A glândula pineal, via melatonina (MEL), desempenha uma importante função regulatória no metabolismo de carboidratos e parece ser de fundamental importância nas adaptações metabólicas dos tecidos adiposo e muscular. Evidências mostram que animais pinealectomizados são incapazes de se adaptarem a condições estressantes e não conseguem desenvolver as alterações adaptativas ao exercício. Sabendo que o animal idoso apresenta considerável redução da produção de MEL, o objetivo deste estudo foi investigar a adaptação metabólica ao treinamento físico no animal idoso com e sem reposição de MEL. Para tanto, foram utilizados ratos Wistars, com 12 meses de vida, que foram divididos em 4 grupos: controles sedentários; controles treinados; suplementados com MEL sedentários; suplementados com MEL treinados. A suplementação com MEL teve a duração de 16 semanas, enquanto o treinamento físico teve a duração de 8. Os resultados mostraram que a suplementação com MEL em animais idosos tem grande importância nas adaptações induzidas pelo treinamento físico aeróbio / The pineal gland, melatonin (MEL), plays an important physiological and regulatory function in carbohydrate metabolism and seems to be of fundamental importance in determining the metabolic adaptations of adipose and muscle tissues. Evidence shows that pinealectomized animals are unable to adapt to stressful conditions, thus fail to develop adaptive metabolic changes to aerobic exercise and therefore do not exhibit the same performance as control trained animals. Knowing that the elderly animal presents a considerable reduction in MEL production, the objective of this study was to investigate the metabolic adaptation to exercise training in aged animals with and without replacement of MEL. The animals, Male-Wistar, were divided into four groups: sedentary control, trained control, sedentary treated with MEL, trained treated with MEL. The Supplementation with MEL lasted 16 weeks, while physical training lasted 8 weeks. The results demonstrated that MEL supplementation in elderly animals is of great importance in adaptations induced by aerobic exercise.

Dopamine mechanisms in the central nervous system are important in the control of both normal and abnormal motor function. The recent observations in both animal and human studies, that melatonin, the principal hormone of the pineal gland, may have a role in the control of movement and the pathophysiology of movement disorders, have given rise to the concept that melatonin may have a modulatory influence on central dopaminergic neurotransmission. This study makes use of three animal behavioural models as well as a biochemical model of central dopaminergic function to further investigate the concept. Results from studies using the biochemical model, which investigated the effect of melatonin on dopamine and apomorphine stimulation of dopamine-sensitive adenylate cylase, suggest that melatonin is neither a competitive antagonist nor agonist at the D₁ receptor level, although the possibility of physiological stimulation or antagonism is not excluded. In behavioural studies, prior melatonin mg/kg administration (1 and 10 (8M) ip) inhibited apomorphine induced stereotypy and locomotor activity in normal rats, and apomorphine-induced rotational behaviour in 6-hydroxydopamine and quinolinic acid lesioned rats. The possibility that these results may have physiological significance is borne out by the observation that, under enviromental lighting conditions that are associated with raised endogeous melatonin levels, apomorphine- induced stereotypy and locomotor activity is attenuated. The general conclusion is that melatonin has an inhibitory influence on central nervous system dopaminergic function, suggesting therefore, that the pineal gland and melatonin may have a role in the pathophysiology and treatment of movement and behavioural disorders associated with dopaminergic dysfunction

There is some evidence to suggest that the pineal gland influences neoplastic growth. Either crude or partially purified pineal extracts have been used to treat malignant neoplasms in humans. More compelling evidence indicates that the pineal hormone melatonin, in addition to its well-known antireproductive effects, may also exert oncostatic effects particularly in animal models of human breast cancer. The purpose of this study was to examine a possible direct action of melatonin on the growth morphology and physiology of human breast cancer cells in vitro. Studies are described in which physiological concentrations of melatonin are shown to have markedly inhibitory effects directly on MCF-7 human breast cancer cells grown in culture. This antimitotic effect is not observed in MCF-7 cells at supra- or subphysiological concentrations of melatonin. This growth-inhibitory effect appears to be tissue specific since fibroblastic cells were not affected by melatonin. Other pineal indoles failed to inhibit the proliferation of this human breast cancer cell line, suggesting that this growth-inhibitory effect is specific for melatonin and is not a general characteristic shared among the family of pineal indoles. Reductions in media serum concentrations dramatically suppressed the response of cells to melatonin's inhibitory action. Serum values of 2.5 percent or lower resulted in a loss of melatonin's action as did growing the cells in serum-free medium or medium containing charcoal-treated serum. It appears that certain serum factors are necessary for these cells to respond to melatonin's antiproliferative action. Melatonin, when added to cells grown in media supplemented with 10 percent fetal calf serum decreased the synthesis of proteins and resulted in morphological alterations suggestive of a sublethal toxic injury. Melatonin appears to have a direct role in inhibiting the proliferation of breast cancer cells; however, the presence of melatonin per se does not seem to be the fundamental cause of this antimitotic action since no activity is observed when cells are propagated in media containing charcoal-treated fetal calf serum or serum-free medium. There appears to be a requirement for certain serum factors in this antiproliferative action. Two factors that have proved important in this process are the hormones estradiol and prolactin. (Abstract shortened with permission of author.)

