Spontaneous contractions and some electrophysiologic properties of circular muscle from normal sigmoid colon and ulcerative colitis

The P2Y1 receptor in the colonic myenteric plexus of rats and its correlation with opioid-induced constipation

This study was designed to explore the expression changes of P2Y1 receptors in the distal colonic myenteric layer of rats. An opioid induced constipation(OIC) rat model was generated by intraperitoneal (i.p) injection of loperamide. At 7 days post-treatment, the model rats were assessed by calculating the fecal water content and the gastrointestinal transit ratio. The immunofluorescence (IF)-based histochemical study was used to observe the distribution of P2Y1 receptors in the distal colonic myenteric plexus. Western blotting (WB) was performed to evaluate the expression changes of P2Y1 proteins in the myenteric layer, and the electrophysiological approaches were carried out to determine the regulatory roles of P2Y1 receptors on distal colonic motor function. IF showed that P2Y1 receptors are co-expressed MOR in the enteric nerve cells of the distal colonic myenteric plexus. Moreover, the WB revealed that the protein levels of P2Y1 were significantly decreased in the distal colonic myenteric layer of OIC rats. In vitro tension experiments exhibited that the P2Y1 receptor antagonist MRS2500 enhanced the spontaneous contraction amplitude, adding EM2 and β-FNA did not have any effect on MRS2500. Therefore, P2Y1 receptor expression could be associated with the occurrence of OIC in this rat model and the regulation of colonic motility by MOR may be related to the release of purine neurotransmitters such as ATP in the colonic nervous system.

Distinct patterns of myogenic motor activity identified in isolated human distal colon with high-resolution manometry

BACKGROUND

Colonic high-resolution manometry (HRM) has been used to reveal discrete, propagating colonic motor patterns. To help determine mechanisms underlying these patterns, we used HRM to record contractile activity in human distal colon ex vivo.

METHODS

Surgically excised segments of descending (n = 30) or sigmoid colon (n = 4) were immersed in oxygenated Krebs solution at 36°C (n = 34; 16 female; 67.6 ± 12.4 years; length: 24.7 ± 3.5 cm). Contractility was recorded by HRM catheters. After 30 minutes of baseline recording, 0.3 mM lidocaine and/or 1 mM hexamethonium were applied. Ascending neural pathways were activated by electrical field stimulation (EFS; 10 Hz, 0.5 ms, 50 V, 5-s duration) applied to the anal end before and after drug application.

RESULTS

Spontaneous propagating contractions were recorded in all specimens (0.1-1.5 cycles/minute). Most contractions occurred synchronously across all recording sites. In five specimens, rhythmic antegrade contractions propagated across the full length of the preparation. EFS evoked local contractions at the site of stimulation (latency: 5.5 ± 2.4 seconds) with greater amplitude than spontaneous contractions (EFS; 29.3 ± 26.9 vs 12.1 ± 14.8 mm Hg; P = .02). Synchronous or retrograde propagating motor patterns followed EFS; 71% spanned the entire preparation length. Hexamethonium and lidocaine modestly and only temporarily inhibited spontaneous contractions, whereas TTX increased the frequency of contractile activity while inhibiting EFS-evoked contractions.

CONCLUSIONS AND INFERENCES

Our study suggests that the propagated contractions recorded in the organ bath have a myogenic origin which can be regulated by neural input. Once activated at a local site, the contractions do not require the propulsion of fecal content to sustain long-distance propagation.

Alterations of colonic function in the Winnie mouse model of spontaneous chronic colitis

The Winnie mouse, carrying a missense mutation in Muc2, is a model for chronic intestinal inflammation demonstrating symptoms closely resembling inflammatory bowel disease (IBD). Alterations to the immune environment, morphological structure, and innervation of Winnie mouse colon have been identified; however, analyses of intestinal transit and colonic functions have not been conducted. In this study, we investigated in vivo intestinal transit in radiographic studies and in vitro motility of the isolated colon in organ bath experiments. We compared neuromuscular transmission using conventional intracellular recording between distal colon of Winnie and C57BL/6 mice and smooth muscle contractions using force displacement transducers. Chronic inflammation in Winnie mice was confirmed by detection of lipocalin-2 in fecal samples over 4 wk and gross morphological damage to the colon. Colonic transit was faster in Winnie mice. Motility was altered including decreased frequency and increased speed of colonic migrating motor complexes and increased occurrence of short and fragmented contractions. The mechanisms underlying colon dysfunctions in Winnie mice included inhibition of excitatory and fast inhibitory junction potentials, diminished smooth muscle responses to cholinergic and nitrergic stimulation, and increased number of α-smooth muscle actin-immunoreactive cells. We conclude that diminished excitatory responses occur both prejunctionally and postjunctionally and reduced inhibitory purinergic responses are potentially a prejunctional event, while diminished nitrergic inhibitory responses are probably due to a postjunction mechanism in the Winnie mouse colon. Many of these changes are similar to disturbed motor functions in IBD patients indicating that the Winnie mouse is a model highly representative of human IBD.

NEW & NOTEWORTHY

This is the first study to provide analyses of intestinal transit and whole colon motility in an animal model of spontaneous chronic colitis. We found that cholinergic and purinergic neuromuscular transmission, as well as the smooth muscle cell responses to cholinergic and nitrergic stimulation, is altered in the chronically inflamed Winnie mouse colon. The changes to intestinal transit and colonic function we identified in the Winnie mouse are similar to those seen in inflammatory bowel disease patients.

MAG-EPA reduces severity of DSS-induced colitis in rats

Ulcerative colitis (UC) is a chronic disease characterized by diffuse inflammation of the intestinal mucosa of the large bowel. Omega-3 (ω3) fatty acid supplementation has been associated with a decreased production of inflammatory cytokines involved in UC pathogenesis. The aim of this study was to determine the preventive and therapeutic potential of eicosapentaenoic acid monoglyceride (MAG-EPA) in an in vivo rats model of UC induced by dextran sulfate sodium (DSS). DSS rats were untreated or treated per os with MAG-EPA. Morphological, histological, and biochemical analyses were performed following MAG-EPA administrations. Morphological and histological analyses revealed that MAG-EPA pretreatment (12 days pre-DSS) and treatment (6 days post-DSS) exhibited strong activity in reducing severity of disease in DSS rats. Following MAG-EPA administrations, tissue levels of the proinflammatory cytokines TNF-α, IL-1β, and IL-6 were markedly lower compared with rats treated only with DSS. MAG-EPA per os administration decrease neutrophil infiltration in colon tissues, as depicted by myelohyperoxidase activity. Results also revealed a reduced activation of NF-κB pathways correlated with a decreased expression of COX-2 in colon homogenates derived from MAG-EPA-pretreated and treated rats. Tension measurements performed on colon tissues revealed that contractile responses to methacholine and relaxing effect induced by sodium nitroprusside were largely increased following MAG-EPA treatment. The combined treatment of MAG-EPA and vitamin E displayed an antagonistic effect on anti-inflammatory properties of MAG-EPA in DSS rats.

Fibrosis in ulcerative colitis: mechanisms, features, and consequences of a neglected problem

Chronic intestinal inflammation and impaired tissue repair leading to intestinal fibrosis are a commonly observed complication in inflammatory bowel disease. This is particularly true for small bowel Crohn's disease. However, the development of fibrosis in ulcerative colitis has remained largely unexplored. This is surprising, given knowledge about its prevalence for decades, well described histopathologic features of fibrotic and stricturing ulcerative colitis, the relevance of the extracellular matrix for intestinal inflammation and fibrosis, and the clinical impact of fibrosis on stricture formation, motility, and the necessary discrimination from colonic malignancy. This systematic review summarizes the current knowledge of ulcerative colitis-related fibrosis, including epidemiology, basic mechanisms, histopathology, and clinical implications.

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.

Ulcerative colitis as a progressive disease: the forgotten evidence

In the management of Crohn's disease, earlier aggressive treatment is becoming accepted as a strategy to prevent or retard progression to irreversible bowel damage. It is not yet clear, however, if this same concept should be applied to ulcerative colitis. Hence, we review herein the long-term structural and functional consequences of this latter disease. Disease progression in ulcerative colitis takes six principal forms: proximal extension, stricturing, pseudopolyposis, dysmotility, anorectal dysfunction, and impaired permeability. The precise incidence of these complications and the ability of earlier, more aggressive treatment to prevent them have yet to be determined.

