Member Of NOD-like Receptor Family Research Articles

NLRP3 regulates CIITA/MHC II axis and interferon-γ-inducible chemokines in Malassezia globosa-infected keratinocytes.

CIITA, a member of NOD-like receptor (NLR) family, is the major MHC II trans-activator and mediator of Th1 immunity, but its function and interaction with NLRP3 have been little studied. We found activation of NLRP3 inflammasome, increased expression of CIITA, CBP, pSTAT1, STAT1, MHC II, IFN-γ and IFN-γ-inducible chemokines (CCL1 and CXCL8), and colocalisation of NLRP3 with CIITA in Malassezia folliculitis lesions, Malassezia globosa-infected HaCaT cells and mouse skin. CoIP with anti-CIITA or anti-NLRP3 antibody pulled down NLRP3 or both CIITA and ASC. NLRP3 silencing or knockout caused CIITA downexpression and their colocalisation disappearance in HaCaT cells and mouse skin of Nlrp3-/- mice, while CIITA knockdown had no effect on NLRP3, ASC, IL-1β and IL-18 expression. NLRP3 inflammasome inhibitors and knockdown significantly suppressed IFN-γ, CCL1, CXCL8 and CXCL10 levels in M. globosa-infected HaCaT cells. CCL1 and CXCL8 expression was elevated in Malassezia folliculitis lesions and reduced in Nlrp3-/- mice. These results demonstrate that M. globosa can activate NLRP3 inflammasome, CIITA/MHC II signalling and IFN-γ-inducible chemokines in human keratinocytes and mouse skin. NLRP3 may regulate CIITA by their binding and trigger Th1 immunity by secreting CCL1 and CXCL8/IL-8, contributing to the pathogenesis of Malassezia-associated skin diseases.

NLRP12 downregulates the Wnt/β-catenin pathway via interaction with STK38 to suppress colorectal cancer.

Colorectal cancer (CRC) at advanced stages is rarely curable, underscoring the importance of exploring the mechanism of CRC progression and invasion. NOD-like receptor family member NLRP12 was shown to suppress colorectal tumorigenesis, but the precise mechanism was unknown. Here, we demonstrate that invasive adenocarcinoma development in Nlrp12-deficient mice is associated with elevated expression of genes involved in proliferation, matrix degradation, and epithelial-mesenchymal transition. Signaling pathway analysis revealed higher activation of the Wnt/β-catenin pathway, but not NF-κB and MAPK pathways, in the Nlrp12-deficient tumors. Using Nlrp12-conditional knockout mice, we revealed that NLRP12 downregulates β-catenin activation in intestinal epithelial cells, thereby suppressing colorectal tumorigenesis. Consistent with this, Nlrp12-deficient intestinal organoids and CRC cells showed increased proliferation, accompanied by higher activation of β-catenin in vitro. With proteomic studies, we identified STK38 as an interacting partner of NLRP12 involved in the inhibition of phosphorylation of GSK3β, leading to the degradation of β-catenin. Consistently, the expression of NLRP12 was significantly reduced, while p-GSK3β and β-catenin were upregulated in mouse and human colorectal tumor tissues. In summary, NLRP12 is a potent negative regulator of the Wnt/β-catenin pathway, and the NLRP12/STK38/GSK3β signaling axis could be a promising therapeutic target for CRC.

Aberrant inflammasome activation as a driving force of human autoimmune skin disease.

