HT-29 Intestinal Epithelial Cells Research Articles

Protective Responses of the Intestinal Epithelial Cell Line HT-29 Cells Exposed to Dephosphorylated Salmonella Flagellin [RESEARCH NOTE

This study aimed to describe the effects of Salmonella Typhimurium flagellin (SFL) dephosphorylated by sweet potato purple acid phosphatase (PAP) on the protective responses of the intestinal epithelial cell line HT-29 cells. The enzyme was reported to display a broad substrate specificity for various organic phosphorylated conjugates and phosphoproteins. Dephosphorylation of SFL by sweet potato PAP decreased to 35% in the presence of 0.05 mM vanadate as compared with the negative control (p < 0.05). Intact SFL and the SFL treated with sweet potato PAP did not remarkably induce the activation of caspase-3 in HT-29 cells at all the tested levels of the substrate. Intact SFL maximally induced the release of IL (interleukin)-8 in HT-29 cells at 1000 ng/mL (p < 0.05). However, the SFL treated with the enzyme inhibited the release of IL-8 at over 100 ng/mL of the substrate as compared with intact SFL, resulting in an approximately 8-fold decrease even at 1000 ng/mL (p < 0.05). The SFL treated with the enzyme decreased the activation of the total ERK1/2 in the cells to 1.9 and 1.7–fold at 10 and 1000 ng/mL of the substrate, respectively, as compared with intact SFL (p < 0.05). In conclusion, sweet potato PAP could be a promising tool for controlling excessive inflammation during Salmonella infection in animal husbandry, and the enzyme could be a safe alternative that can overcome the drawbacks of chemotherapy.

Scutellarein ameliorates dextran sulfate sodium-induced ulcerative colitis by inhibiting colonic epithelial cell proinflammation and barrier disruption.

Scutellarein (Scu) is a natural occurring flavonoid found in multiple traditional Chinese medicines such as Oroxylum indicum (L.) Kurz and Scutellaria baicalensis, with various pharmacological activities including anti-inflammation, anti-oxidation and myocardial protection. Here, we investigated the therapeutic efficacy of Scu on ulcerative colitis (UC) and the underlying mechanism. Efficacy of Scu on UC was evaluated in dextran sulfate sodium (DSS) induced colitis mouse model. Inflammation in colonic tissues was assessed by myeloperoxidase activity assay and RT-qPCR. Barrier proteins expression was examined using immunostaining and Western blot. IL-1β-treated HT-29 cells was used for mechanical investigation. Gavage of Scu significantly decreased the DAI score, improved colon shortening, ameliorated the pathological score in DSS-treated mice with better efficacy than the positive drug, 5-aminosalicylic acid. Scu also inhibited the expression levels of cytokines (Il-1β, Tnf-α, Il-1α, Il-6, and Cxcl1) as well as barrier proteins (E-cadherin, Occludin, and ZO-1) in colon tissues of DSS mice. In intestinal epithelial HT-29 cells, Scu attenuated the IL-1β-downregulated expression levels of E-cadherin, occludin, and ZO-1, while reduced IL-1β-upregulated IL-6 and IL-8 mRNA levels. Moreover, Scu inhibited the phosphorylation and nuclear translocation of NF-κB and suppression of NF-κB phosphorylation abolished IL-1β-disrupted epithelial barrier integrity and IL-1β-upregulated proinflammatory mediators expression in HT-29 cells. These data demonstrate that Scu is an efficacious therapeutic agent to treat UC. Inhibition of inflammatory responses and maintenance of epithelial barrier integrity through NF-κB signaling pathway underlines Scu therapeutic effect on UC.

The JAK inhibitor, Tofacitinib, Corrects the Overexpression of CEACAM6 and Limits Susceptibility to AIEC Caused by Reduced Activity of the IBD Associated Gene, PTPN2.

