Neurotoxic morphological changes induced in the medial prefrontal cortex of rats behaviorally sensitized to methamphetamine

Gegen-Qinlian decoction-A traditional Chinese medicine formula-Alleviates methamphetamine withdrawal induced anxiety by targeting GABAergic interneuron-pyramidal neuron pathway in mPFC

Methamphetamine (Meth) withdrawal elicits anxiety, which is a public health concern with limited therapeutic options. Previous studies implied a strong correlation between mPFC and Meth withdrawal. Here, we examined the role of Gegen-Qinlian decoction (GQD) in Meth withdrawal anxiety and explored potential therapeutic targets in mPFC. We found that intra-gastric administration of GQD during the withdrawal period efficiently alleviated anxiety-like behaviours in Meth-withdrawn mice. Further, GQD could restore Meth withdrawal-triggered pathway of GABAergic interneurons (GABA IN)-pyramidal neurons (PN) in the mPFC of Meth-withdrawn mice, especially the prelimbic cortex (PrL) sub-region and PV-positive GABA IN. While, GQD had no obvious effects on the glial cells in the mPFC of Meth-withdrawn mice. By transcriptomic analysis and validation of several gene candidates, we found that genes in the MAPK signalling pathway, especially those related to heat shock proteins, including Hspa1a, Hspa1b and Hspb1, might be GQD-targeting genes in mPFC to treat Meth withdrawal anxiety, as indicated that these genes were up-regulated by Meth withdrawal but rescued by GQD in mPFC. Collectively, our findings identified for the first time that GQD could efficiently alleviate Meth withdrawal anxiety, partially through regulating the local GABA IN-PN pathway and transcriptomic profile of mPFC. The present study confirms that TCM, such as GQD, will be a desirable therapeutic approach in the treatment of drug addiction and related emotional deficits.

A novel gene therapy for methamphetamine- induced cognitive disorder with a hyper-acidified fusion variant of DnaJB1

Methamphetamine (MA) is spread worldwide and is a highly addictive psychostimulant that can induce neurodegeneration and cognitive disorder, which lacks effective treatments. We and other researchers have found that the crucial member of Hsp70 chaperone machinery, DnaJ, is liable to be co-aggregated with aberrant proteins, which has been confirmed a risk factor to promote neurodegeneration. In the current study, we demonstrated that tailing with a hyper-acidic fusion partner, tua2, human DnaJB1 could resist the formation of toxic mutant Tau aggregates both in prokaryote and eukaryote models. We found that aberrant Tau aggregates could deplete the antioxidant enzyme pool and disturb Hsp70 molecular chaperone system by co-aggregating with the principal members of these systems. Stability-enhanced DnaJB1-tua2 could stop the chain reaction of Tau aggregates as well as maintain redox balance and protein homeostasis. With an MA-induced cognitive disorder mouse model, we found that the cognitive disorder of MA mice was rescued and the overactivated inflammatory response was relieved by the expression of DnaJB1-tua2 in the hippocampus. Furthermore, the Tau neurofibrillary tangles and apoptotic neurons were diminished with the escorting of DnaJB1-tua2. These findings demonstrate that delivering DnaJB1-tua2 in hippocampus may have a therapeutic potential in the treatment of MA-induced cognitive disorder.

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.

Bidirectional causality between addiction and cognitive deficits

Cognitive deficits are highly comorbid with substance use disorders. Deficits span multiple cognitive domains, are associated with disease severity across substance classes, and persist long after cessation of substance use. Furthermore, recovery of cognitive function during protracted abstinence is highly predictive of treatment adherence, relapse, and overall substance use disorder prognosis, suggesting that addiction may be best characterized as a disease of executive dysfunction. While the association between cognitive deficits and substance use disorders is clear, determining causalities is made difficult by the complex interplay between these variables. Cognitive dysfunction present prior to first drug use can act as a risk factor for substance use initiation, likelihood of pathology, and disease trajectory. At the same time, substance use can directly cause cognitive impairments even in individuals without preexisting deficits. Thus, parsing preexisting risk factors from substance-induced adaptations, and how they may interact, poses significant challenges. Here, focusing on psychostimulants and alcohol, we review evidence from clinical literature implicating cognitive deficits as a risk factor for addiction, a consequence of substance use, and the role the prefrontal cortex plays in these phenomena. We then review corresponding preclinical literature, highlighting the high degree of congruency between animal and human studies, and emphasize the unique opportunity that animal models provide to test causality between cognitive phenotypes and substance use, and to investigate the underlying neurobiology at a cellular and molecular level. Together, we provide an accessible resource for assessing the validity and utility of forward- and reverse-translation between these clinical and preclinical literatures.

