Propofol depresses angiotensin II-induced cell proliferation in rat cardiac fibroblasts

BACKGROUND

Propofol may have beneficial effects on the prevention of angiotensin II (Ang II)-induced cardiac fibroblast proliferation via its antioxidative properties. The authors hypothesized that propofol may alter Ang II-induced cell proliferation and aimed to identify the putative underlying signaling pathways in rat cardiac fibroblasts.

METHODS

Cultured rat cardiac fibroblasts were pretreated with propofol then stimulated with Ang II; cell proliferation and endothelin-1 gene expression were examined. The effect of propofol on Ang II-induced nicotinamide adenine dinucleotide phosphate-oxidase activity, reactive oxygen species formation, extracellular signal-regulated kinase phosphorylation, and activator protein 1-mediated reporter activity were also examined. The effect of propofol on nitric oxide production and protein kinase B and endothelial nitric oxide synthase phosphorylations were also tested to elucidate the intracellular mechanism of propofol in proliferation.

RESULTS

Ang II (100 nm) increased cell proliferation and endothelin-1 expression, which were partially inhibited by propofol (10 or 30 microm). Propofol also inhibited Ang II-increased nicotinamide adenine dinucleotide phosphate-oxidase activity, reactive oxygen species formation, extracellular signal-regulated kinase phosphorylation, and activator protein 1-mediated reporter activity. Propofol was also found to increase nitric oxide generation and protein kinase B and nitric oxide synthase phosphorylations. Nitric oxide synthase inhibitor (N-nitro-L-arginine methylester) and the short interfering RNA transfection for protein kinase B or endothelial nitric oxide synthase markedly attenuated the inhibitory effect of propofol on Ang II-induced cell proliferation.

CONCLUSIONS

The authors' results suggest that propofol prevents cardiac fibroblast proliferation by interfering with the generation of reactive oxygen species and involves the activation of the protein kinase B-endothelial nitric oxide synthase-nitric oxide 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 [Orn(5)]-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.

Cafestol Inhibits Cyclic-Strain-Induced Interleukin-8, Intercellular Adhesion Molecule-1, and Monocyte Chemoattractant Protein-1 Production in Vascular Endothelial Cells

Moderate coffee consumption is inversely associated with cardiovascular disease mortality; however, mechanisms underlying this causal effect remain unclear. Cafestol, a diterpene found in coffee, has various properties, including an anti-inflammatory property. This study investigated the effect of cafestol on cyclic-strain-induced inflammatory molecule secretion in vascular endothelial cells. Cells were cultured under static or cyclic strain conditions, and the secretion of inflammatory molecules was determined using enzyme-linked immunosorbent assay. The effects of cafestol on mitogen-activated protein kinases (MAPK), heme oxygenase-1 (HO-1), and sirtuin 1 (Sirt1) signaling pathways were examined using Western blotting and specific inhibitors. Cafestol attenuated cyclic-strain-stimulated intercellular adhesion molecule-1 (ICAM-1), monocyte chemoattractant protein- (MCP-) 1, and interleukin- (IL-) 8 secretion. Cafestol inhibited the cyclic-strain-induced phosphorylation of extracellular signal-regulated kinase and p38 MAPK. By contrast, cafestol upregulated cyclic-strain-induced HO-1 and Sirt1 expression. The addition of zinc protoporphyrin IX, sirtinol, or Sirt1 silencing (transfected with Sirt1 siRNA) significantly attenuated cafestol-mediated modulatory effects on cyclic-strain-stimulated ICAM-1, MCP-1, and IL-8 secretion. This is the first study to report that cafestol inhibited cyclic-strain-induced inflammatory molecule secretion, possibly through the activation of HO-1 and Sirt1 in endothelial cells. The results provide valuable insights into molecular pathways that may contribute to the effects of cafestol.

Magnolol depresses urotensin-II-induced cell proliferation in rat cardiac fibroblasts

1. Accumulating evidence suggests that oxidative stress plays a key role in the development of cardiac fibrosis. Urotensin-II (U-II) has been reported to play an important role in cardiac remodelling and fibrosis. Recently, we demonstrated the involvement of reactive oxygen species (ROS) production in U-II-induced cardiac fibroblast proliferation. Magnolol is an anti-oxidant compound extracted from the cortices of Magnolia officinalis. Thus, it is feasible that magnolol may attenuate cardiac fibroblast proliferation by inhibiting ROS production. Therefore, the aims of the present study were to determine whether magnolol alters U-II-induced cell proliferation and to identify the putative underlying signalling pathways in rat cardiac fibroblasts. 2. Cultured rat cardiac fibroblasts were pretreated with magnolol (1, 3 and 10 micromol/L) for 30 min, followed by exposure to U-II (30 nmol/L) for 24 h, after which cell proliferation and endothelin-1 (ET-1) protein secretion was examined. The effects of magnolol on U-II-induced ROS formation and extracellular signal-regulated kinase (ERK) phosphorylation were examined to elucidate the intracellular mechanisms by which magnolol affects cell proliferation and ET-1 expression. 3. Urotensin-II (30 nmol/L) stimulated cell proliferation, ET-1 protein secretion and ERK phosphorylation, all of which were inhibited by magnolol (10 micromol/L). Pretreatment of cardiac fibroblasts with N-acetylcysteine (5 mmol/L) for 30 min prior to exposure to U-II resulted in inhibition of U-II increased ROS formation. Similar effects were observed with 10 micromol/L magnolol. 4. In conclusion, the results suggest that magnolol inhibits cardiac fibroblast proliferation by interfering with ROS generation. Thus, the present study provides important new insights into the molecular pathways involved, which may contribute to our understanding of the effects of magnolol on the cardiovascular system.

