Immunological function of sphingosine 1-phosphate in the intestine

Advances in the composition, efficacy, and mimicking of human milk phospholipids

Phospholipids are the essential components of human milk, contributing to the enhancement of cognitive development, regulation of immune functions, and mitigation of elevated cholesterol levels. Infant formulas supplemented with phospholipids can change the composition, content, and globule membrane structure of milk lipids, improving their digestive properties and nutritional value. However, mimicking phospholipids in infant formulas is currently limited, and the supplemented standards of phospholipid species and amounts in infant formulas are unknown. Consequently, there is a significant difference between the phospholipids in infant formulas and those in human milk. This article reviews the recent progress in human milk phospholipid research, aiming to describe the composition, content, and positive effects of human milk phospholipids, as well as summarises the dietary sources of phospholipid supplementation and the current state of human milk phospholipid mimicking in infant formulas. This review provides clear directions for research on mimicking human milk phospholipids and evaluating the nutritional functions of phospholipids in infants.

Washed microbiota transplantation for Crohn's disease: A metagenomic, metatranscriptomic, and metabolomic-based study

BACKGROUND

Fecal microbiota transplantation (FMT) is a promising therapeutic approach for treating Crohn's disease (CD). The new method of FMT, based on the automatic washing process, was named as washed microbiota transplantation (WMT). Most existing studies have focused on observing the clinical phenomena. However, the mechanism of action of FMT for the effective management of CD-particularly in-depth multi-omics analysis involving the metagenome, metatranscriptome, and metabolome-has not yet been reported.

AIM

To assess the efficacy of WMT for CD and explore alterations in the microbiome and metabolome in response to WMT.

METHODS

We conducted a prospective, open-label, single-center clinical study. Eleven CD patients underwent WMT. Their clinical responses (defined as a decrease in their CD Activity Index score of > 100 points) and their microbiome (metagenome, metatranscriptome) and metabolome profiles were evaluated three months after the procedure.

RESULTS

Seven of the 11 patients (63.6%) showed an optimal clinical response three months post-WMT. Gut microbiome diversity significantly increased after WMT, consistent with improved clinical symptoms. Comparison of the metagenome and metatranscriptome analyses revealed consistent alterations in certain strains, such as Faecalibacterium prausnitzii, Roseburia intestinalis, and Escherichia coli. In addition, metabolomics analyses demonstrated that CD patients had elevated levels of various amino acids before treatment compared to the donors. However, levels of vital amino acids that may be associated with disease progression (e.g., L-glutamic acid, gamma-glutamyl-leucine, and prolyl-glutamine) were reduced after WMT.

CONCLUSION

WMT demonstrated therapeutic efficacy in CD treatment, likely due to the effective reconstruction of the patient's microbiome. Multi-omics techniques can effectively help decipher the potential mechanisms of WMT in treating CD.

Inhibitory effect of Porphyromonas gingivalis-derived phosphoethanolamine dihydroceramide on acid ceramidase expression in oral squamous cells

The maintenance of diminished acid ceramidase (ASAH1) gene expression leading to the accumulation of antiproliferative intracellular ceramides in oral squamous cell carcinoma (OSCC) has emerged as a prospective oral cancer therapeutic regimen. Our published study demonstrated that the key periodontal pathogen Porphyromonas gingivalis downregulates the expression patterns of ASAH1 mRNA in normal epithelial cells in vitro. Therefore, P. gingivalis may also beneficially diminish the expression of ASAH1 in OSCC. Because a uniquely structured P. gingivalis-derived phosphoethanolamine dihydroceramide (PEDHC) inhibits the proliferation of normal human fibroblasts, this study aimed to test the effect of PEDHC on the survival of human oral squamous OECM-1 cells in vitro. We demonstrated that the P. gingivalis dihydroceramide-null (ΔPG1780) strain upregulates the expression of ASAH1 mRNA and promotes aggressive proliferation and migration of OECM-1 cells compared to the parent P. gingivalis-W83 strain. In addition, the intracellular concentration of ceramides was dramatically elevated in OECM-1 cells exposed to PEDHC in vitro. Furthermore, PEDHC inhibited expression patterns of ASAH1 mRNA as well as some genes associated with degradation of the basement membranes and extracellular matrix, for example, MMP-2, ADAM-17 and IL-6, in OECM-1 cells. Altogether, these data indicated that PEDHC produced by P. gingivalis inhibits acid ceramidase expression, promotes intracellular ceramide accumulation and suppresses the survival and migration of OSCC cells in vitro. Further studies are needed to determine molecular mechanisms of PEDHC-mediated inhibitory effect(s) on OSCC using in vivo models of oral cancer.

