Regulation of RANTES promoter activation in gastric epithelial cells infected with Helicobacter pylori

Interleukin-19 enhances eosinophil infiltration through upregulation of epithelium-derived RANTES expression via the ERK/NF-κB signalling pathway in patients with eosinophilic CRSwNP

BACKGROUD

The recurrence rate of chronic rhinosinusitis with nasal polyps (CRSwNP) is positively correlated with eosinophil infiltration. Increased interleukin (IL)-19 and eosinophil chemokine RANTES levels have been reported in patients with CRSwNP. This study aimed to clarify the role of IL-19 in mediating RANTES expression and eosinophilic infiltration in eosinophilic CRSwNP (Eos CRSwNP).

METHODS

Nasal tissue samples were obtained from patients with CRSwNP and controls. The expression of IL-19, its receptors, ECP, and RANTES in tissues was investigated. Primary human nasal epithelial cells (HNECs) and nasal polyp tissue blocks were cultured, then stimulated by IL-19; ERK phosphorylation, NF-κB pathway activation, RANTES level, eosinophils migration and infiltration were detected using RT-qPCR, ELISA, western blotting, HE, immunohistochemistry, immunofluorescence staining, confocal microscopy, and transwell migration assay.

RESULTS

The expression of IL-19 and its receptors (IL-20R1/IL-20R2), eosinophil cationic protein, and RANTES in nasal tissues from patients with Eos CRSwNP was significantly increased compared to that in non-Eos CRSwNP and control subjects. IL-19 co-localized with RANTES in nasal tissues and significantly elevated RANTES expression in HNECs. IL-19-blocking antibody and siRNA knockdown of IL-20R1 ameliorated the effect of IL-19 on RANTES secretion in HNECs. Moreover, IL-19-induced RANTES upregulation was associated with the activation of the ERK and NF-κB pathways. NF-κB activation was mediated by the ERK pathway in IL-19-treated HNECs, and IL-19 enhanced eosinophil infiltration in nasal polyp tissue blocks.

CONCLUSIONS

Our findings indicate that IL-19 promotes RANTES expression via the ERK/NF-κB pathway in HNECs and is implicated in eosinophil infiltration in patients with Eos CRSwNP.

Immune Biology and Persistence of Helicobacter pylori in Gastric Diseases

Helicobacter pylori is a prevalent pathogen, which affects more than 40% of the global population. It colonizes the human stomach and persists in its host for several decades or even a lifetime, if left untreated. The persistent infection has been linked to various gastric diseases, including gastritis, peptic ulcers, and an increased risk for gastric cancer. H. pylori infection triggers a strong immune response directed against the bacterium associated with the infiltration of innate phagocytotic immune cells and the induction of a Th1/Th17 response. Even though certain immune cells seem to be capable of controlling the infection, the host is unable to eliminate the bacteria as H. pylori has developed remarkable immune evasion strategies. The bacterium avoids its killing through innate recognition mechanisms and manipulates gastric epithelial cells and immune cells to support its persistence. This chapter focuses on the innate and adaptive immune response induced by H. pylori infection, and immune evasion strategies employed by the bacterium to enable persistent infection.

Induction and Regulation of the Innate Immune Response in Helicobacter pylori Infection

Gastric cancer (GC) is the fifth most common cancer and the fourth most common cause of cancer-related death worldwide. The intestinal type of GC progresses from acute to chronic gastritis, multifocal atrophic gastritis, intestinal metaplasia, dysplasia, and carcinoma. Infection of the stomach by Helicobacter pylori, a Gram-negative bacterium that infects approximately 50% of the world's population, is the causal determinant that initiates the gastric inflammation and then disease progression. In this context, the induction of the innate immune response of gastric epithelial cells and myeloid cells by H. pylori effectors plays a critical role in the outcome of the infection. However, only 1% to 3% of infected patients develop gastric adenocarcinoma, emphasizing that other mechanisms regulate the localized non-specific response, including the gastric microbiota and genetic factors. This review summarizes studies describing the factors that induce and regulate the mucosal innate immune response during H. pylori infection.

Helicobacter pylori-induced REDD1 modulates Th17 cell responses that contribute to gastritis

OBJECTIVE

Regulated in development and DNA damage responses-1 (REDD1) is a conserved and ubiquitous protein, which is induced in response to multiple stimuli. However, the regulation, function and clinical relevance of REDD1 in Helicobacter pylori-associated gastritis are presently unknown.

APPROACH

Immunohistochemistry, real-time PCR and Western blot analyses were performed to examine the levels of REDD1 in gastric samples from H. pylori-infected patients and mice. Gastric tissues from Redd1-/- and wildtype (WT, control) mice were examined for inflammation. Gastric epithelial cells (GECs), monocytes and T cells were isolated, stimulated and/or cultured for REDD1 regulation and functional assays.

RESULTS

REDD1 was increased in gastric mucosa of H. pylori-infected patients and mice. H. pylori induced GECs to express REDD1 via the phosphorylated cytotoxin associated gene A (cagA) that activated MAPKp38 pathway to mediate NF-κB directly binding to REDD1 promoter. Human gastric REDD1 increased with the severity of gastritis, and mouse REDD1 from non-marrow chimera-derived cells promoted gastric inflammation that was characterized by the influx of MHCII+ monocytes. Importantly, gastric inflammation, MHCII+ monocyte infiltration, IL-23 and IL-17A were attenuated in Redd1-/- mice. Mechanistically, REDD1 in GECs regulated CXCL1 production, which attracted MHCII+ monocytes migration by CXCL1-CXCR2 axis. Then H. pylori induced MHCII+ monocytes to secrete IL-23, which favored IL-17A-producing CD4+ cell (Th17 cell) polarization, thereby contributing to the development of H. pylori-associated gastritis.

CONCLUSIONS

The present study identifies a novel regulatory network involving REDD1, which collectively exert a pro-inflammatory effect within gastric microenvironment. Efforts to inhibit this REDD1-dependent pathway may prove valuable strategies in treating of H. pylori-associated gastritis.

