压力超负荷心力衰竭大鼠心室肌电生理失稳态及缝隙连接蛋白Cx43 的变化

目的观察压力超负荷所致心力衰竭（HF）大鼠心室肌电生理失稳态和缝隙连接蛋白Cx43表达的变化。方法采用腹主动脉缩窄法建立压力超负荷大鼠HF模型,取左室舒张末压≥15mmHg的存活大鼠入HF组,另设假结扎对照组。术后32周两组大鼠以颈总动脉插管法和心脏B超测定心功能,并检测电生理指标,以免疫印迹方法检测心肌细胞Cx43蛋白表达的变化,通过透射电镜观察心室肌缝隙连接分布的变化。结果HF大鼠出现明显电生理失稳态和心功能不全,左室舒张末压明显增高而心室有效不应期明显延长,左室射血分数明显下降,同时大鼠心室肌中缝隙连接蛋白Cx43表达明显下调（0．929±0．095VS1．250±0．083,P〈0．05）并出现空间重构。结论压力超负荷所致HF大鼠心室肌存在明显缝隙连接重构,这可能是导致HF时心肌电生理重构的重要机制。     

心衰患者重构心肌组织细胞外基质的变化

目的 探讨心衰患者重构心肌组织细胞外基质（ECM）纤连蛋白（FN）和肌腱蛋白（TN-C）与心功能损害的关系。 方法 选择因二尖瓣关闭不全心脏病接受二尖瓣置换术的CHF病人39例，正常对照38例（其中8例来自意外伤亡的器官捐献者）。光镜检查心肌组织病理变化，免疫沉淀法检测心肌组织FN、TN-C蛋白表达，免疫荧光法检查心肌组织细胞外基质FN、TN-C的分布。 结果 瓣膜病所致心力衰竭病人心肌组织呈典型的心肌重构病理改变。心肌组织TN-C蛋白表达吸光度值（A）（A/β-actin）比值正常对照组分别为0，心功能Ⅱ级组1.69±0.05，心功能Ⅲ级组1.89±0.06，心功能Ⅳ级组3.36±0.40, 各CHF组与正常对照组相比差异有统计学意义（P<0.05 或0.01）; 相反，心肌组织FN蛋白表达（A/β-actin）比值，正常组分别为2.01±0.02，心功能Ⅱ级组1.13±0.01，心功能Ⅲ级组0.70±0.02，心功能Ⅳ级组0.42±0.05，各CHF组与正常对照组相比差异有统计学意义（P<0.05 或0.01）。 结论 心衰患者TN-C表达量的增高及FN的降低参与心肌重构的病理过程，重构心肌组织通过改变心肌细胞外基质进一步恶化心功能。     

血管紧张素Ⅱ与基质金属蛋白酶及其抑制剂在糖尿病大鼠心肌中的表达及影响

目的研究糖尿病（DM）大鼠心肌间质重构与血管紧张素Ⅱ（AngⅡ）、转化生长因子（TGF）-β1、基质金属蛋白酶（MMP）-1及其抑制剂（TIMP-1）的关系。方法20只sD大鼠分为正常对照组（10只），DM组（10只），用STZ法建立DM模型，10W时麻醉处死大鼠，免疫组化法检测Ⅰ和Ⅲ型胶原的表达，TGF—β1、MMP-1和TIMP-1蛋白的表达，RT—PCR法检测TIMP-1和MMP-1mRNA的表达。结果DM组心脏指数和左心室指数显著高于正常组（P〈0．05），I、Ⅲ型胶原的表达也增加，存在着心肌间质重构，同时AngⅡ，TGF—β1，TIMP-1蛋白及TIMP-1mRNA表达增高，MMP-1蛋白及mRNA表达减少（P〈0．05）。结论DM大鼠可能因肾素-血管紧张素系统（RAS）的激活，AngⅡ表达增加，直接或间接的影响TGF—β1及MMPs的表达，导致心肌间质重构。     

