Christophe Vanormelingen

Psychological stress and corticotropin-releasing hormone increase intestinal permeability in humans by a mast cell-dependent mechanism

Objective Intestinal permeability and psychological stress have been implicated in the pathophysiology of IBD and IBS. Studies in animals suggest that stress increases permeability via corticotropin-releasing hormone (CRH)-mediated mast cell activation. Our aim was to investigate the effect of stress on intestinal permeability in humans and its underlying mechanisms. Design Small intestinal permeability was quantified by a 2 h lactulose–mannitol urinary excretion test. In a first study, 23 healthy volunteers were subjected to four different conditions: control; indomethacin; public speech and anticipation of electroshocks. In a second study, five test conditions were investigated in 13 volunteers: control; after pretreatment with disodium cromoglycate (DSCG); administration of CRH; DSCG+CRH and DSCG+public speech. Results Indomethacin, as a positive comparator (0.071±0.040 vs 0.030±0.022; p<0.0001), and public speech (0.059±0.040; p<0.01), but not the shock protocol increased intestinal permeability. Similarly, salivary cortisol was only increased after public speech. Subgroup analysis demonstrated that the effect of public speech on permeability was only present in subjects with a significant elevation of cortisol. CRH increased the lactulose–mannitol ratio (0.042±0.021 vs 0.028±0.009; p=0.02), which was inhibited by the mast cell stabiliser DSCG. Finally, intestinal permeability was unaltered by public speech with DSCG pretreatment. Conclusions Acute psychological stress increases small intestinal permeability in humans. Peripheral CRH reproduces the effect of stress and DSCG blocks the effect of both stress and CRH, suggesting the involvement of mast cells. These findings provide new insight into the complex interplay between the central nervous system and GI function in man.

Management of Gastroparesis: Beyond Basics

Opinion statementGastroparesis is defined as the presence of delayed gastric emptying in the absence of mechanical obstruction, with a variety of upper gastrointestinal symptoms. Although measurement of gastric emptying is necessary for the diagnostic labeling, this finding has little impact in terms of explaining the symptom pattern and determining the prognosis and therapeutic approach. Clinical management is based on ruling out of mechanical causes and serum electrolyte imbalances, followed by initial medical treatment with a gastroprokinetic agent in most cases. However, the evidence that these drugs provide substantial symptomatic benefit is weak. Recent attempts to establish efficacy with newer prokinetics, including serotonin-4, motilin, and ghrelin receptor agonists, have seen few successes, but a new group of agents is under evaluation. More recently, also, no benefit was found with treatment with a tricyclic antidepressant in idiopathic gastroparesis. In refractory cases, especially when there is weight loss, invasive therapeutics such as insertion of feeding tubes, intrapyloric injection of botulinum toxin, implantable gastric electrical stimulation, or surgical (partial) gastrectomy are occasionally considered, but there is little evidence of efficacy, and these are not devoid of potentially major complications. Gastroparesis is likely to remain a challenging condition in the clinic in the foreseeable future.

Subacute stress and chronic stress interact to decrease intestinal barrier function in rats

Abstract Psychological stress increases intestinal permeability, potentially leading to low-grade inflammation and symptoms in functional gastrointestinal disorders. We assessed the effect of subacute, chronic and combined stress on intestinal barrier function and mast cell density. Male Wistar rats were allocated to four experimental groups (n = 8/group): 1/sham; 2/subacute stress (isolation and limited movement for 24 h); 3/chronic crowding stress for 14 days and 4/combined subacute and chronic stress. Jejunum and colon were collected to measure: transepithelial electrical resistance (TEER; a measure of epithelial barrier function); gene expression of tight junction molecules; mast cell density. Plasma corticosterone concentration was increased in all three stress conditions versus sham, with highest concentrations in the combined stress condition. TEER in the jejunum was decreased in all stress conditions, but was significantly lower in the combined stress condition than in the other groups. TEER in the jejunum correlated negatively with corticosterone concentration. Increased expression of claudin 1, 5 and 8, occludin and zonula occludens 1 mRNAs was detected after subacute stress in the jejunum. In contrast, colonic TEER was decreased only after combined stress, and the expression of tight junction molecules was unaltered. Increased mast cell density was observed in the chronic and combined stress condition in the colon only. In conclusion, our data show that chronic stress sensitizes the gastrointestinal tract to the effects of subacute stress on intestinal barrier function; different underlying cellular and molecular alterations are indicated in the small intestine versus the colon.

