DJ-1蛋白在去氧肾上腺素诱导的心肌细胞肥厚中的作用

目的 探讨DJ-1对去氧肾上腺素（phenylephrine,PE）诱导的心肌细胞肥厚的调控作用.方法 应用PE诱导乳鼠导致心肌细胞肥厚;通过Western blot观察心肌细胞DJ-1在PE刺激下的表达量改变;通过腺病毒载体过表达DJ-1,检测过表达效率;荧光定量聚合酶链反应（polymerase chain reaction,PCR）检测心肌肥厚标志物心房利钠肽（atrial natriuretic peptide,ANP）和B型利钠肽（B type-natriuretic peptide,BNP） mRNA表达水平改变;显微镜观察心肌细胞面积改变.结果 在PE诱导的心肌细胞肥厚过程中,DJ-1表达水平下调;PE可诱导ANP和BNP表达水平升高,心肌细胞面积增加;过表达DJ-1则显著抑制ANP和BNP的上调,减少心肌细胞面积的增大.结论 DJ-1可抑制PE诱导的心肌细胞肥厚.     

替米沙坦对血管紧张素II诱导的心肌肥大的作用及可能机制

目的探讨替米沙坦对血管紧张素II(AngII)诱发的肥大心肌细胞膜AT1和AT2受体表达变化的影响。方法体外培养心肌细胞,分为三组:对照组,AngII处理组,替米沙坦处理组。构建AngII诱发心肌细胞肥大模型,提取各组心肌细胞膜蛋白,免疫印记(Western Blotting)观察肥大心肌细胞中AT1和AT2表达。结果相对于对照组,AngII处理组心房利钠肽(ANP),脑钠肽(BNP)基因表达明显上升(P<0.05),AT1和AT2受体表达也显著上升(P<0.05);相对于AngII组,替米沙坦处理组ANP,BNP基因和AT1受体表达明显下降(P<0.05)。结论替米沙坦可以明显抑制AngII诱发的心肌细胞肥大,其机制与其降低因AngII诱发AT1受体表达升高和维持AngII引起的AT2受体高表达有关。     

微小RNA-155调节钙调磷酸酶和活化T细胞核因子4表达对心肌细胞肥大的影响

目的研究微小(microRNA,miR)-155对心肌细胞肥大的影响及对钙调磷酸酶(CaN-β)和活化T细胞核因子4(NFAT-4)表达的调控作用。方法培养大鼠心肌细胞H9C2(2-1),血管紧张素(Ang)Ⅱ诱导心肌细胞肥大,脂质体转染法将miR-155模拟物和miR-155抑制物转染入心肌细胞。分为对照组、AngⅡ组、mimics组、inhibitors组、AngⅡ+mimics组和AngⅡ+inhibitors组。实时荧光定量PCR检测心肌细胞miR-155的表达。逆转录PCR法检测心房钠尿肽(ANP)、β-肌球蛋白重链(β-MHC)和CaN-βmRNA表达水平。Western blot法检测CaN-β和NFAT-4蛋白表达水平。结果与AngⅡ组比较,AngⅡ+mimics组ANP、β-MHC、心肌细胞表面积、CaN-βmRNA和蛋白表达及NFAT-4蛋白表达明显降低,差异有统计学意义(P<0.05)。结论 CaN-β可能为miR-155的作用靶点,miR-155可通过负性调控CaN-β和NFAT-4的表达,减少心肌细胞ANP和β-MHC表达,抑制心肌细胞肥大。     

