Role of MAPK kinase 6 in arthritis: distinct mechanism of action in inflammation and cytokine expression

The Challenges of Local Intra-Articular Therapy

Fibroblast-like synoviocytes (FLSs) are among the main disease-driving players in most cases of monoarthritis (MonoA), oligoarthritis, and polyarthritis. In this review, we look at the characteristics and therapeutic challenges at the onset of arthritis and during follow-up management. In some cases, these forms of arthritis develop into autoimmune polyarthritis, such as rheumatoid arthritis (RA), whereas local eradication of the RA synovium could still be combined with systemic treatment using immunosuppressive agents. Currently, the outcomes of local synovectomies are well studied; however, there is still a lack of a comprehensive analysis of current local intra-articular treatments highlighting their advantages and disadvantages. Therefore, the aim of this study is to review local intra-articular therapy strategies. According to publications from the last decade on clinical studies focused on intra-articular treatment with anti-inflammatory molecules, a range of novel slow-acting forms of steroidal drugs for the local treatment of synovitis have been investigated. As pain is an essential symptom, caused by both inflammation and cartilage damage, various molecules acting on pain receptors are being investigated in clinical trials as potential targets for local intra-articular treatment. We also overview the new targets for local treatment, including surface markers and intracellular proteins, non-coding ribonucleic acids (RNAs), etc.

Identification of circulating autoantibodies to non-modified proteins associated with ACPA status in early rheumatoid arthritis

OBJECTIVE

The objective of this study was to discover autoantibodies to non-modified proteins associated with the presence/absence of ACPAs in RA.

METHODS

The autoantibody repertoire of 80 ACPA-negative and 80 ACPA-positive RA subjects from the Swedish population-based Epidemiological Investigation of RA (EIRA) cohort was screened using a suspension bead array built on protein fragments earlier described as autoimmunity targets. Four autoantibodies positive in the initial screening were validated in another set of EIRA samples containing 317 ACPA-positive, 302 ACPA-negative and 372 age- and sex-matched controls. The relationship between the four autoantibodies and lung abnormalities on high-resolution CT (HRCT) was examined in 93 early-RA patients from the LURA cohort. Association between the autoantibodies, smoking and MHC class II alleles was assessed by logistic regression analysis.

RESULTS

Anti-ANOS1 and anti-MURC IgG levels were associated with ACPA-positive status [odds ratio (OR) = 3.02; 95% CI 1.87-4.89; and OR = 1.86; 95% CI 1.16-2.97, respectively] and increased in ACPA-positive patients compared with controls. Anti-ANOS1 IgG was associated with smoking habit (OR = 2.11; 95% CI 1.22-3.69) and anti-MURC IgG with the presence of the MHC class II 'shared-epitope' genes (OR = 1.95; 95% CI 1.11-3.46). Anti-TSPYL4 IgG was associated with being ACPA negative (OR = 0.41; 95% CI 0.19-0.89). Anti-TSPYL4 IgG and anti-MAP2K6 IgG levels were increased in the ACPA-negative patients compared with controls. Presence of anti-MAP2K6 IgG and anti-TSPYL4 IgG correlated negatively with HRCT-defined lung abnormalities.

CONCLUSION

These four autoantibodies may be useful in diagnostics and in predicting clinical phenotypes of RA.

Current status and future prospects of p38α/MAPK14 kinase and its inhibitors

P38α (which is also named MAPK14) plays a pivotal role in initiating different disease states such as inflammatory disorders, neurodegenerative diseases, cardiovascular cases, and cancer. Inhibitors of p38α can be utilized for treatment of these diseases. In this article, we reviewed the structural and biological characteristics of p38α, its relationship to the fore-mentioned disease states, as well as the recently reported inhibitors and classified them according to their chemical structures. We focused on the articles published in the literature during the last decade (2011-2020).

Non-'classical' MEKs: A review of MEK3-7 inhibitors

The MAPK pathways are an enduring area of interest due to their essential roles in cell processes. Increased expression and activity can lead to a multitude of diseases, sparking research efforts in developing inhibitors against these kinases. Though great strides have been made in developing MEK1/2 inhibitors, there is a notable lack of chemical probes for MEK3-7, given their central role in stimuli response, cell growth, and development. This review summarizes the progress that has been made on developing small molecule probes for MEK3-7, the specific disease states in which they have been studied, and their potential to become novel therapeutics.

Restoring synovial homeostasis in rheumatoid arthritis by targeting fibroblast-like synoviocytes

Rheumatoid arthritis (RA) is a chronic immune-mediated disease that primarily affects the synovium of diarthrodial joints. During the course of RA, the synovium transforms into a hyperplastic invasive tissue that causes destruction of cartilage and bone. Fibroblast-like synoviocytes (FLS), which form the lining of the joint, are epigenetically imprinted with an aggressive phenotype in RA and have an important role in these pathological processes. In addition to producing the extracellular matrix and joint lubricants, FLS in RA produce pathogenic mediators such as cytokines and proteases that contribute to disease pathogenesis and perpetuation. The development of multi-omics integrative analyses have enabled new ways to dissect the mechanisms that imprint FLS, have helped to identify potential FLS subsets with distinct functions and have identified differences in FLS phenotypes between joints in individual patients. This Review provides an overview of advances in understanding of FLS biology and highlights omics approaches and studies that hold promise for identifying future therapeutic targets.

