EP2 Induces p38 Phosphorylation via the Activation of Src in HEK 293 Cells

Prostaglandin E2 (PGE2), a major product of cyclooxygenase, binds to four different prostaglandin E2 receptors (EP1, EP2, EP3, and EP4) which are G-protein coupled transmembrane receptors (GPCRs). Although GPCRs including EP receptors have been shown to be associated with their specific G proteins, recent evidences suggest that GPCRs can regulate MAPK signaling via non-G protein coupled pathways including Src. EP2 is differentially expressed in various tissues and the expression of EP2 is induced by extracellular stimuli. We hypothesized that an increased level of EP2 expression may affect MAPK signaling. The overexpression of EP2 in HEK 293 cells resulted in significant increase in intracellular cAMP levels response to treatment with butaprost, a specific EP2 agonist, while overexpression of EP2 alone did not increase intracellular cAMP levels. However, EP2 overexpression in the absence of PGE2 induced an increase in the level of p38 phosphorylation as well as the kinase activity of p38, suggesting that up-regulation of EP2 may promote p38 activation via non-G protein coupled pathway. Inhibition of Src completely blocked EP2-induced p38 phosphorylation and overexpression of Src increased the level of p38 phosphorylation, indicating that Src is upstream kinase for EP2-induced p38 phosphorylation. EP2 overexpression also increased the Src activity and EP2 protein was co-immunoprecipitated with Src. Furthermore, sequential co-immunoprecipitation studies showed that EP2, Src, and beta-arrestin can form a complex. Our study found a novel pathway in which EP2 is associated with Src, regulating p38 pathway.

Prostaglandin E2 Receptors on Upper Respiratory Tract / 대한이비인후과학회지

Prostaglandin (PG) E2 exerts its actions by acting on a group of G-protein-coupled receptors (GPCRs). GPCRs responding to PGE2 consist of four subtypes namely E-prostanoid 1 (EP1), E-prostanoid 2 (EP2), E-prostanoid 3 (EP3), and E-prostanoid 4 (EP4) and multiple splicing isoforms of the subtype EP3. The EP subtypes exhibit differences in signal transduction pathway, tissue localization, and regulation of expression. This molecular and biochemical heterogeneity of PGE2 receptors leads to PGE2 being the most variable prostanoid. Studies on knockout mice deficient in each EP subtype and selective agonist and antagonist have defined PGE2 actions mediated by each subtype and identified the role each EP subtype plays in various physiological and pathophysiological responses. We summarize and review PGE2 receptor research.

Effect of CLA (Conjugated Linoleic Acid) on the Anti-Atherosclerotic Factors in Human Hepatoma HepG2 Cells

Conjugated linoleic acid (CLA) is the mixture of positional and geometric isomers of linoleic acid (LA), which is found abundantly in dairy products and meats. This study was performed to investigate the anticarcinogenic effect of CLA in HepG2 hepatoma cells. HepG2 cell were treated with LA and CLA at the various concentrations of 10, 20, 40, 80 uM each at different incubation times. After each incubation times, cell proliferation, fatty acids incorporation into cell, peroxidation and postaglandin E2 (PGE2) and thromboxane A2 (TXA2) for the eicosanoid metabolism were measured. LA treated HepG2 cells were increased cell growth 6 - 70% of control whereas CLA increased cell death the half of those in LA group (p < 0.001). LA and CLA were incorporated very well into the cellular membranes four times higher than in control according to concentration and longer incubation times. Moreover, LA synthesized significantly arachidonic acids corresponding with LA concentration compared to CLA supplementation. The supplementation with LA increased intracellular lipid peroxides concentration corresponding with LA concentration and five times higher than those in CLA significantly at any incubation times (p < 0.001). PGE2 and TXA2 levels were three to twenty times lower in condition of CLA treatments than LA, respectively. Overall, the dietary CLA might change the HepG2 cell growth by the changes of cell composition, production of lipid peroxide. Since CLA have not changed the levels of arachidonic acid of cell membrane, which was sources of eicosanoids, eicosanoid synthesis was not increased in CLA compared to LA. Our results was suggest CLA has a possibility to protect the progress of atherosclerosis because CLA does not produce lipid production and endothelial contraction factors in liver.

Protective effects of G CSF on lungs in rats with acute cholangitis / 中华肝胆外科杂志

Objective To investigate the protective effects of G CSF on lungs of rats with acute cholangitis and changes in blood TNF and TXA 2/PGI 2 by treating the rats with G CSF. Methods Seventy two Wistar rats were randomized into the control, infected and treated groups. We established the model of cholangitis in the rats with injection of E. coli 25922 into the bile duct. The animals in the treated group were pretreated with G CSF 500 ng/day bid) for 5 days before the E. coli injection. The levels of blood TNF and TXA 2/PGI 2 were measured at the 3rd, 6th and 12th h after the injection. Meanwhile, the morphological changes in lungs of the rats were observed. Results The morphological changes in lungs were milder and levels of blood TNF and TXA 2/PGI 2 were significantly lower in the treated group than in the infected one (P