TLR2 expression is regulated by microRNA miR-19 in rheumatoid fibroblast-like synoviocytes

Resident cells, such as fibroblast-like synoviocytes (FLS), play a crucial role in rheumatoid arthritis (RA). They are implicated in the inflammatory response and play a key role in osteoarticular destruction. Moreover, RA FLS spread RA to unaffected joints. Pathogen-associated molecular patterns and damage-associated molecular patterns have been found to activate RA FLS by interacting with pattern recognition receptors, such as TLR. RA FLS express a large number of TLR, and TLR2 was demonstrated to be involved in RA inflammation. Because microRNA have emerged as important controllers of TLR expression and signaling, the aim of this study was to evaluate their potential involvement in the control of TLR2 expression by RA FLS. We first showed that Tlr2 expression is strongly upregulated in RA FLS in response to TLR2 ligands. Using a microRNA microarray analysis, we identified one miRNA in activated RA FLS, miR-19b, which was downregulated and predicted to target Tlr2 mRNA. Downregulation of miR-19b and miR-19a, which belongs to the same cluster, was confirmed by real-time quantitative PCR. Transfection of RA FLS with miR-19a/b mimics decreased TLR2 protein expression. In parallel, we found that both IL-6 and matrix metalloproteinase 3 secretion was significantly downregulated in activated FLS transfected with either mimic. Moreover, using a luciferase assay, we showed that miR-19a/b directly target Tlr2 mRNA. Taken together, our data point toward an important role for miR-19a/b in the regulation of IL-6 and matrix metalloproteinase 3 release by controlling TLR2 expression, as well as provide evidence that miR-19a/b can act as negative regulators of inflammation in humans.     

TL1A increased IL-6 production on fibroblast-like synoviocytes by preferentially activating TNF receptor 2 in rheumatoid arthritis

TNF-like protein 1A (TL1A), a member of tumor necrosis factor family, recognized as a ligand of death receptor 3 (DR3) and decoy receptor 3 (DcR3). The interaction of TL1A and DR3 may participate in the pathogenesis of some autoimmune diseases including rheumatoid arthritis (RA). Our previous results showed that high concentrations of TL1A could be found in synovial and serum in RA patients, and it was correlated with disease severity. In addition, TL1A could promote Th17 differentiation induced by TGF-β and IL-6 and increased the production of IL-17A. In the present study, we found that TL1A could promote the expression of IL-6 on fibroblast-like synoviocytes (FLS) of RA patients via NF-κB and JNK signaling pathway. TL1A-stimulated FLS increased the percentage of Th17 of peripheral blood mononuclear cells (PBMC) in RA via the production of IL-6, a critical cytokine involved in the differentiation of Th17. Moreover, the blocking of tumor necrosis factor receptor 2 (TNFR2) decreased TL1A-stimulated IL-6 production by RA FLS. Our results suggest that TL1A was capable of acting on RA FLS to elevate IL-6 expression, which promoted the production of Th17. More importantly, we showed that TL1A could influence RA FLS through binding to TNFR2 rather than DR3 on FLS, which indicated that the treatment of TNF inhibitors not only blocked the TNF but also suppressed the TL1A in RA patients.     

Cyr61 induces IL-6 production by fibroblast-like synoviocytes promoting Th17 differentiation in rheumatoid arthritis

