ERK1/2通路参与15-羟二十碳四烯酸收缩缺氧大鼠肺动脉的过程

缺氧诱导的15-羟二十碳四烯酸（15-hydroxyeicosatetraenoic acid,15-HETE）是引起肺动脉收缩的重要介导因子。15-HETE引起肺动脉收缩的信号转导途径尚不清楚。本研究旨在确定细胞外信号调节激酶1／2（extracellular signal-regulated kinase-1／2,ERK1／2）信号转导通路是否参与15-HETE收缩缺氧火鼠肺动脉的过程。采用组织浴槽肺动脉环张力检测、蛋白质免疫印迹Western blot）和免疫细胞化学方法。制备缺氧大鼠动物模型,成年雄性Wistar大鼠在低氧环境下（吸入氧分数为0．12）正常喂养9d。显微分离直径1-1．5mm肺动脉,剪成长为3mm的动脉环,进行血管张力检测。用ERK1／2上游激酶（MEK）抑制剂PD98059抑制ERK1／2活性。结果显示,PD98059可明显抑制15-HETE对缺氧大鼠肺动脉环的收缩作用。在去除内皮的肺动脉环,PD98059仍叮明显降低15-HETE的缩血管作用。Western blot和免疫细胞化学结果都显示,15-HETE能促进ERK1／2磷酸化。由此表明ERK1／2信号转导通路参与15-HETE收缩缺氧大鼠肺动脉的过程。     

Kv3.4通道参与15-羟二十碳四烯酸诱导的大鼠肺动脉收缩

通过组织浴槽血管环方法观察Kv3．4通道特异阻断剂BDS-Ⅰ对15-羟二十碳四烯酸（15-hydroxyeicosatetraenoic acid,15-FETE）收缩肺动脉血管的影响;通过酶法分离、培养Wistar大鼠肺动脉血管平滑肌细胞（pulmonary artery smooth musclecells,PASMCs）,RT-PCR和Western blot技术观察15-HETE对大鼠PASMCs上Kv3．4通道表达的影响,以探讨Kv3．4通道在15-HETE收缩肺动脉过程中的作用。结果如下：（1）15-HETE以浓度依赖方式使肺动脉环张力增加,对缺氧组大鼠肺动脉环张力作用更为明显,与正常对照组相比差异显著;（2）除去肺动脉内皮后,15-HETE引起血管收缩的强度较内皮完整时增强,呈剂量依赖性收缩反应;（3）阻断Kv3．4通道可抑制15-HETE收缩肺动脉;（4）15-HETE下调PASMCs膜上Kv3．4通道mRNA及蛋白质表达。上述观察结果提示Kv3．4通道参与由15-HETE引起的缺氧肺动脉血管收缩（hypoxic pulmonary vasoconstriction,HPV）。     

黄芪甲苷Ⅳ通过影响β-actin对内皮型一氧化氮合酶的调节作用

目的：研究黄芪甲苷Ⅳ（AS-Ⅳ）对体外培养脐静脉内皮细胞中内皮型一氧化氮合酶（eNOS）的调节作用及可能的机制。方法：培养人脐静脉内皮细胞系EA-Hy926,用AS-Ⅳ进行干预,同时给予或不给予骨架蛋白β—actin聚合稳定剂phalloidin,用免疫共沉淀方法检测eNOS与单体8-actin结合状态的变化,用L-3H．精氨酸转化为L-SH-瓜氨酸的同位素法测定eNOS活性,I^125环-磷酸鸟苷（cGMP）放射免疫法检测细胞内cGMP水平,Westernblotting方法检测细胞中eNOS和蛋白激酶B（Akt）磷酸化水平,总蛋白水平。结果：（1）AS-IV作用10min后,细胞内单体β—actin与eNOS的结合明显增加（P〈0．05或P〈0．01）,预先给予phalloidin显著抑制了AS．IV引起的两者结合的增加（P〈0．01）。②AS—IV明显增加了eNOS活性（P〈0．05）、cGMP含量（P〈0．01）、eNOSSer-1177磷酸化水平（P〈0．01）、AktSer-473磷酸化水平（P〈0．001）,预先给予phalloidin明显降低了AS—IV引起的eNOS活性（P〈0．05）、cGMP含量（P〈0．01）和磷酸化水平的增加（P〈0．01）,但对Akt的磷酸化没有影响。结论：单体β—actin与eNOS的结合在AS-IV激活eNOS的过程中起着不可或缺作用,其主要是通过促进Akt对eNOSSer—1177的磷酸化来实现的。     

