J Korean Rheum Assoc.  2010 Sep;17(3):238-245.

IL-15 Induced an Increased SDF-1 Expression in the Synovial Fibroblasts of Patients with Rheumatoid Arthritis

• Park YE
• Kim SI
• Park SH
• Baek SH
• Oh HJ
• Heo YM
• Cho ML

Abstract

OBJECTIVE
Interleukin-15 (IL-15) recruits and activates synovial T cells, and IL-15 plays an important role in amplifying and perpetuating inflammation in the pathogenesis of rheumatoid arthritis (RA). Stromal cell-derived factor-1 (SDF-1) is a potent chemoattractant for memory T cells in the inflamed RA synovium. This study investigated the effect of IL-15 on SDF-1 production in RA fibroblast-like synoviocytes (FLS).
METHODS
The expressions of IL-15 and SDF-1 were determined from the synovium of patients with RA and osteoarthritis (OA) by performing immunohistochemistry. The expressions of SDF-1 was measured from the RA FLS that were cultured with IL-15 and IL-17 by real-time RT-PCR and ELISA. The SDF-1 expression was also measured, via ELISA, from the RA FLS stimulated by IL-15 together with the inhibitors of such intracellular signal molecules as phosphatidylinositol 3-kinase (PI 3-kinase, LY294002), STAT3 (AG490), MAP Kinase (PD98059), NF-kappaB (parthenolide) and activator protein 1 (AP-1, curcumin).
RESULTS
IL-15 and SDF-1 were mainly expressed in the RA synovium compared to that of the OA synovium. IL-15 increased the SDF-1 expressions and it, and had an additive effect with IL-17 on the SDF-1 expressions in the cultured RA FLS. The IL-15 induced increase of the SDF-1 expression in the cultured RA FLS was blocked by the inhibitors of PI 3-kinase, NF-kappaB and AP-1.
CONCLUSION
The SDF-1 expression was increased in the RA synovium and it was up-regulated by IL-15 in the RA FLS through the PI 3-kinase, NF-kappaB, and AP-1 pathways. These results imply that the IL-15 induced increase of the SDF-1 expressions may be involved in the immunopathogenesis of RA.

Keyword

IL-15; Stromal cell-derived factor-1; IL-17; Fibroblast-like synoviocytes; Rheumatoid arthritis

MeSH Terms

Arthritis, Rheumatoid
Enzyme-Linked Immunosorbent Assay
Fibroblasts
Humans
Immunohistochemistry
Inflammation
Interleukin-15
Interleukin-17
Memory
NF-kappa B
Osteoarthritis
Phosphatidylinositol 3-Kinase
Phosphatidylinositol 3-Kinases
Phosphotransferases
Synovial Membrane
T-Lymphocytes
Transcription Factor AP-1
Interleukin-15
Interleukin-17
NF-kappa B
Phosphatidylinositol 3-Kinase
Phosphatidylinositol 3-Kinases
Phosphotransferases
Transcription Factor AP-1

Figure

• 

  Fig. 1. Immunohistochemical staining for stromal-cell derived factor-1 (SDF-1) and interleukin-15 (IL-15) on the synovium of patients with rheumatoid arthritis (RA) and osteoarthritis (OA). IL-15 and SDF-1 were significantly more expressed in the RA synovium compared to that of the OA synovium (original magnification, ×400).

• 

  Fig. 2. The expressions of SDF-1 from the RA synovial fibroblasts stimulated with various concentrations of IL-15 (0, 0.1, 1, 10 and 50 ng/mL) were determined by real-time RT-PCR (A) and ELISA (B). IL-15 increased the SDF-1 expression in a dose-dependent manner.

• 

  Fig. 3. The productions of SDF-1 from the RA FLS stimulated with IL-15 and IL-17 were determined by ELISA. IL-15 and IL-17 up-regulated SDF-1 production. IL-17 had an additive effect with IL-15 on the SDF-1 production. ∗p<0.01 compared to nil, †0.05 compared to IL-15 1 ng/mL, ‡<0.01 compared to IL-15 10 ng/mL

• 

  Fig. 4. (A) The IL-15 induced increase of SDF-1 was blocked by the inhibitors of PI3-kinase, NF-kB and AP-1. RA FLS that were, pre-treated with the inhibitors of PI3-kinase (LY294002), STAT3 (AG490), MAPK (PD98059), NF-kB (parthenolide) and AP-1 (curcumin), were cultured with IL-15; the production of SDF-1 was determined by ELISA. Up-regulation of SDF-1 by IL-15 was blocked by the inhibitors of PI3-kinase, NF-kB and AP-1. (B) MTT assay was done to confirm that the inhibitors did not have cell toxicity. This assay showed that there was no difference in cell viability after all the stimulations and/or inhibitions. ∗p<0.05 compared to IL-15 10 ng/mL, †<0.01 compared to IL-15 10 ng/mL.

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