Reduced fractional anisotropy in projection, association, and commissural fiber networks in neonates with prenatal methamphetamine exposure

Prenatal exposure to methamphetamine is associated with neurostructural changes, including alterations in white matter microstructure. This study investigated the effects of methamphetamine exposure on microstructure of global white matter networks in neonates. Pregnant women were interviewed beginning in mid-pregnancy regarding their methamphetamine use. Diffusion weighted imaging sets were acquired for 23 non-sedated neonates. White matter bundles associated with pairs of target regions within five networks (commissural fibers, left and right projection fibers, and left and right association fibers) were estimated using probabilistic tractography, and fractional anisotropy (FA) and diffusion measures determined within each connection. Multiple regression analyses showed that increasing methamphetamine exposure was significantly associated with reduced FA in all five networks, after control for potential confounders. Increased exposure was associated with lower axial diffusivity in the right association fiber network and with increased radial diffusivity in the right projection and left and right association fiber networks. Within the projection and association networks a subset of individual connections showed a negative correlation between FA and methamphetamine exposure. These findings are consistent with previous reports in older children and demonstrate that microstructural changes associated with methamphetamine exposure are already detectable in neonates.

LC3 and ATG5 overexpression and neuronal cell death in the prefrontal cortex of postmortem chronic methamphetamine users

Methamphetamine (METH) abuse is accompanied by oxidative stress, METH-induced neurotoxicity, and apoptosis. Oxidative stress has devastating effects on the structure of proteins and cells. Autophagy is an evolutionarily conserved intracellular regulated mechanism for orderly degradation of dysfunctional proteins or removing damaged organelles. The precise role of autophagy in oxidative stress-induced apoptosis of dopaminergic neuronal cells caused by METH has not clarified completely. In this study, we sought to evaluate the effects of METH abuse on autophagy in the prefrontal cortex of postmortem users, mainly focusing on the ATG5 and LC3 during neuroinflammation. Postmortem molecular and histological examination was done for two groups containing 12 non-addicted and 14 METH addicted cases. ATG5 and LC3 expression were analyzed by real-time PCR and immunohistochemistry (IHC) methods. Histopathological analysis was performed by stereological cell counting of neuronal cells using Hematoxylin and Eosin (H & E) staining technique. In order to detect DNA damage in the prefrontal lobe, Tunnel staining was performed. Real-time PCR and IHC assay showed overexpression of ATG5 and LC3 protein in the prefrontal cortex of Meth users. The cell death and neuronal degeneration were increased significantly based on Tunel assay and the stereological analysis in the Prefrontal cortex. Chronic METH exposure probably induces ATG5 and LC3 overexpression and neuronal cell death in the Prefrontal cortex of the postmortem cases.

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.

Differential gene expression and stereological analyses of the cerebellum following methamphetamine exposure

Methamphetamine (METH) is a highly addictive psychostimulant that profoundly aimed at monoaminergic systems in the brain. Despite the leading role of cerebellum in sensorimotor control as well as augmented locomotor activity under the influence of METH, there are few studies examining the effect of METH administration on gene expression profiling and structural consequences in the cerebellar region. Thus, we sought to explore the effects of METH on the cerebellum, from gene expression changes to structural alterations. In this respect, we investigated genome-wide mRNA expression using high throughput RNA-seq technology and confirmatory quantitative real-time PCR, accompanied by stereological analysis of cerebellar layers along with identification of reactive astrogliosis by glial fibrillary acidic protein and behavioral assessment following METH exposure. According to our RNA-seq data, 473 unique differentially expressed genes (DEG) were detected upon METH injections in which a large number of these genes engage basically in biological regulations and metabolic processes, chiefly located in nucleus and membrane. In addition, pathway analysis of METH-induced DEG revealed several enriched signaling cascades related largely to immune response, neurotransmission, cell growth, and death. Further, METH induced a significant reduction in volumes of cerebellar layers (molecular, granular, and Purkinje) and a decrease in the white matter volume along with a rise in astrogliosis as well as increased locomotor activity. In conclusion, considering gene expression changes combined with structural alterations of the cerebellum in response to METH, these data suggest METH-induced neurotoxicity in the cerebellar region.

Methamphetamine induces neuronal death: Evidence from rodent studies

Animal studies have consistently observed neuronal death following methamphetamine (MA) administration, however, these have not been systematically reviewed. This systematic review aims to present the evidence for MA-induced neuronal death in animals (rodents) and identify the regions affected. Locating the brain regions in which neuronal death occurs in animal studies will provide valuable insight into the linkage between MA consumption and the structural alterations observed in the human brain. The data were collected from three databases: Scopus, Ovid, and the Web of Science. Thirty-seven studies met the inclusion criteria and were divided into two sub-groups, i.e. acute and repeated administration. Twenty-six (of 27) acute and ten (of 11) repeated administration studies observed neuronal death. A meta-analysis was not possible due to different variables between studies, i.e. species, treatment regimens, withdrawal periods, methods of quantification, and regions studied. Acute MA treatment induced neuronal death in the frontal cortex, striatum, and substantia nigra, but not in the hippocampus, whereas repeated MA administration led to neuronal loss in the hippocampus, frontal cortex, and striatum. In addition, when animals self-administered the drug, neuronal death was observed at much lower doses than the doses administered by experimenters. There is some overlap in the regions where neuronal death occurred in animals and the identified regions from human studies. For instance, gray matter deficits have been observed in the prefrontal cortex and hippocampus of MA users. The findings presented in this review implicate that not only does MA induce neuronal death in animals, but it also damages the same regions affected in human users. Despite the inter-species differences, animal studies have contributed significantly to addiction research, and are still of great assistance for future research with a more relevant model of compulsive drug use in humans.

