Ginsenoside Rb1 prevents homocysteine-induced endothelial dysfunction via PI3K/Akt activation and PKC inhibition

Hyperhomocysteinemia (HHcy), a risk factor for cardiovascular disease, is associated with endothelial dysfunction. Ginsenoside Rb1, the major active constituent of ginseng, potently attenuates homocysteine (Hcy)-induced endothelial damage. However, the underlying mechanism remains unknown. In this study, we have investigated the effect of Ginsenoside Rb1 on Hcy-induced endothelial dysfunction and its underlying signal pathway in vivo and in vitro. Ginsenosides prevented Hcy-induced impairment of endothelium-dependent relaxation and Rb1 reversed Hcy-induced reduction of NO production in a dose-dependent manner as detected by nitrate reductase method. Rb1 activated serine-1177 phosphorylation of endothelial nitric oxide synthase (eNOS) and serine-473 phosphorylation of Akt, while inhibited threonine-495 phosphorylation of eNOS as detected by western blotting. Rb1-induced phosphorylation of serine-1177 was significantly inhibited by wortmannin, PI3K inhibitor or SH-5, an Akt inhibitor, and partially reversed by Phorbol 12-myristate 13-acetate (PMA), a PKC activator. PMA also stimulated phosphorylation of threonine-495 which was inhibited by Rb1. Here we show for the first time that Rb1 prevents Hcy-induced endothelial dysfunction via PI3K/Akt activation and PKC inhibition. These findings demonstrate a novel mechanism of the action of Rb1 that may have value in prevention of HHcy associated cardiovascular disease.     

Protocatechuic Acid Induces Angiogenesis through PI3K‐Akt‐eNOS‐VEGF Signalling Pathway

In this study, we sought to elucidate whether protocatechuic acid contributes to induce angiogenesis as well as its mechanisms. To this end, we examined the role of protocatechuic acid on human brain microvascular endothelial cell line (HBMEC) proliferation, invasion and tube formation in in vitro. For the study of mechanisms involved, the phosphoinositide 3 kinase (PI3K)‐Akt inhibitor LY294002, the endothelial nitric oxide synthase (eNOS) inhibitor L ‐NAME, vascular endothelial growth factor (VEGF), antagonist sFlt‐1 and VEGF receptor blocker SU‐1498 were used. Proliferation of HBMEC was tested by MTT. Scratch adhesion test was used to assess the ability of invasion. A Matrigel tube formation assay was performed to test capillary tube formation ability. PI3K‐Akt‐eNOS‐VEGF pathway activation in HBMEC was tested by Western blot. Our data suggested that protocatechuic acid induces angiogenesis in vitro by increasing proliferation, invasion and tube formation. VEGF expression was increasing by protocatechuic acid and counteracted by VEGF antagonist sFlt‐1, LY294002 and L‐NAME in HBMEC. Tube formation was increased by protocatechuic acid and counteracted by VEGF receptor blocker‐SU1498, LY294002 and L‐NAME. These data suggest that protocatechuic acid may be a candidate therapy for stroke recovery by promoting angiogenesis via a programmed PI3K/Akt/eNOS/VEGF signalling axis.     

Immediate and delayed VEGF-mediated NO synthesis in endothelial cells: role of PI3K,PKC and PLC pathways

1. The mechanism(s) by which vascular endothelial growth factor (VEGF) induces endothelial nitric oxide synthase (eNOS) activation remain(s) unclear up to a certain extent. Therefore, we sought to evaluate the contribution of numerous pathways in VEGF-induced nitric oxide (NO) synthesis by measuring cGMP production. In addition, as VEGF induces the synthesis of NO and platelet-activating factor (PAF), we wanted to assess if the induction of PAF and NO is contributing to the synthesis of each other. 2. Herein, we show that a treatment of endothelial cells with a phospholipase C (PLC) inhibitor (U73122), a calmodulin antagonist (W-7) or with intracellular calcium chelators (EGTA/AM, BAPTA/AM) prevented VEGF-mediated eNOS Ser(1177)-phosphorylation and NO synthesis measured by cGMP production. 3. Pretreatment with phosphatidylinositol 3-kinase (PI3K) (Wortmannin, LY294002) or protein kinase C (PKC) (GF109203X, Ro318220) inhibitors attenuated eNOS Ser(1177)-phosphorylation mediated by VEGF, but did not alter immediate (0-10 min) cGMP synthesis induced by VEGF, but abrogated by up to 84% the delayed (10-30 min) cGMP synthesis. 4. Pretreatment with PAF synthesis inhibitors or with PAF receptor antagonists did not abrogate neither eNOS Ser(1177)-phosphorylation nor cGMP synthesis mediated by VEGF. 5. In conclusion, VEGF induces an immediate cGMP synthesis through the PLC-Ca2+/CaM pathway, and that the induction of delayed cGMP synthesis implies Akt and PKC activity.     

