Expression of Interleukin-18, a Th1 cytokine, in human gastric mucosa is increased in Helicobacter pylori infection

NOD1 mediates interleukin-18 processing in epithelial cells responding to Helicobacter pylori infection in mice

The interleukin-1 family members, IL-1β and IL-18, are processed into their biologically active forms by multi-protein complexes, known as inflammasomes. Although the inflammasome pathways that mediate IL-1β processing in myeloid cells have been defined, those involved in IL-18 processing, particularly in non-myeloid cells, are still not well understood. Here we report that the host defence molecule NOD1 regulates IL-18 processing in mouse epithelial cells in response to the mucosal pathogen, Helicobacter pylori. Specifically, NOD1 in epithelial cells mediates IL-18 processing and maturation via interactions with caspase-1, instead of the canonical inflammasome pathway involving RIPK2, NF-κB, NLRP3 and ASC. NOD1 activation and IL-18 then help maintain epithelial homoeostasis to mediate protection against pre-neoplastic changes induced by gastric H. pylori infection in vivo. Our findings thus demonstrate a function for NOD1 in epithelial cell production of bioactive IL-18 and protection against H. pylori-induced pathology.

Application progress of liquid biopsy in gastric cancer

Gastric cancer (GC) is one of the most common malignant tumors globally. Guiding the individualized treatment of GC is the focus of research. Obtaining representative biological samples to study the biological characteristics of GC is the focus of diagnosis and treatment of GC. Liquid biopsy technology can use high-throughput sequencing technology to detect biological genetic information in blood. Compared with traditional tissue biopsy, liquid biopsy can determine the dynamic changes of tumor. As a noninvasive auxiliary diagnostic method, liquid biopsy can provide diagnostic and prognostic information concerning the progression of the disease. Liquid biopsy includes circulating tumor cells, circulating tumor DNA, circulating tumor RNA, tumor educated platelets, exosomes, and cytokines. This article describes the classification of liquid biopsy and its application value in the occurrence, development, and therapeutic efficacy of GC.

HP-NAP of Helicobacter pylori: The Power of the Immunomodulation

The miniferritin HP-NAP of Helicobacter pylori was originally described as a neutrophil-activating protein because of the capacity to activate neutrophils to generate oxygen radicals and adhere to endothelia. Currently, the main feature for which HP-NAP is known is the ability to promote Th1 responses and revert the immune suppressive profile of macrophages. In this review, we discuss the immune modulating properties of the protein regarding the H. pylori infection and the evidence that support the potential clinical application of HP-NAP in allergy and cancer immunotherapy.

Adverse pregnancy outcomes and Helicobacter pylori infection: A meta-analysis

INTRODUCTION

Helicobacter pylori infection during pregnancy has some adverse effects, but its effects are still conflicting. This meta-analysis study was performed to assess the relationship between H pylori infection and adverse effects during pregnancy.

METHODS

Through a systematic literature search up to August 2020, 31 studies included 16 887 pregnant females at baseline and reported a total of 5852 H pylori infection positive and 8196 H pylori infection negative pregnant females, were found recording relationships between H pylori infection and adverse effects during pregnancy. Odds ratio (OR) with 95% confidence intervals (CIs) was calculated between H pylori infection positive vs H pylori infection negative in adverse effects during pregnancy using the dichotomous methods with a random or fixed-effect model.

RESULTS

H pylori infection positive during pregnancy was significantly related to higher rate of preeclampsia (OR, 2.68; 95% CI, 2.02-3.56, P < .001), foetal growth restriction (OR, 1.45; 95% CI, 1.26-1.66, P < .001), gestational diabetes mellitus (OR, 2.63; 95% CI, 1.51-4.59, P < .001), and hyperemesis gravidarum (OR, 14.45; 95% CI, 10.24-20.38, P < .001) compared with H pylori infection negative. However, H pylori infection positive during pregnancy was not significantly correlated with spontaneous onset of labour (OR, 1.00; 95% CI, 0.83-1.21, P = .98) compared with H pylori infection negative.

CONCLUSIONS

H pylori infection may have an independent relationship with certain adverse effects during pregnancy. H pylori infection positive during pregnancy was significantly related to a higher rate of preeclampsia, foetal growth restriction, gestational diabetes mellitus, and hyperemesis gravidarum compared with H pylori infection negative. This relationship encouraged us to recommend screening and treating females for H pylori infection before and during pregnancy to avoid any possible complications.

Helicobacter pylori-Induced Inflammation: Possible Factors Modulating the Risk of Gastric Cancer

Chronic inflammation and long-term tissue injury are related to many malignancies, including gastric cancer (GC). Helicobacter pylori (H. pylori), classified as a class I carcinogen, induces chronic superficial gastritis followed by gastric carcinogenesis. Despite a high prevalence of H. pylori infection, only about 1–3% of people infected with this bacterium develop GC worldwide. Furthermore, the development of chronic gastritis in some, but not all, H. pylori-infected subjects remains unexplained. These conflicting findings indicate that clinical outcomes of aggressive inflammation (atrophic gastritis) to gastric carcinogenesis are influenced by several other factors (in addition to H. pylori infection), such as gut microbiota, co-existence of intestinal helminths, dietary habits, and host genetic factors. This review has five goals: (1) to assess our current understanding of the process of H. pylori-triggered inflammation and gastric precursor lesions; (2) to present a hypothesis on risk modulation by the gut microbiota and infestation with intestinal helminths; (3) to identify the dietary behavior of the people at risk of GC; (4) to check the inflammation-related genetic polymorphisms and role of exosomes together with other factors as initiators of precancerous lesions and gastric carcinoma; and (5) finally, to conclude and suggest a new direction for future research.

NLRC4 biology in immunity and inflammation

Inflammasomes are cytosolic multiprotein complexes that sense microbial infections or host cell damage, triggering cytokine production and a proinflammatory form of cell death, called pyroptosis. Whereas pyroptosis and cytokine production may often promote host resistance to infections, uncontrolled inflammasome activation leads to autoinflammatory diseases in humans. Among the multiple inflammasomes described, the neuronal apoptosis inhibitory protein/nucleotide-binding domain leucine-rich repeat-containing protein family caspase activation and recruitment domain-containing protein 4 (NLRC4) inflammasome emerged as a critical component for the restriction of bacterial infections. Accordingly, our understanding of this inflammasome advanced remarkably over the last 10 yr, expanding our knowledge about ligand-receptor interaction; cryo-EM structure; and downstream effectors and substrates, such as gasdermin-D, caspase-1, caspase-8, and caspase-7. In this review, we discuss recent advances on the biology of the NLRC4 inflammasome, in terms of structure and activation mechanisms, importance in bacterial and nonbacterial diseases, and the identification of NLRC4 gain-of-function mutations leading to NLRC4-associated autoinflammatory diseases in humans.

