Anita Hartog

Diet-Derived Short Chain Fatty Acids Stimulate Intestinal Epithelial Cells To Induce Mucosal Tolerogenic Dendritic Cells

The gastrointestinal tract is continuously exposed to many environmental factors that influence intestinal epithelial cells and the underlying mucosal immune system. In this article, we demonstrate that dietary fiber and short chain fatty acids (SCFAs) induced the expression of the vitamin A–converting enzyme RALDH1 in intestinal epithelial cells in vivo and in vitro, respectively. Furthermore, our data showed that the expression levels of RALDH1 in small intestinal epithelial cells correlated with the activity of vitamin A–converting enzymes in mesenteric lymph node dendritic cells, along with increased numbers of intestinal regulatory T cells and a higher production of luminal IgA. Moreover, we show that the consumption of dietary fiber can alter the composition of SCFA-producing microbiota and SCFA production in the small intestines. In conclusion, our data illustrate that dietary adjustments affect small intestinal epithelial cells and can be used to modulate the mucosal immune system.

Locomotion and muscle mass measures in a murine model of collagen-induced arthritis

BackgroundRheumatoid arthritis (RA) is characterized by chronic poly-arthritis, synovial hyperplasia, erosive synovitis, progressive cartilage and bone destruction accompanied by a loss of body cell mass. This loss of cell mass, known as rheumatoid cachexia, predominates in the skeletal muscle and can in part be explained by a decreased physical activity. The murine collagen induced arthritis (CIA) model has been proven to be a useful model in RA research since it shares many immunological and pathological features with human RA. The present study explored the interactions between arthritis development, locomotion and muscle mass in the CIA model.MethodsCIA was induced in male DBA/1 mice. Locomotion was registered at different time points by a camera and evaluated by a computerized tracing system. Arthritis severity was detected by the traditionally used semi-quantitative clinical scores. The muscle mass of the hind-legs was detected at the end of the study by weighing. A methotrexate (MTX) intervention group was included to study the applicability of the locomotion and muscle mass for testing effectiveness of interventions in more detail.ResultsThere is a strong correlation between clinical arthritis and locomotion. The correlations between muscle mass and locomotion or clinical arthritis were less pronounced. MTX intervention resulted in an improvement of disease severity accompanied by an increase in locomotion and muscle mass.ConclusionThe present data demonstrate that registration of locomotion followed by a computerized evaluation of the movements is a simple non invasive quantitative method to define disease severity and evaluate effectiveness of therapeutic agents in the CIA model.

A potential role for regulatory T-cells in the amelioration of DSS induced colitis by dietary non-digestible polysaccharides

Inflammatory bowel diseases (IBD) including ulcerative colitis (UC) and Crohns disease (CD) are chronic relapsing inflammatory disorders of the gastrointestinal tract. The interaction between a disturbed microbial composition, the intestinal mucosal barrier and the mucosal immune system plays an important role in IBD and its chronicity. It has been indicated that due to the altered microbial composition the balance between T regulatory cells (Treg) and T helper cells (Th) 17 is disturbed, leading to an inflammatory state. The present study shows that oral intake of a specific multi fibre mix (MF), designed to match the fibre content of a healthy diet, counteracts IBD-like intestinal inflammation and weight loss in dextran sodium sulphate treated mice. This reduction in inflammation might be brought about, at least in part, by the MF-induced decrease in inflammatory cytokines, increase in IL-10 and the relative increase in Treg cells in the mesenteric lymph nodes (MLN). Moreover, the Treg percentage in the MLN correlates with the percentage of tolerogenic lamina propria derived CD103+RALDH+dendritic cells in the MLN, suggesting that these play a role in the observed effects. In children with CD exclusive enteral nutrition (EEN) is a widely used safe and effective therapy. Optimizing enteral nutritional concepts with the tested fibre mix, know to modulate the gut microbiota composition, SCFA production and inflammatory status (as indicated by the present study) could possibly further improve efficacy in inducing remission.

Systematic review of the mechanisms and evidence behind the hypocholesterolaemic effects of HPMC, pectin and chitosan in animal trials

Dietary fibres have diverse mechanisms in reducing plasma cholesterol, which could be useful for treating high levels of low-density lipoprotein cholesterol (LDL-C). The objective of this review is to determine the state of the evidence for the cholesterol-lowering effects of three selected fibres and their mechanisms, using the most recent animal trials. Therefore, a systematic review was conducted for hydroxypropyl methylcellulose (HPMC), pectin and chitosan in Pubmed, Embase and the Cochrane Library. All fibres reviewed reduced total cholesterol, very low-density lipoprotein cholesterol (VLDL-C) and LDL-C. Pectin gave a small, and chitosan an impressive rise in high-density lipoprotein cholesterol (HDL-C). A limitation of this study is the variety of animal models, each with distinct cholesterol profiles. Possible publication bias was also detected. In conclusion, chitosan seems to be the most promising of the studied fibres. A dietary fibre could be designed that yields the best cholesterol-lowering effect, using experiences in tailoring physicochemical properties and primarily exploiting the biophysical mechanisms of action.