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.     

Metformin attenuates ventricular hypertrophy by activating the AMP-activated protein kinase-endothelial nitric oxide synthase pathway in rats

1. Metformin is an activator of AMP‐activated protein kinase (AMPK). Recent studies suggest that pharmacological activation of AMPK inhibits cardiac hypertrophy. In the present study, we examined whether long‐term treatment with metformin could attenuate ventricular hypertrophy in a rat model. The potential involvement of nitric oxide (NO) in the effects of metformin was also investigated. 2. Ventricular hypertrophy was established in rats by transaortic constriction (TAC). Starting 1 week after the TAC procedure, rats were treated with metformin (300 mg/kg per day, p.o.), N^G‐nitro‐l‐ arginine methyl ester (l ‐NAME; 50 mg/kg per day, p.o.) or both for 8 weeks prior to the assessment of haemodynamic function and cardiac hypertrophy. 3. Cultured cardiomyocytes were used to examine the effects of metformin on the AMPK–endothelial NO synthase (eNOS) pathway. Cells were exposed to angiotensin (Ang) II (10^?6 mol/L) for 24 h under serum‐free conditions in the presence or absence of metformin (10^?3 mol/L), compound C (10^?6 mol/L), l ‐NAME (10^?6 mol/L) or their combination. The rate of incorporation of [³H]‐leucine was determined, western blotting analyses of AMPK–eNOS, neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) were undertaken and the concentration of NO in culture media was determined. 4. Transaortic constriction resulted in significant haemodynamic dysfunction and ventricular hypertrophy. Myocardial fibrosis was also evident. Treatment with metformin improved haemodynamic function and significantly attenuated ventricular hypertrophy. Most of the effects of metformin were abolished by concomitant l ‐NAME treatment. l ‐NAME on its own had no effect on haemodynamic function and ventricular hypertrophy in TAC rats. 5. In cardiomyocytes, metformin inhibited AngII‐induced protein synthesis, an effect that was suppressed by the AMPK inhibitor compound C or the eNOS inhibitor l ‐NAME. The improvement in cardiac structure and function following metformin treatment was associated with enhanced phosphorylation of AMPK and eNOS and increased NO production. 6. The findings of the present study indicate that long‐term treatment with metformin could attenuate ventricular hypertrophy induced by pressure overload via activation of AMPK and a downstream signalling pathway involving eNOS–NO.     

Angiostatin Inhibition of Vascular Endothelial Growth Factor– Stimulated Nitric Oxide Production in Endothelial Cells

Angiostatin (AS), a proteolytic fragment of plasminogen, is a potent antiangiogenic factor. It was reported that AS attenuates the vasodilatory response to vascular endothelial growth factor (VEGF) in isolated interventricular arterioles. Here, we investigated the effect of AS on nitric oxide (NO) production in human umbilical vein endothelial cells (HUVECs). AS inhibited VEGF-stimulated NO production in a dose-dependent manner, whereas AS alone did not affect basal NO production. Disruption of kringle structures by reduction of disulfide bonds resulted in the loss of the inhibitory effect of AS on VEGF-stimulated NO production. To elucidate how AS might impair VEGF activation of endothelial NO synthase (eNOS), we further examined whether AS would affect Ca²⁺-dependent and -independent pathways of eNOS activation. AS had no effect on the transient increase in cytosolic Ca²⁺ levels elicited by VEGF. In contrast, AS prevented VEGF-potentiated eNOS phosphorylation at Ser1177. These results clearly indicate that AS inhibits VEGF-stimulated NO production in HUVECs without affecting basal NO production. The kringle structures of AS are required for this effect, and impairment of Ser1177 phosphorylation of eNOS might be involved in the inhibition of VEGF-stimulated NO production by AS.     