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

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

Activation of Trace Amine-Associated Receptor 1 Stimulates an Antiapoptotic Signal Cascade via Extracellular Signal-Regulated Kinase 1/2

Methamphetamine (MA) is highly addictive and neurotoxic, causing cell death in humans and in rodent models. MA, along with many of its analogs, is an agonist at the G protein-coupled trace amine-associated receptor 1 (TAAR1). TAAR1 activation protects against MA-induced degeneration of dopaminergic neurons, suggesting that TAAR1 plays a role in regulating MA-induced neurotoxicity. However, the mechanisms involved in TAAR1's role in neurotoxicity and cell death have not been described in detail. In this study, we investigated the apoptosis pathway in Taar1 wild-type (WT) and knockout (KO) mice and in cells expressing the recombinant receptor. Bcl-2, an antiapoptotic protein, was upregulated ∼3-fold in the midbrain area (substantial nigra and ventral tegmental area) in Taar1 KO compared with WT mice, and MA significantly increased Bcl-2 expression in WT mice but decreased Bcl-2 expression in KO mice. The proapoptotic protein Bax did not differ across genotype or in response to MA. Bcl-2 expression was significantly upregulated by the TAAR1 agonist RO5166017 ((S)-4-[(ethyl-phenyl-amino)-methyl]-4,5-dihydro-oxazol-2-ylamine) in cells expressing the recombinant mouse TAAR1. Additionally, activation of TAAR1 by RO5166017 increased phosphorylation of extracellular signal-regulated kinase (ERK) 1/2, and protein kinase B (AKT), but only inhibition of ERK1/2 phosphorylation prevented TAAR1-induced increases in Bcl-2 levels, indicating that TAAR1 activation increases Bcl-2 through an ERK1/2-dependent pathway. All changes to ERK1/2 pathway intermediates were blocked by the TAAR1 antagonist, N-(3-ethoxyphenyl)-4-(1-pyrrolidinyl)-3-(trifluoromethyl) benzamide. These findings suggest that TAAR1 activation protects against MA-induced cell apoptosis and TAAR1 may play a role in cell death in neurodegenerative diseases. SIGNIFICANCE STATEMENT: Methamphetamine stimulates TAAR1, a G protein-coupled receptor. The role and mechanisms for TAAR1 in methamphetamine-induced neurotoxicity are not known. Here, we report that, in genetic mouse models and cells expressing the recombinant receptor, TAAR1 activates the ERK1/2 pathway but not the AKT pathway to upregulate the antiapoptotic protein Bcl-2, which protects cells from drug-induced toxicity.

Methamphetamine causes neurotoxicity by promoting polarization of macrophages and inflammatory response

Macrophages, especially their activation state, are closely related to the progression of neurotoxicity. Classically activated macrophages (M1) are proinflammatory effectors, while alternatively activated macrophages (M2) exhibit anti-inflammatory properties. As a powerful addictive psychostimulant drug, coupled with its neurotoxicity, methamphetamine (Meth) abuse may lead to long-lasting abnormalities in the neuronal system. The present study investigated the effect of Meth at subtoxic concentration on macrophage activation state and its underlying toxicity to neuronal cells. PC12 and Murine RAW264.7 cells were coincubated with Meth to test its toxicity. 3-(4,5-Dimethylthiazol)-2,5-diphenyltetrazolium-bromide, enzyme-linked immunosorbent assay, real-time polymerase chain reaction, and Western blot assays were performed to evaluate the toxicity, cytokine secretion, gene, and protein expression. Results showed that cytotoxicity was enhanced on PC12 cells after coculturing with RAW264.7 stimulated with Meth. RAW264.7 macrophages tended to switch to the M1 phenotype, releasing more nitric oxide and proinflammatory cytokines, including tumor necrosis factor α (TNFα), interleukin (IL)-12, and IL-1β, while decreasing the release of anti-inflammatory cytokine IL-10 after treatment with Meth. Meth upregulated the gene expression of IL-6, IL-1β, and TNFα and downregulated the expression of Arg-1, IL-10, and KLF4. Meth could also upregulate the protein expression of IL-1β and TNF α and downregulate the expression of Arg-1 and KLF4. However, the abovementioned effects induced by Meth were abolished by the addition of dopamine receptor D3 antagonist. In conclusion, our study demonstrated that Meth promoted macrophage polarization from M0 to M1 and enhanced inflammatory response, which provided the scientific rationale for the neurotoxicity caused by the chronic use of Meth.

Impaired skeletal health and neuromuscular function among amphetamine users in clinical treatment

SUMMARY

This study examined musculoskeletal health in amphetamine users, compared with healthy age-matched controls. We show that amphetamine users have reduced bone mass at several skeletal sites and attenuated maximal muscle strength and force development capacity in the lower extremities.

