氯沙坦对自发性高血压大鼠细胞外信号调节激酶活性和B型利钠肽表达的影响

目的　探讨氯沙坦治疗高血压心肌肥厚的作用机制。方法　选择同周龄WistarKyoto(WKY)大鼠作正常对照,将2 1只14周龄雄性自发性高血压大鼠(SHR)随机分成3组:模型组、肼屈嗪组(10mg·kg- 1·d- 1)和氯沙坦组(10mg·kg- 1·d- 1)。用West ern印迹方法检测大鼠心肌总细胞外信号调节激酶(t ERK)、磷酸化ERK(p ERK)及有丝分裂素激活蛋白激酶磷酸酶 1(MKP 1)水平;用RT PCR法半定量测定大鼠心肌中B型利钠肽(BNP)mRNA的含量;酶联免疫吸附法检测大鼠血浆BNP水平。结果喂药10周后,氯沙坦组和肼屈嗪组血压相似,均显著低于模型组(n =7,P <0 .0 1)。氯沙坦组心肌肥厚指数显著低于肼屈嗪组和模型组(n =7,P <0 .0 1) ,与WKY组无差异(n =7,P >0 .0 5 ) ;肼屈嗪组和模型组心肌肥厚指数无差异(n =7,P >0 .0 5 )。4组大鼠t ERK水平无显著性差异(n =7,P >0 .0 5 ) ;氯沙坦组心肌p ERK ,p ERK/t ERK及MKP 1水平均显著低于SHR肼屈嗪组和SHR模型组(n =7,P <0 .0 5 ) ,与WKY组无差异(n =7,P >0 .0 5 )。肼屈嗪组和模型组心肌p ERK ,p ERK/t ERK及MKP 1水平无差异(n =7,P >0 .0 5 )。氯沙坦组大鼠心肌BNPmRNA和血浆BNP水平显著低于SHR肼屈嗪组和模型组(n =7,P <0 .0 5 ) ,与WKY组无差异(n =7,P >0 .0 5 ) ;肼屈嗪组和SHR模型组大鼠     

Angiotensin-(1–7) ameliorates myocardial remodeling and interstitial fibrosis in spontaneous hypertension: Role of MMPs/TIMPs

Angiotensin-(1–7) displays antihypertensive and antiproliferative properties although its effect on cardiac remodeling and hypertrophy in hypertension has not been fully elucidated. The present study was designed to examine the effect of chronic angiotensin-(1–7) treatment on myocardial remodeling, cardiac hypertrophy and underlying mechanisms in spontaneous hypertension. Adult male spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats were treated with or without angiotensin-(1–7) or the angiotensin-(1–7) antagonist A-779 for 24 weeks. Mean arterial pressure, left ventricular geometry, expression of the hypertrophic markers ANP and β-MHC, collagen contents (type I and III), collagenase (MMP-1), matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of MMPs-1 (TIMP-1) were evaluated in WKY and SHR rats with or without treatment. Our data revealed that chronic angiotensin-(1–7) treatment significantly suppressed hypertension, left ventricular hypertrophy, expression of ANP and β-MHC as well as myocardial fibrosis in SHR rats, the effects of which were nullified by the angiotensin-(1–7) receptor antagonist A-779. In addition, angiotensin-(1–7) treatment significantly counteracted hypertension-induced changes in the mRNA expression of MMP-2 and TIMP-1 and collagenase activity, the effects of which were blunted by A-779. In vitro study revealed that angiotensin-(1–7) directly increased the activity of MMP-2 and MMP-9 while decreasing the content of TIMP-1 and TIMP-2. Taken together, our results revealed a protective effect of angiotensin-(1–7) against cardiac hypertrophy and collagen deposition, which may be related to concerted changes in MMPs and TIMPs levels. These data indicated the therapeutic potential of angiotensin-(1–7) in spontaneous hypertension-induced cardiac remodeling.     

