高温应激对大鼠心肌血管紧张素Ⅱ的影响及其与心肌p22phox表达的关系

目的 观察高温应激对大鼠心肌血管紧张素Ⅱ（AngⅡ)的影响,探讨心肌AngⅡ与心肌p22phox表达的关系。方法 将24只成年雄性SD大鼠,随机分为:对照组、高温组、高温高湿组,每组8只。喂养4周后,颈动脉插管测定平均动脉压。用放射免疫法测定血浆和心肌AngⅡ浓度。用比色法测定心肌活性氧(ROS)水平。应用逆转录聚合酶链式反应（RT-PCR）和免疫组化法检测心肌p22phox mRNA及蛋白的表达水平。结果 高温组和高温高湿组大鼠平均动脉压、AngⅡ浓度、ROS水平、p22phox mRNA及蛋白的表达水平与对照组比较,均有显著升高（P<0.01）;高温高湿组与高温组比较,无显著性差异。结论 高温应激使大鼠血压升高,这可能与AngⅡ水平上调有关。AngⅡ介导ROS生成增加,其机制可能是高温应激引起p22phox超常表达所致,提示高温应激可引起心脏损害。     

血管紧张素Ⅱ和NADPH氧化酶与血管衰老的相关性研究

目的探讨血管紧张素Ⅱ（AngⅡ）和NADPH氧化酶在血管衰老中的地位及作用机理.方法健康Wistar大鼠分为青年组、老龄组、Valsantan组,分析各组大鼠主动脉形态结构及功能;测定血浆和主动脉AngⅡ水平、主动脉活性氧水平;分别应用RT-PCR和Western bolt检测各组大鼠AngⅡ1型和2型受体（AT1R和AT2R）、NADPH氧化酶p22phox的mRNA及蛋白表达.结果随增龄大鼠主动脉管壁增厚,纤维化程度增高,内皮功能受损,活性氧产生增加;主动脉AngⅡ含量增高,AT2R、p22phox的mRNA及蛋白表达上调,AT1R表达下降;Valsantan（AngⅡ1型受体特异性阻断剂）干预后,p22phox表达下降,活性氧水平降低,衰老血管形态结构和功能异常有所改善.结论衰老血管有其特征性结构和功能改变;AngⅡ经由AT1R上调NADPH氧化酶的基因表达可能是血管衰老的重要机制之一.     

阿托伐他汀对血管紧张素Ⅱ诱导的高血压患者肠系膜动脉平滑肌细胞内NADPH氧化酶-活性氧通路和细胞增殖的影响的研究

目的:探讨阿托伐他汀钙对血管紧张素(Ang)Ⅱ诱导的高血压患者肠系膜动脉平滑肌细胞内NADPH氧化酶-活性氧通路传导和促细胞增殖的干预作用。方法:用培养的第2至4代高血压患者肠系膜动脉平滑肌细胞作为实验标本;以四甲基偶氮唑盐(MTT)法比色测定各组平滑肌细胞增殖率;流式细胞仪检测被双氢乙酰乙酸-二氯荧光黄(DCFH-DA)标记的细胞内活性氧;逆转录聚合酶链式反应(RT-PCR)方法检测细胞内p22phox蛋白mRNA的表达变化。结果:与空白对照组比较,AngⅡ组的细胞增殖率、细胞内活性氧生成量、细胞内p22phoxmRNA的表达均明显增高。与浓度为10-6mol/LAngⅡ孵育组比较,AngⅡ加阿托伐他汀钙组的细胞增殖率、细胞内活性氧、细胞内p22phox蛋白mRNA的表达均明显下降。结论:阿托伐他汀钙可以部分抑制高血压患者体内AngⅡ的促平滑肌细胞增殖及诱导细胞内NADPH氧化酶-活性氧通路。     

