Increased risk of Parkinson's disease in individuals hospitalized with conditions related to the use of methamphetamine or other amphetamine-type drugs

Rare but relevant: Methamphetamine and Parkinson's disease

Evidence from a number of paradigms suggests that methamphetamine use is associated with increased risk for the development of Parkinson's disease and parkinsonism, and that it may be associated with the premature development of Parkinson's disease. Prevalence of Parkinson's disease and parkinsonism is greater in both methamphetamine users and people who previously used methamphetamine, and evidence from animal studies provides a plausible mechanism for this observation. Despite this increased risk, Parkinson's disease is rarely diagnosed in methamphetamine users. Reasons for this may include under-detection, premature mortality, and individual and substance use characteristics which moderate the risk, including higher rates of smoking. Clinicians should be vigilant to signs and symptoms of Parkinson's disease and parkinsonism in methamphetamine users.

Do prescription stimulants increase risk of Parkinson's disease among adults with attention-deficit hyperactivity disorder? A retrospective cohort study

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disorder in older adults that is associated with neuroinflammation, oxidative stress, and characterized by loss of dopaminergic cells. Illicit stimulants increase oxidative stress and are associated with increased risk of PD. Prescription stimulants are similar in mechanism to illicit stimulants, yet their influence on PD is not well described. This study aims to determine if prescription stimulants influence risk of PD among older adults with attention-deficit and hyperactivity disorder (ADHD).

METHODS

We implemented a retrospective observational cohort design utilizing the TriNetX database which sources from the electronic health records of 57 healthcare organizations. Inclusion criteria were ADHD diagnosis and age ≥50. Those exposed to stimulants and the unexposed controls were matched based on demographics and known risk factors for PD. The outcome of interest was the incidence of PD over a 30-year follow-up period. We utilized TriNetX software for hazard ratio (HR) analysis.

RESULTS

Among the 59,471 individuals treated with prescription stimulants 131 of them developed PD, and there were 272 individuals who developed PD that were not prescribed stimulants. This analysis yielded a HR of 0.419 (HR = 0.419 [95% CI 0.34, 0.516], P = 0.0013).

CONCLUSION

Illicit stimulants are associated with increased risk of PD, but this study suggests prescribed stimulants may not impart that same risk. The reduced risk in this cohort may be due to protection from illicit substance use and oxidative stress, however additional study exploring the relationship between prescription stimulants and PD is warranted.

Neurological Effects of Stimulants and Hallucinogens

In this article, we will discuss the history, pharmacodynamics, and neurotoxicity of psychostimulants and hallucinogens. The drugs discussed are widely used and have characteristic toxidromes and potential for neurological injuries with which the practicing clinician should be familiar. Psychostimulants are a class of drugs that includes cocaine, methamphetamine/amphetamines, and cathinones, among others, which produce a crescendoing euphoric high. Seizures, ischemic and hemorrhagic strokes, rhabdomyolysis, and a variety of movement disorders are commonly encountered in this class. Hallucinogens encompass a broad class of drugs, in which the user experiences hallucinations, altered sensorium, distorted perception, and cognitive dysfunction. The experience can be unpredictable and dysphoric, creating a profound sense of anxiety and panic in some cases. Recognizing the associated neurotoxicities and understanding the appropriate management is critical in caring for these patient populations. Several of these agents are not detectable by standard clinical laboratory analysis, making identification and diagnosis an even greater challenge.

Microglia contribute to methamphetamine reinforcement and reflect persistent transcriptional and morphological adaptations to the drug

Methamphetamine use disorder (MUD) is a chronic, relapsing disease that is characterized by repeated drug use despite negative consequences and for which there are currently no FDA-approved cessation therapeutics. Repeated methamphetamine (METH) use induces long-term gene expression changes in brain regions associated with reward processing and drug-seeking behavior, and recent evidence suggests that methamphetamine-induced neuroinflammation may also shape behavioral and molecular responses to the drug. Microglia, the resident immune cells in the brain, are principal drivers of neuroinflammatory responses and contribute to the pathophysiology of substance use disorders. Here, we investigated transcriptional and morphological changes in dorsal striatal microglia in response to methamphetamine-taking and during methamphetamine abstinence, as well as their functional contribution to drug-taking behavior. We show that methamphetamine self-administration induces transcriptional changes associated with protein folding, mRNA processing, immune signaling, and neurotransmission in dorsal striatal microglia. Importantly, many of these transcriptional changes persist through abstinence, a finding supported by morphological analyses. Functionally, we report that microglial ablation increases methamphetamine-taking, possibly involving neuroimmune and neurotransmitter regulation. In contrast, microglial depletion during abstinence does not alter methamphetamine-seeking. Taken together, these results suggest that methamphetamine induces both short and long-term changes in dorsal striatal microglia that contribute to altered drug-taking behavior and may provide valuable insights into the pathophysiology of MUD.

Neurotoxic Methamphetamine Doses Alter CDCel-1 Levels and Its Interaction with Vesicular Monoamine Transporter-2 in Rat Striatum

In recent years, methamphetamine METH misuse in the US has been rapidly increasing and there is no FDA-approved pharmacotherapy for METH use disorder (MUD). In addition to being dependent on the drug, people with MUD develop a variety of neurological problems related to the toxicity of this drug. A variety of molecular mechanisms underlying METH neurotoxicity has been identified, including dysfunction of the neuroprotective protein parkin. However, it is not known whether parkin loss of function within striatal dopaminergic (DAergic) terminals translates into a decrease in DA storage capacity. This study examined the relationship between parkin, its substrate cell division cycle related-1 (CDCrel-1), and vesicular monoamine transporter-2 (VMAT2) in METH neurotoxicity in male Sprague Dawley rats. To also assess individual differences in response to METH's neurotoxic effects, a large group of rats was treated with binge METH or saline and sacrificed 1h or 24h later. This study is the first to show that binge METH alters the levels and subcellular localization of CDCrel-1 and that CDCrel-1 interacts with VMAT2 and increases its levels at the plasma membrane. Furthermore, we found wide individual differences in the responses of measured indices to METH. Proteomic analysis of VMAT-2-associated proteins revealed upregulation of several proteins involved in the exocytosis/endocytosis cycle. The results suggest that at 1h after METH binge, DAergic neurons are engaged in counteracting METH-induced toxic effects, including oxidative stress- and hyperthermia-induced inhibition of synaptic vesicle cycling, with the responses varying between individual rats. Studying CDCrel-1, VMAT2, and other proteins in large groups of outbred rats can help define individual genetic and molecular differences in responses to METH neurotoxicity which, in turn, will aid treating humans suffering from METH use disorder and its neurological consequences.

No evidence of structural abnormality of the substantia nigra in adult attention-deficit/hyperactivity disorder: a pilot cross-sectional cohort study

Background

Abnormal expansion of the echogenic substantia nigra (SN+) is a common observation in Parkinson's disease (PD) and considered a potential trait marker within this context. However, SN+ was also frequently detected in children diagnosed with attention-deficit/hyperactivity disorder (ADHD), where it has been discussed as a biomarker of maturational dopaminergic dysfunction. Interestingly, ADHD was recently linked to an elevated risk of PD in epidemiological studies, particularly among individuals treated with psychostimulants. Here, we investigated the potential of SN echogenicity as a disease biomarker in adults with ADHD and its relation to psychostimulant treatment.

Methods

In an exploratory cross-sectional cohort study, we performed transcranial sonography of the SN in 30 adults (mean age 33.3 ± 7.6 years, 19 males/11 females) diagnosed with ADHD according to DSM-V criteria.

Results and conclusions

In this pilot study, we observed no evidence of structural abnormalities of the SN among adults diagnosed with ADHD, thus questioning the potential of SN+ as a biomarker for ADHD in this population. Moreover, we found no evidence of treatment-related SN echogenicity changes that would link therapeutic psychostimulant use to alterations in the structural integrity of the SN.

The Effectiveness of Mindfulness in the Treatment of Methamphetamine Addiction Symptoms: Does Neuroplasticity Play a Role?

INTRODUCTION

Methamphetamine is a highly stimulating psychoactive drug that causes life-threatening addictions and affects millions of people around the world. Its effects on the brain are complex and include disturbances in the neurotransmitter systems and neurotoxicity. There are several known treatment methods, but their effectiveness is moderate. It must be emphasised that no drugs have been approved for treatment. For this reason, there is an urgent need to develop new, effective, and safe treatments for methamphetamine. One of the potential treatments is mindfulness meditation. In recent years, this technique has been researched extensively in the context of many neurological and psychiatric disorders.

METHODS

This review explores the use of mindfulness in the treatment of methamphetamine addiction. Searches were conducted in the PubMed/Medline, Research Gate, and Cochrane databases.

RESULTS

Ten studies were identified that used mindfulness-based interventions in the treatment of methamphetamine addiction. The results show that mindfulness is an effective form of reducing hunger, risk of relapses, stress indicators, depression, and aggression, alone or in combination with transcranial direct current stimulation (tDCS). Mindfulness also improved the cognitive function in addicts. The included studies used only behavioural measures. The potential mechanisms of mindfulness in addiction were explained, and it was proposed that it can induce neuroplasticity, alleviating the symptoms of addiction.

