Apoptosis In Gastric Epithelial Cells Research Articles

Helicobacter pylori Infection Inhibits Phagocyte Clearance of Apoptotic Gastric Epithelial Cells

Increased apoptotic death of gastric epithelial cells is a hallmark of Helicobacter pylori infection, and altered epithelial cell turnover is an important contributor to gastric carcinogenesis. To address the fate of apoptotic gastric epithelial cells and their role in H. pylori mucosal disease, we investigated phagocyte clearance of apoptotic gastric epithelial cells in H. pylori infection. Human gastric mononuclear phagocytes were analyzed for their ability to take up apoptotic epithelial cells (AECs) in vivo using immunofluorescence analysis. We then used primary human gastric epithelial cells induced to undergo apoptosis by exposure to live H. pylori to study apoptotic cell uptake by autologous monocyte-derived macrophages. We show that HLA-DR(+) mononuclear phagocytes in human gastric mucosa contain cytokeratin-positive and TUNEL-positive AEC material, indicating that gastric phagocytes are involved in AEC clearance. We further show that H. pylori both increased apoptosis in primary gastric epithelial cells and decreased phagocytosis of the AECs by autologous monocyte-derived macrophages. Reduced macrophage clearance of apoptotic cells was mediated in part by H. pylori-induced macrophage TNF-α, which was expressed at higher levels in H. pylori-infected, compared with uninfected, gastric mucosa. Importantly, we show that H. pylori-infected gastric mucosa contained significantly higher numbers of AECs and higher levels of nonphagocytosed TUNEL-positive apoptotic material, consistent with a defect in apoptotic cell clearance. Thus, as shown in other autoimmune and chronic inflammatory diseases, insufficient phagocyte clearance may contribute to the chronic and self-perpetuating inflammation in human H. pylori infection.

Effects of broth culture filtrate protein of VacA+ Helicobacter pylori on the proliferation and apoptosis of gastric epithelial cells

Background Infection with Helicobacter pylori (H. pylori) may lead to chronic inflammation of the stomach epithelium, mucosal atrophy, imbalance of proliferation and apoptosis of epithelial cells; resulting in chronic gastritis, peptic ulcer, gastric cancer, and many other clinical outcomes. Why and how H. pylorus leads to gastric cancer is not clear yet. Through in vitro experiments, this study evaluated the effects of broth culture filtrate protein (BCF-P) from the supernatant of liquid culture media of H. pylori on proliferation and apoptosis of immortalized human gastric epithelial cell lines (GES-1) and gastric cancer cell lines (AGS). Methods For the study, GES-1 and AGS cell lines mix with BCF-P and epidermal growth factor (EGF). MTT assay and flow cytometry (FCM) determined the levels of proliferation and apoptosis. Detected expression levels of cyclooxygenase-2 (COX-2) and Fas mRNA by reverse transcription (RT)-PCR. Also did analysis of the effects of BCF-P on epidermal growth factor receptor (EGFR) tyrosine kinase activity of GES-1 and AGS cells by non-radioactive enzyme-linked assay. The Student’s t test and one-way analysis of variance (ANOVA) were used for statistical analysis. Results BCF-P inhibited proliferation of GES-1 and AGS cells in a concentration-dependent manner. The inhibition rates are respectively 68.7% in AGS and 61.4% in GES-1. With the same dose and time for inhibiting the proliferation, BCF-P failed to induce apoptosis of GES-1 and AGS cells. Effects of BCF-P reduced the expression of Fas mRNA of GES-1 and AGS cells (P <0.05). This is consistent with the effects of EGF. BCF-P reduced the expression of COX-2 mRNA of AGS cells (P <0.05). This is opposite to the effects of EGF (P <0.05). Effects of BCF-P improved more than three times the EGFR tyrosine kinase activity of GES-1 and AGS cells. Conclusions BCF-P inhibited the proliferation of AGS and GES-1 cells in vitro, unrelated to apoptosis. Effects of BCF-P on gastric epithelial cells in vitro are not equivalent to that of EGF.

