Advances in Nod-like receptors (NLR) biology

Study on the physicochemical properties and immune regulatory mechanism of polysaccharide fraction from Aronia Melanocarpa fruit

Aronia Melanocarpa (Michx.) Elliott fruit has been extensively used in the food and medicinal fields. This study aimed to analyze the physicochemical properties of a polysaccharide fraction (AMP2) isolated from this fruit for the first time and investigated its immune regulatory mechanism. The physicochemical properties of AMP2 were determined using high-performance gel permeation chromatography, PMP derivatization-high performance liquid chromatography, Ultraviolet spectroscopy, and infrared spectroscopy. The metagenomic technology was applied to investigate the regulatory effects and mechanisms of AMP2 on the gut microbiota of immunosuppressed mice. The results showed that molecular weight of AMP2 was 83,444 Da, which was mainly composed of D-arabinose, D-xylose, D-mannose, D-rhamnose and D-glucose, and both β-type and α-type glycosidic bonds contained in its structure. AMP2 changed the composition of gut microbiota by increasing the number of beneficial and probiotic bacteria, thereby regulated the intestinal mucosal immune system of host. AMP2 improved intestinal immune system response and antimicrobial capacity through positive regulation of the NOD-like receptor signaling pathway and neutrophil extracellular trap formation. The results demonstrate the potential of AMP2 in immune regulation, providing a new perspective for its subsequent development and contributing to the development and application of related health foods.

SGLT2 inhibitors and NLRP3 inflammasome: potential target in diabetic kidney disease

Diabetic kidney disease (DKD) remains the leading cause of chronic kidney disease (CKD) worldwide. The pathogenesis of DKD is influenced by functional, histopathological, and immune mechanisms, including NLRP3 inflammasome activity and oxidative stress. The sodium-glucose cotransporter 2 inhibitors (SGLT2i) have shown metabolic benefits and the ability to slow the progression of DKD in several clinical studies over the years. Recent studies suggest that the antidiabetic activity also extends to inhibition of the inflammatory response, including modulation of the NLRP3 inflammasome, reduction of pro-inflammatory markers and reduction of oxidative stress. Here we review the efficacy of SGLT2i in the treatment of CKD and discuss the role of the inflammatory response in the development of DKD, including its relationship to the NLRP3 inflammasome and oxidative stress.

Nod-like receptors: The relevant elements of glioblastoma`s prognostic puzzle

Despite considerable improvements in understanding the biology of glioblastoma (GB), it still remains the most lethal type of brain tumor in adults. The role of innate immune cells in the development of GB was recently described. In particular, the tumor-immune cell interactions are thought to be critical in enabling tumor tolerance and even protection against therapeutics. Interestingly, the GB cells express proteins belonging to the family of intracellular pattern-recognition receptors, namely the NOD-like receptors (NLRs). Their activation may trigger the formation of the inflammasome complex leading to the secretion of mature IL-1β and IL-18 and thus resulting in cell death. Intrudingly, the expression of most NLRs was found to be correlated with tumor progression and poor prognosis. We speculate that recognizing the role of NOD-like receptors in GB has the potential to improve the effectiveness of diagnostic tools and prognosis, while also encouraging the development of novel precision medicine-based therapies.

Fine particulate matter aggravates smoking induced lung injury via NLRP3/caspase-1 pathway in COPD

BACKGROUND

Exposure to noxious particles, including cigarette smoke and fine particulate matter (PM2.5), is a risk factor for chronic obstructive pulmonary disease (COPD) and promotes inflammation and cell death in the lungs. We investigated the combined effects of cigarette smoking and PM2.5 exposure in patients with COPD, mice, and human bronchial epithelial cells.

METHODS

The relationship between PM2.5 exposure and clinical parameters was investigated in patients with COPD based on smoking status. Alveolar destruction, inflammatory cell infiltration, and pro-inflammatory cytokines were monitored in the smoking-exposed emphysema mouse model. To investigate the mechanisms, cell viability and death and pyroptosis-related changes in BEAS-2B cells were assessed following the exposure to cigarette smoke extract (CSE) and PM2.5.

RESULTS

High levels of ambient PM2.5 were more strongly associated with high Saint George's respiratory questionnaire specific for COPD (SGRQ-C) scores in currently smoking patients with COPD. Combined exposure to cigarette smoke and PM2.5 increased mean linear intercept and TUNEL-positive cells in lung tissue, which was associated with increased inflammatory cell infiltration and inflammatory cytokine release in mice. Exposure to a combination of CSE and PM2.5 reduced cell viability and upregulated NLRP3, caspase-1, IL-1β, and IL-18 transcription in BEAS-2B cells. NLRP3 silencing with siRNA reduced pyroptosis and restored cell viability.

CONCLUSIONS

PM2.5 aggravates smoking-induced airway inflammation and cell death via pyroptosis. Clinically, PM2.5 deteriorates quality of life and may worsen prognosis in currently smoking patients with COPD.

MSC therapy ameliorates experimental gouty arthritis hinting an early COX-2 induction

Objective

The specific effect of Adipose-Derived Mesenchymal Stem Cells (Ad-MSC) on acute joint inflammation, where the response mostly depends on innate immunity activation, remains elusive. The pathogenesis of gouty arthritis, characterized by the deposition of monosodium urate (MSU) crystals in the joints, associated to acute flares, has been associated to NLRP3 inflammasome activation and subsequent amplification of the inflammatory response. Our aim was to study the effect of human Ad-MSC administration in the clinical inflammatory response of rabbits after MSU injection, and the molecular mechanisms involved.

Methods

Ad-MSC were administered by intraarterial route shortly after intraarticular MSU crystal injections. Joint and systemic inflammation was sequentially studied, and the mechanisms involved in NLRP3 inflammasome activation, and the synthesis of inflammatory mediators were assessed in the synovial membranes 72h after insult. Ad-MSC and THP-1-derived macrophages stimulated with MSU were co-cultured in transwell system.

Results

A single systemic dose of Ad-MSC accelerated the resolution of local and systemic inflammatory response. In the synovial membrane, Ad-MSC promoted alternatively M2 macrophage presence, inhibiting NLRP3 inflammasome and inducing the production of anti-inflammatory cytokines, such as IL-10 or TGF-β, and decreasing nuclear factor-κB activity. Ad-MSC induced a net anti-inflammatory balance in MSU-stimulated THP-1 cells, with a higher increase in IL-10 and IDO expression than that observed for IL-1β and TNF.

Conclusion

Our in vivo and in vitro results showed that a single systemic dose of Ad-MSC decrease the intensity and duration of the inflammatory response by an early local COX-2 upregulation and PGE2 release. Ad-MSCs suppressed NF-kB activity, NLRP3 inflammasome, and promoted the presence of M2 alternative macrophages in the synovium. Therefore, this therapeutic approach could be considered as a pharmacological alternative in patients with comorbidities that preclude conventional treatment.

The role of NOD-like receptors in innate immunity

The innate immune system in vertebrates and invertebrates relies on conserved receptors and ligands, and pathways that can rapidly initiate the host response against microbial infection and other sources of stress and danger. Research into the family of NOD-like receptors (NLRs) has blossomed over the past two decades, with much being learned about the ligands and conditions that stimulate the NLRs and the outcomes of NLR activation in cells and animals. The NLRs play key roles in diverse functions, ranging from transcription of MHC molecules to initiation of inflammation. Some NLRs are activated directly by their ligands, while other ligands may have indirect effects on the NLRs. New findings in coming years will undoubtedly shed more light on molecular details involved in NLR activation, as well as the physiological and immunological outcomes of NLR ligation.

SARS-CoV-2 induces "cytokine storm" hyperinflammatory responses in RA patients through pyroptosis

Background

The coronavirus disease (COVID-19) is a pandemic disease that threatens worldwide public health, and rheumatoid arthritis (RA) is the most common autoimmune disease. COVID-19 and RA are each strong risk factors for the other, but their molecular mechanisms are unclear. This study aims to investigate the biomarkers between COVID-19 and RA from the mechanism of pyroptosis and find effective disease-targeting drugs.

