A focus on parietal cells as a renewing cell population

The fact that the acidsecreting parietal cells undergo continuous renewal has been ignored by many gastroenterologists and cell biologists. In the past, it was thought that these cells were static. However, by using 3Hthymidine radioautography in combination with electron microscopy, it was possible to demonstrate that parietal cells belong to a continuously renewing epithelial cell lineage. In the gastric glands, stem cells anchored in the isthmus region are responsible for the production of parietal cells. The stem cells give rise to three main progenitors: prepit, preneck and preparietal cells. Parietal cells develop either directly from the noncycling preparietal cells or less commonly via differentiation of the cycling prepit and preneck cell progenitors. The formation of a parietal cell is a sequential process which involves diminishment of glycocalyx, production of cytoplasmic tubulovesicles, an increase in number and length of microvilli, an increase in number and size of mitochondria, and fi nally, expansion and invagination of the apical membrane with the formation of an intracellular canalicular system. Little is known about the genetic counterparts of these morphological events. However, the time dimension of parietal cell production and the consequences of its alteration on the biological features of the gastric gland are well documented. The production of a new parietal cell takes about 2 d. However, mature parietal cells have a long lifespan during which they migrate bidirectionally while their functional activity for acid secretion gradually diminishes. Following an average lifespan of about 54 d, in mice, old parietal cells undergo degeneration and elimination. Various approaches for genetic alteration of the development of parietal cells have provided evidence in support of their role as governors of the stem/progenitor cell proliferation and differentiation programs. Revealing the dynamic features and the various roles of parietal cells would help in a better understanding of the biological features of the gastric glands and would hopefully help in providing a basis for the development of new strategies for prevention, early detection and/or therapy of various gastric disorders in which parietal cells are involved, such as atrophic gastritis, peptic ulcer disease and gastric cancer.

Dynamic functional and ultrastructural changes of gastric parietal cells induced by water immersion-restraint stress in rats

AIM： To investigate the dynamic functional and ultrastructural changes of gastric parietal cells induced by water immersion-restraint stress （WRS） in rats.METHODS： WRS model of Sprague-Dawley （SD） rats was established. Fifty-six male SD rats were randomly divided into control group, stress group and post-stress group. The stress group was divided into 1, 2 and 4 h stress subgroups. The post-stress group was divided into 24, 48 and 72 h subgroups. The pH value of gastric juice, ulcer index （UI） of gastric mucosa and H^＋, K^＋- ATPase activity of gastric parietal cells were measured. Ultrastructural change of parietal cells was observed under transmission electron microscope （TEM）.RESULTS： The pH value of gastric juice decreased time-dependently in stress group and increased in post-stress group. The H^＋, K^＋-ATPase activity of gastric parietal cells and the UI of gastric mucosa increased time-dependently in stress group and decreased in poststress group. Compared to control group, the pH value decreased remarkably （P = 0.0001）, the UI and H^＋, K^＋- ATPase activity increased significantly （P = 0.0001, P = 0.0174） in 4 h stress subgroup. UI was positively related with stress time （r = 0.9876, P 〈 0.01） but negatively with pH value （r = -0.8724, P 〈 0.05）. The parietal cells became active in stress group, especially in 4 h stress subgroup, in which plenty of intracellular canalicular and mitochondria were observed under TEM. In post-stress group, the parietal cells recovered to resting state.CONCOUSION： The acid secretion of parietal cells is consistent with their ultrastructural changes during the development and healing of stress ulcer induced by WRS and the degree of gastric mucosal lesions, suggesting gastric acid play an important role in the development of stress ulcer and is closely related with the recovery of gastric mucosal lesions induced by WRS.

