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.

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.

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.

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.

Feasibility and effect of high-intensity training on the progression of motor symptoms in adult individuals with Parkinson's disease: A systematic review and meta-analysis

BACKGROUND

To determine the feasibility and effect of high-intensity interval training (HIIT) in individuals with Parkinson's and their effect on symptom modification and progression.

METHODS

We conducted this systematic review following the Preferred Reporting Items for systematic review and meta-analysis (PRISMA). All studies were searched in seven databases: MEDLINE (PubMed), Cochrane Central Register of Controlled Trials, Web of Science, EMBASE, SPORTDiscus, Virtual Health Library (VHL) and SCOPUS in September 2020 and updated in June 2023. The risk of bias was assessed by the Cochrane Collaboration tool and Grading of Recommendations Assessment, Development and Evaluation (GRADE) tool. We used standardized mean difference (SMD) with a 95% confidence interval (CI) and random effects models, as well as the non-parametric Cochran's Q test and I2 inconsistency test to assess heterogeneity.

RESULTS

A total of 15 randomized clinical trials with 654 participants (mean age, 65.4 years). The majority of studies included high intensity training interventions versus moderate intensity, usual care, or control group. The meta-analysis comparing high-intensity exercise versus control group showed an improvement in the disease severity (MD = -4.80 [95%CI, -6.38; -3.21 high evidence certainty); maximum oxygen consumption (MD = 1.81 [95%CI, 0.36; 3.27] very low evidence certainty) and quality of life (MD = -0.54 [95%CI, -0.94; -0.13] moderate evidence certainty). The results showed that high-intensity exercise compared with moderate intensity exercise group showed a improve motor function and functional mobility measured by the TUG test (MD = -0.38 [95%CI, -0.91; 0.16] moderate evidence certainty) with moderate heterogeneity between studies.

CONCLUSION

High-intensity exercise performed in both continuous and interval modes when compared with control groups may provide motor function benefits for individuals with Parkinson's disease. HIIT may be feasible, but the intensity of the exercise may influence individuals with Parkinson's disease. However, there was a lack of evidence comparing high intensity and moderate intensity for this population, as the results showed heterogeneity.

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.

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.

The Influence of Prenatal Exposure to Methamphetamine on the Development of Dopaminergic Neurons in the Ventral Midbrain

Methamphetamine, a highly addictive central nervous system (CNS) stimulant, is used worldwide as an anorexiant and attention enhancer. Methamphetamine use during pregnancy, even at therapeutic doses, may harm fetal development. Here, we examined whether exposure to methamphetamine affects the morphogenesis and diversity of ventral midbrain dopaminergic neurons (VMDNs). The effects of methamphetamine on morphogenesis, viability, the release of mediator chemicals (such as ATP), and the expression of genes involved in neurogenesis were evaluated using VMDNs isolated from the embryos of timed-mated mice on embryonic day 12.5. We demonstrated that methamphetamine (10 µM; equivalent to its therapeutic dose) did not affect the viability and morphogenesis of VMDNs, but it reduced the ATP release negligibly. It significantly downregulated Lmx1a, En1, Pitx3, Th, Chl1, Dat, and Drd1 but did not affect Nurr1 or Bdnf expression. Our results illustrate that methamphetamine could impair VMDN differentiation by altering the expression of important neurogenesis-related genes. Overall, this study suggests that methamphetamine use may impair VMDNs in the fetus if taken during pregnancy. Therefore, it is essential to exercise strict caution for its use in expectant mothers.

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.

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.

Reducing neuroinflammation via therapeutic compounds and lifestyle to prevent or delay progression of Parkinson's disease

Parkinson's disease (PD) is the second most common age-associated neurodegenerative disorder and is characterised by progressive loss of dopamine neurons in the substantia nigra. Peripheral immune cell infiltration and activation of microglia and astrocytes are observed in PD, a process called neuroinflammation. Neuroinflammation is a fundamental response to protect the brain but, when chronic, it triggers neuronal damage. In the last decade, central and peripheral inflammation were suggested to occur at the prodromal stage of PD, sustained throughout disease progression, and may play a significant role in the pathology. Understanding the pathological mechanisms of PD has been a high priority in research, primarily to find effective treatments once symptoms are present. Evidence indicates that early life exposure to neuroinflammation as a consequence of life events, environmental or behaviour factors such as exposure to infections, pollution or a high fat diet increase the risk of developing PD. Many studies show healthy habits and products that decrease neuroinflammation also reduce the risk of PD. Here, we aim to stimulate discussion about the role of neuroinflammation in PD onset and progression. We highlight that reducing neuroinflammation throughout the lifespan is critical for preventing idiopathic PD, and present epidemiological studies that detail risk and protective factors. It is possible that introducing lifestyle changes that reduce neuroinflammation at the time of PD diagnosis may slow symptom progression. Finally, we discuss compounds and therapeutics to treat the neuroinflammation associated with PD.

