Background & seeks Chronic liver disease is characterized by fibrosis that may progress to cirrhosis. Results Nod2 deficiency protected mice from cholestatic but not toxin-induced liver injury and fibrosis. Most notably the hepatic bile acid concentration was lower in Nod2?/? mice than wild type mice following bile duct ligation for Rabbit polyclonal to APE1. 3 weeks. In contrast to wild type mice Nod2?/? mice had increased urinary excretion of bile acids including sulfated bile acids and an upregulation of the bile acid efflux Glycitein transporters MRP2 and MRP4 in tubular epithelial cells of the kidney. MRP2 and MRP4 were downregulated by IL-1β Glycitein in a Nod2 dependent fashion. Conclusions Our findings indicate that Nod2 deficiency protects mice from cholestatic liver injury and fibrosis through enhancing renal excretion of bile acids that in turn contributes to decreased concentration of bile acids in the hepatocyte. results IL-1β treatment resulted in a marked reduction of MRP2 and MRP4 mRNA expression while MRP3 expression was not affected by IL-1β (Fig. 4E). To further substantiate our data IL-1β was administered to wild type mice and renal transporters were assessed. IL-1β inhibited gene expression of MRP2 and MRP4 but not of MRP3 (Fig. 4F). Opposite effects were observed in the liver (Suppl. Fig. 5A). Consistent with data Glycitein IL-1β induced MRP2 and MRP4 expression in primary mouse hepatocytes (Suppl. Fig 5B). Furthermore the effect of MDP on bile acid transporters in the kidney was determined in wild type and Nod2 deficient mice. Following administration of MDP mRNA levels Glycitein of MRP2 and MRP4 but not MRP3 were inhibited in wild type mice while no inhibitory effect was observed in Nod2 deficient mice (Fig. 4G). Blocking IL-1β signaling with the IL-1 receptor antagonist Anakinra abolished MDP-mediated inhibition of MRP2 and MRP4 (Fig. 4G). Blocking IL-1β signaling with Anakinra in bile duct ligated wild type mice significantly reduced collagen α1(I) expression in the liver (Fig. 4H left panel). Total hepatic bile acids were reduced by approximately 39% after Anakinra treatment (Fig. 4H right panel) which is similar to a 42% reduction in Nod2?/? mice as compared with wild type mice after bile duct ligation (Fig. 2A). Anakinra increased total (Fig. 4I left panel) but not sulfated urinary bile acid levels (Suppl. Fig. 6A). A significant induction of renal MRP2 and MRP4 gene expression was observed in bile duct ligated mice following Anakinra treatment (Fig. 4I right panel) while SULT2A1 expression in the kidney was not significantly altered (Suppl. Fig. 6B). These results suggest that Nod2 dependent IL-1β expression inhibits bile acid efflux transporters in the kidney. Fig. 4 Nod2-dependent IL-1β release decreases bile acid export transporter expression in renal tubular epithelial cells Discussion The cytotoxic effects of retained bile acids in cholestasis can be limited by decreasing bile acid synthesis by decreasing bile acid uptake or increasing bile acid efflux at either pole of the hepatocyte or by hydroxylation and sulfation of the retained bile acids to decrease their intrinsic hepatotoxicity. And indeed an increase in renal elimination of bile acids ameliorates cholestatic liver injury and fibrosis [18 19 In the OSTα?/? mouse hepatic toxicity and fibrosis following bile duct ligation is decreased by an increase in urinary bile acid excretion which is mediated by a reduction in the renal apical bile acid uptake transporter ASBT and an increase in the apical efflux transporters MRP2 and MRP4 . In this study we investigated the role of Nod2 in experimental models of liver fibrosis. Nod2 deficiency protected from cholestatic but not from liver toxin-induced fibrosis. This finding could not be explained by a cell protective effect on hepatocytes or a reduction in liver inflammation. We found that Nod2 deficiency results in an increased Glycitein renal excretion of bile acids which was mediated by an increased expression of MRP2 and MRP4 in kidney tubular epithelial cells. These changes were associated with lower IL-1β expression in the kidney of Nod2 deficient mice and a lower IL-1β mediated suppression of MRP2 and MRP4. More bile acids were eliminated via the urine with a subsequent decrease of the hepatic bile acid concentration causing less hepatocyte damage and fibrosis (Fig. 4J). Although macrophages are considered an important cell type for Nod2-induced IL-1β production [7 8 there was no evidence for IL-1β Glycitein synthesis by F4/80 positive macrophages in the kidney following bile duct.