替米沙坦、安体舒通及两者合用对心肌梗死后非心力衰竭大鼠作用的对比研究

目的　评价醛固酮受体拮抗剂安体舒通和血管紧张素Ⅱ受体拮抗剂替米沙坦对心肌梗死 (AMI)不伴有心功能异常大鼠的作用和相关激素表达的影响。方法　SD大鼠心肌梗死模型建立 2 4h后 ,随机分为 4组 :AMI组、替米沙坦组 (10mg·kg-1·d-1)、安体舒通组 (2 0mg·kg-1·d-1)和合用组 ,并以假手术组为对照。 6w后 ,心脏超声、血流动力学、形态学检测心功能和心室重塑过程 ,并检测血浆、心肌血管紧张素Ⅱ、醛固酮和TNF -α水平。结果　各组心肌梗死面积差异没有显著性 (P >0 0 5 ) ,替米沙坦组和合用组显著降低LVEDP并增加了LVESP ,安体舒通组仅仅减少了LVEDP ,各组CVF表达均显著下降 (P <0 0 5 ,0 0 1) ,合用组没有进一步的下降。AMI组心肌醛固酮和AngⅡ表达分别增加 3 3和 2 1倍 ,替米沙坦组和合用组表达显著下降 ,(P <0 0 5 ,0 0 1)。结论　AMI后组织特异性的激活RAS系统 ,替米沙坦干预可以改善心室重塑 ,抑制心肌RAS的表达 ,与安体舒通合用没有协同作用。     

Beneficial effects of combination of ACE inhibitor and angiotensin II type 1 receptor blocker on cardiac remodeling in rat myocardial infarction

OBJECTIVE: Angiotensin-converting enzyme (ACE) inhibitor and angiotensin II type I receptor blockers (ARB) prevent cardiac remodeling after myocardial infarction (MI). However, it is controversial whether combination therapy of ACE inhibitor and ARB is more effective on cardiac remodeling than each agent alone. In this study, we compared the effects of an ACE inhibitor (temocapril), an ARB (CS-866), and their combination on cardiac remodeling after MI. METHODS: Temocapril at 3 or 30 mg/kg/day, CS-866 at 1 or 10 mg/kg/day, or combined temocapril and CS-866 at 1.5 and 0.5 mg/kg/day or at 15 and 5 mg/kg/day, respectively, were administered to rats after MI. At 4 weeks after MI, we assessed hemodynamics, cardiac function by Doppler echocardiography and non-infarcted myocardial mRNA expression. RESULTS: Animals treated with a combination of the two drugs had hemodynamics, heart weights and dimensions similar to the other treated animals. However, the combination of the two drugs suppressed ANP, BNP and other gene expressions related to contractile proteins of fetal type and collagens more effectively than ACE inhibitor or ARB alone. CONCLUSION: These data suggest that combination of the two drugs, independent of the hemodynamic effect, may improve left ventricular phenotypic change, collagen accumulation and diastolic function.     

An angiotensin II type 1 receptor blocker, candesartan, increases myocardial apoptosis in rats with acute ischemia-reperfusion.

Angiotensin II (Ang II) and apoptosis contribute significantly to myocardial ischemia-reperfusion (I-R) injury. Evidence indicates that Ang II may activate apoptosis in myocytes. The present study was undertaken to investigate the effects of angiotensin receptor blockers (ARBs), candesartan, on the apoptosis of cardiac myocytes in rats after I-R. Rats were divided into a control group, a candesartan group I (0.015 mg/kg), and a candesartan group II (0.03 mg/kg). Candesartan was intravenously administered 30 min before ischemia. All rats were subjected to 30 min of coronary occlusion followed by 3 h of reperfusion. The data showed that left ventricular (LV) systolic pressure and LV +dp/dt was decreased after administration of candesartan, but increased after reperfusion in the candesartan group II, compared with those in the candesartan group I and control group. LV -dp/dt was decreased after candesartan administration in candesartan group II. The number of apoptotic cells in the candesartan groups (497+/-204 and 543+/-254, respectively) was higher than that in the control group (287+/-166; p<0.05). There was no significant difference in infarct size among the three groups. However, plasma CPK was lower in the candesartan groups than in the control group. Northern blot analysis showed that p53 mRNA was upregulated in the candesartan groups, in association with increased expression of bax mRNA. Immunohistochemical analysis showed that p53 and bax immunoreactivity were increased in both of the candesartan groups. In conclusion, candesartan increased apoptosis in the rat hearts after acute I-R, and this increase was possibly mediated by upregulation of p53 and bax gene expressions. In addition, candesartan was shown to improve LV function, in association with reduction of CPK release.     

