全反式维甲酸对高血压大鼠体内apelin-APJ信号系统的影响

目的:探讨全反式维甲酸(atRA)对高血压大鼠体内心血管活性多肽apelin及其受体APJ信号的影响。方法:采用12周龄雄性自发性高血压大鼠(SHR)及其同源对照WKY大鼠,经腹腔注射atRA,为期1月。分别用实时荧光定量多聚酶链式反应(PCR)与免疫印迹技术测定atRA治疗后SHR体内apelin和APJ受体的表达情况。结果:与WKY对照组相比,SHR心脏组织中apelin及其受体APJ的 mRNA和蛋白表达明显下调(P均<0.01)。而atRA治疗后SHR(低、高剂量atRA组)大鼠心脏组织中apelin、APJ表达出现上调(P均<0.05)。结论:长期atRA治疗促进SHR大鼠心脏组织中apelin及其受体APJ的表达增加,提示转录调节剂atRA很可能对人类高血压病防治具有积极作用。     

全反式维甲酸对高血压大鼠体内ACE2表达与一氧化氮信号的影响

目的:探讨全反式维甲酸(atRA)对高血压大鼠体内血管紧张素转换酶2(ACE 2)基因表达及一氧化氮(NO)信号的影响。方法:采用自发性高血压大鼠(SHR)及其同源对照W KY大鼠,经腹腔注射atRA,为期1月。分别用实时荧光定量PCR,N orthern印迹及免疫印迹技术测定atRA治疗后SHR体内ACE 2、血管紧张素Ⅱ1型受体(AT1)的表达情况,以硝酸还原酶法检测血清NO水平。结果:与W KY对照组相比,SHR心脏ACE 2的mRNA和蛋白表达下调[mRNA拷贝数比值:(0.06±0.02)vs.1;蛋白吸光度比值:(0.73±0.05)vs.1,P均<0.01],atRA(低、高剂量atRA组)治疗后SHR心脏ACE 2表达上调[mRNA:(0.23±0.08),(0.53±0.18)vs.(0.06±0.02);蛋白水平上升:(0.9±0.07),(0.92±0.08)vs.(0.73±0.05),P均<0.05],同时出现AT1表达降低、血清NO水平增高以及血压下降(P均<0.05)。结论:长期atRA治疗促进SHR大鼠心脏ACE 2的表达增加,导致体内NO增加,血压下降,提示转录调节剂atRA很可能对人类高血压病防治具有一定的价值。     

葡萄籽原花青素对自发性高血压大鼠左室重塑和氧化应激的影响

目的观察葡萄籽原花青素(GSP)对自发性高血压大鼠(SHR)左室重塑和氧化应激的影响。方法 8周龄雄性SHR 24只随机分成4组(每组6只):SHR组、GSP低剂量组(50 mg·kg~(-1)·d~(-1))和GSP高剂量组(200 mg·kg~(-1)·d~(-1))及卡托普利组(30 mg·kg~(-1)·d~(-1))。6只同龄雄性Wistar-Kyoto大鼠设为对照组。治疗8 w后,测定尾动脉收缩压(SBP)、全心重量指数(HW/BW)和左心室重量指数(LVW/BW);生化法检测左室心肌组织中丙二醛(MDA)含量、超氧化物歧化酶(SOD)活性和抑制羟自由基(OH·)能力;HE和Masson染色下观察心肌细胞形态和胶原分布,并测定心肌细胞横截面积(CSA)与心肌胶原容积分数(CVF);Western印迹法检测左室心肌组织p47phox蛋白表达。结果 GSP能显著降低SHR的SBP(P0.01),改善左室重塑参数、减少心肌组织MDA含量及p47phox蛋白表达(P0.05),提高SOD活性及抑制OH·能力(P0.05),GSP高剂量组作用尤为显著(P0.01)。结论 GSP对SHR左室重塑有减轻作用,可能与降低SBP、抑制氧化应激及下调p47phox蛋白表达有关。     

