Rodent Models Of Rheumatoid Arthritis Research Articles

ALOX5 drives the pyroptosis of CD4+ T cells and tissue inflammation in rheumatoid arthritis.

Pyroptosis, an inflammatory form of programmed cell death, is linked to the pathology of rheumatoid arthritis (RA). Here, we investigated the molecular mechanism underlying pyroptosis in T cells isolated from patients with RA. Compared with healthy individuals, patients with RA had more pyroptotic CD4+ T cells in blood and synovia, which correlated with clinical measures of disease activity. Moreover, the mRNA expression and protein abundance of arachidonate 5-lipoxygenase (ALOX5), which converts arachidonic acid to leukotriene A4 (LTA4), were increased in CD4+ T cells from patients with RA and, among patients with RA, were lowest in those in clinical remission. Knockdown or pharmacological inhibition of ALOX5 suppressed CD4+ T cell pyroptosis and improved symptoms in two rodent models of RA. Mechanistically, the increase in ALOX5 activity in RA CD4+ T cells enhanced the production of the LTA4 derivative LTB4, which stimulated Ca2+ influx through ORAI3 channels, leading to the activation of NLRP3 inflammasomes and pyroptosis. Our findings reveal a role for ALOX5 in RA and provide a molecular basis for further exploring the clinical utility of ALOX5 inhibition in RA and for using ALOX5 as a biomarker to distinguish active disease and remission in RA.

Evaluation of anti-inflammatory and immunomodulatory potential of Lawsone (2-hydroxy-1,4-naphthoquinone) using pre-clinical rodent model of rheumatoid arthritis.

Background: Lawsone (2-hydroxy-1,4-naphthoquinone) is naturally present in Lawsonia Inermis and flowers of Eicchornia crassipes. This study assessed the anti-arthritic potential of Lawsone, using FCA-induced Sprague-Dawley rats. Methods: Arthritic progress was analyzed through a macroscopic scoring scale, measurement of paw edema, and histopathological changes. Effects of Lawsone on mRNA expression levels of inflammatory markers were examined using the reverse transcription PCR technique. ELISA technique was used to evaluate the PGE2 levels. Moreover, levels of biochemical and hematological parameters were also analyzed. Results: The research elucidated that Lawsone showed an inhibitory potential towards arthritic progress and ameliorated the paw edema. The histopathological analysis also validated the inhibition in arthritic development. Treatment with Lawosne reduced the expression levels of inflammatory markers in rats i.e., VEGF, TNF-α, MMP-2, MMP-3, NF-κB, IL-1β, and IL-6. PGE2 levels (all p < 0.001) were also found reduced in treatment groups. Lab investigations showed improved results of hematological and hepatic parameters in the treated groups as compared to the positive control. This study found no hepatotoxic or nephrotoxic effects of Lawsone in the test doses. Conclusion: Lawsone possesses an anti-arthritic property which could be ascribed to its immunomodulatory and anti-inflammatory effects.

M-134, a novel HDAC6-selective inhibitor, markedly improved arthritic severity in a rodent model of rheumatoid arthritis when combined with tofacitinib.

Although tofacitinib has shown highly significant efficacy for rheumatoid arthritis (RA), there are still a considerable number of patients that are non-responders owing to its limited effectiveness and various adverse effects. Thus, alternative options with better efficacy and lower toxicity are desired. Here, M-134, a recently developed HDAC6 inhibitor, was examined for its therapeutic potential when combined with tofacitinib in a rat model of RA. The single or combined administration of M-134 and tofacitinib was examined in complete Freund's adjuvant-induced arthritis (AIA) or collagen-induced arthritis (CIA) rodent models. To evaluate the therapeutic and adverse effects, the following factors were observed: macroscopic or microscopic scoring of all four paws; the expression of ICAM-1, VCAM-1, and IP-10 in the joints and that of various cytokines and chemokines in the plasma; the weight of the thymus and the liver; and changes in hematological enzymes. Combination treatment showed strong synergistic effects as measured by the clinical score and histological changes, without adverse effects such as weight loss in the thymus and increased liver enzymes (ALT and AST). Additionally, it also reduced ICAM-1, VCAM-1, and IP-10 expression in the joints, and M-134 increased the efficacy of tofacitinib by regulating various cytokines, such as interleukin (IL)-1β, IL-17, and TNF-α, in the serum of AIA rats. Differences in the cytokine expression for each drug were found in the CIA model. M-134 and tofacitinib combination therapy is a potential option for the treatment of RA through the regulation of cytokines, chemokines, and adhesion molecules.

