Adherens junctions as targets of microorganisms: a focus on Helicobacter pylori

The Helicobacter pylori infection alters the intercellular junctions on the pancreas of gerbils (Meriones unguiculatus)

Helicobacter pylori is a common resident in the stomach of at least half of the world's population and recent evidence suggest its emergence in other organs such as the pancreas. In this organ, the presence of H. pylori DNA has been reported in cats, although the functional implications remain unknown. In this work, we determined distinct features related to the H. pylori manifestation in pancreas in a rodent model, in order to analyse its functional and structural effect. Gerbils inoculated with H. pylori exhibited the presence of this bacterium, as revealed by the expression of some virulence factors, as CagA and OMPs in stomach and pancreas, and confirmed by urease activity, bacterial culture, PCR and immunofluorescence assays. Non-apparent morphological changes were observed in pancreatic tissue of infected animals; however, delocalization of intercellular junction proteins (claudin-1, claudin-4, occludin, ZO-1, E-cadherin, β-catenin, desmoglein-2 and desmoplakin I/II) and rearrangement of the actin-cytoskeleton were exhibited. This structural damage was consistent with alterations in the distribution of insulin and glucagon, and a systemic inflammation, event demonstrated by elevated IL-8 levels. Overall, these findings indicate that H. pylori can reach the pancreas, possibly affecting its function and contributing to the development of pancreatic diseases.

Identification of host protein ENO1 (alpha-enolase) interacting with Cryptosporidium parvum sporozoite surface protein, Cpgp40

BACKGROUND

Cryptosporidium parvum is an apicomplexan zoonotic parasite causing the diarrheal illness cryptosporidiosis in humans and animals. To invade the host intestinal epithelial cells, parasitic proteins expressed on the surface of sporozoites interact with host cells to facilitate the formation of parasitophorous vacuole for the parasite to reside and develop. The gp40 of C. parvum, named Cpgp40 and located on the surface of sporozoites, was proven to participate in the process of host cell invasion.

METHODS

We utilized the purified Cpgp40 as a bait to obtain host cell proteins interacting with Cpgp40 through the glutathione S-transferase (GST) pull-down method. In vitro analysis, through bimolecular fluorescence complementation assay (BiFC) and coimmunoprecipitation (Co-IP), confirmed the solid interaction between Cpgp40 and ENO1. In addition, by using protein mutation and parasite infection rate analysis, it was demonstrated that ENO1 plays an important role in the C. parvum invasion of HCT-8 cells.

RESULTS

To illustrate the functional activity of Cpgp40 interacting with host cells, we identified the alpha-enolase protein (ENO1) from HCT-8 cells, which showed direct interaction with Cpgp40. The mRNA level of ENO1 gene was significantly decreased at 3 and 24 h after C. parvum infection. Antibodies and siRNA specific to ENO1 showed the ability to neutralize C. parvum infection in vitro, which indicated the participation of ENO1 during the parasite invasion of HCT-8 cells. In addition, we further demonstrated that ENO1 protein was involved in the regulation of cytoplasmic matrix of HCT-8 cells during C. parvum invasion. Functional study of the protein mutation illustrated that ENO1 was also required for the endogenous development of C. parvum.

CONCLUSIONS

In this study, we utilized the purified Cpgp40 as a bait to obtain host cell proteins ENO1 interacting with Cpgp40. Functional studies illustrated that the host cell protein ENO1 was involved in the regulation of tight junction and adherent junction proteins during C. parvum invasion and was required for endogenous development of C. parvum.

Comparative proteomics reveals Cryptosporidium parvum infection disrupts cellular barriers

Cryptosporidium is a protozoan parasite capable of infecting humans and animals and is a leading cause of diarrheal disease and early childhood mortality. The molecular mechanisms underlying invasive infection and its pathogenesis remain largely unknown. To better understand the molecular mechanism of the interaction between C. parvum and host cells, we profiled the changes of host cells membrane proteins extracted using native membrane protein extraction kit between C. parvum-infected HCT-8 cells and the control group after C. parvum infected 6 h combined with quantitative Tandem Mass Tags (TMT) liquid chromatography-dual mass spectrometry proteomic analysis. Among the 4844 quantifiable proteins identified, the expression levels of 625 were upregulated, and those of 116 were downregulated at 6 h post-infection compared with controls (1.5-fold difference in abundance, p < 0.05). Enrichment analysis of the function, protein domain and Kyoto Encyclopedia of Genes and Genomes pathway of the differentially expressed proteins revealed that the differentially expressed proteins were mainly related to biological functions related to the cytoskeleton and cytoplasmic matrix. We also found that infection with C. parvum may destroy HCT-8 intercellular space adhesion. Six proteins were further verified using quantitative real-time reverse transcription polymerase chain reaction and western blotting. Through systematic analysis of proteomics related to HCT-8 cell membranes infected by C. parvum, we found many host membrane proteins that can serve as potential receptors in C. parvum adhesion or invasion. C. parvum infection destroyed host cell barrier function and caused extensive changes in host cytoskeleton proteins, providing a deeper understanding of the molecules and their functions involved in the host-C. parvum interaction. SIGNIFICANCE: There is a lack of systematic research on the molecular mechanisms underlying the interaction of C. parvum with host cells. Changes of host cell membrane proteins after C. parvum infection may be used to examine the host cell receptors for parasite adhesion and invasion, and how the parasite interacts with these receptors. It is of great significance that host cells undergo membrane fusion to mediate invasion. Through proteomic studies on the host cell membrane after infection with HCT-8 cells by C. parvum, we observed disruption of the host cell cellular barrier function and widespread alteration of host cytoskeletal proteins caused by C. parvum infection, providing a deeper understanding of the molecules and their functions involved in host-C. parvum interaction.

