Interleukin-36-receptor antagonist deficiency and generalized pustular psoriasis

Recurrent Fevers for the Pediatric Immunologist: It's Not All Immunodeficiency

Autoinflammatory diseases are disorders of the innate immune system, characterized by systemic inflammation independent of infection and autoreactive antibodies or antigen-specific T cells. Similar to immunodeficiencies, these immune dysregulatory diseases have unique presentations, genetics, and available therapies. Given the presentation of fevers, rashes, and mucosal symptoms in many of the disorders, the allergist/immunologist is the appropriate medical home for these patients: to appropriately rule out immunodeficiencies, evaluate for allergic disease, and diagnose and treat recurrent fever disorders. However, many practicing physicians are unfamiliar with the clinical presentation, diagnosis, and treatment of autoinflammatory disorders. This review will focus on understanding the signs and symptoms of classic autoinflammatory disorders, introduce newly described monogenic and polygenic disorders, and address the approach to the patient with recurrent fevers to distinguish autoinflammation from immunodeficiency and autoimmunity.

Genetically defined autoinflammatory diseases

Autoinflammatory diseases are hyperinflammatory, immune dysregulatory conditions that typically present in early childhood with fever and rashes and disease-specific patterns of organ inflammation. This review provides a historic background of autoinflammatory disease research, an overview of the currently genetically defined autoinflammatory diseases, and insights into treatment strategies derived from understanding of the disease pathogenesis. The integrative assessment of autoinflammatory conditions led to the identification of innate pro-inflammatory cytokine 'amplification loops' as the cause of the systemic and organ-specific disease manifestations, which initially centered around increased IL-1 production and signaling. More recently, additional innate pro-inflammatory cytokine amplification loops resulting in increased Type I IFN, IL-17, IL-18, or IL-36 signaling or production have led to the successful use of targeted therapies in some of these conditions. Clinical findings such as fever patterns, type of skin lesions, genetic mutation testing, and the prevalent cytokine abnormalities can be used to group autoinflammatory diseases.

Neutrophils in animal models of autoimmune disease

Neutrophils have traditionally been thought to play only a peripheral role in the genesis of many autoimmune and inflammatory diseases. However, recent studies in a variety of animal models suggest that these cells are central to the initiation and propagation of autoimmunity. The use of mouse models, which allow either deletion of neutrophils or the targeting of specific neutrophil functions, has revealed the many complex ways these cells contribute to autoimmune/inflammatory processes. This includes generation of self antigens through the process of NETosis, regulation of T-cell and dendritic cell activation, production of cytokines such as BAFF that stimulate self-reactive B-cells, as well as indirect effects on epithelial cell stability. In comparing the many different autoimmune models in which neutrophils have been examined, a number of common underlying themes emerge - such as a role for neutrophils in stimulating vascular permeability in arthritis, encephalitis and colitis. The use of animal models has also stimulated the development of new therapeutics that target neutrophil functions, such as NETosis, that may prove beneficial in human disease. This review will summarize neutrophil contributions in a number of murine autoimmune/inflammatory disease models.

Production of biologically active IL-36 family cytokines through insertion of N-terminal caspase cleavage motifs

Recent evidence has strongly implicated IL-36 cytokines as key initiators of inflammation in the skin barrier. IL-36 cytokines belong to the extended IL-1 family and, similar to most members of this family, are expressed as inactive precursors that require proteolytic processing for activation. Because the proteases responsible for activation of members of the IL-36 subfamily have not been reported, we have developed a method for the production of biologically active IL-36 through introduction of a caspase cleavage motif, DEVD, within the N-termini of these cytokines. Here, we show that DEVD-modified IL-36α, IL-36β and IL-36γ cytokines were highly soluble and were readily processed and activated by caspase-3. Caspase-3-processed IL-36 family cytokines exhibited robust biological activity on a range of responsive cell types, including primary keratinocytes. We also generated specific polyclonal antibodies against all three IL-36 family members through immunization with purified recombinant IL-36 cytokines. The modified forms of IL-36 described herein will be useful for production of large quantities of biologically active IL-36 for structure and function studies on these important proinflammatory cytokines.

One SNP at a Time: Moving beyond GWAS in Psoriasis

Although genome-wide association studies have revealed important insights into the global genetic basis of psoriasis, the findings require further investigation. At present, the known genetic risk loci are largely uncharacterized in terms of the variant or gene responsible for the association, the biological pathway involved, and the main cell type driving the pathology. This review primarily focuses on current approaches toward gaining a complete understanding of how these known genetic loci contribute to an increased disease risk in psoriasis.

