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

Expression of Matrix Metalloproteinases in the Circulating Immune Cells in Children with Helicobacter pylori Infection-Correlation with Clinical Factors

H. pylori gastritis is strongly associated with the upregulation of the expression of several matrix metalloproteinases (MMPs) in the gastric mucosa. However, the role of MMP-2 and MMP-9, and their inhibitors (tissue inhibitors of metalloproteinases -TIMPs) produced by immune cells in infected children have not been clearly defined. Moreover, the effects of H. pylori eradication therapy on MMPs and TIMPs production has not been evaluated. A total of 84 children were studied: 24-with newly diagnosed H. pylori gastritis, 25-after H. pylori eradication therapy (17 of them after successful therapy), 24-with H. pylori-negative gastritis, and 11-controls. Plasma levels of MMP-2, MMP-9, TIMP-1, and TIMP-2 by ELISA; MMPs and TIMPs expression in lymphocytes; neutrophils and monocytes in peripheral blood by multiparameter flow cytometry; and mucosal mRNA expression levels of MMPs and TIMP-1 in gastric biopsies by RT-PCR were evaluated. Children with H. pylori-related gastritis showed the following: (1) increased MMP-2 and TIMP-2 plasma levels, (2) increased intracellular expression of MMP-2 in the circulating lymphocytes and neutrophils, (3) low frequencies of circulating TIMP-1+ and TIMP-2+ leukocytes, and (4) high expression of mRNA for MMP-9 along with low expression of mRNA for MMP-2 in the gastric mucosa. Unsuccessful H. pylori eradication was associated with the following: (1) high plasma levels of MMP-9 and TIMP-1, (2) increased pool of TIMP-1+ lymphocytes as well as high expression of MMP-9 in circulating lymphocytes, and (3) high expression of mRNA for MMP-9 in the gastric mucosa. Our data suggest that MMPs are important contributors to stomach remodelling in children with H. pylori-related gastritis. Unsuccessful H. pylori eradication is associated with increased MMP-9 in plasma, circulating lymphocytes, and gastric mucosa.

Subsite-specific metastatic organotropism and risk in gastric cancer: A population-based cohort study of the US SEER database and a Chinese single-institutional registry

BACKGROUND

Studies exploring whether metastatic organotropism and risk in gastric cancer (GC) differ by primary anatomical site are scarce.

METHODS

This study included 15,260 and 1623 patients diagnosed with GC from the Surveillance, Epidemiology, and End Results (SEER) registry database and the Nanfang Hospital in China, respectively. Patients were stratified according to primary site of GC, and the incidence of metastasis to different organs was used to determine the metastatic organotropism for each GC subsite. Finally, the metastatic organotropism and risk were compared among the different subsite groups.

RESULTS

Liver metastasis was the most common metastasis site in cardia GC, whereas other-site metastases were more common in the body, antrum, overlapping lesions, and unspecified GCs. Liver and other-site metastases were also frequently observed in the fundus, pylorus, lesser curvature, and greater curvature GCs. Patients with GC with definite primary tumor sites in the SEER and validation Nanfang hospital cohorts were compared by grouping as proximal and distal GCs for further analysis. In the SEER cohort, the top three metastatic sites of proximal GC were liver (21.4%), distant lymph node (LN) (14.6%), and other-site (mainly peritoneum, 11.9%), whereas those of distal GC were other-site (mainly peritoneum, 19.5%), liver (11.8%), and distant LN (9.5%). The incidence of metastasis to the liver, distant LN, lung, and brain was significantly higher in patients with proximal GC than in those with distal GC in both the SEER and Nanfang cohorts (p < 0.05). However, metastasis to other-site/peritoneum was significantly lower in patients with proximal GC compared to those with distal GC in the Nanfang Hospital and SEER cohorts, respectively (p < 0.05).

CONCLUSION

Liver and distant LN are the preferred metastatic sites for proximal GC, whereas peritoneal metastasis is more common in distal GC. Proximal GC has a higher risk of lymphatic and hematogenous metastases, and a lower risk of transcoelomic metastasis than distal GC. Our findings highlight the need to stratify GC by its primary subsite to aid in planning and decision-making related to metastatic management in clinical practice.

