Alterations in Helicobacter pylori triggered by contact with gastric epithelial cells

Optimization of Helicobacter pylori Biofilm Formation in In Vitro Conditions Mimicking Stomach

Helicobacter pylori is one of the most common bacterial pathogens worldwide and the main etiological agent of numerous gastric diseases. The frequency of multidrug resistance of H. pylori is growing and the leading factor related to this phenomenon is its ability to form biofilm. Therefore, the establishment of a proper model to study this structure is of critical need. In response to this, the aim of this original article is to validate conditions of the optimal biofilm development of H. pylori in monoculture and co-culture with a gastric cell line in media simulating human fluids. Using a set of culture-based and microscopic techniques, we proved that simulated transcellular fluid and simulated gastric fluid, when applied in appropriate concentrations, stimulate autoaggregation and biofilm formation of H. pylori. Additionally, using a co-culture system on semi-permeable membranes in media imitating the stomach environment, we were able to obtain a monolayer of a gastric cell line with H. pylori biofilm on its surface. We believe that the current model for H. pylori biofilm formation in monoculture and co-culture with gastric cells in media containing host-mimicking fluids will constitute a platform for the intensification of research on H. pylori biofilms in in vitro conditions that simulate the human body.

Toll-like receptor-guided therapeutic intervention of human cancers: molecular and immunological perspectives

Toll-like receptors (TLRs) serve as the body's first line of defense, recognizing both pathogen-expressed molecules and host-derived molecules released from damaged or dying cells. The wide distribution of different cell types, ranging from epithelial to immune cells, highlights the crucial roles of TLRs in linking innate and adaptive immunity. Upon stimulation, TLRs binding mediates the expression of several adapter proteins and downstream kinases, that lead to the induction of several other signaling molecules such as key pro-inflammatory mediators. Indeed, extraordinary progress in immunobiological research has suggested that TLRs could represent promising targets for the therapeutic intervention of inflammation-associated diseases, autoimmune diseases, microbial infections as well as human cancers. So far, for the prevention and possible treatment of inflammatory diseases, various TLR antagonists/inhibitors have shown to be efficacious at several stages from pre-clinical evaluation to clinical trials. Therefore, the fascinating role of TLRs in modulating the human immune responses at innate as well as adaptive levels directed the scientists to opt for these immune sensor proteins as suitable targets for developing chemotherapeutics and immunotherapeutics against cancer. Hitherto, several TLR-targeting small molecules (e.g., Pam3CSK4, Poly (I:C), Poly (A:U)), chemical compounds, phytocompounds (e.g., Curcumin), peptides, and antibodies have been found to confer protection against several types of cancers. However, administration of inappropriate doses of such TLR-modulating therapeutics or a wrong infusion administration is reported to induce detrimental outcomes. This review summarizes the current findings on the molecular and structural biology of TLRs and gives an overview of the potency and promises of TLR-directed therapeutic strategies against cancers by discussing the findings from established and pipeline discoveries.

Strategies adopted by gastric pathogen Helicobacter pylori for a mature biofilm formation: Antimicrobial peptides as a visionary treatment

Enormous efforts in recent past two decades to eradicate the pathogen that has been prevalent in half of the world's population have been problematic. The biofilm formed by Helicobacter pylori provides resistance towards innate immune cells, various combinatorial antibiotics, and human antimicrobial peptides, despite the fact that these all are potent enough to eradicate it in vitro. Biofilm provides the opportunity to secrete various virulence factors that strengthen the interaction between host and pathogen helping in evading the innate immune system and ultimately leading to persistence. To our knowledge, this review is the first of its kind to explain briefly the journey of H. pylori starting with the chemotaxis, the mechanism for selecting the site for colonization, the stress faced by the pathogen, and various adaptations to evade these stress conditions by forming biofilm and the morphological changes acquired by the pathogen in mature biofilm. Furthermore, we have explained the human GI tract antimicrobial peptides and the reason behind the failure of these AMPs, and how encapsulation of Pexiganan-A(MSI-78A) in a chitosan microsphere increases the efficiency of eradication.

ptk2 and mt2a Genes Expression in Gastritis and Gastric Cancer Patients with Helicobacter pylori Infection

BACKGROUND

ptk2 and mt2a genes contribute to the cell cycle during proliferation and apoptosis, respectively. Designing a case-control study including gastric adenocarcinoma and gastritis patients with and without Helicobacter pylori infection would lead to determinate of the correlations between ptk2 and mt2a genes expression with H. pylori infection in gastric antral epithelial cells.