The important role played by chemokines influence the clinical outcome of Helicobacter pylori infection

The extended infection with Helicobacter pylori (H. pylori), one of the most frequent infectious agents in humans, may cause gastritis, peptic ulcers, gastric mucosa-associated lymphoid tissue (MALT) lymphoma, and gastric cancer. During H. pylori infection, different kinds of inflammatory cells such as dendritic cells, macrophages, neutrophils, mast cells, eosinophils, T cells and B cells are accumulated into the stomach. The interactions between chemokines and their respective receptors recruit particular types of the leukocytes that ultimately determine the nature of immune response and therefore, have a main influence on the consequence of infection. The suitable production of chemokines especially in the early stages of H. pylori infection shapes appropriate immune responses that contribute to the H. pylori elimination. The unbalanced expression of the chemokines can contribute in the induction of inappropriate responses that result in the tissue damage or malignancy. Thus, chemokines and their receptors may be promising potential targets for designing the therapeutic strategies against various types H. pylori-related gastrointestinal disorders. In this review, a comprehensive explanation regarding the roles played by chemokines in H. pylori-mediated peptic ulcer, gastritis and gastric malignancies was provided while presenting the potential utilization of these chemoattractants as therapeutic elements.

DNA methyltransferases and gastric cancer: insight into targeted therapy

Gastric cancer is a major health problem worldwide occupying most frequent causes of cancer-related mortality. In addition to genetic modifications, epigenetic alterations catalyzed by DNA methyltransferases (DNMTs) are a well-characterized epigenetic hallmark in gastric cancer. The reversible nature of epigenetic alterations and central role of DNA methylation in diverse biological processes provides an opportunity for using DNMT inhibitors to enhance the efficacy of chemotherapeutics. In this review, we discussed key factors or mechanisms such as SNPs, infections and genetic modifications that trigger DNMTs level modification in gastric cancer, and their potential roles in cancer progression. Finally, we focused on how inhibitors of the DNMTs can most effectively be used for the treatment of gastric cancer with multidrug resistance.

Lactobacillus paracasei strain 06TCa19 suppresses inflammatory chemokine induced by Helicobacter pylori in human gastric epithelial cells

Helicobacter (H.) pylori infection is an important risk factor for gastric cancer that causes gastric inflammation. Inflammatory chemokines such as interleukin (IL)-8 and regulated on activation normal T cell expressed and secreted (RANTES) are elevated in the gastric mucosa by H. pylori. This study aimed to investigate the effects of Lactobacillus paracasei strain 06TCa19, a probiotic strain, on IL-8 and RANTES expression and production induced by H. pylori using human gastric epithelial cell lines. Strain 06TCa19 was shown to suppress H. pylori-mediated elevation of gene expression related to these chemokines in MKN45 cells. The strain also suppressed the increase in IL-8 and RANTES products induced by H. pylori in AGS cells as well as in MKN45 cells. In MKN45 cells inoculated with H. pylori, strain 06TCa19 was shown to downregulate the activation of NF-κB and p38 MAPK signaling pathways. Additionally, the level of the CagA virulence protein of H. pylori in the MKN45 cells and the number of viable H. pylori adhering to MKN45 cells decreased with the addition of strain 06TCa19. Moreover, the strain 06TCa19 notably increased lactic acid in the supernatant of MKN45 cells. Thus, lactic acid released from strain 06TCa19 might have inhibited the adhesion of H. pylori to MKN45 cells and prevented the insertion of H. pylori CagA into the cells, and elevation of IL-8 and RANTES genes and proteins might be suppressed by downregulating the NF-κB and p38 MAPK pathways. Therefore, use of strain 06TCa19 may prevent H. pylori-associated gastric inflammation.

A Gain-Of-Function Mutation in the Plcg2 Gene Protects Mice from Helicobacter felis-Induced Gastric MALT Lymphoma

Gastric mucosa-associated lymphoid tissue (MALT) lymphomas develop from a chronic Helicobacter infection. Phospholipase C gamma 2 (PLCG2) is important for B-cell survival and proliferation. We used BALB/c mice with a gain-of-function mutation in the Plcg2 gene (Ali5) to analyze its role in the development of gastric MALT lymphoma. Heterozygous BALB/c Plcg2^Ali5/+ and wildtype (WT) mice were infected with Helicobacter felis (H. felis) and observed up to 16 months for development of gastric MALT lymphomas. In contrast to our initial hypothesis, Plcg2^Ali5/+ mice developed MALT lymphomas less frequently than their WT littermates after long-term infection of 16 months. Infected Plcg2^Ali5/+ mice showed downregulation of proinflammatory cytokines and decreased H. felis-specific IgG1 and IgG2a antibody responses. These results suggested a blunted immune response of Plcg2^Ali5/+ mice towards H. felis infection. Intriguingly, Plcg2^Ali5/+ mice harboured higher numbers of CD73 expressing regulatory T cells (Tregs), possibly responsible for impaired immune response towards Helicobacter infection. We suggest that Plcg2^Ali5/+ mice may be protected from developing gastric MALT lymphomas as a result of elevated Treg numbers, reduced response to H. felis and decrease of proinflammatory cytokines.

Helicobacter pylori virulence factors in development of gastric carcinoma

Helicobacter pylori plays a vital role in the pathogenesis of gastric carcinoma. However, only a relatively small proportion of individuals infected with H. pylori develop gastric carcinoma. Differences in the incidence of gastric carcinoma among infected individuals can be explained, at least partly, by the different genotypes of H. pylori virulence factors. Thus far, many virulence factors of H. pylori, such as Cag PAI, VacA, OMPs and DupA, have been reported to be involved in the development of gastric cancer. The risk of developing gastric cancer during H. pylori infection is affected by specific host-microbe interactions that are independent of H. pylori virulence factors. In this review, we discuss virulence factors of H. pylori and their role in the development of gastric carcinoma that will provide further understanding of the biological interactions of H. pylori with the host.

Haemophilus parasuis infection activates chemokine RANTES in PK-15 cells

RANTES is a member of the CC chemokine involved in inflammation and immune response during pathogen infection. In our previous study, Haemophilus parasuis (H. parasuis), which is responsible for the great economic losses in the pig industry worldwide, has been shown to enhance RANTES expression in PK-15 cells. However, the mechanisms behind this biological phenomenon have remained unclear. In this study, we showed that H. parasuis infection significantly upregulated RANTES gene transcription in a time- and dose-dependent manner. Promoter analysis by site-directed mutagenesis indicated that the nuclear factor NF-κB binding site was the most important cis-regulatory element controlling H. parasuis-induced RANTES transcription. Inhibition of NF-κB and JNK activity also significantly reduced H. parasuis-induced RANTES production. In addition, TLRs signaling pathway was found to be involved in H. parasuis induced-RANTES expression. These results represent an important molecular mechanism whereby H. parasuis induced RANTES in the inflammatory response.

