Experimental evidence and mathematical modeling of thermal effects on human colonic smooth muscle contractility.

It has been shown, in animal models, that gastrointestinal tract (GIT) motility is influenced by temperature; nevertheless, the basic mechanism governing thermal GIT smooth muscle responses has not been fully investigated. Studies based on physiologically tuned mathematical models have predicted that thermal inhomogeneity may induce an electrochemical destabilization of peristaltic activity. In the present study, the effect of thermal cooling on human colonic muscle strip (HCMS) contractility was studied. HCMSs were obtained from disease-free margins of resected segments for cancer. After removal of the mucosa and serosa layers, strips were mounted in separate chambers. After 30 min, spontaneous contractions developed, which were measured using force displacement transducers. Temperature was changed every hour (37, 34, and 31°C). The effect of cooling was analyzed on mean contractile activity, oscillation amplitude, frequency, and contraction to ACh (10(-5) M). At 37°C, HCMSs developed a stable phasic contraction (~0.02 Hz) with a significant ACh-elicited mean contractile response (31% and 22% compared with baseline in the circular and longitudinal axis, respectively). At a lower bath temperature, higher mean contractile amplitude was observed, and it increased in the presence of ACh (78% and 43% higher than the basal tone in the circular and longitudinal axis, respectively, at 31°C). A simplified thermochemomechanical model was tuned on experimental data characterizing the stress state coupling the intracellular Ca(2+) concentration to tissue temperature. In conclusion, acute thermal cooling affects colonic muscular function. Further studies are needed to establish the exact mechanisms involved to better understand clinical consequences of hypothermia on intestinal contractile activity.

Acid reflux episodes sensitize the esophagus to perception of weakly acidic and mixed reflux in non-erosive reflux disease patients.

BACKGROUND: Non-erosive reflux disease (NERD) patients are more sensitive than erosive esophagitis patients to weakly acidic reflux and to the presence of gas in the refluxate. Intra-esophageal acid perfusion sensitizes esophageal receptors to mechanical and chemical stimuli. METHODS: To establish whether acid sensitization plays a role in the perception of weakly acidic and mixed reflux episodes, 29 NERD patients, responders and 14 non-responders to proton pump inhibitors (PPIs), underwent pH-impedance monitoring. Non-responders repeated the study while on PPIs. To assess the effect of acid exposure on symptom perception, the time period with pH below 4 was measured in 15- and 30-minute time-windows preceding the onset of each reflux episode. KEY RESULTS: Considering weakly acidic and mixed refluxes, both in responder and non-responder patients (off PPIs), the symptomatic refluxes were preceded by a significantly higher cumulative acid exposure than the asymptomatic refluxes. In all patients, following acid reflux, the percentage of symptomatic weakly acidic reflux episodes was significantly higher than that of asymptomatic refluxes. Non-responder patients, off-treatment, were characterized by a lower proportion of weakly acidic reflux and mixed reflux episodes. In the non-responder patients on PPI, only mixed and weakly symptomatic reflux episodes were preceded by a higher cumulative acid exposure. CONCLUSIONS & INFERENCES: In NERD patients, spontaneous acid reflux enhances subsequent reflux perception, regardless of acidity or liquid/mixed composition of episodes; in non-responder patients on PPIs, only the perception of mixed and weakly acidic reflux episodes seems to be mediated by a preceding acid exposure.

Platelet-activating factor and distinct chemokines are elevated in mucosal biopsies of erosive compared with non-erosive reflux disease patients and controls.

BACKGROUND: A distinction between symptomatic non-erosive reflux disease (NERD) and erosive esophagitis (EE) patients is supported by the presence of inflammatory response in the mucosa of EE patients, leading to a damage of mucosal integrity. To explore the underlying mechanism of this difference, we assessed inflammatory mediators in mucosal biopsies from EE and NERD patients and compared them with controls. METHODS: Nineteen NERD patients, 15 EE patients, and 16 healthy subjects underwent endoscopy after a 3-week washout from PPI or H(2) antagonists. Biopsies obtained from the distal esophagus were examined by quantitative real-time polymerase chain reaction (qPCR) and multiplex enzyme-linked immunosorbent assay for selected chemokines and lyso-PAF acetyltransferase (LysoPAF-AT), the enzyme responsible for production of platelet-activating factor (PAF). KEY RESULTS: Expression of LysoPAF-AT and multiple chemokines was significantly increased in mucosal biopsies derived from EE patients, when compared with NERD patients and healthy controls. Upregulated chemokines included interleukin 8, eotaxin-1, -2, and -3, macrophage inflammatory protein-1α (MIP-1α), and monocyte chemoattractant protein-1 (MCP-1). LysoPAF-AT and the chemokine profile in NERD patients were comparable with healthy controls. CONCLUSIONS & INFERENCES: Levels of selected cytokines and Lyso-PAF AT were significantly higher in the esophageal mucosa of EE patients compared with NERD and control patients. This difference may explain the distinct inflammatory response occurring in EE patients' mucosa. In contrast, as no significant differences existed between the levels of all mediators in NERD and control subjects, an inflammatory response does not appear to play a major role in the pathogenesis of the abnormalities found in NERD patients.

