NALP inflammasomes: a central role in innate immunity

Celastrol Regulates the Hsp90-NLRP3 Interaction to Alleviate Rheumatoid Arthritis

Previous studies have verified that celastrol (Cel) protects against rheumatoid arthritis (RA) by inhibiting the NLRP3 inflammasome signaling pathway, but the molecular mechanism by which Cel regulates NLRP3 has not been clarified. This study explored the specific mechanisms of Cel in vitro and in vivo. A type II collagen-induced arthritis (CIA) mouse model was used to study the antiarthritic activity of Cel; analysis of paw swelling, determination of the arthritis score, and pathological examinations were performed. The antiproliferative and antimigratory effects of Cel on TNF-α induced fibroblast-like synoviocytes (FLSs) were tested. Proinflammatory factors were evaluated using enzyme-linked immunosorbent assay (ELISA). The expression of NF-κB/NLRP3 pathway components was determined by western blotting and immunofluorescence staining in vitro and in vivo. The putative binding sites between Cel and Hsp90 were predicted through molecular docking, and the binding interactions were determined using the Octet RED96 system and coimmunoprecipitation. Cel decreased arthritis severity and reduced TNF-α-induced FLSs migration and proliferation. Additionally, Cel inhibited NF-κB/NLRP3 signaling pathway activation, reactive oxygen species (ROS) production, and proinflammatory cytokine secretion. Furthermore, Cel interacted directly with Hsp90 and blocked the interaction between Hsp90 and NLRP3 in FLSs. Our findings revealed that Cel regulates NLRP3 inflammasome signaling pathways both in vivo and in vitro. These effects are induced through FLSs inhibition of the proliferation and migration by blocking the interaction between Hsp90 and NLRP3.

TLR4 sensing of IsdB of Staphylococcus aureus induces a proinflammatory cytokine response via the NLRP3-caspase-1 inflammasome cascade

IMPORTANCE

The prevalence of multidrug-resistant Staphylococcus aureus is of global concern, and vaccines are urgently needed. The iron-regulated surface determinant protein B (IsdB) of S. aureus was investigated as a vaccine candidate because of its essential role in bacterial iron acquisition but failed in clinical trials despite strong immunogenicity. Here, we reveal an unexpected second function for IsdB in pathogen-host interaction: the bacterial fitness factor IsdB triggers a strong inflammatory response in innate immune cells via Toll-like receptor 4 and the inflammasome, thus acting as a novel pathogen-associated molecular pattern of S. aureus. Our discovery contributes to a better understanding of how S. aureus modulates the immune response, which is necessary for vaccine development against the sophisticated pathogen.

The NLRP3 Inflammasome as a Pathogenic Player Showing Therapeutic Potential in Rheumatoid Arthritis and Its Comorbidities: A Narrative Review

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease characterized by chronic synovitis and the progressive destruction of cartilage and bone. RA is commonly accompanied by extra-articular comorbidities. The pathogenesis of RA and its comorbidities is complex and not completely elucidated. The assembly of the NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome activates caspase-1, which induces the maturation of interleukin (IL)-1β and IL-18 and leads to the cleavage of gasdermin D with promoting pyroptosis. Accumulative evidence indicates the pathogenic role of NLRP3 inflammasome signaling in RA and its comorbidities, including atherosclerotic cardiovascular disease, osteoporosis, and interstitial lung diseases. Although the available therapeutic agents are effective for RA treatment, their high cost and increased infection rate are causes for concern. Recent evidence revealed the components of the NLRP3 inflammasome as potential therapeutic targets in RA and its comorbidities. In this review, we searched the MEDLINE database using the PubMed interface and reviewed English-language literature on the NLRP3 inflammasome in RA and its comorbidities from 2000 to 2023. The current evidence reveals that the NLRP3 inflammasome contributes to the pathogenesis of RA and its comorbidities. Consequently, the components of the NLRP3 inflammasome signaling pathway represent promising therapeutic targets, and ongoing research might lead to the development of new, effective treatments for RA and its comorbidities.

Interleukin-18: a biomarker with therapeutic potential in adult-onset Still's disease

INTRODUCTION

Adult-onset Still's disease (AOSD) is an autoinflammatory disease driven by the innate immune response. Given the ambiguity in clinical presentation and lack of specific diagnostic biomarkers, AOSD diagnosis is usually delayed in the early stage. Because AOSD is a rare disease with clinical heterogeneity, there is no consensus on its treatment currently. This review summarizes the current research evidence regarding the pathogenic role and the diagnostic or therapeutic potential of interleukin (IL)-18 in AOSD.

AREAS COVERED

We searched the MEDLINE database using the PubMed interface and reviewed English-language literature from 1971 to 2022. This review focusing on IL-18 discusses its pathogenic role and clinical implications in AOSD.

EXPERT OPINION

NLRP3-inflammasome activation with IL-18 overproduction plays a pathogenic role in AOSD. IL-18 is closely linked to the clinical manifestations and disease activity of AOSD and may be a diagnostic biomarker. Given its pathogenic role in AOSD, IL-18 could become a potential therapeutic target. IL-18 binding protein (IL-18BP) negatively regulates the biological activity of IL-18 by inhibiting IL-18 signaling, and a clinical trial revealed that IL-18BP (Tadekinig alfa) treatment was well-tolerated and effective for AOSD. Recently, monoclonal antibodies against IL-18 have been under evaluation in a phase 1b trial.

Polyphenols, flavonoids and inflammasomes: the role of cigarette smoke in COPD

COPD is predicted to become the third leading cause of morbidity and mortality worldwide by 2030. Cigarette smoking (active or passive) is one of its chief causes, with about 20% of cigarette smokers developing COPD from cigarette smoke (CS)-induced irreversible damage and sustained inflammation of the airway epithelium. Inflammasome activation leads to the cleavage of pro-interleukin (IL)-1β and pro-IL-18, along with the release of pro-inflammatory cytokines via gasdermin D N-terminal fragment membrane pores, which further triggers acute phase pro-inflammatory responses and concurrent pyroptosis. There is currently intense interest in the role of nucleotide-binding oligomerisation domain-like receptor family, pyrin domain containing protein-3 inflammasomes in chronic inflammatory lung diseases such as COPD and their potential for therapeutic targeting. Phytochemicals including polyphenols and flavonoids have phyto-medicinal benefits in CS-COPD. Here, we review published articles from the last decade regarding the known associations between inflammasome-mediated responses and ameliorations in pre-clinical manifestations of CS-COPD via polyphenol and flavonoid treatment, with a focus on the underlying mechanistic insights. This article will potentially assist the development of drugs for the prevention and therapy of COPD, particularly in cigarette smokers.

This review compiles current investigations into the role of polyphenols/flavonoids in the alleviation of cigarette smoke-induced inflammasome; notably it provides a promising hit for rectifying the treatment of COPD.https://bit.ly/36OcUO9

Viroporins: Structure, function, and their role in the life cycle of SARS-CoV-2

Viroporins are indispensable for viral replication. As intracellular ion channels they disturb pH gradients of organelles and allow Ca²⁺ flux across ER membranes. Viroporins interact with numerous intracellular proteins and pathways and can trigger inflammatory responses. Thus, they are relevant targets in the search for antiviral drugs. Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) underlies the world-wide pandemic of COVID-19, where an effective therapy is still lacking despite impressive progress in the development of vaccines and vaccination campaigns. Among the 29 proteins of SARS-CoV-2, the E- and ORF3a proteins have been identified as viroporins that contribute to the massive release of inflammatory cytokines observed in COVID-19. Here, we describe structure and function of viroporins and their role in inflammasome activation and cellular processes during the virus replication cycle. Techniques to study viroporin function are presented, with a focus on cellular and electrophysiological assays. Contributions of SARS-CoV-2 viroporins to the viral life cycle are discussed with respect to their structure, channel function, binding partners, and their role in viral infection and virus replication. Viroporin sequences of new variants of concern (α–ο) of SARS-CoV-2 are briefly reviewed as they harbour changes in E and 3a proteins that may affect their function.

Promising Therapeutic Candidate for Myocardial Ischemia/Reperfusion Injury: What Are the Possible Mechanisms and Roles of Phytochemicals?

