-
[show abstract]
[hide abstract]
ABSTRACT: Methamphetamine (METH) addiction is associated with several neuropsychiatric symptoms. Little is known about the effects of METH on gene expression and epigenetic modifications in the rat nucleus accumbens (NAC). Our study investigated the effects of a non-toxic METH injection (20 mg/kg) on gene expression, histone acetylation, and the expression of the histone acetyltransferase (HAT), ATF2, and of the histone deacetylases (HDACs), HDAC1 and HDAC2, in that structure. Microarray analyses done at 1, 8, 16 and 24 hrs after the METH injection identified METH-induced changes in the expression of genes previously implicated in the acute and longterm effects of psychostimulants, including immediate early genes and corticotropin-releasing factor (Crf). In contrast, the METH injection caused time-dependent decreases in the expression of other genes including Npas4 and cholecystokinin (Cck). Pathway analyses showed that genes with altered expression participated in behavioral performance, cell-to-cell signaling, and regulation of gene expression. PCR analyses confirmed the changes in the expression of c-fos, fosB, Crf, Cck, and Npas4 transcripts. To determine if the METH injection caused post-translational changes in histone markers, we used western blot analyses and identified METH-mediated decreases in histone H3 acetylated at lysine 9 (H3K9ac) and lysine 18 (H3K18ac) in nuclear sub-fractions. In contrast, the METH injection caused time-dependent increases in acetylated H4K5 and H4K8. The changes in histone acetylation were accompanied by decreased expression of HDAC1 but increased expression of HDAC2 protein levels. The histone acetyltransferase, ATF2, showed significant METH-induced increased in protein expression. These results suggest that METH-induced alterations in global gene expression seen in rat NAC might be related, in part, to METH-induced changes in histone acetylation secondary to changes in HAT and HDAC expression. The causal role that HATs and HDACs might play in METH-induced gene expression needs to be investigated further.
PLoS ONE 01/2012; 7(3):e34236. · 4.09 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Repeated injections of cocaine cause blunted responses to acute cocaine challenge-induced increases in the expression of immediate early genes (IEGs).
The aim of this study was to test if chronic methamphetamine (METH) exposure might cause similar blunting of acute METH-induced increases in IEG expression.
Repeated saline or METH injections were given to rats over 14 days. After 1 day of withdrawal, they received a single injection of saline or METH (5 mg/kg). Acute injection of METH increased c-fos, fosB, fra2, junB, Egr1-3, Nr4a1 (Nur77), and Nr4a3 (Nor-1) mRNA levels in the striatum of saline-pretreated rats. Chronic METH treatment alone reduced the expression of AP1, Erg1-3, and Nr4a1 transcription factors below control levels. Acute METH challenge normalized these values in METH-pretreated rats. Unexpectedly, acute METH challenge to METH-pretreated animals caused further decreases in Nr4a2 (Nurr1) mRNA levels. In contrast, the METH challenge caused significant but blunted increases in Nr4a3 and Arc expression in METH-pretreated rats. There were also chronic METH-associated decreases in the expression of cAMP responsive element binding protein (CREB) which modulates IEG expression via activation of the cAMP/PKA/CREB signal transduction pathway. Chronic METH exposure also caused significant decreases in preprotachykinin, but not in prodynorphin, mRNA levels.
These results support the accumulated evidence that chronic administration of psychostimulants is associated with blunting of their acute stimulatory effects on IEG expression. The METH-induced renormalization of the expression of several IEGs in rats chronically exposed to METH hints to a potential molecular explanation for the recurrent self-administration of the drug by human addicts.