Collagen hydrolysate inhibits zymosan-induced inflammation.

During the past years, evidence accumulated showing that glycine comprises anti-inflammatory activities. These effects occur, at least in part, via the activation of glycine-gated chloride channels (GlyR). Glycine is one of the major structural units of collagen, making up about 30% of the amino acids. This study aims to investigate the anti-inflammatory potential of collagen hydrolysate (CH) using the zymosan-induced ear-skin inflammation mouse model. After oral intake of 12.5, 25 or 50 mg CH the plasma levels of glycine increased in a concentration-dependent manner. CH was able to counteract zymosan-induced ear-skin inflammation locally (ear swelling) as well as systemically (IL-6 production by lipopolysaccharide (LPS)-stimulated whole blood cells). The LPS-stimulated IL-6 production in whole blood correlated positively with the ear swelling response. This correlation was abolished by strychnine (a glycine receptor antagonist), indicating the involvement of GlyR. Collectively, these data show that CH is able to modulate inflammatory responses both locally as well as systemically. This effect might be constituted by inhibiting pro-inflammatory cytokine production via GlyR.

Lipoproteins attenuate TLR2 and TLR4 activation by bacteria and bacterial ligands with differences in affinity and kinetics

BackgroundThe small intestine is a specialized compartment were close interactions take place between host, microbes, food antigens and dietary fatty acids. Dietary fats get absorbed by epithelial cells and processed into a range of lipoprotein particles after which they are basolaterally secreted and collected in the lymphatics. In contrast to the colon, the small intestine is covered only by a thin mucus coat that allows for intimate interactions between host-cells and microbes. Lipoproteins have long been recognized as protective factors in infectious diseases via the neutralization of bacterial toxins like lipopolysaccharides. Much less attention has been given to the potential role of lipoproteins as factors contributing to the maintenance of small intestinal immune homeostasis via modulating bacteria-induced immune responses.ResultsLipoproteins VLDL, LDL and HDL were found to neutralize TLR responses towards specific TLR-ligands or a selection of gram-negative and gram-positive bacteria. Attenuation of TLR2 activity was acute and only slightly improved by longer pre-incubation times of ligands and lipoproteins with no differences between bacterial-lipopeptides or bacteria. In contrast, attenuation of TLR4 responses was only observed after extensive preincubation of lipoproteins and LPS. Preincubation of bacteria and lipoproteins led only to a modest attenuation of TLR4 activity. Moreover, compared to TLR2, TLR4 activity could only be attenuated by lipoproteins over a small ligand dose range.ConclusionsThese results demonstrate the ability of lipoproteins VLDL, LDL and HDL to inhibit TLR responses towards bacterial-ligands and bacteria. Presence of lipoproteins was found to modulate the MAMP-induced cytokine release by primary human monocytes measured as changes in the release of IL-6, TNFα, GM-CSF and IFNγ. Using TLR2 and TLR4-reporter cells, lipoproteins were found to inhibit TLR responses with differences in affinity and kinetics. These data establish a role for lipoproteins as immunoregulatory molecules, attenuating TLR-responses and thereby positively contributing to mucosal homeostasis.

In Vitro and In Vivo Modulation of Cartilage Degradation by a Standardized Centella asiatica Fraction

Osteoarthritis (OA) is a degenerative joint disease in which focal cartilage destruction is one of the primary features. The present study aims to evaluate the effect of a Centella asiatica fraction on in vitro and in vivo cartilage degradation. Bovine cartilage explants and bovine chondrocytes cultured in alginate were stimulated with IL-1β in the presence or absence of different concentrations (2, 5 and 10 μg/ml) of a standardized Centella asiatica triterpenes (CAT) fraction. The CAT fraction inhibited the IL-1β-induced proteoglycan (PG) release and nitric oxide (NO) production by cartilage explants in a dose-dependent manner. The IL-1β-induced reduction in PG synthesis and proliferation of chondrocytes cultured in alginate were counteracted by the CAT fraction at a concentration of 10 μg/ml. In a zymosan-induced acute arthritis model, the CAT fraction inhibited PG depletion without modulating joint swelling and inflammatory cell infiltration. In conclusion, the present study demonstrated for the first time that the tested Centella asiatica fraction was able to inhibit the zymosan-induced cartilage degradation in vivo without affecting the zymosan-induced inflammatory cell infiltration and joint swelling. The in vitro data indicate that the cartilage protective activity might at least partially be induced by the inhibition of NO production. The overall results indicate a possible disease modifying osteoarthritic activity of the Centella asiatica fraction.

