Sinisa Savic

Histone deacetylases are dysregulated in rheumatoid arthritis and a novel histone deacetylase 3–selective inhibitor reduces interleukin‐6 production by peripheral blood mononuclear cells from rheumatoid arthritis patients

OBJECTIVE To characterize the role of histone deacetylase (HDAC) activity in rheumatoid arthritis (RA) and to evaluate the effects of MI192, a novel HDAC-3-selective inhibitor, compared with the established nonselective HDAC inhibitor trichostatin A (TSA), on proinflammatory cytokine production. METHODS Activity of HDAC and histone acetyltransferase was measured in peripheral blood mononuclear cells (PBMCs) from RA patients by spectrophotometric assay, prior to and after 12 weeks of etanercept therapy. The effects of HDAC inhibitor treatment on cytokine production in both RA and healthy PBMCs were assessed by enzyme-linked immunosorbent assay. RESULTS RA PBMCs exhibited significantly increased HDAC activity (P = 0.007) compared to PBMCs from healthy individuals, and the increase was unaltered after 12 weeks of etanercept therapy. TSA was a potent inhibitor of tumor necrosis factor (TNF) and interleukin-6 (IL-6) production in both RA and healthy PBMCs and of interferon-γ (IFNγ) production in healthy PBMCs; IFNγ was not produced by RA PBMCs. MI192 inhibited TNF production at high concentrations and dose-dependently inhibited IL-6 in RA PBMCs but not healthy PBMCs, across a dose range of 10 μM-5 nM. CONCLUSION HDAC activity is dysregulated in RA PBMCs and is a potential target for therapeutic intervention, as it is not affected by conventional anti-TNF treatment with etanercept. Both the selective and the nonselective HDAC inhibitors (MI192 and TSA, respectively) were found to regulate cytokine production from PBMCs, but their effects were cell type and compound specific. HDAC inhibitors have potential in the treatment of RA, and HDAC-selective inhibition may improve the therapeutic margin of safety; however, further clinical characterization and evaluation for adverse effects is needed.

Familial autoinflammation with neutrophilic dermatosis reveals a regulatory mechanism of pyrin activation

A mutation in pyrin that disrupts regulation leads to autoinflammatory disease. Guarding inflammation The innate immune system is hard-wired to protect people from infection. However, mutations in these protective genes can lead to uncontrolled inflammation, resulting in autoinflammatory disease. Now, Masters et al. describe a family with an autoinflammatory disease caused by a previously unreported mutation in pyrin. This mutation disrupts pyrin regulation and mimics the effect of pathogen sensing by pyrin, leading to proinflammatory interleukin-1β (IL-1β) production. Indeed, targeting IL-1β resolved disease in one patient. These data suggest that pyrin is regulated through a guard-like mechanism, which guards against autoinflammation in humans. Pyrin responds to pathogen signals and loss of cellular homeostasis by forming an inflammasome complex that drives the cleavage and secretion of interleukin-1β (IL-1β). Mutations in the B30.2/SPRY domain cause pathogen-independent activation of pyrin and are responsible for the autoinflammatory disease familial Mediterranean fever (FMF). We studied a family with a dominantly inherited autoinflammatory disease, distinct from FMF, characterized by childhood-onset recurrent episodes of neutrophilic dermatosis, fever, elevated acute-phase reactants, arthralgia, and myalgia/myositis. The disease was caused by a mutation in MEFV, the gene encoding pyrin (S242R). The mutation results in the loss of a 14-3-3 binding motif at phosphorylated S242, which was not perturbed by FMF mutations in the B30.2/SPRY domain. However, loss of both S242 phosphorylation and 14-3-3 binding was observed for bacterial effectors that activate the pyrin inflammasome, such as Clostridium difficile toxin B (TcdB). The S242R mutation thus recapitulated the effect of pathogen sensing, triggering inflammasome activation and IL-1β production. Successful therapy targeting IL-1β has been initiated in one patient, resolving pyrin-associated autoinflammation with neutrophilic dermatosis. This disease provides evidence that a guard-like mechanism of pyrin regulation, originally identified for Nod-like receptors in plant innate immunity, also exists in humans.