Psychopharmacologia 01/2011; 215(2):353-65. · 4.08 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The use of fenfluramines can increase the risk of developing pulmonary arterial hypertension (PAH) in humans, but the mechanisms responsible are unresolved. A recent study reported that female mice lacking the gene for tryptophan hydroxylase-1 (Tph1(-/-) mice) were protected from PAH caused by chronic dexfenfluramine, suggesting a pivotal role for peripheral serotonin (5-HT) in the disease process. Here we tested two alternative hypotheses which might explain the lack of dexfenfluramine-induced PAH in Tph1(-/-) mice. We postulated that: 1) Tph1(-/-) mice express lower levels of pulmonary 5-HT transporter (SERT) when compared to wild-type controls, and 2) Tph1(-/-) mice display adaptive changes in the expression of non-serotonergic pulmonary genes which are implicated in PAH. SERT was measured using radioligand binding methods, whereas gene expression was measured using microarrays followed by quantitative real time PCR (qRT-PCR). Contrary to our first hypothesis, the number of pulmonary SERT sites was modestly up-regulated in female Tph1(-/-) mice. The expression of 51 distinct genes was significantly altered in the lungs of female Tph1(-/-) mice. Consistent with our second hypothesis, qRT-PCR confirmed that at least three genes implicated in the pathogenesis of PAH were markedly up-regulated: Has2, Hapln3 and Retlna. The finding that female Tph1(-/-) mice are protected from dexfenfluramine-induced PAH could be related to compensatory changes in pulmonary gene expression, in addition to reductions in peripheral 5-HT. These observations emphasize the intrinsic limitation of interpreting data from studies conducted in transgenic mice that are not fully characterized.
PLoS ONE 01/2011; 6(3):e17735. · 4.09 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Methamphetamine (METH) is a toxic drug of abuse, which can cause significant decreases in the levels of monoamines in various brain regions. However, animals treated with progressively increasing doses of METH over several weeks are protected against the toxic effects of the drug. In the present study, we tested the possibility that this pattern of METH injections might be associated with transcriptional changes in the rat striatum, an area of the brain which is known to be very sensitive to METH toxicity and which is protected by METH preconditioning. We found that the presence and absence of preconditioning followed by injection of large doses of METH caused differential expression in different sets of striatal genes. Quantitative PCR confirmed METH-induced changes in some genes of interest. These include small heat shock 27 kD proteins 1 and 2 (HspB1 and HspB2), brain derived neurotrophic factor (BDNF), and heme oxygenase-1 (Hmox-1). Our observations are consistent with previous studies which have reported that ischemic or pharmacological preconditioning can cause reprogramming of gene expression after lethal ischemic insults. These studies add to the growing literature on the effects of preconditioning on the brain transcriptome.
Dose-Response 01/2011; 9(2):165-81. · 1.91 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Dopamine (DA), the most abundant catecholamine in the basal ganglia, participates in the regulation of motor functions and of cognitive processes such as learning and memory. Abnormalities in dopaminergic systems are thought to be the bases for some neuropsychiatric disorders including addiction, Parkinson's disease, and Schizophrenia. DA exerts its arrays of functions via stimulation of D1-like (D1 and D5) and D2-like (D2, D3, and D4) DA receptors which are located in various regions of the brain. The DA D1 and D2 receptors are very abundant in the basal ganglia where they exert their functions within separate neuronal cell types. The present paper focuses on a review of the effects of stimulation of DA D1 receptors on diverse signal transduction pathways and gene expression patterns in the brain. We also discuss the possible involvement of the DA D1 receptors in DA-mediated toxic effects observed both in vitro and in vivo. Future studies using more selective agonist and antagonist agents and the use of genetically modified animals should help to further clarify the role of these receptors in the normal physiology and in pathological events that involve DA.
CNS & neurological disorders drug targets 11/2010; 9(5):526-38. · 3.57 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Dopamine (DA), the most abundant catecholamine in the basal ganglia, participates in the regulation of motor functions and of cognitive processes such as learning and memory. Abnormalities in dopaminergic systems are thought to be the bases for some neuropsychiatric disorders including addiction, Parkinson's disease, and Schizophrenia. DA exerts its arrays of functions via stimulation of D1-like (D1 and D5) and D2-like (D2, D3, and D4) DA receptors which are located in various regions of the brain. The DA D1 and D2 receptors are very abundant in the basal ganglia where they exert their functions within separate neuronal cell types. The present paper focuses on a review of the effects of stimulation of DA D1 receptors on diverse signal transduction pathways and gene expression patterns in the brain. We also discuss the possible involvement of the DA D1 receptors in DA-mediated toxic effects observed both in vitro and in vivo. Future studies using more selective agonist and antagonist agents and the use of genetically modified animals should help to further clarify the role of these receptors in the normal physiology and in pathological events that involve DA.