依那普利对肾性与自发性高血压大鼠左心室Eno1及GSTM2表达的影响

目的观察依那普利对肾性与自发性高血压大鼠左心室α-烯醇化酶(α-enolase,Eno1)及谷胱甘肽-s-转移酶,μ2(glutathione-s-transferase,μ2,GSTM2)表达的影响。方法实验共分5组:(1)对照组;(2)两肾两夹高血压大鼠组;(3)两肾两夹高血压大鼠+依那普利组;(4)自发性高血压大鼠组;(5)自发性高血压大鼠+依那普利组。检测各组大鼠血压及左室重量指数,行超声心动图检查,并运用Western blot检测各组大鼠左心室Eno1、GSTM2及β-肌球蛋白重链(β-myosin heavy chain,β-MHC)的表达情况。结果两肾两夹及自发性高血压大鼠血压与左室重量指数均明显高于对照组,依那普利治疗后,其左心室肥厚均得到明显逆转。与两肾两夹组相比,Eno1在自发性高血压大鼠中的表达明显上调;与对照组相比,GSTM2在自发性高血压大鼠中的表达明显下调,而两肾两夹组无变化,经依那普利治疗后,二者的表达变化均未得到明显逆转;β-MHC在两种模型中的表达均上调,而依那普利治疗后,β-MHC在二者中的表达均明显下调。结论依那普利能明显逆转β-MHC在两种模型中的差异表达,但不能逆转Eno1和GSTM2在二者中的差异表达。     

替米沙坦对肾性高血压大鼠心肌β-肌球蛋白重链表达的影响

目的观察替米沙坦对肾性高血压大鼠心肌β-肌球蛋白重链(β-MHC)的影响。方法雄性SD大鼠30只,随机分为假手术组、模型组和替米沙坦组,每组10只。模型组及替米沙坦组采用两肾一夹法,制备肾血管性高血压模型,替米沙坦组用替米沙坦(10 mg.kg-1.d-1)灌胃干预。术后8周,经动脉插管测血压,经超声心动图评估心脏结构及功能,HE染色观察心肌病理改变;RT-PCR法检测心肌β-MHC mRNA水平。结果与假手术组相比,模型组大鼠血压显著升高,心肌肥厚(均P<0.01),细胞直径增大,排列不整齐。与模型组相比,替米沙坦组大鼠血压明显下降,心肌无明显肥厚(均P<0.01),其心肌β-MHC mRNA表达水平较模型组明显降低(P<0.05)。结论替米沙坦可下调肥厚心肌β-MHC基因表达水平,可能与其逆转心肌肥厚相关。     

Ca2+ buffering function of sarcoplasmic reticulum in rat tail arteries: comparison in normotensive and spontaneously hypertensive rats

The superficial buffer barrier function of the sarcoplasmic reticulum (SR) during rest and that during stimulation with Bay k 8644, an agonist of L-type Ca2+ channels, were compared in endothelium-denuded strips of tail arteries from 13-week-old normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR), by measuring the effects of cyclopiazonic acid (CPA) and thapsigargin that inhibit SR Ca2+-ATPase and the effect of ryanodine that depletes SR Ca2+. The addition of 10 microM CPA induced a transient contraction that was not significantly different between WKY and SHR. The CPA-induced contraction was strongly inhibited by 100 nM nifedipine and was abolished by Ca2+-free solution in both strains. Thapsigargin (100 nM) or ryanodine (10 microM) induced similar, small transient contractions in the two strains. The addition of Bay k 8644 (1-100 nM) almost failed to induce a contraction in both WKY and SHR. When the strips were preincubated with 10 microM CPA, 100 nM thapsigargin or 10 microM ryanodine, Bay k 8644 induced similar concentration-dependent contractions in the two strains. The amount of Ca2+ stored in the SR, as estimated from the 20 mM caffeine-induced contraction, was not significantly different between WKY and SHR. Our results suggest that the SR of rat tail arteries can buffer a large amount of Ca2+ that enters the cell during the rest and the Bay k 8644 stimulation, and these functions are not altered in SHR.     