TRPA1 Ion Channel Determines Beneficial and Detrimental Effects of GYY4137 in Murine Serum-Transfer Arthritis.

Modulation of nociception and inflammation by sulfide in rheumatoid arthritis and activation of transient receptor potential ankyrin 1 (TRPA1) ion channels by sulfide compounds are well documented. The present study aims to investigate TRPA1-mediated effects of sulfide donor GYY4137 in K/BxN serum-transfer arthritis, a rodent model of rheumatoid arthritis. TRPA1 and somatostatin sst4 receptor wild-type (WT) and knockout mice underwent K/BxN serum transfer and were treated daily with GYY4137. Functional and biochemical signs of inflammation were recorded, together with histological characterization. These included detection of hind paw mechanical hyperalgesia by dynamic plantar esthesiometry, hind paw volume by plethysmometry, and upside-down hanging time to failure. Hind paw erythema, edema, and passive movement range of tibiotarsal joints were scored. Somatostatin release from sensory nerve endings of TRPA1 wild-type and knockout mice in response to polysulfide was detected by radioimmunoassay. Polysulfide formation from GYY4137 was uncovered by cold cyanolysis. GYY4137 aggravated mechanical hyperalgesia in TRPA1 knockout mice but ameliorated it in wild-type ones. Arthritis score was lowered by GYY4137 in TRPA1 wild-type animals. Increased myeloperoxidase activity, plasma extravasation, and subcutaneous MIP-2 levels of hind paws were detected in TRPA1 knockout mice upon GYY4137 treatment. Genetic lack of sst4 receptors did not alter mechanical hyperalgesia, edema formation, hanging performance, arthritis score, plasma extravasation, or myeloperoxidase activity. TRPA1 WT animals exhibited smaller cartilage destruction upon GYY4137 administration. Sodium polysulfide caused TRPA1-dependent somatostatin release from murine nerve endings. Sulfide released from GYY4137 is readily converted into polysulfide by hypochlorite. Polysulfide potently activates human TRPA1 receptors expressed in Chinese hamster ovary (CHO) cells. According to our data, the protective effect of GYY4137 is mediated by TRPA1, while detrimental actions are independent of the ion channel in the K/BxN serum-transfer arthritis model in mice. At acidic pH in inflamed tissue sulfide is released from GYY4137 and reacts with neutrophil-derived hypochlorite. Resulting polysulfide might be responsible for TRPA1-mediated antinociceptive and anti-inflammatory as well as TRPA1-independent pro-inflammatory effects.

Cholinergic system is involved in the therapeutic effect of madecassoside on collagen-induced arthritis in rats

Our previous studies demonstrated that oral administration of madecassoside could markedly attenuate collagen-induced arthritis in rats, a rodent model of rheumatoid arthritis. As the autonomic nervous system is critically involved in the modulation of peripheral inflammation and immune response, the present study aims to explore the possible involvement of adrenergic and cholinergic nerves in the effect of madecassoside on rheumatoid arthritis. Arthritis was induced by chicken collagen in rats, and madecassoside was orally administered daily for two weeks from day 14 after the primary immunization. The antagonists of adrenoceptor and cholinergic receptors were co-administered with madecassoside, respectively. Unilateral cervical vagotomy was performed four days before the arthritis induction. The results showed that madecassoside (30 mg/kg) treatment markedly ameliorated arthritis symptoms in rats, mainly evidenced by the reduction of paw swelling and arthritis index scores. Co-administration of madecassoside with atropine (an antagonist of the muscarinic acetylcholine receptor) or hexamethonium (an antagonist of the nicotinic acetylcholine receptor) markedly diminished the therapeutic effects of madecassoside in arthritis. However, co-administration with phentolamine (an antagonist of the α-adrenoceptor) or propranolol (an antagonist of the β-adrenoceptor) did not alter the effect of madecassoside on arthritis. Furthermore, unilateral cervical vagotomy significantly reduced the anti-arthritis efficacy of madecassoside, including the amelioration of clinical symptoms, as well as the inhibition of the production of pro-inflammatory cytokines except T lymphocytes-related cytokines. These findings suggest that madecassoside exerts inhibitory effects on collagen-induced arthritis through, at least partially, the peripheral cholinergic system.