Helicobacter pylori regulates TIFA turnover in gastric epithelial cells

The human pathogen Helicobacter pylori induces a strong inflammatory response in gastric mucosa manifested by the recruitment of neutrophils and macrophages to the places of infection, and by changes in epithelial integrity and function. At the molecular level, this innate immune response is essentially dependent on the activation of NF-κB transcription factors regulating the expression of chemotactic factors, e.g., IL-8. Recently, it has been demonstrated that the NF-κB signaling pathway is triggered by the bacterial heptose metabolites, which activate the host ALPK1-TIFA axis. TIFA has been suggested to promote oligomerization and activity of the E3 ubiquitin ligase TRAF6, which further stimulates TAK1-IKK signaling. Here, we demonstrate that ALPK1-dependent TIFA activation in H. pylori-infected gastric epithelial cells is followed in time by a decline in TIFA levels, and that this process is impeded by inhibitors of the proteasomal and lysosomal degradation. According to our data, TRAF2, TRAF6, TAK1 or NEMO are not required for TIFA degradation. Additionally, H. pylori promotes the interaction of TIFA with free polyubiquitin as well as with optineurin, TAX1BP1 and LAMP1, which are known protein adaptors involved in intracellular trafficking to lysosomes.

Activation of Laminin γ2 by Helicobacter pylori Promotes Invasion and Survival of Gastric Cancer Cells With E-Cadherin Defects

BACKGROUND

Helicobacter pylori infection induces cellular phenotypes relevant for cancer progression, namely cell motility and invasion. We hypothesized that the extracellular matrix (ECM) could be involved in these deleterious effects.

METHODS

Microarrays were used to uncover ECM interactors in cells infected with H. pylori. LAMC2, encoding laminin γ2, was selected as a candidate gene and its expression was assessed in vitro and in vivo. The role of LAMC2 was investigated by small interference RNA (siRNA) combined with a set of functional assays. Laminin γ2 and E-cadherin expression patterns were evaluated in gastric cancer cases.

RESULTS

Laminin γ2 was found significantly overexpressed in gastric cancer cells infected with H. pylori. This finding was validated in vitro by infection with clinical isolates and in vivo by using gastric biopsies of infected and noninfected individuals. We showed that laminin γ2 overexpression is dependent on the bacterial type IV secretion system and on the CagA. Functionally, laminin γ2 promotes cell invasion and resistance to apoptosis, through modulation of Src, JNK, and AKT activity. These effects were abrogated in cells with functional E-cadherin.

CONCLUSIONS

These data highlight laminin γ2 and its downstream effectors as potential therapeutic targets, and the value of H. pylori eradication to delay gastric cancer onset and progression.

Matrix Metalloproteinases in Helicobacter pylori-Associated Gastritis and Gastric Cancer

Gastric cancer is one of the leading causes of the cancer-related mortality worldwide. The etiology of this disease is complex and involves genetic predisposition and environmental factors, including Helicobacter pylori. Infection of the stomach with H. pylori leads to gastritis and gastric atrophy, which can progress stepwise to gastric cancer. Matrix metalloproteinases (MMPs) actively participate in the pathology development. The further progression of gastric cancer seems to be less dependent on bacteria but of intra-tumor cell dynamics. Bioinformatics data confirmed an important role of the extracellular matrix constituents and specific MMPs in stomach carcinoma invasion and metastasis, and revised their potential as predictors of the disease outcome. In this review, we describe, in detail, the impact of MMPs in H. pylori-associated gastritis and gastric cancer.

Glucagon-like peptide-1 receptor activation maintains extracellular matrix integrity by inhibiting the activity of mitogen-activated protein kinases and activator protein-1

Disruption of the intervertebral disc extracellular matrix (ECM) is a hallmark of intervertebral disc degeneration (IDD), which is largely attributed to excessive oxidative stress. However, there is a lack of clinically feasible approaches to promote the reconstruction of the disc ECM. Glucagon-like peptide-1 (GLP-1), a safe polypeptide hormone adopted to treat type 2 diabetes mellitus, has shown great potential for relieving oxidative stress-related damage. To our knowledge, this is the first study to reveal that exenatide, a GLP-1 receptor (GLP-1R) agonist, can upregulate disc ECM synthesis and attenuate oxidative stress-induced ECM degradation and IDD. Mechanistically, we found that exenatide inhibited the activation of mitogen-activated protein kinases (MAPK) signaling pathway and the formation of BATF/JUNs heterodimers (an index of activator protein-1 (AP-1) activity). The restoration of MAPK signaling activation reversed the protective effects of exenatide and enhanced downstream BATF/JUNs binding. BATF overexpression was also found to aggravate disc ECM damage, even in the presence of exenatide. In summary, exenatide is an effective agent that regulates ECM anabolic balance and restores disc degeneration by inhibiting MAPK activation and its downstream AP-1 activity. The present study provides a therapeutic rationale for activating the GLP-1 receptor against IDD and establishes the important role of AP-1 activity in the pathogenesis of IDD.

