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.
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ABSTRACT: Disease-modifying therapies capable to stop or slow Parkinson’s disease progression are still elusive due to severe shortcomings in the understanding of PD etiopathogenesis as well as limitations in routine clinically- based diagnosis precluding PD detection during its early course. Proteomics has recently emerged as one of the most attractive approaches to unravel the complex nature of PD processes and to investigate PD potential biomarkers. In contrast to traditional candidate-based studies, it offers global and high-throughput strategies to systematically analyze proteins – the pathological effectors themselves – without the need to establish a priori hypotheses. This review aims to summarize the latest advances in PD research in the context of proteomics. After an overview of some methodological aspects, the most recent PD-related findings will be discussed together with the limitations and perspectives of current proteomic workflows.12/2014; 4-5. DOI:10.1016/j.trprot.2014.08.001
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ABSTRACT: A number of studies suggest that the ubiquitin-proteasome system (UPS) impairment may underlie neuronal death in Parkinson's disease. Celastrol is a neuroprotective agent with anti-inflammatory and antioxidant properties. The aim of this study was to determine whether celastrol may exert neuroprotective effects both in vitro and in vivo under conditions of the lactacystin-induced UPS inhibition. In the in vitro study, mouse primary cortical neurons and neuroblastoma SH-SY5Y cells were incubated with lactacystin for 48 h (2.5 and 10 μg/ml, respectively). The animal study was performed on male Wistar rats injected unilaterally with lactacystin (5 μg/2 μl) into the substantia nigra (SN) pars compacta. In the in vitro study, we did not found any protective effects of celastrol, given either in the pre- or co-treatment mode. Moreover, in the higher concentrations, celastrol itself reduced cell viability, and enhanced the lactacystin-induced cell death in both types of cells. In the in vivo study, none of the celastrol doses (0.3-3 mg/kg) attenuated the lactacystin-induced decrease in the level of dopamine (DA) and its metabolites or protected nigral dopaminergic neurons against the lactacystin-induced degeneration. The highest celastrol dose potentiated the lactacystin-induced decrease in the level of DA and its metabolites in the lesioned striatum, and accelerated the lactacystin-induced increase in the oxidative and total metabolism of DA. Moreover, when given alone, this dose of celastrol bilaterally decreased the number and/or density of dopaminergic neurons in the SN. Our results demonstrate that celastrol does not induce neuroprotective effects under conditions of UPS inhibition.Neurotoxicity Research 10/2014; 26(3):255-273. DOI:10.1007/s12640-014-9477-9 · 3.15 Impact Factor
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ABSTRACT: 6-Hydroxydopamine (6-OHDA) is a neurotoxin that is commonly employed to induce lesions of the dopaminergic pathways to generating experimental models of Parkinson’s disease (PD) in rodents. Antioxidant and anti-inflammatory therapy approaches have been the focus of attention in the treatment of neurodegenerative. PD and Alzheimer’s diseases, and oxidative stress have been implicated in these diseases. In this study, we investigated the neuroprotective effects of minocycline and the signalling pathway that is possibly involved in a PC12 cell model of PD. The results indicated that 6-OHDA cytotoxicity was accompanied by an increment in lactate dehydrogenase (LDH) release, an increase in caspase-3 protein activity, an increase in ROS generation, MDA content and decrease in the SOD, CAT activities and cell viability. Moreover, treatment with 6-OHDA alone for 24 h resulted in ICAD degradation, increased nuclear translocation of NF-κB, and increased p53 expression. However, pretreatment with minocycline (5, 10, 20 µM) for 24 h significantly reduced LDH release, reduced caspase-3 protein production, reduced ROS production, MDA content and attenuated the decrease in SOD, CAT activities and cell viability. Additionally, minocycline (20 µM) markedly decreased the levels of cleaved ICAD protein, down-regulated p53 activity and inhibited the nuclear translocation of NF-κB. The neuroprotective effects of minocycline were attributable to its potent antioxidant activities, which prevented the nuclear translocation of NF-κB and the subsequent promotion of cell death. Therefore, the present study supports the notion that minocycline may be a promising neuroprotective agent for the treatment of Parkinson’s disease.Brain Research 10/2014; 1586. DOI:10.1016/j.brainres.2014.08.001 · 2.83 Impact Factor