β1肾上腺素能受体阻断剂与β2肾上腺素能受体激动剂联用对心力衰竭大鼠心功能及心肌细胞凋亡的影响

目的 在一定范围内激活β2肾上腺素能受体（AR）可以在不加重心室重构的前提下改善心力衰竭（心衰）大鼠心功能,推测β1AR阻断剂联合β2AR激动剂有可能进一步改善心衰大鼠心功能并减轻心肌细胞凋亡,该实验对此进行了研究并探讨了其机制。方法 随机选取9只雄性Wistar大鼠为对照组。将异丙基肾上腺素诱导的心衰大鼠随机分为美托洛尔组（n=11）,联合治疗组（n=11）,安慰剂组（n=10）。美托洛尔组给予美托洛尔50mg／kg,一日两次灌胃。联合治疗组给予非诺特罗125μg／kg,美托洛尔50mg／kg一日两次灌胃。安慰剂组给予等量生理盐水一日两次灌胃。对照组不予处理。治疗8周后应用超声心动图评价心功能,TUNEL法检测心肌细胞凋亡指数,测定Caspase-3酶活性,Westernblot测定bcl-2及bax蛋白质表达,测定脏器重量／体重,组织病理学测定胶原容积分数（CVF）。结果 （1）美托洛尔组及联合治疗组均较安慰剂组左室舒张末期直径（LVEDd）、左室收缩末期直径（LVESd）、E峰A峰比值（E／A）明显下降,短轴缩短率（FS）、射血分数（EF）则有明显增高。联合治疗组较美托洛尔组LVEDd、LVESd有进一步降低（均为P〈0．05）,FS、EF则有进一步增高（均为P〈0．01）。（2）美托洛尔组及联合治疗组较安慰剂组左室重量体重比（LVW／BW）、肺脏重量体重比（PW／BW）及CVF明显降低（均为P〈0．01）。联合治疗组LVW／BW及PW／BW较美托洛尔组进一步降低（P〈0．01）,但两组之间CVF无显著差异。（3）美托洛尔组及联合治疗组较安慰剂组心肌细胞凋亡指数（AI）及Caspase．3活性均有明显减低。联合治疗组较美托洛尔组有进一步减低（均为P〈0．01）。（4）与安慰剂组相比,美托洛尔组及联合治疗组bax蛋白表达有明显下降而bcl-2／bax显著升高,并且以联合治疗组改善更为显著（均为P〈0．01）。结论 β1AR阻断剂联合β2AR激动剂较单用β1AR阻断剂进一步改善心衰大鼠的心功能,减轻心室重构。明显降低bax蛋白表达及bcl-2／bax,减轻心肌细胞凋亡很可能是其疗效提高的机制之一。     

钙通道阻滞剂改善内质网应激抑制压力过负荷高血压大鼠的心肌重构

目的:研究在压力过负荷应激状态下钙通道阻滞剂拉西地平对内质网应激（endoplasmic reticulum stress,ERS）分子钙网蛋白（calreticulin,CRT）和细胞凋亡效应分子-12(caspase-12)在大鼠心肌组织中的表达及对心肌重构的影响。方法: 将30只雄性Sprague-Dawly(SD)大鼠随机分为3组,即假手术组(Sham组)、腹主动脉缩窄组（TAC组）及TAC＋拉西地平干预组（简称拉西地平组）,每组10只。通过颈动脉插管测定各组大鼠的血流动力学,心脏超声心动图检查左心室的形态结构。采用免疫组化染色法检测大鼠心肌中CRT及caspase-12蛋白的表达水平,TUNEL荧光染色法检测心肌细胞的凋亡率。结果: 与Sham组相比较,TAC组大鼠的平均动脉压(MAP)、室间隔厚度(IVST)、左室后壁厚度(LVPWT)、左室质量指数(LVWI)、CRT和caspase-12蛋白表达水平及心肌细胞的凋亡率比较,均有显著升高(P<0.01)。拉西地平组大鼠MAP、IVST、LVPWT、LVWI、CRT和caspase-12蛋白的表达水平及心肌细胞的凋亡率较TAC组明显下降(P<0.05)。结论: 内质网应激可能参与了压力过负荷高血压大鼠心肌重构的过程。钙通道阻滞剂拉西地平可能通过降低CRT及caspase-12的表达及减少心肌细胞的凋亡干预ERS介导的压力负荷所致高血压大鼠心肌肥厚的信号通路,从而通过改善内质网应激发挥对心脏的保护作用。     