CNS & Neurological Disorders - Drug Targets (Formerly Current Drug Targets - CNS & Neurological Disorders) 10/2010; 9(5):526-538. · 3.81 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Methamphetamine (METH) is a psychostimulant that can cause long-lasting neurodegenerative effects in humans and animals. These toxic effects appear to occur, in part, via activation of dopamine (DA) D1 receptors. This paper assessed the possibility that the DA D1 receptor antagonist, SCH23390, might inhibit METH-induced changes in the expression of several members of immediate early genes (IEGs) which are known to control more delayed expression of other genes. We found that injections of METH (4x10 mg/kg, given at 2 h intervals) caused significant increases in c-fos and fra-2 expression which lasted from 30 min to 4 h. Pre-treatment with SCH23390, given 30 min before each METH injection, completely blocked METH-induced expression of c-fos, but only partially inhibited fra-2 mRNA expression. These results were confirmed by Western blot analysis which showed METH-induced changes in c-Fos protein expression that were blocked by pretreatment with SCH23390. There were also delayed METH-induced DA D1 receptor-dependent effects on fosB mRNA expression. Even though fra-1 expression was not affected by pretreatment with METH alone, the repeated injections of SCH23390 caused substantial decreases in fra-1 mRNA expression in both the presence and absence of METH. The repeated injections of METH caused no changes in the mRNAs for c-jun, junB or junD. However, there were significant increases in the phosphorylation of c-Jun protein (ser63). Phosphorylation of c-Jun occurred in a delayed fashion (16 and 24 h after the last METH injections) and was attenuated by SCH23390 pretreatment. Interestingly, SCH23390 given alone caused significant decreases in phospho-c-Jun at all time-points. The METH injections also caused delayed induction in the expression of members of the Egr family of transcription factors in a DA D1 receptor-dependent fashion. Repeated injections of SCH23390 caused substantial suppression of basal striatal egr-1 and egr-2 mRNA expression but not of that of egr-3. Both crem and arc mRNA levels were induced by METH in a SCH23390-sensitive fashion. Moreover, multiple injections of SCH23390 given alone caused marked inhibition of basal arc expression. These results show that multiple injections of METH can differentially affect the expression of several IEGs, some of which occurred in a DA D1 receptor dependent fashion. The SCH23390-mediated suppression of basal fra-1, egr-1, and egr-2 mRNA levels suggests that their basal expression in the striatum might be dependent on tonic stimulation of the DA D1 receptor.
Brain research 03/2010; 1318:1-10. · 2.46 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Methamphetamine (meth) is an illicit psychostimulant that is abused throughout the world. Repeated passive injections of the drug given in a single day or over a few days cause significant and long-term depletion of dopamine and serotonin in the mammalian brain. Because meth self-administration may better mimic some aspects of human drug-taking behaviors, we examined to what extent this pattern of drug treatment might also result in damage to monoaminergic systems in the brain. Rats were allowed to intravenously self-administer meth (yoked control rats received vehicle) 15 hours per day for 8 days before being euthanized at either 24 hours or at 7 and 14 days after cessation of drug taking. Meth self-administration by the rats was associated with a progressive escalation of daily drug intake to 14 mg/kg per day. Animals that self-administered meth exhibited dose-dependent decreases in striatal dopamine levels during the period of observation. In addition, there were significant reductions in the levels of striatal dopamine transporter and tyrosine hydroxylase proteins. There were also significant decreases in the levels of dopamine, dopamine transporter, and tyrosine hydroxylase in the cortex. In contrast, meth self-administration caused only transient decreases in norepinephrine and serotonin levels in the two brain regions, with these values returning to normal at seven days after cessation of drug taking. Importantly, meth self-administration was associated with significant dose-dependent increases in glial fibrillary acidic protein in both striatum and cortex, with these changes being of greater magnitude in the striatum. These results suggest that meth self-administration by rats is associated with long-term biochemical changes that are reminiscent of those observed in post-mortem brain tissues of chronic meth abusers.
