Conjugated linoleic acids produced by Lactobacillus dissociates IKK-gamma and Hsp90 complex in Helicobacter pylori-infected gastric epithelial cells

Effect of Lactobacillus plantarum ZFM4 in Helicobacter pylori-infected C57BL/6 mice: prevention is better than cure

Objectives

This study was performed to explore the preventive and therapeutic effects of Lactobacillus plantarum ZFM4 on H. pylori infections of the stomach tissue in C57BL/6 mice.

Methods

In this study, 40 specific-pathogen-free female C57BL/6 mice were randomly divided into five groups, namely, the control, ZFM4 pretreatment) ZFM4 pretreatment before H. pylori infected), model (H. pylori infected), triple therapy (H. pylori infected and treated with triple therapy), and ZFM4 treatment groups (H. pylori infected and treated with ZFM4). The preventive and therapeutic effects of Lactobacillus plantarum ZFM4 were evaluated in H. pylori-infected C57BL/6 mice by assessing gastric tissue morphology, inflammatory cytokine levels, microbial composition, and microbial diversity.

Results

Lactobacillus plantarum ZFM4 was able to survive in low gastric pH and play a role in preventing H. pylori infection. This was evident from a reduction in both, the gastric inflammatory response and expression of inflammatory factors caused by H. pylori infection. Lactobacillus plantarum ZFM4 could also inhibit the growth of H. pylori via its beneficial impact on the gastric microbiota.

Conclusion

Our findings suggest that Lactobacillus plantarum ZFM4 offers superior preventive effects against H. pylori infections when used alone. However, the therapeutic effect on established infections is weaker. Further clinical trials are needed to confirm the specific dosage, duration, and other aspects of administration.

Role of Probiotics in Eradication Therapy for Helicobacter pylori Infection

Probiotics are defined as, "Live microorganisms that, when administered in adequate amounts, confer a health benefit on the host", and have various effects including inhibitory capabilities on pathogens, stimulation of organ functions and activation of immune responses in the human. Probiotics were reported to inhibit Helicobacter pylori not only in vitro, but also in vivo studies. The mechanisms by which probiotics inhibit H. pylori infection include competition for nutrients, production of bactericidal substances, competitive inhibition of adherence and stimulation of host functions and immunity. In addition, probiotics are clinically used for eradication therapy of H. pylori infection, and the effects of probiotics as single treatment and combination use with other drugs including proton pump inhibitors and antibiotics against H. pylori are reported. It has been testified that probiotics increase the eradication rate and prevent adverse events including diarrhea, nausea, vomiting and taste disorder. In the Maastrich V/Florence Consensus Report 2017, it was stated that some probiotics may have a beneficial effect on H. pylori eradication and are effective in reducing side effects of eradication therapy, but more research is needed to answer several questions concerning the mechanisms of probiotics action. In addition, strain specificity, dosages and duration times of probiotics used for H. pylori eradication therapy need to be clarified in future studies.

Potential role of probiotics in the management of gastric ulcer

Gastric ulcer is one of the most common chronic gastrointestinal diseases characterized by a significant defect in the mucosal barrier. Helicobacter pylori (H. pylori) infection and the frequent long-term use of non-steroidal anti-inflammatory drugs are major factors involved in gastric ulcer development. Acid inhibitors and antibiotics are commonly used to treat gastric ulcer. However, in the last few decades, the accumulating evidence for resistance to antibiotics and the side effects of antibiotics and acid inhibitors have drawn attention to the possible use of probiotics in the prevention and treatment of gastric ulcer. Probiotics are live microorganisms that when administered in adequate amounts confer health benefits on the host. Currently, the available experimental and clinical studies indicate that probiotics are promising for future applications in the management of gastric ulcers. This review aims to provide an overview of the general health benefits of probiotics on various systemic and gastrointestinal disorders with a special focus on gastric ulcer and the involved cellular and molecular mechanisms: i) Protection of gastric mucosal barrier; ii) upregulation of prostaglandins, mucus, growth factors and anti-inflammatory cytokines; iii) increased cell proliferation to apoptosis ratio; and iv) induction of angiogenesis. Finally, some of the available data on the possible use of probiotics in H. pylori eradication are discussed.