C1q promotes recognition and engulfment of H. pylori infected AGS cells and modulates inflammatory cytokine production in macrophages. (P4019)

Abstract H pylori resides in the gastric lumen and is a significant risk factor for gastritis and gastric cancer. This organism promotes apoptosis of gastric epithelial cells that are subsequently cleared by local phagocytes. C1q, the recognition component of the complement cascade, is an important molecule in immune regulation where it promotes uptake of apoptotic cells and modulates inflammation. We demonstrated that H pylori infection induces apoptosis of gastric AGS cells in vitro and that apoptotic epithelial cells are recognized and engulfed by macrophages independent of the method of cell death. Further, C1q binds to apoptotic cells and is important in the interaction between apoptotic cells and macrophages. We show that the absence of serum reduced attachment of AGS cells to phagocytes by up to 90% and the addition of 40μg/ml of C1q was sufficient to restore normal binding. A comparable effect of C1q on internalization of AGS cells was observed using a flow cytometric assay. C1q, in the absence of serum, attenuated IL-6, TNF-α and IL-1β production induced by 100 ng/ml of LPS or 100 MOI H. pylori compared to controls (45-60% reductions). In conclusion, we show that C1q is important in the resolution of inflammation by facilitating the engulfment of apoptotic cells and inhibiting the pro-inflammatory cytokine responses. Further, the inhibition of host responses attributed to the engulfment of apoptotic cells may be induced by extracellular factors including C1q.

Sa1911 Curcumin Restores Apoptosis in Gastric Epithelial Cells With Helicobacter pylori-Induced DNA Damage by Increasing Phospho-p38 and p53 Levels

Sa1911 Curcumin Restores Apoptosis in Gastric Epithelial Cells With Helicobacter pylori-Induced DNA Damage by Increasing Phospho-p38 and p53 Levels

Helicobacter pylori infection and relationship with gastric epithelial cell proliferation and apoptosis

To evaluate the effects of Helicobacter pylori on cell proliferation and apoptosis in gastric cancer (GC) both at tumoral and nontumoral sites and in gastritis. Materials and methods: Biopsies from 96 patients (gastric cancer = 52, gastritis = 44) were examined immunohistochemically and histopathologically. Results: In H. pylori-positive GC patients the average proliferative index (PI) in tumor and nontumor sites was 40.7% and 24.8%, while in H. pylori-negative patients it was 32.9% and 17.8%, respectively. The PI was significantly higher in the tumor than in the nontumor sites, regardless of H. pylori infection. Cell proliferation was also significantly associated with intestinal metaplasia in nontumor sections. The apoptotic index (AI) in H. pylori-positive GC tumor and nontumor sites showed an average of 61.8% and 50.0%, while in H. pylori-negative patients it was 38.1% and 25.0%, respectively. The AI was significantly higher in both groups in the presence of H. pylori. In gastritis, H. pylori infections lead to a significantly higher PI than AI. H. pylori infection increased the PI and the AI in cases of GC. Conclusion: H. pylori induced higher proliferative and apoptotic activities in both tumor and nontumor sites of the GC sections, a fact that provides supportive evidence for its effect.

Effect of Di(2-ethylhexyl)phthalate onHelicobacter pylori-Induced Apoptosis in AGS Cells

Plastic products are wildly used in human life. Di(2-ethylhexyl)phthalate (DEHP) is an essential additive in plastic manufacturing and is used as plasticizer for many products including plastic food packaging. DEHP is a teratogenic compound and can cause potent reproductive toxicity. DEHP can also cause liver damage, peroxisome proliferation, and carcinogenesis. DEHP is also strongly associated with peptic ulcers and gastric cancer; however, the underlying effect and mechanism of DEHP on the gastrointestinal tract are not entirely clear. The oral infection route of H. pylori parallels the major ingestion route of DEHP into the human body. Therefore, we wanted to study the effect of DEHP and H. pylori exposure on the human gastric epithelial cell line, AGS (gastric adenocarcinoma). The viability of the AGS cell line was significantly lower in 80 μM-DEHP and H. pylori (MOI = 100 : 1) coexposure than DEHP or H. pylori alone. DEHP and H. pylori coexposure also induced caspase-3 activation, and increased Bax/Bcl-2 ratio and DNA fragmentation in AGS cells. These results indicate that DEHP can enhance H. pylori cytotoxicity and induce gastric epithelial cell apoptosis. Therefore, it is possible that DEHP and H. pylori coexposure might enhance the disruption of the gastric mucosa integrity and potentially promote the pathogenesis of gastric carcinogenesis.

