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.

Long-term protective effects of methamphetamine preconditioning against single-day methamphetamine toxic challenges

Methamphetamine (METH) use is associated with neurotoxic effects which include decreased levels of dopamine (DA), serotonin (5-HT) and their metabolites in the brain. We have shown that escalating METH dosing can protect against METH induced neurotoxicity in rats sacrificed within 24 hours after a toxic METH challenge. The purpose of the current study was to investigate if the protective effects of METH persisted for a long period of time. We also tested if a second challenge with a toxic dose of METH would cause further damage to monoaminergic terminals. Saline-pretreated rats showed significant METH-induced decreases in striatal DA and 5-HT levels in rats sacrificed 2 weeks after the challenge. Rats that received two METH challenges showed no further decreases in striatal DA or 5-HT levels in comparison to the single METH challenge. In contrast, METH-pretreated rats showed significant protection against METH-induced striatal DA and 5-HT depletion. In addition, the METH challenge causes substantial decreases in cortical 5-HT levels which were not further potentiated by a second drug challenge. METH preconditioning provided almost complete protection against METH -induced 5-HT depletion. These results are consistent with the idea that METH pretreatment renders the brain refractory to METH-induced degeneration of brain monoaminergic systems.

Transcriptional responses to reinforcing effects of cocaine in the rat hippocampus and cortex

The psychostimulant effects of cocaine are thought to result from its ability to block dopamine (DA) uptake and increase DA levels in ventral striatum. In addition, cocaine causes biochemical changes in the brain areas involved in learning and memory, including hippocampus and cortex, whose role in drug reinforcement is now being actively investigated. Thus, we studied molecular events in the hippocampus and frontal cortex of rats treated with cocaine conditioned place preference (CPP) paradigm. After exposure to cocaine conditioning (cocaine paired), cocaine alone (cocaine non-paired) or saline rats were tested for place conditioning. Cocaine (10 mg/kg) caused increases in time spent in the drug-paired compartment. By using microarray analyses, we examined gene expression in the hippocampi and frontal cortices of cocaine-paired rats, cocaine non-paired and saline-treated controls. Our study revealed that 214 transcripts were differentially regulated in the hippocampi of cocaine-paired rats. These include genes that play roles in protein phosphorylation, RNA processing and protein synthesis, ubiquitin-dependent protein degradation and cytoskeleton organization. In contrast, 39 genes were differently expressed in the frontal cortex. Our data support the possibility that molecular changes in the hippocampus might participate in the formation and maintenance of memory patterns induced by cocaine in the brain. Differences in the transcriptional responses in the hippocampus and cortex suggest the primary importance of the hippocampus for recent memory processing associated with cocaine-induced CPP.

Profile of genes showing increased expression following dopamine and methamphetamine exposure in an immortalized neuronal cell line

Methamphetamine (METH) is a drug of abuse with well-described neurodegenerative effects. Some of the METH-induced degenerative manifestations are thought to be due to increased dopamine (DA) release in the cytoplasm of nerve terminals and subsequent extravasation in the synaptic cleft. Using an immortalized neural cell line, we have made use of the comprehensive cDNA array technology in order to compare and contrast the molecular effects of DA and METH. We found that the two compounds do have many similar but also different effects. Since these neural cells produce no DA, these results demonstrate that many of the METH-induced responses attributed to DA might, in fact, be intrinsic to METH itself. More biochemical studies are needed to investigate DA-independent METH deleterious events in the central nervous system.

