scholarly journals Pyroptosis: A Common Feature of Immune Cells of Haemodialysis Patients

Toxins ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 839
Author(s):  
Christof Ulrich ◽  
Leonie Kneser ◽  
Roman Fiedler ◽  
Julia Beckert ◽  
Susann Wildgrube ◽  
...  
Keyword(s):  
Cell Death ◽  
Inflammatory Cell ◽  
Risk Groups ◽  
Model System ◽  
Inflammasome Activation ◽  
Uremic Toxin ◽  
Caspase 1 ◽  
Regulated Cell Death ◽  
Patient Groups ◽  
Intact Kidney

NLRP-3 inflammasome activation can result in interleukin-1β (IL-1β) release and inflammatory cell death (pyroptosis). Caspase-1 is able to trigger both processes. However, other caspases, caspase-4, -5 and -8, are believed to initiate pyroptosis without affecting IL-1 secretion. In this study, we evaluated two cardiovascular risk groups, haemodialysis patients (HD) and patients with intact kidney function but high blood pressure (BP), to analyse the mechanisms driving pyroptosis. Twenty HD were age-, gender- and diabetes-matched to BP. We found a common pyroptotic pattern in both patient groups, at which pyroptosis rates but not IL-1 β levels were significantly higher in monocytes (HD vs. BP: p < 0.05), granulocytes (p < 0.01) and lymphocytes (p < 0.01) of HD patients. As uremic toxins are drivers of inflammation and regulated cell death, we applied a monocyte- and macrophage-like THP-1 model system to demonstrate that the protein-bound uremic toxin indoxyl sulfate (IS) is an inducer of pyroptotic cell death, particularly engaging caspase-4/caspase-5 and to a lesser extent caspase-8 and caspase-1. These data suggest that the uremic toxin IS can mediate pyroptosis in HD patients and the inflammatory caspase-4 and/or caspase-5 contribute to pyroptosis rates to a higher extent in comparison to caspase-1.

scholarly journals New insights in caspase-11 functions in noncanonical inflammasome signalling

Inflammasome ◽  
2014 ◽  
Vol 1 (1) ◽  
Author(s):  
Mélanie Bodnar ◽  
Virginie Petrilli
Keyword(s):  
Cell Death ◽  
Inflammatory Cell ◽  
Protein Complexes ◽  
Inflammasome Activation ◽  
Gram Negative Bacteria ◽  
Nucleotide Binding Domain ◽  
Gram Negative ◽  
Caspase 1 ◽  
Nlrp3 Inflammasome Activation ◽  
Dependent Pathway

AbstractInflammasomes are multi-protein complexes that play a crucial role in innate immunity. They are assembled by cytosolic sensors of the Nucleotide-binding domain and Leucine-rich repeat containing Receptor (NLR) and PYrin and HIN (PYHIN) domain-containing protein families upon sensing various pathogens and danger signals. Inflammasome formation culminates in caspase-1 activation, which causes the cleavage of pro-IL-1β and pro- IL-18 into active cytokines; this eventually results in the induction of an inflammatory cell death called pyroptosis. Recent data using Gram-negative bacteria suggests a role for caspase-11 not only in NLRP3 inflammasome activation but also in a caspase-1- and inflammasome-independent cell death. This novel caspase-11-dependent pathway is critical to control infection by Gram-negative bacteria and has been named the noncanonical inflammasome.

scholarly journals SARS-CoV-2 infects blood monocytes to activate NLRP3 and AIM2 inflammasomes, pyroptosis and cytokine release

2021 ◽  
Author(s):  
Caroline Junqueira ◽  
Ângela Crespo ◽  
Shahin Ranjbar ◽  
Mercedes Lewandrowski ◽  
Jacob Ingber ◽  
...  
Keyword(s):  
Cell Death ◽  
Inflammatory Cell ◽  
Infectious Virus ◽  
Multiorgan Failure ◽  
Inflammasome Activation ◽  
Invasive Infection ◽  
Blood Monocytes ◽  
Fluorescent Reporter ◽  
Caspase 1 ◽  
Monocytes And Macrophages