Percutaneous coronary intervention (PCI) is one of the most effective reperfusion strategies for acute myocardial infarction (AMI) despite myocardial ischemia/reperfusion (I/R) injury, causing one of the causes of most cardiomyocyte injuries and deaths. The pathological processes of myocardial I/R injury include apoptosis, autophagy, and irreversible cell death caused by calcium overload, oxidative stress, and inflammation. Eventually, myocardial I/R injury causes a spike of further cardiomyocyte injury that contributes to final infarct size (IS) and bound with hospitalization of heart failure as well as all-cause mortality within the following 12 months. Therefore, the addition of adjuvant intervention to improve myocardial salvage and cardiac function calls for further investigation. Phytochemicals are non-nutritive bioactive secondary compounds abundantly found in Chinese herbal medicine. Great effort has been put into phytochemicals because they are often in line with the expectations to improve myocardial I/R injury without compromising the clinical efficacy or to even produce synergy. We summarized the previous efforts, briefly outlined the mechanism of myocardial I/R injury, and focused on exploring the cardioprotective effects and potential mechanisms of all phytochemical types that have been investigated under myocardial I/R injury. Phytochemicals deserve to be utilized as promising therapeutic candidates for further development and research on combating myocardial I/R injury. Nevertheless, more studies are needed to provide a better understanding of the mechanism of myocardial I/R injury treatment using phytochemicals and possible side effects associated with this approach.

The structure of NLRP9 reveals a unique C-terminal region with putative regulatory function

Nucleotide-binding and oligomerization domain-like receptors (NLRs) can form inflammasomes that activate caspase-1 and pro-interleukin-1β and induce pyroptosis. NLR family pyrin domain-containing 9 (NLRP9) forms an inflammasome and activates innate immune responses during virus infection, but little is known about this process. Here, we report the crystal and cryo-electron microscopy structures of NLRP9 in an ADP-bound state, revealing inactive and closed conformations of NLRP9 and its similarities to other structurally characterised NLRs. Moreover, we found a C-terminal region interacting with the concave surface of the leucine-rich repeat domain of NLRP9. This region is unique among NLRs and might be involved in the specific function of NLRP9. These data provide the structural basis for understanding the mechanism of NLRP9 regulation and activation.

Rotavirus activates MLKL-mediated host cellular necroptosis concomitantly with apoptosis to facilitate dissemination of viral progeny

Reprogramming the host cellular environment is an obligatory facet of viral pathogens to foster their replication and perpetuation. One of such reprogramming events is the dynamic cross-talk between viruses and host cellular death signaling pathways. Rotaviruses (RVs) have been reported to develop multiple mechanisms to induce apoptotic programmed cell death for maximizing viral spread and pathogenicity. However, the importance of non-apoptotic programmed death events has remained elusive in context of RV infection. Here, we report that RV-induced apoptosis accompanies another non-apoptotic mode of programmed cell death pathway called necroptosis to promote host cellular demise at late phase of infection. Phosphorylation of mixed lineage kinase-domain like (MLKL) protein indicative of necroptosis was observed to concur with caspase-cleavage (apoptotic marker) beyond 6 hours of RV infection. Subsequent studies demonstrated phosphorylated-MLKL to oligomerize and to translocate to plasma membrane in RV infected cells, resulting in loss of plasma membrane integrity and release of alarmin molecules e.g., high mobility group box protein 1 (HMGB1) in the extracellular media. Moreover, inhibiting caspase-cleavage and apoptosis could not fully rescue virus-induced cell death but rather potentiated the necroptotic trigger. Interestingly, preventing both apoptosis and necroptosis by small molecules significantly rescued virus-induced host cytopathy by inhibiting viral dissemination.

1,25-Dihydroxyvitamin D3 attenuates IL-1β secretion by suppressing NLRP1 inflammasome activation by upregulating the NRF2-HO-1 pathway in epidermal keratinocytes

The nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing protein (NLRP) inflammasome is a key inflammatory signaling pathway activated via a two-step signaling process consisting of priming and activation steps. Several studies have shown that 1,25-dihydroxyvitamin D3 (1,25(OH)2VD3) inhibits the priming step required for NLRP3 inflammasome activation in immune cells. However, as activating the NLRP1 inflammasome in keratinocytes does not necessarily require a priming step, whether 1,25(OH)2VD3 inhibits NLRP1 activation in unprimed keratinocytes is currently unknown. In this study, we showed that 1,25(OH)2VD3 inhibits nigericin-induced NLRP1 inflammasome activation in unprimed keratinocytes. 1,25(OH)2VD3 suppressed nigericin-induced interleukin-1β (IL-1β) secretion and caspase-1 activation in human primary keratinocytes. In addition, 1,25(OH)2VD3 significantly inhibited the formation of apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) oligomers and specks, but not caspase-1 enzymatic activity, suggesting that 1,25(OH)2VD3 prevents NLRP1-ASC complex assembly in keratinocytes. Vitamin D receptor (VDR)-knockdown abolished the inhibitory effects of 1,25(OH)2VD3 on nigericin-induced ASC oligomerization and IL-1β secretion, suggesting that 1,25(OH)2VD3 suppresses inflammasome activation via VDR signaling. Furthermore, nigericin induced K+ efflux and cellular reactive oxygen species (ROS) production, and 1,25(OH)2VD3 pretreatment suppressed nigericin-induced ROS production. 1,25(OH)2VD3 increased the expression of both nuclear factor erythroid 2-related factor 2 (NRF2) and heme oxygenase-1 (HO-1), whereas HO-1 inhibition or NRF2 and HO-1 knockdown abrogated the inhibitory effects of 1,25(OH)2VD3 on IL-1β secretion. Our results indicate that 1,25(OH)2VD3 inhibits nigericin-induced activation step of NLRP1 inflammasome activation in unprimed keratinocytes. Our findings reveal the mechanism underlying the inhibitory effect of 1,25(OH)2VD3, which involves NRF2-HO-1 pathway activation through the VDR, providing further insight into the potential function of 1,25(OH)2VD3 as a therapeutic agent for inflammasome-related skin diseases.

Genetic targeting of Card19 is linked to disrupted NINJ1 expression, impaired cell lysis, and increased susceptibility to Yersinia infection

Cell death plays a critical role in inflammatory responses. During pyroptosis, inflammatory caspases cleave Gasdermin D (GSDMD) to release an N-terminal fragment that generates plasma membrane pores that mediate cell lysis and IL-1 cytokine release. Terminal cell lysis and IL-1β release following caspase activation can be uncoupled in certain cell types or in response to particular stimuli, a state termed hyperactivation. However, the factors and mechanisms that regulate terminal cell lysis downstream of GSDMD cleavage remain poorly understood. In the course of studies to define regulation of pyroptosis during Yersinia infection, we identified a line of Card19-deficient mice (Card19lxcn) whose macrophages were protected from cell lysis and showed reduced apoptosis and pyroptosis, yet had wild-type levels of caspase activation, IL-1 secretion, and GSDMD cleavage. Unexpectedly, CARD19, a mitochondrial CARD-containing protein, was not directly responsible for this, as an independently-generated CRISPR/Cas9 Card19 knockout mouse line (Card19Null) showed no defect in macrophage cell lysis. Notably, Card19 is located on chromosome 13, immediately adjacent to Ninj1, which was recently found to regulate cell lysis downstream of GSDMD activation. RNA-seq and western blotting revealed that Card19lxcn BMDMs have significantly reduced NINJ1 expression, and reconstitution of Ninj1 in Card19lxcn immortalized BMDMs restored their ability to undergo cell lysis in response to caspase-dependent cell death stimuli. Card19lxcn mice exhibited increased susceptibility to Yersinia infection, whereas independently-generated Card19Null mice did not, demonstrating that cell lysis itself plays a key role in protection against bacterial infection, and that the increased infection susceptibility of Card19lxcn mice is attributable to loss of NINJ1. Our findings identify genetic targeting of Card19 being responsible for off-target effects on the adjacent gene Ninj1, disrupting the ability of macrophages to undergo plasma membrane rupture downstream of gasdermin cleavage and impacting host survival and bacterial control during Yersinia infection.

