Activation of the interferon-gamma signaling pathway in systemic lupus erythematosus peripheral blood mononuclear cells

Arthritis Rheum. 2009 May;60(5):1463-71. doi: 10.1002/art.24449.

Abstract

Objective: To investigate interferon-gamma (IFNgamma) signaling in peripheral blood mononuclear cells (PBMCs) from patients with systemic lupus erythematosus (SLE) by analyzing IFNgamma receptor (IFNgammaR) expression, STAT-1 expression and phosphorylation, and the regulation of IFNgamma-inducible genes.

Methods: Fluorocytometry was used to investigate expression of STAT-1, pSTAT-1, CD95, HLA-DR, class I major histocompatibility complex (MHC), IFNgamma-inducible 10-kd protein (IP-10), monokine induced by IFNgamma (Mig), and IFNgammaR in PBMCs from SLE patients and healthy individuals. STAT-1 phosphorylation was determined by fluorocytometry and Western blotting after stimulation with IFNalpha or IFNgamma. Quantitative polymerase chain reaction was used to assess messenger RNA (mRNA) expression of the IFNgamma-inducible genes IP-10 and Mig shortly after preparation or after stimulation with IFNgamma in monocytes.

Results: STAT-1 expression was increased in PBMCs from SLE patients and correlated significantly with disease activity and with the IFN-inducible expression of CD95 and HLA-DR. STAT-1 expression also showed a trend toward association with class I MHC expression. In addition, the expression of other IFNgamma-inducible genes, such as IP-10 or Mig, was increased in SLE monocytes. While STAT-1 phosphorylation in SLE PBMCs and PBMCs from healthy individuals was similar after IFNalpha stimulation, incubation with IFNgamma induced STAT-1 phosphorylation only in SLE lymphocytes. Moreover, SLE monocytes showed a considerably higher increase in pSTAT-1 expression upon IFNgamma stimulation than monocytes from healthy individuals. Increased responsiveness of SLE monocytes to IFNgamma was also confirmed on the mRNA level, where expression of the IFN-inducible, STAT-1-dependent genes IP-10 and Mig was more efficiently increased in SLE cells. However, IFNgammaR was similarly expressed on SLE lymphocytes and monocytes and those from healthy individuals.

Conclusion: In addition to supporting the role of IFNs in SLE immunopathogenesis in general, the findings of the present study support a role of IFNgamma in this disease.

MeSH terms

  • Blotting, Western
  • Chemokine CXCL10
  • Chemokine CXCL9 / analysis
  • Gene Expression
  • HLA-DR Antigens / analysis
  • Humans
  • Interferon-gamma / physiology*
  • Leukocytes, Mononuclear / chemistry
  • Leukocytes, Mononuclear / physiology*
  • Lupus Erythematosus, Systemic / blood*
  • Major Histocompatibility Complex
  • Phosphorylation
  • Polymerase Chain Reaction
  • Receptors, Interferon / analysis
  • STAT1 Transcription Factor / analysis
  • Signal Transduction
  • fas Receptor / analysis

Substances

  • CXCL10 protein, human
  • Chemokine CXCL10
  • Chemokine CXCL9
  • HLA-DR Antigens
  • Receptors, Interferon
  • STAT1 Transcription Factor
  • fas Receptor
  • interferon gamma receptor
  • Interferon-gamma