Microglia-specific overexpression of alpha-Synuclein leads to severe dopaminergic neurodegeneration by phagocytic exhaustion and oxidative toxicity
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE157536 | GEO | 2021/09/13
REPOSITORIES: GEO
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Project description:Recent findings in human samples and animal models support the involvement of inflammation in the development of Parkinson's disease. Nevertheless, it is currently unknown whether microglial activation constitutes a primary event in neurodegeneration. We generated a new mouse model by lentiviral-mediated selective α-synuclein (αSYN) accumulation in microglial cells. Surprisingly, these mice developed progressive degeneration of dopaminergic (DA) neurons without endogenous αSYN aggregation. Transcriptomics and functional assessment revealed that αSYN-accumulating microglial cells developed a strong reactive state with phagocytic exhaustion and excessive production of oxidative and proinflammatory molecules. This inflammatory state created a molecular feed-forward vicious cycle between microglia and IFNγ-secreting immune cells infiltrating the brain parenchyma. Pharmacological inhibition of oxidative and nitrosative molecule production was sufficient to attenuate neurodegeneration. These results suggest that αSYN accumulation in microglia induces selective DA neuronal degeneration by promoting phagocytic exhaustion, an excessively toxic environment and the selective recruitment of peripheral immune cells.
| S-EPMC8556263 | biostudies-literature
Project description:Increasing evidence from recent findings in human samples and animal models support the involvement of inflammation in the development of Parkinson’s disease (PD). Nevertheless, it is currently unknown whether microglia activation could also be a primary event leading to neurodegeneration in PD. We have generated a new mouse model with strictly selective alpha-Synuclein (aSYN) accumulation in microglial cells by inducible gene expression through lentiviral transduction in the nigral tissue. Surprisingly, these mice develop progressive and restricted degeneration of dopaminergic (DA) neurons without any sign of aSYN endogenous aggregation. aSYN accumulating microglial cells exhibit a strong inflammatory status with production of pro-inflammatory cytokines and chemokines. Bulk and scRNA-sequencing of the immune cellular infiltrate identify a complex cellular composition with numerous peripheral populations of the innate and adaptive immune system with specific transcriptional signatures. Molecular profiling and functional assessment reveal that intoxicated microglia develop exhausted phagocytosis and high production of oxidative molecules creating a molecular feed-forward vicious cycle with IFNg secreting immune cells infiltrated in the brain parenchyma. In these animals, pharmacological inhibition of the oxidative and nitrosative molecule production is sufficient to attenuate neurodegeneration. These results suggest that aSYN accumulation in microglia exerts selective DA neuronal degeneration by promoting phagocytic exhaustion, excessive toxic environment and selective recruitment of peripheral immune cells.
2021-09-13 | GSE157533 | GEO
Project description:Increasing evidence from recent findings in human samples and animal models support the involvement of inflammation in the development of Parkinson’s disease (PD). Nevertheless, it is currently unknown whether microglia activation could also be a primary event leading to neurodegeneration in PD. We have generated a new mouse model with strictly selective alpha-Synuclein (aSYN) accumulation in microglial cells by inducible gene expression through lentiviral transduction in the nigral tissue. Surprisingly, these mice develop progressive and restricted degeneration of dopaminergic (DA) neurons without any sign of aSYN endogenous aggregation. aSYN accumulating microglial cells exhibit a strong inflammatory status with production of pro-inflammatory cytokines and chemokines. Bulk and scRNA-sequencing of the immune cellular infiltrate identify a complex cellular composition with numerous peripheral populations of the innate and adaptive immune system with specific transcriptional signatures. Molecular profiling and functional assessment reveal that intoxicated microglia develop exhausted phagocytosis and high production of oxidative molecules creating a molecular feed-forward vicious cycle with IFNg secreting immune cells infiltrated in the brain parenchyma. In these animals, pharmacological inhibition of the oxidative and nitrosative molecule production is sufficient to attenuate neurodegeneration. These results suggest that aSYN accumulation in microglia exerts selective DA neuronal degeneration by promoting phagocytic exhaustion, excessive toxic environment and selective recruitment of peripheral immune cells.
2021-09-13 | GSE157534 | GEO
Project description:Microglia-specific overexpression of alpha-Synuclein leads to severe dopaminergic neurodegeneration by phagocytic exhaustion and oxidative toxicity
| PRJNA661576 | ENA
Project description:Microglia-specific overexpression of alpha-Synuclein leads to severe dopaminergic neurodegeneration by phagocytic exhaustion and oxidative toxicity [bulk RNA-Seq]
| PRJNA661580 | ENA
Project description:Microglia-specific overexpression of alpha-Synuclein leads to severe dopaminergic neurodegeneration by phagocytic exhaustion and oxidative toxicity [single-cell RNA-Seq]
| PRJNA661582 | ENA
Project description:Missense mutations in the leucine-rich repeat kinase 2 (LRRK2) gene can cause late-onset Parkinson disease. Past studies have provided conflicting evidence for the protective effects of LRRK2 knockdown in models of Parkinson disease as well as other disorders. These discrepancies may be caused by uncertainty in the pathobiological mechanisms of LRRK2 action. Previously, we found that LRRK2 knockdown inhibited proinflammatory responses from cultured microglia cells. Here, we report LRRK2 knockout rats as resistant to dopaminergic neurodegeneration elicited by intracranial administration of LPS. Such resistance to dopaminergic neurodegeneration correlated with reduced proinflammatory myeloid cells recruited in the brain. Additionally, adeno-associated virus-mediated transduction of human ?-synuclein also resulted in dopaminergic neurodegeneration in wild-type rats. In contrast, LRRK2 knockout animals had no significant loss of neurons and had reduced numbers of activated myeloid cells in the substantia nigra. Although LRRK2 expression in the wild-type rat midbrain remained undetected under nonpathological conditions, LRRK2 became highly expressed in inducible nitric oxide synthase (iNOS)-positive myeloid cells in the substantia nigra in response to ?-synuclein overexpression or LPS exposures. Our data suggest that knocking down LRRK2 may protect from overt cell loss by inhibiting the recruitment of chronically activated proinflammatory myeloid cells. These results may provide value in the translation of LRRK2-targeting therapeutics to conditions where neuroinflammation may underlie aspects of neuronal dysfunction and degeneration.
