Down-regulation of Bcl-2 is mediated by NF-κB activation in Helicobacter pylori-induced apoptosis of gastric epithelial cells.
ABSTRACT Bcl-2 family is involved in the regulation of apoptosis. NF-κB activation is associated with either the expression of Bcl-2 or down-regulation of Bcl-2 depending on cell types and stimuli. Previously, we showed NF-κB activation, decrease in the level of Bcl-2, and apoptosis in Helicobacter pylori (H. pylori)-infected gastric epithelial cells. The present study aims to investigate the relation of Bcl-2 expression and NF-κB activation in H. pylori-induced apoptotic cell death of AGS (gastric adenocarcinoma) cells.
AGS cells were transfected with mutant IκBα to suppress NF-κB activation or Bcl-2 gene to induce overexpression of Bcl-2. mRNA expression of Bcl-2, p53 and Bax, DNA fragmentation, cell viability, and the numbers of apoptotic cells were determined.
H. pylori induced decrease in Bcl-2, but increase in p53 and Bax at the levels of mRNA and protein in AGS cells. H. pylori-induced increment of apoptotic cells and decrease in Bcl-2 level were inhibited in the cells transfected with mutant IκBα gene as compared with the cells transfected with control vector. H. pylori-induced apoptosis determined by apoptotic cells, DNA fragmentation, and cell viability was inhibited in the cells transfected with Bcl-2 gene.
Down-regulation of Bcl-2 is mediated by NF-κB activation, which may be the underlying mechanism of apoptosis in H. pylori-infected gastric epithelial cells.
- SourceAvailable from: Tone Tannæs[show abstract] [hide abstract]
ABSTRACT: The association between Helicobacter pylori infection and upper gastrointestinal disease is well established. However, only a small fraction of H. pylori carriers develop disease, and there are great geographical differences in disease penetrance. The explanation to this enigma lies in the interaction between the bacterium and the host. H. pylori Outer Membrane Phospholipase A (OMPLA) has been suggested to play a role in the virulence of this bacterium. The aim of this study was to profile the most significant cellular pathways and biological processes affected in gastric epithelial cells during 24 h of H. pylori exposure, and to study the inflammatory response to OMPLA⁺ and OMPLA⁻ H. pylori variants. Interleukin-8 was the most significantly up-regulated gene and appears to play a paramount role in the epithelial cell response to H. pylori infection and in the pathological processes leading to gastric disease. MAPK and NF-kappaB cellular pathways were powerfully activated, but did not seem to explain the impressive IL-8 response. There was marked up-regulation of TP53BP2, whose corresponding protein ASPP2 may interact with H. pylori CagA and cause marked p53 suppression of apoptosis. Other regulators of apoptosis also showed abberant regulation. We also identified up-regulation of several oncogenes and down-regulation of tumor suppressor genes as early as during the first 24 h of infection. H. pylori OMPLA phase variation did not seem to influence the inflammatory epithelial cell gene response in this experiment. In whole genome analysis of the epithelial response to H. pylori exposure, IL-8 demonstrated the most marked up-regulation, and was involved in many of the most important cellular response processes to the infection. There was dysregulation of apoptosis, tumor suppressor genes and oncogenes as early as in the first 24 h of H. pylori infection, which may represent early signs of gastric tumorigenesis. OMPLA⁺/⁻ did not affect the acute inflammatory response to H. pylori.BMC Microbiology 01/2012; 12:9. · 3.10 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: Helicobacter pylori infection reprograms host gene expression and influences various cellular processes, which have been investigated by cDNA microarray using in vitro culture cells and in vivo gastric biopsies from patients of the Chronic Abdominal Complaint. To further explore the effects of H. pylori infection on host gene expression, we have collected the gastric antral mucosa samples from 6 untreated patients with gastroscopic and pathologic confirmation of chronic superficial gastritis. Among them three patients were infected by H. pylori and the other three patients were not. These samples were analyzed by a microarray chip which contains 14,112 cloned cDNAs, and microarray data were analyzed via BRB ArrayTools software and Ingenuity Pathways Analysis (IPA) website. The results showed 34 genes of 38 differentially expressed genes regulated by H. pylori infection had been annotated. The annotated genes were involved in protein metabolism, inflammatory and immunological reaction, signal transduction, gene transcription, trace element metabolism, and so on. The 82% of these genes (28/34) were categorized in three molecular interaction networks involved in gene expression, cancer progress, antigen presentation and inflammatory response. The expression data of the array hybridization was confirmed by quantitative real-time PCR assays. Taken together, these data indicated that H. pylori infection could alter cellular gene expression processes, escape host defense mechanism, increase inflammatory and immune responses, activate NF-κB and Wnt/β-catenin signaling pathway, disturb metal ion homeostasis, and induce carcinogenesis. All of these might help to explain H. pylori pathogenic mechanism and the gastroduodenal pathogenesis induced by H. pylori infection.PLoS ONE 01/2012; 7(3):e33030. · 3.73 Impact Factor