Quantitative histological study of mucosal inflammatory cell densities in endoscopic duodenal biopsy specimens from dyspeptic patients using computer linked image analysis

Role of the duodenal microbiota in functional dyspepsia

BACKGROUND

Functional dyspepsia (FD) is a common and debilitating gastrointestinal disorder attributed to altered gut-brain interactions. While the etiology of FD remains unknown, emerging research suggests the mechanisms are likely multifactorial and heterogenous among patient subgroups. Small bowel motor disturbances, visceral hypersensitivity, chronic microinflammation, and increased intestinal tract permeability have all been linked to the pathogenesis of FD. Recently, alterations to the gut microbiome have also been implicated to play an important role in the disease. Changes to the duodenal microbiota may either trigger or be a consequence of immune and neuronal disturbances observed in the disease, but the mechanisms of influence of small intestinal flora on gastrointestinal function and symptomatology are unknown.

PURPOSE

This review summarizes and synthesizes the literature on the link between the microbiota, low-grade inflammatory changes in the duodenum and FD. This review is not intended to provide a complete overview of FD or the small intestinal microbiota, but instead outline some of the key conceptual advances in understanding the interactions between altered gastrointestinal bacterial communities; dietary factors; host immune activation; and stimulation of the gut-brain axes in patients with FD versus controls. Current and emerging treatment approaches such as dietary interventions and antibiotic or probiotic use that have demonstrated symptom benefits for patients are reviewed, and their role in modulating the host-microbiota is discussed. Finally, suggested opportunities for diagnostic and therapeutic improvements for patients with this condition are presented.

Role of the Duodenum in the Pathogenesis of Functional Dyspepsia: A Paradigm Shift

Functional dyspepsia (FD) is a common disorder characterized by chronic epigastric pain or burning, or bothersome postprandial fullness or early satiation, without a definitive organic cause. The pathogenesis of FD is likely heterogeneous. Classically, motor disorders, visceral hypersensitivity, and brain-gut interactions have been implicated in the pathophysiology of FD, but recently an important role for chronic low-grade inflammation and infection in FD has been reported and confirmed. Duodenal low-grade inflammation is frequently observed in FD in those with and without documented previous gastroenteritis. Duodenal eosinophils and in some cases mast cells may together or separately play a key role, and immune activation (eg, circulating homing small intestinal T cells) has been observed in FD. Low-grade intestinal inflammation in patients with FD may provoke impairment in motor-sensory abnormalities along the gastrointestinal neural axis. Among FD patients, the risk of developing dyspeptic symptoms after a bout of gastroenteritis is 2.54 (95% CI, 1.76–3.65) at more than 6 months after acute gastroenteritis. Gut host and microbial interactions are likely important, and emerging data demonstrate both quantitative and qualitative changes of duodenal mucosal and fecal microbiota in FD. Food antigens (eg, wheat proteins) may also play a role in inducing duodenal inflammation and dyspepsia. While causation is not established, the hypothesis that FD is a disorder of microscopic small intestinal inflammation in a major subset is gaining acceptance, opening the possibility of novel treatment approaches that may be able to alter the natural history of the disorder.

Micro-inflammation in functional dyspepsia: A systematic review and meta-analysis

Functional dyspepsia (FD) is a gastrointestinal disorder of unknown etiology. Although micro-inflammation appears to be important in the pathogenesis, studies evaluating immune activation in FD have been inconsistent. A systematic review of literature and meta-analysis was performed to compare immunologic cell counts and cytokine levels in the mucosa and peripheral blood of individuals with FD and healthy controls. PubMed, Embase, and the Cochrane library were searched. Data on immunologic cell counts and cytokines levels among individuals with FD and control groups were extracted and compared by calculating standard mean differences (SMD). Thirty-seven studies met the inclusion criteria. Mast cell (SMD = 0.94, 95%CI 0.26-1.62, P = .007) and eosinophil counts (SMD = 0.36, 95%CI 0.06-0.68, P = .03) in the stomach were increased, among individuals with FD compared to controls. Similarly, mast cell (SMD = 0.66, 95%CI 0.20-1.13, P = 0.005) and eosinophil (SMD = 0.95, 95%CI 0.66-1.24; P < .001) counts in the duodenum were also increased in those with FD compared to controls. In a subgroup analysis, elevated eosinophil counts in the duodenum were observed in both post-prandial distress syndrome (SMD = 0.97, 95%CI 0.46-1.47, P = .0002) and epigastric pain syndrome subtypes (SMD = 1.16, 95%CI 0.48-1.83, P = .0008). No differences in mucosal intraepithelial lymphocyte, enterochromaffin cell, and neutrophil counts, as well as, peripheral interlukin-6 (IL-6) and IL-10 levels were observed among individuals with FD and controls. Micro-inflammation in the form of local immune cell infiltration, particularly eosinophils and mast cells, characterizes the pathogenesis of FD.