Effect of Mica Monomer Powder on Chief and Parietal Cells as well as G and D Cells in Gastric Mucosa of Chronic Atrophic Gastritis in Rats

Objective： To study the regulative action of mica monomer powder preparation on the chief and parietal cells as well as G and D cells in the gastric mucosa of the experimental atrophic gastritis （CAG） rats. Methods： Intervention therapy was given to the experimental CAG rats at three different doses of mica monomer powder preparation to evaluate the changes of chief and parietal cells as well as G and D cells in the gastric mucosa and the histopathological changes of gastric mucosa. Results： Mica monomer powder preparation at three different doses could increase the amount of chief and parietal cells as well as G and D cells in gastric mucosa of the experimental CAG rats and alleviate and control the inflammation of gastric mucosa and the atrophy of gastric mucosa glands. Especially, better effects were shown in the mid and high dose groups. Conclusion： Mica has the pharmacological action of protecting the gastric mucosa, promoting the regeneration of gastric glands, enhancing blood flow of the gastric mucosa, and consequently improving the inflammatory responses of the gastric mucosa. One of the mechanisms is associated with promoting the secretion of gastric acid and gastric pepsin and regulating the neuroendocrine mechanism including gut hormone secretion （gastrin and somatostatin） by increasing the number of chief and parietal cells as well as G and D cells.

Atp4b promoter directs the expression of Cre recombinase in gastric parietal cells of transgenic mice

Parietal cells are one of the largest epithelium cells of the mucous membrane of the stomach that secrete hydrochloric acid. To study the function of gastric parietal cells during gastric epithelium homeostasis, we generated a transgenic mouse line, namely, Atp4b-Cre, in which the expression of Cre recombinase was controlled by a 1.0 kb promoter of mouse β-subunit of H^＋-, K^＋-ATPase gene （Atp4b）. In order to test the tissue distribution and excision activity of Cre recombinase in vivo, the Atp4b-Cre transgenic mice were bred with the reporter strain ROSA26 and a mouse strain that carries Smad4 conditional alleles （Smad4Ca/Co）. Multiple-tissue PCR of Atp4b-Cre;Smad4Co/＋ mice revealed that the recombination only happened in the stomach. As indicated by LacZ staining, ROSA26;Atp4b-Cre double transgenic mice showed efficient expression of Cre recombinase within the gastric parietal cells. These results showed that this Atp4b-Cre mouse line could be used as a powerful tool to achieve conditional gene knockout in gastric parietal cells.

Pernicious anemia: New insights from a gastroenterological point of view

Pernicious anemia （PA） is a macrocytic anemia that is caused by vitamin B12 deficiency, as a result of intrinsic factor deficiency. PA is associated with atrophic body gastritis （ABG）, whose diagnosis is based on histological confirmation of gastric body atrophy. Serological markers that suggest oxyntic mucosa damage are increased fasting gastrin and decreased pepsinogen I. Without performing Schilling＇s test, intrinsic factor deficiency may not be proven, and intrinsic factor and parietal cell antibodies are use- ful surrogate markers of PA, with 73% sensitivity and 100% specificity. PA is mainly considered a disease of the elderly, but younger patients represent about 15% of patients. PA patients may seek medical advice due to symptoms related to anemia, such as weak-ness and asthenia. Less commonly, the disease is suspected to be caused by dyspepsia. PA is frequently associated with autoimmune thyroid disease （40%） and other autoimmune disorders, such as diabetes mellitus （10%）, as part of the autoimmune polyen-docrine syndrome. PA is the end-stage of ABG. Long- standing Helicobacter pylori infection probably plays a role in many patients with PA, in whom the active infectious process has been gradually replaced by an autoimmune disease that terminates in a burned-out infection and the irreversible destruction of the gastric body mucosa. Human leucocyte antigen-DR genotypes suggest a role for genetic susceptibility in PA. PA patients should be managed by cobalamin replacement treatment and monitoring for onset of iron deficiency. Moreover, they should be advised about possible gastrointestinal long-term consequences, such as gastric cancer and carcinoids.

