Activation Of Inflammasome Pathway Research Articles

Radiation exposure induces inflammasome pathway activation in immune cells.

Radiation exposure induces cell and tissue damage, causing local and systemic inflammatory responses. Because the inflammasome pathway is triggered by cell death and danger-associated molecular patterns, we hypothesized that the inflammasome may signal acute and chronic immune responses to radiation. Using a mouse radiation model, we show that radiation induces a dose-dependent increase in inflammasome activation in macrophages, dendritic cells, NK cells, T cells, and B cells as judged by cleaved caspase-1 detection in cells. Time course analysis showed the appearance of cleaved caspase-1 in cells by day 1 and sustained expression until day 7 after radiation. Also, cells showing inflammasome activation coexpressed the cell surface apoptosis marker annexin V. The role of caspase-1 as a trigger for hematopoietic cell losses after radiation was studied in caspase-1(-/-) mice. We found less radiation-induced cell apoptosis and immune cell loss in caspase-1(-/-) mice than in control mice. Next, we tested whether uric acid might mediate inflammasome activation in cells by treating mice with allopurinol and discovered that allopurinol treatment completely blocked caspase-1 activation in cells. Finally, we demonstrate that radiation-induced caspase-1 activation occurs by a Nod-like receptor family protein 3-independent mechanism because radiation-exposed Nlrp3(-/-) mice showed caspase-1 activation profiles that were indistinguishable from those of wild-type mice. In summary, our data demonstrate that inflammasome activation occurs in many immune cell types following radiation exposure and that allopurinol prevented radiation-induced inflammasome activation. These results suggest that targeting the inflammasome may help control radiation-induced inflammation.

CD24 activates the NLRP3 inflammasome through c-Src kinase activity in a model of the lining epithelium of inflamed periodontal tissues.

Chronic periodontitis is characterized by perturbation of the epithelial attachment to the tooth with subsequent migration of the lining epithelium and formation of a cleft or pocket. This non-keratinized lining epithelium provides initial responses to bacterial products by signalling through receptors of innate immunity to activate inflammasome pathways. These comprise an intracellular network of regulatory and effector molecules leading to synthesis and activation of pro-inflammatory cytokines. Conversely, CD24 is characteristically strongly expressed by the pocket epithelium and is reported to function as an important negative regulator for danger signals, protecting tissues from excessive leukocyte activity. The objective of the study was to determine the impact of ligation of CD24 on expression of inflammasome components. An epithelial mimic of pocket epithelium was used to evaluate activation of the NLRP3 inflammasome pathway. Surprisingly, antibody ligation of CD24 enhanced expression of NLRP3 together with co-activators ASC and caspase-1 resulting in burst release of activated interleukin (IL)-18. Potent product inhibition was detected with IL-18 suppressing expression of NLRP3, ASC, and caspase-1. Scant distribution of these products within pocket epithelium compared with healthy gingival attachment provided indication of potential cycling of NLRP3 inflammasome expression. As subjects with mild chronic periodontitis have increased titres of serum antibodies auto-reactive with CD24 compared with those of subjects with severe periodontitis, a molecular mechanism for regulated expression of the NLRP3 inflammasome mediated by c-Src kinase activity, is proposed. This pathway could be regionally disrupted by products of pathogenic bacteria with profound downregulation in the dysbiosis associated with severe disease.

Investigation of caspase-1 activity and interleukin-1β production in murine macrophage cell lines infected with Leishmania major

ObjectiveTo investigate the caspase-1 dependent inflammatory pathway activity and interleukin-1β (IL-1β) secretion in murine macrophage cell lines J774G8 infected with Leishmania major (L. major) using caspase-1 activity assay and ELISA. MethodsNovy-MacNeal-Nicolle biphasic medium was applied to produce promastigote form of L. major. Metacyclic promastigotes in the stationary phase were applied to infect macrophage. Caspase-1 activity and IL-1β secretion were assessed by the CPP32/caspase-1 fluorometric protease assay and ELISA IL-1β kits, respectively, with time intervals of 6, 18 and 30 h. ResultsOur study showed an increase in caspase-1 activity and IL-1β secretion in infected samples compared to non-infected macrophages. The highest increase in IL-1β production was observed after 6 h of infection. ConclusionsThese results arise that the activation of inflammasome pathway could be one of the innate immunity pathways against L. major.

