The multiple physiological effects of the indoleamine hormone melatonin, are mediated primarily by its two G protein-coupled MT1 and MT2 receptors. Our group has shown an upregulation of melatonin receptors following treatment with histone deacetylase (HDAC) inhibitors, including valproic acid (VPA) and Trichostatin A, in cultured cells and/or in the rat brain. VPA increases histone H3 acetylation at the MT1 gene promoter region in rat C6 glioma cells, indicating that this epigenetic mechanism underlies its upregulation of MT1 expression. Since HDAC inhibitors can also alter DNA methylation, the possible involvement of this second major epigenetic mechanism in the regulation of MT1 expression, was examined. C6 cells were treated with the DNA demethylating agent, azacytidine (AZA, 1 - 25 µM), for 24 or 48 hours. Treatment of C6 cells with AZA caused a significant upregulation of MT1 mRNA expression, as compared with controls (DMSO 0.05%). Moreover, treatment with AZA (10 or 20 µM) for 24 or 48 hours, suppressed or abolished DNMT1 protein expression, and inhibited DNMT1 mRNA expression, which indicates inhibition of the DNMT1 enzyme activity. A combination of VPA and AZA caused a trend toward additive upregulation of the MT1 receptor. These results show that DNA demethylation plays a role in the regulation of the MT1 receptor, consistent with the well-known effects of this epigenetic mechanism on gene transcription. Epigenetic regulation of melatonin receptor expression could provide a novel strategy for modulating the therapeutic effects of this hormone and its clinically relevant agonists, such as agomelatine, and could also provide avenues for enhancing the antioxidant, neuroprotective, oncostatic and other benefits of this hormone and its agonists. / Thesis / Master of Science (MSc) / The hormone, melatonin, is involved in maintenance of the sleep cycle, and has many neuroprotective effects, initiated by its binding to specific proteins called receptors. Epigenetic or reversible chemical modifications which alter DNA, without changing its sequence, can alter the levels of these receptors. This process can be modulated by drugs, which can increase levels of the melatonin receptor. In this study, the drug 5-Azacytidine (AZA) was used to cause specific chemical changes to DNA, termed demethylation. This thesis shows for the first time, that AZA causes an increase in melatonin receptors. AZA’s ability to cause demethylation was confirmed by observing decreased levels of the protein responsible for DNA methylation, DNA methyltransferase. Melatonin receptors in the brain exhibit changes in disorders such as Alzheimer’s and Parkinson’s disease. Understanding the mechanisms underlying the regulation of these receptors could provide avenues for enhancing the neuroprotective benefits of melatonin and related drugs.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/24771 |
| Date | January 2019 |
| Creators | Hartung, Emily |
| Contributors | Niles, Lennard, Medical Sciences (Division of Physiology/Pharmacology) |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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