Dysregulation of gastric H,K-ATPase by cigarette smoke extract

AIM:To test whether the expression and activity of H,K-ATPase in parietal cells would be affected by cigarette smoke extract.METHODS: Extracts of cigarette smoke were administered into mice by gastric gavage (5 mg/kg body weight/day) for 3 d or in drinking water for 7 or 14 d. For the latter, each day a mouse consumed 5 mL water containing extracts of two cigarettes, on average. Control littermate mice received only vehicle. To compare the amount of H,K-ATPase in control and smoke-treated mice, the stomach was processed for Western blotting and immunohistochemical analysis using monoclonal antibodies specific for α- or β-subunits of H,K-ATPase. The p-nitrophenylphospatase activity assay was used as a measurement for K-dependent H,K-ATPase activity.RESULTS: Probed transblots showed an increase in the amount of H,K-ATPase in smoke-treated mice which was confirmed by immunohistochemistry and was found to be due to increased amounts of protein per parietal cell rather than an increased parietal cell number. The increase in the amount of H,K-ATPase was associated with an enhancement of its enzymatic activity. K-dependent activity in control and smoke-treated mice was significantly different (respectively, 0.12 μmol/mg vs 0.27 μmol/mg per minute, P<0.05).CONCLUSION: Administration of cigarette smoke extract is associated with an increase in the amount and activity of H,K-ATPase and hence, smokers are susceptible to development of peptic ulcer.

Role of potassium in acid secretion

Potassium (K+) ions are critical for the activation and catalytic cycle of the gastric H+,K+-ATPase, resulting in the secretion of hydrochloric acid into the parietal cell canaliculus. As both symptom, severity and esophageal mucosal damage in gastro-esophageal reflux disease (GERD) are related to the degree of acid exposure, K+ is a logical target for approaches to inhibit acid production.The probable K+ binding site on the gastric H+,K+-ATPase has recently been described and studies are elucidating how K+ activates the enzyme. K+ channels in the apical membrane of the parietal cell are implicated in the recycling of K+ and, to date, three potential K+ channels (KCNQ1, Kir2.1 and Kir4.1) have been identified. The channels represent theoretical sites for agents to control acid secretion but it will be difficult to develop selective blockers. An alternative strategy is to prevent K+ from activating gastric H+,K+-ATPase; the potassiumcompetitive acid blocker (P-CAB) class inhibits acidsecretion by binding at or near the K+ binding site.Ongoing research is further defining the role of K+ in the functioning of the gastric H+,K+-ATPase, as well as determining the clinical utility of agents directed toward this important cation.

Gastric autoimmune disorders in patients with chronic hepatitis C before,during and after interferon-alpha therapy

AIM:To explore the prevalence of autoimmune gastritis in chronic hepatitis C virus (HCV) patients and the influence of α-interferon (IFN) treatment on autoimmune gastritis. METHODS:We performed a prospective study on 189 patients with positive anti-HCV and viral RNA enrolled in a 12-month IFN protocol.We evaluated:a) the baseline prevalence of autoimmune gastritis,b) the impact of IFN treatment on development of biochemical signs of autoimmune gastritis (at 3,6 and 12 months),c) the evolution after IFN withdrawal (12 months) in terms of anti-gastric-parietal-cell antibodies (APCA),gastrin,anti-thyroid,and anti-non-organ- specific antibodies. RESULTS:APCA positivity and 3-fold gastrin levels were detected in 3 (1.6%) and 9 (5%) patients,respectively,at baseline,in 25 (13%) and 31 (16%) patients at the end of treatment (both P<0.001,vs baseline),and in 7 (4%) and 14 (7%) patients 12 months after withdrawal (P=0.002 and P=0.01 respectively,vs baseline;P=not significant vs end of treatment).The development of autoimmune gastritis was strictly associated with the presence of autoimmune thyroiditis (P=0.0001),no relationship was found with other markers of autoimmunity. CONCLUSION:In HCV patients,IFN frequently precipitates latent autoimmune gastritis,particularly in females.Following our 12-month protocol,the phenomenon generally regressed.Since APCA positivity and high gastrin levels are associated with the presence of antithyroid antibodies, development of autoimmune thyroiditis during IFN treatment may provide a surrogate preliminary indicator of possible autoimmune gastritis to limit the need for invasive examinations.

