scholarly journals Priming enables a NEK7-independent route of NLRP3 activation

2019 ◽  
Author(s):  
Niklas A. Schmacke ◽  
Moritz M. Gaidt ◽  
Inga Szymanska ◽  
Fionan O’Duill ◽  
Che A. Stafford ◽  
...  
Keyword(s):  
Nlrp3 Inflammasome ◽  
Mitotic Spindle ◽  
Inflammasome Activation ◽  
Human Macrophages ◽  
Antimicrobial Defense ◽  
Inflammatory Conditions ◽  
Activation Factor ◽  
Independent Mechanism ◽  
Nlrp3 Activity

ABSTRACTThe NLRP3 inflammasome plays a central role in antimicrobial defense, as well as in sterile inflammatory conditions. NLRP3 activity is governed by two independent signals. The first signal primes NLRP3, allowing it to respond to its activation signal. In the murine system, the mitotic spindle kinase NEK7 has been identified as a crucial factor in relaying the activation signal to NLRP3. Here we show that the requirement for NEK7 can be bypassed by TAK1-dependent post-translational priming. Under pro-inflammatory conditions that activate TAK1, NEK7 was dispensable for NLRP3 inflammasome formation in human and murine cells. Intriguingly, dissecting the NEK7 requirement in iPSC-derived primary human macrophages revealed that this NEK7-independent mechanism constitutes the predominant NLRP3 priming pathway in these cells. In summary, our results suggest that NEK7 functions as an NLRP3 priming – rather than activation – factor that can work in synergy or redundancy with other priming pathways to accelerate inflammasome activation.

scholarly journals Internalization of the Membrane Attack Complex Triggers NLRP3 Inflammasome Activation and IL-1β Secretion in Human Macrophages

2021 ◽  
Vol 12 ◽  
Author(s):  
Ines Diaz-del-Olmo ◽  
Jonathan Worboys ◽  
Fatima Martin-Sanchez ◽  
Anna Gritsenko ◽  
Ashley R. Ambrose ◽  
...  
Keyword(s):  
Nlrp3 Inflammasome ◽  
Pore Formation ◽  
Membrane Attack Complex ◽  
Inflammasome Activation ◽  
Adapter Protein ◽  
Human Macrophages ◽  
Danger Signals ◽  
Nlrp3 Inflammasome Activation ◽  
Golgi Network ◽  
Stimulation Of

Interleukin 1β (IL-1β) plays a major role in inflammation and is secreted by immune cells, such as macrophages, upon recognition of danger signals. Its secretion is regulated by the inflammasome, the assembly of which results in caspase 1 activation leading to gasdermin D (GSDMD) pore formation and IL-1β release. During inflammation, danger signals also activate the complement cascade, resulting in the formation of the membrane attack complex (MAC). Here, we report that stimulation of LPS-primed human macrophages with sub-lytic levels of MAC results in activation of the NOD-like receptor 3 (NLRP3) inflammasome and GSDMD-mediated IL-1β release. The MAC is first internalized into endosomes and then colocalizes with inflammasome components; adapter protein apoptosis associated speck-like protein containing a CARD (ASC) and NLRP3. Pharmacological inhibitors established that MAC-triggered activation of the NLRP3 inflammasome was dependent on MAC endocytosis. Internalization of the MAC also caused dispersion of the trans-Golgi network. Thus, these data uncover a role for the MAC in activating the inflammasome and triggering IL-1β release in human macrophages.

scholarly journals IIIM-941, a Stilbene Derivative Inhibits NLRP3 Inflammasome Activation by Inducing Autophagy

2021 ◽  
Vol 12 ◽  
Author(s):  
Mehboob Ali ◽  
Mehak Gupta ◽  
Abubakar Wani ◽  
Ankita Sharma ◽  
Mohd Abdullaha ◽  
...  
Keyword(s):  
Nlrp3 Inflammasome ◽  
Inhibitory Activity ◽  
Inflammatory Diseases ◽  
Inflammasome Activation ◽  
Synthetic Compound ◽  
Nlrp3 Inflammasome Activation ◽  
Tnf Α ◽  
Pathological Development ◽  
Inflammasome Activity ◽  
Nlrp3 Activity