Autoimmune skin diseases are understood as conditions in which the adaptive immune system with autoantigen-specific T cells and autoantibody-producing B cells reacting against self-tissues plays a crucial pathogenic role. However, there is increasing evidence that inflammasomes, which are large multiprotein complexes that were first described 20 years ago, contribute to autoimmune disease progression. The inflammasome and its contribution to the bioactivation of interleukins IL-1β and IL-18 play an essential role in combating foreign pathogens or tissue damage, but may also act as a pathogenic driver of myriad chronic inflammatory diseases when dysfunctionally regulated. Inflammasomes containing the NOD-like receptor family members NLRP1 and NLRP3 as well as the AIM2-like receptor family member AIM2 have been increasingly investigated in inflammatory skin conditions. In addition to autoinflammatory diseases, which are often associated with skin involvement, the aberrant activation of the inflammasome has also been implied in autoimmune diseases that can either affect the skin besides other organs such as systemic lupus erythematosus and systemic sclerosis or are isolated to the skin in humans. The latter include, among others, the T-cell mediated disorders vitiligo, alopecia areata, lichen planus and cutaneous lupus erythematosus as well as the autoantibody-driven blistering skin disease bullous pemphigoid. Some diseases are characterized by both autoinflammatory and autoimmune responses such as the chronic inflammatory skin disease psoriasis. Further insights into inflammasome dysregulation and associated pathways as well as their role in forming adaptive immune responses in human autoimmune skin pathology could potentially offer a new field of therapeutic options in the future.

Ameliorative effect of cheqianzi decoction on hyperuricemia and kidney injury and underlying mechanism in rats

Cheqianzi Decoction (CQD) is a Traditional Chinese Medicine (TCM) formula comprising four herbs and is recorded in the Ancient Materia Medica “Shengji Zonglu”. Individually, these four herbs have been shown to reduce uric acid (UA) levels, to treat hyperuricemia (HUA), and alleviate kidney damage. However, the therapeutic efficacy of the CQD and related mechanism are not yet clear.In this study, high performance liquid chromatography (HPLC) analysis confirmed that the contents of the chemical components of the four herbal medicines were in accordance with the provisions of the Chinese Pharmacopoeia. A total of 99 potential targets were identified in the network pharmacology analysis of CQD, indicating its involvement in the regulation of inflammatory and apoptotic signaling pathways, and potential value for treating HUA and alleviating kidney injury. In vivo pharmacodynamic studies showed that compared with the Model group, significantly decreased levels of serum uric acid (SUA), serum creatinine (SCr), blood urea nitrogen (BUN) (all P < 0.05), and inflammatory factors (P < 0.01) were detected in the CQD group. Quantitative real-time PCR and Western blot analyses showed that compared with the Model group, adenosine triphosphate (ATP)-binding cassette efflux transporter G2 (ABCG2) expression in the CQD group was significantly upregulated (P < 0.01) at both the mRNA and protein levels, while mRNA expression of Caspase3 and NOD-like receptor family member 3 (NLRP3) (P < 0.05) and protein expression of NLRP3 (P < 0.01) were significantly downregulated.In conclusion, CQD promotes UA excretion by activating ABCG2, and induces inflammasome NLRP3-mediated reduction in inflammatory and apoptotic factors to achieve renal protection. Thus, our findings indicate the therapeutic potential of CQD in HUA with kidney injury.

Ribosome-rescuer PELO catalyzes the oligomeric assembly of NOD-like receptor family proteins via activating their ATPase enzymatic activity

NOD-like receptors (NLRs) are pattern recognition receptors for diverse innate immune responses. Self-oligomerization after engagement with a ligand is a generally accepted model for the activation of each NLR. We report here that a catalyzer was required for NLR self-oligomerization. PELO, a well-known surveillance factor in translational quality control and/or ribosome rescue, interacted with all cytosolic NLRs and activated their ATPase activity. In the case of flagellin-initiated NLRC4 inflammasome activation, flagellin-bound NAIP5 recruited the first NLRC4 and then PELO was required for correctly assembling the rest of NLRC4s into the NLRC4 complex, one by one, by activating the NLRC4 ATPase activity. Stoichiometric and functional data revealed that PELO was not a structural constituent of the NLRC4 inflammasome but a powerful catalyzer for its assembly. The catalytic role of PELO in the activation of cytosolic NLRs provides insight into NLR activation and provides a direction for future studies of NLR family members.

NLRP3 inflammasome and NLRP3-related autoinflammatory diseases: From cryopyrin function to targeted therapies.

