These data demonstrate that IL-17 activates RhoA/Rho-kinase leading to endothelial dysfunction and hypertension. Inhibitors of IL-17 or Rho-kinase may prove useful as anti-hypertensive drugs in IL-17-associated autoimmune diseases.

Rat and human biliary epithelium is morphologically and functionally heterogeneous. Since no information exists on the heterogeneity of the murine intrahepatic biliary epithelium, and with increased usage of transgenic mouse models to study liver disease pathogenesis, we sought to evaluate the morphological, secretory and proliferative phenotypes of small and large bile ducts and purified cholangiocytes in normal and cholestatic mouse models.MethodsFor morphometry, normal and BDL mouse livers (C57/BL6) were dissected into blocks of 2-4 μm2, embedded in paraffin, sectioned, and stained with H&E. Sizes of bile ducts and cholangiocytes were evaluated by using SigmaScan to measure the diameters of bile ducts and cholangiocytes. In small and large normal and BDL cholangiocytes, we evaluated the expression of cholangiocyte specific markers, keratin-19 (KRT19), secretin receptor (SR), cystic fibrosis transmembrane conductance regulator (CFTR), and chloride bicarbonate anion exchanger 2 (Cl-/HCO-3 AE2) by immunofluorescence and western blot; and intracellular cAMP levels and chloride efflux in response to secretin (100 nM). To evaluate cholangiocyte proliferative responses after bile duct ligation (BDL), small and large cholangiocytes were isolated from BDL mice. The proliferation status was determined by analysis of the cell cycle by FACS and bile duct mass was determined by the number of KRT19-positive bile ducts in liver sections.ResultsIn situ morphometry established that the biliary epithelium of mice is morphologically heterogeneous, which smaller cholangiocyte lining smaller bile ducts and larger cholangiocytes lining larger ducts. Both small and large cholangiocytes express KRT19 and only large cholangiocytes from normal and BDL mice express SR, CFTR, and Cl-/HCO-3 exchanger and respond to secretin with increased cAMP levels and chloride efflux. Following BDL, only large mouse cholangiocytes proliferate.ConclusionSimilar to rats, mouse intrahepatic biliary epithelium is morphologically, and functionally heterogeneous. The mouse is a suitable model for defining the heterogeneity of the biliary tree.

During bile duct ligation (BDL), the growth of large cholangiocytes is regulated by the cyclic adenosine monophosphate (cAMP)/extracellular signal-regulated kinase 1/2 (ERK1/ 2) pathway and is closely associated with increased secretin receptor (SR) expression. Although it has been suggested that SR modulates cholangiocyte growth, direct evidence for secretin-dependent proliferation is lacking. SR wild-type (WT) (SR) mice underwent sham surgery or BDL for 3 or 7 days. We evaluated SR expression, cholangiocyte proliferation, and apoptosis in liver sections and proliferating cell nuclear antigen (PCNA) protein expression and ERK1/2 phosphorylation in purified large cholangiocytes from WT and SR 2/2 BDL mice. Normal WT mice were treated with secretin (2.5 nmoles/kg/day by way of osmotic minipumps for 1 week), and biliary mass was evaluated. Small and large cholangiocytes were used to evaluate the in vitro effect of secretin (100 nM) on proliferation, protein kinase A (PKA) activity, and ERK1/2 phosphorylation. SR expression was also stably knocked down by short hairpin RNA, and basal and secretin-stimulated cAMP levels (a functional index of biliary growth) and proliferation were determined. SR was expressed by large cholangiocytes. Knockout of SR significantly decreased large cholangiocyte growth induced by BDL, which was associated with enhanced apoptosis. PCNA expression and ERK1/2 phosphorylation were decreased in large cholangiocytes from SR 2/2 BDL compared with WT BDL mice. In vivo administration of secretin to normal WT mice increased ductal mass. In vitro, secretin increased proliferation, PKA activity, and ERK1/2 phosphorylation of large cholangiocytes that was blocked by PKA and mitogen-activated protein kinase kinase inhibitors. Stable knockdown of SR expression reduced basal cholangiocyte proliferation. SR is an important trophic regulator sustaining biliary growth. Conclusion: The current study provides strong support for the potential use of secretin as a therapy for ductopenic liver diseases. (HEPATO-LOGY 2010;52:204-214)