NLR, the nucleotide-binding domain leucine-rich repeat containing gene family

NOD2 dependent neutrophil recruitment is required for early protective immune responses against infectious Litomosoides sigmodontis L3 larvae

Nucleotide-binding oligomerization domain-containing protein 2 (NOD2) recognizes muramyl dipeptide (MDP) of bacterial cell walls, triggering NFκB-induced pro-inflammation. As most human pathogenic filariae contain Wolbachia endobacteria that synthesize the MDP-containing cell wall precursor lipid II, NOD2’s role during infection with the rodent filaria Litomosoides sigmodontis was investigated. In NFκB reporter-cells, worm-extract containing Wolbachia induced NOD2 and NOD1. NOD2-deficient mice infected with L. sigmodontis had significantly more worms than wildtype controls early in infection. Increased worm burden was not observed after subcutaneous infection, suggesting that protective NOD2-dependent immune responses occur within the skin. Flow cytometry demonstrated that neutrophil recruitment to the skin was impaired in NOD2^−/− mice after intradermal injection of third stage larvae (L3), and blood neutrophil numbers were reduced after L. sigmodontis infection. PCR array supported the requirement of NOD2 for recruitment of neutrophils to the skin, as genes associated with neutrophil recruitment and activation were downregulated in NOD2^−/− mice after intradermal L3 injection. Neutrophil depletion before L. sigmodontis infection increased worm recovery in wildtype mice, confirming that neutrophils are essential against invading L3 larvae. This study indicates that NOD-like receptors are implemented in first-line protective immune responses against filarial nematodes.

Enhancement of Muramyl Dipeptide-Dependent NOD2 Activity by a Self-Derived Peptide

Nucleotide-binding and oligomerization domain like receptors (NLR) are pattern recognition receptors used to provide rapid immune response by detecting intracellular pathogen-associated molecules. Loss of NLR activity is implicated in genetic disorders, disruption of adaptive immunity, and chronic inflammation. One NLR protein, NOD2, is frequently mutated in Crohn's disease (CD), which is an inflammatory disease of the gastrointestinal tract. Three commonly occurring CD-associated NOD2 mutations, R702W, G908R, and L1007fs, are clustered near the regulatory domain, leucine rich region (LRR), and lowers the activity of NOD2 in response to muramyl dipeptide (MDP). As LRR is also the ligand binding domain, this suggests that the mutations either affect the binding of MDP or how the molecule responds to ligand binding. To model the role of R702 in ligand-dependent activation of NOD2, we used homology modeling to map the residue R702 to the interface between the oligomerization domain and LRR. We show that a peptide derived from NOD2(697-718) binds LRR in vitro, and upon co-expressing or importing the peptide into HEK293 expressing NOD2, there is an increase in the MDP-dependent NOD2 activity. The study thus suggests that the R702W mutation interferes with the conformational changes needed for MDP binding and activation. J. Cell. Biochem. 118: 1227-1238, 2017. © 2016 Wiley Periodicals, Inc.

Activation of STING requires palmitoylation at the Golgi

Stimulator of interferon genes (STING) is essential for the type I interferon response against DNA pathogens. In response to the presence of DNA and/or cyclic dinucleotides, STING translocates from the endoplasmic reticulum to perinuclear compartments. However, the role of this subcellular translocation remains poorly defined. Here we show that palmitoylation of STING at the Golgi is essential for activation of STING. Treatment with palmitoylation inhibitor 2-bromopalmitate (2-BP) suppresses palmitoylation of STING and abolishes the type I interferon response. Mutation of two membrane-proximal Cys residues (Cys88/91) suppresses palmitoylation, and this STING mutant cannot induce STING-dependent host defense genes. STING variants that constitutively induce the type I interferon response were found in patients with autoimmune diseases. The response elicited by these STING variants is effectively inhibited by 2-BP or an introduction of Cys88/91Ser mutation. Our results may lead to new treatments for cytosolic DNA-triggered autoinflammatory diseases.

STING is essential for the type I interferon immune response to foreign DNA. Here, the authors show that palmitoylation of STING at the Golgi is required for activating downstream signalling, and increased Golgi localization of certain STING variants may cause autoimmune disease in some cases.

Epidermal NLRP10 contributes to contact hypersensitivity responses in mice

The nucleotide binding and oligomerization domain-like receptor (NLR) protein NLRP10 is highly expressed in the epidermis and contributes to cell-autonomous responses against invasive bacteria. To investigate the role of NLRP10 in inflammatory responses of the skin we analyzed the effect of full-body and keratinocyte-specific depletion of NLRP10 in croton oil-induced irritant contact dermatitis (ICD) and 1-fluoro-2,4-dinitrobenzene (DNFB)-induced contact hypersensitivity (CHS) in mice. Nlrp10(-/-) mice were phenotypically normal and skin repair after wounding was not affected by lack of NLRP10. Similarly, we did not detect a contribution of NLRP10 to the ICD response induced by croton oil. In contrast, Nlrp10(-/-) mice showed significantly reduced inflammation in the DNFB-induced CHS response as compared to control animals. Microscopic analysis revealed significantly reduced numbers of CD4(+) and CD8(+) T cells in the infiltrates of animals lacking NLRP10 expression after CHS challenge. Epidermis-specific deletion of Nlrp10 by keratin-14 promotor driven Cre-recombinase was sufficient to account for this phenotype, although lymphocyte recruitment seemed to be unaltered in animals lacking NLRP10 expression in keratinocytes. Taken together, we provide evidence that NLRP10 contributes to T-cell-mediated inflammatory responses in the skin and highlight a physiological role of NLRP10 in epidermal keratinocytes.

An endogenous caspase-11 ligand elicits interleukin-1 release from living dendritic cells

Dendritic cells (DCs) use pattern recognition receptors to detect microorganisms and activate protective immunity. These cells and receptors are thought to operate in an all-or-nothing manner, existing in an immunologically active or inactive state. Here, we report that encounters with microbial products and self-encoded oxidized phospholipids (oxPAPC) induce an enhanced DC activation state, which we call "hyperactive." Hyperactive DCs induce potent adaptive immune responses and are elicited by caspase-11, an enzyme that binds oxPAPC and bacterial lipopolysaccharide (LPS). oxPAPC and LPS bind caspase-11 via distinct domains and elicit different inflammasome-dependent activities. Both lipids induce caspase-11-dependent interleukin-1 release, but only LPS induces pyroptosis. The cells and receptors of the innate immune system can therefore achieve different activation states, which may permit context-dependent responses to infection.