A cohort of patients with inflammatory bowel disease (IBD) exhibit expansion of the gut pathobiont, adherent-invasive E. coli (AIEC). Loss of activity of the IBD susceptibility gene, protein tyrosine phosphatase type 2 (PTPN2), results in dysbiosis of the gut microbiota both in human subjects and mice. Further, constitutive Ptpn2 knock-out (Ptpn2-KO) mice display expansion of AIEC compared to wildtype littermates. CEACAM6, a host cell surface glycoprotein, is exploited by AIEC to attach to and enter intestinal epithelial cells (IECs). Here, we investigate the role of IEC-specific PTPN2 in restricting AIEC invasion. Biopsies from IBD patients heterozygous (CT) or homozygous (CC) for the PTPN2 SNP (single nucleotide polymorphism) rs1893217 were processed for immunohistochemistry. HT-29 intestinal epithelial cells (IEC) were transfected with control shRNA (PTPN2-CTL), or a shRNA targeted towards PTPN2 (PTPN2-KD). The rs1893217 SNP was inserted (PTPN2-KI), or a complete knock-out of PTPN2 (PTPN2-KO) was generated, with CRISPR-Cas9 gene editing of Caco-2BBe IEC lines. Adherence and invasion assays were performed with either the human IBD AIEC isolate, LF82, or a novel fluorescent-tagged mouse adherent-invasive E. coli (mAIECred) at multiplicity of infection (MOI) of 10. IL-6 and the pan-JAK inhibitor tofacitinib were administered to interrogate JAK-STAT signaling. Protein expression was determined by western blotting and densitometry. CEACAM6 expression was elevated (colon and ileum) in IBD patients carrying the PTPN2 rs1893217 SNP (CT, CC) compared to wildtype (TT) IBD patients. HT-29 and Caco-2BBe cell lines deficient in PTPN2 expressed significantly higher levels of CEACAM6. Further, PTPN2-KI and PTPN2-KO cell lines also displayed greater adherence and invasion by AIEC LF82 and higher mAIECred invasion. CEACAM6 expression was further elevated after administration of IL-6 in PTPN2-deficient cell lines compared to untreated controls. Silencing of STAT1 and 3 partially reduced CEACAM6 protein expression. Tofacitinib significantly reduced the elevated CEACAM6 protein expression and the higher AIEC adherence and invasion in PTPN2-KI and PTPN2-KO cell lines compared to DMSO controls. Our findings highlight a crucial role for PTPN2 in restricting pathobiont entry into host cells. Our study also describes a role for the FDA-approved drug, tofacitinib (Xeljanz) in correcting the JAK-STAT-mediated over-expression of CEACAM6, used by pathobionts as an entry portal into host cells. These findings suggest a role for JAK-inhibitors in mitigating AIEC colonization in IBD-susceptible hosts.

In Vitro Effects of Postmetabolites from Limosilactobacillus fermentum 53 on the Survival and Proliferation of HT-29 Cells.

Naturally fermented dairy products are an important component of the human diet. They are a valuable source of nutrients as well as vitamins and minerals. Their importance as a source of probiotic bacterial strains should not be overlooked. A number of studies highlight the positive effects of species of the probiotic lactic acid bacteria on the intestinal microbiome and the overall homeostasis of the body, as well as a complementary treatment for some diseases. However, data on the effects on the intestinal epithelial cells of postmetabolites released by probiotic bacteria are incomplete. This is likely due to the fact that these effects are species- and strain-specific. In the present study, we investigated the effects of postmetabolites produced by a pre-selected candidate probiotic strain Limosilactobacillus fermentum on HT-29 intestinal epithelial cells. Our data showed a pronounced proliferative effect, evaluated by flow cytometry, quantification of the cell population and determination of the mitotic index. This was accompanied by the stabilization of the cell monolayer, measured by an increase in TEER (transepithelial electric resistance) and the reorganization of actin filaments. The data obtained are a clear indication of the positive effects that the products secreted by L. fermentum strain 53 have on intestinal epithelial cells.

Allergenic Shrimp Tropomyosin Distinguishes from a Non-Allergenic Chicken Homolog by Pronounced Intestinal Barrier Disruption and Downstream Th2 Responses in Epithelial and Dendritic Cell (Co)Culture.

