Role of p21-activated kinase 1 in regulating the migration and invasion of fibroblast-like synoviocytes from rheumatoid arthritis patients

Coptisine inhibits aggressive and proliferative actions of fibroblast like synoviocytes and exerts a therapeutic potential for rheumatoid arthritis

OBJECTIVE

Coptisine, a natural bioactive small molecular compound extracted from traditional Chinese herb Coptis chinensis, has been shown to exhibit anti-tumor effect. However, its contribution to autoimmune diseases such as rheumatoid arthritis (RA) is unknown. Here, we evaluate the effect of coptisine in controlling fibroblast-like synoviocytes (FLS)-mediated synovial proliferation and aggression in RA and further explore its underlying mechanism(s).

METHODS

FLS were separated from synovial tissues obtained from patients with RA. Protein expression was measured by Western blot or immunohistochemistry. Gene expression was detected by quantitative RT-PCR. The EdU incorporation was used to measure cell proliferation. Migration and invasion were determined by Boyden chamber assay. RNA sequencing analysis was used to seek for the target of coptisine. The in vivo effect of coptisine was evaluated in collagen-induced arthritis (CIA) model.

RESULTS

Treatment with coptisine reduced the proliferation, migration, and invasion, but not apoptosis of RA FLS. Mechanistically, we identified PSAT1, an enzyme that catalyzes serine/one-carbon/glycine biosynthesis, as a novel targeting gene of coptisine in RA FLS. PSAT1 expression was increased in FLS and synovial tissues from patients with RA compared to healthy control subjects. Coptisine treatment or PSAT1 knockdown reduced the TNF-α-induced phosphorylation of p38, ERK1/2, and JNK MAPK pathway. Interestingly, coptisine administration improved the severity of arthritis and reduced synovial PSAT1 expression in mice with CIA.

CONCLUSIONS

Our data demonstrate that coptisine treatment suppresses aggressive and proliferative actions of RA FLS by targeting PSAT1 and sequential inhibition of phosphorylated p38, ERK1/2, and JNK MAPK pathway. Our findings suggest that coptisine might control FLS-mediated rheumatoid synovial proliferation and aggression, and be a novel potential agent for RA treatment.

Proteomic analysis identifies subgroups of patients with active systemic lupus erythematosus

OBJECTIVE

Systemic lupus erythematosus (SLE) is a clinically and biologically heterogenous autoimmune disease. We aimed to investigate the plasma proteome of patients with active SLE to identify novel subgroups, or endotypes, of patients.

METHOD

Plasma was collected from patients with active SLE who were enrolled in the British Isles Lupus Assessment Group Biologics Registry (BILAG-BR). The plasma proteome was analysed using a data-independent acquisition method, Sequential Window Acquisition of All theoretical mass spectra mass spectrometry (SWATH-MS). Unsupervised, data-driven clustering algorithms were used to delineate groups of patients with a shared proteomic profile.

RESULTS

In 223 patients, six clusters were identified based on quantification of 581 proteins. Between the clusters, there were significant differences in age (p = 0.012) and ethnicity (p = 0.003). There was increased musculoskeletal disease activity in cluster 1 (C1), 19/27 (70.4%) (p = 0.002) and renal activity in cluster 6 (C6) 15/24 (62.5%) (p = 0.051). Anti-SSa/Ro was the only autoantibody that significantly differed between clusters (p = 0.017). C1 was associated with p21-activated kinases (PAK) and Phospholipase C (PLC) signalling. Within C1 there were two sub-clusters (C1A and C1B) defined by 49 proteins related to cytoskeletal protein binding. C2 and C6 demonstrated opposite Rho family GTPase and Rho GDI signalling. Three proteins (MZB1, SND1 and AGL) identified in C6 increased the classification of active renal disease although this did not reach statistical significance (p = 0.0617).

CONCLUSIONS

Unsupervised proteomic analysis identifies clusters of patients with active SLE, that are associated with clinical and serological features, which may facilitate biomarker discovery. The observed proteomic heterogeneity further supports the need for a personalised approach to treatment in SLE.

STAT3/HIF-1α/fascin-1 axis promotes RA FLSs migration and invasion ability under hypoxia

Rheumatoid arthritis (RA) synovium was identified as "tumor-like" tissues because of the hypoxic microenvironment, significant cell proliferation, and invasion phenotypes. It was reported that hypoxia promoted tumor aggressiveness via up-regulated expression of fascin-1 in cancer. However, the role of fascin-1 in RA synovial hyperplasia and joint injury progression remains unknown. In the current study, we first identified that both fascin-1 and HIF-1α were highly expressed in the RA synovium, in which they were widely colocalized, compared to osteoarthritis(OA). As well, levels of fascin-1 in RA fibroblast-like synoviocytes(FLSs) were found significantly higher than those in OA FLSs. Further, it was demonstrated that the mRNA and protein levels of fascin-1 in RA FLSs were up-regulated in hypoxia (3 % O₂) and experimental hypoxia induced by cobalt chloride. Mechanistically, the HIF-1α-mediated hypoxia environment activated the gene expression of the fascin-1 protein, which in turn promoted the migration and invasion of RA FLSs. Accordingly, the restoration of FLSs migration and invasion was observed following siRNA-mediated silencing of fascin-1 and HIF-1α expression. Notably, under the experimental hypoxia, we found that the expression levels of fascin-1, HIF-1α, and p-STAT3 were increased in a time-dependent manner, and fascin-1and HIF-1α expressions were dependent on p-STAT3. Our results indicated that hypoxia-induced fascin-1 up-regulation promoted RA FLSs migration and invasion through the STAT3/HIF-1α/fascin-1 axis, which might represent a novel therapeutic target for the treatment of RA.