氧化氮对抗脑缺血再灌注所致脑细胞凋亡的机制探讨

目的探讨一氧化氮（nitric oxide,NO）对局灶性脑缺血再灌注所致神经细胞损伤的影响及影响机制。方法将SD大鼠随机分为假手术组（N组）、脑缺血再灌注组（MCAO组）、脑缺血再灌注加侧脑室微量注射20mmol／L的L-Arg5肚组（L-Arg组）及脑缺血再灌注加侧脑室微量注射20mmol／L的L-NAME5 μl组（L-NAME组）,作脑缺血30min,再灌注12h、24h和2d,冰冻切片,相邻切片分别作焦油紫染色、NOS免疫组化、NOSmRNA原位杂交、TUNEL法原位检测凋亡细胞。结果N组NOS的活性弱阳性表达;MCAO组术后24hNOS的表达明显增强,与各组比较,P〈0．05;L-Arg组术后12h小血管内皮细胞出现NOS的阳性高表达,术后24h神经细胞NOS的阳性表达最高,与各组比较,P〈0．05;L-NAME组各时间点NOS活性的表达为阴性或可疑阳性,与各组比较P〈0．05,NOS的活性明显受到抑制。凋亡细胞的计数结果为N组26．3±4、2个,MCAO组62±4．2个,L-Arg组40、6±2．7个,L-NAME组78．3±3．3个,P〈0．05。结论适量NO可有效降低细胞凋亡的发生,减轻脑缺血再灌注所致的神经细胞的损伤。     

20-羟-二十烷四烯酸对血管内皮细胞的作用研究进展

20-羟-二十烷四烯酸(20-hydroxyeicosatetraenoic acid,20-HETE)是花生四烯酸的细胞色素P-450代谢途径的一个重要代谢产物。近年来研究发现20-HETE对血管内皮细胞发挥重要的生理和病理生理作用。20-HETE可激活内皮细胞烟酰胺腺嘌呤二核苷酸(nicotinamide adenine dinucleoti-de phosphate,NADPH)氧化酶系统和核因子-кB(nuclear factor-кB,NF-кB)通路发挥氧化应激和促炎作用;20-HETE可介导血管内皮细胞内皮型一氧化氮合酶(endothelial nitric oxide synthase,eNOS)的解离、降低NO的生物利用度及诱导血管紧张素转换酶,调节血管的舒张和收缩功能;20-HETE还可促进内皮细胞的增生而促进血管新生。但国内对20-HETE研究甚少,因此本文对近年来国际上关于20-HETE对血管内皮细胞的研究作一综述。     

组胺对肺动脉内皮细胞一氧化氮合酶基因表达的影响

本实验研究了组胺对原代培养的肺动脉内皮细胞一氧化氮合酶(nitric oxidCsynthase,NOS)基因表达的影响及分子机制。采用RT-PCR和免疫印迹技术分别检测mRNA和蛋白质的表达水平,用荧光素酶报告基因实验检测eNOS基因转录起始点上游长1.6-kb的启动子活性,用硝酸还原酶法检测NO的产量。结果发现,组胺增强eNOS表达,呈浓度和时间依赖性,10μmol/L组胺处理肺动脉内皮细胞24h可使eNOS mRNA和蛋白质的表达达到高峰,eNOS mRNA水平为正常对照组的160.8±12.2%(P<0.05),蛋白质水平为正常对照组的136.2±11.2%(P<0.05)。特异性CaMK Ⅱ抑制剂KN-93可抑制组胺的这一效应,表明组胺可通过激活CaMK Ⅱ增强肺动脉内皮细胞eNOS基因的表达。报告基因实验表明,10μmol/L组胺处理24h后肺动脉内皮细胞eNOS基因启动子的活性增强,为正常对照组的148.2±33.7%(P<0.05)。组胺可使肺动脉内皮细胞产生NO增加。这些结果表明组胺在转录水平增强肺动脉内皮细胞eNOS基因的表达,并使细胞产生NO增加,这可能是组胺调节肺血管张力的机制之一。CaMK Ⅱ可能是组胺增强肺动脉内皮细胞eNOS基因表达的途径之一。     

