Design, synthesis and <i>in vitro</i> activity of 1,4-disubstituted piperazines and piperidines as triple reuptake inhibitors

Paudel, Suresh,Acharya, Srijan,Yoon, Goo,Kim, Kyeong-Man,Cheon, Seung Hoon Pergamon 2017 Bioorganic & medicinal chemistry Vol.25 No.7

<P><B>Abstract</B></P> <P>Monoamine transporters regulate the concentration of monoamine neurotransmitters, which are essential for vital physiological processes, and their dysfunction can cause several central nervous system diseases. Monoamine transporters currently appear to be the potential target in the management of these disorders. In this study, homologation and bioisosterism techniques have been used in the designing of new 1,4-disubstituted piperazines and piperidines. These derivatives were synthesized and evaluated as potential triple reuptake inhibitors for studying the structure-activity relationships. The most advanced compound, 1-(4-(5-benzhydryl-1<I>H</I>-tetrazol-1-yl)butyl)-4-(3-phenylpropyl)piperazine (<B>2i</B>), was able to inhibit monoamine neurotransmitter reuptake in an <I>in vitro</I> test (IC<SUB>50</SUB> =158.7nM for 5-HT, 99nM for NE and 97.5nM for DA). These novel potent triple reuptake inhibitor-based 1,4-disubstituted piperazine and piperidine scaffolds deserve further systematic optimization and pharmacological evaluation.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Catalpol and Mannitol, Two Components of Rehmannia glutinosa, Exhibit Anticonvulsant Effects Probably via GABAA Receptor Regulation

( Mikyung Kim ),( Srijan Acharya ),( Chrislean Jun Botanas ),( Raly James Custodio ),( Hyun Jun Lee ),( Leandro Val Sayson ),( Arvie Abiero ),( Yong Soo Lee ),( Jae Hoon Cheong ),( Kyeong-man Kim ),( 한국응용약물학회 2020 Biomolecules & Therapeutics(구 응용약물학회지) Vol.28 No.2

Epilepsy is a brain disorder that affects millions of people worldwide and is usually managed using currently available antiepileptic drugs, which result in adverse effects and are ineffective in approximately 20-25% of patients. Thus, there is growing interest in the development of new antiepileptic drugs with fewer side effects. In a previous study, we showed that a Rehmannia glutinosa (RG) water extract has protective effects against electroshock- and pentylenetetrazol (PTZ)-induced seizures, with fewer side effects. In this study, the objective was to identify the RG components that are responsible for its anticonvulsant effects. Initially, a number of RG components (aucubin, acteoside, catalpol, and mannitol) were screened, and the anticonvulsant effects of different doses of catalpol, mannitol, and their combination on electroshock- and chemically (PTZ or strychnine)-induced seizures in mice, were further assessed. Gamma-aminobutyric acid (GABA) receptor binding assay and electroencephalography (EEG) analysis were conducted to identify the potential underlying drug mechanism. Additionally, treated mice were tested using open-field and rotarod tests. Catalpol, mannitol, and their combination increased threshold against electroshock-induced seizures, and decreased the percentage of seizure responses induced by PTZ, a GABA antagonist. GABA receptor binding assay results revealed that catalpol and mannitol are associated with GABA receptor activity, and EEG analysis provided evidence that catalpol and mannitol have anticonvulsant effects against PTZ-induced seizures. In summary, our results indicate that catalpol and mannitol have anticonvulsant properties, and may mediate the protective effects of RG against seizures.

Design, synthesis, and systematic evaluation of 4-arylpiperazine- and 4-benzylpiperidine napthyl ethers as inhibitors of monoamine neurotransmitters reuptake

Paudel, Suresh,Min, Xiao,Acharya, Srijan,Khadka, Daulat Bikram,Yoon, Goon,Kim, Kyeong-Man,Cheon, Seung Hoon Elsevier 2018 Bioorganic & medicinal chemistry Vol.26 No.20

<P><B>Abstract</B></P> <P>Two series of 4-arylpiperazine- and 4-benzylpiperidine naphthyl ethers were designed based on structure-activity relationship (SAR) and docking model of reported monoamine neurotransmitters reuptake inhibitors. The compounds were synthesized in 3-simple steps and their biological activities were evaluated. Several compounds were proven to be potent inhibitors of serotonin and norepinephrine reuptake. Computer docking was performed to study the interaction of the most potent compound <B>35</B> with human serotonin transporter. The results of the analyses suggest that 4-arylpiperazine- and 4-benzylpiperidine naphthyl ethers might be promising antidepressants worthy of further studies.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Triple reuptake inhibitors: Design, synthesis and structure–activity relationship of benzylpiperidine–tetrazoles

Paudel, Suresh,Min, Xiao,Acharya, Srijan,Khadka, Daulat Bikram,Yoon, Goo,Kim, Kyeong-Man,Cheon, Seung Hoon Pergamon 2017 Bioorganic & medicinal chemistry Vol.25 No.20

<P><B>Abstract</B></P> <P>Monoamine transporters are important targets in the treatment of various central nervous disorders. Several limitations of traditional reuptake inhibitors, like delayed onset of action, insomnia, and sexual dysfunction, have compelled the search for safer, more effective compounds. In this study, we have sought to identify novel monoamine reuptake inhibitors. Based upon the docking study of compounds that we had reported previously, aromatic rings (A1) were modified to generate a novel series of benzylpiperidine–tetrazoles. Thirty-one compounds were synthesized and evaluated for their triple reuptake inhibition of serotonin, norepinephrine and dopamine. Triple reuptake inhibitor, compound <B>2q</B>, in particular, showed potent serotonin reuptake inhibition, validating our design approach.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Structural Requirements for Modulating 4-Benzylpiperidine Carboxamides from Serotonin/Norepinephrine Reuptake Inhibitors to Triple Reuptake Inhibitors

