Methamphetamine modulation of gene expression in the brain: analysis using customized cDNA microarray system with the mouse homologues of KIAA genes

Augmentation of intracranial self-stimulation induced by amphetamine-like drugs in Period circadian regulator 2 knockout mice is associated with intracellular Ca2+ levels

Over the past decade, new psychoactive substances (NPS) have emerged in the illegal drug market and have continued to attract attention from the international community. Among these, amphetamine-like NPS, classified as stimulants, constitute a significant proportion. However, the pharmacological characteristics and mechanisms underlying addiction to amphetamine-like NPS remain poorly understood. Given that circadian rhythms are linked to the brain stimulation effects of methamphetamine (METH) and amphetamine, we investigated the effects of METH, 1-(4-methoxyphenyl)-N-methylpropan-2-amine (PMMA), and 1-(benzofuran-5-yl)-N-ethylpropan-2-amine (5-EAPB) on intracranial self-stimulation (ICSS) in wild-type (WT) or Period circadian regulator 2 knockout mice. Amphetamine-like drugs increase intracellular Ca2+ levels to provoke dopamine release, so we examined the impact of Per2 knockdown on intracellular Ca2+ levels in PC12 cells to elucidate a potential mechanism underlying NPS-induced ICSS enhancement. Our ICSS results showed that METH and PMMA significantly increased brain stimulation in Per2 knockout mice compared to WT mice. Similarly, METH and PMMA induced higher Ca2+ fluorescence intensity in Per2 knockdown PC12 cells than in control cells. In contrast, 5-EAPB did not produce significant changes in either ICSS or Ca2+ signaling. These findings suggest that Per2 plays a crucial role in the brain stimulation effects of amphetamine-like drugs through the regulation of intracellular Ca2+.

Effects of congeners of amphetamine on the human heart

Central stimulatory and hallucinogenic drugs of abuse like amphetamine and most congeners of amphetamine can have cardiac harmful effects. These cardiac side effects can lead to morbidities and death. In this paper, we review current knowledge on the direct and indirect effects of these amphetamine congeners on the mammalian heart-more specifically, the isolated human heart muscle preparation. In detail, we address the question of whether and how these drugs affect cardiac contractility and their mechanisms of action. Based on this information, further research areas are defined, and further research efforts are proposed.

Differentially Expressed Genes in Period 2-Overexpressing Mice Striatum May Underlie Their Lower Sensitivity to Methamphetamine Addiction-Like Behavior

Previous reports have demonstrated that genetic mechanisms greatly mediate responses to drugs of abuse, including methamphetamine (METH). The circadian gene Period 2 (Per2) has been previously associated with differential responses towards METH in mice. While the behavioral consequences of eliminating Per2 have been illustrated previously, Per2 overexpression has not yet been comprehensively described; although, Per2-overexpressing (Per2 OE) mice previously showed reduced sensitivity towards METH-induced addiction-like behaviors. To further elucidate this distinct behavior of Per2 OE mice to METH, we identified possible candidate biomarkers by determining striatal differentially expressed genes (DEGs) in both drug-naïve and METH-treated Per2 OE mice relative to wild-type (WT), through RNA sequencing. Of the several DEGs in drug naïve Per2 OE mice, we identified six genes that were altered after repeated METH treatment in WT mice, but not in Per2 OE mice. These results, validated by quantitative real-time polymerase chain reaction, could suggest that the identified DEGs might underlie the previously reported weaker METH-induced responses of Per2 OE mice compared to WT. Gene network analysis also revealed that Asic3, Hba-a1, and Rnf17 are possibly associated with Per2 through physical interactions and predicted correlations, and might potentially participate in addiction. Inhibiting the functional protein of Asic3 prior to METH administration resulted in the partial reduction of METH-induced conditioned place preference in WT mice, supporting a possible involvement of Asic3 in METH-induced reward. Although encouraging further investigations, our findings suggest that these DEGs, including Asic3, may play significant roles in the lower sensitivity of Per2 OE mice to METH.

Methamphetamine-induced changes in myocardial gene transcription are sex-dependent

BACKGROUND

Prior work demonstrated that female rats (but not their male littermates) exposed to methamphetamine become hypersensitive to myocardial ischemic injury. Importantly, this sex-dependent effect persists following 30 days of subsequent abstinence from the drug, suggesting that it may be mediated by long term changes in gene expression that are not rapidly reversed following discontinuation of methamphetamine use. The goal of the present study was to determine whether methamphetamine induces sex-dependent changes in myocardial gene expression and whether these changes persist following subsequent abstinence from methamphetamine.

