Rapid Release of Interleukin-1β from Human Platelets Is Independent of NLRP3 and Caspase

2021 ◽  
Author(s):  
Gabrielle J. Pennings ◽  
Caroline J. Reddel ◽  
Mathew Traini ◽  
Magdalena Lam ◽  
Maaike Kockx ◽  
...  
Keyword(s):  
Nlrp3 Inflammasome ◽  
Human Platelets ◽  
Interleukin 1Β ◽  
Enzyme Linked Immunosorbent Assay ◽  
Thrombin Receptor ◽  
Classical Pathway ◽  
Receptor Agonists ◽  
Caspase 1 ◽  
Rapid Release ◽  
Transmission Electron

Abstract Objective Platelets are critical in mediating both rapid responses to injury and the development and progression of coronary disease. Several studies have shown that, after prolonged exposure to agonists, they produce and release inflammatory mediators including interleukin-1β (IL-1β), via the classical pathway (NLRP3 inflammasome and caspase-1 cleavage to release active IL-1β) as described for leukocytes. This study aimed to determine whether there is rapid release of IL-1β in response to soluble platelet agonists and whether such rapid release is NLRP3- and caspase-1-dependent. Methods and Results Using flow cytometry to detect platelet activation (and release of α and dense granule contents) and the combination of Western blotting, enzyme-linked-immunosorbent assay, and immunogold labeling transmission electron and immunofluorescence microscopy, we identified that resting human platelets contain mature IL-1β. Platelets release IL-1β within minutes in response to adenosine diphosphate (ADP), collagen, and thrombin receptor agonists, but not in response to conventional NLRP3 inflammasome agonists—lipopolysaccharide and adenosine triphosphate. The rapid release of IL-1β in response to ADP and thrombin receptor agonists was independent of caspases (including caspase-1) and NLRP3. Immature and mature IL-1β were identified as low-abundance proteins on transmission electron microscopy of human platelets, and were localized to the platelet cytosol, open canalicular system, and the periphery of α granules. Conclusion Unlike monocytes and neutrophils, human platelets are capable of rapid agonist- and time-dependent release of IL-1β by a mechanism which is independent of caspase-1 and NLRP3.

scholarly journals Shiga Toxins Activate the NLRP3 Inflammasome Pathway To Promote Both Production of the Proinflammatory Cytokine Interleukin-1β and Apoptotic Cell Death

2015 ◽  
Vol 84 (1) ◽  
pp. 172-186 ◽  
Author(s):  
Moo-Seung Lee ◽  
Haenaem Kwon ◽  
Eun-Young Lee ◽  
Dong-Jae Kim ◽  
Jong-Hwan Park ◽  
...  
Keyword(s):  
Cell Death ◽  
Nlrp3 Inflammasome ◽  
Apoptotic Cell ◽  
Apoptotic Cell Death ◽  
Interleukin 1Β ◽  
Dependent Manner ◽  
Shiga Toxins ◽  
Caspase 1 ◽  
Immune Signaling Pathway ◽  
Tnf Α

Shiga toxin (Stx)-mediated immune responses, including the production of the proinflammatory cytokines tumor necrosis-α (TNF-α) and interleukin-1β (IL-1β), may exacerbate vascular damage and accelerate lethality. However, the immune signaling pathway activated in response to Stx is not well understood. Here, we demonstrate that enzymatically active Stx, which leads to ribotoxic stress, triggers NLRP3 inflammasome-dependent caspase-1 activation and IL-1β secretion in differentiated macrophage-like THP-1 (D-THP-1) cells. The treatment of cells with a chemical inhibitor of glycosphingolipid biosynthesis, which suppresses the expression of the Stx receptor globotriaosylceramide and subsequent endocytosis of the toxin, substantially blocked activation of the NLRP3 inflammasome and processing of caspase-1 and IL-1β. Processing and release of both caspase-1 and IL-1β were significantly reduced or abolished in Stx-intoxicated D-THP-1 cells in which the expression of NLRP3 or ASC was stably knocked down. Furthermore, Stx mediated the activation of caspases involved in apoptosis in an NLRP3- or ASC-dependent manner. In Stx-intoxicated cells, the NLRP3 inflammasome triggered the activation of caspase-8/3, leading to the initiation of apoptosis, in addition to caspase-1-dependent pyroptotic cell death. Taken together, these results suggest that Stxs trigger the NLRP3 inflammasome pathway to release proinflammatory IL-1β as well as to promote apoptotic cell death.