阿托伐他汀对自发性高血压大鼠主动脉活性氧、AT1受体和p22phox表达的影响

目的探讨自发性高血压大鼠(SHR)主动脉活性氧(ROS)、AT1受体和p22phox mRNA表达的相关性及阿托伐他汀治疗对其影响.方法以正常血压大鼠为对照,观察SHR给予阿托伐他汀50 mg*kg-1*d-1灌胃30 d后,血压、血浆血管紧张素Ⅱ(AngⅡ)、血清一氧化氮(NO)、主动脉ROS含量、AT1受体蛋白和mRNA以及p22phox mRNA表达的变化.结果阿托伐他汀治疗30 d后,SHR血压、血浆AngⅡ、主动脉ROS含量、AT1受体蛋白和mRNA及p22phox mRNA表达下降,血清NO水平上升.多元逐步回归分析显示AT1受体为血管ROS的主要影响因素.结论血管AT1受体mRNA表达增加引起p22phox亚单位表达上调,导致ROS合成增加是高血压血管ROS增多的重要机制.阿托伐他汀可下调血管AT1受体和p22phox亚单位表达,减少ROS,减轻血管内皮功能受损.     

自发性高血压鼠心脏组织肌球蛋白轻链磷酸酶水平的研究

目的:比较自发性高血压大鼠(SHR)和正常血压大鼠(WKY)心脏组织的心肌肌球蛋白磷酸酶(MLCP)的130000、38000、21000亚单位含量的差异,以探讨MLCP与SHR心脏舒缩机制的关系。方法:在4℃的环境下,取SHR与WKY大鼠各10只断头处死,迅速取其心脏组织,称重速冻后将其磨成匀浆,置于缓冲液中并通过离心提取蛋白质,校正2组总蛋白的浓度后,分别应用SDS-PAGE、Western印迹杂交和化学发光的方法测定SHR与WKY心脏组织MLCP的130000、38000、21000亚单位的含量,对显影结果进一步进行吸光度扫描分析。结果:SHR和WKY大鼠心脏组织的MLCP的亚单位的含量不同,SHR的MLCP的130000、38000、21000亚单位含量均高于WKY大鼠(P<0.01)。结论:SHR与WKY大鼠心脏组织MLCP的130000、38000、21000亚单位含量有着明显的差异,提示心脏组织的MLCP结构或功能的异常可能与SHR高血压的病理机制有关。     

血管紧张素转化酶抑制剂和抗氧化剂对湿热应激性大鼠心肌AngⅡ和p22phox表达的影响

目的:观察血管紧张素转化酶抑制剂(ACEI)卡托普利(Captopril,CTP)和抗氧化剂（维生素C,VitC）对湿热应激(HHS)大鼠心肌组织中血管紧张素Ⅱ（AngⅡ)、活性氧簇（ROS）和p22phox表达的影响。方法: 将32只成年雄性SD大鼠随机分为:对照组、HHS组、CTP组(HHS+CTP)及VitC组(HHS+VitC),每组8只。喂养4周后,颈动脉插管测定大鼠血压,计算大鼠左心室质量指数。用放射免疫法测定心肌组织中AngⅡ的浓度。用比色法测定心肌组织中ROS的水平。应用RT-PCR检测p22phox mRNA的表达。用免疫组化染色法检测大鼠心肌中p22phox的分布特征。结果: 平均动脉压、AngⅡ和ROS和p22phox的水平,HHS组与对照组比较,VitC组和CTP组与HHS组比较,均有非常显著性差异（P<0.01）;两个药物组之间比较无统计学意义。结论: HHS可增加大鼠心肌组织中AngⅡ表达,同时上调p22phox mRNA和其蛋白的表达,介导心肌细胞内ROS生成增加。用抗氧化剂和ACEI阻滞后,AngⅡ表达减少,p22phox mRNA和其蛋白的表达降低,心肌细胞内ROS生成减少,其机制可能与HHS导致AngⅡ诱导ROS产生有关。以上提示,HHS可引起心脏损害,抗氧化剂和ACEI对HHS性心脏损害具有拮抗作用。     