CONCLUSIONS

Evidence from the studies suggest that mindfulness may be an effective treatment option for methamphetamine addiction, used alone or in combination with tDCS. However, further high-quality research is required to establish the role of this treatment option in this field. The use of neuroimaging and neurophysiological measures is fundamental to understand the mechanisms of mindfulness.

Role of dopamine neuron activity in Parkinson's disease pathophysiology

Neural activity is finely tuned to produce normal behaviors, and disruptions in activity likely occur early in the course of many neurodegenerative diseases. However, how neural activity is altered, and how these changes influence neurodegeneration is poorly understood. Here, we focus on evidence that the activity of dopamine neurons is altered in Parkinson's disease (PD), either as a compensatory response to degeneration or as a result of circuit dynamics or pathologic proteins, based on available human data and studies in animal models of PD. We then discuss how this abnormal activity may augment other neurotoxic phenomena in PD, including mitochondrial deficits, protein aggregation and spread, dopamine toxicity, and excitotoxicity. A more complete picture of how activity is altered and the resulting effects on dopaminergic neuron health and function may inform future therapeutic interventions to target and protect dopamine neurons from degeneration.

α-synuclein-lack expression rescues methamphetamine-induced mossy fiber degeneration in dorsal hippocampal CA3

Methamphetamine (METH) - induced cognitive impairments may be related to synaptic degeneration at mossy fiber terminals, critical for spatial memory formation in hippocampal circuits. We have previously found METH-induced neurodegeneration in the striatum by increasing the α-synuclein (α-SYN) level. However, whether and how the METH-induced mossy fiber degeneration is also blamed for the abnormal accumulation of α-SYN remains to be elucidated. Chronic METH exposure decreased mossy fiber density but upregulatedα-SYN and phosphorylated TAU (TAU-pSer396) in hippocampal CA3, associated with glial cell overactivation, axonal neuropathies, and memory impairment. Notably, the knockout of the α-SYN gene significantly alleviated the METH-induced mossy fiber degeneration and memory impairment. Meanwhile, the TAU-pSer396 accumulation and glial activation were ameliorated by α-SYN knockout. Our findings suggest an essential role of α-SYN in mediating METH-induced mossy fiber degeneration, providing promising therapeutic and prophylactic targets for METH-related neurodegenerative diseases.

Microglia contribute to methamphetamine reinforcement and reflect persistent transcriptional and morphological adaptations to the drug

Methamphetamine use disorder (MUD) is a chronic, relapsing disease that is characterized by repeated drug use despite negative consequences and for which there are currently no FDA-approved cessation therapeutics. Repeated methamphetamine (METH) use induces long-term gene expression changes in brain regions associated with reward processing and drug-seeking behavior, and recent evidence suggests that methamphetamine-induced neuroinflammation may also shape behavioral and molecular responses to the drug. Microglia, the resident immune cells in the brain, are principal drivers of neuroinflammatory responses and contribute to the pathophysiology of substance use disorders. Here, we investigated transcriptional and morphological changes in dorsal striatal microglia in response to methamphetamine-taking and during methamphetamine abstinence, as well as their functional contribution to drug-taking behavior. We show that methamphetamine self-administration induces transcriptional changes associated with protein folding, mRNA processing, immune signaling, and neurotransmission in dorsal striatal microglia. Importantly, many of these transcriptional changes persist through abstinence, a finding supported by morphological analyses. Functionally, we report that microglial ablation increases methamphetamine-taking, possibly involving neuroimmune and neurotransmitter regulation, and that post-methamphetamine microglial repopulation attenuates drug-seeking following a 21-day period of abstinence. In contrast, microglial depletion during abstinence did not alter methamphetamine-seeking. Taken together, these results suggest that methamphetamine induces both short and long-term changes in dorsal striatal microglia that contribute to altered drug-taking behavior and may provide valuable insights into the pathophysiology of MUD.

The cortical thickness of tricenarian cocaine users assembles features of an octogenarian brain

It has been suggested that substance use disorders could lead to accelerated biological aging, but only a few neuroimaging studies have investigated this hypothesis so far. In this cross-sectional study, structural neuroimaging was performed to measure cortical thickness (CT) in tricenarian adults with cocaine use disorder (CUD, n1  = 30) and their age-paired controls (YC, n1  = 30), and compare it with octogenarian elder controls (EC, n1  = 20). We found that CT in the right fusiform gyrus was similar between CUD and EC, thinner than the expected values of YC. We also found that regarding CT of the right inferior temporal gyrus, right inferior parietal cortex, and left superior parietal cortex, the CUD group exhibited parameters that fell in between EC and YC groups. Finally, CT of the right pars triangularis bordering with orbitofrontal gyrus, right superior temporal gyrus, and right precentral gyrus were reduced in CUD when contrasted with YC, but those areas were unrelated to CT of EC. Despite the 50-year age gap between our age groups, CT of tricenarian cocaine users assembles features of an octogenarian brain, reinforcing the accelerated aging hypothesis in CUD.

Isradipine, an L-type calcium channel inhibitor, attenuates cue-associated methamphetamine-seeking in mice

Methamphetamine (meth) is an addictive psychostimulant and there are no FDA-approved treatment options for patients suffering from meth use disorders. In addition to being addictive, meth is also neurotoxic and chronic administration results in degeneration of substantia nigra pars compacta (SNc) dopamine and locus coeruleus (LC) norepinephrine neurons in mice. Optimal treatment strategies for meth use disorders would attenuate maladaptive meth-seeking behavior as well as provide neuroprotection. The L-type calcium channel inhibitor isradipine and the monoamine oxidase (MAO) inhibitor rasagiline both prevent chronic meth-induced SNc and LC degeneration but effects on meth-seeking are unknown. To test whether these clinically available compounds can mitigate meth-seeking, mice were implanted with chronic indwelling jugular vein catheters and allowed to self-administer meth (0.1 mg/kg/infusion) for 10 consecutive days (2-hrs/day) on a fixed ratio (FR) 1 schedule of reinforcement with meth infusions paired to a cue light. One day after the last self-administration session mice were tested for cue-associated meth-seeking behavior wherein the meth-associated cue light was contingently presented but meth reinforcement withheld. Isradipine (3 mg/kg) attenuated cue-associated meth-seeking in both male and female mice. In contrast, rasagiline (1 mg/kg) had no effect on seeking in either sex. These results suggest that isradipine may have the potential to serve as a dual-purpose pharmacotherapy for meth use disorders by attenuating seeking behavior and providing neuroprotection.

Modeling Methamphetamine Use Disorder and Relapse in Animals: Short- and Long-term Epigenetic, Transcriptional., and Biochemical Consequences in the Rat Brain

Methamphetamine use disorder (MUD) is a neuropsychiatric disorder characterized by binge drug taking episodes, intervals of abstinence, and relapses to drug use even during treatment. MUD has been modeled in rodents and investigators are attempting to identify its molecular bases. Preclinical experiments have shown that different schedules of methamphetamine self-administration can cause diverse transcriptional changes in the dorsal striatum of Sprague-Dawley rats. In the present review, we present data on differentially expressed genes (DEGs) identified in the rat striatum following methamphetamine intake. These include genes involved in transcription regulation, potassium channel function, and neuroinflammation. We then use the striatal data to discuss the potential significance of the molecular changes induced by methamphetamine by reviewing concordant or discordant data from the literature. This review identified potential molecular targets for pharmacological interventions. Nevertheless, there is a need for more research on methamphetamine-induced transcriptional consequences in various brain regions. These data should provide a more detailed neuroanatomical map of methamphetamine-induced changes and should better inform therapeutic interventions against MUD.

Oxidative Stress and Inflammatory Biomarkers in People with Methamphetamine Use Disorder

Objective

This study aimed to investigate the blood serum levels of biomarkers specifying oxidative stress status and systemic inflammation between people using methamphetamine (METH) and the control group (CG). Serum thiol/disulfide balance and ischemia-modified albumin levels were studied to determine oxidative stress, and serum interleukin-6 (IL-6) levels and complete blood count (CBC) were to assess inflammation.

Methods

Fifty patients with METH use disorder (MUD) and 36 CG participants were included in the study. Two tubes of venous blood samples were taken to measure oxidative stress, serum thiol/disulfide balance, ischemia-modified albumin, and IL-6 levels between groups. The correlation of parameters measuring oxidative stress and inflammation between groups with sociodemographic data was investigated.

Results

In this study, serum total thiol, free thiol levels, disulfide/native thiol percentage ratios, and serum ischemia- modified albumin levels of the patients were statistically significantly higher than the healthy controls. No difference was observed between the groups in serum disulfide levels and serum IL-6 levels. Considering the regression analysis, only the duration of substance use was a statistically significant factor in explaining serum IL-6 levels. The parameters showing inflammation in the CBC were significantly higher in the patients than in the CG.

