title: Uridine enhances neurite outgrowth in nerve growth factor-differentiated PC12 [corrected].
abstract: During rapid cell growth the availability of phospholipid precursors like cytidine triphosphate and diacylglycerol can become limiting in the formation of key membrane constituents like phosphatidylcholine. Uridine, a normal plasma constituent, can be converted to cytidine triphosphate in PC12 [corrected] cells and intact brain, and has been shown to produce a resulting increase in phosphatidylcholine synthesis. To determine whether treatments that elevate uridine availability also thereby augment membrane production, we exposed PC12 [corrected] cells which had been differentiated by nerve growth factor to various concentrations of uridine, and measured the numbers of neurites the cells produced. After 4 but not 2 days uridine significantly and dose-dependently increased the number of neurites per cell. This increase was accompanied by increases in neurite branching and in levels of the neurite proteins neurofilament M [corrected] and neurofilament 70. Uridine treatment also increased intracellular levels of cytidine triphosphate, which suggests that uridine may affect neurite outgrowth by enhancing phosphatidylcholine synthesis. Uridine may also stimulate neuritogenesis by a second mechanism, since the increase in neurite outgrowth was mimicked by exposing the cells to uridine triphosphate, and could be blocked by various drugs known to antagonize P2Y receptors (suramin; Reactive Blue 2; pyridoxal-phosphate-6-azophenyl-2',4' disulfonic acid). Treatment of the cells with uridine or uridine triphosphate stimulated their accumulation of inositol phosphates, and this effect was also blocked by pyridoxal-phosphate-6-azophenyl-2',4' disulfonic acid. Moreover, degradation of nucleotides by apyrase blocked the stimulatory effect of uridine on neuritogenesis. Taken together these data indicate that uridine can regulate the output of neurites from differentiating PC12 [corrected] cells, and suggest that it does so in two ways, i.e. both by acting through cytidine triphosphate as a precursor for phosphatidylcholine biosynthesis and through uridine triphosphate as an agonist for P2Y receptors.
authors.affiliation: Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, 45 Carleton Street, Cambridge, MA 02139, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Pooler
authors.forename: D H
authors.initials: DH
authors.lastname: Guez
authors.forename: R
authors.initials: R
authors.lastname: Benedictus
authors.forename: R J
authors.initials: RJ
authors.lastname: Wurtman
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001081:Apyrase / Q000494:pharmacology; D015153:Blotting, Western / Q000379:methods; D002454:Cell Differentiation / Q000187:drug effects*; D003570:Cytidine Triphosphate / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D007150:Immunohistochemistry / Q000379:methods; D007381:Intermediate Filament Proteins / Q000378:metabolism; D020932:Nerve Growth Factor / Q000494:pharmacology*; D016501:Neurites / Q000187:drug effects*; D016900:Neurofilament Proteins / Q000378:metabolism; D016716:PC12 Cells; D010673:Pheochromocytoma / Q000473:pathology*; D010716:Phosphatidylinositols / Q000378:metabolism; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D013997:Time Factors; D014529:Uridine / Q000494:pharmacology*; D014544:Uridine Triphosphate / Q000378:metabolism / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D007381:Intermediate Filament Proteins; D016900:Neurofilament Proteins; D010716:Phosphatidylinositols; D018048:Receptors, Purinergic P2; C061195:neurofilament protein M; C070305:neurofilament protein NF 70; D003570:Cytidine Triphosphate; D020932:Nerve Growth Factor; D001081:Apyrase; D014544:Uridine Triphosphate; D014529:Uridine