TFF2/SP-deficient mice show decreased gastric proliferation, increased acid secretion, and increased susceptibility to NSAID injury. (57/406)

Trefoil factor family 2 (TFF2), also known as spasmolytic polypeptide, is a member of the trefoil family of peptides and is expressed primarily in the mucous neck cells of the gastric mucosa. To study the physiologic role of TFF2, we have generated TFF2-deficient mice through targeted gene disruption. Homozygous mutant mice were viable and fertile without obvious gastrointestinal abnormalities. However, quantitative measurements revealed a significant decrease in gastric mucosal thickness and in gastric mucosal proliferation rates. In addition, there was a twofold increase in activated parietal cells resulting in a twofold increase in basal and stimulated gastric acid output and an undetectable serum gastrin level. The TFF2-deficient mice also showed a significant increase in the degree of gastric ulceration after administration of indomethacin. Taken together, these results suggest a physiologic role for TFF2 to promote mucosal healing through the stimulation of proliferation and downregulation of gastric acid secretion.  (+info)

Autoimmune gastritis: distinct histological and immunohistochemical findings before complete loss of oxyntic glands. (58/406)

Autoimmune gastritis (AG) can be easily recognized when the histological features are fully developed, but recognizing AG before the complete loss of the oxyntic mucosa is more challenging. One feature of fully developed AG is enterochromaffin cell-like (ECL) hyperplasia, but its presence or absence in earlier stages of AG has not been fully evaluated. A retrospective study of biopsy specimens from 40 patients was performed; all of the patients were originally diagnosed with possible AG based on the presence of lymphocytic infiltration and damage to oxyntic glands and/or the presence of metaplastic epithelium that disproportionately involved the body mucosa. Nineteen cases had follow-up serological studies for anti-parietal cells and/or anti-intrinsic factor antibodies: 13 were positive and 6 negative. The remaining 21 cases were indeterminate because of incomplete testing. The histological findings were similar in the patients who were serologically positive and those who were indeterminate for AG. In all of these cases, the oxyntic mucosa showed lymphoplasmacytic infiltrates within the lamina propria with focal gland infiltration and damage. Sixty-five percent (22/34) of the cases showed intestinal and/or pyloric metaplasia, and 85% (29/34) showed parietal cell pseudohypertrophy. Chromogranin stains were performed in 11 of 13 cases with positive serological markers for AG, and all showed at least linear ECL cell hyperplasia. In contrast, none of the six cases with negative serological studies had linear ECL cell hyperplasia, P <.001. In conclusion, the following constellation of findings supports a diagnosis of AG before the complete loss of oxyntic mucosa: deep or diffuse lymphoplasmacytic infiltrates within the lamina propria with foci of gland infiltration and damage, epithelial metaplasia, parietal cell pseudohypertrophy, and ECL cell hyperplasia at the linear or greater level.  (+info)

Helicobacter pylori, parietal cell antibodies and autoimmune gastropathy in type 1 diabetes mellitus. (59/406)

BACKGROUND: Fifteen to 20% of type 1 diabetic patients exhibit parietal cell antibodies (PCA), which are associated with autoimmune gastritis, hypochlorhydria, iron deficiency and pernicious anaemia. AIM: To examine whether Helicobacter pylori infection could explain the high prevalence of PCA and autoimmune gastropathy in diabetes. If so, H. pylori eradication could prevent autoimmune gastritis. METHODS: In 229 type 1 diabetics (M/F: 135/94; age: 41 +/- 12 years) PCA were measured. H. pylori infection was assessed by serology, urea breath test in all and by histology (updated Sydney system) in 88 subjects. Pentagastrin tests were performed in 42 patients. RESULTS: Sixty-nine patients were PCA-positive. H. pylori infection was present in 72 patients and was negatively associated with HLA-DQA1*0103-B1*0603 (OR=0.12, P=0.015) and positively with DQA1*0501-B1*0201 (OR=1.9, P=0.032). PCA-positivity was linked to HLA-DQA1*0501-B1*0301 (OR=3.9, P=0.017). A link between H. pylori and PCA was observed when PCA-positivity was defined as a titre > or = 1/20 (OR=2.0, P=0.03), but not if > or =1/40 was the cut-off point. PCA-positivity, but not H. pylori infection, was associated with iron deficiency anaemia (OR=2.7, P=0.008), pernicious anaemia (OR= 33.5, P < 0.0001), hypochlorhydria (OR=12.1, P=0.0008) and autoimmune gastritis (OR=12.5, P < 0.0001). CONCLUSIONS: The HLA-bound susceptibility of H. pylori and PCA differed. PCA-positivity but not ongoing H. pylori infection is associated with autoimmune gastritis. Low titres of PCA might reflect H. pylori infection rather than autoimmune gastropathy.  (+info)