From Intestinal Permeability to Dysmotility: The Biobreeding Rat as a Model for Functional Gastrointestinal Disorders

Background Impaired intestinal barrier function, low-grade inflammation and altered neuronal control are reported in functional gastrointestinal disorders. However, the sequence of and causal relation between these events is unclear, necessitating a spontaneous animal model. The aim of this study was to describe the natural history of intestinal permeability, mucosal and neuromuscular inflammation and nitrergic motor neuron function during the lifetime of the BioBreeding (BB) rat. Methods Normoglycemic BB-diabetes prone (DP) and control rats were sacrificed at different ages and jejunum was harvested to characterize intestinal permeability, inflammation and neuromuscular function. Results Both structural and functional evidence of increased intestinal permeability was found in young BB-DP rats from the age of 50 days. In older animals, starting in the mucosa from 70 days and in half of the animals also in the muscularis propria from 110 days, an inflammatory reaction, characterized by an influx of polymorphonuclear cells and higher myeloperoxidase activity, was observed. Finally, in animals older than 110 days, coinciding with a myenteric ganglionitis, a loss of nitrergic neurons and motor function was demonstrated. Conclusion In the BB-rat, mucosal inflammatory cell infiltration is preceded by intestinal barrier dysfunction and followed by myenteric ganglionitis and loss of nitrergic function. This sequence supports a primary role for impaired barrier function and provides an insightful model for the pathogenesis of functional gastrointestinal disorders.

A Spontaneous Animal Model of Intestinal Dysmotility Evoked by Inflammatory Nitrergic Dysfunction

Background and Aims Recent reports indicate the presence of low grade inflammation in functional gastrointestinal disorders (FGID), in these cases often called “post-inflammatory” FGIDs. However, suitable animal models to study these disorders are not available. The Biobreeding (BB) rat consists of a diabetes-resistant (BBDR) and a diabetes-prone (BBDP) strain. In the diabetes-prone strain, 40–60% of the animals develop diabetes and concomitant nitrergic dysfunction. Our aim was to investigate the occurrence of intestinal inflammation, nitrergic dysfunction and intestinal dysmotility in non-diabetic animals. Methods Jejunal inflammation (MPO assay, Hematoxylin&Eosin staining and inducible nitric oxide synthase (iNOS) mRNA expression), in vitro jejunal motility (video analysis) and myenteric neuronal numbers (immunohistochemistry) were assessed in control, normoglycaemic BBDP and diabetic BBDP rats. To study the impact of iNOS inhibition on these parameters, normoglycaemic BBDP rats were treated with aminoguanidine. Results Compared to control, significant polymorphonuclear (PMN) cell infiltration, enhanced MPO activity, increased iNOS mRNA expression and a decreased ratio of nNOS to Hu-C/D positive neurons were observed in both normoglycaemic and diabetic BBDP rats. Aminoguanidine treatment decreased PMN infiltration, iNOS mRNA expression and MPO activity. Moreover, it restored the ratio of nNOS to Hu-C/D positive nerves in the myenteric plexus and decreased the abnormal jejunal elongation and dilation observed in normoglycaemic BBDP rats. Conclusions Aminoguanidine treatment counteracts the inflammation-induced nitrergic dysfunction and prevents dysmotility, both of which are independent of hyperglycaemia in BB rats. Nitrergic dysfunction may contribute to the pathophysiology of “low-grade inflammatory” FGIDs. Normoglycaemic BBDP rats may be considered a suitable animal model to study the pathogenesis of FGIDs.