Methods

We obtained the common gene shared by COVID-19, RA (GSE55235), and pyroptosis using bioinformatics analysis and then did the principal component analysis(PCA). The Co-genes were evaluated by Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and ClueGO for functional enrichment, the protein-protein interaction (PPI) network was built by STRING, and the k-means machine learning algorithm was employed for cluster analysis. Modular analysis utilizing Cytoscape to identify hub genes, functional enrichment analysis with Metascape and GeneMANIA, and NetworkAnalyst for gene-drug prediction. Network pharmacology analysis was performed to identify target drug-related genes intersecting with COVID-19, RA, and pyroptosis to acquire Co-hub genes and construct transcription factor (TF)-hub genes and miRNA-hub genes networks by NetworkAnalyst. The Co-hub genes were validated using GSE55457 and GSE93272 to acquire the Key gene, and their efficacy was assessed using receiver operating curves (ROC); SPEED2 was then used to determine the upstream pathway. Immune cell infiltration was analyzed using CIBERSORT and validated by the HPA database. Molecular docking, molecular dynamics simulation, and molecular mechanics-generalized born surface area (MM-GBSA) were used to explore and validate drug-gene relationships through computer-aided drug design.

Results

COVID-19, RA, and pyroptosis-related genes were enriched in pyroptosis and pro-inflammatory pathways(the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome complex, death-inducing signaling complex, regulation of interleukin production), natural immune pathways (Network map of SARS-CoV-2 signaling pathway, activation of NLRP3 inflammasome by SARS-CoV-2) and COVID-19-and RA-related cytokine storm pathways (IL, nuclear factor-kappa B (NF-κB), TNF signaling pathway and regulation of cytokine-mediated signaling). Of these, CASP1 is the most involved pathway and is closely related to minocycline. YY1, hsa-mir-429, and hsa-mir-34a-5p play an important role in the expression of CASP1. Monocytes are high-caspase-1-expressing sentinel cells. Minocycline can generate a highly stable state for biochemical activity by docking closely with the active region of caspase-1.

Conclusions

Caspase-1 is a common biomarker for COVID-19, RA, and pyroptosis, and it may be an important mediator of the excessive inflammatory response induced by SARS-CoV-2 in RA patients through pyroptosis. Minocycline may counteract cytokine storm inflammation in patients with COVID-19 combined with RA by inhibiting caspase-1 expression.

Viral Infection and Airway Epithelial Immunity in Asthma

Viral respiratory tract infections are associated with asthma development and exacerbation in children and adults. In the course of immune responses to viruses, airway epithelial cells are the initial platform of innate immunity against viral invasion. Patients with severe asthma are more vulnerable than those with mild to moderate asthma to viral infections. Furthermore, in most cases, asthmatic patients tend to produce lower levels of antiviral cytokines than healthy subjects, such as interferons produced from immune effector cells and airway epithelial cells. The epithelial inflammasome appears to contribute to asthma exacerbation through overactivation, leading to self-damage, despite its naturally protective role against infectious pathogens. Given the mixed and complex immune responses in viral-infection-induced asthma exacerbation, this review examines the diverse roles of airway epithelial immunity and related potential therapeutic targets and discusses the mechanisms underlying the heterogeneous manifestations of asthma exacerbations.

The Role of H2S Regulating NLRP3 Inflammasome in Diabetes

Nucleotide-binding oligomeric domain (NOD)-like receptor protein 3 (NLRP3) is a recently discovered cytoplasmic multiprotein complex involved in inflammation. The NLRP3 inflammasome contains NLRP3, apoptosis-related specific protein (ASC) and precursor caspase-1. The NLRP3 inflammasome is involved in many diseases, including diabetes. H₂S is a harmful gas with a rotten egg smell. Recently, it has been identified as the third gas signal molecule after nitric oxide and carbon monoxide. It has many biological functions and plays an important role in many diseases, including diabetes. In recent years, it has been reported that H₂S regulation of the NLRP3 inflammasome contributes to a variety of diseases. However, the mechanism has not been fully understood. In this review, we summarized the recent role and mechanism of H₂S in regulating the NLRP3 inflammasome in diabetes, in order to provide a theoretical basis for future research.

Pathogenic Mechanisms of Fusobacterium nucleatum on Oral Epithelial Cells

Periodontitis is an oral chronic inflammatory disease and may cause tooth loss in adults. Oral epithelial cells provide a barrier for bacteria and participate in the immune response. Fusobacterium nucleatum (F. nucleatum) is one of the common inhabitants of the oral cavity and has been identified as a potential etiologic bacterial agent of oral diseases, such as periodontitis and oral carcinomas. F. nucleatum has been shown to be of importance in the development of diverse human cancers. In the dental biofilm, it exhibits a structural role as a bridging organism, connecting primary colonizers to the largely anaerobic secondary colonizers. It expresses adhesins and is able to induce host cell responses, including the upregulation of defensins and the release of chemokines and interleukins. Like other microorganisms, its detection is achieved through germline-encoded pattern-recognition receptors (PRRs) and pathogen-associated molecular patterns (PAMPs). By identification of the pathogenic mechanisms of F. nucleatum it will be possible to develop effective methods for the diagnosis, prevention, and treatment of diseases in which a F. nucleatum infection is involved. This review summarizes the recent progress in research targeting F. nucleatum and its impact on oral epithelial cells.

Role of Pyroptosis in Respiratory Diseases and its Therapeutic Potential

Pyroptosis is an inflammatory type of regulated cell death that is dependent on inflammasome activation and downstream proteases such as caspase-1 or caspase 4/5/11. The main executors are gasdermins, which have an inherent pore-forming function on the membrane and release inflammatory cytokines, such as interleukin (IL)-1β, IL-18 and high mobility group box 1. Emerging evidence demonstrates that pyroptosis is involved in the pathogenesis of various pulmonary diseases. In this review, we mainly discuss the biological mechanisms of pyroptosis, explore the relationship between pyroptosis and respiratory diseases, and discuss emerging therapeutic strategies for respiratory diseases.

Pattern recognition receptors in health and diseases

Pattern recognition receptors (PRRs) are a class of receptors that can directly recognize the specific molecular structures on the surface of pathogens, apoptotic host cells, and damaged senescent cells. PRRs bridge nonspecific immunity and specific immunity. Through the recognition and binding of ligands, PRRs can produce nonspecific anti-infection, antitumor, and other immunoprotective effects. Most PRRs in the innate immune system of vertebrates can be classified into the following five types based on protein domain homology: Toll-like receptors (TLRs), nucleotide oligomerization domain (NOD)-like receptors (NLRs), retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs), C-type lectin receptors (CLRs), and absent in melanoma-2 (AIM2)-like receptors (ALRs). PRRs are basically composed of ligand recognition domains, intermediate domains, and effector domains. PRRs recognize and bind their respective ligands and recruit adaptor molecules with the same structure through their effector domains, initiating downstream signaling pathways to exert effects. In recent years, the increased researches on the recognition and binding of PRRs and their ligands have greatly promoted the understanding of different PRRs signaling pathways and provided ideas for the treatment of immune-related diseases and even tumors. This review describes in detail the history, the structural characteristics, ligand recognition mechanism, the signaling pathway, the related disease, new drugs in clinical trials and clinical therapy of different types of PRRs, and discusses the significance of the research on pattern recognition mechanism for the treatment of PRR-related diseases.

The role of interleukin-1β in the immune response to contact allergens

Interleukin-1β (IL-1β) is an important pro-inflammatory cytokine that has an effect on almost every cell lineage in the body. By blocking IL-1β and investigating the IL-1β signaling pathway, several studies have demonstrated a central role of IL-1β in the response to contact allergens. This review summarizes the current literature regarding the basic immunological mechanisms mediated by IL-1β in the different phases of allergic contact dermatitis (ACD) and highlights potential IL-1β-targeted treatment options, which in the future may be relevant in the treatment of patients with ACD. This review is based primarily on studies using various mouse models and human in vitro studies, since clinical studies on the effect of IL-1β in ACD are lacking.