Three-dimensional reconstruction of cytoplasmic membrane networks in parietal cells. (60/406)

There is general agreement that stimulation and consequent secretion of gastric parietal cells result in a great expansion of the apical canalicular membrane at the expense of an extensive intracellular network of membranes rich in the gastric proton pump (H,K-ATPase). However, there is ongoing controversy as to the precise nature of the intracellular membrane network, conventionally called tubulovesicles. At the heart of this controversy lies the question of whether tubulovesicles are a distinct membrane compartment or whether they are continuous with the apical plasma membrane. To address this controversy we used high-pressure, rapid freezing techniques to fix non-stimulated (resting) rabbit gastric glands for electron microscopy. Ultra-thin (60-70 nm) serial sections were used for conventional TEM; 400-500 nm sections were used for tomography. Images were digitized and models constructed using Midas and Imod software (http://bio3d.colorado.edu ). Images were aligned and contours drawn on specific cellular structures. The contours from a stack of serial sections were arranged into objects and meshed into 3D structures. For resting parietal cells our findings are as follows: (1) The apical canaliculus is a microvilli-decorated, branching membrane network that extends into and throughout the parietal cell. This agrees well with a host of previous studies. (2) The plentiful mitochondria form an extensive reticular network throughout the cytoplasm. This has not previously been reported for the parietal cell, and the significance of this observation and the dynamics of the mitochondrial network remain unknown. (3) H,K-ATPase-rich membranes do include membrane tubules and vesicles; however, the tubulovesicular compartment is chiefly comprised of small stacks of cisternae. Thus a designation of tubulocisternae seems appropriate; however, in the resting cell there are no continuities between the apical canaliculus and the tubulocisternae or between tubulocisternae. These data support the recruitment-recycling model of parietal cell stimulation.  (+info)

Requirements for autoimmune responses to mouse gastric autoantigens. (61/406)

Autoimmune gastritis, in which the H+/K(+)-ATPase of parietal cells is the major antigen, is one of the most common autoimmune diseases. Here we examined if specific properties of the H+/K(+)-ATPase or parietal cells are involved in rendering them autoimmune targets. The model antigens beta-galactosidase and ovalbumin (OVA) were expressed in parietal cells of transgenic mice. On experimental induction of autoimmune gastritis by neonatal thymectomy, autoantibodies to beta-galactosidase developed in mice expressing beta-galactosidase in parietal cells, a response that was independent of either the response to the gastric H+/K(+)-ATPase or gastric inflammation. In contrast, mice that expressed OVA in parietal cells did not exhibit an antibody response to OVA after thymectomy. However, increasing the frequency of anti-OVA T lymphocytes in OVA-expressing mice resulted in autoantibodies to OVA and gastritis. These studies indicate that parietal cells can present a variety of antigens to the immune system. Factors such as the identity and expression level of the autoantigen and the frequency of autoreactive T cells play a role in determining the prevalence and outcome of the particular immune response. In addition, as not all mice of a particular genotype displayed autoimmunity, random events are involved in determining the target of autoimmune recognition.  (+info)

Specific localization of an inwardly rectifying K(+) channel, Kir4.1, at the apical membrane of rat gastric parietal cells; its possible involvement in K(+) recycling for the H(+)-K(+)-pump. (62/406)