The NLRP3 inflammasome is one of the NOD-like receptor family members with the most functional characterization and acts as a key player in innate immune system, participating in several physiological processes including, among others, the modulation of the immune system response and the coordination of host defences. Activation of the inflammasome is a crucial signaling mechanism that promotes both an acute and a chronic inflammatory response, which can accelerate the production of pro-inflammatory cytokines, mainly Interleukin (IL)-1β and IL-18, leading to an exacerbated inflammatory network. Cryopyrin associated periodic syndrome (CAPS) is a rare inherited autoinflammatory disorder, clinically characterized by cutaneous and systemic, musculoskeletal, and central nervous system inflammation. Gain-of-function mutations in NLRP3 gene are causative of signs and inflammatory symptoms in CAPS patients, in which an abnormal activation of the NLRP3 inflammasome, resulting in an inappropriate release of IL-1β and gasdermin-D-dependent pyroptosis, has been demonstrated both in in vitro and in ex vivo studies. During recent years, two new hereditary NLRP3-related disorders have been described, deafness autosomal dominant 34 (DFN34) and keratitis fugax hereditaria (KFH), with an exclusive cochlear- and anterior eye- restricted autoinflammation, respectively, and caused by mutations in NLRP3 gene, thus expanding the clinical and genetic spectrum of NLRP3-associated autoinflammatory diseases. Several crucial mechanisms involved in the control of activation and regulation of the NLRP3 inflammasome have been identified and researchers took advantage of this to develop novel target therapies with a significant improvement of clinical signs and symptoms of NLRP3-associated diseases. This review provides a broad overview of NLRP3 inflammasome biology with particular emphasis on CAPS, whose clinical, genetic, and therapeutic aspects will be explored in depth. The latest evidence on two “new” diseases, DFN34 and KFH, caused by mutations in NLRP3 is also described.

The latest breakthrough on NLRP6 inflammasome.

NLRP6, a Nod-like receptor family member, has been shown to affect intestinal homeostasis and microbial colonization through organizing a huge protein complex called inflammasome. NLRP6 inflammasome promotes the cleavage and secretion of inflammatory cytokines or the cleavage of pore-forming Gasdermin D to initiate the inflammatory cell death called pyroptosis, which plays important roles in responding to pathogen invasion. However, questions about the ligand(s) that trigger NLRP6 inflammasome activation, or the mechanisms that how a ligand triggers NLRP6 inflammasome assembly, are emerging. In this mini-review, we summarize the current understandings of ligand recognition of NLRP6, the role of liquid-liquid phase separation in NLRP6 inflammasome assembly, and potential links with human health and diseases.

Lactobacillus rhamnosus GR-1 attenuates foodborne Bacillus cereus-induced NLRP3 inflammasome activity in bovine mammary epithelial cells by protecting intercellular tight junctions

BackgroundBacillus cereus is an important pathogen that causes human food poisoning, specifically diarrhea and vomiting. B. cereus can also induce mastitis in dairy cows and has a strong survival ability in milk, as it cannot be inactivated by high-temperature short-time pasteurization. Therefore, B. cereus can enter the market through pasteurized milk and other dairy products, imposing enormous hidden dangers on food safety and human health.ResultsIn this study, B. cereus 2101 (BC) was isolated from milk samples of cows with mastitis. BC grew rapidly with strong hemolysis, making it difficult to prevent mastitis and ensure food security. MAC-T cells were treated with BC and/or Lactobacillus rhamnosus GR-1 (LGR-1). Pretreatment with LGR-1 protected the integrity of tight junctions and the expression of zonula occludens-1 (ZO-1) and occludin destroyed by BC. Furthermore, LGR-1 pretreatment reduced the expression of NOD-like receptor family member pyrin domain-containing protein 3 (NLRP3), caspase recruitment and activation domain (ASC), Caspase-1 p20, gasdermin D (GSDMD) p30, inflammatory factors (interleukin (IL)-1β and IL-18), and cell death induced by BC. Moreover, LGR-1 pretreatment reduced NLRP3 inflammasome activity and increased expressions of ZO-1 and occludin induced by lipopolysaccharides (LPS) + ATP stimulation. MAC-T cells were transfected with NLRP3 siRNA or MCC950 and/or treated with BC and/or LGR-1. NLRP3-siRNA transfection and MCC950 attenuated BC-induced NLRP3 inflammasome activity. Expression of inflammatory cytokines and cell death suggested that the inflammatory pathway might play an important role in the induction of the NLRP3 inflammasome by BC and the protection of LGR-1.ConclusionsThese results suggest that LGR-1 might be a probiotic alternative to antibiotics and could be administered to prevent mastitis in dairy cows, thus ensuring food security.

