Toll-like receptor 2 (TLR2) and -4 mediate signals from a great variety of bacterial gut products, giving the host a panel of microbe-recognizing receptors. Under homeostatic conditions, TLRs act as protective receptors of the intestinal epithelium. When homeostasis is disrupted in diseases such as inflammatory bowel disease, TLR2 and -4 are deregulated. Our study demonstrates, by using a trinitrobenzene sulfonic acid-induced colitis model of Crohn's disease, the constitutive expression and the up-regulation of TLR2 and -4 at messenger and protein levels in colon extracts, as well as in macrophages, dendritic cells, and lymphocytes from mesenteric lymphoid nodes. Vasoactive intestinal peptide (VIP) treatment induced a decrease of TLR2 and -4 expressions approaching ethanol control levels. Our results suggest that VIP modulation of TLR2 and -4 could be explained by two possible mechanisms. The first one would be the secondary reduction of TLR2 and -4 caused by the VIP-mediated decrease of inflammatory mediators such as interleukin-1beta and interferon-gamma, which synergize with bacterial products, contributing to the amplification of TLR presence in the intestine. The other possible mechanism would involve a VIP-mediated decrease of nuclear factor-kappaB, which would cause a direct down-regulation of TLR expression. In summary, the resultant physiological effect is the decrease of TLR2 and -4 expressions to homeostatic levels. Our study describes for the first time the role of a peptide present in the gut microenvironment as an effective modulator of the initial steps of acute inflammation, acting at local and systemic levels and leading to the restoration of the homeostasis lost after an established inflammatory/autoimmune disease.

Crohn's disease (CD) is a chronic inflammatory pathology of the intestine, characterized by diarrhea and weight loss. A healing effect of vasoactive intestinal peptide (VIP) in the murine model of CD based on 2,4,6-trinitrobencene sulfonic acid (TNBS) administration has been previously shown. The aim of this work was to analyze the expression of several mediators related to the inflammatory cascade in colitic and VIP-treated animals. With this aim, mice received either only TNBS or TNBS and VIP treatment on alternate days. cDNA microarray analysis and real-time polymerase chain reaction were performed on total mRNA from colon to study the expression of a battery of proinflammatory molecules such as the enzyme COX-2, the chemokines CX3CL1, CXCL12, CXCL13, CXCL14, CCR5, and CXCR2, and the cytokines interleukin (IL)-1beta, IL-12, IL-18, IL-10, interferon-gamma, and IL-4. TNBS administration induced the expression of all the proinflammatory mediators studied, whereas VIP treatment reduced their levels, increasing the anti-inflammatory IL-10 and the TH2 cytokine IL-4, explaining its beneficial action through inhibition of the inflammatory/TH1 response. These data describe not only the relation of several proinflammatory mediators to the development of TNBS colitis, reporting their time-course, but also show the beneficial action of VIP in this model through complete blockage of the inflammatory cascade and recovery of the colon homeostasis, providing a potential new alternative for CD therapy.

Vasoactive intestinal peptide (VIP) is a potent anti-inflammatory agent with immunoregulatory properties, skewing the immune response to a Th2 pattern of cytokine production. Here, we studied the effect of treatment with VIP in the development of diabetes in nonobese diabetic (NOD) mice, an animal model of type 1 diabetes. Mice treated with VIP from 4 weeks of age did not develop diabetes and showed milder insulitis than nontreated mice. The protective mechanism of VIP was associated with a reduction in the circulating levels of Th1 cytokines. In the pancreas of VIP-treated animals, regulatory T cell markers predominate, as indicated by the upregulation of FoxP3 and transforming growth factor-beta (TGF-beta), and the downregulation of the transcription factor, T-bet. These findings indicate that VIP restores tolerance to pancreatic islets by promoting the local differentiation and function of regulatory T cells.

IntroductionThe mammalian adult heart maintains a continuous, low cardiomyocyte turnover rate throughout life. Although many cardiac stem cell populations have been studied, the natural source for homeostatic repair has not yet been defined. The Polycomb protein BMI1 is the most representative marker of mouse adult stem cell systems. We have evaluated the relevance and role of cardiac Bmi1+ cells in cardiac physiological homeostasis.MethodsBmi1CreER/+;Rosa26YFP/+ (Bmi1-YFP) mice were used for lineage tracing strategy. After tamoxifen (TM) induction, yellow fluorescent protein (YFP) is expressed under the control of Rosa26 regulatory sequences in Bmi1+ cells. These cells and their progeny were tracked by FACS, immunofluorescence and RT-qPCR techniques from 5 days to 1 year.ResultsFACS analysis of non-cardiomyocyte compartment from TM-induced Bmi1-YFP mice showed a Bmi1+-expressing cardiac progenitor cell (Bmi1-CPC: B-CPC) population, SCA-1 antigen-positive (95.9 ± 0.4 %) that expresses some stemness-associated genes. B-CPC were also able to differentiate in vitro to the three main cardiac lineages. Pulse-chase analysis showed that B-CPC remained quite stable for extended periods (up to 1 year), which suggests that this Bmi1+ population contains cardiac progenitors with substantial self-maintenance potential. Specific immunostaining of Bmi1-YFP hearts serial sections 5 days post-TM induction indicated broad distribution of B-CPC, which were detected in variably sized clusters, although no YFP+ cardiomyocytes (CM) were detected at this time. Between 2 to 12 months after TM induction, YFP+ CM were clearly identified (3 ± 0.6 % to 6.7 ± 1.3 %) by immunohistochemistry of serial sections and by flow cytometry of total freshly isolated CM. B-CPC also contributed to endothelial and smooth muscle (SM) lineages in vivo.ConclusionsHigh Bmi1 expression identifies a non-cardiomyocyte resident cardiac population (B-CPC) that contributes to the main lineages of the heart in vitro and in vivo.Electronic supplementary materialThe online version of this article (doi:10.1186/s13287-015-0196-9) contains supplementary material, which is available to authorized users.