自发性高血压大鼠肾上腺髓质素含量与中性内肽酶分布的关系

目的测定自发性高血压大鼠(SHR) 与WKY大鼠组织肾上腺髓质素(ADM)含量和中性内肽酶(NEP)活性及其表达水平,以探讨NEP的变化在高血压时组织ADM水平升高中的意义.方法采用放射免疫分析方法和荧光分光光度法分别检测血浆和组织的ADM含量和NEP的活性,同时用半定量RT-PCR和免疫组织化学染色法分别检测组织NEP mRNA和NEP蛋白的表达和分布.结果 ADM和NEP广泛分布于大鼠的血浆和组织,SHR的ADM含量在各组织普遍高于WKY大鼠.SHR心脏和小肠NEP的活性和mRNA表达均显著低于WKY大鼠,ADM含量与NEP活性呈负相关.反之,SHR血浆和肾脏NEP活性、肾脏NEP mRNA水平与蛋白量均高于WKY大鼠,ADM含量与NEP活性呈正相关.在肺脏和主动脉,NEP的活性无明显变化.结论 NEP在自发性高血压大鼠各组织器官中的变化与ADM含量的变化不一致,提示高血压时组织局部的NEP对ADM含量的影响不同.     

自发性高血压大鼠肾上腺髓质素含量与中性内肽酶分布的关系

目的 测定自发性高血压大鼠(SHR)与WKY大鼠组织肾上腺髓质素(ADM)含量和中性内肽酶(NEP)活性及其表达水平，以探讨NEP的变化在高血压时组织ADM水平升高中的意义。方法 采用放射免疫分析方法和荧光分光光度法分别检测血浆和组织的ADM含量和NEP的活性，同时用半定量RT-PCR和免疫组织化学染色法分别检测组织NEP mRNA和NEP蛋白的表达和分布。结果 ADM和NEP广泛分布于大鼠的血浆和组织，SHR的ADM含量在各组织普遍高于WKY大鼠。SHR心脏和小肠NEP的活性和mRNA表达均显著低于WKY大鼠，ADM含量与NEP活性呈负相关。反之，SHR血浆和肾脏NEP活性、肾脏NEP mRNA水平与蛋白量均高于WKY大鼠，ADM含量与NEP活性呈正相关。在肺脏和主动脉，NEP的活性无明显变化。结论 NEP在自发性高血压大鼠各组织器官中的变化与ADM含量的变化不一致，提示高血压时组织局部的NEP对ADM含量的影响不同。     

心肌组织和血浆IGF—Ⅰ的相关性

本研究采用放射免疫分析法测定自发性高血压大鼠(SHR)和正常血压的Witar-Kyoto大鼠(WKY)血浆和心肌组织中的IGF-Ⅰ水平,以心脏湿重(HW)和心脏湿重/体重(HW/BW)来判定心肌肥厚.结果显示:SHR的HW较WKY有显著升高(P<0.05),HW/BM则较WKY有高度显著升高(P<0.01).两组大鼠心肌组织中IGF-Ⅰ与血浆中的IGF-Ⅰ显示正相关(WKY:r=0.8485 P<0.05;SHR:r=0.9529(P<0.005).试验结果提示不论心脏生理和病理情况下,心脏合成和分泌的IGF-Ⅰ对循环中的IGF-Ⅰ水平均有影响,而在心肌肥厚,心肌组织中的IGF-Ⅰ病理水平增高时,影响更为明显.     

早期运动训练延缓自发性高血压大鼠心脏病理变化的作用及机制

目的观察高血压前期有氧运动对自发性高血压大鼠(SHR)血压、心脏功能与结构以及心肌血管紧张素转换酶2(ACE2)信号通路的影响,探讨运动训练改善心脏病理变化的作用机制。方法 5周龄雄性SHR和正常血压大鼠(WKY)各24只,随机分成安静组(S)和运动训练组(E)。运动训练大鼠进行16周中低强度的跑台运动。运动结束,评估4组大鼠血压、左心室收缩和舒张功能、左心室肥厚和纤维化程度。实时荧光定量聚合酶链反应(realtime PCR)和Western blot分别检测左心室心肌ACE2、Mas受体mRNA和蛋白表达,酶联免疫吸附试验(ELISA)法检测左心室心肌组织血管紧张素(1-7)[Ang(1-7)]水平。结果 16周运动显著降低SHR收缩压(P0.01)和左心室舒张末期内压(LVEDP)(P0.01),增强左心室内压最大下降速率(P0.01)。运动训练还降低SHR左心室质量(LVM)、心肌胶原容积分数(CVF)和血管周围胶原面积(PVCA)(均P0.05),16周运动上调SHR左心室心肌ACE2和Mas受体mRNA和蛋白表达(均P0.01),增加心肌Ang(1-7)水平(P0.01)。16周运动不引起WKY左心室肥厚,但上调左心室心肌ACE2mRNA和Mas受体mRNA表达(均P0.05)及Ang(1-7)水平(P0.05)。结论高血压前期运动训练显著降低SHR血压、改善左心室功能并减轻心肌纤维化,其机制可能与运动增强心脏组织ACE2-Ang(1-7)-Mas轴功能有关。     