Methamphetamine causes differential regulation of pro-death and anti-death Bcl-2 genes in the mouse neocortex

Bcl-2, an inner mitochondrial membrane protein, inhibits apoptotic neuronal cell death. Expression of Bcl-2 inhibits cell death by decreasing the net cellular generation of reactive oxygen species. Studies by different investigators have provided unimpeachable evidence of a role for oxygen-based free radicals in methamphetamine (METH) -induced neurotoxicity. In addition, studies from our laboratory have shown that immortalized rat neuronal cells that overexpress Bcl-2 are protected against METH-induced apoptosis in vitro. Moreover, the amphetamines can cause differential changes in the expression of Bcl-X splice variants in primary cortical cell cultures. These observations suggested that METH might also cause perturbations of Bcl-2-related genes when administered to rodents. Thus, the present study was conducted to determine whether the use of METH might indeed be associated with transcriptional and translational changes in the expression of Bcl-2-related genes in the mouse brain. Here we report that a toxic regimen of METH did cause significant increases in the pro-death Bcl-2 family genes BAD, BAX, and BID. Concomitantly, there were significant decreases in the anti-death genes Bcl-2 and Bcl-XL. These results thus support the notion that injections of toxic doses of METH trigger the activation of the programmed death pathway in the mammalian brain.

Temporal profiling of methamphetamine-induced changes in gene expression in the mouse brain: Evidence from cDNA array

Methamphetamine (METH) is a neurodegenerative drug of abuse. Its toxicity is characterized by destruction of monoaminergic terminals and by apoptosis in cortical and striatal cell bodies. Multiple factors appear to control METH neurotoxicity, including free radicals and transcription factors. Here, using cDNA arrays, we show the temporal profile of gene expression patterns in the cortex of mice treated with this drug. We obtained two patterns of changes from 588 genes surveyed. First, an early pattern is characterized by upregulation of transcription factors, including members of the jun family. Second, a delayed pattern includes genes related to cell death and to DNA repair. A number of trophic factors were also activated at the later timepoint. These observations suggest that METH can activate a multigene machinery that participates in the production of its toxic effects. The resulting degenerative effects of the drug are thus the result of a balance between protoxic and antiapoptotic mechanisms triggered by its administration to these animals. These observations are of clinical relevance because of the recent identification of degenerative changes in the brains of METH abusers.

Dual mechanism of Fas-induced cell death in neuroglioma cells: a role for reactive oxygen species

ApoI/Fas belongs to the tumor necrosis factor receptor (TNFR) superfamily and mediates cell death in various cell types. A dual mode of Fas-triggered cell death has been reported depending on cell types used in the experiments. The present study was carried out to test the possible role of reactive oxygen species in this dual mechanism in neuroglioma cells. Anti-Fas antibody caused dose-dependent and time-dependent increase in cell death measured by lactate dehydrogenase (LDH) release in control neuroglioma cells and in cells that were transfected with catalase cDNA. However, cells transfected with copper/zinc superoxide dismutase (Cu/ZnSOD) cDNA showed marked attenuation of Fas-induced LDH release. Moreover, flow cytometry and confocal microscopy revealed that Fas-induced cell death in control cells occur mostly through an apoptotic process. This process was also completely abrogated in cells overexpressing catalase or copper/zinc superoxide dismutase (Cu/ZnSOD). Further experiments revealed that Fas-induced cell death was associated with increased formation of superoxide anions in control neuroglioma cells and in cells overexpressing catalase. These increases were significantly suppressed by Cu/ZnSOD overexpression. These data indicate that Fas-mediated cell death in neuroglioma cells occur, in part, through the production of reactive oxygen species (ROS). These observations also suggest that Fas-induced cell death in these cells occur through apoptosis and necrosis. Thus overexpression of Cu/ZnSOD caused the suppression of both types of Fas-induced cell death whereas catalase prevented apoptotic but not necrotic cell death. These observations are discussed in terms of their support for a role for both peroxides and superoxide radicals in Fas-induced cell death.

