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The potential of natural phytochemicals in mitigating depression has been supported by substantial evidence. This study evaluated a total of 88 natural phytochemicals with potential antidepressant properties by targeting serotonin (5-HT) receptors (5-HT1A, 5-HT4, and 5-HT7) using molecular docking, ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) analysis, internal coordinates normal mode analysis (NMA), molecular dynamics simulation (MDS), and free energy calculation. Five evaluated compounds (Genistein, Kaempferol, Daidzein, Peonidin, and glycitein) exhibited favorable pharmacokinetic properties and improved binding scores, indicating their potential as effective antidepressants. Redocking and superimposition analysis of 5-HT with cocrystal structures validated these findings. Furthermore, NMA, MDS, and free energy calculations confirmed the stability and deformability of the ligand-receptor complexes, suggesting that these phytochemicals can effectively interact with 5-HT receptors to modulate depressive symptoms. These powerful phytochemicals, abundantly found in soybeans, fruits, vegetables, and herbs, represent a promising avenue for developing natural treatments for depression. Further in vitro and in vivo studies are warranted to explore their efficacy in alleviating stress and depression through their interactions with 5-HT receptors., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Context: Alzheimer's disease (AD) is the leading cause of dementia around the world, totaling about 55 million cases, with an estimated growth to 74.7 million cases in 2030, which makes its treatment widely desired. Several studies and strategies are being developed considering the main theories regarding its origin since it is not yet fully understood. Among these strategies, the 5-HT 6 receptor antagonism emerges as an auspicious and viable symptomatic treatment approach for AD. The 5-HT 6 receptor belongs to the G protein-coupled receptor (GPCR) family and is closely implicated in memory loss processes. As a serotonin receptor, it plays an important role in cognitive function. Consequently, targeting this receptor presents a compelling therapeutic opportunity. By employing antagonists to block its activity, the 5-HT 6 receptor's functions can be effectively modulated, leading to potential improvements in cognition and memory., Methods: Addressing this challenge, our research explored a promising avenue in drug discovery for AD, employing Artificial Neural Networks-Quantitative Structure-Activity Relationship (ANN-QSAR) models. These models have demonstrated great potential in predicting the biological activity of compounds based on their molecular structures. By harnessing the capabilities of machine learning and computational chemistry, we aimed to create a systematic approach for analyzing and forecasting the activity of potential drug candidates, thus streamlining the drug discovery process. We assembled a diverse set of compounds targeting this receptor and utilized density functional theory (DFT) calculations to extract essential molecular descriptors, effectively representing the structural features of the compounds. Subsequently, these molecular descriptors served as input for training the ANN-QSAR models alongside corresponding biological activity data, enabling us to predict the potential efficacy of novel compounds as 5-hydroxytryptamine receptor 6 (5-HT 6 ) antagonists. Through extensive analysis and validation of ANN-QSAR models, we identified eight new promising compounds with therapeutic potential against AD., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The recently developed and used molecular modeling approach to search for privileged amino acids for halogen bonding (XB hot spots) through XSAR sets has been applied to 5-HT 7 R. Herein, among all identified 5-HT 7 R XB hot spots, the S5x42 was employed in a virtual screening protocol as a constraint. Through a designed virtual screening protocol, 63 XSAR sets (156 compounds) were selected from more than 8 million commercially available compounds and examined using in vitro assay toward 5-HT 7 R. A 68% accuracy was found in predicting halogenated derivatives with higher affinity for 5-HT 7 R than their unsubstituted analogs. Moreover, it was observed that a halogen bond formed between S5x42 and a chlorine atom at the 3-position of the arylpiperazine fragment caused the most remarkable, 35.4-fold increase in binding affinity for 5-HT 7 R when compared to the nonhalogenated analog. Interestingly, molecular dynamics simulations showed the formation of a bifurcated halogen bond with S5x42.

Background: Multiple neurodegenerative diseases are induced by the formation and deposition of protein aggregates. In particular, the microtubule-associated protein Tau leads to the development of so-called tauopathies characterized by the aggregation of hyperphosphorylated Tau within neurons. We recently showed that the constitutive activity of the serotonin receptor 7 (5-HT7R) is required for Tau hyperphosphorylation and aggregation through activation of the cyclin-dependent kinase 5 (CDK5). We also demonstrated physical interaction between 5-HT7R and CDK5 at the plasma membrane suggesting that the 5-HT7R/CDK5 complex is an integral part of the signaling network involved in Tau-mediated pathology., Methods: Using biochemical, microscopic, molecular biological, computational and AI-based approaches, we investigated structural requirements for the formation of 5-HT7R/CDK5 complex., Results: We demonstrated that 5-HT7R domains responsible for coupling to Gs proteins are not involved in receptor interaction with CDK5. We also created a structural model of the 5-HT7R/CDK5 complex and refined the interaction interface. The model predicted two conserved phenylalanine residues, F278 and F281, within the third intracellular loop of 5-HT7R to be potentially important for complex formation. While site-directed mutagenesis of these residues did not influence Gs protein-mediated receptor signaling, replacement of both phenylalanines by alanine residues significantly reduced 5-HT7R/CDK5 interaction and receptor-mediated CDK5 activation, leading to reduced Tau hyperphosphorylation and aggregation. Molecular dynamics simulations of 5-HT7R/CDK5 complex for wild-type and receptor mutants confirmed binding interface stability of the initial model., Conclusions: Our results provide a structural basis for the development of novel drugs targeting the 5-HT7R/CDK5 interaction interface for the selective treatment of Tau-related disorders, including frontotemporal dementia and Alzheimer's disease., (© 2024. The Author(s).)

Since the number of people with Alzheimer's disease (AD) continues to rise, new and effective drugs are urgently needed to not only slow down the progression of the disease, but to stop or even prevent its development. Serotonin 5-HT 6 receptor (5-HT 6 R) ligands are still a promising therapeutic target for the treatment of AD. 1,3,5-Triazine derivatives, as novel structures lacking an indole or a sulfone moiety, have proven to be potent ligands for this receptor. In present work, new derivatives of the compound MST4 (4-((2-isopropyl-5-methylphenoxy)methyl)-6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine), the potent 5-HT 6 R antagonist (K i = 11 nM) with promising ADMET and in vivo properties, were designed. The synthesized compounds were tested for their affinity towards 5-HT 6 R and other receptor (off)targets (serotonin 5-HT 2A , 5-HT 7 and dopamine D 2 ). Based on the new results, 4-(2-tert-butylphenoxy)-6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine ( 3 ) was selected for extended in vitro studies as a potent and selective 5-HT 6 R ligand (K i = 13 nM). Its ability to permeate the blood-brain barrier (BBB) and its hepatotoxicity were evaluated. In addition, X-ray crystallography and solubility studies were also performed. The results obtained confirm that 6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine derivatives, especially compound 3 , are promising structures for further pharmacological studies as 5-HT 6 R ligands.

Long-chain arylpiperazine scaffold is a versatile template to design central nervous system (CNS) drugs that target serotonin and dopamine receptors. Here we describe the synthesis and biological evaluation of ten new arylpiperazine derivatives designed to obtain an affinity profile at serotonin 5-HT 1A , 5-HT 2A , 5-HT 7 receptor, and dopamine D 2 receptor of prospective drugs to treat the core symptoms of autism spectrum disorder (ASD) or psychosis. Besides the structural features required for affinity at the target receptors, the new compounds incorporated structural fragments with antioxidant properties to counteract oxidative stress connected with ASD and psychosis. All the new compounds showed CNS MultiParameter Optimization score predictive of desirable ADMET properties and cross the blood-brain barrier. We identified compound 12a that combines an affinity profile compatible with antipsychotic activity (5-HT 1A K i = 41.5 nM, 5-HT 2A K i = 315 nM, 5-HT 7 K i = 42.5 nM, D 2 K i = 300 nM), and compound 9b that has an affinity profile consistent with studies in the context of ASD (5-HT 1A K i = 23.9 nM, 5-HT 2A K i = 39.4 nM, 5-HT 7 K i = 45.0 nM). Both compounds also had antioxidant properties. All compounds showed low in vitro metabolic stability, the only exception being compound 9b , which might be suitable for studies in vivo.

