25C-NBF, a new psychoactive substance, has addictive and neurotoxic potential in rodents

Transient receptor potential ankyrin 1 channel modulates the abuse-related mechanisms of methamphetamine through interaction with dopamine transporter

BACKGROUND AND PURPOSE

Methamphetamine (METH) use disorder has risen dramatically over the past decade, and there are currently no FDA-approved medications due, in part, to gaps in our understanding of the pharmacological mechanisms related to METH action in the brain.

EXPERIMENTAL APPROACH

Here, we investigated whether transient receptor potential ankyrin 1 (TRPA1) mediates each of several METH abuse-related behaviours in rodents: self-administration, drug-primed reinstatement, acquisition of conditioned place preference, and hyperlocomotion. Additionally, METH-induced molecular (i.e., neurotransmitter and protein) changes in the brain were compared between wild-type and TRPA1 knock-out mice. Finally, the relationship between TRPA1 and the dopamine transporter was investigated through immunoprecipitation and dopamine reuptake assays.

KEY RESULTS

TRPA1 antagonism blunted METH self-administration and drug-primed reinstatement of METH-seeking behaviour. Further, development of METH-induced conditioned place preference and hyperlocomotion were inhibited by TRPA1 antagonist treatment, effects that were not observed in TRPA1 knock-out mice. Similarly, molecular studies revealed METH-induced increases in dopamine levels and expression of dopamine system-related proteins in wild-type, but not in TRPA1 knock-out mice. Furthermore, pharmacological blockade of TRPA1 receptors reduced the interaction between TRPA1 and the dopamine transporter, thereby increasing dopamine reuptake activity by the transporter.

CONCLUSION AND IMPLICATIONS

This study demonstrates that TRPA1 is involved in the abuse-related behavioural effects of METH, potentially through its modulatory role in METH-induced activation of dopaminergic neurotransmission. Taken together, these data suggest that TRPA1 may be a novel therapeutic target for treating METH use disorder.

Serotonin 2C receptors are also important in head-twitch responses in male mice

RATIONALE

Serotonergic psychedelics exert their effects via their high affinity for serotonin (5-HT) receptors, particularly through activating 5-HT2A receptors (5-HT2AR), employing the frontal cortex-dependent head-twitch response (HTR). Although universally believed to be so, studies have not yet fully ascertained whether 5-HT2AR activation is the sole initiator of these psychedelic effects. This is because not all 5-HT2AR agonists exhibit similar pharmacologic properties.

OBJECTIVE

This study aims to identify and discriminate the roles of 5-HT2AR and 5-HT2CR in the HTR induced by Methallylescaline (MAL) and 4-Methyl-2,5,β-trimethoxyphenethylamine (BOD) in male mice. Also, an analysis of their potential neurotoxic properties was evaluated.

METHODS

Male mice treated with MAL and BOD were evaluated in different behavioral paradigms targeting HTR and neurotoxicity effects. Drug affinity, pharmacological blocking, and molecular analysis were also conducted to support the behavioral findings. The HTR induced by DOI has been extensively characterized in male mice, making it a good positive control for this study, specifically for comparing the pharmacological effects of our test compounds.

RESULTS

The activation of 5-HT2CR, alone or in concert with 5-HT2AR, produces a comparable degree of HTRs (at a dose of 1 mg·kg-1), with divergent 5-HT2CR- and 5-HT2AR-Gqα11-mediated signaling and enhanced neurotoxic properties (at a dose of 30 mg·kg-1) coupled with activated pro-inflammatory cytokines. These findings show these compounds' potential psychedelic and neurotoxic effects in male mice.

CONCLUSION

These findings showed that while 5-HT2AR is the main initiator of HTR, the 5-HT2CR also has a distinct property that renders it effective in inducing HTR in male mice.

Prebiotics modulate the microbiota-gut-brain axis and ameliorate cognitive impairment in APP/PS1 mice

PURPOSE

Prebiotics, including fructo-oligosaccharides (FOS) and galacto-oligosaccharides (GOS), stimulate beneficial gut bacteria and may be helpful for patients with Alzheimer's disease (AD). This study aimed to compare the effects of FOS and GOS, alone or in combination, on AD mice and to identify their underlying mechanisms.

METHODS

Six-month-old APP/PS1 mice and wild-type mice were orally administered FOS, GOS, FOS + GOS or water by gavage for 6 weeks and then subjected to relative assays, including behavioral tests, biochemical assays and 16S rRNA sequencing.

