Cellular mucosal defense during Helicobacter pylori infection: a review of the role of glutathione and the oxidative pentose pathway

The effect of altered pH growth conditions on the production, composition, and proteomes of Helicobacter pylori outer membrane vesicles

Gram-negative bacteria release outer membrane vesicles (OMVs) that contain cargo derived from their parent bacteria. Helicobacter pylori is a Gram-negative human pathogen that produces urease to increase the pH of the surrounding environment to facilitate colonization of the gastric mucosa. However, the effect of acidic growth conditions on the production and composition of H. pylori OMVs is unknown. In this study, we examined the production, composition, and proteome of H. pylori OMVs produced during acidic and neutral pH growth conditions. H. pylori growth in acidic conditions reduced the quantity and size of OMVs produced. Additionally, OMVs produced during acidic growth conditions had increased protein, DNA, and RNA cargo compared to OMVs produced during neutral conditions. Proteomic analysis comparing the proteomes of OMVs to their parent bacteria demonstrated significant differences in the enrichment of beta-lactamases and outer membrane proteins between bacteria and OMVs, supporting that differing growth conditions impacts OMV composition. We also identified differences in the enrichment of proteins between OMVs produced during different pH growth conditions. Overall, our findings reveal that growth of H. pylori at different pH levels is a factor that alters OMV proteomes, which may affect their subsequent functions.

Irigenin, a novel lead from Iris confusa for management of Helicobacter pylori infection with selective COX-2 and HpIMPDH inhibitory potential

The development of new natural drugs for Helicobacter pylori (H. pylori) management has recently received significant attention. Iris confusa (I. confusa) was long used for the treatment of bacterial infections and gastritis. This study aimed at evaluating its effect on management of H. pylori infection and exploring its bioactive metabolites. The inhibitory potential of the polar (PF), non-polar (NPF) fractions and the isolated compounds against H. pylori using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay in addition to their cyclooxygenases (COX-1 and COX-2), and nitric oxide (NO) inhibitory activities were assessed. The most biologically active compound was tested for its selective H. pylori inosine-5'-monophosphate dehydrogenase (HpIMPDH) inhibitory potential. Chromatographic purification of PF and NPF allowed isolation of tectoridin, orientin, irigenin, tectorigenin, isoarborinol and stigmasterol. The PF exhibited significant anti-H. pylori (MIC 62.50 µg/mL), COX-1, COX-2 (IC50 of 112.08 ± 0.60 and 47.90 ± 1.50 µg/mL respectively, selectivity index SI of 2.34), and NO (IC50 47.80 ± 0.89 µg/mL) inhibitory activities, while irigenin was the most potent isolated compound. Irigenin was found to have a promising activity against HpIMPDH enzyme (IC50 of 2.07 ± 1.90 μM) with low activity against human hIMPDH2 (IC50 > 10 μM) than clarithromycin, assuring its selectivity. Overall, I. confusa and its isolated compounds may serve as a potential source of plant-based drugs for H. pylori control. This study scientifically validated the claimed anti-bacterial activity of I. confusa and revealed irigenin potential as a novel lead exhibiting anti H. pylori activity in a first record.

Association of Helicobacter pylori Infection and Host Cytokine Gene Polymorphism with Gastric Cancer

The global cancer burden of new cases of various types rose with millions of death in 2018. Based on the data extracted by GLOBOCAN 2018, gastric cancer (GC) is the third leading cause of mortality related to cancer across the globe. Carcinogenic or oncogenic infections associated with Helicobacter pylori (Hp) are regarded as one of the essential risk factors for GC development. It contributes to the increased production of cytokines that cause inflammation prior to their growth in the host cells. Hp infections and specific types of polymorphisms within the host cells encoding cytokines are significant contributors to the host's increased susceptibility in terms of the development of GC. Against the backdrop of such an observation is that only a small portion of the cells infected can become malignant. The diversities are a consequence of the differences in the pathogenic pathway of the Hp, susceptibility of the host, environmental conditions, and interplay between these factors. It is evident that hosts carrying cytokine genes with high inflammatory levels and polymorphism tend to exhibit an increased risk of development of GC, with special emphasis being placed on the host cytokines gene polymorphisms.

Mating type specific transcriptomic response to sex inducing pheromone in the pennate diatom Seminavis robusta

Sexual reproduction is a fundamental phase in the life cycle of most diatoms. Despite its role as a source of genetic variation, it is rarely reported in natural circumstances and its molecular foundations remain largely unknown. Here, we integrate independent transcriptomic datasets to prioritize genes responding to sex inducing pheromones (SIPs) in the pennate diatom Seminavis robusta. We observe marked gene expression changes associated with SIP treatment in both mating types, including an inhibition of S phase progression, chloroplast division, mitosis, and cell wall formation. Meanwhile, meiotic genes are upregulated in response to SIP, including a sexually induced diatom specific cyclin. Our data further suggest an important role for reactive oxygen species, energy metabolism, and cGMP signaling during the early stages of sexual reproduction. In addition, we identify several genes with a mating type specific response to SIP, and link their expression pattern with physiological specialization, such as the production of the attraction pheromone diproline in mating type − (MT−) and mate-searching behavior in mating type + (MT+). Combined, our results provide a model for early sexual reproduction in pennate diatoms and significantly expand the suite of target genes to detect sexual reproduction events in natural diatom populations.

