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

Objective - To determine the role of prostacyclin (PGI(2)) in protecting endothelial cells (ECs) from apoptosis and elucidate the protective mechanism. Methods and Results - To evaluate the effect of PGI(2) on EC survival, we treated ECs with Ad-COX1/PGIS (Ad-COPI), which augmented selectively PGI(2) production or carbaprostacyclin (cPGI(2)) followed by H2O2 for 4 hours. Ad-COPI inhibited annexin V - positive cells and blocked caspase 3 activation. cPGI(2) inhibited apoptosis in a concentration-dependent manner. L-165041 had a similar effect, suggesting the involvement of peroxisome proliferator-activated receptor-delta (PPAR delta). ECs expressed functional PPAR delta. PPAR delta overexpression enhanced whereas PPAR delta knockdown by small interfering RNA abrogated the antiapoptotic action of cPGI(2) and L-165041. Our results show for the first time that PGI(2) stimulated 14-3-3 epsilon expression via PPAR delta activation. cPGI(2) and L-165041 induced binding oaf PPAR delta to PPAR response elements located between -1426 and -1477 of 14-3-3 epsilon promoter region, thereby activating 14-3-3 epsilon promoter activity and protein expression. Upregulation of 14-3-3 epsilon proteins resulted in an increase in Bad binding to 14-3-3 epsilon and a reduction in Bad translocation to mitochondria. Conclusions - PGI(2) protects ECs from H2O2-induced apoptosis by inducing PPAR delta binding to 14-3-3 epsilon promoter, thereby upregulating 14-3-3 epsilon protein expression. Elevated 14-3-3 epsilon augments Bad sequestration and prevents Bad-triggered apoptosis.