Helicobacter pylori virulence and cancer pathogenesis

Helicobacter pylori is human gastric pathogen that causes chronic and progressive gastric mucosal inflammation and is responsible for the gastric inflammation-associated diseases, gastric cancer and peptic ulcer disease. Specific outcomes reflect the interplay between host-, environmental- and bacterial-specific factors. Progress in understanding putative virulence factors in disease pathogenesis has been limited and many false leads have consumed scarce resources. Few in vitro-in vivo correlations or translational applications have proved clinically relevant. Reported virulence factor-related outcomes reflect differences in relative risk of disease rather than specificity for any specific outcome. Studies of individual virulence factor associations have provided conflicting results. Since virulence factors are linked, studies of groups of putative virulence factors are needed to provide clinically useful information. Here, the authors discuss the progress made in understanding the role of H. pylori virulence factors CagA, vacuolating cytotoxin, OipA and DupA in disease pathogenesis and provide suggestions for future studies.

Helicobacter pylori outer membrane vesicle proteins induce human eosinophil degranulation via a β2 Integrin CD11/CD18- and ICAM-1-dependent mechanism

Eosinophil cationic protein (ECP), a cytotoxic protein contained in eosinophils granules, can contribute to various inflammatory responses. Although Helicobacter pylori infection increases infiltration of eosinophils, the mechanisms of eosinophil degranulation by H. pylori infection are largely unknown. The goal of this study was to investigate the role of H. pylori outer membrane vesicles (OMVs) in modulating eosinophil degranulation. We found that eosinophils treated with H. pylori OMVs released significantly more ECP compared with untreated controls. In addition, eosinophils cocultured with OMV-preexposed primary gastric epithelial cells exhibited significantly increased ECP release. Similarly, eosinophils cocultured with culture supernatant (CM) from primary gastric epithelial cells exposed to OMVs (OMV-CM) released significantly higher amounts of ECP compared with eosinophils cocultured with CM from unexposed control cells. Furthermore, OMVs and OMV-CM both induced the upregulation of ICAM-1 on gastric epithelial cells and β2 integrin CD11b on eosinophils. In addition, both transduction of ICAM-1 shRNA into gastric epithelial cells and treatment with neutralizing mAbs to CD18 significantly decreased OMV-mediated or OMV-CM-mediated release of ECP. These results suggest that the eosinophil degranulation response to H. pylori OMVs occurs via a mechanism that is dependent on both β2 integrin CD11/CD18 and ICAM-1.

Outer membrane inflammatory protein A, a new virulence factor involved in the pathogenesis of Helicobacter pylori

Outer membrane proteins (OMPs) represent an important class of proteins that are observed in gram-negative bacteria, mitochondria and chloroplasts. These proteins play diverse biological roles in protein translocation, cell-cell communication and signal transduction. A variety of OMPs have been identified in the gastrointestinal pathogen Helicobacter pylori (H. pylori) since it was first isolated in 1983. Among these proteins, outer membrane inflammatory protein A (OipA), which is encoded by hopH and unique to this pathogen, is a differentially expressed outer membrane protein that has been confirmed to be directly linked to H. pylori colonization, as well as to the pathogenesis of H. pylori and disease outcome. In this review, we will describe the progress of recent studies on OipA, particularly those on the functions and biological significance of this unique protein.

The combination of an oxygen-dependent degradation domain-regulated adenovirus expressing the chemokine RANTES/CCL5 and NK-92 cells exerts enhanced antitumor activity in hepatocellular carcinoma

Oncolytic adenoviruses are modified based on adenovirus serotype 5 (Ad5), which belongs to subgroup C and depends on Coxsackie-adenovirus receptor (CAR) to recognize target cells. However, expression of CAR is generally low or lost in certain tumors including hepatocellular carcinoma (HCC). By contrast, CD46 is highly expressed in various types of malignant tumor cells. Therefore, we constructed an adenovirus vector expressing the human RANTES/CCL5 gene regulated by oxygen-dependent degradation domain (ODD) and analyzed its antitumor effects in vitro and in vivo. The human RANTES/CCL5 gene was fused with ODD by PCR and the recombinant oncolytic adenovirus containing RANTES-ODD, SG511-CCL5-ODD, was constructed by the Gateway system, which infected cells by binding CD46. Viral replication experiments were performed to evaluate the selective replication ability of SG511-CCL5-ODD. RANTES expression was determined by ELISA. The chemotactic test was used to analyze the ability of the expressed RANTES to recruit NK92 cells. The antitumor effects of SG511-CCL5-ODD were examined in HCC xenografts in nude mice. A chimeric oncolytic adenovirus, SG511-CCL5-ODD, was constructed successfully. Cells infected with the recombinant virus were able to express RANTES selectively in different environments controlled by ODD and the expressed RANTES was able to recruit NK92 cells by its chemotactic effect in vitro and improve the anticancer immune response in HCC xenografts in nude mice. The chimeric adenovirus SG511-CCL5-ODD highly expressed the RANTES-ODD fusion gene in the hypoxia of HCC under the control of the ODD and effectively attracted NK92 cells and a high number of immunocytes. These factors had complementary advantages and, in combination, exerted enhanced antitumor efficacy.

Helicobacter pylori-associated regulation of forkhead transcription factors FoxO1/3a in human gastric cells

BACKGROUND

Interaction of Helicobacter pylori with gastric mucosa leads to marked cellular and humoral host immunologic responses. The signaling pathways initiated by bacteria-host interaction that result in perturbations in cell structure and function remain unclear. Forkhead transcription factors of class O (FoxO) are implicated in the regulation of apoptosis, cell survival, and pathogenesis. H. pylori infection of gastric epithelial cells induces phosphoinositide-3 kinase (PI3K)-dependent Akt activation and cell survival signaling. We investigated the role of H. pylori-activated PI3K/Akt in the regulation of FoxO1/3a in gastric cells.

METHODS

Immunoblot, immunoprecipitation, and fluorescence microscopy were used to assess the effect of infection of gastric epithelial cells with wild-type H. pylori and their isogenic cag pathogenicity island (PAI) or oipA mutants on the FoxO1/3a signaling pathways. Interleukin-8 release was determined by enzyme-linked immunosorbent assays.

RESULTS

 H. pylori infection resulted in activation of the PI3K p85 subunit and inactivation of FoxO1 and FoxO3a by their phosphorylation and translocation of from the nucleus to the cytoplasm. Inhibition of PI3K or Akt kinase activity reduced FoxO1/3a phosphorylation. Akt, FoxO1, or FoxO3a siRNA reduced H. pylori-induced interleukin-8 production. Infection with oipA mutants reduced PI3K/Akt activation and inhibited FoxO1/3a phosphorylation, whereas infection with cag PAI mutants reduced PI3K/Akt activity but did not inhibit FoxO1/3a activation.

