Role of apoptosis in gastric epithelial turnover

A Rapid Self-Assembling Peptide Hydrogel for Delivery of TFF3 to Promote Gastric Mucosal Injury Repair

Self-assembled peptide-based nanobiomaterials exhibit promising prospects for drug delivery applications owing to their commendable biocompatibility and biodegradability, facile tissue uptake and utilization, and minimal or negligible unexpected toxicity. TFF3 is an active peptide autonomously secreted by gastric mucosal cells, possessing multiple biological functions. It acts on the surface of the gastric mucosa, facilitating the repair process of gastric mucosal damage. However, when used as a drug, TFF3 faces significant challenges, including short retention time in the gastric mucosal cavity and deactivation due to degradation by stomach acid. In response to this challenge, we developed a self-assembled short peptide hydrogel, Rqdl10, designed as a delivery vehicle for TFF3. Our investigation encompasses an assessment of its properties, biocompatibility, controlled release of TFF3, and the mechanism underlying the promotion of gastric mucosal injury repair. Congo red/aniline blue staining revealed that Rqdl10 promptly self-assembled in PBS, forming hydrogels. Circular dichroism spectra indicated the presence of a stable β-sheet secondary structure in the Rqdl10 hydrogel. Cryo-scanning electron microscopy and atomic force microscopy observations demonstrated that the Rqdl10 formed vesicle-like structures in the PBS, which were interconnected to construct a three-dimensional nanostructure. Moreover, the Rqdl10 hydrogel exhibited outstanding biocompatibility and could sustainably and slowly release TFF3. The utilization of the Rqdl10 hydrogel as a carrier for TFF3 substantially augmented its proliferative and migratory capabilities, while concurrently bolstering its anti-inflammatory and anti-apoptotic attributes following gastric mucosal injury. Our findings underscore the immense potential of the self-assembled peptide hydrogel Rqdl10 for biomedical applications, promising significant contributions to healthcare science.

Can Pyomelanin Produced by Pseudomonas aeruginosa Promote the Regeneration of Gastric Epithelial Cells and Enhance Helicobacter pylori Phagocytosis?

Helicobacter pylori (H. pylori) infection is the most common cause of chronic gastritis, peptic ulcers and gastric cancer. Successful colonization of the stomach by H. pylori is related to the complex interactions of these bacteria and its components with host cells. The growing antibiotic resistance of H. pylori and various mechanisms of evading the immune response have forced the search for new biologically active substances that exhibit antibacterial properties and limit the harmful effects of these bacteria on gastric epithelial cells and immune cells. In this study, the usefulness of pyomelanin (PyoM) produced by Pseudomonas aeruginosa for inhibiting the metabolic activity of H. pylori was evaluated using the resazurin reduction assay, as well as in vitro cell studies used to verify the cytoprotective, anti-apoptotic and pro-regenerative effects of PyoM in the H. pylori LPS environment. We have shown that both water-soluble (PyoMsol) and water-insoluble (PyoMinsol) PyoM exhibit similar antibacterial properties against selected reference and clinical strains of H. pylori. This study showed that PyoM at a 1 μg/mL concentration reduced H. pylori-driven apoptosis and reactive oxygen species (ROS) production in fibroblasts, monocytes or gastric epithelial cells. In addition, PyoM enhanced the phagocytosis of H. pylori. PyoMsol showed better pro-regenerative and immunomodulatory activities than PyoMinsol.

Construction of anoikis-related lncRNAs risk model: Predicts prognosis and immunotherapy response for gastric adenocarcinoma patients

Background: Anoikis acts as a programmed cell death that is activated during carcinogenesis to remove undetected cells isolated from ECM. Further anoikis based risk stratification is expected to provide a deeper understanding of stomach adenocarcinoma (STAD) carcinogenesis. Methods: The information of STAD patients were acquired from TCGA dataset. Anoikis-related genes were obtained from the Molecular Signatures Database and Pearson correlation analysis was performed to identify the anoikis-related lncRNAs (ARLs). We performed machine learning algorithms, including Univariate Cox regression and Least Absolute Shrinkage and Selection Operator (Lasso) analyses on the ARLs to build the OS-score and OS-signature. Clinical subgroup analysis, tumor mutation burden (TMB) detection, drug susceptibility analysis, immune infiltration and pathway enrichment analysis were further performed to comprehensive explore the clinical significance. Results: We established a STAD prognostic model based on five ARLs and its prognostic value was verified. Survival analysis showed that the overall survival of high-risk score patients was significantly shorter than that of low-risk score patients. The column diagrams show satisfactory discrimination and calibration. The calibration curve verifies the good agreement between the prediction of the line graph and the actual observation. TIDE analysis and drug sensitivity analysis showed significant differences between different risk groups. Conclusion: The novel prognostic model based on anoikis-related lncRNAs we identified could be used for prognosis prediction and precise therapy in gastric adenocarcinoma.