阿托伐他汀在1-磷酸鞘氨醇诱导心肌细胞肥大中的作用

目的研究阿托伐他汀对1-磷酸鞘氨醇(S1P)诱导乳鼠心肌细胞肥大反应中的作用。方法原代培养乳鼠心肌细胞,测定心肌细胞体积和[3H]-亮氨酸掺入量作为心肌细胞肥大的指标。乳鼠心肌细胞使用不同浓度的阿托伐他汀(atorvastatin),加入S1P,[3H]-亮氨酸掺入量作为心肌细胞蛋白摄取量;分别用qPCR和Western blot法检测心肌细胞的β-肌球蛋白(β-MHC)的mRNA和蛋白质表达水平;用qPCR检测心肌细胞的心房利钠肽(ANF)的mRNA表达水平。结果与S1P组比较,阿托伐他汀10μmol/L处理组[3H]-亮氨酸掺入率减少[(234.89%±31.23%)比(342.23%±31.60%),P=0.205],β-MHC的mRNA和蛋白表达水平下降[(0.59±0.14)比(0.84±0.20),P=0.318]和[(0.55±0.09)比(0.98±0.15),P=0.223],ANF的mRNA表达水平降低[(0.51±0.13)比(0.76±0.19),P=0.445];与S1P组比较,阿托伐他汀20μmol/L处理组[3H]-亮氨酸掺入率明显减少[(189.07%±17.69%)比(342.23%±31.60%),P<0.01],β-MHC的mRNA和蛋白表达水平显著下降[(0.50±0.12)比(0.84±0.20),P<0.01]和[(0.35±0.08)比(0.98±0.15),P<0.01],ANF的mRNA水平明显降低[(0.47±0.12)比(0.76±0.19),P<0.01]。结论阿托伐他汀可抑制S1P诱导的心肌细胞肥大,并可减少S1P诱导的β-MHC和ANF表达。     

大鼠甲状旁腺素对体外培养心室肌细胞的促肥大作用

目的 观察不同浓度大鼠甲状旁腺素1-34（rat parathyroid hormone 1-34,rPTH1-34）对体外培养心室肌细胞的致肥大作用,观察细胞外信号调节激酶1/2（extracellular signal regulated kinases 1/2,ERK1/2）的变化。方法 体外培养新生大鼠心室肌细胞,以1×10-8～1×10-6 mol/L rPTH1-34分别孵育24 h,测定细胞直径、3H-亮氨酸(3H-Leu)掺入率、心房钠尿肽（atrial natriuretic peptide,ANP）mRNA、ERK1/2、磷酸化ERK1/2(p-ERK1/2)蛋白的表达。结果 与正常组相比,1×10-8 mol/L rPTH 1-34可使体外培养的心肌细胞直径、细胞蛋白合成速率轻度增加,ANP mRNA表达轻度升高,但无统计学意义;1×10-7,1×10-6 mol/L rPTH1-34 均可显著增加心肌细胞直径（P<0.01）,细胞蛋白合成速率（P<0.01）和ANP mRNA表达（P<0.01）。与正常组比较,PTH呈浓度依赖性地增加了ERK1/2和p-ERK1/2的表达（P<0.01）。结论 1×10-7,1×10-6 mol/L rPTH1-34能在体外诱导新生大鼠心室肌细胞发生肥大反应,且呈一定的浓度依赖性;PTH能呈浓度依赖性地刺激心肌ERK1/2过度表达。     

微小RNA-1负性调控L-钙通道β_2亚基抑制心肌细胞肥大的机制研究

目的:研究微小RNA-1(miR-1)对L-钙通道β2亚基的调控作用及对心肌细胞肥大的影响。方法:ISO诱导心肌细胞肥大。qRT-PCR和Western blot法分别检测心肌细胞ANP、β-MHC、miR-1和β2亚基mRNA和蛋白表达水平。应用Targetscan预测miR-1的靶基因。构建的重组质粒和miR-1共转染HEK293细胞。转染miR-1mimic使其过表达。RNAi干扰β2蛋白表达。激光共聚焦显微镜检测心肌细胞内钙离子浓度。结果:①ISO诱导心肌细胞肥大时,miR-1表达明显降低;转染miR-1mimic使其过表达,心肌细胞表面积、ANP和β-MHC mRNA表达均显著降低。②Targetscan预测显示,L-钙通道β2亚基为miR-1的潜在靶基因;将miR-1和含β23′UTR报告基因共转染HEK293细胞,其萤光值显著降低;转染miR-1mimic使其过表达,可明显抑制β2蛋白的表达。③ISO诱导心肌细胞肥大时,β2蛋白表达明显增加;RNAi干扰β2蛋白表达可明显抑制心肌细胞表面积、ANP和β-MHC mRNA表达的增加;④转染miR-1mimic使其过表达或RNAi干扰β2蛋白表达,心肌细胞内钙离子浓度均明显降低。结论:L-钙通道β2亚基为miR-1的靶基因。MiR-1可能通过负性调控L-钙通道β2亚基的表达,降低细胞内钙离子浓度,抑制心肌细胞肥大。     