Tropomyosins (TM) from vertebrates are generally non-allergenic, while invertebrate homologs are potent pan-allergens. This study aims to compare the risk of sensitization between chicken TM and shrimp TM through affecting the intestinal epithelial barrier integrity and type 2 mucosal immune activation. Epithelial activation and/or barrier effects upon exposure to 2-50 μg/mL chicken TM, shrimp TM or ovalbumin (OVA) as a control allergen, were studied using Caco-2, HT-29MTX, or HT-29 intestinal epithelial cells. Monocyte-derived dendritic cells (moDC), cocultured with HT-29 cells or moDC alone, were exposed to 50 μg/mL chicken TM or shrimp TM. Primed moDC were cocultured with naïve Th cells. Intestinal barrier integrity (TEER), gene expression, cytokine secretion and immune cell phenotypes were determined in these human in vitro models. Shrimp TM, but not chicken TM or OVA exposure, profoundly disrupted intestinal barrier integrity and increased alarmin genes expression in Caco-2 cells. Proinflammatory cytokine secretion in HT-29 cells was only enhanced upon shrimp TM or OVA, but not chicken TM, exposure. Shrimp TM enhanced the maturation of moDC and chemokine secretion in the presence or absence of HT-29 cells, while only in the absence of epithelial cells chicken TM activated moDC. Direct exposure of moDC to shrimp TM increased IL13 and TNFα secretion by Th cells cocultured with these primed moDC, while shrimp TM exposure via HT-29 cells cocultured with moDC sequentially increased IL13 expression and IL4 secretion in Th cells. Shrimp TM, but not chicken TM, disrupted the epithelial barrier while triggering type 2 mucosal immune activation, both of which are key events in allergic sensitization.

Inhibition of ESCRT-independent extracellular vesicles biogenesis suppresses enterovirus 71 replication and pathogenesis in mice

Enterovirus 71 (EV71) causes hand-foot-and-mouth disease (HFMD), neurological complications, and even fatalities in infants. Clinically, the increase of extracellular vesicles (EVs) in EV71 patients' serum was highly associated with the severity of HFMD. EV71 boosts EVs biogenesis in an endosomal sorting complex required for transport (ESCRT)-dependent manner to facilitate viral replication. Yet, the impact of EVs-derived from ESCRT-independent pathway on EV71 replication and pathogenesis is highly concerned. Here, we assessed the effects of EV71-induced EVs from ESCRT-independent pathway on viral replication and pathogenesis by GW4869, a neutral sphingomyelinase inhibitor. Detailly, in EV71-infected mice, blockade of the biogenesis of tissue-derived EVs in the presence of GW4869 restored body weight loss, attenuated clinical scores, and improved survival rates. Furthermore, GW4869 dampens EVs biogenesis to reduce viral load and pathogenesis in multiple tissues of EV71-infected mice. Consistently, GW4869 treatment in a human intestinal epithelial HT29 cells decreased the biogenesis of EVs, in which the progeny EV71 particle was cloaked, leading to the reduction of viral infection and replication. Collectively, GW4869 inhibits EV71-induced EVs in an ESCRT-independent pathway and ultimately suppresses EV71 replication and pathogenesis. Our study provides a novel strategy for the development of therapeutic agents in the treatment for EV71-associated HFMD.

RNA-Based Anti-Inflammatory Effects of Membrane Vesicles Derived from Lactiplantibacillus plantarum.

Bacteria generally release extracellular membrane vesicles (MVs), which are nanoparticles that play important roles in bacterial-bacterial and bacterial-host communication. As probiotics, lactic acid bacteria provide diverse health benefits to their hosts. In this study, we found that the Gram-positive lactic acid bacteria Lactiplantibacillus plantarum subsp. plantarum NBRC 15891 produce high amounts of MVs (LpMVs), and that LpMVs inhibit interleukin (IL)-8 production induced by lipopolysaccharide in intestinal epithelial HT29 cells. Heat- or UV-killed bacterial cells did not exhibit anti-inflammatory effects, and there was no uptake of these bacterial cells; contrarily, LpMVs were taken up into the cytoplasm of HT29 cells. Small RNAs extracted from LpMVs also suppressed IL-8 production in HT29 cells, suggesting that RNAs in the cytoplasm of bacterial cells are encapsulated in the MVs and released from the cells, which may be delivered to HT29 cells to exert their anti-inflammatory effects. In addition, administration of LpMVs to mice with dextran sodium sulfate-induced colitis alleviated colitis-induced weight loss and colon length shortening, indicating that LpMV intake is likely to be effective in preventing or ameliorating colitis.

Distribution of P2Y and P2X purinergic receptor expression within the intestine.