The expression of RIPK3 is associated with cell turnover of gastric mucosa in the mouse and human stomach

Necroptosis is a novel manner of programmed cell death and important for tissue development, homeostasis, damage, and repair. Activation of receptor-interacting protein kinase 3 (RIPK3), a key member of receptor-interacting protein family in contributing significantly to necroptosis, in tissues is a hallmark of cells dying by necroptosis. However, there are few studies that examine the expression of RIPK3 in the glandular cells of stomachs under physiological condition. We have therefore conducted this study to immunohistochemically characterize the key element of necroptosis, RIPK3, in the mouse and human stomach. Results showed that RIPK3 positive cells could be observed in the surface mucosal cells, granular cells, and lamina propria cells in both mouse and human stomach tissues. Ratios of PCNA/RIPK3 positive cells in the glandular cells were ~ 2.1 in mouse and ~ 4.15 in human sections respectively. Morphological and double immunofluorescence analysis confirmed that these RIPK3 positive cells were mucous, parietal and lamina propria cells. Our results indicate that the expression of RIPK3 in different cell types might contribute to cell turnover of gastric mucosa in the mouse and human stomach under physiological condition.

Honey and apoptosis in human gastric mucosa

BACKGROUND

Gastric cancer is the fourth most common malignancy in the world. Honey is a complex mixture of special biological active constituents. Honey possesses antioxidant and antitumor properties. Nutritional studies have indicated that consumption of honey modulates the risk of developing gastric cancer. On the other hand, apoptosis has been reported to play a decisive role in precancerous changes. Our chief study was conducted to assess the relationship between consumption of honey and apoptosis in human gastric mucosa.

METHOD

This cross-sectional study was conducted on 98 subjects over 18 years old, referred to two hospitals in Tabriz, Iran. Subjects were undergone an upper gastrointestinal endoscopy, 62 subjects were finally enrolled. Honey consumption was assessed by a Food Frequency Questionnaire (FFQ) and apoptosis was detected by TUNEL technique. We tested polynomial curve to find the best fit between honey consumption and apoptosis.

RESULTS

A positive relation between honey consumption and apoptosis was found (P=0.024). Our results indicated that the final and the best fit curve was: apoptosis = 1.714+1.648(honey amount) - 0.533(honey amount)2 +1.833×10-5(honey amount)7.

CONCLUSION

Honey consumption had positive effects on gastric cancer by inducing apoptosis in gastric mucosa.

Sodium metabisulfite induces lipid peroxidation and apoptosis in rat gastric tissue

Sodium metabisulfite (Na 2S2O5) is used as an antioxidant and antimicrobial agent in a variety of drugs and functions as a preservative in many food preparations. This study was performed to elucidate the dose-dependent effects of sodium metabisulfite ingestion on rat gastric tissue apoptotic changes and lipid peroxidation. Forty male wistar rats, aged 3 months were used. They were randomly divided into four groups: control (C), the group treated with Na2S2O5 (10 mg/kg; S1), the group treated with Na2S2O5 (100 mg/kg; S2), the group treated with Na2S2O5 (260 mg/kg; S3). Na 2S2O5 was given by intragastric intubation for 35 days. In the S2 and S3 groups, malondialdehyde (MDA) levels increased markedly when compared with the control group. High doses of sulfite administration elevated number of apoptotic cells both in mucosa and submucosa layers of stomach in parallel with increased MDA levels. These results suggest that sodium metabisulfite increased lipid peroxidation and thus number of apoptotic cells on gastric tissue in dose-dependent manner.

