Elements of the Endotoxin Theory of Human Physiology and Pathology

The involvement of intestinal flora endotoxin (ET) in the regulation of immune homeostasis, namely, the maintenance of the physiological tone of all components of the immune system (so-called systemic endotoxinemia, SEE) is postulated. Excessive endotoxin in the systemic blood flow under conditions of the failure of endotoxin-binding and endotoxin-eliminating systems results in another phenomenon, endotoxin aggression (EA), which is regarded as a common factor of pathogenesis of various human diseases. An important role of endotoxin insufficiency in the development of immunodeficiencies is hypothesized.     

The Impact of Lactobacillus plantarum WCFS1 Teichoic Acid D-Alanylation on the Generation of Effector and Regulatory T-cells in Healthy Mice

To date it remains unclear how probiotics affect the immune system. Bacterial envelope components may play an essential role, as these are the first to establish bacterial-host cell interactions. Teichoic acids (TAs), and especially lipoteichoic acids, are the most pro-inflammatory components of the gram-positive bacterial envelope. This effect is dependent on D-alanyl substitution of the TA backbone and interactions with TLR2 on host cells. Although the pro-inflammatory properties of TAs have been established in vitro, it remains unclear how TAs affect immunomodulation in vivo. In this study, we investigated the role of TA D-alanylation on L. plantarum–induced intestinal and systemic immunomodulation in vivo. For this, we compared the effect of L. plantarum WCFS1 and its TA D-Alanylation negative derivative (dltX-D) on the distribution of dendritic cell and T cell populations and responses in healthy mice. We demonstrated that the majority of the L. plantarum-induced in vivo immunomodulatory effects were dependent on D-alanylation (D-Ala), as some L. plantarum WCFS1-induced immune changes were not observed in the dltX-D-treated group and some were only observed after treatment with dltX-D. Strikingly, not only pro-inflammatory immune responses were abolished in the absence of D-Ala substitution, but also anti-inflammatory responses, such as the L. plantarum-induced generation of regulatory T cells in the spleen. With this study we provide insight in host-microbe interactions, by demonstrating the involvement of D-alanylation of TAs on the bacterial membrane in intestinal and systemic immunomodulation in healthy mice.     

Food components and immune function

PURPOSE OF REVIEW: Enhancing immune function or alternatively dampening inflammatory processes by specific food components has received a lot of interest. The purpose of this review is to summarize recent findings with the emphasis on underlying mechanisms. RECENT FINDINGS: Dietary beta-glucans are relatively new candidates in the field of immune modulation by diet. In-vitro and animal studies suggest that beta-glucans shift inflammatory profiles to a Th1 type, which may enhance resistance against bacterial and parasitic infections. Regarding polyunsaturated fatty acids, there is evidence that n-3 fatty acids from fish oils (eicosapentaenoic acid and docosahexaenoic acid) dampen inflammatory responses. Whether eicosapentaenoic acid or docosahexaenoic acid is responsible for this phenomenon remains controversial. It is also inconclusive whether the plant-derived n-3 fatty acid alpha-linolenic acid has the same antiinflammatory effects as observed for fish oils. Saturated fatty acids may activate toll-like receptors and consequently the inflammatory pathway. The effect of total fat intake is controversial, since high-fat diets have been found to suppress immune function, while also improving intestinal barrier function. Finally, Gingko biloba was found to lower nuclear factor kappaB and activator protein 1 activation, possibly due to its high content of polyphenols. SUMMARY: In this review we discuss the nutritional components able to enhance immune function or show antiinflammatory effects. It can be concluded that diet certainly has the potential to direct immune responses. Apart from studies on fish oils, however, evidence from human studies is limited.     