Helicobacter pylori Exploits the NLRC4 Inflammasome to Dampen Host Defenses

Helicobacter pylori colonizes the stomach of around 50% of humans. This chronic infection can lead to gastric pathologic conditions such as gastric ulcers and gastric adenocarcinomas. The strong inflammatory response elicited by H. pylori is characterized by the induction of the expression of several cytokines. Among those, IL-18 is found highly upregulated in infected individuals, and its expression correlates with the severity of gastric inflammation. IL-18 is produced as inactive proform and has to be cleaved by the multiprotein complex inflammasome to be active. In immune cells, the NLRC4 inflammasome, which is activated by flagellin or bacterial secretion systems, was shown to be dispensable for H. pylori-induced inflammasome activation. However, apart from immune cells, gastric epithelial cells can also produce IL-18. In this study, we analyzed the role of the NLRC4 inflammasome during H. pylori infection. Our results indicate that NLRC4 and a functional type IV secretion system are crucial for the production of IL-18 from human and murine gastric epithelial cells. In vivo, Nlrc4^-/- mice failed to produce gastric IL-18 upon H. pylori infection. Compared with wild type mice, Nlrc4^-/- mice controlled H. pylori better without showing strong inflammation. Moreover, H. pylori-induced IL-18 inhibits β-defensin 1 expression in a NF-κB-dependent manner, resulting in higher bacterial colonization. At the same time, inflammasome activation enhances neutrophil infiltration, resulting in inflammation. Thus, NLRC4 inflammasome activation and subsequent IL-18 production favors bacterial persistence by inhibiting antimicrobial peptide production and, at the same time, contributes to gastric inflammation.

The risk of Helicobacter pylori infection for adverse pregnancy outcomes: A systematic review and meta-analysis

OBJECTIVE

To estimate the current evidence regarding the association between Helicobacter pylori infection during pregnancy and adverse pregnancy outcomes.

MATERIALS AND METHODS

A systematic literature search for relevant publications was conducted using PubMed, EMBASE, Cochrane Library, and Web of science databases through November 17th, 2018. The pooled odds ratios (ORs) with their corresponding 95% confidence intervals (CIs) were selected as the effect size. Subgroup analysis and sensitivity analysis were performed.

RESULTS

Thirty-one studies with a total of 22 845 participants were identified. There was significant association of H pylori infection with preeclampsia (OR: 2.51; 95% CI: 1.88-3.34; P < 0.001), fetal growth restriction (OR: 2.28; 95% CI: 1.21-4.32; P = 0.01), gestational diabetes mellitus (OR: 2.03; 95% CI: 1.56-2.64; P < 0.001), spontaneous abortion (OR: 1.50; 95% CI: 1.05-2.14; P = 0.024), and birth defect (OR: 1.63; 95% CI: 1.05-2.54; P = 0.03). Sensitivity analysis showed the significant association between H pylori infection and low birthweight (OR: 1.59; 95% CI: 1.05-2.40; P = 0.03).

CONCLUSION

The present meta-analysis offers proof to support that H pylori infection during pregnancy can increase the risk on adverse pregnancy outcomes. Screening and treating for H pylori infection before pregnancy should be taken into account.

The lipoprotein HP1454 of Helicobacter pylori regulates T-cell response by shaping T-cell receptor signalling

Helicobacter pylori (HP) is a Gram-negative bacterium that chronically infects the stomach of more than 50% of human population and represents a major cause of gastric cancer, gastric lymphoma, gastric autoimmunity, and peptic ulcer. It still remains to be elucidated, which HP virulence factors are important in the development of gastric disorders. Here, we analysed the role of the HP protein HP1454 in the host-pathogen interaction. We found that a significant proportion of T cells isolated from HP patients with chronic gastritis and gastric adenocarcinoma proliferated in response to HP1454. Moreover, we demonstrated in vivo that HP1454 protein drives Th1/Th17 inflammatory responses. We further analysed the in vitro response of human T cells exposed either to an HP wild-type strain or to a strain with a deletion of the hp1454 gene, and we revealed that HP1454 triggers the T-cell antigen receptor-dependent signalling and lymphocyte proliferation, as well as the CXCL12-dependent cell adhesion and migration. Our study findings prove that HP1454 is a crucial bacterial factor that exerts its proinflammatory activity by directly modulating the T-cell response. The relevance of these results can be appreciated by considering that compelling evidence suggest that chronic gastric inflammation, a condition that paves the way to HP-associated diseases, is dependent on T cells.

Could the inhibition of IL-17 or IL-18 be a potential therapeutic opportunity for gastric cancer?

Chronic inflammation is recognized as a key tumor-promoting factor in a number of epithelial cancers, including gastric cancer (GC). The production of pro-inflammatory cytokines in the tumor microenvironment by both the innate and the adaptive immune response can activate signaling pathways that are associated with increased cell survival and proliferation of cancer cells. Among the cytokines that have most commonly been linked to inflammation-associated cancers, are the Th17 cell-associated cytokines IL-17A, IL-23, IL-22, and the IL-1 family members IL-1β and IL-18. However, whether their contribution to inflammation-associated cancers is universal, or specific to individual types of cancers, remains to be elucidated. This review will explore our current understanding of the known roles of these cytokines in gastritis and discuss how their therapeutic inhibition may be useful for GC.

Regulation and functions of inflammasome-mediated cytokines in Helicobacter pylori infection

Persistent stomach infection with Helicobacter pylori causes chronic mucosal inflammation (gastritis), which is widely recognized as an essential precursor to gastric cancer. The IL-1 interleukin family cytokines IL-1β and IL-18 have emerged as central mediators of mucosal inflammation. Here, we review the regulation and functions of these cytokines in H. pylori-induced inflammation and carcinogenesis.

Lansoprazole Increases Serum IgG and IgM in H. Pylori-Infected Patients

Proton-pump inhibitors have been reported to influence the human immune system, we therefore evaluated the effect of lansoprazole, a proton-pump inhibitor, on humoral immunity. Patients with gastric ulcer received lansoprazole 30 mg/day for 8 weeks, and serum immunoglobulins were evaluated before and upon completion of the treatment. There were 79 patients with gastric ulcer; 51 were H. pylori-infected and 28 were H. pylori-uninfected. Eighteen patients positive for H. pylori were receiving at least one non-steroidal anti-inflammatory drug, and 12 patients negative for H. pylori received one non-steroidal anti-inflammatory drug. H. pylori-infected patients showed significant increases in serum immunoglobulins G and M 8 weeks after the start of lansoprazole treatment ( P<0.001 for IgG and P<005 for IgM), but uninfected patients did not. Even when H. pylori-infected patients receiving a non-steroidal anti-inflammatory drug or low-dose aspirin were analyzed separately, these increases were seen ( P<0.001 for IgG and P<0.005 for IgM). Lansoprazole elevated serum levels of immunoglobulins G and M in gastric ulcer patients with H. pylori infection, particularly in those receiving non-steroidal anti-inflammatory drugs. Deducing from these observations, lansoprazole might alter the Th1 shift in the immune response induced by H. pylori infection.

