Gastric epithelial cell proliferation and cagA status in Helicobacter pylori gastritis at different gastric sites

An Immunohistochemical Assessment of Ki-67 and P53 Over-expression in Helicobacter pylori-positive Gastritis

AIM: Helicobacter pylori infection of the stomach is a common disease and the resulting changes from it are many and deserve to be in the focus of researchers’ attention, to assess the expression of mutant P53 protein and Ki-67 markers in patients with gastritis secondary to H. pylori. METHODS: Thirty samples with positive H. pylori gastritis were included in a retrospective study in Mosul/Iraq. The histological parameters were assessed using the Sydney system, then, the expression of Ki-67 and P53 expression was studied by immunohistochemical methods. The significance level was appointed at (0.05). RESULTS: Ki-67 and P53 expression were found in 83.3% of the total cases. The study results show that 92% of positive Ki-67 and P53 cases had chronic inflammatory cell infiltration, polymorph nuclear cells infiltration, and atrophy. Whereas 96% of positive Ki-67 cases had no metaplasia, 92% of the positive P53 cases had no metaplasia. The results also showed that only 16% of the positive Ki-67 cases had dysplastic changes, and 24% of the positive cases of P53 cases were showed dysplasia. whenever P53 was negative; there is neither metaplasia nor dysplasia in the tissue, this does not apply to Ki-67 negative cases. CONCLUSIONS: Ki-67 and P53 expressions increase with chronicity of Helicobacter pylori-positive gastritis. P53 expression is amplified when atrophy is present in these samples.

Trefoil factor 1 and gastrokine 2 inhibit Helicobacter pylori-induced proliferation and inflammation in gastric cardia and distal carcinogenesis

Helicobacter pylori (H. pylori) infection has been associated with non-cardia adenocarcinoma in the stomach, while its role in gastric cardia adenocarcinoma (GCA) remains controversial. In addition, the association between H. pylori and the protective factors trefoil factor 1 (TFF1) and gastrokine 2 (GKN2) in gastroesophageal adenocarcinomas has not been fully investigated. Therefore, the mRNA and protein expression levels of TFF1 and GKN2 in GCA and distal gastric adenocarcinoma (DGA) were analyzed using quantitative PCR (qPCR) and immunohistochemistry, and the association with H. pylori infection was investigated. In addition, the effects of TFF1 and GKN2 overexpression on H. pylori-induced cells were investigated using western blot and reverse transcription-qPCR analysis. The comparative analysis of 16S rRNA-positive mRNA expression between GCA and DGA showed no statistically significant difference. However, the rate of the H. pylori vacuolating toxin A (VacA) genotype was significantly higher in GCA (49.2%) compared with that in DGA (26.9%; P<0.05). H. pylori infection downregulated the mRNA and protein expression levels of TFF1 and GKN2 in gastric tumor tissues, and the mRNA expression level of TFF1 and GKN2 was also markedly decreased in vitro. Furthermore, the cell proliferation varied in H. pylori total protein treatment group with the different doses. Notably, treatment with 20 µg/ml H. pylori total protein for 24 h resulted in the highest cellular proliferation rate. In addition, TFF1 and GKN2 overexpression inversely inhibited H. pylori-induced cell proliferation and upregulated NF-κB, tumor necrosis factor-α, IL-1β, IL-2, IL-4 and IL-6. The results of the present study indicate that H. pylori, particularly the VacA+ strain, plays an important role in GCA pathogenesis in high-risk areas of China, while TFF1/GKN2 inhibits H. pylori-induced cell proliferation and inflammation in GCA and DGA.

Water-induced modulation of Helicobacter pylori virulence properties

While the influence of water in Helicobacter pylori culturability and membrane integrity has been extensively studied, there are little data concerning the effect of this environment on virulence properties. Therefore, we studied the culturability of water-exposed H. pylori and determined whether there was any relation with the bacterium’s ability to adhere, produce functional components of pathogenicity and induce inflammation and alterations in apoptosis in an experimental model of human gastric epithelial cells. H. pylori partially retained the ability to adhere to epithelial cells even after complete loss of culturability. However, the microorganism is no longer effective in eliciting in vitro host cell inflammation and apoptosis, possibly due to the non-functionality of the cag type IV secretion system. These H. pylori-induced host cell responses, which are lost along with culturability, are known to increase epithelial cell turnover and, consequently, could have a deleterious effect on the initial H. pylori colonisation process. The fact that adhesion is maintained by H. pylori to the detriment of other factors involved in later infection stages appears to point to a modulation of the physiology of the pathogen after water exposure and might provide the microorganism with the necessary means to, at least transiently, colonise the human stomach.