PLoS ONE 01/2010; 5(1):e8790. · 4.09 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Unilateral injections of 6-hydroxydopamine into the medial forebrain bundle are used extensively as a model of Parkinson's disease. The present experiments sought to identify genes that were affected in the dopamine (DA)-denervated striatum after 6-hydroxydopamine-induced destruction of the nigrostriatal dopaminergic pathway in the rat. We also examined whether a single injection of methamphetamine (METH) (2.5 mg/kg) known to cause changes in gene expression in the normally DA-innervated striatum could still influence striatal gene expression in the absence of DA. Unilateral injections of 6-hydroxydopamine into the medial forebrain bundle resulted in METH-induced rotational behaviors ipsilateral to the lesioned side and total striatal DA depletion on the lesioned side. This injection also caused decrease in striatal serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) levels. DA depletion was associated with increases in 5-HIAA/5-HT ratios that were potentiated by the METH injection. Microarray analyses revealed changes (±1.7-fold, p<0.025) in the expression of 67 genes on the lesioned side in comparison to the intact side of the saline-treated hemiparkinsonian animals. These include follistatin, neuromedin U, and tachykinin 2 which were up-regulated. METH administration caused increases in the expression of c-fos, Egr1, and Nor-1 on the intact side. On the DA-depleted side, METH administration also increased the expression of 61 genes including Pdgf-d and Cox-2. There were METH-induced changes in 16 genes that were common in the DA-innervated and DA-depleted sides. These include c-fos and Nor-1 which show greater changes on the normal DA side. Thus, the present study documents, for the first time, that METH mediated DA-independent changes in the levels of transcripts of several genes in the DA-denervated striatum. Our results also implicate 5-HT as a potential player in these METH-induced alterations in gene expression because the METH injection also caused significant increases in 5-HIAA/5-HT ratios on the DA-depleted side.
PLoS ONE 01/2010; 5(12):e15643. · 4.09 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Pretreatment with methamphetamine (METH) can attenuate toxicity due to acute METH challenges. The majority of previous reports have focused mainly on the effects of the drug on the striatal dopaminergic system. In the present study, we used a regimen that involves gradual increases in METH administration to rats in order to mimic progressively larger doses of the drug used by some human METH addicts. We found that this METH preconditioning was associated with complete protection against dopamine depletion caused by a METH challenge (5 mg/kg x 6 injections given 1 h apart) in the striatum and cortex. In contrast, there was no preconditioning-mediated protection against METH-induced serotonin depletion in the striatum and hippocampus, with some protection being observed in the cortex. There was also no protection against METH-induced norepinephrine (NE) depletion in the hippocampus. These results indicate that, in contrast to the present dogmas, there might be differences in the mechanisms involved in METH toxicity on monoaminergic systems in the rodent brain. Thus, chronic injections of METH might activate programs that protect against dopamine toxicity without influencing drug-induced pathological changes in serotoninergic systems. Further studies will need to evaluate the cellular and molecular bases for these differential responses.
Neurotoxicity Research 05/2009; 15(3):252-9. · 3.51 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Methamphetamine (METH) is an illicit toxic psychostimulant which is widely abused. Its toxic effects depend on the release of excessive levels of dopamine (DA) that activates striatal DA receptors. Inhibition of DA-mediated neurotransmission by the DA D1 receptor antagonist, SCH23390, protects against METH-induced neuronal apoptosis. The initial purpose of the present study was to investigate, using microarray analyses, the influence of SCH23390 on transcriptional responses in the rat striatum caused by a single METH injection at 2 and 4 hours after drug administration. We identified 545 out of a total of 22,227 genes as METH-responsive. These include genes which are involved in apoptotic pathways, endoplasmic reticulum (ER) stress, and in transcription regulation, among others. Of these, a total of 172 genes showed SCH23390-induced inhibition of METH-mediated changes. Among these SCH23390-responsive genes were several genes that are regulated during ER stress, namely ATF3, HSP27, Hmox1, HSP40, and CHOP/Gadd153. The secondary goal of the study was to investigate the role of DA D1 receptor stimulation on the expression of genes that participate in ER stress-mediated molecular events. We thus used quantitative PCR to confirm changes in the METH-responsive ER genes identified by the microarray analyses. We also measured the expression of these genes and of ATF4, ATF6, BiP/GRP78, and of GADD34 over a more extended time course. SCH23390 attenuated or blocked METH-induced increases in the expression of the majority of these genes. Western blot analysis revealed METH-induced increases in the expression of the antioxidant protein, Hmox1, which lasted for about 24 hours after the METH injection. Additionally, METH caused DA D1 receptor-dependent transit of the Hmox1 regulator protein, Nrf2, from cytosolic into nuclear fractions where the protein exerts its regulatory functions. When taken together, these findings indicate that SCH23390 can provide protection against neuronal apoptosis by inhibiting METH-mediated DA D1 receptor-mediated ER stress in the rat striatum. Our data also suggest that METH-induced toxicity might be a useful model to dissect molecular mechanisms involved in ER stress-dependent events in the rodent brain.
