Pain and mechanical properties of the rectum in patients with active ulcerative colitis

Mechanical experimentation of the gastrointestinal tract: a systematic review

The gastrointestinal (GI) organs of the human body are responsible for transporting and extracting nutrients from food and drink, as well as excreting solid waste. Biomechanical experimentation of the GI organs provides insight into the mechanisms involved in their normal physiological functions, as well as understanding of how diseases can cause disruption to these. Additionally, experimental findings form the basis of all finite element (FE) modelling of these organs, which have a wide array of applications within medicine and engineering. This systematic review summarises the experimental studies that are currently in the literature (n = 247) and outlines the areas in which experimentation is lacking, highlighting what is still required in order to more fully understand the mechanical behaviour of the GI organs. These include (i) more human data, allowing for more accurate modelling for applications within medicine, (ii) an increase in time-dependent studies, and (iii) more sophisticated in vivo testing methods which allow for both the layer- and direction-dependent characterisation of the GI organs. The findings of this review can also be used to identify experimental data for the readers' own constitutive or FE modelling as the experimental studies have been grouped in terms of organ (oesophagus, stomach, small intestine, large intestine or rectum), test condition (ex vivo or in vivo), number of directions studied (isotropic or anisotropic), species family (human, porcine, feline etc.), tissue condition (intact wall or layer-dependent) and the type of test performed (biaxial tension, inflation-extension, distension (pressure-diameter), etc.). Furthermore, the studies that investigated the time-dependent (viscoelastic) behaviour of the tissues have been presented.

Bowel Urgency in Ulcerative Colitis: Current Perspectives and Future Directions

Bowel urgency (BU), the sudden or immediate need for a bowel movement, is one of the most common and disruptive symptoms experienced by patients with ulcerative colitis (UC). Distinct from the separate symptom of increased stool frequency, BU has a substantial negative impact on quality of life and psychosocial functioning. Among patients with UC, BU is one of the top reasons for treatment dissatisfaction and one of the symptoms patients most want improved. Patients may not discuss BU often due to embarrassment, and healthcare providers may not address the symptom adequately due to the lack of awareness of validated tools and/or knowledge of the importance of assessing BU. The mechanism of BU in UC is multifactorial and includes inflammatory changes in the rectum that may be linked to hypersensitivity and reduced compliance of the rectum. Responsive and reliable patient-reported outcome measures of BU are needed to provide evidence of treatment benefits in clinical trials and facilitate communication in clinical practice. This review discusses the pathophysiology and clinical importance of BU in UC and its impact on the quality of life and psychosocial functioning. Patient-reported outcome measures developed to assess the severity of BU in UC are discussed alongside overviews of treatment options and clinical guidelines. Implications for the future management of UC from the perspective of BU are also explored.

The alleviating effect and mechanism of GLP-1 on ulcerative colitis

Ulcerative Colitis (UC) is a major type of chronic inflammatory bowel disease of the colonic mucosa and exhibits progressive morbidity. The incidence and prevalence of UC is increasing worldwide. The global burden of UC, which can substantially reduce quality of life, is clearly increasing. These data highlight the need for research into prevention of UC and innovations in health-care systems to manage this complex and costly disease. Glucagon-like peptide-1 (GLP-1), a new antidiabetic drug, is used to treat Type 2 Diabetes Mellitus (T2DM). Accumulating evidence suggests that GLP-1 has additional roles other than glucose-lowering effects. Despite the abundance of GLP-1 research, studies in UC have been less consistent, especially body weight; for example, body weight, colon length, colon injury score, intestinal microbiota, remain to be studied further. To date, the molecular mechanism of the protective effect of GLP-1 on UC remains obscure. The effect of GLP-1 was studied by using a dextran sulfate sodium (DSS)-induced colitic mice and lipopolysaccharide (LPS) treated RAW264.7 cells (macrophage cell line) under in vivo and in vitro conditions, respectively. Our results indicate that GLP-1 significantly relieves ulcerative colitis as it represses the production of proinflammatory mediators. In addition, GLP-1 blocks the activation of the protein kinase B (AKT)/nuclear factor-κB (NF-κB), and mitogen-activated protein kinase (MAPK) signaling pathways. GLP-1 also alleviates DSS-induced injury to the intestinal mucosa and dysbiosis of gut microbiota. Altogether, GLP-1 has protection effect on ulcerative colitis. Thus, GLP-1 can be considered as a potential therapeutic candidate for the treatment of UC.

Mechanobiological considerations in colorectal stapling: Implications for technology development

Technological advancements in minimally invasive surgery have led to significant improvements in patient outcomes. One such technology is surgical stapling, which has evolved into a key component of many operating rooms by facilitating ease and efficacy in resection and repair of diseased or otherwise compromised tissue. Despite such advancements, adverse post-operative outcomes such as anastomotic leak remain a persistent problem in surgical stapling and its correlates (i.e., hand-sewing), most notably in low colorectal or coloanal procedures. Many factors may drive anastomotic leaks, including tissue perfusion, microbiome composition, and patient factors such as pre-existing disease. Surgical intervention induces complex acute and chronic changes to the mechanical environment of the tissue; however, roles of mechanical forces in post-operative healing remain poorly characterized. It is well known that cells sense and respond to their local mechanical environment and that dysfunction of this "mechanosensing" phenomenon contributes to a myriad of diseases. Mechanosensing has been investigated in wound healing contexts such as dermal incisional and excisional wounds and development of pressure ulcers; however, reports investigating roles of mechanical forces in adverse post-operative gastrointestinal wound healing are lacking. To understand this relationship well, it is critical to understand: 1) the intraoperative material responses of tissue to surgical intervention, and 2) the post-operative mechanobiological response of the tissue to surgically imposed forces. In this review, we summarize the state of the field in each of these contexts while highlighting areas of opportunity for discovery and innovation which can positively impact patient outcomes in minimally invasive surgery.

Clinical Effect of Mirikizumab Treatment on Bowel Urgency in Patients with Moderately to Severely Active Ulcerative Colitis and the Clinical Relevance of Bowel Urgency Improvement for Disease Remission

Background

Bowel urgency reduces ulcerative colitis patients' quality of life. Mirikizumab, a p19-directed anti-IL-23 antibody, demonstrates ulcerative colitis efficacy. Mirikizumab efficacy to reduce bowel urgency and bowel urgency association with other endpoints were analyzed in 2 Phase 3 trials.

Methods

LUCENT-1 (Induction): 1162 patients randomized 3:1 to intravenous 300 mg mirikizumab or placebo every 4 weeks for 12 weeks. LUCENT-2 (Maintenance): 544 mirikizumab responders during induction were re-randomized 2:1 to subcutaneous mirikizumab 200 mg or placebo every 4 weeks for 40 weeks (52 weeks of continuous treatment). Bowel urgency was measured using the Urgency Numeric Rating Scale (0-10); for patients with LUCENT-1 baseline score ≥3, bowel urgency clinically meaningful improvement (≥3-point decrease) and remission (score ≤1) rates in mirikizumab versus placebo groups were compared at Weeks 12 and 52. Associations between bowel urgency and other efficacy endpoints were assessed at Weeks 12 and 52.

Results

A significantly higher proportion of mirikizumab patients versus placebo achieved clinically meaningful improvement in bowel urgency and remission at Weeks 12 and 52. Significantly higher percentages of patients achieving bowel urgency clinically meaningful improvement or remission, compared with those who did not, also achieved endpoints for clinical, corticosteroid-free, endoscopic, and symptomatic remission; clinical response; normalized fecal calprotectin and C-reactive protein; and improved quality of life.

Conclusions

In patients with ulcerative colitis, bowel urgency improvement was associated with better clinical outcomes than in patients without improvement during induction and maintenance. A greater proportion of mirikizumab patients achieved sustainable bowel urgency improvement and remission compared to placebo patients.

Impact of Bowel Urgency on Quality of Life and Clinical Outcomes in Patients With Ulcerative Colitis

Background

Bowel urgency is commonly experienced by patients with ulcerative colitis (UC) and is associated with reduced health-related quality of life (QoL). Mirikizumab, a humanized monoclonal antibody directed against the p19 subunit of IL-23, significantly reduced bowel urgency in a double-blind, randomized, placebo-controlled Phase 2 clinical trial in patients with moderate-to-severe UC (NCT02589665).