Activation of PTH1R alleviates epididymitis and orchitis through Gq and β-arrestin-1 pathways

Inflammation in the epididymis and testis contributes significantly to male infertility. Alternative therapeutic avenues treating epididymitis and orchitis are expected since current therapies using antibiotics have limitations associated to side effects and are commonly ineffective for inflammation due to nonbacterial causes. Here, we demonstrated that type 1 parathyroid hormone receptor (PTH1R) and its endogenous agonists, parathyroid hormone (PTH) and PTH-related protein (PTHrP), were mainly expressed in the Leydig cells of testis as well as epididymal epithelial cells. Screening the secretin family G protein-coupled receptor identified that PTH1R in the epididymis and testis was down-regulated in mumps virus (MuV)- or lipopolysaccharide (LPS)-induced inflammation. Remarkably, activation of PTH1R by abaloparatide (ABL), a Food and Drug Administration-approved treatment for postmenopausal osteoporosis, alleviated MuV- or LPS-induced inflammatory responses in both testis and epididymis and significantly improved sperm functions in both mouse model and human samples. The anti-inflammatory effects of ABL were shown to be regulated mainly through the Gq and β-arrestin-1 pathway downstream of PTH1R as supported by the application of ABL in Gnaq± and Arrb1-/- mouse models. Taken together, our results identified an important immunoregulatory role for PTH1R signaling in the epididymis and testis. Targeting to PTH1R might have a therapeutic effect for the treatment of epididymitis and orchitis or other inflammatory disease in the male reproductive system.

Causal contributors to tissue stiffness and clinical relevance in urology

Mechanomedicine is an emerging field focused on characterizing mechanical changes in cells and tissues coupled with a specific disease. Understanding the mechanical cues that drive disease progression, and whether tissue stiffening can precede disease development, is crucial in order to define new mechanical biomarkers to improve and develop diagnostic and prognostic tools. Classically known stromal regulators, such as fibroblasts, and more recently acknowledged factors such as the microbiome and extracellular vesicles, play a crucial role in modifications to the stroma and extracellular matrix (ECM). These modifications ultimately lead to an alteration of the mechanical properties (stiffness) of the tissue, contributing to disease onset and progression. We describe here classic and emerging mediators of ECM remodeling, and discuss state-of-the-art studies characterizing mechanical fingerprints of urological diseases, showing a general trend between increased tissue stiffness and severity of disease. Finally, we point to the clinical potential of tissue stiffness as a diagnostic and prognostic factor in the urological field, as well as a possible target for new innovative drugs.

Emerging therapeutic targets for gastric cancer from a host-Helicobacter pylori interaction perspective

INTRODUCTION

Gastric cancer (GC) has the higher genetic, cytologic, and architectural heterogeneity compared to other gastrointestinal cancers. By inducing gastric inflammation, Helicobacter pylori (HP) may lead to GC through combining bacterial factors with host factors. In this regard, identification of the major therapeutic targets against the host-HP interactions plays a critical role in GC prevention, diagnosis, and treatment.

AREAS COVERED

This study offers new insights into the promising therapeutic targets against the angiogenesis, invasion, or metastasis of GC from a host-HP interaction perspective. To this end, MEDLINE, EMBASE, LILACS, AIM, and IndMed databases were searched for relevant articles since 1992.

EXPERT OPINION

Wnt signaling and COX pathway have a well-documented history in the genesis of GC by HP and might be considered as the most promising targets for early GC treatment. Destroying HP may decrease the risk of GC, but it cannot fully hinder the GC development induced by HP infection. Therefore, targeting HP-activated pathways, especially COX-2/Wnt/beta-catenin/VEGF, TLR2/TLR9/COX-2, COX2-PGE2, and NF-κB/COX-2, as well as EPHA2, MMPs, and miR-543/SIRT1 axis, can be an effective measure in the early treatment of GC. However, different clinical trials and large, multi-center cohorts are required to validate these potentially effective targets for GC therapy.

Ddr1-induced neutrophil extracellular traps drive pancreatic cancer metastasis

Pancreatic ductal adenocarcinoma (PDAC) tumors are characterized by a desmoplastic reaction resulting in dense deposition of collagen that is known to promote cancer progression. A central mediator of pro-tumorigenic collagen signaling is the receptor tyrosine kinase discoid domain receptor 1 (DDR1). DDR1 is a critical driver of a mesenchymal and invasive cancer cell PDAC phenotype. Previous studies have demonstrated that genetic or pharmacologic inhibition of DDR1 reduces PDAC tumorigenesis and metastasis. Here, we investigated whether DDR1 signaling has cancer cell non-autonomous effects that promote PDAC progression and metastasis. We demonstrate that collagen-induced DDR1 activation in cancer cells is a major stimulus for CXCL5 production, resulting in the recruitment of tumor-associated neutrophils (TANs), the formation of neutrophil extracellular traps (NETs) and subsequent cancer cell invasion and metastasis. Moreover, we have identified that collagen-induced CXCL5 production was mediated by a DDR1-PKCθ-SYK-NFkB signaling cascade. Together, these results highlight the critical contribution of collagen I-DDR1 interaction in the formation of an immune microenvironment that promotes PDAC metastasis.

