Cholecystokinin octapeptide significantly suppresses collagen-induced arthritis in mice by inhibiting Th17 polarization primed by dendritic cells

Cholecystokinin octapeptide (CCK-8) is a neuropeptide, and is shown to be a potent immunomodulator with predominant anti-inflammatory effects. Although the regulatory effect of CCK-8 on macrophages and B cells has been defined, the effect of CCK-8 on dendritic cells (DCs) and T cells is not well understood. In this study, we showed that CCK-8 reduced the expression of CD80, CD86, and MHCII on DCs. Moreover, CCK-8 promoted Th1 and inhibited Th17 polarization by increasing the production of IL-12 and decreasing the production of IL-6 and IL-23 on DCs in vitro and in vivo. In addition, intraperitoneal administration of CCK-8 to mice with collagen-induced arthritis (CIA) was found to effectively reduce the incidence of arthritis, delay its onset and prevent the occurrence of joint damage. Collectively, these results suggest that CCK-8 significantly suppresses the incidence and severity of CIA in mice, through the inhibition of DC mediated Th17 polarization.     

Substance P ameliorates collagen II-induced arthritis in mice via suppression of the inflammatory response

Current rheumatoid arthritis (RA) therapies such as biologics inhibiting pathogenic cytokines substantially delay RA progression. However, patient responses to these agents are not always complete and long lasting. This study explored whether substance P (SP), an 11 amino acids long endogenous neuropeptide with the novel ability to mobilize mesenchymal stem cells (MSC) and modulate injury-mediated inflammation, can inhibit RA progression. SP efficacy was evaluated by paw swelling, clinical arthritis scoring, radiological analysis, histological analysis of cartilage destruction, and blood levels of tumor necrosis factor-alpha (TNF-α) interleukin (IL)-10, and IL-17 in vivo. SP treatment significantly reduced local inflammatory signs, mean arthritis scores, degradation of joint cartilage, and invasion of inflammatory cells into the synovial tissues. Moreover, the SP treatment markedly reduced the size of spleens enlarged by excessive inflammation in CIA, increased IL-10 levels, and decreased TNF-α and IL-17 levels. Mobilization of stem cells and induction of T_reg and M2 type macrophages in the circulation were also increased by the SP treatment. These effect of SP might be associated with the suppression of inflammatory responses in RA and, furthermore, blockade of RA progression. Our results propose SP as a potential therapeutic for autoimmune-related inflammatory diseases.     

Anergic cells generated by blocking CD28 and CD40 costimulatory pathways in vitro ameliorate collagen induced arthritis

Collagen type II induced arthritis is an experimental model for studying the pathological mechanisms of therapeutic agents for human rheumatoid arthritis. In this study, we have investigated the effects of anergic cells on the development and disease progression of CIA. Anergic cells inhibited the proliferative response to collagen II primed lymphocytes, whereas the supernatant from anergic cell culture had no suppressive effect. Administration of anergic cells reduced the clinical score of CIA and ameliorated the development of CIA. The messenger RNA levels of IL-2 and IFN-γ were significantly decreased, whereas mRNA levels of IL-4, IL-10 and TGF-β showed no significant differences. A decrease in the collagen-specific Th1 associated IgG_2a response was observed, whereas IgG₁ was unaffected. This effective treatment is associated with a reduction in IFN-γ production and through cell-cell contact. Our results suggest that anergic cells may be beneficial for the treatment of rheumatoid arthritis.     

Protection against collagen-induced arthritis by electrotransfer of an expression plasmid for the interleukin-4

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease, leading to cartilage and bone destruction. We investigated whether the electrotransfer of IL-4 DNA could regulate the disease progress of murine collagen-induced arthritis (CIA). The maximum serum level of mIL-4 was measured by 340 pg/ml on day 1 following DNA transfer. The onset of severe CIA and the degree of synovitis and cartilage erosion were significantly reduced in mice treated with IL-4 DNA (P<0.05). The beneficial effect of IL-4 gene transfer lasted for at least 17 days subsequent to treatment. The expression of IL-1beta was considerably decreased in the paws by IL-4 DNA transfer (P<0.01). On the contrary, the ratio of TIMP2 to MMP2 significantly increased in the IL-4 DNA-treated group (P<0.01). These data demonstrated that electroporation-mediated gene transfer could provide a new approach as an IL-4 therapy for autoimmune arthritis.     