An examination of the relationship between the endoscopic appearance of duodenitis and the histological findings in patients with epigastric pain

The endoscopic appearance of duodenitis is a common finding in patients undergoing endoscopy because of epigastric pain however, the relationship of the visual findings to histology is poorly defined. We set out to ascertain if there was a correlation between the endoscopic and histological appearances of the duodenal mucosa. Consecutive patients with epigastric pain referred for diagnostic gastroduodenoscopy were studied. The visual appearances of 'duodenitis' (erythema, erosions and sub-epithelial haemorrhage) were reported independently by two endoscopists. Duodenal biopsies were taken and assessed for: neutrophil infiltrate, mononuclear infiltrate, gastric metaplasia, villous atrophy and a breach in the mucosa. H pylori status was determined. Of the 93 patients with endoscopic features of duodenitis an increase in histological markers of inflammation was found in 75 (81%). However, histological inflammation was absent or minimal in 68 (73%). Conversely, biopsies from normal-looking mucosa revealed histological evidence of inflammation in 26 (27%). For patients with the endoscopic features of duodenitis the positive & negative predictive value for neutrophilic infiltrate was 39% and 98% respectively. Biopsies from erosions confirmed a breach in the mucosa in only 2 of 40 patients. Neutrophilic infiltrate occurred with NSAI ingestion and infection with H pylori. The endoscopic appearance of the duodenal mucosa is unreliable in determining the presence of histological inflammation. The endoscopic appearance of 'erosions' is not usually associated with a mucosal breach.

The study on the role of inflammatory cells and mediators in post-infectious functional dyspepsia

OBJECTIVE

Functional dyspepsia is a common gastrointestinal disorder. The pathogenesis of functional dyspepsia remains unclear. Functional dyspepsia may begin after a bout of gastroenteritis (post-infectious functional dyspepsia) or de novo (nonspecific functional dyspepsia). The aim of this study was to investigate the prevalence and probable mechanisms of post-infectious functional dyspepsia.

MATERIAL AND METHODS

Functional dyspepsia patients with a history of unsanitary food intake and acute gastroenteritis 6-12 months ago were enrolled. (13)C-UBT confirmed absence of H. pylori infection. Controls consisted of healthy nondyspeptic volunteers and patients with nonspecific functional dyspepsia. Gastric biopsies were used for routine histology, immunohistochemistry, electron microscopy, ELISA, HPLC assays and Western blot examination.

RESULTS

Eighty-five subjects were entered including 35 with post-infectious functional dyspepsia, 30 with nonspecific functional dyspepsia, and 20 healthy controls. The number of mast cells in post-infectious functional dyspepsia and nonspecific functional dyspepsia were significantly greater than that in healthy controls. The number of enterochromaffin cells (ECs) in post-infectious functional dyspepsia was significantly higher than those in nonspecific functional dyspepsia or in healthy controls. The number of mast cells and ECs increased with the density of chronic inflammatory cells. The release of histamine and 5-hydroxytryptamine from gastric mucosa of post-infectious functional dyspepsia patients was significantly greater than those from nonspecific functional dyspepsia or healthy controls. Tryptase protein expression was higher in post-infectious functional dyspepsia and nonspecific functional dyspepsia than in healthy controls. The histological score of chronic gastric inflammation was greater in post-infectious functional dyspepsia versus patients with nonspecific functional dyspepsia or healthy controls. Electron microscopy showed secreting granules in the cytoplasm of both mast cells and ECs. The number of activated mast cells and Ecs at a distance of < 5 microm of nerve fibers were significantly greater in post-infectious functional dyspepsia versus nonspecific functional dyspepsia or controls.