Upregulation of angiotensin-converting enzyme 2 by all-trans retinoic acid in spontaneously hypertensive rats

There is increasing evidence that all-trans retinoic acid (atRA) influences gene expression of components of renin-angiotensin system (RAS), which plays a pivotal role in the pathophysiology of essential hypertension. To further validate effects of atRA on the RAS and to assess the possibility that atRA affects the activity of angiotensin-converting enzyme 2 (ACE2), gene, and protein expression of ACE2 have been examined by real-time polymerase chain reaction and Western blot methods in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. Rats were treated with atRA (10 or 20 mg x kg(-1) x day(-1)) or placebo given as daily intraperitoneal injection for 1 month. ACE2 expression was markedly decreased in placebo-treated SHR when compared with WKY rats. However, in atRA-treated SHR, a significant upregulation of ACE2 expression was observed in heart and kidney. In conclusion, chronic atRA treatment increases gene and protein expressions of ACE2, resulting in the reduction of blood pressure and the attenuation of myocardial damage in SHR, which suggests that atRA may be an attractive candidate for the potential prevention and treatment of human essential hypertension.     

Effects of all-trans retinoic acid on orphan receptor APJ signaling in spontaneously hypertensive rats

OBJECTIVE: Studies show general agreement that all-trans retinoic acid (atRA) has been linked to the regulation of G protein-coupled receptor (GPCRs) signaling. To further validate effects of atRA on the cardiovascular GPCRs, the present study was designed to assess whether atRA will modulate orphan receptor APJ, a homologue of angiotensin II type 1 (AT(1)) receptor. METHODS: Real-time polymerase chain reaction and Western blot methods were performed to examine the expression of APJ and its endogenous ligand apelin in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats after chronic atRA treatment. RESULTS: APJ and apelin expression were markedly depressed in placebo-treated SHR, compared with WKY rats (p<0.01). However, in atRA-treated SHR, a significant upregulation of APJ and apelin expression was observed in both heart and aorta (p<0.05), accompanied by a reduction of AT(1) expression, an elevation of serum nitric oxide levels and a subsequent decrease of blood pressure. CONCLUSIONS: Chronic atRA treatment activates gene and protein expression of APJ and apelin and reduces blood pressure in SHR, suggesting that atRA may regulate the balance between apelin-APJ and angiotensin II-AT(1) signaling and have potential clinical value in the prevention and treatment of human hypertension.     

Activation of protein kinase C and nicotinamide adenine dinucleotide phosphate oxidase in leukocytes of spontaneously hypertensive rats.

The involvement of oxidative stress in polymorphonuclear leukocytes (PMN) in the pathogenesis of hypertension remains to be elucidated. We analyzed the generation of reactive oxygen species (ROS) by the circulating and peritoneally infiltrating PMN from spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). Flow cytometric analysis revealed that ROS generation by PMN from SHR was higher than that from WKY before (at 6 weeks of age) and after (at 16 weeks of age) the onset of hypertension. In vivo, ROS generation by PMN from SHR, but not that by PMN from WKY, was significantly suppressed by 10-week treatment with 50 mg/kg/day carvedilol, and this treatment did not affect blood pressure. Western blotting analysis revealed that protein kinase C alpha (PKCalpha), but not PKCbetaI or betaII, was activated more strongly in PMN from SHR than in PMN from WKY. Furthermore, expression of p47phox of nicotinamide adenine dinucleotide phosphate oxidase, but not of p67phox, in PMN from SHR was higher than that in PMN from WKY. These results suggest that ROS generation by PMN is principally enhanced in SHR through activation of PKCalpha and p47phox.     