Targeting Aβ and p-Tau Clearance in Methamphetamine-Induced Alzheimer’s Disease-Like Pathology: Roles of Syntaxin 17 in Autophagic Degradation in Primary Hippocampal Neurons

Methamphetamine (Meth), a central nervous system (CNS) stimulant with strong neurotoxicity, causes progressive cognitive impairment with characterized neurodegenerative changes. However, the mechanism underlying Meth-induced pathological changes remains poorly understood. In the current study, Meth elicited a striking accumulation of the pathological proteins hyperphosphorylated tau (p-tau) and amyloid beta (Aβ) in primary hippocampal neurons, while the activation of autophagy dramatically ameliorated the high levels of these pathological proteins. Interestingly, after the Meth treatment, Aβ was massively deposited in autophagosomes, which were remarkably trapped in early endosomes. Mechanistically, syntaxin 17 (Stx17), a key soluble n-ethylmaleimide-sensitive fusion protein (NSF) attachment protein receptor (SNARE) protein responsible for autophagosome and mature endosome/lysosome fusion, was significantly downregulated and hindered in combination with autophagosomes. Notably, adenovirus overexpression of Stx17 in primary neurons facilitated autophagosome-mature endosome/lysosome fusion, which dramatically reversed the Meth-induced increases in the levels of p-tau, Aβ, beta-secretase (Bace-1), and C-terminal fragments (CTFs). Immunofluorescence assays showed that Stx17 retarded the Meth-induced Aβ, p-tau, and Bace-1 accumulation in autophagosomes and facilitated the translocation of these pathological proteins to lysosomes, which indicated the importance of Stx17 via enhanced autophagosome-mature endosome/lysosome fusion. Therefore, the current study reveals a novel mechanism involving Meth-induced high levels of pathological proteins in neurons. Targeting Stx17 may provide a novel therapeutic strategy for Meth-induced neurodegenerative changes.

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.

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.

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.

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.

Pathological methamphetamine exposure triggers the accumulation of neuropathic protein amyloid-β by inhibiting UCHL1

Methamphetamine (METH), a powerful psychoactive drug, causes damage to the nervous system and leads to degenerative changes similar to Alzheimer's disease (AD), however, the molecular mechanism between the toxicity of METH and AD-related symptoms remains poorly understood. In this study, we investigated the effect of METH exposure on the accumulation of amyloid-β by establishing the animal and cell models. The results showed that METH exposure increased amyloid precursor protein (APP) and β-secretase (BACE1), contributed to the accumulation of amyloid-β, and which was alleviated with the pretreatment of BACE1 inhibitor. In addition, METH exposure decreased ubiquitin carboxy-terminal hydrolases L1 (UCHL1) which was related to the degradation of BACE1, and therefore led to the up-regulation of BACE1. In summary, the study could provide a new insight into the molecular mechanisms of METH toxicity and new evidence for the link between METH abuse and AD.

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.

Measurement of the adult human midbrain with transcranial ultrasound

Background

Transcranial sonography is increasingly used to aid clinical diagnoses of movement disorders, for example, to identify an enlarged area of substantia nigra echogenicity in patients with Parkinson’s disease.

Objective

The current study investigated characteristics of the midbrain at the anatomical plane for quantification of substantia nigra echogenicity. METHODS: Area of substantia nigra echogenicity, cross-sectional area of the midbrain, and interpeduncular angle were quantified in two groups of adults aged 18–50 years: 47 healthy non-drug-using controls (control group) and 22 individuals with a history of methamphetamine use (methamphetamine group), a cohort with a high prevalence of enlarged substantia nigra echogenicity and thus risk of Parkinson’s disease.

Results

In the control group, cross-sectional area of the midbrain (4.47±0.44 cm²) and interpeduncular angle were unaffected by age, sex, or image acquisition side. In the methamphetamine group, cross-sectional midbrain area (4.72±0.60 cm²) and area of substantia nigra echogenicity were enlarged compared to the control group, and the enlargement was sex-dependent (larger in males than females). Whole midbrain area and interpeduncular angle were found to be weak predictors of area of substantia nigra echogenicity after accounting for group and sex.

Conclusions

History of methamphetamine use is associated with an enlarged midbrain and area of substantia nigra echogenicity, and the abnormality is more pronounced in males than females. Thus, males may be more susceptible to methamphetamine-induced changes to the brainstem, and risk of Parkinson’s disease, than females.

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.

