title: Oxidative stress, induced by 6-hydroxydopamine, reduces proteasome activities in PC12 cells: implications for the pathogenesis of Parkinson's disease.
abstract: Mutations in familial Parkinson's disease (PD) have been associated with the failure of protein degradation through the ubiquitin-proteasome system (UPS). Impairment of proteasome function has also been suggested to play a role in the pathogenesis of sporadic PD. We examined the proteasome activity in PC12 cells treated with 6-hydroxydopamine (6-OHDA), the dopamine synthetic derivate used in models of PD. We found that 6-OHDA treatment increased protein oxidation, as indicated by carbonyl group accumulation, and increased caspase-3 activity. In addition, there was an increase in trypsin-, chymotrypsin-, and postacidic-like proteasome activities in cells treated with 10-100 microM 6-OHDA, whereas higher doses caused a marked decline. 6-OHDA exposure also increased mRNA expression of the 19S regulatory subunit in a dose-dependent manner, whereas the expression of 20S- and 11S-subunit mRNAs did not change. Administration of the antioxidant N-acetylcysteine to 6-OHDA-treated cells prevented the alteration in proteasome functions. Moreover, reduction in cell viability owing to administration of proteasome inhibitor MG132 or lactacystin was partially prevented by the endogenous antioxidant-reduced glutathione. In conclusion, our data indicate that mild oxidative stress elevates proteasome activity in response to increase in protein damage. Severe oxidative insult might cause UPS failure, which leads to protein aggregation and cell death. Moreover, in the case of UPS inhibition or failure, the blockade of physiological reactive oxygen species production during normal aerobic metabolism is enough to ameliorate cell viability. Control of protein clearance by potent, brain-penetrating antioxidants might act to slow down the progression of PD.
authors.affiliation: Felsenstein Medical Research Center and the Department of Neurology, Rabin Medical Center, Tel-Aviv University-Sackler School of Medicine, Petah-Tikva, 49100, Israel.
authors.forename: Hanoch
authors.initials: H
authors.lastname: Elkon
authors.forename: Eldad
authors.initials: E
authors.lastname: Melamed
authors.forename: Daniel
authors.initials: D
authors.lastname: Offen
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002918:Chymotrypsin / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005978:Glutathione / Q000378:metabolism / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D016627:Oxidopamine / Q000494:pharmacology*; D016716:PC12 Cells; D010300:Parkinson Disease / Q000378:metabolism / Q000503:physiopathology; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D014357:Trypsin / Q000378:metabolism
chemical_list: D000975:Antioxidants; D004791:Enzyme Inhibitors; D021122:Protein Subunits; D012333:RNA, Messenger; D016627:Oxidopamine; D002918:Chymotrypsin; D014357:Trypsin; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D046988:Proteasome Endopeptidase Complex; D005978:Glutathione; D004298:Dopamine