by Sze Shun Fai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1992. / Includes bibliographical references (leaves 132-139). / Abstract --- p.1 / Chapter Chapter 1 --- General Introduction / Chapter 1.1 --- The pineal gland --- p.5 / Chapter 1.2 --- Discovery of melatonin --- p.5 / Chapter 1.3 --- Synthesis of melatonin --- p.5 / Chapter 1.4 --- Physiology of melatonin and its derivatives --- p.6 / Chapter 1.5 --- In vitro tumor biology of melatonin and its derivatives --- p.7 / Chapter 1.6 --- In vivo tumor biology of melatonin --- p.10 / Chapter 1.7 --- Macrophages --- p.11 / Chapter 1.8 --- Lymphocytes --- p.14 / Chapter Chapter 2 --- Toxicity of pineal indoles on tumor cell lines / Chapter 2.1 --- General introduction --- p.17 / Chapter 2.2 --- Material and methods --- p.18 / Chapter 2.3 --- Results --- p.22 / Chapter 2.4 --- Discussion --- p.23 / Chapter Chapter 3 --- Activation of murine peritoneal macrophages by melatonin and methoxytryptamine / Chapter 3.1 --- General introduction --- p.37 / Chapter 3.2 --- Material and methods --- p.38 / Chapter 3.3 --- Results --- p.55 / Chapter 3.4 --- Discussion --- p.61 / Chapter Chapter 4 --- Activation of murine splenocytes by melatonin and methoxytryptamine / Chapter 4.1 --- General introduction --- p.81 / Chapter 4.2 --- Material and methods --- p.82 / Chapter 4.3 --- Results --- p.91 / Chapter 4.4 --- Discussion --- p.128 / Chapter Chapter 5 --- General discussion --- p.132 / References

Cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) act as second messengers in intracellular signaling cascades to influence neuronal responses. Hippocampal cAMP signaling is thought to underlie the pathophysiology of major depressive disorder (MDD) and antidepressant action; however, little is known about the possible role of cGMP signaling. Furthermore, circadian rhythm disturbances can occur as part of the clinical symptoms of MDD and resolve with antidepressant therapy. The pineal gland is relevant to circadian rhythms as it secretes the hormone melatonin following activation of cAMP signaling and the rate-limiting enzyme for its synthesis, arylalkylamine N-acetyltransferase (AA-NAT). Little is known about the contribution of the phosphodiesterase (PDE) system to antidepressant-induced alterations in pineal cAMP signaling and melatonin synthesis. There is a need to clarify the trajectory of cAMP and cGMP concentrations, their synthesis by cyclases, and degradation by PDEs to understand the role of cyclic mononucleotide signaling in the effect of chronic antidepressant therapy. Using quantitative real-time PCR and enzyme immunoassay, we systematically studied elements of intracellular signaling in the hippocampus of rats chronically treated with imipramine, fluoxetine, and amitriptyline and in the pineal gland of rats treated chronically with fluoxetine. In the hippocampus, we found chronic imipramine downregulated cAMP signaling with decreased cAMP, increased PDEs and decreased adenylate cyclase mRNA. In contrast, repeated fluoxetine and amitriptyline increased hippocampal cGMP signaling, with increased cGMP and decreased PDE mRNA. We conclude that in contrast to the assumption of antidepressant-mediated increases in cAMP levels, increased hippocampal cGMP signaling might underlie the efficacy of chronic antidepressant treatment. A follow up study using cultured embryonic rat hippocampal cells in vitro treated with the PDE type 5 inhibitor, sildenafil, demonstrated increased cAMP content following acute and chronic treatment, indicating either crosstalk between cAMP and cGMP pathways or a non-specific inhibitory effect of sildenafil on other PDEs. In the pineal gland, we found elevated melatonin synthesis with increased pineal AA-NAT mRNA and daytime plasma melatonin and downregulated cAMP signaling with increased PDE and unchanged AC pineal mRNA, and decreased pineal cAMP. We conclude that chronic fluoxetine increases daytime plasma melatonin and pineal AA-NAT mRNA despite downregulated pineal cAMP signaling.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Thesis (M. Sc.)--University of Adelaide, 1988. / Includes bibliographical references (leaves 131-150).

Thesis (Ph. D.)--Carleton University, 2005. / Includes bibliographical references (p. 183-193). Also available in electronic format on the Internet.

