Enhanced interferon regulatory factor 3 binding to the interleukin-23p19 promoter correlates with enhanced interleukin-23 expression in systemic lupus erythematosus

• Published in: Arthritis & rheumatology (Hoboken, N.J.) Vol. 64; no. 5; pp. 1601 - 1609
• Main Authors: Smith, Siobhán, Gabhann, Joan Nı´, Higgs, Rowan, Stacey, Kevin, Wahren-Herlenius, Marie, Espinosa, Alexander, Totaro, Maria Grazia, Sica, Antonio, Ball, Elizabeth, Bell, Aubrey, Johnston, James, Browne, Peter, O'Neill, Lorraine, Kearns, Grainne, Jefferies, Caroline A.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01-05-2012; Wiley; Wiley Subscription Services, Inc
• Subjects: Animals; Biological and medical sciences; Bone Marrow Cells - drug effects; Bone Marrow Cells - metabolism; Chromatin Immunoprecipitation; Disease Models, Animal; Diseases of the osteoarticular system; Female; Gene Expression Regulation; Genes; Humans; Interferon Regulatory Factor-3 - genetics; Interferon Regulatory Factor-3 - metabolism; Interleukin-23 Subunit p19 - genetics; Interleukin-23 Subunit p19 - metabolism; Kinases; Lupus; Lupus Erythematosus, Systemic - metabolism; Macrophages - drug effects; Macrophages - metabolism; Male; Medical sciences; Medicin och hälsovetenskap; Mice; Mice, Inbred C57BL; Mice, Knockout; Monocytes - metabolism; Poly I-C - pharmacology; Protein Array Analysis - methods; Protein Binding; Protein-Serine-Threonine Kinases - pharmacology; Sarcoidosis. Granulomatous diseases of unproved etiology. Connective tissue diseases. Elastic tissue diseases. Vasculitis; Toll-Like Receptor 3 - immunology; Promoter; Immunopathology; Connective tissue disease; Skin disease; Systemic lupus erythematosus; Systemic disease; Rheumatology; Autoimmune disease; Interferon
• ISSN: 0004-3591; 2326-5191; 1529-0131; 1529-0131; 2326-5205
• DOI: 10.1002/art.33494

Objective
To examine the role of interferon regulatory factor 3 (IRF‐3) in the regulation of interleukin‐23 (IL‐23) production in patients with systemic lupus erythematosus (SLE).
Methods
Bone marrow–derived macrophages were isolated from both wild‐type and IRF3−/− C57BL/6 mice. These cells were stimulated with the Toll‐like receptor 3 (TLR‐3) agonist poly(I‐C), and IL‐23p19 cytokine levels were analyzed by enzyme‐linked immunosorbent assay. IRF‐3 binding to the IL‐23p19 gene promoter region in monocytes from patients with SLE and healthy control subjects was analyzed by chromatin immunoprecipitation (ChIP) assay. Luciferase reporter gene assays were performed to identify key drivers of IL‐23p19 promoter activity. TANK‐binding kinase 1 (TBK‐1) protein levels were determined by Western blotting.
Results
ChIP assays demonstrated that IRF‐3 was stably bound to the human IL‐23p19 promoter in monocytes; this association increased following TLR‐3 stimulation. Patients with SLE demonstrated increased levels of IRF‐3 bound to the IL‐23p19 promoter compared with control subjects, which correlated with enhanced IL‐23p19 production in monocytes from patients with SLE. Investigations of the TLR‐3–driven responses in monocytes from patients with SLE revealed that TBK‐1, which is critical for regulating IRF‐3 activity, was hyperactivated in both resting and TLR‐3–stimulated cells.
Conclusion
Our results demonstrate for the first time that patients with SLE display enhanced IL‐23p19 expression as a result of hyperactivation of TBK‐1, resulting in increased binding of IRF‐3 to the promoter. These findings provide novel insights into the molecular pathogenesis of SLE and the potential role for TLR‐3 in driving this response.