Helicobacter pylori and mitogen-activated protein kinases mediate activator protein-1 (AP-1) subcomponent protein expression and DNA-binding activity in gastric epithelial cells

Induction of MMP-3 and MMP-9 expression during Helicobacter pylori infection via MAPK signaling pathways

BACKGROUND AND AIMS

Helicobacter pylori (H. pylori)-induced gastric pathology involves remodeling of extracellular matrix mediated by aberrant activity of matrix metalloproteinases (MMPs). We have previously shown that in vitro H. pylori infection leads to MMP-3 and MMP-9 overexpression, associated with phosphorylation of bacterial oncoprotein CagA. We extended these findings in an in vivo model of H. pylori infection and further assessed the involvement of MAPK pathways in MMP expression.

MATERIALS AND METHODS

C57BL/6 mice were infected with H. pylori strains HPARE, HPARE ΔCagA, and SS1, for 6 and 9 months. Transcriptional expression of Mmp-3 and Mmp-9 was evaluated via qPCR while respective protein levels in the gastric mucosa were determined immunohistochemically. Epithelial cell lines AGS and GES-1 were infected with H. pylori strain P12 in the presence of chemical inhibitors of JNK, ERK1/2, and p38 pathways, for 24 h. mRNA and protein expression of MMP-3 and MMP-9 were determined via qPCR and Western blot, respectively.

RESULTS

We observed transcriptional activation of Mmp-3 and Mmp-9 as well as aberrant MMP-3 and MMP-9 protein expression in murine gastric tissue following H. pylori infection. CagA expression was associated with MMP upregulation, particularly during the early time points of infection. We found that inhibition of ERK1/2 resulted in reduced mRNA and protein expression of MMP-3 and MMP-9 during H. pylori infection, in both cell lines. Expressed protein levels of both MMPs were also found reduced in the presence of JNK pathway inhibitors in both cell lines. However, p38 inhibition resulted in a more complex effect, probably attributed to the accumulation of phospho-p38 and increased phospho-ERK1/2 activity due to crosstalk between MAPK pathways.

CONCLUSIONS

H. pylori colonization leads to the upregulation of MMP-3 and MMP-9 in vivo, which primarily involves ERK1/2 and JNK pathways. Therefore, their inhibition may potentially offer a protective effect against gastric carcinogenesis and metastasis.

Comprehensive insight into altered host cell-signaling cascades upon Helicobacter pylori and Epstein-Barr virus infections in cancer

Cancer is characterized by mutagenic events that lead to disrupted cell signaling and cellular functions. It is one of the leading causes of death worldwide. Literature suggests that pathogens, mainly Helicobacter pylori and Epstein-Barr virus (EBV), have been associated with the etiology of human cancer. Notably, their co-infection may lead to gastric cancer. Pathogen-mediated DNA damage could be the first and crucial step in the carcinogenesis process that modulates numerous cellular signaling pathways. Altogether, it dysregulates the metabolic pathways linked with cell growth, apoptosis, and DNA repair. Modulation in these pathways leads to abnormal growth and proliferation. Several signaling pathways such RTK, RAS/MAPK, PI3K/Akt, NFκB, JAK/STAT, HIF1α, and Wnt/β-catenin are known to be altered in cancer. Therefore, this review focuses on the oncogenic roles of H. pylori, EBV, and its associated signaling cascades in various cancers. Scrutinizing these signaling pathways is crucial and may provide new insights and targets for preventing and treating H. pylori and EBV-associated cancers.

Gastric Epithelial Barrier Disruption, Inflammation and Oncogenic Signal Transduction by Helicobacter pylori

Helicobacter pylori exemplifies one of the most favourable bacterial pathogens worldwide. The bacterium colonizes the gastric mucosa in about half of the human population and constitutes a major risk factor for triggering gastric diseases such as stomach cancer. H. pylori infection represents a prime example of chronic inflammation and cancer-inducing bacterial pathogens. The microbe utilizes a remarkable set of virulence factors and strategies to control cellular checkpoints of inflammation and oncogenic signal transduction. This chapter emphasizes on the pathogenicity determinants of H. pylori such as the cytotoxin-associated genes pathogenicity island (cagPAI)-encoded type-IV secretion system (T4SS), effector protein CagA, lipopolysaccharide (LPS) metabolite ADP-glycero-β-D-manno-heptose (ADP-heptose), cytotoxin VacA, serine protease HtrA, and urease, and how they manipulate various key host cell signaling networks in the gastric epithelium. In particular, we highlight the H. pylori-induced disruption of cell-to-cell junctions, pro-inflammatory activities, as well as proliferative, pro-apoptotic and anti-apoptotic responses. Here we review these hijacked signal transduction events and their impact on gastric disease development.

