Small GTP-binding protein Rho-mediated signaling promotes proliferation of rheumatoid synovial fibroblasts

Peptidomic analysis reveals novel peptide PDLC promotes cell proliferation in hepatocellular carcinoma via Ras/Raf/MEK/ERK pathway

Hepatocellular carcinoma (HCC) still presents poor prognosis with low overall survival rates and limited therapeutic options available. Recently, attention has been drawn to peptidomic analysis, an emerging field of proteomics for the exploration of new potential peptide drugs for the treatment of various diseases. However, research on the potential function of HCC peptides is lacking. Here, we analyzed the peptide spectrum in HCC tissues using peptidomic techniques and explored the potentially beneficial peptides involved in HCC. Changes in peptide profiles in HCC were examined using liquid chromatography-mass spectrometry (LC-MS/MS). Analyze the physicochemical properties and function of differently expressed peptides using bioinformatics. The effect of candidate functional peptides on HCC cell growth and migration was evaluated using the CCK-8, colony formation, and transwell assays. Transcriptome sequencing analysis and western blot were employed to delve into the mode of action of potential peptide on HCC. Peptidomic analysis of HCC tissue yielded a total of 8683 peptides, of which 452 exhibited up-regulation and 362 showed down-regulation. The peptides that were differentially expressed, according to bioinformatic analysis, were closely linked to carbon metabolism and the mitochondrial inner membrane. The peptide functional validation identified a novel peptide, PDLC (peptide derived from liver cancer), which was found to dramatically boost HCC cell proliferation through the Ras/Raf/MEK/ERK signaling cascade. Our research defined the peptide's properties and pattern of expression in HCC and identified a novel peptide, PDLC, with a function in encouraging HCC progression, offering an entirely new potential therapeutic target the disease.

MYLK*FLNB and DOCK1*LAMA2 gene-gene interactions associated with rheumatoid arthritis in the focal adhesion pathway

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease caused by a combination of genetic and environmental factors. Rare variants with low predicted effects in genes participating in the same biological function might be involved in developing complex diseases such as RA. From whole-exome sequencing (WES) data, we identified genes containing rare non-neutral variants with complete penetrance and no phenocopy in at least one of nine French multiplex families. Further enrichment analysis highlighted focal adhesion as the most significant pathway. We then tested if interactions between the genes participating in this function would increase or decrease the risk of developing RA disease. The model-based multifactor dimensionality reduction (MB-MDR) approach was used to detect epistasis in a discovery sample (19 RA cases and 11 healthy individuals from 9 families and 98 unrelated CEU controls from the International Genome Sample Resource). We identified 9 significant interactions involving 11 genes (MYLK, FLNB, DOCK1, LAMA2, RELN, PIP5K1C, TNC, PRKCA, VEGFB, ITGB5, and FLT1). One interaction (MYLK*FLNB) increasing RA risk and one interaction decreasing RA risk (DOCK1*LAMA2) were confirmed in a replication sample (200 unrelated RA cases and 91 GBR unrelated controls). Functional and genomic data in RA samples or relevant cell types argue the key role of these genes in RA.

Exploring the therapeutic promise of targeting Rho kinase in rheumatoid arthritis

Rheumatoid arthritis (RA) is a prevalent systemic autoimmune disease caused by dysregulated inflammatory reactions, T lymphocyte invasion into the joints, and articular thickening. Immune cells, primarily tumor necrosis factor-alpha (TNF-α) and chemokines (interleukin or IL-1), which are predominantly generated by activated macrophages cells, have also been involved with the pathogenesis of rheumatoid arthritis. Rho GTPases are integral factors of biochemical cascades utilized by antigens, and also by cellular receptors, cytokines, and chemokines, to modulate inflammatory reactions, according to growing data. The Rho family is a group of G proteins that govern a variety of biological and physiological activities such as mobility, actin stress fiber production, growth, and polarity. Research suggests that the Rho A and Rho-associated coiled-coil kinase (ROCK) regulatory cascade could be essential in several autoimmune conditions, including RA. ROCK is activated in the synovial of rheumatoid arthritis patients, while the blocking of ROCK with fasudil could also decrease IL-6, TNF-α, and IL-1. This review covers current developments in understanding the overactivation of Rho enzyme activity in RA suppressed by ROCK inhibitors which can be utilized for the treatment of autoimmune disease. We offer an outline of the function of ROCK inhibitors in immune cells and discuss findings which emphasize the rising participation of this category of kinases within the pathological process of autoimmune disorders. Assuming the potential ability of ROCK as a therapeutic, we define approaches that might be used to inhibit Rho kinase activity in rheumatoid disorders.