The Interleukin-1 Family

The interleukin-1 (IL-1) family consists of several pro- or anti-inflammatory proteins, with pro-inflammatory IL-1β being its best characterized member. IL-1β is one of the most prominent mediators of inflammation resulting in fever and immune activation via binding to IL-1 receptor 1. Due to its potency, its secretion is tightly regulated. First the transcription of the biologically inactive proform is induced by TLR activation, TNF, or IL-1 receptor activation by mature IL-1α or IL-1β. For the secretion of IL-1β, inflammasome activation as second stimulus is needed. Inflammasomes are cytosolic protein complexes whose activation results in the maturation of inflammatory caspases such as caspase-1. Caspase-1 then cleaves the inactive pro-IL-1β into its mature form which is then being secreted. While IL-1α and IL-1β are considered pro-inflammatory, IL-1Ra as a naturally occurring receptor antagonist acts as an inhibitor on IL-1 receptor signaling. Further members of the IL-1 family, such as IL-18, IL-33, or IL-36, are even involved in T-helper-cell differentiation and will also be discussed in this chapter.

Integrative genomic analysis of interleukin-36RN and its prognostic value in cancer

Interleukin (IL)-36RN, previously known as IL1-F5 and IL-1δ, shares a 360-kb region of chromosome 2q13 with members of IL-1 systems. IL-36RN encodes an anti-inflammatory cytokine, IL-36 receptor antagonist (IL-36Ra). In spite of IL-36Ra showing the highest homology to IL-1 receptor (IL-1R) antagonist, it differs from the latter in aspects including its binding to IL-lRrp2 but not to IL-1R1. IL-36RN is mainly expressed in epithelial cells and has important roles in inflammatory diseases. In the present study, IL-36RN was identified in the genomes of 27 species, including human, chimpanzee, mouse, horse and dolphin. Human IL-36RN was mainly expressed in the eye, head and neck, fetal heart, lung, testis, cervix and placenta; furthermore, it was highly expressed in bladder and parathyroid tumors. Furthermore, a total of 30 single nucleotide polymorphisms causing missense mutations were determined, which are considered to be the causes of various diseases, such as generalized pustular psoriasis. In addition, the link between IL-36RN and the prognosis of certain cancer types was revealed through meta-analysis. Tumor-associated transcriptional factors c-Fos, activator protein-1, c-Jun and nuclear factor κB were found to bind to the upstream region in the IL-36RN gene. This may indicate that IL-36RN is involved in tumorigenesis and tumor progression through the regulation of tumor-associated transcriptional factors. The present study identified IL-36RN in various species and investigated the associations between IL-36RN and cancer prognosis, which would determine whether IL-36RN drove the evolution of the various species with regard to tumorigenesis.

A Case of Acute Generalized Pustular Psoriasis of von Zumbusch Triggered by Hypocalcemia

Psoriasis is an autoimmune disease triggered by different conditions in genetically susceptible people. It is characterized by variable cutaneous manifestations including localized or disseminated pustules. Generalized pustular psoriasis (GPP) has two main clinical forms: von Zumbusch psoriasis, characterized by severe erythrodermia and scaling skin after the resolution of pustules, and the annular form. GPP may also present severe extracutaneous manifestations including pneumonitis, heart failure and hepatitis. Old reports showed a relationship between hypoparathyroidism and hypocalcemia as triggers for GPP highlighting the importance of adequate workup of the patient and possible therapeutic changes in acute situations. Here, we present a case of severe von Zumbusch psoriasis with life-threatening complications triggered by severe hypocalcemia secondary to hypoparathyroidism successfully treated with aggressive calcium reposition.

Juvenile generalized pustular psoriasis with IL36RN mutation treated with short-term infliximab

A 8-year-old Chinese boy with generalized pustular psoriasis (GPP) refractory to cyclosporine and methylprednisolone was treated successfully with two infusions of infliximab 3.3 mg/kg. He remained in remission for 21 months. Direct sequencing of IL36RN gene showed a homozygous mutation, c.115 + 6T>C. Juvenile GPP is a rare severe form of psoriasis occasionally associated with life-threatening complications. Like acitretin, cyclosporine and methotrexate, infliximab has been reported to be effective for juvenile GPP in case reports. However, there is a lack of data in the optimal treatment course of infliximab for juvenile GPP. Prolonged administration of these medications may cause toxic or fatal complications. We suggest that short-term infliximab regimen should be recommended as a choice for acute juvenile GPP refractory to traditional systemic therapies. WBC count and CRP are sensitive parameters to reflect the disease activity and evaluate the effectiveness of treatment. Monitoring CD4 T lymphocyte count, preventing and correcting CD4 lymphocytopenia are important in the treatment course of juvenile GPP.