Characterization of motor patterns in isolated human colon: are there differences in patients with slow-transit constipation?

The patterns of motor activity that exist in isolated full-length human colon have not been described. Our aim was to characterize the spontaneous motor patterns in isolated human colon and determine whether these patterns are different in whole colons obtained from patients with slow-transit constipation (STC). The entire colon (excluding the anus), was removed from patients with confirmed STC and mounted longitudinally in an organ bath ∼120 cm in length, containing oxygenated Krebs' solution at 36°C. Changes in circular muscle tension were recorded from multiple sites simultaneously along the length of colon, by use of isometric force transducers. Recordings from isolated colons from non-STC patients revealed cyclical colonic motor complexes (CMCs) in 11 of 17 colons, with a mean interval and half-duration of contractions of 4.0 ± 0.6 min and 51.5 ± 15 s, respectively. In the remaining six colons, spontaneous irregular phasic contractions occurred without CMCs. Interestingly, in STC patients robust CMCs were still recorded, although their CMC pacemaker frequencies were slower. Intraluminal balloon distension of the ascending or descending colon evoked an ascending excitatory reflex contraction, or evoked CMC, in 8 of 30 trials from non-STC (control) colons, but not from colons obtained from STC patients. In many control segments of descending colon, spontaneous CMCs consisted of simultaneous ascending excitatory and descending inhibitory phases. In summary, CMCs can be recorded from isolated human colon, in vitro, but their intrinsic pacemaker frequency is considerably faster in vitro compared with previous human recordings of CMCs in vivo. The observation that CMCs occur in whole colons removed from STC patients suggests that the intrinsic pacemaker mechanisms underlying their generation and propagation are preserved in vitro, despite impaired transit along these same regions in vivo.

Ion channel remodeling in gastrointestinal inflammation

BACKGROUND

 Gastrointestinal inflammation significantly affects the electrical excitability of smooth muscle cells. Considerable progress over the last few years have been made to establish the mechanisms by which ion channel function is altered in the setting of gastrointestinal inflammation. Details have begun to emerge on the molecular basis by which ion channel function may be regulated in smooth muscle following inflammation. These include changes in protein and gene expression of the smooth muscle isoform of L-type Ca(2+) channels and ATP-sensitive K(+) channels. Recent attention has also focused on post-translational modifications as a primary means of altering ion channel function in the absence of changes in protein/gene expression. Protein phosphorylation of serine/theronine or tyrosine residues, cysteine thiol modifications, and tyrosine nitration are potential mechanisms affected by oxidative/nitrosative stress that alter the gating kinetics of ion channels. Collectively, these findings suggest that inflammation results in electrical remodeling of smooth muscle cells in addition to structural remodeling.

PURPOSE

The purpose of this review is to synthesize our current understanding regarding molecular mechanisms that result in altered ion channel function during gastrointestinal inflammation and to address potential areas that can lead to targeted new therapies.

Persistent gut motor dysfunction in a murine model of T-cell-induced enteropathy

BACKGROUND

Inflammatory bowel disease (IBD) patients in remission often experience irritable bowel syndrome (IBS)-like symptoms. We investigated the mechanism for intestinal muscle hypercontractility seen in T-cell-induced enteropathy in recovery phase.

METHODS

BALB/c mice were treated with an anti-CD3 antibody (100 microg per mouse) and euthanized at varying days post-treatment to investigate the histological changes, longitudinal smooth muscle cell contraction, cytokines (Th1, Th2 cytokines, TNF-alpha) and serotonin (5-HT)-expressing enterochromaffin cell numbers in the small intestine. The role of 5-HT in anti-CD3 antibody-induced intestinal muscle function in recovery phase was assessed by inhibiting 5-HT synthesis using 4-chloro-DL-phenylalanine (PCPA).

KEY RESULTS

Small intestinal tissue damage was observed from 24 h after the anti-CD3 antibody injection, but had resolved by day 5. Carbachol-induced smooth muscle cell contractility was significantly increased from 4 h after injection, and this muscle hypercontractility was evident in recovery phase (at day 7). Th2 cytokines (IL-4, IL-13) were significantly increased from 4 h to day 7. 5-HT-expressing cells in the intestine were increased from day 1 to day 7. The 5-HT synthesis inhibitor PCPA decreased the anti-CD3 antibody-induced muscle hypercontractility in recovery phase.

CONCLUSIONS & INFERENCES

Intestinal muscle hypercontractility in remission is maintained at the smooth muscle cell level. Th2 cytokines and 5-HT in the small intestine contribute to the maintenance of the altered muscle function in recovery phase.

The paradoxical role of the transient receptor potential vanilloid 1 receptor in inflammation

The transient potential receptor vanilloid 1 (TRPV1) receptor is a non-selective cation channel that is chemically activated by capsaicin, the pungent component of hot peppers. In addition, endogenous compounds, in particular the endogenous cannabinoid receptor activator, anandamide, have been demonstrated to activate TRPV1 in vivo. TRPV1 receptors are also activated by temperatures within the noxious range (>43 degrees C) and low pH (<pH 6.0). TRPV1 receptors are predominantly expressed in primary afferent fibres which are peptidergic sensory neurones, such as the thinly myelinated A-delta and unmyelinated C-fibres. TRPV1 receptors have also been demonstrated to be present in non-neuronal cells. Historically, TRPV1 has been considered as a pro-inflammatory receptor due to its key role in several conditions, including neuropathic pain, joint inflammation and inflammatory bowel disease, amongst others. However, the purpose of this review is to underline the emerging new evidence which demonstrate paradoxical, protective functions for this unique receptor in vivo. For example, in experimentally induced sepsis, TRPV1 null mice demonstrated elevated levels of pathological markers in comparison to wild-type mice. In addition to the pro-inflammatory and protective roles of TRPV1 in pathophysiological states, TRPV1 has also been shown to have important functions under normal physiological conditions, for example in urinary bladder function, thermoregulation and neurogenesis. The emerging functions of TRPV1 highlight the necessity for further research in light of increasing reports of potential TRPV1 antagonists undergoing pre-clinical experimentations.

Pouch colon associated with anorectal malformations fails to show spontaneous contractions but responds to acetylcholine and histamine in vitro

PURPOSE

Congenital pouch colon (CPC) associated with anorectal malformation (ARM) is most commonly reported from Northern India. So far, no physiologic study comparing the detailed contractile status of CPC with non-CPC conditions are available. The present article deals with the contractile study and histopathologic observations in CPC, which may be useful for better surgical management.

METHODS

Freshly excised 12 neonatal CPC and similar number of non-CPC (control) specimens were transferred to ice-cold (4 degrees C-6 degrees C) Krebs-Ringer solution bubbled with 100% oxygen. Longitudinally prepared 2 to 4 colonic strips were obtained from central part of each specimen and subjected to the contraction recording after exposure to cumulative concentrations of acetylcholine (ACh) and histamine. Acetylcholine-induced contractions were evaluated after application of atropine (muscarinic blocker), and histaminergic contractions were recorded after pheniramine (H(1) blocker), lignocaine (neuronal blocker), and atropine. Histopathologic observations were made by using H&E and Masson trichrome stains.

RESULTS

Control specimens showed spontaneous contractions, but CPC strips did not. Both control and CPC responded to ACh and histamine. The response to histamine was greater (P < .05) in CPC as compared to control, whereas the response to ACh was more (P < .05) in control. In CPC, response of histamine (100 micromol/L) was blocked by pheniramine (0.32 mmol/L) and lignocaine (4 mmol/L) by 97% and 80%, respectively, and enhanced by 57% after preapplication of atropine (10 micromol/L). Acetylcholine (100 micromol/L)-induced contractions were attenuated (86%) in presence of atropine. Histopathologic examination showed fewer mature ganglion cells with various changes in muscle layers including fibrosis, disruption, hypertrophy, atrophy, and constriction bands.

CONCLUSION

Congenital pouch colon associated with ARM lacks normal spontaneous contractions but retains ACh and histamine-induced contractility. In view of the functional and histologic abnormalities, we propose that CPC associated with ARM is an abnormally functional and developed tissue. Therefore, resection of the pouch should be considered for better functional outcome of the remaining bowel.