Linc02381 Exacerbates Rheumatoid Arthritis Through Adsorbing miR-590-5p and Activating the Mitogen-Activated Protein Kinase Signaling Pathway in Rheumatoid arthritis-fibroblast-like synoviocytes

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease. New evidence suggested that linc02381 suppressed colorectal cancer progression by regulating PI3 K signaling pathway, but the role of linc02381 in other diseases, such as RA, remains unclear. This study aimed to reveal the mechanism of linc02381 in RA progression. In vivo and in vitro, we found that linc02381 was upregulated in RA synovial tissues or RA fibroblast-like synoviocytes (RA-FLSs, P < 0.01), which were detected by quantitative real-time polymerase chain reaction. Cell Counting Kit-8, EDU, and Transwell assays revealed that linc02381 overexpression enhanced cell proliferation and invasion, and linc02381 knockdown inhibited cell proliferation and invasion in FLSs. Moreover, the results of bioinformatics analysis, luciferase reporter gene assay, and pull-down assay verified that linc02381 could directly bind with miR-590-5p. MiR-590-5p was downregulated in RA-FLSs, and overexpression of linc02381 suppressed expression of miR-590-5p that post-transcriptionally suppressed the expression of mitogen-activated protein kinase kinase 3 (MAP2K3), and overexpression of miR-590-5p reversed the effect of linc02381 overexpression on MAP2K3 expression. MiR-590-5p inhibitor reversed the inhibition effect of linc02381 knockdown on proliferation and invasion of FLSs, which enhanced expression of MAP2K3, and activation of p38 and AP-1 in the MAPK signaling pathway. In summary, linc02381 was upregulated in RA synovial tissues and RA-FLSs, and it exacerbated RA by adsorbing miR-590-5p to activate the MAPK signaling pathway.

A novel MKK gene (EcMKK6) in Epinephelus coioides: Identification, characterization and its response to Vibrio alginolyticus and SGIV infection

Mitogen-activated protein kinase 6 (MKK6) is one of the major important central regulatory proteins response to environmental and physiological stimuli. In this study, a novel MKK6, EcMKK6, was isolated from Epinephelus coioides, an economically important cultured fish in China and Southeast Asian counties. The open reading frame (ORF) of EcMKK6 is 1077 bp encoding 358 amino acids. EcMKK6 contains a serine/threonine protein kinase (S_TKc) domain, a tyrosine kinase catalytic domain, a conserved dual phosphorylation site in the SVAKT motif and a conserved DVD domain. By in situ hybridization (ISH) with Digoxigenin-labeled probe, EcMKK6 mainly located at the cytoplasm of cells, and a little appears in the nucleus. EcMKK6 mRNA can be detected in all eleven tissues examined, but the expression level is different in these tissues. After challenge with Vibrio alginolyticus and Singapore grouper iridovirus (SGIV), the transcription level of EcMKK6 was apparently up-regulated in the tissues examined. The data demonstrated that the sequence and the characters of EcMKK6 were conserved, EcMKK6 showed tissue-specific expression profiles in healthy grouper, and the expression was significantly varied after pathogen infection, indicating that EcMKK6 may play important roles in E. coioides during pathogen-caused inflammation.

MAP2K6 is associated with radiation resistance and adverse prognosis for locally advanced nasopharyngeal carcinoma patients

BACKGROUND

Although radiotherapy is the primary therapeutic option for nasopharyngeal carcinoma (NPC), local recurrence and distant metastasis caused by radioresistance are still the major barriers for some NPC patients who cannot benefit from radiotherapy. In this study, we analyzed the association between MAP2K6 expression and radioresistance in patients with locally advanced NPC.

METHODS

We collected 120 NPC patients who received radiotherapy in the Xiangya Hospital of Central South University from August 2008 to July 2012. The clinical data and tissue samples of patients were collected. Detection of MAP2K6 was performed using immunohistochemical staining.

RESULTS

The rates of two groups were 19.4% and 4.2%, and significant difference was observed between MAP2K6 high expression group and low expression group (χ2=5.817, P=0.016). The Kaplan-Meier analysis suggested a significant difference in the survival rate between two groups (P<0.05). The results from multivariate Cox regression indicated that the MAP2K6 was independently related to adverse prognosis in NCP patients (HR =3.40, 95% CI =1.13-10.26, P=0.030).

CONCLUSION

The present study indicated that MAP2K6 was correlated with radioresistance, and the elevated expression of MAP2K6 predicted poor prognosis in NPC patients. MAP2K6 may be a new therapy target for radioresistance of NPC.

Reciprocal regulation of pro-inflammatory Annexin A2 and anti-inflammatory Annexin A1 in the pathogenesis of rheumatoid arthritis

Annexin A2 has been implicated in several immune modulated diseases including Rheumatoid arthritis (RA) pannus formation. The most relied treatment option for RA pathogenesis is glucocorticoids. Glucocorticoids regulate the synthesis, phosphorylation and cellular deposition of Annexin A1. This annexin mediates the anti-inflammatory actions of glucocorticoids. These two first characterized members of annexin superfamily proteins acts reciprocally, one as an anti-inflammatory and the other proinflammatory in nature. The possibility of these molecules as soluble biomarkers and as an upstream regulator of major cytokine devastation at RA microenvironment has not been previously explored. Current study elucidates the reciprocal regulation of these two annexins in RA pathogenesis. These Annexin A2/A1 and downstream cytokines in RA serum were analysed by ELISA. Western blot, Immunocytochemistry, immunoprecipitation and Immunohistochemistry were adapted to analyse these molecules in tissue and synovial fibroblasts and also in different experimental conditions. Significant increase in the level of Annexin A2 was noticed in naïve RA patients compared to controls (14.582 ± 1.766 ng/ml vs. 7.37 ± 1.450 ng/ml; p ≤ 0.001). In remission cases significant low levels was detected. On the contrary, significant decrease in the level of Annexin A1 was noticed in naïve RA patients compared to healthy controls (12.322 ± 2.91 vs. 16.998 ± 4.298 ng/ml; p ≤ 0.001), wherein remission cases serum Annexin A1 was significantly high. The knockdown of proinflammatory Annexin A2 by siRNA/antibody treatment could mimic the glucocorticoid treatment as which induced cellular Annexin A1 and membrane translocation resulting in the terminal action. Current data elucidating the regulatory interplay between Annexin A2 and Annexin A1 in RA pathogenesis.

