Pathogenesis Of Collagen-induced Arthritis Research Articles

Role of the CXCR4-Gnαq-Plcβ signaling pathway in the pathogenesis of collagen-induced arthritis in rats

Rheumatoid arthritis (RA) is a chronic autoimmune disease in which immune cells and inflammatory cytokines are abnormally activated, leading to immunoregulatory dysfunction in the body and triggering systemic inflammatory responses. The interaction between CXC chemokine receptor 4 (CXCR4) and heterotrimeric G-protein α-subunit Gαq (Gnαq) activates phospholipase Cβ (PLCβ), which influences the expression of downstream effectors and participates widely in the onset and development of various diseases, thus suggesting the potential involvement of these molecules in RA pathogenesis. Therefore, the present study aimed to determine whether the CXCR4-Gnαq-PLCβ signaling pathway participates in the onset and development of RA. Using a collagen-induced arthritis (CIA) rat model, we found that compared with the control (healthy) rat group, CIA rats exhibited highly time-dependent arthritis, with the maximum arthritis score occurring in week 3. In contrast to the splenic and joint tissue of control rats, CIA rats showed obvious hyperplasia in the lymphoid white pulp and main germination centers of the spleen, narrowing of joint cavities, and inflammatory cellular infiltration on articular surfaces. The serum levels of expression of IL-1β, IL-4, IL-6, and TNF-α were significantly elevated (P < 0.05, P < 0.01). Core genes of the CXCR4-Gnαq-PLCβ pathway, namely CXCR4, Gnαq, PLCβ1, MMP1, and MMP3, also showed a significant increase in mRNA and protein expression levels (P < 0.05, P < 0.01). Proteins related to the CXCR4-Gnαq-PLCβ pathway were mainly localized to the red and white pulp regions in the spleen as well as in stromal, endothelial, and subdifferentiated synovial cells in the joints. These results indicated that CXCR4 is dependent on Gnαq for inducing the expression of PLCβ1 and stimulation of secretion of inflammatory cytokines by inflammatory cells. This consequently affects the expression of matrix metalloproteinases (MMPs), which serve as downstream effectors, thereby promoting RA pathogenesis. Our findings play an important role in elucidating the mechanisms of the onset and development of RA.

Long non-coding RNA ENSMUST00000197208 promotes a shift in the Th17/Treg ratio via the P2X7R-NLRP3 inflammasome axis in collagen-induced arthritis.

Recently, long non‑coding RNAs (lncRNAs) have been implicated in several human diseases, including arthritis. However, the role of lncRNAs in regulating the Th17/Treg ratio during the progression of collagen-induced arthritis (CIA) is poorly understood. Therefore, the aim of this study was to determine the role of the lncRNA ENSMUST00000197208 and the P2X7R-NLRP3 inflammasome axis in changes in the Th17/Treg ratio in CIA. To achieve this, the distribution of T cell subgroups in the spleen cells of a CIA mouse model and control mice was examined. Additionally, we examined the expression profile of ENSMUST00000197208 in a CIA mouse model and healthy mice. The results showed that ENSMUST00000197208 expression was significantly upregulated in the CIA models compared with the control group. Additionally, the P2X7R-NLRP3 inflammasome axis participated in the pathogenesis of CIA and knockdown of ENSMUST00000197208 inhibited CD4+ T cell differentiation into Th17 cells. Compared with the control group, joint inflammation was less visible in NLRP3 knockout mice. Additionally, the P2X7R-NLRP3 inflammasomeaxis, which is downstream of ENSMUST00000197208, can be positively targeted and regulated by ENSMUST00000197208 through miR-107. Overall, the findings of this study showed that the "lncRNA ENSMUST00000197208-miR 107-P2X7R/NLRP3" axis plays an important role in CIA and knocking down ENSMUST00000197208 can efficiently inhibit Th17 differentiation bysuppressing the P2X7R-NLRP3 inflammasomeaxis. Therefore, targeting this axis may represent a novel strategy for arthritis treatment.