CONCLUSIONS

FoxO1 and FoxO3a are novel nuclear substrates of H. pylori-induced PI3K/Akt cell survival signaling pathways that partially control interleukin-8 production. OipA-regulated interleukin-8 release through PI3K/Akt is dependent on FoxO1/3a inactivation, whereas cag PAI-mediated interleukin-8 production employs FoxO1/3-independent signaling.

Helicobacter pylori infection of gastrointestinal epithelial cells in vitro induces mesenchymal stem cell migration through an NF-κB-dependent pathway

The role of bone marrow-derived mesenchymal stem cells (MSC) in the physiology of the gastrointestinal tract epithelium is currently not well established. These cells can be recruited in response to inflammation due to epithelial damage, home, and participate in tissue repair. In addition, in the case of tissue repair failure, these cells could transform and be at the origin of carcinomas. However, the chemoattractant molecules responsible for MSC recruitment and migration in response to epithelial damage, and particularly to Helicobacter pylori infection, remain unknown although the role of some chemokines has been suggested. This work aimed to get insight into the mechanisms of mouse MSC migration during in vitro infection of mouse gastrointestinal epithelial cells by H. pylori. Using a cell culture insert system, we showed that infection of gastrointestinal epithelial cells by different H. pylori strains is able to stimulate the migration of MSC. This mechanism involves the secretion by infected epithelial cells of multiple cytokines, with a major role of TNFα, mainly via a Nuclear Factor-kappa B-dependent pathway. This study provides the first evidence of the role of H. pylori infection in MSC migration and paves the way to a better understanding of the role of bone marrow-derived stem cells in gastric pathophysiology and carcinogenesis.

Paxillin is a novel cellular target for converging Helicobacter pylori-induced cellular signaling

Paxillin is involved in the regulation of Helicobacter pylori-mediated gastric epithelial cell motility. We investigated the signaling pathways regulating H. pylori-induced paxillin phosphorylation and the effect of the H. pylori virulence factors cag pathogenicity island (PAI) and outer inflammatory protein (OipA) on actin stress fiber formation, cell phenotype, and IL-8 production. Gastric cell infection with live H. pylori induced site-specific phosphorylation of paxillin tyrosine (Y) 31 and Y118 in a time- and concentration-dependent manner. Activated paxillin localized in the cytoplasm at the tips of H. pylori-induced actin stress fibers. Isogenic oipA mutants significantly reduced paxillin phosphorylation at Y31 and Y118 and reduced actin stress fiber formation. In contrast, cag PAI mutants only inhibited paxillin Y118 phosphorylation. Silencing of epidermal growth factor receptor (EGFR), focal adhesion kinase (FAK), or protein kinase B (Akt) expression by small-interfering RNAs or inhibiting kinase activity of EGFR, Src, or phosphatidylinositol 3-kinase (PI3K) markedly reduced H. pylori-induced paxillin phosphorylation and morphologic alterations. Reduced FAK expression or lack of Src kinase activity suppressed H. pylori-induced IL-8 production. Compared with infection with the wild type, infection with the cag PAI mutant and oipA mutant reduced IL-8 production by nearly 80 and 50%. OipA-induced IL-8 production was FAK- and Src-dependent, although a FAK/Src-independent pathway for IL-8 production also exists, and the cag PAI may be mainly involved in this pathway. We propose paxillin as a novel cellular target for converging H. pylori-induced EGFR, FAK/Src, and PI3K/Akt signaling to regulate cytoskeletal reorganization and IL-8 production in part, thus contributing to the H. pylori-induced diseases.

Host transcription factors in the immediate pro-inflammatory response to the parasitic mite Psoroptes ovis

Background

Sheep scab, caused by infestation with the ectoparasitic mite Psoroptes ovis, results in the rapid development of cutaneous inflammation and leads to the crusted skin lesions characteristic of the disease. We described previously the global host transcriptional response to infestation with P. ovis, elucidating elements of the inflammatory processes which lead to the development of a rapid and profound immune response. However, the mechanisms by which this response is instigated remain unclear. To identify novel methods of intervention a better understanding of the early events involved in triggering the immune response is essential. The objective of this study was to gain a clearer understanding of the mechanisms and signaling pathways involved in the instigation of the immediate pro-inflammatory response.

Results

Through a combination of transcription factor binding site enrichment and pathway analysis we identified key roles for a number of transcription factors in the instigation of cutaneous inflammation. In particular, defined roles were elucidated for the transcription factors NF-kB and AP-1 in the orchestration of the early pro-inflammatory response, with these factors being implicated in the activation of a suite of inflammatory mediators.

Conclusions

Interrogation of the host temporal response to P. ovis infestation has enabled the further identification of the mechanisms underlying the development of the immediate host pro-inflammatory response. This response involves key regulatory roles for the transcription factors NF-kB and AP-1. Pathway analysis demonstrated that the activation of these transcription factors may be triggered following a host LPS-type response, potentially involving TLR4-signalling and also lead to the intriguing possibility that this could be triggered by a P. ovis allergen.

Inhibitory effects of casticin on migration of eosinophil and expression of chemokines and adhesion molecules in A549 lung epithelial cells via NF-κB inactivation

ETHNOPHARMACOLOGICAL RELEVANCE

The fruits of Vitex rotundifolia L. have long been used for the treatment of inflammation of the respiratory tract in East Asia.

AIM

To determine if casticin, one of the constituents of Vitex rotundifolia L., has anti-allergic and anti-inflammatory effects in asthma.

MATERIALS AND METHODS

The in vitro anti-inflammatory activity of casticin was studied in A549 human type II-like epithelial lung cells using an eotaxin inhibition assay. Additionally, its effects on eotaxin, regulated on activation normal T cell expressed and secreted (RANTES), vascular cell adhesion molecule (VCAM)-1, and inter-cellular adhesion molecule (ICAM)-1 expression were investigated by real time-polymerase chain reaction (real time-PCR). The inhibition of nuclear factor κB (NF-κB) activity in the presence of casticin was determined by analyzing confocal microscopy images of fluorescence immunocytochemical analysis while the suppression of inhibitory κB (IκB)-α phosphorylation was studied using Western blot analysis. Finally, the inhibitory effect of casticin on eosinophil migration toward prestimulated A549 cell media was measured using the human eosinophilic leukemia cell line.

RESULTS AND DISCUSSION

Casticin significantly suppressed eotaxin production in cytokine activated A549 lung epithelial cells. Casticin also suppressed the mRNA expression levels of eotaxin, RANTES, VCAM-1, and ICAM-1, which subsequently contributed to the inhibition of eosinophil migration. Furthermore, casticin inhibited IκB-α phosphorylation and nuclear translocation of p65 in A549 cells.

