TGFβ-induced matrix production by bronchial fibroblasts in asthma: budesonide and formoterol effects

To investigate the mechanisms of enhanced airway deposition of subepithelial collagen in asthma and its sensitivity to drug therapy with combination of an inhaled glucocorticosteroid (GC) and a long-acting β(2)-agonist (LABA), a cell model system involving bronchial fibroblasts derived from biopsies from patients with stable mild-to-moderate asthma has been used. To mimic unstable conditions and severe asthma, fibroblasts were stimulated ex vivo with TGFβ1. Primary fibroblasts established from central bronchial biopsies from 8 asthmatic patients were incubated for 24 h with 0.4% serum or TGFβ1 (10 ng/ml) with/without the GC budesonide (BUD; 10 nM) and/or the LABA formoterol (FORM; 0.1 nM). Procollagen peptide I (PICP), metalloproteinase (MMP)-1 and tissue inhibitor of MMPs (TIMP-1) were determined in culture media using ELISA while the activity of MMP-2, -3, -9 by zymography. Metabolically labeled proteoglycans, biglycan and decorin, associated with collagen fibrillation/deposition, were separated using chromatography and SDS-PAGE. The levels of PICP and biglycan were increased 2-fold by TGFβ1 (p < 0.05). The BUD and FORM combination reduced the PICP increase by 58% (p < 0.01) and the biglycan by 36% (p < 0.05) while each drug alone had no effect. Decorin levels were reduced by TGFβ1 in fibroblasts of most patients; BUD alone and BUD and FORM completely counteracted this decrease. MMPs and TIMP-1 were not affected by TGFβ1 or the drugs. These results suggest that BUD and FORM combination therapy, without affecting metalloproteolytic balance, has a potential to counteract enhanced collagen production by bronchial fibroblasts in asthma and to normalize the production of small proteoglycans which may affect collagen fibrillation and deposition.