The pharmacologically characterized receptor subtype of the serotonin family, the 5HT1A receptor is implicated in the pathophysiology and treatment of depression and anxiety-related disorders. Being the most extensively targeted receptor for developing novel antidepressants and anxiolytics, a near-ideal theoretical model can aid in high-throughput screening of promising drug candidates. However, the design of potential drug candidates suffers owing to a lack of complete structural information. In this work, homology models of 5-HT1A receptor are generated using two distinct alignments (CW and PSTA) and model building methods (KB and EB). The developed models are validated for virtual screening using a ligand dataset of agonists and antagonists. The best-suited model was efficient in discriminating agonist/antagonist binding. Correlation plots between pKi and docking (R 2 agonist ≥ 0.6, R 2 antagonist ≥ 0.7) and MM-GBSA dG bind values (R 2 agonist ≥ 0.5, R 2 antagonist ≥ 0.7) revealed optimum corroboration between in vitro and in silico outcomes, which further suggested the usefulness of the developed model for the design of high-affinity probes for the neurological disorders.Communicated by Ramaswamy H. Sarma.

Protecting neurons from death during oxidative and neuroexcitotoxic stress is key for preventing cognitive dysfunction. We uncovered a novel neuroprotective mechanism involving interaction between neurotrophic factor-α1 (NF-α1/carboxypeptidase E, CPE) and human 5-HTR1E, a G protein-coupled serotonin receptor with no previously known neurological function. Co-immunoprecipitation and pull-down assays confirmed interaction between NFα1/CPE and 5-HTR1E and 125 I NF-α1/CPE-binding studies demonstrated saturable, high-affinity binding to 5-HTR1E in stably transfected HEK293 cells (Kd = 13.82 nM). Treatment of 5-HTR1E stable cells with NF-α1/CPE increased pERK 1/2 and pCREB levels which prevented a decrease in pro-survival protein, BCL2, during H 2 O 2 -induced oxidative stress. Cell survival assay in β-arrestin Knockout HEK293 cells showed that the NF-α1/CPE-5-HTR1E-mediated protection against oxidative stress was β-arrestin-dependent. Molecular dynamics studies revealed that NF-α1/CPE interacts with 5-HTR1E via 3 salt bridges, stabilized by several hydrogen bonds, independent of the serotonin pocket. Furthermore, after phosphorylating the C-terminal tail and intracellular loop 3 (ICL3) of NF-α1/CPE-5-HTR1E, it recruited β-arrestin1 by forming numerous salt bridges and hydrogen bonds to ICL2 and ICL3, leading to activation of β-arrestin1. Immunofluorescence studies showed 5-HTR1E and NF-α1/CPE are highly expressed and co-localized on cell surface of human hippocampal neurons. Importantly, knock-down of 5-HTR1E in human primary neurons diminished the NF-α1/CPE-mediated protection of these neurons against oxidative stress and glutamate neurotoxicity-induced cell death. Thus, NF-α1/CPE uniquely interacts with serotonin receptor 5-HTR1E to activate the β-arrestin/ERK/CREB/BCL2 pathway to mediate stress-induced neuroprotection., (© 2021. This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply.)

Background: Migraine has a great impact on public health. Current acute therapies do not satisfy all migraineurs. The novel serotonin 5-HT 1F receptor agonist appears more promising for aborting migraine attacks., Objective: To evaluate the clinical efficacy and safety of lasmiditan in treating acute migraine attacks., Methods: The literature search was performed in PubMed, Embase, and the Cochrane Central Register of Controlled Trials for randomized controlled trials (RCTs) which assessed the effect and safety of lasmiditan on migraine. The risk of bias was assessed using the Cochrane Collaboration's risk of bias tool. Results were extracted and pooled as risk ratios (RRs) with a fixed or random-effects model., Results: Based on the four included RCTs, pooled estimates showed that lasmiditan with the 50 mg, 100 mg, and 200 mg doses was superior to placebo at 2 h after the first dose in terms of pain freedom, absence of migraine-associated symptoms, headache relief, no/mild disability, and global impression of change (very much/much better) (RRs ranged from 1.13 to 1.96), except for nausea-free and vomiting-free. Both lasmiditan 100 mg and 200 mg resulted in significantly fewer patients using rescue medication (100 mg: RR = 0.75, 95% CI (0.61, 0.92), P = 0.007; 200 mg: RR = 0.81, 95% CI (0.66, 0.99), P = 0.04) at 2-24 h postdose, compared with placebo. Safety data showed that the proportion of patients reporting at least one treatment-emergent adverse event (TEAE) and the incidence of most common TEAEs such as dizziness, paresthesia, fatigue, somnolence, and nausea was higher in the lasmiditan groups (50 mg, 100 mg, and 200 mg), compared with placebo. There was no significant difference between lasmiditan and placebo in terms of cardiovascular-related TEAEs (RR = 2.75, 95% CI (0.81, 9.37), P = 0.11). Compared with lasmiditan 100 mg, lasmiditan 200 mg was more effective in pain freedom at 2 h after the first dose (RR = 0.83, 95% CI (0.74, 0.94), P = 0.004) but associated with a higher risk of reporting at least one TEAE (RR = 0.88, 95% CI (0.81, 0.96), P = 0.006)., Conclusions: Lasmiditan with the 50 mg, 100 mg, and 200 mg doses are effective and safe in acute migraine treatment. Lasmiditan 200 mg is more effective than lasmiditan 100 mg in pain freedom, while lasmiditan 100 mg is better tolerated in the short-term follow-up. Further larger sample-size RCTs are required to verify the applicability and tolerability in the long term., Competing Interests: The authors declare that they have no conflict interests., (Copyright © 2021 Ping Gu et al.)

Among the serotonin receptors, one of the most recently discovered 5-HT 6 subtype is an important protein target and its ligands may play a key role in the innovative treatment of cognitive disorders. However, none of its selective ligands have reached the pharmaceutical market yet. Recently, a new chemical class of potent 5-HT 6 receptor agents, the 1,3,5-triazine-piperazine derivatives, has been synthesized. Three members, the ortho and meta dichloro- ( 1 , 2 ) and the unsubstituted phenyl ( 3 ) derivatives, proved to be of special interest due to their high affinities ( 1 , 2 ) and selectivity ( 3 ) toward 5-HT 6 receptor. Thus, a broader pharmacological profile for 1-3 , including comprehensive screening of the receptor selectivity and drug-like parameters in vitro as well as both, pharmacokinetic and pharmacodynamic properties in vivo, have been investigated within this study. A comprehensive analysis of the obtained results indicated significant procognitive-like activity together with beneficial drug-likeness in vitro and pharmacokinetics in vivo profiles for both, ( RS )-4-[1-(2,3-dichlorophenoxy)propyl]-6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine ( 2 ) and ( RS )-4-(4-methylpiperazin-1-yl)-6-(1-phenoxypropyl)-1,3,5-triazin-2-amine ( 3 ), but insensibly predominant for compound 2 . Nevertheless, both compounds ( 2 and 3 ) seem to be good Central Nervous System drug candidates in search for novel therapeutic approach to dementia diseases, based on the 5-HT 6 receptor target.