Impairment and restoration of spontaneous contractile activity of longitudinal smooth muscles in the TNBS-inflamed hamster distal colon

In the present study, we aimed to determine how inflammation affects spontaneous motility in the longitudinal direction of a hamster colon preparation. Trinitrobenzene sulfonic acid (TNBS) injected into the distal colon caused diarrhea 4-7 days after the treatment, but diarrhea was not observed in hamsters kept for 4 weeks. At 1 week after induction of colitis, spontaneous motility in the longitudinal direction was strongly suppressed. Contraction of longitudinal smooth muscles induced by electrical field stimulation was impaired, but not that induced by exogenously applied acetylcholine, indicating that acute inflammation preferentially impairs neurotransmissions with a minor effect on contractility of the longitudinal smooth muscle itself. The spontaneous motility reappeared in the colonic preparation isolated from the hamster maintained for 4 weeks after induction of colitis. The reappearance of the motility accompanied cholinergic and nitrergic regulations of contractile activity. These results demonstrated that impairment and following restoration of spontaneous contractile activity of longitudinal smooth muscles in the TNBS-inflamed distal colon of the hamster may depend on the damage and recovery of neural factors, rather than alteration of muscle contractility.

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.

Lower prevalence of diverticulosis in patients with ulcerative colitis

PURPOSE

Colonic diverticulosis is characterized by abnormal thickening of the bowel wall, associated with luminal overpressure and increase of sigmoid contractility. However, patients with ulcerative colitis show chronic inflammatory alterations determining a reduction of both bowel wall muscle tone and contractility. Thus, we could presume ulcerative colitis and colonic diverticulosis as two pathophysiologically and mutually excluding diseases. This study was designed to evaluate the prevalence of colonic diverticulosis in patients with ulcerative colitis compared with a control endoscopic population.

METHODS

We prospectively analyzed the prevalence of colonic diverticulosis in 85 patients, older than aged 45 years, with known ulcerative colitis compared with that in 85 age/gender-matched patients without colitis. All patients underwent pancolonoscopy with ulcerative colitis and colonic diverticulosis diagnosis made by endoscopy and histopathology. The patients with ulcerative colitis also were divided in three subgroups according to the age at diagnosis (<30 years, 30-45 years, >45 years) and extension of disease (sigmoiditis, left colitis, extensive colitis).

RESULTS

Colonic diverticulosis was present in 7 of 85 patients with and in 24 patients without ulcerative colitis (8.2 vs. 28.2 percent; P < 0.001; relative risk, 3.4; 95 percent confidence interval, 1.56-7.52). All seven patients with both diseases were diagnosed with ulcerative colitis when older than age 45 years. No differences were found between the two groups in terms of extension of diverticula.

CONCLUSIONS

Patients with ulcerative colitis show a significantly lower prevalence of colonic diverticulosis, with this finding probably reflecting the motor alterations caused by chronic bowel wall inflammation. In the patients affected by ulcerative colitis with late onset of the disease, the reduced prevalence of colonic diverticulosis is not evident.

Impairment of PAR-2-mediated relaxation system in colonic smooth muscle after intestinal inflammation

Protease-activated receptor (PAR)-2 plays important roles in intestinal inflammatory responses. Changes in PAR-2-mediated smooth muscle function may contribute pathophysiologically to the intestinal motility disorders often observed in inflammatory bowel disease (IBD). Stimulation of PAR-2 by trypsin-induced relaxation of carbachol- and KCl-induced contractions in normal rat colonic smooth muscle was completely resolved by tissue pretreatment with apamin, but not by pretreatment with l-NMMA or a cocktail of neuronal blockers (tetrodotoxin, hexamethonium and propranolol). In colon inflamed by dextran sodium sulphate (DSS), trypsin-induced inhibitory effects were significantly reduced. Relaxation induced by SLIGRL-NH(2), a selective PAR-2-activating peptide, was also reduced in DSS-treated rat colon. However, inhibitory effects of 1-ethylbenzimidazolin-2-one, an activator of small conductance Ca(2+)-activated K(+) channel, were unaffected. Expression of PAR-2 mRNA in colonic muscularis externa was significantly lower in DSS-treated rats than in control rats. These results suggest that the PAR-2 mediated relaxation system in colonic smooth muscle is suppressed in this experimental colitis rat model, and may contribute to motility disorders in IBD.

Different susceptibilities of spontaneous rhythmicity and myogenic contractility to intestinal muscularis inflammation in the hapten-induced colitis

We examined the time-dependent changes in the immunoreactivity of the smooth muscle region and the accompanying motility disorder in a hapten-induced rat model of colitis. Histological analysis and myeloperoxidase (MPO) activity indicated that inflammatory cells infiltrated into the muscle layer at 2 days after 2,4,6-trinitrobenzenesulphonic acid (TNBS) treatment. The infiltrated immune cells then gradually decreased in number, but were still present at 14 days. The expression of proinflammatory cytokine mRNAs (TNF-alpha, IL-1beta and IL-6) and proteins in the muscle layer was increased at 2 days, then began to decrease, returning to control levels at 14 days. The frequency of spontaneous rhythmicity was suppressed at 2 and 7 days, and returned to control levels at 14 days. Consistent with these observations, the immunoreactivity of the interstitial cells of Cajal network was disrupted at 2 and 7 days, which then gradually reformed at 14 days. On the other hand, the myogenic contractions induced by high K(+) and carbachol were decreased at 2 days, and were still inhibited at 14 days. These results suggest that spontaneous rhythmicity dysfunction may improve more rapidly than myogenic contractility dysfunction in a hapten-induced rat model of colitis.

Colorectal motor and sensitivity features in patients affected by ulcerative proctitis with constipation: a radiological and manometric controlled study

BACKGROUND AND AIM

Constipation may be present in ulcerative proctitis (UP), but its pathogenesis has not yet been evaluated. The aim of this article is to investigate functional and morphologic features of the anorectal region in patients with UP and constipation.

MATERIALS AND METHODS

Eleven patients with quiescent clinical, endoscopic, and histological UP and constipation and 10 patients with functional constipation (FC) underwent radiologic evaluation of intestinal transit time, anorectal manometry, and defecography. Transit time was measured with radiograms at 72 h after ingestion of radiopaque markers. Manometry was carried out using a continuous perfused catheter and a balloon inflated with increasing volumes of air. Defecography was performed after the injection of a barium-sulfate solution in the rectum, with the registration of videotapes during straining, squeezing, and evacuation.

RESULTS

Manometry showed in UP significantly lower values of rectal compliance than those in FC (3.10 and 5 mL/mmHg, respectively) (P = 0.03). Rectal sensitivity threshold was increased but without significant differences in UP and FC (30 and 50 mL air, respectively). At defecography, the median value of rectosacral space was increased in UP in comparison with FC (1.30 vs 0.8; P = 0.002). Lateral rectal diameter in UP was lower than in FC (6 and 8.8 cm, respectively; P = 0.016). Nonsymptomatic rectocele, mucosal prolapse, descending perineum, and abdominopelvic dyssynergy were equally present in UP and FC. The majority of UP patients showed a prolonged intestinal transit time similar to FC patients, and, more frequently, they showed low transit in the left colon in comparison with the right colon in comparison with FC patients.

CONCLUSIONS

This study suggests that constipation in UP may be correlated with rectal fibrosis, which reduces the transit of stools from the left colon. The concomitance of asymptomatic anorectal organic or functional alteration may contribute to worsen constipation.

Role of TNF-alpha in muscularis inflammation and motility disorder in a TNBS-induced colitis model: clues from TNF-alpha-deficient mice

Macroscopic and histological analysis revealed that the colonic inflammation induced by 2,4,6-trinitrobenzenesulphonic acid (TNBS) was of lower grade in tumour necrosis factor-alpha (TNF-alpha)(-/-) mice than in wild-type mice. Myeloperoxidase activity, an indicator of neutrophilic infiltration, was also low in both the mucosal and smooth muscle layer of the TNF-alpha(-/-) mouse colon. After the induction of inflammation with TNBS, the levels of proinflammatory cytokines, such as TNF-alpha, interleukin-1beta and interleukin-6, were elevated both in the inflamed mucosa and muscle layers in the wild-type mice; however, the productions of these cytokines were greatly reduced in the TNF-alpha(-/-) mouse colon. The contractions of isolated colonic smooth muscle strips induced by several stimulatory agents were significantly decreased after treatment with TNBS in wild-type mice; however, these contractions were scarcely affected in TNF-alpha(-/-) mice. Finally, using the organ culture method, we found that TNF-alpha directly (independent of mucosal inflammation) disturbs the smooth muscle function. These results suggest that TNF-alpha plays an essential role not only in mucosal inflammation but also in muscularis inflammation in the colon of mice with TNBS-induced colitis, and that TNF-alpha directly induces motor dysfunctions by acting on the smooth muscle.