Amylin prevents TRAIL-mediated apoptotic effects of reserpine in the rat gastric mucosa

We have previously shown that amylin has a protective effect upon the damaged rat gastric mucosa via a cytokine-mediated mechanism. Here, the effects of amylin on the proapoptotic cytokine TNF-related-apoptosis-inducing-ligand (TRAIL) were tested in the rat gastric mucosa damaged by reserpine administration in vivo. Intraperitoneal administration of reserpine in adult male Sprague-Dawley rats resulted in increased TRAIL expression in the gastric mucosa. Immunohistochemistry showed that the TRAIL death-receptor 5 (DR5) was constitutively expressed by the mucosa cells. Western blot showed that pretreatment of reserpine-treated rats with amylin was associated with attenuated expression of TRAIL. In the same samples, we also investigated about TRAIL-related signaling and observed that activation of caspases-8 and -3 occurs in parallel to increased TRAIL expression in rats treated with reserpine. Similarly to the latter, activation of caspases was attenuated in rats pretreated with amylin. Treatment with reserpine was associated with increased expression of the proapoptotic protein Bax, whereas that of the antiapoptotic protein Bcl-2 was significantly decreased. Amylin prevented the effects of reserpine on these genes. Reserpine sets into motion mechanisms of apoptosis in the rat gastric mucosa, which appear mediated, at least in part, by TRAIL. In addition, TRAIL downstream signaling is activated along with subversion of gene expression related to apoptosis. Amylin was able to prevent detrimental effects of reserpine. Finally, amylin and related molecules may be envisioned as protective agent in gastric mucosa damage.

Immune response to Helicobacter pylori and its association with the dynamics of chronic gastritis in the antrum and corpus

The aim of the study was to establish possible factors which play a role in progression of gastritis to atrophic gastritis in long-term follow-up among the Estonian population, to assess the association between the host immune response and different Helicobacter pylori antigens and autoantigens in relation to the histological parameters of gastritis in the antrum and corpus. ELISA and immunoblot were used for detection of IgG to H. pylori acid glycine-extracted cell surface proteins, CagA protein, and H. pylori HSP60. Anticanalicular autoantibodies (ACAB) in the serum were evaluated according to Faller et al. (1996). Apoptosis was evaluated using the TUNEL method. Study subjects were 1958 persons from an unselected Estonian population, and 70 persons from a sample from Saaremaa Island, who had been investigated over a period of 18 years. Seropositivity for CagA was a sign of gastritis activity [OR=14.8 (4.5-50.3)] and atrophy [OR=7.0 (2.1-23.1)] and might predict development of atrophy, particularly in the corpus [OR=7.1 (1.8-27.7)]. The prevalence of ACAB increased significantly with duration of H. pylori gastritis from 22% in 1985 to 46% in 1997 (p=0.004). Immune response to H. pylori HSP60 indicates chronic inflammation in the antrum (p=0.003). Apoptosis of gastric epithelial cells is largely dependent on grade of activity of gastritis, and, particularly in the antrum, on grade of H. pylori colonization (p=0.01; p=0.02), but is not associated with development of atrophy. Seropositivity for different H. pylori antigens (CagA, HSP 60) serves as a marker of different histological manifestations in the antrum and corpus mucosa.

Effects of leptin on stress-induced changes of caspases in rat gastric mucosa

BACKGROUND

In this study, we investigated the effect of leptin on caspase-3, caspase-8, and caspase-9 immunoreactivity and lipid peroxidation in the stomachs of rats exposed to cold-restraint stress.

METHODS

Thirty-two male Wistar Albino rats were used. Rats pretreated with leptin (10 microg/kg per day for 7 days) were restrained in a wire cage for 4 h at 4 degrees C. Spectrophotometric techniques were used for detection of malondialdehyde (MDA) and glutathione (GSH) levels, and immunoreactivity of caspases was investigated by immunohistochemistry.

RESULTS

While the stomach MDA level of the cold-restraint stress group was increased significantly, the level of GSH was decreased when compared with the control group. Caspase-9 and caspase-3 immunoreactivities of the stress group were not changed, while caspase-8 immunoreactivity was decreased. Leptin administration prevented the increase in the MDA level and the decrease in the GSH content of the gastric mucosa in animals subjected to stress. Leptin administration produced no significant change in caspase-8 immunoreactivity but caused a decrease in caspase-3 immunoreactivity.

CONCLUSIONS

Cold-restraint stress decreases the antioxidant capacity of stomach tissue while activating oxidants, and induces apoptosis by an increase in caspase immunoreactivity. The presence of leptin reverses these mechanisms and suppresses the apoptosis.

