Aliskiren protects against myocardial ischaemia‐reperfusion injury via an endothelial nitric oxide synthase dependent manner

Aliskiren, a direct renin inhibitor, has shown potent ability to attenuate hypertension. Our previous research has found that aliskiren protected against myocardial ischaemia‐reperfusion (I/R) injury and enhanced phosphorylation of endothelial nitric oxide synthase (eNOS) in spontaneously hypertensive rats. However, whether the cardioprotective effect of aliskiren against myocardial I/R injury was eNOS‐dependent is unknown. In the present study, 12‐week‐old male eNOS knockout (eNOS^?/?) and wild‐type C57BL/6J mice (WT) were orally administrated with the dose of 50 mg/kg per day of aliskiren. After a 4‐week treatment, aliskiren decreased blood pressure in eNOS^?/? mice, and reduced renin‐angiotension II levels in both eNOS^?/? and WT mice. Aliskiren also improved left ventricular ejection fraction (EF) and fractional shortening (FS), decreased myocardial infarct size, reduced creatine kinase (CK) and lactate dehydrogenase (LDH) activity in plasma, attenuated dihydroethidium (DHE) fluorescence and levels of malondialdehyde (MDA), enhanced superoxide dismutase (SOD) activity and total antioxidant capacity (T‐AOC) in myocardium, increased SOD and thioredoxin (Trx) proteins expression in WT mice subjected to 30 minutes of ischaemia followed by reperfusion for 24 hours. However, aliskiren failed to restore all of the above indices in eNOS^?/? mice subjected to the same I/R injury. Our study indicated that aliskiren protected against myocardial I/R injury via an eNOS dependent manner.     

内皮源性超极化因子对内皮一氧化氮合酶基因表达的调节

目的　以内皮细胞产生NO的关键酶———eNOS(内皮一氧化氮合酶 )为研究目标 ,探讨外源性内皮源性超极化因子EDHF(EETs)对内皮细胞合成NO的影响。方法　在原代培养 3～ 4代以内的牛主动脉内皮细胞中 ,分别加入不同浓度 (5 0～ 2 0 0nmol·L-1)的 8,9 EET、11,12 EET、14 ,15 EET ,作用 1h后用不同的方法收获细胞。用WesternBlot以及NorthernBlot方法检测EETs对eNOS基因表达的影响 ;同时通过检测L [3 H] 精氨酸转化为L [3 H] 瓜氨酸的量研究EETs对NOS活性的影响。结果　显示 8,9 EET、11,12 EET、14 ,15 EET均呈浓度依赖性地增加eNOS蛋白质的表达 ,并提高eNOSmRNA表达水平以及NOS酶活性。结论　外源性EDHF对eNOS基因表达是一种正反馈调节作用 ,从而能够促进内皮细胞NO的产生 ,通过药物调节内皮表氧化酶进而促进eNOS基因表达可作为防治心血管疾病的新策略     

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.     

内源性一氧化氮合酶抑制物:一种新的内皮功能不全预测因子

血管内皮功能不全是多种心血管疾病的共同病理基础 .内源性一氧化氮合酶 (NOS)抑制物能阻止内皮细胞 (NO)合成 ,导致血管内皮功能降低 .高血压 ,动脉粥样硬化 ,糖尿病血管并发症等心血管疾病的内皮功能不全与内源性 NOS抑制物含量升高密切相关 .内源性 NOS抑制物可作为内皮功能不全的预测因子 ;阻止或抑制内源性 NOS抑制物生成可能是寻找防治心血管疾病药物的新途径 .     

Elevated serum endogenous inhibitor of nitric oxide synthase and endothelial dysfunction in aged rats

1. The purpose of the present study was to determine the relationship between endothelial dysfunction and the endogenous inhibitor of nitric oxide synthase NG,NG'-asymmetric dimethylarginine (ADMA) in aged rats. 2. Studies were performed in male adult Sprague-Dawley rats (6 months old; n = 8) and in aged rats (20 months old; n = 8). Serum levels of ADMA and L-arginine were measured by high-performance liquid chromatography and responses of endothelium-intact aortic rings to acetylcholine (ACh) were tested. Nitric oxide synthase activity in kidney tissue and serum concentrations of nitrite, a stable end-product of nitric oxide, were assayed and serum contents of malondialdehyde, derived from lipid peroxidation and serum lipid and creatinine level were determined. 3. Serum levels of ADMA increased significantly in aged rats compared with adult rats (P < 0.01), whereas serum levels of L-arginine were similar in both groups (P = NS). Accordingly, the ratio of L-arginine/ADMA in old rats was lower than that in young rats (P < 0.01). Endothelium-dependent relaxation responses to ACh in aortic rings from aged rats were impaired and these impaired responses were improved by pre-incubation of aortic rings with L-arginine. 4. Nitric oxide synthase activity in the kidney, together with serum concentration of nitrite, was significantly decreased and serum contents of malondialdehyde, cholesterol and triglycerides were increased in old compared with young rats. However, the serum creatinine level was not significantly different between adult and aged rats. 5. Endogenous ADMA may be a contributor to age-related endothelial dysfunction and increases in endogenous ADMA may be linked to lipid peroxidation in aged rats.     

