NF-kappa B regulation by I kappa B kinase-2 in rheumatoid arthritis synoviocytes

Insights into the mechanism of transcription factors in Pb2+-induced apoptosis

The health risks associated with exposure to heavy metals, such as Pb2+, are increasingly concerning the public. Pb2+ can cause significant harm to the human body through oxidative stress, autophagy, inflammation, and DNA damage, disrupting cellular homeostasis and ultimately leading to cell death. Among these mechanisms, apoptosis is considered crucial. It has been confirmed that transcription factors play a central role as mediators during the apoptosis process. Interestingly, these transcription factors have different effects on apoptosis depending on the concentration and duration of Pb2+ exposure. In this article, we systematically summarize the significant roles of several transcription factors in Pb2+-induced apoptosis. This information provides insights into therapeutic strategies and prognostic biomarkers for diseases related to Pb2+ exposure.

DNA hypomethylation ameliorates erosive inflammatory arthritis by modulating interferon regulatory factor-8

Epigenetic regulation plays a crucial role in the pathogenesis of autoimmune diseases such as inflammatory arthritis. DNA hypomethylating agents, such as decitabine (DAC), have been shown to dampen inflammation and restore immune homeostasis. In the present study, we demonstrate that DAC elicits potent anti-inflammatory effects and attenuates disease symptoms in several animal models of arthritis. Transcriptomic and epigenomic profiling show that DAC-mediated hypomethylation regulates a wide range of cell types in arthritis, altering the differentiation trajectories of anti-inflammatory macrophage populations, regulatory T cells, and tissue-protective synovial fibroblasts (SFs). Mechanistically, DAC-mediated demethylation of intragenic 5'-Cytosine phosphate Guanine-3' (CpG) islands of the transcription factor Irf8 (interferon regulatory factor 8) induced its re-expression and promoted its repressor activity. As a result, DAC restored joint homeostasis by resetting the transcriptomic signature of negative regulators of inflammation in synovial macrophages (MerTK, Trem2, and Cx3cr1), TREGs (Foxp3), and SFs (Pdpn and Fapα). In conclusion, we found that Irf8 is necessary for the inhibitory effect of DAC in murine arthritis and that direct expression of Irf8 is sufficient to significantly mitigate arthritis.

Prolactin Inhibits or Stimulates the Inflammatory Response of Joint Tissues in a Cytokine-dependent Manner

The close association between rheumatoid arthritis (RA), sex, reproductive state, and stress has long linked prolactin (PRL) to disease progression. PRL has both proinflammatory and anti-inflammatory outcomes in RA, but responsible mechanisms are not understood. Here, we show that PRL modifies in an opposite manner the proinflammatory actions of IL-1β and TNF-α in mouse synovial fibroblasts in culture. Both IL-1β and TNF-α upregulated the metabolic activity and the expression of proinflammatory factors (Il1b, Inos, and Il6) via the activation of the nuclear factor-κB (NF-κB) signaling pathway. However, IL-1β increased and TNF-α decreased the levels of the long PRL receptor isoform in association with dual actions of PRL on synovial fibroblast inflammatory response. PRL reduced the proinflammatory effect and activation of NF-κB by IL-1β but increased TNF-α-induced inflammation and NF-κB signaling. The double-faceted role of PRL against the 2 cytokines manifested also in vivo. IL-1β or TNF-α with or without PRL were injected into the knee joints of healthy mice, and joint inflammation was monitored after 24 hours. IL-1β and TNF-α increased the joint expression of proinflammatory factors and the infiltration of immune cells. PRL prevented the actions of IL-1β but was either inactive or further increased the proinflammatory effect of TNF-α. We conclude that PRL exerts opposite actions on joint inflammation in males and females that depend on specific proinflammatory cytokines, the level of the PRL receptor, and the activation of NF-κB signaling. Dual actions of PRL may help balance joint inflammation in RA and provide insights for development of new treatments.

New insights into the Lck-NF-κB signaling pathway

Lck is essential for the development, activity, and proliferation of T cells, which may contribute to pathological progression and development of human diseases, such as autoimmune disorders and cancers when functioning aberrantly. Nuclear factor-κB (NF-κB) was initially discovered as a factor bound to the κ light-chain immunoglobulin enhancer in the nuclei of activated B lymphocytes. Activation of the nuclear factor-κB pathway controls expression of several genes that are related to cell survival, apoptosis, and inflammation. Abnormal expression of Lck and nuclear factor-κB has been found in autoimmune diseases and malignancies, including rheumatoid arthritis, systemic lupus erythematosus, acute T cell lymphocytic leukemia, and human chronic lymphocytic leukemia, etc. Nuclear factor-κB inhibition is effective against autoimmune diseases and malignancies through blocking inflammatory responses, although it may lead to serious adverse reactions that are unexpected and unwanted. Further investigation of the biochemical and functional interactions between nuclear factor-κB and other signaling pathways may be helpful to prevent side-effects. This review aims to clarify the Lck-nuclear factor-κB signaling pathway, and provide a basis for identification of new targets and therapeutic approaches against autoimmune diseases and malignancies.

Indigenous Nigeria medicinal herbal remedies: A potential source for therapeutic against rheumatoid arthritis

Rheumatoid arthritis (RA) is a debilitating disease associated with locomotion impairment, and conventional therapeutic drugs are not optimal for managing RA. There is an avalanche of medications used for the management of RA. Still, studies have shown that they are associated with severe side effects, including hepatotoxicity, retinopathy, and cardiotoxicity disorders of the central nervous system (CNS), skin, blood, and infections. Complementary and alternative medicine (CAM) is currently gaining attention as a novel panacea for managing debilitating diseases, such as RA. Nigerian folk herbal remedies are replete with a plethora of curative medicine, albeit unvalidated scientifically but with seemingly miraculous provenance. Studies of the identification of bioactive compounds present in these botanicals using advanced spectral analytical techniques have enhanced our understanding of the role of Nigerian herbal remedies in the treatment and management of RA. Interestingly, experimental studies abound that the bioactive compounds present in the extracts of plant botanicals protected animals from the development of RA in different experimental models and reduced the toxicity associated with conventional therapeutics. Validated mechanisms of RA amelioration in human and animal models include suppression of the expression of NF-κB, IL-1β, TNF-α, IL-6, IL-8, IL-17, IL-23, chemokines, TGF-β, RANKL, RANK, iNOS, arginase, COX-2, VEGFA, VEGFR, NFATC1, and TRAP in the synoviocytes. Decreased ROS, NO, MDA, carbonyl groups, and PGE₂ in the synovial fluid increased the expression of PPARα/γ; antioxidant and anti-inflammatory molecules also improve RA etiology. In this mini-review, we discuss the global burden of RA, the novel role of plant-based botanicals as potential therapeutics against signaling pathways in RA. Also addressed is the possible repurposing/reprofiling of plant botanicals to increase their therapeutic index among RA patients that patronize traditional healers in Nigeria with a global projection.

Protective effect of a novel polyherbal formulation on experimentally induced osteoarthritis in a rat model

Osteoarthritis (OA) is a musculoskeletal disorder mainly found in elderly individuals. Modern treatment of OA, like nonsteroidal anti-inflammatory drugs, corticosteroids, hyaluronic acid injections, etc., is linked to long-term side effects. We evaluated the anti-osteoarthritic properties of a novel joint health formula (JHF) containing Bisdemethoxycurcumin enriched curcumin, 3-O-Acetyl-11-keto-beta-Boswellic acid-enriched Boswellia, and Ashwagandha in monosodium iodoacetate (MIA)-induced knee OA in rats. Twenty-eight female rats were distributed into four groups: Control, OA, OA + JHF (100 mg/kg), and OA + JHF (200 mg/kg). JHF decreased the right joint diameters but increased the paw area and stride length compared to the OA group with no treatment. JHF significantly reduced the arthritic conditions after four weeks of supplementation (p < 0.05). JHF significantly decreased TNF-α, IL-1β, IL-10, COMP, and CRP in the serum of osteoarthritic rats (p < 0.0001). We observed reduced lipid peroxidation but increased SOD, GSH-Px, and CAT activities in response to JHF treatment in OA animals. JHF down-regulated MMP-3, COX-2, and LOX-5 and improved the histological structure of the knee joint of osteoarthritic rats. JHF demonstrated a protective effect against osteoarthritis, possibly due to anti-inflammatory and antioxidant activity in experimentally induced osteoarthritis in rats, and could be an effective option in the management of OA.