Effect of statins on toll-like receptors: a new insight to pleiotropic effects

The toll-like receptors (TLRs) are a class of transmembrane-spanning receptors that are sentinels of both innate and adaptive immunity. Statins (3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors) are the most commonly prescribed therapeutic agents for treating hypercholesterolemia globally. However, statin therapy appears to have pleiotropic effects including attenuation of chronic low-grade inflammation and modulation of TLR activity. Statins through abolition of TLR4 expression and regulation of the TLR4/Myd88/NF-κB signaling pathway may slow the progression of atherosclerosis and other inflammatory diseases. In this review, we have focused on the impact and mechanism of action of statins on cardiovascular and non-cardiovascular diseases.

Paeoniflorin inhibits Rho kinase activation in joint synovial tissues of rats with collagen-induced rheumatoid arthritis

Paeoniflorin (PF) has many effects, such as anti-inflammation, immune-regulation, abirritation, and so on. However, the protective mechanisms of PF on rheumatoid arthritis (RA) was not completely known. Thus, we explored deeply the protective mechanisms in a collagen-induced RA (CIA) rat model. CIA was induced in rats by intradermal injection of bovine type II collagen in complete Freund's adjuvant. Later, the CIA rats received oral administration of PF (50 and 100 mg/kg) once a day from the day 21, with the treatment lasting for 14 days. A variety of indicators were measured for evaluation of anti-rheumatism effect, including paw swelling, arthritis scores, and histopathological changes. And the contents of pro-inflammatory cytokines, including tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6) in the serum, as well as p-NF-κB p65 and p-MYPT1 in the joint synovial tissues were detected to explore the possible mechanisms. The results demonstrated that PF treatment significantly ameliorated the symptoms in CIA rats, reduced the levels of pro-inflammatory cytokines and paw swelling, down-regulated the expressions of p-NF-κB p65 and p-MYPT1. The present results revealed that PF could effectively improve collagen-induced RA in rats by inhibiting Rho kinase activation in the joint synovial tissues, in turn down-regulating expression of p-NF-κB p65 and reducing contents of pro-inflammatory cytokines. Moreover, PF may be an effective agent for RA.

Gene Expression Analysis before and after Treatment with Adalimumab in Patients with Ankylosing Spondylitis Identifies Molecular Pathways Associated with Response to Therapy

The etiology of Ankylosing spondylitis (AS) is still unknown and the identification of the involved molecular pathogenetic pathways is a current challenge in the study of the disease. Adalimumab (ADA), an anti-tumor necrosis factor (TNF)-alpha agent, is used in the treatment of AS. We aimed at identifying pathogenetic pathways modified by ADA in patients with a good response to the treatment. Gene expression analysis of Peripheral Blood Cells (PBC) from six responders and four not responder patients was performed before and after treatment. Differentially expressed genes (DEGs) were submitted to functional enrichment analysis and network analysis, followed by modules selection. Most of the DEGs were involved in signaling pathways and in immune response. We identified three modules that were mostly impacted by ADA therapy and included genes involved in mitogen activated protein (MAP) kinase, wingless related integration site (Wnt), fibroblast growth factor (FGF) receptor, and Toll-like receptor (TCR) signaling. A separate analysis showed that a higher percentage of DEGs was modified by ADA in responders (44%) compared to non-responders (12%). Moreover, only in the responder group, TNF, Wnt, TLRs and type I interferon signaling were corrected by the treatment. We hypothesize that these pathways are strongly associated to AS pathogenesis and that they might be considered as possible targets of new drugs in the treatment of AS.

Effect of adrenomedullin on intestinal permeability in rats with ulcerative colitis

AIM: To investigate the possible mechanism of adrenomedullin (AM) to protect the intestinal epithelial barrier function in a rat model of ulcerative colitis (UC).

METHODS: Twenty-four male Sprague-Dawley rats were randomly divided into three groups: a normal control group, a model group and an AM group. Each group contained 8 rats. All the rats except those in the normal control group were administered with TNBS to induce colitis. Rats in the normal control group was given physiological saline instead. Forty-eight hours after inducing colitis, in the AM group, AM (1.0 μg of AM diluted in 1.0 mL of saline) was injected into the lumen of the colon. Rats in the normal control group and model group were given 1.0 mL of saline instead. All of them were treated for seven consecutive days. Blood samples were collected to measure serum tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) levels by ELISA. Colon tissues were taken to detect the protein expression of RhoA, Rho associated kinase 1 (ROCK1), MLCK, nuclear factor-κB (NF-κB) p65 and Occludin by Western blot analysis.

