Colitis induces CRF expression in hypothalamic magnocellular neurons and blunts CRF gene response to stress in rats

Comorbid anxiety-like behavior in a rat model of colitis is mediated by an upregulation of corticolimbic fatty acid amide hydrolase

Peripheral inflammatory conditions, including those localized to the gastrointestinal tract, are highly comorbid with psychiatric disorders such as anxiety and depression. These behavioral symptoms are poorly managed by conventional treatments for inflammatory diseases and contribute to quality of life impairments. Peripheral inflammation is associated with sustained elevations in circulating glucocorticoid hormones, which can modulate central processes, including those involved in the regulation of emotional behavior. The endocannabinoid (eCB) system is exquisitely sensitive to these hormonal changes and is a significant regulator of emotional behavior. The impact of peripheral inflammation on central eCB function, and whether this is related to the development of these behavioral comorbidities remains to be determined. To examine this, we employed the trinitrobenzene sulfonic acid-induced model of colonic inflammation (colitis) in adult, male, Sprague Dawley rats to produce sustained peripheral inflammation. Colitis produced increases in behavioral measures of anxiety and elevations in circulating corticosterone. These alterations were accompanied by elevated hydrolytic activity of the enzyme fatty acid amide hydrolase (FAAH), which hydrolyzes the eCB anandamide (AEA), throughout multiple corticolimbic brain regions. This elevation of FAAH activity was associated with broad reductions in the content of AEA, whose decline was driven by central corticotropin releasing factor type 1 receptor signaling. Colitis-induced anxiety was reversed following acute central inhibition of FAAH, suggesting that the reductions in AEA produced by colitis contributed to the generation of anxiety. These data provide a novel perspective for the pharmacological management of psychiatric comorbidities of chronic inflammatory conditions through modulation of eCB signaling.

Supraspinal Mechanisms of Intestinal Hypersensitivity

Gut inflammation or injury causes intestinal hypersensitivity (IHS) and hyperalgesia, which can persist after the initiating pathology resolves, are often referred to somatic regions and exacerbated by psychological stress, anxiety or depression, suggesting the involvement of both the spinal cord and the brain. The supraspinal mechanisms of IHS remain to be fully elucidated, however, over the last decades the series of intestinal pathology-associated neuroplastic changes in the brain has been revealed, being potentially responsible for the phenomenon. This paper reviews current clinical and experimental data, including the authors' own findings, on these functional, structural, and neurochemical/molecular changes within cortical, subcortical and brainstem regions processing and modulating sensory signals from the gut. As concluded in the review, IHS can develop and maintain due to the bowel inflammation/injury-induced persistent hyperexcitability of viscerosensory brainstem and thalamic nuclei and sensitization of hypothalamic, amygdala, hippocampal, anterior insular, and anterior cingulate cortical areas implicated in the neuroendocrine, emotional and cognitive modulation of visceral sensation and pain. An additional contribution may come from the pathology-triggered dysfunction of the brainstem structures inhibiting nociception. The mechanism underlying IHS-associated regional hyperexcitability is enhanced NMDA-, AMPA- and group I metabotropic receptor-mediated glutamatergic neurotransmission in association with altered neuropeptide Y, corticotropin-releasing factor, and cannabinoid 1 receptor signaling. These alterations are at least partially mediated by brain microglia and local production of cytokines, especially tumor necrosis factor α. Studying the IHS-related brain neuroplasticity in greater depth may enable the development of new therapeutic approaches against chronic abdominal pain in inflammatory bowel disease.

Brain corticotropin-releasing factor signaling: Involvement in acute stress-induced visceral analgesia in male rats

BACKGROUND

Water avoidance stress (WAS) induces a naloxone-independent visceral analgesia in male rats under non-invasive conditions of monitoring. The objective of the study was to examine the role of brain CRF signaling in acute stress-induced visceral analgesia (SIVA).

METHODS

Adult male Sprague-Dawley rats were chronically implanted with an intracerebroventricular (ICV) cannula. The visceromotor response (VMR) to graded phasic colorectal distension (CRD: 10, 20, 40, 60 mm Hg, 20 seconds, 4 minutes intervals) was monitored using manometry. The VMR to a first CRD (baseline) was recorded 5 minutes after an ICV saline injection, followed 1 hour later by ICV injection of either CRF (30, 100, or 300 ng and 1, 3, or 5 μg/rat) or saline and a second CRD, 5 minutes later. Receptor antagonists against CRF₁ /CRF₂ (astressin-B, 30 μg/rat), CRF₂ (astressin₂ -B, 10 μg/rat), oxytocin (tocinoic acid, 20 μg/rat), or vehicle were injected ICV 5 minutes before CRF (300 ng/rat, ICV) or 15 minutes before WAS (1 hour).

KEY RESULTS

ICV CRF (100 and 300 ng) reduced the VMR to CRD at 60 mm Hg by -36.6% ± 6.8% and -48.7% ± 11.7%, respectively, vs baseline (P < 0.001), while other doses had no effect and IP CRF (10 µg/kg) induced visceral hyperalgesia. Astressin-B and tocinoic acid injected ICV induced hyperalgesia and prevented the analgesic effect of ICV CRF (300 ng/rat) and WAS, while astressin₂ -B only blocked WAS-induced SIVA.

CONCLUSIONS & INFERENCES

These data support a role for brain CRF signaling via CRF₂ in SIVA in a model of WAS and CRD likely mediated by the activation of brain oxytocin pathway.

Electroacupuncture ameliorates abnormal defaecation and regulates corticotrophin-releasing factor in a rat model of stress

Objective

To examine the effect of electroacupuncture (EA) treatment on abnormal defaecation in a rat model of chronic heterotypic stress (CHS) and investigate the underlying mechanisms.

