Metabolic reprogramming by Syntenin-1 directs RA FLS and endothelial cell-mediated inflammation and angiogenesis.

A novel rheumatoid arthritis (RA) synovial fluid protein, Syntenin-1, and its receptor, Syndecan-1 (SDC-1), are colocalized on RA synovial tissue endothelial cells and fibroblast-like synoviocytes (FLS). Syntenin-1 exacerbates the inflammatory landscape of endothelial cells and RA FLS by upregulating transcription of IRF1/5/7/9, IL-1ß, IL-6, and CCL2 through SDC-1 ligation and HIF1α, or mTOR activation. Mechanistically, Syntenin-1 orchestrates RA FLS and endothelial cell invasion via SDC-1 and/or mTOR signaling. In Syntenin-1 reprogrammed endothelial cells, the dynamic expression of metabolic intermediates coincides with escalated glycolysis along with unchanged oxidative factors, AMPK, PGC-1α, citrate, and inactive oxidative phosphorylation. Conversely, RA FLS rewired by Syntenin-1 displayed a modest glycolytic-ATP accompanied by a robust mitochondrial-ATP capacity. The enriched mitochondrial-ATP detected in Syntenin-1 reprogrammed RA FLS was coupled with mitochondrial fusion and fission recapitulated by escalated Mitofusin-2 and DRP1 expression. We found that VEGFR1/2 and Notch1 networks are responsible for the crosstalk between Syntenin-1 rewired endothelial cells and RA FLS, which are also represented in RA explants. Similar to RA explants, morphological and transcriptome studies authenticated the importance of VEGFR1/2, Notch1, RAPTOR, and HIF1α pathways in Syntenin-1 arthritic mice and their obstruction in SDC-1 deficient animals. Consistently, dysregulation of SDC-1, mTOR, and HIF1α negated Syntenin-1 inflammatory phenotype in RA explants, while inhibition of HIF1α impaired synovial angiogenic imprint amplified by Syntenin-1. In conclusion, since the current therapies are ineffective on Syntenin-1 and SDC-1 expression in RA synovial tissue and blood, targeting this pathway and its interconnected metabolic intermediates may provide a novel therapeutic strategy.

T-cell Large Granular Lymphocytic Leukemia and Felty Syndrome in Rheumatoid Arthritis: A Case Report.

T-cell large granular lymphocytic (LGL) leukemia is characterized by a clonal proliferation of CD3+ T-cells and has been associated with rheumatoid arthritis (RA). Splenomegaly is a common finding and a majority of cases present with cytopenia. Felty syndrome (FS) is characterized by neutropenia and splenomegaly and is also classically described in the literature for its association with RA. Similarities in clinical features, pathogenesis, management, genetics, and immunologic basis of FS and T-cell LGL leukemia have led to the suggestion that they exist on the same spectrum of disease. We present a case of T-cell LGL leukemia in an RA patient with clinical features not distinguishable from features of FS.

Syntenin-1-mediated arthritogenicity is advanced by reprogramming RA metabolic macrophages and Th1 cells.

