Acute or repeated cocaine administration generates reactive oxygen species and induces antioxidant enzyme activity in dopaminergic rat brain structures

Exploring peripheral biomarkers in psychostimulant use: A systematic review on neurotrophins, stress-related hormones, oxidative stress molecules and genetic factors

BACKGROUND

This systematic review aims to comprehensively explore the impact of psychostimulant substances on neurotrophic and inflammatory pathways, including brain-derived neurotrophic factor (BDNF), pro-BDNF, cortisol, dehydroepiandrosterone sulfate (DHEAS), thiobarbituric acid reactive substances (TBARS), interleukins, and the role of genetic factors. The study seeks to address existing gaps in the literature by providing a thorough evaluation of neurotrophic and inflammatory system alterations associated with different stages of psychostimulant dependence for a more nuanced understanding of substance use disorder (SUD) neurobiology.

METHODS

A systematic review was conducted in PubMed, Scopus, and Web of Science databases following the PRISMA guidelines. The research encompasses 50 studies with a participant pool totaling 6792 individuals using psychostimulant substances.

RESULTS

Key findings include diverse impacts of cocaine on BDNF levels, mainly consisting of their significant increase during withdrawal. In contrast, NGF showed an opposite behavior, reducing during withdrawal. Cortisol and DHEAS levels exhibited relevant increases after psychostimulant use, while TBARS showed conflicting results. Genetic investigations predominantly focused on the Val66Met polymorphism of the BDNF gene, revealing associations with susceptibility to stimulant addiction.

CONCLUSIONS

Neurotrophins and inflammatory molecules play a significant role in the pathophysiological mechanisms following psychostimulant use. A better understanding of their complex interplay could aid clinicians in identifying biomarkers of different disease stages. Moreover, clinical interventions designed to interfere with neurotrophic and inflammatory pathways could possibly lead to craving-modulatory strategies and reduce pathological neuronal and systemic consequences of psychostimulant use.

The ubiquitin-proteasome system and learning-dependent synaptic plasticity - A 10 year update

Over 25 years ago, a seminal paper demonstrated that the ubiquitin-proteasome system (UPS) was involved in activity-dependent synaptic plasticity. Interest in this topic began to expand around 2008 following another seminal paper showing that UPS-mediated protein degradation controlled the "destabilization" of memories following retrieval, though we remained with only a basic understanding of how the UPS regulated activity- and learning-dependent synaptic plasticity. However, over the last 10 years there has been an explosion of papers on this topic that has significantly changed our understanding of how ubiquitin-proteasome signaling regulates synaptic plasticity and memory formation. Importantly, we now know that the UPS controls much more than protein degradation, is involved in plasticity underlying drugs of abuse and that there are significant sex differences in how ubiquitin-proteasome signaling is used for memory storage processes. Here, we aim to provide a critical 10-year update on the role of ubiquitin-proteasome signaling in synaptic plasticity and memory formation, including updated cellular models of how ubiquitin-proteasome activity could be regulating learning-dependent synaptic plasticity in the brain.

Cocaine Destroys Gray Matter Brain Cells and Accelerates Brain Aging

Introduction: Cocaine use disorder (CUD) is a substance use disorder characterized by a strong desire to obtain, consume, and misuse cocaine. Little is known about how cocaine affects the structure of the brain. In this study, we first investigated the anatomical brain changes in individuals with CUD compared to their matched healthy controls, and then explored whether these anatomical brain abnormalities contribute to considerably accelerated brain aging among this population. Methods: At the first stage, we used anatomical magnetic resonance imaging (MRI) data, voxel-based morphometry (VBM), and deformation-based morphometry techniques to uncover the morphological and macroscopic anatomical brain changes in 74 CUD patients compared to 62 age- and sex-matched healthy controls (HCs) obtained from the SUDMEX CONN dataset, the Mexican MRI dataset of patients with CUD. Then, we computed brain-predicted age difference (i.e., brain-PAD: the brain-predicted age minus the actual age) in CUD and HC groups using a robust brain age estimation framework. Using a multiple regression analysis, we also investigated the regional gray matter (GM) and white matter (WM) changes associated with the brain-PAD. Results: Using a whole-brain VBM analysis, we observed widespread gray matter atrophy in CUD patients located in the temporal lobe, frontal lobe, insula, middle frontal gyrus, superior frontal gyrus, rectal gyrus, and limbic lobe regions compared to the HCs. In contrast, we did not observe any swelling in the GM, changes in the WM, or local brain tissue atrophy or expansion between the CUD and HC groups. Furthermore, we found a significantly higher brain-PAD in CUD patients compared to matched HCs (mean difference = 2.62 years, Cohen's d = 0.54; t-test = 3.16, p = 0.002). The regression analysis showed significant negative changes in GM volume associated with brain-PAD in the CUD group, particularly in the limbic lobe, subcallosal gyrus, cingulate gyrus, and anterior cingulate regions. Discussion: The results of our investigation reveal that chronic cocaine use is linked to significant changes in gray matter, which hasten the process of structural brain aging in individuals who use the drug. These findings offer valuable insights into the impact of cocaine on the composition of the brain.

Influence of Redox and Dopamine Regulation in Cocaine-Induced Phenotypes Using Drosophila

Reactive Oxidative Species (ROS) are produced during cellular metabolism and their amount is finely regulated because of negative consequences that ROS accumulation has on cellular functioning and survival. However, ROS play an important role in maintaining a healthy brain by participating in cellular signaling and regulating neuronal plasticity, which led to a shift in our understanding of ROS from being solely detrimental to having a more complex role in the brain. Here we use Drosophila melanogaster to investigate the influence of ROS on behavioral phenotypes induced by single or double exposure to volatilized cocaine (vCOC), sensitivity and locomotor sensitization (LS). Sensitivity and LS depend on glutathione antioxidant defense. Catalase activity and hydrogen peroxide (H₂O₂) accumulation play a minor role, but their presence is necessary in dopaminergic and serotonergic neurons for LS. Feeding flies the antioxidant quercetin completely abolishes LS confirming the permissive role of H₂O₂ in the development of LS. This can only partially be rescued by co-feeding H₂O₂ or the dopamine precursor 3,4-dihydroxy-L-phenylalanine (L-DA) showing coordinate and similar contribution of dopamine and H₂O₂. Genetic versatility of Drosophila can be used as a tool for more precise dissection of temporal, spatial and transcriptional events that regulate behaviors induced by vCOC.

Lithium engages autophagy for neuroprotection and neuroplasticity: translational evidence for therapy

Here an overview is provided on therapeutic/neuroprotective effects of Lithium (Li⁺) in neurodegenerative and psychiatric disorders focusing on the conspicuous action of Li⁺ through autophagy. The effects on the autophagy machinery remain the key molecular mechanisms to explain the protective effects of Li⁺ for neurodegenerative diseases, offering potential therapeutic strategies for the treatment of neuropsychiatric disorders and emphasizes a crossroad linking autophagy, neurodegenerative disorders, and mood stabilization. Sensitization by psychostimulants points to several mechanisms involved in psychopathology, most also crucial in neurodegenerative disorders. Evidence shows the involvement of autophagy and metabotropic Glutamate receptors-5 (mGluR5) in neurodegeneration due to methamphetamine neurotoxicity as well as in neuroprotection, both in vitro and in vivo models. More recently, Li⁺ was shown to modulate autophagy through its action on mGluR5, thus pointing to an additional way of autophagy engagement by Li⁺ and to a substantial role of mGluR5 in neuroprotection related to neural e neuropsychiatry diseases. We propose Li⁺ engagement of autophagy through the canonical mechanisms of autophagy machinery and through the intermediary of mGluR5.