METHODS

Overall, 50 and 30 gastric antral biopsy samples of gastric cancer (case group) and gastritis (control group) patients were included into study, respectively. All biopsy samples were collected considering the exclusion criteria including patients with a history of consumption of tobacco, alcohol, and anti-H. pylori drugs. Each patient group is divided into with and without H. pylori infection to detect cDNA fold changes of ptk2 and mt2a genes by using Real Time RT PCR. Furthermore, the presence of H. pylori virulence genes was detected directly by using specific primers and simple PCR on cDNA synthesized from total RNA of gastric antral biopsy samples.

RESULTS

A negative correlation was revealed between age and clinical manifestations with the ΔCt value of the ptk2 gene (P < 0.05). The H. pylori iceA1/2 and cagE genes revealed positive and negative correlations with the ΔCt value of the ptk2 gene (P < 0.05), respectively. Furthermore, a weak correlation was detectable between H. pylori babA2/B, oipA, and cagY genes and the ΔCt value of the mt2a gene in gastric antral epithelial cells of patients (P < 0.1).

CONCLUSIONS

The results of the current study opened a view for more investigation on the stunning roles of H. pylori infection in clinical outcomes through mt2a and ptk2 gene expression in gastric antral epithelial cells.

Eating Animal Products, a Common Cause of Human Diseases

The human population is plagued by hundreds of infectious agents that cause diseases, and many of these agents can infect a range of wild and domesticated animals as well. In fact, a large proportion of current pathological conditions in humans is caused by our close association with nonhuman animals, some of which we keep as pets, but most of which we raise, prepare as food sources, and ingest. It is well established that most of these diseases are caused by a variety of infectious agents, the most important being bacteria, viruses, prions, and protozoans. In this article, we shall consider these agents and discuss their transmission from various animals and animal products to humans. It is noted that virtually none of these agents are obtained by eating plant-derived products unless the plants are grown and prepared with contaminated water. Consequently, we suggest that Homo sapiens could avoid a significant fraction of the diseases that plague us by shifting to a more vegetarian diet.

The role of transferrin receptor in the Helicobacter pylori pathogenesis; L-ferritin as a novel marker for intestinal metaplasia

Helicobacter pylori growth requirements is a prerequisite to invade gastric epithelium and the process of injury to gastric cells will eventually lead to gastric cancer. The aim of this study is to investigate the effect of iron challenge on the expression of genes involved in iron homeostasis. The presence of Phosphoglucosamine mutase (glmM), cytotoxin-associated gene A (cagA) and vacuolating cytotoxin A (vacA) genes and mRNA expression of Iron Regulatory Protein 2 (IRP2), Transferrin Receptor (TFRC) and Ferritin Light Chain (FTL) genes in samples of 28 normal gastric mucosa, 33 chronic gastritis, 29 gastritis with intestinal metaplasia, 29 intestinal type adenocarcinoma patients were examined by real-time PCR. Immunohistochemistry was used to analyze cellular localization and protein levels. In the all H. pylori positive tissues, particularly in the basal regions of foveolar cells, TFRC was overexpressed (P < 0.05), and regardless of the H. pylori infection, FTL was overexpressed in all patient, exclusively in metaplastic glandular cells (P < 0.05). Furthermore, overexpression of IRP2 was associated with H. pylori positive chronic gastritis and intestinal metaplasia (P < 0.05). Our findings confirm the role of transferrin receptor in H. pylori attachment into the gastric mucosa to capture iron. Overexpression of FTL gene in metaplastic cells could be considered as a research background to investigate the role of this gene in the differentiation of gastric cells into intestinal metaplasia. In addition, this gene could be suggested as a diagnostic marker to be included among the other markers routinely performed by clinical diagnostic laboratories.