Anti-TRIM21 autoantibody and inflammasome interaction in pathogenesis of Sjogren's syndrome (BA3P.200)

Abstract Sjögren’s syndrome is a chronic autoimmune disorder mainly affecting the exocrine glands and is commonly associated with autoantibodies to TRIM21. This study was undertaken to determine the role of TRIM21-reactive antibodies in pathogenesis of Sjögren’s syndrome. NZM mouse strains (2758, 2328, 2410) were immunized with recombinant TRIM21 protein adsorbed on to alum. Mice were monitored for autoantibodies, serum cytokines and pilocarpine induced salivation. Although all NZM mouse strains generated a robust anti-TRIM21 antibody response, salivary gland dysfunction only occurred in the NZM2758 mice. Moreover, alum immunized NZM2758 mice also displayed some loss of glandular function. Serum levels of IL-1α and CXCL1 were upregulated in alum and alum-TRIM21 treated groups of NZM2758 mice. In contrast, levels of IL-2, IL-5, IL-6 and IL-17 were upregulated, only in the alum-TRIM21 treated mice. Antibodies from TRIM21 immunized mice penetrated live cells in vitro, and showed cytoplasmic staining. Passive transfer of sera from TRIM21 immunized mice induced salivary gland dysfunction in recipient mice, only if the recipients were pre primed with alum. Our study shows that in a genetically susceptible mouse strain, anti-TRIM21 antibodies directly affected salivary gland function and this phenomenon was dependent on the activation of inflammasome pathway. Thus, interaction between innate and adaptive immunity is critical for pathogenesis of Sjögren’s syndrome.

AIM2 inflammasome is protective in regulating adaptive responses to oxidative stress in the liver (INM6P.410)

Abstract Inflammasome activation leads to activation of caspase1 and maturation of IL1β/IL18 in immune cells. Our previous data showed a novel role for caspase1 in hepatoprotection after redox stress by induction of mitochondrial autophagy, and this is independent of IL1β/IL18. Here, we further investigated inflammasome activation pathways after redox stress in liver. Mice deficient in known main inflammasome components NLRP1a, NLRP3, AIM2 or WT control (C57BL/6) mice underwent hemorrhagic shock with resuscitation (HS/R). NLRP3-/- mice had comparable IL18 levels, liver damage and hepatocyte (HC) caspase1-cleavage as WT mice at 6h. Knockdown of NLRP1a significantly suppressed levels of circulating IL-18 (162±21 vs 101±11pg/ml, p<0.01, control vs NLRP1a knockdown) after HS/R, but similar liver damage and HC caspase1 cleavage to control mice. AIM2-/- mice had similar levels of plasma IL18 as control mice (128±15 vs 135±29pg/ml), but significantly elevated liver injury (195±12 vs 995±287 IU/L, p<0.01) after HS/R, similarly to caspase1-/- mice. Similarly, in vitro AIM2-/- HC had decreased beclin1 expression (2.7 fold decrease in comparison with WT HC) and decreased mitochondrial clearance during redox stress as compared with WT cells. Taken together our data suggest that NLRP1-inflammasome regulates caspase1-activation in immune cells after redox stress, but that AIM2-inflammsome regulates caspase1-activation and mitophagy in HC/liver and is hepatoprotective after HS/R.

Characterization of porcine NLRP3 inflammasome activation and its upstream mechanism

Inflammasomes, which are intracellular sensors of endogenous or exogenous danger signals, activate caspase-1, resulting in interleukin (IL)-1β maturation. Although most studies on inflammasomes have been performed in human and/or mouse-derived macrophages, porcine inflammasome activation has not been elucidated even though pigs are considered one of the best animal models for translational and preclinical investigations. In this study, we optimized detection of porcine IL-1β secretion, which is the most well established indicator of inflammasome activation, and compared inflammasome activation between miniature and domestic pigs as well as between porcine and murine macrophages. In our results, anti-sera against murine IL-1β had higher affinity to porcine IL-1β than anti-sera against human IL-1β, even though the amino acid sequence of porcine IL-1β was more similar to that of human IL-1β. In addition, there was no significant difference in inflammasome activation between miniature and domestic pigs. Furthermore, well established inflammasome triggers (ATP, nigericin, and crystals) in humans and mice had similar effects on porcine NLRP3 inflammasome activation. We further elucidated the upstream signaling pathway of porcine inflammasome activation using pharmacological inhibitors. Similar to the mechanisms of inflammasome activation in humans and mice, potassium efflux and reactive oxygen species generation were confirmed as key pathways in porcine inflammasome activation. Thus, inflammasome activation in pigs is not different from that in humans or mice.