Methods

All patients (N = 249) reported symptoms including absence or presence of bowel urgency. Absence of urgency was defined as no urgency for the 3 consecutive days prior to each scheduled visit. Missing urgency data were imputed as present. After 12 weeks of induction treatment, patients who achieved clinical response continued maintenance mirikizumab treatment through Week 52. We assessed the relationship of urgency with QoL, clinical outcomes, and inflammatory biomarkers at Weeks 12 and 52.

Results

Patients with absence of urgency demonstrated significantly greater improvement in Inflammatory Bowel Disease Questionnaire (IBDQ) scores even after adjusting for rectal bleeding (RB) and stool frequency (SF), significantly higher rates of all clinical outcomes at Weeks 12 and 52, and a greater decrease in inflammatory biomarkers C-reactive protein and fecal calprotectin compared to those with presence of urgency. Absence of urgency at Week 12 was associated with improved IBDQ scores at Week 52, while Week 12 RB or SF status was not.

Conclusions

Absence of urgency is strongly associated with improvement in QoL as well as clinical measures of UC disease activity. These findings suggest urgency may be a useful surrogate marker of disease activity and an important treatment target for UC.

Incorporating patient experience into drug development for ulcerative colitis: development of the Urgency Numeric Rating Scale, a patient-reported outcome measure to assess bowel urgency in adults

Background

Bowel urgency, the sudden or immediate need to have a bowel movement, is a common, bothersome and disruptive symptom of ulcerative colitis (UC). UC treatment goals include control of urgency; however, it is not consistently assessed in UC clinical trials. The Urgency Numeric Rating Scale (NRS) is a new patient-reported measure to assess severity of bowel urgency in adults with UC developed in accordance with Food and Drug Administration guidelines.

Methods

Qualitative interviews were used to develop Urgency NRS. The scale asks patients to report the immediacy status of their UC symptom over the past 24 h on an 11-point horizontal numeric rating scale [0 (No urgency) to 10 (Worst possible urgency)]. Higher scores indicate worse urgency severity. A 2-week diary study assessed floor and ceiling effects, test–retest reliability (intraclass correlation coefficient (ICC) (2,1) between Week 1 and 2), and construct validity (Spearman correlation using Week 1 scores). Weekly scores were calculated as mean score over each 7-day period.

Results

Qualitative interviews with 16 UC patients (mean age 37.9 ± 11.6 years; 50% female; 56% White) confirmed relevance, content, and comprehensiveness. The 2-week diary study included 41 UC patients (mean age 44.2 ± 14.6 years; 51% female; 56% White). No ceiling or floor effects were identified. Test–retest reliability was high (ICC = 0.877). Average Urgency NRS and patient global rating of severity scores were highly correlated, with a moderate correlation between average Urgency NRS and stool frequency, demonstrating construct validity.

Conclusions

Bowel urgency is a distinct symptom of UC. The Urgency NRS is a well-defined, content-valid, and reliable measurement of bowel urgency in adults with UC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41687-022-00439-w.

Local Colonic Administration of a Serine Protease Inhibitor Improves Post-Inflammatory Visceral Hypersensitivity in Rats

Dysregulation of the protease–antiprotease balance in the gastrointestinal tract has been suggested as a mechanism underlying visceral hypersensitivity in conditions such as inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS). We aimed to study the potential therapeutic role of an intracolonically administered serine protease inhibitor for the treatment of abdominal pain in a post-inflammatory rat model for IBS. An enema containing 2,4,6-trinitrobenzene sulfonic acid (TNBS) was used to induce colitis in male Sprague–Dawley rats, whereas controls received a saline solution. Colonoscopies were performed to confirm colitis and follow-up mucosal healing. In the post-inflammatory phase, the serine protease inhibitor UAMC-00050 (0.1–5 mg/kg) or its vehicle alone (5% DMSO in H₂O) was administered in the colon. Thirty minutes later, visceral mechanosensitivity to colorectal distensions was quantified by visceromotor responses (VMRs) and local effects on colonic compliance and inflammatory parameters were assessed. Specific proteolytic activities in fecal and colonic samples were measured using fluorogenic substrates. Pharmacokinetic parameters were evaluated using bioanalytical measurements with liquid chromatography–tandem mass spectrometry. Post-inflammatory rats had increased trypsin-like activity in colonic tissue and elevated elastase-like activity in fecal samples compared to controls. Treatment with UAMC-00050 decreased trypsin-like activity in colonic tissue of post-colitis animals. Pharmacokinetic experiments revealed that UAMC-00050 acted locally, being taken up in the bloodstream only minimally after administration. Local administration of UAMC-00050 normalized visceral hypersensitivity. These results support the role of serine proteases in the pathophysiology of visceral pain and the potential of locally administered serine protease inhibitors as clinically relevant therapeutics for the treatment of IBS patients with abdominal pain.

Spinal neuron-glia-immune interaction in cross-organ sensitization

Inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS), historically considered as regional gastrointestinal disorders with heightened colonic sensitivity, are increasingly recognized to have concurrent dysfunction of other visceral and somatic organs, such as urinary bladder hyperactivity, leg pain, and skin hypersensitivity. The interorgan sensory cross talk is, at large, termed "cross-organ sensitization." These organs, anatomically distant from one another, physiologically interlock through projecting their sensory information into dorsal root ganglia (DRG) and then the spinal cord for integrative processing. The fundamental question of how sensitization of colonic afferent neurons conveys nociceptive information to activate primary afferents that innervate distant organs remains ambiguous. In DRG, primary afferent neurons are surrounded by satellite glial cells (SGCs) and macrophage accumulation in response to signals of injury to form a neuron-glia-macrophage triad. Astrocytes and microglia are major resident nonneuronal cells in the spinal cord to interact, physically and chemically, with sensory synapses. Cumulative evidence gathered so far indicate the indispensable roles of paracrine/autocrine interactions among neurons, glial cells, and immune cells in sensory cross-activation. Dichotomizing afferents, sensory convergency in the spinal cord, spinal nerve comingling, and extensive sprouting of central axons of primary afferents each has significant roles in the process of cross-organ sensitization; however, more results are required to explain their functional contributions. DRG that are located outside the blood-brain barrier and reside upstream in the cascade of sensory flow from one organ to the other in cross-organ sensitization could be safer therapeutic targets to produce less central adverse effects.

The Macro- and Micro-Mechanics of the Colon and Rectum I: Experimental Evidence

Many lower gastrointestinal diseases are associated with altered mechanical movement and deformation of the large intestine, i.e., the colon and rectum. The leading reason for patients' visits to gastrointestinal clinics is visceral pain, which is reliably evoked by mechanical distension rather than non-mechanical stimuli such as inflammation or heating. The macroscopic biomechanics of the large intestine were characterized by mechanical tests and the microscopic by imaging the load-bearing constituents, i.e., intestinal collagen and muscle fibers. Regions with high mechanical stresses in the large intestine (submucosa and muscularis propria) coincide with locations of submucosal and myenteric neural plexuses, indicating a functional interaction between intestinal structural biomechanics and enteric neurons. In this review, we systematically summarized experimental evidence on the macro- and micro-scale biomechanics of the colon and rectum in both health and disease. We reviewed the heterogeneous mechanical properties of the colon and rectum and surveyed the imaging methods applied to characterize collagen fibers in the intestinal wall. We also discussed the presence of extrinsic and intrinsic neural tissues within different layers of the colon and rectum. This review provides a foundation for further advancements in intestinal biomechanics by synergistically studying the interplay between tissue biomechanics and enteric neurons.

Sacral Nerve Modulation Has No Effect on the Postprandial Response in Irritable Bowel Syndrome

Purpose

Irritable bowel syndrome is a common gastrointestinal disorder with a global prevalence of approximately 11%. Onset or worsening of symptoms following digestion is one of the characteristics of the condition. The present study aimed at evaluating the postprandial sensory and motor response before and after treatment with sacral nerve modulation.

Patients and Methods

Twenty-one irritable bowel syndrome patients, 12 diarrhea-predominant and 9 mixed, were eligible for a 6-week sacral nerve modulation test period. Patients were investigated with multimodal impedance planimetry including a standardized meal at baseline and at the end of 2 weeks of suprasensory stimulation embedded in the 6-week sacral nerve modulation period.

