title: Addition of Dexamethasone Alters the Bile Acid Composition by Inducing CYP8B1 in Primary Cultures of Human Hepatocytes.
abstract: BACKGROUND
  Primary human hepatocytes offer the best human in vitro model for studies on human liver cell metabolism. Investigators use a variety of different media supplements and matrix biocoatings and the type of culture system used may influence the outcome.
  
  
  OBJECTIVE
  To optimize in vitro conditions for primary human hepatocytes with regard to bile acid synthesis.
  
  
  METHODS
  Human hepatocytes were isolated and cultured on collagen type I or EHS matrigel in cell media with or without dexamethasone. The glucocorticoid receptor (GR) antagonist RU486 was used to elucidate the involvement of GR.
  
  
  RESULTS
  Hepatocytes cultured on EHS matrigel produced more bile acids and expressed higher levels of cholesterol 7α-hydroxylase (CYP7A1) than cells cultured on rat tail collagen. Supplementation with dexamethasone increased the formation of cholic acid (CA) and decreased chenodeoxycholic acid formation. In line with these results, the mRNA expression of sterol 12α-hydroxylase (CYP8B1) increased following dexamethasone treatment. Surprisingly, the mRNA expression of CYP7A1 and CYP27A1 was not increased to the same extent. By using the GR antagonist RU486, we concluded that CYP8B1 induction is mediated via a GR-independent pathway. An altered expression of retinoid-related orphan receptor (ROR) α and ROR α target gene Glucose-6-phosphatase (G6Pase) suggests that ROR α signaling may regulate CYP8B1 expression.
  
  
  CONCLUSIONS
  Primary human hepatocytes have an increased bile acid synthesis rate when cultured on matrigel as compared to collagen. Exposure to glucocorticoid hormones stimulates the expression of CYP8B1, leading to an increased formation of CA and alteration of the bile acid composition. The effect is most likely mediated through a GR-independent pathway, possibly through ROR α.
authors: Department of Clinical Science, Intervention and Technology (CLINTEC), Karolinska Institutet, Stockholm, Sweden.
authors: Lisa-Mari
authors: LM
authors: Mörk
authors: Department of Laboratory Medicine, Division of Pathology, Karolinska Institute, Sweden.
authors: Stephen C
authors: SC
authors: Strom
authors: Department of Biosciences and Nutrition, Karolinska Institutet, Stockholm, Sweden.
authors: Agneta
authors: A
authors: Mode
authors: Department of Clinical Science, Intervention and Technology (CLINTEC), Karolinska Institutet, Stockholm, Sweden.
authors: Ewa C S
authors: EC
authors: Ellis
keywords: BSEP, bile salt export pump; CA, cholic acid; CDCA, chenodeoxycholic acid; CYP27A1, sterol 27α-hydroxylase; CYP7A1, cholesterol 7α-hydroxylase; CYP8B1, sterol 12α-hydroxylase; FXR, farnesoid X receptor; G6Pase, glucose-6-phosphatase; GR, glucocorticoid receptor; NTCP, Na+-taurocholate cotransporting polypeptide; PXR, pregnane X receptor; ROR, retinoid-related orphan receptor; chenodeoxycholic acid; cholic acid; dexamethasone; matrigel; primary hepatocytes