Conclusion

CBC can be used to evaluate systemic inflammation in patients with MUD. Parameters measuring thiol/disulfide homeostasis and ischemia-modified albumin can be, also, used to assess oxidative stress.

Repeated Methamphetamine Administration Results in Axon Loss Prior to Somatic Loss of Substantia Nigra Pars Compacta and Locus Coeruleus Neurons in Male but Not Female Mice

Methamphetamine (meth) is a neurotoxic psychostimulant that increases monoamine oxidase (MAO)-dependent mitochondrial oxidant stress in axonal but not somatic compartments of substantia nigra pars compacta (SNc) and locus coeruleus (LC) neurons. Chronic meth administration results in the degeneration of SNc and LC neurons in male mice, and MAO inhibition is neuroprotective, suggesting that the deleterious effects of chronic meth begin in axons before advancing to the soma of SNc and LC neurons. To test this hypothesis, mice were administered meth (5 mg/kg) for 14, 21, or 28 days, and SNc and LC axonal lengths and numbers of neurons were quantified. In male mice, the SNc and LC axon lengths decreased with 14, 21, and 28 days of meth, whereas somatic loss was only observed after 28 days of meth; MAO inhibition (phenelzine; 20 mg/kg) prevented axonal and somatic loss of SNc and LC neurons. In contrast, chronic (28-day) meth had no effect on the axon length or numbers of SNc or LC neurons in female mice. The results demonstrate that repeated exposure to meth produces SNc and LC axonal deficits prior to somatic loss in male subjects, consistent with a dying-back pattern of degeneration, whereas female mice are resistant to chronic meth-induced degeneration.

Stimulant and hallucinogenic novel psychoactive substances; an update

INTRODUCTION

The renewed interest in considering a range of stimulants, psychedelics and dissociatives as therapeutics emphasizes the need to draft an updated overview of these drugs' clinical and pharmacological issues.

AREAS COVERED

The focus here was on: stimulants (e.g. amphetamines, methamphetamine, and pseudoephedrine; phenethylamines; synthetic cathinones; benzofurans; piperazines; aminoindanes; aminorex derivatives; phenmetrazine derivatives; phenidates); classical (e.g. ergolines; tryptamines; psychedelic phenethylamines), and atypical (e.g. PCP/ketamine-like dissociatives) psychedelics.Stimulant and psychedelics are associated with: a) increased central DA levels (psychedelic phenethylamines, synthetic cathinones and stimulants); b) 5-HT receptor subtypes' activation (psychedelic phenethylamines; recent tryptamine and lysergamide derivatives); and c) antagonist activity at NMDA receptors, (phencyclidine-like dissociatives).

EXPERT OPINION

Clinicians should be regularly informed about the range of NPS and their medical, psychobiological and psychopathological risks both in the acute and long term. Future research should focus on an integrative model in which pro-drug websites' analyses are combined with advanced research approaches, including computational chemistry studies so that in vitro and in vivo preclinical studies of index novel psychoactives can be organized. The future of psychedelic research should focus on identifying robust study designs to convincingly assess the potential therapeutic benefits of psychedelics, molecules likely to present with limited dependence liability levels.

Movement disorders associated with substance use in adults living in precarious housing or homelessness

OBJECTIVE

Many individuals living in precarious housing or homelessness have multimorbid illnesses, including substance use, psychiatric, and neurological disorders. Movement disorders (MDs) associated substance use are amongst the poorly studied subtopics of drug-induced MDs. The aim of the present study was, therefore, to determine the proportion affected and severity of different signs of MDs, as well as their associations with substance use in a community-based sample of precariously housed and homeless individuals.

METHODS

Participants were recruited from an impoverished urban neighborhood and were assessed for substance dependence and self-reported substance use (alcohol, cannabis, cocaine, methamphetamine, nicotine, and opioids), as well as for the severity of signs of MDs (akathisia, dyskinesia, dystonia, and parkinsonism). Adjusted regression models were used to estimate the associations of the severity of signs with the frequency of substance use over the past 4 weeks and with the baseline diagnosis of substance dependence.

RESULTS

The proportion of the sample with clinically relevant signs of MDs in any of the four categories was 18.6% (n = 401), and these participants demonstrated lower levels of functioning than those without signs. Of the different types of substance use, only methamphetamine (its frequency of use and dependence) was significantly associated with greater severity of overall signs of MDs. Frequency of methamphetamine use significantly interacted with age and sex, whereby older female participants exhibited the greatest overall severity with increased methamphetamine use. Of the different signs of MDs, methamphetamine use frequency was positively associated with the severity of trunk/limb dyskinesia and hypokinetic parkinsonism. Relative to no use, concurrent use of antipsychotics demonstrated lower severity of trunk/limb dyskinesia and greater severity of hypokinetic parkinsonism with methamphetamine use, and greater severity of dystonia with cocaine use.

CONCLUSIONS

Our study found a high proportion of MDs in a relatively young sample, and their severity was consistently associated with methamphetamine use, moderated by participant demographics and antipsychotic use. These disabling sequelae represent an important and understudied neurological condition that may affect quality of life and will require further study.

Substance abuse and neurodegenerative diseases: focus on ferroptosis

Psychostimulants and alcohol are widely abused substances with the adverse effects on global public health. Substance abuse seriously harms people's health and causes various diseases, especially neurodegenerative diseases. Neurodegenerative diseases include Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). The pathogenesis of neurodegenerative diseases is complex and diverse, usually involving oxidative stress, mitochondrial dysfunction, metal homeostasis disorder, and neuro-inflammation. The precise molecular mechanisms underlying neurodegeneration remain unclear, which is a major obstacle to therapeutic approaches. Therefore, it is urgent to improve the understanding of the molecular mechanisms of neurodegenerative processes and to identify the therapeutic targets for treatment and prevention. Ferroptosis is a regulatory cell necrosis caused by iron ion catalysis and lipid peroxidation induced by reactive oxygen species (ROS), which is thought to be associated with nervous system diseases, particularly neurodegenerative diseases. This review overviewed the ferroptosis process and explored the relationship of ferroptosis with substance abuse and neurodegenerative diseases, which provides a new way to study the molecular mechanisms of neurodegenerative diseases induced by alcohol, cocaine, and methamphetamine (MA), and also provides the potential therapeutic targets for substance abuse-induced neurodegenerative diseases.

Neuroprotective effect of thyroid hormones on methamphetamine-induced neurotoxicity via cell surface receptors

Thyroid hormones (THs) have an essential role in normal brain development and function. Methamphetamine (MA) is a widely abused psychostimulant that induces irreversible damages to neuronal cells. In the current study, we used rat primary hippocampal neurons (PHNs) to investigate the neuroprotective effect of THs against MA neurotoxicity. PHNs were prepared from 18-day rat embryos and cell viability was assessed using MTT assay, following treatment with various concentrations of MA, T3, T4 or tetrac, an integrin αvβ3 cell surface receptor antagonist. Our results showed that 7 mM MA induced an approximately 50 % reduction in the PHNs viability. Treatment with 800 nM T3 or 8 μM T4 protected PHNs against MA toxicity, an effect which was blocked in the presence of tetrac. These findings suggest that THs protect PHNs against MA-induced cell death by the activation of integrin αvβ3 cell surface receptors. So, targeting integrin αvβ3 receptors or using THs can be considered as promising therapeutic strategies to overcome MA neurotoxicity.

Human Induced Pluripotent Stem Cell Phenotyping and Preclinical Modeling of Familial Parkinson's Disease

Parkinson's disease (PD) is primarily idiopathic and a highly heterogenous neurodegenerative disease with patients experiencing a wide array of motor and non-motor symptoms. A major challenge for understanding susceptibility to PD is to determine the genetic and environmental factors that influence the mechanisms underlying the variations in disease-associated traits. The pathological hallmark of PD is the degeneration of dopaminergic neurons in the substantia nigra pars compacta region of the brain and post-mortem Lewy pathology, which leads to the loss of projecting axons innervating the striatum and to impaired motor and cognitive functions. While the cause of PD is still largely unknown, genome-wide association studies provide evidence that numerous polymorphic variants in various genes contribute to sporadic PD, and 10 to 15% of all cases are linked to some form of hereditary mutations, either autosomal dominant or recessive. Among the most common mutations observed in PD patients are in the genes LRRK2, SNCA, GBA1, PINK1, PRKN, and PARK7/DJ-1. In this review, we cover these PD-related mutations, the use of induced pluripotent stem cells as a disease in a dish model, and genetic animal models to better understand the diversity in the pathogenesis and long-term outcomes seen in PD patients.