Localization of TFF3 peptide in human esophageal submucosal glands and gastric cardia: differentiation of two types of gastric pit cells along the rostro-caudal axis

TFF3 (trefoil factor family 3), which is a major secretory product of the gastric antrum and the intestine, but which is nearly absent in the gastric corpus, plays a key role in the maintenance of mucosal integrity. Here, we have systematically investigated TFF3 expression in the esophagus and gastric cardia by the use of reverse transcription/polymerase chain reaction (RT-PCR) analysis and immunohistochemistry. Synthesis of TFF3, but not TFF1 or TFF2, is detectable in esophageal submucosal glands. The stratified squamous epithelium is devoid of TFF synthesis. Prominent TFF3 expression starts at the Z-line with a sharply decreasing gradient toward the cardia. Immunohistochemistry has localized TFF3 to surface mucous cells of the proximal cardia. TFF3 distribution differs characteristically from that of TFF1 (secreted primarily by superficial surface mucous cells), whereas TFF3, together with the mucin MUC5AC, is also found in deeper lying cells toward the isthmus. This is the first report of TFF3 as a typical secretory peptide of esophageal submucosal glands and gastric cardia. The different expression patterns of TFF3 and TFF1 in the cardia suggest a stepwise maturation of surface mucous cells from TFF3/MUC5AC-positive cells close to the isthmus to TFF1/TFF3/MUC5AC-positive cells at the pit. The gradient of TFF3 expression along the gastric rostro-caudal axis defines two types of gastric pit cells: those secreting TFF3 in the cardia and the antrum and those nearly devoid of TFF3 synthesis in the corpus. This indicates the special requirement, particularly of the esophagogastric junction, for TFF3-triggered protection and repair.

Apoptosis in Helicobacter pylori gastritis is related to cagA status

BACKGROUND

Helicobacter pylori infection increases gastric epithelial cell apoptosis; however, the influence of cagA status is still controversial. We aimed to investigate if cagA status is related to apoptosis in H. pylori gastritis at different anatomic sites of the gastric mucosa.

MATERIALS AND METHODS

We studied by immunohistochemistry (streptavidin-biotin method) pro-apoptotic (Bax and Bak) and antiapoptotic (Bcl-2 and Bcl-x) proteins expression, scored from 0 to 4, in gastric biopsies, at the antrum (lesser and greater curvatures), incisura, and corpus (greater curvature) from 50 patients with H. pylori gastritis (22 males, 28 females, median age 40 years) and eight non-infected patients (6 males, median age 39.6 years). H. pylori and cagA status were determined by polymerase chain reaction.

RESULTS

Apoptotic proteins were expressed in a granular pattern, in the cytoplasm of foveolar cells; Bax and Bak expression was higher than Bcl-2 and Bcl-x in most cases and was significantly higher in patients infected by cagA-positive strains than in those infected by cagA-negative strains (p = .001). Bak expression was higher at the lesser curvature (antrum and incisura) than in the other regions (p = .002) and was correlated with atrophy. Anti-apoptotic proteins were significantly more expressed at the antral lesser curvature than in the other regions of the stomach (Bcl-2: p = .02; Bcl-x: p < .001).

CONCLUSIONS

Infection with cagA-positive strains is significantly associated with overexpression of pro-apoptotic proteins in the gastric mucosa, mainly at the antral lesser curvature, which may have a role on atrophy development. Anti-apoptotic proteins were also overexpressed at the lesser curvature, which may occur to keep epithelial cell turnover or might be related to malignant transformation.

Molecular analysis of anoikis resistance in oral cavity squamous cell carcinoma

Oral cavity squamous cell carcinoma (OSCC) is one of the leading causes of cancer deaths worldwide and most of these deaths result from local-regional recurrence and metastases. Evasion of apoptosis is an important hallmark of cancer development and progression, and previous studies have shown that evasion of anoikis, or detachment-induced apoptosis, correlates with a more aggressive phenotype of carcinoma cells in OSCC. To elucidate the cytogenetic and molecular characteristics of anoikis resistance, we generated several cell lines and clones that displayed this cellular phenotype. To test the hypothesis that chromosomal alterations may underlie this phenotypic transformation, we used karyotype analysis to observe changes in the chromosomal structure of anoikis-sensitive and anoikis-resistant cell lines. We further hypothesized that a unique pattern of gene expression was induced by cell-detachment of anoikis-resistant cell lines, and cDNA microarray analysis was performed using a panel of anoikis-resistant oral cancer cell lines grown under attached and detached growth conditions. We identified S100P, KLK6 and CTNNAL1 as genes whose expression levels were differentially regulated in the anoikis-resistant cell lines compared to the anoikis-sensitive cells under detached conditions. These results were verified using real-time RT-PCR. The anoikis-resistant phenotype of squamous cell carcinoma has a distinct genetic expression pattern that is marked by chromosomal alterations that may contribute to differential expression of genes involved in diverse cellular functions. Therapies targeting these potential mediators of anoikis resistance may prove to be beneficial in the treatment of metastatic squamous cell carcinoma.