Comparison of calcium-current in isolated atrial myocytes from failing and nonfailing human hearts

To identify possible alterations of the L-type calcium currents (I(Ca),L) in cardiomyopathy, I(Ca),L were recorded in atrial myocytes dissociated from the nonfailing heart (NF) of patients undergoing corrective open-heart surgery and explanted failing heart (FH) of patients with dilated cardiomyopathy undergoing heart transplantation. The patch-clamp technique was applied in the single-electrode whole-cell mode. The electrophysiological properties of I(Ca),L, including cell capacitance and current density, were similar in atrial myocytes from both groups of patients. Further to identify possible alterations of the myocardial beta-adrenergic pathway in cardiomyopathy, we examined the effects of isoproterenol, forskolin, 8-Br-cAMP and IBMX on I(Ca),L in both groups of atrial myocytes. Perfusion of isoproterenol (1 microM) significantly increased the peak I(Ca),L by 515 +/- 44% in 6 atrial myocytes from NF but increased only by 135 +/- 25% in 27 atrial myocytes from FH. However, forskolin (1 microM) or 8-Br-cAMP (0.1 mM) increased the peak I(Ca),L to a similar extent in atrial myocytes from NF and FH. IBMX (20 microM) also induced a comparable increase in the peak I(Ca),L by 213 +/- 31% (n = 5) and 207 +/- 59% (n = 4) in atrial myocytes from NF and FH, respectively. The above findings suggest that in atrial myocytes obtained from FH the beta-adrenoceptor numbers might be decreased but no impairment of the signal transduction cascade occurred beyond the GTP binding proteins level.

Intracellular Acid-extruding regulators and the effect of lipopolysaccharide in cultured human renal artery smooth muscle cells

Homeostasis of the intracellular pH (pHi) in mammalian cells plays a pivotal role in maintaining cell function. Thus far, the housekeeping Na(+)-H(+) exchanger (NHE) and the Na(+)-HCO3(-) co-transporter (NBC) have been confirmed in many mammalian cells as major acid extruders. However, the role of acid-extruding regulators in human renal artery smooth muscle cells (HRASMCs) remains unclear. It has been demonstrated that lipopolysaccharide (LPS)-induced vascular occlusion is associated with the apoptosis, activating calpain and increased [Ca(2+)]i that are related to NHE1 activity in endothelia cells. This study determines the acid-extruding mechanisms and the effect of LPS on the resting pHi and active acid extruders in cultured HRASMCs. The mechanism of pHi recovery from intracellular acidosis (induced by NH4Cl-prepulse) is determined using BCECF-fluorescence in cultured HRASMCs. It is seen that (a) the resting pHi is 7.19 ± 0.03 and 7.10 ± 0.02 for HEPES- and CO2/HCO3(-)- buffered solution, respectively; (b) apart from the housekeeping NHE1, another Na(+)-coupled HCO3(-) transporter i.e. NBC, functionally co-exists to achieve acid-equivalent extrusion; (c) three different isoforms of NBC: NBCn1 (SLC4A7; electroneutral), NBCe1 (SLC4A4; electrogenic) and NBCe2 (SLC4A5), are detected in protein/mRNA level; and (d) pHi and NHE protein expression/activity are significantly increased by LPS, in both a dose- and time- dependent manner, but NBCs protein expression is not. In conclusion, it is demonstrated, for the first time, that four pHi acid-extruding regulators: NHE1, NBCn1, NBCe1 and NBCe2, co-exist in cultured HRASMCs. LPS also increases cellular growth, pHi and NHE in a dose- and time-dependent manner.