OBJECTIVES: Syntenin-1, a novel endogenous ligand, was discovered to be enriched in rheumatoid arthritis (RA) specimens compared with osteoarthritis synovial fluid and normal synovial tissue (ST). However, the cellular origin, immunoregulation and molecular mechanism of syntenin-1 are undescribed in RA. METHODS: RA patient myeloid and lymphoid cells, as well as preclinical models, were used to investigate the impact of syntenin-1/syndecan-1 on the inflammatory and metabolic landscape. RESULTS: Syntenin-1 and syndecan-1 (SDC-1) co-localise on RA ST macrophages (MΦs) and endothelial cells. Intriguingly, blood syntenin-1 and ST SDC-1 transcriptome are linked to cyclic citrullinated peptide, erythrocyte sedimentation rate, ST thickness and bone erosion. Metabolic CD14+CD86+GLUT1+MΦs reprogrammed by syntenin-1 exhibit a wide range of proinflammatory interferon transcription factors, monokines and glycolytic factors, along with reduced oxidative intermediates that are downregulated by blockade of SDC-1, glucose uptake and/or mTOR signalling. Inversely, IL-5R and PDZ1 inhibition are ineffective on RA MΦs-reprogrammed by syntenin-1. In syntenin-1-induced arthritis, F4/80+iNOS+RAPTOR+MΦs represent glycolytic RA MΦs, by amplifying the inflammatory and glycolytic networks. Those networks are abrogated in SDC-1-/- animals, while joint prorepair monokines are unaffected and the oxidative metabolites are moderately replenished. In RA cells and/or preclinical model, syntenin-1-induced arthritogenicity is dependent on mTOR-activated MΦ remodelling and its ability to cross-regulate Th1 cells via IL-12 and IL-18 induction. Moreover, RA and joint myeloid cells exposed to Syntenin-1 are primed to transform into osteoclasts via SDC-1 ligation and RANK, CTSK and NFATc1 transcriptional upregulation. CONCLUSION: The syntenin-1/SDC-1 pathway plays a critical role in the inflammatory and metabolic landscape of RA through glycolytic MΦ and Th1 cell cross-regulation (graphical abstract).

Peripheral Ulcerative Keratitis: A Review.

Peripheral ulcerative keratitis (PUK) is a rare but serious ocular condition that is an important clinical entity due to its ophthalmological and systemic implications. It is characterized by progressive peripheral corneal stromal thinning with an associated epithelial defect and can be associated with an underlying local or systemic pro-inflammatory condition, or present in an idiopathic form (Mooren ulcer). Associated conditions include autoimmune diseases, systemic and ocular infections, dermatologic diseases, and ocular surgery. Cell-mediated and auto-antibody-mediated immune responses have been implicated in the pathogenesis of PUK, destroying peripheral corneal tissue via matrix metalloproteinases. Clinically, patients with PUK present with painful vision loss, a peripheral corneal ulcer, and often adjacent scleritis, episcleritis, iritis, or conjunctivitis. Diagnostic evaluation should be focused on identifying the underlying etiology and ruling out conditions that may mimic PUK, including marginal keratitis and Terrien marginal degeneration. Treatment should be focused on reducing local disease burden with topical lubrication, while simultaneously addressing the underlying cause with antimicrobials or anti-inflammatory when appropriate. Existing and emerging biologic immunomodulatory therapies have proven useful in PUK due to autoimmune conditions. Surgical treatment is generally reserved for cases of severe thinning or corneal perforation.

Metabolic regulation of RA macrophages is distinct from RA fibroblasts and blockade of glycolysis alleviates inflammatory phenotype in both cell types.

Recent studies have shown the significance of metabolic reprogramming in immune and stromal cell function. Yet, the metabolic reconfiguration of RA macrophages (MΦs) is incompletely understood during active disease and in crosstalk with other cell types in experimental arthritis. This study elucidates a distinct regulation of glycolysis and oxidative phosphorylation in RA MΦs compared to fibroblast (FLS), although PPP (Pentose Phosphate pathway) is similarly reconfigured in both cell types. 2-DG treatment showed a more robust impact on impairing the RA M1 MΦ-mediated inflammatory phenotype than IACS-010759 (IACS, complexli), by reversing ERK, AKT and STAT1 signaling, IRF8/3 transcription and CCL2 or CCL5 secretion. This broader inhibitory effect of 2-DG therapy on RA M1 MΦs was linked to dysregulation of glycolysis (GLUT1, PFKFB3, LDHA, lactate) and oxidative PPP (NADP conversion to NADPH), while both compounds were ineffective on oxidative phosphorylation. Distinctly, in RA FLS, 2-DG and IACS therapies constrained LPS/IFNγ-induced AKT and JNK signaling, IRF5/7 and fibrokine expression. Disruption of RA FLS metabolic rewiring by 2-DG or IACS therapy was accompanied by a reduction of glycolysis (HIF1α, PFKFB3) and suppression of citrate or succinate buildup. We found that 2-DG therapy mitigated CIA pathology by intercepting joint F480+iNOS+MΦ, Vimentin+ fibroblast and CD3+T cell trafficking along with downregulation of IRFs and glycolytic intermediates. Surprisingly, IACS treatment was inconsequential on CIA swelling, cell infiltration, M1 and Th1/Th17 cytokines (IFN-γ/IL-17) and joint glycolytic mediators. Collectively, our results indicate that blockade of glycolysis is more effective than inhibition of complex 1 in CIA, in part due to its effectiveness on the MΦ inflammatory phenotype.