VASE-containing N-CAM isoforms are increased in the hippocampus in bipolar disorder but not schizophrenia

The neural cell adhesion molecule (N-CAM) is a cell recognition molecule that is involved in cellular migration, synaptic plasticity, and CNS development. In schizophrenia, a 105- to 115-kDa N-CAM protein is increased in CSF and in the hippocampus and prefrontal cortex. The variable alternatively spliced exon (VASE) of N-CAM is developmentally regulated and can be spliced into any of the major 120-, 140-, and 180-kDa N-CAM isoforms. We determined that the variable alternative spliced exon of N-CAM (VASE) also is increased in bipolar disorder by quantitative Western immunoblot. VASE immunoreactive proteins (triplet bands around 140 kDa and a single band around 145 kDa) were identified in soluble and membrane brain extracts and quantified in the hippocampus. Soluble VASE 140 kDa was increased in the hippocampus of patients with bipolar disorder as compared to controls, patients with schizophrenia, and suicide cases. Membrane-extracted VASE 140 and 145 kDa were unchanged in the same groups. Multiple 145-kDa VASE-immunoreactive proteins that also reacted to an N-CAM antibody were separated by isoelectric focusing and electrophoresis followed by western immunoblotting; however, the VASE 140-kDa proteins were only weakly N-CAM immunoreactive. By immunohistochemistry, VASE colocalized with GFAP-positive astrocytes in the hippocampus. VASE immunostaining was also observed in the cytoplasm of CA4 pyramidal neurons that were positive for phosphorylated high molecular weight neurofilament and synaptophysin terminals. Thus no differences in VASE were found in patients with schizophrenia, but there was a marked increase of VASE immunoreactive proteins in bipolar disorder. It is possible that abnormal regulation of N-CAM proteins results in differing patterns of abnormal expression in neuropsychiatric disorders.

Overexpression of superoxide dismutase and catalase in immortalized neural cells: toxic effects of hydrogen peroxide

Hydrogen peroxide (H2O2) is a known toxicant which causes its damage via the production of hydroxyl radicals. It has been reported to cause both necrotic and apoptotic cell death. The present study was undertaken to evaluate the mode of H2O2-induced cell death and to assess if overexpression of catalase could protect against its toxicity. H2O2 causes cell death of immortalized CSM 14.1 neural cells in a dose-dependent manner. H2O2-induced death was associated with DNA laddering as shown by agarose gel electrophoresis. Stable overexpression of catalase by transfection of a vector containing human cDNA into these cells markedly attenuated H2O2-induced toxic effects. Transfection of a vector containing a SOD cDNA afforded no protection. These results indicate that H2O2 can lead to the activation of endonuclease enzyme that breaks DNA into oligosomes. These cells which overexpress catalase or SOD will help to determine the specific role of H2O2 or O2- in the deleterious effects of a number of toxins.

Species- and brain region-specific dopamine transporters: immunological and glycosylation characteristics

Dopamine transporters (DATs) from the caudate nucleus of four species (rat, mouse, dog, and human) and four regions of rat brain (striatum, nucleus accumbens, prefrontal cortex, and midbrain) were photoaffinity labeled and analyzed by immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis for cross-reactivity to four epitope-specific rat antipeptide antibodies. Each of these antibodies varied in its efficiency at recognizing DAT. The DATs from the rat brain regions exhibited the same degree of recognition by each of the four sera, a result compatible with these proteins being the product of a single gene. The DATs from the different species were recognized by all four sera but with different efficiencies, possibly relating to amino acid sequence differences within the immunizing epitope. All of the photolabeled, immunoprecipitated DATs migrated with a molecular mass of approximately 80 kDa, and no lower molecular mass forms were found. The DATs from all species and brain regions tested were shown by enzymatic deglycosylation to contain N-linked carbohydrates and sialic acids in amounts comparable with rat striatal DATs. The finding that no photolabeled DAT forms < 80 kDa were isolated from membranes indicates that partially or incompletely glycosylated forms are not present, even in the midbrain cell bodies where immature forms might be expected to be found. These findings verify the utility of these anti-rat antibodies as biochemical tools for studying DATs from other species and extend our knowledge of biochemical characteristics of DATs from these species and brain regions.