RESULTS

Methamphetamine induced changes in the myocardial transcriptome were significantly greater in female hearts than male hearts both in terms of the number of genes affected and the magnitude of the changes. The largest changes in female hearts involved genes that regulate the circadian clock (Dbp, Per3, Per2, BMal1, and Npas2) which are known to impact myocardial ischemic injury. These genes were unaffected by methamphetamine in male hearts. All changes in gene expression identified at day 11 returned to baseline by day 30.

CONCLUSIONS

These data demonstrate that female rats are more sensitive than males to methamphetamine-induced changes in the myocardial transcriptome and that methamphetamine does not induce changes in myocardial transcription that persist long term after exposure to the drug has been discontinued.

Stress-induced neural activation is altered during early withdrawal from chronic methamphetamine

Chronic methamphetamine (MA) use can lead to increased symptoms of depression and anxiety during abstinence. Less is known about the specific brain regions that are altered following repeated MA that may be associated with these behavioral perturbations. Furthermore, MA has been reported to recruit and activate microglia in the brain, which may exacerbate stress-associated behavioral changes. In the present study, male and female mice were injected with MA (5 mg/kg) or saline once daily for 10 days, and during early withdrawal were assessed for alterations in immediate early gene (c-Fos) responses to a forced swim stressor. Chronic MA exposure increased floating and decreased swim time in the forced swim test in male and female mice tested 48 h after the final dose, indicating elevated depressive-like behavior. Furthermore, assessment of nest building, a measure of distress or despair-like behavior, revealed a sex-specific effect with only MA-treated females showing impairments. The c-Fos response to forced swim was attenuated by prior MA exposure in the central amygdala, CA3 hippocampal region, prefrontal cortex, and bed nucleus of the stria terminalis (BST). In the BST this attenuation occurred only in males. Neither the total number of microglia or activated microglia were altered by chronic MA exposure in regions examined. The primary findings indicate that chronic MA exposure attenuates activation of select stress-associated brain regions, a dysregulation that might contribute to alterations in mood-related behaviors.

Regional Analysis of the Brain Transcriptome in Mice Bred for High and Low Methamphetamine Consumption

Transcriptome profiling can broadly characterize drug effects and risk for addiction in the absence of drug exposure. Modern large-scale molecular methods, including RNA-sequencing (RNA-Seq), have been extensively applied to alcohol-related disease traits, but rarely to risk for methamphetamine (MA) addiction. We used RNA-Seq data from selectively bred mice with high or low risk for voluntary MA intake to construct coexpression and cosplicing networks for differential risk. Three brain reward circuitry regions were explored, the nucleus accumbens (NAc), prefrontal cortex (PFC), and ventral midbrain (VMB). With respect to differential gene expression and wiring, the VMB was more strongly affected than either the PFC or NAc. Coexpression network connectivity was higher in the low MA drinking line than in the high MA drinking line in the VMB, oppositely affected in the NAc, and little impacted in the PFC. Gene modules protected from the effects of selection may help to eliminate certain mechanisms from significant involvement in risk for MA intake. One such module was enriched in genes with dopamine-associated annotations. Overall, the data suggest that mitochondrial function and glutamate-mediated synaptic plasticity have key roles in the outcomes of selective breeding for high versus low levels of MA intake.

Neurobiological Functions of the Period Circadian Clock 2 Gene, Per2

Most organisms have adapted to a circadian rhythm that follows a roughly 24-hour cycle, which is modulated by both internal (clock-related genes) and external (environment) factors. In such organisms, the central nervous system (CNS) is influenced by the circadian rhythm of individual cells. Furthermore, the period circadian clock 2 (Per2) gene is an important component of the circadian clock, which modulates the circadian rhythm. Per2 is mainly expressed in the suprachiasmatic nucleus (SCN) of the hypothalamus as well as other brain areas, including the midbrain and forebrain. This indicates that Per2 may affect various neurobiological activities such as sleeping, depression, and addiction. In this review, we focus on the neurobiological functions of Per2, which could help to better understand its roles in the CNS.