IRAK4 inhibition: a promising strategy for treating RA joint inflammation and bone erosion.

Flares of joint inflammation and resistance to currently available biologic therapeutics in rheumatoid arthritis (RA) patients could reflect activation of innate immune mechanisms. Herein, we show that a TLR7 GU-rich endogenous ligand, miR-Let7b, potentiates synovitis by amplifying RA monocyte and fibroblast (FLS) trafficking. miR-Let7b ligation to TLR7 in macrophages (MΦs) and FLSs expanded the synovial inflammatory response. Moreover, secretion of M1 monokines triggered by miR-Let7b enhanced Th1/Th17 cell differentiation. We showed that IRAK4 inhibitor (i) therapy attenuated RA disease activity by blocking TLR7-induced M1 MΦ or FLS activation, as well as monokine-modulated Th1/Th17 cell polarization. IRAK4i therapy also disrupted RA osteoclastogenesis, which was amplified by miR-Let7b ligation to joint myeloid TLR7. Hence, the effectiveness of IRAK4i was compared with that of a TNF inhibitor (i) or anti-IL-6R treatment in collagen-induced arthritis (CIA) and miR-Let7b-mediated arthritis. We found that TNF or IL-6R blocking therapies mitigated CIA by reducing the infiltration of joint F480+iNOS+ MΦs, the expression of certain monokines, and Th1 cell differentiation. Unexpectedly, these biologic therapies were unable to alleviate miR-Let7b-induced arthritis. The superior efficacy of IRAK4i over anti-TNF or anti-IL-6R therapy in miR-Let7b-induced arthritis or CIA was due to the ability of IRAK4i therapy to restrain the migration of joint F480+iNOS+ MΦs, vimentin+ fibroblasts, and CD3+ T cells, in addition to negating the expression of a wide range of monokines, including IL-12, MIP2, and IRF5 and Th1/Th17 lymphokines. In conclusion, IRAK4i therapy may provide a promising strategy for RA therapy by disconnecting critical links between inflammatory joint cells.

TLR7 endogenous ligands remodel glycolytic macrophages and trigger skin-to-joint crosstalk in psoriatic arthritis.

Thirty percent of psoriasis patients develop psoriatic arthritis (PsA), nevertheless the mechanism remains unknown. Endogenous GU-rich miRNAs activate endosomal TLR7 that plays a critical role in autoimmune diseases. We found that endogenous TLR7 ligands, miR-29 and miR-Let7b, were markedly increased in PsA compared to osteoarthritis (OA) synovial fluid (SF)s. We showed that intradermal (i.d.) miR-Let7b injection promoted skin inflammation, which was characterized by amplified Th1 cells, CD68+ M1 macrophages, and transcriptional upregulation of glycolytic mediators, GLUT1, C-MYC, and HIF1α. Expansion of skin Th1 cells driven by miR-Let7b was also linked to elevated M1-associated IRFs. Interestingly, i.d. miR-Let7b administration exacerbated suboptimal joint inflammation along with metabolic reconfiguration of the PsA-like preclinical model. Moreover, TLR7 agonist, R837, potentiated metabolic reprogramming and expression of IL-1ß, IL-6, and IL-12 in murine macrophages, enabling myeloid-to-T-cell crosstalk. Consistently, treatment with glycolytic inhibitors, 2-DG and/or HIF1αi, reversed R837-induced metabolic remodeling and disrupted the TLR7-driven inflammatory phenotype in myeloid and lymphoid cells. Similar to miR-Let7b, R837 also differentiates progenitor cells into mature osteoclasts, primarily through RANKL induction. Taken together, this study indicates that TLR7-instigated metabolic rewiring of macrophages and their cross-regulation of T cells connects skin immunopathology to joint inflammation.