Alkaline sphingomyelinase (NPP7) impacts the homeostasis of intestinal T lymphocyte populations

Background and aim

Alkaline sphingomyelinase (NPP7) is expressed by intestinal epithelial cells and is crucial for the digestion of dietary sphingomyelin. NPP7 also inactivates proinflammatory mediators including platelet-activating factor and lysophosphatidylcholine. The aim of this study was to examine a potential role for NPP7 in the homeostasis of the intestinal immune system.

Methods

We quantified the numbers of B-lymphocytes, plasma cells, T-lymphocytes including regulatory T-lymphocytes (T_regs), natural killer cells, dendritic cells, macrophages, and neutrophils, in the small and large intestines, the mesenteric lymph nodes and the spleens of heterozygous and homozygous NPP7 knockout (KO) and wildtype (WT) mice. Tissues were examined by immunohistochemistry and stainings quantified using computerized image analysis.

Results

The numbers of both small and large intestinal CD3ε⁺, CD4⁺, and CD8α⁺ T-lymphocytes were significantly higher in NPP7 KO compared to WT mice (with a dose-response relationship in the large intestine), whereas T_reg numbers were unchanged, and dendritic cell numbers reduced. In contrast, the numbers of CD3ε⁺ and CD4⁺ T-lymphocytes in mesenteric lymph nodes were significantly reduced in NPP7 KO mice, while no differences were observed in spleens. The numbers of B-lymphocytes, plasma cells, natural killer cells, macrophages, and neutrophils were similar between genotypes.

Conclusion

NPP7 contributes to the regulation of dendritic cell and T-lymphocyte numbers in mesenteric lymph nodes and both the small and large intestines, thus playing a role in the homeostasis of gut immunity. Although it is likely that the downstream effects of NPP7 activity involve the sphingomyelin metabolites ceramide and spingosine-1-phosphate, the exact mechanisms behind this regulatory function of NPP7 need to be addressed in future studies.

Low fish meal diet supplemented with probiotics ameliorates intestinal barrier and immunological function of Macrobrachium rosenbergii via the targeted modulation of gut microbes and derived secondary metabolites

The unsuitable substitution ratio of fish meal by plant protein will reshape the intestinal microbial composition and intestine immunity. However, previous studies were mostly limited to investigating how different feed or probiotics characterized the microbial composition but ignored the biological interactions between bacteria and host physiology through secondary metabolites. Therefore, this study integrates the apparent indicators monitoring, 16S rDNA sequencing, and metabonomics to systematically investigate the effects of cottonseed protein concentrate (CPC) substitution of fish meal and Bacillus coagulans intervention on gut microbes, secondary metabolites, and intestinal immunity of Macrobrachium rosenbergii. Prawns were fed with three diets for 70 days: HF diets contained 25% fish meal, CPC in LF diets were replaced with 10% fish meal, and LF diets supplemented with 2 × 108 CFU/g diet B. coagulans were designated as BC diets. Results showed that CPC substitution induced a significant decrease in digestive enzyme activities (trypsin and lipase) and gut barrier protein PT-1 expression and a significant increase in γ-GT enzyme activity and inflammatory-related factors (Relish and Toll) expression. B. coagulans treatment mitigated the negative changes of the above indicators. Meanwhile, it significantly improved the expression levels of the barrier factor PT-1, the reparative cytokine IL-22, and Cu/Zn-SOD. CPC substitution resulted in a remarkable downregulated abundance of Firmicutes phyla, Flavobacterium spp., and Bacillus spp. B. coagulans treatment induced the callback of Firmicutes abundance and improved the relative abundance of Sphingomonas, Bacillus, and Ralstonia. Functional prediction indicated that CPC substitution resulted in elevated potential pathogenicity of microbial flora, and B. coagulans reduces the pathogenesis risk. Pearson's correlation analysis established a significant positive correlation between differential genera (Sphingomonas, Bacillus, and Ralstonia) and secondary metabolites (including sphingosine, dehydrophytosphingosine, amino acid metabolites, etc.). Meanwhile, the latter were significantly associated with intestinal immunoregulation-related genes (Cu/Zn-SOD, IL-22, PT-1, Toll, and Relish). This study indicated that B. coagulans could mediate specific gut microbes and the combined action of multiple functional secondary metabolites to affect intestinal barrier function, digestion, and inflammation. Our study revealed the decisive role of gut microbes and derived secondary metabolites in the model of dietary composition-induced intestinal injury and probiotic treatment from a new perspective.