Interleukin 2, interleukin 2 receptor, and interferon-gamma synthesis and mRNA expression in phorbol myristate acetate and calcium ionophore A23187-stimulated T cells from elderly humans

The levels of interleukin 2 (IL-2), interleukin 2 receptor (IL-2R), and interferon-gamma (IFN-gamma) specific mRNA and their gene products were examined in phorbol myristate acetate (PMA) and calcium ionophore A23187-costimulated purified T cells from young and elderly humans. In addition, the number of high-affinity IL-2R per activated cell, the high-affinity IL-2R density, and the proliferative response of the cells were measured. Among PMA/A23187-stimulated T cells, there was no statistically significant age-related difference in IL-2 or IL-2R specific mRNA accumulation or in the amount of IL-2 or IL-2R synthesized. IFN-gamma specific mRNA was increased significantly in T cells from elderly individuals and the amount of IFN-gamma synthesized by PMA/A23187-activated T cells was nearly double that produced by cells from young individuals. Quantification of the number of high-affinity IL-2R by [125I]IL-2 binding demonstrated there was no decrease in either the mean number or the dissociation constant of the high-affinity IL-2R on activated T cells of the elderly. Despite producing large amounts of IL-2 and having comparable numbers of both low- and high-affinity IL-2R. PMA/A23187-stimulated T cells from elderly subjects still proliferated less vigorously than did T cells from young persons. The addition of exogenous IL-2 to the cultured cells did not fully correct this age difference. Our findings that the expression of the IL-2, IL-2R, and IFN-gamma genes are not constitutionally defective in the elderly support the hypothesis that the age-related decline in proliferation observed in mitogen-stimulated T cells of the elderly is most likely attributable to alterations in the transmission of signals from the cell membrane to the nucleus.

Abundant alkali-sensitive sites in DNA of human and mouse sperm

The DNA of human and mouse sperm cells was analyzed by single-cell microgel electrophoresis, by agarose gel electrophoresis, and by alkaline elution--three techniques that can detect single-strand DNA breaks and/or labile sites. Under these conditions a surprisingly large number of single-strand DNA breaks, approximately 10(6) to 10(7) per genome, were detected in human and mouse sperm but not in human lymphocytes or in mouse bone marrow cells. These breaks were also present in chicken erythrocyte DNA, which is also highly condensed. These breaks were not observed under neutral pH conditions nor under denaturing conditions not involving alkali, suggesting that these sites are alkali-sensitive and do not represent preexisting single-strand breaks. The high frequency of such sites in sperm from healthy mouse and human donors suggests that they represent a functional characteristic of condensed chromatin rather than DNA damage.

Expression of interleukin 2 and the interleukin 2 receptor in aging rats

Lymphocytes of aged animals exhibit a marked decrease in proliferative capacity in response to mitogen stimulation when compared to those of younger animals. In humans and mice the decreased proliferation is due at least in part (i) to the inability of lymphocytes to synthesize sufficient interleukin 2 (IL-2) and (ii) to decreased expression of IL-2 receptors (IL-2R) on the surface of aged lymphocytes. We compared proliferative abilities, IL-2 production, and IL-2R expression in splenocyte cultures of 4- to 5- and 22- to 24-month-old Fischer 344 rats stimulated with either concanavalin A (Con A) or A23187 and phorbol myristate acetate (PMA). Proliferation was significantly decreased in aged lymphocytes (30-50%) with both treatment protocols. However, unlike mice and humans we observed no difference in IL-2 activity, IL-2 mRNA levels, or IL-2R cell surface expression of lymphocytes from young and aged rats stimulated with either Con A or A23187 and PMA. These results indicate that factors other than decreased expression of IL-2 and IL-2R are responsible for the diminished proliferative capacity of aged rat lymphocytes following mitogen stimulation.

