Gene expression profiling in AGS cells stimulated with Helicobacter pylori isogenic strains (cagA positive or cagA negative)

Proteomic and transcriptomic studies of BGC823 cells stimulated with Helicobacter pylori isolates from gastric MALT lymphoma

BACKGROUND

The correlation between the infection of H. pylori and the occurrence of gastric MALT lymphoma (GML) has been well documented. However, the mechanism of how GML is caused by this bacterium is not well understood, although some immunologic mechanisms are thought to be involved.

MATERIALS AND METHODS

In this study, we performed both transcriptomic and proteomic analyses on gastric cancer cells infected by H. pylori isolates from GML patients and the gastric ulcer strain 26695 to investigate the differentially expressed molecular signatures that were induced by GML isolates.

RESULTS

Transcriptomic analyses revealed that the differentially expressed genes (DEGs) were mainly related to binding, catalytic activity, signal transducer activity, molecular transducer activity, nucleic acid binding transcription factor activity, and molecular function regulator. Fifteen pathways, including the Wnt signaling pathway, the mTOR signaling pathway, the NOD-like receptor signaling pathway and the Hippo signaling pathway, were revealed to be related to GML isolates. Proteomic analyses results showed that there were 116 differentially expressed proteins (DEPs). Most of these DEPs were associated with cancer, and 29 have been used as biomarkers for cancer diagnosis. We also found 63 upstream regulators that can inhibit or activate the expression of the DEPs. Combining the proteomic and transcriptomic analyses revealed 12 common pathways. This study provides novel insights into H. pylori-associated GML. The DEPs we found may be good candidates for GML diagnosis and treatment.

CONCLUSIONS

This study revealed specific pathways related to GML and potential biomarkers for GML diagnosis.

Distinct transcriptome signatures of Helicobacter suis and Helicobacter heilmannii strains upon adherence to human gastric epithelial cells

The porcine Helicobacter suis and canine-feline H. heilmannii are gastric Helicobacter species with zoonotic potential. However, little is known about the pathogenesis of human infections with these Helicobacter species. To gain more insight into the interactions of both zoonotic Helicobacter species with human gastric epithelial cells, we investigated bacterial genes that are differentially expressed in a H. suis and H. heilmannii strain after adhesion to the human gastric epithelial cell line MKN7. In vitro Helicobacter-MKN7 binding assays were performed to obtain bacterial RNA for sequencing analysis. H. suis and H. heilmannii bacteria attached to the gastric epithelial cells (i.e. cases) as well as unbound bacteria (i.e. controls) were isolated, after which prokaryotic RNA was purified and sequenced. Differentially expressed genes were identified using the DESeq2 package and SARTools pipeline in R. A list of 134 (83 up-regulated and 51 down-regulated) and 143 (60 up-regulated and 83 down-regulated) differentially expressed genes (p_adj ≤ 0.01; fold change ≥ 2) were identified for the adherent H. suis and H. heilmannii strains, respectively. According to BLASTp analyses, only 2 genes were commonly up-regulated and 4 genes commonly down-regulated in both pathogens. Differentially expressed genes of the H. suis and H. heilmannii strains belonged to multiple functional classes, indicating that adhesion of both strains to human gastric epithelial cells evokes pleiotropic adaptive responses. Our results suggest that distinct pathways are involved in human gastric colonization of H. suis and H. heilmannii. Further research is needed to elucidate the clinical significance of these findings.

Association of Helicobacter pylori with colorectal cancer development

Background: Helicobacter pylori (H. pylori) may be associated with colorectal cancer. However, the underlying mechanisms are still unclear. Objectives: Explore the serostatus of H. pylori cytotoxicity-associated gene A product (CagA) in patients with colorectal carcinoma, and assess the association of H. pylori with colorectal cancer via c-Myc and MUC-2 proteins at tumor tissues. Methods: H. pylori CagA IgG antibodies were screened using enzyme-linked immunosorbent assay (ELISA) in 30 patients with colorectal carcinoma and 30 cancer-free control subjects. Paraffin-embedded blocks were examined for the expression of c-Myc and MUC-2 protein by immunohistochemistry. Results: H. pylori CagA seropositivity increased significantly among colorectal cancer patients (p <0.05). The expression of c-Myc and MUC-2 in colorectal carcinoma patients was over-expressed (80%), and downexpressed (63%) in resection margins (p <0.05). c-Myc over-expression and MUC-2 down-expression were associated with CagA-positive rather than CagA-negative H. pylori patients. In 16 CagA seropositive vs. 14 CagA seronegative patients, the expression rate was 97.3% vs. 64.2% and 33.3% vs. 78.5% for cMyc and MUC-2, respectively. CagA IgG level was significantly higher in positive than in negative c-Myc patients (p= 0.036), and in negative than in positive MUC-2 patients (p= 0.044). c-Myc and MUC-2 were positively and inversely correlated with CagA IgG level (p <0.05). Conclusions: CagA-seropositive H. pylori is most probably associated with colorectal cancer development. Part of the underlying mechanism for such association might be via alterations in expression of MUC-2, which depletes the mucous protective layer in the colo-rectum, and c-Myc, which stimulates the growth of cancerous cells.

How Can Elispot Add Information to Improve Knowledge on Tropical Diseases?

Elispot has been used as an important tool for detecting immune cells' products and functions and has facilitated the understanding of host-pathogen interaction. Despite the incredible diversity of possibilities, two main approaches have been developed: the immunopathogenesis and diagnosis/prognosis of infectious diseases as well as cancer research. Much has been described on the topics of allergy, autoimmune diseases, and HIV-Aids, however, Elispot can also be applied to other infectious diseases, mainly leishmaniasis, malaria, some viruses, helminths and mycosis usually classified as tropical diseases. The comprehension of the function, concentration and diversity of the immune response in the infectious disease is pointed out as crucial to the development of infection or disease in humans and animals. In this review we will describe the knowledge already obtained using Elispot as a method for accessing the profile of immune response as well as the recent advances in information about host-pathogen interaction in order to better understand the clinical outcome of a group of tropical and neglected diseases.

Helicobacter pylori modulates host cell survival regulation through the serine-threonine kinase, 3-phosphoinositide dependent kinase 1 (PDK-1)

BACKGROUND

Helicobacter pylori (H. pylori) infection affects cell survival signaling pathways including cell apoptosis and proliferation, which are considered risk factors for the development of gastric cancer when unregulated. In the present study, we investigated the effect of H. pylori infection on the phosphorylation state of 3-phosphoinositide-dependent kinase-1 (PDK-1), a master kinase that regulates phosphorylation of Akt (also known as protein kinase B, PKB) and cell survival.

METHODS

The activity of PDK-1 was examined in human gastric epithelial cells incubated in the presence or absence of different H. pylori strains. In addition, the role of H. pylori type IV secretion system and the mechanism of H. pylori effect on PDK-1 activity was examined.