Cysteine-rich protein 61 (Cyr61)/CCN1 is a product of an immediate early gene and functions in mediating cell adhesion and inducing cell migration. We previously showed that increased production of Cyr61 by fibroblast-like synoviocytes (FLS) in rheumatoid arthritis (RA) promotes FLS proliferation and participates in RA pathogenesis with the IL-17-dependent pathway. However, whether Cyr61 in turn regulates Th17 cell differentiation and further enhances inflammation of RA remained unknown. In the current study, we explored the potential role of Cyr61 as a proinflammatory factor in RA pathogenesis. We found that Cyr61 treatment dramatically induced IL-6 production in FLS isolated from RA patients. Moreover, IL-6 production was attenuated by Cyr61 knockdown in FLS. Mechanistically, we showed that Cyr61 activated IL-6 production via the αvβ5/Akt/NF-κB signaling pathway. Further, using a coculture system consisting of purified CD4(+) T cells and RA FLS, we found that RA FLS stimulated Th17 differentiation, and the pro-Th17 differentiation effect of RA FLS can be attenuated or stimulated by Cyr61 RNA interference or addition of exogenous Cyr61, respectively. Finally, using the collagen-induced arthritis animal model, we showed that treatment with the anti-Cyr61 mAb led to reduction of IL-6 levels, decrease of Th17 response, and attenuation of inflammation and disease progression in vivo. Taken together, our results reveal a novel role of Cyr61 in promoting Th17 development in RA via upregulation of IL-6 production by FLS, thus adding a new layer into the functional interplay between FLS and Th17 in RA pathogenesis. Our study also suggests that targeting of Cyr61 may represent a novel strategy in RA treatment.     

Andrographolide induces cell cycle arrest and apoptosis in human rheumatoid arthritis fibroblast-like synoviocytes

The pseudo-tumoral expansion of fibroblast-like synoviocytes is a hallmark of rheumatoid arthritis (RA), and targeting rheumatoid arthritis fibroblast-like synoviocytes (RAFLSs) may have therapeutic potentials in this disease. Andrographolide, a diterpenoid compound isolated from the herb Andrographis paniculata, has been reported to have potent anti-inflammatory activity. In the present study, we aimed to investigate the effects of andrographolide on human RAFLSs and the underlying molecular mechanism(s). RAFLSs were isolated from patients with RA and treated with or without various concentrations (i.e., 10, 20, and 30 μM) of andrographolide for 48 h. 3-[4,5-Dimethyl-2-yl]-2,5-diphenyl tetrazolium bromide assay revealed that andrographolide treatment decreased the proliferation of RAFLSs in a dose-dependent manner. Cell cycle analysis using propidium iodide (PI) staining showed a G0/G1 cell cycle arrest in andrographolide-treated RAFLSs. Immunoblotting analysis of key cell cycle regulators demonstrated that andrographolide treatment caused a dose-dependent increase in the expression of cell-cycle inhibitors p21 and p27 and a concomitant reduction of cyclin-dependent kinase 4. Exposure to andrographolide-induced apoptosis of RAFLSs measured by annexin V/PI double staining, which was coupled with promotion of cytochrome C release from mitochondria and activation of caspase-3. Moreover, andrographolide-treated RAFLSs displayed a significant decrease in the Bcl-2/Bax ratio compared to untreated cells. In conclusion, our data demonstrate that andrographolide exerts anti-growth and pro-apoptotic effects on RAFLSs, thus may have therapeutic potential for the treatment of RA.     

Cyr61 is involved in neutrophil infiltration in joints by inducing IL-8 production by fibroblast-like synoviocytes in rheumatoid arthritis

Introduction

It is well known that neutrophils play very important roles in the development of rheumatoid arthritis (RA) and interleukin (IL)-8 is a critical chemokine in promoting neutrophil migration. We previously showed that increased production of Cyr61 by fibroblast-like synoviocytes (FLS) in RA promotes FLS proliferation and Th17 cell differentiation, thus Cyr61 is a pro-inflammatory factor in RA pathogenesis. In this study, we explored the role of Cyr61 in neutrophil migration to the joints of RA patients.

Methods

RA FLS were treated with Cyr61 and IL-8 expression was analyzed by real-time PCR and ELISA. The migration of neutrophils recruited by the culture supernatants was determined by the use of a chemotaxis assay. Mice with collagen-induced arthritis (CIA) were treated with anti-Cyr61 monoclonal antibodies (mAb), or IgG1 as a control. Arthritis severity was determined by visual examination of the paws and joint destruction was determined by hematoxylin-eosin (H&E) staining. Signal transduction pathways in Cyr61-induced IL-8 production were investigated by real-time PCR, western blotting, confocal microscopy, luciferase reporter assay or chromatin immunoprecipitation (ChIP) assay.