Chronic Methamphetamine Exposure Attenuates Neural Activation in Hypothalamic-Pituitary-Adrenal Axis-Associated Brain Regions in a Sex-specific Manner

Sex differences in methamphetamine (MA) abuse and consequences of MA have been reported with females showing an increased addiction phenotype and withdrawal symptoms. One mechanism through which these effects might occur is via sex-specific alterations in the hypothalamic-pituitary-adrenal (HPA) axis and its associated brain regions. In this study, mice were administered MA (5 mg/kg) or saline for 10 consecutive days. During early withdrawal, anxiety-like behaviors were assessed in the open field, light/dark box, and elevated plus maze. At ten days of withdrawal, mice were injected with a final dose of MA (5 mg/kg) or saline. Chronic MA did not alter anxiety-like behaviors or corticosterone responses to a final dose of MA, although females showed elevated corticosterone responses compared to males. Chronic MA attenuated final MA-induced c-Fos in both sexes in the paraventricular hypothalamus (PVH), bed nucleus of the stria terminalis (BNST), cingulate cortex, central and basolateral amygdala. In CA1 and CA3 hippocampal areas, c-Fos attenuation by chronic MA occurred only in females. Within the PVH, final MA injection increased c-Fos to a greater extent in females compared to males regardless of prior MA exposure. Dual-labeling of c-Fos with glucocorticoid receptor revealed a specific attenuation of neural activation within this cell type in the PVH, central and basolateral amygdala, and BNST. Together these findings demonstrate that chronic MA can suppress subsequent activation of HPA axis-associated brain regions and cell phenotypes. Further, in select regions this reduction is sex-specific. These changes may contribute to reported sex differences in MA abuse patterns.

Involvement of the N-methyl-D-aspartate receptor GluN2D subunit in phencyclidine-induced motor impairment, gene expression, and increased Fos immunoreactivity

Background

Noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonists evoke a behavioral and neurobiological syndrome in experimental animals. We previously reported that phencyclidine (PCP), an NMDA receptor antagonist, increased locomotor activity in wildtype (WT) mice but not GluN2D subunit knockout mice. Thus, the aim of the present study was to determine whether the GluN2D subunit is involved in PCP-induced motor impairment.

Results

PCP or UBP141 (a GluN2D antagonist) induced potent motor impairment in WT mice but not GluN2D KO mice. By contrast, CIQ, a GluN2C/2D potentiator, induced severe motor impairment in GluN2D KO mice but not WT mice, suggesting that the GluN2D subunit plays an essential role in the effects of PCP and UBP141, and an appropriate balance between GluN2C and GluN2D subunits might be needed for appropriate motor performance. The level of the GluN2D subunit in the mature mouse brain is very low and restricted. GluN2D subunits exist in brainstem structures, the globus pallidus, thalamus, and subthalamic nucleus. We found that the expression of the c-fos gene increased the most among PCP-dependent differentially expressed genes between WT and GluN2D KO mice, and the number of Fos-positive cells increased after PCP administration in the basal ganglia motor circuit in WT mice but not GluN2D KO mice.

Conclusion

These results suggest that the GluN2D subunit within the motor circuitry is a key subunit for PCP-induced motor impairment, which requires an intricate balance between GluN2C- and GluN2D-mediated excitatory outputs.

MOP Reduction During Long-Term Methamphetamine Withdrawal was Restored by Chronic Post-Treatment with Fluoxetine

Previously, we found fluoxetine reduces methamphetamine preference in mice. However, effects of fluoxetine on developed methamphetamine preference and on methamphetamine induced gene expression changes have been largely unknown. The present study investigates effects of post-treatment with fluoxetine on methamphetamine dependence and on gene expressions after long-term withdrawal in mice. First, we examined whether chronic post-treatment with fluoxetine attenuated methamphetamine-conditioned place preference. Next, we examined the changes in gene expression levels after long-term withdrawal (with saline or fluoxetine treatment) following chronic methamphetamine treatment. Using mRNA from the pooled frontal cortices of 10 mice per group, gene expression analyses were performed using a custom-developed cDNA array and a real-time quantitative reverse transcription-PCR. Chronic post-treatments with fluoxetine abolished the conditioned place preference developed by methamphetamine administrations. Even after long-term withdrawal from repeated methamphetamine administration, µ-opioid receptor (MOP) gene expression was significantly reduced in the frontal cortex. The reduced MOP gene expression in the frontal cortex was restored by chronic administration with fluoxetine. These changes were confirmed by Western blot analyses. These findings suggest that the chronic post-treatments with fluoxetine might be effective for restoring the reduction of MOP levels in the frontal cortex following long-term abstinence from methamphetamine.

