UDP acts as a growth factor for vascular smooth muscle cells by activation of P2Y₆receptors

Abstract

linge. UDP acts as a growth factor for vascular smooth muscle cells by activation of P2Y 6 receptors. Am J Physiol Heart Circ Physiol 282: H784-H792, 2002; 10.1152/ajpheart.00997.2000.-Mitogenic effects of the extracellular nucleotides ATP and UTP are mediated by P2Y 1, P2Y2, and P2Y4 receptors. However, it has not been possible to examine the highly expressed UDP-sensitive P2Y6 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 pEC50 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) (UDP␤S) was specific for P2Y 6 with no effect on P2Y1, P2Y2, or P2Y4 receptors. UDP␤S 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-␦, and a tyrosine kinase pathway but independent of G i proteins, eicosanoids, and protein kinase A. The half-life of P2Y6 receptor mRNA was Ͻ1 h by competitive RT-PCR. The mitogen-activated protein kinase kinase inhibitor PD-098059 significantly suppressed, whereas ATP and interleukin-1␤ upregulated, expression of P2Y6 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. uridine 5Ј-diphosphate; gene expression THE CARDIOVASCULAR EFFECTS of extracellular nucleotides have received increasing attention since the beneficial effects of the platelet inhibitory ADP receptor antagonist clopidogrel were demonstrated in atherosclerotic disease (2). Several other receptors for extracellular nucleotides (P2 receptors) have been cloned and found to be involved in other processes in cardiovascular regulation. Previous studies demonstrated that the extracellular nucleotides ATP and UTP act as growth factors for vascular smooth muscle cells (VSMC) by activation of P2Y 1 , P2Y 2 , and P2Y 4 receptors (10, 14). However, it has not been possible to examine the UDPactivated P2Y 6 receptor, which has the highest mRNA expression in the media of the rat aorta (11), because of the lack of selective agonists and antagonists.UTP is present in all cells at ϳ10% of ATP levels and is formed through both salvage and de novo pathways. UTP can be released from both platelets and endothelial cells under physiologically relevant stimuli (1,20,30,34). Released uridine nucleotides are catabolized by ectonucleotidases that are present on a variety of tissues and cells, suggesting that the concentration of extracellular UTP also reflects the concentration of extracellular UDP (9). So far, there is no assay for UDP quantification, so we do not know in what concen...

P2Y6 Nucleotide Receptors Activate NF-κB and Increase Survival of Osteoclasts

“…Moreover, the dependence of NF-B translocation and osteoclast survival on UDP concentration observed in the present study is consistent with the concentration dependence reported for P2Y6 receptor-mediated responses in other systems (e.g. 34,35). In the present study, concentrations of INS48823 as low as 1 M stimulated osteoclast survival, perhaps reflecting its greater stability compared with UDP, which is hydrolyzed rapidly by ectonucleotidases (35).…”

“…34,35). In the present study, concentrations of INS48823 as low as 1 M stimulated osteoclast survival, perhaps reflecting its greater stability compared with UDP, which is hydrolyzed rapidly by ectonucleotidases (35).…”

Pathophysiology and Therapeutic Potential of Purinergic Signaling

“…A novel role for P2Y 2 receptors in the development of atherosclerosis has been suggested, whereby UTP induces vascular cell adhesion molecule-1 expression in coronary artery endothelial cells that mediate the recruitment of monocytes (Seye et al, 2003). The long-term (trophic) roles of purinergic signaling in vascular smooth muscle and endothelial cell proliferation and death have been implicated in atherosclerosis and restenosis and suggest the exploration of therapeutic strategies in relation to these events (Erlinge et al, 1998;Burnstock, 2002b;Hou et al, 2002;Wang et al, 2003b).…”

Knockout Mice Reveal a Role for P2Y6 Receptor in Macrophages, Endothelial Cells, and Vascular Smooth Muscle Cells

“…UDP has been shown to provoke the contraction of mouse mesenteric arteries, rat and human cerebral arteries, and mouse renal arteries (Vial and Evans, 2002;Malmsjö et al, 2003;Vonend et al, 2005). Furthermore, UDP is a growth factor for aortic smooth muscle cells in vitro (Hou et al, 2002). UDP induced an endothelium-dependent relaxation of the mouse aorta, which, like a similar action of UTP, was maintained in P2Y 2 Ϫ/Ϫ mice, suggesting the possible involvement of the P2Y 6 receptor (Guns et al, 2005(Guns et al, , 2006.…”