Chemically Induced Models of Parkinson's Disease: History and Perspectives for the Involvement of Ferroptosis

Ferroptosis is a newly discovered form of necrotic cell death characterized by its dependency on iron and lipid peroxidation. Ferroptosis has attracted much attention recently in the area of neurodegeneration since the involvement of ferroptosis in Parkinson’s disease (PD), a major neurodegenerative disease, has been indicated using animal models. Although PD is associated with both genetic and environmental factors, sporadic forms of PD account for more than 90% of total PD. Following the importance of environmental factors, various neurotoxins are used as chemical inducers of PD both in vivo and in vitro. In contrast to other neurodegenerative diseases such as Alzheimer’s and Huntington’s diseases (AD and HD), many of the characteristics of PD can be reproduced in vivo by the use of specific neurotoxins. Given the indication of ferroptosis in PD pathology, several studies have been conducted to examine whether ferroptosis plays role in the loss of dopaminergic neurons in PD. However, there are still few reports showing an authentic form of ferroptosis in neuronal cells during exposure to the neurotoxins used as PD inducers. In this review article, we summarize the history of the uses of chemicals to create PD models in vivo and in vitro. Besides, we also survey recent reports examining the possible involvement of ferroptosis in chemical models of PD.

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.

3,4-Methylenedioxypyrovalerone: Neuropharmacological Impact of a Designer Stimulant of Abuse on Monoamine Transporters

Methylenedioxypyrovalerone (MDPV) is an abused synthetic cathinone, commonly referred to as a "bath salt." Because the dopamine (DA) transporter (DAT) and vesicular monoamine transporter-2 (VMAT-2) are key regulators of both the abuse and neurotoxic potential of structurally and behaviorally related agents, the impact of MDPV on these transporters was investigated. Results revealed that a single in vivo MDPV administration rapidly (within 1 hour) and reversibly increased both rat striatal DAT and VMAT-2 activity, as assessed via [³H]DA uptake in synaptosomes and synaptic vesicles, respectively, prepared from treated rats. There was no evidence of an MDPV-induced increase in plasmalemmal membrane DAT surface expression. Plasma concentrations of MDPV increased dose-dependently as assessed 1 hour after 2.5 and 5.0 mg/kg (s.c.) administration and returned to levels less than 10 ng/ml by 18 hours after 2.5 mg/kg (s.c.). Neither pretreatment with a D1 receptor (SCH23390), a D2 receptor (eticlopride), nor a nicotinic receptor (mecamylamine) antagonist attenuated the MDPV-induced increase in DAT activity. In contrast, eticlopride pretreatment attenuated both the MDPV-induced increase in VMAT-2-mediated DA uptake and an associated increase in cytoplasmic-associated vesicle VMAT-2 immunoreactivity. SCH23390 did not attenuate the MDPV-induced increase in VMAT-2 activity. Repeated MDPV injections did not cause persistent DAergic deficits, as assessed 7 to 8 days later. The impact of MDPV on striatal and hippocampal serotonergic assessments was minimal. Taken together, these data contribute to a growing pharmacological rubric for evaluating the ever-growing list of designer cathinone-related stimulants. The profile of MDPV compared with related psychostimulants is discussed. SIGNIFICANCE STATEMENT: Pharmacological characterization of the synthetic cathinone, 3,4-methylenedioxypyrovalerone (MDPV; commonly referred to as a "bath salt"), is critical for understanding the abuse liability and neurotoxic potential of this and related agents. Accordingly, the impact of MDPV on monoaminergic neurons is described and compared with that of related psychostimulants.

Alpha-Synuclein deficiency ameliorates chronic methamphetamine induced neurodegeneration in mice

The α-Synuclein (α-syn) and tau have synergistic effects on neurodegenerative diseases induced by environmental factors or genetic mutation. Thus, we investigated the role of α-syn and tau in neurodegeneration induced by chronic methamphetamine (METH) exposure (1.0∼20.0 mg/kg/d body weight, for 14 consecutive days). Here, we present a mice model with evidences of α-syn and tau participating in toxicology in chronic METH. METH increased α-syn level in the stratum oriens, pyramidal layer, stratum radiatum and stratum moleculare of hippocampal CA1, CA2 and CA3, polymorph layer of hippocampal dentate gyrus (DG), and substantia nigra (SN). The subcellular locations of the upregulated α-syn were mainly found in mitochondria and axons. The METH upregulated α-syn may directly induce mitochondrial damage, myelin sheath destruction, and synaptic failure. Also, the excess α-syn might indirectly promote tau phosphorylation through tau kinase GSK3β and CDK5, leading to microtubule depolymerization and eventually fusion deficit of autophagosome and lysosome. In the in vitro experiment, the autophagic vacuoles failed to fuse with the lysosome. The neuropathology induced by both the direct and indirect effects of α-syn could be alleviated by α-syn knockout. Taking together, these results indicate that the α-syn mediates the neurodegenerative process induced by chronic METH and that reducing α-syn might be a potential approach to protect the toxic effects of METH and also be, to a broader view, of therapeutic value in neurodegenerative diseases.

