Prevention of allergic airway hyperresponsiveness and remodeling in mice by Astragaliradix antiasthmatic decoction

Abstract

Background: Astragali radix Antiasthmatic Decoction (AAD), a traditional Chinese medication, is found effective in treating allergic diseases and chronic cough. The purpose of this study is to determine whether this medication could suppress allergen-induced airway hyperresponsiveness (AHR) and remodeling in mice, and its possible mechanisms.

Methods: A mouse model of chronic asthma was used to investigate the effects of AAD on the airway lesions. Mice were sensitized and challenged with ovalbumin (OVA), and the extent of AHR and airway remodeling were characterized. Cells and cytokines in the bronchoalveolar lavage fluid (BALF) were examined.

Results: AAD treatment effectively decreased OVA-induced AHR, eosinophilic airway inflammation, and collagen deposition around the airway. It significantly reduced the levels of IL-13 and TGF-β1, but exerted inconsiderable effect on INF-γ and IL-10.

Conclusions: AAD greatly improves the symptoms of allergic airway remodeling probably through inhibition of Th2 cytokines and TGF-β1.

Figure 1

AAD prevented AHR in chronic OVA-challenged mice. Airway hyperresponsiveness (AHR) of mice was determined in the means of response to methacholine on 24 h after the last OVA (or NS) challenge by using the Buxco system as described in the Methods section. Data are presented as means ± SE for 8–10 mice in each group of three independent experiments. H + OVA: OVA challenged and treated with high dose AAD, L + OVA: OVA challenged and treated with low dose AAD. *P < 0.05 compared with the data of OVA group.

Figure 2

AAD reduced total leukocytes and eosinophils in the BALF of allergic mice. The bronchoalveolar lavage fluid (BALF) of mice were harvested at 48 h after the final OVA (or NS) challenge. Subsequently, total leukocytes cell counts (Left) were carried out using a Neubauer chamber. Smears of BALF cells were prepared and eosinophil counts (Right) were performed in light microscopy according to standard morphologic criteria by the smears following Wrights-Giemsa staining, at least 400 cells were counted per slide. The values represent the mean ± SE for 8–10 mice in each group of three independent experiments. H + OVA: OVA challenged and treated with high dose AAD, L + OVA: OVA challenged and treated with low dose AAD. ^#p < 0.05 compared with NS. *P < 0.05 compared with OVA group.

Figure 3

AAD ameliorated Ova-induced inflammatory infiltration in lung tissue of mice. Histologic analysis of the lung sections were performed with HE to visualize inflammatory cell recruitment, representative photomicrographs of lung inflammation expression are shown (A). White arrows indicate areas with clear infiltrated inflammatory cells. With semi-quantitated (score: 0–4) under Olympus microscope (10 × 20 magnification), the level of inflammatory cell infiltration (B) was assessed by two observers independently. Data are presented as means ± SE for 8–10 mice per group. H + OVA: OVA challenged and treated with high dose AAD, L + OVA: OVA challenged and treated with low dose AAD. ^#p < 0.05 compared with NS. *P < 0.05 compared with OVA group.

Figure 4

AAD decreased the collagen deposition in the model of chronic asthma. Lung sections were stained with Masson trichrome to detect collagen deposition around airways. Representative photomicrographs of collagen deposition in different group are shown in (A). White arrows indicate areas with clear collagen deposition. Quantitatively, collagen area on the basal membrane of airway was analyzed and the result was expressed as collagen staining area per micrometer length of basement membrane of bronchioles (B). Data are presented as means ± SE for 8–10 mice per group. H + OVA: OVA challenged and treated with high dose AAD, L + OVA: OVA challenged and treated with low dose AAD. ^#p < 0.05 compared with NS. *P < 0.05 compared with OVA group.

Figure 5

AAD modulated the levels of cytokines in BALF of mice. The BALF was harvested at 48 h after the final OVA (or NS) challenge. Levels of IL-13 (A), TGF-β (B), IFN-γ (C), and IL-10 (D) in the supernatant of BALF were evaluated by ELISA. Data are presented as means ± SE for 8–10 mice per group. H + OVA: OVA challenged and treated with high dose AAD, L + OVA: OVA challenged and treated with low dose AAD. ^#p < 0.05 compared with NS. *P < 0.05 compared with OVA group. NS means not significant.