Reducing Lung ATP Levels and Alleviating Asthmatic Airway Inflammation through Adeno-Associated Viral Vector-Mediated CD39 Expression

Asthma is a chronic respiratory inflammatory disease. Patients usually suffer long-term symptoms and high medical expenses. Extracellular ATP (eATP) has been identified as a danger signal in innate immunity and serves as a potent inflammatory mediator for asthma. Hydrolyzing eATP in lungs might be a potential approach to alleviate asthmatic inflammation. Recombinant adeno-associated virus (rAAV) vectors that contain tissue-specific cap protein have been demonstrated to efficiently transfer exogenous genes into the lung tissues. To test anti-inflammation efficacy of rAAV-mediated CD39 gene transfer, rAAV-CD39 was generated and applied to OVA-mediated asthmatic mice. BALB/c mice were sensitized intraperitoneally and challenged intratracheally with OVA and treated with rAAV-CD39. At the end of procedure, some inflammatory features were examined. rAAV-CD39 treatment downregulated the levels of pulmonary eATP by the rescued expression of CD39. Several asthmatic features, such as airway hyperresponsiveness, eosinophilia, mucin deposition, and IL-5/IL-13 production in the lungs were decreased in the rAAV-CD39-treated mice. Reduced IL-5/IL-13 production and increased frequency of CD4⁺FoxP3⁺ regulatory T cells were detected in draining lymph nodes of rAAV-CD39 treated mice. This evidence suggested that rAAV-mediated CD39 gene transfer attenuated the asthmatic airway inflammation locally. The results suggest that rAAV-CD39 might have therapeutic potential for asthma.

Necroptosis and its role in infectious diseases

Necroptosis is a noncaspase-dependent and precisely regulated mechanism of cell death. Necroptosis is mainly initiated by members of the tumor necrosis factor receptor (TNFR) and Toll-like receptor (TLR) families, interferon, intracellular RNA and DNA sensors and other mediators. Subsequently, the protein kinase RIPK1 (receptor-interacting protein kinase 1) and RIPK3 interact with the receptor protein, which transduces death signals and further recruits and phosphorylates MLKL (mixed lineage kinase domain-like protein). MLKL serves as the initiator of cell death and eventually induces necroptosis. It was found that necroptosis is not only involved in the physiological regulation but also in the occurrence, development and prognosis of some necrotic diseases, especially infectious diseases. Intervention in the necroptosis signaling pathway is helpful for removing pathogens, inhibiting the development of lesions, and promoting the remodeling of tissue. In-depth study of the molecular regulation mechanism of necroptosis and its relationship with the pathogenesis of infectious diseases will help to provide new ideas and directions for research of the pathological mechanisms and clinical prevention of infectious diseases.

Calcium Pyrophosphate Dihydrate Crystals Increase the Granulocyte/Monocyte Progenitor (GMP) and Enhance Granulocyte and Monocyte Differentiation In Vivo

Calcium pyrophosphate dihydrate (CPPD) crystals are formed locally within the joints, leading to pseudogout. Although the mobilization of local granulocytes can be observed in joints where pseudogout has manifested, the mechanism of this activity remains poorly understood. In this study, CPPD crystals were administered to mice, and the dynamics of splenic and peripheral blood myeloid cells were analyzed. As a result, levels of both granulocytes and monocytes were found to increase following CPPD crystal administration in a concentration-dependent manner, with a concomitant decrease in lymphocytes in the peripheral blood. In contrast, the levels of other cells, such as dendritic cell subsets, T-cells, and B-cells, remained unchanged in the spleen, following CPPD crystal administration. Furthermore, an increase in granulocytes/monocyte progenitors (GMPs) and a decrease in megakaryocyte/erythrocyte progenitors (MEPs) were also observed in the bone marrow. In addition, CPPD administration induced production of IL-1β, which acts on hematopoietic stem cells and hematopoietic progenitors and promotes myeloid cell differentiation and expansion. These results suggest that CPPD crystals act as a “danger signal” to induce IL-1β production, resulting in changes in course of hematopoietic progenitor cell differentiation and in increased granulocyte/monocyte levels, and contributing to the development of gout.

NLRP9 in innate immunity and inflammation

The nucleotide-binding domain leucine-rich repeat containing receptors (NLRs) are a family of evolutionarily conserved proteins. Several members of NLRs, notably NLRP1, NLRP3 and NLRC4, are able to form cytosolic oligomeric signalling platforms termed inflammasomes to mediate immune response towards pathogens, damage and stress. However, the functions of many NLRs still remain elusive. In the past few years, a couple of less-characterized NLR members are emerging as important signalling molecules with fundamental functions in host defence and inflammation. Among them, NLRP9 is an NLR originally proposed to be expressed and function solely in the reproductive system. Recent evidence has suggested that NLRP9 is also capable of initiating inflammasome formation in the intestine to restrict replication and damage brought by rotavirus infection. Here, we highlight the latest progress in characterization of the role of NLRP9 in infectious and inflammatory diseases, as well as the newest crystallographic and biochemical studies on NLRP9. Finally, we discuss some important questions remained to be answered regarding the molecular and cellular mechanisms governing NLRP9's function in innate immunity and inflammation.

The pivotal roles of the NOD-like receptors with a PYD domain, NLRPs, in oocytes and early embryo development†

Nucleotide-binding oligomerization domain (NOD)-like receptors with a pyrin domain (PYD), NLRPs, are pattern recognition receptors, well recognized for their important roles in innate immunity and apoptosis. However, several NLRPs have received attention for their new, specialized roles as maternally contributed genes important in reproduction and embryo development. Several NLRPs have been shown to be specifically expressed in oocytes and preimplantation embryos. Interestingly, and in line with divergent functions, NLRP genes reveal a complex evolutionary divergence. The most pronounced difference is the human-specific NLRP7 gene, not identified in rodents. However, mouse models have been extensively used to study maternally contributed NLRPs. The NLRP2 and NLRP5 proteins are components of the subcortical maternal complex (SCMC), which was recently identified as essential for mouse preimplantation development. The SCMC integrates multiple proteins, including KHDC3L, NLRP5, TLE6, OOEP, NLRP2, and PADI6. The NLRP5 (also known as MATER) has been extensively studied. In humans, inactivating variants in specific NLRP genes in the mother are associated with distinct phenotypes in the offspring, such as biparental hydatidiform moles (BiHMs) and preterm birth. Maternal-effect recessive mutations in KHDC3L and NLRP5 (and NLRP7) are associated with reduced reproductive outcomes, BiHM, and broad multilocus imprinting perturbations. The precise mechanisms of NLRPs are unknown, but research strongly indicates their pivotal roles in the establishment of genomic imprints and post-zygotic methylation maintenance, among other processes. Challenges for the future include translations of findings from the mouse model into human contexts and implementation in therapies and clinical fertility management.

The therapeutic potential of colchicine in the complications of COVID19. Could the immunometabolic properties of an old and cheap drug help?

The present study analyzes the importance of the inflammasome that involves the NLRP3 complex in the state of hypercytokinemia observed in patients with COVID-19, significantly increasing IL-1β, IL18, IL-6, and TNF. Unfortunately, improving the immune response can sometimes worsen the outcome of the disease. Studies show that colchicine, among other actions, inhibits the assembly of NLRP3 complex that is responsible for generating the active form of Caspase-1 that will convert Pro-IL-1β and Pro-IL-18 into their active forms. We suggest using colchicine, a class of drugs with low-cost, extensively tested, well-tolerated medicine as a complementary treatment for patients with COVID-19, in early stages of the disease based on knowledge of its immunomodulatory properties.

[Inhibitory effect of Biejiajian pills against diethylnitrosamine-induced hepatocarcinogenesis in rats]

OBJECTIVE

To study the inhibitory effect of Biejiajian pills (BJJ) agaisnt diethylnitrosamine (DEN)-induced hepatocarcinogenesis and explore the relation between this effect and the inflammasome signaling pathway.

METHODS

Sixty-five male SD rats were randomly divided into control group, DEN model group, and 3 BJJ treatment groups at low, medium and high dose (with daily dose of 0.55, 1.1 and 2.2 g/kg, respectively, for 12 consecutive weeks starting from the 5th week after modeling). The pathological changes of the liver tissue were observed with HE and Masson staining, and serum levels of alanine transaminase (ALT), glutamic oxaloacetic transaminase (AST), alkaline phosphatase (ALP) and total bilirubin (TBIL) of the rats were detected using ELISA. Oxidation stress in the liver tissue was assessed with ELISA, and Western blotting and ELISA were used to detect the molecular expressions of inflammasome-related pathway.

RESULTS

BJJ significantly inhibited tumor growth in the liver of the rats. HE and Masson staining showed that BJJ treatment obviously ameliorated liver fibrosis and reduced cancer cell and inflammatory cell infiltration in the liver. BJJ significantly reduced elevations of serum ALT, AST, ALP and TBIL levels, increased the contents of superoxide dismutase, catalase and glutathione peroxidase in the liver and suppressed malondialdehyde in Den-treated rats. BJJ also dose-dependently decreased the expressions of NLRP3, apoptosis-associated speck-like protein (ASC), caspase-1, pro-IL-1β, pro-IL-18, IL-1β and IL-18 in the liver of Den-treated rats.

