Induction of apoptosis and expression of apoptosis related genes in human epithelial carcinoma cells by Helicobacter pylori VacA toxin

Helicobacter pylori VacA-induced mitochondrial damage in the gastric pit cells of the antrum and therapeutic rescue

Exploring host cell specificity, pathogenicity, and molecular mechanisms of the vacuolating cytotoxin A (VacA), secreted by Helicobacter pylori (Hp) is crucial for developing novel treatment strategies. VacA affects subcellular events, particularly mitochondria, at a cell-type-specific level. However, the lack of reliable models that mimic VacA-induced subcellular damages and enable novel drug screening linked to the human stomach clinically limits our understanding of the mitochondrial networks in vivo. Here, human antrum gastric organoids (hAGOs) and tissue samples from Hp-infected patients were used to show the toxic effects of VacA-induced mitochondrial damage mainly in mucus-producing gastric pit cells by employing transcriptional, translational, and functional analyses. In VacA-intoxicated or Hp-infected hAGOs, robust mitochondrial fragmentation in gastric pit cells reduced ATP production during respiration, and loss of mucosal barrier integrity was first demonstrated experimentally. Using hAGOs, clinically relevant small molecules were screened for efficacy, and MLN8054, an Aurora kinase A inhibitor, reversed VacA-induced mitochondrial damage and loss of gastric epithelium integrity. MLN8054 was effective in VacA-treated and Hp-infected hAGOs and mice, highlighting hAGOs as a promising drug-screening model. These findings suggest that mitochondrial quality control may serve as a promising therapeutic target for Hp VacA-mediated toxicity and disease progression.

There Are No Insurmountable Barriers: Passage of the Helicobacter pylori VacA Toxin from Bacterial Cytoplasm to Eukaryotic Cell Organelle

The Gram-negative bacterium Helicobacter pylori is a very successful pathogen, one of the most commonly identified causes of bacterial infections in humans worldwide. H. pylori produces several virulence factors that contribute to its persistence in the hostile host habitat and to its pathogenicity. The most extensively studied are cytotoxin-associated gene A (CagA) and vacuolating cytotoxin A (VacA). VacA is present in almost all H. pylori strains. As a secreted multifunctional toxin, it assists bacterial colonization, survival, and proliferation during long-lasting infections. To exert its effect on gastric epithelium and other cell types, VacA undergoes several modifications and crosses multiple membrane barriers. Once inside the gastric epithelial cell, VacA disrupts many cellular-signaling pathways and processes, leading mainly to changes in the efflux of various ions, the depolarization of membrane potential, and perturbations in endocytic trafficking and mitochondrial function. The most notable effect of VacA is the formation of vacuole-like structures, which may lead to apoptosis. This review focuses on the processes involved in VacA secretion, processing, and entry into host cells, with a particular emphasis on the interaction of the mature toxin with host membranes and the formation of transmembrane pores.

AI-2 Induces Urease Expression Through Downregulation of Orphan Response Regulator HP1021 in Helicobacter pylori

Helicobacter pylori causes gastric infections in more than half of the world's population. The bacterium's survival in the stomach is mediated by the abundant production of urease to enable acid acclimation. In this study, our transcriptomic analysis demonstrated that the expression of urease structural proteins, UreA and UreB, is induced by the autoinducer AI-2 in H. pylori. We also found that the orphan response regulator HP1021 is downregulated by AI-2, resulting in the induction of urease expression. HP1021 represses the expression of urease by directly binding to the promoter region of ureAB, ranging from −47 to +3 with respect to the transcriptional start site. The study findings suggest that quorum sensing via AI-2 enhances acid acclimation when bacterial density increases, and might enable bacterial dispersal to other sites when entering gastric acid.

Construction and preservation of a stable and highly expressed recombinant Helicobacter pylori vacuolating cytotoxin A with apoptotic activity

Background

H. pylori is closely related to the occurrence and development of various digestive gastritis, peptic ulcer and mucosa-associated lymphoid tissue (MALT) lymphoma. H. pylori is also a class I carcinogen of gastric cancer. VacA is the only exocrine toxin of H. pylori, which plays a very important role in the pathogenesis of H. pylori. The production of VacA in natural circumstances is complex with heavy workload and low yield. Therefore, it is very important to obtain recombinant VacA protein which is stable and biologically active. This study therefore aims to explore the expression, purification and stable storage of VacA toxin of H. pylori in E.coli, and to provide experimental basis for further exploration of the role of VacA in H. pylori -induced inflammation of cancer.

Results

A 2502-bp fragment and VacA gene were identified. An 89.7-kDa VacA^34–854 recombinant protein was expressed and purified from the recombinant engineering bacteria and was preserved stably in 50 mM acetic acid buffer (pH 2.9). The amount of the recombinant protein was larger in the inclusion bodies than in the supernatant. In addition, after a 24-h culture with VacA recombinant protein, GES-1 cells demonstrated evidence of apoptosis including early nuclear immobilization and clustering under inverted microscope and TEM. It was found that VacA recombinant protein induced apoptosis by TUNEL assay.

Conclusions

A VacA recombinant protein that is stably and highly expressed and possesses pro-apoptotic activity is successfully constructed. The protein is stably preserved in 50 mM acetic acid buffer (pH 2.9).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02262-7.

The Role and Clinical Implications of the Retinoblastoma (RB)-E2F Pathway in Gastric Cancer

Gastric cancer is the most common malignant tumor in the digestive tract, with very high morbidity and mortality in developing countries. The pathogenesis of gastric cancer is a complex biological process mediated by abnormal regulation of proto-oncogenes and tumor suppressor genes. Although there have been some in-depth studies on gastric cancer at the molecular level, the specific mechanism has not been fully elucidated. RB family proteins (including RB, p130, and p107) are involved in cell cycle regulation, a process that largely depends on members of the E2F gene family that encode transcriptional activators and repressors. In gastric cancer, inactivation of the RB-E2F pathway serves as a core transcriptional mechanism that drives cell cycle progression, and is regulated by cyclins, cyclin-dependent kinases, cyclin-dependent kinase inhibitors, p53, Helicobacter pylori and some other upstream molecules. The E2F proteins are encoded by eight genes (i.e. E2F1 to E2F8), each of which may play a specific role in gastric cancer. Interestingly, a single E2F such as E2F1 can activate or repress transcription, and enhance or inhibit cell proliferation, depending on the cell environment. Thus, the function of the E2F transcription factor family is very complex and needs further exploration. Importantly, the presence of H. pylori in stomach mucosa may affect the RB and p53 tumor suppressor systems, thereby promoting the occurrence of gastric cancer. This review aims to summarize recent research progress on important roles of the complex RB-E2F signaling network in the development and effective treatment of gastric cancer.

Escherichia coli vacuolating factor, involved in avian cellulitis, induces actin contraction and binds to cytoskeleton proteins in fibroblasts

Background

Avian pathogenic Escherichia coli (APEC) isolated from avian cellulitis lesions produces a toxin, named Escherichia coli vacuolating factor (ECVF), that causes cell vacuolization and induces inflammatory response in broiler chicken.

Methods

We investigated the intracellular activities of ECVF in avian fibroblasts using fluorescence staining, electron microscopy, MTT and LDH measurements. As ECVF act specifically in avian cells, we performed blotting assay followed by mass spectrometry to better understand its initial intracellular protein recognition.

