Interleukin-36-receptor antagonist deficiency and generalized pustular psoriasis

Untangling the web of systemic autoinflammatory diseases

The innate immune system is involved in the pathophysiology of systemic autoinflammatory diseases (SAIDs), an enlarging group of disorders caused by dysregulated production of proinflammatory cytokines, such as interleukin-1β and tumor necrosis factor-α, in which autoreactive T-lymphocytes and autoantibodies are indeed absent. A widely deranged innate immunity leads to overactivity of proinflammatory cytokines and subsequent multisite inflammatory symptoms depicting various conditions, such as hereditary periodic fevers, granulomatous disorders, and pyogenic diseases, collectively described in this review. Further research should enhance our understanding of the genetics behind SAIDs, unearth triggers of inflammatory attacks, and result in improvement for their diagnosis and treatment.

IL-6 as a druggable target in psoriasis: focus on pustular variants

Psoriasis vulgaris (PV) is a cutaneous inflammatory disorder stemming from abnormal, persistent activation of the interleukin- (IL-)23/Th17 axis. Pustular psoriasis (PP) is a clinicopathological variant of psoriasis, histopathologically defined by the predominance of intraepidermal collections of neutrophils. Although PP pathogenesis is thought to largely follow that of (PV), recent evidences point to a more central role for IL-1, IL-36, and IL-6 in the development of PP. We review the role of IL-6 in the pathogenesis of PV and PP, focusing on its cross-talk with cytokines of the IL-23/Th17 axis. Clinical inhibitors of IL-6 signaling, including tocilizumab, have shown significant effectiveness in the treatment of several inflammatory rheumatic diseases, including rheumatoid arthritis and juvenile idiopathic arthritis; accordingly, anti-IL-6 agents may potentially represent future promising therapies for the treatment of PP.

DNAX-activating protein 10 (DAP10) membrane adaptor associates with receptor for advanced glycation end products (RAGE) and modulates the RAGE-triggered signaling pathway in human keratinocytes

The receptor for advanced glycation end products (RAGE) is involved in the pathogenesis of many inflammatory, degenerative, and hyperproliferative diseases, including cancer. Previously, we revealed mechanisms of downstream signaling from ligand-activated RAGE, which recruits TIRAP/MyD88. Here, we showed that DNAX-activating protein 10 (DAP10), a transmembrane adaptor protein, also binds to RAGE. By artificial oligomerization of RAGE alone or RAGE-DAP10, we found that RAGE-DAP10 heterodimer formation resulted in a marked enhancement of Akt activation, whereas homomultimeric interaction of RAGE led to activation of caspase 8. Normal human epidermal keratinocytes exposed to S100A8/A9, a ligand for RAGE, at a nanomolar concentration mimicked the pro-survival response of RAGE-DAP10 interaction, although at a micromolar concentration, the cells mimicked the pro-apoptotic response of RAGE-RAGE. In transformed epithelial cell lines, A431 and HaCaT, in which endogenous DAP10 was overexpressed, and S100A8/A9, even at a micromolar concentration, led to cell growth and survival due to RAGE-DAP10 interaction. Functional blocking of DAP10 in the cell lines abrogated the Akt phosphorylation from S100A8/A9-activated RAGE, eventually leading to an increase in apoptosis. Finally, S100A8/A9, RAGE, and DAP10 were overexpressed in the psoriatic epidermis. Our findings indicate that the functional interaction between RAGE and DAP10 coordinately regulates S100A8/A9-mediated survival and/or apoptotic response of keratinocytes.

Pustular psoriasis complicated with acute generalized exanthematous pustulosis

BACKGROUND

Pustular psoriasis of the digits (acrodermatitis continua of Hallopeau) may be localized to one or more digits for over an extended period of time. Characteristic presentation is that of tender, diffusely eroded, and fissured pustular plaques on one or more digits. Transition to other forms of psoriasis and to generalized pustular psoriasis is known to occur. These patients have an increased risk of acute generalized exanthematous pustulosis (AGEP) compared to the general population. Pustular psoriasis is often therapy resistant.