泛素蛋白酶体抑制剂抑制钙调神经磷酸酶依赖的心肌细胞肥大

目的 研究泛素蛋白酶体抑制剂MG262对钙调神经磷酸酶信号通路的影响,探讨其抑制心肌细胞肥大的机制。方法 在去甲肾上腺素诱导培养的乳鼠肥大心肌细胞中加入MG262,通过Phalloidin染色观察细胞的形态,RNA Dot Blot检测胚胎蛋白基因表达,Western blot检测细胞中钙调神经磷酸酶蛋白含量,免疫荧光标记观察活化T细胞核因子c4（NFATc4）蛋白在细胞内分布。结果 去甲肾上腺素使细胞面积增大近1.1倍,胚胎基因心房利钠因子（ANF）、脑钠肽（BNP）、β肌球蛋白重链（β-MHC）的mRNA表达上调,细胞核内NFATc4蛋白表达水平增加。MG262明显抑制去甲肾上腺素诱导的细胞肥大（P<0.05）和ANP、BNP、β-MHC的mRNA表达上调（P<0.05）,细胞面积下降了33%;同时MG262使去甲肾上腺素诱导的细胞钙调神经磷酸酶蛋白表达水平下降,抑制NFATc4核内转位。结论 MG262可能通过抑制钙调神经磷酸酶信号通路,减轻心肌细胞肥大。     

4,4′-二异硫氰基芪-2,2′-二磺酸对血管紧张素Ⅱ诱导心肌细胞肥大的作用

目的探讨氯通道阻滞剂4,4′-二异硫氰基芪-2,2′-二磺酸(DIDS)对血管紧张素Ⅱ(AngⅡ)诱导H9C2心肌细胞肥大的作用及其可能机制。方法应用AngⅡ1μmol/L刺激心肌H9C2细胞株,构建心肌细胞肥大模型,观察12、24、36、48和72h各项表达,另给予50、100、200μmol/L DIDS预处理H9C2细胞,细胞分组:空白组、AngⅡ组、DIDS组、AngⅡ+DIDS组;免疫荧光染色测量细胞表面积,BCA法检测蛋白含量,实时定量PCR法检测心肌肥厚基因心房钠尿肽(ANP)和肌球蛋白重链(β-MHC)mRNA表达,二氯荧光素二乙酸检测活性氧水平。结果48h细胞表面积最大(50 166±2697)μm2和总蛋白含量最大(1.68±0.06)mg/107个,36hANP mRNA为4.08±0.38和β-MHC mRNA为2.80±0.18,表达量均最高。与空白对照组比较,AngⅡ组心肌细胞表面积、总蛋白含量、ANP、β-MHC mRNA表达量和细胞内活性氧水平明显增加(P0.05),DIDS组无显著差异(P0.05);与AngⅡ组比较,DIDS+AngⅡ组的心肌细胞表面积明显减小(P0.05)、总蛋白含量明显减少(P0.05)、ANP mRNA和β-MHC mRNA表达量明显减低(P0.05)、细胞内活性氧水平明显下降(P0.05)。结论 DIDS可以有效抑制AngⅡ诱导的H9C2心肌细胞肥大,其机制可能与降低活性氧的水平有关。     