Association Between IL-17, IL-8 and IL-18 Expression in Peripheral Blood and Helicobacter Pylori Infection in Mongolian Gerbils

Background:

Persistent Helicobacter pylori infection confers an increased risk for serious illnesses such as peptic ulcers and gastric cancer. Various cytokines are involved in the regulation of inflammatory immune response in H. pylori-infected gastric mucosa.

Objectives:

The current study aimed to obtain evidence regarding the association between IL-17, IL-8 and IL-18 expression in peripheral blood and H. pylori infection in Mongolian gerbils.

Materials and Methods:

Mongolian gerbils were inoculated with H. pylori by a metal stomach catheter. After sacrifice, their gastric mucosae were examined in macroscopic, histological and electron microscopy levels. In addition, enzyme linked immunosorbent assay (ELISA) assay was performed on the IL-17, IL-8 and IL-18 cytokines in the blood samples.

Results:

Serum levels of IL-17, IL-8 and IL-18 were remarkably up-regulated compared to those of the control group. There was an obvious correlation between the increase of IL-17 and the serious extent of gastritis in the current study. However, the serum levels of IL-8 and IL-18 without getting increasingly more for repetitive intragastric administration. There were plenty of neutrophils infiltrating in the infected group mucosal. Intestinal metaplasia and gastric ulcers were also founded in H. pylori infected animals after enhanced inoculation. The edema, degeneration and necrosis changes could be found in organelles by transmission electron microscopy. More serious pathological changes were detected in the enhanced inoculation groups compared to the cycle group.

Conclusions:

The serum levels of IL-17, but not IL-8 and IL-18 may serve as a potential biomarker for diagnosis and predicting the prognosis of gastritis caused by H. pylori.

Association between interleukin-18 gene polymorphism and Helicobacter pylori infection in the Korean population

Interleukin-18 (IL-18) is a pleiotropic, pro-inflammatory cytokine that is capable of promoting the Th1 response. A predominant Th1 response induces chronic and persistent inflammatory changes in the gastric mucosa in response to Helicobacter pylori (H. pylori) infection. The aim of this study was to investigate the potential association between IL-18 gene polymorphisms and susceptibility to H. pylori infection in the Korean population. A total of 678 subjects who underwent a routine health check-up were enrolled. The IL-18 gene polymorphisms at positions −656, −607, −137, +113, and +127 were genotyped. H. pylori positivity was demonstrated in 456 subjects (67.3%). The allele frequencies of IL-18 gene polymorphisms at position −137 (rs187238) were different based on the status of H. pylori infection (G vs. C, adjusted OR 0.64 CI: 0.47–0.87, P = 0.005). The results indicate that the genetic variants in the IL-18 gene may be associated with susceptibility to H. pylori infection in the Korean population, suggesting that IL-18 plays a role in the pathogenesis of H. pylori-associated diseases. However, this finding requires further replication and validation.

Helicobacter pylori-an infectious risk factor for atherosclerosis?

Accumulating evidence implicates Helicobacter pylori (H. pylori) infection in the pathogenesis of certain diseases localized outside the stomach, particularly those characterized by persistent and low-grade systematic inflammation. Recently, the role of H. pylori infection in the development of atherosclerosis and its clinical complications has received attention. Atherosclerosis is a high-cost disease, and acute events resulting from this condition rank first among morbidity and mortality statistics in most industrialized countries. Atherosclerosis is a multifactorial disorder, and traditional risk factors explain only 50% of its etiology. Therefore, identifying new risk factors for atherosclerosis is necessary. Serological studies indicate that chronic H. pylori infection, especially that with more virulent strains, may predispose patients to the onset of atherosclerosis and related adverse clinical events, and PCR studies have detected H. pylori DNA in atherosclerotic plaques, although this finding remains controversial. If this association were to be confirmed, its importance to public health would be substantial, as the eradication of H. pylori is more straightforward and less costly than the long-term treatment of other risk factors. This review investigates the potential relationship between H. pylori infection and atherosclerosis from both epidemiological and pathogenic perspectives and characterizes the potential mechanisms underlying this correlation.

Histologic Findings and Inflammatory Reactions After Long-term Colonization of Helicobacter felis in C57BL/6 Mice

Background:

The Helicobacter felis (H. felis) mouse model has been developed for the research regarding pathogenesis of chronic gastritis and gastric cancer. The aim of this study was to investigate long-term H. felis colonization in the stomachs of C57BL/6 mice and subsequent histologic findings and inflammatory reactions including pro-inflammatory cytokines.

Methods:

Twenty-three female C57BL/6 mice at 4 weeks of age were gavaged with H. felis, and 13 control mice served as vehicle only. The mice were sacrificed at 4, 24, and 52 weeks after inoculation. The infection status and degree of inflammation were determined by culture and histopathology. The level of gastric mucosal myeloperoxidase (MPO), tumor necrosis factor alpha (TNF-α), and interleukin-1beta (IL-1β) were measured by ELISA.

Results:

The overall infection rate was 100%, as determined by the culture and histology. At 4, 24, and 52 weeks, the neutrophil and monocyte scores were significantly higher in infected mice than in control mice. At 24 weeks after inoculation, most of the infected mice showed mucosal atrophy with or without metaplasia, and a few showed focal dysplasia. Adenocarcinoma was observed in one mouse at 52 week post-infection. Gastric mucosal MPO and IL-1β levels were significantly higher in infected mice than those in control mice at 24 and 52 weeks. However, the expression of gastric mucosal TNF-α was not significantly different between the infected and control mice at any time-point.

Conclusions:

Long-term H. felis-infection in C57BL/6 mice provoked a severe inflammatory reaction and it progressed into atrophy, metaplasia, dysplasia and cancer. IL-1β might play an important role in the inflammatory response of mice to Helicobacter species.

Pattern-recognition receptors and gastric cancer

Chronic inflammation has been associated with an increased risk of several human malignancies, a classic example being gastric adenocarcinoma (GC). Development of GC is known to result from infection of the gastric mucosa by Helicobacter pylori, which initially induces acute inflammation and, in a subset of patients, progresses over time to chronic inflammation, gastric atrophy, intestinal metaplasia, dysplasia, and finally intestinal-type GC. Germ-line encoded receptors known as pattern-recognition receptors (PRRs) are critical for generating mature pro-inflammatory cytokines that are crucial for both Th1 and Th2 responses. Given that H. pylori is initially targeted by PRRs, it is conceivable that dysfunction within genes of this arm of the immune system could modulate the host response against H. pylori infection, and subsequently influence the emergence of GC. Current evidence suggests that Toll-like receptors (TLRs) (TLR2, TLR3, TLR4, TLR5, and TLR9), nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) (NOD1, NOD2, and NLRP3), a C-type lectin receptor (DC-SIGN), and retinoic acid-inducible gene (RIG)-I-like receptors (RIG-I and MDA-5), are involved in both the recognition of H. pylori and gastric carcinogenesis. In addition, polymorphisms in genes involved in the TLR (TLR1, TLR2, TLR4, TLR5, TLR9, and CD14) and NLR (NOD1, NOD2, NLRP3, NLRP12, NLRX1, CASP1, ASC, and CARD8) signaling pathways have been shown to modulate the risk of H. pylori infection, gastric precancerous lesions, and/or GC. Further, the modulation of PRRs has been suggested to suppress H. pylori-induced inflammation and enhance GC cell apoptosis, highlighting their potential relevance in GC therapeutics. In this review, we present current advances in our understanding of the role of the TLR and NLR signaling pathways in the pathogenesis of GC, address the involvement of other recently identified PRRs in GC, and discuss the potential implications of PRRs in GC immunotherapy.