Boswellia serrata extract attenuates inflammatory mediators and oxidative stress in collagen induced arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease which leads to destruction of joints. Current treatment modalities for RA either produce symptomatic relief (NSAIDs) or modify the disease process (DMARDs). Though effective, their use is also limited by their side effects. As a result, the interest in alternative, well tolerated anti-inflammatory remedies has re-emerged. Our aim was to evaluate the antioxidant and antiarthritic activity of Boswellia serrata gum resin extract (BSE) in collagen induced arthritis. Arthritis was induced in male Wistar rats by collagen induced arthritis (CIA) method. BSE was administered at doses of 100 and 200 mg/kg body weight once daily for 21 days. The effects of treatment in the rats were assessed by biochemical (articular elastase, MPO, LPO, GSH, catalase, SOD and NO), inflammatory mediators (IL-1β, IL-6, TNF-α, IL-10, IFN-γ and PGE₂), and histological studies in joints. BSE was effective in bringing significant changes on all the parameters (articular elastase, MPO, LPO, GSH, catalase, SOD and NO) studied. Oral administration of BSE resulted in significantly reduced levels of inflammatory mediators (IL-1β, IL-6, TNF-α, IFN-γ and PGE₂), and increased level of IL-10. The protective effects of BSE against RA were also evident from the decrease in arthritis scoring and bone histology. The abilities to inhibit proinflammatory cytokines and modulation of antioxidant status suggest that the protective effect of Boswellia serrata extract on arthritis in rats might be mediated via the modulation of immune system.     

Exercise prevents the effects of experimental arthritis on the metabolism and function of immune cells

Active lymphocytes (LY) and macrophages (MΦ) are involved in the pathophysiology of rheumatoid arthritis (RA). Due to its anti‐inflammatory effect, physical exercise may be beneficial in RA by acting on the immune system (IS). Thus, female Wistar rats with type II collagen‐induced arthritis (CIA) were submitted to swimming training (6 weeks, 5 days/week, 60 min/day) and some biochemical and immune parameters, such as the metabolism of glucose and glutamine and function of LY and MΦ, were evaluated. In addition, plasma levels of some hormones and of interleukin‐2 (IL‐2) were also determined. Results demonstrate that CIA increased lymphocyte proliferation (1.9‐ and 1.7‐fold, respectively, in response to concanavalin A (ConA) and lipopolysaccharide (LPS)), as well as macrophage H₂O₂ production (1.6‐fold), in comparison to control. Exercise training prevented the activation of immune cells, induced by CIA, and established a pattern of substrate utilization similar to that described as normal for these cells. Exercise also promoted an elevation of plasma levels of corticosterone (22.2%), progesterone (1.7‐fold) and IL‐2 (2.6‐fold). Our data suggest that chronic exercise is able to counterbalance the effects of CIA on cells of the IS, reinforcing the proposal that the benefits of exercise may not be restricted to aerobic capacity and/or strength improvement. Copyright © 2010 John Wiley & Sons, Ltd.     

Utilization of two seven-transmembrane, G protein-coupled receptors, formyl peptide receptor-like 1 and formyl peptide receptor, by the synthetic hexapeptide WKYMVm for human phagocyte activation

Trp-Lys-Tyr-Val-D-Met (WKYMVm) is a synthetic leukocyte-activating peptide postulated to use seven-transmembrane, G protein-coupled receptor(s). In the study to characterize the receptor(s) for WKYMVm, we found that this peptide induced marked chemotaxis and calcium flux in human phagocytes. The signaling induced by WKYMVm in phagocytes was attenuated by high concentrations of the bacterial chemotactic peptide fMLP, suggesting that WKYMVm might use receptor(s) for fMLP. This hypothesis was tested by using cells over expressing genes encoding two seven-transmembrane receptors, formyl peptide receptor (FPR) and formyl peptide receptor-like 1 (FPRL1), which are with high and low affinity for fMLP, respectively. Both FPR- and FPRL1-expressing cells mobilized calcium in response to picomolar concentrations of WKYMVm. While FPRL1-expressing cells migrated to picomolar concentrations of WKYMVm, nanomolar concentrations of the peptide were required to induce migration of FPR-expressing cells. In contrast, fMLP elicited both calcium flux and chemotaxis only in FPR-expressing cells with an efficacy comparable with WKYMVm. Thus, WKYMVm uses both FPR and FPRL1 to stimulate phagocytes with a markedly higher efficacy for FPRL1. Our study suggests that FPR and FPRL1 in phagocytes react to a broad spectrum of agonists and WKYMVm as a remarkably potent agonist provides a valuable tool for studying leukocyte signaling via these receptors.     

