Helicobacter pylori alters gastric epithelial cell cycle events and gastrin secretion in Mongolian gerbils

BACKGROUND & AIMS: Human colonization with Helicobacter pylori increases the risk for distal gastric adenocarcinoma, possibly by altering gastric epithelial cell cycle events and/or gastrin secretion. This study aimed to determine whether H. pylori virulence-related characteristics affect apoptosis, proliferation, and gastrin levels in a rodent model of gastric adenocarcinoma. METHODS: Mongolian gerbils were challenged with H. pylori wild-type or isogenic cagA(-) and vacA(-) mutants, and apoptotic and proliferating cells were identified by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling and proliferating cell nuclear antigen immunohistochemistry, respectively. Serum gastrin levels were determined by radioimmunoassay. RESULTS: Gastric epithelial cell turnover was no different after infection with the wild-type, cagA(-), or vacA(-) strains. H. pylori infection significantly increased antral apoptosis 2-4 weeks after challenge, before apoptotic indices decreased to baseline. In contrast, antral proliferation rates were significantly higher 16-20 weeks after inoculation, but then decreased by 40 weeks. Antral proliferation was significantly related to serum gastrin levels, whereas antral apoptosis was inversely related to acute inflammation and lymphoid follicles. CONCLUSIONS: In H. pylori-infected gerbils, enhanced antral apoptosis is an early and transient cell cycle event. Epithelial cell proliferation peaks later and is significantly related to increased gastrin levels, suggesting that epithelial cell growth in H. pylori-colonized mucosa may be mediated by gastrin-dependent mechanisms.     

17Beta-estradiol modulates gastroduodenal preneoplastic alterations in rats exposed to the carcinogen N-methyl-N'-nitro-nitrosoguanidine.

Gastric cancers are a significant cause of morbidity worldwide. Epidemiological studies and animal models show that males have higher incidences of gastric cancers compared with females, suggesting that sex hormones may modulate gastric cancer risk. An animal model of the initiation phase of gastric cancer was used to determine the effects of systemic estrogen administration on morphological progression of preneoplastic lesions and to define cell populations at which estrogens may act. Preneoplastic progression in antral and duodenal mucosa was examined in male rats that received the chemical carcinogen, N-methyl-N'-nitro-nitrosoguanidine (MNNG), during treatment with implants containing 17beta-estradiol or oil vehicle. Histopathological changes in antral and duodenal gland morphology, numbers of proliferating cells and apoptotic bodies, and antral gastrin cell numbers and protein storage levels were determined 4 weeks later. With MNNG treatment, duodenal villous heights were significantly decreased, and epithelial cells displayed histological features of hyperplasia and dysplasia. Antral glands showed epithelial hyperplasia and dysplasia, increased mucosal height, and decreased mucin levels. Antral gastrin storage protein levels were decreased by MNNG. Systemic treatment with 17beta-estradiol significantly reversed MNNG-induced alterations in duodenal gland heights while increasing mucin and gastrin levels in antral glands. Cell proliferation and apoptosis rates were not significantly different between groups. The present results indicate that systemic 17beta-estradiol treatment influences antral and duodenal gland differentiation during the initiation phase of chemical gastroduodenal carcinogenesis in male rats. These results explain, in part, a potential pathway through which protective effects of estrogens on chemical carcinogenesis are mediated in the upper gastrointestinal tract.     

Growth hormone-releasing factor (somatocrinin) stimulates epithelial cell proliferation in the rat digestive tract

The possible influence of growth hormone-releasing factor (GHRF) on epithelial cell proliferation in the digestive tract was investigated. Fasted young rats received five hourly subcutaneous injections of either GHRF or saline. They were killed 6, 12, or 18 h after the initial injection and 45 min after [3H]thymidine pulse labeling. At the time of death, blood was taken to determine circulating growth hormone and gastrin levels. After radioautography, DNA synthetic and mitotic activities were estimated in the fundic, antral, duodenal, jejunal, and colonic mucosae. Growth hormone-releasing factor significantly increased labeling indices 6, 12, and 18 h after the initial injection in fundic mucosa, and 6 and 18 h after injection in antral and duodenal mucosae. Furthermore, GHRF significantly increased mitotic indices at 12 h in fundic mucosa and at 12 and 18 h in jejunal mucosa. No effect was seen in the colon. At the three checkpoint times, circulating growth hormone showed no change, but plasma gastrin was increased in the rats treated with GHRF as compared with controls. However, whether the reported stimulatory effect of the GHRF on target cells is direct or indirect remains to be determined.     

