MPP+-induced degeneration is potentiated by dicoumarol in cultures of the RCSN-3 dopaminergic cell line. Implications of neuromelanin in oxidative metabolism of dopamine neurotoxicity
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We have tested the idea that oxidative metabolism of dopamine may be involved in MPTP toxicity using the RCSN-3 cell line derived from the substantia nigra of an adult rat. Treatment with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) (10 μM), MPTP combined with 40 μM dicoumarol (an inhibitor of DT-diaphorase) and dicoumarol alone, did not induce toxicity in RCSN-3 cells after 72 h incubation. The lack of toxicity MPTP-treated RCSN-3 cells may be explained by the fact that they are unable to metabolize MPTP to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridinium ion (MPP+) as determined by HPLC. Incubation for 72 h with 100 μM MPP+ induced 6.6±1.4% cell death of RCSN-3 cells compared to 3.5±0.4 observed in control cells. However, when the cells were treated with 100 μM MPP+ and 40 μM dicoumarol, cell death increased 4-fold compared to that of cells treated solely with MPP+ (27±2%;P<0.001). Underthese conditions, a significant increase in DNA fragmentation (3-fold compared to MPP+ alone;P<0.01) and in calpain activation (P <0.05 compared to control) was evident. The inhibition of DT-diaphorase by dicoumarol supports the idea that oxidative metabolism of dopamine is involved in MPP+ toxicity in RCSN-3 cells.
KeywordsMPTP Dicoumarol Dopamine DT-Diaphorase Neurotoxicity DNA Fragmentation Calpain
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