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The search for biomarkers of Parkinson's disease (PD) typically focuses on cerebrospinal fluid components, with very few reports on simple biomarkers identifiable by blood analysis. In this report, we determined the level of oxidized DJ-1 protein (oxDJ-1) in red blood cells by ELISA and examined the association with MIBG myocardial scintigraphy. Levels of oxDJ-1 were higher in unmedicated patients with PD (142.2 ± 21.8 ng oxDJ-1/mg protein; n = 13) compared to the L-DOPA-treated group (85.6 ± 10.1 ng oxDJ-1/mg protein; n = 10) and controls (56.0 ± 6.2 ng oxDJ-1/mg protein; n = 17), thereby showing significant intergroup differences. Intervention with L-DOPA showed a tendency to decrease oxDJ-1 levels in patients. The diagnostic sensitivity of oxDJ-1 measurement was 87% and that of simultaneously conducted MIBG scintigraphy was 89%; this showed that the diagnostic sensitivity was comparable. Our results showed that measurement of oxDJ-1 levels in red blood cells can be useful and oxDJ-1 can be used as a biomarker for the early diagnosis of PD. (Receieved July 31, 2013; Accepted October 16, 2013; Published April 1, 2014).

Parkinson's disease is a degenerative disorder of the central nervous system caused by selective dopamine-generating cell death, and oxidative stress and mitochondrial dysfunction are thought to be responsible for the onset of Parkinson's disease. While most cases of Parkinson's disease are idiopathic, 5-10% of cases are attributed to genetic factors. DJ-1 was first identified as an activated ras-dependent oncogene and later found to be a causative gene for a familial form of Parkinson's disease, PARK7. We and others found that DJ-1 plays roles in transcriptional regulation and anti-oxidative stress function, and loss of its function is thought to affect the onset of Parkinson's disease. DJ-1 is mainly located in the cytoplasma and nucleus and partially in mitochondria. When mice or mouse cells were treated with bisphenol A, an endocrine disruptor and inducer of reactive oxygen species, DJ-1 was translocated into mitochondria to maintain mitochondrial complex I activity. We also found that DJ-1 directly bound to and was co-localized with NDUFA4 and ND1, nuclear and mitochondrial DNA-encoding subunits of mitochondrial complex I, respectively, and that these associations were enhanced by oxidative stress. Furthermore, complex I activity was reduced in two types of DJ-1-knockdown NIH3T3 and HEK293 cells. These findings suggest that DJ-1 is an integral mitochondrial protein and maintains mitochondrial complex I activity to regulate mitochondrial homeostasis.

Parkinson disease (PD), is a movement disorder pathologically characterized by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Although the inherited forms of PD account for only 5 to 10% of PD cases, the identification of gene mutations in the genes implicated in familial PD in the past 10 years, including the findings regarding the a-synuclein, Parkin, ubiquitin-C-terminal hydrolase-L1 (UCH-L1), PINK1, DJ-1 and the ATP13A2 genes, has advanced understanding of the molecular mechanisms in each case of genetic PD. Most familial forms of PD develop at an early onset. However, recent identification of the leucine-rich repeat kinase (LRRK) 2 gene for a late-onset PD, the clinicopathological feature of which closely resembles that of sporadic PD, is expected to enable the clarification of the underlying causes of general PD. Recent studies on the physiological and pathological functions of these identified gene products have revealed overlapping pathogenetic pathways. The common features of these aberrant pathways are impaired protein degradation/quality control, mitochondrial dysfunction, and altered vesicle transport. Several attempts have been made towards developing molecular-targeted therapies directed against mitochondria (e.g., antioxidants, permeability transition pore modulators, and mitochondrial biogenesis stimulators), protein quality control and vesicle transport (e.g., gene silencing, immunization of asynuclein, and protofibril-destabilizing reagents). To ensure the successful implementation of such strategies, it is important to understand the events occuring at an early stage of PD. Further, studies using mammalian PD models for pharmacological analysis combined with studies employing lower organisms for genetic analyses such as worm, fly, and yeast will be helpful to determine effective prevention and treatment strategies for PD, which will replace the conventional symptomatic treatments for PD.

Parkinson disease (PD) and dystonia are two major part of neurodegenerative disorders. The underlying cause of PD development has been considered to be a combination of genetic factors and environmental substrates. In case of dystonia, which includes primary sporadic dystonia, such as task specific dystonia, cervical dystonia and so on, are also considered to associate with unknown vulnerable genetic factors. In this paper, the clinical features and causative genes for PD and dystonia were described; especially in particular, the description of those genes associated with the PARK and DYT series were provided. Most of the identified causative genes for PD are associated with the protein degradation and cell death process via convergent mechanisms such as ubiquitin-proteasome system, mitochondrial dysfunction, oxidative stress, and lysosomal system (autophagia). On the other hand, the pathogenic mechanism for dystonia is gradually discovered to be divergent suggested by identified genes, such as torsinA, GCH1, etc, which is compatible and well understood with the divergent expression of dystonia phenotype. Another breakthroughs are required to investigate the treatment of both PD and dystonia based on the pathogenic mechanisms.

