Does interleukin-1 affect intracellular calcium in osteoblast-like cells (UMR-106)?
Interleukin-1 (IL-1) enhances bone resorption and formation in vitro, presumably through a primary action on osteoblasts, but the mechanism by which IL-1 activates bone cells is unknown. We investigated the possibility that the effect of IL-1 on osteoblasts is mediated through an increase in intracellular calcium [Ca++]i by studying the effects of purified human monocyte-derived IL-1 (hIL-1) and recombinant human IL-1 alpha (rhIL alpha) and beta (rhIL-1 beta) on [Ca++]i in the rat osteogenic sarcoma cell line UMR 106 using indo-1, a new-generation fluorescent Ca++-sensitive probe. hIL-1 (1 U/ml) resulted in an 85.5% rise in [Ca++]i over baseline that reached a peak after 30 seconds and returned to basal levels within 60 seconds. A similar transient rise in calcium was obtained upon exposure of the UMR cells to both the hIL-1 suspension buffer and to the concentration of fetal bovine serum present in the hIL-1 buffer. This effect was not abolished either by heat inactivation of both hIL-1 and serum or by pretreatment of hIL-1 with specific rabbit antihuman-IL-1 antibody. Moreover, exposure of the UMR cells to either rhIL-1 alpha or rhIL-1 beta or to a mixture of both at concentrations of 1 to 100 U/ml was not followed by any change in [Ca++]i. Our data do not support the idea that IL-1 can stimulate osteoblasts through a calcium-mediated pathway.
Pacifici
R
R
Division of Bone and Mineral Metabolism, Jewish Hospital of St. Louis, MO.
Civitelli
R
R
Rifas
L
L
Halstead
L
L
Avioli
L V
LV
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D005456:Fluorescent Dyes; D007211:Indoles; D007375:Interleukin-1 / Q000494:pharmacology*; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D012516:Osteosarcoma; D051381:Rats; D013050:Spectrometry, Fluorescence
D005456:Fluorescent Dyes; D007211:Indoles; D007375:Interleukin-1; C048960:indo-1; D002118:Calcium