NO前体对高肺血流时肺动脉胱硫醚-γ-裂解酶基因表达的调节作用

目的：研究一氧化氮（NO）前体L-精氨酸（L—Arg）对高肺血流时肺动脉胱硫醚-γ-裂解酶（内源性硫化氢生成酶）的调节作用,以探讨NO体系对高肺血流肺动脉高压及肺血管结构重建调节作用的机制。方法：30只雄性SD大鼠随机分为对照组,分流组和分流＋L—Arg组。对后两组大鼠行腹主动脉-下腔静脉分流术。观察术后11周大鼠肺动脉平均压（mPAP）、右心室肥厚和肺动脉相对中膜面积的改变,用竞争逆转录聚合酶链反应（RT-PCR）对肺组织CSEmRNA表达进行定量分析,同时用化学法测定肺组织硫化氢产出率。结果：分流组大鼠mPAP及肺动脉相对中膜面积明显高于对照组（P〈0．01）,而分流＋L—Arg组大鼠mPAP及肺动脉相对中膜面积明显低于分流组（P〈0．01）。分流组CSEmRNA表达与对照组相比明显降低（P〈0．01）,而分流组＋L—Arg组CSEmRNA表达又明显高于分流组（P〈0．05）：分流组大鼠肺组织硫化氢产出率明显低于对照组（P〈0．01）,而分流组＋L—Arg组大鼠肺组织硫化氢产出率及血浆硫化氢含量明显高于分流组（P〈0．01）。结论：高肺血流可致肺动脉CSEmRNA下调,外源性NO能够缓解CSEmRNA的改变,从而对高肺血流所致肺血管结构重建和肺动脉高压起调节作用。     

表氧化二十碳三烯对eNOS磷酸化水平的影响及其相关信号转导通路

内皮源性一氧化氮合酶(eNOS)是一氧化氮(NO)参与的血管稳态调节过程中的关键酶. 多种体液因子和机械刺激都可以通过磷酸化修饰调节eNOS的活性, 但具体的信号转导通路因刺激物不同而异. 最近发现花生四烯酸细胞色素P450(CYP)表氧化酶代谢产物表氧化二十碳三烯(EETs)可以显著上调eNOS的蛋白表达并增强其活性, 但其分子机制尚不清楚. 通过在4代以内培养的牛主动脉内皮细胞中直接加入外源性EETs和转染CYP表氧化酶基因CYP2C11和CYPF87V, 并同时给予实验组不同信号转导抑制剂进行干预, 观察其对总的eNOS表达及其在Ser1179 和Thr497位点磷酸化水平的影响. 结果显示, 内外源性EETs均可以显著上调eNOS的蛋白表达并增强及其在Ser1179和Thr497位点的磷酸化水平; PI3K抑制剂LY294002可以阻断EETs对eNOS-Ser1179的磷酸化上调作用, 但它对eNOS-Thr(P)497并无影响, 而Akt抑制剂却可以抑制eNOS在这两个位点的磷酸化, 且这两种抑制剂都可以阻断EETs对eNOS的蛋白表达上调作用.结果提示: (i) EETs对eNOS的活性调节可能与PI3K/Akt所介导的eNOS-Ser1179和Akt所介导的eNOS- Thr497磷酸化水平改变相关; (ii) PI3K/Akt信号通路可能参与了EETs对eNOS的蛋白表达上调过程.     