Beneficial effect of the oligomerized polyphenol oligonol on high glucose-induced changes in eNOS phosphorylation and dephosphorylation in endothelial cells

Background and purpose:

Hyperglycaemia is known to reduce nitric oxide (NO) bioavailability by modulating endothelial NO synthase (eNOS) activity, and polyphenols are believed to have cardiovascular benefit. One possible mechanism could be through interaction with eNOS.

Experimental approach:

The effects of the oligomerized polyphenol oligonol on eNOS phosphorylation status and activity were examined in porcine aortic endothelial cells cultured in high glucose concentrations.

Key results:

Exposure to high glucose concentrations strongly inhibited eNOS phosphorylation at Ser-1177 and dephosphorylation at Thr-495 in bradykinin (BK)-stimulated cells. These inhibitory effects of high glucose were significantly prevented by treatment with oligonol. Akt and p38 mitogen-activated protein kinase (MAPK) were activated in BK-stimulated cells. High glucose inhibited Akt activation but enhanced p38 MAPK activation, both of which were reversed by oligonol treatment. The phosphatidylinositol 3-kinase inhibitor wortmannin blocked the reversal by oligonol of phosphorylation at Ser-1177, but not dephosphorylation at Thr-495, in BK-stimulated cells exposed to high glucose. The effect of oligonol on BK dephosphorylation under high glucose was mimicked by protein kinase C (PKC) ε-neutralizing peptides. These data suggest that the effects of oligonol on high glucose-induced attenuation of eNOS Ser-1177 phosphorylation and Thr-495 dephosphorylation may be regulated by Akt activation and PKCε inhibition respectively. Oligonol also prevented high glucose-induced attenuation of BK-stimulated NO production.

Conclusions and implications:

Oligonol prevented the impairment of eNOS activity induced by high glucose through reversing altered eNOS phosphorylation status. This mechanism may underlie the beneficial cardiovascular health effects of this oligomerized polyphenol.     

Mechanisms underlying nebivolol-induced endothelial nitric oxide synthase activation in human umbilical vein endothelial cells

1. Nebivolol (NEB) has been shown to be a selective blocker of beta1-adrenoceptors with additional vasodilating properties that are mediated, at least in part, by an endothelial-dependent liberation of nitric oxide (NO). In the present study, we investigated the underlying mechanisms of NEB-induced vasodilation. 2. Immunohistochemical staining of endothelial nitric oxide synthase (eNOS) was performed in the absence and presence of NEB in human umbilical vein endothelial cells (HUVEC). In addition, we measured the release of nitric oxide (NO) using diaminofluorescein. Metoprolol (MET) was used for comparison. 3. Nebivolol, but not MET (each at 10 micromol/L), caused a time-dependent increase in NO release from HUVEC, as demonstrated by an increase in DAF fluorescence at 0 versus 10 min (+234 +/- 7 and 55 +/- 22% basal, respectively). Blockade of beta3-adrenoceptors by SR 59230A (1 micromol/L) partially reduced the NEB-induced increase in DAF fluorescence. Complete inhibition of NEB-induced NO liberation was achieved by the simultaneous blockade of beta3-adrenoceptors and oestrogen receptors (with 1 micromol/L ICI 182,780). 4. Application of NEB significantly increased eNOS translocation and serine 1177 phosphorylation of eNOS. However, NEB did not alter eNOS-phosphorylation at threonine 495 and at serine 114. 5. In conclusion, the endothelium-dependent NO liberation induced by NEB is due to stimulation of beta3-adrenoceptors and oestrogen receptors and coincides with eNOS translocation and a phosphorylation at eNOS-serine 1177. These characteristics of NEB may be beneficial not only when treating patients suffering from cardiovascular disease, but may also prevent further deterioration of endothelial dysfunction.     

