Progranulin antibodies in autoimmune diseases

Progranulinopathy: A diverse realm of disorders linked to progranulin imbalances

Progranulin (PGRN), encoded by the GRN gene in humans, was originally isolated as a secreted growth factor that implicates in a multitude of processes ranging from regulation of tumorigenesis, inflammation to neural proliferation. Compelling evidence indicating that GRN mutation can lead to various common neuronal degenerative diseases and rare lysosomal storage diseases. These findings have unveiled a critical role for PGRN as a lysosomal protein in maintaining lysosomal function. The phenotypic spectrum of PGRN imbalance has expanded to encompass a broad spectrum of diseases, including autoimmune diseases, metabolic, musculoskeletal and cardiovascular diseases. These diseases collectively referred to as Progranulinopathy- a term encompasses the wide spectrum of disorders influenced by PGRN imbalance. Unlike its known extracellular function as a growth factor-like molecule associated with multiple membrane receptors, PGRN also serves as an intracellular co-chaperone engaged in the folding and traffic of its associated proteins, particularly the lysosomal hydrolases. This chaperone activity is required for PGRN to exert its diverse functions across a broad range of diseases, encompassing both the central nervous system and peripheral systems. In this comprehensive review, we present an update of the emerging role of PGRN in Progranulinopathy, with special focus on elucidating the intricate interplay between PGRN and a diverse array of proteins at various levels, ranging from extracellular fluids and intracellular components, as well as various pathophysiological processes involved. This review seeks to offer a comprehensive grasp of PGRN's diverse functions, aiming to unveil intricate mechanisms behind Progranulinopathy and open doors for future research endeavors.

Autoimmunity and Frontotemporal Lobar Degeneration: From Laboratory Study to Clinical Practice

Frontotemporal lobar degeneration (FTLD) is a group of neurodegenerative diseases with heterogenous clinical, genetic, and pathological characteristics that show similar impairment of areas in the frontal and/or temporal lobes. Prime doctors' lack of awareness of this complex disease makes early identification and accurate intervention difficult. Autoimmune diseases and autoantibodies are manifestations of different levels of autoimmune reactions. This review presents research findings examining the relationship between autoimmunity and FTLD in terms of autoimmune diseases and autoantibodies with a focus on identifying potential diagnosis and treatment approaches. The findings indicate that the same or similar pathophysiological mechanisms may exist from clinical, genetic, and pathological perspectives. However, the existing evidence is not sufficient to extract substantial conclusions. On the basis of the current situation, we propose future research patterns using prospective studies on large populations and combined clinical and experimental research. Autoimmune reactions or, more generally, inflammatory reactions should receive increased attention from doctors and scientists of all disciplines.

Progranulin in Musculoskeletal Inflammatory and Degenerative Disorders, Focus on Rheumatoid Arthritis, Lupus and Intervertebral Disc Disease: A Systematic Review

Progranulin (PGRN) is a glycoprotein formed by 593 amino acids encoded by the GRN gene. It has an important role in immunity and inflammatory response, as well as in tissue recovery. Its role in musculoskeletal inflammatory diseases such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and intervertebral disc degeneration disease (IVDD), is, nowadays, an important target to investigate. The objective of this review is to systematically sum up all the recent findings concerning PGRN as a target in the development and resolution of the inflammatory diseases. PubMed was examined with the terms combinations (Progranulin) AND (Lupus Erythematosus, Systemic), (Progranulin) AND (Arthritis, Rheumatoid), and (Progranulin) AND (Intervertebral Disc Degeneration). PubMed was examined with the terms combinations (Atsttrin) AND (Lupus Erythematosus, Systemic), (Atsttrin) AND (Arthritis, Rheumatoid), and (Atsttrin) AND (Intervertebral Disc Degeneration). Moreover, research through Web of Science was performed searching the same items. The inclusion criteria were: studies whose main topic were progranulin, or atsttrin, with emphasis on the three selected diseases. On the other hand, the exclusion criteria were studies that only focused on diseases not related to RA, lupus or IVDD, in addition to the previous published literature reviews. Since few results were obtained, we did not filter by year. The records assessed for eligibility were 23, including all the studies with the information in state of art of progranulin and its capability to be a potential target or treatment for each one of the selected diseases. As these results are descriptive and not clinical trials, we did not perform risk of bias methods. Within these results, many studies have shown an anti-inflammatory activity of PGRN in RA. PGRN levels in serum and synovial fluids in RA patients were reported higher than controls. On the other hand, serum levels were directly correlated with SLE disease activity index, suggesting an important role of PGRN as a player in the progression of inflammatory diseases and a therapeutical approach for the recovery. This review has some limitations due to the small number of studies in this regard; therefore, we highlight the importance and the necessity of further investigation. No external funding was implicated in this systematical review.

Advances in Potential Cerebrospinal Fluid Biomarkers for Autoimmune Encephalitis: A Review

Autoimmune encephalitis (AE) is a severe inflammatory disease of the brain. Patients with AE demonstrate amnesia, seizures, and psychosis. Recent studies have identified numerous associated autoantibodies (e.g., against NMDA receptors (NMDARs), LGI1, etc.) involved in the pathogenesis of AE, and the levels of diagnosis and treatment are thus improved dramatically. However, there are drawbacks of clinical diagnosis and treatment based solely on antibody levels, and thus the application of additional biomarkers is urgently needed. Considering the important role of immune mechanisms in AE development, we summarize the relevant research progress in identifying cerebrospinal fluid (CSF) biomarkers with a focus on cytokines/chemokines, demyelination, and nerve damage.

Autoantibodies against interleukin-1 receptor antagonist in multisystem inflammatory syndrome in children: a multicentre, retrospective, cohort study

Background

Multisystem inflammatory syndrome in children (MIS-C) is a rare but serious complication of infection with SARS-CoV-2. A possible involvement of pathogenetically relevant autoantibodies has been discussed. Recently, neutralising autoantibodies against inflammatory receptor antagonists progranulin and interleukin-1 receptor antagonist (IL-1Ra) were found in adult patients with critical COVID-19. The aim of this study was to investigate the role of such autoantibodies in MIS-C.

Methods

In this multicentre, retrospective, cohort study, plasma and serum samples were collected from patients (0–18 years) with MIS-C (as per WHO criteria) treated at five clinical centres in Germany and Spain. As controls, we included plasma or serum samples from children with Kawasaki disease, children with inactive systemic juvenile idiopathic arthritis, and children with suspected growth retardation (non-inflammatory control) across four clinical centres in Germany and Spain (all aged ≤18 years). Serum samples from the CoKiBa trial were used as two further control groups, from healthy children (negative for SARS-CoV-2 antibodies) and children with previous mild or asymptomatic COVID-19 (aged ≤17 years). MIS-C and control samples were analysed for autoantibodies against IL-1Ra and progranulin, and for IL-1Ra concentrations, by ELISA. Biochemical analysis of plasma IL-1Ra was performed with native Western blots and isoelectric focusing. Functional activity of the autoantibodies was examined by an in vitro IL-1β-signalling reporter assay.

Findings

Serum and plasma samples were collected between March 6, 2011, and June 2, 2021. Autoantibodies against IL-1Ra could be detected in 13 (62%) of 21 patients with MIS-C (11 girls and ten boys), but not in children with Kawasaki disease (n=24; nine girls and 15 boys), asymptomatic or mild COVID-19 (n=146; 72 girls and 74 boys), inactive systemic juvenile idiopathic arthritis (n=10; five girls and five boys), suspected growth retardation (n=33; 13 girls and 20 boys), or in healthy controls (n=462; 230 girls and 232 boys). Anti-IL-1Ra antibodies in patients with MIS-C belonged exclusively to the IgG1 subclass, except in one patient who had additional IL-1Ra-specific IgM antibodies. Autoantibodies against progranulin were only detected in one (5%) patient with MIS-C. In patients with MIS-C who were positive for anti-IL-1Ra antibodies, free plasma IL-1Ra concentrations were reduced, and immune-complexes of IL-1Ra were detected. Notably, an additional, hyperphosphorylated, transiently occurring atypical isoform of IL-1Ra was observed in all patients with MIS-C who were positive for anti-IL-1Ra antibodies. Anti-IL-1Ra antibodies impaired IL-1Ra function in reporter cell assays, resulting in amplified IL-1β signalling.