Methamphetamine Use and Antipsychotic-related Extrapyramidal Side-effects in Patients with Psychotic Disorders

Objective: Extrapyramidal side-effects (EPSE) are frequent in patients treated with antipsychotics and comorbid substance use disorders (SUDs). Methamphetamine has been shown to act as a dopaminergic neurotoxin. We aimed to determine whether EPSE occur more often in patients with psychotic disorders and co-occurring methamphetamine (MA) use disorders, and we examined the relationship between MA use, antipsychotic type, dose and EPSE. Methods: This study was a secondary analysis of data from three separate primary studies. Across all studies, psychiatric and SUD diagnoses were determined using the SCID-I for DSM-IV. EPSE were determined using the Simpson-Angus Scale (SAS) for Parkinsonism, the Barnes Akathisia Rating scale (BARS), and the Abnormal Involuntary Movement Scale (AIMS) for tardive dyskinesia. Participants were classified as having any EPSE if they scored above the cutoff on any of the EPSE scales (SAS, BARS, AIMS). We analyzed data using multivariable logistic regression analysis. Results: The sample included 102 patients with non-affective or affective psychotic disorders. Of the total sample, 65.7% were male, 54.9% had schizophrenia spectrum disorders, 20.5% bipolar type I disorder with psychotic features, 11.7% schizoaffective disorder and 12.7% had substance-induced psychosis. A diagnosis of a methamphetamine use disorder (abuse or dependence) was present in 25.5% of participants. EPSE occurred in 38.2% of patients and were significantly associated with MA use in the unadjusted and adjusted analysis, OR_adj = 4.01, 95% CI [1.07, 14.98], p = .039. Patients with MA dependence and MA use >3 years were significantly more likely to have EPSE. We found a significant interaction effect between MA use disorders and standardized antipsychotic dose on the occurrence of EPSE, OR_adj = 1.01, 95% CI [1.00, 1.01], p = .042, with MA users having a disproportionally higher likelihood of having EPSE compared to MA non-users as antipsychotic dosage increased. There were no significant associations of EPSE with comorbid alcohol, cannabis, or methaqualone use disorders. Conclusions: Patients with a MA use disorder were significantly more likely to have EPSE with evidence for a dose-response effect. Clinicians should carefully titrate antipsychotic dosage from lower to higher doses to avoid EPSE in patients with MA use disorders.

Differential Responses of LINE-1 in the Dentate Gyrus, Striatum and Prefrontal Cortex to Chronic Neurotoxic Methamphetamine: A Study in Rat Brain

Methamphetamine (METH) is a widely abused psychostimulant with the potential to cause a broad range of severe cognitive deficits as well as neurobehavioral abnormalities when abused chronically, particularly at high doses. Cognitive deficits are related to METH neurotoxicity in the striatum and hippocampus. The activation of transposable Long INterspersed Nuclear Element 1 (LINE-1) is associated with several neurological diseases and drug abuse, but there are very limited data regarding the effects of high-dose METH on the activity of LINE-1 in the adult brain. Using real-time quantitative PCR, the present study demonstrates that the chronic administration of neurotoxic METH doses results in the increased expression of LINE-1-encoded Open Reading Frame 1 (ORF-1) in rat striatum shortly after the last dose of the drug and decreased ORF-1 expression during METH withdrawal, with dentate gyrus potentially developing "tolerance" to these METH effects. LINE-1 activation may be a new factor mediating the neurotoxic effects of chronic METH in the striatum and, therefore, a new drug target against METH-induced psychomotor impairments in chronic METH users.

Age of Onset of Methamphetamine Consumption among the Iranian Youth Aged 19-29: A Cross-sectional Study

Background

Around the world, one of the main concerns and risky behaviors among youths is methamphetamine consumption. Since the age of onset of methamphetamine use is decreasing, therefore, it is important to identify the effective factors on the age of onset of methamphetamine consumption. In the present study, factors affecting the age of onset of methamphetamine consumption was studied in Iranian youths aged 19-29 years.

Methods

In this cross-sectional nationwide study, individuals aged 19-29 years were selected through multistage cluster sampling and convenience sampling method from 13 provinces in Iran. People completed the questionnaire pertaining to knowledge, attitude, and history of methamphetamine consumption. In order to investigate the factors effective on the age of onset of methamphetamine consumption, we used the Weibull parametric model for data with doubly censored characteristic.

Findings

3246 people participated in this study, half of whom were men and mostly single (60.3%), university student or graduate (50.2%), and unemployed (58.1%). Nearly 6% of participants have ever used methamphetamine. Mean and standard deviation (SD) of age of onset of methamphetamine use was 20.3 ± 3.3 years. Data analysis indicated that the variables of gender, marital status, education, knowing a methamphetamine consumer, knowing an ecstasy consumer, ecstasy consumption, illegitimate sex, attitude towards methamphetamine, and age group were the factors affecting the age of onset of methamphetamine consumption.

