Toll-like receptor 4 surface expression on human monocytes and B cells is modulated by IL-2 and IL-4

Human Toll-like receptor 4 (TLR4) has recently been identified, and it has been shown to be the main protein involved in recognizing gram-negative bacteria. We examined the regulation of TLR4 surface expression in human peripheral blood monocytes and B cells by interleukin-2 (IL-2) and IL-4. IL-2 up-regulated TLR4 surface expression on human peripheral blood monocytes, but did not change expression on human peripheral B cells. By contrast, IL-4 down-regulated TLR4 surface expression on human peripheral blood monocytes, but up-regulated TLR4 surface expression on human peripheral B cells. These results indicate that Th1 cytokine IL-2 enhances receptors involved in the response to gram-negative bacteria and that activation of cellular immunity may enhance defense against these pathogens through monocytes, but not B cells, whereas Th2 cytokine IL-4 modulates the receptor response to gram-negative bacteria and that activation of humoral immunity may enhance defense against these pathogens through B cells, but not monocytes.     

Proteinase-activated receptor2 agonists upregulate granulocyte colony-stimulating factor, IL-8, and VCAM-1 expression in human bronchial fibroblasts

Proteinase-activated receptors (PARs) are a novel family of G-protein-coupled receptors. PAR2 has been implicated in inflammatory airways disease. Although fibroblasts are pathologically important in the airways, the proinflammatory role of PAR2 in these cells remains unknown. We assessed PAR expression and functionality in human primary bronchial fibroblasts (HPBFs) before assessing PAR2-mediated HPBF proliferation, cytokine production, and adhesion molecule expression. RT-PCR and flow cytometry demonstrated that HPBFs express hPAR1, hPAR2, and hPAR3, but not hPAR4. Intracellular calcium signaling in HPBFs in response to PAR agonists showed that only hPAR1 and hPAR2 were functional receptors. We used the MTT assay to assess HPBF proliferation. Of the PAR2 agonist proteinases or selective PAR2-activating peptides (PAR2-APs) tested, none stimulated HPBF proliferation, whereas thrombin was a HPBF growth factor. mRNA for IL-8 and granulocyte colony-stimulating factor (G-CSF) was upregulated after addition of SLIGKV-NH2 when assessed by RT-PCR. No significant increase in G-CSF or IL-8 protein was detected. Trypsin stimulated IL-8 and G-CSF release from HPBF in a time- and dose-dependent manner. Leupeptin and soya trypsin inhibitor abrogated trypsin-stimulated cytokine release, indicating a requirement for trypsin's proteolytic activity. Trypsin and SLIGKV-NH2 stimulated an increase in VCAM-1 expression at 12 h after treatment, which declined thereafter. PAR2-driven upregulation of VCAM-1 cell surface expression and the release of IL-8 and G-CSF from bronchial fibroblasts may be important in promoting neutrophilic airways inflammation.     

Toll-like receptor 2 ligand mediates the upregulation of angiogenic factor, vascular endothelial growth factor and interleukin-8/CXCL8 in human rheumatoid synovial fibroblasts

Rheumatoid arthritis (RA) is characterized by infiltrations of inflammatory cells accompanied by neovascularization in the joint. We hypothesized that cell activation via the toll-like receptor (TLR) may be involved in the induction of angiogenic molecules, which are relevant to the pathogenesis of RA. RA fibroblast like synoviocytes (FLS) were stimulated with TLR-2 ligand bacterial peptidoglycan (PGN), TLR-4 ligand lipopolysaccharide (LPS) and various cytokines. Vascular endothelial growth factor (VEGF) and IL-8 were measured by ELISA in culture supernatants; mRNA levels were assessed by RT-PCR and real time PCR. The levels of TLR-2, VEGF and IL-8 were analyzed by dual immunohistochemistry in RA synovium and compared with osteoarthritis (OA). Regulation of MyD88, IRAK4, IRAK1, IRAK-M and TRAF-6 mRNA expression levels by PGN were analyzed by RT-PCR. Phosphorylation of I kappa B alpha was evaluated by western blotting. Levels of VEGF and IL-8 were upregulated in culture supernatants of RA FLS stimulated with PGN, similar to the levels of IL-1beta and IL-17 stimulation. Neutralization of TLR-2 with a blocking monoclonal antibody significantly reduced both VEGF and IL-8 levels (P<0.05), which reflected the functional relevance of TLR-2 activation to the induction of VEGF and IL-8 production. Downstream intracellular signaling following TLR-2 stimulation involved MyD88-IRAK-4-TRAF-6 pathways, resulting in NF-kappaB activation. Thus, TLR-2 activation in RA FLS by microbial constituents could be involved in the induction of VEGF and IL-8 and thereby promote inflammation either directly or via angiogenesis. This possibly contributes to the perpetuation of synovitis in patients with RA.     