Signal transduction of Helicobacter pylori during interaction with host cell protein receptors of epithelial and immune cells

Helicobacter pylori infections can induce pathologies ranging from chronic gastritis, peptic ulceration to gastric cancer. Bacterial isolates harbor numerous well-known adhesins, vacuolating cytotoxin VacA, protease HtrA, urease, peptidoglycan, and type IV secretion systems (T4SS). It appears that H. pylori targets more than 40 known host protein receptors on epithelial or immune cells. A series of T4SS components such as CagL, CagI, CagY, and CagA can bind to the integrin α 5β 1 receptor. Other targeted membrane-based receptors include the integrins αvβ 3, αvβ 5, and β 2 (CD18), RPTP-α/β, GP130, E-cadherin, fibronectin, laminin, CD46, CD74, ICAM1/LFA1, T-cell receptor, Toll-like receptors, and receptor tyrosine kinases EGFR, ErbB2, ErbB3, and c-Met. In addition, H. pylori is able to activate the intracellular receptors NOD1, NOD2, and NLRP3 with important roles in innate immunity. Here we review the interplay of various bacterial factors with host protein receptors. The contribution of these interactions to signal transduction and pathogenesis is discussed.

The association of interleukin-18 promoter polymorphisms and serum levels with duodenal ulcer, and their correlations with bacterial CagA and VacA virulence factors

BACKGROUND

We analyzed the impact of interleukin (IL)-18 promoter polymorphisms on IL-18 serum levels in Helicobacter pylori-infected duodenal ulcer (DU) patients and healthy asymptomatic (AS) carriers. We also aimed to determine the association of the H. pylori virulence factors CagA and VacA antibodies with serum concentrations of IL-18 in order to elucidate any correlation between them.

METHODS

Three groups of patients were enrolled: DU patients (67 individuals), AS carriers (48 individuals), and H. pylori-negative subjects (26 individuals). Serum concentrations of IL-18 were determined by ELISA. Patient sera were tested by Western blot method to determine the presence of serum antibodies to bacterial CagA and VacA. Genotyping of IL-18 promoter polymorphisms at positions - 137G/C and - 607C/A were performed by allele-specific primer PCR protocol.

RESULTS

Our study revealed that serum IL-18 levels are positively influenced by CagA-positive H. pylori strains, so that maximum levels of IL-18 were detected in DU patients with the CagA(+) phenotype, regardless of the presence of the anti-VacA antibody. Regarding IL-18 promoter polymorphisms, the AA genotype and A allele at position - 607C/A were found to be significantly lower in DU patients than in AS carriers and H. pylori-negative subjects (p = 0.032 and 0.043, respectively).

CONCLUSIONS

The IL-18 - 607C variant was associated with higher levels of serum IL-18 and an increased risk of DU. Moreover, our findings indicated that serum concentrations of IL-18 were influenced by CagA factor, irrespective of the VacA status, suggesting that high levels of IL-18 in CagA-positive subjects predisposes to susceptibility to DU.

Life in the human stomach: persistence strategies of the bacterial pathogen Helicobacter pylori

The bacterial pathogen Helicobacter pylori has co-evolved with humans and colonizes approximately 50% of the human population, but only causes overt gastric disease in a subset of infected hosts. In this Review, we discuss the pathogenesis of H. pylori and the mechanisms it uses to promote persistent colonization of the gastric mucosa, with a focus on recent insights into the role of the virulence factors vacuolating cytotoxin (VacA), cytotoxin-associated gene A (CagA) and CagL. We also describe the immunobiology of H. pylori infection and highlight how this bacterium manipulates the innate and adaptive immune systems of the host to promote its own persistence.

Optimising the quantification of cytokines present at low concentrations in small human mucosal tissue samples using Luminex assays

Sensitive measurement of multiple cytokine profiles from small mucosal tissue biopsies, for example human gastric biopsies obtained through an endoscope, is technically challenging. Multiplex methods such as Luminex assays offer an attractive solution but standard protocols are not available for tissue samples. We assessed the utility of three commercial Luminex kits (VersaMAP, Bio-Plex and MILLIPLEX) to measure interleukin-17A (IL-17) and interferon-gamma (IFNγ) concentrations in human gastric biopsies and we optimised preparation of mucosal samples for this application. First, we assessed the technical performance, limits of sensitivity and linear dynamic ranges for each kit. Next we spiked human gastric biopsies with recombinant IL-17 and IFNγ at a range of concentrations (1.5 to 1000 pg/mL) and assessed kit accuracy for spiked cytokine recovery and intra-assay precision. We also evaluated the impact of different tissue processing methods and extraction buffers on our results. Finally we assessed recovery of endogenous cytokines in unspiked samples. In terms of sensitivity, all of the kits performed well within the manufacturers' recommended standard curve ranges but the MILLIPLEX kit provided most consistent sensitivity for low cytokine concentrations. In the spiking experiments, the MILLIPLEX kit performed most consistently over the widest range of concentrations. For tissue processing, manual disruption provided significantly improved cytokine recovery over automated methods. Our selected kit and optimised protocol were further validated by measurement of relative cytokine levels in inflamed and uninflamed gastric mucosa using Luminex and real-time polymerase chain reaction. In summary, with proper optimisation Luminex kits (and for IL-17 and IFNγ the MILLIPLEX kit in particular) can be used for the sensitive detection of cytokines in mucosal biopsies. Our results should help other researchers seeking to quantify multiple low concentration cytokines in small tissue samples.

Relationship between Helicobacter pylori infection and serum interleukin-18 in patients with carotid atherosclerosis

BACKGROUND

Helicobacter pylori (H. pylori) infection stimulates the production of proinflammatory cytokines associated with the development of atherosclerosis. Levels of circulating interleukin-18 (IL-18) have been positively correlated with carotid intima-media thickness (IMT) and coronary plaque area and have identified IL-18 levels as important predictors of coronary events and cardiovascular mortality. This study aimed to examine the relationship between serum IL-18 and H. pylori-IgG antibody as a sign of H. pylori infection in patients with carotid atherosclerosis.

