Icariin enhances endothelial nitric-oxide synthase expression on human endothelial cells in vitro

Icariin, a flavonoid isolated from Epimedii herba, is considered to be the major therapeutical constituent of E. herba. The aim of this study was to investigate the possible protective effects and to clarify the mechanism of icariin on endothelial cells in vitro. Incubation of human umbilical vein endothelial cells (HUVEC) derived EA. hy926 cells with icariin(0.1, 1, 10 micromol l(-1)) from 6 h to 72 h, then the production of NO was measured to evaluate the protective effects of icariin. RT-PCR was employed to confirm the mRNA expression of endothelial nitric oxide synthase (eNOS). Western blotting was used to evaluate the protein expression of eNOS. NO production was enhanced in a time- and concentration-dependent manner (P<0.05), which was well matched with the expression of eNOS mRNA (up to 2.4-fold) and protein (up to 2.5-fold) after long-term incubation with icariin in endothelial cells (P<0.05). Moreover, activated NF-kappaB was increased in EA. hy926 cells incubated with icariin for 24 h, in association with an increase in the expression of eNOS gene. In addition to its long-term effects on eNOS expression, icariin also enhanced the production of bioactive NO in the short-term (after a 5 min incubation, P<0.05). In concert with other effects, the protective effects of icariin on endothelial cells may contribute to the cardiovascular protective effects.     

Puerarin activates endothelial nitric oxide synthase through estrogen receptor-dependent PI3-kinase and calcium-dependent AMP-activated protein kinase

The cardioprotective properties of puerarin, a natural product, have been attributed to the endothelial nitric oxide synthase (eNOS)-mediated production of nitric oxide (NO) in EA.hy926 endothelial cells. However, the mechanism by which puerarin activates eNOS remains unclear. In this study, we sought to identify the intracellular pathways underlying eNOS activation by puerarin. Puerarin induced the activating phosphorylation of eNOS on Ser1177 and the production of NO in EA.hy926 cells. Puerarin-induced eNOS phosphorylation required estrogen receptor (ER)-mediated phosphatidylinositol 3-kinase (PI3K)/Akt signaling and was reversed by AMP-activated protein kinase (AMPK) and calcium/calmodulin-dependent kinase II (CaMKII) inhibition. Importantly, puerarin inhibited the adhesion of tumor necrosis factor (TNF)-α-stimulated monocytes to endothelial cells and suppressed the TNF-α induced expression of intercellular cell adhesion molecule-1. Puerarin also inhibited the TNF-α-induced nuclear factor-κB activation, which was attenuated by pretreatment with N^G-nitro-l-arginine methyl ester, a NOS inhibitor. These results indicate that puerarin stimulates eNOS phosphorylation and NO production via activation of an estrogen receptor-mediated PI3K/Akt- and CaMKII/AMPK-dependent pathway. Puerarin may be useful for the treatment or prevention of endothelial dysfunction associated with diabetes and cardiovascular disease.     

2-(2,4-dihydroxyphenyl)-5-(E)-propenylbenzofuran promotes endothelial nitric oxide synthase activity in human endothelial cells

