Hung Hsing Chao

Role of Reactive Oxygen Species-Sensitive Extracellular Signal-Regulated Kinase Pathway in Angiotensin II-Induced Endothelin-1 Gene Expression in Vascular Endothelial Cells

Background: Circulating angiotensin II (Ang II) increases vascular endothelin-1 (ET-1) tissue levels, which in turn mediate a major part of Ang II-stimulated vascular growth and hypertension in vivo. Ang II also stimulates the generation of reactive oxygen species (ROS) within vascular endothelial cells. However, whether ROS are involved in Ang II-induced ET-1 gene expression, and the related intracellular mechanisms occurring within vascular endothelial cells remain unclear. Methods: Cultured endothelial cells were stimulated with Ang II, and the thus elicited ET-1 gene expression was examined by Northern blotting and a promoter activity assay. Antioxidant pretreatment of endothelial cells was performed prior to Ang II-induced extracellular signal-regulated kinase (ERK) phosphorylation in order to elucidate the redox-sensitive pathway for ET-1 gene expression. Results: The ET-1 gene was induced with Ang II, which was inhibited with Ang II type 1 receptor antagonist (irbesartan). Ang II-enhanced intracellular ROS levels were inhibited by irbesartan and several antioxidants, and antioxidants also suppressed Ang II-induced ET-1 gene expression. Further, Ang II-activated ERK phosphorylation was also significantly inhibited by certain antioxidants. An ERK inhibitor, U0126, inhibited Ang II-induced ET-1 expression completely. Cotransfection of the dominant negative mutant of Ras, Raf and MEK1 (ERK kinase) attenuated the Ang II-enhanced ET-1 promoter activity, suggesting that the Ras/Raf/ERK pathway is required for Ang II-induced ET-1 gene expression. Ang II-induced activator protein-1 (AP-1) reporter activities were inhibited by antioxidants. Moreover, mutational analysis of the ET-1 gene promoter showed that the AP-1 binding site was an important cis element in Ang II-induced ET-1 gene expression. Conclusions: Our data suggest that ROS are involved in Ang II-induced ET-1 gene expression within endothelial cells. The redox-sensitive ERK-mediated AP-1 transcriptional pathway plays an important role in Ang II-induced ET-1 gene expression.

Uric acid stimulates endothelin-1 gene expression associated with NADPH oxidase in human aortic smooth muscle cells

AbstractAim:Recent experimental and human studies have shown that hyperuricemia is associated with hypertension and cardiovascular diseases. Elevated levels of endothelin-1 (ET-1) has been regarded as one of the most powerful independent predictors of cardiovascular diseases. For investigating whether uric acid-induced vascular diseases are related to ET-1, the uric acid-induced ET-1 expression in human aortic smooth muscle cells (HASMC) was examined.Methods:Cultured HASMC treated with uric acid, cell proliferation and ET-1 expression were examined. Antioxidant pretreatments on uric acid-induced extracellular signal-regulated kinases (ERK) phosphorylation were carried out to elucidate the redox-sensitive pathway in proliferation and ET-1 gene expression.Results:Uric acid was found to increase HASMC proliferation, ET-1 expression and reactive oxygen species production. The ability of both N-acetylcysteine and apo-cynin (l-[4-hydroxy-3-methoxyphenyl]ethanone, a NADPH oxidase inhibitor) to inhibit uric acid-induced ET-1 secretion and cell proliferation suggested the involvement of intracellular redox pathways. Furthermore, apocynin, and p47phox small interfering RNA knockdown inhibited ET-1 secretion and cell proliferation induced by uric acid. Inhibition of ERK by U0126 (1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio]butadiene) significantly suppressed uric acid-induced ET-1 expression, implicating this pathway in the response to uric acid. In addition, uric acid increased the transcription factor activator protein-1 (AP-1) mediated reporter activity, as well as the ERK phosphorylation. Mutational analysis of the ET-1 gene promoter showed that the AP-1 binding site was an important cis-element in uric acid-induced ET-1 gene expression.Conclusion:This is the first observation of ET-1 regulation by uric acid in HASMC, which implicates the important role of uric acid in the vascular changes associated with hypertension and vascular diseases.