Selective Regulation of MAPK Signaling Mediates RANKL-dependent Osteoclast Differentiation

Different stimuli often activate the same intracellular signaling molecules but trigger distinct cell responses. We explored whether or not MAPK signaling induced by macrophage colony-stimulating factor (M-CSF), which is responsible for osteoclast proliferation, differs from that induced by receptor activator of NF-κB ligand (RANKL), which is essential for inducing osteoclast differentiation. The activation of MAPKs by M-CSF or RANKL differed in terms of the extent and duration of ERK, p38, and JNK phosphorylation as well as the isoform specificity of JNK phosphorylation. In particular, RANKL induced a second wave of MAPK activation coincident with the onset of osteoclast differentiation, whereas M-CSF triggered only a monophasic response. M-CSF was also able to trigger a full MAPK response on restimulation of cells earlier than was RANKL, representing that MAPK resensitization by M-CSF differs from that by RANKL. Furthermore, the adapter protein TRAF6 recruitment to the cytoplasmic tail of RANK in a submembrane compartment is specifically required for RANKL-induced activation of p38 MAPK, expression of osteoclastogenic transcription factors, and osteoclast differentiation, indicating that the switch from proliferation to differentiation in osteoclast precursors is dependent on p38 activation via the RANKL-RANK-TRAF6 axis. Our results suggest that selective control of MAPK signaling induced by M-CSF and by RANKL mediates the proliferation versus differentiation decision in osteoclast precursors.

Fragment-based drug discovery of potent and selective MKK3/6 inhibitors

The MAPK signaling cascade, comprised of several linear and intersecting pathways, propagates signaling into the nucleus resulting in cytokine and chemokine release. The Map Kinase Kinase isoforms 3 and 6 (MKK3 and MKK6) are responsible for the phosphorylation and activation of p38, and are hypothesized to play a key role in regulating this pathway without the redundancy seen in downstream effectors. Using FBDD, we have discovered efficient and selective inhibitors of MKK3 and MKK6 that can serve as tool molecules to help further understand the role of these kinases in MAPK signaling, and the potential impact of inhibiting kinases upstream of p38.

A de novo 1.58 Mb deletion, including MAP2K6 and mapping 1.28 Mb upstream to SOX9, identified in a patient with Pierre Robin sequence and osteopenia with multiple fractures

Defects of long-range regulatory elements of dosage-sensitive genes represent an under-recognized mechanism underlying genetic diseases. Haploinsufficiency of SOX9, the gene essential for development of testes and differentiation of chondrocytes, results in campomelic dysplasia, a skeletal malformation syndrome often associated with sex reversal. Chromosomal rearrangements with breakpoints mapping up to 1.6 Mb up- and downstream to SOX9, and disrupting its distant cis-regulatory elements, have been described in patients with milder forms of campomelic dysplasia, Pierre Robin sequence, and sex reversal. We present an ∼1.58 Mb deletion mapping ∼1.28 Mb upstream to SOX9 that encompasses its putative long-range cis-regulatory element(s) and MAP2K6 in a patient with Pierre Robin sequence and osteopenia with multiple fractures. Low bone mass panel testing using massively parallel sequencing of 23 nuclear genes, including COL1A1 and COL1A2 was negative. Based on the previous mouse model of Map2k6, suggesting that Sox9 is likely a downstream target of the p38 MAPK pathway, and our previous chromosome conformation capture-on-chip (4C) data showing potential interactions between SOX9 promoter and MAP2K6, we hypothesize that deletion of MAP2K6 might have affected SOX9 expression and contributed to our patient's phenotype.

Roles of p38α mitogen-activated protein kinase in mouse models of inflammatory diseases and cancer

The p38α mitogen‐activated protein kinase pathway not only regulates the production of inflammatory mediators, but also controls processes related to tissue homeostasis, such as cell proliferation, differentiation and survival, which are often disrupted during malignant transformation. The versatility of this signaling pathway allows for the regulation of many specific functions depending on the cell type and context. Here, we discuss mouse models that have been used to identify in vivo functions of p38α signaling in the pathogenesis of inflammatory diseases and cancer. Experiments using genetically modified mice and pharmacological inhibitors support that targeting the p38α pathway could be therapeutically useful for some inflammatory diseases and tumor types.

The discoidin domain receptor 2/annexin A2/matrix metalloproteinase 13 loop promotes joint destruction in arthritis through promoting migration and invasion of fibroblast-like synoviocytes

OBJECTIVE

Discoidin domain receptor 2 (DDR-2)/matrix metalloproteinase (MMP) signaling is an important pathway involved in cartilage destruction in rheumatoid arthritis (RA). However, the molecular mechanisms of this pathway have not been clearly identified. This study was undertaken to screen key molecules involved in this pathway and evaluate their biologic functions in synovium invasion of RA.