Decreased proliferation, interleukin 2 synthesis, and interleukin 2 receptor expression are accompanied by decreased mRNA expression in phytohemagglutinin-stimulated cells from elderly donors

Using cDNA probes to human interleukin 2 (IL2) and interleukin 2 receptor (IL2R), the amount of IL2 and IL2R mRNA produced by PHA stimulated peripheral blood mononuclear cells from young (less than 40 yr) and old (greater than 60 yr) donors was quantitated. Stimulated cell cultures from each individual were also examined for proliferative ability, expression of membrane IL2R, membrane IL2R density, and for the amount of IL2R shed into the culture supernatant. Induction of IL2 and IL2R mRNAs were decreased in cells from elderly individuals, as were the levels of IL2 secretion, the percentage of IL2R+ T cells and the density of membrane IL2R per cell. The results suggest that decreased expression of both IL2 and IL2R mRNA contributes to the low synthesis of IL2 and membrane IL2R, respectively, and is partially responsible for the diminished proliferative activity observed in lymphocytes from the elderly.

A simple technique for quantitation of low levels of DNA damage in individual cells

Human lymphocytes were either exposed to X-irradiation (25 to 200 rads) or treated with H2O2 (9.1 to 291 microM) at 4 degrees C and the extent of DNA migration was measured using a single-cell microgel electrophoresis technique under alkaline conditions. Both agents induced a significant increase in DNA migration, beginning at the lowest dose evaluated. Migration patterns were relatively homogeneous among cells exposed to X-rays but heterogeneous among cells treated with H2O2. An analysis of repair kinetics following exposure to 200 rads X-rays was conducted with lymphocytes obtained from three individuals. The bulk of the DNA repair occurred within the first 15 min, while all of the repair was essentially complete by 120 min after exposure. However, some cells demonstrated no repair during this incubation period while other cells demonstrated DNA migration patterns indicative of more damage than that induced by the initial irradiation with X-rays. This technique appears to be sensitive and useful for detecting damage and repair in single cells.

Intraoperative localization of parathyroid glands using methylthionine chloride / tetramethylthionine chloride in secondary hyperparathyroidism

Over an 18 month interval at the University of Louisville Affiliated Hospitals, 40 patients were evaluated in a nonrandomized prospective study to determine the value of methylthionine chloride / tetramethylthionine chloride (methylene blue--MB) as an aid for the rapid intraoperative identification of parathyroid hyperplasia of end-stage renal disease (ESRD). Patients assigned to the MB infusion subgroup had infusion of 1 per cent MB (5.5 milligrams per kilogram) over a time interval of 25 to 60 minutes (mean of 43.9) prior to anesthetic induction. A total of 159 glands were identified in both the control and MB infusion groups (3.98 glands per patient) of which the predominant histopathologic diagnosis on frozen section was chief cell hyperplasia (78.3 per cent). Of 91 hyperplastic glands submitted for analysis after subtotal parathyroidectomy in those in the MB infusion group, 82 glands (90.1 per cent) were observed to have positive staining with identifiable differentiation from surrounding tissues. Analyses of the correlation of the serum calcium value and probability of MB staining or its relation to serum intact parathyroid hormone (intact-PTH) values were not statistically significant (p greater than 0.05, correlation coefficient equals 0.149). Furthermore, no relationship existed between the glandular size (millimeter to the third power) and probability of MB staining (chi-square equals 1.750, p greater than 0.05) or between hyperplastic size and serum intact-PTH value (correlation coefficient equals 0.068). Conversely, analysis of MB gland staining with regard to intact PTH concentration disclosed 59 of 59 glands stained intensely with MB when intact-PTH concentration was not less than 700 picograms per milliliter (p less than 0.01). Non-staining of hyperplastic parathyroid tissue was observed in 28.1 per cent of glands submitted for histopathologic analysis in which preoperative intact PTH values were more than 699 picograms per milliliter. Time of operation was reduced from 119.0 +/- 47.53 minutes (mean +/- S.E.M.) in control patients to 92.1 +/- 20.12 minutes (mean +/- S.E.M.) for the MB infusion group (V per cent equals 21.85, p less than 0.01). Furthermore, this technique appears to have value in the detection of ectopically located parathyroid tissue as demonstrated by the in vivo staining of seven ectopic glands in six patients of the infused group. Complications were restricted to the patients in the MB infusion group (21.7 per cent) and included: pseudo-cyanosis in three; pain in the infusion site in two, wound hematoma in one patient, pancreatitis in one and angina in one.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of mechanical performance in four types of external fixators