Biochemical Neuroadaptations in the Rat Striatal Dopaminergic System after Prolonged Exposure to Methamphetamine Self-Administration

Perturbations in striatal dopamine (DA) homeostasis might underlie the behavioral and pathobiological consequences of METH use disorder in humans. To identify potential consequences of long-term METH exposure, we modeled the adverse consequence DSM criterion of substance use disorders by giving footshocks to rats that had escalated their intake of METH during a drug self-administration procedure. Next, DA D1 receptor antagonist, SCH23390 was injected. Thereafter, rats were euthanized to measure several indices of the striatal dopaminergic system. Footshocks split the METH rats into two phenotypes: (i) shock-sensitive that decreased their METH-intake and (ii) shock-resistant that continued their METH intake. SCH23390 caused substantial dose-dependent reduction of METH taking in both groups. Stopping SCH23390 caused re-emergence of compulsive METH taking in shock-resistant rats. Compulsive METH takers also exhibited greater incubation of METH seeking than non-compulsive rats during withdrawal from METH SA. Analyses of DA metabolism revealed non-significant decreases (about 35%) in DA levels in resistant and sensitive rats. However, striatal contents of the deaminated metabolites, DOPAL and DOPAC, were significantly increased in sensitive rats. VMAT2 and DAT protein levels were decreased in both phenotypes. Moreover, protein expression levels of the D1-like DA receptor, D5R, and D2-like DA receptors, D3R and D4R, were significantly decreased in the compulsive METH takers. Our results parallel findings in post-mortem striatal tissues of human METH users who develop Parkinsonism after long-term METH intake and support the use of this model to investigate potential therapeutic interventions for METH use disorder.

Methamphetamine induced neurotoxic diseases, molecular mechanism, and current treatment strategies

Methamphetamine (MA) is a extremely addictive psychostimulant drug with a significant abuse potential. Long-term MA exposure can induce neurotoxic effects through oxidative stress, mitochondrial functional impairment, endoplasmic reticulum stress, the activation of astrocytes and microglial cells, axonal transport barriers, autophagy, and apoptosis. However, the molecular and cellular mechanisms underlying MA-induced neurotoxicity remain unclear. MA abuse increases the chances of developing neurotoxic conditions such as Parkinson's disease (PD), Alzheimer's disease (AD) and other neurotoxic diseases. MA increases the risk of PD by increasing the expression of alpha-synuclein (ASYN). Furthermore, MA abuse is linked to high chances of developing AD and subsequent neurodegeneration due to biological variations in the brain region or genetic and epigenetic variations. To date, there is no Food and Drug Administration (FDA)-approved therapy for MA-induced neurotoxicity, although many studies are being conducted to develop effective therapeutic strategies. Most current studies are now focused on developing therapies to diminish the neurotoxic effects of MA, based on the underlying mechanism of neurotoxicity. This review article highlights current research on several therapeutic techniques targeting multiple pathways to reduce the neurotoxic effects of MA in the brain, as well as the putative mechanism of MA-induced neurotoxicity.

Population-based comparison of cancer survival outcomes in patients with and without psychiatric disorders

BACKGROUND

Individuals with psychiatric disorders (PD) have a high prevalence of tobacco use. Patients with PD also potentially receive substandard care in comparison to the general population. Previous research has shown that individuals with PD have a decreased risk of receiving a tobacco related (TR) cancer diagnosis. To further assess this trend, this study assesses the survival of patients with a TR cancer with or without a PD.

MATERIALS AND METHODS

Our study utilized multiple databases, with methods described elsewhere,⁶ to identify people in British Columbia that have been diagnosed with psychiatric disorders and appendicitis (our control group). From these groups, we selected individuals who also had a TR cancer. We subsequently extracted information pertaining to these patients from these databases.

RESULTS

Thirty-nine thousand eight hundred forty-one patients with cancer were included in our study. Analyses of these patients were controlled for by age, gender, cancer type and diagnosis year. This analysis displayed shorter survival time among patients who were diagnosed with depression (HR = 1.16; p = 0.01; 95% CI: 1.04-1.29), schizophrenia (HR = 1.62; p < 0.01; 95% CI: 1.43-1.84), or bipolar disorder (HR = 1.35; p < 0.01; 95% CI: 1.12-1.64) compared to the cancer patients without a PD, all of which were statistically significant. People that were diagnosed with anxiety disorders did not have a survival time that was significantly different from our control population (HR = 1.07; p = 0.22; 95% CI: 0.96-1.19).

CONCLUSIONS

Individuals with PD, except for those with anxiety, were found to have a shorter survival time following diagnosis with a TR cancer as compared to our control group. We hypothesize several factors, which may account for this statistically significant difference: (1) delayed diagnosis, (2) poor access to care, (3) poor assessment or follow-up, or (4) physician beliefs of poor treatment adherence.

Differential vulnerability of locus coeruleus and dorsal raphe neurons to chronic methamphetamine-induced degeneration

Methamphetamine (meth) increases monoamine oxidase (MAO)-dependent mitochondrial stress in axons of substantia nigra pars compacta (SNc), and ventral tegmental area (VTA) dopamine neurons. Chronic administration of meth results in SNc degeneration and MAO inhibition is neuroprotective, whereas, the VTA is resistant to degeneration. This differential vulnerability is attributed, at least in part, to the presence of L-type Ca²⁺ channel-dependent mitochondrial stress in SNc but not VTA dopamine neurons. MAO is also expressed in other monoaminergic neurons such as noradrenergic locus coeruleus (LC) and serotonergic dorsal raphe (DR) neurons. The impact of meth on mitochondrial stress in LC and DR neurons is unknown. In the current study we used a genetically encoded redox biosensor to investigate meth-induced MAO-dependent mitochondrial stress in LC and DR neurons. Similar to SNc and VTA neurons, meth increased MAO-dependent mitochondrial stress in axonal but not somatic compartments of LC norepinephrine and DR serotonin neurons. Chronic meth administration (5 mg/kg; 28-day) resulted in degeneration of LC neurons and MAO inhibition was neuroprotective whereas DR neurons were resistant to degeneration. Activating L-type Ca²⁺ channels increased mitochondrial stress in LC but not DR axons and inhibiting L-type Ca²⁺ channels in vivo with isradipine prevented meth-induced LC degeneration. These data suggest that similar to recent findings in SNc and VTA dopamine neurons, the differential vulnerability between LC and DR neurons can be attributed to the presence of L-type Ca²⁺ channel-dependent mitochondrial stress. Taken together, the present study demonstrates that both meth-induced MAO- and L-type Ca²⁺ channel-dependent mitochondrial stress are necessary for chronic meth-induced neurodegeneration.

Dopamine D1 receptors mediate methamphetamine-induced dopaminergic damage: involvement of autophagy regulation via the AMPK/FOXO3A pathway

RATIONALE

Clinical studies have revealed that methamphetamine abuse increases risk for developing Parkinson's diseases. It is thus important to elucidate the mechanisms by which methamphetamine damages dopaminergic neurons.

OBJECTIVES

The present study was designed to elucidate the role of the dopamine D1 receptor in methamphetamine-mediated dopaminergic neuronal damage and its underlying mechanisms.

METHODS

Mice were treated for 4 days with vehicle, methamphetamine, or the D1 agonist SKF38393 and then assessed for locomotion and performance in the pole and rotarod tests. Cellular indices of autophagy, LC3, P62, and Beclin-1, tyrosine hydroxylase, and the AMPK/FOXO3A pathway were analyzed in striatal tissue from treated mice, in PC12 cells, and in D1 receptor mutant mice.

RESULTS

Repeated treatment with a relatively high dose of methamphetamine for 4 days induced both loss of dopaminergic neurons and activation of autophagy in the striatum as evidenced by increased expression of LC3 and P62. However, such treatment did not induce either loss of dopaminergic neurons or activation of autophagy in D1 receptor knockout mice. D1 receptor-mediated activation of autophagy was also confirmed in vitro using dopaminergic neuronal PC12 cells. Further studies demonstrated that the AMPK/FOXO3A signaling pathway is responsible for D1 receptor-mediated activation of autophagy.

CONCLUSIONS

The present data indicate a novel mechanism for methamphetamine-induced dopaminergic neuronal damage and reveal an important role for D1 receptors in the neurotoxicity of this drug.

Adenosine A1 receptor ligands bind to α-synuclein: implications for α-synuclein misfolding and α-synucleinopathy in Parkinson's disease

Background

Accumulating α-synuclein (α-syn) aggregates in neurons and glial cells are the staples of many synucleinopathy disorders, such as Parkinson’s disease (PD). Since brain adenosine becomes greatly elevated in ageing brains and chronic adenosine A1 receptor (A1R) stimulation leads to neurodegeneration, we determined whether adenosine or A1R receptor ligands mimic the action of known compounds that promote α-syn aggregation (e.g., the amphetamine analogue 2-aminoindan) or inhibit α-syn aggregation (e.g., Rasagiline metabolite 1-aminoindan). In the present study, we determined whether adenosine, A1R receptor agonist N⁶-Cyclopentyladenosine (CPA) and antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) could directly interact with α-syn to modulate α-syn aggregation and neurodegeneration of dopaminergic neurons in the substantia nigra (SN).

Methods

Nanopore analysis and molecular docking were used to test the binding properties of CPA and DPCPX with α-syn in vitro. Sprague–Dawley rats were administered with 7-day intraperitoneal injections of the A1R ligands and 1- and 2-aminoindan, and levels of α-syn aggregation and neurodegeneration were examined in the SN pars compacta and hippocampal regions using confocal imaging and Western blotting.

