The modulation of the expression of IL-6 and its receptor in human osteoblasts in vitro.
Interleukin 6 (IL-6) probably plays a central role in the acute phase response and in haemopoiesis and may be involved in the control of bone turnover. We have studied the release of IL-6 from human trabecular bone cells treated with a variety of stimuli using a specific bioassay. In serum free medium, unstimulated human osteoblast-like cells produced IL-6 in the range of 1000-2050 pg/ml/24 h. Recombinant human interleukin 1 (IL-1 alpha) (10(-13)-10(-11) M), tumor necrosis factor alpha (TNF alpha) (10(-9)-10(-7) M) and lipopolysaccharide (5-500 ng/ml) all stimulated release of IL-6 from human bone cells. Maximal levels of 17,000 pg/ml were observed using the highest concentration of IL-1. 1,25(OH)2D3 and PTH did not stimulate IL-6 release. Using a specific sheep antihuman IL-6 antibody, all IL-6 activity could be neutralized. In parallel studies, ROS 17/2.8 rat osteosarcoma cells released around 50 pg/ml of IL-6 under basal conditions which were increased to a maximum of 900 pg/ml by treatment with PTH (10(-9) M). The cytokines were less effective and 1,25(OH)2D3 again had no effect. Modulation of expression of IL-6 mRNA in human osteoblast cells was examined using a human complementary deoxyribonucleic acid probe. The mRNA was constitutively expressed, and IL-1 (10(-11) M) and TNF (10(-7) M) induced further mRNA expression within 2 h, which was sustained over 24 h. 1,25(OH)2D3 (10(-7) M), IL-6 (2000 pg/ml), and PTH (10(-9) M) exerted no effects at any time point. Dexamethasone (10(-6) M) suppressed both basal and IL-1- and TNF-induced IL-6 mRNA expression. IL-6 receptor mRNA was constitutively expressed but was not regulated by any of the above agents. It is clear that rodent and human osteoblasts differ in their production of IL-6 and its modulation. These data support the hypothesis that IL-6 is produced locally in human bone by osteoblasts under the direction of other cytokines. This could have implications in bone remodeling, haemopoiesis, and systemic responses to local injury.
Littlewood
A J
AJ
Bath Institute for Rheumatic Diseases, University of Bath, United Kingdom.
Russell
J
J
Harvey
G R
GR
Hughes
D E
DE
Russell
R G
RG
Gowen
M
M
D015152:Blotting, Northern; D002117:Calcitriol / Q000494:pharmacology; D002460:Cell Line; D002478:Cells, Cultured; D015342:DNA Probes; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology*; D015850:Interleukin-6 / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008070:Lipopolysaccharides / Q000494:pharmacology; D009500:Neutralization Tests; D010006:Osteoblasts / Q000187:drug effects / Q000276:immunology*; D010281:Parathyroid Hormone / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics; D011971:Receptors, Immunologic / Q000096:biosynthesis* / Q000187:drug effects / Q000235:genetics; D019947:Receptors, Interleukin-6; D011994:Recombinant Proteins / Q000494:pharmacology; D019379:Teriparatide; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D015342:DNA Probes; D007375:Interleukin-1; D015850:Interleukin-6; D008070:Lipopolysaccharides; D010281:Parathyroid Hormone; D010446:Peptide Fragments; D012333:RNA, Messenger; D011971:Receptors, Immunologic; D019947:Receptors, Interleukin-6; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D019379:Teriparatide; D012313:RNA; D002117:Calcitriol