5-HT 7 R belongs to a family of G protein-coupled receptors and is associated with a variety of physiological processes in the central nervous system via the activation of the neurotransmitter serotonin (5-HT). To develop selective and biased 5-HT 7 R ligands, we designed and synthesized a series of pyrazolyl-diazepanes 2 and pyrazolyl-piperazines 3 , which were evaluated for binding affinities to 5-HTR subtypes and functional selectivity for G protein and β-arrestin signaling pathways of 5-HT 7 R. Among them, 1-(3-(3-chlorophenyl)-1 H -pyrazol-4-yl)-1,4-diazepane 2c showed the best binding affinity for 5-HT 7 R and selectivity over other 5-HTR subtypes. It was also revealed as a G protein-biased antagonist. The self-grooming behavior test was performed with 2c in vivo with Shank3 -/- transgenic (TG) mice, wherein 2c significantly reduced self-grooming duration time to the level of wild-type mice. The results suggest that 5-HT 7 R could be a potential therapeutic target for treating autism spectrum disorder stereotypy.

An emerging feature of several high-resolution GPCR structures is the presence of closely bound cholesterol molecules. In this Perspective, we share the excitement of the recent advancements in GPCR structural biology. We further highlight our laboratory's journey in comprehensively elucidating functional sensitivity of GPCRs (using the serotonin 1A receptor as a representative neurotransmitter GPCR) to membrane cholesterol and validation using a variety of assays and molecular dynamics simulations. Although high-resolution structures of many GPCRs have been reported in the last few years, the structure of the serotoin 1A receptor proved to be elusive for a long time. Very recently the cryo-EM structure of the serotoin 1A receptor displaying 10 bound cholesterol molecules has been reported. We conclude by providing a critical analysis of caveats involved in GPCR structure determination., (Copyright © 2021 Elsevier B.V. All rights reserved.)

There has been significant attention concerning the biased agonism of G protein-coupled receptors (GPCRs), and it has resulted in various pharmacological benefits. 5-HT 7 R belongs to a GPCR, and it is a promising pharmaceutical target for the treatment of neurodevelopmental and neuropsychiatric disorders. Based on our previous research, we synthesized a series of 6-chloro-2'-methoxy biphenyl derivatives 1 , 2 , and 3 with a variety of amine scaffolds. These compounds were evaluated for their binding affinities to 5-HTR subtypes and their functional selectivity toward the Gs protein and the β-arrestin signaling pathways of 5-HT 7 R. Among them, 2-(6-chloro-2'-methoxy-[1,1'-biphenyl]-3-yl)- N -ethylethan-1-amine, 2b , was found to be a G-protein-biased ligand of 5-HT 7 R. In an in vivo study with Shank3 transgenic mice, the self-grooming behavior test was performed with 2b , which increased the duration of self-grooming. The experiments further suggested that 5-HT 7 R is associated with autism spectrum disorders (ASDs) and could be a therapeutic target for the treatment of stereotypy in ASDs.

A new ligand for 5-HT1A and 5-HT7 receptors, an arylpiperazine salicylamide derivative with an inflexible spacer, is investigated to identify preferred fragments capable of creating essential intermolecular interactions in different solvates. To fully identify and characterize the obtained crystalline materials, various methods including powder and single-crystal X-ray diffraction, solid-state NMR, and thermal analysis were employed, supplemented by periodic ab initio calculations. The molecular conformation in different solvates, types, and hierarchy of intermolecular interactions as well as the crystal packing were investigated to provide data for future research focused on studying protein-ligand interactions. Based on various methods of crystal structure analysis, including the interaction energy calculation and programs using an artificial neural network, a salicylamide fragment was found to be crucial for intermolecular contacts, mostly of dispersion and electrostatic character. A supramolecular 2D kite-type layer of {4,4} topology was found to form in crystals. The closed voids between layers contain disordered solvents, very weakly interacting with the molecule and the layer. It has been postulated that the separation of the layers might be influenced by an increase in temperature or the size of the solvent; hence, only methanol and ethanol hemi-solvates could be obtained from a series of various alcohols.

Introduction: Depression and anxiety disorders contribute to the global disease burden. Ursolic acid (UA), a natural compound present in many vegetables, fruits and medicinal plants, was tested in vivo for its effect on (1) enhancing resistance to stress and (2) its effect on life span., Methods: The compound was tested for its antioxidant activity in C. elegans. Stress resistance was tested in the heat and osmotic stress assay. Additionally, the influence on normal life span was examined. RT-PCR was used to assess possible serotonin targets., Results: UA prolonged the life span of C. elegans. Additionally, UA significantly lowered reactive oxygen species (ROS). Molecular docking studies, PCR analysis and microscale thermophoresis (MST) supported the results that UA acts through serotonin receptors to enhance stress resistance., Discussion: Considering the urgent need for new and safe medications in the treatment of depression and anxiety disorders, our results indicate that UA may be a promising new drug candidate.

Background/objective: Mirtazapine has traditionally been used for the treatment of major depressive disorder, with an added benefit in patients who have comorbid insomnia or anxiety. Recent studies describe its usefulness in treating refractory pruritus of various causes as well. Our goal is to better define the use of mirtazapine in the treatment of refractory pruritus., Method: Through a thorough literature review of PubMed, we identified all reports of the use of mirtazapine for pruritus., Results: Upon examination of 8 supporting articles, we found mirtazapine has quality evidence for the treatment of intra-thecal morphine-induced pruritus. Mirtazapine may also be effective in treating pruritus related to various other conditions, including psoriasis, atopic dermatitis, cutaneous malignancies (primary or metastatic), hematologic malignancies (lymphomas and leukemias), liver failure, renal failure, cholestasis, as well as pruritus of unknown origin., Conclusions: Mirtazapine plays a role in treatment for intra-thecel morphine-induced pruritis yet high-quality trials are needed to confirm its efficacy in other dermatologic conditions.

Serotonin (5-hydroxytryptamine [5-HT]) receptors (5-HTRs) mediate neuroendocrine signaling via interactions with the ligand serotonin (5-HT). The 5-HT signaling system has been well studied in vertebrates, but rarely known in invertebrate animals, especially in the marine invertebrates. In this study, we identified and characterized a novel 5-HTR from the sea cucumber Apostichopus japonicus (Aj5-HT 4/6 ). The cloned Aj5-HT 4/6 open reading frame comprised 1290 bp and encoded 429 amino acids. Bioinformatic analysis of the receptor indicated that it was a member of the class A of the G protein-coupled receptor family. Further experiments using Aj5-HT 4/6 -transfected HEK293 cells demonstrated that treatment with 5-HT could induce rapid internalization of Aj5-HT 4/6 fused with enhanced green fluorescent protein from the cell surface into the cytoplasm and triggered a significant increase in levels of the second messenger cAMP as well as mitogen-activated protein kinase phosphorylation in a 5-HT dose-dependent manner. Quantitative real time-polymerase chain reaction demonstrated that Aj5-HT 4/6 was predominantly expressed in the muscle and respiratory tree, and its expression was significantly decreased during estivation. Taken together, these results imply that Aj5-HT 4/6 is potentially involved in the movement and metabolism of the sea cucumber., (© 2021 Wiley Periodicals LLC.)

Primary cilia are hair-like projections of the cell membrane supported by an inner microtubule scaffold, the axoneme, which polymerizes out of a membrane-docked centriole at the ciliary base. By working as specialized signaling compartments, primary cilia provide an optimal environment for many G protein-coupled receptors (GPCRs) and their effectors to efficiently transmit their signals to the rest of the cell. For this to occur, however, all necessary receptors and signal transducers must first accumulate at the ciliary membrane. Serotonin receptor 6 (HTR6) and Somatostatin receptor 3 (SSTR3) are two GPCRs whose signaling in brain neuronal cilia affects cognition and is implicated in psychiatric, neurodegenerative, and oncologic diseases. Over a decade ago, the third intracellular loops (IC3s) of HTR6 and SSTR3 were shown to contain ciliary localization sequences (CLSs) that, when grafted onto non-ciliary GPCRs, could drive their ciliary accumulation. Nevertheless, these CLSs were dispensable for ciliary targeting of HTR6 and SSTR3, suggesting the presence of additional CLSs, which we have recently identified in their C-terminal tails. Herein, we review the discovery and mapping of these CLSs, as well as the state of the art regarding how these CLSs may orchestrate ciliary accumulation of these GPCRs by controlling when and where they interact with the ciliary entry and exit machinery via adaptors such as TULP3, RABL2 and the BBSome., (© 2021 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.)