What Goes Wrong during Early Development of Artificially Reproduced European Eel Anguilla anguilla? Clues from the Larval Transcriptome and Gene Expression Patterns

Simple Summary

Closing the life cycle of the European eel in captivity is urgently needed to gain perspective for the commercial production of juvenile glass eels. Larvae are produced weekly at our facilities, but large variations in larval mortality are observed during the first week after hatching. Although much effort has been devoted to investigating ways to prevent early larval mortality, it remains unclear what the causes are. The aim of this study was to perform a transcriptomic study on European eel larvae in order to identify genes and physiological pathways that are differentially regulated in the comparison of larvae from batches that did not survive for longer than three days vs. larvae from batches that survived for at least a week up to 22 days after hatching (non-viable vs. viable larvae). In contrast to earlier published studies on European eel, we conclude that larvae exhibit immune competency. Non-viable larvae initiated an inflammatory and host protection immune response and tried to maintain osmoregulatory homeostasis. As a perspective, microbial control and salinity reduction might benefit eel larvae in terms of lower mortality and improved development by lowering the costs of immune functioning and osmoregulation.

Abstract

In eels, large variations in larval mortality exist, which would impede the viable production of juvenile glass eels in captivity. The transcriptome of European eel larvae was investigated to identify physiological pathways and genes that show differential regulation between non-viable vs. viable larvae. Expression of genes involved in inflammation and host protection was higher, suggesting that non-viable larvae suffered from microbial infection. Expression of genes involved in osmoregulation was also higher, implying that non-viable larvae tried to maintain homeostasis by strong osmoregulatory adaptation. Expression of genes involved in myogenesis, neural, and sensory development was reduced in the non-viable larvae. Expression of the major histocompatibility complex class-I (mhc1) gene, M-protein (myom2), the dopamine 2B receptor (d2br), the melatonin receptor (mtr1), and heat-shock protein beta-1 (hspb1) showed strong differential regulation and was therefore studied in 1, 8, and 15 days post-hatch (dph) larvae by RT-PCR to comprehend the roles of these genes during ontogeny. Expression patterning of these genes indicated the start of active swimming (8 dph) and feed searching behavior (15 dph) and confirmed immunocompetence immediately after hatching. This study revealed useful insights for improving larval survival by microbial control and salinity reduction.

Combining of transcriptomic and proteomic data to mine immune-related genes and proteins in the liver of Cynoglossus semilaevis challenged with Vibrio anguillarum

The liver is a multi-functional organ including metabolism, substance synthesis, detoxification, and various immune functions, and its role in immunity has attracted more and more attention. However, research on the liver immune response of fish infected by pathogenic bacteria is currently lacking. In this study, the transcriptomics and proteomics of the liver of Cynoglossus semilaevis infected with Vibrio anguillarum were analyzed. A total of 1470 genes and 497 proteins were differentially expressed in the pairwise comparison of obvious symptoms of infection (HOSG), no obvious symptoms of infection (NOSG) and PBS treatment (CG). Gene ontology and KEGG enrichment pathways analysis showed that differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) were mainly enriched in toll-like receptors (TLRs), complement and coagulation cascades, nucleotide oligomerization domain (NOD)-like receptors (NLRs), mitogen-activated protein kinase (MAPK) and phagosome signaling pathways, which suggested the combined action of the five pathways were significant to enhance the liver immune defense. The combination of transcriptomic and proteomic analysis showed that ITGβ1, C3, C5 and MRC1 were significantly up-regulated, which might play an important role in the liver immune response to the recognition of V. anguillarum, inflammatory response and phagocytosis. The transcriptome and proteome data we obtained provide information on some key genes and proteins for further study of the mechanism of liver immune response.

Kuijieling, a Chinese medicine alleviates DSS-induced colitis in C57BL/6Jmouse by improving the diversity and function of gut microbiota

Ulcerative colitis (UC) is a gastrointestinal disease. The link between gut microbiota and the inflammatory response in the gut has been recently established. Restoration of gut microbiota suppresses inflammatory signaling. Kuijieling (KJL) decoction, an experimental Chinese medicine formula could ameliorate the symptom of colitis. However, the involvement of gut microbiota in its curative effect remains known. Here, we would like to assess the therapeutic effect of KJL in DSS-induced UC model. Mouse feces were collected, followed by 16S rRNA sequencing. Kuijieling decoction improved gut microbial homeostasis and suppressed inflammation in the UC model. A 5-fold cross-validation and random forest analysis identified seven signature bacterial taxa representing the DSS-mediated pathogenic condition and recovery stage upon KJL decoction treatment. Overall, the findings support the notion of KJL decoction-mediated restoration of gut microbiota as a critical step of inducing remission and alleviating UC symptoms. In the present investigation, we aimed to address the question of whether KJL decoction alleviates the UC symptoms by manipulating the gut microbial structure and function.

Structural and Evolutionary Adaptation of NOD-Like Receptors in Birds

NOD-like receptors (NLRs) are intracellular sensors of the innate immune system that recognize intracellular pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs). Little information exists regarding the incidence of positive selection in the evolution of NLRs of birds or the structural differences between bird and mammal NLRs. Evidence of positive selection was identified in four avian NLRs (NOD1, NLRC3, NLRC5, and NLRP3) using the maximum likelihood approach. These NLRs are under different selection pressures which is indicative of different evolution patterns. Analysis of these NLRs showed a lower percentage of codons under positive selection in the LRR domain than seen in the studies of Toll-like receptors (TLRs), suggesting that the LRR domain evolves differently between NLRs and TLRs. Modeling of human, chicken, mammalian, and avian ancestral NLRs revealed the existence of variable evolution patterns in protein structure that may be adaptively driven.

New Insights into Pathomechanisms and Treatment Possibilities for Lung Silicosis

Inhalation of silica particles is an environmental and occupational cause of silicosis, a type of pneumoconiosis. Development of the lung silicosis is a unique process in which the vicious cycle of ingestion of inhaled silica particles by alveolar macrophages and their release triggers inflammation, generation of nodular lesions, and irreversible fibrosis. The pathophysiology of silicosis is complex, and interactions between the pathomechanisms have not been completely understood. However, elucidation of silica-induced inflammation cascades and inflammation-fibrosis relations has uncovered several novel possibilities of therapeutic targeting. This article reviews new information on the pathophysiology of silicosis and points out several promising treatment approaches targeting silicosis-related pathways.

The Role of the Effects of Endoplasmic Reticulum Stress on NLRP3 Inflammasome in Diabetes

Endoplasmic reticulum (ER) is an important organelle for the protein synthesis, modification, folding, assembly, and the transport of new peptide chains. When the folding ability of ER proteins is impaired, the accumulation of unfolded or misfolded proteins in ER leads to endoplasmic reticulum stress (ERS). The nucleotide-binding oligomerization domain-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome, can induce the maturation and secretion of interleukin-1beta (IL-1β) and IL-18 through activating caspase-1. It is associated with many diseases. Studies have shown that ERS can regulate NLRP3 inflammasome in many diseases including diabetes. However, the mechanism of the effects of ERS on NLRP3 inflammasome in diabetes has not been fully understood. This review summarizes the recent researches about the effects of ERS on NLRP3 inflammasome and the related mechanism in diabetes to provide ideas for the relevant basic research in the future.

NLRP7 deubiquitination by USP10 promotes tumor progression and tumor-associated macrophage polarization in colorectal cancer

BACKGROUND

NOD-like receptors affect multiple stages of cancer progression in many malignancies. NACHT, LRR, and PYD domain-containing protein 7 (NLRP7) is a member of the NOD-like receptor family, although its role in tumorigenesis remains unclear. By analyzing clinical samples, we found that NLRP7 protein levels were upregulated in colorectal cancer (CRC). We proposed the hypothesis that a high level of NLRP7 in CRC may promote tumor progression. Here, we further investigated the role of NLRP7 in CRC and the underlying mechanism.

METHODS

NLRP7 expression in human CRC and adjacent non-tumorous tissues was examined by quantitative real-time polymerase chain reaction (qRT-PCR), western blotting, and immunohistochemistry. The effect of NLRP7 in CRC progression was investigated in vitro and in vivo. Proteins interacting with NLRP7 were identified by immunoprecipitation and mass spectrometry analysis while immunofluorescence staining revealed the cellular location of the proteins. Cellular ubiquitination and protein stability assays were applied to demonstrate the ubiquitination effect on NLRP7. Cloning and mutagenesis were used to identify a lysine acceptor site that mediates NLRP7 ubiquitination. Cytokines/chemokines affected by NLRP7 were identified by RNA sequencing, qRT-PCR, and enzyme-linked immunosorbent assay. Macrophage phenotypes were determined using qRT-PCR, flow cytometry, and immunohistochemistry.