Results

We found that Cyr61 induced IL-8 production by RA FLS in an IL-1β and TNF-α independent pathway. Moreover, we identified that Cyr61-induced IL-8-mediated neutrophil migration in vitro. Using a CIA animal model, we found that treatment with anti-Cyr61 mAb led to a reduction in MIP-2 (a counterpart of human IL-8) expression and decrease in neutrophil infiltration, which is consistent with an attenuation of inflammation in vivo. Mechanistically, we showed that Cyr61 induced IL-8 production in FLS via AKT, JNK and ERK1/2-dependent AP-1, C/EBPβ and NF-κB signaling pathways.

Conclusions

Our results here reveal a novel role of Cyr61 in the pathogenesis of RA. It promotes neutrophil infiltration via up-regulation of IL-8 production in FLS. Taken together with our previous work, this study provides further evidence that Cyr61 plays a key role in the vicious cycle formed by the interaction between infiltrating neutrophils, proliferated FLS and activated Th17 cells in the development of RA.     

NLRP3 promotes autophagy of urate crystals phagocytized by human osteoblasts

Introduction

Monosodium urate (MSU) microcrystals present in bone tissues of chronic gout can be ingested by nonprofessional phagocytes like osteoblasts (OBs) that express NLRP3 (nucleotide-binding domain and leucine-rich repeat region containing family of receptor protein 3). MSU is known to activate NLRP3 inflammasomes in professional phagocytes. We have identified a new role for NLRP3 coupled to autophagy in MSU-stimulated human OBs.

Methods

Normal human OBs cultured in vitro were investigated for their capacity for phagocytosis of MSU microcrystals by using confocal microscopy. Subsequent mineralization and matrix metalloproteinase activity were evaluated, whereas regulatory events of phagocytosis were deciphered by using signaling inhibitors, phosphokinase arrays, and small interfering RNAs. Statistics were carried out by using paired or unpaired t tests, and the one-way ANOVA, followed by multiple comparison test.

Results

Most of the OBs internalized MSU in vacuoles. This process depends on signaling via PI3K, protein kinase C (PKC), and spleen tyrosine kinase (Syk), but is independent of Src kinases. Simultaneously, MSU decreases phosphorylation of the protein kinases TOR (target of rapamycin) and p70S6K. MSU activates the cleavage of microtubule-associated protein light chain 3 (LC3)-I into LC3-II, and MSU microcrystals are coated with GFP-tagged LC3. However, MSU-stimulated autophagy in OBs absolutely requires the phagocytosis process. We find that MSU upregulates NLRP3, which positively controls the formation of MSU-autophagosomes in OBs. MSU does not increase death and late apoptosis of OBs, but reduces their proliferation in parallel to decreasing their competence for mineralization and to increasing their matrix metalloproteinase activity.

Conclusions

MSU microcrystals, found locally encrusted in the bone matrix of chronic gout, activate phagocytosis and NLRP3-dependent autophagy in OBs, but remain intact in permanent autophagosomes while deregulating OB functions.     

Chemokines regulate IL-6 and IL-8 production by fibroblast-like synoviocytes from patients with rheumatoid arthritis.

Rheumatoid arthritis (RA) is characterized by proliferation of synoviocytes that produce inflammatory cytokines and chemokines. The expressed chemokines are thought to be involved in the migration of inflammatory cells into the synovium. In this study we show that CCL2/monocyte chemotactic protein-1, CCL5/RANTES, and CXCL12/stromal cell-derived factor-1 enhanced IL-6 and IL-8 production by fibroblast-like synoviocytes (FLS) from patients with RA, and their corresponding receptors, CCR2, CCR5, and CXCR4, respectively, were expressed by RA FLS. The chemokines stimulated RA FLS more effectively than skin fibroblasts. Culture with CCL2 enhanced phosphorylation of extracellular signal-related kinase 1 (ERK1) and ERK2, but not phosphorylation of p38 or Src. Moreover, activation of ERK1/2 was inhibited by pertussis toxin, a G(i)-coupled protein inhibitor, and RS-504393, CCR2 antagonist, suggesting that ERK1/2 was activated by CCL2 via CCR2 and G(i)-coupled protein. On the other hand, CCL2, CCL5, and CXCL12 were expressed on RA FLS, and their production was regulated by TNF-alpha, IL-1beta, and TGF-beta1. Our results indicate that the chemokines not only play a role in inflammatory cell migration, but are also involved in the activation of FLS in RA synovium, possibly in an autocrine or paracrine manner.     