Increased TRPV1 gene expression in esophageal mucosa of patients with non-erosive and erosive reflux disease.

BACKGROUND: Transient receptor potential channel vanilloid subfamily member-1 (TRPV1) may play a role in esophageal perception. TRPV1 mRNA and protein expression were examined in the esophageal mucosa of non-erosive reflux disease (NERD) and erosive esophagitis (EE) patients and correlated to esophageal acid exposure. METHODS: Seventeen NERD patients, eight EE patients and 10 healthy subjects underwent endoscopy after a 3-week washout from proton pump inhibitors or H2 antagonists. Biopsies, obtained from the distal esophagus, were used for conventional histology, for Western blot analysis and/or quantitative real-time polymerase chain reaction (qPCR). Overall 13 NERD patients, four EE patients and five controls underwent ambulatory pH-testing. KEY RESULTS: TRPV1 expression was increased in all NERD and EE patients, as measured by Western blot analysis (0.65 +/- 0.07 and 0.8 +/- 0.05 VS 0.34 +/- 0.04 in controls; P < 0.01) and by qPCR (1.98 +/- 0.21 and 2.52 +/- 0.46 VS 1.00 +/- 0.06; P < 0.01). Neutrophilic infiltration, in the mucosa, was detected only in EE patients. CONCLUSIONS & INFERENCES: Non-erosive reflux disease and EE patients presented increased TRPV1 receptors mRNA and protein, although no correlation with acid exposure was demonstrated. Increased TRPV1 in the esophageal mucosa may contribute to symptoms both in NERD and EE patients and possibly account for peripheral mechanisms responsible for esophageal hypersensitivity in NERD patients.

Effect of ursodeoxycholic acid on inflammatory infiltrate in gallbladder muscle of cholesterol gallstone patients.

BACKGROUND: Reduced gallbladder (GB) contractility and chronic inflammatory changes in the mucosa have been reported in patients with cholesterol gallstones (GS). Ursodeoxycholic acid (UDCA) restores GB contractility and antagonises liver macrophage activation. In the colon, hydrophobic bile acid, not hydrophilic UDCA, induces mast cell degranulation. We studied the presence of monocyte/macrophage infiltrate, cyclooxygenase (COX)-2, inducible nitric oxide synthase (iNOS) expression, the number of total and degranulated mast cells in the GB muscle layer of cholesterol GS patients, and the effect of UDCA administration. METHODS: Gallbladder tissue was obtained from cholesterol GS patients, either treated or untreated with UDCA (10 mg kg(-1) day(-1)) for 30 days prior to surgery. Gallbladders removed for neoplastic diseases, not involving GB, were evaluated for control purposes. The presence of monocytes/macrophages (CD68 positive), granulocytes, and mast cells, and the COX-2 and iNOS expression, was determined immunohistochemically. KEY RESULTS: The number of CD68, granulocytes, mast cells, COX-2 and iNOS positive cells was significantly higher in the muscle layer of GS patients than in controls. Compared to untreated patients, those treated with UDCA showed significantly lower levels of CD68, COX-2 positive cells and degranulated mast cells and a lesser number of iNOS positive cells and granulocytes. CONCLUSIONS & INFERENCES: An inflammatory monocyte/macrophage, mast cell and granulocyte infiltrate is present in the GB muscle layer of GS patients. Ursodeoxycholic acid decreases macrophages, degranulated mast cells and COX-2 expression. These results suggest that monocytes/macrophages and degranulating mast cells contribute to muscle cell dysfunction in cholesterol GS patients and support the anti-inflammatory effect of UDCA.

Impaired contractility of colonic muscle cells in a patient with chronic intestinal pseudo-obstruction.

