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.

The multi-herbal drug STW 5 (Iberogast) has prosecretory action in the human intestine

There is growing evidence that STW 5 (Iberogast), fixed combination of hydroethanolic herbal extracts), besides being effective in functional dyspepsia, also improves symptoms in irritable bowel syndrome (IBS). Clinical data indicate that modulation of mucosal secretion is a promising approach to treat intestinal disorders associated with IBS. We therefore explored the effect of STW 5 on secretion in the human intestine and the mechanisms by which it acts. The Ussing chamber technique was used to measure mucosal secretion in human intestinal mucosa/submucosa preparations and in human epithelial cell line T84. In addition, we recorded STW 5 effects on human enteric neurons with voltage sensitive dye imaging. In human tissue and T84 cells STW 5 induced a dose-dependent increase in ion secretion that was significantly reduced by the Na-K-Cl cotransporter blocker bumetanide, the adenylate cyclase inhibitor MDL-12 330, the non-specific and selective cystic fibrosis transmembrane conductance regulator (CFTR) inhibitors glibenclamide and CFTR(inh)-172, respectively, and the blocker of calcium dependent Cl(-) channels (ClCa) SITS (4-acetamido-4-isothiocyanatostilbene-2,2-disulphonic acid). It was unaffected by amiloride, a blocker of epithelial Na(+) channels. In human tissue, the nerve blocker tetrodotoxin significantly suppressed the STW 5 response. STW 5 evoked an increased spike discharge in 51% of human submucous neurons. Results suggest that STW 5 is a secretogogue in the human intestine by direct epithelial actions and through activation of enteric neurons. The prosecretory effect is due to increased epithelial Cl(-) fluxes via CFTR and Ca-dependent ClCa channels. STW 5 may be a novel option to treat secretory disorders associated with IBS and constipation.

Clinical relevance of measuring colonic permeability

BACKGROUND

Gastroduodenal and small intestinal permeability are increased in patients with Crohn's disease (CD) and intensive care patients. The relevance of colonic permeability has not yet been adequately investigated. The aim of this study was to investigate the clinical value of sucralose excretion as indicator for colonic permeability in these patient groups.

DESIGN

After oral administration of four sugars and subsequent analysis of urinary excretion, gastroduodenal and intestinal permeability were calculated from saccharose excretion and lactulose/mannitol (L/M) ratio over 5 h, and sucralose excretion from 5 to 26 h in 100 healthy controls, 29 CD and 35 patients after coronary surgery (CABG).

RESULTS

In controls, sucralose excretion was highly variable (0.67+/-0.92%) and not related to small intestinal permeability. In CD and CABG, L/M ratio was increased (0.054+/-0.060; 0.323+/-0.253 vs. 0.018+/-0.001 in controls). Sucralose excretion was increased in 77% of CABG but only in 7% of CD. There was an association between gastroduodenal and intestinal permeability in CD and CABG (r=0.72, and r=0.51), but sucralose excretion was not related to either one of these two parameters. Other than a weak association between sucralose and length of stay in intensive care in CABG patients (P=0.099), sucralose excretion was not related to clinical outcome.

CONCLUSIONS

The proposed cut-off for normal sucralose excretion is 2.11%, but its high variability and lack of association to gastrointestinal permeability or clinical outcome leave it open, if it can provide information beyond established permeability tests.

Altered intestinal permeability in patients with primary fibromyalgia and in patients with complex regional pain syndrome

OBJECTIVES

The pain intensity of patients with FM has recently been reported to be correlated with the degree of small intestinal bacterial overgrowth (SIBO). SIBO is often associated with an increased intestinal permeability (IP). Increased IP, if shown in FM, may have pathogenetic relevance because it leads to the exposure of immune cells to luminal antigens and consequent immune modulation. It is currently unknown whether IP is altered in FM. We therefore examined the IP in a group of patients with primary FM and in two control groups, healthy volunteers and patients with an unrelated chronic pain syndrome, complex regional pain syndrome (CRPS). We hypothesized that patients with FM, but not volunteers or those patients with CRPS, would have altered IP.

METHODS

Both gastroduodenal and small IP were assessed using an established three-sugar test, where urinary disaccharide excretion reflecting intestinal uptake was measured using HPLC.

