Targeting integrin α5β1 ameliorates severe airway hyperresponsiveness in experimental asthma
Aparna Sundaram, … , Xiaozhu Huang, Dean Sheppard
Aparna Sundaram, … , Xiaozhu Huang, Dean Sheppard
Published December 5, 2016
Citation Information: J Clin Invest. 2017;127(1):365-374. https://doi.org/10.1172/JCI88555.
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Research Article Muscle biology Pulmonology

Targeting integrin α5β1 ameliorates severe airway hyperresponsiveness in experimental asthma

Abstract

Treatment options are limited for severe asthma, and the need for additional therapies remains great. Previously, we demonstrated that integrin αvβ6-deficient mice are protected from airway hyperresponsiveness, due in part to increased expression of the murine ortholog of human chymase. Here, we determined that chymase protects against cytokine-enhanced bronchoconstriction by cleaving fibronectin to impair tension transmission in airway smooth muscle (ASM). Additionally, we identified a pathway that can be therapeutically targeted to mitigate the effects of airway hyperresponsiveness. Administration of chymase to human bronchial rings abrogated IL-13–enhanced contraction, and this effect was not due to alterations in calcium homeostasis or myosin light chain phosphorylation. Rather, chymase cleaved fibronectin, inhibited ASM adhesion, and attenuated focal adhesion phosphorylation. Disruption of integrin ligation with an RGD-containing peptide abrogated IL-13–enhanced contraction, with no further effect from chymase. We identified α5β1 as the primary fibronectin-binding integrin in ASM, and α5β1-specific blockade inhibited focal adhesion phosphorylation and IL-13–enhanced contraction, with no additional effect from chymase. Delivery of an α5β1 inhibitor into murine airways abrogated the exaggerated bronchoconstriction induced by allergen sensitization and challenge. Finally, α5β1 blockade enhanced the effect of the bronchodilator isoproterenol on airway relaxation. Our data identify the α5β1 integrin as a potential therapeutic target to mitigate the severity of airway contraction in asthma.

Authors

Aparna Sundaram, Chun Chen, Amin Khalifeh-Soltani, Amha Atakilit, Xin Ren, Wenli Qiu, Hyunil Jo, William DeGrado, Xiaozhu Huang, Dean Sheppard

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Figure 2

Chymase impairs smooth muscle adhesion to fibronectin and focal adhesion complex phosphorylation.

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Chymase impairs smooth muscle adhesion to fibronectin and focal adhesion...
(A) Schematic of alternate pathways important in the transmission of tension. Vh, vinculin head domain; Vt, vinculin tail domain. (B) Adhesion of human ASM cells to fibronectin measured by absorbance of crystal violet at 595 nm. Fibronectin (0.1 μg/ml) or cells were treated with the indicated doses of rhChy for 20 minutes and then chymostatin (10 μg/ml) prior to assessment of adhesion. (C) Adhesion of human ASM cells to collagen I (0.1 μg/ml), vitronectin (0.3 μg/ml), or laminin I (10 μg/ml), as measured by absorbance of crystal violet at 595 nm. Ligands were treated with the indicated doses of rhChy for 20 minutes and then chymostatin (10 μg/ml) prior to assessment of adhesion. (B and C) Data represent the mean ± SEM from triplicate experiments. (D) Representative Western blots and quantitative densitometry for phosphorylated and total vinculin and FAK in human ASM cells plated on poly-l-lysine (300 μg/ml) alone or poly-l-lysine with either fibronectin (1 μg/ml) or collagen I (1 μg/ml), with the addition of rhChy (30 nM) or vehicle for 20 minutes, followed by chymostatin (10 μg/ml). GAPDH was used as a loading control. Poly, poly-l-lysine; FN, fibronectin; C, collagen I. *P < 0.05 and **P < 0.01 versus Poly; #P < 0.05 and ##P < 0.01 versus Poly/FN by 2-way ANOVA. n = 3 distinct experiments.