FRA-1 suppresses apoptosis of Helicobacter pylori infected MGC-803 cells

Previous research has demonstrated a correlation between elevated expression of Fos-related antigen 1 (FRA-1) and malignancies. Nevertheless, the role of FRA-1 in Helicobacter pylori infected gastric cancer cells remains vague. Our study aims to investigate whether FRA-1 plays a role in the apoptosis of MGC-803 induced by H. pylori and possible mechanisms. MGC-803 cells were used in vitro to establish a cell model of H. pylori infection. After stimulation with H. pylori, the expression of FRA-1 was increased in MGC-803 cells. H. pylori infection promoted the apoptosis of MGC-803 cells, and led to cell cycle arrest and increased oxidative stress levels. Furthermore, the knockdown of FRA-1 reinforced these changes. H. pylori decreased the expression of Bcl2, Caspase3 and Caspase9, while increased the level of BAX, Cleaved-Caspase3 and Cleaved-Caspase9; in addition, it led to the decrease of major proteins in Ras/Erk and PI3K/AKT signaling pathway. As expected, these changes were augmented by FRA-1 knockdown. Our results demonstrated that high expression of FRA-1 induced by H. pylori suppresses apoptosis in MGC-803 cells which may be regulated by oxidative stress and cycle arrest through caspase family, Ras/Erk and PI3K/AKT signaling pathway.

Xenophagy in cancer

Macroautophagy (herein autophagy) is an intracellular pathway in which cytoplasmic components are captured by double-membrane vesicles (autophagosomes) that eventually fuse with lysosomes to degrade the cargo. Basal levels of autophagy in all eukaryotic cells maintain cellular homeostasis and under conditions of stress, organelles and proteins not essential for survival are degraded. Apart from these functions, cargoes like aggregated proteins, damaged organelles and intracellular pathogens, which are otherwise harmful to cells, are also selectively captured by autophagy and are destined for degradation. In terms of infectious diseases, pathogens are cleared by a specific form of autophagy known as xenophagy. This lysosomal mediated degradation of pathogens also increases the antigen presentation of cells thereby inducing a further immune response. The process of xenophagy provides a broad spectrum of defense mechanism to capture bacterial, viral and protozoan pathogens. However, pathogens have developed ingenious mechanisms to modulate xenophagy to enhance their intracellular survival. Meanwhile, certain pathogens also induce deleterious effects such as chronic inflammation and overexpression of oncogenes in the host system. This over time can increase the susceptibility of the host for tumorigenesis. Hence targeting tumor through anti-microbial mechanisms like xenophagy could be a novel strategy for combinatorial anti-cancer therapy. The recent developments in understanding the role of xenophagy in combating cancer causing pathogens will be discussed in this review.

The effect of Helicobacter pylori on the expression of FRA-1 in gastric epithelial cells and its mechanism

Gastric cancer is a major global health threat and is often related with Helicobacter pylori (H. pylori) infection. FRA-1 is a subunit of the activator protein-1 transcription factor complex, which played a central role in cell proliferation and migration. It has also been implicated in stomach inflammation and malignancy. The present study aimed to clarify the relationship between H. pylori infection and production of FRA-1 in controlling cell proliferation and migration and its molecular mechanisms. Cell proliferation was measured by colony formation assay. Cell migration was monitored by transwell migration assay. Gastric mucosal epithelial cells were treated with FRA-1-specific siRNA with or without H. pylori infection in vitro, and RNA and proteins were extracted. The expression of FRA-1 and indicators in cells was determined by RT-PCR and western blot analysis. β-Catenin and TGF-β activities were then assessed by western blotting and immunofluorescence. The expression of FRA-1 increased after H. pylori infection. Additional analysis identified that knockdown of FRA-1 attenuated the H. pylori-induced proliferative activity and migration of gastric cancer cells. Furthermore, upregulation of FRA-1 by H. pylori led to increase in Wnt/β-Catenin levels and TGF-β dependent signaling events. These results demonstrate that the upregulation of FRA-1 in H. pylori-infected gastric epithelial cells plays a key role in the carcinogenic process.