Results

There was no statistical significant difference in the sensory response to heat or cold before and after sacral nerve modulation, p>0.05. At baseline, wall tension increased after the meal (mean 124.79 [range 82.5 to 237.3] mmHg.mm before the meal, mean 207.76 [range, 143.5 to 429] mmHg.mm after the meal), p=0.048 indicating a postprandial response. During sacral nerve modulation, the postprandial increase in wall tension did not reach statistical significance (mean 86.79 [range 28.8 to 204.5] mmHg.mm before the meal, mean 159.71 [range 71.3 to 270.8] mmHg.mm after the meal), p=0.277. However, there was no statistically significant difference between the postprandial wall tension at baseline and during sacral nerve modulation, p=0.489. Likewise, we found no difference between pressure or stretch ratio at baseline and during sacral nerve modulation, p>0.05.

Conclusion

Sacral nerve modulation does not exert its positive treatments effects in diarrhea-predominant and mixed irritable bowel syndrome through a modulation of the postprandial response.

Bladder-bowel interactions: Do we understand pelvic organ cross-sensitization? International Consultation on Incontinence Research Society (ICI-RS) 2018

AIMS

Mounting evidence from experimental animal and human studies suggests that cross-sensitization exists between different organs. Lower urinary tract (LUT) and bowel dysfunction commonly overlap, and the role of cross-sensitization between pelvic visceral organs is uncertain.

METHODS

At the International Consultation on Incontinence Research Society (ICI-RS) meeting in 2018, a panel of clinicians participated in a discussion on bladder and bowel interactions in the context of pelvic organ cross-sensitization.

RESULTS

Bladder and bowel problems commonly co-occur in adults and children across different disorders, and the mechanism responsible for overlapping dysfunction is uncertain in most instances. At a neuronal level, cross-sensitization occurs as a result of afferent signaling from the LUT and lower bowel through different central and peripheral mechanisms. Studies in animals and humans have demonstrated evidence for cross-organ sensitization following experimental inflammation or distension of the lower bowel, affecting the LUT. Nerve stimulation is an effective treatment for different functional LUT and bowel disorders, and whether this treatment may influence cross-organ sensitization remains uncertain. The role of physiologically dormant C-fibers, the bladder-gut-brain axis, and gut microbiome in cross-sensitization are speculative.

CONCLUSION

Recommendations for research were made to explore the role of cross-organ sensitization in the pathogenesis of co-occurring LUT and bowel dysfunction in humans.

Rumex japonicus Houtt. alleviates dextran sulfate sodium-induced colitis by protecting tight junctions in mice

Background

Rumex japonicus Houtt. (RJ) is widely distributed in Korea, Japan, and China. The root of RJ has traditionally been used to treat constipation, jaundice, hematemesis, dysfunctional uterine bleeding, and gastrointestinal diseases. According to recent studies, plants of the genus Rumex have beneficial functionalities such as anti-microbial, antioxidative, and anti-inflammatory effects. Inflammatory bowel disease, including Crohn's disease and ulcerative colitis, is a chronic inflammatory disease characterized by an abnormal immune response and epithelial barrier dysfunction. This study evaluates the protective effect of RJ against dextran sulfate sodium (DSS)-induced colitis.

Methods

Male 8-week-old C57BL/6 N mice were treated with methanolic extract of RJ for 14 days, and DSS-induced groups were administered 2.5% DSS for last 7 days. After sacrifice, the length and weight of the colon were measured, and colon sections were subjected to H&E staining, immunohistochemistry and Western blotting to investigate the changes of inflammatory cytokines, tight junction and apoptosis-related factors.

Results

The colon of DSS-treated mouse was significantly shorter and heavier than the normal mouse. Moreover, DSS exposure induced an increase of tumor necrosis factor-α, interleukin (IL)-1β, IL-6, occludin, zonula occludens-1, p21, p53 and Bcl-2, and decreased the expressions of IL-10, claudin-2 and cleaved caspase-3 in the colon tissue. These DSS-induced changes were inhibited by RJ treatment.

Conclusion

Our results indicate that RJ effectively suppresses DSS-induced colitis by protecting tight junction connections in the colonic tissue. We therefore infer that RJ has the potential as a medicine or ingredient for treating colitis.

Inflammation without pain: Immune-derived opioids hold the key

Visceral pain is commonly associated with acute or remitting inflammatory bowel disease (IBD). In marked contrast, chronic IBD is often painless, even in the presence of active inflammation. This suggests that inflammation in itself is insufficient to sustain altered nociceptive signaling and raises the possibility that there is an endogenous analgesic system in effect in chronic disease. A new study by Basso et al. published in this issue of Neurogastroenterology & Motility provides additional support for an immune-mediated mechanism that suppresses visceral hypersensitivity. The authors examined visceral pain in the IL-10-piroxicam model of chronic colitis, which differs from other experimental IBD models in that it involves immune suppression. During active inflammation, responses by these mice to graded increases in colorectal distension were equivalent to healthy controls, consistent with normal afferent signaling. However, treatment with a peripherally restricted opioid receptor antagonist resulted in marked visceral hypersensitivity to the same stimuli. This effect was attributed to the production of endogenous opioids by colitogenic CD4⁺ T cells present in the mucosa. This mini-review provides a brief overview of analgesia by immune-derived opioids under inflammatory conditions and highlights how the work of Basso et al. contributes to this area of research. Potential pharmacological approaches to harness or mimic this system are provided. These strategies may prove to be an effective means through which targeted and sustained relief of IBD pain may be achieved.

Remission Effects of Dietary Soybean Isoflavones on DSS-Induced Murine Colitis and an LPS-Activated Macrophage Cell Line

Inflammatory bowel diseases (IBDs), including ulcerative colitis and Crohn's disease, are chronic disorders of the gastrointestinal tract, although the exact causes of IBD remain unknown. Present treatments for IBDs have poor tolerability and insufficient therapeutic efficacy, thus, alternative therapeutic approaches are required. Soybean-derived isoflavones have multiple bioactivities such as anti-inflammation. However, the low water solubility of soybean isoflavones limits their bioavailability and practical use. Therefore, in order to study the preventive effects of water-soluble soybean isoflavones on colonic inflammatory status, we examined soybean-derived isoflavone glycosides (SIFs) in a dextran sodium sulfate (DSS)-induced murine colitis model and in lipopolysaccharide (LPS)-activated RAW264.7 macrophages. Oral administration of SIF (0.5 w/v%) attenuated DSS-induced colitis in terms of body weight decrease, colon shortening, epithelial apoptosis, histological score, mRNA levels of inflammatory cytokines, and immune cell infiltration in colon tissues. In the in vitro assessment, we observed the inhibitory effects of SIF on the production of nitric oxide and prostaglandin E2, via suppression of inducible nitric oxide synthase and cyclooxygenase-2 expression in RAW264.7 macrophages in response to LPS. Furthermore, we confirmed that the expression of inflammatory cytokines and chemokines were decreased by pre-treatment with SIF in LPS-activated RAW264.7 macrophages. Moreover, we demonstrated that SIF suppressed inflammatory mediators involved in nuclear factor-κB signaling pathway via inhibitory κB kinase phosphorylation and degradation of inhibitory κB. Our results suggested that SIF may be beneficial for the remission of colonic inflammatory status including IBDs.

The influence of the brain-gut axis in inflammatory bowel disease and possible implications for treatment

Brain-gut interactions affect psychological wellbeing and symptom reporting in functional gastrointestinal disorders; the presence of anxiety or depression is associated with the development of new-onset gastrointestinal symptoms, and the presence of gastrointestinal symptoms is associated with the development of psychological disorders de novo. In inflammatory bowel diseases (IBD), the reporting of irritable bowel syndrome (IBS)-type symptoms by patients with quiescent disease is common, and is associated with psychological disorders, impaired quality of life, and increased health-care use. In IBD, data from observational studies suggest that psychological disorders might be associated with relapse of disease activity, and that inflammatory activity is associated with the development of new psychological disorders, as has been described for functional gastrointestinal disorders such as IBS and functional dyspepsia. The brain-gut axis provides the physiological link between the CNS and gastrointestinal tract that might facilitate these relationships. In IBS, treatments targeting disordered brain-gut axis activity, including psychological therapies and antidepressants, might lead to improved symptoms and quality of life. However, in IBD, the benefit of these treatments is less certain because of a scarcity of interventional studies. Despite the scarcity of trials, observational data suggest that the effect of disordered brain-gut axis activity in IBD is substantial, and scope remains for further well designed trials of psychological therapies and antidepressants, particularly in the subset of patients who have coexistent psychological disorders, or in those who report IBS-type symptoms. Integrating these treatments into a biopsychosocial model of care has the potential to improve both psychological wellbeing and quality of life in some patients with IBD, reducing health-care use and altering the natural history of disease.

