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Cocaine and epigenetics: Gene expression in dopaminergic brain structures of rats self-administrating cocaine
Abstracts / Toxicology Letters 205S (2011) S19–S35
methodologies to influence the ways they can be applied, improve preclinical efficacy and hazard evaluation, and deliver more predictive, effective and translational endpoints. A wide range of imaging technologies are available within GlaxoSmithKline R&D Preclinical Development. These include Computed Tomography, Positron Emission Tomography and Single Photon Emission Computed Tomography, Magnetic Resonance Imaging, Ultrasound, Densitometry. These technologies provide both unique and complimentary quantitative information on organ and tissue structure, including visualization of anatomy and pathology in real time, and function from the level of an individual organ down to molecular interactions. In the context of preclinical safety assessment of NCE, imaging applications are playing a key role in terms of predictivity and hazard identification. These imaging modalities indeed contribute in the evaluation compound efficacy in disease animal models, as well as the pharmacodynamic effects and biodistribution of new chemical entities. Refinement and reduction of animal use, allowing the design of longitudinal studies, according to 3Rs principles (Replacement, Refinement and Reduction of animals in research, www.nc3rs.org.uk), and the development of innovative and predictive biomarkers, bridging the gap of the translational endpoints, increase the advantages of using imaging applications in the preclinical arena. doi:10.1016/j.toxlet.2011.05.100
W05-5 Molecular imaging in non-clinical species and humans – Options and reality in safety assessment
S25
Regulation of gene expression is known to contribute to the long-term adaptations taking place in brain structures in response to drugs of abuse. Recent studies highlight the regulation of gene transcription in neurons by chromatin remodeling, a process governed by the interplay of DNA methylation and post-translational modifications of histones. To test the involvement of epigenetic regulation on drug reinforcing properties, we submitted rats to the cocaine self-administration paradigm. We found that the histone deacetylase (HDAC) inhibitors trichostatin A (TsA) and phenylbutyrate reduced cocaine self-administration. Under a progressive ratio schedule, both TsA and depudecin significantly reduced the breaking point, indicating that HDAC inhibition attenuated the motivation of rats for cocaine. We then investigated alterations in gene expression in dopaminergic structures of rats self-administering cocaine and treated with TsA. Cocaine self-administration was accompanied by an increased synthesis of epigenetic parameters. To fully characterize genes regulated by TsA, we used the oligonucleotide microarray technology that revealed 722 probe sets in the cortex and 136 probe sets in the nucleus accumbens differentially expressed between vehicle and TsA-treated rats that self-administered cocaine. Microarray data were validated by real-time PCR for seven genes. Using immunohistochemistry, we further investigated the expression of Lis1 and reelin genes, since they belong to the same signal transduction pathway and mutations within both genes cause lissencephaly. The data indicate that the two proteins, and the signal transduction pathway to which they belong, contribute to establish neurobiological mechanisms underlying brain plasticity whereby TsA lowers the motivation for cocaine. doi:10.1016/j.toxlet.2011.05.103
M. Bergstroem Imaging Sciences, F. Hoffmann-La Roche AG, Basel, Switzerland Molecular imaging bears promises of non-invasive recording of biochemical and physiological features of organs in humans and pre-clinical species. It is hence an attractive potential for assessment of beneficial and adverse effects by drugs on organs and is considered in relation to early assessment of the therapeutic window. Molecular imaging may give supportive evidence of minimal dose needed to, e.g. saturate the target or induce cellular response in the targeted organ and might indicate the minimal dose at which other organs physiology is unaffected. However, molecular imaging as a tool for toxicology assessments bears two inherent problems: only one biochemical parameter at a time can be evaluated and the method is too expensive and specialized to allow evaluations of sporadically occurring events. This presentation will indicate some of the options of molecular imaging to assess effect and adverse effects and also indicate some of the major limitations. It will indicate the translational potentials of molecular imaging and propose some scenarios for its use in early drug development. doi:10.1016/j.toxlet.2011.05.101
W6 Neurotoxicity and Drug Dependence of Psychostimulants
W06-1 Cocaine and epigenetics: Gene expression in dopaminergic brain structures of rats self-administrating cocaine J. Zwiller Université De Strasbourg, LINC, UMR 7237, CNRS, Strasbourg, France
W06-2 Neuroadaptive changes induced by cocaine self-administration E. Ambrosio 1,∗ , M. Miguéns 1 , N. del Olmo 2 , A. Higuera-Matas 1 , C. García-Lecumberri 1 1
Departmento de Psicobiologia, Universidad Nacional de Educación a Distancia (UNED), Madrid, Spain, 2 Ciencias Farmaceúticas y de la Alimentación, Universidad San Pablo-CEU, Boadilla del Monte, Madrid, Spain Cocaine is among the most widely abused central drug stimulants. Although cocaine abuse is associated with a wide range of psychiatric and other medical disorders, at the present time there are no suitable medications for the treatment of cocaine abuse and dependence. Studies on the neurobiology of cocaine abuse suggest that cocaine affects key elements of the brain reward system, particularly mesocorticolimbic dopamine pathways. Chronic cocaine administration produces an abundance of long-lasting neuroadaptations in several neurotransmitter systems that might contribute to an increased vulnerability to cocaine relapse. The aim of this work is to present evidences provided by self-administration paradigms on the dopaminergic, opioidergic, glutamatergic, cholinergic, serotoninergic and CRF systems. Genetic differences in the neuroadaptive response to cocaine will also be considered for having a comprehensive view of this subject. Similarly, the importance of differences related to contingent versus non-contingent exposition to cocaine and its effects during the extinction will be analyzed. The results discussed in this work might help to develop more effective therapeutic approaches for cocaine treatment and relapse in cocaine addiction. Supported by grants from the Ministerio de Educación y Ciencia (SAF2007-064890); Ministerio de Sanidad y Consumo
