Publications

The field of G protein-coupled receptor (GPCR) research has greatly benefited from the spatiotemporal resolution provided by light controllable, i.e., photoswitchable ligands. Most of the developed tools have targeted the Rhodopsin-like family (Class A), the largest family of GPCRs. However, to date, all such Class A photoswitchable ligands were designed to act at the orthosteric binding site of these receptors. Herein, we report the development of the first photoswitchable allosteric modulators of Class A GPCRs, designed to target the M-1 muscarinic acetylcholine receptor. The presented benzyl quinolone carboxylic acid (BQCA) derivatives, Photo-BQCisA and Photo-BQCtrAns, exhibit complementary photopharmacological behavior and allow reversible control of the receptor using light as an external stimulus. This makes them valuable tools to further investigate M-1 receptor signaling and a proof of concept for photoswitchable allosteric modulators at Class A receptors.

JTD Keywords: Agonist, Allosterism, Gpcr, Muscarinic ligands, Photopharmacology, Photoswitc, Selective activation, Serie

Peripheral inputs continuously shape brain function and can influence memory acquisition, but the underlying mechanisms have not been fully understood. Cannabinoid type-1 receptor (CB1R) is a well-recognized player in memory performance, and its systemic modulation significantly influences memory function. By assessing low arousal/non-emotional recognition memory in mice, we found a relevant role of peripheral CB1R in memory persistence. Indeed, the peripherally-restricted CB1R specific antagonist AM6545 showed significant mnemonic effects that were occluded in adrenalectomized mice, and after peripheral adrenergic blockade. AM6545 also transiently impaired contextual fear memory extinction. Vagus nerve chemogenetic inhibition reduced AM6545-induced mnemonic effect. Genetic CB1R deletion in dopamine β-hydroxylase-expressing cells enhanced recognition memory persistence. These observations support a role of peripheral CB1R modulating adrenergic tone relevant for cognition. Furthermore, AM6545 acutely improved brain connectivity and enhanced extracellular hippocampal norepinephrine. In agreement, intra-hippocampal β-adrenergic blockade prevented AM6545 mnemonic effects. Altogether, we disclose a novel CB1R-dependent peripheral mechanism with implications relevant for lengthening the duration of non-emotional memory.© 2022. The Author(s), under exclusive licence to American College of Neuropsychopharmacology.

JTD Keywords: antagonist, consolidation, contextual fear memory, electrical-stimulation, hippocampal function, improves memory, locus-coeruleus, reconsolidation, stress, Vagus nerve-stimulation

The ability to control neural activity is essential for research not only in basic neuroscience, as spatiotemporal control of activity is a fundamental experimental tool, but also in clinical neurology for therapeutic brain interventions. Transcranial-magnetic, ultrasound, and alternating/direct current (AC/DC) stimulation are some available means of spatiotemporal controlled neuromodulation. There is also light-mediated control, such as optogenetics, which has revolutionized neuroscience research, yet its clinical translation is hampered by the need for gene manipulation. As a drug-based light-mediated control, the effect of a photoswitchable muscarinic agonist (Phthalimide-Azo-Iper (PAI)) on a brain network is evaluated in this study. First, the conditions to manipulate M2 muscarinic receptors with light in the experimental setup are determined. Next, physiological synchronous emergent cortical activity consisting of slow oscillations-as in slow wave sleep-is transformed into a higher frequency pattern in the cerebral cortex, both in vitro and in vivo, as a consequence of PAI activation with light. These results open the way to study cholinergic neuromodulation and to control spatiotemporal patterns of activity in different brain states, their transitions, and their links to cognition and behavior. The approach can be applied to different organisms and does not require genetic manipulation, which would make it translational to humans.

JTD Keywords: brain states, light-mediated control, muscarinic acetylcholine receptors, neuromodulation, Activation, Alternating/direct currents, Basal forebrain, Brain, Brain states, Clinical research, Clinical translation, Controlled drug delivery, Cortex, Forebrain cholinergic system, Genetic manipulations, Higher frequencies, Hz oscillation, Light‐, Light-mediated control, Mediated control, Muscarinic acetylcholine receptors, Muscarinic agonists, Muscarinic receptor, Neurology, Neuromodulation, Neurons, Noradrenergic modulation, Parvalbumin-positive interneurons, Photopharmacology, Receptor-binding, Slow, Spatiotemporal control, Spatiotemporal patterns

Tricyclic chemical structures are the core of many important drugs targeting all neurotransmitter pathways. These medicines enable effective therapies to treat from peptic ulcer disease to psychiatric disorders. However, when administered systemically, they cause serious adverse effects that limit their use. To obtain localized and on-demand pharmacological action using light, we have designed photoisomerizable ligands based on azobenzene that mimic the tricyclic chemical structure and display reversibly controlled activity. Pseudo-analogues of the tricyclic antagonist pirenzepine demonstrate that this is an effective strategy in muscarinic acetylcholine receptors, showing stronger inhibition upon illumination both in vitro and in cardiac atria ex vivo. Despite the applied chemical modifications to make pirenzepine derivatives sensitive to light stimuli, the most potent candidate of the set, cryptozepine-2, maintained a moderate but promising M-1 vs M-2 subtype selectivity. These photoswitchable crypto-azologs of tricyclic drugs might open a general way to spatiotemporally target their therapeutic action while reducing their systemic toxicity and adverse effects.

JTD Keywords: Binding, Dose-response relationship, drug, Drug design, Humans, M1, Molecular structure, Muscarinic antagonists, Pirenzepine, Rat-brain, Receptor, Receptors, muscarinic, Structure-activity relationship

Modulation of metabotropic glutamate receptor 5 (mGlu5) with partial allosteric antagonists has received increased interest due to their favourable in vivo activity profiles compared to the unfavourable side-effects of full inverse agonists. Here we report on a series of bispyridine benzene derivatives with a functional molecular switch affecting antagonistic efficacy, shifting from inverse agonism to partial antagonism with only a single change in the substitution pattern of the benzene ring. These efficacy changes are explained through computational docking, revealing two different receptor conformations of different energetic stability and different positional isomer binding preferences.

JTD Keywords: mGlu5, Isomers, Partial efficacy, NAM, Antagonist, Inverse agonist

Compound 11 (3-(benzyloxy)-1′-methyl-1′-azonia-4H-1′-azaspiro[isoxazole-5,3′-bicyclo[2.2.2]octane] iodide) was selected from a previous set of nicotinic ligands as a suitable model compound for the design of new silent agonists of α7 nicotinic acetylcholine receptors (nAChRs). Silent agonists evoke little or no channel activation but can induce the α7 desensitized Ds state, which is sensitive to a type II positive allosteric modulator, such as PNU-120596. Introduction of meta substituents into the benzyloxy moiety of 11 led to two sets of tertiary amines and quaternary ammonium salts based on the spirocyclic quinuclidinyl-Δ2-isoxazoline scaffold. Electrophysiological assays performed on Xenopus laevis oocytes expressing human α7 nAChRs highlighted four compounds that are endowed with a significant silent-agonism profile. Structure–activity relationships of this group of analogues provided evidence of the crucial role of the positive charge at the quaternary quinuclidine nitrogen atom. Moreover, the present study indicates that meta substituents, in particular halogens, on the benzyloxy substructure direct specific interactions that stabilize a desensitized conformational state of the receptor and induce silent activity

JTD Keywords: Agonists, Cycloaddition, Nitrogen heterocycles, Receptors, Spiro compounds