Escherichia coli Nissle 1917 restores epithelial permeability alterations induced by irritable bowel syndrome mediators.

BACKGROUND: Intestinal permeability is altered in a subgroup of irritable bowel syndrome (IBS) patients and may contribute to symptom development. The aim of this study was to evaluate the in vitro effect of the probiotic Escherichia coli Nissle 1917 (EcN) on Caco-2 permeability alterations induced by mediators released by IBS mucosal biopsies compared to asymptomatic controls (AC). METHODS: Caco-2 cells were used as an in vitro model of intestinal permeability. Seven AC and 28 well-phenotyped IBS (9 IBS-D, 8 IBS-C, and 11 IBS-M) patients were enrolled. Mucosal mediators spontaneously released (SUP) by IBS and AC biopsies were collected. Two concentrations of EcN (108 and 106 ) were applied to Caco-2 with or without SUP or SLIGRL (a protease-activated receptor-2 activating peptide), tumor necrosis factor-α, and interferon-γ. Paracellular permeability was assessed by evaluating the flow of sulfonic-acid conjugated to fluorescein through Caco-2 monolayer. KEY RESULTS: EcN 108 significantly reinforced Caco-2 monolayer compared to cells incubated with medium alone. IBS SUP induced a significant increase in paracellular permeability compared to AC SUP, independently of IBS bowel habit. EcN 108 induced a significant recovery of permeability rate compared to IBS SUP. Permeability increase induced by IBS SUP significantly correlated with severity and frequency of abdominal pain and abdominal distension. The co-incubation of EcN and IBS SUP abolished the above significant correlations. CONCLUSIONS AND INFERENCES: EcN reinforces the integrity of Caco-2 monolayer and reverts the increase of permeability induced by mediators released by IBS biopsies. Future studies should investigate EcN therapeutic potentials in IBS.

INPP4B overexpression and c-KIT downregulation in human achalasia.

BACKGROUND: Achalasia is a rare motility disorder characterized by myenteric neuron and interstitial cells of Cajal (ICC) abnormalities leading to deranged/absent peristalsis and lack of relaxation of the lower esophageal sphincter. The mechanisms contributing to neuronal and ICC changes in achalasia are only partially understood. Our goal was to identify novel molecular features occurring in patients with primary achalasia. METHODS: Esophageal full-thickness biopsies from 42 (22 females; age range: 16-82 years) clinically, radiologically, and manometrically characterized patients with primary achalasia were examined and compared to those obtained from 10 subjects (controls) undergoing surgery for uncomplicated esophageal cancer (or upper stomach disorders). Tissue RNA extracted from biopsies of cases and controls was used for library preparation and sequencing. Data analysis was performed with the "edgeR" option of R-Bioconductor. Data were validated by real-time RT-PCR, western blotting and immunohistochemistry. KEY RESULTS: Quantitative transcriptome evaluation and cluster analysis revealed 111 differentially expressed genes, with a P ≤ 10-3 . Nine genes with a P ≤ 10-4 were further validated. CYR61, CTGF, c-KIT, DUSP5, EGR1 were downregulated, whereas AKAP6 and INPP4B were upregulated in patients vs controls. Compared to controls, immunohistochemical analysis revealed a clear increase in INPP4B, whereas c-KIT immunolabeling resulted downregulated. As INPP4B regulates Akt pathway, we used western blot to show that phospho-Akt was significantly reduced in achalasia patients vs controls. CONCLUSIONS & INFERENCES: The identification of altered gene expression, including INPP4B, a regulator of the Akt pathway, highlights novel signaling pathways involved in the neuronal and ICC changes underlying primary achalasia.

Multimodal Surgical Approach for Adult Patients With Chronic Intestinal Pseudo-Obstruction: Clinical and Psychosocial Long-term Outcomes.