Cytokine and Chemokine Profile in Amicrobial Pustulosis of the Folds: Evidence for Autoinflammation

Autoinflammation has recently been suggested in the pathogenesis of neutrophilic dermatoses but systematic studies on their cytokine profile are lacking. Notably, amicrobial pustulosis of the folds (APF), classified among neutrophilic dermatoses, has been studied only in small case series. In our University Hospital, we conducted an observational study on 15 APF patients, analyzing their clinical and laboratory features with a follow-up of 9 months to 20 years. Skin cytokine pattern of 9 of them was compared to that of 6 normal controls. In all patients, primary lesions were pustules symmetrically involving the skin folds and anogenital region with a chronic-relapsing course and responding to corticosteroids. Dapsone, cyclosporine, and tumor necrosis factor blockers were effective in refractory cases. In skin samples, the expressions of interleukin (IL)-1β, pivotal cytokine in autoinflammation, and its receptors I and II were significantly higher in APF (P = 0.005, 0.018, and 0.034, respectively) than in controls. Chemokines responsible for neutrophil recruitment such as IL-8 (P = 0.003), CXCL 1/2/3 (C-X-C motif ligand 1/2/3) (P = 0.010), CXCL 16 (P = 0.045), and RANTES (regulated on activation, normal T cell expressed and secreted) (P = 0.034) were overexpressed. Molecules involved in tissue damage like matrix metalloproteinase-2 (MMP-2) (P = 0.010) and MMP-9 (P = 0.003) were increased. APF is a pustular neutrophilic dermatosis with a typical distribution in all patients. The disorder may coexist with an underlying autoimmune/dysimmune disease but is often associated only with a few autoantibodies without a clear autoimmunity. The overexpression of cytokines/chemokines and molecules amplifying the inflammatory network supports the view that APF has an important autoinflammatory component.

Correlation of IL36RN mutation with different clinical features of pustular psoriasis in Chinese patients

Different studies have reported various values for the percentage of patients with IL36RN mutations, and it has also been reported that the sites of these mutations differ among different ethnicities. The current study was a cross-sectional study conducted to investigate the risk factors predicting IL36RN mutation in Chinese patients with different clinical features of pustular psoriasis. 57 Han Chinese patients, including 32 with generalized pustular psoriasis, 14 with palmoplantar pustulosis, 9 with plaque-type psoriasis with pustules, and 2 with erythrodermic psoriasis, were enrolled between March 2013 and July 2014. Blood samples were collected, genomic DNA was extracted from leukocytes, and polymerase chain reaction (PCR)-based Sanger sequencing was used to analyze the coding exons and flanking introns of the IL36RN gene. The patients with generalized pustular psoriasis exhibited the highest IL36RN mutation rate (75 %) among the aforementioned patient types, with the subgroup consisting of those patients who had features of acrodermatitis continua of Hallopeau exhibiting the highest c.115+6T>C mutation rate (93.8 %). In addition, early onset, ever generalized pustular psoriasis (more than two attacks), ever acrodermatitis continua of Hallopeau, inverse psoriasis, and a family history of pustular psoriasis were associated with IL36RN mutation. The c.115+6T>C mutation was the most common and the most important variant in all subtypes of pustular psoriasis with IL36RN mutations among our sample of Chinese patients.

CARD14 alterations in Tunisian patients with psoriasis and further characterization in European cohorts

BACKGROUND

Rare highly penetrant gain-of-function mutations in caspase recruitment domain family, member 14 (CARD14) can lead to psoriasis, a chronic inflammatory disease of the skin and other organs.

OBJECTIVES

To investigate the contribution of rare CARD14 variants to psoriasis in the Tunisian population and to expand knowledge of CARD14 variants in the European population.

METHODS

CARD14 coding exons were resequenced in patients with psoriasis and controls from Tunisia and Europe, including 16 European cases with generalized pustular psoriasis (GPP). Novel variants were evaluated for their effect on nuclear factor (NF)-κB signalling.

RESULTS

Rare variants in CARD14 were significantly enriched in Tunisian cases compared with controls. Three were collectively found in 5% of Tunisian cases, and all affected the N-terminal region of the protein harbouring its caspase recruitment domain or coiled-coil domain. These variants were c.349G>A (p.Gly117Ser), c.205C>T (p.Arg69Trp) and c.589G>A (p.Glu197Lys). c.589G>A (p.Glu197Lys) led to upregulation of NF-κB activity in a similar manner to that of previously described psoriasis-associated mutations. p.Arg69Trp led to sevenfold downregulation of NF-κB activity. One Tunisian case harboured a c.1356+5G>A splice alteration that is predicted to lead to loss of exon 9, which encodes part of the coiled-coil domain. No cases of GPP harboured an interleukin-36RN mutation, but one of 16 cases of GPP with a family history of psoriasis vulgaris harboured a c.1805C>T (p.Ser602Leu) mutation in CARD14.

CONCLUSIONS

These observations provide further insights into the genetic basis of psoriasis in the Tunisian population and provide functional information on novel CARD14 variants seen in cases from Tunisia and other populations.

