Choon-Gon Jang

HDAC6 is a promising therapeutic target for the treatment of cancer and neurodegenerative and inflammatory diseases. We have developed a thiazolyl alkyl hydroxamate scaffold as an HDAC6-selective inhibitor. Herein, we synthesized new thiazolyl hydroxamate derivatives to investigate the effects of aliphatic linker length and cap group rigidity on HDAC6 selectivity. N-Hydroxy-3-(2-(6-methoxynaphthalen-2-yl)thiazol-4-yl)propanamide (5h) was identified as a potent HDAC6 inhibitor (IC₅₀ = 25.56 nM) with ∼500-fold selectivity over HDAC1. Docking and MD simulations revealed that the 6-methoxy-β-naphthalene cap of 5h stably occupies a hydrophobic pocket containing HDAC6-specific nonconserved residues, providing a rationale for novel HDAC6 inhibitor design. Treatment with 5h upregulated BDNF (exons I and IV), and other neurogenesis-related genes in neural progenitor cells. In vivo, 5h improved memory performance in scopolamine-treated memory-impaired mice in the passive avoidance test. These findings suggest that 5h enhances neuroplasticity-related pathways and warrants further investigation as a potential therapeutic candidate for neurodegenerative diseases.

Extensive research has focused on developing anti-nociceptive therapy by targeting specific molecular pathways. Among these, the serotonin 2A receptor (5-HT2AR) and metabotropic glutamate receptor 5 (mGluR5) are recognized as key mediators of neuropathic pain. However, the therapeutic potential of their simultaneous inhibition remains largely unexplored. In this study, we evaluated the efficacy of dual antagonism of 5-HT2AR and mGluR5 using spinal nerve ligation (SNL) and formalin-induced pain models in male Sprague–Dawley rats. Co-administration of selective antagonists significantly enhanced anti-allodynic and anti-nociceptive effects, as evidenced by increased withdrawal thresholds and reduced pain-related behaviors compared to monotherapy. The analgesic efficacy of dual antagonism was comparable to that of gabapentin and morphine. Additionally, novel small molecules designed to concurrently inhibit 5-HT2AR and mGluR5 exerted dose-dependent anti-nociceptive effects by suppressing excitatory postsynaptic responses and inhibiting the phosphorylation of ERK and AKT signaling molecules. Importantly, unlike morphine, repeated administration of the dual antagonist maintained anti-allodynic efficacy with a low potential of abuse. These findings may indicate the promise of simultaneous 5-HT2AR and mGluR5 antagonism as a novel and potentially safer strategy for managing chronic neuropathic pain.

Jee-Yeon Seo, Jisoo Kim, Yong-Hyun Ko, Bo-Ram Lee, Kwang-Hyun Hur, Young Hoon Jung, Hyun-Ju Park, Seok-Yong Lee and Choon-Gon Jang. Biomolecules & Therapeutics -0001;0:. https://doi.org/10.4062/biomolther.2024.110

Drug addiction therapies commonly fail because continued drug use promotes the release of excessive and pleasurable dopamine levels. Because the connection between pleasure and drug use becomes hard-wired in the nucleus accumbens (NAc), which interfaces motivation, effective therapies need to modulate this mesolimbic reward system. Here, we report that mice with knockdown of the cation channel TRPA1 (transient receptor potential ankyrin 1) were resistant to the drug-seeking behavior and reward effects of cocaine compared to their wildtype litter mates. In our study, we demonstrate that TRPA1 inhibition in the NAc reduces cocaine activity and dopamine release, and conversely, that TRPA1 is critical for cocaine-induced synaptic strength in dopamine receptor 1-expressing medium spiny neurons. Taken together, our data support that cocaine-induced reward-related behavior and synaptic release of dopamine in the NAc are controlled by TRPA1 and suggest that TRPA1 has therapeutic potential as a target for drug misuse therapies.