RESULTS

In the presence of H. pylori, phosphorylation of the activation loop (serine 241) PDK-1 was rapidly lost suggesting that dephosphorylation of PDK-1 is a target for H. pylori to modulate cell survival. The extent of dephosphorylation was strain dependent with H. pylori 60190 being the most effective. H. pylori infection of gastric epithelial cells resulted in altered phosphorylation and degradation of Akt, suggesting that PDK-1 dephosphorylation affects cell survival pathways and thereby may contribute to disease pathogenesis.

CONCLUSION

We propose that dephosphorylation of PDK-1 and the resulting changes to Akt phosphorylation is one of the mechanisms by which infection with H. pylori alter the balance between apoptosis and cell proliferation and identify a host molecular mechanism regulated by H. pylori that ultimately contributes to carcinogenesis. Our studies therefore provide insights into one of the mechanisms by which H. pylori infection contributes to gastric cancer by regulating the activity of a cell survival signaling pathway.

The Helicobacter pylori autotransporter ImaA (HP0289) modulates the immune response and contributes to host colonization

The human pathogen Helicobacter pylori employs a diverse collection of outer membrane proteins to colonize, persist, and drive disease within the acidic gastric environment. In this study, we sought to elucidate the function of the host-induced gene HP0289, which encodes an uncharacterized outer membrane protein. We first generated an isogenic H. pylori mutant that lacks HP0289 and found that the mutant has a colonization defect in single-strain infections and is greatly outcompeted in mouse coinfection experiments with wild-type H. pylori. Furthermore, we used protease assays and biochemical fractionation coupled with an HP0289-targeted peptide antibody to verify that the HP0289 protein resides in the outer membrane. Our previous findings showed that the HP0289 promoter is upregulated in the mouse stomach, and here we demonstrate that HP0289 expression is induced under acidic conditions in an ArsRS-dependent manner. Finally, we have shown that the HP0289 mutant induces greater expression of the chemokine interleukin-8 (IL-8) and the cytokine tumor necrosis factor alpha (TNF-α) in gastric carcinoma cells (AGS). Similarly, transcription of the IL-8 homolog keratinocyte-derived chemokine (KC) is elevated in murine infections with the HP0289 mutant than in murine infections with wild-type H. pylori. On the basis of this phenotype, we renamed HP0289 ImaA for immunomodulatory autotransporter protein. Our work has revealed that genes induced in vivo play an important role in H. pylori pathogenesis. Specifically, the outer membrane protein ImaA modulates a component of the host inflammatory response, and thus may allow H. pylori to fine tune the host immune response based on ImaA expression.

Deletion and down-regulation of HRH4 gene in gastric carcinomas: a potential correlation with tumor progression

BACKGROUND

Histamine is an established growth factor for gastrointestinal malignancies. The effect of histamine is largely determined locally by the histamine receptor expression pattern. Histamine receptor H4 (HRH4), the newest member of the histamine receptor family, is positively expressed on the epithelium of the gastrointestinal tract, and its function remains to be elucidated. Previously, we reported the decreased expression of HRH4 in colorectal cancers and revealed its correlation with tumor proliferation. In the current study, we aimed to investigate the abnormalities of HRH4 gene in gastric carcinomas (GCs).

METHODOLOGY/PRINCIPAL FINDINGS

We analyzed H4R expression in collected GC samples by quantitative PCR, Western blot analysis, and immunostaining. Our results showed that the protein and mRNA levels of HRH4 were reduced in some GC samples, especially in advanced GC samples. Copy number decrease of HRH4 gene was observed (17.6%, 23 out of 131), which was closely correlated with the attenuated expression of H4R. In vitro studies, using gastric cancer cell lines, showed that the alteration of HRH4 expression on gastric cancer cells influences tumor growth upon exposure to histamine.

CONCLUSIONS/SIGNIFICANCE

We show for the first time that deletion of HRH4 gene is present in GC cases and is closely correlated with attenuated gene expression. Down-regulation of HRH4 in gastric carcinomas plays a role in histamine-mediated growth control of GC cells.

Rosiglitazone inhibits cell invasion and metastasis in human gastric cancer cell lines SGC7901 and SGC7901/VCR

AIM: To investigate the effect of rosiglitazone (ROS) on cell invasion and metastasis in human gastric cancer cell lines SGC7901 and SGC7901/VCR and to explore possible mechanisms involved.

METHODS: Wound healing assay and in vitro invasion assay were used to investigate the antimetastatic activities of ROS in SGC7901 and SGC7901/VCR cells. After treating SGC7901 and SGC7901/VCR cells with ROS (40 μmol/L) for 24 h, the mRNA levels of LIMK1 and cofilin-1 were assessed by reverse transcription-polymerase chain reaction (RT-PCR), and the protein levels of LIMK1, cofilin-1 and p-cofilin-1 were assessed by Western blot.

RESULTS: Treatment with ROS at a concentration of 40 μmol/L for 24 h significantly inhibited cellular invasion and metastasis (P < 0.05), down-regulated the expression of LIMK1 mRNA and protein and the level of p-cofilin-1 (all P < 0.05) but showed no significant impact on cofilin-1-1 mRNA level (P > 0.05).

CONCLUSION: ROS elicited a significant inhibition of in vitro cell migration and invasion in human gastric cancer cell lines SGC7901 and SGC7901/VCR possibly by down-regulating the expression of LIMK1 and inhibiting cofilin-1 activation.

Differential expression of MYC in H. pylori-related intestinal and diffuse gastric tumors

Evidence suggests that the carcinogenic process guided by Helicobacter pylori is related to the expression of cell cycle and apoptosis proteins as BCL-2, BAX, and MYC. However, the literature is conflicting regarding the expression frequency in the histological subtypes and did not consider cagA gene presence. To investigate the expression of these proteins considering the histological subtypes of gastric cancer associated with H. pylori (cagA), a total of 89 cases were used. H. pylori infection and cagA status were determined by PCR. Immunodetection was performed for MYC, BCL-2, and BAX proteins. H. pylori was found in 95.5% of the patients, among them, 65.8% were cagA(+). Nuclear MYC was detected in 36.4%, BAX in 55.7%, while BCl-2 in just 5%. Nuclear MYC staining was significantly lower in the intestinal than diffuse subtype (p = 0.008) and was related with the presence of H. pylori cagA(+). Additionally, most of the few cases cytoplasmic MYC positive were in the intestinal subtype. In diffuse tumors, although most nuclear MYC positive cases were cagA(+), it was not significant. No difference was observed between BCL-2 or BAX expression considering the presence of cagA gene in the histological subtypes. It seems that MYC could be relevant for the diffuse tumorigenic pathway associated with H. pylori and possibly influenced by the presence of cagA gene, while in intestinal tumors, the tumorigenic pathway does not occur through the MYC expression.