Protective effect of ligustrazine against myocardial ischaemia reperfusion in rats: the role of endothelial nitric oxide synthase

1. The aim of the present study was to determine whether ligustrazine (2,3,5,6-tetramethylpyrazine; TMP) exerts a cardioprotective effect during myocardial ischaemia reperfusion (IR), and to investigate the underlying mechanisms and the role of endothelial nitric oxide synthase (eNOS) in cardioprotection. 2. Sprague-Dawley rats were divided into a sham group and five IR groups: IR control, TMP pretreated, TMP + wortmannin (a phosphatidylinositol 3-kinase (PI3K) inhibitor), N(G) -nitro-L-arginine methyl ester (L-NAME; a NOS inhibitor) and TMP + L-NAME. IR was produced by 35 min of regional ischaemia followed by 120 min of reperfusion. Myocardial infarct size, oxidative stress, myocardial apoptosis, nitric oxide (NO) production, and expression of phosphorylated protein kinase B (Akt) and eNOS were measured. 3. TMP markedly decreased infarct size and attenuated myocardial apoptosis, as evidenced by a decrease in the apoptotic index and reduced caspase-3 activity. TMP treatment caused a marked increase in NO production. Cotreatment with wortmannin or L-NAME completely blocked the TMP-induced NO increase. TMP induced phosphorylation of Akt at Ser 473 (1.61 ± 0.18 vs 0.79 ± 0.10 in the IR control group) and phosphorylation of eNOS at Ser1177 (1.87 ± 0.33 vs 0.94 ± 0.22 in the IR control group). Wortmannin abrogated the phosphorylation of Akt and eNOS induced by TMP. 4. These data suggest that ligustrazine has anti-apoptotic and cardioprotective effects against myocardial IR injury and that it acts through the PI3K/Akt pathway. In addition, the phosphorylation of eNOS with subsequent NO production was found to be an important downstream effector that contributes significantly to the cardioprotective effect of TMP.     

Regulation of endothelial nitric oxide synthase and asymmetric dimethylarginine by matrine attenuates isoproterenol-induced acute myocardial injury in rats

Objectives This study was designed to investigate the cardioprotective effects of matrine on regulation of endothelial nitric oxide synthase (eNOS) and asymmetric dimethylarginine (ADMA) in isoproterenol‐induced acute myocardial ischaemic rats. Methods Male Sprague–Dawley rats were pretreated with matrine (200, 100 and 50 mg/kg) orally for 10 days. Acute myocardial injury was induced in rats by subcutaneous injection of isoproterenol. Serum and haemodynamic parameters, histopathological variables and expression of protein levels were analysed. Key findings Oral administration of matrine (200, 100 and 50 mg/kg) significantly attenuated isoproterenol‐induced cardiac necrosis and left ventricular dysfunction. Matrine treatment restored impaired ventricular Akt and eNOS protein expression with concomitant increased phosphorylation of Akt (Ser473) and eNOS (Ser1177), and also restored glycogen synthase kinase 3β activity, as indicated by increased phosphorylation at Ser 9. Moreover, treatment with matrine had no effect on the isoproterenol‐induced elevated protein arginine methyltransferase 1 protein expression, but could significantly normalize the reduced dimethylarginine dimethylaminohydrolase 2 expression and attenuate the increased serum level of ADMA. The expression of catechol‐o‐methyltransferase and monoamine oxidase did not differ among all groups (all P > 0.05). Conclusions Our results suggested that matrine protects against isoproterenol‐induced myocardial ischaemia via eNOS and ADMA pathway.     

Hyperinsulinaemia increases the gene expression of endothelial nitric oxide synthase and the phosphatidylinositol 3-kinase/Akt pathway in rat aorta

