The αvβ6 integrin modulates airway hyperresponsiveness in mice by regulating intraepithelial mast cells
Kotaro Sugimoto, Makoto Kudo, Aparna Sundaram, Xin Ren, Katherine Huang, Xin Bernstein, Yanli Wang, Wilfred W. Raymond, David J. Erle, Magnus Åbrink, George H. Caughey, Xiaozhu Huang, Dean Sheppard
Kotaro Sugimoto, Makoto Kudo, Aparna Sundaram, Xin Ren, Katherine Huang, Xin Bernstein, Yanli Wang, Wilfred W. Raymond, David J. Erle, Magnus Åbrink, George H. Caughey, Xiaozhu Huang, Dean Sheppard
View: Text | PDF
Research Article Inflammation

The αvβ6 integrin modulates airway hyperresponsiveness in mice by regulating intraepithelial mast cells

Abstract

Allergic asthma is the most common form of asthma, affecting more than 10 million Americans. Although it is clear that mast cells have a key role in the pathogenesis of allergic asthma, the mechanisms by which they regulate airway narrowing in vivo remain to be elucidated. Here we report that mice lacking αvβ6 integrin are protected from exaggerated airway narrowing in a model of allergic asthma. Expression microarrays of the airway epithelium revealed mast cell proteases among the most prominent differentially expressed genes, with expression of mouse mast cell protease 1 (mMCP-1) induced by allergen challenge in WT mice and expression of mMCP-4, -5, and -6 increased at baseline in β6-deficient mice. These findings were most likely explained by loss of TGF-β activation, since the epithelial integrin αvβ6 is a critical activator of latent TGF-β, and in vitro–differentiated mast cells showed TGF-β–dependent expression of mMCP-1 and suppression of mMCP-4 and -6. In vitro, mMCP-1 increased contractility of murine tracheal rings, an effect that depended on intact airway epithelium, whereas mMCP-4 inhibited IL-13–induced epithelial-independent enhancement of contractility. These results suggest that intraepithelial activation of TGF-β by the αvβ6 integrin regulates airway responsiveness by modulating mast cell protease expression and that these proteases and their proteolytic substrates could be novel targets for improved treatment of allergic asthma.

Authors

Kotaro Sugimoto, Makoto Kudo, Aparna Sundaram, Xin Ren, Katherine Huang, Xin Bernstein, Yanli Wang, Wilfred W. Raymond, David J. Erle, Magnus Åbrink, George H. Caughey, Xiaozhu Huang, Dean Sheppard

×

Figure 4

Differential expression of mast cell transcripts and mast cell number in the airway epithelium of allergen-challenged WT and β6 KO mice.

Options: View larger image (or click on image) Download as PowerPoint
Differential expression of mast cell transcripts and mast cell number in...
(A) qRT-PCR of mast cell protease transcripts identified by microarray analysis. Epithelial RNA was harvested from saline- or allergen-challenged mice, reverse transcribed, and amplified by qRT-PCR. Values for each mRNA were normalized to Gapdh, and relative quantity was calculated relative to expression in saline-treated WT mice. Data are mean ± SEM for 5 independent samples. ***P < 0.001 vs. WT saline. (B) Example of epithelial cell (arrow) and mast cell (arrowhead) identified from cytospin preparation of brushing samples via chymase-like chloroacetate esterase activity. Sample is from an untreated β6 KO mouse. Original magnification, ×400. (C) Mast cell ratios in cytospin preparations of epithelial samples. Ratios were calculated by counting cells under light microscopy. Data are mean ± SEM; n = 4–5 per group. *P < 0.05, **P < 0.01 vs. WT saline. (D) Section of mouse trachea obtained from untreated β6 KO mouse stained with toluidine blue. Arrow denotes mast cell. Higher-magnification view of the boxed region is also shown. Original magnification, ×100 (left), ×400 (right). (E) Intraepithelial mast cell number in tracheal sections. Data are mean ± SEM; n = 4–5 per group. **P < 0.01 vs. WT.