Pathogenesis of Collagen-Induced Arthritis: Role of Immune Cells with Associated Cytokines and Antibodies, Comparison with Rheumatoid Arthritis

Collagen-induced arthritis is the most com­monin vivomodel of rheumatoid arthritis used for investigation of new potential therapies in preclinical research. Rheumatoid arthritis is a systemic inflammatory and autoimmune disease affecting joints, accompanied by significant extra-articular symptoms. The pathogenesis of rheumatoid arthritis and collagen-induced arthritis involves a so far properly unexplored network of immune cells, cytokines, antibodies and other factors. These agents trigger the autoimmune response leading to polyarthritis with cell infiltration, bone and cartilage degeneration and synovial cell proliferation. Our review covers the knowledge about cytokines present in the rat collagen-induced arthritis model and the factors affecting them. In addition, we provide a comparison with rheumatoid arthritis and a description of their important effects on the development of both diseases. We discuss the crucial roles of various immune cells (subtypes of T and B lymphocytes, dendritic cells, monocytes, macrophages), fibroblast-like synoviocy­tes, and their related cytokines (TNF-α, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-17, IL-23, GM-CSF, TGF-β). Finally, we also focus on key antibodies (rheu­matoid factor, anti-citrullinated protein antibodies, anti-collagen II antibodies) and tissue-degrading enzymes (matrix metalloproteinases).

Transplantation of IL-1β siRNA-modified bone marrow mesenchymal stem cells ameliorates type II collagen-induced rheumatoid arthritis in rats.

Rheumatoid arthritis (RA) is a chronic autoimmune disease that causes erosion of articular cartilage and bone and has adverse effects on both patients and livestock animals. The aim of the present study was to investigate the role of interleukin-1β (IL-1β) in the pathogenesis of RA, and to further determine whether injection of IL-1β small interfering RNA (siRNA) or transplantation of IL-1β siRNA + bone marrow mesenchymal stem cells (BMSCs) can ameliorate RA in rats. A collagen-induced arthritis (CIA) rat model was established by injecting type II collagen for 4 weeks. Next, CIA rats were randomly divided into three groups and injected or transplanted with PBS, IL-1β siRNA and IL-1β siRNA + BMSCs for another 4 weeks. The CIA rat model was successfully established, as demonstrated by the higher toe swelling value, thymus and spleen/body weight, immobility time and serum IL-1β concentration, as well as lower body weight, climbing time and mRNA expression of programmed death-1 (PD-1), transforming growth factor-β1 (TGF-β1) and forkhead box protein 3 (Foxp3) in the spleen, compared with control rats. Furthermore, histopathology results demonstrated that joint swelling and redness were observed in the knee joints of CIA rats. H&E results revealed that CIA rats presented erosive destruction of the bone and ulceration of the articular cartilage. In addition, in vitro results demonstrated that IL-1β expression was successfully silenced after IL-1β siRNA transfection in lipopolysaccharide-stimulated BMSCs. When compared with the results of PBS rats, both IL-1β siRNA injection and IL-1β siRNA + BMSC transplantation significantly increased the body weight, climbing time and mRNA expression of PD-1, TGF-β1 and Foxp3 in the spleen, while significantly reduced the immobility time and serum IL-1β concentration. In addition, when compared with that of IL-1β siRNA injection, IL-1β siRNA + BMSC transplantation exhibited markedly higher therapeutic efficacy against CIA. These results demonstrated that higher IL-1β contributed to the pathogenesis of CIA, and that IL-1β siRNA injection ameliorated CIA, while its combination with BMSCs exerted synergistic effects, which may be beneficial against RA.

Differential inflammation-mediated function of prokineticin 2 in the synovial fibroblasts of patients with rheumatoid arthritis compared with osteoarthritis

Prokineticin 2 (PK2) is a secreted protein involved in several pathological and physiological processes, including the regulation of inflammation, sickness behaviors, and circadian rhythms. Recently, it was reported that PK2 is associated with the pathogenesis of collagen-induced arthritis in mice. However, the role of PK2 in the pathogenesis of rheumatoid arthritis (RA) or osteoarthritis (OA) remains unknown. In this study, we collected synovial tissue, plasma, synovial fluid, and synovial fibroblasts (SF) from RA and OA patients to analyze the function of PK2 using immunohistochemistry, enzyme-linked immunosorbent assays, and tissue superfusion studies. PK2 and its receptors prokineticin receptor (PKR) 1 and 2 were expressed in RA and OA synovial tissues. PKR1 expression was downregulated in RA synovial tissue compared with OA synovial tissue. The PK2 concentration was higher in RA synovial fluid than in OA synovial fluid but similar between RA and OA plasma. PK2 suppressed the production of IL-6 from TNFα-prestimulated OA-SF, and this effect was attenuated in TNFα-prestimulated RA-SF. This phenomenon was accompanied by the upregulation of PKR1 in OA-SF. This study provides a new model to explain some aspects underlying the chronicity of inflammation in RA.

