Overexpression of Helicobacter pylori VacA N-terminal fragment induces proinflammatory cytokine expression and apoptosis in human monocytic cell line through activation of NF-κB

An emphasis on the interaction of signaling pathways highlights the role of miRNAs in the etiology and treatment resistance of gastric cancer

Gastric cancer (GC) is 4th in incidence and mortality rates globally. Several genetic and epigenetic factors, including microRNAs (miRNAs), affect its initiation and progression. miRNAs are short chains of nucleic acids that can regulate several cellular processes by controlling their gene expression. So, dysregulation of miRNAs expressions is associated with GC initiation, progression, invasion capacity, apoptosis evasions, angiogenesis, promotion and EMT enhancement. Of important pathways in GC and controlled by miRNAs are Wnt/β-catenin signaling, HMGA2/mTOR/P-gp, PI3K/AKT/c-Myc, VEGFR and TGFb signaling. Hence, this review was conducted to review an updated view of the role of miRNAs in GC pathogenesis and their modulatory effects on responses to different GC treatment modalities.

Helicobacter pylori promotes inflammatory factor secretion and lung injury through VacA exotoxin-mediated activation of NF-κB signaling

Previous reports have shown that Helicobacter pylori (H. pylori) infection is associated with respiratory diseases. However, the pathogenesis remains unclear. Vacuolating cytotoxin A (VacA) is a major H. pylori exotoxin. In this study, we investigated the signaling pathways involved in the inflammatory response to H. pylori infection and VacA. Mice were treated with H. pylori and VacA, and histopathological analysis of lung tissues was performed using hematoxylin-eosin, Masson’s trichrome, and periodic acid Schiff staining. The secretion of inflammatory cytokines was evaluated by enzyme-linked immunosorbent assay. The expression of VacA, nuclear factor-kappa B (NF-κB), and p65 NF-κB was analyzed by Western blotting and immunofluorescence. Cell proliferation and apoptosis were assessed using the MTS assay and flow cytometry, respectively. In mice, H. pylori infection and VacA treatment promoted the secretion of the inflammatory factors interleukin 1β (IL-1β), tumor necrosis factor α (TNF-α), IL-6, and IL-8, increased p65 NF-κB protein phosphorylation, and induced lung injury. Furthermore, H. pylori infection promoted VacA production. In an in vitro cell model, VacA treatment significantly suppressed the proliferation of WI-38 and BEAS-2B cells, promoted apoptosis, induced TNF-α, IL-1β, IL-6, and IL-8 secretion, and promoted p65 NF-κB protein phosphorylation and NF-κB nuclear transfer. The NF-κB inhibitor BAY11-7082 alleviated VacA-induced inflammation and apoptosis and increased cell viability. In conclusion, VacA promotes the secretion of inflammatory factors and induces lung injury through NF-κB signaling.

Mechanism of action of NF-κB related cell signaling pathways in progression of gastritis to carcinoma

Gastric cancer (GC) is a major global public health problem. The evolvement pattern of "superficial gastritis-chronic atrophic gastritis-intestinal metaplasia-dysplasia-gastric carcinoma" is common in related gastric diseases. As a key factor involved in systemic stress response, inflammatory response, and apoptosis, the regulation of NF-κB related to inflammation and apoptosis is a necessary link between inflammation and cancer progression. NF-κB is activated in most solid tumors and lymphomas. In the critical mechanism of gastric cancer induced by gastritis with various etiologies, the upstream and downstream molecules in the NF-κB signaling pathway are changed, and the cells are exposed to the microenvironment of inflammatory response for a long time, which ultimately leads to the development of their carcinogenic potential. This article discusses the mechanism of NF-κB in the key risk factors for the progression of gastric disease.

