Plasma α-synuclein is decreased in subjects with Parkinson's disease
Introduction
Parkinson's disease (PD) is the second most common neurodegenerative disorder affecting 1% of the population over age 65. The pathological hallmark of PD in the brain is cytoplasmic inclusions termed Lewy bodies (LBs) which contain an important constituent, α-synuclein (αSN). The presence of mutations and gene multiplication in the αSN gene in early-onset autosomal dominant Parkinsonism provides support that altered metabolism of αSN may be a key to the molecular mechanism of the disease (Polymeropoulos, 2000, Singleton et al., 2003). Studies in mouse models that either lack the αSN gene (knock-out) or overexpress human αSN (transgenic) support a role of αSN in the development of PD (Abeliovich et al., 2000, Dauer et al., 2002, Giasson et al., 2002, Lee et al., 2002, Masliah et al., 2000).
At present, diagnosis in life depends on clinical features and Parkinson's disease can be mistaken for other forms of Parkinsonism, even by experienced clinicians, especially in the early stage of disease (Hughes, 1997). Reliable diagnostic markers are therefore needed, especially if disease modifying agents become available.
The expression or solubility of αSN is altered in subjects with LBs suggesting that this could serve as a biochemical marker for LB disease in post-mortem brain (Campbell et al., 2000, Culvenor et al., 1999, Dickson et al., 1999, Kahle et al., 2001). Altered αSN metabolism in the central nervous system may also be reflected in the peripheral tissues. αSN has been found in body fluids including cerebrospinal fluid and plasma (Borghi et al., 2000, El-Agnaf et al., 2003). While αSN lacks an endoplasmic reticulum (ER) targeting signal sequence and is considered to be exclusively a cytoplasmic protein, recent evidence points to the possibility of physiological secretion (Dixon et al., 2005, Lee et al., 2005). It is possible that αSN may reach the plasma by secretion and/or by alternate mechanisms. While enriched in neurons, αSN is also present in other peripheral cells such as skin (Michell et al., 2005), platelets (Li et al., 2002, Michell et al., 2005), and vascular cells (Tamo et al., 2002).
There are relatively few studies investigating the presence of αSN in human extracellular fluids (Borghi et al., 2000, Jakowec et al., 1998) or plasma (El-Agnaf et al., 2003), and these usually employ enrichment techniques. In this study we have used a western blotting technique with direct loading of plasma samples demonstrating the possibility of measuring plasma αSN levels as a diagnostic aid.
Section snippets
Subjects and plasma collection
Human plasma was prepared from freshly collected blood of subjects with PD or age-matched controls. PD was diagnosed on the basis of standard clinical criteria (Hughes, 1997). All subjects had PD for more than 5 years and had experienced stable reliable response to l-Dopa in the first 5 years of treatment. In all cases disease began unilaterally. Patients in whom cognitive impairment, eye signs, postural or autonomic instability were prominent within the first 5 years of disease were excluded.
Clinical details of PD patients and age-matched controls
Plasma was obtained from 27 subjects with PD and 11 healthy control subjects aged between 50 and 84 years (mean 67.2 ± 8.3) (Table 1). Patients (n = 13) where PD commenced before the age of 55 were classified as early-onset PD (EO PD) cases and patients (n = 14) where PD commenced after the age of 55 were classified as late-onset PD (LO PD) cases. The mean age of onset of EO PD was 43.9 ± 7.7 years (ranging from 28 to 54 years), whereas mean age of onset of LO PD was 61.7 ± 7.1 years (ranging from 55 to
Discussion
This study demonstrates that αSN, which is reactive with three different epitope specific antibodies and is indistinguishable from human brain αSN, can be detected in human plasma without enrichment. Previous studies reported that αSN was either undetectable (Jakowec et al., 1998) or could only be detected in plasma and in cerebrospinal fluid following immunoprecipitation (Borghi et al., 2000, El-Agnaf et al., 2003).
In this study, αSN was directly detected in plasma by employing the high
Acknowledgments
This study is supported by the Australian NHMRC and the Brain Foundation of Australia. We thank Drs. Pekka Jäkälä and Tobias Hartmann for the antibody Ab42580 and Professor Takeshi Iwatsubo for antibody LB509.
References (39)
- et al.
Mice lacking alpha-synuclein display functional deficits in the nigrostriatal dopamine system
Neuron
(2000) - et al.
CSF markers for pathogenic processes in Alzheimer's disease: diagnostic implications and use in clinical neurochemistry
Brain Res. Bull.
(2003) - et al.
Full length alpha-synuclein is present in cerebrospinal fluid from Parkinson's disease and normal subjects
Neurosci. Lett.
(2000) - et al.
Plasma and CSF markers of oxidative stress are increased in Parkinson's disease and influenced by antiparkinsonian medication
Neurobiol. Dis.
(2004) - et al.
Accumulation of insoluble alpha-synuclein in dementia with Lewy bodies
Neurobiol. Dis.
(2000) - et al.
Non-Abeta component of Alzheimer's disease amyloid (NAC) revisited. NAC and alpha-synuclein are not associated with Abeta amyloid
Am. J. Pathol.
(1999) - et al.
Widespread alterations of alpha-synuclein in multiple system atrophy
Am. J. Pathol.
(1999) - et al.
Neuronal alpha-synucleinopathy with severe movement disorder in mice expressing A53T human alpha-synuclein
Neuron
(2002) - et al.
Epitope mapping of LB509, a monoclonal antibody directed against human alpha-synuclein
Neurosci. Lett.
(1999) - et al.
The native form of alpha-synuclein is not found in the cerebrospinal fluid of patients with Parkinson's disease or normal controls
Neurosci. Lett.
(1998)
Selective insolubility of alpha-synuclein in human Lewy body diseases is recapitulated in a transgenic mouse model
Am. J. Pathol.
Skin and platelet alpha-synuclein as peripheral biomarkers of Parkinson's disease
Neurosci. Lett.
Unaltered alpha-synuclein blood levels in juvenile Parkinsonism with a parkin exon 4 deletion
Neurosci. Lett.
A di-acidic (DXE) code directs concentration of cargo during export from the endoplasmic reticulum
J. Biol. Chem.
Expression of alpha-synuclein, the precursor of non-amyloid beta component of Alzheimer's disease amyloid, in human cerebral blood vessels
Neurosci. Lett.
Decreased alpha-synuclein in cerebrospinal fluid of aged individuals and subjects with Parkinson's disease
Biochem. Biophys. Res. Commun.
Aggregation of α-synuclein in Lewy bodies of sporadic Parkinson's disease and dementia with Lewy bodies
Am. J. Pathol.
The solubility of alpha-synuclein in multiple system atrophy differs from that of dementia with Lewy bodies and Parkinson's disease
J. Neurochem.
Dopamine promotes alpha-synuclein aggregation into SDS-resistant soluble oligomers via a distinct folding pathway
FASEB J.
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2022, Neuroscience LettersCitation Excerpt :The progression of various symptoms of PD has been shown to be correlated with the propagation of alpha-synuclein (a-syn) pathology in anatomically interconnected areas of the brain [3,4]. The biomarker potential of a-syn and its different modified (post-translational) forms including phosphorylated form i.e., phosphorylated-Ser129-a-syn (p-Ser129-a-syn) has been widely studied over the years [5,6]. Studies show p-Ser129-a-syn levels are significantly higher in peripheral body fluids of PD patients compared to control group [7].