Methods

20 male Sprague-Dawley rats were randomly divided into three groups: normal (n=6), CHS (n=7), and CHS+EA (n=7). Rats in the CHS group and CHS+EA groups received four different types of stressors for 7 days. For rats in the CHS+EA group, EA was applied at ST36 in the bilateral hind legs for 30 min before each stress-loading session. Rats in the normal group did not receive stressors or EA treatment. The faecal pellets of each rat were collected and weighed at a fixed time every day. Protein expression of corticotrophin-releasing factor (CRF) in the hypothalamus and colorectal tissues was measured by Western blotting at the end of the experiment on the 7th day.

Results

After 7 consecutive days of CHS, the number of faecal pellets, faecal wet weight, and faecal water content were significantly increased in the CHS group compared with the normal group (p=0.035, p=0.008 and p=0.008, respectively). All three parameters were significantly decreased in CHS+EA versus CHS groups (p=0.030, p=0.011 and p=0.006, respectively). Stress significantly increased CRF expression in both the hypothalamus and colorectal tissues. The excessive CRF responses seen following CHS were significantly suppressed by EA treatment.

Conclusions

EA treatment can ameliorate stress loading induced abnormal defaecation in rats and decrease protein expression of CRF centrally (hypothalamus) and peripherally (colorectal tissues), suggesting a potentially therapeutic role for EA in stress-related responses.

Impairment of gastric accommodation induced by water-avoidance stress is mediated by 5-HT2B receptors

BACKGROUND

Psychological stress has been shown to impair gastric accommodation (GA), but its mechanism has not been elucidated. This study was conducted to clarify the role of 5-HT2B receptors in a guinea pig model of stress-induced impairment of GA.

METHODS

Gastric accommodation was evaluated by measuring the intrabag pressure in the proximal stomach after administration of a liquid meal. The guinea pigs were subjected to water-avoidance stress. The role of 5-HT2B receptors in impairment of GA was investigated by administering a 5-HT2B receptor agonist (BW723C86) or antagonist (SB215505), the traditional Japanese medicine rikkunshito (RKT), a muscarinic M3 receptor antagonist (1,1-dimethyl-4-diphenylacetoxypiperidium iodide [4-DAMP]), or a nitric oxide synthase inhibitor (Nω -nitro-L-arginine [L-NNA]).

KEY RESULTS

In normal animals, liquid meal-induced GA was inhibited by BW723C86, but was not affected by SB215505. The inhibition of GA by BW723C86 was reversed by co-administration of 4-DAMP. Compared to normal animals, GA in stressed animals was significantly inhibited. SB215505 and RKT significantly suppressed stress-induced impairment of GA. After meal administration, the level of cyclic guanosine monophosphate in gastric fundus tissue increased by approximately twofold in normal animals, but did not change in stressed animals. The inhibition of GA by L-NNA was suppressed by SB215505 or RKT. At a dose that did not affect GA in normal animals, BW723C86 exacerbated the impairment of GA in stressed animals.

CONCLUSIONS AND INFERENCES

Stress-induced impairment of GA may be mediated by an increased responsiveness of 5-HT2B receptors, and activation of the 5-HT2B receptor signaling pathway may have an inhibitory effect on nitric oxide function.

Behavioral despair associated with a mouse model of Crohn's disease: Role of nitric oxide pathway

Crohn's disease (CD) is associated with increased psychiatric co-morbidities. Nitric oxide (NO) is implicated in inflammation and tissue injury in CD, and it may also play a central role in pathogenesis of the accompanying behavioral despair. This study investigated the role of the NO pathway in behavioral despair associated with a mouse model of CD. Colitis was induced by intrarectal (i.r.) injection of 2,4,6-trinitrobenzenesulfonic acid (10mg TNBS in 50% ethanol). Forced swimming test (FST), pharmacological studies and tissues collection were performed 72 h following TNBS administration. To address a possible inflammatory origin for the behavioral despair following colitis induction, tumor necrosis factor-alpha (TNF-α) level was measured in both the hippocampal and colonic tissue samples. In parallel, hippocampal inducible nitric oxide synthase (iNOS) and nitrite level were evaluated. Pharmacological studies targeting the NO pathway were performed 30-60 min before behavioral test. Colitis was confirmed by increased colonic TNF-α level and microscopic score. Colitic mice demonstrated a significantly higher immobility time in the FST associated to a significant increase of hippocampal TNF-α, iNOS expression and nitrite content. Acute NOS inhibition using either Nω-nitro-l-arginine methyl ester (a non-specific NOS inhibitor) or aminoguanidine hydrochloride (a specific iNOS inhibitor) decreased the immobility time in colitic groups. Moreover, acute treatment with both NOS inhibitors decreased the TNF-α level and nitrite content in the hippocampal samples. This study suggests that the NO pathway may be involved in the behavioral effects in the mouse TNBS model of CD. These findings endow new insights into the gut-brain communication during the development of colonic inflammation, which may ultimately lead to improved therapeutic strategies to combat behavior changes associated with gastrointestinal disorders.