Antioxidant and Antiulcerogenic Activity of the Dry Extract of Pods of Libidibia ferrea Mart. ex Tul. (Fabaceae)

Ethnomedicinal studies in the Amazon community and in the Northeast region of Brazil highlight the use of Libidibia ferrea fruits for the treatment of gastric problems. However, there are no data in the literature of this pharmacological activity. Thus, the aim of this paper is to provide a scientific basis for the use of the dry extract of L. ferrea pods (DELfp) for the treatment of peptic ulcers. Phytochemical characterization was performed by HPLC/MS. In vitro antioxidant activity was assessed using DPPH, ABTS, phosphomolybdenum, and superoxide radical scavenging activity. The gastroprotective activity, the ability to stimulate mucus production, the antisecretory activity, and the influence of -SH and NO compounds on the antiulcerogenic activity of DELfp were evaluated. The healing activity was determined by the acetic acid-induced chronic ulcer model. Anti-Helicobacter pylori activity was investigated. HPLC/MS results identified the presence of phenolic compounds, gallic acid and ellagic acid, in DELfp. The extract showed antioxidant activity in vitro. In ulcers induced by absolute ethanol and acidified ethanol, the ED₅₀ values of DELfp were 113 and 185.7 mg/kg, respectively. DELfp (100, 200, and 400 mg/kg) inhibited indomethacin-induced lesions by 66.7, 69.6, and 65.8%, respectively. DELfp (200 mg/kg) reduced gastric secretion and H⁺ concentration in the gastric contents and showed to be independent of nitric oxide (NO) and dependent on sulfhydryl (-SH) compounds in the protection of the gastric mucosa. In the chronic ulcer model, DELfp reduced the area of the gastric lesion. DELfp also showed anti-H. pylori activity. In conclusion, DELfp showed antioxidant, gastroprotective, healing, and antiulcerogenic activities. The mechanism of these actions seems to be mediated by different pathways and involves the reduction of gastric secretion and H⁺ concentration, dependence on sulfhydryl compounds, and anti-H. pylori activity. All these actions support the medicinal use of this species in the management of peptic ulcers.

Subversion of Schwann Cell Glucose Metabolism by Mycobacterium leprae

Mycobacterium leprae, the intracellular etiological agent of leprosy, infects Schwann promoting irreversible physical disabilities and deformities. These cells are responsible for myelination and maintenance of axonal energy metabolism through export of metabolites, such as lactate and pyruvate. In the present work, we observed that infected Schwann cells increase glucose uptake with a concomitant increase in glucose-6-phosphate dehydrogenase (G6PDH) activity, the key enzyme of the oxidative pentose pathway. We also observed a mitochondria shutdown in infected cells and mitochondrial swelling in pure neural leprosy nerves. The classic Warburg effect described in macrophages infected by Mycobacterium avium was not observed in our model, which presented a drastic reduction in lactate generation and release by infected Schwann cells. This effect was followed by a decrease in lactate dehydrogenase isoform M (LDH-M) activity and an increase in cellular protection against hydrogen peroxide insult in a pentose phosphate pathway and GSH-dependent manner. M. leprae infection success was also dependent of the glutathione antioxidant system and its main reducing power source, the pentose pathway, as demonstrated by a 50 and 70% drop in intracellular viability after treatment with the GSH synthesis inhibitor buthionine sulfoximine, and aminonicotinamide (6-ANAM), an inhibitor of G6PDH 6-ANAM, respectively. We concluded that M. leprae could modulate host cell glucose metabolism to increase the cellular reducing power generation, facilitating glutathione regeneration and consequently free-radical control. The impact of this regulation in leprosy neuropathy is discussed.

Targeted anti-colon cancer activities of a millet bran-derived peroxidase were mediated by elevated ROS generation

Foxtail millet (Setaria italica) is the sixth most important cereal in the world.