Effect of age and of hypertrophy on cardiac Ca2+ antagonist binding sites

We explored the effect of age and of hypertrophy on Ca2+ antagonist binding site density (Bmax), affinity (Kd), and selectivity in cardiac membranes harvested from the hearts of young adult (9-week-old) and older (25-week-old) Sprague Dawley (SD) rats, Wistar Kyoto rats (WKY), and spontaneously hypertensive rats (SHR). Radioligand binding studies with (+)[3H]PN200-110 failed to show a significant difference between the Bmax obtained for the cardiac membranes of 9-week-old SD, WKY, or SHR. Similarly, at 25 weeks, the Bmax values were the same for each group, but in each group the Bmax tended to increase with age. The Kd and selectivity were unchanged. For (-)[3H]D888 binding, the Kd values changed with age, but there was no hypertension or hypertrophy-linked increase in Bmax. In the SD and SHR series, but not in the WKY, there was a tendency for the Bmax to increase with age. We interpreted these results to mean that age may contribute to the different Kd and Bmax values described for cardiac membranes from 25-week-old WKY and SHR.     

四氢姜黄素对压力负荷引起的小鼠心肌肥厚的保护作用

目的 探究四氢姜黄素（THC）能否减轻压力负荷引起的成年小鼠病理性心肌肥厚。方法 24只C57BL/6小鼠随机分为4组：假手术（Sham）组、THC组、主动脉弓缩窄（TAC）组及TAC+THC组,每组6只。通过TAC术建立小鼠心肌肥厚模型,Sham组和THC组不结扎主动脉弓。TAC术后每日通过饮水摄入THC（120 mg/kg）。TAC术后4周检测小鼠心脏功能,分离心脏和肺脏计算心脏/体质量比和肺脏/体质量比,HE 染色计算心肌细胞平均横截面积,Masson 染色观察心脏组织胶原沉积程度,Western blotting 检测 α-肌球蛋白重链（α-MHC）、β-肌球蛋白重链（β- MHC）蛋白表达,实时定量PCR（real-time PCR）检测心房钠尿肽（ANP）mRNA表达情况。结果 TAC术后4周,小鼠发生病理性心肌肥厚,表现为心脏/体质量比、肺脏/体质量比、心肌细胞平均横截面积、心脏组织胶原沉积、β-MHC和ANP表达较Sham组小鼠明显增高,而左室射血分数（LVEF）、左室短轴缩短率（LVFS）和α-MHC表达较Sham组小鼠明显降低。与TAC组相比,THC处理可以明显缓解TAC引起的病理性心肌肥厚,改善心脏功能,提高α-MHC表达,降低心脏/体质量比、肺脏/体质量比、心肌细胞平均横截面积、心脏组织胶原沉积、β-MHC和ANP表达（均P＜ 0.05）。结论 THC能够有效减轻压力负荷引起的病理性心肌肥厚。     

EFFECTS OF VERATRIDINE ON THE ACTION POTENTIALS AND CONTRACTILITY OF RIGHT AND LEFT VENTRICLES FROM NORMO- AND HYPERTENSIVE RATS

1. We have studied the effects of prolonging the opening of sodium channels with veratridine on the action potentials (AP) and contractility of isolated right and left ventricles of Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). It was examined whether the effects of veratridine were altered in the SHR right ventricle in the absence of hypertrophy. The main aim of the present study was to test the hypothesis that the effects of veratridine were altered in the SHR left ventricle in the presence of hypertrophy. 2. The tail-cuff pressures of 14- and 22-week-old, but not 5-week-old, SHR were greater than those of the WKY rat. At 14 weeks of age the SHR left, but not right, ventricle had developed hypertension-associated hypertrophy. 3. The AP and contractions and the ability of veratridine to prolong the AP and act as a positive inotrope were similar in the right ventricles from 22-week-old WKY rats and SHR. The effects of veratridine and the AP and contractions of left ventricles of 5-, 14- and 22-week-old WKY rats and of 5- and 14-week-old SHR were also similar. 4. The AP of the left ventricles of 22-week-old SHR were prolonged by 3 ms at the action potential duration (APD)₅₀ and APD₉₀ levels. The contractions to cardiac stimulation and the maximum combined force responses to cardiac stimulation and isoprenaline were reduced in the left ventricles of 22-week-old SHR compared with WKY rats and younger SHR. 5. The effectiveness of veratridine in prolonging the AP and augmenting the contractions to cardiac stimulation was reduced in the hypertrophied left ventricle of 22-week-old, but not 14-week-old, SHR. 6. In summary, the response to prolonging the opening of sodium channels with veratridine is not altered in the SHR right ventricle. However, in left ventricles of the hypertrophied 22-week-old, but not 14-week-old, SHR the effects of veratridine are reduced and this demonstrates that the response to prolonging the opening of sodium channels is changed in persistent hypertension-associated hypertrophy.     

