Genetic deficiency of tartrate-resistant acid phosphatase associated with skeletal dysplasia, cerebral calcifications and autoimmunity

Inhibition of tartrate-resistant acid phosphatase 5 can prevent cardiac fibrosis after myocardial infarction

BACKGROUND

Myocardial infarction (MI) leads to enhanced activity of cardiac fibroblasts (CFs) and abnormal deposition of extracellular matrix proteins, resulting in cardiac fibrosis. Tartrate-resistant acid phosphatase 5 (ACP5) has been shown to promote cell proliferation and phenotypic transition. However, it remains unclear whether ACP5 is involved in the development of cardiac fibrosis after MI. The present study aimed to investigate the role of ACP5 in post-MI fibrosis and its potential underlying mechanisms.

METHODS

Clinical blood samples were collected to detect ACP5 concentration. Myocardial fibrosis was induced by ligation of the left anterior descending coronary artery. The ACP5 inhibitor, AubipyOMe, was administered by intraperitoneal injection. Cardiac function and morphological changes were observed on Day 28 after injury. Cardiac CFs from neonatal mice were extracted to elucidate the underlying mechanism in vitro. The expression of ACP5 was silenced by small interfering RNA (siRNA) and overexpressed by adeno-associated viruses to evaluate its effect on CF activation.

RESULTS

The expression of ACP5 was increased in patients with MI, mice with MI, and mice with Ang II-induced fibrosis in vitro. AubipyOMe inhibited cardiac fibrosis and improved cardiac function in mice after MI. ACP5 inhibition reduced cell proliferation, migration, and phenotypic changes in CFs in vitro, while adenovirus-mediated ACP5 overexpression had the opposite effect. Mechanistically, the classical profibrotic pathway of glycogen synthase kinase-3β (GSK3β)/β-catenin was changed with ACP5 modulation, which indicated that ACP5 had a positive regulatory effect. Furthermore, the inhibitory effect of ACP5 deficiency on the GSK3β/β-catenin pathway was counteracted by an ERK activator, which indicated that ACP5 regulated GSK3β activity through ERK-mediated phosphorylation, thereby affecting β-catenin degradation.

CONCLUSION

ACP5 may influence the proliferation, migration, and phenotypic transition of CFs, leading to the development of myocardial fibrosis after MI through modulating the ERK/GSK3β/β-catenin signaling pathway.

Spondyloenchondrodysplasia With Immune Dysregulation, but Without Skeletal Dysplasia, in a Six-Year-Old Boy: A Case Report

Spondyloenchondrodysplasia with immune dysregulation (SPENCDI) is a rare autosomal recessive genetic disorder caused by a homozygous mutation of the ACP5 gene. Spondyloenchondrodysplasia is a type of immune-osseous dysplasia manifesting with skeletal dysplasia, immunologic dysfunction, and neurological manifestations. We report the case of a six-year-old boy with SPENCDI who presented with post-viral illness Coombs-positive hemolytic anemia, thrombocytopenia, and fever, based on which he was diagnosed with Evans syndrome. He was previously diagnosed with spastic diplegia, short stature, and celiac disease. The diagnosis was confirmed with genetic testing which displayed a homozygous frameshift mutation of the ACP5 gene c.549del p.(Gln184Serfs*28). This case report discusses the clinical presentation of SPENCDI and highlights the importance of considering this rare genetic disorder in patients presenting with short stature, immunologic dysregulation, and neurological involvement.

Rare SH2B3 coding variants in lupus patients impair B cell tolerance and predispose to autoimmunity

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease with a clear genetic component. While most SLE patients carry rare gene variants in lupus risk genes, little is known about their contribution to disease pathogenesis. Amongst them, SH2B3-a negative regulator of cytokine and growth factor receptor signaling-harbors rare coding variants in over 5% of SLE patients. Here, we show that unlike the variant found exclusively in healthy controls, SH2B3 rare variants found in lupus patients are predominantly hypomorphic alleles, failing to suppress IFNGR signaling via JAK2-STAT1. The generation of two mouse lines carrying patients' variants revealed that SH2B3 is important in limiting the number of immature and transitional B cells. Furthermore, hypomorphic SH2B3 was shown to impair the negative selection of immature/transitional self-reactive B cells and accelerate autoimmunity in sensitized mice, at least in part due to increased IL-4R signaling and BAFF-R expression. This work identifies a previously unappreciated role for SH2B3 in human B cell tolerance and lupus risk.

Macrophage expressed tartrate-resistant acid phosphatase 5 promotes pulmonary fibrosis progression

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disorder involving scarring of pulmonary tissue and a subsequent decrease in respiratory capacity, ultimately resulting in death. Tartrate resistant acid phosphatase 5 (ACP5) plays a role in IPF but the exact mechanisms are yet to be elucidated. In this study, we have utilized various perturbations of the bleomycin mouse model of IPF including genetic knockout, RANKL inhibition, and macrophage adoptive transfer to further understand ACP5's role in pulmonary fibrosis. Genetic ablation of Acp5 decreased immune cell recruitment to the lungs and reduced the levels of hydroxyproline (reflecting extracellular matrix-production) as well as histological damage. Additionally, gene expression profiling of murine lung tissue revealed downregulation of genes including Ccl13, Mmp13, and Il-1α that encodes proteins specifically related to immune cell recruitment and macrophage/fibroblast interactions. Furthermore, antibody-based neutralization of RANKL, an important inducer of Acp5 expression, reduced immune cell recruitment but did not decrease fibrotic lung development. Adoptive transfer of Acp5-/- bone marrow-derived monocyte (BMDM) macrophages 7 or 14 days after bleomycin administration resulted in reductions of cytokine production and decreased levels of lung damage, compared to adoptive transfer of WT control macrophages. Taken together, the data presented in this study suggest that macrophage derived ACP5 plays an important role in development of pulmonary fibrosis and could present a tractable target for therapeutic intervention in IPF.

Autoimmune Hemolytic Anemia Due to Spondyloenchondrodysplasia with Spastic Paraparesis and Intracranial Calcification due to Mutation in ACP5

Spondyloenchondrodysplasia (SPENCD) is a rare spondylometaphyseal skeletal dysplasia with characteristic lesions mimicking enchondromatosis and resulting in short stature. A large spectrum of immunologic abnormalities may be seen in SPENCD, including immune deficiencies and autoimmune disorders. SPENCD is caused by loss of tartrate-resistant acid phosphatase activity, due to homozygous mutations in ACP5 , playing a role in nonnucleic-acid-related stimulation/regulation of the type I interferon pathway. In this article, we presented a 19-year-old boy with SPENCD, presenting with recurrent autoimmune hemolytic anemia episodes since he was 5 years old. He had short stature, platyspondyly, metaphyseal changes, intracranial calcification, spastic paraparesis, and mild intellectual disability. He also had recurrent pneumonia attacks. The clinical diagnosis of SPENCD was confirmed by sequencing of the ACP5 gene, and a homozygous c.155A > C (p.K52T) variation was found, which was reported before as pathogenic. In conclusion, in early onset chronic autoimmune cytopenias an immune dysregulation may often have a role in the etiology. Associating findings and immunologic functions should be carefully evaluated in such patients in the light of the literature. The present case shows the importance of multisystemic evaluation for the detection of SPENCD that has a monogenic etiology.