Nucleotides are potent extracellular signaling molecules during homeostasis, infection, and injury due to their ability to activate purinergic receptors. The nucleotide ATP activates P2X receptors (P2RXs), whereas the nucleotides ADP, ATP, UTP, and UDP-glucose selectively activate different P2Y receptors (P2RYs). Several studies have established crucial roles for P2 receptors during intestinal inflammatory and infectious diseases, yet the most extensive characterization of purinergic signaling has focused on immune cells and the central and enteric nervous systems. As epithelial cells serve as the first barrier against irritants and infection, we hypothesized that the gut epithelium may express multiple purinergic receptors that respond to extracellular nucleotide signals. Using the Human Protein Atlas and Gut Cell Survey, we queried single-cell RNA sequencing (RNAseq) data for the P2 purinergic receptors in the small and large intestines. In silico analysis reveals robust mRNA expression of P2RY1, P2RY2, P2RY11, and P2RX4 throughout the gastrointestinal tract. Human intestinal organoids exhibited a similar expression pattern with a prominent expression of P2RY1, P2RY2, and P2RX4, but this purinergic receptor repertoire was not conserved in T84, Caco2, and HT29 intestinal epithelial cell lines. Finally, P2YR1 and P2YR2 agonists elicited robust calcium responses in human intestinal organoids, but calcium responses were weaker or absent in the cell lines. These findings suggest that the gastrointestinal epithelia respond to extracellular purinergic signaling via P2RY1, P2RY2, P2RY11, and P2RX4 receptors and highlight the benefit of using intestinal organoids as a model of intestinal purinergic signaling.NEW & NOTEWORTHY Several studies have revealed crucial roles for P2 receptors during inflammatory and infectious diseases, however, these have largely been demonstrated in immune cells and the enteric nervous system. Although epithelial cells serve as the first barrier against infection and inflammation, the role of purinergic signaling within the gastrointestinal tract remains largely unknown. This work expands our knowledge of purinergic receptor distribution and relative expression along the intestine.

Transcriptional responses of human intestinal epithelial HT-29 cells to spore-displayed p40 derived from Lacticaseibacillus rhamnosus GG

BackgroundsThe aims of this study were to construct spore-displayed p40, a Lacticaseibacillus rhamnosus GG-derived soluble protein, using spore surface display technology and to evaluate transcriptional responses in human intestinal epithelial cells.Resultsp40 was displayed on the surface of Bacillus subtilis spores using spore coat protein CotG as an anchor protein. Effects of spore-displayed p40 (CotG-p40) on gene expression of intestinal epithelial cell line HT-29 were evaluated by transcriptome analysis using RNA-sequencing. As a result of differentially expressed gene (DEG) analysis, 81 genes were up-regulated and 82 genes were down-regulated in CotG-p40 stimulated cells than in unstimulated cells. Gene ontology enrichment analysis showed that CotG-p40 affected biological processes such as developmental process, metabolic process, cell surface receptor linked signaling pathway, and retinoic acid metabolic process. Gene-gene network analysis suggested that 10 DEGs (EREG, FOXF1, GLI2, PTGS2, SPP1, MMP19, TNFRSF1B, PTGER4, CLDN18, and ALDH1A3) activated by CotG-p40 were associated with probiotic action.ConclusionsThis study demonstrates the regulatory effects of CotG-p40 on proliferation and homeostasis of HT-29 cells. This study provided comprehensive insights into the transcriptional response of human intestinal epithelial cells stimulated by CotG-p40.

High-Molecular-Weight Dextran-Type Exopolysaccharide Produced by the Novel Apilactobacillus waqarii Improves Metabolic Syndrome: In Vitro and In Vivo Analyses.

Metabolic syndrome is a leading medical concern that affects one billion people worldwide. Metabolic syndrome is defined by a clustering of risk factors that predispose an individual to cardiovascular disease, diabetes and stroke. In recent years, the apparent role of the gut microbiota in metabolic syndrome has drawn attention to microbiome-engineered therapeutics. Specifically, lactic acid bacteria (LAB) harbors beneficial metabolic characteristics, including the production of exopolysaccharides and other microbial byproducts. We recently isolated a novel fructophilic lactic acid bacterium (FLAB), Apilactobacillus waqarii strain HBW1, from honeybee gut and found it produces a dextran-type exopolysaccharide (EPS). The objective of this study was to explore the therapeutic potential of the new dextran in relation to metabolic syndrome. Findings revealed the dextran’s ability to improve the viability of damaged HT-29 intestinal epithelial cells and exhibit antioxidant properties. In vivo analyses demonstrated reductions in body weight gain and serum cholesterol levels in mice supplemented with the dextran, compared to control (5% and 17.2%, respectively). Additionally, blood glucose levels decreased by 16.26% following dextran supplementation, while increasing by 15.2% in non-treated mice. Overall, this study displays biotherapeutic potential of a novel EPS to improve metabolic syndrome and its individual components, warranting further investigation.

