Pathophysiological basis of liver disease in cystic fibrosis employing a DeltaF508 mouse model.

The molecular pathogenesis of cystic fibrosis (CF) liver disease is unknown. This study investigates its earliest pathophysiological manifestations employing a mouse model carrying DeltaF508, 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 approximately 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 beta-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.

Hepatitis B in children.

Childhood hepatitis B virus (HBV) infection presents both medical and public health challenges. Infants who acquire HBV perinatally have up to 90% risk of developing chronic HBV infection. Many HBV-infected children have normal alanine aminotransferase values and minimal chronic hepatitis. Children with chronic HBV infection are usually asymptomatic but may develop chronic liver disease or hepatocellular carcinoma. Both interferon-alfa and lamivudine are available for the treatment of chronic hepatitis B in children, but the optimal treatment of children with chronic HBV infection is evolving as the indications, timing, efficacy, and side effects of the treatments are better understood. Universal infant vaccination has been shown to decrease the frequency of HBV infection and its sequelae. This article addresses aspects of HBV infection that are either unique to or different in children.