Downregulation of CXCR1 and CXCR2 expression on human neutrophils by Helicobacter pylori: a new pathomechanism in H. pylori infection?

Role of chemokine receptors in gastrointestinal mucosa

Chemokine receptors are essential for the immune response in the oral and gut mucosa. The gastrointestinal mucosa is characterized by the presence of immune populations because it is susceptible to inflammatory and infectious diseases, necessitating immune surveillance. Chemokine receptors are expressed on immune cells and play a role in gastrointestinal tissue-homing, although other non-immune cells also express them for various biological functions. CCR9, CXCR3 and CXCR6 play an important role in the T cell response in inflammatory and neoplastic conditions of the gastrointestinal mucosa. However, CXCR6 could also be found in gastric cancer cells, highlighting the different roles of chemokine receptors in different pathologies. On the other hand, CCR4 and CCR8 are critical for Treg migration in gastrointestinal tissues, correlating with poor prognosis in mucosal cancers. Other chemokine receptors are also important in promoting myeloid infiltration with context-dependent roles. Further, CXCR4 and CXCR7 are also present in gastrointestinal tumor cells and are known to stimulate proliferation, migration, and invasion into other tissues, among other pro-tumorigenic functions. Determining the processes underlying mucosal immunity and creating tailored therapeutic approaches for gastrointestinal diseases requires an understanding of the complex interactions that occur between chemokine receptors and their ligands in these mucosal tissues.

Outer Membrane Vesicles (OMVs) as Biomedical Tools and Their Relevance as Immune-Modulating Agents against H. pylori Infections: Current Status and Future Prospects

Outer membrane vesicles (OMVs) are lipid-membrane-bounded nanoparticles that are released from Gram-negative bacteria via vesiculation of the outer membrane. They have vital roles in different biological processes and recently, they have received increasing attention as possible candidates for a broad variety of biomedical applications. In particular, OMVs have several characteristics that enable them to be promising candidates for immune modulation against pathogens, such as their ability to induce the host immune responses given their resemblance to the parental bacterial cell. Helicobacter pylori (H. pylori) is a common Gram-negative bacterium that infects half of the world's population and causes several gastrointestinal diseases such as peptic ulcer, gastritis, gastric lymphoma, and gastric carcinoma. The current H. pylori treatment/prevention regimens are poorly effective and have limited success. This review explores the current status and future prospects of OMVs in biomedicine with a special focus on their use as a potential candidate in immune modulation against H. pylori and its associated diseases. The emerging strategies that can be used to design OMVs as viable immunogenic candidates are discussed.

Helicobacter pylori Immune Response in Children Versus Adults

H. pylori is perhaps the most prevalent human pathogen worldwide and infects almost half of the world's population. Despite the decreasing prevalence of infection overall, it is significant in developing countries. Most infections are acquired in childhood and persist for a lifetime unless treated. Children are often asymptomatic and often develop a tolerogenic immune response that includes T regulatory cells and their products, immunosuppressive cytokines, such as interleukin (IL)-10, and transforming growth factor-β (TGF-β). This contrasts to the gastric immune response seen in H. pylori-infected adults, where the response is mainly inflammatory, with predominant Th1 and Th17 cells, as well as, inflammatory cytokines, such as TNF-α, IFN-γ, IL-1, IL-6, IL-8, and IL-17. Therefore, compared to adults, infected children generally have limited gastric inflammation and peptic ulcer disease. H. pylori surreptitiously subverts immune defenses to persist in the human gastric mucosa for decades. The chronic infection might result in clinically significant diseases in adults, such as peptic ulcer disease, gastric adenocarcinoma, and mucosa-associated lymphoid tissue lymphoma. This review compares the infection in children and adults and highlights the H. pylori virulence mechanisms responsible for the pathogenesis and immune evasion.