Dual Targeting of Autophagy and NF-κB Pathway by PPARγ Contributes to the Inhibitory Effect of Demethoxycurcumin on NLRP3 Inflammasome Priming

2021 ◽  
Vol 14 ◽  
Author(s):  
Jing Tang ◽  
Xiaoxue Tan ◽  
Xiangmi Huang ◽  
Jie Zhang ◽  
Liang Chen ◽  
...  
Keyword(s):  
Nlrp3 Inflammasome ◽  
Nuclear Translocation ◽  
Inhibitory Effect ◽  
Caspase 1 ◽  
Dual Targeting ◽  
Transmission Electron ◽  
Subsequent Activation ◽  
Natural Derivative ◽  
Pparγ Expression

Background: Demethoxycurcumin (DMC), a natural derivative of curcumin, has anti-inflammatory activities. However, the mechanism has not been fully elucidated. Objective: The aim of the current study was to investigate the role of DMC on NLRP3 inflammasome priming. Methods: Protein expression was quantified by western blotting. Inflammatory cytokines were measured by ELISA. Autophagosomes were evaluated by transmission electron microscopy. Results: DMC inhibited LPS-stimulated NLRP3, pro-caspase-1, and pro-IL-1β expression. Meanwhile, DMC diminished NLRP3-dependent IL-1β maturation, caspase-1 activation, IL-1β and IL-18 production caused by LPS plus ATP. Moreover, DMC induced autophagy and autophagy inhibitor 3-MA abrogated the role of DMC on NLRP3 inflammasome priming and subsequent activation. DMC also inhibited LPS-stimulated phosphorylation and nuclear translocation of p65 NF-κB. Additionally, DMC significantly increased the PPARγ expression and the effects of DMC in NF-κB inhibition, autophagy, and NLRP3 inflammasome priming were abrogated by specific PPARγ antagonist T0070907. Conclusion: The evidence presented here has confirmed that DMC increases PPARγ expression, resulting in autophagy and NF-κB inhibition, and subsequently inhibits LPS-induced NLRP3 inflammasome priming and subsequent activation.

scholarly journals The RNA- and TRIM25-Binding Domains of Influenza Virus NS1 Protein Are Essential for Suppression of NLRP3 Inflammasome-Mediated Interleukin-1β Secretion

2016 ◽  
Vol 90 (8) ◽  
pp. 4105-4114 ◽  
Author(s):  
Miyu Moriyama ◽  
I-Yin Chen ◽  
Atsushi Kawaguchi ◽  
Takumi Koshiba ◽  
Kyosuke Nagata ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Nlrp3 Inflammasome ◽  
Influenza A ◽  
Rna Binding ◽  
Nonstructural Protein ◽  
Binding Domain ◽  
Interleukin 1Β ◽  
Ns1 Protein ◽  
Caspase 1 ◽  
Nonstructural Protein 1

ABSTRACTInflammasomes are cytosolic multimolecular protein complexes that stimulate the activation of caspase-1 and the release of mature forms of interleukin-1β (IL-1β) and IL-18. We previously demonstrated that the influenza A virus M2 protein stimulates IL-1β secretion following activation of the nucleotide-binding oligomerization domain (NOD)-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome. The nonstructural protein 1 (NS1) of influenza virus inhibits caspase-1 activation and IL-1β secretion. However, the precise mechanism by which NS1 inhibits IL-1β secretion remains unknown. Here, we showed that J774A.1 macrophages stably expressing the NS1 protein inhibited IL-1β secretion after infection with recombinant influenza virus lacking the NS1 gene. Coimmunoprecipitation assay revealed that the NS1 protein interacts with NLRP3. Importantly, the NS1 protein inhibited the NLRP3/ASC-induced single-speck formation required for full activation of inflammasomes. The NS1 protein of other influenza virus strains, including a recent pandemic strain, also inhibited inflammasome-mediated IL-1β secretion. The NS1 RNA-binding domain (basic residues 38 and 41) and TRIM25-binding domain (acidic residues 96 and 97) were required for suppression of NLRP3 inflammasome-mediated IL-1β secretion. These results shed light on a mechanism by which the NS1 protein of influenza virus suppresses NLRP3 inflammasome-mediated IL-1β secretion.IMPORTANCEInnate immune sensing of influenza virus via pattern recognition receptors not only plays a key role in generating type I interferons but also triggers inflammatory responses. We previously demonstrated that the influenza A virus M2 protein activates the NLRP3 inflammasome, leading to the secretion of interleukin-1β (IL-1β) and IL-18 following the activation of caspase-1. Although the nonstructural protein 1 (NS1) of influenza virus inhibits IL-1β secretion, the precise mechanism by which it achieves this remains to be defined. Here, we demonstrate that the NS1 protein interacts with NLRP3 to suppress NLRP3 inflammasome activation. J774A.1 macrophages stably expressing the NS1 protein suppressed NLRP3-mediated IL-1β secretion. The NS1 RNA-binding domain (basic residues 38 and 41) and TRIM25-binding domain (acidic residues 96 and 97) are important for suppression of NLRP3 inflammasome-mediated IL-1β secretion. These results will facilitate the development of new anti-inflammatory drugs.