氯沙坦对糖尿病大鼠肾小管转化生长因子β_1及蛋白激酶Cβ表达的影响

目的探讨血管紧张素受体拮抗剂氯沙坦在糖尿病大鼠早期肾损伤中的保护作用及其机制。方法将36只实验动物随机分为正常对照组、糖尿病组及氯沙坦治疗组。链脲佐菌素(STZ)60 m g/kg制作糖尿病动物模型,检测各组大鼠的血糖、血肌酐、尿白蛋白、肾脏肥大指数的变化,免疫组织化学检测转化生长因子1β(TGF-1β)、蛋白激酶Cβ(PKCβ)的表达水平。结果治疗第8周末,氯沙坦治疗组较非治疗组白蛋白明显减少(P<0.01),肾脏肥大指数改善(P<0.05),免疫组织化学显示,糖尿病组大鼠肾小管TGF-1β和PK Cβ蛋白表达增多,氯沙坦治疗组TG F-1β和PKCβ蛋白表达均明显减少。结论氯沙坦对糖尿病早期肾脏病变有一定的保护作用,其机制可能是通过下调糖尿病大鼠TGF-1β和PKCβ的表达实现的。     

Release of atrial natriuretic peptide from rat myocardium in vitro: effect of minoxidil-induced hypertrophy.

1. Ventricular hypertrophy is characterized by stimulation of ventricular synthesis of atrial natriuretic peptide (ANP). To examine the role of ventricular ANP levels in the secretion of ANP into the circulation, atrial and ventricular levels of immunoreactive-ANP (IR-ANP) as well as ANP messenger RNA (mRNA), and the release of IR-ANP from isolated perfused hearts, both before and after atrialectomy, were measured simultaneously in control and minoxidil-treated Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats. 2. IR-ANP levels in the ventricles of untreated, 12 month-old SHR with severe ventricular hypertrophy were increased when compared to age-matched WKY rats. Minoxidil treatment for 8 weeks in both strains resulted in a decrease in mean arterial pressure and increases in ventricular weight to body weight ratios, plasma IR-ANP concentrations (in WKY from 133 +/- 20 to 281 +/- 34 pg ml-1, P less than 0.01; in SHR from 184 +/- 38 to 339 +/- 61 pg ml-1, P less than 0.05), and in ventricular IR-ANP contents (in WKY: 53%; in SHR: 41%). A highly significant correlation was found between ventricular IR-ANP content and ventricular weight to body weight ratio (r = 0.59, P less than 0.001, n = 26). 3. When studied in vitro, in isolated perfused heart preparations, the hypertrophied ventricular tissue after atrialectomy secreted more ANP into the perfusate than ventricles of the control hearts; ventricles contributed 28%, 22%, 18% and 15% of the total ANP release to perfusate in the minoxidil-treated SHR, control SHR, minoxidil-treated WKY and control WKY, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ambient air PM2.5 exposure induces heart injury and cardiac hypertrophy in rats through regulation of miR-208a/b, α/β-MHC,and GATA4

Ambient air fine particulate matter (PM_2.5) may increase cardiovascular disease risks. In this study, we investigated the miR-208/GATA4/myosin heavy chain (MHC) regulation mechanisms on cardiac injury in rats after PM_2.5 exposure via an animal inhalation device. The results showed that PM_2.5 exposure for 2 months caused pathological heart injury, reduced nucleus-cytoplasm ratio, and increased the levels of CK-MB and cTnI, showing cardiac hypertrophy. Oxidative stress and inflammatory responses were also observed in rats’ hearts exposed to PM_2.5. Of note, PM_2.5 exposure for 2-month significantly elevated GATA4 and β-MHC mRNA and protein expression compared with the corresponding controls, along with the high-expression of miR-208b. The ratios of β-MHC/α-MHC expression induced by PM_2.5 were remarkably raised in comparison to their controls. It suggested that the up-regulation of miR-208b/β-MHC and GATA4 and the conversion from α-MHC to β-MHC may be the important causes of cardiac hypertrophy in rats incurred by PM_2.5.     