Evodiamine Inhibits Helicobacter pylori Growth and Helicobacter pylori-Induced Inflammation

Helicobacter pylori (H. pylori) classified as a class I carcinogen by the World Health Organization (WHO) plays an important role in the progression of chronic gastritis and the development of gastric cancer. A major bioactive component of Evodia rutaecarpa, evodiamine, has been known for its anti-bacterial effect and anti-cancer effects. However, the inhibitory effect of evodiamine against H. pylori is not yet known and the inhibitory mechanisms of evodiamine against gastric cancer cells are yet to be elucidated concretely. In this study, therefore, anti-bacterial effect of evodiamine on H. pylori growth and its inhibitory mechanisms as well as anti-inflammatory effects and its mechanisms of evodiamine on H. pylori-induced inflammation were investigated in vitr. Results of this study showed the growth of the H. pylori reference strains and clinical isolates were inhibited by evodiamine. It was considered one of the inhibitory mechanisms that evodiamine downregulated both gene expressions of replication and transcription machineries of H. pylori. Treatment of evodiamine also induced downregulation of urease and diminished translocation of cytotoxin-associated antigen A (CagA) and vacuolating cytotoxin A (VacA) proteins into gastric adenocarcinoma (AGS) cells. This may be resulted from the reduction of CagA and VacA expressions as well as the type IV secretion system (T4SS) components and secretion system subunit protein A (SecA) protein which are involved in translocation of CagA and VacA into host cells, respectively. In particular, evodiamine inhibited the activation of signaling proteins such as the nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) and the mitogen-activated protein kinase (MAPK) pathway induced by H. pylori infection. It consequently might contribute to reduction of interleukin (IL)-8 production in AGS cells. Collectively, these results suggest anti-bacterial and anti-inflammatory effects of evodiamine against H. pylori.

Neutrophil chemoattractant receptors in health and disease: double-edged swords

Neutrophils are frontline cells of the innate immune system. These effector leukocytes are equipped with intriguing antimicrobial machinery and consequently display high cytotoxic potential. Accurate neutrophil recruitment is essential to combat microbes and to restore homeostasis, for inflammation modulation and resolution, wound healing and tissue repair. After fulfilling the appropriate effector functions, however, dampening neutrophil activation and infiltration is crucial to prevent damage to the host. In humans, chemoattractant molecules can be categorized into four biochemical families, i.e., chemotactic lipids, formyl peptides, complement anaphylatoxins and chemokines. They are critically involved in the tight regulation of neutrophil bone marrow storage and egress and in spatial and temporal neutrophil trafficking between organs. Chemoattractants function by activating dedicated heptahelical G protein-coupled receptors (GPCRs). In addition, emerging evidence suggests an important role for atypical chemoattractant receptors (ACKRs) that do not couple to G proteins in fine-tuning neutrophil migratory and functional responses. The expression levels of chemoattractant receptors are dependent on the level of neutrophil maturation and state of activation, with a pivotal modulatory role for the (inflammatory) environment. Here, we provide an overview of chemoattractant receptors expressed by neutrophils in health and disease. Depending on the (patho)physiological context, specific chemoattractant receptors may be up- or downregulated on distinct neutrophil subsets with beneficial or detrimental consequences, thus opening new windows for the identification of disease biomarkers and potential drug targets.

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

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

Mechanisms of Inflammasome Signaling, microRNA Induction and Resolution of Inflammation by Helicobacter pylori