Evaluation of apoptosis along with BCL-2 and Ki-67 expression in patients with intestinal metaplasia

The primary aim is to compare individuals with intestinal metaplasia (IM), chronic active gastritis (CAG), and normal gastric mucosa (NGM) in terms of apoptosis, proliferation, and Bcl-2 expression. The secondary aim is to determine whether these parameters are different between patients with and without gastric cancer in first-degree relatives. We enrolled 106 patients whose histopathological results were consistent with IM (n: 42), CAG (n: 51), or NGM (n: 13). Antral biopsies were immunohistochemically stained for Bcl-2 and Ki-67 expression. Apoptosis was detected using TUNEL assay. While no significant difference was determined between three groups with regard to apoptosis and Bcl-2 expression (p>0.05), Ki-67 expression was significantly higher in the IM group when compared with the CAG and NGM groups (29.90±22.87 vs. 18.18±16.22 vs. 18.54±20, respectively; p=0.012). Helicobacter pylori was determined to increase apoptosis (49.3% vs. 25.7%, p<0.05), nevertheless, it had no significant effect on proliferation and Bcl-2 expression. Bcl-2 and Ki-67 expression and apoptosis were not different among patients with and without a history of gastric cancer in first degree relatives. Although intestinal metaplasia cases demonstrate an increase in proliferation, no elevation is observed in apoptosis. This can be an important factor in the progression to gastric cancer.

Conversion of Helicobacter pylori CagA from senescence inducer to oncogenic driver through polarity-dependent regulation of p21

The Helicobacter pylori CagA bacterial oncoprotein plays a critical role in gastric carcinogenesis. Upon delivery into epithelial cells, CagA causes loss of polarity and activates aberrant Erk signaling. We show that CagA-induced Erk activation results in senescence and mitogenesis in nonpolarized and polarized epithelial cells, respectively. In nonpolarized epithelial cells, Erk activation results in oncogenic stress, up-regulation of the p21(Waf1/Cip1) cyclin-dependent kinase inhibitor, and induction of senescence. In polarized epithelial cells, CagA-driven Erk signals prevent p21(Waf1/Cip1) expression by activating a guanine nucleotide exchange factor-H1-RhoA-RhoA-associated kinase-c-Myc pathway. The microRNAs miR-17 and miR-20a, induced by c-Myc, are needed to suppress p21(Waf1/Cip1) expression. CagA also drives an epithelial-mesenchymal transition in polarized epithelial cells. These findings suggest that CagA exploits a polarity-signaling pathway to induce oncogenesis.

Neither genotype nor the gastric colonization site of Helicobacter pylori are predictive factors for the development of erosive esophagitis in patients with peptic ulcer disease, 1 year after eradication

CONTEXT

Whether Helicobacter pylori infection is a protective or predisposing factor for the development of gastroesophageal reflux disease remains controversial. The most virulent strains, such as those expressing the cytotoxin-associated gene A (CagA), and the site of gastric colonization have been correlated with the prevention or development of esophagitis.

AIM

To determine the incidence of erosive esophagitis following eradication of H. pylori in patients with peptic ulcer disease and to evaluate the association of erosive esophagitis with virulent strains of H. pylori and the site of gastric colonization.

METHODS

Triple therapy with lansoprazole, amoxicillin and clarithromycin was administered to 159 patients with peptic ulcer disease. Endoscopy, histopathology, urease and carbon-14 urea breath tests were performed prior to treatment, at 3 months and 1 year following treatment. Genotyping of H. pylori strains using polymerase chain reaction was performed separately on samples from the corpus and antrum.