The Effects of Adoptively Transferred IL-23/IL-18-Polarized Neutrophils on Tumor and Collagen-Induced Arthritis in Mice.

BackgroundNeutrophils present great diverse phenotypes in various microenvironments and play different immune regulatory functions. Neutrophils generally classified into inflammatory phenotype N1 and anti-informatory phenotype N2. Our recent studies showed that IL-23 alone stimulated neutrophils to express IL-17A, IL-17F and IL-22 and displayed a gene transcriptional profile similar to Th17 cells. In the present study, we tried to identify potential cytokines to promote IL-23-induced neutrophil polarization.MethodsMouse bone marrow-derived neutrophils and human peripheral blood neutrophils were treated with IL-23 (10 ng/mL) plus IL-18 (25 ng/mL) to induce Th17-like subset in vitro and detected by real-time PCR, flow cytometry, ELISA, immunofluorescence and RNA-seq assays. In vivo, collagen-induced arthritis (CIA) mouse model and EL4 tumor-bearing mouse model were used to characterize the potential roles of N(IL-23+IL-18) in inflammation and tumor.ResultsReal-time PCR, ELISA and flow cytometry assays showed that IL-18 could significantly enhance IL-23-induced IL-17A, IL-17F and IL-22 expressions in mouse and human neutrophils in a synergistic way, although IL-18 alone failed to induce these cytokines expression. RNA-seq and molecular studies showed that the polarization of N(IL-23+IL-18) is mainly mediated by the JNK/p38-STAT3-BATF signaling pathway. Adoptive transfer of the induced N(IL-23+IL-18) neutrophils significantly accelerated the tumor growth in EL4 tumor-bearing mice and enhanced disease progression in the CIA mouse model. IL-17A-deficient N(IL-23+IL-18) neutrophils failed to enhance the CIA pathogenesis in this model, suggesting that IL-17A may be involved in the N(IL-23+IL-18) neutrophils-promoted arthritis in mice.ConclusionThe Th17-type subpopulation N(IL-23+IL-18) has pro-tumor and pro-inflammatory properties. Recognizing the different functional polarization of neutrophils would significantly help us to understand the distinctive protective/pathological roles of neutrophils in physiological and different pathological situations.

Activation of formyl peptide receptor 1 elicits therapeutic effects against collagen-induced arthritis.

Rheumatoid arthritis (RA) is an autoimmune disorder which shows production of autoantibodies, inflammation, bone erosion, swelling and pain in joints. In this study, we examined the effects of an immune‐modulating peptide, WKYMVm, that is an agonist for formyl peptide receptors (FPRs). Administration of WKYMVm into collagen‐induced arthritis (CIA) mice, an animal model for RA, attenuated paw thickness, clinical scores, production of type II collagen‐specific antibodies and inflammatory cytokines. WKYMVm treatment also decreased the numbers of TH1 and TH17 cells in the spleens of CIA mice. WKYMVm attenuated TH1 and TH17 differentiation in a dendritic cell (DC)‐dependent manner. WKYMVm‐induced beneficial effects against CIA and WKYMVm‐attenuated TH1 and TH17 differentiation were reversed by cyclosporin H but not by WRW4, indicating a crucial role of FPR1. We also found that WKYMVm augmented IL‐10 production from lipopolysaccharide‐stimulated DCs and WKYMVm failed to suppress TH1 and TH17 differentiation in the presence of anti‐IL‐10 antibody. The therapeutic administration of WKYMVm also elicited beneficial outcome against CIA. Collectively, we demonstrate that WKYMVm stimulation of FPR1 in DCs suppresses the generation of TH1 and TH17 cells via IL‐10 production, providing novel insight into the function of FPR1 in regulating CIA pathogenesis.