A Novel Method for the Culture and Polarized Stimulation of Human Intestinal Mucosa Explants

Few models currently exist to realistically simulate the complex human intestine''s micro-environment, where a variety of interactions take place. Proper homeostasis directly depends on these interactions, as they shape an entire immunological response inducing tolerance against food antigens while at the same time mounting effective immune responses against pathogenic microbes accidentally ingested with food.Intestinal homeostasis is preserved also through various complex interactions between the microbiota (including food-associated beneficial bacterial strains) and the host, that regulate the attachment/degradation of mucus, the production of antimicrobial peptides by the epithelial barrier, and the "education" of epithelial cells'' that controls the tolerogenic or immunogenic phenotype of unique, gut-resident lymphoid cells'' populations. These interactions have been so far very difficult to reproduce with in vitro assays using either cultured cell lines or peripheral blood mononuclear cells. In addition, mouse models differ substantially in components of the intestinal mucosa (mucus layer organization, commensal bacteria community) with respect to the human gut. Thus, studies of a variety of treatments to be brought in the clinics for important stress-related or pathological conditions such as irritable bowel syndrome, inflammatory bowel disease or colorectal cancer have been difficult to carry out.To address these issues, we developed a novel system that enables us to stimulate explants of human intestinal mucosa that retain their in situ conditioning by the host microbiota and immune response, in a polarized fashion. Polarized apical stimulation is of great importance for the outcome of the elicited immune response. It has been repeatedly shown that the same stimuli can produce completely different responses when they bypass the apical face of the intestinal epithelium, stimulating epithelial cells basolaterally or coming into direct contact with lamina propria components, switching the phenotype from tolerogenic to immunogenic and causing unnecessary and excessive inflammation in the area.We achieved polarized stimulation by gluing a cave cylinder which delimited the area of stimulation on the apical face of the mucosa as will be described in the protocol. We used this model to examine, among others, differential effects of three different Lactobacilli strains. We show that this model system is very powerful to assess the immunomodulatory properties of probiotics in healthy and disease conditions.     

地衣芽孢杆菌对南美白对虾零水交换养殖系统细菌群落的影响

【目的】地衣芽孢杆菌（Bacillus licheniformis）对南美白对虾（Penaeus vannamei）免疫反应、抗病性和营养的影响已被广泛研究，但零水交换养殖系统下地衣芽孢杆菌对对虾肠道和养殖水环境微生物群落的影响尚不清楚。【方法】通过收集添加地衣芽孢杆菌在饲料或水中后，对虾肠道、池水和池低沉积物样品，通过16S rRNA基因测序和线性判别分析（linear discriminant analysis effect size，LEfSe）进行微生物分析。【结果】结果表明，添加地衣芽孢杆菌对对虾的生长影响较小。此外，添加方式的不同对对虾肠道菌群的影响较小。但添加地衣芽孢杆菌可以有效地改变对虾肠道微生物群落，并改善对虾免疫力。【结论】这些结果有助于全面了解在零水交换养殖系统中，通过饲料和水添加地衣芽孢杆菌后对虾肠道和环境的变化，从而为选择正确的益生菌以及如何添加益生菌维持对虾健康提供基础信息。     

Current knowledge on potential health benefits of Spirulina

Spirulina is a microscopic filamentous alga that is rich in proteins, vitamins, essential amino acids, minerals and essential fatty acids like γ-linolenic acid (GLA). It is produced commercially and sold as a food supplement in health food stores around the world. Up to very recently, the interest in Spirulina was mainly in its nutritive value. Currently, however, numerous people are looking into the possible therapeutic effects of Spirulina. Many pre-clinical studies and a few clinical studies suggest several therapeutic effects ranging from reduction of cholesterol and cancer to enhancing the immune system, increasing intestinal lactobacilli, reducing nephrotoxicity by heavy metals and drugs and radiation protection. This paper presents a critical review of some published and unpublished data on therapeutic effects of Spirulina.     

Nutritional characterization of sake cake (sake-kasu) after heat-drying and freeze-drying

ABSTRACT

Sake cake contains rice-derived components, as well as cell components and metabolites of Aspergillus oryzae and Saccharomyces cerevisiae. In this study, the effect of food processing on sake cake (sake-kasu) ingredients was investigated. Sake cake, obtained through brewing liquefied rice, was heat-dried (HD) or freeze-dried (FD) and analyzed. There were no differences in the amounts of proteins, lipids, carbohydrates, vitamin B₆, choline, betaine, nicotinic acid, β-glucan and resistant proteins in HD and FD. There was also no difference in the amount of hydrolyzed amino acids in HD and FD, but many free amino acids were observed in HD. S-adenosyl methionine (SAM) was found to be abundant in FD. Meanwhile, nucleic acid-related components were found to be increased in HD, which seems to be due to the degradation of microbial metabolites. When considering the health benefits of sake cake, it is necessary to pay attention to the effects of processing method.

