Role of lipoamide dehydrogenase and metallothionein on 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine-induced neurotoxicity.
In the present study, we investigated the effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on lipoamide dehydrogenase activity and metallothionein content. Lipoamide dehydrogenase is a flavoprotein enzyme, which reduces lipoamide and low molecular weight thiols. This enzyme has also been involved in the conversion of ubiquinone (coenzyme Q-10, oxidized form) to ubiquinol (reduced form). Lipoamide dehydrogenase activity was measured spectrophotometrically following its incubation with different doses of MPTP, MPP+, and divalent metals. MPTP at higher concentrations inhibited the lipoamide dehydrogenase activity, whereas it's potent toxic metabolite 1-methyl-4-phenylpyridinium (MPP+) had a similar effect at lower concentration. Calcium and copper did not affect the enzyme activity at any of the doses tested, whereas, zinc dose dependently enhanced the lipoamide dehydrogenase activity. Additionally, levels of metallothionein in the mouse nigrostriatal system were measured by cadmium affinity method following administration of MPTP. Metallothionein content was significantly reduced in the substantia nigra (SN), and not in the nucleus caudatus putamen (NCP) following a single administration of MPTP (30 mg/kg, i.p.). Our results suggests that both lipoamide dehydrogenase activity and metallothionein levels may be critical for dopaminergic neuronal survival in Parkinson's disease and provides further insights into the neurotoxic mechanisms involved in MPTP-induced neurotoxicity.
Dhanasekaran
Muralikrishnan
M
Division of Pharmacology and Toxicology, Department of Pharmacal Sciences, Harrison School of Pharmacy, Auburn University, Auburn, AL 36849, USA. dhanamu@auburn.edu
Albano
Christian B
CB
Pellet
Lori
L
Karuppagounder
Senthilkumar S
SS
Uthayathas
Subramaniam
S
Suppiramaniam
Vishnu
V
Brown-Borg
Holly
H
Ebadi
Manuchair
M
D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine / Q000378:metabolism / Q000494:pharmacology*; D015655:1-Methyl-4-phenylpyridinium / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D003300:Copper / Q000378:metabolism; D003342:Corpus Striatum / Q000378:metabolism; D008058:Dihydrolipoamide Dehydrogenase / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D008668:Metallothionein / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000187:drug effects*; D009498:Neurotoxins / Q000494:pharmacology*; D015032:Zinc / Q000378:metabolism
D009498:Neurotoxins; D003300:Copper; D008668:Metallothionein; D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; D008058:Dihydrolipoamide Dehydrogenase; D015032:Zinc; D015655:1-Methyl-4-phenylpyridinium; D002118:Calcium