Epigenetic drug development for autoimmune and inflammatory diseases

ES-62 is the major secreted protein of the parasitic filarial nematode, Acanthocheilonema viteae. The molecule exists as a large tetramer (MW, ~240kD), which possesses immunomodulatory properties by virtue of multiple phosphorylcholine (PC) moieties attached to N-type glycans. By suppressing inflammatory immune responses, ES-62 can prevent disease development in certain mouse models of allergic and autoimmune conditions, including joint pathology in collagen-induced arthritis (CIA), a model of rheumatoid arthritis (RA). Such protection is associated with functional suppression of "pathogenic" hyper-responsive synovial fibroblasts (SFs), which exhibit an aggressive inflammatory and bone-damaging phenotype induced by their epigenetic rewiring in response to the inflammatory microenvironment of the arthritic joint. Critically, exposure to ES-62 in vivo induces a stably-imprinted CIA-SF phenotype that exhibits functional responses more typical of healthy, Naïve-SFs. Consistent with this, ES-62 "rewiring" of SFs away from the hyper-responsive phenotype is associated with suppression of ERK activation, STAT3 activation and miR-155 upregulation, signals widely associated with SF pathogenesis. Surprisingly however, DNA methylome analysis of Naïve-, CIA- and ES-62-CIA-SF cohorts reveals that rather than simply preventing pathogenic rewiring of SFs, ES-62 induces further changes in DNA methylation under the inflammatory conditions pertaining in the inflamed joint, including targeting genes associated with ciliogenesis, to programme a novel "resolving" CIA-SF phenotype. In addition to introducing a previously unsuspected aspect of ES-62's mechanism of action, such unique behaviour signposts the potential for developing DNA methylation signatures predictive of pathogenesis and its resolution and hence, candidate mechanisms by which novel therapeutic interventions could prevent SFs from perpetuating joint inflammation and destruction in RA. Pertinent to these translational aspects of ES-62-behavior, small molecule analogues (SMAs) based on ES-62's active PC-moieties mimic the rewiring of SFs as well as the protection against joint disease in CIA afforded by the parasitic worm product.

The protein-protein interaction between connective tissue growth factor and annexin A2 is relevant to pannus formation in rheumatoid arthritis

Background

Connective tissue growth factor (CTGF)-induced angiogenesis is a crucial factor in rheumatoid arthritis (RA), but CTGF-interacting protein and related molecular mechanism of their interaction have not been fully elucidated.

Methods

CTGF-interacting proteins were identified through the LC-MS/MS analysis of the Co-IP products from fibroblast-like synoviocyte (FLS) lysates, and the interaction between CTGF and annexin A2 (ANXA2) was further confirmed through Co-IP and BiFC assay. The binding domain, mutant, mechanism, and angiogenesis function were assessed by homology modeling, molecular docking, MTT, cell scratch, tube formation, and chick chorioallantoic membrane (CAM) assays. Additionally, severe combined immunodeficiency (SCID) mouse co-implantation model was constructed to confirm the effect of ANXA2/CTGF-TSP1 in the process of RA in vivo.

Results

ANXA2 was identified and verified as an interaction partner of CTGF for the first time by Co-IP and LC-MS/MS analysis. Co-localization of CTGF and ANXA2 was observed in RA-FLS, and direct interaction of the TSP-1 domain of CTGF and ANXA2 was determined in HEK293T cells. The spatial conformation and stable combination of the ANXA2/CTGF-TSP1 complex were assessed by homology modeling in the biomimetic environment. The function of the ANXA2/CTGF-TSP1 complex was proved on promoting FLS proliferation, migration, and angiogenesis in vitro and deteriorating FLS invasion and joint damage in SCID mice.

Conclusions

TSP-1 is the essential domain in CTGF/ANXA2 interaction and contributes to FLS migration and pannus formation, inducing the process of RA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02656-y.