BACKGROUND: Clinical and psychosocial outcomes of a multimodal surgical approach for chronic intestinal pseudo-obstruction were analyzed in 24 patients who were followed over a 2- to 12-year period in a single center after surgery or intestinal/multivisceral transplant (CTx). METHODS: The main reasons for surgery were sub-occlusion in surgery and parenteral nutrition-related irreversible complications with chronic intestinal failure in CTx. RESULTS: At the end of follow-up (February 2015), 45.5% of CTx patients were alive: after transplantation, improvement in intestinal function was observed including a tendency toward recovery of oral diet (81.8%) with reduced parenteral nutrition support (36.4%) in the face of significant mortality rates and financial costs (mean, 202.000 euros), frequent hospitalization (mean, 8.8/re-admissions/patient), as well as limited effects on pain or physical wellness. CONCLUSIONS: Through psychological tests, transplant recipients perceived a significant improvement of mental health and emotional state, showing that emotional factors were more affected than were functional/cognitive impairment and social interaction.

Comparison between small bowel manometric patterns and full-thickness biopsy histopathology in severe intestinal dysmotility.

BACKGROUND: Intestinal manometry is the current standard for direct evaluation of small bowel dysmotility. Patients with abnormal motility can either be diagnosed of pseudo-obstruction when there are radiological findings mimicking mechanical intestinal obstruction or of enteric dysmotility when these findings are absent. The aim of the present study was to prospectively compare small bowel manometric abnormalities with histopathological findings in intestinal full-thickness biopsies in patients with severe dysmotility disorders. METHODS: We investigated 38 patients with intestinal manometry and a subsequent full-thickness intestinal biopsy. Manometric recordings were read by 4 investigators and a diagnostic consensus was obtained in 35 patients. Histopathological analysis, including specific immunohistochemical techniques of small bowel biopsies was performed and compared to manometric readings. KEY RESULTS: Patients with abnormal intestinal manometry had abnormal histopathological findings in 73% of cases. However, manometric patterns did not match with the specific neuromuscular abnormalities. Among patients with a neuropathic manometry pattern and abnormal histopathology, only 23% had an enteric neuropathy, whereas 62% had neuromuscular inflammation, and 15% an enteric myopathy. On the other hand, patients with a myopathic manometry pattern all had abnormal histopathology, however, none of them with signs of enteric myopathy. CONCLUSION & INFERENCES: Small bowel dysmotility detected by intestinal manometry is often associated with abnormal neuromuscular findings in full-thickness biopsies. However, there is no correlation between the specific manometric patterns and the histopathological findings.

Gelatin tannate and tyndallized probiotics: a novel approach for treatment of diarrhea.

OBJECTIVE: Intestinal permeability impairment is implicated in many gastrointestinal (GI) diseases. Chronic diarrhea, defined as the presence of diarrhea for more than 3 weeks in adults and 2 weeks in children, requires a different diagnostic and therapeutic work-up than acute diarrhea. Gelatin tannate, by reducing the clinical activity of acute colitis and the proinflammatory effects of lipopolysaccharide (LPS), is emerging as a mucosal barrier protector. MATERIALS AND METHODS: New therapeutic strategies focusing on the physiological function of the intestinal barrier, may offer an innovative approach for the clinical improvement of highly debilitating chronic GI diseases. We review the available data on the role of gelatin tannate and tyndallized probiotics in the treatment of diarrhea. RESULTS: Gelatin tannate and tyndallized probiotics can be used to re-establish the physiological functions of the gut barrier, as well as for preventing dysbiosis. There is evidence that due to their particular properties, gelatin tannate and tyndallized probiotics are highly effective in the treatment of acute gastroenteritis and may be especially indicated in the management of moderate and prolonged diarrhea. CONCLUSIONS: Gelatin tannate and tyndallized probiotics may be effective in the management of chronic diarrhea. Further clinical trials are necessary to further explore their effects in clinical practice.

Randomised clinical trial: the analgesic properties of dietary supplementation with palmitoylethanolamide and polydatin in irritable bowel syndrome.