Functional analysis of discoidin domain receptor 2 in synovial fibroblasts in rheumatoid arthritis

In order to know whether any protein tyrosine kinase (PTK) is involved in the over-proliferation and erosiveness of synovial fibroblasts (SF) of rheumatoid arthritis (RA) patients, RT-PCR and RNA dot blotting were done to analyse PTKs profile in RA SF. Platelet-derived growth factor receptor A (PDGFRA), insulin-like growth factor 1 receptor (IGF-1R), Janus kinase 1 (JAK1), TYK2, discoidin domain receptor 2 (DDR2), and Lyn were expressed in SF, and the expression of PDGFRA, IGF-1R, and DDR2 in SF of RA were higher than that of osteoarthritis (OA, as control). Immunoblotting and gelatinase zymography showed that DDR2 in RA SF, which still secreted active matrix metalloproteinase 1 (MMP-1) in vitro, were in active form. Stimulation of collagen II could make NIH-3T3 cells (as control) produce MMP-1, which could be inhibited by soluble extracellular part of DDR2. These results indicated that the over-expression of MMP-1 in RA SF might be related to the activation of DDR2, and collagen II, act as DDR2 ligand, might be one of the stimulators of the over-expression of MMP-1 of RA SF.     

IL-13 receptor alpha 2: a regulator of IL-13 and IL-4 signal transduction in primary human fibroblasts

BACKGROUND: IL-13 and IL-4 share many functional properties as a result of their use of a common receptor complex comprising IL-13 receptor alpha 1 (IL-13Ralpha1) and IL-4 receptor alpha (IL-4Ralpha). The nonsignaling receptor IL-13 receptor alpha 2 (IL-13Ralpha2) binds IL-13 with high affinity and specificity and is believed to be a decoy receptor for IL-13. OBJECTIVE: We sought to examine the inhibitory effects of soluble and membrane-bound IL-13Ralpha2 on IL-13- and IL-4-mediated effects. METHODS: Primary human fibroblasts were grown from endobronchial biopsy specimens obtained from volunteers. Upregulation of IL-13Ralpha2 mRNA was measured by means of RT-PCR, and the level of surface expression was measured by means of FACS. RESULTS: We found that a recombinant soluble form of IL-13Ralpha2 blocked the effects of IL-13, but not IL-4, in fibroblasts in vitro. However, we found that the transmembrane form of IL-13Ralpha2 could attenuate both IL-13 and IL-4 responses, even though the response to TNF-alpha was unaffected. Furthermore, we found that IL-13Ralpha2 became associated with IL-4Ralpha in the presence of IL-4. Addition of a blocking antibody to the extracellular domain of IL-13Ralpha2 restored responses of both IL-13 and IL-4. CONCLUSION: The ability of IL-13Ralpha2 to regulate IL-4 was previously unrecognized in primary airway cells. These data reveal a novel role for IL-13Ralpha2 as a negative regulator of both IL-13 and IL-4 signaling in human bronchial fibroblasts. CLINICAL IMPLICATIONS: It appears that IL-13Ralpha2 might be a powerful suppressor of TH2-mediated responses and thus represents a potential therapeutic target for the treatment of asthma.     

