Takinib Inhibits Inflammation in Human Rheumatoid Arthritis Synovial Fibroblasts by Targeting the Janus Kinase-Signal Transducer and Activator of Transcription 3 (JAK/STAT3) Pathway

TGF β-activated kinase 1 (TAK1) is an important participant in inflammatory pathogenesis for diseases such as rheumatoid arthritis (RA) and gouty arthritis. The central position it occupies between the mitogen activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) pathways makes it an attractive therapeutic target. As this field has developed in recent years, several novel inhibitors have been presented as having specific activity that reduces the TAK1 function either covalently as in the case of 5Z-7-oxozeanol (5Z7O) or reversibly (NG-25). However, the mechanism through which takinib elicits its anti-inflammatory activity remains elusive. While this inhibitor shows great promise, a thorough analysis of its inhibitor function and its potential off-target effects is necessary before addressing its clinical potential or its use in inflammatory conditions. An analysis through Western blot showed an unexpected increase in IL-1β-induced TAK1 phosphorylation—a prerequisite for and indicator of its functional potential—by takinib while simultaneously demonstrating the inhibition of the JAK/STAT pathway in human rheumatoid arthritis synovial fibroblasts (RASFs) in vitro. In THP-1 monocyte-derived macrophages, takinib again led to the lipopolysaccharide-induced phosphorylation of TAK1 without a marked inhibition of the TAK1 downstream effectors, namely, of c-Jun N-terminal kinase (JNK), phospho-c-Jun, NF-κB phospho-p65 or phospho-IκBα. Taken together, these findings indicate that takinib inhibits inflammation in these cells by targeting multiple signaling pathways, most notably the JAK/STAT pathway in human RASFs.

Rationale and Design of the Orencia Atherosclerosis and Rheumatoid Arthritis Study (ORACLE Arthritis Study): Implications of Biologics against Rheumatoid Arthritis and the Vascular Complications, Subclinical Atherosclerosis

To explore the biological and immunological basis of human rheumatoid arthritis and human atherosclerosis, we planned and reported a detailed design and rationale for Orencia Atherosclerosis and Rheumatoid Arthritis Study (ORACLE Arthritis Study) using highly sensitive, high-throughput, human autoantibody measurement methods with cell-free protein synthesis technologies. Our previous study revealed that subjects with atherosclerosis had various autoantibodies in their sera, and the titers of anti-Th2 cytokine antibodies were correlated with the severity of atherosclerosis. Because rheumatoid arthritis is a representative autoimmune disease, we hypothesized that both rheumatoid arthritis and atherosclerosis are commonly developed by autoantibody-mediated autoimmune processes, leading to incessant inflammatory changes in both articular joint tissues and vessel walls. We planned a detailed examination involving carotid artery ultrasonography, measurements of adhesion molecules, such as ICAM-1 (intercellular adhesion molecule 1) and VCAM-1 (vascular cell adhesion molecule 1) for the evaluation of atherosclerosis progression, and high-throughput, high-sensitivity, autoantibody analyses using cell-free technologies, with detailed examinations of the disease activity of rheumatoid arthritis. Analyses of correlations and associations between biological markers and degrees of carotid atherosclerosis over time under consistent conditions may enable us to understand the biological and humoral immunity background of human atherosclerosis and autoimmune diseases.

A Network Biology Approach to Understanding the Tissue-Specific Roles of Non-Coding RNAs in Arthritis

Discovery of non-coding RNAs continues to provide new insights into some of the key molecular drivers of musculoskeletal diseases. Among these, microRNAs have received widespread attention for their roles in osteoarthritis and rheumatoid arthritis. With evidence to suggest that long non-coding RNAs and circular RNAs function as competing endogenous RNAs to sponge microRNAs, the net effect on gene expression in specific disease contexts can be elusive. Studies to date have focused on elucidating individual long non-coding-microRNA-gene target axes and circular RNA-microRNA-gene target axes, with a paucity of data integrating experimentally validated effects of non-coding RNAs. To address this gap, we curated recent studies reporting non-coding RNA axes in chondrocytes from human osteoarthritis and in fibroblast-like synoviocytes from human rheumatoid arthritis. Using an integrative computational biology approach, we then combined the findings into cell- and disease-specific networks for in-depth interpretation. We highlight some challenges to data integration, including non-existent naming conventions and out-of-date databases for non-coding RNAs, and some successes exemplified by the International Molecular Exchange Consortium for protein interactions. In this perspective article, we suggest that data integration is a useful in silico approach for creating non-coding RNA networks in arthritis and prioritizing interactions for further in vitro and in vivo experimentation in translational research.