Opposite effects of gastrin on cell proliferation in the antrum and other parts of the upper-gastrointestinal tract in the rat

The effect of gastrin on DNA synthesis and mitotic activity in the mucosa of the uppergastrointestinal tract was explored in unanesthetized rats with a gastric fistula. Animals were killed at 4-hr intervals, after starting a 3-hr intravenous infusion with the lowest dose of gastrin provoking a maximal acid output. Tritiated thymidine was injected 1 hr before killing. Autoradiography was used, and labeling and mitotic indices were estimated in the fundic, antral, duodenal, and jejunal mucosa. The proliferative activity in the fundic, duodenal, and jejunal glands was significantly increased 16 hr after the administration of gastrin. In the antral glands, however, a significant decrease in both labeling and mitotic indices was observed. Rhythmic variations in proliferative activity were observed in the antral, duodenal, and jejunal mucosa in control animals. They were different from those in the gastrin-treated animals. Our data confirm the trophic action of gastrin in the fundic, duodenal, and jejunal mucosa. They also indicate an inhibitory effect of this hormone on cell proliferation in the antral mucosa.This study was supported in part by grants from the Fonds voor Geneeskundig Wetenschappelijk Onderzoek and the Nationaal Fonds voor Wetenschappelijk Onderzoek, Belgium.     

Gastric fundic epithelial proliferation after pancreaticobiliary diversion. Studies with quantitative histological analysis and autoradiography in the hamster.

The effect of pancreaticobiliary diversion (PBD) with hypercholecystokininemia on the gastric fundic mucosa was studied in the Syrian golden hamster over 5 and 24 days. Sham-operated animals served as controls. Basal plasma gastrin concentrations were significantly decreased on days 5 and 24. Five days after PBD, there was a significant increase in the scintigraphically measured [3H]-thymidine incorporation into fundic tissue. Correspondingly, there was a significant increase in the number of cells with [3H]-thymidine-labeled DNA in the proliferative zone of the fundic mucosa. The total number of cells in the gastric pits, the number of cells in the proliferative zone and the proliferation index were also significantly increased 5 days after PBD. Although the mean values of all variables were higher after PBD than in the control group on day 24, these increases were not significant. It is concluded that PBD at least transiently stimulates gastric fundic epithelial proliferation in the hamster. Whether this is an effect of hypercholecystokininemia remains to be definitely proven in further studies.     

The effect of chemical sympathectomy on insulin-stimulated gastric secretion in dogs

Administration of 6-hydroxydopamine (6-OHDA) causes selective acute degeneration of the adrenergic nerve terminals--that is, a reversible chemical sympathectomy. The effect of this drug was studied on the insulin-stimulated gastric secretion. Insulin-stimulated (0.15-0.4 IU/kg) gastric acid and pepsin output and serum gastrin were measured before and after 6-OHDA treatment (40 mg/kg) in gastric fistula dogs. Chemical sympathectomy resulted in a highly significant increase in acid and pepsin secretion. However, the hypoglycemic gastrin release was unaltered except the peak response, which showed a significant reduction. These data confirm earlier observations that the sympathetic innervation of the stomach has an inhibitory effect on gastric secretion in the dog. Furthermore it seems that the adrenergic fibers in the vagus nerve might have some modulating effect on the insulin-induced gastrin release.     

Regulatory mechanism of bombesin on gastrin release

Bombesin has been demonstrated to stimulate gastrin release by an atropine-resistant mechanism. In the present study, the effects of truncal vagotomy and chemical sympathectomy on the gastrin release by exogenous and endogenous bombesin using rat antral mucosa in tissue culture were studied. Exogenous bombesin 10^-8 mol/l significantly stimulated gastrin release. The stimulation of gastrin release by bombesin was abolished by truncal vagotomy, but not altered by chemical sympathectomy. Bombesin antiserum inhibited gastrin release by blocking the effect of endogenous bombesin. The inhibition of gastrin release by bombesin antiserum was abolished by truncal vagotomy, but not altered by chemical sympathectomy. In addition, the concentrations of bombesin-like immunoreactivity in antral mucosa were not altered by truncal vagotomy. These results suggest that the mechanism of gastrin release by bombesin is influenced by non-cholinergic local nerves under vagal control.     

