Protection of Endothelial Survival by Peroxisome Proliferator-Activated Receptor-δ Mediated 14-3-3 Upregulation

Abstract

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 H 2 O 2 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-δ (PPARδ). ECs expressed functional PPARδ. PPARδ overexpression enhanced whereas PPARδ 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 14-3-3α expression via PPARδ activation. cPGI 2 and L-165041 induced binding oaf PPARδ to PPAR response elements located between −1426 and −1477 of 14-3-3α promoter region, thereby activating 14-3-3α promoter activity and protein expression. Upregulation of 14-3-3α proteins resulted in an increase in Bad binding to 14-3-3α and a reduction in Bad translocation to mitochondria. Conclusions— PGI 2 protects ECs from H 2 O 2 -induced apoptosis by inducing PPARδ binding to 14-3-3α promoter, thereby upregulating 14-3-3α protein expression. Elevated 14-3-3α augments Bad sequestration and prevents Bad-triggered apoptosis.