scholarly journals A Purified Biflavonoid Extract From Selaginella moellendorffii Alleviates Gout Arthritis via NLRP3/ASC/Caspase-1 Axis Suppression

2021 ◽  
Vol 12 ◽  
Author(s):  
Xueyan Zhang ◽  
Yingbo Liu ◽  
Guangrui Deng ◽  
Bisheng Huang ◽  
Guoyin Kai ◽  
...  
Keyword(s):  
Mouse Model ◽  
Nlrp3 Inflammasome ◽  
Enzyme Linked Immunosorbent Assay ◽  
Acute Gout ◽  
Paw Edema ◽  
Inflammation Model ◽  
Caspase 1 ◽  
Cellular Inflammation ◽  
Tnf Α ◽  
Selaginella Moellendorffii

Background: Activation of nucleotide oligomerization domain-like receptor protein 3 (NLRP3) inflammasome plays a crucial role in gout. Selaginella moellendorffii has been confirmed effective for the treatment of gout in hospital preparations. Flavonoids, such as amentoflavone (AM), are the main active components of this medicine.Purpose: We aimed to investigate the flavonoid extract (TF) and AM's effects on NLRP3 inflammasome in vitro and their preventive effects on gout in vivo.Methods: LC-MS method was employed to investigate the chemical profile of TF. The cellular inflammation model was established by lipopolysaccharide (LPS) or monosodium urate (MSU) stimulation. The cell membrane integrality and morphological characteristics were determined by using Lactate dehydrogenase (LDH) assay kits, propidium iodide (PI) stain, and scanning electron microscopy (SEM). The inflammatory cytokines and NLRP3 inflammasome activation were determined using enzyme-linked immunosorbent assay (ELISA), quantitative real-time polymerase chain reaction (RT-PCR), immunofluorescence staining, and western blotting. The acute gout mouse model was induced by MSU injection into footpads, and then the paw edema, inflammatory mediators, and histological examination (HE) were analyzed.Results: The main constituents in TF are AM and robustaflavone. In the cellular inflammation model, TF down-regulated the levels of nitric oxide (NO), TNF-α, and LDH, suppressed NLRP3 inflammasome-derived interleukin-1β (IL-1β) secretion, decreased caspase-1 activation, repressed mature IL-1β expression, inhibited ASC speck formation and NLRP3 protein expression. In an acute gout mouse model, oral administration of TF to mice effectively alleviated paw edema, reduced inflammatory features, and decreased the levels of IL-1β in mouse foot tissue. Similarly, the characteristic constituent AM was also able to down-regulated the levels of NO, TNF-α, and LDH, down-regulate the mRNA expression of IL-1β, TNF-α, caspase-1, and NLRP3. Besides, the foot thickness, lymphocyte infiltration, and IL-1β level were also prevented by AM.Conclusion: The results indicated that TF and its main constituent AM alleviate gout arthritis via NLRP3/ASC/Caspase-1 axis suppression.

scholarly journals Cold-Inducible RNA-Binding Protein (CIRP) Potentiates Uric Acid-Induced IL-1β Production

2021 ◽  
Author(s):  
Yuya Fujita ◽  
Toru Yago ◽  
Haruki Matsumoto ◽  
Tomoyuki Asano ◽  
Naoki Matsuoka ◽  
...  
Keyword(s):  
Uric Acid ◽  
Nlrp3 Inflammasome ◽  
Rna Binding ◽  
Binding Protein ◽  
Rna Binding Protein ◽  
Human Neutrophils ◽  
Enzyme Linked Immunosorbent Assay ◽  
Inflammasome Activation ◽  
Dependent Manner ◽  
Caspase 1

