Lactobacillus paracasei CNCM I-4034 and its culture supernatant modulate Salmonella-induced inflammation in a novel transwell co-culture of human intestinal-like dendritic and Caco-2 cells

Absorption and intracellular accumulation of food-borne dicarbonyl precursors of advanced glycation end-product in a Caco-2 human cell transwell model

This study aimed to better understand whether and how the reactive 1,2-dicarbonyl precursors of advanced glycation end products (AGEs), glyoxal (GO) and methylglyoxal (MGO), cross the intestinal barrier by studying their transport in the in vitro Caco-2 transwell system. The results reveal that GO, MGO and Nε-(carboxymethyl)lysine (CML), the latter studied for comparison, are transported across the intestinal cell layer via both active and passive transport and accumulate in the cells, albeit all to a limited extent. Besides, the transport of the dicarbonyl compounds was only partially affected by the presence of amino acids and protein, suggesting that scavenging by a food matrix will not fully prevent their intestinal absorption. Our study provides new insights into the absorption of the two major food-borne dicarbonyl AGE precursors and provides evidence of their potential systemic bioavailability but also of factors limiting their contribution to the overall exposome.

A host-microbial metabolite interaction gut-on-a-chip model of the adult human intestine demonstrates beneficial effects upon inulin treatment of gut microbiome

Background: The gut and its microbiome have a major impact on many aspects of health and are therefore also an attractive target for drug- or food-based therapies. Here, we report on the added value of combining a microbiome screening model, the i-screen, with fresh intestinal tissue explants in a microfluidic gut-on-a-chip model, the Intestinal Explant Barrier Chip (IEBC). Methods: Adult human gut microbiome (fecal pool of 6 healthy donors) was cultured anaerobically in the i-screen platform for 24 h, without and with exposure to 4 mg/mL inulin. The i-screen cell-free culture supernatant was subsequently applied to the luminal side of adult human colon tissue explants (n = 3 donors), fixed in the IEBC, for 24 h and effects were evaluated. Results: The supplementation of the media with inulin promoted the growth of Anaerostipes, Bifidobacterium, Blautia, and Collinsella in the in vitro i-screen, and triggered an elevated production of butyrate by the microbiota. Human colon tissue exposed to inulin-treated i-screen cell-free culture supernatant or control i-screen cell-free culture supernatant with added short-chain fatty acids (SCFAs) showed improved tissue barrier integrity measured by a 28.2%-34.2% reduction in FITC-dextran 4000 (FD4) leakage and 1.3 times lower transport of antipyrine. Furthermore, the release of pro-inflammatory cytokines IL-1β, IL-6, IL-8, and TNF-α was reduced under these circumstances. Gene expression profiles confirmed these findings, but showed more profound effects for inulin-treated supernatant compared to SCFA-supplemented supernatant. Conclusion: The combination of i-screen and IEBC facilitates the study of complex intestinal processes such as host-microbial metabolite interaction and gut health.

Identification and Characterization of Probiotic Lactiplantibacillus plantarum BI-59.1 Isolated from tejuino and Its Capacity to Produce Biofilms

Tejuino is a popular and traditional beverage consumed in north and western of Mexico, due to its biological properties, it is considered a natural source of probiotics. Nevertheless, few studies have been performed on Tejuino microbiota. In this work, the probiotic potential of the tejuino isolated Lactiplantibacillus plantarum BI-59.1 strain was investigated. Its effectiveness was compared with a commercial Lactobacillus spp and identified by 16S rDNA sequence homology. Lactiplantibacillus plantarum BI-59.1 strain showed probiotic properties, i.e., production of antimicrobial compounds (lactic acid and presence of plantaricin A gene), inhibition of entero-pathogens by planktonic cells and metabolites (Salmonella enterica serovar Typhimurium inhibition to HT29-MTX adhesion), biofilm formation, bacterial adhesion (HT29-MTX, 3.96 CFU/cell), and tolerance to stimulated gastrointestinal conditions (tolerance to pH 3 and bile salts). The strain was gamma hemolytic, susceptible to most antibiotics and negative for gelatinase production; thus, the Lactiplantibacillus. plantarum BI-59.1 strain is suitable for its use as a probiotic for nutraceutical or pharmaceutical formulations.