miR-296-5p suppresses EMT of hepatocellular carcinoma via attenuating NRG1/ERBB2/ERBB3 signaling

BACKGROUND

Accumulation of evidence indicates that miRNAs have crucial roles in the regulation of EMT-associated properties, such as proliferation, migration and invasion. However, the underlying molecular mechanisms are not entirely illustrated. Here, we investigated the role of miR-296-5p in hepatocellular carcinoma (HCC) progression.

METHODS

In vitro cell morphology, proliferation, migration and invasion were compared between HCC cell lines with up- or down-regulation of miR-296-5p. Immunofluorescence and Western blot immunofluorescence assays were used to detect the expression of EMT markers. Bioinformatics programs, luciferase reporter assay and rescue experiments were used to validate the downstream targets of miR-296-5p. Xenograft nude mouse models were established to observe tumor growth and metastasis. Immunohistochemical assays were conducted to study the relationships between miR-296-5p expression and Neuregulin-1 (NRG1)/EMT markers in human HCC samples and mice.

RESULTS

miR-296-5p was prominently downregulated in HCC tissues relative to adjacent normal liver tissues and associated with favorable prognosis. Overexpression of miR-296-5p inhibited EMT along with migration and invasion of HCC cells via suppressing NRG1/ERBB2/ERBB3/RAS/MAPK/Fra-2 signaling in vitro. More importantly, miR-296-5p disrupted intrahepatic and pulmonary metastasis in vivo. NRG1, as a direct target of miR-296-5p, mediates downstream biological responses. In HCC tissues from patients and mice, the levels of miR-296-5p and NRG1 also showed an inverse relationship.

CONCLUSIONS

miR-296-5p inhibited EMT-related metastasis of HCC through NRG1/ERBB2/ERBB3/RAS/MAPK/Fra-2 signaling.

Helicobacter pylori enhances CIP2A expression and cell proliferation via JNK2/ATF2 signaling in human gastric cancer cells

Helicobacter pylori (H. pylori) infection plays an important role in the development of gastric carcinomas. Cancerous inhibitor of protein phosphatase 2A (CIP2A) is a novel human oncoprotein that functions as an important regulator of cell growth and malignant transformation. In the present study, we aimed to investigate the potential mechanisms by which H. pylori upregulates the expression of CIP2A and the functional impact of H. pylori-induced CIP2A in gastric cancer cells. We demonstrated that infection of MKN-45 cells with H. pylori led to a marked increase in the expression of CIP2A at the mRNA and protein levels. H. pylori-induced CIP2A was associated with increased cell proliferation. In addition, H. pylori was found to activate the JNK2 pathway. Importantly, both H. pylori-induced CIP2A production and cell proliferation were partially reversed by inhibition of JNK2 signaling. Similarly, the blockade of H. pylori-induced CIP2A expression by siRNA against CIP2A also inhibited cell proliferation. Thus, H. pylori appears to stimulate the expression of CIP2A and proliferation of gastric cancer cells via JNK2 signaling. These findings suggest that H. pylori-induced upregulation of CIP2A contributes to the development and progression of gastric cancer. Further in vivo studies are warranted to explore the biological role of CIP2A and its interaction with JNK2 signaling in gastric cancer.

Protein kinase C isozymes regulate matrix metalloproteinase-1 expression and cell invasion in Helicobacter pylori infection

BACKGROUND

Protein kinase C (PKC) signalling is often dysregulated in gastric cancer and therefore represents a potential target in cancer therapy. The Gram-negative bacterium Helicobacter pylori, which colonises the human stomach, plays a major role in the development of gastritis, peptic ulcer and gastric adenocarcinoma.

OBJECTIVE

To analyse the role of PKC isozymes as mediators of H pylori-induced pathogenesis.

METHODS

PKC phosphorylation was evaluated by immunoblotting and immunohistochemistry. Gene reporter assays, RT-PCR and invasion assays were performed to assess the role of PKC in the regulation of activator protein-1 (AP-1), matrix metalloproteinase-1 (MMP-1) and the invasion of H pylori-infected epithelial cells.