NLRX1 Deficiency Alters the Gut Microbiome and Is Further Exacerbated by Adherence to a Gluten-Free Diet.

Patients with gluten sensitivities present with dysbiosis of the gut microbiome that is further exacerbated by a strict adherence to a gluten-free diet (GFD). A subtype of patients genetically susceptible to gluten sensitivities are Celiac Disease (CeD) patients, who are carriers of the HLA DR3/DQ2 or HLA DR4/DQ8 haplotypes. Although 85-95% of all CeD patients carry HLA DQ2, up to 25-50% of the world population carry this haplotype with only a minority developing CeD. This suggests that CeD and other gluten sensitivities are mediated by factors beyond genetics. The contribution of innate immune system signaling has been generally understudied in the context of gluten sensitivities. Thus, here we examined the role of NOD-like receptors (NLRs), a subtype of pattern recognition receptors, in maintaining the composition of the gut microbiome in animals maintained on a GFD. Human transcriptomics data revealed significant increases in the gene expression of multiple NLR family members, across functional groups, in patients with active CeD compared to control specimens. However, NLRX1 was uniquely down-regulated during active disease. NLRX1 is a negative regulatory NLR that functions to suppress inflammatory signaling and has been postulate to prevent inflammation-induced dysbiosis. Using Nlrx1-/- mice maintained on either a normal or gluten-free diet, we show that loss of NLRX1 alters the microbiome composition, and a distinctive shift further ensues following adherence to a GFD, including a reciprocal loss of beneficial microbes and increase in opportunistic bacterial populations. Finally, we evaluated the functional impact of an altered gut microbiome by assessing short- and medium-chain fatty acid production. These studies revealed significant differences in a selection of metabolic markers that when paired with 16S rRNA sequencing data could reflect an overall imbalance and loss of immune system homeostasis in the gastrointestinal system.

NOD2 is involved in regulating odontogenic differentiation of DPSCs suppressed by MDP through NF-κB/p65 signaling.

Dental pulp stem cells (DPSCs) are well known for their capable of both self-renewal and multilineage differentiation. Dental tissue diseases, include caries, are often accompanied by inflammatory microenvironment, and muramyl dipeptide (MDP) is involved in the inflammatory stimuli to influence the differentiation of DPSCs. Nucleotide-binding oligomerization domain 2 (NOD2), a member of the cytosolic Nod-like receptor (NLR) family, plays a key role in inflammatory homeostasis regulation, but the role of NOD2 in DPSCs differentiation under inflammatory is still unclear. In this study, we identified that MDP suppressed odontogenic differentiation of DPSCs via NOD2/ NF-κB/p65 signaling pathway. Alizarin red staining and ALP activity showed the odontogenic differentiation was suppressed by MDP in a concentration-dependent manner, and the expression of dentin differentiation marker protein dentin matrix protein 1 (DMP-1) and dentin Sialophosphoprotein (DSPP) also indicated the same results. The expression of NOD2 increased gradually with the concentration of MDP as well as the phosphorylation and nuclear translocation of p65, which meant NF-κB signaling pathway was activated. Further, the interference of NOD2 inhibited the phosphorylation and nuclear translocation of p65 and reversed the MDP-mediated decrease of odontoblast differentiation of DPSCs. Our study showed that MDP can inhibit the odontoblast differentiation of DPSCs in a concentration-dependent manner. The NF-κB signaling pathway was activated by increasing expression of NOD2. Interference of NOD2 reversed the negative ability odontoblast differentiation of DPSCs in the inflammatory environment. Our study might provide a theoretical basis for the clinical treatment for dentinogenesis of DPSCs.