类风湿性关节炎滑膜成纤维细胞骨保护素和骨形态发生蛋白-2的表达及干预

目的 探讨甲氨蝶呤（MTX）及白细胞介素-6受体（IL-6R）抗体对类风湿关节炎（RA）滑膜成纤维细胞增殖的干预及对骨保护素（OPG）、骨形态发生蛋白-2（BMP-2）的影响.方法 获取RA患者滑膜组织,消化并传代培养成纤维细胞.CCK-8法检测IL-6R抗体、甲氨蝶呤（MTX）对RA滑膜成纤维细胞活性影响;荧光定量（qRT）-PCR检测OPG和BMP-2表达.结果 与空白组相比,MTX组、IL-6R抗体组成纤维细胞的活性受到抑制（F=29.30,34.22,P＜0.05）,MTX联合IL-6R抗体组成纤维细胞的活性显著受到抑制（F=52.04,P ＜0.01）.qRT-PCR显示与空白组相比,IL-6R抗体组、MTX联合IL-6R抗体组OPG、BMP-2的表达均上升（P＜0.05）.与MTK组相比,IL-6R抗体组OPG、BMP-2的表达增加（P＜0.05）.结论 IL-6R抗体单独或联合MTK使用均能明显抑制RA滑膜成纤维细胞的活性,与MTX相比,IL-6R抗体能升高OPG、BMP-2的表达.本研究为应用IL-6R抗体预防和治疗RA关节破坏提供实验依据.     

Evidence for enhanced interleukin 2 (IL-2) secretion and IL-2 receptor presentation by synovial fluid lymphocytes in rheumatoid arthritis.

Synovial fluid lymphocytes (SFL) and peripheral blood lymphocytes (PBL) from patients with rheumatoid arthritis (RA) and reactive oligoarthritis were investigated for activated T cells (Ia+SIg-), IL-2 receptor bearing cells (Tac+) and IL-2 production in vivo and in vitro. In contrast to negative results with blood, the synovial fluid of the arthritic joints contains considerable amounts of IL-2 activity (median: 11.8 mu/ml), elevated proportions of Ia+SIg- activated T cells (median: 12.5%) and of IL-2 receptor bearing cells (median: 2.5%). In vitro, after stimulation with several Concanavalin A (Con A) doses, SFL develop proportions of IL-2 receptor cells comparable to PBL. Furthermore, they produce higher values of IL-2 activity than comparable PBL cultures. The proportions of Ia+SIg- activated T cells increase only moderately after Con A stimulation compared to in vivo data, indicating different activated T cell subsets in the synovial fluid (Ia+SIg-, Tac+). The findings are discussed as an expression of an acute hyperactivation of lymphocytes in an inflamed joint.     

A novel negative regulator for IL-1 receptor and Toll-like receptor 4

The Toll-IL-1 receptor (TIR) superfamily, defined by the presence of an intracellular TIR domain, initiates innate immunity via NF-kappaB activation, leading to production of proinflammatory cytokines. ST2 is a member of the TIR family that does not activate NF-kappaB and has been suggested as an important effector molecule of type 2 T helper cell responses. We have recently demonstrated that the membrane bound form of ST2 (ST2L) negatively regulated IL-1RI and TLR4 but not TLR3 signaling by sequestrating the adaptors MyD88 and Mal. In contrast to wild-type mice, ST2 deficient mice failed to develop endotoxin tolerance. Thus, ST2 suppresses IL-1R and TLR4 signaling via MyD88- and Mal-dependent pathways and modulates innate immunity. The results provide a molecular explanation for the role of ST2 in T(H)2 responses since inhibition of TLRs will promote a T(H)2 response and also identify ST2 as a key regulator of endotoxin tolerance.     