Abstract SARS-CoV-2 causes acute respiratory distress that can progress to multiorgan failure and death in a minority of patients. Although severe COVID-19 disease is linked to exuberant inflammation, how SARS-CoV-2 triggers inflammation is not understood. Monocytes and macrophages are sentinel immune cells in the blood and tissue, respectively, that sense invasive infection to form inflammasomes that activate caspase-1 and gasdermin D (GSDMD) pores, leading to inflammatory death (pyroptosis) and processing and release of IL-1 family cytokines, potent inflammatory mediators. Here we show that expression quantitative trait loci (eQTLs) linked to higher GSDMD expression increase the risk of severe COVID-19 disease (odds ratio, 1.3, p<0.005). We find that about 10% of blood monocytes in COVID-19 patients are infected with SARS-CoV-2. Monocyte infection depends on viral antibody opsonization and uptake of opsonized virus by the Fc receptor CD16. After uptake, SARS-CoV-2 begins to replicate in monocytes, as evidenced by detection of double-stranded RNA and subgenomic RNA and expression of a fluorescent reporter gene. However, infection is aborted, and infectious virus is not detected in infected monocyte supernatants or patient plasma. Instead, infected cells undergo inflammatory cell death (pyroptosis) mediated by activation of the NLRP3 and AIM2 inflammasomes, caspase-1 and GSDMD. Moreover, tissue-resident macrophages, but not infected epithelial cells, from COVID-19 lung autopsy specimens showed evidence of inflammasome activation. These findings taken together suggest that antibody-mediated SARS-CoV-2 infection of monocytes/macrophages triggers inflammatory cell death that aborts production of infectious virus but causes systemic inflammation that contributes to severe COVID-19 disease pathogenesis.

Abstract P295: The Inflammasome Is Involved in Myocardial Ischemia-Reperfusion Injury

2011 ◽  
Vol 109 (suppl_1) ◽  
Author(s):  
Masafumi Takahashi ◽  
Masanori Kawaguchi ◽  
Fumitake Usui ◽  
Hiroaki Kimura ◽  
Shun'ichiro Taniguchi ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Myocardial Ischemia ◽  
Inflammatory Cell ◽  
Bone Marrow Cells ◽  
Cardiac Fibroblasts ◽  
Ischemia Reperfusion ◽  
Inflammatory Cell Infiltration ◽  
Inflammasome Activation ◽  
Caspase 1 ◽  
Myocardial Ischemia Reperfusion

Background: Accumulating evidence indicates that inflammation is involved in the pathophysiology of myocardial ischemia-reperfusion (I/R) injury. However, the mechanism of I/R-initiated inflammation remains to be determined. The inflammasome is a multiprotein complex consisting of nod-like receptor (NLR), apoptosis-associated speck-like adaptor protein (ASC), and caspase-1, and regulates caspase-1-dependent maturation of IL-1beta and IL-18. In the present study, we investigated the role of inflammasome in myocardial I/R injury. Methods and Results: Wild-type (WT), ASC−/−, and caspase-1−/− mice were subjected to 30 min LAD ligation, followed by reperfusion. ASC and caspase-1 were expressed at the site of myocardial I/R injury. Deficiency of ASC and caspase-1 reduced inflammatory responses, such as inflammatory cell infiltration and cytokine expression, and subsequent injuries such as infarct development, myocardial fibrosis, and dysfunction in myocardial I/R injury. To determine the contribution of inflammasome in bone marrow cells, we produced bone marrow transplant mice and found that inflammasome activation was critical not only in bone marrow cells but also in myocardial resident cells. Since myocardial damage was observed before the inflammatory cell infiltration after I/R, we hypothesized that myocardial resident cells are responsible for an initial activation of inflammasome. To test this hypothesis, we examined whether hypoxia/reoxygenation (H/R) stimuli could induce inflammasome activation in cardiac fibroblasts and cardiomyocytes in vitro. Interestingly, inflammasome activation was detected only in cardiac fibroblasts, but not in cardiomyocytes, and mediated through reactive oxygen species (ROS) and potassium efflux. Conclusion: These findings indicate that inflammasome activation in cardiac fibroblasts is essential for inflammation and injury after myocardial I/R, and suggest that the inflammasome is a potential novel therapeutic target for myocardial I/R injury.

scholarly journals A Type III Effector NleF from EHEC Inhibits Epithelial Inflammatory Cell Death by Targeting Caspase-4