Estradiol Enhances CD4+ T-Cell Anti-Viral Immunity by Priming Vaginal DCs to Induce Th17 Responses via an IL-1-Dependent Pathway

Clinical and experimental studies have shown that estradiol (E2) confers protection against HIV and other sexually transmitted infections. Here, we investigated the underlying mechanism. Better protection in E2-treated mice, immunized against genital HSV-2, coincided with earlier recruitment and higher proportions of T_h1 and T_h17 effector cells in the vagina post-challenge, compared to placebo-treated controls. Vaginal APCs isolated from E2-treated mice induced 10-fold higher T_h17 and T_h1 responses, compared to APCs from progesterone-treated, placebo-treated, and estradiol-receptor knockout mice in APC-T cell co-cultures. CD11c⁺ DCs in the vagina were the predominant APC population responsible for priming these T_h17 responses, and a potent source of IL-6 and IL-1β, important factors for T_h17 differentiation. T_h17 responses were abrogated in APC-T cell co-cultures containing IL-1β KO, but not IL-6 KO vaginal DCs, showing that IL-1β is a critical factor for T_h17 induction in the genital tract. E2 treatment in vivo directly induced high expression of IL-1β in vaginal DCs, and addition of IL-1β restored T_h17 induction by IL-1β KO APCs in co-cultures. Finally, we examined the role of IL-17 in anti-HSV-2 memory T cell responses. IL-17 KO mice were more susceptible to intravaginal HSV-2 challenge, compared to WT controls, and vaginal DCs from these mice were defective at priming efficient T_h1 responses in vitro, indicating that IL-17 is important for the generation of efficient anti-viral memory responses. We conclude that the genital mucosa has a unique microenvironment whereby E2 enhances CD4⁺ T cell anti-viral immunity by priming vaginal DCs to induce T_h17 responses through an IL-1-dependent pathway.     

Bone-Targeting Endogenous Secretory Receptor for Advanced Glycation End Products Rescues Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory synovitis that leads to the destruction of bone and cartilage. The receptor for advanced glycation end products (RAGE) is a multiligand membrane-bound receptor for high-mobility group box-1 (HMGB1) associated with development of RA by inducing production of proinflammatory cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-1 and IL-6. We developed a bone-targeting therapeutic agent by tagging acidic oligopeptide to a nonmembrane-bound form of RAGE (endogenous secretory RAGE [esRAGE]) functioning as a decoy receptor. We assessed its tissue distribution and therapeutic effectiveness in a murine model of collagen-induced arthritis (CIA). Acidic oligopeptide–tagged esRAGE (D₆-esRAGE) was localized to mineralized region in bone, resulting in the prolonged retention of more than 1 wk. Weekly administration of D₆-esRAGE with a dose of 1 mg/kg to RA model mice significantly ameliorated inflammatory arthritis, synovial hyperplasia, cartilage destruction and bone destruction, while untagged esRAGE showed little effectiveness. Moreover, D₆-esRAGE reduced plasma levels of proinflammatory cytokines including TNF-α, IL-1 and IL-6, while esRAGE reduced the levels of IL-1 and IL-6 to a lesser extent, suggesting that production of IL-1 and IL-6 reduced along the blockade of HMGB1 receptor downstream signals by D₆-esRAGE could be attributed to remission of CIA. These findings indicate that D₆-esRAGE enhances drug delivery to bone, leading to rescue of clinical and pathological lesions in murine CIA.     

Designing Lipid Nanostructures for Local Delivery of Biologically Active Macromolecules

