血管内皮生长因子对培养内皮细胞合成一氧化氮的影响

目的 :探讨血管内皮生长因子 （VEGF） /血管渗透因子 （VPF）对内皮细胞 （EC）分泌一氧化氮 （NO）的影响。方法 :将培养的人脐静脉内皮细胞 （HUVEC）随机分为 6组 （n=6 /组 ） :1正常对照组 ;2 VEGF 1ng/ m l;3VEGF 10ng/ m l;4VEGF 10 0 ng/ m l;5低氧组 ;6低氧组 +VEGF 10 0 ng/ m l。采用硝酸还原酶法测定培养液中的 NO2 - ,NO3 -的含量以反映 NO水平。结果 :VEGF促进正常 EC分泌 NO,在一定浓度范围内呈剂量依赖性 ;低氧损伤 EC,使其分泌 NO减少 ;VEGF 10 0 ng/ ml预处理可保护 EC免受低氧损害 ,保持正常分泌 NO的功能。结论 :VEGF能够调节 EC的功能 ,为其促血管形成作用中 EC分裂、增殖、迁移奠定物质基础     

Melatonin inhibits endothelial nitric oxide production in vitro

Endothelial cell function is a major player on the regulation of both vascular tonus and permeability. Activation of nitric oxide synthase (NOS) by bradykinin is one physiological pathway for the well-known vascular relaxation mediated by endothelial-derived nitric oxide (NO). In this study we investigated if melatonin, which is known to modulate endothelial cell function and NO production in other tissues, is able to impair bradykinin-induced NO production in vitro. Rat microvascular endothelial cells were incubated with fluorescent dyes to detect either NO or Ca2+. In addition, cGMP levels were measured by enzyme immunoassay. We found that while bradykinin (1-100 nm) increased both cytosolic Ca2+ and NO production, melatonin (1 nm) abolished this NO production but not cytosolic Ca2+ elevation. N-acetylserotonin (0.1 and 1 nm) had the same effect, while the selective agonist for MT3 receptors (5-MCA-NAT, 1 nm) had no effect. Moreover, nonselective and MT2-selective antagonists did not alter the effect of melatonin, suggesting that it is not mediated by MT melatonin receptors. A possible direct inhibition of calmodulin was also discarded as melatonin did not mimic the effect of calmidazolium on cytosolic Ca2+. Melatonin also abolished cGMP production induced by 1 microm bradykinin, indicating that the NO downstream effect is impaired. Thus, here we show that melatonin reduces NO production induced by bradykinin by a mechanism upstream to the interaction of Ca2+ -calmodulin with NOS. Moreover, this effect might be the basis of the diurnal variation in endothelial cell function.     

Oxidized low-density lipoprotein inhibits nitric oxide-mediated coronary arteriolar dilation by up-regulating endothelial arginase I

Oxidized low-density lipoprotein (OxLDL) causes impairment of endothelium-dependent, nitric oxide (NO)-mediated vasodilation involving l-arginine deficiency. However, the underlying mechanism remains elusive. Since arginase and endothelial NO synthase (eNOS) share the substrate l-arginine, we hypothesized that OxLDL may reduce l-arginine availability to eNOS for NO production, and thus vasodilation, by up-regulating arginase. To test this hypothesis, porcine subepicardial arterioles (70-130 μm) were isolated for vasomotor study and for immunohistochemical detection of arginase and eNOS expressions. The coronary arterioles dilated dose-dependently to the endothelium-dependent NO-mediated vasodilator serotonin. This vasodilation was inhibited in the same manner by NOS inhibitor N(G)-nitro-l-arginine methyl ester and by lumenal OxLDL (0.5 mg protein/mL). The inhibitory effect of OxLDL was reversed after treating the vessels with either l-arginine (3 mM) or arginase inhibitor difluoromethylornithine (DFMO; 0.4 mM). Consistent with vasomotor alterations, OxLDL inhibited serotonin-induced NO release from coronary arterioles and this inhibition was reversed by DFMO. Vascular arginase activity was significantly elevated by OxLDL. Immunohistochemical analysis indicated that OxLDL increased arginase I expression in the vascular wall without altering eNOS expression. Taken together, these results suggest that OxLDL up-regulates arginase I, which contributes to endothelial dysfunction by reducing l-arginine availability to eNOS for NO production and thus vasodilation.     

