Prostaglandin E2-EP4 Receptor Promotes Endothelial Cell Migration via ERK Activation and Angiogenesis in Vivo

Abstract

Prostaglandin E2 (PGE 2 ), a major product of cyclooxygenase, exerts its functions by binding to four G protein-coupled receptors (EP1-4) and has been implicated in modulating angiogenesis. The present study examined the role of the EP4 receptor in regulating endothelial cell proliferation, migration, and tubulogenesis. Primary pulmonary microvascular endothelial cells were isolated from EP4 flox/flox mice and were rendered null for the EP4 receptor with adenoCre virus. Whereas treatment with PGE 2 or the EP4 selective agonists PGE 1 -OH and ONO-AE1-329 induced migration, tubulogenesis, ERK activation and cAMP production in control adenovirus-transduced endothelial EP4 flox/flox cells, no effects were seen in adenoCre-transduced EP4 flox/flox cells. The EP4 agonist-induced endothelial cell migration was inhibited by ERK, but not PKA inhibitors, defining a functional link between PGE 2 -induced endothelial cell migration and EP4-mediated ERK signaling. Finally, PGE 2 , as well as PGE 1 -OH and ONO-AE1-329, also promoted angiogenesis in an in vivo sponge assay providing evidence that the EP4 receptor mediates de novo vascularization in vivo.Angiogenesis, the process of new blood vessel formation from pre-existing vessels, is a multistep event that requires endothelial cell proliferation, migration, and tube formation. Angiogenesis is controlled by diverse factors, including cytokines, growth factors, as well as cyclooxygenase-2-derived eicosanoids (1, 2). The pro-angiogenic effects of cyclooxygenase-2 are mediated primarily by three products of arachidonic acid metabolism: thromboxane A 2 , prostaglandin E 2 (PGE 2 ), 2 and prostaglandin I 2 . These pro-angiogenic eicosanoids directly stimulate the synthesis of angiogenic factors, promote vascular sprouting, migration, tube formation, as well as enhance endothelial cell survival (1, 2).PGE 2 exerts its cellular effects by binding to four distinct E-prostanoid receptors (EP1-4) that belong to the family of seven transmembrane G protein-coupled rhodopsin-type receptors (3). Even though there is similar signaling mechanisms among these receptors, it is clear that each receptor has different and often opposing biological effects (4). For example, although the EP2 and EP4 receptors are both Gs coupled receptors and up-regulate intracellular cAMP levels, they mediate differential phosphorylation of cAMP response element-binding proteins (5). In addition, following activation, these two receptors exert different downstream effects on important intracellular mediators, including the PI3K and ERK pathways (6, 7). Moreover, the EP3 receptor usually counteracts EP2-and EP4-mediated up-regulation of cAMP by preferentially coupling to G i proteins (3).Some information regarding the role of PGE 2 in angiogenesis has been obtained using cancer models in mice where the receptors have been deleted by homologous recombination. In this context, mice lacking the EP2 receptor produce significantly fewer and less vascularized tumors than wild type mice in a two-stage skin carcinogenesi...

Fas Signal Promotes Lung Cancer Growth by Recruiting Myeloid-Derived Suppressor Cells via Cancer Cell-Derived PGE2

“…In vivo blockade of COX-2/ PGE 2 with SC58125 not only decreased MDSC and Treg accumulation in 3LL/Fas-WT tumor tissues, but also reduced the tumor growth and prolonged the survival of 3LL/Fas-WT-bearing mice, thus further indicating that PGE 2 plays an important role in the promotion of 3LL lung cancer growth by Fas signal. PGE 2 receptors EP2 and EP4 are involved in the PGE 2 -mediated DC migration (30,31). We confirmed that both EP2 and EP4 were expressed in MDSC by RT-PCR, also EP2/EP4 were expressed in 3LL cells.…”

“…As PGE 2 can promote migration of cells including DC (29,30) and endothelial cells (31). Then we tested whether the increased production of PGE 2 by Fas-ligated cancer cells was responsible for the increased chemoattraction of MDSC.…”

Protocadherin-12 Cleavage Is a Regulated Process Mediated by ADAM10 Protein

“…Furthermore, endothelial cells regulate PCDH12 shedding in response to cytokines known to induce the cAMP or the PKC pathways. Endothelial cells mainly express PGE 2 receptors EP2 and EP4, two G protein-coupled receptors that both stimulate adenylate cyclase via stimulatory subunit Gs, whereas VEGF activates the phospholipase C-PKC pathway through VEGFR2 (33,34). As expected, VEGF enhanced PCDH12 shedding, whereas PGE 2 inhibited basal as well as VEGF-induced cleavage.…”

“…HUVECs were challenged either with VEGF that activates PKC, with PGE 2 that stimulates cAMP synthesis, or with histamine, which activates both pathways through H1 and H2 receptors, respectively (33,34). Both VEGF and histamine significantly increased PCDH12 shedding, and PGE 2 diminished basal PCDH12 shedding (Fig.…”

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“…Предыдущие исследования по-казывают, что глюкокортикоиды подавляют ангиогенез путем ингибирования синтеза VEGF [18,19,20], что до-казывает ингибирующее действие кортизола на сиг-нальные пути, который инициирует образование тубул.…”