Humanized Mouse Models of Rheumatoid Arthritis for Studies on Immunopathogenesis and Preclinical Testing of Cell-Based Therapies.

Rodent models of rheumatoid arthritis (RA) have been used over decades to study the immunopathogenesis of the disease and to explore intervention strategies. Nevertheless, mouse models of RA reach their limit when it comes to testing of new therapeutic approaches such as cell-based therapies. Differences between the human and the murine immune system make it difficult to draw reliable conclusions about the success of immunotherapies. To overcome this issue, humanized mouse models have been established that mimic components of the human immune system in mice. Two main strategies have been pursued for humanization: the introduction of human transgenes such as human leukocyte antigen molecules or specific T cell receptors, and the generation of mouse/human chimera by transferring human cells or tissues into immunodeficient mice. Recently, both approaches have been combined to achieve more sophisticated humanized models of autoimmune diseases. This review discusses limitations of conventional mouse models of RA-like disease and provides a closer look into studies in humanized mice exploring their usefulness and necessity as preclinical models for testing of cell-based therapies in autoimmune diseases such as RA.

RTA 1701 is an oral RORγt inhibitor that suppresses the IL-17A response in non-human primates

Abstract RTA 1701 is an orally-bioavailable, selective RORγt inhibitor. RORγt orchestrates the differentiation of Th17 cells and contributes to autoimmune disease pathogenesis. Inhibition of RORγt suppresses Th17 cells and the associated secretion of the effector pro-inflammatory cytokine IL-17A. As such, RTA 1701 is highly efficacious in rodent models of rheumatoid arthritis and multiple sclerosis. This study was conducted to evaluate the pharmacokinetics of RTA 1701 and its effects on ex vivo stimulation of IL-17A production in whole blood after oral administration to naïve healthy cynomolgus monkeys. Monkeys received a single administration of RTA 1701 (0.3, 3, 30, or 300 mg/kg). After a one-week washout, monkeys received the same doses of RTA 1701 once daily for 14 consecutive days. Blood was collected after a single dose and after 14 days of dosing for analysis of plasma RTA 1701 concentrations through 72 hours post-dose and for evaluation of RTA 1701 effects on ex vivo stimulation of IL-17A at 24, 30, and 72 hours post-dose. RTA 1701 exhibited oral bioavailability in monkeys with dose-dependent increases in exposure over the wide range of doses evaluated. Further, oral administration produced systemic exposure to RTA 1701 at sufficient levels to produce significant and dose-dependent suppression of ex vivo stimulation of IL-17A secretion in whole blood at 24 and 30 hours after single and repeat dosing, with IL-17A levels returning to baseline within 72 hours after a single dose. Collectively, these data demonstrate that RTA 1701 is orally bioavailable in non-human primates and significantly suppresses the IL-17A response. These data also support the future clinical development of RTA 1701 for the potential treatment of autoimmune diseases.

Sympathetic Nerve Hyperactivity in the Spleen: Causal for Nonpathogenic-Driven Chronic Immune-Mediated Inflammatory Diseases (IMIDs)?