Inhibition of angiotensin II induced endothelin-1 gene expression by 17-β-oestradiol in rat cardiac fibroblasts

Objective: To examine whether 17-β-oestradiol (E2) may alter angiotensin II (Ang II) induced cell proliferation and to identify the putative underlying signalling pathways in rat cardiac fibroblasts. Design: Cultured rat cardiac fibroblasts were preincubated with E2 then stimulated with Ang II. [3H]Thymidine incorporation and endothelin-1 (ET-1) gene expression were examined. The effect of E2 on Ang II induced NADPH oxidase activity, reactive oxygen species (ROS) formation, and extracellular signal regulated kinase (ERK) phosphorylation were tested to elucidate the intracellular mechanism of E2 in proliferation and ET-1 gene expression. Results: Ang II increased DNA synthesis, which was inhibited with E2 (1–100 nmol/l). E2, but not 17-α-oestradiol, inhibited Ang II induced ET-1 gene expression as shown by northern blotting and promoter activity assay. This effect was prevented by co-incubation with the oestrogen receptor antagonist ICI 182 780 (1 µmol/l). E2 also inhibited Ang II increased NADPH oxidase activity, ROS formation, ERK phosphorylation, and activator protein-1 mediated reporter activity. Conclusions: The results suggest that E2 inhibits Ang II induced cell proliferation and ET-1 gene expression, partially by interfering with the ERK pathway through attenuation of ROS generation. Thus, this study provides important new insight regarding the molecular pathways that may contribute to the proposed beneficial effects of oestrogen on the cardiovascular system.

Nicorandil inhibits angiotensin-II-induced proliferation of cultured rat cardiac fibroblasts

Background/Aims: Nicorandil, an ATP-sensitive potassium (KATP) channel opener, nitric oxide (NO) donor and antioxidant, was shown to exert a variety of pharmacological effects including cardioprotective properties. However, its mechanisms of action are not completely understood. The aims of this study were to examine whether nicorandil may alter angiotensin-II (Ang II)-induced cell proliferation and to identify the putative underlying signaling pathways in rat cardiac fibroblasts. Methods: Cultured rat cardiac fibroblasts were pretreated with nicorandil, then stimulated with Ang II, and cell proliferation and endothelin-1 (ET-1) expression were examined. The effects of nicorandil on Ang-II-induced reactive oxygen species (ROS) formation and extracellular signal-regulated kinase (ERK) phosphorylation were also examined. In addition, the effects of nicorandil on NO production and endothelial nitric oxide synthase (eNOS) phosphorylation were tested to elucidate the intracellular mechanism. Results: Nicorandil (0.1–10 µmol/l) caused a concentration-dependent inhibition of Ang-II-increased cell proliferation and ET-1 expression which were prevented by the KATP channel blocker glibenclamide (1 µmol/l). Nicorandil also inhibited Ang-II-increased ROS and ERK phosphorylation. In addition, nicorandil was found to increase the NO and eNOS phosphorylation. N-nitro-L-arginine methyl ester, an inhibitor of NOS, and the short interfering RNA transfection for eNOS markedly attenuated the inhibitory effect of nicorandil on Ang-II-induced cell proliferation. Conclusion: Our results suggest that nicorandil prevents cardiac fibroblast proliferation, and the inhibitory effect might be associated with the opening KATP channels, by interfering with the generation of ROS, and the activation of the eNOS-NO pathway.

Urotensin II induces interleukin 8 expression in human umbilical vein endothelial cells.

Background Urotensin II (U-II), an 11-amino acid peptide, exerts a wide range of actions in cardiovascular systems. Interleukin-8 (IL-8) is secreted by endothelial cells, thereby enhancing endothelial cell survival, proliferation, and angiogenesis. However, the interrelationship between U-II and IL-8 as well as the detailed intracellular mechanism of U-II in vascular endothelial cells remain unclear. The aim of this study was to investigate the effect of U-II on IL-8 expression and to explore its intracellular mechanism in human umbilical vein endothelial cells. Methods/Principal Findings Primary human umbilical vein endothelial cells were used. Expression of IL-8 was determined by real-time quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, and luciferase reporter assay. Western blot analyses and experiments with specific inhibitors were performed to reveal the downstream signaling pathways as concerned. U-II increased the mRNA/protein levels of IL-8 in human umbilical vein endothelial cells. The U-II effects were significantly inhibited by its receptor antagonist [Orn5]-URP. Western blot analyses and experiments with specific inhibitors indicated the involvement of phosphorylation of p38 mitogen-activated protein kinase and extracellular signal-regulated kinase in U-II-induced IL-8 expression. Luciferase reporter assay further revealed that U-II induces the transcriptional activity of IL-8. The site-directed mutagenesis indicated that the mutation of AP-1 and NF-kB binding sites reduced U-II-increased IL-8 promoter activities. Proliferation of human umbilical vein endothelial cells induced by U-II could be inhibited significantly by IL-8 RNA interference. Conclusion/Significance The results show that U-II induces IL-8 expression in human umbilical vein endothelial cells via p38 mitogen-activated protein kinase and extracellular signal-regulated kinase signaling pathways and IL-8 is involved in the U-II-induced proliferation of human umbilical vein endothelial cells.