The return of metabolism: biochemistry and physiology of the pentose phosphate pathway

The pentose phosphate pathway (PPP) is a fundamental component of cellular metabolism. The PPP is important to maintain carbon homoeostasis, to provide precursors for nucleotide and amino acid biosynthesis, to provide reducing molecules for anabolism, and to defeat oxidative stress. The PPP shares reactions with the Entner–Doudoroff pathway and Calvin cycle and divides into an oxidative and non-oxidative branch. The oxidative branch is highly active in most eukaryotes and converts glucose 6-phosphate into carbon dioxide, ribulose 5-phosphate and NADPH. The latter function is critical to maintain redox balance under stress situations, when cells proliferate rapidly, in ageing, and for the ‘Warburg effect’ of cancer cells. The non-oxidative branch instead is virtually ubiquitous, and metabolizes the glycolytic intermediates fructose 6-phosphate and glyceraldehyde 3-phosphate as well as sedoheptulose sugars, yielding ribose 5-phosphate for the synthesis of nucleic acids and sugar phosphate precursors for the synthesis of amino acids. Whereas the oxidative PPP is considered unidirectional, the non-oxidative branch can supply glycolysis with intermediates derived from ribose 5-phosphate and vice versa, depending on the biochemical demand. These functions require dynamic regulation of the PPP pathway that is achieved through hierarchical interactions between transcriptome, proteome and metabolome. Consequently, the biochemistry and regulation of this pathway, while still unresolved in many cases, are archetypal for the dynamics of the metabolic network of the cell. In this comprehensive article we review seminal work that led to the discovery and description of the pathway that date back now for 80 years, and address recent results about genetic and metabolic mechanisms that regulate its activity. These biochemical principles are discussed in the context of PPP deficiencies causing metabolic disease and the role of this pathway in biotechnology, bacterial and parasite infections, neurons, stem cell potency and cancer metabolism.

N-acetyl cysteine as an adjunct to standard anti-Helicobacter pylori eradication regimen in patients with dyspepsia: A prospective randomized, open-label trial

Background:

Increasing antibiotic resistance of Helicobacter pylori (H. pylori) which is associated with diseases of the upper gastrointestinal tract, has made alternative treatments necessary. This study compares the efficacy of adding N-acetyl cysteine (NAC) to standard regimen for H. pylori eradication.

Materials and Methods:

We conducted a randomized, open-label trial, comparing the efficacy of 14 days of quadruple therapy with Amoxicillin, Bismuth citrate, Omeprazole, Clarithromycin (group A) versus 14 days of above regimen plus NAC (group B) in adult patients with dyspepsia. Primary objective was H. pylori eradication. Compliance and side effects were determined by questionnaires. Our analysis was by intention-to-treat (ITT) and per-protocol. This study is registered with www.IRCT.ir, number: IRCT201201078634N1.

Result:

A total of 121 participants aged 21-76 years with a mean age of 44.5 ± 14.1, and 52.9% female, were randomly allocated a treatment: 60 with 14-day standard therapy and 61 with 14-day standard therapy with NAC. The eradication rate in groups A and B with ITT analyses was 49/60 (81.7%; 95% [confidence intervals] CI = 71.6-91.8%) and 50/61 (82%; 95% CI = 72-91.9%), respectively (P = 0.96). In per-protocol analysis, the rate of H. pylori eradication in groups A and B was 45/54 (83.3%; 95% CI = 73.1-93.6%) and 45/53 (84.9%; 95% CI = 74.9-94.9%), respectively (P = 0.82). Minor well tolerated side effects were reported in 15 (34.9%) and 21 (35.6%) patients of groups A and B, respectively, and only one therapy cessation in group A was created.

Conclusion:

Standard 14-day triple-drug therapy with NAC is not preferable to standard drug regimens for H. pylori infection.

Oxidative stress: an essential factor in the pathogenesis of gastrointestinal mucosal diseases

Reactive oxygen species (ROS) are generated as by-products of normal cellular metabolic activities. Superoxide dismutase, glutathione peroxidase, and catalase are the enzymes involved in protecting cells from the damaging effects of ROS. ROS are produced in response to ultraviolet radiation, cigarette smoking, alcohol, nonsteroidal anti-inflammatory drugs, ischemia-reperfusion injury, chronic infections, and inflammatory disorders. Disruption of normal cellular homeostasis by redox signaling may result in cardiovascular, neurodegenerative diseases and cancer. ROS are produced within the gastrointestinal (GI) tract, but their roles in pathophysiology and disease pathogenesis have not been well studied. Despite the protective barrier provided by the mucosa, ingested materials and microbial pathogens can induce oxidative injury and GI inflammatory responses involving the epithelium and immune/inflammatory cells. The pathogenesis of various GI diseases including peptic ulcers, gastrointestinal cancers, and inflammatory bowel disease is in part due to oxidative stress. Unraveling the signaling events initiated at the cellular level by oxidative free radicals as well as the physiological responses to such stress is important to better understand disease pathogenesis and to develop new therapies to manage a variety of conditions for which current therapies are not always sufficient.

