Psychological stress reactivates dextran sulfate sodium-induced chronic colitis in mice

Protective Effects of Inulin on Stress-Recurrent Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic inflammatory condition of the digestive tract and is closely associated with the homeostasis of the gut microbiota. Inulin, as a natural prebiotic, displays anti-inflammatory activity and maintains equilibrium of the intestinal microbiota. In this study, our research aimed to explore the potential of inulin in enhancing intestinal immunity and reducing inflammation in stress-recurrent IBD. In this study, a co-culture intestinal epithelium model and a stress-recurrent IBD mouse model was used to examine the protective effects of inulin. It was observed that inulin digesta significantly reduced pro-inflammatory cytokine expression (CXCL8/IL8 and TNFA) and increased MUC2 expression in intestinal epithelial cells. In vivo, our findings showed that Inulin intake significantly prevented IBD symptoms. This was substantiated by a decrease in serum inflammatory markers (IL-6, CALP) and a downregulation of inflammatory cytokine (Il6) in colon samples. Additionally, inulin intake led to an increase in short-chain fatty acids (SCFAs) in cecal contents and a reduction in the expression of endoplasmic reticulum (ER) stress markers (CHOP, BiP). Our results highlight that inulin can improve stress-recurrent IBD symptoms by modulating microbiota composition, reducing inflammation, and alleviating ER stress. These findings suggested the therapeutic potential of inulin as a dietary intervention for ameliorating stress-recurrent IBD.

Genetic and Pharmacological Blockade of Sigma-1 Receptors Attenuates Inflammation-Associated Hypersensitivity during Acute Colitis in CD1 Mice

Sigma-1 receptors (σ1Rs) are implicated in nociception, including pain sensitization, and inflammation. We assessed the role of σ1Rs on acute colitis-associated hypersensitivity using both genetic (constitutive knockout) and pharmacological blockade of the receptor. Colitis was induced in CD1 wild-type (WT) and σ1R KO mice (exposure to dextran sodium sulfate, 3%). A von Frey test was used to assess referred mechanosensitivity (abdominal and plantar withdrawal responses). The effects of the selective σ1R antagonists BD1063 and E-52862 were also assessed in WT animals. The expression of immune and sensory-related markers (RT-qPCR, Western blot) was assessed in the colon and lumbosacral spinal cord. The genetic ablation or pharmacological blockade of σ1Rs attenuated acute colonic inflammation in a similar manner. Mechanosensitivity was similar in WT and σ1R KO mice before colitis. In WT mice, but not in σ1R KO, colitis was associated with the development of referred mechanical hypersensitivity, manifested as a reduction in the withdrawal thresholds to mechanical probing (paw and abdominal wall). In WT mice, BD1063 and E-52862 blocked colitis-associated hypersensitivity. A genotype- and treatment-related differential regulation of sensory-related markers was detected locally (colon) and within the spinal cord. σ1Rs are involved in the development of acute intestinal inflammation and its associated referred mechanical hypersensitivity. The selective modulation of sensory-related pathways within the colon and spinal cord might be part of the underlying mechanisms. These observations support the pharmacological use of σ1R antagonists for the treatment of intestinal inflammation-induced hypersensitivity.

Effect of Polycan, a β-Glucan from Aureobasidium pullulans SM-2001, on Inflammatory Response and Intestinal Barrier Function in DSS-Induced Ulcerative Colitis

Ulcerative colitis (UC), a subtype of inflammatory bowel disease, is a chronic gastrointestinal inflammatory disease with unclear etiology and pathophysiology. Herein, we determined the effects of extracellular polysaccharides purified from Aureobasidium pullulans SM-2001 (Polycan) on tight junction protein expression, inflammation, and apoptosis in a dextran sodium sulfate (DSS)-induced acute colitis model. Fifty mice were divided into normal, DSS, DSS + Polycan 250 mg/kg (Polycan 250), DSS + Polycan 500 mg/kg (Polycan 500), and DSS + 5-aminosalicylic acid 100 mg/kg (5-ASA) groups. Their body weights, colon lengths, histological changes in colon tissue, and tight junction function were observed. Results showed that Polycan 250, Polycan 500, and 5-ASA significantly inhibited body weight loss compared with DSS. Similar to 5-ASA, Polycan 500 exhibited preventive effects on colon length shortening and histological changes in colon tissues. Polycan inhibited the DSS-induced decrease in fluorescein isothiocyanate-dextran permeability and myeloperoxidase activity. Moreover, Polycan significantly recovered serum cytokine (e.g., tumor necrosis factor-α, interleukin (IL)-6, and IL-1β) or mRNA expression in colon tissue compared with DSS. Polycan also inhibited apoptosis by reducing caspase-3 activity and the Bcl-2 associated X/B-cell lymphoma 2 (Bcl-2) ratio. Additionally, DSS treatment significantly reduced microbial abundance and diversity, but the administration of Polycan reversed this effect. Collectively, Polycan protected intestinal barrier function and inhibited inflammation and apoptosis in DSS-induced colitis.

Network pharmacology-based identification of bioavailable anti-inflammatory agents from Psoralea corylifolia L. in an experimental colitis model

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional oriental medicine, the dried seeds of Psoralea corylifolia L. (PC) have been used to treat various diseases, including gastrointestinal, urinary, orthopedic, diarrheal, ulcer, and inflammatory disorders.

AIM OF THE STUDY

Although its various biological properties are well-known, there is no information on the therapeutic effects and bioavailable components of PC against inflammatory bowel disease. Therefore, we focused on the relationship between hydroethanolic extract of PC (EPC) that ameliorates colitis in mice and bioactive constituents of EPC that suppress pro-inflammatory cytokines in macrophages.

MATERIALS AND METHODS

We investigated the therapeutic effects of EPC in a dextran sulfate sodium-induced colitis mouse model and identified the orally absorbed components of EPC using UPLC-MS/MS analysis. In addition, we evaluated and validated the mechanism of action of the bioavailable constituents of EPC using network pharmacology analysis. The effects on nitric oxide (NO) and inflammatory cytokines were measured by Griess reagent and enzyme linked immunosorbent assay in lipopolysaccharide (LPS)-induced macrophages.

RESULTS

In experimental colitis, EPC improved body weight loss, colon length shortening, and disease activity index. Moreover, EPC reduced the serum levels of pro-inflammatory cytokines and histopathological damage to the colon. Network pharmacological analysis identified 13 phytochemicals that were bioavailable following oral administration of EPC, as well as their potential anti-inflammatory effects. 11 identified EPC constituents markedly reduced the overproduction of NO, tumor necrosis factor-α, and/or interleukin-6 in macrophages induced by LPS. The LPS-induced expression of the nuclear factor kappa-light-chain-enhancer of activated B cells reporter gene was reduced by the 4 EPC constituents.

CONCLUSIONS

The results indicate that the protective activity of EPC against colitis is a result of the additive effects of each constituent on the expression of inflammatory cytokines. Therefore, it suggests that 11 bioavailable phytochemicals of EPC could aid in the management of intestinal inflammation, and also provides useful insights into the clinical application of PC for the treatment of inflammatory bowel diseases.

Long-lasting visceral hypersensitivity in a model of DSS-induced colitis in rats

BACKGROUND

Persistent visceral hypersensitivity is a key component of functional and inflammatory gastrointestinal diseases. Current animal models fail to fully reproduce the characteristics of visceral pain in humans, particularly as it relates to persistent hypersensitivity. This work explores the validity of DSS-induced colitis in rats as a model to mimic chronic intestinal hypersensitivity.