Abstract Background Gout is an autoinflammatory disease driven by interleukin-1 (IL-1) induction in response to uric acid crystals. IL-1β production is dependent on inflammasome activation, which requires a priming signal, followed by an activating signal. The cold-inducible RNA-binding protein (CIRP) has been recently identified as a damage-associated molecular pattern (DAMP). In this study, we evaluated the roles of CIRP in monosodium urate (MSU)-mediated IL-1β secretion using human neutrophils. Methods Human neutrophils were stimulated by MSU in the presence or absence of CIRP priming to determine NLRP3 inflammasome activation and subsequent caspase-1 activation and IL-1β production. Cellular supernatants were analyzed by enzyme-linked immunosorbent assay (ELISA) to determine the presence of IL-1β or caspase-1 (p20). The cellular supernatants and lysates were also analyzed by immunoblotting using anti-cleaved IL-1β or anti-cleaved caspase-1 antibodies. Additionally, pro-IL-1β and NLRP3 transcript levels were analyzed by real-time reverse transcription-PCR (RT-PCR). Results Neither CIRP nor MSU stimulation alone induced sufficient IL-1β secretion from neutrophils. However, MSU stimulation induced IL-1β secretion from CIRP-primed neutrophils in a dose-dependent manner. This MSU-induced IL-1β secretion from CIRP-primed neutrophils was accompanied by the induction of cleaved IL-1β (p17). Furthermore, cleaved caspase-1 was induced in the cellular lysates of CIRP/MSU-treated neutrophils. Additionally, CIRP stimulation induced the expression of pro-IL-1β mRNA and protein in neutrophils. Conclusions Our data indicate that CIRP, an endogenous stress molecule, triggers uric acid-induced mature IL-1β induction as a priming stimulus for NLRP3 inflammasome in human neutrophils. We propose that CIRP acts as an important proinflammatory stimulant that primes and activates inflammasome and pro-IL-1β processing in response to uric acid in innate immune cells.

scholarly journals NLRP3 Inflammasome Activation in THP-1 Target Cells Triggered by Pathogenic Naegleria fowleri

2016 ◽  
Vol 84 (9) ◽  
pp. 2422-2428 ◽  
Author(s):  
Jong-Hyun Kim ◽  
Hae-Jin Sohn ◽  
Jong-Kyun Yoo ◽  
Heekyoung Kang ◽  
Gi-Sang Seong ◽  
...  
Keyword(s):  
Nlrp3 Inflammasome ◽  
Enzyme Linked Immunosorbent Assay ◽  
Human Macrophage ◽  
Target Cells ◽  
Inflammasome Activation ◽  
Naegleria Fowleri ◽  
Content Type ◽  
Inflammatory Reactions ◽  
Caspase 1 ◽  
Nægleria Fowleri

Naegleria fowleri, known as the brain-eating amoeba, causes acute primary amoebic meningoencephalitis. During swimming and other recreational water activities,N. fowleritrophozoites penetrate the nasal mucosa and invade the olfactory bulbs, resulting in intense inflammatory reactions in the forebrain tissue. To investigate what kinds of inflammasome molecules are expressed in target cells due toN. fowleriinfection, human macrophage cells (THP-1 cells) were cocultured withN. fowleritrophozoites in a noncontact system, and consequently, interleukin-1β (IL-1β) production was estimated. Caspase-1 activation and IL-1β production from THP-1 cells by Western blotting and the culture supernatant by enzyme-linked immunosorbent assay analysis were observed at 3 h after cocultivation. In addition, the increased expression of ASC and NLRP3, which make up an inflammasome complex, was also observed at 3 h after cocultivation. To confirm the caspase-1 activation and IL-1β production via the NLRP3 inflammasome in THP-1 cells triggered byN. fowleritrophozoites, THP-1 cells were pretreated with several inhibitors. The inhibition assay showed that CA-074 (a cathepsin B inhibitor), glybenclamide (an NLRP3 molecule inhibitor), andN-benzyloxycarbony-Val-Ala-Asp(O-methyl)-fluoromethylketone (Z-VAD-FMK; a caspase-1 inhibitor) reduced the levels of caspase-1 activation and IL-1β production from THP-1 cells. This study suggests thatN. fowleriinfection induces the NLRP3 inflammasome, which activates caspase-1 and subsequently produces IL-1β, thus resulting in inflammation.