methodologies to influence the ways they can be applied, improve preclinical efficacy and hazard evaluation, and deliver more predictive, effective and translational endpoints. A wide range of imaging technologies are available within GlaxoSmithKline R&D Preclinical Development. These include Computed Tomography, Positron Emission Tomography and Single Photon Emission Computed Tomography, Magnetic Resonance Imaging, Ultrasound, Densitometry. These technologies provide both unique and complimentary quantitative information on organ and tissue structure, including visualization of anatomy and pathology in real time, and function from the level of an individual organ down to molecular interactions. In the context of preclinical safety assessment of NCE, imaging applications are playing a key role in terms of predictivity and hazard identification. These imaging modalities indeed contribute in the evaluation compound efficacy in disease animal models, as well as the pharmacodynamic effects and biodistribution of new chemical entities. Refinement and reduction of animal use, allowing the design of longitudinal studies, according to 3Rs principles (Replacement, Refinement and Reduction of animals in research, www.nc3rs.org.uk), and the development of innovative and predictive biomarkers, bridging the gap of the translational endpoints, increase the advantages of using imaging applications in the preclinical arena. doi:10.1016/j.toxlet.2011.05.100
W05-5 Molecular imaging in non-clinical species and humans – Options and reality in safety assessment
S25
Regulation of gene expression is known to contribute to the long-term adaptations taking place in brain structures in response to drugs of abuse. Recent studies highlight the regulation of gene transcription in neurons by chromatin remodeling, a process governed by the interplay of DNA methylation and post-translational modifications of histones. To test the involvement of epigenetic regulation on drug reinforcing properties, we submitted rats to the cocaine self-administration paradigm. We found that the histone deacetylase (HDAC) inhibitors trichostatin A (TsA) and phenylbutyrate reduced cocaine self-administration. Under a progressive ratio schedule, both TsA and depudecin significantly reduced the breaking point, indicating that HDAC inhibition attenuated the motivation of rats for cocaine. We then investigated alterations in gene expression in dopaminergic structures of rats self-administering cocaine and treated with TsA. Cocaine self-administration was accompanied by an increased synthesis of epigenetic parameters. To fully characterize genes regulated by TsA, we used the oligonucleotide microarray technology that revealed 722 probe sets in the cortex and 136 probe sets in the nucleus accumbens differentially expressed between vehicle and TsA-treated rats that self-administered cocaine. Microarray data were validated by real-time PCR for seven genes. Using immunohistochemistry, we further investigated the expression of Lis1 and reelin genes, since they belong to the same signal transduction pathway and mutations within both genes cause lissencephaly. The data indicate that the two proteins, and the signal transduction pathway to which they belong, contribute to establish neurobiological mechanisms underlying brain plasticity whereby TsA lowers the motivation for cocaine. doi:10.1016/j.toxlet.2011.05.103
M. Bergstroem Imaging Sciences, F. Hoffmann-La Roche AG, Basel, Switzerland Molecular imaging bears promises of non-invasive recording of biochemical and physiological features of organs in humans and pre-clinical species. It is hence an attractive potential for assessment of beneficial and adverse effects by drugs on organs and is considered in relation to early assessment of the therapeutic window. Molecular imaging may give supportive evidence of minimal dose needed to, e.g. saturate the target or induce cellular response in the targeted organ and might indicate the minimal dose at which other organs physiology is unaffected. However, molecular imaging as a tool for toxicology assessments bears two inherent problems: only one biochemical parameter at a time can be evaluated and the method is too expensive and specialized to allow evaluations of sporadically occurring events. This presentation will indicate some of the options of molecular imaging to assess effect and adverse effects and also indicate some of the major limitations. It will indicate the translational potentials of molecular imaging and propose some scenarios for its use in early drug development. doi:10.1016/j.toxlet.2011.05.101
W6 Neurotoxicity and Drug Dependence of Psychostimulants
W06-1 Cocaine and epigenetics: Gene expression in dopaminergic brain structures of rats self-administrating cocaine J. Zwiller Université De Strasbourg, LINC, UMR 7237, CNRS, Strasbourg, France
W06-2 Neuroadaptive changes induced by cocaine self-administration E. Ambrosio 1,∗ , M. Miguéns 1 , N. del Olmo 2 , A. Higuera-Matas 1 , C. García-Lecumberri 1 1
Departmento de Psicobiologia, Universidad Nacional de Educación a Distancia (UNED), Madrid, Spain, 2 Ciencias Farmaceúticas y de la Alimentación, Universidad San Pablo-CEU, Boadilla del Monte, Madrid, Spain Cocaine is among the most widely abused central drug stimulants. Although cocaine abuse is associated with a wide range of psychiatric and other medical disorders, at the present time there are no suitable medications for the treatment of cocaine abuse and dependence. Studies on the neurobiology of cocaine abuse suggest that cocaine affects key elements of the brain reward system, particularly mesocorticolimbic dopamine pathways. Chronic cocaine administration produces an abundance of long-lasting neuroadaptations in several neurotransmitter systems that might contribute to an increased vulnerability to cocaine relapse. The aim of this work is to present evidences provided by self-administration paradigms on the dopaminergic, opioidergic, glutamatergic, cholinergic, serotoninergic and CRF systems. Genetic differences in the neuroadaptive response to cocaine will also be considered for having a comprehensive view of this subject. Similarly, the importance of differences related to contingent versus non-contingent exposition to cocaine and its effects during the extinction will be analyzed. The results discussed in this work might help to develop more effective therapeutic approaches for cocaine treatment and relapse in cocaine addiction. Supported by grants from the Ministerio de Educación y Ciencia (SAF2007-064890); Ministerio de Sanidad y Consumo