Role of prostaglandin E2 receptor 4 in cardiovascular diseases / 生理学报

Prostaglandin E2 (PGE2) is a cyclooxygenase metabolite of arachidonic acid. It acts as a bioactive lipid and plays an important role in regulating many biological processes. PGE2 binds to 4 different G protein-coupled receptors including prostaglandin E2 receptor subtypes EP1, EP2, EP3 and EP4. The EP4 receptor is widely expressed in most of human organs and tissues. Increasing evidence demonstrates that EP4 is essential for cardiovascular homeostasis and participates in the pathogenesis of many cardiovascular diseases. Here we summarize the role of EP4 in the regulation of cardiovascular function and discuss potential mechanisms by which EP4 is involved in the development of cardiovascular disorders with a focus on its effect on inflammation.

Role of prostaglandin E receptor EP4 in the regulation of adipogenesis and adipose metabolism / 生理学报

Adipose tissue is the energy storage organ of the body, and excess energy is stored in adipocytes in the form of lipid droplets. The homeostasis of adipose tissue is the basis for the body to maintain normal metabolic activity. Prostaglandin E (PGE) is an important lipid mediator in the body. It is synthesized in almost all tissues and participates in the regulation of many physiological processes such as blood pressure, glucose and lipid metabolism, and inflammation. PGE is abundant in white adipose tissue, where it is involved in the regulation of fat metabolism. PGE plays its biological role through binding to four G protein coupled receptors (prostaglandin E receptors), including EP-1, -2, -3, and -4. The EP4 subtype has been proved to play an important role in adipogenesis and adipose metabolism: it could inhibit adipogenesis while it was activated, whereas its knockout could promote lipolysis. This review summarized the relationship between EP4 and adipose metabolism, hoping to identify new targets of drug development for metabolic disorders.

Paricalcitol attenuates lipopolysaccharide-induced inflammation and apoptosis in proximal tubular cells through the prostaglandin E₂ receptor EP4

BACKGROUND: Vitamin D is considered to exert a protective effect on various renal diseases but its underlying molecular mechanism remains poorly understood. This study aimed to determine whether paricalcitol attenuates inflammation and apoptosis during lipopolysaccharide (LPS)-induced renal proximal tubular cell injury through the prostaglandin E₂ (PGE₂) receptor EP4. METHODS: Human renal tubular epithelial (HK-2) cells were pretreated with paricalcitol (2 ng/mL) for 1 hour and exposed to LPS (1 μg/mL). The effects of paricalcitol pretreatment in relation to an EP4 blockade using AH-23848 or EP4 small interfering RNA (siRNA) were investigated. RESULTS: The expression of cyclooxygenase-2, PGE₂, and EP4 were significantly increased in LPS-exposed HK-2 cells treated with paricalcitol compared with cells exposed to LPS only. Paricalcitol prevented cell death induced by LPS exposure, and the cotreatment of AH-23848 or EP4 siRNA offset these cell-protective effects. The phosphorylation and nuclear translocation of p65 nuclear factor-kappaB (NF-κB) were decreased and the phosphorylation of Akt was increased in LPS-exposed cells with paricalcitol treatment. AH-23848 or EP4 siRNA inhibited the suppressive effects of paricalcitol on p65 NF-κB nuclear translocation and the activation of Akt. The production of proinflammatory cytokines and the number of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive cells were attenuated by paricalcitol in LPS exposed HK-2 cells. The cotreatment with an EP4 antagonist abolished these anti-inflammatory and antiapoptotic effects. CONCLUSION: EP4 plays a pivotal role in anti-inflammatory and antiapoptotic effects through Akt and NF-κB signaling after paricalcitol pretreatment in LPS-induced renal proximal tubule cell injury.

Media of rat macrophage NR8383 cells with prostaglandins E2-induced VEGF over-expression promotes migration and tube formation of human umbilical vein endothelial cells / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effect of prostaglandins E2 (PGE2) in enhancing vascular endothelial growth factor (VEGF) expression in a rat macrophage cell line and the effect of the media from PGE2-inuced rat macrophages on angiogenetic ability of human umbilical vein endothelial cells (HUVECs) in vitro.</p><p><b>METHODS</b>Western blotting and qPCR were employed to investigate the expressions of VEGF protein and mRNAs in rat macrophage cell line NR8383 stimulated by PGE2 in the presence or absence of EP2 receptor inhibitor (AH6809) and EP4 receptor inhibitor (AH23848). Conditioned supernatants were obtained from different NR8383 subsets to stimulate HUVECs, and the tube formation ability and migration of the HUVECs were assessed with Transwell assay.</p><p><b>RESULTS</b>PGE2 stimulation significantly enhanced the expression of VEGF protein and mRNAs in NR8383 cells in a dose-dependent manner. The supernatants from NR8383 cells stimulated by PGE2 significantly enhanced tube formation ability of HUVECs (P<0.05) and promoted the cell migration. Such effects of PGE2 were blocked by the application of AH6809 and AH23848.</p><p><b>CONCLUSION</b>PGE2 can dose-dependently increase VEGF expression in NR8383 cells, and the supernatants derived from PGE2-stimulated NR8383 cells can induce HUVEC migration and accelerate the growth of tube like structures. PGE2 are essential to corpus luteum formation by stimulating macrophages to induce angiogenesis through EP2/EP4.</p>

Endometrial changes induced by prostaglandin E2 and EP4 receptor agonist in albino rats

Prostaglandin E2 [PGE2] plays a vital role in the endometrium at the initial phases of pregnancy in laboratory rodents. PGE2 exerts its effects by coupling to four subtypes of receptors designated as EP1, EP2, EP3, and EP4. Recently, a substance that acts specifically on the EP4 receptor was developed [EP4 receptor agonist=EP4A, APS-999 Na]. Endometrial stromal collagen I, total glycosaminoglycans, hyaluronic acid, and CD44 molecule are commonly subjected to drastic changes at the implantation window. This study was conducted to investigate changes in the expression of these components after administration of PGE2 and the EP4A in rat. Immature female albino rats were injected once with normal saline, 50microg of PGE2, of 50microg of EP4A and killed 24 h later. Light microscopy and immunohistochemistry were used in this study. The study results revealed fraying and disintegration of stromal collagen I; accumulation of matrix glycosaminoglycans and hyaluronic acid after PGE2 as well as EP4A injections compared with the control. In addition, EP4A and PGE2 induced the expression of the molecule CD44 on the endometrial luminal and glandular epithelia Edema of the endometrial stroma was obtained after PGE2 and EP4A treatments. This study revealed that PGE2 and EP4A enhanced endometrial factors that are essential for the success of the implantation process. As long as EP4A produced similar effects to PGE2, it could be concluded that PGE2 mediated these actions partially through the EP4 receptor. PGE2 and EP4A may prove to be promising tools for implantation disorders in the clinical field