The role of the inflammasome in cardiovascular diseases

Inflammasome is a very important signaling platform sensing a variety of triggers of the innate immune system. Inflammasome promotes the production of important pro-inflammatory cytokines such as IL-1β and IL-18. Tight control of inflammasome activity is, therefore, essential and occurs at multiple levels. The activation of inflammasome pathways is linked to the pathogenesis of various prevalent disorders including cardiovascular disease such as atherosclerosis, ischemic injury, cardiomyopathy, and Kawasaki disease. The study of the inflammasome in the cardiovascular system has led to the identification of important triggers and endogenous modulators, and to the exploration of new treatment strategies based on the inhibition of inflammasome activation or its end products, i.e., IL-1β and IL-18. In summary, the discovery of the inflammasome has greatly advanced our understanding of how the innate immune system interferes with cardiovascular disease development and progression, and targeting inflammasome provides new avenues for the treatment and management of cardiovascular diseases.

Porphyromonas gingivalis-impaired innate immune response via NLRP3 proteolysis in endothelial cells

Porphyromonas gingivalis (Pg) is involved in the link between periodontal diseases and atherosclerosis worsening. In periodontal cells, Pg modifies IL-1β expression via the NLRP3 inflammasome pathway activation. Our aim was to investigate NLRP3 inflammasome activation in endothelial cells (ECs) after Pg infection and Pg-LPS stimulation. In both situations, RT-PCR experiments demonstrated an increase of the NLRP3 mRNA level that can be potentiated by pre-treatment of ECs with 5 mM ATP. However, Western blotting analysis revealed that Pg infection induced a proteolysis of NLRP3 protein and a major decrease of the native protein. After ATP pre-treatment and/or Pg-LPS stimulation, this proteolysis was not observed, while NLRP3 protein levels were increased. Proteolysis of the NLRP3 protein was not observed with heat-killed Pg and inhibition of ECs protein synthesis with cycloheximide did not abolish the NLRP3 protein degradation induced by Pg infection in ATP pre-treated cells. Additionally, significant increases of secreted IL-1β were measured after ATP pre-treatment and/or Pg-LPS stimulation, but not after Pg infection. These data showed that Pg and Pg-LPS differentially controlled the NLRP3 inflammasome pathway in ECs, and suggested a novel potential mechanism developed by Pg to reduce IL-1β secretion and to escape host immune response.

Innate immunity but not NLRP3 inflammasome activation correlates with severity of stable COPD

BackgroundIn models of COPD, environmental stressors induce innate immune responses, inflammasome activation and inflammation. However, the interaction between these responses and their role in driving pulmonary inflammation in stable COPD...

Macrophage Specific Caspase-1/11 Deficiency Protects against Cholesterol Crystallization and Hepatic Inflammation in Hyperlipidemic Mice

