Genome-wide DNA hydroxymethylation identifies potassium channels in the nucleus accumbens as discriminators of methamphetamine addiction and abstinence.

Epigenetic consequences of exposure to psychostimulants are substantial but the relationship of these changes to compulsive drug taking and abstinence is not clear. Here, we used a paradigm that helped to segregate rats that reduce or stop their methamphetamine (METH) intake (nonaddicted) from those that continue to take the drug compulsively (addicted) in the presence of footshocks. We used that model to investigate potential alterations in global DNA hydroxymethylation in the nucleus accumbens (NAc) because neuroplastic changes in the NAc may participate in the development and maintenance of drug-taking behaviors. We found that METH-addicted rats did indeed show differential DNA hydroxymethylation in comparison with both control and nonaddicted rats. Nonaddicted rats also showed differences from control rats. Differential DNA hydroxymethylation observed in addicted rats occurred mostly at intergenic sites located on long and short interspersed elements. Interestingly, differentially hydroxymethylated regions in genes encoding voltage (Kv1.1, Kv1.2, Kvb1 and Kv2.2)- and calcium (Kcnma1, Kcnn1 and Kcnn2)-gated potassium channels observed in the NAc of nonaddicted rats were accompanied by increased mRNA levels of these potassium channels when compared with mRNA expression in METH-addicted rats. These observations indicate that changes in differentially hydroxymethylated regions and increased expression of specific potassium channels in the NAc may promote abstinence from drug-taking behaviors. Thus, activation of specific subclasses of voltage- and/or calcium-gated potassium channels may provide an important approach to the beneficial treatment for METH addiction.

Differential effects of prenatal and postnatal expressions of mutant human DISC1 on neurobehavioral phenotypes in transgenic mice: evidence for neurodevelopmental origin of major psychiatric disorders.

Strong genetic evidence implicates mutations and polymorphisms in the gene Disrupted-In-Schizophrenia-1 (DISC1) as risk factors for both schizophrenia and mood disorders. Recent studies have shown that DISC1 has important functions in both brain development and adult brain function. We have described earlier a transgenic mouse model of inducible expression of mutant human DISC1 (hDISC1) that acts in a dominant-negative manner to induce the marked neurobehavioral abnormalities. To gain insight into the roles of DISC1 at various stages of neurodevelopment, we examined the effects of mutant hDISC1 expressed during (1) only prenatal period, (2) only postnatal period, or (3) both periods. All periods of expression similarly led to decreased levels of cortical dopamine (DA) and fewer parvalbumin-positive neurons in the cortex. Combined prenatal and postnatal expression produced increased aggression and enhanced response to psychostimulants in male mice along with increased linear density of dendritic spines on neurons of the dentate gyrus of the hippocampus, and lower levels of endogenous DISC1 and LIS1. Prenatal expression only resulted in smaller brain volume, whereas selective postnatal expression gave rise to decreased social behavior in male mice and depression-like responses in female mice as well as enlarged lateral ventricles and decreased DA content in the hippocampus of female mice, and decreased level of endogenous DISC1. Our data show that mutant hDISC1 exerts differential effects on neurobehavioral phenotypes, depending on the stage of development at which the protein is expressed. The multiple and diverse abnormalities detected in mutant DISC1 mice are reminiscent of findings in major mental diseases.

Heavy marijuana users show increased serum apolipoprotein C-III levels: evidence from proteomic analyses.

Marijuana (MJ) is the most commonly used illicit drug in the United States. Its abuse is associated with cognitive dysfunctions and increased resistance to blood flow in the cerebral vasculature. In addition, MJ abuse is associated with increased risks of potentially serious cardiovascular disorders. In the present study, we used the protein chip platform based on surface-enhanced laser desorption/ionization time-of-flight mass spectroscopy (SELDI-TOF-MS) to test the possibility that MJ abuse might be associated with changes in serum protein levels. Indeed, MJ users showed significant increases in three protein peaks, which were identified as three isoforms of apolipoprotein (apo) C-III. Immunoprecipitation using an apoC-III antibody also validated the identification of the proteins. Marijuana-induced increases in apoC-III levels might occur through chronic stimulation of hepatic cannabinoid receptors (CB1 and/or CB2) by its active ingredient, Delta(9)tetrahydrocannibol (THC). Thus, chronic MJ abuse might cause increased transcription and/or translation of apoC-III in the liver with corresponding changes reflected in the plasma of these patients. In any case, because apoC-III is a cardiovascular risk factor, the increased levels observed in MJ users might explain, in part, the cardiac and cerebral abnormalities reported in these patients.