Effect of human mesenchymal stem cell secretome administration on morphine self-administration and relapse in two animal models of opioid dependence

The present study investigates the possible therapeutic effects of human mesenchymal stem cell-derived secretome on morphine dependence and relapse. This was studied in a new model of chronic voluntary morphine intake in Wistar rats which shows classic signs of morphine intoxication and a severe naloxone-induced withdrawal syndrome. A single intranasal-systemic administration of MSCs secretome fully inhibited (>95%; p < 0.001) voluntary morphine intake and reduced the post-deprivation relapse intake by 50% (p < 0.02). Since several studies suggest a significant genetic contribution to the chronic use of many addictive drugs, the effect of MSCs secretome on morphine self-administration was further studied in rats bred as high alcohol consumers (UChB rats). Sub-chronic intraperitoneal administration of morphine before access to increasing concentrations of morphine solutions and water were available to the animals, led UChB rats to prefer ingesting morphine solutions over water, attaining levels of oral morphine intake in the range of those in the Wistar model. Intranasally administered MSCs secretome to UChB rats dose-dependently inhibited morphine self-administration by 72% (p < 0.001); while a single intranasal dose of MSC-secretome administered during a morphine deprivation period imposed on chronic morphine consumer UChB rats inhibited re-access morphine relapse intake by 80 to 85% (p < 0.0001). Both in the Wistar and the UChB rat models, MSCs-secretome administration reversed the morphine-induced increases in brain oxidative stress and neuroinflammation, considered as key engines perpetuating drug relapse. Overall, present preclinical studies suggest that products secreted by human mesenchymal stem cells may be of value in the treatment of opioid addiction.

Evidence of methylphenidate effect on mitochondria, redox homeostasis, and inflammatory aspects: Insights from animal studies

Methylphenidate (MPH) is a central nervous system (CNS) stimulant known for its effectiveness in the treatment of Attention Deficit Hyperactivity Disorder (ADHD), a neuropsychiatric condition that has a high incidence in childhood and affects behavior and cognition. However, the increase in its use among individuals who do not present all the diagnostic criteria for ADHD has become a serious public health problem since the neurological and psychiatric consequences of this unrestricted use are not widely known. In addition, since childhood is a critical period for the maturation of the CNS, the high prescription of MPH for preschool children also raises several concerns. This review brings new perspectives on how MPH (in different doses, routes of administration and ages) affects the CNS, focusing on animal studies that evaluated changes in mitochondrial (bioenergetics), redox balance and apoptosis, as well as inflammatory parameters. MPH alters brain energy homeostasis, increasing glucose consumption and impairing the activity of enzymes in the Krebs cycle and electron transport chain, as well as ATP levels and Na⁺,K⁺-ATPase activity. MPH induces oxidative stress, increasing the levels of reactive oxygen and nitrogen species and altering enzymatic and non-enzymatic antioxidant defenses, which, consequently, is related to damage to proteins, lipids, and DNA. Among the harmful effects of MPH, studies also demonstrate its ability to induce inflammation as well as alter the apoptosis pathway. It is important to highlight that age, treatment time, administration route, and dose are factors that can influence MPH effects. However, young animals seem to be more susceptible to damage caused by MPH. It is possible that changes in mitochondrial function and markers of status oxidative, apoptosis and inflammation may be exerting important mechanisms associated with MPH toxicity and, therefore, the unrestricted use of this drug can cause brain damage.

Protective Role of Lactobacillus rhamnosus Probiotic in Reversing Cocaine-Induced Oxidative Stress, Glial Activation and Locomotion in Mice

Cocaine abuse is known to cause inflammation, oxidative injury and alterations in the gut microbiota. Although emerging studies have demonstrated the role of gut microbiota in modulating neurological complications and behavior, the mechanism(s) underlying these processes remain unclear. In the present study, we investigated the protective effect of Lactobacillus rhamnosus probiotic on cocaine-induced oxidative stress, glial activation, and locomotion in mice. In this study, groups of male C56BL6 mice were administered gut-resident commensal bacteria L. rhamnosus probiotic (oral gavage) concurrently with cocaine (20 mg/kg, i.p.) or saline for 28 days and assessed for oxidative stress and cellular activation in both the gut and brain as well as alterations in locomotion behavior. Cocaine-induced gut dysregulation was associated with increased formation of 4-hydroxynonenal (4-HNE) adducts, increased expression of pERK-1/2, pNF-kB-p65 and antioxidant mediators (SOD1, GPx1). In cocaine administered mice, there was increased activation of both microglia and astrocytes in the striatum and cortex of the brain as shown by enhanced expression of CD11b and GFAP, respectively. Cocaine administration also resulted in increased locomotor activity in the open field test in these mice. Administration of L. rhamnosus attenuated cocaine-induced gut oxidative stress and inflammation as well as glial activation and locomotion. These results suggest the potential of microbial-based interventions to attenuate cocaine-mediated behavioral responses and neuroinflammation, in addition to systemic inflammation and oxidative damage.

Role of Mitochondrial Dynamics in Cocaine's Neurotoxicity

The dynamic balance of mitochondrial fission and fusion maintains mitochondrial homeostasis and optimal function. It is indispensable for cells such as neurons, which rely on the finely tuned mitochondria to carry out their normal physiological activities. The potent psychostimulant cocaine impairs mitochondria as one way it exerts its neurotoxicity, wherein the disturbances in mitochondrial dynamics have been suggested to play an essential role. In this review, we summarize the neurotoxicity of cocaine and the role of mitochondrial dynamics in cellular physiology. Subsequently, we introduce current findings that link disturbed neuronal mitochondrial dynamics with cocaine exposure. Finally, the possible role and potential therapeutic value of mitochondrial dynamics in cocaine neurotoxicity are discussed.

CYP3A1 metabolism-based neurotoxicity of strychnine in rat

Strychnine is one of the main bioactive and toxic constituents of Semen Strychni. In the present study, the neurotoxic effects of strychnine, and the role of individual differences in metabolism on susceptibility to neurotoxicity of strychnine were investigated. The acute toxicity was observed by a single dose of strychnine (2.92 mg/kg, i.g.) in rats, the epileptic stages of rats were scored according to Racine's scale. The neurotoxicity of strychnine was evaluated by the levels of ROS, MDA, SOD and GSH in hippocampus, striatum, and cortex tissues measurements and histopathological analysis. The concentrations of strychnine in the plasma, hippocampus, striatum, and cortex tissues were determined using high performance liquid chromatography tandem mass spectrometry (LC-MS/MS). The expressions of the cytochrome P450, which is the most critical protein family involved in drugs metabolism, were detected by proteomics. The mechanism of susceptibility to neurotoxicity of strychnine was elucidated by correlation analysis among above indicators. The results indicated that striatum and cortex were the main toxic targets of strychnine, and the CYP3A1 might be a susceptible biomarker to neurotoxicity of strychnine. These results provide valuable insights into the neurotoxic susceptibility of strychnine that will aid in the rational clinical use of strychnine (possibly including Semen Strychni).

Crossroads of Drug Abuse and HIV Infection: Neurotoxicity and CNS Reservoir

Drug abuse is a common comorbidity in people infected with HIV. HIV-infected individuals who abuse drugs are a key population who frequently experience suboptimal outcomes along the HIV continuum of care. A modest proportion of HIV-infected individuals develop HIV-associated neurocognitive issues, the severity of which further increases with drug abuse. Moreover, the tendency of the virus to go into latency in certain cellular reservoirs again complicates the elimination of HIV and HIV-associated illnesses. Antiretroviral therapy (ART) successfully decreased the overall viral load in infected people, yet it does not effectively eliminate the virus from all latent reservoirs. Although ART increased the life expectancy of infected individuals, it showed inconsistent improvement in CNS functioning, thus decreasing the quality of life. Research efforts have been dedicated to identifying common mechanisms through which HIV and drug abuse lead to neurotoxicity and CNS dysfunction. Therefore, in order to develop an effective treatment regimen to treat neurocognitive and related symptoms in HIV-infected patients, it is crucial to understand the involved mechanisms of neurotoxicity. Eventually, those mechanisms could lead the way to design and develop novel therapeutic strategies addressing both CNS HIV reservoir and illicit drug use by HIV patients.

