The role of P2Y₂ nucleotide receptors in vascular inflammation

The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file (viewed on March 12, 2008)Vita.Includes bibliographical references.Thesis (Ph. D.) University of Missouri-Columbia 2007.Dissertations, Academic -- University of Missouri--Columbia -- Biochemistry (Agriculture)Extracellular nucleotides act on P2 receptors to regulate vascular tone. Large amounts of extracellular nucleotides are released at the sites of tissue injury and may play an important role in the vascular inflammation. In vascular injury models, P2Y₂ mRNA was significantly up-regulated. Activation of up-regulated P2Y₂ receptors in the injured artery increased monocyte/macrophage infiltration and intimal hyperplasia. In this dissertation, we showed that activation of the P2Y₂ receptor modulates the expression of VCAM-1 in vascular endothelial cells that is important for monocyte recruitment. We report here that P2Y₂ receptor-induced VCAM-1 expression is mediated by rapid tyrosine phosphorylation of VEGFR-2 in HCAEC. RNA interference (RNAi) targeting of VEGFR-2 expression or inhibition of VEGFR-2 tyrosine kinase activity abolished P2Y₂ receptor-mediated VCAM-1 expression. We also discovered that the P2Y₂ receptor is linked to the cytoskeleton through direct interaction with the actin-binding protein filamin A (FLNa), which is a large protein of 280 kD and serves as a cross-linker of actin polymers and as a scaffolding protein for various signaling molecules. This interaction was mapped to the C-terminal tail of the P2Y2 receptor (amino acids 322 to 333) and is required for FLNa phosphorylation, spreading and migration of smooth muscle cells induced by extracellular nucleotides. These results encourage drug design targeting the P2Y₂ receptor as a means to prevent and/or treat arterial disease

P2 receptors in atherosclerosis and postangioplasty restenosis

Atherosclerosis is an immunoinflammatory process that involves complex interactions between the vessel wall and blood components and is thought to be initiated by endothelial dysfunction [Ross (Nature 362:801–09, 1993); Fuster et al. (N Engl J Med 326:242–50, 1992); Davies and Woolf (Br Heart J 69:S3–S11, 1993)]. Extracellular nucleotides that are released from a variety of arterial and blood cells [Di Virgilio and Solini (Br J Pharmacol 135:831–42, 2002)] can bind to P2 receptors and modulate proliferation and migration of smooth muscle cells (SMC), which are known to be involved in intimal hyperplasia that accompanies atherosclerosis and postangioplasty restenosis [Lafont et al. (Circ Res 76:996–002, 1995)]. In addition, P2 receptors mediate many other functions including platelet aggregation, leukocyte adherence, and arterial vasomotricity. A direct pathological role of P2 receptors is reinforced by recent evidence showing that upregulation and activation of P2Y2 receptors in rabbit arteries mediates intimal hyperplasia [Seye et al. (Circulation 106:2720–726, 2002)]. In addition, upregulation of functional P2Y receptors also has been demonstrated in the basilar artery of the rat double-hemorrhage model [Carpenter et al. (Stroke 32:516–22, 2001)] and in coronary artery of diabetic dyslipidemic pigs [Hill et al. (J Vasc Res 38:432–43, 2001)]. It has been proposed that upregulation of P2Y receptors may be a potential diagnostic indicator for the early stages of atherosclerosis [Elmaleh et al. (Proc Natl Acad Sci U S A 95:691–95, 1998)]. Therefore, particular effort must be made to understand the consequences of nucleotide release from cells in the cardiovascular system and the subsequent effects of P2 nucleotide receptor activation in blood vessels, which may reveal novel therapeutic strategies for atherosclerosis and restenosis after angioplasty