Remission of collagen-induced arthritis is associated with high levels of transforming growth factor-beta expression in the joint

Undenatured type II collagen protects against collagen-induced arthritis by restoring gut-joint homeostasis and immunity

Oral administration of harmless antigens can induce suppression of reactive immune responses, a process that capitalises on the ability of the gastrointestinal tract to tolerate exposure to food and commensal microbiome without triggering inflammatory responses. Repeating exposure to type II collagen induces oral tolerance and inhibits induction of arthritis, a chronic inflammatory joint condition. Although some mechanisms underlying oral tolerance are described, how dysregulation of gut immune networks impacts on inflammation of distant tissues like the joints is unclear. We used undenatured type II collagen in a prophylactic regime -7.33 mg/kg three times/week- to describe the mechanisms associated with protective oral immune-therapy (OIT) in gut and joint during experimental Collagen-Induced Arthritis (CIA). OIT reduced disease incidence to 50%, with reduced expression of IL-17 and IL-22 in the joints of asymptomatic mice. Moreover, whilst the gut tissue of arthritic mice shows substantial damage and activation of tissue-specific immune networks, oral administration of undenatured type II collagen protects against gut pathology in all mice, symptomatic and asymptomatic, rewiring IL-17/IL-22 networks. Furthermore, gut fucosylation and microbiome composition were also modulated. These results corroborate the relevance of the gut-joint axis in arthritis, showing novel regulatory mechanisms linked to therapeutic OIT in joint disease.

The use of animal models in rheumatoid arthritis research

The pathological hallmark of rheumatoid arthritis (RA) is a synovial pannus that comprises proliferating and invasive fibroblast-like synoviocytes, infiltrating inflammatory cells, and an associated neoangiogenic response. Animal models have been established to study these pathological features of human RA. Spontaneous and induced animal models of RA primarily reflect inflammatory aspects of the disease. Among various induced animal models, collagen-induced arthritis (CIA) and collagen antibody-induced arthritis (CAIA) models are widely used to study the pathogenesis of RA. Improved transplantation techniques for severe combined immunodeficiency (SCID) mouse models of RA can be used to evaluate the effectiveness of potential therapeutics in human tissues and cells. This review provides basic information on various animal models of RA, including CIA and CAIA. In addition, we describe a SCID mouse coimplantation model that can measure the long-distance migration of human RA synoviocytes and cartilage destruction induced by these cells.

Local inhibition of TGF-β1 signaling improves Th17/Treg balance but not joint pathology during experimental arthritis

TGF-β1 is an important growth factor to promote the differentiation of T helper 17 (Th17) and regulatory T cells (Treg). The potential of TGF-β1 as therapeutic target in T cell-mediated diseases like rheumatoid arthritis (RA) is unclear. We investigated the effect of TGF-β1 inhibition on murine Th17 differentiation in vitro, on human RA synovial explants ex vivo, and on the development of experimental arthritis in vivo. Murine splenocytes were differentiated into Th17 cells, and the effect of the TGF-βRI inhibitor SB-505124 was studied. Synovial biopsies were cultured in the presence or absence of SB-505124. Experimental arthritis was induced in C57Bl6 mice and treated daily with SB-505124. Flow cytometry analysis was performed to measure different T cell subsets. Histological sections were analysed to determine joint inflammation and destruction. SB-505124 potently reduced murine Th17 differentiation by decreasing Il17a and Rorc gene expression and IL-17 protein production. SB-505124 significantly suppressed IL-6 production by synovial explants. In vivo, SB-505124 reduced Th17 numbers, while increased numbers of Tregs were observed. Despite this skewed Th17/Treg balance, SB-505124 treatment did not result in suppression of joint inflammation and destruction. Blocking TGF-β1 signalling suppresses Th17 differentiation and improves the Th17/Treg balance. However, local SB-505124 treatment does not suppress experimental arthritis.