CONCLUSIONS

BJJ treatment can dose-dependently inhibit DEN-induced hepatocarcinogenesis by enhancing antioxidant capacity and down-regulating inflammatory-related pathways in rats.

Artemisinin suppresses myocardial ischemia-reperfusion injury via NLRP3 inflammasome mechanism

Artemisinin is known for its pharmaceutical effect against malaria and received increased attention for its other potential function. Mounting evidence suggest that artemisinin could also exert cardioprotective effects while the understanding of its regulatory mechanism is still limited. This study is designed to investigate the role of artemisinin in myocardial ischemia/reperfusion (I/R) injury and the involvement of NLRP3 inflammasome. Artemisinin was administrated for 14 consecutive days intragastrically before I/R injury. Cardiac function was assessed by echocardiography. Infarct area was observed through HE and TTC staining. Apoptosis and autophagy were assessed by TUNEL and Western blotting. The artemisinin-treated myocardial I/R rats demonstrated less severe myocardial I/R injury (smaller infarct size and lower CK-MB, LDH), significant inhibition of cardiac autophagy (decreased LC3II/I and increased p62), improved mitochondrial electron transport chain activity, concomitant with decreased activation of NLRP3 inflammasome (decreased NLRP3, ASC, cleaved caspase-1, IL-1β). In conclusion, our findings further confirmed that activation of the NLRP3 inflammasome pathway is involved in myocardial I/R injury, whereas artemisinin preconditioning could effectively protect against myocardial I/R injury through suppression of NLRP3 inflammasome activation. Therefore, the NLRP3 inflammasome might serve as a promising therapeutic target providing new mechanisms for understanding the effect of artemisinin during the evolution of myocardial infarction.

Crystal structure of the human NLRP9 pyrin domain reveals a bent N-terminal loop that may regulate inflammasome assembly

Members of the NLR family pyrin domain containing (NLRPs) are pattern recognition receptors that participate in innate immunity. They form inflammasomes, which are platforms for caspase-1 recruitment and activation. The NLRP pyrin domain (PYD) is critical for the assembly of inflammasomes due to its ability to mediate protein interactions. Despite intensive structural studies on inflammasomes with PYDs, the structure of the PYD of NLRP9-the least studied member of the family-remains unknown. Herein, we report the crystal structure of the human NLRP9 PYD at 2.1 Å resolution, which reveals a kinked N-terminal loop oriented toward the interior of the helical bundle. Based on our findings, we propose a regulatory role for the kinked N-terminal loop of NLRP9 PYD in inflammasome assembly.

To protect or adversely affect? The dichotomous role of the NLRP1 inflammasome in human disease

NLRP1 is an inflammasome forming pattern recognition receptor (PRR). When activated by pathogen- and damage- associated molecular patterns (PAMPS/DAMPS), NLRP1 inflammasome formation leads to inflammation through the production of proinflammatory cytokines IL-18 and IL-1β. As with other inflammasome forming NLR family members, NLRP1 also regulates cell death processes, termed pyroptosis. The domain structure of NLRP1 differs between mice and humans, making it possible for the function of the inflammasome to differ between species and adds complexity to the study of this NLR family member. In humans, mutations in both coding and non-coding regions of the NLRP1 gene are linked to a variety of diseases. Likewise, interruption of NLRP1 inhibitors or changes in the prevalence of NLRP1 activators can also impact disease pathobiology. Adding to its complexity, the NLRP1 inflammasome plays a dichotomous role in human diseases, functioning to either attenuate or augment miscellaneous biological processes in a tissue specific manner. For example, NLRP1 plays a protective role in the gastrointestinal tract by modulating the microbiome composition; however, it augments neurological disorders, cardio-pulmonary diseases, and cancer through promoting inflammation. Thus, it is critical that the role of NLRP1 in each of these disease processes be robustly defined. In this review, we summarize the current research landscape to provide a better understanding of the mechanisms associated with NLRP1 function and dysfunction in human disease pathobiology. We propose that a better understanding of these mechanisms will ultimately result in improved insight into immune system dysfunction and therapeutic strategies targeting inflammasome function in multiple human diseases.

Systematic analysis of genetic variants in cancer-testis genes identified two novel lung cancer susceptibility loci in Chinese population

Cancer-testis (CT) genes played important roles in the progression of malignant tumors and were recognized as promising therapeutic targets. However, the roles of genetic variants in CT genes in lung cancer susceptibility have not been well depicted. This study aimed to evaluate the associations between genetic variants in CT genes and lung cancer risk in Chinese population. A total of 22,556 qualified SNPs from 268 lung cancer associated CT genes were initially evaluated based on our previous lung cancer GWAS (Genome-wide association studies) with 2,331 cases and 3,077 controls. As a result, 17 candidate SNPs were further genotyped in 1,056 cases and 1,053 controls using Sequenom platform. Two variants (rs6941653, OPRM1, T > C, screening: OR = 1.24, 95%CI: 1.12-1.38, P = 2.40×10^-5; validation: OR = 1.18, 95%CI: 1.01-1.37, P = 0.039 and rs402969, NLRP8, C > T, screening: OR = 1.15, 95%CI: 1.04-1.26, P = 0.006; validation: OR = 1.16, 95%CI: 1.02-1.33, P = 0.028) were identified as novel lung cancer susceptibility variants. Stratification analysis indicated that the effect of rs6941653 was stronger in lung squamous cell carcinoma (OR = 1.36) than that in lung adenocarcinoma (OR = 1.15, I² = 77%, P = 0.04). Finally, functional annotations, differential gene expression analysis, pathway and gene ontology analyses were performed to suggest the potential functions of our identified variants and genes. In conclusion, this study identified two novel lung cancer risk variants in Chinese population and provided deeper insight into the roles of CT genes in lung tumorigenesis.

Gut-Liver Axis and Inflammasome Activation in Cholangiocyte Pathophysiology

The Nlrp3 inflammasome is a multiprotein complex activated by a number of bacterial products or danger signals and is involved in the regulation of inflammatory processes through caspase-1 activation. The Nlrp3 is expressed in immune cells but also in hepatocytes and cholangiocytes, where it appears to be involved in regulation of biliary damage, epithelial barrier integrity and development of fibrosis. Activation of the pathways of innate immunity is crucial in the pathophysiology of hepatobiliary diseases, given the strong link between the gut and the liver. The liver secretes bile acids, which influence the bacterial composition of the gut microbiota and, in turn, are heavily modified by microbial metabolism. Alterations of this balance, as for the development of dysbiosis, may deeply influence the composition of the bacterial products that reach the liver and are able to activate a number of intracellular pathways. This alteration may be particularly important in the pathogenesis of cholangiopathies and, in particular, of primary sclerosing cholangitis, given its strong association with inflammatory bowel disease. In the present review, we summarize current knowledge on the gut–liver axis in cholangiopathies and discuss the role of Nlrp3 inflammasome activation in cholestatic conditions.

Viroporins and inflammasomes: A key to understand virus-induced inflammation

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The article provides a summary on cellular receptors involved in virus immunity.

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It summarizes key findings on viroporins, a novel class of viral proteins and their role in the virus life cycle and host cell interactions.

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It presents an overview of the current understanding of inflammasomes complex activation, with special focus on NLRP3.

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It discusses the correlation between viroporins and inflammasomes activation and aggravated inflammatory cytokines production.

Viroporins are virus encoded proteins that alter membrane permeability and can trigger subsequent cellular signals. Oligomerization of viroporin subunits results in formation of a hydrophilic pore which facilitates ion transport across host cell membranes. These viral channel proteins may be involved in different stages of the virus infection cycle. Inflammasomes are large multimolecular complexes best recognized for their ability to control activation of caspase-1, which in turn regulates the maturation of interleukin-1 β (IL-1β) and interleukin 18 (IL-18). IL-1β was originally identified as a pro-inflammatory cytokine able to induce both local and systemic inflammation and a febrile reaction in response to infection or injury. Excessive production of IL-1β is associated with autoimmune and inflammatory diseases. Microbial derivatives, bacterial pore-forming toxins, extracellular ATP and other pathogen-associated molecular patterns trigger activation of NLRP3 inflammasomes. Recent studies have reported that viroporin activity is capable of inducing inflammasome activity and production of IL-1β, where NLRP3 is shown to be regulated by fluxes of K⁺, H⁺ and Ca²⁺ in addition to reactive oxygen species, autophagy and endoplasmic reticulum stress. The aim of this review is to present an overview of the key findings on viroporin activity with special emphasis on their role in virus immunity and as possible activators of inflammasomes.