ACEI对大鼠急性脑损伤致心肌损害作用的影响

目的探讨血管紧张素转化酶抑制剂（ACEI）对颅脑损伤大鼠心肌损害、循环和心肌局部血管紧张素Ⅱ（AngⅡ）及其受体的影响。方法建立颅脑损伤及ACEI药物干预大鼠模型,测定大鼠血浆AngⅡ水平和血清肌酸磷酸激酶同工酶（CK-MB）含量,免疫组化方法检测心肌AngⅡ和血管紧张素受体1（AT1R）表达,并观察心肌HE染色及超微结构病理形态学改变。结果大鼠颅脑损伤后血浆AngⅡ、心肌组织AngⅡ和AT1R水平显著升高,血清CK—MB含量显著增高（P〈0．05或〈0．01）,HE染色和超微结构的病理观察可见心肌损害;ACEI干预组血浆和心肌AngⅡ含量及血清CK—MB水平较单纯损伤组显著降低,HE染色和超微结构可见心肌损伤程度减轻。结论颅脑损伤可引起明显的心肌损害,肾素一血管紧张素系统可能是参与颅脑损伤后心肌损害的机制之一;ACEI具有防止颅脑损伤后心肌损害的作用。     

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.     

阿托伐他汀对血管紧张素Ⅱ诱导的人肠系膜动脉平滑肌细胞增殖和细胞内NADPH氧化酶-活性氧通路的影响

目的观察阿托伐他汀钙对血管紧张素Ⅱ的促人肠系膜动脉平滑肌细胞增殖和其诱导的平滑肌细胞内NADPH氧化酶-活性氧通路的干预作用。方法用组织贴块法培养的第2～4代人肠系膜动脉平滑肌细胞作为实验标本;以四甲基偶氮唑盐(MTF)法比色测定各组平滑肌细胞增殖率;流式细胞仪检测被双氢乙酰乙酸-二氯荧光黄(DCFH-DA)标记的细胞内活性氧;反转录聚合酶链式反应(RT-PCR)方法检测细胞内p22phox蛋白mRNA的表达变化。结果 (1)与空白对照组比较,加入血管紧张素Ⅱ药物组的细胞增殖率、细胞内活性氧物质生成量、细胞内p22phox mRNA的表达均明显增高(P0.01)。(2)与浓度为10~(-6)mol/L血管紧张素Ⅱ孵育组比较,血管紧张素Ⅱ和阿托伐他汀钙共孵育组的细胞增殖率[阿托伐他汀组(0.242±0.018)比血管紧张素Ⅱ组(0.359±0.024),P0.01]、细胞内活性氧[阿托伐他汀组(130±29)比血管紧张素Ⅱ组(180±34),P0.01]、细胞内p22phox蛋白mRNA的表达[阿托伐他汀组(0.47±0.07)比血管紧张素Ⅱ组(0.71±0.05),P0.01]均降低。结论阿托伐他汀钙可以部分抑制血管紧张素Ⅱ的促人肠系膜动脉平滑肌细胞增殖和其诱导的细胞内NADPH氧化酶-活性氧通路的作用。     

多聚二磷酸腺苷核糖合成酶抑制剂对血管紧张素Ⅱ刺激培养心肌细胞异常基因表达的阻止作用

目的:观察多聚二磷酸腺苷(ADP)核糖合成酶(PARP)抑制剂对血管紧张素Ⅱ(AngⅡ)刺激的乳鼠心脏心肌重构的预防作用.方法:新生大鼠心肌细胞原代培养,传代,用PARP抑制剂3-AB预处理细胞,观察PARP抑制剂对AngⅡ诱导心肌细胞PARP激活、PARPl表达,细胞内ROS产生和c-fos,ANP,β/aMHC基因表达的影响.结果:AngⅡ显著诱导心肌细胞PARP激活,ROS产生增加,PARPl、c-los、β/a-MHC、ANP基因表达增加.给予3-AB预处理可显著抑制AngⅡ诱导的上述变化.结论:AngⅡ可以诱导培养的心肌细胞内PARP激活,PARPl蛋白表达增加,3-AB预处理可以明显降低AngⅡ诱导的心肌细胞内异常基因表达增加,提示PARPl参与了心室重构的发生发展过程.     

