Structure and function of endocrine cells in the oxyntic (acid-secreting) mucosa of human stomach

Influence of hypergastrinemia secondary to long-term proton pump inhibitor treatment on ECL cell tumorigenesis in human gastric mucosa

Proton pump inhibitor (PPI) therapy causes hypergastrinemia, which could promote the development and progression of neuroendocrine tumors (NETs). Concerns have been raised about the safety of long-term PPI use due to a possible increased risk of NETs. This study aimed to investigate the association between hypergastrinemia and the risk of NETs. Twenty outpatients presenting with serum gastrin levels greater than 400 pg/mL after long-term PPI treatment were registered in this study. Immunohistochemical analyses for chromogranin A (CgA), Ki67, gastrin and CCK/B gastrin receptor (CCKBR) were performed, and positive cell numbers were counted. There were no NET or gastric epithelial neoplasia cases observed among any of the 20 patients examined throughout the PPI treatment period. Histologically, ECL cell hyperplasia were shown in all patients. However, no relationship was found between serum gastrin levels and the number of CgA positive ECL cells. There was also no relationship between serum gastrin levels and the proportion of Ki67 positive cells or the density of CCKBR positive cells. The data indicate no relationship may exist between NETs and hypergastrinemia secondary to PPI treatment in patients having no, or mild, atrophic gastritis.

IL-10 Plays a Pivotal Role in Tamoxifen-Induced Spasmolytic Polypeptide-Expressing Metaplasia in Gastric Mucosa

Background/Aims

Gastric cancer evolves in the pathologic mucosal milieu, and its development is characterized by both the loss of acid-secreting parietal cells and mucosal cell metaplasia, called spasmolytic polypeptide-expressing metaplasia (SPEM). Cytokines, such as interleukin (IL)-10, IL-1β, and IL-6, play a key role in gastric carcinogenesis. However, changes in the cytokine profile of SPEM have not been evaluated.

Methods

To induce SPEM in mouse stomachs, C57BL/6 mice were intraperitoneally injected with tamoxifen and sacrificed at 3, 10, and 21 days after treatment. RNA-sequencing (RNA-seq) and a multiplex bead array were used to measure cytokines in the stomachs of tamoxifen-treated/control mice.

Results

The administration of tamoxifen led to the rapid development and histological normalization of SPEM 3 and 10 days after administration, respectively. RNA-seq revealed that the expression of IL-10 was decreased 3 days after tamoxifen administration. The multiplex assay identified a significant decline in IL-10 levels 3 days after tamoxifen treatment (58.38±34.44 pg/mL vs 94.09±4.98 pg/mL, p=0.031), which normalized at 10 and 21 days after tamoxifen treatment. Immunofluorescence staining confirmed that IL-10 expression was markedly decreased at the time of SPEM development and subsequently returned to normal, accompanied by a reversal in histologic changes.

Conclusions

IL-10 may play a pivotal role in the tamoxifen-induced acute development of gastric SPEM.

Changes of gastric mucosal architecture during long-term omeprazole therapy: results of a randomized clinical trial

BACKGROUND

The impact of long-term acid suppression on the gastric mucosa remains controversial.

AIM

To report further observations on an established cohort of patients with gastro-oesophageal reflux disease, after 7 years of follow-up.

METHODS

Of the original cohort randomized to either antireflux surgery or omeprazole, 117 and 98 patients remained in the medical and surgical arms, respectively. Gastric biopsies were taken at baseline and throughout the study.

RESULTS

Fifty-three antireflux surgery and 39 omeprazole-treated patients had Helicobacter pylori infection at randomization. Eighty-three omeprazole-treated and 60 antireflux surgery patients remained H. pylori negative over the 7 years, and no change was observed in mucosal morphology except for a change in endocrine cell population (linear and diffuse hyperplasia, P = 0.03). During the 7-year study many patients, who were initially H. pylori infected, had the infection eradicated leaving only 13 omeprazole and 12 antireflux surgery patients still infected. In these patients, omeprazole induced a deterioration of the mucosal inflammation scores (P = 0.01) with a numerical increase of glandular atrophy.

