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This Article Full Text Full Text (PDF) All Versions of this Article: 294/6/G1411    most recent 00181.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Freudenberg, F. Articles by Carey, M. C. PubMed PubMed Citation Articles by Freudenberg, F. Articles by Carey, M. C.

LIVER AND BILIARY TRACT

Pathophysiological basis of liver disease in cystic fibrosis employing a F508 mouse model

¹Department of Medicine, Harvard Medical School and Harvard Digestive Diseases Center, Boston; ²Department of Medicine, Gastroenterology Division, Brigham and Women's Hospital, Boston; ³Combined Program of Gastroenterology and Nutrition, Children's Hospital, Boston; and ⁴Pathology Department, Harvard Medical School and Brigham and Women's Hospital, Boston, Massachusetts

Submitted 25 April 2007 ; accepted in final form 20 April 2008

The molecular pathogenesis of cystic fibrosis (CF) liver disease is unknown. This study investigates its earliest pathophysiological manifestations employing a mouse model carrying F508, the commonest human CF mutation. We hypothesized that, if increased bile salt spillage into the colon occurs as in the human disease, then this should lead to a hydrophobic bile salt profile and to "hyperbilirubinbilia" because of induced enterohepatic cycling of unconjugated bilirubin. Hyperbilirubinbilia may then lead to an increased bile salt-to-phospholipid ratio in bile and, following hydrolysis, precipitation of divalent metal salts of unconjugated bilirubin. We document in CF mice elevated fecal bile acid excretion and biliary secretion of more hydrophobic bile salts compared with control wild-type mice. Biliary secretion rates of bilirubin monoglucuronosides, bile salts, phospholipids, and cholesterol are increased significantly with an augmented bile salt-to-phospholipid ratio. Quantitative histopathology of CF livers displays mild early cholangiopathy in 53% of mice and multifocal divalent metal salt deposition in cholangiocytes. We conclude that increased fecal bile acid loss leads to more hydrophobic bile salts in hepatic bile and to hyperbilirubinbilia, a major contributor in augmenting the bile salt-to-phospholipid ratio and endogenous β-glucuronidase hydrolysis of bilirubin glucuronosides. The confluence of these perturbations damages intrahepatic bile ducts and facilitates entrance of unconjugated bilirubin into cholangiocytes. This study of the earliest stages of CF liver disease provides a framework for investigating the molecular pathophysiology of more advanced disease in murine models and in humans with CF.

cystic fibrosis transmembrane conductance regulator; gallstones; enterohepatic cycling; bilirubin; metal salts