Inoculation of VacA- and CagA- Helicobacter pylori delays gastric ulcer healing in the rat

Local Use of Apisan Gel, A New Oral Care Product in the Treatment of Experimental Periodontitis Against the Background of Hyperacid Gastritis and Intoxication with Tobacco Smoke

OBJECTIVES

The aim of the work was to substantiate the use of a newly created oral care product in the treatment of periodontal disease reconstructed against the background of hyperacidic gastritis under the conditions of tobacco smoke intoxication.

MATERIALS AND METHODS

The study was conducted in 2 stages. In the first stage, all experimental animals were divided into 4 groups: 1) intact, 2) with simulated periodontitis, 3) with reproduced periodontitis against the background of reproduced hyperacidic gastritis, 4) with reproduced periodontitis against the background of hyperacid gastritis under the conditions of tobacco smoking. Biochemical studies of gum homogenate with periodontitis in rats were conducted to determine the impact of stomach pathology and tobacco smoke as endogenous and exogenous risk factors. In stage 2, the effectiveness of local therapy with the use of the newly created oral care product and a comparator was studied in rats with reproduced periodontitis against the background of hyperacidic gastritis under the conditions of smoking.

RESULTS

In the experimental periodontitis against the background of hyperacidic gastritis under the conditions of tobacco smoking, there were significant changes in the periodontal tissues characteristic of the inflammatory process: the activity of peroxide oxidation of lipid (POL) increased, activity of the antioxidant system decreased, and inflammatory markers increased when nonspecific protection was reduced. Local therapy in the rats using the new "Apisan" gel resulted in the correction of certain metabolic disorders, faster elimination of the harmful effects of the damaging factors, and restoration of the condition of periodontal tissues compared with the use of the comparator, the Asepta gel.

CONCLUSION

The therapeutic effectiveness of the new Apisan gel is due to the normalizing effect on the processes of POL, and inflammation and activation of the oral cavity protective systems during inflammatory periodontal disease occurring against the background of a concomitant stomach pathology, hyperacidic gastritis.

Helicobacter pylori-induced gastric pathology: insights from in vivo and ex vivo models

Gastric colonization with Helicobacter pylori induces diverse human pathological conditions, including superficial gastritis, peptic ulcer disease, mucosa-associated lymphoid tissue (MALT) lymphoma, and gastric adenocarcinoma and its precursors. The treatment of these conditions often relies on the eradication of H. pylori, an intervention that is increasingly difficult to achieve and that does not prevent disease progression in some contexts. There is, therefore, a pressing need to develop new experimental models of H. pylori-associated gastric pathology to support novel drug development in this field. Here, we review the current status of in vivo and ex vivo models of gastric H. pylori colonization, and of Helicobacter-induced gastric pathology, focusing on models of gastric pathology induced by H. pylori, Helicobacter felis and Helicobacter suis in rodents and large animals. We also discuss the more recent development of gastric organoid cultures from murine and human gastric tissue, as well as from human pluripotent stem cells, and the outcomes of H. pylori infection in these systems.

Helicobacter pylori induces gastritis and intestinal metaplasia but no gastric adenocarcinoma in Mongolian gerbils

OBJECTIVE

The Mongolian gerbil is considered as the model of choice when studying adenocarcinoma related to Helicobacter pylori infection. The purpose of this study was to compare two different H. pylori strains and elucidate whether adenocarcinomas developed in gerbils.

MATERIAL AND METHODS

Male gerbils were separated into three groups: one control and two groups infected with two different strains of H. pylori, TN2GF4 and SS1. At 3, 6, 12 or 18 months after inoculation 5 animals from each group were sacrificed. The stomach was used for culture, and for histology.

RESULTS

Inflammation was seen after 3 months in all the infected animals. In the controls no pathology was found at any time. Intestinal metaplasia was found in both the infected groups. Glands buried in the submucusal layer, changes that might be misinterpreted as adenocarcinoma, were found in 10% of the SS1 and in 65% of the TN2GF4 animals. Adenocarcinoma was not found in any of the gerbils.