Effects of gastric fundectomy and antrectomy on the colonic mucosa in the hamster.

The effects of gastric fundectomy and antrectomy on the colonic mucosa were studied in hamsters over 5 and 25 days. Sham-operated animals served as controls. Basal plasma gastrin concentrations were significantly increased after fundectomy and significantly decreased after antrectomy. Five days after fundectomy, there was a significant increase in scintigraphically determined colonic tissue [3H]-thymidine uptake and [3H]-thymidine labeling index of goblet cells, both of which were reduced 5 days after antrectomy. After fundectomy, the labeling index was maximal in differentiating-proliferative cells in the midportion of the colonic crypts, whereas the labeling index of the immature proliferative cells at the base of the crypts did not differ from that in the controls. On day 25, the crypt size and the number and percentage of goblet cells in the crypts were significantly increased in fundectomized animals. The number and percentage of goblet cells in antrectomized animals were significantly reduced on day 25. It is concluded that fundectomy in the hamster induces colonic mucosal hyperplasia with goblet cell proliferation, whereas antrectomy leads to retardation of colonic goblet cell proliferation.     

Influence of pineal indoleamines on the mitotic activity of gastric and colonic mucosa epithelial cells in the rat: Interaction with omeprazole

We have investigated the effects of melatonin (Mel) and N-acetylserotonin (NAc-5HT) on the mitotic activity of gastric and colonic mucosa in adult male rats under basal conditions and after an administration of omeprazole (OM) (H+,K(+)-ATPase inhibitor). The metaphase-arrest technique was applied in the study. Additionally, serum gastrin levels were measured by RIA method in the OM-treated group and in respective polyethyleneglycol (PEG)-administered controls. We have found that: 1) OM-treatment increased serum gastrin levels in rats; 2) OM enhanced the mitotic activity of the colonic mucosa cells, although, unexpectedly, it did not exert such an effect on the gastric mucosa cells; 3) Mel suppressed the OM-induced increase of the colonic epithelium cell proliferation, while NAc-5HT failed to reveal that action: 4) NAc-5HT decreased the proliferation of gastric mucosa epithelial cells. The value of the mean mitotic activity rate (MMAR) of gastric mucosa after Mel-treatment also decreased, but that change was not statistically significant. The obtained data are in compliance with previous results from our laboratory concerning the inhibitory effect of pineal indoleamines on the jejunal epithelium mitotic activity. The stimulatory effect of OM on the proliferation of colonic epithelium is probably mediated by OM-induced hypergastrinaemia. The possibility of Mel interaction with intestinal gastrin receptors (a structural similarity occurs between Mel and benzotript, a specific gastrin receptor antagonist), as well as of the opposite effects of Mel and gastrin on intracellular cAMP content in the gut, are considered in the discussion of results.     

Relationship between gastrin cell number, serum, antral mucosa and luminal gastrin concentration and gastric acidity in antral atrophic gastritis.

The aim of our study was to investigate the relationship between gastrin producing cell density with antral mucosa, luminal and serum gastrin concentration in antral atrophic gastritis. Our study group consisted of 17 patients: six with mild atrophic gastritis, seven with moderate atrophic gastritis and four with severe atrophic gastritis. None of the patients had type-A atrophic gastritis but the body mucosa was affected by superficial gastritis at various extent in some. A group of 15 healthy subjects served as control. All subjects underwent gastroscopic examination with multiple bioptic sampling. Radioimmunoassay was used for gastrin determination and photomicroscopy for gastrin producing cell density assessment. Electron microscopy was used to assess the gastrin producing granule density index. Patients with moderate and severe atrophic gastritis showed a lower gastric acidity and acid output as compared to control. Serum gastrin did not show significant differences among the groups. In moderate and severe atrophic gastritis, gastrin producing cell granule density index, gastrin producing cell density and antral mucosa gastrin concentration were significantly lower when compared with control and decreased with advancing of the severity of atrophic gastritis. In atrophic gastritis, however, the latter two measurements were not correlated. In moderate and severe atrophic gastritis luminal gastrin concentration significantly increased, compared with control, after the severity of atrophic gastritis. Gastrin producing cell granule density index and luminal gastrin concentration showed a significant correlation with gastric pH. These data suggest that in antral atrophic gastritis with reduced gastric acidity, the decrement of gastrin producing cells is followed by gastrin producing cell hyperfunction with increased luminal release of gastrin.     

