A cytokine-centric view of the pathogenesis and treatment of autoimmune arthritis

The Anti-Inflammatory and Immunomodulatory Activities of Natural Products to Control Autoimmune Inflammation

Inflammation is an integral part of autoimmune diseases, which are caused by dysregulation of the immune system. This dysregulation involves an imbalance between pro-inflammatory versus anti-inflammatory mediators. These mediators include various cytokines and chemokines; defined subsets of T helper/T regulatory cells, M1/M2 macrophages, activating/tolerogenic dendritic cells, and antibody-producing/regulatory B cells. Despite the availability of many anti-inflammatory/immunomodulatory drugs, the severe adverse reactions associated with their long-term use and often their high costs are impediments in effectively controlling the disease process. Accordingly, suitable alternatives are being sought for these conventional drugs. Natural products offer promising adjuncts/alternatives in this regard. The availability of specific compounds isolated from dietary/medicinal plant extracts have permitted rigorous studies on their disease-modulating activities and the mechanisms involved therein. Here, we describe the basic characteristics, mechanisms of action, and preventive/therapeutic applications of 5 well-characterized natural product compounds (Resveratrol, Curcumin, Boswellic acids, Epigallocatechin-3-gallate, and Triptolide). These compounds have been tested extensively in animal models of autoimmunity as well as in limited clinical trials in patients having the corresponding diseases. We have focused our description on predominantly T cell-mediated diseases, such as rheumatoid arthritis, multiple sclerosis, Type 1 diabetes, ulcerative colitis, and psoriasis.

Traditional Tibetan medicine: therapeutic potential in rheumatoid arthritis

Rheumatoid arthritis (RA) is a severe inflammatory autoimmune disease characterized by the failed spontaneous resolution of inflammation. The induction of immune regulation and resolution of inflammatory pathways are effective in alleviating inflammation in RA. As the oldest medical system in the world, traditional Tibetan medicine (TTM) has a long history of preventing and treating RA. This review provides a comprehensive overview of medicinal plants with anti-RA activity in the TTM system, using classic books of Tibetan medicine, modern research literature, and drug standards. A total of 27 species have been found to be effective in treating RA, including Tinospora sinensis (Lour.) Merr., Terminalia chehula Retz., P. hookeri (C. B. Clarke) Hock.), and Aconitum pendulum Busch. Alkaloids, flavonoids, polyphenols, and terpenoids have turned out to be the major bioactive components for RA treatment. The inhibition of pro-inflammatory cytokine expression by mediating the NF-κB, MAPK, and JAK/STAT pathways is the core mechanism in RA treatment. In conclusion, this review provides key information and research perspectives for further research on the anti-RA effects of TTM.

Inflammatory Responses in Periodontitis with or Without Rheumatoid Arthritis Alter Salivary Metallothionein and Zinc

Periodontitis (PD) and rheumatoid arthritis (RA) are causally linked by their common inflammatory responses, yet it is largely unknown if these inflammatory responses might have an impact on salivary metallothionein (MT), zinc (Zn), and calcium (Ca) content. In this study, we analysed salivary concentrations of pro-inflammatory (IFN-γ, IL-6, and IL-17) and anti-inflammatory (IL-4 and IL-10) cytokines, as well as MT, Zn, and Ca in four groups of participants, namely control (without PD or RA, n = 21), PD (n = 21), RA (n = 21), or RAPD (n = 19). As expected, an increased amount of salivary pro-inflammatory cytokines were observed in the PD, RA, and RAPD groups. While Ca concentration was not significantly different between the groups, Zn concentration was lower in the PD, RA, and RAPD groups compared to the control group (p < 0.05). These groups also expressed higher MT/Zn ratios compared to the control group (p < 0.05). Unlike the control group, concentrations of inflammatory cytokines, MT, Zn, and Ca correlated with each other in the PD, RA, and RAPD groups (p < 0.05). Additionally, comorbidity of PD and RA appears to have a cumulative immuno-pathological impact that warrants further investigation. This study suggests that, in addition to inflammatory cytokines, salivary MT and Zn could reflect the severity of PD with or without RA, hence providing an important biomarker for diagnosis.

Manual acupuncture at ST36 attenuates rheumatoid arthritis by inhibiting M1 macrophage polarization and enhancing Treg cell populations in adjuvant-induced arthritic rats

OBJECTIVES

Acupuncture has been found to be effective at relieving many inflammatory pain conditions, including rheumatoid arthritis (RA). We aimed to assess the anti-inflammatory potential of manual acupuncture (MA) treatment of RA using adjuvant-induced arthritic (AIA) rats and to explore the underlying mechanisms.

METHODS

The anti-inflammatory and analgesic actions of MA at ST36 (Zusanli) in AIA rats were assessed using paw withdrawal latency and swelling, histological examination and cytokine detection by enzyme-linked immunoassay (ELISA). The cell-cell communication (CCC) network was analyzed with a multiplex immunoassay of 24 immune factors expressed in the inflamed joints, and the macrophage and Treg populations and associated cytokines regulated by MA were investigated using reverse-transcription quantitative polymerase chain reaction (RT-qPCR), ELISA and flow cytometry.

RESULTS

MA markedly decreased heat hyperalgesia and paw swelling in AIA rats. MA-treated rats also exhibited decreased levels of pro-inflammatory cytokines (tumor necrosis factor (TNF)-α, interleukin (IL)-1β) coupled with increased anti-inflammatory cytokines (IL-10, transforming growth factor (TGF)-β1) in the ankle joints at protein and mRNA levels. CCC network analysis confirmed that macrophages are of critical importance and are potential therapeutic targets in RA. Repeated treatment with MA triggered a macrophage phenotypic switch in the paws, with fewer M1 macrophages. Prominent increases in the Treg cell population and TGF-β1 in the popliteal lymph nodes demonstrated the immunomodulatory effects of MA. Furthermore, a selective TGF-β1-receptor inhibitor, SB431542, attenuated the anti-inflammatory effects of MA and MA-induced suppression of the levels of M1-released cytokines.

CONCLUSION

These findings provide novel evidence that the anti-inflammatory and analgesic effects of MA on RA act through phenotypic modulation involving the inhibition of M1 macrophage polarization and an increase in the Treg cell population, highlighting the potential therapeutic advantages of acupuncture in controlling pain and ameliorating inflammatory conditions.

Phytowaste as nutraceuticals in boosting public health

The utilization of bioactive constituent of peels and seeds provide an effective, environment friendly and inexpensive therapy for different forms of human disease, and the production, improvement and documentation of novel nutraceuticals. This review systematically presents findings and further understanding of the reported benefits and therapeutic applications of peel and seed extracts on innovative cell culture and animal studies, as well as phased clinical human trial research. The extracts of seed and peels were reported to possess high quantities of bioactive substances with antioxidative, antidiabetic, hepatorenal protective, antithyroidal, anti-inflammatory, antibacterial, cardiovascular protective, neuro-protective effects, anticancer and wound healing activities. Therapeutic activities of the bioactive substances of peel and seed extracts include elevation of Superoxide dismutase (SOD), GSH-Px, t-GPx, Catalase and GST activities, with the suppression of MDA levels, hydroperoxide generation and lipid peroxidized products, the extracts also regulate inflammatory mediators and cytokines as they are reported to suppress the secretion of inflammatory cytokines, which include; IL-1β, PGE2, TGF-β and TNF-α and induces apoptosis and cell differentiation. This review revealed the therapeutic importance and best utilization of peels and seed extracts of fruits and vegetables.