Evaluation of Potential Probiotic Properties of Limosilactobacillus fermentum Derived from Piglet Feces and Influence on the Healthy and E. coli-Challenged Porcine Intestine

In this work, we evaluated the probiotic properties of Limosilactobacillus fermentum strains (FL1, FL2, FL3, FL4) isolated from feces of healthy piglets. The in vitro auto-aggregation, hydrophobicity, biofilm-forming capacity, survival in the gastrointestinal tract, antimicrobial activity and anti-oxidation capacity were evaluated. Four strains were resistant to simulated gastrointestinal conditions, including low pH, pepsin, trypsin and bile salts. They also maintained strong self-aggregation and cell surface hydrophobicity. Limosilactobacillus fermentum FL4, which had the strongest adhesion ability and antimicrobial effect on Enterotoxigenic Escherichia coli K88 (ETEC K88), was then tested in porcine intestinal organoid models. The in vitro experiments in basal-out and apical-out organoids demonstrated that L. fermentum FL4 adhered to the apical surfaces more efficiently than basolateral surfaces, had the ability to activate the Wnt/β-catenin pathway to protect the mucosal barrier integrity, stimulated the proliferation and differentiation of the intestinal epithelium, and repaired ETEC K88-induced damage. Moreover, L. fermentum FL4 inhibited inflammatory responses induced by ETEC K88 through the reduced expression of pro-inflammatory cytokines (TNF-α, IL-1β and IFN-γ) and higher levels of anti-inflammatory cytokines (TGF-β and IL-10). These results show that L. fermentum FL4 isolated from feces of healthy Tunchang piglets has the potential to be used as an anti-inflammatory probiotic and for mitigation of intestinal damage in piglets.

A low-carbon high inulin diet improves intestinal mucosal barrier function and immunity against infectious diseases in goats

Introduction

Abrupt weaning is a major stressful event, contributing to intestinal abnormalities and immune system dysfunction in weaned kids. Inulin is a prebiotic fiber with many positive functions, including promoting intestinal fermentation and enhancing host immunity in monogastric animals. However, the effects of a high-inulin, energy-rich diet on ruminal fermentation characteristics, methane emission, growth performance, and immune systems of weaned kids have not been investigated.

Methods

A fully automated in vitro fermentation system was used to investigate ruminal fermentation characteristics and methane emission of a mixed substrate of inulin and fat powder (1.31: 1) in comparison with maize grain-based starter concentrate. During a 1-week adaptation and 4-week trial phase, 18 weaned kids (8.97 ± 0.19 kg) were randomly assigned to two groups, one with a conventional diet (83% maize grain; CON) and the other with a low-carbon, high-inulin diet (41.5% maize grain, 14.4% fat powder, 18.9% inulin; INU).

Results

In the in vitro rumen fermentation experiment, the total gas production was not different (p > 0.05); however, a lower (p < 0.05) methane production was observed for INU as compared to CON. The average daily gain and the ratio of feed intake and growth performance of kids fed with INU were higher (p < 0.05) than those fed with CON. Serum concentrations of alanine transaminase (ALT) and lactate dehydrogenase (LDH) were lower (p < 0.05), whereas the concentration of high-density lipoprotein (HDL) and cholesterol (CHOL) were higher (p < 0.05) in kids fed with the INU diet as compared CON. Dietary inulin significantly increased (p < 0.05) the secretion of immunoglobulins (IgA, IgG, and IgM) and inflammatory cytokines (IFN-γ and IL-10) in ileum tissue. Although no differences (p > 0.05) were observed in mRNA expression of tight junction markers, the INU diet tended to increase (p = 0.09) gene expression of ribosomal protein S6 kinase beta-1 (P70S6K) in the mammalian target of rapamycin (mTOR) pathway of longissimus dorsi muscle.

Conclusion

Our findings highlighted that a low-carbon high-inulin energy-rich diet could be used as a promising strategy to improve gut immunity and growth performance of weaned kids under abrupt weaning stress and reduce methane production.

Transepithelial Effect of Probiotics in a Novel Model of Gut Lumen to Nerve Signaling

Recent studies have shown that the gut microbiome changes brain function, behavior, and psychiatric and neurological disorders. The Gut-Brain Axis (GBA) provides a neuronal pathway to explain this. But exactly how do commensal bacteria signal through the epithelial layer of the large intestine to activate GBA nerve afferents? An in vitro model is described. We differentiated two human cell lines: Caco2Bbe1 into mature epithelium on 0.4-micron filters and then SH-SY5Y into mature neurons in 24-well plates. These were co-cultured by placing the epithelium-laden filters 1 mm above the neurons. Twenty-four hours later they were tri-cultured by apical addition of 10⁷Lactobacillus rhamnosus or Lactobacillus fermentum which settled on the epithelium. Alone, the Caco2bbe1 cells stimulated neurite outgrowth in underlying SH-SY5Y. Beyond this, the lactobacilli were well tolerated and stimulated further neurite outgrowth by 24 h post-treatment, though not passing through the filters. The results provide face validity for a first-of-kind model of transepithelial intestinal lumen-to nerve signaling. The model displays the tight junctional barrier characteristics found in the large intestine while at the same time translating stimulatory signals from the bacteria through epithelial cells to attracted neurons. The model is easy to set-up with components widely available.