METHODS

DDR-2-interacting proteins were examined in vitro by immunoprecipitation and mass spectrometry, and annexin A2 was acquired. The effects of annexin A2 on fibroblast-like synoviocyte (FLS) migration were evaluated using a Transwell invasion assay and an Erasion trace test. In Ddr2(-/-) mice with collagen-induced arthritis (CIA), hematoxylin and eosin (H&E) staining, immunohistochemical analysis, and Western blot analysis were used to assess expression of DDR-2, annexin A2, and MMP-13, as well as synovial hyperplasia. Rats with CIA were treated with lentivirus annexin A2 small interfering RNA (siRNA), and annexin A2 siRNA effects on joint damage were analyzed based upon arthritis index scores and results of micro-computed tomography and H&E staining. The differences between annexin A2 expression in clinical samples from RA and osteoarthritis patients were compared using Western blotting.

RESULTS

Annexin 2 was identified for the first time as a DDR-2 binding protein. It may be phosphorylated by phospho-DDR-2, leading to MMP-13 secretion. The annexin A2 phosphorylation level and MMP-13 expression level were decreased and collagen-induced joint damage greatly reduced in Ddr2(-/-) mice. Joint damage in rats with CIA was significantly ameliorated when annexin A2 was down-regulated. Annexin A2 expression and phosphorylation were elevated in human RA synovial tissue.

CONCLUSION

Annexin A2 is a key molecule in the DDR-2/annexin A2/MMP-13 loop, the activation of which contributes to joint destruction in RA, mainly through promoting invasion of FLS. Annexin A2 might therefore become a novel clinical target for RA treatment.

Small-molecule inhibitors for autoimmune arthritis: success, failure and the future

Treatment of patients with aggressive autoimmune arthritis, such as rheumatoid arthritis (RA), is a considerable challenge for physicians, particularly rheumatologists. Because of the nature of autoimmune arthritis, effective and complete suppression of disease activity has been the primary therapeutic goal. Although currently available disease-modifying antirheumatic drugs (DMARDs) can successfully control the disease progression in a large proportion of patients, the benefit/risk ratio is not very much satisfied. The introduction of biologic agents such as anti-tumor necrosis factor-α, anti-interleukin-6, and anti-CD20 brings significant help to those patients with an inadequate response to treatment with DMARDs. In considering the limitation of currently available DMARDs and biologics, the development of new DMARDs, small-molecule inhibitors (SMIs), has recently emerged. In the past few years, a great volume of knowledge has been revealed from the experience of examining the usefulness of several SMIs for therapeutics of autoimmune arthritis. This paper addresses the up-to-date knowledge regarding autoimmune arthritis, therapeutics, findings from recently developed SMIs and the benefits and drawbacks of the development of SMIs. In addition, perspectives on the future development of SMIs for autoimmune arthritis will be described and discussed.

Monocytic cell differentiation from band-stage neutrophils under inflammatory conditions via MKK6 activation

During inflammation, neutrophils are rapidly mobilized from the bone marrow storage pool into peripheral blood (PB) to enter lesional sites, where most rapidly undergo apoptosis. Monocytes constitute a second wave of inflammatory immigrates, giving rise to long-lived macrophages and dendritic cell subsets. According to descriptive immunophenotypic and cell culture studies, neutrophils may directly "transdifferentiate" into monocytes/macrophages. We provide mechanistic data in human and murine models supporting the existence of this cellular pathway. First, the inflammatory signal-induced MKK6-p38MAPK cascade activates a monocyte differentiation program in human granulocyte colony-stimulating factor-dependent neutrophils. Second, adoptively transferred neutrophils isolated from G-CSF-pretreated mice rapidly acquired monocyte characteristics in response to inflammatory signals in vivo. Consistently, inflammatory signals led to the recruitment of osteoclast progenitor cell potential from ex vivo-isolated G-CSF-mobilized human blood neutrophils. Monocytic cell differentiation potential was retained in left-shifted band-stage neutrophils but lost in neutrophils from steady-state PB. MKK6-p38MAPK signaling in HL60 model cells led to diminishment of the transcription factor C/EBPα, which enabled the induction of a monocytic cell differentiation program. Gene profiling confirmed lineage conversion from band-stage neutrophils to monocytic cells. Therefore, inflammatory signals relayed by the MKK6-p38MAPK cascade induce monocytic cell differentiation from band-stage neutrophils.

Differential regulation of anti-inflammatory genes by p38 MAP kinase and MAP kinase kinase 6

Background

Conventional p38α inhibitors have limited efficacy in rheumatoid arthritis, possibly because p38 blockade suppresses the counter-regulatory mechanisms that limit inflammation. In contrast, targeting the upstream MAP kinase kinases, MKK3 and MKK6, partially maintains p38-mediated anti-inflammatory responses in bone marrow-derived macrophages (BMDM). In this study, we explored the mechanisms that preserve anti-inflammatory gene expression by evaluating differential regulation of IL-10 and p38-dependent anti-inflammatory genes in MKK3−/−, MKK6−/−, and p38 inhibitor-treated wildtype cells.

Methods

BMDM from wild type (WT), MKK3−/−, and MKK6−/− mice were pre-treated with p38 inhibitor SB203580 (SB), JNK inhibitor SP600125 (SP), and/or ERK inhibitor PD98059 (PD) and stimulated with LPS. Supernatant protein levels were measured by multiplex bead immunoassay. mRNA expression was determined by qPCR and protein expression by Western blot analysis. De novo IL-10 mRNA synthesis was quantified in cells treated with ethynyl-uridine and LPS followed by reverse transcription and qPCR. mRNA half-life was measured in LPS-treated cells that were then incubated with actinomycin D ± SB203580.