Results

ECVF induced actin contraction, mitochondrial damage and membrane permeability alterations. Ultrastructural analysis showed intracellular alterations, as nuclear lobulation and the presence of degraded structures inside the vacuoles. Moreover, ECVF induced cell death in fibroblasts. ECVF-biotin associates to at least two proteins only in avian cell lysates: alpha-actinin 4 and vinculin, both involved in cytoskeleton structure.

Conclusion

These findings demonstrated that ECVF plays an important role in avian cellulitis, markedly in initial steps of infection. Taken together, the results place this toxin as a target for drug and/or vaccine development, instead of the use of large amounts antibiotics.

Isoforms of the p53 Family and Gastric Cancer: A Ménage à Trois for an Unfinished Affair

Simple Summary

The p53 family is a complex family of transcription factors with different cellular functions that are involved in several physiological processes. A massive amount of data has been accumulated on their critical role in the tumorigenesis and the aggressiveness of cancers of different origins. If common features are observed, there are numerous specificities that may reflect particularities of the tissues from which the cancers originated. In this regard, gastric cancer tumorigenesis is rather remarkable, as it is induced by bacterial and viral infections, various chemical carcinogens, and familial genetic alterations, which provide an example of the variety of molecular mechanisms responsible for cell transformation and how they impact the p53 family. This review summarizes the knowledge gathered from over 40 years of research on the role of the p53 family in gastric cancer, which still displays one of the most elevated mortality rates amongst all types of cancers.

Abstract

Gastric cancer is one of the most aggressive cancers, with a median survival of 12 months. This illustrates its complexity and the lack of therapeutic options, such as personalized therapy, because predictive markers do not exist. Thus, gastric cancer remains mostly treated with cytotoxic chemotherapies. In addition, less than 20% of patients respond to immunotherapy. TP53 mutations are particularly frequent in gastric cancer (±50% and up to 70% in metastatic) and are considered an early event in the tumorigenic process. Alterations in the expression of other members of the p53 family, i.e., p63 and p73, have also been described. In this context, the role of the members of the p53 family and their isoforms have been investigated over the years, resulting in conflicting data. For instance, whether mutations of TP53 or the dysregulation of its homologs may represent biomarkers for aggressivity or response to therapy still remains a matter of debate. This uncertainty illustrates the lack of information on the molecular pathways involving the p53 family in gastric cancer. In this review, we summarize and discuss the most relevant molecular and clinical data on the role of the p53 family in gastric cancer and enumerate potential therapeutic innovative strategies.

The effect of Helicobacter pylori infection and different H. pylori components on the proliferation and apoptosis of gastric epithelial cells and fibroblasts

Background

Helicobacter pylori colonizes the human gastric mucosa, causing chronic inflammation, peptic ulcers and gastric cancer. A cascade of harmful processes results from the interaction of these bacteria with the gastric epithelium.

Aim

To investigate these processes in terms of upregulation of oxidative stress and cell apoptosis and downregulation of the pro-regenerative activity of cells.

Methods

We employed an in vivo guinea pig model at 7 or 28 days postinoculation with H. pylori, corresponding to an acute or chronic stage of infection, respectively, and an in vitro model of guinea pig primary gastric epithelial cells and fibroblasts treated with bacterial components: glycine acid extract (GE), urease subunit A (UreA), cytotoxin-associated gene A protein (CagA) and lipopolysaccharide (LPS). Cells were evaluated for metabolic activity (MTT reduction), myeloperoxidase (MPO) and metalloproteinase (MMP-9) secretion, lipid peroxidation (4-hydroxynonenal (4HNE)), migration (wound healing), proliferation (Ki-67 antigen) and cell apoptosis (TUNEL assay; Bcl-xL, Bax, Bcl-2 expression; caspase 3 cleavage).

Results

Significant infiltration of the gastric mucosa by inflammatory cells in vivo in response to H. pylori was accompanied by oxidative stress and cell apoptosis, which were more intense 7 than 28 days after inoculation. The increase in cell proliferation was more intense in chronic than acute infection. H. pylori components GE, CagA, UreA, and LPS upregulated oxidative stress and apoptosis. Only H. pylori LPS inhibited cell migration and proliferation, which was accompanied by the upregulation of MMP-9.

Conclusions

H. pylori infection induces cell apoptosis in conjunction with increased oxidative stress. Elevated apoptosis protects against deleterious inflammation and neoplasia; however, it reduces cell integrity. Upregulation of cell migration and proliferation in response to injury in the milieu of GE, CagA or UreA facilitates tissue regeneration but increases the risk of neoplasia. By comparison, downregulation of cell regeneration by H. pylori LPS may promote chronic inflammation.

Helicobacter pylori VacA, a distinct toxin exerts diverse functionalities in numerous cells: An overview

BACKGROUND

Helicobacter pylori, gastric cancer-causing bacteria, survive in their gastric environment of more than 50% of the world population. The presence of H. pylori in the gastric vicinity promotes the development of various diseases including peptic ulcer and gastric carcinoma. H. pylori produce and secret Vacuolating cytotoxin A (VacA), a major toxin facilitating the bacteria against the host defense system. The toxin causes multiple effects in epithelial cells and immune cells, especially T cells, B cells, and Macrophages.

METHODS

This review describes the diverse functionalities of protein toxin VacA. The specific objective of this review is to address the overall structure, mechanism, and functions of VacA in various cell types. The recent advancements are summarized and discussed and thus conclusion is drawn based on the overall reported evidences.

RESULTS

The searched articles on H. pylori VacA were evaluated and limited up to 66 articles for this review. The articles were divided into four major categories including articles on vacA gene, VacA toxin, distinct effects of VacA toxin, and their effects on various cells. Based on these studies, the review article was prepared.

CONCLUSIONS

This review describes an overview of how VacA is secreted by H. pylori and contributes to colonization and virulence in multiple ways by affecting epithelial cells, T cells, Dendritic cells, B cells, and Macrophages. The reported evidence suggests that the comprehensive outlook need to be developed for understanding distinctive functionalities of VacA.

Beyond the antibody: B cells as a target for bacterial infection

It is well established that B cells play an important role during infections beyond antibody production. B cells produce cytokines and are APCs for T cells. Recently, it has become clear that several pathogenic bacterial genera, such as Salmonella, Brucella, Mycobacterium, Listeria, Francisella, Moraxella, and Helicobacter, have evolved mechanisms such as micropinocytosis induction, inflammasome down-regulation, inhibitory molecule expression, apoptosis induction, and anti-inflammatory cytokine secretion to manipulate B cell functions influencing immune responses. In this review, we summarize our current understanding of B cells as targets of bacterial infection and the mechanisms by which B cells become a niche for bacterial survival and replication away from extracellular immune responses such as complement and antibodies.