Changes in cardiac energy metabolism during early development of female SHR

We investigated effects of hypertension and early development on myocardial energy metabolism as reflected by maximal enzyme activities, glucose transporter content, and endogenous substrates in female Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). Left ventricular hypertrophy and systolic hypertension were evident in SHR at 6 weeks of age and these differences increased at 14 and 22 weeks of age. 3-Hydroxyacyl-CoA dehydrogenase (HOAD) activity in the left ventricle was 18% lower in 6-week-old rats than both 14- and 22-week-old rats, but not different between WKY rats and SHR. Hexokinase activity was 15% lower in 6-week-old SHR than WKY rats and decreased progressively with age in both strains. Glucose transporter (GLUT) 1 content was nearly twofold greater in 6-week-old rats than both 14- and 22-week-old rats. We found no difference in citrate synthase activity or GLUT4 content among groups. Glycogen concentration was 44% lower in SHR than WKY rats, whereas triglyceride was slightly (16%) higher in SHR than WKY rats. Older animals had higher levels both glycogen and triglyceride than younger animals. We conclude that the left ventricle of both SHR and WKY rats may change from predominantly glucose to fatty acid oxidation for energy production during early development.     

Reversal of endothelial nitric oxide synthase uncoupling and up-regulation of endothelial nitric oxide synthase expression lowers blood pressure in hypertensive rats.

OBJECTIVES: We sought to examine the hypothesis that a pharmacologic up-regulation of endothelial nitric oxide synthase (eNOS) combined with a reversal of eNOS uncoupling provides a protective effect against cardiovascular disease. BACKGROUND: Many cardiovascular diseases are associated with oxidant stress involving protein kinase C (PKC) and uncoupling of eNOS. METHODS: Messenger ribonucleic acid (mRNA) expression was analyzed with RNase protection assay or quantitative real-time polymerase chain reaction, vascular nitric oxide (NO) with spin trapping, and reactive oxygen species (ROS) with dihydroethidium fluorescence. RESULTS: Aortas of spontaneously hypertensive rats (SHR) showed an elevated production of ROS when compared with aortas of Wistar-Kyoto rats (WKY). The aortic expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits (Nox1, Nox2, Nox4, and p22phox) was higher in SHR compared with WKY. In SHR, aortic production of ROS was reduced by the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME), indicating eNOS "uncoupling" in hypertension. Oral treatment with the PKC inhibitor midostaurin reduced aortic Nox1 expression, diminished ROS production, and reversed eNOS uncoupling in SHR. Aortic levels of (6R)-5,6,7,8-tetrahydro-L-biopterin (BH4) were significantly reduced in SHR compared with WKY. Midostaurin normalized BH4 levels in SHR. In both WKY and SHR, midostaurin increased aortic expression of eNOS mRNA and protein, stimulated bioactive NO production, and enhanced relaxation of the aorta to acetylcholine. Midostaurin lowered blood pressure in SHR and, to a lesser extent, in WKY; the compound did not change blood pressure in WKY made hypertensive with L-NAME. CONCLUSIONS: Pharmacologic interventions that combine eNOS up-regulation and reversal of eNOS uncoupling can markedly increase bioactive NO in the vasculature and produce beneficial hemodynamic effects such as a reduction of blood pressure.     

Wine polyphenols improve endothelial function in large vessels of female spontaneously hypertensive rats

