Targeted disruption of pyrin, the FMF protein, causes heightened sensitivity to endotoxin and a defect in macrophage apoptosis

Experimental models in Familial Mediterranean Fever (FMF): Insights into pathophysiology and therapeutic strategies

Familial Mediterranean Fever (FMF) is a recurrent polyserositis characterized by self-limiting episodes or attacks of fever along with serosal inflammation. It mainly impacts people of the Mediterranean and Middle Eastern basin. FMF is a recessive autoinflammatory condition caused by mutation in the MEFV gene located on chromosome 16p13. MEFV mutations lead to the activation of the pyrin inflammasome resulting in an uncontrolled release of IL-1β. Various in vitro, in vivo and ex vivo experimental models have been developed to further comprehend the etiology and pathogenesis of FMF. These models have been proven to be clinically relevant to human FMF and can provide significant information about biological systems with respect to this condition. Additionally, these models have provided pertinent contributions to the development of potent therapeutic strategies against FMF. In this review, we describe the different experimental models utilized in FMF and we focus primarily on the most widely used models that have produced prominent insights into the pathophysiology of the disease.

Multipronged regulation of autophagy and apoptosis: emerging role of TRIM proteins

TRIM proteins are characterized by their conserved N-terminal RING, B-box, and coiled-coil domains. These proteins are efficient regulators of autophagy, apoptosis, and innate immune responses and confer immunity against viruses and bacteria. TRIMs function as receptors or scaffold proteins that target substrates for autophagy-mediated degradation. Most TRIMs interact with the BECN1-ULK1 complex to form TRIMosomes, thereby efficiently targeting substrates to autophagosomes. They regulate the functions of ATG proteins through physical interactions or ubiquitination. TRIMs affect the lipidation of MAP1LC3B1 to form MAP1LC3B2, which is a prerequisite for phagophore and autophagosome formation. In addition, they regulate MTOR kinase and TFEB, thereby regulating the expression of ATG genes. TRIM proteins are efficient regulators of apoptosis and are crucial for regulating cell proliferation and tumor formation. Many TRIM proteins regulate intrinsic and extrinsic apoptosis via the cell surface receptors TGFBR2, TNFRSF1A, and FAS. Mitochondria modulate the anti- and proapoptotic functions of BCL2, BAX, BAK1, and CYCS. These proteins use a multipronged approach to regulate the intrinsic and extrinsic apoptotic pathways, culminating in coordinated activation or inhibition of the initiator and executor CASPs. Furthermore, TRIMs can have a dual effect in determining cell fate and are therefore crucial for cellular homeostasis. In this review, we discuss mechanistic insights into the role of TRIM proteins in regulating autophagy and apoptosis, which can be used to better understand cellular physiology. These findings can be used to develop therapeutic interventions to prevent or treat multiple genetic and infectious diseases.

Colchicine-responsive chronic recurrent multifocal osteomyelitis associated with familial Mediterranean fever in the presence of MEFV mutation: A case report

A 38-year-old female was referred with a history of fever, polyarthralgia, and bone pain. She was diagnosed with chronic recurrent multifocal osteomyelitis based on imaging and biopsy findings. Non-steroidal anti-inflammatory drugs and bisphosphonate caused no improvement. Then, she developed recurrent diarrhoea and abdominal pain. Genetic testing revealed MEFV mutation. Based on the symptoms and genetic mutation results that emerged during the course of these events, she was diagnosed with familial Mediterranean fever. All symptoms, including bone pain, improved with daily colchicine administration. This case was considered familial Mediterranean fever complicated with a clinical diagnosis of chronic recurrent multifocal osteomyelitis, which is included in the spectrum of pyrine autoinflammatory diseases. Considering this case, patients with chronic recurrent multifocal osteomyelitis with MEFV gene variants may respond to colchicine.

Phosphoprotein phosphatase activity positively regulates oligomeric pyrin to trigger inflammasome assembly in phagocytes

IMPORTANCE

Pyrin, a unique cytosolic receptor, initiates inflammatory responses against RhoA-inactivating bacterial toxins and effectors like Yersinia's YopE and YopT. Understanding pyrin regulation is crucial due to its association with dysregulated inflammatory responses, including Familial Mediterranean Fever (FMF), linked to pyrin gene mutations. FMF mutations historically acted as a defense mechanism against plague. Negative regulation of pyrin through PKN phosphorylation is well established, with Yersinia using the YopM effector to promote pyrin phosphorylation and counteract its activity. This study highlights the importance of phosphoprotein phosphatase activity in positively regulating pyrin inflammasome assembly in phagocytic cells of humans and mice. Oligomeric murine pyrin has S205 phosphorylated before inflammasome assembly, and this study implicates the dephosphorylation of murine pyrin S205 by two catalytic subunits of PP2A in macrophages. These findings offer insights for investigating the regulation of oligomeric pyrin and the balance of kinase and phosphatase activity in pyrin-associated infectious and autoinflammatory diseases.

Detection of a rare variant in PSTPIP1 through three generations in a family with an initial diagnosis of FMF/MKD-overlapping phenotype

OBJECTIVE

The presence of FMF cases without MEFV (MEFV innate immunity regulator, pyrin) pathogenic variants led us to search for other genes' involvement in the disease development. Here, we describe the presence of genetic heterogeneity in a three-generation family with an FMF/mevalonate kinase deficiency (MKD)-overlapping phenotype without MEFV/MVK (mevalonate kinase) pathogenic variants.

METHOD

Targeted sequencing revealed a rare, fully penetrant variant in PSTPIP1 (p.Arg228Cys, rs781341816). Computational stability analyses of PSTPIP1 protein were performed. PSTPIP1-pyrin protein interaction was examined by immunoprecipitation and immunoblotting in peripheral blood mononuclear cells (PBMCs) of patients and healthy controls. PBMCs were cultured, and inflammation was induced by LPS+ATP treatment, followed by protein level measurements of caspase-1, IL1ß, pyrin and PSTPIP1 in cell lysates and mature caspase-1 and mature IL1ß in supernatants.

RESULTS

The conserved, rare (GnomAD, 0.000028) PSTPIP1 p.Arg228Cys variant, previously reported in ClinVar as a variant with uncertain significance, showed complete penetrance in the family presenting an autosomal dominant pattern. Computational analyses showed a potentially destabilizing effect of the variant on PSTPIP1 protein. Accordingly, PSTPIP1-pyrin interaction was increased in patients harboring the variant, which resulted in elevated levels of mature caspase-1 and IL1ß in the inflammation-induced patient samples.

CONCLUSIONS

Unlike previously described cases with pyogenic arthritis, pyoderma gangrenosum, and acne (PAPA)-associated PSTPIP1 variants, our patients with the p.Arg228Cys variant presented with an FMF/MKD-overlapping phenotype. As additional data on the genetic heterogeneity in the variable clinical spectrum of autoinflammatory syndromes, we suggest that the p.Arg228Cys variant in PSTPIP1 is related to inflammation responses through strong PSTPIP1-pyrin interaction and pyrin inflammasome activation.

No NLRP3 inflammasome activity in kidney epithelial cells, not even when the NLRP3-A350V Muckle-Wells variant is expressed in podocytes of diabetic mice

Background

The NLRP3 inflammasome integrates several danger signals into the activation of innate immunity and inflammation by secreting IL-1β and IL-18. Most published data relate to the NLRP3 inflammasome in immune cells, but some reports claim similar roles in parenchymal, namely epithelial, cells. For example, podocytes, epithelial cells critical for the maintenance of kidney filtration, have been reported to express NLRP3 and to release IL-β in diabetic kidney disease, contributing to filtration barrier dysfunction and kidney injury. We questioned this and hence performed independent verification experiments.