( Suresh Paudel ),( Eunae Kim ),( Anlin Zhu ),( Srijan Acharya ),( Xiao Min ),( Seung Hoon Cheon ),( Kyeong-man Kim ) 한국응용약물학회 2021 Biomolecules & Therapeutics(구 응용약물학회지) Vol.29 No.4

In this study, we determined the effect of 24 different synthetic 4-benzylpiperidine carboxamides on the reuptake of serotonin, norepinephrine, and dopamine (DA), and characterized their structure-activity relationship. The compounds with a two-carbon linker inhibited DA reuptake with much higher potency than those with a three-carbon linker. Among the aromatic ring substituents, biphenyl and diphenyl groups played a critical role in determining the selectivity of the 4-benzylpiperidine carboxamides toward the serotonin transporter (SERT) and dopamine transporter (DAT), respectively. Compounds with a 2-naphthyl ring were found to exhibit a higher degree of inhibition on the norepinephrine transporter (NET) and SERT than those with a 1-naphthyl ring. A docking simulation using a triple reuptake inhibitor 8k and a serotonin/norepinephrine reuptake inhibitor 7j showed that the regions spanning transmembrane domain (TM)1, TM3, and TM6 form the ligand binding pocket. The compound 8k bound tightly to the binding pocket of all three monoamine reuptake transporters; however, 7j showed poor docking with DAT. Co-expression of DAT with the dopamine D₂ receptor (D₂R) significantly inhibited DA-induced endocytosis of D₂R probably by reuptaking DA into the cells. Pretreatment of the cells with 8f, which is one of the compounds with good inhibitory activity on DAT, blocked DAT-induced inhibition of D₂R endocytosis. In summary, this study identified critical structural features contributing to the selectivity of a molecule for each of the monoamine transporters, critical residues on the compounds that bound to the transporters, and the functional role of a DA reuptake inhibitor in regulating D₂R function.

Molecular Signature That Determines the Acute Tolerance of G Protein-Coupled Receptors

Min, Chengchun,Zhang, Xiaohan,Zheng, Mei,Sun, Ningning,Acharya, Srijan,Zhang, Xiaowei,Kim, Kyeong-Man The Korean Society of Applied Pharmacology 2017 Biomolecules & Therapeutics(구 응용약물학회지) Vol.25 No.3

Desensitization and acute tolerance are terms used to describe the attenuation of receptor responsiveness by prolonged or intermittent exposure to an agonist. Unlike desensitization of G protein-coupled receptors (GPCRs), which is commonly explained by steric hindrance caused by the ${\beta}$-arrestins that are translocated to the activated receptors, molecular mechanisms involved in the acute tolerance of GPCRs remain unclear. Our studies with several GPCRs and related mutants showed that the acute tolerance of GPCRs could occur independently of agonist-induced ${\beta}$-arrestin translocation. A series of co-immunoprecipitation experiments revealed a correlation between receptor tolerance and interactions among receptors, ${\beta}$-arrestin2, and $G{\beta}{\gamma}$. $G{\beta}{\gamma}$ displayed a stable interaction with receptors and ${\beta}$-arrestin2 in cells expressing GPCRs that were prone to undergo tolerance compared to the GPCRs that were resistant to acute tolerance. Strengthening the interaction between $G{\beta}{\gamma}$ and ${\beta}$-arrestin rendered the GPCRs to acquire the tendency of acute tolerance. Overall, stable interaction between the receptor and $G{\beta}{\gamma}$ complex is required for the formation of a complex with ${\beta}$-arrestin, and determines the potential of a particular GPCR to undergo acute tolerance. Rather than turning off the signal, ${\beta}$-arrestins seem to contribute on continuous signaling when they are in the context of complex with receptor and $G{\beta}{\gamma}$.

Molecular Signature That Determines the Acute Tolerance of G Protein-Coupled Receptors

( Chengchun Min ),( Xiaohan Zhang ),( Mei Zheng ),( Ningning Sun ),( Srijan Acharya ),( Xiaowei Zhang ),( Kyeong-man Kim ) 한국응용약물학회 2017 Biomolecules & Therapeutics(구 응용약물학회지) Vol.25 No.3

Desensitization and acute tolerance are terms used to describe the attenuation of receptor responsiveness by prolonged or intermittent exposure to an agonist. Unlike desensitization of G protein-coupled receptors (GPCRs), which is commonly explained by steric hindrance caused by the β-arrestins that are translocated to the activated receptors, molecular mechanisms involved in the acute tolerance of GPCRs remain unclear. Our studies with several GPCRs and related mutants showed that the acute tolerance of GPCRs could occur independently of agonist-induced β-arrestin translocation. A series of co-immunoprecipitation experiments revealed a correlation between receptor tolerance and interactions among receptors, β-arrestin2, and Gβγ. Gβγ displayed a stable interaction with receptors and b-arrestin2 in cells expressing GPCRs that were prone to undergo tolerance compared to the GPCRs that were resistant to acute tolerance. Strengthening the interaction between Gβγ and β-arrestin rendered the GPCRs to acquire the tendency of acute tolerance. Overall, stable interaction between the receptor and Gβγ complex is required for the formation of a complex with β-arrestin, and determines the potential of a particular GPCR to undergo acute tolerance. Rather than turning off the signal, β-arrestins seem to contribute on continuous signaling when they are in the context of complex with receptor and Gβγ.