Effects of aldosterone and angiotensin II receptor blockade on cardiac angiotensinogen and angiotensin-converting enzyme 2 expression in Dahl salt-sensitive hypertensive rats

BACKGROUND: We previously reported that a high-sodium diet activates the local renin-angiotensin-aldosterone system (RAAS) in cardiovascular tissues of Dahl salt-sensitive hypertensive (DS) rats. Angiotensin-converting enzyme 2 (ACE2) is a novel regulator of blood pressure (BP) and cardiac function. The effect of blockade of aldosterone or angiotensin II (Ang II) on cardiac angiotensinogen and ACE2 in DS rats is unknown. METHODS: The BP, plasma renin activity (PRA), plasma aldosterone concentration (PAC), heart weight, endothelium-dependent relaxation (EDR), and messenger RNA (mRNA) levels of collagen III, angiotensinogen, ACE, and ACE2 in the heart were measured in DS rats and in Dahl salt-resistant (DR) rats fed high or low salt diets. The rats were treated orally with or without eplerenone (100 mg/kg/d), candesartan (10 mg/kg/d), or both drugs combined for 8 weeks. RESULTS: A high salt diet increased BP (140%), heart/body weight (132%), and collagen III mRNA levels (146%) and decreased PRA and PAC concomitant with increased expression of cardiac angiotensinogen mRNA and decreased mRNA levels of ACE2 in DS rats. Eplerenone or candesartan significantly decreased the systolic BP from 240 +/- 5 mm Hg to 164 +/- 4 mm Hg or to 172 +/- 10 mm Hg, respectively (P < .05). Eplerenone or candesartan partially improved heart/body weight and cardiac fibrosis, improved EDR and decreased cardiac ACE and angiotensinogen mRNA levels in DS rats. Candesartan increased ACE2 mRNA levels in the heart. Combination therapy normalized BP and further improved cardiac hypertrophy, fibrosis, and EDR. CONCLUSIONS: In DS rats, blockade of aldosterone or Ang II protects cardiac hypertrophy and fibrosis by inactivation of the local RAAS in the heart.     

Effects of angiotensin II receptor antagonist on impaired endothelium-dependent and endothelium-independent relaxations in type II diabetic rats

BACKGROUND: Diabetes mellitus is an important risk factor for cardiovascular diseases, and vasodilator dysfunction may contribute to vascular complications in diabetes. We previously demonstrated that the angiotensin II receptor blocker (ARB) corrected the impaired endothelium-derived hyperpolarizing factor (EDHF)-mediated arterial hyperpolarization and relaxation associated with hypertension or aging, partially independently of blood pressure. OBJECTIVE: To test whether EDHF-mediated, as well as endothelium-independent, relaxations would be altered in arteries from type II diabetic Goto-Kakizaki rats, and whether ARB would correct these alterations. METHODS: Goto-Kakizaki rats were treated with either the ARB candesartan or a combination of hydralazine and hydrochlorothiazide for 8 weeks, beginning at 10 weeks of age. Membrane potentials and contractile responses were recorded from the isolated mesenteric arteries. RESULTS: The two treatments lowered blood pressure comparably. Acetylcholine-induced, EDHF-mediated hyperpolarization and relaxation in mesenteric arteries were markedly impaired in untreated Goto-Kakizaki rats compared with age-matched Wistar rats, and neither ARB nor the combination therapy improved these responses. On the other hand, relaxations to endothelium-derived nitric oxide, assessed in rings precontracted with high potassium solution, were similar among the four groups. Relaxation to the nitric oxide donor sodium nitroprusside and that to levcromakalim, an ATP-sensitive K-channel opener, were also impaired in untreated Goto-Kakizaki rats, and the response to sodium nitroprusside was partially improved in treated Goto-Kakizaki rats. CONCLUSIONS: These findings suggest that EDHF-mediated hyperpolarization and relaxation and endothelium-independent relaxations are both impaired in arteries of type II diabetic rats, and antihypertensive treatment with or without ARB partially corrects endothelium-independent relaxations to the nitric oxide donor but not EDHF-mediated responses.     