Lacticaseibacillus rhamnosus R0011 secretome attenuates Salmonella enterica serovar Typhimurium secretome-induced intestinal epithelial cell monolayer damage and pro-inflammatory mediator production in intestinal epithelial cell and antigen-presenting cell co-cultures.

Certain lactic acid bacteria (LAB) are associated with immune modulatory activities including down-regulation of pro-inflammatory gene transcription and expression. While host antigen-presenting cells (APCs) and intestinal epithelial cells (IEC) can interact directly with both pathogenic and commensal bacteria through innate immune pattern recognition receptors, recent evidence indicates indirect communication through secreted molecules is an important inter-domain communication mechanism. This communication route may be especially important in the context of IEC and APC interactions which shape host immune responses within the gut environment. We have previously shown that the Lacticaseibacillus rhamnosus R0011 secretome (LrS) dampens pro-inflammatory gene transcription and mediator production from Tumor Necrosis Factor-α and Salmonella enterica serovar Typhimurium secretome (STS)-challenged HT-29 IECs through the induction of negative regulators of innate immunity. However, many questions remain about interactions mediated through these bacterial-derived soluble components and the resulting host immune outcomes in the context of IEC and APC interactions. In the present study, we examined the ability of the LrS to down-regulate pro-inflammatory gene transcription and cytokine production from STS-challenged T84 human IEC and THP-1 human monocyte co-cultures. Cytokine and chemokine profiling revealed that apically delivered LrS induces apical secretion of macrophage inhibitory factor (MIF) and down-regulates STS-induced pro-inflammatory mediator secretion into the apical and basolateral chambers of the T84/THP-1 co-culture. Transcriptional profiling confirmed these results, as the LrS attenuated STS challenge-induced CXCL8 and NFκB1 expression in T84 IECs and THP-1 APCs. Interestingly, the LrS also reversed STS-induced damage to monolayer transepithelial resistance (TER) and permeability, results which were confirmed by ZO-1 gene expression and immunofluorescence visualization of ZO-1 expression in T84 IEC monolayers. The addition of a MIF-neutralizing antibody abrogated the ability of the LrS to reverse STS-induced damage to T84 IEC monolayer integrity, suggesting a novel role for MIF in maintaining IEC barrier function and integrity in response to soluble components derived from LAB. The results presented here provide mechanistic evidence for indirect communication mechanisms used by LAB to modulate immune responses to pathogen challenge, using in vitro approaches which allow for IEC and APC cell communication in a context which more closely mimics that which occurs in vivo.

Functional screen of inflammatory bowel disease genes reveals key epithelial functions

BackgroundGenetic studies have been tremendously successful in identifying genomic regions associated with a wide variety of phenotypes, although the success of these studies in identifying causal genes, their variants, and their functional impacts has been more limited.MethodsWe identified 145 genes from IBD-associated genomic loci having endogenous expression within the intestinal epithelial cell compartment. We evaluated the impact of lentiviral transfer of the open reading frame (ORF) of these IBD genes into the HT-29 intestinal epithelial cell line via transcriptomic analyses. By comparing the genes in which expression was modulated by each ORF, as well as the functions enriched within these gene lists, we identified ORFs with shared impacts and their putative disease-relevant biological functions.ResultsAnalysis of the transcriptomic data for cell lines expressing the ORFs for known causal genes such as HNF4a, IFIH1, and SMAD3 identified functions consistent with what is already known for these genes. These analyses also identified two major clusters of genes: Cluster 1 contained the known IBD causal genes IFIH1, SBNO2, NFKB1, and NOD2, as well as genes from other IBD loci (ZFP36L1, IRF1, GIGYF1, OTUD3, AIRE and PITX1), whereas Cluster 2 contained the known causal gene KSR1 and implicated DUSP16 from another IBD locus. Our analyses highlight how multiple IBD gene candidates can impact on epithelial structure and function, including the protection of the mucosa from intestinal microbiota, and demonstrate that DUSP16 acts a regulator of MAPK activity and contributes to mucosal defense, in part via its regulation of the polymeric immunoglobulin receptor, involved in the protection of the intestinal mucosa from enteric microbiota.ConclusionsThis functional screen, based on expressing IBD genes within an appropriate cellular context, in this instance intestinal epithelial cells, resulted in changes to the cell’s transcriptome that are relevant to their endogenous biological function(s). This not only helped in identifying likely causal genes within genetic loci but also provided insight into their biological functions. Furthermore, this work has highlighted the central role of intestinal epithelial cells in IBD pathophysiology, providing a scientific rationale for a drug development strategy that targets epithelial functions in addition to the current therapies targeting immune functions.