CONCLUSIONS

Dyspepsia may occur after an acute onset of gastroenteritis in a part of patients. Potent chemicals derived from mast cells and ECs, including histamine, tryptase and 5-hydroxytryptamine may be involved in the pathogenesis of post-infectious functional dyspepsia.

Intestinal immune activation in presumed post-infectious functional dyspepsia

Functional dyspepsia (FD) symptoms may develop after an acute gastroenteritis. In post-infectious (PI) irritable bowel syndrome, persisting low-grade colonic inflammation and increased enterochromaffine cells (EC) counts have been reported. The aim was to compare signs of inflammation and EC hyperplasia on duodenal biopsies in presumed PI-FD and unspecified-onset (U-)FD. Duodenal biopsies were obtained in 12 U-FD and 12 PI-FD (on average 13 months after the acute event) patients. The presence of intra-epithelial, intravillar, and the number of CD3, CD4, CD8 and CD68+ cells per crypts, and the mean number of Chromogranine A (CA) positive cells per villus were compared. We also measured gastric emptying and assessed proximal stomach function with a barostat. Data are shown as mean +/- SEM. Focal aggregates of T cells and focal CD8+ aggregates, were found in PI-FD but not in U-FD patients (respectively 5/12 vs 0/12, P = 0.02 and 5/9 vs 0/11, P < 0.01). In patients with focal aggregates, gastric emptying was delayed (189 +/- 37 min vs 98 +/- 11 min, P = 0.002). The number of CD4+ cells per crypt (0.52 +/- 1.6 vs 1.22 +/- 2.18, P = 0.04), and the number of intravillar CD4+ cells (0.5 +/- 0.2 vs 2.7 +/- 0.7, P = 0.01) were reduced, while the number of CD68+ cells per crypt was increased (0.64 +/- 0.13 vs 0.40 +/- 0.05, P = 0.03) in PI-FD. The number of EC and CA were comparable. PI-FD is associated with persisting focal T-cell aggregates, decreased CD4+ cells and increased macrophage counts surrounding the crypts. This may indicate impaired ability of the immune system to terminate the inflammatory response after acute insult.

Applied principles of neurogastroenterology: physiology/motility sensation

Many of the symptoms prominent in the functional gastrointestinal disorders (FGIDs) are consistent with dysfunction of the sensory and/or motor apparatus of the digestive tract. Assessment of these phenomena in man can be undertaken by using a wide variety of invasive and noninvasive techniques, some well established and others requiring further validation. By using such techniques, alterations in both sensory and motor function have been reported in the FGIDs; various combinations of such dysfunction occur in different regions of the digestive tract in the FGIDs. Our understanding of the origins of this gut sensorimotor dysfunction is gradually increasing. Thus, inflammatory, immunologic, and other processes, as well as psychosocial factors such as stress, can alter the normal patterns of sensitivity and motility through alterations in local reflex activity or via altered neural processing along the brain-gut axis. In this context, a potential role of genetic factors, early-life influences, enteric flora, dietary components, and autonomic dysfunction also should be considered in the disease model. A firm relationship between sensorimotor dysfunction and the production of symptoms, however, has been difficult to show, and so the clinical relevance of the former requires continuing exploration. Based on the conceptual framework established to date, a number of recommendations for further progress can be made.

Importance of changes in epithelial cell turnover during Helicobacter pylori infection in gastric carcinogenesis

The role of Helicobacter pylori in gastric carcinogenesis is supported almost exclusively by epidemiological data and prospective histopathological studies. From biological and molecular points of view, there is no evidence that H pylori or its cytotoxic products have any mutagenic effects. Nevertheless, this infection is associated with profound changes in the pattern of epithelial cell turnover in gastric glands, though the importance of these changes in gastric carcinogenesis is still controversial. H pylori infection increases cell proliferation and alters the distribution of cycling cells within these glands, but these changes can be reversed by successful eradication of the infection. Apoptosis seems to be increased in gastric epithelial cells during H pylori infection, as shown by in vitro studies. There is some, though no conclusive, evidence that this finding also occurs in H pylori positive subjects. It seems that cagA status influences the effect of H pylori on epithelial apoptosis in infected patients. An association of in vitro H pylori induced apoptosis with changes in the expression of pro- and anti-apoptotic genes is reported in the literature, but further study is necessary to clarify the effect of H pylori infection on the molecular events of the apoptotic pathway.