Impact of enteric bacterial infections at and beyond the epithelial barrier

The mucosal lining of the gut has co-evolved with a diverse microbiota over millions of years, leading to the development of specialized mechanisms to actively limit the invasion of pathogens. However, some enteric microorganisms have adapted against these measures, developing ways to hijack or overcome epithelial micro-integrity mechanisms. This breach of the gut barrier not only enables the leakage of host factors out of circulation but can also initiate a cascade of detrimental systemic events as microbiota, pathogens and their affiliated secretions passively leak into extra-intestinal sites. Under normal circumstances, gut damage is rapidly repaired by intestinal stem cells. However, with substantial and deep perturbation to the gut lining and the systemic dissemination of gut contents, we now know that some enteric infections can cause the impairment of host regenerative processes. Although these local and systemic aspects of enteric disease are often studied in isolation, they heavily impact one another. In this Review, by examining the journey of enteric infections from initial establishment to systemic sequelae and how, or if, the host can successfully repair damage, we will tie together these complex interactions to provide a holistic overview of the impact of enteric infections at and beyond the epithelial barrier.

Surface layer protein A from hypervirulent Clostridioides difficile ribotypes induce significant changes in the gene expression of tight junctions and inflammatory response in human intestinal epithelial cells

BACKGROUND

Surface layer protein A (SlpA), the primary outermost structure of Clostridioides difficile, plays an essential role in C. difficile pathogenesis, although its interaction with host intestinal cells are yet to be understood. The aim of this study was to investigate the effects of SlpA extracted from C. difficile on tight junction (TJ) proteins expression and induction of pro-inflammatory cytokines in human colon carcinoma cell line HT-29. SlpA was extracted from three toxigenic C. difficile clinical strains including RT126, RT001, RT084 as well as C. difficile ATCC 700057 as non-toxigenic strain. Cell viability was performed by MTT assay, and the mRNA expression of TJ proteins and inflammation-associated genes was determined using quantitative RT-PCR. Additionally, the secretion of IL-8, IL-1β and TNF-α cytokines was measured by ELISA.

RESULTS

C. difficile SlpA from selected RTs variably downregulated the expression level of TJs-assassinated genes and increased the expression level of TLR-4 and pro-inflammatory cytokines in HT-29 treated cells. SlpA from RT126 significantly (padj<0.05) decreased the gene expression level of claudins family and JAM-A and increased the secretion of IL-8, TNF-α and IL1-β as compared to untreated cells. Moreover, only SlpA from RT001 could significantly induce the expression of IL-6 (padj<0.05).

CONCLUSION

The results of the present study highlighted the importance of SlpA in the pathogenesis of CDI and C. difficile-induced inflammatory response in the gut. Further studies are required to unravel the significance of the observed results in promoting the intestinal inflammation and immune response induced by C. difficile SlpA from different RTs.

Inflammatory and Oxidative Pathways Are New Drug Targets in Multiple Episode Schizophrenia and Leaky Gut, Klebsiella pneumoniae, and C1q Immune Complexes Are Additional Drug Targets in First Episode Schizophrenia

Breakdown of paracellular and vascular pathways and activated neuroimmune and oxidative pathways was established in (deficit) schizophrenia. The aim of this study was to delineate (a) the differences in these pathways between stable-phase, first (FES) and multiple (MES) episode schizophrenia and (b) the pathways that determine the behavioral-cognitive-physical-psychosocial (BCPS) deterioration in FES/MES. This study included 21 FES and 58 FES patients and 40 healthy controls and measured indicants of serum C1q circulating immune complexes (CIC), leaky gut, immune activation, and oxidative stress toxicity (OSTOX). We constructed a BCPS-worsening index by extracting a latent vector from symptomatic, neurocognitive, and quality of life data. FES was associated with higher IgA CIC-C1q, IgA directed to cadherin, catenin, and plasmalemma vesicle-associated protein, and IgA/IgM to Gram-negative bacteria as compared with FES and controls. In FES patients, the BCPS-worsening score was predicted (48.7%) by IgA to Klebsiella pneumoniae and lowered paraoxonase 1 activity. In MES patients, the BCPS-worsening score was explained (42.7%) by increased tumor necrosis factor-α, OSTOX, and number of episodes. In schizophrenia, 34.0% of the variance in the BCPS-worsening score was explained by IgA to K. pneumoniae, OSTOX, and number of episodes. Increased IgA to K. pneumoniae was the single best predictor of residual psychotic symptoms in FES and MES. This study delineated different mechanistic processes in FES, including breakdown of adherens junctions, bacterial translocation, and IgA CIC-C1q formation, and MES, including immune and oxidative neurotoxic pathways. FES and MES comprise different staging subtypes, i.e., FES and MES with and without worsening.