MAIN OBSERVATIONS

We report the case of a 54-year-old Caucasian woman who presented with a pustular psoriasis flare complicated by AGEP. Treatment course included hospital admission, cyclosporine, acitretin, and discontinuation of cephalexin.

CONCLUSION

The precipitating factor in the course of treatment is thought to be cephalexin. When treating patients with pustular psoriasis the occurrence of druginduced complications should be carefully examined. Our case suggests that avoidance of β-lactam antibiotics in these patients is warranted unless absolutely indicated.

Monogenic autoinflammatory diseases

During the past 15 years, a growing number of monogenic inflammatory diseases have been described and their respective responsible genes identified. The proteins encoded by these genes are involved in the regulatory pathways of inflammation and are mostly expressed in cells of the innate immune system. Diagnosis remains clinical, with genetic confirmation where feasible. Although a group of patients exhibit episodic systemic inflammation (periodic fevers), these disorders are mediated by continuous overproduction and release of pro-inflammatory mediators, such as IL-1 and IL-6, and TNF and are best considered as autoinflammatory diseases rather than periodic fevers. Treatment with biologic agents that block these cytokines, particularly IL-1, has proved to be dramatically effective in some patients. Still, in many cases of autoinflammation no genetic abnormalities are detected and treatment remains suboptimal, raising the question of novel pathogenic mutations in unexplored genes and pathways.

IL-36 promotes myeloid cell infiltration, activation, and inflammatory activity in skin

The IL-1 family members IL-36α (IL-1F6), IL-36β (IL-1F8), and IL-36γ (IL-1F9) and the receptor antagonist IL-36Ra (IL-1F5) constitute a novel signaling system that is poorly understood. We now show that these cytokines have profound effects on the skin immune system. Treatment of human keratinocytes with IL-36 cytokines significantly increased the expression of CXCL1, CXCL8, CCL3, CCL5, and CCL20, potent chemotactic agents for activated leukocytes, and IL-36α injected intradermally resulted in chemokine expression, leukocyte infiltration, and acanthosis of mouse skin. Blood monocytes, myeloid dendritic cells (mDC), and monocyte-derived DC (MO-DC) expressed IL-36R and responded to IL-36. In contrast, no direct effects of IL-36 on resting or activated human CD4(+) or CD8(+) T cells, or blood neutrophils, could be demonstrated. Monocytes expressed IL-1A, IL-1B, and IL-6 mRNA and IL-1β and IL-6 protein, and mDC upregulated surface expression of CD83, CD86, and HLA-DR and secretion of IL-1β and IL-6 after treatment with IL-36. Furthermore, IL-36α-treated MO-DC enhanced allogeneic CD4(+) T cell proliferation, demonstrating that IL-36 can stimulate the maturation and function of DC and drive T cell proliferation. These data indicate that IL-36 cytokines actively propagate skin inflammation via the activation of keratinocytes, APC, and, indirectly, T cells.

AP1S3 mutations are associated with pustular psoriasis and impaired Toll-like receptor 3 trafficking

Adaptor protein complex 1 (AP-1) is an evolutionary conserved heterotetramer that promotes vesicular trafficking between the trans-Golgi network and the endosomes. The knockout of most murine AP-1 complex subunits is embryonically lethal, so the identification of human disease-associated alleles has the unique potential to deliver insights into gene function. Here, we report two founder mutations (c.11T>G [p.Phe4Cys] and c.97C>T [p.Arg33Trp]) in AP1S3, the gene encoding AP-1 complex subunit σ1C, in 15 unrelated individuals with a severe autoinflammatory skin disorder known as pustular psoriasis. Because the variants are predicted to destabilize the 3D structure of the AP-1 complex, we generated AP1S3-knockdown cell lines to investigate the consequences of AP-1 deficiency in skin keratinocytes. We found that AP1S3 silencing disrupted the endosomal translocation of the innate pattern-recognition receptor TLR-3 (Toll-like receptor 3) and resulted in a marked inhibition of downstream signaling. These findings identify pustular psoriasis as an autoinflammatory phenotype caused by defects in vesicular trafficking and demonstrate a requirement of AP-1 for Toll-like receptor homeostasis.