Oxytocin Regulates Stress-Induced Crf Gene Transcription through CREB-Regulated Transcription Coactivator 3

The major regulator of the neuroendocrine stress response in the brain is corticotropin releasing factor (CRF), whose transcription is controlled by CREB and its cofactors CRTC2/3 (TORC2/3). Phosphorylated CRTCs are sequestered in the cytoplasm, but rapidly dephosphorylated and translocated into the nucleus following a stressful stimulus. As the stress response is attenuated by oxytocin (OT), we tested whether OT interferes with CRTC translocation and, thereby, Crf expression. OT (1 nmol, i.c.v.) delayed the stress-induced increase of nuclear CRTC3 and Crf hnRNA levels in the paraventricular nucleus of male rats and mice, but did not affect either parameter in the absence of the stressor. The increase in Crf hnRNA levels at later time points was parallel to elevated nuclear CRTC2/3 levels. A direct effect of Thr(4) Gly(7)-OT (TGOT) on CRTC3 translocation and Crf expression was found in rat primary hypothalamic neurons, amygdaloid (Ar-5), hypothalamic (H32), and human neuroblastoma (Be(2)M17) cell lines. CRTC3, but not CRCT2, knockdown using siRNA in Be(2)M17 cells prevented the effect of TGOT on Crf hnRNA levels. Chromatin-immunoprecipitation demonstrated that TGOT reduced CRTC3, but not CRTC2, binding to the Crf promoter after 10 min of forskolin stimulation. Together, the results indicate that OT modulates CRTC3 translocation, the binding of CRTC3 to the Crf promoter and, ultimately, transcription of the Crf gene.

SIGNIFICANCE STATEMENT

The neuropeptide oxytocin has been proposed to reduce hypothalamic-pituitary-adrenal (HPA) axis activation during stress. The underlying mechanisms are, however, elusive. In this study we show that activation of the oxytocin receptor in the paraventricular nucleus delays transcription of the gene encoding corticotropin releasing factor (Crf), the main regulator of the stress response. It does so by sequestering the coactivator of the transcription factor CREB, CRTC3, in the cytosol, resulting in reduced binding of CRTC3 to the Crf gene promoter and subsequent Crf gene expression. This novel oxytocin receptor-mediated intracellular mechanism might provide a basis for the treatment of exaggerated stress responses in the future.

The brain-gut axis in health and disease

The interaction between the brain and the gut has been recognized for many centuries. This bidirectional interaction occurs via neural, immunological and hormonal routes, and is important not only in normal gastrointestinal function but also plays a significant role in shaping higher cognitive function such as our feelings and our subconscious decision-making. Therefore, it remains unsurprising that perturbations in normal signalling have been associated with a multitude of disorders, including inflammatory and functional gastrointestinal disorders, and eating disorders.

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.

Key role of CRF in the skin stress response system

The discovery of corticotropin-releasing factor (CRF) or CRH defining the upper regulatory arm of the hypothalamic-pituitary-adrenal (HPA) axis, along with the identification of the corresponding receptors (CRFRs 1 and 2), represents a milestone in our understanding of central mechanisms regulating body and local homeostasis. We focused on the CRF-led signaling systems in the skin and offer a model for regulation of peripheral homeostasis based on the interaction of CRF and the structurally related urocortins with corresponding receptors and the resulting direct or indirect phenotypic effects that include regulation of epidermal barrier function, skin immune, pigmentary, adnexal, and dermal functions necessary to maintain local and systemic homeostasis. The regulatory modes of action include the classical CRF-led cutaneous equivalent of the central HPA axis, the expression and function of CRF and related peptides, and the stimulation of pro-opiomelanocortin peptides or cytokines. The key regulatory role is assigned to the CRFR-1α receptor, with other isoforms having modulatory effects. CRF can be released from sensory nerves and immune cells in response to emotional and environmental stressors. The expression sequence of peptides includes urocortin/CRF→pro-opiomelanocortin→ACTH, MSH, and β-endorphin. Expression of these peptides and of CRFR-1α is environmentally regulated, and their dysfunction can lead to skin and systemic diseases. Environmentally stressed skin can activate both the central and local HPA axis through either sensory nerves or humoral factors to turn on homeostatic responses counteracting cutaneous and systemic environmental damage. CRF and CRFR-1 may constitute novel targets through the use of specific agonists or antagonists, especially for therapy of skin diseases that worsen with stress, such as atopic dermatitis and psoriasis.

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.

Brain-gut interactions in inflammatory bowel disease

Psycho-neuro-endocrine-immune modulation through the brain-gut axis likely has a key role in the pathogenesis of inflammatory bowel disease (IBD). The brain-gut axis involves interactions among the neural components, including (1) the autonomic nervous system, (2) the central nervous system, (3) the stress system (hypothalamic-pituitary-adrenal axis), (4) the (gastrointestinal) corticotropin-releasing factor system, and (5) the intestinal response (including the intestinal barrier, the luminal microbiota, and the intestinal immune response). Animal models suggest that the cholinergic anti-inflammatory pathway through an anti-tumor necrosis factor effect of the efferent vagus nerve could be a therapeutic target in IBD through a pharmacologic, nutritional, or neurostimulation approach. In addition, the psychophysiological vulnerability of patients with IBD, secondary to the potential presence of any mood disorders, distress, increased perceived stress, or maladaptive coping strategies, underscores the psychological needs of patients with IBD. Clinicians need to address these issues with patients because there is emerging evidence that stress or other negative psychological attributes may have an effect on the disease course. Future research may include exploration of markers of brain-gut interactions, including serum/salivary cortisol (as a marker of the hypothalamic-pituitary-adrenal axis), heart rate variability (as a marker of the sympathovagal balance), or brain imaging studies. The widespread use and potential impact of complementary and alternative medicine and the positive response to placebo (in clinical trials) is further evidence that exploring other psycho-interventions may be important therapeutic adjuncts to the conventional therapeutic approach in IBD.

Stress-induced visceral analgesia assessed non-invasively in rats is enhanced by prebiotic diet

AIM

To investigate the influence of repeated water avoidance stress (rWAS) on the visceromotor response (VMR) to colorectal distension (CRD) and the modulation of the response by a prebiotic diet in rats using a novel surgery-free method of solid-state manometry.