NLR-regulated pathways in cancer: opportunities and obstacles for therapeutic interventions

NLRs (nucleotide-binding domain, leucine-rich repeat containing receptors) are pattern recognition receptors associated with immunity and inflammation in response to endogenous and exogenous pathogen and damage associated molecular patterns (PAMPs and DAMPs respectively). Dysregulated NLR function is associated with several diseases including cancers, metabolic diseases, autoimmune disorders and autoinflammatory syndromes. In the last decade, distinct cell and organ specific roles for NLRs have been identified however; their roles in cancer initiation, development and progression remain controversial. This review summarizes the emerging role of NLRs in cancer and their possible future as targets for cancer therapeutics.

Beyond the inflammasome: regulatory NOD-like receptor modulation of the host immune response following virus exposure

A complex interaction exists between elements of the host innate immune system and viral pathogens. It is essential that the host mount a robust immune response during viral infection and effectively resolve inflammation once the pathogen has been eliminated. Members of the nucleotide-binding domain leucine-rich repeat [NBD-LRR; known as NOD-like receptor (NLR)] family of cytosolic pattern-recognition receptors are essential components of these immunological processes and have diverse functions in the host antiviral immune response. NLRs can be subgrouped based on their general function. The inflammasome-forming subgroup of NLRs are the best-characterized family members, and several have been found to modulate the maturation of IL-1β and IL-18 following virus exposure. However, the members of the regulatory NLR subgroups are significantly less characterized. These NLRs uniquely function to modulate signalling pathways initiated by other families of pattern-recognition receptors, such as Toll-like receptors and/or Rig-I-like helicase receptors. Regulatory NLRs that augment pro-inflammatory pathways include nucleotide-binding oligomerization domain-containing protein 1 (NOD1) and NOD2, which have been shown to form a multiprotein complex termed the NODosome that significantly modulates IFN and NF-κB signalling following viral infection. Conversely, a second subgroup of regulatory NLRs functions to negatively regulate inflammation. These inhibitory NLRs include NLRX1, NLRP12 and NLRC3, which have been shown to interact with TRAF molecules and various kinases to modulate diverse cellular processes. Targeting NLR signalling following infection with a virus represents a novel and promising therapeutic strategy. However, significant effort is still required to translate the current understanding of NLR biology into effective therapies.

Integration of Innate Immune Signaling

The last decades of research in innate immunology have revealed a multitude of sensing receptors that evaluate the presence of microorganisms or cellular damage in tissues. In the context of a complex tissue, many such sensing events occur simultaneously. Thus, the downstream pathways need to be integrated to launch an appropriate cellular response, to tailor the magnitude of the reaction to the inciting event, and to terminate it in a manner that avoids immunopathology. Here, we provide a conceptual overview of the crosstalk between innate immune receptors in the initiation of a concerted immune reaction to microbial and endogenous triggers. We classify the known interactions into categories of communication and provide examples of their importance in pathogenic infection.

Atypical Inflammasomes

Pattern recognition receptors, including members of the NLR and PYHIN families, are essential for recognition of both pathogen- and host-derived danger signals. A number of molecules in these families are capable of forming multiprotein complexes termed inflammasomes that result in the activation of caspase-1. In addition to NLRP1, NLRP3, NLRC4, and AIM2, which form well-described inflammasome complexes, IFI16, NLRP6, NLRP7, NLRP12, and NLRC5 have also been proposed to form inflammasomes under specific conditions. The structure and function of these atypical inflammasomes will be highlighted here.

The NLRP3 inflammasome is critically involved in the development of bronchopulmonary dysplasia

The pathogenesis of bronchopulmonary dysplasia (BPD), a devastating lung disease in preterm infants, includes inflammation, the mechanisms of which are not fully characterized. Here we report that the activation of the NLRP3 inflammasome is associated with the development of BPD. Hyperoxia-exposed neonatal mice have increased caspase-1 activation, IL1β and inflammation, and decreased alveolarization. Nlrp3(-/-) mice have no caspase-1 activity, no IL1β, no inflammatory response and undergo normal alveolarization. Treatment of hyperoxia-exposed mice with either IL1 receptor antagonist to block IL1β or glyburide to block the Nlrp3 inflammasome results in decreased inflammation and increased alveolarization. Ventilated preterm baboons show activation of the NLRP3 inflammasome with increased IL1β:IL1ra ratio. The IL1β:IL1ra ratio in tracheal aspirates from preterm infants with respiratory failure is predictive of the development of BPD. We conclude that early activation of the NLRP3 inflammasome is a key mechanism in the development of BPD, and represents a novel therapeutic target for BPD.

Random mutagenesis of the nucleotide-binding domain of NRC1 (NB-LRR Required for Hypersensitive Response-Associated Cell Death-1), a downstream signalling nucleotide-binding, leucine-rich repeat (NB-LRR) protein, identifies gain-of-function mutations in the nucleotide-binding pocket

Plant nucleotide-binding, leucine-rich repeat (NB-LRR) proteins confer immunity to pathogens possessing the corresponding avirulence proteins. Activation of NB-LRR proteins is often associated with induction of the hypersensitive response (HR), a form of programmed cell death. NRC1 (NB-LRR Required for HR-Associated Cell Death-1) is a tomato (Solanum lycopersicum) NB-LRR protein that participates in the signalling cascade leading to resistance to the pathogens Cladosporium fulvum and Verticillium dahliae. To identify mutations in NRC1 that cause increased signalling activity, we generated a random library of NRC1 variants mutated in their nucleotide-binding domain and screened them for the ability to induce an elicitor-independent HR in Nicotiana tabacum. Screening of 1920 clones retrieved 11 gain-of-function mutants, with 10 of them caused by a single amino acid substitution. All substitutions are located in or very close to highly conserved motifs within the nucleotide-binding domain, suggesting modulation of the signalling activity of NRC1. Three-dimensional modelling of the nucleotide-binding domain of NRC1 revealed that the targeted residues are centred around the bound nucleotide. Our mutational approach has generated a wide set of novel gain-of-function mutations in NRC1 and provides insight into how the activity of this NB-LRR is regulated.

Impact of IL-1 inhibition on fatigue associated with autoinflammatory syndromes

Cryopyrin-associated periodic syndromes (CAPS) is a rare group of autoinflammatory disorders that includes familial cold autoinflammatory syndrome or FCAS, Muckle-wells syndrome or MWS, and neonatal-onset multisystem inflammatory disease or NOMID. CAPS is caused by a mutation in the NOD-like receptor family, pyrin domain containing 3 (NLRP3) gene. This ultimately leads to increased production of interleukin (IL)-1β. IL-1β is a biologically active member of the IL-1 family. It is not only a pro-inflammatory cytokine responsible for features such as fever, rash, and arthritis, but is also a major mediator in the central pathways of fatigue. Fatigue is a major component of CAPS and is associated with severely compromised quality of life. In clinical studies, fatigue was measured using functional assessment of chronic illness therapy-fatigue or FACIT-F and short form-36 or SF-36, physical component score instruments. These questionnaires can also be used to monitor improvement of fatigue following initiation of therapy. IL-1 inhibitors block the IL-1 signaling cascade, thereby preventing systemic inflammation in CAPS. The decrease in systemic inflammation is accompanied by improvement in fatigue.

