D-161, a novel pyran-based triple monoamine transporter blocker: behavioral pharmacological evidence for antidepressant-like action

Dopamine transporter (DAT) knockdown in the nucleus accumbens improves anxiety- and depression-related behaviors in adult mice

Many epidemiological and clinical studies have demonstrated a strong comorbidity between anxiety and depression, and a number of experimental studies indicates that the dopamine transporter (DAT) is involved in the pathophysiology of anxiety and depression. However, studies using laboratory animals have yielded inconclusive results. The aim of the present study was to examine the effects of DAT manipulation on anxiety- and depression-like behaviors in mice. For this purpose, animals were stereotaxically injected with DAT siRNA-expressing lentiviral vectors (siDAT) in the caudate putamen (CPu) or in the nucleus accumbens (Nacc) and the behavioral outcomes were assessed using the open-field (OF), elevated-plus maze (EPM), light-dark box (LDB), sucrose preference (SPT), novelty suppressed feeding (NSF), and forced-swim (FST) tests. The results showed that in the Nacc, but not in the CPu, siDAT increased the time spent at the center of the arena and decreased the number of fecal boli in the OF test. In the EPM and LDB tests, Nacc siDAT injection increased the entries and time spent on open arms, and increased the time spent in the light side of the box, respectively, suggesting an anxiolytic-like activity. In addition, siDAT, in the Nacc, induced significant antidepressant-like effects, evidenced by increased sucrose preference, shorter latency to feed in the NSF test, and decreased immobility time in the FST. Most importantly, Pearson's test clearly showed significant correlations between DAT mRNA in the Nacc with anxiety and depression parameters. Overall, these results suggest that low DAT levels, in the Nacc, might act as protective factors against anxiety and depression. Therefore, targeting DAT activity might be a very attractive approach to tackle affective disorders.

Prediction of new drug indications based on clinical data and network modularity

Drug repositioning is commonly done within the drug discovery process in order to adjust or expand the application line of an active molecule. Previous computational methods in this domain mainly focused on shared genes or correlations between genes to construct new drug-disease associations. We propose a method that can not only handle drugs or diseases with or without related genes but consider the network modularity. Our method firstly constructs a drug network and a disease network based on side effects and symptoms respectively. Because similar drugs imply similar diseases, we then cluster the two networks to identify drug and disease modules, and connect all possible drug-disease module pairs. Further, based on known drug-disease associations in CTD and using local connectivity of modules, we predict potential drug-disease associations. Our predictions are validated by testing their overlaps with drug indications reported in published literatures and CTD, and KEGG enrichment analysis are also made on their related genes. The experimental results demonstrate that our approach can complement the current computational approaches and its predictions can provide new clues for the candidate discovery of drug repositioning.

Development of potent dopamine-norepinephrine uptake inhibitors (DNRIs) based on a (2S,4R,5R)-2-benzhydryl-5-((4-methoxybenzyl)amino)tetrahydro-2H-pyran-4-ol molecular template

Current therapy of depression is less than ideal with remission rates of only 25-35% and response rates of 45-60%. It has been hypothesized that a dysfunctional dopaminergic system in the mesocorticolimbic pathway in depressive disorder may lead to development of anhedonia associated with loss of pleasure and interest along with loss of motivation. The current antidepressants do not address dopamine dysfunction which might explain their low efficacy. In this report, we have described an SAR study on our pyran-based triple reuptake inhibitors (TRIs) which are being investigated as the next-generation antidepressants. In the present work we demonstrate that our lead TRIs can be modified with appropriate aromatic substitutions to display a highly potent SSRI profile for compounds 2a and 4a (Ki (SERT); 0.71 and 2.68nM, respectively) or a potent DNRI profile for compounds 6b and 6h (Ki (DAT/NET); 8.94/4.76 and 13/7.37nM, respectively). Compounds 4g-4i exhibited potencies at all three monoamine transporters. The results provide insights into the structural requirements for developing selective dual- and triple-uptake inhibitors from a unique pyran molecular template for an effective management of depression and related disorders.