Innate immunity triggers IL-32 expression by fibroblast-like synoviocytes in rheumatoid arthritis

Introduction  

Interleukin-32 (IL-32) is a recently described cytokine that is a strong inducer of pro-inflammatory cytokines such as tumor necrosis factor (TNF)-α, IL-1β, IL-6, and IL-8. The expression of this cytokine is highly increased in the rheumatoid synovium and correlated with the severity of joint inflammation. Little is known regarding the innate immune-related regulation of IL-32 by fibroblast-like synoviocytes (FLSs). We therefore investigated the effect of innate immune stimulation by ligands of Toll-like receptor (TLR)2, TLR3, and TLR4, and cytokines such as TNF-α and interferon (IFN)-γ, on IL-32 expression by FLSs.     

Expression and regulation of inducible IkappaB kinase (IKK-i) in human fibroblast-like synoviocytes

IkappaB kinase (IKK) plays a key role in the regulation of nuclear factor kappaB (NF-kappaB). We previously demonstrated the expression of two kinases, IKK1 and IKK2, in fibroblast-like synoviocytes (FLS) and determined their functional consequences for inflammatory gene expression in vitro and in vivo. Recently, a novel inducible IkappaB kinase has been described, namely, IKK-i or IKK-epsilon, which is functionally and structurally distinct from constitutively expressed IKK1 and IKK2. Therefore, we investigated the expression and regulation of this novel kinase in FLS from patients with rheumatoid arthritis and osteoarthritis. Interestingly, constitutive gene expression and protein expression were observed in all cell lines examined. TNFalpha stimulation for 24 h increased IKK-i expression 7.2 +/- 1.8-fold in FLS (P < 0.02). IL-1 also significantly increased IKK-i gene expression. Time course experiments demonstrated that IKK-i gene expression increased within 3 h of TNFalpha stimulation and persisted for at least 24 h. Dose-response studies showed that as little as 1 ng/ml of TNFalpha increased IKK-i gene expression. Constitutive IKK-1 gene expression was also noted in rheumatoid arthritis, osteoarthritis, and normal synovium. This is the first report demonstrating constitutive expression and cytokine regulation of this novel kinase in primary human synovial cells.     

MicroRNA-192 suppresses cell proliferation and induces apoptosis in human rheumatoid arthritis fibroblast-like synoviocytes by downregulating caveolin 1

Heart disease causing cardiac cell death due to ischemia–reperfusion injury is a major cause of morbidity and mortality in the United States. Coronary heart disease and cardiomyopathies are the major cause for congestive heart failure, and thrombosis of the coronary arteries is the most common cause of myocardial infarction. Cardiac injury is followed by post-injury cardiac remodeling or fibrosis. Cardiac fibrosis is characterized by net accumulation of extracellular matrix proteins in the cardiac interstitium and results in both systolic and diastolic dysfunctions. It has been suggested by both experimental and clinical evidence that fibrotic changes in the heart are reversible. Hence, it is vital to understand the mechanism involved in the initiation, progression, and resolution of cardiac fibrosis to design anti-fibrotic treatment modalities. Animal models are of great importance for cardiovascular research studies. With the developing research field, the choice of selecting an animal model for the proposed research study is crucial for its outcome and translational purpose. Compared to large animal models for cardiac research, the mouse model is preferred by many investigators because of genetic manipulations and easier handling. This critical review is focused to provide insight to young researchers about the various mouse models, advantages and disadvantages, and their use in research pertaining to cardiac fibrosis and hypertrophy.     