CAPS--pathogenesis, presentation and treatment of an autoinflammatory disease

The cryopyrin-associated periodic syndrome (CAPS) is a severity spectrum of rare diseases. CAPS comprises the three conditions previously described as familial cold autoinflammatory syndrome (FCAS), Muckle-Wells syndrome (MWS), and neonatal-onset multisystem inflammatory disorder (NOMID), also known as chronic infantile neurologic, cutaneous, and articular (CINCA) syndrome. The clinical phenotype of CAPS is characterized by systemic inflammation. General symptoms are fatigue and fever. Local manifestations affect multiple tissues such as skin, joints, muscles, eyes, and the central nervous system. Distinct clinical features are characteristic for each subphenotype. In FCAS, these are cold-induced urticaria and fever, in MWS systemic amyloidosis and hearing loss and in NOMID/CINCA central nervous system inflammation and bone deformities. CAPS is caused by single heterozygous germline or somatic gain of function mutations in the NLRP3 gene encoding the protein cryopyrin. Cryopyrin nucleates an NLRP3 inflammasome, which regulates the activation and cleavage of caspase-1 that cleaves the pro-inflammatory cytokines, IL-1β and IL-18. IL-1β plays the key role in the induction of inflammation in CAPS. This has been confirmed by the application of IL-1 blocking agents, which lead not only to a rapid and sustained reversal of daily symptoms but also to some extent of long-term disease sequelae. To prevent CAPS-induced organ damage, early diagnosis and swift initiation of effective treatment are mandatory.

RIG-I in RNA virus recognition

Antiviral immunity is initiated upon host recognition of viral products via non-self molecular patterns known as pathogen-associated molecular patterns (PAMPs). Such recognition initiates signaling cascades that induce intracellular innate immune defenses and an inflammatory response that facilitates development of the acquired immune response. The retinoic acid-inducible gene I (RIG-I) and the RIG-I-like receptor (RLR) protein family are key cytoplasmic pathogen recognition receptors that are implicated in the recognition of viruses across genera and virus families, including functioning as major sensors of RNA viruses, and promoting recognition of some DNA viruses. RIG-I, the charter member of the RLR family, is activated upon binding to PAMP RNA. Activated RIG-I signals by interacting with the adapter protein MAVS leading to a signaling cascade that activates the transcription factors IRF3 and NF-κB. These actions induce the expression of antiviral gene products and the production of type I and III interferons that lead to an antiviral state in the infected cell and surrounding tissue. RIG-I signaling is essential for the control of infection by many RNA viruses. Recently, RIG-I crosstalk with other pathogen recognition receptors and components of the inflammasome has been described. In this review, we discuss the current knowledge regarding the role of RIG-I in recognition of a variety of virus families and its role in programming the adaptive immune response through cross-talk with parallel arms of the innate immune system, including how RIG-I can be leveraged for antiviral therapy.

Protective effect of leaf essential oil from Cinnamomum osmophloeum Kanehira on endotoxin-induced intestinal injury in mice associated with suppressed local expression of molecules in the signaling pathways of TLR4 and NLRP3

Endotoxin is a potent microbial mediator implicated in sepsis. We investigated the anti-inflammatory effect of leaf essential oil from Cinnamomum osmophloeum Kanehira (CO) of the linalool chemotype on endotoxin-injected mice. Mice were administered CO or vehicle by gavage before endotoxin injection and were killed 12 h after injection. Neither growth nor the organ weight or tissue weight to body weight ratio was affected by CO treatment. CO significantly lowered peripheral levels of tumor necrosis factor-α, interleukin (IL)-1β, IL-18, interferon-γ, and nitric oxide and inhibited the expression of toll-like receptor 4 (TLR4), myeloid differentiation primary response gene (88), myeloid differentiation factor 2, apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC), caspase-1, and Nod-like receptor family, pyrin domain containing 3 (NLRP3). CO also inhibited the activation of nuclear factor-ĸB, inhibited the activity of caspase-1 in small intestine, and ameliorated intestinal edema. Our data provide strong evidence for a protective effect of CO of the linalool chemotype in the endotoxin-induced systemic inflammatory response in close association with suppression of the TLR4 and NLRP3 signaling pathways in intestine.

Anti-inflammatory effect of resveratrol in old mice liver

Inflammation is a hallmark of aging. Caloric restriction and resveratrol (RSV) have shown important effects on prevention of oxidative stress and inflammation. Here, we investigate the progression of proinflammatory markers in liver during aging and the effect of RSV on inflammation markers in the liver of old male C57BL/6J mice. Young (2 months), mature (12 months) and old (18 months) mice were fed during 6 months with RSV. Levels of IL-1β, IL-6, IL-10, IL-17 and TNF-α were evaluated by ELISA in mice liver. Levels of pro-inflammatory cytokines, IL-1β, IL-6, IL-17 and TNF-α and also their respective mRNA increased in the liver from old mice. However, RSV decreased these levels in the case of IL-1β and TNF-α but only in old mice showing no effect on young and mature animals. This reduction was also found at the mRNA level. Levels of mRNA of the components of NALP-3 inflammasome, ASC, CASP-1, NALP-1 and NALP-3, also showed an age-dependent increase that was reversed by RSV. Furthermore, cyclooxygenase 2 levels, a marker of proinflammatory innate immune activity, were also upregulated in aged liver and reversed again by RSV. In conclusion, our study confirms that aging is accompanied by an increase in the proinflammatory pattern in the liver and that RSV reduces this pattern in old mice liver.

The role of dendritic cells in driving genital tract inflammation and HIV transmission risk: are there opportunities to intervene?

Effective prevention of new HIV infections will require an understanding of the mechanisms involved in HIV acquisition. HIV transmission across the female genital tract is the major mode of new HIV infections in sub-Saharan Africa and involves complex processes, including cell activation, inflammation and recruitment of HIV target cells. Activated CD4(+) T-cells, dendritic cells (DC) and macrophages have been described as targets for HIV at the genital mucosa. Activation of these cells may occur in the presence of sexually-transmitted infections, disturbances of commensal flora and other inflammatory processes. In this review, we discuss causes and consequences of inflammation in the female genital tract, with a focus on DC. We describe the central role these cells may play in facilitating or preventing HIV transmission across the genital mucosa, and in the initial recognition of HIV and other pathogens, allowing activation of an adaptive immune response to infection. We discuss studies that investigate interventions to limit DC activation, inflammation and HIV transmission. This knowledge is essential in the development of novel strategies for effective HIV control, including microbicides and pre-exposure prophylaxis.