Clusterin exacerbates interleukin-1β-induced inflammation via suppressing PI3K/Akt pathway in human fibroblast-like synoviocytes of knee osteoarthritis

This study aimed to examine, a multifaceted chaperon-like protein exerting anti-inflammatory action, clusterin (CLU), mRNA and protein levels in the systemic and local joint environment of knee osteoarthritis (OA) patients and to determine whether CLU inhibited interleukin (IL)-1β-induced inflammation in knee OA fibroblast-like synoviocytes (FLSs) through modulating phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathway. CLU protein and mRNA expressions in the synovium and its protein levels in plasma and synovial fluid of knee OA patients were measured using immunohistochemistry, real-time PCR, and ELISA, respectively. Anti-inflammatory effect of CLU was further elucidated in knee OA FLSs treated with IL-1β in the absence or presence of CLU, CLU alone, or PI3K inhibitor (LY294002) along with IL-1β and CLU. In a clinical study, compared with knee OA patients without synovitis, CLU protein and mRNA were expressed in the synovium of knee OA patients with synovitis, especially those with high-grade, consistent with analyses of its plasma and synovial fluid levels. CLU mRNA and protein levels were both associated with synovitis severity. An in vitro study uncovered that CLU significantly alleviated IL-1β-induced overproduction of nitric oxide and IL-6 in knee OA FLSs. Furthermore, CLU significantly attenuated inflammation and extracellular matrix degradation induced by IL-1β via down-regulating expressions of IL-6, nuclear factor kappa B, and matrix metalloproteinase-13. Mechanistically, CLU significantly impeded IL-1β-induced Akt phosphorylation in knee OA FLSs, in line with addition of LY294002 along with IL-1β and CLU. These findings suggest that CLU may have potential as a novel therapeutic target for synovitis and cartilage destruction in knee OA.

Bromelain Extract Exerts Antiarthritic Effects via Chondroprotection and the Suppression of TNF-α-Induced NF-κB and MAPK Signaling

Bromelain, a mixture of proteases in pineapple rhizome, has beneficial biological properties. Following absorption, the compound remains biologically active in mammalian blood and tissues. Bromelain has multiple clinical and therapeutic applications because of its anti-arthritic activities. Anti-inflammation is one of the putative therapeutic effects of bromelain on osteoarthritis (OA) and rheumatoid arthritis (RA), but the molecular mechanisms in cartilage and synovial fibroblast has not been reported. Thus, in this study, interleukin (IL)-1β/oncostatin M-induced porcine cartilage and TNF-α-induced synovial fibroblast were used as the inflamed OA and RA models, respectively. The results demonstrated the chondroprotective effects of bromelain on cartilage degradation and the downregulation of inflammatory cytokine (tumor necrosis factor (TNF)-α, IL-1β, IL-6, IL-8) expression in TNF-α-induced synovial fibroblasts by suppressing NF-κB and MAPK signaling. The evidence from this study supported and explained the anti-inflammatory and analgesic effects of bromelain on arthritis in animal models and clinical studies.

Anti-inflammatory activity of Jatropha curcas L. in brain glial cells primary cultures

ETHNOPHARMACOLOGICAL RELEVANCE

Jatropha curcas L. (Euphorbiaceae), a medicinal plant known in Brazil as "Pinhão Manso", is highly adaptable, being cultivated in different tropical and subtropical regions of the world. Antimicrobial, antioxidant and antiinflammatory activities have been attributed to different parts of the plant. In the central nervous sytem (CNS), neuroinflammation is mediated by glial cells, mainly by astrocytes and microglia, a process that plays an important role in neurodegenerative diseases and other CNS disorders. In this study, we investigated the anti-inflammatory activity of the methanolic extract obtained from the leaves of J. curcas L. (MEJc) in primary cultures of glial cells submited to inflammatory stimulus.

MATERIALS AND METHODS

Primary cultures of glial cells obtained from the cerebral cortex of neonate Wistar rats were treated with MEJc (0.1-50,000 μg mL^-1) and its fractions (F_nJc) (0.1 μg mL^-1) with or without lipopolysaccharide of Escherichia coli (LPS) (1 μg mL^-1). Cell viability was determined with MTT test. Modifications in glial cell morphology were investigated by means of phase contrast microscopy and May-Grünwald staining. The reactivity of astrocytes and microglia were investigated with immunocytochemistry for GFAP, Iba1 and transcription factor NF-kB, as well as with Greiss reaction to determine the nitric oxide (NO) production.

RESULTS

MEJc at 0.1-1000 μg mL^-1 was non-toxic to glial cells and the DE₅₀ was 10.794 μg mL^-1. The treatment with LPS induced the activation of astrocytes and microglia marked by morphological modifications and changes in the expression of GFAP and Iba1, as well as the increase in NF-kB expression and NO production. Treatment with MEJc inhibited the morphological modifications, changes in GFAP and Iba1 expression, and the increase in NF-kB and NO production induced by LPS.

CONCLUSION

This study demonstrates that the MEJc and its fractions modulate inflammatory response of astrocytes and microglia to LPS and may be considered as a potential therapeutic strategy for neuroinflammation-related diseases.

Mango ginger (curcuma amada) inhibits collagen-induced arthritis by modulating inflammatory cytokine levels in rats

Background/aim

Mango ginger (MG: curcuma amada) has antioxidant and antiinflammatory activities. The aim was to evaluate the antiarthritic potential efficacy of MG on collagen-induced arthritis.

Materials and methods

Twenty-one female Wistar-albino rats were divided into three groups. Arthritis was induced by intradermal injections of type II collagen and Freund’s adjuvant. MG extract was orally administered starting from the first collagen injection. TNF-α, IL-6, IL-17, obestatin, sclerostin, and DKK-1 serum levels were determined, and perisynovial inflammation and cartilage-bone destruction in the paws were histologically evaluated. Moreover, joint tissue TNF-α, IL-17, NF-κB, and COX-2 levels were analyzed.

Results

TNF-α, IL-17, IL-6, and DKK-1 serum levels were increased, and obestatin and sclerostin serum levels were decreased in the arthritis group compared to the control group. However, MG supplements decreased TNF-α, IL-17, IL-6, and DKK-1 serum levels and increased obestatin and sclerostin serum levels. Similarly, while collagen injection increased tissue TNF-α, IL-17, NF-κB, and COX-2 levels, MG decreased TNF-α, IL-17, and NF-κB levels. Moreover, MG ameliorated perisynovial inflammation and cartilage-bone destruction in the paws.

Conclusion

MG ameliorates arthritis via actions on inflammatory ways and wingless (Wnt) signaling pathway. These results suggest that MG may have a considerable potential efficacy for the treatment of rheumatoid arthritis.