Inflammasome-controlled transcription and subsequent cleavage-mediated activation of mature IL-1β and IL-18 cytokines exemplify a crucial innate immune mechanism to combat intruding pathogens. Helicobacter pylori represents a predominant persistent infection in humans, affecting approximately half of the population worldwide, and is associated with the development of chronic gastritis, peptic ulcer disease, and gastric cancer. Studies in knockout mice have demonstrated that the pro-inflammatory cytokine IL-1β plays a central role in gastric tumorigenesis. Infection by H. pylori was recently reported to stimulate the inflammasome both in cells of the mouse and human immune systems. Using mouse models and in vitro cultured cell systems, the bacterial pathogenicity factors and molecular mechanisms of inflammasome activation have been analyzed. On the one hand, it appears that H. pylori-stimulated IL-1β production is triggered by engagement of the immune receptors TLR2 and NLRP3, and caspase-1. On the other hand, microRNA hsa-miR-223-3p is induced by the bacteria, which controls the expression of NLRP3. This regulating effect by H. pylori on microRNA expression was also described for more than 60 additionally identified microRNAs, indicating a prominent role for inflammatory and other responses. Besides TLR2, TLR9 becomes activated by H. pylori DNA and further TLR10 stimulated by the bacteria induce the secretion of IL-8 and TNF, respectively. Interestingly, TLR-dependent pathways can accelerate both pro- and anti-inflammatory responses during H. pylori infection. Balancing from a pro-inflammation to anti-inflammation phenotype results in a reduction in immune attack, allowing H. pylori to persistently colonize and to survive in the gastric niche. In this chapter, we will pinpoint the role of H. pylori in TLR- and NLRP3 inflammasome-dependent signaling together with the differential functions of pro- and anti-inflammatory cytokines. Moreover, the impact of microRNAs on H. pylori-host interaction will be discussed, and its role in resolution of infection versus chronic infection, as well as in gastric disease development.

Immune response and immune escape mechanism in Helicobacter pylori infection

Helicobacter pylori (H. pylori) is a Gram-negative bacterium which is parasitic on the surface of the gastric mucosa, and it is a causative agent in the development of chronic gastritis, gastric and duodenal peptic ulcer, gastric adenocarcinoma, and lymphoid tissue lymphoma associated with the gastric mucosa. After H. pylori infection, the bacterium is first recognized by the pattern recognition receptors of immune cells, which in turn causes the innate immune and adaptive immune responses, but these responses are usually insufficient to eliminate bacterial infections. H. pylori can evade the identification and clearance by the immune system by modifying and attenuating the immunogenicity of its pathogen-associated molecular patterns, regulating the immune responses of innate immune cells and T cells, and leading to persistent infection. A thorough understanding of the immune response and immune escape mechanism in H. pylori infection is of great significance for eliminating H. pylori infection and controlling the occurrence of H. pylori infection-related diseases.

Systems-wide analyses of mucosal immune responses to Helicobacter pylori at the interface between pathogenicity and symbiosis

Helicobacter pylori is the dominant member of the gastric microbiota in over half of the human population of which 5-15% develop gastritis or gastric malignancies. Immune responses to H. pylori are characterized by mixed T helper cell, cytotoxic T cell and NK cell responses. The presence of Tregs is essential for the control of gastritis and together with regulatory CX3CR1+ mononuclear phagocytes and immune-evasion strategies they enable life-long persistence of H. pylori. This H. pylori-induced regulatory environment might contribute to its cross-protective effect in inflammatory bowel disease and obesity. Here we review host-microbe interactions, the development of pro- and anti-inflammatory immune responses and how the latter contribute to H. pylori's role as beneficial member of the gut microbiota. Furthermore, we present the integration of existing and new data into a computational/mathematical model and its use for the investigation of immunological mechanisms underlying initiation, progression and outcomes of H. pylori infection.

Resolvins Decrease Oxidative Stress Mediated Macrophage and Epithelial Cell Interaction through Decreased Cytokine Secretion