Host-Viral Interactions: Role of Pattern Recognition Receptors (PRRs) in Human Pneumovirus Infections

Acute respiratory tract infection (RTI) is a leading cause of morbidity and mortality worldwide and the majority of RTIs are caused by viruses, among which respiratory syncytial virus (RSV) and the closely related human metapneumovirus (hMPV) figure prominently. Host innate immune response has been implicated in recognition, protection and immune pathological mechanisms. Host-viral interactions are generally initiated via host recognition of pathogen-associated molecular patterns (PAMPs) of the virus. This recognition occurs through host pattern recognition receptors (PRRs) which are expressed on innate immune cells such as epithelial cells, dendritic cells, macrophages and neutrophils. Multiple PRR families, including Toll-like receptors (TLRs), RIG-I-like receptors (RLRs) and NOD-like receptors (NLRs), contribute significantly to viral detection, leading to induction of cytokines, chemokines and type I interferons (IFNs), which subsequently facilitate the eradication of the virus. This review focuses on the current literature on RSV and hMPV infection and the role of PRRs in establishing/mediating the infection in both in vitro and in vivo models. A better understanding of the complex interplay between these two viruses and host PRRs might lead to efficient prophylactic and therapeutic treatments, as well as the development of adequate vaccines.

Nedd8 regulates inflammasome-dependent caspase-1 activation

Caspase-1 is activated by the inflammasome complex to process cytokines like interleukin-1β (IL-1β). Pro-caspase-1 consists of three domains, CARD, p20, and p10. Association of pro-caspase-1 with the inflammasome results in initiation of its autocatalytic activity, culminating in self-cleavage that generates catalytically active subunits (p10 and p20). In the current study, we show that Nedd8 is required for efficient self-cleavage of pro-caspase-1 to generate its catalytically active subunits. Nedd8 silencing or treating cells with the neddylation inhibitor MLN4924 led to diminished caspase-1 processing and reduced IL-1β maturation following inflammasome activation. Coimmunoprecipitation and mass spectrometric analysis of 293 cells overexpressing pro-caspase-1 (and CARD) and Nedd8 suggested possible neddylation of caspase-1 CARD. Following inflammasome activation in primary macrophages, we observed colocalization of endogenous Nedd8 with caspase-1. Similarly, interaction of endogenous Nedd8 with caspase-1 CARD was detected in inflammasome-activated macrophages. Furthermore, enhanced autocatalytic activity of pro-caspase-1 was observed following Nedd8 overexpression in 293 cells, and such activity in inflammasome-activated macrophages was drastically diminished upon treatment of cells with MLN4924. Thus, our studies demonstrate a role of Nedd8 in regulating caspase-1 activation following inflammasome activation, presumably via augmenting autoprocessing/cleavage of pro-caspase-1 into its corresponding catalytically active subunits.

Rutin modulates ASC expression in NLRP3 inflammasome: a study in alcohol and cerulein-induced rat model of pancreatitis

Inflammasomes are protein complexes formed in response to tissue injury and inflammation to regulate the formation of proinflammatory cytokines. Nod-like receptor pyrin domain containing 3 (NLRP3) is one such inflammasome involved in pancreatic inflammation. Caspase activation recruitment domain (CARD) is an interaction motif found in all the major components of NLRP3 inflammasome such as apoptosis associated speck-like CARD containing protein (ASC) and procaspase-1. NLRP3 activates procaspase-1 with the concerted action of CARD domain of ASC. In the present study, the effect of rutin, a natural flavonoid on the expression of ASC of NLRP3, was investigated in rats treated with ethanol (EtOH) and cerulein (Cer). Male albino Wistar rats were divided into four groups. Groups 1 and 2 rats were fed normal diet, whereas groups 3 and 4 rats were fed EtOH (36 % of total calories) containing diet for a total period of 5 weeks and also administered Cer (20 µg/kg body weight i.p.) thrice weekly for the last 3 weeks. In addition, groups 2 and 4 rats received daily 100 mg/kg body weight of rutin from third week. Rutin co-administration significantly decreased the level of pancreatic marker enzymes, oxidative stress markers, inflammatory markers, mRNA expression of caspase-1, cytokines, ASC-NLRP3, and protein expression of caspase-1 and ASC in rats received EtOH-Cer. The results of the study revealed that rutin can reduce inflammation in pancreas probably by influencing the down regulation of ASC-NLRP3 which might result in the reduced activation of caspase-1 and controlled cytokine production.

Single Nucleotide Polymorphisms of NLRP12 Gene and Association with Non-specific Digestive Disorder in Rabbit

The NLRP12 (NLR family, pyrin domain containing 12) serves as a suppressor factor in the inflammatory response and protects the host against inflammation-induced damage. In the present study, we aimed to study the polymorphisms of NLRP12 gene and its association with susceptibility to non-specific digestive disorder (NSDD) in rabbits. We re-sequenced the entire coding region of the rabbit NLRP12 gene and detected a total of 19 SNPs containing 14 synonymous and five non-synonymous variations. Among them, the coding SNP (c.1682A>G), which would carry a potential functional implication, was subsequently subjected to genotyping for case-control association study (272 cases and 267 controls). The results revealed that allele A was significantly protective against NSDD with an odds ratio value of 0.884 (95% confidence interval, 0.788 to 0.993; p = 0.038). We also experimentally induced NSDD in growing rabbits by feeding a fibre-deficient diet and subsequently investigated NLRP12 mRNA expression. The mRNA expression of NLRP12 in healthy status was significantly higher than that in severe NSDD (p = 0.0016). The highest expression was observed in individuals carrying the protective genotype AA (p = 0.0108). These results suggested that NLRP12 was significantly associated with the NSDD in rabbits. However, the precise molecular mechanism of NLRP12 involving in the development of rabbit NSDD requires further research.

Pattern recognition receptors and the inflammasome in kidney disease

Toll-like receptors (TLRs) and nucleotide-binding oligomerization domain receptors (NLRs) are families of pattern recognition receptors that, together with inflammasomes, sense and respond to highly conserved pathogen motifs and endogenous molecules released upon cell damage or stress. Evidence suggests that TLRs, NLRs and the NACHT, LRR and PYD domains-containing protein 3 (NLRP3) inflammasome have important roles in kidney diseases through regulation of inflammatory and tissue-repair responses to infection and injury. In this Review, we discuss the pathological mechanisms that are related to TLRs, NLRs and NLRP3 in various kidney diseases. In general, these receptors are protective in the host defence against urinary tract infection, but can sustain and self-perpetuate tissue damage in sterile inflammatory and immune-mediated kidney diseases. TLRs, NLRs and NLRP3, therefore, have become promising drug targets to enable specific modulation of kidney inflammation and suppression of immunopathology in kidney disease.