NF-κB signaling in rheumatoid arthritis with focus on fibroblast-like synoviocytes

The nuclear factor-κB (NF-κB) signaling pathway regulates multiple processes in innate and adaptive immune cells. This pathway is involved in inflammation through the regulation of cytokines, chemokines, and adhesion molecules expression. The NF-κB transcription factor also participates in the survival, proliferation, and differentiation of cells. Therefore, deregulated NF-κB activation contributes to the pathogenesis of inflammatory diseases. Rheumatoid arthritis (RA) is classified as a heterogeneous and complex autoimmune inflammatory disease. Although different immune and non-immune cells contribute to the RA pathogenesis, fibroblast-like synoviocytes (FLSs) play a crucial role in disease progression. These cells are altered during the disease and produce inflammatory mediators, including inflammatory cytokines and matrix metalloproteinases, which result in joint and cartilage erosion. Among different cell signaling pathways, it seems that deregulated NF-κB activation is associated with the inflammatory picture of RA. NF-κB activation can also promote the proliferation of RA-FLSs as well as the inhibition of FLS apoptosis that results in hyperplasia in RA synovium. In this review, the role of NF-κB transcription factor in immune and non-immune cells (especially FLSs) that are involved in RA pathogenesis are discussed.

The Role of HMGB1, a Nuclear Damage-Associated Molecular Pattern Molecule, in the Pathogenesis of Lung Diseases

Significance: High-mobility group protein box 1 (HMGB1), a ubiquitous nuclear protein, regulates chromatin structure and modulates the expression of many genes involved in the pathogenesis of lung cancer and many other lung diseases, including those that regulate cell cycle control, cell death, and DNA replication and repair. Extracellular HMGB1, whether passively released or actively secreted, is a danger signal that elicits proinflammatory responses, impairs macrophage phagocytosis and efferocytosis, and alters vascular remodeling. This can result in excessive pulmonary inflammation and compromised host defense against lung infections, causing a deleterious feedback cycle. Recent Advances: HMGB1 has been identified as a biomarker and mediator of the pathogenesis of numerous lung disorders. In addition, post-translational modifications of HMGB1, including acetylation, phosphorylation, and oxidation, have been postulated to affect its localization and physiological and pathophysiological effects, such as the initiation and progression of lung diseases. Critical Issues: The molecular mechanisms underlying how HMGB1 drives the pathogenesis of different lung diseases and novel therapeutic approaches targeting HMGB1 remain to be elucidated. Future Directions: Additional research is needed to identify the roles and functions of modified HMGB1 produced by different post-translational modifications and their significance in the pathogenesis of lung diseases. Such studies will provide information for novel approaches targeting HMGB1 as a treatment for lung diseases.

IKKβ regulates the expression of coagulation and fibrinolysis factors through the NF-κB canonical pathway in LPS-stimulated alveolar epithelial cells type II

Aim: Hypercoagulation and fibrinolysis inhibition in the alveolar cavity are important characteristics in acute respiratory distress syndrome (ARDS). Alveolar epithelial cells type II (AEC II) have been confirmed to have significant role in regulating alveolar hypercoagulation and fibrinolysis inhibition, but the mechanism is unknown. Nuclear factor-κB (NF-κB) signaling pathway has been demonstrated to participate in the pathogenesis of these two abnormalities in ARDS. The purpose of the present study is to explore whether controlling the upstream crucial factor IκB kinase (IKK)β could regulate coagulation and fibrinolysis factors in LPS-stimulated AEC II. Materials and methods: An IKKβ gene regulation model (IKKβ^+/+ and IKKβ^−/−) was prepared using lentiviral vector transfection. The models with wild type cells were all stimulated by lipopolysaccharide (LPS) or saline for 24 h. Expression of the related proteins were determined by western-blotting, ELISA and revere transcription-PCR respectively. Tissue factor (TF) procoagulant activity and nuclear p65 protein level were also detected. Results: IKKβ increased in IKKβ^+/+ cells but decreased in IKKβ^−/− cells. LPS stimulation promoted the expression of p-IκBα, p65, p-p65 and p-IKKβ as well as TF and plasminogen activator inhibitor (PAI)-1, at the mRNA or protein level, and this was significantly enhanced by IKKβ upregulation but weakened by IKKβ downregulation. TF procoagulant activity presented the same changes as the molecules above. ELISAs showed additional increases in the concentrations of as thrombin antithrombin, procollagen III propeptide, thrombomodulin and PAI-1 in IKKβ^+/+ cell supernatant under LPS stimulation, however they decreased in IKKβ^−/−. The level of as antithrombin III however, appeared to show the opposite change to those other factors. Immunofluorescence demonstrated a greatly enhanced expression of p65 in the nucleus by IKKβ upregulation, which was reduced by IKKβ downregulation. Conclusions: IKKβ could regulate the expression and secretion of coagulation and fibrinolysis factors in LPS-stimulated AEC II via the NF-κB p65 signaling pathway. The IKKβ molecule is expected to be a new target for prevention of coagulation and fibrinolysis abnormalities in ARDS.

Sonic Hedgehog Signaling Pathway Mediates Proliferation and Migration of Fibroblast-Like Synoviocytes in Rheumatoid Arthritis via MAPK/ERK Signaling Pathway

Fibroblast-like synoviocytes (FLSs) are the major effector cells that lead to rheumatoid arthritis (RA) synovitis and joint destruction. Our previous studies showed that Sonic Hedgehog (SHH) signaling pathway is involved in aberrant activation of RA-FLSs and inhibition of SHH pathway decreases proliferation and migration of RA-FLSs. The objective of this study was to investigate if the SHH pathway mediates proliferation and migration of RA-FLSs via the mitogen-activated protein kinases/extracellular signal-regulated kinases (MAPK/ERK) signaling pathway. SHH signaling was studied by using SHH agonist (Purmorphamine) and antagonist (Cyclopamine) targeting the Smoothened (SMO) in FLSs. U0126-EtOH was used to inhibit the MAPK/ERK signaling pathway. The phosphorylation of ERK 1/2 (p-ERKl/2) was examined by western blot. Cell viability was detected using cell proliferation and cytotoxicity kit-8 (CCK8), and cell cycle distribution and proliferating cells were evaluated by the flow cytometry. Cell migration was examined by Transwell assay. Results showed that, compared with the control group, Purmorphamine increased the levels of p-ERK1/2 in concentration-and time-dependent manners (P < 0.01). Co-treated with Purmorphamine and U0126-EtOH or Cyclopamine both decreased the levels of p-ERK1/2 (P < 0.05). RA-FLSs treated with Purmorphamine resulted in alteration of cell cycle distribution, increasing of proliferating cells, cell viability, and migration cells compared to controls (P < 0.01). However, the above phenomenon can be abolished by U0126-EtOH (P < 0.05). The findings suggest that SHH signaling pathway mediates proliferation and migration of RA-FLSs via MAPK/ERK pathway and may contribute to progression of RA. Targeting SHH signaling may have a therapeutic potential in patients with RA.

Mechanical stress protects against osteoarthritis via regulation of the AMPK/NF-κB signaling pathway

Mechanical stress plays a key role in regulating cartilage degradation in osteoarthritis (OA). The aim of this study was to evaluate the effects and mechanisms of mechanical stress on articular cartilage. A total of 80 male Sprague‐Dawley rats were randomly divided into eight groups (n = 10 for each group): control group (CG), OA group (OAG), and CG or OAG subjected to low‐, moderate‐, or high‐intensity treadmill exercise (CL, CM, CH, OAL, OAM, and OAH, respectively). Chondrocytes were obtained from the knee joints of rats; they were cultured on Bioflex 6‐well culture plates and subjected to different durations of cyclic tensile strain (CTS) with or without exposure to interleukin‐1β (IL‐1β). The results of the histological score, immunohistochemistry, enzyme‐linked immunosorbent assay, and western‐blot analyses indicated that there were no differences between CM and CG, but OAM showed therapeutic effects compared with OAG. However, CH and OAH experienced more cartilage damage than CG and OAG, respectively. CTS had no therapeutic effects on collagen II of normal chondrocytes, which is consistent with findings after treadmill exercise. However, CTS for 4 hr could alleviate the chondrocyte damage induced by IL‐1β by activating AMP‐activated protein kinase (AMPK) phosphorylation and suppressing nuclear translocation of nuclear factor (NF)‐κB p65. Our findings indicate that mechanical stress had no therapeutic effects on normal articular cartilage and chondrocytes; mechanical stress only caused damage with excessive stimulation. Still, moderate biomechanical stress could reduce sensitization to the inflammatory response of articular cartilage and chondrocytes through the AMPK/NF‐κB signaling pathway.