Estrogen inhibits cardiac hypertrophy: role of estrogen receptor-beta to inhibit calcineurin

Estrogen has been reported to prevent development of cardiac hypertrophy in female rodent models and in humans. However, the mechanisms of sex steroid action are incompletely understood. We determined the cellular effects by which 17beta-estradiol (E2) inhibits angiotensin II (AngII)-induced cardiac hypertrophy in vivo. Two weeks of angiotensin infusion in female mice resulted in marked hypertrophy of the left ventricle, exacerbated by the loss of ovarian steroid hormones from oophorectomy. Hypertrophy was 51% reversed by the administration of E2 (insertion of 0.1 mg/21-d-release tablets). The effects of E2 were mainly mediated by the estrogen receptor (ER) beta-isoform, because E2 had little effect in ERbeta-null mice but comparably inhibited AngII-induced hypertrophy in wild-type or ERalpha-null mice. AngII induced a switch of myosin heavy chain production from alpha to beta, but this was inhibited by E2 via ERbeta. AngII-induced ERK activation was also inhibited by E2 through the beta-receptor. E2 stimulated brain natriuretic peptide protein expression and substantially prevented ventricular interstitial cardiac fibrosis (collagen deposition) as induced by AngII. Importantly, E2 inhibited calcineurin activity that was stimulated by AngII, related to E2 stimulating the modulatory calcineurin-interacting protein (MCIP) 1 gene and protein expression. E2 acting mainly through ERbeta mitigates the important signaling by AngII that produces cardiac hypertrophy and fibrosis in female mice.     

Impact of sphingosine kinase 2 deficiency on the development of TNF-alpha-induced inflammatory arthritis

Sphingolipids are components of the plasma membrane whose metabolic manipulation is of interest as a potential therapeutic approach in a number of diseases. Sphingosine kinase 1 (SphK1), the major kinase that phosphorylates sphingosine to sphingosine-1-phosphate (S1P), was previously shown by our group and others to modulate inflammation in murine models of inflammatory arthritis, inflammatory bowel disease and asthma. Sphingosine kinase 2’s (SphK2) impact on inflammation is less well known, as variable results were reported depending on the disease model. A specific SphK2 inhibitor inhibited inflammatory arthritis in one model, while siRNA knockdown of SphK2 worsened arthritis in another. We previously demonstrated that SphK1 deficient mice are protected against development of hTNF-α-induced arthritis. To investigate the role of SphK2 in TNF-α-induced arthritis, we developed SphK2 deficient hTNF-α overexpressing mice and separately treated hTNF-α mice with ABC294640, a SphK2-specific inhibitor. Our data show that genetic inhibition of SphK2 did not significantly impact the severity or progression of inflammatory arthritis, while pharmacologic inhibition of SphK2 led to significantly more severe arthritis. Compared to vehicle-treated mice, ABC294640 treated mice also had less S1P in whole blood and inflamed joint tissue, although the differences were not significant. ABC294640 treatment did not affect SphK1 activity in the inflamed joint while little SphK2 activity was detected in the joint. We conclude that the differences in the inflammatory phenotype in genetic inhibition versus pharmacologic inhibition of SphK2 can be attributed to the amount of ABC294640 used in the experiments versus the impact of acute inhibition of SphK2 with ABC294640 versus genetically induced life-long SphK2 deficiency. Thus, inhibition of SphK2 appears to be proinflammatory in contrast to the clear anti-inflammatory effects of blocking SphK1. Therapies directed at this sphingosine kinase pathways will need to be specific in their targeting of sphingosine kinases.     