Update on psoriasis immunopathogenesis and targeted immunotherapy

Over recent years, significant progress has been made in characterisation of the underlying pathogenic mechanisms in psoriasis, a common cutaneous disease that is associated with major systemic co-morbidity and reduced life expectancy. Basic science discoveries have informed the design of novel therapeutic approaches, many of which are now under evaluation in late-stage clinical trials. Here we describe the complex interplay between immune cell types and cytokine networks that acts within self-perpetuating feedback loops to drive cutaneous inflammation in psoriasis. Genetic studies have been pivotal in the construction of the disease model and more recently have uncovered a distinct aetiology for rare, pustular variants of psoriasis. The translation of mechanistic insights into potential advancements in clinical care will also be described, including several treatments that target the interleukin-23 (IL-23)/T17 immune axis.

[Recurrent fevers in childhood]

Recurrent fevers are defined as multiple stereotypical febrile episodes separated by spontaneous symptom-free intervals and occurring for months and years. Hereditary recurrent fevers are rare prototype Mendelian diseases due to inherited mutations in genes encoding partners of the innate immunity. Recurrent episodes of fever plus acute features of inflammation starting during childhood with family history are the main clues for suspecting HRF. Their common associated complication is AA amyloidosis. The diagnosis is made on clinical grounds but the genetic diagnosis may contribute in most cases of monogenic hereditary recurrent fevers. Recurrent fevers must be distinguished from intermittent fevers, mostly infectious, characterized by variation in associated symptoms from episode-to-episode and without periodicity.

Interleukin-1 Family Cytokines in Liver Diseases

The gene encoding IL-1 was sequenced more than 30 years ago, and many related cytokines, such as IL-18, IL-33, IL-36, IL-37, IL-38, IL-1 receptor antagonist (IL-1Ra), and IL-36Ra, have since been identified. IL-1 is a potent proinflammatory cytokine and is involved in various inflammatory diseases. Other IL-1 family ligands are critical for the development of diverse diseases, including inflammatory and allergic diseases. Only IL-1Ra possesses the leader peptide required for secretion from cells, and many ligands require posttranslational processing for activation. Some require inflammasome-mediated processing for activation and release, whereas others serve as alarmins and are released following cell membrane rupture, for example, by pyroptosis or necroptosis. Thus, each ligand has the proper molecular process to exert its own biological functions. In this review, we will give a brief introduction to the IL-1 family cytokines and discuss their pivotal roles in the development of various liver diseases in association with immune responses. For example, an excess of IL-33 causes liver fibrosis in mice via activation and expansion of group 2 innate lymphoid cells to produce type 2 cytokines, resulting in cell conversion into pro-fibrotic M2 macrophages. Finally, we will discuss the importance of IL-1 family cytokine-mediated molecular and cellular networks in the development of acute and chronic liver diseases.

Practice parameter for the diagnosis and management of primary immunodeficiency

The American Academy of Allergy, Asthma & Immunology (AAAAI) and the American College of Allergy, Asthma & Immunology (ACAAI) have jointly accepted responsibility for establishing the "Practice parameter for the diagnosis and management of primary immunodeficiency." This is a complete and comprehensive document at the current time. The medical environment is a changing environment, and not all recommendations will be appropriate for all patients. Because this document incorporated the efforts of many participants, no single individual, including those who served on the Joint Task Force, is authorized to provide an official AAAAI or ACAAI interpretation of these practice parameters. Any request for information about or an interpretation of these practice parameters by the AAAAI or ACAAI should be directed to the Executive Offices of the AAAAI, the ACAAI, and the Joint Council of Allergy, Asthma & Immunology. These parameters are not designed for use by pharmaceutical companies in drug promotion.

Psoriasis

Psoriasis is an immune-mediated, genetic disease manifesting in the skin or joints or both. A diverse team of clinicians with a range of expertise is often needed to treat the disease. Psoriasis provides many challenges including high prevalence, chronicity, disfiguration, disability, and associated comorbidity. Understanding the role of immune function in psoriasis and the interplay between the innate and adaptive immune system has helped to manage this complex disease, which affects patients far beyond the skin. In this Seminar, we highlight the clinical diversity of psoriasis and associated comorbid diseases. We describe recent developments in psoriasis epidemiology, pathogenesis, and genetics to better understand present trends in psoriasis management. Our key objective is to raise awareness of the complexity of this multifaceted disease, the potential of state-of-the-art therapeutic approaches, and the need for early diagnosis and comprehensive management of patients with psoriasis.

