Stilbenoids are anti-inflammatory and antioxidant compounds, with resveratrol being the most investigated molecule in this class. However, the actions of most other stilbenoids are much less studied. This study compares five monomeric (resveratrol, piceatannol, pterostilbene, pinostilbene, and trimethoxy-resveratrol) and two dimeric (dehydro-δ-viniferin and trans-δ-viniferin) stilbenoids for their capability to modulate the production of bacteria-induced cytokines (IL-12, IL-10, and TNF-α), as well as lipopolysaccharide (LPS)-induced reactive oxygen species (ROS), in murine bone marrow-derived dendritic cells. All monomeric species showed dose-dependent inhibition of E. coli-induced IL-12 and TNF-α, whereas only resveratrol and piceatannol inhibited IL-10 production. All monomers, except trimethoxy-resveratrol, inhibited L. acidophilus-induced IL-12, IL-10, and TNF-α production. The dimer dehydro-δ-viniferin remarkably enhanced L. acidophilus-induced IL-12 production. The contrasting effect of resveratrol and dehydro-δ-viniferin on IL-12 production was due, at least in part, to a divergent inactivation of the mitogen-activated protein kinases by the two stilbenoids. Despite having moderate to high total antioxidant activity, dehydro-δ-viniferin was a weak inhibitor of LPS-induced ROS formation. Conversely, resveratrol and piceatannol potently inhibited LPS-induced ROS formation. Methylated monomers showed a decreased antioxidant capacity compared to resveratrol, also depending on the methylation site. In summary, the immune-modulating effect of the stilbenoids depends on both specific structural features of tested compounds and the stimulating bacteria.

Methicillin resistant Staphylococcus aureus (MRSA) has developed resistance to most β-lactam antibiotics leaving few treatment options against infections with MRSA. Through mannose receptors, mannan potentiates IL-12 production induced by Gram-positive bacteria, a cytokine crucial in the clearance of S. aureus infection. We investigated the IL-12 potentiating effect of mannan pre-treatment of bone marrow-derived dendritic cells prior to stimulation with clinical MRSA strains. Mannan almost doubled IL-12 as well as IFN-β production in response to USA300, also when USA300 was treated with the β-lactam cefoxitin. The MRSA-induced IL-12 production was dependent on bacterial uptake and reactive oxygen species (ROS). Mannan alone induced ROS production, and in combination with USA300, the ROS produced corresponded to the sum induced by mannan and USA300. Addition of a monoclonal antibody against the mannose receptor likewise enhanced USA300-induced IL-12 and induced ROS production. Mannan addition further increased the endocytosis as well as the rate of endosomal killing of bacteria. Pre-treatment with soluble β-glucans also induced ROS and potentiated the USA300-induced IL-12 indicating that other C-type receptors may play a similar role. In the presence of the pro-inflammatory mediators, GM-CSF or IFN-γ, the mannan-enhanced IL-12 production increased further. The USA300-induced and the mannan-facilitated enhanced IFN-β and IL-12 showed same dependency on MAPK c-Jun N-terminal kinase signaling, suggesting that mannan enhances the signals already induced by the bacteria, rather than changing them. We suggest that the C-type lectin-induced ROS production is a key factor in the IFN-β and IL-12 potentiation.

Compared to the well‐defined immune‐modulating effect of butyrate, the understanding of the effect of other protein fermentation metabolites is limited. This study aimed to investigate the impact of protein‐derived metabolites (valerate, branched‐chain fatty acids, ammonium, phenol, p‐Cresol, indole, and hydrogen sulfide) on cytokine production in murine bone marrow‐derived dendritic cells (BMDCs) stimulated with lipopolysaccharides (LPS), Lactobacillus acidophilus NCFM, or Staphylococcus aureus USA300. Some of the metabolites, but not the short‐chain fatty acids (SCFAs), strongly affected cell viability. After short‐term treatment and depending on the microbial stimulus, SCFAs affected the cytokine profile similarly but weaker than butyrate, as reflected by inhibition of IL‐12p70 and IL‐10 but enhanced IL‐23 (LPS and S. aureus USA300) and IL‐1β production. Compared to butyrate, valerate exhibited a weaker and slower effect on cytokine expression. Two‐day treatment with valerate and butyrate resulted in similar effects, that is, LPS‐induced IL‐12 abrogation and IL‐10 enhancement, increased aryl hydrocarbon receptor ( Ahr ) expression, and after LPS stimulation, increased expression of dual specificity phosphatase 1 ( Dusp1 ). In conclusion, SCFAs exhibited low toxicity and modulated microbially stimulated BMDCs. Valerate and butyrate showed the strongest effect, which was dependent on the specific microbial stimulation and the course of the SCFA treatment. Our work adds knowledge regarding the role of protein‐derived metabolites from gut bacterial fermentation on the immune system.