RESULTS

H pylori induced phosphorylation of PKC isozymes α, δ, θ in AGS cells, which was accompanied by the phosphorylation of PKC substrates, including PKCμ and myristoylated alanine-rich C kinase substrate (MARCKS), in a CagA-independent manner. Phospholipase C, phosphatidylinositol 3-kinase and Ca(2+) were crucial for PKC activation on infection; inhibition of PKC diminished AP-1 induction and, subsequently, MMP-1 expression. Invasion assays confirmed PKC involvement in H pylori-induced MMP-1 secretion. In addition, analysis of biopsies from human gastric mucosa showed increased phosphorylation of PKC in active H pylori gastritis and gastric adenocarcinoma.

CONCLUSION

The targeting of certain PKC isozymes might represent a suitable strategy to interfere with the MMP-1-dependent remodelling of infected tissue and to overcome the invasive behaviour of gastric cancer cells.

Interleukin-8 is the single most up-regulated gene in whole genome profiling of H. pylori exposed gastric epithelial cells

BACKGROUND

The association between Helicobacter pylori infection and upper gastrointestinal disease is well established. However, only a small fraction of H. pylori carriers develop disease, and there are great geographical differences in disease penetrance. The explanation to this enigma lies in the interaction between the bacterium and the host. H. pylori Outer Membrane Phospholipase A (OMPLA) has been suggested to play a role in the virulence of this bacterium. The aim of this study was to profile the most significant cellular pathways and biological processes affected in gastric epithelial cells during 24 h of H. pylori exposure, and to study the inflammatory response to OMPLA⁺ and OMPLA⁻ H. pylori variants.

RESULTS

Interleukin-8 was the most significantly up-regulated gene and appears to play a paramount role in the epithelial cell response to H. pylori infection and in the pathological processes leading to gastric disease. MAPK and NF-kappaB cellular pathways were powerfully activated, but did not seem to explain the impressive IL-8 response. There was marked up-regulation of TP53BP2, whose corresponding protein ASPP2 may interact with H. pylori CagA and cause marked p53 suppression of apoptosis. Other regulators of apoptosis also showed abberant regulation. We also identified up-regulation of several oncogenes and down-regulation of tumor suppressor genes as early as during the first 24 h of infection. H. pylori OMPLA phase variation did not seem to influence the inflammatory epithelial cell gene response in this experiment.

CONCLUSION

In whole genome analysis of the epithelial response to H. pylori exposure, IL-8 demonstrated the most marked up-regulation, and was involved in many of the most important cellular response processes to the infection. There was dysregulation of apoptosis, tumor suppressor genes and oncogenes as early as in the first 24 h of H. pylori infection, which may represent early signs of gastric tumorigenesis. OMPLA⁺/⁻ did not affect the acute inflammatory response to H. pylori.

Human gastrin mRNA expression up-regulated by Helicobacter pylori CagA through MEK/ERK and JAK2-signaling pathways in gastric cancer cells

BACKGROUND

Helicobacter pylori-cytotoxin-associated protein A (CagA) and gastrin are believed to play an important role in gastric carcinogenesis, but their interaction has been incompletely clear.

METHODS

We constructed a eukaryotic expression vector pcDNA3.1/cagA and a luciferase reporter vector pGL/gastrin promoter, and then co-transfected them into gastric cancer AGS and SGC-7901 cells. The two kinds of gastric cancer cells were, respectively, infected with cagA-positive H. pylori NCTC11637, and then the gastrin promoter activity and gastrin mRNA level were detected with a Dual-Luciferase reporter assay system and quantitative reverse transcription polymerase chain reaction (RT-PCR), respectively. Next, after the MEK/ERK and JAK2-signaling pathway inhibitors, U0126 and AG490, were used to treat the two cell lines, or the ERK1 and JAK2 genes were knocked down by siRNAs (small interference RNAs) in the two cell lines, the gastrin promoter activity and gastrin mRNA level were observed again.

RESULTS

The results indicated that CagA could activate the gastrin promoter and up-regulate gastrin mRNA expression in AGS and SGC-7901 cells, but these effects could be inhibited by the inhibitors U0126 and AG490, and the CagA-induced gastrin mRNA expression was down-regulated in the cells whose ERK1 or JAK2 gene was knocked down.

