title: Modulation of tyrosine hydroxylase expression by melatonin in human SH-SY5Y neuroblastoma cells.
abstract: We have previously reported in vivo preservation of tyrosine hydroxylase (TH), the rate-limiting enzyme in dopamine synthesis, following treatment with physiological doses of melatonin, in a 6-hydroxydopamine model of Parkinson's disease. Based on these findings, we postulated that melatonin would similarly modulate the expression of TH in vitro. Therefore, using human SH-SY5Y neuroblastoma cells which can differentiate into dopaminergic neurons following treatment with retinoic acid, we first examined whether these cells express melatonin receptors. Subsequently, the physiological dose-dependent effects of melatonin on TH expression were examined in both undifferentiated and differentiated cells. The novel detection of the G protein-coupled melatonin MT(1) receptor in SH-SY5Y cells by RT-PCR was confirmed by sequencing and Western blotting. In addition, following treatment of SH-SY5Y cells with melatonin (0.1-100 nM) for 24h, Western analysis revealed a significant increase in TH protein levels. A biphasic response, with significant increases in TH protein at 0.5 and 1 nM melatonin and a reversal at higher doses was seen in undifferentiated cells; whereas in differentiated cells, melatonin was effective at doses of 1 and 100 nM. These findings suggest a physiological role for melatonin in modulating TH expression, possibly via the MT(1) receptor.
authors.affiliation: Department of Psychiatry and Behavioural Neurosciences, McMaster University, HSC-4N77, 1200 Main Street West, Hamilton, Ontario, Canada L8N 3Z5.
authors.forename: Catherine R
authors.initials: CR
authors.lastname: McMillan
authors.forename: Rohita
authors.initials: R
authors.lastname: Sharma
authors.forename: Tom
authors.initials: T
authors.lastname: Ottenhof
authors.forename: Lennard P
authors.initials: LP
authors.lastname: Niles
mesh_terms: D015153:Blotting, Western; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression; D006801:Humans; D008550:Melatonin / Q000494:pharmacology*; D009447:Neuroblastoma / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects*; D018696:Neuroprotective Agents / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis; D044122:Receptor, Melatonin, MT1 / Q000187:drug effects / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014446:Tyrosine 3-Monooxygenase / Q000096:biosynthesis* / Q000187:drug effects
chemical_list: D018696:Neuroprotective Agents; D012333:RNA, Messenger; D044122:Receptor, Melatonin, MT1; D014446:Tyrosine 3-Monooxygenase; D008550:Melatonin