Gastric graft-versus-host disease revisited: does proton pump inhibitor therapy affect endoscopic gastric biopsy interpretation?

Accurate diagnosis of gastrointestinal graft-versus-host disease (GvHD) is important, as it contributes significantly to postallogeneic stem cell transplant (SCT) morbidity and mortality. To test the hypothesis that proton pump inhibitor (PPI) therapy may interfere with histologic evaluation of gastric GvHD by inducing apoptosis, we evaluated epithelial apoptotic body counts in antral and fundic biopsies from SCT recipients and control patients, both taking and not taking PPIs at the time of endoscopic biopsy. Hematoxylin and eosin-stained slides of gastric biopsies from 130 patients (75 allogeneic SCT with GvHD on clinical and histologic grounds, and a comparison group of 55 age- and sex-matched nontransplant patients with histologically normal gastric biopsies) were reviewed. The groups were further stratified into patients taking (PPI+) and not taking PPIs (PPI-) at the time of biopsy. Apoptotic bodies (AB)/10 (400 x) high power fields (HPF) were quantified for each case. Mean apoptotic body counts were then calculated for each case group. Seventy antral cases (31 control and 39 transplant) were also evaluated via gastrin immunohistochemistry, and the mean number of gastrin positive cells/400 x HPF calculated. In the PPI- groups, apoptosis was increased in biopsies from transplant patients, compared with controls, both in antral and fundic mucosa. In PPI+ patients, there was significantly more apoptosis in the gastric body in transplant patients than in controls. However, comparing antral biopsies from control and transplant PPI+ patients, there was no significant difference in AB quantitation. More apoptosis was seen in antral biopsies from PPI+ control patients when compared with PPI- control patients (P = 0.009). Mean numbers of gastrin positive cells/400 x HPF were increased in both control and transplant patients taking PPIs (85 and 58, respectively) compared with samples from those patients not taking PPIs (48 and 51, respectively). PPI therapy is associated with increased apoptosis in antral biopsies and may interfere with the evaluation of GvHD in biopsies from this site. A similar increase in apoptosis was not seen in fundic biopsies; biopsy of the gastric fundus rather than antrum may be preferable for the diagnosis of upper gastrointestinal GvHD.

Cell proliferation and inflammation on biopsy samples with multifocal atrophic gastritis before and 1 year after Helicobacter pylori eradication

CONTEXT

Results of clinical trials that have assessed whether gastric cancer is preventable with Helicobacter pylori eradication therapy remain inconclusive. These trials have used atrophy, intestinal metaplasia, and dysplasia as histopathologic end points that reflect possible preneoplastic lesions. Trial results would be more compelling if cell proliferation and inflammatory markers improved simultaneously with histopathologic lesions.

OBJECTIVE

To study the presence of cell proliferation markers and type of inflammatory cells in biopsy specimens with gastritis, atrophy, and intestinal metaplasia before and 1 year after H pylori therapy and to determine if immunohistochemistry can be used to study these.

DESIGN

We evaluated 12 subjects with gastritis and 16 with gastritis and multiple foci of atrophy and intestinal metaplasia by using immunohistochemical assays for tumor suppressor protein p53, proliferation marker Ki-67, cell cycle regulator cyclin D1, T and B lymphocytes, macrophages, and TUNEL (terminal deoxynucleotide transferase deoxyuridine triphosphate nick end labeling) assay for apoptosis. The biopsy specimens were selected from a randomized clinical trial that studied improvement of histopathologic gastric lesions after H pylori eradication.

RESULTS

Groups of surface epithelial cells that expressed p53 and Ki-67 were observed more often in subjects with atrophy and intestinal metaplasia compared with those with gastritis alone. T lymphocytes in the lamina propria were frequently observed 1 year after treatment in subjects with atrophy and intestinal metaplasia.

CONCLUSIONS

Immunohistochemical assays for cell proliferation and inflammatory cell markers showed different distribution patterns in these gastric biopsy specimens. The presence of T lymphocytes and groups of cells that expressed proliferation markers in subjects with multiple foci of atrophy and intestinal metaplasia needs further study.