Chronic intestinal pseudo-obstruction represents a cause of persistent functional intestinal failure either "secondary" to specific conditions or "chronic intestinal idiopathic pseudo-obstruction" in origin. The diagnosis is mainly clinical, supported by radiological and/or endoscopic findings excluding any mechanical cause of intestinal obstruction. We reported a case of a 39-year-old woman with chronic intestinal idiopathic pseudo-obstruction, who underwent colectomy with ileorectal anastomosis; histological examination of the surgical specimen did not reveal myogenic or neurogenic defects or other pathological abnormalities indicative of an underlying neuromuscular impairment. Because of the apparent integrity of the gut neuromuscular layer, we tested whether a functional impairment affected colonic single smooth muscle cells. Muscle cells were isolated from the right colon and their contractile response to a receptor-dependent agonist evaluated in comparison to that obtained from controls. The cell contraction induced by acetylcholine in a dose response manner was markedly decreased in the patient affected by chronic intestinal idiopathic pseudo-obstruction compared with cells from controls (percentage of cell shortening with maximal dose of acetylcholine [10(-6)M]: 10.7+/-3% versus 34.2+/-4%, respectively). The present findings indicate a specific defect of colonic smooth muscle cells likely related to an ineffective response to acetylcholine.

Presence of gas in the refluxate enhances reflux perception in non-erosive patients with physiological acid exposure of the oesophagus.

OBJECTIVE: The mechanisms underlying symptoms in gastro-oesophageal reflux disease, particularly in non-erosive reflux disease (NERD), remain to be fully elucidated. Weakly acidic reflux and the presence of gas in the refluxate could be relevant in the pathogenesis of symptoms. METHODS: To assess the relationship between symptoms and weakly acidic, acid and mixed (liquid-gas) reflux, 24 h oesophageal pH-impedance monitoring was performed in 32 NERD and in 20 oesophagitis patients. In 12 NERD patients the study was repeated following 4 weeks treatment with a proton pump inhibitor (PPI). Impedance-pH data were compared with those of 10 asymptomatic controls. Heartburn and acid regurgitation were considered in the analysis of symptoms. RESULTS: 15 NERD patients showed a physiological acid exposure time (pH-negative). Weakly acidic reflux was significantly less frequent in patients (25% (2%), mean (SE)) than in controls (54% (4%), p<0.01). Gas was present in 45-55% of reflux events in patient groups and controls, and decreased following PPI treatment. In NERD pH-negative patients, weakly acidic reflux accounted for 32% (10%) (vs 22% (6%) in NERD pH-positive and 12% (8%) in oesophagitis patients) and mixed reflux for more than two-thirds of all symptom-related refluxes. Multivariate logistic analysis showed that in NERD pH-negative patients, the risk of reflux perception was significantly higher when gas was present in the refluxate (odds ratio, 3.2; 95% CI, 1.2 to 10; p<0.01). CONCLUSIONS: The large majority of symptoms, in all patients, are related to acid reflux. In NERD patients, the presence of gas in the refluxate significantly enhances the probability of reflux perception. These patients are also more sensitive to less acidic reflux than oesophagitis patients.

Effect of oesophagitis on proximal extent of gastro-oesophageal reflux.

Proximal oesophageal acid reflux is increased in gastro-oesophageal reflux disease (GORD) patients with oesophageal and extra-oesophageal symptoms, the latter particularly in presence of oesophagitis. This study was aimed to assess the proximal extent of reflux, both acid and weakly acidic, in GORD patients with and without oesophagitis and to characterize, using an animal model of GORD, the relationship between acute oesophagitis and proximal extent of reflux. Proximal extent of reflux was evaluated during 24-h pH-impedance monitoring in 17 oesophagitis, 27 non-erosive reflux disease (NERD) patients and 10 asymptomatic controls. In five adult cats, reflux events were simulated by intra-oesophageal retrograde injection of a radiopaque solution. Proximal extent of simulated reflux was fluoroscopically assessed before and after inducing acute oesophagitis. The percentage of proximal reflux was 11% in controls, 22% in NERD and 38% in oesophagitis patients (P < 0.05 vs NERD). Weakly acidic reflux showed higher proximal extent in oesophagitis than in NERD patients but it was less proximally propagated than acid reflux. In cats, proximal reflux was significantly increased during acute oesophagitis. Oesophagitis patients show higher proximal extent of reflux, acid and weakly acidic, when compared with NERD patients and controls. In the experimental model, acute oesophagitis favours proximal migration of simulated reflux.

