A key role of PGC‐1α transcriptional coactivator in production of VEGF by a novel angiogenic agent COA‐Cl in cultured human fibroblasts

We previously demonstrated a potent angiogenic effect of a newly developed adenosine‐like agent named COA‐Cl. COA‐Cl exerted tube forming activity in human umbilical vein endothelial cells in the presence of normal human dermal fibroblasts (NHDF). We therefore explored whether and how COA‐Cl modulates gene expression and protein secretion of VEGF, a master regulator of angiogenesis, in NHDF. RT‐PCR and ELISA revealed that COA‐Cl upregulated VEGF mRNA expression and protein secretion in NHDF. HIF1α (hypoxia‐inducible factor 1α), a transcription factor, and PGC‐1α (peroxisome proliferator‐activated receptor‐γ coactivator‐1α), a transcriptional coactivator, are known to positively regulate the VEGF gene. Immunoblot and RT‐PCR analyses revealed that COA‐Cl markedly upregulated the expression of PGC‐1α protein and mRNA. COA‐Cl had no effect on the expression of HIF1α protein and mRNA in both hypoxia and normoxia. Silencing PGC‐1α gene, but not HIF1α gene, by small interfering RNA attenuated the ability of COA‐Cl to promote VEGF secretion. When an N‐terminal fragment of PGC‐1α was cotransfected with its partner transcription factor ERR α (estrogen‐related receptor‐α) in COS‐7 cells, COA‐Cl upregulated the expression of the endogenous VEGF mRNA. However, COA‐Cl had no effect on the expression of VEGF, when HIF1α was transfected. COA‐Cl induces VEGF gene expression and protein secretion in fibroblasts. The transcriptional coactivator PGC‐1α, in concert with ERR α, plays a key role in the COA‐Cl‐induced VEGF production. COA‐Cl‐induced activation of PGC‐1α‐ERR α‐VEGF pathway has a potential as a novel means for therapeutic angiogenesis.