Interleukin (IL) 18 stimulates osteoclast formation through synovial T cells in rheumatoid arthritis: comparison with IL1 beta and tumour necrosis factor alpha.
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 IL1 beta and TNF alpha.


METHODS
Resting T cells were isolated from peripheral blood of healthy donors, and stimulated with 2 microg/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-kappa B ligand (RANKL), osteoprotegerin (OPG), IFN gamma, 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, IL1 beta, or TNFalpha increased soluble RANKL production and membrane bound RANKL expression in a dose dependent manner. IL18, IL1 beta, and TNF alpha did not induce M-CSF, GM-CSF, IFN gamma, 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 IL1 beta, but less potent than that of TNF alpha. In the coculture system, OPG completely blocked osteoclast induction by IL18 or IL1 beta, and greatly inhibited induction by TNF alpha.


CONCLUSIONS
IL18, IL1 beta, or TNF alpha can indirectly stimulate osteoclast formation through up regulation of RANKL production from T cells in RA synovitis; IL18 is as effective as IL1 beta, but less potent than TNF alpha.
Department of Bioregulation, Institute of Medical Science, St Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa 216-8512, Japan.
S-M
SM
Dai
K
K
Nishioka
K
K
Yudoh
D000704:Analysis of Variance; D001172:Arthritis, Rheumatoid / Q000276:immunology* / Q000473:pathology; D001862:Bone Resorption / Q000473:pathology; D002352:Carrier Proteins / Q000032:analysis; D002478:Cells, Cultured; D005434:Flow Cytometry; D006023:Glycoproteins / Q000032:analysis; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000032:analysis; D006801:Humans; D007371:Interferon-gamma / Q000032:analysis; D007375:Interleukin-1 / Q000494:pharmacology; D020382:Interleukin-18 / Q000494:pharmacology*; D008213:Lymphocyte Activation; D016173:Macrophage Colony-Stimulating Factor / Q000032:analysis; D008562:Membrane Glycoproteins / Q000032:analysis; D008934:Mitogens / Q000494:pharmacology; D010010:Osteoclasts / Q000187:drug effects / Q000473:pathology*; D053244:Osteoprotegerin; D010835:Phytohemagglutinins / Q000494:pharmacology; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear / Q000032:analysis; D018124:Receptors, Tumor Necrosis Factor; D013583:Synovial Membrane / Q000276:immunology*; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D002352:Carrier Proteins; D006023:Glycoproteins; D007375:Interleukin-1; D020382:Interleukin-18; D008562:Membrane Glycoproteins; D008934:Mitogens; D053244:Osteoprotegerin; D010835:Phytohemagglutinins; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; C505686:TNFRSF11A protein, human; C506030:TNFRSF11B protein, human; C505688:TNFSF11 protein, human; D014409:Tumor Necrosis Factor-alpha; D016173:Macrophage Colony-Stimulating Factor; D007371:Interferon-gamma; D016178:Granulocyte-Macrophage Colony-Stimulating Factor