Results

Using nanopore analysis, we showed that the A1R agonists (CPA and adenosine) interacted with the N-terminus of α-syn, similar to 2-aminoindan, which is expected to promote a “knot” conformation and α-syn misfolding. In contrast, the A1R antagonist DPCPX interacted with the N- and C-termini of α-syn, similar to 1-aminoindan, which is expected to promote a “loop” conformation that prevents α-syn misfolding. Molecular docking studies revealed that adenosine, CPA and 2-aminoindan interacted with the hydrophobic core of α-syn N-terminus, whereas DPCPX and 1-aminoindan showed direct binding to the N- and C-terminal hydrophobic pockets. Confocal imaging and Western blot analyses revealed that chronic treatments with CPA alone or in combination with 2-aminoindan increased α-syn expression/aggregation and neurodegeneration in both SN pars compacta and hippocampus. In contrast, DPCPX and 1-aminoindan attenuated the CPA-induced α-syn expression/aggregation and neurodegeneration in SN and hippocampus.

Conclusions

The results indicate that A1R agonists and drugs promoting a “knot” conformation of α-syn can cause α-synucleinopathy and increase neuronal degeneration, whereas A1R antagonists and drugs promoting a “loop” conformation of α-syn can be harnessed for possible neuroprotective therapies to decrease α-synucleinopathy in PD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40035-022-00284-3.

Oxytocin, a Novel Treatment for Methamphetamine Use Disorder

The treatment of substance abuse with oxytocin is a novel approach to a challenging public health issue that continues to contribute to a growing economic cost for societies worldwide. Methamphetamine addiction is one of the leading causes of mortality worldwide, and despite advances in understanding the neurobiology of methamphetamine addiction, treatment options are limited. There are no medications that the Food and Drug Administration currently approves for stimulant use disorder. Off-label use of therapies for stimulant misuse include antidepressants, anxiolytics, and milder stimulants as replacement agents. Due to the shortcomings of these attempts to treat a complicated psychiatric disorder, recent attention to oxytocin therapy (OT) has gained momentum in clinical studies as a possible therapy in the context of social stress, social anxiety, social cognition, and psychosis. Oxytocin produces enhanced connectivity between cortical regions. The results from studies in rodents with OT suggest that central neuromodulation of oxytocin may be beneficial across transition states of stimulant dependence and may alleviate intense withdrawal symptoms. Studies of oxytocin in the context of other drugs of abuse, including cocaine, cannabis, and alcohol, also support the potential of oxytocin to treat stimulant use disorder, methamphetamine type. Methamphetamine abuse continues to be a significant cause of distress and dysfunction throughout the world. The effects of oxytocin on methamphetamine use outlined in this review should act as a catalyst for further investigation into the efficacy of treating stimulant use disorder, methamphetamine type with oxytocin in humans. More human-based research should initiate studies involving the long-term efficacy, side effects, and patient selection.

Dopamine and Methamphetamine Differentially Affect Electron Transport Chain Complexes and Parkin in Rat Striatum: New Insight into Methamphetamine Neurotoxicity

Methamphetamine (METH) is a highly abused psychostimulant that is neurotoxic to dopaminergic (DAergic) nerve terminals in the striatum and increases the risk of developing Parkinson’s disease (PD). In vivo, METH-mediated DA release, followed by DA-mediated oxidative stress and mitochondrial dysfunction in pre- and postsynaptic neurons, mediates METH neurotoxicity. METH-triggered oxidative stress damages parkin, a neuroprotective protein involved in PD etiology via its involvement in the maintenance of mitochondria. It is not known whether METH itself contributes to mitochondrial dysfunction and whether parkin regulates complex I, an enzymatic complex downregulated in PD. To determine this, we separately assessed the effects of METH or DA alone on electron transport chain (ETC) complexes and the protein parkin in isolated striatal mitochondria. We show that METH decreases the levels of selected complex I, II, and III subunits (NDUFS3, SDHA, and UQCRC2, respectively), whereas DA decreases the levels only of the NDUFS3 subunit in our preparations. We also show that the selected subunits are not decreased in synaptosomal mitochondria under similar experimental conditions. Finally, we found that parkin overexpression does not influence the levels of the NDUFS3 subunit in rat striatum. The presented results indicate that METH itself is a factor promoting dysfunction of striatal mitochondria; therefore, it is a potential drug target against METH neurotoxicity. The observed decreases in ETC complex subunits suggest that DA and METH decrease activities of the ETC complexes via oxidative damage to their subunits and that synaptosomal mitochondria may be somewhat “resistant” to DA- and METH-induced disruption in mitochondrial ETC complexes than perikaryal mitochondria. The results also suggest that parkin does not regulate NDUFS3 turnover in rat striatum.

Paroxysmal Hypothermia With Prominent Parkinsonian Features After Suprachiasmatic Tumor Resection

Paroxysmal hypothermia (PH) is a rare syndrome of stereotyped episodes of hypothermia, bradycardia, and altered mental status occurring in patients with hypothalamic lesions. Prior cases have mentioned bradykinesia, ataxia, and dysarthria, but parkinsonism has not been described as a specific feature of PH. We report two patients, an adult and a child, who developed PH after suprachiasmatic tumor resection, both with clinical presentations notable for prominent parkinsonian features despite no evidence of parkinsonism during the intervening months and years. We propose a diagnostic algorithm and scoring tool to aid in the clinical diagnosis of PH presenting as parkinsonism.

Methamphetamine Dysregulation of the Central Nervous System and Peripheral Immunity

Methamphetamine (METH) is a potent psychostimulant that increases extracellular monoamines, such as dopamine and norepinephrine, and affects multiple tissue and cell types in the central nervous system (CNS) and peripheral immune cells. The reinforcing properties of METH underlie its significant abuse potential and dysregulation of peripheral immunity and central nervous system functions. Together, the constellation of METH's effects on cellular targets and regulatory processes has led to immune suppression and neurodegeneration in METH addicts and animal models of METH exposure. Here we extensively review many of the cell types and mechanisms of METH-induced dysregulation of the central nervous and peripheral immune systems. SIGNIFICANCE STATEMENT: Emerging research has begun to show that methamphetamine regulates dopaminergic neuronal activity. In addition, METH affects non-neuronal brain cells, such as microglia and astrocytes, and immunological cells of the periphery. Concurrent disruption of bidirectional communication between dopaminergic neurons and glia in the CNS and peripheral immune cell dysregulation gives rise to a constellation of dysfunctional neuronal, cell, and tissue types. Therefore, understanding the pathophysiology of METH requires consideration of the multiple targets at the interface between basic and clinical neuroscience.

Chronic methamphetamine-induced neurodegeneration: Differential vulnerability of ventral tegmental area and substantia nigra pars compacta dopamine neurons

Methamphetamine (meth) increases monoamine oxidase (MAO)-dependent mitochondrial stress in substantia nigra pars compacta (SNc) axons; chronic administration produces SNc degeneration that is prevented by MAO inhibition suggesting that MAO-dependent axonal mitochondrial stress is a causal factor. To test whether meth similarly increases mitochondrial stress in ventral tegmental area (VTA) axons, we used a genetically encoded redox biosensor to assess mitochondrial stress ex vivo. Meth increased MAO-dependent mitochondrial stress in both SNc and VTA axons. However, despite having the same meth-induced stress as SNc neurons, VTA neurons were resistant to chronic meth-induced degeneration indicating that meth-induced MAO-dependent mitochondrial stress in axons was necessary but not sufficient for degeneration. To determine whether L-type Ca2+ channel-dependent stress differentiates SNc and VTA axons, as reported in the soma, the L-type Ca2+ channel activator Bay K8644 was used. Opening L-type Ca2+ channels increased axonal mitochondrial stress in SNc but not VTA axons. To first determine whether mitochondrial stress was necessary for SNc degeneration, mice were treated with the mitochondrial antioxidant mitoTEMPO. Chronic meth-induced SNc degeneration was prevented by mitoTEMPO thereby confirming the necessity of mitochondrial stress. Similar to results with the antioxidant, both MAO inhibition and L-type Ca2+ channel inhibition also prevented SNc degeneration. Taken together the presented data demonstrate that both MAO- and L-type Ca2+ channel-dependent mitochondrial stress is necessary for chronic meth-induced degeneration.

Identification of Tobacco-Related Cancer Diagnoses among Individuals with Psychiatric Disorders: A Population-Based Matched Cohort Study Using a Competing Risks Approach from British Columbia

BACKGROUND

Individuals with psychiatric disorders (PD) have a high prevalence of tobacco use. Therefore, we assessed the hazard of receiving a tobacco-related (TR) cancer diagnosis among individuals with PD.

