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

Abstract

Peroxisome proliferator-activated receptor (PPAR)δ is known to be expressed ubiquitously and involved in lipid and glucose metabolism. Recent studies have demonstrated that PPARδ is expressed in endothelial cells (ECs) and plays a potential role in endothelial survival and proliferation. Although PPARα and PPARγ are well recognized to play anti-inflammatory, antiproliferative, and antiangiogenic roles in ECs, the general effect of PPARδ on angiogenesis in ECs remains unclear. Thus, we investigated the effect of the PPARδ 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 PPARδ-dependent using GW501516 and PPARδ siRNA. GW501516 treatment did not inhibit VEGF-induced angiogenesis, and transfection of PPARδ siRNA did not reverse this antiangiogenic effect of L-165041, suggesting that the antiangiogenic effect of L-165041 on ECs is PPARδ-independent. Together, these data indicate that the PPARδ ligand L-165041 inhibits VEGF-stimulated angiogenesis by suppressing the cell cycle progression independently of PPARδ. This study highlights the therapeutic potential of L-165041 in the treatment of many disorders related to pathological angiogenesis.

Establishing the Role of PPARβ/δ in Carcinogenesis

“…In contrast, secretion of VEGF was increased in a human colon cancer cell line by knockdown of PPARβ/δ, and ligand activation of PPARβ/δ inhibited secretion of VEGF, an effect that was mitigated by knockdown of PPARβ/δ [20]. Examination of human umbilical vein endothelial cells (HUVEC) cells revealed that L165041 also inhibits VEGF protein expression, tube formation and HUVEC proliferation and migration, and angiogenesis in vivo [40, 41]. However, the decrease is VEGF secretion and HUVEC migration were not mediated by PPARβ/δ, in one study [41].…”

“…Examination of human umbilical vein endothelial cells (HUVEC) cells revealed that L165041 also inhibits VEGF protein expression, tube formation and HUVEC proliferation and migration, and angiogenesis in vivo [40, 41]. However, the decrease is VEGF secretion and HUVEC migration were not mediated by PPARβ/δ, in one study [41]. While it is not clear that VEGF is a bona fide PPARβ/δ target gene, there is strong evidence that ANGPTL4 is directly regulated by ligand activation of PPARβ/δ, and also by PPARα and PPARγ [42].…”

Peroxisome Proliferator-Activated Receptor Modulation during Metabolic Diseases and Cancers: Master and Minions

“…Confirming these data, L-165041 was found to inhibit VEGF-stimulated angiogenesis by suppressing the cell cycle progression independently of PPAR δ : in particular, it reduces the number of endothelial cells in the S phase and the expression levels of cell cycle regulatory proteins such as cyclin A, cyclin E, cyclin-dependent kinase (CDK) 2, and CDK4 [36]. Furthermore, a recent in vitro study found that L-165041 significantly inhibits high glucose-induced interleukin-6 and TNF- α production, receptor for advanced glycation end products expression, and NF- κ B translocation in human embryonic kidney 293 (HEK) cells; in addition, it increases superoxide dismutase expression and attenuates apoptosis in HEK and mesangial cells [37].…”

Peroxisome proliferator-activated receptor delta and cardiovascular disease

“…Of M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 5 note, at these high concentrations the PPARD ligands have been shown to also activate PPARA and PPARG [9,10]. Interestingly, a recent study by Park et al demonstrated that the PPARD agonist L-165041 suppresses the cell cycle progression in ECs independently of PPARD since siRNA targeting PPARD could not reverse the anti-angiogenic effect of L-165041 [11]. In summary, these studies suggest that PPARD is pro-angiogenic and that the anti-angiogenic effects are PPARD-independent and probably due to off target effects specific to the compound in question.…”