Partial connectomes of labeled dopaminergic circuits reveal non-synaptic communication and axonal remodeling after exposure to cocaine

Dopaminergic (DA) neurons exert profound influences on behavior including addiction. However, how DA axons communicate with target neurons and how those communications change with drug exposure remains poorly understood. We leverage cell type-specific labeling with large volume serial electron microscopy to detail DA connections in the nucleus accumbens (NAc) of the mouse (Mus musculus) before and after exposure to cocaine. We find that individual DA axons contain different varicosity types based on their vesicle contents. Spatially ordering along individual axons further suggests that varicosity types are non-randomly organized. DA axon varicosities rarely make specific synapses (<2%, 6/410), but instead are more likely to form spinule-like structures (15%, 61/410) with neighboring neurons. Days after a brief exposure to cocaine, DA axons were extensively branched relative to controls, formed blind-ended 'bulbs' filled with mitochondria, and were surrounded by elaborated glia. Finally, mitochondrial lengths increased by ~2.2 times relative to control only in DA axons and NAc spiny dendrites after cocaine exposure. We conclude that DA axonal transmission is unlikely to be mediated via classical synapses in the NAc and that the major locus of anatomical plasticity of DA circuits after exposure to cocaine are large-scale axonal re-arrangements with correlated changes in mitochondria.

Role of hippocampal NF-κB and GluN2B in the memory acquisition impairment of experiences gathered prior to cocaine administration in rats

Cocaine can induce severe neurobehavioral changes, among others, the ones involved in learning and memory processes. It is known that during drug consumption, cocaine-associated memory and learning processes take place. However, much less is known about the effects of this drug upon the mechanisms involved in forgetting.The present report focuses on the mechanisms by which cocaine affects memory consolidation of experiences acquired prior to drug administration. We also study the involvement of hippocampus in these processes, with special interest on the role of Nuclear factor kappa B (NF-κB), N-methyl-D-aspartate glutamate receptor 2B (GluN2B), and their relationship with other proteins, such as cyclic AMP response element binding protein (CREB). For this purpose, we developed a rat experimental model of chronic cocaine administration in which spatial memory and the expression or activity of several proteins in the hippocampus were assessed after 36 days of drug administration. We report an impairment in memory acquisition of experiences gathered prior to cocaine administration, associated to an increase in GluN2B expression in the hippocampus. We also demonstrate a decrease in NF-κB activity, as well as in the expression of the active form of CREB, confirming the role of these transcription factors in the cocaine-induced memory impairment.

Activation of Antioxidant and Proteolytic Pathways in the Nigrostriatal Dopaminergic System After 3,4-Methylenedioxymethamphetamine Administration: Sex-Related Differences

3,4-Methylenedioxymethamphetamine (MDMA, “ecstasy”) is an amphetamine-related drug that may damage the dopaminergic nigrostriatal system. To investigate the mechanisms that sustain this toxic effect and ascertain their sex-dependence, we evaluated in the nigrostriatal system of MDMA-treated (4 × 20 mg/kg, 2 h apart) male and female mice the activity of superoxide dismutase (SOD), the gene expression of SOD type 1 and 2, together with SOD1/2 co-localization with tyrosine hydroxylase (TH)-positive neurons. In the same mice and brain areas, activity of glutathione peroxidase (GPx) and of β2/β5 subunits of the ubiquitin-proteasome system (UPS) were also evaluated. After MDMA, SOD1 increased in striatal TH-positive terminals, but not nigral neurons, of males and females, while SOD2 increased in striatal TH-positive terminals and nigral neurons of males only. Moreover, after MDMA, SOD1 gene expression increased in the midbrain of males and females, whereas SOD2 increased only in males. Finally, MDMA increased the SOD activity in the midbrain of females, without affecting GPx activity, decreased the β2/β5 activities in the striatum of males and the β2 activity in the midbrain of females. These results suggest that the mechanisms of MDMA-induced neurotoxic effects are sex-dependent and dopaminergic neurons of males could be more sensitive to SOD2- and UPS-mediated toxic effects.

Activation of proline metabolism maintains ATP levels during cocaine-induced polyADP-ribosylation

Cocaine is a commonly abused drug worldwide. Acute as well as repeated exposure to cocaine activates persistent cellular and molecular changes in the brain reward regions. The effects of cocaine are predominantly mediated via alterations in neuronal gene expression by chromatin remodeling. Poly(ADP-ribose) polymerase-1 (PARP-1) catalyzed PARylation of chromatin has been reported as an important regulator of cocaine-mediated gene expression. PARP-1 dependent ADP-ribosylation is an energy-dependent process. In this study, we investigated the cellular energy response to cocaine-induced upregulation of PARP-1 expression. Exposure of differentiated SH-SY5Y cells to varying concentrations of cocaine resulted in the induction of PARP-1 dependent PARylation of p53 tumor suppressor. Further analysis revealed that PARylation of p53 by cocaine treatment resulted in nuclear accumulation of p53. However, induction and nuclear accumulation of p53 did not correlate with neuronal apoptosis/cell death upon cocaine exposure. Interestingly, cocaine-induced p53 PARylation resulted in the induction of proline oxidase (POX)—a p53 responsive gene involved in cellular metabolism. Given that cocaine-induced p53 PARylation is an energy-dependent process, we observed that cocaine-induced PARP-1/p53/POX axes alters cellular energy metabolism. Accordingly, using pharmacological and genetic studies of PARP-1, p53, and POX, we demonstrated the contribution of POX in maintaining cellular energy during neuronal function. Collectively, these studies highlight activation of a novel metabolic pathway in response to cocaine treatment.

The role of mitochondria in cocaine addiction

The incidence of cocaine abuse is increasing especially in the U.K. where the rates are among the highest in Europe. In addition to its role as a psychostimulant, cocaine has profound effect on brain metabolism, impacting glycolysis and impairing oxidative phosphorylation. Cocaine exposure alters metabolic gene expression and protein networks in brain regions including the prefrontal cortex, the ventral tegmental area and the nucleus accumbens, the principal nuclei of the brain reward system. Here, we focus on how cocaine impacts mitochondrial function, in particular through alterations in electron transport chain function, reactive oxygen species (ROS) production and oxidative stress (OS), mitochondrial dynamics and mitophagy. Finally, we describe the impact of cocaine on brain energy metabolism in the developing brain following prenatal exposure. The plethora of mitochondrial functions altered following cocaine exposure suggest that therapies maintaining mitochondrial functional integrity may hold promise in mitigating cocaine pathology and addiction.

Single Low Dose of Cocaine-Structural Brain Injury Without Metabolic and Behavioral Changes

Chronic cocaine use has been shown to lead to neurotoxicity in rodents and humans, being associated with high morbidity and mortality rates. However, recreational use, which may lead to addictive behavior, is often neglected. This occurs, in part, due to the belief that exposure to low doses of cocaine comes with no brain damage risk. Cocaine addicts have shown glucose metabolism changes related to dopamine brain activity and reduced volume of striatal gray matter. This work aims to evaluate the morphological brain changes underlying metabolic and locomotor behavioral outcome, in response to a single low dose of cocaine in a pre-clinical study. In this context, a Balb-c mouse model has been chosen, and animals were injected with a single dose of cocaine (0.5 mg/kg). Control animals were injected with saline. A behavioral test, positron emission tomography (PET) imaging, and anatomopathological studies were conducted with this low dose of cocaine, to study functional, metabolic, and morphological brain changes, respectively. Animals exposed to this cocaine dose showed similar open field activity and brain metabolic activity as compared with controls. However, histological analysis showed alterations in the prefrontal cortex and hippocampus of mice exposed to cocaine. For the first time, it has been demonstrated that a single low dose of cocaine, which can cause no locomotor behavioral and brain metabolic changes, can induce structural damage. These brain changes must always be considered regardless of the dosage used. It is essential to alert the population even against the consumption of low doses of cocaine.

