Helicobacter pylori infection: pathogenesis

Exosomal CagA from Helicobacter pylori aggravates intestinal epithelium barrier dysfunction in chronic colitis by facilitating Claudin-2 expression

BACKGROUND

The chronic infection with Helicobacter pylori (H. pylori), especially cytotoxin-associated gene A-positive (CagA⁺) strains, has been associated with various extragastric disorders. Evaluating the potential impacts of virulence factor CagA on intestine may provide a better understanding of H. pylori pathogenesis such as colitis. The intestinal mucosal barrier is essential for maintaining its integrity and functions. However, how persistent CagA⁺ H. pylori colonization influences barrier disruption and thereby affects chronic colitis is not fully understood.

RESULTS

Chronic colitis models of CagA⁺ H. pylori-colonized mice treated with 2% Dextran sulphate sodium (DSS) were established to assess the disease activity and pertinent expression of tight junction proteins closely related to mucosal integrity. The aggravating effect of CagA⁺ H. pylori infection on DSS-induced chronic colitis was confirmed in mouse models. In addition, augmented Claudin-2 expression was detected in CagA⁺ H. pylori infection conditions and selected for mechanistic analysis. Next, GES-1 human gastric epithelial cells were cultured with CagA⁺ H. pylori or a recombinant CagA protein, and exosomes isolated from conditioned media were then identified. We assessed the Claudin-2 levels after exposure to CagA⁺ exosomes, CagA^- exosomes, and IFN-γ incubation, revealing that CagA⁺ H. pylori compromised the colonic mucosal barrier and facilitated IFN-γ-induced intestinal epithelial destruction through CagA-containing exosome-mediated mechanisms. Specifically, CagA upregulated Claudin-2 expression at the transcriptional level via a CDX2-dependent mechanism to slow the restoration of wounded mucosa in colitis in vitro.

CONCLUSIONS

These data suggest that exosomes containing CagA facilitate CDX2-dependent Claudin-2 maintenance. The exosome-dependent mechanisms of CagA⁺ H. pylori infection are indispensable for damaging the mucosal barrier integrity in chronic colitis, which may provide a new idea for inflammatory bowel disease (IBD) treatment.

An exploratory study on the presence of Helicobacter heilmannii and Helicobacter billis in the faces of companion dogs

Background

Companion animals like dogs play an important role in the lives of many people and are often considered to be members of families, but definitely, any contact with them poses an inherent risk of transmitting zoonotic pathogens. One of these pathogens is the genus Helicobacter which is linked to many disorders in human and animal.

Objectives

The aim of this study was to investigate the presence of some zoonotic species of genus Helicobacter in companion dogs.

Results

Through culturing in a special medium, nine samples (9%) were detected as infected (two pure and seven mixed culture). Based on multiplex‐PCR, 13 samples (13%) were infected by Helicobacter spp. although none of them were infected by H. pylori. Species‐specific PCR indicated that 38.5% or 5/13 of the samples were infected with H. heilmannii, while 15.45% or 2/13 of the samples were infected by H. billis. Multivariate logistic regression analysis showed that the age factor had a significant effect on Helicobacter spp. infection (odds ratio [OR] = 2.42, p = 0.01).

Conclusion

This study revealed the negligible faecal transmission of H. pylori. Moreover, due to the detection of H. Heilmannii and H. billis in feces and their association with human gastric diseases, dog owners should be educated about the risks and transmission modes of zoonotic bacterial infections of dogs.