The Mammalian Circadian Timing System: Organization and Coordination of Central and Peripheral Clocks

Most physiology and behavior of mammalian organisms follow daily oscillations. These rhythmic processes are governed by environmental cues (e.g., fluctuations in light intensity and temperature), an internal circadian timing system, and the interaction between this timekeeping system and environmental signals. In mammals, the circadian timekeeping system has a complex architecture, composed of a central pacemaker in the brain's suprachiasmatic nuclei (SCN) and subsidiary clocks in nearly every body cell. The central clock is synchronized to geophysical time mainly via photic cues perceived by the retina and transmitted by electrical signals to SCN neurons. In turn, the SCN influences circadian physiology and behavior via neuronal and humoral cues and via the synchronization of local oscillators that are operative in the cells of most organs and tissues. Thus, some of the SCN output pathways serve as input pathways for peripheral tissues. Here we discuss knowledge acquired during the past few years on the complex structure and function of the mammalian circadian timing system.

Circadian phase in sleep-disturbed adolescents with a history of substance abuse: a pilot study

The relationship between actigraphy- or diary-based sleep parameters and salivary melatonin-based dim light melatonin onsets (DLMOs) was examined in 21 adolescents with a history of substance abuse and current complaints of sleep difficulties. The adolescents displayed relationships between diary-based sleep times and DLMO that were of comparable strength with those reported for adult insomniacs and healthy adolescents during the school year, but weaker than those observed in healthy adults and healthy adolescents on summer vacation. When the sample was divided into adolescents with late and early DLMOs, the 2 groups had significantly different phase angles between DLMO and sleep variables but no other significant differences in sleep parameters. However, circadian phase and its relationship to sleep may have sleep and behavioral consequences.

Genetic deletion of vesicular monoamine transporter-2 (VMAT2) reduces dopamine transporter activity in mesencephalic neurons in primary culture

Our aim was to investigate whether a defect in vesicular monoamine transporter-2 (VMAT2) activities would affect dopaminergic cell functions or not. We examined mesencephalon dopaminergic cultures prepared from VMAT2 wild-type, heterozygous or homozygous knockout (KO) 14-day-old mouse fetuses to determine the number of tyrosine hydroxylase (TH)-positive cells and dopamine transporter activity. The number of TH-positive cells remained unchanged in the VMAT2-KO cultures. Of interest, the dopamine transporter activity in the homozygous cells was significantly decreased, but not in the heterozygous cells, suggesting that complete deletion of VMAT2 inhibited dopamine transporter function. Furthermore, dopamine transporter activity was prominently decreased in the synaptosomal fraction of neonatal homozygous VMAT2-KO mice compared with that of wild-type/heterozygous VMAT2-KO ones, indicating that VMAT2 activity might be one of the factors regulating dopamine transporter activities. To test this possibility, we used reserpine, a VMAT2 inhibitor. Reserpine (1muM) decreased dopamine transporter activity (approx. 50%) in wild-type and heterozygous VMAT2-KO cultures but not in homozygous ones, indicating that blockade of VMAT2 activity reduced dopamine transporter activity. To investigate possible mechanisms underlying the decreased dopamine transporter activity in VMAT2-KO mice, we measured dopamine transporter activities after 24-48h exposure of primary cultures of mesencephalic neurons to dopamine receptor antagonists, PKC inhibitor, PI(3)K inhibitor, and l-DOPA. Among these drugs, l-DOPA slightly reduced the dopamine transporter activities of all genotypes, but the other drugs could not. Since the ratios of reduction in dopamine transporter activity of each genotype treated with l-DOPA were similar, substrate inhibition of dopamine transporters was not the main mechanism underlying the reduced dopamine transporter activity due to genetic deletion of VMAT2. Our results demonstrate that genetic deletion of VMAT2 did not induce immediate cell death but did markedly inhibit dopamine transporter activity.

