Involvement of apoptosis and calcium mobilization in tetrahydrobiopterin-induced dopaminergic cell death.
Parkinson's disease is a neurodegenerative disorder associated with selective loss of the dopaminergic neurons in the substantia nigra. We have previously shown that tetrahydrobiopterin (BH4), the obligatory cofactor for dopamine synthesis, exerts selective toxicity on dopamine-producing cells. In the present study we determined, both in vitro and in vivo, whether the cell death induced by this endogenous molecule involves apoptosis, resembling that which occurs in Parkinson's disease. Transmission electron microscopic analysis revealed that the dopamine-producing CATH.a cells underwent ultrastructural changes typical of apoptosis, such as cell shrinkage and chromatin condensation, upon exposure to BH4. The BH4 treatment also caused intranuclear DNA fragmentation as determined by TUNEL staining. A similar phenomenon also occurred in vivo, as the nigral cells became TUNEL-positive upon injection of BH4 into the substantia nigra. The BH4-induced CATH.a cell death seemed to involve macromolecule synthesis because cycloheximide and actinomycin D had protective effects. Concurrent treatment with the caspase inhibitor Z-VAD-FMK also suppressed cell death. BH4 treatment led to increases in the ratio of Bax/Bcl-x(L) mRNA and protein levels. Ca(2+) seemed to play a role in BH4-induced cell death, because BH4 caused an increase in Ca(2+) uptake and the intracellular Ca(2+) release blocker dantrolene, intracellular Ca(2+) chelator BAPTA/AM, and extracellular Ca(2+) chelator EGTA each attenuated the toxicity. These data provide evidence that the dopaminergic cell death induced by BH4 involves apoptosis and suggest relevance of this cell death to degeneration of the dopaminergic system in Parkinson's disease.
Choi
Hyun Jin
HJ
Department of Biochemistry, University of Ulsan College of Medicine, Seoul 138-736, Korea.
Kim
Seong Who
SW
Lee
So Yeon
SY
Moon
Young Wha
YW
Hwang
Onyou
O
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001708:Biopterins / Q000031:analogs & derivatives* / Q000633:toxicity*; D002118:Calcium / Q000378:metabolism*; D016923:Cell Death; D002460:Cell Line; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D053938:DNA Fragmentation; D004298:Dopamine / Q000378:metabolism; D005260:Female; D020287:In Situ Nick-End Labeling; D051379:Mice; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D010300:Parkinson Disease / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D000590:Amino Acid Chloromethyl Ketones; D015853:Cysteine Proteinase Inhibitors; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D001708:Biopterins; C003402:sapropterin; D002118:Calcium; D004298:Dopamine