腺苷A1受体与к阿片肽受体激活对异丙肾上腺素诱导的心肌细胞肥大的交互作用

目的观察腺苷A1受体与κ阿片肽受体(κ-OR)激活对异丙肾上腺素(Iso)诱导的心肌细胞肥大的交互作用及机制。方法体外培养大鼠乳鼠心肌细胞,以Iso 10μmol/L诱导心肌细胞肥大,观察腺苷A1受体激动剂R(-)-N6-(2-phenylIsopropyl)adenosine(R-PIA)1μmol/L和κ-OR激动剂U50,488H1μmol/L对其作用,进一步探讨腺苷A1受体拮抗剂8-cyclopentyl-1,3-dipropylxanthine(CPDPX)0.1μmol/L存在时κ-OR的激活对细胞肥大的影响和κ-OR拮抗剂nor-binaltorphimine(NOR-BNI)1μmol/L存在时腺苷A1受体的激活对心肌细胞肥大的影响。通过Lowry法测心肌细胞蛋白含量;消化分离法及计算机图像分析系统测细胞体积;以Fluo-3/AM为荧光探针,共聚焦显微镜下测量心肌细胞内[Ca2+]i变化;RT-PCR法检测心肌细胞心房钠尿肽(ANP)的mRNA表达。结果 10μmol/LIso可以诱导心肌细胞肥大,1μmol/L的R-PIA(腺苷A1受体激动剂)可以明显抑制Iso诱导的心肌细胞蛋白合成增加、体积增大、ANPmRNA表达增加、心肌细胞内[Ca2+]i荧光强度增大,该抑制作用可以被1μmol/Lκ-OR拮抗剂NOR-BNI部分阻断;κ-OR激动剂U50,488H1μmol/L可以明显抑制Iso诱导的心肌细胞蛋白合成增加、体积增大、ANPmRNA表达增加、心肌细胞内[Ca2+]i荧光强度增大,该抑制作用可以被腺苷A1受体拮抗剂CPDPX部分阻断。结论腺苷可通过激动A1受体、阿片肽可通过激动κ受体抑制Iso诱导的心肌肥大,二者可以通过影响心肌细胞内[Ca2+]i浓度的增大而交互抑制Iso诱导的心肌肥大。     

银杏叶提取物抑制培养的乳鼠心肌细胞肥大及其信号传导机制的实验研究

目的在原代培养的新生大鼠心肌细胞上,探讨银杏叶提取物（EGb）及其单体槲皮素（Que）对血管紧张素Ⅱ（AngⅡ）诱导的心肌细胞肥大的抑制作用及其机制.方法采用Lowry法测定心肌细胞总蛋白含量;相差显微镜测量细胞大小;测定超氧化物歧化酶活性和丙二醛含量观察氧自由基代谢的变化;采用Western blot方法检测p-ERK1/2、p-JNK和p-P38蛋白的表达.结果EGb和Que能明显抑制AngⅡ引起的心肌细胞总蛋白含量及直径的增加,并能显著提高心肌细胞超氧化物歧化酶活性,降低丙二醛含量.AngⅡ诱导的心肌细胞p-ERK1/2、p-JNK和p-P38表达均明显增强.Que能明显抑制AngⅡ诱导的p-JNK表达.结论EGb和Que对AngⅡ诱导的心肌细胞肥大有明显的抑制作用.Que的作用可能与ROS/JNK信号传导通路有关.     

Sphingosine kinase 2: a controversial role in arthritis

SphK2 is a nuclear protein that suppresses cell proliferation by inhibiting DNA synthesis, while also enhancing apoptosis in diverse cell types. ABC294640 (a selectively SphK2 inhibitor) attenuated the knee joint histological damage and pain associated with MIA-induced OA in rats. However, recent studies revealed that genetic inhibition of SphK2 did not significantly impact the severity or progression of inflammatory arthritis, while pharmacologic inhibition of SphK2 led to significantly more severe arthritis. Therefore, SphK2 plays a controversial role in arthritis.     