Emerging evidence for the interrelationship of xenobiotic exposure and circadian rhythms: a review

The circadian clock controls many aspects of mammalian physiology and behaviour with a periodicity of approximately 24 h. These include the anticipation of, and adaptation to, daily environmental changes such as the light-dark cycle, temperature fluctuations and the availability of food. The toxicity of many drugs is dependent on the circadian phase at which they are administered, and recent work has begun to unravel the molecular basis for circadian variations in sensitivity to xenobiotic exposure. Between 2 and 10% of the transcriptome is expressed in a circadian manner, including many key genes associated with the metabolism and transport of xenobiotics. Furthermore, a number of xenobiotics may directly alter the expression of genes that control circadian rhythms. This review discusses the emerging evidence for the regulation of circadian rhythm genes having an important impact on molecular response to xenobiotics.

Repeated methamphetamine administration alters expression of the NMDA receptor channel epsilon2 subunit and kinesins in the mouse brain

Repeated amphetamine administration results in behavioral sensitization. Behavioral sensitization related to abuse and/or relapse may be associated with stable changes in gene expression. To explore the participating genes, we examined the changes in gene expression levels 24 h or 21 days (long-term withdrawal period) after chronic methamphetamine (METH) treatment for 2 weeks. The expression of several genes related to glutamatergic neural transmission was altered, although changes in the corresponding protein expression were not always consistent with the results for mRNA expression. Of interest, in the frontal cortex of mice treated with METH for 2 weeks, protein expression levels of KIF17 and the N-methyl-D-asparate (NMDA) receptor channel epsilon2 subunit (NRepsilon2) were concomitantly increased. The alteration in expression of these proteins, KIF17 and NRepsilon2, might be a part of the molecular basis of the behavioral sensitization to METH.

MicroArray Facility: a laboratory information management system with extended support for Nylon based technologies

Background

High throughput gene expression profiling (GEP) is becoming a routine technique in life science laboratories. With experimental designs that repeatedly span thousands of genes and hundreds of samples, relying on a dedicated database infrastructure is no longer an option.

GEP technology is a fast moving target, with new approaches constantly broadening the field diversity. This technology heterogeneity, compounded by the informatics complexity of GEP databases, means that software developments have so far focused on mainstream techniques, leaving less typical yet established techniques such as Nylon microarrays at best partially supported.

Results

MAF (MicroArray Facility) is the laboratory database system we have developed for managing the design, production and hybridization of spotted microarrays. Although it can support the widely used glass microarrays and oligo-chips, MAF was designed with the specific idiosyncrasies of Nylon based microarrays in mind. Notably single channel radioactive probes, microarray stripping and reuse, vector control hybridizations and spike-in controls are all natively supported by the software suite. MicroArray Facility is MIAME supportive and dynamically provides feedback on missing annotations to help users estimate effective MIAME compliance. Genomic data such as clone identifiers and gene symbols are also directly annotated by MAF software using standard public resources. The MAGE-ML data format is implemented for full data export. Journalized database operations (audit tracking), data anonymization, material traceability and user/project level confidentiality policies are also managed by MAF.

Conclusion

MicroArray Facility is a complete data management system for microarray producers and end-users. Particular care has been devoted to adequately model Nylon based microarrays. The MAF system, developed and implemented in both private and academic environments, has proved a robust solution for shared facilities and industry service providers alike.

GEDA: new knowledge base of gene expression in drug addiction

Abuse of drugs can elicit compulsive drug seeking behaviors upon repeated administration, and ultimately leads to the phenomenon of addiction. We developed a procedure for the standardization of microarray gene expression data of rat brain in drug addiction and stored them in a single integrated database system, focusing on more effective data processing and interpretation. Another characteristic of the present database is that it has a systematic flexibility for statistical analysis and linking with other databases. Basically, we adopt an intelligent SQL querying system, as the foundation of our DB, in order to set up an interactive module which can automatically read the raw gene expression data in the standardized format. We maximize the usability of this DB, helping users study significant gene expression and identify biological function of the genes through integrated up-to-date gene information such as GO annotation and metabolic pathway. For collecting the latest information of selected gene from the database, we also set up the local BLAST search engine and nonredundant sequence database updated by NCBI server on a daily basis. We find that the present database is a useful query interface and data-mining tool, specifically for finding out the genes related to drug addiction. We apply this system to the identification and characterization of methamphetamine-induced genes' behavior in rat brain.