title: Role of brain cytochrome P450 mono-oxygenases in bilirubin oxidation-specific induction and activity.
abstract: In the Crigler-Najjar type I syndrome, the genetic absence of efficient hepatic glucuronidation of unconjugated bilirubin (UCB) by the uridine 5'-diphospho-glucuronosyltransferase1A1 (UGT1A1) enzyme produces the rise of UCB level in blood. Its entry to central nervous system could generate toxicity and neurological damage, and even death. In the past years, a compensatory mechanism to liver glucuronidation has been indicated in the hepatic cytochromes P450 enzymes (Cyps) which are 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.
authors.affiliation: Italian Liver Foundation (Fondazione Italiana Fegato), Bldg. Q, AREA Science Park, SS 14, Km 163.5, Basovizza, 34149, Trieste, Italy.|Instituto de Trasplante Multiorgánico, Fundación Favaloro, Av. Belgrano 1746, C1093AAS, Buenos Aires, Argentina.
authors.forename: Sabrina E
authors.initials: SE
authors.lastname: Gambaro
authors.affiliation: Italian Liver Foundation (Fondazione Italiana Fegato), Bldg. Q, AREA Science Park, SS 14, Km 163.5, Basovizza, 34149, Trieste, Italy.|Centro Binacional (Argentina-Italia) de Investigaciones en Criobiología Clínica y Aplicada (CAIC), Avenida Arijon 28 bis, S2000, Rosario, Argentina.
authors.forename: Maria C
authors.initials: MC
authors.lastname: Robert
authors.affiliation: Italian Liver Foundation (Fondazione Italiana Fegato), Bldg. Q, AREA Science Park, SS 14, Km 163.5, Basovizza, 34149, Trieste, Italy.|Dipartimento di Scienze Mediche Chirurgiche e della Salute, Università degli Studi di Trieste, Strada di Fiume 447, Osp. diCattinara, 34149, Trieste, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Tiribelli
authors.affiliation: Italian Liver Foundation (Fondazione Italiana Fegato), Bldg. Q, AREA Science Park, SS 14, Km 163.5, Basovizza, 34149, Trieste, Italy. silvia.gazzin@csf.units.it.
authors.forename: Silvia
authors.initials: S
authors.lastname: Gazzin
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism; D001663:Bilirubin / Q000378:metabolism* / Q000494:pharmacology; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002525:Cerebellar Cortex / Q000166:cytology / Q000378:metabolism; D002531:Cerebellum / Q000166:cytology / Q000378:metabolism; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000378:metabolism; D019388:Cytochrome P-450 CYP1A2 / Q000235:genetics / Q000378:metabolism; D065637:Cytochrome P-450 CYP2A6 / Q000235:genetics / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D010084:Oxidation-Reduction; D011078:Polychlorinated Biphenyls / Q000494:pharmacology; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D019324:beta-Naphthoflavone / Q000494:pharmacology*
chemical_list: D017382:Reactive Oxygen Species; D019324:beta-Naphthoflavone; D003577:Cytochrome P-450 Enzyme System; D011078:Polychlorinated Biphenyls; C585519:Cyp2a3 protein, rat; C017170:Cyp1a2 protein, rat; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2; D065637:Cytochrome P-450 CYP2A6; D001663:Bilirubin; C028451:3,4,3',4'-tetrachlorobiphenyl
keywords: Astrocytes; Bilirubin oxidation; Cytochrome P450 enzymes (Cyp); EROD/MROD; Kernicterus; βNF