Karel Geboes

Anti-tumor necrosis factor treatment restores the gut barrier in Crohn’s disease

OBJECTIVES:A primary defect of the tight junctions and, hence, increased intestinal epithelial permeability has been proposed as a basic pathogenic event in Crohns disease. Challenge of the mucosal immune system by the commensal gut flora would then result in chronic inflammation. Alternatively, increased permeability could be the result of inflammation. Our aim was to study intestinal permeability in refractory Crohns disease before and after treatment with monoclonal chimeric antibodies directed against tumor necrosis factor (TNF) to investigate whether the abnormal permeability persists after control of inflammation.METHODS:Twenty-three patients with active Crohns disease were evaluated before and 4 wk after a single infusion of 5 mg/kg infliximab. Intestinal permeability was studied by measurement of urinary excretion of 51Cr-EDTA after oral intake.RESULTS:The increased permeation of 51Cr-EDTA through the small intestine (1.63% interquartile range [IQR] 1.06–2.07) and the overall permeation (3.27% IQR 2.40–4.38) before therapy decreased significantly after infliximab infusion to values (1.04% IQR 0.74–1.54 and 2.42% IQR 2.03–2.80, respectively) in the range of those found in normal volunteers (1.12% IQR 0.85–1.58 and 2.28% IQR 1.88–2.86, respectively).CONCLUSION:Inhibiting the proinflammatory cytokine tumor necrosis factor dramatically reduces gut inflammation and largely restores the gut barrier in Crohns disease. Our data confirm the central role of TNF in gut barrier modulation in inflammatory conditions in vivo.

Adalimumab induces apoptosis of human monocytes: a comparative study with infliximab and etanercept

Background :u2002Adalimumab, a fully human monoclonal antibody to tumour necrosis factor, was recently introduced for therapy of Crohns disease.

Short exposure of oesophageal mucosa to bile acids, both in acidic and weakly acidic conditions, can impair mucosal integrity and provoke dilated intercellular spaces.

Background: Severe duodeno-gastro-oesophageal reflux (DGOR) is a risk factor for oesophagitis and Barrett’s oesophagus. Patients with non-erosive reflux disease (NERD) have a slight increase in DGOR. Patients with gastro-oesophageal reflux disease (GORD), who are taking proton pump inhibitors (PPIs), still have reflux but of weakly acidic pH and persistence of bile. In these two groups of patients, heartburn might be due to increased oesophageal mucosal permeability and dilated intercellular spaces (DIS). We aimed to assess whether experimental short exposure of the oesophageal mucosa to bile acids, in low concentrations (at acidic, weakly acidic and neutral conditions) can increase mucosal permeability and provoke DIS. Methods: Rabbit oesophageal mucosa was studied in diffusion and Ussing chambers. We assessed the effects of different solutions containing bile acids, applied to the mucosal side, on transepithelial electrical resistance (RT) and permeability to fluorescein. The diameter of intercellular spaces was assessed by using transmission electron microscopy. Results: Incubation of oesophageal mucosa with acidic solutions (pH 2.0) containing a range of bile acids (0.5–5 mmol/l) markedly decreased RT and increased mucosal permeability. Weakly acidic solutions (pH 5.0), and to some extent neutral solutions (pH 7.4), containing some bile acids also decreased RT and increased permeability, although the effects were much less marked and in some combinations no effect was seen. Exposure to bile acids provoked DIS in acid and weakly acidic conditions but not in neutral (pH 7.4) solutions. Conclusions: Experimental short exposure of the oesophageal mucosa to solutions with a bile acid concentration and acidity similar to that observed in the gastric contents of patients with NERD or ERD, and who are taking PPIs, may impair oesophageal mucosal integrity and even induce dilated intercellular spaces. Such a situation could, theoretically, underlie the occurrence and/or persistence of symptoms in these patients.

Critical role of stress in increased oesophageal mucosa permeability and dilated intercellular spaces

Background: In patients with non-erosive gastroesophageal reflux disease, heartburn can occur when acid reaches sensory nerve endings through oesophageal-mucosa-dilated intercellular spaces. Stressful life events may increase heartburn perception. In the rat, acute stress increases gastric and intestinal mucosa permeability. We investigated whether acute stress can also increase oesophageal mucosa permeability and contribute to the dilation of mucosa intercellular spaces. Methods: Male Sprague–Dawley rats were submitted to partial restraint stress. Oesophageal mucosa from stressed and control rats was mounted in diffusion chambers. The permeability to 51Cr-EDTA (400 Da), fluorescein isothiocyanate (FITC)-dextran 4000 Da (FD4) and FITC-dextran 20 000 Da (FD20) was assessed after tissue incubation either with Krebs (control) or HCl pH 2.0+ pepsin 1 mg/ml. The diameter of intercellular spaces was assessed using transmission electron microscopy. Results: Acute stress increased faecal output, small-intestinal permeability and glycaemia. Exposure of oesophageal mucosa from control rats to acid-pepsin did not increase permeability to any of the tested molecules. Stress increased the number of submucosal mast cells and, by itself, increased the permeability to the smallest molecule (22.8±7.1 pmol/cm2 vs 5.8±2.1 pmol/cm2) (p<0.001). Exposure of mucosa from stressed rats to acid-pepsin significantly increased permeability to all molecules tested. Electron microscopy showed dilated intercellular spaces only in mucosa from stressed rats (with and without exposure to acid-pepsin). Conclusions: Acute stress can increase, by itself, oesophageal mucosa permeability. There is a potentiation between stress and exposure of the oesophageal mucosa to acid-pepsin, leading to increased permeability and dilated intercellular spaces.