Evidence of NLRP3-inflammasome activation in rheumatoid arthritis (RA); genetic variants within the NLRP3-inflammasome complex in relation to susceptibility to RA and response to anti-TNF treatment

Background The NLRP3-inflammasome, implicated in the pathogenesis of several inflammatory disorders, has been analysed in rheumatoid arthritis (RA). Methods Relative gene expression of NLRP3-inflammasome components was characterised in PBMCs of 29 patients receiving infliximab. A total of 1278 Caucasian patients with RA from the Biologics in Rheumatoid Arthritis Genetics and Genomics Study Syndicate (BRAGGSS) cohort receiving tumour necrosis factor (TNF) antagonists (infliximab, adalimumab and etanercept) were genotyped for 34 single nucleotide polymorphisms (SNPs), spanning the genes NLRP3, MEFV and CARD8. Regression analyses were performed to test for association between genotype and susceptibility and treatment response (disease activity score across 28 joints (DAS28) and EULAR improvement criteria) at 6 months, with secondary expression quantitative trait loci (eQTL) analyses. Results At baseline, gene expression of ASC, MEFV, NLRP3-FL, NLRP3-SL and CASP1 were significantly higher compared with controls whereas CARD8 was lower in the patients. Caspase-1 and interleukin-18 levels were significantly raised in patients with RA. SNPs in NLRP3 showed association with RA susceptibility and EULAR response to anti-TNF in the BRAGGSS cohort, and in monocytes but not B cells, in eQTL analysis of 283 healthy controls. CARD8 SNPs were associated with RA susceptibility and DAS28 improvement in response to anti-TNF and eQTL effects in monocytes and B cells. Conclusions This study found evidence of modulation of the NLRP3-inflammasome in patients with RA prior to receiving infliximab and some evidence of association for SNPs at NLRP3 and CARD8 loci with RA susceptibility and response to anti-TNF. The SNPs associated with susceptibility/response are not the main eQTL variants for either locus, and the associations with treatment response require replication in an independent cohort.

Familial Mediterranean fever and related periodic fever syndromes/autoinflammatory diseases.

Purpose of reviewThe spectrum of periodic fever syndromes (PFS)/autoinflammation diseases is continuously expanding. This review provides an overview of the primary research and an update on the main clinical developments in these disorders published in the past 12–18 months. Recent findingsIL-1&bgr; is pivotal to the pathogenesis of most of the PFS. In familial Mediterranean fever (FMF) MEFV mutations lead to gain of pyrin function, resulting in inappropriate IL-1&bgr; release that is dependent on ASC but not the NLRP3 inflammasome. Anti-IL-1 therapy is effective in tumour necrosis factor receptor-associated periodic syndrome (TRAPS), whilst both spontaneous and pathogen-associated molecular patterns (PAMPs) induced IL-1&bgr; release have been demonstrated in NLRP12-associated periodic syndrome (NAPS12). Somatic NLRP3/CIAS1 mosaicism is a significant cause of cryopyrin-associated periodic syndromes (CAPS). Close connections have also been established between metabolic and inflammatory pathways. In TRAPS increased reactive oxygen species (ROS) of mitochondrial origin leads to production of pro-inflammatory cytokines, whilst NLRP3 inflammasome activation in type 2 diabetes (T2D) is induced by oligomers of islet amyloid polypeptides (IAPP). SummaryCaspase 1 activation and IL-1&bgr; release is central to the pathogenesis of many autoinflammatory syndromes. This is supported by the effectiveness of anti-IL-1 biologics in treatment of these disorders.

