Effects of TGF-β1 type I receptor antagonist on airway inflammation and remodeling in a murine model of chronic bronchial asthma

Abstract

Objective To investigate the effects of TGF-β1 type I receptor antagonist on airway inflammation and remodeling in murine model of chronic bronchial asthma （asthma）, providing a potential approach for the therapy of asthma. Methods Forty BALB/c mice were randomly divided into 4 groups：a normal group, an asthma group, a budesonide group and a SB 431542 group, with 10 mice in each. The mice were sensitized and challenged with ovalbumin （OVA） to establish routine model of chronic asthma. The budesonide group and SB 431542 group were intervened with aerosolized budesonide and intranasal SB 431542 three times a week respectively. Alterations of the airway inflammation and collagen deposition were observed by the means of haematoxylin-eosin （HE） and Masson staining. The global cells were quantified by periodic acid schiff （PAS）. The expression of a-smooth muscle actin （a-SMA） in lungs was evaluated by immunohistochemistry. The levels of interleukin （IL）-4, IL-5, TGF- β1 ,MMP-9 and TIMP-1 in BALF, and the total level of IgE in serum were evaluated by enzyme linked immunosorbent assay （ELISA）. The protein expression of Smad3,phosphorylation of Smad3 （p-Smad3） and Smad7 were detected by Western blot. Results There were mass inflammatory cells infiltration, airway stenosis, bronchial smooth muscle hypertrophy and collagen fiber increasing in the asthmatic group, these alterations were lessen in budesonide group. The inflammatory cells infiltration in SB 431542 group were more relievable than asthma group, but still worse than budesonide group, while the bronchial smooth muscle hypertrophy and collagen fiber increasing were equal to budesonide group （ P〈 0.05）. A significant increase in the number of PAS-positive epithelial cells was found in the asthma group compared with the control group （ P〈0.05）. Treatment with budesonide or SB 431541 reduced the number of PAS-positive cells （ P 〈0.05）. The area of the a-SMA-stained smooth muscle layer in the asthmatic group were significantly larger than those in the control group （P 〈 0.05 ）, while administration of budesonide or SB 431542 reduced the a-SMA immunostained area （ P 〈0.05）. The levels of total serum IgE and BALF IL-4, IL-5, TGF-β1 were increased in asthma group compared to control group（ P 〈0.05）, but there were no significant differences between the asthma group and SB 431542 group （P 〈0.05）, while the levels of mentioned indexes above were decreased in budesonide group （ P 〈0.05）. MMP-9 and TIMP-1 levels were significantly raised in asthma group （ P 〈0.05）, both budesonide and SB 431542 intervene could reduced MMP-9 and TIMP-1 levels （ P 〈0.05）. The lung Smad3 protein were expressed similarly in all groups （ P 〈0.05）, but the p-Smad3 in budesonide group were higher then control group （ P 〈0.05）, while it was significantly decreased in the budesonide group and the SB 431542 group（ P 〈0.05）. The Smad7 protein was observed lower in asthma group compared to the control group（ P 〈0.05）, administration of budsonide or SB 431542 could restore the express of Smad7 protein （ P 〈0.05）, there were no significant differences between the budsonide group and SE 431542 group （ P 〈0.05）. Conclusions SB 431542 alleviated the extracellular matrix deposition and airway smooth muscle thickening, partially by regulating the levels of MMP-9 and TIMP-1. However, we did not observe significant improvement of inflammation infiltration in asthmatic mice airway, this may imply that airway inflammation in asthma is not dependent on TGF-β1/Smads signaling pathway. Key words: Asthma; Airway remodeling ; Transforming growth factor-β1 ; SB 431542