Hypervirulent Klebsiella pneumoniae infection in a woman with a CDH1 gene mutation

The CDH1 gene, which encodes E-cadherin, may be associated with cancer when mutated, but the significance of mutations in the context of infection is unknown. In this report, we describe a case of disseminated hypervirulent Klebsiella pneumoniae infection in a 49 year old Caucasian woman with a documented CDH1 mutation.

Virulence factors impair epithelial junctions during bacterial infection

Epithelial cells are typically connected through different types of cell junctions that are localized from the apical membrane to the basal surface. In this way, epithelium cells form the first barrier against pathogenic microorganisms and prevent their entry into internal organs and the circulatory system. Recent studies demonstrate that bacterial pathogens disrupt epithelial cell junctions through targeting junctional proteins by secreted virulence factors. In this review, we discuss the diverse strategies used by common bacterial pathogens, including Pseudomonas aeruginosa, Helicobacter pylori, and enteropathogenic Escherichia coli, to disrupt epithelial cell junctions during infection. We also discuss the potential of targeting the pathogenic mechanisms in the treatment of pathogen-associated diseases.

Identification of functional mutations associated with environmental variance of litter size in rabbits

Background

Environmental variance (V_E) is partly under genetic control and has recently been proposed as a measure of resilience. Unravelling the genetic background of the V_E of complex traits could help to improve resilience of livestock and stabilize their production across farming systems. The objective of this study was to identify genes and functional mutations associated with variation in V_E of litter size (LS) in rabbits. To achieve this, we combined the results of a genome-wide association study (GWAS) and a whole-genome sequencing (WGS) analysis using data from two divergently selected rabbit lines for high and low V_E of LS. These lines differ in terms of biomarkers of immune response and mortality. Moreover, rabbits with a lower V_E of LS were found to be more resilient to infections than animals with a higher V_E of LS.

Results

By using two GWAS approaches (single-marker regression and Bayesian multiple-marker regression), we identified four genomic regions associated with V_E of LS, on chromosomes 3, 7, 10, and 14. We detected 38 genes in the associated genomic regions and, using WGS, we identified 129 variants in the splicing, UTR, and coding (missense and frameshift effects) regions of 16 of these 38 genes. These genes were related to the immune system, the development of sensory structures, and stress responses. All of these variants (except one) segregated in one of the rabbit lines and were absent (n = 91) or fixed in the other one (n = 37). The fixed variants were in the HDAC9, ITGB8, MIS18A, ENSOCUG00000021276 and URB1 genes. We also identified a 1-bp deletion in the 3′UTR region of the HUNK gene that was fixed in the low V_E line and absent in the high V_E line.

Conclusions

This is the first study that combines GWAS and WGS analyses to study the genetic basis of V_E. The new candidate genes and functional mutations identified in this study suggest that the V_E of LS is under the control of functions related to the immune system, stress response, and the nervous system. These findings could also explain differences in resilience between rabbits with homogeneous and heterogeneous V_E of litter size.

Mechanisms of the Epithelial-Mesenchymal Transition and Tumor Microenvironment in Helicobacter pylori-Induced Gastric Cancer

Helicobacter pylori (H. pylori) is one of the most common human pathogens, affecting half of the world's population. Approximately 20% of the infected patients develop gastric ulcers or neoplastic changes in the gastric stroma. An infection also leads to the progression of epithelial-mesenchymal transition within gastric tissue, increasing the probability of gastric cancer development. This paper aims to review the role of H. pylori and its virulence factors in epithelial-mesenchymal transition associated with malignant transformation within the gastric stroma. The reviewed factors included: CagA (cytotoxin-associated gene A) along with induction of cancer stem-cell properties and interaction with YAP (Yes-associated protein pathway), tumor necrosis factor α-inducing protein, Lpp20 lipoprotein, Afadin protein, penicillin-binding protein 1A, microRNA-29a-3p, programmed cell death protein 4, lysosomal-associated protein transmembrane 4β, cancer-associated fibroblasts, heparin-binding epidermal growth factor (HB-EGF), matrix metalloproteinase-7 (MMP-7), and cancer stem cells (CSCs). The review summarizes the most recent findings, providing insight into potential molecular targets and new treatment strategies for gastric cancer.