Endothelial nitric oxide synthase (eNOS) mediates important vaso-protective and immunomodulatory effects. Aim of this study was to examine whether lignan derivatives isolated from the roots of the anti-inflammatory medicinal plant Krameria lappacea influence eNOS activity and endothelial nitric oxide (NO) release. The study was performed using cultured human umbilical vein endothelial cells (HUVECs) and HUVEC-derived EA.hy926 cells. Among the eleven isolated compounds only 2-(2,4-dihydroxyphenyl)-5-(E)-propenylbenzofuran (DPPB) was able to increase eNOS enzyme activity. DPPB (1-10μM) treatment for 24h induced a significant and dose-dependent increase in eNOS activity as determined by the [(14)C]l-arginine/[(14)C]l-citrulline conversion assay. Immunoblotting studies further revealed a time-dependent DPPB-induced increase in eNOS-Ser(1177) and decrease in eNOS-Thr(495) phosphorylation, as well as increased AMPK phosphorylation at Thr(172), whereas Akt phosphorylation at Ser(473) was not affected. Si-RNA-mediated knockdown of AMPK and inhibition of CaMKKβ by STO 609, as well as intracellular Ca(2+) chelation by Bapta AM abolished the stimulating effect of DPPB on eNOS-Ser(1177) and AMPK-Thr(172) phosphorylation. Furthermore, we could show that DPPB increases intracellular Ca(2+) concentrations assessed with the fluorescent dye Fluo-3-AM. DPPB enhances eNOS activity and endothelial NO release by raising intracellular Ca(2+) levels and increases signaling through a CaMKKβ-AMPK dependent pathway.     

Role of eNOS phosphorylation at Ser-116 in regulation of eNOS activity in endothelial cells

Endothelial nitric oxide synthase (eNOS) catalyzes the conversion of L-arginine to L-citrulline and nitric oxide (NO), an important modulator of vascular function. eNOS is regulated post-translationally through phosphorylation/dephosphorylation at a number of specific phosphorylation sites including Ser-116 in the bovine eNOS sequence. Whether phosphorylation of eNOS at Ser-116 in endothelial cells is stimulatory or inhibitory has not previously been definitively determined. In this study we show that mimicking phosphorylation of eNOS at Ser-116 by Asp mutation reduces basal NO release from endothelial cells. Preventing phosphorylation at this site by Ala mutation increases the amount of NO release from endothelial cells in response to agonist stimulation. In addition, mimicking phosphorylation of Ser-116 increases eNOS association with caveolin-1 and reduces the vascular reactivity of intact aortic rings. eNOS phosphorylation at Ser-116, therefore, appears to contribute to negative modulation of eNOS activity and hence to regulation of vascular tone.     

NADPH oxidases regulate endothelial inflammatory injury induced by PM2.5 via AKT/eNOS/NO axis

Fine particulate matter (PM_2.5)-induced detrimental cardiovascular effects have been widely concerned, especially for endothelial cells, which is the first barrier of the cardiovascular system. Among potential mechanisms involved, reactive oxidative species take up a crucial part. However, source of oxidative stress and its relationship with inflammatory response have been rarely studied in PM_2.5-induced endothelial injury. Here, as a key oxidase that catalyzes redox reactions, NADPH oxidase (NOX) was investigated. Human umbilical vein endothelial cells (EA.hy926) were exposed to Standard Reference Material 1648a of urban PM_2.5 for 24 h, which resulted in NOX-sourced oxidative stress, endothelial dysfunction, and inflammation induction. These are manifested by the up-regulation of NOX, increase of superoxide anion and hydrogen peroxide, elevated endothelin-1 (ET-1) and asymmetric dimethylarginine (ADMA) level, reduced nitric oxide (NO) production, and down-regulation of phosphorylation of endothelial NO synthase (eNOS) with increased levels of inducible NO synthase, as well as the imbalance between tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor 1 (PAI-1), and changes in the levels of pro-inflammatory and anti-inflammatory factors. However, administration of NOX1/4 inhibitor GKT137831 alleviated PM_2.5-induced elevated endothelial dysfunction biomarkers (NO, ET-1, ADMA, iNOS, and tPA/PAI-1), inflammatory factors (IL-1β, IL-10, and IL-18), and adhesion molecules (ICAM-1, VCAM-1, and P-selectin) and also passivated NOX-dependent AKT and eNOS phosphorylation that involved in endothelial activation. In summary, PM_2.5-induced NOX up-regulation is the source of ROS in EA.hy926, which activated AKT/eNOS/NO signal response leading to endothelial dysfunction and inflammatory damage in EA.hy926 cells.     