Regular hemodialysis reverses gastric mucosal atrophy of patients with chronic renal failure

BACKGROUND/AIMS: Gastric mucosa of patients with chronic renal failure on regular hemodialysis is known to retain fundic glands relatively intact, but no evidence for regeneration of fundic glands by hemodialysis has been provided to date. This study was performed to investigate endoscopically and histopathologically if hemodialysis to treat renal failure would regenerate the background gastric mucosa and to elucidate factors associated with the mucosal regeneration. METHODOLOGY: First, the relationship between duration of hemodialysis and the degree of atrophy of the background gastric mucosa was investigated in patients with chronic renal failure treated and not treated by hemodialysis. Treated patients were further divided into long-term group treated for 4 years or longer and short-term group treated for shorter than 4 years. The degree of atrophy of gastric mucosa was evaluated by hematoxylin-eosin staining, PAS-alucian blue staining and immunohistochemical staining to detect Ki-67 expression using biopsy specimens obtained from gastric mucosa. The labeling index is the proportion of positively labeled cells with respect to the total number of cells. The proliferative index was calculated by multiplying the labeling index and the proliferative zone (length of the area between the uppermost and lowest labeled cells). Serum gastrin, glucagon and cholecystokinin were assayed as well as urine epidermal growth factor to elucidate factors associated with regeneration of gastric mucosa. Helicobacter pylori infection was examined by ELISA. RESULTS: In the long-term group, the degree of atrophy of gastric mucosa was endoscopically evaluated to be C1 type. In both of the two hemodialysis groups, endoscopically identified fundic gland region was histologically confirmed to be fundic glands by both hematoxylin-eosin staining and PAS-alucian blue staining. Epithelial cell proliferative index was significantly higher in long-term and short-term hemodialysis group than non-hemodialysis group (P=0.0001). No significant difference in serum gastrin, glucagon and cholecystokinin as well as urine epidermal growth factor was detectable among the three groups. Most patients of both hemodialysis groups were H. pylori-negative. CONCLUSIONS: A possibility of regeneration of the background gastric mucosa in proportion to the duration of hemodialysis was suggested on the basis of histopathological evidence. The observed regeneration of gastric mucosa was ascribable to elimination of factors associated with atrophy of gastric mucosa including H. pylori by hemodialysis.     

Effect of Helicobacter pylori infection on gastric epithelial proliferation in progression from normal mucosa to gastriccarcinoma

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Serum gastrin concentration affects the self replication rate of the enterochromaffin like cells in the rat stomach.

The influence of antrectomy and antrum exclusion on the enterochromaffin like cell kinetics in the gastric mucosa of the rat was studied using a combination of histamine immunocytochemistry and autoradiography after in vivo labelling with tritiated thymidine. In all experimental groups, the enterochromaffin like cells were found to incorporate the DNA precursor, thus indicating an ability to divide. The serum gastrin concentration was raised by antrum exclusion and reduced by antrectomy. After antrum exclusion, the enterochromaffin like cell proliferation rate increased as indicated by a doubling of the labelling index and by the resulting enterochromaffin like cell hyperplasia (after six weeks). After antrectomy, the enterochromaffin like cell labelling index decreased to reach 25% of the control value; at this time the enterochromaffin like cell density had not decreased significantly. The observed correlation between the enterochromaffin like cell labelling indices and the serum gastrin concentration supports the hypothesis that enterochromaffin like cell proliferation is influenced by serum gastrin.     