CONCLUSION

Casiticin inhibited the eosinophil migration and activity of chemokines and adhesion molecules involved in the inflammatory process of asthma by suppressing the NF-κB pathway. These results suggest that casticin has the potential for use in the treatment of allergic asthma.

Molecular cloning of the porcine RANTES promoter: functional characterization of dsDNA/dsRNA response elements in PK-15 cells

The chemokine RANTES plays an essential role in inflammation and immune response. In this study, we cloned the nucleotide sequence of the 5'-flanking region of the porcine RANTES (poRANTES) gene and characterized the regulatory elements that activate transcription. Analyses of a series of 5' deletion constructs demonstrated that a 266 bp region (-220/+46) that spanned the potential transcription start site of the poRANTES gene was sufficient to activate transcription in PK-15 cells. Furthermore, our results indicated that dsDNA/dsRNA significantly induced poRANTES promoter activity and expression of mRNA levels in a time- and dose-dependent manner. Promoter deletions and mutagenesis experiments indicated that an interferon-stimulated responsive element (ISRE) was critical for dsDNA/dsRNA-induced poRANTES transcription. In addition, porcine interferon regulatory factor 3 (IRF-3) and IRF-7 play important roles in dsDNA/dsRNA-induced poRANTES expression.

Role of virulence factors and host cell signaling in the recognition of Helicobacter pylori and the generation of immune responses

Helicobacter pylori colonizes a large proportion of the world's population, with infection invariably leading to chronic, lifelong gastritis. While the infection often persists undiagnosed and without causing severe pathology, there are a number of host, bacterial and environmental factors that can influence whether infection provokes a mild inflammatory response or results in significant morbidity. Intriguingly, the most virulent H. pylori strains appear to deliberately induce the epithelial signaling cascades responsible for activating the innate immune system. While the reason for this remains unclear, the resulting adaptive immune responses are largely ineffective in clearing the bacterium once infection has become established and, as a result, inflammation likely causes more damage to the host itself.

Helicobacter pylori: gastric cancer and beyond

Helicobacter pylori is the dominant species of the human gastric microbiome, and colonization causes a persistent inflammatory response. H. pylori-induced gastritis is the strongest singular risk factor for cancers of the stomach; however, only a small proportion of infected individuals develop malignancy. Carcinogenic risk is modified by strain-specific bacterial components, host responses and/or specific host-microbe interactions. Delineation of bacterial and host mediators that augment gastric cancer risk has profound ramifications for both physicians and biomedical researchers as such findings will not only focus the prevention approaches that target H. pylori-infected human populations at increased risk for stomach cancer but will also provide mechanistic insights into inflammatory carcinomas that develop beyond the gastric niche.

Helicobacter pylori: gastric cancer and beyond

Helicobacter pylori is the dominant species of the human gastric microbiome, and colonization causes a persistent inflammatory response. H. pylori-induced gastritis is the strongest singular risk factor for cancers of the stomach; however, only a small proportion of infected individuals develop malignancy. Carcinogenic risk is modified by strain-specific bacterial components, host responses and/or specific host-microbe interactions. Delineation of bacterial and host mediators that augment gastric cancer risk has profound ramifications for both physicians and biomedical researchers as such findings will not only focus the prevention approaches that target H. pylori-infected human populations at increased risk for stomach cancer but will also provide mechanistic insights into inflammatory carcinomas that develop beyond the gastric niche.

A new compound, 1H,8H-pyrano[3,4-c]pyran-1,8-dione, suppresses airway epithelial cell inflammatory responses in a murine model of asthma

Clinical and experimental studies have established eosinophilia as a sign of allergic disorders. Activation of eosinophils in the airways is believed to cause epithelial tissue injury, contraction of airway smooth muscle and increased bronchial responsiveness. As part of the search for new antiasthmatic agents produced by medicinal plants, the effects of 270 standardized medicinal plant extracts on cytokine-activated A549 human lung epithelial cells were evaluated. After several rounds of activity-guided screening, the new natural compound, 1H,8H-Pyrano[3,4-c]pyran-1,8-dione (PPY), was isolated from Vitex rotundifolia L. To elucidate the mechanism by which the anti-asthmatic responses of PPY occurred in vitro, lung epithelial cells (A549 cell) were stimulated with TNF-alpha, IL-4 and IL-1beta to induce the expression of chemokines and adhesion molecules involved in eosinophil chemotaxis. PPY treatments reduced the expression of eotaxin, IL-8, IL-16 and VCAM-1 mRNA significantly. Additionally, PPY reduced eotaxin secretion in a dose-dependent manner and significantly inhibited eosinophil migration toward A549 medium. In addition, PPY treatment suppressed the phosphorylation of p65 and ERK1/2, suggesting that it can inhibit the MAPK/NF-KB pathway. To clarify the anti-inflammatory and antiasthmatic effects of PPY in vivo, we examined the influence of PPY on the development of pulmonary eosinophilic inflammation in a murine model of asthma. To accomplish this, mice were sensitized and challenged with ovalbumin (OVA) and then examined for the following typical asthmatic reactions: an increase in the number of eosinophils in BALF; the presence of Th2 cytokines such as IL-4 and IL-5 in the BALF; the presence of allergen-specific IgE in the serum; and a marked influx of inflammatory cells into the lung. Taken together, our results revealed that PPY exerts profound inhibitory effects on the accumulation of eosinophils into the airways while reducing the levels of IL-4, IL-5, and IL-13 in the BALF. Therefore, these results suggest that PPY may be useful as a new therapeutic drug for the treatment of allergic asthma.

Effects of anthrax lethal toxin on human primary keratinocytes

AIMS

To investigate the effects of anthrax lethal toxin (LeTx) on human primary keratinocytes.

METHODS AND RESULTS

We show here that human primary keratinocytes are resistant to LeTx-triggered cytotoxicity. All but one of the MEKs (mitogen-activated protein kinase kinases) are cleaved within 3 h, and the cleavage of MEKs in keratinocytes leads to their subsequent proteasome-mediated degradation at different rates. Moreover, LeTx reduced the concentration of several cytokines except RANTES in culture.

CONCLUSIONS

Our results indicate that primary keratinocytes are resistant to LeTx cytotoxicity, and MEK cleavage does not correlate with LeTx cytotoxicity. Although LeTx is considered as an anti-inflammatory agent, it upregulates RANTES.