Background

Inflammation is a key hallmark of ALI and is mediated through ungoverned cytokine signaling. One such cytokine, interleukin-1beta (IL-1β) has been demonstrated to be the most bioactive cytokine in ALI patients. Macrophages are the key players responsible for IL-1β secretion into the alveolar space. Following the binding of IL-1β to its receptor, “activated” alveolar epithelial cells show enhanced barrier dysfunction, adhesion molecule expression, cytokine secretion, and leukocyte attachment. More importantly, it is an important communication molecule between the macrophage and alveolar epithelium. While the molecular determinants of this inflammatory event have been well documented, endogenous resolution processes that decrease IL-1β secretion and resolve alveolar epithelial cell activation and tissue inflammation have not been well characterized. Lipid mediator Aspirin-Triggered Resolvin D1 (AT-RvD1) has demonstrated potent pro-resolutionary effects in vivo models of lung injury; however, the contribution of the alveoli to the protective benefits of this molecule has not been well documented. In this study, we demonstrate that AT-RvD1 treatment lead to a significant decrease in oxidant induced macrophage IL-1β secretion and production, IL-1β-mediated cytokine secretion, adhesion molecule expression, leukocyte adhesion and inflammatory signaling.

Methods

THP-1 macrophages were treated with hydrogen peroxide and extracellular ATP in the presence or absence of AT-RvD1 (1000–0.1 nM). A549 alveolar-like epithelial cells were treated with IL-1β (10 ng/mL) in the presence or absence of AT-RvD1 (0.1 μM). Following treatment, cell lysate and cell culture supernatants were collected for Western blot, qPCR and ELISA analysis of pro-inflammatory molecules. Functional consequences of IL-1β induced alveolar epithelial cell and macrophage activation were also measured following treatment with IL-1β ± AT-RvD1.

Results

Results demonstrate that macrophages exposed to H₂O₂ and ATP in the presence of resolvins show decreased IL-1β production and activity. A549 cells treated with IL-1β in the presence of AT-RvD1 show a reduced level of proinflammatory cytokines IL-6 and IL-8. Further, IL-1β-mediated adhesion molecule expression was also reduced with AT-RvD1 treatment, which was correlated with decreased leukocyte adhesion. AT-RvD1 treatment demonstrated reduced MAP-Kinase signaling. Taken together, our results demonstrate AT-RvD1 treatment reduced IL-1β-mediated alveolar epithelial cell activation. This is a key step in unraveling the protective effects of resolvins, especially AT-RvD1, during injury.

Immune evasion strategies used by Helicobacter pylori

Helicobacter pylori (H. pylori) is perhaps the most ubiquitous and successful human pathogen, since it colonizes the stomach of more than half of humankind. Infection with this bacterium is commonly acquired during childhood. Once infected, people carry the bacteria for decades or even for life, if not treated. Persistent infection with this pathogen causes gastritis, peptic ulcer disease and is also strongly associated with the development of gastric cancer. Despite induction of innate and adaptive immune responses in the infected individual, the host is unable to clear the bacteria. One widely accepted hallmark of H. pylori is that it successfully and stealthily evades host defense mechanisms. Though the gastric mucosa is well protected against infection, H. pylori is able to reside under the mucus, attach to gastric epithelial cells and cause persistent infection by evading immune responses mediated by host. In this review, we discuss how H. pylori avoids innate and acquired immune response elements, uses gastric epithelial cells as mediators to manipulate host T cell responses and uses virulence factors to avoid adaptive immune responses by T cells to establish a persistent infection. We also discuss in this review how the genetic diversity of this pathogen helps for its survival.

The NOD-like receptor signalling pathway in Helicobacter pylori infection and related gastric cancer: a case-control study and gene expression analyses

Background

Currently, it is well established that cancer arises in chronically inflamed tissue. A number of NOD-like receptors (NLRs) form inflammasomes, intracellular multiprotein complexes critical for generating mature pro-inflammatory cytokines (IL-1β and IL-18). As chronic inflammation of the gastric mucosa is a consequence of Helicobacter pylori infection, we investigated the role of genetic polymorphisms and expression of genes involved in the NLR signalling pathway in H. pylori infection and related gastric cancer (GC).