Results

Pre-treatment of WT BMDM with p38 inhibitor significantly reduced IL-10 production in the three groups, while ERK and JNK inhibitors had minimal effects. IL-10 production was significantly decreased in MKK3−/− BMDM compared with either WT or MKK6−/− cells. IL-10 mRNA expression was modestly reduced in MKK3−/− BMDM but was preserved in MKK6−/− cells compared with WT. De novo IL-10 mRNA synthesis was inhibited in MKK3−/− and p38 inhibitor pre-treated cells, but not MKK6−/− cells compared with WT. IL-10 mRNA half-life was markedly reduced in p38 inhibitor-treated WT cells while MKK-deficiency had minimal effect. DUSP1 mRNA levels were preserved in MKK-deficient cells but not in p38 inhibitor-treated WT cells. Tristetraprolin mRNA and protein levels were reduced in p38 inhibitor-treated WT cells compared with MKK6−/− cells.

Conclusion

Unlike p38-inhibition, the absence of MKK6 mostly preserves IL-10 and TTP protein expression in BMDM. MKK6-deficiency also spares DUSP1 and IL-1RA, which are key negative regulators of the inflammatory response. Together, these data suggest that MKK6 is a potential therapeutic target in RA.

Differential roles of MAPK kinases MKK3 and MKK6 in osteoclastogenesis and bone loss

Bone mass is maintained by osteoclasts that resorb bone and osteoblasts that promote matrix deposition and mineralization. Bone homeostasis is altered in chronic inflammation as well as in post-menopausal loss of estrogen, which favors osteoclast activity that leads to osteoporosis. The MAPK p38α is a key regulator of bone loss and p38 inhibitors preserve bone mass by inhibiting osteoclastogenesis. p38 function is regulated by two upstream MAPK kinases, namely MKK3 and MKK6. The goal of this study was to assess the effect of MKK3- or MKK6-deficiency on osteoclastogenesis in vitro and on bone loss in ovariectomy-induced osteoporosis in mice. We demonstrated that MKK3 but not MKK6, regulates osteoclast differentiation from bone marrow cells in vitro. Expression of NFATc1, a master transcription factor in osteoclastogenesis, is decreased in cells lacking MKK3 but not MKK6. Expression of osteoclast-specific genes Cathepsin K, osteoclast-associated receptor and MMP9, was inhibited in MKK3−/− cells. The effect of MKK-deficiency on ovariectomy-induced bone loss was then evaluated in female WT, MKK3−/− and MKK6−/− mice by micro-CT analysis. Bone loss was partially inhibited in MKK3−/− as well as MKK6−/− mice, despite normal osteoclastogenesis in MKK6−/− cells. This correlated with the lower osteoclast numbers in the MKK-deficient ovariectomized mice. These studies suggest that MKK3 and MKK6 differentially regulate bone loss due to estrogen withdrawal. MKK3 directly mediates osteoclastogenesis while MKK6 likely contributes to pro-inflammatory cytokine production that promotes osteoclast formation.

Molecular network and chemical fragment-based characteristics of medicinal herbs with cold and hot properties from Chinese medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Chinese herbal medicines (HMs) is one of the great herbal systems of the world, which play an important role in current health care system in many countries. In the view of tradition Chinese medicine (TCM) theory, Yin-yang and five-elements theory is the central theory, which is used to explain how the world and body work. Under the guidance of such philosophy, TCM considers that HMs have different properties, which are the important factors for prescribing herbal formulae; such prescriptions are based on TCM pattern classification in clinical practice. The cold and hot property are commonly defined for HM property identification; however, the biological activities that are related to the HM property remain a mystery because of a lack of appropriate methods. A bioinformatics approach was applied to identify the distinguishing biological activities of HMs that have these cold and hot properties.

MATERIAL AND METHODS

Twenty HMs with typical cold and hot properties (10 cold and 10 hot) were selected based on TCM clinical application records and Chinese pharmacopeia. The active target proteins of each HM were searched in the PubChem database and were analyzed in Ingenuity Pathway Analysis (IPA) platform to find out the HM property-related biological activities. In addition, the main compounds of the HMs were fragmented using a fragment-based approach and were analyzed for the purpose of deciphering the properties.

RESULTS

The main biological networks of HMs with cold and hot properties include cell cycle, cellular growth, proliferation and development, cancer, cytokine signaling, and intracellular and second messenger signaling; 11 specific pathways are presented to be perturbed only by HMs with the hot property, and the 27 specific target protein molecules include PRKACA, PRKCA, PRKCB, PRKCD, PRKCE, PRKCG, PRKD1, TLR4, TLR7, TLR8, TLR9, HTR4, HTR6, HTR7, HTR2A, HTR1B, HTR2B, GNAO1, GNAI1, TNF, IL8, ROCK2, AKT1, MAPK1, RPS6KA1, RPS6KA3 and JAK2, which are involved in the biological network. One specific pathway is detected to be involved in the biological network of HMs with the cold property, the specific molecules are RAN and KPNB1. Cold propertied HMs show intensive toxicity in the heart, liver and kidney compared with hot HMs, which is likely to be correlated with the specific chemical fragments constructions in the HMs with the cold property, such as long chain alkenes, Benzo heterocycle and azotic heterocycle according to the chemical fragment analysis for the HMs.