[Autoinflammatory syndromes in childhood]

Systemic autoinflammatory diseases are a group of hereditary and non-hereditary diseases of the innate immune system, characterized by inflammation with no apparent cause, recurrence at irregular intervals and manifestation on the skin, mucous membranes, joints, bone, gastrointestinal tract, blood vessels and the central nervous system (CNS). Amyloidosis and other possibly severe long-term complications are important. Advances in genetics and molecular biology have improved understanding of the pathogenesis of these diseases, including familial Mediterranean fever, mevalonate kinase deficiency syndrome, tumor necrosis factor receptor-associated periodic syndrome, cryopyrin-associated periodic syndrome and improved others. The vast majority of these diseases are based on activation of the interleukin-1 (IL-1) pathway, so that inhibition of IL-1 provides a therapeutic option. Other syndromes are characterized by a granulomatous inflammation. Newer autoinflammatory diseases, such as chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperature (CANDLE) and stimulator of interferon genes (STING)-associated vasculopathy with onset in infancy (SAVI) are, however, driven by interferons.

Redox distress and genetic defects conspire in systemic autoinflammatory diseases

Inflammation is initiated by innate immune cell activation after contact with pathogens or tissue injury. An increasing number of observations have suggested that cellular stress, in the absence of infection or evident damage, can also induce inflammation. Thus, inflammation can be triggered by exogenous pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs)-so-called classic inflammation-or by endogenous stress resulting from tissue or cellular dysfunction. External triggers and cellular stress activate the same molecular pathways, possibly explaining why classic and stress-induced inflammation have similar clinical manifestations. In some systemic autoinflammatory diseases (SAIDs), inflammatory cells exhibit reduction-oxidation (redox) distress, having high levels of reactive oxygen species (ROS), which promote proinflammatory cytokine production and contribute to the subversion of mechanisms that self-limit inflammation. Thus, SAIDs can be viewed as a paradigm of stress-related inflammation, being characterized by recurrent flares or chronic inflammation (with no recognizable external triggers) and by a failure to downmodulate this inflammation. Here, we review SAID pathophysiology, focusing on the major cytokines and DAMPs, and on the key roles of redox distress. New therapeutic opportunities to tackle SAIDs by blocking stress-induced pathways and control the response to stress in patients are also discussed.

Deep Sequencing of the T-cell Receptor Repertoire Demonstrates Polyclonal T-cell Infiltrates in Psoriasis

It is well known that infiltration of pathogenic T-cells plays an important role in psoriasis pathogenesis. However, the antigen specificity of these activated T-cells is relatively unknown. Previous studies using T-cell receptor polymerase chain reaction technology (TCR-PCR) have suggested there are expanded T-cell receptor (TCR) clones in psoriatic skin, suggesting a response to an unknown psoriatic antigen. Here we describe the results of high-throughput deep sequencing of the entire αβ- and γδ- TCR repertoire in normal healthy skin and psoriatic lesional and non-lesional skin. From this study, we were able to determine that there is a significant increase in the abundance of unique β- and γ- TCR sequences in psoriatic lesional skin compared to non-lesional and normal skin, and that the entire T-cell repertoire in psoriasis is polyclonal, with similar diversity to normal and non-lesional skin. Comparison of the αβ- and γδ- TCR repertoire in paired non-lesional and lesional samples showed many common clones within a patient, and these close were often equally abundant in non-lesional and lesional skin, again suggesting a diverse T-cell repertoire. Although there were similar (and low) amounts of shared β-chain sequences between different patient samples, there was significantly increased sequence sharing of the γ-chain in psoriatic skin from different individuals compared to those without psoriasis. This suggests that although the T-cell response in psoriasis is highly polyclonal, particular γδ- T-cell subsets may be associated with this disease. Overall, our findings present the feasibility of this technology to determine the entire αβ- and γδ- T-cell repertoire in skin, and that psoriasis contains polyclonal and diverse αβ- and γδ- T-cell populations.

Elderly-Onset Generalized Pustular Psoriasis without a Previous History of Psoriasis Vulgaris

Generalized pustular psoriasis (GPP) is characterized by sudden fever and extensive erythema with pustules and occurs in patients with or without preceding psoriasis vulgaris. We report an 83-year-old man showing irregularly shaped erythema with pustules on the trunk and extremities. He initially had no fever and came to our clinic a few days after the onset of the skin lesions because of high fever and general malaise. We found an extension and new development of erythema and pustules on the whole body. The patient also manifested night delirium. Histological examination revealed neutrophil infiltration into the upper epidermis, which formed a spongiform pustule of Kogoj. Pustular fluid cultures were negative for bacteria. We diagnosed GPP without preceding psoriasis vulgaris. Mutation analysis revealed no significant mutations in IL36RN and CARD14. Previous reports indicated that onset of GPP at the age of 83 years is definitely rare. In older individuals, general disease characteristics include an atypical clinical course, an especially slow appearance and cure, and mental disorder. Our case also revealed such characteristics. Thus, it is necessary to be aware of the clinical course and mental problems in elderly patients with GPP.