苯那普利及坎地沙坦对自发性高血压大鼠心肌肥厚过程中SMAD蛋白的影响

目的观察自发性高血压大鼠(SHR)心肌肥厚程度与转化生长因子β1(TGF-β1)、Smad3和Smad7蛋白的表达及苯那普利、坎地沙坦的治疗作用。方法12wk龄SHR连续灌胃给予苯那普利或(和)坎地沙坦,每2wk测定尾动脉压,12wk后检测心脏构型、心脏指数、心肌细胞大小、心肌和血浆AngⅡ含量、心肌中TGF-β1、Smad3和Smad7蛋白的表达。结果SHR血压、心脏指数、心肌细胞大小及心肌组织中TGF-β1、Smad3蛋白明显增加,苯那普利或坎地沙坦治疗均能使上述指标减轻,联合应用具有协同作用,且能降低心肌和血浆AngⅡ含量;苯那普利或坎地沙坦治疗能增加在SHR中表达下降的Smad7蛋白,但两者合用对Smad7表达改善不明显。结论苯那普利和坎地沙坦联合应用对改善自发性高血压大鼠心肌肥厚具有协同作用,可能与调节AngⅡ水平、减少高血压心肌肥厚过程中TGF-β1和Smad3表达有关。     

Possible mechanism of the potent vasoconstrictor actions of ryanodine on femoral arteries from spontaneously hypertensive rats.

1. The Ca2+ buffering function of sarcoplasmic reticulum (SR) in the resting state of arteries from spontaneously hypertensive rats (SHR) was examined. Differences in the effects of ryanodine that removes the function of SR, on tension and cellular Ca2+ level were assessed in endothelium-denuded strips of femoral arteries from 13-week-old SHR and normotensive Wistar-Kyoto rats (WKY). 2. The addition of ryanodine to the resting strips caused a concentration-dependent contraction in SHR. This contraction was extremely small in WKY. In the presence of 10(-5) M ryanodine, caffeine (20 mM) failed to cause a further contraction in SHR, but it caused a small contraction in WKY. After washout of the strips with a Krebs solution, the resting tone was greatly elevated in SHR when compared with WKY. 3. The elevated resting tone in SHR strips was abolished by 10(-7) M nifedipine. The ryanodine-induced contraction was also abolished by 10(-7) M nifedipine. Nifedipine itself caused a relaxation from the resting tone of SHR strips, suggesting the maintenance of myogenic tone. 4. In strips preloaded with fura-PE3, the addition of 10(-5) M ryanodine caused a large and moderate elevation of cytosolic Ca2+ level ([Ca2+]i) in SHR and WKY, respectively. After washout, the resting [Ca2+]i was greatly elevated in SHR. The ryanodine-induced elevation of [Ca2+]i was decreased by 5 x 10(-6) M verapamil in SHR. Verapamil itself caused a decrease in resting [Ca2+]i which was significantly greater in SHR than in WKY, and caused a relaxation only in SHR. 5. The resting Ca2+ influx in arteries measured by a 5 min incubation with 45Ca was significantly increased in SHR when compared with WKY. The resting Ca2+ influx was not increased by 10(-5) M ryanodine in both SHR and WKY. The net cellular Ca2+ uptake in arteries measured by a 30 min incubation with 45Ca was decreased by 10(-5) M ryanodine in both strains. 6. The resting Ca2+ influx was decreased by 10(-7) M nifedipine in the SHR artery, but it was unchanged in the WKY artery. 7. These results suggest that (1) the Ca2+ influx via L-type voltage-dependent Ca2+ channels was increased in the resting state of the SHR femoral artery, (2) the greater part of the increased Ca2+ influx was buffered by Ca2+ uptake into the SR and some Ca2+ reached the myofilaments resulting in the maintenance of the myogenic tone, and (3) therefore the functional removal of SR by ryanodine caused a potent contraction in this artery.     