Intestinal dysmotility in inflammatory bowel disease: mechanisms of the reduced activity of smooth muscle contraction

Inflammation suppresses intestinal motility, which secondarily induces abnormal growth of intestinal flora. Disturbance of this flora plays a role in the pathogenesis of mucosal inflammation, which in turn aggravates the intestinal dysmotility. Therefore, it is important to know the mechanism of alteration in motor function in the inflamed intestine. Recent studies have shown molecular mechanisms responsible for the motility disorder in the inflamed gut. These include an increase in the activity of myosin light-chain phosphatase and an alteration of ion channel activity in smooth muscle cells.

NK2 Receptor-Mediated Spontaneous Phasic Contractions in Normal and Ulcerative Colitis Human Sigmoid Colon

Human colonic circular muscle produces spontaneous phasic contractions that are reduced in ulcerative colitis. How the spontaneous phasic contractions develop and why they decrease in ulcerative colitis are not known. We found that spontaneous phasic contractions of normal sigmoid circular muscle strips were significantly reduced by 90-min incubation with tetrodotoxin (10(-5) M), which blocked neurokinin A release in basal conditions and in response to electrical stimulation. In addition, spontaneous contraction of human sigmoid colon was significantly decreased by the NK2 receptor antagonists MEN10376 (Asp-Tyr-D-Trp-Val-D-Trp-D-Trp-Lys-NH2) and NK2ra (Bz-Ala-Ala-D-Trp-Phe-D-pro-Pro-Nle-NH2) but not by atropine or by the NK1 antagonist FK888 (N2-[(4R)-4-hydroxyl-1-(1-methyl-1H-indol-3-yl)carbonyl-l-prolyl]-N-methyl-N-phenylmethyl-3-(2-naphthyl)-l-alaninamide), suggesting that NK2 receptors are involved in their development. The spontaneous phasic contractions were abolished by thapsigargin and cyclopiazonic acid and significantly decreased by the protein kinase C inhibitor chelerythrine and by the calmodulin inhibitor CGS9343B (1,3-dihydro-1-[1-[(4-methyl-4H,6H-pyrrolo[1,2-a]-[4,1]-benzoxazepin-4-yl)methyl]-4-piperidinyl]-2H-benzimidazol-2-one (1:1) maleate), suggesting that spontaneous phasic contractions may be mediated by Ca2+ release from intracellular stores and by a protein kinase C- and calmodulin-dependent pathway. In strips from patients with ulcerative colitis, spontaneous contractions were significantly reduced, and this reduction was partially restored by the hydrogen peroxide scavenger catalase. Neurokinin A release, however, was not affected. We conclude that spontaneous phasic contractions of human sigmoid circular smooth muscle may be mediated by activation of NK2 receptors, calcium release from intracellular stores, and activation of calmodulin and protein kinase C. In ulcerative colitis patients, spontaneous phasic contractions are decreased, and this decrease may be in part due to overproduction of hydrogen peroxide affecting sigmoid circular muscle.

CB1 and TRPV1 receptors mediate protective effects on colonic electrophysiological properties in mice

CB1 and TRPV1 receptors modulate enteric neurotransmission and colonic inflammation. This study investigates early electrophysiological changes in distal colon of wild-type and receptor deficient mice after an inflammatory insult set by dinitrobenzene sulfonic acid (DNBS). Colitis was induced by DNBS in CB1(-/-) mice, TRPV1(-/-) mice, and their respective wild-type littermates. Electrophysiological properties consisting of membrane potentials and electrically induced inhibitory junction potentials (IJP) of circular smooth muscle cells were evaluated at different time points. Additionally a histological colitis severity score was evaluated in CB1(+/+) and CB1(-/-) mice 24 h after DNBS. Inflammation caused spontaneous atropine insensitive rhythmic action potentials in CB1(-/-) and TRPV1(-/-) mice but not in wild-type animals. This indicates that membrane stability is disturbed, which in turn indicates a lack of protective mechanisms. Focal electrical neuronal stimulation of the myenteric plexus induced IJP in the smooth muscle cells. Twenty-four hours after initiation of inflammation, the duration of the IJP is prolonged in all animals, indicating disturbances within neuromuscular interaction. In CB1(-/-) mice, it is interesting that the duration of IJP was significantly extended, as compared to CB1(+/+) mice pointing toward missing protective mechanisms in the CB1(-/-) mice. Inflammatory insults in the mouse colon induce reproducible changes in the electrophysiological properties and such changes correlate with duration of colitis. In mutants, these electrophysiological changes display different patterns, suggesting the lack of protective properties for neuromuscular interactions and membrane stability.

Production of IL-1β, hydrogen peroxide, and nitric oxide by colonic mucosa decreases sigmoid smooth muscle contractility in ulcerative colitis

We have previously shown that sigmoid circular muscle cells from patients with ulcerative colitis (UC) exhibit reduced contraction and Ca2+signaling in response to the neurotransmitter neurokinin A (NKA) and that IL-1β and H2O2may contribute to these reduced responses in UC. In addition, we have found that nitric oxide (NO) levels were significantly increased in UC circular muscle. To establish the site of origin for IL-1β, H2O2, and NO, we assembled an in vitro system in which normal or UC mucosa were sealed between two chambers filled with oxygenated Krebs solution. Because the mucosa consists of full-thickness mucosa and submucosa, it is expected that whatever is released into the undernatant from the submucosal side may diffuse to the circular muscle layer in the intact colon. Treatment of normal sigmoid circular muscle cells for 2 h with undernatants collected from the UC submucosal side (UCS) significantly decreased contraction induced by NKA and thapsigargin and the NKA- and caffeine-induced Ca2+signal in Ca2+-free medium. In addition, UC mucosa released into the undernatant on its submucosal side significantly more H2O2, IL-1β, and NO than normal mucosa. The reduction in contraction and Ca2+signal induced by UCS was partially reversed by pretreatment with an IL-1β antibody or with catalase. The NO scavenger hemoglobin partially prevented UCS-induced reduction in contraction and Ca2+signaling in response to NKA but not the reduced response to thapsigargin or caffeine. Sodium nitroprusside inhibited NKA but not the caffeine-induced Ca2+signal. We conclude that in UC the mucosa releases IL-1β, H2O2, and NO, which may contribute to the impaired Ca2+release and altered sigmoid muscle contractility.

Role of nitric oxide in the impairment of circular muscle contractility of distended, uninflamed mid-colon in TNBS-induced acute distal colitis in rats

AIM: To evaluate the role of nitric oxide (NO) in the motor disorders of the dilated uninflamed mid-colon (DUMC) from trinitrobenzene sulfonic acid (TNBS)-induced acute distal colitis in rats.

METHODS: Colitis was induced in male Sprague-Dawley rats by a single intracolonic administration of TNBS. Control rats received an enema of 0.9% saline. The rats were killed 48 h after TNBS or saline administration. Macroscopic and histologic lesions of the colon were evaluated. Myeloperoxidase (MPO) and nitric oxide synthase (NOS) activity were measured on the colonic tissue. In TNBS rats, we evaluated spontaneous and evoked contractile activity in circular muscle strips derived from DUMC in comparison to the same colonic segment of control rats, both in the presence and in the absence of a non-selective NOS isoforms inhibitor N-nitro-L-arginine (L-NNA). Pharmacological characterization of electric field stimulation (EFS)-evoked contractile responses was also performed.

RESULTS: In TNBS rats, the distal colon showed severe histological lesions and a high MPO activity, while the DUMC exhibited normal histology and MPO activity. Constitutive NOS activity was similar in TNBS and control rats, whereas inducible NOS activity was significantly increased only in the injured distal colon of TNBS rats. Isometrically recorded mechanical activity of circular muscle strips from DUMC of TNBS rats showed a marked reduction of the force and frequency of spontaneous contractions compared to controls, as well as of the contractile responses to a contracting stimulus. In the presence of L-NNA, the contractile activity and responses displayed a significantly greater enhancement compared to controls. The pharmacological characterization of EFS contractile responses showed that a cooperative-like interaction between cholinergic muscarinic and tachykinergic neurokinin 1 and 2 receptors mediated transmission in DUMC of TNBS rats vs a simple additive interaction in controls.