Aberrant activation of NLRP3 inflammasome has been implicated in several inflammatory diseases. Autophagy is one of the primary mechanisms that regulate NLRP3 inflammasome activity. In this study, we attempted to target NLRP3 inflammasome activity by a synthetic compound IIIM-941. We found that IIIM-941 inhibits ATP induced NLRP3 inflammasome by induction of autophagy through AMPK pathway in bone marrow derived macrophages (BMDMs) and J774A.1 cells. It was interesting to observe that IIIM-941 did not show any inhibitory activity against LPS induced pro-inflammatory cytokines TNF-α and IL-6. The anti-NLRP3 activity of IIIM-941 was significantly reversed when we attempted to block autophagy by using either pharmacological inhibitor bafilomycin A1or by using siRNA against AMPK. Further, we found that IIIM-941 downregulated the expression of NLRP3 and prevented the oligomerization of ASC to exert its anti-NLRP3 inflammasome effect in J774A.1 cells. We validated inhibitory activity of IIIM-941 against NLRP3 in three different mice models. The anti-inflammatory effect of IIIM-941 was highly significant in ATP induced peritoneal inflammation model. IIIM-941 was similarly effective in suppressing MSU induced IL-1β in the air pouch model of inflammation without affecting the levels of TNF-α and IL-6. Finally, oral efficacy of IIIM-941 was also proved in MSU indued foot paw edema model of inflammation in mice at 10 and 20 mg/kg (b.w.). The compounds like IIIM-941 can be explored further for the development of therapies against diseases such as Alzheimer’s disease and Parkinson’s disease, where hampered autophagy and NLRP3 activation play a crucial role in the pathological development.

scholarly journals β-Glucan–induced reprogramming of human macrophages inhibits NLRP3 inflammasome activation in cryopyrinopathies

2020 ◽  
Vol 130 (9) ◽  
pp. 4561-4573 ◽  
Author(s):  
Giorgio Camilli ◽  
Mathieu Bohm ◽  
Alícia Corbellini Piffer ◽  
Rachel Lavenir ◽  
David L. Williams ◽  
...  
Keyword(s):  
Nlrp3 Inflammasome ◽  
Inflammasome Activation ◽  
Human Macrophages ◽  
Nlrp3 Inflammasome Activation

scholarly journals Nuclear Receptors as Multiple Regulators of NLRP3 Inflammasome Function

2021 ◽  
Vol 12 ◽  
Author(s):  
Ahmad Alatshan ◽  
Szilvia Benkő
Keyword(s):  
Immune Responses ◽  
Nuclear Receptors ◽  
Nlrp3 Inflammasome ◽  
Inflammasome Activation ◽  
Inflammatory Conditions ◽  
Physiological Processes ◽  
Nlrp3 Inflammasome Activation ◽  
Wide Range ◽  
Multiple Levels ◽  
Approved Drugs

Nuclear receptors are important bridges between lipid signaling molecules and transcription responses. Beside their role in several developmental and physiological processes, many of these receptors have been shown to regulate and determine the fate of immune cells, and the outcome of immune responses under physiological and pathological conditions. While NLRP3 inflammasome is assumed as key regulator for innate and adaptive immune responses, and has been associated with various pathological events, the precise impact of the nuclear receptors on the function of inflammasome is hardly investigated. A wide variety of factors and conditions have been identified as modulators of NLRP3 inflammasome activation, and at the same time, many of the nuclear receptors are known to regulate, and interact with these factors, including cellular metabolism and various signaling pathways. Nuclear receptors are in the focus of many researches, as these receptors are easy to manipulate by lipid soluble molecules. Importantly, nuclear receptors mediate regulatory mechanisms at multiple levels: not only at transcription level, but also in the cytosol via non-genomic effects. Their importance is also reflected by the numerous approved drugs that have been developed in the past decade to specifically target nuclear receptors subtypes. Researches aiming to delineate mechanisms that regulate NLRP3 inflammasome activation draw a wide range of attention due to their unquestionable importance in infectious and sterile inflammatory conditions. In this review, we provide an overview of current reports and knowledge about NLRP3 inflammasome regulation from the perspective of nuclear receptors, in order to bring new insight to the potentially therapeutic aspect in targeting NLRP3 inflammasome and NLRP3 inflammasome-associated diseases.