人参强心方对慢性心衰大鼠AngⅡ及其受体AT1 mRNA表达的影响

目的 观察人参强心方对慢性心衰大鼠血浆AngⅡ含量与心肌组织AngⅡ受体AT1 mRNA表达的影响,揭示人参强心方治疗慢性心衰的作用机制.方法 采用腹主动脉缩窄法复制慢性心衰大鼠模型,随机分为假手术组、模型组、阳性药对照组和人参强心方高、低剂量组.检测大鼠血浆AngⅡ的含量和心肌组织AT1 mRNA的表达变化.结果 模型组大鼠血浆AngⅡ含量明显增加,心肌组织中AT1 mRNA的表达明显增多;给药后,各治疗组大鼠AngⅡ的含量明显减少, AT1 mRNA的表达明显降低.结论 人参强心方能降低AngⅡ的含量,抑制AT1 mRNA的表达,可能是其治疗慢性心衰的分子机制之一.     

心肌AngⅡ和NADPH氧化酶源性的ROS在心肌肥厚中的作用

目的探讨心肌组织NADPH氧化酶源性的活性氧（ROS）在血管紧张素II（AngⅡ）调控心肌肥厚发生发展中的作用。方法采用腹主动脉缩窄术（AC）构建大鼠压力超负荷心肌肥厚模型,给予血管紧张素转换酶抑制剂（ACEI）卡托普利和NADPH氧化酶抑制剂Apocynin（Apo）干预8周,测定左心室重/体重比（LV/Bwt）;放免法检测心肌AngⅡ含量;激光共聚焦显微镜检测心肌组织O2.-水平;免疫组化检测心肌NADPH氧化酶的表达。结果⑴AC术后大鼠心肌组织AngⅡ含量、NADPH氧化酶表达及O2.-水平均升高;（2）卡托普利干预可显著降低心肌中AngⅡ含量、NADPH氧化酶表达及O2.-水平,并使心室肥厚程度显著降低;（3）Apo干预对肥厚心肌中AngⅡ含量、NAD-PH氧化酶表达无明显影响,但可部分降低心肌O2.-水平并抑制心室肥厚。结论持续压力超负荷致心肌AngⅡ含量升高可调控NADPH氧化酶表达上调,进而引起O2.-水平升高,这可能是压力超负荷致心室肥厚的重要调控路径。     

吡哆胺对血管紧张素Ⅱ诱导的自发性高血压大鼠血管平滑肌细胞增殖的影响

目的:探讨吡哆胺对血管紧张素Ⅱ( AngⅡ)诱导的自发性高血压大鼠血管平滑肌细胞(VSMCs)增殖的影响及其作用机制.方法:原代培养自发性高血压大鼠胸主动脉VSMCs,选3～4代处于对数生长期的细胞进行药物干预.以未加任何干预的自发性高血压大鼠VSMCs为对照组,以10-7 mol/L AngⅡ刺激作为AngⅡ组,以不同浓度(0.1 mmol/L、1.0 mmol/L、10.0 mmol/L)吡哆胺预处理作为吡哆胺组.采用四唑盐比色法检测吡哆胺对VSMCs增殖的影响,酶联免疫吸附法检测细胞上清液晚期糖基化终末产物(AGEs)水平,流式细胞仪分析细胞内活性氧簇(ROS)水平,实时荧光半定量PCR检测晚期糖基化终末产物受体(RAGE)、核因子κB( NFκB)P65、还原型烟酰胺腺嘌呤二核苷磷酸(NADPH)氧化酶P47phox的mRNA水平.结果:与对照组相比,Ang Ⅱ组促进细胞增殖(P＜0.01),升高细胞上清液中AGEs浓度(P＜0.01),使细胞内ROS生成增多(P＜0.01),胞内RAGE、NF-κB P65、NADPH氧化酶P47phox mRNA相对量的表达均较对照组显著升高(P＜0.01);1.0mmol/L和10.0 mmol/L吡哆胺预处理可以逆转AngⅡ作用下的细胞增殖(P＜0.01),降低细胞上清液中AGEs 浓度(P＜0.01),减少ROS生成(P＜0.01),使RAGE、NF-κB P65、NADPH氧化酶P47phoxmRNA表达下降(P＜0.01),且吡哆胺10 mmol/L作用比1 mmol/L更显著(P＜0.01).结论:毗哆胺可能通过抑制AGEs的形成、降低胞内ROS水平,减少RAGE、NF-κB P65、NADPH氧化酶P47phox表达,从而有效抑制AngⅡ诱导的VSMCs增殖作用.     