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Ting Song ◽  
Kaiwu Li ◽  
Wei Zhou ◽  
Jing Zhou ◽  
Yuan Jin ◽  
...  
Keyword(s):  
Cell Death ◽  
Inflammatory Cell ◽  
Gastrointestinal Disease ◽  
Highly Pathogenic ◽  
E Coli ◽  
Caspase 1 ◽  
T3ss Effector ◽  
Inflammatory Caspases ◽  
Epithelial Cell Death ◽  
Host Inflammatory Response

EnterohemorrhagicE. coli(EHEC) is a highly pathogenic bacterial strain capable of inducing severe gastrointestinal disease. Here, we show that EHEC uses the T3SS effector NleF to counteract the host inflammatory response by dampening caspase-4-mediated inflammatory epithelial cell death and by preventing the production of IL-1β. The other two inflammatory caspases, caspase-1 and caspase-5, are not involved in EHEC ΔnleF-induced inflammatory cell death. We found that NleF not only interrupted the heterodimerization of caspase-4-p19 and caspase-4-p10, but also inhibited the interaction of caspase-1 and caspase-4. The last four amino acids of the NleF carboxy terminus are essential in inhibiting caspase-4-dependent inflammatory cell death.

Evasion of Necroptosis and Inflammasome Activation Promotes Myeloid Leukemogenesis

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 2856-2856
Author(s):  
Ulrike Höckendorf ◽  
Yabal Monica ◽  
Christian Peschel ◽  
Philipp J. Jost
Keyword(s):  
Stem Cells ◽  
Cell Death ◽  
Hematopoietic Stem Cells ◽  
Progenitor Cells ◽  
Protein Level ◽  
Inflammatory Cell ◽  
Leukemic Cells ◽  
Inflammasome Activation ◽  
Short Term ◽  
Hematopoietic Stem

Abstract Acute myeloid leukemia (AML) is a heterogeneous group of hematopoietic neoplasms driven partly by the loss of differentiation and theblockade of cell death. AML is sustained by leukemia-initiating cells (LICs) that arise from pre-leukemic hematopoietic stem and progenitor cells (HSPCs) that carry genetic alterations being selected for during leukemogenesis. The resistance of LICs to standard chemotherapies presents a major clinical challenge as they eventually cause disease relapse and death. Understanding the mechanisms of LIC resistance to undergoing cell death is therefore critical for a curative therapy of AML. While the regulatory factors that maintain HSPC proliferation and differentiation under normal conditions are well understood, significantly less is known about how LIC fate is regulated. As many hematopoietic disorders are characterized by the overproduction of pro-inflammatory cytokines, we hypothesized that necroptosis controlled cytokine secretion and inflammatory cell death might influence AML development. We therefore addressed the role of MLKL and XIAP in AML and tested whether deletion of Mlkl or Xiap would affect disease progression. Here we show that MLKL limits oncogene-mediated leukemogenesis by promoting the inflammatory cell death of common myeloid progenitors (CMPs) and short-term hematopoietic stem cells (HSCs) in experimental mice. Upon oncogenic stress MLKL-dependent necroptosis and subsequent inflammasome activation were triggered, promoting the production of IL-1β, a potent stimulator of HSPC differentiation and maturation, thus, suppressing the emergence of LICs and limiting leukemogenesis. In a murine bone marrow transplantation model of AML the absence of MLKL accelerated AML development significantly. The enhanced disease was due to the expansion of common myeloid progenitors (CMPs) and short-term hematopoietic stem cells (ST-HSCs), being the cellular compartments to contain LICs. The survival advantage of Mlkl-/- HSPCs became apparent in colony-forming assays and liquid cultures specifically within the CMP and ST-HSC compartments. Sorted ST-HSCs from Mlkl-/- produced more GEMM colonies than WT, the colony type harboring the multipotential myeloid progenitor cells, and both ST-HSCs and CMPs retained significantly more lineage-negative cells in liquid culture. In addition, Mlkl-/- colonies showed a reduction in propidium iodide (PI)-positive dead cells compared with WT colonies. Importantly, WT cells showed caspase activation and produced substantial amounts of the inflammatory cytokine IL-1β which was severely blunted by Mlkl deficiency. We also observed reduced expression of MLKL in leukemic cells on both mRNA and protein level, implying that suppression of cell death was beneficial for the survival of LICs. In contrast, deletion of Xiap did not alter survival or differentiation of leukemic cells when compared with WT cells. Furthermore, XIAP was not differentially expressed on mRNA or protein level compared with WT, indicating that XIAP does not play a critical role in leukemogenesis. In agreement with the murine data, gene expression analysis from primary leukemia cells from two large patient cohorts newly diagnosed with AML showed significantly lower expression of MLKL, but not XIAP, in a variety of AML subtypes compared to healthy controls. Overall, our data demonstrate a key role for MLKL-mediated cell death and activation of the inflammasome in AML and represents a novel tumor-suppressive mechanism. Disclosures Peschel: MophoSys: Honoraria.