Methods

We studied the expression of inflammasome components in human and mouse kidneys and human podocytes using single-cell transcriptome analysis. Human podocytes were exposed to NLRP3 inflammasome agonists in vitro and we induced diabetes in mice with a podocyte-specific expression of the Muckle-Wells variant of NLRP3, leading to overactivation of the Nlrp3 inflammasome (Nphs2Cre;Nlrp3A350V) versus wildtype controls. Phenotype analysis included deep learning-based glomerular and podocyte morphometry, tissue clearing, and STED microscopy of the glomerular filtration barrier. The Nlrp3 inflammasome was blocked by feeding ß-hydroxy-butyrate.

Results

Single-cell transcriptome analysis did not support relevant NLRP3 expression in parenchymal cells of the kidney. The same applied to primary human podocytes in which NLRP3 agonists did not induce IL-1β or IL-18 secretion. Diabetes induced identical glomerulomegaly in wildtype and Nphs2Cre;Nlrp3A350V mice but hyperfiltration-induced podocyte loss was attenuated and podocytes were larger in Nphs2Cre;Nlrp3A350V mice, an effect reversible with feeding the NLRP3 inflammasome antagonist ß-hydroxy-butyrate. Ultrastructural analysis of the slit diaphragm was genotype-independent hence albuminuria was identical.

Conclusion

Podocytes express low amounts of the NLRP3 inflammasome, if at all, and do not produce IL-1β and IL-18, not even upon introduction of the A350V Muckle-Wells NLRP3 variant and upon induction of podocyte stress. NLRP3-mediated glomerular inflammation is limited to immune cells.

Possible Association of Mutations in the MEFV Gene with the Intestinal Phenotype of Behçet's Disease and Refractoriness to Treatment

BACKGROUND

Mediterranean fever (MEFV) gene mutations are responsible for familial Mediterranean fever (FMF) and associated with other inflammatory diseases. However, the effects of MEFV gene mutations on intestinal Behçet's disease (BD) are unknown. In this study, we investigated these mutations and clinical features in patients with intestinal BD.

METHODS

MEFV gene analysis was performed in 16 patients with intestinal BD, 10 with BD without intestinal lesions, and 50 healthy controls. Clinical features of patients with intestinal BD were retrospectively assessed.

RESULTS

The rates of MEFV gene mutations in patients with intestinal BD, BD without intestinal lesions, and healthy controls were 75%, 50%, and 38%, respectively. Only 2 of 12 patients with intestinal BD harboring MEFV gene mutations (17%) were controlled without immunosuppressive treatment, while 8 patients (67%) required therapy with tumor necrosis factor (TNF) inhibitors. Among patients with intestinal BD without MEFV gene mutations (four patients), three (75%) were controlled by the administration of 5-aminosalicylic acid with or without colchicine, and one (25%) required TNF inhibitors. All patients who underwent intestinal resection had MEFV gene mutations. Immunohistochemical analysis and in situ hybridization with interleukin-1β (IL-1β) showed a high expression of IL-1β only in injured areas, suggesting that IL-1β may be involved in the formation of ulcers in patients with intestinal BD carrying MEFV gene mutations.

CONCLUSION

Mutations in the MEFV gene may be associated with intestinal lesions of BD and refractoriness to treatment.

A review on gout: Looking back and looking ahead

Gout is a metabolic disease caused by the deposition of monosodium urate (MSU) crystals inside joints, which leads to inflammation and tissue damage. Increased concentration of serum urate is an essential step in the development of gout. Serum urate is regulated by urate transporters in the kidney and intestine, especially GLUT9 (SLC2A9), URAT1 (SLC22A12) and ABCG. Activation of NLRP3 inflammasome bodies and subsequent release of IL-1β by monosodium urate crystals induce the crescendo of acute gouty arthritis, while neutrophil extracellular traps (NETs) are considered to drive the self-resolving of gout within a few days. If untreated, acute gout may eventually develop into chronic tophaceous gout characterized by tophi, chronic gouty synovitis, and structural joint damage, leading the crushing burden of treatment. Although the research on the pathological mechanism of gout has been gradually deepened in recent years, many clinical manifestations of gout are still unable to be fully elucidated. Here, we reviewed the molecular pathological mechanism behind various clinical manifestations of gout, with a view to making contributions to further understanding and treatment.

Canonical Inflammasomes

The innate immune response represents the first line of host defense, and it is able to detect pathogen- and damage-associated molecular patterns (PAMPs and DAMPs, respectively) through a variety of pattern recognition receptors (PRRs). Among these PRRs, certain cytosolic receptors of the NLRs family (specifically NLRP1, NLRP3, NLRC4, and NAIP) or those containing at least a pyrin domain (PYD) such as pyrin and AIM2, activate the multimeric complex known as inflammasome, and its effector enzyme caspase-1. The caspase-1 induces the proteolytic maturation of the pro-inflammatory cytokines IL-1ß and IL-18, as well as the pore-forming protein gasdermin D (GSDMD). GSDMD is responsible for the release of the two cytokines and the induction of lytic and inflammatory cell death known as pyroptosis. Each inflammasome receptor detects specific stimuli, either directly or indirectly, thereby enhancing the cell's ability to sense infections or homeostatic disturbances. In this chapter, we present the activation mechanism of the so-called "canonical" inflammasomes.

Red Algae “Sarcodia suieae” Acetyl-Xylogalactan Downregulate Heat-Induced Macrophage Stress Factors Ddit3 and Hyou1 Compared to the Aquatic Animal Model of Nile Tilapia (Oreochromis niloticus) Brain Arachidonic Acid Expression

Anthropogenic climate change is known to be an increased stress that affects aquatic animal behavior and physiological alternations, which can induce the animal's death. In order to known whether the extracted acetyl-xylogalactan function on the regulation of the external high temperature induced death, we first selected the mammalian cell line "RAW 264.7" used in the previous experiment to evaluate the extracted acetyl-xylogalactan function. We aimed to evaluate the effects of the acetyl-xylogalactan on the RAW 264.7 macrophages and Nile Tilapia stress factor expression under the heat environment. In the in vitro cell observation, we assessed the cell survival, phagocytic activity, intracellular Ca²⁺ level, mitochondria potential exchange, apoptotic assay findings, galactosidase activity, RNA-seq by NGS and real-time polymerase chain reaction (QPCR) expression. In the in vivo Nile Tilapia observation aimed to evaluate the blood biochemical indicator, brain metabolites exchange and the liver morphology. In our evaluation of RAW 264.7 macrophages, the RNA sequencing and real-time polymerase chain reaction (PCR) was shown to upregulate the expression of the anti-apoptosis Cflar gene and downregulate the expression of the apoptosis factors Ddit3 and Hyou1 to protect macrophages under heat stress. We already knew the extracted acetyl-xylogalactan function on the mammalian "RAW 264.7" system. Following, we used the aquatic Nile Tilapia model as the anthropogenic climate change high temperature experiment. After feeding the Nile Tilapia with the acetyl-xylogalactan, it was found to reduce the brain arachidonic acid (AA) production, which is related to the NF-κB-induced apoptosis mechanism. Combined with the in vitro and in vivo findings, the acetyl-xylogalactan was able to reduce the heat induced cell or tissue stress.