INTRODUCTION

Amphetamine use may cause poor bone quality and elevated risk of osteoporosis. The purpose of this study was to investigate whether amphetamine users exhibit reduced regional and whole body bone mineral density (BMD), altered bone metabolism, and how muscle function may relate to the patient groups' skeletal health.

METHODS

We assessed hip, lumbar spine and whole body BMD, and trabecular bone score (TBS) by dual x-ray absorptiometry (DXA), and bone metabolism markers in serum and maximal strength and force development capacity in 36 amphetamine users (25 men, 30 ± 7 years; 11 women 35 ± 10 years) and in 37 healthy controls (23 men, 31 ± 9 years; 14 women, 35 ± 7 years).

RESULTS

Whole body BMD was lower in amphetamine users (8% in males and 7% females, p < 0.01), as were BMD at the total hip and sub-regions of the hip (9-11% in men and 10-11 % in women, p < 0.05). Male users had 4% lower TBS (p < 0.05) and higher serum level of type 1 collagen amino-terminal propeptide (p < 0.01). This coincided with reduced lower extremity maximal strength of 30% (males, p < 0.001) and 25% (females, p < 0.05) and 27% slower muscular force development in males compared to controls (p < 0.01).

CONCLUSIONS

These findings demonstrate that amphetamine users suffer from a generalized reduction in bone mass, which was associated with attenuated maximal muscle strength and force development capacity in the lower extremities.

Does physical activity protect against drug abuse vulnerability?

BACKGROUND

The current review examined recent literature to determine our state of knowledge about the potential ability of physical activity serve as a protectant against drug abuse vulnerability.

METHODS

Both preclinical and clinical studies were examined using either associational or random assignment study designs. In addition to examining drug use as an outcome variable, the potential neural mediators linking physical activity and drug abuse vulnerability were examined.

CONCLUSIONS

Several important conclusions may be drawn. First, the preclinical evidence is solid in showing that physical activity in various forms is able to serve as both a preventive and treatment intervention that reduces drug use, although voluntary alcohol drinking appears to be an exception to this conclusion. Second, the clinical evidence provides some evidence, albeit mixed, to suggest a beneficial effect of physical activity on tobacco dependent individuals. In contrast, there exists only circumstantial evidence that physical activity may reduce use of drugs other than nicotine, and there is essentially no solid information from random control studies to know if physical activity may prevent initiation of problem use. Finally, both preclinical and clinical evidence shows that various brain systems are altered by physical activity, with the medial prefrontal cortex (mPFC) serving as one potential node that may mediate the putative link between physical activity and drug abuse vulnerability. It is concluded that novel neurobehavioral approaches taking advantage of novel techniques for assessing the physiological impact of physical activity are needed and can be used to inform the longitudinal random control studies that will answer definitively the question posed.

Comparison of noradrenaline, dopamine and serotonin in mediating the tachycardic and thermogenic effects of methamphetamine in the ventral medial prefrontal cortex

Methamphetamine (METH) is a psychostimulant that disrupts monoaminergic neurotransmission to evoke profound behavioral and physiological effects. Rapidly distributing to forebrain regions to increase synaptic concentrations of three monoamines (dopamine (DA), serotonin (5-HT) and noradrenaline (NA)), the medial prefrontal cortex (mPFC) is important in METH-altered behavioral and psychological profiles. Activation of the ventral mPFC can modify physiological variables, however, METH-evoked autonomic changes from this region are unknown. Therefore, the aim of this study was to characterize the respiratory, metabolic and cardiovascular effects of microinjection of METH, DA, 5-HT and NA into the ventral mPFC in urethane-anesthetized Sprague-Dawley rats. METH and NA microinjection evoked dose-related increases in heart rate, interscapular brown adipose tissue temperature and expired CO2, a pattern of response characteristic of non-shivering thermogenesis. NA and 5-HT microinjection elicited pressor and depressor responses, respectively, with matching baroreflex adjustments in sympathetic nerve activity while METH and DA evoked no change in vasomotor outflow. Low doses of METH and DA may evoke respiratory depression. These data suggest that METH's actions in the ventral mPFC, likely via adrenergic receptors, evoke non-shivering thermogenesis which may contribute to the increased body temperature and tachycardia seen in those that abuse METH.

Recent advances in methamphetamine neurotoxicity mechanisms and its molecular pathophysiology

Methamphetamine (METH) is a sympathomimetic amine that belongs to phenethylamine and amphetamine class of psychoactive drugs, which are widely abused for their stimulant, euphoric, empathogenic, and hallucinogenic properties. Many of these effects result from acute increases in dopamine and serotonin neurotransmission. Subsequent to these acute effects, METH produces persistent damage to dopamine and serotonin release in nerve terminals, gliosis, and apoptosis. This review summarized the numerous interdependent mechanisms including excessive dopamine, ubiquitin-proteasome system dysfunction, protein nitration, endoplasmic reticulum stress, p53 expression, inflammatory molecular, D₃ receptor, microtubule deacetylation, and HIV-1 Tat protein that have been demonstrated to contribute to this damage. In addition, the feasible therapeutic strategies according to recent studies were also summarized ranging from drug and protein to gene level.

