title: Ursodeoxycholic acid decreases bilirubin-induced osteoblast apoptosis.
abstract: BACKGROUND
  Low bone turnover osteoporosis is common in cholestatic diseases. Ursodeoxycholic acid (UDCA) counteracts the damaging effects of bilirubin or lithocholic acid (LCA) on osteoblast viability, proliferation and mineralisation. UDCA is anti-apoptotic in various cell lines, but this effect in bone cells is unknown. Therefore, the consequences of bilirubin and LCA on apoptosis, and whether UDCA has anti-apoptotic effects have been assessed on osteoblasts.
  
  
  METHODS
  Human osteoblasts (hOB) and osteosarcoma cell line (Saos-2) were treated with camptothecin as a pro-apoptotic agent, and UDCA, LCA and bilirubin. Apoptosis was determined by DNA fragmentation, flow cytometry, caspase-3 activity and expression of pro-apoptotic (Bcl-2-associated X protein BAX) and anti-apoptotic (BCL2 and BCL2-like 1 protein, BCL2L) genes.
  
  
  RESULTS
  Both LCA (10 μM) and bilirubin (50 μM) induced apoptosis as indicated by DNA fragmentation (4·7- and 3·7-fold, respectively, P < 0·001), caspase-3 activity and flow cytometry in Saos-2 and hOB. UDCA (10 μM) reduced the apoptotic effects of camptothecin (0·5 μM) by 61%, (P < 0·001) and counteracted the apoptotic effects of LCA and bilirubin determined by DNA fragmentation (56% and 60%, respectively, P < 0·001), cytometry and caspase-3 activity in Saos-2, with lower effects in hOB. UDCA (10 μM) downregulated BAX (75%), upregulated BCL2L (10-fold, P < 0·01) genes, and neutralised BAX upregulation (P < 0·01) and BCL2L downregulation (P < 0·01) induced by LCA and bilirubin.
  
  
  CONCLUSIONS
  Bilirubin and LCA induce apoptosis in osteoblastic cells. UDCA counteracts the apoptotic consequences of these two substances, and therefore, it may have further beneficial effects on the decreased bone formation in the cholestasis.
authors.affiliation: Centro de Investigación Biomédica en Red en Enfermedades Hepáticas y Digestivas (CIBERehd), Hospital Clínic, IDIBAPS, University of Barcelona, Barcelona, Spain; Metabolic Bone Diseases Unit, Department of Rheumatology, Hospital Clínic, IDIBAPS, University of Barcelona, Barcelona, Spain; Liver Unit, Digestive Diseases Institute, Hospital Clínic, IDIBAPS, University of Barcelona, Barcelona, Spain.
authors.forename: Silvia
authors.initials: S
authors.lastname: Ruiz-Gaspà
authors.forename: Marta
authors.initials: M
authors.lastname: Dubreuil
authors.forename: Nuria
authors.initials: N
authors.lastname: Guañabens
authors.forename: Andrés
authors.initials: A
authors.lastname: Combalia
authors.forename: Pilar
authors.initials: P
authors.lastname: Peris
authors.forename: Ana
authors.initials: A
authors.lastname: Monegal
authors.forename: Albert
authors.initials: A
authors.lastname: Parés
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001663:Bilirubin / Q000494:pharmacology*; D002166:Camptothecin / Q000494:pharmacology; D045744:Cell Line, Tumor; D002756:Cholagogues and Choleretics / Q000494:pharmacology*; D003902:Detergents / Q000494:pharmacology; D006801:Humans; D008095:Lithocholic Acid / Q000494:pharmacology; D010006:Osteoblasts / Q000187:drug effects*; D015854:Up-Regulation; D014580:Ursodeoxycholic Acid / Q000494:pharmacology*; D051028:bcl-2-Associated X Protein / Q000187:drug effects / Q000235:genetics
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D000975:Antioxidants; D002756:Cholagogues and Choleretics; D003902:Detergents; D051028:bcl-2-Associated X Protein; D008095:Lithocholic Acid; D014580:Ursodeoxycholic Acid; D001663:Bilirubin; D002166:Camptothecin
keywords: Bile acids; bone turnover; cholestasis; osteoporosis; primary biliary cirrhosis