环加氧酶-2抑制剂尼美舒利通过改善内皮功能和增加NO含量对抗大鼠心肌氧化应激损伤

本文旨在研究冠状动脉内皮和NO在选择性环加氧酶2（cyclooxygenase2,COX-2）抑制剂尼美舒利（nimesulide）对抗心肌氧化损伤中的作用。离体大鼠心脏行Langendorff灌流,给予H2O2（140Bmol／L）观察心脏收缩功能。用U-46619灌流心脏,使冠状动脉预收缩后,观察冠状动脉对内皮依赖性舒张因子5-HT和内皮非依赖性舒张因子硝普钠（sodiumnitroprusside,SNP）的反应。结果显示：（1）与空白对照组（100％）相比,H202灌流20min后,左心室发展压[left ventriculardevelo pedpressure,LVDP,（54．8±4．0）％],和心室内压最大变化速率【±dp／dtmax（50．8±3．1）％和（46．2±2．9）％]明显降低。H2O2灌流前尼美舒利（5μmol/L）预处理10min,能够显著抑制H2O2引起的LVDP和μdp/dtmax下降[（79．9±2．8）％,（80．3±2．6）％和（81．4±2．6）％,P〈0．0l]。（2）与空白对照组相比,H2O2灌流后,5-HT和SNP引起内皮依赖性和内皮非依赖性血管舒张功能均明显下降;而尼美舒利预处理10min能明显对抗内皮依赖性血管舒张功能的下降[（-22．2±4．2）％vsH2O2组（-6．0±2．5）％,P〈0．0l],但对其内皮非依赖性血管舒张功能的下降没有明显作用[（-2．0±1．8）％vsH202组（-7．0±3．5）％,P〉0．05]。（3）一氧化氮合酶（nitric oxide synthase,NOS）抑制剂L-NAME能够部分取消尼美舒利预处理对H20,应激心脏心功能指标的改善作用ILVDP和±dp/dtmax分别为（60．2±2．1）％,（63．9±2．4）％和（63．1±2．9）％,P〈0．01]。同时尼美舒利预处理10min能使H202应激心肌NO含量增加[（2．63±0．40）vs（1．36±0．23）nmol／gprotein,P〈0．051,而L-NAME抑制此作用。（4）选择性COX-1抑制剂吡罗昔康（piroxicam）预处理不能抑制H202引起的LVDP和±dp/dtmax下降,但促进左心室舒张末压（1eftventricular end diastolicpressure,LVEDP）升高;吡罗昔康对H202引起的内皮依赖性和内皮非依赖性血管舒张功能下降无显著作用。以上结果提示,选择性COX-2抑制剂尼美舒利能够对抗大鼠离体心肌氧化应激损伤,其机制可能是通过改善内皮依赖性血管舒张功能和增加心肌NO含量起作用。     

中国人eNOS基因VNTR多态性的基因型与等位基因频率

一氧化氮合酶（nitric oxide synthase,NOS）催化L－精氨酸的氧化反应生成L－瓜氨酸和一氧化氮（nitric oxide,NO）。NO可通过cGMP依赖的信号传导途径介导平滑肌细胞舒张,是调节血管张力的重要信使分子。NO尚可抑制血小板凝集,对血栓形成起重要调节作用。目前在哺乳动物中已发现细胞来源、表达方式和活性调节不同的3种NOS同工酶,分别为神经元型NOS（neuronal NOS,nNOS）、诱导型NOS（inducible NOS,iNOS）和内皮细胞型NOS(endothelial NOS,eNOS）。人的eNOS基因位于第7号染色体长臂（7q36）,全长约21kb,含有26个外显子和25个内含子。eNOS基因存在多个与心脑血管疾病相关的基因多态性位点。其中位于第4内含子的一个以27bp为核心的数目可变性串联重复序列（variable number of tandem repeat,VNTR）多态性位点,已被证实与原发性高血压、心肌梗死和静脉血栓形成有关。目前在我国尚缺乏NOS基因多态性在正常人群中基因型及等位基因频率分布的统计资料。为此,我们从316名健康中国人的基因组DNA检测了eNOS基因第4内含子VNTR多态性的基因型和等位基因,鉴定出重复6次、5次和4次的3种等位基因,以及6／5杂合、5／5纯合、5／4杂合和4／4纯合的4种基因型。同时我们将正常中国人eNOS基因VNTR多态性的基因型和等位基因频率与其他种族的相关资料进行了统计对比。结果表明,中国人eNOS基因VNTR的各种基因型和等位基因频率与日本人相似,4／4纯合基因型频率与高加索人差异显著,各种基因型和等位基因频率与非裔美国人均存在显著差异。     

Cellular mechanisms and intracellular signaling pathways for the modulation of eNOS in pulmonary arteries by 15-HETE

