Inflammatory cytokine and microRNA responses of primary human dendritic cells cultured with Helicobacter pylori strains

Helicobacter pylori-activated fibroblasts as a silent partner in gastric cancer development

The discovery of Helicobacter pylori (Hp) infection of gastric mucosa leading to active chronic gastritis, gastroduodenal ulcers, and MALT lymphoma laid the groundwork for understanding of the general relationship between chronic infection, inflammation, and cancer. Nevertheless, this sequence of events is still far from full understanding with new players and mediators being constantly identified. Originally, the Hp virulence factors affecting mainly gastric epithelium were proposed to contribute considerably to gastric inflammation, ulceration, and cancer. Furthermore, it has been shown that Hp possesses the ability to penetrate the mucus layer and directly interact with stroma components including fibroblasts and myofibroblasts. These cells, which are the source of biophysical and biochemical signals providing the proper balance between cell proliferation and differentiation within gastric epithelial stem cell compartment, when exposed to Hp, can convert into cancer-associated fibroblast (CAF) phenotype. The crosstalk between fibroblasts and myofibroblasts with gastric epithelial cells including stem/progenitor cell niche involves several pathways mediated by non-coding RNAs, Wnt, BMP, TGF-β, and Notch signaling ligands. The current review concentrates on the consequences of Hp-induced increase in gastric fibroblast and myofibroblast number, and their activation towards CAFs with the emphasis to the altered communication between mesenchymal and epithelial cell compartment, which may lead to inflammation, epithelial stem cell overproliferation, disturbed differentiation, and gradual gastric cancer development. Thus, Hp-activated fibroblasts may constitute the target for anti-cancer treatment and, importantly, for the pharmacotherapies diminishing their activation particularly at the early stages of Hp infection.

MicroRNA-5112 Targets IKKγ to Dampen the Inflammatory Response and Improve Clinical Symptoms in Both Bacterial Infection and DSS-Induced Colitis

Inflammation is a double-edged sword that can be induced by various PAMPs, resulting in the control of infection by invading pathogens or injuries. The inflammatory response requires strict and precise control and regulation. MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate gene expression via translational inhibition or mRNA degradation. However, the role of miRNAs in inflammation induced by flagellin (ligand of TLR5) has yet to be fully determined. In this study, we identified differentially expressed miRNAs in murine bone marrow-derived dendritic cells (BMDCs) between flagellin treatment and medium alone using miRNA microarray. We found that flagellin stimulation downregulated miR-5112 expression in BMDCs and spleen DCs in vitro and in vivo. The overexpression of miR-5112 decreased inflammatory cytokine production, accompanied by a reduction of IKKγ in flagellin-stimulated BMDCs. We demonstrated that miR-5112 could directly target IKKγ to inhibit inflammatory cytokine production. Furthermore, miR-5112 inhibited the inflammatory response induced by flagellin or Salmonella infection in vivo. Interestingly, miR-5112 could also dampen the inflammatory response and alleviate dextran sulfate sodium (DSS)-induced colitis in C57BL/6 mice. These results suggest that miR-5112 could be a novel therapeutic target for both bacterial infection and DSS-induced colitis model.

Statins' Regulation of the Virulence Factors of Helicobacter pylori and the Production of ROS May Inhibit the Development of Gastric Cancer

Conventionally, statins are used to treat high cholesterol levels. They exhibit pleiotropic effects, such as the prevention of cardiovascular disease and decreased cancer mortality. Gastric cancer (GC) is one of the most common cancers, ranking as the third leading global cause of cancer-related deaths, and is mainly attributed to chronic Helicobacter pylori infection. During their co-evolution with hosts, H. pylori has developed the ability to use the cellular components of the host to evade the immune system and multiply in intracellular niches. Certain H. pylori virulence factors, including cytotoxin-associated gene A (CagA), vacuolating cytotoxin A (VacA), and cholesterol-α-glucosyltransferase (CGT), have been shown to exploit host cholesterol during pathogenesis. Therefore, using statins to antagonize cholesterol synthesis might prove to be an ideal strategy for reducing the occurrence of H. pylori-related GC. This review discusses the current understanding of the interplay of H. pylori virulence factors with cholesterol and reactive oxygen species (ROS) production, which may prove to be novel therapeutic targets for the development of effective treatment strategies against H. pylori-associated GC. We also summarize the findings of several clinical studies on the association between statin therapy and the development of GC, especially in terms of cancer risk and mortality.