Colonic Transit Disorder Mediated by Downregulation of Interstitial Cells of Cajal/Anoctamin-1 in Dextran Sodium Sulfate-induced Colitis Mice

Background/Aims

Interstitial cells of Cajal (ICC) and their special calcium-activated chloride channel, anoctamin-1 (ANO1) play pivotal roles in regulating colonic transit. This study is designed to investigate the role of ICC and the ANO1 channel in colonic transit disorder in dextran sodium sulfate (DSS)-treated colitis mice.

Methods

Colonic transit experiment, colonic migrating motor complexes (CMMCs), smooth muscle spontaneous contractile experiments, intracellular electrical recordings, western blotting analysis, and quantitative polymerase chain reaction were applied in this study.

Results

The mRNA and protein expressions of c-KIT and ANO1 channels were significantly decreased in the colons of DSS-colitis mice. The colonic artificial fecal-pellet transit experiment in vitro was significantly delayed in DSS-colitis mice. The CMMCs and smooth muscle spontaneous contractions were significantly decreased by 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), an ANO1 channel blocker, and NG-Nitro-L-arginine methyl ester hydrochloride (L-NAME), an inhibitor of nitric oxide synthase activity, in DSS-colitis mice compared with that of control mice. Intracellular electrical recordings showed that the amplitude of NPPB-induced hyperpolarization was more positive in DSS-colitis mice. The electric field stimulation-elicited nitric-dependent slow inhibitory junctional potentials were also more positive in DSS-colitis mice than those of control mice.

Conclusion

The results suggest that colonic transit disorder is mediated via downregulation of the nitric oxide/ICC/ANO1 signalling pathway in DSS-colitis mice.

Enteric Glia: A New Player in Abdominal Pain

Chronic abdominal pain is the most common gastrointestinal issue and contributes to the pathophysiology of functional bowel disorders and inflammatory bowel disease. Current theories suggest that neuronal plasticity and broad alterations along the brain-gut axis contribute to the development of chronic abdominal pain, but the specific mechanisms involved in chronic abdominal pain remain incompletely understood. Accumulating evidence implicates glial cells in the development and maintenance of chronic pain. Astrocytes and microglia in the central nervous system and satellite glia in dorsal root ganglia contribute to chronic pain states through reactive gliosis, the modification of glial networks, and the synthesis and release of neuromodulators. In addition, new data suggest that enteric glia, a unique type of peripheral glia found within the enteric nervous system, have the potential to modify visceral perception through interactions with neurons and immune cells. Understanding these emerging roles of enteric glia is important to fully understand the mechanisms that drive chronic pain and to identify novel therapeutic targets. In this review, we discuss enteric glial cell signaling mechanisms that have the potential to influence chronic abdominal pain.

What Is the Future of Impedance Planimetry in Gastroenterology?

The gastrointestinal (GI) tract is efficient in transporting ingested material to the site of delivery in healthy subjects. A fine balance exists between peristaltic forces, the mixing and delivery of the contents, and sensory signaling. This fine balance is easily disturbed by diseases. It is mandatory to understand the pathophysiology to enhance our understanding of GI disorders. The inaccessibility and complex nervous innervation, geometry and mechanical function of the GI tract make mechanosensory evaluation difficult. Impedance planimetry is a distension technology that assesses luminal geometry, mechanical properties including muscle dynamics, and processing of nociceptive signals from the GI tract. Since standardized models do not exist for GI muscle function in vivo, models, concepts, and terminology must be borrowed from other medical fields such as cardiac mechanophysiology. The review highlights the impedance planimetric technology, muscle dynamics assessment, and 3 applied technologies of impedance planimetry. These technologies are the multimodal probes that assesses sensory function, the functional luminal imaging probe that dynamically measures the geometry of the lumen it distends, and Fecobionics that is a simulated feces providing high-resolution measurements during defecation. The advanced muscle analysis and 3 applied technologies can enhance the quality of future interdisciplinary research for gaining more knowledge about mechanical function, sensory-motor disorders, and symptoms. This is a step in the direction of individualized treatment for GI disorders based on diagnostic subtyping. There seems to be no better alternatives to impedance planimetry, but only the functional luminal imaging probe is currently commercially available. Wider use depends on commercialization of the multimodal probe and Fecobionics.

Systematic review: interventions for abdominal pain management in inflammatory bowel disease

BACKGROUND

Abdominal pain is frequently reported by people with inflammatory bowel disease (IBD), including in remission. Pain is an under-treated symptom.

AIM

To systematically review evidence on interventions (excluding disease-modifying interventions) for abdominal pain management in IBD.

METHODS

Databases (MEDLINE, EMBASE, PsycInfo, CINAHL, Scopus, Cochrane Library) were searched (February 2016). Two researchers independently screened references and extracted data.

RESULTS

Fifteen papers were included: 13 intervention studies and two cross-sectional surveys. A variety of psychological, dietary and pharmacological interventions were reported. Four of six studies reported pain reduction with psychological intervention including individualised and group-based relaxation, disease anxiety-related Cognitive Behavioural Therapy and stress management. Both psychologist-led and self-directed stress management in inactive Crohn's disease reduced pain compared with controls (symptom frequency reduction index=-26.7, -11.3 and 17.2 at 6-month follow-up, respectively). Two dietary interventions (alcoholic drinks with high sugar content and fermentable carbohydrate with prebiotic properties) had an effect on abdominal pain. Antibiotics (for patients with bacterial overgrowth) and transdermal nicotine patches reduced abdominal pain. Current and past cannabis users report it relieves pain. One controlled trial of cannabis reduced SF-36 and EQ-5D pain scores (1.84 and 0.7, respectively). These results must be treated with caution: data were derived from predominantly small uncontrolled studies of moderate to low quality.

CONCLUSIONS

Few interventions have been tested for IBD abdominal pain. The limited evidence suggests that relaxation and changing cognitions are promising, possibly with individualised dietary changes. There is a need to develop interventions for abdominal pain management in IBD.

Regional gastrointestinal transit times in severe ulcerative colitis

BACKGROUND

Gastrointestinal (GI) dysmotility may present secondary to inflammatory bowel disease. The main aim of this study was to investigate GI motility in ulcerative colitis (UC) patients during severe disease activity.

METHODS

Twenty patients with severe UC were studied with a novel telemetric capsule system (3D-Transit) designed for minimally invasive, ambulatory assessment of total and regional GI transit times. Ten patients were available for follow-up during remission. Data were compared to those of 20 healthy subjects (HS).

KEY RESULTS

Total GI transit time was significantly longer in patients with severe UC (median 44.5 h [range 9.9-102.7 h]) than in HS (median 27.6 h [range 9.6-56.4 h]) (p = 0.032). Additionally, during severe UC, transit time was prolonged through the proximal colon (p = 0.003) and there were strong trends toward longer than normal small intestinal transit time (HS: median 4.9 h [range 3.4-8.3 h] vs severe UC patients: median 5.9 h [range 3.9-11.9 h]; p = 0.053) and colorectal transit times (HS: median 18.2 h [range 1.5-43.7] vs severe UC patients: median 34.9 h [range 0.4-90.9 h]; p = 0.056). Our data further indicate that total GI and colorectal transit times may be prolonged in UC during early remission.

CONCLUSIONS & INFERENCES

Total GI transit times are significantly prolonged during severe UC.

Abnormal neuronal response to rectal and anal stimuli in patients with idiopathic fecal incontinence

BACKGROUND

The pathophysiology behind idiopathic fecal incontinence (IFI) is poorly understood. We hypothesized abnormal sensory pathways along the brain-gut axis as a key player in this disease, reflected in cortical evoked potentials (CEP) from mechanical stimuli of the rectum and the anal canal.