Macrophages are the primary effector cells in IL-7-induced arthritis.

Synovial macrophages are crucial in the development of joint inflammation and bone damage; however, the pathways that control macrophage remodeling in inflammatory M1 cells or bone-eroding osteoclasts are not fully understood. We determined that elevated IL-7R/CD127 expression is the hallmark of rheumatoid arthritis (RA) M1 macrophages and that these cells are highly responsive to interleukin-7 (IL-7)-driven osteoclastogenesis. We established that lipopolysaccharide (LPS), interferon-γ (IFNγ), and tumor necrosis factor-α (TNFα), the classic M1 macrophage mediators, enhance IL-7R expression in RA and murine macrophages. The local expression of IL-7 provokes arthritis, predominantly through escalating the number of F480+iNOS+ cells rather than CD3+ T cells. Ectopic LPS injection stabilizes IL-7-induced arthritis by increasing myeloid IL-7R expression, in part via IFNγ induction. Hence, in RAG-/- mice, IL-7-mediated arthritis is suppressed because of the reduction in myeloid IL-7R expression due to the lack of IFNγ. Moreover, the amelioration of IL-7-induced arthritis by anti-TNF therapy is due to a decrease in the number of cells in the unique F480+iNOS+IL-7R+CCL5+ subset, with no impact on the F480+Arginase+ cell or CD3+ T cell frequency. Consistent with the preclinical findings, the findings of a phase 4 study performed with RA patients following 6 months of anti-TNF therapy revealed that IL-7R expression was reduced without affecting the levels of IL-7. This study shifts the paradigm by discovering that IL-7-induced arthritis is dependent on F480+iNOS+IL-7R+CCL5+ cell function, which activates TH-1 cells to amplify myeloid IL-7R expression and disease severity.

CCL21/CCR7 signaling in macrophages promotes joint inflammation and Th17-mediated osteoclast formation in rheumatoid arthritis.

In rheumatoid arthritis (RA), synovial tissue abundantly expresses CCL21, a chemokine strongly associated with RA susceptibility. In this study, we aimed to characterize the functional significance of CCL21/CCR7 signaling in different phases of RA pathogenesis. We determined that CCR7 is a hallmark of RA M1 synovial fluid (SF) macrophages, and its expression in RA monocytes and in vitro differentiated macrophages is closely associated with disease activity score (DAS28). In early stages of RA, monocytes infiltrate the synovial tissue. However, blockade of SF CCL21 or CCR7 prevents RA SF-mediated monocyte migration. CCR7 expression in the newly migrated macrophages can be accentuated by LPS and IFNγ and suppressed by IL-4 treatment. We also uncovered that CCL21 stimulation increases the number of M1-polarized macrophages (CD14+CD86+), resulting in elevated transcription of IL-6 and IL-23. These CCL21-induced M1 cytokines differentiate naïve T cells to Th17 cells, without affecting Th1 cell polarization. In the erosive stages of disease, CCL21 potentiates RA osteoclastogenesis through M1-driven Th17 polarization. Disruption of this intricate crosstalk, by blocking IL-6, IL-23, or IL-17 function, impairs the osteoclastogenic capacity of CCL21. Consistent with our in vitro findings, we establish that arthritis mediated by CCL21 expands the joint inflammation to bone erosion by connecting the differentiation of M1 macrophages with Th17 cells. Disease progression is further exacerbated by CCL21-induced neovascularization. We conclude that CCL21 is an attractive novel target for RA therapy, as blockade of its function may abrogate erosive arthritis modulated by M1 macrophages and Th17 cell crosstalk.

Short-term progression of interstitial lung disease in systemic sclerosis predicts long-term survival in two independent clinical trial cohorts.

