UDP acts as a growth factor for vascular smooth muscle cells by activation of P2Y(6) receptors.

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Abstract

Mitogenic effects of the extracellular nucleotides ATP and UTP are mediated by P2Y(1), P2Y(2), and P2Y(4) receptors. However, it has not been possible to examine the highly expressed UDP-sensitive P2Y(6) receptor because of the lack of stable, selective agonists. In rat aorta smooth muscle cells (vascular smooth muscle cells; VSMC), UDP and UTP stimulated (3)H-labeled thymidine incorporation with similar pEC(50) values (5.96 and 5.69). Addition of hexokinase did not reduce the mitogenic effect of UDP. In cells transfected with P2Y receptors the stable pyrimidine agonist uridine 5'-O-(2-thiodiphosphate) (UDPbetaS) was specific for P2Y(6) with no effect on P2Y(1), P2Y(2), or P2Y(4) receptors. UDPbetaS stimulated [(3)H]thymidine and [(3)H]leucine incorporation and increased cell number in VSMC. Flow cytometry demonstrated that UDP stimulated cell cycle progression to both the S and G(2) phases. The intracellular signal pathways were dependent on phospholipase C, possibly protein kinase C-delta, and a tyrosine kinase pathway but independent of G(i) proteins, eicosanoids, and protein kinase A. The half-life of P2Y(6) receptor mRNA was <1 h by competitive RT-PCR. The mitogen-activated protein kinase kinase inhibitor PD-098059 significantly suppressed, whereas ATP and interleukin-1beta upregulated, expression of P2Y(6) receptor mRNA. The results demonstrate that UDP stimulates mitogenesis through activation of P2Y(6) receptors and that the receptor is regulated by factors important in the development of vascular disease.

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Subject classification (UKÄ) – MANDATORY

  • Physiology

Keywords

  • Flavones : pharmacology, Growth Substances : pharmacology, Inositol Phosphates : metabolism, Mitogen-Activated Protein Kinase Kinases : antagonists & inhibitors : metabolism, Muscle Smooth Vascular : cytology : drug effects : metabolism, Phospholipase C : metabolism, Protein Kinases : metabolism, Rats, Rats Sprague-Dawley, Receptors Purinergic P2 : agonists : metabolism, Support Non-U.S. Gov't, Thionucleotides : pharmacology, Thymidine : pharmacokinetics, Tritium : diagnostic use, Uridine Triphosphate : analogs & derivatives : pharmacology, Uridine Diphosphate : analogs & derivatives : pharmacology, Epithelial Cells : cytology : metabolism, Enzyme Inhibitors : pharmacology, DNA : biosynthesis, Animal, Aorta : cytology, Cell Survival : drug effects, Cells Cultured, Cyclic AMP : pharmacology
Original languageEnglish
Pages (from-to)H784-H792
JournalAmerican Journal of Physiology: Heart and Circulatory Physiology
Volume282
Issue number2
Publication statusPublished - 2002
Publication categoryResearch
Peer-reviewedYes