METHODS

CEPs were recorded during repeated rapid balloon distensions of the rectum and anal canal in 19 women with IFI (mean age: 60 ± 14, mean Wexner score: 14.7 ± 2.9) and in 19 healthy women (mean age: 56 ± 11, mean Wexner score: 1.1 ± 1.3). Latencies, amplitudes and topography of CEPs elicited by rectal distension were compared between the groups. CEPs from both rectal and anal distensions were examined using spectral band analysis of single sweeps determining the relative amplitude of five spectral bands as a proxy of neuronal processing.

KEY RESULTS

Compared to controls IFI patients had prolonged latency of CEPs from rectal distension by up to 27% (p < 0.001) while amplitudes and topography were similar (all p > 0.7 and all p > 0.23). Spectral analysis of CEPs from rectal distensions showed no difference (all p > 0.1) between groups. However, analysis of CEPs following distension of the anal canal resulted in abnormally low activity in beta (8-12 Hz; p < 0.001) band and high activity in the gamma (32-70 Hz; p = 0.04) band in patients.

CONCLUSIONS & INFERENCES

IFI seems to be associated with impaired ano-rectal sensory functions in both the afferent fibers to the brain and the cortical processing of anal sensory pathways. This may play a central role for the pathogenesis of IFI.

Systematic mechanism-orientated approach to chronic pancreatitis pain

Pain in chronic pancreatitis (CP) shows similarities with other visceral pain syndromes (i.e., inflammatory bowel disease and esophagitis), which should thus be managed in a similar fashion. Typical causes of CP pain include increased intrapancreatic pressure, pancreatic inflammation and pancreatic/extrapancreatic complications. Unfortunately, CP pain continues to be a major clinical challenge. It is recognized that ongoing pain may induce altered central pain processing, e.g., central sensitization or pro-nociceptive pain modulation. When this is present conventional pain treatment targeting the nociceptive focus, e.g., opioid analgesia or surgical/endoscopic intervention, often fails even if technically successful. If central nervous system pain processing is altered, specific treatment targeting these changes should be instituted (e.g., gabapentinoids, ketamine or tricyclic antidepressants). Suitable tools are now available to make altered central processing visible, including quantitative sensory testing, electroencephalograpy and (functional) magnetic resonance imaging. These techniques are potentially clinically useful diagnostic tools to analyze central pain processing and thus define optimum management approaches for pain in CP and other visceral pain syndromes. The present review proposes a systematic mechanism-orientated approach to pain management in CP based on a holistic view of the mechanisms involved. Future research should address the circumstances under which central nervous system pain processing changes in CP, and how this is influenced by ongoing nociceptive input and therapies. Thus we hope to predict which patients are at risk for developing chronic pain or not responding to therapy, leading to improved treatment of chronic pain in CP and other visceral pain disorders.

Sacral nerve stimulation changes rectal sensitivity and biomechanical properties in patients with irritable bowel syndrome

BACKGROUND

Sacral nerve stimulation (SNS) has been demonstrated to alleviate symptoms and improve quality of life in selected patients with irritable bowel syndrome (IBS). The mechanisms of action, however, remain unknown. The aim of the study was to evaluate the effects of SNS on rectal sensitivity and biomechanical properties in patients with IBS.

METHODS

Twenty patients with diarrhea-predominant (n = 11) or mixed (n = 9) IBS were treated with SNS in a controlled, randomized crossover trial. They were randomized to either 1 month of SNS (ON) or placebo (OFF) with the opposite setting for the next month. Sensory and biomechanical parameters were assessed by multimodal rectal stimulation at the end of each period. IBS-specific symptoms were evaluated at baseline and at the end of each treatment period.

KEY RESULTS

Cold stimuli were better tolerated in the ON period (19.9 °C[± 0.6]) compared to the OFF period (21.8 °C[± 0.6]; p = 0.03). Significantly lower cross-sectional areas were needed to elicit sensory responses in the ON period (1545 mm(2) [± 95]) compared to the OFF period (1869 mm(2) [± 92]; p = 0.015). The association between reduced sensory threshold and improvement of constipation was of borderline significance (p = 0.05). Wall stiffness was significantly lower in the ON period (192 mmHg[± 10]) compared to the OFF period (234 mmHg[± 10]; p = 0.004). Reduced wall stiffness was significantly associated with improved overall GSRS-IBS symptom score (p = 0.01). Reduced sensory threshold to stretch (p = 0.02) and reduced wall stiffness (p < 0.001) were predictors of the GSRS-IBS symptom score.

CONCLUSIONS & INFERENCES

SNS for diarrhea-predominant and mixed IBS relaxes the rectal wall, while making it more sensitive to stretch and less sensitive to cold. Reduced wall stiffness and increased sensitivity to stretch are associated with improved GSRS-IBS symptom score.

Neuroplasticity and dysfunction after gastrointestinal inflammation

The gastrointestinal tract is innervated by several distinct populations of neurons, whose cell bodies either reside within (intrinsic) or outside (extrinsic) the gastrointestinal wall. Normally, most individuals are unaware of the continuous, complicated functions of these neurons. However, for patients with gastrointestinal disorders, such as IBD and IBS, altered gastrointestinal motility, discomfort and pain are common, debilitating symptoms. Although bouts of intestinal inflammation underlie the symptoms associated with IBD, increasing preclinical and clinical evidence indicates that infection and inflammation are also key risk factors for the development of other gastrointestinal disorders. Notably, a strong correlation exists between prior exposure to gut infection and symptom occurrence in IBS. This Review discusses the evidence for neuroplasticity (structural, synaptic or intrinsic changes that alter neuronal function) affecting gastrointestinal function. Such changes are evident during inflammation and, in many cases, long after healing of the damaged tissues, when the nervous system fails to reset back to normal. Neuroplasticity within distinct populations of neurons has a fundamental role in the aberrant motility, secretion and sensation associated with common clinical gastrointestinal disorders. To find appropriate therapeutic treatments for these disorders, the extent and time course of neuroplasticity must be fully appreciated.

Cortical evoked potentials in response to rapid balloon distension of the rectum and anal canal

BACKGROUND

Neurophysiological evaluation of anorectal sensory function is hampered by a paucity of methods. Rapid balloon distension (RBD) has been introduced to describe the cerebral response to rectal distension, but it has not successfully been applied to the anal canal.

METHODS

Nineteen healthy women received 30 RBDs in the rectum and the anal canal at intensities corresponding to sensory and unpleasantness thresholds, and response was recorded as cortical evoked potentials (CEPs) in 64-channels. The anal canal stimulations at unpleasantness level were repeated after 4 min to test the within-day reproducibility. CEPs were averaged, and to overcome latency variation related to jitter the spectral content of single sweeps was also computed.

KEY RESULTS

Repeated stimulation of the anal canal generated CEPs with similar latencies but smaller amplitudes compared to those from the rectum. Due to latency jitter, reproducibility of averaged CEPs was lower than what was found in the rectum. The most reproducible feature was N2P2 peak-to-peak amplitude with intra-class correlation coefficient (ICC) of 0.7 and coefficient of variation (CV) of 18%. Spectral content of the single sweeps showed reproducibility with ICCs for all bands >0.8 and corresponding CVs <7%.

CONCLUSIONS & INFERENCES

Cortical potentials evoked from the anal canal are challenged by latency jitter likely related to variability in muscle tone due to the distensions. Using single-sweep analysis, anal CEPs proved to be reproducible and should be used in future evaluation of the anal function.

A systematic review of the evidence for central nervous system plasticity in animal models of inflammatory-mediated gastrointestinal pain

BACKGROUND

Abdominal pain frequently accompanies inflammatory disorders of the gastrointestinal tract (GIT), and animal models of GIT inflammation have been developed to explore the role of the central nervous system (CNS) in this process. Here, we summarize the evidence from animal studies for CNS plasticity following GIT inflammation.

METHODS

A systematic review was conducted to identify studies that: (1) used inflammation of GIT organs, (2) assessed pain or visceral hypersensitivity, and (3) presented evidence of CNS involvement. Two hundred and eight articles were identified, and 79 were eligible for analysis.

