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Peripheral monocyte entry is required for alpha-Synuclein induced inflammation and Neurodegeneration in a model of Parkinson disease.

ABSTRACT: Accumulation of alpha-synuclein (?-syn) in the central nervous system (CNS) is a core feature of Parkinson disease (PD) that leads to activation of the innate immune system, production of inflammatory cytokines and chemokines, and subsequent neurodegeneration. Here, we used heterozygous reporter knock-in mice in which the first exons of the fractalkine receptor (CX3CR1) and of the C-C chemokine receptor type 2 (CCR2) are replaced with fluorescent reporters to study the role of resident microglia (CX3CR1+) and infiltrating peripheral monocytes (CCR2+), respectively, in the CNS. We used an ?-syn mouse model induced by viral over-expression of ?-syn. We find that in vivo, expression of full-length human ?-syn induces robust infiltration of pro-inflammatory CCR2+ peripheral monocytes into the substantia nigra. Genetic deletion of CCR2 prevents ?-syn induced monocyte entry, attenuates MHCII expression and blocks the subsequent degeneration of dopaminergic neurons. These results demonstrate that extravasation of pro-inflammatory peripheral monocytes into the CNS plays a key role in neurodegeneration in this model of PD synucleinopathy, and suggest that peripheral monocytes may be a target of neuroprotective therapies for human PD.

SUBMITTER: Harms AS

PROVIDER: S-EPMC5759972 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Peripheral monocyte entry is required for alpha-Synuclein induced inflammation and Neurodegeneration in a model of Parkinson disease.

Harms Ashley S AS Thome Aaron D AD Yan Zhaoqi Z Schonhoff Aubrey M AM Williams Gregory P GP Li Xinru X Liu Yudong Y Qin Hongwei H Benveniste Etty N EN Standaert David G DG

Experimental neurology 20171116

Accumulation of alpha-synuclein (α-syn) in the central nervous system (CNS) is a core feature of Parkinson disease (PD) that leads to activation of the innate immune system, production of inflammatory cytokines and chemokines, and subsequent neurodegeneration. Here, we used heterozygous reporter knock-in mice in which the first exons of the fractalkine receptor (CX3CR1) and of the C-C chemokine receptor type 2 (CCR2) are replaced with fluorescent reporters to study the role of resident microglia ...[more]

PMID: 29155051

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Project description:BACKGROUND:Parkinson's disease (PD) is characterized by intracellular alpha-synuclein (?-syn) inclusions, progressive death of dopaminergic neurons in the substantia nigra pars compacta (SNpc), and activation of the innate and adaptive immune systems. Disruption of immune signaling between the central nervous system (CNS) and periphery, such as through targeting the chemokine receptor type 2 (CCR2) or the major histocompatibility complex II (MHCII), is neuroprotective in rodent models of PD, suggesting a key role for innate and adaptive immunity in disease progression. The purpose of this study was to investigate whether genetic knockout or RNA silencing of the class II transactivator (CIITA), a transcriptional co-activator required for MHCII induction, is effective in reducing the neuroinflammation and neurodegeneration observed in an ?-syn mouse model of PD. METHODS:In vitro, we utilized microglia cultures from WT or CIITA -/- mice treated with ?-syn fibrils to investigate inflammatory iNOS expression and antigen processing via immunocytochemistry (ICC). In vivo, an adeno-associated virus (AAV) was used to overexpress ?-syn in WT and CIITA -/- mice as a model for PD. Concurrently with AAV-mediated overexpression of ?-syn, WT mice received CIITA-targeted shRNAs packaged in lentiviral constructs. Immunohistochemistry and flow cytometry were used to assess inflammation and peripheral cell infiltration at 4 weeks post transduction, and unbiased stereology was used 6 months post transduction to assess neurodegeneration. RESULTS:Using ICC and DQ-ovalbumin, we show that CIITA -/- microglial cultures failed to upregulate iNOS and MHCII expression, and had decreased antigen processing in response to ?-syn fibrils when compared to WT microglia. In vivo, global knock-out of CIITA as well as local knockdown using lentiviral shRNAs targeting CIITA attenuated MHCII expression, peripheral immune cell infiltration, and ?-syn-induced neurodegeneration. CONCLUSION:Our data provide evidence that CIITA is required for ?-syn-induced MHCII induction and subsequent infiltration of peripheral immune cells in an ?-syn mouse model of PD. Additionally, we demonstrate that CIITA in the CNS drives neuroinflammation and neurodegeneration. These data provide further support that the disruption or modulation of antigen processing and presentation via CIITA is a promising target for therapeutic development in preclinical animal models of PD.

Project description:A global isotopic labeling strategy combined with multidimensional liquid chromatographies and tandem mass spectrometry was used for quantitative proteome analysis of a presymptomatic A53T alpha-synuclein Drosophila model of Parkinson disease (PD). Multiple internal standard proteins at different concentration ratios were spiked into samples from PD-like and control animals to assess quantification accuracy. Two biological replicates isotopically labeled in forward and reverse directions were analyzed. A total of 253 proteins were quantified with a minimum of two identified peptide sequences (for each protein); 180 ( approximately 71%) proteins were detected in both forward and reverse labeling measurements. Twenty-four proteins were differentially expressed in A53T alpha-synuclein Drosophila; up-regulation of troponin T and down-regulation of fat body protein 1 were confirmed by Western blot analysis. Elevated expressions of heat shock protein 70 cognate 3 and ATP synthase are known to be directly involved in A53T alpha-synuclein-mediated toxicity and PD; three up-regulated proteins (muscle LIM protein at 60A, manganese-superoxide dismutase, and troponin T) and two down-regulated proteins (chaoptin and retinal degeneration A) have literature-supported associations with cellular malfunctions. That these variations were observed in presymptomatic animals may shed light on the etiology of PD. Protein interaction network analysis indicated that seven proteins belong to a single network, which may provide insight into molecular pathways underlying PD. Gene Ontology analysis indicated that the dysregulated proteins are primarily associated with membrane, endoplasmic reticulum, actin cytoskeleton, mitochondria, and ribosome. These associations support prior findings in studies of the A30P alpha-synuclein Drosophila model (Xun, Z. Y., Sowell, R. A., Kaufman, T. C., and Clemmer, D. E. (2007) Protein expression in a Drosophila model of Parkinson's disease. J. Proteome Res. 6, 348-357; Xun, Z. Y., Sowell, R. A., Kaufman, T. C., and Clemmer, D. E. (2007) Lifetime proteomic profiling of an A30P alpha-synuclein Drosophila model of Parkinson's disease. J. Proteome Res. 6, 3729-3738) that defects in cellular components such as actin cytoskeleton and mitochondria may contribute to the development of later symptoms.

Dataset Information

Peripheral monocyte entry is required for alpha-Synuclein induced inflammation and Neurodegeneration in a model of Parkinson disease.

Publications

Peripheral monocyte entry is required for alpha-Synuclein induced inflammation and Neurodegeneration in a model of Parkinson disease.

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