Uncoupling of ATP-depletion and cell death in human dopaminergic neurons.
The mitochondrial inhibitor 1-methyl-4-phenylpyridinium (MPP(+)) is the toxicologically relevant metabolite of 1-methyl-4-phenyltetrahydropyridine (MPTP), which causes relatively selective degeneration of dopaminergic neurons in the substantia nigra. Dopaminergic LUHMES cells were used to investigate whether ATP-depletion can be uncoupled from cell death as a downstream event in these fully post-mitotic human neurons. Biochemical assays indicated that in the homogeneously differentiated cell cultures, MPP(+) was taken up by the dopamine transporter (DAT). MPP(+) then triggered oxidative stress and caspase activation, as well as ATP-depletion followed by cell death. Enhanced survival of the neurons in the presence of agents interfering with mitochondrial pathology, such as the fission inhibitor Mdivi-1 or a Bax channel blocker suggested a pivotal role of mitochondria in this model. However, these compounds did not prevent cellular ATP-depletion. To further investigate whether cells could be rescued despite respiratory chain inhibition by MPP(+), we have chosen a diverse set of pharmacological inhibitors well-known to interfere with MPP(+) toxicity. The antioxidant ascorbate, the iron chelator desferoxamine, the stress kinase inhibitor CEP1347, and different caspase inhibitors reduced cell death, but allowed ATP-depletion in protected cells. None of these compounds interfered with MPP(+) accumulation in the cells. These findings suggest that ATP-depletion, as the initial mitochondrial effect of MPP(+), requires further downstream processes to result in neuronal death. These processes may form self-enhancing signaling loops, that aggravate an initial energetic impairment and eventually determine cell fate.
University of Konstanz, D-78457 Konstanz, Germany. Dominik.Poeltl@uni-konstanz.de
Dominik
D
Pöltl
Stefan
S
Schildknecht
Christiaan
C
Karreman
Marcel
M
Leist
D015655:1-Methyl-4-phenylpyridinium / Q000378:metabolism / Q000633:toxicity*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D061945:Caspase Inhibitors / Q000494:pharmacology; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D019610:Cytoprotection; D050483:Dopamine Plasma Membrane Transport Proteins / Q000378:metabolism; D059290:Dopaminergic Neurons / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D004734:Energy Metabolism / Q000187:drug effects*; D004789:Enzyme Activation; D017930:Genes, Reporter; D006801:Humans; D007502:Iron Chelating Agents / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D018384:Oxidative Stress / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection; D014475:Uncoupling Agents / Q000494:pharmacology
D000975:Antioxidants; D061945:Caspase Inhibitors; D050483:Dopamine Plasma Membrane Transport Proteins; D007502:Iron Chelating Agents; D047428:Protein Kinase Inhibitors; D014475:Uncoupling Agents; D000255:Adenosine Triphosphate; D020169:Caspases; D015655:1-Methyl-4-phenylpyridinium