Effect of pertussis toxin and herbimycin A on proteinase-activated receptor 2-mediated cyclooxygenase 2 expression in Helicobacter pylori-infected gastric epithelial AGS cells

Helicobacter pylori (H. pylori) is an important risk factor for chronic gastritis, peptic ulcer, and gastric cancer. Proteinase-activated receptor 2 (PAR2), subgroup of G-protein coupled receptor family, is highly expressed in gastric cancer, and chronic expression of cyclooxygenase-2 (COX-2) plays an important role in H. pylori-associated gastric carcinogenesis and inflammation. We previously demonstrated that H. pylori induced the expression of PAR2 and COX-2 in gastric epithelial cells. Present study aims to investigate whether COX-2 expression induced by H. pylori in Korean isolates is mediated by PAR2 via activation of G(i) protein and Src kinase in gastric epithelial AGS cells. Results showed that H. pylori-induced COX-2 expression was inhibited in the cells transfected with antisense oligonucleotide for PAR2 or treated with Gi protein blocker pertussis toxin, Src kinase inhibitor herbimycin A and soybean trypsin inbitor, indicating that COX-2 expression is mediated by PAR2 through activation of Gi protein and Src kinase in gastric epithelial cells infected with H. pylori in Korean isolates. Thus, targeting the activation of PAR2 may be beneficial for prevention or treatment of gastric inflammation and carcinogenesis associated with H. pylori infection.

Tribbles 3: a novel regulator of TLR2-mediated signaling in response to Helicobacter pylori lipopolysaccharide

Helicobacter pylori causes chronic gastritis, peptic ulcers, and gastric carcinoma. Gastric epithelial cells provide the first point of contact between H. pylori and the host. TLRs present on these cells recognize various microbial products, resulting in the initiation of innate immunity. Although previous reports investigated TLR signaling in response to intact H. pylori, the specific contribution of H. pylori LPS with regard to functional genomics and cell-signaling events has not been defined. This study set out to define downstream signaling components and altered gene expression triggered by H. pylori LPS and to investigate the role of the signaling protein tribbles 3 (TRIB3) during the TLR-mediated response to H. pylori LPS. Cotransfections using small interfering RNA and dominant-negative constructs demonstrated that H. pylori LPS functions as a classic TLR2 ligand by signaling through pathways involving the key TLR signaling components MyD88 adaptor-like, MyD88, IRAK1, IRAK4, TNFR-associated factor 6, IκB kinase β, and IκBα. Microarray analysis, real-time PCR, and ELISA revealed the induction of a discrete pattern of chemokines as a direct effect of LPS:TLR2 signaling. H. pylori infection was associated with decreased expression of TRIB3 in human gastric epithelial cell lines and tissue samples. Additionally, H. pylori decreased expression of C/EBP homologous protein and activating transcription factor 4, the transcription factors involved in the induction of TRIB3 expression. Furthermore, knockdown of TRIB3 and C/EBP homologous protein enhanced TLR2-mediated NF-κB activation and chemokine induction in response to H. pylori LPS. Thus, modulation of TRIB3 by H. pylori and/or its products may be an important mechanism during H. pylori-associated pathogenesis.

Helicobacter pylori in a Korean isolate expressed proteins differentially in human gastric epithelial cells

PURPOSE

The proteins expressed in gastric epithelial cells infected with Helicobacter pylori (H. pylori) may determine the clinical outcome such as chronic gastritis, peptic ulcer, and gastric carcinoma. The present study aims to determine the differentially expressed proteins in human gastric epithelial AGS cells that were infected with H. pylori in a Korean isolate, a cagA+, vacA s1b m2 iceA1 H. pylori by proteomic analysis. The differentially expressed proteins, whose expression levels were more or less than twofold in H. pylori-infected cells, were analyzed.

RESULTS

Ten proteins (chromatin assembly factor-1, proliferating cell nuclear antigen, 14-3-3 protein tau, eukaryotic translation initiation factor 6, heat-shock protein 90beta, dimethylarginine dimethylaminohydrolase-1, L-lactate dehydrogenase B chain, prohibitin, triosephosphate isomerase, protein disulfide isomerase) were up-regulated while eight proteins (heat-shock gp96 precursor, nucleophosmin, ornithine aminotransferase, Ku70, L-arginine-glycine amidinotransferase, Smad anchor for receptor activation, ADP-ribosylation factor, WD repeat-containing protein isoform 1) were down-regulated by H. pylori infection in AGS cells. These proteins are related to cell proliferation, cell adhesion, carcinogenesis, cell-defense mechanisms against oxidative stress, membrane trafficking, and energy metabolism.

CONCLUSIONS

Oxidative stress, cell proliferation, cell adhesion, and membrane trafficking may be involved in the pathogenesis of gastric diseases including cancer associated with H. pylori in a Korean isolate.

Time-series gene expression profiles in AGS cells stimulated with Helicobacter pylori

AIM: To extend the knowledge of the dynamic interaction between Helicobacter pylori (H. pylori) and host mucosa.

METHODS: A time-series cDNA microarray was performed in order to detect the temporal gene expression profiles of human gastric epithelial adenocarcinoma cells infected with H. pylori. Six time points were selected to observe the changes in the model. A differential expression profile at each time point was obtained by comparing the microarray signal value with that of 0 h. Real-time polymerase chain reaction was subsequently performed to evaluate the data quality.

RESULTS: We found a diversity of gene expression patterns at different time points and identified a group of genes whose expression levels were significantly correlated with several important immune response and tumor related pathways.

CONCLUSION: Early infection may trigger some important pathways and may impact the outcome of the infection.

Gene expression of AGS cells stimulated with released proteins by Helicobacter pylori

BACKGROUND AND AIM

Interactions between released proteins by Helicobacter pylori (H. pylori) and the cells of gastric epithelium to which it adheres may contribute to gastric inflammation and epithelial damage. The present study was performed to evaluate the gene expression of AGS gastric cancer cells stimulated with released proteins by H. pylori.

METHODS

Gene expression of AGS cells to the stimulation by H. pylori-released proteins (G27 strain) were monitored using oligonucleotide microarrays.

RESULTS

Eighty-eight genes (0.88%) and eight genes (0.08%) were up- or downregulated, respectively, by treating AGS cells with H. pylori-released proteins but not by H. pylori adhesion after 12 h of coculture. Out of the selected 40 up- and five downregulated genes, 29 upregulated genes classified as general RNA polymerase II transcription factor activity (GTF2B, PPARGC1A), SH3/SH2 adaptor activity (CRKL), transferase activity (ACLY, CRKL, PIGC, PLK4), and oxidoreductase activity (IDH1) were confirmed to be upregulated by released proteins and not by H. pylori adhesion by real-time reverse transcription-polymerase chain reaction. When the concentrated H. pylori-cultured supernatant prepared by our protocol was treated by boiling, the upregulations of 26 of these 29 genes (89.7%) except for CD160, ZNF268, and PSAT1 disappeared. This confirmed that most of these upregulations were caused by released proteins.