The immunogenetics of Psoriasis: A comprehensive review

Psoriasis vulgaris is a common, chronic inflammatory skin disease with a complex etiology involving genetic risk factors and environmental triggers. Here we describe the many known genetic predispositions of psoriasis with respect to immune genes and their encoded pathways in psoriasis susceptibility. These genes span an array of functions that involve antigen presentation (HLA-Cw6, ERAP1, ERAP2, MICA), the IL-23 axis (IL12Bp40, IL23Ap19, IL23R, JAK2, TYK2), T-cell development and T-cells polarization (RUNX1, RUNX3, STAT3, TAGAP, IL4, IL13), innate immunity (CARD14, c-REL, TRAF3IP2, DDX58, IFIH1), and negative regulators of immune responses (TNIP1, TNFAIP3, NFKBIA, ZC3H12C, IL36RN, SOCS1). The contribution of some of these gene products to psoriatic disease has also been revealed in recent years through targeting of key immune components, such as the Th17/IL-23 axis which has been highly successful in disease treatment. However, many of the genetic findings involve immune genes with less clear roles in psoriasis pathogenesis. This is particularly the case for those genes involved in innate immunity and negative regulation of immune specific pathways. It is possible that risk alleles of these genes decrease the threshold for the initial activation of the innate immune response. This could then lead to the onslaught of the pathogenic adaptive immune response known to be active in psoriatic skin. However, precisely how these various genes affect immunobiology need to be determined and some are speculated upon in this review. These novel genetic findings also open opportunities to explore novel therapeutic targets and potentially the development of personalized medicine, as well as discover new biology of human skin disease.

Unprocessed Interleukin-36α Regulates Psoriasis-Like Skin Inflammation in Cooperation With Interleukin-1

Generalized pustular psoriasis is a severe skin disease characterized by epidermal hyperplasia, neutrophil-rich abscesses within the epidermis, and a mixed inflammatory infiltrate in the dermis. The disease may be caused by missense mutations in the IL-36 receptor antagonist, IL-36Ra. Curiously, the related IL-1Ra has therapeutic effects in some of these latter patients. Here, using an experimental mouse model of psoriasiform skin inflammation, we demonstrate in vivo connections between IL-36 and IL-1 expression. After disease initiation, IL-36α-deficient mice exhibited dramatically diminished skin pathology, including absence of epidermal neutrophils, reduced keratinocyte acanthosis, and less dermal edema. In contrast, IL-36β and IL-36γ knockout mice developed disease indistinguishable from that of wild-type mice. The endogenous IL-36α was not processed through proteolysis. Although IL-36α expression was strongly induced in an IL-1 signaling-dependent manner during disease, expression of IL-1α was also dependent upon IL-36α. Hence, after being upregulated by IL-1α, IL-36α acts through a feedback mechanism to boost IL-1α levels. Analyses of double knockout mice further revealed that IL-36α and IL-1α cooperate to promote psoriasis-like disease. In conclusion, IL-1α and IL-36α form a self-amplifying inflammatory loop in vivo that in patients with insufficient counter regulatory mechanisms may become hyper-engaged and/or chronic.

The interleukin (IL)-1 cytokine family--Balance between agonists and antagonists in inflammatory diseases

The interleukin (IL)-1 family of cytokines comprises 11 members, including 7 pro-inflammatory agonists (IL-1α, IL-1β, IL-18, IL-33, IL-36α, IL-36β, IL-36γ) and 4 defined or putative antagonists (IL-1R antagonist (IL-1Ra), IL-36Ra, IL-37, and IL-38) exerting anti-inflammatory activities. Except for IL-1Ra, IL-1 cytokines do not possess a leader sequence and are secreted via an unconventional pathway. In addition, IL-1β and IL-18 are produced as biologically inert pro-peptides that require cleavage by caspase-1 in their N-terminal region to generate active proteins. N-terminal processing is also required for full activity of IL-36 cytokines. The IL-1 receptor (IL-1R) family comprises 10 members and includes cytokine-specific receptors, co-receptors and inhibitory receptors. The signaling IL-1Rs share a common structure with three extracellular immunoglobulin (Ig) domains and an intracellular Toll-like/IL-1R (TIR) domain. IL-1 cytokines bind to their specific receptor, which leads to the recruitment of a co-receptor and intracellular signaling. IL-1 cytokines induce potent inflammatory responses and their activity is tightly controlled at the level of production, protein processing and maturation, receptor binding and post-receptor signaling by naturally occurring inhibitors. Some of these inhibitors are IL-1 family antagonists, while others are IL-1R family members acting as membrane-bound or soluble decoy receptors. An imbalance between agonist and antagonist levels can lead to exaggerated inflammatory responses. Several genetic modifications or mutations associated with dysregulated IL-1 activity and autoinflammatory disorders were identified in mouse models and in patients. These findings paved the road to the successful use of IL-1 inhibitors in diseases that were previously considered as untreatable.