Inhibition of inducible nitric oxide synthase attenuates acute endotoxin-induced lung injury in rats

1. In the present study, we investigated the effects of the inducible nitric oxide (iNOS) inhibitors S-methylisothiourea (SMT) and l-N(6)-(1-iminoethyl)-lysine (l-Nil) on endotoxin-induced acute lung injury (ALI), as well as the associated physiological, biomedical and pathological changes, in anaesthetized Sprague-Dawley rats and in rat isolated perfused lungs. 2. Endotoxaemia was induced by an intravenous (i.v.) infusion of lipopolysaccharide (LPS; Escherichia coli 10 mg/kg). Lipopolysaccharide produced systemic hypotension and tachycardia. It also increased the lung weight/bodyweight ratio, lung weight gain, exhaled nitric oxide (NO), the protein concentration in bronchoalveolar lavage and microvascular permeability. 3. Following infusion of LPS, plasma nitrate/nitrite, methyl guanidine, pro-inflammatory cytokines (tumour necrosis factor-alpha and interleukin-1beta) were markedly elevated. Pathological examination revealed severe pulmonary oedema and inflammatory cell infiltration. Pretreatment with SMT (3 mg/kg, i.v.) or l-Nil (3 mg/kg, i.v.) significantly attenuated the LPS-induced changes and ALI. 4. The results suggest that the inflammatory responses and ALI following infusion of LPS are due to the production of NO, free radicals and pro-inflammatory cytokines through the iNOS system. Inhibition of iNOS is effective in mitigating the endotoxaemic changes and lung pathology. Inhibitors of iNOS may be potential therapeutic agents for clinical application in patients with acute respiratory distress syndrome.     

Differential sensitivity of basal and acetylcholine-induced activity of nitric oxide to blockade by asymmetric dimethylarginine in the rat aorta

Background and purpose:

Previous work has shown that N^G-monomethyl-l-arginine (l-NMMA) paradoxically inhibits basal, but not ACh-stimulated activity of nitric oxide in rat aorta. The aim of this study was to determine if the endogenously produced agent, asymmetric N^G, N^G-dimethyl-l-arginine (ADMA), also exhibits this unusual selective blocking action.

Experimental approach:

The effect of ADMA on basal nitric oxide activity was assessed by examining its ability to enhance phenylephrine (PE)-induced tone in endothelium-containing rings. Its effect on ACh-induced relaxation was assessed both in conditions where ADMA greatly enhanced PE tone and where tone was carefully matched with control tissues at a range of different levels.

Key results:

ADMA (100 µM) potentiated PE-induced contraction, consistent with inhibition of basal nitric oxide activity. Higher concentrations (300–1000 µM) had no greater effect. Although ADMA (100 µM) also appeared to block ACh-induced relaxation when it enhanced PE tone to maximal levels, virtually no block was seen at intermediate levels of tone in the presence of ADMA. Even ADMA at 1000 µM had no effect on the maximal relaxation to ACh, although it produced a small (two- to threefold) reduction in sensitivity. ADMA and l-NMMA, like l-arginine (all at 1000 µM), protected ACh-induced relaxation against blockade by l-NAME (30 µM).

Conclusions and implications:

In the rat aorta, ADMA, like l-NMMA, blocks basal activity of nitric oxide, but has little effect on that stimulated by ACh. Further studies are required to explain these seemingly anomalous actions of ADMA and l-NMMA.     

同型半胱氨酸对内皮细胞一氧化氮合酶活力及基因表达的影响

目的 观察同型半胱氨酸(Hcy)对培养的人脐静脉内皮细胞(HUVEC)一氧化氮合酶(eNOS)活力及其基因表达的动态影响.方法 10、30、100、300 μmol · L-1Hcy与HUVEC分别培养24、48、72 h后,用HPLC测定细胞内不对称二甲基精氨酸(ADMA)的含量,反转录聚合酶链反应(RT-PCR)检测细胞内eNOS mRNA的表达,并分别测定细胞二甲基精氨酸二甲基氨基水解酶(DDAH)、eNOS的活力和NO的含量.结果 HUVEC经不同浓度Hcy分别处理24、48、72 h后,其细胞内ADMA聚积增多,DDAH活性和eNOS活力降低,NO生成减少,且呈时间和浓度依赖性.但只有100 μmol · L-1 Hcy与HUVEC作用72 h时,才引起eNOS mRNA表达的减少.结论 Hcy对内皮功能的损伤可能通过抑制DDAH活性,引起ADMA聚积,从而降低eNOS活力,导致NO生成减少.此外,eNOS mRNA表达的抑制也是Hcy诱导的内皮功能障碍的机制之一.     

