Project description:Background and Aims: We have shown in several controlled rat and human infection studies that dietary calcium improves intestinal resistance and strengthens the mucosal barrier. Reinforcement of gut barrier function is also relevant for inflammatory bowel disease (IBD). Therefore, we investigated the effect of supplemental calcium on spontaneous colitis development in HLA-B27 transgenic rats, an experimental animal model of IBD. Methods: HLA-B27 transgenic rats were fed a purified high-fat diet containing either a low or high calcium content (30 and 120 mmol CaHPO4/kg diet, respectively) for almost 7 weeks. Inert chromium ethylenediamine-tetraacetic acid (CrEDTA) was added to the diets to quantify intestinal permeability by measuring urinary CrEDTA excretion. Relative fecal dry-weight was determined to quantify diarrhea. Colonic inflammation was determined histologically, and by measuring mucosal interleukin-1M-NM-2. In addition, colonic mucosal gene expression of individual rats was analyzed, using whole genome microarrays. Interesting results were verified by Q-PCR. Results: The high-calcium diet significantly prevented the increase in intestinal permeability and diarrhea with time in HLA-B27 rats developing colitis as compared to the low-calcium group. The histological colitis score and mucosal interleukin-1M-NM-2 levels were lower in high-calcium fed rats. Supplemental calcium prevented the colitis-induced increase in the expression of extracellular matrix remodeling genes (e.g. matrix metalloproteinases, procollagens and fibronectin), which was confirmed by Q-PCR. Conclusions: Dietary calcium inhibits colitis development in HLA-B27 transgenic rats. Calcium prevents the colitis-related increase in intestinal permeability, diminishes diarrhea, and lowers the inflammatory response in the mucosa, resulting in less extracellular matrix breakdown. Keywords: nutritional intervention Female HLA-B27/M-NM-22-microglobulin transgenic rats on an inbred Fisher 344 background (n=8 in experimental group and n=9 in control group) (Taconic Farms, Inc, Germantown, NY), 8-10 weeks old and with a mean body weight of 128 g at the start of the experiment, were housed individually in metabolic cages. Animals were kept in a temperature- and humidity-controlled environment and in a 12-h light-dark cycle. Rats were fed a purified M-bM-^@M-^XhumanizedM-bM-^@M-^Y Western diet which contained in the control situation (per kg): 200 g acid casein, 326 g corn starch, 174 g glucose, 160 g palm oil, 40 g corn oil, 50 g cellulose and 5.16 g CaHPO4.2H2O (corresponding to 30 mmol calcium/kg diet; Sigma-Aldrich, St Louis, MO). Vitamins and minerals (other than calcium) were added to all diets according to the recommendations of the American Institute of Nutrition 1993.17 The experimental diet contained more calcium (120 mmol calcium/kg diet) at the expense of glucose. All samples were individually labelled and hybridized (Cy5). Equal amounts of Cy3 cRNA of all animals were pooled to serve as standard reference pool.

Project description:Background: Inflammatory bowel diseases (IBD) may be caused in part by aberrant immune responses to commensal intestinal microbes including Bacteroides thetaiotaomicron (B.theta). Healthy, germ-free HLA-B27 transgenic (Tg) rats develop chronic colitis when colonized with complex gut commensal bacteria whereas non-transgenic (nTg) rats remain disease-free. However, the role of B.theta, a well-characterized anaerobic commensal bacterium, in causing disease in Tg rats is unknown nor is much known about how microbes respond to host inflammation. Methods: Tg and nTg rats were monoassociated with a human isolate of B.theta. Colonic inflammation was quantified by blinded histological scoring and real-time RT-PCR assays of pro-inflammatory cytokines. Cecal bacterial concentrations were measured by quantitative plating. Whole genome transcriptional profiling of B.theta recovered from ceca was performed using custom GeneChips and data analyzed using dChip, Significance Analysis of Microarrays, and Gene Set Enrichment Analysis (GSEA) software. Results: B.theta monoassociated Tg rats had significantly more colonic inflammation and increased colonic levels of pro-inflammatory cytokine mRNAs compared to nTg controls. Transcriptional profiles of cecal B.theta were significantly different in Tg vs. nTg rats. GSEA revealed that the Gene Ontology molecular function of receptor activity, which is comprised mainly of genes that encode nutrient binding proteins, was significantly enriched with genes upregulated in B.theta from Tg rats. KEGG canonical pathways of ribosome, oxidative phosphorylation, pyrimidine metabolism, purine metabolism, peptidoglycan biosynthesis, and metabolism were significantly enriched with genes downregulated in B.theta from Tg rats. Numbers of viable bacteria/gram cecal contents in Tg vs. nTg rats were not significantly different. Conclusions: B.theta induces mild colitis in HLA-B27 Tg rats, which is associated with changes in the expression of microbial metabolic and nutrient binding pathways, but no difference in concentrations of luminal bacteria. Mechanistic studies of differentially expressed B.theta genes may reveal novel pathways that contribute to IBD. The fully-sequenced human fecal isolate of B.theta (VPI-5482) was grown on Brain-Heart Infusion (BHI) agar and in BHI broth under strict anaerobic conditions using pre-reduced media. Adult germ-free HLA-B27/b2 microglobulin transgenic rats and adult germ-free non-transgenic littermate were monoassociated with B.theta for six weeks in gnotobiotic isolators at the National Gnotobiotic Rodent Resource Center at UNC Chapel Hill. Bacterial RNA was isolated from rat cecal contents and hybridized on Affymetrix human gut microbiota community GeneChip.