PLoS ONE 02/2009; 4(6):e6092. · 4.09 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Methamphetamine (METH) is an illicit drug which is neurotoxic to the mammalian brain. Numerous studies have revealed significant decreases in dopamine and serotonin levels in the brains of animals exposed to moderate-to-large METH doses given within short intervals of time. In contrast, repeated injections of small nontoxic doses of the drug followed by a challenge with toxic METH doses afford significant protection against monoamine depletion. The present study was undertaken to test the possibility that repeated injections of the drug might be accompanied by transcriptional changes involved in rendering the nigrostriatal dopaminergic system refractory to METH toxicity. Our results confirm that METH preconditioning can provide significant protection against METH-induced striatal dopamine depletion. In addition, the presence and absence of METH preconditioning were associated with substantial differences in the identity of the genes whose expression was affected by a toxic METH challenge. Quantitative PCR confirmed METH-induced changes in genes of interest and identified additional genes that were differentially impacted by the toxic METH challenge in the presence of METH preconditioning. These genes include small heat shock 27 kD 27 protein 2 (HspB2), thyrotropin-releasing hormone (TRH), brain derived neurotrophic factor (BDNF), c-fos, and some encoding antioxidant proteins including CuZn superoxide dismutase (CuZnSOD), glutathione peroxidase (GPx)-1, and heme oxygenase-1 (Hmox-1). These observations are consistent, in part, with the transcriptional alterations reported in models of lethal ischemic injuries which are preceded by ischemic or pharmacological preconditioning. Our findings suggest that multiple molecular pathways might work in tandem to protect the nigrostriatal dopaminergic pathway against the deleterious effects of the toxic psychostimulant. Further analysis of the molecular and cellular pathways regulated by these genes should help to provide some insight into the neuroadaptive potentials of the brain when repeatedly exposed to drugs of abuse.
PLoS ONE 01/2009; 4(11):e7812. · 4.09 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Methamphetamine (METH), a highly addictive drug, can cause degeneration of monoaminergic terminals and neuronal apoptosis in the mammalian brain. In the present article, we have used serial analysis of gene expression (SAGE) to investigate patterns of gene expression in the striata of rats that were given a neurotoxic dose of the drug. SAGE libraries were generated from animals treated with either saline or METH (40 mg/kg) and sacrificed 2 h later. A total of 315 transcripts were differentially expressed between the two libraries (P < 0.05), with 179 (56%) being upregulated and 136 (44%) being downregulated by the METH injection. Of these, CAATT enhancer-binding protein homologous protein (CHOP)/GADD153 (growth arrest- and DNA damage-inducible gene 153) was found to be upregulated by about threefold. Analysis of the expression of genes downstream of CHOP (DOCs) revealed significant METH-induced increases in their expression. Because DOC1 is an analog of carbonic anhydrase (CA) which is involved in the interconversion between carbon dioxide and the bicarbonate ion, we also measured the effects of METH on the expression of several CAs. These were significantly upregulated by METH in a time-dependent fashion. These results indicate that METH toxicity is mediated, in part, by drug-induced perturbations of physiological processes that are dependent on normal pH and CO(2) homeostasis.