RESULTS

One year after treatment, 148 successfully treated patients were reevaluated. Twenty-eight patients (19%) had erosive esophagitis, classified as Los Angeles grade A in 24 and B in 4. The samples taken from the corpus were CagA-positive in 18 patients (64%), while the samples taken from the antrum were CagA-positive in 21 patients (75%).

CONCLUSIONS

The incidence of erosive esophagitis in peptic ulcer patients who had their H. pylori eradicated was 19%. No correlation was found between the gastric site colonized by H. pylori or strains expressing CagA and the prevention or development of erosive esophagitis in patients with peptic ulcer disease, 1 year after infection eradication.

Effect of Helicobacter pylori eradication on oncogenes and cell proliferation

BACKGROUND

Helicobacter pylori , the main cause of chronic gastritis, is a class 1 gastric carcinogen. However, it remains unclear whether H. pylori affects molecular alterations in chronic gastritis. Thus, this study was designed to investigate the effect of H. pylori eradication on the expression of human telomerase RNA (hTR), human telomerase reverse transcriptase (hTERT), c-myc and proliferation nuclear cell antigen (PCNA) in H. pylori associated chronic gastritis.

MATERIALS AND METHODS

hTR was determined by in situ hybridization, hTERT, c-myc and PCNA were detected by immunohistochemistry using stomach tissues obtained from 39 H. pylori-infected and 21 H. pylori-negative patients with chronic gastritis before and after H. pylori eradication therapy or treatment for symptom relief only.

RESULTS

Levels of hTR, hTERT, c-myc and PCNA were significantly higher in H. pylori-infected mucosa (51.3%, 53.8%, 53.8% and 16.8 +/- 5.8, respectively) when compared to H. pylori-negative mucosa before therapy (19.0%, 23.8%, 28.6%, 8.8 +/- 3.4, respectively; P < 0.05 in all cases). In patients with successful eradication of H. pylori the levels of hTR, hTERT, c-myc and PCNA (55.5%, 59.3%, 59.3%, 16.8 +/- 5.8, respectively) were significantly reduced after the therapy (22.2%, 22.2%, 14.8%, 7.0 +/- 5.0, respectively; P < 0.05 in all cases). In the H. pylori failed eradication and H. pylori-negative groups, there was no statistical difference in all four measurements.

CONCLUSIONS

H. pylori infection may induce the overexpression of hTR, hTERT, c-myc and stimulate cell proliferation. Eradication of H. pylori may reverse the aberrant expression of these oncoproteins and thus correct the abnormal cell proliferation.

Effects of H pylori infection on gap-junctional intercellular communication and proliferation of gastric epithelial cells in vitro

AIM: To explore the effects of H pylori infection on gap-junctional intercellular communication (GJIC) and proliferation of gastric epithelial cells in vitro.

METHODS: A human gastric epithelial cell line (SGC-7901) cultured on coverslips was exposed overnight to intact H pylori (CagA⁺ or CagA^- strains) and sonicated extracts, respectively. GJIC between the cells was detected by fluorescence redistribution after photobleaching (FRAP) technique. Proliferation of SGC cells was determined by methylthiazolyl tetrazolium (MTT) assay.

RESULTS: When compared with control in which cells were cultured with simple medium alone, both CagA⁺ and CagA^-H pylori isolates could inhibit GJIC (CagA⁺: F = 57.98, P < 0.01; CagA^-: F = 29.59, P < 0.01) and proliferation (CagA⁺: F = 42.65, P < 0.01; CagA^-: F = 58.14, P < 0.01) of SGC-7901 cells. Compared with CagA^- strains, CagA⁺H pylori more significantly down-regulated GJIC of gastric cells (intact H pylori: t = 13.86, P < 0.01; sonicated extracts: t = 11.87, P < 0.01) and inhibited proliferation gastric cells to a lesser extent in vitro (intact H pylori: t = 3.06, P < 0.05; sonicated extracts: t = 3.94, P < 0.01).

CONCLUSION: Compared with CagA^-H pylori strains, CagA⁺ strains down-regulate GJIC of gastric epithelial cells more significantly and inhibit proliferation of gastric cells to a lesser extent in vitro. H pylori, especially CagA⁺ strains, may play an important role in gastric carcinogenesis.