血管紧张素Ⅱ受体拮抗剂对梗死心脏纤连蛋白的调节

目的探讨血管紧张素Ⅱ(AngⅡ)受体(AT1,AT2)拮抗剂对梗死心脏心肌基质金属蛋白酶(MMP)及细胞外基质纤连蛋白(fibronectin,FN)的影响。方法结扎大鼠左冠状动脉建立心肌梗死模型,术前7天起分别用安慰剂、AT1受体拮抗剂缬沙坦(10mg.kg-1.d-1)、AT2受体拮抗剂PD123319(30mg.kg-1.d-1)。术后1、3、7天免疫沉淀法分别检测左心室游离壁(LVFW)、室间隔、右室壁心肌组织基质金属蛋白酶MMP-2、3、9及基质金属蛋白酶抑制物-1(TIMP-1)及细胞外基质FN的表达,免疫荧光检测LVFW、室间隔、右心室心肌FN的分布。结果术后7天右心室心肌排列基本正常,室间隔心肌肥厚,LVFW心肌有不同程度的坏死、肥厚及纤维化。术后1、3、7天室间隔MMP-2、3、9蛋白表达呈逐渐增加的趋势,TIMP-1及FN表达逐渐减少,各时相点与基础值相比差异有统计学意义(P<0.01);术后1、3、7天LVFWMMP-2、3、9蛋白表达一直处于高水平,TIMP-1和FN蛋白表达处于低水平,各时相点与基础值比较差异有统计学意义(P<0.01)。FN在右心室心肌组织中表达较多,其次为室间隔和LVFW,MMP-2、3、9表达与FN表达结果相反。室间隔和LVFWMMP表达,手术+缬沙坦组低于手术组和手术+PD123319组(均P<0.01),手术组与手术+PD123319组比较差异无统计学意义。手术+缬沙坦组室间隔及LVFWFN表达高于手术组和手术+PD123319组(P<0.01),手术组与手术+PD123319组比较差异无统计学意义。手术组心肌梗死面积(51.0%±2.8%)高于手术+缬沙坦组(40.4%±2.1%,P<0.05),手术组与手术+PD123319组(49.5%±2.1%)比较,差异无统计学意义。结论血管紧张素Ⅱ受体AT1拮抗剂通过增加MMP-2、3、9的表达而降解心肌细胞外基质FN参与心肌重构的病理过程,进一步恶化心功能。     

Ventricular remodeling and transforming growth factor-beta 1 mRNA expression after nontransmural myocardial infarction in rats: effects of angiotensin converting enzyme inhibition and angiotensin II type 1 receptor blockade