Heterogeneous Family of Cyclomodulins: Smart Weapons That Allow Bacteria to Hijack the Eukaryotic Cell Cycle and Promote Infections

Some bacterial pathogens modulate signaling pathways of eukaryotic cells in order to subvert the host response for their own benefit, leading to successful colonization and invasion. Pathogenic bacteria produce multiple compounds that generate favorable conditions to their survival and growth during infection in eukaryotic hosts. Many bacterial toxins can alter the cell cycle progression of host cells, impairing essential cellular functions and impeding host cell division. This review summarizes current knowledge regarding cyclomodulins, a heterogeneous family of bacterial effectors that induce eukaryotic cell cycle alterations. We discuss the mechanisms of actions of cyclomodulins according to their biochemical properties, providing examples of various cyclomodulins such as cycle inhibiting factor, γ-glutamyltranspeptidase, cytolethal distending toxins, shiga toxin, subtilase toxin, anthrax toxin, cholera toxin, adenylate cyclase toxins, vacuolating cytotoxin, cytotoxic necrotizing factor, Panton-Valentine leukocidin, phenol soluble modulins, and mycolactone. Special attention is paid to the benefit provided by cyclomodulins to bacteria during colonization of the host.

Oscarellin, an Anthranilic Acid Derivative from a Philippine Sponge, Oscarella stillans, as an Inhibitor of Inflammatory Cytokines in Macrophages

A new anthranilic acid derivative (1) was isolated from a Philippine sponge, Oscarella stillans (Bergquist and Kelly). The structure of compound 1, named oscarellin, was determined as 2-amino-3-(3'-aminopropoxy)benzoic acid from spectroscopic data and confirmed by synthesis. We examined the immunomodulating effect of compound 1 and its mechanism in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. Our data indicated that the expression of tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 were significantly reduced by the pretreatment of 1 (0.1-10 μM) for 2 h. In addition, compound 1 suppressed activation of extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun NH₂-termimal kinase (JNK), but not p38 mitogen-activated protein kinase (MAPK) in LPS-stimulated RAW 264.7 cells. Compound 1 abrogated LPS-induced nuclear factor-κB (NF-κB) and activator protein-1 (AP-1) activities, whereas the induction of activating transcription factor-3 (ATF-3) was increased. Taken together, our results suggest that compound 1 attenuates pro-inflammatory cytokines via the suppression of JNK, ERK, AP-1, and NF-κB and the activation of the ATF-3 signaling pathway.

Molecular and Proteomic Analysis of Levofloxacin and Metronidazole Resistant Helicobacter pylori

Antibiotic resistance in bacteria incurs fitness cost, but compensatory mechanisms may ameliorate the cost and sustain the resistance even under antibiotics-free conditions. The aim of this study was to determine compensatory mechanisms of antibiotic resistance in H. pylori. Five strains of levofloxacin-sensitive H. pylori were induced in vitro to develop resistance. In addition, four pairs of metronidazole-sensitive and -resistant H. pylori strains were isolated from patients carrying dual H. pylori populations that consist of both sensitive and resistant phenotypes. Growth rate, virulence and biofilm-forming ability of the sensitive and resistant strains were compared to determine effects of compensatory response. Proteome profiles of paired sensitive and resistant strains were analyzed by liquid chromatography/mass spectrophotometry (LC/MS). Although there were no significant differences in growth rate between sensitive and resistant pairs, bacterial virulence (in terms of abilities to induce apoptosis and form biofilm) differs from pair to pair. These findings demonstrate the complex and strain-specific phenotypic changes in compensation for antibiotics resistance. Compensation for in vitro induced levofloxacin resistance involving mutations of gyrA and gyrB was functionally random. Furthermore, higher protein translation and non-functional protein degradation capabilities in naturally-occuring dual population metronidazole sensitive-resistant strains may be a possible alternative mechanism underlying resistance to metronidazole without mutations in rdxA and frxA. This may explain the lack of mutations in target genes in ~10% of metronidazole resistant strains.

Vacuolating cytotoxin A (VacA) - A multi-talented pore-forming toxin from Helicobacter pylori

Helicobacter pylori is associated with severe and chronic diseases of the stomach and duodenum such as peptic ulcer, non-cardial adenocarcinoma and gastric lymphoma, making Helicobacter pylori the only bacterial pathogen which is known to cause cancer. The worldwide rate of incidence for these diseases is extremely high and it is estimated that about half of the world's population is infected with H. pylori. Among the bacterial virulence factors is the vacuolating cytotoxin A (VacA), which represents an important determinant of pathogenicity. Intensive characterization of VacA over the past years has provided insight into an ample variety of mechanisms contributing to host-pathogen interactions. The toxin is considered as an important target for ongoing research for several reasons: i) VacA displays unique features and structural properties and its mechanism of action is unrelated to any other known bacterial toxin; ii) the toxin is involved in disease progress and colonization by H. pylori of the stomach; iii) VacA is a potential and promising candidate for the inclusion as antigen in a vaccine directed against H. pylori and iv) the vacA gene is characterized by a high allelic diversity, and allelic variants contribute differently to the pathogenicity of H. pylori. Despite the accumulation of substantial data related to VacA over the past years, several aspects of VacA-related activity have been characterized only to a limited extent. The biologically most significant effect of VacA activity on host cells is the formation of membrane pores and the induction of vacuole formation. This review discusses recent findings and advances on structure-function relations of the H. pylori VacA toxin, in particular with a view to membrane channel formation, oligomerization, receptor binding and apoptosis.

Lobaric Acid Inhibits VCAM-1 Expression in TNF-α-Stimulated Vascular Smooth Muscle Cells via Modulation of NF-κB and MAPK Signaling Pathways

Lichens have been known to possess multiple biological activities, including anti-proliferative and anti-inflammatory activities. Vascular cell adhesion molecule-1 (VCAM-1) may play a role in the development of atherosclerosis. Hence, VCAM-1 is a possible therapeutic target in the treatment of the inflammatory disease. However, the effect of lobaric acid on VCAM-1 has not yet been investigated and characterized. For this study, we examined the effect of lobaric acid on the inhibition of VCAM-1 in tumor necrosis factor-alpha (TNF-α)-stimulated mouse vascular smooth muscle cells. Western blot and ELISA showed that the increased expression of VCAM-1 by TNF-α was significantly suppressed by the pre-treatment of lobaric acid (0.1–10 μg/ml) for 2 h. Lobaric acid abrogated TNF-α-induced NF-κB activity through preventing the degradation of IκB and phosphorylation of extracellular signal-regulated kinases (ERK), c-Jun N-terminal kinases (JNK), and p38 mitogen activated protein (MAP) kinase. Lobaric acid also inhibited the expression of TNF-α receptor 1 (TNF-R1). Overall, our results suggest that lobaric acid inhibited VCAM-1 expression through the inhibition of p38, ERK, JNK and NF-κB signaling pathways, and downregulation of TNF-R1 expression. Therefore, it is implicated that lobaric acid may suppress inflammation by altering the physiology of the atherosclerotic lesion.

Cortactin Mediates Apoptosis of Gastric Epithelial Cells Induced by VacA Protein of Helicobacter pylori

BACKGROUND

Vacuolating cytotoxin antigen (VacA) is one of the major virulence factors in Helicobacter pylori (H. pylori), which is responsible for cell vacuolar degeneration and apoptotic cell death. A candidate host factor which mediates this process is cortactin, a protein associated with the processes of colonization and adhesion of H. pylori in gastric epithelium.

AIM

To investigate the role of cortactin in VacA-induced apoptosis of gastric epithelial cells.

METHODS

Cortactin expression and shRNA lentiviral constructs were developed and transduced into the human gastric cancer cell line, AGS. VacA protein was purified from H. pylori cultures, acid-activated, and co-incubated with the transduced cell populations. Apoptosis was detected by flow cytometry, and the levels of the pro- and anti-apoptotic proteins Bax and Bcl-2 were determined by Western blot.

