Optochemical control of slow-wave sleep in the nucleus accumbens of male mice by a photoactivatable allosteric modulator of adenosine A2A receptors.

Optochemistry, an emerging pharmacologic approach in which light is used to selectively activate or deactivate molecules, has the potential to alleviate symptoms, cure diseases, and improve quality of life while preventing uncontrolled drug effects. The development of in-vivo applications for optochemistry to render brain cells photoresponsive without relying on genetic engineering has been progressing slowly. The nucleus accumbens (NAc) is a region for the regulation of slow-wave sleep (SWS) through the integration of motivational stimuli. Adenosine emerges as a promising candidate molecule for activating indirect pathway neurons of the NAc expressing adenosine A2A receptors (A2ARs) to induce SWS. Here, we developed a brain-permeable positive allosteric modulator of A2ARs (A2AR PAM) that can be rapidly photoactivated with visible light (λ > 400 nm) and used it optoallosterically to induce SWS in the NAc of freely behaving male mice by increasing the activity of extracellular adenosine derived from astrocytic and neuronal activity.

Positive allosteric adenosine A2A receptor modulation suppresses insomnia associated with mania- and schizophrenia-like behaviors in mice.

Background: Insomnia is associated with psychiatric illnesses such as bipolar disorder or schizophrenia. Treating insomnia improves psychotic symptoms severity, quality of life, and functional outcomes. Patients with psychiatric disorders are often dissatisfied with the available therapeutic options for their insomnia. In contrast, positive allosteric modulation of adenosine A2A receptors (A2ARs) leads to slow-wave sleep without cardiovascular side effects in contrast to A2AR agonists. Methods: We investigated the hypnotic effects of A2AR positive allosteric modulators (PAMs) in mice with mania-like behavior produced by ablating GABAergic neurons in the ventral medial midbrain/pons area and in a mouse model of schizophrenia by knocking out of microtubule-associated protein 6. We also compared the properties of sleep induced by A2AR PAMs in mice with mania-like behavior with those induced by DORA-22, a dual orexin receptor antagonist that improves sleep in pre-clinical models, and the benzodiazepine diazepam. Results: A2AR PAMs suppress insomnia associated with mania- or schizophrenia-like behaviors in mice. A2AR PAM-mediated suppression of insomnia in mice with mania-like behavior was similar to that mediated by DORA-22, and, unlike diazepam, did not result in abnormal sleep. Conclusion: A2AR allosteric modulation may represent a new therapeutic avenue for sleep disruption associated with bipolar disorder or psychosis.

Design and Synthesis of Orexin 1 Receptor-Selective Agonists.

Orexins are a family of neuropeptides that regulate various physiological events, such as sleep/wakefulness as well as emotional and feeding behavior, and that act on two G-protein-coupled receptors, i.e., orexin 1 (OX1R) and orexin 2 receptors (OX2R). Since the discovery that dysfunction of the orexin/OX2R system causes the sleep disorder narcolepsy, several OX2R-selective and OX1/2R dual agonists have been disclosed. However, an OX1R-selective agonist has not yet been reported, despite the importance of the biological function of OX1R. Herein, we report the discovery of a potent OX1R-selective agonist, (R,E)-3-(4-methoxy-3-(N-(8-(2-(3-methoxyphenyl)-N-methylacetamido)-5,6,7,8-tetrahydronaphthalen-2-yl)sulfamoyl)phenyl)-N-(pyridin-4-yl)acrylamide [(R)-YNT-3708; EC50 = 7.48 nM for OX1R; OX2R/OX1R EC50 ratio = 22.5]. The OX1R-selective agonist (R)-YNT-3708 exhibited antinociceptive and reinforcing effects through the activation of OX1R in mice.

Design and synthesis of novel orexin 2 receptor agonists with a 1,3,5­trioxazatriquinane skeleton.

A novel series of 1,3,5­trioxazatriquinane with multiple effective residues (TriMER) derivatives with amino-methylene side chains was designed and synthesized based on the docking-simulation results between orexin receptors (OXRs) and TriMER-type OXR antagonists. In vitro screening against orexin receptors identified six TriMER derivatives with a cis side-chain configuration, and, among these, 20d and 28d showed full agonist activity against OX2R at a concentration of 10 µM. To determine the absolute stereochemistry of these hit compounds, we also conducted the first asymmetric synthesis of a 1,3,5­trioxazatriquinane skeleton using a Katsuki-Sharpless asymmetric epoxidation as the key reaction and obtained a set of the individual stereoisomers. After evaluating their activity, (+)-20d (EC50 = 3.87 µM for OX2R) and (+)-28d (EC50 = 1.62 µM for OX2R) were determined as eutomers for OX2R agonist activity. Our results provide a new class of skeleton consisting of an (R)-1,3,5­trioxazatriquinane core with flexible methylene linkers and hydrophobic substituents at the terminals of the side chains via carbamates/sulfonamides as OX2R agonists.

Discovery of novel orexin receptor antagonists using a 1,3,5-trioxazatriquinane bearing multiple effective residues (TriMER) library.

Structurally diverse small compounds are utilized to obtain hit compounds that have suitable pharmacophores in appropriate three-dimensional conformations for the target drug receptors. We have focused on the 1,3,5-trioxazatriquinane skeleton, which has a rigid bowl-like structure enabling the diverse orientation of side chain units, leading to a novel small-scale focused library based on the skeleton. In the library screening for the orexin receptor, some of the compounds showed orexin receptor antagonistic activity with a high hit rate of 7%. By optimizing the hit compounds, we discovered a potent dual orexin receptor antagonist, 38b, and a selective orexin 1 receptor antagonist, 41b carrying the same plane structure. Both compounds showed reasonable brain permeability and beneficial effects when administered intraperitoneally to wild-type mice. Docking simulations of their eutomers, (-)-38b and (+)-41b, with orexin receptors suggested that the interaction between the 1,3,5-trioxazatriquinane core structure and the hydrophobic subpocket in orexin receptors enables a U-shape structure, which causes tight van der Waals interactions with the receptors similar to SB-334867, a selective orexin 1 receptor antagonist. These results indicate that the library approach utilizing the 1,3,5-trioxazatriquinanes bearing multiple effective residues (TriMERs) might be useful for the hit discovery process targeting not only opioid and orexin receptors but other G-protein coupled receptors.

Discovery of orexin 2 receptor selective and dual orexin receptor agonists based on the tetralin structure: Switching of receptor selectivity by chirality on the tetralin ring.

A novel series of 1-amino-tetralin derivatives were designed and synthesized based on the putative binding mode of the naphthalene-type orexin receptor agonist 5 and their agonist activities against orexin receptors were evaluated. The introduction of N-methyl-(3-methoxyphenyl)acetamide unit onto the 1-amino-tetralin skeleton remarkably enhanced the potency of the agonist. The asymmetric synthesis of 6 revealed that (-)-6 having a (S)-1-amino-tetralin skeleton showed a OX2R selective agonist activity (EC50 = 2.69 nM for OX2R, OX1R/OX2R = 461) yet its enantiomer (R)-(+)-6 showed a potent OX1/2R dual agonist activity (EC50 = 13.5 nM for OX1R, 0.579 nM for OX2R, OX1R/OX2R = 23.3). These results suggested that upward orientation of the amide side chain against the tetralin scaffold (S-configuration) would be selective for OX2R activation, and the downward orientation (R-configuration) would be significant for dual agonist activity. To our best knowledge, there have been no reports thus far that the stereochemistry of one carbon center on the agonist structure regulates the orexin receptor selectivity. Our results would provide important information for the development of OX1R selective agonists.