RESULTS

Through behavioral tests, we found that GOS had the best effect on reversing cognitive impairment in APP/PS1 mice, followed by FOS + GOS, while FOS had no effect. Through biochemical techniques, we found that GOS and FOS + GOS had effects on multiple targets, including diminishing Aβ burden and proinflammatory IL-1β and IL-6 levels, and changing the concentrations of neurotransmitters GABA and 5-HT in the brain. In contrast, FOS had only a slight anti-inflammatory effect. Moreover, through 16S rRNA sequencing, we found that prebiotics changed composition of gut microbiota. Notably, GOS increased relative abundance of Lactobacillus, FOS increased that of Bifidobacterium, and FOS + GOS increased that of both. Furthermore, prebiotics downregulated the expression levels of proteins of the TLR4-Myd88-NF-κB pathway in the colons and cortexes, suggesting the involvement of gut-brain mechanism in alleviating neuroinflammation.

CONCLUSION

Among the three prebiotics, GOS was the optimal one to alleviate cognitive impairment in APP/PS1 mice and the mechanism was attributed to its multi-target role in alleviating Aβ pathology and neuroinflammation, changing neurotransmitter concentrations, and modulating gut microbiota.

A molecular analysis of substituted phenylethylamines as potential microtubule targeting agents through in silico methods and in vitro microtubule-polymerization activity

Natural phenethylamines are trace amine neurotransmitters associated with dopamine transmission and related illnesses such Parkinson's disease, and addiction. Synthetic phenethylamines can have psychoactive and hallucinogenic effects due to their high affinity with the 5-HT2A receptor. Evidence indicates phenethylamines can directly alter the microtubule cytoskeleton being structurally similar to the microtubule destabilizing agent colchicine, however little work has been done on this interaction. As microtubules provide neuron structure, intracellular transport, and influence synaptic plasticity the interaction of phenethylamines with microtubules is important for understanding the potential harms, or potential pharmaceutical use of phenethylamines. We investigated 110 phenethylamines and their interaction with microtubules. Here we performed molecular docking of these compounds at the colchicine binding site and ranked them via binding energy. The top 10% of phenethylamines were further screened based on pharmacokinetic and physicochemical properties derived from SwissADME and LightBBB. Based on these properties 25B-NBF, 25C-NBF, and DMBMPP were tested in in vitro microtubule polymerization assays showing that they alter microtubule polymerization dynamics in a dose dependent manner. As these compounds can rapidly cross the blood brain barrier and directly affect cytoskeletal dynamics, they have the potential to modulate cytoskeletal based neural plasticity. Further investigations into these mechanisms are warranted.

Designer Drug, 25D-NBOMe, Has Reinforcing and Rewarding Effects through Change of a Dopaminergic Neurochemical System

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-HT2A 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.

Dysfunction of GluN3A subunit is involved in depression-like behaviors through synaptic deficits

BACKGROUND

N-methyl-d-aspartate receptor (NMDAR) has been implicated in the pathophysiology of depression. However, as the unique inhibitory subunit of NMDARs, the role of GluN3A in depression is largely unclear.

METHODS

Firstly, expression of GluN3A was examined in a mouse model of depression induced by chronic restraint stress (CRS). Then, rescue experiment with rAAV-Grin3a injection into hippocampus of CRS mice was carried out. Lastly, GluN3A knockout (KO) mouse was generated via CRISPR/Cas9 technique, and the molecular mechanism underlying involvement of GluN3A in depression was initially explored using RNA-seq technique, RT-PCR and western blotting.

RESULTS

GluN3A expression in hippocampus was significantly decreased in CRS mice. Depression-like behaviors induced by CRS were ameliorated when the decrease of GluN3A expression in mice exposed to CRS was restored. GluN3A KO mice exhibited symptoms of anhedonia reported as reduced sucrose preference, and symptoms of despair assayed by a longer immobility time in FST. Transcriptome analysis revealed genetic ablation of GluN3A was associated with downregulation of genes implicated in synapse and axon development. Postsynaptic protein PSD95 was decreased in GluN3A KO mice. More importantly, reduction of PSD95 in CRS mice can be rescued by viral mediated Grin3a re-expression.

LIMITATIONS

The mechanism underlying GluN3A involvement in depression is not fully determined.

CONCLUSIONS

Our data suggested that GluN3A dysfunction is involved in depression, which might be mediated by synaptic deficits. These findings will facilitate the understanding of the role of GluN3A in depression, and they might provide a new strategy for the development of subunit-selective NMDAR antagonists as antidepressant drugs.

Mepirapim, a novel synthetic cannabinoid, induces Parkinson's disease-related behaviors by causing maladaptation of the dopamine system in the brain

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.

Scutellarin Modulates the Microbiota-Gut-Brain Axis and Improves Cognitive Impairment in APP/PS1 Mice

BACKGROUND

Scutellarin, a flavonoid purified from the Chinese herb Erigeron breviscapus, has been reported to prevent Alzheimer's disease (AD) by affecting Aβ assembly. Given the low brain uptake rate of scutellarin, we hypothesize that the microbiota-gut-brain axis may be a potential route by which scutellarin prevents AD.

