Photocontrol of Muscarinic Receptors and Applications In Vivo

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. We present a method to modulate cardiac function with light through a photoswitchable compound and without genetic manipulation. A new light-regulated drug, named PAI, was designed and synthesized to be active on M2 muscarinic acetylcholine receptor (mAChR). PAI can be reversibly photoisomerized between cis and trans conformations under UV and visible light. In cell lines overexpressing M2 receptors, PAI is able to photocontrol the cytosolic calcium oscillations, indicative of M2 activation, in a light dependent manner. We show that PAI has different light-dependent cardiac effects in a mammalian animal model. Finally, we demonstrate the reversible, real-time photocontrol of cardiac function in translucent wildtype tadpoles: PAI induced bradycardia and this effect could be reversibly switched using UV and visible illumination. PAI can also effectively activate M2 receptors using two-photon excitation with near-infrared light, which overcomes the scattering and low penetration of short-wavelength illumination. Such a new approach may enable enhanced spatial and temporal selectivity for cardiovascular drugs.