Conclusion

The results can contribute to the policy-makers to take the necessary interventions on the factors affecting the age of onset of methamphetamine consumption to reduce the methamphetamine consumption, especially in the critical young ages.

Prevalence of self-reported movement dysfunction among young adults with a history of ecstasy and methamphetamine use

BACKGROUND

Illicit stimulant use is associated with long-lasting changes in movement and movement-related brain regions. The aim of our study was to investigate the prevalence of movement dysfunction in this population. We hypothesized that prevalence of self-reported movement dysfunction is higher among stimulant users than non-stimulant users.

METHODS

Three groups of adults completed a survey containing questions about demographics, health, drug use, and movement. The groups consisted of ecstasy users with no history of methamphetamine use (ecstasy group, n = 190, 20 ± 3 yrs.), methamphetamine users (methamphetamine group, n = 331, 23 ± 5 yrs.), and non-stimulant users (control group, n = 228, 25 ± 8 yrs.). Movement data was analyzed with logistic regression.

RESULTS

In the unadjusted logistic regression model, group had a significant effect on fine hand control, tremor, and voice/speech questions, but not on other movement domain questions. The prevalence of tremor and abnormal fine hand control was significantly higher in the ecstasy and methamphetamine groups than in the control group (p < 0.018), and changes in voice/speech was more prevalent in the ecstasy group than in the control group (p = 0.015). Age and use of cannabis and hallucinogens were confounding variables. However, inspection of chi-square tables suggests that the effect of these parameters on the movement data is likely to be minor.

CONCLUSIONS

The prevalence of self-reported tremor and changes in fine hand control and voice/speech is significantly higher in stimulant users than in non-stimulant users. Inclusion of these common and noticeable changes in body function may aid public health campaigns that target prevention or harm minimization.

Use of illicit amphetamines is associated with long-lasting changes in hand circuitry and control

OBJECTIVE

The study aim was to determine if use of illicit amphetamines or ecstasy is associated with abnormal excitability of the corticomotoneuronal pathway and manipulation of novel objects with the hand.

METHODS

Three groups of adults aged 18-50 years were investigated: individuals with a history of illicit amphetamine use, individuals with a history of ecstasy use but minimal use of other stimulants, and non-drug users. Transcranial magnetic stimulation was delivered to the motor cortex and the electromyographic response (motor evoked potential; MEP) was recorded from a contralateral hand muscle. Participants also gripped and lifted a novel experimental object consisting of two strain gauges and an accelerometer.

RESULTS

Resting MEP amplitude was larger in the amphetamine group (6M, 6F) than the non-drug and ecstasy groups (p < 0.005) in males but not females. Overestimation of grip force during manipulation of a novel object was observed in the amphetamine group (p = 0.020) but not the ecstasy group.

CONCLUSIONS

History of illicit amphetamine use, in particular methamphetamine, is associated with abnormal motor cortical and/or corticomotoneuronal excitability in males and abnormal manipulation of novel objects in both males and females.

SIGNIFICANCE

Abnormal excitability and hand function is evident months to years after cessation of illicit amphetamine use.

Significance of protein kinase C in the neuropsychotoxicity induced by methamphetamine-like psychostimulants

The abuse of methamphetamine (MA), an amphetamine (AMPH)-type stimulant, has been demonstrated to be associated with various neuropsychotoxicity, including memory impairment, psychiatric morbidity, and dopaminergic toxicity. Compelling evidence from preclinical studies has indicated that protein kinase C (PKC), a large family of serine/threonine protein kinases, plays an important role in MA-induced neuropsychotoxicity. PKC-mediated N-terminal phosphorylation of dopamine transporter has been identified as one of the prerequisites for MA-induced synaptic dopamine release. Consistently, it has been shown that PKC is involved in MA (or AMPH)-induced memory impairment and mania-like behaviors as well as MA drug dependence. Direct or indirect regulation of factors related to neuronal plasticity seemed to be critical for these actions of PKC. In addition, PKC-mediated mitochondrial dysfunction, oxidative stress or impaired antioxidant defense system has been suggested to play a role in psychiatric and cognitive disturbance induced by MA (or AMPH). In MA-induced dopaminergic toxicity, particularly PKCδ has been shown to trigger oxidative stress, mitochondrial dysfunction, pro-apoptotic changes, and neuroinflammation. Importantly, PKCδ may be a key mediator in the positive feedback loop composed of these detrimental events to potentiate MA-induced dopaminergic toxicity. This review outlines the role of PKC and its individual isozymes in MA-induced neuropsychotoxicity. Better understanding on the molecular mechanism of PKCs might provide a great insight for the development of potential therapeutic or preventive candidates for MA (or AMPH)-associated neuropsychotoxicity.