Inhibitory effect of trilinolein on angiotensin II-induced cardiomyocyte hypertrophy

The myocardial protective effects of trilinolein, isolated from the Chinese herb Sanchi (Panax notoginseng), may be related to its antioxidant effects. In the present study, we investigated the effects of trilinolein on angiotensin II-induced cardiomyocyte hypertrophy. Cultured neonatal rat cardiomyocytes were stimulated with angiotensin II, [3H]leucine incorporation and the beta-myosin heavy chain promoter activity were examined. We also examined the effects of trilinolein on angiotensin II-induced intracellular reactive oxygen species generation. Trilinolein significantly inhibited angiotensin II-increased protein synthesis, beta-myosin heavy chain promoter activity, and intracellular reactive oxygen species generation. Antioxidant N-acetylcysteine also decreased angiotensin II-increased protein synthesis and beta-myosin heavy chain promoter activity. Furthermore, trilinolein and N-acetylcysteine decreased angiotensin II- or hydrogen peroxide (H2O2)-activated mitogen-activated protein kinases (MAPKs) phosphorylation, and activator protein-1 (AP-1)- [or nuclear factor-kappaB (NF-kappaB)]-reporter activities. These data indicate that trilinolein inhibits angiotensin II-induced cardiomyocyte hypertrophy and beta-myosin heavy chain promoter activity via attenuation of reactive oxygen species generation.

Tanshinone IIA attenuates cyclic strain-induced endothelin-1 expression in human umbilical vein endothelial cells

1. Tanshinone IIA, one of the active components of the Radix of Salvia miltiorrhiza, is used in traditional Chinese medicine to treat cardiovascular diseases. However, the intracellular mechanism of action of tanshinone IIA remain to be determined. The aims of the present study were to test the hypothesis that tanshinone IIA alters strain-induced endothelin (ET)-1 expression and nitric oxide (NO) production, as well as to identify the putative signalling pathways involved, in human umbilical vein endothelial cells (HUVEC). 2. Cultured HUVEC were exposed to cyclic strain in the presence of 1-10 μmol/L tanshinone IIA. Expression of ET-1 was examined by reverse transcription-polymerase chain reaction and ELISA. Phosphorylation of endothelial NO synthase (eNOS) and activating transcription factor (ATF) 3 was assessed by western blot analysis. 3. Tanshinone IIA (3 and 10 μmol/L) inhibited strain-induced ET-1 expression. In contrast, NO production, eNOS phosphorylation and ATF3 expression were enhanced by tanshinone IIA. The eNOS inhibitor N(G) -nitro-L-arginine methyl ester (l-NAME; 100 μmol/L), the phosphatidylinositol 3-kinase inhibitor LY294002 (5 μmol/L) and the soluble guanylyl cyclase inhibitor 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one (ODQ; 10 μmol/L) inhibited tanshinone IIA-induced increases in ATF3 expression. Moreover, treatment of HUVEC with either an NO donor (3,3-bis [aminoethyl]-1-hydroxy-2-oxo-1-triazene; 500 μmol/L) or an ATF3 activator (carbobenzoxy-L-leucyl-L-leucyl-L-leucinal; 5 μmol/L) resulted in the repression of strain-induced ET-1 expression. The inhibitory effect of tanshinone IIA on strain-induced ET-1 expression was significantly attenuated by l-NAME, ODQ and the transfection of small interfering RNA for ATF3. 4. In conclusion, tanshinone IIA inhibits strain-induced ET-1 expression by increasing NO and upregulating ATF3 in HUVEC. The present study provides important new insights into the molecular pathways that may contribute to the beneficial effects of tanshinone IIA in the cardiovascular system.

Antiarrhythmic effects of dehydroevodiamine in isolated human myocardium and cardiomyocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Dehydroevodiamine alkaloid (DeHE), a bioactive component of the Chinese herbal medicine Wu-Chu-Yu (Evodiae frutus), exerted antiarrhythmic effect in guinea-pig ventricular myocytes. We further characterize the electromechanical effects of DeHE in the human atrial and ventricular tissues obtained from hearts of patients undergoing corrective cardiac surgery or heart transplantation.

MATERIALS AND METHODS

The transmembrane potentials of human myocardia were recorded with a traditional microelectrode technique while sarcolemmal Na(+) and Ca(2+) currents in single human cardiomyocytes were measured by a whole-cell patch-clamp technique. The intracellular pH (pHi) and Na(+)-H(+) exchanger (NHE) activity were determined using BCECF-fluorescence in human atria.

RESULTS

In human atria, DeHE (0.1-0.3 μM) depressed upstroke velocity, amplitude of action potential, and contractile force, both in slow and fast response action potential. Moreover, the similar depressant effects of DeHE were found in human ventricular myocardium. Both in isolated human atrial and ventricular myocytes, DeHE (0.1-1 μM) reversibly, concentration-dependently decreased the Na(+) and Ca(2+)currents. Moreover, DeHE (0.1 and 0.3 μM) suppressed delayed afterdepolarizations and aftercontractions, induced by epinephrine and high [Ca(2+)]o in atria. In human ventricular myocardium, the strophanthidin-induced triggered activities were attenuated by pretreating DeHE (0.3 μM). The resting pHi and NHE activity were also significantly increased by DeHE (0.1-0.3 μM).

CONCLUSIONS

We concluded for the first time that, in the human hearts, DeHE could antagonize triggered arrhythmias induced by cardiotonic agents through a general reduction of the Na(+) and Ca(2+) inward currents, while increase of resting pHi and NHE activity.