Expression of mBD4, mBD3 and CRAMP during type II collagen-induced arthritis/CIA and their association with inflammation and bone-remodeling markers

The aim of this study was to analyze the expression of mBD4, mBD3 and CRAMP in joint of mice with type II collagen-induced arthritis/CIA and to explore its possible association with IL-10, IL-4, IFN-γ, IL-17, MMP3, RANK/RANKL/OPG and histological parameters.

METHODS

CIA was induced in 44 DBA/1 J mice. The joints from mice were classified into the onset, peak and remission phase of CIA. Histological sections were stained with hematoxylin-eosin and safranin O. The expression of CRAMP, mBD-3, mBD-4, and MMP-3 was evaluated using reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry. The expression of IL-10, IL-4, IFN-γ, IL-17, RANK/RANKL/OPG was analyzed by RT-PCR.

RESULTS

We observed that inflammation and immunostained cells for CRAMP increased in the peak and remission phases compared to the control group. In addition, increments in relative expressions of CRAMP were detected for the remission phase and in IL-4 and IL-17 in the peak phase compared to the control and onset phase. In addition, an increase in IL-10 in a peak phase compared to the control, as well as the relative expression of IFN-γ in remission phase was higher than in the onset phase. This was accompanied by an increase in cartilage damage in the peak phase compared to the control. Cells immunostained to MMP3 increased in the peak phase compared to the onset and control group, and relative expression of MMP3 was detected in the peak phase compared to the onset, remission, and control group. We observed that the relative expression of RANK and RANKL in the peak phase was higher than in control and onset phase. Finally, the relative expression of OPG in the peak phase compared to the onset, remission, and control group was detected. Regarding CRAMP behavior in the different phases studied, it was positively correlated with IL-4 and RANK, and showed a negative correlation with IFN-γ, IL-17, IL-10, RANKL, OPG and RANKL/OPG ratio in the control group. Also was positively correlated with IFN-γ, IL-17, IL-4, IL-10, as well as with RANK, RANKL, and OPG in the onset and peak phases of the CIA. In the peak phase, CRAMP showed a positive association with MMP3, and we observed a direct correlation between CRAMP and IFN-γ and RANKL/OPG ratio in remission phase. mBD3 correlates positively with IFN-γ, IL-17, IL-10, RANKL, OPG and RANKL/OPG ratio, and showed a negative correlation with CRAMP, MMP3, and RANK in the control group. Also, it was directly associated with IFN-γ, IL-17, IL-4, IL-10 and RANKL in the onset phase while it was inversely associated with CRAMP, MMP-3, RANK, RANKL, and OPG in the peak phase. Finally, mBD3 was inversely correlated with MMP3 in the remission phase and was directly associated with CRAMP, IFN-γ and RANKL/OPG ratio in this phase. mBD4 was directly associated with CRAMP, IFN-γ, IL-17, IL-4, IL-10, RANKL / OPG in the onset phase, and with CRAMP, IFN-γ, IL-17, IL-4, IL-10, MMP3, RANK, RANKL and OPG in the peak phase. Finally, mBD4 was positively associated with mBD3, IFN-γ, IL-17, IL-10, RANK, RANKL OPG and RANKL/OPG in the CIA remission phase.

CONCLUSIONS

Our results demonstrate that CRAMP plays an important role in CIA progress and suggest that its abundance is associated with local pro- and anti-inflammatory status. This makes us propose CRAMP as a possible contributor of bone reconstruction in the last stage of CIA.