β-arrestin-2 alleviates rheumatoid arthritis injury by suppressing NLRP3 inflammasome activation and NF- κB pathway in macrophages

Rheumatoid arthritis (RA) is a chronic inflammatory joint disorder that inflicts damage to the joints of the hands and wrist. The aim of this study was to investigate the protective effect of β-Arrestin-2 (βArr2) on RA in vivo and in vitro. The βArr2 adenovirus (βArr2-Ad) or the control (Con-Ad) was injected into the ankle joint cavity of collagen-induced arthritis (CIA) mice. According to the results, an improvement was shown in the symptoms and pathological injury of RA after an upregulation of βArr2. Correspondingly, the inflammatory response was attenuated, as evidenced by the decreased serum pro-inflammatory cytokines levels and NF-κB pathway-related proteins. Nucleotide-binding domain leucine-rich repeat and pyrin domain containing receptor 3 (NLRP3) inflammasome activation was inhibited in CIA mice treated with βArr2-Ad injection, as reflected by the diminished IL-18 level and declined protein levels of inflammasome components in the ankle joint. Likewise, the anti-inflammatory effect of macrophages was also validated by in vitro experiments. In summary, βArr2 effectively ameliorates ankle inflammation in CIA mice via NF-κB/NLRP3 inflammasome, providing theoretical and clinical basis for RA therapy.

Microbiota-Derived Metabolites, Indole-3-aldehyde and Indole-3-acetic Acid, Differentially Modulate Innate Cytokines and Stromal Remodeling Processes Associated with Autoimmune Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation of the synovial joints. Inflammation, new blood vessel formation (angiogenesis) and bone resorption (osteoclastogenesis) are three key processes involved in the joint damage and deformities of arthritis. Various gut microbiota-derived metabolites are implicated in RA pathogenesis. However, there is barely any information about the impact of two such metabolites, indole-3-aldehyde (IAld) and indole-3-acetic acid (I3AA), on arthritis-related processes. We conducted a comparative analysis of IAld and I3AA using established cell-based models to understand how they might influence RA pathogenesis. Although structurally similar, the bioactivities of these two metabolites were profoundly different. IAld but not I3AA, inhibited the expression of pro-inflammatory cytokines (IL-1β and IL-6) in RAW 264.7 (RAW) cells stimulated with heat-killed M. tuberculosis sonicate (Mtb) and lipopolysaccharide (LPS). IAld also exhibited pro-angiogenic activity and pro-osteoclastogenic activity. In contrast, I3AA exhibited anti-angiogenic activity on endothelial cell tube formation but had no effect on osteoclastogenesis. Both IAld and I3AA have been proposed as aryl hydrocarbon receptor (AhR) agonists. Use of CH-223191, an inhibitor of the AhR, suppressed the anti-angiogenic activity of I3AA but failed to mitigate the effects of IAld. Further investigation of the anti-inflammatory activities of IAld and I3AA in LPS-treated RAW cells indicated that inhibition of MyD88-dependent activation of NF-κB and MAPK pathways was not likely involved. Our results suggest that the relative bioavailability of these indole derivatives may differentially impact RA progression and possibly other diseases that share similar cellular processes.

Tangeretin: a mechanistic review of its pharmacological and therapeutic effects

To date, a large number of synthetic drugs have been developed for the treatment and prevention of different disorders, such as neurodegenerative diseases, diabetes mellitus, and cancer. However, these drugs suffer from a variety of drawbacks including side effects and low efficacy. In response to this problem, researchers have focused on the plant-derived natural products due to their valuable biological activities and low side effects. Flavonoids consist of a wide range of naturally occurring compounds exclusively found in fruits and vegetables and demonstrate a number of pharmacological and therapeutic effects. Tangeretin (TGN) is a key member of flavonoids that is extensively found in citrus peels. It has different favorable biological activities such as antioxidant, anti-inflammatory, antitumor, hepatoprotective, and neuroprotective effects. In the present review, we discuss the various pharmacological and therapeutic effects of TGN and then, demonstrate how this naturally occurring compound affects signaling pathways to exert its impacts.

Associations of four common VDR polymorphisms with rheumatoid arthritis and systemic lupus erythematosus: evidence from a meta-analysis

Associations of polymorphisms in vitamin D receptor ( VDR) with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) have already been explored by many studies. The aim of this meta-analysis was to better clarify associations between polymorphisms in VDR and RA/SLE by combing the results of all relevant studies. Eligible studies were searched from Pubmed, Embase, WOS and CNKI. We used Review Manager to combine the results of eligible studies. Thirty-seven studies were included in this meta-analysis. VDR rs1544410 (recessive comparison: odds ratio (OR) = 1.36, 95% confidence interval (CI) 1.06–1.76; over-dominant comparison: OR = 0.81, 95% CI 0.71–0.93) and rs731236 (over-dominant comparison: OR = 0.77, 95% CI 0.63–0.94) polymorphisms were found to be significantly associated with RA in overall combined analyses. Besides, VDR rs1544410 (dominant comparison: OR = 0.61, 95% CI 0.46–0.82; over-dominant comparison: OR = 1.45, 95% CI 1.16–1.81; allele comparison: OR = 0.75, 95% CI 0.62–0.92), rs2228570 (dominant comparison: OR = 0.58, 95% CI 0.50–0.67; recessive comparison: OR = 1.57, 95% CI 1.21–2.03; allele comparison: OR = 0.69, 95% CI 0.60–0.80) and rs731236 (dominant comparison: OR = 0.69, 95% CI 0.50–0.96; allele comparison: OR = 0.80, 95% CI 0.70–0.90) polymorphisms were also found to be significantly associated with SLE in overall combined analyses. Subgroup analyses revealed that significant associations for VDR polymorphisms and RA/SLE were mainly driven by Asians. Collectively, this meta-analysis proved that VDR rs7975232, rs1544410, rs2228570 and rs731236 polymorphisms may confer susceptibility to RA and SLE, especially for Asians.

Inhibition of the IL-18 Receptor Signaling Pathway Ameliorates Disease in a Murine Model of Rheumatoid Arthritis

Interleukin (IL)-18 expression in synovial tissue correlates with the severity of joint inflammation and the levels of pro-inflammatory cytokines. However, the role of the IL-18/IL-18 receptor-alpha (Rα) signaling pathway in autoimmune arthritis is unknown. Wild-type (WT) and IL-18Rα knockout (KO) mice were immunized with bovine type II collagen before the onset of arthritis induced by lipopolysaccharide injection. Disease activity was evaluated by semiquantitative scoring and histologic assessment. Serum inflammatory cytokine and anticollagen antibody levels were quantified by an enzyme-linked immunosorbent assay. Joint cytokine and matrix metalloproteinases-3 levels were determined by a quantitative polymerase chain reaction. Splenic suppressors of cytokine signaling (SOCS) were determined by Western blot analysis as indices of systemic immunoresponse. IL-18Rα KO mice showed lower arthritis and histological scores in bone erosion and synovitis due to reductions in the infiltration of CD4+ T cells and F4/80+ cells and decreased serum IL-6, -18, TNF, and IFN-γ levels. The mRNA expression and protein levels of SOCS3 were significantly increased in the IL-18Rα KO mice. By an up-regulation of SOCS, pro-inflammatory cytokines were decreased through the IL-18/IL-18Rα signaling pathway. These results suggest that inhibitors of the IL-18/IL-18Rα signaling pathway could become new therapeutic agents for rheumatoid arthritis.

The role of Ca2+ in acid-sensing ion channel 1a-mediated chondrocyte pyroptosis in rat adjuvant arthritis

Rheumatoid arthritis is an autoimmune disease with a poor prognosis. Pyroptosis is a type of proinflammatory programmed cell death that is characterised by the activation of caspase-1 and secretion of the proinflammatory cytokines interleukin (IL)-1β/18. Previous reports have shown that pyroptosis is closely related to the development of some autoimmune diseases, such as rheumatoid arthritis. The decrease in the pH of joint fluid is a main pathogenic feature of RA and leads to excessive apoptosis in chondrocytes. Acid-sensitive ion channels (ASICs) are extracellular H⁺-activated cation channels that mainly influence Na⁺ and Ca²⁺ permeability. In this study, we investigated the role of Ca²⁺ in acid-sensing ion channel 1a-mediated chondrocyte pyroptosis in an adjuvant arthritis rat model. The expression of apoptosis-associated speck-like protein, NLRP3, caspase-1, ASIC 1a, IL-1β and IL-18 was upregulated in the joints of rats compared with that in normal rats, but the expression of Col2a in cartilage was decreased. However, these changes were reversed by amiloride, which is an inhibitor of ASIC1a. Extracellular acidosis significantly increased the expression of ASIC1a, IL-1β, IL-18, ASC, NLRP3 and caspase-1 and promoted the release of lactate dehydrogenase. Interestingly, Psalmotoxin-1 (Pctx-1) and BAPTA-AM inhibited these effects. These results indicate that ASIC1a mediates pyroptosis in chondrocytes from AA rats. The underlying mechanism may be associated with the ability of ASIC1a to promote [Ca²⁺]_i and upregulate the expression of the NLRP3 inflammasome.