Genistein prevents myocardial hypertrophy in 2-kidney 1-clip renal hypertensive rats by restoring eNOS pathway

Genistein has been shown to increase nitric oxide (NO) production derived from endothelial nitric oxide synthase (eNOS). This study was to investigate whether genistein could prevent myocardial hypertrophy in the 2-kidney 1-clip (2K1C) renohypertensive rat through the NO pathway and to clarify the underlying mechanisms. After the 2K1C operation, plasma angiotensin II increased, and the rats developed significant left ventricular hypertrophy (LVH) and increased collagen I expression. Phosphorylated eNOS, NOS activity, NO production and cGMP contents were markedly decreased in ventricular tissues of 2K1C rats. Chronic administration of genistein to 2K1C rats restored NO, NOS activity, phosphorylated eNOS expression, cGMP in ventricular tissues, and the restoration was parallel with the improvement of LVH and attenuated the excessive ventricular collagen I expression. Genistein also elevated angiotensin II type 2 receptor (AT2) expression, and the effects of genistein on LVH could be completely abolished by an AT2 antagonist, PD123319. The antagonist also reversed the increase in eNOS activity, NO and cGMP restored by genistein in hypertensive rats. We further explored the mechanisms by which genistein restored NO in hypertension and found that genistein significantly enhanced phosphorylated eNOS but left relatively unchanged total eNOS and the eNOS dimer/monomer ratio. In addition, genistein decreased the binding of eNOS with caveolin 3 and simultaneously promoted its binding with calmodulin and heat shock protein 90. We conclude that the preventive effects of genistein on cardiac remodeling induced by 2K1C hypertension are mediated by AT2-dependent NO production.     

银杏黄酮苷对氧化损伤内皮细胞产生NO、eNOS和ICAM-1的影响

目的观察银杏黄酮苷对氧化损伤的人脐静脉内皮细胞（HUVEC）产生NO、内皮型一氧化氮合酶（eNOS）和人可溶性细胞间黏附分子（ICAM-1）的影响。方法体外培养HUVEC,传至3代后,以不同浓度的银杏黄酮苷分别作用于HUVEC,然后进行氧化损伤处理。以硝酸还原酶法测定培养液上清中的NO水平,免疫细胞化学法检测内皮细胞eNOS的表达,ELISA法测定细胞培养液中ICAM-1的含量。结果HUVEC在氧化损伤（H2O2100μmol/L,2h）后产生NO的量显著减少（P〈0.01）,eNOS表达下调,ICAM-1表达上调;银杏黄酮苷可以剂量依赖性的增加内皮细胞NO生成量,上调eNOS的表达,下调ICAM-1表达。结论银杏黄酮苷可能通过增加HUVEC eNOS的表达增加N0的释放、抑制ICAM-1的表达等机制对内皮细胞起保护作用。     

A preliminary study on protective effect of L-citrulline against ischemia-reperfusion induced gastric mucosal lesions in rat

Objectives:

This study was designed to investigate the gastroprotective effect of L-citrulline against gastric ischemia-reperfusion injury.

Materials and Methods:

Sodium pentobarbital-anesthetized rats underwent occlusion of the celiac artery for 30 min, followed by 60 min of reperfusion. Sixty minutes before ischemia, L-citrulline at doses of 300, 600, 900 mg/kg was administered intragastrically. Based on this animal model of gastric ischemia-reperfusion injury, the gastroprotective effect of L-citrulline was assessed by determining and comparing the ulcerative index and the estimation of myeloperoxidase (MPO) activity and malondialdehyde (MDA) level in the gastric mucosal tissues. Moreover, the expression of inducible nitric oxide synthase (iNOS), neuronal nitric oxide synthase (nNOS), and endothelial nitric oxide synthase (eNOS) protein was also determined.

Results:

Intragastric administration of L-citrulline (600 and 900 mg/kg) 60 min before ischemia significantly ameliorated the gastric mucosal damage and inhibited the increase in MPO and MDA contents. Also, the increase in expression of iNOS protein was also prevented by L-citrulline. The expression of nNOS and eNOS was not affected significantly by I/R or L-citrulline.