心梗后大鼠心肌NF-κB与MMP-9的关系及卡托普利的作用

目的：探讨心梗后大鼠心肌组织中核因子kappa—B（nuclear factor—kappa B,NF—κB）与基质金属蛋白酶-9（matrix metalloproteinases-9,MMP-9）表达的变化及卡托普利对其的影响,阐明NF-κB、MMP-9与心室重构的病理意义及卡托普利的作用途径。方法通过结扎冠状动脉左前降支（LAD）,随机选择40只雄性SD大鼠建立急性心肌梗死模型作为心肌梗死组,另设假手术组（丙组,n=20）为对照。冠脉结扎后24h,心肌梗死组再随机分为卡托普利治疗组（甲组,n=19）及心肌梗死对照组（乙组,n=18）。此后6周,每日以10mg／kg卡托普利灌胃处理甲组大鼠．并以等量生理盐水处理乙组、丙组大鼠。6周末测量各组大鼠心／体比值,免疫组化法检测左室心尖部心肌中NF—κB与MMP-9蛋白表达。结果左室心尖部心肌中NF—κB、MMP-9的表达及心／体比值,甲、乙组均显著高于丙组（P〈0．05）,而甲组心／体比值较乙组下降（P〈0．05）,NF-κB、MMP-9的表达也较乙组有差异（p〈0．05）。结论NF-κB、MMP-9参与心梗后大鼠心室重构,卡托普利通过抑制NF-κB与MMP-9蛋白的表达逆转心梗后心室重构。     

心肌细胞凋亡和NF-κB在卡维地洛改善大鼠心梗后心功能不全中的作用

目的观察卡维地洛对大鼠心肌梗死后心功能不全的作用,并探讨其对心肌细胞凋亡和NF-κB激活的影响,进一步阐明卡维地洛的作用机制。方法雄性SD大鼠左冠前降支永久结扎建立心肌梗死后心功能不全模型。24h后存活的大鼠随机分为心肌梗死组和卡维地洛治疗组（10mg.kg-1.d-1灌胃）,并以假手术组为对照。8w后以血流动力学测定判断心功能情况,TUNEL染色法检测心肌细胞凋亡和免疫组化法测定心肌细胞核阳染率以反映心肌细胞NF-κB的激活情况。结果心肌梗死组平均动脉压（MBP）,＋dp/dt均显著低于假手术组,左室舒张末期压力（LVEDP）值较假手术组明显增高,提示形成了心功能不全。卡维地洛治疗组的左室/体重较心肌梗死组明显降低;卡维地洛治疗组的胶原含量CVF（%）较心肌梗死组明显降低。卡维地洛治疗后显著减少了心肌肥厚、心肌纤维化程度和改善了心功能。卡维地洛显著减少了心肌细胞凋亡,增加了NF-κB的激活。结论心肌细胞凋亡和NF-κB的激活参与了大鼠心肌梗死后心室重塑和心功能不全的发生。卡维地洛改善心室重塑和心功能的作用与减少心肌细胞凋亡和增加心肌细胞NF-κB的激活有关。     

高血压大鼠不同时期心肌细胞及血管内皮细胞中VEGF的表达变化

目的观察血管内皮细胞生长因子（VEGF）在高血压不同阶段心肌细胞和血管内皮细胞的分布变化。方法选用遗传性盐敏感型高血压大鼠（DahlS）和遗传性盐抵抗型高血压大鼠（DahlR），在5周龄投与8％食盐饲料，分别在10、11、12W时取材，制作心肌组织切片。应用免疫组织化学方法观察VEGF在心肌组织中的表达变化情况，计算单位面积心肌组织VEGF的阳性细胞数和血管内皮细胞的阳性表达。结果VEGF免疫细胞在Dahls和DahlR组大鼠的心肌细胞及血管内皮细胞中均有表达，Dahls组VEGF阳性细胞数均较同时期DahlR组增多（P〈0．01）。Dahls组自10w起至12W心肌细胞VEGF阳性细胞数逐渐增多（P〈0．01）。DahlR组在高血压不同时期VEGF无显著性变化。心肌组织的血管内皮细胞的表达强度，DaHS组VEGF由（＋）到（＋＋），且均可见组织内毛细血管增多。Dahl—R组无变化。结论VEGF在心肌细胞和心肌细胞间的血管上均有表达，并随高血压的病程延长呈上升趋势。     