CONCLUSION

Host genes involving transcription, signaling and stress are significantly modulated by the proteins released by H. pylori. This might strengthen the gastroduodenal pathogenesis induced by H. pylori.

Discovering differential protein expression caused by CagA-induced ERK pathway activation in AGS cells using the SELDI-ProteinChip platform

AIM

To identify the protein expression differences related to the CagA-induced ERK pathway activation in AGS cells.

METHODS

Human AGS cells transfected with cagA and blank vector were treated with specific mitogen-activated protein kinase kinase (MEK) inhibitor. Total cell proteins were combined by strong anion exchange (SAX2) and weak cation exchange (CM10) ProteinChip arrays and analyzed using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS) proteomics technology. Protein expression profiles were compared with those of inhibitor-untreated cagA transfectants. SwissProt/TrEMBL database searching for differentially expressed proteins was carried out using the TagIdent tool with the pI and mass information.

RESULTS

When a total of 16 proteins that showed expression differences in inhibitor-untreated cagA transfectants were compared with vector transfectants, three proteins with m/z 4229, 8162 and 9084 were found to have no expression differences after treatment with MEK inhibitor, while the other 13 maintained the same expression differences after inhibitor treatment. Seven pieces of meaningful matching information for the three proteins were obtained from database searching.

CONCLUSION

Biomarkers with m/z 4229, 8162 and 9084 are ERK1/2 phosphorylation dependent, and therefore are the downstream molecules of ERK1/2 in the ERK/MAPK signaling pathway. The three biomarkers may be important cancer-associated proteins according to SwissProt/TrEMBL database information.

Gene expression profiling in human gastric mucosa infected with Helicobacter pylori

Pathogenic mechanisms associated with Helicobacter pylori infection enhance susceptibility of the gastric epithelium to carcinogenic conversion. We have characterized the gene expression profiles of gastric biopsies from 69 French Caucasian patients, of which 43 (62%) were infected with H. pylori. The bacterium was detected in 27 of the 42 antral biopsies examined and in 16 of the 27 fundic biopsies. Infected biopsies were selected for the presence of chronic active gastritis, in absence of metaplasia and dysplasia of the gastric mucosa. Infected antral and fundic biopsies exhibited distinct transcriptional responses. Altered responses were linked with: (1) the extent of polymorphonuclear leukocyte infiltration, (2) bacterial density, and (3) the presence of the virulence factors vacA, babA2, and cagA. Robust modulation of transcripts associated with Toll-like receptors, signal transduction, the immune response, apoptosis, and the cell cycle was consistent with expected responses to Gram-negative bacterial infection. Altered expression of interferon-regulated genes (IFITM1, IRF4, STAT6), indicative of major histocompatibility complex (MHC) II-mediated and Th1-specific responses, as well as altered expression of GATA6, have previously been described in precancerous states. Upregulation of genes abundantly expressed in cancer tissues (UBD, CXCL13, LY96, MAPK8, MMP7, RANKL, CCL18) or in stem cells (IFITM1 and WFDC2) may reveal a molecular switch towards a premalignant state in infected tissues. Tissue microarray analysis of a large number of biopsies, which were either positive or negative for the cag-A virulence factor, when compared to each other and to noninfected controls, confirmed observed gene alterations at the protein level, for eight key transcripts. This study provides 'proof-of-principle' data for identifying molecular mechanisms driving H. pylori-associated carcinogenesis before morphological evidence of changes along the neoplastic progression pathway.

Analysis of Gene Expression Profile of AGS Cells Stimulated by Helicobacter pylori Adhesion

BACKGROUND/AIMS

Interactions between H. pylori and gastric epithelial cells contribute to gastric inflammation and epithelial damage. This study was performed to evaluate the gene expression profile of AGS cells by adhesion of H. pylori.

METHODS

Changes in AGS cell gene expression induced by co-culturing with H. pylori (G69a strain) (4, 12, 24, 48 hours) were monitored using oligonucleotide microarray. Real-time reverse transcription-polymerase chain reaction (RT-PCR) was performed for data validation by the Assay-on-Demand Gene Expression product method.

RESULTS

A total of 270 (2.66%) and 19 genes (0.19%) were up-regulated in AGS cells by H. pylori adhesion. Gene ontology analysis showed that up-regulated genes were categorized into endolipidase activity (17 genes), receptor binding (17 genes), integrin binding (4 genes), and two down-regulated genes into GTP binding category. The expression levels of 20 up- and 5 down-regulated genes were quantified by real-time RT-PCR. Sixteen genes involving cytokine activity (IL8, IL1B, TNF), hydrolase activity (PTP4A1, ERCC1, CASP8, CASP7, ACIN1), VIP receptor activity (VIPR2), and neuropeptide Y receptor activity (GPR83) were confirmed to be up-regulated. Five genes, namely, ARF3, M17S2, DDB2, AWP1, and WTAP were confirmed to be down-regulated.

CONCLUSIONS

Host genes are significantly changed by H. pylori adhesion, which might explain the gastroduodenal pathogenesis induced by H. pylori infection.

Global analysis of the human gastric epithelial transcriptome altered by Helicobacter pylori eradication in vivo

OBJECTIVE

The transcriptional profile of gastric epithelial cell lines cocultured with Helicobacter pylori and the global gene expression of whole gastric mucosa has been described previously. We aimed to overcome limitations of previous studies by determining the effects of H pylori eradication on the transcriptome of purified human gastric epithelium using each patient as their own control.

DESIGN

Laser capture microdissection (LCM) was used to extract mRNA from paraffin-embedded antral epithelium from 10 patients with peptic ulcer disease, before and after H pylori eradication. mRNA was reverse transcribed and applied on to Affymetrix cDNA microarray chips customised for formalin-fixed tissue. Differentially expressed genes were identified and a subset validated by real-time polymerase chain reaction (PCR).

RESULTS

A total of 13 817 transcripts decreased and 9680 increased after H pylori eradication. Applying cut-off criteria (p<0.02, fold-change threshold 2.5) reduced the sample to 98 differentially expressed genes. Genes detected included those previously implicated in H pylori pathophysiology such as interleukin 8, chemokine ligand 3, beta defensin and somatostatin, as well as novel genes such as GDDR (TFIZ1), chemokine receptors 7 and 8, and gastrokine.

CONCLUSIONS

LCM of archival specimens has enabled the identification of gastric epithelial genes whose expression is considerably altered after H pylori eradication. This study has confirmed the presence of genes previously implicated in the pathogenesis of H pylori, as well as highlighted novel candidates for further investigation.