1. Hyperinsulinaemia has been reported to be an independent risk factor for cardiovascular diseases. Insulin stimulates both the phosphatidylinositol 3-kinase (PI3-K)/Akt and mitogen-activated protein kinase (MAPK) pathways. To investigate the direct effects of insulin on vascular tissues, we examined the gene and protein expression of insulin signalling molecules, endothelial nitric oxide synthase (eNOS) and MAPK in aortas obtained from established hyperinsulinaemic rats under deep urethane anaesthesia (1.2 g/kg, i.p.). 2. High plasma insulin levels significantly enhanced the gene and protein expression of eNOS in aortas. This was accompanied not only by increased mRNA levels of insulin receptor substrate (IRS)-1, IRS-2, PI3-K and Akt, but also by a high protein content of Akt and phospho-Akt (Ser473). 3. In contrast, MAPK mRNA levels were decreased in hyperinsulinaemic rats compared with normoinsulinaemic rats. 4. Insulin receptor mRNA levels were also lower in insulin-treated rats rather than controls. The overexpression of mRNA for vascular endothelial growth factor (VEGF) and insulin-like growth factor (IGF)-I receptor was also observed in aortas from hyperinsulinaemic rats. 5. To our knowledge, these data provide the first direct measurements of the mRNA of insulin signalling molecules and the downstream eNOS and MAPK. We conclude that hyperinsulinaemia itself can lead to the upregulation of eNOS and the PI3-K/Akt pathway in the vasculature and may also induce the overexpression of VEGF and IGF-I receptor genes.     

PGC-1α ameliorates AngiotensinII-induced eNOS dysfunction in human aortic endothelial cells

Increasing evidences support that PGC-1α participates in regulating endothelial homeostasis, in part by mediating endothelial nitric oxide (NO) synthase (eNOS) activity and NO production. However, the molecular mechanisms by which PGC-1α regulates eNOS activity are not completely understood. In the present study, we investigated the effects of PGC-1α on eNOS dysfunction and further explore the underlying mechanisms. The results showed that PGC-1α expression was downregulated after AngiotensinII (AngII) treatment and paralleled with the decreased NO generation in human aortic endothelial cells. Overexpression of PGC-1α with adenovirus or pharmacological agonist ameliorated AngII-induced the decrease of NO generation, evidenced by the restoration of cGMP and nitrite concentration. Rather than affecting eNOS expression and uncoupling, PGC-1α inhibited AngII-induced decrease of eNOS serine 1177 phosphorylation through activation of PI3K/Akt signaling. In addition, PGC-1α overexpression suppressed AngII-induced the increase of PP2A-A/eNOS interaction and PP2A phosphatase activity, with a concomitant decrease in PP2A phosphorylation, leading to eNOS serine 1177 phosphorylation. However, pharmacological inhibition of PI3K/Akt signaling blunted the observed effect of PGC-1α on PP2A activity. Taken together, our findings suggest that PGC-1α overexpression improves AngII-induced eNOS dysfunction and that improved eNOS dysfunction is associated with activated PI3K/Akt pathway, impaired PP2A activity and reduced PP2A-A/eNOS association. These date indicate that forced PGC-1α expression may be a novel therapeutic approach for endothelial dysfunction.     

Aliskiren improves endothelium‐dependent relaxation of thoracic aorta by activating PI3K/Akt/eNOS signal pathway in SHR

Aliskiren, a direct renin blocker, has been approved for the treatment of hypertension. However, the potential role of aliskiren on vascular endothelial function in spontaneously hypertensive rats (SHR) remains unclear. In the present study, male SHRs at 12 weeks of age were orally administrated 30 mg/kg per day or 60 mg/kg per day aliskiren. After a 4‐week treatment, aliskiren showed a significant effect on the reduction of blood pressure at a dosage of 60 mg/kg per day, but not of 30 mg/kg per day. Moreover, both dosages of aliskiren improved endothelium‐dependent relaxation, reduced dihydroethidium fluorescence intensity, decreased level of malondialdehyde but heightened total antioxidant capacity and superoxide dismutase activity in thoracic aorta in SHR. Aliskiren also markedly increased expression of p85α, an important subunit of phosphatidylinositol 3 kinase (PI3K), enhancing phosphorylation of protein kinase B (Akt) at Ser473 and endothelial nitric oxide synthase (eNOS) at Ser1177, as well as cyclic guanosine‐3′5′‐monophosphate (cGMP, a sensitive index of biological activity of nitric oxide) concentration. Furthermore, both anti‐oxidative and endothelium protective effects of aliskiren were diminished when PI3K was inhibited in vivo. The data presented here indicates that, aliskiren improves endothelium‐dependent relaxation of thoracic aorta in SHR, predominantly through attenuating oxidative stress and activation of the PI3K/Akt/eNOS pathway. These data might propose novel strategies to prevent and improve vascular endothelial dysfunction.     

