β-Ionone facilitates ex vivo airway smooth muscle relaxation via extraocular opsin-3 light receptor activation.

Recent studies have linked deficiencies in β-carotene ingestion and its metabolites with an increased risk and severity of asthma exacerbations. We demonstrate that β-ionone, a β-carotene metabolite, dose-dependently relaxes upper and lower airways in vitro using wire myography of tracheal rings and phase-contrast microscopy of precision-cut lung slices (PCLSs). We demonstrate that β-ionone-induced relaxation is mediated through extraocular opsin-3 (OPN3) receptor activation via pharmacological competitive inhibition with chromophore 9-cis retinal and through the decreased relaxation demonstrated in Opn3-null PCLSs. We implicate a mechanistic pathway suggestive of Gαs activation that is in agreement with our previous findings. Finally, we confirmed OPN3 expression in airway smooth muscle cells by immunofluorescence and mRNA expression. Our findings implicate β-ionone as a potential therapeutic agent for conditions characterized by bronchoconstriction, such as asthma and COPD. Moreover, this study underscores the significance of dietary intake, particularly of β-carotene-rich foods, in maintaining respiratory health.NEW & NOTEWORTHY This research investigates β-ionone's potential as a therapeutic agent for bronchoconstriction. It sheds light on the mechanism of action of β-ionone's activation of extraocular opsin-3 receptors, offering insights into dietary influences on respiratory health. Notably, β-ionone induces dose-dependent relaxation in both upper and lower airways, with attenuated relaxation in Opn3-knockout models confirming receptor selectivity. This study presents a novel approach to addressing respiratory ailments and underscores the significance of dietary components in managing airway pathology.