Implications of alpha-synuclein nitration at tyrosine 39 in methamphetamine-induced neurotoxicity in vitro and in vivo

Methamphetamine is an amphetamine-type psychostimulant that can damage dopaminergic neurons and cause characteristic pathological changes similar to neurodegenerative diseases such as Parkinson’s disease. However, its specific mechanism of action is still unclear. In the present study, we established a Parkinson’s disease pathology model by exposing SH-SY5Y cells and C57BL/6J mice to methamphetamine. In vitro experiments were performed with 0, 0.5, 1.0, 1.5, 2.0 or 2.5 mM methamphetamine for 24 hours or 2.0 mM methamphetamine for 0-, 2-, 4-, 8-, 16-, and 24-hour culture of SH-SY5Y cells. Additional experimental groups of SH-SY5Y cells were administered a nitric oxide inhibitor, 0.1 mM N-nitro-L-arginine, 1 hour before exposure to 2.0 mM methamphetamine for 24 hours. In vivo experiments: C57BL/6J mice were intraperitoneally injected with N-nitro-L-arginine (8 mg/kg), eight times, at intervals of 12 hours. Methamphetamine 15 mg/kg was intraperitoneally injected eight times, at intervals of 12 hours, but 0.5-hour after each N-nitro-L-arginine injection in the combined group. Western blot assay was used to determine the expression of nitric oxide synthase, α-synuclein (α-Syn), 5G4, nitrated α-synuclein at the residue Tyr39 (nT39 α-Syn), cleaved caspase-3, and cleaved poly ADP-ribose polymerase (PARP) in cells and mouse brain tissue. Immunofluorescence staining was conducted to measure the positive reaction of NeuN, nT39 α-Syn and 5G4. Enzyme linked immunosorbent assay was performed to determine the dopamine levels in the mouse brain. After methamphetamine exposure, α-Syn expression increased; the aggregation of α-Syn 5G4 increased; nT39 α-Syn, nitric oxide synthase, cleaved caspase-3, and cleaved PARP expression increased in the cultures of SH-SY5Y cells and in the brains of C57BL/6J mice; and dopamine levels were reduced in the mouse brain. These changes were markedly reduced when N-nitro-L-arginine was administered with methamphetamine in both SH-SY5Y cells and C57BL/6J mice. These results suggest that nT39 α-Syn aggregation is involved in methamphetamine neurotoxicity.

Prolonged increase in ser31 tyrosine hydroxylase phosphorylation in substantia nigra following cessation of chronic methamphetamine

Methamphetamine (MA) exposure may increase the risk of motor or cognitive impairments similar to Parkinson's disease (PD) by middle age. Although damage to nigrostriatal or mesoaccumbens dopamine (DA) neurons may occur during or early after MA exposure, overt PD-like symptoms at a younger age may not manifest due to compensatory mechanisms to maintain DA neurotransmission. One possible compensatory mechanism is increased tyrosine hydroxylase (TH) phosphorylation. In the rodent PD 6-OHDA model, nigrostriatal lesion decreases TH protein in both striatum and substantia nigra (SN). However, DA loss in the SN is significantly less than that in the striatum. An increase in ser31 TH phosphorylation in the SN may increase TH activity in response to TH loss. To determine if similar compensatory mechanisms may be engaged in young mice after MA exposure, TH expression, phosphorylation, and DA tissue content were evaluated, along with dopamine transporter expression, 21 days after cessation of MA (24 mg/kg, daily, 14 days). DA tissue content was unaffected by the MA regimen in striatum, nucleus accumbens, SN, or ventral tegmental area (VTA), despite decreased TH protein in SN and VTA. In the SN, but not striatum, ser31 phosphorylation increased over 2-fold. This suggests that increased ser31 TH phosphorylation may be an inherent compensatory mechanism to attenuate DA loss against TH loss, similar to that in an established PD model. These results also indicate the somatodendritic compartments of DA neurons are more vulnerable to TH protein loss than terminal fields following MA exposure.

The Main Molecular Mechanisms Underlying Methamphetamine- Induced Neurotoxicity and Implications for Pharmacological Treatment

Methamphetamine (METH) is a popular new-type psychostimulant drug with complicated neurotoxicity. In spite of mounting evidence on METH-induced damage of neural cell, the accurate mechanism of toxic effect of the drug on central nervous system (CNS) has not yet been completely deciphered. Besides, effective treatment strategies toward METH neurotoxicity remain scarce and more efficacious drugs are to be developed. In this review, we summarize cellular and molecular bases that might contribute to METH-elicited neurotoxicity, which mainly include oxidative stress, excitotoxicity, and neuroinflammation. We also discuss some drugs that protect neural cells suffering from METH-induced neurotoxic consequences. We hope more in-depth investigations of exact details that how METH produces toxicity in CNS could be carried out in future and the development of new drugs as natural compounds and immunotherapies, including clinic trials, are expected.