METHODS

Male Wistar rats fed a standard diet with or without 4% enzyme-treated rice fiber (ERF) for 5 wk were subjected to rWAS (1 h daily x 10 d) or no stress. The VMR to graded phasic CRD was assessed by intraluminal colonic pressure recording on days 0 (baseline), 1 and 10 (45 min) and 11 (24 h) after rWAS and expressed as percentage change from baseline. Cecal content of short chain fatty acids and distal colonic histology were assessed on day 11.

RESULTS

WAS on day 1 reduced the VMR to CRD at 40 and 60 mmHg similarly by 28.9% ± 6.6% in both diet groups. On day 10, rWAS-induced reduction of VMR occurred only at 40 mmHg in the standard diet group (36.2% ± 17.8%) while in the ERF group VMR was lowered at 20, 40 and 60 mmHg by 64.9% ± 20.9%, 49.3% ± 11.6% and 38.9% ± 7.3% respectively. The visceral analgesia was still observed on day 11 in ERF- but not in standard diet-fed rats. By contrast the non-stressed groups (standard or ERF diet) exhibited no changes in VMR to CRD. In standard diet-fed rats, rWAS induced mild colonic histological changes that were absent in ERF-fed rats exposed to stress compared to non-stressed rats. The reduction of cecal content of isobutyrate and total butyrate, but not butyrate alone, was correlated with lower visceral pain response. Additionally, ERF diet increased rWAS-induced defecation by 26% and 75% during the first 0-15 min and last 15-60 min, respectively, compared to standard diet, and reduced rats' body weight gain by 1.3 fold independently of their stress status.

CONCLUSION

These data provide the first evidence of psychological stress-related visceral analgesia in rats that was enhanced by chronic intake of ERF prebiotic.

Psychological stress and the severity of post-inflammatory visceral hyperalgesia

OBJECTIVES

Lowered visceral sensory thresholds are a key finding in at least a subgroup of patients with functional bowel disorders. Stress and inflammation contribute to this altered visceral sensory function. We aimed to elucidate the role of repetitive stress and acute mucosal inflammation, alone and in combination, on sensory function.

METHODS

In randomized order, trinitrobenzenesulfonic acid (TNBS) plus the equal amount of ethanol or saline were instilled into the colorectum of female Lewis rats. Colorectal distensions (CRD) were performed with a barostat device (3 min/40 mmHg); to quantify the visceromotor response (VMR) to CRD, electromyographic activity (EMG) of the abdominal muscles was recorded. In randomized order, equal numbers of both treatment groups underwent either seven days (1 h/day) repetitive water avoidance stress (WAS) or sham WAS. CRD's were conducted 28 days later. Colonic tissue samples were obtained to characterize inflammation and blood samples were taken at day 28 to measure plasma IL-2 levels by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Compared to controls (662+/-114 microV) TNBS (1081+/-227 microV), WAS (1366+/-125 microV) and the combination of both (1477+/-390 microV) significantly augmented the VMR to CRD. TNBS and/or WAS caused significant inflammatory changes at day 5, while only TNBS+WAS also showed signs of mucosal inflammation on day 14 and significantly elevated IL-2 levels on day 28.

CONCLUSIONS

Stress and inflammation cause long lasting alterations of visceral sensory function. Concomitant stress further increases post-inflammatory visceral hyperalgesia.

Psychological Stress Induces Visceral Analgesic or Hyperalgesic Response in Rodents: A Role of Preconditions

A dual action of stress on pain modulation has been well characterized in the somatic pain studies, while much less is known in the visceral field. In the context of clinical observations that stress plays a critical role in the pathophysiology, symptoms presentation and clinical outcome of functional gastrointestinal disorders such as irritable bowel syndrome (IBS), a number of acute and chronic stress models have been developed in rodents. Recent data have demonstrated that the state of the animal tested (naïve vs. exposed to surgery), its social environment (group housing vs. single housing), the methods used to record visceromotor responses (EMG requiring surgery and antibiotic after surgery vs. manometry not requiring surgery/antibiotic) can significantly affect the analgesic response to exteroceptive stressors. Growing body of evidence indicates that a new noninvasive solid-state manometric method to monitor viscero motor response is valuable to unravel both analgesia and hyperalgesia without confounding factors. This is of critical importance regarding the recently recognized role of a compromised engagement of the inhibitory descending pain pathways in IBS patients. Better understanding of mechanisms of stress-related modulation of visceral pain leading to analgesia and hyperalgesia, along with the role of sex-dependent factors and complex interactions of the brain-gut-enteric microbiota axis may lead to new therapeutic targets in IBS.

Imbalance in the stress-adaptation system in patients with inflammatory bowel disease

AIM

Though inflammatory bowel disease (IBD) is known as a stress-related disorder, basic evidence for this claim is lacking. The current study was performed to investigate the function of the neuroendocrine-immune system as a main pathway in stress response and stress-coping ability and the associations among stress response, stress-coping ability, and disease activity in IBD patients.

METHOD

A questionnaire was administered to obtain information concerning stress state and stress-coping ability (self-efficacy and sense of coherence [SOC]) in 78 IBD patients and 21 healthy volunteers. Blood samples were taken for determining the serum levels of various stress-related hormones and cytokines before and after a calculation stress test.

RESULTS

Self-efficacy was significantly decreased in patients, though the degree of perceived stress and SOC did not differ between patients and controls. Basal levels of cortisol did not differ, but levels of adrenocorticotropic hormone, β-endorphin and interleukin (IL)-6 were significantly higher in patients than in controls. In addition, the control group, but not the patient group, demonstrated significant differences in the basal cortisol levels between low and high SOC subgroups and between low and high perceived stress subgroups. Furthermore, IL-6 levels were significantly increased following the calculation stress test in patients only.