Characterization of myenteric neuropathy in the jejunum of spontaneously diabetic BB-rats

Abstractu2002 Decreased gastric expression and function of neuronal nitric oxide synthase (nNOS) has been proposed as a potential mechanism underlying diabetic gastroparesis. As gastric nNOS expression is vagally controlled, these changes might occur secondarily to vagal neuropathy. In addition, it is unclear whether other inhibitory neurotransmitters are also involved. We used the type 1 diabetic BioBreeding (BB)‐rat model to study jejunal motor control and nNOS expression, which is independent of the vagus. Jejunal segments were used for in vitro contractility studies, and measurement of nNOS expression after 8 or 16u2003weeks of diabetes compared with age‐ and sex‐matched controls. Unlike electrical field stimulation and acetylcholine (ACh)‐induced contractions, non‐adrenergic non‐cholinergic (NANC) relaxations were significantly reduced in diabetic rats. In contrast to control rats, NANC relaxations in diabetic rats were Nω‐nitro‐l‐arginine methyl ester (l‐NAME) insensitive. Jejunal nNOS expression was significantly decreased in diabetic rats. Both in diabetic and in control animals, l‐NAME resistant relaxations were sensitive to P2‐receptor antagonists. In the jejunum of spontaneously diabetic rats, decreased nitric oxide responsiveness and decreased nNOS protein expression occur while purinergic transmission is unaffected. These findings indicate that nitrergic enteric neuropathy may be a primary dysfunction in diabetes, independent from vagal dysfunction.

Whipple's disease : a histological, immunocytochemical and electronmicroscopic study of the immune response in the small intestinal mucosa

Whipples disease is a multisystem disorder with protean manifestations and with poorly understood aetiopathogenesis. It is unclear how the immune system reacts, whether it functions normally or not, whether it protects the organism or is defeated in one way or another by the ‘Whipple bacillus’. The purpose of our study was to assess humoral and cellular immunity at the level of the intestinal mucosa. This histochemical, immunocytochemical and electronmicroscopic study, based on 16 cases, has shown that the changes in components of the mucosal immune system in Whipples disease are quite different from normal. The phagocytic capacity of the macrophages, assessed microscopically, is abnormal, the number of intra‐epithelial lymphocytes is increased, the CD 4/CD 8 cell ratio is decreased and the IgM positive cells in the lamina propria outnumber the IgA positive cells. These changes may be inter‐dependent.

Neural mechanisms of early postinflammatory dysmotility in rat small intestine

Abstractu2002 Although human postinflammatory dysmotility is known, so far animal studies have primarily investigated changes during inflammation. Here, we focused on postinflammatory changes in rat jejunal myenteric plexus and jejunal motility. Evolution of ethanol/2,4,6‐tri‐nitrobenzene sulphonic acid (TNBS)‐induced inflammation was assessed histologically and by measuring myeloperoxidase activity (MPO). Electromyography and immunohistochemistry were performed 1u2003week after ethanol/TNBS and also after NG‐nitro‐l‐arginine methyl ester (l‐NAME) administration. Ethanol/TNBS induced a transient inflammation, with normalization of MPO and histological signs of an early phase of recovery after 1u2003week. The number of cholinergic neurones was not altered, but myenteric neuronal nitric oxide synthase (nNOS)‐immunoreactivity was significantly lower in the early phase of recovery after TNBS compared with water (1.8u2003±u20030.2 vs 3.5u2003±u20030.2 neuronesu2003ganglion−1, Pu2003<u20030.001). Interdigestive motility was disrupted with a loss of phase 1 quiescence, an increase of migrating myoelectric complex cycle length, a higher number of non‐propagated activity fronts and a decrease of adequately propagated phase 3u2003s after TNBS. Administration of l‐NAME resulted in a similar disruption of interdigestive motility patterns. In the early phase of recovery after ethanol/TNBS‐induced jejunal inflammation, a loss of motor inhibition occurs due to a decrease of myenteric nNOS activity. These observations may provide a model for early postinflammatory dysmotility syndromes.