Promotion of Autoimmune Arthritis via Tryptophan Metabolism and Production of the Bacterial-Derived Tryptophan Metabolite Indole

Abstract Dysbiosis of gut bacterial communities in autoimmunity is a noted phenomenon in both murine models and human patients; however, the mechanisms of dysbiosis that promote disease pathogenesis remain unclear. In agreement with such studies, our lab has published that administration of antibiotics to deplete the microbiota late in the course of murine collagen-induced arthritis (CIA) significantly ameliorated disease. To understand the mechanisms by which microbiota depletion would significantly decrease CIA, we analyzed cecal metabolites by LC-MS during CIA and after antibiotic treatment and observed significant changes in various tryptophan metabolite levels. Interestingly, mice placed on a tryptophan-free diet had significantly decreased CIA development and increased in regulatory T cell (Treg) populations in the spleen. Further studies identified increases in indole, a bacterial-derived, tryptophan metabolite that strongly correlated with CIA progression. Direct administration of indole during CIA promoted disease and led to increases in T follicular cell (Tfh) and B cell populations in the peyer’s patches and mesenteric lymph nodes. Ex vivo stimulation of murine splenic B cells with indole resulted in significantly increased IgG production and a ≈10% increase in the frequency of CD23+ B cells. Our results suggest that gut dysbiosis due to CIA results in altered tryptophan metabolism and indole production, which promotes CIA pathogenesis via activation of T and B cell populations and antibody production. Precise understanding of which indole metabolites are involved and how they influence mucosal and systemic immune responses will help elucidate the role of intestinal dysbiosis in autoimmunity.

Standardized Xylocarpus moluccensis fruit fraction mitigates collagen-induced arthritis in mice by regulating immune response

This study was undertaken to evaluate the effect of Xylocarpus moluccensis fruit fraction (F018) on the pathogenesis of collagen-induced arthritis in mice. Arthritis was induced by intradermal injection of collagen (2mg/ml) with complete Freund's adjuvant in DBA/1J mice. F018 was administered orally at 1, 3 and 10mg/kg for 20days. Disease progression and mechanism were assessed by micro-CT analysis, RT-PCR, flow cytometry assay, myeloperoxidase (MPO) and MTT assay. F018 at 3 and 10mg/kg significantly reduced paw thickness, clinical score, mononuclear cell infiltration and collagen layer depletion in the knee section of collagen-induced arthritis (CIA) mice when compared with collagen-induced arthritis mice alone. Furthermore, F018 treatment in collagen-induced arthritis mice significantly recovered bone volume and trabecular number and decreased the trabecular space by modulating RANKL and OPG mRNA expression in the synovial tissue. F018 treatment in collagen-induced arthritis mice significantly attenuated spleen index, lymphocyte proliferation and paw myeloperoxidase (MPO) activity, pro-inflammatory cytokine TNFα, IL1β, and IL6 mRNA expression and enhanced IL10 mRNA expression in paw tissue. Furthermore, F018 treatment in collagen-induced arthritis mice significantly reduced splenic dendritic cell maturation and Th17 cells. In culture, F018 significantly decreased collagen-induced arthritis-FLS proliferation and promoted apoptosis. F018 may serve as a potential curative agent for arthritis.

Histone deacetylase 1 (HDAC1): A key player of T cell-mediated arthritis

Rheumatoid Arthritis (RA) represents a chronic T cell-mediated inflammatory autoimmune disease. Studies have shown that epigenetic mechanisms contribute to the pathogenesis of RA. Histone deacetylases (HDACs) represent one important group of epigenetic regulators. However, the role of individual HDAC members for the pathogenesis of arthritis is still unknown. In this study we demonstrate that mice with a T cell-specific deletion of HDAC1 (HDAC1-cKO) are resistant to the development of Collagen-induced arthritis (CIA), whereas the antibody response to collagen type II was undisturbed, indicating an unaltered T cell-mediated B cell activation. The inflammatory cytokines IL-17 and IL-6 were significantly decreased in sera of HDAC1-cKO mice. IL-6 treated HDAC1-deficient CD4+ T cells showed an impaired upregulation of CCR6. Selective inhibition of class I HDACs with the HDAC inhibitor MS-275 under Th17-skewing conditions inhibited the upregulation of chemokine receptor 6 (CCR6) in mouse and human CD4+ T cells. Accordingly, analysis of human RNA-sequencing (RNA-seq) data and histological analysis of synovial tissue samples from human RA patients revealed the existence of CD4+CCR6+ cells with enhanced HDAC1 expression. Our data indicate a key role for HDAC1 for the pathogenesis of CIA and suggest that HDAC1 and other class I HDACs might be promising targets of selective HDAC inhibitors (HDACi) for the treatment of RA.