Distribution of Toll-like receptor 1 and Toll-like receptor 2 in human lymphoid tissue

To determine how distinct receptors of the immune system can contribute to innate immunity, we investigated the pattern of Toll-like receptor 1 (TLR1) and TLR2 expression in human lymphoid tissue. We found that TLR1 and TLR2 were co-expressed on cells of the innate immune system, including macrophages and dendritic cells. In addition, TLR1 and TLR2 were expressed in mucosa-associated lymphoid tissue on tonsillar crypt epithelium. Of the lymphoid tissue examined, spleen expressed the highest levels of TLR2. Although TLR1- and TLR2-positive cells were in close proximity to T lymphocytes in vivo, lymphocytes themselves were devoid of TLR1 and TLR2 expression. The co-expression of TLR1 and TLR2 on myeloid cells in lymphoid tissue provides the host with the ability to respond to a variety of microbial ligands at sites conducive to the generation of an immune response.     

Chemerin induces CCL2 and TLR4 in synovial fibroblasts of patients with rheumatoid arthritis and osteoarthritis

IntroductionChemerin stimulates migration of leukocytes to sites of inflammation and also increases inflammatory signaling in chondrocytes suggesting a function of chemerin in joint inflammation. Synovial fibroblasts (SF) are critically involved in synovitis and subsequent cartilage destruction. Here, we analyzed whether synovial fibroblasts express chemerin and its receptor CMKLR1. Further, the role of chemerin in synovial fibroblast chemotaxis, proliferation, insulin response and release of inflammatory proteins was studied.MethodsSynovial tissue sections were labeled with chemerin antibody and chemerin was measured in synovial fluid by ELISA. Chemerin mRNA and protein as well as CMKLR1 expression were determined in SFs from patients with osteoarthritis (OA) and rheumatoid arthritis (RA). Effects of chemerin on cytokines, chemokines and matrix metalloproteinases (MMP), and on proliferation, migration and insulin signaling were analyzed appropriately.ResultsSFs expressed CMKLR1 and chemerin mRNA, and chemerin protein was found in cell supernatants of synovial fibroblasts. Immunohistochemistry detected chemerin in synovial tissue predominantly localized within the lining layer. Chemerin was present in synovial fluids of RA, OA and psoriatic arthritis patients in similar concentrations. Chemerin neither increased IL-6 levels nor MMP-2 or ? 9 activity in SFs. Also, it did not act as a chemoattractant for these cells. With respect to intracellular signaling, neither basal nor insulin-mediated phosphorylation of Akt was affected. However, chemerin significantly increased TLR4 mRNA and synthesis of CCL2 in SFs while CCL4 and ? 5 were not altered. Cell proliferation of SFs, however, was modestly reduced by chemerin.ConclusionsThese data show that human SFs express both chemerin and its receptor. As chemerin enhanced expression of TLR4 and induced release of CCL2 in SFs, a role of this protein in innate immune system-associated joint inflammation is proposed.     

Expression and regulation of Toll-like receptor 2 in rheumatoid arthritis synovium

Toll-like receptors (TLRs) are involved in mediating cell activation on stimulation with microbial constituents. We investigated the role for TLRs in synovial fibroblast (SF) activation in rheumatoid arthritis (RA). We analyzed whether stimulation with interleukin-1 beta and tumor necrosis factor-alpha, cytokines present in RA synovium, influences expression of TLR genes in SFs. The effects were compared with those of treatment with lipopolysaccharide and a synthetic lipopeptide (sBLP). Gene expression was examined using quantitative polymerase chain reaction. TLR2-mediated cell activation was investigated by electromobility shift assay for nuclear factor-kappa B. To localize TLR2 expression in joint tissue sections of RA patients were stained using in situ hybridization. Expression of TLR2 in RA SFs was increased after treatment with interleukin-1 beta, tumor necrosis factor-alpha, lipopolysaccharide, and sBLP. Nuclear factor-kappa B translocation in SFs was triggered by TLR2-mediated cell stimulation. Synovial tissues from RA joints expressed TLR2 predominantly at sites of attachment and invasion into cartilage and bone. The observed elevated expression of TLR2 in RA SFs could be a consequence of direct exposure to microbial compounds or of the presence of inflammatory mediators in the joint. TLR-associated signaling pathways may contribute to the pathogenesis of RA, either by initiating or perpetuating activation of SFs.     