CONCLUSION

Gastrin promoter may be the transcriptional target of CagA, and CagA activates the gastrin promoter to up-regulate gastrin mRNA expression through the MEK/ERK and JAK1-signaling pathway in gastric cancer cells.

Helicobacter pylori induction of eosinophil migration is mediated by the cag pathogenicity island via microbial-epithelial interactions

The host immune response directed against Helicobacter pylori is ineffective in eliminating the organism and strains harboring the cag pathogenicity island augment disease risk. Because eosinophils are a prominent component of H. pylori-induced gastritis, we investigated microbial and host mechanisms through which H. pylori regulates eosinophil migration. Our results indicate that H. pylori increases production of the chemokines CCL2, CCL5, and granulocyte-macrophage colony-stimulating factor by gastric epithelial cells and that these molecules induce eosinophil migration. These events are mediated by the cag pathogenicity island and by mitogen-activated protein kinases, suggesting that eosinophil migration orchestrated by H. pylori is regulated by a virulence-related locus.

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.

Interleukin-33 expression is specifically enhanced in inflamed mucosa of ulcerative colitis

BACKGROUND

Interleukin (IL)-33 is a cytokine belonging to the IL-1 family. IL-33 has been shown to elicit a Th2-like cytokine response in immune cells. In this study, we investigated IL-33 expression in the inflamed mucosa of patients with inflammatory bowel disease (IBD), and characterized the molecular mechanisms responsible for IL-33 expression in human colonic subepithelial myofibroblasts (SEMFs).

METHODS

IL-33 mRNA expression was determined by real-time polymerase chain reaction (PCR). IL-33 expression in the IBD mucosa was evaluated by immunohistochemical methods.

RESULTS

IL-33 mRNA expression was significantly elevated in active lesions from patients with ulcerative colitis (UC), but was not detected in inactive lesions from UC patients or in lesions from patients with either active or inactive Crohn's disease. Colonic SEMFs were identified as a major source of IL-33 in the mucosa. IL-1β and tumor necrosis factor-α (TNF-α) significantly enhanced IL-33 mRNA and protein expression in isolated colonic SEMFs. IL-1β and TNF-α did not affect IL-33 expression in intestinal epithelial cell lines (HT-29 and Caco-2 cells). This IL-1β- and TNF-α-induced IL-33 mRNA expression was mediated by p42/44 mitogen activated protein kinase (MAPK) pathway-dependent activation of nuclear factor (NF)-κB and activator protein (AP)-1.

CONCLUSIONS

IL-33, derived from colonic SEMFs, may play an important role in the pathophysiology of UC.

Helicobacter pylori induction of the gastrin promoter through GC-rich DNA elements

BACKGROUND

Helicobacter pylori (H. pylori) infection has been linked to the development of chronic gastritis, duodenal ulcer disease, and gastric cancer. Helicobacter pylori- infected patients and animal models develop hypergastrinemia, chronic gastritis, and gastric atrophy. Since gastrin is an important regulator of gastric acid secretion and cell growth, H. pylori regulation of this hormone has been implicated in its pathogenesis.

OBJECTIVES

To investigate the effect of H. pylori on gastrin gene expression in mice and of human bacterial isolates on gastrin mRNA expressed in a human cell line.

METHODS

Gastrin mRNA was measured by qRT-PCR in H. pylori-infected mice. H. pylori were co-cultured with AGS cells to study regulation of human gastrin gene expression. Various MAP kinases were implicated in signal transduction from the bacteria using specific inhibitors. Gastrin reporter constructs and gel shift assays were used to map DNA responsive elements.

RESULTS

In addition to an increase in gastrin mRNA in H. pylori-infected mice, H. pylori induced the endogenous human gastrin gene through MAP kinase-dependent signaling but not NFκB-dependent signaling. Activation of gastrin through MAPK signaling did not require CagA or VacA virulence factors. Transfection studies demonstrated that a GC-rich motif mediated H. pylori-induction of the gastrin promoter and that the motif inducibly binds Sp1 and Sp3 transcription factors.

CONCLUSIONS

Direct contact of live H. pylori bacteria with human cells is sufficient to induce gastrin gene expression.