METHODS

The carotid IMT, traditional atherosclerotic risk factors, levels of serum H. pylori-IgG and IL-18 were measured in 573 health checkup examinees.

RESULTS

Serum IL-18 and H. pylori-IgG levels were significantly increased in subjects with increased IMT in comparison with those with normal IMT. In subjects with increased IMT, serum H. pylori-IgG was positively correlated with serum IL-18 (r = .402, p = .002), and the association was independent of traditional atherosclerotic risk factors (β = 0.310, p < .001).

CONCLUSIONS

In health checkup examinees with increased IMT, serum IL-18 and H. pylori-IgG were independently correlated and were significantly higher than in subjects with normal IMT.

Chemical synthesis of Helicobacter pylori lipopolysaccharide partial structures and their selective proinflammatory responses

Helicobacter pylori is a common cause of gastroduodenal inflammatory diseases such as chronic gastritis and peptic ulcers and also an important factor in gastric carcinogenesis. Recent reports have demonstrated that bacterial inflammatory processes, such as stimulation with H. pylori lipopolysaccharide (LPS), initiate atherosclerosis. To establish the structures responsible for the inflammatory response of H. pylori LPS, we synthesized various kinds of lipid A structures (i.e., triacylated lipid A and Kdo-lipid A compounds), with or without the ethanolamine group at the 1-phosphate moiety, by a new divergent synthetic route. Stereoselective α-glycosylation of Kdo N-phenyltrifluoroacetimidate was achieved by use of microfluidic methods. None of the lipid A and Kdo-lipid A compounds were a strong inducer of IL-1β, IL-6, or IL-8, suggesting that H. pylori LPS is unable to induce acute inflammation. In fact, the lipid A and Kdo-lipid A compounds showed antagonistic activity against cytokine induction by E. coli LPS, except for the lipid A compound with the ethanolamine group, which showed very weak agonistic activity. On the other hand, these H. pylori LPS partial structures showed potent IL-18- and IL-12-inducing activities. IL-18 has been shown to correlate with chronic inflammation, so H. pylori LPS might be implicated in the chronic inflammatory responses induced by H. pylori. These results also indicated that H. pylori LPS can modulate the immune response: NF-κB activation through hTLR4/MD-2 was suppressed, whereas production of IL-18 and IL-12 was promoted.

Protein interaction network related to Helicobacter pylori infection response

AIM

To understand the complex reaction of gastric inflammation induced by Helicobacter pylori (H pylori) in a systematic manner using a protein interaction network.

METHODS

The expression of genes significantly changed on microarray during H pylori infection was scanned from the web literary database and translated into proteins. A network of protein interactions was constructed by searching the primary interactions of selected proteins. The constructed network was mathematically analyzed and its biological function was examined. In addition, the nodes on the network were checked to determine if they had any further functional importance or relation to other proteins by extending them.

RESULTS

The scale-free network showing the relationship between inflammation and carcinogenesis was constructed. Mathematical analysis showed hub and bottleneck proteins, and these proteins were mostly related to immune response. The network contained pathways and proteins related to H pylori infection, such as the JAK-STAT pathway triggered by interleukins. Activation of nuclear factor (NF)-kappaB, TLR4, and other proteins known to function as core proteins of immune response were also found. These immune-related proteins interacted on the network with pathways and proteins related to the cell cycle, cell maintenance and proliferation, and transcription regulators such as BRCA1, FOS, REL, and zinc finger proteins. The extension of nodes showed interactions of the immune proteins with cancer-related proteins. One extended network, the core network, a summarized form of the extended network, and cell pathway model were constructed.

CONCLUSION

Immune-related proteins activated by H pylori infection interact with proto-oncogene proteins. The hub and bottleneck proteins are potential drug targets for gastric inflammation and cancer.

Protein interaction network related to Helicobacter pylori infection response

AIM

To understand the complex reaction of gastric inflammation induced by Helicobacter pylori (H pylori) in a systematic manner using a protein interaction network.

METHODS

The expression of genes significantly changed on microarray during H pylori infection was scanned from the web literary database and translated into proteins. A network of protein interactions was constructed by searching the primary interactions of selected proteins. The constructed network was mathematically analyzed and its biological function was examined. In addition, the nodes on the network were checked to determine if they had any further functional importance or relation to other proteins by extending them.

RESULTS

The scale-free network showing the relationship between inflammation and carcinogenesis was constructed. Mathematical analysis showed hub and bottleneck proteins, and these proteins were mostly related to immune response. The network contained pathways and proteins related to H pylori infection, such as the JAK-STAT pathway triggered by interleukins. Activation of nuclear factor (NF)-kappaB, TLR4, and other proteins known to function as core proteins of immune response were also found. These immune-related proteins interacted on the network with pathways and proteins related to the cell cycle, cell maintenance and proliferation, and transcription regulators such as BRCA1, FOS, REL, and zinc finger proteins. The extension of nodes showed interactions of the immune proteins with cancer-related proteins. One extended network, the core network, a summarized form of the extended network, and cell pathway model were constructed.

CONCLUSION

Immune-related proteins activated by H pylori infection interact with proto-oncogene proteins. The hub and bottleneck proteins are potential drug targets for gastric inflammation and cancer.

Gastric mucosal interleukin-17 and -18 mRNA expression in Helicobacter pylori-induced Mongolian gerbils

Helicobacter pylori infection causes characteristic mucosal infiltration of inflammatory cells, resulting in the development of peptic ulcers and gastric cancer in approximately 10% of cases. Different clinical expressions of the infection may reflect different patterns of cytokine expression. Interleukin (IL)-1ss, tumor necrosis factor (TNF)-alpha, IL-17, and IL-18 have been reported to be involved in H. pylori-induced gastric mucosal inflammation, but the details and relation to different patterns of inflammation remain unclear. Moreover, the proinflammatory virulence factor outer inflammatory protein (OipA) was reported to be associated with gastric mucosal inflammatory cytokine levels. To clarify these findings, Mongolian gerbils were infected for up to 12 months with wild-type H. pylori 7.13 or with isogenic oipA mutants for 3 months, and mucosal cytokines (IL-1ss, IL-17, IL-18, and TNF-alpha) mRNA levels were then assessed using real-time RT-PCR. Antral mucosal IL-1beta and IL-18 mRNA levels peaked 1 month after infection, whereas the peak of TNF-alpha mRNA was at 6-12 months; IL-17 levels peaked at 12 months. The inflammatory cell infiltration and mRNA levels of all cytokines studied were significantly lower in oipA mutants than in wild-type-infected gerbils. Mucosal IL-1ss, IL-17, and TNF-alpha expression, but not that of IL-18, were significantly associated with the grade of inflammatory cell infiltration. The pattern of increased inflammatory cytokines differed relative to the phase of the infection and pattern of inflammation. OipA appears to play a role in IL-1ss, IL-17, and TNF-alpha expression and the resulting inflammation.

