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

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.