Effect of bilirubin on ABCc1 expression in brain selective regions of Gunn rats

ANDREA L. BERENGENO; SILVIA GAZZIN; CRISTINA BELLAROSA; M. CELESTE ROBERT; CLAUDIO TIRIBELLI

Innsbruck

Congreso; 3rd FEBS Special Meeting on ABC Proteins; 2010

Effect of bilirubin on ABCc1 expression in brain selective regions of Gunn rats Berengeno Andrea, Gazzin Silvia, Bellarosa Cristina, Robert M.Celeste, Tiribelli Claudio. Background: In infants severe unconjugated bilirubin (UCB) levels can lead into a brain UCB accumulation that produces Kernicterus. Recently we demonstrated that the Tissue UCB (TUCB) content was similar in damaged and not- damaged brain regions. We also showed a strong down regulation of Mrp1 (ABCc1) in the Blood Cerebrospinal Fluid Barrier of Jaundiced Gunn rats, the animal model for Kernicterus. Among the ABC transporters, Mrp1 presents the highest affinity for UCB. In neurons, astrocytes and neuroblastoma cells the increased susceptibility to UCB toxicity was closely correlated with the decrease in the Mrp1 expression. The relocation of Mrp1 from Golgi to plasma membrane in primary culture of astrocyte elicited by UCB exposition. Aim: To compare in vivo the Mrp1 protein and gene expression in UCB damaged (cerebellum, striatum) and not damaged (cerebral cortex, hippocampus) regions of CNS between controls (JJ) and hyperbilirubinemic (jj) animals. Methods: Homozygous hyperbilirubinemic (jj) Gunn rats, were examined at 9 days after birth. Homozygous (JJ) littermates served as control. Cerebellum (Cll), striatum (St), cerebral cortex (Cx), hippocampus (Hip) were divided in two parts immediately after dissection: one for proteomic and another one for genomic study. Mrp1 relative protein expression was assessed by quantitative Western blot (ref. sample P60 Jj Cx pool), while Mrp1 mRNA level was determined by RT-qPCR (ref. sample P9 JJ Cx). Results: No significant differences were found in Mrp1 protein expression in Cll, St and Hip in hyperbilirubinemic (jj) respect to normal (JJ) animals at 9 days. On the contrary, an increase of Mrp1 protein was detected in Cx of jj respect to JJ animals. In normal (JJ) animals Mrp1 protein was similar in Cx, Cll, St and Hip. At mRNA level, Mrp1 is unchanged in all tissues analyzed. Mrp1 mRNA was similar in Cx, Cll, St and Hip on normal (JJ) rats. No relevant differences between JJ and jj animals were detected. Conclusions: Bilirubin seems not able to modulate in vivo the Mrp1 protein and mRNA levels in Cx, Cll, St and Hip of Gunn rats. Mrp1 could be not a principal player involved in protection on UCB damage in the central nervous system.