RESULTS

Rats were most widely used (76%). Most studies used adult animals (42%) with a bias toward males (74%). Colitis was the most frequently used model (78%) and 2,4,6-trinitrobenzenesulfonic acid the preferred inflammatory agent (33%). Behavioral (58%), anatomical/molecular (44%), and physiological (24%) approaches were used alone or in combination to assess CNS involvement during or after GIT inflammation. Measurement times varied widely (<1 h-> 2 wk after inflammation). Blinded outcomes were used in 42% studies, randomization in 10%, and evidence of visceral inflammation in 54%. Only 3 studies fulfilled our criteria for high methodological quality, and no study reported sample size calculations.

CONCLUSIONS

The included studies provide strong evidence for CNS plasticity following GIT inflammation, specifically in the spinal cord dorsal horn. This evidence includes altered visceromotor responses and indices of referred pain, elevated neural activation and peptide content, and increased neuronal excitability. This evidence supports continued use of this approach for preclinical studies; however, there is substantial scope to improve study design.

Severity of fecal urgency and incontinence in inflammatory bowel disease: clinical, manometric and sonographic predictors

BACKGROUND

Fecal incontinence (FI) and urgency are prevalent symptoms in patients with inflammatory bowel diseases (IBD). It is unclear which factors determine their severity. We evaluated associations of clinical activity, anorectal motility, and endoanal sonography with FI severity in IBD.

METHODS

Fifty-eight consecutive IBD patients and 14 healthy volunteers participated in a cross-sectional, tertiary-center study. Active disease was defined as Crohn's disease activity index ≥ 150 and as simple clinical colitis index > 2. We assessed anal pressures and fatigue rate index (FRI) of the external anal sphincter (EAS) by manometry, rectal compliance and sensitivity by balloon distension, and sphincter defects by endoanal ultrasound. Significant bivariate associations between these parameters and the fecal incontinence severity scale (FISS) were evaluated in multivariate analysis.

RESULTS

Twenty-seven patients (47%) reported urgency, 13 of which (22%) reported FI. Defects of the internal anal sphincter (IAS) and the EAS were diagnosed in 14 (24%) and 13 patients (22%), respectively. Patients had significantly lower rectal compliance and FRI compared with controls. FISS demonstrated significant bivariate associations with clinical disease activity (P = 0.0115), FRI (P = 0.0018), sonographic IAS and EAS defects (P < 0.0001 and 0.0059), rectal compliance (P = 0.0001), and volume at the threshold of a constant urge (Vurge, P = 0.0002). In multivariate analysis, FISS was associated with clinical disease activity (P = 0.0325), FRI (P = 0.0367), Vurge (P = 0.0091), and sonographic IAS defect(s) (P = 0.0008). The derived model explained 62% of the variance in FISS (P < 0.0001).

CONCLUSIONS

Clinical disease activity and manometric and sonographic anorectal parameters are associated with FI severity in IBD. Prospective studies are warranted to evaluate their predictive value in continence outcomes.

Translational aspects of rectal evoked potentials: a comparative study in rats and humans

Inconsistencies between species has stunted the progress of developing new analgesics. To increase the success of translating results between species, improved comparable models are required. Twelve rats received rectal balloon distensions on 2 different days separated by 24.3 (SD 24.6) days. Rectal balloon distensions were also performed in 18 humans (mean age: 34 yr; range: 21-56 yr; 12 men) on two separate occasions, separated by 9.3 (SD 5.5) days. In rats, cerebral evoked potentials (CEPs) were recorded by use of implanted skull-electrodes to distension pressure of 80 mmHg. In humans surface electrodes and individualized pressure, corresponding to pain detection threshold, were used. Comparison of morphology was assessed by wavelet analysis. Within- and between-day reproducibility was assessed in terms of latencies, amplitudes, and frequency content. In rats CEPs showed triphasic morphology. No differences in latencies, amplitudes, and power distribution were seen within or between days (all P ≥ 0.5). Peak-to-peak amplitude between the first positive and negative potential were the most reproducible characteristic within and between days (evaluated by intraclass correlation coefficients, ICC) (ICC = 0.99 and ICC = 9.98, respectively). In humans CEPs showed a triphasic morphology. No differences in latencies, amplitudes, or power distribution were seen within or between days (all P ≥ 0.2). Latency to the second negative potential (ICC = 0.98) and the second positive potential (ICC = 0.95) was the most reproducible characteristic within and between days. A unique and reliable translational platform was established assessing visceral sensitivity in rats and humans, which may improve the translational process of developing new drugs targeting visceral pain.

A low dose of fermented soy germ alleviates gut barrier injury, hyperalgesia and faecal protease activity in a rat model of inflammatory bowel disease

Pro-inflammatory cytokines like macrophage migration inhibitory factor (MIF), IL-1β and TNF-α predominate in inflammatory bowel diseases (IBD) and TNBS colitis. Increased levels of serine proteases activating protease-activated receptor 2 (PAR-2) are found in the lumen and colonic tissue of IBD patients. PAR-2 activity and pro-inflammatory cytokines impair epithelial barrier, facilitating the uptake of luminal aggressors that perpetuate inflammation and visceral pain. Soy extracts contain phytoestrogens (isoflavones) and serine protease inhibitors namely Bowman-Birk Inhibitors (BBI). Since estrogens exhibit anti-inflammatory and epithelial barrier enhancing properties, and that a BBI concentrate improves ulcerative colitis, we aimed to evaluate if a fermented soy germ extract (FSG) with standardized isoflavone profile and stable BBI content exert cumulative or synergistic protection based on protease inhibition and estrogen receptor (ER)-ligand activity in colitic rats. Female rats received orally for 15 d either vehicle or FSG with or without an ER antagonist ICI 182.780 before TNBS intracolonic instillation. Macroscopic and microscopic damages, myeloperoxidase activity, cytokine levels, intestinal paracellular permeability, visceral sensitivity, faecal proteolytic activity and PAR-2 expression were assessed 24 h, 3 d and 5 d post-TNBS. FSG treatment improved the severity of colitis, by decreasing the TNBS-induced rise in gut permeability, visceral sensitivity, faecal proteolytic activity and PAR-2 expression at all post-TNBS points. All FSG effects were reversed by the ICI 182.780 except the decrease in faecal proteolytic activity and PAR-2 expression. In conclusion, the anti-inflammatory properties of FSG treatment result from two distinct but synergic pathways i.e an ER-ligand and a PAR-2 mediated pathway, providing rationale for potential use as adjuvant therapy in IBD.

Up-regulation of brain-derived neurotrophic factor is regulated by extracellular signal-regulated protein kinase 5 and by nerve growth factor retrograde signaling in colonic afferent neurons in colitis

Brain-derived neurotrophic factor (BDNF) plays an essential role in sensory neuronal activation in response to visceral inflammation. Here we report that BDNF up-regulation in the primary afferent neurons in the dorsal root ganglia (DRG) in a rat model of colitis is mediated by the activation of endogenous extracellular signal-regulated protein kinase (ERK) 5 and by nerve growth factor (NGF) retrograde signaling. At 7 days of colitis, the expression level of BDNF is increased in conventional neuronal tracing dye Fast Blue labeled primary afferent neurons that project to the distal colon. In these neurons, the phosphorylation (activation) level of ERK5 is also increased. In contrast, the level of phospho-ERK1/2 is not changed in the DRG during colitis. Prevention of the ERK5 activation in vivo with an intrathecal application of the MEK inhibitor PD98059 significantly attenuates the colitis-induced increases in BDNF expression in the DRG. Further studies show that BDNF up-regulation in the DRG is triggered by NGF retrograde signaling which also involves activation of the MEK/ERK pathways. Application of exogenous NGF exclusively to the compartment containing DRG nerve terminals in an ex vivo ganglia-nerve preparation markedly increases the BDNF expression level in the DRG neuronal cell body that is placed in a different compartment; this BDNF elevation is attenuated by U0126, PD98059 and a specific ERK5 inhibitor BIX02188. These results demonstrate the mechanisms and pathways by which BDNF expression is elevated in primary sensory neurons following visceral inflammation that is mediated by increased activity of ERK5 and is likely to be triggered by the elevated NGF level in the inflamed viscera.

