Monogenic autoinflammatory diseases: Cytokinopathies

Presenting signs and clinical outcome in dogs with metaphyseal osteopathy: 39 cases (2009-2018)

OBJECTIVE

To describe the presenting signs, concurrent conditions, treatment and outcome of dogs with metaphyseal osteopathy.

MATERIALS AND METHODS

Multi-centre retrospective review of medical records from January 2009 to September 2018 at four referral centres to identify dogs with a radiographic diagnosis of metaphyseal osteopathy.

RESULTS

Thirty-nine dogs were identified. The median age at onset was 14 weeks old (range, 8 to 32 weeks old). There was a higher proportion of male dogs (29 of 39 male entire, nine of 39 female entire, one of 39 female neutered and no male neutered dogs). Where information was available, median time from the most recent vaccination was 20 days (range, 2 to 144 days). The most commonly recorded clinical signs were pyrexia (34 of 39), lethargy (32 of 39), pain (30 of 39), and being non-ambulatory (17 of 39). Thirty-five dogs required hospitalisation for analgesia and supportive care, 19 of 39 were discharged on prednisolone (median dose 2.0 mg/kg/day; range, 0.9 to 2.6 mg/kg/day), 18 of 39 were discharged on non-steroidal anti-inflammatories, two of 39 did not receive NSAIDs or prednisolone at any time point. The median duration of hospitalisation for those admitted was 5 days (range, 1 to 21 days). Where follow-up was available, relapse occurred in eight of 25 cases before reaching skeletal maturity. At the time of metaphyseal osteopathy diagnosis, five of 39 cases had concurrent conditions. Where follow-up was available, four of 25 developed future immune-mediated conditions.

CLINICAL SIGNIFICANCE

Metaphyseal osteopathy should be considered in non-ambulatory painful young dogs. Some dogs developed future immune-mediated conditions, which may support the hypothesis that metaphyseal osteopathy is an autoinflammatory bone disorder. Further studies with a larger cohort are required to determine the clinical significance of this.

1,25-Dihydroxyvitamin D3 attenuates IL-1β secretion by suppressing NLRP1 inflammasome activation by upregulating the NRF2-HO-1 pathway in epidermal keratinocytes

The nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing protein (NLRP) inflammasome is a key inflammatory signaling pathway activated via a two-step signaling process consisting of priming and activation steps. Several studies have shown that 1,25-dihydroxyvitamin D3 (1,25(OH)2VD3) inhibits the priming step required for NLRP3 inflammasome activation in immune cells. However, as activating the NLRP1 inflammasome in keratinocytes does not necessarily require a priming step, whether 1,25(OH)2VD3 inhibits NLRP1 activation in unprimed keratinocytes is currently unknown. In this study, we showed that 1,25(OH)2VD3 inhibits nigericin-induced NLRP1 inflammasome activation in unprimed keratinocytes. 1,25(OH)2VD3 suppressed nigericin-induced interleukin-1β (IL-1β) secretion and caspase-1 activation in human primary keratinocytes. In addition, 1,25(OH)2VD3 significantly inhibited the formation of apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) oligomers and specks, but not caspase-1 enzymatic activity, suggesting that 1,25(OH)2VD3 prevents NLRP1-ASC complex assembly in keratinocytes. Vitamin D receptor (VDR)-knockdown abolished the inhibitory effects of 1,25(OH)2VD3 on nigericin-induced ASC oligomerization and IL-1β secretion, suggesting that 1,25(OH)2VD3 suppresses inflammasome activation via VDR signaling. Furthermore, nigericin induced K+ efflux and cellular reactive oxygen species (ROS) production, and 1,25(OH)2VD3 pretreatment suppressed nigericin-induced ROS production. 1,25(OH)2VD3 increased the expression of both nuclear factor erythroid 2-related factor 2 (NRF2) and heme oxygenase-1 (HO-1), whereas HO-1 inhibition or NRF2 and HO-1 knockdown abrogated the inhibitory effects of 1,25(OH)2VD3 on IL-1β secretion. Our results indicate that 1,25(OH)2VD3 inhibits nigericin-induced activation step of NLRP1 inflammasome activation in unprimed keratinocytes. Our findings reveal the mechanism underlying the inhibitory effect of 1,25(OH)2VD3, which involves NRF2-HO-1 pathway activation through the VDR, providing further insight into the potential function of 1,25(OH)2VD3 as a therapeutic agent for inflammasome-related skin diseases.