With the application of early reperfusion therapy after acute MI, the incidence and importance of nontransmural infarction is increasing. In a rat model with nontransmural infarction, we evaluated 1) the changes of LV dimension, LV interstitial fibrosis and transforming growth factor-β1 (TGF-β1) mRNA expression and 2) the effects of angiotensin converting enzyme (ACE) inhibitor and angiotensin II type 1 (AT1) receptor antagonist treatment. Female Sprague-Dawley rats were subjected to 45 min of coronary occlusion followed by reperfusion, and five days after the operation the animals were randomized to untreated (n = 19), captopril-treated (n = 15) and losartan-treated (n = 14) groups. Twenty-six days after MI, echocardiographic examination revealed a remarkable dilatation of LV. Captopril or losartan treatment reduced the extent of LV cavity dilatation. Collagen volume fractions in noninfarcted septum as well as in peri-infarct area decreased with captopril or losartan treatment, compared to those of the untreated rats. In noninfarcted septum of untreated rats, TGF-β1 mRNA expression increased more than two fold (P < 0.05 vs. pre-MI) 5 and 10 days after MI. Captopril or losartan treatment suppressed the acute induction of TGF-β1 mRNA expressions. These results indicate that ACE inhibitor or AT1 receptor antagonist treatment after nontransmural infarction 1) attenuates LV remodeling as in transmural infarction and 2) decreases interstitial fibrosis at least partly by blocking the acute induction of TGF-β1 mRNA expression. Received: 10 December 1998, Returned for revision: 29 January 1999, Revision received: 15 March 1999, Accepted: 22 March 1999     

Effects of angiotensin II receptor blocker (candesartan) in daunorubicin-induced cardiomyopathic rats

BACKGROUND: Daunorubicin is an anthracycline anti-tumor agent; anthracycline chemotherapy in cancer can cause severe cardiomyopathy leading to a frequently fatal congestive heart failure; the first-line treatment is diuretics and digoxin. Recently, angiotensin-converting enzyme inhibitors have been shown to be effective in the treatment of such toxicity. The purpose of this study was to investigate the effects of angiotensin II type-1 receptor antagonist (candesartan) in a rat model of daunorubicin-induced cardiomyopathy. METHODS: Rats were treated with a cumulative dose of 9 mg/kg body weight daunorubicin (i.v.). 28 days later, after the development of cardiomyopathy, animals were randomly assigned to candesartan-treated (5 mg/kg/day, p.o.) or vehicle-treated groups; age-matched normal rats were used as the control group. Candesartan treatment was continued for 28 days. Hemodynamic and echocardiographic parameters were measured, cardiac protein and mRNA were analyzed, and histopathological analyses of myocardial fibrosis, cell size and apoptosis were conducted. RESULTS: Following cardiomyopathy, left ventricular end diastolic pressure and left ventricular systolic dimension were significantly elevated; while % fractional shortening and Doppler E/A ratio were significantly reduced. Cardiomyopathic hearts showed significant increases in % fibrosis, % apoptosis, and myocyte diameter/body weight ratio; candesartan treatment reversed these changes. Fas-L protein overexpression in myopathic hearts was significantly suppressed by treatment with candesartan. Moreover, SERCA2 mRNA and protein expression were both down-regulated in myopathic hearts and restored to normal by candesartan treatment, significantly. CONCLUSIONS: Our findings suggest that candesartan treatment significantly improved the left ventricular function and reversed the myocardial pathological changes investigated in this model of daunorubicin-induced cardiomyopathy; suggesting its potentials in limiting daunorubicin cardiotoxicity.     

Addition of angiotensin II type 1 receptor blocker to CCR2 antagonist markedly attenuates crescentic glomerulonephritis

The monocyte chemoattractant protein-1 (MCP-1)/CC-chemokine receptor 2 (CCR2) pathway plays a critical role in the development of antiglomerular basement membrane (anti-GBM) nephritis. We recently showed angiotensin II (Ang II) infusion in rats activated MCP-1 and transforming growth factor-β1 (TGF-β1), which in turn induced macrophage infiltration of renal tissues. This study was performed to demonstrate that combination therapy with a CCR2 antagonist (CA) and an Ang II type 1 receptor blocker (ARB) ameliorated renal injury in the anti-GBM nephritis model. An anti-GBM nephritis rat model developed progressive proteinuria and glomerular crescent formation, accompanied by increased macrophage infiltration and glomerular expression of MCP-1, angiotensinogen, Ang II, and TGF-β1. Treatment with CA alone or ARB alone moderately ameliorated kidney injury; however, the combination treatment with CA and ARB dramatically prevented proteinuria and markedly reduced glomerular crescent formation. The combination treatment also suppressed the induction of macrophage infiltration, MCP-1, angiotensinogen, Ang II, and TGF-β1 and reversed the fibrotic change in the glomeruli. Next, primary cultured glomerular mesangial cells (MCs) stimulated by Ang II showed significant increases in MCP-1 and TGF-β1 expression. Furthermore, cocultured model consisting of MCs, parietal epithelial cells, and macrophages showed an increase in Ang II-induced cell proliferation and collagen secretion. ARB treatment attenuated these augmentations. These data suggest that Ang II enhances glomerular crescent formation of anti-GBM nephritis. Moreover, our results demonstrate that inhibition of the MCP-1/CCR2 pathway with a combination of ARB effectively reduces renal injury in anti-GBM nephritis.     