CONCLUSION: The results of this study show that, during TNBS-induced acute distal colitis, circular muscle intrinsic contractile mechanisms and possible enteric neural excitatory activity are inhibited in the distended uninflamed mid-colon. Suppression of NO synthesis markedly improves spontaneous and evokes muscle contractions, in spite of any evident change in local NO activity.

Impaired capsaicin and neurokinin-evoked colonic motility in inflammatory bowel disease

BACKGROUND

Inflammatory bowel disease (IBD) is associated with altered sensory and motor function in the human colon. The aim of the present study was to compare neuromuscular function in normal and IBD-affected colon in vitro, with emphasis on inhibitory enteric nerves, sensory neuropeptides and stimulation of axon collaterals.

METHODS

Strips of longitudinal and circular muscle were prepared following colectomy from six patients with intestinal carcinoma (mean age 64.2 +/- 4.8 years) and six patients with IBD (Crohn's disease, n = 3; ulcerative colitis, n = 3: mean age 35.8 +/- 5.7 years). Responses were measured to electrical field stimulation, potassium chloride, 1,1-dimethyl-4-phenylpiperazinium iodide, isoprenaline, calcitonin gene-related peptide (CGRP), capsaicin and neurokinin (NK)-1 and -2 receptor subtype-specific agonists, alone or after muscle precontraction.

RESULTS

The NK-1 and CGRP receptor-mediated relaxation was reduced in the circular (by 44%, P < 0.05) and longitudinal (by 61%, P < 0.05) muscle from IBD-affected colon, respectively. Maximal NK-2 receptor-mediated contraction was also significantly decreased in both longitudinal (71%, P < 0.001) and circular (51%, P < 0.01) muscle. Capsaicin evoked relaxation in precontracted colonic longitudinal and circular muscle; this was significantly diminished in the IBD-affected colon (by 63%, P < 0.001 and 76%, P < 0.01, respectively). Responses evoked by stimulation of enteric inhibitory nerves were not significantly altered.

CONCLUSIONS

Colonic muscle strips from patients with IBD exhibited impaired CGRP and NK-1 receptor-mediated relaxation and NK-2 receptor-mediated contraction. Capsaicin-activated relaxation of colonic smooth muscle is deficient in IBD-affected colon. These results suggest a discrete effect of IBD on sensory-motor coupling and tachykinin-mediated effects on colonic motility.

Interleukin 1β-Induced Production of H2O2Contributes to Reduced Sigmoid Colonic Circular Smooth Muscle Contractility in Ulcerative Colitis

We have shown that neurokinin A-induced contraction of human sigmoid circular muscle (HSCM) is reduced in patients with ulcerative colitis and that interleukin (IL)-1beta may play a role in this change. We now examine changes in the signal transduction pathway mediating neurokinin A-induced contraction of HSCM and explore the role of IL-1beta and of H(2)O(2) in these changes. In Fura 2-AM-loaded ulcerative colitis HSCM cells, neurokinin A- and caffeine-induced peak Ca(2+) increase and cell shortening were significantly reduced. In normal cells, neurokinin A-induced contraction was decreased by protein kinase C inhibitor chelerythrine and by calmodulin inhibitor CGS9343B [1,3-dihydro-1-[1-[(4-methyl-4H,6H-pyrrolo[1,2-a][4,1]-benzoxazepin-4-yl)methyl]-4-piperidinyl]-2H-benzimidazol-2-one (1:1) maleate]. In ulcerative colitis muscle cells, contraction was inhibited only by chelerythrine but not by CGS9343B. IL-1beta treatment of normal HSCM strips and cells reproduced the changes observed in ulcerative colitis. IL-1beta-induced reduction in caffeine-induced peak Ca(2+) increase and contraction was reversed by catalase, suggesting a role of H(2)O(2). IL-1beta-induced H(2)O(2) production was inhibited by mitogen-activated protein kinase (MAPK) kinase inhibitor PD98059 (2'-amino-3'-methoxyflavone) and by cytosolic phospholipase A2 (cPLA(2)) inhibitor AACOCF3 (arachidonyltrifluoromethyl ketone), but neither by p38 MAPK inhibitor SB203580 [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-1H-imidazole] nor by nuclear factor-kappaB (NF-kappaB) inhibitory peptide NF-kappaB SN50 (H-Ala-Ala-Val-Ala-Leu-Leu-Pro-Ala-Val-Leu-Leu-Ala-Leu-Leu-Ala-Pro-Val-Gln-Arg-Lys-Arg-Gln-Lys-Leu-Met-Pro-OH). IL-1beta significantly increased the phosphorylation of extracellular signal-regulated kinase 1 (ERK1)/ERK2 MAPKs and cPLA(2) and IL-1beta-induced cPLA(2) phosphorylation was blocked by PD98059. We conclude that Ca(2+) stores of HSCM cells may be reduced in ulcerative colitis and that the signal transduction pathway of neurokinin A-induced contraction switches from calmodulin- and protein kinase C-dependent in normal cells to protein kinase C-dependent in ulcerative colitis cells. IL-1beta reproduces these changes, possibly by production of H(2)O(2) via sequential activation of MAPKs (ERK1/ERK2) and cPLA(2).

Age-related changes in the morphology of the myenteric plexus of the human colon

Aging is believed to affect the structure and function of the enteric nervous system, but little specific information on this topic is available, particularly in humans. The aim of this study was to investigate the effect of age on the structure of myenteric ganglia in the human colon. We examined myenteric ganglia in colonic specimens obtained from 168 patients aged 10 days to 91 years. Nerves were stained in whole mount preparations using the vital fluorescent dye 4-(4-dimethylaminostyryl)-methylpyridinium iodide (4-Di-2-ASP) and other staining methods. Human myenteric ganglia were classified into three types: normal, those containing empty spaces ('cavities') and those containing large nerve fiber bundles. We found a statistically significant increase with age in the proportion of ganglia with cavities. Conversely, there was a decrease with age in the proportion of normal ganglia. The proportion of fiber-containing ganglia did not change with age. These findings indicate that there is an increase with age in the number of abnormally appearing myenteric ganglia in the human colon, which may contribute to the disturbed colonic motility in the aging population.

Hydrogen peroxide contributes to motor dysfunction in ulcerative colitis

Ulcerative colitis (UC) affects colonic motor function, but the mechanism responsible for this motor dysfunction is not well understood. We have shown that neurokinin A (NKA) may be an endogenous neurotransmitter mediating contraction of human sigmoid colonic circular muscle (HSCCM). To elucidate factors responsible for UC motor dysfunction, we examined the role of hydrogen peroxide (H(2)O(2)) in the decrease of NKA-induced response of HSCCM. As previously demonstrated, NKA-induced contraction or Ca(2+) increase of normal muscle cells is mediated by release of Ca(2+) from intracellular stores, because it was not affected by incubation in Ca(2+)-free medium (CFM) containing 200 microM BAPTA. In UC, however, CFM reduced both cell contraction and NKA-induced Ca(2+) increase, suggesting reduced Ca(2+) release from intracellular stores. In normal Ca(2+) medium, NKA and KCl caused normal Ca(2+) signal in UC cells but reduced cell shortening. The decreased Ca(2+) signal and contraction in response to NKA or thapsigargin were partly recovered in the presence of H(2)O(2) scavenger catalase, suggesting involvement of H(2)O(2) in UC-induced dysmotility. H(2)O(2) levels were higher in UC than in normal HSCCM, and enzymatically isolated UC muscle cells contained much higher levels of H(2)O(2) than normal cells, which were significantly reduced by catalase. H(2)O(2) treatment of normal cells in CFM reproduced the reduction of NKA-induced Ca(2+) release observed in UC cells. In addition, H(2)O(2) caused a measurable, direct release of Ca(2+) from intracellular stores. We conclude that H(2)O(2) may contribute to reduction of NKA-induced Ca(2+) release from intracellular Ca(2+) stores in UC and contribute to the observed colonic motor dysfunction.