Strong inflammatory signatures in the neutrophils of PAMI syndrome

PSTPIP1 (proline-serine-threonine phosphatase-interactive protein 1)–associated myeloid-related proteinemia inflammatory (PAMI) syndrome is a rare autoinflammatory disease caused by heterozygous gain-of-function mutation in PSTPIP1. As one of the PSTPIP1-associated inflammatory diseases (PAIDs), neutropenia is a distinct manifestation to separate PAMI syndrome from other PAIDs. This study aimed to investigate the potential role of neutrophils and inflammatory signatures in the pathogenesis of PAMI. PAMI neutrophils displayed markedly increased production of interleukin-1β (IL-1β) and IL-18 by enzyme linked immunosorbent assay (ELISA) assay and intracellular cytokine staining. ASC speck formation and lactic dehydrogenase (LDH) release are also increased in patient neutrophils suggesting elevated pyrin inflammasome activation followed by upregulated cell death in PAMI neutrophils. RNA sequencing result showed strong inflammatory signals in both nuclear-factor kappa B (NF-κB) pathway and interferon (IFN) pathway in patient neutrophils. This study highlighted that elevated proinflammatory cytokines IL-1β and IL-18, increased pyrin inflammasome activation, and upregulation of NF-κB and IFN signaling pathways in neutrophils play important roles in pathogenicity of PAMI syndrome.

Repeated Necrotizing Lymphadenitis with MEFV Gene Mutations

We herein report a 36-year-old man with repeated necrotizing lymphadenitis due to MEFV gene mutations. The patient's chief complaints were a fever and painful cervical lymphadenopathy. We diagnosed him with necrotizing lymphadenitis based on the pathological findings of the lymph nodes and the exclusion of other differential diseases. The same episode recurred four times. We speculated the involvement of autoinflammatory backgrounds and detected MEFV gene mutations of E148Q (homo), P369S, and R408Q. Considering the elevation of interleukin-18, these mutations probably played roles in the repeated necrotizing lymphadenitis.

TRIMs: Generalists Regulating the NLRP3 Inflammasome Signaling Pathway

Inflammation is a double-edged sword. The moderate inflammatory response is a fundamental defense mechanism produced by the body's resistance to dangerous stimuli and a repair process of the body itself. Increasing studies have confirmed that the overactivation of the inflammasome is involved in the occurrence and development of inflammatory diseases. Strictly controlling the overactivation of the inflammasome and preventing excessive inflammatory response have always been the research focus on inflammatory diseases. However, the endogenous regulatory mechanism of inflammasome is not completely clear. The tripartite motif (TRIM) protein is one of the members of E3 ligases in the process of ubiquitination. The universality and importance of the functions of TRIM members are recognized, including the regulation of inflammatory response. This article will focus on research on the relationship between TRIMs and NLRP3 Inflammasome, which may help us make some references for future related research and the discovery of treatment methods.

Focus on the Mechanisms and Functions of Pyroptosis, Inflammasomes, and Inflammatory Caspases in Infectious Diseases

Eukaryotic cells can initiate several distinct self-destruction mechanisms to display essential roles for the homeostasis maintenance, development, and survival of an organism. Pyroptosis, a key response mode in innate immunity, also referred to as caspase-1-dependent proinflammatory programmed necrotic cell death activated by human caspase-1/4/5, or mouse caspase-1/11, plays indispensable roles in response to cytoplasmic insults and immune defense against infectious diseases. These inflammatory caspases are employed by the host to eliminate pathogen infections such as bacteria, viruses, protozoans, and fungi. Gasdermin D requires to be cleaved and activated by these inflammatory caspases to trigger the pyroptosis process. Physiological rupture of cells results in the release of proinflammatory cytokines, the alarmins IL-1β and IL-18, symbolizing the inflammatory potential of pyroptosis. Moreover, long noncoding RNAs play direct or indirect roles in the upstream of the pyroptosis trigger pathway. Here, we review in detail recently acquired insights into the central roles of inflammatory caspases, inflammasomes, and pyroptosis, as well as the crosstalk between pyroptosis and long noncoding RNAs in mediating infection immunity and pathogen clearance.

Evaluation of S100A12 protein levels in children with familial Mediterranean fever

Background/aim

Familial Mediterranean fever (FMF), the most common autoinflammatory disease in children, is characterized by recurrent febrile episodes. FMF is known to progress with chronic inflammation, particularly during attack periods. This study aimed to investigate the relationship of S100A12, an inflammatory marker, with attacks and inflammatory events in FMF patients.

Materials and methods

The study included 57 patients diagnosed with FMF, 43 in an attack-free period and 14 in an attack period, and 31 healthy children as the control group. Only white blood cell (WBC) count, C-reactive protein (CRP) level, erythrocyte sedimentation rate (ESR), and S100A12 level were analyzed in the control group. In addition, serum amyloid A (SAA), and fibrinogen levels were measured, and a mutation analysis was performed in the patient group. The results were compared among the attack-free period, acute attack FMF and control groups.

Results

The mean age of patients and control group was 10 (2.5–18) and 9.5 (2.5–16) years, respectively. The CRP (p = 0.001), S100A12 (p = 0.003) and ESR (p= 0.001) values differed significantly between the FMF and control groups. S100A12 level (p = 0.027), WBC count (p = 0.003), CRP level (p = 0.0001), ESR (p = 0.004), and fibrinogen level (p = 0.001) differed significantly between the acute attack and attack-free period groups. SAA level (p = 0.05), ESR (p = 0.001), fibrinogen level (p = 0.001), WBC count (p = 0.001), and S100A12 level (p = 0.027) were higher in M694V homozygous FMF patients than in other FMF patients.

Conclusion

Patients with FMF had higher S100A12 levels than the control group, while the mean S100A12 concentration was higher in acute attack period patients than in attack-free period patients. S100A12 level might be an important indicator in the monitoring of chronic inflammation in patients with FMF.

Decoding Cell Death: From a Veritable Library of Babel to Vade Mecum?

Programmed cell death (PCD) is a requisite feature of development and homeostasis but can also be indicative of infections, injuries, and pathologies. In concordance with these heterogeneous contexts, an array of disparate effector responses occur downstream of cell death and its clearance-spanning tissue morphogenesis, homeostatic turnover, host defense, active dampening of inflammation, and tissue repair. This raises a fundamental question of how a single contextually appropriate response ensues after an event of PCD. To explore how complex inputs may together tailor the specificity of the resulting effector response, here we consider (a) the varying contexts during which different cell death modalities are observed, (b) the nature of the information that can be passed on by cell corpses, and (c) the ways by which efferocyte populations synthesize signals from dying cells with those from the surrounding microenvironment.

Techniques to Study Inflammasome Activation and Inhibition by Small Molecules

Inflammasomes are immune cytosolic oligomers involved in the initiation and progression of multiple pathologies and diseases. The tight regulation of these immune sensors is necessary to control an optimal inflammatory response and recover organism homeostasis. Prolonged activation of inflammasomes result in the development of chronic inflammatory diseases, and the use of small drug-like inhibitory molecules are emerging as promising anti-inflammatory therapies. Different aspects have to be taken in consideration when designing inflammasome inhibitors. This review summarizes the different techniques that can be used to study the mechanism of action of potential inflammasome inhibitory molecules.