BACKGROUND: Intestinal immune activation is involved in irritable bowel syndrome (IBS) pathophysiology. While most dietary approaches in IBS involve food avoidance, there are fewer indications on food supplementation. Palmithoylethanolamide, structurally related to the endocannabinoid anandamide, and polydatin are dietary compounds which act synergistically to reduce mast cell activation. AIM: To assess the effect on mast cell count and the efficacy of palmithoylethanolamide/polydatin in patients with IBS. METHODS: We conducted a pilot, 12-week, randomised, double-blind, placebo-controlled, multicentre study assessing the effect of palmithoylethanolamide/polydatin 200 mg/20 mg or placebo b.d. on low-grade immune activation, endocannabinoid system and symptoms in IBS patients. Biopsy samples, obtained at screening visit and at the end of the study, were analysed by immunohistochemistry, enzyme-linked immunoassay, liquid chromatography and Western blot. RESULTS: A total of 54 patients with IBS and 12 healthy controls were enrolled from five European centres. Compared with controls, IBS patients showed higher mucosal mast cell counts (3.2 ± 1.3 vs. 5.3 ± 2.7%, P = 0.013), reduced fatty acid amide oleoylethanolamide (12.7 ± 9.8 vs. 45.8 ± 55.6 pmol/mg, P = 0.002) and increased expression of cannabinoid receptor 2 (0.7 ± 0.1 vs. 1.0 ± 0.8, P = 0.012). The treatment did not significantly modify IBS biological profile, including mast cell count. Compared with placebo, palmithoylethanolamide/polydatin markedly improved abdominal pain severity (P < 0.05). CONCLUSIONS: The marked effect of the dietary supplement palmithoylethanolamide/polydatin on abdominal pain in patients with IBS suggests that this is a promising natural approach for pain management in this condition. Further studies are now required to elucidate the mechanism of action of palmithoylethanolamide/polydatin in IBS. ClinicalTrials.gov number, NCT01370720.

An expert consensus definition of failure of a treatment to provide adequate relief (F-PAR) for chronic constipation - an international Delphi survey.

BACKGROUND: As treatments for constipation become increasingly available, it is important to know when to progress along the treatment algorithm if the patient is not better. AIM: To establish the definition of failure of a treatment to provide adequate relief (F-PAR) to support this management and referral process in patients with chronic constipation. METHODS: We conducted an international Delphi Survey among gastroenterologists and general practitioners with a special interest in chronic constipation. An initial questionnaire based on recognised rating scales was developed following a focus group. Data were collected from two subsequent rounds of questionnaires completed by all authors. Likert scales were used to establish a consensus on a shorter list of more severe symptoms. RESULTS: The initial focus group yielded a first round questionnaire with 84 statements. There was good consensus on symptom severity and a clear severity response curve, allowing 67 of the symptom-severity pairings to be eliminated. Subsequently, a clear consensus was established on further reduction to eight symptom statements in the final definition, condensed by the steering committee into five diagnostic statements (after replicate statements had been removed). CONCLUSIONS: We present an international consensus on chronic constipation, of five symptoms and their severities, any of which would be sufficient to provide clinical evidence of treatment failure. We also provide data representing an expert calibration of commonly used rating scales, thus allowing results of clinical trials expressed in terms of those scales to be converted into estimates of rates of provision of adequate relief.

Chronic intestinal pseudo-obstruction in children and adults: diagnosis and therapeutic options.

BACKGROUND: Chronic intestinal pseudo-obstruction (CIPO) represents the most severe form of gastrointestinal dysmotility with debilitating and potentially lethal consequences. Symptoms can be non-specific, and result in this condition being diagnosed incorrectly or too late with consequences for morbidity and even mortality. PURPOSE: The present article aims to provide pediatric and adult gastroenterologists with an up to date review about clinical features, diagnosis and therapeutic options for CIPO. Although pediatric and adult CIPO share many clinical aspects distinctive features can be identified. There is no single diagnostic test or pathognomonic finding of CIPO, thus a stepwise approach including radiology, endoscopy, laboratory, manometry, and histopathology should be considered in the diagnostic work-up. Treatment of patients with CIPO is challenging and requires a multidisciplinary effort with participation of appropriately experienced gastroenterologists, pathologists, dieticians, surgeons, psychologists, and other subspecialists based on the presence of comorbidities. Current treatment options invariably involve surgery and specialized nutritional support, especially in children. Medical therapies are mainly aimed to avoid complications such as sepsis or intestinal bacterial overgrowth and, where possible, restore intestinal propulsion. More efficacious therapeutic options are eagerly awaited for such difficult patients.