The flavone eupatilin inhibits eotaxin expression in an NF-κB-dependent and STAT6-independent manner

The CC chemokine eotaxin contributes to epithelium-induced inflammation in airway diseases such as asthma. Eupatilin (5,7-dihydroxy-3',4',6'-trimethoxyflavone), a bioactive component of Artemisia asiatica Nakai (Asteraceae), is reported to inhibit the adhesion of eosinophils to bronchial epithelial cells. However, little is known about the molecular mechanism of eupatilin-induced attenuation of bronchial epithelium-induced inflammation. In this study, we investigated the effect of eupatilin on expression of eotaxin-1 (CCL11), a potent chemoattractant for eosinophils. Eupatilin significantly inhibited eotaxin expression in bronchial epithelial cells stimulated with TNF-α, while NF-κB and IκBα kinase (IKK) activities declined concurrently. Eupatilin also inhibited mitogen-activated protein kinase (MAPK) activity; however, all of these anti-inflammatory activities were reversed by MAPK overexpression. In contrast, eupatilin did not affect the signal transducer and activator of transcription 6 (STAT6) signalling in bronchial epithelial cells stimulated with IL-4. Furthermore, eupatilin significantly attenuated TNF-α-induced eosinophil migration. These results suggest that the eupatilin inhibits the signalling of MAPK, IKK, NF-κB and eotaxin-1 in bronchial epithelial cells, leading to inhibition of eosinophil migration.

Use of probiotics in the fight against Helicobacter pylori

After the discovery of Helicobacter pylori (H. pylori), and the evidence of its relationship with gastric diseases, antibiotic-based therapies were developed, which efficacy was however limited by antibiotic resistance and lack of patient compliance. A vaccine would overcome these drawbacks, but currently there is not any H. pylori vaccine licensed. In the frame of the studies aimed at finding alternative therapies or at increasing the efficacy of the current ones and/or reducing their side effects, the investigation on the use of probiotics plays an interesting role. In vitro and preclinical studies have shown the feasibility of this approach. Several clinical trials indicated that administration of probiotics can reduce the side effects of H. pylori eradication treatment, increasing tolerability, and often increases the overall efficacy. The results of these trials vary, likely reflecting the variety of probiotics assessed and that of the eradication treatment, as well as the differences in the geographic area that imply different H. pylori strains distribution, host susceptibility, and therapy efficacy. In conclusion, the use of probiotics appears promising as an adjuvant for the current H. pylori eradication treatment, though it still requires optimization.

Mitogen-activated protein kinase/IκB kinase/NF-κB-dependent and AP-1-independent CX3CL1 expression in intestinal epithelial cells stimulated with Clostridium difficile toxin A

Clostridium difficile toxin A causes acute colitis associated with inflammatory cell infiltration and increased production of proinflammatory mediators. Although CX3CL1 (fractalkine) plays a role in chemoattracting monocytes/macrophages, NK cells, and T cells, little information is available on the regulated expression of CX3CL1 in response to toxin A stimulation. In this study, we investigated the role of C. difficile toxin A on CX3CL1 induction in intestinal epithelial cells. Stimulation of murine intestinal epithelial cells with toxin A resulted in the upregulation of CX3CL1. Expression of CX3CL1 was dependent on nuclear factor-kappaB (NF-κB) and IκB kinase (IKK) activation, while the suppression of activator protein-1 (AP-1) did not affect toxin A-induced CX3CL1 expression. Suppression of p38 mitogen-activated protein kinase (MAPK) significantly inhibited IKK-NF-κB signaling leading to CX3CL1 induction in C. difficile toxin A-stimulated cells. CX3CL1 was mainly secreted from the basolateral surfaces in toxin A-treated cells. Furthermore, inhibition of p38 activity attenuated the toxin A-induced upregulation of CX3CL1 in the mouse ileum in vivo. These results suggest that a pathway, including p38 MAPK, IKK, and NF-κB activation, is required for CX3CL1 induction in intestinal epithelial cells exposed to C. difficile toxin A and may regulate the development of intestinal inflammation induced by infection with toxigenic C. difficile.

KEY MESSAGE

C. difficile toxin A causes colitis with inflammatory cell infiltration. CX3CL1 plays a role in chemoattracting immune cells. MAPK-NF-κB signaling is required for CX3CL1 induction in toxin A-exposed cells. CX3CL1 is mainly secreted from the basolateral surfaces. CX3CL1 may contribute to the regulation of toxigenic C. difficile infection.

Helicobacter pylori and interleukin-8 in gastric cancer

Helicobacter pylori (H. pylori) is a major etiological factor in the development of gastric cancer. Large-scale epidemiological studies have confirmed the strong association between H. pylori infection and both cancer development and progression. Interleukin-8 (IL-8) is overexpressed in gastric mucosa exposed to H. pylori. The expression of IL-8 directly correlates with a poor prognosis in gastric cancer. IL-8 is multifunctional. In addition to its potent chemotactic activity, it can induce proliferation and migration of cancer cells. In this review, we focus on recent insights into the mechanisms of IL-8 signaling associated with gastric cancer. The relationship between IL-8 and H. pylori is discussed. We also summarize the current therapeutics against IL-8 in gastric cancer.

