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.

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:The hepatocyte growth factor (HGF)/c-Met signaling pathway is known to mediate vascularization. We have previously demonstrated that expression of a human HGF transgene in the small airways produced mice (HGF TG) that were more susceptible to the tobacco carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). We also have observed that HGF TG mice display significantly enhanced vascularization in the lungs that increases over time compared to wild-type (WT) littermates. To analyze which genes might contribute to increased vascularization from HGF overexpression in the airways, RNA and protein were isolated from whole lungs of individual HGF TG and WT adult mice. We profiled the mRNA expression of several hundred genes representative of six biological pathways involved in transformation, angiogenesis, and tumorigenesis using two commercial microarrays. Significant changes in expression over a 1.5-fold boundary were also observed in lung tumors derived from NNK-treated HGF TG mice. Lung tumors were induced by exposing mice to four weekly i.p. injections of 3mg NNK (15μg/μl) over 2 weeks. Whole lungs from control untreated animals were dissected after sacrifice at 10, 20, or 40 wks of age, and NNK induced lung tumors were dissected from the animals at 20 or 40 weeks of age. Total RNA was extracted from whole lung or isolated tumors from HGF TG or WT mice using TRIzol reagent and the Array Grade Total RNA Isolation Kit. The cDNA was generated and labeled using the TrueLabeling-AMP Linear RNA Amplication Kit. RNA was analyzed from 28 mice in total. The angiogenesis array was used to analyze 10 samples taken from 40 week old mice (HGF TG untreated [n=4], WT untreated [n=4], HGF TG NNK treated [n=1], WT NNK treated [n=1]) and 6 samples from 20 week old mice (HGF TG untreated [n=2], WT untreated [n=2], HGF TG NNK treated [n=1], WT NNK treated [n=1]). The cancer gene array was used to analyze 8 samples taken from 40 week old mice (HGF TG untreated [n=2], WT untreated [n=2], HGF TG NNK treated [n=2], WT NNK treated [n=2]) and 4 samples from 20 week old mice (HGF TG untreated [n=2], WT untreated [n=2]).

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