The mechanistic basis for psoriasis immunopathogenesis: translating genotype to phenotype. Report of a workshop, Venice, 2012

The International Psoriasis Council, a global nonprofit organization dedicated to advancing psoriasis research and treatment, led an initiative to better define the pathogenic mechanisms that constitute psoriasis. In September 2012, a workshop was held at the 42nd Annual European Society for Dermatological Research in Venice, Italy. By assembling a panel of global dermatology and immunology experts, the objective was to evaluate the current status of the science explaining the mechanism of disease in psoriasis, e.g. dysregulation of the skin immune system and perturbations of epidermal homeostasis. The workshop consisted of four oral presentations, which addressed key topics in psoriasis, delivered by Hervé Bachelez (Paris, France), Antonio Costanzo (Rome, Italy), Michelle Lowes (New York, NY, U.S.A.) and Frank Nestle (London, U.K.). A global expert panel was assembled to stimulate dialogue and debate: Kevin Cooper (Cleveland, OH, U.S.A.), Michel Gilliet (Lausanne, Switzerland), Joerg Prinz (Munich, Germany), Martin Röcken (Tubingen, Germany), Jens Schroeder (Kiel, Germany), Manuelle Viguier (Paris, France), Mayte Suárez-Fariñas (New York, NY, U.S.A.) and Cristina Zielinski (Berlin, Germany). Collectively, the presentations demonstrated the significant advances in understanding immune regulation that have occurred over the past decade by virtue of the study of psoriasis subtypes, phenotypic manifestations and genetic associations. Elucidating the pathogenic and genetic basis of psoriasis holds the promise of a complete understanding of disease mechanisms, predictors of treatment response, novel drug development strategies and customized therapeutic regimens for the individual patient.

Autoinflammatory syndromes for the dermatologist

While autoimmunity as cause of disease is well-established, other categories of immune-mediated diseases that are not produced by targeting of self-antigens by antibodies is in the process of being described. These so-called autoinflammatory diseases arise when an inappropriate activation of antigen-independent mechanisms occurs. Autoinflammatory diseases course with recurrent attacks of fever and multisystemic inflammation; however, the skin may also be affected by a variety of inflammatory manifestations that often alert the clinician about the presence of an autoinflammatory disease. Recognizing the cutaneous features of these syndromes will aid for prompt diagnosis and early treatment that is key for the quality of life and survival of the affected patients. In this paper, we focus on the skin manifestations of autoinflammatory diseases in children, which is the usual period of appearing of the first symptoms and signs.

The interleukin-1 family: back to the future

Interleukin-1 (IL-1) is a central mediator of innate immunity and inflammation. The IL-1 family includes seven ligands with agonist activity (IL-1α and IL-1β, IL-18, IL-33, IL-36α, IL-36β, IL-36γ), three receptor antagonists (IL-1Ra, IL-36Ra, IL-38), and an anti-inflammatory cytokine (IL-37). Members of the IL-1 Receptor (IL-1R) family include six receptor chains forming four signaling receptor complexes, two decoy receptors (IL-1R2, IL-18BP), and two negative regulators (TIR8 or SIGIRR, IL-1RAcPb). A tight regulation via receptor antagonists, decoy receptors, and signaling inhibitors ensures a balance between amplification of innate immunity and uncontrolled inflammation. All cells of the innate immune system express and/or are affected by IL-1 family members. Moreover, IL-1 family members play a key role in the differentiation and function of polarized innate and adaptive lymphoid cells. Here we will review the key properties of IL-1 family members, with emphasis on pathways of negative regulation and orchestration of innate and adaptive immunity.

Advances in the genetics of spondyloarthritis and clinical implications

Spondyloarthritis (SpA) is a group of inflammatory rheumatic diseases whose main clinical feature is inflammation of the axial spine. Articular, periarticular, and extra-articular manifestations can also occur, depending on the type of spondyloarthritis. The most common clinical subsets of SpA are ankylosing spondylitis (AS) and psoriatic arthritis (PsA). SpA is a major health challenge given the propensity to affect young adults and the potential requirement for lifelong treatment. Although the precise etiology of SpA is unknown, there is mounting evidence that these diseases are a result of complex interplay of genetic, environmental, and immunological factors. In this review on SpA, we will discuss genetic variants with genome-wide significance, highlight potential clinical application of genetic variants, and discuss challenges in further elucidating the genetic basis of SpA.