Molecular biology of autoinflammatory diseases

The long battle between humans and various physical, chemical, and biological insults that cause cell injury (e.g., products of tissue damage, metabolites, and/or infections) have led to the evolution of various adaptive responses. These responses are triggered by recognition of damage-associated molecular patterns (DAMPs) and/or pathogen-associated molecular patterns (PAMPs), usually by cells of the innate immune system. DAMPs and PAMPs are recognized by pattern recognition receptors (PRRs) expressed by innate immune cells; this recognition triggers inflammation. Autoinflammatory diseases are strongly associated with dysregulation of PRR interactomes, which include inflammasomes, NF-κB-activating signalosomes, type I interferon-inducing signalosomes, and immuno-proteasome; disruptions of regulation of these interactomes leads to inflammasomopathies, relopathies, interferonopathies, and proteasome-associated autoinflammatory syndromes, respectively. In this review, we discuss the currently accepted molecular mechanisms underlying several autoinflammatory diseases.

Crosstalk between Interleukin-1β and Type I Interferons Signaling in Autoinflammatory Diseases

Interleukin-1β (IL-1β) and type I interferons (IFNs) are major cytokines involved in autoinflammatory/autoimmune diseases. Separately, the overproduction of each of these cytokines is well described and constitutes the hallmark of inflammasomopathies and interferonopathies, respectively. While their interaction and the crosstalk between their downstream signaling pathways has been mostly investigated in the frame of infectious diseases, little information on their interconnection is still available in the context of autoinflammation promoted by sterile triggers. In this review, we will examine the respective roles of IL-1β and type I IFNs in autoinflammatory/rheumatic diseases and analyze their potential connections in the pathophysiology of some of these diseases, which could reveal novel therapeutic opportunities.

KN3014, a piperidine-containing small compound, inhibits auto-secretion of IL-1β from PBMCs in a patient with Muckle-Wells syndrome

NLRP3, an intracellular pattern recognition receptor, recognizes numerous pathogens and/or its own damage-associated molecules, and forms complexes with the adaptor protein ASC. These complexes constitute the NLRP3 inflammasome, a platform for processing interleukin (IL)-1β and/or IL-18. Several NLRP3 mutations result in constitutive activation of the NLRP3 inflammasome, causing cryopyrin-associated periodic syndrome (CAPS). To the best of our knowledge, small compounds that specifically inhibit inflammasome activation through the pyrin domain (PYD) have not yet been developed. This study describes an attempt to develop small compounds targeting the NLRP3 inflammasome. A core chemical library of 9,600 chemicals was screened against reconstituted NLRP3 inflammasome in a cell-free system with an amplified luminescence proximity homogeneous assay and a cell-based assay by human peripheral blood mononuclear cells (PBMCs). Inflammasome activation was evaluated by ASC-speck formation in human PBMCs, accompanied by IL-1β secretion and processing, and by using IL-1β-based dual operating luciferase (IDOL) mice. The activity of these compounds was evaluated clinically using PBMCs from a patient with Muckle–Wells syndrome (MWS), a type of CAPS, with an R260W mutation in NLRP3. Screening identified KN3014, a piperidine-containing compound targeting the interaction between NLRP3 and ASC through the PYD. KN3014 reduced ASC-speck formation in human PBMCs, luminescence from IDOL mice, and auto-secretion of IL-1β by PBMCs from the patient with MWS. These findings suggest that KN3014 may be an attractive candidate for treatment of MWS, as well as other NLRP3 inflammasomopathies.

Current State of Precision Medicine in Primary Systemic Vasculitides

Precision medicine (PM) is an emerging data-driven health care approach that integrates phenotypic, genomic, epigenetic, and environmental factors unique to an individual. The goal of PM is to facilitate diagnosis, predict effective therapy, and avoid adverse reactions specific for each patient. The forefront of PM is in oncology; nonetheless, it is developing in other fields of medicine, including rheumatology. Recent studies on elucidating the genetic architecture of polygenic and monogenic rheumatological diseases have made PM possible by enabling physicians to customize medical treatment through the incorporation of clinical features and genetic data. For complex inflammatory disorders, the prevailing paradigm is that disease susceptibility is due to additive effects of common reduced-penetrance gene variants and environmental factors. Efforts have been made to calculate cumulative genetic risk score (GRS) and to relate specific susceptibility alleles for use of target therapies. The discovery of rare patients with single-gene high-penetrance mutations informed our understanding of pathways driving systemic inflammation. Here, we review the advances in practicing PM in patients with primary systemic vasculitides (PSVs). We summarize recent genetic studies and discuss current knowledge on the contribution of epigenetic factors and extracellular vesicles (EVs) in disease progression and treatment response. Implementation of PM in PSVs is a developing field that will require analysis of a large cohort of patients to validate data from genomics, transcriptomics, metabolomics, proteomics, and epigenomics studies for accurate disease profiling. This multi-omics approach to study disease pathogeneses should ultimately provide a powerful tool for stratification of patients to receive tailored optimal therapies and for monitoring their disease activity.

