Cytokines induce upregulation of vascular P2Y2 receptors and increased mitogenic responses to UTP and ATP

P2Y(2) receptors, which mediate contractile and mitogenic effects of extracellular nucleotides in vascular smooth muscle cells (VSMCs), are upregulated in the synthetic phenotype of VSMCs and in the neointima after balloon angioplasty, suggesting a role in the development of atherosclerosis. Because released cytokines in atherosclerotic lesions mediate multiple effects on gene transcription in VMSCs, we speculated that cytokines could be involved in the regulation of P2Y(2) receptor expression Using a competitive reverse transcription-polymerase chain reaction, we detected that interleukin (IL)-1 beta induced a time- and dose-dependent upregulation of P2Y(2) receptor mRNA, which was dramatically enhanced when combined with interferon-gamma or tumor necrosis factor-alpha. Lipopolysaccharide also significantly increased the expression of P2Y(2) receptor MRNA. The upregulation of P2Y(2) receptor mRNA was paralleled at the functional level because IL-1 beta significantly increased the UTP-stimulated DNA synthesis and the release of intracellular Ca2+. Actinomycin D completely blocked the upregulation of P2Y(2) receptor mRNA expression by IL-1 beta, indicating de novo mRNA synthesis. There was no cAMP accumulation in the cells stimulated with IL-1 beta. The,cyclooxygenase inhibitor indomethacin and the protein kinase C inhibitor RO-31-8220 inhibited IL-1 beta-induced upregulation of P2Y(2) receptor mRNA expression, whereas; rapamycin and PD098059 had no effects.. Furthermore, neither P38 mitogen-activated protein kinase inhibitor SB20358 alone nor its combination with PD098059 blocked the effect of IL-1 beta on the expression of P2Y(2) receptor mRNA. Our results demonstrate that inflammatory mediators upregulate vascular P2Y(2) receptors at the transcriptional and at the functional level through protein kinase C and cyclooxygenase but not cAMP, extracellular signal-regulated kinases 1 and 2, or P38-dependent pathways. This may result in increased growth-stimulatory or contractile effects of extracellular UTP and ATP, which may be of importance in the development of vascular disease.