Effect of phorbol ester on the release of atrial natriuretic peptide from the hypertrophied rat myocardium.

1. To determine the cellular mechanisms of atrial natriuretic peptide (ANP) release from ventricular cardiomyocytes, the secretory and the cardiac effects of a phorbol ester, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), known to stimulate protein kinase C activity in heart cells, were studied in isolated, perfused heart preparations from 2- and 21-month-old Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats. TPA was added to the perfusion fluid for 30 min at a concentration of 46 nM after removal of atrial tissue. Additionally, atrial and ventricular levels of immunoreactive ANP (IR-ANP) and ANP mRNA, the distribution of ANP within ventricles as well as the relative contribution of atria and ventricles in the release of ANP were studied. 2. Ventricular hypertrophy that gradually developed in hypertensive rats resulted in remarkable augmentation of ANP gene expression, as reflected by elevated levels of immunoreactive ANP and ANP mRNA. The total amount of IR-ANP in the ventricles of the SHR rats increased 41 fold and ANP mRNA levels 12.9 fold from the age of 2 to 21 months. At the age of 21 months, levels of IR-ANP and ANP mRNA in the ventricles of SHR rats were 5.4 fold and 3.7 fold higher, respectively, than in the normotensive WKY rats. Immunohistochemical studies demonstrated ANP granules within the hypertrophic ventricles of the old SHR rats, but not within normal ventricular tissue. 3. In isolated perfused heart preparations, the severely hypertrophied ventricular tissue of SHR rats after atrialectomy secreted more ANP into the perfusate than did the control hearts.(ABSTRACT TRUNCATED AT 250 WORDS)     

Blood pressure and alpha-vascular reactivity in hypertensive rats treated with amlodipine and dietary Ca

It has been suggested that the combination of dietary Ca and Ca2+ channel antagonists could have a synergic antihypertensive effect. In this study, 3-week-old male spontaneously hypertensive rats (SHR) were randomized into four groups of animals. Two of these groups were fed on a normal Ca diet (Ca 1%) and the other two groups were fed on a Ca-enriched diet (Ca 2.5%). One of the groups fed on each diet also received amlodipine (1 mg/kg/day) in their drinking water. Systolic and diastolic arterial blood pressure were measured weekly in the rats, from the 6th week of life until the 25th week of life, by the tail-cuff method, and we also calculated the corresponding pulse pressure values (systolic blood pressure-diastolic blood pressure). Determination of plasma Ca levels by colourimetric methods, and measurement in pithed rats of the pressor responses to the alpha-adrenoceptor agonists methoxamine and B-HT 920 (5-allyl-2-amino-5,6,7,8-tetrahydro-4H-thiazolo-(4,5-d)-acepin-dihydrochloride, talixepole) were also performed using 16- and 23-week-old animals from the different groups. The Ca-enriched diet decreased systolic and diastolic blood pressure in SHR. Almodipine also decreased systolic and diastolic blood pressure in SHR, and this drug intensified the antihypertensive effect of the Ca 2.5% diet in the SHR between weeks 13 and 18. Nevertheless, in the 19- to 25-week-old SHR amlodipine antagonized the effect of dietary Ca on arterial blood pressure. A decrease in the pulse pressure was seen only in the 15- to 20-week-old SHR which had been simultaneously treated with dietary Ca and amlodipine. All the treatments used increased calcaemia, and the highest plasma Ca levels were obtained in the animals which had received the combined treatment with Ca and amlodipine. The responses to methoxamine and to B-HT 920 in the pithed 16-week-old SHR were similar in the four groups of animals. The responses to these agonists in the pithed 23-week-old SHR fed on the Ca-enriched diet were smaller than the corresponding responses in 23-week-old SHR of the untreated group. By contrast, the responses to these agonists were slightly higher in the pithed 23-week-old SHR which were treated with amlodipine than in the pithed 23-week-old SHR in the untreated group. Moreover, amlodipine partially reversed the effect of dietary Ca on alpha-vascular reactivity. According to our results, it would seem inadvisable to use dietary Ca with a Ca2+ channel antagonist with the aim of controlling arterial blood pressure.     