Abbreviations

CE-TOFMS: capillary electrophoresis time-of-flight mass spectrometry     

Molecular and cellular studies on the absorption,function, and safety of food components in intestinal epithelial cells

The intestinal tract comes into direct contact with the external environment despite being inside the body. Intestinal epithelial cells, which line the inner face of the intestinal tract, have various important functions, including absorption of food substances, immune functions such as cytokine secretion, and barrier function against xenobiotics by means of detoxification enzymes. It is likely that the functions of intestinal epithelial cells are regulated or modulated by these components because they are frequently exposed to food components at high concentrations. This review summarizes our research on the interaction between intestinal epithelial cells and food components at cellular and molecular levels. The influence of xenobiotic contamination in foods on the cellular function of intestinal epithelial cells is also described in this review.     

Lactobacillus helveticus SBT2171 alleviates allergic symptoms in a murine model for pollen allergy

ABSTRACT

Lactic acid bacteria are known to have various health-promoting effects and are highly expected to find applications in anti-allergic food materials. In this study, we focused on Lactobacillus helveticus SBT2171 (LH2171), which reportedly modifies some unique immune responses and ameliorated symptoms of patients allergic to mites and house dust in the previous studies. We examined the effect of LH2171 on cytokine production by antigen-stimulated murine naïve splenocytes in vitro and demonstrated that it inhibited IL-4 and IL-13 production while enhancing IFN-γ and IL-10 production. Then, we examined the anti-allergic effect of LH2171 in vivo using a murine model of pollen allergy and found that LH2171 reduced the sneezing frequency when orally administered to mice. We successfully confirmed the immune modulatory activity of LH2171 and its anti-allergic activity against inhaled antigens. These evidences would contribute to identifying the anti-allergic mechanism of LH2171.

Abbreviations: ALDH: aldehyde dehydrogenase; EGCG: epigallocatechin gallate; LAB: lactic acid bacteria; LH2171: Lactobacillus helveticus SBT2171; NALT: nasal-associated lymphoid tissue; OVA: ovalbumin     

Functional analysis for gut microbes of the brown tree frog (Polypedates megacephalus) in artificial hibernation

Background

Annual hibernation is an adaptation that helps many animals conserve energy during food shortage in winter. This natural cycle is also accompanied by a remodeling of the intestinal immune system, which is an aspect of host biology that is both influenced by, and can itself influence, the microbiota. In amphibians, the bacteria in the intestinal tract show a drop in bacterial counts. The proportion of pathogenic bacteria is greater in hibernating frogs than that found in nonhibernating frogs. This suggests that some intestinal gut microbes in amphibians can be maintained and may contribute to the functions in this closed ecosystem during hibernation. However, these results were derived from culture-based approaches that only covered a small portion of bacteria in the intestinal tract.

Methods

In this study, we use a more comprehensive analysis, including bacterial appearance and functional prediction, to reveal the global changes in gut microbiota during artificial hibernation via high-throughput sequencing technology.

Results

Our results suggest that artificial hibernation in the brown tree frog (Polypedates megacephalus) could reduce microbial diversity, and artificially hibernating frogs tend to harbor core operational taxonomic units that are rarely distributed among nonhibernating frogs. In addition, artificial hibernation increased significantly the relative abundance of the red-leg syndrome-related pathogenic genus Citrobacter. Furthermore, functional predictions via PICRUSt and Tax4Fun suggested that artificial hibernation has effects on metabolism, disease, signal transduction, bacterial infection, and primary immunodeficiency.

Conclusions

We infer that artificial hibernation may impose potential effects on primary immunodeficiency and increase the risk of bacterial infections in the brown tree frog.

