Functional induction of the cystine-glutamate exchanger system Xc(-) activity in SH-SY5Y cells by unconjugated bilirubin.
We have previously reported that exposure of SH-SY5Y neuroblastoma cells to unconjugated bilirubin (UCB) resulted in a marked up-regulation of the mRNA encoding for the Na(+)-independent cystine∶glutamate exchanger System X(c)(-) (SLC7A11 and SLC3A2 genes). In this study we demonstrate that SH-SY5Y cells treated with UCB showed a higher cystine uptake due to a significant and specific increase in the activity of System X(c)(-), without the contribution of the others two cystine transporters (X(AG)(-) and GGT) reported in neurons. The total intracellular glutathione content was 2 folds higher in the cells exposed to bilirubin as compared to controls, suggesting that the internalized cystine is used for gluthathione synthesis. Interestingly, these cells were significantly less sensitive to an oxidative insult induced by hydrogen peroxide. If System X(c)(-) is silenced the protection is lost. In conclusion, these results suggest that bilirubin can modulate the gluthathione levels in neuroblastoma cells through the induction of the System X(c)(-), and this renders the cell less prone to oxidative damage.
Centro Studi Fegato, Fondazione Italiana Fegato, Trieste, Italy.
Pablo J
PJ
Giraudi
Cristina
C
Bellarosa
Carlos D
CD
Coda-Zabetta
Paolo
P
Peruzzo
Claudio
C
Tiribelli
D027182:Amino Acid Transport System y+ / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001663:Bilirubin / Q000494:pharmacology*; D045744:Cell Line, Tumor; D017931:DNA Primers; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering; D060888:Real-Time Polymerase Chain Reaction
D027182:Amino Acid Transport System y+; D017931:DNA Primers; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C118895:SLC7A11 protein, human; D005978:Glutathione; D001663:Bilirubin