The leaves of Homalomena aromatica are traditionally used in Bangladesh for the treatment of different chronic ailments. The purpose of this study was to explore in vitro antioxidant, thrombolytic activities, and in vivo neuropharmacological effects of methanolic extract of Homalomena aromatica (MEHA) leaves. Antioxidant activity of MEHA was assessed by a DPPH free radical scavenging assay and total phenolics content, total flavonoids content were also measured. The thrombolytic activity was determined by percentage of clot lysis and neuropharmacological activities by hole board, tail suspension, forced swimming and elevated plus maze tests. The results showed that the IC 50 value of the extract against DPPH was 199.51 μg/mL. Quantitative analysis displayed higher contents of phenolics and flavonoids (147.71 mg gallic acid equivalent/g & 66.65 mg quercetin equivalent/g dried extract, respectively). The extract also showed a significant clot lysis (33.31%) activity. In case of anxiolytic activity, the elevate plus maze (EPM) test demonstrated an increase in time spent in open arms, and in case of hole board test, the number of head dipping was also significantly increased ( p < 0.05). All the test compared with control (1% Tween in water) and standard (diazepam 1 mg/kg), significant dose (200 & 400 mg/kg) dependent anxiolytic activity was found. In antidepressant activity, there was a significant decrease in period of immobility in both test models (tail suspension and forced swimming) ( p < 0.05). Moreover, 13 compounds were identified as bioactive, showed good binding affinities to xanthine oxidoreductase, tissue plasminogen activator receptor, potassium channel receptor, human serotonin receptor targets in molecular docking experiments. Furthermore, ADME/T analysis revealed their drug-likeness, likely pharmacological actions and non-toxic upon consumption. Taken together, our finding support the traditional medicinal use of this plant, which may provide a potential source for future drug discovery.

Serotonin receptor 6 (5-HT 6 R), a typical G protein-coupled receptor (GPCR) mainly expressed in the neurogenic area with constitutive activity, is of particular interest as a promising target for emotional impairment. Here, we found that 5-HT 6 R was highly expressed in human NSCs and activation of the receptor promoted self-renewal of human NSCs, and thus induced the expansion and folding of human cerebral organoids; dysfunction of receptor or inhibition of its constitutive activity resulted in the premature differentiation of NSCs, which ultimately depleted the NSC pool. The following mechanistic study revealed that EPAC-CREB signaling was involved in 5-HT 6 R regulation. Furthermore, we showed that mice with genetic deletion of 5-HT 6 R or knockin A268R mutant presented depression-like behaviors and impaired hippocampal neurogenesis for progressive decrease of the NSC pool. Thus, this study indicates that the modulation of 5-HT 6 R and its constitutive activity may provide a therapeutic alternative to alleviate depression., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Piperidines are biogenic amines studied mainly in toxicology because they were initially found as alkaloids from peppers and insect venoms. Piperidines are also produced in the human body, and their actions seem to be related to wakefulness/sleep and other cognitive phenomena. Piperidines have been minimally characterized for therapeutic applications. In this context, 1-Boc-piperidine-4-carboxaldehyde (1-Boc-piperidine) is a piperidine-derivative molecule with no mechanism of action reported, although its uses include the synthesis of GPR119 selective agonists that have been patented as anti-obesity drugs., Objectives: The aim of this work was to study the effects of 1-Boc-piperidine on binge-eating behaviour and anxiety in Wistar rats., Methods: In experimental protocol 1, binge-eating behaviour was induced in animals that received pre-treatment (i.p.) with (i) vehicle (methanol 10%; 1 mL/kg), (ii) 1-Boc-piperidine (1 µmol kg-1), or (iii) 1-Boc-piperidine (10 µmol kg-1). In experimental protocol 2, mildly stressed animals were evaluated in the elevated plus maze under the acute effects of the pre-treatments applied in experimental protocol 1., Results and Conclusions: 1-Boc-piperidine decreased, in a dose-dependent manner, the intake of calories from a succulent hyper-caloric food in a binge-eating protocol in female rats, whereas the acute exposition to this piperidine exerted an anxiolytic effect in the male rat. In both effects, the mechanism of action remains to be characterized., (© 2021 S. Karger AG, Basel.)

This study concerns synthesis and evaluation of pharmacodynamic and pharmacokinetic profile for all four stereoisomers of MF-8 (5-(4-fluorophenyl)-3-(2-hydroxy-3-(4-(2-methoxyphenyl)piperazin-1-yl)propyl)-5-methylimidazolidine-2,4-dione), the previously described, highly potent 5-HT 7 R ligand with antidepressant activity on mice. The combination of DFT calculations of 1 H NMR chemical shifts with docking and dynamic simulations, in comparison to experimental screening results, provided prediction of the configuration for one of two present stereogenic centers. The experimental data for stereoisomers (MF-8A-MF-8D) confirmed the significant impact of stereochemistry on both, 5-HT 7 R affinity and antagonistic action, with K i and K b values in the range of 3-366 nM and 0.024-99 μM, respectively. We also indicated the stereochemistry-dependent influence of the tested compounds on P-glycoprotein efflux, absorption in Caco-2 model, metabolic pathway as well as CYP3A4 and CYP2C9 activities., (Copyright © 2020 Elsevier Inc. All rights reserved.)

G protein-coupled receptors (GPCRs) are the most common pharmacological target in human clinical practice. To perform their functions, many GPCRs must accumulate inside primary cilia, microtubule-based plasma membrane protrusions working as cellular antennae. Nevertheless, the molecular mechanisms underlying GPCR ciliary targeting remain poorly understood. Serotonin receptor 6 (HTR6) and somatostatin receptor 3 (SSTR3) are two brain-enriched ciliary GPCRs involved in cognition and pathologies such as Alzheimer's disease and cancer. Although the third intracellular loops (IC3) of HTR6 and SSTR3 suffice to target non-ciliary GPCRs to cilia, these IC3s are dispensable for ciliary targeting of HTR6 and SSTR3 themselves, suggesting these GPCRs contain additional ciliary targeting sequences (CTSs). Herein, we discover and characterize novel CTSs in HTR6 and SSTR3 C-terminal tails (CT). These CT-CTSs (CTS2) act redundantly with IC3-CTSs (CTS1), each being sufficient for ciliary targeting. In HTR6, RKQ and LPG motifs are critical for CTS1 and CTS2 function, respectively, whereas in SSTR3 these roles are mostly fulfilled by AP[AS]CQ motifs in IC3 and juxtamembrane residues in CT. Furthermore, we shed light on how these CTSs promote ciliary targeting by modulating binding to ciliary trafficking adapters TULP3 and RABL2., (© 2020 Barbeito et al.)