Differential modulation of voltage-dependent K+ currents in colonic smooth muscle by oxidants

The effect of oxidants on voltage-dependent K+ currents was examined in mouse colonic smooth muscle cells. Exposure to either chloramine-T (Ch-T), an agent known to oxidize both cysteine and methionine residues, or the colon-specific oxidant monochloramine (NH2Cl) completely suppressed the transient outward K+ current (Ito) while simultaneously enhancing the sustained delayed rectifier K+ current (Idr). In contrast, the cysteine-specific oxidants hydrogen peroxide (H2O2) and 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) exhibited partial and slow suppression of Ito by inducing a shift in channel availability of -18 mV without affecting Idr. After enhancement by NH2Cl or Ch-T, Idr was sensitive to 10 mM tetraethylammonium but not to other K+ channel blockers, suggesting that it represented activation of the resting Idr and not a separate K+ conductance. Extracellular dithiothreitol (DTT) partially reversed the effect of H2O2 and DTNB on Ito but not the actions of NH2Cl and Ch-T on either Idr or Ito. Dialysis of myocytes with GSH (5 mM) or DTT (5 mM) prevented suppression of Ito by H2O2 and DTNB but did not alter the effects of NH2Cl or Ch-T on either Idr or Ito. Ch-T and NH2Cl completely blocked Ito generated by murine K(v)4.1, 4.2, and 4.3 in Xenopus oocytes, an effect not reversible by intracellular DTT. In contrast, intracellular DTT reversed the effect of H2O2 and DTNB on the cloned channels. These results suggest that I(to) is suppressed via modification of both methionine and cysteine residues, whereas enhancement of Idr likely results from methionine oxidation alone.

Decrease in activity of smooth muscle L-type Ca2+ channels and its reversal by NF-kappaB inhibitors in Crohn's colitis model

We investigated the mechanisms of dysmotility of the colonic circular muscle of the Crohn's disease rat model. Contractions induced by KCl, carbachol, and Bay K 8644 were decreased in circular smooth muscles isolated from 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis rat colon. However, the absolute force and Ca2+ sensitivity of contractile proteins were not affected as assessed in alpha-toxin permeabilized smooth muscle. The current density of the L-type Ca2+ channel in circular smooth muscle cells was significantly decreased in the TNBS-treated colonic cells. However, expressions of the L-type Ca2+ channel mRNA and protein did not differ between control and TNBS-treated preparations. Pretreatment with the NF-kappaB inhibitors pyrrolidinedithiocarbamate and sulfasalazine partially recovered the decreased contractility and current density of the L-type Ca2+ channel by TNBS treatment. These results suggest that the decrease in the contraction of circular smooth muscle isolated from TNBS-induced colitis rat colon, which may be related to gut dysmotility in Crohn's disease, is attributable to the decreased activity of the L-type Ca2+ channel. The dysfunction of the L-type Ca2+ channel may be mediated by NF-kappaB-dependent pathways.

GI distension in severe ulcerative colitis

OBJECTIVES

In previous retrospective studies in patients with severe ulcerative colitis (UC), small bowel distension was found to characterize a subgroup of patients at higher risk for both toxic megacolon (TMC) and multiple organ dysfunction syndrome (MODS). In this study we prospectively evaluated the prevalence of GI distension and its relationship to clinical outcome in patients with severe UC.

METHODS

Of 109 consecutive inpatients with acute UC (admitted to the GI Unit of the University of Rome during the period 1995-2000), 45 had severe colitis. Routine blood tests and acid-base balance and plain abdominal film evaluations were performed upon admission and repeated every 1-3 days. The gas content of the stomach and small and large intestines was evaluated on plain abdominal films. All patients were submitted to the standard Oxford intensive medical regimen; clinical improvement, occurrence of major complications, need for surgery, and mortality were evaluated. Statistical analysis was carried out using Student's t, chi2, Fisher's exact, Mann-Whitney, and Wilcoxon rank sum tests, when appropriate.

RESULTS

Of 45 patients with severe UC, 24 (53%) had GI distension. Three of these 24 patients had TMC on admission (all underwent surgery and survived), 21 showed increased GI gas content (four developed TMC 1-4 days after the detection of GI distension and were operated on, two developed MODS and died, and eight did not improve but were submitted to surgery and survived). None of the 21 patients with normal GI gas content had complications; all survived (five did not improve and required surgery).

CONCLUSIONS

In severe UC, persistent GI distension characterized a subgroup of patients with poor response to medical therapy and at higher risk for TMC and of need for surgery. The development of MODS was the most important predicting factor for fatal outcome.

Direct clinical evidence for spinal hyperalgesia in a patient with irritable bowel syndrome

OBJECTIVE

Our objective was to evaluate GI motor and sensory function and spinal cord testing in a patient with severe irritable bowel syndrome.

METHODS

A patient is described who underwent an extensive assessment of GI motor and sensory function including transit studies, colonic and rectal barostat studies, sensory and manometric studies of the small bowel, and colon and anorectal physiology testing. The patient also underwent testing with spinal cord stimulation and spinal drug delivery as part of a pain management assessment.

RESULTS

The viscerosomatic referral pain pattern resulting from rectal distention was consistent with spinal hyperalgesia. The patient underwent testing for spinal cord stimulation and spinal drug delivery.

CONCLUSION

This novel finding provides direct clinical evidence for the presence of spinal hyperalgesia in a patient with irritable bowel syndrome, consistent with the existing indirect clinical evidence and animal data.

Alterations in spontaneous contractions in vitro after repeated inflammation of rat distal colon

In inflammatory bowel disease, smooth muscle function reportedly varies with disease duration. The aim of these studies was to determine changes in the control of spontaneous contractions in a model of experimental colitis that included reinflammation of the healed area. The amplitude and frequency of spontaneous contractions in circular smooth muscle were determined after intrarectal administration of trinitrobenzenesulfonic acid in rat distal colon. With the use of a novel paradigm, rats were studied 4 h (acute) or 28 days (healed) after the initial inflammation. At 28 days, rats were studied 4 h after a second inflammation (reinflamed) of the colon. Colitis induced transient increases in the amplitude of spontaneous contractions coincident with a loss of nitric oxide synthase activity. The frequency of contractions was controlled by constitutive nitric oxide in controls. Frequency was increased in healed and reinflamed colon and was associated with a shift in the dominance of neural constitutive nitric oxide synthase control to that of inducible nitric oxide synthase (iNOS). The initial colitis induced a remodeling of the neural control of spontaneous contractions reflecting changes in their regulation by constitutive nitric oxide synthase and iNOS.

Abnormal contractile properties of rectal smooth muscle in chronic ulcerative colitis

BACKGROUND

Patients with ulcerative colitis have abnormal rectal motility.

AIM

To compare the contractile properties of rectal smooth muscle from patients with ulcerative colitis and controls.

METHODS

Rectal smooth muscle strips from patients undergoing resection for ulcerative colitis or cancer (control) were mounted in an organ bath. The effects of carbachol (receptor-mediated) and potassium (causes membrane depolarization) were studied. Acetylcholinesterase histochemistry was performed and nerve counts compared.

RESULTS

Ulcerative colitis (n=41) and control (n=34) strips contracted in response to potassium and carbachol. Mean (S.E. M.) maximum response to potassium in the control and ulcerative colitis groups was 1.07 (0.06) g/mg and 1.02 (0.09) g/mg tissue, respectively (P=N.S.). EC50s (concentrations required to give 50% of maximal response) were 75 (1) mM and 73 (1) mM, respectively (P=N.S. ). Although maximum responses to carbachol were similar, 2.12 (0.12) g/mg and 1.95 (0.12) g/mg tissue (P=N.S.), ulcerative colitis strips exhibited an increased sensitivity to carbachol, EC50s: 5.05 x 10-6 (0.55 x 10-6) M vs. 8.36 x 10-6 (0.88 x 10-6) M, P=0.002). There was no significant difference in nerve counts between the tissues, as assessed by staining for acetylcholinesterase.

CONCLUSIONS

Ulcerative colitis tissue has an increased sensitivity to carbachol and this is not due to denervation; it may result from increased calcium release from intracellular stores since contraction due to membrane depolarization is not altered. Modulation of this pathway could potentially be used to alter rectal motility in patients with ulcerative colitis.

Nitric oxide production is diminished in colonic circular muscle from acquired megacolon

PURPOSE

Nitric oxide modulates human colonic smooth muscle function. To determine whether nitric oxide production is altered in colon from acquired megacolon, we measured cholinergic nerve-mediated contractions in vitro before and after inhibition of nitric oxide synthase.

