naphthoquinones and Parkinson-Disease--Secondary

The dopamine precursor 3,4‑dihydroxyphenyl‑ l‑alanine (L‑DOPA) is the most widely used symptomatic treatment for Parkinson's disease (PD); however, its prolonged use is associated with L‑DOPA‑induced dyskinesia in more than half of patients after 10 years of treatment. The present study investigated whether co‑treatment with β‑Lapachone, a natural compound, and L‑DOPA has protective effects in a 6‑hydroxydopamine (6‑OHDA)‑induced mouse model of PD. Unilateral 6‑OHDA‑lesioned mice were treated with vehicle or β‑Lapachone (10 mg/kg/day) and L‑DOPA for 11 days. Abnormal involuntary movements (AIMs) were scored on days 5 and 10. β‑Lapachone (10 mg/kg) co‑treatment with L‑DOPA decreased the AIMs score on both days 5 and 10. β‑Lapachone was demonstrated to have a beneficial effect on the axial and limb AIMs scores on day 10. There was no significant suppression in dopamine D1 receptor‑related and ERK1/2 signaling in the DA‑denervated striatum by β‑Lapachone‑cotreatment with L‑DOPA. Notably, β‑Lapachone‑cotreatment with L‑DOPA increased phosphorylation at the Ser9 site of glycogen synthase kinase 3β (GSK‑3β), indicating suppression of GSK‑3β activity in both the unlesioned and 6‑OHDA‑lesioned striata. In addition, astrocyte activation was markedly suppressed by β‑Lapachone‑cotreatment with L‑DOPA in the striatum and substantia nigra of the unilateral 6‑OHDA model. These findings suggest that β‑Lapachone cotreatment with L‑DOPA therapy may have therapeutic potential for the suppression or management of the development of L‑DOPA‑induced dyskinesia in patients with PD.

Topics: Animals; Dyskinesias; Levodopa; Male; Mice; Naphthoquinones; Oxidopamine; Parkinson Disease, Secondary

Parkinson disease (PD) is a chronic neurodegenerative disease characterized by a slow and progressive degeneration of dopaminergic neurons in substantia nigra. The pathophysiological mechanisms underlying PD remain unclear. Pin1, a major peptidyl-prolyl isomerase, has recently been associated with certain diseases. Notably, Ryo et al. (Ryo, A., Togo, T., Nakai, T., Hirai, A., Nishi, M., Yamaguchi, A., Suzuki, K., Hirayasu, Y., Kobayashi, H., Perrem, K., Liou, Y. C., and Aoki, I. (2006) J. Biol. Chem. 281, 4117-4125) implicated Pin1 in PD pathology. Therefore, we sought to systematically characterize the role of Pin1 in PD using cell culture and animal models. To our surprise we observed a dramatic up-regulation of Pin1 mRNA and protein levels in dopaminergic MN9D neuronal cells treated with the parkinsonian toxicant 1-methyl-4-phenylpyridinium (MPP(+)) as well as in the substantia nigra of the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model. Notably, a marked expression of Pin1 was also observed in the substantia nigra of human PD brains along with a high co-localization of Pin1 within dopaminergic neurons. In functional studies, siRNA-mediated knockdown of Pin1 almost completely prevented MPP(+)-induced caspase-3 activation and DNA fragmentation, indicating that Pin1 plays a proapoptotic role. Interestingly, multiple pharmacological Pin1 inhibitors, including juglone, attenuated MPP(+)-induced Pin1 up-regulation, α-synuclein aggregation, caspase-3 activation, and cell death. Furthermore, juglone treatment in the MPTP mouse model of PD suppressed Pin1 levels and improved locomotor deficits, dopamine depletion, and nigral dopaminergic neuronal loss. Collectively, our findings demonstrate for the first time that Pin1 is up-regulated in PD and has a pathophysiological role in the nigrostriatal dopaminergic system and suggest that modulation of Pin1 levels may be a useful translational therapeutic strategy in PD.

Topics: 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; 1-Methyl-4-phenylpyridinium; Animals; Apoptosis; Brain; Cells, Cultured; Dopaminergic Neurons; Gene Expression; Humans; Immunoblotting; Immunohistochemistry; Male; Mice; Mice, Inbred C57BL; Motor Activity; Naphthoquinones; Neurotoxins; NIMA-Interacting Peptidylprolyl Isomerase; Parkinson Disease; Parkinson Disease, Secondary; Peptidylprolyl Isomerase; RNA Interference; RNA-Directed DNA Polymerase; Substantia Nigra; Up-Regulation

Dysfunction of mitochondria, the ubiquitin proteasome system (UPS), and lysosomes are believed to contribute to the pathogenesis of Parkinson's disease (PD). If it were possible to rescue functionally compromised, but still viable neurons early in the disease process, this would slow the rate of neurodegeneration. Here, we used a catecholaminergic neuroblastoma cell line (SH-SY5Y) as a model of susceptible neurons in PD. To identify a target early in the cell death process that was common to all neurodegenerative processes linked with PD, cells were exposed to toxins that mimic cell death mechanisms associated with PD. The sub-cellular abnormalities that occur shortly after toxin exposure were determined. 3 h of exposure to either naphthazarin, to inhibit lysosomal function, Z-Ile-Glu(OBu(t))-Ala-Leu-H (PSI), to inhibit the UPS, or rotenone, to inhibit mitochondrial complex I, caused depolarisation of the mitochondrial membrane potential (2.5-fold, twofold, and 4.6-fold change, respectively compared to vehicle), suggesting impaired mitochondrial function. Following 24 h exposure to the same toxins, UPS and lysosomal function were also impaired, and ubiquitin levels were increased. Thus, following exposure to toxins that mimic three important, but disparate cell death mechanisms associated with PD, catecholaminergic cells initially experience mitochondrial dysfunction, which is then followed by abnormalities in UPS and lysosomal function. Thus, mitochondrial dysfunction is an early event in cell stress. We suggest that, in patients with PD, the surviving cells of the substantia nigra pars compacta are most susceptible to mitochondrial impairment. Thus, targeting the mitochondria may be useful for slowing the progression of neurodegeneration in PD.

Topics: Cell Death; Cell Line, Tumor; Humans; Lysosomes; Mitochondria; Naphthoquinones; Neurons; Parkinson Disease, Secondary; Proteasome Endopeptidase Complex; Rotenone; Time Factors; Ubiquitin