RESULTS

NLRP7 protein levels, but not mRNA levels, were upregulated in CRC, and increased NLRP7 protein expression was associated with poor survival. NLRP7 promoted tumor cell proliferation and metastasis in vivo and in vitro and interacted with ubiquitin-specific protease 10, which catalyzed its deubiquitination in CRC cells. NLRP7 stability and protein levels in CRC cells were modulated by ubiquitination and deubiquitination, and NLRP7 was involved in the ubiquitin-specific protease 10 promotion of tumor progression and metastasis in CRC. K379 was an important lysine acceptor site that mediates NLRP7 ubiquitination in CRC cells. In CRC, NLRP7 promoted the polarization of pro-tumor M2-like macrophages by inducing the secretion of C-C motif chemokine ligand 2. Furthermore, NLRP7 promoted NF-κB nuclear translocation and activation of C-C motif chemokine ligand 2 transcription.

CONCLUSIONS

We showed that NLRP7 promotes CRC progression and revealed an as-yet-unidentified mechanism by which NLRP7 induces the polarization of pro-tumor M2-like macrophages. These results suggest that NLRP7 could serve as a biomarker and novel therapeutic target for the treatment of CRC.

The Role of the Interplay Between Autophagy and NLRP3 Inflammasome in Metabolic Disorders

Autophagy is an important and conserved cellular pathway in which cells transmit cytoplasmic contents to lysosomes for degradation. It plays an important role in maintaining the balance of cell composition synthesis, decomposition and reuse, and participates in a variety of physiological and pathological processes. The nucleotide-binding oligomerization domain-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome can induce the maturation and secretion of Interleukin-1 beta (IL-1β) and IL-18 by activating caspase-1. It is involved in many diseases. In recent years, the interplay between autophagy and NLRP3 inflammasome has been reported to contribute to many diseases including metabolic disorders related diseases. In this review, we summarized the recent studies on the interplay between autophagy and NLRP3 inflammasome in metabolic disorders to provide ideas for the relevant basic research in the future.

Polymeric Micelles in Cancer Immunotherapy

Cancer immunotherapies have generated some miracles in the clinic by orchestrating our immune system to combat cancer cells. However, the safety and efficacy concerns of the systemic delivery of these immunostimulatory agents has limited their application. Nanomedicine-based delivery strategies (e.g., liposomes, polymeric nanoparticles, silico, etc.) play an essential role in improving cancer immunotherapies, either by enhancing the anti-tumor immune response, or reducing their systemic adverse effects. The versatility of working with biocompatible polymers helps these polymeric nanoparticles stand out as a key carrier to improve bioavailability and achieve specific delivery at the site of action. This review provides a summary of the latest advancements in the use of polymeric micelles for cancer immunotherapy, including their application in delivering immunological checkpoint inhibitors, immunostimulatory molecules, engineered T cells, and cancer vaccines.

Blue Light Induces Impaired Autophagy through Nucleotide-Binding Oligomerization Domain 2 Activation on the Mouse Ocular Surface

In this study, we investigated the effects of blue light exposure on nucleotide-binding oligomerization domain 2 (NOD2) expression on the mouse ocular surface and evaluated the role of NOD2 activation in light-induced cell death. Mice were divided into wild-type (WT), NOD2-knock out (KO), WT + blue light (WT + BL), and NOD2-KO + blue light (NOD2-KO + BL) groups, and the mice in the WT+BL and NOD2-KO + BL groups were exposed to blue light for 10 days. After 10 days of blue light exposure, increased reactive oxygen species and malondialdehyde were observed in the WT + BL and NOD2-KO + BL groups, and the WT + BL group showed a higher expression of NOD2 and autophagy related 16 like 1. Although both WT+BL and NOD2-KO + BL groups showed an increase in the expression of light chain 3-II, NOD2-KO + BL mice had a significantly lower p62 expression than WT + BL mice. In addition, NOD2-KO+BL mice had significantly lower corneal epithelial damage and apoptosis than WT + BL mice. In conclusion, blue light exposure can induce impaired autophagy by activation of NOD2 on the ocular surface. In addition, the reactive oxygen species (ROS)-NOD2-autophagy related 16 like 1 (ATG16L) signaling pathway may be involved in the blue-light-induced autophagy responses, resulting in corneal epithelial apoptosis.

The Next Generation of Pattern Recognition Receptor Agonists: Improving Response Rates in Cancer Immunotherapy

The recent success of checkpoint blocking antibodies has sparked a revolution in cancer immunotherapy. Checkpoint inhibition activates the adaptive immune system leading to durable responses across a range of tumor types, although this response is limited to patient populations with pre-existing tumor-infiltrating T cells. Strategies to stimulate the immune system to prime an antitumor response are of intense interest and several groups are now working to develop agents to activate the Pattern Recognition Receptors (PRRs), proteins which detect pathogenic and damageassociated molecules and respond by activating the innate immune response. Although early efforts focused on the Toll-like Receptor (TLR) family of membrane-bound PRRs, TLR activation has been associated with both pro- and antitumor effects. Nonetheless, TLR agonists have been deployed as potential anticancer agents in a range of clinical trials. More recently, the cytosolic PRR Stimulator of IFN Genes (STING) has attracted attention as another promising target for anticancer drug development, with early clinical data beginning to emerge. Besides STING, several other cytosolic PRR targets have likewise captured the interest of the drug discovery community, including the RIG-Ilike Receptors (RLRs) and NOD-like Receptors (NLRs). In this review, we describe the outlook for activators of PRRs as anticancer therapeutic agents and contrast the earlier generation of TLR agonists with the emerging focus on cytosolic PRR activators, both as single agents and in combination with other cancer immunotherapies.

Xenophagy in innate immunity: A battle between host and pathogen

Autophagy is a fundamental bulk intracellular degradation and recycling process that directly eliminates intracellular microorganisms through "xenophagy" in various types of cells, especially in macrophages. Meanwhile, bacteria have evolved strategies and cellular self-defense mechanisms to prevent autophagosomal degradation and even attack the immune system of host. The lack of knowledge about the roles of autophagy in innate immunity severely limits our understanding of host defensive system and the development of farmed industry consisting of aquaculture. Increasing evidence in recent decades has shown the importance of autophagy. This review focuses on the triggering of xenophagy, targeting of invading pathogens to autophagosomes and elimination in the autophagolysosomes during pathogen infection. How the pathogen can escape from the xenophagy pathway was also discussed. Overall, we aim to reduce diseases and improve industrial production in aquaculture by providing theoretical and technical guidance on xenophagy.

The microbiome and cytosolic innate immune receptors

The discovery of innate immune sensors (pattern recognition receptors, PRRs) has profoundly transformed the notion of innate immunity, in providing a mechanistic basis for host immune interactions with a wealth of environmental signals, leading to a variety of immune-mediated outcomes including instruction and activation of the adaptive immune arm. As part of this growing understanding of host-environmental cross talk, an intimate connection has been unveiled between innate immune sensors and signals perceived from the commensal microbiota, which may be regarded as a hub integrating a variety of environmental cues. Among cytosolic PRRs impacting on host homeostasis by interacting with the commensal microbiota are nucleotide-binding domain, leucine-rich repeat-containing protein receptors (NLRs), together with a number of cytosolic DNA sensors and the family of absent in melanoma (AIM)-like receptors (ALRs). NLR sensors have been a particular focus of research, and some NLRs have emerged as key orchestrators of inflammatory responses and host homeostasis. Some NLRs achieve this through the formation of cytoplasmic multiprotein complexes termed inflammasomes. More recently discovered PRRs include retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs), cyclic GMP-AMP synthase (cGAS), and STING. In the present review, they summarize recent advancements in knowledge on structure and function of cytosolic PRRs and their roles in host-microbiota cross talk and immune surveillance. In addition, we discuss their relevance for human health and disease and future therapeutic applications involving modulation of their activation and signaling.