Interactions of HIV and methamphetamine: cellular and molecular mechanisms of toxicity potentiation.

Methamphetamine (METH) is a highly addictive psychostimulant drug, whose abuse has reached epidemic proportions worldwide. METH use is disproportionally represented among populations at high risks for developing HIV infection or who are already infected with the virus. Psychostimulant abuse has been reported to exacerbate the cognitive deficits and neurodegenerative abnormalities observed in HIV-positive patients. Thus, the purpose of the present paper is to review the clinical and basic observations that METH potentiates the adverse effects of HIV infection. An additional purpose is to provide a synthesis of the cellular and molecular mechanisms that might be responsible for the increased toxicity observed in co-morbid patients. The reviewed data indicate that METH and HIV proteins, including gp120, gp41, Tat, Vpr and Nef, converge on various caspase-dependent death pathways to cause neuronal apoptosis. The role of reactive microgliosis in METH- and in HIV-induced toxicity is also discussed.

Epigenetics and addiction.

Addictions are public health menaces. However, despite advances in addiction research, the cellular or molecular mechanisms that cause transition from recreational use to addiction remain to be elucidated. We have recently suggested that addiction may be secondary to long-term epigenetic modifications that determine the clinical course of substance use disorders. A better understanding of epigenetic mechanisms in animal models that mimic human conditions should help to usher in a new area of drug development against addiction.

Null mutation of c-fos causes exacerbation of methamphetamine-induced neurotoxicity.

Methamphetamine neurotoxicity has been demonstrated in rodents and nonhuman primates. These neurotoxic effects may be associated with mechanisms involved in oxidative stress and the activation of immediate early genes (IEG). It is not clear, however, whether these IEG responses are involved in a methamphetamine-induced toxic cascade or in protective mechanisms against the deleterious effects of the drug. As a first step toward clarifying this issue further, the present study was thus undertaken to assess the toxic effects of methamphetamine in heterozygous and homozygous c-fos knock-out as well as wild-type mice. Administration of methamphetamine caused significant reduction in [(125)I]RTI-121-labeled dopamine uptake sites, dopamine transporter protein, and tyrosine hydroxylase-like immunohistochemistry in the striata of wild-type mice. These decreases were significantly exacerbated in heterozygous and homozygous c-fos knock-out mice, with the homozygous showing greater loss of striatal dopaminergic markers. Moreover, in comparison with wild-type animals, both genotypes of c-fos knock-out mice showed more DNA fragmentation, measured by the number of terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labeled nondopaminergic cells in their cortices and striata. In contrast, wild-type mice treated with methamphetamine demonstrated a greater number of glial fibrillary acidic protein-positive cells than did c-fos knock-out mice. These data suggest that c-fos induction in response to toxic doses of methamphetamine might be involved in protective mechanisms against this drug-induced neurotoxicity.

Quantitative neuroanatomy in schizophrenia. A controlled magnetic resonance imaging study.

Twenty-four patients with schizophrenia and 14 normal control subjects underwent magnetic resonance imaging scans using a 0.5-tesla scanner and 600-ms inversion recovery technique. A midsagittal section and twelve 1-cm coronal sections beginning at the frontal pole were obtained, and linear, area, and signal intensity measurements were made on nine brain regions. Volume estimates were made by summing consecutive sections for four of the following regions: the precallosal frontal lobes, temporal lobes, lateral ventricles, amygdala-hippocampal complexes, and cerebral hemispheres. The area of the third ventricle in its most anterior coronal slice was increased by 73% in schizophrenic subjects (0.83 +/- 0.08 cm2) in comparison with controls (0.48 +/- 0.04 cm2). Lateral ventricular volume was increased by 62% in schizophrenic subjects (24.7 +/- 2.6 mL) in comparison with controls (15.2 +/- 1.4 mL). The lateral ventricular enlargement in schizophrenic subjects was more pronounced posteriorly than anteriorly, especially at the level of the anterior thalamus and the colliculi. There were no other significant differences between schizophrenic and control groups in any other spatial or signal intensity measures. There was no brain region the size of which correlated with ventricular size. These data corroborate third and lateral ventriculomegaly in schizophrenia using magnetic resonance imaging but fail to further localize the structural abnormality.