CYLD suppression enhances the pro-inflammatory effects and hyperproliferation of rheumatoid arthritis fibroblast-like synoviocytes by enhancing NF-κB activation

Background

Rheumatoid arthritis fibroblast-like synoviocytes (RA-FLSs) actively drive joint inflammation and degradation by producing inflammatory cytokines and matrix-degrading molecules, making them key factors in the pathogenesis of RA. Cylindromatosis (CYLD) is a tumor suppressor that downregulates nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation by deubiquitinating NF-κB essential modulator and tumor necrosis factor receptor-associated factors 2 and 6. In this study, we aimed to determine CYLD expression in the synovium of patients with RA, analyze its correlation with NF-κB activation and clinical disease activity, further investigate CYLD expression in RA-FLSs, and explore CYLD’s roles and mechanisms in the pro-inflammatory effects, proliferation, apoptosis, and cell cycles of RA-FLSs.

Methods

We obtained synovia from 50 patients with active RA and 20 with osteoarthritis (OA) and then cultured FLSs from the samples. We determined CYLD expression in the synovia of RA patients and in FLSs via reverse transcription polymerase chain reaction (RT-PCR). CYLD was depleted by lentiviral CYLD short hairpin ribonucleic acid. We used RT-PCR and enzyme-linked immunosorbent assay to analyze the expression of pro-inflammatory cytokines, matrix metalloproteinases (MMPs), and receptor activator of nuclear factor kappa-B ligand (RANKL). We detected cell proliferation using Cell Counting Kit-8 and examined cell apoptosis and cell cycle using flow cytometry.

Results

We obtained the following results:

In synovia from patients with RA, CYLD expression was significantly downregulated while NF-κB expression was distinctly upregulated, compared with synovia from patients with OA. Thus, there is a significant inverse correlation between CYLD and NF-κB in synovia affected by RA.

CYLD expression significantly decreased in RA-FLSs compared with OA-FLSs.

CYLD suppression enhanced the production of pro-inflammatory cytokines, MMPs, and RANKL by activating NF-κB in RA-FLSs.

CYLD suppression enhanced proliferation, reduced apoptosis, and increased cell division of RA-FLSs and aggravated the activity of NF-κB in RA-FLSs.

Conclusions

Via its regulation of NF-κB activation, CYLD may be involved in the pathogenesis of synovial inflammation in RA as well as in the pro-inflammatory effects and hyperproliferation of RA-FLSs. CYLD may therefore provide a potential target for the treatment of RA.

The p55TNFR-IKK2-Ripk3 axis orchestrates arthritis by regulating death and inflammatory pathways in synovial fibroblasts

NFκB activation and regulated cell death are important in tissue homeostasis, inflammation and pathogenesis. Here we show the role of the p55TNFR–IKK2l–Ripk3 axis in the regulation of synovial fibroblast homeostasis and pathogenesis in TNF-mediated mouse models of arthritis. Mesenchymal-specific p55TNFR triggering is indispensable for arthritis in acute and chronic TNF-dependent models. IKK2 in joint mesenchymal cells is necessary for the development of cartilage destruction and bone erosion; however, in its absence synovitis still develops. IKK2 deletion affects arthritic and antiapoptotic gene expression leading to hypersensitization of synovial fibroblasts to TNF/Ripk1-mediated death via district mechanisms, depending on acute or chronic TNF signals. Moreover, Ripk3 is dispensable for TNF-mediated arthritis, yet it is required for synovitis in mice with mesenchymal-specific IKK2 deletion. These results demonstrate that p55TNFR–IKK2–Ripk3 signalling orchestrates arthritogenic and death responses in synovial fibroblasts, suggesting that therapeutic manipulation of this pathway in arthritis may require combinatorial blockade of both IKK2 and Ripk3 signals.

TNF is a major therapeutic target for rheumatoid arthritis (RA) and synovial fibroblasts are central to the pathogenesis of RA. Here the authors dissect TNF-induced death and activation signalling in RA synovial fibroblasts and TNF-driven arthritis and indicate that a successful therapeutic strategy might be to target both IKK2 and RIPK3 at the same time.

[Interleukin?22 promotes proliferation of fibroblast?like synoviocytes from patients with rheumatoid arthritis by inducing STAT3 phosphorylation]

OBJECTIVE

To clarify the mechanism by which interleukin?22 (IL?22) promotes the proliferation of fibroblast?like synoviocytes (FLS) from patients with rheumatoid arthritis (RA).

METHODS

FLS were isolated from the synovial tissues of patients with RA and identified by immunohistochemistry for vimentin/CD68. The cells were subcultured and incubated with different concentrations of IL?22 for 24, 48, or 72 h, and their proliferation was examined using MTT assay. After treatment of the cells with IL?22 and AG490, alone or in combination, the expressions of the total and phosphorylated proteins of STAT3, ERK1/2 and P38 were detected with Western blotting.

RESULTS

IL?22 significantly increased the proliferation of FLS in a dose?dependent manner (P<0.05). The total protein of STAT3 in the cells showed no significant changes with extended time of IL?22 treatment (P=0.68), but the expression of phosphorylated STAT3 protein increased significantly (P<0.001). The total and phosphorylated proteins of ERK1/2 and P38 underwent no significant changes after IL?22 treatment (P>0.05). A combined treatment with 50 ng/mL IL?22 and 100 µmol/L AG490 resulted in a significant decrease in the proliferation of FLS as compared with IL?22 treatment alone (P<0.01).

CONCLUSION

IL?22 can dose?dependently promote the proliferation of FLS from patients with RA by inducing phosphorylation of STAT3 protein but not through ERK1/2 or P38 signal pathway.

Inhibitory Effect of Low-Intensity Pulsed Ultrasound on the Expression of Lipopolysaccharide-Induced Inflammatory Factors in U937 Cells

OBJECTIVES

Low-intensity pulsed ultrasound (US) has been reported to promote periodontal tissue regeneration and reduce inflammation in soft tissues and in bone infectious diseases. Here we investigated the effect of low-intensity pulsed US on the expression of lipopolysaccharide (LPS)-induced inflammatory factors in U937 macrophage cells.

METHODS

U937 cells were stimulated with different concentrations of LPS and exposed to different intensities of low-intensity pulsed US. Cell viability and apoptosis of U937 cells were determined by cell-counting kit assays and flow cytometry. A real-time polymerase chain reaction and an enzyme-linked immunosorbent assay were used to test the expression of inflammatory factors. The expression levels of toll-like receptor 4, p65, p-IκBα, and IκBα were assessed by western blots.

RESULTS

Tumor necrosis factor α began to increase in U937 cells on induction with 1-μg/mL LPS. Low-intensity pulsed US at the intensity of 60 mW/cm² was more effective in reducing interleukin 8 (IL-8) expression. Furthermore, LPS inhibited the viability and increased apoptosis of U937 cells, whereas low-intensity pulsed US significantly reversed these effects (P < .05). Low-intensity pulsed US reduced the protein expression of IL-6 and IL-8 at both gene and protein levels in U937 cells. The western blot and immunofluorescence showed that low-intensity pulsed US primarily suppressed the degradation and phosphorylation of IκBα and the translocation of p65 into the nuclei.

CONCLUSIONS

Low-intensity pulsed US alleviated the expression of inflammatory factors induced by LPS in U937 cells. This process was modulated by suppressing the toll-like receptor 4-nuclear factor κB signaling pathway. Therefore, low-intensity pulsed US might be a potential immunomodulatory therapy for the treatment of periodontitis.