Supernatants of irritable bowel syndrome mucosal biopsies impair human colonic smooth muscle contractility.

BACKGROUND: Changes in intestinal motility are likely to contribute to irritable bowel syndrome (IBS) pathophysiology. The aim of the study was to investigate the effects of IBS mucosal supernatants on human colonic muscle contractility. METHODS: Supernatants were obtained from biopsies of 18 IBS patients-nine with constipation (IBS-C) and nine with diarrhea-predominant IBS (IBS-D)-and nine asymptomatic subjects, used as controls. Colonic circular smooth muscle strips or isolated cells (SMC) were exposed to control or IBS supernatants. Spontaneous phasic contractions on strips and morphofunctional parameters on cells were evaluated in basal conditions and in response to acetylcholine (Ach). Incubation with IBS supernatants was also conducted in the presence of antagonists and inhibitors (namely histamine, protease and prostaglandin antagonists, nuclear factor-kappa B inhibitor, catalase, NADPH oxidase inhibitor, and the cAMP- and/or cGMP-cyclase inhibitors). KEY RESULTS: Exposure to IBS-C and IBS-D supernatants induced a significant reduction in basal tone and Ach-elicited contraction of muscle strips and a significant shortening and impairment of Ach contraction of SMCs. The NADPH oxidase inhibitor prevented the effect of supernatants, while the protease antagonist only IBS-C effect. No effect was observed with the other antagonists and inhibitors. Dilution of IBS-D supernatants partially restored the effects only on SMCs, whereas dilution of IBS-C supernatants significantly reverted the effects on muscle strips and Ach-elicited response on SMC. CONCLUSIONS & INFERENCES: Supernatants from mucosal biopsies of IBS patients reduce colonic contractility. The observed impairment was concentration dependent, likely occurring through intracellular oxidative stress damage, involving different neuromotor mechanisms depending on the IBS subtype.

Review article: adherence to Rome criteria in therapeutic trials in functional dyspepsia.

BACKGROUND: The Rome criteria are currently required by health authorities for the inclusion of patients affected by functional dyspepsia in therapeutic trials. However, the degree of adherence to these criteria has not been formally verified. AIM: To review adherence to the Rome criteria for inclusion criteria, outcome measures and endpoints in therapeutic trials on functional dyspepsia and the potential impact on the conclusions that can be drawn from these studies. METHODS: A total of 1818 articles were screened. Fifty-eight trials claiming to include adults affected by functional dyspepsia as defined by the Rome criteria published as full articles in English between 2000 and 2013 were considered. RESULTS: Lack of full adherence to the Rome criteria of inclusion criteria was found in 54% of the studies, due to inclusion of patients with symptoms not reported in the Rome criteria or definitions of dyspeptic symptom that varied from those proposed by the Rome criteria. Ninety-five per cent of clinical trials adopted therapeutic outcome measures that were not adherent to the Rome criteria, using questionnaires that did not include all dyspeptic symptoms or including symptoms other than those proposed by the Rome criteria. CONCLUSIONS: Stringent criteria have not been adopted for inclusion criteria and outcome measures in the vast majority of published studies on functional dyspepsia that claim to have been carried out according to the Rome criteria. Appropriate questionnaires should be developed to promote adherence to internationally accepted definitions of the syndrome in future studies.

[Some practical questions on chronic stipsis treatment with prucalopride]. / Alcune domande pratiche sulla terapia della stipsi cronica con prucalopride.

Chronic constipation is a frequent pathological condition bearing relevant socioeconomic burdens, mainly due to uncertain management and unsatisfactory response to traditional laxatives. Prucalopride is a novel enterokinetic drug, that has been demonstrated to improve bowel functions and relieve a broad spectrum of digestive symptoms in patients with severe chronic constipation who had failed to respond to various traditional laxatives. In this paper we discussed the practical aspects of chronic constipation treatment, in particular focusing on some questions about the practical use of prucalopride. Prucalopride is a potent, selective, high-affinity agonist of the 5-HT4 receptors widely expressed in the gastrointestinal tract. Unlike other 5-HT4 agonists, such as cisapride and tegaserod, it is devoid of adverse cardiovascular effects. Furthermore, it is characterized by a low potential for interactions with other drugs, due to its pharmacokinetic characteristics. Prucalopride was approved, in 2009, by the European Medicines Agency for the symptomatic treatment of chronic constipation in women in whom laxatives fail to provide adequate relief, however, there are ongoing studies to extend the use of the drug even to males.