Pharmacological and behavioral characterization of D-473, an orally active triple reuptake inhibitor targeting dopamine, serotonin and norepinephrine transporters

Major depressive disorder (MDD) is a debilitating disease affecting a wide cross section of people around the world. The current therapy for depression is less than adequate and there is a considerable unmet need for more efficacious treatment. Dopamine has been shown to play a significant role in depression including production of anhedonia which has been one of the untreated symptoms in MDD. It has been hypothesized that drugs acting at all three monoamine transporters including dopamine transporter should provide more efficacious antidepressants activity. This has led to the development of triple reuptake inhibitor D-473 which is a novel pyran based molecule and interacts with all three monoamine transporters. The monoamine uptake inhibition activity in the cloned human transporters expressed in HEK-293 cells (70.4, 9.18 and 39.7 for DAT, SERT and NET, respectively) indicates a serotonin preferring triple reuptake inhibition profile for this drug. The drug D-473 exhibited good brain penetration and produced efficacious activity in rat forced swim test under oral administration. The optimal efficacy dose did not produce any locomotor activation. Microdialysis experiment demonstrated that systemic administration of D-473 elevated extracellular level of the three monoamines DA, 5-HT, and NE efficaciously in the dorsal lateral striatum (DLS) and the medial prefrontal cortex (mPFC) area, indicating in vivo blockade of all three monoamine transporters by D-473. Thus, the current biological data from D-473 indicate potent antidepressant activity of the molecule.

Design and synthesis of new series of coumarin-aminopyran derivatives possessing potential anti-depressant-like activity

A new series of coumarin based aminopyran derivatives were designed, synthesized and evaluated for their preclinical antidepressant effect on Swiss albino mice. Among the series, compounds 21, 25, 26, 27, 32 and 33 exhibited significant activity profile in forced swimming test (FST). Compound 27 was most efficacious, which at a very low dose of 0.5mg/kg reduced the time of immobility by 86.5% as compared to the standard drug fluoxetine (FXT) which reduced the immobility time by 69.8% at the dose of 20mg/kg, ip. In addition, all active compounds were screened in dose dependent manner (at doses of 0.25, 0.5, 1mg/kg ip) in FST and tail suspension test (TST). Interestingly, all active compounds did not caused any significant alteration of locomotor activity in mice as compared to control, indicating that the hybrids did not produce any motor impairment effects. The results indicate that coumarin-aminopyran derivatives may have potential therapeutic value for the management of mental depression.

Antidepressant-like activity of YL-0919: a novel combined selective serotonin reuptake inhibitor and 5-HT1A receptor agonist

It has been suggested that drugs combining activities of selective serotonin reuptake inhibitor and 5-HT1A receptor agonist may form a novel strategy for higher therapeutic efficacy of antidepressant. The present study aimed to examine the pharmacology of YL-0919, a novel synthetic compound with combined high affinity and selectivity for serotonin transporter and 5-HT1A receptors. We performed in vitro binding and function assays and in vivo behavioral tests to assess the pharmacological properties and antidepressant-like efficacy of YL-0919. YL-0919 displayed high affinity in vitro to both 5-HT1A receptor and 5-HT transporter prepared from rat cortical tissue. It exerted an inhibitory effect on forskolin-stimulated cAMP formation and potently inhibited 5-HT uptake in both rat cortical synaptosomes and recombinant cells. After acute p.o. administration, very low doses of YL-0919 reduced the immobility time in tail suspension test and forced swimming test in mice and rats, with no significant effect on locomotor activity in open field test. Furthermore, WAY-100635 (a selective 5-HT1A receptor antagonist, 0.3 mg/kg) significantly blocked the effect of YL-0919 in tail suspension test and forced swimming test. In addition, chronic YL-0919 treatment significantly reversed the depressive-like behaviors in chronically stressed rats. These findings suggest that YL-0919, a novel structure compound, exerts dual effect on the serotonergic system, as both 5-HT1A receptor agonist and 5-HT uptake blocker, showing remarkable antidepressant effects in animal models. Therefore, YL-0919 may be used as a new option for the treatment of major depressive disorder.

Flexible and biomimetic analogs of triple uptake inhibitor 4-((((3S,6S)-6-benzhydryltetrahydro-2H-pyran-3-yl)amino)methyl)phenol: Synthesis, biological characterization, and development of a pharmacophore model

In this study we have generated a pharmacophore model of triple uptake inhibitor compounds based on novel asymmetric pyran derivatives and the newly developed asymmetric furan derivatives. The model revealed features important for inhibitors to exhibit a balanced activity against dopamine transporter (DAT), serotonin transporter (SERT), and norepinephrine transporter (NET). In particular, a 'folded' conformation was found common to the active pyran compounds in the training set and was crucial to triple uptake inhibitory activity. Furthermore, the distances between the benzhydryl moiety and the N-benzyl group as well as the orientation of the secondary nitrogen were also important for TUI activity. We have validated our findings by synthesizing and testing novel asymmetric pyran analogs. The present work has also resulted in the discovery of a new series of asymmetric tetrahydrofuran derivatives as novel TUIs. Lead compounds 41 and 42 exhibited moderate TUI activity. Interestingly, the highest TUI activity by lead tetrahydrofuran compounds for example, 41 and 42, was exhibited in a stereochemical preference similar to pyran TUI for example, D-161.