Silencing of miR490-3p by H. pylori activates DARPP-32 and induces resistance to gefitinib

Infection with Helicobacter pylori (H. pylori) is the main risk factor for gastric carcinogenesis. In this study, we investigated the expression, molecular functions, and downstream effectors of miR490-3p in gastric cancer. We used in vitro and in vivo models to investigate the role of H. pylori in regulating miR490-3p, DARPP-32-dependent functions, and therapeutic resistance. Human and mouse neoplastic gastric lesions demonstrated a negative correlation between DARPP-32 and miR490-3p expression (R = -0.58, P < 0.01). This was also detected following infection with H. pylori (R = -0.66, P < 0.01). Molecular assays confirmed DARPP-32 as a direct target of miR490-3p. CHRM2, the host gene of miR490-3p, was hypermethylated and downregulated in neoplastic gastric tissues (P < 0.05). H. pylori induced methylation and downregulation of CHRM2 and miR490-3p. Functionally, the reconstitution of miR490-3p sensitized cancer cells to gefitinib by inactivating DRAPP-32-dependent AKT and STAT3 pathways. Patients with low miR490-3p or high DARPP-32 expression had decreased overall survival (P < 0.05). Hypermethylation-mediated silencing of CHRM2 and miR490-3p by H. pylori increased DARPP-32 expression. Downregulation of miR490-3p in gastric cancer plays a role in gefitinib response by inducing DARPP-32-mediated activation of PI3K/AKT, STAT3 signaling pathways.

Detection of Anti-CagA Antibodies in Sera of Helicobacter pylori-Infected Patients Using an Immunochromatographic Test Strip

The cagA gene of Helicobacter pylori that encodes an immunodominant CagA protein provokes severe mucosal damage and acts as a risk factor for the development of peptic ulcer disease and gastric cancer. Our aim is to develop an immunochromatographic test strip (ICTS) using our previously developed recombinant CagA (rCagA) protein and anti-rCagA monoclonal antibody (Mab) for the detection of anti-CagA antibodies in sera of infected patients. The rCagA was firstly conjugated to gold nanoparticle and placed into the conjugate pad. A nonconjugated rCagA and anti-rCagA Mab (CK-02) were immobilized on the test line and control line, respectively. Biopsy and serum samples from 30 H. pylori-infected patients were used. The presence of cagA gene in biopsy samples was first detected by PCR (Polymerase Chain Reaction), and 22 patients were found positive while 8 were negative. When serum samples were tested by our developed ICTS, 21 were positive for anti-CagA antibodies while 9 were negative. The serum samples were also tested by a commercial ELISA (Enzyme Linked Immunosorbent Assay), and when compared to the ICTS a sensitivity of 95% and a specificity of 100% were obtained. The ICTS can be used for rapid detection of CagA-positive H. pylori infection instead of expensive, time consuming and laborious invasive approaches.

Helicobacter pylori-induced cell death is counteracted by NF-κB-mediated transcription of DARPP-32

OBJECTIVE

DARPP-32 is a frequently amplified and overexpressed gene that promotes several oncogenic functions in gastric cancer. Herein, we investigated the relationship between Helicobacter pylori infection, proinflammatory NF-κB activation and regulation of DARPP-32.

DESIGN

The study used in vivo and in vitro experiments. Luciferase reporter, quantitative real-time PCR, immunoblot, chromatin immunoprecipitation (ChIP), cell viability, H. pylori infection, tissue microarrays and immunohistochemical assays were used.

RESULTS

Our results indicated that H. pylori infection increased the DARPP-32 mRNA and protein levels in gastric cancer cell lines and gastric mucosa of mice. H. pylori infection increased the activity of NF-κB reporter and p-NF-κB (S536) protein level in vitro and in vivo. To investigate the transcriptional regulation of DARPP-32, we cloned a 3019 bp of the DARPP-32 promoter into the luciferase reporter (pGL3-Luc). Both H. pylori infection and tumour necrosis factor-α treatment induced DARPP-32 reporter activity (p<0.01). Using deletion constructs of DARPP-32 promoter and ChIP assay, we demonstrated that the sequence -996 to -1008 bp containing putative NF-κB-binding sites is the most active region. The induction of DARPP-32 expression by H. pylori infection counteracted H. pylori-induced cell death through activation of serine/threonine-specific protein kinase (AKT), as determined by ATP-Glo and clonogenic survival assays. Immunohistochemistry analysis demonstrated a significant positive correlation between NF-κB and DARPP-32 expression levels in gastric cancer tissues (r²=0.43, p<0.01).