OBJECTIVE: To assess survival and identify predictors of survival in patients with systemic sclerosis-interstitial lung disease (SSc-ILD) who participated in the Scleroderma Lung Studies (SLS) I and II. METHODS: SLS I randomised 158 patients with SSc-ILD to 1 year of oral cyclophosphamide (CYC) vs placebo. SLS II randomised 142 patients to 1 year of oral CYC followed by 1 year of placebo vs 2 years of mycophenolate mofetil. Counting process Cox proportional hazard modelling identified variables associated with long-term mortality in SLS I and II. Internal validation was performed using joint modelling. RESULTS: After a median follow-up of 8 years, 42% of SLS I patients died, and when known the cause of death was most often attributable to SSc. There was no significant difference in the time to death between treatment arms in SLS I or II. Higher baseline skin score, older age, and a decline in the forced vital capacity (FVC) and the diffusing capacity for carbon monoxide (DLCO) over 2 years were independently associated with an increased risk of mortality in SLS I. The Cox model identified the same mortality predictor variables using the SLS II data. CONCLUSION: In addition to identifying traditional mortality risk factors in SSc (skin score, age), this study demonstrated that a decline in FVC and DLCO over 2 years was a better predictor of mortality than baseline FVC and DLCO. These findings suggest that short-term changes in surrogate measures of SSc-ILD progression may have important effects on long-term outcomes.

IL-11 facilitates a novel connection between RA joint fibroblasts and endothelial cells.

IL-11 has been detected in inflamed joints; however, its role in the pathogenesis of arthritis is not yet clear. Studies were conducted to characterize the expression and functional significance of IL-11 and IL-11Rα in rheumatoid arthritis (RA). IL-11 levels were elevated in RA synovial fluid (SF) compared to osteoarthritis (OA) SF and plasma from RA, OA and normal individuals (NLs). Morphologic studies established that IL-11 was detected in lining fibroblasts and macrophages in addition to sublining endothelial cells and macrophages at higher levels in RA compared to NL synovial tissues. Since IL-11Rα was exclusively expressed in RA fibroblasts and endothelial cells, macrophages were not involved in IL-11 effector function. Ligation of IL-11 to IL-11Rα strongly provoked fibroblast infiltration into RA joint, while cell proliferation was unaffected by this process. Secretion of IL-8 and VEGF from IL-11 activated RA fibroblasts was responsible for the indirect effect of IL-11 on endothelial cell transmigration and tube formation. Moreover, IL-11 blockade impaired RA SF capacity to elicit endothelial cell transmigration and tube formation. We conclude that IL-11 binding to endothelial IL-11Rα can directly induce RA angiogenesis. In addition, secretion of proangiogenic factors from migrating fibroblasts potentiated by IL-11 can indirectly contribute to RA neovascularization.

Differential impact of obesity on the pathogenesis of RA or preclinical models is contingent on the disease status.

OBJECTIVE: Studies were performed to uncover the significance of obesity in rheumatoid arthritis (RA) and preclinical models. METHODS: Preclinical arthritis models were used to examine the impact of obesity on disease onset and remission. Conditioned media from RA adipose tissues were used to investigate the mechanism contributing to joint neutrophil influx and M1 macrophage differentiation observed in early and remission phases of arthritis. RESULTS: We report that mice fed with high fat diet (HFD) have an earlier onset of collagen-induced arthritis (CIA) compared with mice on regular diet. However, the differences in CIA joint swelling between the two diet groups are lost once disease is established. We found that early arthritis triggered by obesity is due to elevated joint MIP2/interleukin-8 levels detected in CIA as well as in the RA and mouse adipose tissues and the effect of this chemokine on neutrophil recruitment. Although active disease progression is similarly affected in both diet groups, arthritis resolution is accelerated in lean mice while joint inflammation is sustained in obese mice. We document that HFD can prolong toll-like receptor (TLR)4-induced arthritis by increasing joint monocyte migration and further remodelling the recruited cells into M1 macrophages. Consistently, we show that adipose condition media can transform RA and wild-type naïve myeloid cells into M1 macrophages; however, this function is impaired by TLR4 blockade or deficiency. CONCLUSIONS: We conclude that despite established disease being unaffected by obesity, the early and the resolution phases of RA are impacted by obesity through different mechanisms.