Salidroside improves endothelial function and alleviates atherosclerosis by activating a mitochondria-related AMPK/PI3K/Akt/eNOS pathway

Salidroside (SAL) is a phenylpropanoid glycoside isolated from the medicinal plant Rhodiola rosea. A recent study has reported that SAL can efficiently decrease atherosclerotic plaque formation in low-density lipoprotein receptor-deficient mice. This study was to investigate the molecular mechanism of antiatherogenic effects of SAL. Given the importance of endothelial nitric oxide synthase (eNOS) in atherosclerosis, we sought to elucidate whether SAL could stimulate eNOS activation and also to explore its upstream signaling pathway. Six-week old apoE^−/− male mice were fed a high-fat diet for 8 weeks and then were administered with SAL for another 8 weeks. SAL significantly improved endothelial function associated with increasing eNOS activation, thus reduced the atherosclerotic lesion area. SAL increased eNOS-Ser1177 phosphorylation and decreased eNOS-Thr495 phosphorylation, indicative of eNOS activation in endothelium. The aortic sinus lesions in SAL treated mice displayed reduced inflammation. SAL significantly activated AMP-activated protein kinase (AMPK). Both AMPK inhibitor and AMPK small interfering RNA (siRNA) abolished SAL-induced Akt-Ser473 and eNOS-Ser1177 phosphorylation. In contrast, LY294002, the PI3k/Akt pathway inhibitor, abolished SAL-induced phosphorylation and expression of eNOS. High performance liquid chromatography (HPLC) analysis revealed that SAL decreased cellular ATP content and increased the cellular AMP/ATP ratio, which was associated with the activation of AMPK. SAL was found to decrease the mitochondrial membrane potential (ΔΨm), which is a likely consequence of reduced ATP production. The action of SAL to reduce atherosclerotic lesion formation may at least be attributed to its effect on improving endothelial function by promoting nitric oxide (NO) production, which was associated with mitochondrial depolarization and subsequent activation of the AMPK/PI3K/Akt/eNOS pathway. Taken together, our data described the effects of SAL on mitochondria, which played critical roles in improving endothelial function in atherosclerosis.     

ZnS nanoarchitectures induced dysfunction of vascular endothelial cells in vitro and in vivo

ZnS nanoarchitectures have been intensively investigated recently because of their applications in optoelectronics and adsorption capacity. The potential hazard of ZnS nanoarchitectures is not well known. In this study, we investigated the toxicity of ZnS nanoarchitectures on vascular endothelial cell (VEC) in vitro and in vivo. The results showed that ZnS could inhibit human umbilical vein endothelial cell (HUVEC) proliferation at 50 and 200 μg/mL. Endothelial nitric oxide synthase (eNOS) activity, nitric oxide (NO), and reactive oxygen species productions were increased, which was companied with the decrease in caveolin‐1 level. The endothelium of the aortic root was damaged and the NO levels in serum were elevated in the mice treated with 5 or 10 mg/kg ZnS for 3 and 6 days, but the body could repair the damage. The data suggested that the high concentration of ZnS could induce dysfunction of VECs through decreasing caveolin‐1 and elevation of the eNOS activity and thus present toxicity. © 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 755–768, 2015.     

Chronic activation of AMP-activated protein kinase prevents 20-hydroxyeicosatetraenoic acid-induced endothelial dysfunction

1. 20-Hydroxyeicosatetraenoic acid (20-HETE) is a potent vasoconstrictor involved in vascular dysfunction and blood pressure regulation. Studies have revealed strong associations between 20-HETE and endothelial dysfunction; however, the signalling mechanisms are largely unknown. Therefore, the aim of the present study was to investigate the effect of 20-HETE on the association between endothelial nitric oxide synthase (eNOS) and heat shock protein 90 (Hsp90). 2. In mouse aortic rings, 20-HETE significantly enhanced the constriction to phenylephrine and inhibited the relaxation to acetylcholine (P=0.05 vs control rings). In mice with chronic AMP-activated protein kinase (AMPK) activation, this protected against the negative effects of 20-HETE (P<0.05). Immunoprecipitation of eNOS in human umbilical vein endothelial cells treated with 20-HETE revealed a decrease in basal and vascular endothelial growth factor-stimulated Hsp90 association with eNOS (P<0.05). Pretreatment of cells with 5'-aminoimidazole-4-carboxyamide-ribonucleoside (AICAR; a chronic activator of AMPK) prevented the loss of Hsp90 association with eNOS following 20-HETE treatment. Treatment with 20-HETE for 24 h induced an increase in eNOS phosphorylation that was not seen following acute treatment (30 min). The increased eNOS phosphorylation was accompanied by transient changes in Akt phosphorylation. 3. In conclusion, 20-HETE impairs eNOS-Hsp90 association, which can be reversed by chronic activation of AMPK. This provides a mechanism for reduced nitric oxide bioactivity and endothelial dysfunction in diseases with elevated 20-HETE levels, such as hypertension.     