Materials and Methods

Fifty-one genetic polymorphisms were genotyped in 310 ethnic Chinese (87 non-cardia GC cases and 223 controls with functional dyspepsia). In addition, gene expression of 84 molecules involved in the NLR signalling pathway was assessed in THP-1 cells challenged with two H. pylori strains, GC026 (GC) and 26695 (gastritis).

Results

CARD8-rs11672725, NLRP3-rs10754558, NLRP3-rs4612666, NLRP12-rs199475867 and NLRX1-rs10790286 showed significant associations with GC. On multivariate analysis, CARD8-rs11672725 remained a risk factor (OR: 4.80, 95% CI: 1.39–16.58). Further, NLRP12-rs2866112 increased the risk of H. pylori infection (OR: 2.13, 95% CI: 1.22–3.71). Statistical analyses assessing the joint effect of H. pylori infection and the selected polymorphisms revealed strong associations with GC (CARD8, NLRP3, CASP1 and NLRP12 polymorphisms). In gene expression analyses, five genes encoding NLRs were significantly regulated in H. pylori-challenged cells (NLRC4, NLRC5, NLRP9, NLRP12 and NLRX1). Interestingly, persistent up-regulation of NFKB1 with simultaneous down-regulation of NLRP12 and NLRX1 was observed in H. pylori GC026-challenged cells. Further, NF-κB target genes encoding pro-inflammatory cytokines, chemokines and molecules involved in carcinogenesis were markedly up-regulated in H. pylori GC026-challenged cells.

Conclusions

Novel associations between polymorphisms in the NLR signalling pathway (CARD8, NLRP3, NLRP12, NLRX1, and CASP1) and GC were identified in Chinese individuals. Our genetic polymorphisms and gene expression results highlight the relevance of the NLR signalling pathway in gastric carcinogenesis and its close interaction with NF-κB.

Upregulation of C-X-C chemokine receptor type 1 expression is associated with late-stage gastric adenocarcinoma

Chemokine receptors play multiple roles in the development and progression of various tumor types. The aim of this study was to examine C-X-C chemokine receptor type 1 (CXCR1) protein expression in gastric adenocarcinoma and to investigate the clinical implications of CXCR1 upregulation. Expression of CXCR1 protein in 83 specimens of sporadic gastric adenocarcinoma and their corresponding non-neoplastic mucosa obtained by gastrectomy was assayed using immunohistochemistry. The intensity of immunostaining in tumor tissue was considered strong when tumor tissue staining was more intense than in the corresponding non-neoplastic mucosa; the intensity was null when staining was weaker in the tumor than in the corresponding non-neoplastic mucosa; and the intensity was weak when staining was similar in both tissues. Microvascular density in tumor tissue and its corresponding non-neoplastic mucosa was measured using monoclonal antibody against CD34. A strong correlation was observed between elevated CXCR1 protein expression and tumor stage (P<0.05). T stage, N stage and overall stage positively correlated with CXCR1 protein expression. Microvascular density was higher in tumors with strong CXCR1 protein expression, but the correlation with CXCR1 was not linear (P=0.07). Multiple logistic regression analyses showed that, compared to no or weak expression, overexpression of CXCR1 protein was a significant risk factor for high N stage (N2, N3). These results indicate that CXCR1 may be considered as a new and promising target for gastric adenocarcinoma therapy.

Norepinephrine promotes the β1-integrin-mediated adhesion of MDA-MB-231 cells to vascular endothelium by the induction of a GROα release