Identification of a Novel Toll-like Receptor 7 Endogenous Ligand in Rheumatoid Arthritis Synovial Fluid That Can Provoke Arthritic Joint Inflammation.

OBJECTIVE: Levels of Toll-like receptor 7 (TLR-7) are elevated in rheumatoid arthritis (RA), but the impact on RA is unknown because the endogenous ligand for TLR-7 has not been identified. The aim of this study was to identify a TLR-7 endogenous ligand and to determine its role in the pathogenesis of RA. METHODS: The presence of an endogenous TLR-7 ligand, microRNA let-7b (miR-let-7b), was examined by real-time polymerase chain reaction (PCR) analysis. Using RA knockdown cells, TLR-7-knockout mice, or antagonist, the specificity of miR-let-7b as a potential ligand for TLR-7 was tested. The mechanism by which ligation of miR-let-7b to TLR-7 promotes disease was investigated in RA myeloid cells by real-time PCR, enzyme-linked immunosorbent assay, and fluorescence-activated cell sorting. We also established the effect of ectopic miR-let-7b expression on arthritic joint inflammation. RESULTS: We found that a TLR-7 endogenous ligand resides mainly in RA synovial fluid macrophages. The GU-rich domain in miR-let-7b was found to be essential for TLR-7 ligation, since miR-147, the positive control for GU, was able to stimulate TLR-7+ myeloid cells, whereas miR-124, the negative, non-GU, control, was not. We demonstrated that miR-let-7b or exosomes containing miR-let-7b could transform the RA and/or mouse naive or antiinflammatory macrophages into inflammatory M1 macrophages via TLR-7 ligation. Consistently, we showed that miR-let-7b provokes arthritis by remodeling naive myeloid cells into M1 macrophages via TLR-7 ligation, since joint swelling and M1 macrophages are absent in TLR-7-deficient mice. CONCLUSION: The results of this study underscore the importance of miR-let-7b ligation to TLR-7 in the joint during the effector phase of RA.

Computed Tomography of the Esophagus in Scleroderma and Lung Disease.

Systemic sclerosis, or scleroderma, is a collagen vascular disease characterized by hardening of the skin and involvement of internal organs, most commonly the esophagus. The most frequent cause of death in these patients is lung disease. Esophageal dysfunction has been implicated in the pathogenesis of interstitial lung disease. We previously developed a standard for the esophageal diameter on chest computed tomography (CT) and hypothesized that patients with esophageal dilation would be more likely to have interstitial lung disease than those without. In this study, we test this in 121 systemic sclerosis patients with interstitial lung disease and 48 of those without interstitial lung disease. For controls, we evaluated 121 patients followed at a general pulmonary clinic and the previously studied normal healthy standards. This study demonstrated that esophageal dilation is common in systemic sclerosis patients (66.3% for the maximal esophageal diameter more than or equal to 15 mm), that systemic sclerosis patients with interstitial lung disease have more dilated esophagi than those without interstitial lung disease (median 19.4 mm vs. 14.1 mm), and that esophageal parameters are negatively correlated with pulmonary function. We also found that patients from general pulmonary clinic were more likely to have dilated esophagi than normal controls (median 12.1 mm vs. 9.7 mm). The CT measurement of esophageal diameter may be a useful marker of patients at risk for developing lung disease.

Characterising the expression and function of CCL28 and its corresponding receptor, CCR10, in RA pathogenesis.