Outer inflammatory protein a (OipA) of Helicobacter pylori is regulated by host cell contact and mediates CagA translocation and interleukin-8 response only in the presence of a functional cag pathogenicity island type IV secretion system

OipA is a phase-variable virulence factor of Helicobacter pylori. Mutations in oipA to turn the gene phase on in a cag pathogenicity island (PAI)-negative strain of H. pylori (J68) or phase off in a cag PAI-positive strain (26695) demonstrated that phase on oipA alleles in both strains had both increased oipA mRNA and human gastric adenocarcinoma (AGS) cell adherence compared to isogenic oipA phase off mutants. An oipA phase off mutant of H. pylori 26695 demonstrated decreased IL-8 secretion by AGS cells and failure to translocate the cag PAI effector CagA. Increased attachment by OipA expressing cag PAI-negative H. pylori J68 failed to alter secreted IL-8 levels. Thus, OipA is necessary but not sufficient for the induction of IL-8; however, it is necessary for translocation of the oncoprotein CagA. Perhaps the nearly invariant phase on status of oipA alleles among cag PAI-positive H. pylori isolates relates to the role of this outer membrane protein in effective translocation of CagA. oipA mRNA comparisons between AGS cell-adherent and non-adherent H. pylori 26695 revealed significantly greater levels in the adherent cells. This may allow H. pylori to adapt to conditions of host cell contact by altering expression of this virulence factor.

KCTD5 and Ubiquitin Proteasome Signaling Are Required for Helicobacter pylori Adherence

In order to establish infection, bacterial pathogens modulate host cellular processes by using virulence factors, which are delivered from the bacteria to the host cell leading to cellular reprogramming. In this context, several pathogens regulate the ubiquitin proteasome system in order to regulate the cellular effectors required for their successful colonization and persistance. In this study, we investigated how Helicobacter pylori affect the ubiquitination of the host proteins to achieve the adherence to the cells, using AGS gastric epithelial cells cultured with H. pylori strains, H. pylori 26695 and two isogenic mutants H. pylori cag::cat and vacA::apha3, to characterize the ability of H. pylori to reprogram the ubiquitin proteasome systems. The infection assays suggest that the ubiquitination of the total proteins does not change when cells were co-culture with H. pylori. We also found that the proteasome activity is necessary for H. pylori adhesion to AGS cells and the adherence increases when the level of KCTD5, an adaptor of Cullin-3, decrease. Moreover, we found that KCTD5 is ubiquitinated and degraded by the proteasome system and that CagA and VacA played no role on reducing KCTD5 levels. Furthermore, H. pylori impaired KCTD5 ubiquitination and did not increase global proteasome function. These results suggest that H. pylori affect the ubiquitin-proteasome system (UPS) to facilitate the adhesion of this microorganism to establish stable colonization in the gastric epithelium and improve our understanding of how H. pylori hijack host systems to establish the adherence.

The Helicobacter pylori Autotransporter ImaA Tempers the Bacterium's Interaction with α5β1 Integrin

The human pathogen Helicobacter pylori uses the host receptor α₅β₁ integrin to trigger inflammation in host cells via its cag pathogenicity island (cag PAI) type IV secretion system (T4SS). Here, we report that the H. pylori ImaA protein (HP0289) decreases the action of the cag PAI T4SS via tempering the bacterium's interaction with α₅β₁ integrin. Previously, imaA-null mutants were found to induce an elevated inflammatory response that was dependent on the cag PAI T4SS; here we extend those findings to show that the elevated response is independent of the CagA effector protein. To understand how ImaA could be affecting cag PAI T4SS activity at the host cell interface, we utilized the Phyre structural threading program and found that ImaA has a region with remote homology to bacterial integrin-binding proteins. This region was required for ImaA function. Unexpectedly, we observed that imaA mutants bound higher levels of α₅β₁ integrin than wild-type H. pylori, an outcome that required the predicted integrin-binding homology region of ImaA. Lastly, we report that ImaA directly affected the amount of host cell β1 integrin but not other cellular integrins. Our results thus suggest a model in which H. pylori employs ImaA to regulate interactions between integrin and the T4SS and thus alter the host inflammatory strength.

