This thesis examines both behavioral and anatomical effects of prenatal exposure of Valproic Acid (VPA) on Long Evans rats. Tactile stimulation (TS) is then used to investigate its’ effect on remediating any abnormalities VPA may produce. Several behavioral tests were done to assess the behavioral effects of VPA and TS. It was found that VPA had an effect of many of the tasks, whereas, TS had almost none with the exception of an effect on females in the elevated plus maze. However, anatomical data showed that TS had a profound effect on neuronal branch order, cell complexity, and spine density in pyramidal neurons in the medial prefrontal cortex, the orbitofrontal cortex and the amygdala. Where VPA decreased the above in all of these areas, TS increased neuronal complexity in the aforementioned structures. This study demonstrates that prenatal exposure to VPA is a viable model of autism in rats and that TS has significant anatomical effects in these animals as well as in control animals / xi, 98 leaves; 29 cm

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2009.

Introdução: O Transtorno do Espectro do Autismo (TEA) é caracterizado por prejuízos na interação social e comunicação, e por comportamentos repetitivos e repertório restrito de interesses. Alterações em diferentes sistemas de neurotransmissores, como o serotoninérgico, GABAérgico e glutamatérgico já foram estudadas e relatadas no TEA. Surpreendentemente, o sistema histaminérgico recebeu pouca atenção e poucos estudos sobre histamina (HA) e TEA estão disponíveis na literatura. Além disso, ligantes do receptor histaminérgico 3 (H3R) são considerados agentes terapêuticos promissores para o tratamento de diferentes desordens neurológicas e prejuízos cognitivos, mas seus efeitos em características do tipo autista ainda não foram determinados. Objetivos: Avaliar o efeito do ciproxifan (CPX), um agonista inverso do H3R, sobre o modelo animal de autismo induzido por exposição pré-natal ao ácido valpróico (VPA, do inglês: valproic acid) e medir a concentração de HA e os níveis do mRNA de H3R e H4R em diferentes estruturas encefálicas desse modelo. Além disso, investigar o papel do H3R no comportamento social e estereotipado. Métodos: Camundongos Swiss sofreram exposição pré-natal ao VPA no dia embrionário 11 e, aos 50 dias de vida pós-natal foram submetidos à avaliação de comportamento social, limiar de nocicepção e comportamento repetitivo, com ou sem tratamento com CPX. Após as avaliações comportamentais, os animais foram eutanasiados por exsanguinação depois de terem sido anestesiados com isoflurano. Córtex cerebral, estriado e hipocampo foram removidos, congelados em nitrogênio líquido e armazenados a -80°C para quantificação de mRNA do H3R e H4R por qPCR e de conteúdo de HA por cromatografia líquida de alta eficiência (HPLC, do inglês: High Performance Liquide Chromatography). Camundongos H3R KO e WT C57BL/6J, aos 50 dias de vida, foram usados nos testes com o aparato de três câmaras e marble burying para determinação do papel do H3R na sociabilidade e comportamento estereotipado. Resultados: O grupo VPA apresentou menor índice se sociabilidade quando comparado aos animais do grupo Controle, e o tratamento com CPX foi capaz de reverter completamente este efeito. Entretanto, o aumento no limiar de nocicepção observado no grupo VPA não foi revertido pelo tratamento. No teste marble burying, o grupo VPA enterrou um maior número de bolinhas de gude em relação ao grupo Controle, indicando comportamento repetitivo, um efeito também prevenido pelo CPX. Além disso, a análise molecular entre os grupos VPA e Controle mostrou um aumento significativo nos níveis de mRNA do H3R, bem como uma maior concentração de HA no estriado de animais VPA. O