Background/Purpose: Syndecans are cell-surface heparan sulfate proteoglycans (HSPGs) that modulate the receptor/ligand binding of chemokines, cytokines, and growth factors in order to facilitate cellular signaling. Two extracellular sulfatase enzymes, namely Sulf-1 and Sulf-2, cleave 6-O-sulfates to dynamically edit the sulfation pattern of syndecans and other membrane-bound HSPGs in response to the microenvironment. However, the role of syndecans and sulfatases in inflammatory condition such as rheumatoid arthritis (RA) remains poorly understood.

Methods: Sulf-1, Sulf-2, and syndecans expression were evaluated in de-identified synovial tissues (ST) and isolated synovial fibroblasts (SFs) from RA and non-diseased (NL) donors under the IRB approved protocol, and in the rat adjuvant-induced arthritis (AIA) model of RA. Effect of TNF-α or IL-1β on the expression of Sulf-1, Sulf-2, and syndecans in RASFs was determined. The effect of OKN-007, a known Sulf-2 inhibitor, on TNF-α-induced IL-6 and IL-8 production in RASFs was determined using an ELISA assay. The role of nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPKs) in TNF-α-induced Sulf-1 and Sulf-2 expression was evaluated using known chemical inhibitors. Statistical value of p<0.05 was considered significant.

Results: Human RASTs showed an increased expression of Sulf-1 and Sulf-2 protein compared to the NLSTs, which also correlated with a selective increase in syndecan-2 expression in RASTs (p<0.05; n=5). Furthermore, Sulf-1 and Sulf-2 expression in the joints of AIA rats showed a concerted increase with the disease severity, where their expression increased around day 8 (onset of arthritis) and peaked around day 18 (established arthritis) in AIA, and concomitantly correlated with a robust expression in syndecan-2 (p<0.01 for day 18; n=5). Stimulation of RASFs with TNF-α (0.1-20 ng/mL) or IL-1β (0.1-10 ng/mL) showed a dose-dependent increase in Sulf-1 and Sulf-2 expression that increased to >2-fold when compared to the non-stimulated samples. Evaluation of the signaling pathways using chemical inhibitors showed that among the inhibitors tested, the inhibitor of TAK1 (5Z-7-oxozeanoel) and NF-κB (PDTC) were most effective in inhibiting TNF-α-induced Sulf-1 and Sulf-2 expression. Furthermore, pretreatment of RASFs with Sulf-2 inhibitor (OKN-007; 40-200 μM) reduced TNF-α-induced IL-6 and IL-8 production by ~50% and ~20%, respectively, suggesting its anti-inflammatory potential in RA. However, we did not observe a significant reduction in TNF-α-induced MAPKs (ERK, JNK, or p38) by OKN-007, suggesting that TNF-α induces Sulf-1 and Sulf-2 expression in RASF potentially via TAK1-NF-κB pathway.

Conclusion: Our preliminary findings suggest that the Sulf-1 and Sulf-2 expression is increased in RASTs and in rat AIA, and may potentially play an important role in modulating cytokine signaling. Understanding their role in HSPG processing may help elucidate the pathology of aggressive RASFs and may direct our studies towards targeted drug design for treatment of RA.

« Back to 2018 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/elucidating-the-expression-and-role-of-heparan-sulfate-proteoglycan-editing-sulfatases-in-human-rheumatoid-arthritis-synovium-and-a-rat-adjuvant-induced-arthritis-model/