Gene-expression profiles in gastric epithelial cells stimulated with spiral and coccoid Helicobacter pylori

Human gastric epithelial immortalized GES-1 cells were infected with spiral and coccoid Helicobacter pylori. Scanning electron microscopy was used to determine the ability of the two forms of H. pylori to adhere to GES-1 cells. GES-1 cell apoptosis induced by coccoid and spiral H. pylori was analysed using flow cytometry. A cDNA microarray for 22,000 human genes was used to identify the gene-expression differences in GES-1 cells infected with the two forms of H. pylori, and the gene expression identified by the cDNA microarray was confirmed by RT-PCR. Scanning electron microscope observation showed that both coccoid and spiral bacteria can adhere to GES-1 cells. After 4 h infection, apoptosis induction was 27.4% for spiral-form infection and 10.2% for coccoid-form infection. Of 268 differentially expressed genes identified by cDNA microarray, 166 showed higher expression with the spiral H. pylori infection than with the coccoid H. pylori infection. To the best of the authors' knowledge, this is the first report that GES-1 cells infected with spiral H. pylori have higher expression of cxcl10, ccl11, ccl5, groalpha, TLR5, ATF3, fos, fosl2, gadd45a and myc. The cells infected with coccoid H. pylori had higher expression of survivin. The global profile of gene expression in GES-1 cells infected with coccoid and spiral H. pylori is described for the first time.

Oxidative stress in Helicobacter pylori-induced gastric cell injury

Oxygen radicals are supposed to be involved in inflammation and cell proliferation. Helicobacter pylori induces decrease in antioxidant defense factors, such as GSH, mucus and constitutive nitric oxide (NO), gastric mucosal injury and inflammation. Inflammation and injury might be caused by oxidant-mediated expression of inflammatory cytokine interleukin-8 (IL-8) and inflammatory enzymes such as cyclooxtgenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), which were mediated by oxidant-sensitive transcription factors such as nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1), possibly with mitogen activated protein kinase (MAPK) activation. H. pylori-induced alterations in protein expression demonstrate the involvement of oxidative stress in the pathogenesis of H. pylori-induced gastric diseases. The differentially expressed genes and proteins may be useful as prognostic indices for gastric diseases associated with H. pylori infection. In conclusion, oxygen radicals are produced in gastric epithelial cells infected with H. pylori, which may reduce the antioxidant defense mechanism and turn on the expression of inflammatory genes, adhesion molecules and mediators stimulating cell proliferation, as well as defensive molecular chaperones in gastric epithelial cells.

Gene expression and protein profiling of AGS gastric epithelial cells upon infection with Helicobacter pylori

Helicobacter pylori, one of the most common bacterial pathogens, colonizes the human stomach and causes a variety of gastric diseases. This pathogen elicits a range of phenotypic responses in infected cultured AGS gastric epithelial cells, including expression of proinflammatory genes and changes in the actin cytoskeleton. Some of these responses are mediated by the type IV secretion system (T4SS) encoded by the cag pathogenicity island. We have used two global approaches, namely 2-DE combined with PMF and cDNA expression array analyses, to study in both a comprehensive and quantitative manner the protein profile and the temporal patterns of mRNA accumulation in AGS cells upon infection with H. pylori and isogenic T4SS mutants. We identified 140 transcripts and detected 190 protein species that were differentially regulated upon infection. Infection with wild-type H. pylori induced expression of a variety of host genes and changes in protein pattern involved in transcriptional responses, cell shape regulation and signal transduction. Among them, some were differentially regulated in a cag PAI-dependent manner, as shown by both the proteomic and cDNA expression array approaches. While 2-DE and PMF allowed us to examine the protein profiles in the infected host, array analysis enabled us to demonstrate dynamic temporal changes in host gene expression profile. In conclusion, our combined application of the two global approaches provides further molecular details on how the host cell responds to infection by H. pylori and its isogenic T4SS mutants on both transcriptional and protein levels. The findings pinpoint host proteins such as serine/threonine and tyrosine kinases, transcription factors, cell cycle related components and actin cytoskeletal signaling molecules as potential targets of individual H. pylori virulence determinants. This study serves as a basis for future work on transcription and proteome analyses of the H. pylori infection model.

Effects of transfection reagents and Helicobacter pylori on morphology of AGS cells

AIM: To investigate the effects of different transfection reagents on the morphology of AGS cells and to explore whether these reagents can induce humming bird type of AGS cells as Helicobacter pylori (H. pylori) does.

METHODS: AGS cells were transfected with polycation transfection reagents (polyethylenimine, Sofast Cell Transfection reagent) and the new generation of lipid transfection reagents (Effectene Transfection Reagent). Then morphological changes of the cells were observed. Meanwhile, AGS cells were infected with H. pylori 26695, and then the morphology of the cells was compared with that of the cells transfected with transfection reagents.

RESULTS: H. pylori 26695 induced humming bird type of AGS cells 4 h after infection. Both polycation transfection reagents also induced humming bird type of AGS cells, and the cells were elongated in shape, which was similar to that induced by H. pylori 26695. The humming bird type always appeared whether the cells were transfected with DNA or without DNA at 4 h. The morphological changes were positively related with the dosages of the reagents. The apoptosis of the cells were observed when 10 µL reagents were used, and it became severe as the dosage reached 15 µL. The new generation of lipid transfection reagents had no effect on the morphology of AGS cells.

CONCLUSION: Polycation transfection reagents should not be used in the research of AGS cell morphology. Further study should be performed to find out whether there are some common pathways between the morphology variation induced by H　pylori and polycation transfection reagents.

NF-kappaB and ERK-signaling pathways contribute to the gene expression induced by cag PAI-positive-Helicobacter pylori infection

AIM

To elucidate the sequential gene expression profile in AGS cells co-cultured with wild-type Helicobacter pylori (H pylori) as a model of H pylori-infected gastric epithelium, and to further examine the contribution of cag-pathogenicity islands (cagPAI)-coding type IV secretion system and the two pathways, nuclear factor kappa B (NF-kappaB) and extracellular signal-regulated kinases (ERK) on wild-type H pylori-induced gene expression.

METHODS

Gene expression profiles induced by H pylori were evaluated in AGS gastric epithelial cells using cDNA microarray, which were present in the 4 600 independent clones picked up from the human gastric tissue. We also analyzed the contribution of NF-kappaB and ERK signaling on H pylori-induced gene expression by using inhibitors of specific signal pathways. The isogenic mutant with disrupted cagE (Delta cagE) was used to elucidate the role of cagPAI-encoding type IV secretion system in the gene expression profile.

RESULTS

According to the expression profile, the genes were classified into four clusters. Among them, the clusters characterized by continuous upregulation were most conspicuous, and it contained many signal transducer activity-associated genes. The role of cagPAI on cultured cells was also investigated using isogenic mutant cagE, which carries non-functional cagPAI. Then the upregulation of more than 80% of the induced genes (476/566) was found to depend on cagPAI. Signal transducer pathway through NF-kappaB or ERK are the major pathways which are known to be activated by cagPAI-positive H pylori. The role of these pathways in the whole signal activation by cagPAI-positive H pylori was analyzed. The specific inhibitors against NF-kappaB or ERK pathway blocked the activation of gene expression in 65% (367/566) or 76% (429/566) of the genes whose activation appealed to depend on cagPAI.