Bacteroides fragilis enterotoxin upregulates lipocalin-2 expression in intestinal epithelial cells

Enterotoxigenic Bacteroides fragilis (ETBF) produces an ≈ 20 kDa B. fragilis enterotoxin (BFT), which plays an essential role in mucosal inflammation. Lipocalin (Lcn)-2, a siderophore-binding antimicrobial protein, is critical for control of bacterial infection; however, expression of Lcn-2 in BFT-exposed intestinal epithelial cells has not been elucidated. In the present study, stimulation of human intestinal epithelial cells with BFT resulted in the upregulation of Lcn-2 expression that was a relatively late response of intestinal epithelial cells compared with human β-defensin (hBD)-2 expression. The upregulation of Lcn-2 was dependent on AP-1 but not on NF-κB signaling. Lcn-2 induction via AP-1 was regulated by mitogen-activated protein kinases (MAPKs) including ERK and p38. Lcn-2 was secreted from the apical and basolateral surfaces in BFT-treated cells. These results suggest that a signaling pathway involving MAPKs and AP-1 is required for Lcn-2 induction in intestinal epithelial cells exposed to BFT, after which the secreted Lcn-2 may facilitate antimicrobial activity within ETBF-infected mucosa.

The guggulsterone derivative GG-52 inhibits NF-κB signaling in gastric epithelial cells and ameliorates ethanol-induced gastric mucosal lesions in mice

Gastric mucosal inflammation can develop after challenge with noxious stimuli such as alcohol. Specially, alcohol stimulates the release of inflammatory cytokines but does not increase gastric acid secretion, leading to gastric mucosal damage. The plant sterol guggulsterone and its novel derivative GG-52 have been reported to inhibit nuclear factor-κB (NF-κB) signaling in intestinal epithelial cells and experimental colitis. In the present study, we investigated the anti-inflammatory effects of GG-52 on gastric epithelial cells and on ethanol-induced gastric mucosal inflammation in mice. GG-52 inhibited the expression of interleukin-8 (IL-8) in gastric epithelial AGS and MKN-45 cell lines stimulated with tumor necrosis factor (TNF)-α in a dose-dependent manner. Pretreatment with GG-52 suppressed TNF-α-induced activation of IκB kinase (IKK) and NF-κB signaling in MKN-45 cells. In contrast, the inactive analog GG-46 did not produce significant changes in IL-8 expression or NF-κB activation. In a model of ethanol-induced murine gastritis, administration of GG-52 significantly reduced the severity of gastritis, as assessed by macroscopic and histological evaluation of gastric mucosal damage. In addition, the ethanol-induced upregulation of chemokine KC, a mouse homolog of IL-8, and phosphorylated p65 NF-κB signals were significantly inhibited in murine gastric mucosa pretreated with GG-52. These results indicate that GG-52 suppresses NF-κB activation in gastric epithelial cells and ameliorates ethanol-induced gastric mucosal lesions in mice, suggesting that GG-52 may be a potential gastroprotective agent.

Lactobacillus acidophilus upregulates intestinal NHE3 expression and function

A major mechanism of electroneutral NaCl absorption in the human ileum and colon involves coupling of Na(+)/H(+) and Cl(-)/HCO(3)(-) exchangers. Disturbances in these mechanisms have been implicated in diarrheal conditions. Probiotics such as Lactobacillus have been indicated to be beneficial in the management of gastrointestinal disorders, including diarrhea. However, the molecular mechanisms underlying antidiarrheal effects of probiotics have not been fully understood. We have previously demonstrated Lactobacillus acidophilus (LA) to stimulate Cl(-)/HCO3- exchange activity via an increase in the surface levels and expression of the Cl(-)/HCO3- exchanger DRA in vitro and in vivo. However, the effects of LA on NHE3, the Na(+)/H(+) exchanger involved in the coupled electroneutral NaCl absorption, are not known. Current studies were, therefore, undertaken to investigate the effects of LA on the function and expression of NHE3 and to determine the mechanisms involved. Treatment of Caco2 cells with LA or its conditioned culture supernatant (CS) for 8-24 h resulted in a significant increase in Na(+)/H(+) exchange activity, mRNA, and protein levels of NHE3. LA-CS upregulation of NHE3 function and expression was also observed in SK-CO15 cells, a human colonic adenocarcinoma cell line. Additionally, LA treatment increased NHE3 promoter activity, suggesting involvement of transcriptional mechanisms. In vivo, mice gavaged with live LA showed significant increase in NHE3 mRNA and protein expression in the ileum and colonic regions. In conclusion, LA-induced increase in NHE3 expression may contribute to the upregulation of intestinal electrolyte absorption and might underlie the potential antidiarrheal effects of probiotics.