Biochemical and structural aspects of the ATP-binding domain in inflammasome-forming human NLRP proteins

Nucleotide-binding domain and leucine-rich repeat-containing receptors (NLRs) regulate innate immunity by activating inflammatory responses in a variety of biological systems following the recognition of pathogen- or disease-associated molecular patterns. NLRs are characterized by a central nucleotide-binding and oligomerization (NACHT) domain found in P-loop NTPases. In this review, we detail the functional and structural properties of the NACHT domain of a subfamily of NLRs, the NLRPs (NLR containing a pyrin domain), based on previous studies, sequence analysis, homology modeling, and structure predictions. Several NLRPs have been found to regulate inflammatory responses through the assembly of oligomeric caspase 1-activating platforms known as inflammasomes, the 3-dimensional structure of the NLRP NACHT domain has still not been solved. Homology modeling suggests that sequence variability within the NACHT domains of different NLRP family members may alter the topology of the ATP-binding pocket. Based on this finding, we discuss the potential therapeutic prospects aligned with the NACHT domain and the development of selective inhibitors of inflammasome activity.

Gene expression profile of type II spinal cord decompression sickness

STUDY DESIGN

This study was an experimental, controlled, animal study.

OBJECTIVE

This study was to determine the changes of molecular pathology in spinal cord decompression sickness (SC-DCS) based on a rabbit model of SC-DCS with the aid of an all-gene expression profile chip.

SETTING

Qingdao, Shandong Province, China.

METHODS

A gene expression profile chip containing 43 803 genes was used to compare the gene expressions in the spinal cords of four male New Zealand white rabbits in the SC-DCS and control groups, respectively. Selected differentially expressed genes were identified with quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) and immunohistochemistry.

RESULTS

The chip hybridization results showed that the SC-DCS group had nine upregulated and seventeen downregulated genes, compared with the control group. These genes were mainly related to inflammation, ion channels, the cell cycle, material transfer and apoptosis. The qRT-PCR results showed that parathyroid hormone and tumor necrosis factor alpha (TNF-α) genes were upregulated compared with the control group (P<0.01). However, the acyl-CoA synthetase and voltage-gated channel genes were downregulated (P<0.05). The immunohistochemical staining results confirmed that there were significantly greater expression levels of TNF-α in the spinal cord tissues of the SC-DCS group compared with the control group.

CONCLUSIONS

The spinal cord lesions of SC-DCS involve multiple gene changes in the rabbit; however, the significance of these findings needs further research. Meanwhile, the gene expression profile chip results provide us with a better understanding of the pathogenesis of DCS.

An important role for mitochondrial antiviral signaling protein in the Kaposi's sarcoma-associated herpesvirus life cycle

Kaposi's sarcoma-associated herpesvirus (KSHV) has been shown to be recognized by two families of pattern recognition receptors (PRRs), Toll-like receptors (TLRs) and NOD-like receptors (NLRs). Here we show that MAVS and RIG-I (retinoic acid-inducible gene 1), an RLR family member, also have a role in suppressing KSHV replication and production. In the context of primary infection, we show that in cells with depleted levels of MAVS or RIG-I, KSHV transcription is increased, while beta interferon (IFN-β) induction is attenuated. We also observed that MAVS and RIG-I are critical during the process of reactivation. Depletion of MAVS and RIG-I prior to reactivation led to increased viral load and production of infectious virus. Finally, MAVS depletion in latent KSHV-infected B cells leads to increased viral gene transcription. Overall, this study suggests a role for MAVS and RIG-I signaling during different stages of the KSHV life cycle.

IMPORTANCE

We show that RIG-I and its adaptor protein, MAVS, can sense KSHV infection and that these proteins can suppress KSHV replication following primary infection and/or viral reactivation.

Nod-like receptors: key molecular switches in the conundrum of cancer

It is believed the immune system can contribute to oncogenic transformation especially in settings of chronic inflammation, be activated during immunosurveillance to destroy early neoplastic cells before they undergo malignant outgrowth, and finally, can assist growth of established tumors by preventing clearance, remodeling surrounding tissue, and promoting metastatic events. These seemingly opposing roles of the immune system at the different stages of cancer development must all be mediated by innate signaling mechanisms that regulate the overall state of immune activation. Recently, the cytosolic nod-like receptor (NLR) pathway of innate immunity has gained a lot of attention in the tumor immunology field due to its known involvement in promoting inflammation and immunity, and conversely, in regulating tissue repair processes. In this review, we present all the current evidence for NLR involvement in the different stages of neoplasia to understand how a single molecular pathway can contribute to conflicting immunological interactions with cancer.

Airway epithelial regulation of pulmonary immune homeostasis and inflammation

Recent genetic, structural and functional studies have identified the airway and lung epithelium as a key orchestrator of the immune response. Further, there is now strong evidence that epithelium dysfunction is involved in the development of inflammatory disorders of the lung. Here we review the characteristic immune responses that are orchestrated by the epithelium in response to diverse triggers such as pollutants, cigarette smoke, bacterial peptides, and viruses. We focus in part on the role of epithelium-derived interleukin (IL)-25, IL-33 and thymic stromal lymphopoietin (TSLP), as well as CC family chemokines as critical regulators of the immune response. We cite examples of the function of the epithelium in host defense and the role of epithelium dysfunction in the development of inflammatory diseases.

Malarial pigment hemozoin and the innate inflammatory response

Malaria is a deadly infectious disease caused by the intraerythrocytic protozoan parasite Plasmodium. The four species of Plasmodium known to affect humans all produce an inorganic crystal called hemozoin (HZ) during the heme detoxification process. HZ is released from the food vacuole into circulation during erythrocyte lysis, while the released parasites further infect additional naive red blood cells. Once in circulation, HZ is rapidly taken up by circulating monocytes and tissue macrophages, inducing the production of pro-inflammatory mediators, such as interleukin-1β (IL-1β). Over the last few years, it has been reported that HZ, similar to uric acid crystals, asbestos, and silica, is able to trigger IL-1β production via the activation of the NOD-like receptor containing pyrin domain 3 (NLRP3) inflammasome complex. Additionally, recent findings have shown that host factors, such as fibrinogen, have the ability to adhere to free HZ and modify its capacity to activate host immune cells. Although much has been discovered regarding NLRP3 inflammasome induction, the mechanism through which this intracellular multimolecular complex is activated remains unclear. In the present review, the most recent discoveries regarding the capacity of HZ to trigger this innate immune complex as well as the impact of HZ on several other inflammatory signaling pathways will be discussed.

Innate immune viral recognition: relevance to CNS infections

Innate immune responses mediated by mononuclear phagocytes represent the initial host response to acute viral infection. PRRs, including TLRs, retinoic RLRs,and NOD-like receptors, recognize viral nucleic acid and localized injury signals to initiate proinflammatory responses and activation of adaptive immunity. These responses are host- and viral-dependent. Neurotropic viruses, such as HSV, West Nile virus, and HIV activate and evade innate immune signaling mechanisms by distinct mechanisms. These highly complex pathogen-host interactions determine establishment of infection, severity of clinical disease, development of chronic inflammatory processes, and success of vaccination strategies.