CONCLUSION

These results suggest that more than half of the genes induced by cagPAI-positive H pylori depend on NF-kappaB and ERK signaling activation, and these pathways may play a role in the gene expression induced by host-bacterial interaction which may associate with H pylori-related gastro-duodenal diseases.

Global analysis of gene expression in gastric ischemia-reperfusion: a future therapeutic direction for mucosal protective drugs

Gastric ischemia-reperfusion is a relatively common condition leading to mucosal injury and may affect mucosal repair via modulating the gene expression of growth factors. Therefore, precise understanding of the molecular mechanism of ischemia or ischemia-reperfusion may lead to the discovery of new mucosal protective drugs. DNA microarray analysis followed by powerful data analysis has the potential to uncover previously undescribed genes involved in gastric injury and lead to an increased understanding of gastric mucosal cytoprotection. We introduced the laser-assisted microdissection to obtain cell-specific RNA from gastric mucosa in vivo and obtained sufficient amounts of cRNA for GeneChip analysis. This comprehensive approach enabled the simultaneous analysis of many genes, including transcriptional factors, as well as the generation of novel hypothesis on the mechanism of action of gastro-protective agents.

Functional antagonism between Helicobacter pylori CagA and vacuolating toxin VacA in control of the NFAT signaling pathway in gastric epithelial cells

Chronic infection with cagA-positive Helicobacter pylori is associated with the development of atrophic gastritis, peptic ulcers, and gastric adenocarcinoma. The cagA gene product CagA is injected into gastric epithelial cells, where it undergoes tyrosine phosphorylation by Src family kinases. Translocated CagA disturbs cellular functions by physically interacting with and deregulating intracellular signaling transducers through both tyrosine phosphorylation-dependent and -independent mechanisms. To gain further insights into the pathophysiological activities of CagA in gastric epithelial cells, we executed a genome-wide screening of CagA-responsive genes by using DNA microarray and identified nuclear factor of activated T cells (NFAT) transcription factors whose binding sites were overrepresented in the promoter regions of CagA-activated genes. Results of reporter assays confirmed that CagA was capable of activating NFAT in a manner independent of CagA phosphorylation. Expression of CagA in gastric epithelial cells provoked translocation of NFATc3, a member of the NFAT family, from the cytoplasm to the nucleus and activated an NFAT-regulated gene, p21WAF1/Cip1. CagA-mediated NFAT activation was abolished by inhibiting calcineurin or phospholipase Cgamma activity. Furthermore, treatment of cells with H. pylori VacA (vacuolating toxin), which inhibits NFAT activity in T lymphocytes, counteracted the ability of CagA to activate NFAT in gastric epithelial cells. These findings indicate that the two major H. pylori virulence factors inversely control NFAT activity. Considering the pleiotropic roles of NFAT in cell growth and differentiation, deregulation of NFAT, either positively or negatively, depending on the relative exposure of cells to CagA and VacA, may contribute to the various disease outcomes caused by H. pylori infection.

Molecular analysis of Helicobacter pylori-associated gastric inflammation in naïve versus previously immunized mice

To identify mechanisms of immunity against Helicobacter pylori, we performed microarray analysis on gastric tissue from infected mice and mice vaccinated prior to challenge. RNA from gastric tissue was used to screen over 10,000 genes. MHC antigens and GTP binding proteins were upregulated in both groups. Infected mice were characterized by expression of innate host defense markers while immune mice expressed many IFN-gamma response genes and T cell markers. Results were confirmed for several genes by RT-PCR. CD4+ spleen cells from immune mice produced significantly more IFN-gamma than from infected mice. These results support a role for T cell regulated inflammation in H. pylori immunity.

Cellular stress-related protein expression in Helicobacter pylori-infected gastric epithelial AGS cells

Helicobacter pylori infection leads to gastroduodenal inflammation, peptic ulceration, and gastric carcinoma. Moreover, H. pylori may induce disease-specific protein expression in gastric epithelial cells. The present study was aimed at determining differentially expressed proteins in H. pylori-infected gastric epithelial AGS cells. AGS cells were treated with H. pylori at a bacterium/cell ratio of 300:1 for 12 h. Altered protein patterns as separated by two-dimensional electrophoresis using pH gradients of 4-7 were conclusively identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) analysis of the peptide digests. Four differentially expressed proteins, whose expression levels were increased by more than two-fold in H. pylori-infected cells, were analyzed. These proteins (14-3-3 protein alpha/beta, cullin homolog 3, alpha-enolase, ezrin) are known to be related to cell proliferation, cell adhesion, and carcinogenesis, and may be mediated by cellular stress, such as reactive oxygen species. In conclusion, the identification of these differentially expressed proteins provide valuable information for the understanding of the pathophysiologic mechanisms of H. pylori-induced gastric diseases, and may be useful as prognostic indices of H. pylori-related gastric disorders.

Strain-specific expression profiles of virulence genes in Helicobacter pylori during infection of gastric epithelial cells and granulocytes

Helicobacter pylori expresses a variety of known virulence-associated factors, whose expression is likely to be dependent on the ecological niche of this pathogen. Here, we compared the temporal changes in the level of virulence-associated gene transcription in H. pylori strains isolated from patients with different pathology. Our aim was to study the coordinated gene expression profiles of these virulence factors during infection of AGS gastric epithelial cells and granulocytes. Using real-time quantitative (TaqMan) RT-PCR, we determined the mRNA expression of cagA, ureA, napA, katA, vacAs1 and vacAs2 alleles in a time course up to 6 h. The expression profiles of the investigated genes vary according to the strain, and were mainly either upregulated or unchanged upon bacterial contact with AGS cells. In contrast, upon contact with granulocytes, the majority of the genes were repressed in H. pylori. The following major results were obtained: (i) genetically diverse H. pylori exhibit different mRNA expression profiles, (ii) the expression patterns were strain-specific and time-dependent and (iii) the regulation of expression profiles was host cell dependent. These data were statistically significant and suggest that contact with target cells leads to an active cross-talk between the pathogen and its host. The use of Taqman-PCR to analyse the expression of mRNA of a bacterial pathogen in response to a changing host environment enabled us to identify variable and strain-specific transcription profiles in a sensitive and reproducible manner.