METHODS

Intramural nerves in circular smooth muscle from histologically normal colon (n = 12) and acquired megacolon (n = 3) were activated by electrical field stimulation.

RESULTS

In controls blockade of nitric oxide synthase by N(G)-Nitro-L-Arginine induced increases (P < 0.05) in amplitude of contractions; these increases in amplitudes were blocked by L-Arginine (analysis of variance; P < 0.05). By contrast, blockade of nitric oxide synthase did not increase amplitudes of contractions with circular smooth muscle from acquired megacolon. An immediate phasic contraction was blocked by atropine sulfate.

CONCLUSIONS

The results support the concept that nitric oxide production modulates cholinergic nerve-mediated contractions in normal colonic circular muscle, whereas acquired megacolon is associated with altered release of this inhibitory neurochemical. Potential explanations include depletion of tissue L-Arginine, decreased capacity to recycle citrulline to arginine, or decreased release of vasoactive intestinal peptide from circular smooth muscle in acquired megacolon.

Impaired nitrergic innervation in rat colitis induced by dextran sulfate sodium

BACKGROUND & AIMS

The pathophysiological role of neuronal nitric oxide synthase (nNOS) in colitis remains unknown.

METHODS

We investigated colonic transit, nonadrenergic, noncholinergic (NANC) relaxation, nNOS activity, and nNOS synthesis in the myenteric plexus in dextran sulfate sodium (DSS)-induced colitis in rats.

RESULTS

Oral administration of 5% DSS for 7 days induced predominant distal colitis and delayed colonic transit. In the proximal colon, carbachol-, sodium nitroprusside-, and electrical field stimulation (EFS)-induced responses were not different between control and DSS-treated rats. In the distal colon, EFS-evoked cholinergic contraction, NANC relaxation, and orphanin FQ-induced contraction were significantly impaired in DSS-treated rats compared with those in control rats, but carbachol- and sodium nitroprusside-induced responses remained intact in DSS-treated rats. The number of nNOS-immunopositive cells, catalytic activity of NOS, and nNOS synthesis in the colonic wall were significantly reduced in the distal colon of DSS-treated rats. In contrast, the number of PGP 9.5-immunopositive cells and PGP 9.5 synthesis in the colonic wall remained intact in the distal colon of DSS-treated rats.

CONCLUSIONS

These results suggest that impaired NANC relaxation in the distal colon is associated with reduced activity and synthesis of nNOS in the myenteric plexus in DSS-induced colitis.

Monochloramine directly modulates Ca(2+)-activated K(+) channels in rabbit colonic muscularis mucosae

BACKGROUND & AIMS

Mesenteric ischemia, infection, and inflammatory bowel disease may eventuate in severe colitis, complicated by toxic megacolon with impending intestinal perforation. Monochloramine (NH(2)Cl) is a membrane-permeant oxidant generated during colitis by the large amount of ambient luminal NH(3) in the colon. Reactive oxygen metabolites can modulate smooth muscle ion channels and thereby affect colonic motility, which is markedly impaired in colitis.

METHODS

Effects of NH(2)Cl on ionic currents in the innermost smooth muscle layer of the colon, the tunica muscularis mucosae, were examined using the patch clamp technique. Membrane potential in whole tissue strips was measured using high-resistance microelectrodes.

RESULTS

Whole cell voltage clamp experiments showed that NH(2)Cl (3-30 micromol/L) enhanced outward currents in a dose-dependent manner, increasing currents more than 8-fold at a test potential of +30 mV. Tail current analysis showed that the currents enhanced by NH(2)Cl were K(+) currents. Inhibition by tetraethylammonium and iberiotoxin suggested that these currents represented activation of large-conductance, Ca(2+)-activated K(+) channels. The membrane-impermeant oxidant taurine monochloramine, however, had no effect on whole cell currents. Single-channel studies in inside-out patches showed that NH(2)Cl increased open probability of a 257-pS channel in symmetrical (140 mmol/L) K(+). In the presence of NH(2)Cl, the steady-state voltage dependence of activation was shifted by -22 mV to the left with no change in the single-channel amplitude. The sulfhydryl alkylating agent N-ethylmaleimide prevented NH(2)Cl-induced channel activation. NH(2)Cl also hyperpolarized intact muscle strips, an effect blocked by iberiotoxin.

CONCLUSIONS

NH(2)Cl, at concentrations expected to be found during colitis, may contribute to smooth muscle dysfunction by a direct oxidant effect on maxi K(+) channels.

Relapsing ulcerative colitis associated with spinal cord stimulation

Spinal cord stimulation is an increasingly popular form of pain treatment. An electrode positioned on the dorsal aspect of the spinal cord at the level of the nerve roots from the painful area stimulates the spinal cord. Current from the electrode is supplied by a pulse generator in the lower anterior abdominal wall. Spinal cord stimulation has not previously been associated with ulcerative colitis. A man with left-sided ulcerative colitis in remission experienced two successive relapses related to the use of a spinal cord stimulation system. After removal of the system, remission returned and remained. This case suggests that electrical current may influence the course of ulcerative colitis.

Differential changes in ACh-, motilin-, substance P-, and K(+)-induced contractility in rabbit colitis

To test the hypothesis that the changes in intestinal contractility, which accompany inflammation of the gut, are agonist specific, we compared the response of inflamed strips to substance P (SP), motilin, ACh, and K(+) as a function of time. In parallel experiments, changes in the general mechanical properties (passive tension, optimal stretch) of the colitic tissue were evaluated. Colitis was induced by trinitrobenzenesulfonic acid, and rabbits were killed after 1, 2, 3, 5, or 8 days. Passive tension was increased starting from day 2 until day 8, and maximal active tension (T(max)) was generated at less stretch from day 5. A 50% decrease in T(max) was observed for ACh and K(+) between days 2 and 3 and for motilin and SP between days 3 and 5. For all compounds, T(max) returned to normal after 8 days. The pEC(50) value (negative logarithm of the concentration that induces 50% of the maximal contractile activity) for ACh was increased from day 3 until day 8 and for SP at day 3, whereas for motilin it was decreased at day 1. The changes in passive tension and optimal stretch indicate generalized structural alterations of smooth muscle tissue. However, the different time profiles of the changes in active tension and contractile potency for different contractile agents suggest that inflammation specifically affects receptor-mediated mechanisms.

Neural injury, repair, and adaptation in the GI tract. IV. Pathophysiology of GI motility related to interstitial cells of Cajal

Our understanding of the physiological roles played by interstitial cells of Cajal (ICC) in relation to gastrointestinal (GI) motility is still rudimentary. Nevertheless, studies into the pathophysiology of ICC are emerging at a rapid pace. Caution should be exercised, however, in assuming correlations between changes in Kit immunoreactivity, findings of ultrastructural abnormalities in ICC, and the pathophysiology and symptoms of the patients. Recent studies have revealed reduced numbers or the absence of ICC in small intestine and colon that do not exhibit normal peristaltic activity. Furthermore, important evidence is emerging that motor abnormalities in newborns may be associated with delayed maturation of the ICC network. These preliminary clinical studies provide plausible hypotheses toward the pathophysiology of certain motor disorders and strongly encourage basic scientific studies directed toward discovering the intrinsic properties of ICC as well as obtaining a deeper understanding of the physiological roles played by these cells.

Inflammation modulates in vitro colonic myoelectric and contractile activity and interstitial cells of Cajal

Inflammation suppresses phasic contractile activity in vivo. We investigated whether inflammation also suppresses in vitro phasic contractile activity and, if so, whether this could in part be due to the alteration of specific slow wave characteristics and morphology of the interstitial cells of Cajal (ICC). Circular muscle strips were obtained from normal and inflamed distal canine colon. Inflammation was induced by mucosal exposure to ethanol and acetic acid. The amplitudes of spontaneous, methacholine-induced, substance P-induced, and electrical field stimulation-induced contractions were smaller in inflamed muscle strips than in normal muscle strips. Inflammation reduced the resting membrane potential and the amplitude and duration of slow waves in circular muscle cells. Inflammation did not affect the amplitude of inhibitory junction potentials but did decrease their duration. Ultrastructural studies showed expansion of the extracellular space between circular muscle cells, reduction in the density of ICC and associated neural structures, damage to ICC processes, vacuolization of their cytoplasm, and blebbings of the plasma membrane. We conclude that inflammation-induced alterations of slow wave characteristics contribute to the suppression of phasic contractions. These alterations may, in part, be due to the damage to ICC. Inflammation impairs both the myogenic and neural regulation of phasic contractions.