CONCLUSIONS

Inflammation and immunity regulation are more related to HMs with the hot property, and cold propertied HMs possess the tendency to impact cell growth, proliferation and development. Integrative bioinformatics analysis and chemical structure analysis are a promising methods for identifying the biological activity of HM properties.

Cellular targeting in autoimmunity

Many biologic agents that were first approved for the treatment of malignancies are now being actively investigated and used in a variety of autoimmune diseases such as rheumatoid arthritis (RA), antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, systemic lupus erythematosus (SLE), and Sjogren's syndrome. The relatively recent advance of selective immune targeting has significantly changed the management of autoimmune disorders and in part can be attributed to the progress made in understanding effector cell function and their signaling pathways. In this review, we will discuss the recent FDA-approved biologic therapies that directly target immune cells as well as the most promising investigational drugs affecting immune cell function and signaling for the treatment of autoimmune disease.

Antiinflammatory functions of p38 in mouse models of rheumatoid arthritis: advantages of targeting upstream kinases MKK-3 or MKK-6

OBJECTIVE

Inhibitors of p38 demonstrate limited benefit in rheumatoid arthritis (RA), perhaps due to the antiinflammatory functions of p38α. This study was performed to determine if selective deletion of p38α in macrophages affects the severity of arthritis and whether blocking upstream kinases in the p38 pathway, such as MKK-3 or MKK-6, avoids some of the limitations of p38 blockade.

METHODS

Wild-type (WT) mice and mice with selective deletion of p38α in macrophages (p38α(ΔLysM) ) were injected with K/BxN sera. Antigen-induced arthritis was also induced in p38α(ΔLysM) mice. Mouse joint extracts were evaluated by enzyme-linked immunosorbent assay, quantitative polymerase chain reaction (qPCR), and Western blot analysis. Bone marrow-derived macrophages (BMMs) were stimulated with lipopolysaccharide (LPS) and were evaluated by qPCR and Western blotting. Bone marrow chimeras were generated using MKK-3(-/-) and MKK-6(-/-) mice, and K/BxN serum was administered to induce arthritis.

RESULTS

Compared to WT mice, p38α(ΔLysM) mice had increased disease severity and delayed resolution of arthritis, which correlated with higher synovial inflammatory mediator expression and ERK phosphorylation. In contrast to WT BMMs cultured in the presence of a p38α/β inhibitor, LPS-stimulated MKK-6- and MKK-3-deficient BMMs had suppressed LPS-mediated interleukin-6 (IL-6) expression but had normal IL-10 production, dual-specificity phosphatase 1 expression, and MAPK phosphorylation. WT chimeric mice with MKK-6- and MKK-3-deficient bone marrow had markedly decreased passive K/BxN arthritis severity.

CONCLUSION

Inhibiting p38α in a disease that is dominated by macrophage cytokines, such as RA, could paradoxically suppress antiinflammatory functions and interfere with clinical efficacy. Targeting an upstream kinase that regulates p38 could be more effective by suppressing proinflammatory cytokines while preventing decreased IL-10 expression and increased MAPK activation.

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.

Dual-specificity phosphatase 1-null mice exhibit spontaneous osteolytic disease and enhanced inflammatory osteolysis in experimental arthritis

OBJECTIVE

Bone formation and destruction are usually tightly linked; however, in disorders such as rheumatoid arthritis, periodontal disease, and osteoporosis, elevated osteoclast activity leads to bone destruction. Osteoclast formation and activation are controlled by many signaling pathways, including p38 MAPK. Dual-specificity phosphatase 1 (DUSP-1) is a factor involved in the negative regulation of p38 MAPK. The purpose of this study was to examine the effect of Dusp1 deficiency on bone destruction.

METHODS

Penetrance, onset, and severity of collagen-induced arthritis were recorded in DUSP-1+/+ and DUSP-1-/- mice. Bone destruction was assessed by histologic and micro-computed tomographic examination of the joints. The in vitro formation and activation of osteoclasts from DUSP-1+/+ and DUSP-1-/- precursors were assessed in the absence or presence of tumor necrosis factor (TNF).

RESULTS

The formation and activation of osteoclasts in vitro in the presence of TNF were enhanced by Dusp1 gene disruption. DUSP-1-/- mice exhibited higher penetrance, earlier onset, and increased severity of experimental arthritis, accompanied by greater numbers of osteoclasts in inflamed joints and more extensive loss of bone. A DUSP-1-/- mouse colony of mixed genetic background also demonstrated striking spontaneous osteolytic destruction of distal phalanges.

CONCLUSION

DUSP-1 is a critical regulator of osteoclast activity and limits bone destruction in an experimental model of rheumatoid arthritis. Defects in the expression or activity of DUSP1 in humans may correlate with a propensity to develop osteolytic lesions in arthritis.

The p38 MAPK Pathway in Rheumatoid Arthritis: A Sideways Look

The p38 mitogen-activated protein kinase (MAPK) signaling pathway has been strongly implicated in many of the processes that underlie the pathology of rheumatoid arthritis (RA). For many years it has been considered a promising target for development of new anti-inflammatory drugs with which to treat RA and other chronic immune-mediated inflammatory diseases. However, several recent clinical trials have concluded in a disappointing manner. Why is this so, if p38 MAPK clearly contributes to the excessive production of inflammatory mediators, the destruction of bone and cartilage? We argue that, to explain the apparent failure of p38 inhibitors in the rheumatology clinic, we need to understand better the complexities of the p38 pathway and its many levels of communication with other cellular signaling pathways. In this review we look at the p38 MAPK pathway from a slightly different perspective, emphasising its role in post-transcriptional rather than transcriptional control of gene expression, and its contribution to the off-phase rather than the on-phase of the inflammatory response.

