title: Effect of transforming growth factor beta on synthesis of glycosaminoglycans by human lung fibroblasts.
abstract: The processes of lung growth, injury, and repair are characterized by alterations in fibroblast synthesis and interstitial distribution of extracellular matrix components. Transforming growth factor beta (TGF-beta), which is postulated to play a role in modulating lung repair, alters the distribution of several matrix components such as collagen and fibronectin. We studied the effect of TGF-beta on the synthesis and distribution of the various glycosaminoglycans (GAGs) and whether these effects may explain its role in lung repair. Human diploid lung fibroblasts (IMR-90) were exposed to various concentrations of TGF-beta (0-5 nM) for variable periods of time (0-18 h). Newly synthesized GAGs were labeled with either [3H]glucosamine or [35S]sulfate. Individual GAGs were separated by size exclusion chromatography after serial enzymatic and chemical digestions and quantitated using scintillation counting. There was a dose-dependent increase in total GAG synthesis with maximal levels detected after 6 h of exposure. This increase was noted in all individual GAG types measured and was observed in both the cell associated GAGs (cell-matrix fraction) as well as the GAGs released into the medium (medium fraction). In the cell-matrix fraction, TGF-beta increased the proportion of heparan sulfate that was membrane bound as well as the proportion of dermatan sulfate in the intracellular compartment. In the medium fraction, TGF-beta increased the proportion of hyaluronic acid, chondroitin sulfate and dermatan sulfate released. We conclude that the role of TGF-beta in lung growth and repair may be related to increased synthesis of GAGs by human lung fibroblasts as well as alterations in the distribution of individual GAGs.
authors.affiliation: Veterans Administration Medical Center, Allen Park, Michigan 48101.
authors.forename: B A
authors.initials: BA
authors.lastname: Dubaybo
authors.forename: L A
authors.initials: LA
authors.lastname: Thet
mesh_terms: D002460:Cell Line; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005944:Glucosamine / Q000378:metabolism; D006025:Glycosaminoglycans / Q000096:biosynthesis*; D006801:Humans; D008168:Lung / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D013431:Sulfates / Q000378:metabolism; D013462:Sulfur Radioisotopes; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014316:Tritium
chemical_list: D006025:Glycosaminoglycans; D013431:Sulfates; D013462:Sulfur Radioisotopes; D016212:Transforming Growth Factor beta; D014316:Tritium; D005944:Glucosamine