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.

Bifidobacterium longum subsp. infantis CECT 7210 Reduces Inflammatory Cytokine Secretion in Caco-2 Cells Cultured in the Presence of Escherichia coli CECT 515

Previous works have described the activity of Bifidobacterium longum subsp. infantis CECT 7210 (also commercially named B. infantis IM-1^®) against rotavirus in mice and intestinal pathogens in piglets, as well as its diarrhea-reducing effect on healthy term infants. In the present work, we focused on the intestinal immunomodulatory effects of B. infantis IM-1^® and for this purpose we used the epithelial cell line isolated from colorectal adenocarcinoma Caco-2 and a co-culture system of human dendritic cells (DCs) from peripheral blood together with Caco-2 cells. Single Caco-2 cultures and Caco-2: DC co-cultures were incubated with B. infantis IM-1^® or its supernatant either in the presence or absence of Escherichia coli CECT 515. The B. infantis IM-1^® supernatant exerted a protective effect against the cytotoxicity caused by Escherichia coli CECT 515 on single cultures of Caco-2 cells as viability reached the values of untreated cells. B. infantis IM-1^® and its supernatant also decreased the secretion of pro-inflammatory cytokines by Caco-2 cells and the co-cultures incubated in the presence of E. coli CECT 515, with the response being more modest in the latter, which suggests that DCs modulate the activity of Caco-2 cells. Overall, the results obtained point to the immunomodulatory activity of this probiotic strain, which might underlie its previously reported beneficial effects.

Investigation of Host-Microbe-Parasite Interactions in an In Vitro 3D Model of the Vertebrate Gut

In vitro models of the gut-microbiome axis are in high demand. Conventionally, intestinal monolayers grown on Transwell setups are used to test the effects of commensals/pathogens on the barrier integrity, both under homeostatic and pathophysiological conditions. While such models remain valuable for deepening the understanding of host-microbe interactions, often, they lack key biological components that mediate this intricate crosstalk. Here, a 3D in vitro model of the vertebrate intestinal epithelium, interfaced with immune cells surviving in culture for over 3 weeks, is developed and applied to proof-of-concept studies of host-microbe interactions. More specifically, the establishment of stable host-microbe cocultures is described and functional and morphological changes in the intestinal barrier induced by the presence of commensal bacteria are shown. Finally, evidence is provided that the 3D vertebrate gut models can be used as platforms to test host-microbe-parasite interactions. Exposure of gut-immune-bacteria cocultures to helminth "excretory/secretory products" induces in vivo-like up-/down-regulation of certain cytokines. These findings support the robustness of the modular in vitro cell systems for investigating the dynamics of host-microbe crosstalk and pave the way toward new approaches for systems biology studies of pathogens that cannot be maintained in vitro, including parasitic helminths.

Gut health benefit and application of postbiotics in animal production

Gut homeostasis is of importance to host health and imbalance of the gut usually leads to disorders or diseases for both human and animal. Postbiotics have been applied in manipulating of gut health, and utilization of postbiotics threads new lights into the host health. Compared with the application of probiotics, the characteristics such as stability and safety of postbiotics make it a potential alternative to probiotics. Studies have reported the beneficial effects of components derived from postbiotics, mainly through the mechanisms including inhibition of pathogens, strengthen gut barrier, and/or regulation of immunity of the host. In this review, we summarized the characteristics of postbiotics, main compounds of postbiotics, potential mechanisms in gut health, and their application in animal production.

Reactive oxygen species limit intestinal mucosa-bacteria homeostasis in vitro

Interactions between epithelial and immune cells with the gut microbiota have wide-ranging effects on many aspects of human health. Therefore, there is value in developing in vitro models capable of performing highly controlled studies of such interactions. However, several critical factors that enable long term homeostasis between bacterial and mammalian cultures have yet to be established. In this study, we explored a model consisting of epithelial and immune cells, as well as four different bacterial species (Bacteroides fragilis KLE1958, Escherichia coli MG1655, Lactobacillus rhamnosus KLE2101, or Ruminococcus gnavus KLE1940), over a 50 hour culture period. Interestingly, both obligate and facultative anaerobes grew to similar extents in aerobic culture environments during the co-culture period, likely due to measured microaerobic oxygen levels near the apical surface of the epithelia. It was demonstrated that bacteria elicited reactive oxygen species (ROS) production, and that the resulting oxidative damage heavily contributed to observed epithelial barrier damage in these static cultures. Introduction of a ROS scavenger significantly mitigated oxidative damage, improving cell monolayer integrity and reducing lipid peroxidation, although not to control (bacteria-free culture) levels. These results indicate that monitoring and mitigating ROS accumulation and oxidative damage can enable longer term bacteria-intestinal epithelial cultures, while also highlighting the significance of additional factors that impact homeostasis in mammalian cell-bacteria systems.