Analysis of gene expression profile in gastric cancer cells stimulated with Helicobacter pylori isogenic strains

To understand the biological processes within host cells induced by VacA, isogenic strains of Helicobacter pylori (NCTC 11638 or 11638-DeltavacA) were used to stimulate gastric cancer cells SGC7901, and differentially expressed genes in host cells were identified using cDNA microarray technology. More than 300 genes were found to alter their mRNA expression at different time points, among which 68 were related to the cytoskeleton, 87 were associated with cell cycle, cell death and proliferation, IL8 expression was also found to be up-regulated. Cells co-cultured with broth-culture supernatant (BCS) of NCTC 11638 showed more alteration in microtubule cytoskeleton morphology, as observed by laser scanning confocal microscopy, and a lower apoptosis rate, detected by flow cytometry, compared with those co-cultured with BCS of 11638-DeltavacA. The supernatants of cells co-cultured with NCTC 11638 showed significantly higher IL8 expression than those co-cultured with 11638-DeltavacA. It is concluded that VacA disrupts cytoskeletal architecture by influencing the expression of cytoskeleton-associated genes. VacA breaks the balance between cell proliferation and cell death by inducing the maladjustment of genes related to cell cycle. VacA is also able to induce the inflammatory response.

Profiling of microdissected gastric epithelial cells reveals a cell type-specific response to Helicobacter pylori infection

BACKGROUND AND AIMS

Helicobacter pylori colonizes the epithelial lining of the human stomach and is associated with disorders ranging from chronic gastritis to peptic ulcers and gastric cancer. We have explored the transcriptional response of the epithelium globally by applying a whole-genome approach to a murine model of infection.

METHODS

The 3 major epithelial lineages of the stomach-the parietal, mucus-producing, and chief cells-were harvested from cryosections of infected and uninfected murine stomachs by laser microdissection and subjected to gene expression profiling. The localization and quantity of selected transcripts were verified by in situ hybridization and quantitative real-time reverse-transcription polymerase chain reaction.

RESULTS

Each cell type is characterized by a transcriptional signature profile. The parietal cell profile is highly enriched for factors involved in mitochondrial energy generation, whereas the chief cell predominantly expresses digestive enzymes and glycosylation-associated proteins. In contrast, the mucus cell signature is distinguished by an abundance of cell-surface receptors, signaling molecules, and factors involved in antigen presentation. All of these indicate a role in sampling, sensing, and responding to environmental stimuli. In line with this biological function, we measured a strong transcriptional response to Helicobacter pylori infection only in this cell type. The genes that are differentially expressed upon infection are implicated in a proinflammatory and mucosal defense response as well as modulation of angiogenesis, iron availability, and tumor suppression.

CONCLUSIONS

Laser microdissection-assisted transcriptional profiling is a useful tool to explore the biology of specific cell populations and is sensitive enough to measure the transcriptional response to bacterial infection in vivo.

Gastric transcription profile of Helicobacter pylori infection in the rhesus macaque

Infection with Helicobacter pylori is usually asymptomatic but sometimes progresses to peptic ulcer disease or gastric adenocarcinoma. The development of disease involves both host and bacterial factors. In order to better understand host factors in pathogenesis, we studied the gastric transcription profile of H. pylori infection in the rhesus macaque by using DNA microarrays. Significant changes were found in the expression of genes important for innate immunity, chemokines and cytokines, cell growth and differentiation, apoptosis, structural proteins, and signal transduction and transcription factors. This broad transcription profile demonstrated expected up-regulation of cell structural elements and the host inflammatory and immune response, as well as the novel finding of down-regulation of heat shock proteins. These results provide a unique view of acute H. pylori infection in a relevant animal model system and will direct future studies regarding the host response to H. pylori infection.

Oxidative-stress-related proteome changes in Helicobacter pylori-infected human gastric mucosa

Helicobacter pylori infection leads to gastroduodenal inflammation, peptic ulceration and gastric carcinoma. Proteomic analysis of the human gastric mucosa from the patients with erosive gastritis, peptic ulcer or gastric cancer, which were either infected or not with H. pylori, was used to determine the differentially expressed proteins by H. pylori in the human gastric mucosa in order to investigate the pathogenic mechanism of H. pylori -induced gastric diseases. Prior to the experiment, the expression of the main 18 proteins were identified in the gastric mucosa and used for a proteome map of the human gastric mucosa. Using two-dimensional electrophoresis of the protein isolated from the H. pylori -infected tissues, Coomassie Brilliant Blue staining and computerized analysis of the stained gel, the expression of eight proteins were altered in the H. pylori -infected tissues compared with the non-infected tissues. MS analysis (matrix-assisted laser desorption/ionization-time of flight MS) of the tryptic fragment and a data search allowed the the identification of the four increased proteins (78 kDa glucose-regulated protein precursor, endoplasmin precursor, aldehyde dehydrogenase 2 and L-lactate dehydrogenase B chain) and the four decreased proteins (intracellular chloride channel protein 1, glutathione S-transferase, heat-shock protein 60 and cytokeratin 8) caused by H. pylori infection in the gastric mucosa. These proteins are related to cell proliferation, carcinogenesis, cytoskeletal function and cellular defence mechanism. The common feature is that these proteins are related to oxidative-stress-mediated cell damage. In conclusion, the established gastric mucosal proteome map might be useful for detecting the disease-related protein changes. The H. pylori -induced alterations in protein expression demonstrate the involvement of oxidative stress in the pathogenesis of H. pylori -induced gastric diseases, including inflammation, ulceration and carcinogenesis.

Inflammatory gene profiles in gastric mucosa during Helicobacter pylori infection in humans

Helicobacter pylori infection is associated with an inflammatory response in the gastric mucosa, ultimately leading to cellular hyperproliferation and malignant transformation. Hitherto, only expression of a single gene, or a limited number of genes, has been investigated in infected patients. cDNA arrays were therefore used to establish the global pattern of gene expression in gastric tissue of healthy subjects and of H. pylori-infected patients. Two main gene expression profiles were identified based on cluster analysis. The data obtained suggest a strong involvement of selected Toll-like receptors, adhesion molecules, chemokines, and ILs in the mucosal response. This pattern is clearly different from that observed using gastric epithelial cell lines infected in vitro with H. pylori. The presence of a "Helicobacter-infection signature," i.e., a set of genes that are up-regulated in biopsies from H. pylori-infected patients, could be derived from this analysis. The genotype of the bacteria (presence of genes encoding cytotoxin-associated Ag, vacuolating cytotoxin, and blood group Ag-binding adhesin) was analyzed by PCR and shown to be associated with differential expression of a subset of genes, but not the general gene expression pattern. The expression data of the array hybridization was confirmed by quantitative real-time PCR assays. Future studies may help identify gene expression patterns predictive of complications of the infection.