SIGNIFICANCE AND IMPACT OF THE STUDY

According to a current view, the action of LeTx results in downregulation of the inflammatory response, as evidenced by diminished expression of several inflammatory biomarkers. Paradoxically, LeTx has been reported to attract neutrophils to cutaneous infection sites. This paper, which shows that RANTES, a chemoattractant for immune cells, is upregulated after exposure of keratinocytes to LeTx, although a number of other markers of the inflammatory response are downregulated. Our results might explain why the exposure of keratinocytes to LeTx results in the recruitment of neutrophils to cutaneous infection sites, while the expression of several inflammatory biomarkers is diminished.

Helicobacter pylori activate epidermal growth factor receptor- and phosphatidylinositol 3-OH kinase-dependent Akt and glycogen synthase kinase 3beta phosphorylation

The signalling pathways leading to the development of Helicobacter pylori-induced gastric cancer remain poorly understood. We tested the hypothesis that H. pylori infections involve the activation of Akt signalling in human gastric epithelial cancer cells. Immunoblot, immunofluorescence and kinase assays show that H. pylori infection of gastric epithelial cells induced phosphorylation of Akt at Ser 473 and Thr 308. Mutations in the H. pylori virulence factor OipA dramatically reduced phosphorylation of Ser 473, while the cag pathogenicity island mutants predominantly inhibited phosphorylation of Thr 308. As the downstream of Akt activation, H. pylori infection inactivated the inactivation of glycogen synthase kinase 3beta at Ser 9 by its phosphorylation. As the upstream of Akt activation, H. pylori infection activated epidermal growth factor receptor (EGFR) at Tyr 992, phosphatidylinositol 3-OH kinase (PI3K) p85 subunit and PI3K-dependent kinase 1 at Ser 241. Pharmacologic inhibitors of PI3K or mitogen-activated protein kinase kinase (MEK), Akt knock-down and EGFR knock-down showed that H. pylori infection induced the activation of EGFR-->PI3K-->PI3K-dependent kinase 1-->Akt-->extracellular signal-regulated kinase signalling pathways, the inactivation of glycogen synthase kinase 3beta and interleukin-8 production. The combined functions of cag pathogenicity island and OipA were necessary and sufficient for full activation of signalling at each level. We propose activation of these pathways as a novel mechanism for H. pylori-mediated carcinogenesis.

Geographic differences in gastric cancer incidence can be explained by differences between Helicobacter pylori strains

Certain populations with high incidences of Helicobacter pylori infection, such as those in East Asian countries, have high incidences of gastric cancer, while other highly infected populations, such as those in Africa and South Asia, do not. The various rates of gastric cancer associated with different geographic areas can be explained, at least in part, by the differences in the genotypes of H. pylori cagA and vacA. Populations expressing a high incidence of gastric cancer are mostly identical with regions where East Asian type CagA is predominant. In contrast, incidence of gastric cancer is low in Africa, South Asia, and Europe, where strains typically possess Western type CagA. Within East Asia, strains from northern parts, where the incidence of gastric cancer is high, predominantly possess the vacA m1 genotype, whereas the m2 genotype is predominant in southern parts where the gastric cancer incidence is low.

In vitro treatment with killed Helicobacter pylori downregulates the production of RANTES by peripheral blood mononuclear cells

The mechanisms by which Helicobacter pylori colonizes and persists within the gastric mucosa are poorly understood. The gastric immune response observed in vivo during H. pylori infection, is characterized by a polarization of Th1 cell type that seems to be responsible for gastric pathology. The purpose of this study was to test the direct effect of H. pylori cagA(+)/vacA(+ )(live and/or gentamicin-killed) on human peripheral blood mononuclear cells (PBMCs) in order to evaluate the production of regulated activation normal T cell expressed and secreted (RANTES) in vitro. We also evaluated the possible relationship between RANTES release and the presence of IL-12 and IFN-gamma in supernatants of the same cells. In the present study, we show for the first time that the low amount of RANTES in supernatants of PBMC incubated with killed H. pylori is linked, at least in part, to the inhibition of IL-12 and IFN-gamma 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.

Regulation of gastric carcinogenesis by Helicobacter pylori virulence factors

Helicobacter pylori is the strongest known risk factor for gastric adenocarcinoma, and strains that possess the cag secretion system, which translocates the bacterial effector CagA into host cells, augment cancer risk. H. pylori strains that express the vacuolating cytotoxin or the outer membrane protein OipA are similarly associated with severe pathologic outcomes. We previously reported that an in vivo adapted H. pylori strain, 7.13, induces gastric adenocarcinoma in rodent models of gastritis. In the current study, we used carcinogenic strain 7.13 as a prototype to define the role of virulence constituents in H. pylori-mediated carcinogenesis. Mongolian gerbils were infected with wild-type strain 7.13 or cagA(-), vacA(-), or oipA(-) mutants for 12 to 52 weeks. All infected gerbils developed gastritis; however, inflammation was significantly attenuated in animals infected with the cagA(-) but not the vacA(-) or oipA(-) strains. Gastric dysplasia and cancer developed in >50% of gerbils infected with either the wild-type or vacA(-) strain but in none of the animals infected with the cagA(-) strain. Inactivation of oipA decreased beta-catenin nuclear localization in vitro and reduced the incidence of cancer in gerbils. OipA expression was detected significantly more frequently among H. pylori strains isolated from human subjects with gastric cancer precursor lesions versus persons with gastritis alone. These results indicate that loss of CagA prevents the development of cancer in this model. Inactivation of oipA attenuates beta-catenin nuclear translocation and also decreases the incidence of carcinoma. In addition to defining factors that mediate H. pylori-induced cancer, these results provide insight into mechanisms that may regulate the development of other malignancies arising within the context of inflammatory states.

Quantitative analysis of the effect of Helicobacter pylori on the expressions of SOX2, CDX2, MUC2, MUC5AC, MUC6, TFF1, TFF2, and TFF3 mRNAs in human gastric carcinoma cells

OBJECTIVE

To investigate the phenotypic characters of carcinoma cells and the response of gastric epithelial cells to Helicobacter pylori (H. pylori) infection using the gastric carcinoma cell lines.

MATERIAL AND METHODS

Real-time reverse transcription-polymerase chain reaction (RT-PCR) was used to assess the effect of H. pylori infection on mRNA levels of transcription factors (SOX2 and CDX2), mucin core proteins (MUC2, MUC5AC, and MUC6), and trefoil factor family peptides (TFF) (TFF1, TFF2, and TFF3) in gastric carcinoma cells (AGS, MKN45, and KATO III cells). H. pylori ATCC 43504 and its isogenic cag pathogenicity island (PAI) deleted mutant were used.