Interferon-γ resets muscle cell fate by stimulating the sequential recruitment of JARID2 and PRC2 to promoters to repress myogenesis

The inflammatory cytokine interferon-γ (IFN-γ) orchestrates a diverse array of fundamental physiological processes. IFN-γ and the class II transactivator (CIITA) play essential roles in inhibiting muscle development during the inflammatory response. We describe the mechanism through which IFN-γ and CIITA inhibit myogenesis by repressing gene expression in muscle cells subjected to inflammation. In mice, the presence of increased amounts of circulating IFN-γ resulted in the increased abundance of Polycomb repressive complex 2 (PRC2) in muscle fibers, a tissue in which PRC2 is not normally present in the adult. We showed that CIITA first interacted with the Jumonji family protein JARID2, a noncatalytic subunit of PRC2, which caused an RNA polymerase II (RNAPII), phosphorylated at serine-5, to pause at target promoters. Additional subunits of the PRC2 complex, including the catalytic subunit EZH2, were then recruited in a JARID2-dependent manner that was concurrent with the loss of RNAPII and the methylation of Lys(27) of histone H3 (H3K27), which is associated with gene repression. IFN-γ and CIITA act to both promote the abundance of PRC2 subunits, which are not normally present during muscle differentation, and recruit the PRC2 complex to block myogenesis. Together, these data indicate that increased amounts of IFN-γ reset myogenic cell fate through a multistep mechanism that culminates in the recruitment of PRC2 to silence muscle-specific genes.

Canakinumab in patients with cryopyrin-associated periodic syndrome: an update for clinicians

The cryopyrin-associated periodic syndrome (CAPS) is a very rare disease. It is estimated that there are 1-2 cases for every 1 million people in the US and 1 in every 360,000 in France. However, many patients are diagnosed very late or not at all, meaning the real prevalence is likely to be higher. CAPS encompasses the three entities of familial cold auto-inflammatory syndrome (FCAS), Muckle-Wells syndrome (MWS), and neonatal-onset multisystem inflammatory disease (NOMID)/chronic infantile neurologic, cutaneous and articular (CINCA) syndrome. They have in common a causative mutation in the NLRP3 gene. The altered gene product cryopyrin leads to activation of the inflammasome which in turn is responsible for excessive production of interleukin (IL)-1β. IL-1β causes the inflammatory manifestations in CAPS. These appear as systemic inflammation including fever, headache or fatigue, rash, eye disease, progressive sensorineural hearing loss, musculoskeletal manifestations and central nervous system (CNS) symptoms (NOMID/CINCA only). With the advent of IL-1 Inhibitors, safe and effective therapeutic options became available for this devastating disease. To prevent severe and possible life-threatening disease sequelae, early and correct diagnosis and immediate initiation of therapy are mandatory in most patients. Canakinumab is a fully human monoclonal IgG1 anti-IL-1β antibody. It provides selective and prolonged IL-1β blockade and has demonstrated a rapid (within hours), complete and sustained response in most CAPS patients without any consistent pattern of side effects. Long-term follow-up trials have demonstrated sustained efficacy, safety and tolerability. Canakinumab is approved by the US Food and Drug Administration for FCAS and MWS and by European Medicines Agency for treatment of all three phenotypes of CAPS.

Beneficial and Detrimental Roles of NLRs in Carcinogenesis

Inflammation plays a critical role in tumorigenesis and can contribute to oncogenic mutations, tumor promotion, and angiogenesis. Tumor-promoting inflammation is driven by many factors including the presence of the pro-inflammatory cytokines interleukin (IL)-1β and IL-18. One major source of IL-1β and IL-18 secretion is through the activation of inflammasomes. Inflammasomes are multi-protein complexes that upon activation lead to the processing and secretion of IL-1β and IL-18 mediated by the cysteine protease caspase-1. Several inflammasomes, including NLRP3, NLRC4, and NLRP6, have been implicated in tumorigenesis. However, inflammasomes play divergent roles in different types of cancer reflecting the complexity of inflammation during tumorigenesis. Understanding the role of inflammasome activation during specific stages of tumorigenesis and also during cancer immunotherapy will help identify novel therapeutic targets that could improve treatment strategies for cancer patients. Here we will discuss recent advances in understanding the mechanism by which NLRs regulate carcinogenesis.

Inhibition of the NF-κB pathway as a candidate therapeutic strategy for cryopyrin-associated periodic syndrome

OBJECTIVES

Cryopyrin-associated periodic syndrome (CAPS) is caused by unrestricted IL-1β release due to mutation of the gene coding NLRP3. This study aimed to clarify whether NLRP3-related IL-1β release is dependent on the NF-κB pathway.

METHODS

Peripheral blood mononuclear cells (PBMCs) from healthy subjects or patients with Muckle-Wells syndrome were primed with LPS and subsequently stimulated by ATP. Human umbilical vein endothelial cells (HUVECs) were cultured with the supernatant obtained from LPS-plus ATP-stimulated PBMCs. Expression of proinflammatory molecules was estimated using RT-PCR, ELISA or immunochemical staining, in the presence or absence of an NF-κB inhibitor (-)-dehydroxymethylepoxyquinomicin (DHMEQ).

RESULTS

DHMEQ inhibited expression of proIL-1β and NLRP3 by normal PBMCs primed with LPS, resulting in inhibition of caspase-1 activation and IL-1β secretion by the cells after subsequent stimulation with ATP. DHMEQ also inhibited expression of IL-1β, TNFα, IL-6 and VCAM-1 by HUVECs. Patient cells released IL-1β spontaneously or by ATP-stimulation even without LPS-priming. Both the spontaneous and stimulated IL-1β releases were inhibited by DHMEQ without affecting viability of the cells.

CONCLUSIONS

These results clearly indicate that IL-1β production through the NLRP3 inflammasome is dependent on the NF-κB pathway, which could be a good target for the development of a novel therapeutic strategy for CAPS.

Adjuvant immunotherapies as a novel approach to bacterial infections

The rapid emergence of multidrug-resistant pathogens, especially Gram-negative bacteria and mycobacteria, represents one of the major medical challenges of the 21st century. The gradual loss of effective classical antibiotics for many bacterial pathogens, combined with an increasing population density and mobility, urgently calls for the development of novel treatments. Here, we discuss the potential of adjuvant immunotherapies to selectively stimulate protective immune responses as a treatment option for bacterial infections. In order to elicit appropriate immune responses and to avoid unwanted inflammatory tissue damage, it is essential to identify ligands and receptor pathways that specifically control protective responses at the site of infection. We summarize existing data and discuss suitable candidate targets for future immunotherapies of infectious diseases.