Lactobacillus rhamnosus GR-1 Prevents Escherichia coli-Induced Apoptosis Through PINK1/Parkin-Mediated Mitophagy in Bovine Mastitis

Escherichia coli is one of the most important pathogens that cause clinical mastitis in dairy cattle worldwide and lead to severe economic losses. Antibiotics are often used to treat this inflammatory disease; however, antimicrobial resistance and environmental pollution cannot be ignored. Probiotic is the best alternative; however, its mechanisms of action to prevent mastitis remain unclear. Moreover, the role of probiotics in regulating mitophagy, a selective autophagy that maintains mitochondrial quality, needs to be explored. E. coli infection induced NOD-like receptor family member pyrin domain-containing protein 3 (NLRP3) inflammasome assembly, Caspase-1 activation, and apoptosis in MAC-T cells. Infection also resulted in mitochondrial damage and subsequent increase in reactive oxygen species (ROS) production. Moreover, inhibition of ROS release by scavenger N-acetyl-L-cysteine (NAC) abrogated the importance of ROS in NLRP3 assembly and apoptosis in MAC-T cells. Pretreatment with Lactobacillus rhamnosus GR-1 (LGR-1), a probiotic, alleviated E. coli-induced NLRP3 inflammasome activation and apoptosis via ROS inhibition. Besides, E. coli infection inhibited mitophagy while LGR-1 pretreatment augmented PINK1/Parkin–mediated mitophagy activation, which further blocked ROS generation. To explore the effect of LGR-1 in vivo, a mouse mastitis model was established. The results showed that LGR-1 pretreatment had preventive and protective effects on E. coli induced mastitis, and could reduce cytokines levels such as IL-1β and TNF-α. In accordance with the results in vitro, E. coli can inhibit mitophagy and activate NLRP3 inflammasome and apoptosis, while LGR-1 can weaken the effect of E. coli. Taken together, our data indicated that LGR-1 pretreatment induced PINK1/Parkin-mediated mitophagy that eliminated damaged mitochondria and reduced ROS production and NLRP3 inflammasome activation, which subsequently decreased E. coli-induced apoptosis. To conclude, our study suggests that therapeutic strategies aiming at the upregulation of mitophagy under E. coli-induced mastitis may preserve mitochondrial function and provide theoretical support for the application of probiotics in bovine mastitis.

Preventive and Prebiotic Effect of α-Galacto-Oligosaccharide against Dextran Sodium Sulfate-Induced Colitis and Gut Microbiota Dysbiosis in Mice.

β-Galacto-oligosaccharide (β-GOS) showed great potential in ulcerative colitis (UC) adjuvant therapy. Herein, the preventive and prebiotic effect of enzymatic-synthesized α-linked galacto-oligosaccharide (α-GOS) was investigated in dextran sodium sulfate-induced colitis and gut microbiota dysbiosis mice. Compared with β-GOS, the α-GOS supplement was more effective in improving preventive efficacy, promoting colonic epithelial barrier integrity, and alleviating inflammation cytokines. Moreover, the activation of the NOD-like receptor (NLR) family member NLRP3 inflammasome-mediated inflammation was significantly inhibited by both α-GOS and β-GOS. Gut microbiota analysis showed that α-GOS treatment reshaped the dysfunctional gut microbiota. The subsequent Spearman's correlation coefficient analysis indicated that these gut microbiota changes were significantly correlated with the inflammatory parameters. These results suggested that the enzymatic-synthesized α-GOS is a promising therapeutic agent in UC prevention and adjuvant treatment by maintaining intestinal homeostasis.