RESULTS

Acid-activated purified VacA induced apoptosis in the parental AGS cells. Increased expression of cortactin (AGS/cortactin) led to a greater percentage of cells undergoing apoptosis. In contrast, knockdown of cortactin with shRNA (AGS/cortactin-shRNA) decreased the percentage of apoptotic cells. The protein levels of pro- and anti-apoptotic proteins Bax and Bcl-2 were increased and decreased in AGS/cortactin cells relative to the parental AGS cells. In the AGS/cortactin-shRNA cells, Bax protein levels were decreased, while Bcl-2 protein was increased.

CONCLUSIONS

The results indicate that cortactin is involved in the regulation of apoptosis induced by VacA in gastric cells.

Microbial Regulation of p53 Tumor Suppressor

p53 tumor suppressor has been identified as a protein interacting with the large T antigen produced by simian vacuolating virus 40 (SV40). Subsequent research on p53 inhibition by SV40 and other tumor viruses has not only helped to gain a better understanding of viral biology, but also shaped our knowledge of human tumorigenesis. Recent studies have found, however, that inhibition of p53 is not strictly in the realm of viruses. Some bacterial pathogens also actively inhibit p53 protein and induce its degradation, resulting in alteration of cellular stress responses. This phenomenon was initially characterized in gastric epithelial cells infected with Helicobacter pylori, a bacterial pathogen that commonly infects the human stomach and is strongly linked to gastric cancer. Besides H. pylori, a number of other bacterial species were recently discovered to inhibit p53. These findings provide novel insights into host–bacteria interactions and tumorigenesis associated with bacterial infections.

This review focuses on a novel aspect of host–bacteria interactions: the direct interplay between bacterial pathogens and tumor suppression mechanisms that protect the host from cancer development. Recent studies revealed that various pathogenic bacteria actively inhibit the major tumor suppression pathway mediated by p53 protein that plays a key role in the regulation of multiple cellular stress responses and prevention of cancerogenesis. Bacterial degradation of p53 was first discovered in the context of Helicobacter pylori infection, which is currently the strongest known risk factor for adenocarcinoma of the stomach. This phenomenon, however, is not limited to H. pylori, and many other bacterial pathogens inhibit p53 using various mechanisms. Inhibition of p53 by bacteria is linked to bacterial modulation of the host cellular responses to DNA damage, metabolic stress, and, potentially, other stressors. This is a dynamic area of research that will continue to evolve and make important contributions to a better understanding of host–microbe interactions and tumorigenesis. These studies may offer new molecular targets and opportunities for drug development.

Ramalin inhibits VCAM-1 expression and adhesion of monocyte to vascular smooth muscle cells through MAPK and PADI4-dependent NF-kB and AP-1 pathways

Cell adhesion molecules play a critical role in inflammatory processes and atherosclerosis. In this study, we investigated the effect of ramalin, a chemical compound from the Antarctic lichen Ramalina terebrata, on vascular cell adhesion molecule-1 (VCAM-1) expression induced by TNF-α in vascular smooth muscular cells (VSMCs). Pretreatment of VSMCs with ramalin (0.1-10 μg/mL) concentration-dependently inhibited TNF-α-induced VCAM-1 expression. Additionally, ramalin inhibited THP-1 (human acute monocytic leukemia cell line) cell adhesion to TNF-α-stimulated VSMCs. Ramalin suppressed TNF-α-induced production of reactive oxygen species (ROS), PADI4 expression, and phosphorylation of p38, ERK, and JNK. Moreover, ramalin inhibited TNF-α-induced translocation of NF-κB and AP-1. Inhibition of PADI4 expression by small interfering RNA or the PADI4-specific inhibitor markedly attenuated TNF-α-induced activation of NF-κB and AP-1 and VCAM-1 expression in VSMCs. Our study provides insight into the mechanisms underlying ramalin activity and suggests that ramalin may be a potential therapeutic agent to modulate inflammation within atherosclerosis.

Chinese yam extracts containing β-sitosterol and ethyl linoleate protect against atherosclerosis in apolipoprotein E-deficient mice and inhibit muscular expression of VCAM-1 in vitro

Atherosclerosis is a chronic inflammatory disease, which is associated with increased expression of adhesion molecules and monocyte recruitment into the arterial wall. This study evaluated whether hexane extracts from the edible part (DB-H1) or bark region (DB-H2) of Dioscorea. batatas Decne have anti-atherosclerotic properties in vivo and in vitro experiments. We also identified bioactive components in the hexane extracts. Thirty-six apolipoprotein E (ApoE(-/-) ) mice and 12 control (C57BL/6J) mice were given a Western-type diet for 11 or 21 wk. To examine the effects of yam extracts on lesion development, ApoE(-/-) mice were orally administered DB-H1 or DB-H2 for the duration of the study (200 mg/kg b.w./day, 3 times per wk). Both DB-H1 and DB-H2 significantly reduced the total atherosclerotic lesion area in the aortic root. In addition, plasma concentrations of total cholesterol, oxidized-low-density lipoprotein, and c-reactive protein were decreased by administration of DB-H1 and DB-H2. Consistent with the in vivo observations, DB-H1 and DB-H2 inhibited tumor necrosis factor (TNF)-α-induced vascular cell adhesion molecule-1 expression and adhesion of THP-1 monocytes to TNF-α-activated vascular smooth muscle cells. It was also found that treatment with DB-H1 or DB-H2 resulted in the inhibition nitric oxide (NO) and reactive oxygen species production and iNOS expression in macrophages. Thus, DB-H1 and DB-H2 seem to influence atherosclerosis by affecting the production of inflammatory mediators in vivo. Our results suggest that yam extracts have the potential to be used in the prevention of atherosclerosis.

Role of connexin 43 in Helicobacter pylori VacA-induced cell death

Helicobacter pylori colonizes the human stomach and confers an increased risk for the development of peptic ulceration, noncardia gastric adenocarcinoma, and gastric lymphoma. A secreted H. pylori toxin, VacA, can cause multiple alterations in gastric epithelial cells, including cell death. In this study, we sought to identify host cell factors that are required for VacA-induced cell death. To do this, we analyzed gene trap and short hairpin RNA (shRNA) libraries in AZ-521 human gastric epithelial cells and selected for VacA-resistant clones. Among the VacA-resistant clones, we identified multiple gene trap library clones and an shRNA library clone with disrupted expression of connexin 43 (Cx43) (also known as gap junction protein alpha 1 [GJA1]). Further experiments with Cx43-specific shRNAs confirmed that a reduction in Cx43 expression results in resistance to VacA-induced cell death. Immunofluorescence microscopy experiments indicated that VacA did not colocalize with Cx43. We detected production of the Cx43 protein in AZ-521 cells but not in AGS, HeLa, or RK-13 cells, and correspondingly, AZ-521 cells were the most susceptible to VacA-induced cell death. When Cx43 was expressed in HeLa cells, the cells became more susceptible to VacA. These results indicate that Cx43 is a host cell constituent that contributes to VacA-induced cell death and that variation among cell types in susceptibility to VacA-induced cell death is attributable at least in part to cell type-specific differences in Cx43 production.