Helicobacter pylori infection upregulates interleukin-18 production from gastric epithelial cells

BACKGROUND

Helicobacter pylori infection induces a biased T helper type 1 (Th1) response that produces IFN-gamma and Fas ligand (FasL). Th1 cytokines are associated with apoptosis in the gastric epithelial cells.

AIM

We aimed to define the role of the recently cloned IL-18, a IFN-gamma inducing factor, in gastric mucosal injury induced by H. pylori infection.

METHODS

Twenty-seven gastric ulcer (GU) patients and 20 functional dyspepsia (FD) patients were enrolled in this study. Mucosal biopsy samples were obtained from the gastric antrum and GU site during endoscopy. Samples were used for histological examination, H. pylori culture and in-situ stimulation for 48 h in the presence of 10 microg/ml phytohemagglutinin-P. IL-18, IFN-gamma, and soluble FasL (sFasL) levels in culture supernatants were assayed by the enzyme-linked immunosorbent assay method. IL-18, IL-1beta-converting enzyme (ICE) and caspase-3 were evaluated by western blotting in gastric cancer cell lines (MKN45) cocultured with H. pylori.

RESULTS

All 27 GU patients and ten out of 20 FD patients were found to be H. pylori-positive, whereas ten FD patients were H. pylori-negative. Antral mucosal tissues from H. pylori-positive FD patients contained (P<0.01) higher levels of IL-18, IFN-gamma, and sFasL than those from uninfected FD patients. IL-18, IFN-gamma, and sFasL levels at the ulcer site were significantly (P<0.01) higher than those at distant sites in the antrum. A significant relationship was seen between IL-18 and IFN-gamma levels at the ulcer site (r=0.7, P<0.01). H. pylori eradication led to a significant decrease in the levels of IL-18, IFN-gamma, and sFasL at the ulcer site. Western blotting showed that IL-18, ICE, and caspase-3 were activated in gastric cancer cell lines cocultured with H. pylori.

CONCLUSION

This study suggests that H. pylori infection enhanced mucosal injury by stimulating a Th1 response, which was mediated by IL-18 upregulation as well as activation of ICE and caspase-3.

Levels of interleukin-18 are markedly increased in Helicobacter pylori-infected gastric mucosa among patients with specific IL18 genotypes

BACKGROUND

The cellular immune response in gastric mucosa infected with Helicobacter pylori is proposed to be predominantly of the T helper cell type 1 type.

METHODS

Interleukin (IL)-18, IL-12, and interferon (IFN)-gamma levels were measured in gastric mucosal biopsy specimens by reverse-transcription polymerase chain reaction (PCR) and by enzyme-linked immunosorbent assay; IL18 polymorphisms were determined by PCR.

RESULTS

Biopsy specimens from 128 patients (56 with nonulcer dyspepsia, 28 with gastric ulcers, 28 with duodenal ulcers, and 16 with gastric cancer) were examined; 96 patients had H. pylori infection. IL-18 levels were markedly up-regulated in mucosa infected with H. pylori (P < .001), whereas IL-12 and IFN-gamma levels were independent of H. pylori status. IL-18 levels correlated with IFN-gamma levels only in infected patients (R = 0.31 to R = 0.51). IL-18 levels were the determining factor for monocyte infiltration in H. pylori-infected mucosa (P < .001). H. pylori-infected patients displaying IL18 -607C/C and -137G/G had higher IL-18 levels than did those with other genotypes and were more likely to experience treatment failure.

CONCLUSION

H. pylori infection induces IL-18 in the gastric mucosa. H. pylori-infected patients with IL18 -607C/C and -137G/G have higher IL-18 levels, which causes severe gastric inflammation. IL18 genotype might be a marker for predicting the effects of eradication therapy.

Enhanced gastric IL-18 mRNA expression in Helicobacter pylori-infected children is associated with macrophage infiltration, IL-8, and IL-1 beta mRNA expression

OBJECTIVE

To investigate IL-18 mRNA expression in the gastric mucosa in Helicobacter pylori-infected children and its association with macrophage infiltration, IL-8, and IL-1 beta mRNA expression.

METHODS

From 39 children, blood samples were taken for IL-1 beta gene polymorphism analysis and antral biopsies were obtained for histology (including macrophage immunostaining), culture and semiquantitative analysis of IL-18, IL-8, IL-1 beta, and CD14 mRNA expression by reverse transcription-PCR (RT-PCR). RT-PCR was used for H. pylori ureA and cagA mRNA detection in gastric tissue.

RESULTS

H. pylori-infected patients had significantly higher IL-18, IL-8, and IL-1 beta transcript levels and macrophage numbers in the antral mucosa than H. pylori-negative children. IL-1 beta-511/31 gene polymorphism had no impact on gastric IL-1 beta mRNA levels. IL-18 mRNA expression correlated with mRNA expression of IL-8 and IL-1 beta, and transcript levels of all three cytokines were associated with macrophage infiltration and CD14 mRNA expression in the gastric tissue. Significant correlation was also observed between macrophage numbers and histological parameters of gastritis.

CONCLUSION

These results suggest that interleukin(IL)-18 and macrophages may have an important function in gastric inflammatory response to H. pylori infection in children. IL-18, and possibly CD14 receptor signalling pathway, may be involved in macrophage activation and subsequent IL-8 and IL-1 beta release.

Regulation of IL-18 in Helicobacter pylori infection

The gastric mucosal immune response is thought to be comprised predominantly of the Th1 type; however, there are limited data regarding the role of IL-18 in Helicobacter pylori-induced inflammation. We investigated IL-18 levels in gastric mucosal biopsy specimens as well as in isolated gastric epithelial cells and lamina propria mononuclear cells. We also investigated IL-18 levels in gastric epithelial cells and the monocyte cell line THP-1 cocultured with H. pylori. In both systems, IL-18 levels were markedly enhanced in H. pylori-infected epithelial cells and monocytes. IL-18 levels in H. pylori-infected gastric mucosa were well correlated with the severity of gastric inflammation, confirming that H. pylori-induced IL-18 plays an important role in gastric injury. Virulence factors of H. pylori; the cag pathogenicity island and OipA affected IL-18 induction in different manners. Up-regulation of IL-18 mRNA/protein in epithelial cells was dependent on both virulence factors. Interestingly, up-regulation of IL-18 mRNA in monocytes was independent of both factors, whereas IL-18 protein was OipA dependent-cag pathogenicity island independent, indicating that OipA regulates IL-18 induction in monocytes at the posttranscriptional level. IL-18 levels in the gastric biopsy specimens showed similar patterns to those in lamina propria mononuclear cells with respect to virulence factors, suggesting that submucosal monocytes/macrophages are the main source of IL-18 induced by H. pylori infection. H. pylori appeared to regulate the ERK/JNK-->AP-1 pathway in both cell types. In addition, OipA and its related p38 pathway may be closely involved in IL-18 induction in H. pylori-infected gastric mucosa and may contribute to gastric injury.