Role of erythroblast-like Ter cells in the pathogenesis of collagen-induced arthritis

To explore the role of Ter cells in the development of the collagen-induced arthritis (CIA), we detected their quantity changes in the spleen of different stages of CIA mice and analyzed the correlation between Ter cells and the joint scores, and we also analyzed the correlation between Ter cells and the frequencies of T and B cell subsets, so as to further understand the pathogenesis of rheumatoid arthritis. The six to eight weeks DBA/1 mice were used to prepare CIA model. After the second immunization, we began to evaluate the joint score. According to the time of CIA onset and the joint score, the CIA mice were divided into three stages: early, peak and late stages. According to the final joint score, the CIA mice at the peak stage were subdivided into the high score group (score>8) and the low score group (score≤8). The frequencies of Ter cells in the spleen of the naïve mice and the CIA mice at various stages and the frequencies of T and B cell subsets in the spleen of the CIA mice at the peak stage were detected by flow cytometry, then we carried on the correlation analysis. The frequencies of Ter cells in the spleen of the CIA mice was significantly higher than those of the naïve mice (8.522%±2.645% vs. 1.937%±0.725%, P<0.01), the frequencies of Ter cells in the spleen of the high score group mice was significantly lower than those of the low score group (6.217%±0.841% vs. 10.827%±0.917%, P<0.01). The frequencies of Th1 cells in the spleen of the high score group mice was significantly higher than those of the low score group mice (1.337%±0.110% vs. 0.727%±0.223%, P<0.05). The frequencies of Th17 cells in the spleen of the high score group mice was higher than those of the low score group mice (0.750%±0.171% vs. 0.477%±0.051%, P=0.099). The frequencies of germinal center B cells in the spleen of the high score group mice was significantly higher than those of the low score group mice (1.243%±0.057% vs. 1.097%±0.015%, P<0.05). Correlation analysis results showed that the frequencies of Ter cells in the spleen of the CIA mice at the peak stage was strongly negatively correlated with the frequencies of CD4+ T, Th1, Th17, and germinal center B cells, and was strongly positively correlated with the frequencies of B10 cells, indicating that these cells might have a protective effect in CIA. Studies on dynamic changes showed that the frequencies of Ter cells in the spleen of the CIA mice at the late stage was significantly lower than those at the peak stage (0.917%±0.588% vs. 8.522%±2.645%, P<0.001), suggesting the protective effect of these cells in arthritis. Ter cells were significantly increased in the spleen of the CIA mice at peak stage, and were negatively correlated with joint scores and pathogenic immune cells, and positively correlated with protective immune cells. Ter cells were significantly decreased in the spleen of the CIA mice at the late stage. What we mentioned above suggests that Ter cells might be involved in the progression of rheumatoid arthritis as an immunomodulatory cell,but further in vivo and in vitro experiments are needed to verify its specific effects and mechanism.

MIF and MIF2 have distinct but synergistic roles in CIA pathogenesis

Abstract Rheumatoid arthritis (RA) is a relapsing autoimmune disease with progressive joint destruction. High expression alleles of the cytokine macrophage migration inhibitory factor (MIF) are associated with severe erosive RA. MIF and MIF family member D-dopachrome tautomerase (MIF2) signal through the receptor CD74. Previously we reported on the presence of CD74 expressing effector memory T cells in the collagen-induced arthritis (CIA) mouse model and identified CD74+ T cells in human RA synovium fluid. We studied MIF and MIF2 signaling on CD74+ T cells and inflammatory CD74high MΦ in the CIA model. We observed infiltration of CD74+ T cells (1.7 fold increase, p&amp;lt;0.001) and inflammatory CD74high MΦ (2 fold increase, p&amp;lt;0.001) in the joints of WT mice on day 28 post CIA induction. CD74+ T cell infiltration into paws positively correlated with CIA disease score (r=0.731, p=0.003). CD74+ T cells and CD74high MΦ failed to expand or infiltrate in the paws of Mif−/− mice in CIA. Interestingly, CIA induction in Mif2−/− mice expand CD74+ T cells in lymph nodes (0.5 fold increase, p=0.024), but fail to expand in other secondary lymphoid organs or infiltrate joints. Macrophage precursor Gr1high CD74+ monocytes expand in the spleen (3 fold, p&amp;lt;0.001) and blood (1 fold, p&amp;lt;0.001) of Mif2−/− mice, no change in CD74high MΦ levels is observed. The MIF inhibitor MIF098 ameliorates joint inflammation but did not inhibit the expansion or joint infiltration of CD74+ T cells (2 fold, p&amp;lt;0.001), Gr1high CD74+ monocytes, and CD74high MΦ (0.7 fold, p&amp;lt;0.01). Our findings provide evidence for a pathogenic role of novel MIF responsive CD74+ T cell in RA and suggest separate but crucial roles for both MIF and MIF2 in the development and localization for CD74+ T cells and CD74high MΦ in CIA.