Helicobacter-stimulated IL-10-producing B cells suppress differentiation of lipopolysaccharide/Helicobacter felis-activated stimulatory dendritic cells

Regulatory B cells (Bregs) produce antiinflammatory cytokines and inhibits proinflammatory response. Recently, immunosuppressive roles of Bregs in the effector functions of dendritic cells (DCs) were demonstrated. However, cross talk between Bregs and DCs in Helicobacter infection remains unknown. Here, we showed that direct stimulation of bone marrow-derived DCs (BM-DCs) with Helicobacter felis (H. felis) antigen upregulates their CD86 surface expression and causes the production of interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), interleukin-12 (IL-12), and interleukin-10 (IL-10). Furthermore, prestimulation of DCs with supernatants derived from both Helicobacter-stimulated IL-10^– B (Hf_stim-IL-10^– B) or IL-10⁺ B (Hf_stim-IL-10⁺) cells suppresses the secretion of TNF-α and IL-6, but does not affect the expression of CD86 and secretion of IL-12 by lipopolysaccharide (LPS) or H. felis-activated BM-DCs. Remarkably, soluble factors secreted by Hf_stim-IL-10^– B cells, but not by Hf_stim-IL-10⁺ B cells, suppress the secretion of IL-10 by BM-DCs upon subsequent LPS stimulation. In contrast, prestimulation with BM-DCs with supernatants of Hf_stim-IL-10⁺ B cells before H. felis antigen stimulation induces significantly their IL-10 production. Collectively, our data indicated that prestimulation with soluble factors secreted by Hf_stim-IL-10⁺ B cells, DCs exhibit a tolerogenic phenotype in response to LPS or Helicobacter antigen by secreting high levels of IL-10, but decreased levels of IL-6 and TNF-α.

MiRNA-200c, MiRNA-139 and ln RNA H19; new predictors of treatment response in H-pylori- induced gastric ulcer or progression to gastric cancer

Recent evidence indicates that the pathogenesis of gastric ulcer and progression to gastric cancer could be attributed to altered inflammatory/immunological response and associated differential non-coding RNAs expression signatures. However, co-expression profiling of lncRNA-miRNAs in GU/GC patients are scarcely focused on. Therefore, in the present study the expression of H19 and related miRNAs including miR-139, and miR-200 were assayed in the plasma samples of treatment responsive GU vs nonresponsive GC patients. This study is a case-control study carried out on 130 subjects recruited from the Gastrointestinal Endoscopy Unit in Al-Kasr Al-Aini Hospital, in Egypt. All recruited patients were diagnosed with H-pylori infection, 50 of them were gastric cancer patients (GC), with previous H-pylori induced gastric ulcer but were treatment non-respondent. Real-time PCR was performed to evaluate the expression level of serum non-coding RNA; miRNA-200c, miR-139, Ln RNA H19 in patients with peptic ulcer treatment non-respondent, who progressed to GC vs non-progressed gastric ulcer patients (GU) (n = 50), and compared to early diagnosed H-pylori-gastric ulcer patients (n = 30). The association between these miRNAs and the FGF-18/FGF-R signaling indicators of H-pylori-GC pathogenesis were then investigated. RESULTS: showed that the H19 level was significantly elevated while miR-139 and miR-200c expression were significantly down-regulated in GC patients, compared to GU participants (P < 0.01). The herein investigated ncRNAs are correlated to the disease duration with Ln H19 being significantly correlated with all inflammatory markers; TNF-α, INF-γ, TAC, MMP-9, and FGF18/FGFR2. A significant correlation was also observed between miRNA 200c and each of miRNA 139 and FGFR2. Moreover, ROC analysis revealed that miRNA 200c showed the highest AUC (0.906) and 81.2% sensitivity and 100% specificity. Moreover, the combined analysis of miRNA 200c/miRNA 139 revealed superior AUC (0.96) and 93% sensitivity and 100% specificity, than each separately. As for discriminative accuracy between stages III to IV of gastric cancer, LncRNA H19 showed the highest diagnostic accuracy (95.5%), specificity (100%), and sensitivity (90.9%). The current study demonstrated that the combination of serum miRNA 200c/miRNA 139 expression levels (down-regulation) could provide a new potential prognostic panel for GU predictive response and potential sequelae. In conclusion, LncRNA H19 and related miRNAs, miRNA 200c/miRNA 139, could serve as a potential diagnostic biomarker for early gastric cancer diagnosis.

