Abstract 218: Orphan Nuclear Receptor Nur77 is a Novel Negative Regulator of ET-1 Expression in Vascular Endothelial Cells
Objective Endothelin-1 (ET-1), a vasoactive peptide mainly produced by vascular endothelial cells, plays an important role in the regulation of vascular tone and the development of cardiovascular diseases. The objective of the present study is to identify the novel regulators implicated in the regulation of ET-1 expression in vascular endothelial cells (ECs), and to determine the molecular mechanism involved.
Method and Results by using quantitative real-time PCR (qRT-PCR) and Enzyme-linked immunosorbent assay (ELISA), we showed that either ectopic expression of Nur77 or pharmacological activation of Nur77 by 6-mercaptopurine (6-MP) substantially inhibited the ET-1 expression, under both basal and thrombin stimulated conditions, in human umbilical vein endothelial cells (HUVECs). Furthermore, knockdown of Nur77 enhances both basal and thrombin induced ET-1 expression, suggesting that Nur77 is a negative regulator of the ET-1 expression in vascular ECs. Inhibition of ET-1 expression by Nur77 mainly occurs at the gene transcriptional levels, since Nur77 potently inhibited the ET-1 promoter activity, without affecting the ET-1 mRNA stability. As shown in electrophoretic mobility shift assay (EMSA), Nur77 over-expression substantially inhibited both basal and thrombin stimulated transcriptional activity of AP-1, which is a critical transcriptional factor implicated in the ET-1 expression in ECs. Mechanistically, we found that Nur77 specially interacts with c-Jun in the nuclear fraction of endothelial cells by immunoprecipitation and inhibits the AP-1 dependent c-Jun promoter activity, which eventually leads to the decreased expression of c-Jun, a critical component for both AP-1 transcriptional activity and ET-1 expression in ECs.
Conclusions These results demonstrate for the first time that Nur77 is a novel negative regulator of the ET-1 expression in vascular ECs through an inhibitory interaction with c-Jun/AP-1 pathway. Targeting Nur77 may represent a potentially novel therapeutic strategy for preventing certain cardiovascular diseases, such as atherosclerosis, vascular complications of diabetes, and pulmonary artery hypertension.
- © 2013 by American Heart Association, Inc.