Hydrochloric acid (HCl) is produced in parietal cells of gastric epithelium by a H(+)-K(+) pump. Protons are secreted into the gastric lumen in exchange for K(+) by the action of the H(+)-K(+)-ATPase. Luminal K(+) is essential for the operation of the pump and is thought to be supplied by unidentified K(+) channels localized at the apical membrane of parietal cells. In this study, we showed that histamine- and carbachol-induced acid secretion from isolated parietal cells monitored by intracellular accumulation of aminopyrine was depressed by Ba(2+), an inhibitor of inwardly rectifying K(+) channels. Among members of the inwardly rectifying K(+) channel family, we found with reverse transcriptase-polymerase chain reaction analyses that Kir4.1, Kir4.2 and Kir7.1 were expressed in rat gastric mucosa. With immunohistochemical analyses, Kir4.1 was found to be expressed in gastric parietal cells and localized specifically at their apical membrane. The current flowing through Kir4.1 channel expressed in HEK293T cells was not affected by reduction of extracellular pH from 7.4 to 3. These results suggest that Kir4.1 may be involved in the K(+) recycling pathway in the apical membrane which is required for activation of the H(+)-K(+) pump in gastric parietal cells.  (+info)

Serum pepsinogen and gastrin levels in HIV-positive patients: relationship with CD4+ cell count and Helicobacter pylori infection. (63/406)

BACKGROUND: The relationship between serum parameters of gastric function and Helicobacter pylori infection in human immunodeficiency virus (HIV)-positive patients is almost unknown. AIMS: To investigate in HIV-infected patients: (i) the relationship between serum gastrin and serum pepsinogens over the progressive phases of HIV-related disease; (ii) the impact of H. pylori infection on gastrin and pepsinogen serum levels and its relation to antral histology; (iii) the prevalence of parietal cell autoantibodies. METHODS: Fifty-nine HIV-positive patients were studied by upper endoscopy plus gastric antral biopsy. Serum samples were tested for gastrin, pepsinogen A, pepsinogen C and parietal cell autoantibodies. RESULTS: In patients without overt acquired immunodeficiency syndrome (AIDS), or with a CD4+ count of > 100 x 10(6) cells/L, mean serum levels of gastrin and pepsinogen C were higher than in subjects with AIDS or with a CD4+ count of < 100 x 10(6) cells/L (P < 0.01). Only one patient was found to be positive for parietal cell autoantibodies. H. pylori infection was associated with increased values of gastrin and pepsinogen C only in HIV-positive patients without AIDS or with a CD4+ count of > 100 x 10(6) cells/L. Atrophy was more frequent in patients with overt AIDS than in those without overt AIDS (57% vs. 33%, P=N.S.), and/or in patients with a CD4+ count of < 100 x 10(6) cells/L than in those with a CD4+ count of > 100 x 10(6) cells/L (62% vs. 26%, P < 0.05). CONCLUSIONS: HIV-positive patients without overt AIDS have increased serum levels of gastrin and pepsinogen C compared with HIV-positive patients with overt AIDS.  (+info)

Regulation and function of COX-2 gene expression in isolated gastric parietal cells. (64/406)

We examined expression, function, and regulation of the cyclooxygenase (COX)-2 gene in gastric parietal cells. COX-2-specific mRNA was isolated from purified (>95%) canine gastric parietal cells in primary culture and measured by Northern blots using a human COX-2 cDNA probe. Carbachol was the most potent inducer of COX-2 gene expression. Gastrin and histamine exhibited minor stimulatory effects. Carbachol-stimulated expression was inhibited by intracellular Ca(2+) chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-AM (90%), protein kinase C (PKC) inhibitor GF-109203X (48%), and p38 kinase inhibitor SB-203580 (48%). Nuclear factor (NF)-kappaB inhibitor 1-pyrrolidinecarbodithioic acid inhibited carbachol-stimulated expression by 80%. Similar results were observed in the presence of adenoviral vector Ad.dom.neg.IkappaB, which expresses a repressor of NF-kappaB. Addition of SB-203580 with Ad.dom.neg.IkappaB almost completely blocked carbachol stimulation of COX-2 gene expression. We examined the effect of carbachol on PGE(2) release by enzyme-linked immunoassay. Carbachol induced PGE(2) release. Ad.dom.neg.IkappaB, alone or with SB-203580, produced, respectively, partial (70%) and almost complete (>80%) inhibition of carbachol-stimulated PGE(2) production. Selective COX-2 inhibitor NS-398 blocked carbachol-stimulated PGE(2) release without affecting basal PGE(2) production. In contrast, indomethacin inhibited both basal and carbachol-stimulated PGE(2) release. Carbachol induces COX-2 gene expression in the parietal cells through signaling pathways that involve intracellular Ca(2+), PKC, p38 kinase, and activation of NF-kappaB. The functional significance of these effects seems to be stimulation of PGE(2) release.  (+info)