Gene transfer of endothelial nitric oxide synthase alters endothelium-dependent relaxations in aortas from diabetic rabbits

Aims/hypothesis. Cardiovascular disease is the leading cause of death in diabetes mellitus. Abnormal endothelium-dependent relaxation is observed both in humans and in animal models of diabetes mellitus and decreased bioavailability of nitric oxide (NO) is thought to be involved in this defect. Therefore, the aim of this study was to test whether adenovirus-mediated gene transfer of endothelial nitric oxide synthase (eNOS) alters vascular reactivity of diabetic vessels.¶Methods. Vascular reactivity was first assessed in thoracic aortas and carotid arteries from nine alloxan-induced diabetic (plasma glucose, 26.5 ± 1.2 mmol/l; HbA_{1 c}, 6.4 ± 0.3 %) and nine control rabbits (plasma glucose, 11.1 ± 1.3 mmol/l; HbA_{1 c}, 2.1 ± 0.1 %). Vascular reactivity was next examined in thoracic aortas of diabetic animals after ex vivo transduction with replication-deficient adenovirus encoding gene for eNOS (AdeNOS) or β-galactosidase (Adβ gal).¶Results. After 10 weeks of hyperglycaemia, endothelium-dependent relaxation to acetylcholine was impaired in diabetic aorta, but was normal in carotid arteries from diabetic rabbits. In contrast, responses of both vessels to calcium ionophore and nitric oxide donor were normal. Histochemical staining for β-galactosidase and immunohistochemistry for eNOS showed transgene expression in the endothelium and adventitia in Adβ gal and AdeNOS transduced vessels, respectively. During submaximum contractions with phenylephrine, relaxations to low concentrations of acetylcholine (3 × 10^–8 to 10^–7 mol/l) were augmented in AdeNOS transduced diabetic vessels.¶Conclusion/interpretation. These findings suggest that adenovirus-mediated gene transfer of eNOS to diabetic aorta alters vascular reactivity. [Diabetologia (2000) 43: 340–347]     

Proapoptotic nitric oxide production in amyloid beta protein-treated cerebral microvascular endothelial cells

OBJECTIVE: The objective of this study was to investigate the effects of amyloid beta protein (Abeta) on cerebral microvascular endothelium, and their possible involvement in Abeta-induced apoptosis in the neighboring cells. METHODS: Cultured bovine brain microvascular endothelial cells (BBECs) were incubated with Abeta for 24 h. Production of nitric oxide (NO) was assessed by nitric oxide-sensitive fluorescent dye, DAF-2, and the expression of NO synthase (NOS) proteins was examined by Western blotting. Effects of Abeta-treated microvascular endothelium on the DNA damage of the neighboring cells were assessed by single-cell gel electrophoresis. RESULTS: Abeta increased the expression of iNOS protein, but did not affect eNOS and nNOS expressions in BBECs. Abeta-treated BBECs showed spontaneous NO production in the presence of L-arginine. The neural cell line PC12 showed marked apoptosis after being co-cultured with Abeta-treated BBECs for 48 h, and the apoptosis was as potent as that induced by the inflammatory stimuli lipopolysaccharide and interferon-gamma. The DNA damage of PC12 cells evoked by co-culture with Abeta-treated BBECs was prevented by L-NG-nitroarginine methyl ester, an inhibitor of NOS. CONCLUSIONS: These results indicate that Abeta induces the expression of iNOS in BBECs, and that microvascular endothelium-derived NO may induce apoptosis in neighboring neural cells.     