Effects of betulinic acid on synovial inflammation in rats with collagen-induced arthritis

Betulinic acid (BA) inhibits the migration, invasion, and cytoskeletal reorganization of fibroblast-like synoviocytes (RA-FLS) in patients with rheumatoid arthritis. Here, to further explore the mechanism of action of BA in collagen-induced arthritis (CIA) rats, we investigated the pharmacodynamic effects of BA on synovial inflammation in a rat model of type II CIA. After inducing hind paw swelling, the rats were divided into four groups: healthy controls (normal), and rats that underwent CIA and received methotrexate treatment (MTX), BA treatment (BA), or no treatment (CIA). Body weight and hind paw swelling were determined regularly, and arthritis scores were calculated weekly. On day 35, rats were sacrificed and their hind ankle joints sectioned and stained with hematoxylin and eosin for histopathological evaluation. BA significantly reduced CIA-induced hind paw swelling, synovial tissue proliferation, cartilage destruction, and vasospasm. BA treatment also decreased serum interleukin (IL)-1β, IL-6, and tumor necrosis factor-alpha (TNF-α) levels in rats with CIA. The CCK-8 assay was used to detect the proliferation of isolated vimentin⁺CD68^- RA-FLS; RA-FLS were stimulated with TNF-α in vitro. BA significantly inhibited TNF-α-stimulated RA-FLS proliferation, as well as IL-1β and IL-6 secretion. BA also downregulated the transcription of vascular endothelial growth factor (VEGF) and transforming growth factor β (TGF-β) and decreased the expression of the NF-кB pathway proteins (NF-kB-P65, IkBα, and IKKα/β) in the TNF-α-stimulated RA-FLS. These results indicate that BA alleviated the symptoms of CIA by inhibiting synoviocyte proliferation, modifying TNF-α- and NF-кB-related inflammatory pathways, and downregulating inflammatory mediators and growth factors including IL-1β, IL-6, VEGF, and TGF-β.

Up-regulation of P21-activated kinase 1 in osteoarthritis chondrocytes is responsible for osteoarthritic cartilage destruction

Osteoarthritis is mainly caused by a degenerative joint disorder, which is characterized by the gradual degradation of articular cartilage and synovial inflammation. The chondrocyte, the unique resident cell type of articular cartilage, is crucial for the development of osteoarthritis. Previous studies revealed that P21-activated kinase-1 (PAK1) was responsible for the initiation of inflammation. The purpose of the present study was to determine the potential role of PAK1 in osteoarthritis. The level of PAK1 expression was measured by Western blot and quantitative real-time PCR in articular cartilage from osteoarthritis model rats and patients with osteoarthritis. In addition, the functional role of aberrant PAK1 expression was detected in the chondrocytes. We found that the expression of PAK1 was significantly increased in chondrocytes treated with osteoarthritis-related factors. Increased expression of PAK1 was also observed in knee articular cartilage samples from patients with osteoarthritis and osteoarthritis model rats. PAK1 was found to inhibit chondrocytes proliferation and to promote the production of inflammatory cytokines in cartilages chondrocytes. Furthermore, we found that PAK1 modulated the production of extracellular matrix and cartilage degrading enzymes in chondrocytes. Results of the present studies demonstrated that PAK1 might play an important role in the pathogenesis of osteoarthritis.

Transcriptome-wide association study identifies susceptibility genes for rheumatoid arthritis

Objective

To identify rheumatoid arthritis (RA)-associated susceptibility genes and pathways through integrating genome-wide association study (GWAS) and gene expression profile data.

Methods

A transcriptome-wide association study (TWAS) was conducted by the FUSION software for RA considering EBV-transformed lymphocytes (EL), transformed fibroblasts (TF), peripheral blood (NBL), and whole blood (YBL). GWAS summary data was driven from a large-scale GWAS, involving 5539 autoantibody-positive RA patients and 20,169 controls. The TWAS-identified genes were further validated using the mRNA expression profiles and made a functional exploration.

Results

TWAS identified 692 genes with P_TWAS values < 0.05 for RA. CRIPAK (P^EL = 0.01293, P^TF = 0.00038, P^NBL = 0.02839, P^YBL = 0.0978), MUT (P^EL = 0.00377, P^TF = 0.00076, P^NBL = 0.00778, P^YBL = 0.00096), FOXRED1 (P^EL = 0.03834, P^TF = 0.01120, P^NBL = 0.01280, P^YBL = 0.00583), and EBPL (P^EL = 0.00806, P^TF = 0.03761, P^NBL = 0.03540, P^YBL = 0.04254) were collectively expressed in all the four tissues/cells. Eighteen genes, including ANXA5, AP4B1, ATIC (P_TWAS = 0.0113, downregulated expression), C12orf65, CMAH, PDHB, RUNX3 (P_TWAS = 0.0346, downregulated expression), SBF1, SH2B3, STK38, TMEM43, XPNPEP1, KIAA1530, NUFIP2, PPP2R3C, RAB24, STX6, and TLR5 (P_TWAS = 0.04665, upregulated expression), were validated with integrative analysis of TWAS and mRNA expression profiles. TWAS-identified genes functionally involved in endoplasmic reticulum organization, regulation of cytokine production, TNF signaling pathway, immune response-regulating signaling pathway, regulation of autophagy, etc.

Conclusion

We identified multiple candidate genes and pathways, providing novel clues for the genetic mechanism of RA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02419-9.