Simultaneous analysis of reduced glutathione and glutathione disulfide by capillary zone electrophoresis

This report describes modifications to a CZE method developed by Serru et al. (Clinical Chemistry 2001, 47, 1321-1324) for the simultaneous analysis of reduced glutathione (GSH) and glutathione disulfide (GSSG). Lowering the pH of the run buffer (75 mmol/L boric acid, 25 mmol/L bis-Tris) from pH 8.4 to 7.8 markedly improved GSH peak area reproducibility and allowed multiple samples to be analyzed without changing run buffers due to ion depletion. Sample preparation using red blood cells (RBC) instead of whole blood, combined with glutathione extraction at a lower concentration of metaphosphoric acid (5%), increased assay sensitivity and decreased interference. CZE assay results for clinical samples containing 1000 to 3200 μmol GSH/L RBC and 100 to 400 μmol GSSG/L RBC were highly correlated (r(2) ≥ 0.95) with results obtained using a commercial dithionitrobenze-based glutathione assay. The modified CZE assay has proven useful for the analysis of glutathione in both mouse and human RBC.

Progress in understanding the association between interleukin-1B gene polymorphisms and susceptibility to gastric cancer

Gastric cancer is one of severe diseases threatening human health and has a close association with Helicobacter pylori infection. Interleukin-1B (IL-1B) gene polymorphisms have been suggested to be associated with susceptibility to gastric cancer; however, there is still controversy over this point of view. In this paper we will summarize recent progress in understanding the association between IL-1B gene polymorphisms and susceptibility to gastric cancer in population in different areas or of different races

Genetic variations of mTORC1 genes and risk of gastric cancer in an Eastern Chinese population

Mammalian target of rapamycin complex 1 (mTORC1) plays an important role in maintaining proper cellular functions, and genetic variations in this complex may affect cancer risk. In this study, we examined the associations between eight potential functional single nucleotide polymorphisms in the mTORC1 genes (rs2536T>C and rs1883965G>A for mTOR, rs3160T>C, and rs26865A>G for mLST8, rs3751934C>A, rs1062935T>C, rs3751932T>C, and rs12602885G>A for Raptor, not included in published gastric cancer genome-wide association studies) and gastric cancer risk in 1125 gastric cancer cases and 1196 cancer-free controls. We performed conditional logistic regression and multifactor dimensionality reduction (MDR) analyses to assess their associations with gastric cancer risk. We also used false-positive report probabilities (FPRP) for assessing significant findings. We found that only the rs1883965A variant genotypes were associated with an increased risk of gastric cancer (AG vs. GG: adjusted odds ratio (OR) = 1.26, 95% confidence interval (CI) = 1.00-1.59; AA vs. GG: adjusted OR = 1.85, 95% CI = 0.67-5.16 and dominant model: adjusted OR = 1.28, 95% CI = 1.03-1.61). Patients with ≥1 risk genotypes of mTOR had significant increased risk (adjusted OR = 1.25, 95% CI = 1.04-1.49), compared with those having zero risk genotypes. In the stratified analysis, the risk effect of the rs1883965 AG/AA genotypes was evident in subgroups of ever-smokers, non-gastric cardia adenocarcinoma and clinical stage I + II, which were noteworthy findings as evaluated by FPRP. The MDR analysis identified smoking status and rs1883965 as the strongest two-factors for gastric cancer risk. These data support the hypothesis that functional polymorphisms of mTOR may contribute to gastric cancer risk. Clearly, our results require validation in larger studies with different ethnic populations.

Sleep apnea and risk of peptic ulcer bleeding: a nationwide population-based study

OBJECTIVE

Patients with sleep apnea sustain cessation of breath during sleep, leading to intermittent hypoxia, systemic inflammation, and sympathetic activation. These insults may contribute to initiation or progression of peptic ulcers. This retrospective matched-control cohort study explored the relationship of sleep apnea and subsequent development of peptic ulcer bleeding.

METHODS

From 2000 to 2009, patients with newly diagnosed sleep apnea were identified from the Taiwan National Health Insurance Research Database. A control group without sleep apnea, matched for age, gender, comorbidities, and medications, was selected for comparison. In both groups, subjects with history of peptic ulcer bleeding, nonspecific gastrointestinal bleeding, or malignancy were excluded. The 2 cohorts were followed up and observed for occurrence of peptic ulcer bleeding.

RESULTS

Of the 35,480 sampled patients (7096 patients with sleep apnea vs 28,384 controls), 84 (0.24%) experienced peptic ulcer bleeding during a follow-up period of 3.57±2.61 years, including 32 (0.45% of patients with sleep apnea) from the sleep apnea cohort and 52 (0.18% of control) from the control group (log-rank test, P<.0001). In comparison with subjects without development of peptic ulcer bleeding, those with peptic ulcer bleeding were older and had a higher percentage of sleep apnea, coronary artery disease, peptic ulcer, ischemic stroke, and medication for nonsteroidal anti-inflammatory drugs. By Cox regression analysis, sleep apnea, older age, and peptic ulcer history were independent predictors of peptic ulcer bleeding. Patients with sleep apnea experienced a 2.400-fold (95% confidence interval, 1.544-3.731; P<.001) higher risk for incident peptic ulcer bleeding after adjusting for other variables.

CONCLUSIONS

Sleep apnea may be an independent risk factor for peptic ulcer bleeding.