Effects of IL-1β on the proliferation and apoptosis of gastric epithelial cells and acid secretion from isolated rabbit parietal cells

The aim of the present study was to explore the effects of IL-1β on the proliferation and apoptosis of gastric epithelial cells and acid secretion from isolated rabbit parietal cells. The mechanisms by which these effects are mediated were also investigated. Parietal cells were isolated from rabbit gastric mucosa by elutriation. The AGS human gastric cancer cell line, the GES-1 human gastric epithelial cell line and parietal cells were treated with interleukin (IL)-1β in the presence or absence of Helicobacter pylori (H.pylori) for the times indicated. MTT assay and flow cytometry (FCM) were used to determine the levels of proliferation and apoptosis. The expression levels of cyclooxygenase-2 (COX-2) mRNA and protein were examined by RT-PCR and FCM. Acid secretion by parietal cells was examined using 14C-aminopyrine (14C‑AP) accumulation. H+/K+ATPaseα subunit mRNA expression was assessed by RT-PCR. The results demonstrated that IL-1β (10ng/ml) stimul-ated cellular proliferation and inhibited H.pylori-induced apoptosis in GES-1 and AGS cell lines. IL-1β (10ng/ml) upregulated the mRNA and protein expression of COX‑2 in GES-1 and AGS cells. Acid secretion stimulated by histamine was identified as significantly inhi-bited and mRNA expression of H+/K+ATPaseα subunit was downregulated by treatment with IL-1β (10ng/ml) for 30min and 16h compared with the control in isolated rabbit parietal cells. The present study demonstrates that IL-1β plays a significant role in H.pylori-induced gastric carcinogenesis through 2main mechanisms: i) IL-1β may interfere in gastric epithelial cell growth by upregulating COX-2 expression; ii)IL-1β may inhibit the acid secretion from parietal cells by downregulating H+/K+ATPase expression.

Helicobacter pylori promotes apoptosis, activates cyclooxygenase (COX)-2 and inhibits heat shock protein HSP70 in gastric cancer epithelial cells.

ObjectiveApoptosis plays an important role in the regulation of gastric epithelial cell number and gastrointestinal disorders induced by Helicobacter pylori (Hp). Heat shock proteins (HSPs) are involved in cell integrity, cell growth and in gastric mucosa colonized by Hp. COX-2 was implicated in Hp-induced carcinogenesis but the effects of this germ and CagA cytotoxin on HSP70, COX-2, Bax and Bcl-2 in gastric cancer epithelial cells have been little studied.Material and methodsWe determined the expression for HSP70, Bax and Bcl-2 in human gastric epithelial MKN7 cells incubated with live strain Hp (cagA + vacA+) with or without co-incubation with exogenous CagA and NS-398, the selective COX-2 inhibitor. After 3–48 h of incubation, the expression of HSP70, COX-2, Bax and Bcl-2 mRNA and proteins were determined by RT-PCR and immunoprecipitation.Results Hp inhibited expression for HSP70 and this was significantly potentiated by exogenous CagA. Co-incubation of epithelial cells with Hp, without or with CagA increased Bax expression and simultaneously decreased expression for Bcl-2. The increase in COX-2 mRNA and Bax expression were significantly inhibited by NS-398. We conclude that Hp promotes apoptosis in adenocarcinoma gastric epithelial cells in vitro and this is associated with activation of COX-2 and inhibition of HSP70.