CONCLUSIONS

Given the high frequency of DARPP-32 overexpression and its prosurvival oncogenic functions, the induction of DARPP-32 expression following H. pylori infection and activation of NF-κB provides a link between infection, inflammation and gastric tumourigenesis.

Lactobacillus reuteri strain combination in Helicobacter pylori infection: a randomized, double-blind, placebo-controlled study

GOALS

The goals of this study were to investigate the role of a new probiotic preparation (Lactobacillus reuteri DSM 17938 and L. reuteri ATCC PTA 6475) in Helicobacter pylori infection.

BACKGROUND

Specific probiotic strains play a role in H. pylori infection for their ability to decrease bacterial load and gastritis, prevent antibiotic-associated side effects, and increase the eradication rate.

STUDY

This is a prospective, double-blind, randomized, placebo-controlled study in a tertiary care setting. A total of 100 H. pylori-positive naive patients received either L. reuteri combination (2×10 Colony Forming Units) or placebo during a 3-phase study (pre-eradication, eradication, and follow-up). All underwent C urea breath test (C-UBT), blood assessments of gastrin-17 (G17), endoscopy, and the Gastrointestinal Symptom Rating Scale. Eradication was confirmed by C-UBT 8 weeks after the completion of therapy.

RESULTS

Fifty patients were allocated in each group. During pre-eradication period, C-UBT δ decreased by 13% in L. reuteri combination as compared with a 4% increase in placebo (-13.2±34% vs. 4.3±27%; P<0.03). During eradication, GSRS increased significantly in placebo as compared with L. reuteri combination (6.8±2.9 vs. 4±3.1; P<0.01). Significantly less patients in L. reuteri combination as compared with placebo-reported side effects (40.9% vs. 62.8%; P<0.04). An abnormal G17 value was found in patients receiving placebo as compared with L. reuteri combination (28% vs. 12%; P<0.02). Eradication rate was 75% in L. reuteri combination and 65.9% in placebo (P=NS). L. reuteri combination increased eradication rate by 9.1% (odds ratio: 1.5).

CONCLUSIONS

L. reuteri combination alone is able to exert an inhibitory effect on H. pylori growth, and when administered with eradication therapy, it determines a significant reduction in antibiotic-associated side effects. Moreover, L. reuteri combination was able to decrease serum G17 levels and to (not significantly) increase the H. pylori-eradication rate.

Interaction effects between genes involved in the AKT signaling pathway and phytoestrogens in gastric carcinogenesis: a nested case-control study from the Korean Multi-Center Cancer Cohort

SCOPE

To investigate whether genes involved in AKT/nuclear factor kappa B signaling and/or gene-environment interactions between the genes and phytoestrogens may be susceptible factors for gastric cancer.

METHODS AND RESULTS

The representative single nucleotide polymorphisms (SNPs) identified during the primary analysis (screening a total of 622 SNPs within ± 5 kbp of the 51 target gene locations) were further investigated in 317 matched case-control sets. The summary odds ratios (ORs) and 95% confidence intervals (CIs) for gastric cancer were calculated. Interaction effects between the SNPs and phytoestrogen biomarkers (genistein, daidzein, equol, and enterolactone) were computed. CDK1 rs4145643, FAS rs6586161, and FAS rs1468063 in the AKT signaling pathway presented significant genetic effects on gastric cancer (OR = 0.81 (95% CI: 0.66-0.99) for CDK1 rs4145643; OR = 1.27 (95% CI: 1.03-1.58) for FAS rs6586161; OR = 1.29 (95% CI: 1.03-1.56) for FAS rs1468063; Cochran Q statistics > 0.10). Risk alleles of FAS rs6586161, FAS rs1468063, MAP3K1 rs16886448, and MAP3K1 rs252902 showed significant interaction effects with enterolactone (p(interaction) < 0.05).

