Endothelin-1 Expression In Endothelial Cells Research Articles

Luteolin prevents TNF-α-induced NF-κB activation and ROS production in cultured human placental explants and endothelial cells

IntroductionPreeclampsia (PE) is a serious hypertensive pregnancy disorder and a leading cause of maternal and perinatal morbidity and mortality. Despite the prevalence and complications, there are no approved therapeutics to relieve PE symptoms. Inflammation, oxidative stress, and angiogenic imbalance have been shown to contribute to the PE pathophysiology, though there is a lack of understanding in how best to target these pathways in PE. We recently demonstrated that the bioflavonoid luteolin is a potent inhibitor of the anti-angiogenic and pro-hypertensive soluble fms-like tyrosine kinase 1 (sFlt-1), and here we aimed to determine if luteolin was also capable of reducing inflammation and oxidative stress pathways. MethodsTumor necrosis factor (TNF)-α, which is upregulated in PE, was utilized to stimulate these pathways in human placental explants and endothelial cells. Endothelin-1 (ET-1) and interleukin (IL)-6 in the media from explants and cells were measured via ELISA, and NF-κB localization and reactive oxygen species were detected via fluorescence microscopy. ResultsPretreatment with luteolin demonstrated significant reductions in NF-κB activation, reactive oxygen species, superoxide, and IL-6 and ET-1 expression in endothelial cells. We also saw a significant reduction in phosphorylation of NF-κB in human placental explants. DiscussionThese data demonstrate that luteolin inhibits pathways implicated in the development of PE and should be explored further for its potential as a PE therapeutic.

PKC-Mediated Endothelin-1 Expression in Endothelial Cell Promotes Macrophage Activation in Atherogenesis

Atherosclerosis is a chronic inflammatory disease triggered by endothelial dysfunction and exaggerated by macrophage infiltration. Although endothelin-1 (ET-1) plays an important role in vascular inflammation and reactive oxygen species production, the individual effect of ET-1 in atherogenesis remains unclear. ET-1 expression was increased in mouse atherosclerotic plaques and human umbilical vein endothelial cells (HUVECs) administrated by oxidized low-density lipoprotein stimulation. Moreover, the immunofluorescence co-staining showed upregulated ET-1 expression in endothelial cells. Real-time polymerase chain reaction demonstrated that ET-1 overexpression promoted adhesion molecules and chemokines secretion in HUVECs. Following this intervention, the migration of macrophages and the pro-inflammatory cytokines were increased. More importantly, the endothelial dysfunction regulated by ET-1 and subsequently the effect on macrophage activation were mediated by ETA receptor and largely reversed by protein kinase C (PKC) inhibitor. Eight-week-old male ApoE-/- mice and eET-1/ApoE-/- mice were fed with high-fat diet for 12 weeks. eET-1/ApoE-/- significantly increased atherosclerotic lesions in the whole aorta and aortic sinus, which accompanied by the induction of inflammatory cytokines and macrophages infiltration. ET-1 accelerates atherogenesis by promoting adhesion molecules and chemokines, as well as subsequent macrophage activation. Collected, these evidence suggest that ET-1 might be a potential target for the treatment of atherogenesis.

Palmitic Acid Increases Endothelin-1 Expression in Vascular Endothelial Cells through the Induction of Endoplasmic Reticulum Stress and Protein Kinase C Signaling

Objective: We investigated the regulation of endothelin-1 (ET-1) expression in in vivo high-fat diet (HFD)-fed mice and in vitro cultured human aortic endothelial cells (HAECs). Methods: Male C57BL/6 mice were fed on standard chow, serum was prepared, and ET-1 levels were analyzed using an ELISA kit. Quantitative PCR was performed using iQ SYBR Green Supermix. Statistical significance was assessed using SPSS, with p < 0.05 considered significant. Results: The serum ET-1 content and endothelial expression of ET-1 mRNA were increased in the HFD-fed mice compared to the chow-fed control mice. Moreover, the mRNA expression of ET-1 was significantly increased in cultured HAECs in response to acute (< 24 h) and chronic (12–16 days) treatments with palmitic acid (PA), one of the most abundant saturated fatty acids in obesity. We found that the induction of ET-1 expression by PA was abolished by pretreating the cells with the endoplasmic reticulum (ER) stress inhibitor 4-phenylbutyric acid or the protein kinase C (PKC) inhibitor Gö 6850. Conclusion: Our findings demonstrate for the first time that PA increases ET-1 expression in endothelial cells through the induction of ER stress and the activation of PKC, providing novel mechanistic insights into the pathogenesis of obesity-associated hypertension and cardiovascular diseases.