Manifold role of ubiquitin in Helicobacter pylori infection and gastric cancer

Infection with H. pylori induces a strong host cellular response represented by induction of a set of molecular signaling pathways, expression of proinflammatory cytokines and changes in proliferation. Chronic infection and inflammation accompanied by secretory dysfunction can result in the development of gastric metaplasia and gastric cancer. Currently, it has been determined that the regulation of many cellular processes involves ubiquitinylation of molecular effectors. The binding of ubiquitin allows the substrate to undergo a change in function, to interact within multimolecular signaling complexes and/or to be degraded. Dysregulation of the ubiquitinylation machinery contributes to several pathologies, including cancer. It is not understood in detail how H. pylori impacts the ubiquitinylation of host substrate proteins. The aim of this review is to summarize the existing literature in this field, with an emphasis on the role of E3 ubiquitin ligases in host cell homeodynamics, gastric pathophysiology and gastric cancer.

Chronic High Glucose Concentration Induces Inflammatory and Remodeling Changes in Valvular Endothelial Cells and Valvular Interstitial Cells in a Gelatin Methacrylate 3D Model of the Human Aortic Valve

Calcific aortic valve disease (CAVD), a degenerative disease characterized by inflammation, fibrosis and calcification, is accelerated in diabetes. Hyperglycemia contributes to this process by mechanisms that still need to be uncovered. We have recently developed a 3D model of the human aortic valve based on gelatin methacrylate and revealed that high glucose (HG) induced osteogenic molecules and increased calcium deposits in a pro-osteogenic environment. To further understand the events leading to calcification in diabetic conditions in CAVD, we analyzed here the inflammatory and remodeling mechanisms induced by HG in our 3D model. We exposed valvular endothelial cells (VEC) and interstitial cells (VIC) to normal glucose (NG) or HG for 7 and 14 days, then we isolated and separated the cells by anti-CD31 immunomagnetic beads. The changes induced by HG in the 3D model were investigated by real-time polymerase chain reaction (RT-PCR), Western blot, enzyme-linked immunosorbent assay (ELISA) and immunofluorescence. Our results showed that HG induced expression of different cytokines, cell adhesion molecules and matrix metalloproteinases in VEC and VIC. In addition, protein kinase C was increased in VEC and VIC, indicating molecular mechanisms associated with HG induced inflammation and remodeling in both valvular cells. These findings may indicate new biomarkers and targets for therapy in diabetes associated with CAVD.

Helicobacter pylori-induced matrix metallopeptidase-10 promotes gastric bacterial colonization and gastritis

The interaction between gastric epithelium and immune response plays key roles in H. pylori-associated pathology. We demonstrated a procolonization and proinflammation role of MMP-10 in H. pylori infection. MMP-10 is elevated in gastric mucosa and is produced by gastric epithelial cells synergistically induced by H. pylori and IL-22 via the ERK pathway. Human gastric MMP-10 was correlated with H. pylori colonization and the severity of gastritis, and mouse MMP-10 from non-BM-derived cells promoted bacteria colonization and inflammation. H. pylori colonization and inflammation were attenuated in IL-22-/-, MMP-10-/-, and IL-22-/-MMP-10-/- mice. MMP-10-associated inflammation is characterized by the influx of CD8+ T cells, whose migration is induced via MMP-10-CXCL16 axis by gastric epithelial cells. Under the influence of MMP-10, Reg3a, E-cadherin, and zonula occludens-1 proteins decrease, resulting in impaired host defense and increased H. pylori colonization. Our results suggest that MMP-10 facilitates H. pylori persistence and promotes gastritis.

E2F1 transactivates IQGAP3 and promotes proliferation of hepatocellular carcinoma cells through IQGAP3-mediated PKC-alpha activation

For decades, E2F1 has been recognized as a retinoblastoma protein (RB) binding transcription factor that regulates the cell cycle. E2F1 binds preferentially to RB and accelerates the cell cycle in most cancer cells. However, it is thought that E2F1 modulates cell proliferation in other ways as well. Herein, it has been discovered that in pathological tissues derived from hepatocellular carcinoma (HCC) patients, E2F1 correlates positively with IQGAP3 and that both of these factors are highly expressed (N = 164, R = 0.6716). In addition, a high level of E2F1 or IQGAP3 predicted poor survival in HCC patients. Further study determined that E2F1 transactivates IQGAP3, the GTPase binding protein in MHCC-97H cells. Co-immunoprecipitation analysis indicated that IQGAP3 interacts with PKCδ and competitively inhibits the interaction between PKCδ and PKCα, resulting in phosphorylation of PKCα activation and promotion of cell proliferation. This study reveals that highly expressed E2F1 not only transactivates cell-cycle-related factors but also promotes HCC proliferation by activating the phosphorylation of PKCα.