Mechanisms of NLRP3 Inflammasome Activation: Its Role in the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is a common neurodegenerative disease of progressive dementia which is characterized pathologically by extracellular neuritic plaques containing aggregated amyloid beta (Aβ) and intracellular hyperphosphorylated tau protein tangles in cerebrum. It has been confirmed that microglia-specific nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome-mediated chronic neuroinflammation plays a crucial role in the pathogenesis of AD. Stimulated by Aβ deposition, NLRP3 assembles and activates within microglia in the AD brain, leading to caspase-1 activation along with downstream interleukin (IL)-1β secretion, and subsequent inflammatory events. Activation of the NLRP3 inflammasome mediates microglia to exhibit inflammatory M1 phenotype, with high expression of caspase-1 and IL-1β. This leads to Aβ deposition and neuronal loss in the amyloid precursor protein (APP)/human presenilin-1 (PS1) mouse model of AD. However, NLRP3 or caspase-1 deletion in APP/PS1 mice promotes microglia to transform to an anti-inflammatory M2 phenotype, with decreased secretion of caspase-1 and IL-1β. It also results in improved cognition, enhanced Aβ clearance, and a lower cerebral inflammatory response. This result suggests that the NLRP3 inflammasome may be an appropriate target for reducing neuroinflammation and alleviating pathological processes in AD. In the present review, we summarize the generally accepted regulatory mechanisms of NLRP3 inflammasome activation, and explore its role in neuroinflammation. Furthermore, we speculate on the possible roles of microglia-specific NLRP3 activation in AD pathogenesis and consider potential therapeutic interventions targeting the NLRP3 inflammasome in AD.

The Yersinia Type III Secretion System as a Tool for Studying Cytosolic Innate Immune Surveillance

Microbial pathogens have evolved complex mechanisms to interface with host cells in order to evade host defenses and replicate. However, mammalian innate immune receptors detect the presence of molecules unique to the microbial world or sense the activity of virulence factors, activating antimicrobial and inflammatory pathways. We focus on how studies of the major virulence factor of one group of microbial pathogens, the type III secretion system (T3SS) of human pathogenic Yersinia, have shed light on these important innate immune responses. Yersinia are largely extracellular pathogens, yet they insert T3SS cargo into target host cells that modulate the activity of cytosolic innate immune receptors. This review covers both the host pathways that detect the Yersinia T3SS and the effector proteins used by Yersinia to manipulate innate immune signaling.

Gut Microbiota between Environment and Genetic Background in Familial Mediterranean Fever (FMF)

The gastrointestinal tract hosts the natural reservoir of microbiota since birth. The microbiota includes various bacteria that establish a progressively mutual relationship with the host. Of note, the composition of gut microbiota is rather individual-specific and, normally, depends on both the host genotype and environmental factors. The study of the bacterial profile in the gut demonstrates that dominant and minor phyla are present in the gastrointestinal tract with bacterial density gradually increasing in oro-aboral direction. The cross-talk between bacteria and host within the gut strongly contributes to the host metabolism, to structural and protective functions. Dysbiosis can develop following aging, diseases, inflammatory status, and antibiotic therapy. Growing evidences show a possible link between the microbiota and Familial Mediterranean Fever (FMF), through a shift of the relative abundance in microbial species. To which extent such perturbations of the microbiota are relevant in driving the phenotypic manifestations of FMF with respect to genetic background, remains to be further investigated.

Ancient familial Mediterranean fever mutations in human pyrin and resistance to Yersinia pestis

Familial Mediterranean fever (FMF) is an autoinflammatory disease caused by homozygous or compound heterozygous gain-of-function mutations in MEFV, encoding pyrin, an inflammasome protein. Heterozygous carrier frequencies for multiple MEFV mutations are high in several Mediterranean populations, suggesting that they confer selective advantage. Among 2,313 Turks, we found extended haplotype homozygosity flanking FMF-associated mutations, indicating evolutionarily recent positive selection of FMF-associated mutations. Two pathogenic pyrin variants independently arose >1,800 years ago. Mutant pyrin interacts less avidly with Yersinia pestis virulence factor YopM than wild type human pyrin, thereby attenuating YopM-induced IL-1β suppression. Relative to healthy controls, leukocytes from FMF patients harboring homozygous or compound heterozygous mutations and from asymptomatic heterozygous carriers released heightened IL-1β specifically in response to Y. pestis. Y. pestis-infected Mefv^M680I/M680I FMF knock-in mice exhibited IL-1-dependent increased survival relative to wild-type knock-in mice. Thus, FMF mutations that were positively selected in Mediterranean populations confer heightened resistance to Y. pestis.

Inflammasome activation and regulation: toward a better understanding of complex mechanisms

Inflammasomes are cytoplasmic multiprotein complexes comprising a sensor protein, inflammatory caspases, and in some but not all cases an adapter protein connecting the two. They can be activated by a repertoire of endogenous and exogenous stimuli, leading to enzymatic activation of canonical caspase-1, noncanonical caspase-11 (or the equivalent caspase-4 and caspase-5 in humans) or caspase-8, resulting in secretion of IL-1β and IL-18, as well as apoptotic and pyroptotic cell death. Appropriate inflammasome activation is vital for the host to cope with foreign pathogens or tissue damage, while aberrant inflammasome activation can cause uncontrolled tissue responses that may contribute to various diseases, including autoinflammatory disorders, cardiometabolic diseases, cancer and neurodegenerative diseases. Therefore, it is imperative to maintain a fine balance between inflammasome activation and inhibition, which requires a fine-tuned regulation of inflammasome assembly and effector function. Recently, a growing body of studies have been focusing on delineating the structural and molecular mechanisms underlying the regulation of inflammasome signaling. In the present review, we summarize the most recent advances and remaining challenges in understanding the ordered inflammasome assembly and activation upon sensing of diverse stimuli, as well as the tight regulations of these processes. Furthermore, we review recent progress and challenges in translating inflammasome research into therapeutic tools, aimed at modifying inflammasome-regulated human diseases.

Understanding the Relevance of DNA Methylation Changes in Immune Differentiation and Disease

Immune cells are one of the most complex and diverse systems in the human organism. Such diversity implies an intricate network of different cell types and interactions that are dependently interconnected. The processes by which different cell types differentiate from progenitors, mature, and finally exert their function requires an orchestrated succession of molecular processes that determine cell phenotype and function. The acquisition of these phenotypes is highly dependent on the establishment of unique epigenetic profiles that confer identity and function on the various types of effector cells. These epigenetic mechanisms integrate microenvironmental cues into the genome to establish specific transcriptional programs. Epigenetic modifications bridge environment and genome regulation and play a role in human diseases by their ability to modulate physiological programs through external stimuli. DNA methylation is one of the most ubiquitous, stable, and widely studied epigenetic modifications. Recent technological advances have facilitated the generation of a vast amount of genome-wide DNA methylation data, providing profound insights into the roles of DNA methylation in health and disease. This review considers the relevance of DNA methylation to immune system cellular development and function, as well as the participation of DNA methylation defects in immune-mediated pathologies, illustrated by selected paradigmatic diseases.

An Extraordinary Complication in a Child With Combined Familial Mediterranean Fever and Inflammatory Bowel Disease: Multiple Ileal Perforations

Familial Mediterranean fever (FMF) is a recurrent disease with autosomal recessive trait and fever that is generally self-limiting. Clinical manifestations are pain in the abdomen, chest, and joints as a result of inflammation in the serous surfaces. No case of multiple intestinal perforations has been reported in children with FMF, whereas cases with a single intestinal perforation have been encountered, although very rarely. In addition, co-occurrence of FMF and inflammatory bowel disease is a situation that is very rarely reported in the literature. Here, we report a case of a 5-year-old girl who was being followed up with the diagnosis of FMF and who also had inflammatory bowel disease, which was complicated with multiple ileal perforations. Our aim is to point out a rarely encountered co-occurrence and also the importance of evaluation of additional diseases with FMF that are unresponsive to treatment so as to prevent complications.