5,7-Dihydroxy-3,4,6-trimethoxyflavone inhibits intercellular adhesion molecule 1 and vascular cell adhesion molecule 1 via the Akt and nuclear factor-κB-dependent pathway, leading to suppression of adhesion of monocytes and eosinophils to bronchial epithelial cells

5,7-Dihydroxy-3',4',6'-trimethoxyflavone (eupatilin), the active pharmacological ingredient from Artemisia asiatica Nakai (Asteraceae), is reported to have a variety of anti-inflammatory properties in intestinal epithelial cells. However, little information is known about the molecular mechanism of eupatilin-induced attenuation of bronchial epithelial inflammation. This study investigates the role of eupatilin in the adhesion of inflammatory cells such as monocytes and eosinophils to bronchial epithelial cells. Stimulation of a human bronchial epithelial cell line (BEAS-2B) with tumour necrosis factor-α (TNF-α) increased the expression of surface adhesion molecules, including intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1), in which eupatilin significantly inhibited the expression of those adhesion molecules in a dose-dependent manner. Eupatilin suppressed the TNF-α-induced activation of IκBα and nuclear factor-κB (NF-κB) signals in BEAS-2B cells. The IκB kinase (IKK) activation was also significantly reduced in eupatilin-pre-treated BEAS-2B and primary normal human bronchial epithelial (NHBE) cells. However, eupatilin did not influence AP-1 activity in TNF-α-stimulated cells. Suppression of NF-κB signalling induced by eupatilin resulted in the inhibition of the expression of adhesion molecules and the adhesion of monocytes and eosinophils to BEAS-2B cells. Furthermore, eupatilin suppressed the phosphorylation of Akt in TNF-α-stimulated BEAS-2B and NHBE cells, leading to down-regulation of NF-κB activation and adhesion molecule expression and finally to suppression of the inflammatory cell adhesion to epithelial cells. These results suggest that eupatilin can inhibit the adhesion of inflammatory cells to bronchial epithelial cells via a signalling pathway, including activation of Akt and NF-κB, as well as expression of adhesion molecules.

Probiotic suppression of the H. pylori-induced responses by conjugated linoleic acids in a gastric epithelial cell line

Conjugated linoleic acids (CLA) produced by Lactobacillus acidophilus was reported to decrease the activation of nuclear factor-kappa B. CLA was suggested as one of the anti-inflammatory molecular mechanisms of probiotics. In the present study, the effects of CLA on H. pylori-induced multiple responses were evaluated. IL-8, TNF-α and iNOS were measured in mRNA and/or protein levels in AGS cells after pretreatment with CLA or CLA-containing conditioned medium (CM) produced by Lactobacillus acidophilus or Lactobacillus plantarum. The increased expressions of IL-8 mRNA/protein and TNF-α mRNA were significantly suppressed by pretreatment with CM or CLA. The levels of IL-8 protein and TNF-α mRNA were suppressed by CM pretreatment better than CLA. The expression of iNOS mRNA was also significantly inhibited by CM pretreatment. These results suggest that the suppression of multiple mediators by CLA-containing CM plays a key role in the anti-inflammatory and anti-carcinogenic effects of probiotics on H. pylori infection.

Lactobacillus rhamnosus GG treatment potentiates intestinal hypoxia-inducible factor, promotes intestinal integrity and ameliorates alcohol-induced liver injury

Gut-derived endotoxin is a critical factor in the development and progression of alcoholic liver disease (ALD). Probiotics can treat alcohol-induced liver injury associated with gut leakiness and endotoxemia in animal models, as well as in human ALD; however, the mechanism or mechanisms of their beneficial action are not well defined. We hypothesized that alcohol impairs the adaptive response-induced hypoxia-inducible factor (HIF) and that probiotic supplementation could attenuate this impairment, restoring barrier function in a mouse model of ALD by increasing HIF-responsive proteins (eg, intestinal trefoil factor) and reversing established ALD. C57BJ/6N mice were fed the Lieber DeCarli diet containing 5% alcohol for 8 weeks. Animals received Lactobacillus rhamnosus GG (LGG) supplementation in the last 2 weeks. LGG supplementation significantly reduced alcohol-induced endotoxemia and hepatic steatosis and improved liver function. LGG restored alcohol-induced reduction of HIF-2α and intestinal trefoil factor levels. In vitro studies using the Caco-2 cell culture model showed that the addition of LGG supernatant prevented alcohol-induced epithelial monolayer barrier dysfunction. Furthermore, gene silencing of HIF-1α/2α abolished the LGG effects, indicating that the protective effect of LGG is HIF-dependent. The present study provides a mechanistic insight for utilization of probiotics for the treatment of ALD, and suggests a critical role for intestinal hypoxia and decreased trefoil factor in the development of ALD.

Modern approaches in probiotics research to control foodborne pathogens

Foodborne illness is a serious public health concern. There are over 200 known microbial, chemical, and physical agents that are known to cause foodborne illness. Efforts are made for improved detection, control and prevention of foodborne pathogen in food, and pathogen associated diseases in the host. Several commonly used approaches to control foodborne pathogens include antibiotics, natural antimicrobials, bacteriophages, bacteriocins, ionizing radiations, and heat. In addition, probiotics offer a potential intervention strategy for the prevention and control of foodborne infections. This review focuses on the use of probiotics and bioengineered probiotics to control foodborne pathogens, their antimicrobial actions, and their delivery strategies. Although probiotics have been demonstrated to be effective in antagonizing foodborne pathogens, challenges exist in the characterization and elucidation of underlying molecular mechanisms of action and in the development of potential delivery strategies that could maintain the viability and functionality of the probiotic in the target organ.

