Parkinson-related parkin reduces α-Synuclein phosphorylation in a gene transfer model

α-Synuclein aggregates in Lewy bodies and plays a central role in the pathogenesis of a group of neurodegenerative disorders, known as "Synucleinopathies", including Parkinson's disease. Parkin mutations result in loss of parkin E3-ubiquitin ligase activity and cause autosomal recessive early onset parkinsonism

Toll-Like Receptor 2 Signaling and Current Approaches for Therapeutic Modulation in Synucleinopathies

The innate immune response in the central nervous system (CNS) is implicated as both beneficial and detrimental to health. Integral to this process are microglia, the resident immune cells of the CNS. Microglia express a wide variety of pattern-recognition receptors, such as Toll-like receptors, that detect changes in the neural environment. The activation of microglia and the subsequent proinflammatory response has become increasingly relevant to synucleinopathies, including Parkinson's disease the second most prevalent neurodegenerative disease. Within these diseases there is evidence of the accumulation of endogenous α-synuclein that stimulates an inflammatory response from microglia via the Toll-like receptors. There have been recent developments in both new and old pharmacological agents designed to target microglia and curtail the inflammatory environment. This review will aim to delineate the process of microglia-mediated inflammation and new therapeutic avenues to manage the response

Synuclein and microglial activation in Parkinson's disease

Thesis (Ph.D.)--University of Rochester. School of Medicine and Dentistry. Dept. of Microbiology and Immunology, 2007.Parkinson’s disease (PD) is an age-related slowly progressive neurodegenerative disorder with preferential loss of nigrostriatal dopamine neurons. The pathological hallmark of PD is the presence of intracytoplasmic proteinaceous synuclein positive inclusions, so-called Lewy bodies, in the remaining dopaminergic neurons. It is well documented that over-expression of wild-type (WT) α-synuclein (SYN) or mutant forms, A30P and A53T, play an important role in the pathogenesis of PD. In addition, a growing body of evidence suggests an inflammatory process in the substantia nigra (SN) and striatum (STR), characterized by activation of resident microglial cells in PD patients. Based on this information, we hypothesize that overexpression of WT and mutant SYN will induce microglial-mediated inflammation. Furthermore, we posit that activation of microglia will exacerbate nigrostriatal pathology. To test this hypothesis, we used two transgenic mouse models as well as primary microglial-enriched cell cultures. The first model utilizes human WT SYN overexpression exclusively in tyrosine hydroxylase (TH) containing cells (SYNWT+/+) while the second model employs a similar strategy for overexpression of doublymutated human SYN (A30P and A53T, SYNDM+/+). Utilizing these transgenic models, we determined microglial activation at various ages compared with nontransgenic animals (NTG) and characterized upregulated inflammatory molecules. Furthermore, to examine the direct effect of SYN on microglial activation, we utilized primary microglia-enriched cultures from non-transgenic mice treated with WT and DM SYN. Finally, primary microglia-enriched cell cultures from CD36-deficient vii mice (CD36-/-) were used to determine the necessity of this scavenger receptor for SYN phagocytosis. Together, the results of these studies demonstrated that an early microglia-mediated inflammation occurred in both SYNWT+/+ and SYNDM+/+ transgenic mice, and the degree of inflammation in SYNDM+/+ was much greater than in SYNWT+/+. Furthermore, the early and transient microglial activation in SYNDM+/+ mice was associated with delayed degeneration of striatal nerve terminals within 12 months. In vitro studies showed that both WT and DM SYN were able to activate microglia directly and induce a cascade of inflammatory events, which processes are partially mediated by CD36. To conclude, these studies reveal the pathological effect of SYN overexpression or mutation in triggering microglial activaton as well as the neurotoxic role of microglial activation in dopaminergic neuron dysfunction in the SYN-related transgenic models of Parkinson’s disease

Dataset for: Inflammation alters AMPA-stimulated calcium responses in dorsal striatal D2 but not D1 spiny projection neurons

Neuroinflammation precedes neuronal loss in striatal neurodegenerative diseases and can be exacerbated by the release of proinflammatory molecules by microglia. These molecules can affect trafficking of AMPARs. The preferential trafficking of calcium-permeable versus impermeable AMPARs can result in disruptions of [Ca²⁺]_i and alter cellular functions. In striatal neurodegenerative diseases, changes in [Ca²⁺]_i and L-type voltage-gated calcium channels (VGCCs) have been reported. Therefore, the present study sought to determine whether a proinflammatory environment alters AMPA-stimulated [Ca²⁺]_i through calcium-permeable AMPARs and/or L-type VGCCs in dopamine-2 and dopamine-1 expressing striatal spiny projection neurons (D2 and D1 SPNs) in the dorsal striatum. Mice expressing the calcium indicator protein, GCaMP in D2 or D1 SPNs, were utilized for calcium imaging. Microglial activation was assessed by morphology analyses. To induce inflammation, acute mouse striatal slices were incubated with lipopolysaccharide (LPS). Here we report that LPS treatment potentiated AMPA responses only in D2 SPNs. When a nonspecific VGCC blocker was included, we observed a decrease of AMPA-stimulated calcium fluorescence in D2 but not D1 SPNs. The remaining agonist induced [Ca²⁺]_i was mediated by calcium-permeable AMPARs because the responses were completely blocked by a selective calcium-permeable AMPAR antagonist. We used isradipine, the highly selective L-type VGCC antagonist to determine the role of L-type VGCCs in SPNs treated with LPS. Isradipine decreased AMPA-stimulated responses selectively in D2 SPNs after LPS treatment. Our findings suggest that dorsal striatal D2 SPNs are specifically targeted in proinflammatory conditions and that L-type VGCCs and calcium-permeable AMPARs are important mediators of this effect

α-Synuclein alters Toll-like receptor expression

Parkinson’s disease, an age-related neurodegenerative disorder, is characterized by the loss of dopamine neurons in the substantia nigra, the accumulation of α-synuclein in Lewy bodies and neurites, and neuroinflammation. While the exact etiology of sporadic Parkinson’s disease remains elusive, a growing body of evidence suggests that misfolded α-synuclein promotes inflammation and oxidative stress resulting in neurodegeneration. α-Synuclein has been directly linked to microglial activation in vitro and increased numbers of activated microglia have been reported in an α-synuclein overexpressing mouse model prior to neuronal loss. However, the mechanism by which α-synuclein incites microglial activation has not been fully described. Microglial activation is governed in part, by pattern recognition receptors that detect foreign material and additionally recognize changes in homeostatic cellular conditions. Upon proinflammatory pathway initiation, activated microglia contribute to oxidative stress through release of cytokines, nitric oxide, and other reactive oxygen species, which may adversely impact adjacent neurons. Here we show that microglia are directly activated by α-synuclein in a classical activation pathway that includes alterations in the expression of Toll-like receptors. These data suggest that α-synuclein can act as a danger-associated molecular pattern