Conventional, regulatory, and unconventional T cells in the immunologic response to Helicobacter pylori

Infection by the gastroduodenal pathogen Helicobacter pylori elicits a complex immunologic response in the mucosa involving neutrophils, plasma cells, eosinophils, and lymphocytes, of which T cells are the principal orchestrators of immunity. While so-called classical T cells (e.g. T-helper cells) that are activated by peptide fragments presented on antigen-presenting cells have received much attention in H. pylori infection, there exists a diverse array of other T cell populations that are potentially important for the outcome of the ensuing immune response, some of which have not been extensively studied in H. pylori infection. Pathogen-specific regulatory T cells that control and prevent the development of immunopathology associated with H. pylori infection have been investigated, but these cells can also benefit the bacterium in helping to prolong the chronicity of the infection by suppressing protective immune responses. An overlooked T cell population, the more recently described Th17 cells, may play a role in H. pylori-induced inflammation, due to triggering responses that ultimately lead to the recruitment of polymorphs, including neutrophils. The so-called innate or unconventional T cells, that include two conserved T cell subsets expressing invariant antigen-specific receptors, the CD1d-restricted natural killer T cells which are activated by glycolipids, and the mucosal-associated invariant T cells which play a role in defense against orally acquired pathogens in the intestinal mucosa, have only begun to receive attention. A greater knowledge of the range of T cell responses induced by H. pylori is required for a deeper understanding of the pathogenesis of this bacterium and its ability to perpetuate chronic infection, and could reveal new strategies for therapeutic exploitation.

Helicobacter pylori stimulates a mixed adaptive immune response with a strong T-regulatory component in human gastric mucosa

BACKGROUND

Host factors play an important role in the pathophysiology of Helicobacter pylori infection and development of gastritis and related disease. The established opinion is that the T-cell-mediated immune response to H. pylori infection is of Th1 type. Our earlier immune cell phenotype studies indicate a mixed Th1-Th2 profile of the effector cells. Therefore, an extensive adaptive and regulatory cytokine gene expression profile was conducted by quantitative real-time polymerase chain reaction (qPCR).

MATERIALS AND METHODS

Biopsies from gastric mucosa of 91 patients diagnosed as H. pylori negative, H. pylori positive with gastritis, or H. pylori positive with peptic ulcer were obtained by endoscopy. Gene expressions of nine cytokines and CagA status were measured by qPCR.

RESULTS

All cytokine genes showed higher expression levels in the presence of H. pylori when compared to H. pylori-negative samples (fold increase: IL8: x 11.2; IL12A: x 2.4; TNF-alpha: x 5.2; IFN-gamma: x 4.3; IL4: x 3.6; IL6: x 14.7; and IL10: x 6.7). Patients infected with CagA-positive strains had higher expression of IL1-beta and IL18 compared to patients infected with CagA-negative strains (x 1.6 for IL1-beta and x 2.0 for IL18). Patients with duodenal ulcer had a lower antral Th1/Th2 ratio than other H. pylori-positive patients.

CONCLUSIONS

The cytokine profile of H. pylori-infected gastric mucosa shows a mixed Th1-Th2 profile. Furthermore, a high IL10 expression may indicate that also regulatory T cells play a role in the chronic phase of H. pylori infection.

The neutrophil-activating protein of Helicobacter pylori (HP-NAP) as an immune modulating agent

During evolution microorganisms have developed several immune modulating strategies. The Helicobacter pylori neutrophil-activating protein (HP-NAP) is a virulence factor that attracts and activates neutrophils, and promotes their endothelial adhesion and the production of oxygen radicals and chemokines, including CXCL8, CCL3 and CCL4. HP-NAP, a TLR2 agonist, is an immune modulator able to induce the expression of interleukin-12 (IL-12) and IL-23 by human neutrophils and monocytes. In fact, HP-NAP has the potential to shift antigen-specific T-cell responses from a predominant Th2 to a polarized Th1 cytotoxic phenotype, characterized by high levels of interferon-gamma and tumor necrosis factor-alpha production. Thus, HP-NAP is a key factor driving Th1 inflammation in H. pylori infection and may be a new tool for future therapeutic strategies aimed at redirecting Th2 into Th1 responses, for example in atopy, vaccinology and cancer immunotherapy.

VacA and HP-NAP, Ying and Yang of Helicobacter pylori-associated gastric inflammation

Helicobacter pylori is a Gram-negative bacterium which infects almost half of the population worldwide and represents the major cause of gastroduodenal pathologies, such as duodenal and gastric ulcer, gastric cancer, B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) and autoimmune gastritis. H. pylori colonization is followed by infiltration of the gastric mucosa by polymorphonuclear cells, macrophages and lymphocytes. Two of the major H. pylori virulence factors are the vacuolating cytotoxin (VacA) and the H. pylori neutrophil-activating protein (HP-NAP). VacA has been proposed as a modulator of immune cell function because of its capacity to interfere with antigen presentation and to inhibit T-cell activation. HP-NAP was designated as neutrophil-activating protein because it stimulates high production of oxygen radicals from neutrophils. We have recently demonstrated that HP-NAP is able to recruit leukocytes in vivo and to stimulate either neutrophils or monocytes to release IL-12, a key cytokine for the differentiation of naive Th cells into the Th1 phenotype. Altogether these evidences indicate that both VacA and HP-NAP play a major role in generating and maintaining the gastric inflammatory response associated with the H. pylori infection.

The translation of Helicobacter pylori basic research to patient care

In 1984, Barry Marshall and Robin Warren proposed a role for bacterial infections in the pathogenesis of gastroduodenal disease, which triggered an avalanche of research intended to prove or disprove their theory. The result has been a series of advances that have enhanced our understanding of these diseases and completely modernized the clinical approach to their management. In just over 20 years, many aspects of the immunopathogenesis of these diseases have been dissected at the molecular level, with key pathogenic mechanisms being validated by the identification of genes that are associated with the development of gastric cancer. There has been particular emphasis on understanding the molecular structures associated with Helicobacter pylori and their role in modifying the host responses. Gastric immune and inflammatory responses have emerged as key elements in the pathogenesis of gastritis and epithelial cell damage. This review summarizes important findings emanating from basic research primarily related to the immunopathogenesis of H pylori that have advanced the practice of medicine or our understanding of gastroduodenal disease.

Effect of long-term Helicobacter felis infection in a mouse model of streptozotocin-induced diabetes

BACKGROUND

We previously REPORTED that mice with diabetes and short-term Helicobacter felis infection had an increase in glycated hemoglobin (HbA1c). Here we report the effect of long-term infection.

MATERIALS AND METHODS

Six-week-old C57BL/6 mice were injected with streptozotocin to induce diabetes and started on daily insulin. Following streptozotocin injection, animals were paired according to their HbA1c values and randomized to orally receive either H. felis or culture medium alone. Weight and HbA1c were monitored monthly for 6 months.

