High-Glucose-Induced Prostaglandin E2 and Peroxisome Proliferator-Activated Receptor Promote Mouse Embryonic Stem Cell Proliferation

摘要

Peroxisome proliferator-activated receptor is a nuclear receptor that has been implicated in blastocyst implantation, cell cycle, and pathogenesis of diabetes. However, the signal cascades underlying this effect are largely unknown in embryo stem cells. This study examined whether or not there is an association between the reactive oxygen species-mediated prostaglandin E2 (PGE2)/peroxisome proliferator-activated receptor (PPAR) and the growth response to high glucose levels in mouse ESCs. A high concentration of glucose (25 mM) significantly increased the level of [3H]thymidine incorporation, the level of 5-bromo-2'-deoxyuridine incorporation, and the number of cells. Moreover, 25 mM glucose increased the intracellular reactive oxygen species, phosphorylation of the cytosolic phospholipase A2 (cPLA2), and the release of [3H]arachidonic acid ([3H]AA). In addition, 25 mM glucose also increased the level of cyclooxygenase-2 (COX-2) protein expression, which stimulated the synthesis of PGE2. Subsequently, high glucose-induced PGE2 stimulated PPAR expression directly or through Akt phosphorylation indirectly through the E type prostaglandin receptor receptors. The PPAR antagonist inhibited the 25 mM glucose-induced DNA synthesis. Moreover, transfection with a pool of PPAR-specific small interfering RNA inhibited the 25 mM glucose-induced DNA synthesis and G1/S phase progression. Twenty-five millimolar glucose also increased the level of the cell cycle regulatory proteins (cyclin E/cyclin-dependent kinase [CDK] 2 and cyclin D1/CDK 4) and decreased p21WAF1/Cip1 and p27Kip1, which were blocked by the inhibition of the cPLA2, COX-2, or PPAR pathways. In conclusion, high glucose promotes mouse ESC growth in part through the cPLA2-mediated PGE2 synthesis and in part through PPAR pathways.