Case report: Refractory Evans syndrome in two patients with spondyloenchondrodysplasia with immune dysregulation treated successfully with JAK1/JAK2 inhibition

Biallelic mutations in the ACP5 gene cause spondyloenchondrodysplasia with immune dysregulation (SPENCDI). SPENCDI is characterized by the phenotypic triad of skeletal dysplasia, innate and adaptive immune dysfunction, and variable neurologic findings ranging from asymptomatic brain calcifications to severe developmental delay with spasticity. Immune dysregulation in SPENCDI is often refractory to standard immunosuppressive treatments. Here, we present the cases of two patients with SPENCDI and recalcitrant autoimmune cytopenias who demonstrated a favorable clinical response to targeted JAK inhibition over a period of more than 3 years. One of the patients exhibited steadily rising IgG levels and a bone marrow biopsy revealed smoldering multiple myeloma. A review of the literature uncovered that approximately half of the SPENCDI patients reported to date exhibited increased IgG levels. Screening for multiple myeloma in SPENCDI patients with rising IgG levels should therefore be considered.

Type I Interferonopathies: A Clinical Review

This review will discuss when clinicians should consider evaluating for Type I interferonopathies, review clinical phenotypes and molecular defects of Type I interferonopathies, and discuss current treatments.

Spondyloenchondrodysplasia in five new patients: identification of three novel ACP5 variants with variable neurological presentations

Spondyloenchondrodysplasia (SPENCD) is an immune-osseous disorder caused by biallelic variants in ACP5 gene and is less commonly associated with neurological abnormalities such as global developmental delay, spasticity and seizures. Herein, we describe five new patients from four unrelated Egyptian families with complex clinical presentations including predominant neurological presentations masking the skeletal and immunological manifestations. All our patients had spasticity with variable associations of motor and mental delay or epilepsy. All except for one patient had bilateral calcification in the basal ganglia. One patient had an associated growth hormone deficiency with fair response to growth hormone therapy (GH) where the height improved from -3.0 SD before GH therapy to -2.35 SD at presentation. Patients had different forms of immune dysregulation. All patients except for one had either cellular immunodeficiency (3 patients) or combined immunodeficiency (1 patient). Whole exome sequencing was performed and revealed four ACP5 variants: c.629C > T (p.Ser210Phe), c.526C > T (p.Arg176Ter), c.742dupC (p.Gln248ProfsTer3) and c.775G > A (p.Gly259Arg). Of them, three variants were not described before. Our study reinforces the striking phenotypic variability associated with SPENCD and expands the mutational spectrum of this rare disorder. Further, it documents the positive response to growth hormone therapy in the studied patient.

Spondyloenchondrodysplasia Due to Mutation in ACP5 Gene Presenting with Nephrotic Syndrome: A Case Report

Spondyloenchondrodysplasia (SPENCD) with immune dysregulation (SPENCDI) is a rare autosomal recessive inherited immuno-osseous dysplasia characterized by spondylo-metaphyseal enchondromas, along with immune dysregulation ranging from immunodeficiency to autoimmune disorder. Here, we present two cousins with ACP5 gene mutation who had severe short stature with mild hypogammaglobulinemia, nephrotic syndrome, autoimmune thyroiditis and cerebral calcification (Case 1); and in the other (Case 2), there was no clinical findings other than severe short stature, CD4+−T cell lymphopenia and non-autoimmune compensated hypothyroidism. We wanted to emphasize that monogenic causes should be considered in the etiology of early-onset nephrotic syndrome due to the detection of a mutation in the ACP5 gene (her actual diagnosis was changed to SPENCDI.) 5 years after the diagnosis of nephrotic syndrome in the first case, and that the renal involvement may occur without SLE in patients with ACP5 mutation. Severe short stature was a common finding in both cases. We underlined that the clinic can be different even in the same mutation, due to the absence of cerebral calcification and renal involvement in the second case, which is a cousin with Case 1. As a result, endocrinologists, immunologists, rheumatologists, nephrologists and orthopedists should be aware of this syndrome, because SPENCDI causes a pleiotropic (due to more than one phenotypic effect of a gene) clinical picture. Severe short stature may be the only presenting sign of patients with SPENCDI. In addition, in the presence of early-onset nephrotic syndrome and autoimmune thyroiditis, the patient should be evaluated for this type of monogenic disorders as well.

Association of rare variants in genes of immune regulation with pediatric autoimmune CNS diseases

Background

There is a gap in the literature regarding genetic underpinnings of pediatric autoimmune CNS diseases. This study explored rare gene variants implicated in immune dysregulation within these disorders.

Methods

This was a single-center observational study of children with inflammatory CNS disorder who had genetic testing through next generation focused exome sequencing targeting 155 genes associated with innate or adaptive immunity. For in silico prediction of functional effects of single-nucleotide variants, Polymorphism Phenotyping v2, and Sorting Intolerant from Tolerant were used, and Combined Annotation Dependent Depletion (CADD) scores were calculated. Identified genes were analyzed using Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis.

Results

Of 54 patients, 42 (77.8%) carried variant(s), among which 12 (22.2%) had 3–8 variants. Eighty-eight unique single-nucleotide variants of 55 genes were identified. The most variants were detected in UNC13D, LRBA, LYST, NOD2, DOCK8, RNASEH2A, STAT5B, and AIRE. The majority of variants (62, 70.4%) had CADD > 10. KEGG pathway analysis revealed seven genes associated with primary immunodeficiency (Benjamini 1.40E − 06), six genes with NOD-like receptor signaling (Benjamini 4.10E − 04), five genes with Inflammatory Bowel Disease (Benjamini 9.80E − 03), and five genes with NF-kappa B signaling pathway (Benjamini 1.90E − 02).

Discussion

We observed a high rate of identification of rare and low-frequency variants in immune regulatory genes in pediatric neuroinflammatory CNS disorders. We identified 88 unique single-nucleotide variants of 55 genes with pathway analysis revealing an enrichment of NOD2-receptor signaling, consistent with involvement of the pathway within other autoinflammatory conditions and warranting further investigation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-022-11325-2.