METHODS

Exposure to DSS (5% for 7 days) was used to induce colitis in rats. Thereafter, changes in viscerosensitivity (visceromotor responses to colorectal distension-CRD), the presence of somatic referred pain (mechanosensitivity of the hind paws, von Frey test) and the expression (qRT-PCR) of sensory-related markers (colon, lumbosacral DRGs, and lumbosacral spinal cord) were assessed at different times during the 35 days period after colitis induction.

RESULTS

Following colitis, a sustained increase in visceromotor responses to CRD were observed, indicative of the presence of visceral hypersensitivity. Responses in animals without colitis remained stable over time. In colitic animals, somatic referred hypersensitivity was also detected. DSS-induced colitis was associated to a differential expression of sensory-related markers (with both pro- and anti-nociceptive action) in the colon, lumbosacral DRGs and lumbosacral spinal cord; indicating the presence of peripheral and central sensitization.

CONCLUSIONS AND INFERENCES

DSS-induced colitis in rats is associated to the generation of a long-lasting state of visceral (colonic) hypersensitivity, despite clinical colitis resolution. This model reproduces the changes in intestinal sensitivity characteristics of inflammatory and functional gastrointestinal disorders in humans and can be used in the characterization of new pharmacological treatments against visceral pain.

Chronic stress induces colonic tertiary lymphoid organ formation and protection against secondary injury through IL-23/IL-22 signaling

Psychological stress has been previously reported to worsen symptoms of inflammatory bowel disease (IBD). Similarly, intestinal tertiary lymphoid organs (TLOs) are associated with more severe inflammation. While there is active debate about the role of TLOs and stress in IBD pathogenesis, there are no studies investigating TLO formation in the context of psychological stress. Our mouse model of Crohn's disease-like ileitis, the SAMP1/YitFc (SAMP) mouse, was subjected to 56 consecutive days of restraint stress (RS). Stressed mice had significantly increased colonic TLO formation. However, stress did not significantly increase small or large intestinal inflammation in the SAMP mice. Additionally, 16S analysis of the stressed SAMP microbiome revealed no genus-level changes. Fecal microbiome transplantation into germ-free SAMP mice using stool from unstressed and stressed mice replicated the behavioral phenotype seen in donor mice. However, there was no difference in TLO formation between recipient mice. Stress increased the TLO formation cytokines interleukin-23 (IL-23) and IL-22 followed by up-regulation of antimicrobial peptides. SAMP × IL-23r-/- (knockout [KO]) mice subjected to chronic RS did not have increased TLO formation. Furthermore, IL-23, but not IL-22, production was increased in KO mice, and administration of recombinant IL-22 rescued TLO formation. Following secondary colonic insult with dextran sodium sulfate, stressed mice had reduced colitis on both histology and colonoscopy. Our findings demonstrate that psychological stress induces colonic TLOs through intrinsic alterations in IL-23 signaling, not through extrinsic influence from the microbiome. Furthermore, chronic stress is protective against secondary insult from colitis, suggesting that TLOs may function to improve the mucosal barrier.

Intestinal inflammation-associated hypersensitivity is attenuated in a DSS model of colitis in Sigma-1 knockout C57BL/6 mice

Sigma-1 receptors (σ1R) have been implicated in several pain pathways. We assessed the implication of σ1Rs in the development of intestinal inflammation and inflammation-associated referred hypersensitivity in a model of colitis in σ1R knockout (KO) mice. Colitis was induced with dextran sulfate sodium (DSS) in wild type (WT) and σ1R KO mice. The development of referred mechanical hypersensitivity (von Frey test) was assessed. Colonic and spinal changes in expression of immune- and sensory-related markers were also investigated (RT-qPCR/Western blot). Absence of σ1Rs had little impact in colitis generation and progression, although during the chronic phase a reduction in edema and a down-regulation of iNOS gene expression was observed. In σ1R KO mice, inflammation-associated hypersensitivity was significantly attenuated (paw) or completely prevented (abdomen). During colitis, in WT mice, changes in the colonic expression of nociceptive markers were observed during the acute and chronic phases of inflammation. Although σ1R KO mice showed similar regulation in the acute phase, an attenuated response was observed during the chronic phase of colitis. These differences were especially relevant for CB2 and TRPV1 receptors, which could play an important role in σ1-mediated regulation of sensitivity. No changes were detected on ERK phosphorylation at the level of the lumbosacral spinal cord. In summary, intestinal inflammation-associated referred hyperalgesia was reduced (paw) or absent (abdomen) in σ1R KO mice, thus confirming an important role for σ1R in the development of colitis-associated hypersensitivity. These results identify σ1Rs as a possible therapeutic target for the treatment of hypersensitivity associated to intestinal inflammation.

Irritable Bowel Syndrome and Neurological Deficiencies: Is There A Relationship? The Possible Relevance of the Oxidative Stress Status

Background: Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders, exhibiting complex and controversial pathological features. Both oxidative stress and inflammation-related reactive oxygen species production may be involved in IBS pathological development. Thus, we focused on several aspects regarding the causes of oxidative stress occurrence in IBS. Additionally, in the molecular context of oxidative changes, we tried to discuss these possible neurological implications in IBS. Methods: The literature search included the main available databases (e.g., ScienceDirect, Pubmed/Medline, Embase, and Google Scholar). Articles in the English language were taken into consideration. Our screening was conducted based on several words such as “irritable bowel syndrome”, “gut brain axis”, “oxidative stress”, “neuroendocrine”, and combinations. Results: While no consistent evidence suggests clear pathway mechanisms, it seems that the inflammatory response may also be relevant in IBS. The mild implication of oxidative stress in IBS has been described through clinical studies and some animal models, revealing changes in the main markers such as antioxidant status and peroxidation markers. Moreover, it seems that the neurological structures involved in the brain-gut axis may be affected in IBS rather than the local gut tissue and functionality. Due to a gut-brain axis bidirectional communication error, a correlation between neurological impairment, emotional over-responsiveness, mild inflammatory patterns, and oxidative stress can be suggested. Conclusions: Therefore, there is a possible correlation between neurological impairment, emotional over-responsiveness, mild inflammatory patterns, and oxidative stress that are not followed by tissue destruction in IBS patients. Moreover, it is not yet clear whether oxidative stress, inflammation, or neurological impairments are key determinants or in which way these three interact in IBS pathology. However, the conditions in which oxidative imbalances occur may be an interesting research lead in order to find possible explanations for IBS development.

Complementary and Alternative Medicine Strategies for Therapeutic Gut Microbiota Modulation in Inflammatory Bowel Disease and their Next-Generation Approaches

The human gut microbiome exerts a major impact on human health and disease, and therapeutic gut microbiota modulation is now a well-advocated strategy in the management of many diseases, including inflammatory bowel disease (IBD). Scientific and clinical evidence in support of complementary and alternative medicine, in targeting intestinal dysbiosis among patients with IBD, or other disorders, has increased dramatically over the past years. Delivery of "artificial" stool replacements for fecal microbiota transplantation (FMT) could provide an effective, safer alternative to that of human donor stool. Nevertheless, optimum timing of FMT administration in IBD remains unexplored, and future investigations are essential.