Conclusion:

The results suggest that L-citrulline, administered exogenously, exhibits gastric protection by inhibition of neutrophil infiltration in rats, which may be related in prevention of the increase in iNOS activity.KEY WORDS: Gastric damage, ischemia-reperfusion, l-citrulline, myeloperoxidase, nitric oxide synthase     

Isoflavone genistein and daidzein up-regulate LPS-induced inducible nitric oxide synthase activity through estrogen receptor pathway in RAW264.7 cells

Isoflavones, such as genistein and daidzein, are found in abundance in soybeans. These plant-derived substances have estrogenic activities and can bind to the estrogen receptors (ERs). In this study, we investigated that the effects of 17beta-estradiol (E2), genistein and daidzein on nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) activity in RAW264.7 cells. We found that these isoflavones significantly increased lipopolysaccharide-induced NO production and iNOS expression as much as E2 at physiological concentrations. Moreover, E2 and isoflavone enhanced the production of tumor necrosis factor-alpha that is one of the important cytokines regarding NO production. The enhancing effects of E2 and isoflavones on NO production were markedly inhibited by not only N(G)-nitro-L-arginine methyl ester (an inhibitor of NOS), but also ICI 182780 (ERs antagonist). Two types of ERs were identified as ERalpha and ERbeta. An ERalpha agonist could increase iNOS expression in RAW264.7 cells, while an ERbeta agonist could not. In conclusion, our results suggest E2, genistein and daidzein activate iNOS, and then up-regulate NO production. This enhancing effect is aroused through ERalpha pathway in RAW264.7 cells.     

Sphingosine kinase 1 is critically involved in nitric oxide-mediated human endothelial cell migration and tube formation

Background and purpose:

Sphingosine kinases (SKs) convert sphingosine to sphingosine 1-phosphate (S1P), which is a bioactive lipid that regulates a variety of cellular processes including proliferation, differentiation and migration.

Experimental approach:

We used the human endothelial cell line EA.hy926 to investigate the effect of nitric oxide (NO) donors on SK-1 expression, and on cell migration and tube formation.

Key results:

We showed that exposure of EA.hy926 cells to Deta-NO (125–1000 µM) resulted in a time- and concentration-dependent up-regulation of SK-1 mRNA and protein expression, and activity with a first significant effect at 250 µM of Deta-NO. The increased SK-1 mRNA expression resulted from an enhanced SK-1 promoter activity. A similar effect was also seen with various other NO donors. In mechanistic terms, the NO-triggered effect occurred independently of cGMP, but involved the classical mitogen-activated protein kinase cascade because the MEK inhibitor U0126 abolished the NO-induced SK-1 expression. The effect of NO was also markedly reduced by the thiol-reducing agent N-acetylcysteine, suggesting a redox-dependent mechanism. Functionally, Deta-NO triggered an increase in the migration of endothelial cells in an adapted Boyden chamber assay, and also increased endothelial tube formation in a Matrigel assay. These responses were both abolished in cells depleted of SK-1.

Conclusions and implications:

These data show that NO donors up-regulate specifically SK-1 expression and activity in human endothelial cells, and SK-1 in turn critically contributes to the migratory capability and tube formation of endothelial cells. Thus, SK-1 may be considered an attractive novel target to interfere with pathological processes involving angiogenesis.     