The physiological and behavioral functions of the body are coordinated into daily patterns that are synchronized with the earth's light/dark cycles. This patterning of function is referred to as circadian rhythms. A central pacemaker located in suprachiasmatic nucleus of the brain serves to coordinate the body's rhythms with the light/dark cycle. Disturbances in normal circadian rhythm have been shown to increase the risk of certain types of cancer, including breast cancer. This effect is so significant that the World Health Organization has recently classified shift work as a probable carcinogen. One effect of alteration in the light/dark cycle such as that experienced by shift workers is a change in the production of the pineal hormone melatonin (N-acetyl-5-methoxytryptamine). Secretion of melatonin is regulated by the suprachiasmatic nucleus. Melatonin has a wide variety of functions including physiological regulation of sleep, modulation of the immune system and antioxidant action. Recent studies have determined that melatonin has oncostatic actions in a variety of cancers, including breast, prostate and endometrial cancer. Thus, this thesis explores the effects of melatonin on clock gene expression and growth of a mouse mammary tumor cell line, EMT6. I hypothesized that growth inhibitory actions of melatonin involve alteration in clock gene expression, induction of apoptosis and cell cycle arrest. Thus, this thesis investigates the modulatory effects of melatonin on clock genes, cell cycle parameters and apoptosis. Western blot analysis and immunocytochemistry confirmed expression of melatonin receptors in the EMT6 cell line. I investigated the circadian rhythm of EMT6 cells by measuring the clock gene expression pattern over a 24 hour period. I found a significant rhythm in Per1 and Per2 transcripts. Expression of estrogen and progesterone receptors was measured as they are putative clock controlled genes involved in the development of breast cancer. The results showed significant rhythm in Per1 (p=0.05), Per2 (p=0.03) and estrogen receptors ERalpha (p=0.001) and ERbeta (p=0.028). Peak expression for Period genes and ERalpha is found at 16 hrs and 20 hrs after serum shock, respectively. Peak expression for ERbeta is found at 24 hours after serum shock. Other steroid hormone receptors such as progesterone receptors PRB and PRA+B were not rhythmic. Treatment with melatonin in a concentration range from 10µM to 1nM inhibited growth in the cells. The antiproliferative effect of melatonin was dose and time dependent. At the end of 48 hours, melatonin at a concentration of 10-7 M induced apoptosis in EMT6 cells as indicated by caspase-3 immunocytochemistry. Furthermore, this same treatment caused an upregulation of the clock gene and putative tumor suppressor gene, Per2. These studies provide evidence that melatonin alters growth of EMT6 cells by inducing caspase-3 and apoptosis, which may be regulated through induction of Per2. Thus, disturbance in rhythmic secretion of melatonin may promote tumor progression in breast cancer.

Orientador: Doris Hissako Sumida / Banca: Fernando Yamamoto Chiba / Banca: Sérgio Eduardo de Andrade Perez / Resumo: Pesquisas têm sido realizadas para investigar a relação entre inflamações crônicas na cavidade oral e efeitos deletérios em diversos sistemas do organismo. A doença periodontal (DP) caracterizada como uma infecção e inflamação oral está associada à produção de citocinas inflamatórias, tais como fator de necrose tumoral-alfa (TNF-α) e interleucina-6 (IL-6), as quais aumentam a expressão dos osteoclastos, levando a um aumento da reabsorção óssea alveolar. Além da influência destas citocinas na perda óssea alveolar, evidências científicas apontam que a falta do hormônio melatonina também pode contribuir para uma maior reabsorção óssea. A melatonina é um poderoso regulador da homeostase de diversos tecidos. Assim, este hormônio pode ter um importante papel na proteção de tecidos lesionados, podendo ser visto, como um possível coadjuvante no tratamento de doenças da cavidade oral devido principalmente sua ação antioxidante e imunomoduladora. Portanto, o objetivo deste estudo foi verificar o efeito da suplementação da melatonina na reabsorção óssea alveolar em ratos com doença periodontal e pinealectomizados (PNX), avaliando: 1) concentrações plasmáticas de TNF-α e IL-6 pelo método de ELISA; 2) marcadores ósseos como a fosfatase ácida resistente ao tartarato (TRAP) e Osteocalcina (OCN) por meio de técnica imunoistoquímica; 3) histomorfometria da região comprometida pela DP pelo escaneamento no microtomógrafo em 3D (Micro-CT) (modelo 1172 SkyScan®). Para tanto, oitenta (80) ratos Wi... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: ABSTRACT Researches has been conducted to investigate the relationship between chronic inflammation in the oral cavity and deleterious effects on various systems of the body. Periodontal disease (PD) characterized as an infection and oral inflammation is associated with the production of inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6), which increase the expression of osteoclasts, leading to an increase in alveolar bone resorption. In addition to the influence of these cytokines on alveolar bone loss, scientific evidence indicates that the lack of the hormone melatonin may also contribute to a greater bone resorption. Melatonin is a powerful regulator of homeostasis of various tissues. Thus, this hormone may have an important role in the protection of injured tissues, and can be seen as a possible adjuvant in the treatment of diseases of the oral cavity mainly due to its antioxidant and immunomodulatory action. Therefore, the objective of this study was to verify the effect of melatonin supplementation on alveolar bone resorption in rats with periodontal disease and pinealectomized (PNX), evaluating: 1) plasma concentrations of TNF-α and IL-6 by the ELISA method; 2) bone markers such as tartrate resistant acid phosphatase (TRAP) and Osteocalcin (OCN) by immunohistochemical technique; 3) histomorphometry of the region compromised by PD by scanning in the microtomograph in 3D (Micro-CT) (model 1172 SkyScan®). Therefore, eighty (80) W... (Complete abstract click electronic access below) / Mestre