Cytokines modulate the sensitivity of human fibroblasts to stimulation with insulin-like growth factor-I (IGF-I) by altering endogenous IGF-binding protein production.
Human dermal fibroblasts produce a number of insulin-like growth factor-binding proteins (IGFBPs) including the main circulating form, IGFBP-3. It has been suggested that the regulation of IGFBP secretion may play a major role in modulating insulin-like growth factor (IGF) bioactivity. We have quantified the effects of two cytokines, transforming growth factor-beta 1 (TGF-beta 1) and tumour necrosis factor-alpha (TNF-alpha) which have opposing actions on fibroblast IGFBP-3 production, and examined their subsequent role in IGF-I mitogenesis. TGF-beta 1 caused a dose-dependent increase in IGFBP-3 in serum-free fibroblast-conditioned media. TGF-beta 1 (1 microgram/l) resulted in immunoreactive IGFBP-3 levels reaching 286.5 +/- 22.4% of control after 20 h, the increase being confirmed by Western ligand blot. TNF-alpha caused a dose-dependent decrease in fibroblast IGFBP-3 secretion, 1 microgram TNF-alpha/l reducing IGFBP-3 levels to 32.1 +/- 11.% of control. This effect was not due to cytotoxicity and was not cell-density-dependent. Fibroblast proliferation was examined using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric cytochemical bioassay. The addition of IGF-I resulted in dose-dependent growth stimulation after 48 h, the effective range being 20-100 micrograms/l. The IGF-I analogue Long-R3-IGF-I which has little affinity for the IGFBPs was approximately 20-fold more potent in this assay, and was unaffected by exogenous IGFBP-3.(ABSTRACT TRUNCATED AT 250 WORDS)
Yateman
M E
ME
Department of Endocrinology, St Bartholomew's Hospital, West Smithfield, London, U.K.
Claffey
D C
DC
Cwyfan Hughes
S C
SC
Frost
V J
VJ
Wass
J A
JA
Holly
J M
JM
D015153:Blotting, Western; D002352:Carrier Proteins / Q000096:biosynthesis*; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D008297:Male; D013002:Somatomedins / Q000096:biosynthesis*; D013268:Stimulation, Chemical; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D002352:Carrier Proteins; D016207:Cytokines; D018969:Insulin-Like Growth Factor Binding Proteins; D013002:Somatomedins; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D007334:Insulin-Like Growth Factor I