Disease-related intestinal transplant in adults: results from a single center.

Intestinal transplantation is gaining worldwide acceptance as the main option for patients with irreversible intestinal failure and complicated total parenteral nutrition course. In adults, the main cause is still represented by short bowel syndrome, but tumors (Gardner syndrome) and dismotility disorders (chronic intestinal pseudo-obstruction [CIPO]) have been treated increasingly by this kind of transplantation procedure. We reviewed our series from the disease point of view: although SBS confirmed results achieved in previous years, CIPO is nowadays demonstrating an excellent outcome similar to other transplantation series. Our results showed indeed that recipients affected by Gardner syndrome must be carefully selected before the disease is to advanced to take advantage of the transplantation procedure.

Review article: Linaclotide for the management of irritable bowel syndrome with constipation.

BACKGROUND: Irritable bowel syndrome with constipation (IBS-C) represents a significant burden to patients and healthcare systems due to its prevalence and lack of successful symptomatic resolution with established treatment options. Linaclotide 290 µg has recently been approved by the European Medicines Agency (EMA) for moderate-to-severe IBS-C and by the US Food and Drug Administration for IBS-C (290 µg dose) and for chronic constipation (145 µg dose). AIM: To summarise data leading to the approval of linaclotide for IBS-C, with focus on EMA-pre-specified outcome measures. METHODS: Literature search of a peer-review database (PubMed) and review of congress abstracts on linaclotide preclinical and clinical trial data in IBS-C. RESULTS: Preclinical studies suggest that the guanylate cyclase C agonist (GCCA) linaclotide acts through elevation of cyclic guanosine monophosphate (cGMP) levels, leading to accelerated gastrointestinal (GI) transit through increased fluid secretion and reduced visceral hypersensitivity. Clinical trial data demonstrate that linaclotide improves abdominal symptoms (pain, bloating) and bowel symptoms (constipation) compared with placebo in patients with IBS-C. The most frequent side effect, diarrhoea, results from the therapeutic action of linaclotide. Linaclotide acts locally in the GI tract with minimal systemic exposure, resulting in low oral bioavailability and thus a low risk of relevant systemic adverse effects. CONCLUSION: Linaclotide, a first-in-class GCCA, is a promising new drug with a novel, dual mechanism of action that, unlike more well-established agents, can relieve the abdominal pain, bloating and constipation associated with IBS-C and has a low propensity for systemic side effects.

Effect of prucalopride on symptoms of chronic constipation.

BACKGROUND: Prucalopride is a 5-HT4 receptor agonist with gastrointestinal prokinetic activities. This integrated analysis of data from three 12-week, double-blind trials evaluated the effect of prucalopride 2 mg q.d. on common constipation symptoms in women in whom laxatives had failed to provide adequate relief. The effect of prucalopride on bowel function was outside the scope of the analysis and has been described elsewhere. METHODS: Women with self-reported inadequate relief from laxatives and included in the prucalopride 2 mg or placebo arm of the trials were selected for analysis. Symptom severity was determined with the Patient Assessment of Constipation Symptoms (PAC-SYM) questionnaire. Observed changes from baseline in individual item scores were also evaluated by calculating Cohen's D effect sizes using baseline standard deviation (SD) (>0.2-0.5, >0.5-0.8 and >0.8 for small, moderate and large effects, respectively). KEY RESULTS: Data were analyzed for 936 women. The proportion of women with a PAC-SYM severity score >2 at baseline was 50.0% for abdominal symptoms, 71.4% for stool symptoms, and 15.5% for rectal symptoms. Excluding the women without presence of a symptom at baseline from the effect size calculations showed that prucalopride 2 mg had a large effect (>0.8) on all PAC-SYM items, including abdominal pain, abdominal discomfort, bloating, straining, and painful bowel movements. For abdominal symptoms and stool symptoms, effect sizes with prucalopride 2 mg were 1.3-2.3 times larger than those with placebo. CONCLUSIONS & INFERENCES: Prucalopride 2 mg q.d. for 12 weeks alleviates common constipation symptoms in women in whom laxatives had failed to provide adequate relief.