Inhibitory effect of tanshinone IIA on inflammatory response in rheumatoid arthritis through regulating β-arrestin 2

The current study aimed to investigate the inhibitory effect of tanshinone IIA (Tan IIA) on the inflammatory response in patients with rheumatoid arthritis (RA) and explore its mechanism. A total of 50 patients with RA were randomly separated into the control group (15 cases) and the research group (35 cases). The tumor necrosis factor (TNF)-α and interleukin (IL)-6 levels in serum were determined, and peripheral blood mononuclear cells (PBMCs) were separated from patients with RA and cultured in vitro. The effects of the β-arrestin 2 small interfering (si)RNA incubation, lipopolysaccharide (LPS) stimulation or Tan IIA incubation on TNF-α and IL-6 levels, and the expression levels of β-arrestin 2, NAD-dependent protein deacetylase sirtuin-1 (SIRT1) and transcription factor p65 (p65) proteins were investigated. Prior to treatment, no significant differences in TNF-α and IL-6 levels in serum of patients with RA were identified between the research and control groups. Following treatment, the TNF-α and IL-6 levels in the serum of patients with RA in the research group were significantly lower compared with those in the research group prior to treatment and those in the control group following treatment (P<0.05). Tan IIA inhibited the LPS-induced secretion of TNF-α and IL-6, upregulated the LPS-inhibited expression of the β-arrestin 2 and SIRT1 proteins, and downregulated the LPS-induced expression of the p65 protein in the PBMCs of patients with RA. The β-arrestin 2 small interfering (si)RNA significantly upregulated the secretion of TNF-α and IL-6, inhibited the expression of the SIRT1 protein and upregulated the expression of the p65 protein in PBMCs of patients with RA. Tan II A effectively increased the weight of rats with rheumatoid arthritis, and reduced the circumference of the left posterior ankle, the posterior plantar metatarsal thickness, and the content of serum TNF-α and IL-6. Tan IIA did not significantly reverse these β-arrestin 2 siRNA-induced changes. Tan IIA inhibited the inflammatory response in PBMCs of patients with RA by upregulating β-arrestin 2 expression.

Anti-arthritic and anti-inflammatory effects of (-)-Epicatechin-3-O-β-d-allopyranoside, a constituent of Davallia formosana

BACKGROUND

(-)-Epicatechin-3-O-β-d-allopyranoside (ECAP) is isolated from the popular Chinese herbal medicine Davallia formosana, which has been used to treat bone diseases including bone fracture, arthritis, and osteoporosis.

PURPOSE

To investigate the antiarthritic and the anti-inflammatory effect of ECAP on a mouse model of collagen-induced arthritis (CIA) and in vitro.

METHODS

Male DBA/1 J mice were immunized by administering an intradermal injection of 100 µg of type II collagen in Freund's complete adjuvant. The control groups (vehicle) and ECAP were administered orally at doses of 1 ml/kg (H₂O), 50 and 100 mg/ml/kg once a day from Day 22 to Day 42 after primary immunization. Paw swelling, arthritis severity score, and histological changes were examined. Enzyme-linked immunosorbent assay was used to measure the levels of cytokines, including tumor necrosis factor alpha (TNF-α), interleukin (IL)-10, IL-17, IL-4, and interferon-γ (IFN-γ), in splenocytes. Furthermore, the anti-inflammatory activities of ECAP were investigated in vitro by measuring nitric oxide (NO) levels in lipopolysaccharide (LPS)-activated RAW264.7 macrophages.

RESULTS

In the CIA model, the oral administration of ECAP ameliorated paw edema and reduced the arthritis severity score and disease incidence. Histopathological examination demonstrated that ECAP treatment effectively protected the bone and cartilage of knee joints from erosion, lesion formation, and deformation compared with the vehicle treatment. ECAP also reduced IL-1β and MMP-9 expression in inflamed joints. Compared with the vehicle-treated mice with CIA, the reduced severity of the disease in ECAP-treated mice was associated with decreased levels of TNF-α and IL-17 and increased levels of IL-10 and IL-4 in the supernatants of splenocyte cultures. Flow cytometry analysis demonstrated that ECAP increased the population of CD4⁺CD25⁺ regulatory T cells, thereby inhibiting the B cell population. Anticollagen IgG1 and IgG2a levels decreased in the serum of ECAP-treated mice. ECAP suppressed LPS-induced NO production in RAW264.7 macrophages.

CONCLUSION

The administration of ECAP effectively suppressed inflammation and inflammatory pain and adjuvant-induced arthritis, indicating its therapeutic potential in the treatment of rheumatoid arthritis.

Peptide-directed liposomal delivery improves the therapeutic index of an immunomodulatory cytokine in controlling autoimmune arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation of the synovial tissue of the joints. Inadequately controlled disease may cause severe joint damage and deformity. Currently, the anti-arthritic drugs are given systemically, and therefore, they are widely distributed to other organs that are not the intended therapeutic targets. Accordingly, using a particular dose/regimen of a drug to achieve an effective local concentration of the drug in arthritic joints may lead to expected adverse effects involving other organs. Thus, improved methods of drug delivery are needed for arthritis therapy. One attractive approach is the targeting of a systemically administered drug to the inflamed joints. We describe here a prototypic drug delivery system using a novel peptide ligand denoted as ART-1. We previously reported ART-1 (=ADK) as a peptide that preferentially homes to the inflamed joints of arthritic rats and binds to synovial endothelial cells. We tested the ART-1-coated liposomes encapsulating a fluorescent compound for binding to activated endothelial cells in vitro and homing to arthritic joints in vivo, compared to control liposomes lacking the ART-1 coating. Similar liposomes but encapsulating an immunomodulatory cytokine interleukin-27 (ART-1-IL-27 liposomes) were tested for their anti-arthritic activity compared with control liposomes. ART-1-displaying liposomes showed better binding to endothelial cells as well as in vivo homing to arthritic joints compared to control liposomes. Furthermore, ART-1-IL-27 liposomes, when intravenously injected to arthritic rats after the onset of arthritis, were more effective in suppressing disease progression than control-IL-27 liposomes lacking ART-1 or free IL-27 at an equivalent dose of IL-27. In addition, ART-1-directed liposomal IL-27 had a better safety profile than undirected liposomal IL-27 or free IL-27, thereby offering an improved therapeutic index for IL-27 therapy. These results provide a proof-of concept for the use of a novel joint-homing peptide for targeted delivery of drugs including biologics or small molecule compounds to arthritic joints with enhanced efficacy and reduced systemic exposure. This targeted therapy platform may be suitable for use in RA patients.

IL-35 inhibits human osteoclastogenesis from monocytes induced by receptor-activator of NF-κB ligand

IL-35 is known as a regulatory cytokine produced by regulatory T cells. It has also been reported that IL-35 suppresses the proliferation of Th17 cells, which is involved in the pathogenesis of many autoimmune diseases. However, in rheumatoid arthritis patients, the role of IL-35 is controversial, and the role of IL-35 in bone metabolism has not been clarified. We investigated the effect of IL-35 on human osteoclast differentiation and activation. We first evaluated the effect of rhIL-35 on human osteoclastogenesis from monocytes cultured alone, induced by soluble-RANKL. We also examined the role of IL-35 on the bone-resorption function of mature osteoclasts. Furthermore, we analysed the molecular mechanism of IL-35 function in monocytes or pre-osteoclasts using RT-PCR. rhIL-35 significantly inhibited human osteoclastogenesis in a dose-dependent manner. In addition, rhIL-35 also significantly decreased the area of pit formation by mature osteoclasts. rhIL-35 significantly decreased mRNA expression of RANK in monocytes and RANK and FOS in pre-osteoclasts. Our current findings suggest that IL-35 inhibits osteoclastogenesis and osteoclast activation by inhibiting both RANK and FOS. IL-35 also has an inhibitory effect on osteoclastic-bone resorption, suggesting that IL-35 may have a therapeutic potential for RA.