Impaired endothelial cell proliferative, migratory, and adhesive abilities are associated with the slow endothelialization of polycaprolactone vascular grafts implanted into a hypercholesterolemia rat model

Most small diameter vascular grafts (inner diameter<6 mm) evaluation studies are performed in healthy animals that cannot represent the clinical situation. Herein, an hypercholesterolemia (HC) rat model with thickened intima and elevated expression of pro-inflammatory intercellular adhesion molecular-1 (ICAM-1) in the carotid branch is established. Electrospun polycaprolactone (PCL) vascular grafts (length: 1 cm; inner diameter: 2 mm) are implanted into the HC rat abdominal aortas in an end to end fashion and followed up to 43 days, showing a relative lower patency accompanied by significant neointima hyperplasia, abundant collagen deposition, and slower endothelialization than those implanted into healthy ones. Moreover, the proliferation, migration, and adhesion behavior of endothelial cells (ECs) isolated from the HC aortas are impaired as evaluated under both static and pulsatile flow conditions. DNA microarray studies of the HC aortic endothelium suggest genes involved in EC proliferation (Egr2), apoptosis (Zbtb16 and Mt1), and metabolism (Slc7a11 and Hamp) are down regulated. These results suggest the impaired proliferative, migratory, and adhesive abilities of ECs are associated with the bad performances of grafts in HC rat. Future pre-clinical evaluation of small diameter vascular grafts may concern more disease animal models with clinical complications. STATEMENT OF SIGNIFICANCE: During the development of small diameter vascular grafts (D<6 mm), young and healthy animal models from pigs, sheep, dogs, to rabbits and rats are preferred. However, it cannot represent the clinic situation, where most cardiovascular grafting procedures are performed in the elderly and age is the primary risk factor for disease development or death. Herein, the performance of electrospun polycaprolactone (PCL) vascular grafts implanted into hypercholesterolemia (HC) or healthy rats were evaluated. Results suggest the proliferative, migratory, and adhesive abilities of endothelial cells (ECs) are already impaired in HC rats, which contributes to the observed slower endothelialization of implanted PCL grafts. Future pre-clinical evaluation of small diameter vascular grafts may concern more disease animal models with clinical complications.

Type I interferon-related kidney disorders

Type I interferon (IFN-I) mediates tissue damage in a wide range of kidney disorders, directly affecting the biology and function of several renal cell types including podocytes, mesangial, endothelial and parietal epithelial cells (PECs).Enhanced IFN-I signalling is observed in the context of viral infections, autoimmunity (e.g., systemic lupus erythematosus, SLE), and the type 1 interferonopathies (T1Is), rare monogenic disorders characterised by constitutive activation of the IFN-I pathway. All of these IFN I-related disorders can cause renal dysfunction, and share pathogenic and histopathological features. Collapsing glomerulopathy, a histopathological lesion characterised by podocyte loss, collapse of the vascular tuft and PEC proliferation, is commonly associated with viral infections, has been described in T1Is such as Aicardi-Goutières syndrome and STING-associated vasculopathy with onset in infancy (SAVI), and can also be induced by recombinant IFN-therapy. In all of these conditions, podocytes and PECs seem to be the primary target of IFN I-mediated damage. Additionally, immune-mediated glomerular injury is common to viral infections, SLE, and T1Is such as COPA syndrome and DNASE1L3 deficiency, diseases in which IFN-I apparently promotes immune-mediated kidney injury. Finally, kidney pathology primarily characterised by vascular lesions (e.g., thrombotic microangiopathy, vasculitis) is a hallmark of the T1I ADA2 deficiency as well as of SLE, viral infections and IFN-therapy.Defining the nosology, pathogenic mechanisms and histopathological patterns of IFN I-related kidney disorders has diagnostic and therapeutic implications, especially considering the likely near-term availability of novel drugs targeting the IFN-I pathway.

Genetic Parameter Estimation and Whole Sequencing Analysis of the Genetic Architecture of Chicken Keel Bending

Bone health is particularly important for high-yielding commercial layer chickens. The keel of poultry is an extension of the abdomen side of the sternum along the sagittal plane and is one of the most important bones. In this study, the keel phenotype of White Leghorns laying hen flocks showed significant individual differences. To clarify its genetic mechanism, we first estimated the heritability of keel bend (KB) in White Leghorn, recorded the production performance of the chicken flock, examined the blood biochemical indexes and bone quality in KB and keel normal (KN) chickens, and performed whole-genome pooled sequencing in KB and KN chickens. We then performed selection elimination analysis to determine the genomic regions that may affect the keel phenotypes. The results show that KB is a medium heritability trait. We found that cage height had a significant effect on the KB (p < 0.01). At 48 weeks, there were significant differences in the number of eggs, the number of normal eggs, and eggshell strength (p < 0.05). The content of parathyroid hormone was lower (p < 0.01) and that of calcitonin was higher (p < 0.01) in KB chickens than in KN chickens. The differences in bone mineral density, bone strength, and bone cortical thickness of the humerus and femur were extremely significant (p < 0.01), with all being lower in KB chickens than in KN chickens. In addition, the bones of KB chickens contained more fat organization. A total of 128 genes were identified in selective sweep regions. We identified 10 important candidate genes: ACP5, WNT1, NFIX, CNN1, CALR, FKBP11, TRAPPC5, MAP2K7, RELA, and ENSGALG00000047166. Among the significantly enriched Kyoto Encyclopedia of Genes and Genomes pathways found, we identifed two bone-related pathways, one involving “osteoclast differentiation” and the other the “MAPK signaling pathway.” These results may help us better understand the molecular mechanism of bone traits in chickens and other birds and provide new insights for the genetic breeding of chickens.

Pathogenic insights from genetic causes of autoinflammatory inflammasomopathies and interferonopathies

A number of systemic autoinflammatory diseases arise from gain-of-function mutations in genes encoding IL-1-activating inflammasomes or cytoplasmic nucleic acid sensors including the receptor and sensor STING and result in increased IL-1 and type I interferon production, respectively. Blocking these pathways in human diseases has provided proof-of-concept, confirming the prominent roles of these cytokines in disease pathogenesis. Recent insights into the multilayered regulation of these sensor pathways and insights into their role in amplifying the disease pathogenesis of monogenic and complex genetic diseases spurred new drug development targeting the sensors. This review provides insights into the pathogenesis and genetic causes of these "prototypic" diseases caused by gain-of function mutations in IL-1-activating inflammasomes (inflammasomopathies) and in interferon-activating pathways (interferonopathies) including STING-associated vasculopathy with onset in infancy, Aicardi-Goutieres syndrome, and proteasome-associated autoinflammatory syndromes that link activation of the viral sensors STING, "self" nucleic acid metabolism, and the ubiquitin-proteasome system to "type I interferon production" and human diseases. Clinical responses and biomarker changes to Janus kinase inhibitors confirm a role of interferons, and a growing number of diseases with "interferon signatures" unveil extensive cross-talk between major inflammatory pathways. Understanding these interactions promises new tools in tackling the significant clinical challenges in treating patients with these conditions.

Neuroinflammation Associated With Inborn Errors of Immunity

The advent of high-throughput sequencing has facilitated genotype-phenotype correlations in congenital diseases. This has provided molecular diagnosis and benefited patient management but has also revealed substantial phenotypic heterogeneity. Although distinct neuroinflammatory diseases are scarce among the several thousands of established congenital diseases, elements of neuroinflammation are increasingly recognized in a substantial proportion of inborn errors of immunity, where it may even dominate the clinical picture at initial presentation. Although each disease entity is rare, they collectively can constitute a significant proportion of neuropediatric patients in tertiary care and may occasionally also explain adult neurology patients. We focus this review on the signs and symptoms of neuroinflammation that have been reported in association with established pathogenic variants in immune genes and suggest the following subdivision based on proposed underlying mechanisms: autoinflammatory disorders, tolerance defects, and immunodeficiency disorders. The large group of autoinflammatory disorders is further subdivided into IL-1β-mediated disorders, NF-κB dysregulation, type I interferonopathies, and hemophagocytic syndromes. We delineate emerging pathogenic themes underlying neuroinflammation in monogenic diseases and describe the breadth of the clinical spectrum to support decisions to screen for a genetic diagnosis and encourage further research on a neglected phenomenon.

