Sander de Kivit

Galectin-9 induced by dietary synbiotics is involved in suppression of allergic symptoms in mice and humans

Prebiotic galacto‐ and fructo‐oligosaccharides (scGOS/lcFOS) resembling non‐digestible oligosaccharides in human milk reduce the development of atopic disorders. However, the underlying mechanisms are still unclear. Galectins are soluble‐type lectins recognizing β‐galactoside containing glycans. Galectin‐9 has been shown to regulate mast cell degranulation and T‐cell differentiation. In this study, the involvement of galectin‐9 as a mechanism by which scGOS/lcFOS in combination with Bifidobacterium breve M‐16V protects against acute allergic symptoms was investigated.

Regulation of Intestinal Immune Responses through TLR Activation: Implications for Pro- and Prebiotics

The intestinal mucosa is constantly facing a high load of antigens including bacterial antigens derived from the microbiota and food. Despite this, the immune cells present in the gastrointestinal tract do not initiate a pro-inflammatory immune response. Toll-like receptors (TLRs) are pattern recognition receptors expressed by various cells in the gastrointestinal tract, including intestinal epithelial cells (IEC) and resident immune cells in the lamina propria. Many diseases, including chronic intestinal inflammation (e.g., inflammatory bowel disease), irritable bowel syndrome (IBS), allergic gastroenteritis (e.g., eosinophilic gastroenteritis and allergic IBS), and infections are nowadays associated with a deregulated microbiota. The microbiota may directly interact with TLR. In addition, differences in intestinal TLR expression in health and disease may suggest that TLRs play an essential role in disease pathogenesis and may be novel targets for therapy. TLR signaling in the gut is involved in either maintaining intestinal homeostasis or the induction of an inflammatory response. This mini review provides an overview of the current knowledge regarding the contribution of intestinal epithelial TLR signaling in both tolerance induction or promoting intestinal inflammation, with a focus on food allergy. We will also highlight a potential role of the microbiota in regulating gut immune responses, especially through TLR activation.

Glycan recognition at the interface of the intestinal immune system: target for immune modulation via dietary components.

The intestinal mucosa is constantly exposed to the luminal content, which includes micro-organisms and dietary components. Prebiotic non-digestible oligosaccharides may be supplemented to the diet to exert modulation of immune responses in the intestine. Short chain galacto- and long chain fructo-oligosaccharides (scGOS/lcFOS), functionally mimicking oligosaccharides present in human milk, have been reported to reduce the development of allergy through modulation of the intestinal microbiota and immune system. Nonetheless, the underlying working mechanisms of scGOS/lcFOS are unclear. Intestinal epithelial cells lining the mucosa are known to express carbohydrate (glycan)-binding receptors that may be involved in modulation of the mucosal immune response. This review aims to provide an overview of glycan-binding receptors, in particular galectins, which are expressed by intestinal epithelial cells and immune cells. In addition, their involvement in health and disease will be addressed, especially in food allergy and inflammatory bowel disease, diseases originating from the gastro-intestinal tract. Insight in the recognition of glycans in the intestinal tract may open new avenues for the treatment of intestinal inflammatory diseases by either nutritional concepts or pharmacological intervention.

Oral tolerance induction by partially hydrolyzed whey protein in mice is associated with enhanced numbers of Foxp3+ regulatory T-cells in the mesenteric lymph nodes.

To cite this article: van Esch BCAM, Schouten B, de Kivit S, Hofman GA, Knippels LMJ, Willemsen LEM, Garssen J. Oral tolerance induction by partially hydrolyzed whey protein in mice is associated with enhanced numbers of Foxp3+ regulatory T‐cells in the mesenteric lymph nodes. Pediatr Allergy Immunol 2011: 22: 820–826.

Apical TLR ligation of intestinal epithelial cells drives a Th1-polarized regulatory or inflammatory type effector response in vitro.