     

Redox signaling mediated by the gut microbiota

Abstract

The microbiota that occupies the mammalian intestine can modulate a range of physiological functions, including control over immune responses, epithelial barrier function, and cellular proliferation. While commensal prokaryotic organisms are well known to stimulate inflammatory signaling networks, less is known about control over homeostatic pathways. Recent work has shown that gut epithelia contacted by enteric commensal bacteria rapidly generate reactive oxygen species (ROS). While the induced production of ROS in professional phagocytes via stimulation of formyl peptide receptors (FPRs) and activation of NADPH oxidase 2 (Nox2) is a well-studied process, ROS are also similarly elicited in other cell types, including intestinal epithelia, in response to microbial signals via FPRs and the epithelial NADPH oxidase 1 (Nox1). ROS generated by Nox enzymes have been shown to function as critical second messengers in multiple signal transduction pathways via the rapid and transient oxidative inactivation of a distinct class of sensor proteins bearing oxidant-sensitive thiol groups. These redox-sensitive proteins include tyrosine phosphatases that serve as regulators of MAP kinase pathways, focal adhesion kinase, as well as components involved in NF-κB activation. As microbe-elicited ROS has been shown to stimulate cellular proliferation and motility, and to modulate innate immune signaling, we hypothesize that many of the established effects of the normal microbiota on intestinal physiology may be at least partially mediated by this ROS-dependent mechanism.     

Perinatal Exposure to a Low Dose of Bisphenol A Impaired Systemic Cellular Immune Response and Predisposes Young Rats to Intestinal Parasitic Infection

Perinatal exposure to the food contaminant bisphenol A (BPA) in rats induces long lasting adverse effects on intestinal immune homeostasis. This study was aimed at examining the immune response to dietary antigens and the clearance of parasites in young rats at the end of perinatal exposure to a low dose of BPA. Female rats were fed with BPA [5 µg/kg of body weight/day] or vehicle from gestational day 15 to pup weaning. Juvenile female offspring (day (D)25) were used to analyze immune cell populations, humoral and cellular responses after oral tolerance or immunization protocol to ovalbumin (OVA), and susceptibility to infection by the intestinal nematode Nippostrongylus brasiliensis (N. brasiliensis). Anti-OVA IgG titers following either oral tolerance or immunization were not affected after BPA perinatal exposure, while a sharp decrease in OVA-induced IFNγ secretion occurred in spleen and mesenteric lymph nodes (MLN) of OVA-immunized rats. These results are consistent with a decreased number of helper T cells, regulatory T cells and dendritic cells in spleen and MLN of BPA-exposed rats. The lack of cellular response to antigens questioned the ability of BPA-exposed rats to clear intestinal infections. A 1.5-fold increase in N. brasiliensis living larvae was observed in the intestine of BPA-exposed rats compared to controls due to an inappropriate Th1/Th2 cytokine production in infected jejunal tissues. These results show that perinatal BPA exposure impairs cellular response to food antigens, and increases susceptibility to intestinal parasitic infection in the juveniles. This emphasized the maturing immune system during perinatal period highly sensitive to low dose exposure to BPA, altering innate and adaptative immune response capacities in early life.     

Immunosuppressive effect of mesenchymal stem cells on lung and gut CD8+ T cells in lipopolysaccharide‐induced acute lung injury in mice

ObjectivesAcute lung injury (ALI) not only affects pulmonary function but also leads to intestinal dysfunction, which in turn contributes to ALI. Mesenchymal stem cell (MSC) transplantation can be a potential strategy in the treatment of ALI. However, the mechanisms of synergistic regulatory effects by MSCs on the lung and intestine in ALI need more in‐depth study.Materials and methodsWe evaluated the therapeutic effects of MSCs on the murine model of lipopolysaccharide (LPS)‐induced ALI through survival rate, histopathology and bronchoalveolar lavage fluid. Metagenomic sequencing was performed to assess the gut microbiota. The levels of pulmonary and intestinal inflammation and immune response were assessed by analysing cytokine expression and flow cytometry.ResultsMesenchymal stem cells significantly improved the survival rate of mice with ALI, alleviated histopathological lung damage, improved intestinal barrier integrity, and reduced the levels of inflammatory cytokines in the lung and gut. Furthermore, MSCs inhibited the inflammatory response by decreasing the infiltration of CD8⁺ T cells in both small‐intestinal lymphocytes and Peyer''s patches. The gut bacterial community diversity was significantly altered by MSC transplantation. Furthermore, depletion of intestinal bacterial communities with antibiotics resulted in more severe lung and gut damages and mortality, while MSCs significantly alleviated lung injury due to their immunosuppressive effect.ConclusionsThe present research indicates that MSCs attenuate lung and gut injury partly via regulation of the immune response in the lungs and intestines and gut microbiota, providing new insights into the mechanisms underlying the therapeutic effects of MSC treatment for LPS‐induced ALI.     