H3R pode ter um papel no interesse por novidade social, característica prejudicada no TEA, já que camundongos H3R KO demonstraram comportamento anormal quando testados para este parâmetro no teste com aparato de três câmaras. Conclusões: Uma dose aguda de CPX foi capaz de reverter prejuízo na sociabilidade, bem como comportamento repetitivo apresentados pelo modelo VPA de autismo. Além disso, este é o primeiro relato sobre anormalidades no sistema histaminérgico nesse modelo. Estes achados contribuem para investigações futuras sobre a fisiopatologia do TEA, bem como apontam para um possível novo tratamento para características do tipo autista. Mais estudos são necessários para corroborar e expandir esses dados iniciais. / Introduction: Autism spectrum disorder (ASD) is primarily characterized by impaired social interaction and communication, and by restricted repetitive behaviors and interests. Alterations in different neurotransmitter systems, such as serotonergic, GABAergic and glutamatergic have been studied and reported in ASD. Surprisingly, the histaminergic system has received less attention and few studies are available on the literature about histamine and ASD. In addition, ligands of histamine receptor 3 (H3R) are considered potential therapeutic agents for the treatment of different brain disorders and cognitive impairments, but its effects on autistic-like features have not been evaluated. Objectives: The objective of this study was to evaluate the actions of ciproxifan (CPX), an H3R inverse agonist, on the animal model of autism induced by prenatal exposure to valproic acid (VPA) and to measure the concentration of histamine and the H3R and H4R mRNA levels in different brain structures of this model. In addition, to investigate the role of H3R in sociability and stereotypic behavior. Methods: Swiss mice were prenatally exposed to VPA on embryonic day 11 and assessed for social behavior, nociceptive threshold and repetitive behavior at 50 days of life after treatment with CPX. After the behavioral tests, animals were killed by exsanguination after being anesthetized with isoflurane. Cerebral cortex, striatum and hippocampus were removed, frozen in liquid nitrogen and stored at -80°C for quantification of H3R and H4R mRNA by qPCR and histamine content by HPLC analysis. H3R KO and WT C57BL/6J mice, at 50 days of life, were used in the three-chamber test and marble burying test to determine the role of H3R in sociability stereotypic behavior. Results: The VPA group presented lower sociability index compared to VPA animals that were treated with CPX. Compared to the Control group, VPA animals presented a significantly higher nociceptive threshold, and treatment with CPX was not able to modify this parameter. In the marble burying test, the number of marbles buried by VPA animals was consistent with markedly repetitive behavior. VPA animals that received CPX buried a reduced amount of marbles. A significant increase in H3R mRNA, as well as higher concentration of histamine were detected in striatal samples from the VPA mice. H3R might influence the search for social novelty, a feature that is impaired in ASD, as H3R KO mice displayed abnormal behavior when tested for this parameter in the three chambers test. Conclusions: In summary, an acute dose of CPX is able to revert sociability deficits and stereotypies present in the VPA model of autism. In addition, this is the first report of abnormalities in the histaminergic system of this model. These findings have the potential to help the investigations of both the molecular underpinnings of ASD and of possible treatments to ameliorate the ASD symptomatology, although more research is still necessary to corroborate and expand this initial data.