Surgical Therapy and Histological Abnormalities in Functional Isolated Small Bowel Obstruction and Idiopathic Gastrointestinal Perforation in the Very Low Birth Weight Infant

We examined surgical treatment, outcome, and histological findings in very low birth weight (VLBW) infants with functional isolated small bowel obstruction (FISBO) and idiopathic gastrointestinal perforation (IGIP). The files of 18 neonates (average gestational age 27.5 weeks; average birth weight 880 g), surgically treated for IGIP (n = 12) or FISBO (n = 6), were retrospectively reviewed. In both groups segmental or diffuse dilatation of the small bowel was seen. All but two perforations were localized in the small bowel. In half of the patients a discontinuous absence of the internal layer of the muscularis propria or muscularis mucosae was found. Signs of necrotizing enterocolitis (NEC) were absent. Most of the patients were treated with an enterostomy (IGIP: n = 11; FISBO: n = 4). Overall survival in both groups was 83%. Follow-up after enterostomy closure (mean 23 months) shows normal gastrointestinal function without failure to thrive in 67% of the survivors. Muscular wall abnormalities and small bowel distension are found in both FISBO and IGIP. Although the underlying etiology remains unclear, segmental muscular wall absence may be a major predisposing factor in both conditions. Creation of a temporary enterostomy is a valid surgical option in VLBW infants with minimal risk for recurrent obstruction and/or perforation. Survival and long-term gastrointestinal function is excellent. IGIP should be distinguished from NEC.

Studies on the Relationship between Esophageal Acid Exposure, Mucosal Lesions and Heartburn Using an Acid Exposure Sensor

Background: In vitro studies of a recently developed acid exposure sensor show that the sensor response (SR) to acid < pH 4 is linearly determined by the duration and degree of acidity. The aim was to determine whether SR correlates with the severity of acid-induced esophageal mucosal lesions and acid-induced heartburn. Methods: HCl pH 1.5 or saline was infused into the feline esophagus for 5-20 min. Simultaneously, sensor measurements were performed below the infusion port. The histological damage was scored by an independent pathologist. In 15 normal subjects, HCl pH 1 was infused into the esophagus and the severity of the heartburn (0-5) was scored at 5-min intervals. In 10 subjects who experienced heartburn during acid perfusion, initial perfusion with HCl was repeated during heartburn induction time minus 5 min, followed by perfusion with the subjects own gastric juice, titrated to pH 2; heartburn severity was again scored at 5-min intervals. Acid exposure sensors positioned below the infusion port were removed at heartburn scores 1, 2 and 3. Results: A good correlation was found between SR and the histological score for mucosal damage in the cat esophagus ( r = 0.64, P < 0.005). There was a good relation between heartburn severity score and acid exposure time ( r = 0.84, P < 0.001), and a significant but weaker relation between heartburn severity and SR. Conclusion: In cats, there is a good relation between the severity of acid-induced esophageal mucosal lesions and SR. In men, there is a significant correlation between the severity of acid-induced heartburn and the simultaneously measured SR. Therefore, SR measurement has the potential of yielding clinically relevant information in the investigation of GERD.

Anti-Leu-19 Is a Marker for Nervous Tissue in the Mucosa of the Human Rectum

Despite numerous investigations on the enteric nervous system, the knowledge about the mucosal innervation of the human rectum and colon is very shallow and mainly based on ultrastructural studies. We performed an enzyme (NADH-Ach) and immunohistochemical (NF, synaptophysin, anti-Leu-19) study on cryostat sections of the human rectal mucosa in order to study the possible additional characteristics of the mucosal innervation in depth. Enzyme histochemistry reveals positively staining fibers in the muscularis mucosae. Staining with antibodies against neurofilaments and synaptophysin reveals positively staining fibers in the lamina propria and muscularis mucosae. The latter staining is comparable with the findings obtained with anti-Leu-19. The monoclonal antibody anti-Leu-19 is characterized by a nerve-like staining in the mucosa revealed by nerve-like fibers from the plexus submucosus internus (Meissner) penetrating the muscularis mucosae, and creating a real plexus of fine twisted fibers in the lamina propria, around the crypts and underneath the epithelium. The distribution of the mucosal nerve-like pattern in the areas with mucosa-associated lymphoid follicles differs from the pattern observed in the lamina propria in between. Since the monoclonal antibody anti-Leu-19 and the monoclonal antibody NKH1a show a great similarity, we were interested also in the possible relation between the nerve like mucosal staining pattern and the lymphocytic population. Comparing the distribution pattern of anti-Leu-19 with other lymphocytic markers, there was an apparent similarity with the distribution of the T-helper subgroup. Our data indicate that the monoclonal antibody anti-Leu-19 shows a nerve-like staining pattern in the mucosa.