Anhydroecgonine methyl ester (AEME), a cocaine pyrolysis product, impairs glutathione-related enzymes response and increases lipid peroxidation in the hippocampal cell culture

Psychostimulant and opioid abuse: A perspective from Uruguay

The number of people suffering from substance use disorder (SUD) worldwide has increased 45 % compared to the last decade according to the latest United Nations World Drug Report. This staggering increase, partly due to the recent COVID-19 pandemic, further raises the social and economic burden for nations. Prevention and treatment, two of the main strategies employed to curb the increase in SUD, have shown limited success despite our increasing understanding of the underlying processes of SUD. This review will focus on two main drug categories, psychostimulants, especially cocaine, and opioids since these are two of the most prevalent illicit drugs abused by the general public in low, middle, and high-income countries. The use of active adulterants (e.g. caffeine and illegally manufactured fentanyl, IMF) commonly employed in the preparation of illicit drugs will also be covered considering recent data which has shown that these adulterants may increase the health risk of psychostimulant and opioid users. Especially the high risk of the combined use of cocaine and IMF is detailed. An additional section will address drug abuse in women during pregnancy, as it constitutes a major public health concern due to the negative consequences on newborns and infants. Data from Uruguay is presented and compared to illegal drug use in other countries of South and North America. The rapidly changing drug market, together with the current prevalence of SUD, establishes the urgent need for new strategies and innovative treatments to manage this issue.

Toxicology of anhydroecgonine methyl ester: A systematic review of a cocaine pyrolysis product

Anhydroecgonine Methyl Ester (AEME), also known as methylecgonidine, is the main pyrolysis product of smoking cocaine (cocaine base paste or basuco, crack, or freebase). This review aims to synthesize the available scientific evidence on the toxicokinetic and toxicodynamic effects of AEME. A search of scientific articles published in Science Direct, SCOPUS, and MEDLINE up to May 2024 was conducted. Twenty-four articles, including 13 experimental animal studies, 2 clinical trials, and 3 observational studies, were reviewed. AEME is readily deposited in the alveoli; its absorption improves in combination with cocaine and has a broad tissue distribution. It is metabolized primarily in the liver, with a half-life of approximately one hour, and is mainly excreted through urine. Moreover, AEME acts as a partial agonist of M1 and M3 muscarinic cholinergic receptors, influences dopaminergic system neuroadaptation, increases the production of reactive oxygen species, imbalances the activity of glutathione-associated enzymes, and reduces melatonin levels, affecting its antioxidant regulatory properties. When combined with cocaine, AEME activates the non-apoptotic pathway of caspase-9 and then, the apoptotic pathway via caspase-8, reducing neuronal viability in half the time of cocaine. AEME plays a significant role in cocaine toxicity and AEME itself.

Neurotoxicity of crack cocaine exposure: evidence from a systematic review of in vitro and in vivo studies

Several studies suggest that crack cocaine users exhibit higher prevalence of both psychiatric and psychosocial problems, with an aggressive pattern of drug use. Nevertheless, few experimental studies attempted to verify the neurotoxicity after crack cocaine exposure, especially when compared with other routes of cocaine administration. This systematic review aimed to verify whether in vitro and/or in vivo crack cocaine exposure is more neurotoxic than cocaine exposure (snorted or injected). A search was performed in the PubMed, EMBASE, Scopus, Web of Science, and LILACS databases for in vitro and in vivo toxicological studies conducted with either rats or mice, with no distinction with regard to sex or age. Other methods including BioRxiv, BDTD, Academic Google, citation searching, and specialist consultation were also adopted. Two independent investigators screened the titles and abstracts of retrieved studies and subsequently performed full-text reading and data extraction. The quality of the included studies was assessed by the Toxicological data Reliability assessment Tool (ToxRTool). The study protocol was registered with the Prospective Registry of Systematic Reviews (PROSPERO; CRD42022332250). Of the twelve studies included, three were in vitro and nine were in vivo studies. According to the ToxRTool, most studies were considered reliable either with or without restrictions, with no one being considered as not reliable. The studies found neuroteratogenic effects, decreased threshold for epileptic seizures, schizophrenic-like symptoms, and cognitive deficits to be associated with crack cocaine exposure. Moreover, both in vitro and in vivo studies reported a worsening in cocaine neurotoxic effect caused by the anhydroecgonine methyl ester (AEME), a cocaine main pyrolysis product, which is in line with the more aggressive pattern of crack cocaine use. This systematic review suggests that crack cocaine exposure is more neurotoxic than other routes of cocaine administration. However, before the scarcity of studies on this topic, further toxicological studies are necessary.