Patterns of Adherence of Helicobacter pylori Clinical Isolates to Epithelial Cells, and its Association with Disease and with Virulence Factors

BACKGROUND AND AIM

Adherence to the gastric epithelium is one of the most important steps of Helicobacter pylori to remain and cause disease. The aim of this study was to analyze whether H. pylori isolates from patients with different gastroduodenal diseases present differences in the pattern of adherence to gastric epithelial cells (AGS), in the ability to induce IL-8, and in the presence of virulence genes.

METHODS

We tested 75 H. pylori strains isolated from nonatrophic gastritis, gastric cancer, and duodenal ulcer patients. The adhesion pattern and IL-8 induction were determined in AGS cells, and invasion of AGS cells was studied using a gentamicin protection assay. The IL-8 levels induced were determined by ELISA.

RESULTS

Helicobacter pylori strains presented diffuse adherence (DA) and localized (LA) adherence patterns, similar to those described for enteropathogenic E. coli (EPEC), were observed in AGS cells. A DA pattern was observed in 57% and LA in 43% of the strains, and DA was more frequent in isolates from patients with gastric cancer (p = 0.044). Strains with a LA pattern induced higher levels of IL-8 (p = 0.042) in AGS cells.

CONCLUSION

The adherence pattern was not associated with neither invasiveness nor with the presence of virulence genes. Our study shows that H. pylori strains present adherence patterns to AGS cells resembling those observed in EPEC and that these patterns may be associated with disease and with activity on AGS cells.

Coordination of Candida albicans Invasion and Infection Functions by Phosphoglycerol Phosphatase Rhr2

The Candida albicans RHR2 gene, which specifies a glycerol biosynthetic enzyme, is required for biofilm formation in vitro and in vivo. Prior studies indicate that RHR2 is ultimately required for expression of adhesin genes, such as ALS1. In fact, RHR2 is unnecessary for biofilm formation when ALS1 is overexpressed from an RHR2-independent promoter. Here, we describe two additional biological processes that depend upon RHR2: invasion into an abiotic substrate and pathogenicity in an abdominal infection model. We report here that abiotic substrate invasion occurs concomitantly with biofilm formation, and a screen of transcription factor mutants indicates that biofilm and hyphal formation ability correlates with invasion ability. However, analysis presented here of the rhr2Δ/Δ mutant separates biofilm formation and invasion. We found that an rhr2Δ/Δ mutant forms a biofilm upon overexpression of the adhesin gene ALS1 or the transcription factor genes BRG1 or UME6. However, the biofilm-forming strains do not invade the substrate. These results indicate that RHR2 has an adhesin-independent role in substrate invasion, and mathematical modeling argues that RHR2 is required to generate turgor. Previous studies have shown that abdominal infection by C. albicans has two aspects: infection of abdominal organs and persistence in abscesses. We report here that an rhr2Δ/Δ mutant is defective in both of these infection phenotypes. We find here that overexpression of ALS1 in the mutant restores infection of organs, but does not improve persistence in abscesses. Therefore, RHR2 has an adhesin-independent role in abdominal infection, just as it does in substrate invasion. This report suggests that RHR2, through glycerol synthesis, coordinates adherence with host- or substrate-interaction activities that enable proliferation of the C. albicans population.

High resolution electron microscopy of the Helicobacter pylori Cag type IV secretion system pili produced in varying conditions of iron availability

Helicobacter pylori is a helical-shaped, gram negative bacterium that colonizes the human gastric niche of half of the human population. H. pylori is the primary cause of gastric cancer, the second leading cause of cancer-related deaths worldwide. One virulence factor that has been associated with increased risk of gastric disease is the Cag-pathogenicity island, a 40-kb region within the chromosome of H. pylori that encodes a type IV secretion system and the cognate effector molecule, CagA. The Cag-T4SS is responsible for translocating CagA and peptidoglycan into host epithelial cells. The activity of the Cag-T4SS results in numerous changes in host cell biology including upregulation of cytokine expression, activation of proinflammatory pathways, cytoskeletal remodeling, and induction of oncogenic cell-signaling networks. The Cag-T4SS is a macromolecular machine comprised of sub-assembly components spanning the inner and outer membrane and extending outward from the cell into the extracellular space. The extracellular portion of the Cag-T4SS is referred to as the "pilus". Numerous studies have demonstrated that the Cag-T4SS pili are formed at the host-pathogen interface(. However, the environmental features that regulate the biogenesis of this important organelle remain largely obscure. Recently, we reported that conditions of low iron availability increased the Cag-T4SS activity and pilus biogenesis. Here we present an optimized protocol to grow H. pylori in varying conditions of iron availability prior to co-culture with human gastric epithelial cells. Further, we present the comprehensive protocol for visualization of the hyper-piliated phenotype exhibited in iron restricted conditions by high resolution scanning electron microscopy analyses.

