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Enhancement of dopaminergic neurotoxicity by the mercapturate of dopamine: relevance to Parkinson's disease. The mechanisms that underlie dopaminergic neurodegeneration in Parkinson's disease (PD) are not known but have been proposed to involve oxidation of dopamine and related catechols. In other organ systems, cytotoxicity from catechol oxidation is profoundly influenced by mercapturate metabolism. Here we have tested the hypothesis that catechol thioethers produced in the mercapturic acid pathway may act as dopaminergic neurotoxins. A rat mesencephalic/neuroblastoma hybrid (MES) cell line was exposed to dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), or eight different catechol thioethers for up to 24 h, and the extent of apoptosis was quantified by a microculture kinetic assay. Apoptosis also was confirmed morphologically with Giemsa-stained cultures and by demonstration of internucleosomal DNA fragmentation. The results showed that dopamine at 5-50 microM produced concentration-dependent increases in the percentage of apoptotic MES cells. At 25 and 50 microM dopamine, the maximal proportions of apoptotic cells were detected at approximately 19 (20.7 +/- 2.0%) and 14 h (30.3 +/- 3.5%), respectively. None of the catechol thioethers (up to 5 microM) alone induced significant apoptosis in MES cells. However, when MES cells were incubated with dopamine (25 microM) and catechol thioethers (5 microM) to mimic pathological conditions, 5-S-N-acetylcysteinyldopamine, 5-S-homocysteinyldopamine, and 5-S-homocysteinyl-DOPAC significantly increased the percentage of apoptotic cells compared with dopamine alone. These results suggest that mercapturate metabolism of endogenous catechols may yield products that facilitate dopaminergic neurodegeneration. J Neurochem 2000 Mar;74(3):970-8 Zhang J, Kravtsov V, Amarnath V, Picklo MJ, Graham DG, Montine TJ Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA. [log in to unmask] PMID: 10693927, UI: 20155594 http://www.ncbi.nlm.nih.gov/htbin-post/Entrez/query?uid=10693927&form=6&db=m&Dopt=b janet paterson 52 now / 41 dx / 37 onset a new voice: http://www.geocities.com/janet313/ 613 256 8340 PO Box 171 Almonte Ontario Canada K0A 1A0