Regression of cholangiocyte proliferation after cessation of ANIT feeding is coupled with increased apoptosis

Abstract

Cholangiocyte proliferation and loss through apoptosis occur in cholestatic liver diseases. Our aim was to determine the mechanisms of apoptosis in an animal model of ductal hyperplasia. Rats were fed alpha-naphthylisothiocyanate (ANIT) for 2 wk and subsequently fed normal chow for 1, 2, and 4 wk. Proliferation was assessed in sections by morphometry and in small and large cholangiocytes by proliferating cellular nuclear antigen immunoblots and measurement of cAMP levels. Apoptosis and reactive oxygen species (ROS) levels were also assessed. ANIT feeding increased small and large cholangiocyte proliferation and apoptosis. Cessation of ANIT feeding was associated with decreased proliferation and a further increase in apoptosis in small and large cholangiocytes. Cholangiocytes from ANIT-fed rats or exposed to ANIT in vitro showed increased apoptosis and ROS generation. ANIT-induced duct injury results in enhanced proliferation and apoptosis in small and large cholangiocytes. The mechanism of ANIT-induced apoptosis may be due to ROS generation induced directly by ANIT. Our model has implications for understanding the pathophysiology of cholangiopathies (characterized by the coexistence of cholangiocyte apoptosis and proliferation).

Bile acid feeding increased proliferative activity and apical bile acid transporter expression in both small and large rat cholangiocytes

“…12 In the intrahepatic biliary tree, there are different proliferative compartments that differentially respond to the aforementioned liver injury/toxins. 3,6,8,9,11 Consistent with this novel concept, in rats with BDL only large cholangiocytes undergo replication with enhanced DNA replication and increased number of large bile ducts. 3 Furthermore, a single dose of CCl 4 (administered to rats by gastric gavage) induces ductopenia of large ducts whereas small ducts de novo proliferate to compensate for the loss of proliferative activity of large ducts.…”

“…In animal models, cholangiocytes markedly proliferate in response to a number of pathological maneuvers including bile duct ligation (BDL), [2][3][4][5][6] partial hepatectomy, 7,8 or feeding of carbon tetrachloride (CCl 4 ), 6,9 ␣-naphthylisothiocyanate (ANIT), 10,11 or specific bile salts. 12 In the intrahepatic biliary tree, there are different proliferative compartments that differentially respond to the aforementioned liver injury/toxins.…”

Considerations for the use of plasma cytokeratin 18 as a biomarker in pancreatic cancer

“…A marked correlation was seen between the concurrent bilirubin levels and circulating CK18 levels. This observation is likely to be explained on the basis that obstruction of the main bile duct with consequent dilatation and epithelial disruption directly influences the balance of proliferation and cell death within the biliary epithelium (Lesage et al, 2001;Alpini et al, 2003). Low-grade cholangitis is quite common following biliary stenting and may also represent an additional confounding factor, as both generalised sepsis (Roth et al, 2004) and cholangitis (Yagmur et al, 2007) raise circulating CK18 concentrations.…”

H3 histamine receptor agonist inhibits biliary growth of BDL rats by downregulation of the cAMP-dependent PKA/ERK1/2/ELK-1 pathway

“…We evaluated cholangiocyte apoptosis by terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) analysis 33 in paraffin-embedded liver sections (5 mm, three slides evaluated for each group) from the selected group of animals. Following counterstaining with hematoxylin solution, liver sections were examined by light microscopy with an Olympus BX-40 microscope (Tokyo, Japan) equipped with a camera.…”

“…We measured PCNA (an index of cell replication) 33 protein expression by immunoblots in protein (10 mg) whole-cell lysate from brain (positive control) or purified cholangiocytes from BDL rats treated with NaCl or RAMH for 1 week. Proteins were visualized using chemiluminescence (ECL Plus kit, Amersham Life Science).…”