Rapid reduction of ATP synthesis and lack of free radical formation by MPP+ in rat brain synaptosomes and mitochondria.
MPTP is a neurotoxin thought to damage dopaminergic neurons through free radical formation. MPTP is metabolized in the brain to MPP(+), which is taken up into dopaminergic neurons via the dopamine transporter and assumed to impair mitochondrial function. We used striatal synaptosomes and telencephalic mitochondria to further investigate MPP(+) mechanism of action. For comparison, the respiratory toxins FCCP, a cyanide analog that uncouples mitochondrial ATP production, and rotenone, a NADH dehydrogenase inhibitor, were also tested. FCCP, MPP(+) and rotenone caused a rapid but stable decrease in [3H]dopamine (DA) uptake by striatal synaptosomes. Two free radical scavengers, the salen-manganese complex EUK-134, and the spin trap s-PBN, did not prevent MPP(+)-induced decrease in DA uptake. However, addition of ATP during synaptosome preparation resulted in partial recovery of MPP(+)-induced [3H]DA uptake decrease. Generation of oxygen free radicals by treatment of telencephalic mitochondria with MPP(+), FCCP, or rotenone, was evaluated by measuring DCF fluorescence, while light emission by the luciferin-luciferase complex was used to determine ATP levels. MPP(+), unlike rotenone, did not produce oxygen free radicals, but rather blocked ATP production in mitochondria, as did FCCP and rotenone. Taken together, these results suggest that MPP(+) toxicity, at least during its initial stages, is primarily due to a decrease in ATP synthesis by mitochondria and not to free radical formation.
Fonck
Carlos
C
Neuroscience Program, HNB124, USC, Los Angeles, CA 90089-2520, USA.
Baudry
Michel
M
D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000096:biosynthesis*; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D003497:Cyclic N-Oxides; D004298:Dopamine / Q000378:metabolism; D015259:Dopamine Agents / Q000378:metabolism*; D018765:Dopamine Uptake Inhibitors / Q000378:metabolism; D005609:Free Radicals / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D008454:Mazindol / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D017072:Neostriatum / Q000187:drug effects / Q000378:metabolism; D009589:Nitrogen Oxides / Q000494:pharmacology; D009942:Organometallic Compounds / Q000494:pharmacology; D011726:Pyridinium Compounds / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012402:Rotenone / Q000494:pharmacology; D012459:Salicylates / Q000494:pharmacology; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism*; D014475:Uncoupling Agents / Q000494:pharmacology
D000975:Antioxidants; D003497:Cyclic N-Oxides; D015259:Dopamine Agents; D018765:Dopamine Uptake Inhibitors; C433928:EUK-134; D005609:Free Radicals; D009589:Nitrogen Oxides; D009942:Organometallic Compounds; D011726:Pyridinium Compounds; D012459:Salicylates; D014475:Uncoupling Agents; D012402:Rotenone; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; C029217:phenyl-N-tert-butylnitrone; C026560:1-(4-methoxyphenyl)pyridinium; D000255:Adenosine Triphosphate; D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; D008454:Mazindol; D004298:Dopamine