Amino acid-based formula affects the gastrointestinal cytokine milieu of children with non-IgE mediated cow’s milk allergy.

Food Allergy (FA) presents a significant health and economic burden in the western world. Children with non-IgE mediated cows milk allergy (CMA) are being increasingly seen in clinic. Diagnosis is largely based on delayed onset of symptoms, primarily affecting the gastrointestinal (GI) mucosa. Treatment involves an elimination diet supplemented with amino acid-based formula (AAF) which in some children results in effective symptom relief. To understand the beneficial effects of AAF at the molecular level, herein we characterized the GI cytokine milieu ex vivo from children with or without AAF in their elimination diets.

Anti-inflammatory features of the amino acid-based formula Neocate

Amino acid-based formulas (AAF) are used for the dietary management of cow’s milk allergy and multiple food protein intolerances. A recent study showed that intake of AAF, in addition to a milk-, egg-, wheat- and soy-free diet, results in a reduced colonic inflammatory status in pediatric patients (≤ 5 years, both control and formula group were negative for eosinophilia, [1] ). The present study aimed to evaluate the immune modulating effect of an amino acid-based formula (Neocate) and its pure total amino acid fraction. Human peripheral blood mononuclear cells (PBMCs) were stimulated for 20 hours with lipopolysaccharide (LPS) in the presence and absence of the complete formula, its amino acid fraction, or individual amino acids. Cytokine production was analyzed in the culture supernatant, by ELISA. The influence on CXCL8-induced neutrophil chemotaxis was measured using Boyden chambers. AAF and its amino acid fraction significantly inhibit the LPS-induced TNFα production in a concentration dependent manner. However, the LPS-induced IL-8 production was not affected. In addition to the tested complete formula and amino acid fraction, the single amino acid glycine is able to inhibit the LPS-induced TNFα production. Other amino acids tested, including taurine, lysine and glutamine did not affect the LPS induced TNFα production. CXCL8-induced neutrophil chemotaxis was inhibited by the amino acids fraction and glycine but not by the complete amino acid-based formula. The present study demonstrates that the amino acids in Neocate are able to dampen specific inflammatory responses. This effect might be mediated through specific amino acids or combinations thereof, including glycine. These in vitro studies show that the anti-inflammatory capacity of amino acid-based formulas (as indicated in [1] ) could, at least partially, be induced by the amino acid composition of the formula used.

Oral exposure to the free amino acid glycine inhibits the acute allergic response in a model of cow's milk allergy in mice

The conditionally essential amino acid glycine functions as inhibitory neurotransmitter in the mammalian central nervous system. Moreover, it has been shown to act as an anti-inflammatory compound in animal models of ischemic perfusion, post-operative inflammation, periodontal disease, arthritis and obesity. Glycine acts by binding to a glycine-gated chloride channel, which has been demonstrated on neurons and immune cells, including macrophages, polymorphonuclear neutrophils and lymphocytes. The present study aims to evaluate the effect of glycine on allergy development in a cows milk allergy model. To this end, C3H/HeOuJ female mice were supplemented with glycine by oral gavage (50 or 100 mg/mouse) 4 hours prior to sensitization with cows milk whey protein, using cholera toxin as adjuvant. Acute allergic skin responses and anaphylaxis were assessed after intradermal allergen challenge in the ears. Mouse mast cell protease-1 (mMCP-1) and whey specific IgE levels were detected in blood collected 30 minutes after an oral allergen challenge. Jejunum was dissected and evaluated for the presence of mMCP-1-positive cells by immunohistochemistry. Intake of glycine significantly inhibited allergy development in a concentration dependent manner as indicated by a reduction in; acute allergic skin response, anaphylaxis, serum mMCP-1 and serum levels of whey specific IgE. In addition, in-vitro experiments using rat basophilic leukemia cells (RBL), showed that free glycine inhibited cytokine release but not cellular degranulation. These findings support the hypothesis that the onset of cows milk allergy is prevented by the oral intake of the amino acid glycine. An adequate intake of glycine might be important in the improvement of tolerance against whey allergy or protection against (whey-induced) allergy development.