Scaffold Hopping Toward Agomelatine: Novel 3, 4-Dihydroisoquinoline Compounds as Potential Antidepressant Agents

A Potential Strategy for Treatment of Neurodegenerative Disorders by Regulation of Adult Hippocampal Neurogenesis in Human Brain

Abstract:

Adult hippocampal neurogenesis is a multistage mechanism that continues throughout the lifespan of human and non-human mammals. These adult-born neurons in the central nervous system (CNS) play a significant role in various hippocampus-dependent processes, including learning, mood regulation, pattern recognition, etc. Reduction of adult hippocampal neurogenesis, caused by multiple factors such as neurological disorders and aging, would impair neuronal proliferation and differentiation and result in memory loss. Accumulating studies have indicated that functional neuron impairment could be restored by promoting adult hippocampal neurogenesis. In this review, we summarized the small molecules that could efficiently promote the process of adult neurogenesis, particularly the agents that have the capacity of crossing the blood-brain barrier (BBB), and showed in vivo efficacy in mammalian brains. This may pave the way for the rational design of drugs to treat humnan neurodegenerative disorders in the future.

Design, Synthesis, and Biological Activity of Chalcone Analogs Containing 4-Phenylquinolin and Benzohydrazide

A series of chalcone derivatives (3a-3m) containing 4-phenylquinoline and benzohydrazide were designed and synthesized, and their anti-inflammatory, analgesic, and antidepressant activities were evaluated. Using the classic antidepressant model, except for compounds 3a and 3d, 11 compounds all showed certain antidepressant activity at a dose of 100 mg/kg, among which compounds 3f, 3h, and 3m showed good antidepressant activity (inhibition rate, respectively 63.0 %, 73.2 %, and 76.4 %), which was equivalent to the positive control fluoxetine (inhibition rate of 70.0 %). Secondly, the inhibitory activity of these compounds on mouse MAO_A was evaluated. At 10 mM, compounds 3f and 3j showed a certain selective inhibitory effect on mouse MAO_A , while compounds 3b, 3d, 3g, 3i, and 3m had a good inhibitory effect on mouse MAO_A (inhibition rate is 42.3-71.4 %). The mouse ear edema model was used to evaluate the anti-inflammatory activity of compounds 3a-3m. At 30 mg/kg, compounds 3b, 3c, 3e, 3f, 3g, and 3m showed certain anti-inflammatory effects (inhibition rate of 51.5-99.9 %), which was equivalent to the positive control indomethacin (inhibition rate of 69.7 %). Results of the acetic acid-induced abdominal writhing test showed that, at 30 mg/kg, excepted for compounds 3a, 3b and 3d, all the other 10 compounds can show certain analgesic activity (inhibition rate 67-99.9 %). The use of Auto dock Vina (simina) to simulate molecular target docking shows that the development of quinoline and benzohydrazide groups is of great significance to MAO_A inhibitors.

Synthesis and Biological Activity of Novel Pyrazol-5-yl-benzamide Derivatives as Potential Succinate Dehydrogenase Inhibitors

To promote the discovery and development of new fungicides, a series of novel pyrazol-5-yl-benzamide derivatives were designed, synthesized by hopping and inversion of amide groups of pyrazole-4-carboxamides, and evaluated for their antifungal activities. The bioassay data revealed that compound 5IIc exhibited an excellent in vitro activity against Sclerotinia sclerotiorum with an EC₅₀ value of 0.20 mg/L, close to that of commercial fungicide Fluxapyroxad (EC₅₀ = 0.12 mg/L) and Boscalid (EC₅₀ = 0.11 mg/L). For Valsa mali, compound 5IIc (EC₅₀ = 3.68 mg/L) showed a significantly higher activity than Fluxapyroxad (EC₅₀ = 12.67 mg/L) and Boscalid (EC₅₀ = 14.83 mg/L). In addition, in vivo experiments proved that compound 5IIc has an excellent protective fungicidal activity with an inhibitory rate of 97.1% against S. sclerotiorum at 50 mg/L, while the positive control Fluxapyroxad showed a 98.6% inhibitory effect. The molecular docking simulation revealed that compound 5IIc interact with TRP173, SER39, and ARG43 of succinate dehydrogenase (SDH) through a hydrogen bond and p-π interaction, which could explain the probable mechanism of the action between compound 5IIc and target protein. Also, the SDH enzymatic inhibition assay was carried out to further validate its mode of action. These results demonstrate that compound 5IIc could be a promising fungicide candidate and provide a valuable reference for further investigation.