Design, synthesis and biological evaluation of 1H-indazole derivatives as novel ASK1 inhibitors.

Apoptosis signal-regulating kinase 1 (ASK1, MAP3K5), a member of the mitogen-activated protein kinase (MAPK) signaling pathway, is involved in cell survival, differentiation, stress response, and apoptosis. ASK1 kinase inhibition has emerged as a promising therapeutic strategy for inflammatory disease. A series of novel ASK1 inhibitors with 1H-indazole scaffold were designed, synthesized and evaluated for their ASK1 kinase activity and AP1-HEK293cell inhibitory effect. Systematic structure-activity relationship (SAR) efforts led to the discovery of promising compound 15, which showed excellent invitro ASK1 kinase activity and potent inhibitory effects on ASK1 in AP1-HEK293cells. In a tumor necrosis factor-α (TNF-α)-induced HT-29 intestinal epithelial cell model, compound 15 exhibited a significantly protective effect on cell viability comparable to that of GS-4997; moreover, compound 15 exhibited no obvious cytotoxicity against HT-29cells at concentrations up to 25μM. Mechanistic research demonstrated that compound 15 suppresses phosphorylation in the ASK1-p38/JNK signaling pathway in HT-29cells, and regulates the expression levels of apoptosis-related proteins. Altogether, these results show that compound 15 may serve as a potential candidate compound for the treatment of inflammatory bowel disease (IBD).

Differential effects of oligosaccharides on the effectiveness of ampicillin against Escherichia coli in vitro

BackgroundThe mounting antibiotic resistance emphasizes an urgent need for alternatives. Recent investigations indicate that non-digestible oligosaccharides (NDOs), besides their prebiotic properties, can directly interact with pathogenic bacteria. In this study, the protective effect of alginate-oligosaccharides (AOS), chitosan-oligosaccharides (COS), galacto-oligosaccharides (GOS) and fructo-oligosaccharides, against enteropathogenicEscherichia. coli was investigated. MethodsThe effect of these NDOs onE. coli growth, adhesion and E. coli-induced inflammatory response (IL-8 release) of HT-29 intestinal epithelial cells were determined in vitro in the presence or absence of ampicillin, using minimum inhibitory concentration (MIC) assay, anti-adhesion assay and ELISA, respectively. ResultsAt low concentrations 0.5 % and 1%, AOS decreased theE. coli growth, while high GOS concentrations (6%, 8%, 10 %) were effective. Interestingly, the combination of the low concentrations of AOS with ampicillin (2 μg/mL) exerted a 2-fold decrease in the MIC level of ampicillin against E. coli. AOS also concentration dependently reduced the adherence of E. coli to HT-29 cells. The combination of AOS with ampicillin further increased these anti-adhesive properties. Pre-incubation of HT-29 cells with AOS, COS or GOS significantly hampered the E. coli-induced IL-8 release. ConclusionCurrent study highlights the direct effects of NDOs onE. coli growth, adhesion and inflammatory responses of HT-29 cells in vitro.

Protective Role of Natural and Semi-Synthetic Tocopherols on TNFα-Induced ROS Production and ICAM-1 and Cl-2 Expression in HT29 Intestinal Epithelial Cells.

Vitamin E, a fat-soluble compound, possesses both antioxidant and non-antioxidant properties. In this study we evaluated, in intestinal HT29 cells, the role of natural tocopherols, α-Toc and δ-Toc, and two semi-synthetic derivatives, namely bis-δ-Toc sulfide (δ-Toc)2S and bis-δ-Toc disulfide (δ-Toc)2S2, on TNFα-induced oxidative stress, and intercellular adhesion molecule-1 (ICAM-1) and claudin-2 (Cl-2) expression. The role of tocopherols was compared to that of N-acetylcysteine (NAC), an antioxidant precursor of glutathione synthesis. The results show that all tocopherol containing derivatives used, prevented TNFα-induced oxidative stress and the increase of ICAM-1 and Cl-2 expression, and that (δ-Toc)2S and (δ-Toc)2S2 are more effective than δ-Toc and α-Toc. The beneficial effects demonstrated were due to tocopherol antioxidant properties, but suppression of TNFα-induced Cl-2 expression seems not only to be related with antioxidant ability. Indeed, while ICAM-1 expression is strongly related to the intracellular redox state, Cl-2 expression is TNFα-up-regulated by both redox and non-redox dependent mechanisms. Since ICAM-1 and Cl-2 increase intestinal bowel diseases, and cause excessive recruitment of immune cells and alteration of the intestinal barrier, natural and, above all, semi-synthetic tocopherols may have a potential role as a therapeutic support against intestinal chronic inflammation, in which TNFα represents an important proinflammatory mediator.