Down-regulation of miR-10a-5p promotes proliferation and restricts apoptosis via targeting T-box transcription factor 5 in inflamed synoviocytes

Synoviocytes from rheumatoid arthritis (RA) patients share certain features with tumor cells, such as over proliferation and invasion. Anomalous microRNA (miRNA) expression may participate in the pathogenesis of RA in different ways. The objective of the present study was to observe the role of miR-10a-5p targeting T-box transcription factor 5 (TBX5) gene on synoviocyte proliferation and apoptosis in RA. Human synovial sarcoma cell line, SW982 cells stimulating with interleukin-1β (IL-1β) were transfected with miR-10a-5p mimic and siRNA of TBX5. The real-time quantitative polymerase chain reaction (RT-qPCR) and Western blotting analysis were used to evaluate the expression level of miR-10a-5p and TBX5 in SW982 cells respectively. Further, the proliferation and apoptosis of SW982 cells after treatment were determined by cell counting kit (CCK-8) and flow cytometry analysis respectively. We found that the miR-10a-5p showed down-regulated while TBX5 showed up-regulated expression in synoviocytes after stimulation with IL-1β. The miR-10a-5p mimic treatment showed a decline in cell proliferation while the increased rate of cell apoptosis as compared with control. Moreover, knockdown of TBX5 favored the apoptosis and reduced the cell proliferation as compared with control group. We conclude that down-regulation of miR-10a-5p promotes proliferation and restricts apoptosis via targeting TBX5 in inflamed synoviocytes.

Immunomodulation of autoimmune arthritis by pro-inflammatory cytokines

Pro-inflammatory cytokines promote autoimmune inflammation and tissue damage, while anti-inflammatory cytokines help resolve inflammation and facilitate tissue repair. Over the past few decades, this general feature of cytokine-mediated events has offered a broad framework to comprehend the pathogenesis of autoimmune and other immune-mediated diseases, and to successfully develop therapeutic approaches for diseases such as rheumatoid arthritis (RA). Anti-tumor necrosis factor-α (TNF-α) therapy is a testimony in support of this endeavor. However, many patients with RA fail to respond to this or other biologics, and some patients may suffer unexpected aggravation of arthritic inflammation or other autoimmune effects. These observations combined with rapid advancements in immunology in regard to newer cytokines and T cell subsets have enforced a re-evaluation of the perceived pathogenic attribute of the pro-inflammatory cytokines. Studies conducted by others and us in experimental models of arthritis involving direct administration of IFN-γ or TNF-α; in vivo neutralization of the cytokine; the use of animals deficient in the cytokine or its receptor; and the impact of the cytokine or anti-cytokine therapy on defined T cell subsets have revealed paradoxical anti-inflammatory and immunoregulatory attributes of these two cytokines. Similar studies in other models of autoimmunity as well as limited studies in arthritis patients have also unveiled the disease-protective effects of these pro-inflammatory cytokines. A major mechanism in this regard is the altered balance between the pathogenic T helper 17 (Th17) and protective T regulatory (Treg) cells in favor of the latter. However, it is essential to consider that this aspect of the pro-inflammatory cytokines is context-dependent such that the dose and timing of intervention, the experimental model of the disease under study, and the differences in individual responsiveness can influence the final outcomes. Nevertheless, the realization that pro-inflammatory cytokines can also be immunoregulatory offers a new perspective in fully understanding the pathogenesis of autoimmune diseases and in designing better therapies for controlling them.

Buddleja thyrsoides Lam. crude extract presents antinociceptive effect on an arthritic pain model in mice

Arthritis is a chronic inflammatory disease which reduces the life quality of affected individuals. Therapeutic tools used for treating inflammatory pain are associated with several undesirable effects. Buddleja thyrsoides Lam., known as ‘Barbasco’ or ‘Cambara’, is mostly used in several disorders and possesses antirheumatic, anti-inflammatory, and analgesic properties. Here, we investigated the antinociceptive and anti-inflammatory effects of the B. thyrsoides crude extract applied orally and topically in acute pain models and an arthritic pain model induced by complete Freund's adjuvant (CFA) paw injection in male mice (25–30 g). The high-performance liquid chromatography (HPLC) of the B. thyrsoides extract crude revealed the presence of the lupeol, stigmasterol, and β-sitosterol. The stability study of the B. thyrsoides gel did not show relevant changes at low temperatures. The oral treatment with the B. thrysoides extract prevented the capsaicin-induced spontaneous nociception and the acetic acid-induced abdominal writhing, but did not alter the thermal threshold in the tail immersion test. The B. thyrsoides antinociceptive effect was not reversed by naloxone in the capsaicin test. The B. thyrsoides oral or topical treatment reversed the CFA-induced mechanical allodynia and thermal hyperalgesia with maximum inhibition (Imax) of 69 ± 6 and 68 ± 5% as well as 78 ± 15 and 87 ± 12%, respectively. Moreover, the topical but not oral treatment inhibited the CFA-induced cell infiltration, but did not reduce the paw edema significantly. The oral treatment with B. thyrsoides did not cause adverse effects. These findings suggest that the oral or topical treatment with B. thyrsoides presents antinociceptive actions in an arthritic pain model without causing adverse effects.

YKL-40 and cytokines - a New Diagnostic Constellation in Rheumatoid Arthritis?

BACKGROUND

Rheumatoid arthritis (RA) causes chronic inflammation and alteration of articular tissue and joints. The pathogenesis of the disease remains unclear although it is known that proinflammatory cytokines play a major role in its induction. YKL-40 is a chitinase-like glycoprotein produced by activated macrophages, neutrophils, arthritic chondrocytes and cancer cells. It has been shown that YKL-40 is implicated in tissue remodeling, angiogenesis and inflammation.

AIM

to investigate serum and synovial YKL-40 levels in relation to IL-1β, TNF-α, and IL-6 in RA patients.

MATERIALS AND METHODS

Serum and synovial concentrations of YKL-40, TNF-α, IL- 6, and IL-1β were determined by ELISA in 39 patients (mean age 53.18 ± 16.54 yrs) with active RA.

RESULTS

Serum YKL-40 levels were increased in all patients. The highest levels were found in synovial fluid (P<0.01). Our study showed a strong association between serum and synovial levels of YKL-40 and serum TNF-α and IL-1 β (P<0.05).

CONCLUSION

This is the first study finding a significant correlation between serum TNF-α and IL-1β and YKL-40 in active RA. We suggest that these molecules together might play a dominant role in the pathogenesis and disease activity and could possibly serve as a new diagnostic constellation in rheumatoid arthritis.

Heterogeneity of the cytokinome in undifferentiated arthritis progressing to rheumatoid arthritis and its change in the course of therapy. Move toward personalized medicine

OBJECTIVES

To conduct a comprehensive analysis of cytokine concentrations in sera and mononuclear cell supernatants in order to examine inter- and intra-individual cytokine variations in undifferentiated arthritis progressing to rheumatoid arthritis and healthy control groups.

METHODS

Patients with UA (undifferentiated arthritis) developing RA (rheumatoid arthritis) (UA→RA) (n=16) and healthy controls (n=16) were enrolled into the study. UA→RA patients were followed up for six months since the final RA diagnosis. Cytokines IFN-γ, IL-10, TNF, IL-17A, IL-6, IL-1β, IL-2 in sera and mononuclear cell supernatants in 72h and 120h culture variants with- and without anti-CD3 stimulations were assayed using flow cytometric bead array.

RESULTS

The cytokine profile of UA→RA differs from the healthy individual cytokine profile. It is possible to observe specific cytokine pattern characterizing each patient, which alters during course of disease. Specifically, we can distinguish three UA→RA cohorts: the group of patients susceptible to the therapy, characterized by the drop of cytokine levels between 1st and 3rd visit with visible decrease of cytokines in 2nd visit and then secondary slighter increase in 3rd visit; the group of patients refractory or clinically worsening on the therapy, characterized by the highest cytokine levels at 2nd visit with secondary decrease in 3rd visit; and the group of patients with variable responses to the therapy without any specific common cytokine pattern. The cytokine patterns in supernatants of PBMC stimulated anti-CD3 for 72h and 120h are very similar.