Lactobacillus fermentum (MTCC-5898) alleviates Escherichia coli-induced inflammatory responses in intestinal epithelial cells by modulating immune genes and NF-κB signalling

AIM

Dietary intervention using probiotic bacteria has emerged as a promising preventive strategy in addressing foodborne infections or gastrointestinal disorders. This study investigated the immunomodulatory effects of Lactobacillus fermentum (MTCC-5898) on Escherichia coli-induced inflammatory responses in intestinal epithelial cells.

METHODS AND RESULTS

The immune response of intestinal cells (Caco-2) in the presence of probiotic Lact. fermentum was determined during exclusion, competition and displacement of E. coli as the inflammatory agent. To achieve this objective, transcriptional modulation of key immune-related genes (cytokines, pattern recognition receptors and NF-κB), release of cytokines and nuclear translocation of the NF-κB subunit p-65 were studied. Expression of pro-inflammatory cytokines IL-8, TNF-α, IFN-ϒ and IL-23 was high in E. coli-exposed intestinal cells. However, overexpression of these E. coli-induced pro-inflammatory cytokines was prevented by Lact. fermentum during exclusion and competition assays. It also modulated the transcriptional expression of regulatory cytokines (IL-10 and TGF-β), pattern recognition receptors (TLR-2 and TLR-4) and genes associated with master inflammatory regulators (NF-κB and SIGIRR) to reduce E. coli-induced inflammation. The protective effect of Lact. fermentum was further confirmed by suppression of nuclear translocation of cytoplasmic NF-κB subunit (p-65).

CONCLUSION

Lactobacillus fermentum alleviated E. coli-induced inflammatory responses by modulating the NF-κB signalling besides pro-inflammatory and regulatory cytokines expression.

SIGNIFICANCE AND IMPACT OF THE STUDY

Lactobacillus fermentum holds significant promise as a potent nutraceutical that prevents and manages inflammatory gut-associated dysfunctions.

Postbiotics against Pathogens Commonly Involved in Pediatric Infectious Diseases

The Sustainable Development goals for 2020 included reducing all causes associated with infant and perinatal mortality in their priorities. The use of compounds with bioactive properties has been proposed as a therapeutic strategy due to their stimulating effect on the host's immune system. Additionally, biotherapeutic products such as postbiotics, tentatively defined as compounds produced during a fermentation process that support health and well-being, promote intestinal barrier integrity without posing considerable risks to children's health. Although this is a concept in development, there are increasing studies in the field of nutrition, chemistry, and health that aim to understand how postbiotics can help prevent different types of infections in priority populations such as minors under the age of five. The present review aims to describe the main mechanisms of action of postbiotics. In addition, it presents the available current evidence regarding the effects of postbiotics against pathogens commonly involved in pediatric infections. Postbiotics may constitute a safe alternative capable of modulating the cellular response and stimulating the host's humoral response.

Transport, metabolism and remedial potential of functional food extracts (FFEs) in Caco-2 cells monolayer: A review

Caco-2, a human intestinal carcinoma cell line, has been used to test the absorption and transport mechanism of functional foods and drugs across the intestinal epithelium in order to study their antioxidant, anticancer and anti-inflammatory activities. Caco-2 cells represent the morphological and functional characteristics of small intestinal cells and capable of expressing brush borders, tight junctions, intestinal efflux and uptake transporters which regulate permeation of drugs and functional food extracts from intestinal lumen to systemic circulation. The integrity of the Caco-2 monolayer is controlled by establishing the TEER between 200 and 1000 O per cm². FFEs affect intestinal permeability by adjusting the tight junction proteins between the cells in order to maintain the epithelial barrier function. Because of the side effects of medicines, there is an increased interest in functional food extracts (FFEs) as drug substitutes. Functional foods undergo intricate transport processes and biotransformation after oral administration. Metabolism and transport studies of FFEs in Caco-2 cells are very important for determining their bioavailability. Functional foods and their constituents produce anti-proliferative and anti-cancer effects through apoptosis, cell cycle arrest and inhibition of various signal transduction pathways across Caco-2 cell lines. The current review has summarized the anti-inflammation, anticancer, antioxidant and cholesterol lowering potential of FFEs using Caco-2 cells through reducing local inflammatory signals, production of ROS and lipid accumulation. The transport, bioavailability, metabolism, mechanisms of actions, cellular pathways adopted by FFEs across Caco-2 cell lines are predominantly affected by their molecular weight, structures and physicochemical properties. These studies are beneficial for investigating the different mechanisms of action of FFEs in the human body.