NLRP3 Inflammasome Blockade Reduces Cocaine-Induced Microglial Activation and Neuroinflammation

Cocaine use disorder is a major health crisis that is associated with increased oxidative stress and neuroinflammation. While the role of NLRP3 inflammasome in mediating neuroinflammation is well-recognized, whether cocaine induces this response remains unexplored. Based on the premise that cocaine induces both reactive oxygen species (ROS) as well as microglial activation, we hypothesized that cocaine-mediated microglial activation involves both ROS and NLRP3 signaling pathways. We examined activation of the NLRP3 pathway in microglia exposed to cocaine, followed by validation in mice administered either cocaine or saline for 7 days, with or without pretreatment with the NLRP3 inhibitor, MCC950, and in postmortem cortical brain tissues of chronic cocaine-dependent humans. We found that microglia exposed to cocaine exhibited significant induction of NLRP3 and mature IL-1β expression. Intriguingly, blockade of ROS (Tempol) attenuated cocaine-mediated priming of NLRP3 and microglial activation (CD11b). Blockade of NLRP3 by both pharmacological (MCC950) as well as gene silencing (siNLRP3) approaches underpinned the critical role of NLRP3 in cocaine-mediated activation of inflammasome and microglial activation. Pretreatment of mice with MCC950 followed by cocaine administration for 7 days mitigated cocaine-mediated upregulation of mature IL-1β and CD11b, in both the striatum and the cortical regions. Furthermore, cortical brain tissues of chronic cocaine-dependent humans also exhibited upregulated expression of the NLRP3 pathway mediators compared with non-cocaine dependent controls. Collectively, these findings suggest that cocaine activates microglia involving the NLRP3 inflammasome pathway, thereby contributing to neuroinflammation. NLRP3 can thus be considered as a potential therapeutic target for alleviating cocaine-mediated neuroinflammation.

Aspirin and N-acetylcysteine co-administration markedly inhibit chronic ethanol intake and block relapse binge drinking: Role of neuroinflammation-oxidative stress self-perpetuation

Chronic alcohol intake leads to neuroinflammation and cell injury, proposed to result in alterations that perpetuate alcohol intake and cued relapse. Studies show that brain oxidative stress is consistently associated with alcohol-induced neuroinflammation, and literature implies that oxidative stress and neuroinflammation perpetuate each other. In line with a self-perpetuating mechanism, it is hypothesized that inhibition of either oxidative stress or neuroinflammation could reduce chronic alcohol intake and relapse. The present study conducted on alcohol-preferring rats shows that chronic ethanol intake was inhibited by 50% to 55% by the oral administration of low doses of either the antioxidant N-acetylcysteine (40 mg/kg/d) or the anti-inflammatory aspirin (ASA; 15 mg/kg/d), while the co-administration of both dugs led to a 70% to 75% (P < .001) inhibition of chronic alcohol intake. Following chronic alcohol intake, a prolonged alcohol deprivation, and subsequent alcohol re-access, relapse drinking resulted in blood alcohol levels of 95 to 100 mg/dL in 60 minutes, which were reduced by 60% by either N-acetylcysteine or aspirin and by 85% by the co-administration of both drugs (blood alcohol: 10 to 15 mg/dL; P < .001). Alcohol intake either on the chronic phase or following deprivation and re-access led to a 50% reduction of cortical glutamate transporter GLT-1 levels, while aspirin administration fully returned GLT-1 to normal levels. N-acetylcysteine administration did not alter GLT-1 levels, while N-acetylcysteine may activate the cystine/glutamate transport xCT, presynaptically inhibiting relapse. Overall, the study suggests that a neuroinflammation/oxidative stress self-perpetuation cycle maintains chronic alcohol intake and relapse drinking. The co-administration of anti-inflammatory and antioxidant agents may have translational value in alcohol-use disorders.

HIV Neuropathogenesis in the Presence of a Disrupted Dopamine System

Antiretroviral therapy (ART) has transformed HIV into a chronic condition, lengthening and improving the lives of individuals living with this virus. Despite successful suppression of HIV replication, people living with HIV (PLWH) are susceptible to a growing number of comorbidities, including neuroHIV that results from infection of the central nervous system (CNS). Alterations in the dopaminergic system have long been associated with HIV infection of the CNS. Studies indicate that changes in dopamine concentrations not only alter neurotransmission, but also significantly impact the function of immune cells, contributing to neuroinflammation and neuronal dysfunction. Monocytes/macrophages, which are a major target for HIV in the CNS, are responsive to dopamine. Therefore, defining more precisely the mechanisms by which dopamine acts on these cells, and the changes in cellular function elicited by this neurotransmitter are necessary to develop therapeutic strategies to treat neuroHIV. This is especially important for vulnerable populations of PLWH with chemically altered dopamine concentrations, such as individuals with substance use disorder (SUD), or aging individuals using dopamine-altering medications. The specific neuropathologic and neurocognitive consequences of increased CNS dopamine remain unclear. This is due to the complex nature of HIV neuropathogenesis, and logistical and technical challenges that contribute to inconsistencies among cohort studies, animal models and in vitro studies, as well as lack of demographic data and access to human CNS samples and cells. This review summarizes current understanding of the impact of dopamine on HIV neuropathogenesis, and proposes new experimental approaches to examine the role of dopamine in CNS HIV infection. Graphical abstract HIV Neuropathogenesis in the Presence of a Disrupted Dopamine System. Both substance abuse disorders and the use of dopaminergic medications for age-related diseases are associated with changes in CNS dopamine concentrations and dopaminergic neurotransmission. These changes can lead to aberrant immune function, particularly in myeloid cells, which contributes to the neuroinflammation, neuropathology and dysfunctional neurotransmission observed in dopamine-rich regions in HIV+ individuals. These changes, which are seen despite the use antiretroviral therapy (ART), in turn lead to further dysregulation of the dopamine system. Thus, in individuals with elevated dopamine, the bi-directional interaction between aberrant dopaminergic neurotransmission and HIV infection creates a feedback loop contributing to HIV associated neurocognitive dysfunction and neuroHIV. However, the distinct contributions and interactions made by HIV infection, inflammatory mediators, ART, drugs of abuse, and age-related therapeutics are poorly understood. Defining more precisely the mechanisms by which these factors influence the development of neurological disease is critical to addressing the continued presence of neuroHIV in vulnerable populations, such as HIV-infected older adults or drug abusers. Due to the complexity of this system, understanding these effects will require a combination of novel experimental modalities in the context of ART. These will include more rigorous epidemiological studies, relevant animal models, and in vitro cellular and molecular mechanistic analysis.

Glutathione peroxidase-1 knockout potentiates behavioral sensitization induced by cocaine in mice via σ-1 receptor-mediated ERK signaling: A comparison with the case of glutathione peroxidase-1 overexpressing transgenic mice

We demonstrated that the gene of glutathione peroxidase-1 (GPx-1), a major antioxidant enzyme, is a potential protectant against the neurotoxicity and conditioned place preference induced by cocaine. Because the sigma (σ)-1 receptor is implicated in cocaine-induced drug dependence, we investigated whether the GPx-1 gene modulates the σ-1 receptor in the behavioral sensitization induced by cocaine. Cocaine-induced behavioral sensitization was more pronounced in GPx-1 knockout (KO) than wild-type (WT) mice and was less pronounced in GPx-1 overexpressing transgenic (GPx-1 TG) than non-TG mice. Cocaine treatment significantly enhanced the oxidative burden and reduced the GSH levels in the striatum of WT, GPx-1 KO, and non-TG mice but not in that of GPx-1 TG mice. In addition, cocaine significantly increased the nuclear translocation, its DNA binding activity of nuclear factor erythroid-2-related factor 2 (Nrf2) as well as the mRNA expression of γ-glutamylcysteine (GCL). The genetic depletion of GPx-1 inhibited the Nrf2-related glutathione system, whereas the genetic overexpression of GPx-1 activated this system against behavioral sensitization. BD1047, a σ-1 receptor antagonist, and U0126, an ERK inhibitor significantly induced the Nrf2-related antioxidant potential against behavioral sensitization. Unlike BD1047, U0126 did not affect the cocaine-induced σ-1 receptor immunoreactivity, suggesting that the σ-1 receptor is an upstream molecule for ERK signaling. Importantly, BD1047 and U0126 failed to affect the σ-1 receptor immunoreactivity and ERK phosphorylation induced by cocaine in GPx-1 TG mice. Our results suggest that GPx-1 is a critical mediator for the attenuation of cocaine-induced behavioral sensitization via modulating σ-1 receptor-mediated ERK activation by the induction of the Nrf2-related system.