Increased salt-sensitivity in endothelial nitric oxide synthase-knockout mice

BACKGROUND: Although impaired nitric oxide production contributes importantly to salt-sensitivity, the role of the endothelial isoform of nitric oxide synthase (eNOS) has received little attention. In the present study we compared the effects of a high-salt diet on the blood pressure response of eNOS knockout (eNOS-/-) and control (eNOS+/+) mice. METHODS: Mean arterial pressure (MAP), heart rate, pulse pressure, and activity levels were recorded by telemetry in mice fed a regular-salt diet (0.7% NaCl) followed by 6 weeks on either a high-salt (8% NaCl) or regular-salt diet. RESULTS: The eNOS-/- mice exhibited a 15% increase in MAP and a 2- to 2.5-fold increase in salt-sensitivity relative to the control strain. Salt-induced increases in MAP were well sustained in eNOS-/-, whereas in eNOS+/+ the initial increase was biphasic. The effects of salt on MAP were particularly pronounced during locomotor activity, during the dark phase, and at the peak levels of MAP recorded over the course of the day. The high-salt diet also led to a transient increase in the proportion of time spent active. Levels of heart rate and pulse pressure were relatively unaffected by the high-salt diet. CONCLUSION: The eNOS-/- mice exhibit an increased blood pressure response to a high-salt diet. This finding suggests that eNOS normally provides an important contribution to the body's adaptation to a salt load and that reduced production of NO by eNOS may promote salt-sensitivity and salt-induced hypertension.     

非诺贝特促进人内皮细胞内皮一氧化氮合酶复偶联的作用研究

目的探讨非诺贝特能否对脂多糖（LPS）诱导的血管内皮一氧化氮合酶（eNOS）脱偶联发挥保护作用。方法体外培养人脐静脉内皮细胞（HUVECs）,用非诺贝特预处理HUVECs 2 h,再与LPS共孵育24 h,采用高效液相色谱法检测细胞四氢生物蝶呤（BH4）的表达水平,ELISA检测细胞eNOS表达水平和细胞上清一氧化氮（NO）浓度,利用Confocal方法检测细胞内活性氧（ROS）产生水平。结果与对照组比较,单纯LPS刺激组内皮细胞BH4表达水平降低,伴有eNOS表达下调和NO水平降低,而内皮细胞内ROS产生增加（P均〈0.05）。与单纯LPS刺激组比较,非诺贝特预处理组内皮细胞BH4表达水平升高,同时伴有eNOS表达上调和NO水平增加,而内皮细胞内ROS产生降低（P均〈0.05）。结论非诺贝特通过上调BH4水平,对LPS诱导的血管内皮细胞eNOS脱偶联有逆转作用,这可能是其发挥血管内皮保护作用的机制之一。     

比索洛尔对缺氧/复氧内皮细胞一氧化氮生成的影响

目的 :观察比索洛尔对培养的人脐静脉内皮细胞 （HU VECs）在缺氧 /复氧 （A/ R）过程中一氧化氮 （NO）生成的影响。方法 :将 HUVECs暴露于缺氧环境中 30 m in后复氧 ,并加入比索洛尔 （1,5 0和 5 0 0 μmol/ L）或空白对照 ,测量复氧前、复氧后 1和 4h培养液上清 NO含量。结果 :对照组 NO产量在复氧后 1h,4h与复氧前相比有显著下降 （均 P<0 .0 1）。比索洛尔 5 0 μm ol/ L 组和 5 0 0 μmol/ L 组 NO产量在复氧后 1h,4h与复氧前相比无显著差异 （均P>0 .0 5 ） ,而与对照组和 1μmol/ L 组同一时间相比均有显著增加 （均 P<0 .0 1）。结论 :比索洛尔可以阻止 A/ R期间内皮细胞 NO产量的下降 ,因此 NO可能参与了 β阻滞剂减少缺血再灌注损伤的过程。     

Endogenous adipose-derived factors diminish coronary endothelial function via inhibition of nitric oxide synthase

Adipocytokines may be the molecular link between obesity and vascular disease. However, the effects of these factors on coronary vascular function have not been discerned. Accordingly, the goal of this investigation was to delineate the mechanisms by which endogenous adipose-derived factors affect coronary vascular endothelial function. Both isolated canine coronary arteries and coronary blood flow in anesthetized dogs were studied with and without exposure to adipose tissue. Infusion of adipose-conditioned buffer directly into the coronary circulation did not change baseline hemodynamics; however, endothelial-dependent vasodilation to bradykinin was impaired both in vitro and in vivo. Coronary vasodilation to sodium nitroprusside was unaltered by adipose tissue. Oxygen radical formation did not cause the impairment because quantified dihydroethidium staining was decreased by adipose tissue and neither a superoxide dismutase mimetic nor catalase improved endothelial function. Inhibition of nitric oxide (NO) synthase with L-NAME diminished bradykinin-mediated relaxations and eliminated the subsequent vascular effects of adipose tissue. In vitro measurement of NO demonstrated that adipose tissue exposure quickly lowered baseline NO and abolished bradykinin-induced NO production. The results indicate that adipose tissue releases factor(s) that selectively impair endothelial-dependent dilation via inhibition of NO synthase-mediated NO production.     