NLRP7 is expressed in the ovine ovary and associated with in vitro pre-implantation embryo development

NLRP (NACHT, LRR and PYD domain-containing proteins) family plays pivotal roles in mammalian reproduction. Mutation of NLRP7 is often associated with human recurrent hydatidiform moles. Few studies regarding the functions of NLRP7 have been performed in other mammalian species rather than humans. In the current study, for the first time, the function of NLRP7 has been explored in ovine ovary. NLRP7 protein was mainly located in ovarian follicles and in in vitro pre-implantation embryos. To identify its origin, 763 bp partial CDS of NLRP7 deriving from sheep cumulus oocyte complexes (COCs) was cloned, it showed a great homology with Homo sapiens. The high levels of mRNA and protein of NLRP7 were steadily expressed in oocytes, parthenogenetic embryos or IVF embryos. NLRP7 knockdown by the combination of siRNA and shRNA jeopardized both the parthenogenetic and IVF embryo development. These results strongly suggest that NLRP7 plays an important role in ovine reproduction. The potential mechanisms of NLRP7 will be fully investigated in the future.

Functional characterization of NLRX1 in rabbit during enterohemorrhagic Escherichia coli infection

Nucleotide oligomerization domain (NOD) like receptor X1 (NLRX1) is a member of pattern recognition receptor, which has been linked to viral response, cancer, and inflammatory diseases. In this study, rabbit NLRX1 (rNLRX1) was firstly cloned from RK-13 cells, which protein contained a NACHT domain and seven LRRs. rNLRX1 was widely expressed in tissues of rabbits, and highly increased in liver, spleen, kidney, and colon after infected with enterohemorrhagic Escherichia coli (EHEC). Overexpression of rNLRX1 negatively regulated NF-κB signaling, and impaired the expression of pro-inflammatory cytokines and defensins. Moreover, deficient of rNLRX1 in RK-13 cells was performed to investigate the possible roles of rNLRX1. Upon EHEC stimulation, knockdown of rNLRX1 markedly enhanced NF-κB activation and downstream responsive cytokines (IL1β and TNFα) and β-defensins (DEFB114, DEFB124, and DEFB125). Furthermore, overexpression of rNLRX1 promoted the proliferation of EHEC, whereas knockdown of rNLRX1 inhibited its growth. Our study identified that rNLRX1 acts as a negative regulatory in anti-microbial responses after EHEC infection.

Integrated transcriptomic and proteomic analyses of grass carp intestines after vaccination with a double-targeted DNA vaccine of Vibrio mimicus

Intestinal mucosal immunity plays a vital role against Vibrio mimicus infection because it is an enteric pathogen causing serious vibriosis in fish. In the previous studies, we developed an oral double-targeted DNA vaccine of V. mimicus and demonstrated that the vaccine could elicit significantly higher intestinal mucosal immune response than did naked DNA vaccine. But, little is known underlying regulatory molecular mechanisms of the enhanced intestinal mucosal immunity. Here the transcriptome and proteome in the intestines of the grass carps immunized or not with the double-targeted DNA vaccine were investigated by using RNA-seq and iTRAQ-coupled LC-MS/MS. Compared with the control group, a total of 5339 differentially expressed genes (DEGs) and 1173 differentially expressed proteins (DEPs) were identified in the immunized fish intestines. Subsequently, the integrated analysis between transcriptome and proteome data revealed that 250 DEPs were matched with the corresponding DEGs (named associated DEPs/DEGs) at both transcriptome and proteome levels. Fifty of all the associated DEPs/DEGs were immune-related and mainly enriched in phagosome, antigen-processing and presentation, complement and coagulation cascades, NLRs and MAPK signaling pathways via Gene Ontology and KEGG pathway analyses, which suggested the coordination of the five activated pathways was essential to the enhanced intestinal mucosal immune response in the immunized fish. The protein-protein interaction analysis showed that 60 of the 63 immune-related DEPs to form an integrated network. Additionally, randomly selected DEGs and DEPs were respectively validated by quantitative real-time RT-PCR and multiple reaction monitoring (MRM) assay, indicating that the both RNA-Seq and iTRAQ results in the study were reliable. Overall, our comprehensive transcriptome and proteome data provide some key genes and their protein products for further research on the regulatory molecular mechanisms underlying the enhanced intestinal mucosal immunity.

Persistent Breeding-Induced Endometritis in Mares - a Multifaceted Challenge: From Clinical Aspects to Immunopathogenesis and Pathobiology

Post-breeding endometritis (i.e., inflammation/infection of the endometrium), is a physiological reaction taking place in the endometrium of mares within 48 hours post-breeding, aimed to clear seminal plasma, excess sperm, microorganisms, and debris from the uterine lumen in preparation for the arrival of an embryo. Mares are classified as susceptible or resistant to persistent breeding-induced endometritis (PBIE) based on their ability to clear this inflammation/infection by 48 hours post-breeding. Mares susceptible to PBIE, or those with difficulty clearing infection/inflammation, have a deficient immune response and compromised physical mechanisms of defense against infection. Molecular pathways of the innate immune response known to be involved in PBIE are discussed herein. The role of the adaptive uterine immune response on PBIE remains to be elucidated in horses. Advances in the pathobiology of microbes involved in PBIE are also revised here. Traditional and non-traditional therapeutic modalities for endometritis are contrasted and described in the context of clinical and molecular aspects. In recent years, the lack of efficacy of traditional therapeutic modalities, alongside the ever-increasing incidence of antibiotic-resistant microorganisms, has enforced the development of non-traditional therapies. Novel biological products capable of modulating the endometrial inflammatory response are also discussed here as part of the non-traditional therapies for endometritis.

Transcriptional analysis of THP-1 cells infected with Leishmania infantum indicates no activation of the inflammasome platform

Leishmaniasis is caused by intracellular parasites transmitted to vertebrates by sandfly bites. Clinical manifestations include cutaneous, mucosal or visceral involvement depending upon the host immune response and the parasite species. To assure their survival inside macrophages, these parasites developed a plethora of highly successful strategies to manipulate various immune system pathways. Considering that inflammasome activation is critical for the establishment of a protective immune response in many parasite infections, in this study we determined the transcriptome of THP-1 cells after infection with L. infantum, with a particular focus on the inflammasome components. To this end, the human cell line THP-1, previously differentiated into macrophages by PMA treatment, was infected with L. infantum promastigotes. Differentiated THP-1 cells were also stimulated with LPS to be used as a comparative parameter. The gene expression signature was determined 8 hours after by RNA-seq technique. Infected or uninfected THP-1 cells were stimulated with nigericin (NIG) to measure active caspase-1 and TNF-α, IL-6 and IL-1β levels in culture supernatants after 8, 24 and 48 hours. L. infantum triggered a gene expression pattern more similar to non-infected THP-1 cells and very distinct from LPS-stimulated cells. Some of the most up-regulated genes in L. infantum-infected cells were CDC20, CSF1, RPS6KA1, CD36, DUSP2, DUSP5, DUSP7 and TNFAIP3. Some up-regulated GO terms in infected cells included cell coagulation, regulation of MAPK cascade, response to peptide hormone stimulus, negative regulation of transcription from RNA polymerase II promoter and nerve growth factor receptor signaling pathway. Infection was not able to induce the expression of genes associated with the inflammasome signaling pathway. This finding was confirmed by the absence of caspase-1 activation and IL-1β production after 8, 24 and 48 hours of infection. Our results indicate that L. infantum was unable to activate the inflammasomes during the initial interaction with THP-1 cells.

Visceral leishmaniasis, caused by Leishmania infantum, is a disease that affects millions of people worldwide. The entry of microorganisms into the host is commonly associated with activation of a multiprotein platform called inflammasome whose assembly culminates in caspase-1 activation and IL-1β production. ILβ activates other cells and effector mechanisms leading to clearance of pathogens. However, the involvement of inflammasomes in the human infection with L. infantum is poorly known. To investigate the parasite-host interaction is fundamental to understand the immunopathogenesis of visceral leishmaniasis and to allow the development of new therapeutic strategies. In this study, we used RNA-seq, a tool that allowed to investigate the global gene expression of THP-1 cells, which is a macrophage-like human cell line, infected with L. infantum. By using computational analysis, this approach allowed us to evaluate the expression of genes that compose the inflammasomes pathway and other gene networks and signaling pathways triggered after infection. This analysis indicated that, unlike species causing cutaneous leishmaniasis, L. infantum did not induce the expression of genes of inflammasome pathways, nor caspase-1 activation or IL-1β production, possibly reflecting a parasite strategy to manipulate immune system and therefore, to allow its survival inside the cells.