Background and Purpose: Cytoplasmic fragile X messenger ribonucleoprotein 1 (FMR1)‐interacting protein 2 (CYFIP2), as a component of the Wiskott–Aldrich syndrome protein family verprolin‐homologous protein (WAVE) regulatory complex, is involved in actin polymerization, contributing to neuronal development and structural plasticity. Mutating serine‐968 to phenylalanine (S968F) in CYFIP2 causes an altered cocaine response in mice. The neuronal mechanisms underlying this response remain unknown.Experimental Approach: We performed cocaine reward‐related behavioural tests and examined changes in synaptic protein phenotypes and neuronal morphology in the nucleus accumbens (NAc), using CYFIP2 S968F knock‐in mice to investigate the role of CYFIP2 in regulating cocaine reward.Key Results: CYFIP2 S968F mutation attenuated cocaine‐induced behavioural sensitization and conditioned place preference. Cocaine‐induced c‐Fos was not observed in the NAc of CYFIP2 S968F knock‐in mice. However, c‐Fos induction was still evident in the medial prefrontal cortex (mPFC). CYFIP2 S968F mutation altered cocaine‐associated CYFIP2 signalling, glutamatergic protein expression and synaptic density in the NAc following cocaine exposure. To further determine the role of CYFIP2 in NAc neuronal activity and the mPFC projecting to the NAc activity‐mediating reward response, we used optogenetic tools to stimulate the NAc or mPFC‐NAc pathway and observed that optogenetic activation of the NAc or mPFC‐NAc pathway induced reward‐related behaviours. This effect was not observed in the S968F mutation in CYFIP2.Conclusion and Implications: These results suggest that CYFIP2 plays a role in controlling cocaine‐mediated neuronal function and structural plasticity in the NAc, and that CYFIP2 could serve as a target for regulating cocaine reward.

Novel psychoactive substances (NPSs) are new psychotropic drugs designed to evade substance regulatory policies. 25E-NBOMe (2-(4-ethyl-2,5-dimethoxyphenyl)-N-(2-methoxybenzyl)ethanamine) has recently been identified as an NPS, and its recreational misuse has been reported to be rapidly increasing. However, the psychopharmacological effects and mechanisms of 25E-NBOMe have not been studied. We examined the abuse potential of 25E-NBOMe using the conditioned place preference in male mice and self-administration paradigms in male rats. Additionally, immunoblot assay, enzyme-linked immunosorbent assay, and microdialysis were used to determine the molecular effects of 25E-NBOMe in the nucleus accumbens (NAc). Our data demonstrated that 25E-NBOMe induces conditioned place preference, and the dopaminergic signaling in the NAc mediates these. Following 25E-NBOMe administration, expression of dopamine transporter and dopamine D1 receptor (D1DR) were enhanced in the NAc of male mice, and NAc dopamine levels were reduced in both male mice and rats. Induction of intracellular dopaminergic pathways, DARPP32, and phosphorylation of CREB in the NAc of male mice was also observed. Significantly, pharmacological blockade of D1DR or chemogenetic inhibition of D1DR-expressing medium spiny neurons in the NAc attenuated 25E-NBOMe-induced conditioned place preference in male mice. We also examined the hallucinogenic properties of 25E-NBOMe using the head twitch response test in male mice and found that this behavior was mediated by serotonin 2A receptor activity. Our findings demonstrate that D1DR signaling may govern the addictive potential of 25E-NBOMe. Moreover, our study provides new insights into the potential mechanisms of substance use disorder and the improvement of controlled substance management.