The host protein calprotectin modulates the Helicobacter pylori cag type IV secretion system via zinc sequestration

Transition metals are necessary for all forms of life including microorganisms, evidenced by the fact that 30% of all proteins are predicted to interact with a metal cofactor. Through a process termed nutritional immunity, the host actively sequesters essential nutrient metals away from invading pathogenic bacteria. Neutrophils participate in this process by producing several metal chelating proteins, including lactoferrin and calprotectin (CP). As neutrophils are an important component of the inflammatory response directed against the bacterium Helicobacter pylori, a major risk factor for gastric cancer, it was hypothesized that CP plays a role in the host response to H. pylori. Utilizing a murine model of H. pylori infection and gastric epithelial cell co-cultures, the role CP plays in modifying H. pylori -host interactions and the function of the cag Type IV Secretion System (cag T4SS) was investigated. This study indicates elevated gastric levels of CP are associated with the infiltration of neutrophils to the H. pylori-infected tissue. When infected with an H. pylori strain harboring a functional cag T4SS, calprotectin-deficient mice exhibited decreased bacterial burdens and a trend toward increased cag T4SS -dependent inflammation compared to wild-type mice. In vitro data demonstrate that culturing H. pylori with sub-inhibitory doses of CP reduces the activity of the cag T4SS and the biogenesis of cag T4SS-associated pili in a zinc-dependent fashion. Taken together, these data indicate that zinc homeostasis plays a role in regulating the proinflammatory activity of the cag T4SS.

Xenophagy in Helicobacter pylori- and Epstein-Barr virus-induced gastric cancer

Helicobacter pylori and Epstein-Barr virus (EBV) account for roughly 80% and 10%, respectively, of gastric carcinomas worldwide. Autophagy is an evolutionarily conserved and intricately regulated cellular process that involves the sequestration of cytoplasmic proteins and organelles into double-membrane autophagosomes that eventually fuse with lysosomes for degradation of the engulfed content. Emerging evidence indicates that xenophagy, a form of selective autophagy, plays a crucial role in the pathogenesis of H. pylori- and EBV-induced gastric cancer. Xenophagy specifically recognizes intracellular H. pylori and EBV and physically targets these pathogens to the autophagosomal-lysosomal pathway for degradation. In this connection, H. pylori or EBV-induced dysregulation of autophagy may be causally linked to gastric tumourigenesis and therefore can be exploited as therapeutic targets. This review will discuss how H. pylori and EBV infection activate autophagy and how these pathogens evade recognition and degradation by the autophagic pathway. Elucidating the molecular aspects of H. pylori- and EBV-induced autophagy will help us better understand the pathogenesis of gastric cancer and promote the development of autophagy modulators as antimicrobial agents.

In depth analysis of the Helicobacter pylori cag pathogenicity island transcriptional responses

The severity of symptoms elicited by the widespread human pathogen Helicobacter pylori is strongly influenced by the genetic diversity of the infecting strain. Among the most important pathogen factors that carry an increased risk for gastric cancer are specific genotypes of the cag pathogenicity island (cag-PAI), encoding a type IV secretion system (T4SS) responsible for the translocation of the CagA effector oncoprotein. To date, little is known about the regulatory events important for the expression of a functional cag-T4SS. Here we demonstrate that the cag-PAI cistrons are subjected to a complex network of direct and indirect transcriptional regulations. We show that promoters of cag operons encoding structural T4SS components display homogeneous transcript levels, while promoters of cag operons encoding accessory factors vary considerably in their basal transcription levels and responses. Most cag promoters are transcriptionally responsive to growth-phase, pH and other stress-factors, although in many cases in a pleiotropic fashion. Interestingly, transcription from the Pcagζ promoter controlling the expression of transglycolase and T4SS stabilizing factors, is triggered by co-culture with a gastric cell line, providing an explanation for the increased formation of the secretion system observed upon bacterial contact with host cells. Finally, we demonstrate that the highly transcribed cagA oncogene is repressed by iron limitation through a direct apo-Fur regulation mechanism. Together the results shed light on regulatory aspects of the cag-PAI, which may be involved in relevant molecular and etiological aspects of H. pylori pathogenesis.

