title: Pro-fibrotic processes in human lung fibroblasts are driven by an autocrine/paracrine endothelinergic system.
abstract: OBJECTIVE
  Since endothelin (ET) may act as pro-fibrotic mediator, expression and release of ET isoforms, their receptors and potential pro-fibrotic ET effects were studied in human lung fibroblasts.
  
  
  METHODS
  MRC-5 and primary human lung fibroblasts (phLFb) were cultured. Expression of prepro-ET isoforms was determined by qPCR and release of ET-1 by elisa. ET receptor function was analysed by real-time measurement of dynamic mass redistribution (DMR). Incorporation of [(3) H]-thymidine was determined as measure of proliferation and that of [(3) H]-proline for collagen synthesis. Phospho-p42/44 MAP kinase was determined by Western blot.
  
  
  RESULTS
  ET-1 is the predominant ET in human lung fibroblasts (hLF), and TGF-β caused a further, selective and sustained up-regulation of ET-1 resulting in increased extracellular ET-1 accumulation. hLFb express mRNA encoding ET-A and ET-B receptors. Expression of both receptors was confirmed at protein level. ET-1 induced marked DMR signals, an effect that involved ET-A and ET-B receptors. Stimulatory effects of ET-1 on hLFb proliferation and collagen synthesis were mediated exclusively via ET-A receptors. ET-1, again via ET-A receptors, induced rapid activation of ERK MAPK, shown to be a crucial cellular signal in ET-1-induced collagen synthesis. ET-1-induced activation of ERK and collagen synthesis was, in contrast to corresponding effect of a muscarinic agonist, largely insensitive to pertussis toxin.
  
  
  CONCLUSIONS
  hLFb are endowed with all elements necessary to build a functional autocrine/paracrine endothelinergic system, which appears to drive pro-fibrotic airway and lung remodelling processes, effects for which only ET-A, but not ET-B receptors appear to be of significance.
authors.affiliation: Institute of Pharmacology & Toxicology, University of Bonn, Bonn, Germany.
authors.forename: A S
authors.initials: AS
authors.lastname: Ahmedat
authors.forename: M
authors.initials: M
authors.lastname: Warnken
authors.forename: W K
authors.initials: WK
authors.lastname: Seemann
authors.forename: K
authors.initials: K
authors.lastname: Mohr
authors.forename: E
authors.initials: E
authors.lastname: Kostenis
authors.forename: U R
authors.initials: UR
authors.lastname: Juergens
authors.forename: K
authors.initials: K
authors.lastname: Racké
mesh_terms: D002460:Cell Line; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D065128:Endothelin Receptor Antagonists; D016232:Endothelins / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D005355:Fibrosis / Q000378:metabolism*; D006801:Humans; D008168:Lung / Q000166:cytology; D008297:Male; D011392:Proline / Q000378:metabolism; D020033:Protein Isoforms / Q000378:metabolism; D017466:Receptors, Endothelin / Q000378:metabolism; D013936:Thymidine / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology
chemical_list: D065128:Endothelin Receptor Antagonists; D016232:Endothelins; D020033:Protein Isoforms; D017466:Receptors, Endothelin; D016212:Transforming Growth Factor beta; D003094:Collagen; D011392:Proline; D013936:Thymidine