N-acetylcysteine decreased nicotine reward-like properties and withdrawal in mice

N-acetylcysteine for smoking cessation among dual users of tobacco and cannabis: Protocol and rationale for a randomized controlled trial

BACKGROUND

Tobacco and cannabis co-use is a growing public health problem. The synergistic effects of cannabis and nicotine on neurobiological systems that mediate reward and shared environmental cues reinforcing use may make tobacco smoking cessation more difficult. N-acetylcysteine (NAC), an FDA-approved medication and over-the-counter supplement, has shown promise in animal studies and randomized controlled trials (RCTs) in reducing tobacco and cannabis craving and use. NAC's potential efficacy in treating addiction may be attributable to its central nervous system effects in reducing excessive glutamatergic activity, oxidative stress, and inflammation. To date, no RCT has examined NAC for smoking cessation among dual users of tobacco and cannabis.

METHOD

In a double-blind, placebo-controlled RCT, we will examine NAC for smoking cessation among dual users of tobacco and cannabis. Sixty adult cigarette-cannabis co-users are randomized to receive NAC 3600 mg per day or placebo over 8 weeks. Participants in both groups receive 8 weekly cognitive behavioral therapy sessions addressing smoking cessation and cannabis reduction. Outcomes are assessed at Weeks 0, 4, 8, and 12. Primary aims are to determine NAC's efficacy in decreasing cigarette craving, nicotine dependence, and use; and cannabis craving and use. Exploratory aims include examination of changes in neurocognition with NAC and their potential mediational effects on cigarette and cannabis use outcomes.

CONCLUSION

Results will inform smoking cessation treatment among dual users of tobacco and cannabis.

CLINICALTRIALS

gov Identifier: NCT04627922.

The Potential of N-Acetyl-L-Cysteine (NAC) in the Treatment of Psychiatric Disorders

N-acetyl-L-cysteine (NAC) is a compound of increasing interest in the treatment of psychiatric disorders. Primarily through its antioxidant, anti-inflammatory, and glutamate modulation activity, NAC has been investigated in the treatment of neurodevelopmental disorders, schizophrenia spectrum disorders, bipolar-related disorders, depressive disorders, anxiety disorders, obsessive compulsive-related disorders, substance-use disorders, neurocognitive disorders, and chronic pain. Whilst there is ample preclinical evidence and theoretical justification for the use of NAC in the treatment of multiple psychiatric disorders, clinical trials in most disorders have yielded mixed results. However, most studies have been underpowered and perhaps too brief, with some evidence of benefit only after months of treatment with NAC. Currently NAC has the most evidence of having a beneficial effect as an adjuvant agent in the negative symptoms of schizophrenia, severe autism, depression, and obsessive compulsive and related disorders. Future research with well-powered studies that are of sufficient length will be critical to better understand the utility of NAC in the treatment of psychiatric disorders.

Systemic administration of N-acetylcysteine during the extinction period and on the reinstatement day decreased the maintenance of morphine rewarding properties in the rats

Many animal studies and early clinical trials suggested that N-acetylcysteine (NAC) may benefit addiction treatment. The present study tried to evaluate whether chronic administration of systemic NAC during the extinction period and acute administration of systemic NAC on the reinstatement day could reduce the maintenance of the morphine rewarding properties in the conditioned place preference (CPP) paradigm in the rats. Ninety-six adult male Wistar rats (190-220 g) were examined with morphine (7 mg/kg; sc) and saline (1 mL/kg; sc) during the 3-day conditioning phase in the CPP paradigm. After the acquisition of morphine CPP, different doses of NAC were daily administered during the extinction period (5, 10, 25, and 50 mg/kg; ip), or 30 min before the CPP test on the reinstatement day (2, 5, 10, 25, and 50 mg/kg; ip). Conditioning score and locomotor activity were recorded by the video tracking system and Ethovision software after acquisition on the post-conditioning day, the extinction period, and reinstatement day. Daily NAC administration in high doses (25 and 50 mg/kg; ip) reduced extinction-responding compared with the vehicle-control group during the extinction period. Although a single injection of NAC in doses 10, 25, 50 mg/kg decreased the reinstatement of morphine-induced CPP, two lower doses (2 and 5 mg/kg) could not significantly reduce the CPP scores. These are the first data suggesting that NAC's application during the extinction period could attenuate the morphine reward-associated behaviors in the rats. Moreover, NAC could inhibit the reinstatement of morphine CPP, which adds to the growing appreciation that the NAC may have potential therapeutic use in combating morphine dependence. It can be consistent with the hypothesis of the involvement of the glutamatergic system in the pathophysiology of addiction.