Targeting Chronic Inflammation of the Digestive System in Cancer Prevention: Modulators of the Bioactive Sphingolipid Sphingosine-1-Phosphate Pathway

Incidence of gastrointestinal (GI) cancers is increasing, and late-stage diagnosis makes these cancers difficult to treat. Chronic and low-grade inflammation are recognized risks for most GI cancers. The GI mucosal immune system maintains healthy homeostasis and signalling molecules made from saturated fats, bioactive sphingolipids, play essential roles in healthy GI immunity. Sphingosine-1-phosphate (S1P), a bioactive sphingolipid, is a key mediator in a balanced GI immune response. Disruption in the S1P pathway underlies systemic chronic metabolic inflammatory disorders, including diabetes and GI cancers, providing a strong rationale for using modulators of the S1P pathway to treat pathological inflammation. Here, we discuss the effects of bioactive sphingolipids in immune homeostasis with a focus on S1P in chronic low-grade inflammation associated with increased risk of GI carcinogenesis. Contemporary information on S1P signalling involvement in cancers of the digestive system, from top to bottom, is reviewed. Further, we discuss the use of novel S1P receptor modulators currently in clinical trials and their potential as first-line drugs in the clinic for chronic inflammatory diseases. Recently, ozanimod (Zeposia^TM) and etrasimod have been approved for clinical use to treat ulcerative colitis and eosinophilic oesophagitis, respectively, which may have longer term benefits in reducing risk of GI cancers.

Signaling through the S1P-S1PR Axis in the Gut, the Immune and the Central Nervous System in Multiple Sclerosis: Implication for Pathogenesis and Treatment

Sphingosine 1-phosphate (S1P) is a signaling molecule with complex biological functions that are exerted through the activation of sphingosine 1-phosphate receptors 1–5 (S1PR1–5). S1PR expression is necessary for cell proliferation, angiogenesis, neurogenesis and, importantly, for the egress of lymphocytes from secondary lymphoid organs. Since the inflammatory process is a key element of immune-mediated diseases, including multiple sclerosis (MS), S1PR modulators are currently used to ameliorate systemic immune responses. The ubiquitous expression of S1PRs by immune, intestinal and neural cells has significant implications for the regulation of the gut–brain axis. The dysfunction of this bidirectional communication system may be a significant factor contributing to MS pathogenesis, since an impaired intestinal barrier could lead to interaction between immune cells and microbiota with a potential to initiate abnormal local and systemic immune responses towards the central nervous system (CNS). It appears that the secondary mechanisms of S1PR modulators affecting the gut immune system, the intestinal barrier and directly the CNS, are coordinated to promote therapeutic effects. The scope of this review is to focus on S1P−S1PR functions in the cells of the CNS, the gut and the immune system with particular emphasis on the immunologic effects of S1PR modulation and its implication in MS.

