Protection of endothelial survival by peroxisome proliferator-activated receptor-delta mediated 14-3-3 upregulation.

To determine the role of prostacyclin (PGI2) in protecting endothelial cells (ECs) from apoptosis and elucidate the protective mechanism. To evaluate the effect of PGI2 on EC survival, we treated ECs with Ad-COX1/PGIS (Ad-COPI), which augmented selectively PGI2 production or carbaprostacyclin (cPGI2) followed by H2O2 for 4 hours. Ad-COPI inhibited annexin V-positive cells and blocked caspase 3 activation. cPGI2 inhibited apoptosis in a concentration-dependent manner. L-165041 had a similar effect, suggesting the involvement of peroxisome proliferator-activated receptor-delta (PPARdelta). ECs expressed functional PPARdelta. PPARdelta overexpression enhanced whereas PPARdelta knockdown by small interfering RNA abrogated the antiapoptotic action of cPGI2 and L-165041. Our results show for the first time that PGI2 stimulated 14-3-3alpha expression via PPARdelta activation. cPGI2 and L-165041 induced binding oaf PPARdelta to PPAR response elements located between -1426 and -1477 of 14-3-3alpha promoter region, thereby activating 14-3-3alpha promoter activity and protein expression. Upregulation of 14-3-3alpha proteins resulted in an increase in Bad binding to 14-3-3alpha and a reduction in Bad translocation to mitochondria. PGI2 protects ECs from H2O2-induced apoptosis by inducing PPARdelta binding to 14-3-3alpha promoter, thereby upregulating 14-3-3alpha protein expression. Elevated 14-3-3alpha augments Bad sequestration and prevents Bad-triggered apoptosis.