Dilated intercellular spaces and acid reflux at the distal and proximal oesophagus in patients with non-erosive gastro-oesophageal reflux disease.

BACKGROUND: Acid exposure of proximal oesophagus and dilated intercellular space diameters of oesophageal epithelium are relevant in the perception of gastro-oesophageal reflux. AIM: To explain the relationship between gastro-oesophageal reflux disease symptoms, acid exposure and intercellular space diameter along the oesophageal epithelium and to assess time-related variability of intercellular space diameter. METHODS: Thirty-three non-erosive reflux disease (NERD), six erosive oesophagitis patients and 12 asymptomatic controls underwent oesophageal manometry and 24-h dual-channel oesophageal pH-monitoring following endoscopy. Biopsies were taken 5 cm above the LES and 10 cm below the UES, at comparable levels, as pH sensors. A total of 100 intercellular space diameters per patient/control were measured blindly at transmission electron microscopy. In 15 patients, the investigation was repeated after 1 year. RESULTS: In all NERD patients, acid exposure was higher at mid-proximal oesophagus (P < 0.01) and mean intercellular space diameters, at distal and mid-proximal oesophagus, was three- and twofold higher (1.5 and 0.82 micro m, respectively) compared with controls. Intra-patient intercellular space diameter values were stable over time, not overlapping with those of controls. CONCLUSIONS: Dilation of intercellular space diameter occurs along the distal and proximal oesophageal epithelium in NERD patients and could be responsible for the enhanced perception of proximal acid reflux. This finding appears to be time-reproducible and to represent a sensitive, histopathological marker of NERD.

Effect of hiatal hernia on proximal oesophageal acid clearance in gastro-oesophageal reflux disease patients.

BACKGROUND: Proximal acid reflux is common in gastro-oesophageal reflux disease and is a determinant of symptoms. Patients with hiatal hernia complain of more symptoms than those without and are less responsive to proton-pump inhibitors. AIM: To evaluate the role of hiatal hernia on spatiotemporal characteristics of acid reflux. METHODS: Thirty seven consecutive gastro-oesophageal reflux disease patients underwent endoscopy, videofluoroscopy, manometry and multichannel 24-h pH test. Data were compared with those of 15 asymptomatic controls. Multivariate linear regression was used for statistical analysis. RESULTS: At videofluoroscopy, hiatal hernia was found in 16 of 37 patients. The mean size of hiatal hernia was 3.4 cm. Patients showed significantly prolonged acid clearance time, both at proximal and distal oesophagus, compared with controls. Hiatal hernia patients showed a significantly delayed acid clearance, along the oesophageal body, compared with non-hiatal hernia patients. The prolonged acid exposure was maintained during upright and supine position. The presence of hiatal hernia significantly predicted acid clearance delay in the distal and proximal oesophagus [at 10 cm below upper oesophageal sphincter: Delta + 2.5 min (95% confidence interval: 0.4-4.5); P < 0.02]. CONCLUSIONS: The presence of hiatal hernia is a strong predictor of more prolonged proximal oesophageal acid exposure and clearance. Hiatal hernia is likely to play a role in the pathophysiology of gastro-oesophageal reflux disease symptoms, and should be taken into greater consideration in the treatment strategies of the disease.

Effect of endoscopic augmentation of the lower oesophageal sphincter (Gatekeeper reflux repair system) on intraoesophageal dynamic characteristics of acid reflux.

BACKGROUND AND AIMS: Improvements in symptoms following endoscopic procedures for gastro-oesophageal reflux disease (GORD) are seldom supported by normalisation of acid exposure time at the distal oesophagus. However, the distribution of gastric acid within the proximal oesophagus is a main determinant of symptom generation in GORD patients. In this study, our aim was to assess the effect of endoscopic insertion of hydrogel expandable prostheses into the oesophageal submucosa on spatiotemporal characteristics of gastro-oesophageal reflux. METHODS: Oesophageal manometry and multichannel ambulatory 24 hour pH monitoring were carried out in nine patients before and six months after the endoscopic procedure. Dynamic characteristics of gastro-oesophageal reflux in patients were also compared with those in 13 asymptomatic controls. RESULTS: Acid exposure time (AET) at the distal oesophagus decreased from 11.7% (95% confidence interval 6.1-21.8) at baseline to 7.7% (3.7-11.6) at follow up (NS). Of the nine patients, distal AET normalised in three. AET at the middle (7.6% (2.9-12.3)) and proximal (2.4% (0.1-4.8)) oesophagus decreased significantly in all patients (2.4% (0.3-4.5), p <0.01; 1.2% (0.2-2.2), p<0.05 respectively). Proximal extent of acid events significantly decreased in all patients at follow up (37.3% v 9.5%), reaching values observed in asymptomatic controls. Median GORD health related quality of life scores significantly improved from 35.5 at baseline to 9.4. CONCLUSIONS: Despite the lack of a significant improvement in traditional pH variables, endoscopic implant of hydrogel prostheses above the lower oesophageal sphincter significantly decreases proximal spread of acid reflux into oesophageal body. This effect would explain the improvement in symptoms in patients six months after therapy.