CD38 Deficiency Downregulates the Onset and Pathogenesis of Collagen-Induced Arthritis through the NF-κB Pathway.

Aim The RelB gene plays an important role in guiding the progression of arthritis. We have previously demonstrated that the expression of the RelB gene is decreased significantly in bone marrow DCs of CD38−/− mice. In this study, we demonstrate that the cluster of the differentiation (CD38) gene could be a potentially therapeutic target for autoimmune arthritis. Method Collagen-induced arthritis (CIA) models were generated with both the wild-type (WT) C57BL/6 and CD38−/− mice. The expression of the RelB gene and maturation of bone marrow-derived dendritic cells (DCs) from the WT and CD38−/− mice were detected. Antigen-specific T cell responses, joint damage, and expression of proinflammatory cytokines were assessed. The effects of the Nuclear Factor Kappa B (NF-κB) transcription factor and its mechanisms were characterized. Results We demonstrated that in CD38−/− mice, the expression of the RelB gene and major histocompatibility complex II (MHC II) was decreased, accompanied with the inhibited T cell reaction in a mixed lymphocyte reaction (MLR) in bone marrow-derived DCs. Compared to the serious degeneration of the cartilage and the enlarged gap of the cavum articular in WT CIA mice, joint pathological changes of the CD38−/− CIA mice revealed marked attenuation, while the joint structures were well preserved. The preserved effects were observed by the inhibition of proinflammatory cytokines and promotion of anti-inflammatory cytokines. Furthermore, decreased phosphorylation of NF-κB was also observed in CD38−/− CIA mice. Conclusion We demonstrate that CD38 could regulate CIA through NF-κB and this regulatory molecule could be a novel target for the treatment of autoimmune inflammatory joint disease.

3'-Sialyllactose as an inhibitor of p65 phosphorylation ameliorates the progression of experimental rheumatoid arthritis.

Background and Purpose3′‐Sialyllactose (3′‐SL) is a safe compound that is present in high levels in human milk. Although it has anti‐inflammatory properties and supports immune homeostasis, its effect on collagen‐induced arthritis (CIA) is unknown. In this study, we investigated the prophylactic and therapeutic effect of 3′‐SL on the progression of rheumatoid arthritis (RA) in in vitro and in vivo models.Experimental ApproachThe anti‐arthritic effect of 3′‐SL was analysed with fibroblast‐like synoviocytes in vitro and an in vivo mouse model of CIA. RT‐PCR, Western blotting and ELISA were performed to evaluate its effects in vitro. Histological analysis of ankle and knee joints of mice with CIA was performed using immunohistochemistry, as well as safranin‐O and haematoxylin staining.Key Results3′‐SL markedly alleviated the severity of CIA in the mice by reducing paw swelling, clinical scores, incidence rate, serum levels of inflammatory cytokines and autoantibody production. Moreover, 3′‐SL reduced synovitis and pannus formation and suppressed cartilage destruction by blocking secretion of chemokines, pro‐inflammatory cytokines, https://en.wikipedia.org/wiki/Matrix_metalloproteinases and osteoclastogenesis via NF‐κB signalling. Notably, phosphorylation of p65, which is a key protein in the NF‐κB signalling pathway, was totally blocked by 3′‐SL in the RA models.Conclusions and Implications3′‐SL ameliorated pathogenesis of CIA by suppressing catabolic factor expression, proliferation of inflammatory immune cells and osteoclastogenesis. These effects were mediated via blockade of the NF‐κB signalling pathway. Therefore, 3′‐SL exerted prophylactic and therapeutic effects and could be a novel therapeutic agent for the treatment of RA.