Tartrate-resistant acid phosphatase 5 promotes pulmonary fibrosis by modulating β-catenin signaling

Idiopathic pulmonary fibrosis (IPF) is a fatal interstitial lung disease with limited therapeutic options. Tartrate-resistant acid phosphatase 5 (ACP5) performs a variety of functions. However, its role in IPF remains unclear. Here, we demonstrate that the levels of ACP5 are increased in IPF patient samples and mice with bleomycin (BLM)-induced pulmonary fibrosis. In particular, higher levels of ACP5 are present in the sera of IPF patients with a diffusing capacity of the lungs for carbonmonoxide (DLCO) less than 40% of the predicted value. Additionally, Acp5 deficiency protects mice from BLM-induced lung injury and fibrosis coupled with a significant reduction of fibroblast differentiation and proliferation. Mechanistic studies reveal that Acp5 is upregulated by transforming growth factor-β1 (TGF-β1) in a TGF-β receptor 1 (TGFβR1)/Smad family member 3 (Smad3)-dependent manner, after which Acp5 dephosphorylates p-β-catenin at serine 33 and threonine 41, inhibiting the degradation of β-catenin and subsequently enhancing β-catenin signaling in the nucleus, which promotes the differentiation, proliferation and migration of fibroblast. More importantly, the treatment of mice with Acp5 siRNA-loaded liposomes or Acp5 inhibitor reverses established lung fibrosis. In conclusions, Acp5 is involved in the initiation and progression of pulmonary fibrosis and strategies aimed at silencing or suppressing Acp5 could be considered as potential therapeutic approaches against pulmonary fibrosis.

Idiopathic pulmonary fibrosis is a fatal lung disease with limited treatment options. Here the authors show that tartrate-resistant acid phosphatase 5 (Acp5) promotes lung fibrosis by enhancing beta-catenin signaling and that inhibition of Acp5 can reverse stablished pulmonary fibrosis.

The type I interferonopathies: 10 years on

As brutally demonstrated by the COVID-19 pandemic, an effective immune system is essential for survival. Developed over evolutionary time, viral nucleic acid detection is a central pillar in the defensive armamentarium used to combat foreign microbial invasion. To ensure cellular homeostasis, such a strategy necessitates the efficient discrimination of pathogen-derived DNA and RNA from that of the host. In 2011, it was suggested that an upregulation of type I interferon signalling might serve as a defining feature of a novel set of Mendelian inborn errors of immunity, where antiviral sensors are triggered by host nucleic acids due to a failure of self versus non-self discrimination. These rare disorders have played a surprisingly significant role in informing our understanding of innate immunity and the relevance of type I interferon signalling for human health and disease. Here we consider what we have learned in this time, and how the field may develop in the future.

Novel Mutations in ACP5 and SAMHD1 in a Patient With Pediatric Systemic Lupus Erythematosus

BACKGROUND

The study of genetic predisposition to pediatric systemic lupus erythematosus (pSLE) has brought new insights into the pathophysiology of SLE, as it is hypothesized that genetic predisposition is greater in children. Furthermore, identifying genetic variants and linking disrupted genes to abnormal immune pathways and clinical manifestations can be beneficial for both diagnosis and treatment. Here, we identified genetic alterations in a patient with childhood-onset SLE and analyzed the immunological mechanisms behind them to support future diagnosis, prognosis, and treatment.

METHODS

Whole exome sequencing (WES) was adopted for genetic analysis of a patient with childhood-onset SLE. Gene mutations were confirmed by Sanger sequencing. Clinical data of this patient were collected and summarized. Ingenuity Pathway Analysis was used to provide interacting genes of the perturbed genes. Online Enrichr tool and Cytoscape software were used to analysis the related pathways of these genes.

RESULTS

We present a case of a 2-year-old girl who was diagnosed with idiopathic thrombocytopenic purpura (ITP) and SLE. The patient was characterized by cutaneous bleeding spots on both lower extremities, thrombocytopenia, decreased serum complements levels, increased urinary red blood cells, and positive ANA and dsDNA. The patient was treated with methylprednisolone and mycophenolate, but clinical remission could not be achieved. The genomic analysis identified three novel mutations in this pSLE patient, a double-stranded missense mutation in ACP5 (c.1152G>T and c.420G>A) and a single-stranded mutation in SAMHD1 (c.1423G>A). Bioinformatic analysis showed that these two genes and their interacting genes are enriched in the regulation of multiple immune pathways associated with SLE, including cytokine signaling and immune cell activation or function. Analysis of the synergistic regulation of these two genes suggests that abnormalities in the type I interferon pathway caused by genetic variants may contribute to the pathogenesis of SLE.

CONCLUSION

The combined complexity of polymorphisms in the coding regions of ACP5 and SAMHD1 influences the susceptibility to SLE. Alterations in these genes may lead to abnormalities in the type I interferon pathway. Our study extends the spectrum of mutations in the ACP5 and SAMHD1 genes. The identification of these mutations could aid in the diagnosis of SLE with genetic counseling and suggest potential precise treatments for specific pathways.

Spondylenchondrodysplasia mimicking a systemic lupus erythematosus: A diagnostic challenge in a pediatric patient

Spondyloenchondrodysplasia (SPENCD) is a rare autosomal recessive skeletal dysplasia caused by biallelic mutations in the ACP5 gene that encodes tartrate-resistant acid phosphatase (TRAP). The extra-osseous phenotype of SPENCD is extremely pleiotropic and is characterized by neurological impairment and immune dysfunction. This phenotype can mimic systemic lupus erythematosus. Herein, we report a child presented with systemic lupus erythematosus-like symptoms, including multisystem inflammation, autoimmunity, and immunodeficiency, but was subsequently diagnosed as SPENCD.

Type I Interferonopathies in Children: An Overview

Notable advances in gene sequencing methods in recent years have permitted enormous progress in the phenotypic and genotypic characterization of autoinflammatory syndromes. Interferonopathies are a recent group of inherited autoinflammatory diseases, characterized by a dysregulation of the interferon pathway, leading to constitutive upregulation of its activation mechanisms or downregulation of negative regulatory systems. They are clinically heterogeneous, but some peculiar clinical features may lead to suspicion: a familial "idiopathic" juvenile arthritis resistant to conventional treatments, an early necrotizing vasculitis, a non-infectious interstitial lung disease, and a panniculitis associated or not with a lipodystrophy may represent the "interferon alarm bells." The awareness of this group of diseases represents a challenge for pediatricians because, despite being rare, a differential diagnosis with the most common childhood rheumatological and immunological disorders is mandatory. Furthermore, the characterization of interferonopathy molecular pathogenetic mechanisms is allowing important steps forward in other immune dysregulation diseases, such as systemic lupus erythematosus and inflammatory myositis, implementing the opportunity of a more effective target therapy.