Interpretation

Anti-IL-1Ra autoantibodies were observed in a high proportion of patients with MIS-C and were specific to these patients. Generation of these autoantibodies might be triggered by an atypical, hyperphosphorylated isoform of IL-1Ra. These autoantibodies impair IL-1Ra bioactivity and might thus contribute to increased IL-1β-signalling in MIS-C.

Funding

NanoBioMed fund of the University of Saarland, José Carreras Center for Immuno and Gene Therapy, Dr Rolf M Schwiete Stiftung, Staatskanzlei Saarland, German Heart Foundation, Charity of the Blue Sisters, Bavarian Ministry of Health, the Center for Interdisciplinary Clinical Research at University Hospital Münster, EU Horizon 2020.

Injectable recombinant block polymer gel for sustained delivery of therapeutic protein in post traumatic osteoarthritis

Protein-based biomaterials offer several advantages over synthetic materials, owing to their unique stimuli-responsive properties, biocompatibility and modular nature. Here, we demonstrate that E5C, a recombinant protein block polymer, consisting of five repeats of elastin like polypeptide (E) and a coiled-coil domain of cartilage oligomeric matrix protein (C), is capable of forming a porous networked gel at physiological temperature, making it an excellent candidate for injectable biomaterials. Combination of E5C with Atsttrin, a chondroprotective engineered derivative of anti-inflammatory growth factor progranulin, provides a unique biochemical and biomechanical environment to protect against post-traumatic osteoarthritis (PTOA) onset and progression. E5C gel was demonstrated to provide prolonged release of Atsttrin and inhibit chondrocyte catabolism while facilitating anabolic signaling in vitro. We also provide in vivo evidence that prophylactic and therapeutic application of Atsttrin-loaded E5C gels protected against PTOA onset and progression in a rabbit anterior cruciate ligament transection model. Collectively, we have developed a unique protein-based gel capable of minimally invasive, sustained delivery of prospective therapeutics, particularly the progranulin-derivative Atsttrin, for therapeutic application in OA.

Progranulin as a Potential Therapeutic Target in Immune-Mediated Diseases

Progranulin (PGRN), a secretory glycoprotein consisting of 593 amino acid residues, is a key actor and regulator of multiple system functions such as innate immune response and inflammation, as well as tissue regeneration. Recently, there is emerging evidence that PGRN is protective in the development of a variety of immune-mediated diseases, including rheumatoid arthritis (RA), inflammatory bowel disease (IBD), type 1 diabetes mellitus (T1DM) and multiple sclerosis (MS) by regulating signaling pathways known to be critical for immunology, particularly the tumor necrosis factor alpha/TNF receptor (TNF-α/TNFR) signaling pathway. Whereas, the role of PGRN in psoriasis, systemic lupus erythematosus (SLE) and systemic sclerosis (SSc) is controversial. This review summarizes the immunological functions of PGRN and its role in the pathogenesis of several immune-mediated diseases, in order to provide new ideas for developing therapeutic strategies for these diseases.

Glycoprotein Pathways Altered in Frontotemporal Dementia With Autoimmune Disease

Behavioral variant frontotemporal dementia (bvFTD) is a younger onset form of neurodegeneration initiated in the frontal and/or temporal lobes with a slow clinical onset but rapid progression. bvFTD is highly complex biologically with different pathological signatures and genetic variants that can exhibit a spectrum of overlapping clinical manifestations. Although the role of innate immunity has been extensively investigated in bvFTD, the involvement of adaptive immunity in bvFTD pathogenesis is poorly understood. We analyzed blood serum proteomics to identify proteins that are associated with autoimmune disease in bvFTD. Eleven proteins (increased: ATP5B, CALML5, COLEC11, FCGBP, PLEK, PLXND1; decreased: APOB, ATP8B1, FAM20C, LOXL3, TIMD4) were significantly altered in bvFTD with autoimmune disease compared to those without autoimmune disease. The majority of these proteins were enriched for glycoprotein-associated proteins and pathways, suggesting that the glycome is targeted in bvFTD with autoimmune disease.

Identification of the atypically modified autoantigen Ars2 as the target of B-cell receptors from activated B-cell-type diffuse large B-cell lymphoma

It has been suggested that stimulation of B-cell receptors (BCR) by specific antigens plays a pathogenic role in diffuse large B-cell lymphoma (DLBCL). Here, it was the aim to screen for specific reactivities of DLBCL-BCR in the spectrum of autoantigens and antigens of infectious origin. Arsenite resistance protein 2 (Ars2) was identified as the BCR target of three of five activated B-cell type DLBCL cell lines and two of 11 primary DLBCL cases. Compared to controls, Ars2 was hypophosphorylated exclusively in cases and cell lines with Ars2-specific BCR. In a validation cohort, hypophosphorylated Ars2 was found in eight of 31 activated B-cell type DLBCL, but in only one of 20 germinal center B-cell like type DLBCL. Incubation with Ars2 induced BCR-pathway activation and increased proliferation, while an Ars2/ETA’ toxin conjugate induced killing of cell lines with Ars2-reactive BCR. Ars2 appears to play a role in a subgroup of activated B-cell-type DLBCL. Moreover, transformed DLBCL lines with Ars2-reactive BCR still showed growth advantage after incubation with Ars2. These results provide knowledge about the pathogenic role of a specific antigen stimulating the BCR pathway in DLCBL.

Tweaking Progranulin Expression: Therapeutic Avenues and Opportunities

Frontotemporal dementia (FTD) is a neurodegenerative disease, leading to behavioral changes and language difficulties. Heterozygous loss-of-function mutations in progranulin (GRN) induce haploinsufficiency of the protein and are associated with up to one-third of all genetic FTD cases worldwide. While the loss of GRN is primarily associated with neurodegeneration, the biological functions of the secreted growth factor-like protein are more diverse, ranging from wound healing, inflammation, vasculogenesis, and metabolic regulation to tumor cell growth and metastasis. To date, no disease-modifying treatments exist for FTD, but different therapeutic approaches to boost GRN levels in the central nervous system are currently being developed (including AAV-mediated GRN gene delivery as well as anti-SORT1 antibody therapy). In this review, we provide an overview of the multifaceted regulation of GRN levels and the corresponding therapeutic avenues. We discuss the opportunities, advantages, and potential drawbacks of the diverse approaches. Additionally, we highlight the therapeutic potential of elevating GRN levels beyond patients with loss-of-function mutations in GRN.

TDP-43 and Inflammation: Implications for Amyotrophic Lateral Sclerosis and Frontotemporal Dementia

The abnormal mislocalisation and ubiquitinated protein aggregation of the TAR DNA binding protein 43 (TDP-43) within the cytoplasm of neurons and glia in the central nervous system (CNS) is a pathological hallmark of early-onset neurodegenerative disorders amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The pathomechanisms underlying abnormal mislocalisation and aggregation of TDP-43 remain unknown. However, there is a growing body of evidence implicating neuroinflammation and immune-mediated mechanisms in the pathogenesis of neurodegeneration. Importantly, most of the evidence for an active role of immunity and inflammation in the pathogenesis of ALS and FTD relates specifically to TDP-43, posing the question as to whether immune-mediated mechanisms could hold the key to understanding TDP-43’s underlying role in neurodegeneration in both diseases. Therefore, this review aims to piece together key lines of evidence for the specific association of TDP-43 with key immune and inflammatory pathways to explore the nature of this relationship and the implications for potential pathomechanisms underlying neurodegeneration in ALS and FTD.