This study focuses on the possible therapeutic utility of liposomes in the local treatment of inflammatory disorders, specifically rheumatoid arthritis (RA). Our purpose was to design a depot delivery system of an anti-inflammatory glycoprotein, lactoferrin (Lf), using positive multivesicular liposomes and to investigate its in vivo efficiency. Lactoferrin (Lf) has previously been shown to have therapeutic potential in mice with collagen-induced arthritis (CIA) after intra-articular (i.a.) injection. In order to protect Lf from enzymatic degradation and to maintain an adequate concentration in the joint, liposomes have been used as carriers for controlled drug delivery. Based on our previous findings we compared the ability of free Lf and Lf encapsulated in liposomes to suppress established joint inflammation and to modulate the cytokine response of lymph node (LN) T lymphocytes in DBA/1 mice with CIA. The anti-inflammatory effect of Lf formulated in positive liposomes was more pronounced compared with the free protein. After a single i.a. injection of liposomal Lf the arthritic score significantly decreased continuously for 2 weeks while in the case of free Lf for only 3–4 days. The cytokine levels produced by LN T cells showed decreased pro-inflammatory cytokines (TNF-α and IFN-γ) accompanied by increased anti-inflammatory cytokines (IL-5 and especcialy IL-10) in encapsulated compared with free Lf. When compared with free Lf, liposomal Lf decreased the expression of costimulatory molecules on DCs, reduced pro-inflammatory (TNF) and increased anti-inflammatory (IL-10) cytokine production. Using CIA model we have studied the liposome trafficking following i.a. administration and we have identified DCs as a target for liposomes in the draining LN. Our results suggest that the entrapment of Lf in liposomes may modify its pharmacodynamic profile and could have great potential as controlled delivery system in the treatment of RA and other local inflammatory conditions.     

Suppression of immune induction of collagen-induced arthritis in IL-17-deficient mice

Interleukin-17 is a T cell-derived proinflammatory cytokine. This cytokine is suspected to be involved in the development of rheumatoid arthritis (RA) because this cytokine expression is augmented in synovial tissues of RA patients. The pathogenic roles of IL-17 in the development of RA, however, still remain to be elucidated. In this study, effects of IL-17 deficiency on collagen-induced arthritis (CIA) model were examined using IL-17-deficient mice (IL-17(-/-) mice). We found that CIA was markedly suppressed in IL-17(-/-) mice. IL-17 was responsible for the priming of collagen-specific T cells and collagen-specific IgG2a production. Thus, these observations suggest that IL-17 plays a crucial role in the development of CIA by activating autoantigen-specific cellular and humoral immune responses.     

Investigation of the role of endosomal Toll-like receptors in murine collagen-induced arthritis reveals a potential role for TLR7 in disease maintenance

Introduction

Endosomal toll-like receptors (TLRs) have recently emerged as potential contributors to the inflammation observed in human and rodent models of rheumatoid arthritis (RA). This study aims to evaluate the role of endosomal TLRs and in particular TLR7 in the murine collagen induced arthritis (CIA) model.

Methods

CIA was induced by injection of collagen in complete Freund''s adjuvant. To investigate the effect of endosomal TLRs in the CIA model, mianserin was administered daily from the day of disease onset. The specific role of TLR7 was examined by inducing CIA in TLR7-deficient mice. Disease progression was assessed by measuring clinical score, paw swelling, serum anti-collagen antibodies histological parameters, cytokine production and the percentage of T regulatory (T_reg) cells.

Results

Therapeutic administration of mianserin to arthritic animals demonstrated a highly protective effect on paw swelling and joint destruction. TLR7^-/- mice developed a mild arthritis, where the clinical score and paw swelling were significantly compromised in comparison to the control group. The amelioration of arthritis by mianserin and TLR7 deficiency both corresponded with a reduction in IL-17 responses, histological and clinical scores, and paw swelling.

Conclusions

These data highlight the potential role for endosomal TLRs in the maintenance of inflammation in RA and support the concept of a role for TLR7 in experimental arthritis models. This study also illustrates the potential benefit that may be afforded by therapeutically inhibiting the endosomal TLRs in RA.     

The Adaptor Molecule Signaling Lymphocytic Activation Molecule (SLAM)-associated Protein (SAP) Is Essential in Mechanisms Involving the Fyn Tyrosine Kinase for Induction and Progression of Collagen-induced Arthritis

Signaling lymphocytic activation molecule-associated protein (SAP) is an Src homology 2 domain-only adaptor involved in multiple immune cell functions. It has also been linked to immunodeficiencies and autoimmune diseases, such as systemic lupus erythematosus. Here, we examined the role and mechanism of action of SAP in autoimmunity using a mouse model of autoimmune arthritis, collagen-induced arthritis (CIA). We found that SAP was essential for development of CIA in response to collagen immunization. It was also required for production of collagen-specific antibodies, which play a key role in disease pathogenesis. These effects required SAP expression in T cells, not in B cells. In mice immunized with a high dose of collagen, the activity of SAP was nearly independent of its ability to bind the protein tyrosine kinase Fyn and correlated with the capacity of SAP to promote full differentiation of follicular T helper (T_FH) cells. However, with a lower dose of collagen, the role of SAP was more dependent on Fyn binding, suggesting that additional mechanisms other than T_FH cell differentiation were involved. Further studies suggested that this might be due to a role of the SAP-Fyn interaction in natural killer T cell development through the ability of SAP-Fyn to promote Vav-1 activation. We also found that removal of SAP expression during progression of CIA attenuated disease severity. However, it had no effect on disease when CIA was clinically established. Together, these results indicate that SAP plays an essential role in CIA because of Fyn-independent and Fyn-dependent effects on T_FH cells and, possibly, other T cell types.     