Isolated intestinal transplant for chronic intestinal pseudo-obstruction in adults: long-term outcome.

BACKGROUND: Chronic intestinal pseudo-obstruction (CIPO) has been treated in adults by total parenteral nutrition (TPN) or, if complications arise, by multivisceral transplantation because the stomach is often involved. Eleven adults with CIPO were transplanted by intestinal graft in our center from 2000 to 2011. METHODS: Nine patients underwent isolated intestinal transplant and 2 patients had multivisceral transplant. Immunosuppression was represented by FK and steroids plus induction with alemtuzumab, daclizumab, or thymoglobulin. Average age at transplant was 33.5 years. We reported 1 graftectomy, followed by retransplantation. RESULTS: Seven patients are currently alive with working small bowel; cause of death was infection in the 4 remaining cases. In 9 isolated intestinal transplants, we performed different digestive reconstructions to allow gastric emptying. In 2 cases we were forced, after transplant, to perform ileostomy to improve intestinal motility. Graft and patient survival after 5 years are 60% and 70%, respectively, while after 10 years, 45% and 56%, respectively. CONCLUSIONS: Adults with CIPO and irreversible TPN complications benefit from isolated intestinal transplant with different surgical techniques to empty the native stomach: this strategy achieves good gastric emptying, with effective establishment of oral feeding and graft and patient survivals comparable to isolated intestinal transplant for short bowel syndrome.

Randomized clinical trial: macrogol/PEG 3350 plus electrolytes for treatment of patients with constipation associated with irritable bowel syndrome.

OBJECTIVES: Polyethylene glycol (PEG) 3350 plus electrolytes (PEG 3350+E) is an established treatment for constipation and has been proposed as a treatment option for constipation associated with irritable bowel syndrome (IBS-C). This study aimed to compare the efficacy and safety of PEG 3350+E vs. placebo in adult patients with IBS-C. METHODS: Following a 14-day run-in period without study medication, patients with confirmed IBS-C were randomized to receive PEG 3350+E (N=68) or placebo (N=71) for 28 days. The primary endpoint was the mean number of spontaneous bowel movements (SBMs) per day in the last treatment week. RESULTS: In both groups, mean weekly number of SBMs (±s.d.) increased from run-in. The difference between the groups in week 4 (PEG 3350+E, 4.40±2.581; placebo, 3.11±1.937) was statistically significant (95% confidence interval: 1.17, 1.95; P<0.0001). Although mean severity score for abdominal discomfort/pain was significantly reduced compared with run-in with PEG 3350+E, there was no difference vs. placebo. Spontaneous complete bowel movements, responder rates, stool consistency, and severity of straining also showed superior improvement in the PEG 3350+E group over placebo in week 4. The most common drug related treatment-emergent adverse events were abdominal pain (PEG 3350+E, 4.5%; placebo, 0%) and diarrhoea (PEG 3350+E, 4.5%; placebo, 4.3%). CONCLUSIONS: In IBS-C, PEG 3350+E was superior to placebo for relief of constipation, and although a statistically significant improvement in abdominal discomfort/pain was observed compared with baseline, there was no associated improvement compared with placebo. PEG 3350+E is a well-established and effective treatment that should be considered suitable for use in IBS-C.

Fiber and macrogol in the therapy of chronic constipation.