RESULTS: All the rats induced with TNBS developed symptoms such as profound and sustained weight loss, bradykinesia and purulent and bloody stools. The levels of serum TNF-α and IFN-γ in model rats were significantly higher than those in the normal group (P < 0.05), however, serum TNF-α and IFN-γ were significantly decreased after AM treatment (P < 0.05). The expression levels of RhoA, ROCKI, MLCK and NF-κB p65 showed a significant increase in the model group compared with the normal group (P < 0.05), while treatment with AM clearly reduced their expression. The expression of Occludin in model rats was significantly decreased (P < 0.05), while in the AM group, the reduced Occludin expression appeared to resume (P < 0.05).

CONCLUSION: AM improves intestinal mucosal barrier function in UC possibly by regulating the NF-κB p65/MLCK signal pathway mediated by RhoA.

RhoA/ROCK-dependent pathway is required for TLR2-mediated IL-23 production in human synovial macrophages: suppression by cilostazol

IL-23 is produced by antigen presenting cells and plays critical roles in immune response in rheumatoid arthritis. In this study, we investigated whether the RhoA/Rho-kinase pathway is required to elevate TLR2-mediated IL-23 production in synovial macrophages from patients with rheumatoid arthritis (RA), and then examined the suppressive effect of cilostazol on these pathways. IL-23 production was elevated by lipoteichoic acid (LTA), a TLR2 ligand, and this elevation was more prominent in RA macrophages than in those from peripheral blood of normal control. LTA increased the activation of RhoA in association with increased the nuclear translocation of NF-κB and its DNA-binding activity. Pretreatment of RA macrophages with the pharmacological inhibitors exoenzyme C3 (RhoA), Y27632 (Rho-kinase) or BAY11-7082 (NF-κB) inhibited IL-23 production by LTA. Inhibition of the RhoA/Rho-kinase pathway by these drugs attenuated NF-κB activation. Cilostazol suppressed the TLR2-mediated activation of RhoA, decreased NF-κB activity with down-regulated IL-23 production, and these effects were reversed by Rp-cAMPS, as an inhibitor of cAMP-dependent protein kinase. The expression of IL-23, which colocalized with CD68⁺ cells in knee joint of CIA mice, was significantly attenuated by cilostazol along with the decreased severity of arthritis. Taken together, the RhoA/Rho-kinase pathway signals TLR2-stimulated IL-23 production in synovial fluid macrophages via activation of NF-κB. Thus it is summarized that cilostazol suppresses TLR2-mediated IL-23 production by suppressing RhoA pathway via cAMP-dependent protein kinase activation.

Serum proteome analysis in patients with rheumatoid arthritis receiving therapy with etanercept, a chimeric tumor necrosis factor-alpha receptor

AIM

Rheumatoid arthritis (RA) is a chronic inflammatory disorder of the synovium resulting in the destruction of affected joint cartilage and bone structures. Etanercept is a biological agent that blocks the tumor necrosis factor-α (TNF-α)-mediated inflammatory processes in RA patients, and has a regenerative effect on cartilage. In order to identify novel disease-related proteins and candidate biomarkers, we performed proteomic profiling of the serum in patients with RA who were treated with etanercept.

METHOD

Serum samples were obtained from eight RA patients before and after etanercept treatment. The low molecular weight proteins in the serum were concentrated and analyzed by liquid chromatography-tandem mass spectrometry. The results before and after etanercept treatment were compared by the spectrum count method.

RESULTS

Among a total of 477 proteins identified, 12 were found to be decreased and five were increased by etanercept treatment. Some of the changed proteins were known to be related to RA, and most of the other changed proteins may play possible roles in the TNF-α signaling pathway or the state of cartilage and extracellular matrix.

CONCLUSION

The present proteomic study identified several proteins that could be involved in the pathogenesis of RA. These findings could thus lead to the identification of novel candidate disease-related protein biomarkers for RA, or indicate new targets for therapy.