The pentose phosphate pathway: an antioxidant defense and a crossroad in tumor cell fate

The pentose phosphate pathway, one of the main antioxidant cellular defense systems, has been related for a long time almost exclusively to its role as a provider of reducing power and ribose phosphate to the cell. In addition to this "traditional" correlation, in the past years multiple roles have emerged for this metabolic cascade, involving the cell cycle, apoptosis, differentiation, motility, angiogenesis, and the response to anti-tumor therapy. These findings make the pentose phosphate pathway a very interesting target in tumor cells. This review summarizes the latest discoveries relating the activity of the pentose phosphate pathway to various aspects of tumor metabolism, such as cell proliferation and death, tissue invasion, angiogenesis, and resistance to therapy, and discusses the possibility that drugs modulating the pathway could be used as potential tools in tumor therapy.

The effect of exopolysaccharide-producing probiotic strains on gut oxidative damage in experimental colitis

BACKGROUND

Oxidative stress plays a role in disease initiation and progression in inflammatory bowel disease (IBD) and manipulation of this pathway may attenuate disease progress. In this study, the effect of exopolysaccharide (EPS)-producing probiotic bacteria on gut oxidative damage was evaluated in a rat model of experimental colitis.

METHODS

Colitis was induced by intracolonic administration of acetic acid. Rats were treated daily with two probiotic strains, L. delbrueckii subsp. bulgaricus B3 strain (EPS of 211 mg/l; high-EPS group) or L. delbrueckii subsp. bulgaricus A13 strain (EPS of 27 mg/l; low-EPS group), which were given directly into the stomach. Non-colitis-fed control and preventative groups were only treated with the high-EPS producing strain. Antioxidant enzyme activities (superoxide dismutase, catalase, total glutathione, reduced glutathione, glutathione disulfide) and lipid peroxidation were measured in colonic tissue samples after a treatment period of 7 days.

RESULTS

Significant oxidative damage was associated with a higher level of malondialdehyde (MDA) activity and reduced antioxidant enzyme activities in the colitis model group. All antioxidant enzyme activities were higher in both probiotic-treated groups compared with those of the colitis model group (P < 0.001). Lipid peroxidation was significantly ameliorated in both probiotic groups. The improvement of oxidative stress parameters was significantly more in the high-EPS group than in the low-EPS group (P < 0.001).

CONCLUSIONS

EPS-producing probiotic bacteria significantly attenuate oxidative stress in experimental colitis. Increased EPS production gives rise to a better probiotic function. These results suggest that EPS molecules could revaluate probiotic strains and exert their beneficial effects on the host and this may have a therapeutic potential.

Novel combination therapy for the eradication of Helicobacter pylori infection in a mouse model

OBJECTIVE

To investigate the combination therapy, consisting of hyperimmune bovine colostrum, N-acetyl cysteine, zinc and amoxicillin on the eradication of Helicobacter pylori in a mouse model.

MATERIAL AND METHODS

C57BL/6 female mice (6 weeks of age) were inoculated with 0.1 ml of 1×10(9) H. pylori via a single oro-gastric gavage and were left infected for 4 weeks. Mice (n=9/group) were randomly allocated to receive by oral gavage (0.1 ml) HNZ (hyperimmune bovine colostrum+N-acetyl cysteine+zinc), HNZA (HNZ+amoxicillin; A), HNZA2 (2× amoxicillin; A2), HNZA5 (5× amoxicillin; A5), triple therapy (TT) or saline twice daily for 10 days. Bacterial load was assessed by culture. Gastric emptying was assessed by 13C-octanoic acid breath test.

RESULTS

Mice receiving HNZ, HNZA, and HNZA2 have a 22%, 44% and 67% eradication rate, respectively. Eradication rate was 100% with HNZA5, TT and those animals receiving A5 alone. In H. pylori infected mice there was an increased gastric emptying time by 7.9, 3.7, 10.1 and 7.7 min for the TT, HNZ, HNZA2, and HNZA5, respectively, compared to saline.

CONCLUSIONS

HNZ with the addition of a high dose of amoxicillin is effective at eradicating H. pylori in vivo as HNZA1 and HNZA2 did not give raise to eradication. The potency of the novel anti-H. pylori combination therapy may be due to the delayed gastric emptying.

HOGG1 polymorphism in atrophic gastritis and gastric cancer after Helicobacter pylori eradication

AIM: To investigate the association between Ser326Cys human oxoguanine glycosylase 1 (hOGG1) polymorphism and atrophic gastritis and gastric cancer after Helicobacter pylori (H. pylori) eradication.

METHODS: A total of 488 subjects (73 patients with gastric cancer, 160 with atrophic gastritis after H. pylori eradication and 255 controls) were prospectively collected. Polymerase chain reaction-restriction fragment length polymorphism analysis was performed to distinguish hOGG1 Ser326Cys polymorphism. Statistical analysis was conducted by two-sample t test for continuous variables and χ² test for categorical variables. Logistic regression models were used to find the risk factors for gastric cancer and atrophic gastritis.