Function and mechanism of pyrin and IL-10 in the regulation of the inflammasome in pulmonary vascular endothelial cells following hemorrhagic shock

The present study aimed to evaluate the function of pyrin and interleukin-10 (IL-10) and the potential mechanisms underlying the regulation of inflammation in pulmonary vascular endothelial cells (ECs) following hemorrhagic shock (HS). Adult female Sprague-Dawley rats were divided into 4 groups (n=6 in each group) to examine the changes in pyrin expression following HS-lipopolysaccharide (LPS) administration, including the following groups: A sham operation (SM) + tracheal injection of saline (SAL) group; a HS + SAL group; a SM + LPS group (with a tracheal injection of endotoxin); and a HS + LPS group. An additional 4 groups were used to evaluate the function of IL-10, by the additional intratracheal injection of recombinant IL-10. Western blot analysis and immunofluorescence were performed in order to investigate the changes to pyrin and IL-10 expression in pulmonary vascular ECs. The expression levels of pyrin in the SM + LPS group were significantly increased in comparison with the SM + SAL group (P<0.01). Additionally, the expression levels of pyrin were significantly increased in the HS + LPS group compared with the HS + SAL group (P<0.01). The expression levels of caspase-1 were significantly increased in the HS + LPS group compared with those in the other three groups (P<0.01). The expression levels of pyrin in the HS + LPS + IL-10 group were significantly increased compared with the HS + LPS group (P<0.01). The expression levels of caspase-1 were significantly decreased following IL-10 treatment compared with those in the HS + LPS group (P<0.01). Therefore, HS attenuated LPS-induced pyrin expression in pulmonary vascular ECs and may also inhibit the expression of IL-10, resulting in the activation of caspase-1 subsequent to a second LPS insult.

The Pyrin Inflammasome in Health and Disease

The pyrin inflammasome has evolved as an innate immune sensor to detect bacterial toxin-induced Rho guanosine triphosphatase (Rho GTPase)-inactivation, a process that is similar to the “guard” mechanism in plants. Rho GTPases act as molecular switches to regulate a variety of signal transduction pathways including cytoskeletal organization. Pathogens can modulate Rho GTPase activity to suppress host immune responses such as phagocytosis. Pyrin is encoded by MEFV, the gene that is mutated in patients with familial Mediterranean fever (FMF). FMF is the prototypic autoinflammatory disease characterized by recurring short episodes of systemic inflammation and is a common disorder in many populations in the Mediterranean basin. Pyrin specifically senses modifications in the activity of the small GTPase RhoA, which binds to many effector proteins including the serine/threonine-protein kinases PKN1 and PKN2 and actin-binding proteins. RhoA activation leads to PKN-mediated phosphorylation-dependent pyrin inhibition. Conversely, pathogen virulence factors downregulate RhoA activity in a variety of ways, and these changes are detected by the pyrin inflammasome irrespective of the type of modifications. MEFV pathogenic variants favor the active state of pyrin and elicit proinflammatory cytokine release and pyroptosis. They can be inherited either as a dominant or recessive trait depending on the variant's location and effect on the protein function. Mutations in the C-terminal B30.2 domain are usually considered recessive, although heterozygotes may manifest a biochemical or even a clinical phenotype. These variants are hypomorphic in regard to their effect on intramolecular interactions, but ultimately accentuate pyrin activity. Heterozygous mutations in other domains of pyrin affect residues critical for inhibition or protein oligomerization, and lead to constitutively active inflammasome. In healthy carriers of FMF mutations who have the subclinical inflammatory phenotype, the increased activity of pyrin might have been protective against endemic infections over human history. This finding is supported by the observation of high carrier frequencies of FMF-mutations in multiple populations. The pyrin inflammasome also plays a role in mediating inflammation in other autoinflammatory diseases linked to dysregulation in the actin polymerization pathway. Therefore, the assembly of the pyrin inflammasome is initiated in response to fluctuations in cytoplasmic homeostasis and perturbations in cytoskeletal dynamics.

NLRP2 is highly expressed and promotes apoptosis in a mouse model of kidney ischemia/reperfusion injury

The aim of this study was to investigate the role of nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin domain containing 2 (NLRP2) in kidney ischemia/reperfusion injury. A mouse model of acute kidney ischemia/reperfusion injury was established to conduct in vivo experiments. Oxygen–glucose deprivation (OGD) and cobalt chloride treatment of the HK-2 and glomerular endothelial cell (GENC) kidney cell lines were performed for the in vitro study. Reverse transcription–quantitative polymerase chain reaction, western blotting, and immunohistochemical staining were used to analyze NLRP2 expression levels. Knockdown of NLRP2 in cells was also performed, and cell apoptosis was detected using flow cytometry. NLRP2 was expressed in normal kidney tissues; however, its expression was significantly increased in the acute kidney injury model and in OGD-treated cells. Conversely, knockdown of NLRP2 reduced apoptosis of cells. These results suggested that NLRP2 was involved in kidney damage and may be an important target for treatment of acute kidney injury.

Dicer regulates activation of the NLRP3 inflammasome

Inflammation plays a critical role in initiation of adaptive immunity, pathogen clearance and tissue repair. Interleukin (IL)-1β is a potent pro-inflammatory cytokine and therefore its production is tightly regulated: its secretion requires the assembly of a macromolecular protein complex, termed the inflammasome. Aberrant activation of the inflammasome has been linked to debilitating human diseases including chronic inflammatory and autoimmune diseases. Thus, there is a great interest in understanding how inflammasomes are regulated. Here we show that Dicer, an enzyme necessary for the production of mature micro-RNAs (miRNAs), is required for optimal activation of NLRP3 inflammasomes in bone marrow macrophages. Our data indicate that miRNAs may play an important role in promoting inflammasome activation.

Genome-wide association study in Turkish and Iranian populations identify rare familial Mediterranean fever gene (MEFV) polymorphisms associated with ankylosing spondylitis

Ankylosing spondylitis (AS) is a highly heritable immune-mediated arthritis common in Turkish and Iranian populations. Familial Mediterranean Fever (FMF) is an autosomal recessive autoinflammatory disease most common in people of Mediterranean origin. MEFV, an FMF-associated gene, is also a candidate gene for AS. We aimed to identify AS susceptibility loci and also examine the association between MEFV and AS in Turkish and Iranian cohorts. We performed genome-wide association studies in 1001 Turkish AS patients and 1011 Turkish controls, and 479 Iranian AS patients and 830 Iranian controls. Serum IL-1β, IL-17 and IL-23 cytokine levels were quantified in Turkish samples. An association of major effect was observed with a novel rare coding variant in MEFV in the Turkish cohort (rs61752717, M694V, OR = 5.3, P = 7.63×10⁻¹²), Iranian cohort (OR = 2.9, P = 0.042), and combined dataset (OR = 5.1, P = 1.65×10⁻¹³). 99.6% of Turkish AS cases, and 96% of those carrying MEFV rs61752717 variants, did not have FMF. In Turkish subjects, the association of rs61752717 was particularly strong in HLA-B27-negative cases (OR = 7.8, P = 8.93×10⁻¹⁵), but also positive in HLA-B27-positive cases (OR = 4.3, P = 7.69×10⁻⁸). Serum IL-1β, IL-17 and IL-23 levels were higher in AS cases than controls. Among AS cases, serum IL-1β and IL-23 levels were increased in MEFV 694V carriers compared with non-carriers. Our data suggest that FMF and AS have overlapping aetiopathogenic mechanisms. Functionally important MEFV mutations, such as M694V, lead to dysregulated inflammasome function and excessive IL-1β function. As IL-1 inhibition is effective in FMF, AS cases carrying FMF-associated MEFV variants may benefit from such therapy.