Campylobacter concisus upregulates PD-L1 mRNA expression in IFN-γ sensitized intestinal epithelial cells and induces cell death in esophageal epithelial cells

ABSTRACT Introduction: Campylobacter concisus is an oral bacterium that is associated with inflammatory bowel disease (IBD) and Barrett’s esophagus (BE). Programmed cell death ligand-1 (PD-L1) is an immune checkpoint protein that is used by tumor cells for immune evasion and has increased expression in patients with IBD and BE. We examined whether C. concisus upregulates PD-L1 expression in intestinal and esophageal epithelial cells. Methods: Human intestinal epithelial HT-29 cells and esophageal epithelial FLO-1 cells with and without interferon (IFN)-γ sensitization were incubated with C. concisus strains. The level of PD-L1 mRNA was quantified using quantitative real-time PCR. Cytokines were measured using Enzyme-Linked Immunosorbent Assay (ELISA). Apoptosis of HT-29 and FLO-1 cells were measured using caspase 3/7 assay. Results: We found that intestinal epithelial cells with IFN-γ sensitization incubated with C. concisus significantly upregulated PD-L1 expression and significantly increased the production of interleukin (IL)-8. Whereas, PD-L1 expression was significantly inhibited in IFN-γ sensitized FLO-1 cells incubated with C. concisus strains. Furthermore, FLO-1 cells with and without IFN-γ sensitization incubated with C. concisus strains both had significantly higher levels of cell death. Conclusion: C. concisushas the potential to cause damage to both intestinal and esophageal epithelial cells, however, with different pathogenic effects.

A clostripain-like protease plays a major role in generating the secretome of enterotoxigenic Bacteroides fragilis.

Bacteroides fragilis toxin (BFT) is a protein secreted by enterotoxigenic (ETBF) strains of B. fragilis. BFT is synthesized as a proprotein (proBFT) that is predicted to be a lipoprotein and that is cleaved into two discrete fragments by a clostripain-like protease called fragipain (Fpn). In this study, we obtained evidence that Fpn cleaves proBFT following its transport across the outer membrane. Remarkably, we also found that the disruption of the fpn gene led to a strong reduction in the level of>100 other proteins, many of which are predicted to be lipoproteins, in the culture medium of an ETBF strain. Experiments performed with purified Fpn provided direct evidence that the protease releases at least some of these proteins from the cell surface. The observation that wild-type cells outcompeted an fpn- strain in co-cultivation assays also supported the notion that Fpn plays an important role in cell physiology and is not simply dedicated to toxin biogenesis. Finally, we found that purified Fpn altered the adhesive properties of HT29 intestinal epithelial cells. Our results suggest that Fpn is a broad-spectrum protease that not only catalyzes the protein secretion on a wide scale but that also potentially cleaves host cell proteins during colonization.

Escherichia coli K12 Upregulates Programmed Cell Death Ligand 1 (PD-L1) Expression in Gamma Interferon-Sensitized Intestinal Epithelial Cells via the NF-κB Pathway.

Programmed cell death ligand-1 (PD-L1) is an immune checkpoint protein which is used by tumor cells for immune evasion. PD-L1 is upregulated in inflamed intestinal tissues. The intestinal tract is colonized by millions of bacteria, most of which are commensal bacterial species. We hypothesized that under inflammatory conditions, some commensal bacterial species contribute to increased PD-L1 expression in intestinal epithelium and examined this hypothesis. Human intestinal epithelial HT-29 cells with and without interferon (IFN)-γ sensitization were incubated with six strains of four enteric bacterial species. The mRNA and protein levels of PD-L1 in HT-29 cells were examined using quantitative real-time PCR and flow cytometry, respectively. The levels of interleukin (IL)-1β, IL-18, IL-6, IL-8, and tumor necrosis factor (TNF)-α secreted by HT-29 cells were measured using enzyme-linked immunosorbent assay. Apoptosis of HT-29 cells was measured using a caspase 3/7 assay. We found that Escherichia coli K12 significantly upregulated both PD-L1 mRNA and protein in IFN-γ-sensitized HT-29 cells. E. coli K12 induced the production of IL-8 in HT-29 cells, however, IL-8 did not affect HT-29 PD-L1 expression. Inhibition of the nuclear factor-kappa B pathway significantly reduced E. coli K12-induced PD-L1 expression in HT-29 cells. The other two E. coli strains and two enteric bacterial species did not significantly affect PD-L1 expression in HT-29 cells. Enterococcus faecalis significantly inhibited PD-L1 expression due to induction of cell death. Data from this study suggest that some gut bacterial species have the potential to affect immune function under inflammatory conditions via upregulating epithelial PD-L1 expression.