C-Src tyrosine kinase mediates high glucose-induced endothelin-1 expression

Endothelin-1 (ET-1) plays an important role in the pathophysiology of diabetes-associated cardiovascular disorders. The molecular mechanisms leading to ET-1 upregulation in diabetes are not entirely defined. c-Src tyrosine kinase regulates important pathophysiological aspects of vascular response to insults. In this study, we aimed to elucidate whether high glucose-activated c-Src signaling plays a role in the regulation of ET-1 expression. Human endothelial cells EAhy926 (ECs) were exposed to normal or high levels of glucose for 24h. Male C57BL/6J mice were rendered diabetic with streptozotocin and then treated with a specific c-Src inhibitor (Src I1) or c-Src siRNA. Real-time PCR, Western blot, and ELISA, were used to investigate ET-1 regulation. The c-Src activity and expression were selectively downregulated by pharmacological inhibition and siRNA-mediated gene silencing, respectively. High glucose dose-dependently up-regulated c-Src phosphorylation and ET-1 gene and protein expression levels in human ECs. Chemical inhibition or silencing of c-Src significantly decreased the high-glucose augmented ET-1 expression in cultured ECs. In vivo studies showed significant elevations in the aortic ET-1 mRNA expression and plasma ET-1 concentration in diabetic mice compared to non-diabetic animals. Treatment with Src I1, as well as in vivo silencing of c-Src, significantly reduced the upregulated ET-1 expression in diabetic mice. These data provide new insights into the regulation of ET-1 expression in endothelial cells in diabetes. Pharmacological targeting of c-Src activity and/or expression may represent a potential therapeutic strategy to reduce ET-1 level and to counteract diabetes-induced deleterious vascular effects.

Histone Methyltransferase SET1 Mediates Angiotensin II-Induced Endothelin-1 Transcription and Cardiac Hypertrophy in Mice.

Endothelin-1 is a potent vasoconstrictor derived from vascular endothelium. Elevated endothelin-1 levels are observed in a host of cardiovascular pathologies including cardiomyopathy. The epigenetic mechanism responsible for endothelin-1 induction in these pathological processes remains elusive. We report here that induction of endothelin-1 expression in endothelial cells by angiotensin II (Ang II) was accompanied by the accumulation of histone H3K4 trimethylation, a preeminent histone modification for transcriptional activation, on the endothelin-1 promoter. In the meantime, Ang II stimulated the expression and the occupancy of Suv, Ez, and Trithorax domain 1 (SET1), a mammalian histone H3K4 trimethyltransferase, on the endothelin-1 promoter, both in vitro and in vivo. SET1 was recruited to the endothelin-1 promoter by activating protein 1 (c-Jun/c-Fos) and synergized with activating protein 1 to activate endothelin-1 transcription in response to Ang II treatment. Knockdown of SET1 in endothelial cells blocked Ang II-induced endothelin-1 synthesis and abrogated hypertrophy of cultured cardiomyocyte. Finally, endothelial-specific depletion of SET1 in mice attenuated Ang II-induced pathological hypertrophy and cardiac fibrosis. Our data suggest that SET1 epigenetically activates endothelin-1 transcription in endothelial cells, thereby contributing to Ang II-induced cardiac hypertrophy. As such, screening of small-molecule compound that inhibits SET1 activity will likely offer a new therapeutic solution to the treatment of cardiomyopathy.

Orphan nuclear receptor Nur77 is a novel negative regulator of endothelin-1 expression in vascular endothelial cells

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.

Herbal Prescription, DSGOST, Prevents Cold-Induced RhoA Activation and Endothelin-1 Production in Endothelial Cells.

