Lactic acid bacteria (LAB) are capable of synthesising metabolites known as exopolysaccharides (EPS) during fermentation. Traditionally, EPS plays an important role in fermented dairy products through their gelling and thickening properties, but they can also be beneficial to human health. This bioactivity has gained attention in applications for functional foods, which leads them to have prebiotic, immunomodulatory, antioxidant, anti-tumour, cholesterol-lowering and anti-obesity activity. Understanding the parameters and conditions is crucial to optimising the EPS yields from LAB for applications in the food industry. This review provides an overview of the functional food market together with the biosynthesis of EPS. Factors influencing the production of EPS as well as methods for isolation, characterisation and quantification are reviewed. Finally, the health benefits associated with EPS are discussed.

Clostridium difficile is the etiological agent of antibiotic-associated diarrhoea (AAD) and pseudomembranous colitis in humans. The role of the surface layer proteins (SLPs) in this disease has not yet been fully explored. The aim of this study was to investigate a role for SLPs in the recognition of C. difficile and the subsequent activation of the immune system. Bone marrow derived dendritic cells (DCs) exposed to SLPs were assessed for production of inflammatory cytokines, expression of cell surface markers and their ability to generate T helper (Th) cell responses. DCs isolated from C3H/HeN and C3H/HeJ mice were used in order to examine whether SLPs are recognised by TLR4. The role of TLR4 in infection was examined in TLR4-deficient mice. SLPs induced maturation of DCs characterised by production of IL-12, TNFα and IL-10 and expression of MHC class II, CD40, CD80 and CD86. Furthermore, SLP-activated DCs generated Th cells producing IFNγ and IL-17. SLPs were unable to activate DCs isolated from TLR4-mutant C3H/HeJ mice and failed to induce a subsequent Th cell response. TLR4^−/− and Myd88^−/−, but not TRIF^−/− mice were more susceptible than wild-type mice to C. difficile infection. Furthermore, SLPs activated NFκB, but not IRF3, downstream of TLR4. Our results indicate that SLPs isolated from C. difficile can activate innate and adaptive immunity and that these effects are mediated by TLR4, with TLR4 having a functional role in experimental C. difficile infection. This suggests an important role for SLPs in the recognition of C. difficile by the immune system. Clostridium difficile is the leading cause of antibiotic-associated diarrhoea among hospital patients and in severe cases can cause pseudomembranous colitis and even death. There is currently limited information regarding how this pathogen is recognised by the immune system and the key mechanisms necessary for clearance of the pathogen. C. difficile expresses a paracrystalline surface protein array, termed an S-layer, composed of surface layer proteins (SLPs). Their location on the outer surface of the bacteria suggests that they may be involved in immune recognition of the pathogen. In this study we demonstrate that these SLPs are recognised by toll-like receptor 4 (TLR4). Activation of TLR4 by SLPs resulted in maturation of dendritic cells and subsequent activation of T helper cell responses which are known to be important in clearance of pathogens. Furthermore, using a murine model of C. difficile infection we show that mice display increased severity of infection in the absence of TLR4. This is the first study to demonstrate a role for TLR4 in infection associated with C. difficile and suggests an important role for SLPs in the generation of the immune response necessary for clearance of this bacterium.

The role of dendritic cells (DCs) in directing the immune response is due in part to their capacity to produce a range of cytokines. Importantly, DCs are a source of cytokines which can promote T cell survival and T helper cell differentiation. While it has become evident that soluble-N-ethylmaleimide-sensitive-factor accessory-protein receptors (SNARE) are involved in membrane fusion and ultimately cytokine release, little is known about which members of this family facilitate the secretion of specific cytokines from DCs. We profiled mRNA of eighteen SNARE proteins in DCs in response to activation with a panel of three toll-receptor (TLR) ligands and show differential expression of SNAREs in response to their stimulus and subsequent secretion patterns. Of interest, STX3 mRNA was up-regulated in response to TLR4 and TLR7 activation but not TLR2 activation. This correlated with secretion of IL-6 and MIP-1α. Abolishment of STX3 from DCs by RNAi resulted in the attenuation of IL-6 levels and to some extent MIP-1α levels. Analysis of subcellular location of STX3 by confocal microscopy showed translocation of STX3 to the cell membrane only in DCs secreting IL-6 or MIP-1α, indicating a role for STX3 in trafficking of these immune mediators. Given the role of IL-6 in Th17 differentiation, these findings suggest the potential of STX3 as therapeutic target in inflammatory disease.

Dendritic cells (DCs) provide an essential link between innate and adaptive immunity. At the site of infection, antigens recognised by DCs via pattern-recognition receptors such as Toll like receptors (TLR), initiate a specific immune response. Depending on the nature of the antigen, DCs secrete distinct cytokines with which they orchestrate homeostasis and pathogen clearance. Dysregulation of this process can lead to unnecessary inflammation which can result in a plethora of inflammatory diseases. Therefore, the secretion of cytokines from DCs is tightly regulated and this regulation is facilitated by highly conserved trafficking protein families. These proteins control the transport of vesicles from the golgi complex to the cell surface and between organelles. In this review we will discuss the role of soluble n-ethylmaleimide-sensitive factor attachment protein receptor proteins (SNAREs) in DCs both as facilitators of secretion and as useful tools to determine the pathways of secretion through their definite locations within the cells and inherent specificity in opposing binding partners on vesicles and target membranes. The role of SNAREs in DC function may present an opportunity to explore these proteins as novel targets in inflammatory disease.

Background The A10 and A7r5 cell lines derived from the thoracic aorta of embryonic rat are widely used as models of non-differentiated, neonatal and neointimal vascular smooth muscle cells in culture. The recent discovery of resident multipotent vascular stem cells within the vessel wall has necessitated the identity and origin of these vascular cells be revisited. In this context, we examined A10 and A7r5 cell lines to establish the similarities and differences between these cell lines and multipotent vascular stem cells isolated from adult rat aortas by determining their differentiation state, stem cell marker expression and their multipotency potential in vitro. MethodsVascular smooth muscle cell differentiation markers (alpha-actin, myosin heavy chain, calponin) and stem cell marker expression (Sox10, Sox17 and S100β) were assessed using immunocytochemistry, confocal microscopy, FACS analysis and real-time quantitative PCR. Results Both A10 and A7r5 expressed vascular smooth muscle differentiation, markers, smooth muscle alpha - actin, smooth muscle myosin heavy chain and calponin. In parallel analysis, multipotent vascular stem cells isolated from rat aortic explants were immunocytochemically myosin heavy chain negative but positive for the neural stem cell markers Sox10 +, a neural crest marker, Sox17 +the endoderm marker, and the glia marker, S100β +. This multipotent vascular stem cell marker profile was detected in both embryonic vascular cell lines in addition to the adventitial progenitor stem cell marker, stem cell antigen-1, Sca1 +. Serum deprivation resulted in a significant increase in stem cell and smooth muscle cell differentiation marker expression, when compared to serum treated cells. Both cell types exhibited weak multipotency following adipocyte inductive stimulation. Moreover, Notch signaling blockade following γ-secretase inhibition with DAPT enhanced the expression of both vascular smooth muscle and stem cell markers. Conclusions We conclude that A10 and A7r5 cells share similar neural stem cell markers to both multipotent vascular stem cells and adventitial progenitors that are indicative of neointimal stem-derived smooth muscle cells. This may have important implications for their use in examining vascular contractile and proliferative phenotypes in vitro.