Infrared radiation from cage bedding moderates rat inflammatory and autoimmune responses in collagen-induced arthritis

The development of collagen type II (CII)-induced arthritis (CIA), a model of rheumatoid arthritis, in rats housed in cages with bedding composed of Celliant fibres containing ceramic particles, which absorb body heat and re-emit the energy back to the body in the form of infrared radiation (+IRF rats), and those housed in cages with standard wooden shaving bedding (-IRF control rats) was examined. The appearance of the first signs of CIA was postponed, while the disease was milder (judging by the arthritic score, paw volume, and burrowing behaviour) in +IRF compared with -IRF rats. This correlated with a lower magnitude of serum anti-CII IgG antibody levels in +IRF rats, and lower production level of IL-17, the Th17 signature cytokine, in cultures of their paws. This could be partly ascribed to impaired migration of antigen-loaded CD11b + dendritic cells and their positioning within lymph nodes in +IRF rats reflecting diminished lymph node expression of CCL19 /CCL21. Additionally, as confirmed in rats with carrageenan-induced paw inflammation (CIPI), the infrared radiation from Celliant fibres, independently from immunomodulatory effects, exerted anti-inflammatory effects (judging by a shift in pro-inflammatory mediator to anti-inflammatory/immunoregulatory mediator ratio towards the latter in paw cultures) and ameliorated burrowing behaviour in CIA rats.

Dynamic transcriptome analysis unveils key proresolving factors of chronic inflammatory arthritis

Despite recent advances in understanding chronic inflammation remission, global analyses have not been explored to systematically discover genes or pathways underlying the resolution dynamics of chronic inflammatory diseases. Here, we performed time-course gene expression profiling of mouse synovial tissues along progression and resolution of collagen-induced arthritis (CIA) and identified genes associated with inflammation resolution. Through network analysis of these genes, we predicted 3 key secretory factors responsible for the resolution of CIA: Itgb1, Rps3, and Ywhaz. These factors were predominantly expressed by Tregs and antiinflammatory M2 macrophages, suppressing production of proinflammatory cytokines. In particular, Ywhaz was elevated in the sera of mice with arthritis resolution and in the urine of rheumatoid arthritis (RA) patients with good therapeutic responses. Moreover, adenovirus-mediated transfer of the Ywhaz gene to the affected joints substantially inhibited arthritis progression in mice with CIA and suppressed expression of proinflammatory cytokines in joint tissues, lymph nodes, and spleens, suggesting Ywhaz is an excellent target for RA therapy. Therefore, our comprehensive analysis of dynamic synovial transcriptomes provides previously unidentified antiarthritic genes, Itgb1, Rps3, and Ywhaz, which can serve as molecular markers to predict disease remission, as well as therapeutic targets for chronic inflammatory arthritis.

Synergistic effect of all-trans-retinal and triptolide encapsulated in an inflammation-targeted nanoparticle on collagen-induced arthritis in mice

Targeted delivery of nano-encapsulated anti-inflammatory agent represents a promising while challenging strategy in the treatment of rheumatoid arthritis (RA). Pro-inflammatory macrophages play a major role in the pathogenesis of RA. In this study, we investigated the effect of a macrophage-targeted pH-sensitive nanoparticle on collagen-induced arthritis (CIA) in mice. To target macrophage, all-trans-retinal was conjugated into dextran backbone through pH-sensitive hydrazone bond, then grafted with galactose (GDR). This nanoparticle was used for the encapsulation of triptolide (TPT), a potent anti-inflammatory compound isolated from Chinese herb. As expected, GDR nanoparticles preferentially accumulated in the inflammatory tissues. Treatment with GDR-TPT nanoparticles resulted in a marked decrease in the infiltration of CD3⁺ T cells and F4/80⁺ macrophages and reduction of the expression of TNF-α, IL-6 and IL-1β in the inflamed lesions of CIA mice. Furthermore, Th1 and Th17 responses were also inhibited. Importantly, anti-arthritic effect of TPT was markedly enhanced while its toxic effect was attenuated by encapsulating with GDR. GDR by itself also had moderate effect in the inhibition of arthritis, due to its intrinsic anti-inflammatory property. Therefore, our results clearly show that GDR-TPT nanoparticle may represent a promising drug delivery system for the treatment of RA.