Scaffold hopping of agomelatine leads to enhanced antidepressant effects by modulation of gut microbiota and host immune responses

The mechanisms underlying the pathophysiology of depression remain elusive, and the development of novel, effective antidepressant drugs remains necessary. A dihydroquinoline analog of agomelatine (AGO), N-(2-(7-methoxy-3,4-dihydroisoquinolin-1-yl)ethyl)acetamide hydrochloride (NMDEA), was synthesized by employing a scaffold-hopping strategy in our previous study. In this study, NMDEA was demonstrated to attenuate depression-related behaviors in mice models of chronic unpredictable mild stress (CUMS), using a sucrose preference test, a forced swimming test, and a tail suspension test. However, the antidepressant mechanism of NMDEA appears to differ from that for AGO. Based on the analysis of fecal microbiota from mice, stress can alter the richness of the gut bacterial community, increasing the expression of immune-modulating microbiota, such as Clostridia, and decreasing the expression of probiotic bacteria, such as Lactobacillus. Treatment with NMDEA was able to recover the richness and to regulate the dysbiosis among bacterial species. Several studies have demonstrated that the gut microbiota population can induce inflammatory processes. To explore the effects of NMDEA on the suppression of pro-inflammatory factors, we used Western blotting to analyze the levels of interleukin 1 beta (IL-1β), interleukin 6 (IL-6), p65, and inducible nitric oxide synthase (iNOS). NMDEA suppressed the activation of IL-1β and IL-6, in the hippocampus, and IL-1β, IL-6, p65, and iNOS, in lipopolysaccharide (LPS)-induced BV-2 cells. These results suggested that NMDEA may affect the microbiota-inflammasome-brain axis, regulating relevant neuro-inflammatory markers and gut microbiota. Our data also suggested that using small molecules to modify the gut microbiota population or alter inflammasome signaling may represent a new therapeutic opportunity for the mitigation of depression.

Fluoxetine exposure for more than 2 days decreases the neuronal plasticity mediated by CRMP2 in differentiated PC12 cells

BACKGROUND

Recent studies indicate that antidepressants treatment restores neuronal plasticity. In contrast, some researchers claim that serotonergic antidepressants, including fluoxetine (FLU), may exacerbate neuronal plasticity, which is contradictory and rarely studied. Since almost those studies exposed cells with drugs for 1-2 days as treatment models of antidepressants, it is possible that FLU exposure for longer periods would have opposite effects on neuronal plasticity.

RESULTS

In the present study, we examined the effects of FLU exposure (up to 3 days) on the neuronal plasticity in differentiated PC12 cells. The cell viability shown a slight decrease at day 2 (93.5 ± 3.5 %), followed by a highly significant decrease at day 3(71.4 ± 4.4 %). As previously reported, neuronal plasticity was significantly upregulated by FLU exposure at day 1. However, the neurite length, activity-regulated cytoskeleton-associated protein (Arc) and c-Fos mRNA were inhibited with FLU exposure at day 3. Similarly, the expression of tubulin, which play important roles in the neuronal plasticity, was the same result. Furthermore, we found α-tubulin interacted with collapsing response mediator protein 2(CRMP2), which is related to neuronal plasticity, and the regulation of CRMP2 activity influenced the neurite length, Arc, c-Fos and tubulin expression.

CONCLUSIONS

The results demonstrated that neuronal plasticity was increased by FLU exposure at day 1, but exposure with FLU for more than 2 days had opposite effect on it. The reduction in neuronal plasticity with FLU exposure for more than 2 days might be involved in some aspects of the therapeutic effect of antidepressant on depression.

5-HTT independent effects of fluoxetine on neuroplasticity

Selective serotonin reuptake inhibitors are among the most prescribed antidepressants. Fluoxetine is the lead molecule which exerts its therapeutic effects, at least in part, by promoting neuroplasticity through increased brain-derived neurotrophic factor (BDNF)/tropomyosin-related receptor kinase B (TrkB) signalling. It is unclear however, to which extent the neuroplastic effects of fluoxetine are solely mediated by the inhibition of the serotonin transporter (5-HTT). To answer this question, the effects of fluoxetine on neuroplasticity were analysed in both wild type (WT) and 5-Htt knock-out (KO) mice. Using Western blotting and RT-qPCR approaches, we showed that fluoxetine 10 µM activated BDNF/TrkB signalling pathways in both CD1 and C57BL/6J mouse primary cortical neurons. Interestingly, effects on BDNF signalling were observed in primary cortical neurons from both 5-Htt WT and KO mice. In addition, a 3-week in vivo fluoxetine treatment (15 mg/kg/d; i.p.) increased the expression of plasticity genes in brains of both 5-Htt WT and KO mice, and tended to equally enhance hippocampal cell proliferation in both genotypes, without reaching significance. Our results further suggest that fluoxetine-induced neuroplasticity does not solely depend on 5-HTT blockade, but might rely, at least in part, on 5-HTT-independent direct activation of TrkB.