Clinical spectrum and features of activated phosphoinositide 3-kinase δ syndrome: A large patient cohort study

Background: Activated phosphoinositide 3‐kinase &dgr; syndrome (APDS) is a recently described combined immunodeficiency resulting from gain‐of‐function mutations in PIK3CD, the gene encoding the catalytic subunit of phosphoinositide 3‐kinase &dgr; (PI3K&dgr;). Objective: We sought to review the clinical, immunologic, histopathologic, and radiologic features of APDS in a large genetically defined international cohort. Methods: We applied a clinical questionnaire and performed review of medical notes, radiology, histopathology, and laboratory investigations of 53 patients with APDS. Results: Recurrent sinopulmonary infections (98%) and nonneoplastic lymphoproliferation (75%) were common, often from childhood. Other significant complications included herpesvirus infections (49%), autoinflammatory disease (34%), and lymphoma (13%). Unexpectedly, neurodevelopmental delay occurred in 19% of the cohort, suggesting a role for PI3K&dgr; in the central nervous system; consistent with this, PI3K&dgr; is broadly expressed in the developing murine central nervous system. Thoracic imaging revealed high rates of mosaic attenuation (90%) and bronchiectasis (60%). Increased IgM levels (78%), IgG deficiency (43%), and CD4 lymphopenia (84%) were significant immunologic features. No immunologic marker reliably predicted clinical severity, which ranged from asymptomatic to death in early childhood. The majority of patients received immunoglobulin replacement and antibiotic prophylaxis, and 5 patients underwent hematopoietic stem cell transplantation. Five patients died from complications of APDS. Conclusion: APDS is a combined immunodeficiency with multiple clinical manifestations, many with incomplete penetrance and others with variable expressivity. The severity of complications in some patients supports consideration of hematopoietic stem cell transplantation for severe childhood disease. Clinical trials of selective PI3K&dgr; inhibitors offer new prospects for APDS treatment.

The NLR network and the immunological disease continuum of adaptive and innate immune-mediated inflammation against self

The nucleotide-binding domain, leucine-rich repeat containing family (NLR) network has provided pivotal genetic and molecular insights into diseases that were hitherto regarded as autoimmune. The NLR-related disorders include rare monogenic autoinflammatory diseases collectively termed cryopyrin-associated periodic syndromes, Crohn’s disease which is a common polygenic disease and also an association at the mechanistic level with gout and pseudogout. Unlike the classical autoimmune diseases where disease immunopathogenesis is played out primarily in the primary and secondary lymphoid organs, the immunopathogenesis of the NLR-related disorders is played out in the tissues where inflammation arises. As the genetic mutations or molecular cascades associated with the NLR-related disorders have a widespread cellular distribution, it has been somewhat enigmatic why these disorders attack certain territories, but not others. This implies that tissue-specific factors in the target organs themselves contribute to disease expression. Such examples include the high abundance of NOD2 expressing cells in the part of the gut most typically afflicted by Crohn’s disease and the preferential deposition of crystals in the joints to where inflammation localises in gout and pseudogout. The NLR network is associated principally with increases in TNF or IL-1 production, both of which are key players in innate immunity. Therefore, the NLR network identifies at the genetic and molecular level a robust paradigm for innate immune activation against self. This tissue-specific-factor-associated inflammation is the diametric opposite of classical autoimmunity. Of note, the MHC class-I-associated diseases including psoriasis (HLA-Cw6) and ankylosing spondylitis (HLA-B27) show striking clinical overlaps with Crohn’s disease and also some rare monogenic diseases. Thus, the NLR innate immune pathway allows the full spectrum of inflammation against self to be viewed along an immunological disease continuum with autoantibody-associated disease at one end, innate immune diseases at the other and MHC class-1-related disorders as an intermediate.

The NLRP3 inflammasome, a target for therapy in diverse disease states

A role for NLRP3 inflammasome in recurrent and chronic inflammation was initially described in a group of rare autoinflammatory conditions, termed cryopyrin‐associated periodic syndrome. Subsequently, inflammasomes have been implicated in the pathology of many common diseases, including cancer, gout and diabetes. Despite diverse pathologies, the central role of the inflammasome in innate defences and tumour elimination suggests common therapeutic approaches to reduce inflammation where appropriate.

TLR dependent XBP-1 activation induces an autocrine loop in rheumatoid arthritis synoviocytes.