Expression and Role of Nucleotide-Binding Oligomerization Domain 2 (NOD2) in the Ocular Surface of Murine Dry Eye

Purpose

To investigate expression and role of nucleotide-binding oligomerization domain 2 (NOD2) in the ocular surface of experimental dry eye (EDE), which is a nod-like receptor member and is involved in innate immune response.

Methods

C57/BL6 female mice were divided into the groups: untreated (UT), EDE, and NOD2 knockout (KO) mice exposed to desiccating stress for 14 days. Clinical parameters and levels of inflammatory cytokine were measured at 3,5,7, and 14 days. Immunofluorescent staining for NOD2 and Western blot for RIP2 and NF-κB were performed at 14 days. Flow cytometry, PAS staining and TUNEL staining were performed.

Results

After EDE induction, NOD2 was expressed in the corneal epithelium of the EDE group. The EDE group showed a significantly increased RIP2 expression compared to the UT and NOD2-KO groups. A significantly lower expression of NF-κB and lower levels of IL-1β, IL-6, IFN-γ, and TNF-α were noted in the NOD2-KO group than in the EDE group. The NOD2-KO group had lower CD11b+ and CD4+CCR5+ T cells, TUNEL-positive cells and corneal staining score and higher density of conjunctival goblet cell density, tear volume, and tear film break-up time than the EDE group. The UT group showed significant differences in inflammatory and clinical parameters compared to the EDE and NOD2-KO groups.

Conclusions

The NOD2 receptor pathway induced inflammation and apoptosis by activation of RIP2 and NF-κB on the ocular surface of EDE, thereby reducing tear secretion. Therefore, NOD2 pathway may be involved in the pathogenesis of dry eye.

Nanoparticle Delivery of Immunostimulatory Agents for Cancer Immunotherapy

Immunostimulatory agents, including adjuvants, cytokines, and monoclonal antibodies, hold great potential for the treatment of cancer. However, their direct administration often results in suboptimal pharmacokinetics, vulnerability to biodegradation, and compromised targeting. More recently, encapsulation into biocompatible nanoparticulate carriers has become an emerging strategy for improving the delivery of these immunotherapeutic agents. Such approaches can address many of the challenges facing current treatment modalities by endowing additional protection and significantly elevating the bioavailability of the encapsulated payloads. To further improve the delivery efficiency and subsequent immune responses associated with current nanoscale approaches, biomimetic modifications and materials have been employed to create delivery platforms with enhanced functionalities. By leveraging nature-inspired design principles, these biomimetic nanodelivery vehicles have the potential to alter the current clinical landscape of cancer immunotherapy.

Targeting NLRP3 Inflammasome Activation in Severe Asthma

Severe asthma (SA) is a chronic lung disease characterized by recurring symptoms of reversible airflow obstruction, airway hyper-responsiveness (AHR), and inflammation that is resistant to currently employed treatments. The nucleotide-binding oligomerization domain-like Receptor Family Pyrin Domain Containing 3 (NLRP3) inflammasome is an intracellular sensor that detects microbial motifs and endogenous danger signals and represents a key component of innate immune responses in the airways. Assembly of the NLRP3 inflammasome leads to caspase 1-dependent release of the pro-inflammatory cytokines IL-1β and IL-18 as well as pyroptosis. Accumulating evidence proposes that NLRP3 activation is critically involved in asthma pathogenesis. In fact, although NLRP3 facilitates the clearance of pathogens in the airways, persistent NLRP3 activation by inhaled irritants and/or innocuous environmental allergens can lead to overt pulmonary inflammation and exacerbation of asthma manifestations. Notably, administration of NLRP3 inhibitors in asthma models restrains AHR and pulmonary inflammation. Here, we provide an overview of the pathophysiology of SA, present molecular mechanisms underlying aberrant inflammatory responses in the airways, summarize recent studies pertinent to the biology and functions of NLRP3, and discuss the role of NLRP3 in the pathogenesis of asthma. Finally, we contemplate the potential of targeting NLRP3 as a novel therapeutic approach for the management of SA.

Adaptive innate immunity or innate adaptive immunity?

The innate immunity is frequently accepted as a first line of relatively primitive defense interfering with the pathogen invasion until the mechanisms of ‘privileged’ adaptive immunity with the production of antibodies and activation of cytotoxic lymphocytes ‘steal the show’. Recent advancements on the molecular and cellular levels have shaken the traditional view of adaptive and innate immunity. The innate immune memory or ‘trained immunity’ based on metabolic changes and epigenetic reprogramming is a complementary process insuring adaptation of host defense to previous infections.

Innate immune cells are able to recognize large number of pathogen- or danger- associated molecular patterns (PAMPs and DAMPs) to behave in a highly specific manner and regulate adaptive immune responses. Innate lymphoid cells (ILC1, ILC2, ILC3) and NK cells express transcription factors and cytokines related to subsets of T helper cells (Th1, Th2, Th17). On the other hand, T and B lymphocytes exhibit functional properties traditionally attributed to innate immunity such as phagocytosis or production of tissue remodeling growth factors. They are also able to benefit from the information provided by pattern recognition receptors (PRRs), e.g. γδT lymphocytes use T-cell receptor (TCR) in a manner close to PRR recognition. Innate B cells represent another example of limited combinational diversity usage participating in various innate responses. In the view of current knowledge, the traditional black and white classification of immune mechanisms as either innate or an adaptive needs to be adjusted and many shades of gray need to be included.

Estrogen receptor alpha regulates the Wnt/β-catenin signaling pathway in colon cancer by targeting the NOD-like receptors

It has been reported that estrogen receptors (ERs) participate in carcinogenesis by directly regulating NOD-like receptors (NLRs). However, the expression profiles of ERs and NLRs in tumor and the ER-NLR regulated signaling pathway are not clear. In this study, we summarized gene expression profiles of ERs and NLRs across normal and tumor tissue by comprehensive data mining. Then we explored the ER-NLR regulated signaling pathway by RNA sequencing (RNA-seq). The results showed that the NLRs and ERs were differentially expressed in different neoplasm tissues. Such expression discrepancies might influence inflammatory regulation and tumorigenesis. Importantly, we identified that ER-NLR regulate Wnt/β-catenin pathway in colon cancer. Taking colon adenocarcinoma (COAD) as example, we found that Wnt2b/LRP8/Dvl1/Axin2/GSK3a/APC/β-catenin genes were differentially expressed in ER^-/- mouse colon tissue and colon cancer cells. The selective ERα antagonist could significantly decrease Wnt2b/LRP8/Dvl1 expression, increase destruction complex (Axin2/GSK3a/APC) expression, and promote degradation of β-catenin in colon carcinoma cell by inhibited NLRP3 expression. In short, the research demonstrates that NLRs are potential biomarkers for cancer, and ERs can regulate the Wnt/β-catenin signaling pathway in cancer by targeting the NLRs. Our results provide a possible signaling pathway in which ER-NLR is correlated with Wnt/β-catenin.

Targeting chronic innate inflammatory pathways, the main road to prevention of osteoarthritis progression

Osteoarthritis (OA) is a chronic joint disease characterized by cartilage degradation, osteophyte formation, subchondral bone sclerosis, and synovitis. Systemic factors such as obesity and the components of the metabolic syndrome seem to contribute to its progression. Breakdown of cartilage ensues from an altered balance between mechanical overload and its absorption by this tissue. There is in this context a status of persistent local inflammation by means of the chronic activation of innate immunity. A broad variety of danger-associated molecular patterns inside OA joint are able to activate pattern recognition receptors, mainly TLR (toll-like receptor) 2 and 4, which are overexpressed in the OA cartilage. Chronic activation of innate immune responses in chondrocytes results in a robust production of pro-inflammatory cytokines and chemokines, as well as of tissue-destructive enzymes, downstream of NF-κB and MAPK (mitogen activated protein kinase) dependent pathways. Besides, the toxic effects of an excess of glucose and/or fatty acids, which share the same pro-inflammatory intracellular signalling pathways, may add fuel to the fire. Not only high concentrations of glucose can render cells prone to inflammation, but also AGEs (advanced glycation end products) are integrated into the TLR signalling network through their own innate immune receptors. Considering these mechanisms, we argue for the control of both primary inflammation and proteolytic catabolism as a preventive strategy in OA, instead of focusing treatment on the enhancement of anabolic responses. Even though this approach would not return to normal already degraded cartilage, it nonetheless might avoid damage extension to the surrounding tissue.