Human milk sphingomyelins and metabolomics: an enigma to be discovered

Sphingomyelins, the most abundant sphingolipids in most mammalian cells, appear to be among the most represented polar lipids in breast milk. Despite the variability of the data reported in the literature, human milk sphingomyelins are qualitatively unique and their quantities are five times higher than in most formula milk. The structural and functional role within the milk fat globule membranes, the involvement in neonatal neurological maturation both in neuro-typical development and in some pathological circumstances, together with the possible contribution in the intestinal development of newborns, are certainly among the main characteristics that have fueled the curiosity of the scientific world. Metabolomics studies, providing a unique metabolic fingerprint, allow an in-depth analysis of the role of these molecules in the extreme variability and uniqueness of breast milk. In the perspective of preventive medicine, at the base of which there is certainly personalized nutrition, it is possible, in the presence of particular conditions, such as neonatal growth retardation or in preterm infants, to consider supplementation of some target nutrients, such as certain sphingomyelins. Nevertheless, further studies are needed to more accurately assess whether and how the type and quantity of sphingomyelins present in breast milk could affect the metabolic health of newborns.HIGHLIGHTSBreast milk is the golden standard for infants' nutritionSphingomyelins are the most represented polar lipids in breast milkThese molecules are involved in both intestinal and neural developments of newbornsMetabolomics is a very useful tool to investigate their precise roleFurther studies are needed to provide eventual nutritional treatment.

[Pharmacological Interaction between Diets and Commensal Bacteria for the Creation of Lipid Environment in the Control of Health and Diseases]

The intestine is exposed to a variety of exogenous materials that are harmful, harmless, or useful, such as pathogenic viruses and bacteria, intestinal bacteria, or food components. As such, the intestinal immune system is important for the regulation of immunological homeostasis and biological defense. Accumulating evidence indicates that gut environmental factors, such as dietary components and intestinal bacteria are critical for controlling intestinal immunity, and thereby, health and disease. Among the important dietary components are fatty acids, which are metabolized to lipid mediators that act as signaling molecules and regulate immune responses. In previous work, we identified lipid mediators derived from ω3 fatty acids, such as 17,18-epoxyeicosatetraenoic acid, 15-hydroxyeicosapentaenoic acid, and 14-hydroxydocosapentaenoic acid, which show potent anti-allergic and anti-inflammatory activities. In addition, we revealed that lipid mediators play key roles in the enhancement of intestinal Immunoglobulin A responses, which provide the first line of defense against viral and bacterial infectious diseases. Here, we review the anti-allergic, anti-inflammatory, and host-protective effects of lipid mediators mainly derived from dietary lipids.

Diversity of energy metabolism in immune responses regulated by micro-organisms and dietary nutrition

Immune metabolism has been recognized as a new paradigm in the regulation of host immunity. In the environment, there are many micro-organisms including pathogenic and non-pathogenic and/or beneficial ones. Immune cells exhibit various responses against different types of microbes, which seem to be associated with changes in energy metabolism. In addition, dietary nutrition influences host metabolism and consequent responses by immune cells. In this review, we describe the complex network of immune metabolism from the perspectives of nutrition, micro-organisms and host immunity for the control of immunologic health and diseases.

Novel mass spectrometry-based comprehensive lipidomic analysis of plasma from patients with inflammatory bowel disease

BACKGROUND AND AIM

Lipids play important roles in inflammation and may be involved in the pathophysiology of inflammatory bowel disease (IBD). Here, we evaluated the characteristics of the plasma lipid profile in patients with IBD.

METHODS

Plasma samples were collected from 20 patients with Crohn's disease (CD), 20 patients with ulcerative colitis (UC), and 10 healthy volunteers (HVs) after overnight fasting. The subjects were men between 20 and 49 years of age with no history of hyperlipidemia. A total of 698 molecular species in 22 lipid classes were analyzed by ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry.

RESULTS

Lipid classes of lysophosphatidic acid, lysophosphatidylserine (LPS), phosphatidylserine (PS), and shingosine-1-phosphate (S1P) were significantly increased in UC patients compared with the HV. The LPS, PS, and S1P levels were significantly increased, while those of lysophosphatidylinositol and phosphatidylcholine were significantly decreased in CD patients compared with HV. Among PS species, the levels of PSacyl (PSa) 40:3, PSa 38:3, and PSa 42:4 were significantly higher in CD patients, both active and remissive stage, than in HV. The LPS 18:0 level was significantly higher in CD and UC patients compared with HV. PSa 40:3 and PSa 38:3 levels positively correlated with the Crohn's Disease Activity Index, erythrocyte sedimentation rate, and platelet count and negatively correlated with hemoglobin, hematocrit, and albumin levels in CD patients.

CONCLUSION

The lipid profile in IBD patients exhibits significant alterations, and PS levels are associated with clinical disease activity in CD patients.