T helper cell subpopulations repertoire in peripheral blood and its correlation with sex of newly diagnosed arthritis patients: A gender based study

Rheumatoid arthritis (RA) is an inflammatory autoimmune disorder. Autoreactive T cells play a very significant role in the pathogenesis of RA. However, the exact mechanisms of disease severity and pathogenesis are poorly understood. We attempted to correlate T-helper cell activities with sexes of newly diagnosed patients with RA. The patients were divided based on their sex and disease severity. Examination of the expression of various factors using quantitative real-time PCR and FACS analysis of peripheral blood mononuclear cells revealed that T-bet, ROR-γt, Foxp3, and the level of cytokines associated with Th1 cells were almost identical among male and female patients with RA. Interestingly, there was a high correlation between Th17 expression and disease severity in female patients with RA. In general, there was no significant correlation between Th1 cell population and the disease severity in newly diagnosed patients with RA. In contrast, the frequency of both Th17 and Treg cells was higher in patients with more severe disease. The results suggested that, in patients with RA, the T-helper cell balance within peripheral blood was skewed towards the Th17 and Treg phenotypes. Besides Th17- and Treg-associated cytokines, elevated expression of IL-27/IL-23 cytokines might also be responsible for increased disease severity in female patients with RA.

Assessment of effectiveness and safety of repeat administration of proinflammatory primed allogeneic mesenchymal stem cells in an equine model of chemically induced osteoarthritis

Background

This study aimed at assessing the effectiveness and safety of repeated administrations of allogeneic bone marrow-derived mesenchymal stem cells (BM-MSCs) primed with tumor necrosis factor (TNF)-α and interferon-γ in an equine model of chemically-induced osteoarthritis. Arthritis was induced in both radio-carpal (RC)-joints by amphotericin-B in 18 ponies, divided into three groups depending on the treatment injected: MSC-naïve (n = 7), MSC-primed (n = 7) and control (n = 4). The study consisted of two phases and used one RC-joint of each animal in each phase, with four months time-lapse, in order to assess two end-points. Clinical, synovial, radiological and ultrasonographic follow-up was performed. At six months, animals were euthanized and both carpi were assessed by magnetic resonance imaging (MRI), gross anatomy, histopathology, histochemistry and gene expression.

Results

Clinical and synovial inflammatory signs were quicker reduced in MSC-treated groups and repeated allogeneic administration did not produce adverse reactions, but MSC-primed group showed slight and transient local inflammation after second injection. Radiology and MRI did not show significant differences between treated and control groups, whereas ultrasonography suggested reduced synovial effusion in MSC-treated groups. Both MSC-treated groups showed enhanced cartilage gross appearance at two compared to six months (MSC-naïve, p < 0.05). Cartilage histopathology did not reveal differences but histochemistry suggested delayed progression of proteoglycan loss in MSC-treated groups. Synovium histopathology indicated decreased inflammation (p < 0.01) in MSC-primed and MSC-naïve at two and six months, respectively. At two months, cartilage from MSC-primed group significantly (p < 0.05) upregulated collagen type II (COL2A1) and transforming growth factor (TGF)-β1 and downregulated cyclooxygenase-2 and interleukin (IL)-1β. At six months, MSC-treatments significantly downregulated TNFα (p < 0.05), plus MSC-primed upregulated (p < 0.05) COL2A1, aggrecan, cartilage oligomeric protein, tissue inhibitor of metalloproteinases-2 and TGF-β1. In synovium, both MSC-treatments decreased (p < 0.01) matrix metalloproteinase-13 expression at two months and MSC-primed also downregulated TNFα (p < 0.05) and IL-1β (p < 0.01).

Conclusions

Both MSC-treatments provided beneficial effects, mostly observed at short-term. Despite no huge differences between MSC-treatments, the findings suggested enhanced anti-inflammatory and regulatory potential of MSC-primed. While further research is needed to better understand these effects and clarify immunogenicity implications, these findings contribute to enlarge the knowledge about MSC therapeutics and how they could be influenced.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1556-3) contains supplementary material, which is available to authorized users.

