Serum amyloid A induces NLRP-3-mediated IL-1β secretion in neutrophils.
OBJECTIVE
Serum amyloid A (SAA) is an acute phase reactant with significant immunological activities, including effects on cytokine synthesis and neutrophil chemotaxis. Neutrophils can also release cytokines with proinflammatory properties. IL-1β is a key proinflammatory cytokine, the secretion of which is controlled by inflammasome. We investigated the proinflammatory effects of SAA in vitro in relation to the NLRP3 inflammasome in neutrophils.


RESULTS
Human neutrophils isolated form healthy subjects were stimulated with serum amyloid A (SAA). The cellular supernatants were analyzed by western blot using anti-IL-1β or anti-caspase-1 antibodies. IL-1β or Nod-like receptor family, pyrin domain containing 3 (NLRP3) mRNA expressions were analyzed by real-time PCR or reverse transcription-PCR (RT-PCR) method. SAA stimulation induced pro-IL-1β mRNA expression in neutrophils. Furthermore, SAA engaged the caspase-1-activating inflammasome, resulting in the production of active IL-1β. SAA-induced pro-IL-1β expression was marginally suppressed by the Syk specific inhibitor, R406, and SAA-induced pro-IL-1β processing in neutrophils was prevented by R406. Furthermore, SAA-induced NLRP3 mRNA expression was completely blocked by R406. Analysis of intracellular signaling revealed that SAA stimulation activated the tyrosine kinase Syk and mitogen-activated protein kinase (MAPK).


CONCLUSIONS
These results demonstrate that the innate neutrophil immune response against SAA involves a two-step activation process: an initial signal promoting expression of pro-IL-1β and a second signal involving Syk-dependent activation of the NLRP3 inflammasome and caspase-1, allowing processing of pro-IL-1β and secretion of mature IL-1β.
Department of Rheumatology and Clinical Research Center, Nagasaki Medical Center, Omura, Nagasaki, Japan.
Kiyoshi
K
Migita
Department of Rheumatology and Clinical Research Center, Nagasaki Medical Center, Omura, Nagasaki, Japan.
Yasumori
Y
Izumi
Department of Rheumatology and Clinical Research Center, Nagasaki Medical Center, Omura, Nagasaki, Japan.
Yuka
Y
Jiuchi
Department of Rheumatology and Clinical Research Center, Nagasaki Medical Center, Omura, Nagasaki, Japan.
Hideko
H
Kozuru
Department of Rheumatology and Clinical Research Center, Nagasaki Medical Center, Omura, Nagasaki, Japan.
Chieko
C
Kawahara
Department of Rheumatology and Clinical Research Center, Nagasaki Medical Center, Omura, Nagasaki, Japan.
Minoru
M
Nakamura
Department of Rheumatology, Shinto Kumamoto Hospital, Kumamoto, Japan.
Tadashi
T
Nakamura
Department of Infection and Host Defense, Graduate School of Medicine, Shinshu University, Matsumoto, Nagano, Japan.
Kazunaga
K
Agematsu
Department of Pathology, Ehime University Graduate School of Medicine and Proteo-Science Center, Toon, Ehime, Japan.
Junya
J
Masumoto
Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki University, Nagasaki, Japan.
Michio
M
Yasunami
Department of Rheumatology, Nagasaki University Hospital, Nagasaki, Japan.
Atsushi
A
Kawakami
Department of Rheumatology, Sasebo City General Hospital, Sasebo, Nagasaki, Japan.
Katsumi
K
Eguchi
D002352:Carrier Proteins / Q000276:immunology* / Q000378:metabolism; D020170:Caspase 1 / Q000276:immunology / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000276:immunology / Q000378:metabolism; D005260:Female; D006801:Humans; D058847:Inflammasomes / Q000276:immunology / Q000378:metabolism; D053583:Interleukin-1beta / Q000276:immunology* / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D008297:Male; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D018375:Neutrophil Activation / Q000187:drug effects / Q000276:immunology*; D009504:Neutrophils / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D010078:Oxazines / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D000685:Serum Amyloid A Protein / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology*; D000072377:Syk Kinase
D002352:Carrier Proteins; C508585:IL1B protein, human; D058847:Inflammasomes; D053583:Interleukin-1beta; D047908:Intracellular Signaling Peptides and Proteins; C510788:N4-(2,2-dimethyl-3-oxo-4H-pyrid(1,4)oxazin-6-yl)-5-fluoro-N2-(3,4,5-trimethoxyphenyl)-2,4-pyrimidinediamine; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C453881:NLRP3 protein, human; D010078:Oxazines; D011725:Pyridines; D000685:Serum Amyloid A Protein; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; D048049:Extracellular Signal-Regulated MAP Kinases; D020170:Caspase 1