Immune-Mediated Inflammatory Diseases (IMIDs) is a descriptive term coined for an eclectic group of diseases or conditions that share common inflammatory pathways, and for which there is no definitive etiology. IMIDs affect the elderly most severely, with many older individuals having two or more IMIDs. These diseases include, but are not limited to, type-1 diabetes, obesity, hypertension, chronic pulmonary disease, coronary heart disease, inflammatory bowel disease, and autoimmunity, such as rheumatoid arthritis (RA), Sjőgren’s syndrome, systemic lupus erythematosus, psoriasis, psoriatic arthritis, and multiple sclerosis. These diseases are ostensibly unrelated mechanistically, but increase in frequency with age and share chronic systemic inflammation, implicating major roles for the spleen. Chronic systemic and regional inflammation underlies the disease manifestations of IMIDs. Regional inflammation and immune dysfunction promotes targeted end organ tissue damage, whereas systemic inflammation increases morbidity and mortality by affecting multiple organ systems. Chronic inflammation and skewed dysregulated cell-mediated immune responses drive many of these age-related medical disorders. IMIDs are commonly autoimmune-mediated or suspected to be autoimmune diseases. Another shared feature is dysregulation of the autonomic nervous system and hypothalamic pituitary adrenal (HPA) axis. Here, we focus on dysautonomia. In many IMIDs, dysautonomia manifests as an imbalance in activity/reactivity of the sympathetic and parasympathetic divisions of the autonomic nervous system (ANS). These major autonomic pathways are essential for allostasis of the immune system, and regulating inflammatory processes and innate and adaptive immunity. Pathology in ANS is a hallmark and causal feature of all IMIDs. Chronic systemic inflammation comorbid with stress pathway dysregulation implicate neural-immune cross-talk in the etiology and pathophysiology of IMIDs. Using a rodent model of inflammatory arthritis as an IMID model, we report disease-specific maladaptive changes in β2-adrenergic receptor (AR) signaling from protein kinase A (PKA) to mitogen activated protein kinase (MAPK) pathways in the spleen. Beta2-AR signal “shutdown” in the spleen and switching from PKA to G-coupled protein receptor kinase (GRK) pathways in lymph node cells drives inflammation and disease advancement. Based on these findings and the existing literature in other IMIDs, we present and discuss relevant literature that support the hypothesis that unresolvable immune stimulation from chronic inflammation leads to a maladaptive disease-inducing and perpetuating sympathetic response in an attempt to maintain allostasis. Since the role of sympathetic dysfunction in IMIDs is best studied in RA and rodent models of RA, this IMID is the primary one used to evaluate data relevant to our hypothesis. Here, we review the relevant literature and discuss sympathetic dysfunction as a significant contributor to the pathophysiology of IMIDs, and then discuss a novel target for treatment. Based on our findings in inflammatory arthritis and our understanding of common inflammatory process that are used by the immune system across all IMIDs, novel strategies to restore SNS homeostasis are expected to provide safe, cost-effective approaches to treat IMIDs, lower comorbidities, and increase longevity.

Suppression and resolution of autoimmune arthritis by rhesus θ-defensin-1, an immunomodulatory macrocyclic peptide.

θ-defensins constitute a family of macrocyclic peptides expressed exclusively in Old World monkeys. The peptides are pleiotropic effectors of innate immunity, possessing broad spectrum antimicrobial activities and immunoregulatory properties. Here we report that rhesus θ-defensin 1 (RTD-1) is highly effective in arresting and reversing joint disease in a rodent model of rheumatoid arthritis (RA). Parenteral RTD-1 treatment of DA/OlaHsd rats with established pristane-induced arthritis (PIA) rapidly suppressed joint disease progression, restored limb mobility, and preserved normal joint architecture. RTD-1 significantly reduced joint IL-1β levels compared with controls. RTD-1 dose-dependently inhibited fibroblast-like synoviocyte (FLS) invasiveness and FLS IL-6 production. Consistent with the inhibition of FLS invasiveness, RTD-1 was a potent inhibitor of arthritogenic proteases including ADAMs 17 and 10 which activate TNFα, and inhibited matrix metalloproteases, and cathepsin K. RTD-1 was non-toxic, non-immunogenic, and effective when administered as infrequently as once every five days. Thus θ-defensins, which are absent in humans, have potential as retroevolutionary biologics for the treatment of RA.

Discovery of Orally Efficacious Phosphoinositide 3-Kinase δ Inhibitors with Improved Metabolic Stability.

Aberrant signaling of phosphoinositide 3-kinase δ (PI3Kδ) has been implicated in numerous pathologies including hematological malignancies and rheumatoid arthritis. Described in this manuscript are the discovery, optimization, and in vivo evaluation of a novel series of pyridine-containing PI3Kδ inhibitors. This work led to the discovery of 35, a highly selective inhibitor of PI3Kδ which displays an excellent pharmacokinetic profile and is efficacious in a rodent model of rheumatoid arthritis.

