Effect of proteasome inhibitor on cultured mesencephalic dopaminergic neurons.
Proteasomal dysfunction has been implicated in the pathogenesis of Parkinson's disease (PD). We examined the effect of a selective proteasomal inhibitor, epoxomicin, on primary cultured mesencephalic neurons. Exposing rat cultured mesencephalic neurons to epoxomicin for 24 h resulted in neurotoxicity in a dose-dependent manner. Epoxomicin caused mitochondrial dysfunction, reduction in reduced glutathione (GSH), and increased generation of free radicals. Neuronal damage was significantly blocked by antioxidative/GSH-augmenting agents. Epoxomicin also increased the expression of Bax and decreased that of Bcl-2, which may cause mitochondrial dysfunction and release of free radicals. Dopaminergic neurons were preferentially resistant to the toxicity of epoxomicin. Inhibiting the synthesis of tetrahydrobiopterin (BH(4)), which has been reported to have antioxidative function, increased the susceptibility of dopaminergic neurons, whereas increasing BH(4) levels protected non-dopaminergic neurons. These findings suggest that BH(4) is at least in part a contributing factor to grand the resistance to dopaminergic neurons against epoxomicin neurotoxicity. Our results suggest that proteasome inhibition causes the neurotoxicity in mesencephalic neurons, but that is not sufficient to reproduce the selective damage to dopaminergic neurons, such as that seen in PD.
Kikuchi
Seiji
S
Department of Neurology, Hokkaido University School of Medicine, Kita 15, Nishi 7, Kita-ku, Hokkaido, Sapporo, Japan. skikuti@med.hokudai.ac.jp
Shinpo
Kazuyoshi
K
Tsuji
Sachiko
S
Takeuchi
Masayoshi
M
Yamagishi
Shoichi
S
Makita
Zenji
Z
Niino
Masaaki
M
Yabe
Ichiro
I
Tashiro
Kunio
K
D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D001708:Biopterins / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000378:metabolism; D018929:Cell Culture Techniques; D002470:Cell Survival; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005978:Glutathione / Q000378:metabolism; D015151:Immunoblotting; D008636:Mesencephalon / Q000187:drug effects* / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000473:pathology; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology*; D010300:Parkinson Disease / Q000378:metabolism / Q000473:pathology; D046988:Proteasome Endopeptidase Complex; D011518:Proto-Oncogene Proteins / Q000187:drug effects / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species; D051028:bcl-2-Associated X Protein
D000975:Antioxidants; C494828:Bax protein, rat; D009097:Multienzyme Complexes; D009842:Oligopeptides; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D051028:bcl-2-Associated X Protein; D001708:Biopterins; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C003402:sapropterin; D005978:Glutathione; D004298:Dopamine; C078846:epoxomicin