Failure to find evidence for deletion of LCE3C and LCE3B genes at PSORS4 contributing to psoriasis susceptibility in Tunisian families

BACKGROUND

Recently, it has been shown that a deletion in the late cornified envelope (LCE) gene cluster (LCE3C_LCE3B-del) is associated with susceptibility to psoriasis in European and Asian populations. However, no study of this deletion has been performed in the North African population. The aim of the present study was to investigate whether this deletion is associated with familial psoriasis in Tunisian population.

METHODS

A total of 34 patients and 55 healthy individuals were recruited from 7 multiplex families and a PCR assay was used to determine the association of this deletion. Its effect on susceptibility to psoriasis was assessed using the PDT program.

RESULTS

We failed to detect any evidence of association between LCE3C_LCE3B-del and psoriasis in Tunisian families. No epistasic effect was found between the deletion and PSORS1 locus.

CONCLUSIONS

These findings indicate that the LCE3C_LCE3B-del does not contribute in a major way to psoriasis susceptibility in Tunisian families.

Anti-IL-36R antibodies, potentially useful for the treatment of psoriasis: a patent evaluation of WO2013074569

The IL-36 family of cytokines and receptors seems to play a role in the pathogenesis of both pustular psoriasis, and the much more common variant, plaque-type psoriasis. Human skin biopsies from patients with psoriasis show overexpression of IL-36 and mice that lack the inhibitory IL-36 receptor (IL-36Ra) antagonist develop psoriasis, suggesting that signaling through the IL-36R may drive the skin lesions of psoriasis. Currently, no drugs targeting IL-36 are used in the treatment of psoriasis. The patent WO2013074569 describes an antibody to the IL-36R that is proposed as a potential therapy for psoriasis.

Autoinflammatory diseases

Autoinflammatory diseases represent an expanding spectrum of genetic and non-genetic inflammatory diseases characterized by recurrent episodes of fever and systemic inflammation affecting the eyes, joints, skin, and serosal surfaces. Thus, these syndromes are recognized as disorders of innate immunity. Confirming this view, most autoinflammatory diseases are uniquely responsive to IL-1β blockade. Although many autoinflammatory diseases have a genetic cause, increasing evidence indicates that the degree of cell stress concurs to the severity of the disease phenotype. In this mini-review, I will discuss the recent advances on pathogenesis, pathophysiology and therapeutic approaches in autoinflammatory syndromes.

Immunology of psoriasis

The skin is the front line of defense against insult and injury and contains many epidermal and immune elements that comprise the skin-associated lymphoid tissue (SALT). The reaction of these components to injury allows an effective cutaneous response to restore homeostasis. Psoriasis vulgaris is the best-understood and most accessible human disease that is mediated by T cells and dendritic cells. Inflammatory myeloid dendritic cells release IL-23 and IL-12 to activate IL-17-producing T cells, Th1 cells, and Th22 cells to produce abundant psoriatic cytokines IL-17, IFN-γ, TNF, and IL-22. These cytokines mediate effects on keratinocytes to amplify psoriatic inflammation. Therapeutic studies with anticytokine antibodies have shown the importance of the key cytokines IL-23, TNF, and IL-17 in this process. We discuss the genetic background of psoriasis and its relationship to immune function, specifically genetic mutations, key PSORS loci, single nucleotide polymorphisms, and the skin transcriptome. The association between comorbidities and psoriasis is reviewed by correlating the skin transcriptome and serum proteins. Psoriasis-related cytokine-response pathways are considered in the context of the transcriptome of different mouse models. This approach offers a model for other inflammatory skin and autoimmune diseases.

What can the genetics of psoriasis teach us about alopecia areata?