Probiotic Lactobacillus and Bifidobacterium Strains Counteract Adherent-Invasive Escherichia coli (AIEC) Virulence and Hamper IL-23/Th17 Axis in Ulcerative Colitis, but Not in Crohn’s Disease

Hypersecretion of proinflammatory cytokines and dysregulated activation of the IL-23/Th17 axis in response to intestinal microbiota dysbiosis are key factors in the pathogenesis of inflammatory bowel diseases (IBD). In this work, we studied how Lactobacillus and Bifidobacterium strains affect AIEC-LF82 virulence mechanisms and the consequent inflammatory response linked to the CCR6–CCL20 and IL-23/Th17 axes in Crohn’s disease (CD) and ulcerative colitis (UC) patients. All Lactobacillus and Bifidobacterium strains significantly reduced the LF82 adhesion and persistence within HT29 intestinal epithelial cells, inhibiting IL-8 secretion while not affecting the CCR6–CCL20 axis. Moreover, they significantly reduced LF82 survival within macrophages and dendritic cells, reducing the secretion of polarizing cytokines related to the IL-23/Th17 axis, both in healthy donors (HD) and UC patients. In CD patients, however, only B. breve Bbr8 strain was able to slightly reduce the LF82 persistence within dendritic cells, thus hampering the IL-23/Th17 axis. In addition, probiotic strains were able to modulate the AIEC-induced inflammation in HD, reducing TNF-α and increasing IL-10 secretion by macrophages, but failed to do so in IBD patients. Interestingly, the probiotic strains studied in this work were all able to interfere with the IL-23/Th17 axis in UC patients, but not in CD patients. The different interaction mechanisms of probiotic strains with innate immune cells from UC and CD patients compared to HD suggest that testing on CD-derived immune cells may be pivotal for the identification of novel probiotic strains that could be effective also for CD patients.

Secretome-Mediated Interactions with Intestinal Epithelial Cells: A Role for Secretome Components from Lactobacillus rhamnosus R0011 in the Attenuation of Salmonella enterica Serovar Typhimurium Secretome and TNF-α-Induced Proinflammatory Responses.

Recent evidence suggests that lactic acid bacteria communicate with host cells via secretome components to influence immune responses but less is known about gut-pathogen secretomes, impact of lactic acid bacteria secretomes on host-pathogen interactions, and the mechanisms underlying these interactions. Genome-wide microarrays and cytokine profiling were used to interrogate the impact of the Lactobacillus rhamnosus R0011 secretome (LrS) on TNF-α and Salmonella enterica subsp. enterica serovar Typhimurium secretome (STS)-induced outcomes in human intestinal epithelial cells. The LrS attenuated both TNF-α- and STS-induced gene expression involved in NF-κB and MAPK activation, as well as expression of genes involved in other immune-related signaling pathways. Specifically, the LrS induced the expression of dual specificity phosphatase 1 (DUSP1), activating transcription factor 3 (ATF3), and tribbles pseudokinase 3 (TRIB3), negative regulators of innate immune signaling, in HT-29 intestinal epithelial cells challenged with TNF-α or STS. TNF-α- and STS-induced acetylation of H3 and H4 histones was attenuated by the LrS, as was the production of TNF-α- and STS-induced proinflammatory cytokines and chemokines. Interestingly, the LrS induced production of macrophage migration inhibitory factor (MIF), a cytokine involved in host-microbe interactions at the gut interface. We propose that the LrS attenuates proinflammatory mediator expression through increased transcription of negative regulators of innate immune activity and changes in global H3 and H4 histone acetylation. To our knowledge, these findings provide novel insights into the complex multifaceted mechanisms of action behind secretome-mediated interdomain communication at the gut-mucosal interface.