Acute experimental colitis decreases colonic circular smooth muscle contractility in rats

Distal colitis decreases the contractility of the underlying circular smooth muscle. We examined how time after injury and lesion severity contribute to the decreased contractility and how colitis alters the calcium-handling properties of the affected muscle. Distal colitis was induced in rats by intrarectal administration of 4% acetic acid. Contractile responses to acetylcholine, increased extracellular potassium, and the G protein activator NaF were determined for circular muscle strips from sham control and colitic rats at days 1, 2, 3, 7, and 14 postenemas. Acetylcholine stimulation of tissues from day 3 colitic rats was performed in a zero calcium buffer, in the presence of nifedipine, and after depletion of intracellular stores of calcium. The colitis was graded macroscopically as mild, moderate, or severe. Regardless of agonist, maximal decrease in force developed 2 to 3 days posttreatment, followed by a gradual return to control by day 14. The inhibitory effect of colitis on contractility increased with increasing severity of inflammation. Limiting extracellular calcium influx had a greater inhibitory effect on tissues from colitic rats; intracellular calcium depletion had a greater inhibitory effect on tissues from control animals. The data suggest that both lesion severity and time after injury affect the contractile response of circular smooth muscle from the inflamed distal colon. Impaired utilization of intracellular calcium may contribute to the decreased contractility.

Acute experimental distal colitis alters colonic transit in rats

Data from humans with active distal colitis suggest that the proximal colon exhibits increased contractile activity and delayed transit, whereas the distal colon shows decreased contractile activity and rapid transit. The present study used the acetic acid rat model of experimental colitis to determine the effect of distal colitis on total and regional colonic transit in vivo and on the in vitro contractility of circular smooth muscle from the proximal and distal colon. Distal colitis was induced in rats by intracolonic administration of 4% acetic acid; sham control rats received saline enemas. Control and colitic rats were studied 2 days postenemas. Total colon transit was determined by calculating the geometric center of distribution of a radiolabeled marker (51Cr) instilled into the proximal colon. Regional transit was assessed by expressing the radioactivity in the cecum, proximal and distal colon, and excreted stool as a percent of total radioactivity. Muscle strips from the proximal and distal colon were stimulated with 100 microM acetylcholine (ACh) and 60 mM KCl and the tension was expressed as kilograms per square centimeter. Distal colitis was characterized by decreased total colon transit, increased retention of marker in the cecum and proximal colon, and decreased retention of marker in the distal colon. In vitro contractility studies revealed that distal colitis increased proximal colon circular smooth muscle contractility and decreased distal colon circular smooth muscle contractility to both ACh and potassium. Distal colitis is associated with regional differences in colonic circular smooth muscle contractility, which may contribute to delayed transit in the proximal colon and rapid transit in the distal colon.

Altered small intestinal smooth muscle function in Crohn's disease

BACKGROUND

Studies in animals indicate that inflammation causes changes in smooth muscle contractility. Because Crohn's disease is associated with altered motility, this study investigated the contractility of intestinal muscle resected from patients with or without Crohn's disease.

METHODS

The isometric contraction of muscle strips from the small bowel of 36 patients with and 24 patients without Crohn's disease was examined.

RESULTS

In longitudinal muscle from patients with Crohn's disease, there was a 55% increase in maximum contraction induced by carbachol but not histamine, but there was no change in the 50% effective dose (ED50) for these agonists. In contrast, in circular muscle from patients with Crohn's disease there was a sevenfold decrease in the ED50 value for carbachol but no change in maximum contraction. There was a 2.5-fold increase in the maximum response to histamine, but no change in ED50, in circular muscle from patients with Crohn's disease. However, there was no change in KCl-induced contraction between the two groups. The carbachol responses were atropine sensitive. Histamine responses were blocked by the H1 antagonist mepyramine but were not altered by a diamine oxidase inhibitor. All responses were tetrodotoxin insensitive.

CONCLUSION

These results show altered receptor-mediated contraction in small intestinal muscle in patients with Crohn's disease.

On the specificity of altered muscle function in experimental colitis in rats

BACKGROUND

Studies on muscle contraction in colitis yield conflicting data that may reflect differences in the manner in which colitis is induced. Therefore, we compared distal colonic longitudinal muscle contraction in four models of colitis in the rat.

METHODS

Distal colitis was induced by intrarectal administration of trinitrobenzene sulfonic, acetic acid, or Trichinella spiralis larvae, or by intraperitoneal injection of mitomycin C. Colonic myeloperoxidase activity was used to monitor acute inflammation.

RESULTS

Myeloperoxidase activity increased in each model of colitis. In trinitrobenzene-treated rats, contractile responses to carbachol, substance P, and KCl decreased by 64%, 76%, and 58%, respectively. In acetic acid treated rats, responses induced by carbachol, substance P, or KCl were each significantly decreased by 73%, 68%, and 55% and were similarly reduced by 42%, 77%, and 46%, respectively, in rats with T. spiralis colitis. In mitomycin-induced colitis, these respective responses also decreased significantly by 71%, 55%, and 54%.

CONCLUSION

Decreased contractility of longitudinal muscle in acute colitis in rats is independent of the manner in which the colitis is induced and is mediated at a receptor-independent locus on the muscle cell.

Nitric oxide affects mammalian distal colonic smooth muscle by tonic neural inhibition

1 The role of the L-arginine-nitric oxide (NO) pathway in tonic neural inhibition of spontaneous mechanical activity of distal colonic circular smooth muscle (DCCSM) was investigated in male Wistar rats. 2 Muscle strips were mounted in organ baths and spontaneous contractions recorded with isometric force transducers. They were characterized as low frequency (LFCs) 0.41 +/- 0.03 N cm-2 or high frequency contractions (HFCs) 0.22 +/- 0.04 N cm-2. The latter occurred intermittently to produce summation contractions (SCs) range 0.5-12 N cm-2. 3 Tetrodotoxin (100 nM) increased the forces of LFCs and SCs. Increase in force to tetrodotoxin did not occur after incubation of the muscle with NG-monomethyl-L-arginine (L-NMMA) 500 microM, an inhibitor of NO biosynthesis. 4 L-NMMA but not its enantiomer D-NMMA increased the force of LFCs (EC50: 200 microM) and SCS (EC50:175 microM) in a concentration-dependent manner which was reversed by L-arginine but not by D-arginine. 5 Muscle, precontracted by acetylcholine, relaxed to sodium nitroprusside (EC50:1.8 microM) NO gas (EV50:70 microliters) and NO solutions (EC50:4 microM) in a concentration-dependent manner. Guanosine 3':5'-cyclic monophosphate tissue concentrations (pmol mg-1 protein) were elevated in muscle after relaxation by sodium nitroprusside (500 microM) from 0.32 +/- 0.06 to 1.2 +/- 0.37 and by 1 ml of NO gas from 0.49 +/- 0.05 to 1.54 +/- 0.14. 6 These data suggest that DCCSM is under tonic neural inhibition mediated by NO biosynthesis.

In vitro changes in the properties of rabbit colonic muscularis mucosae in colitis

BACKGROUND

The muscularis mucosae is the muscle layer closet to the site of elevated inflammatory mediator production in inflammatory bowel disease. Thus, it is the first muscle layer subject to their influence.

METHODS

Using a rabbit trinitrobenzene sulfonic acid model of colitis, changes in the properties of the muscularis mucosae resulting from the inflammatory process were studied in vitro.

RESULTS

Animals developed a mild colitis-like inflammation that was confined to the epithelium, lamina propria, and submucosa. Colitic muscularis mucosae contractile responses to leukotriene D4 and prostaglandins E2 and F2 alpha were significantly attenuated relative to the maximum tissue response to acetylcholine, whereas responses to histamine, substance P, and vasoactive intestinal polypeptide were unchanged. In addition, the stress-generating capacity of the colitic muscularis mucosae was compromised in a stimulus-independent manner and passive tension increased relative to active tension.

CONCLUSIONS

The muscularis mucosae undergoes two significant alterations in colitis: (a) a selective desensitization to the effects of arachidonic acid metabolites and (b) an impairment of its excitation-contraction coupling mechanism. A loss of the ability of the muscularis mucosae to cause mucosal movement and alter luminal surface area may be an important early stage in the pathophysiology of inflammatory bowel disease.