Transforming growth factor beta-dependent sequential activation of Smad, Bim, and caspase-9 mediates physiological apoptosis in gastric epithelial cells

Transforming growth factor beta (TGF-beta) has been implicated in the maintenance of homeostasis in various organs, including the gastric epithelium. In particular, TGF-beta-induced signaling was shown to be required for the differentiation-associated physiological apoptosis of gastric epithelial cells, but its mechanism has not been well understood. In this study, the molecular mechanism of TGF-beta-induced apoptosis was analyzed in a human gastric epithelial cell line, SNU16, as an in vitro model. Expression of Smad7 and Bcl-X(L), but not viral FLIP, was shown to prevent TGF-beta-induced apoptosis, indicating an exclusive requirement of the activation of Smad signaling pathway and mitochondrial dysfunction followed by activation of caspase-9. In addition, treatment with TGF-beta induced binding of Bim, a proapoptotic Bcl-2 homology domain 3 (BH3)-only protein, to Bcl-X(L), which is dependent on the activation of Smad, and reduction in the expression of Bim by RNA interference decreased the sensitivity to TGF-beta-induced apoptosis. Moreover, we found abnormalities in the gastric epithelium of both Bim and caspase-9 knockout mice; these abnormalities were associated with a defect of physiological apoptosis in gastric epithelial cells. These results indicate for the first time that TGF-beta is involved in the physiological loss of gastric epithelial cells by activating apoptosis mediated by Smad, Bim, and caspase-9.

Bax and Bcl-2 protein expression in gastric precancerous lesions: immunohistochemical study

BACKGROUND AND AIMS

Bcl-2 protein prolongs cell survival in the face of classical apoptotic stimuli, and is considered to be a suppressor of apoptosis. Bax plays a key role in apoptosis by accelerating cell death after an apoptotic stimulus. The aim of our study was to determine the roles of the Bax proapoptotic gene and the Bcl-2 antiapoptotic gene in the carcinogenesis of gastric cancer.

METHODS

One hundred and forty-five gastric biopsy specimens of chronic gastritis, atrophic gastritis, intestinal metaplasia and gastric dysplasia were studied. Using immunohistochemical methods, Bax and Bcl-2 protein expression was observed.

RESULTS

Bax was expressed in epithelial cells in all cases of chronic gastritis. Bax was not detected in 26% of specimens of atrophic gastritis. As intestinal metaplasia develops, Bax is further suppressed. In biopsy samples with dysplasia, Bax expression was demonstrated only in 12% of biopsy samples. Although Bcl-2 protein was not detected in chronic gastritis, aberrant expression was found in gastric epithelial intestinal metaplasia and dysplasia.

CONCLUSIONS

The suppression of Bax and overexpression of Bcl-2 protein is an early event in gastric tumorigenesis, before gastric dysplastic changes occur.

Molecular characterization of rat gastric mucosal response to potent acid inhibition

Potent acid inhibition with proton pump inhibitors (PPIs) is widely used in clinical medicine, especially for gastroesophageal reflux disease. PPIs cause profound changes in the intragastric environment with near-neutral pH and increase serum concentration of the gastric secretagogue hormone gastrin. Long-term hypergastrinemia increases mucosal thickness and enterochromaffin-like cell density in gastric corpus mucosa and results in development of gastric carcinoids in experimental animals. Our aim was to study responses to potent acid inhibition by characterizing genome-wide gene expression changes in gastric corpus mucosa in rats dosed with the PPI omeprazole. Nine rats received 400 micromol/kg omeprazole daily for 10 wk. Seven rats received vehicle only. Analysis of gastric corpus with microarrays representing 11,848 genes identified 134 genes with changed gene expression levels in omeprazole-dosed rats. Several of the identified genes were previously known to be affected by potent acid inhibition. Of the 62 genes with known functions that changed gene expression levels after PPI dosing, 27 are known to be involved in proliferation and apoptosis and immune, inflammatory, and stress responses. Our study indicates that microarray analysis can detect relevant gene expression changes in the complex gastric tissue, and that cellular processes involved in cell growth and defense responses are strongly affected by PPI dosing. Many genes are identified that were not previously known to be affected by inhibition of gastric acid secretion or that have unknown biological functions. Characterization of the roles of these genes may give new insight into molecular responses to treatment with PPIs.