The 15-hydroxyeicosatetraenoic acid (15-HETE), a lipid metabolite and vasoconstrictor, plays an important role in hypoxic contraction of pulmonary arteries (PAs) through working on smooth muscle cells (SMCs). Previous studies have shown that vascular endothelium is also involved in PAs tone regulation. However, little is known as to how the pulmonary artery endothelial cells (PAECs) are related to the 15-HETE-induced vasoconstriction and that which intracellular signaling systems are critical. To test this hypothesis, we examined PAs constriction in isolated rat PAs rings, the expression and activity of endothelial nitric oxide synthase (eNOS) with western blot, and nitric oxide (NO) production using the DAF-FM DA fluorescent indicator. The results showed that the 15-HETE-induced PAs constriction was diminished in endothelium-intact rings. In the presence of the eNOS inhibitor L-NAME, vasoconstrictor responses to KCl were greater than the control. The activation of eNOS was activated by Ca²⁺ released from intracellular stores and the PI3K/Akt pathway. Phosphorylations of the eNOS at Ser-1177 and Akt at Ser-473 were necessary for their activity. A prolonged 15-HETE treatment (30?min) led to a decrease in NO production by phosphorylation of eNOS at Thr-495, leading to augmentation of PAs constriction. Therefore, 15-HETE initially inhibited the PAs constriction through the endothelial NO system, and both Ca²⁺ and the PI3K/Akt signaling systems are required for the effects of 15-HETE on PAs tone regulation.     

Nitric oxide contributes to 20-HETE-induced relaxation of pulmonary arteries.

In contrast to its constrictor effects on peripheral arteries, 20-hydroxyeicosatetraenoic acid (20-HETE) is an endothelial-dependent dilator of pulmonary arteries (PAs). The present study examined the hypothesis that the vasodilator effects of 20-HETE in PAs are due to an elevation of intracellular calcium concentration ([Ca(2+)](i)) and the release of nitric oxide (NO) from bovine PA endothelial cells (BPAECs). BPAECs express cytochrome P-450 4A (CYP4A) protein and produce 20-HETE. 20-HETE dilated PAs preconstricted with U-46619 or norepinephrine and treated with the cytochrome P-450 inhibitor 17-octadecynoic acid and the cyclooxygenase inhibitor indomethacin. The dilator effect of 20-HETE was blocked by the NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) or by removal of endothelium. 20-HETE significantly increased [Ca(2+)](i) and NO production in BPAECs. 20-HETE-induced NO release was blunted by removal of extracellular calcium, as well as NO synthase inhibitors (L-NAME). These results suggest that 20-HETE dilates PAs at least in part by increasing [Ca(2+)](i) and NO release in BPAECs.     

Cellular mechanisms and intracellular signaling pathways for the modulation of eNOS in pulmonary arteries by 15-HETE

The 15-hydroxyeicosatetraenoic acid (15-HETE), a lipid metabolite and vasoconstrictor, plays an important role in hypoxic contraction of pulmonary arteries (PAs) through working on smooth muscle cells (SMCs). Previous studies have shown that vascular endothelium is also involved in PAs tone regulation. However, little is known as to how the pulmonary artery endothelial cells (PAECs) are related to the 15-HETE-induced vasoconstriction and that which intracellular signaling systems are critical. To test this hypothesis, we examined PAs constriction in isolated rat PAs rings, the expression and activity of endothelial nitric oxide synthase (eNOS) with western blot, and nitric oxide (NO) production using the DAF-FM DA fluorescent indicator. The results showed that the 15-HETE-induced PAs constriction was diminished in endothelium-intact rings. In the presence of the eNOS inhibitor L-NAME, vasoconstrictor responses to KCl were greater than the control. The activation of eNOS was activated by Ca2? released from intracellular stores and the PI3K/Akt pathway. Phosphorylations of the eNOS at Ser-1177 and Akt at Ser-473 were necessary for their activity. A prolonged 15-HETE treatment (30 min) led to a decrease in NO production by phosphorylation of eNOS at Thr-495, leading to augmentation of PAs constriction. Therefore, 15-HETE initially inhibited the PAs constriction through the endothelial NO system, and both Ca2? and the PI3K/Akt signaling systems are required for the effects of 15-HETE on PAs tone regulation.     