RESULTS: Neither the hOGG1 Ser/Cys nor the Cys/Cys genotype was associated with gastric cancer. Compared with the Ser/Ser genotype, odds ratio (OR) for Ser/Cys was 0.96, (95% CI: 0.51-1.84) and OR for Cys/Cys was 1.1 (95% CI: 0.48-2.1). No association was detected between hOGG1 polymorphism and Lauren type of gastric cancer (P = 0.61) either. However, Ser/Cys and Cys/Cys were significantly associated with atrophic gastritis with OR: 1.76 for Ser/Cys (95% CI: 1.03-3.0) and 2.38 for Cys/Cys (95% CI: 1.34-4.23). After controlling for age, gender, smoking and alcohol, there were still significant associations with OR: 2.05 for Ser/Cys (95% CI: 1.14-3.68) and 2.76 for Cys/Cys (95% CI: 1.47-5.18).

CONCLUSION: HOGG1 polymorphisms (Cys/Cys and Ser/Cys) are associated with atrophic gastritis. No significant association is detected between hOGG1 polymorphisms (Cys/Cys or Ser/Cys) and gastric cancer.

Nrf2-Keap1 signaling as a potential target for chemoprevention of inflammation-associated carcinogenesis

Persistent inflammatory tissue damage is causally associated with each stage of carcinogenesis. Inflammation-induced generation of reactive oxygen species, reactive nitrogen species, and other reactive species not only cause DNA damage and subsequently mutations, but also stimulate proliferation of initiated cells and even metastasis and angiogenesis. Induction of cellular cytoprotective enzymes (e.g., heme oxygenase-1, NAD(P)H:quinone oxidoreductase, superoxide dismutase, glutathione-S-transferase, etc.) has been shown to mitigate aforementioned events implicated in inflammation-induced carcinogenesis. A unique feature of genes encoding these cytoprotective enzymes is the presence of a cis-acting element, known as antioxidant response element (ARE) or electrophile response element (EpRE), in their promoter region. A stress-responsive transcription factor, nuclear factor erythroid-2-related factor-2 (Nrf2), initially recognized as a key transcriptional regulator of various cytoprotective enzymes, is known to play a pivotal role in cellular defense against inflammatory injuries. Activation of Nrf2 involves its release from the cytosolic repressor Kelch-like ECH-associated protein-1 (Keap1) and subsequent stabilization and nuclear localization for ARE/EpRE binding. Genetic or pharmacologic inactivation of Nrf2 has been shown to abolish cytoprotective capability and to aggravate experimentally induced inflammatory injuries. Thus, Nrf2-mediated cytoprotective gene induction is an effective strategy for the chemoprevention of inflammation-associated carcinogenesis.

Association between cytokine gene polymorphisms and gastric precancerous lesions: systematic review and meta-analysis

Polymorphisms within interleukin-1 (IL1) and tumor necrosis factor alpha (TNFA) gene clusters are associated with an increased risk of gastric cancer. However, their role in gastric precancerous lesions remains poorly understood. Our objective was to perform a meta-analysis of studies addressing the association between IL1B-511, IL1RN variable number of tandem repeat, and TNFA-308 gene polymorphisms and gastric precancerous lesions, including original data from Portugal and Mozambique. Published studies on the association between these cytokine gene polymorphisms and gastric precancerous lesions were identified by systematic review, and estimates of the association were combined using random-effects meta-analysis taking into account new data obtained from Portuguese volunteer shipyard workers (n = 215) and Mozambican dyspeptic patients (n = 96) who underwent endoscopic and pathologic evaluation following the same protocol. Odds ratio (OR) estimates for intestinal metaplasia were 2.83 [95% confidence interval (95% CI), 1.15-6.96] for the IL1RN*22 genotype, 1.86 (95% CI, 1.03-3.36) for IL1B-511 T carriers, and 0.59 (95% CI, 0.12-3.04) for the TNFA-308*AA genotype in the Portuguese sample. All Mozambican subjects with intestinal metaplasia were T carriers for IL1B-511 and none had the 2 allele for IL1RN. In meta-analysis, IL1RN*22 genotype was associated with an increased risk of gastric precancerous lesions (22 versus LL: OR, 2.27; 95% CI, 1.40-3.70; I(2) = 26.4%; 12 studies). No such association was found for the IL1B-511 (TT versus CC: OR, 1.34; 95% CI, 0.87-2.07; I(2) = 65.7%; 13 studies) or TNFA-308 genotypes (AA versus GG: OR, 0.93; 95% CI, 0.35-2.43; I(2) = 0.0%; 7 studies). The IL1RN*22 genotype seems to consistently increase the risk of gastric precancerous lesions, supporting a role for this polymorphism in the early stages of gastric carcinogenesis.