Prophylactic effect of the oral administration of transgenic rice seeds containing altered peptide ligands of type II collagen on rheumatoid arthritis

Rheumatoid arthritis is an autoimmune disease associated with the recognition of self proteins secluded in arthritic joints. We generated transgenic rice seeds expressing three types of altered peptide ligands (APL) and the T cell epitope of type II collagen (CII256–271). When these transgenic rice and non-transgenic rice seeds were orally administrated to DBA/1?J mice once a day for 14?days, followed by immunization with CII, the clinical score of collagen-induced arthritis (CIA) was reduced and inflammation and erosion in the joints were prevented in mice fed APL7 transgenic rice only. IL-10 production against the CII antigen significantly increased in the splenocytes and iLN of CIA mice immunized with the CII antigen, whereas IFN-γ, IL-17, and IL-2 levels were not altered. These results suggest that IL-10-mediated immune suppression is involved in the prophylactic effects caused by transgenic rice expressing APL7.     

Cyr61 induces IL-6 production by fibroblast-like synoviocytes promoting Th17 differentiation in rheumatoid arthritis

Cysteine-rich protein 61 (Cyr61)/CCN1 is a product of an immediate early gene and functions in mediating cell adhesion and inducing cell migration. We previously showed that increased production of Cyr61 by fibroblast-like synoviocytes (FLS) in rheumatoid arthritis (RA) promotes FLS proliferation and participates in RA pathogenesis with the IL-17-dependent pathway. However, whether Cyr61 in turn regulates Th17 cell differentiation and further enhances inflammation of RA remained unknown. In the current study, we explored the potential role of Cyr61 as a proinflammatory factor in RA pathogenesis. We found that Cyr61 treatment dramatically induced IL-6 production in FLS isolated from RA patients. Moreover, IL-6 production was attenuated by Cyr61 knockdown in FLS. Mechanistically, we showed that Cyr61 activated IL-6 production via the αvβ5/Akt/NF-κB signaling pathway. Further, using a coculture system consisting of purified CD4(+) T cells and RA FLS, we found that RA FLS stimulated Th17 differentiation, and the pro-Th17 differentiation effect of RA FLS can be attenuated or stimulated by Cyr61 RNA interference or addition of exogenous Cyr61, respectively. Finally, using the collagen-induced arthritis animal model, we showed that treatment with the anti-Cyr61 mAb led to reduction of IL-6 levels, decrease of Th17 response, and attenuation of inflammation and disease progression in vivo. Taken together, our results reveal a novel role of Cyr61 in promoting Th17 development in RA via upregulation of IL-6 production by FLS, thus adding a new layer into the functional interplay between FLS and Th17 in RA pathogenesis. Our study also suggests that targeting of Cyr61 may represent a novel strategy in RA treatment.     

IL-23 Dependent and Independent Stages of Experimental Arthritis: No Clinical Effect of Therapeutic IL-23p19 Inhibition in Collagen-induced Arthritis

IL-23p19 deficient mice have revealed a critical role of IL-23 in the development of experimental autoimmune diseases, such as collagen-induced arthritis (CIA). Neutralizing IL-23 after onset of CIA in rats has been shown to reduce paw volume, but the effect on synovial inflammation and the immunological autoimmune response is not clear. In this study, we examined the role of IL-23 at different stages of CIA and during T cell memory mediated flare-up arthritis with focus on changes in B cell activity and Th1/Th17 modulation. Anti-IL-23p19 antibody (anti-IL23p19) treatment, starting 15 days after the type II collagen (CII)-immunization but before clinical signs of disease onset, significantly suppressed the severity of CIA. This was accompanied with significantly lower CII-specific IgG1 levels and lower IgG2a levels in the anti-IL-23p19 treated mice compared to the control group. Importantly, neutralizing IL-23 after the first signs of CIA did not ameliorate the disease. This was in contrast to arthritic mice that underwent an arthritis flare-up since a significantly lower disease score was observed in the IL-23p19 treated mice compared to the control group, accompanied by lower synovial IL-17A and IL-22 expression in the knee joints of these mice. These data show IL-23-dependent and IL-23-independent stages during autoimmune CIA. Furthermore, the memory T cell mediated flare-up arthritis is IL-23-mediated. These data suggest that specific neutralization of IL-23p19 after onset of autoimmune arthritis may not be beneficial as a therapeutic therapy for patients with rheumatoid arthritis (RA). However, T cell mediated arthritis relapses in patients with RA might be controlled by anti-IL-23p19 treatment.     