Phosphorylation of Smooth Muscle 22α Facilitates Angiotensin II-Induced ROS Production Via Activation of the PKCδ-P47phox Axis Through Release of PKCδ and Actin Dynamics and Is Associated With Hypertrophy and Hyperplasia of Vascular Smooth Muscle Cells In Vitro and In Vivo

Rationale: We have demonstrated that smooth muscle (SM) 22α inhibits cell proliferation via blocking Ras-ERK1/2 signaling in vascular smooth muscle cells (VSMCs) and in injured arteries. The recent study indicates that SM22α disruption can independently promote arterial inflammation through activation of reactive oxygen species (ROS)-mediated NF-κB pathways. However, the mechanisms by which SM22α controls ROS production have not been characterized. Objective: To investigate how SM22α disruption promotes ROS production and to characterize the underlying mechanisms. Methods and Results: ROS level was measured by dihydroethidium staining for superoxide and TBA assay for malondialdehyde, respectively. We showed that downregulation and phosphorylation of SM22α were associated with angiotensin (Ang) II-induced increase in ROS production in VSMCs of rats and human. Ang II induced the phosphorylation of SM22α at Serine 181 in an Ang II type 1 receptor-PKCδ pathway-dependent manner. Phosphorylated SM22α activated the protein kinase C (PKC)δ-p47(phox) axis via 2 distinct pathways: (1) disassociation of PKCδ from SM22α, and in turn binding to p47(phox), in the early stage of Ang II stimulation; and (2) acceleration of SM22α degradation through ubiquitin-proteasome, enhancing PKCδ membrane translocation via induction of actin cytoskeletal dynamics in later oxidative stress. Inhibition of SM22α phosphorylation abolished the Ang II-activated PKCδ-p47(phox) axis and inhibited the hypertrophy and hyperplasia of VSMCs in vitro and in vivo, accompanied with reduction of ROS generation. Conclusions: These findings indicate that the disruption of SM22α plays pivotal roles in vascular oxidative stress. PKCδ-mediated SM22α phosphorylation is a novel link between actin cytoskeletal remodeling and oxidative stress and may be a potential target for the development of new therapeutics for cardiovascular diseases.     

Angiotensin II and endothelin-1 regulate MAP kinases through different redox-dependent mechanisms in human vascular smooth muscle cells

OBJECTIVE: The role of reactive oxygen species (ROS) in mitogen-activated protein kinase (MAPK) signaling by angiotensin (Ang) II and endothelin-1 (ET-1) in human vascular smooth muscle cells (VSMC) was investigated. DESIGN: VSMCs were derived from resistance arteries from healthy subjects. MAPK activity was assessed using phospho-specific antibodies. ROS generation was measured by CMH2DCFDA fluorescence and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity by lucigenin chemiluminescence. RESULTS: Ang II and ET-1 increased MAPK phosphorylation (P < 0.01). Pre-treatment with Tiron and Tempol, *O2 scavengers, attenuated agonist-stimulated phosphorylation of p38MAPK, c-Jun N-terminal kinases (JNK) and ERK5, but not of ERK1/2 (extracellular signal-regulated kinases). Apocynin and diphenylene iodinium (DPI), NAD(P)H oxidase inhibitors, decreased Ang II-induced responses 60-70%. ET-1-mediated MAPK phosphorylation was unaffected by apocynin but was reduced (> 50%) by thenoyltrifluoroacetone (TIFT) and carboxyl cyanide-m-chlorophenylhydrazone (CCCP), mitochondrial inhibitors. Allopurinol and N-nitro-l-arginine methyl ester (l-NAME), xanthine oxidase and nitric oxide synthase (NOS) inhibitors, respectively, did not influence MAPK activation. Intracellular ROS generation, was increased by Ang II and ET-1 (P < 0.01). DPI inhibited Ang II- but not ET-1-mediated ROS production. Expression of p22phox and p47phox and activation of NAD(P)H oxidase were increased by Ang II but not by ET-1. CCCP and TIFT significantly attenuated ET-1-mediated ROS formation (P < 0.05), without influencing Ang II effects. CONCLUSIONS: Ang II activates p38MAPK, JNK and ERK5 primarily through NAD(P)H oxidase-generated ROS. ET-1 stimulates these kinases via redox-sensitive processes that involve mitochondrial-derived ROS. These data suggest that redox-dependent activation of MAPKs by Ang II and ET-1 occur through distinct ROS-generating systems that could contribute to differential signaling by these agonists in VSMCs.     