CONCLUSIONS

The personal profile including multiplexed cytokine patterns in serum and supernatant may be potentially used for optimization of therapy introduction and monitoring.

Negative Regulators of JAK/STAT Signaling in Rheumatoid Arthritis and Osteoarthritis

Elevated levels of pro-inflammatory cytokines are generally thought to be responsible for driving the progression of synovial joint inflammation in rheumatoid arthritis (RA) and osteoarthritis (OA). These cytokines activate several signal transduction pathways, including the Janus kinase/Signal Transducers and Activators of Transcription (JAK/STAT), Stress-Activated/Mitogen-Activated Protein Kinase (SAPK/MAPK) and phosphatidylinositol-3-kinase/Akt/mechanistic target of rapamycin (PI3K/Akt/mTOR) pathways which regulate numerous cellular responses. However, cytokine gene expression, matrix metalloproteinase gene expression and aberrant immune cell and synoviocyte survival via reduced apoptosis are most critical in the context of inflammation characteristic of RA and OA. Negative regulation of JAK/STAT signaling is controlled by Suppressor of Cytokine Signaling (SOCS) proteins. SOCS is produced at lower levels in RA and OA. In addition, gaining further insight into the role played in RA and OA pathology by the inhibitors of the apoptosis protein family, cellular inhibitor of apoptosis protein-1, -2 (c-IAP1, c-IAP2), X (cross)-linked inhibitor of apoptosis protein (XIAP), protein inhibitor of activated STAT (PIAS), and survivin (human) as well as SOCS appears to be a worthy endeavor going forward.

Effect of dietary pristane and other saturated mineral oils (MOSH) on autoimmune arthritis in rats

Pristane and other adjuvants based on mineral oil saturated hydrocarbons (MOSH) may induce autoimmunity in rodents after intradermal injection; however there is a lack of information on immune effects after oral MOSH exposure. The aim of our study was to determine the impact of dietary exposure to pristane and other MOSH on the development of autoimmune arthritis.

Dark Agouti (DA) rats were given feed containing 4000 mg/kg pristane or a broad MOSH mixture in various concentrations (0–4000 mg/kg) for 90 days, or a single intradermal injection of 200 μl pristane (positive control). Arthritis scores, and serum and splenocyte markers previously associated with arthritis development, were determined.

All rats injected with pristane displayed arthritis symptoms and higher levels of certain serum markers. None of the rats fed pristane or MOSH developed arthritis symptoms or demonstrated clear changes in any measured arthritis-associated biological markers in serum or splenocytes.

The absence of clinical arthritis symptoms or any increase in common arthritis-associated biological markers in sera and spleen following dietary exposure to pristane or a broad MOSH mixture in a sub-chronic rat model of arthritis suggest that dietary MOSH have low capacity to promote development of autoimmunity.

Herbal formula Xian-Fang-Huo-Ming-Yin regulates differentiation of lymphocytes and production of pro-inflammatory cytokines in collagen-induced arthritis mice

Background

Xian-Fang-Huo-Ming-Yin (XFHM), a traditional herbal formula, has been used to treat sores and carbuncles for hundreds of years in Asia. Nowadays, its clinical effects in treatment of rheumatoid arthritis (RA) have been validated. In this study, we want to study its possible molecular mechanisms of regulating the differentiation of lymphocytes and production of pro-inflammatory cytokines in collagen-induced arthritis (CIA) mice for RA treatment.

Methods

A high performance liquid chromatography-electrospray ionization/mass spectrometer (HPLC-ESI/MSⁿ) system was used to analyze the constituents of XFHM granules. An arthritics mouse model was induced by collagen and leflunomide (LEF) was used as a positive control medicine. Pathological changes at the metatarsophalangeal joint were studied through Safranin O and immunohistochemical staining. The differentiation of T, B and NK cells was examined by flow cytometry and pro-inflammatory cytokines were assayed using an Inflammation Antibody Array assay. The expression of key molecules of the nuclear factor κB (NF-κB) and Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathways in spleen were studied by western-blot analysis.

Results

In our study. 21 different dominant chemical constituents were identified in XFHM. Treatment with XFHM suppressed the pathological changes in arthrosis of CIA. Additionally, XFHM down-regulated the proliferation and differentiation of CD3⁺ T cells and CD3⁻CD19⁺ B cells significantly. However, XFHM had no significant effect on CD3⁻NK1.1⁺ NK cells. Further study showed that the production of pro-inflammatory cytokines had been suppressed by inhibiting the activation of NF-κB and JAK/STAT signaling.

Conclusions

XFHM can regulate and maintain the immunologic balance of lymphocytic immunity and inhibit the production of pro-inflammatory cytokines, thus suppressing the pathological changes of RA. Therefore, XFHM may be used as an application of traditional medicine against RA in modern complementary and alternative therapeutics.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-016-1526-x) contains supplementary material, which is available to authorized users.

Periploca forrestii Saponin Ameliorates Murine CFA-Induced Arthritis by Suppressing Cytokine Production

Periploca forrestii Schltr. has been used as a Chinese folk medicine due to its versatile pharmacological effects such as promoting wounds and rheumatoid arthritis. However, the antiarthritic activity of Periploca forrestii saponin (PFS) and its active compound Periplocin has still not been demonstrated. Here, we evaluated the antiarthritic effects of PFS in adjuvant-induced arthritis (AIA) rats by intragastric administration at a dose of 50 mg/kg. The anti-inflammatory activities of Periplocin were also examined in LPS-induced AIA splenocytes and synoviocytes. PFS significantly ameliorated joint swelling; inhibited bone erosion in joints; lowered levels of IL-6 and TGF-β1 in AIA rat splenocyte; and reduced joint protein expression levels of phospho-STAT3 and IKKα. Using LPS-induced AIA splenocytes, we demonstrate that Periplocin suppressed the key proinflammatory cytokines levels of IL-6, IFN-γ, TGF-β1, and IL-13 and IL-22 and transcription factor levels of T-bet, GATA3, and C-Jun genes. Periplocin also suppressed LPS-induced cytokine secretion from synoviocytes. Our study highlights the antiarthritic activity of PFS and its derived Periplocin and the underlying mechanisms. These results provide a strong rationale for further testing and validation of the use of Periploca forrestii Schltr. as an alternative modality for the treatment of RA.

Rheumatoid arthritis onset in postmenopausal women: Does the ACPA seropositive subset result from genetic effects, estrogen deficiency, skewed profile of CD4(+) T-cells, and their interactions?

Rheumatoid arthritis (RA) incidence displays a differentiated age-dependent female-to-male ratio in which women outnumber men. Evidence that the peak incidence of RA in women coincides with menopause age, suggests a potential estrogenic role to disease etiology. Estrogens exert physiologically both stimulatory and inhibitory effects on the immune system. Epidemiologic and animal model studies with estrogen deprivation or supplementation suggested estrogens as to play, mainly, a protective role in RA immunopathology. In this review, we propose that some yet unidentified disturbances associated with estrogen circulating levels, differentiated by the menopausal status, play a major role in women's RA susceptibility. We focus on the interaction between estrogen deprivation and genetic risk alleles for anti-citrullinated protein antibodies (ACPA) seropositive RA, as a major driving force for increased immune reactivity and RA susceptibility, in postmenopausal women. This opens up new fields for research concerning the association among different irregular estrogenic conditions, the cytokine milieu, and age/menopausal status bias in RA.

Inhibitory effect of the extract of Phellodendron amurense ruprecht root on collagen-induced arthritis in mice

OBJECTIVE

To investigate whether the dried root of Phellodendron amurense Ruprecht (Phellodendri cortex; PC) extract improves arthritic symptoms through anti-inflammatory and immune-modulatory effects in collagen-induced arthritis in mice.

