Interleukin (IL) 18 stimulates osteoclast formation through synovial T cells in rheumatoid arthritis: comparison with IL1β and tumour necrosis factor α (original) (raw)

Interleukin (IL) 18 stimulates osteoclast formation through synovial T cells in rheumatoid arthritis: comparison with IL1β and tumour necrosis factor α

S-M Dai1,2,
K Nishioka1,
K Yudoh1
1Department of Bioregulation, Institute of Medical Science, St Marianna University School of Medicine, Kawasaki, Japan
2Department of Rheumatology and Immunology, Changhai Hospital, Second Military Medical University, Shanghai, China
Correspondence to:
Dr K Yudoh
Department of Bioregulation, Institute of Medical Science, St Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa 216-8512, Japan; yudomarianna-u.ac.jp

Abstract

Objective: To determine whether IL18 has any indirect effects on osteoclastogenesis mediated by T cells in RA synovium, and compare its effects with those of IL1β and TNFα.

Methods: Resting T cells were isolated from peripheral blood of healthy donors, and stimulated with 2 μg/ml phytohaemagglutinin (PHA) and 0.5 ng/ml IL2 for 24 hours. Synovial T cells were isolated from RA synovial tissue. The levels of soluble receptor activator of the NF-κB ligand (RANKL), osteoprotegerin (OPG), IFNγ, M-CSF, and GM-CSF were determined by ELISA. Membrane bound RANKL expression was analysed by flow cytometry. Commercially available human osteoclast precursors were cocultured with T cells to induce osteoclast formation, which was determined with tartrate resistant acid phosphatase staining and pit formation assay.

Results: In PHA prestimulated T cells or RA synovial T cells, IL18, IL1β, or TNFα increased soluble RANKL production and membrane bound RANKL expression in a dose dependent manner. IL18, IL1β, and TNFα did not induce M-CSF, GM-CSF, IFNγ, or OPG production in PHA prestimulated T cells or RA synovial T cells. IL18 increased the number of osteoclasts and bone resorption area on dentine slices in the coculture of human osteoclast precursors with PHA prestimulated T cells or RA synovial T cells; its ability was equivalent to that of IL1β, but less potent than that of TNFα. In the coculture system, OPG completely blocked osteoclast induction by IL18 or IL1β, and greatly inhibited induction by TNFα.

Conclusion: IL18, IL1β, or TNFα can indirectly stimulate osteoclast formation through up regulation of RANKL production from T cells in RA synovitis; IL18 is as effective as IL1β, but less potent than TNFα.

ELISA, enzyme linked immunosorbent assay
FCS, fetal calf serum
GM-CSF, granulocyte monocyte-colony stimulating factor
IFNγ, interferon γ
IL, interleukin
M-CSF, monocyte/macrophage-colony stimulating factor
α-MEM, α-minimal essential medium
MFI, mean fluorescence intensity
OPG, osteoprotegerin
PBS, phosphate buffered saline
PHA, phytohaemagglutinin
RA, rheumatoid arthritis
RANK, receptor activator of NF-κB
RANKL, receptor activator of NF-κB ligand
TNFα, tumour necrosis factor α
TRAP, tartrate resistant acid phosphatase
interleukin 18
interleukin 1β
tumour necrosis factor α
osteoclasts
rheumatoid arthritis

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