RESULTS

Thirty animals corresponding to 15 pairs were included in the study. H. felis-infected diabetic mice developed significantly more gastritis than uninfected animals. Sixteen mice died during the observation period. As compared to uninfected animals, infected mice died more frequently (40% versus 67%, p = .14) and earlier (160 versus 61 days, p = .20); both variables combined showed that H. felis infection significantly decreased the chances of survival during the study period (p = .045). In addition, infected mice showed a trend for higher increase in their HbA1c (0.97 +/- 2.5% versus - 0.22 +/- 3.0%; p = .21) and lower weight gain (2.0 +/- 3.4 g versus 2.9 +/- 2.0 g; p = .15) than uninfected mice.

CONCLUSION

Long-term H. felis infection had a deleterious effect in mice with streptozotocin-induced diabetes resulting in increased mortality. If the same phenomenon occurs in humans this could lead to interventions to improve the long-term outcome of patients with diabetes.

Citocinas en la patogenia de la enfermedad celíaca

Celiac disease is manifested by an enteropathy caused by intolerance to gluten, a family of proteins found in wheat and other cereals. Following intestinal T-cell activation in predisposed individuals, different inflammatory mechanisms are triggered under the control of the cytokine balance including those with a pro-inflammatory Th1 pattern such as IFNgamma, TNFalpha, IL-15 and IL-18; and regulatory cytokines such as TGFbeta and IL-10. These cytokines, besides increasing the intensity of the activation and the number of immune cells within the intestinal mucosa, regulate the activity of epithelial growth factors and metalloproteinases, a group of molecules involved in the maintenance and turnover of the intestinal mucosa structure; in inflammatory conditions, they also induce the intestinal lesion responsible for malabsorption syndrome.

Helicobacter pylori, T cells and cytokines: the "dangerous liaisons"

Helicobacter pylori infection is the major cause of gastroduodenal pathologies, but only a minority of infected patients develop chronic and life threatening diseases, as peptic ulcer, gastric cancer, B-cell lymphoma, or autoimmune gastritis. The type of host immune response against H. pylori is crucial for the outcome of the infection. A predominant H. pylori-specific Th1 response, characterized by high IFN-gamma, TNF-alpha, and IL-12 production associates with peptic ulcer, whereas combined secretion of both Th1 and Th2 cytokines are present in uncomplicated gastritis. Gastric T cells from MALT lymphoma exhibit abnormal help for autologous B-cell proliferation and reduced perforin- and Fas-Fas ligand-mediated killing of B cells. In H. pylori-infected patients with autoimmune gastritis cytolytic T cells infiltrating the gastric mucosa cross-recognize different epitopes of H. pylori proteins and H+K+ ATPase autoantigen. These data suggest that peptic ulcer can be regarded as a Th1-driven immunopathological response to some H. pylori antigens, whereas deregulated and exhaustive H. pylori-induced T cell-dependent B-cell activation can support the onset of low-grade B-cell lymphoma. Alternatively, H. pylori infection may lead in some individuals to gastric autoimmunity via molecular mimicry.

IL-18 Receptor Expression on Epithelial Cells is Upregulated by TNF Alpha

IL-18 is a multifunctional cytokine that augments both innate and acquired immunity and potentiates Th1 and Th2 reactions. We studied the expression of IL-18 receptor (IL-18R) on renal and respiratory epithelial cell lines. Both cell lines upregulated IL-18R mRNA and IL-18R membrane expression in response to TNF alpha and other proinflammatory cytokines. The function of IL-18R was confirmed by induction of IL-8 release from epithelial cells in response to recombinant IL-18. Epithelial cells may represent an important target for IL-18, mainly under inflammatory conditions associated with TNF alpha release.

Helicobacter pylori infection induces interleukin-18 production in gastric epithelial (AGS) cells

Helicobacter pylori colonization of the stomach results in a chronic-active gastritis characterized by mucosal infiltration of both neutrophils and lymphocytes. A T helper lymphocyte (Th1) profile predominates, which promotes the chronic and persistent inflammatory changes in the gastric mucosa in response to this bacterial pathogen. The cytokine interleukin-18 induces production of interferon-gamma by activated T lymphocytes and promotes a Th1 profile. An in vitro model system was utilized to determine the role of interleukin-18 in response to infection of gastric epithelial cells by H. pylori. H. pylori isolates, characterized with respect to cagE and cagA and VacA status, were employed to infect AGS gastric epithelial cells. Interleukin-18 production was determined by immunoassay. Infection of AGS cells with H. pylori resulted in a 1.8-fold increase in interleukin-18 compared to uninfected cells (22.7+/-2.4 vs. 12.7+/-2.2 pg/ml; P < 0.005). This interleukin-18 response was independent of the cagE status of infecting strains (23.3+/-1.9 vs. 26.3+/-3.6 pg/ml; P = NS). Exposure of AGS cells to recombinant interleukin-18 resulted in dose-dependent and time-dependent secretion of interleukin-8 that was maximal following exposure to 100 pg/ml interleukin-18 for 24 hr (292+/-5 pg/ml, versus 102+/-14 pg/ml in unstimulated cells; P < 0.001). Interleukin-8 secretion was inhibited following pretreatment of cells with anti-interleukin-18 antibody and by pharmacological inhibition of the nuclear transcription factor, NF-kappaB. These findings demonstrate that interleukin-18 can enhance host chemokine response to H. pylori infection.

Vaccine-induced immunity against Helicobacter pylori infection is impaired in IL-18-deficient mice

Protective immunity against Helicobacter pylori infection in mice has been associated with a strong Th1 response, involving IL-12 as well as IFN-gamma, but recent studies have also demonstrated prominent eosinophilic infiltration, possibly linked to local Th2 activity in the gastric mucosa. In this study we investigated the role of IL-18, because this cytokine has been found to be a coregulator of Th1 development as well as involved in Th2-type responses with local eotaxin production that could influence gastric eosinophilia and resistance to infection. We found that IL-18(-/-) mice failed to develop protection after oral immunization with H. pylori lysate and cholera toxin adjuvant, indicating an important role of IL-18 in protection. Well-protected C57BL/6 wild-type (WT) mice demonstrated substantial influx of CD4(+) T cells and eosinophilic cells in the gastric mucosa, whereas IL-18(-/-) mice had less gastritis, few CD4(+) T cells, and significantly reduced numbers of eosinophilic cells. T cells in well-protected WT mice produced increased levels of IFN-gamma and IL-18 to recall Ag. By contrast, unprotected IL-18(-/-) mice exhibited significantly reduced gastric IFN-gamma and specific IgG2a Ab levels. Despite differences in gastric eosinophilic cell infiltration, protected WT and unprotected IL-18(-/-) mice had comparable levels of local eotaxin, suggesting that IL-18 influences protection via Th1 development and IFN-gamma production rather than through promoting local production of eotaxin and eosinophilic cell infiltration.