CONCLUSIONS

All studies claiming to have found H. pylori-induced adenocarcinomas in gerbils describe atypical glands penetrating into the muscularis propria and interpret these as invasive growths due to cancer. An alternative interpretation is that the deranged glandular structures grow in and below the submucosa. It is suggested that atypical glands in the muscularis layer are not enough as a diagnostic criterion for gastric adenocarcinoma. It is concluded that adenocarcinoma has not yet been shown convincingly to develop in Mongolian gerbils infected with H. pylori. Nevertheless, it is a model well suited for studying gastritis, gastric ulcer and premalignant changes such as metaplasia.

Effect of Helicobacter pylori on delay in ulcer healing induced by aspirin in rats

Helicobacter pylori and nonsteroidal anti-inflammatory drugs (NSAIDs) are major pathogenic factors in peptic ulcer disease but whether these two factors exert synergistic or antagonistic effects on ulcer healing has been a subject of controversy. We compared the effect of aspirin alone with that of aspirin combined with H. pylori on gastric acid secretion and healing of acetic acid gastric ulcers in rats. The H. pylori colonization of gastric mucosa was determined by viable H. pylori culture, histology and assessment of bacterial DNA using polymerase chain reaction (PCR). The area of ulcers, gastric blood flow, mucosal generation of prostaglandin E(2) and plasma gastrin levels and expression of cyclooxygenase-1, cyclooxygenase-2 and growth factors was determined. Aspirin delayed significantly the healing of chronic gastric ulcers, decreased the gastric blood flow at the ulcer margin and gastric mucosal prostaglandin E(2) generation being without significant influence on gastric acid output. H. pylori acquisition that produced moderate gastric inflammation at the ulcer margin delayed significantly the healing of gastric ulcers, decreased significantly both the gastric blood flow at the ulcer margin and the gastric secretion while raising significantly the gastric mucosal prostaglandin E(2) generation and plasma gastrin levels. H. pylori infection attenuated the aspirin-induced inhibition of ulcer healing and accompanying fall in the gastric blood flow. Both aspirin and H. pylori up-regulated significantly cyclooxygenase-2 messenger RNA (mRNA) and protein but not that of cyclooxygenase-1 at the ulcer margin. Aspirin reduced significantly the transforming growth factor alpha- and vascular endothelial growth factor mRNAs, but these effects were significantly attenuated by H. pylori. We conclude that H. pylori antagonizes, in part, aspirin-induced delay of ulcer healing due to suppression of acid secretion, the enhancement in prostaglandin E(2) possibly derived from cyclooxygenase-2 and the overexpression of transforming growth factor alpha and vascular endothelial growth factor in the ulcer area.

Apoptosis in gastric epithelium induced by Helicobacter pylori infection: implications in gastric carcinogenesis

OBJECTIVES

Helicobacter pylori is an identified carcinogen for gastric cancer, however, the underlying mechanisms remain to be defined. In this review, we sought to elucidate the role of apoptosis in gastric carcinogenesis, to determine the influence of H. pylori infection on apoptosis, and finally to provide insights into the mechanisms by which H. pylori may lead to gastric carcinogenesis.

METHODS

A broad-based MEDLINE and Current Contents literature search was performed to identify relevant publications between 1966 and March 2000 addressing H. pylori infection, apoptosis, cell proliferation, gastric carcinoma, oncogenes, and tumor suppressor genes, as well as the products of these genes. Abstracts from recent major conferences that provided adequate additional data were also included.