十二指肠胃反流对胃黏膜损害的实验性研究

目的：拟通过大鼠实验模型探讨短期十二指肠胃反流(DGR)对胃黏膜的损害及其特点。方法：健康、雄性SD大鼠分成3组：DGR组、结扎幽门组和对照组。手术后3周处死大鼠,观察胃黏膜损害及病理组织学改变、检测胃液pH值、胆红素水平及血清胃泌素水平,透射电镜下观察胃窦黏膜细胞间的紧密连接,测定组织过氧化物酶(MPO)活性。结果：DGR组大鼠胃黏膜可见散在糜烂、溃疡及出血点,而结扎幽门组及对照组胃黏膜光滑。DGR组胃液pH值和胆红素水平明显高于结扎幽门组及对照组,但血清胃泌素水平未见显著升高。短期DGR可引起胃窦黏膜胃小凹增生,没有肠上皮化生及胃黏膜萎缩等。短期DGR炎性细胞浸润不明显,没有导致组织MPO的水平改变,可引起黏膜细胞间的紧密连接受损。结论：DGR短期内可造成胃黏膜损害,表现为胃小凹增生、细胞间紧密连接受损,但炎性细胞浸润不明显,也不引起MPO活性的变化。     

Distribution of secretory component in non-cancerous human gastric mucosa

Immunological detection of secretory component (SC) in non-cancerous human gastric mucosa was carried out by the peroxidase-anti-peroxidase (PAP) method using several fixatives. SC was detected in the generative zone or mucous neck of normal gastric mucosa without intestinal metaplasia (IM) and in absorptive cells of IM of the stomach. The deep part of complete type IM showed a larger amount of SC than the superficial part. These findings suggested that the appearance of SC in gastric mucosa would be relevant to the immunity of glandular epithelium. In addition, SC was also detected in pyloric gland cells in specimens fixed with cold 95% ethanol. From these results, SC was considered to be a normal constituent and one of the developmental proteins in the gastric mucosa.     

Cell kinetics of slow renewing cell populations in mice stomach

BACKGROUND: The renewal rates of parietal and chief cells in the gastric mucosa and smooth muscle cells of muscularis propria have not been examined as precisely as superficial epithelial cells. To examine cell renewal of these cells, continuous labeling with tritiated ([3H])-thymidine was performed. METHODS: Mice received 112 repeated injections of [3H]-thymidine at 6-hour intervals for 28 days after birth and were killed immediately thereafter, or 60, 120, 200 or 300 days after the last injection. RESULTS: After continuous labeling, most cells in the stomach were labeled. At 60 days, unlabeled parietal cells in the neck area of the gland and unlabeled chief cells in the middle part of the gland appeared. Thereafter, the area of unlabeled cells expanded downwards to the bottom of the gland. Times required for labeling of total cell populations of parietal and chief cells to half were less than 60 days and more than 200 days, respectively. At 300 days, most parietal cells and about half of the chief cells remained labeled in the bottom of the gland. The labeling index of smooth muscle cells was about 100% for 300 days. CONCLUSIONS: The time required for the newly formed parietal and chief cells to reach the lower end of the gland was more than 300 days. As a total cell population, the renewal rate of parietal cells was more rapid than that of chief cells. However, in terms of the downward migrating cell population, the renewal rate of parietal cells was a little slower than that of chief cells. Smooth muscle cells showed almost no renewal.     

Carcinogenic hypergastrinemia: signet-ring cell carcinoma in a patient with multiple endocrine neoplasia type 1 with Zollinger-Ellison's syndrome