The migratory activity of tumor cells and their ability to extravasate from the blood stream through the vascular endothelium are important steps within the metastasis cascade. We have shown previously that norepinephrine is a potent inducer of the migration of MDA-MB-468 human breast carcinoma cells and therefore investigated herein, whether the interaction of these cells as well as MDA-MB-231 and MDA-MB-435S human breast carcinoma cells with the vascular endothelium is affected by this neurotransmitter as well. By means of a flow-through assay under physiologic flow conditions, we show that norepinephrine induces an increase of the adhesion of the MDA-MB-231 cells, but not of MDA-MB-468 and MDA-MB-435S cells to human pulmonary microvascular endothelial cells (HMVEC). The adhesion of MDA-MB-231 cells was based on a norepinephrine-mediated release of GROα from HMVECs. GROα caused a β1-integrin-mediated increase of the adhesion of MDA-MB-231 cells. Most interestingly, this effect of norepinephrine, similar to the aforementioned induction of migration in MDA-MB-468 cells, was mediated by β-adrenergic receptors and therefore abrogated by β-blockers. In conclusion, norepinephrine has cell line-specific effects with regard to certain steps of the metastasis cascade, which are conjointly inhibited by clinically established β-blockers. Therefore, these results may deliver a molecular explanation for our recently published retrospective data analysis of patients with breast cancer which shows that β-blockers significantly reduce the development of metastases.

The role of CXC chemokines in the transition of chronic inflammation to esophageal and gastric cancer

Chronic inflammation may increase the risk to develop cancer, for instance esophagitis or gastritis may lead to development of esophageal or gastric cancer, respectively. The key molecules attracting leukocytes to local inflammatory sites are chemokines. We here provide a systematic review on the impact of CXC chemokines (binding the receptors CXCR1, CXCR2, CXCR3 and CXCR4) on the transition of chronic inflammation in the upper gastrointestinal tract to neoplasia. CXCR2 ligands, including GRO-α,β,γ/CXCL1,2,3, ENA-78/CXCL5 and IL-8/CXCL8 chemoattract pro-tumoral neutrophils. In addition, angiogenic CXCR2 ligands stimulate the formation of new blood vessels, facilitating tumor progression. The CXCR4 ligand SDF-1/CXCL12 also promotes tumor development by stimulating angiogenesis and by favoring metastasis of CXCR4-positive tumor cells to distant organs producing SDF-1/CXCL12. Furthermore, these angiogenic chemokines also directly enhance tumor cell survival and proliferation. In contrast, the CXCR3 ligands Mig/CXCL9, IP-10/CXCL10 and I-TAC/CXCL11 are angiostatic and attract anti-tumoral T lymphocytes and may therefore mediate tumor growth retardation and regression. Thus, chemokines exert diverging, sometimes dual roles in tumor biology as described for esophageal and gastric cancer. Therefore extensive research is needed to completely unravel the complex chemokine code in specific cancers. Possibly, chemokine-targeted cancer therapy will have to be adapted to the individual's chemokine profile.

Interleukins, from 1 to 37, and interferon-γ: receptors, functions, and roles in diseases

Advancing our understanding of mechanisms of immune regulation in allergy, asthma, autoimmune diseases, tumor development, organ transplantation, and chronic infections could lead to effective and targeted therapies. Subsets of immune and inflammatory cells interact via ILs and IFNs; reciprocal regulation and counter balance among T(h) and regulatory T cells, as well as subsets of B cells, offer opportunities for immune interventions. Here, we review current knowledge about ILs 1 to 37 and IFN-γ. Our understanding of the effects of ILs has greatly increased since the discoveries of monocyte IL (called IL-1) and lymphocyte IL (called IL-2); more than 40 cytokines are now designated as ILs. Studies of transgenic or knockout mice with altered expression of these cytokines or their receptors and analyses of mutations and polymorphisms in human genes that encode these products have provided important information about IL and IFN functions. We discuss their signaling pathways, cellular sources, targets, roles in immune regulation and cellular networks, roles in allergy and asthma, and roles in defense against infections.

Gastroesophageal Reflux Disease and Helicobacter pylori: What May Be the Relationship?