The Role of Nrf2 in Cellular Innate Immune Response to Inflammatory Injury

Nuclear factor erythroid derived 2-related factor-2 (Nrf2) is a master transcription regulator of antioxidant and cytoprotective proteins that mediate cellular defense against oxidative and inflammatory stresses. Disruption of cellular stress response by Nrf2 deficiency causes enhanced susceptibility to infection and related inflammatory diseases as a consequence of exacerbated immuneediated hypersensitivity and autoimmunity. The cellular defense capacity potentiated by Nrf2 activation appears to balance the population of CD4⁺ and CD8⁺ of lymph node cells for proper innate immune responses. Nrf2 can negatively regulate the activation of pro-inflammatory signaling molecules such as p38 MAPK, NF-KB, and AP-1. Nrf2 subsequently functions to inhibit the production of pro-inflammatory mediators including cytokines, chemokines, cell adhesion molecules, matrix metalloprotein-ases, COX-2 and iNOS. Although not clearly elucidated, the antioxidative function of genes targeted by Nrf2 may cooperatively regulate the innate immune response and also repress the expression of proinflammatory mediators.

Anti-Helicobacter pylori activity and immunostimulatory effect of extracts from Byrsonima crassa Nied. (Malpighiaceae)

Background

Several in vitro studies have looked at the effect of medicinal plant extracts against Helicobacter pylori (H. pylori). Regardless of the popular use of Byrsonima crassa (B. crassa) as antiemetic, diuretic, febrifuge, to treat diarrhea, gastritis and ulcers, there is no data on its effects against H. pylori. In this study, we evaluated the anti-H. pylori of B. crassa leaves extracts and its effects on reactive oxygen/nitrogen intermediates induction by murine peritoneal macrophages.

Methods

The minimal inhibitory concentration (MIC) was determined by broth microdilution method and the production of hydrogen peroxide (H₂O₂) and nitric oxide (NO) by the horseradish peroxidase-dependent oxidation of phenol red and Griess reaction, respectively.

Results

The methanolic (MeOH) and chloroformic (CHCl₃) extracts inhibit, in vitro, the growth of H. pylori with MIC value of 1024 μg/ml. The MeOH extract induced the production H₂O₂ and NO, but CHCl₃ extract only NO.

Conclusion

Based in our results, B. crassa can be considered a source of compounds with anti-H. pylori activity, but its use should be done with caution in treatment of the gastritis and peptic ulcers, since the reactive oxygen/nitrogen intermediates are involved in the pathogenesis of gastric mucosal injury induced by ulcerogenic agents and H. pylori infections.

Effects of Genetic Polymorphisms of Glutathione S-transferase P1 on Helicobacter pylori-associated Gastric Cancer

BACKGROUND/AIMS

Glutathione S-transferase P1 (GSTP1) scavenges radicals via its peroxidase activity. The purpose of this study was to determine the association of GSTP1 genetic polymorphisms with the expression of H. pylori-associated gastroduodenal disease.

METHODS

This study involved 1,911 subjects, comprising patients with four diseases (gastric cancer, dysplasia, benign gastric ulcer, and duodenal ulcer disease) and controls. Biallelic polymorphisms were genotyped by restriction fragment length polymorphism techniques.

RESULTS

The frequency of the genetic polymorphism at nucleotide 313 of GSTP1 did not differ among the five study groups. However, when the gastric cancer group was subdivided into advanced gastric cancer (AGC) and early gastric cancer, the frequency of the G/G genotype was significantly higher in the AGC group than in all the control subgroups (OR: 1.2, 95% CI: 1.1-4.9). The frequency of this genotype differed significantly in the H. pylori-positive AGC group (OR: 2.7, 95% CI: 1.1-6.3) but not in the H. pylori-negative group. Furthermore, the difference was greater in the intestinal type, and was not found in diffuse types of disease.

CONCLUSIONS

This study found that genetic polymorphisms of GSTP1 were associated with H. pylori-associated gastric cancer only during the advanced stage of gastric cancer, with intestinal-type histology evident in H. pylori-positive subjects.

Immune and proliferative cellular responses to Helicobacter pylori infection in the gastric mucosa of Mexican children

BACKGROUND

Helicobacter pylori infection occurs mostly during childhood, but few studies on this age group have addressed the innate immune and the proliferative response to this infection. Mexico has a high H. pylori prevalence in children, but a low risk of gastric cancer. The aim of this work was to study the cellular responses of the gastric mucosa to this infection in Mexican children.

METHODS

Antral and corpus gastric biopsies were obtained from 44 H. pylori-infected children (mean age 12 +/- 3.2 years) and 44 uninfected children (mean age 10 +/- 3 years). Mucosal cellular responses were studied by immunohistochemistry, using anti-Ki67 antibodies for proliferation studies, antihuman tryptase for mast cells, and antihuman CD68 for macrophages. T and B lymphocytes were stained with a commercial integrated system. The intensity of cellular responses was estimated histologically using the software KS300.