RESULTS

These cell lines expressed mixed gastric and intestinal phenotypes. The intestinal phenotype predominated in AGS cells and gastric phenotypes in MKN45 and KATO III cells. In all three cell lines, H. pylori infection inhibited SOX2 mRNA expression, but induced the three TFFs mRNAs. In AGS cells, H. pylori induced cag PAI-dependent mRNA expression of CDX2, MUC2, MUC5AC, and MUC6. mRNA expressions of CDX2, MUC5AC, and MUC6 were inhibited in KATO III cells, whereas MUC2 mRNA expression was unchanged. In MKN45 cells, H. pylori induced the three MUCs mRNAs but inhibited CDX2 mRNA expression.

CONCLUSIONS

This study provides a useful platform for selecting appropriate cell lines to model H. pylori-related changes in the gastric epithelium that mirror the changes seen in vivo. The outcome of H. pylori infection may reflect changes in the mucus gel layer caused by altered expression of mucins and TFF peptides.

OipA plays a role in Helicobacter pylori-induced focal adhesion kinase activation and cytoskeletal re-organization

The initial signalling events leading to Helicobacter pylori infection associated changes in motility, cytoskeletal reorganization and elongation of gastric epithelial cells remain poorly understood. Because focal adhesion kinase (FAK) is known to play important roles in regulating actin cytoskeletal organization and cell motility we examined the effect of H. pylori in gastric epithelial cells co-cultured with H. pylori or its isogenic cag pathogenicity island (PAI) or oipA mutants. H. pylori induced FAK phosphorylation at distinct tyrosine residues in a dose- and time-dependent manner. Autophosphorylation of FAK Y397 was followed by phosphorylation of Src Y418 and resulted in phosphorylation of the five remaining FAK tyrosine sites. Phosphorylated FAK and Src activated Erk and induced actin stress fibre formation. FAK knock-down by FAK-siRNA inhibited H. pylori-mediated Erk phosphorylation and abolished stress fibre formation. Infection with oipA mutants reduced phosphorylation of Y397, Y576, Y577, Y861 and Y925, inhibited stress fibre formation and altered cell morphology. cag PAI mutants reduced phosphorylation of only FAK Y407 and had less effect on stress fibre formation than oipA mutants. We propose that activation of FAK and Src are responsible for H. pylori-induced induction of signalling pathways resulting in the changes in cell phenotype important for pathogenesis.

Helicobacter pylori environmental interactions: effect of acidic conditions on H. pylori-induced gastric mucosal interleukin-8 production

To explore the interactions between the host, environment and bacterium responsible for the different manifestations of Helicobacter pylori infection, we examined the effect of acidic conditions on H. pylori-induced interleukin (IL)-8 expression. AGS gastric epithelial cells were exposed to acidic pH and infected with H. pylori[wild-type strain, its isogenic cag pathogenicity island (PAI) mutant or its oipA mutant]. Exposure of AGS cells to acidic pH alone did not enhance IL-8 production. However, following exposure to acidic conditions, H. pylori infection resulted in marked enhancement of IL-8 production which was independent of the presence of the cag PAI and OipA, indicating that H. pylori and acidic conditions act synergistically to induce gastric mucosal IL-8 production. In neutral pH environments H. pylori-induced IL-8 induction involved the NF-kappaB pathways, the extracellular signal-regulated kinase (ERK)-->c-Fos/c-Jun-->activating protein (AP-1) pathways, JNK-->c-Jun-->AP-1 pathways and the p38 pathways. At acidic pH H. pylori-induced augmentation of IL-8 production involved markedly upregulated the NF-kappaB pathways and the ERK-->c-Fos-->AP-1 pathways. In contrast, activation of the JNK-->c-Jun-->AP-1 pathways and p38 pathways were pH independent. These results might explain the clinical studies in which patients with duodenal ulcers had higher levels of IL-8 in the antral gastric mucosa than patients with simple H. pylori gastritis.

The use of human cell line reporter gene-based assays in chemical toxicity testing

Genetically modified rodents allow greater sensitivity in monitoring DNA damage or gene expression than traditional rodent bioassays and have become increasingly used for toxicity testing, particularly with the greater availability of protein and DNA-based toxicity biomarkers. Here, the advantages and limitations of several in vitro reporter assays already used to study the mechanisms of toxicity are discussed in relation to the in vivo traditional and reporter-based bioassays for carcinogenicity, mutagenicity, endocrine changes and inflammation endpoints to examine the scope for refining and replacing transgenic in vivo models.

Genetic polymorphisms of NOD1 and IL-8, but not polymorphisms of TLR4 genes, are associated with Helicobacter pylori-induced duodenal ulcer and gastritis

BACKGROUND

Intracellular pathogen receptor NOD1 is involved in the epithelial cell sensing Helicobacter pylori, which results in a considerable interleukin (IL)-8 production. The aim of this study was to evaluate the relationship between NOD1 and IL-8 genetic polymorphisms and the development of H. pylori-induced gastritis and duodenal ulcer (DU), as compared with TLR4 polymorphisms.

MATERIALS AND METHODS

Eighty-five patients with DU and 135 patients with gastritis were enrolled in the study. Seventy-five serologically H. pylori-positive subjects without gastric or duodenal symptoms served as controls. The G796A (E266K) NOD1 polymorphism was determined by restriction fragment length polymorphism, and the -251 IL-8 polymorphism by amplification refractory mutation system method. The TLR4 (ASP/299/Gly and Thr/399/Ile) gene polymorphisms were examined by melting point analysis.

RESULTS

AA homozygote mutant variants of NOD1 were detected in 20% of the H. pylori-positive patients with DU versus 7% of H. pylori-positive patients with gastritis and versus 6% of the H. pylori-positive healthy controls. The IL-8 heterozygote mutant variant was detected with a significantly higher frequency among the DU patients and those with gastritis than among the H. pylori-positive controls. However, no significant correlation concerning the frequency of the TLR4 gene polymorphism could be revealed between any group of patients and the controls.

CONCLUSION

E266K CARD4/NOD1, but not the TLR4 gene polymorphism increases the risk of peptic ulceration in H. pylori-positive patients. The -251 IL-8 polymorphism was significantly associated with either gastritis or DU in H. pylori-infected subjects. Host factors including intracellular pathogen receptors and IL-8 production play an important role in H. pylori-induced gastric mucosal damage.

Pattern of transcription factor activation in Helicobacter pylori-infected Mongolian gerbils

BACKGROUND AND AIMS

Helicobacter pylori interact with epithelial cells resulting in activation of cellular signaling pathways leading to an inflammatory response. The pattern and timing of transcription factor activation in H pylori-infected gastric mucosa remain unclear. We investigated the roles of transcription factors in the gastric mucosa of H pylori-infected gerbils over the course of the infection.