Rho-kinase phosphorylates eNOS at threonine 495 in endothelial cells

Endothelial nitric oxide synthase (eNOS) produces nitric oxide (NO), which is involved in various physiological functions of the cardiovascular system. eNOS is activated by dephosphorylation at Thr495 and phosphorylation at Ser1177. Inhibition of Rho-kinase, an effector of the small GTPase RhoA, leads to activation of Akt/PKB, which phosphorylates eNOS at Ser1177 and thereby promotes NO production. However, little is known about the effects of Rho-kinase on phosphorylation of Thr495. We here found that the constitutively active form of Rho-kinase phosphorylated eNOS at Thr495 in vitro. Expression of the constitutively active form of RhoA or Rho-kinase increased this phosphorylation in COS-7 cells. Addition of thrombin to cultured human umbilical vein endothelial cells induced phosphorylation of eNOS at Thr495. Treatment with Y27632, a Rho-kinase inhibitor, suppressed thrombin-induced phosphorylation at Thr495. These results indicate that Rho-kinase can directly phosphorylate eNOS at Thr495 to suppress NO production in endothelium.     

VEGF-induced relaxation of pulmonary arteries is mediated by endothelial cytochrome P-450 hydroxylase

The cytochrome P-450 metabolite 20-HETE induces calcium-, endothelial-, and nitric oxide (NO)-dependent relaxation of bovine pulmonary arteries (PA). VEGF is an NO-dependent dilator of systemic arteries and plays a key role in maintaining the integrity of the pulmonary vasculature. We tested the effect of VEGF on PA diameter and tone and the contribution of cytochrome P-450 family 4 (CYP4) to vasoactive effects of VEGF. Bovine PA rings (1 mm in diameter) relaxed with VEGF (0.1-10 nM) in an endothelial- and eNOS-dependent manner. This response was blunted by pretreatment with the CYP4 inhibitor dibromododecynyl methyl sulfonamide (DDMS) as well as a mechanistically different CYP4 inhibitor N-hydroxy-N'-(4-butyl-2-methylphenyl)formamidine. PAs also increased in diameter by 6-12% in the presence of VEGF (10 nM), and this increase was attenuated by DDMS. In contrast to that shown in PAs, 20-HETE constricted bovine renal arteries and did not increase intracellular Ca(2+) in renal artery endothelial cells as observed in bovine pulmonary artery endothelial cells (BPAECs). VEGF-evoked increases in intracellular Ca(2+) concentration ([Ca(2+)](i)) in BPAECs were blunted by treatment with DDMS. Both VEGF (10 nM) and 20-HETE (1-5 microM) stimulated NO release from cultured BPAECs, and once again VEGF-induced increases were attenuated by pretreating the cells with DDMS. We conclude that CYP4/20-HETE contributes to VEGF-stimulated NO release and vasodilation in bovine PAs. Given the unique expression of 20-HETE-forming CYP4 in BPAECs vs. systemic arterial endothelial cells, CYP4 may be an important mediator of endothelial-dependent vasoreactivity in PAs.     

Angiotensin type 1 receptor is linked to inhibition of nitric oxide production in pulmonary endothelial cells

We previously demonstrated that angiotensin II (Ang II) stimulates an increase in nitric oxide synthase (NOS) mRNA levels, eNOS protein expression and NO production via the type 2 (AT2) receptor, whereas signaling via the type 1 (AT1) receptor negatively regulates NO production in bovine pulmonary artery endothelial cells (BPAECs). In the present study, we investigated the components of the AT1 receptor-linked signaling pathway(s) that are involved in the downregulation of eNOS protein expression in BPAECs. Treatment of BPAECs with either AT1 receptor antagonists or an anti-AT1 receptor antibody induced eNOS protein expression. Furthermore, intracellular delivery of GP-Antagonist-2A, an inhibitor of Galphaq proteins, and treatment of BPAECs with U73122, a phosphatidylinositol-phospholipase C (PLC)-specific inhibitor, enhanced eNOS protein expression. Treatment of BPAECs with the cell-permeable calcium chelator, BAPTA/AM, increased eNOS protein expression at 8 h, while increasing intracellular calcium with either thapsigargin or A23187 prevented Ang II-induced eNOS protein expression. Phorbol myristate acetate (PMA), a protein kinase C (PKC) activator, completely prevented Ang II-stimulated eNOS protein expression at 8 h, whereas depletion of PKC by long-term treatment with PMA, induced eNOS protein expression. Treatment of BPAECs with a PKCalpha-specific inhibitor or transfection of BPAECs with an anti-PKCalpha neutralizing antibody stimulated eNOS protein expression. Conversely, rottlerin, a PKCdelta specific isoform inhibitor had no effect on basal or Ang II-stimulated eNOS protein expression. Moreover, treatment of BPAECs with U73122, BAPTA/AM and PKCalpha-specific inhibitors increased NO production at 8 h. In conclusion, Ang II downregulates eNOS protein expression via an AT1 receptor-linked pathway involving Galphaq/PLC/calcium/PKCalpha signaling pathway in BPAECs.     