Effects of Sulfonylureas on Periodontopathic Bacteria-Induced Inflammation

2020 ◽  
Vol 99 (7) ◽  
pp. 830-838 ◽  
Author(s):  
Y. Kawahara ◽  
T. Kaneko ◽  
Y. Yoshinaga ◽  
Y. Arita ◽  
K. Nakamura ◽  
...  
Keyword(s):  
Cell Death ◽  
Nlrp3 Inflammasome ◽  
Alveolar Bone ◽  
Periodontal Diseases ◽  
Human Monocyte ◽  
Periodontal Pathogen ◽  
Enzyme Linked Immunosorbent Assay ◽  
Periodontopathic Bacteria ◽  
Caspase 1 ◽  
Culture Supernatants

Interleukin-1β (IL-1β) is an inflammatory cytokine produced by monocytes/macrophages and is closely associated with periodontal diseases. The NLRP3 inflammasome is involved in IL-1β activation through pro–IL-1β processing and pyroptotic cell death in bacterial infection. Recently, glyburide, a hypoglycemic sulfonylurea, has been reported to reduce IL-1β activation by suppressing activation of the NLRP3 inflammasome. Therefore, we evaluated the possibility of targeting the NLRP3 inflammasome pathway by glyburide to suppress periodontal pathogen-induced inflammation. THP-1 cells (a human monocyte cell line) were differentiated to macrophage-like cells by treatment with phorbol 12-myristate 13-acetate and stimulated by periodontopathic bacteria, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, or Fusobacterium nucleatum, in the presence of glyburide. IL-1β and caspase-1 expression in the cells and culture supernatants were analyzed by Western blotting and enzyme-linked immunosorbent assay, and cell death was analyzed by lactate dehydrogenase assay. Stimulation of THP-1 macrophage-like cells with every periodontopathic bacteria induced IL-1β secretion without cell death, which was suppressed by the NLRP3 inhibitor, MCC950, and caspase-1 inhibitor, z-YVAD-FMK. Glyburide treatment suppressed IL-1β expression in culture supernatants and enhanced intracellular IL-1β expression, suggesting that glyburide may have inhibited IL-1β secretion. Subsequently, a periodontitis rat model was generated by injecting periodontal bacteria into the gingiva, which was analyzed histologically. Oral administration of glyburide significantly suppressed the infiltration of inflammatory cells and the number of osteoclasts in the alveolar bone compared with the control. In addition to glyburide, glimepiride was shown to suppress the release of IL-1β from THP-1 macrophage-like cells, whereas other sulfonylureas (tolbutamide and gliclazide) or other hypoglycemic drugs belonging to the biguanide family, such as metformin, failed to suppress IL-1β release. Our results suggest that pharmacological targeting of the NLRP3 pathway may be a strategy for suppressing periodontal diseases.

scholarly journals Abundant Secretion of Bioactive Interleukin-1β by Human Macrophages Induced by Actinobacillus actinomycetemcomitans Leukotoxin

2005 ◽  
Vol 73 (1) ◽  
pp. 453-458 ◽  
Author(s):  
P. Kelk ◽  
R. Claesson ◽  
L. Hänström ◽  
U. H. Lerner ◽  
S. Kalfas ◽  
...  
Keyword(s):  
Actinobacillus Actinomycetemcomitans ◽  
Interleukin 1Β ◽  
Enzyme Linked Immunosorbent Assay ◽  
Necrosis Factor Alpha ◽  
Human Macrophages ◽  
Specific Antibodies ◽  
Protein Levels ◽  
Caspase 1 ◽  
Reverse Transcription Pcr ◽  
Tnf Α

ABSTRACT Actinobacillus actinomycetemcomitans produces a leukotoxin that selectively kills human leukocytes. Recently, we reported that macrophages are highly sensitive to leukotoxin and that their lysis involves activation of caspase 1. In this study, we show that leukotoxin also induces the production and release of proinflammatory cytokines from human macrophages. The macrophages were challenged with leukotoxin or lipopolysaccharide (LPS) from A. actinomycetemcomitans or LPS from Escherichia coli, and the production and secretion of interleukin-1β (IL-1β), IL-6, and tumor necrosis factor alpha (TNF-α) were determined at the mRNA and protein levels by reverse transcription-PCR and enzyme-linked immunosorbent assay, respectively. Leukotoxin (1 to 30 ng/ml) induced abundant production and secretion of IL-1β, while the effects on IL-6 and TNF-α production were limited. Leukotoxin (1 ng/ml) caused a 10-times-higher release of IL-1β than did LPS (100 ng/ml). The secreted IL-1β was mainly the bioactive 17-kDa protein. At higher concentrations (>30 ng/ml), leukotoxin caused secretion of mainly inactive cytokine, the 31-kDa pro-IL-1β. The presence of specific antibodies to IL-1β or of a caspase 1 inhibitor blocked the secretion and production of the cytokine. Supernatants of leukotoxin-challenged macrophages stimulated bone resorption when tested in a mouse calvarial model. The activity could be blocked by an IL-1 receptor antagonist or specific antibodies to IL-1β. We concluded that A. actinomycetemcomitans leukotoxin can trigger abundant production and secretion of bioactive IL-1β by human macrophages, which is mediated by activation of caspase 1.