Bacterial Infection and Non-Hodgkin B-Cell Lymphoma: Interactions between Pathogen, Host and the Tumor Environment

Non-Hodgkin B-cell lymphomas (NHL) are a heterogeneous group of lymphoid neoplasms with complex etiopathology, rich symptomatology, and a variety of clinical courses, therefore requiring different therapeutic approaches. The hypothesis that an infectious agent may initiate chronic inflammation and facilitate B lymphocyte transformation and lymphogenesis has been raised in recent years. Viruses, like EBV, HTLV-1, HIV, HCV and parasites, like Plasmodium falciparum, have been linked to the development of lymphomas. The association of chronic Helicobacter pylori (H. pylori) infection with mucosa-associated lymphoid tissue (MALT) lymphoma, Borrelia burgdorferi with cutaneous MALT lymphoma and Chlamydophila psittaci with ocular adnexal MALT lymphoma is well documented. Recent studies have indicated that other infectious agents may also be relevant in B-cell lymphogenesis such as Coxiella burnettii, Campylobacter jejuni, Achromobacter xylosoxidans, and Escherichia coli. The aim of the present review is to provide a summary of the current literature on infectious bacterial agents associated with B-cell NHL and to discuss its role in lymphogenesis, taking into account the interaction between infectious agents, host factors, and the tumor environment.

Lactobacillus plantarum ZJ316 Attenuates Helicobacter pylori-Induced Gastritis in C57BL/6 Mice

Helicobacter pylori is a highly prevalent human-specific pathogen that causes various gastric diseases. In the present study, Lactobacillus plantarum ZJ316, which could survive well in simulated gastrointestinal conditions, was found to have significant anti-H. pylori ability. Animal assays revealed that L. plantarum ZJ316 had preventive and therapeutic effects on H. pylori-induced gastritis. L. plantarum ZJ316 significantly decreased interferon γ (IFN-γ) and interleukin 6 (IL-6) levels, increased the IL-10 level, and repaired mucosal damage. Moreover, 16S rRNA gene sequencing revealed that the relative abundance of H. pylori could be significantly reduced by L. plantarum ZJ316 administration. Members of the families Dehalobacteriaceae and Geodermatophilaceae were more prevalent in the prevention group, while Lactobacillaceae and Actinomycetaceae were more prevalent in the treatment group. These results indicate that L. plantarum ZJ316 serves as a potential candidate for the prevention and treatment of H. pylori-induced gastritis by regulating the gastric microbiota and reducing mucosal inflammation.

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.

Helicobacter pylori Virulence Factors Exploiting Gastric Colonization and its Pathogenicity

Helicobacter pylori colonizes the gastric epithelial cells of at least half of the world's population, and it is the strongest risk factor for developing gastric complications like chronic gastritis, ulcer diseases, and gastric cancer. To successfully colonize and establish a persistent infection, the bacteria must overcome harsh gastric conditions. H. pylori has a well-developed mechanism by which it can survive in a very acidic niche. Despite bacterial factors, gastric environmental factors and host genetic constituents together play a co-operative role for gastric pathogenicity. The virulence factors include bacterial colonization factors BabA, SabA, OipA, and HopQ, and the virulence factors necessary for gastric pathogenicity include the effector proteins like CagA, VacA, HtrA, and the outer membrane vesicles. Bacterial factors are considered more important. Here, we summarize the recent information to better understand several bacterial virulence factors and their role in the pathogenic mechanism.

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.

Helicobacter pylori VacA induces autophagic cell death in gastric epithelial cells via the endoplasmic reticulum stress pathway