Introdução: O Transtorno do Espectro do Autismo (TEA) é caracterizado por prejuízos na interação social e comunicação, e por comportamentos repetitivos e repertório restrito de interesses. Alterações em diferentes sistemas de neurotransmissores, como o serotoninérgico, GABAérgico e glutamatérgico já foram estudadas e relatadas no TEA. Surpreendentemente, o sistema histaminérgico recebeu pouca atenção e poucos estudos sobre histamina (HA) e TEA estão disponíveis na literatura. Além disso, ligantes do receptor histaminérgico 3 (H3R) são considerados agentes terapêuticos promissores para o tratamento de diferentes desordens neurológicas e prejuízos cognitivos, mas seus efeitos em características do tipo autista ainda não foram determinados. Objetivos: Avaliar o efeito do ciproxifan (CPX), um agonista inverso do H3R, sobre o modelo animal de autismo induzido por exposição pré-natal ao ácido valpróico (VPA, do inglês: valproic acid) e medir a concentração de HA e os níveis do mRNA de H3R e H4R em diferentes estruturas encefálicas desse modelo. Além disso, investigar o papel do H3R no comportamento social e estereotipado. Métodos: Camundongos Swiss sofreram exposição pré-natal ao VPA no dia embrionário 11 e, aos 50 dias de vida pós-natal foram submetidos à avaliação de comportamento social, limiar de nocicepção e comportamento repetitivo, com ou sem tratamento com CPX. Após as avaliações comportamentais, os animais foram eutanasiados por exsanguinação depois de terem sido anestesiados com isoflurano. Córtex cerebral, estriado e hipocampo foram removidos, congelados em nitrogênio líquido e armazenados a -80°C para quantificação de mRNA do H3R e H4R por qPCR e de conteúdo de HA por cromatografia líquida de alta eficiência (HPLC, do inglês: High Performance Liquide Chromatography). Camundongos H3R KO e WT C57BL/6J, aos 50 dias de vida, foram usados nos testes com o aparato de três câmaras e marble burying para determinação do papel do H3R na sociabilidade e comportamento estereotipado. Resultados: O grupo VPA apresentou menor índice se sociabilidade quando comparado aos animais do grupo Controle, e o tratamento com CPX foi capaz de reverter completamente este efeito. Entretanto, o aumento no limiar de nocicepção observado no grupo VPA não foi revertido pelo tratamento. No teste marble burying, o grupo VPA enterrou um maior número de bolinhas de gude em relação ao grupo Controle, indicando comportamento repetitivo, um efeito também prevenido pelo CPX. Além disso, a análise molecular entre os grupos VPA e Controle mostrou um aumento significativo nos níveis de mRNA do H3R, bem como uma maior concentração de HA no estriado de animais VPA. O H3R pode ter um papel no interesse por novidade social, característica prejudicada no TEA, já que camundongos H3R KO demonstraram comportamento anormal quando testados para este parâmetro no teste com aparato de três câmaras. Conclusões: Uma dose aguda de CPX foi capaz de reverter prejuízo na sociabilidade, bem como comportamento repetitivo apresentados pelo modelo VPA de autismo. Além disso, este é o primeiro relato sobre anormalidades no sistema histaminérgico nesse modelo. Estes achados contribuem para investigações futuras sobre a fisiopatologia do TEA, bem como apontam para um possível novo tratamento para características do tipo autista. Mais estudos são necessários para corroborar e expandir esses dados iniciais. / Introduction: Autism spectrum disorder (ASD) is primarily characterized by impaired social interaction and communication, and by restricted repetitive behaviors and interests. Alterations in different neurotransmitter systems, such as serotonergic, GABAergic and glutamatergic have been studied and reported in ASD. Surprisingly, the histaminergic system has received less attention and few studies are available on the literature about histamine and ASD. In addition, ligands of histamine receptor 3 (H3R) are considered potential therapeutic agents for the treatment of different brain disorders and cognitive impairments, but its effects on autistic-like features have not been evaluated. Objectives: The objective of this study was to evaluate the actions of ciproxifan (CPX), an H3R inverse agonist, on the animal model of autism induced by prenatal exposure to valproic acid (VPA) and to measure the concentration of histamine and the H3R and H4R mRNA levels in different brain structures of this model. In addition, to investigate the role of H3R in sociability and stereotypic behavior. Methods: Swiss mice were prenatally exposed to VPA on embryonic day 11 and assessed for social behavior, nociceptive threshold and repetitive behavior at 50 days of life after treatment with CPX. After the behavioral tests, animals were killed by exsanguination after being anesthetized with isoflurane. Cerebral cortex, striatum and hippocampus were removed, frozen in liquid nitrogen and stored at -80°C for quantification of H3R and H4R mRNA by qPCR and histamine content by HPLC analysis. H3R KO and WT C57BL/6J mice, at 50 days of life, were used in the three-chamber test and marble burying test to determine the role of H3R in sociability stereotypic behavior. Results: The VPA group presented lower sociability index compared to VPA animals that were treated with CPX. Compared to the Control group, VPA animals presented a significantly higher nociceptive threshold, and treatment with CPX was not able to modify this parameter. In the marble burying test, the number of marbles buried by VPA animals was consistent with markedly repetitive behavior. VPA animals that received CPX buried a reduced amount of marbles. A significant increase in H3R mRNA, as well as higher concentration of histamine were detected in striatal samples from the VPA mice. H3R might influence the search for social novelty, a feature that is impaired in ASD, as H3R KO mice displayed abnormal behavior when tested for this parameter in the three chambers test. Conclusions: In summary, an acute dose of CPX is able to revert sociability deficits and stereotypies present in the VPA model of autism. In addition, this is the first report of abnormalities in the histaminergic system of this model. These findings have the potential to help the investigations of both the molecular underpinnings of ASD and of possible treatments to ameliorate the ASD symptomatology, although more research is still necessary to corroborate and expand this initial data.