The chemokine receptor CCR7 is a promising target for rheumatoid arthritis therapy.

The chemokine receptor CCR7 and its ligands CCL19 and CCL21 guide the homing and positioning of dendritic and T cells in lymphoid organs, thereby contributing to several aspects of adaptive immunity and immune tolerance. In the present study, we investigated the role of CCR7 in the pathogenesis of collagen-induced arthritis (CIA). By using a novel anti-human CCR7 antibody and humanized CCR7 mice, we evaluated CCR7 as a target in this autoimmune model of rheumatoid arthritis (RA). Ccr7-deficient mice were completely resistant to CIA and presented severely impaired antibody responses to collagen II (CII). Selective CCR7 expression on dendritic cells restored arthritis severity and anti-CII antibody titers. Prophylactic and therapeutic treatment of humanized CCR7 mice with anti-human CCR7 mAb 8H3-16A12 led to complete resistance to CIA and halted CIA progression, respectively. Our data demonstrate that CCR7 signaling is essential for the induction of CIA and identify CCR7 as a potential therapeutic target in RA.

Protein Kinase D1 deletion ameliorates collage-induced arthritis

Abstract Although the etiology of Rheumatoid arthritis (RA) is unknown, it is thought that TLR signaling may be involved in the initiation and progression of the disease. Disruption of the TLR signaling at early stages of RA could be a possible therapeutic strategy. We have previously identified protein kinase D1 (PKD1) as an indispensable component in the MyD88-dependent TLR signaling pathway that plays a critical role in acute and chronic inflammation. Although it is currently not known whether PKD1 plays a pathogenic role in RA in humans, we have previously found that daily treatments of a PKC/PKD inhibitor Gö6976 significantly ameliorated arthritic symptoms in collagen-induced arthritis (CIA). Here, we further investigated the role of PKD1 in pathogenesis of CIA in humanized HLA-DR1 transgenic mice using a tamoxifen-inducible PKD1-gene deletion system. We have found that PKD1 deletion resulted in reduced incidence and severity of arthritis in HLA-DR1 mice immunized with type II collagen. In addition, Gr-1+ myeloid lineage cell infiltration into the joint space was significantly reduced and joint destruction (assessed by joint histopathology study and mCT scanning) was ameliorated in the PKD1-deleted mice compared to wild-type. Our results provide evidences that PKD1 might play an important pathogenic role in inflammatory arthritis and that PKD1 could be a new therapeutic molecular target for arthritis.

Traditional Chinese medicine formula Bi-Qi capsule alleviates rheumatoid arthritis-induced inflammation, synovial hyperplasia, and cartilage destruction in rats

BackgroundTraditional Chinese medicine (TCM) formula Bi-Qi capsule (Bi-Qi) is a commonly prescribed drug to treat rheumatoid arthritis (RA). However, the mechanism of Bi-Qi-mediated amelioration of RA pathogenesis is still a mystery. Collagen induced arthritis (CIA) in rats is an established model that shares many similarities with RA in humans. In this study we investigated the effect of Bi-Qi on the pathogenesis of CIA in rats.MethodsCIA was developed in Sprague-Dawley (S.D) rats (n = 60, female) and used as a model resembling RA in humans. Rats were treated with a high or moderate dose of Bi-Qi, or methotrexate (MTX). Effects of the treatment on local joint and systemic inflammation, synovial hyperplasia, cartilage destruction, and other main features in the pathogenesis of CIA were analyzed.ResultsInflamed and swollen ankles and joints were observed in arthritic rats, while Bi-Qi or MTX treatment alleviated these symptoms. Only the Bi-Qi moderate dose decreased RA-induced serum levels of tumor necrosis factor-alpha (TNF-α). Both Bi-Qi and MTX reduced the interleukin (IL)-18 serum level. Protein levels of cartilage oligomeric matrix protein and osteopontin in serum, synovium, and cartilage were elevated in arthritic rats, while Bi-Qi alleviated these effects. Synovial hyperplasia, inflammatory cell infiltration in synovium and a high degree of cartilage degradation was observed in RA, and Bi-Qi or MTX alleviated this effect. Bi-Qi at the moderate dose was the most effective in mitigating CIA-related clinical complications.ConclusionsOur findings showed that Bi-Qi alleviates CIA-induced inflammation, synovial hyperplasia, cartilage destruction, and the other main features in the pathogenesis of CIA. This provides fundamental evidence for the anti-arthritic properties of Bi-Qi and corroborates the use of Bi-Qi TCM formula for the treatment of RA.

