Control of Cardiac Function in vivo with a Light-Regulated Drug

Remote control of physiological functions with light offers the promise of unveiling their complex spatiotemporal dynamics in vivo, and enabling highly focalized therapeutic interventions with reduced systemic toxicity. Optogenetic methods have been implemented in the heart, but the need of genetic manipulation jeopardizes clinical applicability. This study aims at developing, testing and validating the first light-regulated drug with cardiac effects, in order to avoid the requirement of genetic manipulation offered by optogenetic methods. A M2 muscarinic acetylcholine receptors (mAChRs) light-regulated drug (PAI) was designed, synthesized and pharmacologically characterized. The design was based on the orthosteric mAChRs agonist Iperoxo, an allosteric M2 ligand, and a photoswitchable azobenzene linker. PAI can be reversibly photoisomerized between cis and trans configurations under ultraviolet (UV) and visible light, respectively, and it reversibly photoswitches the activity of M2 muscarinic acetylcholine receptors. We have evaluated in vitro photoresponses using a calcium imaging assay in genetically unmodified receptors overexpressed in mammalian cells. Furthermore, using this new chemical tool, we demonstrate for the first time photoregulation of cardiac function in vivo in wildtype frog tadpoles and in rats with a method that does not require genetic manipulation. Such a new approach may enable enhanced spatial and temporal selectivity for cardiovascular drugs.