Transcriptomic microRNA Profiling of Dendritic Cells in Response to Gut Microbiota-Secreted Vesicles

The interconnection between nutrients, metabolites and microbes is a key factor governing the healthy/pathological status of an individual. Thus, microbiota-based research is essential in order to better understand human health and nutrition. Gut bacteria release membrane vesicles (MVs) as an intercellular communication mechanism that allows the direct delivery of factors that prime the host’s innate immune system. We have previously shown that MVs from intestinal E. coli activate dendritic cells (DCs) in a strain-specific manner. To gain insights into the regulatory mechanisms involved, here, we have used an RNA deep sequencing approach to identify differentially expressed miRNAs (microRNAs) in DCs which are challenged by the MVs of the probiotic Nissle 1917 (EcN) or the commensal ECOR12. MicroRNAs are post-transcriptional regulatory mediators that permit the fine tuning of signaling pathways. This approach allowed the identification of a common set of miRNAs which are modulated by MVs from both strains and miRNAs which are differentially expressed in response to EcN or ECOR12 MVs. Based on the differential expression of the target genes and subsequent validation experiments, we correlated some of the selected miRNAs with the reported cytokine profile and specific T cell responses. As far as we know, this is the first study to analyze the regulation of miRNAs in DCs by MVs released by gut microbiota.

TLR2, TLR4 and TLR10 Shape the Cytokine and Chemokine Release of H. pylori-Infected Human DCs

Helicobacter pylori (H. pylori) is a stomach pathogen that persistently colonizes the gastric mucosa, often leading to chronic inflammation and gastric pathologies. Although infection with H. pylori is the primary risk factor for gastric cancer, the underlying mechanisms of pathogen persistence and consequential chronic inflammation are still not well understood. Conventional dendritic cells (cDCs), which are among the first immune cells to encounter H. pylori in the gastric lining, and the cytokines and chemokines they secrete, contribute to both acute and chronic inflammation. Therefore, this study aimed to unravel the contributions of specific signaling pathways within human CD1c⁺ cDCs (cDC2s) to the composition of secreted cytokines and chemokines in H. pylori infection. Here, we show that the type IV secretion system (T4SS) plays only a minor role in H. pylori-induced activation of cDC2s. In contrast, Toll-like receptor 4 (TLR4) signaling drives the secretion of inflammatory mediators, including IL-12 and IL-18, while signaling via TLR10 attenuates the release of IL-1β and other inflammatory cytokines upon H. pylori infection. The TLR2 pathway significantly blocks the release of CXCL1 and CXCL8, while it promotes the secretion of TNFα and GM-CSF. Taken together, these results highlight how specific TLR-signaling pathways in human cDC2s shape the H. pylori-induced cytokine and chemokine milieu, which plays a pivotal role in the onset of an effective immune response.

Deregulation of miRNA in Helicobacter pylori-Induced Gastric MALT Lymphoma: From Mice to Human

Gastric MALT lymphoma (GML) is directly caused by Helicobacter pylori infection but occurs only in a small number of infected subjects. Mechanisms underlying the initiation and progression of GML remain unclear. MicroRNAs (miRNAs) are small non-coding RNAs that are now considered as major players in inflammation and carcinogenesis, acting as oncogenes or tumor suppressors. Previous laboratory studies have shown in a GML mouse model that overexpression of a distinct set of five miRNAs (miR-21a, miR-135b, miR-142a, miR-150, miR-155) could play a critical role in the pathogenesis of GML. Our goal was to compare the miRNA expression profile obtained in the GML mouse model to that in human GML (11 cases of GML compared to 17 cases of gastritis control population). RTqPCR on the five dysregulated miRNAs in the GML mouse model and PCR array followed by RTqPCR confirmation showed that four miRNAs were up-regulated (miR-150, miR-155, miR-196a, miR-138) and two miRNAs down-regulated (miR-153, miR-7) in the stomachs of GML patients vs. gastritis control population. The analysis of their validated targets allowed us to postulate that these miRNAs (except miR-138) could act synergistically in a common signaling cascade promoting lymphomagenesis and could be involved in the pathogenesis of GML.

miRNAs reshape immunity and inflammatory responses in bacterial infection

Pathogenic bacteria cause various infections worldwide, especially in immunocompromised and other susceptible individuals, and are also associated with high infant mortality rates in developing countries. MicroRNAs (miRNAs), small non-coding RNAs with evolutionarily conserved sequences, are expressed in various tissues and cells that play key part in various physiological and pathologic processes. Increasing evidence implies roles for miRNAs in bacterial infectious diseases by modulating inflammatory responses, cell penetration, tissue remodeling, and innate and adaptive immunity. This review highlights some recent intriguing findings, ranging from the correlation between aberrant expression of miRNAs with bacterial infection progression to their profound impact on host immune responses. Harnessing of dysregulated miRNAs in bacterial infection may be an approach to improving the diagnosis, prevention and therapy of infectious diseases.