Proliferative and apoptotic effects of gastric epithelial cells induced by coccoid Helicobacter pylori

Helicobacter pylori exhibit morphology convertion in a spiral or coccoid form. This study aims to reveal the impact of coccoid H. pylori on the proliferation and apoptosis of gastric epithelial cells. The cagA and vacA genes of H. pylori were detected by semi-quantitative RT-PCR. Proliferation and apoptosis were analyzed by the CCK-8 colorimetric method and TUNEL assay, respectively. Egr-1 mRNA and PCNA expression affected by the ERK1/2-specific inhibitor were detected by RT-PCR and immunochemistry. At low density of infection (MOI < 125:1), coccoid H. pylori exerted a stronger effect on proliferation and a weaker effect on apoptosis than did spiral form. The ERK1/2-specific inhibitor significantly blocked the increased expression in Egr-1 and PCNA induced by coccoid H. pylori. Expression of vacA and cagA in coccoid H. pylori decreased compared with the spiral form, whereas vacA decreased more than cagA. The difference of proliferation and apoptosis may be related to the unequal decreased expression of vacA and cagA in coccoid H. pylori. Activation of the ERK1/2-Egr-1-PCNA signal transduction pathway may play an important role in coccoid H. pylori-induced cell proliferation. Long latency of the coccoid form of H. pylori in gastric tissue may be associated with gastric cancer caused by H. pylori.

The protective of hydrogen on stress-induced gastric ulceration

Stress ulceration frequently occurs as a result of major stressful events and hydroxyl radical (⋅OH) is one of the major causative factors for it. Recently, it has been proved that hydrogen, a potent selectively ⋅OH scavenger, can effectively protect animals against ROS-induced tissue damage. In like manner, we hypothesize that hydrogen may have a protective effect against stress ulceration. Gastric ulceration was induced by the method of cold restraint stress. Rats in the hydrogen treatment group received hydrogen-rich saline (10mL/kg body weight) 5min before the stress. At 6h post-stress, gastric corpus mucosa was harvested for the measurement of malondialdehyde, protein carbonyl, 8-hydroxy-desoxyguanosine, glutathione, superoxide dismutase, myeloperoxidase, TNF-α, IL-1β and cytokine-induced neutrophils chemoattractant-1. In addition, western blotting was used to determine the expression of p38 MAPK, P-p38 MAPK, P-JNk, JNK, Bcl-xl, Bax and cleaved caspase-3. Nuclear translocation of NF-κB was assessed by electrophoretic mobility shift assay. Gastric mucosa structure and mucosal epithelial cells apoptosis were measured at 12h post-stress. Our present study showed that hydrogen treatment lessened the stress-induced lipid peroxidation, protein carbonyl and DNA oxidant and improved tissue antioxidant potential. In addition, hydrogen mitigated inflammatory response and neutrophils infiltration with suppressing the activity of P-p38 MAPK, P-JNk and NF-κB. Importantly, hydrogen ameliorated gastric mucosa damage with preventing cell apoptosis. Furthermore, the up-regulation of cleaved caspase-3, Bax and down-regulation of Bcl-xl expression were blocked by hydrogen treatment. In conclusion, hydrogen treatment effectively ameliorated stress-associated gastric mucosa damage via its anti-oxidant, anti-inflammatory and anti-apoptotic effects.

A Potential Association between Helicobacter pylori CagA EPIYA and Multimerization Motifs with Cytokeratin 18 Cleavage Rate during Early Apoptosis

Helicobacter pylori is a highly diverse pathogen, which encounters epithelial cells as the initial defense barrier during its lifelong infection. The structure of epithelial cells can be disrupted through cleavage of microfilaments. Cytokeratin 18 (CK18) is an intermediate filament, the cleavage of which is considered an early event during apoptosis following activation of effector caspases. Helicobacter pylori strains were isolated from 76 dyspeptic patients. cagA 3' variable region and CagA protein status were analyzed by PCR and western blotting, respectively. Eight hours post-co-culture of AGS cells with different H. pylori strains, flow cytometric analysis was performed using M30 monoclonal antibody specific to CK18 cleavage-induced neo-epitope. Higher rates of CK18 cleavage were detected during co-culture of AGS cells with H. pylori strains bearing greater numbers of cagA EPIYA-C and multimerization (CM) motifs. On the other hand, H. pylori strains with greater numbers of EPIYA-B relative to EPIYA-C demonstrated a decrease in CK18 cleavage rate. Thus, H. pylori-mediated cleavage of CK18 appeared proportional to the number of CagA EPIYA-C and CM motifs, which seemed to be downplayed in the presence of EPIYA-B motifs. Our observation associating the heterogeneity of cagA variants with the potential of H. pylori strains in the induction of CK18 cleavage as an early indication of apoptosis in gastric epithelial cells supports the fact that apoptosis may be a type-specific trait. However, additional cagA-targeted experiments are required to clearly identify the role of EPIYA and CM motifs in apoptosis and/or the responsible effector molecules.