Lung involvement in monogenic interferonopathies

Monogenic type I interferonopathies are inherited heterogeneous disorders characterised by early onset of systemic and organ specific inflammation, associated with constitutive activation of type I interferons (IFNs). In the last few years, several clinical reports identified the lung as one of the key target organs of IFN-mediated inflammation. The major pulmonary patterns described comprise children's interstitial lung diseases (including diffuse alveolar haemorrhages) and pulmonary arterial hypertension but diagnosis may be challenging. Respiratory symptoms may be either mild or absent at disease onset and variably associated with systemic or organ specific inflammation. In addition, associated extrapulmonary clinical features may precede lung function impairment by years, and patients may display severe/endstage lung involvement, although this may be clinically hidden during the long-term disease course. Conversely, a few cases of atypical severe lung involvement at onset have been reported without clinically manifested extrapulmonary signs. Hence, a multidisciplinary approach involving pulmonologists, paediatricians and rheumatologists should always be considered when a monogenic interferonopathy is suspected. Pulmonologists should also be aware of the main pattern of presentation to allow prompt diagnosis and a targeted therapeutic strategy. In this regard, promising therapeutic strategies rely on Janus kinase-1/2 (JAK-1/2) inhibitors blocking the type I IFN-mediated intracellular cascade.

Progressive severe lung impairment may occur clinically hidden during monogenic interferonopathies. Pulmonologists should be aware of the main patterns of presentation in order to allow prompt diagnosis and initiate targeted therapeutic strategy.https://bit.ly/2UeAeLn

[Classification of autoinflammatory diseases based on pathophysiological mechanisms]

Monogenic autoinflammatory diseases present with systemic inflammation with the involvement of multiple organs. With the help of modern molecular genetic techniques a large number of diseases with previously unknown pathomechanisms have been described in recent years. This knowledge can be utilized to group autoinflammatory diseases according to the signalling pathways involved and thus provide a better understanding of these entities.

Monogenic lupus due to spondyloenchondrodysplasia with spastic paraparesis and intracranial calcification: case-based review

Spondyloenchondrodysplasia (SPENCD) is a rare skeletal dysplasia characterized with platyspondyly and metaphyseal lesions of the long bones mimicking enchondromatosis, resulting in short stature. SPENCD often coexists with neurologic disorders and immune dysregulation. Spasticity, developmental delay and intracranial calcification are main neurologic abnormalities. Large spectrum of immunologic abnormalities may be seen in SPENCD, including immune deficiencies and autoimmune disorders with autoimmune thrombocytopenia and systemic lupus erythematosus as the most common phenotypes. SPENCD is caused by loss of tartrate-resistant acid phosphatase (TRAP) activity, due to homozygous mutations in ACP5, playing a role in non-nucleic acid-related stimulation/regulation of the type I interferon pathway. We present two siblings, 13-year-old girl and 25-year-old boy with SPENCD, from consanguineous parents. Both patients had short stature, platyspondyly, metaphyseal changes, spastic paraparesis, mild intellectual disability, and juvenile-onset SLE. The age at disease-onset was 2 years for girl and 19 years for boy. Both had skin and mucosa involvement. The age at diagnosis of SLE was 4 years for girl, and 19 years for boy. The clinical diagnosis of SPENCD was confirmed by sequencing of ACP5 gene, which revealed a homozygous c.155A > C (p.K52T), a variant reported before as pathogenic. Juvenile-onset SLE accounts for about 15-20% of all SLE cases. But, the onset of SLE before 5-years of age and also monogenic SLE are rare. Our case report and the literature review show the importance of multisystemic evaluation in the diagnosis of SPENCD and to remind the necessity of investigating the monogenic etiology in early-onset and familial SLE cases.

Monogenic lupus due to spondyloenchondrodysplasia with spastic paraparesis and intracranial calcification: case-based review

Spondyloenchondrodysplasia (SPENCD) is a rare skeletal dysplasia characterized with platyspondyly and metaphyseal lesions of the long bones mimicking enchondromatosis, resulting in short stature. SPENCD often coexists with neurologic disorders and immune dysregulation. Spasticity, developmental delay and intracranial calcification are main neurologic abnormalities. Large spectrum of immunologic abnormalities may be seen in SPENCD, including immune deficiencies and autoimmune disorders with autoimmune thrombocytopenia and systemic lupus erythematosus as the most common phenotypes. SPENCD is caused by loss of tartrate-resistant acid phosphatase (TRAP) activity, due to homozygous mutations in ACP5, playing a role in non-nucleic acid-related stimulation/regulation of the type I interferon pathway. We present two siblings, 13-year-old girl and 25-year-old boy with SPENCD, from consanguineous parents. Both patients had short stature, platyspondyly, metaphyseal changes, spastic paraparesis, mild intellectual disability, and juvenile-onset SLE. The age at disease-onset was 2 years for girl and 19 years for boy. Both had skin and mucosa involvement. The age at diagnosis of SLE was 4 years for girl, and 19 years for boy. The clinical diagnosis of SPENCD was confirmed by sequencing of ACP5 gene, which revealed a homozygous c.155A > C (p.K52T), a variant reported before as pathogenic. Juvenile-onset SLE accounts for about 15–20% of all SLE cases. But, the onset of SLE before 5-years of age and also monogenic SLE are rare. Our case report and the literature review show the importance of multisystemic evaluation in the diagnosis of SPENCD and to remind the necessity of investigating the monogenic etiology in early-onset and familial SLE cases.

Characterisation of ACP5 missense mutations encoding tartrate-resistant acid phosphatase associated with spondyloenchondrodysplasia

Biallelic mutations in ACP5, encoding tartrate-resistant acid phosphatase (TRACP), have recently been identified to cause the inherited immuno-osseous disorder, spondyloenchondrodysplasia (SPENCD). This study was undertaken to characterize the eight reported missense mutations in ACP5 associated with SPENCD on TRACP expression. ACP5 mutant genes were synthesized, transfected into human embryonic kidney (HEK-293) cells and stably expressing cell lines were established. TRACP expression was assessed by cytochemical and immuno-cytochemical staining with a panel of monoclonal antibodies. Analysis of wild (WT) type and eight mutant stable cell lines indicated that all mutants lacked stainable enzyme activity. All ACP5 mutant constructs were translated into intact proteins by HEK-293 cells. The mutant TRACP proteins displayed variable immune reactivity patterns, and all drastically reduced enzymatic activity, revealing that there is no gross inhibition of TRACP biosynthesis by the mutations. But they likely interfere with folding thereby impairing enzyme function. TRACP exists as two isoforms. TRACP 5a is a less active monomeric enzyme (35kD), with the intact loop peptide and TRACP 5b is proteolytically cleaved highly active enzyme encompassing two subunits (23 kD and 16 kD) held together by disulfide bonds. None of the mutant proteins were proteolytically processed into isoform 5b intracellularly, and only three mutants were secreted in significant amounts into the culture medium as intact isoform 5a-like proteins. Analysis of antibody reactivity patterns revealed that T89I and M264K mutant proteins retained some native conformation, whereas all others were in “denatured” or “unfolded” forms. Western blot analysis with intracellular and secreted TRACP proteins also revealed similar observations indicating that mutant T89I is amply secreted as inactive protein. All mutant proteins were attacked by Endo-H sensitive glycans and none could be activated by proteolytic cleavage in vitro. In conclusion, determining the structure-function relationship of the SPENCD mutations in TRACP will expand our understanding of basic mechanisms underlying immune responsiveness and its involvement in dysregulated bone metabolism.

