intestinal Mucosal Mast Cells and Reduce Dietary Lipid Absorption in Sprague-Dawley Rats

BACKGROUND & AIMS

The gut microbiota affects intestinal permeability and mucosal mast cells (MMCs) responses. Activation of MMCs has been associated with absorption of dietary fat. We investigated whether the gut microbiota contributes to the fat-induced activation of MMCs in rats, and how antibiotics might affect this process.

METHODS

Adult male Sprague-Dawley rats were given streptomycin and penicillin for 4 days (n = 6-8) to reduce the abundance of their gut flora, or normal drinking water (controls, n = 6-8). They underwent lymph fistula surgery and after an overnight recovery were given an intraduodenal bolus of intralipid. We collected intestinal tissues and lymph fluid and assessed activation of MMCs, intestinal permeability, and fat transport parameters.

RESULTS

Compared with controls, intestinal lymph from rats given antibiotics had reduced levels of mucosal mast cell protease II (produced by MMCs) and decreased activity of diamine oxidase (produced by enterocytes) (P < .05). Rats given antibiotics had reduced intestinal permeability in response to dietary lipid compared with controls (P < .01). Unexpectedly, antibiotics also reduced lymphatic transport of triacylglycerol and phospholipid (P < .01), concomitant with decreased levels of mucosal apolipoproteins B, A-I, and A-IV (P < .01). No differences were found in intestinal motility or luminal pancreatic lipase activity between rats given antibiotics and controls. These effects were not seen with an acute dose of antibiotics or 4 weeks after the antibiotic regimen ended.

CONCLUSIONS

The intestinal microbiota appears to activate MMCs after the ingestion of fat in rats; this contributes to fat-induced intestinal permeability. We found that the gut microbiome promotes absorption of lipid, probably by intestinal production of apolipoproteins and secretion of chylomicrons.

Repeated Water Avoidance Stress Alters Mucosal Mast Cell Counts, Interleukin-1β Levels with Sex Differences in the Distal Colon of Wistar Rats

Background/Aims

This study was aimed at evaluating differences in the effects of repeated water avoidance stress (rWAS) on colonic movement, mucosal mast cell counts, cytokine levels, and visceromotor response (VMR) to colorectal distension (CRD) in rats of both sexes.

Methods

Wistar rats were divided into stress and no-stress groups. Rats in the stress group were exposed to rWAS (1 hr/day) for 10 days. Mucosal mast cells were immunohistochemically stained with anti-mast cell tryptase antibody and counted. The colonic mucosal cytokine levels were measured with enzyme-linked immunosorbent assay. The VMR to CRD (visceral analgesia) was assessed by using a barostat and noninvasive manometry.

Results

The mean number of fecal pellets in the rWAS group increased significantly as compared with that in the no-stress group in both sexes. After adjustment for body weight, the female rats had a significantly higher pellet output than the male rats. The mucosal mast cell count of the female rWAS group was higher than that of the male rWAS group (13.0 ± 0.9 vs 8.8 ± 0.6; P < 0.001). The colonic mucosal interleukin-1β level was also higher only in the female rats of the rWAS group than in those of the no-stress group. On days 10 and 11, a decrease in VMR to CRD was observed at 40 and 60 mmHg in both sexes of the rWAS group, without a sex-based difference.

Conclusions

The colonic response to stress appeared to be more sensitive in the female rats than in the male rats. However, stress-induced visceral analgesia had no sex-related difference and the underlying mechanism needs to be further evaluated.

IBS and IBD - separate entities or on a spectrum?

The acute phase of IBD with inflamed gut and often ulcerated mucosa is clearly different from the apparently normal mucosa characteristic of IBS. However, more detailed assessment has detected immune activation, increased gut permeability, increased mucosal serotonin availability, abnormalities of enteric nerve structure and function, and dysbiosis in gut microbiota in IBS - all features seen in IBD. Furthermore, as treatments for inflammation in IBD have become more effective it is now apparent that ∼1 in 3 patients with IBD in remission from inflammation still have persistent abnormalities of sensation, motility and gut microbiota, which might cause IBS-like symptoms. This Perspective explores the overlap between IBS and IBD and their treatments, proposing future directions for research in this stimulating area.

Endoplasmic reticulum stress is involved in the colonic epithelium damage induced by maternal separation

BACKGROUND

Maternal separation (MS) leads to intestinal barrier dysfunction in neonatal mice. Endoplasmic reticulum (ER) stress is associated with apoptosis and pro-inflammatory response induction. We hypothesized that MS induced gut damage is associated with ER stress and that administration of an ER stress inhibitor protects gut damage.

METHODS

C57BL/6 mice received intraperitoneal PBS (n=10) or Salubrinal (1mg/kg/day, n=10). MS was performed soon after treatment for 3h daily between P5 and P9. Ten untreated neonatal mice served as control. The colon was harvested on P9 and analyzed for ER stress markers (BiP, CHOP), apoptosis (CC3), goblet cell number per crypt and crypt length (Alcian blue, hematoxylin/eosin), and transcellular permeability (Ussing chamber). Groups were compared using one-way ANOVA with Bonferroni post-test.