CONCLUSION

CDK1 and FAS genes involved in AKT signaling and influenced by anti-carcinogenic property of phytoestrogens can play a role as susceptible genetic factors in gastric carcinogenesis. FAS and MAP3K1 genes significantly interact with enterolactone, thereby modifying the individual's risk for gastric cancer.

miR-106a is frequently upregulated in gastric cancer and inhibits the extrinsic apoptotic pathway by targeting FAS

Emerging evidence has shown the association of aberrantly expressed miR-106a with cancer development, however, little is known about its potential role in gastric carcinogenesis. In our present study, obviously overexpressed miR-106a was found in gastric cancer tissues compared with their nontumor counterparts. Suppression of miR-106a significantly inhibited gastric cancer cell proliferation and triggered apoptosis. Bioinformatic analysis combining with validation experiments identified FAS as a direct target of miR-106a. Rescue experiments and examination of caspase-8, PARP and caspase-3 further approved that miR-106a could inhibit gastric cancer cell apoptosis through interfering with FAS-mediated apoptotic pathway. Moreover, a significant inverse correlation was found between miR-106a and FAS expression not only in gastric cancer cell lines but also in gastric cancer specimens. Taken together, these findings suggest that ectopicly overexpressed miR-106a may play an oncogenic role in gastric carcinogenesis and impair extrinsic apoptotic pathway through targeting FAS.

Comparative proteomics analysis of chronic atrophic gastritis: changes of protein expression in chronic atrophic gastritis without Helicobacter pylori infection

Chronic atrophic gastritis (CAG) is a very common gastritis and one of the major precursor lesions of gastric cancer, one of the most common cancers worldwide. The molecular mechanism underlying CAG is unclear, but its elucidation is essential for the prevention and early detection of gastric cancer and appropriate intervention. A combination of two-dimensional gel electrophoresis and mass spectrometry was used in the present study to analyze the differentially expressed proteins. Samples from 21 patients (9 females and 12 males; mean age: 61.8 years) were used. We identified 18 differentially expressed proteins in CAG compared with matched normal mucosa. Eight proteins were up-regulated and 10 down-regulated in CAG when compared with the same amounts of proteins in individually matched normal gastric mucosa. Two novel proteins, proteasome activator subunit 1 (PSME1), which was down-regulated in CAG, and ribosomal protein S12 (RPS12), which was up-regulated in CAG, were further investigated. Their expression was validated by Western blot and RT-PCR in 15 CAG samples matched with normal mucosa. The expression level of RPS12 was significantly higher in CAG than in matched normal gastric mucosa (P < 0.05). In contrast, the expression level of PSME1 in CAG was significantly lower than in matched normal gastric mucosa (P < 0.05). This study clearly demonstrated that there are some changes in protein expression between CAG and normal mucosa. In these changes, down-regulation of PSME1 and up-regulation of RPS12 could be involved in the development of CAG. Thus, the differentially expressed proteins might play important roles in CAG as functional molecules.

Murine models of H. pylori-induced gastritis and gastric adenocarcinoma

Laboratory mice have become one of the best animal species for mechanistic studies in gastrointestinal research. Their abundant genetic information, the way of causing carcinogenesis easily by transgenic and gene knockout techniques, limited effort in time and costs, and their practicability provide advantages over other animal models. Meanwhile, several murine practical models have been established for the investigation of the initiation, expansion, and progression of gastritis and gastric carcinoma, for assessing the effects of bacterial, genetic and environmental factors, and for evaluating therapeutic and preventive strategies in gastric diseases. This article gives a review of murine models of gastritis and gastric cancer, placing emphasis on the models associated with Helicobacter pylori infection and techniques used in our laboratory. We discuss matters of murine gastric anatomy, as well as techniques of infection, tissue preparation, and histology.

