Hypergastrinemia in response to gastric inflammation suppresses somatostatin

Gastrin and the Moderate Hypergastrinemias

The antral hormone gastrin potently regulates gastric acid secretion and fundic mucosal growth. Consequently, appropriate gastrin secretion and plasma concentrations are important for the early phases of digestion. This review describes as the first premise the normal biogenesis of gastrin in the antral mucosa, but also mentions the extraantral expression. Subsequently, the molecular nature and concentration levels of gastrin in serum or plasma are overviewed. Third, assays for accurate measurements of plasma or serum concentrations are commented. Finally, the problem of moderate hypergastrinemia due to Helicobacter pylori infections and/or treatment with proton-pump inhibitors (PPI) is discussed. The review concludes that accurate measurement of the true concentrations of bioactive gastrins in plasma is important. Moreover, it suggests that moderate hypergastrinemias are also essential health issues that require serious attention.

Gastric Peptides-Gastrin and Somatostatin

Gastric acid secretion (i) facilitates digestion of protein as well as absorption of micronutrients and certain medications, (ii) kills ingested microorganisms, including Helicobacter pylori, and (iii) prevents bacterial overgrowth and enteric infection. The principal regulators of acid secretion are the gastric peptides gastrin and somatostatin. Gastrin, the major hormonal stimulant for acid secretion, is synthesized in pyloric mucosal G cells as a 101-amino acid precursor (preprogastrin) that is processed to yield biologically active amidated gastrin-17 and gastrin-34. The C-terminal active site of gastrin (Trp-Met-Asp-Phe-NH₂ ) binds to gastrin/CCK₂ receptors on parietal and, more importantly, histamine-containing enterochromaffin-like (ECL) cells, located in oxyntic mucosa, to induce acid secretion. Histamine diffuses to the neighboring parietal cells where it binds to histamine H₂ -receptors coupled to hydrochloric acid secretion. Gastrin is also a trophic hormone that maintains the integrity of gastric mucosa, induces proliferation of parietal and ECL cells, and is thought to play a role in carcinogenesis. Somatostatin, present in D cells of the gastric pyloric and oxyntic mucosa, is the main inhibitor of acid secretion, particularly during the interdigestive period. Somatostatin exerts a tonic paracrine restraint on gastrin secretion from G cells, histamine secretion from ECL cells, and acid secretion from parietal cells. Removal of this restraint, for example by activation of cholinergic neurons during ingestion of food, initiates and maximizes acid secretion. Knowledge regarding the structure and function of gastrin, somatostatin, and their respective receptors is providing novel avenues to better diagnose and manage acid-peptic disorders and certain cancers. Published 2020. Compr Physiol 10:197-228, 2020.

Helicobacter pylori-Induced Changes in Gastric Acid Secretion and Upper Gastrointestinal Disease

Appropriate management of Helicobacter pylori infection of the human stomach is evolving and remains a significant clinical challenge. Acute infection results in hypochlorhydria, whereas chronic infection results in either hypo- or hyperchlorhydria, depending upon the anatomic site of infection. Acute hypochlorhydria facilitates survival of the bacterium and its infection of the stomach. Interestingly, most patients chronically infected with H. pylori manifest a pangastritis with reduced acid secretion due to bacterial virulence factors, inflammatory cytokines, and various degrees of gastric atrophy. While these patients are predisposed to develop gastric adenocarcinoma (~1%), there is increasing evidence from population studies that they are also protected from gastroesophageal reflux disease (GERD), Barrett's esophagus (BE), and esophageal adenocarcinoma (EAC). Eradication of H. pylori, in these patients, may provoke GERD in predisposed individuals and may be a contributory factor for the rising incidence of refractory GERD, BE, and EAC observed in Westernized societies. Only ~10% of chronically infected patients, mainly the young, manifest an antral predominant gastritis with increased acid secretion due to a decrease in somatostatin and increase in gastrin secretion; these patients are predisposed to develop peptic ulcer disease. H. pylori-induced changes in acid secretion, in particular hypochlorhydria, may allow ingested microorganisms to survive transit through the stomach and colonize the distal intestine and colon. Such perturbation of gut microbiota, i.e. dysbiosis, may influence human health and disease.

CagA-positive Helicobacter pylori strain containing three EPIYA C phosphorylation sites produces increase of G cell and decrease of D cell in experimentally infected gerbils (Meriones unguiculatus)

PURPOSE

Human infection by Helicobacter pylori is associated with an increase in the number of gastrin-producing G cells and a concomitant decrease of somatostatin-producing D cells. However, to our knowledge, changes in G and D cell numbers in response to infection with H. pylori CagA-positive strains containing different number of EPIYA-C phosphorylation sites have not been analyzed to date. Therefore, the aim of this study was to perform a quantitative analysis of the number of G and D cells in Mongolian gerbils challenged with H. pylori strains with different numbers of EPIYA-C motifs.

MATERIALS AND METHODS

Mongolian gerbils were inoculated with isogenic H. pylori strains containing one to three phosphorylation sites. Mucosal fragments were evaluated by morphometry and immunohistochemistry using primary polyclonal rabbit anti-gastrin and anti-somatostatin antibodies. Positive cells were counted using an image analyzer.

RESULTS

Forty-five days after infection, there was a decrease in the number of D cells and an increase in the G/D cell ratio in the group with three EPIYA-C. Six months after infection, there was a progressive and significant increase in the number of G cells and in the G/D cell ratio, with a concomitant decrease in the number of D cells, especially in the three EPIYA-C group.

CONCLUSIONS

CagA-positive H. pylori strains containing a large number of EPIYA-C phosphorylation sites induce a decrease in D cell number and an increase in G cell number and G/D ratio, which were correlated with the number of inflammatory cells of the lamina propria.

Helicobacter pylori virulence genes and host genetic polymorphisms as risk factors for peptic ulcer disease

Helicobacter pylori infection plays an important role in the pathogenesis of peptic ulcer disease (PUD). Several factors have been proposed as possible H. pylori virulence determinants; for example, bacterial adhesins and gastric inflammation factors are associated with an increased risk of PUD. However, differences in bacterial virulence factors alone cannot explain the opposite ends of the PUD disease spectrum, that is duodenal and gastric ulcers; presumably, both bacterial and host factors contribute to the differential response. Carriers of the high-producer alleles of the pro-inflammatory cytokines IL-1B, IL-6, IL-8, IL-10, and TNF-α who also carry low-producer allele of anti-inflammatory cytokines have severe gastric mucosal inflammation, whereas carriers of the alternative alleles have mild inflammation. Recent reports have suggested that the PSCA and CYP2C19 ultra-rapid metabolizer genotypes are also associated with PUD.