METHODS

Several population-based provincial databases were used to identify individuals in BC diagnosed with depression, schizophrenia, bipolar disorder, anxiety disorders, or multiple PD between 1990 and 2013. A primary population proxy comparison group (appendicitis) was also identified and matched to the psychiatric cohort based on age at cohort entry, gender, year of cohort entry, and postal code. We linked individuals in the cohort and comparison groups with the BC Cancer Registry. Using a competing risks approach, we estimated the effect of having a PD on the risk of receiving a TR cancer diagnosis, in light of the competing risk of mortality.

RESULTS

In total, 165,289 patients were included. Individuals with depression (HR = 0.81; p < 0.01; 95% CI: 0.73-0.91), anxiety disorders (HR = 0.84; p = 0.02; 95% CI: 0.73-0.97), or multiple PD (HR = 0.74; p < 0.01; 95% CI: 0.66-0.83) had a statistically significant lower risk of a TR cancer diagnosis compared to the comparison group. Individuals with schizophrenia (HR = 0.86; p = 0.40; 95% CI: 0.62-1.21) or bipolar disorder (HR = 0.58; p = 0.12; 95% CI: 0.29-1.14), however, showed no evidence of a statistically significant difference from the comparison group.

INTERPRETATION

We found that individuals with depression, anxiety disorders, or multiple PD diagnoses had a significantly reduced risk of receiving a tobacco-related cancer diagnosis. These results were unexpected and could be explained by individuals with a PD having barriers to a cancer diagnosis rather than a true decreased incidence.

Parkinson's Disease-Related Biomarkers That May Appear in Amphetamine Abusers

Parkinson's disease (PD) is one of the most common neurodegenerative disorders. Amphetamine addiction may cause serious of psychotic and physical damage to humans. There is some evidence that shows that amphetamine may increase the risk of PD. Thus, this study is aimed at comparing the PD serum biomarkers between amphetamine addicts and PD patients and utilizing them as diagnostic biomarkers for the early detection of PD incidence among amphetamine addicts. In the current study, nineteen amphetamine addicts, aged <40, were recruited from the Al Amal Psychiatric hospital, Jazan, Saudi Arabia. Nineteen PD patients and 19 healthy controls, who have never taken amphetamine, were also recruited. Blood samples were withdrawn from all groups. A biomarker multiplex assay from MILLIPLEX was used to assess the levels of serum amyloid-P (SAP), complement C4, C-reactive protein (CRP), and CRP/albumin ratio in serum samples (Vitros 350® slide was used to assess the albumin). All data were statistically analyzed using one-way ANOVA. The results showed that SAP and CRP levels were significantly higher in amphetamine addicts compared to healthy controls (p = 0.0001 and p = 0.0001, respectively). The results of amphetamine addicts were comparable to PD levels. However, there are no significant differences between all studied groups concerning complement C4 level. Moreover, albumin levels were significantly decreased and CRP/Albumin ratio levels were significantly increased in amphetamine addicts (p = 0.01 and p = 0.041, respectively) in contrast with controls. These findings indicate that the increased level of these inflammatory biomarkers (SAP and CRP) in the amphetamine addicts may give a potential possibility of their serum level to be used as screening markers to detect PD development in the amphetamine addict. It may be useful to evaluate the changes in easily accessible and cost-effective parameters such as the serum CRP/albumin ratio.

Manganese Encephalopathy Caused by Homemade Methcathinone (Ephedrone) Prevalence in Poland

Manganese encephalopathy is a known disorder in occupational medicine. A serious phenomenon has been the emergence of manganese encephalopathy in intravenous users of homemade methcathinone (ephedrone). A short survey was developed for clinical environments dealing with people who use psychoactive substances. The data were obtained from 72 rehabilitation therapy centers. Surveys carried out in about a third of Polish centers dealing with providing medical assistance to people addicted to substances other than alcohol and tobacco have shown that over 4% of people treated there had symptoms of manganese encephalopathy, of which more than half are people in whom the probability of a clinical diagnosis of this disorder is significant. It has been shown that knowledge of manganese encephalopathy is none or minimal in more than 70% of the surveyed institutions. An urgent need for personnel training in this field was pointed out. Attention was paid to the importance of disseminating good review articles on new and dynamically developing problem phenomena.

Neurotoxicity of methamphetamine: Main effects and mechanisms

Methamphetamine (METH) is an illicit psychostimulant that is abused throughout the world. METH addiction is also a major public health concern and the abuse of large doses of the drug is often associated with serious neuropsychiatric consequences that may include agitation, anxiety, hallucinations, paranoia, and psychosis. Some human methamphetamine users can also suffer from attention, memory, and executive deficits. METH-associated neurological and psychiatric complications might be related, in part, to METH-induced neurotoxic effects. Those include altered dopaminergic and serotonergic functions, neuronal apoptosis, astrocytosis, and microgliosis. Here we have endeavored to discuss some of the main effects of the drug and have presented the evidence supporting certain of the molecular and cellular bases of METH neurotoxicity. The accumulated evidence suggests the involvement of transcription factors, activation of dealth pathways that emanate from mitochondria and endoplasmic reticulum (ER), and a role for neuroinflammatory mechanisms. Understanding the molecular processes involved in METH induced neurotoxicity should help in developing better therapeutic approaches that might also serve to attenuate or block the biological consequences of use of large doses of the drug by some humans who meet criteria for METH use disorder.

Gut and brain profiles that resemble pre-motor and early-stage Parkinson's disease in methamphetamine self-administering rats

INTRODUCTION

Methamphetamine is a potent psychomotor stimulant, and methamphetamine abusers are up to three times more likely to develop Parkinson's disease (PD) later in life. Prodromal PD may involve gut inflammation and the accumulation of toxic proteins that are transported from the enteric nervous system to the central nervous system to mediate, in part, the degeneration of dopaminergic projections. We hypothesized that self-administration of methamphetamine in rats produces a gut and brain profile that mirrors pre-motor and early-stage PD.

METHODS

Rats self-administered methamphetamine in daily 3 h sessions for two weeks. Motor function was assessed before self-administration, during self-administration and throughout the 56 days of forced abstinence. Assays for pathogenic markers (tyrosine hydroxylase, glial fibrillary acidic protein (GFAP), α-synuclein) were conducted on brain and gut tissue collected at one or 56 days after cessation of methamphetamine self-administration.

RESULTS

Motor deficits emerged by day 14 of forced abstinence and progressively worsened up to 56 days of forced abstinence. In the pre-motor stage, we observed increased immunoreactivity for GFAP and α-synuclein within the ganglia of the myenteric plexus in the distal colon. Increased α-synuclein was also observed in the substantia nigra pars compacta. At 56 days, GFAP and α-synuclein normalized in the gut, but the accumulation of nigral α-synuclein persisted, and the dorsolateral striatum exhibited a significant loss of tyrosine hydroxylase.

CONCLUSION

The pre-motor profile is consistent with gut inflammation and gut/brain α-synuclein accumulation associated with prodromal PD and the eventual development of the neurological disease.

Mitochondrial oxidant stress mediates methamphetamine neurotoxicity in substantia nigra dopaminergic neurons

Methamphetamine abuse is associated with an increased risk of developing Parkinson's disease (PD). Recently, it was found that methamphetamine increases mitochondrial oxidant stress in substantia nigra pars compacta (SNc) dopaminergic neurons by releasing vesicular dopamine (DA) and stimulating mitochondrially-anchored monoamine oxidase (MAO). As mitochondrial oxidant stress is widely thought to be a driver of SNc degeneration in PD, these observations provide a potential explanation for the epidemiological linkage. To test this hypothesis, mice were administered methamphetamine (5 mg/kg) for 28 consecutive days with or without pretreatment with an irreversible MAO inhibitor. Chronic methamphetamine administration resulted in the degeneration of SNc dopaminergic neurons and this insult was blocked by pretreatment with a MAO inhibitor - confirming the linkage between methamphetamine, MAO and SNc degeneration. To determine if shorter bouts of consumption were as damaging, mice were given methamphetamine for two weeks and then studied. Methamphetamine treatment elevated both axonal and somatic mitochondrial oxidant stress in SNc dopaminergic neurons, was associated with a modest but significant increase in firing frequency, and caused degeneration after drug cessation. While axonal stress was sensitive to MAO inhibition, somatic stress was sensitive to Cav1 Ca2+ channel inhibition. Inhibiting either MAO or Cav1 Ca2+ channels after methamphetamine treatment attenuated subsequent SNc degeneration. Our results not only establish a mechanistic link between methamphetamine abuse and PD, they point to pharmacological strategies that could lessen PD risk for patients with a methamphetamine use disorder.