Lipopolysaccharide pretreatment increases protease-activated receptor-2 expression and monocyte chemoattractant protein-1 secretion in vascular endothelial cells

BACKGROUND

This study investigated whether lipopolysaccharide (LPS) increase protease-activated receptor-2 (PAR-2) expression and enhance the association between PAR-2 expression and chemokine production in human vascular endothelial cells (ECs).

METHODS

The morphology of ECs was observed through microphotography in cultured human umbilical vein ECs (EA. hy926 cells) treated with various LPS concentrations (0, 0.25, 0.5, 1, and 2 μg/mL) for 24 h, and cell viability was assessed using the MTT assay. Intracellular calcium imaging was performed to assess agonist (trypsin)-induced PAR-2 activity. Western blotting was used to explore the LPS-mediated signal transduction pathway and the expression of PAR-2 and adhesion molecule monocyte chemoattractant protein-1 (MCP-1) in ECs.

RESULTS

Trypsin stimulation increased intracellular calcium release in ECs. The calcium influx was augmented in cells pretreated with a high LPS concentration (1 μg/mL). After 24 h treatment of LPS, no changes in ECs viability or morphology were observed. Western blotting revealed that LPS increased PAR-2 expression and enhanced trypsin-induced extracellular signal-regulated kinase (ERK)/p38 phosphorylation and MCP-1 secretion. However, pretreatment with selective ERK (PD98059), p38 mitogen-activated protein kinase (MAPK) (SB203580) inhibitors, and the selective PAR-2 antagonist (FSLLRY-NH2) blocked the effects of LPS-activated PAR-2 on MCP-1 secretion.

CONCLUSIONS

Our findings provide the first evidence that the bacterial endotoxin LPS potentiates calcium mobilization and ERK/p38 MAPK pathway activation and leads to the secretion of the pro-inflammatory chemokine MCP-1 by inducing PAR-2 expression and its associated activity in vascular ECs. Therefore, PAR-2 exerts vascular inflammatory effects and plays an important role in bacterial infection-induced pathological responses.

Mechanical stretch induces endothelial nitric oxide synthase gene expression in neonatal rat cardiomyocytes

1. Mechanical stretch leads to cardiac hypertrophy and may ultimately cause heart failure. However, the effect of mechanical stretch on gene induction in cardiomyocytes remains to be determined. 2. In the present study, we compared transcript profiles of mechanically stretched neonatal rat cardiomyocytes with those of unstretched cells using cDNA microarrays. The microarrays contained probes for 480 known genes, including those involved in signal transduction, cell cycle regulation, the cytoskeleton and cell motility. Eighteen genes, including the eNOS gene, were identified as having significantly differential expression in response to mechanical stretch in cardiomyocytes. 3. Northern and western blot analysis further quantified the expression of the eNOS gene. Mechanical stretch increased constitutive NOS activity and nitric oxide (NO) production. The NO donor s-nitroso-N-acetylpenicillamine (SNAP) inhibited mechanical stretch-stimulated protein synthesis, as measured by [3H]-leucine uptake. In addition, cardiomyocytes were infected with adenoviral vectors encoding cDNA for eNOS (Ad-eNOS) and a phosphoglycerate kinase (PGK) empty vector (Ad-PGK). In contrast with Ad-PGK-infected cells, in cardiomyocytes infected with Ad-eNOS, there was increased calcium-dependent NOS activity and nitrite production. Cardiomyocytes infected with Ad-eNOS exhibited diminished mechanical stretch-stimulated protein synthesis. In contrast, in eNOS-knockdown cells, the increased eNOS protein levels and NOS activity induced by mechanical stretch were abolished, but protein synthesis was enhanced. 4. The results of the present study indicate that eNOS gene expression is induced by mechanical stretch, leading to increased constitutive NOS activity and NO production, which may be a negative regulator in cardiomyocyte hypertrophy.

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  μ M). The lycopene (3-10  μ M) 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-3 β ) 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-3 β 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.

Tetramethylpyrazine inhibits angiotensin II-increased NAD(P)H oxidase activity and subsequent proliferation in rat aortic smooth muscle cells

Tetramethylpyrazine (TMP) is the major component extracted from the Chinese herb, Chuanxiong, which is widely used in China for the treatment of cardiovascular problems. The aims of this study were to examine whether TMP may alter angiotenisn II (Ang II)-induced proliferation and to identify the putative underlying signaling pathways in rat aortic smooth muscle cells. Cultured rat aortic smooth muscle cells were preincubated with TMP and then stimulated with Ang II, [3H]-thymidine incorporation and the ET-1 expression was examined. Ang II increased DNA synthesis which was inhibited by TMP (1-100 microM). TMP inhibited the Ang II-induced ET-1 mRNA levels and ET-1 secretion. TMP also inhibited Ang II-increased NAD(P)H oxidase activity, intracellular reactive oxygen species (ROS) levels, and the ERK phosphorylation. Furthermore, TMP and antioxidants such as Trolox and diphenylene iodonium decreased Ang II-induced ERK phosphorylation, and activator protein-1 reporter activity. In summary, we demonstrate for the first time that TMP inhibits Ang II-induced proliferation and ET-1, partially by interfering with the ERK pathway via attenuation of Ang II-increased NAD(P)H oxidase and ROS generation. Thus, this study delivers important new insight in the molecular pathways that may contribute to the proposed beneficial effects of TMP in cardiovascular disease.