CDK7 inhibition suppresses rheumatoid arthritis inflammation via blockage of NF-κB activation and IL-1β/IL-6 secretion

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by joint swelling, joint tenderness and destruction of synovial joints, leading to severe disability. Anti‐inflammatory drugs and disease‐modifying anti‐rheumatic drugs (DMARDs) may improve RA process. However, in most patients the treatment effect is still not satisfactory. Cyclin‐dependent kinase 7 (CDK7) plays a well‐established role in the regulation of the eukaryotic cell division cycle, and recent studies indicated that it exerted anti‐inflammatory effect. In our previous research, we found that inhibition of CDK7 by highly selective inhibitor BS‐181 significantly impeded the development of collagen‐induced arthritis (CIA) mice. However, the underlying mechanism of CDK7 in RA remains to be explored. We elucidated the molecular mechanism of CDK7 inhibition in RA inflammation by administration of CDK7 highly selective inhibitor BS‐181 and siRNA‐CDK7. We found that both IL‐1β, IL‐6, IL‐8 and RANKL transcript levels and IL‐1β/IL‐6 secretion were effectively suppressed by BS‐181 treatment as well as CDK7 knockdown. Furthermore, CDK7 inhibition prevented NF‐κB signalling pathway activation and restrained p65 nuclear translocation. Moreover, CDK7 selective inhibitor BS‐181 also blocked phosphorylation of p65 in MH7A cells. These results strongly indicate that CDK7 inhibition by BS‐181 and siRNA‐CDK7 significantly suppresses rheumatoid arthritis inflammation, which may be via blockage of NF‐κB signalling pathway and IL‐1β/IL‐6 secretion.

Selective regulation of IKKβ/NF-κB pathway involved in proliferation inhibition of HFLS-RA cells induced by 1,7-dihydroxyl-3,4-dimethoxylxanthone

Rheumatoid arthritis is a common autoimmune disease, however, available regimes exert little influence on it's long-term prognosis. The aim of the current study is to investigate potential effects of 1,7-dihydroxyl-3,4-dimethoxyl-xanthone (XAN) in HFLS-RA cells and describe the underlying mechanisms of induction of NF-κB activity. Viability of cells was measured by MTT assay. Flow cytometry was employed to assess the pro-apoptotic effects. Modulation on NF-κB signaling was investigated by RT-qPCR, Western-blot and immunofluorescence methods. It was found that XAN induced proliferation inhibition and apoptosis of HFLS-RA cells in the concentration-dependent manner, which were strengthened by pyrrolidinedithiocarbamic acid but antagonized by IKK16. NF-κB signaling was abrogated shortly after the treatment of XAN via various means including mRNA expression, phosphorylation and nuclear translocation, which leaded to up-regulation of p38 and down-regulation of X-linked inhibitor of apoptosis protein. Simultaneous suppressions on p-IKKβ, p-IκB and p-p65 suggested the regulation on NF-κB was IKKβ mediated. Meanwhile, XAN promoted the expression of IKKα, which has a possible connection to pro-apoptotic effects suggested by the up-regulated cleaved PARP. These findings indicated IKKβ/NF-κB mediates the proliferation of HFLS-RA cells inhibited by XAN, and divergent regulations on IKKs could provide synergic effects on the cells' proliferation.

The effects of different frequency treadmill exercise on lipoxin A4 and articular cartilage degeneration in an experimental model of monosodium iodoacetate-induced osteoarthritis in rats

The aim was to investigate the effects of different frequencies treadmill exercise with total exercise time being constancy on articular cartilage, lipoxin A₄ (LXA₄) and the NF-κB pathway in rat model of monosodium iodoacetate-induced osteoarthritis (OA). Fifty male Sprague-Dawley rats were randomly divided into five groups (n = 10): controls (CG), knee OA model (OAG), OA + treadmill exercise once daily (OAE1), OA + treadmill exercise twice daily, rest interval between exercise>4h (OAE2) and OA + treadmill exercise three times daily, rest interval between exercise>4h (OAE3). Rats were evaluated after completing the treadmill exercise program (speed, 18 m/min; total exercise time 60 min/day; 5 days/week for 8 weeks). Interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and LXA₄ in serum and intra-articular lavage fluid were measured by ELISA. Changes in articular cartilage were evaluated by histology, immunohistochemistry, western blotting and quantitative real-time-PCR. LXA₄ in the serum and intra-articular lavage fluid increased in all OAE groups, and histological evaluation indicated that the OAE3 group had the best treatment response. The expression of COL2A1 and IκB-β in articular cartilage increased in all OAE groups vs the OAG group, whereas expression of IL-1β, TNF-α, matrix metalloproteinase (MMP)-13, and NF-κB p65 was reduced in all OAE groups compared with the OAG. Under the condition of 60 min treadmill exercise with moderate-intensity, to fulfill in three times would have better chondroprotective effects than to fulfill in two or one time on monosodium iodoacetate-induced OA in rats. And it may be worked through the anti-inflammatory activity of LXA₄ and the NF-κB pathway.

2-Hydroxyeupatolide attenuates inflammatory responses via the inhibiting of NF-κB signaling pathways

2-Hydroxyeupatolide (2-HE), a sesquiterpene lactone, is a potential agent to improve LPS-induced acute mouse inflammation damage.

An update on dietary phenolic compounds in the prevention and management of rheumatoid arthritis

Certain nutritional components influence the cellular metabolism and interfere in the pathological inflammatory process, so that they may act as a coadjuvant in the treatment of many chronic inflammatory diseases, including rheumatoid arthritis (RA).

Novel Lys63-linked ubiquitination of IKKβ induces STAT3 signaling

NFκB signaling plays a significant role in human disease, including breast and ovarian carcinoma, insulin resistance, embryonic lethality and liver degeneration, rheumatoid arthritis, aging and Multiple Myeloma (MM). Inhibitor of κB (IκB) kinase β (IKKβ) regulates canonical Nuclear Factor κB (NFκB) signaling in response to inflammation and cellular stresses. NFκB activation requires Lys63-linked (K63-linked) ubiquitination of upstream proteins such as NEMO or TAK1, forming molecular complexes with membrane-bound receptors. We demonstrate that IKKβ itself undergoes K63-linked ubiquitination. Mutations in IKKβ at Lys171, identified in Multiple Myeloma and other cancers, lead to a dramatic increase in kinase activation and K63-linked ubiquitination. These mutations also result in persistent activation of STAT3 signaling. Liquid chromatography (LC)-high mass accuracy tandem mass spectrometry (MS/MS) analysis identified Lys147, Lys418, Lys555 and Lys703 as predominant ubiquitination sites in IKKβ. Specific inhibition of the UBC13-UEV1A complex responsible for K63-linked ubiquitination establishes Lys147 as the predominant site of K63-ubiquitin conjugation and responsible for STAT3 activation. Thus, IKKβ activation leads to ubiquitination within the kinase domain and assemblage of a K63-ubiquitin conjugated signaling platform. These results are discussed with respect to the importance of upregulated NFκB signaling known to occur frequently in MM and other cancers.

EGR-1 and DUSP-1 are important negative regulators of pro-allergic responses in airway epithelium

BACKGROUND

Primary nasal epithelium of house dust mite allergic individuals is in a permanently activated inflammatory transcriptional state.

OBJECTIVE

To investigate whether a deregulated expression of EGR-1 and/or DUSP-1, two potential negative regulators of pro-inflammatory responses, could contribute to the activation of the inflammatory state.

METHODS

We silenced the expression of EGR-1 or DUSP-1 in the airway epithelial cell line NCI-H292. The cell lines were stimulated in a 24-h time course with the house dust mite allergen or poly(I:C). RNA expression profiles of cytokines were established using q-PCR and protein levels were determined in supernatants with ELISA.