Structural exploration of (3S,6S)-6-benzhydryl-N-benzyltetrahydro-2H-pyran-3-amine analogues: identification of potent triple monoamine reuptake inhibitors as potential antidepressants

To further explore the basic structural motifs (3S,6S)-6-benzhydryl-N-benzyltetrahydro-2H-pyran-3-amine and (2S,4R,5R)-2-benzhydryl-5-(benzylamino)tetrahydro-2H-pyran-4-ol, developed by our research group, for monoamine transport inhibition, we designed and synthesized various structurally altered analogues. The new compounds were tested for their affinities for the dopamine transporter (DAT), the serotonin transporter (SERT), and the norepinephrine transporter (NET) in rat brain by measuring their capacity to inhibit the uptake of [(3)H]DA, [(3)H]5-HT, and [(3)H]NE, respectively. Our results point to novel compounds with a TUI, DNRI, SNRI, or SSRI profile. Among the TUIs, compound 2 g exhibited a balanced potency for all three monoamine transporters (K(i): 60, 79, and 70.3 nM for DAT, SERT, and NET, respectively). In the rat forced swim test, compound 2 g produced a significant decrease in immobility in drug-treated rats relative to vehicle, indicating a potential antidepressant property.

Novel C-1 substituted cocaine analogs unlike cocaine or benztropine

Despite a wealth of information on cocaine-like compounds, there is no information on cocaine analogs with substitutions at C-1. Here, we report on (R)-(-)-cocaine analogs with various C-1 substituents: methyl (2), ethyl (3), n-propyl (4), n-pentyl (5), and phenyl (6). Analog 2 was equipotent to cocaine as an inhibitor of the dopamine transporter (DAT), whereas 3 and 6 were 3- and 10-fold more potent, respectively. None of the analogs, however, stimulated mouse locomotor activity, in contrast to cocaine. Pharmacokinetic assays showed compound 2 occupied mouse brain rapidly, as cocaine itself; moreover, 2 and 6 were behaviorally active in mice in the forced-swim test model of depression and the conditioned place preference test. Analog 2 was a weaker inhibitor of voltage-dependent Na+ channels than cocaine, although 6 was more potent than cocaine, highlighting the need to assay future C-1 analogs for this activity. Receptorome screening indicated few significant binding targets other than the monoamine transporters. Benztropine-like "atypical" DAT inhibitors are known to display reduced cocaine-like locomotor stimulation, presumably by their propensity to interact with an inward-facing transporter conformation. However, 2 and 6, like cocaine, but unlike benztropine, exhibited preferential interaction with an outward-facing conformation upon docking in our DAT homology model. In summary, C-1 cocaine analogs are not cocaine-like in that they are not stimulatory in vivo. However, they are not benztropine-like in binding mechanism and seem to interact with the DAT similarly to cocaine. The present data warrant further consideration of these novel cocaine analogs for antidepressant or cocaine substitution potential.

The extracts of Fructus Akebiae, a preparation containing 90% of the active ingredient hederagenin: serotonin, norepinephrine and dopamine reuptake inhibitor

Fructus Akebiae is a traditional Chinese herbal extract that has been used for the treatment of depressive disorders in China. Previous studies demonstrated that Fructus Akebiae extracts (FAE) displayed a potent antidepressant-like activity in animal behavior tests and found that the specific active ingredient from the extracts of Fructus Akebiae is hederagenin. However, the underlying mechanism is unknown. Here we provide evidences that FAE enhances the signaling of central monoamines via inhibition of the reuptake of the extracellular monoamines including serotonin (5-HT), norepinephrine (NE) and dopamine (DA). In rat brain membrane preparations and HEK293 cells transfected with human serotonin transporter (SERT), NE transporter (NET) and DA transporter (DAT), we found that FAE displayed marked affinity to rat and cloned human monoamine transporters in ex vivo and in vitro experiments, using competitive radio ligand binding assay. In uptake assays using rat synaptosomes and transfected cells, FAE was found to significantly inhibit all three monoamine transporters in a dose- and time-dependent manner, with a comparable or better potency to their corresponding specific inhibitors. In contrast, FAE (10 μM), showed no significant affinity to a variety array of receptors tested from CNS. In support of our uptake data, in vivo microdialysis studies showed that administration of FAE (12.6, 25, 50 mg/kg) significantly increased extracellular concentrations of 5-HT, NE and DA in frontal cortex of freely moving rats. Taken together, our current study showed for the first time that FAE is a novel triple inhibitor of monoamine transporters, which may be one the mechanisms of its antidepressant activity.