氧化应激对心衰大鼠ET—l的影响及β—阻滞剂的干预

目的 研究氧化应激对充血性心力衰竭大鼠内皮素—1基因表达的影响，并用不同β—受体阻滞剂(卡维地洛和阿替洛尔)进行干预、比较。方法 30只雌雄各半的Wistar大鼠行腹主动脉缩窄术造成心衰模型，随机分为：①心衰组(n＝10)，②阿替洛尔组(n＝10)，③卡维地洛组(n＝10)，同时设假手术组(n＝10)。药物干预4周，检测各组血液动力学指标、心室质量指数、氧自由基代谢指标，及心肌组织内皮素—1基因的表达水平。结果 心衰组心功能指标恶化(P＜0．01，0．05)，LVMI及RVMI分别升高19％和30％(P＜0．01，0．05)，SOD活性下降而MDA含量明显增高((P＜0．01)，心肌组织ET—1基因表达上调(P＜0．001)。心衰大鼠LVMI与ET—1呈正相关r＝0．672(P＜0．05)，ET—1与心功能恶化程度平行(P＜0．01，0．05)；ET-1与MDA正相关r＝0．836(P＜0．01)，而与SOD负相夹r＝-0．744(P＜0．02)。经卡维地洛治疗后心功能改善，LVMI、RVMI下降，MDA降低，SOD活性上升，且ET—1表达下调(P＜0．01，0．05)，等剂量的阿替洛尔未获得上述改变，仅对心功能有所改善。结论 心衰时氧化应激导致心肌ET—1表达增强，ET—1参与心室重构并提示心衰预后。卡维地洛可抑制心室重构，机制可能与其抗氧化应激、下调ET—1的表达有关。氧化应激对心肌ET—1的表达起调控作用，等剂量的具有抗氧化作用的卡维地洛较第二代β-受体阻滞剂阿替洛尔更有利于心衰预后的改善。     

黄酮、皂苷类中药对促心肌梗死后大鼠缺血心肌血管新生作用及相关生长因子表达的影响

目的观察5种黄酮、皂苷类中药促心肌梗死（MI）后大鼠缺血心肌血管新生作用及对相关生长因子表达的影响。方法雄性Wistar大鼠．结扎左冠状动脉造成急性心肌梗死（AMI）模型，随机分为丹参注射液组、葛根素组、三七总皂苷组、川芎嗪组、醋柳黄酮组、模型组（对照组），并设假手术组。检测各组大鼠缺血心肌中微血管数（MVC）、微血管密度（MVD）及血管内皮生长因子（VEGF）、碱性成纤维细胞生长因子（bFGF）、血小板衍生生长因子β（PDGF—β）、胰岛素样生长因子（IGF-1）蛋白的表达，用病理图像分析系统测定生长因子蛋白表达灰度值，并进行半定量分析。结果模型组、各治疗组大鼠MI边缘区MVC和MVD明显高于假手术组（P〈0．05）；模型组VEGF、bFGF、PDGF-β、IGF—1蛋白表达及其灰度值明显高于假手术组（P〈0．05）；川芎嗪组、三七总皂苷组、葛根素组、丹参注射液组VEGF、bKGF、PDGF-β蛋白表达灰度值明显高于模型组（P〈0．05）。醋柳黄酮组VEGF、bFGF、PDGF-β蛋白表达灰度值低于模型组（P〉0．05），IGF-1蛋白表达灰度值明显高于模型组（P〈0．05）。结论三七总皂苷、川芎嗪注射液、丹参注射液、葛根素注射液有促MI后大鼠缺血心肌血管新生的作用。     

Effects of TCV-116 on expression of NOS and adrenomedullin in failing heart of Dahl salt-sensitive rats