Neurotoxicity Assessment of 1-[(2,3-Dihydro-1-Benzofuran-2-yl)Methyl]Piperazine (LINS01 Series) Derivatives and their Protective Effect on Cocaine-Induced Neurotoxicity Model in SH-SY5Y Cell Culture

Excessive levels of dopamine in the synaptic cleft, induced by cocaine for example, activates dopaminergic receptors, mainly D₁R, D₂R, and D₃R subtypes, contributing to neurotoxic effects. New synthetic 1-[(2,3-dihydro-1-benzofuran-2-yl)methyl]piperazine derivatives (the LINS01 compounds), designed as histaminergic receptor (H₃R) ligands, are also dopaminergic receptor ligands, mainly D₂R and D₃R. This study aims to evaluate the neurotoxicity of these new synthetic LINS01 compounds (LINS01003, LINS01004, LINS01011, and LINS01018), as well as to investigate their protective potential on a cocaine model of dopamine-induced neurotoxicity using SH-SY5Y cell line culture. Neurotoxicity was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), lactate dehydrogenase (LDH), and automated cell counting with fluorescent dyes (acridyl orange and propidium iodide) assays. Concentration-response curves (CRCs) were performed for all LINS compounds and cocaine using MTT assay. The results show that LINS series did not decrease cell viability after 48h of exposure-except for 100 µM LINS01018, which was discontinued from the study. Likewise, MTT, LDH, and fluorescent dyes staining showed no difference is cell viability for LINS compounds at 10 µM. When incubated with 2.5 mM cocaine (lethal concentration 50) for 48h, 10 µM of each LINS compound, metoclopramide (D₂R antagonist) and haloperidol (D₂R/D₃R antagonist), ameliorated cocaine-induced neurotoxicity. However, only metoclopramide, haloperidol, and LINS01011 compound significantly decreased LDH released in the culture medium, suggesting that this new synthetic compound presents a more robust effect. This preliminary in vitro neurotoxicity study suggests that LINS01 compounds are not neurotoxic, and that they play a promising role in preventing cocaine-induced neurotoxicity.

Anhydroecgonine methyl ester, a cocaine pyrolysis product, contributes to cocaine-induced rat primary hippocampal neuronal death in a synergistic and time-dependent manner

Crack cocaine users are simultaneously exposed to volatilized cocaine and to its main pyrolysis product, anhydroecgonine methyl ester (AEME). Although the neurotoxic effects of cocaine have been extensively studied, little is known about AEME or its combination. We investigated cell death processes using rat primary hippocampal cells exposed to cocaine (2 mM), AEME (1 mM) and their combination (C + A), after 1, 3, 6 and 12 h. Cocaine increased LC3 I after 6 h and LC3 II after 12 h, but reduced the percentage of cells with acid vesicles, suggesting failure in the autophagic flux, which activated the extrinsic apoptotic pathway after 12 h. AEME neurotoxicity did not involve the autophagic process; rather, it activated caspase-9 after 6 h and caspase-8 after 12 h leading to a high percentage of cells in early apoptosis. C + A progressively reduced the percentage of undamaged cells, starting after 3 h; it activated both apoptotic pathways after 6 h, and was more neurotoxic than cocaine and AEME alone. Also, C + A increased the phosphorylation of p62 after 12 h, but there was little difference in LC3 I or II, and a small percentage of cells with acid vesicles at all time points investigated. In summary, the present study provides new evidence for the neurotoxic mechanism and timing response of each substance alone and in combination, indicating that AEME is more than just a biological marker for crack cocaine consumption, as it may intensify and hasten cocaine neurotoxicity.

