Bilirubin-induced apoptosis in cultured rat neural cells is aggravated by chenodeoxycholic acid but prevented by ursodeoxycholic acid.
OBJECTIVE
Unconjugated bilirubin (UCB) can be neurotoxic in jaundiced neonates and in patients with Crigler-Najjar syndrome. UCB toxicity may culminate in cell death, however, the occurrence of apoptosis has never been investigated. Ursodeoxycholic acid (UDCA) is a strong modulator of the apoptotic threshold in both hepatic and nonhepatic cells. The aims of this study were to determine whether apoptosis plays a role in neural cell death induced by UCB, and to investigate the ability of UDCA to prevent cell death.


METHODS
Cultured rat astrocytes were incubated with UCB (17 and 86 microM) plus albumin (5.7 and 28.7 microM) for 4-22 h. In addition, astrocytes and neurones were treated with either UCB, 50 microM UDCA, or their combination for 4 h. Cultures were scored for nonviable cells by trypan blue dye exclusion. Apoptosis was assessed by Hoechst staining and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labelling assay.


RESULTS
UCB induced a concentration- and time-dependent decrease in astrocyte viability. Apoptosis was 4- and 7-fold increased after 4 h exposure to 17 and 86 microM UCB, respectively (P < 0.01). UDCA reduced apoptosis to <7%, which represents a appoximately 60% protection (P < 0.01). Cholic acid was not protective, and chenodeoxyholic acid aggravated UCB toxicity (P < 0.05). Finally, neurones showed a 1.5-fold greater sensitivity than astrocytes to UCB, while UDCA was still protective.


CONCLUSIONS
UCB is toxic to both astrocytes and neurones, causing cell death through an apoptotic process. Moreover, UDCA inhibits UCB-induced apoptosis in neural cells and this could not be mimicked by other bile acids.
Silva
R F
RF
Centro de Patogénese Molecular, Faculdade de Farmácia, University of Lisbon, Portugal.
Rodrigues
C M
CM
Brites
D
D
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001253:Astrocytes / Q000187:drug effects / Q000502:physiology; D001647:Bile Acids and Salts / Q000502:physiology; D001663:Bilirubin / Q000494:pharmacology* / Q000506:poisoning; D002478:Cells, Cultured; D002635:Chenodeoxycholic Acid / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects* / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D014580:Ursodeoxycholic Acid / Q000494:pharmacology*
D001647:Bile Acids and Salts; D002635:Chenodeoxycholic Acid; D014580:Ursodeoxycholic Acid; D001663:Bilirubin