Ethanol induces cell cycle arrest and triggers apoptosis via Sp1-dependent p75NTR expression in human neuroblastoma cells

Ethanol exposure has deleterious effects on the central nervous system. Although several mechanisms for ethanol-induced damage have been suggested, the precise mechanism underlying ethanol-induced neuronal cell death remains unclear. Recent studies indicate that the p75 neurotrophin receptor (p75NTR) has a critical role in the regulation of neuronal survival. This study was designed to examine the role of p75NTR in ethanol-induced apoptotic signaling in neuroblastoma cells. Ethanol caused highly increased level of p75NTR expression. The use of small interfering RNA to inhibit p75NTR expression markedly attenuated ethanol-induced cell cycle arrest and apoptosis. DNA binding activity of Sp1 was increased by ethanol, whereas inhibition of Sp1 activity by mithramycin, a Sp1 inhibitor, or short hairpin RNA suppressed ethanol-induced p75NTR expression. In addition, inhibitors of casein kinase 2 (CK2) and extracellular signal-regulated kinase (ERK) augmented ethanol-induced p75NTR expression. Our results also demonstrate that inhibition of ERK and CK2 caused a further increase in the activation of the p75NTR proximal promoter induced by ethanol. This increased activation was partially suppressed by the deletion of the Sp1 binding sites. These results suggest that Sp1-mediated p75NTR expression is regulated at least in part by ERK and CK2 pathways. The present study also showed that treatment with ethanol resulted in significant increases in the expression of p21, but not the levels of p53 and p53 target genes such as Bax, Puma, and Bcl-2. Furthermore, the inhibition of p75NTR expression or Sp1 activity suppressed ethanol-induced p21 expression, cell cycle arrest, and apoptosis. These data suggest that ethanol increases p75NTR expression, and CK2 and ERK signaling inversely regulate Sp1-mediated p75NTR expression in ethanol-treated neuroblastoma cells. Thus, our study provides more insight into the mechanisms underlying ethanol actions.

Suppression of adhesion molecule expression by phenanthrene-containing extract of bulbils of Chinese Yam in vascular smooth muscle cells through inhibition of MAPK, Akt and NF-κB

Atherosclerosis is a chronic inflammatory disease associated with increased expression of adhesion molecules in vascular smooth muscle cells (VSMCs). The objective of this study was to examine the in vitro effects of extract from aerial Bulbil of Dioscorea batatas Decne (Db-Ex) on the ability to suppress the expression of adhesion molecules induced by TNF-α. We also identified bioactive components from a methanol extract. VSMCs pre-exposed to Db-Ex (10-100 μg/ml) were stimulated with TNF-α (10 ng/ml). Preincubation of VSMCs for 2 h with Db-Ex dose-dependently inhibited TNF-α-induced adhesion of THP-1 monocytic cells and mRNA and protein expression of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1). Db-Ex treatment decreased ROS production and the amount of phosphorylated form of p38, ERK, JNK and Akt in TNF-α-stimulated cells, suggesting that Db-Ex inhibits adhesion molecule expression possibly through MAPK and Akt regulation. Db-Ex also suppressed TNF-α-activation NK-κB. This effect was mediated through degradation of IκBα and nuclear translocation of the p65 subunit of NF-κB. These results suggest that Db-Ex inhibits monocyte adhesion and the TNF-α-mediated induction of adhesion molecules in VSMC by downregulating the MAPK/Akt/NF-κB signaling pathway, which may explain the ability of Db-Ex to suppress inflammation within the atherosclerotic lesion.

Stereocalpin A inhibits the expression of adhesion molecules in activated vascular smooth muscle cells

Up-regulation of cell adhesion molecules on vascular smooth muscle cells (VSMCs) and leukocyte recruitment to the vascular wall contribute to vascular inflammation and atherosclerosis. Stereocalpin A, a chemical compound of the Antarctic lichen Ramalina terebarata, displays tumoricidal activity against several different tumor cell types. However, other biological activities of stereocalpin A and its molecular mechanisms remain unknown. In this study, our work is directed toward studying the in vitro effects of stereocalpin A on the ability to suppress the expression of adhesion molecules induced by TNF-α in vascular smooth muscle cells. Pretreatment of VSMCs for 2h with stereocalpin A at nontoxic concentrations of 0.1-10 μg/ml inhibited TNF-α-induced adhesion of THP-1 monocytic cells and expression of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1). Stereocalpin A reduced TNF-α-induced production of intracellular reactive oxygen species (ROS) and phosphorylation of p38, ERK, JNK and Akt. Stereocalpin A also inhibited NK-κB activation induced by TNF-α. Moreover, stereocalpin A inhibited TNF-α-induced ΙκΒ kinase activation, subsequent degradation of ΙκΒα, and nuclear translocation of NF-κB. Hence, we describe a new anti-inflammatory activity and mechanism of stereocalpin A, owing to the negative regulation of TNF-α-induced adhesion molecule and MCP-1 expression, monocyte adhesion and ROS production in vascular smooth muscle cells. These results suggest that stereocalpin A has the potential to exert a protective effect by modulating inflammation within the atherosclerotic lesion.

Sulforaphane suppresses vascular adhesion molecule-1 expression in TNF-α-stimulated mouse vascular smooth muscle cells: involvement of the MAPK, NF-κB and AP-1 signaling pathways

Atherosclerosis is a long-term inflammatory disease of the arterial wall. Increased expression of the cell adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) is associated with increased proliferation of vascular smooth muscle cells (VSMCs), leading to increased neointima or atherosclerotic lesion formation. Therefore, the functional inhibition of adhesion molecules could be a critical therapeutic target of inflammatory disease. In the present study, we investigate the effect of sulforaphane on the expression of VCAM-1 induced by TNF-α in cultured mouse vascular smooth muscle cell lines. Pretreatment of VSMCs for 2h with sulforaphane (1-5μg/ml) dose-dependently inhibited TNF-α-induced adhesion of THP-1 monocytic cells and protein expression of VCAM-1. Sulforaphane also suppressed TNF-α-induced production of intracellular reactive oxygen species (ROS) and activation of p38, ERK and JNK. Furthermore, sulforaphane inhibited NK-κB and AP-1 activation induced by TNF-α. Sulforaphane inhibited TNF-α-induced ΙκΒ kinase activation, subsequent degradation of ΙκΒα and nuclear translocation of p65 NF-κB and decreased c-Jun and c-Fos protein level. This study suggests that sulforaphane inhibits the adhesive capacity of VSMC and downregulates the TNF-α-mediated induction of VCAM-1 in VSMC by inhibiting the MAPK, NF-κB and AP-1 signaling pathways and intracellular ROS production. Thus, sulforaphane may have beneficial effects to suppress inflammation within the atherosclerotic lesion.