New Horizons in the Genetic Etiology of Systemic Lupus Erythematosus and Lupus-Like Disease: Monogenic Lupus and Beyond

Systemic lupus erythematosus (SLE) is a clinically and genetically heterogeneous autoimmune disease. The etiology of lupus and the contribution of genetic, environmental, infectious and hormonal factors to this phenotype have yet to be elucidated. The most straightforward approach to unravel the molecular pathogenesis of lupus may rely on studies of patients who present with early-onset severe phenotypes. Typically, they have at least one of the following clinical features: childhood onset of severe disease (<5 years), parental consanguinity, and presence of family history for autoimmune diseases in a first-degree relative. These patients account for a small proportion of patients with lupus but they inform considerable knowledge about cellular pathways contributing to this inflammatory phenotype. In recent years with the aid of new sequencing technologies, novel or rare pathogenic variants have been reported in over 30 genes predisposing to SLE and SLE-like diseases. Future studies will likely discover many more genes with private variants associated to lupus-like phenotypes. In addition, genome-wide association studies (GWAS) have identified a number of common alleles (SNPs), which increase the risk of developing lupus in adult age. Discovery of a possible shared immune pathway in SLE patients, either with rare or common variants, can provide important clues to better understand this complex disorder, it's prognosis and can help guide new therapeutic approaches. The aim of this review is to summarize the current knowledge of the clinical presentation, genetic diagnosis and mechanisms of disease in patents with lupus and lupus-related phenotypes.

Immune Function and Diversity of Osteoclasts in Normal and Pathological Conditions

Osteoclasts (OCLs) are key players in controlling bone remodeling. Modifications in their differentiation or bone resorbing activity are associated with a number of pathologies ranging from osteopetrosis to osteoporosis, chronic inflammation and cancer, that are all characterized by immunological alterations. Therefore, the 2000s were marked by the emergence of osteoimmunology and by a growing number of studies focused on the control of OCL differentiation and function by the immune system. At the same time, it was discovered that OCLs are much more than bone resorbing cells. As monocytic lineage-derived cells, they belong to a family of cells that displays a wide heterogeneity and plasticity and that is involved in phagocytosis and innate immune responses. However, while OCLs have been extensively studied for their bone resorption capacity, their implication as immune cells was neglected for a long time. In recent years, new evidence pointed out that OCLs play important roles in the modulation of immune responses toward immune suppression or inflammation. They unlocked their capacity to modulate T cell activation, to efficiently process and present antigens as well as their ability to activate T cell responses in an antigen-dependent manner. Moreover, similar to other monocytic lineage cells such as macrophages, monocytes and dendritic cells, OCLs display a phenotypic and functional plasticity participating to their anti-inflammatory or pro-inflammatory effect depending on their cell origin and environment. This review will address this novel vision of the OCL, not only as a phagocyte specialized in bone resorption, but also as innate immune cell participating in the control of immune responses.

Spotlight on anifrolumab and its potential for the treatment of moderate-to-severe systemic lupus erythematosus: evidence to date

Previous reports have described the appearance of systemic lupus erythematosus (SLE) cases following interferon-α (IFN-α) therapy, IFN-regulated gene expression is significantly increased in SLE, and an association between SLE and gene variants belonging to IFN downstream pathways has been shown. Based on this, targeting of IFN and of their signaling pathways has appeared to be interesting developments within the field of SLE therapy. Different specific type I IFN antagonists have been studied in clinical trials and some of those have already reached Phase III. A potential approach would be to target IFN receptors rather than IFN themselves. Anifrolumab (previously MEDI-546) is a fully human monoclonal antibody (Ab) that binds to subunit 1 of the type I IFN receptor (IFNAR1), blocking the action of different type I IFNs (IFN-α, IFN-β and IFN-ω). This drug has been assessed in 11 clinical studies: 9 in SLE, 1 in systemic sclerosis and 1 in rheumatoid arthritis. In SLE, clinical development reached Phase I for 1 study and Phases II and III for 5 and 3 trials, respectively. The Phase IIb, randomized control trial (RCT), double-blind, placebo-controlled study of adults with moderate-to-severe SLE (MUSE trial) showed positive results on the composite primary endpoint SRI-4. Greater efficacy was seen in patients with high baseline IFN gene signature compared with those with low baseline IFN gene signature. Anifrolumab also demonstrated promising results on cutaneous and arthritic manifestations, especially among patients with a high IFN gene signature. The pivotal Treatment of Uncontrolled Lupus via the Interferon IFN Pathway (TULIP 1 and 2 studies are now completed. In August 2018, the promoter announced that the TULIP 1 Phase III trial did not reach its primary endpoint. The release of the completed but not yet published Phase II studies and of the TULIP pivotal trials results will further inform us on the actual therapeutic potential of anifrolumab.

Craniofacial anomalies associated with spondyloenchondrodysplasia: Two case reports

RATIONALE

Spondyloenchondrodysplasia (SPENCD) is an autosomal recessive skeletal dysplasia by biallelic mutations in ACP5 gene encoding tartrate-resistant acid phosphatase (TRAP). The extra-osseous phenotype of SPENCD is pleiotropic and involves neurological impairment and immune dysfunction. Dentofacial abnormalities and orofacial symptoms in SPENCD patients have been little discussed in the literature.

PATIENTS CONCERNS

Herein we present clinical and radiological data regarding 2 siblings with SPENCD. Both patients exhibited short stature, cervical platyspondyly, growth disturbance with multiple skeletal deformities of the wrist, and systemic lupus erythematosus related autoimmunity. They experienced prolonged pain in the temporomandibular joint (TMJ) area and exhibited delayed dental development. One patient presented with midface hypoplasia, retrognathic mandible, and anterior openbite. Computed tomographic images demonstrated delayed spheno-occipital synchondrosis, obtuse cranial base angle, overdeveloped and anteriorly displaced sphenoidal sinuses, and compressed ethmoidal sinuses.

DIAGNOSIS

The genetic analysis revealed heterozygous for a missense mutations at ACP5 in both probands.

INTERVENTIONS

Routine follow-up with conservative treatment were conducted for 12 months.

