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

Systemic administration of a Synthetic Proteasome Inhibitor (PSI) in rats has been described as able to provide a model of Parkinson's disease (PD), characterized by behavioral and biochemical modifications, including loss of dopaminergic neurons in the substantia nigra (SN), as assessed by post-mortem studies. With the present study we aimed to assess in-vivo by Magnetic Resonance (MR) possible morphological and metabolic changes in the nigro-striatal pathway of PSI-treated rats. 10 animals were subcutaneously injected with PSI 6.0 mg/kg dissolved in DMSO 100%. Injections were made thrice weekly over the course of two weeks. 5 more animals injected with DMSO 100% with the same protocol served as controls. The animals underwent MR sessions before and at four weeks after the end of treatment with either PSI or vehicle. MR Imaging was performed to measure SN volume and Proton MR Spectroscopy ((1)H-MRS) was performed to measure metabolites changes at the striatum. Animals were also assessed for motor function at baseline and at 4 and 6 weeks after treatment. Dopamine and dopamine metabolite levels were measured in the striata at 6 weeks after treatment. PSI-treated animals showed volumetric reduction of the SN (p<0.02) at 4 weeks after treatment as compared to baseline. Immunofluorescence analysis confirmed MRI changes in SN showing a reduction of tyrosine hydroxylase expression as compared to neuron-specific enolase expression. A reduction of N-acetyl-aspartate/total creatine ratio (p = 0.05) and an increase of glutamate-glutamine-γ amminobutirrate/total creatine were found at spectroscopy (p = 0.03). At 6 weeks after treatment, PSI-treated rats also showed motor dysfunction compared to baseline (p = 0.02), accompanied by dopamine level reduction in the striatum (p = 0.02). Treatment with PSI produced morphological and metabolic modifications of the nigro-striatal pathway, accompanied by motor dysfunction. MR demonstrated to be a powerful mean to assess in-vivo the nigro-striatal pathway morphology and metabolism in the PSI-based PD animal model.

Topics: 3,4-Dihydroxyphenylacetic Acid; Animals; Corpus Striatum; Disease Models, Animal; Dopamine; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Male; Motor Activity; Neuroimaging; Oligopeptides; Parkinsonian Disorders; Proteasome Inhibitors; Rats; Rats, Sprague-Dawley; Substantia Nigra

Dysfunction of the proteasome function is known to be a potential mechanism for dopaminergic neuron degeneration. Here, we investigated to determine whether systematic administration of proteasome inhibitor, carbobenzoxy-L-gamma-t-butyl-L-glutamyl-L-alanyl-L-leucinal (PSI), causes the increased susceptibility in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice. PSI was injected into MPTP-treated mice over a period of 2 weeks. Thereafter, we evaluated the effect of PSI 2, 4, and 8 weeks after the cessation of treatment with PSI. In the present study with HPLC analysis, PSI did not enhance MPTP-induced dopaminergic neurotoxicity in mice. Our present study with Western blot analysis also demonstrated that the reduction of tyrosine hydroxylase (TH) and glial fibrillary acidic protein (GFAP) protein levels in MPTP-treated mice was more pronounced than that in MPTP + PSI-treated animals. These results suggest that proteasome inhibitor did not enhance MPTP neurotoxicity in mice. Our findings suggest that proteasome inhibition is not a reliable model for PD. Thus, our findings provide further valuable information for the pathogenesis of Parkinson's disease.

Topics: 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; Animals; Cysteine Proteinase Inhibitors; Disease Models, Animal; Dopamine; Drug Synergism; Glial Fibrillary Acidic Protein; Male; Mice; Mice, Inbred C57BL; Neurons; Neurotoxins; Oligopeptides; Parkinsonian Disorders; Proteasome Endopeptidase Complex; Substantia Nigra; Tyrosine 3-Monooxygenase

We investigated to determine whether acute administration of proteasome inhibitor can cause dopaminergic cell loss in mice, in comparison with that of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The four intraperitoneally administrations of MPTP at 1-h intervals to mice decreased significantly the concentration of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the striatum after 5 days, in comparison with vehicle-treated animals. In contrast, the three subcutaneously administrations of carbobenzoxy-L-gamma-t-butyl-L-glutamyl-L-alanyl-L-leucinal (PSI) did not show significant changes in the concentration of dopamine, DOPAC and HVA in the striatum after 5 days, in comparison with vehicle-treated animals. Our Western blot analysis also showed that the four administrations of MPTP at 1-h intervals to mice produced a significant reduction of anti-tyrosine hydroxylase antibody (TH) protein levels in the striatum after 5 days after. In PSI-treated mice. In contrast, no significant change of TH protein levels was observed in the striatum 5 days after the final treatment with PSI. Furthermore, a significant decrease of TH protein levels was observed in the striatum of MPTP-treated mice, as compared with PSI-treated animals. The present study demonstrates that the acute treatment with proteasome inhibitor PSI did not cause the dopaminergic neurotoxicity in mice, as compared with acute treatment with MPTP. Thus, our findings suggest that acute proteasome inhibition is not a reliable model for Parkinson's disease.

Topics: 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; 3,4-Dihydroxyphenylacetic Acid; Animals; Corpus Striatum; Cysteine Proteinase Inhibitors; Disease Models, Animal; Dopamine; Drug Administration Schedule; Homovanillic Acid; Male; Mice; Mice, Inbred C57BL; Nerve Degeneration; Neurons; Neurotoxins; Oligopeptides; Parkinsonian Disorders; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Reproducibility of Results; Time Factors; Tyrosine 3-Monooxygenase

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

Topics: Animals; Cysteine Proteinase Inhibitors; Disease Models, Animal; Humans; Oligopeptides; Parkinson Disease, Secondary; Primates; Rats; Rats, Inbred F344; Rats, Sprague-Dawley; Reproducibility of Results; Substantia Nigra

We recently reported that systemic administration of a proteasome inhibitor induced a progressive levodopa-responsive, bradykinetic syndrome in rats with imaging, pathological, and biochemical features that strikingly resemble what is found in PD. This model has the potential to be a useful tool for studying the mechanism of cell death in Parkinson's disease and for testing putative neuroprotective agents. Since publication of these findings, several laboratories have sought to reproduce the model; some have been successful in replicating our findings, but others have not. The reason for this variability is not known, but resolution is critically important given the potential utility of this model. We have begun to examine various factors that alone or in combination might explain these differences, and we present in this article preliminary results from these studies.

Topics: Animals; Cysteine Proteinase Inhibitors; Disease Models, Animal; Oligopeptides; Parkinson Disease, Secondary; Rats; Rats, Sprague-Dawley; Ubiquitin; Weight Loss

Impaired proteasome function is a potential mechanism for dopaminergic neuron degeneration. To model this molecular defect, we administered systemically the reversible lipophilic proteasome inhibitor, carbobenzoxy-L-isoleucyl-gamma-t-butyl-L-glutamyl-L-alanyl-L-leucinal (PSI), to rodents. In contrast to a previous report, this approach failed to cause any detectable behavioral or neuropathological abnormality in either rats or mice. Although theoretically appealing, this specific model of Parkinson's disease appears to exhibit poor reproducibility.

Topics: Animals; Cell Line; Cysteine Proteinase Inhibitors; Disease Models, Animal; Flow Cytometry; Green Fluorescent Proteins; Humans; Immunohistochemistry; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Neurons; Oligopeptides; Parkinson Disease, Secondary; Rats; Rats, Sprague-Dawley; Tyrosine 3-Monooxygenase