RESULTS

The shRNA-mediated gene silencing reduced expression levels of EGR-1 by 92% (p<0.0001) and of DUSP-1 by 76% (p<0.0001). Both mutant cells lines showed an increased and prolonged response to the HDM allergen. The mRNA induction of IL-6 was 4.6 fold (p=0.02) and 2.4 fold higher (p=0.01) in the EGR-1 and DUSP-1 knock-down, respectively when compared to the induced levels in the control cell line. For IL-8, the induction levels were 4.6 fold (p=0.01) and 13.0 (p=0.001) fold higher. The outcome was largely similar, yet not identical at the secreted protein levels. Furthermore, steroids were able to suppress the poly(I:C) induced cytokine levels by 70-95%.

CONCLUSIONS

Deregulation of EGR-1 and/or DUSP-1 in nasal epithelium could be responsible for the prolonged activated transcriptional state observed in vivo in allergic disease. This could have clinical consequences as cytokine levels after the steroid treatment in EGR-1 or DUSP-1 knock-down remained higher than in the control cell line.

Lunasin inhibits cell proliferation via apoptosis and reduces the production of proinflammatory cytokines in cultured rheumatoid arthritis synovial fibroblasts

Lunasin, a peptide with 43 amino acid residues and initially isolated and identified in soybean cotyledon, has gained extensive attention due to its anti-inflammatory and anticancer properties. However, its treatment efficacy on rheumatoid arthritis (RA) and corresponding mechanisms have not been reported. Herein, the synovial fibroblasts harvested and isolated from patients with RA were treated with lunasin at various concentrations to examine the proliferation, apoptosis status, and corresponding cell cycle of cultured RA synovial fibroblasts. Meanwhile, the underlying mechanisms of lunasin for RA treatment are explored through Western blot, real-time PCR, ELISA, and luciferase reporter assays. Lunasin significantly inhibited the proliferation and induced the apoptosis of cultured RA synovial fibroblasts. In addition, lunasin reduced the production of interleukin-6 (IL-6), IL-8, and matrix metalloproteinase-3 (MMP-3) and suppressed the activation of NF-κB in cultured RA synovial fibroblasts but did not reveal obvious modulation on the secretion and gene expression of MMP-1. Therefore, lunasin will have promising potential as a novel nutritional supplement or drug candidate for RA due to its potency of suppressing synovial cell proliferation and decreasing the production of proinflammatory cytokines and MMPs in synovial cells.

Down-regulating peroxisome proliferator-activated receptor-gamma coactivator-1 beta alleviates the proinflammatory effect of rheumatoid arthritis fibroblast-like synoviocytes through inhibiting extracellular signal-regulated kinase, p38 and nuclear factor-kappaB activation

Introduction

Rheumatoid arthritis (RA) is a chronic inflammatory disease leading to joint destruction and disability. Peroxisome proliferator-activated receptor-gamma coactivator-1beta (PGC-1β) is a transcriptional coactivator that plays important roles in regulating multiple aspects of energy metabolism and cytokine signaling pathways. PGC-1β overexpression leads to the attenuation of macrophage-mediated inflammation. In this study, we aimed to determine the expression of PGC-1β in RA synovium and fibroblast-like synoviocytes (FLS), and explore the mechanisms of PGC-1β on both the proinflammatory effects and apoptosis in RA-FLS.

Methods

Synovium was obtained from 31 patients with active RA, as well as 13 osteoarthritis (OA) and 10 orthopedic arthropathies (Orth.A) as “less inflamed” disease controls. FLS were then isolated and cultured. Synovial PGC-1β expression was determined by immunohistochemistry staining, while FLS PGC-1β expression was detected by immunofluorescence staining, quantitative real-time PCR (qPCR) assay and western blot. PGC-1β was depleted by lentivirus sh-RNA, and up-regulated by pcDNA3.1- PGC-1β. The expression of proinflammatory cytokines, matrix metalloproteinases and receptor activator of nuclear factor-kappaB ligand was analyzed by qPCR, cytometric bead array and western blot. The expression of mitogen-activated protein kinases and nuclear factor-kappaB (NF-κB) was determined by qPCR and western blot. Besides, cell apoptosis was examined using flow cytometry. The interaction between PGC-1β and NF-κB was performed by dual-luciferase reporter gene assays.

Results

(A) Synovial PGC-1β was over-expressed in RA patients compared with OA or Orth.A patients. (B) PGC-1β expression significantly increased in RA-FLS compared with OA-FLS. (C) PGC-1β mediated the expression of proinflammatory cytokines and apoptosis through extracellular signal-regulated kinase (ERK), p38 and NF-κB in RA-FLS. (D) PGC-1β mediated NF-κB transcription in RA-FLS, but did not affect ERK and p38.

Conclusion

The results indicate that PGC-1β may play important roles in the proinflammatory effects and apoptosis of RA-FLS.

Inhibiting IκB kinase-β downregulates inflammatory cytokines in injured discs and neuropeptides in dorsal root ganglia innervating injured discs in rats

STUDY DESIGN

Quantitative and immunohistological analysis of the efficacy of an IκB kinase-β (IKKβ) inhibitor in an injured intervertebral disc (IVD) model.

OBJECTIVE

To elucidate the efficacy of an IKKβ inhibitor on inflammatory cytokine levels in injured IVDs or on neuropeptide levels in the dorsal root ganglia (DRG) neurons innervating injured IVDs in rats.

SUMMARY OF BACKGROUND DATA

Multiple studies have suggested that upregulation of inflammatory cytokines in damaged IVDs causes discogenic low back pain. The efficacy of blocking individual inflammatory cytokines is limited; however, inflammatory cytokine stimuli often require IKKβ to activate nuclear factor-k B.

METHODS

Sprague-Dawley rats were divided into 3 groups: sham, saline (disc-injury plus saline), and IKKβ (disc-injury plus anti-IKKβ). To induce injury, IVDs were repeatedly punctured.Experiment 1: Four, 7, and 14 days postinjury, coccygeal (Co) 5/6, Co6/7, and Co7/8 IVDs were resected and tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 levels were quantified by enzyme-linked immunosorbent assay. Experiment 2: The neurotracer Fluoro-Gold was injected into injured L5-L6 IVDs and uninjured sham group IVDs to detect DRG neurons. One week postsurgery, L1-L6 DRGs were immunolabeled with the neuropeptide calcitonin gene-related peptide. The proportions of Fluoro-Gold-labeled calcitonin gene-related peptide-immunoreactive DRG neurons were assessed.

RESULTS

Experiment 1: IVD levels of tumor necrosis factor-α (through 2 wk), IL-1β (at 4 d), and IL-6 (at 4 d) were significantly higher in the saline group than in the sham group, and significantly lower in the IKKβ group than in the saline group (P < 0.05). Experiment 2: The percentage of calcitonin gene-related peptide-immunoreactive Fluoro-Gold-labeled DRG neurons was significantly higher in the saline group than in the sham group, and significantly lower in the IKKβ group than in the saline group (P < 0.05).

CONCLUSION

Injury-induced upregulation of inflammatory cytokines within IVDs and increased levels of neuropeptides within DRG neurons can be suppressed by inhibiting IKKβ.

LEVEL OF EVIDENCE

N/A.

Lead Screening for Chronic Obstructive Pulmonary Disease of IKK2 Inhibited by Traditional Chinese Medicine

Chronic obstructive pulmonary disease (COPD) is a chronic obstructive lung disease and is frequently found in well-developed countries due to the issue of aging populations. Not all forms of medical treatment are unable to return a patient's limited pulmonary function back to normal and eventually they could require a lung transplant. At this time, COPD is the leading cause of death in the world. Studies surveying I-kappa-B-kinase beta (IKK2) are very relevant to the occurrence and deterioration of the condition COPD. The sinapic acid-4-O-sulfate, kaempferol, and alpha-terpineol were found to be IKK2 inhibitors and helped prevent COPD occurrence and worsening according to a screening of the traditional Chinese medicine (TCM) database. The protein-ligand interaction of these three compounds with regard to IKK2 was also done by molecular dynamics. The docking poses, hydrogen bond variation, and hydrophobic interactions found Asp103 and Lys106 are crucial to IKK2 binding areas for IKK2 inhibition. Finally, we found the three compounds that have an equally strong effect in terms of IKK2 binding proven by the TCM database and perhaps these may be an alternative treatment for COPD in the future.