Mitochondrial targeting liposomes incorporating daunorubicin and quinacrine for treatment of relapsed breast cancer arising from cancer stem cells

Breast cancer stem cells play a crucial role in the relapse of breast cancers because they are resistant to a standard chemotherapy and the residual cancer stem cells are able to proliferate indefinitely. The objectives of present study were to construct a kind of mitochondrial targeting daunorubicin plus quinacrine liposomes for treating and for preventing the recurrence of breast cancer arising from the cancer stem cells. MCF-7 cancer stem cells were identified as CD44(+)/CD24(-) cells and cultured in free-serum medium. Evaluations were performed on MCF-7 cancer stem cells, MCF-7 cancer stem cell mammospheres, and the relapsed tumor by xenografting MCF-7 cancer stem cells into female NOD/SCID mice. The particle size of mitochondrial targeting daunorubicin plus quinacrine liposomes was approximately 98 nm. The mitochondrial targeting liposomes evidently increased the mitochondrial uptake of drugs, were selectively accumulated into mitochondria, activated the pro-apoptotic Bax protein, dissipated the mitochondrial membrane potential, opened the mitochondrial permeability transition pores, released cytochrome C by translocation, and initiated a cascade of caspase 9 and 3 reactions, thereby inducing apoptosis of MCF-7 cancer stem cells. The mitochondrial targeting liposomes showed the strongest efficacy in treating MCF-7 cancer cells in vitro, in treating MCF-7 cancer stem cells in vitro, and in treating the relapsed tumor in mice. Mitochondrial targeting daunorubicin plus quinacrine liposomes would provide a new strategy for treating and preventing the relapse of breast cancers arising from cancer stem cells.

Effect of H. pylori extract on cellular morphology and apoptosis-related gene expression in human gastric cancer BGC-823 cells

AIM: To investigate the effect of H. pylori extract on cellular morphology and apoptosis-related gene expression in human gastric cancer BGC-823 cells.

METHODS: After BGC-823 cells were treated with ultrasonic extract of the east Asia type or the Western type of H. pylori strain, the changes in cellular morphology were observed by microscopy, and the expression of survivin and caspase-3 mRNAs was detected by fluorescent quantitative polymerase chain reaction (QRT-PCR). The possible correlation between the expression of survivin mRNA and that of caspase-3 mRNA was also analyzed.

RESULTS: Hummingbird phenotype was observed in BGC-823 cells 12 h after stimulation H. pylori extract, which was most obvious at 24 h. The percentage of cells showing hummingbird phenotype was significantly higher in cells treated with the extract of the east Asia type than in those treated with the extract of the Western type (29.3 ± 2.1 vs 8.0 ± 2.0, F = 164.73, P < 0.05). The expression of survivin mRNA was significantly higher and that of caspase-3 mRNA was significantly lower in BGC-823 cells treated with H. pylori extract than in control cells (both P < 0.05). Statistical difference was also noted in the expression of survivin and caspase-3 mRNAs between cells treated with the extract of the east Asia type group and those with the extract of the Western type group.

CONCLUSION: H. pylori extract could induce changes in cellular morphology and expression of survivin and caspase-3 mRNAs in human gastric cancer BGC-823 cells. The extract of the east Asia type of H. pylori has more potent biological activity than that of the Western type.

Helicobacter pylori VacA induces programmed necrosis in gastric epithelial cells

Helicobacter pylori is a Gram-negative bacterium that colonizes the human stomach and contributes to the development of peptic ulcer disease and gastric cancer. The secreted pore-forming toxin VacA is one of the major virulence factors of H. pylori. In the current study, we show that AZ-521 human gastric epithelial cells are highly susceptible to VacA-induced cell death. Wild-type VacA causes death of these cells, whereas mutant VacA proteins defective in membrane channel formation do not. Incubation of AZ-521 cells with wild-type VacA results in cell swelling, poly(ADP-ribose) polymerase (PARP) activation, decreased intracellular ATP concentration, and lactate dehydrogenase (LDH) release. VacA-induced death of these cells is a caspase-independent process that results in cellular release of histone-binding protein high mobility group box 1 (HMGB1), a proinflammatory protein. These features are consistent with the occurrence of cell death through a programmed necrosis pathway and suggest that VacA can be included among the growing number of bacterial pore-forming toxins that induce cell death through programmed necrosis. We propose that VacA augments H. pylori-induced mucosal inflammation in the human stomach by causing programmed necrosis of gastric epithelial cells and subsequent release of proinflammatory proteins and may thereby contribute to the pathogenesis of gastric cancer and peptic ulceration.

Pseudomonas aeruginosa exotoxin A reduces chemoresistance of oral squamous carcinoma cell via inhibition of heat shock proteins 70 (HSP70)

PURPOSE

Oral squamous carcinoma (OSCC) cells exhibit resistance to chemotherapeutic agent-mediated apoptosis in the late stage of malignancy. Increased levels of heat shock proteins 70 (HSP70) in cancer cells are known to confer resistance to apoptosis. Since recent advances in the understanding of bacterial toxins have produced new strategies for the treatment of cancers, we investigated the effect of Pseudomonas aeruginosa exotoxin A (PEA) on HSP70 expression and induction of apoptosis in chemoresistant OSCC cell line (YD-9).

MATERIALS AND METHODS

The apoptotic effect of PEA on chemoresistant YD-9 cells was confirmed by MTT, Hoechst and TUNEL stains, DNA electrophoresis, and Western blot analysis.

RESULTS

While YD-9 cells showed high resistance to chemotherapeutic agents such as etoposide and 5-fluorouraci (5-FU), HSP70 antisense oligonucelotides sensitized chemoresistant YD-9 cells to etoposide and 5-FU. On the other hand, PEA significantly decreased the viability of YD-9 cells by deteriorating the HSP70-relating protecting system through inhibition of HSP70 expression and inducing apoptosis in YD-9 cells. Apoptotic manifestations were evidenced by changes in nuclear morphology, generation of DNA fragmentation, and activation of caspases. While p53, p21, and E2F-1 were upregulated, cdk2 and cyclin B were downregulated by PEA treatment, suggesting that PEA caused cell cycle arrest at the G2/M checkpoint.

CONCLUSION

Therefore, these results indicate that PEA reduced the chemoresistance through inhibition of HSP70 expression and also induced apoptosis in chemoresistant YD-9 cells.

Involvement of VDAC1 and Bcl-2 family of proteins in VacA-induced cytochrome c release and apoptosis of gastric epithelial carcinoma cells

OBJECTIVE

It is known that the vacuolating cytotoxin (VacA) could induce apoptosis. However, the mechanism remained to be elucidated. The aim of this study is to investigate the role of Bcl family of proteins (Bcl-2 and Bax) and the mitochondrial voltage-dependent anion channel (VDAC) in VacA-induced apoptosis of AGS cells.

METHODS

Plasmid pGBKT7-VacA p58 was constructed and transfected into the AGS cells. RT-PCR and Western blotting were used to determine the expressions of cytochrome c, caspase-3, Bax, Bcl-2 and VDAC1 mRNA and proteins.

RESULTS

VacA p58 can induce cytochrome c release and activate caspase-3 in AGS cells. It up-regulated the expressions of Bax and VDAC1 mRNA and proteins, and decreased the expression of Bcl-2 in AGS cells.

CONCLUSION

VacA p58 induces apoptosis in AGS cells. This apoptotic process is associated with the up-regulation of Bax/VDAC1 and downregulation of Bcl-2. These findings suggest that the release of cytochrome c by VacA p58 is mainly through VDAC-dependent and Bcl-2 family-dependent pathways.