CONCLUSION

Results indicate that IBD patients may have skewed neuroendocrine-immune systems and that emotional stress may aggravate the disease. Stress-management interventions might be useful, not only for patients' quality of life (QOL) but also for disease control.

Corticotropin-releasing factor signaling and visceral response to stress

Stress may cause behavioral and/or psychiatric manifestations such as anxiety and depression and also impact on the function of different visceral organs, namely the gastrointestinal and cardiovascular systems. During the past years substantial progress has been made in the understanding of the underlying mechanisms recruited by stressors. Activation of the corticotropin-releasing factor (CRF) signaling system is recognized to be involved in a large number of stress-related behavioral and somatic disorders. This review will outline the present knowledge on the distribution of the CRF system (ligands and receptors) expressed in the brain and peripheral viscera and its relevance in stress-induced alterations of gastrointestinal and cardiovascular functions and the therapeutic potential of CRF(1) receptor antagonists.

Current insights in to the pathophysiology of Irritable Bowel Syndrome

Irritable Bowel Syndrome (IBS) represents a functional disorder of gastrointestinal tract without the presence of an anatomic defect, in which abdominal pain is relieved with defecation and is associated with altered bowel habits.

IBS includes a wide range of symptoms while its pathophysiology is very complicated. Recent studies indicate that the most important mechanisms include visceral sensitivity, abnormal gut motility and autonomous nervous system dysfunction. The interactions between these three mechanisms make bowel's function susceptible to many exogenous and endogenous factors like gastrointestinal flora, feeding and psychosocial factors. Recent data indicate that according to the above mechanisms, the influence of genetic factors and polymorphisms of human DNA in the development of IBS is equally important.

Corticotropin releasing factor in the rat colon: expression, localization and upregulation by endotoxin

Little is known about CRF expression and regulation in the rat colon compared to the brain. We investigated CRF gene expression, cellular location, and regulation by endotoxin and corticosterone in the male rat colon at 6h after intraperitoneal (ip) injection. CRF mRNA level, detected by reverse transcription-polymerase chain reaction (RT-PCR) was 1.3-fold higher in the distal than proximal colon and 3.4-fold higher in the proximal colonic submucosa plus muscle layers than in mucosa. CRF immunoreactivity was located in the epithelia, lamina propria and crypts, and co-localized with tryptophan hydroxylase, a marker for enterochromaffin (EC) cells, and in enteric neurons. Lipopolysaccharide (LPS, 100 microg/kg, ip) increased defecation by 2.9-fold and upregulated CRF mRNA by 2.5-fold in the proximal and 1.1-fold in the distal colon while there was no change induced by corticosterone as monitored by quantitative PCR. LPS-induced increased CRF mRNA expression occurred in the submucosa plus muscle layers (1.5-fold) and the mucosa of proximal colon (0.9-fold). LPS increased significantly CRF immunoreactivity in the submucosal and myenteric plexuses of proximal and distal colon compared to saline groups. These results indicate that in rats, CRF is expressed in both proximal and distal colon and more prominently in enteric neurons of the submucosa plus muscle layers and subject to upregulation at the gene and protein levels by LPS through corticosteroid independent pathways. These data suggests that colonic CRF may be part of the local effector limb of the CRF(1) receptor mediated colonic alterations induced by acute stress.

Neuroendocrine control of the gut during stress: corticotropin-releasing factor signaling pathways in the spotlight

Stress affects the gastrointestinal tract as part of the visceral response. Various stressors induce similar profiles of gut motor function alterations, including inhibition of gastric emptying, stimulation of colonic propulsive motility, and hypersensitivity to colorectal distension. In recent years, substantial progress has been made in our understanding of the underlying mechanisms of stress's impact on gut function. Activation of corticotropin-releasing factor (CRF) signaling pathways mediates both the inhibition of upper gastrointestinal (GI) and the stimulation of lower GI motor function through interaction with different CRF receptor subtypes. Here, we review how various stressors affect the gut, with special emphasis on the central and peripheral CRF signaling systems.

The corticotropin-releasing factor system in inflammatory bowel disease: prospects for new therapeutic approaches

Mounting evidence suggests that stress is implicated in the development of inflammatory bowel disease (IBD), via initial nervous disturbance and subsequent immune dysfunction through brain-gut interactions. The corticotropin-releasing factor (CRF) system, being the principal neuroendocrine coordinator of stress responses, is involved in the inflammatory process within the gastrointestinal tract, via vagal and peripheral pathways, as implied by multiple reports reviewed here. Blocking of CRF receptors could theoretically exert beneficial anti-inflammatory effects in colonic tissues. The recently synthesised small-molecule CRF(1) antagonists or alternatively non-peptide CRF(2) antagonists when available, may become new reliable options in the treatment of IBD.