Beneficial effect of immunobiotic strains on attenuation of Salmonella induced inflammatory response in human intestinal epithelial cells

Probiotic bacteria have the ability to modulate host immune responses and have potent therapeutic functional effects against several diseases, including inflammatory diseases. However, beneficial effects of probiotics are strain specific and their interactions with host immune cells to modulate inflammatory response are largely unknown. Intestinal epithelial cells (IECs), which are the first line of defense against invading pathogens, and connects between commensals/probiotics and immune system; therefore, in this study, we used human IECs to assess the probiotic effects of three selected Lactobacillus strains in vitro. An HT-29 colonic epithelial cell and HT-29/blood mononuclear cells co-culture system were stimulated with Lactobacillus followed by Salmonella for different hours, after which the mRNA level of cytokines, β-defensin-2 and negative regulators for TLR signaling and protein levels of ZO-1 and IκB-α were analyzed by real-time polymerase chain reaction and western blot analysis. L. brevis decreased Salmonella induced IL-6, IL-8, MCP-1 and IL-1β levels, whereas L. pentosus suppressed IL-6 and MCP-1 in HT-29 cells. Moreover, L. brevis was able to increase the mRNA levels of A20, Tollip, SIGIRR and IRAKM, while L. pentosus reduced the levels of A20, and IRAKM in response to Salmonella. In addition, decrease in protein level of TNF-α and increase in mRNA level of IL-10 was observed in L. brevis and L. pentosus treated HT-29 cells. Lactobacillus strains were differentially modulated ZO-1 and p-IκB-α in HT-29 cells treated with Salmonella. Overall, the results of this study indicate that Lactobacillus strains attenuate Salmonella induced inflammatory responses through beneficial modulation of TLR negative regulators and the NF-κB pathway.

Utilizing Recombinant Spider Silk Proteins To Develop a Synthetic Bruch's Membrane for Modeling the Retinal Pigment Epithelium

Spider silks are intriguing biomaterials that have a high potential as innovative biomedical processes and devices. The intent of this study was to evaluate the capacity of recombinant spider silk proteins (rSSps) as a synthetic Bruch's membrane. Nonporous silk membranes were prepared with comparable thicknesses (<10 μm) to that of native Bruch's membrane. Biomechanical characterization was performed prior to seeding cells. The ability of RPE cells (ARPE-19) to attach and grow on the membranes was then evaluated with bright-field and electron microscopy, intracellular DNA quantification, and immunocytochemical staining (ZO-1 and F-actin). Controls were cultured on permeable Transwell support membranes and characterized with the same methods. A size-dependent permeability assay, using FITC-dextran, was used to determine cell-membrane barrier function. Compared to Transwell controls, RPE cells cultured on rSSps membranes developed more native-like "cobblestone" morphologies, exhibited higher intracellular DNA content, and expressed key organizational proteins more consistently. Comparisons of the membranes to native structures revealed that the silk membranes exhibited equivalent thicknesses, biomechanical properties, and barrier functions. These findings support the use of recombinant spider silk proteins to model Bruch's membrane and develop more biomimetic retinal models.

Immunobiotic Strains Modulate Toll-Like Receptor 3 Agonist Induced Innate Antiviral Immune Response in Human Intestinal Epithelial Cells by Modulating IFN Regulatory Factor 3 and NF-κB Signaling