Methcathinone decreases dopamine transporter function: Role of protein kinase C

Methcathinone (MCAT) is a psychostimulant of abuse that can cause both persistent striatal dopaminergic and serotonergic, as well as hippocampal serotonergic, deficits. Evidence suggests that the rapid effects of stimulants that are structurally and mechanistically similar to MCAT on monoamine transporter function may contribute to the abuse liability and/or persistent monoaminergic deficits caused by these agents. Thus, effects of MCAT on 1) striatal dopamine (DA) transporter (DAT); and 2) striatal and hippocampal serotonin transporter (SERT) function, as determined in tissues from adult male rats, were assessed. As reported previously, a single administration of MCAT rapidly (within 1 hr) decreases striatal [³ H]DA uptake. Similarly, incubation of rat synaptosomes with MCAT at 37℃ (but not 4˚C) decreased striatal [³ H]DA uptake. Incubation with MCAT likewise decreased [³ H]5HT but not vesicular [³ H]DA uptake. MCAT incubation in vitro was without effect on [³ H]DA uptake in striatal synaptosomes prepared from MCAT-treated rats. The decrease in [³ H]DA uptake caused by MCAT incubation: (a) reflected a decrease in V_max , with minimal change in K_m , and (b) was attenuated by co-incubation with the cell-permeable calcium chelator, N,N'-[1,2-ethanediylbis(oxy-2,1-phenylene)]bis[N-[2-[(acetyloxy)methoxy]-2-oxoethyl]-1,1'-bis[(acetyloxy)methyl] ester-glycine (BAPTA-AM), as well as the non-selective protein kinase-C (PKC) inhibitors bisindolylmaleimide-1 (BIM-1) and 2-[1-3(Aminopropyl)indol-3-yl]-3(1-methyl-1H-indol-3-yl)maleimide (or Bisindolylmaleimide VIII; Ro-31-7549). Taken together, these results suggest that in vitro MCAT incubation may model important aspects of MCAT administration in vivo, and that calcium and PKC contribute to the in vitro effects of MCAT on DAT.

Parkin-deficient rats are resistant to neurotoxicity of chronic high-dose methamphetamine

Methamphetamine (METH) is a highly addictive and powerful central nervous system psychostimulant with no FDA-approved pharmacotherapy. Parkin is a neuroprotective protein and its loss of function contributes to Parkinson's disease. This study used 3-month-old homozygous parkin knockout (PKO) rats to determine whether loss of parkin protein potentiates neurotoxicity of chronic METH to the nigrostriatal dopamine pathway. PKO rats were chronically treated with 10 mg/kg METH for 10 consecutive days and assessed for neurotoxicity markers in the striatum on the 5th and 10th day of withdrawal from METH. The PKO rats showed higher METH-induced hyperthermia; however, they did not display augmented deficits in dopaminergic and serotonergic neurotoxicity markers, astrocyte activation or decreased mitochondrial enzyme levels as compared to wild-type (WT) rats. Interestingly, saline-treated PKO rats had lower levels of dopamine (DA) as well as mitochondrial complex I and II levels while having increased basal levels of glial fibrillary acidic protein (GFAP), a marker of gliosis. These results indicate PKO display a certain resistance to METH neurotoxicity, possibly mediated by lowered DA levels and downregulated mitochondria.

Methamphetamine-induced dopaminergic neurotoxicity as a model of Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disease with a high prevalence, approximately 1 % in the elderly population. Numerous studies have demonstrated that methamphetamine (MA) intoxication caused the neurological deficits and nigrostriatal damage seen in Parkinsonian conditions, and subsequent rodent studies have found that neurotoxic binge administration of MA reproduced PD-like features, in terms of its symptomatology and pathology. Several anti-Parkinsonian medications have been shown to attenuate the motor impairments and dopaminergic damage induced by MA. In addition, it has been recognized that mitochondrial dysfunction, oxidative stress, pro-apoptosis, proteasomal/autophagic impairment, and neuroinflammation play important roles in inducing MA neurotoxicity. Importantly, MA neurotoxicity has been shown to share a common mechanism of dopaminergic toxicity with that of PD pathogenesis. This review describes the major findings on the neuropathological features and underlying neurotoxic mechanisms induced by MA and compares them with Parkinsonian pathogenesis. Taken together, it is suggested that neurotoxic binge-type administration of MA in rodents is a valid animal model for PD that may provide knowledge on the neuropathogenesis of PD.

Substance Use Disorders in Patients With Parkinson's Disease and Adverse Hospitalization Outcomes: A National Inpatient Study

Objectives

To understand the demographic pattern of substance use disorders (SUD) in Parkinson’s disease (PD) inpatients and to evaluate the impact of SUD on hospitalization outcomes including the severity of illness, length of stay (LOS), total charges, and disposition to nursing facilities.

Methods

We used the nationwide inpatient sample and identified adult patients (age, ≥40 years) with PD as a primary diagnosis and comorbid SUD (N = 959) and grouped by co-diagnosis of alcohol (N = 789), cannabis (N = 46), opioid (N = 30), stimulants (N = 54) and barbiturate (N = 40) use disorders. We used a binomial logistic regression model to evaluate the odds ratio (OR) for major loss of functioning and disposition to nursing facilities in PD inpatients. All regression models were adjusted for demographics, including age, sex, race, and median household income.

Results

Alcohol, opioid, and stimulant use disorders were prevalent in old-age adults (60-79 years), males, and whites, but cannabis use was prevalent in middle-aged adults (40-59 years), and barbiturate use among older-age (>80 years). The severity of illness is statistically higher in PD inpatients with comorbid opioid and barbiturate use disorders with major loss of body functioning, closely seconded by alcohol and stimulant use disorder cohorts (27.6% and 25.9%, respectively). Disease severity and loss of body functioning increase with advancing age (>80 years adults, OR 5.8, 95%CI 5.32-6.37), and in blacks (OR 1.7, 95%CI 1.56-1.81), and those with opioid use disorder (OR 3.8, 95%CI 1.96-7.35). PD inpatients with barbiturate use disorder had a higher LOS and charges by 17.4 days and $68,922, and six-fold increased likelihood (95%CI 2.33-15.67) for disposition to nursing facilities.

Conclusions

SUD is prevalent among PD patients and is associated with more severe illnesses with body loss functioning and prolonged care. A multidisciplinary care model including collaborative neuropsychiatric and addiction management is required to manage SUD among PD patients to lessen disease severity, slow down the disease progression and potentially save medical costs.

Autophagy as a gateway for the effects of methamphetamine: From neurotransmitter release and synaptic plasticity to psychiatric and neurodegenerative disorders

As a major eukaryotic cell clearing machinery, autophagy grants cell proteostasis, which is key for neurotransmitter release, synaptic plasticity, and neuronal survival. In line with this, besides neuropathological events, autophagy dysfunctions are bound to synaptic alterations that occur in mental disorders, and early on, in neurodegenerative diseases. This is also the case of methamphetamine (METH) abuse, which leads to psychiatric disturbances and neurotoxicity. While consistently altering the autophagy machinery, METH produces behavioral and neurotoxic effects through molecular and biochemical events that can be recapitulated by autophagy blockade. These consist of altered physiological dopamine (DA) release, abnormal stimulation of DA and glutamate receptors, as well as oxidative, excitotoxic, and neuroinflammatory events. Recent molecular insights suggest that METH early impairs the autophagy machinery, though its functional significance remains to be investigated. Here we discuss evidence suggesting that alterations of DA transmission and autophagy are intermingled within a chain of events underlying behavioral alterations and neurodegenerative phenomena produced by METH. Understanding how METH alters the autophagy machinery is expected to provide novel insights into the neurobiology of METH addiction sharing some features with psychiatric disorders and parkinsonism.

Methamphetamine and heightened risk for early-onset stroke and Parkinson's disease: A review

INTRODUCTION

Methamphetamine users are typically young adults, placing them at risk for significant drug-related harms. Neurological harms include stroke and Parkinson's disease, both of which may develop prematurely in the context of methamphetamine use.

MATERIAL AND METHODS

We conducted a narrative review examining the evidence first, for stroke under 45 years and second, early onset of Parkinson's disease (PD) and parkinsonism related to methamphetamine use. We summarise epidemiological factors and common clinical features, before examining in detail the underlying pathology and causal mechanisms.

RESULTS AND DISCUSSION

Methamphetamine use among young people (<45 years) is associated with heightened risk for haemorrhagic stroke. Compared to age-matched all-cause fatal stroke, haemorrhage secondary to aneurysmal rupture is more common among young people with methamphetamine-related stroke and is associated with significantly poorer prognosis. Aetiology is related primarily to both acute and chronic hypertension associated with methamphetamine's sympathomimetic action. Evidence from a variety of sources supports a link between methamphetamine use and increased risk for the development of PD and parkinsonism, and with their early onset in a subset of individuals. Despite this, direct evidence of degeneration of dopaminergic neurons in methamphetamine users has not been demonstrated to date.

CONCLUSIONS

Stroke and Parkinson's Disease/parkinsonism are neurological harms observed prematurely in methamphetamine users.