Mitochondria in neurons contribute to energy supply, the regulation of synaptic transmission, Ca 2+ homeostasis, neuronal excitability, and stress adaptation. In recent years, several studies have highlighted that the neurotransmitter serotonin (5-HT) plays an important role in mitochondrial biogenesis in cortical neurons, and regulates mitochondrial activity and cellular function in cardiomyocytes. 5-HT exerts its diverse actions by binding to cell surface receptors that are classified into seven distinct families (5-HT1 to 5-HT7). Recently, it was shown that 5-HT3 and 5-HT4 receptors are located on the mitochondrial membrane and participate in the regulation of mitochondrial function. Furthermore, it was observed that activation of brain 5-HT7 receptors rescued mitochondrial dysfunction in female mice from two models of Rett syndrome, a rare neurodevelopmental disorder characterized by severe behavioral and physiological symptoms. Our Western blot analyses performed on cell-lysate and purified mitochondria isolated from neuronal cell line SH-SY5Y showed that 5-HT7 receptors are also expressed into mitochondria. Maximal binding capacity (Bmax) obtained by Scatchard analysis on purified mitochondrial membranes was 0.081 pmol/mg of 5-HT7 receptor protein. Lastly, we evaluated the effect of selective 5-HT7 receptor agonist LP-211 and antagonist (inverse agonist) SB-269970 on mitochondrial respiratory chain (MRC) cytochrome c oxidase activity on mitochondria from SH-SY5Y cells. Our findings provide the first evidence that 5-HT7 receptor is also expressed in mitochondria.

Agonist binding promotes activation of G protein-coupled receptors (GPCRs) and association of active receptors with G protein heterotrimers. The resulting active-state ternary complex is the basis for conventional stimulus-response coupling. Although GPCRs can also associate with G proteins before agonist binding, the impact of such preassociated complexes on agonist-induced signaling is poorly understood. Here we show that preassociation of 5-HT 7 serotonin receptors with G s heterotrimers is necessary for agonist-induced signaling. 5-HT 7 receptors in their inactive state associate with G s , as these complexes are stabilized by inverse agonists and receptor mutations that favor the inactive state. Inactive-state 5-HT 7 -G s complexes dissociate in response to agonists, allowing the formation of conventional agonist-5-HT 7 -G s ternary complexes and subsequent G s activation. Inactive-state 5-HT 7 -G s complexes are required for the full dynamic range of agonist-induced signaling, as 5-HT 7 receptors spontaneously activate G s variants that cannot form inactive-state complexes. Therefore, agonist-induced signaling in this system involves two distinct receptor-G protein complexes, a conventional ternary complex that activates G proteins and an inverse-coupled binary complex that maintains the inactive state when agonist is not present., Competing Interests: The authors declare no competing interest., (Copyright © 2020 the Author(s). Published by PNAS.)

In the light of recent lines of evidence, 5-HT 6 R ligands are a promising tool for future treatment of memory impairment. Hence, this study has supplied highly potent 5-HT 6 R agents with procognitive effects, which represent an original chemical class of 1,3,5-triazines, different from widely studied sulfone and indole-like 5-HT 6 R ligands. The new compounds were rationally designed as modifications of lead, 4-(1-(2-chlorophenoxy)ethyl)-6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine (1), involving an introduction of: (i) two chlorines at benzene ring and (ii) varied linkers joining the triazine ring to aromatic ethers. Synthesis, in vitro and in vivo biological tests and computer-aided SAR analysis for 19 new compounds were carried out. Most of the new triazines displayed high affinity (K i  < 100 nM) and selectivity towards 5-HT 6 R, with respect to 5-HT 2A R, 5-HT 7 R and D 2 R. The crystallography-supported docking studies, including quantum-polarized ligand docking (QPLD), indicated that chlorine atoms may be involved in different type of halogen bonding, however, the linker properties seem to predominately affect the 5-HT 6 R affinity. 4-[1-(2,5-Dichlorophenoxy)propyl]-6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine (9), which displayed: the highest affinity (K i  = 6 nM), very strong 5-HT 6 R antagonistic action (K B  = 27 pM), procognitive effects in vivo in novel object recognition (NOR) test in rats, a very good permeability in PAMPA model and satisfying safety in vitro, was identified as the most potent 1,3,5-triazine agent so far, useful as a new lead for further research., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 The Author(s). Published by Elsevier Masson SAS.. All rights reserved.)

The design of a series of novel flavone derivatives was synthesized as potential broad-spectrum antipsychotics by using multi-receptor affinity strategy between dopamine receptors and serotonin receptors. Among them, 7-(4-(4-(6-fluorobenzo[d]isoxazol-3-yl) piperidin- 1-yl) butoxy)-2,2-dimethylchroman-4-one ( 6j ) exhibited a promising preclinical profile. Compound 6j not only showed high affinity for dopamine D 2 , D 3 , and serotonin 5-HT 1A , 5-HT 2A receptors, but was also endowed with low to moderate activities on 5-HT 2C , α 1 , and H 1 receptors, indicating a low liability to induce side effects such as weight gain, orthostatic hypotension and QT prolongation. In vivo behavioral studies suggested that 6j has favorable effects in alleviating the schizophrenia-like symptoms without causing catalepsy. Taken together, compound 6j has the potential to be further developed as a novel atypical antipsychotic.

In this study, a series of compounds derived from 4-methoxy-1 H -isoindole-1,3(2 H )-dione, potential ligands of phosphodiesterase 10A and serotonin receptors, were investigated as potential antipsychotics. A library of 4-methoxy-1 H -isoindole-1,3(2 H )-dione derivatives with various amine moieties was synthesized and examined for their phosphodiesterase 10A (PDE10A)-inhibiting properties and their 5-HT 1A and 5-HT 7 receptor affinities. Based on in vitro studies, the most potent compound, 18 (2-[4-(1 H -benzimidazol-2-yl)butyl]-4-methoxy-1 H -isoindole-1,3(2 H )-dione), was selected and its safety in vitro was evaluated. In order to explain the binding mode of compound 18 in the active site of the PDE10A enzyme and describe the molecular interactions responsible for its inhibition, computer-aided docking studies were performed. The potential antipsychotic properties of compound 18 in a behavioral model of schizophrenia were also investigated.

Aporphine alkaloids containing a C10 nitrogen motif were synthesized and evaluated for affinity at 5-HT 1A R, 5-HT 2A R, 5-HT 6 R and 5-HT 7A R. Three series of racemic aporphines were investigated: 1,2,10-trisubstituted, C10 N-monosubstituted and compounds containing a C10 benzofused aminothiazole moiety. The 1,2,10-trisubstituted series of compounds as a group displayed modest selectivity for 5-HT 7A R and also had moderate 5-HT 7A R affinity. Compounds from the C10 N-monosubstituted series generally lacked affinity for 5-HT 2A R and 5-HT 6 R and showed strong affinity for 5-HT 1A or 5-HT 7A R. Compounds in this series that contained an N6-methyl group were up to 27-fold selective for 5-HT 7A R over 5-HT 1A R, whereas compounds with an N6-propyl substituent showed a reversal in this selectivity. The C10 benzofused aminothiazole analogues showed a similar binding profile as the C10 N-monosubstituted series i.e. strong affinity for 5-HT 1A R or 5-HT 7A R, with selectivity between the two receptors being similarly influenced by N6-methyl or N6-propyl substituents. Compounds 29 and 34a exhibit high 5-HT 7A R affinity, excellent selectivity versus dopamine receptors and function as antagonists in 5-HT 7A R cAMP-based assays. Compounds 29 and 34a have been identified as new lead molecules for further tool and pharmaceutical optimization., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The novel 1,3,4,11b-tetrahydro-1H-fluoreno[9,1-cd]azepine framework, a structurally rigidified variant of the 1-phenylbenzazepine template, was synthesized via direct arylation as a key reaction. Evaluation of the binding affinities of the rigidified compounds across a battery of serotonin, dopamine, and adrenergic receptors indicates that this scaffold unexpectedly has minimal affinity for D 1 and other dopamine receptors and is selective for the 5-HT 6 receptor. The affinity of these systems at the 5-HT 6 receptor is significantly influenced by electronic and hydrophobic interactions as well as the enhanced rigidity of the ligands. Molecular docking studies indicate that the reduced D 1 receptor affinity of the rigidified compounds may be due in part to weaker H-bonding interactions between the oxygenated moieties on the compounds and specific receptor residues. Key receptor-ligand H-bonding interactions, salt bridges, and π-π interactions appear to be responsible for the 5-HT 6 receptor affinity of the compounds. Compounds 10 (6,7-dimethoxy-2,3,4,11b-tetrahydro-1H-fluoreno[9,1-cd]azepine) and 12 (6,7-dimethoxy-2-methyl-2,3,4,11b-tetrahydro-1H-fluoreno[9,1-cd]azepine) have been identified as structurally novel, high affinity (K i  = 5 nM), selective 5-HT 6 receptor ligands., (© 2020 John Wiley & Sons A/S.)