| S-EPMC4078806 | biostudies-other
Project description:alpha-Synuclein (SYN) is the major component of Lewy bodies, the neuropathological hallmarks of Parkinson's disease (PD). Missense mutations and multiplications of the SYN gene cause autosomal dominant inherited PD. Thus, SYN is implicated in the pathogenesis of PD. However, the mechanism whereby SYN promotes neurodegeneration remains unclear. Familial PD with SYN gene mutations are rare because the majority of PD is sporadic and emerging evidence indicates that sporadic PD may result from genetic and environmental risk factors including neuroinflammation. Hence, we examined the relationship between SYN dysfunction and neuroinflammation in mediating dopaminergic neurodegeneration in mice and dopaminergic neuronal cultures derived from wild-type SYN and mutant A53T SYN transgenic mice in a murine SYN-null (SYNKO) background (M7KO and M83KO, respectively). Stereotaxic injection of an inflammagen, lipopolysaccharide, into substantia nigra of these SYN genetically engineered mice induced similar inflammatory reactions. In M7KO and M83KO, but not in SYNKO mice, the neuroinflammation was associated with dopaminergic neuronal death and the accumulation of insoluble aggregated SYN as cytoplasmic inclusions in nigral neurons. Nitrated/oxidized SYN was detected in these inclusions and abatement of microglia-derived nitric oxide and superoxide provided significant neuroprotection in neuron-glia cultures from M7KO mice. These data suggest that nitric oxide and superoxide released by activated microglia may be mediators that link inflammation and abnormal SYN in mechanisms of PD neurodegeneration. This study advances understanding of the role of neuroinflammation and abnormal SYN in the pathogenesis of PD and opens new avenues for the discovery of more effective therapies for PD.
| S-EPMC2702093 | biostudies-literature
Project description:Parkinson's disease (PD) is characterized by a profound loss of dopaminergic neurons in the substantia nigra, accompanied by chronic neuroinflammation, mitochondrial dysfunction, and widespread accumulation of α-synuclein-rich protein aggregates in the form of Lewy bodies. However, the mechanisms linking α-synuclein pathology and dopaminergic neuronal death to chronic microglial neuroinflammation have not been completely elucidated. We show that activation of the microglial NLR family pyrin domain containing 3 (NLRP3) inflammasome is a common pathway triggered by both fibrillar α-synuclein and dopaminergic degeneration in the absence of α-synuclein aggregates. Cleaved caspase-1 and the inflammasome adaptor protein apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain (ASC) were elevated in the substantia nigra of the brains of patients with PD and in multiple preclinical PD models. NLRP3 activation by fibrillar α-synuclein in mouse microglia resulted in a delayed but robust activation of the NLRP3 inflammasome leading to extracellular interleukin-1β and ASC release in the absence of pyroptosis. Nanomolar doses of a small-molecule NLRP3 inhibitor, MCC950, abolished fibrillar α-synuclein-mediated inflammasome activation in mouse microglial cells and extracellular ASC release. Furthermore, oral administration of MCC950 in multiple rodent PD models inhibited inflammasome activation and effectively mitigated motor deficits, nigrostriatal dopaminergic degeneration, and accumulation of α-synuclein aggregates. These findings suggest that microglial NLRP3 may be a sustained source of neuroinflammation that could drive progressive dopaminergic neuropathology and highlight NLRP3 as a potential target for disease-modifying treatments for PD.
| S-EPMC6483075 | biostudies-literature
Project description:Microglia maintain brain homeostasis by removing neuron-derived components such as myelin and cell debris. The evidence linking microglia to neurodegenerative diseases is growing; however, the precise mechanisms remain poorly understood. Herein, we report a neuroprotective role for microglia in the clearance of neuron-released ?-synuclein. Neuronal ?-synuclein activates microglia, which in turn engulf ?-synuclein into autophagosomes for degradation via selective autophagy (termed synucleinphagy). Synucleinphagy requires the presence of microglial Toll-like receptor 4 (TLR4), which induces transcriptional upregulation of p62/SQSTM1 through the NF-?B signaling pathway. Induction of p62, an autophagy receptor, is necessary for the formation of ?-synuclein/ubiquitin-positive puncta that are degraded by autophagy. Finally, disruption of microglial autophagy in mice expressing human ?-synuclein promotes the accumulation of misfolded ?-synuclein and causes midbrain dopaminergic neuron degeneration. Our study thus identifies a neuroprotective function of microglia in the clearance of ?-synuclein via TLR4-NF-?B-p62 mediated synucleinphagy.
| S-EPMC7069981 | biostudies-literature