Parkinson disease (PD) is the most common neurodegenerative disease, and the majority of PD cases involve the sporadic from of PD. Although the etiology of the sporadic form is unknown, mitochondrial dysfunction and oxidative stress are considered to play a prominent role in its pathogenesis. The discovery of the genes that are linked to the rare familial form of PD has provided crucial insights into the molecular mechanisms involved in the pathogenesis of PD. Recent findings implicate mitochondrial dysfunction associated with oxidative damage (mitochondrial pathway) and abnormal protein accumulation (ubiquitin/ proteosome pathway) as the key molecular mechanisms compromising dopaminergic neurons in familial PD. Mutations in Parkin, PTEN-induced kinase 1 (PINK1) and DJ-1 are found in autosomal recessive forms of PD. Recent studies on these genes suggest the central importance of mitochondrial dysfunction and oxidative stress in PD. The above mentioned 3 proteins may be biologically related to each other and may protect the mitochondria against oxidative stress and other harmful stimulations. In particular, parkin appears to be the most important factor that improves the mitochondrial dysfunction. In this review we focus on the mitochondria and parkin function. We also provide an overview of the most relevant findings in recent years.

PTEN-induced putative kinase 1 (PINK1) is a causative gene for autosomal recessive early onset parkinsonism. Mutations in PINK1 were identified originally in PARK6-linked parkinsonism families from Italy and Spain. PINK1 contains 8 exons spanning 1.8 kb, and encodes a protein of 581 amino acids with a mitochondrial targeting motif and a serine-threonine protein kinase domain. Until now PINK1-mutation positive parkinsonism is the second frequent one next to parkin among autosomal recessive parkinsonism. Most of reported mutations were distributed throughout the serine-threonine protein kinase domain. Thus, loss of function of kinase activity of PINK1 is the most probable disease mechanism. The clinical phenotype of PINK1 -mutation positive parkinsonism is similar to that of parkin mutation positive parkinsonism. Single heterozygous mutations of PINK1 have been also identified sporadic Parkinson's disease (PD) patients. The presence of dopamine hypometabolism in asymptomatic mutation carriers suggests that single heterozygous mutations of PINK1 are risk factors for developing parkinsonism. In addition, some functional data have been shown that PINK1 protein may function as neuroprotective roles for mitochondria. Recent biochemical and morphological studies using drosophila melanogaster suggested that Parkin and PINK1 share a common pathway to maintain mitochondrial function and that PINK1 functions upstream of Parkin. Moreover, co-expression of double mutations of PINK1 and DJ-1 in cultured cells from one family with heterozygous mutations, enhanced susceptibility to MPP+ (1-methyl-4-phenylpyridinium ion)-induced cell death. These data suggest that PINK1, parkin, and/or DJ-1 could play an important role to maintain mitochondrial functions. In the other word, the mitochondrion is a good target for elucidating the pathogenesis of not only sporadic form but also monogenic form of PD.

Parkinson's disease (PD) is the second most common neurodegenerative disorder in the world. The occurrence of PD is largely sporadic, while several families with Mendelian segregation of PD have been reported. PD is thought to be caused by mitochondrial dysfunction, oxidative stress and inflammation based on multiple genetic and environmental factors, resulting in the apoptosis of dopaminergic cells. Six causal genes for Mendelian inherited PD have been identified to date, which indicate the importance of the ubiquitin-proteasome pathway in the molecular pathogenesis of dopaminergic cell death. Recent studies have also indicated the involvement of genetic factors in the pathogenesis of sporadic PD. Many association studies on candidate genes have examined the relationship between PD and polymorphisms; We identified a-synuclein as a definite susceptibility gene for sporadic PD. Since 2001, significant linkage to several loci have been reported in samples of affected sibling pairs. With the recent advances in human genome analyses, genome-wide association studies by SNP chip are being performed to identify susceptibility genes and to establish tailor-made medicine for PD.

The deposition of alpha-synuclein (aS), a product of pathogenic gene for dominantly inherited familial Parkinson's disease (PD; park1), as fibrillary aggregates like Lewy bodies (LB), is a hallmark lesion of a set of neurodegenerative disorders termed synucleinopathies, including sporadic PD and dementia with Lewy bodies (DLB). We found that aS is the major component of LBs and further identified a specific phosphorylation of Ser129 of insoluble aS by mass spectrometric analysis. The roles of DJ-1 and PINK-1, products of pathogenic genes for autosomal recessive forms of early-onset parkinsonism, have subsequently been examined. Overexpression of DJ-1 conferred cultured cells resistance to oxidative stress, suggesting an antioxidant function of DJ-1. We also confirmed the anti-PTEN function of DJ-1 that may promote cell survival, showing decreased phosphorylation of Akt through upregulation of PTEN activity upon siRNA knockdown for DJ-1. PINK-1, that had been identified as a gene upregulated by PTEN overexpression, turned out to be a protein kinase localized in mitochondria. Collectively, information derived from studies on pathogenic genes for familial PD will open up the way toward the clarification of the pathogenesis of PD, underscoring the roles of protein aggregation, proteolysis, oxidative stress and protein phosphorylation in PD.

Parkinson's disease (PD) is the second most common neurodegenerative disorders. Recently, several forms of familial PD have been reported so far. Among them, several causative genes such as alpha-synuclein, UCH-L1, PINK1, and DJ-1 have been identified. Functional analysis on these causative genes may help us to explore the molecular mechanisms of nigral neuronal death in not only FPD but also sporadic form of PD. Thus, the identification of FPD gives us good information of etiologies of PD.