In Vitro Physical and Functional Interaction Assays to Examine the Binding of Progranulin Derivative Atsttrin to TNFR2 and Its Anti-TNFα Activity

TNFα/TNFR signaling plays a critical role in the pathogenesis of various inflammatory and autoimmune diseases, and anti-TNFα therapies have been accepted as the effective approaches for treating several autoimmune diseases. Progranulin (PGRN), a multi-faced growth factor-like molecule, directly binds to TNFR1 and TNFR2, particularly to the latter with higher affinity than TNFα. PGRN derivative Atsttrin is composed of three TNFR-binding domain of PGRN and exhibits even better therapeutic effects than PGRN in several inflammatory disease models, including collagen-induced arthritis. Herein we describe the detailed methodology of using (1) ELISA-based solid phase protein-protein interaction assay to demonstrate the direct binding of Atsttrin to TNFR2 and its inhibition of TNFα/TNFR2 interaction; and (2) tartrate-resistant acid phosphatase (TRAP) staining of in vitro osteoclastogenesis to reveal the cell-based anti-TNFα activity of Atsttrin. Using the protocol described here, the investigators should be able to reproducibly detect the physical inhibition of TNFα binding to TNFR and the functional inhibition of TNFα activity by Atsttrin and various kinds of TNF inhibitors.

Progranulin inhibits LPS-induced macrophage M1 polarization via NF-кB and MAPK pathways

BACKGROUND

Macrophage M1 polarization plays a pivotal role in inflammatory diseases. Progranulin (PGRN) has potential anti-inflammation action, however, the effect of PGRN on macrophage M1 polarization has been poorly studied. Our study aimed to investigate the effect of PGRN on lipopolysaccharide (LPS)-induced macrophage M1 polarization and clarify the underlying mechanisms.

METHODS

RAW264.7 cells were polarized to M1 macrophage by LPS with or without recombinant PGRN (rPGRN) and tumor necrosis factor alpha antibody (anti-TNF-α). A cell counting kit-8 assay (CCK-8), flow cytometry, Quantitative Real-Time PCR assay (q-PCR), Western blot assay and enzyme-linked immunosorbent assay (ELISA) were used to determine the effect of different treatments on cell proliferation, expression of surface phenotype marker and expressions and secretion of inflammatory cytokines. The activation of NF-κB/mitogen-activated protein kinase (MAPK) pathways and the nuclear translocation of NF-κB p65 were detected by Western blot and immunofluorescence respectively. THP-1 and primary bone marrow-derived monocytes (BMDMs) were also used to demonstrate effect of PGRN on expressions and secretion of inflammatory cytokines induced by LPS.

RESULTS

In RAW264.7 cells, rPGRN at concentrations below 80 ng/ml significantly promoted cell proliferation in dose dependent fashion. rPGRN significantly inhibited LPS-induced change of phenotype (CD86/CD206 ratio) and function (tumor necrosis factor (TNF-α) and inducible nitric oxide synthase (iNOS) expressions). LPS-stimulated secretion of TNF-α and activated phosphorylation of IKKα/β, IкBα, p65, JNK and p38 and the nucleus translocation of NF-кB p65 were also significantly downregulated by rPGRN. In addition, recombinant TNF-α (rTNF-α) significantly boosted TNF-α and iNOS expression vs the control group. Moreover, anti-TNF-α significantly inhibited LPS-induced TNF-α and iNOS expression. In THP-1 and BMDM cells, reversing effect of rPGRN on LPS-enhanced expressions of TNF-α and iNOS and secretion of TNF-α was further demonstrated.

CONCLUSIONS

PGRN down-regulates LPS-induced macrophage M1 polarization in phenotype and function via NF-κB/MAPK signaling pathways.

Progranulin deficiency exacerbates spinal cord injury by promoting neuroinflammation and cell apoptosis in mice

PURPOSE

Spinal cord injury (SCI) often results in significant and catastrophic dysfunction and disability and imposes a huge economic burden on society. This study aimed to determine whether progranulin (PGRN) plays a role in the progressive damage following SCI and evaluate the potential for development of a PGRN derivative as a new therapeutic target in SCI.

METHODS

PGRN-deficient (Gr^-/-) and wild-type (WT) littermate mice were subjected to SCI using a weight-drop technique. Local PGRN expression following injury was evaluated by Western blotting and immunofluorescence. Basso Mouse Scale (BMS), inclined grid walking test, and inclined plane test were conducted at indicated time points to assess neurological recovery. Inflammation and apoptosis were examined by histology (Hematoxylin and Eosin (H&E) staining and Nissl staining, TUNEL assays, and immunofluorescence), Western blotting (from whole tissue protein for iNOS/p-p65/Bax/Bcl-2), and ex vivo ELISA (for TNFα/IL-1β/IL-6/IL-10). To identify the prophylactic and therapeutic potential of targeting PGRN, a PGRN derived small protein, Atsttrin, was conjugated to PLGA-PEG-PLGA thermosensitive hydrogel and injected into intrathecal space prior to SCI. BMS was recorded for neurological recovery and Western blotting was applied to detect the inflammatory and apoptotic proteins.

RESULTS

After SCI, PGRN was highly expressed in activated macrophage/microglia and peaked at day 7 post-injury. Grn^-/- mice showed a delayed neurological recovery after SCI at day 21, 28, 35, and 42 post-injury relative to WT controls. Histology, TUNEL assay, immunofluorescence, Western blotting, and ELISA all indicated that Grn^-/- mice manifested uncontrolled and expanded inflammation and apoptosis. Administration of control-released Atsttrin could improve the neurological recovery and the pro-inflammatory/pro-apoptotic effect of PGRN deficiency.

CONCLUSION

PGRN deficiency exacerbates SCI by promoting neuroinflammation and cellular apoptosis, which can be alleviated by Atsttrin. Collectively, our data provide novel evidence of using PGRN derivatives as a promising therapeutic approach to improve the functional recovery for patients with spinal cord injury.

[Physiopathology of giant cell arteritis: From inflammation to vascular remodeling]

Giant cell arteritis (GCA) is a large-vessel vasculitis involving the aorta and its main branches, especially supra aortic branches. Although much progress has been made, the pathophysiology remains incompletely understood. An initial trigger, suspected of infectious origin, lead to the maturation and recruitment of dendritic cells (DC). The lack of migration of these DC allows the local recruitment of T-lymphocytes (LT). These LT- CD4⁺ polarize in Type 1 helper (Th1), Th17 but also Th9. A qualitative and quantitative deficit in regulatory T cells (Treg) is observed under the influence of IL-21 overproduction. In addition, an imbalance in the Th17/Treg balance is favored by IL-6. The secretion of IFN-γ, IL-17, IL-6, IL-33 is responsible for a sustained local inflammatory reaction that is organized around tertiary lymphoid follicles. Locally recruited macrophages secrete reactive forms of oxygen together with VEGF and PDGF. These growth factors, together with neurotrophins and endothelin contribute to increase the proliferation of vascular smooth muscle cells (VSMCs). The imbalance between matrix metalloproteases (MMP)-2, MMP-9 and MMP-14 and tissue inhibitors of metalloproteases (TIMP)-1 and TIMP-2 also contribute to the remodeling process occurring in the vessel wall. Finally, arterial neovascularization contribute to the perpetuation of lymphocyte recruitment. This persistent remodeling is sometimes complicated by ischemic events responsible for the initial severity of the disease.

Progranulin autoantibodies in systemic sclerosis and autoimmune connective tissue disorders: A preliminary study

OBJECTIVE

The present study aimed to investigate progranulin autoantibodies in systemic sclerosis and autoimmune connective tissue disorders. Progranulin is a physiologic tumor necrosis factor (TNF) antagonist. Progranulin antibodies decrease progranulin levels.

METHODS

Serum samples of 123 patients with systemic sclerosis and various autoimmune connective tissue disorders (Sjoegren's syndrome [SjS], mixed connective tissue disorder, polymyositis [PM] and dermatomyositis [DM], antiphospholipid syndrome [APLS], and undifferentiated connective tissue disease [UCTD]) were tested for progranulin antibodies using enzyme-linked immunosorbent assay.