We examined the effects of TCV-116, an angiotensin II type 1 receptor antagonist, on endothelial-cell nitric oxide synthase (eNOS), inducible NOS (iNOS), and adrenomedullin (ADM) expression in the left ventricle (LV) and evaluated these relation to myocardial remodeling in failing heart of Dahl salt-sensitive hypertensive rats (DS) fed a high-salt diet. TCV-116 (DSHF-T, 5 mg/kg/day, subdepressor dose) or vehicle (DSHF-V) were given from left ventricular hypertrophy to heart failure stage for 7 weeks. Markedly increased left ventricular end-diastolic diameter and reduced fractional shortening in DSHF-V was significantly ameliorated in DSHF-T. The eNOS mRNA and protein in the LV was significantly suppressed in DSHF-V compared with control rats (DR-C), and significantly increased in DSHF-T compared with DSHF-V. The iNOS mRNA and protein, ADM mRNA and immunoreactive ADM contents, and type I collagen mRNA in the LV were significantly increased in DSHF-V compared with DR-C, and significantly decreased in DSHF-T compared with DSHF-V. DSHF-V showed a significant increase of the wall-to-lumen ratio, perivascular fibrosis, and myocardial fibrosis, with all these parameters being significantly improved by TCV-116. In conclusion, myocardial remodeling and heart failure in DS rats fed a high-salt diet were significantly ameliorated by a subdepressor dose of TCV-116, which may be due to a increased in eNOS and a decreased in iNOS mRNA and protein expression in the LV. Moreover, the ADM mRNA and immunoreactive ADM contents are upregulated in failing heart of DS rats fed a high-salt diet, and increased ADM expression may have a role in the defense mechanism against further cardiac dysfunction and impaired myocardial remodeling.     

Elastolytic cathepsin induction/activation system exists in myocardium and is upregulated in hypertensive heart failure

Cathepsins are cysteine proteases that participate in various types of tissue remodeling. However, their expressions during myocardial remodeling have not been examined. In this study, we investigated their expressions in the left ventricular (LV) myocardium of rats and humans with hypertension-induced LV hypertrophy or heart failure (HF). Real-time PCR and immunoblot analysis revealed that the abundance of cathepsin S mRNA or protein in the LV tissues was greater in rats or humans with HF than in those with hypertrophy or in control subjects. Immunostaining showed that cathepsin S was localized predominantly to cardiac myocytes and coronary vascular smooth muscle cells, but also overlapped in part with macrophages. Elastic lamina fragmentations significantly increased in the LV intramyocardial coronary arteries of HF rats. The amount of elastolytic activity in the extract of the LV myocardium was markedly increased for HF rats compared with controls, and this activity was mostly because of cathepsin S. Although the amount of elastin mRNA was increased in the LV myocardium of HF rats, the area of interstitial elastin was not. The expression of interleukin 1beta was increased in the LV myocardium of HF rats, and this cytokine was found to increase the expression and activity of cathepsin S in cultured neonatal cardiomyocytes. These results suggest that cathepsin S participates in pathological LV remodeling associated with hypertension-induced HF. This protease is, thus, a potential target for therapeutics aimed at preventing or reversing cardiac remodeling.     

Effects of imidapril on NOS expression and myocardial remodelling in failing heart of Dahl salt-sensitive hypertensive rats

OBJECTIVES: To elucidate the relationship between renin-angiotensin system and nitric oxide in hypertensive heart failure, we evaluated the effects of long-term treatment with imidapril, angiotensin-converting enzyme inhibitor, on endothelial-cell nitric oxide synthase (eNOS) and inducible NOS (iNOS) expression in the left ventricle (LV) and its relation to myocardial remodelling in failing heart of Dahl salt-sensitive hypertensive rats (DS) fed a high-salt diet. METHODS: In DS rats fed an 8% NaCl diet after the age of 6 weeks, a stage of concentric left ventricular hypertrophy at 11 weeks (DSLVH) was followed by a distinct stage of fatal left ventricular failure with chamber dilatation at 18 weeks (DSCHF). Imidapril (DSCHF-I, n = 7, 1 mg/kg/day, subdepressor dose) or vehicle (DSCHF-V, n = 7) were given from DSLVH to DSCHF stage for 7 weeks, and age-matched (18 weeks) Dahl salt-resistant rats fed the same diet were served as control group (DR-C, n = 7). RESULTS: Markedly increased left ventricular end-diastolic diameter and reduced fractional shortening in DSCHF-V was significantly ameliorated in DSCHF-I using transthoracic echocardiography. The level of eNOS mRNA and protein in the LV was significantly suppressed in DSCHF-V compared with DR-C, and significantly increased in DSCHF-I compared with DR-C and DSCHF-V. The iNOS mRNA and protein and the fibrosis factor expression of type I collagen mRNA were significantly increased in DSCHF-V compared with DR-C, and significantly decreased in DSCHF-I compared with DSCHF-V. DSCHF-V demonstrated a significant increase in wall-to-lumen ratio, perivascular fibrosis, and myocardial fibrosis. These changes in the microvasculature were improved significantly by imidapril. CONCLUSIONS: Subdepressor dose of imidapril may ameliorate the endothelial damage not only by inhibiting production of angiotensin II but also by promoting eNOS and inhibiting iNOS mRNA and protein expression in the LV, and this increased eNOS mRNA and protein level may have a role in the improvement of congestive heart failure and myocardial remodelling.     