Genotoxicity, oxidative stress, and inflammatory response induced by crack-cocaine: relevance to carcinogenesis

Crack-cocaine is a cocaine by-product widely consumed by general population in developing countries. The drug is low cost and is associated with more intense effects when compared to other illicit drugs. Genotoxicity, oxidative stress, and inflammatory response are considered crucial events in carcinogenesis, since they actively participate in the multistep process. The purpose of this paper was to provide a mini review regarding the relationship between carcinogenesis and genotoxicity, oxidative stress, and inflammation induced by crack-cocaine. The present study was conducted on search of the scientific literature from the published studies available in PubMed, MEDLINE, Scopus, and Google Scholar for all kind of articles (all publications to November 2020) using the following key words: crack-cocaine, DNA damage, genotoxicity, cellular death, cytotoxicity, mutation, oxidative stress, inflammation, and mutagenicity. The results showed that published papers available were almost all in vivo test system being conducted in humans or rodents. Crack-cocaine was able to induce genotoxicity and oxidative stress in mammalian cells. However, the role of inflammatory response after exposure to crack-cocaine was not conclusive so far. In summary, this study is consistent with the notion that crack-cocaine is a chemical carcinogen as a result of genotoxicity and oxidative stress induced in mammalian and non-mammalian cells.

Glutathione peroxidase-1 and neuromodulation: Novel potentials of an old enzyme

Glutathione peroxidase (GPx) acts in co-ordination with other signaling molecules to exert its own antioxidant role. We have demonstrated the protective effects of GPx,/GPx-1, a selenium-dependent enzyme, on various neurodegenerative disorders (i.e., Parkinson's disease, Alzheimer's disease, cerebral ischemia, and convulsive disorders). In addition, we summarized the recent findings indicating that GPx-1 might play a role as a neuromodulator in neuropsychiatric conditions, such as, stress, bipolar disorder, schizophrenia, and drug intoxication. In this review, we attempted to highlight the mechanistic scenarios mediated by the GPx/GPx-1 gene in impacting these neurodegenerative and neuropsychiatric disorders, and hope to provide new insights on the therapeutic interventions against these disorders.

Neurotoxic effects of pregabalin dependence on the brain frontal cortex in adult male albino rats

Pregabalin (PGB) is an analog of the inhibitory neurotransmitter gamma-aminobutyric acid. The currently available evidence favors the misuse and abuse potential of PGB. However, its neurotoxicity remains unclear. Therefore, this study assessed the toxic effects of chronic pregabalin dependence as well as withdrawal on the cortical neurons of the frontal lobe. This study included eighty adult male albino rats which were divided into three groups. Group I (Control) included 40 rats and was further subdivided into two equal subgroups (IA and IB) as negative and positive controls. Group II (PGB-dependent) included 20 rats which received PGB starting with the therapeutic dose (300 mg/day), then the doses were gradually increased until they reached the dependent dose (3400 mg/day) by the end of the first month. Further, the dependent dose was given daily for another 2 months. Group III (PGB withdrawal) included 20 rats which received PGB as described in group II. After that, administration of PGB was stopped and the rats were kept for another one month. By the end of the experiment, all animals were sacrificed by cervical decapitation. The specimens were taken from the frontal cortex for histologic and immunohistochemical staining as well as morphometric analysis. Sections of the frontal cortex of group II showed changes in the form of disturbed architectural pattern of cortical layers, apoptotic cells, weak immunoexpression of Bcl-2 and VEGF as well as moderate-strong immunoexpression of iNOS and nestin. These expressions were significantly different from the control groups, but they were non-significant in comparison with group III. These findings indicate that chronic PGB dependence induces neurotoxic effects mainly in the form of neuronal apoptosis, gliosis, and oxidative stress injury of the frontal cortex. The PGB- induced neurotoxic effects persisted after withdrawal. The influence of these neurotoxic effects and their relevance to the cognitive or neurologic disorders in PGB-dependent individuals warrants further research. Furthermore, it is recommended to quantify the behavioral changes related to PGB dependence as well as withdrawal in future studies.