Ankylosing spondylitis (AS) is a highly heritable immune-mediated arthritis. To identify new genetic associations with AS, we performed genome-wide association studies in Turkish and Iranian AS patients and controls. We identified a novel rare coding MEFV variant associated with AS. Rare polymorphisms of MEFV, which encodes the protein pyrin, are known to cause Familial Mediterranean Fever (FMF), a monogenic, autosomal recessive, autoinflammatory disease which can be complicated by arthritis. 99.6% of Turkish AS cases, and 96% of those carrying the MEFV variant, did not have FMF, and the association with AS remains excluding cases with FMF. In Turkish subjects, the MEFV variant association was particularly strong in HLA-B27-negative cases, but also positive in HLA-B27-positive cases. This represents the first rare variant association with AS, and has the highest odds ratio for AS of any non-MHC reported hitherto, indicating a major effect on disease pathogenesis. We assessed serum cytokine levels in the cohort, and found that IL-1β, IL-17 and IL-23 levels were higher in AS cases. Furthermore, among AS cases, IL-1β and IL-23 levels were increased in MEFV variant carriers compared with non-carriers. This study has therapeutic implications; as IL-1 inhibition is effective in FMF, AS cases carrying FMF-associated MEFV variants may benefit from such therapy.

Alarmins of the S100-Family in Juvenile Autoimmune and Auto-Inflammatory Diseases

Autoimmune and auto-inflammatory diseases in children are causing chronic inflammation, organ damage, and pain. Although several options for treatment are nowadays available a significant number of patients does not respond sufficiently to current therapies. In these diseases inflammatory processes are triggered by numerous exogenous and endogenous factors. There is now increasing evidence that especially a novel family of pro-inflammatory molecules, named alarmins, play a significant role in inflammatory processes underlying these diseases. Alarmins are endogenous proteins released during stress reactions that confer inflammatory signaling via Pattern Recognition Receptors (PRRs), like the Toll-like receptor 4 (TLR4). The most abundant alarmins in juvenile rheumatic diseases belong to the family of pro-inflammatory calcium-binding S100-proteins. In this review we will give a general introduction in S100-biology. We will demonstrate the functional relevance of these proteins in animal models of autoimmune and auto-inflammatory diseases. We will show the expression patterns of S100-alarmins and correlation to disease activity in different forms of juvenile idiopathic arthritis, auto-inflammatory diseases, and systemic autoimmune disorders. Finally, we will discuss the clinical use of S100-alarmins as biomarkers for diagnosis and monitoring of rheumatic diseases in children and will point out potential future therapeutic approaches targeting inflammatory effects mediated by S100-alarmins.

Francisella induced microparticulate caspase-1/gasdermin-D activation is regulated by NLRP3 independent of Pyrin

Although the study of pathogen sensing by host defense systems continues to uncover a role for inflammasome components specific to particular pathogens, gaps remain in our knowledge. After internalization, Francisella escapes from the phagosome in mononuclear cells and is thought to be detected by intracellular pathogen-response-receptors pyrin and Aim2 in human and murine models, respectively. However, it remains controversial as to the role of pyrin in detecting Francisella. Our current work aims to study the contribution of inflammasome sensor, Pyrin in regulating microparticulate caspase-1/GSDM-D activation by Francisella. Our findings suggest that NLRP3 is central to the activation/release of active caspase-1/GSDM-D encapsulated in microparticles (MP) by Francisella. We also provide evidence that this regulation is independent of pyrin, implicated in sensing cytosolic Francisella in NLRP3-/- conditions where endogenous Pyrin is present. Absence of NLRP3 completely abrogated Francisella mediated MP caspase-1/GSDM-D activation and release both before and after internalization of the pathogen. However, deletion of pyrin not only enhanced both LPS and Francisella mediated MP active caspase-1/GSDM-D release, but pyrin overexpression resulted in a reduction of inflammasome activation and release; suggesting an inhibitory role of pyrin in LPS and Francisella mediated MP responses. This NLRP3 dependence and inhibitory effect of pyrin correlated with cytokine release as well. These observations also correlated with MPs ability to induce cell death; as LPS and Francisella-induced MPs from pyrin-deficient cells were more potent than wild-type monocytes whereas, NLRP3-/- MPs failed to induce cell death. Taken together, we report that NLPR3 not only mediates Francisella induced cytokine responses, but is also critical for cytokine-independent microparticle-induced inflammasome activation and endothelial cell injury independent of pyrin.

Role of Inflammasomes in Neuroimmune and Neurodegenerative Diseases: A Systematic Review

Inflammasomes are multiprotein complexes that can sense pathogen-associated molecular patterns and damage-associated molecular signals. They are involved in the initiation and development of inflammation via activation of IL-1β and IL-18. Many recent studies suggest a strong correlation between inflammasomes and neurological diseases, such as multiple sclerosis (MS), Alzheimer's disease (AD), and Parkinson's disease (PD). Several components of inflammasomes, such as nucleotide-binding oligomerization domain- (NOD-) like receptor, absent in melanoma 2- (AIM2-) like receptors (ALRs), apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and caspase-1, as well as the upstream factors and downstream effectors, are associated with the initiation and development of MS and its animal model, experimental autoimmune encephalomyelitis. Additionally, inflammasomes affect the efficacy of interferon-β therapy in patients with MS. Finally, the strong association of inflammasomes with AD and PD needs to be further studied. In this review of latest literatures, we comprehensively tease out diverse roles of different kinds of inflammasomes in neuroimmune and neurodegenerative diseases, especially in the perspective of double roles involved in pathogenesis, and identify future research priorities.

CBL mutation and MEFV single-nucleotide variant are important genetic predictors of tumor reduction in glucocorticoid-treated patients with chronic myelomonocytic leukemia

Glucocorticoid (GC) therapy occasionally relieves tumor-related fever and promotes tumor reduction in patients with chronic myelomonocytic leukemia (CMML). A mutation analysis of 24 patients with CMML revealed the relationship of GC effectiveness, defined as a monocyte reduction of > 50% within 3 days of methylprednisolone administration, with the MEFV single-nucleotide variant (SNV) and CBL mutation. Lipopolysaccharide-stimulated monocytes harboring MEFV E148Q produced greater amounts of IL-1β and TNF-α than did wild-type monocytes; this was effectively suppressed by GC. Primary CMML cells harboring the MEFV SNV and CBL mutation, and the myelomonocytic leukemia cell line GDM-1, harboring the CBL mutation, were both more significantly suppressed than non-mutated cells following GC treatment in the presence of GM-CSF. A loss-of-function CBL mutation prolonged STAT5 phosphorylation after GM-CSF stimulation, which was rapidly terminated in both patient samples and GDM-1 cells. In conclusion, GC therapy effectively treats CMML cells harboring the MEFV SNV and CBL mutation by reducing inflammatory cytokine production and terminating prolonged STAT5 phosphorylation in the GM-CSF signaling pathway.

Pyrin Inflammasome Regulates Tight Junction Integrity to Restrict Colitis and Tumorigenesis

BACKGROUND & AIMS

Inflammatory bowel diseases (IBD) increase risk for colorectal cancer. Mutations in the Mediterranean fever gene (MEFV or pyrin) are associated with hereditary autoinflammatory disease and severe IBD. Expression of MEFV, a sensor protein that the initiates assembly of the inflammasome complex, is increased in colon biopsies from patients with IBD. We investigated the role of pyrin in intestinal homeostasis in mice.