Red wine polyphenols (RWPs) have been reported to prevent hypertension and endothelial dysfunction. Several individual RWPs exert estrogenic effects. We analyzed the possible in vivo protective effects on blood pressure and endothelial function of RWPs in female spontaneously hypertensive rats (SHR) and its relationship with ovarian function. RWPs (40 mg/kg by gavage) were orally administered for 5 weeks. Ovariectomized rats showed both increased isoprostaglandin F(2alpha) excretion and aortic superoxide production and reduced relaxant response to acetylcholine and contraction to the endothelial nitric oxide synthase (eNOS) inhibitor l-NAME measured in the aorta but similar blood pressure, as compared with sham-operated rats. Moreover, in ovariectomized rats aortic eNOS expression was unchanged, whereas caveolin-1, angiotensin II receptor (AT)-1, and the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits p22(phox) and p47(phox) expression was increased compared with sham-operated rats. In both ovariectomized and sham-operated SHR, RWPs reduced systolic blood pressure, urinary isoprostaglandin F(2alpha) excretion, and aortic O(2)(-) production, improving the endothelium-dependent relaxant response to acetylcholine in SHR. These changes were associated with unchanged aortic eNOS expression, whereas caveolin-1 was increased and the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits p22(phox) and p47(phox) expression was reduced. RWPs had no effect on the AT-1 overexpression found in ovariectomized animals. All these results suggest that a chronic treatment with RWPs reduces hypertension and vascular dysfunction through reduction in vascular oxidative stress in female SHR in a manner independent of the ovarian function.     

Increased expression of vascular endothelial growth factor and capillary density in hearts of spontaneously hypertensive rats

OBJECTIVE: The role of VEGF in vascular remodeling of target organs exposed to chronic hypertension is poorly understood. The authors compared capillary density (CD), capillary-to-fiber ratio (C/F), and VEGF mRNA expression in the hearts (left ventricle [LV]), and skeletal muscles (soleus and anterior tibialis [AT]) of 18-week-old male spontaneously hypertensive rats (SHR) and age-matched male Wistar-Kyoto (WKY) and Sprague-Dawley (SD) rats. METHODS: CD or C/F in LV, soleus, and AT of SHR, WKY, and SD rats was determined by analysis of randomly acquired digital images of cryosections stained with FITC-conjugated GS-I lectin. VEGF mRNA expressions in the tissues were determined by Northern blot. RESULTS: VEGF mRNA expressions in LV of SHR were 3.84- and 5.05-fold higher, compared to SD and WKY rats, respectively (n = 6; p < .01). There were no significant differences in VEGF mRNA expression in soleus or AT among SHR, WKY, and SD rats (p > .05). CD in LV of SHR (4975 +/- 167) was significantly higher than WKY or SD rats, 4151 +/- 169 and 3807 +/- 187 mm(-2), respectively (p < .05). In LV of SHR, C/F increased (35%) more significantly than CD (increased 20%), compared to WKY rats. CD, or C/F in soleus or AT of SHR was similar to that observed in WKY or 8D rats. CONCLUSIONS: VEGF expression, CD, and C/F in the heart (LV) of SHR are significantly increased, compared to WKY and SD rats. The data are consistent with the possibility that VEGF may contribute to capillary growth as a compensatory response to hypertension.     

The Mechanism of Distinct Diurnal Variations of Renin-Angiotensin System in Aorta and Heart of Spontaneously Hypertensive Rats

Diurnal variations in plasminogen activator inhibitor-1 mRNA expression are different between the spontaneously hypertensive rats (SHRs) and the Wistar-Kyoto (WKY) rats, and between the aorta and the heart. To elucidate the mechanisms, we examined diurnal changes in the circulating renin-angiotensin system in the SHR and WKY rats. Diurnal variations in plasma renin activity (PRA), plasma angiotensin I, and aldosterone concentrations were similar between the SHR and WKY rats. On the other hand, plasma angiotensin II (Ang II) concentration in the SHR was lower than that in the WKY rats at most time points, but increased to the level of the WKY rats in the late light phase. Treatment with AT1 receptor antagonist candesartan increased plasma Ang II concentration except at ZT 8 and lessened its diurnal variation in the SHR. At the peak in plasma Ang II in the SHR, Ang II regulated genes such as transforming growth factor-β1 and p22phox were upregulated in the aorta. On the other hand, these genes were upregulated throughout the day in the heart of SHR. Candesartan treatment increased AT1a receptor mRNA expression in the heart but not in the aorta of SHR. These findings suggest that an AT1 receptor-mediated mechanism might cause a surge in plasma Ang II concentration at the late light phase in the SHR. Homologous down-regulation of AT1a receptor by Ang II may dampen the effect of a surge in plasma Ang II concentration in the heart of SHR.