scholarly journals The NLRP3 Inflammasome: Metabolic Regulation and Contribution to Inflammaging

Cells ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 1808 ◽  
Author(s):  
Allison K. Meyers ◽  
Xuewei Zhu
Keyword(s):  
Nlrp3 Inflammasome ◽  
Metabolic Regulation ◽  
Inflammasome Activation ◽  
Immune Effector ◽  
Effector Functions ◽  
Pyrin Domain ◽  
Inflammatory Conditions ◽  
Nlrp3 Inflammasome Activation ◽  
Inflammatory Stimuli ◽  
Pro Inflammatory Cytokines

In response to inflammatory stimuli, immune cells reconfigure their metabolism and bioenergetics to generate energy and substrates for cell survival and to launch immune effector functions. As a critical component of the innate immune system, the nucleotide-binding and oligomerization domain, leucine-rich repeat, and pyrin domain-containing 3 (NLRP3) inflammasome can be activated by various endogenous and exogenous danger signals. Activation of this cytosolic multiprotein complex triggers the release of the pro-inflammatory cytokines interleukin (IL)-1β and IL-18 and initiates pyroptosis, an inflammatory form of programmed cell death. The NLRP3 inflammasome fuels both chronic and acute inflammatory conditions and is critical in the emergence of inflammaging. Recent advances have highlighted that various metabolic pathways converge as potent regulators of the NLRP3 inflammasome. This review focuses on our current understanding of the metabolic regulation of the NLRP3 inflammasome activation, and the contribution of the NLRP3 inflammasome to inflammaging.

scholarly journals A190 ATP-INDUCED INFLAMMASOME ACTIVATION GENERATES MITOCHONDRIAL ROS PRODUCTION IN MACROPHAGES

2021 ◽  
Vol 4 (Supplement_1) ◽  
pp. 206-207
Author(s):  
M Bording-Jorgensen ◽  
H Armstrong ◽  
E Wine
Keyword(s):  
Nlrp3 Inflammasome ◽  
Extracellular Atp ◽  
Inflammasome Activation ◽  
Ros Production ◽  
Bacterial Survival ◽  
Bacterial Killing ◽  
Beneficial Effects ◽  
Inflammatory Conditions ◽  
Mitochondrial Ros

Abstract Background The etiology of Inflammatory Bowel Diseases is unknown; however, a dysfunctional immune response has been well characterized. The role of the NLRP3 inflammasome in IBD is controversial with both beneficial and detrimental results. This pathway is required for the secretion of the proinflammatory cytokine IL-1β. Extracellular ATP is a well characterized inflammasome activator, which we have previously shown can increase the ability of J774A.1 macrophages to clear the mouse pathogen Citrobacter rodentium in an in vitro environment through the generation of reactive oxygen species (ROS). Aims Our objectives were to determine: 1) if extracellular ATP was inducing mitochondrial stress, causing the production of ROS, leading to microbial death; and 2) what effects these activated macropahges have on naïve macrophages. Methods Murine macrophage J774A.1 cells were infected with C. rodentium; extracellular ATP was added as an inflammasome activator and YVAD as an inhibitor. Lysotracker red and MitoSOX were used to determine cellular location of bacteria and quantify mitochondrial ROS, respectively. Secreted cytokines were measured using ELISA and a proteome profiler, ROS was measured using DCFDA, Gasdermin D and Caspase 11 activities were determined by Western Blot. Supernatants taken from infected macrophages were filtered and then added to naïve macrophages during infection with C. rodentium. Results Activation of mitochondrial ROS by ATP was found to be independent of infection. Secreted cytokines sICAM-1, MIP-1α, and MCP-2 were all increased by ATP but not inhibited by YVAD. Cleavage of Gasdermin D was increased with the addition of ATP but not inhibited by YVAD whereas Caspase 11 was unchanged between treatments. Supernatants from ATP-induced macrophages were able to induce IL-1β secretion in naïve macrophages and increase bacterial killing. Conclusions Mitochondrial ROS production in response to extracellular ATP may be involved in the decrease of bacterial survival. ATP induces the secretion of cytokines, chemokines, and other factors that affect newly infected macrophages. Gasdermin D cleavage, independent of caspase 11, suggests that a noncannonical pathway is activated; this may explain the lack of pyroptotic cells in our study. In addition, we have shown that these macrophages are able to illicit the same behavior in naive macrophages, suggesting that a corrected dysfunctional pathway in macrophages can have beneficial effects downstream. Understanding how the NLRP3 inflammasome is activated and what the downstream pathways are may lead to potential therapies for inflammatory conditions, including IBD. Funding Agencies CCC, CIHR