Visceral Inflammation and Immune Activation Stress the Brain

Stress refers to a dynamic process in which the homeostasis of an organism is challenged, the outcome depending on the type, severity, and duration of stressors involved, the stress responses triggered, and the stress resilience of the organism. Importantly, the relationship between stress and the immune system is bidirectional, as not only stressors have an impact on immune function, but alterations in immune function themselves can elicit stress responses. Such bidirectional interactions have been prominently identified to occur in the gastrointestinal tract in which there is a close cross-talk between the gut microbiota and the local immune system, governed by the permeability of the intestinal mucosa. External stressors disturb the homeostasis between microbiota and gut, these disturbances being signaled to the brain via multiple communication pathways constituting the gut-brain axis, ultimately eliciting stress responses and perturbations of brain function. In view of these relationships, the present article sets out to highlight some of the interactions between peripheral immune activation, especially in the visceral system, and brain function, behavior, and stress coping. These issues are exemplified by the way through which the intestinal microbiota as well as microbe-associated molecular patterns including lipopolysaccharide communicate with the immune system and brain, and the mechanisms whereby overt inflammation in the GI tract impacts on emotional-affective behavior, pain sensitivity, and stress coping. The interactions between the peripheral immune system and the brain take place along the gut-brain axis, the major communication pathways of which comprise microbial metabolites, gut hormones, immune mediators, and sensory neurons. Through these signaling systems, several transmitter and neuropeptide systems within the brain are altered under conditions of peripheral immune stress, enabling adaptive processes related to stress coping and resilience to take place. These aspects of the impact of immune stress on molecular and behavioral processes in the brain have a bearing on several disturbances of mental health and highlight novel opportunities of therapeutic intervention.

Chronic social stress in pigs impairs intestinal barrier and nutrient transporter function, and alters neuro-immune mediator and receptor expression

Psychosocial stress is a major factor driving gastrointestinal (GI) pathophysiology and disease susceptibility in humans and animals. The mechanisms governing susceptibility to stress-induced GI disease remain poorly understood. In the present study, we investigated the influence of chronic social stress (CSS) in pigs, induced by 7 d of chronic mixing/crowding stress, on intestinal barrier and nutrient transport function, corticotropin releasing factor (CRF) signaling and immunological responses. Results from this study showed that CSS resulted in a significant impairment of ileal and colonic barrier function indicated by reduced transepithelial electrical resistance (TER) in the ileum and increased FD4 flux in the ileum (by 0.8 fold) and colon (by 0.7 fold). Ileal sodium glucose linked transporter 1 (SGLT-1) function, measured as glucose-induced changes in short-circuit current (Isc), was diminished (by 52%) in CSS pigs, associated with reduced body weight gain and feed efficiency. Although reductions in SGLT-1 function were observed in CSS pigs, mRNA expression for SGLT-1, villus heights were increased in CSS pigs. Corticotropin releasing factor (CRF) mRNA was upregulated (by 0.9 fold) in the ileum of CSS pigs but not in the colon. Urocortin 2 (Ucn2) mRNA was upregulated (by 1.5 fold) in the colon of CSS pigs, but not in the ileum. In CSS pigs, a downregulation of pro-inflammatory cytokines mRNA (IL1B, TNFA, IL8, and IL6) was observed in both ileum and colon, compared with controls. In contrast CSS induced a marked upregulation of mRNA for IL10 and mast cell chymase gene (CMA1) in the ileum and colon. Together, these data demonstrate that chronic stress in pigs results in significant alterations in intestinal barrier and nutrient transport function and neuro-immune mediator and receptor expression.

The intestinal microbiome, barrier function, and immune system in inflammatory bowel disease: a tripartite pathophysiological circuit with implications for new therapeutic directions

We discuss the tripartite pathophysiological circuit of inflammatory bowel disease (IBD), involving the intestinal microbiota, barrier function, and immune system. Dysfunction in each of these physiological components (dysbiosis, leaky gut, and inflammation) contributes in a mutually interdependent manner to IBD onset and exacerbation. Genetic and environmental risk factors lead to disruption of gut homeostasis: genetic risks predominantly affect the immune system, environmental risks predominantly affect the microbiota, and both affect barrier function. Multiple genetic and environmental 'hits' are likely necessary to establish and exacerbate disease. Most conventional IBD therapies currently target only one component of the pathophysiological circuit, inflammation; however, many patients with IBD do not respond to immune-modulating therapies. Hope lies in new classes of therapies that target the microbiota and barrier function.

Effect of genetic background and postinfectious stress on visceral sensitivity in Citrobacter rodentium-infected mice

BACKGROUND

Infectious gastroenteritis is a major risk factor to develop postinfectious irritable bowel syndrome (PI-IBS). It remains unknown why only a subgroup of infected individuals develops PI-IBS. We hypothesize that immunogenetic predisposition is an important risk factor. Hence, we studied the effect of Citrobacter rodentium infection on visceral sensitivity in Th1-predominant C57BL/6 and Th2-predominant Balb/c mice.

METHODS

Eight-week-old mice were gavaged with C. rodentium, followed by 1 h of water avoidance stress (WAS) at 5 weeks PI. At 10, 14 days, and 5 weeks PI, samples were assessed for histology and inflammatory gene expression by RT-qPCR. Visceral sensitivity was evaluated by visceromotor response recordings (VMR) to colorectal distension.

KEY RESULTS

Citrobacter rodentium evoked a comparable colonic inflammatory response at 14 days PI characterized by increased crypt length and upregulation of Th1/Th17 cytokine mRNA levels (puncorrected  < 0.05) in both C57BL/6 and Balb/c mice. At 5 weeks PI, inflammatory gene mRNA levels returned to baseline in both strains. The VMR was maximal at 14 days PI in C57BL/6 (150 ± 47%; p = 0.02) and Balb/c mice (243 ± 52%; p = 0.03). At 3 weeks PI, the VMR remained increased in Balb/c (176 ± 23%; p = 0.02), but returned to baseline in C57BL/6 mice. At 5 weeks PI, WAS could not re-introduce visceral hypersensitivity (VHS).

CONCLUSIONS & INFERENCES

Citrobacter rodentium infection induces transient VHS in C57BL/6 and Balb/c mice, which persisted 1 week longer in Balb/c mice. Although other strain-related differences may contribute, a Th2 background may represent a risk factor for prolonged PI-VHS. As PI-VHS is transient, other factors are crucial for persistent VHS development as observed in PI-IBS.

Effects of early life dextran sulfate sodium administration on pathology and immune response in broilers and layers

Intestinal pathology early in life may affect immune development and therefore immune responses later in life. Dextran sulfate sodium (DSS) induces colitis in rodents and is a widely used model for inflammatory bowel diseases. The present study investigated DSS as a model for early life intestinal pathology and its consequences on intestinal pathology, ileal cytokine, and immunoglobulin mRNA expression levels as well as the antibody response towards an immunological challenge later in life in chickens. Broiler and layer chicks received 2.5% DSS in drinking water during d 11 through d 18 post hatch or plain drinking water as a control. As an immunological challenge all birds received a combination of Escherichia coli lipopolysaccharide (LPS) and human serum albumin (HuSA) intramuscularly (i.m.) at d 35, and antibody titers against LPS, HuSA, and keyhole limpet hemocyanin (KLH) were determined to investigate effects of intestinal inflammation early in life on humoral immunity later in life. DSS treated birds showed a decrease in BW from which broilers quickly recovered, but which persisted for several weeks in layers. Histological examination of intestinal samples showed symptoms similar to those in rodents, including shortening and loss of villi and crypts as well as damage of the epithelial cell layer of different parts of the intestine. Effects of DSS on intestinal morphology were less severe in broilers that also showed a lower mortality in response to DSS than layers. No effect of DSS on ileal cytokine expression levels could be observed, but ileal immunoglobulin expression levels were decreased in DSS treated broilers that also showed lower antibody titers against LPS in response to the challenge. In conclusion, DSS may serve as a model for intestinal pathology early in life, although more research on the appropriate dose is necessary and is likely to differ between breeds. Results from the present study could indicate that broilers are less susceptible to DSS compared with layers or have a better capacity to recover from intestinal pathology.