Indian Hedgehog mediates gastrin-induced proliferation in stomach of adult mice

BACKGROUND & AIMS

Loss of expression of Sonic Hedgehog (Shh) from parietal cells results in hypergastrinemia in mice, accompanied by increased expression of Indian Hedgehog (Ihh) and hyperproliferation of surface mucous cells. We investigated whether hypergastrinemia induces gastric epithelial proliferation by activating Ihh signaling in mice.

METHODS

We studied mice with parietal cell-specific deletion of Shh (PC-Shh(KO)) and hypergastrinemia, crossed with gastrin-deficient (GKO) mice (PC-Shh(KO)/GKO). When mice were 3-4 months old, gastric tissues were collected and analyzed by histology, for incorporation of bromodeoxyuridine, and for expression of the surface mucous cell marker Ulex europaeus. PC-Shh(KO)/GKO mice were given gastrin infusions for 7 days; gastric surface epithelium was collected and expression of Ihh was quantified by laser capture microdissection followed by quantitative reverse transcriptase polymerase chain reaction. Mouse stomach-derived organoids were incubated with or without inhibitors of WNT (DKK1) or Smoothened (vismodegib) and then cocultured with immortalized stomach mesenchymal cells, to assess proliferative responses to gastrin.

RESULTS

Gastric tissues from PC-Shh(KO)/GKO mice with hypergastrinemia had an expanded surface pit epithelium, indicated by a significant increase in numbers of bromodeoxyuridine- and Ulex europaeus-positive cells, but there was no evidence for hyperproliferation. Gastrin infusion of PC PC-Shh(KO)/GKO mice increased expression of Ihh and proliferation within the surface epithelium compared with mice given infusions of saline. In gastric organoids cocultured with immortalized stomach mesenchymal cells, antagonists of WNT and Smoothened inhibited gastrin-induced proliferation and WNT activity. Activity of WNT in media collected from immortalized stomach mesenchymal cells correlated with increased expression of glioma-associated oncogene homolog 1, and was inhibited by DKK1 or vismodegib.

CONCLUSIONS

Ihh signaling mediates gastrin-induced proliferation of epithelial cells in stomachs of adult mice.

Role of the Helicobacter pylori-induced inflammatory response in the development of gastric cancer

Helicobacter pylori (H. pylori) infection causes chronic gastritis and peptic ulceration and is the strongest risk factor for the development of gastric cancer. The pathogenesis of H. pylori is believed to be associated with infection-initiated chronic gastritis, which is characterized by enhanced expression of many inflammatory genes. H. pylori utilizes various virulence factors, targeting different cellular proteins, to modulate the host inflammatory response. In this review, we explore the many different ways by which H. pylori initiates inflammation, leveling many "hits" on the gastric mucosa which can lead to the development of cancer. We also discuss some recent findings in understanding the pathogen-host interactions and the role of transcription factor NF-κB in H. pylori-induced inflammation.

Omeprazole and PGC-formulated heparin binding epidermal growth factor normalizes fasting blood glucose and suppresses insulitis in multiple low dose streptozotocin diabetes model

PURPOSE

Our objective was to develop novel nanocarriers (protected graft copolymer, PGC) that improve the stability of heparin binding EGF (HBEGF) and gastrin and then to use PGC-formulated HBEGF (PGC-HBEGF) and Omeprazole (+/- PGC-gastrin) for normalizing fasting blood glucose (FBG) and improving islet function in diabetic mice.

METHODS

HBEGF, PGC-HBEGF, Omeprazole, Omeprazole + PGC-HBEGF, Omeprazole + PGC-gastrin + PGC-HBEGF and epidermal growth factor (EGF) + gastrin were tested in multiple low dose streptozotocin diabetic mice.

RESULTS

Omeprazole + PGC-HBEGF normalized FBG and is better than EGF + gastrin at improving islet function and decreasing insulitis. Groups treated with Omeprazole, Omeprazole + PGC-HBEGF, or EGF + gastrin have significantly improved islet function versus saline control. All animals that received PGC-HBEGF had significantly reduced islet insulitis versus saline control. Non-FBG was lower for Omeprazole + PGC-gastrin + PGC-HBEGF but Omeprazole + PGC-HBEGF alone showed better FBG and glucose tolerance.

CONCLUSIONS

Omeprazole + PGC-HBEGF provides a sustained exposure to both EGFRA and gastrin, improves islet function, and decreases insulitis in multiple low dose streptozotocin diabetic mice. Although HBEGF or EGF elevates non-FBG, it facilitates a reduction of insulitis and, in the presence of Omeprazole, provides normalization of FBG at the end of treatment. The study demonstrates Omeprazole and PGC-HBEGF is a viable treatment for diabetes.

H. pylori acutely inhibits gastric secretion by activating CGRP sensory neurons coupled to stimulation of somatostatin and inhibition of histamine secretion

Acute Helicobacter pylori infection produces hypochlorhydria. The decrease in acid facilitates survival of the bacterium and its colonization of the stomach. The present study was designed to identify the pathways in oxyntic mucosa by which acute H. pylori infection inhibits acid secretion. In rat fundic sheets in an Ussing chamber, perfusion of the luminal surface with H. pylori in spent broth (10(3)-10(8) cfu/ml) or spent broth alone (1:10(5) to 1:10(0) final dilution) caused a concentration-dependent increase in somatostatin (SST; maximal: 200 ± 20 and 194 ± 9% above basal; P < 0.001) and decrease in histamine secretion (maximal: 45 ± 5 and 48 ± 2% below basal; P < 0.001); the latter was abolished by SST antibody, implying that changes in histamine secretion reflected changes in SST secretion. Both responses were abolished by the axonal blocker tetrodotoxin (TTX), the sensory neurotoxin capsaicin, or the CGRP antagonist CGRP8-37, implying that the reciprocal changes in SST and histamine secretion were due to release of CGRP from sensory neurons. In isolated rabbit oxyntic glands, H. pylori inhibited basal and histamine-stimulated acid secretion in a concentration-dependent manner; the responses were not affected by TTX or SST antibody, implying that H. pylori can directly inhibit parietal cell function. In conclusion, acute administration of H. pylori is capable of inhibiting acid secretion directly as well as indirectly by activating intramural CGRP sensory neurons coupled to stimulation of SST and inhibition of histamine secretion. Activation of neural pathways provides one explanation as to how initial patchy colonization of the superficial gastric mucosa by H. pylori can acutely inhibit acid secretion.