Intestinal epithelial cells (IEC) separate the mucosal immune system from the external milieu. Under inflammatory conditions, Toll-like receptor (TLR) expression by IEC is increased. In a transwell co-culture model immune modulation by IEC upon TLR ligation was studied. Human IEC (HT-29 and T84) grown on filters were apically or basolaterally exposed to TLR4 or TLR9 ligands and co-cultured with CD3/CD28-activated healthy donor PBMC in the basolateral compartment. TLR4 ligation of IEC (HT-29) enhanced the production of TNF-α and IEC-derived MDC and decreased numbers of Foxp3(+) regulatory T cells. Neutralization of TSLP abrogated TLR4-induced TNF-α secretion. In contrast, apical TLR9 ligation of IEC (HT-29 and T84) enhanced IFN-γ and IL-10 secretion and increased the number of activated T(h)1 cells. The increase in IFN-γ secretion depended on the presence of IEC. Furthermore, CD14 expression on monocytes was reduced coinciding with enhanced intracellular IL-10 and decreased TNF-α production. However, basolateral TLR9 ligand exposure of HT-29 cells resulted in enhanced IFN-γ, IL-6 and TNF-α, while IL-10 secretion remained unaltered. TLR4 and TLR9 ligands reduced IL-13 secretion in presence and absence of apically exposed IEC and enhanced IL-12 secretion in presence of IEC. These data suggest that TLR4 ligation of IEC drives an inflammatory, while apical TLR9 ligation drives a regulatory T(h)1 effector immune response in vitro in a polarized manner. IEC may be important modulators of the mucosal effector immune response.

Intestinal Epithelium-Derived Galectin-9 Is Involved in the Immunomodulating Effects of Nondigestible Oligosaccharides

Dietary intervention using nondigestible oligosaccharides, short-chain galacto-oligosaccharides (scGOS)/long-chain fructo-oligosaccharides (lcFOS), in combination with Bifidobacterium breve M-16V prevents allergic disease involving galectin-9. In addition, apical TLR9 signaling contributes to intestinal homeostasis. We studied the contribution of galectin-9 secreted by intestinal epithelial cells (IEC; HT-29 and T84) in Th1 and regulatory T-cell (Treg) polarization in vitro. IEC were grown in transwell filters, cocultured with CD3/CD28-activated human peripheral blood mononuclear cells (PBMC) and apically exposed to genomic DNA derived from B. breve M-16V or synthetic TLR9 ligand in the absence or presence of scGOS/lcFOS. Cytokine production and T-cell phenotype were determined and galectin expression by IEC was assessed. Galectin-9 was neutralized using lactose or a TIM-3-Fc fusion protein. IEC exposed to DNA from B. breve M-16V or TLR9 ligand in the presence of scGOS/lcFOS enhanced IFN-γ secretion by PBMC and increased the percentage of Th1 and Treg cells. Expression and secretion of galectin-9 by IEC was increased and neutralization of galectin-9 prevented the induction of IFN-γ secretion and also suppressed the production of IL-10 by PBMC. Furthermore, we show that galectin-9 induces Treg and Th1 polarization through interaction with antigen-presenting cells. Our findings show that galectin-9 secreted by IEC apically exposed to TLR9 ligand in the presence of scGOS/lcFOS is involved in Th1 and Treg polarization and may be a promising target to prevent or treat allergic disease.

Exposure of intestinal epithelial cells to UV-killed Lactobacillus GG but not Bifidobacterium breve enhances the effector immune response in vitro.