Betulinic acid inhibits cell proliferation, migration, and inflammatory response in rheumatoid arthritis fibroblast-like synoviocytes

Betulinic acid (BA), a pentacyclic triterpene derived from the bark of the white birch tree, has been reported to have a variety of pharmacological effects, including antioxidant, anti-inflammatory, antitumor, immunomodulatory, and antiarthritis properties. However, the role of BA in rheumatoid arthritis (RA) remains unclear. Thus, the objective of this study was to examine the effects of BA on RA fibroblast-like synoviocytes (RA-FLS) proliferation, migration, and inflammatory response, and further explore the potential underlying mechanisms. Our results showed that BA inhibited the proliferation, migration, and invasion of RA-FLSs. BA also attenuated tumor necrosis factor-α (TNF-α), enhanced matrix metalloproteinases (MMPs) expression, and inflammatory cytokines production in RA-FLS. Furthermore, BA prevented the activation of Akt/NF-κB pathway in RA-FLS exposed to TNF-α. In conclusion, these findings indicated that BA inhibits cell proliferation, migration, and inflammatory response in RA-FLS; and the Akt/NF-κB signaling pathway was involved in the protective effect of BA on RA-FLS. Thus, BA might be a potential therapeutic agent for the treatment of RA.

SIRT1 promotes tumor-like invasion of fibroblast-like synoviocytes in rheumatoid arthritis via targeting TIMP1

Suppression of tissue inhibitor of matrix metalloproteinase (TIMP) is associated with the tumor-like invasion of fibroblast-like synoviocytes (FLSs) that occurs during rheumatoid arthritis-related cartilage destruction. Silent information regulator 2 homolog1 (SIRT1), a histone deacetylase, is widely involved in transcriptional regulation, genomic stability, metabolism and DNA repair. Recent studies suggest that SIRT1 may also impact inflammatory response and the proliferation of FLSs in rheumatoid arthritis (RA). However, it is unknown whether SIRT1 has a role in the tumor-like invasion of FLSs in rheumatoid arthritis. Herein we report that SIRT1 contributes to FLS invasion and cartilage destruction via a TIMP1-dependent mechanism. Elevated SIRT1 in RA synovia suppresses TIMP1 expression via deacetylation of TIMP1-associated histones, thereby disrupting the binding of the transcription factor specificity protein 1 (Sp1) to the TIMP1 promoter. In rats with collagen-induced arthritis, depletion of SIRT1 remarkably promoted TIMP1 expression in synovial tissues and ameliorated cartilage destruction. These results describe a new role for SIRT1 and demonstrate its potential value as a therapeutic target for rheumatoid arthritis.

Inhibition of 6-phosphofructo-2-kinase suppresses fibroblast-like synoviocytes-mediated synovial inflammation and joint destruction in rheumatoid arthritis

BACKGROUND AND PURPOSE

Abnormal glycolytic metabolism contributes to joint inflammation in rheumatoid arthritis (RA). The aims of this study were to investigate the role of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), a bifunctional enzyme that controls the glycolytic rate, in regulating fibroblast-like synoviocyte (FLS)-mediated synovial inflammation and invasiveness in RA.

EXPERIMENTAL APPROACH

A specific inhibitor of PFKFB3, PFK15, and siRNA were used to evaluate the role of PFKFB3. Protein expression was measured by Western blotting or immunofluorescence staining. The expression of cytokines was determined by quantitative real-time PCR. Migration and invasion were measured using a Boyden chamber assay. A mouse model of collagen-induced arthritis (CIA) was used to evaluate the in vivo effect of PFK15.

KEY RESULTS

PFKFB3 expression was increased in the synovial tissue and FLSs from RA patients compared with osteoarthritis patients. PFKFB3 inhibition decreased the expression of IL-8, IL-6, CCL-2 and CXCL-10 and the proliferation, migration and invasion of RA FLSs. PFK15 suppressed TNF-α-induced activation of NF-κB and p38, JNK and ERK MAPK signals in RA FLSs. PFK15 treatment also suppressed glucose uptake and lactate secretion. Lactate reversed the inhibitory effect of PFK15 or PFKFB3 siRNA on cytokine expression and migration of RA FLSs. Lactate was also involved in PFKFB3-mediated activation of NF-κB and MAPKs. Intraperitoneal injection of PFK15 in mice with CIA attenuated joint inflammation.

CONCLUSION AND IMPLICATIONS

Elevated PFKFB3 expression might contribute to synovial inflammation and aggressive behaviours of RA FLSs, suggesting a novel strategy of targeting PFKFB3 to prevent synovial inflammation and joint destruction in RA.

Indirubin inhibits the migration, invasion, and activation of fibroblast-like synoviocytes from rheumatoid arthritis patients

OBJECTIVES

To evaluate the inhibition of indirubin in FLSs migration, invasion, activation, and proliferation in RA FLSs.

METHODS

The levels of IL-6 and IL-8 in cultural supernatants were measured by ELISA. RA FLS migration and invasion in vitro were measured by the Boyden chamber method and the scratch assay. Signal transduction protein expression was measured by western blot. FLS proliferation was detected by Edu incorporation. F-actin was measured by immunofluorescence staining.