Long-term blockade of nitric oxide synthesis in rats modulates coronary capillary network remodeling

Long-term blockade of nitric oxide synthesis with N^ω-nitro-L-arginine methyl ester (L-NAME) induces cardiac perivascular fibrosis in rats. Its relationship to expression of angiogenic growth factors and capillary network remodeling is not understood. This study was designed to determine whether capillary proliferation and angiogenic growth factor regulation occur in response to L-NAME. Three groups of rats were studied: C, control; L1, L-NAME 13 mg/kg/day; L2, 130 mg/kg/day. One and eight weeks later the hearts were removed and subjected to morphometric analysis and analysis of gene expressions of molecules related to angiogenesis. Arterial hypertension was observed within 8 weeks in the L1 and L2 groups compared with control. After 1 week immunohistochemical assays demonstrated basic fibroblast growth factor (bFGF) in the arteriolar media. Northern blot analysis revealed increase in bFGF and transforming growth factor-β (TGF-β) mRNA during this period. At 8 weeks arteriolar medial thickening and perivascular fibrosis were seen microscopically in the L1 and L2 groups, which were accompanied by only a modest remodeling of capillary network due to increase in venular or intermediate capillary portions. Concomitantly immunoreactivity for vascular endothelial growth factor (VEGF) and TGF-β were detected in perivascular area. These results suggest that (1) blockade of NO synthesis induces expression of angiogenic growth factors as well as vessel wall remodeling, and (2) TGF-β may counteract angiogenic growth factors and limit subsequent alterations in capillary network remodeling. This revised version was published online in June 2006 with corrections to the Cover Date.     

冠心病患者循环内皮祖细胞与一氧化氮的关系及临床意义

目的探讨冠心病患者循环内皮祖细胞(EPCs)与NO的关系及临床意义。方法78例入选对象均经选择性冠状动脉造影明确有无冠状动脉狭窄,将其分为冠心病组42例,对照组36例。采集入选者外周血测定NO浓度,同时进行循环EPCs分离培养,14天后显微镜下计数细胞克隆形成单位评估循环EPCs水平。结果冠心病组NO水平明显低于对照组(P<0.001),双支、3支冠状动脉病变组较单支病变组NO水平明显降低(P<0.001)。冠心病组循环EPCs水平均明显低于对照组(P<0.01)。NO浓度与循环EPCs水平呈明显正相关(r=0.867,P<0.0001)。结论NO可能在EPCs动员、归巢过程中发挥重要作用,与冠心病发生及临床表现相关。     

高同型半胱氨酸血症诱导eNOS脱偶联损害冠状动脉内皮功能

目的探讨高同型半胱氨酸血症（HHcy）患者冠状动脉内皮功能是否被损伤,以及这种损伤是否通过内皮型一氧化氮合酶（eNOS）脱偶联实现的。方法 71例参与者被分成健康对照组（n=50）和HHcy组（n=21）,利用多普勒超声心动测定腺苷诱导下冠状动脉左前降支的舒张功能的改变,冠脉血流速度储备（CFVR）由最大血流速度与基线水平的比值计算得出。采用ELISA以及高效液相色谱法测定血浆一氧化氮（NO）、四氢生物蝶呤（BH4）的水平。结果与健康对照组相比,HHcy组患者血浆NO、BH4的水平降低（P〈0.05）;HHcy组CFVR低于健康对照组（P〈0.05）;血浆Hcy水平与NO及CFVR呈负相关（P〈0.05）。结论 HHcy可能通过降低BH4生物利用度,诱导eNOS脱偶联,而导致冠状动脉内皮功能损伤,进而促进不良冠脉事件的发生。     