Estrogen receptors participate in carcinogenesis signaling pathways by directly regulating NOD-like receptors

Increasing evidence indicates that the NOD-like receptors (NLRs) family may act as critical back-up defenses and provide synergistic responses when confronted with persistent danger. However, the precise regulatory mechanism of NLRs and the contribution of NLRs to cancer are still unknown. In our previous study, we found that estrogen receptors (ERs) have a close connection with NLRs in the inflammatory response. Here, ERs are first identified as NLRs transcription regulation factors, both regulate NLRs expression and promote inflammasome co-localization. Furthermore, we identified that NLRP3 was differentially expressed in colon normal and cancer cells, selective ERα antagonist could significantly decrease pro-inflammatory cytokines expression, suppress proliferation and promote apoptosis by inhibited NLRP3 expression and inflammasome activity. In short, the research demonstrates that ERs participate in the NLR-associated signaling pathway in cancer by directly regulating NLRs. Our results provide novel insight into ERs as therapeutic targets in NLR-related inflammation and cancer.

The Strategy of Picornavirus Evading Host Antiviral Responses: Non-structural Proteins Suppress the Production of IFNs

Viral infections trigger the innate immune system to produce interferons (IFNs), which play important role in host antiviral responses. Co-evolution of viruses with their hosts has favored development of various strategies to evade the effects of IFNs, enabling viruses to survive inside host cells. One such strategy involves inhibition of IFN signaling pathways by non-structural proteins. In this review, we provide a brief overview of host signaling pathways inducing IFN production and their suppression by picornavirus non-structural proteins. Using this strategy, picornaviruses can evade the host immune response and replicate inside host cells.

Type 1 IFN Induction by Cytosolic Nucleic Acid Is Intact in Neonatal Mononuclear Cells, Contrasting Starkly with Neonatal Hyporesponsiveness to TLR Ligation Due to Independence from Endosome-Mediated IRF3 Activation

Two million infants die each year from infectious diseases before they reach 12 mo; many of these diseases are vaccine preventable in older populations. Pattern recognition receptors represent the critical front-line defense against pathogens. Evidence suggests that the innate immune system does not fully develop until puberty, contributing to impaired response to infection and impaired vaccine responses in neonates, infants, and children. The activity of the pattern recognition receptor family of cytosolic nucleic acid (CNA) sensors in this pediatric population has not been reported. We show that in direct contrast to weak TLR-induced type I IFN in human cord blood mononuclear cells, cord blood mononuclear cells are capable of initiating a potent response to CNA, inducing both antiviral type I IFN and, unexpectedly, proinflammatory TNF-α. A deficiency in Rab11-GTPase endosome formation and consequent lack of IRF3 activation in neonatal monocytes is at least in part responsible for the marked disparity in TLR-induced IFN production between neonatal and adult monocytes. CNA receptors do not rely on endosome formation, and therefore, these responses remain intact in neonates. Heightened neonatal responses to CNA challenge are maintained in children up to 2 y of age and, in marked contrast to TLR4/9 agonists, result in IL-12p70 and IFN-γ generation. CNA sensors induce robust antiviral and proinflammatory pathways in neonates and children and possess great potential for use as immunostimulants or vaccine adjuvants for targeted neonatal and pediatric populations to promote cell-mediated immunity against invasive infectious disease.

NLRP3 inflammasome: A likely target for the treatment of allergic diseases

Allergic diseases, such as asthma, rhinitis, dermatitis, conjunctivitis, and anaphylaxis, have recently become a global public health concern. According to previous studies, the NLRP3 inflammasome is a multi-protein complex known to be associated with many inflammatory conditions. In response to allergens or allergen/damage-associated molecular signals, NLRP3 changes its conformation to allow the assembly of the NLRP3 inflammasome complex and activates caspase-1, which is an evolutionarily conserved enzyme that proteolytically cleaves other proteins, such as the precursors of the inflammatory cytokines IL-1β and IL-18. Subsequently, active caspase-1 cleaves pro-IL-1 and pro-IL-18. Recently, accumulating human and mouse experimental evidence has demonstrated that the NLRP3 inflammasome, IL-1β, and IL-18 are critically involved in the development of allergic diseases. Furthermore, the application of specific NLRP3 inflammasome inhibitors has been demonstrated in animal models. Therefore, these inhibitors may represent potential therapeutic methods for the management of clinical allergic disorders. This review summarizes findings related to the NLRP3 inflammasome and its related factors and concludes that specific NLRP3 inflammasome inhibitors may be potential therapeutic agents for allergic diseases.

The Absent in Melanoma 2-Like Receptor IFN-Inducible Protein 16 as an Inflammasome Regulator in Systemic Lupus Erythematosus: The Dark Side of Sensing Microbes

Absent in melanoma 2 (AIM2)-like receptors (ALRs) are a newly characterized class of pathogen recognition receptors (PRRs) involved in cytosolic and nuclear pathogen DNA recognition. In recent years, two ALR family members, the interferon (IFN)-inducible protein 16 (IFI16) and AIM2, have been linked to the pathogenesis of various autoimmune diseases, among which systemic lupus erythematosus (SLE) has recently gained increasing attention. SLE patients are indeed often characterized by constitutively high serum IFN levels and increased expression of IFN-stimulated genes due to an abnormal response to pathogens and/or incorrect self-DNA recognition process. Consistently, we and others have shown that IFI16 is overexpressed in a wide range of autoimmune diseases where it triggers production of specific autoantibodies. In addition, evidence from mouse models supports a model whereby ALRs are required for IFN-mediated host response to both exogenous and endogenous DNA. Following interaction with cytoplasmic or nuclear nucleic acids, ALRs can form a functional inflammasome through association with the adaptor ASC [apoptosis-associated speck-like protein containing a caspase recruitment domain (CARD)] and with procaspase-1. Importantly, inflammasome-mediated upregulation of IL-1β and IL-18 production positively correlates with SLE disease severity. Therefore, targeting ALR sensors and their downstream pathways represents a promising alternative therapeutic approach for SLE and other systemic autoimmune diseases.

Expression profile of pattern recognition receptors in skeletal muscle of SOD1(G93A) amyotrophic lateral sclerosis (ALS) mice and sporadic ALS patients

AIMS

Amyotrophic lateral sclerosis (ALS) is characterized by degeneration of motoneurons and progressive muscle wasting. Inflammatory processes, mediated by non-neuronal cells, such as glial cells, are known to contribute to disease progression. Inflammasomes consist of pattern recognition receptors (PRRs), apoptosis-associated speck-like protein (ASC) and caspase 1 and are essential for interleukin (IL) processing and a rapid immune response after tissue damage. Recently, we described inflammasome activation in the spinal cord of ALS patients and in SOD1^(G93A) ALS mice. Since pathological changes in the skeletal muscle are early events in ALS, we hypothesized that PRRs might be abnormally expressed in muscle fibre degeneration.

METHODS

Western blot analysis, real-time PCR and immunohistochemistry were performed with muscle tissue from presymptomatic and early-symptomatic male SOD1^(G93A) mice and with muscle biopsies of control and sporadic ALS (sALS) patients. Analysed PRRs include nucleotide-binding oligomerization domain-like (NOD-like) receptor protein 1 (NLRP1), NLR protein 3 (NLRP3), NLR family CARD domain-containing 4 (NLRC4) and absent in melanoma 2. Additionally, expression levels of ASC, caspase 1, interleukin 1 beta (IL1β) and interleukin 18 (IL18) were evaluated.

RESULTS

Expression of PRRs and ASC was detected in murine and human tissue. The PRR NLRC4, caspase 1 and IL1β were significantly elevated in denervated muscle of SOD1^(G93A) mice and sALS patients. Furthermore, levels of caspase 1 and IL1β were already increased in presymptomatic animals.

