IL-1-induced murine osteoblast IL-6 production is mediated by the type 1 IL-1 receptor and is increased by 1,25 dihydroxyvitamin D3.
IL-1-induced osteoblast IL-6 production represents one possible mechanism by which IL-1 augments bone resorption. In this report, we show that the murine osteoblastic cell line (MC3T3-E1) expresses type 1 IL-1 receptors based on 125I-HrIL1 alpha binding, blocked by type 1 IL-1R antibodies (35F5), and analysis of MC3T3 RNA by reverse transcription (RT)-DNA amplification and Northern analysis. MC3T3 cells do not express detectable type 2 IL-1R mRNA by RT-DNA amplification. IL-1 induces (IL-1 ED50, 0.1 pM) IL-6 production through the type 1 IL-1R as 35F5 antibodies block IL-1-stimulated IL-6 production. Vitamin D3 increases IL-1R expression dose- and metabolite-dependently, with 1,25-(OH)2D3 having the greatest potency, and also enhances IL-1's capacity to stimulate IL-6 production at low IL-1 levels. Both IL-1 and 1,25-(OH)2D3 induce type 1 IL-1R and not type 2 IL-1R upregulation based on ligand binding and RT-DNA amplification. Increased IL-1R expression requires a 5-7-h treatment and is protein/RNA synthesis dependent. These observations imply that IL-1-induced IL-6 production in osteoblasts is mediated by type 1 IL-1Rs and that increased IL-1R expression could play a role in mediating IL-1-induced skeletal responses.
Lacey
D L
DL
Department of Pathology, Jewish Hospital of St. Louis, Washington University, Missouri 63110.
Grosso
L E
LE
Moser
S A
SA
Erdmann
J
J
Tan
H L
HL
Pacifici
R
R
Villareal
D T
DT
D016475:3T3 Cells / Q000648:ultrastructure; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D001483:Base Sequence; D001667:Binding, Competitive; D015152:Blotting, Northern; D002117:Calcitriol / Q000494:pharmacology*; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology* / Q000502:physiology; D015850:Interleukin-6 / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D010006:Osteoblasts / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D017472:Receptors, Interleukin-1 / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D011994:Recombinant Proteins / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects
D000906:Antibodies; D007375:Interleukin-1; D015850:Interleukin-6; D012333:RNA, Messenger; D017472:Receptors, Interleukin-1; D011994:Recombinant Proteins; D002117:Calcitriol