Bradykinin-induced IL-6 expression through bradykinin B2 receptor, phospholipase C, protein kinase Cdelta and NF-kappaB pathway in human synovial fibroblasts

Bradykinin (BK) is an inflammatory mediator, and shows elevated levels in regions of severe injury and inflammatory diseases. It has been shown to induce interleukin-6 (IL-6) expression in inflammatory responses in rheumatoid arthritis. We investigated the signaling pathway involved in IL-6 production caused by BK in synovial fibroblasts. BK caused concentration- and time-dependent increases in IL-6 production. By using pharmacological inhibitors or genetic inhibition of the BK receptor, siRNA revealed that B2 but not B1 BK receptors are involved in BK-mediated up-regulation of IL-6. BK-mediated IL-6 production was attenuated by phospholipase C inhibitor (U73122), protein kinase Cdelta inhibitor (rottlerin), NF-kappaB inhibitor (PDTC), IkappaB protease inhibitor (TPCK) and NF-kappaB inhibitor peptide. Stimulation of synovial fibroblasts with BK activated IkappaB kinase alpha/beta (IKK alpha/beta), IkappaBalpha phosphorylation, IkappaBalpha degradation, p65 phosphorylation at Ser(276), p65 and p50 translocation from the cytosol to the nucleus and kappaB-luciferase activity. BK mediated an increase of IKK alpha/beta and IkappaBalpha phosphorylation, kappaB-luciferase activity and p65 and p50 binding to the NF-kappaB element was inhibited by B2 BK receptor antagonist (HOE140), U73122 and rottlerin. Our results suggest that BK increased IL-6 production in synovial fibroblasts via the B2 BK receptor/PI-PLC/PKCdelta/and NF-kappaB signaling pathway.     

Inhibitory effect of triptolide on interleukin-18 and its receptor in rheumatoid arthritis synovial fibroblasts

OBJECTIVE: To determine the effects of triptolide (TP) on the expression of interleukin-18 (IL-18) and its receptor in phorbol 12-myristate 13-acetate (PMA)-stimulated rheumatoid arthritis synovial fibroblasts (RASF). MATERIALS AND METHODS: RASF were obtained from the synovial tissue of patients with RA. RASF were pretreated with TP (0~100 ng/ml) for 2 h before stimulation with PMA (50 ng/ml). The bioactivity of IL-18 in the supernatant was detected based on IFN-gamma secretion from IL-18-responding human myelomonocytic KG-1 cells. IL-18 level was analyzed by ELISA. In situ expression of IL-18Ralpha was determined by immunofluorescence assay. To estimate the protein and mRNA expression of IL-18 and IL-18Ralpha in RASF, western blot and quantitative RT-PCR were performed. Nuclear factor-kappaB (NF-kappaB) activity in the whole-cell extract of treated RASF was also measured using an ELISA-based method. RESULTS: TP effectively inhibited the bioactivity of IL-18 in PMA-stimulated RASF. The expression of IL-18 and IL-18R at protein and gene levels was reduced by TP. NF-kappaB activity in PMA-stimulated RASF was profoundly suppressed by TP. These effects showed a high correlation with TP concentration (0~100 ng/ml). CONCLUSION: TP effectively inhibited the expression of IL-18 and its receptor in PMA-stimulated RASF. These results suggest a mechanism of TP in RA therapy.     