METHODS

Mefv-/- mice and C57/BL6 mice (controls) were given azoxymethane followed by multiple rounds of dextran sodium sulfate (DSS) to induce colitis and tumorigenesis. In some experiments, Mefv-/- mice were given injections of recombinant interleukin 18 (rIL18) or saline (control) during DSS administration. Colon tissues were collected at different time points during colitis development and analyzed by histology, immunohistochemistry, immunoblots, or ELISAs (to measure cytokines). Spleen and mesenteric lymph node were collected, processed, and analyzed by flow cytometry. Colon epithelial permeability was measured in mice with colitis by gavage of fluorescent dextran and quantification of serum levels.

RESULTS

MEFV was expressed in colons of control mice and expression increased during chronic and acute inflammation; high levels were detected in colon tumor and adjacent non-tumor tissues. Mefv-/- mice developed more severe colitis than control mice, with a greater extent of epithelial hyperplasia and a larger tumor burden. Levels of inflammatory cytokines (IL6) and chemokines were significantly higher in colons of Mefv-/- mice than control mice following colitis induction, whereas the level IL18, which depends on the inflammasome for maturation and release, was significantly lower in colons of Mefv-/- mice. Mefv-/- mice had increased epithelial permeability following administration of DSS than control mice, and loss of the tight junction proteins occludin and claudin-2 from intercellular junctions. STAT3 was activated (phosphorylated) in inflamed colon tissues from Mefv-/-, which also had increased expression of stem cell markers (OLFM4, BMI1, and MSI1) compared with colons from control mice. Administration of rIL18 to Mefv-/- mice reduced epithelial permeability, intestinal inflammation, the severity of colitis, and colon tumorigenesis.

CONCLUSIONS

In studies with DSS-induced colitis, we found that pyrin (MEFV) is required for inflammasome activation and IL18 maturation, which promote intestinal barrier integrity and prevent colon inflammation and tumorigenesis. Strategies to increase activity of MEFV or IL18 might be developed for the treatment of IBD and prevention of colitis-associated tumorigenesis.

Inflammasome biology, molecular pathology and therapeutic implications

Inflammasomes are intracellular multiprotein signaling complexes, mainly present in myeloid cells. They commonly assemble around a cytoplasmic receptor of the nucleotide-binding leucine-rich repeat containing receptor (NLR) family, although other cytoplasmic receptors like pyrin have been shown to form inflammasomes. The nucleation of the multiprotein scaffolding platform occurs upon detection of a microbial, a danger or a homeostasis pattern by the receptor that will, most commonly, associate with the adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD) through homotypic domain interactions resulting in recruitment of procaspase-1. This will lead to the autoproteolytic activation of caspase-1, which regulates the secretion of proinflammatory IL1β and IL18 cytokines and pyroptosis, a caspase-1-mediated form of cell death. Pyroptosis occurs through cleavage of Gasdermin D, a membrane pore forming protein. Recently, non-canonical inflammasomes have been described, which directly sense intracellular pathogens through caspase-4 and -5 in humans, leading to pyroptosis. Inflammasomes are important in host defense; however, a deregulated activity is associated with a number of inflammatory, immune and metabolic disorders. Furthermore, mutations in inflammasome receptor coding genes are causal for an increasing number of rare autoinflammatory diseases. Biotherapies targeting the products of inflammasome activation as well as molecules that directly or indirectly inhibit inflammasome nucleation and activation are promising therapeutic areas. This review discusses recent advances in inflammasome biology, the molecular pathology of several inflammasomes, and current therapeutic approaches in autoinflammatory diseases and in selected common multifactorial inflammasome-mediated disorders.

Familial Mediterranean fever mimicking Crohn disease: A case report

RATIONALE

Familial Mediterranean fever (FMF) is the most common form of autoinflammatory disease. We report a rare case of FMF with gastrointestinal lesions mimicking Crohn disease.

PATIENT CONCERNS

A 21-year-old Japanese man was referred to our institution, complaining of refractory diarrhea and weight loss of 14 kg during the past two years. He had presented with recurrent fever, abdominal pain, anal fistula and stomatitis. His father and one of his brothers had ulcerative colitis. Colonoscopy revealed longitudinal ulcers in the terminal ileum and aphthous erosions in the colorectum. Esophagogastroduodenoscopy revealed multiple linear erosions in the gastric corpus and circular erosions in the duodenal second portion. Biopsy from these lesions failed to detect epithelioid cell granulomas.

DIAGNOSES

Analysis of the genomic DNA revealed compound heterozygous mutations of E148Q/L110P in exon 2 of MEFV gene, suggesting a diagnosis of FMF.

INTERVENTIONS

The patient was subsequently given 0.5 mg of colchicine per day.

OUTCOMES

Follow-up colonoscopy 6 months later demonstrated that both the longitudinal ulcers in the terminal ileum and aphthous lesions in the colorectum had completely disappeared.

LESSONS

Our case suggests that patients with FMF possibly manifest gastrointestinal lesions mimicking Crohn disease.

Small Intestinal Bacterial Overgrowth Affects the Responsiveness to Colchicine in Familial Mediterranean Fever

Objective

Familial Mediterranean fever (FMF) is an autosomal recessive disease due to a MEFV gene mutation. Since Helicobacter pylori infection has been described to increase the severity and frequency of FMF attacks, we evaluate if overgrowth of small intestinal bacterial (SIBO), associated with a release of bacterial products, can affect the response to colchicine in FMF patients poorly responsive to colchicine.

Methods

We revised our Periodic Fever Centre database to detect FMF patients who were poorly responsive to colchicine, without a well-defined cause of drug resistance. They were evaluated for SIBO presence, then treated with decontamination therapy.

Results

Among 223 FMF patients, 49 subjects show colchicine resistance, and no other known causes of colchicine unresponsiveness has been found in 25 patients. All 25 patients underwent glucose breath test; 20 (80%) of them were positive, thus affected by SIBO. After a successful decontamination treatment, 11 patients (55%) did not show FMF attacks during the following three months (p < 0.01), while 9 of them revealed a significant reduction of the number of attacks compared to three months before (p < 0.01).

Conclusion

The SIBO eradication improves laboratory and clinical features of FMF patients. Thus, patients with unresponsiveness to colchicine treatment should be investigated for SIBO.

A novel Pyrin-Associated Autoinflammation with Neutrophilic Dermatosis mutation further defines 14-3-3 binding of pyrin and distinction to Familial Mediterranean Fever

OBJECTIVE

Pyrin-Associated Autoinflammation with Neutrophilic Dermatosis (PAAND) is a recently described monogenic autoinflammatory disease. The causal p.S242R MEFV mutation disrupts a binding motif of the regulatory 14-3-3 proteins within pyrin. Here, we investigate a family with clinical features consistent with PAAND in whom the novel p.E244K MEFV mutation, located in the +2 site of the 14-3-3 binding motif in pyrin, has been found.

METHODS

Multiplex cytokine analyses were performed on p.E244K patient and control serum. Peripheral blood mononuclear cells were stimulated ex vivo with lipopolysaccharide (LPS). In vitro, inflammasome complex formation was evaluated by flow cytometry of Apoptosis-associated Speck-like protein containing a Caspase recruitment domain (ASC) specks. Interleukin-1β (IL-1β) and IL-18 production was quantified by ELISA. The ability of the p.E244K pyrin mutation to interact with 14-3-3 was assessed by immunoprecipitation.

RESULTS

PAAND p.E244K patient serum displayed a different cytokine profile compared with patients with Familial Mediterranean Fever (FMF). In overexpression models, p.E244K pyrin was associated with decreased 14-3-3 binding and increased ASC speck formation. THP-1 monocytes expressing PAAND pyrin mutations demonstrated spontaneous caspase-1-dependent IL-1β and IL-18 secretion, as well as cell death, which were significantly greater than those of wild-type and the FMF-associated mutation p.M694V.