Effect of insulin and angiotensin II receptor subtype-1 antagonist on myocardial remodelling in rats with insulin-dependent diabetes mellitus

OBJECTIVES: To assess the role of insulin or an angiotensin II receptor antagonist (losartan), or both, in preventing cardiomyocyte damage in rats suffering from insulin-dependent diabetes mellitus (IDDM), and to correlate it with insulin receptor modulation at the cardiomyocyte, coronary endothelium and skeletal muscle cell level. DESIGN: Animals were divided into groups of normal rats, diabetic rats, and diabetic rats given insulin, each subdivided into a control group and an experimental group treated with losartan. METHODS: The animals were killed 1 month after enrollment to the study. Perfusion of the heart with iodine-125-labelled insulin was carried out for all the groups and the binding kinetics of insulin to its receptors on the coronary endothelial cells and the cardiomyocytes were determined using a physical/mathematical model. In addition, tissue samples from the heart and intercostal skeletal muscle were snap frozen and used for histological, indirect immunofluorescence and western blot analysis. RESULTS: Cardiac muscle from diabetic animals exhibited diffuse cardiomyopathic changes consisting of widespread vacuolation, loss of striation and cellular hypertrophy, which were reduced and even prevented by treatment with insulin and losartan. In addition, losartan seemed to mediate the upregulation of insulin receptor density on cardiomyocytes and skeletal muscle, and increase insulin receptor affinity at the coronary endothelial site. Finally, treatment with losartan induced a significant decrease in glucose concentrations in the diabetic group compared with the appropriate controls. CONCLUSIONS: Addition of losartan to the standard insulin treatment in non-hypertensive animals with IDDM offers new benefits concerning cardiac protection and prevention of damage. This may be attributed, in part, to insulin receptor density and sensitization.     

Overexpression of angiotensin II type I receptor in cardiomyocytes induces cardiac hypertrophy and remodeling

Angiotensin II (AII) is a major determinant of arterial pressure and volume homeostasis, mainly because of its vascular action via the AII type 1 receptor (AT1R). AII has also been implicated in the development of cardiac hypertrophy because angiotensin I-converting enzyme inhibitors and AT1R antagonists prevent or regress ventricular hypertrophy in animal models and in human. However, because these treatments impede the action of AII at cardiac as well as vascular levels, and reduce blood pressure, it has been difficult to determine whether AII action on the heart is direct or a consequence of pressure-overload. To determine whether AII can induce cardiac hypertrophy directly via myocardial AT1R in the absence of vascular changes, transgenic mice overexpressing the human AT1R under the control of the mouse alpha-myosin heavy chain promoter were generated. Cardiomyocyte-specific overexpression of AT1R induced, in basal conditions, morphologic changes of myocytes and nonmyocytes that mimic those observed during the development of cardiac hypertrophy in human and in other mammals. These mice displayed significant cardiac hypertrophy and remodeling with increased expression of ventricular atrial natriuretic factor and interstitial collagen deposition and died prematurely of heart failure. Neither the systolic blood pressure nor the heart rate were changed. The data demonstrate a direct myocardial role for AII in the development of cardiac hypertrophy and failure and provide a useful model to elucidate the mechanisms of action of AII in the pathogenesis of cardiac diseases.