Over-Expression of CD200 Protects Mice from Dextran Sodium Sulfate Induced Colitis

BACKGROUND AND AIM

CD200:CD200 receptor (CD200R) interactions lead to potent immunosuppression and inhibition of autoimmune inflammation. We investigated the effect of "knockout"of CD200 or CD200R, or over-expression of CD200, on susceptibility to dextran sodium sulfate (DSS)-induced colitis, a mouse model of inflammatory bowel disease (IBD).

METHODS

Acute or chronic colitis was induced by administration of dextran sodium sulfate (DSS) in four groups of age-matched C57BL/6 female mice: (1) CD200-transgenic mice (CD200tg); (2) wild-type (WT) mice; (3) CD200 receptor 1-deficient (CD200R1KO) mice; and (4) CD200-deficient (CD200KO) mice. The extent of colitis was determined using a histological scoring system. Colon tissues were collected for quantitative RT-PCR and Immunohistochemical staining. Supernatants from colonic explant cultures and mononuclear cells isolated from colonic tissue were used for ELISA.

RESULTS

CD200KO and CD200R1KO mice showed greater sensitivity to acute colitis than WT mice, with accelerated loss of body weight, significantly higher histological scores, more severe infiltration of macrophages, neutrophils and CD3+ cells, and greater expression of macrophage-derived inflammatory cytokines, whose production was inhibited in vitro (in WT/CD200KO mouse cells) by CD200. In contrast, CD200tg mice showed less sensitivity to DSS compared with WT mice, with attenuation of all of the features seen in other groups. In a chronic colitis model, greater infiltration of Foxp3+ regulatory T (Treg) cells was seen in the colon of CD200tg mice compared to WT mice, and anti-CD25 mAb given to these mice attenuated protection.

CONCLUSIONS

The CD200:CD200R axis plays an immunoregulatory role in control of DSS induced colitis in mice.

Behavioral and molecular processing of visceral pain in the brain of mice: impact of colitis and psychological stress

Gastrointestinal disorders with abdominal pain are associated with central sensitization and psychopathologies that are often exacerbated by stress. Here we investigated the impact of colitis induced by dextran sulfate sodium (DSS) and repeated water avoidance stress (WAS) on spontaneous and nociception-related behavior and molecular signaling in the mouse brain. DSS increased the mechanical pain sensitivity of the abdominal skin while both WAS and DSS enhanced the mechanical and thermal pain sensitivity of the plantar skin. These manifestations of central sensitization were associated with augmented c-Fos expression in spinal cord, thalamus, hypothalamus, amygdala and prefrontal cortex. While WAS stimulated phosphorylation of mitogen-activated protein kinase (MAPK) p42/44, DSS activated another signaling pathway, both of which converged on c-Fos. The DSS- and WAS-induced hyperalgesia in the abdominal and plantar skin and c-Fos expression in the brain disappeared when the mice were subjected to WAS+DSS treatment. Intrarectal allyl isothiocyanate (AITC) evoked aversive behavior (freezing, reduction of locomotion and exploration) in association with p42/44 MAPK and c-Fos activation in spinal cord and brain. These effects were inhibited by morphine, which attests to their relationship with nociception. DSS and WAS exerted opposite effects on AITC-evoked p42/44 MAPK and c-Fos activation, which indicates that these transduction pathways subserve different aspects of visceral pain processing in the brain. In summary, behavioral perturbations caused by colitis and psychological stress are associated with distinct alterations in cerebral signaling. These findings provide novel perspectives on central sensitization and the sensory and emotional processing of visceral pain stimuli in the brain.

Stress-induced visceral pain: toward animal models of irritable-bowel syndrome and associated comorbidities

Visceral pain is a global term used to describe pain originating from the internal organs, which is distinct from somatic pain. It is a hallmark of functional gastrointestinal disorders such as irritable-bowel syndrome (IBS). Currently, the treatment strategies targeting visceral pain are unsatisfactory, with development of novel therapeutics hindered by a lack of detailed knowledge of the underlying mechanisms. Stress has long been implicated in the pathophysiology of visceral pain in both preclinical and clinical studies. Here, we discuss the complex etiology of visceral pain reviewing our current understanding in the context of the role of stress, gender, gut microbiota alterations, and immune functioning. Furthermore, we review the role of glutamate, GABA, and epigenetic mechanisms as possible therapeutic strategies for the treatment of visceral pain for which there is an unmet medical need. Moreover, we discuss the most widely described rodent models used to model visceral pain in the preclinical setting. The theory behind, and application of, animal models is key for both the understanding of underlying mechanisms and design of future therapeutic interventions. Taken together, it is apparent that stress-induced visceral pain and its psychiatric comorbidities, as typified by IBS, has a multifaceted etiology. Moreover, treatment strategies still lag far behind when compared to other pain modalities. The development of novel, effective, and specific therapeutics for the treatment of visceral pain has never been more pertinent.

Repeated predictable stress causes resilience against colitis-induced behavioral changes in mice

Inflammatory bowel disease is associated with an increased risk of mental disorders and can be exacerbated by stress. In this study which was performed with male 10-week old C57Bl/6N mice, we used dextran sulfate sodium (DSS)-induced colitis to evaluate behavioral changes caused by intestinal inflammation, to assess the interaction between repeated psychological stress (water avoidance stress, WAS) and colitis in modifying behavior, and to analyze neurochemical correlates of this interaction. A 7-day treatment with DSS (2% in drinking water) decreased locomotion and enhanced anxiety-like behavior in the open field test and reduced social interaction. Repeated exposure to WAS for 7 days had little influence on behavior but prevented the DSS-induced behavioral disturbances in the open field and SI tests. In contrast, repeated WAS did not modify colon length, colonic myeloperoxidase content and circulating proinflammatory cytokines, parameters used to assess colitis severity. DSS-induced colitis was associated with an increase in circulating neuropeptide Y (NPY), a rise in the hypothalamic expression of cyclooxygenase-2 mRNA and a decrease in the hippocampal expression of NPY mRNA, brain-derived neurotrophic factor mRNA and mineralocorticoid receptor mRNA. Repeated WAS significantly decreased the relative expression of corticotropin-releasing factor mRNA in the hippocampus. The effect of repeated WAS to blunt the DSS-evoked behavioral disturbances was associated with a rise of circulating corticosterone and an increase in the expression of hypothalamic NPY mRNA. These results show that experimental colitis leads to a particular range of behavioral alterations which can be prevented by repeated WAS, a model of predictable chronic stress, while the severity of colitis remains unabated. We conclude that the mechanisms underlying the resilience effect of repeated WAS involves hypothalamic NPY and the hypothalamic-pituitary-adrenal axis.

Case-control study of factors that trigger inflammatory bowel disease flares

AIM: To explore the association between inflammatory bowel diseases (IBD) flares and potential triggers.