Introdução: O Transtorno do Espectro do Autismo (TEA) é caracterizado por prejuízos na interação social e comunicação, e por comportamentos repetitivos e repertório restrito de interesses. Alterações em diferentes sistemas de neurotransmissores, como o serotoninérgico, GABAérgico e glutamatérgico já foram estudadas e relatadas no TEA. Surpreendentemente, o sistema histaminérgico recebeu pouca atenção e poucos estudos sobre histamina (HA) e TEA estão disponíveis na literatura. Além disso, ligantes do receptor histaminérgico 3 (H3R) são considerados agentes terapêuticos promissores para o tratamento de diferentes desordens neurológicas e prejuízos cognitivos, mas seus efeitos em características do tipo autista ainda não foram determinados. Objetivos: Avaliar o efeito do ciproxifan (CPX), um agonista inverso do H3R, sobre o modelo animal de autismo induzido por exposição pré-natal ao ácido valpróico (VPA, do inglês: valproic acid) e medir a concentração de HA e os níveis do mRNA de H3R e H4R em diferentes estruturas encefálicas desse modelo. Além disso, investigar o papel do H3R no comportamento social e estereotipado. Métodos: Camundongos Swiss sofreram exposição pré-natal ao VPA no dia embrionário 11 e, aos 50 dias de vida pós-natal foram submetidos à avaliação de comportamento social, limiar de nocicepção e comportamento repetitivo, com ou sem tratamento com CPX. Após as avaliações comportamentais, os animais foram eutanasiados por exsanguinação depois de terem sido anestesiados com isoflurano. Córtex cerebral, estriado e hipocampo foram removidos, congelados em nitrogênio líquido e armazenados a -80°C para quantificação de mRNA do H3R e H4R por qPCR e de conteúdo de HA por cromatografia líquida de alta eficiência (HPLC, do inglês: High Performance Liquide Chromatography). Camundongos H3R KO e WT C57BL/6J, aos 50 dias de vida, foram usados nos testes com o aparato de três câmaras e marble burying para determinação do papel do H3R na sociabilidade e comportamento estereotipado. Resultados: O grupo VPA apresentou menor índice se sociabilidade quando comparado aos animais do grupo Controle, e o tratamento com CPX foi capaz de reverter completamente este efeito. Entretanto, o aumento no limiar de nocicepção observado no grupo VPA não foi revertido pelo tratamento. No teste marble burying, o grupo VPA enterrou um maior número de bolinhas de gude em relação ao grupo Controle, indicando comportamento repetitivo, um efeito também prevenido pelo CPX. Além disso, a análise molecular entre os grupos VPA e Controle mostrou um aumento significativo nos níveis de mRNA do H3R, bem como uma maior concentração de HA no estriado de animais VPA. O H3R pode ter um papel no interesse por novidade social, característica prejudicada no TEA, já que camundongos H3R KO demonstraram comportamento anormal quando testados para este parâmetro no teste com aparato de três câmaras. Conclusões: Uma dose aguda de CPX foi capaz de reverter prejuízo na sociabilidade, bem como comportamento repetitivo apresentados pelo modelo VPA de autismo. Além disso, este é o primeiro relato sobre anormalidades no sistema histaminérgico nesse modelo. Estes achados contribuem para investigações futuras sobre a