The normoglycaemic biobreeding rat: A spontaneous model for impaired gastric accommodation

Objective Impaired gastric accommodation is reported in patients with functional dyspepsia (FD). Previous findings in postinfectious patients with FD suggest that low-grade inflammation and dysfunction of nitrergic nerves play a role in impaired accommodation. To date, spontaneous animal models to study the relationship between these changes are lacking. We hypothesise that the normoglycaemic BioBreeding diabetes-prone (BB-DP) rat provides an animal model of inflammation-induced impaired gastric motor function. Design Control diabetes-resistant biobreeding, normoglycaemic and hyperglycaemic BB-DP rats were sacrificed at the age of 30, 70 and 220 days and gastric fundus tissue was harvested to study nitrergic motor control, inflammation and expression of neuronal isoform of nitric oxide synthase (nNOS) and inducible isoform of nitric oxide synthase (iNOS). Nutrient-induced changes in intragastric pressure (IGP) were measured in normoglycaemic BB-DP rats to study accommodation. Results No differences in nitrergic function and inflammation were observed between BB-DP and control rats at 30 days. The nitrergic component of the fundic muscle relaxation was reduced in BB-DP rats of 70 and 220 days. This was accompanied by a significant loss of nNOS proteins. IGP significantly increased during nutrient infusion in BB-DP rats of 220 days, indicating impaired accommodation. Infiltration of polymorphonuclear cells, increased myeloperoxidase activity and increased expression of iNOS was observed in the fundic mucosa and muscularis propria of 70-day-old and 220-day-old BB-DP rats. Conclusions BB-DP rats of 220 days display altered fundic motor control and impaired accommodation, which is least partially explained by loss of nitrergic function. This may be related to inflammatory changes in the neuromuscular layer, suggesting that normoglycaemic BB-DP rats provide a spontaneous model for inflammation-induced impaired gastric accommodation.

Validation of Octanoate Breath Test for Measuring Gastric Emptying in Rats

Background/Aims Lack of simple and repeatable tests hampers gastric emptying studies in rats. The aim of this study was to adapt the 14C-octanoate solid gastric emptying breath test for application in rats, and to validate it against radioscintigraphic method. Methods After ingestion of a meal containing 3 mCi 99mTc and 2 µCi 14C-octanoate, 23 male Wistar rats were placed on a gamma camera in a airflow container. Scintigraphic images were taken at regular intervals. The amount of 14CO2 in a regularly replaced hyamine hydroxide solution, capturing CO2 in the outflow air, was counted using liquid scintillation spectrometry. 99mTc gastric retention curves and 14CO2-excretion curves were fitted to their respective data. Three rats underwent the same procedures after administration of atropine. Results Overall Tr10% (time at which 10% of the original amount of 99mTc remained in the stomach) was 355 ± 64 minutes; Te90% (time at which 90% of total amount of 14CO2 was excreted) was 325 ± 106 minutes. Their correlation coefficient was 0.71, R-square 0.50 and P < 0.005. Tr1/2 (50% of original amount of 99mTc remained) was 124 ± 28 minutes; Te1/2 (50% of total amount of 14CO2 excreted) 114 ± 32 minutes. Their correlation coefficient was 0.83 with R-square of 0.69 and P < 0.00005. In 12 immobilized animals correlation was even better: correlation coefficient 0.84; R-square 0.71 and P < 0.001 (Tr10% was 388 ± 117 minutes; Te90% 532 ± 219 minutes; Tr1/2 of 165 ± 54 minutes; Te1/2 of 175 ± 67 minutes). Atropine significantly lengthened all emptying times: 904 ± 307 and 1461 ± 684 minutes for Tr10% and Te90%, respectively; and 432 ± 117 minutes for Tr1/2 and 473 ± 190 minutes for Te1/2. Conclusions We adapted and validated the 14C-octanoate gastric emptying breath test for application in rats.