Pain relieving and protective effects of Astragalus hydroalcoholic extract in rat arthritis models

OBJECTIVES

The evaluation of the pharmacological profile of the dried 50% hydroalcoholic extract (50%HA) of Astragali radix in two different animal models of articular damage resembling osteoarthritis and rheumatoid arthritis.

METHODS

Sodium monoiodoacetate (MIA) or complete Freund's adjuvant (CFA) was intra-articular injected (day 0) in the rat tibiotarsal joint to induce damages mimicking osteoarthritis or rheumatoid arthritis. Pain measurements (responses to non-noxious and noxious stimuli, spontaneous pain, articular pain) were assessed on days 7 and 14. On day 14, the tibiotarsal joints were explanted in order to measure the diameter and to assess histological evaluations. Furthermore, the plasmatic concentrations of inflammatory and anti-inflammatory cytokines were measured.

KEY FINDINGS

A single administration of 50%HA (300 mg/kg per os) significantly reduced both MIA-induced pain and CFA-induced pain (78% and 96% pain relief, respectively). The repeated administration prevented the development of hypersensitivity on day 14. The haematoxylin/eosin staining revealed that 50% HA attenuated joint alterations in MIA-injected rats, and furthermore, the joint inflammatory infiltrate was reduced in both models (by about 50%). In CFA-treated rats, 50%HA lowered the plasmatic levels of the pro-inflammatory cytokines interleukin-1β and tumour necrosis factor-α as well as the joint diameter.

CONCLUSIONS

The 50% hydroalcoholic extract of Astragali radix is a valuable candidate for the adjuvant treatment of articular diseases.

Transcriptome analysis of muskrat scented glands degeneration mechanism

The scented gland, a musk-secreting organ of male muskrats, shows clear seasonal changes. When entering the secreting season in March, scented glands gradually increase in size and active secretion starts. In September, scented glands become gradually smaller and secretion decreases. By November, scented glands are gradually replaced by adipose tissue. In this study, six healthy adult male muskrats were analysed: three from the secreting season (March) and three from the non-secreting season (November). Using RNA-Seq analysis, gene expression profiles of scented glands from both seasons were determined. Using the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, we found that genes involved in calcium and TGF-beta signalling pathways were significantly more expressed in the non-secreting than in the secreting season. These changes in gene expression correlated with alterations in scented gland size. Both calcium and TGF-beta signalling pathways are important regulators of cell apoptosis, which may thus be involved in muskrat scented gland degeneration.

A quantitative mechanistic PK/PD model directly connects Btk target engagement and in vivo efficacy

Correlating target engagement with in vivo drug activity remains a central challenge in efforts to improve the efficiency of drug discovery. Previously we described a mechanistic pharmacokinetic-pharmacodynamic (PK/PD) model that used drug-target binding kinetics to successfully predict the in vivo efficacy of antibacterial compounds in models of Pseudomonas aeruginosa and Staphylococcus aureus infection. In the present work we extend this model to quantitatively correlate the engagement of Bruton's tyrosine kinase (Btk) by the covalent inhibitor CC-292 with the ability of this compound to reduce ankle swelling in an animal model of arthritis. The modeling studies include the rate of Btk turnover and reveal the vulnerability of Btk to engagement by CC-292.