The sigma-1 receptor as a regulator of dopamine neurotransmission: A potential therapeutic target for methamphetamine addiction

Methamphetamine (METH) abuse is a major public health issue around the world, yet there are currently no effective pharmacotherapies for the treatment of METH addiction. METH is a potent psychostimulant that increases extracellular dopamine levels by targeting the dopamine transporter (DAT) and alters neuronal activity in the reward centers of the brain. One promising therapeutic target for the treatment of METH addiction is the sigma-1 receptor (σ1R). The σ1R is an endoplasmic reticulum-localized chaperone protein that is activated by cellular stress, and, unique to this chaperone, its function can also be induced or inhibited by different ligands. Upon activation of this unique "chaperone receptor", the σ1R regulates a variety of cellular functions and possesses neuroprotective activity in the brain. Interestingly, a variety of σ1R ligands modulate dopamine neurotransmission and reduce the behavioral effects of METH in animal models of addictive behavior, suggesting that the σ1R may be a viable therapeutic target for the treatment of METH addiction. In this review, we provide background on METH and the σ1R as well as a literature review regarding the role of σ1Rs in modulating both dopamine neurotransmission and the effects of METH. We aim to highlight the complexities of σ1R pharmacology and function as well as the therapeutic potential of the σ1R as a target for the treatment of METH addiction.

Protective and restorative effects of the traditional Chinese medicine Jitai tablet against methamphetamine-induced dopaminergic neurotoxicity

Background

Methamphetamine (METH) is a psychostimulant with high abuse liability that affects the monoamine neurotransmitter systems, particularly the dopamine system. Currently there are no effective medications for the treatment of METH abuse to restore METH-induced dopaminergic dysfunction. The Jitai tablet (JTT), a commercial traditional Chinese medicinal preparation, has been shown to modulate the dopaminergic function both in heroin addicts and in morphine-dependent rats. The purpose of this study was to investigate, in a rodent model, whether JTT can protect against METH-induced neurotoxicity, and/or restore METH-damaged dopaminergic function.

Methods

Immunohistochemical staining and/or autoradiography staining were used to detect tyrosine hydroxylase (TH) expression in the substantia nigra, and to examine the levels of dopamine transporter (DAT), dopamine D2 receptor (D2R) and TH levels in the striatum. Using a stereotyped behavior rating scale, we evaluated the inhibitory effect of JTT on METH-induced behavioral sensitization.

Results

Repeated METH administration induced obvious stereotyped behavior and neurotoxicity on the dopaminergic system. Pre-treatment with JTT significantly attenuated METH-induced stereotyped responses, and interdicted METH-induced changes in the levels of DAT, D2R and TH expression. Treatment with JTT after METH administration restored DAT, D2R and TH expression to normal levels.

Conclusions

Our results indicated that JTT protects against METH-induced neurotoxicity and restores the dopaminergic function, and thus might be a potential treatment for the dopaminergic deficits associated with METH abuse.

Lack of an association between attention-deficit/hyperactivity disorder (ADHD) and amyotrophic lateral sclerosis (ALS)

BACKGROUND

Lulé, Ludolph, and Ludolph (2008) hypothesized that there may be a pathophysiological link between attention-deficit/hyperactivity disorder (ADHD) and amyotrophic lateral sclerosis (ALS). They summarized common clinical features, specifically enhanced physical and psychological activity, which have been described typically for ADHD patients and also as common personality traits before disease onset in patients with ALS.

METHODS

We assessed the lifetime prevalence rate of ADHD in 104 patients with ALS using valid self-report instruments for ADHD symptoms in childhood (WURS-k) and adulthood (ADHD-SB). Results were compared with a population-based sample (n=2069) and with patients with Parkinson's disease (PD, n=52) using regression analyses and adjusting for sociodemographic differences. Physical activity was assessed by the 21-item exercise dependency scale (EDS-21).

RESULTS

ALS patients reported a lower prevalence of childhood ADHD compared to the general population. Both clinical groups reported significantly lower scores on the WURS-k scale and the attention deficit subscale of the ADHD-SB. The EDS-21 showed significantly longer exercise times in ALS and PD patients.

CONCLUSIONS

We could not show that ADHD is more common in ALS patients. However, our results revealed shared personality traits in ALS and PD with lower rates of premorbid attention deficit symptoms and increased physical activity.