NLRP6 contributes to inflammation and brain injury following intracerebral haemorrhage by activating autophagy.

Inflammation is a crucial factor contributing to secondary brain injury after intracerebral haemorrhage (ICH). NLRP6, a member of nod-like receptors (NLRs) family, has been reported to participate in inflammation and host-defence in multiple diseases. Distinct from the other NLR family members, NLRP6 regulates inflammation in an inflammasome-dependent as well as an inflammasome-independent pathway. However, the role of NLRP6 in regulating signalling pathways during ICH is poorly understood. In the present study, we demonstrated that NLRP6 expression was upregulated after ICH, both in humans and in rats. Subsequently, we developed a rat model of ICH and found that NLRP6 knockdown reduced brain injury, alleviated inflammation, and suppressed autophagy following ICH. Further, results indicated that autophagy involved in NLRP6 mediated inflammation after ICH. Moreover, we found that NLRP6 mediated regulation of autophagy and inflammation was inflammasome-dependent. This study revealed the underlying molecular mechanism of NLRP6 in inflammation and highlights the therapeutic potential of targeting NLRP6 in secondary brain injury after ICH. KEY MESSAGES: • NLRP6 was upregulated following ICH in humans and rats. • NLRP6 knockdown reduced brain injury, alleviated inflammation, and suppressed autophagy following ICH. • NLRP6 aggravated inflammation after ICH by activating autophagy. • NLRP6 regulated inflammation and autophagy after ICH by activating inflammasome pathway.

NLRP6 exerts a protective role via NF-kB with involvement of CCL20 in a mouse model of alcoholic hepatitis

Alcoholic hepatitis (AH) is an important form of alcoholic liver disease (ALD), and its incidence is continuously increasing leading to advanced disease burden. The NOD-like receptors (NLRs) are a specialized group of intracellular pattern recognition receptors, which participate in inflammatory diseases. However, the role of NLRs in the pathogenesis of AH still remain obscure. The animal model of alcoholic hepatitis in mice was established according to National Institute on Alcohol Abuse and Alcoholism (NIAAA) method. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to analyze the expression of NLR family members in liver tissues of the ethanol-fed(EtOH-fed)group and pair-fed group. NLRP6 was overexpressed in mice by injecting Recombinant Adeno-Associated Virus into the tail vein. Mouse Cytokines and Chemokines RT2 Profiler PCR Array was used to analyze the related cytokines and chemokines involved in the development of alcoholic hepatitis. Among the NLR family members, the expression of NLRP6 decreased most significantly in the animal model of AH. Our results demonstrated that overexpression of NLRP6 in vivo obviously alleviated steatosis, inflammation and fibrosis in liver. Meanwhile, the serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in mice also decreased. Besides, Chemokine (C–C motif) ligand 20(CCL20) was one of the most significantly up-regulated chemokines in the mouse AH model and CCL20 was participated in NLRP6-mediated AH. NLRP6 could inhibit the activation of nuclear factor (NF)-κB signaling pathway in vitro and in vivo. Furthermore, the activation, proliferation, and migration of hepatic stellate cells was enhanced after downregulation of NLRP6. In summary, NLRP6 may play a protective role in the development of AH. NLRP6 could inhibit activation of NF-κB signaling pathway in AH.

LRR domain of NLRX1 protein delivery by dNP2 inhibits T cell functions and alleviates autoimmune encephalomyelitis.