Analysis of gene expression profile in gastric cancer cells stimulated with Helicobacter pylori isogenic strains

To understand the biological processes within host cells induced by VacA, isogenic strains of Helicobacter pylori (NCTC 11638 or 11638-DeltavacA) were used to stimulate gastric cancer cells SGC7901, and differentially expressed genes in host cells were identified using cDNA microarray technology. More than 300 genes were found to alter their mRNA expression at different time points, among which 68 were related to the cytoskeleton, 87 were associated with cell cycle, cell death and proliferation, IL8 expression was also found to be up-regulated. Cells co-cultured with broth-culture supernatant (BCS) of NCTC 11638 showed more alteration in microtubule cytoskeleton morphology, as observed by laser scanning confocal microscopy, and a lower apoptosis rate, detected by flow cytometry, compared with those co-cultured with BCS of 11638-DeltavacA. The supernatants of cells co-cultured with NCTC 11638 showed significantly higher IL8 expression than those co-cultured with 11638-DeltavacA. It is concluded that VacA disrupts cytoskeletal architecture by influencing the expression of cytoskeleton-associated genes. VacA breaks the balance between cell proliferation and cell death by inducing the maladjustment of genes related to cell cycle. VacA is also able to induce the inflammatory response.

FLICE/caspase-8 activation triggers anoikis induced by β1-integrin blockade in human keratinocytes

β1-integrin protects keratinocyte stem cells (KSC) from cell-detachment apoptosis (`anoikis'). Here we show that caspase-8 active protein is detected in both young transit amplifying (TA) cells and TA cells, but not in KSC. On suspension, caspases are activated earlier in young TA than in KSC, whereas anti-β1-integrin neutralizing antibody accelerates caspase activation in both KSC and young TA. Caspases 8 and 10 are the first caspases to be activated whereas caspase-8 inhibitor zIETD-fmk delays the activation of Bid, caspase-9 and caspase-3. However, the caspase-9 inhibitor zLEDH-fmk does not block the activation of caspase-8, Bid, caspase-10 and caspase-3. Moreover, caspase-8, but not caspase-9 inhibitor partially prevents keratinocyte anoikis. As FLIP inhibits caspase-8 processing, we retrovirally infected HaCaT keratinocytes with c-FLIPL. Anti-β1-integrin fails to activate caspase-8, Bid, caspase-9 and to induce the release of cytochrome c in c-FLIPL overexpressing keratinocytes. Finally, overexpression of c-FLIPL partially prevents anoikis in both suspended and anti-β1 integrin-treated cells. Taken together, these results indicate that the extrinsic apoptotic pathway triggered by caspase-8 predominates in keratinocyte anoikis. However, the release of cytochrome c and the later activation of caspase-9 seem to suggest that the intrinsic mitochondrial pathway may intervene as a positive feedback loop of caspase activation.

Acquisition of anoikis resistance is a critical step in the progression of oral tongue cancer

We hypothesized that acquisition of resistance to anoikis is a critical step in oral cancer progression. To test this hypothesis, we compared a panel of cell lines derived from human oral tissues across the spectrum of tumor progression from oral keratinocytes (HOK-16B), invasive oral squamous cell carcinoma (Tu167), and finally metastatic carcinoma (TxCS-1, MDA1986) for their sensitivity to detachment from the extracellular matrix. The relationship between stage of tumor progression and anoikis resistance was demonstrated by the apoptotic fractions after 48 h in suspension culture which were 93.33, 61.6, 34.5, and 3.71%, respectively. To further demonstrate that anoikis resistance is important for tumor progression, we selected a highly anoikis resistant cell line, JMAR, by serial passage of the Tu167 cell line in suspension culture. Initially, the JMAR line, and clones derived from it, were characterized for anoikis resistance in vitro, and after 72 h in suspension culture the rates of anoikis in the Tu167 and JMAR lines were found to be 73 and 26%, respectively. The degree of anoikis resistance was found to correlate with survival of nude mice orthotopically injected with 5x10(5) Tu167 or JMAR cells. The JMAR mice had a median survival of 17 days versus over 30 days in mice implanted with the Tu167 line. Finally, we found that in vivo selection in the orthotopic model for a regionally metastatic cell line by implantation of Tu167 into the tongues of nude mice and harvesting and culturing cervical lymph nodes led to production of a cell line, Tu167LN1, which was found to be anoikis-resistant. This cell line had an apoptotic cell fraction of 16.2% (+/-3.14%) after 48 h in suspension culture.

