Blocking of interferon regulatory factor 1 reduces tumor necrosis factor α-induced interleukin-18 bioactivity in rheumatoid arthritis synovial fibroblasts by induction of interleukin-18 binding protein a: role of the nuclear interferon regulatory factor 1-NF-κB-c-jun complex.

Abstract

OBJECTIVE:

To examine the role of interferon regulatory factor 1 (IRF-1) in tumor necrosis factor α (TNFα)-induced interleukin-18 binding protein a (IL-18BPa) expression in rheumatoid arthritis synovial fibroblasts (RASFs).

METHODS:

TNFα-induced IRF-1 expression was assessed by real-time quantitative polymerase chain reaction and Western blotting. The effect of TNFα on IRF-1 was assessed using nuclear and cytoplasmic extracts, Western blots, and immunofluorescence. Chemical inhibitors of NF-κB or MAP kinases were used to analyze the signaling pathways of TNFα-induced IRF-1 expression and IRF-1 nuclear translocation. Control and IRF-1 small interfering RNA (siRNA) were used to analyze the effect of IRF-1 down-regulation on TNFα-induced IL-18BP expression. IL-18BPa expression was assessed by enzyme-linked immunosorbent assay, and IL-18 was assessed at the transcription and bioactivity levels using KG-1 cells.

RESULTS:

TNFα induced RASF IRF-1 expression at the messenger RNA and protein levels, with a maximal effect at 2 hours (P < 0.05; n ≥ 3). Furthermore, TNFα induced nuclear translocation of IRF-1, with maximal translocation at 2 hours (∼6 fold-induction) (P < 0.05; n = 4). Blocking of the NF-κB or JNK-2 pathways reduced TNFα-induced IRF-1 nuclear translocation by 35% and 50%, respectively (P < 0.05; n ≥ 4). Using siRNA to knock down IRF-1, we observed reduced IL-18BPa expression. Additionally, IL-18 bioactivity was higher when siRNA was used to knock down IRF-1 expression.

CONCLUSION:

These results show that IRF-1 is a key regulator of IL-18BPa expression and IL-18 bioactivity in RASFs. Regulation of IRF-1 will be a new therapeutic target in RA.

• Authors: Hubert Marotte, Pei-Suen Tsou, Bradley J Rabquer, Adam J Pinney, Tatiana Fedorova, Nalin Lalwani, Alisa E Koch
• Journal: Arthritis and rheumatism (Arthritis Rheum) Vol. 63 Issue 11 Pg. 3253-62 (Nov 2011) ISSN: 1529-0131 [Electronic] United States
• PMID: 21834067 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2011 by the American College of Rheumatology.

Chemical References

• Intercellular Signaling Peptides and Proteins
• Interferon Regulatory Factor-1
• Interleukin-18
• NF-kappa B
• Proto-Oncogene Proteins c-jun
• Tumor Necrosis Factor-alpha
• interleukin-18 binding protein

Topics

• Arthritis, Rheumatoid (metabolism, pathology)
• Fibroblasts (metabolism, pathology)
• Humans
• Intercellular Signaling Peptides and Proteins (metabolism)
• Interferon Regulatory Factor-1 (antagonists & inhibitors, metabolism)
• Interleukin-18 (metabolism)
• NF-kappa B (metabolism)
• Proto-Oncogene Proteins c-jun (metabolism)
• Signal Transduction (physiology)
• Synovial Membrane (metabolism, pathology)
• Tumor Necrosis Factor-alpha (metabolism)