OUTCOMES

The elder sister's orofacial pain was relieved but the boy showed sustained masticatory and cervical muscle pain and TMJ arthralgia which had changed in accordance with systemic condition. No further teeth eruption or skeletal growth was observed in 2 siblings during the follow-up period.

LESSONS

These findings extend the phenotypic spectrum of SPENCD and indicate that compromised endochondral ossification and the loss of TRAP activity may affect altered dentofacial development and orofacial symptoms.

The Lysosomal Protein Arylsulfatase B Is a Key Enzyme Involved in Skeletal Turnover

Skeletal pathologies are frequently observed in lysosomal storage disorders, yet the relevance of specific lysosomal enzymes in bone remodeling cell types is poorly defined. Two lysosomal enzymes, ie, cathepsin K (Ctsk) and Acp5 (also known as tartrate-resistant acid phosphatase), have long been known as molecular marker proteins of differentiated osteoclasts. However, whereas the cysteine protease Ctsk is directly involved in the degradation of bone matrix proteins, the molecular function of Acp5 in osteoclasts is still unknown. Here we show that Acp5, in concert with Acp2 (lysosomal acid phosphatase), is required for dephosphorylation of the lysosomal mannose 6-phosphate targeting signal to promote the activity of specific lysosomal enzymes. Using an unbiased approach we identified the glycosaminoglycan-degrading enzyme arylsulfatase B (Arsb), mutated in mucopolysaccharidosis type VI (MPS-VI), as an osteoclast marker, whose activity depends on dephosphorylation by Acp2 and Acp5. Similar to Acp2/Acp5^-/- mice, Arsb-deficient mice display lysosomal storage accumulation in osteoclasts, impaired osteoclast activity, and high trabecular bone mass. Of note, the most prominent lysosomal storage accumulation was observed in osteocytes from Arsb-deficient mice, yet this pathology did not impair production of sclerostin (Sost) and Fgf23. Because the influence of enzyme replacement therapy (ERT) on bone remodeling in MPS-VI is still unknown, we additionally treated Arsb-deficient mice by weekly injection of recombinant human ARSB from 12 to 24 weeks of age. We found that the high bone mass phenotype of Arsb-deficient mice and the underlying bone cell deficits were fully corrected by ERT in the trabecular compartment. Taken together, our results do not only show that the function of Acp5 in osteoclasts is linked to dephosphorylation and activation of lysosomal enzymes, they also provide an important proof-of-principle for the feasibility of ERT to correct bone cell pathologies in lysosomal storage disorders. © 2018 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.

Monogenic Lupus: A Developing Paradigm of Disease

Monogenic lupus is a form of systemic lupus erythematosus (SLE) that occurs in patients with a single gene defect. This rare variant of lupus generally presents with early onset severe disease, especially affecting the kidneys and central nervous system. To date, a significant number of genes have been implicated in monogenic lupus, providing valuable insights into a very complex disease process. Throughout this review, we will summarize the genes reported to be associated with monogenic lupus or lupus-like diseases, and the pathogenic mechanisms affected by the mutations involved upon inducing autoimmunity.

Primary immunodeficiency diseases in a tuberculosis endemic region: challenges and opportunities

While individual primary immunodeficiency diseases (PIDs) are rare, collectively they represent a significant burden of disease. Recent estimates show that about one million people in Africa suffer from a PID. However, data from African PID registries reflect only a small percentage of the estimated prevalence. This disparity is partly due to the lack of PID awareness and the masking of PIDs by the endemic pathogens. Over three million tuberculosis (TB) cases were reported in Africa in 2016, with many of these from southern Africa. Despite concerted efforts to address this high burden of disease, the underlying genetic correlates of susceptibility to TB remain poorly understood. High penetrance mutations in immune system genes can cause PIDs that selectively predispose individuals to TB and other mycobacterial diseases. Additionally, the identification of individuals at a heightened risk of developing TB or of presenting with severe or disseminated TB due to their genetic ancestry is crucial to promote a positive treatment outcome. The screening for and identification of PID mutations in TB-endemic regions by next-generation sequencing (NGS) represents a promising approach to improve the understanding of what constitutes an effective immune response to TB, as well as the range of associated PIDs and phenotypes.

Targeting interferons and their pathways in systemic lupus erythematosus

Significant advances in the understanding of the molecular basis of innate immunity have led to the identification of interferons (IFNs), particularly IFN-α, as central mediators in the pathogenesis of Systemic Lupus Erythematosus. Therefore, targeting of IFNs and of their downstream pathways has emerged as important developments for novel drug research in SLE. Based on this, several specific interferon blocking strategies using anti-IFN-α antibodies, anti-type I interferon receptor antibodies, Interferon-α-kinoid, or anti-IFN-γ antibodies have all been assessed in recent clinical trials. Alternative strategies targeting the plasmacytoid dendritic cells (pDCs), Toll-Like Receptors (TLRs)-7/9 or their downstream pathways such as the myeloid differentiation primary-response protein 88 (MYD88), spleen tyrosine kinase (Syk), Janus-kinases (JAKs), interleukin-1 receptor-associated kinase 4 (IRAK4), or the Tyrosine Kinase 2 (TYK2) are also investigated actively in SLE, at more preliminary clinical development stages, except for JAK inhibitors which have reached phase 2 studies. In a near future, in-depth and personalized functional characterization of IFN pathways may provide further guidance for the selection of the most relevant therapeutic strategy in SLE, tailored at the patient-level.

Monogenic lupus: it's all new!

Monogenic lupus is rare, but its study has contributed immensely to a better understanding of the pathogenesis of systemic lupus erythematosus. The first forms identified were inherited complement deficiencies, which predisposed to lupus due to impaired tolerance, and aberrant clearance of apoptotic bodies and immune complexes. In recent years, several new monogenic disorders with a lupus-like phenotype have been described. These include forms that affect nucleic acid repair, degradation and sensing (TREX1, DNASE1L3), the type I interferon (IFN) pathway (SAMHD1, RNASEH2ABC, ADAR1, IFIH1, ISG15, ACP5, TMEM173) and B cell development checkpoints (PRKCD; RAG2). Pathways informed by these newly described disorders have continued to improve our understanding of systemic lupus erythematosus.

Tartrate-resistant acid phosphatase (TRAP/ACP5) promotes metastasis-related properties via TGFβ2/TβR and CD44 in MDA-MB-231 breast cancer cells

BACKGROUND

Tartrate-resistant acid phosphatase (TRAP/ACP5), a metalloenzyme that is characteristic for its expression in activated osteoclasts and in macrophages, has recently gained considerable focus as a driver of metastasis and was associated with clinically relevant parameters of cancer progression and cancer aggressiveness.

METHODS

MDA-MB-231 breast cancer cells with different TRAP expression levels (overexpression and knockdown) were generated and characterized for protein expression and activity levels. Functional cell experiments, such as proliferation, migration and invasion assays were performed as well as global phosphoproteomic and proteomic analysis was conducted to connect molecular perturbations to the phenotypic changes.