Knockdown of IGF-1R Triggers Viral RNA Sensor MDA5- and RIG-I-Mediated Mitochondrial Apoptosis in Colonic Cancer Cells

The important role of insulin-like growth factor-1 receptor (IGF-1R) in tumorigenesis has been well established. The classical model involves IGF-1R binding to IGF-1/2, the following activation of PI3K-Akt-signaling cascades, driving cell proliferation and apoptosis inhibition. Here we report a new signal transduction pathway of IGF-1R in the intestinal epithelium. Using heterozygous knockout mice (Igf1r^+/-), we analyzed the expressions of viral RNA sensors MDA5 and RIG-I in the intestinal epithelium. Igf1r^+/- mice exhibited higher MDA5 and RIG-I than wild-type (WT) mice, indicating that knockdown of IGF-1R could trigger MDA5 and RIG-I. IGF-1R knockdown-triggered MDA5 and RIG-I were further investigated in human colonic cancer cells. Increased MDA5 and RIG-I were clearly seen in the cytoplasm in cancer cells as well as normal human colonic cells with silenced IGF-1R. Notably, the upregulations of MDA5 and RIG-I was not affected by blockage of the PI3K-Akt pathway with LY294002. These results suggested a new signal transduction pathway of IGF-1R. Importantly, IGF-1R knockdown-triggered MDA5 and RIG-I resulted in colorectal cancer apoptosis through activation of the mitochondrial pathway. These in vitro observations were evidenced in the azoxymethane (AOM)-dextran sulfate sodium (DSS) colorectal cancer model of mice. In conclusion, knockdown of IGF-1R triggers viral RNA sensor MDA5- and RIG-I-mediated mitochondrial apoptosis in cancer cells.

Human DPP9 represses NLRP1 inflammasome and protects against autoinflammatory diseases via both peptidase activity and FIIND domain binding

The inflammasome is a critical molecular complex that activates interleukin-1 driven inflammation in response to pathogen- and danger-associated signals. Germline mutations in the inflammasome sensor NLRP1 cause Mendelian systemic autoimmunity and skin cancer susceptibility, but its endogenous regulation remains less understood. Here we use a proteomics screen to uncover dipeptidyl dipeptidase DPP9 as a novel interacting partner with human NLRP1 and a related inflammasome regulator, CARD8. DPP9 functions as an endogenous inhibitor of NLRP1 inflammasome in diverse primary cell types from human and mice. DPP8/9 inhibition via small molecule drugs and CRISPR/Cas9-mediated genetic deletion specifically activate the human NLRP1 inflammasome, leading to ASC speck formation, pyroptotic cell death, and secretion of cleaved interleukin-1β. Mechanistically, DPP9 interacts with a unique autoproteolytic domain (Function to Find Domain (FIIND)) found in NLRP1 and CARD8. This scaffolding function of DPP9 and its catalytic activity act synergistically to maintain NLRP1 in its inactive state and repress downstream inflammasome activation. We further identified a single patient-derived germline missense mutation in the NLRP1 FIIND domain that abrogates DPP9 binding, leading to inflammasome hyperactivation seen in the Mendelian autoinflammatory disease Autoinflammation with Arthritis and Dyskeratosis. These results unite recent findings on the regulation of murine Nlrp1b by Dpp8/9 and uncover a new regulatory mechanism for the NLRP1 inflammasome in primary human cells. Our results further suggest that DPP9 could be a multifunctional inflammasome regulator involved in human autoinflammatory diseases.

