Glial Innate Immunity Generated by Non-Aggregated Alpha-Synuclein in Mouse: Differences between Wild-type and Parkinson's Disease-Linked Mutants

Background: Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized pathologically by the presence in the brain of intracellular protein inclusions highly enriched in aggregated alpha-synuclein (alpha-Syn). Although it has been established that progression of the disease is accompanied by sustained activation of microglia, the underlying molecules and factors involved in these immune-triggered mechanisms remain largely unexplored. Lately, accumulating evidence has shown the presence of extracellular alpha-Syn both in its aggregated and monomeric forms in cerebrospinal fluid and blood plasma. However, the effect of extracellular alpha-Syn on cellular activation and immune mediators, as well as the impact of familial PD-linked alpha-Syn mutants on this stimulation, are still largely unknown.Methods and Findings: In this work, we have compared the activation profiles of non-aggregated, extracellular wild-type and PD-linked mutant alpha-Syn variants on primary glial and microglial cell cultures. After stimulation of cells with alpha-Syn, we measured the release of Th1- and Th2-type cytokines as well as IP-10/CXCL10, RANTES/CCL5, MCP-1/CCL2 and MIP-1 alpha/CCL3 chemokines. Contrary to what had been observed using cell lines or for the case of aggregated alpha-Syn, we found strong differences in the immune response generated by wild-type alpha-Syn and the familial PD mutants (A30P, E46K and A53T).Conclusions: These findings might contribute to explain the differences in the onset and progression of this highly debilitating disease, which could be of value in the development of rational approaches towards effective control of immune responses that are associated with PD

EGCG redirects amyloidogenic polypeptides into unstructured, off-pathway oligomers

The accumulation of beta-sheet–rich amyloid fibrils or aggregates is a complex, multistep process that is associated with cellular toxicity in a number of human protein misfolding disorders, including Parkinson's and Alzheimer's diseases. It involves the formation of various transient and intransient, on- and off-pathway aggregate species, whose structure, size and cellular toxicity are largely unclear. Here we demonstrate redirection of amyloid fibril formation through the action of a small molecule, resulting in off-pathway, highly stable oligomers. The polyphenol (- )-epigallocatechin gallate efficiently inhibits the fibrillogenesis of both alpha-synuclein and amyloid-beta by directly binding to the natively unfolded polypeptides and preventing their conversion into toxic, on-pathway aggregation intermediates. Instead of beta-sheet–rich amyloid, the formation of unstructured, nontoxic alpha-synuclein and amyloid-beta oligomers of a new type is promoted, suggesting a generic effect on aggregation pathways in neurodegenerative diseases