RNA silencing in vivo reveals role of p22phox in rat angiotensin slow pressor response

The angiotensin II (Ang II) slow-pressor response entails an increase in mean arterial pressure and reactive oxygen species. We used double-stranded interfering RNAs (siRNAs) in Sprague Dawley rats in vivo to test the hypothesis that an increase in the p22phox component of NADPH oxidase is required for this response. Reactive oxygen species were assessed from excretion of 8-isoprostane prostaglandin F2alpha and blood pressure by telemetry. Two siRNA sequences to p22phox (sip22phox) reduced mRNA >85% in cultured vascular smooth muscle cells. Rats received rapid (10 second) IV injections (50 to 100 microg) of 1 of 2 different sip22phox, control siRNA, or vehicle (TransIt in saline) during 14 day SC infusions of Ang II (200 ng.kg(-1).min(-1)) or sham infusions. In both groups, sip22phox, relative to control siRNA, led to significant (P<0.001; approximately 50%) reductions in expression of p22phox mRNA and protein and of NADPH oxidase activity in the kidney cortex. In Ang II-infused rats, sip22phox decreased protein expression for Nox-1, -2, and -4 but increased p47phox. Three days after sip22phox, conscious rats infused with Ang II had a reduced excretion of 8-isoprostane (10+/-1 versus 19+/-2 pg.24 h(-1); P<0.01) and a reduced mean arterial pressure (142+/-5 versus 168+/-4 mm Hg; P<0.005). An increase in p22phox is required for increased renal NADPH oxidase activity, expression of Nox proteins and oxidative stress, and contributes < or =50% to hypertension during an Ang II slow-pressor response.     

抑制p22phox表达对高糖所致的内皮细胞活性氧生成和细胞凋亡的影响

目的 探讨p22phox基因沉默在高浓度葡萄糖诱导的内皮细胞活性氧生成和细胞凋亡中的作用.方法 将原代培养的人脐静脉内皮细胞分为对照组、高糖组、高糖+siRNA转染组和siRNA转染组,采用Western-blot检测p22phox蛋白的表达,流式细胞仪检测细胞内活性氧水平及细胞凋亡率.结果 siRNA能有效抑制p22phox表达,高糖能诱导内皮细胞p22phox表达增加.高糖+siRNA转染组的细胞内活性氧水平和细胞凋亡率明显低于高糖组(P<0.05).结论 抑制p22phox表达能降低高糖所致的内皮细胞活性氧生成和细胞凋亡.     

Prevention of hypertension, cardiovascular damage and endothelial dysfunction with green tea extracts

BACKGROUND: We investigated the effect of green tea extract (GTE) in arterial hypertension with high oxidative stress. Angiotensin (Ang) II induces endothelial dysfunction (ED) that is crucial for the development of atherosclerosis and hypertension. METHODS: Male Sprague-Dawley rats, 13 weeks old, randomly assigned to drinking water with or without GTE (6 mg/mL) received a vehicle, a high (700 microg/kg/d) or a low (350 microg/kg/d) Ang II dose for 13 days, by osmotic mini-pumps. Blood pressure (BP) was measured with telemetry. After sacrifice, left ventricular (LV) mass index, small mesenteric artery media-to-lumen ratio, and concentration-response curves of phenylephrine-precontracted arteries to acetylcholine were evaluated. The effect of the superoxide dismutase (SOD-1) analog tempol on artery responses to acetylcholine was assessed. Oxidative stress was measured by plasma hydroperoxides and nitrotyrosine levels. The mRNA of heme oxygenase 1 (HO-1), NADPH oxidase endothelial p22(phox) subunit, and SOD-1 was also measured in the aorta. RESULTS: Compared with vehicle high Ang II increased BP, LV mass index, media-to-lumen ratio, and hydroperoxide radicals. The GTE blunted these increases, prevented the increase in HO-1, p22(phox), and SOD-1 mRNA in aorta caused by Ang II, and reduced them below baseline levels. Low Ang II dose increased BP values and plasma hydroperoxides only during the first week. Both Ang II doses shifted rightward the curves to acetylcholine; this was prevented in vivo by GTE and abolished in vitro by tempol. CONCLUSIONS: The GTE prevented hypertension and target organ damage induced by a high Ang II dose, likely by prevention or scavenging of superoxide anion generation.     