Enhanced immunoregulation of mesenchymal stem cells by IL-10-producing type 1 regulatory T cells in collagen-induced arthritis

Mesenchymal stem cells (MSCs) possess immunomodulatory properties and have potential, however, there have been conflicting reports regarding their effects in rheumatoid arthritis (RA), which causes inflammation and destruction of the joints. Through a comparative analysis of regulatory T (Treg) and IL-10-producing type 1 regulatory T (Tr1) cells, we hypothesized that Tr1 cells enhance the immunoregulatory functions of MSCs, and that a combinatorial approach to cell therapy may exert synergistic immunomodulatory effects in an experimental animal model of rheumatoid arthritis (RA). A combination of MSCs and Tr1 cells prevented the development of destructive arthritis compared to single cell therapy. These therapeutic effects were associated with an increase in type II collagen (CII)-specific CD4+CD25+Foxp3+ Treg cells and inhibition of CII-specific CD4+IL-17+ T cells. We observed that Tr1 cells produce high levels of IL-10-dependent interferon (IFN)-β, which induces toll-like receptor (TLR) 3 expression in MSCs. Moreover, induction of indoleamine 2,3-dioxygenase (IDO) by TLR3 involved an autocrine IFN-β that was dependent on STAT1 signaling. Furthermore, we observed that production of IFN-β and IL-10 in Tr1 cells synergistically induces IDO in MSCs through the STAT1 pathway. These findings suggest co-administration of MSCs and Tr1 cells to be a novel therapeutic modality for clinical autoimmune diseases.

Glucan particles loaded with a NIRF agent for imaging monocytes/macrophages recruitment in a mouse model of rheumatoid arthritis

We report here thein vivorecruitment of immune cells in inflamed sites on a mouse model of rheumatoid arthritis (CIA) by NIRF imaging of fluorescent glucan microspheres (GPs).

Deletion of IFT20 in early stage T lymphocyte differentiation inhibits the development of collagen-induced arthritis

IFT20 is the smallest member of the intraflagellar transport protein (IFT) complex B. It is involved in cilia formation. Studies of IFT20 have been confined to ciliated cells. Recently, IFT20 was found to be also expressed in non-ciliated T cells and have functions in immune synapse formation and signaling in vitro. However, how IFT20 regulates T-cell development and activation in vivo is still unknown. We deleted the IFT20 gene in early and later stages of T-cell development by crossing IFT20(flox/flox) (IFT20(f/f) ) mice with Lck-Cre and CD4-Cre transgenic mice, and investigated the role of IFT20 in T-cell maturation and in the development of T cell-mediated collagen-induced arthritis (CIA). We found that both Lck-Cre/IFT20(f/f) and CD4-Cre/IFT20(f/f) mice were indistinguishable from their wild-type littermates in body size, as well as in the morphology and weight of the spleen and thymus. However, the number of CD4- and CD8-positive cells was significantly lower in thymus and spleen in Lck-Cre/IFT20(f/f) mice. Meanwhile, the incidence and severity of CIA symptoms were significantly decreased, and inflammation in the paw was significantly inhibited in Lck-Cre/IFT20(f/f) mice compared to Lck-Cre/IFT20(+/+) littermates. Deletion IFT20 in more mature T cells of CD4-Cre/IFT20(f/f) mice had only mild effects on the development of T cells and CIA. The expression of IL-1β, IL-6 and TGF-β1 were significantly downregulated in the paw of Lck-Cre/IFT20(f/f) mice, but just slight decreased in CD4-Cre/IFT20(f/f) mice. These results demonstrate that deletion of IFT20 in the early stage of T-cell development inhibited CIA development through regulating T-cell development and the expression of critical cytokines.

Transforming growth factor (TGF)-β signalling is increased in rheumatoid synovium but TGF-β blockade does not modify experimental arthritis