Role of glutamine and arginase in protection against ammonia-induced cell death in gastric epithelial cells

Ammonia is a cytotoxic factor produced during Helicobacter pylori infection that may reduce the survival of surface epithelial cells. Here we examine whether ammonia kills cells and whether L-glutamine (L-Gln) protects against cell death by stimulating ammonia detoxification pathways. Cell viability and vacuolation were quantified in rat gastric epithelial (RGM1) cells incubated with ammonium chloride at pH 7.4 in the presence or absence of L-Gln. Incubation of RGM1 cells with ammonium chloride caused a dose-dependent increase in cell death and vacuolation, which were both inhibited by L-Gln. We show that RGM1 cells metabolize ammonia to urea via arginase, a process that is stimulated by L-Gln and results in reduced ammonia cytotoxicity. L-Gln also inhibits the uptake and facilitates the extrusion of ammonia from cells. Blockade of glutamine synthetase did not reduce the survival of RGM1 cells, demonstrating that the conversion of L-glutamate and ammonia to L-Gln is not involved in ammonia detoxification. Thus our data support a role for L-Gln and arginase in protection against ammonia-induced cell death in gastric epithelial cells.

Roles of tumor necrosis factor-alpha-receptor type 1 and Fas in the Helicobacter pylori-induced apoptosis of gastric epithelial cells

OBJECTIVES

Helicobacter pylori (HP) infection has been reported to accelerate the apoptosis of gastric epithelial cells. This bacteria has also been known to enhance the expression levels of molecules such as Fas antigen and a receptor for tumor necrosis factor-alpha-receptor type 1 (TNF-R1). However, whether Fas and/or TNF-R1 is actually involved in HP-mediated apoptosis has yet to be evaluated. The purpose of this study was therefore to examine the roles of Fas and TNF-R1 in HP-mediated apoptosis.

METHODS

Biopsy samples were collected from 10 HP-negative healthy volunteers and from 39 HP-positive ulcer patients. Gastric epithelial cells were obtained from the samples. The cells were then stained with anti-Fas, anti-TNF-R1 and Annexin V, which detected apoptotic cells. The findings were analyzed by three-color flow cytometry.

RESULTS

The percentages of apoptotic cells were significantly higher in HP-positive patients than in the controls. In HP-negative controls, almost all of the apoptotic cells lacked both Fas and TNF-R1. On the other hand, in HP-positive patients, HP upregulated the expression levels of Fas and TNF-R1 and, consequently, enhanced the apoptosis mediated by receptors such as Fas and TNF-R1. However, even in HP-positive patients, apoptosis was also observed in the cells that lacked both Fas and TNF-R1.

CONCLUSIONS

Fas and TNF-R1 expressed on gastric epithelial cells from HP-infected patients were responsible for the accelerated apoptosis of the cells.

Transforming growth factor-beta1 is responsible for maturation-dependent spontaneous apoptosis of cultured gastric pit cells

In this study, we established a system of high concentration serum-dependent spontaneous apoptosis of guinea pig gastric pit cells in primary culture, which seems to mimic the spontaneous apoptosis of matured gastric pit cells at gastric surface in vivo. In addition to induction of the spontaneous apoptosis, cell growth was inhibited in the presence of 10% serum compared with 0.5% serum. Transforming growth factor-beta1 (TGF-beta1), which is known to cause both apoptosis and growth inhibition in mammalian cells, was present in serum of both fetal calf and guinea pig. The addition of recombinant TGF-beta1 to the culture medium containing 0.5% fetal calf serum caused both induction of apoptosis and inhibition of cell growth. On the other hand, immunodepletion of TGF-beta1 from fetal calf serum caused inability to induce both the spontaneous apoptosis and inhibition of cell growth. These data suggest that TGF-beta1 is involved in the spontaneous apoptosis of guinea pig gastric pit cells in primary culture.

Gastric irritant-induced apoptosis in guinea pig gastric mucosal cells in primary culture

When the gastric mucosa is exposed to various irritants, apoptosis and subsequent gastric mucosal lesion can result in vivo. We here show that gastric irritants induced apoptosis in gastric mucosal cells in primary culture and examined its molecular mechanism. Ethanol, hydrogen peroxide, and hydrochloric acid all induced, in a dose-dependent manner, cell death, apoptotic DNA fragmentation, and chromatin condensation, suggesting that each of these gastric irritants induced apoptosis in vitro. Since each of these irritants decreased the mitochondrial membrane potential and stimulated the release of cytochrome c from mitochondria, gastric irritant-induced apoptosis seems to be mediated by mitochondrial dysfunction. Caspase-3, caspase-8, and caspase-9-like activities were all activated simultaneously by each of these irritants and the activation was concomitantly with cell death and apoptotic DNA fragmentation. Furthermore, pre-treatment of gastric mucosal cells with an inhibitor of caspase-8 suppressed the onset of cell death as well as the stimulation of caspase-3- and caspase-9-like activities caused by each of these gastric irritants. Based on these results, we consider that caspase-8, an initiator caspase, plays an important role in gastric irritant-induced apoptosis.