title: Orphan nuclear receptor Nur77 is a novel negative regulator of endothelin-1 expression in vascular endothelial cells.
abstract: Endothelin-1 (ET-1) produced by vascular endothelial cells plays essential roles in the regulation of vascular tone and development of cardiovascular diseases. The objective of this study is to identify novel regulators implicated in the regulation of ET-1 expression in vascular endothelial cells (ECs). By using quantitative real-time PCR (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA), we show that either ectopic expression of orphan nuclear receptor Nur77 or pharmacological activation of Nur77 by 6-mercaptopurine (6-MP) substantially inhibits ET-1 expression in human umbilical vein endothelial cells (HUVECs), under both basal and thrombin-stimulated conditions. Furthermore, thrombin-stimulated ET expression is significantly augmented in both Nur77 knockdown ECs and aort from Nur77 knockout mice, suggesting that Nur77 is a negative regulator of ET-1 expression. Inhibition of ET-1 expression by Nur77 occurs at gene transcriptional levels, since Nur77 potently inhibits ET-1 promoter activity, without affecting ET-1 mRNA stability. As shown in electrophoretic mobility shift assay (EMSA), Nur77 overexpression markedly inhibits both basal and thrombin-stimulated transcriptional activity of AP-1. Mechanistically, we demonstrate that Nur77 specially interacts with c-Jun and inhibits AP-1 dependent c-Jun promoter activity, which leads to a decreased expression of c-Jun, a critical component involved in both AP-1 transcriptional activity and ET-1 expression in ECs. These findings demonstrate that Nur77 is a novel negative regulator of ET-1 expression in vascular ECs through an inhibitory interaction with the c-Jun/AP-1 pathway. Activation of Nur77 may represent a useful therapeutic strategy for preventing certain cardiovascular diseases, such as atherosclerosis and pulmonary artery hypertension.
authors.affiliation: Center for Translational Medicine, Thomas Jefferson University, Philadelphia, PA 19107, USA; Shanghai Institute of Cardiovascular Disease, Zhongshan Hospital, Fudan University, Shanghai 200032, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Qin
authors.affiliation: Center for Translational Medicine, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: Ming
authors.initials: M
authors.lastname: Chen
authors.affiliation: Center for Translational Medicine, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: Bing
authors.initials: B
authors.lastname: Yi
authors.affiliation: Center for Translational Medicine, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: Xiaohua
authors.initials: X
authors.lastname: You
authors.affiliation: Center for Translational Medicine, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: Ping
authors.initials: P
authors.lastname: Yang
authors.affiliation: Center for Translational Medicine, Thomas Jefferson University, Philadelphia, PA 19107, USA. Electronic address: jianxin.sun@jefferson.edu.
authors.forename: Jianxin
authors.initials: J
authors.lastname: Sun
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D019332:Endothelin-1 / Q000096:biosynthesis / Q000235:genetics*; D020868:Gene Silencing; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1 / Q000502:physiology*; D011401:Promoter Regions, Genetic; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000502:physiology; D014158:Transcription, Genetic
chemical_list: D019332:Endothelin-1; C539821:NR4A1 protein, human; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1
keywords: AP-1; Endothelin-1; Nur77; Transcription; c-Jun