Previous genetic epidemiological studies of psoriasis and alopecia areata demonstrated strong heritability in first-degree relatives and in twins. In recent years, these two conditions have emerged as two skin diseases that are starting to yield their secrets through genome-wide association studies. Both diseases manifest prominent human leukocyte antigen (HLA) associations, psoriasis primarily with major histocompatibility complex (MHC) Class 1, specifically HLA-Cw6, and alopecia areata primarily with MHC Class II. Despite these differences in HLA associations, both diseases have in common a prominent role for CD8+ lymphocytes. The purpose of this brief review is to present the recent developments in the genetics of psoriasis.

A clinical guide to autoinflammatory diseases: familial Mediterranean fever and next-of-kin

Autoinflammatory diseases are associated with abnormal activation of the innate immune system, leading to clinical inflammation and high levels of acute-phase reactants. The first group to be identified was the periodic fever diseases, of which familial Mediterranean fever (FMF) is the most common. In FMF, genetic results are not always straightforward; thus, flowcharts to guide the physician in requesting mutation analyses and interpreting the findings are presented in this Review. The other periodic fever diseases, which include cryopyrin-associated periodic syndromes (CAPS), TNF receptor-associated periodic syndrome (TRAPS) and mevalonate kinase deficiency/hyperimmunoglobulin D syndrome (MKD/HIDS), have distinguishing features that should be sought for carefully during diagnosis. Among this group of diseases, increasing evidence exists for the efficacy of anti-IL-1 treatment, suggesting a major role of IL-1 in their pathogenesis. In the past decade, we have started to learn about the other rare autoinflammatory diseases in which fever is less pronounced. Among them are diseases manifesting with pyogenic lesions of the skin and bone; diseases associated with granulomatous lesions; diseases associated with psoriasis; and diseases associated with defects in the immunoproteasome. A better understanding of the pathogenesis of these autoinflammatory diseases has enabled us to provide targeted biologic treatment at least for some of these conditions.

Monogenic autoinflammatory diseases: disorders of amplified danger sensing and cytokine dysregulation

The pathogenesis of monogenic autoinflammatory diseases converges on the presence of exaggerated immune responses that are triggered through activation of altered pattern recognition receptor (PRR) pathways and result in cytokine/chemokine amplification loops and the inflammatory clinical phenotype seen in autoinflammatory patients. The PRR response can be triggered by accumulation of metabolites, by mutations in sensors leading to their constitutive overactivation, or by mutations in mediator cytokine pathways that lead to amplification and/or inability to downregulate an inflammatory response in hematopoietic and/or nonhematopoietic cells. The study of the pathogenesis of sterile inflammation in patients with autoinflammatory syndromes continues to uncover novel inflammatory pathways.

Decreased expression of interleukin-36α correlates with poor prognosis in hepatocellular carcinoma

Interleukin-36α (IL-36α) has been found to have a prominent role in the pathogenesis of inflammatory disorders; however, little is known about the role of IL-36α in cancer. In this study, we investigated the expression, prognostic value, and the underlying antitumor mechanism of IL-36α in hepatocellular carcinoma (HCC). From immunohistochemistry analysis, IL-36α expression was lower in poorly differentiated HCC cells. In clinicopathological analysis, low IL-36α expression significantly correlated with tumor size, histological differentiation, tumor stage, and vascular invasion, and low intratumoral IL-36α expression had significantly worse overall survival rates and shorter disease-free survival rates. Moreover, intratumoral IL-36α expression was an independent risk factor for overall survival. Consecutive sections were used to detect CD3+, CD8+, and CD4+ tumor-infiltrating lymphocytes (TILs), and we found that high-IL-36α-expressing tumor tissues exhibited a significantly higher proportion of intratumoral CD3+ and CD8+ TILs, but not CD4+ TILs. Our in vitro model confirmed that supernatant from IL-36α-overexpressing human HCC cells had an increased capacity to recruit CD3+ and CD8+ T cells. Consistently, mouse HCC cells engineered to overexpress IL-36α demonstrated markedly delayed growth in vivo, as well as higher levels of intratumoral CD3+ and CD8+ TILs, compared with control mice. In vitro chemotaxis analysis also showed that mouse HCC cells overexpressing IL-36α could recruit more number of CD3+ and CD8+ T cells. These results show that IL-36α expression may play a pivotal role in determining the prognosis of patients with HCC, which we attribute to the activation of adaptive T cell immunity, especially CD8+ T cell immune response.