RESULTS

Compared to controls, MS mice had higher relative protein expression of ER stress and apoptosis markers (p<0.05) and reduced goblet cell number per crypt and crypt length (p<0.001). In comparison to PBS mice, Salubrinal treated mice had higher goblet cell number (p<0.05), crypt length (p<0.001), and lower transcellular permeability (p<0.05).

CONCLUSIONS

Maternal separation induces ER stress and causes colon damage, but ER stress inhibitor protects morphology and permeability. This provides insights on bowel pathogenesis and potential novel treatments for diseases such as necrotizing enterocolitis.

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.

The role of substance P in the maintenance of colonic hypermotility induced by repeated stress in rats

BACKGROUND

The mechanism underlying chronic stress-induced gastrointestinal (GI) dysmotility has not been fully elucidated and GI hormones have been indicated playing a role in mediating stress-induced changes in GI motor function.

AIMS

Our objective was to study the possible role of substance P (SP) in the colonic hypermotility induced by repeated water avoidance stress (WAS) which mimics irritable bowel syndrome.

METHODS

Male Wistar rats were submitted to WAS or sham WAS (SWAS) (1h/day) for up to 10 consecutive days. Enzyme Immunoassay Kit was used to detect the serum level of SP. The expression of neurokinin-1 receptor (NK1R) was investigated by Immunohistochemistry and Western blotting. The spontaneous contraction of muscle strip was studied in an organ bath system. L-type calcium channel currents (ICa,L) of smooth muscle cells (SMCs) were recorded by whole-cell patch-clamp technique.

RESULTS

Fecal pellet expulsion and spontaneous contraction of proximal colon in rats were increased after repeated WAS. The serum level of SP was elevated following WAS. Immunohistochemistry proved the expression of NK1R in mucosa, muscularis and myenteric plexus. Western blotting demonstrated stress-induced up-regulation of NK1R in colon devoid of mucosa and submucosa. Repeated WAS increased the contractile activities of longitudinal muscle and circular muscle strips induced by SP and this effect was reversed by a selective NK1R antagonist. The ICa,L of SMCs in the WAS rats were drastically increased compared to controls after addition of SP.

CONCLUSIONS

Increased serum SP level and up-regulated NK1R in colon may contribute to stress-induced colonic hypermotility. And L-type calcium channels play a potentially important role in the process of WAS-induced dysmotility.

Mast Cells and Irritable Bowel Syndrome: From the Bench to the Bedside

Irritable bowel syndrome (IBS) is traditionally defined as a functional disorder since it lacks demonstrable pathological abnormalities. However, in recent years, low grade inflammatory infiltration, often rich in mast cells, in both the small and large bowel, has been observed in some patients with IBS. The close association of mast cells with major intestinal functions, such as epithelial secretion and permeability, neuroimmune interactions, visceral sensation, and peristalsis, makes researchers and gastroenterologists to focus attention on the key roles of mast cells in the pathogenesis of IBS. Numerous studies have been carried out to identify the mechanisms in the development, infiltration, activation, and degranulation of intestinal mast cells, as well as the actions of mast cells in the processes of mucosal barrier disruption, mucosal immune dysregulation, visceral hypersensitivity, dysmotility, and local and central stress in IBS. Moreover, therapies targeting mast cells, such as mast cell stabilizers (cromoglycate and ketotifen) and antagonists of histamine and serotonin receptors, have been tried in IBS patients, and have partially exhibited considerable efficacy. This review focuses on recent advances in the role of mast cells in IBS, with particular emphasis on bridging experimental data with clinical therapeutics for IBS patients.

Subacute stress and chronic stress interact to decrease intestinal barrier function in rats

Psychological stress increases intestinal permeability, potentially leading to low-grade inflammation and symptoms in functional gastrointestinal disorders. We assessed the effect of subacute, chronic and combined stress on intestinal barrier function and mast cell density. Male Wistar rats were allocated to four experimental groups (n = 8/group): 1/sham; 2/subacute stress (isolation and limited movement for 24 h); 3/chronic crowding stress for 14 days and 4/combined subacute and chronic stress. Jejunum and colon were collected to measure: transepithelial electrical resistance (TEER; a measure of epithelial barrier function); gene expression of tight junction molecules; mast cell density. Plasma corticosterone concentration was increased in all three stress conditions versus sham, with highest concentrations in the combined stress condition. TEER in the jejunum was decreased in all stress conditions, but was significantly lower in the combined stress condition than in the other groups. TEER in the jejunum correlated negatively with corticosterone concentration. Increased expression of claudin 1, 5 and 8, occludin and zonula occludens 1 mRNAs was detected after subacute stress in the jejunum. In contrast, colonic TEER was decreased only after combined stress, and the expression of tight junction molecules was unaltered. Increased mast cell density was observed in the chronic and combined stress condition in the colon only. In conclusion, our data show that chronic stress sensitizes the gastrointestinal tract to the effects of subacute stress on intestinal barrier function; different underlying cellular and molecular alterations are indicated in the small intestine versus the colon.