Chronic constipation is a common condition in the general population. Although the majority of affected individuals do not seek medical consultation and search for remedies for their condition in the pharmacy or herbal shops, the actual health burden caused by this condition is extremely high. Many laxatives are available, but patients are often dissatisfied with the therapies adopted, whether prescribed by a doctor or self prescribed, and this leads to further social and health burdens. All of the available guidelines promote initiating the therapy of any type of constipation by ensuring an adequate intake of dietary fiber and water. However, high amounts of insoluble vegetable fiber such as those normally contained in fruits and vegetables, can lead to a further worsening of the digestive symptoms typical of chronic constipation, such as bloating and distension and pain. Better results can be obtained with soluble fibers, such as psyllium. Among the various available laxatives, polyethylene glycol (PEG), or macrogol, is the product which has been most studied and has produced the best results with the least number of side effects. This is an inert not absorbable molecule that, diluted in water, forms an isotonic solution that prevents part of the water from being absorbed, thus increasing the volume of the intestinal contents, reducing the consistency and facilitating transport and evacuation. The combination of psyllium and PEG could combine the advantages of fiber and isotonic solutions and represent an important therapeutic option for patients suffering from chronic constipation.

Submucous rather than myenteric neurons are activated by mucosal biopsy supernatants from irritable bowel syndrome patients.

BACKGROUND: We previously showed that colonic mucosal biopsy supernatants from patients with irritable bowel syndrome (IBS) activate neurons of the human submucous plexus, an area with densely packed immune cells. Based on the concept that mucosa-nerve signaling is altered in IBS, we tested in this study whether the nerve sensitizing effect of IBS mucosal biopsy supernatants is more prominent in the submucous than myenteric plexus. METHODS: Fast neuroimaging with the voltage-sensitive dye Di-8-ANEPPS was used to record activity of guinea-pig submucous and myenteric neurons after application of constipation (C)- and diarrhea (D)-IBS supernatants (three each) and four supernatants from healthy control subjects. Results are based on recordings from 4731 neurons. KEY RESULTS: Control supernatants did not evoke significant responses in submucous or myenteric neurons. In contrast, all IBS supernatants evoked a significant spike discharge (median 3.6 Hz) in 46% of submucous neurons. This activation was significantly stronger than in the myenteric plexus where even twice the amount of supernatants evoked a lower spike frequency (median 2.1Hz) in only 8.5% of neurons. Pharmacological studies revealed serotonin, histamine, and proteases as components mediating neuronal activation. Individual application of these components revealed that only serotonin evoked a significantly stronger activation of submucous compared with myenteric neurons. CONCLUSIONS & INFERENCES: Direct neuronal activation by IBS mucosal biopsy supernatants is primarily a feature of submucous rather than myenteric neurons. This is associated with a stronger excitation of submucous neurons by serotonin. The plexus-specific effects support the concept that altered mucosa-nerve signaling underlies disturbances in IBS.

Colonic mucosal mediators from patients with irritable bowel syndrome excite enteric cholinergic motor neurons.

BACKGROUND: Mediators released in the mucosal milieu have been suggested to be involved in visceral hypersensitivity and abdominal pain in patients with irritable bowel syndrome (IBS). However, their impact on myenteric neurons remains unsettled. METHODS: Mucosal biopsies were obtained from the descending colon of patients with IBS and controls. Mucosal mast cells were identified immunohistochemically. The impact of spontaneously released mucosal mediators on guinea pig electrically stimulated longitudinal muscle myenteric plexus (LMMP) preparations was assessed in vitro by means of selective receptor antagonists and inhibitors. KEY RESULTS: Patients with IBS showed an increased mast cell count compared with controls. Application of mucosal mediators of IBS to LMMPs potentiated cholinergic twitch contractions, an effect directly correlated with mast cell counts. Enhanced contractions were inhibited by 50.3% with the prostaglandin D2 antagonist BW A868C, by 31.3% and 39% with the TRPV1 antagonists capsazepine and HC-030031, respectively, and by 60.5% with purinergic P2X antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid. Conversely, the serotonin1-4, histamine1-3, tachykinin1-3 receptor blockade, and serine protease inhibition had no significant effect. CONCLUSIONS & INFERENCES: Colonic mucosal mediators from patients with IBS excite myenteric cholinergic motor neurons. These effects were correlated with mast cell counts and mediated by activation of prostanoid receptors, TRPV1, and P2X receptors. These results support the role of mucosal inflammatory mediators and mast cell activation in altered motor function of IBS.