METHODS: Patients evaluated for an acute flare of IBD by a gastroenterologist at the Dallas VA Medical Center were invited to participate, as were a control group of patients with IBD in remission. Patients were systematically queried about nonsteroidal anti-inflammatory drug use, antibiotic use, stressful life events, cigarette smoking, medication adherence, infections, and travel in the preceding 3 mo. Disease activity scores were calculated for each patient at the time of enrollment and each patient’s chart was reviewed. Multivariate regression analysis was performed.

RESULTS: A total of 134 patients with IBD (63 with Crohn’s disease, 70 with ulcerative colitis, and 1 with indeterminate colitis) were enrolled; 66 patients had flares of their IBD and 68 were controls with IBD in remission (for Crohn’s patients, average Crohn’s disease activity index was 350 for flares vs 69 in the controls; for UC patients, Mayo score was 7.6 for flares vs 1 for controls in those with full Mayo available and 5.4p for flares vs 0.1p for controls in those with partial Mayo score). Only medication non-adherence was significantly more frequent in the flare group than in the control group (48.5% vs 29.4%, P = 0.03) and remained significant on multivariate analysis (OR = 2.86, 95%CI: 1.33-6.18). On multivariate regression analysis, immunomodulator use was found to be associated with significantly lower rates of flare (OR = 0.40, 95%CI: 0.19-0.86).

CONCLUSION: In a study of potential triggers for IBD flares, medication non-adherence was significantly associated with flares. These findings are incentive to improve medication adherence.

Stress and antibiotics alter luminal and wall-adhered microbiota and enhance the local expression of visceral sensory-related systems in mice

BACKGROUND

Stress leads to altered gastrointestinal neuro-immune responses. We characterized the interaction between stress and gut commensal microbiota and their role modulating colonic responses to stress, the induction of inflammation, the expression of sensory-related markers, and visceral sensitivity.

METHODS

C57BL/6N female mice were treated (7 days, PO) with non-absorbable-broad spectrum antibiotics (bacitracin/neomycin, 0.4 mg per mouse per day). Simultaneously, mice were subjected to a 1 h per day (7 days) session of psychological stress (water avoidance stress, WAS). Luminal and wall-adhered microbiota were characterized by fluorescent in situ hybridization. Cannabinoid receptors 1 and 2 (CB1/2), tryptophan hydroxylase 1 and 2 (TPH1/2), and inflammatory markers were quantified by reverse transcription-quantitative real-time PCR (RT-qPCR) and secretory-IgA (s-IgA) by ELISA. Visceral sensitivity was assessed after the intracolonic administration of capsaicin.

KEY RESULTS

Antibiotics did not affect the defecatory and endocrine responses to stress. However, antibiotics diminished by 2.5-folds total bacterial counts, induced a specific dysbiosis and favored bacterial wall adherence. Combining antibiotics and stress resulted in further reductions in bacterial counts and a dysbiosis, with enhanced bacterial wall adherence. Luminal s-IgA levels increased in dysbiotic mice. Nevertheless, no alterations consistent with the induction of colonic inflammation were observed. Dysbiosis upregulated CB2 expression and stress upregulated CB2 and TPH1 expression. Stress enhanced visceral pain-related responses, an effect prevented by antibiotic treatment.

CONCLUSIONS & INFERENCES

Manipulations of the commensal microbiota and the interaction host-microbiota are able to modulate the local expression of neuro-immune-endocrine systems within the colon, leading to a modulation of visceral sensitivity. These mechanisms might contribute to the pathogenic and protective roles of microbiota in gastrointestinal homeostasis.

Environmental enrichment and gut inflammation modify stress-induced c-Fos expression in the mouse corticolimbic system

Environmental enrichment (EE) has a beneficial effect on rodent behaviour, neuronal plasticity and brain function. Although it may also improve stress coping, it is not known whether EE influences the brain response to an external (psychological) stressor such as water avoidance stress (WAS) or an internal (systemic) stressor such as gastrointestinal inflammation. This study hence explored whether EE modifies WAS-induced activation of the mouse corticolimbic system and whether this stress response is altered by gastritis or colitis. Male C67BL/6N mice were housed under standard or enriched environment for 9 weeks, after which they were subjected to a 1-week treatment with oral iodoacetamide to induce gastritis or oral dextran sulfate sodium to induce colitis. Following exposure to WAS the expression of c-Fos, a marker of neuronal activation, was measured by immunocytochemistry. EE aggravated experimentally induced colitis, but not gastritis, as shown by an increase in the disease activity score and the colonic myeloperoxidase content. In the brain, EE enhanced the WAS-induced activation of the dentate gyrus and unmasked an inhibitory effect of gastritis and colitis on WAS-evoked c-Fos expression within this part of the hippocampus. Conversely, EE inhibited the WAS-evoked activation of the central amygdala and prevented the inhibitory effect of gastritis and colitis on WAS-evoked c-Fos expression in this region. EE, in addition, blunted the WAS-induced activation of the infralimbic cortex and attenuated the inhibitory effect of gastritis and colitis on WAS-evoked c-Fos expression in this area. These data reveal that EE has a region-specific effect on stress-induced c-Fos expression in the corticolimbic system, which is likely to improve stress resilience. The response of the prefrontal cortex – amygdala – hippocampus circuitry to psychological stress is also modified by the systemic stress of gut inflammation, and this interaction between external and internal stressors is modulated by the housing environment.

Activation of TLR4 by CRF in human intestinal epithelial cells is mediated by the CRF2 receptor

AIM: To investigate the effect of corticotrophin-releasing factor (CRF) on the expression of toll-like receptor 4 (TLR4) in human intestinal epithelial cell line HT-29.

METHODS: HT-29 cells were divided into eight groups: non-treated group, LPS group (treated with 20 μg/L LPS for 24 h), CRF group (treated with 20 μg/L CRF for 24 h), LPS plus CRF group (pretreated with 20 μg/L CRF for 12 h and then treated with 20 μg/L LPS for 12 h), astressin 2B plus CRF group (pretreated with 20 μg/L astressin 2B for 12 h and then treated with 20 μg/L CRF), antalarmin plus CRF group (pretreated with 20 μg/L antalarmin for 12 h and then treated with 20 μg/L CRF), astressin 2B plus LPS group (pretreated with 20 μg/L astressin 2B for 12 h and then treated with 20 μg/L LPS), and antalarmin plus LPS group (pretreated with 20 μg/L antalarmin for 12 h and then treated with 20 μg/L LPS). The expression of TLR4 mRNA and protein was detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting, respectively. The secretion of interleukin-8 in the culture supernatants was determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS: CRF could induce the expression of TLR4 in HT-29 cells and result in increased interleukin-8 secretion (P < 0.05). CRFR2 antagonist astressin 2B inhibited the expression of LR4 (P < 0.05, CRF+LPS group vs CRF group), while CRF1 antagonist antalarmin had no significant effect on the expression of TLR4 (P > 0.05, CRF+LPS group vs CRF group).

CONCLUSION: The induction of TLR4 expression by CRF in human intestinal epithelial cells is mediated by the CRF2 receptor.