fisiopatologia do TEA, bem como apontam para um possível novo tratamento para características do tipo autista. Mais estudos são necessários para corroborar e expandir esses dados iniciais. / Introduction: Autism spectrum disorder (ASD) is primarily characterized by impaired social interaction and communication, and by restricted repetitive behaviors and interests. Alterations in different neurotransmitter systems, such as serotonergic, GABAergic and glutamatergic have been studied and reported in ASD. Surprisingly, the histaminergic system has received less attention and few studies are available on the literature about histamine and ASD. In addition, ligands of histamine receptor 3 (H3R) are considered potential therapeutic agents for the treatment of different brain disorders and cognitive impairments, but its effects on autistic-like features have not been evaluated. Objectives: The objective of this study was to evaluate the actions of ciproxifan (CPX), an H3R inverse agonist, on the animal model of autism induced by prenatal exposure to valproic acid (VPA) and to measure the concentration of histamine and the H3R and H4R mRNA levels in different brain structures of this model. In addition, to investigate the role of H3R in sociability and stereotypic behavior. Methods: Swiss mice were prenatally exposed to VPA on embryonic day 11 and assessed for social behavior, nociceptive threshold and repetitive behavior at 50 days of life after treatment with CPX. After the behavioral tests, animals were killed by exsanguination after being anesthetized with isoflurane. Cerebral cortex, striatum and hippocampus were removed, frozen in liquid nitrogen and stored at -80°C for quantification of H3R and H4R mRNA by qPCR and histamine content by HPLC analysis. H3R KO and WT C57BL/6J mice, at 50 days of life, were used in the three-chamber test and marble burying test to determine the role of H3R in sociability stereotypic behavior. Results: The VPA group presented lower sociability index compared to VPA animals that were treated with CPX. Compared to the Control group, VPA animals presented a significantly higher nociceptive threshold, and treatment with CPX was not able to modify this parameter. In the marble burying test, the number of marbles buried by VPA animals was consistent with markedly repetitive behavior. VPA animals that received CPX buried a reduced amount of marbles. A significant increase in H3R mRNA, as well as higher concentration of histamine were detected in striatal samples from the VPA mice. H3R might influence the search for social novelty, a feature that is impaired in ASD, as H3R KO mice displayed abnormal behavior when tested for this parameter in the three chambers test. Conclusions: In summary, an acute dose of CPX is able to revert sociability deficits and stereotypies present in the VPA model of autism. In addition, this is the first report of abnormalities in the histaminergic system of this model. These findings have the potential to help the investigations of both the molecular underpinnings of ASD and of possible treatments to ameliorate the ASD symptomatology, although more research is still necessary to corroborate and expand this initial data.

