An Optimized Glutamate Receptor Photoswitch with Sensitized Azobenzene Isomerization

A new azobenzene-based photoswitch, <b>2</b>, has been designed to enable optical control of ionotropic glutamate receptors in neurons via sensitized two-photon excitation with NIR light. In order to develop an efficient and versatile synthetic route for this molecule, a modular strategy is described which relies on the use of a new linear fully protected glutamate derivative stable in basic media. The resulting compound undergoes one-photon <i>trans</i>–<i>cis</i> photoisomerization via two different mechanisms: direct excitation of its azoaromatic unit and irradiation of the pyrene sensitizer, a well-known two-photon sensitive chromophore. Moreover, <b>2</b> presents large thermal stability of its <i>cis</i> isomer, in contrast to other two-photon responsive switches relying on the intrinsic nonlinear optical properties of push–pull substituted azobenzenes. As a result, the molecular system developed herein is a very promising candidate for evoking large photoinduced biological responses during the multiphoton operation of neuronal glutamate receptors with NIR light, which require accumulation of the protein-bound <i>cis</i> state of the switch upon repeated illumination

Two-Photon Neuronal and Astrocytic Stimulation with Azobenzene-Based Photoswitches

Synthetic photochromic compounds can be designed to control a variety of proteins and their biochemical functions in living cells, but the high spatiotemporal precision and tissue penetration of two-photon stimulation have never been investigated in these molecules. Here we demonstrate two-photon excitation of azobenzene-based protein switches and versatile strategies to enhance their photochemical responses. This enables new applications to control the activation of neurons and astrocytes with cellular and subcellular resolution

Illuminating Phenylazopyridines To Photoswitch Metabotropic Glutamate Receptors: From the Flask to the Animals

Phenylazopyridines are photoisomerizable compounds with high potential to control biological functions with light. We have obtained a series of phenylazopyridines with light dependent activity as negative allosteric modulators (NAM) of metabotropic glutamate receptor subtype 5 (mGlu₅). Here we describe the factors needed to achieve an operational molecular photoisomerization and its effective translation into <i>in vitro</i> and <i>in vivo</i> receptor photoswitching, which includes zebrafish larva motility and the regulation of the antinociceptive effects in mice. The combination of light and some specific phenylazopyridine ligands displays atypical pharmacological profiles, including light-dependent receptor overactivation, which can be observed both <i>in vitro</i> and <i>in vivo</i>. Remarkably, the localized administration of light and a photoswitchable compound in the peripheral tissues of rodents or in the brain amygdalae results in an illumination-dependent analgesic effect. The results reveal a robust translation of the phenylazopyridine photoisomerization to a precise photoregulation of biological activity