Clostridioides difficile infection damages colonic stem cells via TcdB, impairing epithelial repair and recovery from disease

Gastrointestinal infections often induce epithelial damage that must be repaired for optimal gut function. While intestinal stem cells are critical for this regeneration process [R. C. van der Wath, B. S. Gardiner, A. W. Burgess, D. W. Smith, PLoS One 8, e73204 (2013); S. Kozar et al., Cell Stem Cell 13, 626-633 (2013)], how they are impacted by enteric infections remains poorly defined. Here, we investigate infection-mediated damage to the colonic stem cell compartment and how this affects epithelial repair and recovery from infection. Using the pathogen Clostridioides difficile, we show that infection disrupts murine intestinal cellular organization and integrity deep into the epithelium, to expose the otherwise protected stem cell compartment, in a TcdB-mediated process. Exposure and susceptibility of colonic stem cells to intoxication compromises their function during infection, which diminishes their ability to repair the injured epithelium, shown by altered stem cell signaling and a reduction in the growth of colonic organoids from stem cells isolated from infected mice. We also show, using both mouse and human colonic organoids, that TcdB from epidemic ribotype 027 strains does not require Frizzled 1/2/7 binding to elicit this dysfunctional stem cell state. This stem cell dysfunction induces a significant delay in recovery and repair of the intestinal epithelium of up to 2 wk post the infection peak. Our results uncover a mechanism by which an enteric pathogen subverts repair processes by targeting stem cells during infection and preventing epithelial regeneration, which prolongs epithelial barrier impairment and creates an environment in which disease recurrence is likely.

Flavodoxins as Novel Therapeutic Targets against Helicobacter pylori and Other Gastric Pathogens

Flavodoxins are small soluble electron transfer proteins widely present in bacteria and absent in vertebrates. Flavodoxins participate in different metabolic pathways and, in some bacteria, they have been shown to be essential proteins representing promising therapeutic targets to fight bacterial infections. Using purified flavodoxin and chemical libraries, leads can be identified that block flavodoxin function and act as bactericidal molecules, as it has been demonstrated for Helicobacter pylori (Hp), the most prevalent human gastric pathogen. Increasing antimicrobial resistance by this bacterium has led current therapies to lose effectiveness, so alternative treatments are urgently required. Here, we summarize, with a focus on flavodoxin, opportunities for pharmacological intervention offered by the potential protein targets described for this bacterium and provide information on other gastrointestinal pathogens and also on bacteria from the gut microbiota that contain flavodoxin. The process of discovery and development of novel antimicrobials specific for Hp flavodoxin that is being carried out in our group is explained, as it can be extrapolated to the discovery of inhibitors specific for other gastric pathogens. The high specificity for Hp of the antimicrobials developed may be of help to reduce damage to the gut microbiota and to slow down the development of resistant Hp mutants.

Epidermal growth factor receptor 2 immunoexpression in gastric cells of domestic cats with H. heilmannii infection

The aim of this study was to evaluate the immunoexpression of HER-2 in gastric cells of cats infected with Non H. pylori Helicobacter (NHPH) and to investigate an association with the presence of inflammatory infiltrate. Forty-eight paraffin-embedded gastric samples were retrieved from the archives of the Veterinary Anatomic Pathology Laboratory that had previously been shown to be positive for NHPH with the rapid urease test and cytology. Infection by NHPH was confirmed by histopathology using the Warthin-Starry staining. Hematoxylin-eosin stained sections were reviewed to evaluate inflammatory cell infiltrates. Immunohistochemical analysis was done using anti- H. pylori antibody and anti-HER-2 antibody. Molecular analysis was performed by PCR to confirm the presence of Helicobacter. Statistical analysis was performed to determine whether there was an association between the presence of H. Heilmannii and HER-2 expression in gastric samples. All samples were positive for NHPH, by immunohistochemistry, and confirmed by PCR as H. Heilmannii. On histopathologic analysis, 56,3% of the samples had lymphocytes and plasma cells infiltrates, 52,1% of which were mild and 4,2% moderate. The intensity of the inflammatory infiltrate in the gastric mucosa was significantly greater in the complete plasma membrane of parietal cells of gastric glands that had greater HER-2 immunoexpression (p = 0.0001). A statistically significant association (p = 0.007) between the H. Heilmannii infection score and the expression of HER-2 in the lateral membrane of gastric surface cells was observed. HER-2 expression may be increased in feline gastric cells infected by H. Heilmannii and in parietal cells of gastric glands with an increased inflammatory infiltrate.

Cryptosporidium parvum disrupts intestinal epithelial barrier function via altering expression of key tight junction and adherens junction proteins

Infection with the protozoan parasite Cryptosporidium parvum (CP) causes cryptosporidiosis, a widespread diarrhoeal disease. Impaired intestinal epithelial barrier function and increased permeability are most commonly associated with diarrhoeal diseases caused by enteric infections. However, studies on barrier disruption and underlying mechanisms in cryptosporidiosis are extremely limited. Epithelial tight junctions (TJs) and adherens junctions (AJs) are important in maintaining barrier integrity. Therefore, we examined the effects of CP infection on paracellular permeability and on the expression of the major TJ and AJ proteins utilising in vitro, ex vivo, and in vivo models. CP infection (0.5 × 106  oocysts/well in Transwell inserts, 24 hr) increased paracellular permeability (FITC-dextran flux) in Caco-2 cell monolayers and substantially decreased the protein levels of occludin, claudin 4, and E-cadherin. Claudin 3, zonula occludens-1 (ZO1) and α-catenin were also significantly decreased, whereas claudins 1 and 2 and β-catenin were not altered. Substantial downregulation of occludin, claudin 4, and E-cadherin was also observed in response to CP infection ex vivo in mouse enteroid-derived monolayers and in vivo in the ileal and jejunal mocosa of C57BL/6 mice. The mRNA levels of these proteins were also significantly decreased in CP-infected mouse ileum and jejunum but were unaltered in Caco-2 cells. Further, bafilomycin-A, an inhibitor of lysosomal proton pump, partially abrogated CP effects on occludin expression in Caco-2 cells, suggesting a potential role of posttranslational mechanisms, such as induction of protein degradation pathways, in mediating the effects of the parasite. Our studies suggest that disruption of barrier function via downregulation of specific key components of TJ and AJ could be a major mechanism underlying CP infection-induced diarrhoea.

