The P2Y2 Nucleotide Receptor Mediates UTP-induced Vascular Cell Adhesion Molecule-1 Expression in Coronary Artery Endothelial Cells

Abstract

Extracellular nucleotides cause a wide range of cellular responses and appear to play a role in the regulation of many vascular functions (1, 2). Vascular cells release nucleotides when exposed to stimuli such as ischemia, hypoxia, and chemical or mechanical stress (3, 4). It also is becoming apparent that extracellular nucleotides can promote the development of a variety of pathologies including disorders of the immune system, and neurodegenerative and vascular diseases (1). Indeed, ATP or UTP induces proliferation and migration of vascular smooth muscle cells, two processes involved in the development of intimal lesions found in atherosclerosis and post-angioplasty restenosis. The biological effects of extracellular nucleotides are mediated through activation of P1 and P2 purinergic receptors. P1 receptors are responsive to adenosine, whereas P2 receptors are activated by a variety of nucleotides including ATP and UTP (5, 6). The P2 receptors are subdivided into two distinct categories, the metabotropic Gprotein-coupled (P2Y) receptors and the ionotropic ligandgated channel (P2X) receptors (6, 7). Vascular cells have been shown to express metabotropic P2Y and ionotropic P2X receptors (5, 8). It has been reported that P2Y 2 receptors are upregulated in cells of rat intimal lesions following balloon angioplasty (9). Our recent studies showed that placement of a silicone collar around the rabbit carotid artery promoted upregulation of P2Y 2 receptors in vascular smooth muscle cells and endothelium (10). Subsequently, local infusion of UTP was shown to stimulate intimal hyperplasia and increase intimal monocyte infiltration (10), suggesting a role for P2Y 2 receptors in the recruitment of blood monocytes leading to inflammation in atherosclerosis.Monocyte recruitment into the vessel wall is a complex process that includes cell rolling, firm attachment, and directed migration. It is now becoming evident that adhesion molecules such as VCAM-1 play an important role in leukocyte adherence to vascular endothelial cells (11,12). VCAM-1 expression is induced or up-regulated by proinflammatory cytokines such as TNF-␣ 1 and interleukin 1-␤ on cellular components of the arterial wall including endothelial cells, smooth muscle cells, and fibroblasts (13-15). ATP and UTP have been shown to induce cell-cell adhesion in a monocyte/macrophage lineage and neutrophil adherence to an endothelial cell monolayer (16,17), raising the possibility that released ATP and UTP could induce endothelial cell activation by an autocrine/paracrine mechanism to regulate leukocyte adherence.

Endothelial P2Y2 receptor regulates LPS-induced neutrophil transendothelial migration in vitro

“…Our group has recently demonstrated that the P2Y 2 (and P2Y 6 ) receptor may promote the migration of neutrophils by mediating IL-8 secretion induced by TLR2 activation in human monocytic THP-1 cells . P2Y 2 has also been implicated in the recruitment of monocytes/ macrophages and lymphocytes by inducing vascular cell adhesion molecule-1 (VCAM-1) expression in human endothelial cells and in a submandibular gland cell line, respectively (Seye et al, 2003;Baker et al, 2008). In addition, P2Y 2 may also promote monocyte migration by activating MCP-1 release from murine macrophages .…”

Do not let death do us part: ‘find-me’ signals in communication between dying cells and the phagocytes

“…Furthermore, ATP and UTP can also elicit monocyte migration indirectly by affecting adhesion molecule expression on vascular endothelial cells. 80 Outside of migration, nucleotides can increase microglial phagocytosis through UDP acting on P2Y 6 , although the mechanism is not known. 81 In addition, stimulation of P2 purinergic receptors can increase the phagocytic capacity of macrophages, which is thought to be dependent on increased apoptotic cell-receptor expression, such as α v β 3.…”

Neuroprotective roles of the P2Y2 receptor

“…Deletion of the SH3-binding domains in the P2Y 2 R prevented nucleotides from activating VEGFR-2-dependent VCAM-1 upregulation [22,89]. VCAM-1 expression in endothelial cells also was found to be dependent on increases in [Ca 2+ ] i and p38 and Rho kinase activation but was independent of ERK1/2 activity [92]. Similarly, lymphocyte binding to epithelium is stimulated by P2Y 2 R activation in epithelial cells via EGFR-dependent VCAM-1 upregulation [93].…”

“…The process of leukocyte recruitment involves several steps: the emigration of leukocytes from bone marrow into the circulation, adhesion of circulating leukocytes to vascular endothelial cells, and diapedesis of leukocytes towards chemoattractants released at the site of injury or infection. Although the leukocyte P2Y 2 R is important for controlling the leukocyte migration step [143,239,240], other studies indicate that the endothelial P2Y 2 R promotes both the leukocyte adhesion step, by increasing the expression of VCAM-1 in endothelial cells [22,89,92] and the diapedesis step [102]. A postulated pathway for the regulation of leukocyte diapedesis by the P2Y 2 R is shown in Fig.…”

“…Our previous studies provide strong evidence that P2Y 2 Rs in endothelial cells regulate the binding and the transendothelial migration (i.e., diapedesis) of monocytic cells. As described above, P2Y 2 Rs mediate the Src-dependent transactivation of the vascular endothelial growth factor receptor-2 (VEGFR-2) in endothelial cells that promotes upregulation of monocyte-binding proteins (e.g., VCAM-1) and a decrease in endothelial adherens junction integrity [22,89,92,101,102]. Other studies have shown that microglia are attracted to and surround Aβ plaques in both human AD brain and rodent transgenic models that develop AD-like symptoms [228][229][230][231][232][233][234][235][236][237].…”