Changes in production of tiny cellular RNAs in response to bacterial infection could guide the development of better diagnostics and therapies. MicroRNAs regulate other genes by binding to messenger RNA strands and controlling their translation into proteins. Xikun Zhou, Min Wu and colleagues of the University of North Dakota have now reviewed current knowledge about how microRNA levels shift during infection with various bacterial pathogens. These microRNAs can modulate the immune response as well as pathways that influence metabolic activity and cell survival. Increasing studies have indicated that shifts in microRNA levels in response to different infections could provide a potential bacterial ‘fingerprint’ for achieving accurate diagnosis. With deeper insight into how different microRNAs influence infection, it might one day day become possible to target these molecules with ‘antisense’ or ‘agonist’ drugs that modulate their activity.

Bordetella pertussis pertactin knock-out strains reveal immunomodulatory properties of this virulence factor

Whooping cough, caused by Bordetella pertussis, has resurged and presents a global health burden worldwide. B. pertussis strains unable to produce the acellular pertussis vaccine component pertactin (Prn), have been emerging and in some countries represent up to 95% of recent clinical isolates. Knowledge on the effect that Prn deficiency has on infection and immunity to B. pertussis is crucial for the development of new strategies to control this disease. Here, we characterized the effect of Prn production by B. pertussis on human and murine dendritic cell (DC) maturation as well as in a murine model for pertussis infection. We incubated human monocyte-derived DCs (moDCs) with multiple isogenic Prn knockout (Prn-KO) and corresponding parental B. pertussis strains constructed either in laboratory reference strains with a Tohama I background or in a recently circulating clinical isolate. Results indicate that, compared to the parental strains, Prn-KO strains induced an increased production of pro-inflammatory cytokines by moDCs. This pro-inflammatory phenotype was also observed upon stimulation of murine bone marrow-derived DCs. Moreover, RNA sequencing analysis of lungs from mice infected with B. pertussis Prn-KO revealed increased expression of genes involved in cell death. These in vitro and in vivo findings indicate that B. pertussis strains which do not produce Prn induce a stronger pro-inflammatory response and increased cell death upon infection, suggesting immunomodulatory properties for Prn.

MiR-29b antagonizes the pro-inflammatory tumor-promoting activity of multiple myeloma-educated dendritic cells

Dendritic cells (DCs) have a key role in regulating tumor immunity, tumor cell growth and drug resistance. We hypothesized that multiple myeloma (MM) cells might recruit and reprogram DCs to a tumor-permissive phenotype by changes within their microRNA (miRNA) network. By analyzing six different miRNA-profiling data sets, miR-29b was identified as the only miRNA upregulated in normal mature DCs and significantly downregulated in tumor-associated DCs. This finding was validated in primary DCs co-cultured in vitro with MM cell lines and in primary bone marrow DCs from MM patients. In DCs co-cultured with MM cells, enforced expression of miR-29b counteracted pro-inflammatory pathways, including signal transducer and activator of transcription 3 and nuclear factor-κB, and cytokine/chemokine signaling networks, which correlated with patients' adverse prognosis and development of bone disease. Moreover, miR-29b downregulated interleukin-23 in vitro and in the SCID-synth-hu in vivo model, and antagonized a Th17 inflammatory response. All together, these effects translated into strong anti-proliferative activity and reduction of genomic instability of MM cells. Our study demonstrates that MM reprograms the DCs functional phenotype by downregulating miR-29b whose reconstitution impairs DCs ability to sustain MM cell growth and survival. These results underscore miR-29b as an innovative and attractive candidate for miRNA-based immune therapy of MM.