Conditional deletion of menin results in antral G cell hyperplasia and hypergastrinemia

Antral gastrin is the hormone known to stimulate acid secretion and proliferation of the gastric corpus epithelium. Patients with mutations in the multiple endocrine neoplasia type 1 (MEN1) locus, which encodes the protein menin, develop pituitary hyperplasia, insulinomas, and gastrinomas in the duodenum. We previously hypothesized that loss of menin leads to derepression of the gastrin gene and hypergastrinemia. Indeed, we show that menin represses JunD induction of gastrin in vitro. Therefore, we examined whether conditional deletion of Men1 (Villin-Cre and Lgr5-EGFP-IRES-CreERT2), with subsequent loss of menin from the gastrointestinal epithelium, increases gastrin expression. We found that epithelium-specific deletion of Men1 using Villin-Cre increased plasma gastrin, antral G cell numbers, and gastrin expression in the antrum, but not the duodenum. Moreover, the mice were hypochlorhydric by 12 mo of age, and gastric somatostatin mRNA levels were reduced. However, duodenal mRNA levels of the cyclin-dependent kinase inhibitor p27(Kip1) were decreased, and cell proliferation determined by Ki67 staining was increased. About 11% of the menin-deficient mice developed antral tumors that were negative for gastrin; however, gastrinomas were not observed, even at 12 mo of age. No gastrinomas were observed with conditional deletion of Men1 in the Lgr5 stem cells 5 mo after Cre induction. In summary, epithelium-specific deletion of the Men1 locus resulted in hypergastrinemia due to antral G cell hyperplasia and a hyperproliferative epithelium, but no gastrinomas. This result suggests that additional mutations in gene targets other than the Men1 locus are required to produce gastrin-secreting tumors.

Environmental - lifestyle related factors

The prevalence of gastro-oesophageal reflux disease (GORD) has been increasing worldwide. This increase is likely associated with the increased prevalence of obesity, the ageing of the population and the decreased prevalence of Helicobacter pylori (Hp) infection. These different environmental factors interact with GORD pathogenesis in a potentially negative way. Oesophago-gastric junction (OGJ) competence, oesophageal clearance mechanisms and reflux causticity are involved in GORD pathophysiology. Obesity alters GORD pathogenesis by disrupting the OGJ and increasing intragastric pressure. Additionally, the number of transient lower oesophageal sphincter relaxations is potentially increased in obese patients. The potential effect of obesity on oesophageal peristalsis and the implication of impaired oesophageal clearance in GORD pathogenesis are still to establish. Ageing also plays an important role in GORD pathogenesis by decreasing lower oesophageal sphincter pressure and impairing oesophageal clearance. However a link between these abnormalities and an increased acid oesophageal exposure has not yet been demonstrated in the elderly. The role of H. pylori and its eradication remain controversial. The type of Hp gastritis may explain the controversial effect. Hp with antral predominant gastritis is responsible for an increased gastric acid secretion and thus promotes GORD. On the opposite spectrum, Hp with diffuse gastritis induces a gastric atrophy and in this particular case, the Hp eradication may restore acid secretion and lead to a more caustic refluxate in patients with predisposing conditions for GORD. The association of GORD and the type of Hp gastritis remains to be confirmed.

Bone morphogenetic protein signaling regulates gastric epithelial cell development and proliferation in mice

BACKGROUND & AIMS

We investigated the role of bone morphogenetic protein (BMP) signaling in the regulation of gastric epithelial cell growth and differentiation by generating transgenic mice that express the BMP inhibitor noggin in the stomach.

METHODS

The promoter of the mouse H+/K+-ATPase β-subunit gene, which is specifically expressed in parietal cells, was used to regulate expression of noggin in the gastric epithelium of mice. The transgenic mice were analyzed for noggin expression, tissue morphology, cellular composition of the gastric mucosa, gastric acid content, and plasma levels of gastrin. Tissues were analyzed by immunohistochemical, quantitative real-time polymerase chain reaction, immunoblot, microtitration, and radioimmunoassay analyses.

RESULTS

In the stomachs of the transgenic mice, phosphorylation of Smad 1, 5, and 8 decreased, indicating inhibition of BMP signaling. Mucosa were of increased height, with dilated glands, cystic structures, reduced numbers of parietal cells, and increased numbers of cells that coexpressed intrinsic factor, trefoil factor 2, and Griffonia (Bandeiraea) simplicifolia lectin II, compared with wild-type mice. In the transgenic mice, levels of the H+/K+-ATPase α-subunit protein and messenger RNA were reduced, whereas those of intrinsic factor increased. The transgenic mice were hypochloridric and had an increased number of Ki67- and proliferating cell nuclear antigen-positive cells; increased levels of plasma gastrin; increased expression of transforming growth factor-α, amphiregulin, and gastrin; and activation of extracellular signal-regulated kinase 2.

CONCLUSIONS

Inhibiting BMP signaling in the stomachs of mice by expression of noggin causes loss of parietal cells, development of transitional cells that express markers of mucus neck and zymogenic lineages, and activation of proliferation. BMPs are therefore important regulators of gastric epithelial cell homeostasis.

Influence of cigarette smoking on the level of mRNA of somatostatin receptor 3 (SSTR3) in the gastric mucosa of patients with functional dyspepsia

PURPOSE

Helicobacter pylori (H. pylori) infection and smoking of cigarettes increase individual risk to gastric carcinoma. In stomach tumors, an expression of somatostatin receptor 3 (SSTR3) is diminished or completely lost. The purpose of these studies was to determine the influence of smoking cigarettes and H. pylori infection on the expression of SSTR3 in patients with functional dyspepsia.

MATERIALS AND METHODS

The study comprised 109 patients with functional dyspepsia in the age range 28-61 years. The total 218 biopsies used for analysis were divided into two groups: group I - 176 biopsies from non-smokers (72 from H. pylori positive ones), and group II - 42 biopsies from cigarette smokers (28 from H. pylori positive patients). The SSTR3 mRNA amount in the gastric mucosa (1 biopsy from the antrum and 1 biopsy from the corpus) was determined by real time RT-PCR. The presence of H. pylori colonization in the stomach tissue was evaluated by multiplex PCR.

RESULTS

In the H. pylori negative samples the amount of the SSTR3 mRNA was significantly lower for smokers than for non-smokers (by 40%, p < 0.010). Infection with H. pylori caused reduction of the level of SSTR3 mRNA in non-smoking patients by ca. 30% (p < 0.01), while in samples from smokers the SSTR3 mRNA level was similar regardless of H. pylori infection.