Multiple sclerosis (MS) is a demyelinating inflammatory disease of the central nervous system (CNS), which is a chronic progressive disease and is caused by uncontrolled activation of myelin antigen specific T cells. It has high unmet medical needs due to the difficulty of efficient drug delivery into the CNS to control tissue inflammation. In this study, we demonstrate that a fusion protein of NOD-like receptor family member X1 (NLRX1) and blood brain barrier (BBB)-permeable peptide, dNP2 ameliorates experimental autoimmune encephalomyelitis (EAE).Methods: We purified recombinant LRR or NBD regions of NLRX1 protein conjugated with dNP2. To examine intracellular delivery efficiency of the recombinant protein, we incubated the proteins with Jurkat T cells or murine splenic T cells and their delivery efficiency was analyzed by flow cytometry. To investigate the therapeutic efficacy in an EAE model, we injected the recombinant protein into mice with 3 different treatment schemes e.g., prevention, semi-therapeutic, and therapeutic. To analyze their functional roles in T cells, we treated MACS-sorted naïve CD4 T cells with the proteins during their activation and differentiation into Th1, Th17, and Treg cells.Results: dNP2-LRR protein treatment showed significantly higher delivery efficiency than TAT-LRR or LRR alone in Jurkat T cells and mouse splenic T cells. In all three treatment schemes of EAE experiments, dNP2-LRR administration showed ameliorated tissue inflammation and disease severity with reduced number of infiltrating T cells producing inflammatory cytokines such as IFNγ. In addition, dNP2-LRR inhibited T cell activation, cytokine production, and Th1 differentiation.Conclusion: These results suggest that dNP2-LRR is a novel agent, which regulates effector T cell functions and could be a promising molecule for the treatment of CNS autoimmune diseases such as multiple sclerosis.

Deubiquitinase enzyme STAMBP plays a broad role in both Toll-like and Nod-like receptor mediated inflammation

The innate immune system in mammals include pattern recognition receptors (PRRs), which initiate immune responses to microbial infection via several mechanisms. These PRRs include cell surface Toll-like receptors (TLRs) and cytosolic Nod-like receptors (NLRs) that recognizes extracellular and intracellular danger signals respectively. NLRs are poised to respond specifically to pathogens that access the host cell cytosol. The molecular mechanisms by which NLRs are activated to form inflammasomes and exert downstream inflammatory responses remain poorly understood. Additionally, very little is known about the regulation of cytosolic pathogen sensory NLR family members, except for NLRP3. Recently a deubiquitinase known as STAMBP has been implicated as a regulator of NLRP7 inflammasome assembly. We have investigated the role of STAMBP in regulation of other inflammasome components and its broader role in inflammation using genetic removal of STAMBP protein from cells using CRISPR/Cas9 gene editing and challenging these gene edited cells with an inflammatory stimuli. Our study demonstrated that STAMBP has a critical role in inflammation both in the context of NLR pathway, through NLRP stabilization and TLR pathway, through JNK signaling and downstream cytokine production. The findings indicate that STAMBP has a wider role in inflammation than previously thought to be the case.

Cloning and functional analysis the first NLRC4-like gene from the sea cucumber Apostichopus japonicus

The NOD-like receptor family member 4 (NLRC4) plays a crucial role in regulating the innate immune responses and cell apoptosis pathways in vertebrates. However, the function of the NLRC4 counterpart in invertebrates remains elusive. In this study, the first NLRC4-like gene was cloned and characterized from Apostichopus japonicus (designated as AjNLRC4-like) with RACE technology. The full-length cDNA of the AjNLRC4-like gene was 4065 bp, which consisted of a 5′-untranslated region (UTR) of 387 bp, a 3′-UTR of 159 bp, and a complete open reading frame of 3519 bp encoding a polypeptide of 1172 amino acid residues. Structural analysis revealed that AjNLRC4-like protein contained two IG domains (31–132 and 251–353 amino acids), a common NACHT (600–757 amino acids), and no LRR and CARD domains compared with the vertebrate NLRC4. Spatial expression analysis revealed that the AjNLRC4-like was ubiquitously expressed in all the examined tissues with larger magnitude in the intestine. The mRNA expression of the AjNLRC4-like was significantly upregulated by 2.86- and 2.92-fold at 24 h after the Vibrio splendidus challenge in vivo and the lipopolysaccharide (LPS) treatment in vitro, respectively, compared with that of the control group. The purified recombinant AjNLRC4–NACHT protein displayed higher binding activities to various pathogen-associated molecular patterns (PAMPs), including LPS, peptidoglycan, and mannan. Further functional analysis indicated that the apoptosis of coelomocytes was significantly inhibited by 11.37% after specific AjNLRC4-like siRNA treatment, and the inflammatory caspase Ajcaspase-1 was synchronously decreased by 0.28-fold in the same condition. Collectively, these results supported that the uncanonical AjNLRC4-like protein may share similar functions to the vertebrate NLRC4 as the pattern recognition receptor and in mediating coelomocyte apoptosis in the pathogen-challenged sea cucumber.