Herbal prescription, Danggui-Sayuk-Ga-Osuyu-Saenggang-tang (DSGOST), has long been used to treat Raynaud's phenomenon (RP) in traditional Chinese medicine (TCM). However, a biological mechanism by which DSGOST ameliorates RP is yet deciphered. In this study, we demonstrate that DSGOST inhibits cold-induced activation of RhoA, in both vascular smooth muscle cells (VSMC) and endothelial cells (EC), and blocks endothelin-1-mediated paracrine path for cold response on vessels. While cold induced RhoA activity in both cell types, DSGOST pretreatment prevented cold-induced RhoA activation. DSGOST inhibition of cold-induced RhoA activation further blocked α2c-adrenoreceptor translocation to the plasma membrane in VSMC. In addition, DSGOST inhibited endothelin-1-mediated RhoA activation and α2c-adrenoreceptor translocation in VSMC. Meanwhile, DSGOST inhibited cold-induced or RhoA-dependent phosphorylation of FAK, SRC, and ERK. Consistently, DSGOST inhibited cold-induced endothelin-1 expression in EC. Therefore, DSGOST prevents cold-induced RhoA in EC and blocks endothelin-1-mediated paracrine path between EC and VSMC. In conclusion, our data suggest that DSGOST is beneficial for treating RP-like syndrome.

Reactive oxygen species mediate oxidized low-density lipoprotein-induced endothelin-1 gene expression via extracellular signal-regulated kinase in vascular endothelial cells

Oxidized low-density lipoprotein (oxLDL) promotes expression and secretion of endothelin-1 (ET-1), however, the precise mechanism involved is unclear. This study was designed to identify the regulatory mechanism of oxLDL-induced ET-1 expression in endothelial cells. ET-1 mRNA expression, secretion and promoter activity were evaluated by reverse transcriptase-PCR (RT-PCR), enzyme immunometric and luciferase assays, respectively. oxLDL (35 microg/ml) significantly enhanced reactive oxygen species (ROS), mRNA expression, secretion and promoter activity of ET-1 in human umbilical vein endothelial cells (HUVECs), all of which were nullified by the antioxidant N-acetyl cysteine (NAC). oxLDL stimulated the extracellular signal-regulated kinase (ERK) phosphorylation in HUVECs, which was blocked by NAC and the mitogen-activated protein/extracellular signal-regulated kinase (MEK) inhibitor PD98059. NAC and PD98059 stopped oxLDL-elicited increase in mRNA expression, secretion and promoter activity of ET-1. Fusion plasmids with decreasing length of 5'-flanking sequence of ET-1 from -566 bpLuc to -250 bpLuc displayed increased luciferase activity after 24 h of oxLDL treatment. Interestingly, fusion plasmid from -233 and -185 bpLuc significantly reduced the luciferase activity in control and oxLDL-treated HUVECs. In addition, transfection of the reporter construct -250Luc, which contains a 2 bp mutation at activator protein-1 site, abolished both basal and oxLDL-stimulated ET-1 promoter activities. Collectively, our data favor the notion that oxLDL stimulates ERK phosphorylation via ROS accumulation, which in turn stimulates vascular endothelial transcriptional factor activator protein-1 and ET-1 expression as well as secretion.

Signaling by ALK5 mediates TGF-β-induced ET-1 expression in endothelial cells: a role for migration and proliferation

Endothelin-1 (ET-1) is a potent endothelial-derived 21-amino-acid vasoconstrictor peptide and its expression is potently regulated by the cytokine transforming growth factor-beta (TGF-beta). Most cell types contain a TGF-beta type I receptor form known as activin receptor-like kinase 5 (ALK5). However, endothelial cells coexpress an additional type I receptor named ALK1. These forms do not constitute redundant receptors with the same function, but they activate different Smad-mediated expression programmes leading to specific endothelial phenotypes. The aim of our study was to characterize the TGF-beta-induced pathway leading to ET-1 expression in endothelial cells and the contribution of the TGF-beta-mediated enhancement of ET-1 to the regulation of the endothelial cell migration and proliferation capacity. Our experiments indicate that TGF-beta induces ET-1 expression preferentially through the ALK5/Smad3 pathway. Specific ALK5 inhibition totally blocked the anti-angiogenic effect of TGF-beta. Antagonism of ET receptors partially reverted the effect of TGF-beta, indicating that a significant portion of the anti-migratory and anti-proliferative actions of this cytokine is mediated by ET-1 acting in an autocrine manner on endothelial cells.