Inhibitory effect of ginsenoside Rb1 on calcineurin signal pathway in cardiomyocyte hypertrophy induced by prostaglandin F2α

Aim： To examine the antihypertrophic effect of ginsenoside Rb1 （Rb1） induced by prostaglandin F2α （PGF2α） in vitro and to investigate the possible mechanisms involved in the calcineurin （CAN） signal transduction pathway. Methods： The cardiomyocyte hypertrophy induced by PGF2α and the antihypertrophic effect of Rb1 were evaluated in primary culture by measuring the cell diameter, protein content, and atrial natriuretic peptide （ANP） mRNA expression. ANP and CaN mRNA expressions, CaN and its downstream effectors NFAT3 and GATA4 protein expressions, and the intracellular free Ca^2＋ concentration （[Ca^2＋]i） were assayed by RT-PCR, Western blot, and fluorescent determination using Fura 2/AM, respectively. Results： PGF2α （100 nmol/L） significantly increased the cardiomyocyte diameter, protein content and [Ca^2＋]i, and promoted ANP, CaN mRNA, and CaN/NFAT3/GATA4 protein expressions, which were inhibited by either Rb1 in a concentration-dependent manner （50, 100, and 200 μg/mL） or L-arginine （1 mmol/L）. N^G-nitro-L-arginine-methyl ester, a nitric oxide synthase inhibitor, could abolish the effects of L-arginine, but failed to change the effects of Rb1 in the experiments above. Conclusion： The present data implicate that Rb1 attenuates cardiac hypertrophy, the underlying mechanism may be involved in the inhibition of the Ca^2＋-CaN signal transduction pathway.     

番石榴叶总黄酮对高血压模型大鼠心肌肥厚的改善作用

目的 研究番石榴叶总黄酮对高血压模型大鼠心肌肥厚的改善作用.方法 从60只健康SD大鼠中随机取10只作为正常组;另外50只大鼠复制高血压模型,将其中建模成功的44只采用随机体质量排序法分为模型组、茴香霉素组[p38丝裂原活化蛋白激酶(p38 MAPK)激活剂,1 mg/kg]、番石榴叶总黄酮+茴香霉素组(200 mg/...     

钙调神经磷酸酶在L-精氨酸抗心肌肥厚中的作用

目的研究L-精氨酸抗右心室心肌肥厚作用及其与钙调神经磷酸酶(calcineurin,CaN)信号通路的关系。方法利用野百合碱(monocrotaline,MCT)诱导大鼠右心室心肌肥厚模型和前列腺素F2α(prostaglandin F2α,PGF2α)诱导心肌细胞肥大模型,分别以右心室肥厚指数(right ventricle hypertro-phy index,RVHI,即右心室/左心室+室间隔)、心肌细胞直径、蛋白含量和心房利钠肽(atrial natriuretic peptide,ANP)mRNA表达为心肌肥厚指标。用RT-PCR法检测mRNA的表达;Western blot法检测蛋白表达;荧光法检测细胞内钙[Ca2+]i的变化情况。结果L-精氨酸200mg.kg-1.d-1预防和治疗给药均明显抑制MCT诱导的大鼠心肌肥厚,降低MCT所致心肌CaN mRNA和蛋白及其下游因子NFAT3及GATA4蛋白表达的增加。L-精氨酸1mmol.L-1也明显抑制PGF2α100nmol.L-1诱导的大鼠心肌细胞肥大和[Ca2+]i升高,阻遏其诱导的CaN mRNA及CaN-,NFAT3-,GATA4-蛋白表达升高。在体和离体实验中一氧化氮合成酶抑制剂NG-硝基-L-精氨酸-甲酯均可完全阻断L-精氨酸的作用。结论L-精氨酸可能通过降低[Ca2+]i,从而抑制CaN信号转导通路而产生抗右心室心肌肥厚作用。     