X-box binding protein 1 (XBP1) is a central regulator of the endoplasmic reticulum (ER) stress response. It is induced via activation of the IRE1 stress sensor as part of the unfolded protein response (UPR) and has been implicated in several diseases processes. XBP1 can also be activated in direct response to Toll-like receptor (TLR) ligation independently of the UPR but the pathogenic significance of this mode of XBP1 activation is not well understood. Here we show that TLR-dependent XBP1 activation is operative in the synovial fibroblasts (SF) of patients with active rheumatoid arthritis (RA). We investigated the expression of ER stress response genes in patients with active RA and also in patients in remission. The active (spliced) form of (s)XBP1 was significantly overexpressed in the active RA group compared to healthy controls and patients in remission. Paradoxically, expression of nine other ER stress response genes was reduced in active RA compared to patients in remission, suggestive of a UPR-independent process. However, sXBP1 was induced in SF by TLR4 and TLR2 stimulation, resulting in sXBP1-dependent interleukin-6 and tumour necrosis factor (TNF) production. We also show that TNF itself induces sXBP1 in SF, thus generating a potential feedback loop for sustained SF activation. These data confirm the first link between TLR-dependent XBP1 activation and human inflammatory disease. sXBP1 appears to play a central role in this process by providing a convergence point for two different stimuli to maintain activation of SF.

CVID patients with autoimmunity have elevated T cell expression of granzyme B and HLA-DR and reduced levels of Treg cells

Aims Common variable immunodeficiency (CVID) is a primary antibody immunodeficiency with approximately 20% of patients reporting additional autoimmune symptoms. The primary aim of this study was to compare the levels of activated and regulatory T cells (Treg cells) in CVID patients in an attempt to clarify their possible interactions leading to the generation of autoimmunity. Methods Immunophenotyping of T cells was performed by flow cytometry using a whole blood approach. Surface expression of human leukocyte antigen HLA class II DR and intracellular levels of granzyme B in T cell subsets were assessed; Treg levels were measured using CD4 CD25, FOXp3 and CTLA-4. Results CVID patients had higher levels of granzyme B and HLA-DR on CD8+ T cells compared with control values (mean of 59% vs 30% and 45% vs 21%, respectively). Patients also had reduced levels of Treg cells compared with control values (con mean=3.24% vs pat=2.54%). Patients with autoimmunity (5/23) had a similar level of T cell activation markers to the rest of the patients but with lower Treg cells (mean of 1.1%) and reduced CD25 and CTLA-4 expression. Patients with autoimmunity had a higher ratio of activated to Treg cells compared with patients with no autoimmune symptoms. Conclusions These results highlight that reduced levels of Treg cells were associated with elevated levels of activated T cells, suggesting that reduced Treg cells in these patients may have functional consequences in allowing exaggerated T cell responses.

Differential effects of infliximab on absolute circulating blood leucocyte counts of innate immune cells in early and late rheumatoid arthritis patients

Anti‐tumour necrosis factor (TNF) biologics have revolutionized therapy of rheumatoid arthritis (RA). We compared the effects of infliximab on numbers of circulating leucocyte subsets in early RA (disease/symptom duration of ≤1 year) and late RA patients (>1 year). A control group consisted of early RA patients treated with a combination of methotrexate (MTX) and methylprednisolone. Blood samples were obtained at baseline (pre‐therapy) from all RA patients, divided into three groups: (i) late RA receiving infliximab/MTX, (ii) early RA–infliximab/MTX, (iii) early RA–steroid/MTX, and also from follow‐up patients at 2 and 14 weeks. Significant differences in absolute counts of monocytes and granulocytes were observed between healthy controls and RA patients. At baseline CD14bright monocytes and CD16+ granulocytes were increased in both early RA and late RA patients. CD4+ T cells, CD8+ T cells and B cells were all increased at baseline in early RA, but not in late RA. At 2 weeks following infliximab treatment decreased granulocytes were observed in both early and late RA and decreased natural killer (NK) cells in late RA. CD16+ granulocytes and NK cells were also decreased at 14 weeks post‐infliximab in early RA. Biotinylated infliximab was used to detect membrane‐associated TNF (mTNF)‐expressing leucocytes in RA patients. CD16+ granulocytes, NK cells and CD14dim monocytes all expressed higher levels of mTNF in RA patients. In summary infliximab is associated with decreased CD16+ granulocyte and NK cell counts, possibly through binding of mTNF. Differential effects of infliximab between early and late RA suggest that pathogenic mechanisms change as disease progresses.