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 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.

scholarly journals The Role of NLRP3 Inflammasome Activities in Bone Diseases and Vascular Calcification

Inflammation ◽  
2020 ◽  
Author(s):  
Chenyang Yu ◽  
Caihua Zhang ◽  
Zhihui Kuang ◽  
Qiang Zheng
Keyword(s):  
Vascular Calcification ◽  
Nlrp3 Inflammasome ◽  
Periodontal Diseases ◽  
Bone Destruction ◽  
Bone Diseases ◽  
Sterile Inflammation ◽  
Inflammatory Factors ◽  
Bone Homeostasis ◽  
Caspase 1

Abstract Continuous stimulation of inflammation is harmful to tissues of an organism. Inflammatory mediators not only have an effect on metabolic and inflammatory bone diseases but also have an adverse effect on certain genetic and periodontal diseases associated with bone destruction. Inflammatory factors promote vascular calcification in various diseases. Vascular calcification is a pathological process similar to bone development, and vascular diseases play an important role in the loss of bone homeostasis. The NLRP3 inflammasome is an essential component of the natural immune system. It can recognize pathogen-related molecular patterns or host-derived dangerous signaling molecules, recruit, and activate the pro-inflammatory protease caspase-1. Activated caspase-1 cleaves the precursors of IL-1β and IL-18 to produce corresponding mature cytokines or recognizes and cleaves GSDMD to mediate cell pyroptosis. In this review, we discuss the role of NLRP3 inflammasome in bone diseases and vascular calcification caused by sterile or non-sterile inflammation and explore potential treatments to prevent bone loss.

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.

Suppression of NLRP3 Inflammasome, Pyroptosis, and Cell Death by NIM811 in Rotenone-Exposed Cells as an in vitro Model of Parkinson’s Disease

2020 ◽  
pp. 1-11
Author(s):  
Minghao Zhang ◽  
Qingping He ◽  
Guisheng Chen ◽  
P. Andy Li
Keyword(s):  
Cell Death ◽  
Nlrp3 Inflammasome ◽  
Mitochondrial Membrane ◽  
In Vitro Model ◽  
Ros Production ◽  
Double Staining ◽  
Caspase 1 ◽  
Vitro Model ◽  
Pass Through

<b><i>Background:</i></b> Parkinson’s disease (PD) is characterized by the selective death of dopaminergic neurons in the substantia nigra. Recently, NLRP3 inflammasome and pyroptosis were found to be associated with PD. Cyclosporine A (CsA), an immunosuppressant, reduces neuronal death in PD. However, CsA could hardly pass through the blood-brain barrier (BBB) and high dose is associated with severe side effects and toxicity. N-methyl-4-isoleucine-cyclosporine (NIM811) is a CsA derivate that can pass through the BBB. However, little is known about its effect on PD. <b><i>Objective:</i></b> The objectives of this study were to explore the mechanism of rotenone-induced cell damage and to examine the protective effects of NIM811 on the neurotoxicity of a Parkinson-like in vitro model induced by rotenone. <b><i>Methods:</i></b> Murine hippocampal HT22 cells were cultured with the mitochondrial complex I inhibitor rotenone, a widely used pesticide that has been used for many years as a tool to induce a PD model in vitro and in vivo and proven to be reproducible. NIM811 was added to the culture media 3 h prior to the rotenone incubation. Cell viability was determined by resazurin assay, reactive oxygen species (ROS) production by dihydroethidine (DHE), and mitochondrial membrane potential by tetramethyl rhodamine methyl ester (TMRM). TUNEL and caspase-1 immunofluorescent double staining was used to detect pyroptosis. NLRP3, caspase-1, pro-caspase-1, GSDMD, and interleukin-18 (IL-18) were measured using Western blotting after 24 h of rotenone incubation. The reactivity of interleukin-1β (IL-1β) was determined by ELISA. <b><i>Results:</i></b> Our results demonstrated that rotenone caused more than 40% of cell death, increased ROS production, and reduced mitochondrial membrane potential, while NIM811 reversed these alterations. Immunofluorescent double staining showed that rotenone increased the percentage of caspase-1 and TUNEL double-labelled cells, an indication of pyroptosis, after 24 h of incubation. The protein expression of NLRP3, caspase-1, pro-caspase-1, GSDMD, IL-18, and IL-1β was significantly increased after 24 h of rotenone incubation. NIM811 suppressed rotenone-induced pyroptosis and downregulated the protein expression of NLRP3, caspase-1, pro-caspase-1, GSDMD, IL-1β, and IL-18. <b><i>Conclusion:</i></b> These results provide evidence that rotenone activates the NLRP3 inflammomere and induces pyroptosis. NIM811 protects the cell from rotenone-induced damage and inhibits NLRP3 inflammasome and pyroptosis. NIM811 might serve as a potential therapeutic drug in the treatment of PD.