Longitudinal patterns of illicit drug use, antiretroviral therapy exposure and plasma HIV-1 RNA viral load among HIV-positive people who use illicit drugs

OBJECTIVES

HIV-positive people who use illicit drugs (PWUD) experience elevated rates of HIV-associated morbidity and mortality compared with members of other key affected populations. Although suboptimal levels of access and adherence to antiretroviral therapy (ART) are common among HIV-positive PWUD, there is a need for studies investigating the possible biological impacts of noninjection illicit drug use among people living with HIV in real-world settings.

METHODS

We accessed data from the ACCESS study, an ongoing prospective cohort of illicit drug users with systematic HIV viral load monitoring in a setting with universal care and ART dispensation records. We used multivariable generalized linear mixed models to estimate the longitudinal associations between noninjection use of crack cocaine, powder cocaine, opioids, methamphetamine, cannabis and alcohol on plasma HIV-1 RNA viral load, adjusted for ART exposure and relevant confounders.

RESULTS

Between 2005 and 2018, 843 individuals from the ACCESS cohort were included and contributed to 8698 interviews. At baseline, the mean age was 43 years, 566 (67%) reported male sex and 659 (78%) used crack cocaine in the previous 6 months. In multivariable models adjusted for ART exposure, only crack cocaine use in the last 6 months was found to be significantly associated with higher HIV viral load.

CONCLUSION

We observed significantly higher HIV viral load during periods of crack cocaine use independent of ART exposure. Our findings support further research to investigate the possible biological mechanisms of this effect.

Effects of childhood trauma on BDNF and TBARS during crack-cocaine withdrawal

Objective:

To evaluate the association between childhood trauma (CT) and serum levels of brain-derived neurotrophic factor (BDNF) and thiobarbituric acid-reactive substances (TBARS) during crack-cocaine withdrawal.

Method:

Thirty-three male crack-cocaine users were recruited at admission to a public addiction treatment unit. Serum BDNF and TBARS levels were evaluated at intake and discharge. Information about drug use was assessed by the Addiction Severity Index-6th Version (ASI-6); CT was reported throughout the Childhood Trauma Questionnaire (CTQ). CTQ scores were calculated based on a latent analysis model that divided the sample into low-, medium-, and high-level trauma groups.

Results:

There was a significant increase in BDNF levels from admission to discharge, which did not differ across CT subgroups. For TBARS levels, we found a significant time vs. trauma interaction (F_2,28 = 6.357, p = 0.005,η_p² = 0.312). In participants with low trauma level, TBARS decreased, while in those with a high trauma level, TBARS increased during early withdrawal.

Conclusion:

TBARS levels showed opposite patterns of change in crack-cocaine withdrawal according to baseline CT. These results suggest that CT could be associated with more severe neurological impairment during withdrawal.

Angiotensin II modulates amphetamine-induced glial and brain vascular responses, and attention deficit via angiotensin type 1 receptor: Evidence from brain regional sensitivity to amphetamine

Amphetamine-induced neuroadaptations involve vascular damage, neuroinflammation, a hypo-functioning prefrontal cortex (PFC), and cognitive alterations. Brain angiotensin II, through angiotensin type 1 receptor (AT₁ -R), mediates oxidative/inflammatory responses, promoting endothelial dysfunction, neuronal oxidative damage and glial reactivity. The present work aims to unmask the role of AT₁ -R in the development of amphetamine-induced changes over glial and vascular components within PFC and hippocampus. Attention deficit was evaluated as a behavioral neuroadaptation induced by amphetamine. Brain microvessels were isolated to further evaluate vascular alterations after amphetamine exposure. Male Wistar rats were administered with AT₁ -R antagonist, candesartan, followed by repeated amphetamine. After one week drug-off period, animals received a saline or amphetamine challenge and were evaluated in behavioral tests. Afterward, their brains were processed for cresyl violet staining, CD11b (microglia marker), GFAP (astrocyte marker) or von Willebrand factor (vascular marker) immunohistochemistry, and oxidative/cellular stress determinations in brain microvessels. Statistical analysis was performed by using factorial ANOVA followed by Bonferroni or Tukey tests. Repeated amphetamine administration increased astroglial and microglial markers immunoreactivity, increased apoptotic cells, and promoted vascular network rearrangement at the PFC concomitantly with an attention deficit. Although the amphetamine challenge improved the attentional performance, it triggers detrimental effects probably because of the exacerbated malondialdehyde levels and increased heat shock protein 70 expression in microvessels. All observed amphetamine-induced alterations were prevented by the AT₁ -R blockade. Our results support the AT₁ -R involvement in the development of oxidative/inflammatory conditions triggered by amphetamine exposure, affecting cortical areas and increasing vascular susceptibility to future challenges.

The Sigma-1 Receptor: When Adaptive Regulation of Cell Electrical Activity Contributes to Stimulant Addiction and Cancer

The sigma-1 receptor (σ1R) is an endoplasmic reticulum (ER)-resident chaperone protein that acts like an inter-organelle signaling modulator. Among its several functions such as ER lipid metabolisms/transports and indirect regulation of genes transcription, one of its most intriguing feature is the ability to regulate the function and trafficking of a variety of functional proteins. To date, and directly relevant to the present review, σ1R has been found to regulate both voltage-gated ion channels (VGICs) belonging to distinct superfamilies (i.e., sodium, Na⁺; potassium, K⁺; and calcium, Ca²⁺ channels) and non-voltage-gated ion channels. This regulatory function endows σ1R with a powerful capability to fine tune cells’ electrical activity and calcium homeostasis—a regulatory power that appears to favor cell survival in pathological contexts such as stroke or neurodegenerative diseases. In this review, we present the current state of knowledge on σ1R’s role in the regulation of cellular electrical activity, and how this seemingly adaptive function can shift cell homeostasis and contribute to the development of very distinct chronic pathologies such as psychostimulant abuse and tumor cell growth in cancers.

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

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AEME and cocaine decreased GPx, GR and GST activities after 3 and 6 h of exposure.

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AEME and cocaine increased MDA after 48 h of exposure.

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AEME-cocaine combination decreased GPx, GR and GST activities after 3 and 6 h.

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AEME-cocaine combination showed an additive effect on MDA after 48 h of exposure.

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A higher neurotoxic effect after crack cocaine use is suggested.

Crack cocaine smokers inhale, alongside with cocaine, its pyrolysis product, anhydroecgonine methyl ester (AEME). We have previously described AEME neurotoxic effect and its additive effect when co-incubated with cocaine. Our aim was to evaluate, the effect of AEME, cocaine and AEME-cocaine combination on glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione S-transferase (GST) activities after 3 and 6 h of exposure, periods previous to neuronal death. Lipid peroxidation was evaluated through malonaldehyde (MDA) levels at 3, 6, 24 and 48 h of exposure. All treated groups reduced neuronal viability after 24 h of exposure. AEME and cocaine decreased GPx, GR and GST activities after 3 and 6 h, with an increase in MDA levels after 48 h. AEME-cocaine combination decreased the enzymes activities after 3 and 6 h, showing an additive effect in MDA levels after 48 h. These data show that the glutathione-related enzymes imbalance caused by AEME, cocaine or AEME-cocaine combination exposure preceded neuronal death and lipid peroxidation. Moreover, the additive effect on lipid peroxidation observed with AEME-cocaine exposure after 48 h, suggest a higher neurotoxic effect after crack cocaine use when compared to cocaine alone.