METHODS

Rheumatoid arthritis (RA) was induced in male DBA/1 mice by immunization with type II collagen (ColII). CIA mice were divided into 5 groups (n=10 per a group) with normal, CIA control, PC extract (50 mg/kg and 100 mg/kg)-treated, and meloxicam (50 mg/kg)-treated as the reference drug. The PC extract or meloxicam were administered orally in CIA mice once a day for 14 days after arthritis induction. Arthritic score, levels of anti-ColII IgG_2a antibody, prostaglandin E₂ (PGE₂), tumor necrosis factor (TNF)-α, and interleukin (IL)-17 in the sera of CIA mice were measured. Histopathological changes in the ankle joints of CIA mice were also analyzed by staining with hematoxylin and eosin (H and E), safranin-O and immunohistochemistry using anti-TNF-α and anti-IL-17 antibodies.

RESULTS

The arthritic score was increased in CIA mice in a time-dependent manner, as were the serum levels of anti-ColII IgG_2a antibody, PGE₂, TNF-α, and IL-17. However, the oral administration of PC extract at 50 and 100 mg/kg in CIA mice significantly decreased the arthritic scores, and the serum levels of anti-ColII IgG_2a, PGE₂, TNF-α, and IL-17 compared with those in the CIA group (P<0.05 or P<0.01). Furthermore, histopathological improvement of the joint architecture in CIA mice was observed after administration of PC extract. PC extract also significantly inhibited the expression of TNF-α and IL-17 in the joints of CIA mice by suppressing the expression of their mRNA and proteins.

CONCLUSION

PC extract may improve the pathological progression of RA through the inhibition of joint destruction by synovial inflammation and immune-stimulation, therefore, it would be a potential anti-arthritic agent in RA.

Understanding the role of cytokines in the pathogenesis of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, inflammatory autoimmune disease of unknown etiology. It is characterized by the presence of rheumatoid factor and anti-citrullinated peptide antibodies. Initial phase of RA involves the activation of both T and B cells. Cytokines have a crucial role in the pathophysiology of RA as pro-inflammatory cytokines such as TNFα, IL-1, IL-17 stimulates inflammation and degradation of bone and cartilage. There occurs an imbalance between the pro- and anti-inflammatory cytokine activities which leads to multisystem immune complications. There occurs a decline in the number of Treg cells which may also play an important role in pathophysiology of the disease. In RA patients, serum or plasma level of cytokines may indicate the severity of disease. Cytokine gene polymorphism could be used as markers of susceptibility and severity of RA. Anti-cytokine agents seem to emerge as potent drug molecules to treat RA. Many clinical trials are ongoing and several positive results have been obtained. There is a need to develop potential anti-cytokine agents that target numerous pathways involved in the pathogenesis of RA. This review article describes the effector functions of pro- and anti-inflammatory cytokines and the role of cytokine gene polymorphism in the pathogenesis of RA. Anti-cytokine agents that are currently available and those that are still in clinical trials have also been summarized.

Evaluation of humoral and cellular immune responses to a DNA vaccine encoding chicken type II collagen for rheumatoid arthritis in normal rats

A major challenge in the development of effective therapies for rheumatoid arthritis (RA) is finding a method for the specific inhibition of the inflammatory disease processes without the induction of generalized immunosuppression. Of note, the development of therapeutic DNA vaccines and boosters that may restore immunological tolerance remains a high priority. pcDNA-CCOL2A1 is a therapeutic DNA vaccine encoding chicken type II collagen(CCII). This vaccine was developed by our laboratory and has been shown to exhibit efficacy comparable to that of the current "gold standard" treatment, methotrexate (MTX). Here, we used enzyme-linked immunosorbent assays with anti-CII IgG antibodies, quantified the expression levels of Th1, Th2, and Th3 cytokines, and performed flow cytometric analyses of different T-cell subsets, including Th1, Th2, Th17, Tc, Ts, Treg, and CD4(+)CD29(+)T cells to systemically evaluate humoral and cellular immune responses to pcDNA-CCOL2A1 vaccine in normal rats. Similar to our observations at maximum dosage of 3 mg/kg, vaccination of normal rats with 300 μg/kg pcDNA-CCOL2A1 vaccine did not induce the production of anti-CII IgG. Furthermore, no significant changes were observed in the expression levels of pro-inflammatory cytokines interleukin (IL)-1α, IL-5, IL-6, IL-12(IL-23p40), monocyte chemotactic protein (MCP)-1, macrophage inflammatory protein (MIP)-1α, regulated on activation in normal T-cell expressed and secreted (RANTES), receptor activator for nuclear factor-κB ligand (RANKL), and granulocyte colony-stimulating factor (G-CSF) or anti-inflammatory cytokines IL-4 and IL-10 in vaccinated normal rats relative to that in controls(P > 0.05). However, transforming growth factor (TGF)-β levels were significantly increased on days 10 and 14, while interferon (IFN)-γ and tumor necrosis factor (TNF)-α levels were significantly decreased on days 28 and 35 after vaccination(P < 0.05). Similarly, there were no significant differences in the percentages of Tc, Ts, Th1/Th2, and Th17 cells between the 2 groups(P > 0.05), with the exception of Treg cells, which were significantly reduced on days 14 and 21 after vaccination (P < 0.05), and CD4(+)CD29(+)T cells, which were significantly increased on days 7 and 14 after vaccination(P < 0.05).Taken together, these results suggested that pcDNA-CCOL2A1 vaccine did not markedly affect the balance of immune system components in vaccinated normal rats, indicating that this DNA vaccine may have clinical applications in the treatment of RA.

Decrease of CD68 Synovial Macrophages in Celastrol Treated Arthritic Rats

Background

Rheumatoid arthritis (RA) is a chronic immune-mediated inflammatory disease characterized by cellular infiltration into the joints, hyperproliferation of synovial cells and bone damage. Available treatments for RA only induce remission in around 30% of the patients, have important adverse effects and its use is limited by their high cost. Therefore, compounds that can control arthritis, with an acceptable safety profile and low production costs are still an unmet need. We have shown, in vitro, that celastrol inhibits both IL-1β and TNF, which play an important role in RA, and, in vivo, that celastrol has significant anti-inflammatory properties. Our main goal in this work was to test the effect of celastrol in the number of sublining CD68 macrophages (a biomarker of therapeutic response for novel RA treatments) and on the overall synovial tissue cellularity and joint structure in the adjuvant-induced rat model of arthritis (AIA).

Methods

Celastrol was administered to AIA rats both in the early (4 days after disease induction) and late (11 days after disease induction) phases of arthritis development. The inflammatory score, ankle perimeter and body weight were evaluated during treatment period. Rats were sacrificed after 22 days of disease progression and blood, internal organs and paw samples were collected for toxicological blood parameters and serum proinflammatory cytokine quantification, as well as histopathological and immunohistochemical evaluation, respectively.

Results

Here we report that celastrol significantly decreases the number of sublining CD68 macrophages and the overall synovial inflammatory cellularity, and halted joint destruction without side effects.

Conclusions

Our results validate celastrol as a promising compound for the treatment of arthritis.

Aryl hydrocarbon receptor antagonism and its role in rheumatoid arthritis

Although rheumatoid arthritis (RA) is the most common autoimmune disease, affecting approximately 1% of the population worldwide, its pathogenic mechanisms are poorly understood. Tobacco smoke, an environmental risk factor for RA, contains several ligands of aryl hydrocarbon receptor (Ahr), also known as dioxin receptor. Ahr plays critical roles in the immune system. We previously demonstrated that Ahr in helper T-cells contributes to development of collagen-induced arthritis, a mouse model of RA. Other studies have shown that cigarette smoke condensate and pure Ahr ligands exacerbate RA by altering bone metabolism and inducing proinflammatory responses in fibroblast-like synoviocytes. Consistent with these findings, several Ahr antagonists such as α-naphthoflavone, resveratrol, and GNF351 reverse the effect of Ahr ligands in RA pathogenesis. In this review, we summarize the current knowledge of Ahr function in the immune system and the potential clinical benefits of Ahr antagonism in treating RA.