Induction of Endothelin-1 Production in Endothelial Cells Via Co-Operative Action Between CD40 and Lectin-like Oxidized LDL Receptor (LOX-1)

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), originally identified as the major receptor for oxidized low-density lipoprotein in endothelial cells, mediates the interaction between activated platelets and endothelial cells. Stimulation of LOX-1 causes various functional changes in endothelial cells relevant to 'endothelial dysfunction'. This study investigated the cellular responses to platelet binding via LOX-1, comparing it with CD40, which also mediates platelet-binding in endothelial cells. Activated platelets, which bind both LOX-1 and CD40, induced endothelin-1 production via co-operation of LOX-1 and CD40. Stimulation of LOX-1 by oxidized low-density lipoprotein induced the expression of CD40 as well as LOX-1 itself, and stimulation of CD40 by CD40L induced the expression of LOX-1 as well as CD40. Activated platelets induced both LOX-1 and CD40 expression via these two systems in endothelial cells. Application of superoxide dismutase suppressed LOX-1-mediated, but not CD40-mediated, induction of endothelin-1. LOX-1 and CD40 synergistically, but through a distinct pathway, work to induce endothelin-1 expression in endothelial cells. This co-operative action between LOX-1 and CD40 might play a key role in the induction of endothelial dysfunction.

Functional cooperation between Smad proteins and activator protein-1 regulates transforming growth factor-beta-mediated induction of endothelin-1 expression.

Endothelin-1 (ET-1) is a 21-amino-acid potent vasoconstrictor peptide that is mainly produced by vascular endothelial cells. Expression of the ET-1 gene is subject to complex regulation by numerous factors, among which transforming growth factor-beta (TGF-beta) is one of the most important. It has been widely documented that TGF-beta increases ET-1 mRNA and peptide levels. We have explored the mechanism by which TGF-beta upregulates ET-1 expression in endothelial cells. Transcriptional activation of the ET-1 promoter accounted for the TGF-beta-induced increase in ET-1 mRNA levels. We have identified within the ET-1 promoter two DNA elements indispensable for TGF-beta-mediated induction of ET-1: an activator protein-1 (AP-1) site at -108/-102, known to be important for constitutive and induced expression, and a novel regulatory sequence located at -193/-171, which constitutes a specific binding site for Smad transcription factors. Mutation of both elements abolished TGF-beta responsiveness. Binding of Smad3/Smad4 and c-Jun to their corresponding DNA elements was evidenced by electrophoretic mobility shift assays. Furthermore, the coactivator CREB-binding protein (CBP)/p300 was found to play an essential role in the induction of the gene. The simultaneous requirement for two distinct and independent DNA elements suggests that Smads and activator protein-1 functionally cooperate through CBP/p300 to mediate TGF-beta-induced transcriptional activation of the ET-1 gene.

Molecular Regulation of the Endothelin-1 Gene by Hypoxia: CONTRIBUTIONS OF HYPOXIA-INDUCIBLE FACTOR-1, ACTIVATOR PROTEIN-1, GATA-2, AND p300/CBP

Endothelin-1 (ET-1) is a peptide hormone with potent vasoconstrictor properties which is synthesized and secreted predominantly by vascular endothelial cells. Its production is regulated by numerous stimuli including ischemia and hypoxia, and the enhanced levels that occur during myocardial ischemia may contribute to the progression of heart failure. We reported previously a preliminary characterization of a hypoxia-inducible factor-1 (HIF-1) binding site in the human ET-1 promoter which contributed to the activation of ET-1 expression in endothelial cells. We report here that the HIF-1 binding site alone is not sufficient for the response to hypoxia but requires an additional 50 base pairs of flanking sequence that includes binding sites for the factors activator protein-1 (AP-1), GATA-2, and CAAT-binding factor (NF-1). Mutation of any one of these sites or the HIF-1 site eliminated induction by hypoxia. Mutations of the AP-1 and GATA-2 sites, but not the HIF-1 site, were complemented by overexpressing AP-1, GATA-2, HIF-1alpha, or the activator protein p300/CBP, restoring the response to hypoxia. Binding studies in vitro confirmed physical associations among GATA-2, AP-1, and HIF-1 factors. Overexpression or depletion of p300/CBP modulated the level of ET-1 promoter expression as well as the endogenous ET-1 transcript but did not change the fold induction by hypoxia in either case. Regulation of the ET-1 promoter by hypoxia in non-endothelial cells required overexpression of GATA-2 and HIF-1alpha. The results support essential roles for AP-1, GATA-2, and NF-1 in stabilizing the binding of HIF-1 and promoting recruitment of p300/CBP to the ET-1 hypoxia response complex.