The classification, genetic diagnosis and modelling of monogenic autoinflammatory disorders

Monogenic autoinflammatory disorders are an increasingly heterogeneous group of conditions characterised by innate immune dysregulation. Improved genetic sequencing in recent years has led not only to the discovery of a plethora of conditions considered to be 'autoinflammatory', but also the broadening of the clinical and immunological phenotypic spectra seen in these disorders. This review outlines the classification strategies that have been employed for monogenic autoinflammatory disorders to date, including the primary innate immune pathway or the dominant cytokine implicated in disease pathogenesis, and highlights some of the advantages of these models. Furthermore, the use of the term 'autoinflammatory' is discussed in relation to disorders that cross the innate and adaptive immune divide. The utilisation of next-generation sequencing (NGS) in this population is examined, as are potential in vivo and in vitro methods of modelling to determine pathogenicity of novel genetic findings. Finally, areas where our understanding can be improved are highlighted, such as phenotypic variability and genotype-phenotype correlations, with the aim of identifying areas of future research.

Inflammasomes and dermatology

Inflammasomes are intracellular multiprotein complexes that comprise part of the innate immune response. Since their definition, inflammasome disorders have been linked to an increasing number of diseases. Autoinflammatory diseases refer to disorders in which local factors lead to the activation of innate immune cells, causing tissue damage when in the absence of autoantigens and autoantibodies. Skin symptoms include the main features of monogenic inflammasomopathies, such as Cryopyrin-Associated Periodic Syndromes (CAPS), Familial Mediterranean Fever (FMF), Schnitzler Syndrome, Hyper-IgD Syndrome (HIDS), PAPA Syndrome, and Deficiency of IL-1 Receptor Antagonist (DIRA). Concepts from other pathologies have also been reviewed in recent years, such as psoriasis, after the recognition of a combined contribution of innate and adaptive immunity in its pathogenesis. Inflammasomes are also involved in the response to various infections, malignancies, such as melanoma, autoimmune diseases, including vitiligo and lupus erythematosus, atopic and contact dermatitis, acne, hidradenitis suppurativa, among others. Inhibition of the inflammasome pathway may be a target for future therapies, as already occurs in the handling of CAPS, through the introduction of IL-1 inhibitors. This study presents a literature review focusing on the participation of inflammasomes in skin diseases.

Understanding Human Autoimmunity and Autoinflammation Through Transcriptomics

Transcriptomics, the high-throughput characterization of RNAs, has been instrumental in defining pathogenic signatures in human autoimmunity and autoinflammation. It enabled the identification of new therapeutic targets in IFN-, IL-1- and IL-17-mediated diseases. Applied to immunomonitoring, transcriptomics is starting to unravel diagnostic and prognostic signatures that stratify patients, track molecular changes associated with disease activity, define personalized treatment strategies, and generally inform clinical practice. Herein, we review the use of transcriptomics to define mechanistic, diagnostic, and predictive signatures in human autoimmunity and autoinflammation. We discuss some of the analytical approaches applied to extract biological knowledge from high-dimensional data sets. Finally, we touch upon emerging applications of transcriptomics to study eQTLs, B and T cell repertoire diversity, and isoform usage.

Genetic and Epigenetic Determinants in Autoinflammatory Diseases

The concept of autoinflammation has evolved over the past 20 years, beginning with the discovery that mutations in the Mediterranean Fever (MEFV) gene were causative of Familial Mediterranean Fever. Currently, autoinflammatory diseases comprise a wide range of disorders with the common features of recurrent fever attacks, prevalence of hyperreactive innate immune cells, and signs of inflammation that can be systemic or organ specific in the absence of pathogenic infection of autoimmunity. Innate immune cells from the myeloid compartment are the main effectors of uncontrolled inflammation that is caused in great extent by the overproduction of inflammatory cytokines such as IL-1β and IL-18. Defects in several signaling pathways that control innate immune defense, particularly the hyperreactivity of one or more inflammasomes, are at the core of pathologic autoinflammatory phenotypes. Although many of the autoinflammatory syndromes are known to be monogenic, some of them are genetically complex and are impacted by environmental factors. Recently, epigenetic dysregulation has surfaced as an additional contributor to pathogenesis. In the present review, we discuss data that are currently available to describe the contribution of epigenetic mechanisms in autoinflammatory diseases.