Oxymatrine ameliorates agomelatine-induced hepatocyte injury through promoting proteasome-mediated CHOP degradation

BACKGROUND

The novel antidepressant drug agomelatine has been observed to cause adverse effect of hepatotoxicity in clinical applications. This study was designed to explore protective agents and investigated the underlying mechanism on L02 cells.

METHOD

L02 cells were treated with agomelatine and oxymatrine (OMT) and cell apoptosis were analyzed through flow cytometric analysis, CCK-8 assay and TUNEL assay. In a separate experiment, the expressions of ER stress-related proteins were determined by western blot. In addition, MG132, chloroquine (CQ) and bafilomycinA1(BafA1) were used to investigate the potential pathway participating in CHOP degradation.

RESULTS

OMT significantly rescued agomelatine-induced hepatocyte apoptosis. Agomelatine treatment resulted in accumulation of CHOP protein in L02 cells, and this phenomenon could be significantly reduced by OMT, whereas abolished by MG132 treatment.

CONCLUSION

We have demonstrated for the first time that OMT ameliorates the hepatocyte toxicity induced by agomelatine through decreasing CHOP on protein level. The underlying mechanism was proved to involve the molecular events that OMT promotes CHOP degradation via proteasome pathway. Overall, these results suggest that using OMT in combination with agomelatine may provide a safety strategy for clinical depression treatment.

Facile Route to the Synthesis of 1,3-Diazahetero-Cycle-Fused [1,2-a]Quinoline Derivatives via Cascade Reactions

A one-step protocol without transition-metal catalysts with simple post-treatment for the synthesis of 1,3-diazaheterocycle-fused [1,2-a]quinoline derivatives via the cascade reaction of 2-fluorobenzaldehyde (1) and heterocyclic ketene aminals (2) was developed. In the one-step cascade reaction, C=C and C-N bonds were constructed, and the targeted compound can be efficiently obtained by filtering without column chromatography. This protocol describes a valuable route to concisely and feasibly obtain 1,3-diazaheterocycle-fused [1,2-a]quinoline derivatives. The synthetic methodology is particularly attractive because of the following features: low-cost solvent, mild temperature, atom economy, high yield, and potential biological activity of the product.

Discovery of Potent EGFR Inhibitors through the Incorporation of a 3D-Aromatic-Boron-Rich-Cluster into the 4-Anilinoquinazoline Scaffold: Potential Drugs for Glioma Treatment

New 1,7-closo-carboranylanilinoquinazoline hybrids have been identified as EGFR inhibitors, one of them with higher affinity than the parent compound erlotinib. The comparative docking analysis with compounds bearing bioisoster-substructures, demonstrated the relevance of the 3D aromatic-boron-rich moiety for interacting into the EGFR ATP binding region. The capability to accumulate in glioma cells, the ability to cross the blood-brain barrier and the stability on simulated biological conditions, render these molecules as lead compounds for further structural modifications to obtain dual action drugs to treat glioblastoma.

Design, Synthesis, and Fungicidal Evaluation of Novel Pyrazole-furan and Pyrazole-pyrrole Carboxamide as Succinate Dehydrogenase Inhibitors

The identification of novel succinate dehydrogenase (SDH) inhibitors represents one of the most attractive directions in the field of fungicide research and development. During our continuous efforts to pursue inhibitors belonging to this class, some structurally novel pyrazole-furan carboxamide and pyrazole-pyrrole carboxamide derivatives have been discovered via the introduction of scaffold hopping and bioisosterism to compound 1, a remarkably potent lead obtained by pharmacophore-based virtual screening. As a result of the evaluation against three destructive fungi, including Sclerotinia sclerotiorum, Rhizoctonia solani, and Pyricularia grisea, a majority of them displayed potent fungicidal activities. In particular, compounds 12I-i, 12III-f, and 12III-o exhibited excellent fungicidal activity against S. sclerotiorum and R. solani comparable to that of commercial SDHI thifluzamide and 1.

Discovery of 1,3-diyne compounds as novel and potent antidepressant agents: synthesis, cell-based assay and behavioral studies

1,3-Diynes compound 7a protected the corticosterone-injured PC12 cells through regulation of the apoptosis related proteins and exerted antidepressant effect in mice forced swim test in a concentration-dependent manner.