title: Dual effect of adenosine on vascular smooth muscle [(3)H]-thymidine DNA labeling: receptor-mediated modulation of DNA synthesis and inhibition of thymidine uptake.
abstract: This study examined the contribution of cAMP signaling to the modulation of vascular smooth muscle cell (VSMC) proliferation by adenosine. At a concentration of 1 mM, adenosine inhibited [(3)H]-thymidine uptake, measured as the initial rate of isotope influx, by 10-fold. Diminution of [(3)H]-thymidine uptake by adenosine was independent of the presence of A(1)- and A(2)-receptor antagonists, indicating that adenosine competes with thymidine for plasma membrane transporter-binding sites. Considering these results, in order to estimate [(3)H]-thymidine DNA labeling, VSMCs were preincubated with adenosine for 48 h, and adenosine was then omitted during the subsequent 2 h of incubation in [(3)H]-thymidine-containing medium. In serum-depleted VSMCs, preincubation with 100 microM or 1,000 microM adenosine augmented DNA synthesis by approximately 6- and 3-fold, respectively, whereas the increment of DNA synthesis triggered by serum was decreased in the presence of adenosine by 20-30%. Both cAMP production and inhibition of DNA synthesis by adenosine in serum-supplied cells were independent of the presence of the A(1)-antagonist 1,2-dipropyl-8-cyclopentylxanthine (DPCPX), but were abolished by the A(2)-antagonist 1,3-dimethyl-7-propylxanthine (DMPX). In contrast, the activation of DNA synthesis in serum-depleted cells by adenosine was decreased in the presence of DPCPX and DMPX by approximately 30 and 40%, respectively. Both in serum-supplied and -depleted VSMCs, dose-dependent elevation of cAMP production with an adenylate cyclase activator, forskolin, reduced DNA synthesis by up to 40-60%. Thus, our results show that in addition to suppressing thymidine uptake, adenosine depresses the DNA synthesis triggered by serum-derived growth factors and stimulates DNA synthesis in serum-depleted cells. These data also suggest that the inhibition of DNA synthesis is mediated by cAMP production where the activation of DNA synthesis is independent of cAMP signaling.
authors.affiliation: Research Center, Centre hospitalier de l'Université de Montréal - Hôtel-Dieu, Montréal, Québec, Canada.
authors.forename: N
authors.initials: N
authors.lastname: Thorin-Trescases
authors.forename: Y
authors.initials: Y
authors.lastname: Ono
authors.forename: J
authors.initials: J
authors.lastname: Tremblay
authors.forename: P
authors.initials: P
authors.lastname: Hamet
authors.forename: S N
authors.initials: SN
authors.lastname: Orlov
mesh_terms: D000241:Adenosine / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D001667:Binding, Competitive; D001790:Blood Physiological Phenomena; D002417:Cattle; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D003470:Culture Media / Q000494:pharmacology; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D004261:DNA Replication / Q000187:drug effects*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects*; D058915:Purinergic P1 Receptor Antagonists; D051381:Rats; D011914:Rats, Inbred BN; D018047:Receptors, Purinergic P1 / Q000502:physiology; D015290:Second Messenger Systems / Q000502:physiology*; D013805:Theobromine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism*; D014316:Tritium / Q000378:metabolism; D014970:Xanthines / Q000494:pharmacology
chemical_list: D003470:Culture Media; D016895:Culture Media, Serum-Free; D058915:Purinergic P1 Receptor Antagonists; D018047:Receptors, Purinergic P1; D014970:Xanthines; D014316:Tritium; D005576:Colforsin; C057837:3,7-dimethyl-1-propargylxanthine; C051360:1,3-dipropyl-8-cyclopentylxanthine; D000242:Cyclic AMP; D000241:Adenosine; D013805:Theobromine; D013936:Thymidine