Colitis induces calcitonin gene-related peptide expression and Akt activation in rat primary afferent pathways

Previous study has shown that colitis-induced increases in calcitonin gene-related peptide (CGRP) immunoreactivity in bladder afferent neurons result in sensory cross-sensitization. To further determine the effects of colitis on CGRP expression in neurons other than bladder afferents, we examined and compared the levels of CGRP mRNA and immunoreactivity in the lumbosacral dorsal root ganglia (DRG) and spinal cord before and during colitis in rats. We also examined the changes in CGRP immunoreactivity in colonic afferent neurons during colitis. Results showed increases in CGRP mRNA levels in L1 (2.5-fold, p<0.05) and S1 DRG (1.9-2.4-fold, p<0.05). However, there were no changes in CGRP mRNA levels in L1 and S1 spinal cord during colitis. CGRP protein was significantly increased in L1 (2.5-fold increase, p<0.05) but decreased in S1 (50% decrease, p<0.05) colonic afferent neurons, which may reflect CGRP release from these neurons during colitis. In L1 spinal cord, colitis caused increases in the number of CGRP nerve fibers in the deep lamina region extending to the gray commissure where the number of phospho-Akt neurons was also increased. In S1 spinal cord, colitis caused the increases in the intensity of CGRP fibers in the regions of dorso-lateral tract, and caused the increases in the level of phospho-Akt in the superficial dorsal horn of the spinal cord. In spinal cord slice culture, exogenous CGRP increased the phosphorylation level of Akt but not the phosphorylation level of extracellular-signal regulated kinase ERK1/2 even though our previous studies showed that colitis increased the phosphorylation level of ERK1/2 in L1 and S1 spinal cord. These results suggest that CGRP is synthesized in the DRG and may transport to the spinal cord where it initiates signal transduction during colitis.

Pain and inflammatory bowel disease

Abdominal pain is a common symptom of inflammatory bowel disease (IBD: Crohn's disease, ulcerative colitis). Pain may arise from different mechanisms, which can include partial blockage and gut distention as well as severe intestinal inflammation. A majority of patients suffering from acute flares of IBD will experience pain, which will typically improve as disease activity decreases. However, a significant percentage of IBD patients continue experiencing symptoms of pain despite resolving inflammation and achieving what appears to be clinical remission. Current evidence suggests that sensory pathways sensitize during inflammation, leading to persistent changes in afferent neurons and central nervous system pain processing. Such persistent pain is not only a simple result of sensory input. Pain processing and even the activation of sensory pathways is modulated by arousal, emotion, and cognitive factors. Considering the high prevalence of iatrogenic as well as essential neuropsychiatric comorbidities including anxiety and depression in IBD patients, these central modulating factors may significantly contribute to the clinical manifestation of chronic pain. The improved understanding of peripheral and central pain mechanisms is leading to new treatment strategies that view pain as a biopsychosocial problem. Thus, improving the underlying inflammation, decreasing the excitability of sensitized afferent pathways, and altering emotional and/or cognitive functions may be required to more effectively address the difficult and disabling disease manifestations.

Biomechanical changes in oxazolone-induced colitis in BALB/C mice

Ulcerative colitis (UC) is associated with intestinal and extra intestinal clinical manifestations. The profound organic changes in UC indicate that the colonic mechanical and mechanosensory functions are affected. The aim was to study acute morphological and biomechanical properties of the distal colon in oxazolone-induced UC in BALB/C mice. Six normal male BALB/C mice and 10 oxazolone-induced UC mice were studied. UC was induced by epicutaneous and intrarectal administration of oxazolone. The mechanical test was done as a distension experiment where the colon was distended up to 20 cmH2O. The pressure, outer diameter and length were recorded simultaneously. Circumferential and longitudinal stresses and strains were computed. The intestinal specimens were processed for histology. The mucosa was infiltrated with acute and chronic inflammatory cells. Mucosal bleeding, irregular ulcers crypt abscess, and destruction of the epithelial border were observed. Although, the mucosa in ulcers was much thinner than in the normal controls, the mucosa and submucosa around the ulcer were thicker than in the normal controls (P<0.05). Oxazolone-induced colitis increased the circumferences and wall cross-sectional area (P<0.01), the opening angle and residual strain at the serosa increased (P<0.01). Furthermore, the circumferential and longitudinal stiffness increased in the UC wall and was most pronounced in longitudinal direction. The opening angle and residual strain was linearly correlated to the wall thickness, area and inflammation degree. In conclusion, morphological and biomechanical changes of the colon occurred during the development of UC. The increased stiffness may contribute to the abnormal function in patients with UC.

Basic and clinical aspects of gastrointestinal pain

The gastrointestinal (GI) tract is a system of organs within multicellular animals which facilitates the ingestion, digestion, and absorption of food with subsequent defecation of waste. A complex arrangement of nerves and ancillary cells contributes to the sensorimotor apparatus required to subserve such essential functions that are with the exception of the extreme upper and lower ends of the GI tract normally subconscious. However, it also has the potential to provide conscious awareness of injury. Although this function can be protective, when dysregulated, particularly on a chronic basis, the same system can lead to considerable morbidity. The anatomical and molecular basis of gastrointestinal nociception, conditions associated with chronic unexplained visceral pain, and developments in treatment are presented in this review.

Functional gastrointestinal disorders and visceral hypersensitivity in children and adolescents suffering from Crohn's disease

BACKGROUND

Symptoms of abdominal pain are reported by children with active Crohn's disease (CD). During remissions abdominal pain improves in most children but some of them continue to experience pain. We hypothesized that these patients may suffer from protracted abdominal pain related to functional gastrointestinal disorders (FGID) and visceral hypersensitivity. The objective was to characterize the symptoms and to measure the rectal sensory threshold for pain (RSTP) by barostat in CD children and adolescents suffering from abdominal pain despite remission.

METHODS

Eight patients (median age 14.5 years; range 9.8-17) with quiescent CD but suffering from chronic abdominal pain were studied by rectal barostat. At the same time they completed validated questionnaires to assess FGID, anxiety, and depression. They were compared to 10 control children and 8 children with FGID also investigated in our laboratory.

RESULTS

All patients fulfilled Rome II criteria for irritable bowel syndrome (n = 5), functional abdominal pain (n = 2), and functional dyspepsia (n = 1). RSTP was significantly lower in CD patients compared to the normal controls: median (range) 25 mmHg (15-29) versus 40 mmHg (30-48) (P < 0.01). RSTP was similar in patients and children with FGID. Rectal compliance was similar in patients, children with FGID, and controls. Seven of the 8 patients had scores indicating an anxiety problem.

CONCLUSIONS

Protracted abdominal pain that affects children and adolescents with quiescent CD is related to FGID associated with visceral hypersensitivity and anxiety. The incidence of FGID in children suffering from CD requires further investigation.

Multimodal sensory testing of the rectum and rectosigmoid: development and reproducibility of a new method

Evaluation of rectal and rectosigmoid sensation is important in basic, clinical and pharmacological studies. New methods to evoke and assess multimodal (electrical, thermal and mechanical) experimental pain of the upper gut activate distinct pathways and mimics clinical pain. The aims of the current study were to characterize the sensory response and reproducibility to multimodal stimulation of rectum and the rectosigmoid. A multimodal rectal probe was developed. Mucosal electrostimulation was delivered at the recto-sigmoid junction. In Rectum, impedance planimetry was used for measurement of cross-sectional area (CSA) during distension. Circulation of water within the bag at either 4 or 60 degrees C was applied for thermal stimulation. The method was tested in 12 healthy volunteers (six men mean age 32 years) on two subsequent days. Mechanical and sensory responses and referred pain areas were assessed. Stimulation with electrical, thermal and mechanical modalities resulted in different sensory perceptions. The relationship between stimulus intensity and sensory response was linear for all modalities. Sensory response to different modalities did not differ between investigation days (all P-values > 0.1). Approximately 75% of subjects felt referred pain in distinct skin locations. Between-days reproducibility was good for all modalities [intra-class correlation (ICC) > or = 0.6]. At sensory threshold, CSA showed best reproducibility (ICC > or = 0.9). At pain detection threshold stretch ratio, CSA and electrostimulation showed best reproducibility (ICC = 1.0; 0.9; 0.9). The present model was easily implemented, robust and showed good reproducibility. It can be used to study pathophysiology or pharmacological interventions in healthy controls and in patients with diseases involving the distal hindgut.

Is the pain in chronic pancreatitis of neuropathic origin? Support from EEG studies during experimental pain

AIM: To prove the hypothesis that patients with chronic pancreatitis would show increased theta activity during painful visceral stimulation.