Interactions between Intestinal Microflora/Probiotics and the Immune System

The digestive tract is home to millions of microorganisms and is the main and most important part of bacterial colonization. On one hand, the abundant bacterial community in intestinal tissues may pose potential health challenges such as inflammation and sepsis in cases of opportunistic invasion. Thus, the immune system has evolved and adapted to maintain the symbiotic relationship between host and microbiota. On the other hand, the intestinal microflora also exerts an immunoregulatory function to maintain host immune homeostasis, which cannot be neglected. In addition, the interaction of either microbiota or probiotics with immune system in regard to therapeutic applications is an area of great interest, and novel therapeutic strategies remain to be investigated. The review will elucidate interactions between intestinal microflora/probiotics and the immune system as well as novel therapeutic strategies.

Sphingosine-1-phosphate signaling and the gut-liver axis in liver diseases

The liver is the central organ involved in lipid metabolism and the gastrointestinal (GI) tract is responsible for nutrient absorption and partitioning. Obesity, dyslipidemia and metabolic disorders are of increasing public health concern worldwide, and novel therapeutics that target both the liver and the GI tract (gut-liver axis) are much needed. In addition to aiding fat digestion, bile acids act as important signaling molecules that regulate lipid, glucose and energy metabolism via activating nuclear receptor, G protein-coupled receptors (GPCRs), Takeda G protein receptor 5 (TGR5) and sphingosine-1-phosphate receptor 2 (S1PR2). Sphingosine-1-phosphate (S1P) is synthesized by two sphingosine kinase isoforms and is a potent signaling molecule that plays a critical role in various diseases such as fatty liver, inflammatory bowel disease (IBD) and colorectal cancer. In this review, we will focus on recent findings related to the role of S1P-mediated signaling pathways in the gut-liver axis.

Lipids in human milk

Fat is the main energy providing component in human milk and comprising a complex mixture of different lipid species, with quantitative dominance of triglycerides. After elucidating the fatty acid composition, more recent research has looked at influencing factors and the importance of specific lipids. Here we review quantitative aspects of maternal metabolism which contribute to the milk fatty acid composition, especially considering essential fatty acids and their long chain polyunsaturated derivatives. In this context studies with stable isotopes have indicated the importance of maternal body pools for mediating the effects of diet on milk composition. Furthermore, the importance of positioning of palmitic acid at the glycerol backbone of triglycerides is discussed, and the phospholipids of the milk fat globule membrane are described and examples for their potential importance for infant development are presented.

Benefits of Lactoferrin, Osteopontin and Milk Fat Globule Membranes for Infants

The provision of essential and non-essential amino acids for breast-fed infants is the major function of milk proteins. In addition, breast-fed infants might benefit from bioactivities of milk proteins, which are exhibited in the intestine during the digestive phase and by absorption of intact proteins or derived peptides. For lactoferrin, osteopontin and milk fat globule membrane proteins/lipids, which have not until recently been included in substantial amounts in infant formulas, in vitro experiments and animal models provide a convincing base of evidence for bioactivities, which contribute to the protection of the infant from pathogens, improve nutrient absorption, support the development of the immune system and provide components for optimal neurodevelopment. Technologies have become available to obtain these compounds from cow´s milk and the bovine compounds also exhibit bioactivities in humans. Randomized clinical trials with experimental infant formulas incorporating lactoferrin, osteopontin, or milk fat globule membranes have already provided some evidence for clinical benefits. This review aims to compare findings from laboratory and animal experiments with outcomes of clinical studies. There is good justification from basic science and there are promising results from clinical studies for beneficial effects of lactoferrin, osteopontin and the milk fat globule membrane complex of proteins and lipids. Further studies should ideally be adequately powered to investigate effects on clinically relevant endpoints in healthy term infants.