Biological therapies for psoriasis

INTRODUCTION

Biological therapies have revolutionized moderate-to-severe psoriasis treatment. Increased understanding of disease pathogenesis has yielded multiple therapeutic targets involving the IL-23/Th17 pathway, while current therapies continue to be monitored for long-term efficacy and safety.

AREAS COVERED

This review details current understanding of psoriasis immunopathogenesis specifically related to therapeutic targets. Approved and emerging biological psoriasis therapies targeting TNF-α, IL-12/23p40, IL-17 and IL-23p19 are covered. Biological agent uses in special circumstances are reviewed together with the emerging debate on biosimilar therapies and their potential future role in psoriasis and other inflammatory diseases.

EXPERT OPINION

Psoriasis treatment has expanded and has become more effective due to increased understanding of disease pathogenesis. However, lack of efficacy in select psoriasis patients, safety concerns and limited treatment efficacy in psoriasis variants (e.g., pustular) are areas which still need improvement. As such, pharmacogenomics will be of vital importance in future for individualized psoriasis care. Further, a better understanding of the multiple psoriasis comorbidities, especially cardiovascular disease, continues to be of significant interest in the psoriasis community. Last, the emergence of biosimilar agents has the potential to change psoriasis treatment, especially as it relates to better access for the psoriasis community worldwide.

The expanding spectrum of rare monogenic autoinflammatory diseases

Monogenic autoinflammatory diseases are a group of hereditary disorders characterized by a clinical and biological inflammatory syndrome in which there is little or no evidence of autoimmunity. The discovery of the first causative gene in 1997 was rapidly followed by the identification of many others from the same group. The mutated proteins can be directly or indirectly involved in the regulation of inflammation. The available literature includes numerous reviews, which address the principle diseases, but we wanted to focus on the most recent rare syndromes. A comprehensive review is thus provided, including taxonomic, genetic, and epidemiological data, along with characteristics defining positive and differential diagnoses and treatment. We believe that this update will assist physicians in correctly naming their patient’s illness. This is an essential step for the effective and targeted management of an orphan disease.

First clinical description of an infant with interleukin-36-receptor antagonist deficiency successfully treated with anakinra

YM is the first son of Tunisian consanguineous parents who developed, at 2 weeks of life, an erythematous and scaly eruption, with subsequent rapid evolution toward generalized pustular psoriasis. Afterward, cutaneous flares of diffuse erythematous rash and pustules involving the whole body appeared, with a once weekly periodicity. Intense irritability was present during flares without fever. Moreover, since 1 month of age the infant presented with diarrhea, dysphagia, and reduced feeding rate, with failure to thrive. Laboratory tests during acute flares showed marked leukocytosis, thrombocytosis, and anemia without C-reactive protein elevation. Skin biopsy and clinical presentation were consistent with pustular psoriasis; nevertheless, the patient did not respond to high-potency topical corticosteroids and retinoid acid. As the patient presented with repeated skin flares early after birth, as well as serious constitutional distress with failure to thrive, an autoinflammatory syndrome like interleukine-1-receptor antagonist deficiency or interleukin-36-receptor antagonist deficiency (DITRA) was considered. The hypothesis was reinforced by parental consanguinity, and absence of skin lesion improvement under standard topical treatment. Genetic analyses showed a homozygous mutation in the IL36RN gene (L27P), which represents the same mutation recently described in DITRA patients. At age 6 months we started treatment with the recombinant interleukin-1 receptor antagonist anakinra with efficacy both on constitutional symptoms and skin involvement. DITRA is a recently described autoinflammatory disease characterized by repeated flares of generalized pustular psoriasis, high fever, asthenia, and systemic inflammation. We report herein the first exhaustive clinical description of an infant with DITRA who was successfully treated with anakinra.