scholarly journals Priming is dispensable for NLRP3 inflammasome activation in human monocytes

2020 ◽  
Author(s):  
Anna Gritsenko ◽  
Shi Yu ◽  
Fatima Martin-Sanchez ◽  
Ines Diaz del Olmo ◽  
Eva-Maria Nichols ◽  
...  
Keyword(s):  
Nlrp3 Inflammasome ◽  
Inflammasome Activation ◽  
Human Monocytes ◽  
Nlrp3 Gene ◽  
Caspase 1 ◽  
Inflammatory Conditions ◽  
Nlrp3 Inflammasome Activation ◽  
Inflammatory Processes ◽  
Infection And Inflammation ◽  
Subsequent Activation

ABSTRACTInterleukin (IL)-1 family of cytokines modulate immune responses during infection and inflammation. IL-18 and IL-1β are members of the IL-1 family, which contribute to inflammatory conditions such as rheumatoid arthritis and Alzheimer’s disease. IL-18 and IL-1β are produced as inactive precursors that are activated by large macromolecular complexes called inflammasomes upon sensing damage or pathogenic signals. Canonical NLRP3 inflammasome activation is regarded to require a priming step that causes NLRP3 and IL-1β gene upregulation, and also NLRP3 post-translational licencing. A subsequent activation step leads to the assembly of the inflammasome and the cleavage of pro-IL-18 and pro-IL-1β by caspase-1 into their mature forms, allowing their release. Here we show that in primary human monocytes, the initial priming step is dispensable to form an active NLRP3 inflammasome. We found that, in the absence of priming, the NLRP3 activator nigericin caused the processing and release of constitutively expressed IL-18. Another IL-1 family member, IL-37, is constitutively cleaved but the release of its mature form was mediated by inflammasome activation, also in the absence of a priming step. This NLRP3 activation was characterised by ASC oligomerisation as well as caspase-1 and GSDMD cleavage and was blocked by the NLRP3 inhibitor MCC950 and in NLRP3 deficient cells. IL-18 and IL-37 release were impaired in GSDMD deficient THP-1s, suggesting that pyroptosis is required for release of these cytokines. This work highlights the readiness of the NLRP3 inflammasome to assemble in the absence of priming and hence contribute to sterile inflammatory processes in health and disease.Significance StatementThe NLRP3 inflammasome is a driver of inflammation through the processing of Interleukins (IL)-1β and IL-18. Human monocytes coordinate the innate immune response through inflammasome activation following exposure to pathogens and damage signals. We currently think of NLRP3 activation as a 2 step process: priming (NLRP3 gene upregulation and post-translational licencing) and assembly. Here we show that the priming step is dispensable for NLRP3 inflammasome activation in human monocytes. The second signal alone is sufficient for caspase-1 activation, leading to cell death and the release of the constitutively expressed IL-18 and mIL-37. This reveals that in human monocytes, the NLRP3 inflammasome is already licenced and able to quickly assemble to mount an inflammatory response.

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