Helicobacter pylori Affects the Antigen Presentation Activity of Macrophages Modulating the Expression of the Immune Receptor CD300E through miR-4270

Helicobacter pylori (Hp) is a Gram-negative bacterium that infects the human gastric mucosa, leading to chronic inflammation. If not eradicated with antibiotic treatment, the bacterium persists in the human stomach for decades increasing the risk to develop chronic gastritis, gastroduodenal ulcer, and gastric adenocarcinoma. The lifelong persistence of Hp in the human stomach suggests that the host response fails to clear the infection. It has been recently shown that during Hp infection phagocytic cells promote high Hp loads rather than contributing to bacterial clearance. Within these cells Hp survives in "megasomes," large structures arising from homotypic fusion of phagosomes, but the mechanism that Hp employs to avoid phagocytic killing is not completely understood. Here, we show that Hp infection induces the downregulation of specific microRNAs involved in the regulation of transcripts codifying for inflammatory proteins. miR-4270 targets the most upregulated gene: the immune receptor CD300E, whose expression is strictly dependent on Hp infection. CD300E engagement enhances the pro-inflammatory potential of macrophages, but in parallel it affects their ability to express and expose MHC class II molecules on the plasma membrane, without altering phagocytosis. This effect compromises the possibility for effector T cells to recognize and activate the killing potential of macrophages, which, in turn would become a survival niche for the bacterium. Taken together, our data add another piece to the complicate puzzle represented by the long-life coexistence between Hp and the human host and contribute with new insights toward understanding the regulation and function of the immune receptor CD300E.

Deregulation of MicroRNAs in Gastric Lymphomagenesis Induced in the d3Tx Mouse Model of Helicobacter pylori Infection

Helicobacter pylori infection is considered as an excellent model of chronic inflammation-induced tumor development. Our project focuses on gastric MALT lymphoma (GML) related to H. pylori infection and mediated by the chronic inflammatory process initiated by the infection. Recently, microRNAs (miRNAs) have emerged as a new class of gene regulators, which play key roles in inflammation and carcinogenesis acting as oncogenes or tumor suppressors. Their precise characterization in the development of inflammation and their contribution in regulating host cells responses to infection by H. pylori have been little explored. Our goal was to analyze the changes in miRNAs in a GML mouse model using BALB/c mice thymectomized at day 3 post-birth (d3Tx model) and to clarify their implication in GML pathogenesis. PCR array followed by RT-qPCR identified five miRNAs (miR-21a, miR-135b, miR-142a, miR-150, miR-155) overexpressed in the stomachs of GML-developing d3Tx mice infected by H. pylori. The analysis of their putative targets allowed us to identify TP53INP1, an anti-proliferative and pro-apoptotic protein, as a common target of 4 of the 5 up-regulated miRNAs. We postulate that these miRNAs may act in synergy to promote the development of GML. miR-142a was also overexpressed in mouse sera samples and therefore could serve as a diagnostic marker. In situ hybridization on gastric samples with miR-142a revealed a global up-regulation of this miRNA by the tumor microenvironment at the lymphoma stage. Dysregulation of miR-21a, miR-135b, miR-142a, miR-150, miR-155 could play a critical role in the pathogenesis of GML and might offer potential applications as therapeutic targets and novel biomarkers for this disease.

Role of MicroRNA in the Lung's Innate Immune Response

The immune response to respiratory pathogens must be robust enough to defend the host yet properly constrained such that inflammation-induced tissue damage is avoided. MicroRNA (miRNA) are small noncoding RNA which posttranscriptionally influence gene expression. In this review, we discuss recent experimental evidence of the contribution of miRNA to the lung's response to bacterial and viral pathogens.

Characterisation of inflammatory processes in Helicobacter pylori-induced gastric lymphomagenesis in a mouse model

Gastric MALT lymphoma (GML) can be induced by Helicobacter pylori infection in BALB/c mice thymectomised at day 3 post-birth (d3Tx). This represented a unique opportunity to investigate the inflammatory process involved in the recruitment, proliferation and structuration of lymphoid infiltrates in the gastric mucosa of mice developing GML. Complementary molecular and proteomic approaches demonstrated that Th1 and Th2 cytokines were upregulated, along with activators/regulators of the lymphoid response and numerous chemokines. Interleukin-4, interferon γ, lymphotoxin-α and -β were significantly upregulated and correlated with the inflammatory scores for all the d3Tx mice. GML lesions in d3Tx mice infected with H. pylori were associated with the presence of the inflammatory response. The dysregulation of numerous members of the tumour necrosis factor superfamily was also evident and suggests that they could play an important role in GML pathology, especially in light of their ability to promote and control lymphocyte proliferation.