The iminodipropionitrile (IDPN)-induced dyskinetic syndrome: behavioral and biochemical pharmacology.

Chronic administration of iminodipropionitrile causes a persistent behavioral syndrome which is characterized by lateral and vertical head shakes, random circling, hyperactivity and increased acoustic startle response in rodents. These behavioral abnormalities are similar to those observed after the acute administration of serotonin (5-HT) and dopamine (DA) agonists, and of some peptides including thyrotropin-releasing hormone (TRH) and the enkephalins. The data available so far indicate that the 5-HT system which interacts with some other neurotransmitters such as DA and norepinephrine (NE) in both reciprocal and nonreciprocal ways may be primarily involved in the manifestations of this persistent dyskinetic syndrome. Preliminary evaluation of the peptidergic systems has also revealed possible involvement of opiate peptides in the IDPN-induced dyskinetic phenomena. More studies are needed to assess the role of specific molecular events which may occur at cortical, subcortical, and/or spinal levels to cause this interesting psychomotor syndrome.

Free radical mechanisms in schizophrenia and tardive dyskinesia.

The present article discusses the distribution of free radical processes in the central nervous system (CNS). Specifically, we discuss the involvement of oxyradicals in the normal metabolism of catecholamine. We also review some proposals related to the possible importance of these compounds in the development of neuropsychiatric and movement disorders such as schizophrenia and neuroleptic-induced tardive dyskinesia (TD), respectively. Clinical studies have shown that antioxidant treatment can attenuate the movement abnormalities observed in TD. Further studies are necessary to evaluate the status of specific scavenging systems in these two disorders. The prophylactic use of antioxidants in patients who are treated with neuroleptics needs also to be considered.

Bone morphogenetic protein-6 reduces ischemia-induced brain damage in rats.

BACKGROUND AND PURPOSE: Bone morphogenetic protein-6 (BMP6) and its receptors are expressed in adult and fetal brain. Receptors for BMP6 are upregulated in adult brain after injury, leading to the suggestion that BMP6 is involved in the physiological response to neuronal injury. The purpose of this study was to determine whether there was a neuroprotective effect of BMP6 in vivo and in vitro. METHODS: Lactate dehydrogenase and microtubule-associated protein-2 (MAP-2) activities were used to determine the protective effect of BMP6 against H(2)O(2) in primary cortical cultures. The neuroprotective effects of BMP6 were also studied in chloral hydrate-anesthetized rats. BMP6 or vehicle was injected into right cerebral cortex before transient right middle cerebral artery (MCA) ligation. Animals were killed for triphenyl-tetrazolium chloride staining, caspase-3 immunoreactivity and enzymatic assays, and TUNEL assay. A subgroup of animals were used for locomotor behavioral assays. RESULTS: Application of H(2)O(2) increased lactate dehydrogenase activity and decreased the density of MAP-2(+) neurons in culture. Both responses were attenuated by BMP6 pretreatment. Complementary in vivo studies showed that pretreatment with BMP6 increased motor performance and generated less cerebral infarction induced by MCA ligation/reperfusion in rats. Pretreatment with BMP6 did not alter cerebral blood flow or physiological parameters. There was decreased ischemia-induced caspase-3 immunoreactivity, caspase-3 enzymatic activity, and density of TUNEL-positive cells in ischemic cortex in BMP6-treated animals. CONCLUSIONS: BMP6 reduces ischemia/reperfusion injury, perhaps by attenuating molecular events underlying apoptosis.

Neurophysiological signs of cocaine dependence: increased electroencephalogram beta during withdrawal.