Variants in Autophagy Genes Affect Susceptibility to Both Crohn's Disease and Helicobacter pylori Infection

Helicobacter pylori (H pylori) is a Gram-negative, microaerophilic bacterium that selectively colonizes the stomachs of half the world’s human population. H pylori is the etiologic agent of several gastric diseases, including chronic gastritis and peptic ulcers. Long-term, chronic inflammation subsequently increases the risk for the development of mucosa-associated lymphoid tissue lymphoma and gastric cancer.1,2 During a well-choreographed interaction between the bacteria and the host gastric epithelium, H pylori infection initiates an immune response that leads to a massive infiltration of inflammatory cells.1 An evolutionarily conserved cellular mechanism, autophagy, functions as an innate defense lysosomal pathway in response to infection to degrade intracellular micro-organisms attempting to establish a replicative niche in the host epithelial cell cytoplasm.3 Unfortunately, H pylori utilizes a novel escape mechanism to evade lysosomal destruction in host epithelial cells that subsequently supports chronic infection. A study in this month’s issue of Gastroenterology identifies, for the first time, an autophagy gene as a candidate for host susceptibility to H pylori infection and disease progression.4

Lactobacillus plantarumB7 inhibitsHelicobacter pylorigrowth and attenuates gastric inflammation

To determine the anti-Helicobacter property of Lactobacillus plantarum B7 (L. plantarum) B7 supernatants in vitro and the protective effects of L. plantarum B7 on serum tumor necrosis factor-alpha (TNF-α), gastric malondialdehyde (MDA) level, apoptosis, and histopathology in Helicobacter pylori (H. pylori)-induced gastric inflammation in rats. In vitro, the inhibition of H. pylori growth was examined using L. plantarum B7 supernatants at pH 4 and pH 7 and at the concentration of 1×, 5× and 10× on plates inoculated with H. pylori. The inhibitory effect of H. pylori was interpreted by the size of the inhibition zone. In vitro, male Sprague-Dawley rats were randomly divided into four groups including group 1 (control group), group 2 (H. pylori infected group), group 3 (H. pylori infected with L. plantarum B7 10(6) CFUs/mL treated group) and group 4 (H. pylori infected with L. plantarum B7 10(10) CFUs/mL treated group). One week after H. pylori inoculation, L. plantarum B7 10(6) CFUs/mL or 10(10) CFUs/mL were fed once daily to group 3 and group 4, respectively, for one week. Blood and gastric samples were collected at the end of the study. In vitro, at intact pH 4, mean inhibitory zone diameters of 8.5 mm and 13 mm were noted at concentrations of 5× and 10× of L. plantarum B7 supernatant disks, respectively. At adjusted pH 7, L. plantarum B7 supernatants at concentrations of 5× and 10× yielded mean inhibitory zone diameters of 6.5 mm and 11 mm, respectively. In the in vitro study, in group 2, stomach histopathology revealed mild to moderate H. pylori colonization and inflammation. The level of gastric MDA and epithelial cell apoptosis were significantly increased compared with group 1. The serum TNF-α level was significant decreased in group 3 compared with group 2 (P < 0.05). In addition, L. plantarum B7 treatments resulted in a significant improvement in stomach pathology, and decreased gastric MDA level and apoptotic epithelial cells. L. plantarum B7 supernatant inhibits H. pylori growth. This inhibition was dose-dependent and greater at pH 4. Moreover, L. plantarum B7 attenuated H. pylori-induced gastric inflammation.