RESULTS

We identified an association between metastasis-related properties of TRAP-overexpressing MDA-MB-231 breast cancer cells and a TRAP-dependent regulation of Transforming growth factor (TGFβ) pathway proteins and Cluster of differentiation 44 (CD44). Overexpression of TRAP increased anchorage-independent and anchorage-dependent cell growth and proliferation, induced a more elongated cellular morphology and promoted cell migration and invasion. Migration was increased in the presence of the extracellular matrix (ECM) proteins osteopontin and fibronectin and the basement membrane proteins collagen IV and laminin I. TRAP-induced properties were reverted upon shRNA-mediated knockdown of TRAP or treatment with the small molecule TRAP inhibitor 5-PNA. Global phosphoproteomics and proteomics analyses identified possible substrates of TRAP phosphatase activity or signaling intermediates and outlined a TRAP-dependent regulation of proteins involved in cell adhesion and ECM organization. Upregulation of TGFβ isoform 2 (TGFβ2), TGFβ receptor type 1 (TβR1) and Mothers against decapentaplegic homolog 2 (SMAD2), as well as increased intracellular phosphorylation of CD44 were identified upon TRAP perturbation. Functional antibody-mediated blocking and chemical inhibition demonstrated that TRAP-dependent migration and proliferation is regulated via TGFβ2/TβR, whereas proliferation beyond basal levels is regulated through CD44.

CONCLUSION

Altogether, TRAP promotes metastasis-related cell properties in MDA-MB-231 breast cancer cells via TGFβ2/TβR and CD44, thereby identifying a potential signaling mechanism associated to TRAP action in breast cancer cells.

Increased amount of phosphorylated proinflammatory osteopontin in rheumatoid arthritis synovia is associated to decreased tartrate-resistant acid phosphatase 5B/5A ratio

Background

Osteopontin (OPN) is an immunoregulatory protein which production increases in both rheumatoid arthritis (RA) and osteoarthritis (OA). Phosphorylated osteopontin (Phospho-OPN) is known to increase macrophage and osteoclast activation, this process is controlled by extracellular tartrate-resistant acid phosphatase (TRAcP), also a biomarker for RA. Here, we evaluated the phosphorylation status of OPN in RA and OA synovia, as well as its correlation with TRAcP isoforms.

Methods

Synovial tissue and fluid were obtained from 24 RA (14 seropositive and 10 seronegative) and 24 OA patients. Western blotting was used to analyze the extent of OPN phosphorylation. TRAcP isoforms were measured in synovial fluid using ELISA; immunohistochemistry assessed the distribution of OPN and TRAcP expressing cells in the synovial tissue, especially distinguishing between the TRAcP isoforms.

Results

Full-length OPN was more phosphorylated in RA than in OA (p<0.05). The thrombin cleaved C-terminal end of OPN was also more phosphorylated in RA (p<0.05). RA patients had a lower concentration of TRAcP 5B and higher concentration of less active 5A in their synovial fluid compared to OA patients. The TRAcP 5B/5A ratio was decreased in RA and correlated negatively with the amount of phospho-OPN (p<0.05). TRAcP positive cells for both isoforms were found all along the synovial lining; OPN antibody staining was localized in the extracellular matrix.

Conclusion

Our data suggests that in RA the synovial fluid contains insufficient amounts of TRAcP 5B which increase levels of the proinflammatory phospho-OPN. This may lead to increased macrophage and osteoclast activation, resulting in the increased local inflammation and bone resorption present in RA joints.

Bone Alkaline Phosphatase and Tartrate-Resistant Acid Phosphatase: Potential Co-regulators of Bone Mineralization

Phosphorylated osteopontin (OPN) inhibits hydroxyapatite crystal formation and growth, and bone alkaline phosphatase (BALP) promotes extracellular mineralization via the release of inorganic phosphate from the mineralization inhibitor inorganic pyrophosphate (PPi). Tartrate-resistant acid phosphatase (TRAP), produced by osteoclasts, osteoblasts, and osteocytes, exhibits potent phosphatase activity towards OPN; however, its potential capacity as a regulator of mineralization has not previously been addressed. We compared the efficiency of BALP and TRAP towards the endogenous substrates for BALP, i.e., PPi and pyridoxal 5'-phosphate (PLP), and their impact on mineralization in vitro via dephosphorylation of bovine milk OPN. TRAP showed higher phosphatase activity towards phosphorylated OPN and PPi compared to BALP, whereas the activity of TRAP and BALP towards PLP was comparable. Bovine milk OPN could be completely dephosphorylated by TRAP, liberating all its 28 phosphates, whereas BALP dephosphorylated at most 10 phosphates. OPN, dephosphorylated by either BALP or TRAP, showed a partially or completely attenuated phosphorylation-dependent inhibitory capacity, respectively, compared to native OPN on the formation of mineralized nodules. Thus, there are phosphorylations in OPN important for inhibition of mineralization that are removed by TRAP but not by BALP. In conclusion, our data indicate that both BALP and TRAP can alleviate the inhibitory effect of OPN on mineralization, suggesting a potential role for TRAP in skeletal mineralization. Further studies are warranted to explore the possible physiological relevance of TRAP in bone mineralization.

Posttranslational Modification as a Critical Determinant of Cytoplasmic Innate Immune Recognition

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

Toward an Inclusive, Congruent, and Precise Definition of Autoinflammatory Diseases

Autoinflammatory disease was introduced as a concept in 1999, demarcating an entirely new group of diseases in clinical, immunological, and conceptual terms. During recent years, the preconditions for the definition of autoinflammatory conditions have changed. This includes the recent discovery of a number of monogenic autoinflammatory conditions with complex phenotypes that combine autoinflammation with defects of the adaptive and/or innate immune system, resulting in the occurrence of infection, autoimmunity, and/or uncontrolled hyperinflammation in addition to autoinflammation. Further, there are strong indications that classical IL-1-driven autoinflammatory diseases are associated with activation of adaptive immunity. As suggested by this development, we are of the opinion that an all-encompassing definition of autoinflammatory diseases should regard autoinflammatory conditions and innate dysregulation as inseparable and integral parts of the immune system as a whole. Hence, in this article, we try to advance the conceptual understanding of autoinflammatory disease by, proposing a modification of the definition by Daniel Kastner et al., which allows for a congruent and precise description of conditions that expand the immunological spectrum of autoinflammatory disease.

Dermatologic Manifestations of Monogenic Autoinflammatory Diseases

Autoinflammatory disorders are sterile inflammatory conditions characterized by episodes of early-onset fever, rash, and disease-specific patterns of organ inflammation. Gain-of-function mutations in innate danger-sensing pathways, including the inflammasomes and the nucleic acid sensing pathways, play critical roles in the pathogenesis of IL-1 and Type-I IFN-mediated disorders and point to an important role of excessive proinflammatory cytokine signaling, including interleukin (IL)-1b , Type-I interferons, IL-18, TNF and others in causing the organ specific immune dysregulation. The article discusses the concept of targeting proinflammatory cytokines and their signaling pathways with cytokine blocking treatments that have been life changing for some patients.