Relationship between Helicobacter pylori (H. pylori) and gastroesophageal reflux disease (GERD) is controversial. We aimed to review the possible relationship between H. pylori infection and GERD. Epidemiological data indicate an inverse relationship between frequency of H. pylori infection and prevalence of GERD and its complications like Barrett's esophagus and esophageal adenocarcinoma. H. pylori eradication in patients with peptic ulcer disease may be associated with increased risk of development of GERD compared with untreated patients. Infection with cagA bearing strains of H. pylori was associated with less severe GERD including endoscopic esophagitis, possibly due to pangastritis leading to hypochlorhydria. Recent studies on inflammatory markers (IL-1β and IL-1RN) suggest pro-inflammatory genotypes to be protective against development of severe GERD, especially in patients with H. pylori infection. Identification of candidate genes playing an important role in gastric acid secretion and visceral hypersensitivity to the esophageal epithelium might help in early detection of individuals susceptible to develop GERD. Interplay between H. pylori and host factors play an important role in the pathogenesis of GERD.

Biofilms and chronic wound inflammation

In contrast to the commonly accepted hypothesis of host-centred pathology, it is possible that surface bacteria, not host dysfunction, cause the chronicity and perpetual inflammation associated with chronic non-healing wounds.

Anaplasma phagocytophilum-induced gene expression in both human neutrophils and HL-60 cells

Anaplasma phagocytophilum (Ap), the etiologic agent of the tick-borne disease human granulocytic anaplasmosis, is an obligate intracellular pathogen unique in its ability to target and replicate within neutrophils. We define and compare the spectra of host gene expression in response to Ap infection of human neutrophils and of HL-60 cells using long (70-mer)-oligonucleotide array technology. In addition to apoptosis-related genes, genes involved in signaling pathways, transcriptional regulation, immune response, host defense, cell adhesion, and cytoskeleton were modulated in neutrophils infected with Ap. Ap infection affected the same pathways in HL-60 cells but transcriptional changes occurred more slowly and in a reduced spectrum of genes. Gene expression changes detected by microarray were confirmed for randomly selected genes by QRT-PCR and Western blot studies. These studies demonstrate for the first time that the ERK pathway is activated in Ap-infected neutrophils and also define multiple pathways that are activated during intracellular Ap infection, which together serve to prolong the cell survival that is needed to allow bacterial replication and survival in neutrophils, which otherwise would rapidly apoptose.

Triggering receptor expressed on myeloid cells-1 (TREM-1) expression on gastric epithelium: implication for a role of TREM-1 in Helicobacter pylori infection

In Helicobacter pylori gastritis gastric epithelium plays a central role in the innate immunity to H. pylori. However, epithelial receptors interacting with H. pylori have been poorly characterized so far. Recently a new triggering receptor expressed on myeloid cells-1 (TREM-1) has been identified on human neutrophils and monocytes. On these cells TREM-1 triggers innate immunity by stimulating the secretion of interleukin (IL)-8 and tumour necrosis factor (TNF)-alpha and thus amplifies bacterial-induced inflammation. In this study expression and function of TREM-1 in gastric epithelium exposed to H. pylori has been investigated. TREM-1 mRNA and protein were expressed on gastric epithelial cell lines as demonstrated by reverse transcription-polymerase chain reaction (RT-PCR) and fluorescence activated cell sorter analysis. Gastric epithelial TREM-1 expression was up-regulated directly by H. pylori and was independent of epithelial IL-8 induced by H. pylori. Immunohistochemistry and tissue RT-PCR demonstrated significantly stronger TREM-1 expression in H. pylori gastritis compared with the non-inflamed gastric mucosa supporting in vivo that epithelial TREM-1 is up-regulated during H. pylori infection. Stimulation of gastric epithelial TREM-1 receptor resulted in IL-8 up-regulation on mRNA and protein level, as shown by real-time PCR and immunoassay. This is the first study localizing TREM-1 on gastric epithelium. Functional data suggest that TREM-1 expressed on gastric epithelium amplifies inflammation of the underlying gastric mucosa by up-regulation of IL-8.