RESULTS

We found that indirubin reduced migration, invasion, inflammation, and proliferation in RA FLSs. In addition, we demonstrated that indirubin inhibited lamellipodium formation during cell migration. To gain insight into molecular mechanisms, we evaluated the effect of indirubin on PAK1 and MAPK activation. Our results indicated that indirubin inhibited the activity of PAK1 and MAPK.

CONCLUSIONS

Our observations suggest that indirubin may be protective against joint destruction in RA by regulating synoviocyte migration, invasion, activation, and proliferation.

Triptolide inhibits the migration and invasion of rheumatoid fibroblast-like synoviocytes by blocking the activation of the JNK MAPK pathway

Triptolide, a primary active ingredient extracted from a traditional Chinese herb, Tripterygium wilfordii Hook F, has been demonstrated to have a positive therapeutic effect on patients with rheumatoid arthritis (RA); however, its mechanism of action against RA is not well established. Therefore, in the present study, we observed the effect of triptolide on the aggressive behavior of RA fibroblast-like synoviocytes (RA FLSs), and we explored its underlying signal mechanisms. We found that triptolide treatment significantly reduced the migratory and invasive capacities of RA FLSs in vitro. We also demonstrated that the invasion of RA FLSs into the cartilage, evaluated in the severe combined immunodeficiency (SCID) mouse co-implantation model, was attenuated by treatment with triptolide in vivo. Additionally, the immunofluorescence results showed that triptolide treatment decreased the polymerization of F-actin and the activation of matrix metalloproteinase 9 (MMP-9). To gain insight into the molecular signal mechanisms, we determined the effect of triptolide on the activation of MAPK signal pathways. Our results indicate that triptolide treatment reduced the TNF-α-induced expression of phosphorylated JNK, but did not affect the expression of phosphorylated p38 and ERK. A JNK-specific inhibitor decreased the migration of RA FLSs. We also observed that triptolide administration improved clinical arthritic conditions and joint destruction in mice with collagen-induced arthritis (CIA). Thus, our findings suggest that the therapeutic effects of triptolide on RA might be, in part, due to its contribution to the aggressive behavior of RA FLSs.

Inhibition of p21-Activated Kinase 1 by IPA-3 Promotes Locomotor Recovery After Spinal Cord Injury in Mice

STUDY DESIGN

Ninety-six male adult CD-1 mice were randomly divided into sham, spinal cord injury (SCI) + vehicle, and SCI + IPA-3 groups. Expression of matrix metalloproteinase (MMP)-2 and MMP-9, production of tumor necrosis factors (TNF)-α and interleukin (IL)-1β, tissue edema, blood-spinal cord barrier penetrability, neural cell apoptosis, and neurological function recovery were measured.

OBJECTIVE

The aim of the study was to evaluate the effect of specific inhibition of p21-activated kinase 1 (PAK1) by IPA-3 on SCI and the underlying mechanisms thereof.

SUMMARY OF BACKGROUND DATA

SCI is a devastating clinical condition that may result in long-lasting and deteriorating functional deficits. The major goal of SCI treatment is to limit the development of secondary injury. IPA-3, a PAK1 inhibitor, exhibited neuroprotection against secondary damage after traumatic brain injury and subarachnoid hemorrhage (SAH).

METHODS

MMP-2, MMP-9, and cleaved caspase-3 expression were assessed by Western blot. Inflammatory cytokines TNF-α and IL-1β were detected by enzyme-linked immunosorbent assay (ELISA). The blood-spinal cord barrier disruption was measured by water content and Evans blue extravasation of the spinal cord. Neuronal apoptosis was evaluated by Nissl staining and Terminal-deoxynucleoitidyl Transferase Mediated Nick End Labeling (TUNEL) assay. The locomotor behavior of hind limb was evaluated by Basso Mouse Scale (BMS) at 1, 3, 7, 14, and 28 days post-injury.

RESULTS

Compared with SCI + vehicle mice, IPA-3 treatment showed decreased p-PAK1, MMP-2, MMP-9, cleaved caspase-3, TNF-α, and IL-1β expression. Moreover, inhibition of PAK1 by IPA-3 reduced spinal cord water content and Evans blue extravasation, increased neuronal survival, and reduced TUNEL-positive cells at 24 hours after SCI. Furthermore, IPA-3 improved spinal cord functional recovery 7 days after SCI.

CONCLUSION

Inhibition of PAK1 by IPA-3 promoted recovery of neurological function, possibly by downregulating the expression of MMP-2, MMP-9, TNF-α, and IL-1β. Our data suggest that PAK1 may be a potential therapeutic target in patients with SCI.

LEVEL OF EVIDENCE

1.

Activation of dickkopf-1 and focal adhesion kinase pathway by tumour necrosis factor α induces enhanced migration of fibroblast-like synoviocytes in rheumatoid arthritis

OBJECTIVE

The objective of this study was to investigate the roles of dickkopf-1 (DKK-1) and integrin-related focal adhesion kinase (FAK) by TNF-α on the migration of fibroblast-like synoviocytes (FLSs) in RA.