RESULTS

Forty patients with primary FM, 57 age- and sex-matched volunteers and 17 patients with CRPS were enrolled in this study. In the FM group, 13 patients had raised gastroduodenal permeability and 15 patients had raised small intestinal permeability, but only one volunteer had increased gastroduodenal permeability (P < 0.0001, chi-square test for the three groups). The IP values were significantly increased in the patient groups (P < 0.0003 for all comparisons, one-way analysis of variance).

CONCLUSIONS

The IPs in primary FM and, unexpectedly, CRPS are increased. This study should stimulate further research to determine the implication of altered IP in the disease pathophysiology of FM and CRPS.

Barrier function of the gut and multiple organ dysfunction after cardiac surgery

We studied the influence of sequential involvement of the gastrointestinal (GI) tract on the development of multiple organ dysfunction (MOD) after cardiopulmonary bypass (CPB). One hundred and forty-six patients undergoing elective cardiac surgery were included in this prospective observational study. Standardized oral inert-sugar tests (sucrose, lactulose, mannitol, sucralose) were performed before and after CPB in different patients. Enzyme-linked immunosorbent assay of plasma levels of endotoxin core antibodies (EndoCAb) were performed peri-operatively. The functional mucosal surface was calculated from the amount of mannitol absorbed from the GI tract. Lower urine concentrations of absorbed mannitol were observed pre-operatively in patients developing MOD. In binary logistic regression this was an independent parameter. Decreased plasma concentrations of EndoCAb after surgery were seen in every patient, but were more significant in patients developing MOD. A reduced pre-operative functional mucosal surface may predict the early occurrence of MOD after surgery.

Genetic basis for increased intestinal permeability in families with Crohn's disease: role of CARD15 3020insC mutation?

BACKGROUND AND AIMS

A genetically impaired intestinal barrier function has long been suspected to be a predisposing factor for Crohn's disease (CD). Recently, mutations of the capsase recruitment domain family, member 15 (CARD15) gene have been identified and associated with CD. We hypothesise that a CARD15 mutation may be associated with an impaired intestinal barrier.

METHODS

We studied 128 patients with quiescent CD, 129 first degree relatives (CD-R), 66 non-related household members (CD-NR), and 96 healthy controls. The three most common CARD15 polymorphisms (R702W, G908R, and 3020insC) were analysed and intestinal permeability was determined by the lactulose/mannitol ratio.

RESULTS

Intestinal permeability was significantly increased in CD and CD-R groups compared with CD-NR and controls. Values above the normal range were seen in 44% of CD and 26% of CD-R but only in 6% of CD-NR, and in none of the controls. A household community with CD patients, representing a common environment, was not associated with increased intestinal permeability in family members. However, 40% of CD first degree relatives carrying a CARD15 3020insC mutation and 75% (3/4) of those CD-R with combined 3020insC and R702W mutations had increased intestinal permeability compared with only 15% of wild-types, indicating a genetic influence on barrier function. R702W and G908R mutations were not associated with high permeability.

CONCLUSIONS

In healthy first degree relatives, high mucosal permeability is associated with the presence of a CARD15 3020insC mutation. This indicates that genetic factors may be involved in impairment of intestinal barrier function in families with IBD.

Pseudoallergic reactions in chronic urticaria are associated with altered gastroduodenal permeability

BACKGROUND

In a subgroup of patients with chronic urticaria (CU) the disease is caused by pseudoallergic reactions to food. The aim of this study was to investigate whether disturbances of the gastrointestinal barrier function play a role in the pathomechanism of the disease.

METHODS

In 55 patients with CU gastrointestinal permeability was measured with an in vivo triple-sugar-test before and after 24 days of a diet low in pseudoallergens. Sucrose served as marker for gastroduodenal permeability, lactulose/mannitol ratio for intestinal permeability.

RESULTS

Basal gastroduodenal and intestinal permeability were significantly higher in patients with urticaria as compared to controls. In 29 of the 55 patients skin symptoms decreased or completely disappeared during the diet (responders). Compared to nonresponders (n = 26), responders had a significantly higher gastroduodenal permeability before treatment (0.36 +/- 0.04 vs 0.15 +/- 0.01% sucrose; P < 0.001), which decreased after the diet (0.17 +/- 0.02; P < 0.001). The number of patients with Helicobacter pylori infections did not differ between the two groups.

CONCLUSIONS

The results indicate that in a subgroup of patients with CU and pseudoallergy an impaired gastroduodenal barrier function may be of pathophysiological importance. The underlying mechanisms seem to be independent of H. pylori infection.