Regulatory role of SphK1 in TLR7/9-dependent type I interferon response and autoimmunity

FASEB J. 2020 Mar;34(3):4329-4347. doi: 10.1096/fj.201902847R. Epub 2020 Jan 23.

Abstract

Plasmacytoid dendritic cells (pDCs) express Toll like receptors (TLRs) that modulate the immune response by production of type I interferons. Here, we report that sphingosine kinase 1 (SphK1) which produces the bioactive sphingolipid metabolite, sphingosine 1-phosphate (S1P), plays a critical role in the pDC functions and interferon production. Although dispensable for the pDC development, SphK1 is essential for the pDC activation and production of type I IFN and pro-inflammatory cytokines stimulated by TLR7/9 ligands. SphK1 interacts with TLRs and specific inhibition or deletion of SphK1 in pDCs mitigates uptake of CpG oligonucleotide ligands by TLR9 ligand. In the pristane-induced murine lupus model, pharmacological inhibition of SphK1 or its genetic deletion markedly decreased the IFN signature, pDC activation, and glomerulonephritis. Moreover, increases in the SphK1 expression and S1P levels were observed in human lupus patients. Taken together, our results indicate a pivotal regulatory role for the SphK1/S1P axis in maintaining the balance between immunosurveillance and immunopathology and suggest that specific SphK1 inhibitors might be a new therapeutic avenue for the treatment of type I IFN-linked autoimmune disorders.

Keywords: auto-immunity; interferon; plasmacytoid dendritic cells; sphingosine 1-Phosphate; sphingosine kinase; systemic lupus erythematosus.

Publication types

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

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism
  • Animals
  • Autoimmunity / genetics
  • Autoimmunity / physiology*
  • Blotting, Western
  • HEK293 Cells
  • Humans
  • Interferon Regulatory Factor-3 / genetics
  • Interferon Regulatory Factor-3 / metabolism
  • Interferon Regulatory Factor-7 / genetics
  • Interferon Regulatory Factor-7 / metabolism
  • Interferon Type I / genetics
  • Interferon Type I / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Models, Biological
  • Toll-Like Receptor 7 / genetics
  • Toll-Like Receptor 7 / metabolism*
  • Toll-Like Receptor 9 / genetics
  • Toll-Like Receptor 9 / metabolism*

Substances

  • Adaptor Proteins, Signal Transducing
  • IRF3 protein, human
  • IRF7 protein, human
  • Interferon Regulatory Factor-3
  • Interferon Regulatory Factor-7
  • Interferon Type I
  • SPHKAP protein, human
  • Toll-Like Receptor 7
  • Toll-Like Receptor 9