Helicobacter pylori-controlled c-Abl localization promotes cell migration and limits apoptosis

BACKGROUND

Deregulated c-Abl activity has been intensively studied in a variety of solid tumors and leukemia. The class-I carcinogen Helicobacter pylori (Hp) activates the non-receptor tyrosine kinase c-Abl to phosphorylate the oncoprotein cytotoxin-associated gene A (CagA). The role of c-Abl in CagA-dependent pathways is well established; however, the knowledge of CagA-independent c-Abl processes is scarce.

METHODS

c-Abl phosphorylation and localization were analyzed by immunostaining and immunofluorescence. Interaction partners were identified by tandem-affinity purification. Cell elongation and migration were analyzed in transwell-filter experiments. Apoptosis and cell survival were examined by FACS analyses and MTT assays. In mice experiments and human biopsies, the involvement of c-Abl in Hp pathogenesis was investigated.

RESULTS

Here, we investigated the activity and subcellular localization of c-Abl in vitro and in vivo and unraveled the contribution of c-Abl in CagA-dependent and -independent pathways to gastric Hp pathogenesis. We report a novel mechanism and identified strong c-Abl threonine 735 phosphorylation (pAbl^T735) mediated by the type-IV secretion system (T4SS) effector D-glycero-β-D-manno-heptose-1,7-bisphosphate (βHBP) and protein kinase C (PKC) as a new c-Abl kinase. pAbl^T735 interacted with 14-3-3 proteins, which caused cytoplasmic retention of c-Abl, where it potentiated Hp-mediated cell elongation and migration. Further, the nuclear exclusion of pAbl^T735 attenuated caspase-8 and caspase-9-dependent apoptosis. Importantly, in human patients suffering from Hp-mediated gastritis c-Abl expression and pAbl^T735 phosphorylation were drastically enhanced as compared to type C gastritis patients or healthy individuals. Pharmacological inhibition using the selective c-Abl kinase inhibitor Gleevec confirmed that c-Abl plays an important role in Hp pathogenesis in a murine in vivo model.

CONCLUSIONS

In this study, we identified a novel regulatory mechanism in Hp-infected gastric epithelial cells by which Hp determines the subcellular localization of activated c-Abl to control Hp-mediated EMT-like processes while decreasing cell death.

Proteolysis in Helicobacter pylori-Induced Gastric Cancer

Persistent infections with the human pathogen and class-I carcinogen Helicobacter pylori (H. pylori) are closely associated with the development of acute and chronic gastritis, ulceration, gastric adenocarcinoma and lymphoma of the mucosa-associated lymphoid tissue (MALT) system. Disruption and depolarization of the epithelium is a hallmark of H. pylori-associated disorders and requires extensive modulation of epithelial cell surface structures. Hence, the complex network of controlled proteolysis which facilitates tissue homeostasis in healthy individuals is deregulated and crucially contributes to the induction and progression of gastric cancer through processing of extracellular matrix (ECM) proteins, cell surface receptors, membrane-bound cytokines, and lateral adhesion molecules. Here, we summarize the recent reports on mechanisms how H. pylori utilizes a variety of extracellular proteases, involving the proteases Hp0169 and high temperature requirement A (HtrA) of bacterial origin, and host matrix-metalloproteinases (MMPs), a disintegrin and metalloproteinases (ADAMs) and tissue inhibitors of metalloproteinases (TIMPs). H. pylori-regulated proteases represent predictive biomarkers and attractive targets for therapeutic interventions in gastric cancer.

Helicobacter pylori: A Paradigm Pathogen for Subverting Host Cell Signal Transmission

Helicobacter pylori colonizes the gastric mucosa in the human stomach and represents a major risk factor for peptic ulcer disease and gastric cancer. Here, we summarize our current knowledge of the complex impact of H. pylori on manipulating host signalling networks, that is, by the cag pathogenicity island (cagPAI)-encoded type IV secretion system (T4SS). We show that H. pylori infections reflect a paradigm for interspecies contact-dependent molecular communication, which includes the disruption of cell-cell junctions and cytoskeletal rearrangements, as well as proinflammatory, cell cycle-related, proliferative, antiapoptotic, and DNA damage responses. The contribution of these altered signalling cascades to disease outcome is discussed.