METHODS

Wound scratch assays were performed to assess FLS migration. Western blotting was used to measure the levels of DKK-1, Wnt signalling molecules and FAK signalling molecules. Quantitative real-time PCR was used to measure the expression levels of DKK-1, integrin αv, laminin, fibronectin, E-cadherin, MMP-8 and MMP-13. The concentrations of DKK-1, TNF-α and GSK-3β were measured by ELISA. Genetic silencing of TNF-α was achieved by the transfection of small interfering RNA into cells.

RESULTS

Migrating RA FLSs exhibited higher levels of DKK-1 and TNF-α expression compared with those in OA FLSs and/or stationary RA FLSs. Moreover, migrating FLSs exhibited significantly higher levels of FAK, p-JNK, paxillin and cdc42 expression, whereas the level of cytosolic β-catenin was lower. WAY-262611, Wnt pathway agonist via inhibition of DKK-1, markedly inhibited cell migration of RA FLSs through the accumulation of cytosolic β-catenin and suppression of FAK-related signalling pathways. TNF-α treatment to RA FLSs up-regulated expression of DKK-1, integrin αv, fibronectin, laminin and MMP-13. TNF-α stimulation also suppressed cytosolic β-catenin and E-cadherin expression in a time-dependent manner. Moreover, TNF-α small interfering RNA-transfected migrating FLSs exhibited decreased activation of integrin-related FAK, paxillin, p-JNK and cdc42 signalling pathways.

CONCLUSION

This study demonstrates that the activation of DKK-1 and the integrin-related FAK signalling pathway stimulated by TNF-α induces the dissociation of β-catenin/E-cadherin, thus promoting RA FLS migration.

Micro-Ribonucleic Acid Profiles From Microarray in Ankylosing Spondylitis

Objectives

This study aims to detect candidate micro-ribonucleic acids (miRNAs) from microarray within peripheral blood mononuclear cells and synovial fluid mononuclear cells in patients with ankylosing spondylitis (AS).

Patients and methods

Samples from three AS patients (3 males, mean age 37.3±2.5 years; range 35 to 40 years) and three healthy controls (3 males, mean age 39.0±2.6 years; range 37 to 42 years) were obtained for miRNA microarray. The microarray experiment proceeded only when the quality of total RNAs were considered to have "passed", and their integrity was good by total RNA quality control using Agilent Bioanalyzer 2100. Hierarchical clustering was performed to understand the impact of the storage condition on the miRNA expression profiles. MiScript primer assays were used for semiquantitative determination of the expression of human miRNAs to validate results from miRNA microarray.

Results

A total of 887 miRNAs were screened by microarray among groups. After normalization of the raw data, we noted that the expression of five miRNAs was significantly lower (fold change ≤0.5 and p≤0.05) and only hsa-miR-424-5p was significantly higher in AS peripheral blood mononuclear cell (fold change ≥2 and p≤0.05). In AS synovial fluid mononuclear cells, we identified that expressions of 16 miRNAs were significantly down regulated whereas only hsa-miR-424-5p was significantly upregulated (fold change ≥2 and p≤0.05). All above-mentioned miRNAs were reevaluated for further validation. Finally, significantly increased hsa-miR-424-5p and decreased hsa-miR-377 were found in synovial fluid mononuclear cells from AS patients compared with healthy controls. Based on target prediction programs and published papers, potential target genes and its pathways were screened.

Conclusion

miR-424-5p was increased and miR-377 was decreased in synovial fluid mononuclear cells from patients with AS. These two miRs might have functional roles in patients with arthritis via different pathways.

Protein Inhibitor of Activated STAT3 Regulates Migration, Invasion, and Activation of Fibroblast-like Synoviocytes in Rheumatoid Arthritis

The aggressive phenotype displayed by fibroblast-like synoviocytes (FLSs) is a critical factor of cartilage destruction in rheumatoid arthritis (RA). Increased FLSs migration and subsequent degradation of the extracellular matrix are essential to the pathology of RA. Protein inhibitor of activated STAT (PIAS), whose family members include PIAS1, PIAS2 (PIASx), PIAS3, and PIAS4 (PIASy), play important roles in regulating various cellular events, such as cell survival, migration, and signal transduction in many cell types. However, whether PIAS proteins have a role in the pathogenesis of RA is unclear. In this study, we evaluated the role of PIAS proteins in FLSs migration, invasion, and matrix metalloproteinases (MMPs) expression in RA. We observed increased expression of PIAS3, but not PIAS1, PIAS2, or PIAS4, in FLSs and synovial tissues from patients with RA. We found that PIAS3 knockdown by short hairpin RNA reduced migration, invasion, and MMP-3, MMP-9, and MMP-13 expression in FLSs. In addition, we demonstrated that PIAS3 regulated lamellipodium formation during cell migration. To gain insight into molecular mechanisms, we evaluated the effect of PIAS3 knockdown on Rac1/PAK1 and JNK activation. Our results indicated that PIAS3-mediated SUMOylation of Rac1 controlled its activation and modulated the Rac1 downstream activity of PAK1 and JNK. Furthermore, inhibition of Rac1, PAK1, or JNK decreased migration and invasion of RA FLSs. Thus, our observations suggest that PIAS3 suppression may be protective against joint destruction in RA by regulating synoviocyte migration, invasion, and activation.