METHODS: Eight patients and 12 healthy controls underwent an experiment where the esophagus was electrically stimulated at the pain threshold using a nasal endoscope. The electroencephalogram (EEG) was recorded from 64 surface electrodes and “topographic matching pursuit” was used to extract the EEG information in the early brain activation after stimulation.

RESULTS: A major difference between controls and patients were seen in delta and theta bands, whereas there were only minor differences in other frequency bands. In the theta band, the patients showed higher activity than controls persisting throughout the 450 ms of analysis with synchronous brain activation between the channels. The main theta components oscillated with 4.4 Hz in the patients and 5.5 Hz in the controls. The energy in the delta (0.5-3.5 Hz) band was higher in the controls, whereas the patients only showed scattered activity in this band.

CONCLUSION: The differences in the theta band indicate that neuropathic pain mechanisms are involved in chronic pancreatitis. This has important implications for the understanding and treatment of pain in these patients, which should be directed against drugs with effects on neuropathic pain disorders.

Transient receptor potential vanilloid 4 mediates protease activated receptor 2-induced sensitization of colonic afferent nerves and visceral hyperalgesia

Protease-activated receptor (PAR(2)) is expressed by nociceptive neurons and activated during inflammation by proteases from mast cells, the intestinal lumen, and the circulation. Agonists of PAR(2) cause hyperexcitability of intestinal sensory neurons and hyperalgesia to distensive stimuli by unknown mechanisms. We evaluated the role of the transient receptor potential vanilloid 4 (TRPV4) in PAR(2)-induced mechanical hyperalgesia of the mouse colon. Colonic sensory neurons, identified by retrograde tracing, expressed immunoreactive TRPV4, PAR(2), and calcitonin gene-related peptide and are thus implicated in nociception. To assess nociception, visceromotor responses (VMR) to colorectal distension (CRD) were measured by electromyography of abdominal muscles. In TRPV4(+/+) mice, intraluminal PAR(2) activating peptide (PAR(2)-AP) exacerbated VMR to graded CRD from 6-24 h, indicative of mechanical hyperalgesia. PAR(2)-induced hyperalgesia was not observed in TRPV4(-/-) mice. PAR(2)-AP evoked discharge of action potentials from colonic afferent neurons in TRPV4(+/+) mice, but not from TRPV4(-/-) mice. The TRPV4 agonists 5',6'-epoxyeicosatrienoic acid and 4alpha-phorbol 12,13-didecanoate stimulated discharge of action potentials in colonic afferent fibers and enhanced current responses recorded from retrogradely labeled colonic dorsal root ganglia neurons, confirming expression of functional TRPV4. PAR(2)-AP enhanced these responses, indicating sensitization of TRPV4. Thus TRPV4 is expressed by primary spinal afferent neurons innervating the colon. Activation of PAR(2) increases currents in these neurons, evokes discharge of action potentials from colonic afferent fibers, and induces mechanical hyperalgesia. These responses require the presence of functional TRPV4. Therefore, TRPV4 is required for PAR(2)-induced mechanical hyperalgesia and excitation of colonic afferent neurons.

Review article: gastrointestinal sensory and motor disturbances in inflammatory bowel disease - clinical relevance and pathophysiological mechanisms

BACKGROUND

It is well known that inflammation has a profound impact on the neuromuscular apparatus of the gastrointestinal tract during the inflammatory insult and in periods of remission, at the site of inflammation and at distance from this site. The importance of this interaction is illustrated by the higher prevalence of functional gut disorders in patients with inflammatory bowel disease.

AIMS

To document the epidemiological and clinical significance of functional alterations of gut motility and sensitivity in patients with inflammatory bowel disease and to formulate potential pathophysiological mechanisms.

RESULTS AND CONCLUSIONS

Functional gut disorders occur frequently in patients with inflammatory bowel disease, both during inflammatory episodes and in periods of remission, and have a major impact on their quality of life. The clinical manifestations of these motility and sensitivity disorders vary and are often difficult to treat, mainly because therapeutic guidelines and specific diagnostic tests to distinguish inflammatory bowel disease from functional gut disorders are lacking. Chronic bowel inflammation results in a complicated interaction between neuroendocrine serotonin-predominant cells of the mucosa, inflammatory cells (particularly mast cells) in the submucosa, the intrinsic and extrinsic innervation and the muscular apparatus including the interstitial cells of Cajal. The outcome of this interaction is a perturbation of gastrointestinal motor function, both locally and at distance from the site of inflammation and during both acute inflammation and remission.

Acute colitis enhances responsiveness of lumbosacral spinal neurons to colorectal distension in rats

Aim of this study was to examine excitability and responsiveness of lumbosacral spinal neurons to colorectal distension (CRD) in rats with colitis induced by dextran sulphate sodium (DSS). Extracellular potentials of single L6-S2 spinal neurons were recorded in pentobarbital anesthetized and paralyzed rats. Results showed that 40/154 (26%) and 53/156 (34%) neurons responded to noxious CRD (80 mmHg, 20 s) in DSS-treated and control animals, respectively. Neurons with long-lasting and low-threshold excitatory responses to CRD were more frequently encountered in DSS-treated than in control groups (P < 0.05). The mean maximal excitatory responses of neurons to noxious CRD in DSS-treated animals were significantly greater and the duration of responses was longer than those in control animals (P < 0.05). It was suggested that lumbosacral spinal neurons with colorectal input had increased excitability and responsiveness following colitis, which might play an important role in development of colonic hypersensitivity and viscerosomatic referred pain.

Pain in chronic pancreatitis: the role of reorganization in the central nervous system

BACKGROUND & AIMS

In various chronic pain conditions cortical reorganization seems to play a role in the manifestations. The aim of this study was to investigate cortical reorganization in patients with pain caused by chronic pancreatitis.

METHODS

Twelve healthy subjects and 10 patients with chronic pancreatitis were included. The esophagus, stomach, and duodenum were stimulated electrically at the pain threshold using a nasal endoscope. The electroencephalogram was recorded from 64 surface electrodes and event-related brain potentials (EPs) were obtained.

RESULTS

As compared with healthy subjects, the patient group showed decreased latencies of the early EP components (N1, P < .001; P1, P = .02), which is thought to reflect the exogenous brain pain processing specifically. Source analysis showed that the dipolar activities corresponding to the early EPs were located consistently in the bilateral insula, in the anterior cingulate gyrus, and in the bilateral secondary somatosensory area. The bilateral insular dipoles were localized more medial in the patient group than in the healthy subjects after stimulation of all 3 gut segments (P < .01). There also were changes in the cingulate cortex where the neuronal source was more posterior in patients than in controls to stimulation of the esophagus (P < .05).

CONCLUSIONS

The findings indicate that pain in chronic pancreatitis leads to changes in cortical projections of the nociceptive system. Such findings also have been described in somatic pain disorders, among them neuropathic pain. Taken together with the clinical data this suggests a neuropathic component in pancreatic pain, which may influence the approach to treatment.

Geometric and mechanosensory properties of the sigmoid colon evaluated with magnetic resonance imaging

The aim of this study was to use magnetic resonance imaging (MRI) to evaluate the three-dimensional geometry and mechanosensory properties of the sigmoid colon. The sigmoid colon was stepwise distended by a water-filled bag in eight subjects. Simultaneous MRI, bag pressure recording and sensory assessment were performed before and after smooth muscle relaxation with butylscopolamine. The surface distributions of principal curvature radii, wall thickness, tension, stress and circumferential strain were calculated. The geometry of the distended sigmoid colon was complex and the spatial distributions of the biomechanical parameters were non-homogeneous. The circumferential length, strain, pressure and wall stress increased as a function of bag volume (all P < 0.001). In response to butylscopolamine, the pressure and wall stress were reduced (P < 0.05) and the stress-strain curves were shifted to the right. The sensory response was a linear function of the biomechanical parameters (all P < 0.001) and decreased in response to butylscopolamine as a function of volume (P = 0.02). The stimulus-response data indicate that the mechanosensitive afferents are affected by smooth muscle tone. The present study provides a method for characterizing the complex geometry and mechanical properties of the sigmoid colon, including the role of smooth muscle tone. This may be valuable in understanding of the biomechanical and mechanosensory functions in colonic diseases.