NAD+ cellular redox and SIRT1 regulate the diurnal rhythms of tyrosine hydroxylase and conditioned cocaine reward

The diurnal regulation of dopamine is important for normal physiology and diseases such as addiction. Here we find a novel role for the CLOCK protein to antagonize CREB-mediated transcriptional activity at the tyrosine hydroxylase (TH) promoter, which is mediated by the interaction with the metabolic sensing protein, Sirtuin 1 (SIRT1). Additionally, we demonstrate that the transcriptional activity of TH is modulated by the cellular redox state, and daily rhythms of redox balance in the ventral tegmental area (VTA), along with TH transcription, are highly disrupted following chronic cocaine administration. Furthermore, CLOCK and SIRT1 are important for regulating cocaine reward and dopaminergic (DAergic) activity, with interesting differences depending on whether DAergic activity is in a heightened state and if there is a functional CLOCK protein. Taken together, we find that rhythms in cellular metabolism and circadian proteins work together to regulate dopamine synthesis and the reward value for drugs of abuse.

Glutathione peroxidase-1 gene rescues cocaine-induced conditioned place preference in mice by inhibiting σ-1 receptor expression

The aim of this study was to investigate whether the glutathione peroxidase-1 gene (GPx-1) affects cocaine-induced conditioned place preference (CPP) using a mouse model. Cocaine-induced CPP was accompanied by an increase in the level of σ-1 receptor in the nucleus accumbens (NAc). This phenomenon was more pronounced in the GPx-1 gene knockout (GPx-1 KO) than in wild type (WT) mice. In contrast, the CPP and expression of σ-1 receptor were much less pronounced in GPx-1-overexpressing transgenic (GPx-1 TG) mice than non-transgenic (non-TG) mice. Treatment of the mice with BD1047, a σ-1 receptor antagonist, significantly attenuated both cocaine-induced CPP and c-Fos-immunoreactivity (c-Fos-IR) in WT and GPx-1 KO mice, although the effects were more evident in the latter group. Despite the protective effects of BD1047 on cocaine-induced CPP and c-Fos in non-TG mice, there were no additional protective effects in cocaine-treated GPx-1 TG mice, indicating that the σ-1 receptor is a critical target for GPx-1-mediated psychoprotective activity. Overall, our results suggest that GPx-1 attenuates cocaine-induced CPP via inhibition of σ-1 receptor expression.

Intranasal mesenchymal stem cell secretome administration markedly inhibits alcohol and nicotine self-administration and blocks relapse-intake: mechanism and translational options

BACKGROUND

Chronic consumption of most drugs of abuse leads to brain oxidative stress and neuroinflammation, which inhibit the glutamate transporter GLT-1, proposed to perpetuate drug intake. The present study aimed at inhibiting chronic ethanol and nicotine self-administration and relapse by the non-invasive intranasal administration of antioxidant and anti-inflammatory secretome generated by adipose tissue-derived activated mesenchymal stem cells. The anti-addiction mechanism of stem cell secretome is also addressed.

METHODS

Rats bred for their alcohol preference ingested alcohol chronically or were trained to self-administer nicotine. Secretome of human adipose tissue-derived activated mesenchymal stem cells was administered intranasally to animals, both (i) chronically consuming alcohol or nicotine and (ii) during a protracted deprivation before a drug re-access leading to relapse intake.

RESULTS

The intranasal administration of secretome derived from activated mesenchymal stem cells inhibited chronic self-administration of ethanol or nicotine by 85% and 75%, respectively. Secretome administration further inhibited by 85-90% the relapse "binge" intake that occurs after a protracted drug deprivation followed by a 60-min drug re-access. Secretome administration fully abolished the oxidative stress induced by chronic ethanol or nicotine self-administration, shown by the normalization of the hippocampal oxidized/reduced glutathione ratio, and the neuroinflammation determined by astrocyte and microglial immunofluorescence. Knockdown of the glutamate transporter GLT-1 by the intracerebral administration of an antisense oligonucleotide fully abolished the inhibitory effect of the secretome on ethanol and nicotine intake.

CONCLUSIONS

The non-invasive intranasal administration of secretome generated by human adipose tissue-derived activated mesenchymal stem cells markedly inhibits alcohol and nicotine self-administration, an effect mediated by the glutamate GLT-1 transporter. Translational implications are envisioned.

Drp1 Mitochondrial Fission in D1 Neurons Mediates Behavioral and Cellular Plasticity during Early Cocaine Abstinence

Altered brain energy homeostasis is a key adaptation occurring in the cocaine-addicted brain, but the effect of cocaine on the fundamental source of energy, mitochondria, is unknown. We demonstrate an increase of dynamin-related protein-1 (Drp1), the mitochondrial fission mediator, in nucleus accumbens (NAc) after repeated cocaine exposure and in cocaine-dependent individuals. Mdivi-1, a demonstrated fission inhibitor, blunts cocaine seeking and locomotor sensitization, while blocking c-Fos induction and excitatory input onto dopamine receptor-1 (D1) containing NAc medium spiny neurons (MSNs). Drp1 and fission promoting Drp1 are increased in D1-MSNs, consistent with increased smaller mitochondria in D1-MSN dendrites after repeated cocaine. Knockdown of Drp1 in D1-MSNs blocks drug seeking after cocaine self-administration, while enhancing the fission promoting Drp1 enhances seeking after long-term abstinence from cocaine. We demonstrate a role for altered mitochondrial fission in the NAc, during early cocaine abstinence, suggesting potential therapeutic treatment of disrupting mitochondrial fission in cocaine addiction.

Supraphysiologic-dose anabolic-androgenic steroid use: A risk factor for dementia?

Supraphysiologic-dose anabolic-androgenic steroid (AAS) use is associated with physiologic, cognitive, and brain abnormalities similar to those found in people at risk for developing Alzheimer's Disease and its related dementias (AD/ADRD), which are associated with high brain β-amyloid (Aβ) and hyperphosphorylated tau (tau-P) protein levels. Supraphysiologic-dose AAS induces androgen abnormalities and excess oxidative stress, which have been linked to increased and decreased expression or activity of proteins that synthesize and eliminate, respectively, Aβ and tau-P. Aβ and tau-P accumulation may begin soon after initiating supraphysiologic-dose AAS use, which typically occurs in the early 20s, and their accumulation may be accelerated by other psychoactive substance use, which is common among non-medical AAS users. Accordingly, the widespread use of supraphysiologic-dose AAS may increase the numbers of people who develop dementia. Early diagnosis and correction of sex-steroid level abnormalities and excess oxidative stress could attenuate risk for developing AD/ADRD in supraphysiologic-dose AAS users, in people with other substance use disorders, and in people with low sex-steroid levels or excess oxidative stress associated with aging.

A ketogenic diet diminishes behavioral responses to cocaine in young adult male and female rats

Ketogenic diets (KDs) are high fat, low carbohydrate formulations traditionally used to treat epilepsy; more recently, KDs have shown promise for a wide range of other neurological disorders. Drug addiction studies suggest that repeated exposure to drugs of abuse, including cocaine, results in a suite of neurobiological changes that includes neuroinflammation, decreased glucose metabolism, and disordered neurotransmission. Given that KDs positively regulate these factors, we addressed whether administration of a KD has potential as a novel therapy for drug addiction. In this study, male and female Sprague-Dawley rats were placed on a KD or a control diet (CD), beginning at five weeks of age and continuing through the end of behavioral testing. Three weeks after initiation of dietary treatments, rats received daily i.p. injections of cocaine (15 mg/kg) or saline vehicle for one week, were drug free for a subsequent week, and then all animals received a final challenge injection of 15 mg/kg cocaine. In the absence of cocaine injections, stereotyped locomotor responses were minimal and were unaffected by dietary treatment. In contrast, both males and females fed a KD exhibited decreased cocaine-induced stereotyped responses as compared to CD-fed rats. The sensitization of ambulatory responses was also disrupted in KD-fed rats. These results suggest that KDs directly impact dopamine-mediated behaviors, and hence may hold potential as a therapy for drug addiction.