CONCLUSIONS

The cigarettes smoking and H. pylori infection are independent factors leading to decreasing of the SSTR3 mRNA level in gastric mucosa of patients with functional dyspepsia.

Short-term therapy with celecoxib and lansoprazole modulates Th1/ Th2 immune response in human gastric mucosa

BACKGROUND

Selective cyclooxygenase-2 (COX-2) inhibitors and proton pump inhibitors may exert immune-mediated effects in human gastric mucosa. T-cell immune response plays a role in Helicobacter pylori-induced pathogenesis. This study evaluated effects of celecoxib and lansoprazole on T-helper (Th) 1 and Th2 immune response in human gastric mucosa.

METHODS

Dyspeptic patients with or without osteoarticular pain were given one of the following 4-week therapies: celecoxib 200 mg, celecoxib 200 mg plus lansoprazole 30 mg, and lansoprazole 30 mg daily. Expression of COX-2, T-bet, and pSTAT6 and production of prostaglandin E₂ (PGE₂), interferon (IFN)-γ, and interleukin (IL)-4 were determined in gastric biopsies before and after therapy. Histology was evaluated.

RESULTS

Cyclooxygenase-2 expression and PGE₂ production was higher, and Th1 signaling pathway was predominant in H. pylori-infected vs. uninfected patients. T-bet expression and IFN-γ production increased, while STAT6 activation and IL-4 production decreased following therapy with celecoxib and celecoxib plus lansoprazole, respectively. Th1 and Th2 signaling pathways down-regulated after therapy with lansoprazole, and this was associated with an improvement of gastritis. Effect of therapy was not affected by H. pylori status.

CONCLUSION

Celecoxib and lansoprazole modulate Th1/Th2 immune response in human gastric mucosa. The use of these drugs may interfere with long-term course of gastritis.

Somatostatin stimulates menin gene expression by inhibiting protein kinase A

Somatostatin is a potent inhibitor of gastrin secretion and gene expression. Menin is a 67-kDa protein product of the multiple endocrine neoplasia type 1 (MEN1) gene that when mutated leads to duodenal gastrinomas, a tumor that overproduces the hormone gastrin. These observations suggest that menin might normally inhibit gastrin gene expression in its role as a tumor suppressor. Since somatostatin and ostensibly menin are both inhibitors of gastrin, we hypothesized that somatostatin signaling directly induces menin. Menin protein expression was significantly lower in somatostatin-null mice, which are hypergastrinemic. We found by immunohistochemistry that somatostatin receptor-positive cells (SSTR2A) express menin. Mice were treated with the somatostatin analog octreotide to determine whether activation of somatostatin signaling induced menin. We found that octreotide increased the number of menin-expressing cells, menin mRNA, and menin protein expression. Moreover, the induction by octreotide was greater in the duodenum than in the antrum. The increase in menin observed in vivo was recapitulated by treating AGS and STC cell lines with octreotide, demonstrating that the regulation was direct. The induction required suppression of protein kinase A (PKA) since forskolin treatment suppressed menin protein levels and octreotide inhibited PKA enzyme activity. Small-interfering RNA-mediated suppression of PKA levels raised basal levels of menin protein and prevented further induction by octreotide. Using AGS cells, we also showed for the first time that menin directly inhibits endogenous gastrin gene expression. In conclusion, somatostatin receptor activation induces menin expression by suppressing PKA activation.

Hip1r is expressed in gastric parietal cells and is required for tubulovesicle formation and cell survival in mice

Huntingtin interacting protein 1 related (Hip1r) is an F-actin- and clathrin-binding protein involved in vesicular trafficking. In this study, we demonstrate that Hip1r is abundantly expressed in the gastric parietal cell, predominantly localizing with F-actin to canalicular membranes. Hip1r may provide a critical function in vivo, as demonstrated by extensive changes to parietal cells and the gastric epithelium in Hip1r-deficient mice. Electron microscopy revealed abnormal apical canalicular membranes and loss of tubulovesicles in mutant parietal cells, suggesting that Hip1r is necessary for the normal trafficking of these secretory membranes. Accordingly, acid secretory dynamics were altered in mutant parietal cells, with enhanced activation and acid trapping, as measured in isolated gastric glands. At the whole-organ level, gastric acidity was reduced in Hip1r-deficient mice, and the gastric mucosa was grossly transformed, with fewer parietal cells due to enhanced apoptotic cell death and glandular hypertrophy associated with cellular transformation. Hip1r-deficient mice had increased expression of the gastric growth factor gastrin, and mice mutant for both gastrin and Hip1r exhibited normalization of both proliferation and gland height. Taken together, these studies demonstrate that Hip1r plays a significant role in gastric physiology, mucosal architecture, and secretory membrane dynamics in parietal cells.

Control of gastric acid secretion in health and disease

Recent milestones in the understanding of gastric acid secretion and treatment of acid-peptic disorders include the (1) discovery of histamine H(2)-receptors and development of histamine H(2)-receptor antagonists, (2) identification of H(+)K(+)-ATPase as the parietal cell proton pump and development of proton pump inhibitors, and (3) identification of Helicobacter pylori as the major cause of duodenal ulcer and development of effective eradication regimens. This review emphasizes the importance and relevance of gastric acid secretion and its regulation in health and disease. We review the physiology and pathophysiology of acid secretion as well as evidence regarding its inhibition in the management of acid-related clinical conditions.

Regulated expression of the human gastrin gene in mice

Gastrin is secreted from neuroendocrine cells residing in the adult antrum called G cells, but constitutively low levels are also expressed in the duodenum and fetal pancreas. Gastrin normally regulates gastric acid secretion by stimulating the proliferation of enterochromaffin-like cells and the release of histamine. Gastrin and progastrin forms are expressed in a number of pathological conditions and malignancies. However, the DNA regulatory elements in the human versus the mouse gastrin promoters differ suggesting differences in their transcriptional control. Thus, we describe here the expression of the human gastrin gene using a bacterial artificial chromosome (BAC) in the antral and duodenal cells of gastrin null mice. All 5 founder lines expressed the 253 kb human gastrin BAC. hGasBAC transgenic mice were bred onto a gastrin null background so that the levels of human gastrin peptide could be analyzed by immunohistochemistry and radioimmunoassay without detecting endogenous mouse gastrin. We have shown previously that chronically elevated gastrin levels suppress somatostatin. Indeed, infusion of amidated rat gastrin depressed somatostatin levels, stimulated gastric acid secretion and an increase in the numbers of G cells in the antrum and duodenum. In conclusion, human gastrin was expressed in mouse enteroendocrine cells and was regulated by somatostatin. This mouse model provides a unique opportunity to study regulation of the human gastrin promoter in vivo by somatostatin and possibly other extracellular regulators contributing to our understanding of the mechanisms involved in transcriptional control of the human gene.