Heat shock protein: hard worker or bad offender for gastric diseases

Heat shock proteins (HSPs) have core housekeeping functions in the cells where they are built-in components of folding, signal transduction pathways, and quality control functions for which they proofread the structure of proteins and repair misfolded conformers. Helicobacter pylori (H. pylori) infection leads to significant inflammations in the gastric mucosa, which is closely associated with development of either precancerous lesion including chronic atrophic gastritis or gastric cancer in addition to, peptic ulcer disease, and mucosa-associated lymphoid tissue (MALT) lymphoma. Therefore, the association between H. pylori infection and role of HSP has been focused as an important issue because there had been rather conflicting publications showing that HSPs as a good worker for defense against H. pylori infection, whereas HSPs as a bad offender contributing to the progression of H. pylori-associated gastric carcinogenesis in addition to aggravation of gastric inflammation. In this paper regarding proteomic discovery of HSPs related to H. pylori-associated gastric diseases, we introduce several evidences obtained from proteomic analysis dealing with friend or foe role of HSP in H. pylori infection from a cellular level to human diseases. The implication of HSPs in alcoholic or NSAIDs-induced gastritis and the intervening of HSPs in biological changes exemplified with TGF-β signaling, key tumor suppressor growth factors regulating inflammation, immune function, and carcinogenesis were further introduced.

Proteomic analysis reveals molecular biological details in varioliform gastritis without Helicobacter pylori infection

AIM: To investigate and elucidate the molecular mechanism underlying varioliform gastritis for early detection, prevention and intervention of gastric cancer.

METHODS: A combination of two-dimensional gel electrophoresis and mass spectrometry was used to detect the differentially expressed proteins between varioliform gastritis and matched normal mucosa. The selected proteins were confirmed by Western blotting and reverse transcription polymerase chain reaction (RT-PCR) in additional samples and the function of some proteins in varioliform gastritis was analyzed by bio-method preliminarily.

RESULTS: We identified 21 differentially expressed proteins in varioliform gastritis, and compared them with matched normal mucosa. Eleven proteins were upregulated and ten downregulated in varioliform gastritis when compared with the same proteins in individual-matched normal gastric mucosa. These proteins are related to metabolism, oxidation, cytoskeleton, apoptosis, signal transduction and other aspects of cells. Two novel proteins, thioredoxin domain-containing protein 5 (TXNDC5) upregulated in varioliform gastritis, and neuropolypeptide h3 [phosphatidylethanolamine-binding protein 1 (PEBP1)] downregulated in varioliform gastritis, were further investigated. Their expressions were validated by Western blotting and RT-PCR in 12 cases of varioliform gastritis which was matched with normal mucosa. The expression level of PEBP1 in varioliform gastritis was significantly lower (P < 0.05) while that of TXNDC5 was significantly higher than that in matched normal gastric mucosa (P < 0.05).

CONCLUSION: There are some changes of protein expression in varioliform gastritis. Downregulation of PEBP1 and upregulation of TXNDC5 are involved in the development of varioliform gastritis.

Interaction of Helicobacter pylori with gastric epithelial cells is mediated by the p53 protein family

BACKGROUND & AIMS

Although the p53 tumor suppressor has been extensively studied, many critical questions remain unanswered about the biological functions of p53 homologs, p73 and p63. Accumulating evidence suggests that both p73 and p63 play important roles in regulation of apoptosis, cell differentiation, and therapeutic drug sensitivity.

METHODS

Gastric epithelial cells were cocultured with Helicobacter pylori, and the roles of p63 and p73 proteins were assessed by luciferase reporter, real-time polymerase chain reaction, immunoblotting, and cell survival assays. Short hairpin RNA and dominant-negative mutants were used to inhibit activity of p73 and p63 isoforms. Human and murine gastric tissues were analyzed by immunohistochemistry with p73 and p63 antibodies and modified Steiner's silver method.