Enigma of IL-17 and Th17 Cells in Rheumatoid Arthritis and in Autoimmune Animal Models of Arthritis.

Rheumatoid arthritis (RA) is one of the most common autoimmune disorders characterized by the chronic and progressive inflammation of various organs, most notably the synovia of joints leading to joint destruction, a shorter life expectancy, and reduced quality of life. Although we have substantial information about the pathophysiology of the disease with various groups of immune cells and soluble mediators identified to participate in the pathogenesis, several aspects of the altered immune functions and regulation in RA remain controversial. Animal models are especially useful in such scenarios. Recently research focused on IL-17 and IL-17 producing cells in various inflammatory diseases such as in RA and in different rodent models of RA. These studies provided occasionally contradictory results with IL-17 being more prominent in some of the models than in others; the findings of such experimental setups were sometimes inconclusive compared to the human data. The aim of this review is to summarize briefly the recent advancements on the role of IL-17, particularly in the different rodent models of RA.

Investigative Drugs for Rheumatoid Arthritis: Novel Targets

The last 15 years has seen a revolution in the development of a drug therapy armamentarium for treating patients with rheumatoid arthritis (RA) [1]. Prior to that general practitioners and rheumatologists were relatively limited in the number of agents which had shown clinical efficacy in the treatment of RA patients. Besides the use of gold in some RA patients, non-steroidal anti-inflammatory drugs (NSAIDs) [2], corticosteroids [2] anti-malarial drugs [3], sulfasalazine [4], methotrexate [4], the latter employed as either a monotherapy or in combinations with salfasalzine and/or hydroxychloroquine [4], and leflunomide [5] were among the most commonly employed disease-modifying anti-rheumatic drugs (DMARDs) for the treatment of RA. However, research and development created a new class of biologic drugs which are now commonly prescribed for the medical therapy of RA, including those that have shown robust clinical efficacy through the blockade of several forms of interleukin and/or tumor necrosis factor-α. These developments arose after many years of basic research; first using in vitro pre-clinical model cell culture systems, the results of which were then extended for evaluation of these biologic drugs in well-validated rodent models of RA [6]. Most recently, the development of the selective small molecule inhibitors (SMIs) of Janus Kinase-3, exemplified by tofacitinib, have also significantly advanced the choices that rheumatologists have for RA therapy [7]. In fact, this novel discovery is likely to provide the impetus for further basic research into the nature of signal transduction pathways [8] which drive RA pathogenesis and progression in response to the abnormally elevated levels of pro-inflammatory cytokines, chemokines, adhesion molecules [9], and growth factors [10], all of which have been implicated as playing prominent roles in RA pathology.

Protective effects of hydroxytyrosol-supplemented refined olive oil in animal models of acute inflammation and rheumatoid arthritis

Virgin olive oil is the primary source of fat in the Mediterranean diet, and its beneficial health effects have been related with oleic acid and phenolic compounds content.Hydroxytyrosol, a typical virgin olive oil phenolic compound, has beneficial antioxidant and anti-inflammatory properties as previously reported. The aim of this study was to evaluate the effect of hydroxytyrosol-supplemented refined olive oil at 0.5 and 5 mg/kg in a rodent model of rheumatoid arthritis. Rheumatoid arthritis was induced by intradermic administration, in male Wistar rats, of Freund’s adjuvant with collagen type II on days 1 and 21. Hydroxytyrosol-supplemented refined olive oils were administrated by gavage from day 23 until day 35. The treatment at 5-mg/kg dose significantly decreased paw edema (P<.01), histological damage, cyclooxygenase-2 and inducible nitric oxide synthase expression, and markedly reduced the degree of bone resorption, soft tissue swelling and osteophyte formation, improving articular function in treated animals. Acute inflammation, induced by carrageenan, was also evaluated for hydroxytyrosol-supplemented refined olive oils at 0.5 and 5 mg/kg. Both doses significantly reduced paw edema (P<.001). Our results suggest that the supplementation of refined olive oil with hydroxytyrosol may be advantageous in rheumatoid arthritis with significant impact not only on chronic inflammation but also on acute inflammatory processes.