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.     

The effect of puerarin on serum nitric oxide concentration and myocardial eNOS expression in rats with myocardial infarction

Puerarin (1) is a major effective ingredient extracted from the traditional Chinese medicine Ge-gen (Radix Puerariae, RP). Recently, puerarin has been used to treat patients with coronary artery diseases (CAD). However, the mechanisms of puerarin on CAD are still not very clear. In this study, we investigated the role of puerarin on serum nitric oxide (NO) concentration, myocardial endothelial nitric oxide synthase (eNOS) gene expression, the protein expression of eNOS and inducible nitric oxide synthase (iNOS), as well as the level of protein kinase B (Akt/PKB) phosphorylation in rats with myocardial infarction. We found that puerarin (120 mg/kg/day, i.p.) could increase serum nitrite concentration in rat with myocardial ischemia (MI). It also induced the gene expression or activation of eNOS, protein expression of eNOS, and the Akt/PKB phosphorylation. From these results, we suggested that puerarin could increase serum nitric oxide level of rat with myocardial infarction, which should be one of the mechanisms of the therapeutic effect of puerarin on CAD. The increased expression of eNOS and the Akt/PKB pathway may be the underlying mechanism by which puerarin stimulates NO production.     

The effect of puerarin on serum nitric oxide concentration and myocardial eNOS expression in rats with myocardial infarction

Puerarin (1) is a major effective ingredient extracted from the traditional Chinese medicine Ge-gen (Radix Puerariae, RP). Recently, puerarin has been used to treat patients with coronary artery diseases (CAD). However, the mechanisms of puerarin on CAD are still not very clear. In this study, we investigated the role of puerarin on serum nitric oxide (NO) concentration, myocardial endothelial nitric oxide synthase (eNOS) gene expression, the protein expression of eNOS and inducible nitric oxide synthase (iNOS), as well as the level of protein kinase B (Akt/PKB) phosphorylation in rats with myocardial infarction. We found that puerarin (120 mg/kg/day, i.p.) could increase serum nitrite concentration in rat with myocardial ischemia (MI). It also induced the gene expression or activation of eNOS, protein expression of eNOS, and the Akt/PKB phosphorylation. From these results, we suggested that puerarin could increase serum nitric oxide level of rat with myocardial infarction, which should be one of the mechanisms of the therapeutic effect of puerarin on CAD. The increased expression of eNOS and the Akt/PKB pathway may be the underlying mechanism by which puerarin stimulates NO production.     

氨氯地平对高胆固醇大鼠心肌缺血再灌注时一氧化氮合酶的影响

目的 :探讨高胆固醇血症大鼠心肌缺血 再灌注损伤时氨氯地平对内皮型一氧化氮合酶 (eNOS)和诱导型一氧化氮合酶 (iNOS)在冠脉血管内皮表达的影响。方法 :雄性Wistar大鼠分 4组 :单纯高胆固醇血症组 ;氨氯地平组 ;氨氯地平 N 甲基亚硝基左旋精氨酸甲酯组 ;氨氯地平 假手术组。大鼠经高胆固醇喂养 6周后 ,开胸结扎左冠状动脉 ,缺血30min后 ,行再灌注 2 0min、2h。分别用免疫组织化学ABC法检测冠脉血管内皮eNOS和iNOS的表达水平。结果 :缺血前 ,氨氯地平可显著降低冠脉血管内皮iNOS表达 (P <0 .0 1)。缺血 30min ,高胆固醇血症组eNOS、iNOS表达明显减少 (P <0 .0 1) ,氨氯地平组eNOS表达上调 (P <0 .0 1) ,iNOS下调 ;再灌注 2 0min时 ,高胆固醇血症组冠脉血管内皮表达iNOS增多 ,氨氯地平组eNOS、iNOS表达明显下调 ;再灌注 2h时 ,氨氯地平组NO水平及eNOS、iNOS表达较高胆固醇血症组轻度降低。各时相点L NAME均可部分阻断氨氯地平对eNOS、iNOS的效应。结论 :在高胆固醇血症时、缺血期及再灌注早期 ,氨氯地平可调节eNOS、iNOS表达 ,减少心肌缺血 再灌注损伤。     