Intra-oesophageal distribution and perception of acid reflux in patients with non-erosive gastro-oesophageal reflux disease.

BACKGROUND: The majority of patients with gastro-oesophageal reflux disease do not present with erosive oesophagitis and make up a heterogeneous group. Patients with non-erosive gastro-oesophageal reflux disease are less responsive than patients with oesophagitis to acid-suppressive therapy. AIM: To assess the role of acid reflux in gastro-oesophageal reflux disease symptoms. METHODS: The spatio-temporal characteristics of reflux events were analysed and related to reflux perception in 45 patients with non-erosive gastro-oesophageal reflux disease and 20 patients with erosive oesophagitis. RESULTS: Compared with healthy controls, all patients showed a higher intra-oesophageal proximal spread of acid, which was prominent in patients with non-erosive gastro-oesophageal reflux disease (> 50% of events lasting for 1-2 min). Irrespective of mucosal injury, the risk of reflux perception was very high when acid reached proximal sensors (odds ratio, 7.6; 95% confidence interval, 4.6-12.5), being maximal in patients with non-erosive gastro-oesophageal reflux disease with normal acid exposure time (odds ratio, 11; 95% confidence interval, 5.2-22.3). CONCLUSIONS: Patients with non-erosive gastro-oesophageal reflux disease are characterized by a significantly higher proportion of proximal acid refluxes and a higher sensitivity to short-lasting refluxes when compared with patients with oesophagitis. The highest proximal acid exposure and highest perception occurred in patients with non-erosive gastro-oesophageal reflux disease presenting with a normal pH-metric profile. The assessment of acid distribution and its perception in the oesophageal body can better identify reflux patients who should benefit from acid-suppressive treatment.

Outcome of endoscopic sphincterotomy in post cholecystectomy patients with sphincter of Oddi dysfunction as predicted by manometry and quantitative choledochoscintigraphy.

BACKGROUND: Sphincter of Oddi dysfunction is diagnosed at manometry and, after cholecystectomy, non-invasively at quantitative choledochoscintigraphy. Patients may benefit from endoscopic sphincterotomy. AIMS: The aim of this study was to assess the usefulness of choledochoscintigraphy compared with manometry in predicting outcome of sphincterotomy in post cholecystectomy patients with sphincter of Oddi dysfunction. PATIENTS AND METHODS: Thirty patients with biliary-type pain complying with the Rome diagnostic criteria of sphincter of Oddi dysfunction and belonging to biliary group I and II were subjected to clinical evaluation, choledochoscintigraphic assessment of the hepatic hilum-duodenum transit time, endoscopic retrograde cholangiopancreatography, and perendoscopic manometry. Twenty two biliary group I and II patients with prolonged hepatic hilum-duodenum transit times were invited to undergo sphincterotomy. Fourteen patients underwent sphincterotomy; eight refused. Clinical and scintigraphic assessments were performed at follow up. RESULTS: Hepatic hilum-duodenum transit time was delayed in all patients with manometric evidence of sphincter of Oddi dysfunction, in all biliary group I patients and in 64% of biliary group II patients. At follow up, all patients who underwent sphincterotomy were symptom free and hepatic hilum-duodenum transit time had either normalised or significantly improved. A favourable post sphincterotomy outcome was predicted in 93% of cases at choledochoscintigraphy and in 57% at manometry. CONCLUSIONS: Quantitative choledochoscintigraphy is a useful and non-invasive test to diagnose sphincter of Oddi dysfunction as well as a reliable predictor of sphincterotomy outcome in post cholecystectomy biliary group I and II patients, irrespective of clinical classification and manometric findings.