Symbiont-derived sphingolipids modulate mucosal homeostasis and B cells in teleost fish

Symbiotic bacteria and mucosal immunoglobulins have co-evolved for millions of years in vertebrate animals. Symbiotic bacteria products are known to modulate different aspects of the host immune system. We recently reported that Flectobacillus major is a predominant species that lives in the gill and skin mucosal surfaces of rainbow trout (Oncorhynchus mykiss). F. major is known to produce sphingolipids of a unique molecular structure. Here we propose a role for F. major and its sphingolipids in the regulation of B cell populations in rainbow trout, as well as an essential role for sphingolipids in trout mucosal homeostasis. We found that F. major-specific IgT titers are confined to the gill and skin mucus, whereas F. major-specific IgM titers are only detected in serum. Live F. major cells are able to stimulate sustained IgT expression and secretion in gills. F. major sphingolipids modulate the growth of trout total skin and gill symbiotic bacteria. In vivo systemic administration of F. major sphingolipids changes the proportion of IgT⁺ to IgM⁺ B cells in trout HK. These results demonstrate the key role of the symbiont F. major and its sphingolipids in mucosal homeostasis via the modulation of mucosal and systemic Igs and B cells.

Transcriptional modulation of SLC26A3 (DRA) by sphingosine-1-phosphate

SLC26A3 or Downregulated in adenoma (DRA) is the major Cl(-)/HCO3 (-) exchanger involved in electroneutral NaCl absorption in the mammalian intestine. Alterations in DRA function and expression have been implicated in diarrheal diseases associated with inflammation or infection. Therefore, agents that upregulate DRA activity may serve as potential antidiarrheals. In this regard, sphingosine-1-phosphate (S1P), a member of the bioactive sphingolipid family, has been shown to modulate various cellular processes including improvement of intestinal barrier function. However, the role of S1P in modulating intestinal chloride absorption by regulating DRA is not known. Therefore, the present studies were designed to examine the direct effects of S1P on apical Cl(-)/HCO3 (-) exchange activity and DRA expression. S1P significantly increased Cl(-)/HCO3 (-) exchange activity and also significantly increased DRA mRNA and protein expression. Increased DRA mRNA by S1P was accompanied by enhanced DRA promoter activity, indicating involvement of transcriptional mechanisms. The specific S1P receptor subtype-2 (S1PR2) antagonist JTE-013 blocked the stimulatory effects of S1P on DRA promoter activity, indicating the involvement of S1PR2 S1P-mediated increase in DRA promoter activity involved PI3K/Akt pathway. Progressive deletions of the DRA promoter indicated that the putative S1P-responsive elements are present in the -790/-398 region of the DRA promoter. Furthermore, results obtained from electrophoretic mobility shift assay showed that S1P stimulated DRA promoter activity via increased binding of Ying-Yang1 (YY1) in the S1P-responsive region. In conclusion, transcriptional modulation of DRA expression and function in response to S1P through a PI3/Akt pathway represents a novel role of S1P as a potential proabsorptive agent.

Role of Sphingolipids in Infant Gut Health and Immunity

Sphingomyelin (SM), glycosphingolipids, and gangliosides are important polar lipids in the milk fat globule membrane but are not found in standard milk replacement formulas. Because digestion and absorption of SM and glycosphingolipids generate the bioactive metabolites ceramide, sphingosine, and sphingosine-1-phosphate (S1P), and because intact gangliosides may have beneficial effects in the gut, this may be important for gut integrity and immune maturation in the neonate. The brush border enzymes that hydrolyze milk SM, alkaline sphingomyelinase (nucleotide phosphodiesterase pyrophosphatase 7), and neutral ceramidase are expressed at birth in both term and preterm infants. Released sphingosine is absorbed, phosphorylated to S1P, and converted to palmitic acid via S1P-lyase in the gut mucosa. Hypothetically, S1P also may be released from absorptive cells and exert important paracrine actions favoring epithelial integrity and renewal, as well as immune function, including secretory IgA production and migration of T lymphocyte subpopulations. Gluco-, galacto-, and lactosylceramide are hydrolyzed to ceramide by lactase-phlorizin hydrolase, which also hydrolyzes lactose. Gangliosides may adhere to the brush border and is internalized, modified, and possibly transported into blood, and may exert protective functions by their interactions with bacteria, bacterial toxins, and the brush border.