scholarly journals Type I interferon signaling is required for activation of the inflammasome during Francisella infection

2007 ◽  
Vol 204 (5) ◽  
pp. 987-994 ◽  
Author(s):  
Thomas Henry ◽  
Anna Brotcke ◽  
David S. Weiss ◽  
Lucinda J. Thompson ◽  
Denise M. Monack
Keyword(s):  
Cell Death ◽  
Type I Interferon ◽  
Infection Type ◽  
Host Responses ◽  
Inflammasome Activation ◽  
Type I ◽  
Type I Ifn ◽  
Caspase 1 ◽  
Dependent Cell

Francisella tularensis is a pathogenic bacterium whose virulence is linked to its ability to replicate within the host cell cytosol. Entry into the macrophage cytosol activates a host-protective multimolecular complex called the inflammasome to release the proinflammatory cytokines interleukin (IL)-1β and -18 and trigger caspase-1–dependent cell death. In this study, we show that cytosolic F. tularensis subspecies novicida (F. novicida) induces a type I interferon (IFN) response that is essential for caspase-1 activation, inflammasome-mediated cell death, and release of IL-1β and -18. Extensive type I IFN–dependent cell death resulting in macrophage depletion occurs in vivo during F. novicida infection. Type I IFN is also necessary for inflammasome activation in response to cytosolic Listeria monocytogenes but not vacuole-localized Salmonella enterica serovar Typhimurium or extracellular adenosine triphosphate. These results show the specific connection between type I IFN signaling and inflammasome activation, which are two sequential events triggered by the recognition of cytosolic bacteria. To our knowledge, this is the first example of the positive regulation of inflammasome activation. This connection underscores the importance of the cytosolic recognition of pathogens and highlights how multiple innate immunity pathways interact before commitment to critical host responses.

scholarly journals Phenothiazine Inhibits Neuroinflammation and Inflammasome Activation Independent of Hypothermia After Ischemic Stroke

2021 ◽  
Author(s):  
Sichao Guo ◽  
Xiaokun Geng ◽  
Hangil Lee ◽  
Yuchuan Ding
Keyword(s):  
Cell Death ◽  
Ischemic Stroke ◽  
Brain Activity ◽  
Ischemia Reperfusion ◽  
Inflammasome Activation ◽  
Mrna Levels ◽  
Sprague Dawley ◽  
Neuroinflammatory Response ◽  
Protein Levels ◽  
Caspase 1

Abstract A depressive or hibernation-like effect of chlorpromazine and promethazine (C + P) on brain activity was reported to induce neuroprotection, with or without induced-hypothermia. However, the underlying mechanisms remain unclear. The current study evaluated the pharmacological function of C + P on the inhibition of neuroinflammatory response and inflammasome activation after ischemia/reperfusion. A total of 72 adult male Sprague-Dawley rats were subjected to 2 h middle cerebral artery occlusion (MCAO) followed by 6 or 24 h reperfusion. At the onset of reperfusion, rats received C + P (8 mg/kg) with temperature control. Brain cell death was detected by measuring CD68 and myeloperoxidase (MPO) levels. Inflammasome activation was measured by mRNA levels of NLRP3, IL-1β, and TXNIP, and protein quantities of NLRP3, IL-1β, TXNIP, cleaved-Caspase-1, and IL-18. Activation of JAK2/STAT3 pathway was detected by the phosphorylation of STAT3 (p-STAT3) and JAK2 (p-JAK2), and the co-localization of p-STAT3 and NLRP3. Activation of the p38 pathway was assessed with the protein levels of p-p38/p38. The mRNA and protein levels of HIF-1α, FoxO1, and p-FoxO1, and the co-localization of p-STAT3 with HIF-1α or FoxO1 were quantitated. As expected, C + P significantly reduced cell death and attenuated the neuroinflammatory response as determined by reduced CD68 and MPO. C + P decreased ischemia-induced inflammasome activation, shown by reduced mRNA and protein expressions of NLRP3, IL-1β, TXNIP, cleaved-Caspase-1, and IL-18. Phosphorylation of JAK2/STAT3 and p38 pathways and the co-localization of p-STAT3 with NLRP3 were also inhibited by C + P. Furthermore, mRNA levels of HIF-1α and FoxO1 were decreased in the C + P group. While C + P inhibited HIF-1α protein expression, it increased FoxO1 phosphorylation, which promoted the exclusion of FoxO1 from the nucleus and inhibited FoxO1 activity. At the same time, C + P reduced the co-localization of p-STAT3 with HIF-1α or FoxO1. In conclusion, C + P treatment conferred neuroprotection in stroke by suppressing neuroinflammation and NLRP3 inflammasome activation. The present study suggests that JAK2/STAT3/p38/HIF-1α/FoxO1 are vital regulators and potential targets for efficacious therapy following ischemic stroke.