Intra-articular administration of an antibody against CSF-1 receptor reduces pain-related behaviors and inflammation in CFA-induced knee arthritis

Several studies have shown that blockade of colony stimulating factor-1 (CSF-1) or its receptor (CSF-1R) inhibits disease progression in rodent models of rheumatoid arthritis (RA); however, the role of the CSF-1/CSF-1R pathway in RA-induced pain and functional deficits has not been studied. Thus, we examined the effect of chronic intra-articular administration of a monoclonal anti-CSF-1R antibody (AFS98) on spontaneous pain, knee edema and functional disabilities in mice with arthritis. Unilateral arthritis was produced by multiple injections of complete Freund's adjuvant (CFA) into the right knee joint of adult male ICR mice. CFA-injected mice were then treated twice weekly from day 10 until day 25 with anti-CSF-1R antibody (3 and 10μg/5μL per joint), isotype control (rat IgG 10μg/5μL per joint) or PBS (5μl/joint). Knee edema, spontaneous flinching, vertical rearing and horizontal exploratory activity were assessed at different days. Additionally, counts of peripheral leukocytes and body weight were measured to evaluate general health status. Intra-articular treatment with anti-CSF-1R antibody significantly increased horizontal exploratory activity and vertical rearing as well as reduced spontaneous flinching behavior and knee edema as compared to CFA-induced arthritis mice treated with PBS. Treatment with this antibody neither significantly affect mouse body weight nor the number of peripheral leukocytes. These results suggest that blockade of CSF-1R at the initial injury site (joint) could represent a therapeutic alternative for improving the functional disabilities and attenuating pain and inflammation in patients with RA.

Targeting α- and β-Adrenergic Receptors Differentially Shifts Th1, Th2, and Inflammatory Cytokine Profiles in Immune Organs to Attenuate Adjuvant Arthritis.

The sympathetic nervous system (SNS) regulates host defense responses and restores homeostasis. SNS-immune regulation is altered in rheumatoid arthritis (RA) and rodent models of RA, characterized by nerve remodeling in immune organs and defective adrenergic receptor (AR) signaling to immune cell targets. The SNS typically promotes or suppresses inflammation via α- and β2-AR activation, respectively, and indirectly drives humoral immunity by blocking Th1 cytokine secretion. Here, we investigate how β2-AR stimulation and/or α-AR blockade at disease onset affects disease pathology and cytokine profiles in relevant immune organs from male Lewis rats with adjuvant-induced arthritis (AA). Rats challenged to induce AA were treated with terbutaline (TERB), a β2-AR agonist (600 μg/kg/day) and/or phentolamine (PHEN), an α-AR antagonist (5.0 mg/kg/day) or vehicle from disease onset through severe disease. We report that in spleen, mesenteric (MLN) and draining lymph node (DLN) cells, TERB reduces proliferation, an effect independent of IL-2. TERB also fails to shift T helper (Th) cytokines from a Th1 to Th2 profile in spleen and MLN (no effect on IFN-γ) and DLN (greater IFN-γ) cells. In splenocytes, TERB, PHEN, and co-treatment (PT) promotes an anti-inflammatory profile (greater IL-10) and lowers TNF-α (PT only). In DLN cells, drug treatments do not affect inflammatory profiles, except PT, which raised IL-10. In MLN cells, TERB or PHEN lowers MLN cell secretion of TNF-α or IL-10, respectively. Collectively, our findings indicate disrupted β2-AR, but not α-AR signaling in AA. Aberrant β2-AR signaling consequently derails the sympathetic regulation of lymphocyte expansion, Th cell differentiation, and inflammation in the spleen, DLNs and MLs that is required for immune system homeostasis. Importantly, this study provides potential mechanisms through which reestablished balance between α- and β2-AR function in the immune system ameliorates inflammation and joint destruction in AA.

FRI0364 Hm71224, A Novel BTK Inhibitor Demonstrates Potent Activities in Rodent Models of Arthritis

BackgroundBTK is a member of the Tec family kinase of non-receptor protein tyrosine kinases1. BTK is mostly expressed in hematopoietic cells such as B cells, mast cells and macrophages2. BTK...

Methotrexate and a spleen tyrosine kinase inhibitor cooperate to inhibit responses to peripheral blood B cells in rheumatoid arthritis.