The aim of this study was to analyse the distribution of regulatory and inhibitory mothers against decapentaplegic homologue (Smad) proteins as markers of active transforming growth factor (TGF)-β signalling in rheumatoid arthritis (RA) synovial tissue and to investigate the effect of TGF-β blockade in the development and progression of collagen-induced arthritis. The expression of Smad proteins in synovial tissues from RA, osteoarthritic and healthy controls was analysed by immunohistochemistry. Arthritis was induced in DBA/1 mice by immunization with chicken type-II collagen (CII). TGF-β was blocked in vivo with the specific peptide p17 starting at the time of immunization or on the day of arthritis onset. T cell population frequencies and specific responses to CII were analysed. The expression of cytokines and transcription factors was quantified in spleen and joint samples. Statistical differences between groups were compared using the Mann-Whitney U-test or one-way analysis of variance (anova) using the Kruskal-Wallis test. p-Smad-2/3 and inhibitory Smad-7 expression were detected in RA and control tissues. In RA, most lymphoid infiltrating cells showed nuclear p-Smad-2/3 without Smad-7 expression. Treatment with TGF-β antagonist did not affect clinical severity, joint inflammation and cartilage damage in collagen-induced arthritis. Frequency of T cell subsets, mRNA levels of cytokines and transcription factors, specific proliferation to CII, serum interleukin (IL)-6 and anti-CII antibodies were comparable in p17 and phosphate-buffered saline (PBS)-treated groups. The pattern of Smad proteins expression demonstrates active TGF-β signalling in RA synovium. However, specific TGF-β blockade does not have a significant effect in the mice model of collagen-induced arthritis.

What Have We Learned about the Pathogenesis of Rheumatoid Arthritis from TNF-Targeted Therapy?

Studies of cytokine regulation in rheumatoid arthritis led to the development of TNFα inhibitors which are now used for a number of indications, including rheumatoid arthritis, inflammatory bowel disease, psoriasis, psoriatic arthritis, and ankylosing spondylitis. The widespread use of biologics in the clinic offers unique opportunities for probing disease pathogenesis and this paper provides an overview of rheumatoid arthritis, with a particular emphasis on the impact of anti-TNFα therapy on pathogenetic mechanisms. An overview is also provided on the most commonly used animal models that mimic RA, including adjuvant-induced arthritis, collagen-induced arthritis, TNFα-transgenic mice, and the K/BxN and SKG models. These models have led to significant discoveries relating to the importance of pro-inflammatory cytokines in the pathogenesis of rheumatoid arthritis, resulting from disregulation of the normally finely tuned balance of pro- and anti-inflammatory cytokine signalling. In addition, experimental evidence is discussed suggesting how genetic and environmental factors can contribute to disease susceptibility. The role of effector and regulatory T cells is discussed in the light of the relatively disappointing therapeutic effects of T cell modifying agents such as anti-CD4 antibody and cyclosporin. It is concluded that comprehensive analyses of mechanisms of action of biologics and other drugs entering the clinic will be essential to optimise therapy, with the ultimate aim of providing a cure.

Antiarthritis effect of a novel Bruton's tyrosine kinase (BTK) inhibitor in rat collagen-induced arthritis and mechanism-based pharmacokinetic/pharmacodynamic modeling: relationships between inhibition of BTK phosphorylation and efficacy

Bruton's tyrosine kinase (BTK) plays a critical role in the development, differentiation, and proliferation of B-lineage cells, making it an attractive target for the treatment of rheumatoid arthritis. The objective of this study was to evaluate the antiarthritis effect of GDC-0834 [R-N-(3-(6-(4-(1,4-dimethyl-3-oxopiperazin-2-yl)phenylamino)-4-methyl-5-oxo-4,5-dihydropyrazin-2-yl)-2-methylphenyl)-4,5,6,7-tetrahydrobenzo[b]thiophene-2-carboxamide], a potent and selective BTK inhibitor, and characterize the relationship between inhibition of BTK phosphorylation (pBTK) and efficacy. GDC-0834 inhibited BTK with an in vitro IC(50) of 5.9 and 6.4 nM in biochemical and cellular assays, respectively, and in vivo IC(50) of 1.1 and 5.6 μM in mouse and rat, respectively. Administration of GDC-0834 (30-100 mg/kg) in a rat collagen-induced arthritis (CIA) model resulted in a dose-dependent decrease of ankle swelling and reduction of morphologic pathology. An integrated disease progression pharmacokinetic/pharmacodynamic model where efficacy is driven by pBTK inhibition was fit to ankle-diameter time-course data. This model incorporated a transit model to characterize nondrug-related decreases in ankle swelling occurring at later stages of disease progression in CIA rats. The time course of ankle swelling in vehicle animals was described well by the base model. Simultaneous fitting of data from vehicle- and GDC-0834-treated groups showed that overall 73% inhibition of pBTK was needed to decrease the rate constant describing the ankle swelling increase (k(in)) by half. These findings suggest a high degree of pBTK inhibition is required for maximal activity of the pathway on inflammatory arthritis in rats.