Stimulation of dendritic cells with Helicobacter pylori vacuolating cytotoxin negatively regulates their maturation via the restoration of E2F1

Helicobacter pylori induces an infiltration of dendritic cells (DCs) into the infected gastric mucosa. Although DCs play an important role in the regulation of inflammation, the effects of H. pylori vacuolating cytotoxin (VacA) on DC maturation process have not yet been elucidated. The role of VacA in DC maturation following co-exposure to Escherichia coli lipopolysaccharide (LPS) was investigated. The treatment of immature DCs with LPS up-regulated the expression of surface molecules [e.g. CD40, CD80, CD86 and major histocompatibility complex (MHC) class II], as well as the production of cytokines [e.g. interleukin (IL)-1β, IL-12p70 and tumour necrosis gactor (TNF)-α] compared with those of unstimulated controls. Co-stimulation with H. pylori VacA significantly reduced the up-regulated DC maturation markers induced by LPS. In addition, VacA sustained the immature state of DCs with high endocytosis and low migratory capacity. The LPS-induced down-regulation of E2F1 expression in DCs was recovered by co-stimulation with VacA. Moreover, suppression of E2F1 by small interfering RNA resulted in a significant recovery of the inhibited DC maturation by VacA. In contrast, VacA did not affect nuclear factor (NF)-κB responses to LPS and the NF-κB signal was not associated with VacA-induced inhibition of DC maturation. These results suggest that the exposure of DCs to H. pylori VacA negatively regulates DC maturation via the restoration of E2F1. The immunomodulatory action of VacA on DCs may contribute to the ability of VacA-producing H. pylori to establish a persistent infection in the gastric mucosa.

A mechanism for the action of the compound DA-6034 on NF-κB pathway activation in Helicobacter pylori-infected gastric epithelial cells

DA-6034 is a synthetic derivative of eupatilin, a flavonoid with anti-inflammatory effects. The aim of this study was to investigate the effects of DA-6034 on the interactions between IκB kinase (IKK) and heat shock protein 90 (Hsp90), and activation of the nuclear factor-kappaB (NF-κB) signalling pathway in human gastric epithelial cells infected with Helicobacter pylori. MKN-45 gastric epithelial cell line was treated with DA-6034 and H. pylori. DA-6034 significantly inhibited NF-κB activation and upregulated the expressions of interleukin-8 (IL-8) and monocyte chemoattractant protein-1 in MKN-45 cells infected with H. pylori. However, DA-6034 did not influence activator protein-1 DNA binding activity in H. pylori-infected gastric epithelial cells. Pretreatment with DA-6034 attenuated the H. pylori-induced increase in IKK activity, and Hsp90 was associated with IKK-α and IKK-γ in MKN-45 cells. Treatment with DA-6034 dissociated the Hsp90 and IKK-γ complex in H. pylori-infected cells, leading to the inhibition of IL-8 expression. These results suggest that the eupatilin derivative 7-carboxymethyloxy-3',4',5-trimethoxy flavone has anti-inflammatory activity in gastric epithelial cells infected with H. pylori through the promotion of the dissociation of the IKK-γ-Hsp90 complex and suppression of NF-κB signalling.

Bacteroides fragilis enterotoxin upregulates intercellular adhesion molecule-1 in endothelial cells via an aldose reductase-, MAPK-, and NF-κB-dependent pathway, leading to monocyte adhesion to endothelial cells

Enterotoxigenic Bacteroides fragilis (ETBF) produces a ∼ 20-kDa heat-labile enterotoxin (BFT) that plays an essential role in mucosal inflammation. Although a variety of inflammatory cells is found at ETBF-infected sites, little is known about leukocyte adhesion in response to BFT stimulation. We investigated whether BFT affected the expression of ICAM-1 and monocytic adhesion to endothelial cells (ECs). Stimulation of HUVECs and rat aortic ECs with BFT resulted in the induction of ICAM-1 expression. Upregulation of ICAM-1 was dependent on the activation of IκB kinase (IKK) and NF-κB signaling. In contrast, suppression of AP-1 did not affect ICAM-1 expression in BFT-stimulated cells. Suppression of NF-κB activity in HUVECs significantly reduced monocytic adhesion, indicating that ICAM-1 expression is indispensable for BFT-induced adhesion of monocytes to the endothelium. Inhibition of JNK resulted in a significant attenuation of BFT-induced ICAM-1 expression in ECs. Moreover, inhibition of aldose reductase significantly reduced JNK-dependent IKK/NF-κB activation, ICAM-1 expression, and adhesion of monocytes to HUVECs. These results suggest that a signaling pathway involving aldose reductase, JNK, IKK, and NF-κB is required for ICAM-1 induction in ECs exposed to BFT, and may be involved in the leukocyte-adhesion cascade following infection with ETBF.