Effect of imidapril on myocardial remodeling in L-NAME-induced hypertensive rats is associated with gene expression of NOS and ACE mRNA

Chronically administered N(omega)nitro-L-arginine methyl ester (L-NAME) produces vascular structural changes and fibrosis of the left ventricle (LV). However, very few studies have evaluated whether the beneficial effects of angiotensin-converting enzyme (ACE) inhibitors on these myocardial remodelings are associated with local gene expression of nitric oxide synthase (NOS) and ACE mRNA in the LV. Effects of long term treatment with imidapril, an ACE inhibitor, on gene expression of endothelial-cell NOS (eNOS) and ACE mRNA in the LV and its relation to myocardial remodeling in L-NAME-induced hypertensive rats were evaluated. Fifteen male Sprague-Dawley rats were given L-NAME (60 mg/ kg/day) in drinking water for 6 weeks to induce hypertension, and then treated with imidapril (L-NAME-I, n = 8, 1 mg/kg/day, subdepressor dose), or a vehicle (L-NAME-V, n = 7) for 4 weeks. Age-matched rats (C, n = 7) served as a control group. Blood pressure in L-NAME-V and L-NAME-I was similar and significantly higher than that in C. The level of eNOS mRNA in the LV was significantly decreased in L-NAME-V compared with C, and was significantly increased in L-NAME-I compared with C and L-NAME-V. The ACE mRNA and type I collagen mRNA expression levels were significantly increased in L-NAME-V compared with C, and significantly suppressed in L-NAME-I compared with L-NAME-V. L-NAME-V demonstrated a significant increase in wall-to-lumen ratio, perivascular fibrosis, and myocardial fibrosis. These changes in the microvasculature were improved significantly by imidapril. Myocardial remodeling in L-NAME-induced hypertensive rats was significantly ameliorated by a subdepressor dose of imidapril, which may be due to an increase in local eNOS mRNA expression and a decrease in angiotensin II in the LV.     

Waon therapy attenuates cardiac hypertrophy and promotes myocardial capillary growth in hypertensive rats: a comparative study with fluvastatin

Cardiac hypertrophy and fibrosis in heart failure with preserved ejection fraction are associated with a pro-inflammatory state and reduced NO bioavailability. Effects on myocardial structural and molecular alterations were compared between Waon therapy (WT; repeated dry sauna therapy) and statin in hypertensive rats. Seven-week-old Dahl salt-sensitive rats were assigned to 4 groups: low-salt (LS) diet, high-salt (HS) diet, HS diet with oral fluvastatin (FL; 10 mg/kg/day for 4 weeks) starting from the age of 9 weeks, and HS diet with WT treatment in a far-infrared dry sauna (39 °C for 15 min followed by 34 °C for 20 min once daily for 4 weeks). HS rats developed left ventricular (LV) hypertrophy with preserved LV systolic function. WT reduced LV wall thickness and myocyte cross-sectional area along with decreased levels of myocardial ANP and BNP mRNA expression compared with HS rats. Reduction in LV fibrosis and increase in capillary density in WT animals were accompanied by reductions in myocardial levels of TGF-β1, MMP2, p22^phox and gp91^phox mRNA expression, and increases in myocardial levels of VEGF and HSP90 mRNA and phosphorylated eNOS protein. These effects were comparable between WT and FL animals. WT improves structural and molecular alterations in salt-induced hypertensive rats similarly to fluvastatin.     