OBJECTIVE: This study was conducted to determine the expression pattern, regulation and function of CCL28 and CCR10 in rheumatoid arthritis (RA) pathogenesis. METHODS: Expression of CCL28 and CCR10 was assessed in RA compared with other arthritis synovial tissues (STs) or fluids (SFs) by histology or ELISA. The factors modulating CCL28 and CCR10 expression were identified in RA myeloid and endothelial cells by ELISA, FACS and Western blotting. The mechanism by which CCL28 ligation promotes RA angiogenesis was examined in control and CCR10-knockdown endothelial cell chemotaxis and capillary formation. RESULTS: CCL28 and/or CCR10 expression levels were accentuated in STs and SFs of patients with joint disease compared with normal controls and they were predominately coexpressed in RA myeloid and endothelial cells. We show that protein expression of CCL28 and CCR10 was modulated by tumour necrosis factor (TNF)-α and toll-like receptor 4 ligation in RA monocytes and endothelial cells and by interleukin (IL)-6 stimulation in RA macrophages. Neutralisation of CCL28 in RA SF or blockade of CCR10 on human endothelial progenitor cells (EPCs) significantly reduced SF-induced endothelial migration and capillary formation, demonstrating that ligation of joint CCL28 to endothelial CCR10+ cells is involved in RA angiogenesis. We discovered that angiogenesis driven by ligation of CCL28 to CCR10 is linked to the extracellular signal regulated kinase (ERK) cascade, as CCR10-knockdown cells exhibit dysfunctional CCL28-induced ERK signalling, chemotaxis and capillary formation. CONCLUSIONS: The overexpression of CCL28 and CCR10 in RA ST and their contribution to EPC migration into RA joints support the CCL28/CCR10 cascade as a potential therapeutic target for RA.

Ligation of TLR5 promotes myeloid cell infiltration and differentiation into mature osteoclasts in rheumatoid arthritis and experimental arthritis.

Our aim was to examine the impact of TLR5 ligation in rheumatoid arthritis (RA) and experimental arthritis pathology. Studies were conducted to investigate the role of TLR5 ligation on RA and mouse myeloid cell chemotaxis or osteoclast formation, and in addition, to uncover the significance of TNF-α function in TLR5-mediated pathogenesis. Next, the in vivo mechanism of action was determined in collagen-induced arthritis (CIA) and local joint TLR5 ligation models. Last, to evaluate the importance of TLR5 function in RA, we used anti-TLR5 Ab therapy in CIA mice. We show that TLR5 agonist, flagellin, can promote monocyte infiltration and osteoclast maturation directly through myeloid TLR5 ligation and indirectly via TNF-α production from RA and mouse cells. These two identified TLR5 functions are potentiated by TNF-α, because inhibition of both pathways can more strongly impair RA synovial fluid-driven monocyte migration and osteoclast differentiation compared with each factor alone. In preclinical studies, flagellin postonset treatment in CIA and local TLR5 ligation in vivo provoke homing and osteoclastic development of myeloid cells, which are associated with the TNF-α cascade. Conversely, CIA joint inflammation and bone erosion are alleviated when TLR5 function is blocked. We found that TLR5 and TNF-α pathways are interconnected, because TNF-α is produced by TLR5 ligation in RA myeloid cells, and anti-TNF-α therapy can markedly suppress TLR5 expression in RA monocytes. Our novel findings demonstrate that a direct and an indirect mechanism are involved in TLR5-driven RA inflammation and bone destruction.

Tocilizumab in the treatment of rheumatoid arthritis and beyond.

Rheumatoid arthritis (RA) is a systemic inflammatory disease characterized by joint pain, swelling, stiffness, and progressive destruction of the small joints of the hands and feet. Treatment of RA has improved over the past decade. With multiple cytokines well-known now to play a role in the pathogenesis of RA, including tumor necrosis factor alpha, interleukin (IL)-1ß, and IL-6, many targeted biological treatments against these cytokines have emerged, changing the treatment of this disease. Tocilizumab (TCZ) is a recombinant humanized monoclonal antibody against the IL-6 receptor and has been approved in many countries, including the United States, for the treatment of moderate to severe RA in patients who have not adequately responded to one or more disease-modifying antirheumatic drugs (DMARDs) or cannot tolerate other approved drug classes for RA. The aim of this review is to discuss the role of IL-6 in RA, and to provide an overview of the mode of action, pharmacokinetics, and safety of TCZ. Furthermore, efficacy studies of TCZ as both monotherapy and combination therapy will be evaluated. There have been several important clinical trials evaluating the efficacy and safety of TCZ in RA patients; this review summarizes this data from 14 key trials with emphasis on Phase III trials. Review of these trials provides strong evidence that its use, both as monotherapy and in combination with methotrexate or other DMARDs, is an effective treatment in reducing the signs and symptoms of RA. TCZ showed tolerable safety but care is required for its use since there are some important safety concerns including elevated liver enzymes, elevated low-density lipoprotein, infections, and gastrointestinal perforations. Additionally, given the efficacy of TCZ in the treatment of RA, this review discusses how TCZ may be beneficial in the treatment of other autoimmune diseases, spinal disease, cardiovascular disease, organ transplantation, and malignancies where elevated levels of IL-6 may play a role in the pathogenesis of these diseases.

