Project description:Background: Vitamin A is an essential nutrient that mammals obtain from dietary carotenoids and retinyl esters. Bile salts aid in the intestinal absorption of vitamin A, after which it is stored in the stellate cells of the liver. Vitamin A-metabolites, such as retinoic acids, are important for cell differentiation, proliferation and immunological processes, and act mostly by activating the nuclear receptors Retinoic Acid Receptor (RAR) and Retinoid Xreceptor (RXR). These receptors also perform key functions in the liver by regulating bile salt, lipid and glucose homeostasisas well is the intrahepatic immune response. Chronic liver diseases are characterized by hepatic vitamin A loss often leading to vitamin A deficiency (VAD). We found that VAD strongly aggravates liver damage in bile duct ligated (BDL) rats and in biliary atresia patients. Here, we performed a transcriptome analysis to characterize the cell biological processes in the rat liver that are disturbed in obstructive cholestasis under VADconditions. Methods: Rats were made VAD by omitting vitamin A from the diet for 16 weeks, followed by ligation of the common bile duct (BDL). 7 days later, the animals were sacrificed. During the 7 days of BDL, half of the animals received daily IP injections with retinyl-palmitate (vitamin A therapy). Bile salt concentrations and liver damage markers (AST/ALT) were determined in serum. Whole genome gene expression in liver tissue was analyzed with the Illumina platform RatRef-12 beadchip. False discovery rate (FDR) was set at a stringent 1%. Data were confirmed by quantitative real time PCR, Western blotting and/or histochemistry. Results: BDL induced dramatic liver damage in VAD rats with serum liver damage markers (AST/ALT)approximately 10-fold increased compared to BDL rats receiving a vitamin A-sufficient (VAS) diet. Only 20 genes were differentially expressed between sham-treated VAS and VAD rats and clustered in the vitamin A metabolism, immune response, carbohydrate and lipid homeostasis. In contrast, 1583 genes were differentially expressed between the BDL-treated VAS and VAD rats. The strongest effects were observed in genes from the vitamin A metabolism, immune response, collagen production and oxidative stress response. Importantly, all the liver damage markers were efficiently reversed by retinyl-palmitate therapy, which was mirrored by an almost complete normalisation of the transcript profile in VAS-BDL rats. Conclusions: We conclude that vitamin A deficiency dramatically aggravates liver damage caused by obstructive cholestasis. The transcriptome analysis suggests that a disturbed immune response may be the predominant causative factor.

Project description:Enterohemorrhagic Escherichia coli (EHEC), including serotype O157:H7, cause severe food-borne illness. On route to the human colon, they encounter and resist, numerous anti-microbial ingestion stresses. We hypothesize that these stresses cue EHEC to alter virulence properties. This study investigated the impact of bile salts on virulence properties and examined the genetic basis of the phenotypes. Established assays were used to examine adhesion to human epithelial cells, motility, verotoxin (VT) production and antimicrobial resistance with/without bile salt stress. Bacteria treated for 90 minute in DMEM plus 0.15% (w/v) bile salt mix demonstrated significantly enhanced adhesion to epithelial cells and resistance to several antibiotics but did not increase motility or VT production. To determine the genetic basis of these phenotypes a microarray experiment was conducted. EHEC strain 86-24, in mid-log phase of growth, were grown in DMEM pH 7.4 (control), or DMEM plus bile salt mix (0.15% w/v), for 90 minutes, statically at 37˚C, 5% CO2 prior to harvesting RNA for the microarray study. Four biological replicates were produced for each treatment. Microarray and gene expression analysis (semi-quantitative RT-PCR and beta-galactosidase reporter assays) of bile salt-treated EHEC revealed significant up-regulation of genes for lipid A modification, fimbriae, an efflux pump, and a two-component regulatory system relative to the bacteria grown in DMEM alone. This work points to several mechanisms that EHEC employs to resist the stresses of the human small intestine, notably efflux, antimicrobial resistance, and outer membrane alterations. Bile salts enhanced the virulence-related properties of increased adhesion and resistance to antimicrobials but not VT production or motility. This research contributes to our understanding of how EHEC senses and responds to host environmental signals and the mechanisms this pathogen uses to successfully colonize and infect the human host. Bacteria were grown in LB broth overnight with shaking, then subcultured into DMEM and grown statically at 37˚C, 5%CO2 to mid-log phase. Bacteria were then subjected to one of two 90 minute treatments: 1) Control: DMEM pH 7.4, or 2) Bile Salt Stress: DMEM pH 7.4 plus 0.15%, grown statically at 37˚C, 5%CO2.

Project description:Enterohemorrhagic Escherichia coli (EHEC), including serotype O157:H7, cause severe food-borne illness. On route to the human colon, they encounter and resist, numerous anti-microbial ingestion stresses. We hypothesize that these stresses cue EHEC to alter virulence properties. This study investigated the impact of bile salts on virulence properties and examined the genetic basis of the phenotypes. Established assays were used to examine adhesion to human epithelial cells, motility, verotoxin (VT) production and antimicrobial resistance with/without bile salt stress. Bacteria treated for 90 minute in DMEM plus 0.15% (w/v) bile salt mix demonstrated significantly enhanced adhesion to epithelial cells and resistance to several antibiotics but did not increase motility or VT production. To determine the genetic basis of these phenotypes a microarray experiment was conducted. EHEC strain 86-24, in mid-log phase of growth, were grown in DMEM pH 7.4 (control), or DMEM plus bile salt mix (0.15% w/v), for 90 minutes, statically at 37˚C, 5% CO2 prior to harvesting RNA for the microarray study. Four biological replicates were produced for each treatment. Microarray and gene expression analysis (semi-quantitative RT-PCR and beta-galactosidase reporter assays) of bile salt-treated EHEC revealed significant up-regulation of genes for lipid A modification, fimbriae, an efflux pump, and a two-component regulatory system relative to the bacteria grown in DMEM alone. This work points to several mechanisms that EHEC employs to resist the stresses of the human small intestine, notably efflux, antimicrobial resistance, and outer membrane alterations. Bile salts enhanced the virulence-related properties of increased adhesion and resistance to antimicrobials but not VT production or motility. This research contributes to our understanding of how EHEC senses and responds to host environmental signals and the mechanisms this pathogen uses to successfully colonize and infect the human host.

Dataset Information

Ena-DATASET-KCL-CS-01-04-2014-19:21:08:940-7 - samples

Publications

Massive gene amplification drives paediatric hepatocellular carcinoma caused by bile salt export pump deficiency.

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