Gastric electrical stimulation modulates hypothalamic corticotropin-releasing factor-producing neurons during post-operative ileus in rat

High-frequency/low-energy gastric electrical stimulation (GES) is an efficient therapy to treat gastric emptying-related disorders but its mechanism of action remains poorly understood. We aimed to assess the effects of high-frequency/low-energy GES on corticotropin-releasing factor (CRF)-producing neurons in the paraventricular nucleus of the hypothalamus (PVN), which are involved in gastric ileus induced by laparotomy. Two electrodes were implanted in the rat gastric antrum during laparotomy, then stimulation (amplitude: 2 mA; pulse duration 330 micros; frequency: 2 Hz; 1 min ON/2 min OFF) or sham stimulation (control group) were applied. Using immunohistochemistry, the number of c-Fos protein-expressing neurons (c-Fos protein-immunoreactive cells, Fos-IR) was quantified in the PVN after 1 h of stimulation. The number of neurons expressing simultaneously c-Fos protein and CRF mRNA was measured by means of immunocytochemistry combined with in situ hybridization. Finally, c-Fos and CRF mRNA levels in the hypothalamus were determined by in situ hybridization or quantitative reverse transcriptase-polymerase chain reaction. Fos-IR in the PVN was significantly decreased 1 h after GES (P<0.05) but was not affected by sub-diaphragmatic vagotomy. The number of neurons containing c-Fos protein and CRF mRNA was lower in the GES group compared with the control group (P<0.05). In addition, c-Fos and CRF mRNA levels in the PVN were significantly decreased by GES (P<or=0.05). It is concluded that acute GES reduces the number of CRF-producing neurons and decreases CRF expression in the PVN during post-operative gastric ileus.

Stress maladjustment in the pathoetiology of ulcerative colitis

BACKGROUND

The aims of this study were (1) to measure levels of cytokines and stress hormones in ulcerative colitis (UC) patients and determine whether there were any disturbances in the nervous, endocrine, or immune systems, and (2) to measure the ability of UC patients to cope with stress (using a sense of coherence, SOC, test) and their perceived self-efficacy, and to elucidate their response to a stress load.

METHODS

We administered questionnaires to and took blood samples from 42 outpatients and eight inpatients whose UC was in remission, and 21 healthy volunteers. In addition, we evaluated blood samples from the inpatients and healthy volunteers following a mental calculation stress test.

RESULTS

The questionnaire results revealed that self-efficacy was significantly decreased in the patient groups. Levels of adrenocorticotropic hormone, beta-endorphin and interleukin (IL)-6 were significantly higher in the outpatient than in the control group. IL-6 levels significantly increased following the mental calculation stress test in UC patients compared with in the volunteers.

CONCLUSIONS

These results indicate that UC patients (1) have hypersensitive nervous, endocrine, and immune systems, and (2) this hypersensitivity was augmented by the mental calculation stress test.

Role of neuropeptides in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic, relapsing condition involving complex interactions between genes and the environment. The mechanisms triggering the initial attack and relapses, however, are not well understood. In the past several years the enteric nervous system (ENS) has been implicated in the pathophysiology of IBD. Both the ENS and the central nervous system (CNS) can amplify or modulate aspects of intestinal inflammation through secretion of neuropeptides that serve as a link between the ENS and CNS. Neuropeptides are defined as any peptide released from the nervous system that serves as an intercellular signaling molecule. Neuropeptides thought to play a potentially key role in IBD include substance P, corticotropin-releasing hormone, neurotensin, vasoactive intestinal peptide, mu-opioid receptor agonists, and galanin. This review focuses on the role of these neuropeptides in the pathophysiology of IBD and discusses the cell types and mechanisms involved in this process. The available evidence that neuropeptide blockade may be considered a therapeutic approach in both Crohn's disease and ulcerative colitis will also be discussed.

Luminally released serotonin stimulates colonic motility and accelerates colonic transit in rats

Enterochromaffin (EC) cells of the epithelial cells release 5-HT into the lumen, as well as basolateral border. However, the physiological role of released 5-HT into the lumen is poorly understood. Concentrations of 5-HT in the colonic mucosa, colonic lumen, and feces were measured by HPLC in rats. To investigate whether intraluminal 5-HT accelerates colonic transit, 5-HT and (51)Cr were administered into the lumen of the proximal colon, and colonic transit was measured. To investigate whether 5-HT is released into the lumen, we used an ex vivo model of isolated vascularly and luminally perfused rat proximal colon. To investigate whether luminal 5-HT is involved in regulating stress-induced colonic motility, the distal colonic motility was recorded under the stress loading, and a 5-HT(3) receptor antagonist (ondansetron, 10(-6) M, 0.5 ml) was administered intraluminally of the distal colon. Tissue content of 5-HT in the proximal colon (15.2 +/- 4.3 ng/mg wet tissue) was significantly higher than that in the distal colon (3.3 +/- 0.7 ng/mg wet tissue), while fecal content and luminal concentration of 5-HT was almost the same between the proximal and distal colon. Luminal administration of 5-HT (10(-6)-10(-5) M) significantly accelerated colonic transit. Elevation of intraluminal pressure by 10 cmH(2)O significantly increased the luminal concentration of 5-HT but not the vascular concentration of 5-HT. Stress-induced stimulation of the distal colonic motility was significantly attenuated by the luminal administration of ondansetron. These results suggest that luminally released 5-HT from EC cells plays an important role in regulating colonic motility in rats.

Water avoidance stress activates colonic myenteric neurons in female rats

Stress stimulates colonic motor function and plays a role in functional bowel disorders, prevalently in women. We examined, in conscious female rats, the influence of water avoidance stress for 60 min on colonic myenteric neuron activity using immunohistochemical detection of Fos as a marker of neuronal activity. In control rats, Fos immunoreactive nuclei were rare in proximal and distal colon and no defecation was observed. Water avoidance stimulated fecal pellet output, which was associated with Fos expression in myenteric ganglia of proximal and distal colon including in a population of peripheral choline acetyltransferase-immunoreactive neurons. Atropine blocked fecal pellet output but not Fos expression in myenteric ganglia. These results indicate that psychological stress stimulates the activity of colonic cholinergic myenteric neurons.