Interaction between inflammatory mediators and miRNAs in Helicobacter pylori infection

Helicobacter pylori cause chronic inflammation favouring gastric carcinogenesis, and its eradication may prevent malignant transformation. We evaluated whether H. pylori infection and its eradication modify the expression of inflammatory mediators in patients with chronic gastritis. Furthermore, we assessed whether microRNAs modulate inflammatory pathways induced by H. pylori and identified miRNA–gene interaction networks. mRNA and protein expression of TNFA, IL6, IL1B, IL12A, IL2 and TGFBRII and miRNAs miR‐103a‐3p, miR‐181c‐5p, miR‐370‐3p, miR‐375 and miR‐223‐3p were evaluated in tissue samples from 20 patients with chronic gastritis H. pylori negative (Hp−) and 31 H. pylori positive (Hp+), before and three months after bacterium eradication therapy, in comparison with a pool of Hp− normal gastric mucosa. Our results showed that H. pylori infection leads to up‐regulation of TNFA, IL6, IL12A and IL2 and down‐regulation of miRNAs. Bacterium eradication reduces the expression of TNFA and IL6 and up‐regulates TGFBRII and all investigated miRNAs, except miR‐223‐3p. Moreover, transcriptional profiles of inflammatory mediators and miRNAs after eradication are different from the non‐infected group. Deregulated miRNA–mRNA interaction networks were observed in the Hp+ group before and after eradication. Therefore, miRNAs modulated cytokine expression in the presence of H. pylori and after its eradication, suggesting that miRNAs participate in the pathological process triggered by H. pylori in the gastric mucosa.

Apoptotic-like Leishmania exploit the host's autophagy machinery to reduce T-cell-mediated parasite elimination

Apoptosis is a well-defined cellular process in which a cell dies, characterized by cell shrinkage and DNA fragmentation. In parasites like Leishmania, the process of apoptosis-like cell death has been described. Moreover upon infection, the apoptotic-like population is essential for disease development, in part by silencing host phagocytes. Nevertheless, the exact mechanism of how apoptosis in unicellular organisms may support infectivity remains unclear. Therefore we investigated the fate of apoptotic-like Leishmania parasites in human host macrophages. Our data showed—in contrast to viable parasites—that apoptotic-like parasites enter an LC3⁺, autophagy-like compartment. The compartment was found to consist of a single lipid bilayer, typical for LC3-associated phagocytosis (LAP). As LAP can provoke anti-inflammatory responses and autophagy modulates antigen presentation, we analyzed how the presence of apoptotic-like parasites affected the adaptive immune response. Macrophages infected with viable Leishmania induced proliferation of CD4⁺ T-cells, leading to a reduced intracellular parasite survival. Remarkably, the presence of apoptotic-like parasites in the inoculum significantly reduced T-cell proliferation. Chemical induction of autophagy in human monocyte-derived macrophage (hMDM), infected with viable parasites only, had an even stronger proliferation-reducing effect, indicating that host cell autophagy and not parasite viability limits the T-cell response and enhances parasite survival. Concluding, our data suggest that apoptotic-like Leishmania hijack the host cells´ autophagy machinery to reduce T-cell proliferation. Furthermore, the overall population survival is guaranteed, explaining the benefit of apoptosis-like cell death in a single-celled parasite and defining the host autophagy pathway as a potential therapeutic target in treating Leishmaniasis.

Correlation Between IL-10 and microRNA-187 Expression in Epileptic Rat Hippocampus and Patients with Temporal Lobe Epilepsy

Accumulating evidence is emerging that microRNAs (miRNAs) are key regulators in controlling neuroinflammatory responses that are known to play a potential role in the pathogenesis of temporal lobe epilepsy (TLE). The aim of the present study was to investigate the dynamic expression pattern of interleukin (IL)-10 as an anti-inflammatory cytokine and miR-187 as a post-transcriptional inflammation-related miRNA in the hippocampus of a rat model of status epilepticus (SE) and patients with TLE. We performed a real-time quantitative PCR and western blot on rat hippocampus 2 h, 7 days, 21 days and 60 days following pilocarpine-induced SE, and on hippocampus obtained from TLE patients and normal controls. To detect the relationship between IL-10 and miR-187 on neurons, lipopolysaccharide (LPS) and IL-10-stimulated neurons were performed. Furthermore, we identified the effect of antagonizing miR-187 by its antagomir on IL-10 secretion. Here, we reported that IL-10 secretion and miR-187 expression levels are inversely correlated after SE. In patients with TLE, the expression of IL-10 was also significantly upregulated, whereas miR-187 expression was significantly downregulated. Moreover, miR-187 expression was significantly reduced following IL-10 stimulation in an IL-10-dependent manner. On the other hand, antagonizing miR-187 promoted the production of IL-10 in hippocampal tissues of rat model of SE. Our findings demonstrate a critical role of miR-187 in the physiological regulation of IL-10 anti-inflammatory responses and elucidate the role of neuroinflammation in the pathogenesis of TLE. Therefore, modulation of the IL-10 / miR-187 axis may be a new therapeutic approach for TLE.