A potential epidemic factor from the bacteria, Vibrio cholerae WO7

Certain species of Vibrio cholerae have evolved mechanisms to become pathogenic to humans, with the potential to cause a severe life-threatening diarrheal disease, cholera. Cholera can emerge as explosive outbreaks in the human population. V. cholerae illness is produced primarily through the expression of a potent toxin (cholera toxin) within the human intestine. The present study has been carried out on a novel toxin purified from V. cholerae W07, an epidemic cholera strain devoid of cholera toxin gene (ctx). A modified method of purification improved purification fold as well as yield of this toxin. Heating was found to be the essential and sufficient condition for dissociation of the two subunits (58 kDa and 40 kDa) of this toxin (pI 5.2). The 40-kDa subunit of the purified toxin was identified as the carbohydrate binding subunit. This toxin was found to induce apoptosis in HEp-2 cells. Thus, the WO7 toxin seems to have potential importance in the pathogenesis of disease associated with Vibrio cholerae WO7.

Prodigiosin isolated from Hahella chejuensis suppresses lipopolysaccharide-induced NO production by inhibiting p38 MAPK, JNK and NF-kappaB activation in murine peritoneal macrophages

Prodigiosin was isolated from marine bacteria Hahella chejuensis which has been recently discovered from Marado, Cheju Island, Republic of Korea. Immunosuppressive properties have been reported for prodigiosin members such as undecylprodigiosin, metacycloprodigiosin, prodigiosin and its synthetic analogue PNU156804 (PNU). However, the effect of this agent on macrophage function has not been characterized in detail. In the present study, we examined the effects of prodigiosin on the production of inflammatory cytokines and nitric oxide (NO) in lipopolysaccharide (LPS)-activated murine macrophage. When thioglycollate-elicited macrophages pre-exposed to prodigiosin (1-100 ng/ml) were stimulated with LPS, pretreatment with prodigiosin resulted in the inhibition of NO production and inducible nitric oxide synthase (iNOS) protein and mRNA expression in a concentration-dependent manner. In contrast, the production of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1) and IL-6 was not altered. Inhibition of iNOS protein expression appears to be at the transcriptional level, since prodigiosin decreased LPS-induced NF-kappaB activity through preventing the degradation of IkBalpha, with significant inhibition achieved following pretreatment with prodigiosin. However, prodigiosin did not exert any effect on AP-1 activity. Prodigiosin blocked phosphorylation of p38 mitogen-activated protein kinase (MAPK) and c-Jun NH(2)-terminal kinase (JNK), but not that of extracellular signal-regulated kinase 1/2 (ERK 1/2). These results indicate that the inhibition of these signaling molecules expression was correlated with the reduced production of NO in macrophages. Taken together, the present data suggest that prodigiosin reduces NO production and iNOS expression by inhibiting LPS-triggered p38 MAPK and JNK phosphorylation and NF-kappaB activation, thereby implicating a mechanism by which prodigiosin may exert its immunosuppressive effects.

CML-1 inhibits TNF-alpha-induced NF-kappaB activation and adhesion molecule expression in endothelial cells through inhibition of IkBalpha kinase

CML-1 is a purified extract from a mixture of 13 oriental herbs (Achyranthis Radix, Angelicae Gigantis Radix, Cinnamomi Cortex Spissus, Eucommiae Cortex, Glycyrrhizae Radix, Hoelen, Lycii Fructus, Paeoniae Radix, Rehmanniae Radix Preparata and Atractylodis Rhizoma, Zingiberis Rhizoma, Zizyphi Semen, Acori Graminei Rhizoma) that have been widely used for the treatment of inflammatory diseases in Asia. Since our previous study has been shown to have the anti-inflammatory activity of CML-1 in vivo and the upregulation of adhesion molecules in response to numerous inducing factors is associated with inflammation, this study examined the effect of CML-1 on the expression of adhesion molecules induced by TNF-alpha in cultured human umbilical vein endothelial cells (HUVECs). Preincubation of HUVECs for 20h with CML-1 (1-100mug/ml) dose-dependently inhibited TNF-alpha (10ng/ml)-induced adhesion of THP-1 monocytic cells, as well as mRNA and protein expression of E-selectin, vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1). CML-1 was also shown to inhibit NK-kB activation induced by TNF-alpha. Furthermore, CML-1 inhibited TNF-alpha-induced IkB kinase activation, subsequent degradation of IkBalpha, and nuclear translocation of NK-kB. Evidence presented in this report demonstrated that CML-1 inhibited the adhesive capacity of HUVEC and the TNF-alpha-mediated induction of E-selectin, ICAM-1 and VCAM-1 in HUVEC by inhibiting the IkB/NF-kB signaling pathway at the level of IkB kinase, which may explain the ability of CML-1 to suppress inflammation and modulate the immune response.

Gamma-irradiation-induced intercellular adhesion molecule-1 (ICAM-1) expression is associated with catalase: activation of Ap-1 and JNK

The ionizing radiation used in cancer therapy frequently produces damage to normal tissues and induces complex responses, including inflammation. The upregulation of the intercellular adhesion molecule-1 (ICAM-1) in response to numerous inducing factors is associated with inflammation. Therefore, this study examined the molecular mechanisms responsible for ICAM-1 expression induced by gamma-irradiation (gammaIR). ICAM-1 mRNA and cell surface expression were induced in A549 human lung epithelial cells after exposing them to gammaIR. Catalase expression and activity were also increased in gammaIR-treated cells. Treatment of the gammaIR-treated cells with catalase resulted in a significant increase in the ICAM-1 cell surface expression level. The catalase inhibitor 3-amino-1,2,4-triazole (AT) reduced the level of ICAM-1. Electrophoretic mobility shift assay (EMSA) analysis showed that activating protein 1 (AP-1) was activated by gammaIR, whereas NF-kappaB was not. Specific Jun N-terminal kinase (JNK) inhibition attenuated the upregulation of gammaIR stimulated ICAM-1. Western blot analysis revealed a marked elevation in activation of JNK. In addition, pretreatment with AT resulted in a decrease in the level of JNK phosphorylation and AP-1 activation. Overall, data suggest that induction of ICAM-1 expression by gammaIR is associated with catalase. Furthermore, catalase, JNKs, and AP-1 activation induce ICAM-1 upregulation through a sequential process.

Inhibition of ICAM-1 expression by garlic component, allicin, in gamma-irradiated human vascular endothelial cells via downregulation of the JNK signaling pathway

Ionizing radiation used in cancer therapy frequently exerts damaging effects on normal tissues and induces a complex response including inflammation. Since the upregulation of adhesion molecules on endothelial cell surface has been known to be associated with inflammation and our previous data showed that irradiation enhanced adhesion molecules expression, interfering with the expression of adhesion molecules may be an important therapeutic target of inflammatory diseases. We examined the effect of allicin, a major component of garlic, on the induction of intercellular adhesion molecule-1 (ICAM-1) by gamma-irradiation (gamma IR) and the mechanisms of its effect in gamma-irradiated human umbilical vein endothelial cells (HUVECs). HUVECs were pretreated for 20 h with allicin (0.01-1 micro g/ml) and then exposed to 8 Gy radiation. Allicin significantly inhibited gamma IR-induced surface expression of ICAM-1 and ICAM mRNA in a dose-dependent manner. In addition, pretreatment with allicin resulted in the decrease of AP-1 activation and phosphorylation of the c-Jun NH2-terminal kinase (JNK) induced by gamma IR. These results suggest that allicin downregulates gamma IR-induced ICAM-1 expression via inhibition of both AP-1 activation and the JNK pathway and may be considered in therapeutic strategies for the management of patients treated with radiation therapy.