Adinazolam (ADZ) is a benzodiazepine-type new psychoactive substance (NPS) with anxiolytic, anticonvulsant, and antidepressant effects. High ADZ doses have been reported to impair psychomotor performance and memory; however, the abuse potential and drug dependence of ADZ have not yet been fully investigated. In this study, we evaluated whether ADZ has abuse potential and leads to drug dependence and withdrawal symptoms. The intravenous self-administration (IVSA) test revealed that ADZ (0.01, 0.03, and 0.1 mg/kg/infusion) was self-administered significantly above vehicle levels, suggesting the reinforcing effect of ADZ. Furthermore, we revealed that treatment discontinuation following chronic ADZ administration (3 and 6 mg/kg) caused several somatic withdrawal symptoms in mice, including body tremor. Moreover, it induced motivational withdrawal signs, such as anxiety-related behavior in the elevated plus maze (EPM) test and memory deficits in the Y-maze test. After the IVSA test, an enzyme-linked immunosorbent assay (ELISA) showed that ADZ administration significantly increased the dopamine contents in the thalamus, nucleus accumbens (NAc), and ventral tegmental area (VTA). This finding was also supported by the results of the Western blot. Taken together, our results suggest that ADZ has abuse potential and can lead to drug dependence and withdrawal syndrome.

2-(2,5-Dimethoxy-4-methylphenyl)-N-(2-methoxybenzyl)_ethanamine (25D-NBOMe), an analogue of the 2C family, is a newly synthesized psychoactive substance. It acts as an agonist at the 5-HT_2A receptor and has a similar mechanism to that of NBOMe compounds. However, the pharmacological mechanism for its rewarding and reinforcing effects has not been revealed. In the present study, intravenous self-administration (IVSA) test and conditioned place preference (CPP) test were performed to investigate whether 25D-NBOMe has abuse potential. We also evaluated the effects of 25D-NBOMe on neurochemical changes using western blot analysis and microdialysis. The IVSA test revealed increased self-administration in 25D-NBOMe (0.03 mg/kg)-treated rats. In addition, the CPP test revealed rewarding effects in 25D-NBOMe (1 mg/kg)-treated mice. In the neurochemical studies, 25D-NBOMe treatment affected the expression of dopamine (DA) receptor D1 (DRD1), DA receptor D2 (DRD2), tyrosine hydroxylase, DA transporter (DAT), and phospho-DAT (p-DAT) in the nucleus accumbens (NAc). In addition, microdialysis revealed that treatment with progressively increasing doses (1, 3, and 10 mg/kg) of 25D-NBOMe increased the extracellular levels of DA, 3,4-dihydroxyphenylacetic acid, and homovanillic acid in the rat NAc. Taken together, our results show the abuse potential and neurochemical changes related to addictive behavior after administration of 25D-NBOMe.

Mepirapim is a novel synthetic cannabinoid that first appeared on the illicit drug market in 2013. In recent years, recreational abuse of Mepirapim has caused serious emergencies, posing a threat to public health. However, there are no legal regulations to prohibit the use of Mepirapim, as there is no scientific evidence for the dangerous pharmacological effects of the drug. In the present study, we investigated the dangerous neurotoxic effects of Mepirapim through behavioral and molecular experiments in mice (ICR/CD1, male, 25–30 g). In particular, based on a previous study that Mepirapim activates the dopamine system, we evaluated whether high-dose Mepirapim [single (15, 30, or 60 mg·kg⁻¹, i.p.) or multiple (8, 15, or 30 mg·kg⁻¹, i.p. × 4 at 2 h intervals)] treatment causes Parkinson’s disease-related symptoms through damage to the dopamine system. In the result, we found that Mepirapim treatment caused comprehensive Parkinson’s disease-related symptoms, including motor impairment, cognitive deficits and mood disorders. Furthermore, we confirmed the maladaptation in dopamine-related neurochemicals, including decreased dopamine levels, decreased tyrosine hydroxylase expression, and increased α-synuclein expression, in the brains of mice treated with Mepirapim. Taken together, these results indicate that Mepirapim has dangerous neurotoxic effects that induces Parkinson’s disease-related behaviors by causing maladaptation of the dopamine system in the brain. Based on these findings, we propose the strict regulation of recreational abuse and therapeutic misuse of Mepirapim.