Kiwifruit cysteine protease actinidin compromises the intestinal barrier by disrupting tight junctions

BackgroundThe intestinal epithelium forms a barrier that food allergens must cross in order to induce sensitization. The aim of this study was to evaluate the impact of the plant-derived food cysteine protease — actinidin (Act d1) on the integrity of intestinal epithelium tight junctions (TJs).MethodsEffects of Act d1 on the intestinal epithelium were evaluated in Caco-2 monolayers and in a mouse model by measuring transepithelial resistance and in vivo permeability. Integrity of the tight junctions was analyzed by confocal microscopy. Proteolysis of TJ protein occludin was evaluated by mass spectrometry.ResultsActinidin (1 mg/mL) reduced the transepithelial resistance of the cell monolayer by 18.1% (after 1 h) and 25.6% (after 4 h). This loss of barrier function was associated with Act d 1 disruption of the occludin and zonula occludens (ZO)-1 network. The effect on intestinal permeability in vivo was demonstrated by the significantly higher concentration of 40 kDa FITC-dextran (2.33 μg/mL) that passed from the intestine into the serum of Act d1 treated mice in comparison to the control group (0.5 μg/mL). Human occludin was fragmented, and putative Act d1 cleavage sites were identified in extracellular loops of human occludin.ConclusionAct d1 caused protease-dependent disruption of tight junctions in confluent Caco-2 cells and increased intestinal permeability in mice.General significanceIn line with the observed effects of food cysteine proteases in occupational allergy, these results suggest that disruption of tight junctions by food cysteine proteases may contribute to the process of sensitization in food allergy.     

Probiotics Can Generate FoxP3 T-Cell Responses in the Small Intestine and Simultaneously Inducing CD4 and CD8 T Cell Activation in the Large Intestine

Most studies on probiotics aim to restore intestinal homeostasis to reduce immune-pathology in disease. Of equal importance are studies on how probiotics might prevent or delay disease in healthy individuals. However, knowledge on mechanisms of probiotic actions in healthy individuals is scarce. To gain more insight in how different bacterial strains may modulate the healthy intestinal immune system, we investigated the effect of the food derived bacterial strains L. plantarum WCFS1, L. salivarius UCC118, and L. lactis MG1363, on the intestinal regulatory immune phenotype in healthy mice. All three bacterial strains induced an upregulation of activity and numbers of CD11c⁺ MHCII⁺ DCs in the immune-sampling Peyer’s Patches. Only L. salivarius UCC118 skewed towards an immune regulatory phenotype in the small intestinal lamina propria (SILP). The effects were different in the large intestine lamina propria. L. salivarius UCC118 induced activation in both CD4 and CD8 positive T-cells while L. plantarum WCFS1 induced a more regulatory phenotype. Moreover, L. plantarum WCFS1 decreased the Th1/Th2 ratio in the SILP. Also L. lactis MG1363 had immunomodulatory effects. L. lactis MG1363 decreased the expression of the GATA-3 and T-bet in the SILP. As our data show that contradictory effects may occur in different parts of the gut, it is recommended to study effects of probiotic in different sites in the intestine. Our strain-specific results suggest that unspecified application of probiotics may not be very effective. Our data also indicate that selection of specific probiotic strain activities on the basis of responses in healthy mice may be a promising strategy to specifically stimulate or suppress immunity in specific parts of the intestine.