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  • Endoplasmic reticulum stress contributes to Helicobacter pylori VacA-induced apoptosis. 24349255

    Vacuolating cytotoxin A (VacA) is one of the important virulence factors produced by H. pylori. VacA induces apoptotic cell death, which is potentiated by ammonia. VacA also causes cell death by mitochondrial damage, via signaling pathways that are not fully defined. Our aim was to determine whether endoplasmic reticulum (ER) stress is associated with VacA-induced mitochondrial dysfunction and apoptosis. We found that C/EBP homologous protein (CHOP), a key signaling protein of ER stress-induced apoptosis, was transcriptionally up-regulated following incubation of gastric epithelial cells with VacA. The effect of VacA on CHOP induction was significantly enhanced by co-incubation with ammonium chloride. Phosphorylation of eukaryotic initiation factor 2 (eIF2)-alpha, which is known to occur downstream of the ER stress sensor PKR-like ER-localized eIF2-alpha kinase (PERK) and to regulate CHOP expression, was also observed following incubation with VacA in the presence of ammonium chloride. Knockdown of CHOP by siRNA resulted in inhibition of VacA-induced apoptosis. Further studies showed that silencing of the PERK gene with siRNA attenuated VacA-mediated phosphorylation of eIF2-alpha, CHOP induction, expression of BH3-only protein Bim and Bax activation, and cell death induced by VacA with ammonium chloride, indicating that ER stress may lead to mitochondrial dysfunction during VacA-induced toxicity. Activation of ER stress and up-regulation of BH3-only proteins were also observed in human H. pylori-infected gastric mucosa. Collectively, this study reveals a possible association between VacA-induced apoptosis in gastric epithelial cells, and activation of ER stress in H. pylori-positive gastric mucosa.
    Document Type:
    Reference
    Product Catalog Number:
    06-536
    Product Catalog Name:
    Anti-Bak Antibody, NT

  • Helicobacter pylori upregulates expression of epidermal growth factor-related peptides, but inhibits their proliferative effect in MKN 28 gastric mucosal cells. 9541490

    Acute exposure to Helicobacter pylori causes cell damage and impairs the processes of cell migration and proliferation in cultured gastric mucosal cells in vitro. EGF-related growth factors play a major role in protecting gastric mucosa against injury, and are involved in the process of gastric mucosal healing. We therefore studied the acute effect of H. pylori on expression of EGF-related growth factors and the proliferative response to these factors in gastric mucosal cells (MKN 28) derived from gastric adenocarcinoma. Exposure of MKN 28 cells to H. pylori suspensions or broth culture filtrates upregulated mRNA expression of amphiregulin (AR) and heparin-binding EGF-like growth factor (HB-EGF), but not TGFalpha. This effect was specifically related to H. pylori since it was not observed with E. coli, and was independent of VacA, CagA, PicA, PicB, or ammonia. Moreover, H. pylori broth culture filtrates stimulated extracellular release of AR and HB-EGF protein by MKN 28 cells. AR and HB-EGF dose-dependently and significantly stimulated proliferation of MKN 28 cells in the absence of H. pylori filtrate, but had no effect in the presence of H. pylori broth culture filtrates. Inhibition of AR- or HB-EGF- induced stimulation of cell growth was not mediated by downregulation of the EGF receptor since EGF receptor protein levels, EGF binding affinity, number of specific binding sites for EGF, or HB-EGF- or AR-dependent tyrosine phosphorylation of the EGF receptor were not significantly altered by incubation with H. pylori broth culture filtrates. Increased expression of AR and HB-EGF were mediated by an H. pylori factor > 12 kD in size, whereas antiproliferative effects were mediated by both VacA and a factor < 12 kD in size. We conclude that H. pylori increases mucosal generation of EGF-related peptides, but in this acute experimental model, this event is not able to counteract the inhibitory effect of H. pylori on cell growth. The inhibitory effect of H. pylori on the reparative events mediated by EGF-related growth factors might play a role in the pathogenesis of H. pylori-induced gastroduodenal injury.
    Document Type:
    Reference
    Product Catalog Number:
    05-104
    Product Catalog Name:
    Anti-EGFR Antibody, clone LA22

  • Effect of Helicobacter pylori eradication on TLR2 and TLR4 expression in patients with gastric lesions. 25873761

    Helicobacter pylori (Hp) is recognized by TLR4 and TLR2 receptors, which trigger the activation of genes involved in the host immune response. Thus, we evaluated the effect of eradication therapy on TLR2 and TLR4 mRNA and protein expression in H. pylori-infected chronic gastritis patients (CG-Hp+) and 3 months after treatment.A total of 37 patients CG-Hp+ were evaluated. The relative quantification (RQ) of mRNA was assessed by TaqMan assay and protein expression by immunohistochemistry.Before treatment both TLR2 and TLR4 mRNA in CG-Hp+ patients were slightly increased (TLR2 = 1.32; TLR4 = 1.26) in relation to Hp-negative normal gastric mucosa (P ≤ 0.05). After successful eradication therapy no significant change was observed (TLR2 = 1.47; TLR4 = 1.53; P greater than 0.05). In addition, the cagA and vacA bacterial genotypes did not influence the gene expression levels, and we observed a positive correlation between the RQ values of TLR2 and TLR4, both before and after treatment. Immunoexpression of the TLR2 and TLR4 proteins confirmed the gene expression results.In conclusion, the expression of both TLR2 and TLR4 is increased in CG-Hp+ patients regardless of cagA and vacA status and this expression pattern is not significantly changed after eradication of bacteria, at least for the short period of time evaluated.
    Document Type:
    Reference
    Product Catalog Number:
    06-1119

  • Chondroitin sulfate proteoglycans in spinal cord contusion injury and the effects of chondroitinase treatment. 18001203

    Chondroitinase treatment of experimental spinal cord injury improves recovery of sensory, motor, and autonomic functions. Chondroitinase catalyzes the cleavage of glycosaminoglycans (GAGs) from the core proteins of chondroitin sulfate proteoglycans (CSPGs). Little is known about changes in production of these proteoglycans in the clinically relevant contusion model of spinal cord injury or if CSPG content is altered by chondroitinase treatment. Female Long-Evans rats were injured with a forceps contusion injury and treated on alternate days with chondroitinase ABCI or control enzyme via an intrathecal catheter. Spinal cords were analyzed at specific times after injury. The cord was divided in 4 mm long segments, one containing the lesion, two rostral and two caudal to the lesion. These segments were assessed for CSPG protein and message content (NG2, neurocan and phosphacan) by Western blotting and real-time PCR. CSPG protein content was increased by one day post injury for all CSPGs investigated, and was increased in all segments examined rostral and caudal to the lesion site. Significant increases in CSPG were observed with peak content detected at 7, 7 and 14 days post injury for NG2, neurocan and phosphacan, respectively. Chondroitinase treatment had little impact upon the CPSG protein content. Changes in message levels of these CSPGs are also reported. This demonstrates that expression patterns of CSPGs in contusion injury are similar to those surrounding surgical hemisection lesions and demonstrates that the sensory and motor function enhancing effects of chondroitinase are likely due to removal of GAG chains rather than reduction in CSPG content.
    Document Type:
    Reference
    Product Catalog Number:
    MAB5212
    Product Catalog Name:
    Anti-Neurocan Antibody, clone 650.24
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