Inhibition of cytokine response to TLR stimulation and alleviation of collagen-induced arthritis in mice by Schistosoma japonicum peptide SJMHE1.

Helminth‐derived products have recently been shown to prevent the development of inflammatory diseases in mouse models. However, most identified immunomodulators from helminthes are mixtures or macromolecules with potentially immunogenic side effects. We previously identified an immunomodulatory peptide called SJMHE1 from the HSP60 protein of Schistosoma japonicum. In this study, we assessed the ability of SJMHE1 to affect murine splenocytes and human peripheral blood mononuclear cells (PBMCs) stimulated by toll‐like receptor (TLR) ligands in vitro and its treatment effect on mice with collagen‐induced arthritis (CIA). We show that SJMHE1 not only modulates the cytokine production of murine macrophage (MΦ) and dendritic cell but also affects cytokine production upon coculturing with allogeneic CD4+ T cell. SJMHE1 potently inhibits the cytokine response to TLR ligands lipopolysaccharide (LPS), CpG oligodeoxynucleotides (CpG) or resiquimod (R848) from mouse splenocytes, and human PBMCs stimulated by LPS. Furthermore, SJMHE1 suppressed clinical signs of CIA in mice and blocked joint erosion progression. This effect was mediated by downregulation of key cytokines involved in the pathogenesis of CIA, such as interferon‐γ (IFN‐γ), tumour necrosis factor‐α (TNF‐α), interleukin (IL)‐6, IL‐17, and IL‐22 and up‐regulation of the inhibitory cytokine IL‐10, Tgf‐β1 mRNA, and CD4+ CD25+Foxp3+ Tregs. This study provides new evidence that the peptide from S. japonicum, which is the ‘safe’ selective generation of small molecule peptide that has evolved during host–parasite interactions, is of great value in the search for novel anti‐inflammatory agents and therapeutic targets for autoimmune diseases.

NLRP3 Inflammasome Plays an Important Role in the Pathogenesis of Collagen-Induced Arthritis.

Objective. To investigate the relationship between NLRP3 and the pathogenesis of collagen-induced arthritis. Methods. We used the collagen-induced arthritis (CIA) mouse model. The mice were divided into two groups: the model group (CIA, n = 16) and the control group (Normal, n = 8). The mice were sacrificed seven weeks after immunization. The arthritis score and imaging evaluation (X-rays, Micro-CT, and MRI) were performed. Synovial tissue NLRP3 expression and peripheral blood cytokine levels were analyzed. Results. The arthritis score (6.00 ± 2.52), imaging score (4.63 ± 0.92), and synovial tissue NLRP3 expression (4.00 ± 2.03) significantly increased in the CIA mice. The expression of synovial NLRP3 was positively correlated with arthritis clinical and radiographic scores (r = 0.792 and r = 0.669, resp.). Conclusions. The synovial NLRP3 expression increased at the early onset of RA. Synovial NLRP3 expression level was correlated with the clinical arthritis severity and extent of radiological destruction, suggesting that NLRP3 is involved in the pathogenesis of RA.

Expression of receptor activator of nuclear factor-κB ligand is related to sex differences in collagen-induced arthritis

Osteoclasts are responsible for bone destruction in rheumatoid arthritis, and women show greater disease activity and functional disability than men. This study aimed to examine differences in the pathogenesis of collagen-induced arthritis and osteoclastogenesis between female and male mice in vivo and in vitro. Female mice exhibited worse disease progression and increased osteoclastogenesis, as measured by tartrate-resistant acid phosphatase (TRAP) staining than male mice. Significantly higher levels of CD11b+ cells were detected in the bone marrow of female mice than that of male mice. Furthermore, the mRNA expression of receptor activator of nuclear factor-κB ligand was higher in female mice that were immunized with or without collagen II. These findings highlighted sex differences in arthritis morbidity and suggested that female mice are more likely to develop arthritis than male mice. Further studies are needed to investigate the mechanisms of sex differences in collagen-induced arthritis.