Requirement of the tissue-restricted homeodomain transcription factor Nkx6.3 in differentiation of gastrin-producing G cells in the stomach antrum

Many homeodomain transcription factors function in organogenesis and cell differentiation. The Nkx family illustrates these functions especially well, and the Nkx6 subfamily controls differentiation in the central nervous system and pancreas. Nkx6.3, a recent addition to this subfamily, overlaps Nkx6.1 and Nkx6.2 in expression in the hindbrain and stomach. Nkx6.3 transcripts localize in the epithelium of the most distal stomach region, the antrum and pylorus; expression in the adult intestine is lower and confined to the proximal duodenum. Nkx6.3(-)(/)(-) mice develop and grow normally, with a grossly intact stomach and duodenum. These mice show markedly reduced gastrin mRNA, many fewer gastrin-producing (G) cells in the stomach antrum, hypogastrinemia, and increased stomach luminal pH, with a corresponding increase in somatostatin mRNA levels and antral somatostatin-producing (D) cells. They express normal levels of other transcription factors required for gastric endocrine cell differentiation, Pdx1, Pax6, and Ngn3; conversely, Ngn3(-)(/)(-) mice, which also show reduced gastrin levels, express Nkx6.3 normally. These studies implicate Nkx6.3 as a selective regulator of G- and D-cell lineages, which are believed to derive from a common progenitor, and suggest that it operates in parallel with Ngn3.

Expression of somatostatin receptor subtype 3 in the gastric mucosa of dyspeptic patients in relation to Helicobacter pylori infection and a family history of gastric cancer

BACKGROUND AND AIM

The cytotoxic activity of Helicobacter pylori contributes significantly to the pathogenesis of gastric carcinoma. A preliminary study suggested that somatostatin receptor subtype 3 (SSTR3) might play a role in cell apoptosis and the growth of gastric cancer. The aim of the present study was to determine the influence of H. pylori infection and a family history of gastric cancer on the expression of SSTR3 in the gastric mucosa of non-cancer patients with dyspepsia.

METHODS

The expression of the SSTR3 gene in the gastric mucosa of the stomach antrum and corpus of 53 patients was determined by the use of quantitative reverse transcription-polymerase chain reaction.

RESULTS

The SSTR3 mRNA level was lower in the H. pylori-infected patients, as compared to the non-infected patients, independently of a family history of gastric cancer and stomach topography. The greatest decrease of approximately 40% and 35% (P < 0.05) was observed for the antrum of the H. pylori-positive patients without and with a family history of gastric cancer, respectively. In the corpus, these differences were much smaller, regardless of a family history of gastric cancer. Interestingly, for H. pylori-negative patients, the density (at the mRNA level) of the SSTR3 receptor in the antrum was higher than in the corpus mucosa.

CONCLUSIONS

A decrease in the density of SSTR3 (especially in the antrum) in individuals with H. pylori infection and particularly with a family history of gastric cancer may point to an environmental and inherited predisposition in the development of distal gastric cancer.

The pathogenesis of Helicobacter pylori-induced gastro-duodenal diseases

Helicobacter pylori is the main cause of peptic ulceration, distal gastric adenocarcinoma, and gastric lymphoma. Only 15% of those colonized develop disease, and pathogenesis depends upon strain virulence, host genetic susceptibility, and environmental cofactors. Virulence factors include the cag pathogenicity island, which induces proinflammatory, pro-proliferative epithelial cell signaling; the cytotoxin VacA, which causes epithelial damage; and an adhesin, BabA. Host genetic polymorphisms that lead to high-level pro-inflammatory cytokine release in response to infection increase cancer risk. Pathogenesis is dependent upon inflammation, a Th-1 acquired immune response and hormonal changes including hypergastrinaemia. Antral-predominant inflammation leads to increased acid production from the uninflamed corpus and predisposes to duodenal ulceration; corpus-predominant gastritis leads to hypochlorhydria and predisposes to gastric ulceration and adenocarcinoma. Falling prevalence of H. pylori in developed countries has led to a falling incidence of associated diseases. However, whether there are disadvantages of an H. pylori-free stomach, for example increased risk of esosphageal adenocarcinoma, remains unclear.

Gene expression profiling in a mouse model of Helicobacter-induced gastric cancer

We have previously reported that a synergistic interaction between hypergastrinemia and Helicobacter felis (H. felis) infection accelerates gastric carcinogenesis in mice, but the precise mechanism for this interaction has not been clarified. Consequently, we undertook an oligonucleotide cDNA microarray study to investigate changes in gene expression in this model system. Male hypergastrinemic transgenic (INS-GAS) mice with 6-months H. felis infection were compared with three different age, strain and gender-matched control groups: (i) INS-GAS mice without H. felis infection; (ii) non-transgenic FVB/N mice with H. felis infection; and (iii) non-transgenic FVB/N mice without H. felis infection. Complementary RNA derived from whole stomach were hybridized to the Affymetrix GeneChip murine U74Av2 array. Among 12 000 cDNA spotted on each chip, 35 cDNA were upregulated and 41 cDNA were downregulated more than twofold in H. felis-infected INS-GAS mice compared with all three control groups. Expression changes were validated in 12 selected genes by northern hybridization and/or quantitative real-time reverse transcription polymerase chain reaction (RT-PCR). Confirmed upregulated genes included Reg I, amphiregulin, MMP-10, MMP-13, claudin-7 and chitinase 3-like 1, while confirmed downregulated genes included H/K-ATPase alpha and beta subunits, intrinsic factor, somatostatin, galectin-2 and apolipoprotein A-I. Immunohistochemical analysis of MMP-10, amphiregulin, H/K-ATPase beta subunit and galectin-2 confirmed these expression changes at the protein level, and MMP-10 was mainly detected in stromal cells of submucosal region, while the other three genes were expressed in gastric epithelial cells. Taken together, gene expression profiling of this mouse model may provide novel insights into Helicobacter-induced gastric carcinogenesis.

Gastrin increases murine intestinal crypt regeneration following injury

BACKGROUND & AIMS

A number of growth factors affect the regeneration of intestinal epithelia following injury, but the effects of amidated gastrin have not previously been assessed. We therefore investigated the effects of gastrin on intestinal regeneration following a range of stimuli.

