alpha-synuclein and diphenyleneiodonium

The accumulation of amyloid fibrils is a feature of amyloid diseases, where cell toxicity is due to soluble oligomeric species that precede fibril formation or are formed by fibril fragmentation, but the mechanism(s) of fragmentation is still unclear. Neutrophil-derived elastase and histones were found in amyloid deposits from patients with different systemic amyloidoses. Neutrophil extracellular traps (NETs) are key players in a death mechanism in which neutrophils release DNA traps decorated with proteins such as elastase and histones to entangle pathogens. Here, we asked whether NETs are triggered by amyloid fibrils, reasoning that because proteases are present in NETs, protease digestion of amyloid may generate soluble, cytotoxic species. We show that amyloid fibrils from three different sources (α-synuclein, Sup35, and transthyretin) induced NADPH oxidase-dependent NETs in vitro from human neutrophils. Surprisingly, NET-associated elastase digested amyloid fibrils into short species that were cytotoxic for BHK-21 and HepG2 cells. In tissue sections from patients with primary amyloidosis, we also observed the co-localization of NETs with amyloid deposits as well as with oligomers, which are probably derived from elastase-induced fibril degradation (amyloidolysis). These data reveal that release of NETs, so far described to be elicited by pathogens, can also be triggered by amyloid fibrils. Moreover, the involvement of NETs in amyloidoses might be crucial for the production of toxic species derived from fibril fragmentation.

Topics: Acetophenones; alpha-Synuclein; Amyloid; Amyloid Neuropathies, Familial; Amyloidosis; Animals; Biomarkers; Cell Nucleus; Cell Survival; Chromatin; Cricetinae; Extracellular Space; Hep G2 Cells; Humans; Immunoglobulin Light-chain Amyloidosis; Lung; Mutation, Missense; NADPH Oxidases; Neutrophils; Onium Compounds; Pancreatic Elastase; Peptide Fragments; Prealbumin; Protein Structure, Quaternary; Proteolysis; Reactive Oxygen Species; Skin

Mechanisms whereby gene-environment interactions mediate chronic, progressive neurodegenerative processes in Parkinson's disease (PD)-the second most common neurodegenerative disease-remain elusive.. We created a two-hit [neuroinflammation and mutant α-synuclein (α-syn) overexpression] animal model to investigate mechanisms through which mutant α-syn and inflammation work in concert to mediate chronic PD neurodegeneration.. We used an intraperitoneal injection of the inflammogen lipopolysaccharide (LPS; 3 × 106 EU/kg) to initiate systemic and brain inflammation in wild-type (WT) mice and transgenic (Tg) mice overexpressing human A53T mutant α-syn. We then evaluated nigral dopaminergic neurodegeneration, α-syn pathology, and neuroinflammation.. After LPS injection, both WT and Tg mice initially displayed indistinguishable acute neuroinflammation; however, only Tg mice developed persistent neuroinflammation, chronic progressive degeneration of the nigrostriatal dopamine pathway, accumulation of aggregated, nitrated α-syn, and formation of Lewy body-like inclusions in nigral neurons. Further mechanistic studies indicated that 4-week infusion of two inhibitors of inducible nitric oxide synthase and NADPH oxidase, major free radical-generating enzymes in activated microglia, blocked nigral α-syn pathology and neurodegeneration in LPS-injected Tg mice.. Microglia-derived oxidative stress bridged neuroinflammation and α-syn pathogenic alteration in mediating chronic PD progression. Our two-hit animal model involving both a genetic lesion and an environmental trigger reproduced key features of PD and demonstrated synergistic effects of genetic predisposition and environmental exposures in the development of PD. The chronic progressive nature of dopaminergic neurodegeneration, which is absent in most existing PD models, makes this new model invaluable for the study of mechanisms of PD progression.

Topics: alpha-Synuclein; Amidines; Animals; Animals, Genetically Modified; Benzylamines; Disease Models, Animal; Injections, Intraperitoneal; Lewy Bodies; Lipopolysaccharides; Mice; NADPH Oxidases; Nerve Degeneration; Neurodegenerative Diseases; Nitric Oxide Synthase Type II; Onium Compounds; Oxidative Stress; Parkinson Disease; Substantia Nigra