The PPARδ ligand L-165041 inhibits VEGF-induced angiogenesis, but the antiangiogenic effect is not related to PPARδ

Peroxisome proliferator-activated receptor (PPAR)d is known to be expressed ubiquitously and involved in lipid and glucose metabolism. Recent studies have demonstrated that PPARd is expressed in endothelial cells (ECs) and plays a potential role in endothelial survival and proliferation. Although PPARa and PPAR? are well recognized to play anti-inflammatory, antiproliferative, and antiangiogenic roles in ECs, the general effect of PPARd on angiogenesis in ECs remains unclear. Thus, we investigated the effect of the PPARd ligand L-165041 on vascular EC proliferation and angiogenesis in vitro as well as in vivo. Our data show that L-165041 inhibited VEGF-induced cell proliferation and migration in human umbilical vein ECs (HUVECs). L-165041 also inhibited angiogenesis in the Matrigel plug assay and aortic ring assay. Flow cytometric analysis indicated that L-165041 reduced the number of ECs in the S phase and the expression levels of cell cycle regulatory proteins such as cyclin A, cyclin E, CDK2, and CDK4; phosphorylation of the retinoblastoma protein was suppressed by pretreatment with L-165041. We confirmed whether these antiangiogenic effects of L-165041 were PPARd-dependent using GW501516 and PPARd siRNA. GW501516 treatment did not inhibit VEGF-induced angiogenesis, and transfection of PPARd siRNA did not reverse this antiangiogenic effect of L-165041, suggesting that the antiangiogenic effect of L-165041 on ECs is PPARd-independent. Together, these data indicate that the PPARd ligand L-165041 inhibits VEGF-stimulated angiogenesis by suppressing the cell cycle progression independently of PPARd. This study highlights the therapeutic potential of L-165041 in the treatment of many disorders related to pathological angiogenesis. J. Cell. Biochem. 113: 19471954, 2012. (C) 2012 Wiley Periodicals, Inc.