The biological challenges and pharmacological opportunities of orally administered nanomedicine delivery

Nano-scale formulations are being developed to improve the delivery of orally administered medicines, and the interactions between nanoformulations and the gastrointestinal luminal, mucosal and epithelial environment is currently being investigated. The mucosal surface of the gastrointestinal tract is capable of trapping and eliminating large particles and pathogens as part of the natural defences of the body, it is becoming clearer that nanoformulation properties such as particle size, charge, and shape, as well as mucous properties such as viscoelasticity, thickness, density, and turn-over time are all relevant to these interactions. However, progress has been slow to utilise this information to produce effective mucous-penetrating particles. Areas covered: This review focuses on delivery method of nanomedicines both into and across the gastrointestinal mucosal surface, and aims to summarise the biological barriers that exist to successful oral nanomedicine delivery and how these barriers may be investigated and overcome. Expert commentary: Despite successes in the laboratory, no nanotechnology-enabled products are currently in clinical use which either specifically target the intestinal mucous surface or cross the epithelial barrier intact. New nanomedicine-based treatments of local diseases (intestinal cancer, inflammation, infection) and systemic diseases are advancing towards clinical use, and offer genuine opportunities to improve therapy.

Helicobacter pylori Employs a Unique Basolateral Type IV Secretion Mechanism for CagA Delivery

The Helicobacter pylori (Hp) type IV secretion system (T4SS) forms needle-like pili, whose binding to the integrin-β1 receptor results in injection of the CagA oncoprotein. However, the apical surface of epithelial cells is exposed to Hp, whereas integrins are basolateral receptors. Hence, the mechanism of CagA delivery into polarized gastric epithelial cells remains enigmatic. Here, we demonstrate that T4SS pilus formation during infection of polarized cells occurs predominantly at basolateral membranes, and not at apical sites. Hp accomplishes this by secreting another bacterial protein, the serine protease HtrA, which opens cell-to-cell junctions through cleaving epithelial junctional proteins including occludin, claudin-8, and E-cadherin. Using a genetic system expressing a peptide inhibitor, we demonstrate that HtrA activity is necessary for paracellular transmigration of Hp across polarized cell monolayers to reach basolateral membranes and inject CagA. The contribution of this unique signaling cascade to Hp pathogenesis is discussed.

Adherens junctions and desmosomes are damaged by Entamoeba histolytica: Participation of EhCPADH complex and EhCP112 protease

Entamoeba histolytica trophozoites adhere to epithelium at the cell-cell contact and perturb tight junctions disturbing the transepithelial electrical resistance. Behind tight junctions are the adherens junctions (AJs) that reinforce them and the desmosomes (DSMs) that maintain the epithelium integrity. The damage produced to AJs and DMSs by this parasite is unknown. Here, we studied the effect of the trophozoites, the EhCPADH complex, and the EhCP112 recombinant enzyme (rEhCP112) on AJ and DSM proteins. We found that trophozoites degraded β-cat, E-cad, Dsp l/ll, and Dsg-2 with the participation of EhCPADH and EhCP112. After contact of epithelial cells with trophozoites, immunofluorescence and transmission electron microscopy assays revealed EhCPADH and rEhCP112 at the intercellular space where they colocalised with β-cat, E-cad, Dsp l/ll, and Dsg-2. Moreover, our results suggested that rEhCP112 could be internalised by caveolae and clathrin-coated vesicles. Immunoprecipitation assays showed the interaction of EhCPADH with β-cat and Dsp l/ll. Besides, in vivo assays demonstrated that rEhCP112 concentrates at the cellular borders of the mouse intestine degrading E-cad and Dsp I/II. Our research gives the first clues on the trophozoite attack to AJs and DSMs and point out the role of the EhCPADH and EhCP112 in the multifactorial event of trophozoites virulence.