The Hoffmann-Vidal triangular apparatus for fracture fixation of the femur, the Volkov-Oganesian device with Steinmann pins in tension, the Kronner device with a plastic elliptic frame, and the Roger-Anderson apparatus (both standard and compression-distraction designs) were studied based on loading and analytic methods established previously. The results were compared with those for the standard Hoffmann-Vidal quadrilateral configuration. The Kronner device, with five connecting bars, was the stiffest under most loading modes, closely followed by the Hoffmann-Vidal quadrilateral apparatus. The standard Roger-Anderson device demonstrated average rigidity; its new design with compression-distraction capability was relatively weak. All devices showed an apparent weakness in antero-posterior bending. The Volkov-Oganesian design demonstrated low overall stiffness but was the most effective apparatus in resisting anteroposterior bending. External fixators provide effective compression at the fracture site, and the amount of compression is proportional to the stiffness of the apparatus.

Lactate dehydrogenase isoenzyme 1. A rapid assay for ischemic myocardial disease

A rapid immunochemical method (Isomune-LD) for the determination of lactate dehydrogenase isoenzyme 1 (LD1) activity in serum was investigated, and the sensitivity and specificity of the assay were determined for the diagnosis of a myocardial infarction (MI). Multiple serum samples were obtained (on admission and at 12, 24, and 48 hours) from 85 patients (30 with proven MI and 55 without MI). The sensitivity of LD1 on admission and at 12, 24, and 48 hours was 43%, 84%, 96%, and 100%, respectively, and the specificity at these same time intervals was 95%, 100%, 97%, and 97%, respectively. Thus, the determination of LD1 by this rapid immunochemical method appears to allow a rapid laboratory evaluation of MI with a high degree of sensitivity and specificity.

Interferences of mannitol with phosphate determination

Methods commonly used for serum phosphate analysis depend upon the combination of inorganic phosphorus with molybdate and subsequent quantitation of the resultant phosphomolybdate by spectrophotometry. This is a case report of mannitol interference with phosphate quantitation by a method not employing dialysis (DuPont ACA) but not with another method which includes a dialysis step (Technicon SMAC). This interference, occurring at an extremely high level of serum mannitol (3.5 g/dl) in a patient with acute renal failure, appears to be due to direct inhibition of the formation of the phosphomolybdate complex by mannitol.

Simulated surgical wound infection in mice: effect of stimulation on nonspecific host defense mechanisms

Experiments were conducted to ascertain whether nonspecific host defenses could be enhanced in a reliable animal model simulating the local bacterial infection that frequently complicates surgical wounds. The test lesion was studied in detail and exemplifies the concept that the ultimate expression of the host-pathogen interaction is the capacity of that pathogen to persist or grow in a given host. Mice were challenged by intramuscular insertion of cotton suture impregnated with 10(7) to 10(8) Escherichia coli K-12. The mice were subsequently killed at intervals, and the suture and muscle mass were retrieved, homogenized, and quantitatively cultured. Numbers of viable organisms in tissue from control animals were compared with those from experimental animals that received BCG (Bacillus Calmette-Guérin) vaccine, a nonspecific immunostimulant, prior to bacterial challenge. Improved tissue antibacterial activity appeared in animals that had received BCG vaccine 13 days prior to bacterial challenge. Differing doses and intervals were not protective. Enhancement of nonspecific host defense mechanisms may be helpful in combination with current measures for improved control of surgical wound infection.