扇贝裙边糖胺聚糖对OX-LDL致血管内皮细胞损伤的保护作用

目的　研究扇贝裙边提取物糖胺聚糖 (SS GAG)对血管内皮细胞的保护作用 ,进而探讨其抗动脉粥样硬化 (AS)作用机制。方法　本研究采用氧化低密度脂蛋白 (OX LDL)建立体外培养的人脐静脉血管内皮细胞株 (HUVEC ,CRL 2 4 80 )损伤模型 ,用MTT法和化学方法分别从细胞和分子水平观察SS GAG对血管内皮细胞增殖活性及细胞内一氧化氮 (NO)水平和内皮型一氧化氮合酶 (eNOS)活性的影响。结果　OX LDL能明显抑制血管内皮细胞的增殖活性 (P <0 0 1) ,降低血管内皮细胞内NO水平及eNOS的活性 (P <0 0 1) ;用SS GAG(终浓度为 5 0 ,10 0 ,2 0 0mg·L-1)预处理后 ,能逆转上述效应 (P <0 0 1)。结论　OX LDL抑制血管内皮细胞的增殖 ,降低内皮型eNOS的活性 ,减少细胞内NO的生成 ;SS GAG对血管内皮细胞的脂质过氧化物损伤有保护作用。     

芍药内酯苷对高糖诱导的人脐静脉内皮细胞损伤的保护作用

目的 研究芍药内酯苷对高糖损伤的人脐静脉内皮细胞（HUVECs）的保护作用及机制.方法 采用33mmol·L-1的高糖培养基建立HUVECs损伤模型,并在造模前给予不同浓度的芍药内酯苷进行预保护,采用MTT法检测细胞活力,流式细胞术检测细胞凋亡,采用试剂盒检测细胞中内源性一氧化氮合酶（eNOS）和半胱天冬酶-3（Caspase-3）活性以及培养液中一氧化氮（NO）和乳酸脱氢酶（LDH）含量.结果 芍药内酯苷能够剂量依赖性增强细胞活力,降低Caspase-3活性和细胞凋亡率（P＜0.05）,并能增强eNOS的活性和NO的释放量（P＜0.05）.结论 芍药内酯苷对高糖诱导的HUVEs损伤具有保护作用,其机制可能与促进eNOS活性提高、NO释放量增加和抑制Caspase-3活性有关.     

外源性硫化氢改善人脐静脉内皮细胞早熟性衰老与eNOS表达的关系

目的拟探讨硫化氢(H₂S)延缓人脐静脉内皮细胞(HUVECs)衰老与内皮型一氧化氮合酶(eNOS)的关系,为延缓HUVECs衰老提供新的靶点。方法建立60μmol/L过氧化氢(H₂O₂)1 h诱导HUVECs衰老模型;通过检测衰老相关β-半乳糖苷酶(SAβ-Gal)染色阳性率来研究评估外源性硫氢化钠(NaHS)预处理对衰老的作用。同时通过Western blot法和RT-PCR法检测内皮细胞中eNOS蛋白和eNOS mRNA的表达,通过硝酸盐还原酶法检测一氧化氮(NO)含量。结果与对照组相比,HUVECs经60μmol/L H₂O₂预处理后,能显著提高细胞SA β-Gal阳性率。而NaHS的预处理可以显著减少细胞SAβ-Gal阳性率,但可增加eNOS蛋白、eNOS mRNA的表达及增加NO含量。结论 NaHS可以通过上调内皮细胞中eNOS的活性和蛋白表达改善H₂O₂诱导的内皮细胞衰老。     

The effects of modulating eNOS activity and coupling in ischemia/reperfusion (I/R)

The in vivo role of endothelial nitric oxide synthase (eNOS) uncoupling mediating oxidative stress in ischemia/reperfusion (I/R) injury has not been well established. In vitro, eNOS coupling refers to the reduction of molecular oxygen to L-arginine oxidation and generation of L-citrulline and nitric oxide NO synthesis in the presence of an essential cofactor, tetrahydrobiopterin (BH(4)). Whereas uncoupled eNOS refers to that the electron transfer becomes uncoupled to L-arginine oxidation and superoxide is generated when the dihydrobiopterin (BH(2)) to BH(4) ratio is increased. Superoxide is subsequently converted to hydrogen peroxide (H(2)O(2)). We tested the hypothesis that promoting eNOS coupling or attenuating uncoupling after I/R would decrease H(2)O(2)/increase NO release in blood and restore postreperfused cardiac function. We combined BH(4) or BH(2) with eNOS activity enhancer, protein kinase C epsilon (PKC ε) activator, or eNOS activity reducer, PKC ε inhibitor, in isolated rat hearts (ex vivo) and femoral arteries/veins (in vivo) subjected to I(20 min)/R(45 min). When given during reperfusion, PKC ε activator combined with BH(4), not BH(2), significantly restored postreperfused cardiac function and decreased leukocyte infiltration (p?相似文献   