Genetics of psoriasis

Psoriasis is a common and debilitating immune-mediated skin disease with a complex genetic basis. Genetic studies have provided critical insights into the pathogenesis of disease. This article focuses on the results of genetic association studies, which provide evidence that psoriasis susceptibility genes are involved in innate and adaptive immunity and skin barrier functions. The potential for disease stratification and the development of more effective treatments with fewer side effects using genetic data are highlighted.

A Review and Proposed Approach to the Neutrophilic Dermatoses of Childhood

Neutrophilic dermatoses (NDs) are inflammatory skin conditions that are not associated with infection. The classification and clinical approach to these conditions in children is poorly described. This review classifies these conditions into five nosological subtypes: Sweet's syndrome, pyoderma gangrenosum, aseptic pustules, neutrophilic urticarial dermatoses, and Marshall's syndrome. In addition, we review the various secondary diseases that need to be excluded in the clinical management of the NDs of childhood, with a focus on the autoinflammatory conditions that the reader may not be familiar with. We propose a practical clinical approach to these disorders.

When less is more: primary immunodeficiency with an autoinflammatory kick

Purpose of review

Next-generation sequencing is revolutionizing the molecular taxonomy of human disease. Recent studies of patients with unexplained autoinflammatory disorders reveal germline genetic mutations that target important regulators of innate immunity.

Recent findings

Whole-exome analyses of previously undiagnosed patients have catalyzed the recognition of two new disease genes. First, a phenotypic spectrum, including livedo racemosa, fever with early-onset stroke, polyarteritis nodosa, and Sneddon syndrome, is caused by loss-of-function mutations in cat eye syndrome chromosome region, candidate 1 (CECR1), encoding adenosine deaminase 2. Adenosine deaminase 2 is a secreted protein expressed primarily in myeloid cells, and a regulator of macrophage differentiation and endothelial development. Disease-associated mutations impair anti-inflammatory M2 macrophage differentiation. Second, patients presenting with cold-induced urticaria, granulomatous rash, autoantibodies, and common variable immunodeficiency, or with blistering skin lesions, bronchiolitis, enterocolitis, ocular inflammation, and mild immunodeficiency harbor distinct mutations in phospholipase Cγ₂, encoding a signaling molecule expressed in natural killer cells, mast cells, and B lymphocytes. These mutations inhibit the function of a phospholipase Cγ₂ autoinhibitory domain, causing increased or constitutive signaling.

Summary

These findings underscore the power of next-generation sequencing, demonstrating how the primary deficiency of key molecular regulators or even regulatory motifs may lead to autoinflammation, and suggesting a possible role for cat eye syndrome chromosome region, candidate 1 and phospholipase Cγ₂ in common diseases.

Interleukin-1 family cytokines and their regulatory proteins in normal pregnancy and pre-eclampsia

Maternal systemic inflammation is a feature of pre-eclampsia, a condition in pregnancy characterized by hypertension and proteinuria. Pre-eclampsia is caused by the placenta; many placental factors contribute to the syndrome's progression, and proinflammatory cytokines have been identified previously as one such mediator. The interleukin (IL)-1 family of cytokines are key regulators of the inflammatory network, and two naturally occurring regulatory molecules for IL-1 family cytokines, IL-1RA and sST2, have been found previously to be elevated in maternal blood from women with pre-eclampsia. Here we investigate more recently identified IL-1 family cytokines and regulatory molecules, IL-1RAcP, IL-37, IL-18BP, IL-36α/β/γ/Ra and IL-38 in pre-eclampsia. Pregnant women have more circulating IL-18BP and IL-36Ra than non-pregnant women, and sIL-1RAcP is elevated from women with pre-eclampsia compared to normal pregnancies. The placenta expresses all the molecules, and IL-37 and IL-18BP are up-regulated significantly in pre-eclampsia placentas compared to those from normal pregnancies. Together, these changes contribute to the required inhibition of maternal systemic cytotoxic immunity in normal pregnancy; however, in pre-eclampsia the same profile is not seen. Interestingly, the increased circulating levels of sIL-1RAcP and increased placental IL-18BP and IL-37, the latter of which we show to be induced by hypoxic damage to the placenta, are all factors which are anti-inflammatory. While the placenta is often held responsible for the damage and clinical symptoms of pre-eclampsia by the research community, here we show that the pre-eclampsia placenta is also trying to prevent inflammatory damage to the mother.