scholarly journals Caspase 1 Involvement in Human Monocyte Lysis Induced by Actinobacillus actinomycetemcomitans Leukotoxin

2003 ◽  
Vol 71 (8) ◽  
pp. 4448-4455 ◽  
Author(s):  
P. Kelk ◽  
A. Johansson ◽  
R. Claesson ◽  
L. Hänström ◽  
S. Kalfas
Keyword(s):  
Periodontal Diseases ◽  
Human Monocyte ◽  
Actinobacillus Actinomycetemcomitans ◽  
Lymphocyte Function ◽  
Human Leukocytes ◽  
Caspase 1 ◽  
Oral Bacterium ◽  
Toxin Exposure ◽  
Apoptotic Activity ◽  
Leukocyte Populations

ABSTRACT Actinobacillus actinomycetemcomitans, an oral bacterium implicated in the etiology of periodontal diseases, produces a leukotoxin that selectively lyses primate neutrophils and monocytes, the major populations of defense cells in the periodontium. Though lysis requires expression of the receptor lymphocyte function-associated molecule 1 (LFA-1) on the cell surface, not all LFA-1-expressing leukocyte populations are equally susceptible to the toxin. In this study, the susceptibility of human leukocytes to leukotoxin-induced lysis is compared to their expression of LFA-1 and the activity of caspase 1. Cytolysis was determined by the activity of lactate dehydrogenase released from peripheral human leukocytes after 1-h exposure to leukotoxin. Monocytes were lysed at leukotoxin concentrations of ≥5 ng/ml, while the corresponding values for neutrophils and lymphocytes were approximately 10 times greater. Similar LFA-1 expression was found in all susceptible cell populations irrespective of their degree of sensitivity to the toxin. Exposure of monocytes to leukotoxin increased their caspase 1 activity about fivefold within 10 to 20 min. Presence of the caspase 1 inhibitor Ac-YVAD-CMK significantly blocked the leukotoxin-induced lysis of monocytes only. At sublytic concentrations, leukotoxin induced no apoptotic activity in monocytes, as revealed by the lack of caspase 3 activation and DNA fragmentation. Monocytes are the most lysis-sensitive leukocytes for A. actinomycetemcomitans leukotoxin. Their lysis by this toxin depends on caspase 1 activation and proceeds through a process that differs from classical apoptosis.

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 The Role of Cytokines Produced via the NLRP3 Inflammasome in Mouse Macrophages Stimulated with Dental Calculus in Osteoclastogenesis

2021 ◽  
Vol 22 (22) ◽  
pp. 12434
Author(s):  
Megumi Mae ◽  
Mohammad Ibtehaz Alam ◽  
Yasunori Yamashita ◽  
Yukio Ozaki ◽  
Kanako Higuchi ◽  
...  
Keyword(s):  
Nlrp3 Inflammasome ◽  
Alveolar Bone ◽  
Mouse Bone Marrow ◽  
Dependent Manner ◽  
Deficient Mouse ◽  
Dental Calculus ◽  
Mouse Macrophages ◽  
D Cells ◽  
Culture Supernatants

Dental calculus (DC) is a common deposit in periodontitis patients. We have previously shown that DC contains both microbial components and calcium phosphate crystals that induce an osteoclastogenic cytokine IL-1β via the NLRP3 inflammasome in macrophages. In this study, we examined the effects of cytokines produced by mouse macrophages stimulated with DC on osteoclastogenesis. The culture supernatants from wild-type (WT) mouse macrophages stimulated with DC accelerated osteoclastogenesis in RANKL-primed mouse bone marrow macrophages (BMMs), but inhibited osteoclastogenesis in RANKL-primed RAW-D cells. WT, but not NLRP3-deficient, mouse macrophages stimulated with DC produced IL-1β and IL-18 in a dose-dependent manner, indicating the NLRP3 inflammasome-dependent production of IL-1β and IL-18. Both WT and NLRP3-deficient mouse macrophages stimulated with DC produced IL-10, indicating the NLRP3 inflammasome-independent production of IL-10. Recombinant IL-1β accelerated osteoclastogenesis in both RANKL-primed BMMs and RAW-D cells, whereas recombinant IL-18 and IL-10 inhibited osteoclastogenesis. These results indicate that DC induces osteoclastogenic IL-1β in an NLRP3 inflammasome-dependent manner and anti-osteogenic IL-18 and IL-10 dependently and independently of the NLRP3 inflammasome, respectively. DC may promote alveolar bone resorption via IL-1β induction in periodontitis patients, but suppress resorption via IL-18 and IL-10 induction in some circumstances.