Large-conductance K channel opener CGS7184 as a regulator of endothelial cell function

Large-conductance Ca²⁺-activated potassium (BK_Ca) channels are present in endothelium, but their regulatory role remains uncharacterized. The aim of the present study was to investigate the pharmacological effects of the BK_Ca channel opener ethyl-1-[[(4-chlorophenyl)amino]oxo]-2-hydroxy-6-trifluoromethyl-1H-indole-3-carboxylate (CGS7184) on endothelium in the aorta and coronary circulation, particularly with regard to nitric oxide (NO)-dependent regulation of vascular tone, as well as effects of CGS7184 on NO production, calcium homeostasis, and mitochondrial function in cultured endothelial cells. The vasorelaxant action of CGS7184 was studied in coronary circulation and in the aorta using isolated perfused guinea pig heart and rat aortic rings, respectively. The effects of CGS7184 on calcium homeostasis, mitochondrial membrane potential, NO production, and mitochondrial respiration were tested in cultures of EA.hy 926 endothelial cells. The BK_Ca channel opener CGS7184 caused a concentration-dependent (0.03-3 µM) relaxation of the rat aorta and coronary vasodilatation in the isolated guinea pig heart. Both responses were profoundly inhibited by the nitric oxide (NO) synthase (NOS) inhibitor N^G-nitro-l-arginine methyl ester (l-NAME) (100 µM). CGS7184 (5 µM) also increased basal NO production in EA.hy 926 cells by approximately two-fold. Moreover, CGS7184 induced a concentration-dependent (0.1-10 µM) elevation in intracellular calcium concentration. Interestingly, CGS7184 affected mitochondrial function by causing mitochondrial potential depolarization and an increase in oxygen consumption in EA.hy 926 endothelial cells. The BK_Ca channel opener CGS7184 activates NOS pathways and modulates mitochondrial function in the endothelium. Both effects may be triggered by the CGS7184-induced modulation of intracellular Ca²⁺ homeostasis in EA.hy 926 endothelial cells.     

二苯乙烯苷对人脐静脉内皮细胞一氧化氮合酶及其基因的调节作用

目的探讨二苯乙烯苷（THSG）对人脐静脉内皮细胞（HUVECs）一氧化氮（NO）含量及内皮型一氧化氮合酶（eNOS）活性的影响及其机制。方法培养HUVECs,分为阴性对照组和THSG 1,10,100 μmol&#8226;L－1组,用分光光度比色法检测HUVECs上清液中NO含量和eNOS活性,RT PCR法检测HUVECs eNOS mRNA水平,Western Blot检测HUVECs eNOS蛋白表达。结果与阴性对照组比较,THSG各剂量组HUVECs中NO含量和NOS活性显著提高,eNOS mRNA和蛋白表达上调（P＜0.05）,并呈剂量依赖性。结论THSG可通过上调血管内皮细胞中eNOS表达来增加NO量,从而发挥舒张血管作用。     

Effects of resistin on insulin signaling in endothelial cells

The objective of this study was to investigate the effects of resistin on insulin signaling in human umbilical vein endothelial cells (HUVECs). HUVECs were incubated with recombinant human resistin (0–100 ng/mL) for 24 h. Akt and endothelial nitric oxide synthase (eNOS) phosphorylation levels of endothelial cells under basal or insulin stimulated conditions were measured by Western blot. Nitric oxide (NO) production of HUVECs was also detected. The results showed that resistin could significantly inhibit Akt and eNOS phosphorylation and NO production in endothelial cells under insulin stimulated conditions (P < 0.05 vs control). But under basal conditions, treatment with resistin could result in a decrease in eNOS phosphorylation (P < 0.05 vs control) but had no effect on NO production and Akt phosphorylation levels. These findings suggested that resistin exerted an inhibitory effect on NO production by inhibiting insulin signaling and eNOS phosphorylation in endothelial cells.     