Chronic methamphetamine exposure induces cardiac fas-dependent and mitochondria-dependent apoptosis

Very limited information regarding the influence of chronic methamphetamine exposure on cardiac apoptosis is available. In this study, we evaluate whether chronic methamphetamine exposure will increase cardiac Fas-dependent (type I) and mitochondria-dependent (type II) apoptotic pathways. Thirty-two male Wistar rats at 3-4 months of age were randomly divided into a vehicle-treated group [phosphate-buffered saline (PBS) 0.5 ml SQ per day] and a methamphetamine-treated group (MA 10 mg/kg SQ per day) for 3 months. We report that after 3 months of exposure, abnormal myocardial architecture, more minor cardiac fibrosis and cardiac TUNEL-positive apoptotic cells were observed at greater frequency in the MA group than in the PBS group. Protein levels of TNF-α, Fas ligand, Fas receptor, Fas-associated death domain, activated caspase-8, and activated caspase-3 (Fas-dependent apoptosis) extracted from excised hearts were significantly increased in the MA group, compared to the PBS group. Protein levels of cardiac Bak, t-Bid, Bak to Bcl-xL ratio, activated caspase-9, and activated caspase-3 (mitochondria-dependent apoptosis) were significantly increased in the MA group, compared with the PBS group. The results from this study reveal that chronic methamphetamine exposure will activate cardiac Fas-dependent and mitochondria-dependent apoptotic pathways, which may indicate a possible mechanism for developing cardiac abnormalities in humans with chronic methamphetamine abuse.

Methamphetamine affects cell proliferation in the medial prefrontal cortex: a new niche for toxicity

Methamphetamine addicts demonstrate impaired frontal cortical-dependent cognitive function that could result from methamphetamine-induced maladaptive plasticity in the prefrontal cortex. Reduced adult gliogenesis observed in a rodent model of compulsive methamphetamine self-administration could contribute to the maladaptive plasticity in the medial prefrontal cortex (mPFC) as excessive methamphetamine intake is associated with loss of gliogenesis. The present study explored the vulnerability of mPFC progenitors to the duration of various sessions of methamphetamine self-administration in limited and extended access schedule of reinforcement. Proliferation of progenitors via Ki-67 labeling and apoptosis via activated caspase-3 labeling were studied in rats that intravenously self-administered methamphetamine in a limited access (1h/day: short access (ShA)) or extended access (6h/day: long access (LgA)) paradigm over 4, 13, 22 or 42 sessions, and in rats that experienced 22 sessions and were withdrawn from self-administration for a period of 4weeks. Four sessions of LgA methamphetamine enhanced proliferation and apoptosis and forty-two sessions of ShA and LgA methamphetamine reduced proliferation without effecting apoptosis. Withdrawal from twenty-two sessions of methamphetamine enhanced proliferation in LgA animals. Our findings demonstrate that proliferation of mPFC progenitors is vulnerable to psychostimulant exposure and withdrawal with distinct underlying mechanisms relating to methamphetamine toxicity. The susceptibility of mPFC progenitors to even modest doses of methamphetamine could account for the pronounced neuroadaptation in the mPFC linked to methamphetamine abuse.

Neurotoxicity of methamphetamine and 3,4-methylenedioxymethamphetamine

Amphetamines are a class of psychostimulant drugs that are widely abused for their stimulant, euphoric, empathogenic and hallucinogenic properties. Many of these effects result from acute increases in dopamine and serotonin neurotransmission. Subsequent to these acute effects, methamphetamine and 3,4 methylenedioxymethamphetamine (MDMA) produce persistent damage to dopamine and serotonin nerve terminals. This review summarizes the numerous interdependent mechanisms including excitotoxicity, mitochondrial damage and oxidative stress that have been demonstrated to contribute to this damage. Emerging non-neuronal mechanisms by which the drugs may contribute to monoaminergic terminal damage, as well as the neuropsychiatric consequences of this terminal damage are also presented. Methamphetamine and 3,4-methylenedioxymethamphetamine (MDMA) have similar chemical structures and pharmacologic properties compared to other abused substances including cathinone (khat), as well as a relatively new class of novel synthetic amphetamines known as 'bath salts' that have gained popularity among drug abusers.

Functional and structural brain changes associated with methamphetamine abuse

Methamphetamine (MA) is a potent psychostimulant drug whose abuse has become a global epidemic in recent years. Firstly, this review article briefly discusses the epidemiology and clinical pharmacology of methamphetamine dependence. Secondly, the article reviews relevant animal literature modeling methamphetamine dependence and discusses possible mechanisms of methamphetamine-induced neurotoxicity. Thirdly, it provides a critical review of functional and structural neuroimaging studies in human MA abusers; including positron emission tomography (PET) and functional and structural magnetic resonance imaging (MRI). The effect of abstinence from methamphetamine, both short- and long-term within the context of these studies is also reviewed.