Serotonin receptor (5-HT) is a biogenic amine acting as a neurotransmitter and neuromodulator that mediates various aspects of reproduction and gametogenesis. The full-length nucleotide sequence of Haliotis discus hannai encodes a protein of 417 amino acids with a predicted molecular mass of 46.54 kDa and isoelectric point of 8.94. The structural profile of 5-HT Hdh displayed key features of G protein-coupled receptors, including seven hydrophobic transmembrane domains, putative N-linked glycosylation sites, and several phosphorylation consensus motifs. It shares the highest homology of its amino acid sequence with the 5-HT receptor from Haliotis asinina, and to lesser extent of human 5-HT receptor. The cloned sequence possesses two cysteine residues (Cys-115 and Cys-193), which are likely to form a disulfide bond. Phylogenetic comparison with other known 5-HT receptor genes revealed that the 5-HT Hdh is most closely related to the 5-HT Ha receptor. The three-dimensional structure of the 5-HT Hdh showed multiple alpha helices which is separated by a helix-loop-helix (HLH) structure. Quantitative PCR demonstrated that the receptor mRNA was predominantly expressed in the pleuropedal ganglion. Significant differences in the transcriptional activity of the 5-HT Hdh gene were observed in the ovary at the ripening stage. An exclusive expression was detected in pleuropedal ganglion, testis, and ovary at higher effective accumulative temperature (1000 °C). In situ hybridization showed that the 5-HT Hdh expressing neurosecretory cells were distributed in the cortex of the pleuropedal ganglion. Our results suggest that 5-HT Hdh synthesized in the neural ganglia may be involved in oocyte maturation and spawning of H. discus hannai.

Heterogeneity in disease mechanisms between genetically distinct patients contributes to high attrition rates in late stage clinical drug development. New personalized medicine strategies aim to identify predictive biomarkers which stratify patients most likely to respond to a particular therapy. However, for complex multifactorial diseases not characterized by a single genetic driver, empirical approaches to identifying predictive biomarkers and the most promising therapies for personalized medicine are required. In vitro pharmacogenomics seeks to correlate in vitro drug sensitivity testing across panels of genetically distinct cell models with genomic, gene expression or proteomic data to identify predictive biomarkers of drug response. However, the vast majority of in vitro pharmacogenomic studies performed to date are limited to dose-response screening upon a single viability assay endpoint. In this article we describe the application of multiparametric high content phenotypic screening and the theta comparative cell scoring method to quantify and rank compound hits, screened at a single concentration, which induce a broad variety of divergent phenotypic responses between distinct breast cancer cell lines. High content screening followed by transcriptomic pathway analysis identified serotonin receptor modulators which display selective activity upon breast cancer cell cycle and cytokine signaling pathways correlating with inhibition of cell growth and survival. These methods describe a new evidence-led approach to rapidly identify compounds which display distinct response between different cell types. The results presented also warrant further investigation of the selective activity of serotonin receptor modulators upon breast cancer cell growth and survival as a potential drug repurposing opportunity., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Serotonin (5-HT) receptors are proteins involved in various neurological and biological processes, such as aggression, anxiety, appetite, cognition, learning, memory, mood, sleep, and thermoregulation. They are commonly associated with drug abuse and addiction due to their importance as targets for various pharmaceutical and recreational drugs. However, due to a high sequence similarity/identity among 5-HT receptors and the unavailability of the 3D structure of the different 5-HT receptor, no report was available so far regarding the systematical comparison of the key and selective residues involved in the binding pocket, making it difficult to design subtype-selective serotonergic drugs. In this work, we first built and validated three-dimensional models for all 5-HT receptors based on the existing crystal structures of 5-HT 1B , 5-HT 2B , and 5-HT 2C . Then, we performed molecular docking studies between 5-HT receptors agonists/inhibitors and our 3D models. The results from docking were consistent with the known binding affinities of each model. Sequentially, we compared the binding pose and selective residues among 5-HT receptors. Our results showed that the affinity variation could be potentially attributed to the selective residues located in the binding pockets. Moreover, we performed MD simulations for 12 5-HT receptors complexed with ligands; the results were consistent with our docking results and the reported data. Finally, we carried out off-target prediction and blood-brain barrier (BBB) prediction for Captagon using our established hallucinogen-related chemogenomics knowledgebase and in-house computational tools, with the hope to provide more information regarding the use of Captagon. We showed that 5-HT 2C , 5-HT 5A , and 5-HT 7 were the most promising targets for Captagon before metabolism. Overall, our findings can provide insights into future drug discovery and design of medications with high specificity to the individual 5-HT receptor to decrease the risk of addiction and prevent drug abuse.

In previous structure-activity relationship studies to identify new and selective 5-HT 7 receptor (5-HT 7 R) ligands, we identified the chiral compound, 5-chloro-2-{2-[3,4-dihydroisoquinoline-2(1H)-yl]ethyl}-2-methyl-2,3-dihydro-1H-inden-1-one (SYA 40247), with high-affinity binding to the 5-HT 7 R. Thus, it was of interest to separate the enantiomers in order to evaluate their affinity at the 5-HT 7 R. To achieve this separation, a normal-phase analytical method using HPLC-PDA and a 4.6 × 250 mm Chiralpak AD-H column was developed. Optimized isocratic conditions of 1.00 mL/min 95:5:0.1 v/v/v hexane-ethanol-diethylamine and a 254 nm analysis wavelength yielded a 6.07 min baseline separation. The method was scaled up to a 10 × 250 mm Chiralpak AD-H column, allowing 3 mg of racemate to be separated with a single injection, and 6 mg for an overlapping double injection in the same run. The separated enantiomers were reinjected into the analytical HPLC system, peak identities confirmed by retention time and PDA UV spectra, and the enantiomeric purities determined to be 100% for peak 1 and 100% for peak 2. A Jasco P-1020 polarimeter was used to determine the specific rotation [α] of the enantiomers of peaks 1 and 2, which were -86.2 and +93.3 (deg mL)/(g dm) respectively. No racemization was observed, and the enantiomeric purity remained at 100% for each peak., (© 2019 John Wiley & Sons, Ltd.)

Despite the significant improvement of methodology in the field of the in silico drug discovery, the search for selective drugs is still far from trivial. This is especially relevant in the case of designing new medicaments for treatment of central nervous system disorders. In this work, we present a new approach based on the molecular docking and the following electronic properties analysis of ligands' binding poses (electrostatic potential distribution analysis and quantitative topological analysis of the electron density distribution). The proposed protocol significantly increases the success rate of the selective 5-HT 7 R ligands against 5-HT 1A R selection from the prepared databases (the rise from 33.3% to 77.8% and from 22.7% to 62.5% for training and testing sets, respectively). The presented approach can be applied as a supportive method in the virtual screening of ligands databases., (Copyright © 2019 Elsevier Inc. All rights reserved.)