BackgroundSelective disruption of the spleen tyrosine kinase (Syk) represents a novel strategy to control B-cell functional responses by inhibition of B-cell antigen receptor (BCR) signaling. PRT062607 (P505-15) is a highly selective small molecule Syk inhibitor that potently suppresses B-cell function in human and rodent blood, and reduces inflammation in rodent models of rheumatoid arthritis (RA).AimsIn this study, we sought to determine the potency of Syk inhibition by PRT062607 in whole blood from RA patients, and elucidate covariates that affect the potency of immune-regulation by this compound.Materials and MethodsWhole blood was collected from 30 patients diagnosed with RA as part of a single-center outpatient study. Disease severity, serum protein markers of inflammation, and co-medications were related to each other, and to PRT062607 activity in ex vivo Syk-mediated immune function assays.ResultsWe report here that PRT062607 exhibited greater potency in suppressing BCR mediated B-cell functional responses in whole blood from RA patients who received stable methotrexate (MTX) therapy. We demonstrate that the B-cell functional response to BCR ligation is influenced by cytokines and JAK/STAT signaling.DiscussionMTX is a known cytokine modulating agent, and this mechanism may act in concert with PRT062607 to control B-cell function.ConclusionThese data have important implications for the co-administration of Syk inhibitors and MTX for the treatment of RA.

The Histone Deacetylase Inhibitors MS-275 and SAHA Suppress the p38 Mitogen-Activated Protein Kinase Signaling Pathway and Chemotaxis in Rheumatoid Arthritic Synovial Fibroblastic E11 Cells

MS-275 (entinostat) and SAHA (vorinostat), two histone deacetylase (HDAC) inhibitors currently in oncological trials, have displayed potent anti-rheumatic activities in rodent models of rheumatoid arthritis (RA). To further elucidate their anti-inflammatory mechanisms, the impact of MS-275 and SAHA on the p38 mitogen-activated protein kinase (MAPK) signaling pathway and chemotaxis was assessed in human rheumatoid arthritic synovial fibroblastic E11 cells. MS-275 and SAHA significantly suppressed the expression of p38α MAPK, but induced the expression of MAPK phosphatase-1 (MKP-1), an endogenous suppressor of p38α in E11 cells. At the same time, the association between p38α and MKP-1 was up-regulated and consequently, the activation (phosphorylation) of p38α was inhibited. Moreover, MS-275 and SAHA suppressed granulocyte chemotactic protein-2 (GCP-2), monocyte chemotactic protein-2 (MCP-2) and macrophage migration inhibitory factor (MIF) in E11 cells in a concentration-dependent manner. Subsequently, E11-driven migration of THP-1 and U937 monocytes was inhibited. In summary, suppression of the p38 MAPK signaling pathway and chemotaxis appear to be important anti-rheumatic mechanisms of action of these HDAC inhibitors.

Macrophage-fibroblast interplay: a target for neuropeptide-based treatment of fibrotic disease?

Background Fibrosis is defined as an excessive accumulation of extracellular matrix (ECM) components with an associated loss of normal tissue architecture and function. Fibrosis occurs in many different auto-inflammatory (auto-immune) diseases. Current therapies targeting fibrosis are limited and we are in great need for novel therapeutic regimens. In fibrosis, abnormal fibroblast proliferation and ECM production by fibroblasts is stimulated by factors released by different cell types, amongst which macrophages. Macrophages produce many pro-fibrotic factors, such as IL-6, CCL2, PDGF and TGF-beta. In rodent models of rheumatoid arthritis and inflammatory bowel disease, somatostatin analogues exerted strong anti-inflammatory effects, by inhibition of proinflammatory cytokine secretion. Somatostatin analogues bind to somatostatin receptors (sst) and we demonstrated sst subtype 2 expression on human macrophages. In the present study we investigated the effects of somatostatin, octreotide, a clinically used somatostatin analogue, and cortistatin, an endogenously expressed somatostatin-like peptide, on macrophage-induced fibroblast proliferation.

JAK's SOCS: A Mechanism of Inhibition

SOCS1 and SOCS3 are specific inhibitors for JAK tyrosine kinases. In this issue of Immunity, Babon et al. (2012) discovered the inhibition mechanism of SOCS3 by employing nuclear magnetic resonance and classical enzyme kinetics.