Role of brain cytochrome P450 mono-oxygenases in bilirubin oxidation-specific induction and activity.

GAMBARO SABRINA ELIANA; ROBERT MARIA CELESTE; TIRIBELLI CLAUDIO; GAZZIN SILVIA

ARCHIVES OF TOXICOLOGY.

SPRINGER

Lugar: Berlin; Año: 2014

0340-5761

In the Crigler-Najjar type I syndrome (CNI), the genetic absence of efficient hepatic glucoronidation of unconjugated bilirubin (UCB) by the uridine 5´-diphospho-glucuronosyltransferase1A1 (UGT1A1) enzyme produce the rise of UCB level in blood. Its entry to central nervous system (CNS) could generate toxicity and neurological damage, and even death. In the past years, a compensatory mechanism to liver glucoronidation has been indicated in the hepatic Cytochromes P450 enzymes (Cyps), able to oxidize bilirubin. Cyps are expressed also in the central nervous system, the target of bilirubin toxicity, thus making them theoretically important to confer a protective activity toward bilirubin accumulation and neurotoxicity. We therefore investigated the functional induction (mRNA, EROD/MROD) and the ability to oxidize bilirubin of Cyp1A1, 1A2 and 2A3 in primary astrocytes cultures obtained from two rat brain region (cortex: Cx and cerebellum: Cll). We observed that Cyp1A1 was the Cyp isoform more easily induced by Beta-Naphtoflavone (βNF) in both Cx and Cll astrocytes, but oxidized bilirubin only after uncoupling by 3, 4,3?,4?-tetrachlorobiphenyl (TCB). On the contrary, Cyp1A2 was the most active Cyp in bilirubin clearance without uncoupling, but its induction was confined only in Cx cells. Brain Cyp2a3 was not inducible. In conclusion, the exposure of astrocytes to βNF plus TCB significantly enhanced Cyp1A1 mediating bilirubin clearance, improving cell viability in both regions. These results may be a relevant groundwork for the manipulation of brain Cyps as a therapeutic approach in reducing bilirubin-induced neurological damage.