Effects of crocidolite asbestos on human bronchoepithelial-dependent fibroblast stimulation in coculture: the role of IL-6 and GM-CSF.
Cocultures of human pulmonary epithelial cells (BEAS-2B) and lung fibroblasts (WISTAR-38), representing two cell types of central regulatory potential in (chronic) lung disease, were used as an in vitro model to study the role of interleukin 6 (IL-6) and of granulocyte macrophage-colony stimulating factor (GM-CSF) in early fibrogenesis. For this purpose, epithelial cells were pre-exposed to UICC crocidolite asbestos fibers or titanium dioxide (TiO2) particles for 96 h and subsequently cocultured with fibroblasts for additional 72 h. Gene expression of IL-6 or GM-CSF in both cell types as well as of alpha1 procollagens types I and III in fibroblasts was determined by RT-PCR. Synthesis of IL-6, GM-CSF or collagen I was quantified using IL-6 bioassay or ELISA tests, respectively. Both mediators were directly induced in bronchoepithelial cells by crocidolite but not by TiO2. Likewise, steady-state mRNA levels of procollagens as well as collagen synthesis were upregulated in cocultured fibroblasts. As a result of coculture, cytokine concentrations were synergistically enhanced and further increased by crocidolite in a dose-dependent manner. Suppression of cytokine induction by corresponding neutralizing antibodies consistently abrogated collagen enhancement. Direct stimulation of fibroblast monocultures with recombinant human IL-6 or GM-CSF significantly increased collagen synthesis and transcription in a dose-dependent manner. Thus, our results demonstrate that crocidolite selectively stimulated production of IL-6 and GM-CSF in bronchoepithelial cells. In epithelial-fibroblast interactions, these mediators appear to play a key role in regulating fibroblast activity, indicating a close correlation between these cytokines and the fibrogenic potential of particulates.
Department of Toxicology and Environmental Medicine of the Fraunhofer Society, University Hamburg, Medical School, Vogt-Koelln-Strasse 30, 22527, Hamburg, Germany. dagmarlang@aol.com
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D017638:Asbestos, Crocidolite / Q000633:toxicity*; D015415:Biomarkers; D002273:Carcinogens / Q000633:toxicity*; D002450:Cell Communication / Q000502:physiology; D002460:Cell Line; D018920:Coculture Techniques; D004847:Epithelial Cells / Q000187:drug effects*; D005347:Fibroblasts / Q000187:drug effects; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000096:biosynthesis / Q000502:physiology*; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis / Q000502:physiology*; D008168:Lung / Q000166:cytology; D010316:Particle Size; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014025:Titanium / Q000633:toxicity
D015415:Biomarkers; D002273:Carcinogens; D015850:Interleukin-6; D017638:Asbestos, Crocidolite; C009495:titanium dioxide; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D014025:Titanium