Dextran sodium sulphate colitis mouse model: traps and tricks

Inflammatory bowel disease (IBD) is a complex multifactorial disease of unknown etiology. Thus, dozens of different animal models of IBD have been developed in past decades. Animal models of IBD are valuable and indispensable tools that provide a wide range of options for investigating involvement of various factors into the pathogenesis of IBD and to evaluate different therapeutic options. However, the dextran sulphate sodium (DSS-) induced colitis model has some advantages when compared to other animal models of colitis. It is well appreciated and widely used model of inflammatory bowel disease because of its simplicity. It has many similarities to human IBD, which are mentioned in the paper. In spite of its simplicity and wide applicability, there are also traps that need to be taken into account when using DSS model. As demonstrated in the present paper, various factors may affect susceptibility to DSS-induced lesions and modify results.

Chronic psychosocial stress induces visceral hyperalgesia in mice

Experimental and clinical evidence has shown that chronic stress plays an important role in the onset and/or exacerbation of symptoms of functional gastrointestinal disorders. Here, we aimed to investigate whether exposure to a chronic and temporally unpredictable psychosocial stressor alters visceral and somatic nociception as well as anxiety-related behaviour. In male C57BL/6J mice, chronic stress was induced by repeated exposure to social defeat (SD, 2 h) and overcrowding (OC, 24 h) during 19 consecutive days. Visceral and somatic nociception was evaluated by colorectal distension and a hot plate, respectively. The social interaction test was used to assess social anxiety. Mice exposed to psychosocial stress developed visceral hyperalgesia and somatic hypoalgesia 24 h following the last stress session. SD/OC mice also exhibited social anxiety-like behaviour. All these changes were also associated with physiological alterations, measured as a decreased faecal pellet output and hypothalamic-pituitary-adrenal (HPA) axis disruption. Taken together, these data confirm that this mouse model of chronic psychosocial stress may be useful for studies on the pathophysiological mechanisms underlying such stress-associated disorders and to further test potential therapies.

Chronic stress-induced alterations in mouse colonic 5-HT and defecation responses are strain dependent

Mood disorders and chronic stress are frequently associated with gastrointestinal (GI) symptoms including diarrhoea or constipation. Locally produced serotonin [5-hydroxytryptamine (5-HT)] regulates GI motility and is a key factor in the pathophysiology of stress-associated GI disorders. We aimed to establish whether chronic stress can differentially affect faecal output and colon 5-HT concentration in two inbred mouse strains: BALB/c and C57BL/6 which differ in their ability to cope with stress. Adult male BALB/c and C57BL/6 mice were restrained for 2 h daily for 10 days. Defecation was monitored during each stress session. Twenty-four hours after the last session of stress, plasma corticosterone concentration was higher than control in both strains, indicative of a physiological effect of chronic stress; however, stress-induced diarrhoea was more persistent in C57BL/6 mice. Basal concentration of colon 5-HT was higher in C57BL/6 mice, and stress elicited an increase in colon 5-HT only in this strain. Finally, naïve BALB/c mice had a higher sensitivity (incidence of diarrhoea) to 5-HT (0.33 mg/kg, i.p.) than C57BL/6 mice. Our results suggest that differential defecation responses to stress may be associated with colon 5-HT concentration, which may in turn reflect the individual sensitivity to 5-HT. In addition, C57BL/6 mice emerge as a relevant model for studying GI alterations induced by chronic stress.

Stress and visceral pain: from animal models to clinical therapies

Epidemiological studies have implicated stress (psychosocial and physical) as a trigger of first onset or exacerbation of irritable bowel syndrome (IBS) symptoms of which visceral pain is an integrant landmark. A number of experimental acute or chronic exteroceptive or interoceptive stressors induce visceral hyperalgesia in rodents although recent evidence also points to stress-related visceral analgesia as established in the somatic pain field. Underlying mechanisms of stress-related visceral hypersensitivity may involve a combination of sensitization of primary afferents, central sensitization in response to input from the viscera and dysregulation of descending pathways that modulate spinal nociceptive transmission or analgesic response. Biochemical coding of stress involves the recruitment of corticotropin releasing factor (CRF) signaling pathways. Experimental studies established that activation of brain and peripheral CRF receptor subtype 1 plays a primary role in the development of stress-related delayed visceral hyperalgesia while subtype 2 activation induces analgesic response. In line with stress pathways playing a role in IBS, non-pharmacologic and pharmacologic treatment modalities aimed at reducing stress perception using a broad range of evidence-based mind-body interventions and centrally-targeted medications to reduce anxiety impact on brain patterns activated by visceral stimuli and dampen visceral pain.

Ileal inducible nitric oxide synthase mRNA expression in response to stress is modified in Sprague-Dawley rats exposed to a previous intestinal inflammation

The ability of stress to initiate or reactivate an inflammatory process seems to depend on an individual's susceptibility to stressful stimuli. The aim of this study was to establish whether previous inflammation alters the response to stress in Sprague-Dawley rats, a strain not especially susceptible to stressful stimuli. Stress exposure was performed in rats treated with indomethacin, to induce cyclic intestinal inflammation, during the inactive phase of inflammation. Both control and indomethacin-treated rats submitted to stress showed a decrease in body weight gain and blood leukocyte levels, as well as an increase in fecal pellet output. The increase in intestinal mucosal mast cell count induced by stress was similar in both groups of animals. Moreover, no differences were observed between control and indomethacin-treated rats in the degree of bacterial translocation and myeloperoxidase levels after stress exposure. Despite these similarities, differences between groups were observed in inducible nitric oxide synthase (iNOS) mRNA expression. Although ileal iNOS mRNA expression was inhibited in healthy rats submitted to stress, stress failed to modify this parameter in indomethacin-treated rats. As iNOS is another inflammatory marker, our results may allow the possibility that a previous intestinal inflammation could change the intestinal susceptibility to stress. Whether these differences in ileal iNOS expression can be indicative of a possible change in the predisposition to develop an intestinal inflammatory reaction in response to stress in Sprague-Dawley rats remains to be elucidated.

Stress and animal models of inflammatory bowel disease--an update on the role of the hypothalamo-pituitary-adrenal axis

Chronic psychosocial stress has been repeatedly shown in humans to be a risk factor for the development of several affective and somatic disorders, including inflammatory bowel diseases (IBD). There is also a large body of evidence from rodent studies indicating a link between stress and gastrointestinal dysfunction, resembling IBD in humans. Despite this knowledge, the detailed underlying neuroendocrine mechanisms are not sufficiently understood. This is due, in part, to a lack of appropriate animal models, as most commonly used rodent stress paradigms do not adequately resemble the human situation and/or do not cause the development of spontaneous colitis. Therefore, our knowledge regarding the link between stress and IBD is largely based on rodent models with low face and predictive validity, investigating the effects of unnatural stressors on chemically induced colitis. These studies have consistently reported that hypothalamo-pituitary-adrenal (HPA) axis activation during stressor exposure has an ameliorating effect on the severity of a chemically induced colitis. However, to show the biological importance of this finding, it needs to be replicated in animal models employing more clinically relevant stressors, themselves triggering the development of spontaneous colitis. Important in view of this, recent studies employing chronic/repeated psychosocial stressors were able to demonstrate that such stressors indeed cause the development of spontaneous colitis and, thus, represent promising tools to uncover the mechanisms underlying stress-induced development of IBD. Interestingly, in these models the development of spontaneous colitis was paralleled by decreased anti-inflammatory glucocorticoid (GC) signaling, whereas adrenalectomy (ADX) prior to stressor exposure prevented its development. These findings suggest a more complex role of the HPA axis in the development of spontaneous colitis. In the present review I summarize the available human and rodent data in order to provide a comprehensive understanding of the biphasic role of the HPA axis and/or the GC signaling during stressor exposure in terms of spontaneous colitis development.