Serum levels of innate immunity cytokines are elevated in dogs with metaphyseal osteopathy (hypertrophic osteodytrophy) during active disease and remission

Metaphyseal osteopathy (MO) (hypertrophic osteodystrophy) is a developmental disorder of unexplained etiology affecting dogs during rapid growth. Affected dogs experience relapsing episodes of lytic/sclerotic metaphyseal lesions and systemic inflammation. MO is rare in the general dog population; however, some breeds (Weimaraner, Great Dane and Irish Setter) have a much higher incidence, supporting a hereditary etiology. Autoinflammatory childhood disorders of parallel presentation such as chronic recurrent multifocal osteomyelitis (CRMO), and deficiency of interleukin-1 receptor antagonist (DIRA), involve impaired innate immunity pathways and aberrant cytokine production. Given the similarities between these diseases, we hypothesize that MO is an autoinflammatory disease mediated by cytokines involved in innate immunity. To characterize immune dysregulation in MO dogs we measured serum levels of inflammatory markers in 26 MO and 102 control dogs. MO dogs had significantly higher levels (pg/ml) of serum Interleukin-1beta (IL-1β), IL-18, IL-6, Granulocyte-macrophage colony stimulating factor (GM-CSF), C-X-C motif chemokine 10 (CXCL10), tumor necrosis factor (TNF), and IL-10. Notably, recovered MO dogs were not different from dogs during active MO disease, providing a suggestive mechanism for disease predisposition. This is the first documentation of elevated immune markers in MO dogs, uncovering an immune profile similar to comparable autoinflammatory disorders in children.

[Interleukin-1, inflammasome and autoinflammatory diseases]

Interleukin-1 is a major cytokine of innate immunity and inflammation. It exerts various systemic effects during the inflammatory response, such as fever induction, thrombopoiesis and granulopoiesis, or leukocyte recruitment. Its involvement has been demonstrated in many inflammatory-mediated diseases, such as diabetes or gout. Moreover, interleukin-1 plays a pivotal role in some autoinflammatory diseases, such as cryopyrinopathies or familial Mediterranean fever. In these diseases, a constitutional defect of the inflammasome, a protein complex responsible for the activation of interleukin-1, explains the hypersecretion of interleukin-1. Other autoinflammatory diseases have a more complex pathophysiology involving deregulation of the interleukin-1 pathway, upstream or downstream of the inflammasome, or through more complex mechanisms. In this review, we are detailing the synthesis, the activation, the signalling, and the regulation of interleukin-1. We then describe the autoinflammatory diseases or related-diseases where the pathological role of interleukin-1 has been demonstrated.

Loss-of-function mutations in TNFAIP3 leading to A20 haploinsufficiency cause an early-onset autoinflammatory disease

Systemic autoinflammatory diseases are driven by abnormal activation of innate immunity. Herein we describe a new disease caused by high-penetrance heterozygous germline mutations in TNFAIP3, which encodes the NF-κB regulatory protein A20, in six unrelated families with early-onset systemic inflammation. The disorder resembles Behçet's disease, which is typically considered a polygenic disorder with onset in early adulthood. A20 is a potent inhibitor of the NF-κB signaling pathway. Mutant, truncated A20 proteins are likely to act through haploinsufficiency because they do not exert a dominant-negative effect in overexpression experiments. Patient-derived cells show increased degradation of IκBα and nuclear translocation of the NF-κB p65 subunit together with increased expression of NF-κB-mediated proinflammatory cytokines. A20 restricts NF-κB signals via its deubiquitinase activity. In cells expressing mutant A20 protein, there is defective removal of Lys63-linked ubiquitin from TRAF6, NEMO and RIP1 after stimulation with tumor necrosis factor (TNF). NF-κB-dependent proinflammatory cytokines are potential therapeutic targets for the patients with this disease.

To Extinguish the Fire from Outside the Cell or to Shutdown the Gas Valve Inside? Novel Trends in Anti-Inflammatory Therapies

Cytokines are the most important soluble mediators of inflammation. Rare pediatric diseases provided exemplar conditions to study the anti-inflammatory efficacy of new generation therapies (biologics/biopharmaceuticals) selectively targeting single cytokines. Monoclonal antibodies and recombinant proteins have revolutionized anti-inflammatory therapies in the last two decades, allowing the specific targeting of single cytokines. They are very effective in extinguishing inflammation from outside the cell, even with the risk of an excessive and prolonged immunosuppression. Small molecules can enter the cell and shutdown the valve of inflammation by directly targeting signal proteins involved in cytokine release or in response to cytokines. They are orally-administrable drugs whose dosage can be easily adjusted to obtain the desired anti-inflammatory effect. This could make these drugs more suitable for a wide range of diseases as stroke, gout, or neurological impairment, where inflammatory activation plays a pivotal role as trigger. Autoinflammatory diseases, which have previously put anti-cytokine proteins in the limelight, can again provide a valuable model to measure the real potential of small inhibitors as anti-inflammatory agents.