Collagen binding protein Mip enables Legionella pneumophila to transmigrate through a barrier of NCI-H292 lung epithelial cells and extracellular matrix

Guinea pigs are highly susceptible to Legionella pneumophila infection and therefore have been the preferred animal model for studies of legionellosis. In this study guinea pig infections revealed that the Legionella virulence factor Mip (macrophage infectivity potentiator) contributes to the bacterial dissemination within the lung tissue and the spread of Legionella to the spleen. Histopathology of infected animals, binding assays with components of the extracellular matrix (ECM), bacterial transmigration experiments across an artificial lung epithelium barrier, inhibitor studies and ECM degradation assays were used to elucidate the underlying mechanism of the in vivo observation. The Mip protein, which belongs to the enzyme family of FK506-binding proteins (FKBP), was shown to bind to the ECM protein collagen (type I, II, III, IV, V, VI). Transwell assays with L. pneumophila and recombinant Escherichia coli HB101 strains revealed that Mip enables these bacteria to transmigrate across a barrier of NCI-H292 lung epithelial cells and ECM (NCI-H292/ECM barrier). Mip-specific monoclonal antibodies and the immunosuppressants rapamycin and FK506, which inhibit the peptidyl prolyl cis/trans isomerase (PPIase) activity of Mip, were able to inhibit this transmigration. By using protease inhibitors we found that the penetration of the NCI-H292/ECM barrier additionally requires a serine protease activity. Degradation assays with (35)S-labelled ECM proteins supported the finding of a concerted action of Mip and a serine protease. The described synergism between the activity of the collagen binding Mip protein and the serine protease activity represents an entirely new mechanism for bacterial penetration of the lung epithelial barrier and has implications for other prokaryotic and eukaryotic pathogens.

Helicobacter pylori persistence: an overview of interactions between H. pylori and host immune defenses

Helicobacter pylori is a gram-negative bacterium that persistently colonizes more than half of the global human population. In order to successfully colonize the human stomach, H. pylori must initially overcome multiple innate host defenses. Remarkably, H. pylori can persistently colonize the stomach for decades or an entire lifetime despite development of an acquired immune response. This review focuses on the immune response to H. pylori and the mechanisms by which H. pylori resists immune clearance. Three main sections of the review are devoted to (i) analysis of the immune response to H. pylori in humans, (ii) analysis of interactions of H. pylori with host immune defenses in animal models, and (iii) interactions of H. pylori with immune cells in vitro. The topics addressed in this review are important for understanding how H. pylori resists immune clearance and also are relevant for understanding the pathogenesis of diseases caused by H. pylori (peptic ulcer disease, gastric adenocarcinoma, and gastric lymphoma).

Early transcriptional response of human neutrophils to Anaplasma phagocytophilum infection

Anaplasma phagocytophilum, an unusual obligate intracellular pathogen that persists within neutrophils, causes human anaplasmosis (previously known as human granulocytic ehrlichiosis). To study the effects of this pathogen on the transcriptional profile of its host cell, we performed a comprehensive DNA microarray analysis of the early (4-h) transcriptional response of human neutrophils to A. phagocytophilum infection. A. phagocytophilum infection resulted in the up- and down-regulation of 177 and 67 neutrophil genes, respectively. These data were verified by quantitative reverse transcription-PCR of selected genes. Notably, the up-regulation of many antiapoptotic genes, including the BCL2A1, BIRC3, and CFLAR genes, and the down-regulation of the proapoptotic TNFSF10 gene were observed. Genes involved in inflammation, innate immunity, cytoskeletal remodeling, and vesicular transport also exhibited differential expression. Vascular endothelial growth factor was also induced. These data suggest that A. phagocytophilum may alter selected host pathways in order to facilitate its survival within human neutrophils. To gain further insight into the bacterium's influence on host cell gene expression, this report presents a detailed comparative analysis of our data and other gene expression profiling studies of A. phagocytophilum-infected neutrophils and promyelocytic cell lines.