RESULTS

Apoptotic cells are rare in the glandular neck region (the generative cell zone) of normal gastric mucosa. With progression of atrophic gastritis, the generative cell zone shifts downward and a relatively large number of apoptotic cells occur. In intestinalized glands, both apoptotic cells and proliferative cells are present in deeper portions of the glands, corresponding to the generative zone. A higher frequency of apoptosis has been observed in gastric dysplasia than in coexisting gastric carcinomas, whereas the number of proliferative cells is significantly higher in gastric carcinoma than in dysplasia. Upregulation of oncogene bcl-2 in premalignant lesions and "downregulation" of the gene after malignant change is probably a common event. Accumulation of p53 protein is first detected in dysplasia, although mutation of the pS3 gene may occur in intestinal metaplasia. H. pylori infection induces apoptosis in gastric epithelial cells, which returns to normal after eradication of the infection. Numerous molecules produced by H. pylori including cytotoxin (VacA), lipopolysaccharide, monochloramine, and nitric oxide may directly induce apoptosis. Moreover, H. pylori-stimulated host inflammatory/immune responses lead to release of a large amount of cytokines. Cytokines produced by type 1 T helper cells, such as TNF-alpha and IFN-gamma, markedly potentiate apoptosis. Gastric cell proliferation is significantly higher in patients with H. pylori infection than in normal controls, and eradication of the infection leads to a reduction in cell proliferation. Apoptosis and cell proliferation are also increased in precancerous lesions such as gastric atrophy, intestinal metaplasia, and dysplasia in the presence of H. pylori infection. However, H. pylori-induced apoptosis may no longer be cell cycle-dependent in these lesions because of the occurrence of alterations and mutations of apoptosis-regulating genes, resulting in a loss of balance between apoptosis and cell proliferation.

CONCLUSIONS

It is hypothesized that H. pylori-induced apoptosis may play a key role in gastric carcinogenesis by increasing cell proliferation and/or resulting in gastric atrophy.

Helicobacter pylori modulates lymphoepithelial cell interactions leading to epithelial cell damage through Fas/Fas ligand interactions

Helicobacter pylori causes a common chronic infection of humans that leads to epithelial cell damage. Studies have shown that apoptosis of the gastric epithelium is increased during infection and this response is associated with an expansion of gastric T-helper type 1 (Th1) cells. We report that gastric T cells contribute to apoptosis of the epithelium by a Fas/Fas ligand (FasL) interaction. Fas receptor expression was detected on freshly isolated gastric epithelial cells by flow cytometry and immunohistochemistry, and this level of expression was increased during infection with H. pylori. The expression of Fas receptor on three gastric epithelial cell lines was increased by H. pylori, either alone or in combination with gamma interferon or tumor necrosis factor alpha. The role of Fas in apoptosis of gastric epithelial cell lines was evidenced by DNA fragmentation after cross-linking of Fas with specific antibodies. FasL expression was detected by immunohistochemistry on mononuclear cells in gastric biopsy specimens of infected but not uninfected subjects. Gastric T-cell lines were also shown to express FasL, as evidenced by reverse transcription-PCR and killing of target cells expressing Fas receptor. Moreover, these T-cell lines were capable of killing cultured gastric epithelial target cells and antibodies that block the interaction between Fas receptor and FasL inhibited this cytotoxic activity. These observations demonstrate that local Th1 cells may contribute to the pathogenesis of gastric disease during H. pylori infection by increasing the expression of Fas on gastric epithelial cells and inducing apoptosis through Fas/FasL interactions.

The therapeutic effect of proton pump inhibitors on Helicobacter pylori-positive gastric ulcers

The aim of the present study was to elucidate the risk factors that could delay gastric ulcer healing when either a proton pump inhibitor or an H2-receptor antagonist is used for gastric ulcer treatment. Endoscopically-diagnosed gastric ulcer patients (216 men and 96 women, mean age: 57+/-13 years) were investigated. All patients were consecutively recruited and randomly assigned to receive H2-receptor antagonist (n = 196) or proton pump inhibitor (n = 116) treatment for eight weeks. Chi-squared tests and multivariate analysis to determine factors influencing ulcer healing were used to analyse the patients profiles, endoscopic findings, and Helicobacter pylori-infection status. In the H2-receptor antagonist group, the most important risk factor was a large ulcer size (> 2 cm diam.), followed by a linear shape of the ulcer, undermining tendency of ulcer, previous history of gastric ulcer, and H. pylori infection. In the proton pump inhibitor group, linear shape of the ulcer was the only significant risk factor for slow ulcer healing; other factors, including H. pylori infection, were insignificant. These results indicate that ulcer morphology may be the most important information for predicting ulcer healing, and that H. pylori infection does not delay gastric ulcer healing when proton pump inhibitor treatment is used.