Naphthazarin and methylnaphthazarin cause vascular dysfunction by impairment of endothelium-derived nitric oxide and increased superoxide anion generation.

The effects of the naphthoquinone analogue, naphthazarin (Nap), and its derivative, methylnaphthazarin (MetNap), on vascular reactivity were studied using isolated rat aortic rings and human umbilical vein endothelial cells (HUVECs). In this study, we determined vessel tension, nitric oxide (NO) formation, endothelial nitric oxide synthase (eNOS) activity, eNOS protein expression, and superoxide anion (O2*-) generation in an effort to evaluate the effect of Nap and MetNap on the impairment of the NO-mediated pathway. Lower concentrations of Nap (0.01-1 microM) and MetNap (1-10 microM) concentration-dependently enhanced phenylephrine (PE)-induced vasocontraction and abrogated acetylcholine (ACh)-induced vasorelaxation in an endothelium-dependent manner. On HUVECs, both Nap and MetNap concentration-dependently inhibited NO formation induced by A23187, and also partially inhibited nitric oxide synthase (NOS) activity. eNOS protein expression by HUVECs was not affected by treatment with Nap or MetNap, even within 24h. These data suggest that Nap and MetNap might act as inhibitors of nitric oxide synthesis in the endothelium. In addition, Nap and MetNap were also shown to generate O2*- on HUVECs with short-term treatment. We concluded that Nap and MetNap inhibited agonist-induced relaxation and induced vasocontraction in an endothelium-dependent manner, and these effects might have been due to modification of the NO content by inhibition of NOS activity and bioinactivation through O2*- generation.     

Statins blunt thrombin-induced down-regulation of endothelial nitric oxide synthase expression in human endothelial cells

Thrombin plays a pivotal role in the pathophysiology of acute coronary syndromes by mediating thrombus formation and endothelium-dependent vasomotor dysfunction. In human endothelial cells, prolonged incubation with thrombin down-regulates endothelial nitric oxide synthase (eNOS) expression via activation of Rho. Statins are effective in patients with acute coronary syndromes. These beneficial effects are attributed to their pleiotropic effects and also to an improved lipid profile. We hypothesized that statins may prevent the down-regulation of eNOS induced by thrombin in human endothelial cells. Human umbilical vein endothelial cells were used. Expression and activity of eNOS protein were evaluated by Western blotting and L-citrulline assay, respectively. Rho A membrane translocation was evaluated by Wesern blotting after fractionation. Stimulation of human umbilical vein endothelial cells with thrombin (4 U/mL, 24 h) significantly decreased eNOS expression. The addition of simvastatin significantly prevented thrombin-induced down-regulation of eNOS expression in a concentration-dependent manner (100 nmol/L to 10 micromol/L). Cerivastatin (10 micromol/L) also reversed the down-regulation of eNOS by thrombin. Both simvastatin and cerivastatin-blocked thrombin-induced decrease in NOS activity. Stimulation with thrombin (4 U/mL, 10 min) significantly increased the membrane translocation of Rho A. Simvastatin (10 micromol/L) and cerivastatin (10 micromol/L) significantly decreased thrombin-induced membrane translocation of Rho A. Therefore, statins blunt thrombin-induced down-regulation of eNOS expression in human endothelial cells. This finding provides a novel mechanism of the pleiotropic effects of statins, which may be beneficial for patients with acute coronary syndromes.