Neonatal maternal separation in male rats increases intestinal permeability and affects behavior after chronic social stress

Prolonged maternal separation in rats has several effects on health and behavior. Here we investigated how maternal separation might interact with social stress in adulthood on behavior and gastrointenstinal permeability. The effects of either daily 180 min long term pup-dam separation (LMS) during the stress hyporesponsive period or daily 10 min brief maternal separation (BMS) on behavior, corticosterone and intestinal permeability were investigated, compared to a non-handling (NH) condition in male offspring. The animals from each separation condition were then randomly assigned to adult stress and control conditions, where the stress condition was exposure to 14 days of social instability (CSI). Sucrose preference, elevated plus maze behavior and corticosterone were measured. Colitis was experimentally induced by dextran sulfate sodium for 7 days, followed by measurement of intestinal permeability using the (51)CrEDTA method. Granulocyte marker protein was measured in feces and colons were examined histologically for inflammation. Prior to the social stress, the LMS offspring showed elevated corticosterone levels, lower elevated plus maze activity and less fluid consumption. After social stress, corticosterone levels were suppressed in LMS animals and again they showed less fluid consumption. LMS animals had significantly higher intestinal permeability, but only when also exposed to the social stress in adulthood. The current results support a two-hit model, whereby early life events interact with adult life events in altering animals' vulnerability.

Stress and visceral pain: from animal models to clinical therapies

Epidemiological studies have implicated stress (psychosocial and physical) as a trigger of first onset or exacerbation of irritable bowel syndrome (IBS) symptoms of which visceral pain is an integrant landmark. A number of experimental acute or chronic exteroceptive or interoceptive stressors induce visceral hyperalgesia in rodents although recent evidence also points to stress-related visceral analgesia as established in the somatic pain field. Underlying mechanisms of stress-related visceral hypersensitivity may involve a combination of sensitization of primary afferents, central sensitization in response to input from the viscera and dysregulation of descending pathways that modulate spinal nociceptive transmission or analgesic response. Biochemical coding of stress involves the recruitment of corticotropin releasing factor (CRF) signaling pathways. Experimental studies established that activation of brain and peripheral CRF receptor subtype 1 plays a primary role in the development of stress-related delayed visceral hyperalgesia while subtype 2 activation induces analgesic response. In line with stress pathways playing a role in IBS, non-pharmacologic and pharmacologic treatment modalities aimed at reducing stress perception using a broad range of evidence-based mind-body interventions and centrally-targeted medications to reduce anxiety impact on brain patterns activated by visceral stimuli and dampen visceral pain.

Localization of nesfatin-1 neurons in the mouse brain and functional implication

Nesfatin-1 reduces food intake when injected centrally in rodents. We recently described wide distribution of nucleobindin2 (NUCB2)/nesfatin-1 immunoreactivity in rat brain autonomic nuclei activated by various stressors. We used C57BL/6 mice to localize brain NUCB2/nesfatin-1 immunoreactivity and assessed activation of NUCB2/nesfatin 1 neurons after water avoidance stress (WAS). Gastric emptying of a non-nutrient liquid was also determined. NUCB2/nesfatin-1 immunoreactivity was detected in cortical areas including piriform, insular, cingulate and somatomotor cortices, the limbic system including amygdaloid nuclei, hippocampus and septum, the basal ganglia, bed nucleus of the stria terminalis, the thalamus including paraventricular and parafascicular nuclei, the hypothalamus including supraoptic, periventricular, paraventricular (PVN), arcuate nuclei and ventromedial and lateral hypothalamic areas. Intensely labeled NUCB2/nesfatin-1 neurons were detected in a previously undefined region which we named intermediate dorsomedial hypothalamus. In the brainstem, NUCB2/nesfatin-1 immunoreactivity was detected in the raphe nuclei, Edinger-Westphal nucleus, locus coeruleus (LC), lateral parabrachial nucleus, ventrolateral medulla (VLM) and dorsal vagal complex. WAS induced Fos expression in 35% of NUCB2/nesfatin-1-immunoreactive neurons in the PVN, 50% in the LC, 54% in the rostral raphe pallidus, 58% in the VLM, 39% in the middle part of the nucleus of the solitary tract (NTS) and 33% in the caudal NTS. Nesfatin-1 injected intracerebroventricularly significantly decreased gastric emptying. These data showed that NUCB2/nesfatin-1 immunoreactivity is distributed in mouse brain areas involved in the regulation of stress response and visceral functions activated by an acute psychological stressor suggesting that nesfatin-1 might play a role in the efferent component of the stress response.

Chronic psychosocial stress promotes systemic immune activation and the development of inflammatory Th cell responses

Recent studies indicate that chronic psychosocial stress favors the development of generalized immune dysfunction. During stressor exposure neuroendocrine factors affect numbers and functionality of leukocytes. However, the exact mechanisms leading to systemic changes in immune functions during stress are still not clear. During chronic subordinate colony housing, a model of chronic psychosocial stress, mice developed spontaneous colonic inflammation. Decreased glucocorticoid signaling, induced by a combination of adrenal insufficiency and glucocorticoid resistance, was thought to prevent tempering of local immune cells, and to promote tissue inflammation. In this study we investigated changes in the systemic immune status after chronic subordinate colony housing and analyzed potential mechanisms underlying those alterations. Analysis of T helper cell subsets in peripheral lymph nodes revealed a reduction of regulatory T cells, accompanied by increased T cell effector functions. Generalized activation of T cells was shown by elevated cytokine production upon stimulation. In addition, we observed no apparent shift towards T helper type 2 responses. It is likely, that the previously reported hypocorticism in this stress model led to a steady production of inflammatory Th1, Th2, and Th17 cytokines and obstructed the shift towards an anti-inflammatory response. In conclusion, we established chronic subordinate colony housing as a model to investigate the outcome of stress on the systemic immune status. We also provide evidence that distinct T helper cell subtypes react differentially to the suppressive effect of glucocorticoids.

Epinephrine-primed murine bone marrow-derived dendritic cells facilitate production of IL-17A and IL-4 but not IFN-γ by CD4+ T cells

Sympathetic activation leading to the release of epinephrine and norepinephrine, is known as an important regulatory circuit related to immune-mediated diseases. However, questions still remain on the behavior of antigen presenting cells (APC) dictated by stress-induced sympathetic neurotransmitters. The purpose of this study was to examine the fate of bone marrow-derived dendritic cell (BMDC)-associated influences on resting CD4(+) T cell activation. We hypothesize that pre-exposure of dendritic cells (DCs) can modify the intensity of cytokine production, leading to preference in resting CD4(+) T cell activation. BMDCs were pre-treated with epinephrine for 2h followed by subsequent treatment of lipopolysaccharide (LPS). Subsequently, BMDCs were cocultured with purified CD4(+) T cells from mouse spleen in the absence or presence of anti-CD3 stimulation in epinephrine-free media. Epinephrine pre-treatment enhanced surface expression of MHCII, CD80 and CD86. Quantitative RT-PCR showed that epinephrine pre-treatment induced a significant transcriptional decrease of IL-12p40 and a significant increase of IL-12p35 and IL-23p19. In addition, β2-adrenergic-blockade was shown to reverse these effects. Epinephrine pre-treatment also induced a significant decrease of IL-12p70 and a significant increase of IL-23 and IL-10 cytokine production. Importantly, these changes corresponded with increased IL-4 and IL-17A, but not IFN-g cytokine production by CD4(+) T cells in a b2-adrenergic receptor-dependent manner. These results suggest that exposure to stress-derived epinephrine dictates dendritic cells to generate a dominant Th2/Th17 phenotype in the context of subsequent exposure to a pathogenic stimulus.