Annals of the New York Academy of Sciences 08/2006; 1074:13-30. · 3.15 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Methamphetamine [METH ("speed")] is an abused psychostimulant that can cause psychotic, cognitive, and psychomotor impairment in humans. These signs and symptoms are thought to be related to dysfunctions in basal ganglionic structures of the brain. To identify possible molecular bases for these clinical manifestations, we first used cDNA microarray technology to measure METH-induced transcriptional responses in the striatum of rats treated with an apoptosis-inducing dose of the drug. METH injection resulted in increased expression of members of the Jun, Egr, and Nur77 subfamilies of transcription factors (TFs), changes that were confirmed by quantitative PCR. Because pathways linked to these factors are involved in the up-regulation of Fas ligand (FasL), FasL mRNA was quantified and found to be increased. Immunohistochemical studies also revealed METH-induced increased FasL protein expression in striatal GABAergic neurons that express enkephalin. Moreover, there were METH-mediated increases in calcineurin, as well as shuttling of nuclear factor of activated T cells (NFAT)c3 and NFATc4 from the cytosol to the nucleus of METH-treated rats, mechanisms also known to be involved in FasL regulation. Furthermore, METH induced cleavage of caspase-3 in FasL- and Fas-containing neurons. Finally, the METH-induced changes in the FasL-Fas death pathway were attenuated by pretreatment with the dopamine D1 receptor antagonist, SCH23390, which also caused attenuation of METH-induced apoptosis. These observations indicate that METH causes some of its neurodegenerative effects, in part, via stimulation of the Fas-mediated cell death pathway consequent to FasL up-regulation mediated by activation of multiple TFs.
Proceedings of the National Academy of Sciences 02/2005; 102(3):868-73. · 9.68 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) is a popular drug of abuse. MDMA is pharmacologically classified as an entactogen because of its affinities to classical hallucinogens and stimulants. Oral ingestion of a single dose of the drug is associated with euphoria, elevated self-confidence, and heightened sensory awareness in humans. Evidence for neurotoxicity in the human serotonin (5-HT) system has been provided. In rats, a single injection of MDMA induces hyperthermia and formation of reactive oxygen species. These effects may cause MDMA-associated, long-term 5-HT depletion, with the cortex being quite sensitive to the biochemical effects of MDMA. It has been suggested that these MDMA effects may be associated with molecular changes in this brain region. To test these ideas, we have made use of the cDNA array analysis, which can provide a more global view of the molecular changes secondary to MDMA injections. Our results show that the genes regulated by MDMA encode proteins that belong to signaling pathways, transcription regulators, or xenobiotic metabolism. Our observations indicate that cortical cells respond to the acute administration of MDMA by modulating transcription of several genes that might lead to long-term changes in the brain.
The FASEB Journal 01/2003; 16(14):1887-94. · 5.71 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Amphetamine (AMPH) is a drug of abuse that causes the degeneration of striatal dopamine terminals in mammals. Superoxide radicals seem to participate in AMPH-induced damage because its toxicity is attenuated in Cu/Zn superoxide dismutase transgenic (SOD-tg) mice. To provide a detailed analysis of molecular changes associated with AMPH toxicity, we used cDNA arrays consisting of 1176 genes to detect differential changes in gene expression in the striata of wild-type and SOD-tg mice treated with neurotoxic doses of the drug. We found 42 genes that showed >1.8-fold changes in at least two consecutive time points during the course of the study and were differentially affected by AMPH in the two genotypes. Specifically, more transcription factors and genes involved in responses to injury/inflammation were affected in wild-type mice after AMPH administration. Some of these stimulant-induced superoxide-dependent alterations in gene expression might affect neuronal functions and promote neuronal damage. Other changes might help to provide some degree of protection against AMPH toxicity. These results support the view that the use of global array analysis of gene expression will help to identify novel molecular mediators of AMPH-induced neurodegeneration.