Corticotropin-releasing factor receptors and stress-related alterations of gut motor function

Over the past few decades, corticotropin-releasing factor (CRF) signaling pathways have been shown to be the main coordinators of the endocrine, behavioral, and immune responses to stress. Emerging evidence also links the activation of CRF receptors type 1 and type 2 with stress-related alterations of gut motor function. Here, we review the role of CRF receptors in both the brain and the gut as part of key mechanisms through which various stressors impact propulsive activity of the gastrointestinal system. We also examine how these mechanisms translate into the development of new approaches for irritable bowel syndrome, a multifactorial disorder for which stress has been implicated in the pathophysiology.

Neuronal activity and CRF receptor gene transcription in the brains of rats with colitis

We aimed to characterize neuronal and corticotropin-releasing factor (CRF) pathways at the acute phase of a model of colitis in rats. Male rats received an intracolonic injection of either vehicle (controls) or trinitrobenzenesulfonic acid (TNBS) and were killed 1, 2, 3, 4, 6, 12, or 24 h later. Coronal frozen sections of the brain were cut and mRNAs encoding the rat c-fos, CRF1 receptor, and CRF2alpha,beta receptors were assayed by in situ hybridization histochemistry. Localization of these transcripts within CRF-immunoreactive (CRF-ir) neurons of the paraventricular nucleus (PVN) of the hypothalamus was also determined. Intracolonic TNBS induced c-fos mRNA expression in brain nuclei involved in the autonomic, behavioral, and neuroendocrine response to a stimulus (PVN, amygdala, locus coeruleus, parabrachial nucleus, nucleus of the solitary tract) and in circumventricular organs (lamina terminalis, subfornical organ, area postrema). CRF pathways, particularly in the PVN, were activated in this model as represented by a robust signal of c-fos and CRF1 receptor transcripts in the PVN and numerous CRF-ir neurons expressed c-fos or CRF1 receptor transcripts in the PVN of TNBS-treated animals. No expression of CRF2 receptor transcripts was observed in the PVN, either in basal conditions or after TNBS. These neuroanatomical data argue for an involvement of CRF pathways, through CRF1 receptor, within the PVN in TNBS-induced colitis.

Association of the -1438 G/A and 102 T/C polymorphism of the 5-Ht2A receptor gene with irritable bowel syndrome 5-Ht2A gene polymorphism in irritable bowel syndrome

GOALS

The aim of this study is to investigate whether there were any association between the 102 T/C and -1438 G/A polymorphisms of the 5-HT2A receptor gene and IBS, and abdominal pain, anxiety and depression.

BACKGROUND

Genes involved in serotonin (5-HT) metabolism are good candidates for the pathogenesis of irritable bowel syndrome (IBS). Recently, a silent polymorphism in the 5-HT2A receptor gene was identified that is defined by a T to C transition at position 102. Also, a novel G to A base change at position -1438 of the promoter region has been detected in 5-HT2A receptor gene.

STUDY

Fifty-four patients with IBS diagnosed according to the Rome 1 criteria and 107 healthy individuals were included in the study. PCR was used to amplify a 468-bp (G-->A) and 342-bp (T-->C) fragment of genomic DNA containing the polymorphism. Hospital anxiety and depression scale was used to assess the risk of depression and anxiety. Severity of chronic abdominal pain was determined by visual analogue scale (VAS).

RESULTS

It was shown that there was a high incidence of homozygote C allele of the 102T/C polymorphism (%22.2; OR: 7.89, P = 0.04) and homozygote A allele of the -1438 G/A promoter region (%%37; OR: 11.14, P = 0.01) in patients with IBS. The risk of having an anxiety disorder was 83.3% in patients with C/C genotype, which was higher than other allele carrying patients, and overall mean (%52.7). (chi = 8.56, P = 0.014). The patients with T/T genotype had a VAS score of 54.93 +/- 2.59 mm, which was significantly higher than that of the patients with other genotypes (p1 = 0.02, p2 = 0.001).

CONCLUSION

This study suggests that the patients with homozygote C allele of the 102 T/C polymorphisms or homozygote A allele of the -1438 G/A polymorphism of the 5-HT2A receptor gene, have a high risk of IBS. On the other hand, T/T genotype of 102 T/C polymorphism may be associated with more severe pain in patient with IBS.

Corticotropin-releasing hormone (CRH) requirement in Clostridium difficile toxin A-mediated intestinal inflammation

Clostridium difficile, the causative agent of antibiotic-associated colitis, mediates inflammatory diarrhea by releasing toxin A, a potent 308-kDa enterotoxin. Toxin A-induced inflammatory diarrhea involves many steps, including mucosal release of substance P (SP) corticotropin-releasing hormone (CRH) and neutrophil transmigration. Here we demonstrate that, compared with wild type, mice genetically deficient in CRH (Crh(-/-)) have dramatically reduced ileal fluid secretion, epithelial cell damage, and neutrophil transmigration 4 h after intraluminal toxin A administration. This response is associated with diminished mucosal activity of the neutrophil enzyme myeloperoxidase compared with that of wildtype mice. In wild-type mice, toxin A stimulates an increase in intestinal SP content compared with buffer administration. In contrast, toxin A administration in Crh(-/-) mice fails to result in an increased SP content. Moreover, immunohistochemical experiments showed that CRH and SP are colocalized in some enteric nerves of wild-type mice, and this colocalization is more evident after toxin A administration. These results provide direct evidence for a major proinflammatory role for CRH in the pathophysiology of enterotoxin-mediated inflammatory diarrhea and indicate a SP-linked pathway.