The novel trisubstituted pyran derivative D-142 has triple monoamine reuptake inhibitory activity and exerts potent antidepressant-like activity in rodents

Major depression disorder is a significant health problem with 10-20% of all adults suffering from this disease. The underlying causes of depression are still unclear and 15% of depressed patients are resistant to all known therapies. Monoamine therapies have so far been the most successful approach for treating depression. Triple monoamine reuptake inhibitors have recently been implicated in generation of potent antidepressant activity while possibly exhibiting a low side-effect profile in addition to treating anhedonia. The additional, previously under-appreciated involvement of dopaminergic systems in depression prompted our efforts to develop novel asymmetric trisubstituted and disubstituted pyran derivatives as triple reuptake inhibitors. One of the lead compounds, D-142, exhibited uptake inhibition (K(i)) values of 29.3 nM, 14.7 nM and 59.3 ± 13.7 nM for norepinephrine, serotonin and dopamine transporters, respectively. Its affinity for serotonin transporter was comparable to fluoxetine, a well known SSRI. In the rat forced swimming test, compound D-142 exhibited potent antidepressant activity in the dose range tested (2.5, 5 and 10mg/kg) and was far more efficacious than the reference compound imipramine. In the mouse tail suspension test, compound D-142 reduced immobility in a dose (2.5, 5 and 10mg/kg) dependent manner, indicating a potent antidepressant effect. In locomotor activity tests, compound D-142 did not exhibit any stimulation in the same dose ranges. In the extended CNS receptors screening assay this molecule exhibited little or no non-specific interaction in the CNS, indicating high specificity for monoamine transporters. These results advance D-142 as a potential potent antidepressant.

Characterization of [³H]CFT binding to the norepinephrine transporter suggests that binding of CFT and nisoxetine is not mutually exclusive

The norepinephrine transporter (NET) is an important target for a wide variety of antidepressants and psychostimulants. Despite its prominence as a drug target, there is only one radioligand in use for NET competitive binding assays, [(3)H]nisoxetine. However, traditional [(3)H]nisoxetine binding protocols often give an underestimation for the affinity of certain classes of NET ligands, particularly cocaine and other tropanes. Here, we explore the feasibility of using the phenyltropane [(3)H]CFT for labeling human NET (hNET) in heterologous cell-based binding studies. Assays were optimized for time and protein content and specific, one-site binding was observed. Potencies of tested NET ligands for inhibition of [(3)H]CFT binding to whole cells (at physiological [Na(+)] and 25°C) were similar to potencies observed in the [(3)H]NE uptake assay. Inhibition constants (K(i)) for binding assays were highly correlated with uptake inhibition constants for all compounds tested (R(2)=0.99, p<0.0001). Cell-free membrane preparations did not display the same pharmacological profile. Under conditions routinely used for measuring [(3)H]nisoxetine binding to membrane preparations (4°C for 3h, [Na(+)] at 295 mM), the potency of nisoxetine and desipramine in inhibiting [(3)H]CFT binding became greater than that measured in a functional assay of [(3)H]NE uptake at physiological [Na(+)]. However, the opposite was true for CFT and cocaine. Interestingly, while investigating [(3)H]CFT as a potential NET radioligand, we uncovered evidence suggesting that CFT and nisoxetine are not mutually exclusive in binding to the NET. Dixon plots of the interaction between nisoxetine and CFT in inhibition of [(3)H]dopamine uptake by the NET indicate that the two compounds can simultaneously bind to the transporter.

An improved asymmetric synthetic route to a novel triple uptake inhibitor antidepressant (2S,4R,5R)-2-benzhydryl-5-((4-methoxybenzyl)amino)tetrahydro-2H-pyran-4-ol (D-142)

Triple monoamine reuptake inhibitors have been implicated in the development of a new generation of antidepressants with higher efficacy than the currently existing therapies. In this paper, we have developed an alternative efficient synthetic route for triple monoamine reuptake inhibitor D-142 in 18.5% overall yield in 11 steps starting from diphenylmethane. D-142 was developed by us recently. The key step of the present synthetic strategy is the preferential formation of a bromohydrin from olefin via a cis-bromoinum intermediate, which introduced significant efficiency in the overall synthesis. Furthermore, we have developed an efficient way to recycle the optically active intermediate diol back to the desired chiral epoxide.