Helicobacter pylori vacuolating cytotoxin induces activation of the proapoptotic proteins Bax and Bak, leading to cytochrome c release and cell death, independent of vacuolation

Helicobacter pylori vacuolating cytotoxin, VacA, which causes vacuolation of gastric epithelial cells and other types of cultured cells, is known to stimulate apoptosis via a mitochondria-dependent pathway. In the present study, we examined the mechanisms of VacA-induced mitochondrial damage. Intracellular VacA localization was monitored by immunostaining and confocal microscopy; in AZ-521 cells in which cytochrome c release was stimulated, most of VacA was localized to vacuoles rather than mitochondria. VacA reduced the membrane potential of isolated mitochondria without inducing cytochrome c release, suggesting that it did not act directly to induce cytochrome c release from mitochondria and that in intact cells, VacA-induced cytochrome c release involved apoptosis-related factor(s), such as a proapoptotic Bcl-2 family protein. In agreement, flow cyto-metric analyses using antibodies specific for activated Bax revealed that intracellular Bax was activated by VacA in a concentration- and time-dependent manner. Using active form-specific antibodies, we also observed that the Bcl-2 family protein, Bak, was activated. By confocal microscopy, Bax and Bak were activated in AZ-521 cells in which cyto-chrome c release was induced by VacA. In addition, small interfering RNA-induced silencing of the bax gene resulted in reduction of VacA-stimulated cytochrome c release, consistent with a contribution of VacA-induced Bax activation to cytochrome c release. NH4Cl enhanced both VacA-induced vacuolation and Bax activation, whereas Bax activation was not inhibited by bafilomycin A1, which inhibited vacuolation caused by VacA. These results suggest that VacA acts through different signaling pathways to induce apoptosis via Bax activation, independent of vacuolation.

Helicobacter pylori induces apoptosis of rat gastric epithelial cells in vitro

AIM: To investigate the effect of Helicobacter pylori (H. pylori) sonicated extract on the apoptosis of rat gastric epithelial cells as well as the expression of apoptosis-related genes in vitro.

METHODS: H. pylori sonicated extract from strain Sydney SS-1 was cultured with OUMS-37, a kind of immortalized rat gastric cell lines. Apoptosis of the cells was confirmed according to specific changes of morphology and DNA ladder 24-48 h after co-incubation. The expression of P53 protein was detected by Western blotting and the expression of bax and bcl-2 mRNA were observed by Northern blotting.

RESULTS: The specific morphology of the cells such as shrinkage, condensation, margination of nuclear chromatin and apoptotic bodies were observed under light microscope. DNA ladder was manifested by fragment analysis. Western blotting showed a dose-dependent increased expression of wild-type P53 protein and Northern blotting showed a dose-pendent increased expression of bax mRNA and reduced expression of bcl-2 mRNA in the treated cells.

CONCLUSION: H. pylori sonicated extract induces the apoptosis in vitro through up-regulation of wild-type P53 protein and bax mRNA expression, and down-regulation of bcl-2 mRNA expression, suggesting that H. pylori infection may interrupt the balance between proliferation and apoptosis of the gastric epithelial cells, which plays a key role in gastric carcinogenesis.

RETRACTED: Activation of murine peritoneal macrophages by sulfated exopolysaccharide from marine microalga Gyrodinium impudicum (strain KG03): involvement of the NF-kappa B and JNK pathway

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Editor-in-Chief, as there are concerns about inappropriate re-use of published figures. In this study, the same Western blot has been used to represent different studies with different drugs (methoxychalcone vs ganodermanondiol), cell extracts (macrophages versus hepatocytes) and different targets (Nrf2 vs LKB1). The concern was initially raised in PubPeer, the response from author on PubPeer was not acceptable. The journal Editor in Chief requested the author to provide the explanation, however, the author was not able to fulfil this request. PubPeer - Activation of murine peritoneal macrophages by sulfated exop… [pubpeer.com]

Bacterial toxins that modulate host cell-cycle progression

The mammalian cell cycle is involved in many processes--such as immune responses, maintenance of epithelial barrier functions, and cellular differentiation--that affect the growth and colonization of pathogenic bacteria. Therefore it is not surprising that many bacterial pathogens manipulate the host cell cycle with respect to these functions. Cyclomodulins are a growing family of bacterial toxins and effectors that interfere with the eukaryotic cell cycle. Here, we review some of these cyclomodulins such as cytolethal distending toxins, vacuolating cytotoxin, the polyketide-derived macrolide mycolactone, cycle-inhibiting factor, cytotoxic necrotizing factors, dermonecrotic toxin, Pasteurella multocida toxin and cytotoxin-associated antigen A. We describe and compare their effects on the mammalian cell cycle and their putative role in disease, commensalism and symbiosis. We also discuss a possible link between these cyclomodulins and cancer.

Antigen epitope of Helicobacter pylori vacuolating cytotoxin A

AIM: To construct and select antigen epitopes of vacuolating cytotoxin A (VacA) for nontoxic VacA vaccine against Helicobacter pylori (H pylori ) infection.

METHODS: Eleven VacA epitopes were predicted according to VacA antigenic bioinformatics. Three candidates of VacA epitope were constructed through different combined epitopes. The candidate was linked with E. coli heat-labile enterotoxin B (LTB) by a linker of 7 amino acids, and cloned into plasmid pQE-60 in which fusion LTB-VacA epitope was efficiently expressed. To test the antigencity of the candidate, 6 BALB/c mice were treated with the fusion LTB-VacA epitope through intraperitoneal injection. To explore the ability of inhibiting the toxicity of VacA,cantiserum against the candidate was used to counteract VacA that induced HeLa cells to produce cell vacuoles in vitro.

RESULTS: Serum IgG against the candidate was induced in the BALB/c mice. In vitro, the three antisera against the candidate efficiently counteracted the toxicity of VacA, and decreased the number of cell vacuoles by 14.17%, 20.20% and 30.41% respectively.

CONCLUSION: Two of the three candidates, LZ-VacA1and LZ-VacA2, can be used to further study the mechanism of vacuolating toxicity of VacA, and to construct nontoxic VacA vaccine against H pylori infection.

Helicobacter pylori infection: anything new should we know?

Over the past year, 2003-4, there have been a number of studies consolidating previous work in relation to pathogenesis of disease, diagnosis and management of Helicobacter pylori. Studies into the pathogenesis of disease have identified the main adhesin of H. pylori as an important virulence marker and as a potential target for therapy. Molecular investigations of both the strain and host variations have identified the action of several of the virulence factors, e.g. cagA, vacA, on disrupting host cell signalling and the consequences in respect of the release of chemokines from the damaged gastric epithelium and the effect on apoptosis. Over the past year, there have been further diagnostic kits developed based on modifications of current technology. Two promising areas of research for diagnosis are the use of host/strain genome polymorphisms as a means of identifying high-risk patients who may develop severe disease and the use of proteomics to identify potential antigens of diagnostic (or therapeutic) use. The three main antibiotics that are used in first-line eradication regimens are clarithromycin, metronidazole and amoxycillin. Of these, metronidazole has the highest prevalence of resistance, followed by clarithromycin; amoxycillin resistance is only rarely reported. The decreasing success of current first-line therapy is the driving force for the development of new antibiotic combinations and a search for novel sources for chemotherapeutic agents and novel therapeutic targets.