269 Acute Psychological Stress Increases Small Intestinal Permeability in Healthy Volunteers via CRH-Mediated Activation of Mast Cells

G A A b st ra ct s region, MRP4 was significantly down-regulated compared with expression in biopsies from healthy subjects (P,0.001, n=7-11). Conclusions: Key components of the GC-C/cGMP signalling pathway are expressed within human colonic mucosa. However, expression of the cGMP transporter MRP4 was significantly reduced in rectosigmoid biopsies from patients with IBS-C compared to biopsies from healthy subjects. Reduced MRP4 expression may result in reduced basal release of cGMP from intestinal epithelial cells in these patients and it may underlie some aspects of the pathophysiology of IBS. 1.Gastroenterology,2011,140(5),S1,S-538. Supported by NHMRC Australia, Ironwood Pharmaceuticals Inc.

274 Antioxidant Supplementation Improves Inflammatory Nitrergic Dysfunction in Diabetic Biobreeding Prone Rats

Introduction: Loss of intestinal nitrergic motor control has been reported in Biobreeding diabetes-prone (BBDP) rats (Zandecki 2008). We previously demonstrated that loss of jejunal neuronal nitric oxide synthase (nNOS) mRNA expression occurs in the BBDP, which is related to transient intestinal inflammation (myeloperoxidase: MPO activity) and inducible nitric oxide synthase (iNOS) expression, and which is independent from the development of hyperglycemia (Kindt DDW 2009). Studies in enteric neuron cultures suggest that iNOS overexpression downregulates nNOS expression through oxidative stress (Zandecki 2006). Moreover, aminoguanidine an iNOS inhibitor, counteracts the inflammation-induced nitrergic dysfunction and prevents intestinal elongation and dilatation caused by a 3cm H2O pressure stimulus in normoglycemic BBDP (Masaoka DDW 2011). Aim: To investigate the pathophysiological role of oxidative stress in inflammatory nitrergic dysfunction, we designed a controlled antioxidant supplementation study. Methods: BBDP were fed chow supplemented with 2% vitamin E (α-tocopherol) and 2g/l vitamin C (ascorbic acid) in the drinking water from 21days onwards. After onset of diabetes, 1% vitamin E and 1g/l vitamin C were supplemented to compensate for polyphagia and polydypsia. All rats were sacrificed at 220days. Jejunal inflammation, spontaneous intestinal motility, nitrergic neuron number and nNOS mRNA expression were analyzed respectively by MPO measurements, organ bath (37°C) video analysis, NADPH-diaphorase staining and realtime PCR, both in antioxidant supplemented animals and in a control group of age-matched non-supplemented diabetic animals. Results: Compared with controls (n=7), MPO activity decreased significantly in the antioxidant supplemented group (n=6) (9.9±3.9 vs. 2.1±1.4 U/mg, p 0.05) of a 5-cm jejunum segment in response to intraluminal pressure rise In Vitro. Conclusion: Antioxidant supplementation improves inflammation-induced nitrergic dysfunction and partially prevents intestinal dysmotility in diabetic BBDP.

Tu1994 Nitrergic Neurotransmission is Impaired in Non-Diabetic BB-Rats Gastric Fundus

G A A b st ra ct s CCh were not affected by TS infection (Table). However, in TS-infected rats receiving ketotifen contractile responses to CCh were increased by 60%; an effect completely prevented by pre-incubation with NGF, while the peptide did not affect contractility by itself (Table). Overall, ketotiken had also a tendency to increase cholinergic responses in non-infected animals (Table). L-NNA responses were unaltered by TS infection or ketotifen. Conclusions: During TS infection a significant MMC infiltrate appears in the colon without other structural or functional (as contractility relates) alterations. Altered colonic contractile responses during ketotifen treatment and prevention by NGF suggests that MCs play a protective role normalizing altered motility, likely through a NGF-related mechanism. Overall, these observations suggest that the MMC infiltrate that characterize functional gastrointestinal disorders might represent a protective mechanism aiming the normalization of colonic motility. Contractility (g)