N-acetylcysteine in substance use disorder: a lesson from preclinical and clinical research

Substance use disorder (SUD) is a chronic brain condition, with compulsive and uncontrollable drug-seeking that leads to long-lasting and harmful consequences. The factors contributing to the development of SUD, as well as its treatment settings, are not fully understood. Alterations in brain glutamate homeostasis in humans and animals implicate a key role of this neurotransmitter in SUD, while the modulation of glutamate transporters has been pointed as a new strategy to diminish the excitatory glutamatergic transmission observed after drugs of abuse. N-acetylcysteine (NAC), known as a safe mucolytic agent, is involved in the regulation of this system and may be taken into account as a novel pharmacotherapy for SUD. In this paper, we summarize the current knowledge on the ability of NAC to reduce drug-seeking behavior induced by psychostimulants, opioids, cannabinoids, nicotine, and alcohol in animals and humans. Preclinical studies showed a beneficial effect in animal models of SUD, while the clinical efficacy of NAC has not been fully established. In summary, NAC will be a small add-on to usual treatment and/or psychotherapy for SUD, however, further studies are required.

N-acetylcysteine as a new prominent approach for treating psychiatric disorders

N-acetylcysteine (NAC) is a well-known and safe mucolytic agent, also used in patients with paracetamol overdose. In addition to these effects, recent preclinical and clinical studies have shown that NAC exerts beneficial effects on different psychiatric disorders. Many potential mechanisms have been proposed to underlie the therapeutic effects of NAC, including the regulation of several neurotransmitters, oxidative homeostasis, and inflammatory mediators. In this paper, we summarize the current knowledge on the ability of NAC to ameliorate symptoms and neuropathologies related to different psychiatric disorders, including attention deficit hyperactivity disorder, anxiety, bipolar disorder, depression, obsessive-compulsive disorder, obsessive-compulsive-related disorder, posttraumatic stress disorder, and schizophrenia. Although preclinical studies have shown a positive effect of NAC on animal models of psychiatric disorders, the clinical efficacy of NAC is not fully established. NAC remains a strong candidate for adjunct treatment for many psychiatric disorders, but additional preclinical and clinical studies are needed.

Neurodevelopmental signatures of narcotic and neuropsychiatric risk factors in 3D human-derived forebrain organoids

It is widely accepted that narcotic use during pregnancy and specific environmental factors (e.g., maternal immune activation and chronic stress) may increase risk of neuropsychiatric illness in offspring. However, little progress has been made in defining human-specific in utero neurodevelopmental pathology due to ethical and technical challenges associated with accessing human prenatal brain tissue. Here we utilized human induced pluripotent stem cells (hiPSCs) to generate reproducible organoids that recapitulate dorsal forebrain development including early corticogenesis. We systemically exposed organoid samples to chemically defined "enviromimetic" compounds to examine the developmental effects of various narcotic and neuropsychiatric-related risk factors within tissue of human origin. In tandem experiments conducted in parallel, we modeled exposure to opiates (μ-opioid agonist endomorphin), cannabinoids (WIN 55,212-2), alcohol (ethanol), smoking (nicotine), chronic stress (human cortisol), and maternal immune activation (human Interleukin-17a; IL17a). Human-derived dorsal forebrain organoids were consequently analyzed via an array of unbiased and high-throughput analytical approaches, including state-of-the-art TMT-16plex liquid chromatography/mass-spectrometry (LC/MS) proteomics, hybrid MS metabolomics, and flow cytometry panels to determine cell-cycle dynamics and rates of cell death. This pipeline subsequently revealed both common and unique proteome, reactome, and metabolome alterations as a consequence of enviromimetic modeling of narcotic use and neuropsychiatric-related risk factors in tissue of human origin. However, of our 6 treatment groups, human-derived organoids treated with the cannabinoid agonist WIN 55,212-2 exhibited the least convergence of all groups. Single-cell analysis revealed that WIN 55,212-2 increased DNA fragmentation, an indicator of apoptosis, in human-derived dorsal forebrain organoids. We subsequently confirmed induction of DNA damage and apoptosis by WIN 55,212-2 within 3D human-derived dorsal forebrain organoids. Lastly, in a BrdU pulse-chase neocortical neurogenesis paradigm, we identified that WIN 55,212-2 was the only enviromimetic treatment to disrupt newborn neuron numbers within human-derived dorsal forebrain organoids. Cumulatively this study serves as both a resource and foundation from which human 3D biologics can be used to resolve the non-genomic effects of neuropsychiatric risk factors under controlled laboratory conditions. While synthetic cannabinoids can differ from naturally occurring compounds in their effects, our data nonetheless suggests that exposure to WIN 55,212-2 elicits neurotoxicity within human-derived developing forebrain tissue. These human-derived data therefore support the long-standing belief that maternal use of cannabinoids may require caution so to avoid any potential neurodevelopmental effects upon developing offspring in utero.