Upregulation of P-glycoprotein by probiotics in intestinal epithelial cells and in the dextran sulfate sodium model of colitis in mice

P-glycoprotein (P-gp) mediates efflux of xenobiotics and bacterial toxins from the intestinal mucosa into the lumen. Dysregulation of P-gp has been implicated in inflammatory bowel disease. Certain probiotics have been shown to be effective in treating inflammatory bowel disease. However, direct effects of probiotics on P-gp are not known. Current studies examined the effects of Lactobacilli on P-gp function and expression in intestinal epithelial cells. Caco-2 monolayers and a mouse model of dextran sulfate sodium-induced colitis were utilized. P-gp activity was measured as verapamil-sensitive [(3)H]digoxin transepithelial flux. Multidrug resistant 1 (MDR1)/P-gp expression was measured by real-time quantitative PCR and immunoblotting. Culture supernatant (CS; 1:10 or 1:50, 24 h) of Lactobacillus acidophilus or Lactobacillus rhamnosus treatment of differentiated Caco-2 monolayers (21 days postplating) increased (∼3-fold) MDR1/P-gp mRNA and protein levels. L. acidophilus or L. rhamnosus CS stimulated P-gp activity (∼2-fold, P < 0.05) via phosphoinositide 3-kinase and ERK1/2 MAPK pathways. In mice, L. acidophilus or L. rhamnosus treatment (3 × 10(9) colony-forming units) increased mdr1a/P-gp mRNA and protein expression in the ileum and colon (2- to 3-fold). In the dextran sulfate sodium (DSS)-induced colitis model (3% DSS in drinking water for 7 days), the degree of colitis as judged by histological damage and myeloperoxidase activity was reduced by L. acidophilus. L. acidophilus treatment to DSS-treated mice blocked the reduced expression of mdr1a/P-gp mRNA and protein in the distal colon. These findings suggest that Lactobacilli or their soluble factors stimulate P-gp expression and function under normal and inflammatory conditions. These data provide insights into a novel mechanism involving P-gp upregulation in beneficial effects of probiotics in intestinal inflammatory disorders.

Dual effects of Helicobacter pylori vacuolating cytotoxin on human eosinophil apoptosis in early and late periods of stimulation

Although Helicobacter pylori infections of the gastric mucosa are characterized by the infiltration of inflammatory cells such as eosinophils, the responses of eosinophils to H. pylori vacuolating cytotoxin (VacA) have not been fully elucidated. This study investigates the role of VacA in the apoptosis of human eosinophils. We treated human eosinophils with purified H. pylori VacA and observed that induction of apoptosis is a relatively late event. Expression of cellular inhibitor of apoptosis protein (c-IAP)-2 was upregulated during the early period of VacA stimulation, and transfection with c-IAP2 siRNA augmented apoptotic cell death. VacA caused the translocation of cytoplasmic Bax to the mitochondria and increased cytochrome c release from mitochondria in eosinophils. Transfection of an EoL-1 eosinophil cell line with Bax siRNA decreased the release of cytochrome c and DNA fragmentation. Furthermore, apoptosis facilitated by Bax and cytochrome c was primarily regulated by p38 MAPK in VacA-treated eosinophils. These results suggest that the exposure of human eosinophils to H. pylori VacA induces the early upregulation of c-IAP2 and a relatively late apoptotic response, with the apoptosis progressing through a sequential pathway that includes p38 MAPK activation, Bax translocation, and cytochrome c release.

Bacteroides fragilis enterotoxin induces human beta-defensin-2 expression in intestinal epithelial cells via a mitogen-activated protein kinase/I kappaB kinase/NF-kappaB-dependent pathway

Enterotoxigenic Bacteroides fragilis (ETBF) produces an approximately 20-kDa heat-labile enterotoxin (BFT) that plays an essential role in mucosal inflammation. Although spontaneous disappearance of ETBF infection is common, little information is available on regulated expression of antibacterial factors in response to BFT stimulation. This study investigates the role of BFT in human beta-defensin 2 (hBD-2) induction from intestinal epithelial cells. Stimulation of HT-29 and Caco-2 intestinal epithelial cell lines with BFT resulted in the induction of hBD-2. Activation of a reporter gene for hBD-2 was dependent on the presence of NF-kappaB binding sites. In contrast, suppression of AP-1 did not affect hBD-2 expression in BFT-stimulated cells. Inhibition of p38 mitogen-activated protein kinase (MAPK) using SB203580 and small interfering RNA (siRNA) transfection resulted in a significant reduction in BFT-induced I kappaB kinase (IKK)/NF-kappaB activation and hBD-2 expression. Our results suggest that a pathway including p38 MAPK, IKK, and NF-kappaB activation is required for hBD-2 induction in intestinal epithelial cells exposed to BFT, and may be involved in the host defense following infection with ETBF.