Repeated amphetamine exposure disrupts dopaminergic modulation of amygdala-prefrontal circuitry and cognitive/emotional functioning

Repeated exposure to psychostimulants such as amphetamine (AMPH) disrupts cognitive and behavioral processes mediated by the medial prefrontal cortical (mPFC) and basolateral amygdala (BLA). The present study investigated the effects of repeated AMPH exposure on the neuromodulatory actions of dopamine (DA) on BLA-mPFC circuitry and cognitive/emotional processing mediated by these circuits. Rats received five AMPH (2 mg/kg) or saline injections (controls) over 10 d, followed by 2-4 week drug washout. In vivo neurophysiological extracellular recordings in urethane-anesthetized rats were used to obtain data from mPFC neurons that were either inhibited or excited by BLA stimulation. In controls, acute AMPH attenuated BLA-evoked inhibitory or excitatory responses; these effects were mimicked by selective D(2) or D(1) agonists, respectively. However, in AMPH-treated rats, the ability of these dopaminergic manipulations to modulate BLA-driven decreases/increases in mPFC activity was abolished. Repeated AMPH also blunted the excitatory effects of ventral tegmental area stimulation on mPFC neural firing. Behavioral studies assessed the effect of repeated AMPH on decision making with conditioned punishment, a process mediated by BLA-mPFC circuitry and mesocortical DA. These treatments impaired the ability of rats to use conditioned aversive stimuli (footshock-associated cue) to guide the direction of instrumental responding. Collectively, these data suggest that repeated AMPH exposure can lead to persistent disruption of dopaminergic modulation of BLA-mPFC circuitry, which may underlie impairments in cognitive/emotional processing observed in stimulant abusers. Furthermore, they suggest that impairments in decision making guided by aversive stimuli observed in stimulant abusers may be the result of repeated drug exposure.

Developmental GABAergic deficit enhances methamphetamine-induced apoptosis

RATIONALE

Neuroanatomical evidence suggests that GABAergic deficits and progressive cortical atrophy occur with schizophrenia.

OBJECTIVE

To evaluate the hypothesis that neurodevelopmental deficits affect neurodegeneration occurring with schizophrenia, this study examined a novel animal model for schizophrenia-related neurodevelopmental GABAergic deficit in neurodegenerative progression.

METHODS

The prenatal N-methyl-D-aspartate (NMDA) receptor hypofunction model that induces neurodevelopmental GABAergic deficit in the medial prefrontal cortex (mPFC) was used to examine whether adult offspring of Sprague-Dawley rats exhibited disruption of prepulse inhibition (PPI), enhancement of methamphetamine (METH) (2.5 mg/kg)-induced glutamate release in the mPFC and the emergence of terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL)-positive neurons in this brain region.

RESULTS

Offspring of dams exposed to NMDA receptor antagonist MK-801 on days 15-18 of pregnancy (MK-801 offspring) showed reduced density of parvalbumin-immunoreactive GABAergic interneurons in the mPFC, PPI disruption on postnatal days 63 (P63) and 35 (P35) and an enhanced METH (2.5 mg/kg)-induced glutamate release. Repeated administration of this psychostimulant increased the emergence of TUNEL-positive cells.

CONCLUSION

These findings suggest that prenatal blockade of NMDA receptors induces a neurodevelopmental GABAergic deficit. The decrease in the density of GABAergic neurons might be related to disruption of sensorimotor gating (PPI), enhanced METH-induced release of glutamate in the mPFC and a repeated METH injection-induced increase in apoptosis in this region of the brain in adult animals.

Effects of aripiprazole and haloperidol on progression to schizophrenia-like behavioural abnormalities and apoptosis in rodents

Aripiprazole (APZ) is considered a first-line medication for treating first and multiple episodes of schizophrenia, but its effect on preventing the progressive pathophysiology of schizophrenia remains unclear. This study examined the hypothesis that APZ blocks enhanced glutamate release in the medial prefrontal cortex (mPFC) during psychotic episodes of schizophrenia, thereby preventing progression of the pathophysiology. We examined effects of APZ on methamphetamine (METH)-induced increases in glutamate levels in the mPFC, and on repeatedly administered METH-induced progression to schizophrenia-like behavioural abnormalities involving cross-sensitization to the N-methyl-d-aspartate (NMDA) receptor antagonist, MK-801, deficit of prepulse inhibition (PPI), and expression of TUNEL-positive cells. Additionally, we compared the preventive effects of APZ to those of a conventional antipsychotic: haloperidol (HPD). Results show that APZ (1.0 and 3.0 mg/kg) and HPD (0.1 mg/kg) each blocked METH (2.5 mg/kg)-induced increases in glutamate levels in the mPFC. Furthermore, APZ (3.0 mg/kg) and HPD (0.1 mg/kg), when co-administered repeatedly with METH, each prevented progression to schizophrenia-like behavioural and neuropathological abnormalities. Repeated co-administration of APZ (3.0 mg/kg) with saline did not induce apoptosis, although HPD (0.1 mg/kg) with saline did induce apoptosis. These results indicate that APZ and HPD prevented progressive pathophysiology, which is related to increased glutamate levels, and indicate that repeated administration of HPD, but not APZ, induced apoptosis under conditions without increased glutamate levels. These findings suggest the importance of using APZ and HPD in the appropriate stages of the glutamate-related pathophysiology of schizophrenia.