Orientador: Maria Luiza Silveira Mello / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-20T21:08:55Z (GMT). No. of bitstreams: 1 Felisbino_MarinaBarreto_M.pdf: 5744960 bytes, checksum: 792f3ed20bbe7d53c917089733be679f (MD5) Previous issue date: 2012 / Resumo: O ácido valproico (VPA) é um potente anti-convulsante conhecido como inibidor de deacetilases de histonas (HDACi) de classe I em diversos tipos celulares. Buscando conhecer se a estrutura cromatínica se alteraria quando da ação de HDACi, investigamos a supraorganização cromatínica de células tumorais HeLa e de células NIH 3T3, estas últimas caracterizadas por apresentarem áreas de heterocromatina conspícuas, sob tratamento com VPA. Essas informações foram associadas a da atividade enzimática de HDACs assim como do nível de acetilação das histonas H3 nesses modelos celulares tratados por VPA. As frequências de anomalias cromossômicas, morte celular e índices mitóticos também foram investigados. As células tratadas com VPA nas concentrações 0,05, 0,5 e 1,0 mM por 1-24 h foram submetidas à reação de Feulgen e analisadas através de microespectrofotometria de varredura automática e microscopia óptica. Western blots, análises enzimáticas e ensaio TUNEL também foram utilizados neste estudo. Células tratadas com tricostatina A (TSA), uma HDACi de atividade mais ampla do que o VPA, foram utilizadas como controles positivos. Em todas as condições de tratamento com VPA e TSA foi demonstrada descompactação cromatínica acompanhada de diminuição na atividade de HDACs e aumento na acetilação de histona H3. Essa alteração textural cromatínica também atingiu áreas heterocromáticas de células NIH 3T3. Nenhuma alteração nas frequências de anomalias cromossômicas, índices mitóticos e morte celular foi observada nesses modelos celulares nas condições relatadas, embora tenha ocorrido um aumento de fragmentação de DNA em células HeLa tratadas com VPA por 24 h e por TSA a partir de 4 h. Diminuição na proliferação celular nas células HeLa ocorreu apenas sob tratamento com VPA 5,0 mM por 48 h. Os resultados indicam que o VPA e a TSA promovem remodelação cromatínica em células tumorais HeLa e em células fibroblásticas NIH 3T3, que pode ser atribuída à sua ação de HDACi. Não se pôde descartar, porém, que o VPA atue sobre outras proteínas nucleares, cuja expressão poderia se apresentar diminuída sob sua ação / Abstract: Valproic acid (VPA) is a potent anticonvulsant that inhibits class I histone deacetylases (HDACi) in several cell types. Seeking to know whether the chromatin structure would change when the action of HDACi, we investigated whether VPA would affect chromatin supraorganization of tumoral HeLa cells and NIH 3T3 cells, this latter characterized by presenting areas of conspicuos heterochromatin. This information was associated with enzymatic activity of HDACs as well as the level of H3 histone acetylation in these cell models treated with VPA. The frequency of chromosome abnormalities and cell death and mitotic indices were also investigated. VPA-treated cells at concentration 0.05, 0.5 and 1.0 mM for 1-24 h were subjected to the Feulgen reaction and analysed by automatic scanning microspectrophotometry and optical microscopy. Western blots, enzymatic analysis and TUNEL assay were also performed in this study. Trichostatin A (TSA)-treated cells, an HDACi whose activity is broader than VPA, were used as positive control. Chromatin decondensation was demonstrated under all TSA and VPA treatments and was associated with decrease in HDAC activity and with increase in the level of H3 histone acetylation. This chromatin textural change also affected heterochromatic areas of NIH 3T3 cells. No changes in chromosome abnormalities, mitotic indices or morphologically identified cell death were found in both cellular models with the VPA treatment conditions mentioned above, although there was an increase of DNA fragmentation after a 24 h-VPA treatment and a 4 h-TSA treatment in HeLa cells. Decrease in cell proliferation in HeLa cells ocurred only under a 5.0 mM 48 h-VPA treatment. The results indicate that VPA and TSA promote chromatin remodeling in tumoral HeLa cells and fibroblastic NIH 3T3 cells, which may be attrituted to their HDACi action. It may not be discarded, however, that VPA acts on other nuclear proteins whose expression could be reducted under its action / Mestrado / Biologia Celular / Mestre em Biologia Celular e Estrutural

The enhanced expression of histone deacetylases (HDACs) in a variety of malignancies drew attention to investigate a new category of anti-cancer drugs that are based on the inhibition of those enzymes. Valproic acid (VPA) is a well-known antiepileptic drug that exhibits antitumor activities through inhibition of HDACs class I and IIa. Cancer stem cells (CSCs) have been recognized to drive the tumor growth and progression hence; attention has been given to target this small subpopulation of CSCs rather than the whole bulk tumor cells. CD133 is considered to be a CSC marker in several tumors and its transcription is strongly influenced by epigenetic changes that will be altered upon administration of histone deacetylase inhibitors (HDACi) in cancer treatment. Therefore, we evaluated the epigenetic and cytotoxic effects of treatment with 1 mM VPA in combination with other chemotherapeutics and its influence on the expression of CD133 in human neuroblastoma (NB) cell lines. Our results revealed that addition of VPA to DNA-damaging chemotherapeutics induced a synergistic anti-tumor effect that was associated with caspase-3 dependent induction of apoptosis in UKF-NB-4 cells. This synergism was related to the increase of the acetylation status of histones H3 and H4 and was only produced either by...