Haematopoietic stem cell gene therapy with IL-1Ra rescues cognitive loss in mucopolysaccharidosis IIIA

Mucopolysaccharidosis IIIA is a neuronopathic lysosomal storage disease, characterised by heparan sulphate and other substrates accumulating in the brain. Patients develop behavioural disturbances and cognitive decline, a possible consequence of neuroinflammation and abnormal substrate accumulation. Interleukin (IL)‐1β and interleukin‐1 receptor antagonist (IL‐1Ra) expression were significantly increased in both murine models and human MPSIII patients. We identified pathogenic mechanisms of inflammasome activation, including that disease‐specific 2‐O‐sulphated heparan sulphate was essential for priming an IL‐1β response via the Toll‐like receptor 4 complex. However, mucopolysaccharidosis IIIA primary and secondary storage substrates, such as amyloid beta, were both required to activate the NLRP3 inflammasome and initiate IL‐1β secretion. IL‐1 blockade in mucopolysaccharidosis IIIA mice using IL‐1 receptor type 1 knockout or haematopoietic stem cell gene therapy over‐expressing IL‐1Ra reduced gliosis and completely prevented behavioural phenotypes. In conclusion, we demonstrate that IL‐1 drives neuroinflammation, behavioural abnormality and cognitive decline in mucopolysaccharidosis IIIA, highlighting haematopoietic stem cell gene therapy treatment with IL‐1Ra as a potential neuronopathic lysosomal disease treatment.

High-Density Lipoproteins Decrease Proinflammatory Activity and Modulate the Innate Immune Response

Atherosclerosis, a chronic inflammatory disease of the arterial wall, is the leading cause of cardiac disorders and stroke. The onset and progression of these diseases are linked with the inflammatory response, especially NLRP3 inflammasome activation, inducing the production of proinflammatory cytokines, such as interleukin 1β (IL-1β). Because high-density lipoproteins (HDLs) have shown significant antiatherogenic and anti-inflammatory properties, we evaluated their immunomodulatory activity in response to cholesterol crystals and other innate immune activators. Human primary monocyte-derived macrophages, THP-1 cells, and murine macrophages were stimulated to activate NLRP3 inflammasome and other pattern recognition receptors, in the presence or absence of HDL. Then, HDL immunomodulatory effects were evaluated through IL-1β and IL-6 production by enzyme-linked immunosorbent assay. Furthermore, in vivo HDL anti-inflammatory effects were evaluated in a murine model of peritoneal inflammatory infiltration. HDLs have an immunomodulatory effect on different cellular models, including peripheral blood mononuclear cells, THP-1 cells, and murine macrophages, by affecting the activity of innate immunity sensors, such as Toll-like receptors (TLRs), dectin-1, and inflammasomes. HDL reduces the proinflammatory role of cholesterol crystals, nigericin, and other NLRP3 and AIM2 inflammasome agonists, and several TLR agonists, leading to a decreased production of IL-1β and IL-6. The results suggest that HDLs are highly important in the regulation of the innate immune response and may have a beneficial role in controlling diseases associated with the inflammatory response.

The N-end rule ubiquitin ligase UBR2 mediates NLRP1B inflammasome activation by anthrax lethal toxin

Anthrax lethal toxin (LT) is known to induce NLRP1B inflammasome activation and pyroptotic cell death in macrophages from certain mouse strains in its metalloprotease activity-dependent manner, but the underlying mechanism is unknown. Here, we establish a simple but robust cell system bearing dual-fluorescence reporters for LT-induced ASC specks formation and pyroptotic lysis. A genome-wide siRNA screen and a CRISPR-Cas9 knockout screen were applied to this system for identifying genes involved in LT-induced inflammasome activation. UBR2, an E3 ubiquitin ligase of the N-end rule degradation pathway, was found to be required for LT-induced NLRP1B inflammasome activation. LT is known to cleave NLRP1B after Lys44. The cleaved NLRP1B, bearing an N-terminal leucine, was targeted by UBR2-mediated ubiquitination and degradation. UBR2 partnered with an E2 ubiquitin-conjugating enzyme UBE2O in this process. NLRP1B underwent constitutive autocleavage before the C-terminal CARD domain. UBR2-mediated degradation of LT-cleaved NLRP1B thus triggered release of the noncovalent-bound CARD domain for subsequent caspase-1 activation. Our study illustrates a unique mode of inflammasome activation in cytosolic defense against bacterial insults.

Opportunities for future therapeutic interventions for hyperoxaluria: targeting oxidative stress

INTRODUCTION

Oxalate is a toxic byproduct of metabolism and is normally produced in quantities easily removed from the body. However, under specific circumstances oxalate production is increased resulting in deposition of calcium oxalate (CaOx) crystals in the kidneys as well as other organs causing inflammation and injury. Excessive buildup of crystal deposits in the kidneys causes eventual loss of renal function requiring renal transplantation. Areas covered: Cellular exposure to CaOx crystals induces the production of reactive oxygen species (ROS) with the involvement of renin-angiotensin aldosterone system (RAAS), mitochondria, and NADPH oxidase. Inflammasomes are activated and pro-inflammatory cytokines, such as IL-1β and IL-18 are produced. We reviewed results of experimental and clinical studies of crystal renal epithelial cell interactions with emphasis on cellular injury and ROS production. Expert opinion: Treatment should depend upon the level of hyperoxaluria and whether it is associated with CaOx crystal deposition. Persistent low grade or intermittent hyperoxaluria can be treated with antioxidants, free radical scavengers. Hyperoxaluria associated with CaOx crystal deposition will require administration of angiotensin II receptor blockers, and NADPH oxidase or NLRP3 inflammasome inhibitors. DASH-style diet will be beneficial in both cases.

Association Between Psoriasis and Vitiligo: A Systematic Review and Meta-Analysis

BACKGROUND

The relationship between psoriasis and vitiligo has not been previously confirmed, and we therefore aimed to investigate this association.

METHODS

We conducted a search of the MEDLINE and EMBASE electronic databases on 22 January 2018 for case-control, cross-sectional, and cohort studies examining the association between psoriasis and vitiligo. A customized Newcastle-Ottawa Scale was used to assess the risk of bias of the included studies. We performed a random effects meta-analysis to calculate pooled odds ratios (ORs) with 95% confidence intervals (CIs) for case-control and cross-sectional studies.

RESULTS

Of 2453 citations identified from the literature search, 10 case-control/cross-sectional studies with a total of 120,866 psoriasis cases and 79,907 vitiligo cases were included in our study. Four of these studies were rated as high risk of bias. We found a significantly increased odds for vitiligo in psoriasis patients (summary OR 2.29, 95% CI 1.56-3.37, studies = 7), as well as a significantly elevated odds for psoriasis in vitiligo patients (summary OR 3.43, 95% CI 1.86-6.33, studies = 4).

CONCLUSIONS

Our meta-analysis showed that psoriasis and vitiligo are associated with each other. Several studies had a high risk of bias, and further investigation is needed to confirm this association and amplify treatment options.

The subcortical maternal complex protein Nlrp4f is involved in cytoplasmic lattice formation and organelle distribution

In mammalian oocytes and embryos, the subcortical maternal complex (SCMC) and cytoplasmic lattices (CPLs) are two closely related structures. Their detailed compositions and functions remain largely unclear. Here, we characterized Nlrp4f as a novel component associated with the SCMC and CPLs. Disruption of maternal Nlrp4f leads to decreased fecundity and delayed preimplantation development in the mouse. Lack of Nlrp4f affects organelle distribution in mouse oocytes and early embryos. Depletion of Nlrp4f disrupts CPL formation but does not affect the interactions of other SCMC proteins. Interestingly, the loss of Filia or Tle6, two other SCMC proteins, also disrupts CPL formation in mouse oocytes. Thus, the absence of CPLs and aberrant distribution of organelles in the oocytes disrupted the examined SCMC genes, including previously reported Zbed3, Mater, Floped and Padi6, indicate that the SCMC is required for CPL formation and organelle distribution. Consistent with the SCMC's role in CPL formation, the SCMC forms before CPLs during oogenesis. Together, our results suggest that SCMC protein Nlrp4f is involved in CPL formation and organelle distribution in mouse oocytes.