RESULTS

Progranulin antibodies were found in 34 of 123 (27.6%) patients at least once during their disease. In detail, 2 of 8 (25%) patients with limited cutaneous systemic sclerosis, 10 of 31 (32.3%) patients with diffuse cutaneous systemic sclerosis, 9 of 22 (40.9%) patients with SjS, 1 of 3 (33.33%) patients with mixed connective tissue disease, 4 of 33 (12.1%) patients with DM or PM, 6 of 15 (40%) patients with APLS, and 2 of 11 (18.2%) patients with UCTD were positive for progranulin antibodies during the course of disease.

CONCLUSIONS

Progranulin antibodies are frequently present in patients with systemic sclerosis and other autoimmune connective tissue disorders. Despite the lack of specificity for a given autoimmune disease, progranulin antibodies might not only indicate a potential subtype but also play a pathogenic role in patients with autoimmune connective disorders. Given the important role of TNF-α in inflammatory processes in autoimmune connective tissue disorders, progranulin antibodies might support the proinflammatory environment by neutralizing the TNF blocker progranulin.

The Adipokine Network in Rheumatic Joint Diseases

Rheumatic diseases encompass a diverse group of chronic disorders that commonly affect musculoskeletal structures. Osteoarthritis (OA) and rheumatoid arthritis (RA) are the two most common, leading to considerable functional limitations and irreversible disability when patients are unsuccessfully treated. Although the specific causes of many rheumatic conditions remain unknown, it is generally accepted that immune mechanisms and/or uncontrolled inflammatory responses are involved in their etiology and symptomatology. In this regard, the bidirectional communication between neuroendocrine and immune system has been demonstrated to provide a homeostatic network that is involved in several pathological conditions. Adipokines represent a wide variety of bioactive, immune and inflammatory mediators mainly released by adipocytes that act as signal molecules in the neuroendocrine-immune interactions. Adipokines can also be synthesized by synoviocytes, osteoclasts, osteoblasts, chondrocytes and inflammatory cells in the joint microenvironment, showing potent modulatory properties on different effector cells in OA and RA pathogenesis. Effects of adiponectin, leptin, resistin and visfatin on local and systemic inflammation are broadly described. However, more recently, other adipokines, such as progranulin, chemerin, lipocalin-2, vaspin, omentin-1 and nesfatin, have been recognized to display immunomodulatory actions in rheumatic diseases. This review highlights the latest relevant findings on the role of the adipokine network in the pathophysiology of OA and RA.

Hyper-N-glycosylated SAMD14 and neurabin-I as driver autoantigens of primary central nervous system lymphoma

To address the role of chronic antigenic stimulation in primary central nervous system lymphoma (PCNSL), we searched for autoantigens and identified sterile α-motif domain containing protein 14 (SAMD14) and neural tissue-specific F-actin binding protein I (neurabin-I) as autoantigenic targets of the B-cell receptors (BCRs) from 8/12 PCNSLs. In the respective cases, SAMD14 and neurabin-I were atypically hyper-N-glycosylated (SAMD14 at ASN339 and neurabin-I at ASN1277), explaining their autoimmunogenicity. SAMD14 and neurabin-I induced BCR pathway activation and proliferation of aggressive lymphoma cell lines transfected with SAMD14- and neurabin-I-reactive BCRs. Moreover, the BCR binding epitope of neurabin-I conjugated to truncated Pseudomonas exotoxin-killed lymphoma cells expressing the respective BCRs. These results support the role of chronic antigenic stimulation by posttranslationally modified central nervous system (CNS) driver autoantigens in the pathogenesis of PCNSL, serve as an explanation for their CNS tropism, and provide the basis for a novel specific treatment approach.

Chitinase-3-like Protein 1: A Progranulin Downstream Molecule and Potential Biomarker for Gaucher Disease

We recently reported that progranulin (PGRN) is a novel regulator of glucocerebrosidase and its deficiency associates with Gaucher Diseases (GD) (Jian et al., 2016a; Jian et al., 2018). To isolate the relevant downstream molecules, we performed a whole genome microarray and mass spectrometry analysis, which led to the isolation of Chitinase-3-like-1 (CHI3L1) as one of the up-regulated genes in PGRN null mice. Elevated levels of CHI3L1 were confirmed by immunoblotting and immunohistochemistry. In contrast, treatment with recombinant Pcgin, a derivative of PGRN, as well as imigluerase, significantly reduced the expressions of CHI3L1 in both PGRN null GD model and the fibroblasts from GD patients. Serum levels of CHIT1, a clinical biomarker for GD, were significantly higher in GD patients than healthy controls (51.16±2.824ng/ml vs 35.07±2.099ng/ml, p<0.001). Similar to CHIT1, serum CHI3L1 was also significantly increased in GD patients compared with healthy controls (1736±152.1pg/ml vs 684.7±68.20pg/ml, p<0.001). Whereas the PGRN level is significantly reduced in GD patients as compared to the healthy control (91.56±3.986ng/ml vs 150.6±4.501, p<0.001). Collectively, these results indicate that CHI3L1 may be a previously unrecognized biomarker for diagnosing GD and for evaluating the therapeutic effects of new GD drug(s).

Association of polymorphisms in TNF and GRN genes with ankylosing spondylitis in a Chinese Han population

The aim of this study is to investigate the association of the polymorphisms in tumor necrosis factor (TNF) and granulin (GRN) with ankylosing spondylitis (AS) in a Chinese Han population. Five single nucleotide polymorphisms (SNPs) covering TNF and six SNPs covering GRN were investigated in 861 Chinese Han AS patients and 864 healthy controls. For rs1799964, the C allele was linked to reduced risk of AS (p < 0.0001, OR = 0.60, 95% CI = 0.50-0.71). The carriers of the C/C homozygote showed a significantly lower risk of AS compared with the TT homozygote and the C/T heterozygote under the recessive model (p < 0.0001, OR = 0.23, 95% CI = 0.12-0.45). For rs1800629, the A allele was also linked to reduced risk of AS (p < 0.0001, OR = 0.54, 95% CI = 0.39-0.74). For rs1800630, the A allele was also linked to reduced risk of AS (p < 0.0001, OR = 0.59, 95% CI = 0.48-0.72). The carriers of the A/A homozygote showed a significantly lower risk of AS compared with the C/C homozygote and the A/C heterozygote under the recessive model (p < 0.0001, OR = 0.18, 95% CI = 0.07-0.47). For rs769178, the T allele was linked to increased risk of AS (p < 0.0001, OR = 2.59, 95% CI = 2.18-3.09). The carriers of the T/T homozygote showed a significantly higher risk of AS compared with the GG homozygote and the G/T heterozygote under the recessive model (p < 0.0001, OR = 3.34, 95 %CI = 1.95-5.72). There was no significant difference between the AS patients and the controls in the genotype or allele frequencies of rs361525. For GRN, there was no significant difference between the AS patients and the controls in the genotype or allele frequencies of rs25646, rs3760365, rs3785817, rs4792939, rs5848, rs850713 (p > 0.05). This study indicates that polymorphisms in TNF are related to AS, but polymorphisms in GRN are not related to AS susceptibility in a Chinese Han population.

Identification of potential saliva and tear biomarkers in primary Sjögren's syndrome, utilising the extraction of extracellular vesicles and proteomics analysis

Background

There is a long-lasting need for non-invasive, more accurate diagnostic techniques when evaluating primary Sjögren’s syndrome (pSS) patients. Incorporation of additional diagnostics involving screening for disease-specific biomarkers in biological fluid is a promising concept that requires further investigation. In the current study we aimed to explore novel disease biomarkers in saliva and tears from pSS patients.

Methods

Liquid chromatography-mass spectrometry (LC-MS) was performed on stimulated whole saliva and tears from 27 pSS patients and 32 healthy controls, and salivary and tear proteomic biomarker profiles were generated. LC-MS was also combined with size exclusion chromatography to isolate extracellular vesicles (EVs) from both fluids. Nanoparticle tracking analysis was conducted on joint fractions from the saliva and tears to determine size distribution and concentration of EVs. Further EV characterisation was performed by immunoaffinity capture of CD9-positive EVs using magnetic beads, detected by flow cytometry. The LC-MS data were analysed for quantitative differences between patient and control groups using Scaffold, and the proteins were further analysed using the Database for Annotation, Visualization and Integrated Discovery (DAVID), for gene ontology overrepresentation, and the Search Tool for the Retrieval of Interacting Genes/Proteins for protein-protein interaction network analysis.