In vivo luminescence imaging of NF-κB activity and serum cytokine levels predict pain sensitivities in a rodent model of osteoarthritis

OBJECTIVE

To investigate the relationship between NF-κB activity, cytokine levels, and pain sensitivities in a rodent model of osteoarthritis (OA).

METHODS

OA was induced in transgenic NF-κB-luciferase reporter mice via intraarticular injection of monosodium iodoacetate (MIA). Using luminescence imaging we evaluated the temporal kinetics of NF-κB activity and its relationship to the development of pain sensitivities and serum cytokine levels in this model.

RESULTS

MIA induced a transient increase in joint-related NF-κB activity at early time points (day 3 after injection) and an associated biphasic pain response (mechanical allodynia). NF-κB activity, serum interleukin-6 (IL-6), IL-1β, and IL-10 levels accounted for ∼75% of the variability in pain-related mechanical sensitivities in this model. Specifically, NF-κB activity was strongly correlated with mechanical allodynia and serum IL-6 levels in the inflammatory pain phase of this model (day 3), while serum IL-1β was strongly correlated with pain sensitivities in the chronic pain phase of the model (day 28).

CONCLUSION

Our findings suggest that NF-κB activity, IL-6, and IL-1β may play distinct roles in pain sensitivity development in this model of arthritis and may distinguish the acute pain phase from the chronic pain phase. This study establishes luminescence imaging of NF-κB activity as a novel imaging biomarker of pain sensitivities in this model of OA.

Swertiamarin attenuates inflammation mediators via modulating NF-κB/I κB and JAK2/STAT3 transcription factors in adjuvant induced arthritis

Rheumatoid arthritis (RA) is an autoimmune and chronic inflammatory disease that leads to pannus formation followed by severe joint destruction, characterized by synovial hyperplasia, inflammation and angiogenesis. Swertiamarin is a secoiridoid glycoside that is used as an anti-inflammatory compound, mainly found in Enicostema axillare (Lam) A. Raynal, a medicinal plant used in Indian system of traditional medicine. In the present study, the effect of swertiamarin was evlauated in experimental adjuvant arthritis animal model by the estimation of biochemical (paw thickness, lysosomal enzymes, and urinary degradative products) parameters, proinflammatory cytokines and enzymes along with histopathological and radiographic observations. The proteins of phosphorylated NF-κB/IκB and JAK2/STAT3 transcription factors were also quantified from experimental animals as well as LPS induced RAW 264.7 macrophage cells. In in silico analysis, swertiamarin was docked with proinflammatory enzymes to confirm its potential. The administration of swertiamarin (2, 5, 10mg/kg bw) significantly (P⩽0.05) inhibited the levels of paw thickness, lysosomal enzymes and increased the body weight of experimental animals in a dose dependent manner. In molecular analysis, the treatment decreased the release of proinflammatory cytokines (IL1, TNF, IL-6) and proangiogenic enzymes (MMPs, iNOS, PGE2, PPARγ and COX-2); and also significantly (P⩽0.05) increased the levels of antiinflammatory proteins (IL-10, IL-4) when compared to the disease groups. The swertiamarin treatment significantly (P⩽0.05) inhibited the release of NF-κB p65, p-IκBα, p-JAK2 and p-STAT3 signaling proteins levels on both experimental animals and LPS induced cells. Histopathological and radiological analysis evidenced the curative effect of swertiamarin on bone destruction. The docking studies of swertiamarin on proinflammatory enzymes supported the results from the in vivo experiments. Thus the swertiamarin inhibited the development of arthritis by modulating NF-κB/IκB and JAK2/STAT3 signaling. These findings suggested that swertiamarin acted as an anti-rheumatic agent.

Tyrosine phosphorylation allows integration of multiple signaling inputs by IKKβ

Signaling regulated by NFκB and related transcription factors is centrally important to many inflammatory and autoimmune diseases, cancer, and stress responses. The kinase that directly regulates the canonical NFκB transcriptional pathway, Inhibitor of κB kinase β (IKKβ), undergoes activation by Ser phosphorylation mediated by NIK or TAK1 in response to inflammatory signals. Using titanium dioxide-based phosphopeptide enrichment (TiO2)-liquid chromatography (LC)-high mass accuracy tandem mass spectrometry (MS/MS), we analyzed IKKβ phosphorylation in human HEK293 cells expressing IKKβ and FGFR2, a Receptor tyrosine kinase (RTK) essential for embryonic differentiation and dysregulated in several cancers. We attained unusually high coverage of IKKβ, identifying an abundant site of Tyr phosphorylation at Tyr169 within the Activation Loop. The phosphomimic at this site confers a level of kinase activation and NFκB nuclear localization exceeding the iconic mutant S177E/S181E, demonstrating that RTK-mediated Tyr phosphorylation of IKKβ has the potential to directly regulate NFκB transcriptional activation.

Delphinidin inhibits IL-1β-induced activation of NF-κB by modulating the phosphorylation of IRAK-1(Ser376) in human articular chondrocytes

OBJECTIVE

In OA, there is enhanced expression of pro-inflammatory cytokines such as IL-1β in the affected joint. Delphinidin, an anthocyanidin found in pigmented fruits and vegetables, has been shown to possess anti-inflammatory and antioxidant properties. In the present study we determined whether delphinidin would inhibit the IL-1β-induced activation of NF-κB in human chondrocytes and determined the mechanism of its action.

METHODS

PGE2 levels and activation of NF-κB p65 in human OA chondrocytes were determined by ELISA-based assays. Protein expression of cyclo-oxygenase-2 (COX-2) and phosphorylation of kinases was determined by western immunoblotting. Expression level of mRNAs was determined by TaqMan assays.

RESULTS

Delphinidin inhibited IL-1β-induced expression of COX-2 and production of PGE2 in human chondrocytes. Delphinidin also inhibited IL-1β-mediated phosphorylation of IL-1 receptor-associated kinase-1(Ser376), phosphorylation of IKKα/β, expression of IKKβ, degradation of IκBα, and activation and nuclear translocation of NF-κB/p65. Phosphorylation of TGF-β-activated kinase 1 was not observed but NF-κB-inducing kinase (NIK) was phosphorylated and phosphorylation of NIK was blocked by delphinidin in IL-1β-treated human chondrocytes.

CONCLUSION

These data identify delphinidin as a novel inhibitor of IL-1β-induced production of cartilage-degrading molecule PGE2 via inhibition of COX-2 expression and provide new insight into the mechanism of its action. Our results also identify inhibition of IRAK1(Ser376) phosphorylation by delphinidin in IL-1β-induced activation of NF-κB in human chondrocytes. Given the important role played by IL-1β-induced NF-κB activation, COX-2 expression and PGE2 production in OA, our results may have important implications for the development of novel therapeutic strategies for the prevention/treatment of OA.