Signal transduction pathways in chronic inflammatory autoimmune disease: small GTPases

Ras superfamily small GTPases represent a wide and diverse class of intracellular signaling proteins that are highly conserved during evolution. These enzymes serve as key checkpoints in coupling antigen receptor, growth factor, cytokine and chemokine stimulation to cellular responses. Once activated, via their ability to regulate multiple downstream signaling pathways, small GTPases amplify and diversify signaling cascades which regulate cellular proliferation, survival, cytokine expression, trafficking and retention. Small GTPases, particularly members of the Ras, Rap, and Rho family, critically coordinate the function and interplay of immune and stromal cells during inflammatory respones, and increasing evidence indicates that alterations in small GTPase signaling contribute to the pathological behavior of these cell populations in human chronic inflammatory diseases such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Here, we review how Ras, Rap, and Rho family GTPases contribute to the biology of cell populations relevant to human chronic inflammatory disease, highlight recent advances in understanding how alterations in these pathways contribute to pathology in RA and SLE, and discuss new therapeutic strategies that may allow specific targeting of small GTPases in the clinic.

Mast cell-derived tryptase inhibits apoptosis of human rheumatoid synovial fibroblasts via rho-mediated signaling

OBJECTIVE

An abundance of mast cells are found in the synovium of patients with rheumatoid arthritis (RA). However, the role of mast cells in the pathogenesis of RA remains unclear. This study was undertaken to elucidate a role for mast cells in RA by investigating the antiapoptotic effects of tryptase, a major product of mast cells, on RA synovial fibroblasts (RASFs).

METHODS

RA synovial tissue was obtained from RA patients during joint replacement surgery, and histologic changes in the tissue were examined. The expression of cell surface molecules and apoptotic markers on RASFs were detected by flow cytometry. Rho activation was determined using a pull-down assay.

RESULTS

Mast cells, bearing both c-Kit and tryptase, accumulated in the sublining area of proliferating synovial tissue from RA patients. Protease-activated receptor 2 (PAR-2), a receptor for tryptase, was expressed on RASFs in the lining area, close to tryptase-positive mast cells in the RA synovium. Fas-mediated apoptosis of RASFs was significantly inhibited, in a dose-dependent manner, by the addition of tryptase, and this effect correlated with increased activation of Rho kinase. Furthermore, Y27632, a Rho kinase inhibitor, reduced the antiapoptotic effect of tryptase on RASFs, suggesting that Rho was responsible for the antiapoptotic effects of tryptase.

CONCLUSION

These results demonstrate that tryptase has a strong antiapoptotic effect on RASFs through the activation of Rho. Thus, we propose that the release of tryptase by mast cells leads to the binding of tryptase to PAR-2 on RASFs and inhibits the apoptosis of RASFs via the activation of Rho. Such mechanisms could play a pivotal role in the marked proliferation of RASFs and hyperplasia of synovial tissue seen in RA synovium.

Antiinflammatory effect of Rho kinase blockade via inhibition of NF-kappaB activation in rheumatoid arthritis

OBJECTIVE

There is increasing evidence that the RhoA signaling pathway may play a critical role in the inflammatory response. This study was undertaken to examine the effects of RhoA and its downstream effector Rho kinase (ROK) in synovial inflammation in rheumatoid arthritis (RA).

METHODS

RhoA activity was assessed by pull-down assay. Fasudil and Y27632, both specific inhibitors of ROK, were used to examine the role of ROK in inflammatory responses in vivo and in vitro. Nuclear translocation of NF-kappaB was measured by confocal fluorescence microscopy, and DNA binding activity was assessed with a sensitive multiwell colorimetric assay. Enzyme-linked immunosorbent assay was used to detect cytokine production.

RESULTS

Increased activation of RhoA was found in inflamed synovial membrane cells isolated from patients with RA and from rats with collagen-induced arthritis (CIA). Intraperitoneal administration of fasudil in rats with CIA significantly reduced synovial inflammation and ROK activity. In vitro, treatment with fasudil or Y27632 decreased production of tumor necrosis factor alpha (TNFalpha), interleukin-1beta (IL-1beta), and IL-6 by synovial membrane cells, peripheral blood mononuclear cells, and fibroblast-like synoviocytes from patients with active RA. Inhibition of ROK by specific inhibitors or ROK small interfering RNA suppressed lipopolysaccharide- or TNFalpha-induced NF-kappaB nuclear translocation, DNA binding activity, luciferase reporter gene expression, and IkappaBalpha degradation.

CONCLUSION

The results of this study provide new evidence that blockade of ROK inhibits activation of NF-kappaB and production of proinflammatory cytokines, suggesting a critical role of ROK in the synovial inflammation of RA. Specific inhibition of ROK may be a novel therapeutic approach in RA.