Ubiquitin-protein ligase E3a (UBE3A) as a new biomarker of cardiac hypertrophy in cell models

Cardiac hypertrophy is widely diagnosed in clinical cardiac disorders. The pathophysiology of hypertrophy is complex and multifactorial, a series of molecular and cellular changes are participated, such as activation of different signaling pathways, a switch of fetal gene program in the myocardium, and apoptosis. Some biomarkers have been applied to assess cardiac hypertrophy including atrial natriuretic peptides (ANP), brain/B-type natriuretic peptides (BNP), and α- or β- Myosin Heavy Chain (MHC) in addition to others. Recently, ubiquitin-protein ligase E3A (UBE3A) has been observed to increase in cardiac hypertrophy. Therefore, UBE3A as a new biomarker seems valuable in the clinic. The cardiac hypertrophy is induced in rat-derived heart cell line H9c2 cells by potassium bromate (KBrO3), high glucose (HG), or isoproterenol (Iso), respectively. As an oxidizing agent, KBrO3 increased cell size at concentrations less than 250 μM. Similarly, HG and Iso also induced cardiac hypertrophy in H9c2 cells. Interestingly, each kind of the cell models promoted the gene expression of the well-known biomarkers of cardiac hypertrophy including atrial natriuretic peptides (ANP) and brain/B-type natriuretic peptides (BNP). Additionally, UBE3A is also raised with the signals involved in cardiac hypertrophy such as calcineurin and nuclear factor of activated T-cells (NFAT) determined using Western blots. KBrO3 increased the protein levels of these signals and the specific inhibitor, such as cyclosporine A and tacrolimus, attenuated the signaling in H9c2 cells at concentrations sufficient to inhibit calcineurin in addition to the reduction of mRNA levels of UBE3A, similar to ANP or BNP. Moreover, HG or Iso also significantly increased protein levels of UBE3A in H9c2 cells. Taken together, we provided a new view that UBE3A is markedly raised in cardiac hypertrophy using various cell models, mainly through the activation of the calcineurin/NFAT signaling pathway in H9c2 cells. Therefore, UBE3A could be developed as a new biomarker in the diagnosis of cardiac hypertrophy.     

Ouabain facilitates cardiac differentiation of mouse embryonic stem cells through ERK1/2 pathway

Aim:To investigate the effects of the cardiotonic steroid, ouabain, on cardiac differentiation of murine embyronic stem cells (mESCs).Methods:Cardiac differentiation of murine ESCs was enhanced by standard hanging drop method in the presence of ouabain (20 μmol/L) for 7 d. The dissociated ES derived cardiomyocytes were examined by flow cytometry, RT-PCR and confocal calcium imaging.Results:Compared with control, mESCs treated with ouabain (20 μmol/L) yielded a significantly higher percentage of cardiomyocytes, and significantly increased expression of a panel of cardiac markers including Nkx 2.5, α-MHC, and β-MHC. The α1 and 2- isoforms Na(+)/K(+)-ATPase, on which ouabain acted, were also increased in mESCs during differentiation. Among the three MAPKs involved in the cardiac hypertrophy pathway, ouabain enhanced ERK1/2 activation. Blockage of the Erk1/2 pathway by U0126 (10 μmol/L) inhibited cardiac differentiation while ouabain (20 μmol/L) rescued the effect. Interestingly, the expression of calcium handling proteins, including ryanodine receptor (RyR2) and sacroplasmic recticulum Ca(2+) ATPase (SERCA2a) was also upregulated in ouabain-treated mESCs. ESC-derived cardiomyocyes (CM) treated with ouabain appeared to have more mature calcium handling. As demonstrated by confocal Ca(2+) imaging, cardiomyocytes isolated from ouabain-treated mESCs exhibited higher maximum upstroke velocity (P<0.01) and maximum decay velocity (P<0.05), as well as a higher amplitude of caffeine induced Ca(2+) transient (P<0.05), suggesting more mature sarcoplasmic reticulum (SR).Conclusion:Ouabain induces cardiac differentiation and maturation of mESC-derived cardiomyocytes via activation of Erk1/2 and more mature SR for calcium handling.