CONCLUSION

Our findings suggest that increased inflammasome activation may be involved in skeletal muscle pathology in ALS. Furthermore, elevated levels of NLRC4, caspase 1 and IL1β reflect early changes in the skeletal muscle and may contribute to the denervation process.

De novo assembly of Schizothorax waltoni transcriptome to identify immune-related genes and microsatellite markers

Schizothorax waltoni (S. waltoni) is one kind of the subfamily Schizothoracinae and an indigenous economic tetraploid fish to Tibet in China. It is rated as a vulnerable species in the Red List of China's Vertebrates, owing to overexploitation and biological invasion. S. waltoni plays an important role in ecology and local fishery economy, but little information is known about genetic diversity, local adaptation, immune system and so on. Functional gene identification and molecular marker development are the first and essential step for the following biological function and genetics studies. For this purpose, the transcriptome from pooled tissues of three adult S. waltoni was sequenced and analyzed. Using paired-end reads from the Illumina Hiseq4000 platform, 83 103 transcripts with an N50 length of 2337 bp were assembled, which could be further clustered into 66 975 unigenes with an N50 length of 2087 bp. The majority of the unigenes (58 934, 87.99%) were successfully annotated by 7 public databases, and 15 KEGG pathways of immune-related genes were identified for the following functional research. Furthermore, 19 497 putative simple sequence repeats (SSRs) of 1-6 bp unit length were detected from 14 690 unigenes (21.93%) with an average distribution density of 1 : 3.28 kb. We identified 3590 unigenes (5.36%) containing more than one SSR, providing abundant potential polymorphic markers in functional genes. This is the first reported high-throughput transcriptome analysis of S. waltoni, and it would provide valuable genetic resources for the functional genes involved in multiple biological processes, including the immune system, genetic conservation, and molecular marker-assisted breeding of S. waltoni.

NLR-Dependent Regulation of Inflammation in Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) associated with inappropriate activation of lymphocytes, hyperinflammatory responses, demyelination, and neuronal damage. In the past decade, a number of biological immunomodulators have been developed that suppress the peripheral immune responses and slow down the progression of the disease. However, once the inflammation of the CNS has commenced, it can cause serious permanent neuronal damage. Therefore, there is a need for developing novel therapeutic approaches that control and regulate inflammatory responses within the CNS. Nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) are intracellular regulators of inflammation expressed by many cell types within the CNS. They redirect multiple signaling pathways initiated by pathogens and molecules released by injured tissues. NLR family members include positive regulators of inflammation, such as NLRP3 and NLRC4 and anti-inflammatory NLRs, such as NLRX1 and NLRP12. They exert immunomodulatory effect at the level of peripheral immune responses, including antigen recognition and lymphocyte activation and differentiation. Also, NLRs regulate tissue inflammatory responses. Understanding the molecular mechanisms that are placed at the crossroad of innate and adaptive immune responses, such as NLR-dependent pathways, could lead to the discovery of new therapeutic targets. In this review, we provide a summary of the role of NLRs in the pathogenesis of MS. We also summarize how anti-inflammatory NLRs regulate the immune response within the CNS. Finally, we speculate the therapeutic potential of targeting NLRs in MS.

Measuring NLR Oligomerization I: Size Exclusion Chromatography, Co-immunoprecipitation, and Cross-Linking

Oligomerization of nod-like receptors (NLRs) can be detected by several biochemical techniques dependent on the stringency of protein-protein interactions. Some of these biochemical methods can be combined with functional assays, such as caspase-1 activity assay. Size exclusion chromatography (SEC) allows separation of native protein lysates into different sized complexes by fast protein liquid chromatography (FPLC) for follow-up analysis. Using co-immunoprecipitation (co-IP), combined with SEC or on its own, enables subsequent antibody-based purification of NLR complexes and associated proteins, which can then be analyzed by immunoblot and/or subjected to functional caspase-1 activity assay. Chemical cross-linking covalently joins two or more molecules, thus capturing the oligomeric state with high sensitivity and stability. Apoptosis-associated speck-like protein containing a caspase activation domain (ASC) oligomerization has been successfully used as readout for NLR or AIM2-like receptor (ALR) inflammasome activation in response to various pathogen- or damage-associated molecular patterns (PAMPs or DAMPs) in human and mouse macrophages and THP-1 cells. Here, we provide a detailed description of the methods used for NLRP7 oligomerization in response to infection with Staphylococcus aureus (S. aureus) in primary human macrophages, co-immunoprecipitation and immunoblot analysis of NLRP7 and NLRP3 inflammasome complexes, as well as caspase-1 activity assays. Also, ASC oligomerization is shown in response to dsDNA, LPS/ATP, and LPS/nigericin in mouse bone marrow-derived macrophages (BMDMs) and/or THP-1 cells or human primary macrophages.

NLRX1 modulates differentially NLRP3 inflammasome activation and NF-κB signaling during Fusobacterium nucleatum infection

NOD-like receptors (NLRs) play a large role in regulation of host innate immunity, yet their role in periodontitis remains to be defined. NLRX1, a member of the NLR family that localizes to mitochondria, enhances mitochondrial ROS (mROS) generation. mROS can activate the NLRP3 inflammasome, yet the role of NLRX1 in NLRP3 inflammasome activation has not been examined. In this study, we revealed the mechanism by which NLRX1 positively regulates ATP-induced NLRP3 inflammasome activation through mROS in gingival epithelial cells (GECs). We found that depletion of NLRX1 by shRNA attenuated ATP-induced mROS generation and redistribution of the NLRP3 inflammasome adaptor protein, ASC. Furthermore, depletion of NLRX1 inhibited Fusobacterium nucleatum infection-activated caspase-1, suggesting that it also inhibits the NLRP3 inflammasome. Conversely, NLRX1 also acted as a negative regulator of NF-κB signaling and IL-8 expression. Thus, NLRX1 stimulates detection of the pathogen F. nucleatum via the inflammasome, while dampening cytokine production. We expect that commensals should not activate the inflammasome, and NLRX1 should decrease their ability to stimulate expression of pro-inflammatory cytokines such as IL-8. Therefore, NLRX1 may act as a potential switch with regards to anti-microbial responses in healthy or diseased states in the oral cavity.

Synthetic agonists of NOD-like, RIG-I-like, and C-type lectin receptors for probing the inflammatory immune response

Synthetic agonists of innate immune cells are of interest to immunologists due to their synthesis from well-defined materials, optimized activity, and monodisperse chemical purity. These molecules are used in both prophylactic and therapeutic contexts from vaccines to cancer immunotherapies. In this review we highlight synthetic agonists that activate innate immune cells through three classes of pattern recognition receptors: NOD-like receptors, RIG-I-like receptors, and C-type lectin receptors. We classify these agonists by the receptor they activate and present them from a chemical perspective, focusing on structural components that define agonist activity. We anticipate this review will be useful to the medicinal chemist as a guide to chemical motifs that activate each receptor, ultimately illuminating a chemical space ripe for exploration.

Negative regulators of the RIG-I-like receptor signaling pathway

Upon recognition of specific molecular patterns on microbes, host cells trigger an innate immune response, which culminates in the production of type I interferons, proinflammatory cytokines and chemokines, and restricts pathogen replication and spread within the host. At each stage of this response, there are stimulatory and inhibitory signals that regulate the magnitude, quality, and character of the response. Positive regulation promotes an antiviral state to control and eventually clear infection, whereas negative regulation dampens inflammation and prevents immune-mediated tissue damage. An overexuberant innate response can lead to cell and tissue destruction, and the development of spontaneous autoimmunity. The retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs), RIG-I and melanoma differentiation-associated gene 5 (MDA5), belong to a family of cytosolic host RNA helicases that recognize distinct nonself RNA signatures and trigger innate immune responses against several RNA viruses by signaling through the essential adaptor protein mitochondrial antiviral signaling (MAVS). The RLR signaling pathway is tightly regulated to maximize antiviral immunity and minimize immune-mediated pathology. This review highlights contemporary findings on negative regulators of the RLR signaling pathway, with specific focus on the proteins and biological processes that directly regulate RIG-I, MDA5 and MAVS signaling function.