Identification of TRA2B-DNAH5 fusion as a novel oncogenic driver in human lung squamous cell carcinoma

Lung squamous cell carcinoma (SCC) is one of the major subtypes of lung cancer. Our current knowledge of oncogenic drivers in this specific subtype of lung cancer is largely limited compared with lung adenocarcinoma (ADC). Through exon array analyses, molecular analyses and functional studies, we here identify the TRA2B-DNAH5 fusion as a novel oncogenic driver in lung SCC. We found that this gene fusion occurs exclusively in lung SCC (3.1%, 5/163), but not in lung ADC (0/119). Through mechanistic studies, we further revealed that this TRA2B-DNAH5 fusion promotes lung SCC malignant progression through regulating a SIRT6-ERK1/2-MMP1 signaling axis. We show that inhibition of ERK1/2 activation using selumetinib efficiently inhibits the growth of lung SCC with TRA2B-DNAH5 fusion expression. These findings improve our current knowledge of oncogenic drivers in lung SCC and provide a potential therapeutic strategy for lung SCC patients with TRA2B-DNAH5 fusion.

Interlukin-18 Is a Pivot Regulatory Factor on Matrix Metalloproteinase-13 Expression and Brain Astrocytic Migration

The expression of matrix metalloproteinase-13 (MMP-13) has been shown to be elevated in some pathophysiological conditions and is involved in the degradation of extracellular matrix in astrocytes. In current study, the function of MMP-13 was further investigated. The conditioned medium (CM) collected from activated microglia increased interleukin (IL)-18 production and enhanced MMP-13 expression in astrocytes. Furthermore, treatment with recombinant IL-18 increased MMP-13 protein and mRNA levels in astrocytes. Recombinant IL-18 stimulation also increased the enzymatic activity of MMP-13 and the migratory activity of astrocytes, while administration of MMP-13 or pan-MMP inhibitors antagonized IL-18-induced migratory activity of astrocytes. In addition, administration of recombinant IL-18 to astrocytes led to the phosphorylation of JNK, Akt, or PKCδ, and treatment of astrocytes with JNK, PI3 kinase/Akt, or PKCδ inhibitors significantly decreased the IL-18-induced migratory activity. Taken together, the results suggest that IL-18-induced MMP-13 expression in astrocytes is regulated by JNK, PI3 kinase/Akt, and PKCδ signaling pathways. These findings also indicate that IL-18 is an important regulator leading to MMP-13 expression and cell migration in astrocytes.

Helicobacter pylori virulence factor CagA promotes tumorigenesis of gastric cancer via multiple signaling pathways

Helicobacter pylori (H. pylori) infection is strongly associated with the development of gastric diseases but also with several extragastric diseases. The clinical outcomes caused by H. pylori infection are considered to be associated with a complex combination of host susceptibility, environmental factors and bacterial isolates. Infections involving H. pylori strains that possess the virulence factor CagA have a worse clinical outcome than those involving CagA-negative strains. It is remarkable that CagA-positive H. pylori increase the risk for gastric cancer over the risk associated with H. pylori infection alone. CagA behaves as a bacterial oncoprotein playing a key role in H. pylori-induced gastric cancer. Activation of oncogenic signaling pathways and inactivation of tumor suppressor pathways are two crucial events in the development of gastric cancer. CagA shows the ability to affect the expression or function of vital protein in oncogenic or tumor suppressor signaling pathways via several molecular mechanisms, such as direct binding or interaction, phosphorylation of vital signaling proteins and methylation of tumor suppressor genes. As a result, CagA continuously dysregulates of these signaling pathways and promotes tumorigenesis. Recent research has enriched our understanding of how CagA effects on these signaling pathways. This review summarizes the results of the most relevant studies, discusses the complex molecular mechanism involved and attempts to delineate the entire signaling pathway.

Helicobacter pylori promotes eukaryotic protein translation by activating phosphatidylinositol 3 kinase/mTOR

The innate immune response elicited by Helicobacter pylori in the human gastric mucosa involves a range of cellular signalling pathways, including those implicated in metabolism regulation. In this study, we analysed H. pylori-induced PI3K/Akt/mTOR signalling, which regulates glycolysis and protein synthesis and associates thereby with cellular energy- and nutrients-consuming processes such as growth and proliferation. The immunohistochemical analysis demonstrated that Akt kinase phosphorylation is abundant in gastric biopsies obtained from gastritis, gastric adenoma and adenocarcinoma patients. Infection with H. pylori led to the phosphorylation of Akt effectors mTOR and S6 in a type 4 secretion system (T4SS)-independent manner in AGS cells. We observed that the activation of these molecules was dependent on PI3K and the Src family tyrosine kinases. Furthermore, H. pylori induced the phosphorylation of 4E-BP1 and eIF4E and suppressed the phosphorylation of eEF2, which are important regulators of protein synthesis. Inhibition of PI3K and Akt kinase prevented the phosphorylation of 4E-BP1, suggesting that PI3K signalling is involved in the regulation of translation initiation during H. pylori infection. Metabolic labelling showed that infected cells had higher rates of [(35)S]methionine/cysteine incorporation, and this effect could be prevented using LY294002, an PI3K inhibitor. Thus, H. pylori activates PI3K/Akt signalling, mTOR, eIFs and protein translation, which might impact H. pylori-related gastric pathophysiology.