Chronic Helicobacter pylori infection induces the proliferation and apoptosis in gastric epithelial cells and gastric precancerosis in Mongolian gerbils

To explore the effect of different Helicobacter pylori (H.pylori) clinical strains on the proliferation and apoptosis of gastric epithelial cells, and to observe the effect of H.pylori on gastric mucosa by Mongolian gerbil model infected H.pylori. H.pylori isolates harvested from pathologically documented gastric carcinoma (GC, n=10) or chronic gastritis specimens (CG, n=10) were co-cultured with GES-1 cells individually. MTT assay and flow cytometry were used to determine the proliferation and apoptosis of GES-1 cells induced by H.pylori isolates. Mongolian gerbils were infected by the most (A strain) and the least (B strain) significantly proliferated H.pylori strains. Results When co-cultured with the cell/bacteria concentration ratio 1:1 and 1:50 for 12 h and the cell/bacteria concentration ratio 1:50 for 24 h, H.pylori clinical strains isolated from patients with gastric cancer promoted the proliferation of GES-1 cells, and there was significant difference in the absorbance compared with the group of gastritis strains(P<0.05). The apoptosis rate of the GC and CG groups increased significantly (P<0.05) compared with the control group when co-cultured with the cell/bacteria concentration ratio 1:50 and 1:200, and there was no significant difference between the GC group and the CG group (P>0.05). The incidences of intestinal metaplasia and dysplasia in the A strain group were significantly higher than those in the B strain group (P<0.05). H.pylori strains from different disease sources have different effects on the proliferation of GES-1 cells. H.pylori isolated from gastric cancer can promote the proliferation of cells to different degrees and directly induce gastric precancerosis and gastric cancer.

Spermine Oxidase Mediates the Gastric Cancer Risk Associated With Helicobacter pylori CagA

Helicobacter pylori-induced gastric carcinogenesis has been linked to the microbial oncoprotein cytotoxin-associated gene A (CagA). Spermine oxidase (SMO) metabolizes the polyamine spermine into spermidine and generates H(2)O(2), which causes apoptosis and DNA damage. We determined if pathogenic effects of CagA are attributable to SMO. Levels of SMO, apoptosis, and DNA damage (8-oxoguanosine) were measured in gastric epithelial cell lines infected with cagA(+) or cagA(-)H pylori strains, or transfected with a CagA expression plasmid, in the absence or presence of SMO small interfering RNA, or an SMO inhibitor. The role of CagA in induction of SMO and DNA damage was assessed in H pylori-infected gastritis tissues from humans, gerbils, and both wild-type and hypergastrinemic insulin-gastrin mice, using immunohistochemistry and flow cytometry. cagA(+) strains or ectopic expression of CagA, but not cagA(-) strains, led to increased levels of SMO, apoptosis, and DNA damage in gastric epithelial cells, and knockdown or inhibition of SMO blocked apoptosis and DNA damage. There was increased SMO expression, apoptosis, and DNA damage in gastric tissues from humans infected with cagA(+), but not cagA(-) strains. In gerbils and mice, DNA damage was CagA-dependent and present in cells that expressed SMO. Gastric epithelial cells with DNA damage that were negative for markers of apoptosis accounted for 42%-69% of cells in gerbils and insulin-gastrin mice with dysplasia and carcinoma. By inducing SMO, H pylori CagA generates cells with oxidative DNA damage, and a subpopulation of these cells are resistant to apoptosis and thus at high risk for malignant transformation.

Preconditioning with cobalt protoporphyrin protects human gastric mucosal cells from deoxycholate-induced apoptosis

In this study, a known inducer of heme oxygenase-1 (HO-1) expression, cobalt protoporphyrin, and the introduction of a recombinant plasmid expressing HO-1 were examined for their ability to protect gastric epithelial cells from deoxycholate-induced injury. Physiologic levels of the secondary bile salt induce apoptosis in a human gastric adenocarcinoma mucosal cell line. Cobalt protoporphyrin induced expression of HO-1 protein with maximal levels attaining a plateau at 48 hours. Pretreatment with cobalt protoporphyrin before challenge with 200 μM deoxycholate inhibited cell death, DNA fragmentation, the appearance of cytosolic nucleosomes, and cleavage of caspase-3, caspase-9, and poly-(ADP-ribose) polymerase 1. Similarly, expression of HO-1 by introduction of a recombinant plasmid also showed a resistance to deoxycholate-induced apoptosis. These results implicate a possible role for HO-1 in modulating apoptosis in gastric epithelial cells.

