Transcription of Fgf15 in ileal enterocytes is trans-activated by the nuclear receptor FXR (Farnesoid X Receptor), upon its activation by bile acids [7]. Expression of the FXR gene (Nr1h4) was not affected by Salmonella, regardless of the intestinal bacterial burden (data not shown). In contrast, the expression of other known intestinal FXR target genes, Fabp6

(Fatty acid binding protein 6), Nr0b2 (Small heterodimer partner, Shp) [26] and Osta (Organic solute transporter alpha) [27], was decreased by Salmonella infection see more in a pattern similar to that of Fgf15 with maximal, significant drops in highly-infected animals (Figure 3A). This suggests that activation of gene expression mediated by FXR is impaired during infection. Figure 3 Infection with Salmonella decreases the expression of FXR-target genes in the ileum.

(A) Relative levels of Fabp6, Nr0b2 and Osta transcripts in the ileum of mice orally infected with Salmonella typhimurium SL1344. Animals were arbitrarily grouped into low, medium and high infection levels (100-103, 104-105 and >106 cfu/mg, respectively roughly corresponding to 72, 96 and 120 hours post-infection; UI: uninfected). (B) Fgf15 transcript levels in the ilea of uninfected mice fed 5% cholestyramine diet. Data by qPCR, **p < 0.01; ***p < 0.001; ****p < 0.0001. Colonization of the PX-478 solubility dmso hepatobiliary system by Salmonella induces local pathological damage and inflammation [22], which can result in impaired synthesis buy Staurosporine of bile acids and inflammation-induced cholestasis [28]. This may in turn, compromise intestinal FXR activation and lead to inhibition of Fgf15, Fabp6, Nr0b2

and Osta expression. To test whether the depletion of bile acids would be sufficient to decrease Fgf15 expression in vivo, we fed uninfected C57BL/6 mice with a diet supplemented with the bile acid sequestrant cholestyramine. As shown in Figure 3B mice fed with cholestyramine did have significantly lower levels of Fgf15 transcripts than mice fed with a normal diet. Second, we evaluated the effects of Salmonella infection in bile production and flow. Gallbladder bile volumes were measured before and during infection; a significant reduction in volume was observed 24 hours post-infection, which did not improved over the next 4 days (Figure 4A). An expression analysis of hepatic genes buy H 89 involved in bile synthesis and secretion (Figure 4B), showed striking reductions in the transcript levels of the major transporters of bile acid and cholesterol (Abcb11, Slc10a1, Abcb1a, Abcg5 and Abcg8) and the induction of several genes involved in rescue from cholestasis. The mRNA (Figure 5A) and protein levels (Figure 5B) of CYP7A1, the rate-limiting enzyme in the neutral pathway of bile acids synthesis, were decreased by infection.