title: FLUOXETINE modifies the expression of serotonergic markers in a differentiation-dependent fashion in the mesencephalic neural cell line A1 mes c-myc.
abstract: Serotonin (5-HT) is a neurotransmitter involved in a variety of CNS functions during development and in adulthood. 5-HT neurons are also involved in the pathogenesis of a number of psychiatric disorders. FLUOXETINE (FLX), a prototypic antidepressant, is a selective 5-HT uptake inhibitor (SSRI) with a demonstrated clinical efficacy in these disorders. SSRI, in a short-term period, binds 5-HT transporter (SERT) raising 5-HT levels at the synapse. Nevertheless, clinical improvement is observed only after 3-4 weeks of treatment. Recently, it has been shown that antidepressants, besides interfering with neurotransmission, can also display an effect on neural cells' proliferation and differentiation. Therefore it has been proposed that antidepressant may exert their clinical effects also acting on cellular functions other then neurotransmission. Here we show that a mesencephalic neural cell line, mes-c-myc A1 (A1) produces 5-HT and expresses SERT and both peripheral (TPH1) and CNS-specific (TPH2) form of tryptophan hydroxylase, the limiting enzyme in 5-HT biosynthesis. Cyclic AMP-dependent neuronal differentiation of A1 cells modulates the expression of TPHs. FLX, as well as citalopram (CIT), another SSRI inhibitor, modulates expression of serotonergic markers depending on the differentiation status of the cells. Interestingly, long-term but not short-term FLX treatment selectively modulates mRNA levels of TPH2, only in differentiated A1 cells. Finally, FLX and citalopram selectively decrease the proliferation rate of undifferentiated A1 cells, whereas have no effects on NIH-3T3 fibroblasts proliferation. In conclusion, neuronal differentiation of A1 cells not only modulates the expression of serotonergic markers, but appears to affect the response to FLX.
authors.affiliation: Institute of Genetics and Biophysics A. Buzzati-Traverso, CNR, Naples, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Di Lieto
authors.forename: Damiana
authors.initials: D
authors.lastname: Leo
authors.forename: Floriana
authors.initials: F
authors.lastname: Volpicelli
authors.forename: Umberto
authors.initials: U
authors.lastname: di Porzio
authors.forename: Luca
authors.initials: L
authors.lastname: Colucci-D'Amato
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002452:Cell Count; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D015283:Citalopram / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004622:Embryo, Mammalian; D005473:Fluoxetine / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D008636:Mesencephalon / Q000166:cytology*; D051379:Mice; D009474:Neurons / Q000187:drug effects*; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D012701:Serotonin / Q000378:metabolism*; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology*; D013997:Time Factors; D014365:Tryptophan Hydroxylase / Q000235:genetics / Q000378:metabolism; D050493:Vesicular Monoamine Transport Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D015283:Citalopram; D005473:Fluoxetine; D012333:RNA, Messenger; D012701:Serotonin; D050486:Serotonin Plasma Membrane Transport Proteins; D017367:Selective Serotonin Reuptake Inhibitors; D014365:Tryptophan Hydroxylase; D050493:Vesicular Monoamine Transport Proteins; C493453:Slc18a2 protein, mouse; C493231:Slc6a4 protein, mouse; C487801:Tph1 protein, mouse; C487802:Tph2 protein, mouse