一氧化氮对自发性高血压大鼠血管内皮功能的作用

目的　探讨自发性高血压大鼠 (SHR)内皮舒张功能不全的发生机制。方法　采用体外灌注的方法测定大鼠胸主动脉环对不同浓度乙酰胆碱的舒张反应变化 ,并测定血清中NO-3浓度和动脉组织中环鸟苷酸水平。结果　与魏 凯二氏大鼠 (WKY)比较 ,SHR胸主动脉环对乙酰胆碱的舒张反应明显减弱。左旋硝基精氨酸 (L NNA)可明显抑制大鼠胸主动脉环对乙酰胆碱的舒张反应 ,但并不能消除SHR和WKY对乙酰胆碱舒张反应之间的差异。与WKY比较 ,SHR血中NO-3水平明显降低 (P<0 .0 1) ,动脉组织中环鸟苷酸含量降低 (P<0 .0 1)。结论　SHR内皮依赖的血管舒张功能减低 ;一氧化氮 (NO)的生成或释放不足可能直接参与了SHR血管内皮依赖的舒张功能不全。     

Globular adiponectin upregulates nitric oxide production in vascular endothelial cells

Aims/hypothesis Adiponectin, also called ACRP30, is a novel adipose tissue-specific protein that has been shown to improve insulin sensitivity and to exert anti-atherogenic effects. It is known that knockout mice lacking endothelial NO synthase (eNOS) develop hypertension, insulin resistance, hyperlipidaemia, and show augmented ischaemia-reperfusion damage. Thus, we examined whether globular adiponectin activates eNOS to produce NO.Methods To analyze NO production in bovine aortic endothelial cells (BAE), NOx (nitrite and nitrate) was measured in the medium with an automated NO detector/high-performance liquid chromatography system. eNOS activation was assessed by phosphorylation of the enzyme and its activity was evaluated by citrulline synthesis in human umbilical vein endothelial cells (HUVEC). eNOS mRNA and protein expressions in HUVEC were evaluated by Realtime PCR and Western blot analysis.Results Gobular adiponectin increased NO production in BAE. It also caused eNOS phosphorylation and potentiated eNOS activity in HUVEC. In addition, globular adiponectin up-regulated the eNOS gene to increase protein expression in HUVEC.Conclusion/interpretation Globular adiponectin increases NO production through two mechanisms, namely, by activation of eNOS enzyme activity and via an increase in eNOS expression. Activation and up-regulation of eNOS could explain some of the observed vasoprotective properties of globular adiponectin, as well as its beneficial effects on the cardiovascular system.Abbreviations NO nitric oxide - eNOS endothelial NO synthase - BAE bovine aortic endothelial cells - HUVEC human umbilical vein endothelial cells - ACRP30 adipocyte complement-related protein of 30 kDa - GAPDH glyceraldehyde-3-phosphate dehydrogenase     

New progress in understanding roles of nitric oxide during hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury (HIRI) is a major clinical cause of morbidity and mortality in liver surgery and transplantation. Many studies have found that nitric oxide (NO) plays an important role in the HIRI and its increase or decrease can affect the progression and outcome of HIRI. However, the role of NO in HIRI is controversial and complicated. NO derived by endothelial NO synthase (eNOS) shows a protective role in HIRI, while excessive NO derived by inducible NO synthase (iNOS) accelerates inflammation and increases oxidative stress, further aggravating HIRI. Nevertheless, the overexpression of eNOS may exacerbate HIRI and iNOS-derived NO in some cases reduces HIRI. Here we review the new progress in the understanding of the roles of NO during HIRI: (1) NO possesses different roles in HIRI by increasing NO bioavailability, down-regulating leukotriene C4 synthase, inhibiting the activation of the nuclear factorκB (NFκB) pathway, enhancing cell autophagy, and reducing inflammatory cytokines and reactive oxygen species (ROS). And NO has both protective and deleterious effects by regulating apoptotic factors; (2) eNOS promotes NO production and suppresses its own overexpression, exerting a hepatoprotective effect reversely. Its activation is regulated by the PI3K/Akt and KLF2/AMPK pathways; and (3) iNOS derived NO mainly has deteriorating effects on HIRI, while it may have a protective function under some conditions. Their expression should reach a balance to reduce the adverse side and make NO protective in the treatment of HIRI. Thus, it can be inferred that NO modulating drugs may be a new direction in the treatment of HIRI or may be used as an adjunct to mitigate HIRI for the purpose of protecting the liver.