To determine whether a central nervous system marker of cocaine dependence might exist, the resting electroencephalogram (EEG) of 33 drug-free, cocaine-dependent men (DSM-III-R criteria) was compared with two control groups [nondrug group (n = 10) and drug group who abused drugs, but were not cocaine dependent (n = 20)]. The EEG was recorded from eight sites after about 10 days of monitored abstinence (range 4-15 days) on a closed research ward for the drug-using individuals. The EEG was recorded for the nondrug control group as outpatients. The drug history was determined by the drug history questionnaire and a medical screening interview. The percent of EEG beta activity for the cocaine-dependent subjects was greater than that of both control groups (p < .05) as well as a normative database (HZI: Tarrytown, NY). The percent of EEG beta in frontal and central areas of the cocaine-dependent individuals was correlated with the frequency of cocaine use during the last 30 days. High levels of EEG beta may be a neurophysiological withdrawal sign in cocaine-dependent men.

Neurotoxicity, drugs and abuse, and the CuZn-superoxide dismutase transgenic mice.

Administration of methamphetamine (METH) to animals causes loss of DA terminals in the brain. The manner by which METH causes these changes in neurotoxicity is not known. We have tested the effects of this drug in copper/zinc (CuZn)-superoxide dismutase transgenic (SOD Tg) mice, which express the human CuZnSOD gene. In nontransgenic (non-Tg) mice, acute METH administration causes significant decreases in DA and dihydroxyphenylacetic acid (DOPAC) in the striata of non-Tg mice. In contrast, there were on significant decreases in striatal DA in the METH administration caused decreases in striatal DA and DOPAC in the non-Tg mice, but not in the SOD-Tg mice. Similar studies were carried out with 1-methyl-1,2,3,6-tetrahydropyridine (MPTP), which also causes striatal DA and DOPAC depletion. As in the case of METH, MPTP causes marked depletion of DA and DOPAC in the non-Tg mice, but not in the SOD Tg mice. These results suggest that the mechanisms of toxicity of both METH and MPTP involved superoxide radical formation.

Differential effects of cocaine and cocaine alcohol on neurocognitive performance.

OBJECTIVE: To investigate the dose-related effects of cocaine with or without alcohol use on the CNS by measuring performance on neurobehavioral tests. BACKGROUND: Chronic use of cocaine is associated with persistent decrements in cognitive function that are most pronounced in heavy users. Specific neurobehavioral deficits in areas such as executive function and impulsivity would make it difficult for the cocaine abuser to discontinue using drugs. Because alcohol is often used in conjunction with cocaine, the CNS effects of alcohol when taken with cocaine deserve further investigation. METHOD: The authors evaluated the dose-related effects of cocaine and alcohol use on performance in a variety of neuropsychological tests after 1 to 3 days of abstinence and again after 4 weeks of abstinence. Fifty-six chronic cocaine abusers who had used cocaine during the past 24 to 48 hours volunteered to perform a battery of neuropsychological tests on two separate occasions during a period of enforced abstinence. In addition to using cocaine, most of the volunteers consumed alcohol. Approximately half of the participants consumed more than 10 alcohol-containing drinks per week. RESULTS: After controlling for the effects of age, sex, and intelligence on performance, the authors found dose-related associations between neurobehavioral performance and cocaine dose and alcohol dose. When the influences of cocaine and alcohol on neurobehavioral performance were taken separately, cocaine and alcohol each selectively affected performance on different neurobehavioral tests after 1 to 3 days of abstinence, with these effects persisting after 4 weeks of abstinence. CONCLUSION: The concomitant use of cocaine and alcohol may have additive negative effects on the brain as compared to the use of only one of these two substances.

Dose-related neurocognitive effects of marijuana use.

BACKGROUND: Although about 7 million people in the US population use marijuana at least weekly, there is a paucity of scientific data on persistent neurocognitive effects of marijuana use. OBJECTIVE: To determine if neurocognitive deficits persist in 28-day abstinent heavy marijuana users and if these deficits are dose-related to the number of marijuana joints smoked per week. METHODS: A battery of neurocognitive tests was given to 28-day abstinent heavy marijuana abusers. RESULTS: As joints smoked per week increased, performance decreased on tests measuring memory, executive functioning, psychomotor speed, and manual dexterity. When dividing the group into light, middle, and heavy user groups, the heavy group performed significantly below the light group on 5 of 35 measures and the size of the effect ranged from 3.00 to 4.20 SD units. Duration of use had little effect on neurocognitive performance. CONCLUSIONS: Very heavy use of marijuana is associated with persistent decrements in neurocognitive performance even after 28 days of abstinence. It is unclear if these decrements will resolve with continued abstinence or become progressively worse with continued heavy marijuana use.