The FASEB Journal 09/2002; 16(11):1379-88. · 5.71 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Methamphetamine (METH) is a drug of abuse which can cause apoptosis and degeneration of monoaminergic terminals in the mammalian brain. c-fos appears to play a protective role against METH-induced damage because METH toxicity is exacerbated in c-fos heterozygous knockout mice. In the present study, we used the comprehensive technique of cDNA array to test the idea that heterozygous c-fos knockout mice might show differential METH-induced molecular responses in comparison to wild-type (WT) animals. Of 1,176 genes examined, the expression of 195 genes in either of the two groups of mice was affected by at least 2-fold at 2 or 12 h after METH treatment. More genes were either up- or downregulated in the WT mice. Moreover, there were substantial differences in the pattern of responses between the two genotypes, with more genes involved in DNA repair and protective processes being upregulated in WT mice after METH administration. These results support the idea that the c-fos knockout genotype may render the animals unable to trigger multicomponent responses in order to protect against the multifaceted toxic effects of this illicit neurotoxin.
Synapse 07/2002; 44(4):211-26. · 2.94 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Methamphetamine is a neurotoxic drug of abuse known to cause cell death both in vitro and in vivo. Nevertheless, the molecular and cellular mechanisms involved in this process remain to be clarified. Herein, we show that methamphetamine-induced apoptosis is associated with early (2 h) overexpression of bax, decreases of mitochondrial membrane potential and oxygen consumption as well as release of cytochrome c from mitochondria. In addition, activated caspase-9 was detected at 4 h post-METH exposure. Cell death was detectable by annexin V and propidium iodide staining after 8 h of methamphetamine exposure. At that time, the majority of the cells were stained by annexin V alone, with some cells being stained for both annexin V and propidium iodide. Moreover, cleavage of caspase-3, poly (ADP-ribose) polymerase and DNA fragmentation-related factor 45 was detected at 8 h post drug treatment. These results indicate that methamphetamine-induced apoptotic cell death results from early overexpression of bax, reduction of mitochondrial respiration and membrane potential and release of mitochondrial cytochrome c with subsequent activation of the caspase cascade.
Neuropharmacology 06/2002; 42(6):837-45. · 4.81 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The clinical abuse of methamphetamine (METH) is a major concern because it can cause long-lasting neurodegenerative effects in humans. Current concepts of the molecular mechanisms underlying these complications have centered on the formation of reactive oxygen species. Herein, we provide cDNA microarray evidence that METH administration caused the induction of c-Jun and of other members involved in the pathway leading to c-Jun activation [stress-activated protein kinase/Jun N-terminal kinase (JNK3), Crk-associated substrate-Cas and c-Src] after environmental stresses or cytokine stimulation. Reverse transcription-polymerase chain reaction analysis confirmed these increases and also showed that the expression of JNK1 and JNK3 but not JNK2 was also increased in the METH-treated mice. Western blot analysis showed that METH increased the expression of c-Jun phosphorylated at serine-63 and serine-73 residues. Other upstream members of the JNK pathway, including phosphorylated JNKs, mitogen-activated protein kinase kinase 4, mitogen-activated protein kinase kinase 7, Crk II, Cas, and c-Src were also increased at the protein level. These values returned to baseline by 1 week after drug treatment. These results are discussed in terms of their support for a possible role of the activation of the JNK/Jun pathway in the pathophysiological effects of METH.
Molecular Pharmacology 06/2002; 61(5):1124-31. · 4.88 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Methamphetamine (METH) is an illicit drug that is also neurotoxic. Recent studies suggest that in addition to dopamine terminal
degeneration in the striatum, METH causes apoptosis in cortical neurons. Earlier, we showed that c-fos knockout mice are more
susceptible to the toxic effects of the drug. In order to identify possible pathways related to these differences, we have
used cDNA array that provided us with a comprehensive catalog of METH affected genes. In the present study, we report on the
effects of METH on the integrin family members that were shown to be involved in intracellular signaling cascades effecting
cell survival. We found that, in comparison to wild type animals, c-fos knockout mice have lower baseline levels of the integrins
in the cortex. Moreover, METH caused time-dependent decreases in their transcripts in both strains of mice. Quantitative RT-PCR
confirmed the changes obtained in cDNA array. These findings are discussed in view of the possible role of integrins in METH-induced
toxic effects on the cortical neurons.
Neurotoxicity Research 12/2001; 4(7):617-623. · 3.51 Impact Factor