Initial immunopathogenesis of multiple sclerosis: innate immune response

Multiple sclerosis (MS) is an inflammatory, demyelinating, and neurodegenerative disease of the central nervous system. The hallmark to MS is the demyelinated plaque, which consists of a well-demarcated hypocellular area characterized by the loss of myelin, the formation of astrocytic scars, and the mononuclear cell infiltrates concentrated in perivascular spaces composed of T cells, B lymphocytes, plasma cells, and macrophages. Activation of resident cells initiates an inflammatory cascade, leading to tissue destruction, demyelination, and neurological deficit. The immunological phenomena that lead to the activation of autoreactive T cells to myelin sheath components are the result of multiple and complex interactions between environment and genetic background conferring individual susceptibility. Within the CNS, an increase of TLR expression during MS is observed, even in the absence of any apparent microbial involvement. In the present review, we focus on the role of the innate immune system, the first line of defense of the organism, as promoter and mediator of cross reactions that generate molecular mimicry triggering the inflammatory response through an adaptive cytotoxic response in MS.

Activation and regulation of the pattern recognition receptors in obesity-induced adipose tissue inflammation and insulin resistance

Obesity-associated chronic tissue inflammation is a key contributing factor to type 2 diabetes mellitus, and a number of studies have clearly demonstrated that the immune system and metabolism are highly integrated. Recent advances in deciphering the various immune cells and signaling networks that link the immune and metabolic systems have contributed to our understanding of the pathogenesis of obesity-associated inflammation. Other recent studies have suggested that pattern recognition receptors in the innate immune system recognize various kinds of endogenous and exogenous ligands, and have a crucial role in initiating or promoting obesity-associated chronic inflammation. Importantly, these mediators act on insulin target cells or on insulin-producing cells impairing insulin sensitivity and its secretion. Here, we discuss how various pattern recognition receptors in the immune system underlie the etiology of obesity-associated inflammation and insulin resistance, with a particular focus on the TLR (Toll-like receptor) family protein Radioprotective 105 (RP105)/myeloid differentiation protein-1 (MD-1).

Autoinflammation: From monogenic syndromes to common skin diseases

Autoinflammation is characterized by aberrant regulation of the innate immune system and often manifests as periodic fevers and systemic inflammation involving multiple organs, including the skin. Mutations leading to abnormal behavior or activity of the interleukin 1 beta (IL-1ß)-processing inflammasome complex have been found in several rare autoinflammatory syndromes, for which anticytokine therapy such as IL-1 or tumor necrosis factor-alfa inhibition may be effective. It is becoming clear that features of autoinflammation also affect common dermatoses, some of which were previously thought to be solely autoimmune in origin (eg, vitiligo, systemic lupus erythematosus). Recognizing the pathogenetic role of autoinflammation can open up new avenues for the targeted treatment of complex, inflammatory dermatoses.

Innate immune response to oral bacteria and the immune evasive characteristics of periodontal pathogens

Periodontitis is a chronic inflammation of periodontal tissue caused by subgingival plaque-associated bacteria. Periodontitis has long been understood to be the result of an excessive host response to plaque bacteria. In addition, periodontal pathogens have been regarded as the causative agents that induce a hyperinflammatory response from the host. In this brief review, host-microbe interaction of nonperiodontopathic versus periodontopathic bacteria with innate immune components encountered in the gingival sulcus will be described. In particular, we will describe the susceptibility of these microbes to antimicrobial peptides (AMPs) and phagocytosis by neutrophils, the induction of tissue-destructive mediators from neutrophils, the induction of AMPs and interleukin (IL)-8 from gingival epithelial cells, and the pattern recognition receptors that mediate the regulation of AMPs and IL-8 in gingival epithelial cells. This review indicates that true periodontal pathogens are poor activators/suppressors of a host immune response, and they evade host defense mechanisms.

Inflammation links excess fat to insulin resistance: the role of the interleukin-1 family

A growing body of evidence suggests that cytokines of the interleukin-1 (IL-1) family, particularly IL-1β but also IL-1Ra and IL-18, are involved in obesity-associated inflammation. IL-1β is produced via cleavage of pro-IL-1β by caspase-1, which in turn is activated by a multiprotein complex called the inflammasome. The components of the NLRP3 inflammasome are involved in sensing obesity-associated danger signals, both in mice and in human (obese) subjects, with caspase-1 seemingly the most crucial regulator. Autophagy is upregulated in obesity and may function as a mechanism to control IL-1β gene expression in adipose tissue to mitigate chronic inflammation. All these mechanisms are operative in human adipose tissue and appear to be more pronounced in human visceral compared to subcutaneous tissue. In animal studies, blocking caspase-1 activity results in decreased weight gain, decreased inflammation, and improved insulin sensitivity. Human intervention studies with IL-1Ra (anakinra) have reported beneficial effects in patients with diabetes, yet without significant changes in insulin sensitivity. Clearly, the IL-1 family of cytokines, especially IL-1β, plays an important role in obesity-associated inflammation and insulin resistance and may represent a therapeutic target to reverse the detrimental metabolic consequences of obesity.

Clinical presentation and pathogenesis of cold-induced autoinflammatory disease in a family with recurrence of an NLRP12 mutation

Objective

NLRP12 mutations have been described in patients affected with peculiar autoinflammatory symptoms. This study was undertaken to characterize NLRP12 mutations in patients with autoinflammatory syndromes, particularly a novel missense mutation, p.D294E, affecting a protein sequence crucial for ATP binding, which was identified in a Caucasian family with familial cold-induced autoinflammatory syndrome in some family members.

Methods

Fifty patients were tested for NLRP12 mutations. A Caucasian family with the p.D294E missense mutation of NLRP12 in some family members was clinically characterized. In vitro analysis of the effects of the mutation on NF-κB activity was performed in HEK 293 cells after cotransfection of the cells with a luciferase NF-κB–responsive element and mutant or wild-type (WT) NLRP12 expression plasmids. NF-κB activity was also evaluated 24 hours after stimulation with tumor necrosis factor α in monocytes from individual family members carrying the mutation. Furthermore, secretion of interleukin-1β (IL-1β), production of reactive oxygen species (ROS), and activation of antioxidant systems in patient and healthy donor monocytes, under resting conditions and after stimulation with pathogen-associated molecular patterns (PAMPs), were also assessed.

Results

In the family assessed, the p.D294E mutation segregated in association with a particular sensitivity to cold exposure (especially arthralgias and myalgia), but not always with an inflammatory phenotype (e.g., urticarial rash or fever). In vitro, the mutant protein maintained the same inhibitory activity as that shown by WT NLRP12. Consistently, NLRP12-mutated monocytes showed neither increased levels of p65-induced NF-κB activity nor higher secretion of IL-1β. However, the kinetics of PAMP-induced IL-1β secretion were significantly accelerated, and high production of ROS and up-regulation of antioxidant systems were demonstrated.