Many studies have demonstrated that immunobiotics with immunoregulatory functions improve the outcomes of several bacterial and viral infections by modulating the mucosal immune system. However, the precise mechanisms underlying the immunoregulatory and antiviral activities of immunobiotics have not yet been elucidated in detail. The present study was conducted to determine whether selected lactic acid bacteria (LAB) modulate toll-like receptor 3 (TLR3) agonist polyinosinic:polycytidylic acid (PolyI:C) induced viral response in human intestinal epithelial cells (IECs). PolyI:C increased the expression of interferon-β (IFN-β), interleukin-6 (IL-6), interleukin-8 (IL-8), monocyte chemoattractant protein (MCP-1), and interleukin-1β (IL-1β) in HCT116 cells, and these up-regulations were significantly altered when cells were pre-stimulated with LAB isolated from Korean fermented foods. LAB strains were capable to up-regulate IFN-β but down-regulated IL-6, IL-8, MCP-1, and IL-1β mRNA levels as compared with PolyI: C. HCT-116 cell treatment with LABs beneficially modulated the mRNA levels of C-X-C motif chemokine 10 (CXCL-10), 2-5A oligoadenylate synthetase 1 (OSA1), myxovirus resistance protein (MxA), TLR3, and retinoic acid inducible gene-I (RIG-I), and TLR negative regulators. In addition, LABs increased IFN-β, IFN-α, and interleukin-10 (IL-10) and decreased tumor necrosis factor-α (TNF-α) and IL-1β protein/mRNA levels in THP-1 cells. LABs also protected the cells by maintaining tight-junction proteins (zonula occludens-1 and occludin). The beneficial effects of these LABs were mediated via modulation of the interferon regulatory factor 3 (IRF3) and nuclear factor-kappa B (NF-κB) pathways. Overall, the results of this study indicate that immunobiotics have potent antiviral and anti-inflammatory activities that may use as antiviral substitutes for human and animal applications.

A Novel Gastric Spheroid Co-culture Model Reveals Chemokine-Dependent Recruitment of Human Dendritic Cells to the Gastric Epithelium

BACKGROUND & AIMS

Gastric dendritic cells (DCs) control the adaptive response to infection with Helicobacter pylori, a major risk factor for peptic ulcer disease and gastric cancer. We hypothesize that DC interactions with the gastric epithelium position gastric DCs for uptake of luminal H pylori and promote DC responses to epithelial-derived mediators. The aim of this study was to determine whether the gastric epithelium actively recruits DCs using a novel co-culture model of human gastric epithelial spheroids and monocyte-derived DCs.

METHODS

Spheroid cultures of primary gastric epithelial cells were infected with H pylori by microinjection. Co-cultures were established by adding human monocyte-derived DCs to the spheroid cultures and were analyzed for DC recruitment and antigen uptake by confocal microscopy. Protein array, gene expression polymerase chain reaction array, and chemotaxis assays were used to identify epithelial-derived chemotactic factors that attract DCs. Data from the co-culture model were confirmed using human gastric tissue samples.

RESULTS

Human monocyte-derived DCs co-cultured with gastric spheroids spontaneously migrated to the gastric epithelium, established tight interactions with the epithelial cells, and phagocytosed luminally applied H pylori. DC recruitment was increased upon H pylori infection of the spheroids and involved the activity of multiple chemokines including CXCL1, CXCL16, CXCL17, and CCL20. Enhanced chemokine expression and DC recruitment to the gastric epithelium also was observed in H pylori-infected human gastric tissue samples.

CONCLUSIONS

Our results indicate that the gastric epithelium actively recruits DCs for immunosurveillance and pathogen sampling through chemokine-dependent mechanisms, with increased recruitment upon active H pylori infection.

Mechanisms of Action of Probiotics

Probiotics are living microorganisms that confer health benefits to the host when administered in adequate amounts; however, dead bacteria and their components can also exhibit probiotic properties. Bifidobacterium and strains of lactic acid bacteria are the most widely used bacteria that exhibit probiotic properties and are included in many functional foods and dietary supplements. Probiotics have been shown to prevent and ameliorate the course of digestive disorders such as acute, nosocomial, and antibiotic-associated diarrhea; allergic disorders such as atopic dermatitis (eczema) and allergic rhinitis in infants; and Clostridium difficile-associated diarrhea and some inflammatory bowel disorders in adults. In addition, probiotics may be of interest as coadjuvants in the treatment of metabolic disorders, including obesity, metabolic syndrome, nonalcoholic fatty liver disease, and type 2 diabetes. However, the mechanisms of action of probiotics, which are diverse, heterogeneous, and strain specific, have received little attention. Thus, the aim of the present work was to review the main mechanisms of action of probiotics, including colonization and normalization of perturbed intestinal microbial communities in children and adults; competitive exclusion of pathogens and bacteriocin production; modulation of fecal enzymatic activities associated with the metabolization of biliary salts and inactivation of carcinogens and other xenobiotics; production of short-chain and branched-chain fatty acids, which, in turn, have wide effects not only in the intestine but also in peripheral tissues via interactions with short-chain fatty acid receptors, modulating mainly tissue insulin sensitivity; cell adhesion and mucin production; modulation of the immune system, which results mainly in the differentiation of T-regulatory cells and upregulation of anti-inflammatory cytokines and growth factors, i.e., interleukin-10 and transforming growth factor; and interaction with the brain-gut axis by regulation of endocrine and neurologic functions. Further research to elucidate the precise molecular mechanisms of action of probiotics is warranted.