Different Blood-Borne Human Osteoclast Precursors Respond in Distinct Ways to IL-17A

Osteoclasts are bone-degrading cells that are formed through fusion of their monocytic precursors. Three distinct subsets of monocytes have been identified in human peripheral blood: classical, intermediate, and non-classical monocytes. They are known to play different roles in physiology and pathology, but their capacity to differentiate into osteoclasts and whether inflammatory cytokines influence this differentiation is unknown. We hypothesized that classical, intermediate, and non-classical monocytes generate functionally different osteoclasts and that they respond in different ways to the inflammatory cytokine interleukin-17A (IL-17A). To investigate this, the different monocyte subsets were isolated from human peripheral blood and osteoclastogenesis was induced with the cytokines M-CSF and RANKL, with or without IL-17A. We found that all subsets are able to differentiate into osteoclasts in vitro, and that both osteoclastogenesis and subsequent bone resorption was distinctly affected by IL-17A. Osteoclastogenesis and bone resorption by osteoclasts derived from classical monocytes remained unaffected by IL-17A, while osteoclast formation from intermediate monocytes was inhibited by the cytokine. Surprisingly, bone resorption by osteoclasts derived from intermediate monocytes remained at similar levels as control cultures, indicating an increased bone resorbing activity by these osteoclasts. Limited numbers of osteoclasts were formed from non-classical monocytes on bone and no bone resorption was detected, which suggest that these cells belong to a cell lineage different from the osteoclast. By providing more insight into osteoclast formation from human blood monocytes, this study contributes to the possible targeting of specific osteoclast precursors as a therapeutic approach for diseases associated with inflammatory bone loss.

Tinospora cordifolia inhibits autoimmune arthritis by regulating key immune mediators of inflammation and bone damage

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation of the joints leading to tissue damage. Despite the availability of potent drugs including the biologics, many patients fail to respond to them, whereas others suffer adverse effects following long-term use of these drugs. Accordingly, the use of natural herbal products by RA patients has been increasing over the years. However, limited information about the mechanism of action of these natural products is a major shortcoming that prevents the widespread acceptance of herbal therapy by professionals and patients alike. In this study, we demonstrated the anti-arthritic activity of Tinospora cordifolia extract (TCE) using the rat adjuvant-induced arthritis model of human RA and elaborated the immune mechanisms underlying this effect. TCE treatment suppressed arthritic inflammation and bone and cartilage damage. The anti-inflammatory effect of TCE was mediated via reduction of the pro-inflammatory cytokines such as: IL-1β, TNF-α, IL-6, and IL-17; the frequency of IL-17-producing T cells; and the production of chemokines such as RANTES. Furthermore, TCE treatment limited bone damage by shifting the balance of mediators of bone remodeling (e.g., receptor activator of nuclear factor-kB ligand [RANKL] and MMP-9) in favor of anti-osteoclastic activity. Our results suggest that TCE and its bioactive components should be evaluated for their utility as therapeutic adjuncts to conventional drugs against RA.

The role of cytokines in the pathogenesis of rheumatoid arthritis--Practical and potential application of cytokines as biomarkers and targets of personalized therapy

Rheumatoid arthritis (RA), as a common chronic disease leading to severe disability, requires early diagnosis and introduction of proper treatment. Deregulation in the cytokine network plays an undoubtedly crucial role in the pathogenesis of RA. The understanding of the role of cytokines in RA can be used for patients' benefit. Technological advances had already allowed introduction of the tailor-made cytokine-targeted therapies (so far anti-TNF, anti-IL-1 and anti-IL-6) into clinical practice. This type of treatment is currently developing very fast. Moreover, cytokines are considered to be potential powerful biomarkers of RA with roles predicted to grow in the future. Detailed understanding of the cytokine balance in RA may assist both the diagnostic process and therapy.

Polyfunctional, Pathogenic CD161+ Th17 Lineage Cells Are Resistant to Regulatory T Cell-Mediated Suppression in the Context of Autoimmunity

In autoimmune diseases such as rheumatoid arthritis (RA), regulatory T cells (Tregs) fail to constrain autoimmune inflammation; however, the reasons for this are unclear. We investigated T cell regulation in the RA joint. Tregs from RA synovial fluid suppressed autologous responder T cells; however, when compared with Tregs from healthy control peripheral blood, they were significantly less suppressive. Despite their reduced suppressive activity, Tregs in the RA joint were highly proliferative and expressed FOXP3, CD39, and CTLA-4, which are markers of functional Tregs. This suggested that the reduced suppression is due to resistance of RA synovial fluid responder T cells to Treg inhibition. CD161(+) Th17 lineage cells were significantly enriched in the RA joint; we therefore investigated their relative susceptibility to Treg-mediated suppression. Peripheral blood CD161(+) Th cells from healthy controls were significantly more resistant to Treg-mediated suppression, when compared with CD161(-) Th cells, and this was mediated through a STAT3-dependant mechanism. Furthermore, depletion of CD161(+) Th cells from the responder T cell population in RA synovial fluid restored Treg-mediated suppression. In addition, CD161(+) Th cells exhibited pathogenic features, including polyfunctional proinflammatory cytokine production, an ability to activate synovial fibroblasts, and to survive and persist in the inflamed and hypoxic joint. Because CD161(+) Th cells are known to be enriched at sites of autoinflammation, our finding that they are highly proinflammatory and resistant to Treg-mediated suppression suggests an important pathogenic role in RA and other autoimmune diseases.

Interplay among cytokines and T cell subsets in the progression and control of immune-mediated diseases

Cytokines serve as key mediators of inflammation and tissue damage in a variety of immune-mediated disorders. The induction, progression, and resolution of inflammation in such disorders are characterized by a dynamic balance between both the pro-inflammatory and anti-inflammatory cytokines as well as the pathogenic and protective T cell subsets. Over the past two decades, the roles of the interleukin-17 (IL-17) /IL-23 axis and the T helper 17 (Th17)/ T regulatory (Treg) cell balance in the pathogenesis of autoimmunity and other inflammatory diseases have extensively been analyzed, and their significance validated. However, these studies, coupled with others devoted to well-established Th1/Th2 cytokines, have unraveled some challenging issues including the dual action of cytokines and the plasticity of T cell subsets. Nevertheless, major positive advances have also been made regarding cytokines and T cell subsets as therapeutic targets/agents. In this special issue, "Cytokines in Immune Pathology and Therapy," leading experts have shared their research work and perspectives on the roles of cytokines in the development and control of immune-mediated diseases. An outline of 14 articles in the first volume is presented here. The second volume will follow soon.

Cytokine profiles in axial spondyloarthritis

Objectives

Current studies concentrate on the cytokine network and its role in the pathogenesis of spondyloarthritis (SpA). In this study, we analyzed whether the serum cytokine profile (interleukins: IL-10, IL-11, IL-12, IL-15, IL-17, IL-23 and IL-33) correlates with demographic data, clinical manifestations, disease activity and treatment outcome in a group of patients with axial spondyloarthritis.

Material and methods

Forty-nine patients with an established diagnosis of axial spondyloarthritis (aSpA) and 19 healthy volunteers as controls were enrolled in the study. Clinical evaluation included patient's medical history, 44 joint count, back pain intensity and global disease activity in the preceding week (VAS), the duration of morning stiffness and blood tests. Disease activity was assessed using BASDAI and ASDAS-CRP. Serum concentration of IL-10, IL-11, IL-12, IL-15, IL-17, IL-23 and IL-33 was determined.

Results

In patients with aSpA, elevated serum concentration of IL-10, IL-15, IL-17 and IL-23 was detected. In the aSpA group we detected higher values of serum concentration of IL-23 and IL-33 in the subgroup with anterior uveitis (83.1 ±184.0 pg/ml vs. 14.0 ±17.1 pg/ml, p < 0.0001 and 45.5 ±71.9 pg/ml vs. 18.4 ±14.3 pg/ml, p < 0.0001, respectively). Additionally, in the subgroup with peripheral arthritis, elevation of serum concentration of IL-12 (249.3 ±246.9 pg/ml vs. 99.9 ±105.9 pg/ml, p = 0.0001) was detected. Patients with preradiological SpA had higher serum concentration of IL-17 than patients with established diagnosis of AS (6.37 ±8.50 pg/ml vs. 2.04 ±2.98 pg/ml, p = 0.0295). No differences in serum concentration of analyzed cytokines were found between the subgroup with low to moderate disease activity and the subgroup with high to very high disease activity.