Genes required for assembly of pili associated with the Helicobacter pylori cag type IV secretion system

Helicobacter pylori causes numerous alterations in gastric epithelial cells through processes that are dependent on activity of the cag type IV secretion system (T4SS). Filamentous structures termed "pili" have been visualized at the interface between H. pylori and gastric epithelial cells, and previous studies suggested that pilus formation is dependent on the presence of the cag pathogenicity island (PAI). Thus far, there has been relatively little effort to identify specific genes that are required for pilus formation, and the role of pili in T4SS function is unclear. In this study, we selected 7 genes in the cag PAI that are known to be required for T4SS function and investigated whether these genes were required for pilus formation. cagT, cagX, cagV, cagM, and cag3 mutants were defective in both T4SS function and pilus formation; complemented mutants regained T4SS function and the capacity for pilus formation. cagY and cagC mutants were defective in T4SS function but retained the capacity for pilus formation. These results define a set of cag PAI genes that are required for both pilus biogenesis and T4SS function and reveal that these processes can be uncoupled in specific mutant strains.

Host cell contact induces fur-dependent expression of virulence factors CagA and VacA in Helicobacter pylori

BACKGROUND

Helicobacter pylori, a gram negative bacterium, colonizes the stomach in a majority of the world population. The two major virulence factors of H. pylori VacA and CagA, thought to be associated with chronic inflammation and disease, have been extensively studied, but the regulation of the expression of these virulence genes in H. pylori remains poorly understood.

METHODS

qRT-PCR was performed to quantify gene expression in unadhered and AGS-adhered H. pylori. Δfur mutant was constructed by splicing by overlap extension PCR and allelic exchange.

RESULTS

Adherence of H. pylori to the gastric epithelial cell line AGS strongly induces the expression of both cagA and vacA. Induction of cagA and vacA in the AGS cell-adhered H. pylori Δfur mutant strain was consistently lower than in the adhered parent strain. However, expression of the genes was similar between the wild-type and Δfur mutant strains in the unadhered state, suggesting that Fur has a role in the upregulation of cagA and vacA expression, especially in AGS-adhered H. pylori. Consistent with these results, microscopic observations revealed that infection of AGS cells with H. pylori Δfur mutant strain produced much less damage as compared to that produced by the wild-type H. pylori strain.

CONCLUSIONS

These results suggested that cagA and vacA gene expression is upregulated in H. pylori, especially by host cell contact, and Fur has a role in the upregulation.

Rapid interaction of Helicobacter pylori with microvilli of the polar human gastric epithelial cell line NCI-N87

Infection with Helicobacter pylori results often in chronic gastritis, gastric ulcers or even gastric tumor development. Little is known about the initial interaction between gastric epithelial cells and H. pylori. The aim of the present study was to analyze the initial host contact to the bacteria. Monolayers of the human gastric epithelial cell line NCI-N87 grown on porous membranes were used and the apical side of the epithelium was exposed to the H. pylori wild-type strain P1 for 1 hr. Many epithelial cells were colonized by bacteria within the period of 60 min. Using scanning electron microscopy we detected that the bacteria were in close contact with the epithelia via microvilli. Further, transmission electron microscopy of the contact sites revealed no difference in the morphology of the microvilli in comparison to those not attached to the bacteria. The present study demonstrates the importance of microvilli on apical epithelial cells during the initial contact of the host by colonizing H. pylori. Anat Rec, 296:1800–1805, 2013. © 2013 The Authors. The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology published by Wiley Periodicals, Inc. on behalf of the American Association of Anatomists.