Lycopene inhibits cyclic strain‐induced endothelin‐1 expression through the suppression of reactive oxygen species generation and induction of heme oxygenase‐1 in human umbilical vein endothelial cells

Lycopene is the most potent active antioxidant among the major carotenoids, and its use has been associated with a reduced risk for cardiovascular disease (CVD). Endothelin‐1 (ET‐1) is a powerful vasopressor synthesized by endothelial cells and plays a crucial role in the pathophysiology of CVD. However, the direct effects of lycopene on vascular endothelial cells have not been fully described. This study investigated the effects of lycopene on cyclic strain‐induced ET‐1 gene expression in human umbilical vein endothelial cells (HUVECs) and identified the signal transduction pathways that are involved in this process. Cultured HUVECs were exposed to cyclic strain (20% in length, 1 Hz) in the presence or absence of lycopene. Lycopene inhibited strain‐induced ET‐1 expression through the suppression of reactive oxygen species (ROS) generation through attenuation of p22phox mRNA expression and NAD(P)H oxidase activity. Furthermore, lycopene inhibited strain‐induced ET‐1 secretion by reducing ROS‐mediated extrace‐llular signal‐regulated kinase (ERK) phosphorylation. Conversely, lycopene treatment enhanced heme oxygenase‐1 (HO‐1) gene expression through the activation of phosphoinositide 3‐kinase (PI3K)/Akt pathway, followed by induction of the nuclear factor erythroid 2‐related factor 2 (Nrf2) nuclear translocation; in addition, HO‐1 silencing partially inhibited the repressive effects of lycopene on strain‐induced ET‐1 expression. In summary, our study showed, for the first time, that lycopene inhibits cyclic strain‐induced ET‐1 gene expression through the suppression of ROS generation and induction of HO‐1 in HUVECs. Therefore, this study provides new valuable insight into the molecular pathways that may contribute to the proposed beneficial effects of lycopene on the cardiovascular system.

Renal dysfunction and the risk of postoperative atrial fibrillation after cardiac surgery: role beyond the CHA2DS2-VASc score.

AIMS To investigate whether renal dysfunction is a useful predictor of postoperative atrial fibrillation (POAF) after cardiac surgery. We also aimed to determine whether the addition of renal dysfunction into the scoring system could improve diagnostic accuracy of the CHA2DS2-VASc score to predict POAF. METHODS AND RESULTS The study prospectively enrolled 350 consecutive patients who underwent cardiac surgery. Echocardiography was performed before cardiac surgery. Renal dysfunction was defined as estimated glomerular filtration rate < 60 mL min(-1) 1.73 m(-2). All patients were monitored with continuous electrocardiographic telemetry for the occurrence of POAF until the day of hospital dismissal. Postoperative atrial fibrillation occurred in 103 of 350 patients (29%). Patients with POAF was associated with longer intensive care unit stay compared with those without POAF (3.7 ± 2.2 vs. 3.1 ± 1.4 days, P = 0.002). Both the CHA2DS2-VASc score and renal dysfunction were independent predictors of POAF in multivariate analysis. Renal dysfunction can further stratify patients with a CHA2DS2-VASc score of 0 or 1 into two groups with different POAF rates (3.1% vs. 68.8%, P < 0.001). A new scoring system (R-CHA2DS2-VASc score) derived by assigning an additional point representing renal dysfunction to the CHA2DS2-VASc score could improve its predictive accuracy. The area under the receiver operating characteristic curve increased from 0.68 to 0.71 (P < 0.001). Furthermore, the rate of left ventricular diastolic dysfunction also increased with increasing renal dysfunction. CONCLUSION Renal dysfunction, associated with left ventricular diastolic dysfunction, was a significant risk factor for POAF after cardiac surgery and may improve the diagnostic accuracy of the CHA2DS2-VASc score.

Lycopene Inhibits Urotensin-II-Induced Cardiomyocyte Hypertrophy in Neonatal Rat Cardiomyocytes.

This study investigated how lycopene affected urotensin-II- (U-II-) induced cardiomyocyte hypertrophy and the possible implicated mechanisms. Neonatal rat cardiomyocytes were exposed to U-II (1 nM) either exclusively or following 6 h of lycopene pretreatment (1–10 μM). The lycopene (3–10 μM) pretreatment significantly inhibited the U-II-induced cardiomyocyte hypertrophy, decreased the production of U-II-induced reactive oxygen species (ROS), and reduced the level of NAD(P)H oxidase-4 expression. Lycopene further inhibited the U-II-induced phosphorylation of the redox-sensitive extracellular signal-regulated kinases. Moreover, lycopene treatment prevented the increase in the phosphorylation of serine-threonine kinase Akt and glycogen synthase kinase-3beta (GSK-3β) caused by U-II without affecting the protein levels of the phosphatase and tensin homolog deleted on chromosome 10 (PTEN). However, lycopene increased the PTEN activity level, suggesting that lycopene prevents ROS-induced PTEN inactivation. These findings imply that lycopene yields antihypertrophic effects that can prevent the activation of the Akt/GSK-3β hypertrophic pathway by modulating PTEN inactivation through U-II treatment. Thus, the data indicate that lycopene prevented U-II-induced cardiomyocyte hypertrophy through a mechanism involving the inhibition of redox signaling. These findings provide novel data regarding the molecular mechanisms by which lycopene regulates cardiomyocyte hypertrophy.