Helicobacter pylori induces ERK-dependent formation of a phospho-c-Fos c-Jun activator protein-1 complex that causes apoptosis in macrophages

Macrophages are essential components of innate immunity, and apoptosis of these cells impairs mucosal defense to microbes. Helicobacter pylori is a gastric pathogen that infects half of the world population and causes peptic ulcer disease and gastric cancer. The host inflammatory response fails to eradicate the organism. We have reported that H. pylori induces apoptosis of macrophages by generation of polyamines from ornithine decarboxylase (ODC), which is dependent on c-Myc as a transcriptional enhancer. We have now demonstrated that expression of c-Myc requires phosphorylation and nuclear translocation of ERK, which results in phosphorylation of c-Fos and formation of a specific activator protein (AP)-1 complex. Electromobility shift assay and immunoprecipitation revealed a previously unrecognized complex of phospho-c-Fos (pc-Fos) and c-Jun in the nucleus. Fluorescence resonance energy transfer demonstrated the interaction of pc-Fos and c-Jun. The capacity of this AP-1 complex to bind to putative AP-1 sequences was demonstrated by oligonucleotide pulldown and fluorescence polarization. Binding of the pc-Fos.c-Jun complex to the c-Myc promoter was demonstrated by chromatin immunoprecipitation. A dominant-negative c-Fos inhibited H. pylori-induced expression of c-Myc and ODC and apoptosis. H. pylori infection of mice induced a rapid infiltration of macrophages into the stomach. Concomitant apoptosis depleted these cells, and this was associated with formation of a pc-Fos.c-Jun complex. Treatment of mice with an inhibitor of ERK phosphorylation attenuated phosphorylation of c-Fos, expression of ODC, and apoptosis in gastric macrophages. A unique AP-1 complex in gastric macrophages contributes to the immune escape of H. pylori.

Helicobacter pylori-induced histone modification, associated gene expression in gastric epithelial cells, and its implication in pathogenesis

Histone modifications are critical in regulating gene expression, cell cycle, cell proliferation, and development. Relatively few studies have investigated whether Helicobacter pylori, the major cause of human gastric diseases, affects histone modification. We therefore investigated the effects of H. pylori infection on histone modifications in a global and promoter-specific manner in gastric epithelial cells. Infection of gastric epithelial cells by wild-type H. pylori induced time- and dose-dependent dephosphorylation of histone H3 at serine 10 (H3 Ser10) and decreased acetylation of H3 lysine 23, but had no effects on seven other specific modifications. Different cag pathogenicity island (PAI)-containing-clinical isolates showed similar abilities to induce H3 Ser10 dephosphorylation. Mutation of cagA, vacA, nonphosphorylateable CagA mutant cagA_EPISA, or disruption of the flagella showed no effects, while deletion of the entire cagPAI restored the H3 Ser10 phosphorylation to control levels. Analysis of 27 cagPAI mutants indicated that the genes that caused H3 Ser10 dephosphorylation were similar to those that were previously found to induce interleukin-8, irrespective of CagA translocation. This effect was independent of ERK or p38 pathways and type I interferon signaling. Additionally, c-Jun and hsp70 gene expression was associated with this histone modification. These results demonstrate that H. pylori alters histone modification and host response via a cagA-, vacA-independent, but cagPAI-dependent mechanisms, which contribute to its persistent infection and pathogenesis.

Predicting virulence of Aeromonas isolates based on changes in transcription of c-jun and c-fos in human tissue culture cells

AIMS

To screen for the virulence potential of Aeromonas isolates based on the change in regulation of c-jun and c-fos in the human intestinal tissue culture cell line Caco-2.

METHODS AND RESULTS

Aeromonas cells were added to Caco-2 cells at a ratio of approx. 1 : 1. After 1-, 2- and 3-h incubation at 37 degrees C, mRNA was extracted from the cells and gene expression of two host genes, c-jun and c-fos, quantified. Aeromonas isolates which were pathogenic in the neonatal mouse model demonstrated up-regulation of c-jun and c-fos compared to avirulent isolates.

CONCLUSIONS

Human cell culture results showed that c-jun and c-fos were predictive of Aeromonas virulence.

SIGNIFICANCE AND IMPACT OF THE STUDY

An Aeromonas relative virulence scale is proposed for use in the testing of Aeromonas drinking water isolates.