Hsp90 inhibition as a means to inhibit activation of the NLRP3 inflammasome

Once activated, the intracellular receptor NLRP3 assembles an inflammasome protein complex that facilitates the caspase-1-mediated maturation of IL-1β and IL-18. Inactive NLRP3 is guarded by a protein complex containing Hsp90. In response to stress stimuli, Hsp90 is released, and NLRP3 can be activated to promote inflammation. In this study, we blocked Hsp90 with geldanamycin and studied the fate of NLRP3 in human retinal pigment epithelial (RPE) cells. RPE cells play a central role in the development of age-related macular degeneration (AMD), a progressive eye disease causing severe vision loss in the elderly. IL-1α-primed ARPE-19 cells, human embryonal stem cell (hESC)-derived RPE cells, and primary human RPE cells were exposed to MG-132 and bafilomycin A to activate NLRP3 via the inhibition of proteasomes and autophagy, respectively. Additionally, RPE cells were treated with geldanamycin at different time points and the levels of NLRP3 and IL-1β were determined. Caspase-1 activity was measured using a commercial assay. Geldanamycin prevented the activation of the inflammasome in human RPE cells. NLRP3 released from its protective complex became degraded by autophagy or secreted from the cells. Controlled destruction of NLRP3 is a potential way to regulate the inflammation associated with chronic diseases, such as AMD.

Autoinflammatory disease in the lung

Ascertaining the dominant cell type driving an immunological disease is essential to understanding the causal pathology and, therefore, selecting or developing an effective treatment. Classifying immunological diseases in this way has led to successful treatment regimens for many monogenic diseases; however, when the dominant cell type is unclear and there is no obvious causal genetic mutation, then identifying the correct disease classification and appropriate therapy can be challenging. In this review we focus on pulmonary immunological diseases where an innate immune signature has been identified as a predominant aspect of the immunopathology. We describe the molecular pathology of 'autoinflammatory diseases of the lung' and propose that small molecule and biological therapies, including recombinant interleukin-1 receptor antagonist, that target key innate immune pathways, are likely be beneficial in the control of pulmonary and systemic inflammation in these conditions. In addition, the successful use of macrolide antibiotics to treat lung infections in these conditions further confirms that the innate immune system is the key conductor of inflammation in these pulmonary diseases, as there is a strong body of evidence that macrolides are able to modulate the NLRP3 inflammasome and interleukin-1β and interleukin-18 secretion, both of which are central players in the innate immune response. Throughout this review we highlight the published evidence of autoinflammatory disease in chronic obstructive pulmonary disease, bronchiectasis, cystic fibrosis and rheumatoid lung disease and suggest that the fundamental pathology of these diseases places them towards the autoinflammatory pole of the immunological disease continuum.

Human parvovirus B19 nonstructural protein NS1 activates NLRP3 inflammasome signaling in adult‑onset Still's disease

Dysregulation of inflammasomes serves a pathogenic role in autoinflammatory diseases (AIDs) and adult-onset Still's disease (AOSD) has been categorized as an AID. The present study investigated the expression of NLR family pyrin domain containing proteins (NLRPs) inflammasome in patients with AOSD, the effect of inflammasome inhibitors on NLRP3 signaling and whether human parvovirus B19‑associated antigens can activate NLRP3 in patients with AOSD. mRNA expression levels of NLRPs in peripheral blood mononuclear cells (PBMCs) from 34 patients with AOSD and 14 healthy individuals were determined using reverse transcription‑quantitative polymerase chain reaction. Protein expression of NLRP3 was evaluated by western blotting. Supernatant cytokine levels were measured by ELISA. Among the NLRPs investigated in the present study, NLRP3 transcripts were markedly elevated and expression of NLRP2, NLRP7 and NLRP12 was decreased in patients with AOSD compared with the controls. Treatment with NLRP3 inhibitors significantly reduced downstream NLRP3 signaling in PBMCs form patients with AOSD. B19‑nonstructural protein (NS)1 stimulation of PBMCs from patients with AOSD induced significant upregulation of transcript levels of NLRP3, caspase‑1 and interleukin (IL)‑1β compared with PBMCs from healthy controls. B19‑NS1 stimulation of PBMCs from patients with AOSD induced significant increase in supernatant levels of IL‑1β and protein expression of NLRP3, caspase‑1, IL‑1β, and IL‑18 compared with healthy controls. Elevated expression of NLRP3 and its downstream inflammasome signaling components in patients with AOSD indicated a potential pathogenic role of B19‑NS1. Thus, B19‑NS1 may induce expression of IL‑1β and IL‑18 through activation of caspase‑1‑associated NLRP3‑inflammasome in AOSD.

Elevated Expression of the NLRP3 Inflammasome and Its Correlation with Disease Activity in Adult-onset Still Disease

OBJECTIVE

The dysregulation of the NLRP3 (NLR containing a pyrin domain) inflammasome is involved in autoinflammatory diseases. Adult-onset Still disease (AOSD) is regarded as an autoinflammatory disease. However, the pathogenic involvement of NLRP3 inflammasome in AOSD remains unclear and NLRP3 activators in AOSD are currently unknown.

METHODS

The mRNA expression of NLRP3 inflammasome signaling in peripheral blood mononuclear cells (PBMC) from 34 patients with AOSD and 14 healthy subjects was determined using quantitative-PCR (qPCR). The changes in mRNA and protein levels of NLRP3 inflammasome signaling in PBMC treated with the potential activator [imiquimod (IMQ)] or inhibitor of NLRP3 were evaluated using qPCR and immunoblotting, respectively. The supernatant levels of interleukin (IL)-1β and IL-18 were determined by ELISA.

RESULTS

Significantly higher mRNA levels of NLRP3 inflammasome signaling were observed in patients with AOSD compared with healthy controls. NLRP3 expressions were positively correlated with disease activity in patients with AOSD. IMQ (an effective Toll-like receptor 7 ligand; 10 µg/ml and 25 µg/ml) stimulation of PBMC from patients with AOSD induced dose-dependent increases of mRNA expression of NLRP3 (mean ± standard error of the mean, 2.06 ± 0.46 and 6.05 ± 1.84, respectively), caspase-1 (1.81 ± 0.23 and 4.25 ± 0.48), IL-1β (5.68 ± 1.51 and 12.13 ± 3.71), and IL-18 (2.32 ± 0.37 and 4.81 ± 0.51) compared with controls (all p < 0.005). IMQ stimulation of PBMC from patients similarly induced greater increases in protein expressions of NLRP3 inflammasome compared with controls. The protein expressions of NLRP3, IL-1β, and IL-18 on PBMC significantly decreased after treatment with NLRP3 inhibitor in patients with AOSD.

CONCLUSION

Increased expression of NLRP3 inflammasome and its positive correlation with disease activity in AOSD suggest its involvement in disease pathogenesis. IMQ upregulated expressions of NLRP3 inflammasome signaling, and IMQ might be an activator of NLRP3 inflammasome in AOSD.

Epidermal keratinocytes sense dsRNA via the NLRP3 inflammasome, mediating interleukin (IL)-1β and IL-18 release

Skin epidermis, in addition to its barrier function, is able to actively sense harmful pathogens using pattern recognition receptors. In immune cells, the nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain containing 3 (NLRP3) inflammasome can mediate innate immunity against viral infection via a mechanism involving viral dsRNA recognition. Epidermal keratinocytes express NLRP3 inflammasome, which can sense contact sensitizers and mite allergens, leading to pro-interleukin (IL)-1β and pro-IL-18 cleavage into their active forms. Skin often faces viral infection. However, it is unknown whether viral dsRNA can be detected by the keratinocyte NLRP3 inflammasome. We transfected polyinosinic:polycytidylic acid (poly I:C), a synthetic viral dsRNA analogue, into cultured primary human keratinocytes at the aid of Lipofectamine 2000, and found that transfected poly I:C activated caspase-1 and induced caspase-1-dependent release of IL-1β and IL-18, which were suppressed on transfection with NLRP3 siRNA. The activation of keratinocyte NLRP3 inflammasome by transfected poly I:C was dependent on dsRNA-induced protein kinase (PKR) activation, and priming with type I interferons upregulated NLRP3 inflammasome activation through promoting PKR activation in poly I:C-transfected keratinocytes. In conclusion, the NLRP3 inflammasome can act as a sensor of dsRNA in epidermal keratinocytes, which may be important in both skin innate immune defense against viral infection and skin inflammation.

