http://hdl.handle.net/10468/247 2013-05-22T09:42:42Z 2013-05-22T09:42:42Z Murphy, Carola T. Hall, Lindsay J. Hurley, Grainne Quinlan, Aoife MacSharry, John Shanahan, Fergus Nally, Kenneth Melgar, Silvia http://hdl.handle.net/10468/639 2012-11-22T03:00:10Z 2012-08-01T00:00:00Z

The spingosine-1-phosphate analogue FTY720 impairs mucosal immunity and clearance of the enteric pathogen Citrobacter rodentium Murphy, Carola T.; Hall, Lindsay J.; Hurley, Grainne; Quinlan, Aoife; MacSharry, John; Shanahan, Fergus; Nally, Kenneth; Melgar, Silvia The sphingosine-1-phosphate (S1P) analogue, FTY720, is therapeutically efficacious in multiple sclerosis and in the prevention of transplant rejection. It prevents migration of lymphocytes to sites of pathology by trapping them within the peripheral lymph nodes, the mesenteric lymph nodes (MLNs) and Peyer's patches. However, evidence suggests that its clinical use may increase the risk of mucosal infections. We investigated the impact of FTY720 treatment on susceptibility to gastrointestinal infection with the mouse enteric pathogen, Citrobacter rodentium (C. rodentium). This attaching and effacing bacterium induces a transient bacterial colitis in immunocompetent mice, which resembles human infection with pathogenic Escherichia coli. FTY720 treatment induced peripheral blood lymphopenia, trapped lymphocytes in the MLNs and prevented clearance of bacteria when mice were infected with luciferase-tagged C. rodentium. FTY720-treated C. rodentium-infected mice had enhanced colonic inflammation, with significantly higher colon mass, colonhistopathology and neutrophil infiltration, when compared with vehicle-infected animals. In addition, FTY720-treated infected mice had significantly lower numbers of colonic dendritic cells, macrophages and T cells. Gene expression analysis demonstrated that FTY720-treated infected mice had an impaired innate immuneresponse and a blunted mucosal adaptive immune response including Th1 cytokines. The data demonstrate that the S1P analogue, FTY720, adversely affects the immune response and clearance of C. rodentium.

2012-08-01T00:00:00Z Schellekens, Harriët Clarke, Gerard Jeffery, Ian B. Dinan, Timothy G. Cryan, John F. http://hdl.handle.net/10468/844 2012-12-13T03:00:10Z 2012-03-20T00:00:00Z

Dynamic 5-HT2C receptor editing in a mouse model of obesity Schellekens, Harriët; Clarke, Gerard; Jeffery, Ian B.; Dinan, Timothy G.; Cryan, John F. Bartolomucci, Alessandro The central serotonergic signalling system has been shown to play an important role in appetite control and the regulation of food intake. Serotonin exerts its anorectic effects mainly through the 5-HT1B, 5-HT2C and 5-HT6 receptors and these are therefore receiving increasing attention as principal pharmacotherapeutic targets for the treatment of obesity. The 5-HT2C receptor has the distinctive ability to be modified by posttranscriptional RNA editing on 5 nucleotide positions (A, B, C, D, E), having an overall decreased receptor function. Recently, it has been shown that feeding behaviour and fat mass are altered when the 5-HT2C receptor RNA is fully edited, suggesting a potential role for 5-HT2C editing in obesity. The present studies investigate the expression of serotonin receptors involved in central regulation of food intake, appetite and energy expenditure, with particular focus on the level of 5-HT2C receptor editing. Using a leptin-deficient mouse model of obesity (ob/ob), we show increased hypothalamic 5-HT1A receptor expression as well as increased hippocampal 5-HT1A, 5-HT1B, and 5-HT6 receptor mRNA expression in obese mice compared to lean control mice. An increase in full-length 5-HT2C expression, depending on time of day, as well as differences in 5-HT2C receptor editing were found, independent of changes in total 5-HT2C receptor mRNA expression. This suggests that a dynamic regulation exists of the appetite-suppressing effects of the 5-HT2C receptor in both the hypothalamus and the hippocampus in the ob/ob mice model of obesity. The differential 5-HT1A, 5-HT1B and 5-HT6 receptor expression and altered 5-HT2C receptor editing profile reported here is poised to have important consequences for the development of novel anti-obesity therapies.