Conclusion

Even with a variable range of associated manifestations, the extreme sensitivity to cold represents the main clinical hallmark in an individual carrying the p.D294E mutation of the NLRP12 gene. Although regulation of NF-κB activity is not affected in patients, redox alterations and accelerated secretion of IL-1β are associated with this mild autoinflammatory phenotype.

The role of gut-liver axis in the pathogenesis of liver cirrhosis and portal hypertension

Because of the anatomical position and its unique vascular system, the liver is susceptible to the exposure to the microbial products from the gut. Although large amount of microbes colonize in the gut, translocation of the microbes or microbial products into the liver and systemic circulation is prevented by gut epithelial barrier function and cleansing and detoxifying functions of the liver in healthy subjects. However, when the intestinal barrier function is disrupted, large amount of bacterial products can enter into the liver and systemic circulation and induce inflammation through their receptors. Nowadays, there have been various reports suggesting the role of gut flora and bacterial translocation in the pathogenesis of chronic liver disease and portal hypertension. This review summarizes the current knowledge about bacterial translocation and its contribution to the pathogenesis of chronic liver diseases and portal hypertension.

The mitochondrial proteins NLRX1 and TUFM form a complex that regulates type I interferon and autophagy

The mitochondrial protein MAVS (also known as IPS-1, VISA, and CARDIF) interacts with RIG-I-like receptors (RLRs) to induce type I interferon (IFN-I). NLRX1 is a mitochondrial nucleotide-binding, leucine-rich repeats (NLR)-containing protein that attenuates MAVS-RLR signaling. Using Nlrx1(-/-) cells, we confirmed that NLRX1 attenuated IFN-I production, but additionally promoted autophagy during viral infection. This dual function of NLRX1 paralleled the previously described functions of the autophagy-related proteins Atg5-Atg12, but NLRX1 did not associate with Atg5-Atg12. High-throughput quantitative mass spectrometry and endogenous protein-protein interaction revealed an NLRX1-interacting partner, mitochondrial Tu translation elongation factor (TUFM). TUFM interacted with Atg5-Atg12 and Atg16L1 and has similar functions as NLRX1 by inhibiting RLR-induced IFN-I but promoting autophagy. In the absence of NLRX1, increased IFN-I and decreased autophagy provide an advantage for host defense against vesicular stomatitis virus. This study establishes a link between an NLR protein and the viral-induced autophagic machinery via an intermediary partner, TUFM.

Inflammasomes in liver diseases

Inflammation is a common element in the pathogenesis of most chronic liver diseases that lead to fibrosis and cirrhosis. Inflammation is characterized by activation of innate immune cells and production of pro-inflammatory cytokines IL-1α, IL-1β, and TNFα. Inflammasomes are intracellular multiprotein complexes expressed in both parenchymal and non-parenchymal cells of the liver that in response to cellular danger signals activate caspase-1, and release IL-1β and IL-18. The importance of inflammasome activation in various forms of liver diseases in relation to liver damage, steatosis, inflammation and fibrosis is discussed in this review.

[Cryopyrin-associated periodic syndrome]

The cryopyrin-associated periodic syndrome is a very rare disease. It is estimated that there are 1-2 cases out of 1 million inhabitants in the USA and 1/360,000 in France. However, many patients are diagnosed very late or not at all. Therefore the real prevalence is likely to be higher. CAPS encompasses the three entities familial cold autoinflammatory syndrome (FCAS), the Muckle-Wells syndrome and the neonatal-onset multisystem inflammatory disease (NOMID)/chronic infantile neurologic cutaneous and articular (CINCA) syndrome. They have in common a causative mutation in the NLRP3-gene. The altered gene product cryopyrin leads to activation of the inflammasome which in turn is responsible for excessive production of IL-1β. IL-1β causes the inflammatory manifestations in CAPS. These appear as systemic inflammation including fever, headache or fatigue, rash, eye disease, progressive sensorineural hearing loss, musculoskeletal manifestations and CNS symptoms (NOMID/CINCA only). With the advent of the IL-1 inhibitors anakinra, rilonacept and canakinumab for the first time safe and effective therapeutic options are available for this devastating disease. To prevent severe and possible life-threatening disease sequelae, early and correct diagnosis and immediate initiation of therapy are mandatory.

Implications of protein post-translational modifications in IBD

In recent years our understanding of the pathogenesis of inflammatory bowel disease (IBD) has greatly increased. Hallmarks of IBD include loss of intestinal barrier function, increased cytokine production, and failed resolution of tissue damage. Lasting treatments are still lacking and, therefore, a better understanding of the underlying molecular mechanisms is necessary to design novel therapeutic approaches. Apart from transcriptional and posttranscriptional regulation of relevant genes, mammals have evolved a complex and efficient series of mechanisms to rapidly modify newly made proteins for the purposes of signaling and adaptation. These posttranslational protein modifications include, among others, phosphorylation, hydroxylation, neddylation, and cytokine cleavage by the inflammasome. This review focuses on our current understanding of posttranslational protein modifications with a particular focus on their relevance to IBD pathogenesis.

Biochemical regulation of the inflammasome

The extensively studied cytokine IL-1β is an important mediator of the inflammatory response. However, dysregulated release of IL-1β can be detrimental and is attributed to the progression and pathogenesis of multiple inflammatory diseases including, rhuematoid arthritis (RA), atherosclerosis, type 2 diabetes (T2D), Alzheimers disease and gout. IL-1β is encoded as a pro-protein. A multi-protein molecular scaffold termed the "Inflammasome" is responsible for the tightly controlled and coordinated processing of pro-IL-1β. The activation of several NLR (nucleotide-binding oligomerization domain (NOD)-like receptor) family members and PYHIN (pyrin and HIN domain) proteins can drive the formation of inflammasomes. However, the exact biochemical mechanisms governing their activation have been the subject of much research. Different inflammasomes have been demonstrated to respond to the same pathogen inducing a cooperative immune response accountable for the clearance of infection. Here, we review current knowledge surrounding the biochemical regulation of the NLRP1, NLRP3, NLRC4, AIM2 and IFI16 inflammasomes.

Bridging the gap between the clinician and the patient with cryopyrin-associated periodic syndromes

Cryopyrin-associated periodic syndromes are categorized as a spectrum of three autoinflammatory diseases, namely familial cold auto-inflammatory syndrome, Muckle-Wells syndrome and chronic infantile neurological cutaneous articular syndrome. All are caused by mutations in the NLRP3 gene coding for cryopyrin and result in active interleukin-1 release: their rarity and shared clinical indicators involving skin, joints, central nervous system and eyes often mean that correct diagnosis is delayed. Onset occurs early in childhood, and life-long therapy with interleukin-1 blocking agents usually leads to tangible clinical remission and inflammatory marker normalization in a large number of patients, justifying the need to facilitate early diagnosis and thus avoid irreversible negative consequences for tissues and organs.