神经元型一氧化氮合酶反义寡脱氧核苷酸抑制大鼠吗啡戒断症状

目的　观察鞘内或侧脑室注射神经元型一氧化氮合酶 (nNOS)反义寡脱氧核苷酸对大鼠吗啡戒断症状的影响。方法　根据基因结构设计nNOS或eNOS反义寡脱氧核苷酸片段 ,用逆转录聚合酶链反应 (RT PCR)测定nNOSmR NA表达。结果　吗啡依赖大鼠在纳洛酮激发前 2 4h鞘内注射nNOS反义寡脱氧核苷酸抑制所有大鼠吗啡戒断症状如湿狗摇动、扭体及激惹、腹泻、体重减少、咬牙和流涎。eNOS反义寡脱氧核苷酸对吗啡戒断症状总评分值没有影响 ,但减少腹泻、体重减轻值和咬牙等评分值。侧脑室注射nNOS反义寡脱氧核苷酸减少吗啡戒断症状 ,eNOS反义寡脱氧核苷酸对吗啡戒断症状没有影响。鞘内注射nNOS反义寡脱氧核苷酸后脊髓nNOSmRNA的相对表达几乎消失 ,iNOS的表达增加 ;而eNOS反义寡脱氧核苷酸处理后对nNOS和iNOS的表达没有影响。结论　nNOS基因表达介导了吗啡戒断反应过程 ,抑制nNOS基因表达可增加脊髓i NOS基因的表达。     

戊四唑癫痫大鼠脑组织一氧化氮含量和一氧化氮合酶活性变化

探讨一氧化氮在戊四唑癫病发机制中的作用。方法每天注射戊四唑建立在鼠癫痫模型,测定癫病发作后大鼠大脑皮质,海马一氧化氮和一氧化氮合酶活性变化,结果癫痫发作后海马ＮＯ含量和ＮＯＳ活性显著升高,结 戊四唑诱导的癫痫中具有致痫性。     

噻嗪类利尿剂对自发性高血压大鼠内皮型一氧化氮合酶和内皮素-1表达影响的研究

目的研究噻嗪类利尿剂治疗自发性高血压大鼠时对其内皮型一氧化氮合酶和内皮素-1表达的影响,从而探讨其降压的可能分子机制。方法15只自发性高血压大鼠随机分为3组,分别经胃管给予氢氯噻嗪(HCTZ,10 mg.kg-1.d-1)、吲哒帕胺(IND,0.625 mg.kg-1.d-1)和等量去离子水。每周测血压1次,4 wk后处死动物,分别用RT-PCR和W estern B lot法检测组织中内皮素-1和内皮型一氧化氮合酶mRNA和蛋白质的表达。结果氢氯噻嗪和吲哒帕胺用药1 wk后SHR的血压降低,2wk时降压幅度达到显著水平(P<0.05)。同时两种利尿剂均可在蛋白质水平上调内皮型一氧化氮合酶的表达,在mRNA水平下调内皮素-1的表达。结论噻嗪类利尿剂可能通过上调内皮型一氧化氮合酶及下调内皮素-1而起到调节血压与改善血管内皮功能作用。     

一氧化氮合酶抑制剂的研究进展

一氧化氮（ｎｉｔｒｉｃｏｘｉｄｅ,ＮＯ）是一种能调节细胞多种功能的信息分子,它参与心血管、外周和中枢神经以及免疫等系统生理过程和生物信号的调节。体内组织中的ＮＯ由ＮＯ合酶（Ｎｉｔｒｉｃｏｘｉｄｅｓｙｎｔｈａｓｅ,ＮＯＳ）催化左旋精氨酸而合成,合成后的ＮＯ迅速跨膜扩散释放。各种调节ＮＯ释放的因素均作用于ＮＯＳ催化的化学反应过程,而体内影响该反应的ＮＯＳ在各组织的表达不同。特异性ＮＯＳ抑制剂通过调控ＮＯ的合成,对ＮＯＳ表达相关的各种疾病的预防和治疗具有重要的临床意义。本文对近年来ＮＯＳ抑制剂的研究进展作一概述。     

2,4,6-Trinitrotoluene inhibits endothelial nitric oxide synthase activity and elevates blood pressure in rats

2,4,6-Trinitrotoluene (TNT), which is widely used in explosives, is an important occupational and environmental pollutant. Human exposure to TNT has been reported to be associated with cardiovascular dysfunction, but the mechanism is not well understood. In this study, we examine the endothelial nitric oxide synthase (eNOS) activity and blood pressure value following TNT exposure. With a crude enzyme preparation, we found that TNT inhibited the enzyme activity of eNOS in a concentration-dependent manner (IC₅₀ value=49.4 μM). With an intraperitoneal administration of TNT (10 and 30 mg/kg) to rats, systolic blood pressure was significantly elevated 1 h after TNT exposure (1.2- and 1.3-fold of that of the control, respectively). Under the conditions, however, experiments with the inducible NOS inhibitor aminoguanidine revealed that an adaptive response against hypertension caused by TNT occurs. These results suggest that TNT is an environmental chemical that acts as an uncoupler of constitutive NOS isozymes, resulting in decreased nitric oxide formation associated with hypertension in rats.     

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.