Background & AimsWhile non-alcoholic steatohepatitis (NASH) is characterized by hepatic steatosis combined with inflammation, the mechanisms triggering hepatic inflammation are unknown. In Ldlr-/- mice, we have previously shown that lysosomal cholesterol accumulation in Kupffer cells (KCs) correlates with hepatic inflammation and cholesterol crystallization. Previously, cholesterol crystals have been shown to induce the activation of inflammasomes. Inflammasomes are protein complexes that induce the processing and release of pro-inflammatory cytokines IL-1b and IL-18 via caspase-1 activation. Whereas caspase-1 activation is independent of caspase-11 in the canonical pathway of inflammasome activation, caspase-11 was found to trigger caspase-1-dependent IL-1b and IL-18 in response to non-canonical inflammasome activators. So far, it has not been investigated whether inflammasome activation stimulates the formation of cholesterol crystals. We hypothesized that inflammasome activation in KCs stimulates cholesterol crystallization, thereby leading to hepatic inflammation.Methods Ldlr -/- mice were transplanted (tp) with wild-type (Wt) or caspase-1/11-/- (dKO) bone marrow and fed either regular chow or a high-fat, high-cholesterol (HFC) diet for 12 weeks. In vitro, bone marrow derived macrophages (BMDM) from wt or caspase-1/11-/- mice were incubated with oxLDL for 24h and autophagy was assessed. ResultsIn line with our hypothesis, caspase-1/11-/--tp mice had less severe hepatic inflammation than Wt-tp animals, as evident from liver histology and gene expression analysis in isolated KCs. Mechanistically, KCs from caspase-1/11-/--tp mice showed less cholesterol crystals, enhanced cholesterol efflux and increased autophagy. In wt BMDM, oxLDL incubation led to disturbed autophagy activity whereas BMDM from caspase-1/11-/- mice had normal autophagy activity.ConclusionAltogether, these data suggest a vicious cycle whereby disturbed autophagy and decreased cholesterol efflux leads to newly formed cholesterol crystals and thereby maintain hepatic inflammation during NASH by further activating the inflammasome.

ASC Controls IFN-γ Levels in an IL-18–Dependent Manner in Caspase-1–Deficient Mice Infected with Francisella novicida

The inflammasome is a signaling platform that is central to the innate immune responses to bacterial infections. Francisella tularensis is a bacterium replicating within the host cytosol. During F. tularensis subspecies novicida infection, AIM2, an inflammasome receptor sensing cytosolic DNA, activates caspase-1 in an ASC-dependent manner, leading to both pyroptosis and release of the proinflammatory cytokines IL-1β and IL-18. Activation of this canonical inflammasome pathway is key to limit F. novicida infection. In this study, by comparing the immune responses of AIM2 knockout (KO), ASC(KO), and Casp1(KO) mice in response to F. novicida infection, we observed that IFN-γ levels in the serum of Casp1(KO) mice were much higher than the levels observed in AIM2(KO) and ASC(KO) mice. This difference in IFN-γ production was due to a large production of IFN-γ by NK cells in Casp1(KO) mice that was not observed in ASC(KO) mice. The deficit in IFN-γ production observed in ASC(KO) mice was not due to a reduced Dock2 expression or to an intrinsic defect of ASC(KO) NK cells. We demonstrate that in infected Casp1(KO) mice, IFN-γ production is due to an ASC-dependent caspase-1-independent pathway generating IL-18. Furthermore, we present in vitro data suggesting that the recently described AIM2/ASC/caspase-8 noncanonical pathway is responsible for the caspase-1-independent IL-18 releasing activity. To our knowledge, this study is the first in vivo evidence of an alternative pathway able to generate in a caspase-1-independent pathway bioactive IL-18 to boost the production of IFN-γ, a cytokine critical for the host antibacterial response.

Caspase‐11: The driving factor for noncanonical inflammasomes

Inflammasomes are large multiprotein platforms that mediate the processing of caspase-1, which in turn promotes the maturation and release of IL-1β and IL-18 in response to microbial and danger signals. While the canonical pathway of inflammasome activation has been known for some time, a novel mechanism of noncanonical inflammasome activation mediated by caspase-11 was more recently identified. This pathway engages caspase-11 to trigger both caspase-1-dependent and -independent production of the inflammatory cytokines IL-1β, IL-18, and IL-1α, as well as to promote pyroptosis, a form of genetically programmed cell death that is associated with the release of such cytokines. In this review, we gather together studies on both the mechanisms and implications of caspase-11-mediated noncanonical inflammasome activation, and discuss the emerging importance of this pathway in regulating host defense against intracellular bacterial pathogens.

