Bilirubin-induced apoptosis in cultured rat neural cells is aggravated by chenodeoxycholic acid but prevented by ursodeoxycholic acids

Background/Aims: Unconjugated bilirubin (UCB) can be neurotoxic in jaundice d neonates and in patients with Crigler-Najjar syndrome, UCB toxicity may c ulminate in cell death, however, the occurrence of apoptosis has never been investigated. Ursodeoxycholic acid (UDCA) is a strong modulator of the apo ptotic threshold in both hepatic and nonhepatic cells. The aims of this stu dy were to determine whether apoptosis plays a role in neural cell death in duced by UCB, and to investigate the ability of UDCA to prevent cell death. Methods: Cultured rat astrocytes were incubated with UCB (17 and 86 muM) pl us albumin (5.7 and 28.7 muM) for 4-22 h, In addition, astrocytes and neuro nes were treated with either UCB, 50 muM UDCA, or their combination for 4 h , Cultures were scored for nonviable cells by trypan blue dye exclusion. Ap optosis was assessed by Hoechst staining and terminal deoxynucleotidyl tran sferase-mediated deoxyuridine triphosphate nick end-labelling assay. Results: UCB induced a concentration- and time-dependent decrease in astroc yte viability. Apoptosis was 4- and 7-fold increased after 4 h exposure to 17 and 86 mu ;M UCB, respectively (P < 0.01). UDCA reduced apoptosis to <7% , which represents a similar to 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 t o UCB, while UDCA was still protective. Conclusions: UCB is toxic to both astrocytes and neurones, causing cell dea th through an apoptotic process. Moreover, UDCA inhibits UCB-induced apopto sis in neural cells and this could not be mimicked by other bile acids. (C) 2001 European Association for the Study of the Liver. Published by Else vier Science B,V, All rights reserved.