Ets-2 Propagates IL-6 Trans-Signaling Mediated Osteoclast-Like Changes in Human Rheumatoid Arthritis Synovial Fibroblast

Rheumatoid arthritis synovial fibroblasts (RASFs) contribute to synovial inflammation and bone destruction by producing a pleiotropic cytokine interleukin-6 (IL-6). However, the molecular mechanisms through which IL-6 propels RASFs to contribute to bone loss are not fully understood. In the present study, we investigated the effect of IL-6 and IL-6 receptor (IL-6/IL-6R)-induced trans-signaling in human RASFs. IL-6 trans-signaling caused a significant increase in tartrate-resistant acid phosphatase (TRAP)-positive staining in RASFs and enhanced pit formation by ~3-fold in the osteogenic surface in vitro. IL-6/IL-6R caused dose-dependent increase in expression and nuclear translocation of transcription factor Ets2, which correlated with the expression of osteoclast-specific signature proteins RANKL, cathepsin B (CTSB), and cathepsin K (CTSK) in RASFs. Chromatin immunoprecipitation (ChIP) analysis of CTSB and CTSK promoters showed direct Ets2 binding and transcriptional activation upon IL-6/IL-6R stimulation. Knockdown of Ets2 significantly inhibited IL-6/IL-6R-induced RANKL, CTSB, and CTSK expression and TRAP staining in RASFs and suppressed markers of RASF invasive phenotype such as Thy1 and podoplanin (PDPN). Mass spectrometry analysis of the secretome identified 113 proteins produced by RASFs uniquely in response to IL-6/IL-6R that bioinformatically predicted its impact on metabolic reprogramming towards an osteoclast-like phenotype. These findings identified the role of Ets2 in IL-6 trans-signaling induced molecular reprogramming of RASFs to osteoclast-like cells and may contribute to RASF heterogeneity.

MicroRNA-16-5p Promoted Fibroblast-Like Synoviocyte Proliferation and Suppressed Apoptosis via Targeting Suppressor of Cytokine Signaling 6 (SOCS6) in Human Rheumatoid Arthritis

Accumulating evidence have indicated that MicroRNAs (miRNAs) are key regulators in human rheumatoid arthritis (RA). The aim of this study was to explore the functional roles of miR-16-5p in proliferation, inflammation, and apoptosis of fibroblast-like synoviocytes (FLS). The expression of miR-16-5p and SOCS6 in FLA was detected by quantitative real-time polymerase chain reaction (qRT-PCR). Cell proliferation and apoptosis were measured by CCK-8 assay and flow cytometry, respectively. Luciferase reporter assay was used to verify the direct target of miR-16-5p. Western blot analysis was performed to analysis the levels of SOCS6, Bcl-2, Bax and cleaved caspase 3. miR-16-5p expression was significantly upregulated while SOCS6 level was decreased in RA-FLS compared with normal FLS. In addition, luciferase reporter assay confirmed that SOCS6 was the target of miR-16-5p. Silencing of miR-16-5p inhibited cell proliferation, releases of TNF-α, IL-1β, IL-6 and IL-8, and induced the apoptosis. The effects of miR-16-5p silencing on RA-FLS were reversed by downregulation of SOCS6. In summary, knockdown of miR-16-5p could suppress cell proliferation and accelerate the apoptosis of RA-FLS through targeting SOCS6, which may provide a potential therapeutic target for patients with RA.

Effect of key enzyme inhibition of glycolysis on synovial fibroblasts in Rheumatoid Arthritis

Objective: To observe effects of glycolysis on human rheumatoid arthritis Fibroblast-like synoviocytes (HFLS-RA) by inhibiting glycolysis. Methods: Hexokinase inhibitor (3-bromopyruvate, 3-BrPa), 6-phosphofructokinase 1 inhibitor citric acid and pyruvate kinase inhibitor shikonin were applied to HFLS-RA respectively. Cell count 8 Kit detects cell proliferation activity, the activity of hexokinase, 6-phosphofructokinase 1, and pyruvate kinase, as well as the cellular glucose, lactate and ATP content were detected by kits, and the ELISA kit detects the expression of cellular inflammatory factors TNF-α and TGF-β. Results: 10 μg/mL 3-BrPa, 160 μg/mL citric acid and 5 μg/mL shikonin significantly inhibited cell proliferation activity (P<0.001); and significantly inhibited HFLS-RA hexokinase and fructose 6-phosphate Kinase 1 and pyruvate kinase activity; Glucose, lactate and ATP content decreased; TNF-α expression decreased, while TGF-β expression increased. Conclusion: This study explored the changes in glucose metabolism and the expression of inflammatory factors in HFLS-RA by inhibiting the key enzymes of glycolysis, further confirming the important role of glycolysis in HFLS-RA, and laying a theoretical basis for a deep understanding of the pathogenesis of RA.