OBJECTIVE

This study aimed to explore the microbiota-gut-brain mechanism by which scutellarin prevented AD.

METHODS

Scutellarin was administrated to APP/PS1 mouse model of AD for two months, and the behaviors, pathological changes as well as gut microbial changes in APP/PS1 mice were evaluated after scutellarin treatment.

RESULTS

This study found that scutellarin improved Aβ pathology, neuroinflammation, and cognitive deficits in APP/PS1 mice. It elucidated the effects of scutellarin on the diversity and activity of gut microbiota in APP/PS1 mice and these findings promoted us to focus on inflammation-related bacteria and short-chain fatty acids (SCFAs). Cognitive behaviors were significantly associated with inflammatory cytokines and inflammation-related bacteria, suggesting that microbiota-gut-brain axis was involved in this model and that inflammatory pathway played a crucial role in this axis. Moreover, we observed that cAMP-PKA-CREB-HDAC3 pathway downstream of SCFAs was activated in microglia of AD and inactivated by scutellarin. Furthermore, by chromatin immunoprecipitation (ChIP) assays, we found that the increased association between acetylated histone 3 and interleukin-1β (IL-1β) promoter in AD mice was reversed by scutellarin, leading to a decreased level of IL-1β in scutellarin-treated AD mice.

CONCLUSION

Scutellarin reverses neuroinflammation and cognitive impairment in APP/PS1 mice via beneficial regulation of gut microbiota and cAMP-PKA-CREB-HDAC3 signaling in microglia.

Mepirapim, a Novel Synthetic Cannabinoid, Induces Addiction-Related Behaviors through Neurochemical Maladaptation in the Brain of Rodents

Mepirapim is a synthetic cannabinoid that has recently been abused for recreational purposes. Although serious side effects have been reported from users, the dangerous pharmacological effects of Mepirapim have not been scientifically demonstrated. In this study, we investigated the addictive potential of Mepirapim through an intravenous self-administration test and a conditioned place preference test in rodents. Moreover, to determine whether the pharmacological effects of Mepirapim are mediated by cannabinoid receptors, we investigated whether Mepirapim treatment induces cannabinoid tetrad symptoms in mice. Lastly, to identify Mepirapim induced neurochemical maladaptation in the brains of mice, we performed microdialysis, western blots and neurotransmitter enzyme-linked immunosorbent assays. In the results, Mepirapim supported the maintenance of intravenous self-administration and the development of conditioned place preference. As a molecular mechanism of Mepirapim addiction, we identified a decrease in GABAeric signalling and an increase in dopaminergic signalling in the brain reward circuit. Finally, by confirming the Mepirapim-induced expression of cannabinoid tetrad symptoms, we confirmed that Mepirapim acts pharmacologically through cannabinoid receptor one. Taken together, we found that Mepirapim induces addiction-related behaviours through neurochemical maladaptation in the brain. On the basis of these findings, we propose the strict regulation of recreational abuse of Mepirapim.

Methoxphenidine (MXP) induced abnormalities: Addictive and schizophrenia-related behaviours based on an imbalance of neurochemicals in the brain

BACKGROUND AND PURPOSE

Methoxphenidine is a dissociative-based novel psychoactive designer drug. Although fatal accidents from methoxphenidine abuse have been reported, recreational use of the drug continues. We aim to provide scientific supportfor legal regulation of recreational abuse of methoxphenidine by demonstrating its the pharmacological action.

EXPERIMENTAL APPROACH

Addictive potential of methoxphenidine was examined using intravenous self-administration test with rats and conditioned place preference test with mice. Further, a series of behavioural tests (open field test, elevated plus maze test, novel object recognition test, social interaction test and tail suspension test) performed to assess whether methoxphenidine caused schizophrenia-related symptoms in mice. Additionally, neurotransmitter enzyme-linked immunosorbent assay and western blot were used to confirm methoxphenidine-induced neurochemical changes in specific brain regions related to abnormal behaviours.

KEY RESULTS

Methoxphenidine caused addictive behaviours via reinforcing and rewarding effects. Consistently, methoxphenidine induced over-activation of dopamine pathways in the nuclear accumbens, indicating activation of the brain reward circuit. Also, methoxphenidine caused all categories of schizophrenia-related symptoms, including positive symptoms (hyperactivity, impulsivity), negative symptoms (anxiety, social withdrawal, depression) and cognitive impairment. Consistently, methoxphenidine led to the disruption of the hippocampal-prefrontal cortex pathway that is considered to be pathological involved in schizophrenia.