Anti-inflammatory mechanism of polyunsaturated fatty acids in Helicobacter pylori-infected gastric epithelial cells

Helicobacter pylori is an important risk factor for gastric inflammation, which is mediated by multiple signaling pathways. The aim of this study was to investigate the effects of polyunsaturated fatty acids (PUFAs), such as linoleic acid (LA), alpha-linolenic acid (ALA), and docosahexaenoic acid (DHA), on the expression of the proinflammatory chemokine interleukin-8 (IL-8) in H. pylori-infected gastric epithelial AGS cells. To investigate whether PUFAs modulate H. pylori-induced inflammatory signaling, we determined the activation of epidermal growth factor receptor (EGFR), protein kinase C-δ (PKC δ), mitogen-activated protein kinases (MAPKs), nuclear factor-kappa B (NF- κB), and activator protein-1 (AP-1) as well as IL-8 expression in H. pylori-infected gastric epithelial cells that had been treated with or without PUFAs. We found that PUFAs inhibited IL-8 mRNA and protein expression in H. pylori-infected cells. ω-3 fatty acids (ALA, and DHA) suppressed the activation of EGFR, PKC δ, MAPK, NF- κB, and AP-1 in these infected cells. LA did not prevent EGFR transactivation and exhibited a less potent inhibitory effect on IL-8 expression than did ALA and DHA. In conclusion, PUFAs may be beneficial for prevention of H. pylori-associated gastric inflammation by inhibiting proinflammatory IL-8 expression.

FZD1 activates protein kinase C delta-mediated drug-resistance in multidrug-resistant MES-SA/Dx5 cancer cells

Multidrug-resistant (MDR) cancer is a major clinical problem in chemotherapy of cancer patients. We have noted inappropriate PKCδ hypomethylation and overexpression of genes in the PKCδ/AP-1 pathway in the human uterus sarcoma drug-resistant cell line, MES-SA/Dx5 cells, which also overexpress p-glycoprotein (ABCB1). Recent studies have indicated that FZD1 is overexpressed in both multidrug-resistant cancer cell lines and in clinical tumor samples. These data have led us to hypothesize that the FZD1-mediated PKCδ signal-transduction pathway may play an important role in drug resistance in MES-SA/Dx5 cells. In this work, the PKCδ inhibitor Rottlerin was found to reduce ABCB1 expression and to inhibit the MDR drug pumping ability in the MES-SA/Dx5 cells when compared with the doxorubicin-sensitive parental cell line, MES-SA. PKCδ was up-regulated with concurrent up-regulation of the mRNA levels of the AP-1-related factors, c-JUN and c-FOS. Activation of AP-1 also correlated with up-regulation of the AP-1 downstream genes HGF and EGR1. Furthermore, AP-1 activities were reduced and the AP-1 downstream genes were down-regulated in Rottlerin-treated or PKCδ shRNA-transfected cells. MES-SA/Dx5 cells were resensitized to doxorubicin-induced toxicity by co-treatment with doxorubicin and Rottlerin or PKCδ shRNA. In addition, cell viability and drug pump-out ability were significantly reduced in the FZD1 inhibitor curcumin-treated and FZD1 shRNA-knockdown MES-SA/Dx5 cells, indicating involvement of PKCδ in FZD1-modulated ABCB1 expression pathway. Taken together, our data demonstrate that FZD1 regulates PKCδ, and the PKCδ/AP-1 signalling transduction pathway plays an important role in drug resistance in MES-SA/Dx5 cells.

Protein kinase C mediates enterohemorrhagic Escherichia coli O157:H7-induced attaching and effacing lesions

Enterohemorrhagic Escherichia coli serotype O157:H7 causes outbreaks of diarrhea, hemorrhagic colitis, and the hemolytic-uremic syndrome. E. coli O157:H7 intimately attaches to epithelial cells, effaces microvilli, and recruits F-actin into pedestals to form attaching and effacing lesions. Lipid rafts serve as signal transduction platforms that mediate microbe-host interactions. The aims of this study were to determine if protein kinase C (PKC) is recruited to lipid rafts in response to E. coli O157:H7 infection and what role it plays in attaching and effacing lesion formation. HEp-2 and intestine 407 tissue culture epithelial cells were challenged with E. coli O157:H7, and cell protein extracts were then separated by buoyant density ultracentrifugation to isolate lipid rafts. Immunoblotting for PKC was performed, and localization in lipid rafts was confirmed with an anti-caveolin-1 antibody. Isoform-specific PKC small interfering RNA (siRNA) was used to determine the role of PKC in E. coli O157:H7-induced attaching and effacing lesions. In contrast to uninfected cells, PKC was recruited to lipid rafts in response to E. coli O157:H7. Metabolically active bacteria and cells with intact lipid rafts were necessary for the recruitment of PKC. PKC recruitment was independent of the intimin gene, type III secretion system, and the production of Shiga toxins. Inhibition studies, using myristoylated PKCζ pseudosubstrate, revealed that atypical PKC isoforms were activated in response to the pathogen. Pretreating cells with isoform-specific PKC siRNA showed that PKCζ plays a role in E. coli O157:H7-induced attaching and effacing lesions. We concluded that lipid rafts mediate atypical PKC signal transduction responses to E. coli O157:H7. These findings contribute further to the understanding of the complex array of microbe-eukaryotic cell interactions that occur in response to infection.