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.     

阿司匹林对人主动脉血管内皮细胞炎性损伤的保护作用

目的：研究阿司匹林（aspirin,Asp）对脂多糖（lipopolysaccharide,LPS）诱导人主动脉内皮细胞（human aortic endothelial cells,HAECs）损伤的保护作用,并进一步阐明其对一氧化氮合酶（NOS）及血管内皮生长因子（VEGF）及其相关受体信号的调控。方法：LPS建立HAECs损伤模型。苏木精-伊红（HE）染色观察细胞形态;MTT法、划痕实验分析HAECs损伤修复能力;ELISA测定一氧化氮（NO）含量;Western blot检测内皮型一氧化氮合酶（eNOS）、诱导型一氧化氮合酶（iNOS）、VEGF和血管内皮生长因子受体-2（VEGFR-2）蛋白表达。结果：给药12 h后Asp明显改善LPS（5 mg·L^-1）导致的细胞损伤、提高修复能力（P<0.05）,并上调NO分泌量及VEGF、VEGFR-2的蛋白表达（P<0.01）;升高eNOS蛋白的表达（P<0.01）。而给药24 h后阿司匹林显著下调LPS导致的NO分泌量及iNOS、VEGF、VEGFR-2的蛋白表达升高,同时升高eNOS蛋白的表达（P<0.01）。结论：阿司匹林对LPS诱导的血管内皮细胞炎性损伤的保护作用与调节NOS/NO和VEGF及其受体的动态平衡密切相关。     

Methylglyoxal scavengers attenuate endothelial dysfunction induced by methylglyoxal and high concentrations of glucose

BACKGROUND AND PURPOSE

Endothelial dysfunction is a feature of hypertension and diabetes. Methylglyoxal (MG) is a reactive dicarbonyl metabolite of glucose and its levels are elevated in spontaneously hypertensive rats and in diabetic patients. We investigated if MG induces endothelial dysfunction and whether MG scavengers can prevent endothelial dysfunction induced by MG and high glucose concentrations.

EXPERIMENTAL APPROACH

Endothelium-dependent relaxation was studied in aortic rings from Sprague-Dawley rats. We also used cultured rat aortic and human umbilical vein endothelial cells. The MG was measured by HPLC and Western blotting and assay kits were used.

KEY RESULTS

Incubation of aortic rings with MG (30 µM) or high glucose (25 mM) attenuated endothelium-dependent, acetylcholine-induced relaxation, which was restored by two different MG scavengers, aminoguanidine (100 µM) and N-acetyl cysteine (NAC) (600 µM). Treatment of cultured endothelial cells with MG or high glucose increased cellular MG levels, effects prevented by aminoguanidine and NAC. In cultured endothelial cells, MG and high glucose reduced basal and bradykinin-stimulated nitric oxide (NO) production, cGMP levels, and serine-1177 phosphorylation and activity of endothelial NO synthase (eNOS), without affecting threonine-495 and Akt phosphorylation or total eNOS protein. These effects of MG and high glucose were attenuated by aminoguanidine or NAC.

CONCLUSIONS AND IMPLICATIONS

Our results show for the first time that MG reduced serine-1177 phosphorylation, activity of eNOS and NO production. MG caused endothelial dysfunction similar to that induced by high glucose. Specific and safe MG scavengers have potential to prevent endothelial dysfunction induced by MG and high glucose concentrations.     

Endothelial caveolar subcellular domain regulation of endothelial nitric oxide synthase

相似文献