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

Cell Mol Immunol. 2022 Oct;19(10):1185-1195. doi: 10.1038/s41423-022-00913-x. Epub 2022 Sep 7.


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.

Keywords: Rheumatoid arthritis; Signal transduction; Sulfatase-2; Synovial fibroblasts; TNF-α.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Arthritis, Rheumatoid* / metabolism
  • Cells, Cultured
  • DNA / metabolism
  • Fibroblasts / metabolism
  • Humans
  • JNK Mitogen-Activated Protein Kinases / metabolism
  • Ligands
  • Mice
  • Protein Kinase C-delta / metabolism
  • RNA, Small Interfering / metabolism
  • Receptors, Tumor Necrosis Factor / metabolism
  • Sulfatases / metabolism*
  • Synovial Membrane
  • Transcription Factor AP-1 / metabolism
  • Tumor Necrosis Factor-alpha* / metabolism
  • Tumor Necrosis Factor-alpha* / pharmacology


  • Ligands
  • RNA, Small Interfering
  • Receptors, Tumor Necrosis Factor
  • Transcription Factor AP-1
  • Tumor Necrosis Factor-alpha
  • DNA
  • Protein Kinase C-delta
  • JNK Mitogen-Activated Protein Kinases
  • SULF2 protein, human
  • Sulfatases