Intracellular delivery of oligonucleotides in Helicobacter pylori by fusogenic liposomes in the presence of gastric mucus

The rising antimicrobial resistance contributes to 25000 annual deaths in Europe. This threat to the public health can only be tackled if novel antimicrobials are developed, combined with a more precise use of the currently available antibiotics through the implementation of fast, specific, diagnostic methods. Nucleic acid mimics (NAMs) that are able to hybridize intracellular bacterial RNA have the potential to become such a new class of antimicrobials and additionally could serve as specific detection probes. However, an essential requirement is that these NAMs should be delivered into the bacterial cytoplasm, which is a particular challenge given the fact that they are charged macromolecules. We consider these delivery challenges in relation to the gastric pathogen Helicobacter pylori, the most frequent chronic infection worldwide. In particular, we evaluate if cationic fusogenic liposomes are suitable carriers to deliver NAMs across the gastric mucus barrier and the bacterial envelope. Our study shows that DOTAP-DOPE liposomes post-PEGylated with DSPE-PEG (DSPE Lpx) can indeed successfully deliver NAMs into Helicobacter pylori, while offering protection to the NAMs from binding and inactivation in gastric mucus isolated from pigs. DSPE Lpx thus offer exciting new possibilities for in vivo diagnosis and treatment of Helicobacter pylori infections.

Membrane-bound β-catenin degradation is enhanced by ETS2-mediated Siah1 induction in Helicobacter pylori-infected gastric cancer cells

β-catenin has two different cellular functions: intercellular adhesion and transcriptional activity. The E3 ubiquitin ligase Siah1 causes ubiquitin-mediated degradation of the cytosolic β-catenin and therefore, impairs nuclear translocation and oncogenic function of β-catenin. However, the effect of Siah1 on the cell membrane bound β-catenin has not been studied. In this study, we identified that the carcinogenic bacterium H. pylori increased ETS2 transcription factor-mediated Siah1 protein expression in gastric cancer cells (GCCs) MKN45, AGS and Kato III. Siah1 protein level was also noticeably higher in gastric adenocarcinoma biopsy samples as compared to non-cancerous gastric epithelia. Siah1 knockdown significantly decreased invasiveness and migration of H. pylori-infected GCCs. Although, Siah1 could not increase degradation of the cytosolic β-catenin and its nuclear translocation, it enhanced degradation of the membrane-bound β-catenin in the infected GCCs. This loss of membrane-bound pool of β-catenin was not associated with the proteasomal degradation of E-cadherin. Thus, this work delineated the role of Siah1 in increasing invasiveness of H. pylori-infected GCCs.

Type IV Secretion and Signal Transduction of Helicobacter pylori CagA through Interactions with Host Cell Receptors

Helicobacter pylori is a highly successful human bacterium, which is exceptionally equipped to persistently inhabit the human stomach. Colonization by this pathogen is associated with gastric disorders ranging from chronic gastritis and peptic ulcers to cancer. Highly virulent H. pylori strains express the well-established adhesins BabA/B, SabA, AlpA/B, OipA, and HopQ, and a type IV secretion system (T4SS) encoded by the cag pathogenicity island (PAI). The adhesins ascertain intimate bacterial contact to gastric epithelial cells, while the T4SS represents an extracellular pilus-like structure for the translocation of the effector protein CagA. Numerous T4SS components including CagI, CagL, CagY, and CagA have been shown to target the integrin-β₁ receptor followed by translocation of CagA across the host cell membrane. The interaction of CagA with membrane-anchored phosphatidylserine and CagA-containing outer membrane vesicles may also play a role in the delivery process. Translocated CagA undergoes tyrosine phosphorylation in C-terminal EPIYA-repeat motifs by oncogenic Src and Abl kinases. CagA then interacts with an array of host signaling proteins followed by their activation or inactivation in phosphorylation-dependent and phosphorylation-independent fashions. We now count about 25 host cell binding partners of intracellular CagA, which represent the highest quantity of all currently known virulence-associated effector proteins in the microbial world. Here we review the research progress in characterizing interactions of CagA with multiple host cell receptors in the gastric epithelium, including integrin-β₁, EGFR, c-Met, CD44, E-cadherin, and gp130. The contribution of these interactions to H. pylori colonization, signal transduction, and gastric pathogenesis is discussed.

Adhesion and Invasion of Gastric Mucosa Epithelial Cells by Helicobacter pylori

Helicobacter pylori is the main pathogenic bacterium involved in chronic gastritis and peptic ulcer and a class 1 carcinogen in gastric cancer. Current research focuses on the pathogenicity of H. pylori and the mechanism by which it colonizes the gastric mucosa. An increasing number of in vivo and in vitro studies demonstrate that H. pylori can invade and proliferate in epithelial cells, suggesting that this process might play an important role in disease induction, immune escape and chronic infection. Therefore, to explore the process and mechanism of adhesion and invasion of gastric mucosa epithelial cells by H. pylori is particularly important. This review examines the relevant studies and describes evidence regarding the adhesion to and invasion of gastric mucosa epithelial cells by H. pylori.

E-cadherin roles in animal biology: A perspective on thyroid hormone-influence

The establishment, remodeling and maintenance of tissular architecture during animal development, and even across juvenile to adult life, are deeply regulated by a delicate interplay of extracellular signals, cell membrane receptors and intracellular signal messengers. It is well known that cell adhesion molecules (cell-cell and cell-extracellular matrix) play a critical role in these processes. Particularly, adherens junctions (AJs) mediated by E-cadherin and catenins determine cell-cell contact survival and epithelia function. Consequently, this review seeks to encompass the complex and prolific knowledge about E-cadherin roles during physiological and pathological states, particularly focusing on the influence exerted by the thyroid hormone (TH).