scholarly journals SARS-CoV-2 induces inflammasome-dependent pyroptosis and downmodulation of HLA-DR in human monocytes

2020 ◽  
Author(s):  
André C. Ferreira ◽  
Vinicius Cardoso Soares ◽  
Isaclaudia G. de Azevedo-Quintanilha ◽  
Suelen da Silva Gomes Dias ◽  
Natalia Fintelman-Rodrigues ◽  
...  
Keyword(s):  
Immune Response ◽  
Cell Death ◽  
Severe Acute Respiratory Syndrome ◽  
Inflammatory Response ◽  
Inflammatory Cell ◽  
Viral Infections ◽  
Relevant Information ◽  
Inflammasome Activation ◽  
Human Monocytes ◽  
Hla Dr

AbstractInfection by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been associated with leukopenia and uncontrolled inflammatory response in critically ill patients. A better comprehension of SARS-CoV-2-induced monocyte death is essential for the identification of therapies capable to control the hyper-inflammation and reduce viral replication in patients with COVID-19. Here, we show that SARS-CoV-2 induces inflammasome activation and cell death by pyroptosis in human monocytes, experimentally infected and from patients under intensive care. Pyroptosis was dependent on caspase-1 engagement, prior to IL-1ß production and inflammatory cell death. Monocytes exposed to SARS-CoV-2 downregulate HLA-DR, suggesting a potential limitation to orchestrate the immune response. Our results originally describe mechanisms by which monocytes, a central cellular component recruited from peripheral blood to respiratory tract, succumb to control severe 2019 coronavirus disease (COVID-19).Author summarySince its emergence in China in late 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused thousands of deaths worldwide. Currently, the number of individuals infected with SARS-CoV-2 and in need of antiviral, anti-inflammatory, anticoagulant and more invasive treatments has overwhelmed the health systems worldwide. In our study, we found that SARS-CoV-2 is capable of inducing inflammatory cell death in human monocytes, one of the main cell types responsible for anti-SARS-CoV-2 immune response. As a consequence of this intracellular inflammatory mechanism (inflammasome engagement), an exacerbated production of inflammatory mediators occurs. The infection also decreases the expression of HLA-DR in monocytes, a molecule related to the orchestration of the immune response in case of viral infections. We also demonstrated that the HIV-1 protease inhibitor, atazanavir (ATV), prevented the uncontrolled inflammatory response, cell death and reduction in HLA-DR expression in SARS-CoV-2-infected monocytes. Our study provides relevant information on the effects of SARS-CoV-2 infection on human monocytes, as well as on the effect of ATV in preventing these pathological effects on the host.

scholarly journals Short Exposure to Ethanol Diminishes Caspase-1 and ASC Activation in Human HepG2 Cells In Vitro

2020 ◽  
Vol 21 (9) ◽  
pp. 3196
Author(s):  
Jason-Alexander Hörauf ◽  
Shinwan Kany ◽  
Andrea Janicova ◽  
Baolin Xu ◽  
Teodora Vrdoljak ◽  
...  
Keyword(s):  
Cell Death ◽  
Hepg2 Cells ◽  
Purinergic Receptor ◽  
Short Exposure ◽  
Ros Generation ◽  
Inflammasome Activation ◽  
Ros Production ◽  
Sodium Orthovanadate ◽  
Tyrosine Phosphatases ◽  
Caspase 1

