title: Localization and functionality of the inflammasome in neutrophils.
abstract: Neutrophils represent the major fraction of circulating immune cells and are rapidly recruited to sites of infection and inflammation. The inflammasome is a multiprotein complex that regulates the generation of IL-1 family proteins. The precise subcellular localization and functionality of the inflammasome in human neutrophils are poorly defined. Here we demonstrate that highly purified human neutrophils express key components of the NOD-like receptor family, pyrin domain containing 3 (NLRP3), and absent in melanoma 2 (AIM2) inflammasomes, particularly apoptosis-associated speck-like protein containing a CARD (ASC), AIM2, and caspase-1. Subcellular fractionation and microscopic analyses further showed that inflammasome components were localized in the cytoplasm and also noncanonically in secretory vesicle and tertiary granule compartments. Whereas IL-1β and IL-18 were expressed at the mRNA level and released as protein, highly purified neutrophils neither expressed nor released IL-1α at baseline or upon stimulation. Upon inflammasome activation, highly purified neutrophils released substantially lower levels of IL-1β protein compared with partially purified neutrophils. Serine proteases and caspases were differentially involved in IL-1β release, depending on the stimulus. Spontaneous activation of the NLRP3 inflammasome in neutrophils in vivo affected IL-1β, but not IL-18 release. In summary, these studies show that human neutrophils express key components of the inflammasome machinery in distinct intracellular compartments and release IL-1β and IL-18, but not IL-1α or IL-33 protein. Targeting the neutrophil inflammasome may represent a future therapeutic strategy to modulate neutrophilic inflammatory diseases, such as cystic fibrosis, rheumatoid arthritis, or sepsis.
authors.affiliation: From the Departments of Pediatrics I and.
authors.forename: Martina
authors.initials: M
authors.lastname: Bakele
authors.forename: Melanie
authors.initials: M
authors.lastname: Joos
authors.forename: Sofia
authors.initials: S
authors.lastname: Burdi
authors.forename: Nicolas
authors.initials: N
authors.lastname: Allgaier
authors.forename: Simone
authors.initials: S
authors.lastname: Pöschel
authors.forename: Birgit
authors.initials: B
authors.lastname: Fehrenbacher
authors.forename: Martin
authors.initials: M
authors.lastname: Schaller
authors.forename: Veronica
authors.initials: V
authors.lastname: Marcos
authors.forename: Jasmin
authors.initials: J
authors.lastname: Kümmerle-Deschner
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Rieber
authors.forename: Niels
authors.initials: N
authors.lastname: Borregaard
authors.forename: Amir
authors.initials: A
authors.lastname: Yazdi
authors.forename: Andreas
authors.initials: A
authors.lastname: Hector
authors.forename: Dominik
authors.initials: D
authors.lastname: Hartl
mesh_terms: D000328:Adult; D002352:Carrier Proteins / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D002451:Cell Compartmentation; D020869:Gene Expression Profiling; D006801:Humans; D058847:Inflammasomes / Q000235:genetics / Q000378:metabolism*; D007378:Interleukins / Q000378:metabolism; D042541:Intracellular Space / Q000378:metabolism; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D009504:Neutrophils / Q000378:metabolism* / Q000648:ultrastructure; D021381:Protein Transport; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D057057:Serine Proteases / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D058847:Inflammasomes; D007378:Interleukins; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C453881:NLRP3 protein, human; D012333:RNA, Messenger; D057057:Serine Proteases; D020169:Caspases
keywords: Cytokine; Immunity; Inflammation; Innate Immunity; Neutrophils; Pathogen-associated Molecular Pattern (PAMP); Toll-like Receptor (TLR)