METHODS

Intestinal crypt regeneration was assessed in transgenic mice overexpressing amidated gastrin (INS-GAS) and mice in which hypergastrinemia was induced using omeprazole, following gamma-radiation, 5-fluorouracil, and dextran sulphate sodium (DSS). Abundance of the CCK-2 receptor was assessed in intestinal epithelia and IEC-6 intestinal epithelial cells following gamma-radiation.

RESULTS

Four days following 14 Gy gamma-radiation, or 2 injections of 400 mg/kg 5-fluorouracil, INS-GAS mice exhibited significantly increased small intestinal and colonic crypt survival compared with their wild-type counterparts (FVB/N). INS-GAS mice treated with 3% DSS for 5 days showed less weight loss and increased colonic crypt regeneration at 8 days compared with FVB/N. Increased small intestinal and colonic crypt survival was also demonstrated following gamma-radiation in FVB/N mice rendered hypergastrinemic using omeprazole. The increased crypt survival in INS-GAS mice following 14 Gy gamma-radiation was inhibited by administration of a CCK-2 receptor antagonist (YF476). Increased abundance of the CCK-2 receptor was demonstrated in intestinal epithelia following 14 Gy gamma-radiation by Western blotting and immunohistochemistry. Similarly, increased CCK-2 receptor mRNA abundance and increased 125I-gastrin binding was demonstrated in IEC-6 cells following 4 Gy gamma-radiation.

CONCLUSIONS

Hypergastrinemia increases regeneration of intestinal epithelia following diverse forms of injury. Induction of the CCK-2 receptor in damaged epithelium confers potential for protection against injury by administration of gastrin.

Somatostatin inhibits dendritic cell responsiveness to Helicobacter pylori

Somatostatin is a regulatory peptide found in abundance in the stomach. We have previously shown that somatostatin is required for IL-4-mediated resolution of Helicobacter pylori gastritis. In the current study, we hypothesize that somatostatin acts directly on antigen-presenting cells in the stomach to lessen the severity of gastritis. To test this hypothesis, we first show that CD11c+ dendritic cells are present in the infected tissue of mice with H. pylori-induced gastritis. Pretreatment of bone marrow-derived dendritic cells with somatostatin results in decreased IL-12 production, and lower splenocyte proliferation induced by H. pylori-stimulated dendritic cells. Furthermore, octreotide, a somatostatin analogue, is more potent than somatostatin in suppressing IL-12 release by H. pylori-stimulated dendritic cells through an NF-kappaB-independent pathway. In addition, IL-4 stimulates somatostatin secretion from dendritic cells. In conclusion, somatostatin inhibits dendritic cell activation by H. pylori; a possible mechanism by which IL-4 mediates resolution of gastritis. We suggest that octreotide may be effective in treating immune-mediated diseases of the stomach.

Chronic gastritis in the hypochlorhydric gastrin-deficient mouse progresses to adenocarcinoma

The current study tests the hypothesis that chronic atrophic gastritis from hypochlorhydria in the gastrin-deficient mouse predisposes the stomach to gastric cancer. Gross morphology and histology of 12-month-old wild-type (WT), gastrin-deficient (G-/-) and somatostatin-deficient (SOM-/-) mice were examined. Parietal and G cells, Ki67, TUNEL, villin and MUC2 expression were analysed by immunohistochemistry. RUNX3 and STAT3 expression was analysed by Western blot. Anchorage-independent growth was determined by cell cluster formation in soft agar. Compared to the WT and SOM-/- mice, hypochlorhydric G-/- mice developed parietal cell atrophy, significant antral inflammation and intestinal metaplasia. Areas of metaplasia within the G-/- mouse stomach showed decreased RUNX3 expression with elevated MUC2 and villin expression. Cells isolated from the tumor grew in soft agar. However, the cells isolated from WT, nontransformed G-/- and SOM-/- gastric tissue did not form colonies in soft agar. Consistent with elevated antral proliferation, tumor tissue isolated from the G-/- mice showed elevated phosphorylated STAT3 expression. We then examined the mechanism by which STAT3 was constitutively expressed in the tumor tissue of the G-/- mice. We found that IFNgamma expression was also significantly higher in the tumor tissue of G-/- mice compared to WT and SOM-/- animals. To determine whether STAT3 was regulated by IFNgamma, MKN45 cells were cocultured with IFNgamma or gastrin. IFNgamma significantly stimulated phosphorylation of STAT3 in the MKN45 cell line, but not gastrin. Therefore, we show here that in the hypochlorhydric mouse stomach, the chronic gastritis, atrophy, metaplasia, dysplasia paradigm can be recapitulated in mice. Moreover, neoplastic transformation of the antral gastric mucosa does not require gastrin.

Modulating the cytokine response to treat Helicobacter gastritis

The conventional view of gastric acid secretion is that a negative feedback mechanism arises in response to high acidity, such that somatostatin keeps G-cells and parietal cells from producing more gastrin and acid, respectively. When the stomach becomes infected, for example with Helicobacter pylori (H. pylori), the feedback mechanism is impaired. In animal models, our laboratory has demonstrated that other types of bacteria besides H. pylori can cause gastritis. For example, under conditions of low acidity, gastritis is secondary to bacterial overgrowth, not production of excessive acid, thus suggesting a new paradigm for the regulation of gastric acid secretion under inflammatory conditions. Cytokines, released during the gastric inflammatory response, including IFN gamma, TNF alpha and IL-1 beta stimulate the G-cell to produce gastrin. Gastrin in turn triggers the release of acid, and hypergastrinemia suppresses somatostatin, the inhibitor of acid. The overall response results in maximal gastric acid output that acts as the stomach's most important anti-microbial agent. The increased acid secretion by the stomach in the presence of H. pylori seems to be part of the innate immune response, in that gastrin and somatostatin are reciprocally regulated by Th1 or Th2 cytokines, respectively. In a mouse model, we showed that octreotide, a somatostatin, analog, is an efficacious treatment for Helicobacter gastritis. In humans, octreotide might accelerate recovery from H. pylori infection, reducing the duration of antibiotic therapy.