Repeated psychological stress-induced alterations of visceral sensitivity and colonic motor functions in mice: influence of surgery and postoperative single housing on visceromotor responses

Visceral pain modulation by chronic stress in mice has been little studied. Electromyography (EMG) recording of abdominal muscle contractions, as a proxy to the visceromotor response (VMR), requires electrode implantation and post-surgical single housing (SH) which could affect the VMR to stress. To test this hypothesis, male mice had electrode implantation surgery (S) plus SH, or no surgery and were group housed (NS-GH) or single housed (NS-SH) and exposed to either water avoidance stress (WAS, 1 h/day) or left undisturbed in their home cages for 10 days. The VMR to phasic ascending colorectal distension (CRD) was assessed before (basal) and 24 h after 10 days of WAS or no stress using a surgery-free method of intraluminal colonic pressure (ICP) recording (solid-state manometry). WAS heightened significantly the VMR to CRD at 30, 45, and 60 mmHg in S-SH vs. NS-GH, but not compared to NS-SH conscious mice. Compared to basal CRD, WAS increased VMR at 60 mmHg in the S-SH group and decreased it at 30-60 mmHg in NS-GH mice, while having no effect in NS-SH mice. The average defecation during the hour of repeated WAS over 10 days was 1.9 and 2.4 fold greater in S-SH vs. NS-GH and NS-SH mice, respectively. These data indicate that the combination of S-SH required for VMR monitoring with EMG is an important component of repeated WAS-induced post-stress visceral hypersensitivity and defecation in mice.

Un-promoted issues in inflammatory bowel disease: opportunities to optimize care

Inflammatory bowel diseases (IBD), comprising Crohn's disease (CD) and ulcerative colitis (UC), are chronic inflammatory disorders of the gut, which lead to significant morbidity and impaired quality of life (QoL) in sufferers, without generally affecting mortality. Despite CD and UC being chronic, life-long illnesses, most medical management is directed at acute flares of disease. Moreover, with more intensive medical therapy and the development of biological therapy, there is a risk that management will become even more narrowly focused on acute care, and be directed only at those with more severe disease, rather than encompassing all sufferers and addressing important non-acute issues. This imbalance of concentration of medical attention on 'high-end' care is in part driven by the need to perform and publish randomized clinical trials of newer therapies to obtain registration and licensing for these agents, which thus occupy a large proportion of the recent IBD treatment literature. This leads to less attention on relatively 'low-technology' issues including: (i) the psychosocial burden of chronic disease, QoL and specific psychological comorbidities; (ii) comorbidity with functional gastrointestinal disorders (FGIDs); (iii) maintenance therapy, monitoring and compliance; (iv) smoking (with regard to CD); (v) sexuality, fertility, family planning and pregnancy; and (vi) iron deficiency and anaemia. We propose these to be the 'Un-promoted Issues' in IBD and review the importance and treatment of each of these in the current management of IBD.

Lack of interaction between psychological stress and DSS-induced colitis affecting colonic sensitivity during colorectal distension in mice

Inflammation and stress have been associated to colorectal hypersensitivity in functional gastrointestinal disorders. We explored if colonic inflammation and stress, alone or combined, participate in the development of visceral hypersensitivity in a mouse model. First, female mice were exposed to 3% dextran sulphate sodium (DSS, 5 days) to induce chronic colitis, followed by repeated psychological stress (water avoidance stress, WAS; 1 h daily/10 days). In a separate experiment, female mice were subjected to WAS and thereafter received 3% DSS. Colitis was evaluated at necropsy. Faecal pellet output served as a marker of stress effect on colonic motility. Visceral pain was assessed at fixed time-points monitoring abdominal contractions during colorectal distension (CRD). DSS provoked a mild chronic colitis that was not affected by previous WAS or aggravated by subsequent stress. WAS induced a significant increase in pellet output, although the response was attenuated in animals with colitis. Responses to CRD were similar in all experimental groups, with transient hyperalgesia observed only during acute colitis. Under the present conditions, neither colitis nor stress, alone or in combination, significantly affected the responses to CRD in mice, suggesting that there is not a direct relationship between inflammation and stress and the development of visceral hypersensitivity.

Do NSAIDs, antibiotics, infections, or stress trigger flares in IBD?

Non-steroidal anti-inflammatory drugs (NSAIDs), antibiotics, enteric or other systemic infections, and stress have all been reported to be potential triggers of inflammatory bowel disease (IBD). Although a mechanism of triggering a flare of IBD can be hypothesized for each factor, the associations of these factors with flares of IBD remains confusing. In this review, we analyze the literature that explores these associations. There is some evidence to support an association between NSAID use and flares but little data to associate antibiotic use directly with flares. An important connection between antibiotic use and an exacerbation of symptoms is through the development of Clostridium difficile infections. However, for all enteric infections, including C. difficile, it is unclear whether these infections simply trigger symptoms in patients with IBD that resolve on resolution of the infection, or whether they truly trigger a flare of intestinal inflammation that outlasts the infection. There is a paucity of evidence that other systemic infections trigger flares of IBD. Although there is strong evidence for an association between perceived stress levels and flares, there is a weaker association between a simple accounting of stressful life events and flares. Much of the literature is limited by a lack of adequate control groups and failure to report on base rates in the population under study (i.e., NSAIDs and antibiotic use, occurrence of infections, and stress levels). More large population-based matched cohort or case crossover studies and a continued emphasis on prospective designs are needed to better explore these potential associations. Clinical implications given the current state of knowledge are discussed.

Acute colonic ischaemia in rats results in long-term structural changes without alterations of colonic sensitivity

Colonic ischaemia and mast cells have been involved in the pathophysiology of the functional gastrointestinal disorder irritable bowel syndrome, although the cause-effect relationships remain unknown. We assessed long-term histopathological and functional changes associated to an acute ischaemic episode (1 h) of the colon, followed by 8-week recovery, in rats. Functional colonic alterations [sensitivity during colorectal distension (CRD), compliance and propulsive motility] were assessed regularly during the recovery. Colonic histopathology (presence of inflammation, morphometric alterations and variations in neuronal density in the enteric nervous system) 8-week postischaemia was assessed. Following ischaemia, none of the functional parameters tested (motility, sensitivity and compliance) were affected. At necropsy, the colon presented an overall normal appearance with an increase in weight of the ischaemic area (mg/cm: 99 +/- 6; P < 0.05 vs. control: 81 +/- 4 or sham ischaemia: 81 +/- 3). Histopathological evaluations revealed the presence of a local infiltrate of mast cells in the area of ischaemia (nb of mast cells: 142 +/- 50; P < 0.05 vs. control, 31 +/- 14 or sham ischaemia: 40 +/- 16), without other significant alterations. Animals subjected to colonic ischaemia and treated 8 weeks later with the mast cell degranulator, compound 48/80, showed no changes in CRD-related pain responses. These studies show that acute colonic ischaemia is associated with the presence of a long-term local infiltration of mast cells, located within the serosa and muscle layers, despite the absence of functional changes, including colonic sensitivity. Considering the important pathophysiological functions of mast cells, the observed mast cell infiltration may be involved in ischaemia-induced functional changes yet to be characterized.