TGF-β₂ decreases baseline and IL-13-stimulated mucin production by primary human bronchial epithelial cells

Exp Lung Res. 2013 Feb;39(1):39-47. doi: 10.3109/01902148.2012.748854. Epub 2012 Dec 18.

Abstract

Introduction: Mucus hypersecretion is a major contributor to asthma pathology and occurs as part of a spectrum of structural changes termed airway wall remodeling. Transforming growth factor (TGF)-β is proposed to play a key role in regulating airway matrix remodeling although less is known about the specific action of TGF-β isoforms in regulating mucus production.

Methods: Primary human bronchial epithelial (HBE) cells cultured at air-liquid interface were treated with exogenous TGF-β(1), TGF-β(2), and/or a Th2 cytokine, interleukin (IL)-13. Expression and production of respiratory mucins, MUC5AC and MUC5B, were analyzed by real-time PCR, agarose gel electrophoresis, and western blotting. A murine-transformed Clara cell line (mtCC1-2) transfected with a luciferase reporter driven by the Muc5ac promoter containing Smad4 site-mutated cis sequences was used to determine whether exogenous TGF-β(2) affects Muc5ac promoter function.

Results: Surprisingly, TGF-β(1) showed no measurable effect on MUC5AC or MUC5B production by HBE cells whereas TGF-β(2) caused a decrease in both MUC5AC and MUC5B mRNA and protein. Dual treatment with TGF-β(2) and IL-13 partially attenuated the increase in mucin production found with IL-13 alone. This effect was confirmed by using mtCC1-2 cells where addition of TGF-β(2) reduced the ability of IL-13/EGF to induce Muc5ac promoter expression in wild-type cells; however, this decrease was absent in mutant promoter-transfected cells.

Discussion and conclusion: Findings suggest that normal regulation of MUC5AC and MUC5B production by HBE cells is TGF-β isoform-specific and that TGF-β(2) downregulates both MUC5AC and MUC5B. Furthermore, TGF-β(2) controls baseline and IL-13-driven Muc5ac promoter function in murine Clara cells via an endogenous Smad4 recognition motif.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line, Transformed
  • Cells, Cultured
  • Gene Expression / drug effects
  • Humans
  • Interleukin-13 / pharmacology*
  • Lung / drug effects*
  • Lung / metabolism
  • Lung / pathology
  • Mice
  • Mucin 5AC / genetics
  • Mucin 5AC / metabolism*
  • Mucin-5B / genetics
  • Mucin-5B / metabolism*
  • Respiratory Mucosa / drug effects*
  • Respiratory Mucosa / metabolism
  • Respiratory Mucosa / pathology
  • Transfection
  • Transforming Growth Factor beta2 / pharmacology*

Substances

  • Interleukin-13
  • MUC5AC protein, human
  • MUC5B protein, human
  • Mucin 5AC
  • Mucin-5B
  • Transforming Growth Factor beta2
  • interleukin-13, human