Immunosuppressant MPA Modulates Tight Junction through Epigenetic Activation of MLCK/MLC-2 Pathway via p38MAPK

BACKGROUND

Mycophenolic acid (MPA) is an important immunosuppressive drug (ISD) prescribed to prevent graft rejection in the organ transplanted patients, however, its use is also associated with adverse side effects like sporadic gastrointestinal (GI) disturbances. Recently, we reported the MPA induced tight junctions (TJs) deregulation which involves MLCK/MLC-2 pathway. Here, we investigated the global histone acetylation as well as gene-specific chromatin signature of several genes associated with TJs regulation in Caco-2 cells after MPA treatment.

RESULTS

The epigenetic analysis shows that MPA treatment increases the global histone acetylation levels as well as the enrichment for transcriptional active histone modification mark (H3K4me3) at promoter regions of p38MAPK, ATF-2, MLCK, and MLC-2. In contrast, the promoter region of occludin was enriched for transcriptional repressive histone modification mark (H3K27me3) after MPA treatment. In line with the chromatin status, MPA treatment increased the expression of p38MAPK, ATF-2, MLCK, and MLC-2 both at transcriptional and translational level, while occludin expression was negatively influenced. Interestingly, the MPA induced gene expression changes and functional properties of Caco-2 cells could be blocked by the inhibition of p38MAPK using a chemical inhibitor (SB203580).

CONCLUSIONS

Collectively, our results highlight that MPA disrupts the structure of TJs via p38MAPK-dependent activation of MLCK/MLC-2 pathway that results in decreased integrity of Caco-2 monolayer. These results led us to suggest that p38MAPK-mediated lose integrity of epithelial monolayer could be the possible cause of GI disturbance (barrier dysfunction) in the intestine, leading to leaky style diarrhea observed in the organ-transplanted patients treated with MPA.

Effect of Native Gastric Mucus on in vivo Hybridization Therapies Directed at Helicobacter pylori

Helicobacter pylori infects more than 50% of the worldwide population. It is mostly found deep in the gastric mucus lining of the stomach, being a major cause of peptic ulcers and gastric adenocarcinoma. To face the increasing resistance of H. pylori to antibiotics, antimicrobial nucleic acid mimics are a promising alternative. In particular, locked nucleic acids (LNA)/2'-OMethyl RNA (2'OMe) have shown to specifically target H. pylori, as evidenced by in situ hybridization. The success of in vivo hybridization depends on the ability of these nucleic acids to penetrate the major physical barriers-the highly viscoelastic gastric mucus and the bacterial cell envelope. We found that LNA/2'OMe is capable of diffusing rapidly through native, undiluted, gastric mucus isolated from porcine stomachs, without degradation. Moreover, although LNA/2'OMe hybridization was still successful without permeabilization and fixation of the bacteria, which is normally part of in vitro studies, the ability of LNA/2'OMe to efficiently hybridize with H. pylori was hampered by the presence of mucus. Future research should focus on developing nanocarriers that shield LNA/2'OMe from components in the gastric mucus, while remaining capable of diffusing through the mucus and delivering these nucleic acid mimics directly into the bacteria.

Campylobacter jejuni outer membrane vesicle-associated proteolytic activity promotes bacterial invasion by mediating cleavage of intestinal epithelial cell E-cadherin and occludin

Outer membrane vesicles (OMVs) play an important role in the pathogenicity of Gram-negative bacteria. Campylobacter jejuni produces OMVs that trigger IL-8, IL-6, hBD-3 and TNF-α responses from T84 intestinal epithelial cells and are cytotoxic to Caco-2 IECs and Galleria mellonella larvae. Proteomic analysis of 11168H OMVs identified the presence of three proteases, HtrA, Cj0511 and Cj1365c. In this study, 11168H OMVs were shown to possess proteolytic activity that was reduced by pretreatment with specific serine protease inhibitors. OMVs isolated from 11168H htrA, Cj0511 or Cj1365c mutants possess significantly reduced proteolytic activity. 11168H OMVs are able to cleave both E-cadherin and occludin, but this cleavage is reduced with OMVs pretreated with serine protease inhibitors and also with OMVs isolated from htrA or Cj1365c mutants. Co-incubation of T84 monolayers with 11168H OMVs results in a visible reduction in both E-cadherin and occludin. The addition of 11168H OMVs to the co-culture of live 11168H bacteria with T84 cells results in enhanced levels of bacterial adhesion and invasion in a time-dependent and dose-dependent manner. Further investigation of the cleavage of host cell structural proteins by C. jejuni OMVs should enhance our understanding of the interactions of this important pathogen with intestinal epithelial cells.

Inhibition of Helicobacter pylori growth and its colonization factors by Parthenium hysterophorus extracts

ETHNOPHARMACOLOGICAL RELEVANCE

Parthenium hysterophorus (Asteraceae) is a traditional medicinal plant used to treat gastrointestinal disorders, such as gastritis. Helicobacter pylori have been described as the etiological agent of gastritis, peptic ulcer, as well as gastric adenocarcinoma. 50% of the world's population is infected with this bacterium and the current therapy fails due to the increment in antibiotic resistance; therefore, it is necessary to find new approaches to control H. pylori infection, either by its eradication or by preventing the bacterial colonization.