Intestinal in vitro and ex vivo Models to Study Host-Microbiome Interactions and Acute Stressors

The gut microbiome is extremely important for maintaining homeostasis with host intestinal epithelial, neuronal, and immune cells and this host-microbe interaction is critical during times of stress or disease. Environmental, nutritional, and cognitive stress are just a few factors known to influence the gut microbiota and are thought to induce microbial dysbiosis. Research on this bidirectional relationship as it pertains to health and disease is extensive and rapidly expanding in both in vivo and in vitro/ex vivo models. However, far less work has been devoted to studying effects of host-microbe interactions on acute stressors and performance, the underlying mechanisms, and the modulatory effects of different stressors on both the host and the microbiome. Additionally, the use of in vitro/ex vivo models to study the gut microbiome and human performance has not been researched extensively nor reviewed. Therefore, this review aims to examine current evidence concerning the current status of in vitro and ex vivo host models, the impact of acute stressors on gut physiology/microbiota as well as potential impacts on human performance and how we can parlay this information for DoD relevance as well as the broader scientific community. Models reviewed include widely utilized intestinal cell models from human and animal models that have been applied in the past for stress or microbiology research as well as ex vivo organ/tissue culture models and new innovative models including organ-on-a-chip and co-culture models.

Synbiotic Effects of the Dietary Fiber Long-Chain Inulin and Probiotic Lactobacillus acidophilus W37 Can be Caused by Direct, Synergistic Stimulation of Immune Toll-Like Receptors and Dendritic Cells

SCOPE

Synbiotic effects of dietary fibers and lactobacilli are usually explained by synergistic modulation of gut microbiota. New insight, however, has demonstrated that both dietary fibers and lactobacilli can directly stimulate immune cells and benefit consumer immunity. Here, the synergistic effects of immune active long-chain inulin (lcITF) and Lactobacillus acidophilus W37 (LaW37) on dendritic cells (DCs) are investigated.

METHODS AND RESULTS

Effects of lcITF and LaW37 alone or combined were studied on Toll-like receptor (TLRs) signaling and cytokine secretion by DCs in the presence and absence of media of intestinal epithelial cell (IEC) exposed to the ingredients. Also, the effects of DC responses against Salmonella Typhimurium (STM) were investigated. Synergistic effects were observed on TLR2 and 3. Synergistic effects were not always pro-inflammatory. LaW37 was strongly pro-inflammatory, while cytokine responses were regulatory when combined with lcITF. Exposure of DCs to IECs medium changed the DCs' response, which revealed synergistic enhancing effects of lcITF/LaW37 on production of IL-6 and IL-8. DCs' response in the presence of STM and LaW37 were so strong that lcITF had no additional effect.

CONCLUSION

It is demonstrated that synbiotic effects of dietary fibers and bacteria are not limited to the effects on gut microbiota but can also occur by synergistically directly stimulating IECs and/or immune cells.

The microbiota and autoimmunity: Their role in thyroid autoimmune diseases

Since the 1970s, the role of infectious diseases in the pathogenesis of Graves' disease (GD) has been an object of intensive research. The last decade has witnessed many studies on Yersinia enterocolitica, Helicobacter pylori and other bacterial organisms and their potential impact on GD. Retrospective, prospective and molecular binding studies have been performed with contrary outcomes. Until now it is not clear whether bacterial infections can trigger autoimmune thyroid disease. Common risk factors for GD (gender, smoking, stress, and pregnancy) reveal profound changes in the bacterial communities of the gut compared to that of healthy controls but a pathogenetic link between GD and dysbiosis has not yet been fully elucidated. Conventional bacterial culture, in vitro models, next generation and high-throughput DNA sequencing are applicable methods to assess the impact of bacteria in disease onset and development. Further studies on the involvement of bacteria in GD are needed and may contribute to the understanding of pathogenetic processes. This review will examine available evidence on the subject.

Can probiotics modulate human disease by impacting intestinal barrier function?

Intestinal barrier integrity is a prerequisite for homeostasis of mucosal function, which is balanced to maximise absorptive capacity, while maintaining efficient defensive reactions against chemical and microbial challenges. Evidence is mounting that disruption of epithelial barrier integrity is one of the major aetiological factors associated with several gastrointestinal diseases, including infection by pathogens, obesity and diabetes, necrotising enterocolitis, irritable bowel syndrome and inflammatory bowel disease. The notion that specific probiotic bacterial strains can affect barrier integrity fuelled research in which in vitro cell lines, animal models and clinical trials are used to assess whether probiotics can revert the diseased state back to homeostasis and health. This review catalogues and categorises the lines of evidence available in literature for the role of probiotics in epithelial integrity and, consequently, their beneficial effect for the reduction of gastrointestinal disease symptoms.

