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

Abstract

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 Y 1-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. biliary epithelium; neurotransmitters; proliferation; cell cycle CHOLANGIOCYTES ARE THE TARGET cells in cholangiopathies such as primary biliary cirrhosis and primary sclerosing cholangitis (4).During the course of these diseases and in many other forms of liver injury, a balance between cholangiocyte proliferation and loss is critical for the maintenance of the homeostasis of biliary mass (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.Biliary mass is coordinately regulated by a number of growth factors and hormones during normal and cholestatic states by both autocrine and paracrine signaling (5, 12, 13, 23, 28). After bile duct ligation (BDL), cholangiocytes secrete increased amounts of growth factors such as vascular endothelial growth factor (VEGF) and nerve growth factor (NGF) stimulating biliary proliferation (12, 13). Conversely, proliferating cholangiocytes secrete increased amounts of serotonin (23) and melatonin (28) that inhibit cholangiocyte proliferation. Serotonin and melatonin may be secreted by cholangiocytes to prevent overt biliary proliferation in response to cholestasis.Neuropeptide Y (NPY) is a neurotransm...

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Recent advances in understanding bile duct remodeling and fibrosis

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