Effects of N-acetylcysteine treatment on ethanol's rewarding properties and dopaminergic alterations in mesocorticolimbic and nigrostriatal pathways

Recent reports have shown that N-acetylcysteine (N-AC) has beneficial effects in the treatment of cocaine and nicotine abuse. Considering the similar neurobiologic mechanisms involved in the development of addiction to different drugs, N-AC treatment could be useful in the treatment of ethanol abuse. The rewarding properties of the drugs of abuse plays an important role in the development of addiction and can be studied using the conditioned place preference (CPP) paradigm. Thus, to study the effects of N-AC treatment in the rewarding effects of ethanol, we investigated the effects of N-AC administration in the ethanol-induced CPP and neurochemical alterations within the mesocorticolimbic and the nigrostriatal dopaminergic pathways. Adult male Swiss mice were pretreated with N-AC (60 or 120 mg/kg intraperitoneal) and tested for the development, expression, or extinction of the ethanol-induced CPP. Another cohort of animals received N-AC (60 or 120 mg/kg intraperitoneal) 2-h before an acute administration of ethanol and had their brains removed for dopamine and its metabolites quantification in the mesocorticolimbic and nigrostriatal pathways. Pretreatment with N-AC (120 mg/kg) blocked the development of ethanol-induced CPP. On the other hand, N-AC at both doses did not alter the expression nor the extinction of ethanol-induced CPP. N-AC increased 3,4-dihydroxyphenylacetic acid content in the medial prefrontal cortex and dopaminergic turnover within the substantia nigra. Besides that, there was an increase in dopamine content in the nucleus accumbens of ethanol-treated animals. In summary, N-AC treatment blocked the development of ethanol CPP, without altering ethanol effects on dopaminergic neurotransmission.

Glial cells as therapeutic targets for smoking cessation

Smoking remains the leading cause of morbidity and mortality in the United States, with less than 5% of smokers attempting to quit succeeding. This low smoking cessation success rate is thought to be due to the long-term adaptations and alterations in synaptic plasticity that occur following chronic nicotine exposure and withdrawal. Glial cells have recently emerged as active players in the development of dependence phenotypes due to their roles in modulating neuronal functions and synaptic plasticity. Fundamental studies have demonstrated that microglia and astrocytes are crucial for synapse formation and elimination in the developing brain, likely contributing to why glial dysfunction is implicated in numerous neurological and psychiatric disorders. Recently, there is increasing evidence for the involvement of glial cells in drug dependence and its associated behavioral manifestations. This review summarizes the newly evaluated role of microglia and astrocytes as molecular drivers of nicotine dependence and withdrawal phenotypes. This article is part of the special issue on 'Contemporary Advances in Nicotine Neuropharmacology.