Results

Upregulation of proteins involved in innate immunity (LCN2), cell signalling (CALM) and wound repair (GRN and CALML5) were detected in saliva in pSS. Saliva EVs also displayed biomarkers critical for activation of the innate immune system (SIRPA and LSP1) and adipocyte differentiation (APMAP). Tear analysis indicated overexpression of proteins involved in TNF-α signalling (CPNE1) and B cell survival (PRDX3). Moreover, neutrophil gelatinase-associated lipocalin was upregulated in saliva and tears in pSS. Consistently, DAVID analysis demonstrated pathways of the adaptive immune response in saliva, of cellular component assembly for saliva EVs, and of metabolism and protein folding in tears in pSS patients.

Conclusions

LC-MS of saliva and tears from pSS patients, solely and in combination with size-exclusion chromatography allowed screening for possible novel biomarkers encompassing both salivary and lacrimal disease target organs. This approach could provide additional diagnostic accuracy in pSS, and could possibly also be applied for staging and monitoring the disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1228-x) contains supplementary material, which is available to authorized users.

Serum progranulin levels in Hispanic rheumatoid arthritis patients treated with TNF antagonists: a prospective, observational study

Since progranulin (PGRN) is a natural ligand of TNF receptors, we assessed whether serum PGRN levels predict and/or reflect responsiveness of RA patients to TNF-antagonist therapy. TNF-antagonist-naïve RA patients (N = 35) were started on TNF-antagonist therapy. At baseline and at follow-up visits, DAS28-ESR, DAS28-CRP, and CDAI were calculated, and venous blood was collected for serum PGRN determination. Disease activity and clinical response were based on EULAR criteria. Baseline serum PGRN levels varied considerably and correlated with ESR and CRP. DAS28-ESR, DAS28-CRP, and CDAI were greater in "PGRN-high" than in "PGRN-low". Baseline serum PGRN levels did not predict clinical responsiveness to TNF-antagonist therapy. Nevertheless, changes in serum PGRN levels at 274+ days following initiation of TNF-antagonist therapy correlated with changes in ESR, CRP, DAS28-ESR, DAS28-CRP, and CDAI. At this time, DAS28-ESR, DAS28-CRP, and CDAI in PGRN-high and PGRN-low equalized, but serum PGRN levels remained greater in PGRN-high than in PGRN-low. To our knowledge, the present report is the first prospective study to longitudinally assess changes in serum PGRN levels following initiation of TNF-antagonist therapy. Although pre-treatment serum PGRN levels may not predict clinical responsiveness to TNF-antagonist therapy, changes in serum PGRN levels correlate with changes in disease metrics over time. By inference, administration of PGRN may represent an effective therapeutic option for development in RA patients.

Progranulin: A key player in autoimmune diseases

Autoimmune disease encompasses an array of conditions with a variety of presentations and the involvement of multiple organs. Though the etiologies of many autoimmune conditions are unclear, uncontrolled inflammatory immune response is believed to be a major cause of disease development and progression. Progranulin (PGRN), an anti-inflammatory molecule with therapeutic effect in inflammatory arthritis, was identified as an endogenous antagonist of TNFα by competitively binding to TNFR. PGRN exerts its anti-inflammatory activity through multiple pathways, including induction of T_reg differentiation and IL-10 expression and inhibition of chemokine release from macrophages. In addition, the protective role of PGRN has also been demonstrated in osteoarthritis, inflammatory bowel disease, and psoriasis. Intriguingly, PGRN was reported to contribute to development of insulin resistance in high-fat diet induced diabetes. Emerging evidences indicate that PGRN may also be associated with various autoimmune diseases, including systemic lupus erythematous, systemic sclerosis, multiple sclerosis and Sjogren's syndrome. This review summarizes recent studies of PGRN as a novel target molecule in the field of autoimmune disease, and provides updated information to inspire future studies.

The role of progranulin in arthritis

Progranulin (PGRN) is a growth factor with a unique beads-on-a-string structure that is involved in multiple pathophysiological processes, including anti-inflammation, tissue repair, wound healing, neurodegenerative diseases, and tumorigenesis. This review presents up-to-date information concerning recent studies on the role of PGRN in inflammatory arthritis and osteoarthritis, with a special focus on the involvement of the interactions and interplay between PGRN and tumor necrosis factor receptor (TNFR) family members in regulating such musculoskeletal diseases. In addition, this paper highlights the applications of atsttrin, an engineered protein comprising three TNFR-binding fragments of PGRN, as a promising intervention in treating arthritis.

New discovery rarely runs smooth: an update on progranulin/TNFR interactions

Progranulin (PGRN) is a growth factor implicated in various pathophysiological processes, including wound healing, inflammation, tumorigenesis, and neurodegeneration. It was previously reported that PGRN binds to tumor necrosis factor receptors (TNFR) and has therapeutic effects in inflammatory arthritis (Tang et. al, in Science 332:478-484, 2011); however, Chen et al. reported their inability to demonstrate the PGRN-TNFR interactions under their own conditions (Chen et. al, in J Neurosci 33:9202-9213, 2013). A letter-to-editor was then published by the original group in response to the Chen et al. paper that discussed the reasons for the latter's inability to recapitulate the interactions. In addition, the group published follow-up studies that further reinforced and dissected the interactions of PGRN-TNFR. Recently, the dispute about the legitimacy of PGRN-TNFR interactions appears to be finally settled with independent confirmations of these interactions in various conditions by numerous laboratories. This review presents a chronological update on the story of PGRN-TNFR interactions, highlighting the independent confirmations of these interactions in various diseases and conditions.

New insights into the pathogenesis of giant cell arteritis and hopes for the clinic

Giant cell arteritis is a complex immune-mediated disease that involves large blood vessels in individuals older than 50 years. Recent studies have confirmed a strong association of this form of vasculitis with the HLA region, particularly with HLA class II genes. However, other non-HLA loci, such as protein tyrosine phosphatase non-receptor type 22, may also account for the susceptibility to giant cell arteritis. In addition, genetic variants located in genes encoding proinflammatory cytokines seem to influence the phenotypic expression of the disease, including the risk of severe ischemic complications, the presence of polymyalgia rheumatica and the higher incidence of relapses observed in some patients. The identification of putative genetic markers of disease severity could have clear therapeutic implications, as it may allow us to identify patients who are potentially responders to specific treatments.

Progranulin Is Associated with Disease Activity in Patients with Rheumatoid Arthritis

OBJECTIVE

Progranulin (PGRN) is implicated in the pathogenesis of rheumatoid arthritis (RA). The aim of this study was to assess the relationship between PGRN and disease activity in RA.

METHODS

PGRN levels were evaluated in patients with RA (n = 47) and OA (n = 42) and healthy controls (n = 41). Immunohistochemical analysis of PGRN in synovial tissues was performed. The association between PGRN and C-reactive protein (CRP), disease activity score (DAS28-CRP), and health assessment questionnaire (HAQ) was studied.

RESULTS

Circulating PGRN was elevated in patients with RA and OA compared to healthy controls (227.1 ± 100.2 and 221.5 ± 102.5 versus 128.1 ± 34.7 ng/mL; P < 0.001). Synovial fluid levels of PGRN were higher in patients with RA compared to OA (384.5 ± 275.3 versus 241.4 ± 165.2 ng/mL; P = 0.002). PGRN expression was significantly upregulated in the synovial tissue of RA patients particularly in the inflammatory infiltrates. Serum PGRN levels correlated with DAS28 (r = 0.327, P = 0.049) and HAQ score (r = 0.323, P = 0.032), while synovial fluid PGRN correlated only with HAQ (r = 0.310, P = 0.043) in patients with RA. PGRN levels were not associated with CRP or autoantibodies.

CONCLUSIONS

This study demonstrates increased PGRN expression at local sites of inflammation and association between PGRN levels, disease activity, and functional impairment in patients with RA.