Superoxide Dismutase Mimetic, MnTE-2-PyP, Attenuates Chronic Hypoxia-Induced Pulmonary Hypertension, Pulmonary Vascular Remodeling, and Activation of the NALP3 Inflammasome

Pulmonary hypertension (PH) is characterized by an oxidant/antioxidant imbalance that promotes abnormal vascular responses. Reactive oxygen species, such as superoxide (O(2)(•-)), contribute to the pathogenesis of PH and vascular responses, including vascular remodeling and inflammation. This study sought to investigate the protective role of a pharmacological catalytic antioxidant, a superoxide dismutase (SOD) mimetic (MnTE-2-PyP), in hypoxia-induced PH, vascular remodeling, and NALP3 (NACHT, LRR, and PYD domain-containing protein 3)-mediated inflammation. Mice (C57/BL6) were exposed to hypobaric hypoxic conditions, while subcutaneous injections of MnTE-2-PyP (5 mg/kg) or phosphate-buffered saline (PBS) were given 3× weekly for up to 35 days. SOD mimetic-treated groups demonstrated protection against increased right ventricular systolic pressure, indirect measurements of pulmonary artery pressure, and RV hypertrophy. Vascular remodeling was assessed by Ki67 staining to detect vascular cell proliferation, α-smooth muscle actin staining to analyze small vessel muscularization, and hyaluronan (HA) measurements to assess extracellular matrix modulation. Activation of the NALP3 inflammasome pathway was measured by NALP3 expression, caspase-1 activation, and interleukin 1-beta (IL-1β) and IL-18 production. Hypoxic exposure increased PH, vascular remodeling, and NALP3 inflammasome activation in PBS-treated mice, while mice treated with MnTE-2-PyP showed an attenuation in each of these endpoints. This study is the first to demonstrate activation of the NALP3 inflammasome with cleavage of caspase-1 and release of active IL-1 β and IL-18 in chronic hypoxic PH, as well as its attenuation by the SOD mimetic, MnTE-2-PyP. The ability of the SOD mimetic to scavenge extracellular O(2)(•-) supports our previous observations in EC-SOD-overexpressing mice that implicate extracellular oxidant/antioxidant imbalance in hypoxic PH and implicates its role in hypoxia-induced inflammation.

TLR Agonists Stimulate Nlrp3-Dependent IL-1β Production Independently of the Purinergic P2X7 Receptor in Dendritic Cells and In Vivo

On the basis of studies in mouse macrophages, activation of the nucleotide-binding oligomerization domain-like receptor (NLR) pyrin domain-containing 3 (Nlrp3) inflammasome is thought to require two signals. The first signal is provided by TLR stimulation and triggers the synthesis of the IL-1β precursor and Nlrp3. The second signal can be mediated by stimulation of the purinergic receptor P2X ligand-gated ion channel 7 (P2X7) by millimolar concentrations of ATP. However, these high concentrations of ATP are not found normally in the in vivo extracellular milieu, raising concern about the physiological relevance of the ATP-P2X7 pathway of inflammasome activation. In this article, we show that unlike macrophages, murine bone marrow-derived and splenic dendritic cells (DCs) can secrete substantial amounts of mature IL-1β upon stimulation with TLR ligands in the absence of ATP stimulation. The differential ability of DCs to release IL-1β and activate caspase-1 was associated with increased expression of Nlrp3 under steady-state conditions and of pro-IL-1β and Nlrp3 after stimulation with TLR agonists. IL-1β secretion from stimulated DCs was largely dependent on the Nlrp3 inflammasome, but independent of P2X7 and unaffected by incubation with apyrase. More importantly, i.p. administration of LPS induced IL-1β production in serum, which was abrogated in Nlrp3-null mice but was unaffected in P2X7-deficient mice. These results demonstrate differential regulation of the Nlrp3 inflammasome in macrophages and DCs. Furthermore, they challenge the idea that the ATP-P2X7 axis is critical for TLR-induced IL-1β production via the Nlrp3 inflammasome in vivo.

