title: Pro- and anti-inflammatory cytokines regulate insulin-like growth factor binding protein production by fetal rat lung fibroblasts.
abstract: The inflammatory response of the lung to noxious factors contributes to the pathogenesis of chronic lung injury. Inflammatory mediators regulate the insulin-like growth factor (IGF) system, a key modulator of lung fibroblast proliferation. The activity of IGFs is regulated by IGF-binding proteins (IGFBPs) secreted by lung cells. To investigate the regulation of lung fibroblast IGFBPs by cytokines, we exposed 19-d fetal rat lung fibroblasts to various pro- and anti-inflammatory mediators. IGFBP abundance in conditioned medium (CM) was measured by ligand blot and RNA transcript abundance by RNase protection assays. Fetal rat lung fibroblasts exposed to interleukin (IL)-1beta or tumor necrosis factor (TNF)-alpha for 48 h demonstrated increased abundance of CM IGFBP-3 (5.9- and 4.7-fold increases for IL-1beta and TNF-alpha, respectively) and IGFBP-4 (5.7- and 7.4-fold increases for IL-1beta and TNF-alpha, respectively) that was accompanied by a small increase in IGFBP-4 mRNA and a larger increase in IGFBP-3 mRNA abundance. IGFBP-4 specific proteolysis was examined in CM collected from fetal rat lung fibroblasts after incubation with serum-free medium (SFM), IL-1beta, or TNF-alpha for 48 h. Cell-free aliquots of SFM-CM incubated at 37C for 24 h showed a 65% decrease in IGFBP-4 abundance that was inhibited by 1,10-phenanthroline. In contrast, CM from cells exposed to IL-1beta or TNF-alpha incubated at 37 degrees C for 24 h did not show a significant decrease in IGFBP-4 abundance unless IGF-I was present during the cell-free incubation. Addition of IGFBP-3 to aliquots of SFM-CM reversed the IGF-I-mediated acceleration of IGFBP-4 proteolysis. Similarly, addition of IGFBP-3 to cells in culture increased the accumulation of CM IGFBP-4. These results demonstrate that cytokines regulate IGFBP production and clearance by fetal lung cells and suggest a mechanism by which cytokines regulate cell proliferation following lung injury.
authors.affiliation: Department of Pediatrics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA. waprice@unc.edu
authors.forename: Wayne A
authors.initials: WA
authors.lastname: Price
authors.forename: Billie M
authors.initials: BM
authors.lastname: Moats-Staats
authors.forename: Alan D
authors.initials: AD
authors.lastname: Stiles
mesh_terms: D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology*; D005260:Female; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology; D018836:Inflammation Mediators / Q000494:pharmacology*; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000096:biosynthesis*; D018974:Insulin-Like Growth Factor Binding Protein 4 / Q000096:biosynthesis*; D008168:Lung / Q000196:embryology / Q000473:pathology; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000893:Anti-Inflammatory Agents; D016207:Cytokines; D018836:Inflammation Mediators; D018972:Insulin-Like Growth Factor Binding Protein 3; D018974:Insulin-Like Growth Factor Binding Protein 4