CONCLUSIONS AND IMPLICATIONS

We demonastrate that methoxphenidine causes addictive and schizophrenia-like behaviours and induces neurochemical changes in brain regions associated with these behaviours. We propose that methoxphenidine could be used in developing useful animal disease models and that it also requires legal restrictions on its recreational use.

Molecular Mechanisms of Action of Novel Psychoactive Substances (NPS). A New Threat for Young Drug Users with Forensic-Toxicological Implications

Novel psychoactive substances (NPS) represent a severe health risk for drug users. Even though the phenomenon has been growing since the early 2000s, the mechanisms of action of NPS at the receptors and beyond them are still scarcely understood. The aim of the present study was to provide a systematic review of the updated knowledge regarding the molecular mechanisms underlying the toxicity of synthetic opioids, cannabinoids, cathinones, and stimulants. The study was conducted on the PubMed database. Study eligibility criteria included relevance to the topic, English language, and time of publication (2010–2020). A combined Mesh and free-text protocols search was performed. Study selection was performed on the title/abstract and, in doubtful cases, on the full texts of papers. Of the 580 records identified through PubMed searching and reference checking, 307 were excluded by title/abstract and 78 additional papers were excluded after full-text reading, leaving a total of 155 included papers. Molecular mechanisms of synthetic opioids, synthetic cannabinoids, stimulants, psychedelics, and hallucinogens were reviewed and mostly involved both a receptor-mediated and non-receptor mediated cellular modulation with multiple neurotransmitters interactions. The molecular mechanisms underlying the action of NPS are more complex than expected, with a wide range of overlap among activated receptors and neurotransmitter systems. The peculiar action profile of single compounds does not necessarily reflect that of the structural class to which they belong, accounting for possible unexpected toxic reactions.

Synthesis and Functional Characterization of 2-(2,5-Dimethoxyphenyl)-N-(2-fluorobenzyl)ethanamine (25H-NBF) Positional Isomers

Serotonergic psychedelics, substances exerting their pharmacological action through activation of the serotonin 2A receptor (5-HT_2AR), have continuously comprised a substantial fraction of the over 1000 reported New Psychoactive Substances (NPS) so far. Within this category, N-benzyl derived phenethylamines, such as NBOMes and NBFs, have shown to be of particular relevance. As these substances remain incompletely characterized, this study aimed at synthesizing positional isomers of 25H-NBF, with two methoxy groups placed on different positions of the phenyl group of the phenethylamine moiety. These isomers were then functionally characterized in an in vitro bioassay monitoring the recruitment of β-arrestin 2 to the 5-HT_2AR through luminescent readout via the NanoBiT technology. The obtained results provide insight into the optimal substitution pattern of the phenyl group of the phenethylamine moiety of N-benzyl derived substances, a feature so far mostly explored in the phenethylamines underived at the N-position. In the employed bioassay, the most potent substances were 24H-NBF (EC₅₀ value of 158 nM), 26H-NBF (397 nM), and 25H-NBF (448 nM), with 23H-NBF, 35H-NBF, and 34H-NBF yielding μM EC₅₀ values. A similar ranking was obtained for the compounds' efficacy: taking as a reference LSD (lysergic acid diethylamide), 24H-, 26H-, and 25H-NBF had an efficacy of 106-107%, followed by 23H-NBF (96.1%), 34H-NBF (75.2%), and 35H-NBF (58.9%). The stronger activity of 24H-, 25H-, and 26H-NBF emphasizes the important role of the methoxy group at position 2 of the phenethylamine moiety for the in vitro functionality of NBF substances.

Abuse Potential of Synthetic Cannabinoids: AM-1248, CB-13, and PB-22

Currently, the expanding recreational use of synthetic cannabinoids (SCBs) threatens public health. SCBs produce psychoactive effects similar to those of tetrahydrocannabinol, the main component of cannabis, and additionally induce unexpected pharmacological side effects. SCBs are falsely advertised as legal and safe, but in reality, SCB abuse has been reported to cause acute intoxication and addictive disorders. However, because of the lack of scientific evidence to elucidate their dangerous pharmacological effects, SCBs are weakly regulated and continue to circulate in illegal drug markets. In the present study, the intravenous self-administration (IVSA) paradigm was used to evaluate the abuse potential of three SCBs (AM-1248, CB-13, and PB-22) in rats. All three SCBs maintained IVSA with a large number of infusions and active lever presses, demonstrating their reinforcing effects. The increase of active lever presses was particularly significant during the early IVSA sessions, indicating the reinforcementenhancing effects of the SCBs (AM-1248 and CB-13). The number of inactive lever presses was significantly higher in the SCB groups (AM-1248 and CB-13) than that in the vehicle group, indicating their impulsive effects. In summary, these results demonstrated that SCBs have distinct pharmacological properties and abuse potential.