Overexpression of glycine-extended gastrin inhibits parietal cell loss and atrophy in the mouse stomach

Recently we have reported synergistic effects between glycine-extended gastrin (G-gly) and amidated gastrin-17 on acid secretion in short-term infusion studies. In the present study, we examined the long-term effect of G-gly on the atrophy-promoting effects of amidated gastrin in the mouse stomach with or without Helicobacter infection. Transgenic mice overexpressing amidated gastrin (INS-GAS mice), G-gly (MTI/G-gly mice), and both peptides (INS-GAS/G-gly mice) were used for assessment of acid secretion and ulcer susceptibility and histologic examination and scoring of preneoplastic lesions in response to the 3 and 6 months Helicobacter felis (H. felis) infection. We found that MTI/G-gly mice had normal gastric histology and acid secretion. Double transgenic (INS-GAS/G-gly) mice showed 2-fold increases in acid secretion compared with INS-GAS mice. Acute peptic ulcers after pyloric ligation were noted in 50% of the INS-GAS/G-gly mice but in none of the INS-GAS mice at 6 months of age. Whereas male INS-GAS mice had a >50% decrease in the numbers of parietal cell and enterochromaffin-like cell at 6 months of age, the male double transgenic mice had no such decrease. Overexpression of G-gly reduced the scores of preneoplasia in the stomach; however, it did not prevent the development of amidated gastrin-dependent gastric cancer in both H. felis-infected mice and uninfected mice. We conclude that G-gly synergizes with amidated gastrin to stimulate acid secretion and inhibits parietal cell loss in INS-GAS/G-gly mice. The overexpression of G-gly seems to increase the susceptibility to peptic ulcer disease and delay the development of Helicobacter-mediated gastric preneoplasia in this model.

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Gastric cancer development in mice lacking the SHP2 binding site on the IL-6 family co-receptor gp130

BACKGROUND AND AIMS

We have developed a mouse model of gastric cancer that resembles human intestinal-type adenocarcinoma. The aim of this study was to determine the identity and temporal changes in mediators of IL-6 signaling regulating tumor development.

METHODS

gp130(757F/F) Mice that lack the SHP2-binding site on the IL-6 family receptor gp130 and have increased STAT 3 activity and wild-type littermates were used. Cohorts were assessed by quantitative histology and immunohistochemistry for gastric cell phenotype and proliferation markers from 4 to 40 weeks of tumor development. Northern blotting and in situ hybridization were used to quantify expression of the tumor suppressor TFF1 and the mitogens gastrin and Reg I. Expression of epidermal growth factor receptor (EGFr) and its ligands was measured by RT-PCR analysis. Age-matched differences in gene expression profiles were tested by ANOVA.

RESULTS

Hyperplastic antral tumors with inflammation and ulceration were evident in gp130(757F/F) mice at 4 weeks of age and reached maximum size by 20 weeks. Tumor progression was marked by gastritis, atrophy, intestinal metaplasia, dysplasia, and submucosal invasion after 30 weeks. Both TFF1 and gastrin expression were progressively inhibited during tumorigenesis, whereas Reg I was stimulated. The EGFr and its ligands transforming growth factor (TGF)-alpha and heparin-binding EGF had increased expression corresponding to maximal tumor growth.

CONCLUSIONS

gp130(757F/F) Mice rapidly develop distal stomach tumors, with loss of SHP2/Erk/AP-1 transcriptional regulation exemplified by decreased TFF1 expression and increased STAT1/3 regulated genes such as Reg I. Tumor development occurs in a hypogastrinemic environment. Balanced IL-6 signaling is required for maintaining gastric homeostasis.

Treatment of Helicobacter gastritis with IL-4 requires somatostatin

Fifty percent of the world's population is infected with Helicobacter pylori; however, treatment has been insufficient to eradicate the organisms due to rising antibiotic resistance. Helicobacter infection is characterized by induction of a T helper 1 lymphocyte (Th1) immune response, hypergastrinemia, and suppressed tissue somatostatin (SOM) levels. However, the mechanism by which the immune response regulates acid secretion is not known. We show here that treatment with IFN-gamma, a Th1 cytokine, was sufficient to induce gastritis, increase gastrin, and decrease SOM levels within 7 days. In contrast, the T helper 2 lymphocyte cytokine IL-4 increased SOM levels and effectively suppressed gastrin expression and secretion. This result demonstrated reciprocal regulation of acid regulatory peptides by immune modulators. IL-4 pretreatment prevented gastritis in infected wild-type but not in SOM null mice. Thus, the ability of IL-4 to oppose a Th1-mediated infection required SOM. Immunofluorescence was used to document the presence of IL-4 receptors on the gastric SOM-secreting cell (D cell). Moreover, IL-4 stimulated SOM release from primary D cell cultures. Treatment of mice chronically infected with Helicobacter felis for 2 mo with the SOM analogue octreotide resolved the inflammation. Thus, a mechanism by which IL-4 resolves inflammation in the stomach is by stimulating the release of SOM from gastric D cells.

Role of therapy or monitoring in preventing progression to gastric cancer

It is generally accepted that intestinal-type gastric adenocarcinoma arises through a multistep process originating with chronic gastritis, progressing through stages of atrophy, intestinal metaplasia, and dysplasia and finally invasive carcinoma. This sequential process, known as the "Correa cascade" is in many instances initiated by Helicobacter pylori infection and perpetuated by a number of environmental and host factors. Given that the development of carcinoma can be the end point of this sequential process, there is great interest in determining which if any of these steps may be reversible. Clinical studies have shown that the eradication of H. pylori can lead to resolution of chronic gastritis, and a few studies have suggested some improvement in gastric atrophy. Intestinal metaplasia, however, does not appear to be as reversible. Nevertheless, results of several intriguing studies of high-risk populations support the notion that eradication of H. pylori may decrease or delay progression to gastric carcinoma despite the inability to reverse all mucosal damage. The applicability of these findings to low-risk countries such as the United States and the United Kingdom remain uncertain. Currently, in the United States, there is no widely accepted screening program for H. pylori infection in asymptomatic individuals, and consensus regarding surveillance for gastric intestinal metaplasia or dysplasia is lacking. The purpose of this report is to evaluate the available data regarding the epidemiology of H. pylori and associated carcinoma, discuss relevant human and animal data that address eradication strategies in the prevention of gastric carcinoma, and finally discuss current recommendations regarding screening programs aimed at high-risk populations.

Pharmacological control of gastric acid secretion for the treatment of acid-related peptic disease: past, present, and future

Pharmacological agents, such as histamine H(2) receptor antagonists and acid pump inhibitors, are now the most frequently used treatment for such acid-related diseases as gastroduodenal ulcers and reflux esophagitis. Based on increased understanding of the precise mechanisms of gastric acid secretion at the level of receptors, enzymes, and cytoplasmic signal transduction systems, further possibilities exist for the development of effective antisecretory pharmacotherapy. Gastrin CCK(2) receptor antagonists and locally active agents appear to represent promising therapies for the future. Development of gene targeting techniques has allowed production of genetically engineered transgenic and knockout mice. Such genetic technology has increased the investigative power for pharmacotherapy for not only antisecretory agents, but also treatment of mucosal diseases, such as atrophy, hyperplasia, and cancer. Elucidation of the origin of gastric parietal cells also represents an interesting investigative target that should allow a better understanding of not only acid-related diseases, but also the evolution of the stomach as an acid-secreting organ.

