Challenges and promise of targeting miRNA in rheumatic diseases: a computational approach to identify miRNA association with cell types, cytokines, and disease mechanisms.

MicroRNAs (miRNAs) are small non-coding RNAs that alter the expression of target genes at the post-transcriptional level, influencing diverse outcomes in metabolism, cell differentiation, proliferation, cell survival, and cell death. Dysregulated miRNA expression is implicated in various rheumatic conditions, including ankylosing spondylitis (AS), gout, juvenile idiopathic arthritis (JIA), osteoarthritis (OA), psoriatic arthritis, rheumatoid arthritis (RA), Sjogren's syndrome, systemic lupus erythematosus (SLE) and systemic sclerosis. For this review, we used an open-source programming language- PowerShell, to scan the massive number of existing primary research publications on PubMed on miRNAs in these nine diseases to identify and count unique co-occurrences of individual miRNAs and the disease name. These counts were used to rank the top seven most relevant immuno-miRs based on their research volume in each rheumatic disease. Individual miRNAs were also screened for publication with the names of immune cells, cytokines, and pathological processes involved in rheumatic diseases. These occurrences were tabulated into matrices to identify hotspots for research relevance. Based on this information, we summarize the basic and clinical findings for the top three miRNAs - miR-146, miR-155, and miR-21 - whose relevance spans across multiple rheumatic diseases. Furthermore, we highlight some unique miRNAs for each disease and why some rheumatic conditions lack research in this emerging epigenetics field. With the overwhelming number of publications on miRNAs in rheumatic diseases, this review serves as a 'relevance finder' to guide researchers in selecting miRNAs based on the compiled existing knowledge of their involvement in disease pathogenesis. This approach applies to other disease contexts with the end goal of developing miRNA-based therapeutics.

Extracellular sulfatase-2 is overexpressed in rheumatoid arthritis and mediates the TNF-α-induced inflammatory activation of synovial fibroblasts.

Extracellular sulfatase-2 (Sulf-2) influences receptor-ligand binding and subsequent signaling by chemokines and growth factors, yet Sulf-2 remains unexplored in inflammatory cytokine signaling in the context of rheumatoid arthritis (RA). In the present study, we characterized Sulf-2 expression in RA and investigated its potential role in TNF-α-induced synovial inflammation using primary human RA synovial fibroblasts (RASFs). Sulf-2 expression was significantly higher in serum and synovial tissues from patients with RA and in synovium and serum from hTNFtg mice. RNA sequencing analysis of TNF-α-stimulated RASFs showed that Sulf-2 siRNA modulated ~2500 genes compared to scrambled siRNA. Ingenuity Pathway Analysis of RNA sequencing data identified Sulf-2 as a primary target in fibroblasts and macrophages in RA. Western blot, ELISA, and qRT‒PCR analyses confirmed that Sulf-2 knockdown reduced the TNF-α-induced expression of ICAM1, VCAM1, CAD11, PDPN, CCL5, CX3CL1, CXCL10, and CXCL11. Signaling studies identified the protein kinase C-delta (PKCδ) and c-Jun N-terminal kinase (JNK) pathways as key in the TNF-α-mediated induction of proteins related to cellular adhesion and invasion. Knockdown of Sulf-2 abrogated TNF-α-induced RASF proliferation. Sulf-2 knockdown with siRNA and inhibition by OKN-007 suppressed the TNF-α-induced phosphorylation of PKCδ and JNK, thereby suppressing the nuclear translocation and DNA binding activity of the transcription factors AP-1 and NF-κBp65 in human RASFs. Interestingly, Sulf-2 expression positively correlated with the expression of TNF receptor 1, and coimmunoprecipitation assays demonstrated the binding of these two proteins, suggesting they exhibit crosstalk in TNF-α signaling. This study identified a novel role of Sulf-2 in TNF-α signaling and the activation of RA synoviocytes, providing the rationale for evaluating the therapeutic targeting of Sulf-2 in preclinical models of RA.

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 ß-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-1ß-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.