Mechanisms of transport of polymeric and lipidic nanoparticles across the intestinal barrier

Unraveling the mechanisms of nanoparticle transport across the intestinal barrier is essential for designing more efficient nanoparticles for oral administration. The physicochemical parameters of the nanoparticles (e.g., size, surface charge, chemical composition) dictate nanoparticle fate across the intestinal barrier. This review aims to address the most important findings regarding polymeric and lipidic nanoparticle transport across the intestinal barrier, including the evaluation of critical physicochemical parameters of nanoparticles that affect nanocarrier interactions with the intestinal barrier.

Modulation of Dendritic-Epithelial Cell Responses against Sphingomonas Paucimobilis by Dietary Fibers

Non-fermenting Gram-negative bacilli, such as Sphingomonas paucimobilis (S.paucimobilis), are among the most widespread causes of nosocomial infections. Up to now, no definitive guidelines exist for antimicrobial therapy for S. paucimobilis infections. As we have shown that some dietary fibers exhibit pronounced immune-regulatory properties, we hypothesized that specific immune active dietary fibers might modulate the responses against S. paucimobilis. We studied the immunomodulatory effects of dietary fibers against S. paucimobilis on cytokine release and maturation of human dendritic cells (DCs) in co-cultures of DCs and intestinal epithelial cells (IECs). S. paucimobilis infection resulted in increased release of pro-inflammatory cytokines and chemokines by DCs/IECs; these effects were strongly attenuated by specific dietary fibers. Chicory inulin, sugar beet pectin, and both starches had the strongest regulatory effects. IL-12 and TNF-α were drastically diminished upon exposure to chicory inulin and sugar beet pectin, or both starches. High-maize 260, was more effective in the reduction of chemokine release than the others fibers tested. In summary, chicory inulin, sugar beet pectin, High-maize 260, and Novelose 330 attenuate S. paucimobilis-induced cytokines. These results demonstrate that dietary fibers with a specific chemical composition can be used to manage immune responses against pathogens such as S. paucimobilis.

Evaluation of probiotic properties of Lactobacillus plantarum WLPL04 isolated from human breast milk

Lactobacillus plantarum WLPL04, a specific strain isolated from human breast milk, was investigated for its survival capacity (acid and bile salt tolerance, survival in simulated gastrointestinal tract, inhibition of pathogens, antibiotic susceptibility, yield of exopolysaccharides) and probiotic properties (antiadhesion of pathogens, protection from harmful effect of sodium dodecyl sulfate, and antiinflammatory stress on Caco-2 cells). The results showed that Lb. plantarum WLPL04 had broad-spectrum activity against gram-positive strains (Listeria monocytogenes CMCC54007, Bacillus cereus ATCC14579, and Staphylococcus aureus CMCC26003) and gram-negative strains (Pseudomonas aeruginosa MCC10104, Shigella sonnei ATCC25931, Enterobacter sakazakii ATCC29544, Salmonella typhimurium ATCC13311, and Escherichia coli O157:H7). Antibiotic susceptibility tests showed that Lb. plantarum WLPL04 was susceptible to 8 of 14 antibiotics (e.g., erythromycin and nitrofurantoin) and resistant to 6 of 14 antibiotics (e.g., kanamycin and bacitracin). Lactobacillus plantarum WLPL04 was able to survive at pH 2.5 for 3h and at 0.45% bile salt for 12h, suggesting that it can survive well in the gastrointestinal tract. In addition, the exopolysaccharide yield of Lb. plantarum WLPL04 reached 426.73 ± 65.56 mg/L at 24h. With strategies of competition, inhibition, and displacement, Lb. plantarum WLPL04 reduced the adhesion of E. coli O157:H7 (35.51%), Sal. typhimurium ATCC 13311 (8.10%), and Staph. aureus CMCC 26003 (40.30%) on Caco-2 cells by competition, and subsequently by 59.80, 62.50, and 42.60%, respectively, for the 3 pathogens through inhibition, and by 75.23, 39.97, and 52.88%, respectively, through displacement. Lactobacillus plantarum WLPL04 attenuated the acute stress induced by sodium dodecyl sulfate on Caco-2 cells and significantly inhibited the expression of inflammatory cytokines (IL-6, IL-8 and tumor necrosis factor-α) on Caco-2 cells but increased IL-10 expression in vitro compared with the Salmonella-treated group. In summary, Lb. plantarum WLPL04 from breast milk could be considered as a probiotic candidate for dairy products to promote human health.