Synucleinopathies represent a group of neurodegenerative disorders which are characterized by intracellular accumulation of aggregated α-synuclein. α-synuclein misfolding and oligomer formation is considered a major pathogenic trigger in these disorders. Therefore, targeting α-synuclein species represents an important candidate therapeutic approach. Our aim was to analyze the biological effects of passive immunization targeting α-synuclein and to identify the possible underlying mechanisms in a transgenic mouse model of oligodendroglial α-synucleinopathy. We used PLP-α-synuclein mice overexpressing human α-synuclein in oligodendrocytes. The animals received either antibodies that recognize α-synuclein or vehicle. Passive immunization mitigated α-synuclein pathology and resulted in reduction of total α-synuclein in the hippocampus, reduction of intracellular accumulation of aggregated α-synuclein, particularly significant in the spinal cord. Lowering of the extracellular oligomeric α-synuclein was associated with reduction of the density of activated iba1-positive microglia profiles. However, a shift toward phagocytic microglia was seen after passive immunization of PLP-α-synuclein mice. Lowering of intracellular α-synuclein was mediated by autophagy degradation triggered after passive immunization in PLP-α-synuclein mice. In summary, the study provides evidence for the biological efficacy of immunotherapy in a transgenic mouse model of oligodendroglial synucleinopathy. The different availability of the therapeutic antibodies and the variable load of α-synuclein pathology in selected brain regions resulted in differential effects of the immunotherapy that allowed us to propose a model of the underlying mechanisms of antibody-aided α-synuclein clearance.
Synucleinopathies
are a group of neurodegenerative diseases including
Parkinson’s disease (PD), dementia with Lewy bodies (DLB),
and multiple system atrophy (MSA). These diseases are characterized
by the aggregation and deposition of α-synuclein (α-syn)
in Lewy bodies (LBs) in PD and DLB or as glial cytoplasmic inclusions
in MSA. In healthy brains, only ∼4% of α-syn is phosphorylated
at Ser129 (pS129-α-syn), whereas >90%
pS129-α-syn may be found in LBs, suggesting that
pS129-α-syn could be a useful biomarker for synucleinopathies.
However, a widely available, robust, sensitive, and reproducible method
for measuring pS129-α-syn in biological fluids is
currently missing. We used Meso Scale Discovery (MSD)’s electrochemiluminescence
platform to create a new assay for sensitive detection of pS129-α-syn. We evaluated several combinations of capture and detection
antibodies and used semisynthetic pS129-α-syn as
a standard for the assay at a concentration range from 0.5 to 6.6
× 104 pg/mL. Using the antibody EP1536Y for capture
and an anti-human α-syn antibody (MSD) for detection was the
best combination in terms of assay sensitivity, specificity, and reproducibility.
We tested the utility of the assay for the detection and quantification
of pS129-α-syn in human cerebrospinal fluid, serum,
plasma, saliva, and CNS-originating small extracellular vesicles,
as well as in mouse brain lysates. Our data suggest that the assay
can become a widely used method for detecting pS129-α-syn
in biomedical studies including when only a limited volume of sample
is available and high sensitivity is required, offering new opportunities
for diagnostic biomarkers, monitoring disease progression, and quantifying
outcome measures in clinical trials.
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