5-HT 4 R, 5-HT 6 R, and 5-HT 7A R are three constitutively active G s -coupled 5-HT receptors that have key roles in brain development, learning, memory, cognition, and other physiological processes in the central nervous system. In addition to G s signaling cascade mediated by these three 5-HT receptors, the ERK1/2 signaling which is dependent on cyclic adenosine monophosphate (cAMP) production and protein kinase A (PKA) activation downstream of G s signaling has also been widely studied. In this study, we investigated these two signaling pathways originating from the three G s -coupled 5-HT receptors in AD293 cells. We found that the phosphorylation and activation of ERK1/2 are ligand-induced, in contrast to the constitutively active G s signaling. This indicates that G s signaling alone is not sufficient for ERK1/2 activation in these three 5-HT receptors. In addition to G s , we found that β-arrestin and Fyn are essential for the activation of ERK1/2. Together, these results put forth a novel mechanism for ERK1/2 activation involving the cooperative action of G s , β-arrestin, and Fyn.

Among serotonin receptors, the 5-HT 6 subtype is the most controversial and the least known in the field of molecular mechanisms. The 5-HT 6 R ligands can be pivotal for innovative treatment of cognitive impairment, but none has reached pharmacological market, predominantly, due to insufficient "druglikeness" properties. Recently, 1,3,5-triazine-piperazine derivatives were identified as a new chemical family of potent 5-HT 6 R ligands. For the most active triazine 5-HT 6 R agents found ( 1 - 4 ), a wider binding profile and comprehensive in vitro evaluation of their drug-like parameters as well as behavioral studies and an influence on body mass in vivo were investigated within this work. Results indicated the most promising pharmacological/druglikeness profiles for 4-((1H-indol-3-yl)methyl)-6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine ( 3 ) and 4-((2-isopropyl-5-methylphenoxy)methyl)-6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine ( 4 ), which displayed a significant procognitive action and specific anxiolytic-like effects in the behavioral tests in vivo together with satisfied pharmaceutical and safety profiles in vitro. The thymol derivative ( 4 ) seems to be of higher importance as a new lead candidate, due to the innovative, non-indole and non-sulfone structure with the best 5-HT 6 R binding properties.

Membrane receptors often form complexes with other membrane proteins that directly interact with different effectors of the signal transduction machinery. G-protein-coupled receptors (GPCRs) were for long time considered as single pharmacological entities. However, evidence for oligomerization appeared for various classes and subtypes of GPCRs. This review focuses on metabotropic serotonin (5-hydroxytryptamine, 5-HT) receptors, which belong to the rhodopsin-like class A of GPCRs, and will summarize the convergent evidence that homo- and hetero-dimers containing 5-HT receptors exist in transfected cells and in-vivo. We will show that complexes involving 5-HT receptors may acquire new signal transduction pathways and new physiological roles. In some cases, these complexes participate in disease-specific deregulations, that can be differentially affected by various drugs. Hence, selecting receptor complex-specific responses of these heterodimers may constitute an emerging strategy likely to improve beneficial therapeutic effects., (Copyright © 2019 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.)

The complexes of selected long-chain arylpiperazines with homology models of 5-HT 1A , 5-HT 2A , and 5-HT 7 receptors were investigated using quantum mechanical methods. The molecular geometries of the ligand-receptor complexes were firstly optimized with the Our own N-layered Integrated molecular Orbital and molecular Mechanics (ONIOM) method. Next, the fragment molecular orbitals method with an energy decomposition analysis scheme (FMO-EDA) was employed to estimate the interaction energies in binding sites. The results clearly showed that orthosteric binding sites of studied serotonin receptors have both attractive and repulsive regions. In the case of 5-HT 1A and 5-HT 2A two repulsive areas, located in the lower part of the binding pocket, and one large area of attraction engaging many residues at the top of all helices were identified. Additionally, for the 5-HT 7 receptor, the third area of destabilization located at the extracellular end of the helix 6 was found.

A series of 2-amino-4-(4-methylpiperazin-1-yl)-1,3,5-triazines was designed based on previously published 2-amino-4-benzyl-(4-methylpiperazin-1-yl)-1,3,5-triazines in order to evaluate the role of a linker between the triazine moiety and an aromatic substituent for the human serotonin 5-HT 6 receptor affinity. As new linkers two carbon atoms (ethyl or ethenyl) or an oxyalkyl chain (methoxy, 2-ethoxy, 2-propoxy) were introduced. Affinities of the compounds for the 5-HT 6 R as the main target, and for the 5-HT 1A R, 5-HT 7 R and D 2 R as competitive ones, were determined in the radioligand binding assays. Docking to the 5-HT 6 R homology model was performed to support SAR analysis. Results showed that the branching of the methoxyl linker increased affinity for the human 5-HT 6 R whereas an unsaturated bond within the linker dramatically reduced desirable activity. Both experimental and theoretical studies confirmed the previously postulated beneficial role of the aromatic size for interaction with the 5-HT 6 R. Thus, the largest naphthyl moiety yielded the highest activity. In particular, 4-(4-methylpiperazin-1-yl)-6-(1-(naphthalen-1-yloxy)ethyl)-1,3,5-triazin-2-amine (24), the most potent 5-HT 6 R agent found (K i  = 23 nM), can be a new lead structure for further search and development., (Copyright © 2018 Elsevier Inc. All rights reserved.)

According to early models of GPCR signaling, G proteins only interact with activated receptors. However, some GPCRs were shown to assemble with G proteins before receptor activation, in accordance with more recent models. Previously, we found that the 5-HT 7 receptor, as opposed to the 5-HT 4 receptor, was preassociated with G s , but the molecular determinants for this interaction are still elusive. In a series of chimeric 5-HT 7 receptors with intracellular segments from 5-HT 4 , we determined the receptor-G protein interaction by performing antibody-immobilized fluorescence recovery after photobleaching and fluorescence resonance energy transfer. We identified the intracellular loop 3 and C-tail of the 5-HT 7 receptor to be responsible for the preassociation with G s , and we further delineated the TM5 extension in the intracellular loop 3 and helix 8 in the C-tail as the molecular determinants. These chimeric exchanges converted the 5-HT 7 receptor into a collision-coupled receptor that recruited G proteins only upon agonist activation, whereas reciprocal exchanges converted 5-HT 4 to a preassociated receptor. The 5-HT 7 receptor displayed 2-component agonist-induced G s signaling with high and low potency. In addition, the same segments were involved in low-potency signaling and preassociation. The correspondence between G s preassociation and low-potency G s signaling is a novel aspect of GPCR pharmacology.-Ulsund, A. H., Dahl, M., Frimurer, T. M., Manfra, O., Schwartz, T. W., Levy, F. O., Andressen, K. W. Preassociation between the 5-HT 7 serotonin receptor and G protein G s : molecular determinants and association with low potency activation of adenylyl cyclase.

Investigation of the retention behavior of a wide range of analytes, 43 nitrogen containing heterocyclic and guanidine derivatives such, as imidazoline and serotonin receptor ligands or their related compounds, was performed on mixed-mode stationary phase in the combined reversed-phase (RP) and hydrophilic interaction liquid chromatography (HILIC) modes. Suitability of the linear retention modelling in the HILIC and RP modes was tested including separate contributions from adsorption and partition. For the HILIC retention, the partition model was found to provide better description compared with the adsorption model. In a wider range of the aqueous eluent volume fractions, φ(aq), retention was described as a function of volume fractions and total polarity of mobile phase using the mixed-mode retention modelling. The obtained results revealed that the shift of the chromatographic mode can be calculated from the change of total polarity of mobile phase in a multi-modal relation, logarithm of retention factor vs. total polarity, with the minimum value representing the turning point between the HILIC and the RP mode. Molecular properties of the investigated compounds that influence the retention behavior and the turning point were selected using Multiple Linear Regression (MLR) and Support Vector Machine (SVM). Slightly better statistical results were found for the logk w RP (aq)/MLR, logk w HILIC (org)/MLR, logk b HILIC (aq)/MLR, and φ min (aq)/SVM (RBF) QSRR models than for the logk w RP (aq)/SVM, logk w HILIC (org)/SVM, logk b HILIC (aq)/SVM, and φ min (aq)/MLR modelling. With this insight, it is possible to precisely define and predict the retention characteristics based on physico-chemical properties of imidazoline and piperazine related compounds., (Copyright © 2018 Elsevier B.V. All rights reserved.)