The NLRP3 Inflammasome as a Pharmacological Target.

NLRP3 is a cytosolic receptor member of the nucleotide-binding oligomerization domain NOD-like receptor family that surveys the intracellular environment for the presence of infection, pathogens, and metabolic alarms. Although the surveillance activity of NLRP3 is required to protect the host from several pathogens, uncontrolled activity can be detrimental to the host. Pharmacological and genetic strategies limiting NLRP3 inflammasome activation have been shown to be beneficial in a wide range of experimental models, from common pathologies such as arthritis, cardiovascular disease, and metabolic syndromes to rare genetic disorders such as cryopyrin-associated periodic syndrome. Thus, compounds that prevent NLRP3 inflammasome activation are of common interest with relevant therapeutic potential. The focus of this review is recent developments in NLRP3 inflammasome inhibitors.

NLRC3 expression in dendritic cells attenuates CD4+ T cell response and autoimmunity.

NOD-like receptor (NLR) family CARD domain containing 3 (NLRC3), an intracellular member of NLR family, is a negative regulator of inflammatory signaling pathways in innate and adaptive immune cells. Previous reports have shown that NLRC3 is expressed in dendritic cells (DCs). However, the role of NLRC3 in DC activation and immunogenicity is unclear. In the present study, we find that NLRC3 attenuates the antigen-presenting function of DCs and their ability to activate and polarize CD4+ T cells into Th1 and Th17 subsets. Loss of NLRC3 promotes pathogenic Th1 and Th17 responses and enhanced experimental autoimmune encephalomyelitis (EAE) development. NLRC3 negatively regulates the antigen-presenting function of DCs via p38 signaling pathway. Vaccination with NLRC3-overexpressed DCs reduces EAE progression. Our findings support that NLRC3 serves as a potential target for treating adaptive immune responses driving multiple sclerosis and other autoimmune disorders.

NLRX1 of black carp suppresses MAVS-mediated antiviral signaling through its NACHT domain

NOD-like receptor (NLR) family member X1 (NLRX1) of human localizes on mitochondria and serves as a negative regulator of antiviral signaling. However, the function of NLRX1 in teleost fish still remains elusive. To explore its role in the innate immunity of teleost fish, NLRX1 homologue has been cloned and characterized from black carp (Mylopharyngodon piceus). Black carp NLRX1 (bcNLRX1) consists of 1008 amino acids, which includes a N-terminal mitochondrial targeting sequence, a central NACHT domain and a C-terminal leucine-rich repeat (LRR) domain. bcNLRX1 was identified as a cytosolic protein locating on mitochondria through immunofluorescence (IF) staining. The overlapped subcellular distribution of bcNLRX1 and black carp MAVS (bcMAVS) was detected in IF staining, and the direct interaction between these two molecules in vitro was identified through co-immunoprecipitation assay. When co-expressed with bcMAVS, bcNLRX1 fiercely reduced bcMAVS-mediated IFN induction in reporter assay. Accordingly, the antiviral activity of bcMAVS against both grass carp reovirus (GCRV) and spring viremia of carp virus (SVCV) was forcefully repressed by bcNLRX1 in plaque assay. Mutagenic analyses further revealed that the NACHT domain of bcNLRX1 was essential for it to interact with bcMAVS and to suppress bcMAVS-mediated antiviral signaling. Taken together, our data support the conclusion that bcNLRX1 negatively regulates bcMAVS-mediated antiviral signaling through its NACHT domain during host innate immune activation.