CONCLUSIONS

Long-term omeprazole therapy does not alter the exocrine oxyntic mucosal morphology in H. pylori-negative patients, but mucosal endocrine cells appear to be under proliferative stimulation; in H. pylori-positive patients there are changes in mucosal inflammation and atrophy.

Ultrastructural immunohistochemical localization of gastrin, somatostatin and serotonin in endocrine cells of human antral gastric mucosa

Five types of endocrine cells are found in the human antral gastric mucosa: gastrin (G) cells, somatostatin (D) cells, enterochromaffin (EC) cells and cells with an unknown secretory product (D1 cells and P cells). The content of secretory granules, gastrin, somatostatin and serotonin, was evaluated using electron microscopic immunohistochemistry and was compared with the granular content in G cells, D cells and EC cells as determined by routine electron microscopy. Semi-quantitative scoring of the granular content was performed on a scale 1-4 (empty-full). The content of gastrin (2.5 +/- 0.2) and somatostatin (3.3 +/- 0.2) in the granules was not different from the granular content in G cells (2.5 +/- 0.3; p > 0.05) and D cells (3.5 +/- 0.2; p > 0.05). Gastrin was also found in G cells in a nongranular form. The content of serotonin in granules (2.8 +/- 0.3) was smaller than the granular content in EC cells (3.7 +/- 0.2; p < 0.05). In intermediate-full and intermediate-empty granules, serotonin was localized in the periphery of granules whereas the granular content in EC cells was localized in an eccentric or central pattern. The granular content of D1 cells and P cells was 3.8 +/- 0.2, and 3.4 +/- 0.2, respectively. It is concluded that gastrin and somatostatin immunostaining in granules of G cells and D cells reflects the granular content in G cells and D cells, respectively, whereas serotonin immunostaining does not agree with the granular content of EC cells.

Changes in gastric mucosa and luminal environment during acid-suppressive therapy: a review in depth

Acid-suppressive therapy and subsequent changes in gastric mucosa and luminal environment rank highly amongst the investigated issues in gastroenterology over the past two to three decades. Herewith, we present an overview of these intragastric changes, particularly during long-term administration of acid-suppresive medication and concurrent infection with Helicobacter pylori. Current evidence indicates that: i) Long-term acid suppression facilitates the development of fundic ECL cell hyperplasia, especially in the presence of Helicobacter pylori. No neoplastic changes directly attributable to acid suppression have so far been demonstrated in humans. ii) Acid-suppressive therapy increases the risk of enteric infections. iii) Acid-suppressive therapy does not alter fat and mineral bioavailability, but may decrease the absorption of protein-bound vitamin B12. iv) Acid suppression invariably results in intragastric overgrowth of non-Helicobacter pylori bacterial species. The concurrent infection with Helicobacter pylori may promote this bacterial overgrowth and the intragastric formation of N-nitrosamines. v) Acid-suppressive therapy alters the natural course of Helicobacter pylori gastritis, transforming the antral-predominant pattern into a body-predominant pattern, which in turn may progress to body gland atrophy. The pathophysiology of this phenomenon is currently under investigation. vi) In view of the potential adverse effects of acid suppression in the presence of Helicobacter pylori, the screen-and-treat strategy is advocated for Helicobacter pylori in subjects considered for long-term treatment.

Electron microscopic immunohistochemical investigation of chromogranin A in endocrine cells in human oxyntic gastric mucosa