Smaller volume of prefrontal lobe in polysubstance abusers: a magnetic resonance imaging study.

The present study was conducted to test the hypothesis that individuals with substance abuse disorder exhibit structural deficits in the prefrontal cortex. Volumes of the prefrontal lobe in subjects with histories of polysubstance abuse (n = 25) were measured and compared with those in normal volunteers (n = 14), using high-resolution volumetric magnetic resonance imaging (MRI). The research participants were men, 22 to 41 years of age. Polysubstance abusers were abstinent from drugs of abuse (except nicotine) for at least 15 days before MRI scanning. The total volumes of the prefrontal lobe (left and right hemispheres) were significantly smaller in the substance abuse group than in the control group. When the prefrontal lobe was segmented for gray and white matter, the deficit in the substance abusers was seen as significantly smaller volumes of gray but not of white matter. These results indicate that hypoplasia and/or atrophy in the prefrontal cortex accompany substance abuse and suggest that structural deficits in the prefrontal cortex may play an essential role in the neuropathological basis of functional impairments in substance abuse disorder, as demonstrated by functional brain imaging and cognitive studies.

Partial reversal of the iminodipropionitrile-induced hyperkinetic syndrome in rats by alpha-tocopherol (vitamin E).

Rats were treated with the neurotoxin iminodipropionitrile (IDPN), which causes an irreversible movement disorder accompanied by axonal damage similar to that seen in vitamin E deficiency. Animals that received 2 g/kg vitamin E concurrently with 100 mg/kg IDPN for 10 days demonstrated a significantly reduced severity of IDPN-induced dyskinesia (as measured by vertical head movements) compared to animals that received IDPN alone. When animals were treated with 100 mg/kg IDPN for 10 days and then given either 2 g/kg vitamin E or an equivalent volume of sesame oil for 7 days, vitamin E produced a significant reduction in the severity of IDPN-induced dyskinesia. In both experiments, locomotor activity was unchanged by vitamin E. These data suggest a possible involvement of free radical formation in the neurotoxicity of IDPN.

Neurovascular deficits in cocaine abusers.

The nature of the neurological and cerebrovascular deficits in cocaine abusers and whether they persist in abstinence is unclear. Blood flow velocity of the anterior and middle cerebral arteries was measured by transcranial Doppler sonography in cocaine abusers (n = 50) and control subjects (n = 25). Blood flow velocity was measured within 3 days and again after about 28 days after being admitted to an inpatient research ward to determine whether blood flow velocity improved during monitored abstinence conditions. The mean, systolic, and diastolic velocities as well as the pulsatility index in middle and anterior cerebral arteries significantly differed between controls and cocaine abusers (p < .05). Cerebrovascular resistance is increased in cocaine abusers and the increase persists for over a month of abstinence. Further research is needed to determine whether cerebrovascular resistance can be improved by pharmacological manipulations and whether improved blood flow relates to improved treatment outcome.

Attenuation of 6-hydroxydopamine-induced dopaminergic nigrostriatal lesions in superoxide dismutase transgenic mice.

6-Hydroxydopamine is a neurotoxin that produces degeneration of the nigrostriatal dopaminergic pathway in rodents. Its toxicity is thought to involve the generation of superoxide anion secondary to its autoxidation. To examine the effects of the overexpression of Cu,Zn-superoxide dismutase activity on 6-hydroxydopamine-induced dopaminergic neuronal damage, we have measured the effects of 6-hydroxydopamine on striatal and nigral dopamine transporters and nigral tyrosine hydroxylase-immunoreactive neurons in Cu,Zn-superoxide dismutase transgenic mice. Intracerebroventricular injection of 6-hydroxydopamine (50 microg) in non-transgenic mice produced reductions in the size of striatal area and an enlargement of the cerebral ventricle on both sides of the brains of mice killed two weeks after the injection. In addition, 6-hydroxydopamine caused marked decreases in striatal and nigral [125I]RTI-121-labelled dopamine transporters not only on the injected side but also on the non-injected side of non-transgenic mice; this was associated with decreased cell number and size of tyrosine hydroxylase-immunoreactive dopamine neurons in the substantia nigra pars compacta on both sides in these mice. In contrast, superoxide dismutase transgenic mice were protected against these neurotoxic effects of 6-hydroxydopamine, with the homozygous transgenic mice showing almost complete protection. These results provide further support for a role of superoxide anion in the toxic effects of 6-hydroxydopamine. They also provide further evidence that reactive oxygen species may be the main determining factors in the neurodegenerative effects of catecholamines.