Lactobacillus acidophilus stimulates the expression of SLC26A3 via a transcriptional mechanism

Clinical efficacy of probiotics in treating various forms of diarrhea has been clearly established. However, mechanisms underlying antidiarrheal effects of probiotics are not completely defined. Diarrhea is caused either by decreased absorption or increased secretion of electrolytes and solutes in the intestine. In this regard, the electroneutral absorption of two major electrolytes, Na(+) and Cl(-), occurs mainly through the coupled operation of Na(+)/H(+) exchangers and Cl(-)/OH(-) exchangers. Previous studies from our laboratory have shown that Lactobacillus acidophilus (LA) acutely stimulated Cl(-)/OH(-) exchange activity via an increase in the surface levels of the apical anion exchanger SLC26A3 (DRA). However, whether probiotics influence SLC26A3 expression and promoter activity has not been examined. The present studies were, therefore, undertaken to investigate the long-term effects of LA on SLC26A3 expression and promoter activity. Treatment of Caco-2 cells with LA for 6-24 h resulted in a significant increase in Cl(-)/OH(-) exchange activity. DRA mRNA levels were also significantly elevated in response to LA treatment starting as early as 8 h. Additionally, the promoter activity of DRA was increased by more than twofold following 8 h LA treatment of Caco-2 cells. Similar to the in vitro studies, in vivo studies using mice gavaged with LA also showed significantly increased DRA mRNA ( approximately 4-fold) and protein expression in the colonic regions as assessed by Western blot analysis and immunofluorescence. In conclusion, increase in DRA promoter activity and expression may contribute to the upregulation of intestinal electrolyte absorption and might underlie the potential antidiarrheal effects of LA.

t10c12 conjugated linoleic acid suppresses HER2 protein and enhances apoptosis in SKBr3 breast cancer cells: possible role of COX2

Background

HER2-targeted therapy with the monoclonal antibody trastuzumab (Herceptin®) has improved disease-free survival for women diagnosed with HER2-positive breast cancers; however, treatment resistance and disease progression are not uncommon. Current data suggest that resistance to treatment in HER2 cancers may be a consequence of NF-κB overexpression and increased COX2-derived prostaglandin E2 (PGE₂). Conjugated linoleic acid (CLA) has been shown to have anti-tumor properties and to inhibit NF-κB activity and COX2.

Methods

In this study, HER2-overexpressing SKBr3 breast cancer cells were treated with t10c12 CLA. Protein expression of the HER2 receptor, nuclear NF-κB p65, and total and phosphorylated IκB were examined by western blot and immunofluorescence. PGE₂ levels were determined by ELISA. Proliferation was measured by metabolism of 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), and apoptosis was measured by FITC-conjugated Annexin V staining and flow cytometry.

Results/Conclusions

We observed a significant decrease in HER2 protein expression on western blot following treatment with 40 and 80 µM t10c12 CLA (p<0.01 and 0.001, respectively) and loss of HER2 protein in cells using immunoflourescence that was most pronounced at 80 µM. Protein levels of nuclear NF-κB p65 were also significantly reduced at the 80 µM dose. This was accompanied by a significant decrease in PGE₂ levels (p = 0.05). Pretreatment with t10c12 CLA significantly enhanced TNFα-induced apoptosis and the anti-proliferative action of trastuzumab (p = 0.05 and 0.001, respectively). These data add to previous reports of an anti-tumor effect of t10c12 CLA and suggest an effect on the HER2 oncogene that may be through CLA mediated downregulation of COX2-derived PGE₂.

5,7-dihydroxy-3,4,6-trimethoxyflavone inhibits the inflammatory effects induced by Bacteroides fragilis enterotoxin via dissociating the complex of heat shock protein 90 and I kappaB alpha and I kappaB kinase-gamma in intestinal epithelial cell culture

Enterotoxin produced by enterotoxigenic Bacteroides fragilis (BFT) has been associated with mucosal inflammation and diarrhoeal diseases. In this study, the anti-inflammatory molecular mechanism of 5,7-dihydroxy-3,4,6-trimethoxyflavone (eupatilin) was characterized in an HT-29 intestinal epithelial cell line stimulated with BFT. Pre-treatment of HT-29 cells with eupatilin decreased the production significantly of both interleukin (IL)-8 and prostaglandin E(2) induced by BFT in a dose-dependent manner. BFT-activated nuclear factor-kappaB (NF-kappaB) signals in HT-29 cells and pretreatment with eupatilin suppressed NF-kappaB activation that resulted in the significant inhibition of IL-8 and cyclo-oxygenase-2 expression. BFT-induced phosphorylation of both I kappaB alpha and I kappaB kinase (IKK) signals was prevented in eupatilin-pretreated HT-29 cells. Transfection of siRNA for IKK-alpha and IKK-beta decreased the production of IL-8 and prostaglandin E(2); however, the transfection of IKK-beta siRNA showed a more significant reduction of BFT-induced I kappaB alpha phosphorylation compared with that of IKK-alpha siRNA. In addition, herbimycin A, a specific inhibitor of heat shock protein 90 (Hsp90), decreased the BFT-induced activation of IKK and NF-kappaB, suggesting that Hsp90 is associated with a pathway of IKK-NF-kappaB-IL-8/cyclo-oxygenase-2 gene signalling. Furthermore, eupatilin dissociated the complex between Hsp90 and IKK-gamma in BFT-stimulated HT-29 cells. These results suggest that eupatilin can suppress the NF-kappaB signalling pathway by targeting the Hsp90-IKK-gamma complex in intestinal epithelial cells and may attenuate BFT-induced inflammatory responses.