Role of IL-1 beta in the development of human T(H)17 cells: lesson from NLPR3 mutated patients

Background

T helper 17 cells (T_H-17) represent a lineage of effector T cells critical in host defence and autoimmunity. In both mouse and human IL-1β has been indicated as a key cytokine for the commitment to T_H-17 cells. Cryopyrin-associated periodic syndromes (CAPS) are a group of inflammatory diseases associated with mutations of the NLRP3 gene encoding the inflammasome component cryopyrin. In this work we asked whether the deregulated secretion of IL-1β secondary to mutations characterizing these patients could affect the IL-23/IL-17 axis.

Methodology/Principal Findings

A total of 11 CAPS, 26 systemic onset juvenile idiopathic arthritis (SoJIA) patients and 20 healthy controls were analyzed. Serum levels of IL-17 and IL-6 serum were assessed by ELISA assay. Frequency of T_H17 cells was quantified upon staphylococcus enterotoxin B (SEB) stimulation. Secretion of IL-1β, IL-23 and IL-6 by monocyte derived dendritic cells (MoDCs), were quantified by ELISA assay. A total of 8 CAPS and 11 SoJIA patients were also analysed before and after treatment with IL-1β blockade. Untreated CAPS patients showed significantly increased IL-17 serum levels as well as a higher frequency of T_H17 compared to control subjects. On the contrary, SoJIA patients displayed a frequency of T_H17 similar to normal donors, but were found to have significantly increased serum level of IL-6 when compared to CAPS patients or healthy donors. Remarkably, decreased IL-17 serum levels and T_H17 frequency were observed in CAPS patients following in vivo IL-1β blockade. On the same line, MoDCs from CAPS patients exhibited enhanced secretion of IL-1β and IL-23 upon TLRs stimulation, with a reduction after anti-IL-1 treatment.

Conclusion/Significance

These findings further support the central role of IL-1β in the differentiation of T_H17 in human inflammatory conditions.     

Osteopontin inhibition of miR-129-3p enhances IL-17 expression and monocyte migration in rheumatoid arthritis

BackgroundOsteopontin (OPN) is an important proinflammatory cytokine in rheumatoid arthritis (RA). Levels of OPN have been shown to be significantly correlated with interleukin-17 (IL-17) production and expression of Th17 cells in the synovial fluid of RA patients. Here, we investigated the role of OPN in monocyte migration, IL-17 production and osteoblasts.MethodsOPN and IL-17 expression profiles in osteoarthritis (OA) and RA synovial fluid were determined by enzyme-linked immunosorbent assay (ELISA). The expression of the microRNA, miR-129-3p, in osteoblasts was analyzed by real-time quantitative polymerase chain reaction (qPCR). Immunoreactive proteins were spotted by Western blotting. We used the collagen-induced arthritis (CIA) mouse model to investigate the role of OPN in monocyte migration during RA.ResultsOPN and IL-17 expression were higher in RA synovial fluid as compared to OA samples. We also found that OPN promotes IL-17 expression in osteoblasts and thereby enhances monocyte migration via the Syk/PI3K/Akt signaling pathway. miR-129-3p expression was found to be negatively regulated by OPN via the Syk/PI3K/Akt signal cascade. In contrast, lentiviral vectors expressing short hairpin RNA inhibited OPN expression and ameliorated articular swelling, cartilage erosion and monocyte infiltration in the ankle joints of CIA mice.ConclusionTo our knowledge, our study is the first to describe how OPN promotes monocyte migration by upregulating IL-17 expression in osteoblasts in RA disease.SignificanceThese findings indicate that OPN could serve as a potential therapeutic target for the treatment of RA.