An endogenous neurotoxin, N-methyl(R)salsolinol, has been proved to be involved in the pathogenesis of Parkinson's disease. Increased level of N- methyl(R)salsolinol in the cerebrospinal fluid and high activity of its synthesizing (R)salsolinol N-methyltransferase in lymphocytes were confirmed in the majority of parkinsonian patients. Recently this neurotoxin was found to induce apoptosis in human dopaminergic neuroblastoma SH-SY5Y cells. In this study, we tried to elucidate the intracellular mechanism of apoptosis induced by N-methyl(R)salsolinol, and proved activation of caspase 3 after incubation with this toxin by Western blot analysis. Further, a caspase 3 inhibitor, acetyl-L-aspartyl-L-glutamyl-L-valyl-L-aspartic aldehyde, prevented the nucleosomal DNA fragmentation completely. These results demonstrate that caspase 3 mediates apoptosis induced by an endogenous neurotoxin, N-methyl(R)salsolinol, which may cause apoptotic cell death of dopamine neurons in Parkinson's disease.
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