Introduction: In resource-poor settings, mother-infant dyads are commonly exposed to environmental factors increasing the risk of infectious diseases and possibly influencing the cytokine profile of human milk (HM). Hormones in HM have been proposed to influence appetite-regulation and possibly growth in exclusively breastfed infants. Objective: To compare cytokines and appetite-regulating hormone (ARH) concentrations in HM of mothers from four contrasting populations and investigate associations with infant growth. Method: HM samples from 825 mothers participating in the Mothers, Infants and Lactation Quality Study from Bangladesh (BD), Brazil (BR), Denmark (DK) and The Gambia (GM) were collected between 1–3.5 months postpartum and analysed for tumour-necrosis factor-α, interferon (IFN)-γ, interleukin (IL)-1β, IL-4, IL-6, IL-8, IL-10, IL-33, and insulin, leptin and adiponectin. Infant growth was measured twice between 1–5.99 months postpartum. Analysis of covariance was used to compare geometric means of HM markers between the four sites and associations between HM markers and infant growth were investigated using linear regression analysis. Results: Differences in geometric means of all HM cytokines and ARHs were found among the four study sites after adjustment for possible explanatory variables. Lowest levels of most HM cytokines were found in BD, whereas highest levels of IFN-γ, IL-4, IL-10 and IL-33 were found in DK. In GM, cytokines and ARHs were inversely associated with weight-for-age and weight-for-length Z-scores. Conclusion: We showed significant differences in HM composition of cytokines and ARHs among the four countries. Highest levels of T helper cell type 2 cytokines, which is typically related to increased risk of atopic diseases, were found in DK. The results may reflect the influence of different environmental exposures in the four sites on HM composition, which may be associated with infant growth in GM.

The two probiotic bacteria Lactobacillus helveticus MIMLh5 and L. acidophilus NCFM exhibit homology, are both equipped with an S-layer made up of highly homologous proteins and are capable of stimulating Th1-inducing signals in dendritic cells. In this study, we aimed to compare the two strains as regards the thickness of the S-layer and their capacity to induce the production of the two Th1-inducing cytokines IL-12 and IFN-β. For both bacteria, stimulation with an increasing number of bacteria led to the higher and prompter production of IL-12 and IFN-β, but at all MOIs tested, the IL-12 response induced by NCFM was always the strongest. For both bacteria, the induction of IL-12 peaked at a multiplicity of infection (MOI) of 2–5, while IL-10, known to inhibit the induction of IL-12 cytokines, was induced more slowly and continued to increase at a higher MOI. By employing specific inhibitors, MIMLh5 and NCFM were also shown to activate different MAP kinase pathways. Endocytosed MIMLh5 showed higher survival in the DCs compared to NCFM. In the presence of mannan, previously shown to accelerate endosomal killing of Gram-positive bacteria, the survival of MIMLh5 was strongly decreased, and IL-12 increased to a level close to that induced by NCFM without the addition of mannan, indicating the importance of rapid endosomal degradation for a strong IL-12 response. When measuring the S-layer thickness, MIMLh5’s S-layer appeared to be more than twice the thickness of NCFM and exhibited an elastic modulus approximately twice as high, which is a measure of a cell’s resistance to an applied mechanic stress. When the two strains were depleted of S-layer protein, the elastic modulus was comparable. Together, our data suggests that the thicker S-layer of MIMLh5 compared to NCFM may contribute to its endosomal survival, thus reducing its capacity to induce IL-12. This may constitute an important parameter in the selection of probiotic bacteria for specific purposes.