Allosteric modulator potentiates β2AR agonist–promoted bronchoprotection in asthma models
Seungkirl Ahn, … , Alem W. Kahsai, Robert J. Lefkowitz
Seungkirl Ahn, … , Alem W. Kahsai, Robert J. Lefkowitz
Published July 11, 2023
Citation Information: J Clin Invest. 2023;133(18):e167337. https://doi.org/10.1172/JCI167337.
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Research Article

Allosteric modulator potentiates β2AR agonist–promoted bronchoprotection in asthma models

Abstract

Asthma is a chronic inflammatory disease associated with episodic airway narrowing. Inhaled β2-adrenergic receptor (β2AR) agonists (β2-agonists) promote — with limited efficacy — bronchodilation in asthma. All β2-agonists are canonical orthosteric ligands that bind the same site as endogenous epinephrine. We recently isolated a β2AR-selective positive allosteric modulator (PAM), compound-6 (Cmpd-6), which binds outside of the orthosteric site and modulates orthosteric ligand functions. With the emerging therapeutic potential of G-protein coupled receptor allosteric ligands, we investigated the impact of Cmpd-6 on β2AR-mediated bronchoprotection. Consistent with our findings using human β2ARs, Cmpd-6 allosterically potentiated β2-agonist binding to guinea pig β2ARs and downstream signaling of β2ARs. In contrast, Cmpd-6 had no such effect on murine β2ARs, which lack a crucial amino acid in the Cmpd-6 allosteric binding site. Importantly, Cmpd-6 enhanced β2 agonist–mediated bronchoprotection against methacholine-induced bronchoconstriction in guinea pig lung slices, but — in line with the binding studies — not in mice. Moreover, Cmpd-6 robustly potentiated β2 agonist–mediated bronchoprotection against allergen-induced airway constriction in lung slices obtained from a guinea pig model of allergic asthma. Cmpd-6 similarly enhanced β2 agonist–mediated bronchoprotection against methacholine-induced bronchoconstriction in human lung slices. Our results highlight the potential of β2AR-selective PAMs in the treatment of airway narrowing in asthma and other obstructive respiratory diseases.

Authors

Seungkirl Ahn, Harm Maarsingh, Julia K.L. Walker, Samuel Liu, Akhil Hegde, Hyeje C. Sumajit, Alem W. Kahsai, Robert J. Lefkowitz

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Figure 2

The β2AR selective PAM Cmpd-6 does not affect the bronchoprotective effect of β2-agonist (albuterol) against methacholine-induced airway constriction in vivo in mice.

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The β2AR selective PAM Cmpd-6 does not affect the bronchoprotective effe...
Effect of Cmpd-6 on (A) increasing doses of methacholine-induced (MCh-induced) airway constriction (bronchoprotection protocol) and (B) albuterol-mediated (Alb-mediated) bronchodilation of airways preconstricted with methacholine. Anesthetized and skeletal muscle–relaxed C57BL/6J naive mice (n = 5–7) were i.v. administered Cmpd-6 (50 mM in 100% DMSO; 10 mg/kg) or equivalent volume of 100% DMSO as vehicle control 10 minutes before the start of the bronchoprotection (A) or bronchodilation (B) protocol. For the bronchoprotection protocol (A), bronchospasm was induced by i.v. administration of methacholine (25, 50, 100, 200, and 400 μg/kg). For the bronchodilation protocol (B), methacholine (125 μg/kg) combined with increasing doses of albuterol (1, 3, 10, and 30 μg/kg) was administered i.v. Lung Newtonian resistance (Rn) was calculated using the forced oscillation technique (flexiVent). Data are represented as mean ± SEM of (A) Newtonian resistance (Rn) or (B) percentage (%) change of Rn between the average methacholine (125 μg/kg) dose alone and the methacholine plus albuterol combination doses. General Linear Model repeated measures ANOVA with Tukey’s posthoc test was used to determine the differences of airway responsiveness between DMSO- and Cmpd-6–treated conditions.