Germinal center kinase-like kinase (GLK/MAP4K3) expression is increased in adult-onset Still's disease and may act as an activity marker

BACKGROUND

Germinal center kinase-like kinase (GLK, also termed MAP4K3), a member of the MAP4K family, may regulate gene transcription, apoptosis and immune inflammation in response to extracellular signals. The enhanced expression of GLK has been shown to correspond with disease severity in patients with systemic lupus erythematosus. We investigated the role of GLK in the pathogenesis of adult-onset Still's disease, which shares some similar clinical characteristics with systemic lupus erythematosus.

METHODS

The frequencies of circulating GLK-expressing T-cells in 24 patients with active adult-onset Still's disease and 12 healthy controls were determined by flow cytometry analysis. The expression levels of GLK proteins and transcripts were evaluated in peripheral blood mononuclear cells by immunoblotting and quantitative PCR. Serum levels of T helper (Th)17-related cytokines, including IL-1β, IL-6, IL-17 and TNF-α, were measured by ELISA.

RESULTS

Significantly higher median frequencies of circulating GLK-expressing T-cells were observed in patients with adult-onset Still's disease (31.85%) than in healthy volunteers (8.93%, P <0.001). The relative expression levels of GLK proteins and transcripts were also significantly higher in patients with adult-onset Still's disease (median, 1.74 and 2.35, respectively) compared with those in healthy controls (0.66 and 0.92, respectively, both P <0.001). The disease activity scores were positively correlated with the frequencies of circulating GLK-expressing T-cells (r = 0.599, P <0.005) and the levels of GLK proteins (r = 0.435, P <0.05) or GLK transcripts (r = 0.452, P <0.05) in patients with adult-onset Still's disease. Among the examined Th17-related cytokines, elevated levels of serum IL-6 and IL-17 were positively correlated with the frequencies of circulating GLK-expressing T-cells and the levels of GLK proteins as well as transcripts in patients with adult-onset Still's disease. GLK expression levels decreased significantly after effective therapy in these patients.

CONCLUSIONS

Elevated expression levels of GLK and their positive correlation with disease activity in patients with adult-onset Still's disease indicate that GLK may be involved in the pathogenesis and act as a novel activity biomarker of this disease.

Decreased collagen-induced arthritis severity and adaptive immunity in MKK-6-deficient mice

OBJECTIVE

The MAPK kinases MKK-3 and MKK-6 regulate p38 MAPK activation in inflammatory diseases such as rheumatoid arthritis (RA). Previous studies demonstrated that MKK-3 or MKK-6 deficiency inhibits K/BxN serum-induced arthritis. However, the role of these kinases in adaptive immunity-dependent models of chronic arthritis is not known. The goal of this study was to evaluate MKK-3 and MKK-6 deficiency in the collagen-induced arthritis (CIA) model.

METHODS

Wild-type (WT), MKK-3(-/-) , and MKK-6(-/-) mice were immunized with bovine type II collagen. Disease activity was evaluated by semiquantitative scoring, histologic assessment, and micro-computed tomography. Serum anticollagen antibody levels were quantified by enzyme-linked immunosorbent assay. In vitro T cell cytokine response was measured by flow cytometry and multiplex analysis. Expression of joint cytokines and matrix metalloproteinases (MMPs) was determined by quantitative polymerase chain reaction.

RESULTS

MKK-6 deficiency markedly reduced arthritis severity compared with that in WT mice, while the absence of MKK-3 had an intermediate effect. Joint damage was minimal in arthritic MKK-6(-/-) mice and intermediate in MKK-3(-/-) mice compared with WT mice. MKK-6(-/-) mice had modestly lower levels of pathogenic anticollagen antibodies than did WT or MKK-3(-/-) mice. In vitro T cell assays showed reduced proliferation and interleukin-17 (IL-17) production by lymph node cells from MKK-6(-/-) mice in response to type II collagen. Gene expression of synovial IL-6, MMP-3, and MMP-13 was significantly inhibited in MKK-6-deficient mice.

CONCLUSION

Reduced disease severity in MKK-6(-/-) mice correlated with decreased anticollagen antibody responses, indicating that MKK-6 is a crucial regulator of inflammatory joint destruction in CIA. MKK-6 is a potential therapeutic target in complex diseases involving adaptive immune responses, such as RA.

Overexpression of Ste20-related proline/alanine-rich kinase exacerbates experimental colitis in mice

Inflammatory bowel disease, mainly Crohn's disease and ulcerative colitis, are characterized by epithelial barrier disruption and altered immune regulation. Colonic Ste20-like proline/alanine-rich kinase (SPAK) plays a role in intestinal inflammation, but its underlying mechanisms need to be defined. Both SPAK-transfected Caco2-BBE cells and villin-SPAK transgenic (TG) FVB/6 mice exhibited loss of intestinal barrier function. Further studies demonstrated that SPAK significantly increased paracellular intestinal permeability to FITC-dextran. In vivo studies using the mouse models of colitis induced by dextran sulfate sodium (DSS) and trinitrobenzene sulfonic acid showed that TG FVB/6 mice were more susceptible to DSS and trinitrobenzene sulfonic acid treatment than wild-type FVB/6 mice, as demonstrated by clinical and histological characteristics and enzymatic activities. Consistent with this notion, we found that SPAK increased intestinal epithelial permeability, which likely facilitated the production of inflammatory cytokines in vitro and in vivo, aggravated bacterial translocation in TG mice under DSS treatment, and consequently established a context favorable for the triggering of intestinal inflammation cascades. In conclusion, overexpression of SPAK inhibits maintenance of intestinal mucosal innate immune homeostasis, which makes regulation of SPAK important to attenuate pathological responses in inflammatory bowel disease.