PKCδ-dependent p47phox activation mediates methamphetamine-induced dopaminergic neurotoxicity

Protein kinase C (PKC) has been recognized to activate NADPH oxidase (PHOX). However, the interaction between PKC and PHOX in vivo remains elusive. Treatment with methamphetamine (MA) resulted in a selective increase in PKCδ expression out of PKC isoforms. PKCδ co-immunoprecipitated with p47phox, and facilitated phosphorylation and membrane translocation of p47phox. MA-induced increases in PHOX activity and reactive oxygen species were attenuated by knockout of p47phox or PKCδ. In addition, MA-induced impairments in the Nrf-2-related glutathione synthetic system were also mitigated by knockout of p47phox or PKCδ. Glutathione-immunoreactivity was co-localized in Iba-1-labeled microglial cells and in NeuN-labeled neurons, but not in GFAP-labeled astrocytes, reflecting the necessity for self-protection against oxidative stress by mainly microglia. Buthionine-sulfoximine, an inhibitor of glutathione biosynthesis, potentiated microglial activation and pro-apoptotic changes, leading to dopaminergic losses. These neurotoxic processes were attenuated by rottlerin, a pharmacological inhibitor of PKCδ, genetic inhibitions of PKCδ [i.e., PKCδ knockout mice (KO) and PKCδ antisense oligonucleotide (ASO)], or genetic inhibition of p47phox (i.e., p47phox KO or p47phox ASO). Rottlerin did not exhibit any additive effects against the protective activity offered by genetic inhibition of p47phox. Therefore, we suggest that PKCδ is a critical regulator for p47phox activation induced by MA, and that Nrf-2-dependent GSH induction via inhibition of PKCδ or p47phox, is important for dopaminergic protection against MA insult.

Prior nicotine self-administration attenuates subsequent dopaminergic deficits of methamphetamine in rats: role of nicotinic acetylcholine receptors

Preclinical studies have demonstrated that oral nicotine exposure attenuates long-term dopaminergic damage induced by toxins, including repeated, high doses of methamphetamine. It is suggested that alterations in nicotinic acetylcholine receptor (nAChR) expression, including α4β2* and α6β2* subtypes, likely contribute to this protection. The current study extended these findings by investigating whether nicotine self-administration in male, Sprague-Dawley rats (a) attenuates short-term dopaminergic damage induced by methamphetamine and (b) causes alterations in levels of α4β2* and α6β2* nAChR subtypes. The findings indicate that nicotine self-administration (0.032 mg/kg/infusion for 14 days) per se did not alter α4β2* and α6β2* nAChR expression or dopamine transporter (DAT) expression and function. Interestingly, prior nicotine self-administration attenuated methamphetamine-induced decreases in DAT function when assessed 24 h, but not 1 h, after methamphetamine treatment (4×7.5 mg/kg/injection). The ability of nicotine to attenuate the effects of methamphetamine on DAT function corresponded with increases in α4β2*, but not α6β2*, nAChR binding density. Understanding the role of nAChRs in methamphetamine-induced damage has the potential to elucidate mechanisms underlying the etiology of disorders involving dopaminergic dysfunction, as well as to highlight potential new therapeutic strategies for prevention or reduction of dopaminergic neurodegeneration.

Molecular, Behavioral, and Physiological Consequences of Methamphetamine Neurotoxicity: Implications for Treatment

Understanding the relationship between the molecular mechanisms underlying neurotoxicity of high-dose methamphetamine (METH) and related clinical manifestations is imperative for providing more effective treatments for human METH users. This article provides an overview of clinical manifestations of METH neurotoxicity to the central nervous system and neurobiology underlying the consequences of administration of neurotoxic METH doses, and discusses implications of METH neurotoxicity for treatment of human abusers of the drug.

Role of Mitochondria in Methamphetamine-Induced Dopaminergic Neurotoxicity: Involvement in Oxidative Stress, Neuroinflammation, and Pro-apoptosis-A Review

Methamphetamine (MA), an amphetamine-type psychostimulant, is associated with dopaminergic toxicity and has a high abuse potential. Numerous in vivo and in vitro studies have suggested that impaired mitochondria are critical in dopaminergic toxicity induced by MA. Mitochondria are important energy-producing organelles with dynamic nature. Evidence indicated that exposure to MA can disturb mitochondrial energetic metabolism by inhibiting the Krebs cycle and electron transport chain. Alterations in mitochondrial dynamic processes, including mitochondrial biogenesis, mitophagy, and fusion/fission, have recently been shown to contribute to dopaminergic toxicity induced by MA. Furthermore, it was demonstrated that MA-induced mitochondrial impairment enhances susceptibility to oxidative stress, pro-apoptosis, and neuroinflammation in a positive feedback loop. Protein kinase Cδ has emerged as a potential mediator between mitochondrial impairment and oxidative stress, pro-apoptosis, or neuroinflammation in MA neurotoxicity. Understanding the role and underlying mechanism of mitochondrial impairment could provide a molecular target to prevent or alleviate dopaminergic toxicity induced by MA.