The cellular basis of fetal endoplasmic reticulum stress and oxidative stress in drug-induced neurodevelopmental deficits

Prenatal substance exposure is a growing public health concern worldwide. Although the opioid crisis remains one of the most prevalent addiction problems in our society, abuse of cocaine, methamphetamines, and other illicit drugs, particularly amongst pregnant women, are nonetheless significant and widespread. Evidence demonstrates prenatal drug exposure can affect fetal brain development and thus can have long-lasting impact on neurobehavioral and cognitive performance later in life. In this review, we highlight research examining the most prevalent drugs of abuse and their effects on brain development with a focus on endoplasmic reticulum stress and oxidative stress signaling pathways. A thorough exploration of drug-induced cellular stress mechanisms during prenatal brain development may provide insight into therapeutic interventions to combat effects of prenatal drug exposure.

Astrocytic mobilization of glutathione peroxidase-1 contributes to the protective potential against cocaine kindling behaviors in mice via activation of JAK2/STAT3 signaling

Compelling evidence indicates that oxidative stress contributes to cocaine neurotoxicity. The present study was performed to elucidate the role of the glutathione peroxidase-1 (GPx-1) in cocaine-induced kindling (convulsive) behaviors in mice. Cocaine-induced convulsive behaviors significantly increased GPx-1, p-IkB, and p-JAK2/STAT3 expression, and oxidative burdens in the hippocampus of mice. There was no significant difference in cocaine-induced p-IkB expression between non-transgenic (non-TG) and GPx-1 overexpressing transgenic (GPx-1 TG) mice, but significant differences were observed in cocaine-induced p-JAK2/STAT3 expression and oxidative stress between non-TG and GPx-1 TG mice. Cocaine-induced glial fibrillary acidic protein (GFAP)-labeled astrocytic level was significantly higher in the hippocampus of GPx-1 TG mice. Triple-labeling immunocytochemistry indicated that GPx-1-, p-STAT3-, and GFAP-immunoreactivities were co-localized in the same cells. AG490, a JAK2/STAT3 inhibitor, but not pyrrolidone dithiocarbamate, an NFκB inhibitor, significantly counteracted GPx-1-mediated protective potentials (i.e., anticonvulsant-, antioxidant-, antiapoptotic-effects). Genetic overexpression of GPx-1 significantly attenuated proliferation of Iba-1-labeled microglia induced by cocaine in mice. However, AG490 or astrocytic inhibition (by GFAP antisense oligonucleotide and α-aminoadipate) significantly increased Iba-1-labeled microglial activity and M1 phenotype microglial mRNA levels, reflecting that proinflammatory potentials were mediated by AG490 or astrocytic inhibition. This microglial activation was less pronounced in GPx-1 TG than in non-TG mice. Furthermore, either AG490 or astrocytic inhibition significantly counteracted GPx-1-mediated protective potentials. Therefore, our results suggest that astrocytic modulation between GPx-1 and JAK2/STAT3 might be one of the underlying mechanisms for protecting against convulsive neurotoxicity induced by cocaine.

Cocaine Exposure Modulates Perineuronal Nets and Synaptic Excitability of Fast-Spiking Interneurons in the Medial Prefrontal Cortex

We previously reported that perineuronal nets (PNNs) are required for cocaine-associated memories. Perineuronal nets are extracellular matrix that primarily surrounds parvalbumin (PV)-containing, GABAergic fast-spiking interneurons (FSIs) in the medial prefrontal cortex (mPFC). Here we measured the impact of acute (1 d) or repeated (5 d) cocaine exposure on PNNs and PV cells within the prelimbic and infralimbic regions of the mPFC. Adult rats were exposed to 1 or 5 d of cocaine and stained for PNNs (using Wisteria floribunda agglutinin) and PV intensity 2 or 24 h later. In the prelimbic and infralimbic PFC, PNN staining intensity decreased 2 h after 1 d of cocaine exposure but increased after 5 d of cocaine exposure. Cocaine also produced changes in PV intensity, which generally lagged behind that of PNNs. In the prelimbic PFC, both 1 and 5 d of cocaine exposure increased GAD65/67 puncta near PNN-surrounded PV cells, with an increase in the GAD65/67-to-VGluT1 puncta ratio after 5 d of cocaine exposure. In the prelimbic PFC, slice electrophysiology studies in FSIs surrounded by PNNs revealed that both 1 and 5 d of cocaine exposure reduced the number of action potentials 2 h later. Synaptic changes demonstrated that 5 d of cocaine exposure increased the inhibition of FSIs, potentially reducing the inhibition of pyramidal neurons and contributing to their hyperexcitability during relapse behavior. These early and rapid responses to cocaine may alter the network stability of PV FSIs that partially mediate the persistent and chronic nature of drug addiction.

Targeting redox regulation to treat substance use disorder using N‐acetylcysteine

Substance use disorder (SUD) is a chronic relapsing disorder characterized by transitioning from acute drug reward to compulsive drug use. Despite the heavy personal and societal burden of SUDs, current treatments are limited and unsatisfactory. For this reason, a deeper understanding of the mechanisms underlying addiction is required. Altered redox status, primarily due to drug-induced increases in dopamine metabolism, is a unifying feature of abused substances. In recent years, knowledge of the effects of oxidative stress in the nervous system has evolved from strictly neurotoxic to include a more nuanced role in redox-sensitive signaling. More specifically, S-glutathionylation, a redox-sensitive post-translational modification, has been suggested to influence the response to drugs of abuse. In this review we will examine the evidence for redox-mediating drugs as therapeutic tools focusing on N-acetylcysteine as a treatment for cocaine addiction. We will conclude by suggesting future research directions that may further advance this field.

Efavirenz exposure, alone and in combination with known drugs of abuse, engenders addictive-like bio-behavioural changes in rats

Efavirenz is abused in a cannabis-containing mixture known as Nyaope. The addictive-like effects of efavirenz (5, 10 and 20 mg/kg) was explored using conditioned place preference (CPP) in rats following sub-acute exposure vs. methamphetamine (MA; 1 mg/kg) and Δ⁹-tetrahydrocannabinol (THC; 0.75 mg/kg). The most addictive dose of efavirenz was then compared to THC alone and THC plus efavirenz following sub-chronic exposure using multiple behavioural measures, viz. CPP, sucrose preference test (SPT) and locomotor activity. Peripheral superoxide dismutase (SOD), regional brain lipid peroxidation and monoamines were also determined. Sub-acute efavirenz (5 mg/kg) had a significant rewarding effect in the CPP comparable to MA and THC. Sub-chronic efavirenz (5 mg/kg) and THC + efavirenz were equally rewarding using CPP, with increased cortico-striatal dopamine (DA), and increased lipid peroxidation and SOD. Sub-chronic THC did not produce CPP but significantly increased SOD and decreased hippocampal DA. Sub-chronic THC + efavirenz was hedonic in the SPT and superior to THC alone regarding cortico-striatal lipid peroxidation and sucrose preference. THC + efavirenz increased cortico-striatal DA and decreased serotonin (5-HT). Concluding, efavirenz has dose-dependent rewarding effects, increases oxidative stress and alters regional brain monoamines. Efavirenz is hedonic when combined with THC, highlighting its abuse potential when combined with THC.