Dependence of 6beta-acetoxy-7alpha-hydroxyroyleanone block of Kv1.2 channels on C-type inactivation

Voltage-gated K(+) (Kv) channels exhibit slow or C-type inactivation during continuous depolarization. A selective pharmacological agent targeting C-type inactivation is hitherto lacking. Here, we report that 6beta-acetoxy-7alpha-hydroxyroyleanone (AHR), a diterpenoid compound isolated from Taiwania cryptomerioides, can selectively modify C-type inactivation of Kv1.2 channels. Extracellular, but not intracellular, AHR (50 muM) dramatically accelerated the slow decay of Kv currents and left-shifted the steady-state inactivation curve. AHR blocked Kv currents with an IC(50) of 17.7 muM. AHR did not affect the kinetics and voltage-dependence of Kv1.2 channel activation. Channel block by AHR was independent of intracellular K(+) concentration. In addition, effect of AHR was much attenuated in a Kv1.2 V370G mutant defective in C-type inactivation. Therefore, block of Kv1.2 channels by AHR did not appear to involve direct occlusion of the outer pore but depended on C-type inactivation. AHR could thus be a probe targeting Kv channel C-type inactivation gate.

Hydrogen peroxide-induced intracellular acidosis and electromechanical inhibition in the diseased human ventricular myocardium

Accumulation of oxygen free radicals is an important mediator of post-ischemia/reperfusion cardiac dysfunction. However, oxidative injury has not been well characterized in human cardiac tissues. In the present study, we superfused hydrogen peroxide (H(2)O(2)) into the diseased human ventricle in order to assess the effects of oxygen free radicals on the electromechanical parameters and the intracellular pH (pH(i)), and to test the ability of certain potential cardioprotective agents, including scavengers of hydrogen peroxide (dibenzamidostilbene disulfonic acid; DBDS), the.OH free radical (N-(mercaptopropionyl)-glycine; N-MPG), and the HOCl free radical (L-methionine), to protect against oxidative injury. Disease human ventricular tissues were obtained from patients undergoing heart transplantation. Electrophysiological experiments were performed using a traditional micropipette, while the pH(i) was measured by microspectrofluorimetry. We found that (a) H(2)O(2) (30 microM-3 mM) induced a significant dose-dependent intracellular acidosis, (b) H(2)O(2) (30 microM-3 mM) had a notable dose-dependent biphasic effect on the contractile force (an increase, followed by a decrease), while moderate concentrations of H(2)O(2) also inhibited the generation of action potential and increased the diastolic resting force significantly, and (c) N-MPG caused significant block of both the intracellular acidosis and the electromechanical inhibition induced by 3 mM H(2)O(2), whereas L-methionine and DBDS did not. Our data suggest that the toxic effects of H(2)O(2) are caused mainly through the generation of.OH, which is attributed to the intracellular acidosis seen in the diseased human ventricle.

Antiarrhythmic effects of (-)-epicatechin-3-gallate, a novel sodium channel agonist in cultured neonatal rat ventricular myocytes

(-)-Epicatechin-3-gallate (ECG), a polyphenol extracted from green tea, has been proposed as an effective compound for improving cardiac contractility. However, the therapeutic potential of ECG on the treatment of arrhythmia remains unknown. We investigated the direct actions of ECG on the modulation of ion currents and cardiac cell excitability in the primary culture of neonatal rat ventricular myocyte (NRVM), which is considered a hypertrophic model for analysis of myocardial arrhythmias. By using the whole-cell patch-clamp configurations, we found ECG enhanced the slowly inactivating component of voltage-gated Na(+) currents (I(Na)) in a concentration-dependent manner (0.1-100 μM) with an EC(50) value of 3.8 μM. ECG not only shifted the current-voltage relationship of peak I(Na) to the hyperpolarizing direction but also accelerated I(Na) recovery kinetics. Working at a concentration level of I(Na) enhancement, ECG has no notable effect on voltage-gated K(+) currents and L-type Ca(2+) currents. With culture time increment, the firing rate of spontaneous action potential (sAP) in NRVMs was gradually decreased until spontaneous early after-depolarization (EAD) was observed after about one week culture. ECG increased the firing rate of normal sAP about two-fold without waveform alteration. Interestingly, the bradycardia-dependent EAD could be significantly restored by ECG in fast firing rate to normal sAP waveform. The expression of dominant cardiac sodium channel subunit, Nav1.5, was consistently detected throughout the culture periods. Our results reveal how ECG, the novel I(Na) agonist, may act as a promising candidate in clinical applications on cardiac arrhythmias.