Effect of eradication of Helicobacter pylori on gastric epithelial cell proliferation

BACKGROUND

Helicobacter pylori is associated with B-type gastritis, duodenal ulcer disease, and possibly gastric carcinoma. The object of this study was to assess the effect of eradication of H. pylori infection on gastric epithelial cell proliferation.

METHODS

Gastric epithelial cell proliferation was assessed in 22 H. pylori-positive duodenal ulcer patients before and 6 weeks after 'triple therapy' with bismuth, tetracycline and metronidazole. Cell proliferation was studied either by immunostaining for the proliferating cell nuclear antigen (PCNA) or by a microdissection technique.

RESULTS

Eradication was successful in 10 of the 22 H. pylori-positive patients. Treatment with 'triple therapy' resulted in a significant fall in the rate of gastric epithelial cell proliferation; this effect was seen in both the gastric body and antrum. There was a significant correlation between the number of PCNA-labelled cells and the histological grade of activity (neutrophil inflammation) (r = 0.49, P = 0.02); the same correlation was found for the number of mitoses per gland (r = 0.5, P = 0.02). There was no significant difference in the treatment effect for eradicated or non-eradicated patients or either the body or antrum. Six patients, who had at least one antral biopsy that showed evidence of focal intestinal metaplasia, had a higher rate of cell proliferation.

CONCLUSIONS

The reduction in epithelial cell proliferation in the body and antrum after triple therapy is independent of successful eradication of H. pylori, and it may be due to an anti-inflammatory effect of triple therapy.

Is the irritable gut an inflamed gut?

Recent advances in the field of neuroimmunology have provided clear demonstrations of i) the neuromodulation of immune function, and ii) the involvement of the immune system in responses induced by psychologic stress in animals and in man. This has led to speculation about the role of the immune system in psychosocial disease. The irritable bowel syndrome (IBS) is characterized by chronic gastrointestinal dysfunction, which may reflect in altered motility, epithelial function, or sensory perception in the gut. IBS is heterogeneous not only in terms of its clinical presentation but also in terms of its pathogenesis, and factors ranging from psychoneurotic behavior and emotional stress, to dietary fiber deficiency, food intolerance, and enteric infection have been implicated. There is evidence of an increase in the inflammatory cells present in the gut of some IBS patients and in an emerging literature that demonstrates the immunomodulation of the motor system of the gut. These findings invite speculation that the immune system may play a role in the pathogenesis and pathophysiology of at least a subpopulation of IBS patients.

Mucosal humoral immune response to Helicobacter pylori in patients with duodenitis

The humoral immune response to Helicobacter pylori infection in the duodenum has been investigated by short-term in vitro culture, ELISA, and immunoblotting techniques. H. pylori IgA secretion by duodenal bulb biopsies was significantly increased (P less than 0.001) in patients with duodenitis. The IgA response to H. pylori in patients with duodenitis was restricted to the first part of the duodenum; second part duodenal biopsies secreting significantly (P less than 0.001) less IgA during culture in vitro. H. pylori IgG antibody secretion by cultured biopsies was also significantly increased (P less than 0.01) in patients with duodenitis and those with gastric H. pylori infection but without duodenitis. Immunoblotting of duodenal bulb culture supernatants showed positive recognition by the mucosal IgA response of H. pylori antigens in the region of 120, 90, 61, and 31-26 kDa in patients with duodenitis. Serologically, such patients showed little evidence of IgA H. pylori antibodies by immunoblotting. These results demonstrate that the inflammatory response in the duodenal mucosa of patients with duodenitis represents a specific highly localized humoral response to H. pylori.