High-density lipoproteins attenuate interleukin-6 production in endothelial cells exposed to pro-inflammatory stimuli

The purpose of the present study was to investigate the ability of high-density lipoproteins (HDL) to attenuate endothelial dysfunction, by assessing down-regulation of cytokine-induced interleukin-6 (IL-6) production in cultured endothelial cells, and measuring plasma IL-6 levels in three groups of healthy individuals with low, average, or high plasma HDL-cholesterol. Human plasma HDL caused a concentration-dependent inhibition of TNFalpha-induced IL-6 production in human endothelial cells (by 58.5+/-1.5% at 2 mg of HDL-protein/ml). Reconstituted HDL made with apolipoprotein A-I (apoA-I) and phosphatidylcholine were as effective as plasma HDL, while lipid-free apoA-I or phosphatidylcholine liposomes had no effect. HDL attenuated IL-6 mRNA levels, an effect which occurs through inhibition of p38 MAP kinase. The median plasma IL-6 concentration was significantly higher in subjects with low HDL-cholesterol (2.54 pg/ml) compared with those with average or high HDL-cholesterol (1.31 pg/ml and 1.47 pg/ml, respectively). When all subjects were considered together, a lower HDL-cholesterol was the strongest independent predictor of higher IL-6 (F=25.38, P<0.001). By inhibiting IL-6 production and lowering plasma IL-6 concentration, HDL may limit the pro-atherogenic effects of both acute and chronic inflammatory states, of which IL-6 is a key orchestrator.     

Guggulsterone blocks IL-1beta-mediated inflammatory responses by suppressing NF-kappaB activation in fibroblast-like synoviocytes

Guggulsterone is a plant sterol that is used to treat hyperlipidemia, arthritis, and obesity. Although its anti-inflammatory and anti-hyperlipidemic effects have been well documented, the effect of guggulsterone on fibroblast-like synoviocytes (FLS) has not yet been reported. Therefore, in this study, the effect of guggulsterone on interleukin (IL)-1beta-induced inflammatory responses in the FLS of rheumatic patients was investigated. Treatment of FLS with IL-1beta induced production of chemokines such as RANTES and ENA-78. In addition, Western blot analysis and gelatin zymography revealed that IL-1beta activated matrix metalloproteinase (MMP)-1 and -3 in FLS. However, pre-incubation with guggulsterone completely inhibited the ability of IL-1beta to induce the production of chemokines and to activate MMPs. Although the NF-kappaB binding activity and nuclear p50 and p65 subunit levels, as well as IkappaBalpha degradation in the cytoplasm was greater in cells stimulated with IL-1beta than in unstimulated cells, treatment with guggulsterone abolished all of these increases. Collectively, these results suggest that guggulsterone would be useful as an inhibitor of joint destruction in patients with rheumatoid arthritis.     

N1-methylpseudouridine-incorporated mRNA enhances exogenous protein expression and suppresses immunogenicity in primary human fibroblast-like synoviocytes

Cytotechnology - Studies conducted using murine arthritis models have indicated that the use of in vitro-transcribed messenger RNA (IVT mRNA) is an effective therapeutic approach for joint...     

Preferential production of prostaglandin D2 by lipopolysaccharide stimulated human choriodecidual explants

It has been postulated that the progression of a pregnancy to term is, in part, the result of a relative maternal Th2 immunological state. Prostaglandins (PG) are critical mediators throughout pregnancy. Recent studies have demonstrated that one PG, PGD2, may be a mediator of a Th2 immunological state. To date, very little is known about the factors that regulate of PGD2 production by human gestational tissues. Placentae were collected from women undergoing Caesarean sections at term. Amnion was separated from the choriodecidua and choriodecidual explants established. Explants were allowed to equilibrate overnight in media containing 10% fetal calf serum. The following day, media were replaced with serum free media and then after an additional 24-h, media were collected and the wet weight of the tissues determined. Production rates of PGs were determined using radioimmunoassays. At all concentrations tested, LPS significantly enhanced PGD2 production by human choriodecidual explants compared to PGE2 and PGF2alpha production. Neutralization of TNF-alpha and IL-10 further increased the production of LPS stimulated PGD2 production. We suggest that a novel stimulatory pathway that drives the production of PGD2 has been uncovered.