Peroxisome Proliferator-Activated Receptor Activators Inhibit Thrombin-Induced Endothelin-1 Production in Human Vascular Endothelial Cells by Inhibiting the Activator Protein-1 Signaling Pathway

Abstract

Endothelin-1 (ET-1), a 21-amino acid vasoactive peptide mainly produced by vascular endothelial cells, is involved in the regulation of vascular tone and smooth muscle cell proliferation. Peroxisome proliferator-activated receptors (PPARs), key players in lipid and glucose metabolism, have been implicated in metabolic disorders that are predisposing to atherosclerosis. Because of the potential role of ET-1 in vascular disorders such as hypertension and atherosclerosis, we investigated the regulation of ET-1 expression by PPAR activators. Western blot and reverse transcription-polymerase chain reaction analyses demonstrated that both PPARalpha and PPARgamma are expressed in human coronary artery endothelial cells as well as in endothelial cell lines such as HMEC-1 and ECV304. In bovine aortic endothelial cells and HMEC-1 cells, both PPARalpha and PPARgamma ligands inhibited thrombin-induced ET-1 secretion, whereas basal ET-1 secretion was only slightly suppressed. Reverse transcription-polymerase chain reaction experiments showed that this inhibition of ET-1 production occurs at the gene expression level. Using transient transfection assays, we demonstrated that PPARs downregulate thrombin-activated transcription of the human ET-1 promoter. Transactivation studies with c-Jun and c-Fos expression plasmids indicated that PPARs negatively interfere with the activator protein-1 signaling pathway, which mediates thrombin activation of ET-1 gene transcription. Furthermore, electrophoretic mobility shift assays demonstrated that PPAR activators reduce the thrombin-stimulated binding activity of bovine aortic endothelial cell nuclear extracts as well as c-Jun binding to an activator protein-1 consensus site. Taken together, these data indicate that (1) both PPARalpha and PPARgamma are expressed in human vascular endothelial cells and (2) PPAR activators inhibit thrombin-induced ET-1 biosynthesis, indicating a novel role for PPARs in vascular endothelial function.

Peroxisome Proliferator-Activated Receptor α Agonists Increase Nitric Oxide Synthase Expression in Vascular Endothelial Cells

“…The expression of eNOS and endothelin-1 is known to be coordinately regulated in diverse pharmacological and experimental conditions. 45,46 Since PPAR␣ agonists have the potential to inhibit endothelin-1 expression, 10 our results may give another example of the coordinated regulation between eNOS and endothelin-1 systems. These effects might explain the vasodilator function of PPAR␣ agonists.…”

“…[3][4][5] Such effects may be attributable at least in part to their effects on lipoprotein abnormalities, which are mainly exerted by PPAR␣ expressed in the liver. Several studies 9,10,17,18 have demonstrated that PPAR␣ is also expressed in vascular endothelial cells. Recently, direct roles of fibrates in vascular endothelial cells have become evident, clarifying the inhibitory effects of the PPAR␣ activators on the expression of VCAM-1, IL-6, and endothelin-1.…”

“…7 These authors further showed that patients receiving fenofibrate, a potent fibrate, had lower plasma C-reactive protein, fibrinogen, and IL-6 concentrations. 7 Furthermore, it has been demonstrated that PPAR␣ activators inhibit cytokine-induced vascular cell adhesion molecule-1 (VCAM-1), IL-6 expression, 8,9 and thrombin-induced endothelin-1 expression 10 in vascular endothelial cells, and inhibit tissue factor expression and activity in monocytes. 11 …”

Peroxisome Proliferator-Activated Receptor γ Ligands Increase Release of Nitric Oxide From Endothelial Cells

“…In vascular endothelium, PPAR␥ functions to increase Cu/Zn superoxide dismutase 33 and plasminogen activator inhibitor-1 expression 8 and inhibit cytokine-induced monocyte chemotactic protein-1 production, 34 leukocyte-endothelial interactions, 10 angiogenesis, 11 and thrombin-induced endothelin-1 production. 9 Taken together, these reports suggest that PPAR␥ plays an important role in endothelial biology and the pathogenesis of vascular disease.…”

Peroxisome Proliferator-activated Receptor α Positively Regulates Complement C3 Expression but Inhibits Tumor Necrosis Factor α-mediated Activation of C3 Gene in Mammalian Hepatic-derived Cells

“…There are a number of reports that describe transrepression on gene expression by PPAR␣ through interference with NF-B signaling pathway, including but not limited by cytokine-induced vascular cell adhesion molecule-1 (45) and endothelin-1 (46). Furthermore, PPAR␣ ligands repress acute phase proteins such as fibrinogene (47).…”