Project description:Background The striking association of HLA-B27 with spondyloarthritis (SpA) has been known for 50 years. However, its pathophysiological significance remains incompletely understood. In the HLA-B27/human-β2 microglobulin (hβ2m) transgenic rat (B27 rat) that spontaneously develops inflammatory phenotype characteristic of SpA, myeloid cells expressing the HLA-B27/h2m transgene are critical for disease induction and functionally impaired. Recently, we produced HLA-B27/hβ2m transgenic Drosophila to study non-canonical effects of HLA-B27. We showed that HLA-B27/h2m expressed in Drosophila wing imaginal disc deregulated BMP pathway by interacting physically with the type I bone morphogenetic protein (BMP) receptor (BMPR1) Saxophone (Sax), leading to a loss of crossveins. Methods Genetic interaction was studied between the activin/TGF pathway and HLA-B27/hβ2m in transgenic Drosophila wings. The HLA-B27-bound peptidome was characterized in wing imaginal discs from transgenic Drosophila by high-performance liquid chromatography and mass spectrometry of the peptide fraction eluted from affinity purified HLA-B27. In mesenteric lymph node (mLN) T cells from B27 rats, physical interaction between HLA-B27 and activin receptor-like kinase-2 (ALK2), ALK3 and ALK5 BMPR1s was assessed by proximity ligation assay and phosphorylation of SMADs and proteins of the non-canonical BMP/TGF pathway induced by its ligands was assessed by flow cytometry. Transcript level of several target genes of the TGF pathway was evaluated by real-time quantitative polymerase chain reaction in mLN subsets of T cells from B27 and control nontransgenic rats, with and without treatment by TGF. Results We showed that, in addition to the BMP pathway, inappropriate signaling through the activin/transforming growth factor β (TGFβ) pathway, involving Baboon (Babo) BMPR1, also contributed to the crossveinless wing phenotype. We identified a set of peptides bound to HLA-B27 with canonical binding motif in HLA-B27/hβ2m transgenic Drosophila wing imaginal disc, despite the lack of peptide loading complex. We then demonstrated specific physical interaction, between HLA-B27/h2m and both mammalian orthologues of Sax and Babo, i.e. ALK2 and ALK5 (i.e. TGF receptor I), in the mLN cells from B27 rat. The magnitude of phosphorylation of SMAD2/3 in response to TGFβ1 was increased in T cells from adult and premorbid B27 rats, showing evidence for deregulated TGF pathway. Accordingly, expression of several target genes of the pathway was increased in T cells from B27 rats, in basal conditions and/or after TGFexposure, including Foxp3, Rorc, Runx1 and Maf. Interestingly. Tgfb1 expression was reduced in naïve T cells from B27 rats, even premorbid, an observation consistent with a pro-inflammatory pattern. Conclusions This study highlights a complex interplay between HLA-B27 and the BMP/TGFβ pathways in both Drosophila and B27 rat. Given the importance of the TGF pathway in CD4+ T cells differenciation and regulation, the disturbance caused by HLA-B27 could contribute to the abnormal expansion of pro-inflammatory T helper 17 cells and the altered regulatory T cell phenotype observed in B27 rat.

Project description:Background: Inflammatory bowel diseases (IBD) may be caused in part by aberrant immune responses to commensal intestinal microbes including Bacteroides thetaiotaomicron (B.theta). Healthy, germ-free HLA-B27 transgenic (Tg) rats develop chronic colitis when colonized with complex gut commensal bacteria whereas non-transgenic (nTg) rats remain disease-free. However, the role of B.theta, a well-characterized anaerobic commensal bacterium, in causing disease in Tg rats is unknown nor is much known about how microbes respond to host inflammation. Methods: Tg and nTg rats were monoassociated with a human isolate of B.theta. Colonic inflammation was quantified by blinded histological scoring and real-time RT-PCR assays of pro-inflammatory cytokines. Cecal bacterial concentrations were measured by quantitative plating. Whole genome transcriptional profiling of B.theta recovered from ceca was performed using custom GeneChips and data analyzed using dChip, Significance Analysis of Microarrays, and Gene Set Enrichment Analysis (GSEA) software. Results: B.theta monoassociated Tg rats had significantly more colonic inflammation and increased colonic levels of pro-inflammatory cytokine mRNAs compared to nTg controls. Transcriptional profiles of cecal B.theta were significantly different in Tg vs. nTg rats. GSEA revealed that the Gene Ontology molecular function of receptor activity, which is comprised mainly of genes that encode nutrient binding proteins, was significantly enriched with genes upregulated in B.theta from Tg rats. KEGG canonical pathways of ribosome, oxidative phosphorylation, pyrimidine metabolism, purine metabolism, peptidoglycan biosynthesis, and metabolism were significantly enriched with genes downregulated in B.theta from Tg rats. Numbers of viable bacteria/gram cecal contents in Tg vs. nTg rats were not significantly different. Conclusions: B.theta induces mild colitis in HLA-B27 Tg rats, which is associated with changes in the expression of microbial metabolic and nutrient binding pathways, but no difference in concentrations of luminal bacteria. Mechanistic studies of differentially expressed B.theta genes may reveal novel pathways that contribute to IBD.

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Dietary calcium inhibits colitis development in HLA-B27 transgenic rats

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