From bench to bedside and back again: translational research in autoinflammation

Translational research approaches brought major changes to the understanding and treatment options of autoinflammatory diseases. Patients with common complex multifactorial diseases such as systemic-onset juvenile idiopathic arthritis (sJIA), and particularly those with rare monogenic autoinflammatory diseases such as cryopyrin-associated periodic syndromes (CAPS) or TNF receptor-associated periodic syndrome (TRAPS), benefited from a deeper understanding of the pathophysiological mechanisms and new treatment options emerging from preclinical studies. The study of IL-1 and IL-6 in this context led to novel therapies by forward translation. Conversely, effective treatment of sJIA and TRAPS with IL-1 blockade stimulated reverse translational efforts to study the pathophysiology of these cytokines in autoinflammatory diseases. These translational efforts led to the discovery of biomarkers such as S100 proteins, IL-18 or serum amyloid A, which are components of the inflammatory process, support diagnosis and allow for monitoring of disease activity, helping to predict patient outcomes. The ongoing characterization of autoinflammatory diseases in individual patients has led to classification into heterogeneous subgroups. Further characterization of relevant subgroups and the design of tailored treatment regimens, as well as the identification of new therapeutic targets and treatment options, are the major future challenges in the field of autoinflammatory diseases, particularly for paediatric rheumatologists.

Regulating against the dysregulation: new treatment options in autoinflammation

In autoinflammatory disorders, dysregulation of the innate immune response leads to an excessive cytokine release. The disease course is often characterized by high morbidity and mortality, treatment is mostly difficult and therapeutic options are limited. In most cases, life-long control of ongoing inflammation is necessary in order to improve clinical symptoms and prevent development of damage. Steroids are helpful in many conditions, but the development of serious side effects often limits their long-term use. Other immunosuppressive, steroid-sparing medications are less effective than in the treatment of autoimmune diseases or do not show any effect. So far, anti-IL1α and/or β-blocking agents as well as an IL-6 receptor-blocking monoclonal antibody and, to a lesser extent, TNF-α blocking agents were applied in autoinflammatory disorders and significantly improved the outcome. Although these progresses were made in the last years, there are still numerous challenges in order to improve drug therapy in autoinflammation. This review summarizes the current state of new drug development and discusses advantages and disadvantages of possible targets.

Notch down-regulation in regenerated epidermis contributes to enhanced expression of interleukin-36α and suppression of keratinocyte differentiation during wound healing

BACKGROUND

Notch signaling controls a number of cellular processes, including cell fate decisions, proliferation, differentiation, and survival/apoptosis, in multiple tissues. In the epidermis, Notch1 functions as a molecular switch that controls the transition of cells from an undifferentiated state into a differentiated state.

OBJECTIVE

To clarify the functions of Notch in the regenerated epidermis during wound healing.

METHODS

Wounds on mouse skin were immunostained. To investigate the functions of Notch, Notch was inhibited in primary keratinocytes by treatment with a γ-secretase inhibitor and by small interfering RNA-mediated knockdown, and was activated by a recombinant adenovirus approach.

RESULTS

Notch1 and Notch2 were down-regulated in the regenerated epidermis during wound healing. To clarify the significance of this down-regulation, we examined its effect on expression of the interleukin (IL)-1 family of proinflammatory cytokines because wounds are exposed to pathogens from the outside world. Among the IL-1 family, IL-36α expression was induced by Notch inhibition. This was consistent with the decreased IL-36α expression in Notch-overexpressing keratinocytes. Notch down-regulation in the regenerated epidermis may reinforce defense against stress from the outside world by inducing IL-36α expression. Next, we examined the effects of Notch down-regulation on keratinocyte growth and differentiation. Notch down-regulation did not alter keratinocyte proliferation. On the other hand, Notch1 down-regulation suppressed induction of spinous layer-specific keratins (keratin1 and keratin10) in keratinocytes, which was consistent with the decreased expression of these keratins in the regenerated epidermis. The reduced levels of these keratins would increase cellular flexibility.

CONCLUSION

Notch down-regulation in the epidermis appears to contribute to tissue regeneration during wound healing.

Reactive oxygen species in psoriasis and psoriasis arthritis: relevance to human disease

Psoriasis (Ps) is a chronic, immune-mediated, skin inflammatory disease affecting up to 3% of the population worldwide. Different environmental triggers initiate this complex multifactorial syndrome. Many individuals affected by Ps (6-26%) develop inflammatory disease in other organs, often in the joints as in psoriasis arthritis (PsA). Animal models that reflect the typical Ps syndrome, including both skin and joint pathology as in Ps and PsA, are valuable tools for dissecting disease pathways leading to clinical manifestations. In this context, we developed a new acute Ps and PsA-like disease model that appears after exposure to Saccharomyces cerevisiae mannan in certain mouse strains. The disease was found to be triggered by mannan-activated macrophages, leading to the activation of a pathogenic interleukin-17 pathway involving innate lymphocytes. Interestingly, the production of reactive oxygen species protected the mice from the triggering of this pathway and ameliorated Ps and PsA development.