The role of the metabotropic glutamate receptor 5 in nicotine addiction

This review summarizes the evidence for the potential involvement of metabotropic glutamate receptor 5 (mGluR5) in the development of nicotine addiction. Nicotine is consumed worldwide and is highly addictive. Previous research has extensively investigated the role of dopamine in association with reward learning and addiction, which has provided strong evidence for the involvement of dopaminergic neuronal circuitry in nicotine addiction. More recently, researchers focused on glutamatergic transmission after nicotine abuse, and its involvement in the reinforcing and rewarding effects of nicotine addiction. A number of robust preclinical and clinical studies have shown mGluR5 signaling as a facilitating mechanism of nicotine addiction and nicotine withdrawal. Specifically, clinical studies have illustrated lower cortical mGluR5 density in smokers compared to nonsmokers in the human brain. In addition, mGluR5 might selectively regulate craving and withdrawal. This suggests that mGluR5 could be a key receptor in the development of nicotine addiction and therefore clinical trials to examine the therapeutic potential of mGluR5 agents could help to contribute to reduce nicotine addiction in society.

Potential of Glial Cell Modulators in the Management of Substance Use Disorders

The pervasive and devastating nature of substance use disorders underlies the need for the continued development of novel pharmacotherapies. We now know that glia play a much greater role in neuronal processes than once believed.  The various types of glial cells (e.g., astrocytes, microglial, oligodendrocytes) participate in numerous functions that are crucial to healthy central nervous system function. Drugs of abuse have been shown to interact with glia in ways that directly contribute to the pharmacodynamic effects responsible for their abuse potential. Through their effect upon glia, drugs of abuse also alter brain function resulting in behavioral changes associated with substance use disorders. Therefore, drug-induced changes in glia and inflammation within the central nervous system (neuroinflammation) have been investigated to treat various aspects of drug abuse and dependence. This article presents a brief overview of the effects of each of the major classes of addictive drugs on glia. Next, the paper reviews the pre-clinical and clinical studies assessing the effects that glial modulators have on abuse-related behavioral effects, such as pleasure, withdrawal, and motivation. There is a strong body of pre-clinical literature demonstrating the general effectiveness of several glia-modulating drugs in models of reward and relapse. Clinical studies have also yielded promising results, though not as robust. There is still much to disentangle regarding the integration between addictive drugs and glial cells. Improved understanding of the relationship between glia and the pathophysiology of drug abuse should allow for more precise exploration in the development and testing of glial-directed treatments for substance use disorders.

Behavioral effects of psychostimulants in mutant mice with cell-type specific deletion of CB2 cannabinoid receptors in dopamine neurons

Activation of the endocannabinoid system modulate dopaminergic pathways that are involved in the effects of psychostimulants including amphetamine, cocaine, nicotine and other drugs of abuse. Genetic deletion or pharmacological activation of CB2 cannabinoid receptor is involved in the modulation of the effects of psychostimulants and their rewarding properties. Here we report on the behavioral effects of psychostimulants in DAT-Cnr2 conditional knockout (cKO) mice with selective deletion of type 2 cannabinoid receptors in dopamine neurons. There was enhanced psychostimulant induced hyperactivity in DAT-Cnr2 cKO mice, but the psychostimulant-induced sensitization was absent in DAT-Cnr2 cKO compared to the WT mice. Intriguingly, lower doses of amphetamine reduced locomotor activity of the DAT-Cnr2 cKO mice. While cocaine, amphetamine and methamphetamine produced robust conditioned place preference (CPP) in both DAT-Cnr2 cKO and WT mice, nicotine at the dose used induced CPP only in the WT but not in the DAT-Cn2 cKO mice. However, pre-treatment with the CB2R selective agonist JWH133, blocked cocaine and nicotine induced CPP in the WT mice. The deletion of CB2Rs in dopamine neurons modified the levels of tyrosine hydroxylase, and reduced the expression of dopamine transporter gene expression in DAT-Cnr2 cKO midbrain region. Taken together, our data suggest that CB2Rs play a role in the modulation of dopamine-related effects of psychostimulants and could be exploited as therapeutic target in psychostimulant addiction and other psychiatric disorders associated with dopamine dysregulation.