Involvement of calcineurin in angiotensin II-induced cardiomyocyte hypertrophy and cardiac fibroblast hyperplasia of rats

A rapidly emerging body of literature implicates a pivotal role for the Ca2+-calmodulin-dependent phosphatase, calcineurin, as a cellular target for a variety of Ca2+-dependent signaling pathways culminating in cardiac hypertrophy. The aim of the present study was to test whether calcineurin is involved in the signal transduction of angiotensin II (AngII)-induced cardiac myocyte hypertrophy and fibroblast hyperplasia. Firstly, we observed that calcineurin activity was significantly increased in AngII-stimulated cardiac myocytes as well as fibroblasts, but was markedly inhibited by Losartan (50 micromol/l), H7 (50 micromol/l), and Fura-2/AM (5 micromol/l). It is indicated that AngII-induced activation of calcineurin is through an ATI receptor, may be dependent on the sustained increases of [Ca2+]i, and be regulated by protein kinase C. In a second experiment, we found that cyclosporin (0.1-10micromol/l), a specific inhibitor of calcineurin, decreased the protein synthesis rate in AngII-stimulated cardiomyocytes and the DNA synthesis rate in AngII-treated fibroblasts in a dose-dependent manner. In the latter experiment, calcineurin inhibition reduced the mRNA level of the atrial natriuretic factor gene. These results indicate that calcineurin is involved in the signal transduction of AngII-induced cardiomyocyte hypertrophy and fibroblast hyperplasia.     

丙戊酸对AngⅡ诱导的心肌细胞肥大与HDAC2表达的抑制作用

目的: 观察组蛋白脱乙酰基酶抑制剂—丙戊酸（valproic acid,VPA）抑制心肌细胞肥大和组蛋白脱乙酰基酶2（histone deacetylase 2，HDAC2）的表达。方法: 常规方法培养原代心肌细胞，分为5组:对照组、肥大组、低浓度VPA组(5×10-6 mol/L)、中浓度VPA组(10-5 mol/L)和高浓度VPA组(2×10-5 mol/L)。给予血管紧张素Ⅱ(AngⅡ)刺激心肌细胞造成肥大后，给予不同浓度的VPA进行干预。AngⅡ作用24 h后,于相差显微镜下观察心肌细胞面积的变化。用RT-PCR检测HDAC2 mRNA的表达；免疫组化染色法检测HDAC2蛋白的表达。结果: 经AngⅡ刺激后，在相差显微镜下可见心肌细胞面积变大，HDAC2 mRNA的水平增高，HDAC2蛋白表达亦增加。给予不同浓度的VPA后，上述指标随着VPA浓度的增加而逐渐下降（P<0.05）。结论: AngⅡ致心肌细胞肥大的过程中伴有 HDAC2表达增加，给予HDAC抑制制后，可使心肌细胞面积减少，HDAC2表达减少，提示VPA可抑制心肌细胞的肥大，HDAC2有可能参与心肌细胞肥大的机制。     

Cardiomyocyte-specific knockout and agonist of peroxisome proliferator-activated receptor-gamma both induce cardiac hypertrophy in mice

Peroxisome proliferator-activated receptor (PPAR)-gamma is required for adipogenesis but is also found in the cardiovascular system, where it has been proposed to oppose inflammatory pathways and act as a growth suppressor. PPAR-gamma agonists, thiazolidinediones (TZDs), inhibit cardiomyocyte growth in vitro and in pressure overload models. Paradoxically, TZDs also induce cardiac hypertrophy in animal models. To directly determine the role of cardiomyocyte PPAR-gamma, we have developed a cardiomyocyte-specific PPAR-gamma-knockout (CM-PGKO) mouse model. CM-PGKO mice developed cardiac hypertrophy with preserved systolic cardiac function. Treatment with a TZD, rosiglitazone, induced cardiac hypertrophy in both littermate control mice and CM-PGKO mice and activated distinctly different hypertrophic pathways from CM-PGKO. CM-PGKO mice were found to have increased expression of cardiac embryonic genes (atrial natriuretic peptide and beta-myosin heavy chain) and elevated nuclear factor kappaB activity in the heart, effects not found by rosiglitazone treatment. Rosiglitazone increased cardiac phosphorylation of p38 mitogen-activated protein kinase independent of PPAR-gamma, whereas rosiglitazone induced phosphorylation of extracellular signal-related kinase 1/2 in the heart dependent of PPAR-gamma. Phosphorylation of c-Jun N-terminal kinases was not affected by rosiglitazone or CM-PGKO. Surprisingly, despite hypertrophy, Akt phosphorylation was suppressed in CM-PGKO mouse heart. These data show that cardiomyocyte PPAR-gamma suppresses cardiac growth and embryonic gene expression and inhibits nuclear factor kappaB activity in vivo. Further, rosiglitazone causes cardiac hypertrophy at least partially independent of PPAR-gamma in cardiomyocytes and through different mechanisms from CM-PGKO.     

