GENERATION OF REACTIVE OXYGEN SPECIES ACCOUNTS FOR CYTOTOXICITY OF ANENDOGENOUS DOPAMINERGIC NEUROTOXIN, (R)-N-METHYLSALSOLINOL, TO DIFFERENTIATED DOPAMINERGIC SH-SY5Y CELLS

The mechanism of the cytotoxicity of endogenous dopamine-derived ethyl -6,7-dihydroxy-l,2,3,4-tetrahydroisoquinoline [(R)-N-methylsalsolinol] to differentiated human dopaminergic neuroblastoma SH-SY5Y cells was studied using a reduction-oxidation indicator, Alamar Blue. N-Methylsa lsolinol and its oxidation product, 1,2-dimethyl-6,7-dihydroxyisoquino linium ion, were found to inhibit oxidative phosphorylation, as shown by the Redox capacity. Antioxidants, such as reduced glutathione, cata lase, Tris and n-propyl gallate, reduced the cytotoxicity of N-methyls alsolinol, suggesting that hydroxyl radical was the major reactive oxy gen species for the cytotoxicity. Deprenyl also protected the cells fr om the decrease of the Redox capavity by N-methylsalsolinol. However, antioxidants did not protect the cells from the cytotoxicity of the ca techol isoquinolinium ion. The results suggest that oxidative stress i nduced by hydroxyl radical may be involved in the cell death of dopami nergic neurons by N-methylsalsolinol.