CONTEXT: Gastric neuroendocrine tumors are rare neoplasms that originate from gastric enterochromaffin-like (ECL) cells in the oxyntic mucosa. Gastrin and its derivates have been reported to regulate epithelial cell proliferation, migration, and differentiation. Mutations in the epithelial cadherin (E-cadherin) gene have been shown to be associated with the occurrence of diffuse gastric carcinomas in affected families. OBJECTIVE: In this study we investigated the histopathological and molecular findings in the gastrointestinal wall of a patient with multiple endocrine neoplasia type 1 with malignant duodenal gastrinoma and multiple gastric ECL cell tumors, who additionally developed a signet-ring cell carcinoma of the stomach. DESIGN AND PATIENT: Biopsies from the gastrointestinal tract of a patient with multiple endocrine neoplasia type 1 were immunostained for vesicular monoamine transporter-2 and E-cadherin. Nonamidated gastrin products were measured in the serum of the patient using antibodies that react with progastrin, Gly-extended, and amidated gastrins. Genetic analyses were performed to exclude germ-line mutations within the E-cadherin gene. RESULTS: Immunohistochemical studies of gastric ECL cell tumors showed a largely diminished E-cadherin expression in comparison to gastric surface mucosa cells and a loss of E-cadherin expression in the cells of the signet-ring carcinoma. Detailed biochemical measurements revealed progastrin concentrations that were approximately 20%, and Gly-gastrin concentrations that were approximately 10% the amidated gastrin concentrations in plasma. Molecular analyses revealed no E-cadherin germ-line mutation. CONCLUSION: Our immunohistochemical studies might suggest that the gastrinoma-associated excessive progastrin tissue concentrations led to diminished expression of E-cadherin within the gastric mucosa and promoted tumor development of a signet-ring cell carcinoma.     

Effects of parenteral hydrocortisone sodium succinate on epithelial renewal in hamster gastric mucosa

The aim of this study was to determine whether parenteral administration of steroids affects epithelial renewal in hamster stomach. Male golden hamsters received either hydrocortisone sodium succinate or saline intraperitoneally for three days. In the first experiment, hamsters were sacrificed 1 hr after injection of tritiated thymidine [( 3H]TdR) to label proliferating cells. In the second experiment, hamsters were sacrificed hourly after a single [3H]TdR injection up to 48 hr in order to determine cell cycle time by the method of fraction of labeled mitoses. In the third experiment, hamsters were sacrificed 1, 24, and 72 hr after [3H]TdR injection for the study of epithelial migration and cell turnover time. Sections of fundic and antral mucosae were prepared for light autoradiography. Steroid treatment caused no gross or microscopic injury to gastric mucosa, but the number of [3H]TdR-labeled cells as well as the thickness of the proliferative zone were reduced significantly in fundic mucosa, but not in antral mucosa. The study of the fraction labeled mitoses indicated that steroid treatment lengthened the cell cycle time in fundic mucosa, which was due primarily to prolonged G1 and DNA synthesis phases. Furthermore, epithelial migration was significantly slower in fundic mucosa after steroid treatment, which was associated with a prolonged cell turnover time. Thus, parenteral steroids depress the entire process of epithelial renewal in hamster fundic mucosa.     

Gastrin-mediated alterations in gastric epithelial apoptosis and proliferation in a mastomys rodent model of gastric neoplasia

BACKGROUND/AIMS: Hypergastrinemia secondary to low acid secretion is associated with gastric carcinoid formation in Mastomys. We investigated the effect of gastrin on oxyntic epithelial apoptosis and proliferation in this model. METHODS: Hypergastrinemia and mucosal hyperplasia were induced by irreversible H(2) receptor blockade with loxtidine. Gastrin levels were normalised in some animals by 10 days' loxtidine withdrawal. Serum gastrin was determined by radioimmunoassay, proliferative, enterochromaffin-like cells and Bcl-2 protein family expression by immunohistochemistry, and apoptotic cells by terminal deoxyuridine nucleotide nick end labeling (TUNEL). RESULTS: Proliferating cells were increased 4-fold in loxtidine-treated animals, and returned to normal upon loxtidine withdrawal. Enterochromaffin-like cell number increased 2-fold with loxtidine, and did not decrease after withdrawal. Apoptotic epithelial cells were located at the luminal surface and increased 1.8-fold with loxtidine, returning to control levels upon withdrawal. The ratio of proliferative to apoptotic cells was lower in the control and withdrawn groups than in the loxtidine group (0.26+/-0.05 and 0.26+/-0.08 vs. 0.77+/-0.12). With hypergastrinemia, the expression of Bcl-2 and Bak was increased and Bax decreased in the middle of the gland. CONCLUSION: Hypergastrinemia is associated with alterations in both proliferation and apoptosis in Mastomys gastric mucosa. This may contribute to the pathogenesis of mucosal hyperplasia in this model.