Unaltered α-synuclein blood levels in juvenile Parkinsonism with a parkin exon 4 deletion

Sensitive and specific detection of α-synuclein in human plasma

alpha-Synuclein (alphasyn) mutations, overexpression, misfolding, and aggregation are associated with Parkinson's disease. This protein has been intensively studied in neuronal systems. However, alphasyn is also present in extracellular fluids, such as cerebrospinal fluid and blood plasma. Recent studies have attempted to quantify its levels and compare these in various extracellular fluids of control and Parkinson's disease subjects. Data from these studies have been difficult to interpret, suggesting that more sensitive, standardized, and well-characterized assays of larger cohorts are required. Here, we describe the development of a new ELISA specifically for quantifying alphasyn in human plasma. An initial assay, using a commercial anti-alphasyn monoclonal antibody (211; Santa Cruz Biotechnology, Santa Cruz, CA) and based on a published protocol, was adapted for use in human plasma. In addition, we have developed a novel alphasyn-specific antibody for the assay that has very high sensitivity and signal:noise characteristics. Assays with either antibody showed high specificity for alphasyn, and detected it in a variety of sample types, including plasma. These assays can now be employed on large cohorts of patients and control subjects to determine whether plasma levels are altered in disease. Although measuring extracellular alphasyn levels may prove to be a useful biomarker of Parkinson's disease, it should also be a powerful tool for basic research aimed at understanding the normal and pathological physiology of alphasyn secretion. .

Peripheral biomarkers of Parkinson's disease as early reporters of central neurodegeneration

Parkinson's disease (PD) is the most common age-related movement disorder, with a prevalence of approximately 2% among people over 65 years of age. The diagnosis of PD is currently based on the clinical manifestations of the disease; therefore, the availability of peripheral biomarkers would have a great impact. In this review, we discuss and compare several attempts made to find peripheral biomarkers of PD to achieve early diagnosis, differential diagnosis, therapy assessment and classification of disease subtypes. Several investigators focused on proteins that are involved in PD pathogenesis. However, the best choice for a sensible biomarker-discovery procedure makes use of global approaches such as metabolomics and proteomics. In addition, the tissue or compartment where biomarkers are located, plays a basic role. In this context, lymphocytes are of particular interest because they are circulating dopaminergic cells, and display several functional modifications in PD.

Alpha- and gamma-synuclein proteins are present in cerebrospinal fluid and are increased in aged subjects with neurodegenerative and vascular changes

BACKGROUND

Disease-specific biomarkers should reflect a fundamental feature of neuropathology and be validated in neuropathologically confirmed cases. Several synaptic proteins have been described in cerebrospinal fluid (CSF) of patients with dementia. In Lewy body disease alpha-synuclein is incorporated within Lewy bodies and alpha-, beta- and gamma-synucleins in dystrophic neuritis. These pathological changes are expected to be seen in CSF.

METHODS

A total of 25 CSF post-mortem samples (8 control and 17 subjects with dementia) were used to quantify alpha- and gamma-synucleins and IgG.

RESULTS

We describe for the first time the presence of gamma-synuclein in CSF. There is an elevation of both alpha- and gamma-synucleins in CSF from elderly individuals with Alzheimer's disease, Lewy body disease (LBD) and vascular dementia (CVD), compared to normal controls. gamma-Synuclein showed a greater elevation in LBD, IgG in CVD. The elevation of alpha- and gamma-synucleins was seen from Braak stage III onwards and remained stable until Braak stage VI. These results were not influenced by age at death or post-mortem delay.

CONCLUSIONS

The reported increases in alpha- and gamma-synucleins and IgG in the ventricular CSF of individuals with dementia are novel findings. They now need to be explored further using a greater number of cases in each subgroup, using lumbar CSF samples to determine their applicability and relevance to a clinical diagnostic setting. It needs to be established whether using these markers may help to discriminate LBD from other types of neurodegenerative and vascular dementias.

Role of mitochondrial dysfunction in Parkinson's disease: Implications for treatment

The role of mitochondrial dysfunction as a possible cause of parkinsonism became apparent in the mid-1980s with the discovery of a group of individuals with chronic parkinsonism who had been exposed to the chemical 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and the subsequent elucidation of the mode of action of this toxin as a mitochondrial complex I inhibitor. Thereafter, a defect in mitochondrial complex I was supported by biochemical studies in patients with sporadic Parkinson's disease. Recently, striking genetic findings and biological studies have further substantiated that mitochondrial dysfunction is likely an important disease mechanism in a significant percentage, if not the majority, of patients with Parkinson's disease. These findings have defined novel biochemical pathways that can directly or indirectly affect mitochondrial function and/or integrity. Although various primary insults (genetic or environmental factors) are involved in the aetiology of Parkinson's disease, emerging evidence supports the notion that attempting to prevent or compensate for mitochondrial dysfunction could have therapeutic benefits for a majority of patients with Parkinson's disease.

Plasma alpha-synuclein is decreased in subjects with Parkinson's disease

Alpha-synuclein (alphaSN) is implicated in Parkinson's disease (PD) and is the major component of Lewy bodies (LBs). Although alphaSN is mainly expressed in neuronal cells and exists as a cytoplasmic protein, it has been found in body fluids including cerebrospinal fluid and blood. This study explored plasma alphaSN as a diagnostic marker for PD. Western blot analysis was used to characterize plasma alphaSN compared to brain alphaSN. Plasma alphaSN of 16 kDa migrates with the same mobility as its brain counterpart and recombinant alphaSN on denatured polyacrylamide gels and reacted with three different antibodies against the C-terminal and NAC regions of the alphaSN protein. The alphaSN levels in plasma from PD subjects are significantly lower than that in age-matched controls (p=0.001), and the alphaSN levels in patients with early-onset PD are lower than that in both late-onset PD and controls. This initial study indicates that measurement of alphaSN in plasma can provide support for a clinical diagnosis of Parkinson's disease and warrants further study in a larger population.

Inclusion body formation and neurodegeneration are parkin independent in a mouse model of alpha-synucleinopathy

Mutations in the genes coding for alpha-synuclein and parkin cause autosomal-dominant and autosomal-recessive forms of Parkinson's disease (PD), respectively. Alpha-synuclein is a major component of Lewy bodies, the proteinaceous cytoplasmic inclusions that are the pathological hallmark of idiopathic PD. Lewy bodies appear to be absent in cases of familial PD associated with mutated forms of parkin. Parkin is an ubiquitin E3 ligase, and it may be involved in the processing and/or degradation of alpha-synuclein, as well as in the formation of Lewy bodies. Here we report the behavioral, biochemical, and histochemical characterization of double-mutant mice overexpressing mutant human A53T alpha-synuclein on a parkin null background. We find that the absence of parkin does not have an impact on the onset and progression of the lethal phenotype induced by overexpression of human A53T alpha-synuclein. Furthermore, all major behavioral, biochemical, and morphological characteristics of A53T alpha-synuclein-overexpressing mice are not altered in parkin null alpha-synuclein-overexpressing double-mutant mice. Our results demonstrate that mutant alpha-synuclein induces neurodegeneration independent of parkin-mediated ubiquitin E3 ligase activity in nondopaminergic systems and suggest that PD caused by alpha-synuclein and parkin mutations may occur via independent mechanisms.