Inhibition of voltage-gated K+ channels and Ca2+ channels by diphenidol

BACKGROUND

Although diphenidol has long been deployed as an anti-emetic and anti-vertigo drug, its mechanism of action remains unclear. In particular, little is known as to how diphenidol affects neuronal ion channels. Recently, we showed that diphenidol blocked neuronal voltage-gated Na(+) channels, causing spinal blockade of motor function, proprioception and nociception in rats. In this work, we investigated whether diphenidol could also affect voltage-gated K(+) and Ca(2+) channels.

METHODS

Electrophysiological experiments were performed to study ion channel activities in two neuronal cell lines, namely, neuroblastoma N2A cells and differentiated NG108-15 cells.

RESULTS

Diphenidol inhibited voltage-gated K(+) channels and Ca(2+) channels, but did not affect store-operated Ca(2+) channels.

CONCLUSION

Diphenidol is a non-specific inhibitor of voltage-gated ion channels in neuronal cells.

Nicorandil prevents doxorubicin-induced human umbilical vein endothelial cell apoptosis

Nicorandil is an adenosine triphosphate-sensitive potassium channel opener with additional antioxidant properties. Doxorubicin (DOX) is an anticancer drug that exerts oxidation-mediated adverse cardiovascular effects. This study examined the effects of nicorandil on DOX-induced cytotoxicity in human umbilical vein endothelial cells (HUVECs) and underlying intracellular signaling mechanisms. Cultured HUVECs were pretreated with nicorandil (0.1, 0.3, 1, 3, and 10 μM) for 12 h and then treated with DOX (1 μM) for 24 h. Cell viability and cytotoxicity were measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and lactate dehydrogenase assays, respectively. Cell apoptosis was examined using a caspase-3 activity assay, and DNA fragmentation was detected through TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) staining. Western blot analysis was conducted to determine the related protein expression. DOX markedly increased reactive oxygen species production, p53 expression, caspase-3 activity, cleaved caspase-3 levels, and TUNEL-positive cell numbers but reduced Bcl-2 expression and intracellular antioxidant enzyme levels; these effects were effectively antagonized through nicorandil (3 μM, 12 h) pretreatment, which resulted in HUVECs being protected from DOX-induced apoptosis. Activating transcription factor 3 (ATF3), a stress-induced transcription factor, was induced by nicorandil (3 μM). Furthermore, nicorandil (3 μM) enhanced nuclear factor erythroid 2-related factor 2 (Nrf2) translocation and heme oxygenase-1 (HO-1) expression. ATF3 short interfering RNA significantly attenuated nicorandil-mediated Nrf2 translocation, HO-1 expression, and inhibitory effects on DOX-stimulated reactive oxygen species production and cell apoptosis. In summary, nicorandil may protect HUVECs from DOX-induced apoptosis, in part through ATF3-mediated Nrf2/HO-1 signaling pathways, which potentially protect the vessels from severe DOX toxicity.

Cafestol, a coffee diterpene, inhibits urotensin II-induced interleukin-8 expression in human umbilical vein endothelial cells

Cafestol, a diterpene molecule found in the berries of Coffea arabica L. (Rubiaceae), has been shown to exercise anti-angiogenic and anti-tumorigenic effects. However, cafestol's cellular mechanism has yet to be fully investigated. We previously demonstrated that urotensin II enhanced interleukin-8 secretion by endothelial cells, thereby increasing endothelial cell proliferation. Urotensin II may also participate in angiogenesis and tumor infiltration by macrophages. However, the effects of cafestol on urotensin II-induced interleukin-8 expression and cellular proliferation have not been determined. Here, we showed that pretreatment with cafestol inhibited urotensin II-stimulated endothelial cell proliferation. Further experiments demonstrated that cafestol increased translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and expression of enhanced heme oxygenase-1. Moreover, cafestol inhibited expression of urotensin II-induced interleukin-8. Cafestol's inhibitory effects on interleukin-8 expression and cellular proliferation induced by urotensin II were significantly abrogated by heme oxygenase-1 silencing, suggesting it may be involved in mediating the effects of cafestol. This study reports that cafestol inhibits urotensin II-induced interleukin-8 expression and cell proliferation via Nrf2/heme oxygenase-1-dependent mechanism in endothelial cells. These findings provide novel insight into the signaling pathways that may be important in mediating the effects of cafestol.