IL-6-dependent PGE2 secretion by mesenchymal stem cells inhibits local inflammation in experimental arthritis

Background

Based on their capacity to suppress immune responses, multipotent mesenchymal stromal cells (MSC) are intensively studied for various clinical applications. Although it has been shown in vitro that the immunomodulatory effect of MSCs mainly occurs through the secretion of soluble mediators, the mechanism is still not completely understood. The aim of the present study was to better understand the mechanisms underlying the suppressive effect of MSCs in vivo, using cells isolated from mice deficient in the production of inducible nitric oxide synthase (iNOS) or interleukin (IL)-6 in the murine model of collagen-induced arthritis.

Principal Findings

In the present study, we show that primary murine MSCs from various strains of mice or isolated from mice deficient for iNOS or IL-6 exhibit different immunosuppressive potential. The immunomodulatory function of MSCs was mainly attributed to IL-6-dependent secretion of prostaglandin E2 (PGE2) with a minor role for NO. To address the role of these molecules in vivo, we used the collagen-induced arthritis as an experimental model of immune-mediated disorder. MSCs effectively inhibited collagen-induced inflammation during a narrow therapeutic window. In contrast to wild type MSCs, IL-6-deficient MSCs and to a lesser extent iNOS-deficient MSCs were not able to reduce the clinical signs of arthritis. Finally, we show that, independently of NO or IL-6 secretion or Treg cell induction, MSCs modulate the host response by inducing a switch to a Th2 immune response.

Significance

Our data indicate that MSCs mediate their immunosuppressive effect via two modes of action: locally, they reduce inflammation through the secretion of anti-proliferative mediators, such as NO and mainly PGE2, and systemically they switch the host response from a Th1/Th17 towards a Th2 immune profile.

Schistosoma mansoni infection reduces severity of collagen-induced arthritis via down-regulation of pro-inflammatory mediators

Various experimental and epidemiological studies have demonstrated that helminth infections affect outcomes of allergic or autoimmune disorders. Here, we examined the effects of Schistosoma mansoni infection on mouse collagen-induced arthritis, one of the most widely used animal models for rheumatoid arthritis. Male DBA/1 mice were infected with S. mansoni 2 weeks prior to being immunized with type II collagen (IIC). Cytokine mRNA expression in mouse paws, cytokine production by ConA-stimulated spleen cells, and anti-IIC antibodies were evaluated in addition to the severity of arthritis. S. mansoni infection significantly reduced the severity of arthritis. Anti-IIC IgG and IgG2a levels were lower in infected than uninfected mice. With regard to cytokine producing potentials in the infected mice, the down-regulation of Th1 (IFNgamma) and pro-inflammatory cytokines (TNFalpha and IL-17A), and up-regulation of Th2 (IL-4) and an anti-inflammatory cytokine (IL-10) were observed.In addition, real-time PCR revealed that the augmentation of pro-inflammatory mediators such as IL-1 beta, IL-6 and receptor activator of NFkappaB ligand in inflamed paws was abrogated by S. mansoni infection [corrected]. In conclusion, schistosome infection reduced the severity of autoimmune arthritis via systemic and local suppression of pro-inflammatory mediators, suggesting the potential of parasite-derived materials as therapeutic agents against rheumatoid arthritis.