Effects of Dietary Plant-Origin Glucosylceramide on Bowel Inflammation in DSS-Treated Mice

The effects of dietary plant-origin glucosylceramide (GlcCer) on symptoms similar to those of inflammatory bowel diseasewere investigated in dextran sulfate sodium salt (DSS)-treated mice. Dietary GlcCer suppressed decreases in body weight due to DSS administration. To determine its effects on the colon, we examined its surface under a microscope following toluidine blue staining. Dietary GlcCer decreased DSS-induced chorionic crypt injury and elevated myeloperoxidase levels. Moreover, dietary GlcCer significantly suppressed the production of cytokines by the intestinal mucosa. These results provide evidence for the suppression of DSS-induced inflammation by dietary GlcCer.

Sphingolipids and Epoxidized Lipid Metabolites in the Control of Gut Immunosurveillance and Allergy

The intestinal immune system ingeniously balances the distinct responses of elimination and tolerance of non-self-substances for the creation and maintenance of homeostatic environments. Accumulating evidence has recently shown that various lipids, including dietary one, are involved in the regulation of intestinal immunity and are associated with biophylaxis and immune disorders. Recent advances in the lipidomics allow the identification of novel pathways of lipid metabolism and lipid metabolites for the control of intestinal immunity. In this paper, we describe the effects and functions of lipids, especially sphingolipids and new lipid metabolites originated from dietary oil on the immunomodulation and on the development and pathogenesis of allergic diseases in the intestine.

Dose-dependent effects on sphingoid bases and cytokines in chickens fed diets prepared with fusarium verticillioides culture material containing fumonisins

In chickens, the effect of mycotoxins, especially fumonisins (FB), in the gastrointestinal tract (GIT) is not well documented. Thus, this study in broiler chicks determined the effects of consuming diets prepared with Fusarium verticillioides culture material containing FB on intestinal gene expression and on the sphinganine (Sa)/sphingosine (So) ratio (Sa/So; a biomarker of FB effect due to disruption of sphingolipid metabolism). Male broilers were assigned to 6 diets (6 cages/diet; 6 birds/cage) from hatch to 20 days containing 0.4, 5.6, 11.3, 17.5, 47.8, or 104.8 mg FB/kg diet. Exposure to FB altered the Sa/So ratio in all tissues analyzed, albeit to varying extents. Linear dose-responses were observed in the kidney, jejunum and cecum. The liver and the ileum were very sensitive and data fit a cubic and quadratic polynomial model, respectively. Gene expression in the small intestine revealed low but significant upregulations of cytokines involved in the pro-inflammatory, Th1/Th17 and Treg responses, especially at 10 days of age. Interestingly, the cecal tonsils exhibited a biphasic response. Unlike the sphingolipid analysis, the effects seen on gene expression were not dose dependent, even showing more effects when birds were exposed to 11.3 mg FB/kg. In conclusion, this is the first report on the disruption of the sphingolipid metabolism by FB in the GIT of poultry. Further studies are needed to reach conclusions on the biological meaning of the immunomodulation observed in the GIT, but the susceptibility of chickens to intestinal pathogens when exposed to FB, at doses lower than those that would cause overt clinical symptoms, should be addressed.

The mucosal immune system: From dentistry to vaccine development

The oral cavity is the beginning of the aero-digestive tract, which is covered by mucosal epithelium continuously under the threat of invasion of pathogens, it is thus protected by the mucosal immune system. In the early phase of our scientific efforts for the demonstration of mucosal immune system, dental science was one of major driving forces due to their foreseeability to use oral immunity for the control of oral diseases. The mucosal immune system is divided functionally into, but interconnected inductive and effector sites. Intestinal Peyer's patches (PPs) are an inductive site containing antigen-sampling M cells and immunocompetent cells required to initiate antigen-specific immune responses. At effector sites, PP-originated antigen-specific IgA B cells become plasma cells to produce polymeric IgA and form secretory IgA by binding to poly-Ig receptor expressed on epithelial cells for protective immunity. The development of new-generation mucosal vaccines, including the rice-based oral vaccine MucoRice, on the basis of the coordinated mucosal immune system is a promising strategy for the control of mucosal infectious diseases.