Role of extracellular superoxide dismutase in the mouse angiotensin slow pressor response

Low rates of angiotensin II (Ang II) infusion raise blood pressure, renal vascular resistance (RVR), NADPH oxidase activity, and superoxide. We tested the hypothesis that these effects are ameliorated by extracellular superoxide dismutase (EC-SOD). EC-SOD knockout (-/-) and wild type (+/+) mice were equipped with blood pressure telemeters and infused subcutaneously with Ang II (400 ng/kg per minute) or vehicle for 2 weeks. During vehicle infusion, EC-SOD -/- mice had significantly (P<0.05) higher MAP (+/+: 107+/-3 mm Hg versus -/-: 114+/-2 mm Hg; n=11 to 14), RVR, lipid peroxidation, renal cortical p22(phox) expression, and NADPH oxidase activity. Ang II infusion in EC-SOD +/+ mice significantly (P<0.05) increased MAP, RVR, p22(phox), NADPH oxidase activity, and lipid peroxidation. Ang II reduced SOD activity in plasma, aorta, and kidney accompanied by reduced renal EC-SOD expression. During Ang II infusion, both groups had similar values for MAP (+/+ Ang II: 125+/-3 versus -/- Ang II: 124+/-3 mmHg; P value not significant), RVR, NADPH oxidase activity, and lipid peroxidation. SOD activity in the kidneys of Ang II-infused mice was paradoxically higher in EC-SOD -/- mice (+/+: 8.8+/-1.2 U/mg protein(-1) versus -/-: 13.7+/-1.6 U/mg protein(-1); P<0.05) accompanied by a significant upregulation of mRNA and protein for Cu/Zn-SOD. In conclusion, EC-SOD protects normal mice against oxidative stress by attenuating renal p22(phox) expression, NADPH oxidase activation, and the accompanying renal vasoconstriction and hypertension. However, during an Ang II slow pressor response, renal EC-SOD expression is reduced and, in its absence, renal Cu/Zn-SOD is upregulated and may prevent excessive Ang II-induced renal oxidative stress, renal vasoconstriction, and hypertension.     

Role of NAD(P)H oxidase- and mitochondria-derived reactive oxygen species in cardioprotection of ischemic reperfusion injury by angiotensin II

Reactive oxygen species (ROS) participate in cardioprotection of ischemic reperfusion (I/R) injury via preconditioning mechanisms. Mitochondrial ROS have been shown to play a key role in this process. Angiotensin II (Ang II) exhibits pharmacological preconditioning; however, the involvement of NAD(P)H oxidase, known as an ROS-generating enzyme responsive to Ang II stimuli, in the preconditioning process remains unclear. We compared the effects of 5-hydroxydecanoate (5-HD; an inhibitor of mitochondrial ATP-sensitive potassium channels), apocynin (an NAD(P)H oxidase inhibitor), and 4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl (tempol; a membrane permeable radical scavenger) on pharmacological preconditioning by Ang II in rat cardiac I/R injury in vivo. Treatment with a pressor dose of Ang II before a 30-minute coronary occlusion reduced infarct size as determined 24 hours after reperfusion. The protective effects of Ang II were eliminated by pretreatment with 5-HD or apocynin, similar to tempol. Both 5-HD and apocynin suppressed the enhanced cardiac lipid peroxidation and activation of the apoptosis signal-regulating kinase/p38, c-Jun NH2-terminal kinase (JNK) pathways, but not the Raf/MEK/extracellular signal-regulated kinase pathway, elicited by acutely administered Ang II. Apocynin but not 5-HD suppressed Ang II-induced augmentations of the NAD(P)H oxidase complex formation (p47phox, p22phox, and Rac-1) and its activity in the heart. Finally, 5-HD suppressed superoxide production by isolated cardiac mitochondria without any effect on their respiration. These results suggest that the preconditioning effects of Ang II for cardiac I/R injury may be mediated by cardiac mitochondria-derived ROS enhanced through NAD(P)H oxidase via JNK and p38 mitogen-activated protein kinase activation.