Molecular mechanism of the inhibitory effect of trilinolein on endothelin-1-induced hypertrophy of cultured neonatal rat cardiomyocytes

Trilinolein, isolated from the traditional Chinese herb Sanchi ( Panax notoginseng), has been shown to have myocardial protective effects via its antioxidant ability. However, the cellular and molecular mechanisms of the protective effect of trilinolein in the heart remain to be elucidated. Oxidative mechanisms have been implicated in neonatal cardiomyocyte hypertrophy. We therefore have examined whether trilinolein attenuates reactive oxygen species (ROS) production and thus ET-1-induced hypertrophy of cardiomyocytes. Cultured neonatal rat cardiomyocytes were stimulated with ET-1 (10 nM), [3H]leucine incorporation and the beta-myosin heavy chain (beta-MyHC) promoter activity were examined. Trilinolein (1 and 10 microM) inhibited the ET-1-induced increase of [3H]-leucine incorporation in a concentration-dependent manner. Trilinolein (1 and 10 microM) also inhibited ET-1-induced beta-MyHC promoter activity in cardiomyocytes. We further examined the effects of trilinolein on ET-1-induced intracellular ROS generation by measuring a redox-sensitive fluorescent dye, 2',7'-dichlorofluorescin diacetate, fluorescence intensity. Trilinolein (1 and 10 microM) inhibited ET-1-increased intracellular ROS levels in a concentration-dependent manner. This increase of ROS by ET-1 (10 nM) or H2O2 (25 microM) was significantly inhibited by trilinolein (10 microM) and N-acetylcysteine (10 mM). Moreover, ET-1- or H2O2-induced beta-MyHC promoter activity and protein synthesis were also inhibited by trilinolein (10 microM). These data indicate that trilinolein inhibits ET-1-induced beta-MyHC promoter activity, and subsequent hypertrophy via its antioxidant ability in cardiomyocytes.

Inhibitory effect of trilinolein on endothelin-1-induced c-fos gene expression in cultured neonatal rat cardiomyocytes

Trilinolein, isolated from the traditional Chinese herb Sanchi (Panax notoginseng), has been shown to have myocardial protective effects via its antioxidant ability. However, the cellular and molecular mechanisms of the protective effect of trilinolein in the heart remain to be elucidated. Oxidative mechanisms have been implicated in neonatal cardiomyocyte hypertrophy. We previously reported that ET-1 induces ROS generation via the ET(A) receptor and ROS modulates c-fos gene expression. We have therefore examined whether trilinolein attenuates ROS production and ET-1-induced c-fos gene expression in cardiomyocytes. Cultured neonatal rat cardiomyocytes were stimulated with ET-1 (10 nM), and c-fos gene expression was examined. Trilinolein (1 and 10 microM) inhibited ET-1-induced c-fos gene expression in cardiomyocytes. We also examined the effects of trilinolein on ET-1-increased NADPH oxidase activity and superoxide formation. Trilinolein inhibited ET-1-increased NADPH oxidase activity and superoxide formation in a concentration-dependent manner. This increase in superoxide production by ET-1 was significantly inhibited by trilinolein, diphenyleneiodonium, or N-acetylcysteine. Trilinolein also decreased ET-1- or H2O2-induced extracellular signal-regulated kinase (ERK) phosphorylation, c-Jun NH2-terminal kinase (JNK) phosphorylation, and activator protein-1 activation. These data indicate that trilinolein inhibits ET-1-induced ERK phosphorylation, JNK phosphorylation, and c-fos gene expression via attenuating superoxide production in cardiomyocytes.

Effects of propofol on cyclic strain-induced endothelin-1 expression in human umbilical vein endothelial cells

BACKGROUND

Propofol is one of the most popular intravenous induction agents of general anesthesia. Experimental results revealed that propofol exerted hypotensive and antioxidative effects. However, the intracellular mechanism of propofol remains to be delineated. The aims of this study were to test the hypothesis that propofol may alter strain-induced endothelin-1 (ET-1) secretion and nitric oxide production, and to identify the putative underlying signaling pathways in human umbilical vein endothelial cells.

METHODS

Cultured human umbilical vein endothelial cells were exposed to cyclic strain in the presence of propofol, and ET-1 expression was examined by Northern blotting and enzyme-linked immunosorbent assay kit. Activation of extracellular signal-regulated protein kinase, endothelial nitric oxide synthase, and protein kinase B were assessed by Western blot analysis.

RESULTS

The authors show that propofol inhibits strain-induced ET-1 expression, strain-increased reactive oxygen species formation, and extracellular signal-regulated protein kinase phosphorylation. On the contrary, nitric oxide production, endothelial nitric oxide synthase activity, and protein kinase B phosphorylation were enhanced by propofol treatment. Furthermore, in the presence of PTIO, a nitric oxide scavenger, and KT5823, a specific inhibitor of cyclic guanosine monophosphate-dependent protein kinase, the inhibitory effect of propofol on strain-induced extracellular signal-regulated protein kinase phosphorylation and ET-1 release was reversed.

CONCLUSIONS

The authors demonstrate for the first time that propofol inhibits strain-induced ET-1 secretion and enhances strain-increased nitric oxide production in human umbilical vein endothelial cells. Thus, this study delivers important new insight into the molecular pathways that may contribute to the proposed hypotensive effects of propofol in the cardiovascular system.