Targeting the deubiquitinase STAMBP inhibits NALP7 inflammasome activity

Inflammasomes regulate innate immune responses by facilitating maturation of inflammatory cytokines, interleukin (IL)-1β and IL-18. NACHT, LRR and PYD domains-containing protein 7 (NALP7) is one inflammasome constituent, but little is known about its cellular handling. Here we show a mechanism for NALP7 protein stabilization and activation of the inflammasome by Toll-like receptor (TLR) agonism with bacterial lipopolysaccharide (LPS) and the synthetic acylated lipopeptide Pam3CSK4. NALP7 is constitutively ubiquitinated and recruited to the endolysosome for degradation. With TLR ligation, the deubiquitinase enzyme, STAM-binding protein (STAMBP) impedes NALP7 trafficking to lysosomes to increase NALP7 abundance. STAMBP deubiquitinates NALP7 and STAMBP knockdown abrogates LPS or Pam3CSK4-induced increases in NALP7 protein. A small-molecule inhibitor of STAMBP deubiquitinase activity, BC-1471, decreases NALP7 protein levels and suppresses IL-1β release after TLR agonism. These findings describe a unique pathway of inflammasome regulation with the identification of STAMBP as a potential therapeutic target to reduce pro-inflammatory stress.

Analysis of Pelagia noctiluca proteome Reveals a Red Fluorescent Protein, a Zinc Metalloproteinase and a Peroxiredoxin

Pelagia noctiluca is the most venomous jellyfish in the Mediterranean Sea where it forms dense blooms. Although there is several published research on this species, until now none of the works has been focused on a complete protein profile of the all body constituents of this organism. Here, we have performed a detailed proteomics characterization of the major protein components expressed by P. noctiluca. With that aim, we have considered the study of jellyfish proteins involved in defense, body constituents and metabolism, and furthered explore the significance and potential application of such bioactive molecules. P. noctiluca body proteins were separated by1D SDS-PAGE and 2DE followed by characterization by nanoLC-MS/MS and MALDI-TOF/TOF techniques. Altogether, both methods revealed 68 different proteins, including a Zinc Metalloproteinase, a Red Fluorescent Protein (RFP) and a Peroxiredoxin. These three proteins were identified for the first time in P. noctiluca. Zinc Metalloproteinase was previously reported in the venom of other jellyfish species. Besides the proteins described above, the other 65 proteins found in P. noctiluca body content were identified and associated with its clinical significance. Among all the proteins identified in this work we highlight: Zinc metalloproteinase, which has a ShK toxin domain and therefore should be implicated in the sting toxicity of P. noctiluca.; the RFP which are a very important family of proteins due to its possible application as molecular markers; and last but not least the discovery of a Peroxiredoxin in this organism makes it a new natural resource of antioxidant and anti-UV radiation agents.

Ketogenic Diet and Cancer-a Perspective

Research of the last two decades showed that chronic low-grade inflammation, elevated blood glucose and insulin levels may play role in the onset of a number of non-communicable diseases such as type 2 diabetes and some forms of cancer. Regular exercise and fasting can ameliorate high blood glucose and insulin levels as well as increase the concentration of plasma ketone bodies. These, in consequence, may lead to reduction of inflammation. Exercise or severe restriction of caloric intake is not always advisable for patients, in particular those suffering from cancer. The ketogenic diet (KD), characterized by high fat, moderate protein and very low carbohydrate composition can evoke a physiological state similar to that triggered by exercise or fasting. These attributes of KD prompted its possible use in treatment of a number of metabolic diseases, including several types of malignancies. Although results from clinical studies employing KD in the treatment of cancer are still limited, the results obtained from animal models are encouraging and show that KD presents a viable option as an adjunct therapy for cancer.

Activated microglia trigger inflammasome activation and lysosomal destabilization in human RPE cells

Activation of the innate immune system plays a major role in retinal degenerative diseases including age-related macular degeneration (AMD). In this study, we investigated whether reactive microglia trigger and sustain NLRP3 inflammasome activation in human retinal pigment epithelium (ARPE-19) cells. Specifically, we analyzed the potential of cell culture supernatants from lipopolysaccharide (LPS)-stimulated human microglia in combination with the lysosomal destabilization agent Leu-Leu-O-Me (LLOMe) to activate the inflammasome in ARPE-19 cells. We found disorganization of ARPE-19 cytoskeletal structure after incubation with conditioned media of LPS-stimulated microglia and LLOMe and accumulation of lipid deposits in these cells using Nile Red staining. LC3-II, the active form of the autophagy marker microtubule-associated protein 1 light chain 3 beta (LC3B), was also elevated in ARPE-19 cells after inducing inflammasome activation. Finally, a significant increase of transcripts for IL-6, IL-8, IL-1ß, GM-CSF and CCL-2 was detected in ARPE-19 stimulated with both microglia-conditioned medium and LLOMe. Our findings highlight a potential role of microglia in RPE inflammasome activation.

Are the innate and adaptive immune systems setting hypertension on fire?

Hypertension is the most common chronic cardiovascular disease and is associated with several pathological states, being an important cause of morbidity and mortality around the world. Low-grade inflammation plays a key role in hypertension and the innate and adaptive immune systems seem to contribute to hypertension development and maintenance. Hypertension is associated with vascular inflammation, increased vascular cytokines levels and infiltration of immune cells in the vasculature, kidneys and heart. However, the mechanisms that trigger inflammation and immune system activation in hypertension are completely unknown. Cells from the innate immune system express pattern recognition receptors (PRR), which detect conserved pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) that induce innate effector mechanisms to produce endogenous signals, such as inflammatory cytokines and chemokines, to alert the host about danger. Additionally, antigen-presenting cells (APC) act as sentinels that are activated by PAMPs and DAMPs to sense the presence of the antigen/neoantigen, which ensues the adaptive immune system activation. In this context, different lymphocyte types are activated and contribute to inflammation and end-organ damage in hypertension. This review will focus on experimental and clinical evidence demonstrating the contribution of the innate and adaptive immune systems to the development of hypertension.

Porphyromonas gingivalis activates NFκB and MAPK pathways in human oral epithelial cells

BACKGROUND

The bacterial biofilm at the gingival margin induces a host immune reaction. In this local inflammation epithelial cells defend the host against bacterial challenge. Porphyromonas gingivalis (P. gingivalis), a keystone pathogen, infects epithelial cells. The aim of this study was to investigate the activation of signaling cascades in primary epithelial cells and oral cancer cell lines by a profiler PCR array.

RESULTS

After infection with P. gingivalis membranes the RNA of 16 to 33 of 84 key genes involved in the antibacterial immune response was up-regulated, amongst them were IKBKB (NF-κB signaling pathway), IRF5 (TLR signaling) and JUN, MAP2K4, MAPK14 and MAPK8 (MAPK pathway) in SCC-25 cells and IKBKB, IRF5, JUN, MAP2K4, MAPK14 and MAPK8 in PHGK. Statistically significant up-regulation of IKBKB (4.7 ×), MAP2K4 (4.6 ×), MAPK14 (4.2 ×) and IRF5 (9.8 ×) (p < 0.01) was demonstrated in SCC-25 cells and IKBKB (3.1 ×), MAP2K4 (4.0 ×) MAPK 14 (3.0 ×) (p < 0.05), IRF5 (3.0 ×) and JUN (7.7 ×) (p < 0.01) were up-regulated in PHGK.

CONCLUSIONS

P. gingivalis membrane up-regulates the expression of genes involved in downstream TLR, NFκB and MAPK signaling pathways involved in the pro-inflammatory immune response in primary and malignant oral epithelial cells.

Differential IL-1β secretion by monocyte subsets is regulated by Hsp27 through modulating mRNA stability

Monocytes play a central role in regulating inflammation in response to infection or injury, and during auto-inflammatory diseases. Human blood contains classical, intermediate and non-classical monocyte subsets that each express characteristic patterns of cell surface CD16 and CD14; each subset also has specific functional properties, but the mechanisms underlying many of their distinctive features are undefined. Of particular interest is how monocyte subsets regulate secretion of the apical pro-inflammatory cytokine IL-1β, which is central to the initiation of immune responses but is also implicated in the pathology of various auto-immune/auto-inflammatory conditions. Here we show that primary human non-classical monocytes, exposed to LPS or LPS + BzATP (3'-O-(4-benzoyl)benzyl-ATP, a P2X7R agonist), produce approx. 80% less IL-1β than intermediate or classical monocytes. Despite their low CD14 expression, LPS-sensing, caspase-1 activation and P2X7R activity were comparable in non-classical monocytes to other subsets: their diminished ability to produce IL-1β instead arose from 50% increased IL-1β mRNA decay rates, mediated by Hsp27. These findings identify the Hsp27 pathway as a novel therapeutic target for the management of conditions featuring dysregulated IL-1β production, and represent an advancement in understanding of both physiological inflammatory responses and the pathogenesis of inflammatory diseases involving monocyte-derived IL-1β.