The Helicobacter pylori vacuolating cytotoxin (VacA) can promote progressive vacuolation and gastric injury and may be associated with human gastric cancer. Increasing evidence indicates that autophagy is involved in the cell death induced by VacA, but the specific mechanisms need to be further elucidated. We show here that VacA could induce autophagy and increase cell death in human gastric cancer cell lines. Further investigations revealed that inhibition of autophagy could decrease the VacA-induced cell death in AGS cells. Furthermore, numerous dilated endoplasmic reticula (ER) were observed, and the phosphorylation of a subunit of eukaryotic translation initiation factor 2 subunit 1 also increased in the VacA-treated AGS cells, while repression of ER stress could reduce autophagy and cell death through knockdown of activating transcription factor 4 and DNA-damage-inducible transcript 3. In addition, the expression of pseudokinase tribbles homolog 3 (TRIB3) upon ER stress was triggered by VacA, and knockdown of TRIB3 could also decrease VacA-induced cell death. Finally, inhibition of autophagy could decrease VacA^s1m1-induced cell death and apoptosis, and apoptosis inhibitor Z-VAD had no significant effect on autophagy induced by VacA^s1m1. Thus, these results suggested that VacA causes autophagic cell death via ER stress in gastric epithelial cells.

Lentivirus-induced knockdown of LRP1 induces osteoarthritic-like effects and increases susceptibility to apoptosis in chondrocytes via the nuclear factor-κB pathway

Low-density lipoprotein receptor-related protein 1 (LRP1) is known to regulate cell survival and inflammation. The present study investigated the involvement of LRP1 in the regulation of tumor necrosis factor (TNF)-α-induced expression of matrix metalloproteinase (MMP)-13. Furthermore, the study aimed to elucidate the mechanisms underlying the effects of LRP1 on TNF-α-induced inflammation and apoptosis of chondrocytes. Lentivirus-mediated RNA interference techniques were used to knockdown the LRP1 gene. Subsequently, the effects of LRP1 on TNF-α-induced MMP-13 expression were determined using quantitative polymerase chain reaction, western blot analysis and ELISA. Furthermore, the TNF-α-induced intracellular pathway was investigated using a nuclear factor (NF)-κB inhibitor (Bay 11-7082). In addition, the effect of LRP1 regulation on growth and apoptosis in chondrocytes was investigated using western blot analysis and a TUNEL assay. LRP1 knockdown was shown to increase TNF-α-induced MMP-13 expression via the activation of the NF-κB (p65) pathway, which reduced the expression of collagen type II and cell viability. In addition, LRP1 inhibited cell apoptosis by increasing the expression of phospho-Akt and B-cell lymphoma 2 (Bcl-2), while suppressing the expression of caspase-3 and Bcl-2-associated X protein. The results of the present study indicated that LRP1 was able to inhibit TNF-α-induced apoptosis and inflammation in chondrocytes. Therefore, LRP1 may be an effective osteoarthritis inhibitor, potentially providing a novel approach for antiarthritic therapeutics.

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.

Bidirectional regulation between TMEFF2 and STAT3 may contribute to Helicobacter pylori-associated gastric carcinogenesis

The transmembrane protein with epidermal growth factor and two follistatin motifs 2 (TMEFF2) is a single-pass transmembrane protein, and it is downregulated in human gastric cancer and levels correlate with tumor progression and time of survival. However, the mechanism of its dysregulation in gastric cancer is little known. Here we investigate its regulatory mechanism and the bidirectional regulation between TMEFF2 and STAT3 in gastric carcinogenesis. TMEFF2 expression was decreased after Helicobacter pylori (H. pylori) infection in vivo and in vitro. STAT3 directly binds to the promoter of TMEFF2 and regulates H. pylori-induced TMEFF2 downregulation in normal gastric GES-1 cells and gastric cancer AGS cells. Conversely, TMEFF2 may suppress the phosphorylation of STAT3 and TMEFF2-induced downregulation of STAT3 phosphorylation may depend on SHP-1. A highly inverse correlation between the expression of TMEFF2 and pSTAT3 was also revealed in gastric tissues. We now show the deregulation mechanism of TMEFF2 in gastric carcinogenesis and identify TMEFF2 as a new target gene of STAT3. The phosphorylation of STAT3 may be negatively regulated by TMEFF2, and the bidirectional regulation between TMEFF2 and STAT3 may contribute to H. pylori-associated gastric carcinogenesis.