Downregulation of superoxide dismutase activity and gene expression in cultured rat brain astrocytes after incubation with vitamin C

Reactive oxygen species have been linked with neuropathological changes in the central nervous system. Epidemiological studies supported the beneficial effect of supplementation of antioxidants. Superoxide dismutase (SOD) is an endogenous enzyme which can scavenge reactive oxygen species. This study investigated the effect of supplementation with ascorbic acid (vitamin C) on the changes of SOD in cultured neurological cells. Rat brain astrocytes (RBA-1 cells) were incubated with vitamin C and divided into four groups: a control group (without vitamin C) and three treatment groups with vitamin C at 40, 80, and 160 micromol/l. After short-term (2 days) and long-term (7 days) incubation, SOD activity, SOD mRNA level by Northern blotting, and SOD protein amounts by Western blotting were measured. After 2 days of incubation, vitamin C resulted in a decrease in the activity of SOD in a concentration-dependent manner (Mn-SOD from 14.8 +/- 1.2 to 13.2 +/- 0.5 U/mg protein and Cu/Zn-SOD from 64.8 +/- 1.2 to 51.7 +/- 0.9 U/mg protein; p < 0.05), and vitamin C also attenuated the Cu/Zn-SOD mRNA level from 100 to 86.3 +/- 6.7%; p < 0.01), whereas the protein amounts of these two SODs remained unchanged. After 7 days of incubation with vitamin C, the SOD activity of RBA-1 cells decreased significantly (Mn-SOD from 14.9 +/- 0.3 to 11.8 +/- 0.3 U/mg protein and Cu/Zn SOD from 61.8 +/- 1.8 to 54.6 +/- 0.9 U/mg protein; p < 0.01), and the mRNA level was also attenuated (Mn-SOD from 100 to 86.8 +/- 8.7% and Cu/Zn-SOD from 100 to 84.7 +/- 4.8%; p < 0.01). These results suggest that 2 and 7 days of incubation with relatively high concentrations of vitamin C may downregulate activity and gene expression of SOD in cultured RBA-1 cells.

Possible underlying mechanism for hydrogen peroxide-induced electromechanical suppression in human atrial myocardium

Hydrogen peroxide (H(2)O(2)) and its metabolites have been shown to exert complex effects on the cardiac muscle during cardiac ischemia/reperfusion. The aim of the present study, by perfusing H(2)O(2) or/and different scavengers of oxygen free radicals (OFRs) into the human atrium, is to characterize the electropharmacological effects of H(2)O(2) and explore its possible underlying mechanism. Atrial tissues obtained from the heart of 19 patients undergoing corrective cardiac surgery were used. Transmembrane action potentials were recorded using the conventional microelectrode technique, and contraction of atrial fibers was evaluated in normal [K](o) (4 mM) in the absence and presence of tested agents. H(2)O(2) (30 micro M-3 mM) had a biphasic effect on the contractile force (an increase, followed by a decrease), reduced the 0-phase depolarizing slope (dV/dt), and prolonged the action potential duration (APD) in a concentration-dependent manner. However, even at a concentration as high as 3 mM, H(2)O(2) did not influence diastolic membrane potential (DMP). Pretreatment with N-(mercaptopropionyl)-glycine (N-MPG), a specific scavenger of the. OH free radical, significantly blocked the 3 mM H(2)O(2)-induced electromechanical changes, while the pretreatment with L-methionine (L-M), a specific scavenger of HOCl free radical, did not. Our data suggests that the toxic effects of H(2)O(2) are caused mainly through the generation of. OH, which is attributed to the electropharmacological inhibitory effects seen in the human atrium.

Inhibition of cyclic strain-induced endothelin-1 secretion by tetramethylpyrazine

1. Chuanxiong is a Chinese herb that has been used widely in China to treat vascular disorders. 2,3,5,6-Tetramethylpyrazine (TMP) is one of the major components purified from chuanxiong. Many studies have demonstrated that TMP is effective in the treatment of cardiovascular diseases. However, the mechanism of action by which TMP exerts relaxation in vascular vessels remains unclear. 2. Endothelin (ET)-1 is a potent vasopressor synthesised by endothelial cells both in culture and in vivo. The aims of the present study were to test the hypothesis that TMP may alter strain-induced ET-1 secretion and to identify the putative underlying signalling pathways in endothelial cells. 3. We showed that TMP inhibits strain-induced ET-1 secretion. 2,3,5,6-Tetramethylpyrazine also inhibits the strain-induced formation of reactive oxygen species (ROS) and phosphorylation of extracellular signal-regulated kinases (ERK) 1/2. Furthermore, pretreating cells with TMP or the anti-oxidant N-acetyl-cysteine decreased strain-induced increases in ET-1 secretion and ERK1/2 phosphorylation. Using a reporter gene assay, TMP and N-acetyl-cysteine were demonstrated to also attenuate the strain-induced activity of the activator protein-1 reporter. 4. In summary, we have demonstrated, for the first time, that TMP inhibits strain-induced ET-1 gene expression, in part by interfering with the ERK1/2 pathway via attenuation of ROS formation. Thus, the present study provides important new insights into the molecular pathways that may contribute to the proposed beneficial effects of TMP in the vascular system.