Cytochrome P450 enzymes specific expression and modulation in brain as a tool to treat bilirubin encephalopathy

GAMBARO SABRINA ELIANA; GAZZIN SILVIA; TIRIBELLI CLAUDIO

St. Petersburg

Congreso; 38th FEBS (Federation of European Biochemical Societies) Congress; 2013

Federation of European Biochemical Societies

Bilirubin Encephalopathy, is caused by the deposition of unconjugated bilirubin (UCB) in the brain leading to a damage at specific structures (hippocampus and cerebellum more damaged) [1]. When bilirubin conjugation is impaired in liver, UCB accumulation may be oxidize by alternative mechanisms of the hepatic cytochromes P450 enzymes (Cyp1A1, Cyp1A2 and Cyp2A3; Cyps) [2;3]. Since the role of Brain Cyps (bCyps) in bilirubin clearance is unknown, we used astrocytes primary cultures from cortex (Cx: not damaged) and cerebellum (Cll: damaged) to assess: A) their inducibility by UCB exposure and B) induction of bCyps by B-naphtoflavone: BNF, to increase brain UCB clearance preventing UCB neurotoxicity. A) Bilirubin was able to induce bCyps, both at the mRNA and functional (EROD; MROD) level. Of notice, Cyps (1A1 and 1A2) in astrocytes derived from Cx were more inducible that those from Cll. B) The mRNA bCyps in astrocytes from Cx and Cll exposed to BNF was different both in timing and extent. Cyp1A1 maximal induction (8 fold) in Cx was reached at 6H, while in Cll (12 fold) at 24H. Cyp1A2 induction was 3 folds higher in Cx than Cll. Cyp2A3 was slightly induced in both Cx and Cll. The activity was induced similarly to mRNA expression. These data define the dynamics of Cyp1A1, 1A2 and 2A3 selective induction in different brain regions with different susceptibility to UCB damage, and establish a concrete background for using bCyps to increase local brain bilirubin clearance to limit the damage. [1] Watchko JF (2006) Kernicterus and the molecular mechanisms of bilirubin-induced CNS injury in newborns. Neuromolecular. Med., 8, 513-529. [2] Abu-Bakar A, Arthur DM, Aganovic S, et al. (2011) Inducible bilirubin oxidase: a novel function for the mouse cytochrome P450 2A5. Toxicol. Appl. Pharmacol., 257, 14-22. [3] Kapitulnik J & Gonzalez FJ (1993) Marked endogenous activation of the CYP1A1 and CYP1A2 genes in the congenitally jaundiced Gunn rat. Mol. Pharmacol., 43, 722-725.