CRF1 receptor signaling pathways are involved in stress-related alterations of colonic function and viscerosensitivity: implications for irritable bowel syndrome

1. The characterization of corticotropin releasing factor (CRF) and, more recently, the discovery of additional CRF-related ligands, urocortin 1, urocortin 2 and urocortin 3, the cloning of two distinct CRF receptor subtypes, 1 (CRF(1)) and 2 (CRF(2)), and the development of selective CRF receptor antagonists provided new insight to unravel the mechanisms of stress. Activation of brain CRF(1) receptor signaling pathways is implicated in stress-related endocrine response and the development of anxiety-like behaviors. 2. Compelling evidence in rodents showed also that both central and peripheral injection of CRF and urocortin 1 mimic acute stress-induced colonic response (stimulation of motility, transit, defecation, mucus and watery secretion, increased ionic permeability and occurrence of diarrhea) in rodents. Central CRF enhances colorectal distention-induced visceral pain in rats. Peripheral CRF reduced pain threshold to colonic distention and increased colonic motility in humans. 3. Nonselective CRF(1)/CRF(2) antagonists and selective CRF(1) antagonists inhibit exogenous (central or peripheral) CRF- and acute stress-induced activation of colonic myenteric neurons, stimulation of colonic motor function and visceral hyperalgesia while selective CRF(2) antagonists have no effect. None of the CRF antagonists influence basal or postprandial colonic function in nonstressed animals. 4. These findings implicate CRF(1) receptors in stress-related stimulation of colonic function and hypersensitivity to colorectal distention. Targeting CRF(1)-dependent pathways may have potential benefit against stress or anxiety-/depression-related functional bowel disorders.

Nonpeptide corticotropin-releasing hormone receptor type 1 antagonists and their applications in psychosomatic disorders

Overproduction of corticotropin-releasing hormone (CRH) and stress system abnormalities are seen in psychiatric diseases such as depression, anxiety, eating disorders, and addiction. Investigations of CRH type 1 receptor (CRHR1) nonpeptide antagonists suggest therapeutic potential for treatment of these and other neuropsychiatric diseases. However, overproduction of CRH in the brain and on its periphery and disruption of the hypothalamic-pituitary-adrenal axis are also found in 'somatic' disorders. Some rare forms of Cushing's disease and related pituitary/adrenal disorders are obvious applications for CRHR1 antagonists. In addition, however, these antagonists may also be effective in treating more common somatic diseases. Patients with obesity and metabolic syndrome who often have subtle, but chronic hypothalamic-pituitary-adrenal hyperactivity, which may reflect central dysregulation of CRH and consequently glucocorticoid hypersecretion, could possibly be treated by administration of CRHR1 antagonists. Hormonal, autonomic, and immune aberrations are also present in chronic inflammatory, autoimmune, and allergic diseases, with considerable evidence linking CRH with the observed abnormalities. Furthermore, autonomic dysregulation is a prominent feature of common gastrointestinal disorders, such as irritable bowel syndrome and peptic ulcer disease. Patients with irritable bowel syndrome and other gastrointestinal disorders frequently develop altered pain perception and affective symptoms. CRH acts peripherally to modulate bowel activity both directly through the autonomic system and centrally by processing viscerosensory and visceromotor neural signals. This review presents clinical and preclinical evidence for the role of CRH in the pathophysiology of these disorders and for potential diagnostic and therapeutic applications of CRHR1 antagonists. Recognition of a dysfunctional stress system in these and other diseases will alter the understanding and treatment of 'psychosomatic' disorders.

Compromised neuroimmune status in rats with experimental colitis

In colitis, chronic and recurrent inflammation is associated with a breakdown in host defence mechanisms that leads to local and systemic infection. Whether this is due to a compromised neuroimmune response has not been studied. Our aim was to determine if colitis altered the host neuroimmune response as reflected in either body temperature rhythm or the febrile responses to lipopolysaccharide (LPS). Body temperature was monitored by telemetry from conscious, unrestrained male rats treated with trinitrobenzene sulphonic acid or saline. Twenty-six days after initial induction, colitis was reactivated. Animals were given LPS (50 microg kg-1 Escherichia coli LPS) during colitis and after reactivation. At the peak of colitis, treated rats showed a disruption of circadian body temperature rhythm, manifested as day-time fever followed by night-time hypothermia. In response to LPS, controls displayed a characteristic fever, whereas treated animals had a significantly reduced fever and low plasma levels of interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-alpha). During reactivation of colitis, treated animals did not mount a fever or exhibit increased plasma levels of IL-6 and TNF-alpha after LPS. We conclude that experimental colitis is associated with a compromised neuroimmune status.

Evolving pathophysiologic models of functional gastrointestinal disorders

In contrast to most other disorders of the digestive system, functional disorders of the gut continue to be defined by symptom criteria rather than by biological markers. At the same time, animal models of functional gastrointestinal disorders in which to test pathophysiologic hypotheses are lacking. The aim of this report is to critically review recently proposed conceptual as well as animal models of functional gastrointestinal disorders. Converging disease models have been proposed that postulate an enhanced responsiveness of neural, immune, or neuroimmune circuits in the central nervous system or in the gut to exteroceptive (psychosocial) or interoceptive (tissue irritation, inflammation, infection) perturbations of the organism's homeostasis. The enhanced responsiveness results in dysregulation of gut motility, epithelial function (immune, permeability), and visceral hypersensitivity, which in turn produce irritable bowel syndrome symptoms. These conceptual models provide plausible mechanisms for irritable bowel syndrome symptom generation and are consistent with extensive epidemiologic and pathophysiologic data. Several animal models have recently been proposed that mimic key features of these conceptual disease models. They fall into models triggered by centrally targeted stimuli (neonatal stress, post-traumatic stress disorder) or those triggered by peripherally targeted stimuli (infection, inflammation). Depending on the timing of the trigger (neonatal vs. adult), the changes induced in the animal may be permanent or transient. Future development of existing and novel models involves the use of transgenic and knockout animals, as well as the demonstration of predictive validity in terms of responsiveness to candidate drugs.