The challenge of treating orphan disease

Uncommon or orphan diseases are less frequently addressed in mainstream medical journals and, as a consequence, their understanding and clinical recognition may rely on case series or anecdotal data with limited guidelines and management directions. The study of selected underrepresented autoimmune and allergy conditions is the subject of the present issue of Clinical Reviews in Allergy and Immunology to provide peculiar perspectives on common and rare themes. First, allergy remains a major concern for physicians worldwide despite the limited developments over the past years, particularly for antigens such as mite or Alternaria alternata, and due to the increasing incidence of drug hypersensitivity. Second, the female predominance of autoimmune diseases such as systemic sclerosis is well recognized but enigmatic, and a unifying hypothesis remains elusive. Third, the management of conditions triggered by infectious agents as in Guillain-Barre syndrome or mixed cryoglobulinemia is challenging, and clinical guidelines are needed in the setting of infections and autoimmunity. Fourth, gamma-delta T cells represent major players in innate immunity and are the subject of extensive studies in autoimmune diseases to provide new therapeutic targets for disease prevention or modulation in the near future. Ultimately, we acknowledge the major developments in the broad fields of rheumatology and immunology and expect that microbiota definition, epigenetics studies, and microRNA analysis will provide new exciting avenues toward the understanding and treatment of chronic and acute inflammation.

The molecular basis for development of proinflammatory autoantibodies to progranulin

Recently we identified in a wide spectrum of autoimmune diseases frequently occurring proinflammatory autoantibodies directed against progranulin, a direct inhibitor of TNFR1 & 2 and of DR3. In the present study we investigated the mechanisms for the breakdown of self-tolerance against progranulin. Isoelectric focusing identified a second, differentially electrically charged progranulin isoform exclusively present in progranulin-antibody-positive patients. Alkaline phosphatase treatment revealed this additional progranulin isoform to be hyperphosphorylated. Subsequently Ser81, which is located within the epitope region of progranulin-antibodies, was identified as hyperphosphorylated serine residue by site directed mutagenesis of candidate phosphorylation sites. Hyperphosphorylated progranulin was detected exclusively in progranulin-antibody-positive patients during the courses of their diseases. The occurrence of hyperphosphorylated progranulin preceded seroconversions of progranulin-antibodies, indicating adaptive immune response. Utilizing panels of kinase and phosphatase inhibitors, PKCβ1 was identified as the relevant kinase and PP1 as the relevant phosphatase for phosphorylation and dephosphorylation of Ser81. In contrast to normal progranulin, hyperphosphorylated progranulin interacted exclusively with inactivated (pThr320) PP1, suggesting inactivated PP1 to cause the detectable occurrence of phosphorylated Ser81 PGRN. Investigation of possible functional alterations of PGRN due to Ser81 phosphorylation revealed, that hyperphosphorylation prevents the interaction and thus direct inhibition of TNFR1, TNFR2 and DR3, representing an additional direct proinflammatory effect. Finally phosphorylation of Ser81 PGRN alters the conversion pattern of PGRN. In conclusion, inactivated PP1 induces hyperphosphorylation of progranulin in a wide spectrum of autoimmune diseases. This hyperphosphorylation prevents direct inhibition of TNFR1, TNFR2 and DR3 by PGRN, alters the conversion of PGRN, and is strongly associated with the occurrence of neutralizing, proinflammatory PGRN-antibodies, indicating immunogenicity of this alternative secondary modification.

Microscopic polyangiitis: Advances in diagnostic and therapeutic approaches

Microscopic polyangiitis (MPA) is an idiopathic autoimmune disease characterized by systemic vasculitis. The disease predominantly affects small-calibre blood vessels and is associated with the presence of antineutrophil cytoplasmic autoantibodies (ANCA). Microscopic polyangiitis was considered to be a disease entity by Savage et al. in 1985. Microscopic polyangiitis has a reported low incidence and a slight male predominance. The aetiology of MPA remains unknown. There is, however, increased evidence that MPA is an autoimmune disease in which ANCAs, particularly those reacting with MPO, are pathogenic. MPA belongs to the systemic vasculitides, indicating that multiple organs can be affected. The major organs involved in MPA are the kidneys and the lungs. As expected for an illness that affects multiple organ systems, patients with MPA can present with a myriad of different symptoms. Ear, nose and throat (ENT) manifestations are not considered to be clinical symptoms of MPA, but in the majority of populations described, ENT involvement was found in surprisingly high percentages. MPA is part of the ANCA-associated vasculitides, which are characterized by necrotizing vasculitis of small vessels. Diagnosis is mainly established by clinical manifestations, computed tomography (TC), ANCA antibody detection and renal and pulmonary biopsy. The introduction of aggressive immunosuppressive treatment has substantially improved the prognosis. The standardized therapeutic regimen is based on cyclophosphamide and corticosteroids. Using this regimen, remission can be achieved in most of the patients. Rituximab may represent an important alternative to cyclophosphamide for patients who may not respond adequately to antimetabolite therapies.

Cell biology of the NCL proteins: What they do and don't do

The fatal, primarily childhood neurodegenerative disorders, neuronal ceroid lipofuscinoses (NCLs), are currently associated with mutations in 13 genes. The protein products of these genes (CLN1 to CLN14) differ in their function and their intracellular localization. NCL-associated proteins have been localized mostly in lysosomes (CLN1, CLN2, CLN3, CLN5, CLN7, CLN10, CLN12 and CLN13) but also in the Endoplasmic Reticulum (CLN6 and CLN8), or in the cytosol associated to vesicular membranes (CLN4 and CLN14). Some of them such as CLN1 (palmitoyl protein thioesterase 1), CLN2 (tripeptidyl-peptidase 1), CLN5, CLN10 (cathepsin D), and CLN13 (cathepsin F), are lysosomal soluble proteins; others like CLN3, CLN7, and CLN12, have been proposed to be lysosomal transmembrane proteins. In this review, we give our views and attempt to summarize the proposed and confirmed functions of each NCL protein and describe and discuss research results published since the last review on NCL proteins. This article is part of a Special Issue entitled: "Current Research on the Neuronal Ceroid Lipofuscinoses (Batten Disease)".

Progranulin facilitates conversion and function of regulatory T cells under inflammatory conditions

The progranulin (PGRN) is known to protect regulatory T cells (Tregs) from a negative regulation by TNF-α, and its levels are elevated in various kinds of autoimmune diseases. Whether PGRN directly regulates the conversion of CD4+CD25-T cells into Foxp3-expressing regulatory T cells (iTreg), and whether PGRN affects the immunosuppressive function of Tregs, however, remain unknown. In this study we provide evidences demonstrating that PGRN is able to stimulate the conversion of CD4+CD25-T cells into iTreg in a dose-dependent manner in vitro. In addition, PGRN showed synergistic effects with TGF-β1 on the induction of iTreg. PGRN was required for the immunosuppressive function of Tregs, since PGRN-deficient Tregs have a significant decreased ability to suppress the proliferation of effector T cells (Teff). In addition, PGRN deficiency caused a marked reduction in Tregs number in the course of inflammatory arthritis, although no significant difference was observed in the numbers of Tregs between wild type and PGRN deficient mice during development. Furthermore, PGRN deficiency led to significant upregulation of the Wnt receptor gene Fzd2. Collectively, this study reveals that PGRN directly regulates the numbers and function of Tregs under inflammatory conditions, and provides new insight into the immune regulatory mechanism of PGRN in the pathogenesis of inflammatory and immune-related diseases.