Background: Intestinal bacteria and intestinal epithelial cells (IEC) may modulate the mucosal immune response. In this study, immune modulation by Lactobacillus GG (LGG) and Bifidobacterium breve (Bb1, Bb2) in the presence or absence of IEC was addressed in an in vitro transwell co-culture model. Methods: UV-killed LGG,Bb1, Bb2 or Toll-like receptor (TLR) 2 or nucleotide oligomerization domain (NOD) 2 ligands were added directly to unstimulated or anti-CD3/CD28-stimulated PBMC, or applied apically to human IEC (HT-29) co-cultured with PBMC. A mixture of live bacteria was used as reference. The effect on T helper 1 (IFN-γ, IL-12), T helper 2 (IL-13), inflammatory (TNF-α) and regulatory (IL-10) cytokine secretion was determined. Results: Both UV-killed LGG and Bb enhanced IL-12, IFN-γ, TNF-α and IL-10, and reduced IL-13 secretion when added directly to stimulated PBMC, similar to live bacteria. IEC reduced IL-13, IFN-γ and IL-10 secretion by stimulated PBMC. Apically added LGG, TLR2 and NOD2 ligands,but not Bb, enhanced IFN-γ, IL-12 and/or TNF-α secretion. Bacteria did not induce cytokine secretion when added to HT-29/unstimulated PBMC co-cultures, whereas direct incubations with PBMC did. Conclusion: UV-killed LGG as well as Bb supported a T helper 1 and/or regulatory phenotype when added directly to activated PBMC, similar to live bacteria. In contrast, LGG, TLR2 or NOD2 ligands – but not Bb – enhanced T helper 1 type cytokine secretion when added to IEC, while IL-10 secretion remained suppressed. Co-cultures combining IEC and PBMC may reveal differences between bacterial strains relevant for the in vivo situation.

Minocycline restores spatial but not fear memory in olfactory bulbectomized rats

We investigated the effects of minocycline, a microglia suppressant, on olfactory bulbectomized (OBX) rats, a model of cognitive and behavioral impairments arising from neurodegenerative processes. Previously, we demonstrated that the major OBX-induced behavioral and cognitive impairments develop between day 3 and 7 following bulbectomy. Here we show that the onset of these cognitive changes parallel in time with signs of microglia activation (increased mRNA levels of IL-1β and CD68) in hippocampus. Next, rats were treated with minocycline (50mg/kg, i.p.) once daily for 4 weeks. OBX surgery was done at day 3 of drug treatment. Animals were tested in a battery of behavioral assays: open field, passive avoidance (fear learning and memory-acquired prior to OBX) and T-maze (spatial memory, conducted post bulbectomy). Minocycline normalized OBX-induced hyperactivity in the open field. Minocycline failed to prevent fear memory loss, but protected the OBX rats against hippocampal-dependent spatial memory deficit. Our findings suggest that treatment with minocycline may be effective in the early phase of a neurodegenerative disease.

The neuro-immune axis: prospect for novel treatments for mental disorders.

Disturbed bidirectional pathways between the (central) nervous system and immune system have been implicated in various mental disorders, including depressive and neurodevelopmental disorders. In this minireview, the role of the neuro-immune axis and its targetability in relation to major depression and autism spectrum disorder will be discussed. All together, the management of these and possibly other multi-factorial mental disorders needs a new and integrated therapeutic approach. Pharmacologically bioactive molecules as well as medical nutrition targeting the (gut)-immune-brain axis could be such an approach.

In vitro evaluation of intestinal epithelial TLR activation in preventing food allergic responses

Alterations in the gut microbiota composition are associated with food allergy. Toll-like receptors (TLRs) respond to microbial stimuli. We studied the effects of the ligation of TLRs on intestinal epithelial cells (IECs) in preventing an allergic effector response. IEC monolayers (T84 cells) were co-cultured with CD3/28-activated PBMCs from healthy controls or atopic patients and simultaneously apically exposed to TLR2, TLR4 or TLR9 ligands. The barrier integrity of T84 cell monolayers was significantly reduced upon co-culture with PBMCs of food allergic subjects compared to healthy subjects. Apical exposure of IECs to a TLR9 ligand prevented PBMC-induced epithelial barrier disruption. Using PBMCs from food allergic subjects, apical TLR9 activation on IECs increased the IFN-γ/IL-13 and IL-10/IL-13 ratio, while suppressing pro-inflammatory IL-6, IL-8 and TNF-α production in an IEC-dependent manner. Hence, the activation of apical TLR9 on IECs, potentially by microbiota-derived signals, may play an important role in the prevention of allergic inflammation.