Amphetamine toxicities: classical and emerging mechanisms

The drugs of abuse, methamphetamine and MDMA, produce long-term decreases in markers of biogenic amine neurotransmission. These decreases have been traditionally linked to nerve terminals and are evident in a variety of species, including rodents, nonhuman primates, and humans. Recent studies indicate that the damage produced by these drugs may be more widespread than originally believed. Changes indicative of damage to cell bodies of biogenic and nonbiogenic amine-containing neurons in several brain areas and endothelial cells that make up the blood-brain barrier have been reported. The processes that mediate this damage involve not only oxidative stress but also include excitotoxic mechanisms, neuroinflammation, the ubiquitin proteasome system, as well as mitochondrial and neurotrophic factor dysfunction. These mechanisms also underlie the toxicity associated with chronic stress and human immunodeficiency virus (HIV) infection, both of which have been shown to augment the toxicity to methamphetamine. Overall, multiple mechanisms are involved and interact to promote neurotoxicity to methamphetamine and MDMA. Moreover, the high coincidence of substituted amphetamine abuse by humans with HIV and/or chronic stress exposure suggests a potential enhanced vulnerability of these individuals to the neurotoxic actions of the amphetamines.

Oxidative stress contributes to methamphetamine-induced left ventricular dysfunction

AIMS

Our aim was to test the hypothesis that the repeated, binge administration of methamphetamine would produce oxidative stress in the myocardium leading to structural remodeling and impaired left ventricular function.

METHODS AND RESULTS

Echocardiography and Millar pressure-volume catheters were used to monitor left ventricular structure and function in rats subjected to four methamphetamine binges (3 mg/kg, iv for 4 days, separated by a 10-day drug-free period). Hearts from treated and control rats were used for histological or proteomic analysis. When compared with saline treatment, four methamphetamine binges produced eccentric left ventricular hypertrophy. The drug also significantly impaired systolic function (decreased fractional shortening, ejection fraction, and adjusted maximal power) and produced significant diastolic dysfunction (increased -dP/dt and tau). Dihydroethedium staining showed that methamphetamine significantly increased (285%) the levels of reactive oxygen species in the left ventricle. Treatment with methamphetamine also resulted in the tyrosine nitration of myofilament (desmin, myosin light chain) and mitochondrial (ATP synthase, NADH dehydrogenase, cytochrome c oxidase, prohibitin) proteins. Treatment with the superoxide dismutase mimetic, tempol in the drinking water prevented methamphetamine-induced left ventricular dilation and systolic dysfunction; however, tempol (2.5 mM) did not prevent the diastolic dysfunction. Tempol significantly reduced, but did not eliminate dihydroethedium staining in the left ventricle, nor did it prevent the tyrosine nitration of mitochondrial and contractile proteins.

CONCLUSION

This study shows that oxidative stress plays a significant role in mediating methamphetamine-induced eccentric left ventricular dilation and systolic dysfunction.

Methamphetamine toxicity and messengers of death

Methamphetamine (METH) is an illicit psychostimulant that is widely abused in the world. Several lines of evidence suggest that chronic METH abuse leads to neurodegenerative changes in the human brain. These include damage to dopamine and serotonin axons, loss of gray matter accompanied by hypertrophy of the white matter and microgliosis in different brain areas. In the present review, we summarize data on the animal models of METH neurotoxicity which include degeneration of monoaminergic terminals and neuronal apoptosis. In addition, we discuss molecular and cellular bases of METH-induced neuropathologies. The accumulated evidence indicates that multiple events, including oxidative stress, excitotoxicity, hyperthermia, neuroinflammatory responses, mitochondrial dysfunction, and endoplasmic reticulum stress converge to mediate METH-induced terminal degeneration and neuronal apoptosis. When taken together, these findings suggest that pharmacological strategies geared towards the prevention and treatment of the deleterious effects of this drug will need to attack the various pathways that form the substrates of METH toxicity.

Olanzapine and risperidone block a high dose of methamphetamine-induced schizophrenia-like behavioral abnormalities and accompanied apoptosis in the medial prefrontal cortex

This study aims to propose a comprehensive new model for schizophrenia, which shows PPI disruption at baseline state as an endophenotype, the development of cross-sensitization to an NMDA receptor antagonist, MK-801 as a clinical phenotype of the progression into treatment-resistance, and accompanied induction of apoptosis in the medial prefrontal cortex as a critical possibility during the progression. Repeated administration of a high dose of methamphetamine (METH) (2.5 mg/kg), which could increase glutamate levels in the medial prefrontal cortex (mPFC), induced TUNEL-positive cells in this region, accompanied development of behavioral cross-sensitization to MK-801 in response to a challenge injection of MK-801, and PPI disruption at baseline state without a challenge injection. Olanzapine (OLZ) (1.0 mg/kg) and risperidone (RIS) (0.1 mg/kg), which inhibited and remarkably attenuated METH (2.5 mg/kg)-induced increases in glutamate levels, respectively, blocked not only the induction of TUNEL-positive cells in the mPFC but also the accompanied development of above behavioral abnormalities. These findings suggest that repeating the METH-induced glutamate release produces behavioral abnormalities as a clinical phenotype of schizophrenia, accompanied apoptosis as a critical possibility during the progression, and suggest that sufficient dose of olanzapine and risperidone can block the development of these behavioral abnormalities and accompanied apoptosis during the progression.