PGRN protects against colitis progression in mice in an IL-10 and TNFR2 dependent manner

This study was aimed to determine the role and regulation of progranulin (PGRN) in the pathogenesis of inflammatory bowel diseases (IBD). Dextran sulfate sodium (DSS)−, picrylsulfonic acid (TNBS)-induced, bone marrow chimera and CD4+CD45Rb^hi T cell transfer colitis model were established and analyzed in wild-type and several genetically-modified mice, including PGRN, IL-10 and TNFR2 deficient mice. Elevated levels of PGRN were found in colitis samples from human IBD patients and mouse colitis models in comparison to the corresponding controls. PGRN-deficient mice became highly susceptible to DSS- and TNBS-induced colitis, whereas recombinant PGRN ameliorated the pathology and reduced the histological score in both DSS and TNBS colitis models. In addition, hematopoietic-derived PGRN was critical for protection against DSS-induced colitis, and lack of PGRN signaling in CD4+ T cells also exacerbated experimental colitis. PGRN-mediated protective effect in colitis was compromised in the absence of IL-10 signaling. In addition, PGRN's effect was also largely lost in the TNFR2-deficient colitis model. Collectively, these findings not only provide the new insight into PGRN's anti-inflammatory action in vivo, but may also present PGRN and its derivatives as novel biological agent for treating IBD.

Progranulin antibodies entertain a proinflammatory environment in a subgroup of patients with psoriatic arthritis

INTRODUCTION

Psoriatic arthritis (PsA) is a distinctive inflammatory arthritis which may typically develop in a subgroup of individuals suffering from psoriasis. We recently described progranulin autoantibodies (PGRN-Abs) in the sera of patients with different autoimmune diseases including seronegative polyarthritis. In the present study we investigated the occurrence of PGRN-Abs in PsA.

METHODS

PGRN-Abs were determined in 260 patients with PsA, 100 patients with psoriasis without arthritic manifestations (PsC) and 97 healthy controls using a recently described ELISA. PGRN plasma levels were determined from subgroups by a commercially available ELISA-kit. Possible functional effects of PGRN-antibodies were analysed in vitro by tumour necrosis factor (TNF)-α mediated cytotoxicity assays using WEHI-S and HT1080 cells.

RESULTS

PGRN-Abs were detected with relevant titres in 50/260 (19.23%) patients with PsA, but in 0/100 patients with psoriasis without arthritic manifestations (P = 0.0001). All PGRN-Abs belonged to immunoglobulin G (IgG). PGRN-Abs were significantly more frequent in PsA patients with enthesitis or dactylitis. PGRN-Abs were also more frequent in PsA patients receiving treatment with TNF-α-blockers than in patients treated without TNF-α-blockers (20.8% versus 17.4%; P = 0.016). PGRN plasma levels were significantly lower in PGRN-Ab-positive patients with PsA than in healthy controls and patients with psoriasis without arthritic manifestations (P < 0.001), indicating a neutralizing effect of PGRN-Abs. Moreover cytotoxicity assays comparing PGRN-antibody positive with negative sera from matched patients with PsA, clearly showed a proinflammatory effect of PGRN antibodies.

CONCLUSION

Neutralizing PGRN-Abs occur with relevant titres in a subgroup of patients with PsA, but not in patients without arthritic manifestations (PsC). PGRN-Ab-positive patients had more frequent enthesitis or dactylitis. TNF-α-induced cytotoxicity assays demonstrated that the protective effects of progranulin were inhibited by serum containing PGRN-Abs. This suggests that PGRN-Ab might not only be useful as a diagnostic and prognostic marker, but may provide a proinflammatory environment in a subgroup of patients with PsA.

Proinflammatory progranulin antibodies in inflammatory bowel diseases

BACKGROUND

Recently, we identified neutralizing autoantibodies against progranulin (PGRN) in a wide spectrum of rheumatic diseases including cases with enteropathic spondylarthritis. PGRN is a secreted protein with strong anti-inflammatory effects, believed to be mediated by the direct inhibition of TNF receptors 1&2. Given the central role of TNF-α as proinflammatory cytokine, a neutralizing antibody directed against its physiologic antagonist PGRN might entertain a proinflammatory environment.

OBJECTIVE

The aim of the present study was to investigate a possible occurrence of PGRN-antibodies (PGRN-Abs) in inflammatory bowel disease (IBD), and to investigate a possible pathogenic effect.

MATERIALS AND METHODS

Sera samples of 141 patients with Crohn's disease (CD) and of 71 patients with ulcerative colitis (UC) were tested for PGRN-Abs by ELISA. PGRN plasma levels were detected by ELISA. Proinflammatory effects of progranulin-antibodies were analyzed by TNF-α-mediated cytotoxicity assays using HT29 cells and by examination of possible effects of PGRN and of PGRN-antibodies on TNF-α-induced downmodulation of FOXP3 expression in CD4(+)CD25(hi) Tregs.

RESULTS

PGRN-Abs were found in sera of 23/141 (16.31%) patients with CD, and 15/71 (21.13%) patients with UC. PGRN-Abs were more frequent than anti-neutrophil cytoplasmic autoantibodies (ANCAs) in UC, but less frequent than anti-Saccharomyces cerevisiae antibodies (ASCAs) in CD. PGRN-Abs belonged mostly to IgG1 (71.1%) and IgA (26.3%). They occurred in relevant titres and had significant neutralizing effects on PGRN plasma levels. Cytotoxicity assays comparing PGRN-antibody-positive sera with negative sera from matched patients with IBD showed a proinflammatory effect of PGRN-Abs on HT29 cells. Moreover, PGRN-antibodies led to an increase of TNF-α-induced downmodulation of FOXP3 in CD4(+)CD25(hi) Tregs.

CONCLUSION

The results suggest that PGRN-Abs occur frequently in CD and UC, and have a proinflammatory effect.

Possible involvement of lysosomal dysfunction in pathological changes of the brain in aged progranulin-deficient mice

Introduction

It has been shown that progranulin (PGRN) deficiency causes age-related neurodegenerative diseases such as frontotemporal lobar degeneration (FTLD) and neuronal ceroid lipofuscinosis (NCL), a lysosomal storage disease. Previous studies also suggested that PGRN is involved in modulating lysosomal function. To elucidate the pathophysiological role of PGRN in the aged brain, in the present study, lysosomal function and pathological changes of the brain were investigated using 10- and 90-week-old wild-type and PGRN-deficient mice.

Results

We showed that PGRN deficiency caused enhanced CD68 expression in activated microglia and astrogliosis in the cortex and thalamus, especially in the ventral posteromedial nucleus/ventral posterolateral nucleus (VPM/VPL), in the aged brain. Immunoreactivity for Lamp1 (lysosome marker) in the VPM/VPL and expression of lysosome-related genes, i.e. cathepsin D, V-type proton ATPase subunit d2, and transcription factor EB genes, were also increased by PGRN deficiency. Aggregates of p62, which is selectively degraded by the autophagy-lysosomal system, were observed in neuronal and glial cells in the VPM/VPL of aged PGRN-deficient mice. TAR DNA binding protein 43 (TDP-43) aggregates in the cytoplasm of neurons were also observed in aged PGRN-deficient mice. PGRN deficiency caused enhanced expression of glial cell-derived cytotoxic factors such as macrophage expressed gene 1, cytochrome b-245 light chain, cytochrome b-245 heavy chain, complement C4, tumor necrosis factor-α and lipocalin 2. In addition, neuronal loss and lipofuscinosis in the VPM/VPL and disrupted myelination in the cerebral cortex were observed in aged PGRN-deficient mice.

Conclusions

The present study shows that aged PGRN-deficient mice present with NCL-like pathology as well as TDP-43 aggregates in the VPM/VPL, where a particular vulnerability has been reported in NCL model mice. The present results also suggest that these pathological changes in the VPM/VPL are likely a result of lysosomal dysfunction. How PGRN prevents lysosomal dysfunction with aging remains to be elucidated.

Electronic supplementary material

The online version of this article (doi:10.1186/s40478-014-0078-x) contains supplementary material, which is available to authorized users.