It is well-documented that serotonin (5-HT) exerts its pharmacological effects through a series of 5-HT receptors. The most recently identified member of this family, 5-HT 7 , was first identified in 1993. Over the course of the last 25 years, this receptor has been the subject of intense investigation, and it has been demonstrated that 5-HT 7 plays an important role in a wide range of pharmacological processes. As a result of these findings, modulation of 5-HT 7 activity has been the focus of numerous drug discovery and development programs. This review provides an overview of the roles of 5-HT 7 in normal physiology and the therapeutic potential of this interesting drug target.

Serotonin (5-HT) regulates numerous physiological functions and processes, such as light adaptation, food intake and ovarian maturation, and plays the role through 5-HT receptors. To our knowledge, this is the first study to isolate and characterize the serotonin receptor 7 (5-HT 7 receptor) cDNA encoded in Eriocheir sinensis, an economically important aquaculture species in China, by performing rapid-amplification of cDNA ends. The full-length of 5-HT 7 receptor gene cDNA is 2328 bp and encodes a polypeptide with 590 amino acids that are highly homologous with other crustaceans 5-HT 7 receptor genes. Analysis of the deduced amino acid sequence of the 5-HT 7 , including 7 transmembrane domains and some common features of G protein-coupled receptors (GPCRs), indicated that 5-HT 7 receptor was a member of GPCRs family. A gene expression analysis of the 5-HT 7 receptor by RT-PCR revealed that the 5-HT 7 receptor transcripts were widely distributed in various tissues, in which high expression levels were observed in the cranial ganglia, thoracic ganglia and intestines. Further study about the effects of photoperiods on the 5-HT 7 expression in the tissues showed that a significantly increasing expression of the 5-HT 7 receptor was observed in the thoracic ganglia induced by constant light. In addition, in the eyestalks, the expression levels of 5-HT 7 mRNA in constant darkness and constant light were lower than control treatment. Then, the expression levels of the 5-HT 7 receptor in three feeding statuses displayed that there were significantly increasing expressions in the hepatopancreas and intestines after feeding, compared with before feeding and during the feeding period. Finally, the 5-HT 7 mRNA expression levels in stage III and stage IV were higher than the levels in stage I of ovarian development. Our experimental results showed that the 5-HT 7 receptor structurally belongs to GPCRs, and the thoracic ganglia and eyestalks are the important tissues of the 5-HT 7 receptor for light adaptation. The 5-HT 7 receptor may also be involved in the physiological regulation of the hepatopancreas and intestines after ingestion in E. sinensis. In addition, the 5-HT 7 receptor is involved in the process of ovarian maturation. The study provided a foundation for further research of light adaptation, digestive functions and ovarian maturation of the 5-HT 7 receptor in Decapoda., (Copyright © 2018. Published by Elsevier Inc.)

Serotonin (5-HT) is an important regulator of numerous aspects of flatworm biology, ranging from neuromuscular function to sexual maturation and egg laying. In the parasitic blood fluke Schistosoma mansoni, 5-HT targets several G-protein coupled receptors (GPCRs), one of which has been demonstrated to couple to cAMP and regulate parasite movement. This receptor, Sm.5HTR L , has been successfully co-expressed in mammalian cells alongside a luminescent cAMP-biosensor, enabling pharmacological profiling for candidate anti-schistosomal drugs. Here, we have utilized this assay to perform structure-activity investigations of 143 compounds containing previously identified alkaloid natural product pharmacophores (tryptamines, aporphines and protoberberines) shown to regulate Sm.5HTR L . These experiments mapped regions of the tryptamine pharmacophore amenable and intolerant to substitution, highlighting differences relative to orthologous mammalian 5-HT receptors. Potent Sm.5HTR L antagonists were identified, and the efficacy of these compounds were evaluated against live adult parasites cultured ex vivo. Such structure-activity profiling, characterizing the effect of various modifications to these core ring systems on Sm.5HTR L responses, provides greater understanding of pharmacophores selective for this target to aid future drug development efforts., (Copyright © 2018. Published by Elsevier Ltd.)

Disease-transmitting female mosquitoes require a vertebrate blood meal to produce their eggs. An obligatory hematophagous lifestyle, rapid reproduction, and existence of a large number of transmittable diseases make mosquitoes the world's deadliest animals. Attaining optimal body size and nutritional status is critical for mosquitoes to become reproductively competent and effective disease vectors. We report that blood feeding boosts serotonin concentration and elevates the serotonin receptor Aa5HT2B ( Aedes aegypti 5-hydroxytryptamine receptor, type 2B) transcript level in the fat-body, an insect analog of the vertebrate liver and adipose tissue. Aa5HT2B gene disruption using the CRISPR-Cas9 gene-editing approach led to a decreased body size, postponed development, shortened lifespan, retarded ovarian growth, and dramatically diminished lipid accumulation. Expression of the insulin-like peptide (ILP) genes ilp2 and ilp6 was down-regulated while that of ilp5 and ilp4 was up-regulated in response to Aa5HT2B disruption. CRISPR-Cas9 disruption of ilp2 or ilp6 resulted in adverse phenotypes similar to those of Aa5HT2B disruption, while ilp5 CRISPR-Cas9 disruption had exactly the opposite effect on growth and metabolism, with significantly increased body size and elevated lipid stores. Simultaneous CRISPR-Cas9 disruption of Aa5HT2B and ilp5 rescued these phenotypic manifestations. Aa5HT2B RNAi silencing rendered ilp6 insensitive to serotonin treatment in the cultured fat-body, suggesting a regulatory link between Aa5HT2B and ILP6. Moreover, CRISPR-Cas9 ilp6 disruption affects expression of ilp-2 , - 5 , and - 4 , pointing out on a possible role of ILP6 as a mediator of the Aa5HT2B action., Competing Interests: The authors declare no conflict of interest.

Serotonin 5-HT 7 receptor (5-HT 7 R) has been the subject of intense research efforts because of its presence in brain areas such as the hippocampus, hypothalamus, and cortex. Preclinical data link the 5-HT 7 R to a variety of central nervous system processes including the regulation of circadian rhythms, mood, cognition, pain processing, and mechanisms of addiction. 5-HT 7 R blockade has antidepressant effects and may ameliorate cognitive deficits associated with schizophrenia. 5-HT 7 R has been recently shown to modulate neuronal morphology, excitability, and plasticity, thus contributing to shape brain networks during development and to remodel neuronal wiring in the mature brain. Therefore, the activation of 5-HT 7 R has been proposed as a therapeutic approach for neurodevelopmental and neuropsychiatric disorders associated with abnormal neuronal connectivity. This Perspective celebrates the silver jubilee of the discovery of 5-HT 7 R by providing a survey of recent studies on the medicinal chemistry of 5-HT 7 R ligands and on the neuropharmacology of 5-HT 7 R.

A computational approach combining a structure-activity relationship library of halogenated and the corresponding unsubstituted ligands (called XSAR) with QM-based molecular docking and binding free energy calculations was used to search for amino acids frequently targeted by halogen bonding (hot spots) in a 5-HT 7 R as a case study. The procedure identified two sets of hot spots, extracellular (D2.65, T2.64, and E7.35) and transmembrane (C3.36, T5.39, and S5.42), which were further verified by a synthesized library of halogenated arylsulfonamide derivatives of (aryloxy)ethylpiperidines. It was found that a halogen bond formed between T5.39 and a bromine atom at 3-position of the aryloxy fragment caused the most remarkable, 35-fold increase in binding affinity for 5-HT 7 R when compared to the nonhalogenated analog. The proposed paradigm of halogen bonding hot spots was additionally verified on D 4 dopamine receptor showing that it can be used in rational drug design/optimization for any protein target.