Helicobacter pylori and microRNAs: Relation with innate immunity and progression of preneoplastic conditions

The accepted paradigm for intestinal-type gastric cancer pathogenesis is a multistep progression from chronic gastritis induced by Helicobacter pylori (H. pylori) to gastric atrophy, intestinal metaplasia, dysplasia and ultimately gastric cancer. The genetic and molecular mechanisms underlying disease progression are still not completely understood as only a fraction of colonized individuals ever develop neoplasia suggesting that bacterial, host and environmental factors are involved. MicroRNAs are noncoding RNAs that may influence H. pylori-related pathology through the regulation of the transcription and expression of various genes, playing an important role in inflammation, cell proliferation, apoptosis and differentiation. Indeed, H. pylori have been shown to modify microRNA expression in the gastric mucosa and microRNAs are involved in the immune host response to the bacteria and in the regulation of the inflammatory response. MicroRNAs have a key role in the regulation of inflammatory pathways and H. pylori may influence inflammation-mediated gastric carcinogenesis possibly through DNA methylation and epigenetic silencing of tumor suppressor microRNAs. Furthermore, microRNAs influenced by H. pylori also have been found to be involved in cell cycle regulation, apoptosis and epithelial-mesenchymal transition. Altogether, microRNAs seem to have an important role in the progression from gastritis to preneoplastic conditions and neoplastic lesions and since each microRNA can control the expression of hundreds to thousands of genes, knowledge of microRNAs target genes and their functions are of paramount importance. In this article we present a comprehensive review about the role of microRNAs in H. pylori gastric carcinogenesis, identifying the microRNAs downregulated and upregulated in the infection and clarifying their biological role in the link between immune host response, inflammation, DNA methylation and gastric carcinogenesis.

Inflammatory response of macrophages cultured with Helicobacter pylori strains was regulated by miR-155

MicroRNA-155 plays an important role in the inflammatory response macrophages, while present studies identified that miR-155 was up-expressed in gastritis induced by Helicobacter pylori. We found that miR-155 was over expressed in macrophages infected with H. pylori in vivo or in vitro. Subsequently, inflammatory cytokines IL-23, IL-10, TNF-α and IL-8 were increased significantly, and the expression of CD80, CD86 or COX2, NOS2. Were enhanced in H. pylori infection macrophages by regulated with miR-155mimics. Furthermore, the apoptosis of macrophages induced by H. pylori was increased obviously due to the over-expression of miR-155. Therefore, these observations indicated that miR-155 may act as a inflammatory promoter in H. pylori infected macrophages. These findings contribute us to understand the functions of miR-155 in gastritis induced by H. pylori furtherly.

Helicobacter pylori inhibits dendritic cell maturation via interleukin-10-mediated activation of the signal transducer and activator of transcription 3 pathway

Helicobacter pylori infects the human gastric mucosa causing a chronic infection that is the primary risk factor for gastric cancer development. Recent studies demonstrate that H. pylori promotes tolerogenic dendritic cell (DC) development indicating that this bacterium evades the host immune response. However, the signaling pathways involved in modulating DC activation during infection remain unclear. Here, we report that H. pylori infection activated the signal transducer and activator of transcription 3 (STAT3) pathway in murine bone marrow-derived DCs (BMDCs) and splenic DCs isolated ex vivo. Isogenic cagA-, cagE-, vacA- and urease-mutants exhibited levels of phosphoSTAT3 that were comparable to in the wild-type (WT) parent strain. H. pylori-infected BMDCs produced increased immunosuppressive IL-10, which activated STAT3 in an autocrine/paracrine fashion. Neutralization of IL-10 prevented H. pylori-mediated STAT3 activation in both BMDCs and splenic DCs. In addition, anti-IL-10 treatment of infected H. pylori-BMDCs was associated with increased CD86 and MHC II expression and enhanced proinflammatory IL-1β cytokine secretion. Finally, increased CD86 and MHC II expression was detected in H. pylori-infected STAT3 knockout DCs when compared to WT controls. Together, these results demonstrate that H. pylori infection induces IL-10 secretion in DCs, which activates STAT3, thereby modulating DC maturation and reducing IL-1β secretion. These findings identify a host molecular mechanism by which H. pylori can manipulate the innate immune response to potentially favor chronic infection and promote carcinogenesis.