New Aspects in Immunopathology ofMycobacterium tuberculosis

Our understanding of tuberculosis (TB) pathology and immunology has become extensively deeper and more refined since the identification ofMycobacterium tuberculosis(MTB) as the etiologic agent of disease by Dr. Robert Koch in 1882. A great challenge in chronic disease is to understand the complexities, mechanisms, and consequences of host interactions with pathogens. TB, caused by MTB, is a major health problem in world, with 10 million new cases diagnosed each year. Innate immunity is shown playing an important role in the host defense against the MTB, and the first step in this process is recognition of MTB by cells of the innate immune system. Several classes of pattern recognition receptors (PPRs) are involved in the recognition of MTB, including toll-like receptors (TLRs), C-type lectin receptors (CLRs), and nod-like receptors (NLRs). Among the TLR family, TLR1, TLR2, TLR4, and TLR9 and their down streams, proteins play the most prominent roles in the initiation of the immune response against MTB. Beside of TLRs signaling, recently the activation of inflammasome pathway in the pathogenesis of TB much appreciated. Knowledge about these signaling pathways is crucial for understanding the pathophysiology of TB, on one hand, and for the development of novel strategies of vaccination and treatment such as immunotherapy on the other. Given the critical role of TLRs/inflammasome signaling in innate immunity and initiation of the appropriate adaptive response, the regulation of these pathways is likely to be an important determinant of the clinical outcome of MTB infection. In this review paper we focused on the immune response, which is the recognition of MTB by inflammatory innate immune cells following infection.

Significant Role of IL-1 Signaling, but Limited Role of Inflammasome Activation, in Oviduct Pathology during Chlamydia muridarum Genital Infection

IL-1β has been implicated in the development of oviduct pathology during Chlamydia muridarum genital infection in the mouse model. The goal of this study was to characterize the role of IL-1 signaling and the inflammasome-activation pathways during genital chlamydial infection. Compared with control mice, IL-1R-deficient mice displayed delayed clearance and increased chlamydial colonization. Consistent with the role for IL-1 signaling in infection clearance, mice deficient for the IL-1R antagonist cleared infection at a faster rate. Despite increased infection, IL-1R-deficient mice had significantly reduced oviduct pathology, which was associated with decreased numbers of neutrophils, but more macrophages, in the genital tract. IL-1β secretion is dependent on caspase-1 and apoptosis-associated speck-like protein containing caspase recruitment domain (ASC) inflammasome during in vitro infection of primed macrophages with C. muridarum. To investigate the role of inflammasome components during in vivo genital infection, mice lacking NLRP3, NLRC4, and ASC were tested and found to display no reduction in oviduct pathology compared with control mice. Mice deficient for ASC displayed a prolonged course of infection, which was associated with reduced T cell recruitment and proliferation. Further, ASC-deficient mice displayed normal levels of IL-1β in genital secretions. However, a significant decrease in caspase-1-dependent IL-18 was observed in both ASC- and NLRP3-deficient mice. These data demonstrate a major role for IL-1 signaling, but a limited role for the inflammasome pathway, in IL-1β secretion and development of oviduct pathology during genital chlamydial infection. The data also suggest an IL-1-independent role for ASC in adaptive immunity during genital chlamydial infection.

Asian sand dust enhances murine lung inflammation caused by Klebsiella pneumoniae

Inhaling concomitants from Asian sand dust (ASD) may result in exacerbation of pneumonia by the pathogen. The exacerbating effect of ASD on pneumonia induced by Klebsiella pneumoniae (KP) was investigated in ICR mice. The organic substances adsorbed onto ASD collected from the atmosphere of Iki-island in Japan were excluded by heat treatment at 360 °C for 30 min. ICR mice were instilled intratracheally with ASD at doses of 0.05 mg or 0.2 mg/mouse four times at 2-week intervals (total dose of 0.2 mg or 0.8 mg/mouse) and were administrated with ASD in the presence or absence of KP at the last intratracheal instillation. Pathologically, ASD caused exacerbation of pneumonia by KP as shown by increased inflammatory cells within the bronchiolar and the alveolar compartments. ASD enhanced the neutrophil number dose dependently as well as the expression of cytokines (IL-1β, IL-6, IL-12, IFN-γ, TNF-α) and chemokines (KC, MCP-1, MIP-1α) related to KP in BALF. In an in vitro study using RAW264.7 cells, combined treatment of ASD and KP increased gene expression of IL-1β, IL-6, IFN-β, KC, MCP-1, and MIP-1α. The same treatment tended to increase the protein level of IL-1β, TNF-α and MCP-1 in a culture medium compared to each treatment alone. The combined treatment tended to increase the gene expression of Toll-like receptor 2 (TLR2), and NALP3, ASC and caspase-1 compared with KP alone. These results suggest that the exacerbation of pneumonia by ASD + KP was due to the enhanced production of pro-inflammatory mediators via activation of TLR2 and NALP3 inflammasome pathways in alveolar macrophages.