scholarly journals Colchicine therapy in acute coronary syndrome patients acts on caspase-1 to suppress NLRP3 inflammasome monocyte activation

2016 ◽  
Vol 130 (14) ◽  
pp. 1237-1246 ◽  
Author(s):  
Stacy Robertson ◽  
Gonzalo J. Martínez ◽  
Cloe A. Payet ◽  
Jennifer Y. Barraclough ◽  
David S. Celermajer ◽  
...  
Keyword(s):  
Acute Coronary Syndrome ◽  
Gene Transcription ◽  
Nlrp3 Inflammasome ◽  
Healthy Subjects ◽  
Interleukin 1Β ◽  
Inflammasome Activation ◽  
Monocyte Activation ◽  
Coronary Syndrome ◽  
Caspase 1 ◽  
Colchicine Therapy

Inflammasome activation in monocytes is elevated in acute coronary syndrome (ACS) patients compared with healthy subjects. Acute colchicine therapy dramatically suppresses this activation, via inhibition of caspase-1 gene transcription leading to reduced secretion of interleukin-1β (IL-1β), supporting a beneficial role for colchicine in atherosclerosis.

scholarly journals Synergistic Costimulatory Effect of Chlamydia pneumoniae with Carbon Nanoparticles on NLRP3 Inflammasome-Mediated Interleukin-1β Secretion in Macrophages

2015 ◽  
Vol 83 (7) ◽  
pp. 2917-2925 ◽  
Author(s):  
Junji Matsuo ◽  
Shinji Nakamura ◽  
Seiji Takeda ◽  
Kasumi Ishida ◽  
Tomohiro Yamazaki ◽  
...  
Keyword(s):  
Nlrp3 Inflammasome ◽  
Carbon Nanoparticles ◽  
Actin Polymerization ◽  
Chlamydia Pneumoniae ◽  
Community Acquired Pneumonia ◽  
Interleukin 1Β ◽  
Inflammasome Activation ◽  
Nlrp3 Gene ◽  
Content Type ◽  
Caspase 1

The obligate intracellular bacteriumChlamydia pneumoniaeis not only a causative agent of community-acquired pneumonia but is also associated with a more serious chronic disease, asthma, which might be exacerbated by air pollution containing carbon nanoparticles. Although a detailed mechanism of exacerbation remains unknown, the proinflammatory cytokine interleukin-1β (IL-1β) is a critical player in the pathogenesis of asthma.C. pneumoniaeinduces IL-1β in macrophages via NACHT, LRR, and PYD domain-containing protein 3 (NLRP3) inflammasome activation and Toll-like receptor 2/4 (TLR2/4) stimulation. Carbon nanoparticles, such as carbon nanotubes (CNTs), can also evoke the NLRP3 inflammasome to trigger IL-1β secretion from lipopolysaccharide-primed macrophages. This study assessed whether costimulation ofC. pneumoniaewith CNTs synergistically enhanced IL-1β secretion from macrophages, and determined the molecular mechanism involved. Enhanced IL-1β secretion fromC. pneumoniae-infected macrophages by CNTs was dose and time dependent. Transmission electron microscopy revealed thatC. pneumoniaeand CNTs were engulfed concurrently by macrophages. Inhibitors of actin polymerization or caspase-1, a component of the inflammasome, significantly blocked IL-1β secretion. Gene silencing using small interfering RNA (siRNA) targeting the NLRP3 gene also abolished IL-1β secretion. Other inhibitors (K+efflux inhibitor, cathepsin B inhibitor, and reactive oxygen species-generating inhibitor) also blocked IL-1β secretion. Taken together, these findings demonstrated that CNTs synergistically enhanced IL-1β secretion fromC. pneumoniae-infected macrophages via the NLRP3 inflammasome and caspase-1 activation, providing novel insight into our understanding of howC. pneumoniaeinfection can exacerbate asthma.

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