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

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

Helicobacter pylori and gastritis: the role of extracellular matrix metalloproteases, their inhibitors, and the disintegrins and metalloproteases--a systematic literature review

Helicobacter pylori (H. pylori) is the etiologic agent of gastritis; it has been estimated that 50 % of the world's population could be infected by this bacteria. Gastritis may progress to chronic atrophic gastritis, a condition associated with the development of gastric cancer (GC). Several matrix metalloproteases (MMP) and tissue inhibitors of MMPs (TIMP) as well as disintegrins and metalloproteases (ADAM) have been reported as being involved in gastritis. Among other processes, these protein families participate in remodeling the extracellular matrix, cell signaling, immune response, angiogenesis, inflammation and epithelial mesenchymal transition. This systematic review analyzes the scientific evidence surrounding the relationship between members of the MMP, TIMP and ADAM families and infection by H. pylori in gastritis, considering both in vitro and in vivo studies. Given the potential clinical value of certain members of the MMP, TIMP and ADAM families as molecular markers in gastritis and the association of gastritis with GC, the need for further study is highlighted.

Ca2+/calmodulin-dependent kinase II contributes to inhibitor of nuclear factor-kappa B kinase complex activation in Helicobacter pylori infection

Helicobacter pylori, a class I carcinogen, induces a proinflammatory response by activating the transcription factor nuclear factor-kappa B (NF-κB) in gastric epithelial cells. This inflammatory condition could lead to chronic gastritis, which is epidemiologically and biologically linked to the development of gastric cancer. So far, there exists no clear knowledge on how H. pylori induces the NF-κB-mediated inflammatory response. In our study, we investigated the role of Ca(2+) /calmodulin-dependent kinase II (CAMKII), calmodulin, protein kinases C (PKCs) and the CARMA3-Bcl10-MALT1 (CBM) complex in conjunction with H. pylori-induced activation of NF-κB via the inhibitor of nuclear factor-kappa B kinase (IKK) complex. We use specific inhibitors and/or RNA interference to assess the contribution of these components. Our results show that CAMKII and calmodulin contribute to IKK complex activation and thus to the induction of NF-κB in response to H. pylori infection, but not in response to TNF-α. Thus, our findings are specific for H. pylori infected cells. Neither the PKCs α, δ, θ, nor the CBM complex itself is involved in the activation of NF-κB by H. pylori. The contribution of CAMKII and calmodulin, but not PKCs/CBM to the induction of an inflammatory response by H. pylori infection augment the understanding of the molecular mechanism involved and provide potential new disease markers for the diagnosis of gastric inflammatory diseases including gastric cancer.

Helicobacter pylori in gastric malignancies

Helicobacter pylori infection remains common worldwide and is significantly associated with gastric adenocarcinoma and gastric mucosa-associated lymphoid tissue (MALT)lymphoma. This article reviews recent developments in the field of H. pylori with an emphasis on mechanisms of carcinogenesis, and the bacterial, environmental and host factors that may alter risk of developing gastric cancer or gastric MALT lymphoma. The topic of eradication of H. pylori to prevent the development of malignancy and the possibility of a vaccine against H. pylori are also explored.

Pathogenesis of Helicobacter pylori infection

Although Helicobacter pylori infection is highly prevalent in the global human population, the majority of infected individuals remain asymptomatic. A complex combination of host, environmental, and bacterial factors are considered to determine susceptibility and severity of outcome in the subset of individuals that develop clinical disease. These factors collectively determine the ability of H. pylori to colonize the gastric mucosa and profoundly influence the nature of the interaction that ensues. Many studies over the last year provide new insight into H. pylori virulence strategies and the activities of critical bacterial determinants that modulate the host environment. These latter include the secreted proteins CagA and VacA and adhesins BabA and OipA, which directly interact with host tissues. Observations from several studies extend the functional repertoire of CagA and the cag type IV secretion system in particular, providing further mechanistic understanding of how these important determinants engage and activate host signalling pathways important in the development of disease.