Endogenous nociceptin (orphanin FQ) suppresses basal hedonic state and acute reward responses to methamphetamine and ethanol, but facilitates chronic responses

The opioid peptide nociceptin (orphanin FQ) suppresses drug reward, drug self-administration, and impedes some of the processes believed to underlie the transition to addiction. As virtually all previous studies have used administration of nociceptin receptor agonists to evaluate the role of nociceptin on addiction-like behavior, the current study used a pharmacological (nociceptin receptor antagonist) and genetic (nociceptin receptor knockout mice) approach to elucidate the role of endogenous nociceptin. The nociceptin receptor antagonist UFP-101 induced a modest place preference, and enhanced the conditioned place preference induced by methamphetamine. In agreement with this, nociceptin receptor knockout mice had slightly enhanced methamphetamine and ethanol conditioned place preferences compared to wild-type mice. This effect did not appear to depend on differences in learning ability, as nociceptin receptor knockout mice had slightly weaker-conditioned place aversions to lithium chloride, the kappa-opioid receptor agonist, U50488H, and the general opiate antagonist, naloxone. The development of behavioral sensitization to methamphetamine was lower in nociceptin receptor knockout mice, and attenuated by UFP-101 administration to wild-type mice. Additionally, ethanol consumption and preference in a two-bottle choice test was lower in nociceptin receptor knockout mice, though ethanol-stimulated locomotion was stronger. Whereas the rewarding effect of methamphetamine and ethanol following chronic treatment, as measured by place conditioning, strengthened in wild-type mice, this effect was absent in nociceptin receptor knockout mice. These results suggest that endogenous N/OFQ suppresses basal and drug-stimulated increases in hedonic state, and plays either a permissive or facilitatory role in the development of addiction.

Methamphetamine self-administration and voluntary exercise have opposing effects on medial prefrontal cortex gliogenesis

Psychostimulant abuse produces deficits in prefrontal cortex (PFC) function, whereas physical activity improves PFC-dependent cognition and memory. The present study explored the vulnerability of medial PFC (mPFC) precursor proliferation and survival to methamphetamine self-administration and voluntary exercise, factors that may have opposing effects on mPFC plasticity to facilitate functional consequences. Intermittent 1 h access to methamphetamine (I-ShA) increased, but daily 1 and 6 h access decreased, proliferation and survival, with dose-dependent effects on mature cell phenotypes. All groups showed increased cell death. Voluntary exercise enhanced proliferation and survival but, in contrast to methamphetamine exposure, did not alter cell death or mature phenotypes. Furthermore, enhanced cell survival by I-ShA and voluntary exercise had profound effects on gliogenesis with differential regulation of oligodendrocytes versus astrocytes. In addition, new cells in the adult mPFC stain for the neuronal marker neuronal nuclear protein, although enhanced cell survival by I-ShA and voluntary exercise did not result in increased neurogenesis. Our findings demonstrate that mPFC gliogenesis is vulnerable to psychostimulant abuse and physical activity with distinct underlying mechanisms. The susceptibility of mPFC gliogenesis to even modest doses of methamphetamine could account for the pronounced pathology linked to psychostimulant abuse.

Essential role of D1 but not D2 receptors in methamphetamine-induced impairment of long-term potentiation in hippocampal-prefrontal cortex pathway

Methamphetamine (MA) abuse induces deficits in cognitive performance that are related to dysfunction of the prefrontal cortex (PFC). The medial portion of the prefrontal cortex (mPFC) in rats that is crucial for cognitive function has been shown to undergo long-term potentiation (LTP) in the projections from the hippocampus. However, no study has been performed to evaluate the influence of MA on synaptic plasticity in the hippocampal-mPFC pathways. In the present experiments, we investigated the effects of repeated MA administration on hippocampal-mPFC LTP, together with MA-induced stereotyped behaviors. Repeated MA administration produced behavioral sensitization and LTP impairment in the hippocampal-mPFC pathways. The MA-induced impairment of hippocampal-mPFC LTP was prevented by the pretreatment of dopamine 1 (D1) but not dopamine 2 (D2) receptor antagonists, while D1 and D2 receptor antagonists attenuated the MA-induced stereotyped behaviors. These findings suggest that D1 receptors are crucial for the MA-induced deterioration of synaptic plasticity in the hippocampal-mPFC circuits. Impairment of LTP associated with D1 receptor dysfunction may underlie cognitive deficits in MA-dependent subjects.