Knockout of the neurokinin-1 receptor reduces cholangiocyte proliferation in bile duct-ligated mice

Glaser S, Gaudio E, Renzi A, Mancinelli R, Ueno Y, Venter J, White M, Kopriva S, Chiasson V, DeMorrow S, Francis H, Meng F, Marzioni M, Franchitto A, Alvaro D, Supowit S, DiPette DJ, Onori P, Alpini G. Knockout of the neurokinin-1 receptor reduces cholangiocyte proliferation in bile duct-ligated mice. Am J Physiol Gastrointest Liver Physiol 301: G297-G305, 2011. First published May 19, 2011; doi:10.1152/ajpgi.00418.2010.-In bile duct-ligated (BDL) rats, cholangiocyte proliferation is regulated by neuroendocrine factors such as alpha-calcitonin gene-related peptide (alpha-CGRP). There is no evidence that the sensory neuropeptide substance P (SP) regulates cholangiocyte hyperplasia. Wild-type (WT, (+/+)) and NK-1 receptor (NK-1R) knockout (NK-1R(-/-)) mice underwent sham or BDL for 1 wk. Then we evaluated 1) NK-1R expression, transaminases, and bilirubin serum levels; 2) necrosis, hepatocyte apoptosis and steatosis, and the number of cholangiocytes positive by CK-19 and terminal deoxynucleotidyl transferase biotin-dUTP nick-end labeling in liver sections; 3) mRNA expression for collagen 1 alpha and alpha-smooth muscle (alpha-SMA) actin in total liver samples; and 4) PCNA expression and PKA phosphorylation in cholangiocytes. In cholangiocyte lines, we determined the effects of SP on cAMP and D-myo-inositol 1,4,5-trisphosphate levels, proliferation, and PKA phosphorylation. Cholangiocytes express NK-1R with expression being upregulated following BDL. In normal NK-1R(-/-) mice, there was higher hepatocyte apoptosis and scattered hepatocyte steatosis compared with controls. In NK-1R (-/-) BDL mice, there was a decrease in serum transaminases and bilirubin levels and the number of CK-19-positive cholangiocytes and enhanced biliary apoptosis compared with controls. In total liver samples, the expression of collagen 1 alpha and alpha-SMA increased in BDL compared with normal mice and decreased in BDL NK-1R(-/-) compared with BDL mice. In cholangiocytes from BDL NK-1R (-/-) mice there was decreased PCNA expression and PKA phosphorylation. In vitro, SP increased cAMP levels, proliferation, and PKA phosphorylation of cholangiocytes. Targeting of NK-1R may be important in the inhibition of biliary hyperplasia in cholangiopathies.