PAK1 modulates a PPARγ/NF-κB cascade in intestinal inflammation

P21-activated kinases (PAKs) are multifunctional effectors of Rho GTPases with both kinase and scaffolding activity. Here, we investigated the effects of inflammation on PAK1 signaling and its role in colitis-driven carcinogenesis. PAK1 and p-PAK1 (Thr423) were assessed by immunohistochemistry, immunofluorescence, and Western blot. C57BL6/J wildtype mice were treated with a single intraperitoneal TNFα injection. Small intestinal organoids from these mice and from PAK1-KO mice were cultured with TNFα. NF-κB and PPARγ were analyzed upon PAK1 overexpression and silencing for transcriptional/translational regulation. PAK1 expression and activation was increased on the luminal intestinal epithelial surface in inflammatory bowel disease and colitis-associated cancer. PAK1 was phosphorylated upon treatment with IFNγ, IL-1β, and TNFα. In vivo, mice administered with TNFα showed increased p-PAK1 in intestinal villi, which was associated with nuclear p65 and NF-κB activation. p65 nuclear translocation downstream of TNFα was strongly inhibited in PAK1-KO small intestinal organoids. PAK1 overexpression induced a PAK1-p65 interaction as visualized by co-immunoprecipitation, nuclear translocation, and increased NF-κB transactivation, all of which were impeded by kinase-dead PAK1. Moreover, PAK1 overexpression downregulated PPARγ and mesalamine recovered PPARγ through PAK1 inhibition. On the other hand PAK1 silencing inhibited NF-κB, which was recovered using BADGE, a PPARγ antagonist. Altogether these data demonstrate that PAK1 overexpression and activation in inflammation and colitis-associated cancer promote NF-κB activity via suppression of PPARγ in intestinal epithelial cells.

TGFβ responsive tyrosine phosphatase promotes rheumatoid synovial fibroblast invasiveness

OBJECTIVE

In rheumatoid arthritis (RA), fibroblast-like synoviocytes (FLS) that line joint synovial membranes aggressively invade the extracellular matrix, destroying cartilage and bone. As signal transduction in FLS is mediated through multiple pathways involving protein tyrosine phosphorylation, we sought to identify protein tyrosine phosphatases (PTPs) regulating the invasiveness of RA FLS. We describe that the transmembrane receptor PTPκ (RPTPκ), encoded by the transforming growth factor (TGF) β-target gene, PTPRK, promotes RA FLS invasiveness.

METHODS

Gene expression was quantified by quantitative PCR. PTP knockdown was achieved using antisense oligonucleotides. FLS invasion and migration were assessed in transwell or spot assays. FLS spreading was assessed by immunofluorescence microscopy. Activation of signalling pathways was analysed by Western blotting of FLS lysates using phosphospecific antibodies. In vivo FLS invasiveness was assessed by intradermal implantation of FLS into nude mice. The RPTPκ substrate was identified by pull-down assays.

RESULTS

PTPRK expression was higher in FLS from patients with RA versus patients with osteoarthritis, resulting from increased TGFB1 expression in RA FLS. RPTPκ knockdown impaired RA FLS spreading, migration, invasiveness and responsiveness to platelet-derived growth factor, tumour necrosis factor and interleukin 1 stimulation. Furthermore, RPTPκ deficiency impaired the in vivo invasiveness of RA FLS. Molecular analysis revealed that RPTPκ promoted RA FLS migration by dephosphorylation of the inhibitory residue Y527 of SRC.

CONCLUSIONS

By regulating phosphorylation of SRC, RPTPκ promotes the pathogenic action of RA FLS, mediating cross-activation of growth factor and inflammatory cytokine signalling by TGFβ in RA FLS.

Republished: tracing PAKs from GI inflammation to cancer

P-21 activated kinases (PAKs) are effectors of Rac1/Cdc42 which coordinate signals from the cell membrane to the nucleus. Activation of PAKs drive important signalling pathways including mitogen activated protein kinase, phospoinositide 3-kinase (PI3K/AKT), NF-κB and Wnt/β-catenin. Intestinal PAK1 expression increases with inflammation and malignant transformation, although the biological relevance of PAKs in the development and progression of GI disease is only incompletely understood. This review highlights the importance of altered PAK activation within GI inflammation, emphasises its effect on oncogenic signalling and discusses PAKs as therapeutic targets of chemoprevention.