Conclusions

We report that in aSpA patients, compared to controls, elevated serum concentrations of IL-10, IL-15, IL-17 and IL-23 were observed. Some cytokines may predispose to a more severe course of aSpA.

Cytokine-modulating strategies and newer cytokine targets for arthritis therapy

Cytokines are the key mediators of inflammation in the course of autoimmune arthritis and other immune-mediated diseases. Uncontrolled production of the pro-inflammatory cytokines such as interferon-γ (IFN-γ), tumor necrosis factor α (TNFα), interleukin-6 (IL-6), and IL-17 can promote autoimmune pathology, whereas anti-inflammatory cytokines including IL-4, IL-10, and IL-27 can help control inflammation and tissue damage. The pro-inflammatory cytokines are the prime targets of the strategies to control rheumatoid arthritis (RA). For example, the neutralization of TNFα, either by engineered anti-cytokine antibodies or by soluble cytokine receptors as decoys, has proven successful in the treatment of RA. The activity of pro-inflammatory cytokines can also be downregulated either by using specific siRNA to inhibit the expression of a particular cytokine or by using small molecule inhibitors of cytokine signaling. Furthermore, the use of anti-inflammatory cytokines or cytokine antagonists delivered via gene therapy has proven to be an effective approach to regulate autoimmunity. Unexpectedly, under certain conditions, TNFα, IFN-γ, and few other cytokines can display anti-inflammatory activities. Increasing awareness of this phenomenon might help develop appropriate regimens to harness or avoid this effect. Furthermore, the relatively newer cytokines such as IL-32, IL-34 and IL-35 are being investigated for their potential role in the pathogenesis and treatment of arthritis.

Cytokines pre-determined by genetic factors are involved in pathogenesis of Rheumatoid arthritis

Rheumatoid arthritis (RA) is associated with the presence of autoreactive CD4 T cells that produce pro-inflammatory cytokines. The role of genetic factors in the predilection to develop RA is strongly supported by the increased presence of certain HLA class II molecules in patients. The HLA class II genes are highly polymorphic and are critical for generating an immune response to clear infections. Production of Th1 and Th17 response by the CD4 T cells helps to clear infections. HLA-DQ8 is a promiscuous binder and presents many peptides generating immune response and producing a Th17 response. DRB1∗0401 is associated with the production of both IL-17 and IFN-γ. Thus both DR4 and DQ8 can clear infections by producing TH1/Th17 cytokines, but their presence increases the risk of developing RA. Using transgenic mice expressing human HLA genes, we have shown that HLA polymorphism determines the cytokine profile. DRB1∗04 molecules modulate the DQ8-restricted response and determine the outcome of arthritis in mice carrying DR4/DQ8 haplotype. Thus, interaction between DQ and DR molecules determines the cytokine milieu and propensity of the HLA haplotype to predispose to autoimmunity.

Does a biological link exist between periodontitis and rheumatoid arthritis?

Periodontitis or Periodontal disease (PD) and Rheumatoid arthritis (RA) are two the most common chronic inflammatory diseases. Periodontitis is a biofilm associated destructive inflammatory disease of the periodontium caused by specific microorganisms. Rheumatoid arthritis is an autoimmune condition and is identified by elevated serum autoantibody titre directed against citrullinated peptides or rheumatoid factor. Periodontitis may involve some elements of autoimmunity. Recent studies have established that PD and RA show a common pathway and could be closely associated through a common dysregulation and dysfunction in inflammatory mechanism. The enzyme peptidyl arginine deiminase (PAD), expressed by Porphyromonas gingivalis (P. gingivalis) is responsible for the enzymatic deimination of arginine residuals to citrulline resulting in protein citrullination and its increased accumulation in RA. Citrullination by PAD may act as a putative biologic link between PD and RA. Association of Human leukocytic antigen-DR4 antigen has been established both with RA and PD. Several interleukins and inflammatory mediators (ILs) and Nuclear factor kappa beta ligand are linked to these common chronic inflammatory diseases. Antibodies directed against heat shock protein (hsp 70 ab) of P. gingivalis, P. melanogenicus and P. intermedia are raised in PD as well as RA. Both the conditions share many pathological and immunological similarities. Bacterial infection, genetic susceptibility, altered immune reaction and inflammatory mediators considered responsible for RA are also associated with PD. So it is plausible that a biological link may exist between PD and RA. Therapies aimed at modifying the expression and effect of inflammatory mediators and effector molecules such as matrix metalloproteinases, proinflammatory cytokines and autoantibodies of structural proteins may probably reduce the severity of both RA and PD.

Pristimerin, a naturally occurring triterpenoid, protects against autoimmune arthritis by modulating the cellular and soluble immune mediators of inflammation and tissue damage

Rheumatoid arthritis (RA) is a chronic autoimmune disorder affecting the synovial joints. The currently available drugs for RA are effective only in a proportion of patients and their prolonged use is associated with severe adverse effects. Thus, new anti-arthritic agents are being sought. We tested Pristimerin, a naturally occurring triterpenoid, for its therapeutic activity against rat adjuvant arthritis. Pristimerin effectively inhibited both arthritic inflammation and cartilage and bone damage in the joints. Pristimerin-treated rats exhibited a reduction in the pro-inflammatory cytokines (IL-6, IL-17, IL-18, and IL-23) and the IL-6/IL-17-associated transcription factors (pSTAT3 and ROR-γt), coupled with an increase in the immunomodulatory cytokine IL-10. Also increased was IFN-γ, which can inhibit IL-17 response. In addition, the Th17/Treg ratio was altered in favor of immune suppression and the RANKL/OPG ratio was skewed towards anti-osteoclastogenesis. This is the first report on testing Pristimerin in arthritis. We suggest further evaluation of Pristimerin in RA patients.

Protein kinase small molecule inhibitors for rheumatoid arthritis: Medicinal chemistry/clinical perspectives

Medicinal chemistry strategies have contributed to the development, experimental study of and clinical trials assessment of the first type of protein kinase small molecule inhibitor to target the Janus kinase/Signal Transducers and Activators of Transcription (JAK/STAT) signaling pathway. The orally administered small molecule inhibitor, tofacitinib, is the first drug to target the JAK/STAT pathway for entry into the armamentarium of the medical therapy of rheumatoid arthritis. The introduction of tofacitinib into general rheumatologic practice coupled with increasing understanding that additional cellular signal transduction pathways including the mitogen-activated protein kinase and phosphatidylinositide-3-kinase/Akt/mammalian target of rapamycin pathways as well as spleen tyrosine kinase also contribute to immune-mediated inflammatory in rheumatoid arthritis makes it likely that further development of orally administered protein kinase small molecule inhibitors for rheumatoid arthritis will occur in the near future.

Rheumatoid arthritis pathophysiology: update on emerging cytokine and cytokine-associated cell targets

Biologic therapies that target pathogenic cytokines such as TNF, IL-1β or IL-6 have greatly improved the treatment of RA. Unfortunately, not all RA patients respond to current biologic therapies and responses are not always maintained, suggesting that there are alternative drivers of RA pathogenesis that might serve as promising therapeutic targets. Discovery of the new Th17 subset of Th cells, and their role in autoimmune disease development, has implicated the proinflammatory IL-12 and IL-17 families of cytokines in RA disease pathogenesis. Members of these cytokine families are elevated in the blood and joints of RA patients and have been shown to remain elevated in patients who do not respond to current biologics. In addition, these cytokines have been shown to play roles in joint destruction and erosion. A new subclass of biologics that target the IL-12 and/or IL-17 signalling pathways are under development. Here we review evidence for a role of Th17 cells as well as IL-12 and IL-17 cytokines in RA pathogenesis as the rationale for a subsequent discussion of the ongoing and completed clinical trials of newly emerging biologic therapies directed at IL-12 or IL-17 pathway inhibition.