CONCLUSION

In PAAND, disruption of the +2 position of a 14-3-3 binding motif in pyrin results in its constitutive activation, with spontaneous production of IL-1β and IL-18, associated with inflammatory cell death. The altered serum cytokine profile may explain the different clinical features exhibited by PAAND patients compared with those with FMF.

Molecular Pathophysiology of Gout

Three contradictory clinical presentations of gout have puzzled clinicians and basic scientists for some time: first, the crescendo of sterile inflammation in acute gouty arthritis; second, its spontaneous resolution, despite monosodium urate (MSU) crystal persistence in the synovium; and third, immune anergy to MSU crystal masses observed in tophaceous or visceral gout. Here, we provide an update on the molecular pathophysiology of these gout manifestations, namely, how MSU crystals can trigger the auto-amplification loop of necroinflammation underlying the crescendo of acute gouty arthritis. We also discuss new findings, such as how aggregating neutrophil extracellular traps (NETs) might drive the resolution of arthritis and how these structures, together with granuloma formation, might support immune anergy, but yet promote tissue damage and remodeling during tophaceous gout.

The detection of a novel insertion mutation in exon 2 of the MEFV gene associated with familial mediterranean fever in a moroccan family

Familial Mediterranean fever (FMF) is a hereditary autoinflammatory disease that is inherited in an autosomal recessive manner and is caused by mutations in the MEFV gene. As the name indicates, FMF occurs within families and is more common in individuals of Mediterranean descent than in persons of any other ethnicity. To date, 314 mutations have been reported. We studied a Moroccan family with a total of five members, including a mother who was presenting with symptoms of FMF, while her four children remained asymptomatic. The five patients were screened by DNA sequencing of exon 2 and exon 10 of the MEFV gene. Then, complete exome sequencing analysis of the MEFV gene was done for the patients in whom a novel mutation was detected. This analysis identified a novel single base Cytosine (C) insertion mutation in the coding region of the MEFV gene, named c.441dupC (p. Glu148Argfs*5 or E148RfsX5), which resulted in a mutated Pyrin/Marenostrin protein. This is the first report of a new mutation in exon 2 of the MEFV gene in a Moroccan family. This novel insertion mutation may provide important information for further studies of FMF pathogenesis.

Posttranslational Modification as a Critical Determinant of Cytoplasmic Innate Immune Recognition

Cell surface innate immune receptors can directly detect a variety of extracellular pathogens to which cytoplasmic innate immune sensors are rarely exposed. Instead, within the cytoplasm, the environment is rife with cellular machinery and signaling pathways that are indirectly perturbed by pathogenic microbes to activate intracellular sensors, such as pyrin, NLRP1, NLRP3, or NLRC4. Therefore, subtle changes in key intracellular processes such as phosphorylation, ubiquitination, and other pathways leading to posttranslational protein modification are key determinants of innate immune recognition in the cytoplasm. This concept is critical to establish the “guard hypothesis” whereby otherwise homeostatic pathways that keep innate immune sensors at bay are released in response to alterations in their posttranslational modification status. Originally identified in plants, evidence that a similar guardlike mechanism exists in humans has recently been identified, whereby a mutation that prevents phosphorylation of the innate immune sensor pyrin triggers a dominantly inherited autoinflammatory disease. It is also noteworthy that even when a cytoplasmic innate immune sensor has a direct ligand, such as bacterial peptidoglycan (NOD1 or NOD2), RNA (RIG-I or MDA5), or DNA (cGAS or IFI16), it can still be influenced by posttranslational modification to dramatically alter its response. Therefore, due to their existence in the cytoplasmic milieu, posttranslational modification is a key determinant of intracellular innate immune receptor functionality.

Interleukin-1β as emerging therapeutic target in hematological malignancies and potentially in their complications

Interleukin-1β (IL-1β) is a pleiotropic cytokine that exerts multiple roles in both physiological and pathological conditions. It is produced by different cell subsets, and drives a wide range of inflammatory responses in numerous target cells. Enhanced IL-1β signaling is a common event in patients of hematological malignancies. Recent body of evidence obtained in preclinical models shows the pathogenic role of these alterations, and the promising therapeutic value of IL-1 targeting. In this review, we further highlight a potential contribution of IL-1β linking to complications and autoimmune disease that should be investigated in future studies. Hence, drugs that target IL-1 may be helpful to improve outcome or reduce morbidity in patients. Some of them are FDA-approved, and used efficiently against autoimmune diseases, like IL-1 receptor antagonist. In the clinic, however, this agent seems to have limited properties. Current improved drugs will allow to determine the true potential of IL-1 and IL-1β targeting as therapy in hematological malignancies and their related complications.

TRIM22-Mediated Apoptosis is Associated with Bak Oligomerization in Monocytes

Monocyte apoptosis is a key mechanism that orchestrates host immune responses during sepsis. TRIM22 is constitutively expressed at high levels in monocytes and plays important roles in the antiviral response and inflammation. Overexpression of TRIM22 interferes with the clonogenic growth of monocytic cells, suggesting that TRIM22 may regulate monocyte survival. However, the effect of TRIM22 on monocyte apoptosis remains unknown. In the present report, lipopolysaccharides (LPS)-primed human peripheral blood monocytes expressing higher levels of TRIM22 were more sensitive to apoptosis. This phenomenon was also observed in TRIM22-overexpressing THP-1 monocytes and was associated with the activation of caspase-9 and caspase-3, as well as the increased expression and oligomerization of the pro-apoptotic protein Bak. Similar expression patterns of TRIM22 and Bak were also observed in LPS-primed, apoptotic human peripheral blood monocytes. In addition, the deletion of either the RING domain or the SPRY domain of TRIM22 significantly attenuated TRIM22-mediated monocyte apoptosis and decreased Bak expression and oligomerization. Furthermore, in monocytes from septic patients, TRIM22 levels were down-regulated and positively correlated with Bak levels. Taken together, these results indicate that TRIM22 plays a critical role in monocyte apoptosis by regulating Bak oligomerization and may have a potential function in the pathogenesis of sepsis.

Familial autoinflammation with neutrophilic dermatosis reveals a regulatory mechanism of pyrin activation

Pyrin responds to pathogen signals and loss of cellular homeostasis by forming an inflammasome complex that drives the cleavage and secretion of interleukin-1β (IL-1β). Mutations in the B30.2/SPRY domain cause pathogen-independent activation of pyrin and are responsible for the autoinflammatory disease familial Mediterranean fever (FMF). We studied a family with a dominantly inherited autoinflammatory disease, distinct from FMF, characterized by childhood-onset recurrent episodes of neutrophilic dermatosis, fever, elevated acute-phase reactants, arthralgia, and myalgia/myositis. The disease was caused by a mutation in MEFV, the gene encoding pyrin (S242R). The mutation results in the loss of a 14-3-3 binding motif at phosphorylated S242, which was not perturbed by FMF mutations in the B30.2/SPRY domain. However, loss of both S242 phosphorylation and 14-3-3 binding was observed for bacterial effectors that activate the pyrin inflammasome, such as Clostridium difficile toxin B (TcdB). The S242R mutation thus recapitulated the effect of pathogen sensing, triggering inflammasome activation and IL-1β production. Successful therapy targeting IL-1β has been initiated in one patient, resolving pyrin-associated autoinflammation with neutrophilic dermatosis. This disease provides evidence that a guard-like mechanism of pyrin regulation, originally identified for Nod-like receptors in plant innate immunity, also exists in humans.