This paper discusses how the assembly of pro-caspase-1 and apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC) in macromolecular protein complexes, inflammasomes, activates caspase-1. The present study investigates the molecular mechanisms of inflammasome activation in HepG2 cells and examines how short exposures to ethanol (EtOH) affect inflammasome activation. HepG2 cells were treated with lipopolysaccharide (LPS), ATP or nigericin (NIG) in a two-step model. After LPS priming, ATP or NIG were added. As inhibitors, sodium orthovanadate (general inhibitor of tyrosine phosphatases), AC-YVAD-CMK (caspase-1 inhibitor) or AZ10606120 (purinergic receptor P2X7R inhibitor) were applied after LPS priming. To monitor the inflammasome activation, the caspase-1 activity, ASC speck formation, reactive oxygen species (ROS) production and cell death were analyzed. To elucidate the mechanistical approach of EtOH to the inflammasome assembly, the cells were treated with EtOH either under simultaneous LPS administration or concurrently with ATP or NIG application. The co-stimulation with LPS and ATP induced a significant ASC speck formation, caspase-1 activation, cell death and ROS generation. The inhibition of the ATP-dependent purinoreceptor P2X7 decreased the caspase-1 activation, whereas sodium orthovanadate significantly induced caspase-1. Additional treatment with EtOH reversed the LPS and ATP-induced caspase-1 activation, ASC speck formation and ROS production. The ASC speck formation and caspase-1 induction require a two-step signaling with LPS and ATP in HepG2 cells. Inflammasome activation may depend on P2X7. The molecular pathway of an acute effect of EtOH on inflammasomes may involve a reduction in ROS generation, which in turn may increase the activity of tyrosine phosphatases.

scholarly journals ASC Speck Formation after Inflammasome Activation in Primary Human Keratinocytes

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Nikola Smatlik ◽  
Stefan Karl Drexler ◽  
Marc Burian ◽  
Martin Röcken ◽  
Amir Sadegh Yazdi
Keyword(s):  
Cell Death ◽  
Protein Complexes ◽  
Human Keratinocytes ◽  
Inflammasome Activation ◽  
Primary Human Keratinocytes ◽  
Cytosolic Protein ◽  
Caspase 1 ◽  
Nlrp3 Inflammasome Activation ◽  
Inducible Protein ◽  
Human Primary Keratinocytes

Chronic UV irradiation results in many changes in the skin, including hyperplasia, changes in dermal structures, and alteration of pigmentation. Exposure to UVB leads to cutaneous damage, which results in inflammation characterized by increased NF-κB activation and the induction of inflammatory cytokines, such as tumor necrosis factor (TNF), interleukin- (IL-) 1, or IL-8. IL-1 secretion is the result of inflammasome activation which is besides apoptosis, a result of acute UVB treatment. Inflammasomes are cytosolic protein complexes whose formation results in the activation of proinflammatory caspase-1. Key substrates of caspase-1 are IL-1β and IL-18, and the cytosolic protein gasdermin D (GSDMD), which is involved in inflammatory cell death. Here, we demonstrate that UVB-induced inflammasome activation leads to the formation of ASC specks. Our findings show that UVB provokes ASC speck formation in human primary keratinocytes prior to cell death, and that specks are, opposed to the perinuclear cytosolic localization in myeloid cells, formed in the nucleus. Additionally, we showed by RNAi that NLRP1 and not NLRP3 is the major inflammasome responsible for UVB sensing in primary human keratinocytes. Formation of ASC specks indicates inflammasome assembly and activation as their formation in hPKs depends on the presence of NLRP1 and partially on NLRP3. Nuclear ASC specks are not specific for NLRP1/NLRP3 inflammasome activation, as the activation of the AIM2 inflammasome by cytosolic DNA results in ASC specks too. These nuclear ASC specks putatively link cell death to inflammasome activation, possibly by binding of IFI16 (gamma-interferon-inducible protein) to ASC. ASC can interact upon UVB sensing via IFI16 with p53, linking cell death to ASC speck formation.

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