METHODS

Six-week-old male Mongolian gerbils were inoculated orally with H pylori TN2GF4 or isogenic cagE mutants and examined at 1, 3, 9, and 18 months. We examined the expression of 54 transcription factors using DNA/protein arrays and electrophoretic mobility shift assays. Phosphorylation status of mitogen-activated protein kinases and IkappaB were evaluated by immunoblot and immunohistochemistry.

RESULTS

Ten transcription factors were up-regulated by H pylori infection. Six of these factors, including activator protein-1 (AP-1) and cAMP responsive element binding protein (CREB), reached maximal levels at 3 months and were strongly correlated with cellular inflammation and ulceration. Phosphorylation of extracellular signal-regulated kinase correlated with activation of AP-1 and CREB. Levels of nuclear factor-kappaB and interferon-stimulated responsive element (ISRE) peaked at 18 months and correlated with the presence of severe atrophy and with phosphorylation of Jun-N-terminal kinase (JNK), p38, and IkappaB.

CONCLUSIONS

The gastric mucosal transcription factors induced by H pylori infection differed according to the phase and outcome of infection; AP-1 and CREB levels were early responders related to inflammation and ulceration, whereas NF-kappaB and ISRE were late responders related to atrophy.

Functional and intracellular signaling differences associated with the Helicobacter pylori AlpAB adhesin from Western and East Asian strains

Following adhesion of Helicobacter pylori to gastric epithelial cells, intracellular signaling leads to cytokine production, which causes H. pylori-related gastric injury. Two adjacent homologous genes (alpA and alpB), which encode H. pylori outer membrane proteins, are thought to be associated with adhesion and cytokine induction. We co-cultured gastric epithelial cells with wild type H. pylori strains and their corresponding alpA/alpB-deleted mutants (DeltaalpAB). Results were confirmed by complementation. Flow cytometry confirmed that AlpAB was involved in cellular adhesion. Deletion of alpAB reduced interleukin (IL)-6 induction in gastric epithelial cells. Deletion of alpAB reduced IL-8 induction with East Asian but not with Western strains. All AlpAB-positive strains tested activated the extracellular signal-regulated kinase, c-Fos, and cAMP-responsive element-binding protein. Activation of the Jun-N-terminal kinase, c-Jun, and NF-kappaB was exclusive to AlpAB from East Asian strains. DeltaalpAB mutants poorly colonized the stomachs of C57BL/6 mice and were associated with lower mucosal levels of KC and IL-6. Our results suggest that AlpAB may induce gastric injury by mediating adherence to gastric epithelial cells and by modulating proinflammatory intracellular signaling cascades. Known geographical differences in H. pylori-related clinical outcomes may relate to differential effects of East Asian and Western types of AlpAB on NF-kappaB-related proinflammatory signaling pathways.

The inflammatory and immune response to Helicobacter pylori infection

Lifelong Helicobacter pylori infection and its associated gastric inflammation underlie peptic ulceration and gastric carcinogenesis. The immune and inflammatory responses to H. pylori are doubly responsible: gastric inflammation is the main mediator of pathology, and the immune and inflammatory response is ineffective, allowing lifelong bacterial persistence. However, despite inducing gastric inflammation, most infections do not cause disease, and bacterial, host and environmental factors determine individual disease risk. Although H. pylori avoids many innate immune receptors, specific virulence factors (including those encoded on the cag pathogenicity island) stimulate innate immunity to increase gastric inflammation and increase disease risk. An acquired T helper 1 response upregulates local immune effectors. The extent to which environmental factors (including parasite infection), host factors and H. pylori itself influence T-helper differentiation and regulatory T-cell responses remains controversial. Finally, effective vaccines have still not been developed: a better understanding of the immune response to H. pylori may help.

Balance between polyoma enhancing activator 3 and activator protein 1 regulates Helicobacter pylori-stimulated matrix metalloproteinase 1 expression

Helicobacter pylori infection and elevated expression of tissue matrix metalloproteinase 1 (MMP-1) are both associated with gastric cancer. We investigated the regulation of MMP-1 expression during H. pylori infection. Real-time reverse transcription-PCR was used to examine mucosal MMP-1 mRNA levels in 55 patients with gastric cancers and 61 control patients. Increased MMP-1 mRNA levels in the gastric mucosa and epithelial cells were observed in H. pylori infections in which both the cag pathogenicity island (PAI) and outer inflammatory protein A (OipA) were expressed. The combined induction of c-fos, c-jun, and polyoma enhancing activator-3 (pea-3) by H. pylori caused maximal increase in MMP-1 expression. Activation of the MMP-1 promoter by H. pylori involved occupation of the activator protein 1 (AP-1) sites at -72 and -181 and, surprisingly, vacancy of the -88 PEA-3 site. Electrophoretic mobility shift, supershift, and chromatin immunoprecipitation assays showed increased binding of c-Fos and c-Jun to the -72 and -181 AP-1 sites during H. pylori infection. Importantly, during wild-type H. pylori infection, we detected increased PEA-3 binding to the -72AP-1 site and decreased PEA-3 binding to the -88 PEA-3 site. However, during infection with the cag PAI and oipA mutants, PEA-3 binding to the -88 site was detected. MMP-1 and pea-3 activities are increased in gastric cancers. Maximal activation of MMP-1 transcription requires the cag PAI and OipA, which regulate AP-1 and PEA-3 binding. Thus, cag PAI and OipA provide a possible link between bacterial virulence factors and important host factors related to disease pathogenesis.

Interferon Regulatory Factor 8 Regulates RANTES Gene Transcription in Cooperation with Interferon Regulatory Factor-1, NF-κB, and PU.1

Interferon regulatory factor (IRF)-8 is a member of the IRF family of transcription factors important in interferon-gamma-mediated signaling and in the development and function of dendritic cells. Regulated on activation, normal T cell expressed and secreted (RANTES, or CCL5) is a member of the CC chemokine family of proteins, strongly chemoattractant for several important immune cell types in host defense against infectious agents and cancer. Here we report that RANTES expression in IRF-8-null macrophages stimulated with interferon-gamma and lipopolysaccharide is markedly decreased. IRF-8 can activate RANTES gene transcription in synergism with IRF-1. Interestingly, IRF-8 can activate RANTES transcription independently of IRF-1 through direct physical interactions with NF-kappaB c-Rel and PU.1 via the NF-kappaB element located at -88 to -79 in vitro and in vivo. This study uncovers a novel role of IRF-8 in the regulation of RANTES gene expression and the underlying molecular mechanisms whereby IRF-8 interacts with several other important transcription factors to initiate innate immune responses to pathogenic and inflammatory challenges by activating the RANTES gene.