Article

Synergistic protection of a general caspase inhibitor and MK-801 in bilirubin-induced cell death in human NT2-N neurons.

Department of Pediatric Research, Riskhospitalet-Radiumhospitalet University Hospital, University of Oslo, Norway.
Pediatric Research (impact factor: 2.7). 02/2006; 59(1):72-7. DOI:10.1203/01.pdr.0000191135.63586.08 pp.72-7
Source: PubMed

ABSTRACT Unconjugated bilirubin (UCB) induces both apoptosis and necrosis in neurons. To investigate the role of caspases and excitotoxicity in UCB-induced cell death, we exposed NT2-N neurons to 5 microM UCB (a concentration known to induce apoptosis) or 2 microM staurosporine (positive apoptosis control) and investigated the effects of treatments with the specific caspase-3 inhibitor, zDEVD.FMK (20 and 100 microM), or the general caspase inhibitor, zVAD.FMK (20 and 100 microM), and/or the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 (10 microM) during a 24- or 48-h exposure. UCB increased caspase-3 activity 2.3-fold after 6 h. Despite this, treatment with zDEVD.FMK did not prevent cell death. zVAD.FMK enhanced neuronal survival by reducing apoptotic nuclear fragmentation, while MK-801 enhanced survival by reducing apoptotic nuclear condensation; both without affecting the MTT assays. Combined treatment reduced both apoptotic morphologies (without affecting necrosis), and this effect was also reflected in the MTT assays [corrected] We conclude that NMDA receptor-mediated pathways and caspase-mediated pathways are involved in UCB-induced cell death in human NT2-N neurons. Concomitant inhibition of both pathways results in synergistic protection.

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    PLoS ONE 02/2009; 4(6):e5876. · 4.09 Impact Factor
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    ABSTRACT: 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.
    PLoS ONE 01/2011; 6(12):e29078. · 4.09 Impact Factor
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Keywords

10 microM
 
2 microM staurosporine
 
48-h exposure
 
5 microM UCB
 
apoptotic morphologies
 
caspase-3 activity 2.3-fold
 
cell death
 
Concomitant inhibition
 
general caspase inhibitor
 
human NT2-N neurons
 
induce apoptosis
 
MTT assays [corrected]
 
neuronal survival
 
NMDA receptor-mediated pathways
 
NT2-N neurons
 
pathways results
 
positive apoptosis control
 
specific caspase-3 inhibitor
 
synergistic protection
 
UCB-induced cell death
 

Erik Hankø