Further structure-activity relationship studies on 4-((((3S,6S)-6-benzhydryltetrahydro-2H-pyran-3-yl)amino)methyl)phenol: identification of compounds with triple uptake inhibitory activity as potential antidepressant agents

To investigate structural alterations of the lead triple uptake inhibitor molecule, disubstituted 4-((((3S,6S)-6-benzhydryltetrahydro-2H-pyran-3-yl)amino)methyl)phenol, we have carried out structure-activity relationship (SAR) studies to investigate the effect of alteration of aromatic substitutions and introduction of heterocyclic aromatic moieties on this molecular template. The novel compounds were tested for their affinities for the dopamine transporter (DAT), serotonin transporter (SERT), and norepinephrine transporter (NET) in the brain by measuring their potency in inhibiting the uptake of [(3)H]DA, [(3)H]5-HT, and [(3)H]NE, respectively. SAR results indicate dopamine norepinephrine reuptake inhibitory (DNRI) type activity in thiophene (10g) and pyrrole (10i) derivatives. On the other hand, 3-hydroxyphenyl derivative 10f and 4-methoxyphenyl derivative 10j exhibited a triple reuptake inhibitory (TUI) activity profile, as these molecules exhibited potent uptake inhibition for all the monoamine transporters (K(i) of 31.3, 40, 38.5 and K(i) of 15.9, 12.9, 29.3 for DAT, SERT, and NET for 10f and 10g, respectively). Compound 10f was further evaluated in the rat forced swim test to evaluate its potential antidepressant effect. The results show significant reduction of immobility by TUI 10f at 10 mg/kg dose, indicating potential antidepressant activity.

Synthesis and biological characterization of (3R,4R)-4-(2-(benzhydryloxy)ethyl)-1-((R)-2-hydroxy-2-phenylethyl)-piperidin-3-ol and its stereoisomers for activity toward monoamine transporters

A novel series of optically active molecules based on a 4-(2-(benzhydryloxy)ethyl)-1-((R)-2-hydroxy-2-phenylethyl)-piperidin-3-ol template were developed. Depending on stereochemistry, the compounds exhibit various degrees of affinity for three dopamine, serotonin, and norepinephrine transporters. These molecules have the potential for treating several neurological disorders such as drug abuse, depression, and attention deficit hyperactivity disorder.Herein we describe the synthesis and biological evaluation of a series of asymmetric 4-(2-(benzhydryloxy)ethyl)-1-((R)-2-hydroxy-2-phenylethyl)-piperidin-3-ol-based dihydroxy compounds in which the hydroxy groups are located on both the piperidine ring and the N-phenylethyl side chain. In vitro uptake inhibition data of these molecules indicate high affinity for the dopamine transporter (DAT) in addition to moderate to high affinity for the norepinephrine transporter (NET). Interestingly, compounds 9 b and 9 d exhibit affinities for all three monoamine transporters, with highest potency at DAT and NET, and moderate potency at the serotonin transporter (SERT) (K(i): 2.29, 78.4, and 155 nM for 9 b and 1.55, 14.1, and 259 nM for 9 d, respectively). Selected compounds 9 a, 9 d, and 9 d' were tested for their locomotor activity effects in mice and for their ability to occasion the cocaine-discriminative stimulus in rats. These test compounds generally exhibit a much longer duration of action than cocaine for elevating locomotor activity, and completely generalize the cocaine-discriminative stimulus in a dose-dependent manner.

Drug transporters in the human blood-placental barrier

Studies on the increasing number of transporters found in the placental barrier are gaining momentum, because of their tissue-specific expression, significance in physiology and disease, and the possible utilization of the emerging knowledge in pharmacology. In the placenta, both syncytiotrophoblast and fetal capillary endothelium express transporters. Fetal exposure is determined by the net effect of combination of transporters, their nature and localization in relation to placental cells and their substrate specificity. Although the significance of placental transporters on human fetal drug exposure is almost an unstudied field so far, their potential use to design drugs that do not cross the placenta is already being pursued. It is thus of interest to review the existing knowledge of human placental transporters. Transporters in all groups which take part in drug transport are found in human placenta. Especially, ATP-binding cassette transporters ABCG2/breast cancer resistance protein, ABCB1/P-glycoprotein and ABCC2/MRP2 are all expressed at the apical surface of syncytiotrophoblast facing maternal blood and are putatively important protective proteins both for placental tissue and the fetus, because they are efflux transporters and their substrates include many drugs and also environmental chemicals. Such protective effect has been shown in animals, but these results cannot be directly extrapolated to humans due to interspecies differences in placental structure and function. Experimental models utilizing human placental tissue, especially human placental perfusion, offer valuable possibilities, which have been insufficiently studied so far.