Effect of sildenafil citrate on interleukin-1beta-induced nitric oxide synthesis and iNOS expression in SW982 cells

The purpose of this study was to identify the effect of sildenafil citrate on IL-1beta-induced nitric oxide (NO) synthesis and iNOS expression in human synovial sarcoma SW982 cells. IL-1? stimulated the cells to generate NO in both dose- and time-dependent manners. The IL-1beta-induced NO synthesis was inhibited by guanylate cyclase (GC) inhibitor, LY83583. When the cells were treated with 8-bromo-cGMP, a hydrolyzable analog of cGMP, NO synthesis was increased upto 5-fold without IL-1beta treatment suggesting that cGMP is an essential component for increasing the NO synthesis. Synoviocytes and chondrocytes contain strong cGMP phosphodiesterase (PDE) activity, which has biochemical features of PDE5. When SW982 cells were pretreated with sildenafil citrate (Viagra), a PDE5 specific inhibitor, sildenafil citrate significantly inhibited IL-1beta-induced NO synthesis and iNOS expressions. From this result, we noticed that PDE5 activity is required for IL-1?-induced NO synthesis and iNOS expressions in human synovial sarcoma cells, and sildenafil citrate may be able to suppress an inflammatory reaction of synovium through inhibition of NO synthesis and iNOS expression by cytokines.

The p38 mitogen-activated protein kinase (MAPK) pathway in rheumatoid arthritis

Chronic inflammatory processes are based on a sustained and tightly regulated communication network among different cells types. This network comprises extracellular mediators such as cytokines, chemokines and matrix-degrading proteases, which orchestrate the participation of cells in the chronic inflammatory process. The mirrors of this outside communication world are intracellular transcription factor pathways, which shuttle information about inflammatory stimuli to the cell nucleus. This review examines the function of one key signal transduction pathway of inflammation--the p38 mitogen-activated protein kinases (p38MAPK). The signalling pathway is considered as crucial for the induction and maintenance of chronic inflammation, and its components thus emerge as interesting molecular targets of small molecule inhibitors for controlling inflammation. This review not only summarises the current knowledge of activation, regulation and function of the p38MAPK pathway but also examines the role of this pathway in clinical disease. It gives an overview of current evidence of p38MAPK activation in inflammatory arthritis and elaborates the key molecular determinants which contribute to p38MAPK activation in joint disease.

RhoA-mediated, tumor necrosis factor alpha-induced activation of NF-kappaB in rheumatoid synoviocytes: inhibitory effect of simvastatin

OBJECTIVE

Increasing evidence indicates that RhoA may play a central role in the inflammatory response. This study was conducted to examine the role of RhoA in mediating the activation of NF-kappaB in tumor necrosis factor alpha (TNFalpha)-stimulated rheumatoid synoviocytes, and to evaluate the modulatory effects of statins on the TNFalpha-induced activation of RhoA and NF-kappaB and the secretion of proinflammatory cytokines by rheumatoid synoviocytes.

METHODS

Rheumatoid synoviocytes obtained from patients with active rheumatoid arthritis were stimulated with TNFalpha and incubated with simvastatin (SMV) (1 muM). RhoA activity was assessed by a pull-down assay. NF-kappaB DNA binding activity and nuclear translocation of NF-kappaB were measured by a sensitive multiwell colorimetric assay and confocal fluorescence microscopy, respectively.

RESULTS

TNFalpha stimulation elicited a robust increase in RhoA activity in a dose-dependent manner, and SMV mitigated this increase. TNFalpha also hastened NF-kappaB nuclear translocation of subunit p65 and increased DNA binding activity, luciferase reporter gene expression, degradation of IkappaB, and secretion of interleukin-1beta (IL-1beta) and IL-6. SMV prevented the increase in NF-kappaB activation and rise in IL-1beta and IL-6 levels induced by TNFalpha, whereas mevalonate and geranylgeranyl pyrophosphate reversed the inhibitory effects of SMV on activation of NF-kappaB and RhoA. Furthermore, cotransfection with a dominant-negative mutant of RhoA demonstrated that the TNFalpha-induced signaling pathway involved sequential activation of RhoA, leading to NF-kappaB activation and, ultimately, to secretion of cytokines.

CONCLUSION

This study identifies RhoA as the key regulator of TNFalpha-induced NF-kappaB activation, which ultimately results in the secretion of proinflammatory cytokines in rheumatoid synoviocytes. The findings provide a new rationale for the antiinflammatory effects of statins in inflammatory arthritis.