Oral treatment with SEW2871, a sphingosine-1-phosphate type 1 receptor agonist, ameliorates experimental colitis in interleukin-10 gene deficient mice

SEW2871, a selective sphingosine-1-phosphate type 1 receptor (S1P1) agonist, has been shown to be effective in protecting kidneys against ischaemia-reperfusion injury by reducing CD4(+) T cell infiltration in mice. However, the effects of SEW2871 on colitis remain unclear. The aim of this study was to investigate the effects of SEW2871 on established colitis in interleukin (IL)-10 gene-deficient (IL-10(-/-)) mice, a murine model of Crohn's disease (CD). SEW2871 was administered by gavage at a dose of 20 mg/kg/day for 2 weeks to IL-10(-/-) mice. Severity of colitis, serum amyloid A, tissue myeloperoxidase (MPO), T cells in blood and colon lamina propria (LP) and proinflammatory cytokine productions were evaluated. Furthermore, the phospho-signal transducer and activator of transcription (STAT)-3 (p-STAT-3) expression in lymphocytes isolated from colon LP was also assessed. The 2-week administration of SEW2871 ameliorated established colitis in IL-10(-/-) mice, associated with a reduction of serum amyloid A concentration, a decreased colon MPO concentration, a depletion of the peripheral CD4(+) CD45(+) T cells and a reduction of the homing of T cells into colon LP. Moreover, typical cytokines of T helper type 1 (Th1) and Th17 cells and p-STAT-3 expression were also suppressed by SEW2871 treatment. SEW2871 treatment ameliorates established experimental colitis in IL-10(-/-) mice, which may provide a new therapeutic approach for human CD therapy.

Nutritional components regulate the gut immune system and its association with intestinal immune disease development

The gut is equipped with a unique immune system for maintaining immunological homeostasis, and its functional immune disruption can result in the development of immune diseases such as food allergy and intestinal inflammation. Accumulating evidence has demonstrated that nutritional components play an important role in the regulation of gut immune responses and also in the development of intestinal immune diseases. In this review, we focus on the immunological functions of lipids, vitamins, and nucleotides in the regulation of the intestinal immune system and as potential targets for the control of intestinal immune diseases.

Targeting sphingosine kinase 1 (SphK1) and apoptosis by colon-specific delivery formula of resveratrol in treatment of experimental ulcerative colitis in rats

Ulcerative colitis (UC) is a chronic inflammatory bowel disorder (IBD) that has an elevated risk of developing into colon cancer. In trials to develop new therapeutic alternatives for UC, it is important to fulfill modifying effects on pathogenic targets and to reach the colon in a high concentration. Thus, the current work has investigated a colon-specific delivery formula of resveratrol in targeting sphingosine kinase 1 (SphK1) and apoptotic pathways to control pathogenesis and its progression to any expected neoplasm. This work was conducted on 40 Wister albino rats equally divided into 4 groups where group I served as the normal control group. The untreated oxazolone-induced colitis in group II exhibited significant increase in SphK1 activity as well as activity of both myeloperoxidase (MPO) and caspase-3 with concomitant mild DNA fragmentation in colonic tissue. Colonic SphK1 activity showed significant positive correlation with the disease activity index (DAI) and histopathological score in this group. Comparable with treatment by the native resveratrol formula, nRes (group III), treatment by the colon-specific delivery resveratrol formula, cRes (group IV) caused significant decrease in the activity of SphK1 and MPO with massive DNA fragmentation in colonic tissue and non significant change in caspase-3 activity. The lowest DAI and histopathological score have been recorded in the group treated by the colon-specific delivery resveratrol formula. In conclusion, the anti-inflammatory and apoptotic effects of resveratrol could be attributed to its inhibitory effect on sphingosine kinase 1 (SphK1) providing a useful therapeutic tool to break the link between inflammation and carcinogenesis risk in ulcerative colitis.

Vitamin-mediated regulation of intestinal immunity

The intestine is exposed continuously to complex environments created by numerous injurious and beneficial non-self antigens. The unique mucosal immune system in the intestine maintains the immunologic homeostasis between the host and the external environment. Crosstalk between immunocompetent cells and endogenous (e.g., cytokines and chemokines) as well as exogenous factors (e.g., commensal bacteria and dietary materials) achieves the vast diversity of intestinal immune functions. In addition to their vital roles as nutrients, vitamins now also are known to have immunologically crucial functions, specifically in regulating host immune responses. In this review, we focus on the immunologic functions of vitamins in regulating intestinal immune responses and their roles in moderating the fine balance between physiologic and pathologic conditions of the intestine.