Sphingosine 1-phosphate is a ligand for peroxisome proliferator-activated receptor-γ that regulates neoangiogenesis

Sphingosine 1-phosphate (S1P) is a bioactive lipid that can function both extracellularly and intracellularly to mediate a variety of cellular processes. Using lipid affinity matrices and a radiolabeled lipid binding assay, we reveal that S1P directly interacts with the transcription factor peroxisome proliferator-activated receptor (PPAR)gamma. Herein, we show that S1P treatment of human endothelial cells (ECs) activated a luciferase-tagged PPAR gamma-specific gene reporter by similar to 12-fold, independent of the S1P receptors. More specifically, in silico docking, gene reporter, and binding assays revealed that His323 of the PPAR gamma ligand binding domain is important for binding to S1P. PPAR gamma functions when associated with coregulatory proteins, and herein we identify that peroxisome proliferator-activated receptor-gamma coactivator 1 (PGC1)beta binds to PPAR gamma in ECs and their progenitors (nonadherent endothelial forming cells) and that the formation of this PPAR gamma:PGC1 beta complex is increased in response to S1P. ECs treated with S1P selectively regulated known PPAR gamma target genes with PGC1 beta and plasminogen-activated inhibitor-1 being increased, no change to adipocyte fatty acid binding protein 2 and suppression of CD36. S1P-induced in vitro tube formation was significantly attenuated in the presence of the PPAR gamma antagonist GW9662, and in vivo application of GW9662 also reduced vascular development in Matrigel plugs. Interestingly, activation of PPAR gamma by the synthetic ligand troglitazone also reduced tube formation in vitro and in vivo. To support this, Sphk1(-/-) Sphk2(+/-) mice, with low circulating S1P levels, demonstrated a similar reduction in vascular development. Taken together, our data reveal that the transcription factor, PPAR gamma, is a bona fide intracellular target for S1P and thus suggest that the S1P:PPAR gamma:PGC1 beta complex may be a useful target to manipulate neovascularization.