RESULTS

Interaction of H pylori with gastric epithelial cells leads to robust up-regulation of p73 protein in vitro and in vivo in human gastritis specimens and H pylori-infected mice. The p73 increase resulted in up-regulation of pro-apoptotic genes, NOXA, PUMA, and FAS receptor in gastric epithelial cells. Down-regulation of p73 activity suppressed cell death and Fas receptor induced by H pylori. Bacterial virulence factors within the cag pathogenicity island, c-Abl tyrosine kinase, and interaction with p63 isoforms control the activity of p73.

CONCLUSION

Our findings implicate p73 in H pylori-induced apoptosis and more generally suggest that the p53 family may play a role in the epithelial cell response to H pylori infection.

Influence of Helicobacter pylori genotype on triple eradication therapy

BACKGROUND

The efficiency of Helicobacter pylori eradication varies geographically, as do many parameters that might affect therapeutic efficiency. The aims of this study were to investigate the relationship between different genotypes of H. pylori and bacterium-related histopathological lesions in patients with duodenal ulcer and to determine the effect of genotype on triple eradication therapy.

METHODS

Helicobacter pylori infections were analyzed in 78 duodenal ulcer patients. The cytotoxin-associated gene (cagA) and vacuolating cytotoxin gene (vacA) subtype status of cultured strains were studied by PCR. Histopathological findings were graded using a described grading system. The patients were treated with triple-therapy regimens consisting of a proton pump inhibitor and two antibiotics twice daily for 7 days. Endoscopy was repeated at 4 weeks post-therapy to monitor ulcer healing and H. pylori eradication.

RESULTS

The bacteria were genotyped from 66 patients, 57 of whom had H. pylori eradicated. The absence of cagA was associated with unsuccessful treatment. No difference was found with regard to vacA subtype between the successful and unsuccessful eradication groups. On histopathological examination, high H. pylori colonization density and intestinal metaplasia were associated with low eradication rate, while a high grade of neutrophil infiltration was associated with a significantly higher eradication rate.

CONCLUSIONS

The data confirm the importance of cagA positivity as a predictor of successful eradication. When high H. pylori colonization density and intestinal metaplasia are present, therapy appears to be less effective. Therefore, these histopathological features may be involved in an unsuccessful therapeutic outcome.

Eradication of Helicobacter pylori infection favourably affects altered gastric mucosal MMP-9 levels

BACKGROUND

Helicobacter pylori gastritis is recognized as an important pathogenetic factor in peptic ulcer disease and gastric carcinogenesis, and is accompanied by strongly enhanced gastric mucosal matrix metalloproteinase-9 (MMP-9) levels.

AIM

This study was performed to investigate whether H. pylori-affected gastric mucosal MMP-2 and MMP-9 levels are reversible by successful treatment of the infection.

PATIENTS AND METHODS

Fifty-eight patients with H. pylori-associated gastritis were treated with a combination regimen of acid inhibitory therapy and antibiotics for 14 days. The levels and isoforms of MMP-2 and MMP-9 were measured by semiquantitative gelatin-zymography, bioactivity assay and enzyme-linked immunosorbent assay in gastric mucosal biopsy homogenates.

RESULTS

Latent, active, and total MMP-9 levels decreased consistently and significantly by successful H. pylori eradication, in antrum as well as corpus mucosa, compared with those prior to treatment, irrespective of the therapy regimen used. The elevated levels remained unchanged, however, when treatment failed. MMP-2 levels did not show major alterations after H. pylori therapy.

CONCLUSION

Elevated MMP-9 levels in H. pylori-infected gastric mucosa are reversible by eradication of the infection. No major changes in mucosal MMP-2 levels were observed by H. pylori eradication.

Probiotic intervention decreases serum gastrin-17 in Helicobacter pylori infection

BACKGROUND

Previously we showed that a probiotic combination with L. rhamnosus GG was beneficial as an adjuvant therapy during H. pylori eradication.