Understanding the mechanisms by which probiotics inhibit gastrointestinal pathogens

In recent years, there has been a growing interest in the use of probiotic bacteria for the maintenance of general gastrointestinal health and the prevention or treatment of intestinal infections. Whilst probiotics are documented to reduce or prevent specific infectious diseases of the GI tract, the mechanistic basis of this effect remains unclear. It is likely that diverse modes-of-action contribute to inhibition of pathogens in the gut environment and proposed mechanisms include (i) direct antimicrobial activity through production of bacteriocins or inhibitors of virulence gene expression; (ii) competitive exclusion by competition for binding sites or stimulation of epithelial barrier function; (iii) stimulation of immune responses via increases of sIgA and anti-inflammatory cytokines and regulation of proinflammatory cytokines; and (iv) inhibition of virulence gene or protein expression in gastrointestinal pathogens. In this review, we discuss the modes of action by which probiotic bacteria may reduce gastrointestinal infections, and highlight some recent research which demonstrates the mechanistic basis of probiotic cause and effect.

Clostridium difficile toxin A promotes dendritic cell maturation and chemokine CXCL2 expression through p38, IKK, and the NF-kappaB signaling pathway

Clostridium difficile toxin A causes acute colitis associated with intense infiltrating neutrophils. Although dendritic cells (DCs) play an important role in the regulation of inflammation, little is known about the effects of toxin A on the maturation and neutrophil-attracting chemokine expression in DCs. This study investigated whether C. difficile toxin A could influence the maturation of mouse bone-marrow-derived DCs and chemokine CXCL2 expression. Toxin A increased the DC maturation which was closely related to CXCL2 upregulation. Concurrently, toxin A activated the signals of p65/p50 nuclear factor kappa B (NF-kappaB) heterodimers and phospho-I kappa B kinase (IKK) in DCs. The increased DC maturation, CXCL2 expression, and neutrophil chemoattraction were significantly downregulated in the NF-kappaB knockout mice. In addition, toxin A activated the phosphorylated signals of mitogen-activated protein kinases (MAPKs), such as ERK, p38, and JNK. Of all three MAPK signals, p38 MAPK was significantly related to DC maturation. Thus, suppression of p38 activity using SB203580 and siRNA transfection resulted in the significant reduction of IKK activity, DC maturation, and CXCL2 upregulation by toxin A. These results suggest that p38 MAPK may lead to the activation of IKK and NF-kappaB signaling, resulting in enhanced DC maturation and CXCL2 expression in response to C. difficile toxin A stimulation.

Inhibition of apoptosis in Bacteroides fragilis enterotoxin-stimulated intestinal epithelial cells through the induction of c-IAP-2

Enterotoxigenic Bacteroides fragilis produces an approximately 20-kDa heat-labile enterotoxin (BFT) that plays an essential role in generating mucosal inflammation. Although it is well known that proinflammatory signals are expressed in BFT-stimulated intestinal epithelial cells, cell death processes have not been elucidated. BFT induced apoptosis in HT-29 cells, but the apoptosis was first apparent 36 h after stimulation. During the early period of BFT stimulation, expression of cellular inhibitor of apoptosis protein-2 (c-IAP2) increased, and inhibition of c-IAP2 augmented the apoptotic cell death. Inhibition of BFT-induced COX-2 expression decreased prostaglandin E(2) (PGE(2)) production, which led not only to a decrease of c-IAP2 activity but also to an enhancement of DNA fragmentation in the early period of BFT stimulation. Furthermore, apoptosis inhibition through PGE(2) and c-IAP2 was mainly regulated by a p38 mitogen-activated protein kinase (MAPK). These results suggest that the inhibition of apoptosis may be mediated by a sequential pathway, including MAPK, COX-2, PGE(2) and c-IAP2, in the early period of stimulation. The delay in the onset of epithelial cell apoptosis after enterotoxigenic B. fragilis infection may be important to the host since it can provides sufficient time for epithelial cells to generate signals for the activation of mucosal inflammation and it may increase the chances of bacterial colonization.