Cellular Stress Response and Immune Signaling in Retinal Ischemia-Reperfusion Injury

Ischemia–reperfusion injury is a well-known pathological hallmark associated with diabetic retinopathy, glaucoma, and other related retinopathies that ultimately can lead to visual impairment and vision loss. Retinal ischemia pathogenesis involves a cascade of detrimental events that include energy failure, excitotoxic damage, calcium imbalance, oxidative stress, and eventually cell death. Retina for a long time has been known to be an immune privileged site; however, recent investigations reveal that retina, as well as the central nervous system, elicits immunological responses during various stress cues. Stress condition, such as reperfusion of blood supply post-ischemia results in the sequestration of different immune cells, inflammatory mediators including cytokines, chemokines, etc., to the ischemic region, which in turn facilitates induction of inflammatory conditions in these tissues. The immunological activation during injury or stress per se is beneficial for repair and maintenance of cellular homeostasis, but whether the associated inflammation is good or bad, during ischemia–reperfusion injury, hitherto remains to be explored. Keeping all these notions in mind, the current review tries to address the immune response and host stress response mechanisms involved in ischemia–reperfusion injury with the focus on the retina.

Elevated levels of triglycerides and vldl-cholesterol provoke activation of nlrp1 inflammasome in endothelial cells

BACKGROUND

Soluble stimuli present in the plasma of patients with peripheral arterial disease (PAD) are capable of directly stimulating intracellular signalling in endothelium. Oxidized-LDL (oxLDL) induces NLRP3 inflammasome activation in macrophages. However, it is not clear how lipid profile affect NLRP1 inflammasome gene expression in endothelial cells. In this study, the effect of cholesterol and TG of plasma of patients with PAD on NLRP1 inflammasome gene expression in human arterial endothelial cells (HAECS) was assessed.

METHODS

We included 113 patients with symptomatic PAD. HAECs were stimulated for 2h using the plasma samples of the study participants. The NLRP1 quantification of the transcription was carried out on the 7500 real-time PCR system using the Taqman® Universal PCR Master Mix and Assays on demand. Relative quantification of the NLRP1 expression was carried out using the ΔΔCt (threshold cycle) comparative method.

RESULTS

Plasma from patients with elevated VLDL-cholesterol levels (>33.6mg/dL, the median value of the sample) provoked a higher expression of NLRP1 inflammasome in HAECs (RQ=1.15±0.23 vs. 1.05±0.69; p=0.045), as well as plasma from patients with elevated TGs levels (>168mg/dL, the median value of the sample) (RQ=1.15±0.23 vs. 1.05±0.69; p=0.045). A positive correlation was found between NLRP1 inflammasome expression and VLDL-cholesterol plasma levels (r=0.4; p<0.001) as between NLRP1 inflammasome expression and TG levels (r=0.4; p<0.001).

CONCLUSIONS

Plasma TG and VLDL cholesterol of patients with atherosclerosis, manifested as PAD, promote the in vitro NLRP1 inflammasome expression in HAECs.

Necroptosis inhibitors as therapeutic targets in inflammation mediated disorders - a review of the current literature and patents

INTRODUCTION

Recent studies have shown substantial interplay between the apoptosis and necroptosis pathways. Necroptosis, a form of programmed cell death, has been found to stimulate the immune system contributing to the pathophysiology of several inflammation-mediated disorders. Determining the contribution of necroptotic signaling pathways to inflammation may lead to the development of selective and specific molecular target implicated necroptosis inhibitors. Areas covered: This review summarizes the recently published and patented necroptosis inhibitors as therapeutic targets in inflammation-mediated disorders. The role of several necroptosis inhibitors, focusing on specific signaling molecules, was discussed with particular attention to inflammation-mediated disorders. Data was obtained from Espacenet®, WIPO®, USPTO® patent websites, and other relevant sources (2006-2016). Expert opinion: Necroptosis inhibitors hold promise for treatment of inflammation-mediated clinical conditions in which necroptotic cell death plays a major role. Although necroptosis inhibitors reviewed in this survey showed inhibitory effects against several inflammation-mediated disorders, only a few have passed to the stage of clinical testing and need extensive research for therapeutic practice. Revisiting the existing drugs and developing novel necroptosis inhibiting agents as well as understanding their mechanism are essential. A detailed study of necroptosis function in animal models of inflammation may provide us an alternative strategy for the development of drug-like necroptosis inhibitors.

Fluorofenidone attenuates pulmonary inflammation and fibrosis via inhibiting the activation of NALP3 inflammasome and IL-1β/IL-1R1/MyD88/NF-κB pathway

Interleukin (IL)‐1β plays an important role in the pathogenesis of idiopathic pulmonary fibrosis. The production of IL‐1β is dependent upon caspase‐1‐containing multiprotein complexes called inflammasomes and IL‐1R1/MyD88/NF‐κB pathway. In this study, we explored whether a potential anti‐fibrotic agent fluorofenidone (FD) exerts its anti‐inflammatory and anti‐fibrotic effects through suppressing activation of NACHT, LRR and PYD domains‐containing protein 3 (NALP3) inflammasome and the IL‐1β/IL‐1R1/MyD88/NF‐κB pathway in vivo and in vitro. Male C57BL/6J mice were intratracheally injected with Bleomycin (BLM) or saline. Fluorofenidone was administered throughout the course of the experiment. Lung tissue sections were stained with haemotoxylin and eosin and Masson's trichrome. Cytokines were measured by ELISA, and α‐smooth muscle actin (α‐SMA), fibronectin, collagen I, caspase‐1, IL‐1R1, MyD88 were measured by Western blot and/or RT‐PCR. The human actue monocytic leukaemia cell line (THP‐1) were incubated with monosodium urate (MSU), with or without FD pre‐treatment. The expression of caspase‐1, IL‐1β, NALP3, apoptosis‐associated speck‐like protein containing (ASC) and pro‐caspase‐1 were measured by Western blot, the reactive oxygen species (ROS) generation was detected using the Flow Cytometry, and the interaction of NALP3 inflammasome‐associated molecules were measured by Co‐immunoprecipitation. RLE‐6TN (rat lung epithelial‐T‐antigen negative) cells were incubated with IL‐1β, with or without FD pre‐treatment. The expression of nuclear protein p65 was measured by Western blot. Results showed that FD markedly reduced the expressions of IL‐1β, IL‐6, monocyte chemotactic protein‐1 (MCP‐1), myeloperoxidase (MPO), α‐SMA, fibronectin, collagen I, caspase‐1, IL‐1R1 and MyD88 in mice lung tissues. And FD inhibited MSU‐induced the accumulation of ROS, blocked the interaction of NALP3 inflammasome‐associated molecules, decreased the level of caspase‐1 and IL‐1β in THP‐1 cells. Besides, FD inhibited IL‐1β‐induced the expression of nuclear protein p65. This study demonstrated that FD, attenuates BLM‐induced pulmonary inflammation and fibrosis in mice via inhibiting the activation of NALP3 inflammasome and the IL‐1β/IL‐1R1/MyD88/ NF‐κB pathway.

Inflammation and its role in age-related macular degeneration

Inflammation is a cellular response to factors that challenge the homeostasis of cells and tissues. Cell-associated and soluble pattern-recognition receptors, e.g. Toll-like receptors, inflammasome receptors, and complement components initiate complex cellular cascades by recognizing or sensing different pathogen and damage-associated molecular patterns, respectively. Cytokines and chemokines represent alarm messages for leukocytes and once activated, these cells travel long distances to targeted inflamed tissues. Although it is a crucial survival mechanism, prolonged inflammation is detrimental and participates in numerous chronic age-related diseases. This article will review the onset of inflammation and link its functions to the pathogenesis of age-related macular degeneration (AMD), which is the leading cause of severe vision loss in aged individuals in the developed countries. In this progressive disease, degeneration of the retinal pigment epithelium (RPE) results in the death of photoreceptors, leading to a loss of central vision. The RPE is prone to oxidative stress, a factor that together with deteriorating functionality, e.g. decreased intracellular recycling and degradation due to attenuated heterophagy/autophagy, induces inflammation. In the early phases, accumulation of intracellular lipofuscin in the RPE and extracellular drusen between RPE cells and Bruch's membrane can be clinically detected. Subsequently, in dry (atrophic) AMD there is geographic atrophy with discrete areas of RPE loss whereas in the wet (exudative) form there is neovascularization penetrating from the choroid to retinal layers. Elevations in levels of local and systemic biomarkers indicate that chronic inflammation is involved in the pathogenesis of both disease forms.