Mechanisms by which Stress Affects the Experimental and Clinical Inflammatory Bowel Disease (IBD): Role of Brain-Gut Axis

BACKGROUND

Stress of different origin is known to alter so called "braingut axis" and contributes to a broad array of gastrointestinal disorders including inflammatory bowel disease (IBD), irritable bowel syndrome (IBS) and other functional gastrointestinal diseases. The stressful situations and various stressors including psychosocial events, heat, hypo- and hyperthermia may worsen the course of IBD via unknown mechanism. The aims of this paper were to provide an overview of experimental and clinical evidences that stress activates the brain-gut axis which results in a mucosal mast cells activation and an increase in the production of proinflammatory cytokines and other endocrine and humoral mediators.

METHODS

Research and online content related to effects of stress on lower bowel disorders are reviewed and most important mechanisms are delineated.

RESULTS

Brain conveys the neural, endocrine and circulatory messages to the gut via brain-gut axis reflecting changes in corticotrophin releasing hormone, mast cells activity, neurotransmission at the autonomic nerves system and intestinal barrier function all affecting the pathogenesis of animal colitis and human IBD. Stress triggers the hypothalamus-pituitary axis and the activation of the autonomic nervous system, an increase in cortisol levels and proinflammatory cytokines such as tumor necrosis factor-alpha, interleukin-8, interleukin-1beta and interleukin-6.

CONCLUSION

The acute or chronic stress enhances the intestinal permeability weakening of the tight junctions and increasing bacterial translocation into the intestinal wall. An increased microbial load in the colonic tissue, excessive cytokine release and a partially blunted immune reactivity in response to stress result in its negative impact on IBD.

Cultured enterocytes internalise bacteria across their basolateral surface for, pathogen-inhibitable, trafficking to the apical compartment

In vitro- and in vivo-polarised absorptive epithelia (enterocytes) are considered to be non-phagocytic towards bacteria with invasive pathogenic strains relying on virulence factors to 'force' entry. Here, we report a serendipitous discovery that questions these beliefs. Thus, we uncover in well-established models of human small (Caco-2; TC-7) and large (T84) intestinal enterocytes a polarization-dependent mechanism that can transfer millions of bacteria from the basal to apical compartment. Antibiotic-protection assays, confocal imaging and drug inhibitor data are consistent with a transcellular route in which internalized, basolateral-membrane enclosed bacteria are trafficked to and across the apical surface. Basal-to-apical transport of non-pathogenic bacteria (and inert beads) challenged the idea of pathogens relying on virulence factors to force entry. Indeed, studies with Salmonella demonstrated that it's entry-forcing virulence factor (SPI-I) was not required to enter via the basolateral surface but to promote another virulence-associated event (intra-enterocyte accumulation).

Mitochondrial dysfunction in inflammatory bowel disease

Inflammatory Bowel Disease (IBD) represents a group of idiopathic disorders characterized by chronic or recurring inflammation of the gastrointestinal tract. While the exact etiology of disease is unknown, IBD is recognized to be a complex, multifactorial disease that results from an intricate interplay of genetic predisposition, an altered immune response, changes in the intestinal microbiota, and environmental factors. Together, these contribute to a destruction of the intestinal epithelial barrier, increased gut permeability, and an influx of immune cells. Given that most cellular functions as well as maintenance of the epithelial barrier is energy-dependent, it is logical to assume that mitochondrial dysfunction may play a key role in both the onset and recurrence of disease. Indeed several studies have demonstrated evidence of mitochondrial stress and alterations in mitochondrial function within the intestinal epithelium of patients with IBD and mice undergoing experimental colitis. Although the hallmarks of mitochondrial dysfunction, including oxidative stress and impaired ATP production are known to be evident in the intestines of patients with IBD, it is as yet unclear whether these processes occur as a cause of consequence of disease. We provide a current review of mitochondrial function in the setting of intestinal inflammation during IBD.

Abnormal epithelial cell energy metabolism influences pathogenesis of inflammatory bowel disease

Etiology and pathogenesis of inflammatory bowel disease (IBD) are not clear, but colonic mucosal damage is known to be a critical factor. In recent decades, many studies suggest that interfering with the energy metabolism of epithelial tissue could result in the widening of intestinal epithelial cell gap, increased bacterial translocation across the epithelium, decreased mucus secretion, and intestinal mucosal barrier dysfunction. Bacteria and antigens adhere to the intestinal mucosa, enter into the lamina propria, activate inflammation, and initiate the pathogenesis of IBD. The lack of energy fuel butyrate and mitochondrial dysfunction are the causes of abnormal energy metabolism of the intestinal epithelium. Improving energy metabolism and protection of mitochondrial function can alleviate the seriousness of IBD, reduce recurrence, and provides a new strategy for the treatment of IBD.