Effects of Helicobacter pylori on proliferation of gastric epithelial cells in vitro

OBJECTIVE

H. pylori infection of the gastric mucosa has been associated with an increase in gastric epithelial cell proliferation. However, in vitro adherence of H. pylori to gastric epithelial cells is associated with reduced cell proliferation. Reduction of epithelial cell proliferation may contribute to ulcer formation and delay ulcer healing. The following study was undertaken to elucidate the ability of cagA-positive and -negative strains to impede gastric epithelial cell proliferation.

METHODS

A human gastric adenocarcinoma cell line (AGS) was overlaid with either cagA-positive or cagA-negative H. pylori strains suspended in cell culture medium. Proliferation of AGS cells was analyzed by performing direct cell counts and by measuring metabolism of a soluble tetrazolium compound (MTS), after exposure to H. pylori for 24 h.

RESULTS

When compared with control cells cultured in medium alone, AGS cell proliferation was reduced by 45.6% and 28.5% due to exposure to cagA-negative and cagA-positive strains, respectively. When bacterial-induced cytotoxicity was assessed by measuring release of lactose dehydrogenase (LDH) into the culture medium, cagA-positive strains were shown to induce significantly more cytotoxicity than cagA-negative strains.

CONCLUSIONS

These experiments demonstrate that H. pylori exposure to AGS cells significantly reduces cell proliferation. However, cagA-positive strains that induce more cell injury reduce cell proliferation to a lesser extent than cagA-negative strains. Persistent replication of gastric epithelial cells injured by exposure to cagA-positive strains may be partially responsible for the stronger association with gastric cancer in persons infected with cagA-positive H. pylori strains.

Mouse model of Helicobacter pylori infection: studies of gastric function and ulcer healing

BACKGROUND

Helicobacter pylori infection in humans is a major risk factor for peptic ulcer, but studies on the relation between H. pylori infection and gastric pathology are limited due to a deficiency of convenient animal models resembling this infection in humans.

METHODS

We studied the effects of inoculation of conventional BALB/c mice with CagA and VacA positive (type I) H. pylori or CagA and VacA negative H. pylori (type II) strains on gastric secretion and healing of chronic acetic acid-induced ulcers in mouse stomachs. The ulcer area, gastric blood flow, plasma interleukin (IL)-1beta and IL-12, as well as plasma gastrin and gastric luminal somatostatin were determined. Gastric mucosal biopsy samples were also taken for assessment of the presence of viable H. pylori using a rapid urease test, H. pylori-culture and the RT-PCR analysis of the signal for H. pylori CagA.

RESULTS

Gastric acid and pepsin secretion was reduced by over 50% immediately after H. pylori inoculation and accompanied by a significant increment in plasma gastrin and fall in gastric luminal somatostatin content observed over all test days, particularly in mice infected with type I H. pylori. The area of ulcers in vehicle-treated controls decreased significantly starting from day 2 after ulcer induction and then continued to decline for a further 14 days to heal almost completely after 28 days. In contrast, the ulcers were present until day 28 in all mice infected with type I or type II H. pylori strains, being significantly larger, especially with type I H. pylori infection. The gastric blood flow at the ulcer margin and ulcer crater in vehicle-treated mice gradually increased with decreasing ulcer size, after 14 and 28 days reaching a value which was not significantly different from that in vehicle-administered mice. In contrast, the gastric blood flow in type I H. pylori and, to a lesser extent, in type II H. pylori infected mice was significantly lower than in vehicle controls, both at the margin and at the crater of ulcers at all tested days. Histological changes such as oedema or congestion of surface epithelium were found after 7 days whereas mucosal inflammatory infiltration appeared after 14 days with a further increase after 28 days, especially in type I H. pylori and to a lesser extent in type II H. pylori infected mice. Plasma IL-1beta and IL-12 were significantly elevated at all tested days of ulcer healing and their increments were significantly higher in type I than in type II H. pylori infection.