AIM OF THE STUDY

To investigate the effect of P. hysterophorus extracts on H. pylori growth and upon its colonization-related factors.

MATERIALS AND METHODS

Five different polarity extracts from roots and aerial parts of P. hysterophorus were evaluated in vitro against H. pylori growth by the broth dilution method. Anti-colonization activities were determined as follows: motility in soft agar plates, urease activity by ammonia colorimetrical quantification, and adherence of FITC labeled H. pylori to AGS cells by fluorometrical measurement.

RESULTS

Organic extracts inhibited H. pylori growth. Particularly, the dichloromethane extract from roots showed a MIC of 15.6 µg/ml while the aqueous extracts showed low or null activity. There is a direct correlation between antibacterial activity and inhibition of motility. Urease activity was partially inhibited by organic extracts, at best 46%, except for the roots dichloromethane extract which reached 74% of inhibition with 500 µg/ml (IC50=136.4 µg/ml). Plant extracts inhibited adherence in different ranges but the dichloromethane-methanol ones possessed the highest effect, with a 70% maximal inhibition at 1mg/ml.

CONCLUSION

The results indicate that some P. hysterophorus extracts have various biological activities that could act synergistically against H. pylori. This work contributes to the ethnomedical knowledge of this species and underlines the potential of some organic extracts as a good source for the isolation of bioactive compounds.

Plasma membrane-associated superstructure: Have we overlooked a new type of organelle in eukaryotic cells?

A variety of intriguing plasma membrane-associated regions, including focal adhesions, adherens junctions, tight junctions, immunological synapses, neuromuscular junctions and the primary cilia, among many others, have been described in eukaryotic cells. Emphasizing their importance, alteration in their molecular structures induces or correlates with different pathologies. These regions display surface proteins connected to intracellular molecules, including cytoskeletal component, which maintain their cytoarchitecture, and signalling proteins, which regulate their organization and functions. Based on the molecular similarities and other common features observed, we suggest that, despite differences in external appearances, all these regions are just the same superstructure that appears in different locations and cells. We hypothesize that this superstructure represents an overlooked new type of organelle that we call plasma membrane-associated superstructure (PMAS). Therefore, we suggest that eukaryotic cells include classical organelles (e.g. mitochondria, Golgi and others) and also PMAS. We speculate that this new type of organelle might be an innovation associated to the emergence of eukaryotes. Finally we discuss the implications of the hypothesis proposed.

Transcriptional regulators of claudins in epithelial tight junctions

Human gastrointestinal tract is covered by a monolayer of specialized epithelial cells that constitute a protective barrier surface to external toxic and infectious agents along with metabolic and digestive functions. Intercellular junctions, among epithelial cells, such as desmosomes, adherens, gap, and tight junctions (TJs), not only provide mechanical integrity but also limit movement of molecules across the monolayer. TJ is a complex structure composed of approximately 35 different proteins that interact with each other at the apical side of two adjacent epithelial cells. Claudin family proteins are important members of TJ with so far 24 known isoforms in different species. Claudins are structural proteins of TJ that help to control the paracellular movement by forming fence and barrier across the epithelial monolayer. Altered function of claudins is implicated in different form of cancers, inflammatory bowel diseases (IBDs), and leaky diarrhea. Based on their significant role in the molecular architecture of TJ, diversity, and disease association, further understanding about claudin family proteins and their genetic/epigenetic regulators is indispensable.

Alterations of the apical junctional complex and actin cytoskeleton and their role in colorectal cancer progression

Colorectal cancer represents the fourth highest mortality rate among cancer types worldwide. An understanding of the molecular mechanisms that regulate their progression can prevents or reduces mortality due to this disease. Epithelial cells present an apical junctional complex connected to the actin cytoskeleton, which maintains the dynamic properties of this complex, tissue architecture and cell homeostasis. Several studies have indicated that apical junctional complex alterations and actin cytoskeleton disorganization play a critical role in epithelial cancer progression. However, few studies have examined the existence of an interrelation between these 2 components, particularly in colorectal cancer. This review discusses the recent progress toward elucidating the role of alterations of apical junctional complex constituents and of modifications of actin cytoskeleton organization and discusses how these events are interlinked to modulate cellular responses related to colorectal cancer progression toward successful metastasis.

Mechanisms underlying role of probiotics in recovering Helicobacter pylori-associated intestinal mucosal barrier damage

Helicobacter pylori (H. pylori) is closely associated with many gastrointestinal diseases, including peptic ulcers, chronic gastritis, gastric cancer and gastric mucosa-associated lymphoid tumors. In recent year, traditional triple therapy for H. pylori eradication has become less effective than the past, which is related to the resistance of bacteria. The addition of probiotics into the regimen has been proved to be able to significantly enhance the eradication rate and reduce side effects. Probiotics increase the eradication of H. pylori by recovering the damage of the chemical barrier, biological barrier, mechanical barrier and immune barrier.