Human oxyntic gastric mucosa harbours 6 types of endocrine cells: enterochromaffin-like (ECL) cells, enterochromaffin (EC) cells, somatostatin (D) cells, and cells with an unknown secretory product (P cells, D1 cells and X (A-like) cells). In the present study, intracellular localization and granular content of chromogranin A (CGA) in these cells have been investigated by electron microscopic immunohistochemistry. The content of CGA in granules of the various types of endocrine cells was evaluated and compared with the content of serotonin and somatostatin in EC cells and D cells, respectively. ECL cells, EC cells, P cells, D1 cells and X cells contained CGA in their granules, whereas D cells did not. CGA granular content in ECL cells, P cells, D1 cells and X cells was 3.39 +/- 0.17, 3.41 +/- 0.21, 3.58 +/- 0.18, and 3.55 +/- 0.09, respectively. In ECL cells, CGA was also found in a nongranular form. The CGA content in EC cells (2.95 +/- 0.21) was not significantly different from the serotonin content (2.82 +/- 0.11; p > 0.05) which is in line with the basic significance of CGA as potential amine storage and release protein. The somatostatin content in D cells was 3.30 +/- 0.15. Our study has established high content of CGA in granules of all types of endocrine cells in human oxyntic gastric mucosa except in D cells.

Ultrastructural morphometry of gastric endocrine cells before and after omeprazole. A study in the oxyntic mucosa of duodenal ulcer patients

Long-term toxicological experiments with inhibitors of acid secretion were found to induce hyperplasia and eventually carcinoid tumors of the enterochromaffin-like cells of the oxyntic mucosa. To evaluate the effects of 6 months' treatment with omeprazole in humans, the oxyntic endocrine cells were morphometrically investigated at the ultrastructural level in five patients with active duodenal ulcer. No omeprazole-induced changes were found in the volume density of the total endocrine cell population and specific cell types (including the enterochromaffin-like cell) as well as in the other cytological parameters investigated (number of cell profiles per unit area, mean cross-sectional area of cell profiles, nuclear-cytoplasmic ratio, and density of cytoplasmic secretory granules). Both pretreatment and post-treatment values in our patients with duodenal ulcer significantly differed from those of a previous investigation of healthy volunteers with regard to the volume density of enterochromaffin-like cells and non-granulated cells, which increased, and of D cells, which markedly decreased. The latter result may provide a cellular basis for impairment in the paracrine release of fundic somatostatin in peptic ulcer disease. Finally, morphometric data on endocrine cell volume density provided by electron microscopy were found to correlate with those obtained in the same patients using light microscopy techniques (Grimelius silver impregnation and chromogranin A immunostaining). It is concluded that 6 months' treatment with pharmacological doses of omeprazole is devoid of appreciable trophic effect on endocrine cells of human oxyntic mucosa.

Is hypergastrinaemia dangerous to man?

Achlorhydria has been discussed as a possibly dangerous consequence of therapeutic inhibition of gastric acid secretion since the introduction of H2-receptor antagonists. The risk of long-term hypergastrinaemia has only been considered for about 5 years. The reason for this was the demonstration that gastric carcinoids (ECLomas) observed after life-long treatment of rats with the proton pump inhibitor omeprazole could also be produced in rats by other methods leading to long-lasting profound hypergastrinaemia. Such methods were the 80% resection of the oxyntic mucosa or feeding of ranitidine (2000 mg/day) for 2 years. The endocrine tumours corresponded to the gastric carcinoids found in patients with long-lasting hypergastrinaemia due to pernicious anaemia or with a gastrinoma as part of the MEN I syndrome. Neither in animals nor in man could other endocrine tumours or adenocarcinomas of the gastrointestinal tract be related to hypergastrinaemia. Epidemiologic data do not support gastrin dependence of adenocarcinoma of the stomach or the colon. Experimental findings of gastrin effects on tumour growth in vivo and in vitro have been contradictory and may be explained by the presence of gastrin receptors on tumour cells and the role of gastrin as an autocrine growth factor in some of these tumours. Since acid blockade by proton pump inhibitors or H2-receptor blockers dose-dependently increase serum gastrin levels, patients with ranitidine-resistant peptic ulceration receiving long-term treatment with high-dose omeprazole have been followed up with serial gastric biopsy specimens for up to 5 years. Complete healing, moderate hypergastrinaemia, and a slight hyperplasia but no dysplasia of the ECL cells in the oxyntic mucosa have been observed, which seemed to be correlated to chronic gastritis progressing over the years. Despite these negative findings excessive hypergastrinaemia by overdosage of potent drugs for inhibition of gastric secretion should be avoided and monitoring of plasma gastrin levels is recommended in case of long-term treatment.