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 Insulin amyloid fibrils interact directly with the NLRP3, resulting in inflammasome activation and pyroptotic cell death

2021 ◽  
Vol 35 ◽  
pp. 205873842110383
Author(s):  
Wakako Mori ◽  
Naoe Kaneko ◽  
Ayaka Nakanishi ◽  
Tamotsu Zako ◽  
Junya Masumoto
Keyword(s):  
Cell Death ◽  
Nlrp3 Inflammasome ◽  
Amyloid Fibrils ◽  
Mononuclear Cells ◽  
Polyacrylamide Gel Electrophoresis ◽  
Enzyme Linked Immunosorbent Assay ◽  
Inflammasome Activation ◽  
Amyloid Formation ◽  
Molecular Pattern ◽  
Nlrp3 Inflammasome Activation

Introduction Nucleotide-binding oligomerization domain-like receptor family, pyrin domain containing 3 (NLRP3), an intracellular pattern recognition receptor, recognizes various pathogen-associated molecular pattern and/or damage-associated molecular pattern molecules to constitute inflammasome that act as an interleukin (IL)-1β processing platform. Injected insulin is reported to induce focal amyloidosis and the formation of subcutaneous lumps called insulin balls, but the formation of subcutaneous lumps and the underlying cytotoxic mechanism has not been elucidated. Methods Amyloid formation was evaluated by thioflavin T spectroscopic assay and scanning electron microscopy. Binding between insulin amyloid fibrils and NLRP3 was evaluated by immunoprecipitation followed by native polyacrylamide gel electrophoresis. Inflammasome activation was evaluated by immunofluorescence speck formation called “ASC speck” and Western blotting. IL-1β secretion in culture supernatants of peripheral blood mononuclear cells was evaluated by enzyme-linked immunosorbent assay. Cytotoxicity was measured by lactate dehydrogenase release assay. Results Insulin amyloid fibrils interact directly with NLRP3, resulting in NLRP3 inflammasome activation and pyroptotic cell death. Conclusion Insulin ball formation and cytotoxicity may be associated with NLRP3 inflammasome activation followed by pyroptotic cell death.

scholarly journals Active MLKL triggers the NLRP3 inflammasome in a cell-intrinsic manner

2017 ◽  
Vol 114 (6) ◽  
pp. E961-E969 ◽  
Author(s):  
Stephanie A. Conos ◽  
Kaiwen W. Chen ◽  
Dominic De Nardo ◽  
Hideki Hara ◽  
Lachlan Whitehead ◽  
...  
Keyword(s):  
Cell Death ◽  
Nlrp3 Inflammasome ◽  
Adaptor Protein ◽  
Cell Lysis ◽  
Kinase Domain ◽  
Receptor Protein ◽  
Interacting Protein ◽  
Caspase 1 ◽  
Proinflammatory Mediators ◽  
Death Effector

Necroptosis is a physiological cell suicide mechanism initiated by receptor-interacting protein kinase-3 (RIPK3) phosphorylation of mixed-lineage kinase domain-like protein (MLKL), which results in disruption of the plasma membrane. Necroptotic cell lysis, and resultant release of proinflammatory mediators, is thought to cause inflammation in necroptotic disease models. However, we previously showed that MLKL signaling can also promote inflammation by activating the nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome to recruit the adaptor protein apoptosis-associated speck-like protein containing a caspase activation and recruitment domain (ASC) and trigger caspase-1 processing of the proinflammatory cytokine IL-1β. Here, we provide evidence that MLKL-induced activation of NLRP3 requires (i) the death effector four-helical bundle of MLKL, (ii) oligomerization and association of MLKL with cellular membranes, and (iii) a reduction in intracellular potassium concentration. Although genetic or pharmacological targeting of NLRP3 or caspase-1 prevented MLKL-induced IL-1β secretion, they did not prevent necroptotic cell death. Gasdermin D (GSDMD), the pore-forming caspase-1 substrate required for efficient NLRP3-triggered pyroptosis and IL-1β release, was not essential for MLKL-dependent death or IL-1β secretion. Imaging of MLKL-dependent ASC speck formation demonstrated that necroptotic stimuli activate NLRP3 cell-intrinsically, indicating that MLKL-induced NLRP3 inflammasome formation and IL-1β cleavage occur before cell lysis. Furthermore, we show that necroptotic activation of NLRP3, but not necroptotic cell death alone, is necessary for the activation of NF-κB in healthy bystander cells. Collectively, these results demonstrate the potential importance of NLRP3 inflammasome activity as a driving force for inflammation in MLKL-dependent diseases.

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