The novel role of IL-7 ligation to IL-7 receptor in myeloid cells of rheumatoid arthritis and collagen-induced arthritis.

Although the role of IL-7 and IL-7R has been implicated in the pathogenesis of rheumatoid arthritis (RA), the majority of the studies have focused on the effect of IL-7/IL-7R in T cell development and function. Our novel data, however, document that patients with RA and greater disease activity have higher levels of IL-7, IL-7R, and TNF-α in RA monocytes, suggesting a feedback regulation between IL-7/IL-7R and TNF-α cascades in myeloid cells that is linked to chronic disease progression. Investigations into the involved mechanism showed that IL-7 is a novel and potent chemoattractant that attracts IL-7R(+) monocytes through activation of the PI3K/AKT1 and ERK pathways at similar concentrations of IL-7 detected in RA synovial fluid. To determine whether ligation of IL-7 to IL-7R is a potential target for RA treatment and to identify their mechanism of action, collagen-induced arthritis (CIA) was therapeutically treated with anti-IL-7 Ab or IgG control. Anti-IL-7 Ab treatment significantly reduces CIA monocyte recruitment and osteoclast differentiation as well as potent joint monocyte chemoattractants and bone erosion markers, suggesting that both direct and indirect pathways might contribute to the observed effect. We also demonstrate that reduction in joint MIP-2 levels is responsible for suppressed vascularization detected in mice treated with anti-IL-7 Ab compared with the control group. To our knowledge, we show for the first time that expression of IL-7/IL-7R in myeloid cells is strongly correlated with RA disease activity and that ligation of IL-7 to IL-7R contributes to monocyte homing, differentiation of osteoclasts, and vascularization in the CIA effector phase.

Ligation of TLR7 by rheumatoid arthritis synovial fluid single strand RNA induces transcription of TNFα in monocytes.

OBJECTIVE: The aim of the study was to characterise the expression, regulation and pathogenic role of toll-like receptor 7 (TLR7) and TLR8 in rheumatoid arthritis (RA). METHODS: Expression of TLR7 and TLR8 was demonstrated in RA, osteoarthritis (OA) and normal (NL) synovial tissues (STs) employing immunohistochemistry. The authors next examined the mechanism by which TLR7 and TLR8 ligation mediates proinflammatory response by Western blot analysis and ELISA. Expression of TLR7 and TLR8 in RA monocytes was correlated to disease activity score (DAS28) and tumour necrosis factor α (TNFα) levels. Further, the effect of TLR7 ligation in RA monocytes was determined on synovial fluid (SF)-mediated TNFα transcription. RESULTS: TLR7/8 are predominately expressed in RA ST lining and sublining macrophages. The authors show that NF-κB and/or PI3K pathways are essential for TLR7/8 induction of proinflammatory factors in RA peripheral blood (PB)-differentiated macrophages. Expression of TLR7 in RA monocytes shows a strong correlation with DAS28 and TNFα levels. By contrast, expression of TLR8 in these cells does not correlate with DAS28, TLR7 or TNFα levels. The authors further demonstrate that RNA from RA SF, but not RA or NL plasma, could modulate TNFα transcription from RA monocytes that can be downregulated by antagonising TLR7 ligation or degradation of single stand (ss) RNA. Thus, ssRNA present in RA SF may function as a potential endogenous ligand for TLR7. CONCLUSIONS: These results suggest that expression of TLR7, but not TLR8, may be a predictor for RA disease activity and anti-TNFα responsiveness, and targeting TLR7 may suppress chronic progression of RA.