Tracing PAKs from GI inflammation to cancer

P-21 activated kinases (PAKs) are effectors of Rac1/Cdc42 which coordinate signals from the cell membrane to the nucleus. Activation of PAKs drive important signalling pathways including mitogen activated protein kinase, phospoinositide 3-kinase (PI3K/AKT), NF-κB and Wnt/β-catenin. Intestinal PAK1 expression increases with inflammation and malignant transformation, although the biological relevance of PAKs in the development and progression of GI disease is only incompletely understood. This review highlights the importance of altered PAK activation within GI inflammation, emphasises its effect on oncogenic signalling and discusses PAKs as therapeutic targets of chemoprevention.

Knockdown of sphingosine kinase 1 inhibits the migration and invasion of human rheumatoid arthritis fibroblast-like synoviocytes by down-regulating the PI3K/AKT activation and MMP-2/9 production in vitro

To investigate the potential regulation of sphingosine kinase 1 (SPHK1) on the migration, invasion, and matrix metalloproteinase (MMP) expression in human rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS). RA-FLS were transfected control siRNA or SPHK1 siRNA. The migration and invasion of unmanipulated control, control siRNA or SPHK1 siRNA- transfected RA-FLS in vitro were measured by the transwell system. The relative levels of SPHK1, PI3K, and AKT as well as AKT phosphorylation in RA-FLS were determined by Western blot. The levels of MMP-2/9 secreted by RA-FLS were detected by ELISA. Knockdown of SPHK1 significantly inhibited the spontaneous migration and invasion of RA-FLS, accompanied by significantly reduced levels of PI3K expression and AKT phosphorylation. Similarly, treatment with LY294002, an inhibitor of the PI3K/AKT pathway, inhibited the migration and invasion of RA-FLS. Knockdown of SPHK1 and treatment with the inhibitor synergistically inhibited the migration and invasion of RA-FLS, by further reducing the levels of PI3K expression and AKT phosphorylation. In addition, knockdown of SPHK1 or treatment with LY294002 inhibited the secretion of MMP-2 and MMP-9, and both synergistically reduced the production of MMP-2 and MMP-9 in RA-FLS in vitro. Knockdown of SPHK1 expression inhibits the PI3K/AKT activation, MMP-2 and MMP-9 expression, and human RA-FLS migration and invasion in vitro. Potentially, SPHK1 may be a novel therapeutic target for RA.

PAK signalling during the development and progression of cancer

p21-Activated kinases (PAKs) are positioned at the nexus of several oncogenic signalling pathways. Overexpression or mutational activation of PAK isoforms frequently occurs in various human tumours, and recent data suggest that excessive PAK activity drives many of the cellular processes that are the hallmarks of cancer. In this Review, we discuss the mechanisms of PAK activation in cancer, the key substrates that mediate the developmental and oncogenic effects of this family of kinases, and how small-molecule inhibitors of these enzymes might be best developed and deployed for the treatment of cancer.

Tumor necrosis factor α induces sustained signaling and a prolonged and unremitting inflammatory response in rheumatoid arthritis synovial fibroblasts

OBJECTIVE

The nonresolving character of synovial inflammation in rheumatoid arthritis (RA) is a conundrum. To identify the contribution of fibroblast-like synoviocytes (FLS) to the perpetuation of synovitis, we investigated the molecular mechanisms that govern the tumor necrosis factor α (TNFα)-driven inflammatory program in human FLS.

METHODS

FLS obtained from the synovial tissues of patients with RA or osteoarthritis were stimulated with TNFα and assayed for gene expression and cytokine production by real-time quantitative reverse transcription-polymerase chain reaction analysis and enzyme-linked immunosorbent assay. NF-κB signaling was evaluated by Western blotting. Histone acetylation, chromatin accessibility, and NF-κB p65 and RNA polymerase II (Pol II) occupancy at the interleukin-6 (IL-6) promoter were measured by chromatin immunoprecipitation and restriction enzyme accessibility assays.

RESULTS

In FLS, TNFα induced prolonged transcription of messenger RNA (mRNA) for IL-6 and progressive accumulation of IL-6 protein over 4 days. Similarly, induction of mRNA for CXCL8/IL-8, CCL5/RANTES, matrix metalloproteinase 1 (MMP-1), and MMP-3 after TNFα stimulation was sustained for several days. This contrasted with the macrophage response to TNFα, which characteristically involved a transient increase in the expression of proinflammatory genes. In FLS, TNFα induced prolonged activation of NF-κB signaling and sustained transcriptional activity, as indicated by increased histone acetylation, chromatin accessibility, and p65 and Pol II occupancy at the IL-6 promoter. Furthermore, FLS expressed low levels of the feedback inhibitors A20-binding inhibitor of NF-κB activation 3 (ABIN-3), IL-1 receptor-associated kinase M (IRAK-M), suppressor of cytokine signaling 3 (SOCS-3), and activating transcription factor 3 (ATF-3), which terminate inflammatory responses in macrophages.

CONCLUSION

TNFα signaling is not effectively terminated in FLS, which leads to an uncontrolled inflammatory response. The results suggest that prolonged and sustained inflammatory responses by FLS in response to synovial TNFα contribute to the persistence of synovial inflammation in RA.