Correlation between cold and hot pattern in traditional Chinese medicine and gene expression profiles in rheumatoid arthritis

Clinical manifestations of rheumatoid arthritis (RA) are diversified, and based on the manifestations, the patients with RA could be classified into different patterns under traditional Chinese medicine. These patterns decide the selection of herbal prescription, and thus they can help find a subset of rheumatoid arthritis patients for a type of therapy. In the present study, we combine genome-wide expression analysis with methods of systems biology to identify the functional gene networks for the sets of clinical symptoms that comprise the major information for pattern classification. Clinical manifestations in rheumatoid arthritis were clustered with factor analysis, and two factors (similar to cold and hot patterns in traditional Chinese medicine) were found. Microarray technology was used to reveal gene expression profiles in CD4(+) T cells from 21 rheumatoid arthritis patients. Protein-protein interaction information for these genes from databases and literature data was searched. The highly-connected regions were detected to infer significant complexes or pathways in this protein-protein interaction network. The significant pathways and function were extracted from these subnetworks using the Biological Network Gene Ontology tool. The genes significantly related to hot and cold patterns were identified by correlations analysis. MAPK signalling pathway, Wnt signaling pathway, and insulin signaling pathway were found to be related to hot pattern. Purine metabolism was related to both hot and cold patterns. Alanine, aspartate, and tyrosine metabolism were related to cold pattern, and histindine metabolism and lysine degradation were related to hot pattern. The results suggest that cold and hot patterns in traditional Chinese medicine were related to different pathways, and the network analysis might be used for identifying the pattern classification in other diseases.

Kinase inhibitors: a new approach to rheumatoid arthritis treatment

PURPOSE OF REVIEW

Due to the cost and parenteral mode of administration of biologics, efforts to develop oral small molecule inhibitors to protein kinases involved in cellular signaling that impact inflammatory cytokine production have been ongoing. This article will review the recent publications on these efforts.

RECENT FINDINGS

On preclinical work, p38 mitogen-activated kinases were considered attractive targets to suppress cytokine production. Three different molecules (SCIO_469, Pamapimod, VX-702) that target the p38alpha isoform have been evaluated in phase 2 trials. Unfortunately, clinical efficacy was not observed, and dose-related toxicity was seen. The future of this approach is unclear. Targeting more upstream protein tyrosine kinases such as spleen tyrosine kinase (SyK) and the JAK family of kinases has been associated with greater success in clinical trials, with efficacy demonstrated. Adverse events occurred in a dose-dependent fashion with the SyK inhibitor, such as diarrhea and hypertension. Neutropenia, elevated liver-function tests, serum creatinine elevations and lipid elevations have occurred with JAK-kinase inhibition. Dose modifications have been made based on the phase 2 trial results; phase 3 clinical trials are ongoing.

SUMMARY

Inhibiting downstream proteins involved in cellular signaling, such as p38, has not been successful to date. Inhibitors of more upstream protein-tyrosine kinases involved in cellular signaling appear to be viable molecular candidates for rheumatoid arthritis. If the results seen in phase 2 studies are confirmed in larger phase 3 studies, we may soon have new, oral DMARD therapies available.

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.

"Go upstream, young man": lessons learned from the p38 saga

Despite the success of biological therapies in rheumatoid arthritis (RA), orally active small-molecule drugs are desirable. Signal transduction inhibitors have been the focus of intense efforts, with some recent notable successes and failures. p38alpha is a signalling molecule that regulates proinflammatory cytokines, which makes it a logical target for RA. Unfortunately, selective p38alpha inhibitors have limited efficacy. An attempt is made here to put these studies into perspective and offer possible explanations for the failure of p38alpha blockers. Alternative strategies, such as targeting kinases higher in the signalling cascade or using less selective compounds, might be more successful as suggested by the efficacy seen with Syk and JAK inhibitors.

Recent advances in neutralizing the IL-6 pathway in arthritis

Recent advances in understanding the mechanism(s) of how IL-6 trans-signaling regulates immune cell function and promotes inflammation in autoimmune arthritis are critically reviewed. Serum and/or synovial fluid (SF) IL-6 is markedly elevated in adult and juvenile rheumatoid arthritis (RA), psoriatic arthritis (PsA), ankylosing spondylitis (AS) and osteoarthritis (OA). IL-6, in concert with IL-17, determines the fate of CD4⁺ lymphocytes and therefore TH₁₇ cell differentiation. IL-6 also plays a critical role in modulating B-lymphocyte activity. The recognition that IL-6 trans-signaling regulates inflammation resulted in the development of tocilizumab, a fully humanized monoclonal antibody that neutralizes the biological activity of the IL-6-receptor (IL-6R). Significant clinical benefit was demonstrated as well as reduced serum IL-6 levels with suppression of X-ray progression of disease in several clinical trials in which juvenile or adult RA patients were treated with tocilizumab monotherapy or tocilizumab plus methotrexate. However, levels of serum and/or SF IL-6 cytokine protein superfamily members, adiponectin, oncostatin M, pre-B-cell colony enhancing factor/visfatin and leukemia inhibitory factor are also elevated in RA. Additional studies will be required to determine if anti-IL-6 trans-signaling inhibition strategies with tocilizumab or recombinant soluble IL-6R reduce the level of these cytokines.