Cocaine evokes a profile of oxidative stress and impacts innate antiviral response pathways in astrocytes

HIV-1 and Zika virus (ZIKV) represent RNA viruses with neurotropic characteristics. Infected individuals suffer neurocognitive disorders aggravated by environmental toxins, including drugs of abuse such as cocaine, exacerbating HIV-associated neurocognitive disorders through a combination of astrogliosis, oxidative stress and innate immune signaling; however, little is known about how cocaine impacts the progression of ZIKV neural perturbations. Impaired innate immune signaling is characterized by weakened antiviral activation of interferon signaling and alterations in inflammatory signaling, factors contributing to cognitive sequela associated with cocaine in HIV-1/ZIKV infection. We employed cellular/molecular biology techniques to test if cocaine suppresses the efficacy of astrocytes to initiate a Type 1 interferon response to HIV-1/ZIKV, in vitro. We found cocaine activated antiviral signaling pathways and type I interferon in the absence of inflammation. Cocaine pre-exposure suppressed antiviral responses to HIV-1/ZIKV, triggering antiviral signaling and phosphorylation of interferon regulatory transcription factor 3 to stimulate type I interferon gene transcription. Our data indicate that oxidative stress is a major driver of cocaine-mediated astrocyte antiviral immune responses. Although astrocyte antiviral signaling is activated following detection of foreign pathogenic material, oxidative stress and increased cytosolic double-stranded DNA (dsDNA) can drive antiviral signaling via stimulation of pattern recognition receptors. Pretreatment with the glial modulators propentofylline (PPF) or pioglitazone (PIO) reversed cocaine-mediated attenuation of astrocyte responses to HIV-1/ZIKV. Both PPF/PIO protected against cocaine-mediated generation of reactive oxygen species (ROS), increased dsDNA, antiviral signaling pathways and increased type I interferon, indicating that cocaine induces astrocyte type I interferon signaling in the absence of virus and oxidative stress is a major driver of cocaine-mediated astrocyte antiviral immunity. Lastly, PPF and PIO have therapeutic potential to ameliorate cocaine-mediated dysregulation of astrocyte antiviral immunity possibly via a myriad of protective actions including decreases in reactive phenotype and damaging immune factors.

Identification of biochemical and cytotoxic markers in cocaine treated PC12 cells

Cocaine is one of the powerful addictive drugs, widely abused in most Western countries. Because of high lipophilic nature, cocaine easily reaches various domains of the central nervous system (CNS) and triggers different levels of cellular toxicity. The aim of this investigation was to reproduce cocaine toxicity in differentiated PC12 cells through quantitative knowledge on biochemical and cytotoxicity markers. We differentiated the cells with 0.1 μg/ml nerve growth factor (NGF) for 5 days, followed by treatment with cocaine for 48 h at in vivo and in vitro concentrations. Results indicated that cocaine at in vivo concentrations neither killed the cells nor altered the morphology, but decreased the mitochondrial membrane potential that paralleled with increased lactate and glutathione (GSH) levels. On the other hand, cocaine at in vitro concentrations damaged the neurites and caused cell death, which corresponded with increased reactive oxygen species (ROS) generation, plasma membrane damage, and GSH depletion with no detectable nitric oxide (NO) level. While direct understanding of cocaine and cell interaction under in vivo animal models is impeded due to high complexity, our present in vitro results assisted in understanding the onset of some key events of neurodegenerative diseases in cocaine treated neuronal cells.

HMG-CoA synthase 2 drives brain metabolic reprogramming in cocaine exposure

The brain is a high energy-consuming organ that typically utilizes glucose as the main energy source for cerebral activity. When glucose becomes scarce under conditions of stress, ketone bodies, such as β-hydroxybutyrate, acetoacetate and acetone, become extremely important. Alterations in brain energy metabolism have been observed in psychostimulant abusers; however, the mode of brain metabolic programming in cocaine dependence remains largely unknown. Here, we profiled the metabolites and metabolic enzymes from brain nucleus accumbens (NAc) of mice exposed to cocaine. We found that cocaine modified energy metabolism and markedly activated ketogenesis pathway in the NAc. The expression of HMG-CoA synthase 2 (HMGCS2), a critical rate-limiting ketogenesis enzyme, was markedly up-regulated. After switching metabolic pathways from ketogenesis to glycolysis through activation of glucokinase, cocaine-evoked metabolic reprogramming regained homeostasis, and the cocaine effect was attenuated. Importantly, both the pharmacological and genetic inhibition of HMGCS2 significantly suppressed cocaine-induced ketogenesis and behavior. In conclusion, cocaine induces a remarkable energy reprogramming in the NAc, which is characterized by HMGCS2-driven ketogenesis. Such effect may facilitate adaptations to cocaine-induced energy stress in the brain. Our findings establish an important link between drug-induced energy reprogramming and cocaine effect, and may have implication in the treatment of cocaine addiction.

Chronic treatment with Tempol during acquisition or withdrawal from CPP abolishes the expression of cocaine reward and diminishes oxidative damage

In previous studies, we reported that pretreatment with the antioxidant Tempol attenuated the development and expression of cocaine-induced psychomotor sensitization in rats and diminished cocaine-induced oxidative stress (OS) in the prefrontal cortex (PFC) and nucleus accumbens (NAc), suggesting a potential role for Tempol in interfering with cocaine-related psychomotor sensitization. The aim of the current study was to examine the role of Tempol in reward and reinforcement using the conditioned place preference (CPP) paradigm. We found that administration of Tempol during the conditioning session abolished the expression of cocaine-induced CPP. We also found that OS was significantly elevated following the establishment of CPP, and that cocaine-induced OS was significantly diminished by pretreatment with Tempol during conditioning. Furthermore, we found that repeated, but not single, administration of Tempol for seven days during withdrawal from CPP resulted in significant attenuation in the expression of CPP. Moreover, Tempol did not affect the expression of food reward. Taken together, these findings provide evidence for the involvement of Tempol in regulating cocaine rewarding properties without affecting natural rewards. Since Tempol was found to be effective in reducing OS and expression of CPP following withdrawal, it may be a potential treatment for cocaine addiction.

Casting a Wide Net: Role of Perineuronal Nets in Neural Plasticity

Perineuronal nets (PNNs) are unique extracellular matrix structures that wrap around certain neurons in the CNS during development and control plasticity in the adult CNS. They appear to contribute to a wide range of diseases/disorders of the brain, are involved in recovery from spinal cord injury, and are altered during aging, learning and memory, and after exposure to drugs of abuse. Here the focus is on how a major component of PNNs, chondroitin sulfate proteoglycans, control plasticity, and on the role of PNNs in memory in normal aging, in a tauopathy model of Alzheimer's disease, and in drug addiction. Also discussed is how altered extracellular matrix/PNN formation during development may produce synaptic pathology associated with schizophrenia, bipolar disorder, major depression, and autism spectrum disorders. Understanding the molecular underpinnings of how PNNs are altered in normal physiology and disease will offer insights into new treatment approaches for these diseases.

The Alterations in Mitochondrial DNA Copy Number and Nuclear-Encoded Mitochondrial Genes in Rat Brain Structures after Cocaine Self-Administration

The repeated intake of cocaine evokes oxidative stress that is present even during drug withdrawal. Recent studies demonstrate that cocaine-induced oxidative and/or endoplasmic reticulum stress can affect mitochondrial function and dynamics as well as the expression of mitochondrial and nuclear genes. These alterations in mitochondrial function may determine synaptic and behavioral plasticity. Mitochondria and mitochondrial DNA (mtDNA) seem to play an important role in the initiation of drug addiction. We used a microarray approach to investigate the expression patterns of nuclear-encoded genes relevant for mitochondrial functions and quantitative real-time PCR assays to determine the numbers of copies of mtDNA and of mRNAs corresponding to two mitochondrial proteins in the prefrontal cortex and hippocampus of rats during early cocaine abstinence. We found a significant elevation in the copy number of mtDNA and concomitant increased expression of mitochondrial genes. Moreover, microarray analysis revealed changes in the transcription of nuclear genes engaged in mtDNA replication, nucleoid formation, the oxidative phosphorylation pathway, and mitochondrial fission and fusion. Finally, we observed the upregulation of endoplasmic reticulum stress-induced genes. Cocaine self-administration influences the expression of both nuclear and mitochondrial genes as well as mtDNA replication. To determine whether these alterations serve as compensatory mechanisms to help maintain normal level of ATP production, further studies are necessary.