benzyloxycarbonyl-isoleucyl-glutamyl(o-tert-butyl)-alanyl-leucinal and Parkinson-Disease

The cause of selective dopaminergic neuronal degeneration in Parkinson disease has still not been resolved, but it has been hypothesized that oxidative stress and the ubiquitin-proteasome system are important in the pathogenesis. In this report, we investigated the effect of proteasome inhibition on oxidative stress-induced cytotoxicity in PC12 cells, an in vitro model of Parkinson disease. Treatment with proteasome inhibitors provided significant protection against toxicity by 6-hydroxydopamine and H(2)O(2) in a concentration-dependent manner. The measurement of intracellular reactive oxygen species using 2',7'-dichlorofluorescein diacetate demonstrated that lactacystin, a proteasome inhibitor, significantly reduced 6-hydroxydopamineand H(2)O(2)-induced reactive oxygen species production. Proteasome inhibitors elevated the amount of glutathione and phosphorylated p38 mitogen-activated protein kinase (MAPK) prior to glutathione elevation. The treatment with lactacystin induced the nuclear translocation of NF-E2-related factor 2 (Nrf2) and increased the level of mRNA for gamma-glutamylcysteine synthetase, a rate-limiting enzyme in glutathione synthesis. Furthermore, SB203580, an inhibitor of p38 MAPK, abolished glutathione elevation and cytoprotection by lactacystin. These data suggest that proteasome inhibition afforded cytoprotection against oxidative stress by the elevation of glutathione content, and its elevation was mediated by p38 MAPK phosphorylation.

Topics: Acetylcysteine; Active Transport, Cell Nucleus; Adrenergic Agents; Animals; Cell Nucleus; Cysteine Proteinase Inhibitors; Dose-Response Relationship, Drug; Glutathione; Hydrogen Peroxide; Imidazoles; Models, Biological; NF-E2 Transcription Factor; Oxidants; Oxidative Stress; Oxidopamine; p38 Mitogen-Activated Protein Kinases; Parkinson Disease; PC12 Cells; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Pyridines; Rats; Reactive Oxygen Species; Ubiquitin

Defects in the ubiquitin-proteasome system have been implicated in Parkinson's Disease (PD). Recently, a rat model of PD was developed using a synthetic proteasome inhibitor (PSI), (Z-lle-Glu(OtBu)-Ala-Leu-al). We attempted to transfer this model to mouse studies, where genetics can be more readily investigated due to the availability of genetically modified mice. We treated C57BL/6 (B6) mice with six intraperitoneal injections of 6 mg/kg PSI in 50 mul of 70% ethanol over a 2-week-period. We found significant decreases in nigrostriatal dopamine in PSI-treated mice compared with saline-treated mice. However, we observed similar decreases in the ethanol-treated vehicle control group. Administration of ethanol alone led to significant long-term alterations in dopamine levels. Ethanol significantly eclipses the effects of PSI in the dopamine system, and therefore is a confounding vehicle for this model.

Topics: 3,4-Dihydroxyphenylacetic Acid; Animals; Central Nervous System Depressants; Chromatography, High Pressure Liquid; Cysteine Proteinase Inhibitors; Disease Models, Animal; Dopamine; Ethanol; Homovanillic Acid; Mice; Mice, Inbred C57BL; Neurons; Oligopeptides; Parkinson Disease; Time Factors; Tyrosine 3-Monooxygenase

Proteasomal dysfunction has been recently implicated in the pathogenesis of several neurodegenerative diseases, including Parkinson's disease and diffuse Lewy body disease. We have developed an in vitro model of proteasomal dysfunction by applying pharmacological inhibitors of the proteasome, lactacystin or ZIE[O-tBu]-A-leucinal (PSI), to dopaminergic PC12 cells. Proteasomal inhibition caused a dose-dependent increase in death of both naive and neuronally differentiated PC12 cells, which could be prevented by caspase inhibition or CPT-cAMP. A percentage of the surviving cells contained discrete cytoplasmic ubiquitinated inclusions, some of which also contained synuclein-1, the rat homologue of human alpha-synuclein. However the total level of synuclein-1 was not altered by proteasomal inhibition. The ubiquitinated inclusions were present only within surviving cells, and their number was increased if cell death was prevented. We have thus replicated, in this model system, the two cardinal pathological features of Lewy body diseases, neuronal death and the formation of cytoplasmic ubiquitinated inclusions. Our findings suggest that inclusion body formation and cell death may be dissociated from one another.

Topics: Acetylcysteine; alpha-Synuclein; Amino Acid Chloromethyl Ketones; Animals; Apoptosis; Cell Differentiation; Cyclic AMP; Cysteine Endopeptidases; Immunoblotting; Immunohistochemistry; Inclusion Bodies; Lewy Body Disease; Multienzyme Complexes; Nerve Tissue Proteins; Neuroprotective Agents; Oligopeptides; Parkinson Disease; PC12 Cells; Protease Inhibitors; Proteasome Endopeptidase Complex; Rats; Synucleins; Ubiquitins