Nicorandil attenuates cyclic strain-induced endothelin-1 expression via the induction of activating transcription factor 3 in human umbilical vein endothelial cells.

Nicorandil is an adenosine triphosphate-sensitive potassium channel opener that combines an organic nitrate and a nicotinamide group which respectively confer to nicorandil the additional properties of being a nitric oxide (NO) donor and antioxidant; it also induces vasodilation, decreases the blood pressure, and protects the heart. However, the intracellular mechanism of nicorandil remains to be delineated. The aims of this study were to test the hypothesis that nicorandil alters strain-induced endothelin-1 secretion and NO production, and to identify the putative underlying signaling pathways in human umbilical vein endothelial cells (HUVECs). Cultured HUVECs were exposed to cyclic strain in the presence of nicorandil; endothelin-1 expression was examined by reverse-transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay. Activation of extracellular signal-regulated protein kinase (ERK), endothelial NO synthase (eNOS), and activating transcription factor (ATF)-3 was assessed by Western blot analysis. We show that nicorandil inhibited strain-induced endothelin-1 expression. Nicorandil also inhibited strain-increased reactive oxygen species formation and ERK phosphorylation. On the contrary, NO production, eNOS phosphorylation, and ATF3 expression were enhanced by nicorandil; however, L-NAME (an inhibitor of eNOS) and LY294002 (an inhibitor of phosphatidylinositol 3-kinase) inhibited nicorandil-increased ATF3 expression. Moreover, treatment of HUVECs with either an NO donor (NOC18; 3,3-bis[aminoethyl]-1-hydroxy-2-oxo-1-triazene) or an ATF3 activator (MG-132; carbobenzoxy-L-leucyl-L-leucyl-L-leucinal) resulted in repression of strain-induced endothelin-1 expression. Furthermore, L-NAME, and small interfering RNA transfection of eNOS also partially attenuated the inhibitory effect of nicorandil on strain-induced endothelin-1 expression. We demonstrate for the first time that nicorandil inhibits strain-induced endothelin-1 secretion via an increase in NO and upregulation of ATF3 in HUVECs. This study provides important new insights into the molecular pathways that may contribute to the beneficial effects of nicorandil in the cardiovascular system.

Nicorandil Inhibits Cyclic Strain-Induced Interleukin-8 Expression in Human Umbilical Vein Endothelial Cells

Background: Nicorandil, a mitochondrial adenosine triphosphate-sensitive potassium (mitoKATP) channel opener, exerts protective effects on the cardiovascular system. This study examined the effect of nicorandil on cyclic strain-induced interleukin-8 (IL-8) expression in human umbilical vein endothelial cells (HUVECs). Methods: Cultured HUVECs were exposed to cyclic strain in the presence or absence of nicorandil (1-10 μmol/l); we then analyzed IL-8 expression. We also assessed the effects of nicorandil on heme oxygenase-1 (HO-1) expression and cyclic strain-modulated IL-8 expression after HO-1 silencing in HUVECs. Summary: HUVECs exposed to cyclic strain showed increased IL-8 messenger RNA expression and protein secretion. Nicorandil (1-10 μmol/l) inhibited cyclic strain-induced IL-8 expression, whereas 5-hydroxydecanoate (100 μmol/l), a selective inhibitor of the mitoKATP channel, completely reversed the inhibitory effects of nicorandil on cyclic strain-induced IL-8 expression. We demonstrated that nicorandil increased HO-1 expression in HUVECs. In addition, cobalt protoporphyrin (10 μmol/l), an inducer of HO-1 expression, mimicked the effects of nicorandil and inhibited IL-8 expression under cyclic strain, whereas zinc protoporphyrin IX (10 μmol/l), an inhibitor of HO-1 expression, antagonized the effect of nicorandil. HO-1 silencing significantly abrogated the inhibitory effects of nicorandil on cyclic strain-induced IL-8 expression, suggesting that HO-1 plays a role in the mechanism of action of nicorandil. Key Messages: This study is the first to report that nicorandil inhibits cyclic strain-induced IL-8 expression through the induction of HO-1 expression in HUVECs. This finding provides valuable new insight into the molecular pathways contributing to the vasoprotective effects of nicorandil.