Neuropeptide Y inhibits biliary hyperplasia of cholestatic rats by paracrine and autocrine mechanisms

Sharon Demorrow,Julie Venter,Antonio Franchitto,Gabriel Frampton,Fanyin Meng,Matthew Quinn,Eugenio Gaudio,Paolo Onori,Gianfranco Alpini,Dinorah Leyva-Illades,Heather Francis,Shannon Glaser,Kelly Mcdaniel,Romina Mancinelli,Hae Yong Pae

doi:10.1152/ajpgi.00140.2013

Abstract

Neuropeptide Y (NPY) exerts its functions through six subtypes of receptors (Y₁-Y₆). Biliary homeostasis is regulated by several factors through autocrine/paracrine signaling. NPY inhibits cholangiocarcinoma growth; however, no information exists regarding the autocrine/paracrine role of NPY on biliary hyperplasia during cholestasis. The aims of this study were to determine: 1) the expression of NPY and Y₁-Y₅ in cholangiocytes and 2) the paracrine/autocrine effects of NPY on cholangiocyte proliferation. Normal or bile duct ligation (BDL) rats were treated with NPY, neutralizing anti-NPY antibody, or vehicle for 7 days. NPY and NPY receptor (NPYR) expression was assessed in liver sections and isolated cholangiocytes. NPY secretion was assessed in serum and bile from normal and BDL rats, as well as supernatants from normal and BDL cholangiocytes and normal rat cholangiocyte cell line [intrahepatic normal cholangiocyte culture (NRICC)]. We evaluated intrahepatic bile ductal mass (IBDM) in liver sections and proliferation in cholangiocytes. With the use of NRICC, the effects of NPY or anti-NPY antibody on cholangiocyte proliferation were determined. The expression of NPY and all NPYR were increased after BDL. NPY levels were lower in serum and cholangiocyte supernatant from BDL compared with normal rats. NPY secretion from NRICC was detected at both the basolateral and apical domains. Chronic NPY treatment decreased proliferating cellular nuclear antigen (PCNA) expression and IBDM in BDL rats. Administration of anti-NPY antibody to BDL rats increased cholangiocyte proliferation and IBDM. NPY treatment of NRICC decreased PCNA expression and increased the cell cycle arrest, whereas treatment with anti-NPY antibody increased proliferation. Therapies targeting NPY-mediated signaling may prove beneficial for the treatment of cholangiopathies.

Highlights

CHOLANGIOCYTES ARE THE TARGET cells in cholangiopathies such as primary biliary cirrhosis and primary sclerosing cholangitis [4]
While little information exists regarding the role of NPY in the regulation of biliary function [8, 31], we have previously shown that NPY regulates cholangiocarcinoma proliferation [6]
We evaluated cell proliferation [by immunoblots for proliferating cellular nuclear antigen (PCNA)] [28] of cholangiocytes from bile duct ligation (BDL) rats treated with vehicle, NPY, or anti-NPY antibody

Summary

Introduction

CHOLANGIOCYTES ARE THE TARGET cells in cholangiopathies such as primary biliary cirrhosis and primary sclerosing cholangitis [4]. Effort has gone into identifying the factors regulating biliary loss/proliferation to identify potential therapeutic targets for the maintenance of biliary mass during liver diseases. Proliferating cholangiocytes secrete increased amounts of serotonin [23] and melatonin [28] that inhibit cholangiocyte proliferation. NPY is more highly expressed in the center of these tumors, where it may exert a local antiproliferative and antimigratory effect on cholangiocarcinoma cells, allowing for the recruitment of adequate stromal support. The aims of the current study were to: 1) assess the expression and secretion of NPY from cholangiocytes after BDL; 2) identify a role for NPY in biliary homeostasis; and 3) evaluate the effects of NPY depletion on biliary proliferation

Objectives

Results

Conclusion