The role of inflammatory and anti-inflammatory cytokines in the pathogenesis of osteoarthritis

Osteoarthritis (OA) is the most common chronic disease of human joints. The basis of pathologic changes involves all the tissues forming the joint; already, at an early stage, it has the nature of inflammation with varying degrees of severity. An analysis of the complex relationships indicates that the processes taking place inside the joint are not merely a set that (seemingly) only includes catabolic effects. Apart from them, anti-inflammatory anabolic processes also occur continually. These phenomena are driven by various mediators, of which the key role is attributed to the interactions within the cytokine network. The most important group controlling the disease seems to be inflammatory cytokines, including IL-1β, TNFα, IL-6, IL-15, IL-17, and IL-18. The second group with antagonistic effect is formed by cytokines known as anti-inflammatory cytokines such as IL-4, IL-10, and IL-13. The role of inflammatory and anti-inflammatory cytokines in the pathogenesis of OA with respect to inter- and intracellular signaling pathways is still under investigation. This paper summarizes the current state of knowledge. The cytokine network in OA is put in the context of cells involved in this degenerative joint disease. The possibilities for further implementation of new therapeutic strategies in OA are also pointed.

Plasma cells within granulomatous inflammation display signs pointing to autoreactivity and destruction in granulomatosis with polyangiitis

Introduction

Plasma cells residing in inflamed tissues produce antibodies in chronic inflammatory and systemic autoimmune diseases. This study examined if plasma cells, located within inflamed nasal tissue in granulomatosis with polyangiitis (GPA), express features potentially associated with the autoimmune and destructive character of this disease.

Methods

Ig gene mutation patterns of individual tissue-derived plasma cells from GPA (n = 5) were analyzed, by using laser-assisted microdissection followed by semi-nested polymerase chain reaction (PCR). Signs of B-lymphocyte maturation (ectopic lymphoid structures, ELS) and survival (a proliferation-inducing ligand, APRIL; B-cell maturation antigen, BCMA; transmembrane-activator and calcium modulator and cyclophilin interactor, TACI; receptor activator of nuclear factor κB ligand, RANKL) were examined in nasal tissues or serum, respectively, by using immunohistochemistry/fluorescence and enzyme-linked immunosorbent assay, ELISA.

Results

Plasma-cell derived Ig genes (light- and heavy-chain pairs, n = 4; heavy chains, n = 33) resembled mutation patterns seen in other autoimmune diseases, predominantly displaying selection against replacement mutations within the framework region of Ig genes (10 of 15), which is responsible for structural integrity. Ectopic lymphoid structures were similar between GPA and a disease control (that is, unspecific chronic rhinosinusitis. However, histomorphologic features distinguishing GPA from rhinosinusitis (that is, neutrophilic microabscess and granuloma) expressed considerable amounts of membrane-associated and secreted APRIL, respectively. The latter was co-localized with CD138 and found in close proximity to cells expressing IgG, TACI, and BCMA. Interestingly, plasma cells strongly expressed receptor activator of nuclear factor κB ligand (RANKL), apart from fibroblast-like cells.

Conclusions

Plasma cells within granulomatous inflammation appear to display features that might be required for autoreactivity and, possibly, RANKL-mediated destruction in GPA.

Diagnosis and classification of granulomatosis with polyangiitis (aka Wegener's granulomatosis)

Granulomatosis with polyangiitis (GPA, formerly known as Wegener's Granulomatosis) is an autoimmune small vessel vasculitis which is highly associated with anti-neutrophil cytoplasmic antibodies (ANCA). The hallmarks of this condition are systemic necrotising vasculitis, necrotising granulomatous inflammation, and necrotising glomerulonephritis. The aetiology of granulomatosis with polyangiitis is linked to environmental and infectious triggers inciting onset of disease in genetically predisposed individuals. Anti-neutrophil cytoplasmic antibodies are pathogenic and play an important role in the pathogenesis of this disease, although ANCA positivity is not essential for a clinical diagnosis of granulomatosis with polyangiitis. Granulomatosis with polyangiitis is diagnosed based on clinical manifestations of systemic vasculitis and histological evidence of necrotising vasculitis or granulomatous inflammation. This small vessel vasculitis may present as limited disease of the ears, nose and upper airways or mild, moderate or severe systemic disease. Immunosuppression and adjuvant therapies have contributed to the improved prognosis of granulomatosis with polyangiitis over the past decades. Treatment strategies are tailored to the severity of the disease. They are based on published evidence of the efficacy and safety of the immunosuppressive drugs indicated to manage active vasculitis and maintain clinical remission. This review will summarise the history, aetiology, pathogenesis, classification, diagnosis and management of granulomatosis with polyangiitis.

The diagnosis and classification of microscopic polyangiitis

Microscopic Polyangiitis (MPA) is a small vessel vasculitis. The disease is defined by the 2012 revised Chapel Hill Consensus Conference Nomenclature of Vasculitides [1] as necrotizing vasculitis, with few or no immune deposits, predominantly affecting small vessels (i.e. capillaries, venules, or arterioles). Necrotizing arteritis involving small and medium arteries may be present. Necrotizing glomerulonephritis is very common. Pulmonary capillaritis often occurs. Granulomatous inflammation is absent. MPA belongs to the ANCA-associated vasculitides (AAV). ANCA in MPA are predominantly directed against myeloperoxidase (MPO-ANCA) but may, in a minority of patients, be directed against proteinase 3 (PR3-ANCA). Not all patients, however, have ANCA. Microscopic polyangiitis (MPA) belongs to the anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides. MPA is clinically characterized by small-vessel vasculitis primarily affecting the kidneys and the lungs but other organs may be involved as well. Renal involvement, which can be the only manifestation, is clinically apparent as rapidly progressive glomerulonephritis and histopathologically as pauci-immune necrotizing and crescentic glomerulonephritis. ANCA in MPA are mainly directed to myeloperoxidase (MPO-ANCA). Besides their diagnostic significance, MPO-ANCA appear pathogenic in MPA. Rituximab with steroids is at least as effective as cyclophosphamide with steroids for induction of remission.

The diagnosis and classification of giant cell arteritis

Giant-cell arteritis (GCA) involves the major branches of the aorta with predilection for the extracranial branches of the carotid artery. It occurs in individuals older than 50 years and the incidence increases with age. The signs and symptoms of giant cell arteritis can be classified into four subsets: cranial arteritis, extracranial arteritis, systemic symptoms and polymyalgia rheumatica. Patients may develop any combination of these manifestations, associated with laboratory evidence of an acute-phase reaction. The only test that confirms GCA diagnosis is a temporal artery biopsy, showing vasculitis with mononuclear cell inflammatory infiltrates, often with giant cells. Due to the focal and segmental nature of the infiltrates, areas of inflammation may be missed by the biopsy and the histological examination is normal in about 15% of the cases. Some imaging modalities may aid in the diagnosis of GCA. Among those, color duplex ultrasonography of the temporal arteries is more commonly used. There are no independent validating criteria to determine whether giant cell arteritis is present when a temporal artery biopsy is negative. The American College of Rheumatology criteria for the classification of giant cell arteritis may assist in the diagnosis. However, meeting classification criteria is not equivalent to making the diagnosis in individual patients, and the final diagnosis should be based on all clinical, laboratory, imaging and histological findings. Glucocorticoids are the treatment of choice for GCA. The initial dose is 40-60 mg/day for most uncomplicated cases. Addition of low-dose aspirin (100 mg/d) has been shown to significantly decrease the rate of vision loss and stroke during the course of the disease.

Diagnosis and classification of autoimmune uveitis

Uveitis is the most common ophthalmological finding in the practice of rheumatology and clinical immunology. The condition is frequently idiopathic and defined by the inflammatory status of the uvea, the part of the middle eye that includes the iris, ciliary body and choroid. Anterior uveitis involves the iris and ciliary body, while the posterior form is limited to the retina and choroid. Both forms represent indications for an urgent evaluation by an ophthalmologist as untreated cases may cause blindness. Anterior uveitis is associated with the HLA-B27 allele and is a classification criterion for seronegative arthritis forms such as ankylosing spondylitis, psoriatic arthropathy, arthritis associated with Crohn's disease and ulcerative colitis, and reactive arthritis. Posterior uveitis is associated with Behcet's disease and HLA-B51. The clinical suspicion is raised by self-reported symptoms in the case of anterior involvement and floaters for posterior uveitis while the diagnosis, in the absence of established criteria, is made by an experienced ophthalmologist.