Amyloid fibrils trigger the release of neutrophil extracellular traps (NETs), causing fibril fragmentation by NET-associated elastase.
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.
Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21941-590, Brazil.
Estefania P C
EP
Azevedo
Anderson B
AB
Guimarães-Costa
Guilherme S
GS
Torezani
Carolina A
CA
Braga
Fernando L
FL
Palhano
Jeffery W
JW
Kelly
Elvira M
EM
Saraiva
Debora
D
Foguel
D000098:Acetophenones / Q000494:pharmacology; D000682:Amyloid / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D028227:Amyloid Neuropathies, Familial / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D000686:Amyloidosis / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002843:Chromatin / Q000201:enzymology / Q000378:metabolism*; D006224:Cricetinae; D005110:Extracellular Space / Q000201:enzymology / Q000378:metabolism; D056945:Hep G2 Cells; D006801:Humans; D000075363:Immunoglobulin Light-chain Amyloidosis; D008168:Lung / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D020125:Mutation, Missense; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009504:Neutrophils / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D009861:Onium Compounds / Q000494:pharmacology; D010196:Pancreatic Elastase; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology; D011228:Prealbumin / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D020836:Protein Structure, Quaternary; D059748:Proteolysis; D017382:Reactive Oxygen Species / Q000378:metabolism; D012867:Skin / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D051844:alpha-Synuclein / Q000737:chemistry / Q000235:genetics / Q000502:physiology
D000098:Acetophenones; D000682:Amyloid; D015415:Biomarkers; D002843:Chromatin; D009861:Onium Compounds; D010446:Peptide Fragments; D011228:Prealbumin; D017382:Reactive Oxygen Species; D051844:alpha-Synuclein; C007517:diphenyleneiodonium; C056165:acetovanillone; D019255:NADPH Oxidases; D010196:Pancreatic Elastase