Down-regulation of Bcl-2 is mediated by NF-κB activation in Helicobacter pylori-induced apoptosis of gastric epithelial cells

Objective. 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. Material and methods. 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. Results. 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. Conclusion. 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.

Helicobacter pylori VacA Reduces the Cellular Expression of STAT3 and Pro-survival Bcl-2 Family Proteins, Bcl-2 and Bcl-XL, Leading to Apoptosis in Gastric Epithelial Cells

Helicobacter pylori vacuolating cytotoxin, VacA, stimulates apoptosis via a mitochondria-dependent pathway. VacA induces apoptosis via activation of the pro-apoptotic B-cell lymphoma (Bcl)-2 family proteins, Bcl-2-associated X protein (Bax) and Bcl-2 homologous antagonist/killer (Bak), while the implication of such pro-survival Bcl-2 family members as Bcl-2 and Bcl-XL in the VacA-induced apoptosis remains unknown. Signal transduction and activator of transcription 3 (STAT3) is a pivotal transcription factor that upregulates Bcl-2 and Bcl-XL. This study was conducted to elicit the implication of STAT3 and pro-survival Bcl-2 and Bcl-XL in the intrinsic apoptosis. Immunoblot and reverse transcriptase real-time polymerase chain reaction (RT-PCR) were employed to assess the cellular expression of STAT3, Bcl-2, and Bcl-XL in response to purified VacA in gastric adenocarcinoma cell lines. VacA-induced apoptosis was quantitated morphologically following knockdown by each specific small interfering RNA (siRNA) or in the presence of pharmacological inhibitors. VacA reduced STAT3, Bcl-2, and Bcl-XL expression in a dose-dependent manner. Knockdown of STAT3, Bcl-2, and Bcl-XL by siRNA induced apoptosis to a similar extent in the case of sufficient VacA inoculation. The VacA-mediated reduction of STAT3 expression was independent of cellular vacuolization, since a vacuolar-type ATPase inhibitor, bafilomycin A1, did not inhibit VacA-induced reduction of STAT3, Bcl-2, and Bcl-XL expression. Instead, a c-JUN NH2-terminal kinase (JNK) inhibitor, SP600125, restored the VacA-induced reduction of STAT3 expression to the basal level. VacA-induced apoptosis may be, in part, implicated in the reduction of STAT3 linking to the downregulation of Bcl-2 and Bcl-XL, in association with JNK activity.

Breaking the Stereotype: Virulence Factor–Mediated Protection of Host Cells in Bacterial Pathogenesis

Breaking the Stereotype: Virulence Factor–Mediated Protection of Host Cells in Bacterial Pathogenesis

Cytoprotective effects of acidosis via heat shock protein HSP27 against the anticancer drug doxorubicin

Drug resistance continues to be a stumbling block in achieving better cure rates in several cancers. Doxorubicin is commonly used in treatment of a wide range of cancers. The aim of this study was to look into the mechanisms of how low ambient pH may contribute to down-regulation of apoptotic pathways in a gastric tumour cell line. Low pH culture conditions were found to dramatically prolong cell survival after doxorubicin treatment, an effect that was in part reversed by co-incubation with the specific p38 mitoge-activated protein kinase (MAP kinase) inhibitor SB203580, only mildly inhibited by blockade of the multi-drug resistance 1 (MDR1) transporter, but completely abolished by siRNA-mediated knockdown of the heat shock protein 27 (HSP27). In conclusion, acidic pH causes less accumulation of cytotoxic drug in the nucleus of adeno gastric carcinoma (AGS) cells and HSP27-dependent decrease in FasR-mediated gastric epithelial tumour cell apoptosis.