Mitochondria are important cytosolic organelles present in nearly all eukaryotic cells. The main function of mitochondria are to generate the vast majority of ATP through the process of oxidative phosphorylation. Mitochondria have key roles regarding other systems in the body as well, such as regulation of apoptosis, calcium homeostasis, reactive oxygen production etc. Mitochondrial diseases are caused by impaired mitochondrial function, originating from mutations in either the mitochondrial DNA or the nuclear DNA. Epilepsy is a common symptom of mitochondrial disease, especially in children. The pathophysiology behind mitochondrial epilepsy is primarily based on ATP deficit, leading to a negative effect on a range of different nervous system related functions that in the end leads to seizures. The study aimed to investigate the effect on mitochondrial respiration of two commonly used antiepileptic drugs, namely valproic acid and Topiramate, and the anesthesic drug propofol, commonly used in case of refractory status epilepticus. The three drugs were titrated in different concentrations in a high-resolution respirometer from Oroboros Instruments (n=6). Propofol seemed especially inhibiting of mitochondrial function, and both propofol and topiramate had a significant decrease in mitochondrial respiration within the clinical concentrations. The result of the study supported research stating that propofol should be used with caution in patients with a mitochondrial disease, but further research should be done regarding all three drugs in order to draw definite conclusions.

Melatonin is an indoleamine hormone with neuromodulatory and neuroprotective properties. It mediates many of its effects by its two G protein-coupled receptors, MT1 and MT2. We have shown that valproic acid (VPA) induces melatonin receptor expression in cultured rat C6 glioma cells, and in the rat hippocampus. VPA is known to affect gene expression through several mechanisms, including the modulation of intracellular kinase pathways and/or transcription factors, as well as the inhibition of histone deacetylase (HDAC) activity. In this study, we show that HDAC inhibitors of distinct chemical classifications, including suberanilohydroxamic acid (SAHA) and 4-(dimethylamino)-n-[7-(hydroxyamino)-7-oxoheptyl] benzamide (M344), parallel the effects of VPA on MT1 induction in vitro. However valpromide, a VPA analogue that lacks the ability to inhibit HDAC activity, does not. The observed increase in MT1 expression by VPA is matched by an increase in global histone H3 acetylation. More importantly, an enrichment of histone H3 acetylation occurs along the rat MT1 promoter following treatment with VPA, indicating that histone acetylation and chromatin remodelling are a primary mechanism underlying this induction. Independent of VPA, the rat MT1 gene may be regulated by a number of intracellular kinase pathways and transcription factors, which are also targeted by VPA. KG501-mediated CREB inhibition did not block MT1 upregulation by VPA. Blockade experiments targeting the PKC, PI3K/AKT, or GSK3β signaling pathways suggest that VPA induces melatonin receptor expression independent of these intracellular signaling cascades as well. The relevance of melatonin receptor upregulation was assessed using in vivo VPA and melatonin combination treatments on neuroprotective gene expression. The results of this study provide evidence that expression of the melatonin receptor is epigenetically induced by VPA by means of promoter histone acetylation. Melatonin receptor upregulation by VPA, or other HDAC inhibitors, may represent a therapeutic strategy for the management of several nervous system disorders. / Dissertation / Doctor of Philosophy (PhD)

No description available.