Angiotensin II activates myostatin expression in cultured rat neonatal cardiomyocytes via p38 MAP kinase and myocyte enhance factor 2 pathway

Angiotensin II (AngII) plays a critical role in cardiac remodeling and promotes cardiac myocyte hypertrophy. Myostatin, a negative regulator of muscle growth, is increased in hypertrophied and infarcted heart. The direct effect of AngII on cardiac myocyte myostatin expression has not been previously investigated. We hypothesized that myostatin may act as a cardiac endocrine inhibitor for AngII. AngII-induced myostatin protein expression in cultured rat neonatal cardiomyocytes was dose-dependent. AngII significantly increased myostatin protein and mRNA expression in a time-dependent manner. Addition of losartan, SB203580, or p38 siRNA 30 min before AngII stimulation significantly blocked the increase of myostatin protein by AngII. AngII significantly increased phosphorylation of p38 while SB205380 and losartan attenuated the phosphorylation of p38 induced by AngII. AngII increased, while myostatin-Mut plasmid, SB203580, losartan, and myocyte enhance factor 2 (MEF-2) antibody abolished the myostatin promoter activity. Co-stimulation with myostatin and AngII significantly inhibited the protein synthesis induced by AngII. In conclusion, AngII enhances myostatin expression in cultured rat neonatal cardiomyocytes. The AngII-induced myostatin is mediated through p38 MAP kinase and MEF-2 pathway.     

NADPH oxidase-derived superoxide anion mediates angiotensin II-induced cardiac hypertrophy

Cardiac hypertrophy is an adaptive response to increases in blood pressure. Recent studies indicate that the hypertrophic process is associated with increases in intracellular oxidative stress in cardiomyocytes. We hypothesize that superoxide anion mediates the hypertrophic response and that antioxidant therapy may be effective in attenuating cardiac hypertrophy. Neonatal rat cardiac myocytes were stimulated with angiotensin II (AngII, 1 microM) with and without various antioxidants. N-acetylcysteine (NAC, 10 mM) and probucol (50 microM), and to a lesser extent, vitamin C (500 microM) and reduced glutathione (1 mM), inhibited AngII-induced [(3)H]-leucine uptake and atrial natriuretic factor (ANF) promoter activity. The hypertrophic response is mediated by superoxide anion (O(2)(-).) since cell-permeable polyethylene glycol (PEG)-conjugated superoxide dismutase (50 U/ml), but not PEG-catalase (500 U/ml), attenuated AngII-induced [(3)H]-leucine uptake and ANF promoter activity. Furthermore, NAC blocked AngII-induced increase in myocardial oxidative stress, decreased the expression of ANF and myosin light chain-2v, and inhibited the re-organization of cytoskeletal proteins, desmin and alpha-actinin. These effects of AngII were abolished by angiotensin type 1 receptor blocker, losartan, but not type 2 receptor blocker, PD123319. Indeed, co-administration of losartan (10 mg/kg/d, 14 d) or NAC (200 mg/kg/d, 14 d) inhibited AngII-induced O(2)(-). production and cardiac hypertrophy in rats without affecting blood pressure. These findings indicate that the generation of O(2)(-). contributes to oxidant-induced hypertrophic response and suggest that antioxidant therapy may have beneficial effects in cardiac hypertrophy.