Mechanisms for regulation of gastrin and somatostatin release from isolated rat stomach during gastric distention

AIM: To investigate the intragastric mechanisms for regulation of gastric neuroendocrine functions during gastric distention in isolated vascularly perfused rat stomach.

METHODS: Isolated vascularly perfused rat stomach was prepared, then the gastric lumen was distended with either 5, 10 or 15 mL pH7 isotonic saline during a period of 20 min. During the distention, the axonal blocker tetrodotoxin (TTX), the cholinergic antagonist atropine, or the putative somatostatin-antagonist cyclo [7-aminoheptanoyl-Phe-D-Trp-Lys-Thr(Bzl)] were applied by vascular perfusion. The releases of gastrin and somatostatin were then examined by radioimmunoassay.

RESULTS: The graded gastric distention caused a significant volume-dependent decrease in gastrin secretion [-183 ± 75 (5 mL), -385 ± 86 (10 mL) and -440 ± 85 (15 mL) pg/20 min] and a significant increase of somatostatin secretion [260 ± 102 (5 mL), 608 ± 148 (10 mL) and 943 ± 316 (15 mL) pg/20 min]. In response to 10 mL distention, the infusion of either axonal blocker TTX (10^-6 M) or cholinergic blocker atropine (10^-7 M) had a similar affect. They both attenuated the decrease of gastrin release by approximately 50%, and attenuated the increase of somatostatin release by approximately 40%. The infusion of somatostatin-antagonist cyclo [7-aminoheptanoyl-Phe-D-Trp-Lys-Thr(Bzl)] (10^-6 M) attenuated the decrease of gastrin release by about 60%. Furthermore, combined infusion of the somatostatin-antagonist and atropine completely abolished distention-induced inhibition of gastrin release.

CONCLUSION: The present data suggest that distention of isolated rat stomach stimulates somatostatin release via cholinergic and non-cholinergic TTX-insensitive pathways. Both somatostatin and intrinsic cholinergic pathways are responsible for distention-induced inhibition of gastrin release.

Enhanced calcium signaling and acid secretion in parietal cells isolated from gastrin-deficient mice

Gastrin-deficient mice have impaired basal and agonist-stimulated gastric acid secretion. To analyze whether an intrinsic parietal cell defect contributed to the reduced acid secretion, we analyzed parietal cell calcium responses and acid secretory function in vitro. Parietal cells were purified by light-scatter cell sorting and calcium responses to gastrin, histamine, and carbachol were measured in gastrin-deficient and wild-type mice cell preparations. Surprisingly, basal and histamine-induced calcium concentrations were higher in the mutant cell preparations. [(14)C]aminopyrine uptake analysis in acutely isolated gastric glands revealed that basal acid accumulation was enhanced in gastrin-deficient cell preparations as well as on treatment with carbachol or histamine. These results suggested that an intrinsic parietal cell defect was not responsible for the reduced acid secretion in gastrin-deficient mice. Flow cytometric analysis of dispersed, H(+)-K(+)-ATPase-immunostained gastric mucosal preparations revealed a marked increase in parietal cell number in gastrin-deficient mice, which may have accounted for the enhanced in vitro acid secretion detected in this study. Parietal cells were found to be significantly smaller in the mutant cell preparations, suggesting that gastrin stimulation modulates parietal cell morphology.

Gastric secretion

Overlapping neural, hormonal, and paracrine pathways finely regulate gastric acid secretion. In rats and guinea pigs, most of the intrinsic neural innervation to the gastric mucosa originates in the myenteric plexus. In contrast, human stomachs have a clearly defined submucosal plexus that contains a variety of transmitters including nitric oxide, vasoactive intestinal peptide (VIP), gastrin-releasing peptide (GRP), substance P, and calcitonin gene-related peptide (CGRP). Although GRP is known to participate in meal-stimulated acid secretion by releasing gastrin in a variety of laboratory animals, recent studies were unable to demonstrate a role for endogenous GRP in meal-stimulated gastrin secretion in humans. Pituitary adenylate cyclase-activating polypeptide (PACAP), a member of the secretin-glucagon-VIP family, has been localized to gastric mucosal neurons and may participate in vagally mediated acid secretion. Two novel peptides, ghrelin and leptin, have been localized to the stomach. Peripheral administration of ghrelin stimulates and of leptin inhibits acid secretion. The binding of secretagogues to parietal cells generates changes in second messengers that regulate the translocation and activation of the proton pump, HK-ATPase. In resting cells, HK-ATPase is contained within cytoplasmic tubulovesicles in an inactive form. At stimulation, the tubulovesicles fuse with the apical canaliculi and the HK-ATPase is incorporated into the apical membrane where it actively pumps H ions in exchange for K. Acute infection with Helicobacter pylori results in hypochlorhydria, whereas chronic infection can cause either hypo- or hyperchlorhydria, depending on the distribution of the infection and the degree of corpus gastritis. Recent studies suggest that inflammatory cytokines, produced in response to the organism, can play a role in the perturbations in acid and gastrin secretion induced by H. pylori.

Regulation of parietal cell migration by gastrin in the mouse

Recent studies suggest that gastrin regulates parietal cell maturation. We asked whether it also regulates parietal cell life span and migration along the gland. Dividing cells were labeled with 5'-bromo-2'-deoxyuridine (BrdU), and parietal cells were identified by staining with Dolichos biflorus lectin. Cells positive for D. biflorus lectin and BrdU were reliably identified 10-30 days after BrdU injection in mice in which the gastrin gene had been deleted by homologous recombination (Gas-KO) and wild-type (C57BL/6) mice. The time course of labeling was similar in the two groups. The distribution of BrdU-labeled parietal cells in wild-type mice was consistent with migration to the base of the gland, but in Gas-KO mice, a higher proportion of BrdU-labeled cells was found more superficially 20 and 30 days after BrdU injection. Conversely, in transgenic mice overexpressing gastrin, BrdU-labeled parietal cells accounted for a higher proportion of the labeled pool in the base of the gland 10 days after BrdU injection. Gastrin, therefore, stimulates movement of parietal cells along the gland axis but does not influence their life span.