Overexpression of human copper/zinc superoxide dismutase in transgenic mice attenuates oxidative stress caused by methylenedioxymethamphetamine (Ecstasy).

Administration of 3,4-methylenedioxymethamphetamine (4 x 20 mg/kg) to non-transgenic CD-1 mice caused marked depletion in dopamine, 3,4-dihydroxyphenylacetic acid and 5-hydroxytryptamine in the caudate-putamen. There were no significant changes in serotonergic markers in the hippocampus and frontal cortex. Homozygous and heterozygous copper/zinc superoxide dismutase transgenic mice show partial protection against the toxic effects of 3,4-methylenedioxymethamphetamine on striatal dopaminergic markers. In addition, 3,4-methylenedioxymethamphetamine injections caused marked decreases in copper/zinc superoxide dismutase activity in the frontal cortex, caudate-putamen and hippocampus of wild-type mice. Moreover, there were concomitant 3,4-methylenedioxymethamphetamine-induced decreases in catalase activity in the caudate-putamen and hippocampus, decreases in glutathione peroxidase activity in the frontal cortex as well as increases in lipid peroxidation in the frontal cortex, caudate-putamen, and hippocampus of wild-type mice. In contrast, administration of 3,4-methylenedioxymethamphetamine to homozygous superoxide dismutase transgenic mice caused no significant changes in antioxidant enzyme activities nor in lipid peroxidation. These results provide further substantiation of a role for oxygen-based radicals in 3,4-methylenedioxymethamphetamine-induced neurotoxicity. The present data also suggest that free radicals generated during 3,4-methylenedioxymethamphetamine administration may perturb antioxidant enzymes. Consequently, there might be further overproduction of free radicals with associated peroxidative damage to cell membranes and associated terminal degeneration.

Amphetamine-induced toxicity in dopamine terminals in CD-1 and C57BL/6J mice: complex roles for oxygen-based species and temperature regulation.

In order to examine differential strain susceptibility to neurotoxic effects of amphetamine and to assess the potential role of superoxide radicals in amphetamine-induced dopaminergic damage, the drug was injected to mice with different levels of copper/zinc superoxide dismutase (Cu/Zn SOD) enzyme. Administration of amphetamine (10 mg/kg, i.p., given every 2 h, a total of four times) to wild-type CD-1 and C57BL/6J mice caused significant decreases in dopamine and 3,4-dihydroxyphenylacetic acid levels, in [(125)I]RTI-121-labeled dopamine transporters as well as a significant depletion in the concentration of dopamine transporter and vesicular monoamine transporter 2 proteins. The amphetamine-induced toxic effects were less prominent in CD-1 mice, which have much higher levels of Cu/Zn SOD activity (0.69 units/mg of protein) in their striata than C57BL/6J animals (0.007 units/mg of protein). Transgenic mice on CD-1 and C57BL/6J background, which had striatal levels of Cu/Zn SOD 2.57 and 1.67 units/mg of protein, respectively, showed significant protection against all the toxic effects of amphetamine. The attenuation of toxicity observed in transgenic mice was not caused by differences in amphetamine accumulation in wild-type and mutant animals. However, CD-1-SOD transgenic mice showed marked hypothermia to amphetamine whereas C57-SOD transgenic mice did not show a consistent thermic response to the drug. The data obtained demonstrate distinctions in the neurotoxic profile of amphetamine in CD-1 and C57BL/6J mice, which show some differences in Cu/Zn SOD activity and in their thermic responses to amphetamine administration. Thus, these observations provide evidence for possible complex interactions between thermoregulation and free radical load in the long-term neurotoxic effects of this illicit drug of abuse.