Significant role of IL-1 signaling, but limited role of inflammasome activation in oviduct pathology during Chlamydia muridarum genital infection (110.6)

Abstract IL-1β has been implicated in the development of oviduct pathology during Chlamydia muridarum genital infection in the mouse model. The goal of this study was to characterize the role of IL-1 signaling and the inflammasome activation pathways during C. muridarum genital infection. Compared to control mice, IL-1 receptor KO (knockout) mice display delayed clearance and increased infection burden, but very few incidences of oviduct hydrosalpinx. Consistent with this observation, IL-1R antagonist KO mice display an opposite phenotype of rapid infection clearance. Flow cytometry analysis at day 10 and day 20 post infection reveal significantly more macrophages in the oviducts of IL-1R KO mice in comparison to control mice. Despite increased infection and recruited macrophages, IL-1R-KO mice have less tissue fibrosis and dilation, suggesting an anti-inflammatory role for these cells in the absence of IL-1 signaling. To investigate the role of inflammasome components during in vivo genital infection, mice lacking NLRP3, NLRC4 and ASC were tested. Although IL-1β secretion is dependent on caspase-1 during in vitro infection of primed macrophages and requires ASC, it is independent of NLRP3 and NLRC4 activation. Surprisingly, during in vivo genital infection, mice lacking NLRP3, NLRC4, as well as ASC display no reduction in oviduct pathology. These data suggest a major role for IL-1 signaling but a limited role for inflammasome pathway in development of oviduct pathology.

ATP and the pathogenesis of COPD

Extracellular ATP is a signalling molecule that often serves as a danger signal to alert the immune system of tissue damage. This molecule activates P2 nucleotide receptors, that include the ionotropic P2X receptors and the metabotropic P2Y receptors. Several publications highlight the importance of purinergic signalling in the pathogenesis of chronic airway inflammation. Recently, it has been reported that ATP accumulates in the airways of both animal models and patients with asthma or chronic obstructive pulmonary diseases (COPD); however, the role and function of ATP in the diseases process of COPD are not well understood. In this perspective, a brief overview is given on the role of ATP and P2 receptors in the pathogenesis of lung emphysema and COPD with a focus on neutrophils as messengers in intercellular communication between epithelial cells and macrophages and the activation of inflammasome pathways. Finding the link between purinergic signalling with inflammasome pathways will be a challenge for the future and could lead to the discovery of new therapeutic drugs for suppressing inflammation in the lungs of COPD patients.

Papillomavirus virus-like particles trigger IL-1beta release through the canonical inflammasome activation signaling pathway (136.33)

Abstract Papillomavirus virus-like particles (VLPs), formed by self-assembled caspid L1 protein, are extremely immunogenic. They can be used both as a mucosal delivery vector and an adjuvant for treating human diseases. However, the mechanism(s) by which papillomavirus VLPs function as an adjuvant is still unclear. We hypothesized that papillomavirus VLPs activate inflammasome in antigen-presenting cells to function as an adjuvant. In order to test our hypothesis, we cocultured HPV16, BPV-1 VLPs or a BPV-1 VLP presenting HIV-1 gp41 neutralizing epitope (chimeric HIV-BPV VLPs) respectively with PMA-primed human THP-1 cells and determined IL-1beta release in the presence or absence of inhibitors of the Nlrp3-inflammasome pathway. We found that HPV-16, BPV-1 VLPs and chimeric HIV-BPV VLPs are capable of activating inflammasome in PMA-primed THP-1 cells, which eventually results in the release of IL-1beta. The release of IL-1beta by the VLPs requires the uptake of VLPs by macrophages as inhibition of clathrin-mediated endocytosis blocked IL-1beta release. Furthermore, the inhibition of cathepsin B or caspase-1 abolished IL-1beta release in the presence of the VLPs. Finally, we also found that generation of reactive oxygen species (ROS) is necessary for activating inflammsome since inhibition of ROS production reduced the level of released IL-1beta. Thus, our results demonstrated that papillomavirus VLPs can activate inflammasome through the canonical inflammasome activation pathway.