雷公藤内酯醇对类风湿关节炎滑膜成纤维细胞IL-18及其受体表达的影响

目的:研究雷公藤内酯醇(TP)对佛波酯(PMA)刺激的关节滑膜成纤维细胞(RASF) 白细胞介素18(IL-18)及其受体(IL-18R)表达的影响, 并对其机制进行探讨.方法:RASF先用TP(0～100 μg/L) 预处理2 h, 再用PMA (50 μg/L)刺激.收集上清用 ELISA 法检测上清IL-18水平.利用人IL-18能特异诱导人髓系单核细胞KG-1产生IFN-γ的特性检测上清中IL-18生物学活性.收集处理的RASF, 用Western blot 和荧光定量RT-PCR检测IL-18和IL-18R的蛋白和mRNA表达.NF-κB的活性用类ELISA法检测. 结果:TP能有效抑制PMA刺激的RASF的IL-18生物学活性.TP能够抑制PMA刺激的RASF的IL-18和IL-18R的蛋白和mRNA表达.TP还抑制PMA刺激的RASF 的NF-κB 活性.TP对PMA刺激的RASF 的抑制效应呈剂量相关性.结论:TP能有效抑制PMA刺激的RASF 的IL-18和IL-18R的表达.这些结果说明了TP对RA治疗作用的机制.     

Inflammatory PGE2 production is maintained during hypoxia in rheumatoid synovial fibroblasts

Inflammation Research -     

Human rheumatoid synovial fibroblasts promote osteoclastogenic activity by activating RANKL via TLR-2 and TLR-4 activation

The interplay between the innate immune system and inflammatory bone destruction in the joints of individuals with rheumatoid arthritis (RA) remains unclear. This study was undertaken to explore the effect of toll-like receptor (TLR) signaling in fibroblast-like synoviocytes (FLS) on the expression of RANKL and induction of osteoclastogenic activity. The levels of RANKL mRNA and protein were measured using RT-PCR, real-time PCR, and immunostaining. Monocytes were cocultured with RA -FLS that had been stimulated with TLR ligands in fresh media and subsequently stained for tartrate-resistant acid phosphatase (TRAP) activity. Osteoclast molecule markers were measured using real-time PCR. Expression of TLR-2 and TLR-4 was higher in RA-FLS than in OA-FLS and normal skin fibroblasts. TLR-2 and TLR-4 ligands induced RANKL expression in RA-FLS. TLR stimulation of RA-FLS also induced the production of IL-1beta and TNF-alpha to a lesser extent; however, it had no effect on IL-17 production. Inhibition of TLR induced IL-1beta production, which partially reversed the upregulation of RANKL induced by TLR ligands. RA-FLS stimulated by TLR-2 and TLR-4 ligands and cocultured with human monocytes induced high levels of expression of TRAP, RANK, cathepsin K, calcitonin receptor, and matrix metalloproteinase-9, suggesting that RA-FLS promote osteoclast differentiation. Our results suggest that the TLR signaling pathway, through TLR-2 and TLR-4, induces RANKL expression in RA-FLS and the expression of RANKL promotes the differentiation of osteoclasts in RA synovium. Targeting specific TLRs may be a promising approach to prevent inflammatory bone destruction in the pathogenesis of RA.     

DGLA discoordinately suppresses IL-1 induced metalloproteinase mRNA levels in human synovial fibroblasts

Inflammation Research -     

Combined Toll-like receptor agonists synergistically increase production of inflammatory cytokines in human neonatal dendritic cells

Dendritic cells (DC) are thought to be responsible for the reduced ability of human newborns to induce protective T-helper 1 (Th1) immune responses. The key player in Th1 differentiation, interleukin-12 (IL-12), is primarily produced in response to Toll-like receptor (TLR) binding by adult DC but not by neonatal DC. The potential use of various TLR agonist combinations for initiating neonatal monocyte-derived DC to prime Th1 responses was investigated. Single TLR ligands induced maturation only in adult DC; neonatal DC matured with combined targeting of TLR3/TLR8 or TLR4/TLR8, based on the expression of maturation markers. Similarly, the synergistic effects of combined TLR ligands could also be shown with adult and neonatal cytokine production, but different expression patterns were noted. In particular, IL-12p70 was produced by neonatal DC exclusively after combined TLR stimulation. Surprisingly, it was found that supernatants of combined stimulated neonatal DC could induce interferon-gamma production in autologous na?ve T cells. Moreover, this interferon-gamma secretion was blocked by anti-IL-12p70 antibodies and increased after addition of recombined IL-12. In conclusion, these findings underline the differences between adult and neonatal DC and might suggest new strategies for promoting newborn Th1 immunity in response to pathogens and vaccine antigens.