RESULTS

Epithelium proliferation and infiltration of macrophages and T and B lymphocytes were significantly higher in H. pylori-infected than in uninfected children. A balanced increase of CD4, CD8, and CD20 lymphocytes was observed in infected children. However, activated mast cells were decreased, and infiltration of neutrophil and mononuclear cells was low. Epithelial proliferation was associated with polymorphonuclear infiltration but not with infiltration of macrophages or lymphocytes. Inflammation and proliferation was higher in CagA (+)-infected children.

CONCLUSIONS

Mexican children respond to H. pylori infection with a low inflammatory response, a balanced increase of T and B lymphocytes, and a high regenerative activity.

Metabolism of glutamine and glutathione via gamma-glutamyltranspeptidase and glutamate transport in Helicobacter pylori: possible significance in the pathophysiology of the organism

gamma-Glutamyltranspeptidase (GGT) is a periplasmic enzyme of Helicobacter pylori implicated in its pathogenesis towards mammalian cells. We have cloned and expressed the H. pylori strain 26695 recombinant GGT protein in Escherichia coli and purified it to homogeneity. The purified protein exhibited hydrolysis activity with very high affinities for glutamine and glutathione shown by apparent K(m) values lower than 1 muM. H. pylori cells were unable to take up extracellular glutamine and glutathione directly. Instead, these substances were hydrolysed to glutamate by the action of GGT outside the cells. The glutamate produced was then transported by a Na(+)-dependent reaction into H. pylori cells, where it was mainly incorporated into the TCA cycle and partially utilized as a substrate for glutamine synthesis. These observations show that one of the principle physiological functions of H. pylori GGT is to enable H. pylori cells to utilize extracellular glutamine and glutathione as a source of glutamate. As glutamine and glutathione are important nutrients for maintenance of healthy gastrointestinal tissue, their depletion by the GGT enzyme is hypothesized to account for the damaging of mammalian cells and the pathophysiology of H. pylori.

Interleukin-1beta and interleukin-1 receptor antagonist gene polymorphisms and gastric cancer: a meta-analysis

BACKGROUND

Polymorphisms of interleukin-1B (IL1B) and its receptor antagonist (IL1RN) genes have been inconsistently associated with gastric cancer risk. We examined these associations by performing meta-analyses.

MATERIALS AND METHODS

Twenty-five studies testing the association between IL1B and/or IL1RN gene polymorphisms and gastric cancer were examined: 14 studies of IL1B-511, 14 studies of IL1B-31, 8 studies of IL1B+3954, and 23 studies of IL1RN. Overall and ethnicity-specific summary odds ratios and corresponding 95% confidence intervals for gastric cancer associated with these polymorphisms were estimated using fixed- and random-effects models. Heterogeneity and publication bias were evaluated.

RESULTS

IL1B-511T and IL1RN*2 were associated with gastric cancer risk in Caucasians, but not in Asians. For IL1B-511T, the association in Caucasians was stronger when intestinal-subtype and noncardia gastric cancer cases were examined. A nonsignificant trend was observed between IL1B-31C and gastric cancer in Caucasians. No significant association of IL1B+3954T and gastric cancer risk was detected. Studies with better methodologic characteristics reported stronger effects. There was no evidence of publication bias.

CONCLUSION

IL1B-511T is associated with gastric cancer susceptibility in Caucasians. The meta-analyses suggest that the conflicting results among studies may be explained by variation in allele frequencies among the ethnic groups and variation in tumor types, as well as by the methodologic quality of the studies.

Gastroduodenal mucosal defense

PURPOSE OF REVIEW

The duodenum absorbs nearly all secreted gastric acid. Carbonic anhydrases facilitate transmucosal acid movement. The upper gastrointestinal tract must resist a variety of injuries, including those caused by ingested noxious substances, acid, ischemia/reperfusion, and infections such as Helicobacter pylori. The results are similar, however, regardless of insult: inflammation, ulceration, or metaplasia/dysplasia. In the past year, there have been prominent findings suggesting that oxidative stress and the formation of reactive oxygen species may play a pivotal role in all forms of injury, and that antioxidants may be the key to injury prevention and healing.

RECENT FINDINGS

Oxidative injury may be a common mechanism by which the upper gastrointestinal mucosa responds to noxious insults. Endogenous antioxidants, such as ghrelin, L-carnitine, and annexin-1 attenuate the oxidative-stress response. Similarly, exogenous antioxidants have also been shown to decrease inflammation, upregulate free radical scavengers, and prevent the formation of reactive oxygen species.

SUMMARY

Many studies published in the past year have linked oxidative stress to a variety of upper gastrointestinal insults. Exogenous and endogenous antioxidant compounds prevent the oxidative stress response. The future holds great promise for the development of pharmaceuticals with antioxidant properties that are safe, efficacious, and inexpensive.