6B and Supporting Fig. 6A), strengthening the idea that TGR5 may control ionic composition of bile after PH. In agreement with these data, biliary pH, although similar in WT and TGR5 KO mice before PH, was maintained or slightly increased in WT, but significantly fell in TGR5 KO mice after PH (Fig. 6C). Of note, the defect in ion secretion in bile observed in TGR5 KO mice after PH was not secondary to cholestasis, because BDL (at 48 hours) did not inhibit, but even increased slightly, bile

flow and ionic output in WT, but not in TGR5 KO, mice (Supporting Fig. 6B). Biliary BA concentrations and outputs were not significantly different in WT and TGR5 KO mice, both before and after PH, suggesting that bile flow deregulation in TGR5 KO mice did not result from a reduced BA flow rate (Supporting Fig. 6C). Together, these data strongly suggest that TGR5-mediated signals may control adaptive ion transport in bile under circumstances Paclitaxel order in which BA overload occurs, such as after PH and BDL. Although we did not find any

significant difference in the basal and post-PH mRNA expression of cystic fibrosis transmembrane conductance regulator (CFTR) and anion exchange isoform 2 (AE2) in livers and gallbladders from WT and TGR5 KO mice (Supporting Fig. 7A and data not shown), CFTR mRNA was significantly less up-regulated, both in liver and gallbladders from TGR5 KO, as compared to WT, mice after BDL (Supporting Fig. 7B,C). However, TGR5 may regulate ion exchange in bile at post-translational steps, through cAMP-mediated mechanisms, as proposed earlier.[15, 23] To further understand the mechanisms involved in selleck compound library excessive BA accumulation in TGR5 KO mice after PH, BDL, or upon CA feeding, we explored BA efflux at the kidney level, because TGR5 is significantly expressed in this organ (as reported previously[7, 8] and Supporting Fig. 7F). Because a significant increase in BA

efflux in urine was observed in WT, but not in TGR5 KO, mice after PH, BDL, or a 1% CA-enriched diet (Fig. 7A,B), we studied the expression of renal BA transporter genes in those experimental settings. Although multidrug resistance-related protein MRP2, MRP3, MRP4, and OST-β mRNAs were significantly up-regulated after PH in WT, MRP2 and MRP4 genes were not, or significantly less, induced in TGR5 KO kidneys (Fig. 7C,D, and Supporting Fig. find more 7D-E). These data are in line with the observed weaker BA efflux in urine from TGR5 KO mice, because MRP2 and MRP4 have been reported to transport BA into urine in kidney proximal tubule epithelial cells.[24] In line with these data, western blotting analysis of renal MRP2 revealed a weaker expression in TGR5 KO than in WT mice 48 hours after PH (Fig. 7E). Finally, treatment with the natural TGR5 ligand, oleanolic acid (OA),[25] elicited significantly stronger BA elimination in urines in WT than in TGR5 KO mice upon a 1% CA-enriched diet (Fig. 7B).