Fibroblast growth factor 2 and transforming growth factor beta1 synergism in human bronchial smooth muscle cell proliferation

Am J Respir Cell Mol Biol. 2006 Jun;34(6):746-53. doi: 10.1165/rcmb.2005-0309OC. Epub 2006 Jan 26.

Abstract

Bronchial smooth muscle cell (BSMC) hyperplasia is a typical feature of airway remodeling and contributes to airway obstruction and hyperresponsiveness in asthma. Fibroblast growth factor 2 (FGF-2) and transforming growth factor beta1 (TGF-beta1) are sequentially upregulated in asthmatic airways after allergic challenge. Whereas FGF-2 induces BSMC proliferation, the mitogenic effect of TGF-beta1 remains controversial, and the effect of sequential FGF-2 and TGF-beta1 co-stimulation on BSMC proliferation is unknown. This study aimed to assess the individual and sequential cooperative effects of FGF-2 and TGF-beta1 on human BSMC proliferation and define the underlying mechanisms. Mitogenic response was measured using crystal violet staining and [3H]-thymidine incorporation. Steady-state mRNA and protein levels were measured by semiquantitative RT-PCR, Western blot, and ELISA, respectively. TGF-beta1 (0.1-20 ng/ml) alone had no effect on BSMC proliferation, but increased the proliferative effect of FGF-2 (2 ng/ml) in a concentration-dependent manner (up to 6-fold). Two distinct platelet-derived growth factor receptor (PDGFR) inhibitors, AG1296 and Inhibitor III, as well as a neutralizing Ab against PDGFRalpha, partially blocked the synergism between these two growth factors. In this regard, TGF-beta1 increased PDGF-A and PDGF-C mRNA expression as well as PDGF-AA protein expression. Moreover, FGF-2 pretreatment increased the mRNA and protein expression of PDGFRalpha and the proliferative effect of exogenous PDGF-AA (140%). Our data suggest that FGF-2 and TGF-beta1 synergize in BSMC proliferation and that this synergism is partially mediated by a PDGF loop, where FGF-2 and TGF-beta1 upregulate the receptor (PDGFRalpha) and the ligands (PDGF-AA and PDGF-CC), respectively. This powerful synergistic effect may thus contribute to the hyperplastic phenotype of BSMC in remodeled asthmatic airways.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Bronchi / cytology
  • Bronchi / drug effects*
  • Bronchi / metabolism
  • Cell Proliferation / drug effects*
  • Cells, Cultured
  • DNA / biosynthesis
  • Dose-Response Relationship, Drug
  • Drug Synergism
  • Female
  • Fibroblast Growth Factor 2 / pharmacology*
  • Gene Expression Regulation / drug effects
  • Humans
  • Infant
  • Lymphokines / genetics
  • Lymphokines / metabolism
  • Male
  • Myocytes, Smooth Muscle / cytology
  • Myocytes, Smooth Muscle / drug effects*
  • Myocytes, Smooth Muscle / metabolism
  • Platelet-Derived Growth Factor / genetics
  • Platelet-Derived Growth Factor / metabolism
  • Platelet-Derived Growth Factor / pharmacology
  • Protein Kinase Inhibitors / pharmacology
  • RNA, Messenger / metabolism
  • Receptor, Platelet-Derived Growth Factor alpha / drug effects
  • Receptor, Platelet-Derived Growth Factor alpha / genetics
  • Receptor, Platelet-Derived Growth Factor alpha / metabolism
  • Time Factors
  • Tissue Plasminogen Activator / biosynthesis
  • Tissue Plasminogen Activator / genetics
  • Transforming Growth Factor beta / pharmacology*
  • Transforming Growth Factor beta1
  • Tyrphostins / pharmacology

Substances

  • Lymphokines
  • Platelet-Derived Growth Factor
  • Protein Kinase Inhibitors
  • RNA, Messenger
  • TGFB1 protein, human
  • Transforming Growth Factor beta
  • Transforming Growth Factor beta1
  • Tyrphostins
  • platelet-derived growth factor A
  • platelet-derived growth factor C
  • Fibroblast Growth Factor 2
  • 6,7-dimethoxy-3-phenylquinoxaline
  • DNA
  • Receptor, Platelet-Derived Growth Factor alpha
  • Tissue Plasminogen Activator