2012-03-20T00:00:00Z McLaughlin, Heather P. Xiao, Qiaobin Rea, Rosemarie B. Pi, Hualiang Casey, Pat G. Darby, Trevor Charbit, Alain Sleator, Roy D. Joyce, Susan A. Cowart, Richard E. Hill, Colin Klebba, Phillip E. Gahan, Cormac G. http://hdl.handle.net/10468/840 2012-12-11T03:00:10Z 2012-02-21T00:00:00Z

A putative p-type ATPase required for virulence and resistance to haem toxicity in Listeria monocytogenes McLaughlin, Heather P.; Xiao, Qiaobin; Rea, Rosemarie B.; Pi, Hualiang; Casey, Pat G.; Darby, Trevor; Charbit, Alain; Sleator, Roy D.; Joyce, Susan A.; Cowart, Richard E.; Hill, Colin; Klebba, Phillip E.; Gahan, Cormac G. Cornelis, Pierre Regulation of iron homeostasis in many pathogens is principally mediated by the ferric uptake regulator, Fur. Since acquisition of iron from the host is essential for the intracellular pathogen Listeria monocytogenes, we predicted the existence of Fur-regulated systems that support infection. We examined the contribution of nine Fur-regulated loci to the pathogenicity of L. monocytogenes in a murine model of infection. While mutating the majority of the genes failed to affect virulence, three mutants exhibited a significantly compromised virulence potential. Most striking was the role of the membrane protein we designate FrvA (Fur regulated virulence factor A; encoded by frvA [lmo0641]), which is absolutely required for the systemic phase of infection in mice and also for virulence in an alternative infection model, the Wax Moth Galleria mellonella. Further analysis of the DfrvA mutant revealed poor growth in iron deficient media and inhibition of growth by micromolar concentrations of haem or haemoglobin, a phenotype which may contribute to the attenuated growth of this mutant during infection. Uptake studies indicated that the DfrvA mutant is unaffected in the uptake of ferric citrate but demonstrates a significant increase in uptake of haem and haemin. The data suggest a potential role for FrvA as a haem exporter that functions, at least in part, to protect the cell against the potential toxicity of free haem.

2012-02-21T00:00:00Z Riboulet-Bisson, Eliette Sturme, Mark H. J. Jeffery, Ian B. O'Donnell, Michelle M. Neville, B. Anne Forde, Brian M. Claesson, Marcus J. Harris, Hugh Gardiner, Gillian E. Casey, Patrick G. Lawlor, Peadar G. O'Toole, Paul W. Ross, R. Paul http://hdl.handle.net/10468/827 2012-11-30T03:00:13Z 2012-02-17T00:00:00Z

Effect of Lactobacillus salivarius bacteriocin Abp118 on the mouse and pig intestinal microbiota Riboulet-Bisson, Eliette; Sturme, Mark H. J.; Jeffery, Ian B.; O'Donnell, Michelle M.; Neville, B. Anne; Forde, Brian M.; Claesson, Marcus J.; Harris, Hugh; Gardiner, Gillian E.; Casey, Patrick G.; Lawlor, Peadar G.; O'Toole, Paul W.; Ross, R. Paul Dias-Neto, Emmanuel Lactobacilli are Gram-positive bacteria that are a subdominant element in the human gastrointestinal microbiota, and which are commonly used in the food industry. Some lactobacilli are considered probiotic, and have been associated with health benefits. However, there is very little culture-independent information on how consumed probiotic microorganisms might affect the entire intestinal microbiota. We therefore studied the impact of the administration of Lactobacillus salivarius UCC118, a microorganism well characterized for its probiotic properties, on the composition of the intestinal microbiota in two model animals. UCC118 has anti-infective activity due to production of the bacteriocin Abp118, a broad-spectrum class IIb bacteriocin, which we hypothesized could impact the microbiota. Mice and pigs were administered wild-type (WT) L. salivarius UCC118 cells, or a mutant lacking bacteriocin production. The microbiota composition was determined by pyrosequencing of 16S rRNA gene amplicons from faeces. The data show that L. salivarius UCC118 administration had no significant effect on proportions of major phyla comprising the mouse microbiota, whether the strain was producing bacteriocin or not. However, L. salivarius UCC118 WT administration led to a significant decrease in Spirochaetes levels, the third major phylum in the untreated pig microbiota. In both pigs and mice, L. salivarius UCC118 administration had an effect on Firmicutes genus members. This effect was not observed when the mutant strain was administered, and was thus associated with bacteriocin production. Surprisingly, in both models, L. salivarius UCC118 administration and production of Abp118 had an effect on Gram-negative microorganisms, even though Abp118 is normally not active in vitro against this group of microorganisms. Thus L. salivarius UCC118 administration has a significant but subtle impact on mouse and pig microbiota, by a mechanism that seems at least partially bacteriocin-dependent.

2012-02-17T00:00:00Z