Animal Models of Addiction and Neuropsychiatric Disorders and Their Role in Drug Discovery: Honoring the Legacy of Athina Markou

Each of the co-authors worked with Athina Markou, at different stages of our careers and in different capacities, to develop, optimize, and use animal models of drug addiction and, more generally, mental health disorders such as anxiety, depression, and schizophrenia. Here, we briefly summarize some of our work with Athina, primarily involving the use of the intracranial self-stimulation and intravenous drug self-administration procedures. This work established that excessive consumption of addictive drugs can induce profound dysfunction in brain reward circuits. Such drug-induced reward deficits are likely to play a key role in precipitating the emergence of compulsive drug-seeking behaviors. We also summarize findings suggesting that perturbations in glutamatergic transmission contribute to brain reward deficits in drug-dependent animals and that metabotropic glutamate receptors are potential targets for the development of novel medications to facilitate long-term drug abstinence and prevention of relapse.

Acquisition, Maintenance and Relapse-Like Alcohol Drinking: Lessons from the UChB Rat Line

This review article addresses the biological factors that influence: (i) the acquisition of alcohol intake; (ii) the maintenance of chronic alcohol intake; and (iii) alcohol relapse-like drinking behavior in animals bred for their high-ethanol intake. Data from several rat strains/lines strongly suggest that catalase-mediated brain oxidation of ethanol into acetaldehyde is an absolute requirement (up 80%–95%) for rats to display ethanol’s reinforcing effects and to initiate chronic ethanol intake. Acetaldehyde binds non-enzymatically to dopamine forming salsolinol, a compound that is self-administered. In UChB rats, salsolinol: (a) generates marked sensitization to the motivational effects of ethanol; and (b) strongly promotes binge-like drinking. The specificity of salsolinol actions is shown by the finding that only the R-salsolinol enantiomer but not S-salsolinol accounted for the latter effects. Inhibition of brain acetaldehyde synthesis does not influence the maintenance of chronic ethanol intake. However, a prolonged ethanol withdrawal partly returns the requirement for acetaldehyde synthesis/levels both on chronic ethanol intake and on alcohol relapse-like drinking. Chronic ethanol intake, involving the action of lipopolysaccharide diffusing from the gut, and likely oxygen radical generated upon catechol/salsolinol oxidation, leads to oxidative stress and neuro-inflammation, known to potentiate each other. Data show that the administration of N-acetyl cysteine (NAC) a strong antioxidant inhibits chronic ethanol maintenance by 60%–70%, without inhibiting its initial intake. Intra-cerebroventricular administration of mesenchymal stem cells (MSCs), known to release anti-inflammatory cytokines, to elevate superoxide dismutase levels and to reverse ethanol-induced hippocampal injury and cognitive deficits, also inhibited chronic ethanol maintenance; further, relapse-like ethanol drinking was inhibited up to 85% for 40 days following intracerebral stem cell administration. Thus: (i) ethanol must be metabolized intracerebrally into acetaldehyde, and further into salsolinol, which appear responsible for promoting the acquisition of the early reinforcing effects of ethanol; (ii) acetaldehyde is not responsible for the maintenance of chronic ethanol intake, while other mechanisms are indicated; (iii) the systemic administration of NAC, a strong antioxidant markedly inhibits the maintenance of chronic ethanol intake; and (iv) the intra-cerebroventricular administration of anti-inflammatory and antioxidant MSCs inhibit both the maintenance of chronic ethanol intake and relapse-like drinking.

Disentangling the Role of Astrocytes in Alcohol Use Disorder

Several laboratories recently identified that astrocytes are critical regulators of addiction machinery. It is now known that astrocyte pathology is a common feature of ethanol (EtOH) exposure in both humans and animal models, as even brief EtOH exposure is sufficient to elicit long-lasting perturbations in astrocyte gene expression, activity, and proliferation. Astrocytes were also recently shown to modulate the motivational properties of EtOH and other strongly reinforcing stimuli. Given the role of astrocytes in regulating glutamate homeostasis, a crucial component of alcohol use disorder (AUD), astrocytes might be an important target for the development of next-generation alcoholism treatments. This review will outline some of the more prominent features displayed by astrocytes, how these properties are influenced by acute and long-term EtOH exposure, and future directions that may help to disentangle astrocytic from neuronal functions in the etiology of AUD.