GPx-1-encoded adenoviral vector attenuates dopaminergic impairments induced by methamphetamine in GPx-1 knockout mice through modulation of NF-κB transcription factor

We suggested that selenium-dependent glutathione peroxidase (GPx) plays a protective role against methamphetamine (MA)-induced dopaminergic toxicity. We focused on GPx-1, a major selenium-dependent enzyme and constructed a GPx-1 gene-encoded adenoviral vector (Ad-GPx-1) to delineate the role of GPx-1 in MA-induced dopaminergic neurotoxicity. Exposure to Ad-GPx-1 significantly induced GPx activity and GPx-1 protein levels in GPx-1-knockout (GPx-1-KO) mice. MA-induced dopaminergic impairments [i.e., hyperthermia; increased nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) DNA-binding activity; and decreased dopamine levels, TH activity, and behavioral activity] were more pronounced in GPx-1-KO mice than in WT mice. In contrast, exposure to Ad-GPx-1 significantly attenuated MA-induced dopaminergic loss in GPx-1-KO mice. The protective effect exerted by Ad-GPx-1 was comparable to that exerted by pyrrolidine dithiocarbamate (PDTC), an NF-κB inhibitor against MA insult. Consistently, GPx-1 overexpression significantly attenuated MA dopaminergic toxicity in mice. PDTC did not significantly impact the protective effect of GPx-1 overexpression, suggesting that interaction between NF-κB and GPx-1 is critical for dopaminergic protection. Thus, NF-κB is a potential therapeutic target for GPx-1-mediated dopaminergic protective activity. This study for the first time demonstrated that Ad-GPx-1 rescued dopaminergic toxicity in vivo following MA insult. Furthermore, GPx-1-associated therapeutic interventions may be important against dopaminergic toxicity.

Neuroprotective Effects of Curcumin in Methamphetamine-Induced Toxicity

Curcumin (CUR), a natural polyphenol extracted from rhizome of the Curcuma longa L, has received great attention for its multiple potential health benefits as well as disease prevention. For instance, CUR protects against toxic agents acting on the human body, including the nervous system. In detail, CUR possesses, among others, strong effects as an autophagy activator. The present study indicates that CUR counteracts methamphetamine (METH) toxicity. Such a drug of abuse is toxic by disturbing the autophagy machinery. We profited from an unbiased, low variable cell context by using rat pheochromocytoma PC12 cell line. In such a system, a strong protection was exerted by CUR against METH toxicity. This was associated with increased autophagy flux, merging of autophagosomes with lysosomes and replenishment of autophagy vacuoles with LC3, which instead is moved out from the vacuoles by METH. This is expected to enable the autophagy machinery. In fact, while in METH-treated cells the autophagy substrates α-synuclein accumulates in the cytosol, CUR speeds up α-synuclein clearance. Under the effects of CUR LC3 penetrate in autophagy vacuoles to commit them to cell clearance and promotes the autophagy flux. The present data provide evidence that CUR counteracts the neurotoxic effects induced by METH by promoting autophagy.

Is Attention-Deficit/Hyperactivity Disorder a Risk Syndrome for Parkinson's Disease?

Recent epidemiological evidence indicates that diagnosis of attention-deficit/hyperactivity disorder (ADHD) is associated with increased risk for diseases of the basal ganglia and cerebellum, including Parkinson's disease (PD). The evidence reviewed here indicates that deficits in striatal dopamine are a shared component of the causal chains that produce these disorders. Neuropsychological studies of adult ADHD, prodromal PD, and early-stage PD reveal similar deficits in executive functions, memory, attention, and inhibition that are mediated by similar neural substrates. These and other findings are consistent with the possibility that ADHD may be part of the PD prodrome. The mechanisms that may mediate the association between PD and ADHD include neurotoxic effects of stimulants, other environmental exposures, and Lewy pathology. Understanding the nature of the association between PD and ADHD may provide insight into the etiology and pathogenesis of both disorders. The possible contribution of stimulants to this association may have important clinical and public health implications.

The Role of α-Synuclein in Methamphetamine-Induced Neurotoxicity

Methamphetamine (METH), a highly addictive psychostimulant, is the second most widely used illicit drug. METH produces damage dopamine neurons and apoptosis via multiple inter-regulating mechanisms, including dopamine overload, hyperthermia, oxidative stress, mitochondria dysfunction, endoplasmic reticulum stress, protein degradation system dysfunction, and neuroinflammation. Increasing evidence suggests that chronic METH abuse is associated with neurodegenerative changes in the human brain and an increased risk of Parkinson's disease (PD). METH use and PD may share some common steps in causing neurotoxicity. Accumulation of α-synuclein, a presynaptic protein, is the pathological hallmark of PD. Intriguingly, α-synuclein upregulation and aggregation are also found in dopaminergic neurons in the substantia nigra in chronic METH users. This suggests α-synuclein may play a role in METH-induced neurotoxicity. The mechanism of α-synuclein cytotoxicity in PD has attracted considerable attention; however, how α-synuclein affects METH-induced neurotoxicity has not been reviewed. In this review, we summarize the relationship between METH use and PD, interdependent mechanisms that are involved in METH-induced neurotoxicity and the significance of α-synuclein upregulation in response to METH use. The identification of α-synuclein overexpression and aggregation as a contributor to METH-induced neurotoxicity may provide a novel therapeutic target for the treatment of the deleterious effect of this drug and drug addiction.

Psychostimulant use disorder emphasizing methamphetamine and the opioid -dopamine connection: Digging out of a hypodopaminergic ditch

BACKGROUND

Approved food and drug administration (FDA) medications to treat Psychostimulant Use Disorder (PUD) are needed. Both acute and chronic neurological deficits related to the neurophysiological effects of these powerfully addictive drugs can cause stroke and alterations in mood and cognition.

OBJECTIVE

This article presents a brief review of the psychiatric and neurobiological sequelae of methamphetamine use disorder, some known neurogenetic associations impacted by psychostimulants, and explores treatment modalities and outcomes.

HYPOTHESIS

The authors propose that gentle D2 receptor stimulation accomplished via some treatment modalities can induce dopamine release, causing alteration of D2-directed mRNA and thus enhanced function of D2 receptors in the human. This proliferation of D2 receptors, in turn, will induce the attenuation of craving behavior, especially in genetically compromised high-risk populations.

DISCUSSION

A better understanding of the involvement of molecular neurogenetic opioid, mesolimbic dopamine, and psychostimulant connections in "wanting" supports this hypothesis. While both scientific and, clinical professionals search for an FDA approved treatment for PUD the induction of dopamine homeostasis, via activation of the brain reward circuitry, offers treatment for underlying neurotransmitter functional deficits, potential prophylaxis, and support for recovery efforts.

CONCLUSION

Dopamine regulation may help people dig out of their hypodopaminergia ditch.

Association between amphetamine-related disorders and dementia-a nationwide cohort study in Taiwan

Objective

We have conducted a study to clarify the association between amphetamine‐related disorders (ARD) and the risk of developing dementia.

Methods

This study used a retrospective cohort design by using Taiwan’s National Health Research Institute Database. A random sample of 68,300 subjects between January 1, 2000, and December 31, 2015, was obtained, comprising of 17,075 patients with ARD, and 51,225 controls without ARD (1:3), matched for gender and age group. After adjusting for covariates, a Fine and Gray’s survival analysis (competing with mortality) was used to compare the risk of dementia during a 15‐year follow‐up period.

Results

In the present study, 1,751 of 17,075 patients with ARD and 2,147 of 51,225 in the control group without ARD (883.10 vs 342.83 per 100,000 person‐years) developed dementia. ARD cohort was more likely to develop dementia (hazard ratio = 4.936 [95% CI: 4.609–5.285, P < 0.001). After adjusting for gender, age groups, education, monthly insured premiums, urbanization level, geographic region, comorbidities, the hazard ratio for ARD patients was 5.034 (95% CI: 4.701–5.391, P < 0.001). ARD has been associated with overall dementia, Alzheimer dementia, vascular dementia, and other dementia. Both the amphetamine use disorder and amphetamine‐induced psychotic disorders were associated with the risk of overall dementia, Alzheimer dementia, vascular dementia, and other dementia.

Interpretation

This study shows that patients with ARD, both the amphetamine use disorder and the amphetamine‐induced psychotic disorder, may have a nearly fivefold risk of developing dementia, including Alzheimer dementia and other types of dementia.

Neuroprotection or Neurotoxicity of Illicit Drugs on Parkinson's Disease

Parkinson's Disease (PD) is currently the most rapid growing neurodegenerative disease and over the past generation, its global burden has more than doubled. The onset of PD can arise due to environmental, sporadic or genetic factors. Nevertheless, most PD cases have an unknown etiology. Chemicals, such as the anthropogenic pollutant 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and amphetamine-type stimulants, have been associated with the onset of PD. Conversely, cannabinoids have been associated with the treatment of the symptoms'. PD and medical cannabis is currently under the spotlight, and research to find its benefits on PD is on-going worldwide. However, the described clinical applications and safety of pharmacotherapy with cannabis products are yet to be fully supported by scientific evidence. Furthermore, the novel psychoactive substances are currently a popular alternative to classical drugs of abuse, representing an unknown health hazard for young adults who may develop PD later in their lifetime. This review addresses the neurotoxic and neuroprotective impact of illicit substance consumption in PD, presenting clinical evidence and molecular and cellular mechanisms of this association. This research area is utterly important for contemporary society since illicit drugs' legalization is under discussion which may have consequences both for the onset of PD and for the treatment of its symptoms.