Immunity, inflammation, and vaccines for Helicobacter pylori

Helicobacter pylori colonizes mucosa, activates Toll-like and Nod-like receptors, and usually elicits a gastric T-helper 1/17 (Th1/Th17) type of immune response. Among several bacterial factors, the secreted peptidyl prolyl cis, trans-isomerase of H. pylori represents a key factor driving Th17 inflammation. A complex and fascinating balance between H. pylori and host factors takes part in the gastric niche and is responsible for the chronicity of the infection. Novel insights into the innate and adaptive responses against H. pylori, dealing with gastric epithelial cells, cytokines, and immune evasion have been elucidated over the past year and are discussed for the development of an effective vaccine.

Helicobacter pylori infection: host immune response, implications on gene expression and microRNAs

Helicobacter pylori (H. pylori) infection is the most common bacterial infection worldwide. Persistent infection of the gastric mucosa leads to inflammatory processes and may remain silent for decades or progress causing more severe diseases, such as gastric adenocarcinoma. The clinical consequences of H. pylori infection are determined by multiple factors, including host genetic predisposition, gene regulation, environmental factors and heterogeneity of H. pylori virulence factors. After decades of studies of this successful relationship between pathogen and human host, various mechanisms have been elucidated. In this review, we have made an introduction on H. pylori infection and its virulence factors, and focused mainly on modulation of host immune response triggered by bacteria, changes in the pattern of gene expression in H. pylori-infected gastric mucosa, with activation of gene transcription involved in defense mechanisms, inflammatory and immunological response, cell proliferation and apoptosis. We also highlighted the role of bacteria eradication on gene expression levels. In addition, we addressed the recent involvement of different microRNAs in precancerous lesions, gastric cancer, and inflammatory processes induced by bacteria. New discoveries in this field may allow a better understanding of the role of major factors involved in the pathogenic mechanisms of H. pylori.

A proposed role of human defensins in Helicobacter pylori-related neurodegenerative disorders

Cationic host defence peptides (CHDPs), also known as antimicrobial peptides (AMPs), are essential components of the innate immunity with antimicrobial and pleiotropic immunomodulatory properties. In mammals the two major families of CHDPs are defensins and cathelicidins that comprise an arsenal of innate regulators of principal importance in the host tissues. Research in the last decade has demonstrated that defensins are crucial effectors of both innate and adaptive immunity. Defensins can modulate immune responses, either by stimulation or suppression, thereby controlling inflammatory processes and infections. Currently only few data, mostly hypothetical, focus on the role of defensins in central nervous system (CNS) physiopathology and neurodegeneration. Defensins may function as an initial line of defense within the CNS either as an antimicrobial, immunomodulator, or both. A dysregulation of brain expression of specific defensins might either exacerbate or ameliorate the inflammatory response within the CNS depending upon which extracellular conditions predominate. It is proposed that reduction or abnormal elevation of AMP expression by cerebral microglia, astrocytes or choroid plexus epithelium might contribute to loss of AMP-induced regulation of immune responses, thereby promoting neuronal cell injury and death observed in Alzheimer's disease and possibly in other neurodegenerative disorders. Nevertheless, whether certain AMPs play a crucial role in the onset or promotion of the neuroinflammatory process and neurodegeneration is currently unknown, thereby emphasizing the necessity of further investigation into the regulatory mechanisms that control innate and adaptive immunity within the brain. Recent data indicate that Helicobacter pylori (H. pylori) induces defensins' release associated with chronic inflammatory tissue damage. However, it remains unclear whether and how H. pylori evades the attack by defensins. Moreover, recent evidence indicates that H. pylori infection might contribute to the pathogenesis of neurodegenerative diseases, by releasing several inflammatory mediators that could induce blood-brain barrier breakdown, thereby being involved in the pathogenesis of neurodegeneration. However, currently there are no data regarding the potential impact of human defensins on H. pylori-related neurodegenerative disorders. We herein propose that human defensins might contribute to the pathophysiology of H. pylori-related neurodegenerative disorders by modulating variably innate and adaptive immune system responses. Better understanding of the mechanisms regarding human defensins' possible involvement in H. pylori-induced neurodegeneration might help develop novel therapeutic strategies against H. pylori-related neurodegenerative disorders.