CONCLUSIONS

Conventional mice with gastric ulcers can be successfully infected by both toxigenic and nontoxigenic H. pylori strains, and this infection causes an immediate suppression of gastric secretion and markedly delays the healing of ulcers due to the fall in mucosal microcirculation in the ulcer region, cytokine release and an impairment in the gastrin-somatostatin link that appears to be independent of gastritis and more pronounced with infection of toxigenic than nontoxigenic strains.

Effects of clarithromycin, omeprazole and leminoprazole on gastric ulcer healing in Helicobacter pylori-infected rats

We examined whether a single inoculation of Helicobacter pylori can colonize the stomachs of ulcerated rats and delay their healing and whether an antibiotic drug and acid pump inhibitors can enhance the ulcer healing in infected rats. Ulcers were produced by a submucosal injection of acetic acid solution into the gastric wall. Helicobacter pylori (ATCC-43504) was inoculated into rats with and without gastric ulcers. The animals were killed 2, 4, 6, 8 or 10 weeks after the inoculation and the ulcerated area and H. pylori viability were determined. Each test drug and their combination was administered for 1 or 2 weeks after H. pylori inoculation. Helicobacter pylori could not colonize the stomachs of normal rats, but could colonize stomachs with ulcers for 10 weeks at an incidence of >80%. Spontaneous healing of gastric ulcers was delayed by H. pylori infection during these 10 weeks. Daily treatment with clarithromycin significantly and dose-dependently delayed ulcer healing in infected rats. Both omeprazole and leminoprazole significantly enhanced ulcer healing and inhibited the clarithromycin-delayed ulcer healing. We conclude that: (i) H. pylori can colonize rat stomachs with ulcers and delay ulcer healing; (ii) clarithromycin delays ulcer healing in H. pylori-infected rats; and (iii) acid pump inhibitors inhibited the clarithromycin-delayed ulcer healing.

Bacteria rapidly colonize and modulate healing of gastric ulcers in rats

The stomach is generally regarded as an environment that is not conducive to bacterial colonization. In this study, we examined the possibility that this changes significantly when an ulcer has formed and that colonization of ulcers interferes with the normal healing process. Gastric ulcers were induced by serosal application of acetic acid. The relationship between ulcer healing and bacterial colonization was examined. The effects of antibiotics, induction of Lactobacillus colonization, and selective colonization with an antibiotic resistant strain of Escherichia coli on ulcer healing were examined. Within 6-12 h of their induction, gastric ulcers were colonized by a variety of bacteria, with gram-negative bacteria predominating. Suppression of colonization with antibiotics resulted in marked acceleration of healing. Induction of Lactobacillus colonization also accelerated ulcer healing. The beneficial effects of antibiotics were reversed through selective colonization with antibiotic-resistant E. coli. Bacterial colonization occurred irrespective of the method used to induce the ulcer. This study demonstrates that colonization of gastric ulcers in rats occurs rapidly and significantly impairs ulcer healing. This effect appeared to be primarily attributable to gram-negative bacteria.

A rat model of chronic Helicobacter pylori infection. Studies of epithelial cell turnover and gastric ulcer healing

BACKGROUND

Our aim was to infect rats with Helicobacter pylori and to study the effects of the infection on the gastric mucosa in normal and in ulcer-operated rats.

METHODS

A mouse-adapted H. pylori (cagA-, VacA-) strain was inoculated into 23 rats. Another 20 uninfected rats served as controls. Two months later a gastric ulcer was induced in some rats. The animals were killed 3, 6, or 15 days after the ulcer operation. Tissues were taken for histology and for culture of H. pylori. Serum antibodies were determined.

RESULTS

All inoculated rats were infected by H. pylori after 2 months, mainly in the antrum. In these rats a mild to moderate chronic inflammation and a significantly increased frequency of apoptotic cells were observed in the antrum and in the ulcer margin, the ulcer healing was delayed, and the serum level of H. pylori-specific Ig was increased.

CONCLUSIONS

H. pylori infection in rats was successful and was accompanied by a mild to moderate mucosal inflammation. Gastric ulcer healing was delayed in infected rats, probably due to the inflammation and the increased apoptosis in epithelium.