Histamine 3 receptor activation mediates inhibition of acid secretion during Helicobacter-induced gastritis

AIM:To test the hypothesis that histamine 3 receptor (H3R)activation during Helicobacter infection inhibits gastric acid secretion in vivo and in vitro.METHODS:Helicobacter felis(H.felis)infected and uninfected C57Bl/6 mice were infused with either PBS or the H3 receptor antagonist thioperamide(THIO)for 12 wk.After treatment,mice were analyzed for morphological changes and gastric acid content.Total RNA was prepared from the stomachs of each group and analyzed for changes in somatostatin and gastrin mRNA abundance by real time-polymerase chain reaction(RTPCR).Location of H3 receptors in the stomach was analyzed by co-localization using antibodies specific for the H3 receptor and parietal cell marker H + ,K + -ATPase βsubunit. RESULTS:Inflammation and parietal cell atrophy was observed after 12 wk of H.felis infection.Interestingly, treatment with the H3R antagonist thioperamide(THIO) prior to and during infection prevented H.felis-induced inflammation and atrophy.Compared to the uninfected controls,infected mice also had significantly decreased gastric acid.After eradication of H.felis with THIO treatment,gastric acidity was restored.Compared to the control mice,somatostatin mRNA abundance was decreased while gastrin gene expression was elevated during infection.Despite elevated gastric acid levels, after eradication of H.felis with THIO,somatostatin mRNA was elevated whereas gastrin mRNA was suppressed.Immunofluorescence revealed the presence of H3 receptors on the parietal cells,somatostatin-secreting D-cells as well as the inflammatory cells. CONCLUSION:This study shows that during H.felis infection,gastric acidity is suppressed as a consequence of an inhibitory effect on the parietal cell by H3R activation.The stimulation of gastric mucosal H3Rs increases gastrin expression and release by inhibiting release of somatostatin.

Maternal antibiotic treatment affects offspring gastric sensing for umami taste and ghrelin regulation in the pig

Background:Scarce is knowledge on the process regulating the development of acid secretion,orexigenic signaling,and chemosensing in the stomach of young pigs.Changes of early microbial encounters by suckling pigs can interact with the gut maturation,by the induction of different molecular signaling.Our goal was to assess if the age of offspring and the maternal environment,influenced by sow antibiotic treatment peripartum,could affect gastric morphology and the expression of genes involved in the control of hydrochloric secretion,feed intake,taste,and inflammation in offspring stomach.Methods:84 pigs from sows fed a diet with amoxicillin(on-d10 to+d21 from farrowing,ANT)or without(CON)were sacrificed at d14,d21,d28(weaning)or d42.Samples of oxyntic(OXY),pyloric(PY)and cardiac mucosae close to OXY were collected and parietal and enteroendocrine cells(EECs)were counted.Relative gene expression of a set of 11 key genes(ATP4A,SSTR2,GAST,GHRL,MBOAT4,PCSK1,GNAT1,TAS1R1,TAS1R3,IL8 and TNF)was assessed by qRT-PCR.In addition,40 offspring obtained from the same ANT and CON sows were offered a normal or a fatenriched diet for 4 weeks between 140 and 169 d of age,and then OXY and PY were sampled.Results:The number of parietal and EECs increased with age(P<0.001).ATP4A increased with age(within suckling,P=0.043,post-weaning vs.suckling,P<0.001),SSTR2 increased only after weaning(P<0.001).In OXY,GHRL increased during suckling(P=0.012),and post-weaning as a trend(P=0.088).MBOAT4 tended to increase during suckling(P=0.062).TAS1R1 increased from suckling to post-weaning period(P=0.001)and was lower in ANT offspring(P=0.013).GNAT1 in PY was higher in ANT offspring(P=0.041).Antibiotic treatment of sows peripartum increased expression of GHRL and MBOAT4 in OXY of growing-finishing offspring aged 5 months.Conclusions:Data show that sensing for umami taste and ghrelin regulation can be affected by maternal environment,but the development of acid secretion,orexigenic signaling and taste perception in the stomach are mostly developmentally controlled.