Duality of fibroblast-like synoviocytes in RA: passive responders and imprinted aggressors

Rheumatoid arthritis (RA) is characterized by hyperplastic synovial pannus tissue, which mediates destruction of cartilage and bone. Fibroblast-like synoviocytes (FLS) are a key component of this invasive synovium and have a major role in the initiation and perpetuation of destructive joint inflammation. The pathogenic potential of FLS in RA stems from their ability to express immunomodulating cytokines and mediators as well as a wide array of adhesion molecule and matrix-modelling enzymes. FLS can be viewed as 'passive responders' to the immunoreactive process in RA, their activated phenotype reflecting the proinflammatory milieu. However, FLS from patients with RA also display unique aggressive features that are autonomous and vertically transmitted, and these cells can behave as primary promoters of inflammation. The molecular bases of this 'imprinted aggressor' phenotype are being clarified through genetic and epigenetic studies. The dual behaviour of FLS in RA suggests that FLS-directed therapies could become a complementary approach to immune-directed therapies in this disease. Pathophysiological characteristics of FLS in RA, as well as progress in targeting these cells, are reviewed in this manuscript.

Molecular mechanism of the anti-inflammatory activity of a natural diarylnonanoid, malabaricone C

The spice-derived phenolic, malabaricone C (mal C), has recently been shown to accelerate healing of the indomethacin-induced gastric ulceration in mice. In this study, we explored its anti-inflammatory activity and investigated the underlying mechanism of the action. Mal C suppressed the microvascular permeability and the levels of tumor necrosis factor-α, interleukin-1β, and nitric oxide in the lipopolysaccharide (LPS)-administered mice. At a dose of 10 mg/kg, it showed anti-inflammatory activity comparable to that of omeprazole (5 mg/kg) and dexamethasone (50 mg/kg). It also reduced the expression and activities of inducible nitric oxide synthase, cyclooxygenase-2, as well as the pro- vs anti-inflammatory cytokine ratio in the LPS-treated RAW macrophages. Mal C was found to inhibit LPS-induced NF-kB activation in RAW 264.7 cells by blocking the MyD88-dependent pathway. Mal C suppressed NF-κB activation and iNOS promoter activity, which correlated with its inhibitory effect on IκB phosphorylation and degradation, and NF-κB nuclear translocation, in the LPS-stimulated macrophages. It also inhibited LPS-induced phosphorylation of p38 and JNK, which are also upstream activators of NF-κB, without affecting Akt phosphorylation. Mal C also effectively blocked the PKR-mediated activation of NF-κB. These findings indicate that mal C exerts an anti-inflammatory effect through NF-κB-responsive inflammatory gene expressions by inhibiting the p38 and JNK-dependent canonical NF-κB pathway as well as the PKR pathway, and is a potential therapeutic agent against acute inflammation.

IL-33 regulates TNF-α dependent effects in synovial fibroblasts

The recently described IL-33 acts as a pro-inflammatory cytokine, inducing the expression of multiple responses in the target cells. Although a nuclear localization of IL-33 has been described, its exact functional relevance is presently unknown. The present study was conducted to analyze the effects of IL-33 on the TNF-α induced synthesis of the pro-inflammatory mediators IL-6, IL-8, and monocyte chemotactic protein-1 (MCP-1) and the pro-destructive molecules matrix metalloproteinase-1 (MMP-1), MMP-3, and TIMP-1 of rheumatoid arthritis synovial fibroblast (RA-SFs) using RNA overexpression and silencing. TNF-α significantly induced IL-33 mRNA expression and protein synthesis in RA-SFs. TNF-α-induced IL-33 protein expression was mediated via p38 signaling. Immunohistochemistry for IL-33 clearly showed that nuclear translocation of IL-33 was induced in TNF-α stimulated RA-SFs. IL-33 overexpression enhanced TNF-α-induced pro-inflammatory and pro-destructive functions in RA-SFs. IL-33 silencing significantly downregulated TNF-α-induced pro-inflammatory functions, whereas TNF-α-induced pro-destructive functions were less influenced by IL-33 silencing. This study identifies IL-33 as a critical regulator/enhancer of TNF-α-induced functions in RA-SFs, pointing to a central role of this cytokine in the perpetuation of pro-inflammatory and pro-destructive processes in rheumatoid arthritis (RA) and other inflammatory and degenerative diseases.

Regulation of B cell activating factor (BAFF) receptor expression by NF-ΚB signaling in rheumatoid arthritis B cells

B cells play an important role in the pathogenesis of rheumatoid arthritis (RA). High levels of B cell activating factor (BAFF) are detected in autoimmune diseases. BAFF and BAFF receptor (BAFF-R) are expressed in B and T cells of RA synovium. The study was undertaken to identify the NF-ΚB signal pathway involved in the induction of BAFF-R in human B cells. Immunohistochemical staining of NF-ΚB p65, NF-ΚB p50, BAFF, and BAFF-R was performed on sections of synovium from severe and mild RA and osteoarthritis (OA) patients. Peripheral blood mononuclear cells (PBMCs) were isolated from control and RA patients and B cells were isolated from controls. BAFF-R was analyzed by flow cytometry, realtime PCR and confocal staining after treatment with NF-ΚB inhibitors. NF-ΚB p65, NF-ΚB p50, BAFF, and BAFF-R were highly expressed in severe RA synovium relative to mild RA synovium or OA synovium. BAFF-R expression was reduced by NF-ΚB inhibitors in PBMCs and B cells from normal controls. We also showed reduction in expression of BAFF-R via inhibition of the NF-ΚB pathway in PBMCs of RA patients. BAFF/BAFF-R signaling is an important mechanism of pathogenesis in RA and that BAFF-R reduction by NF-ΚB blocking therapy is another choice for controlling B cells in autoimmune diseases such as RA.

Structural studies of NF-κB signaling

NF-κBs are a family of transcription factors that control a number of essential cellular functions including immune responses, cell proliferation and antiapoptosis. NF-κB activities are tightly regulated through upstream signaling molecules and downstream feedback loops. In this review, structural discoveries in the NF-κB pathway are presented. With the structure information, the following questions may be addressed: (1) How do NF-κBs activate their target genes? (2) How do IκBs inhibit NF-κB activities in the steady state? (3) How do upstream signaling molecules activate the NF-κB pathway? and (4) How do the feedback loops shut down the NF-κB pathway to avoid constitutive NF-κB activation?

Radial shock waves effectively introduced NF-kappa B decoy into rat achilles tendon cells in vitro

The purpose of this study was to test if radial shock waves could enhance the introduction of nuclear factor-kappa B (NF-kappaB) decoy oligodeoxynucleotides, which is reported to markedly inhibit NF-kappaB activation and suppress pro-inflammatory cytokine gene expression, using rat Achilles tendon cells. In the presence of NF-kappaB decoy labeled with or without fluorescein isothiocyanate (FITC) in culture media, radial shock waves were applied to the tendon cells in variable conditions and cultivated for 24 h. The transfection rate was assessed by counting FITC-positive cells, and IL-1-induced NF-kappaB activation in the cells was assessed. Radial shock waves significantly enhanced introduction of NF-kappaB decoy-FITC into the tendon cells. IL-1-induced NF-kappaB activation was significantly inhibited by pretreatment of the cells with NF-kappaB decoy combined with radial shock wave exposure. The present study demonstrated the effectiveness of radial shock waves on introduction of NF-kappaB decoy into tendon cells. Radial shock wave treatment combined with local NF-kappaB decoy administration could be a novel therapeutic strategy for chronic tendinopathy.

Fibroblast-like synoviocytes: key effector cells in rheumatoid arthritis

Rheumatoid arthritis (RA) remains a significant unmet medical need despite significant therapeutic advances. The pathogenesis of RA is complex and includes many cell types, including T cells, B cells, and macrophages. Fibroblast-like synoviocytes (FLS) in the synovial intimal lining also play a key role by producing cytokines that perpetuate inflammation and proteases that contribute to cartilage destruction. Rheumatoid FLS develop a unique aggressive phenotype that increases invasiveness into the extracellular matrix and further exacerbates joint damage. Recent advances in understanding the biology of FLS, including their regulation regulate innate immune responses and activation of intracellular signaling mechanisms that control their behavior, provide novel insights into disease mechanisms. New agents that target FLS could potentially complement the current therapies without major deleterious effect on adaptive immune responses.