Glyoxalase I reduces glycative and oxidative stress and prevents age‐related endothelial dysfunction through modulation of endothelial nitric oxide synthase phosphorylation

Endothelial dysfunction is a major contributor to cardiovascular disease (CVD), particularly in elderly people. Studies have demonstrated the role of glycation in endothelial dysfunction in nonphysiological models, but the physiological role of glycation in age‐related endothelial dysfunction has been poorly addressed. Here, to investigate how vascular glycation affects age‐related endothelial function, we employed rats systemically overexpressing glyoxalase I (GLO1), which detoxifies methylglyoxal (MG), a representative precursor of glycation. Four groups of rats were examined, namely young (13 weeks old), mid‐age (53 weeks old) wild‐type, and GLO1 transgenic (WT/GLO1 Tg) rats. Age‐related acceleration in glycation was attenuated in GLO1 Tg rats, together with lower aortic carboxymethyllysine (CML) and urinary 8‐hydroxydeoxyguanosine (8‐OHdG) levels. Age‐related impairment of endothelium‐dependent vasorelaxation was attenuated in GLO1 Tg rats, whereas endothelium‐independent vasorelaxation was not different between WT and GLO1 Tg rats. Nitric oxide (NO) production was decreased in mid‐age WT rats, but not in mid‐age GLO1 Tg rats. Age‐related inactivation of endothelial NO synthase (eNOS) due to phosphorylation of eNOS on Thr495 and dephosphorylation on Ser1177 was ameliorated in GLO1 Tg rats. In vitro, MG increased phosphorylation of eNOS (Thr495) in primary human aortic endothelial cells (HAECs), and overexpression of GLO1 decreased glycative stress and phosphorylation of eNOS (Thr495). Together, GLO1 reduced age‐related endothelial glycative and oxidative stress, altered phohphorylation of eNOS, and attenuated endothelial dysfunction. As a molecular mechanism, GLO1 lessened inhibitory phosphorylation of eNOS (Thr495) by reducing glycative stress. Our study demonstrates that blunting glycative stress prevents the long‐term impact of endothelial dysfunction on vascular aging.     

Mechanisms of activation of eNOS by 20-HETE and VEGF in bovine pulmonary artery endothelial cells

We have demonstrated that VEGF-induced dilation of bovine pulmonary arteries is associated with activation of cytochrome P-450 family 4 (CYP4) enzymes and eNOS. We hypothesized that VEGF and the CYP4 product 20-HETE would trigger common downstream pathways of intracellular signaling to activate eNOS. We treated bovine pulmonary artery endothelial cells (BPAECs) with 20-HETE (1 microM) or VEGF (8.3 nM) and examined three molecular events known to activate eNOS: 1) phosphorylation at serine 1179, 2) phosphorylation of protein kinase B (Akt), which subsequently phosphorylates eNOS, and 3) association of eNOS with 90-kDa heat shock protein (Hsp90). Both 20-HETE and VEGF increase the phosphorylation of eNOS at serine 1179 and Akt at serine 473. The CYP4 inhibitor dibromododecynyl methyl sulfonamide (DDMS) blocks VEGF-induced phosphorylation of eNOS. VEGF had no effect on the binding of Hsp90 with eNOS, whereas 20-HETE decreased the association of the protein partners. Inhibition of Akt-phosphatidylinositol 3-kinase with wortmannin blocks both 20-HETE and VEGF-induced relaxation of pulmonary arteries, supporting the functional contribution of Akt phosphorylation to the vasoactive actions of both agents. Treatment with radicicol had no effect on 20-HETE-induced relaxation of pulmonary arteries, consistent with an absence of effect on association of Hsp90 to eNOS, whereas radicicol partially blocked VEGF-evoked relaxations, possibly secondary to effects on endpoints other than Hsp90 association with eNOS. In conclusion, VEGF and 20-HETE share eNOS activation pathways, including phosphorylation of serine 1179 and phosphorylation of Akt. Unlike aortic endothelial cells, eNOS activation in BPAECs by either VEGF or 20-HETE does not appear to require increased association of Hsp90.