AIM

To evaluate whether probiotic combination with LGG adheres to the upper gastrointestinal mucosa and modifies H. pylori colonisation and H. pylori induced inflammation.

METHODS

Thirteen patients referred for gastroduodenoscopy received a drink consisting of equal doses (2.5x10(9)CFU) of LGG, L. rhamnosus LC705, Propionibacterium freudenreichii JS and Bifidobacterium lactis Bb12 daily. Recovery of probiotics in biopsies (antrum, corpus, duodenum) and faecal samples was evaluated by strain-specific quantitative polymerase chain reaction. H. pylori colonization and gastric inflammation was investigated by urease activity ((13)C-urea breath test), histology and serum pepsinogen I, II and gastrin-17 measurements.

RESULTS

Twelve patients were fully investigated; of these three of the patients had LGG adhering to the biopsies at end of the intervention. Other probiotic strains were not detected, even though the recovery of all individual probiotic strains from the faeces was significantly increased (p<0.01). After the treatment, the level of (13)C-urea breath test (p=0.063) and gastrin-17 (p=0.046) decreased.

CONCLUSIONS

The decreases in (13)C-urea breath test and gastrin-17 indicate that the probiotic combination exerts a beneficial effect on gastric mucosa in H. pylori infected patients. LGG showed marginal ability to adhere to the upper gastrointestinal tract mucosa.

A follow-up study on the effect of Helicobacter pylori eradication on the severity of gastric histology

Helicobacter pylori genetic diversity and geographic distribution affect the severity of gastric histology; while eradication heals gastritis, the improvement of atrophy and intestinal metaplasia (IM) is still controversial. We investigated whether H. pylori infection and genotypes (cagA-vacA) influence the histological changes and whether eradication resolves these changes. Twenty-one patients (11 duodenal ulcer, 2 gastric ulcer, 8 gastritis) received treatment. Biopsies for CLO, PCR, histology, and culture were collected before and at 1 and 12 months after treatment, and serum samples at 0, 1, 2, 6, and 12 months. H. pylori eradication was achieved in 71% of the patients. Histological scores for H. pylori densities were significantly higher in the antrum and incisura angularis. Scores for mononuclear cell and neutrophil infiltration were significantly higher in regions with a high H. pylori density and improved progressively after eradication. Eight patients with atrophy including five with IM showed no significant changes 12 months after eradication. The cagA gene, detected in 13 (62%), the vacA-sla gene, in 20 (95%), and the vacA-m1 gene, in 12 (57%) of 21 patients were significantly associated with duodenal ulcer. A gradual decline in antibody titer reached an average of 67% 12 months after eradication. H. pylori infection and the associated genotypes (cagA of Western type) affect the severity of the gastric histology (mild forms of atrophy and IM) and the disease outcome. Eradication of H. pylori resulted in healing of gastritis, but with no significant improvement in atrophy or IM.

DNA Damage in Patients Infected by Helicobacter pylori

Helicobacter pylori (H. pylori) is considered to predispose carriers to gastric cancer but its role on gastric carcinogenesis is still unknown. The aim of this study was to investigate DNA damage by the comet assay in gastric epithelial cells from antrum and corpus in H. pylori-infected patients with gastritis of different degrees. H. pylori status, gastric histology, and DNA damage were studied in 62 H. pylori-infected and 18 non-infected patients, all of them non-smokers, non-alcoholics, and non-drug users. DNA damage was significantly higher in H. pylori-infected patients presenting gastritis than in non-infected patients with normal mucosa. A direct correlation between the levels of DNA damage and the intensity of gastritis was observed in H. pylori-infected patients. Association between DNA damage and age was also found. The levels of DNA damage were significantly higher in patients older than 50 years than in younger patients with the same degree of gastritis. Our results indicate that H. pylori infection is associated with DNA damage in gastric epithelial cells, which could be a biomarker of risk for gastric cancer in humans.