Genes of Helicobacter pylori regulated by attachment to AGS cells

Reciprocal interactions between Helicobacter pylori and cells of the gastric epithelium to which it adheres may affect colonization. Changes in gene expression of H. pylori induced by adhesion to AGS gastric cancer cells by coculture were compared to changes in gene expression of H. pylori cultured without AGS cells by using cDNA filter macroarrays. Adhesion was quantitatively verified by confocal microscopy of green fluorescent protein-expressing bacteria. Four experiments showed that 22 and 21 H. pylori genes were consistently up- and down-regulated, respectively. The up-regulated genes included pathogenicity island, motility, outer membrane protein, and translational genes. The sigma(28) factor antagonist flgM, flgG, the stress response gene, flaA, omp11, and the superoxide dismutase gene (sodB) were down-regulated. The up-regulation of cag3, flgB, tonB, rho, and deaD was confirmed by quantitative PCR, and the up-regulation of lpxD, omp6, secG, fabH, HP1285, HP0222, and HP0836 was confirmed by reverse transcription (RT)-PCR. The down-regulation of flaA, sodB, and HP0874 was confirmed by quantitative PCR, and the down-regulation of omp11 was confirmed by RT-PCR. The alteration of gene expression in H. pylori after adhesion to gastric cells in vitro suggests that changes in motility, outer membrane composition, and stress responses, among other changes, may be involved in gastric colonization.

Cell adhesion-related gene expression by Helicobacter pylori in gastric epithelial AGS cells

Helicobacter pylori (H. pylori) infection leads to gastroduodenal inflammation, peptic ulceration and gastric carcinoma. H. pylori may induce disease-specific gene expression in gastric epithelial cells. cDNA microarray for 352 cancer-related genes was used to identify the genes altered by H. pylori (cagA positive) in gastric epithelial AGS cells. Expressions of the genes identified on the microarray and other genes closely associated with these genes were determined by reverse transcriptase-polymerase chain reaction (RT-PCR). Western blot analysis and cell adhesion assay were performed to confirm the protein levels of the genes and the role of the genes on cell adhesion in H. pylori-infected AGS cells. As a result, the expression of four genes (galectin 1, aldolase A, integrin alpha5, LIM domain only 7 (LMO7)) were up-regulated by H. pylori in AGS cells, determined by cDNA microarray. RT-PCR analysis showed that the genes up-regulated by H. pylori were the genes regulating cell-cell adhesion and cell-extracellular matrix interaction, such as galectin-1 and galectin-3, integrin alpha5, and LIM domain only 7 (LMO7), and cancer-related glycolytic enzyme aldolase A and C. Cell adhesion to extracellular matrix proteins such as poly-L-lysine and fibronectin was mediated by H. pylori-induced expression of integrin alpha5. RT-PCR and Western blot analysis showed that E-cadherin, regulating cell adhesion and contact cell inhibition, was decreased by H. pylori in AGS cells. In conclusion, the increased expression of cell adhesion molecules and decrease in E-cadherin expression by H. pylori might contribute to cell adhesion, invasion and possibly cell proliferation in gastric epithelial cells.

The effect of rebamipide on Helicobacter pylori extract-mediated changes of gene expression in gastric epithelial cells

BACKGROUND

Recent studies have shown that Helicobacter pylori affects intracellular signal transduction in host cells, leading to the activation of transcriptional factors and the induction of pro-inflammatory cytokines. On the other hand, rebamipide, an anti-gastritis and anti-ulcer agent, could scavenge reactive oxygen species and reduce interleukin-8 (IL-8) expression in gastric epithelial cells induced by H. pylori-stimulation through the attenuated activation of nuclear factor-kappaB (NF-kappaB).

AIMS

In this study, we investigated the effects of rebamipide on gene expression in H. pylori-stimulated epithelial cells using DNA chip.

METHODS

H. pylori water extract (HPE) was prepared from NCTC11637, the type strain of H. pylori. Total RNA was extracted from MKN45 cells, a human gastric cancer cell line, following HPE-stimulation with and without rebamipide for 3 h, and differences in gene expression profiles were observed using GeneChip and Human 6800 probe array.

RESULTS

The GeneChip analysis demonstrated that 132 up-regulated genes and 873 down-regulated genes, such as growth factors, chemokines and transcription factors, were detected in MKN45 cells 3 h after stimulation of H. pylori. Among them, several genes, including bFGF, RANTES and MIP-2beta, were previously unknown to be expressed in H. pylori-stimulated human gastric cells. Rebamipide reduced expression of 119 genes encoding cytokines, growth factors and their receptors and transcription factors.

CONCLUSIONS

These findings suggest that rebamipide could inhibit inflammatory reactions and tumour progression by modifying H. pylori infection-induced gene expression in gastric epithelial cells.

Genomics of Helicobacter pylori

During this review period, we have definitely entered into the genomic era. The Helicobacter pylori studies reported here illustrate the use of most of the technologies currently available to globally interrogate the genome of a pathogen. Global analysis of the gene content of H. pylori strains gives insight into the extent of its genetic diversity and its in vivo evolution. Our understanding of the particularities of H. pylori as a gastric pathogen colonizing a unique niche has been improved by studies aimed at: (i) the identification of H. pylori-specific genes; (ii) the establishment of correlations between the presence of one or a group of genes (or proteins) with clinical outcome; and (iii) the analysis of global regulatory circuits or responses to the extracellular signals. The response of host cells to H. pylori infection will be developed in the chapter 'H. pylori and gastric malignancies' by Sepulveda and Coehlo. Despite our knowledge of the H. pylori genome, the function of about one third of its total proteins is still unknown. Functional genomics are straightforward approaches for the identification of new gene functions or metabolic pathways as well as for the understanding of cellular processes and the detection of new virulence factors. In silico studies combined with experimental work will undoubtedly continue to develop. To date, the expansion of proteomics with refinements in mass spectrometry technology has illustrated that through immunoproteomics and comparative studies, relevant novel antigens can be identified. Genomics not only provides invaluable information on H. pylori but also opens new perspectives for diagnostic or therapeutic applications.

Cag pathogenicity island-specific responses of gastric epithelial cells to Helicobacter pylori infection

Helicobacter pylori infects over half the world's population and causes a wide range of diseases, including gastritis, peptic ulcer, and two forms of gastric cancer. H. pylori infection elicits a variety of phenotypic responses in cultured gastric epithelial cells, including the expression of proinflammatory genes and changes in the actin cytoskeleton. Both of these responses are mediated by the type IV secretion system (TFSS) encoded by the cag pathogenicity island (cag PAI). We used human cDNA microarrays to examine the temporal transcriptional profiles of gastric AGS cells infected with H. pylori strain G27 and a panel of isogenic mutants to dissect the contributions of various genes in the cag PAI. Infection with G27 induced expression of genes involved in the innate immune response, cell shape regulation, and signal transduction. A mutant lacking the cagA gene, which encodes an effector molecule secreted by the TFSS and required for the host cell cytoskeletal response, induced the expression of fewer cytoskeletal genes. A mutant lacking cagE, which encodes a structural component of the TFSS, failed to up-regulate a superset of host genes, including the cagA-dependent genes, and many of the immune response genes. A mutant lacking the entire cag PAI failed to induce both the cagE-dependent genes and several transiently expressed cagE independent genes. Host cell transcriptional profiling of infection with isogenic strains offered a detailed molecular picture of H. pylori infection and provided insight into potential targets of individual virulence determinants such as tyrosine kinase and Rho GTPase signaling molecules.