The plasminogen-MMP system is more activated in the scar than in viable myocardium 3 months post-MI in the rat

Left ventricular (LV) remodeling following myocardial infarction (MI) is a complex process involving extracellular matrix degradation and fibrosis. While early remodeling is beneficial, chronic remodeling leads to decompensated heart failure (HF). We assessed the hypothesis that activation of the plasminogen-MMP system is involved in the remodeling of the infarct scar and compared it to the remaining viable myocardium. MI was induced by coronary artery ligature in 42 male Wistar rats. Three months following surgery, animals were divided into compensated (n=26) or decompensated (n=16) groups and compared to sham-operated rats (n=17). Scar and remaining viable LV myocardium (LVM) were separately analyzed for MMP-2, -7, -9, urokinase type and tissue type plasminogen activator (uPA and tPA) mRNA levels by RT-PCR. Their protein or activity levels, plus those of plasminogen/plasmin, tissue inhibitor of metalloproteinase-1, -2, -4 (TIMP-1, -2, -4) and plasminogen activator inhibitor-1 (PAI-1) were analyzed in tissue conditioned media by Western blot, ELISA and/or zymography. MMP and plasmin proteolytic activities were increased in the scar as compared to paired LVM thus indicating that activation of plasminogen and pro-MMPs is a key event in scar tissue remodeling. MMP and plasminogen activators (uPA, tPA) mRNAs were increased accordingly. Furthermore, inhibitors of the proteolytic enzymes, TIMP-1 and PAI-1 were increased in the scars from failing hearts and LVM thus suggesting a dynamic interplay between proteolysis and its inhibitors. This study shows a high degree of activation of the MMP-plasminogen system and the balance with their inhibitors in the infarcted myocardium, and suggests that this activation participates more to the remodeling of the scar tissue than to the remaining myocardium.     

Effects of imidapril on endothelin-1 and ACE gene expression in failing hearts of salt-sensitive hypertensive rats

The renin-angiotensin system and endothelin are important regulators of the cardiovascular system. Although increased production of endothelin-1 (ET-1) is reported in patients with heart failure, the detailed mechanism remains to be determined. To elucidate the relationship between the renin-angiotensin system and ET-1 in hypertensive heart failure, we evaluated the effects of long-term treatment with imidapril, an angiotensin converting enzyme (ACE) inhibitor, on preproET-1, endothelin A receptor (ETAR), and ACE mRNA expression in the left ventricle and evaluated these in relation to myocardial remodeling in the failing heart of Dahl salt-sensitive (DS) hypertensive rats fed a high salt diet. In DS rats fed an 8% NaCl diet after the age of 6 weeks, a stage of concentric left ventricular hypertrophy at 11 weeks (DSLVH) was followed by a distinct stage of left ventricular failure with chamber dilatation at 18 weeks (DSHF). Imidapril (DSHF-IM, n = 8, 1 mg/kg/day, subdepressor dose) or vehicle (DSHF-V, n = 8) was given from stage DSLVH to DSHF for 7 weeks, and age-matched (18 weeks) Dahl salt-resistant rats fed the same diet served as the control group (DR-C, n = 8). In both groups, blood pressure was similar and significantly higher than in DR-C. Markedly increased left ventricular end-diastolic diameter and reduced fractional shortening in DSHF-V was significantly ameliorated in DSHF-IM using transthoracic echocardiography. The preproET-1, ETAR, and ACE mRNA levels in the left ventricle were significantly increased in DSHF-V compared with DR-C, and significantly suppressed in DSHF-IM compared with DSHF-V. DSHF-V demonstrated a significant increase in the wall-to-lumen ratio and perivascular fibrosis in coronary arterioles, and myocardial fibrosis, with all these parameters being significantly improved by imidapril. In conclusion, myocardial remodeling and heart failure in DS rats fed a high salt diet were significantly ameliorated by a subdepressor dose of imidapril, which may be attributable to a decrease in ET-1 mRNA expression and angiotensin II in the left ventricle.     

Myocardial matrix degradation and metalloproteinase activation in the failing heart: a potential therapeutic target

A fundamental structural event in the progression of heart failure due to dilated cardiomyopathy is left ventricular (LV) myocardial remodeling. The matrix metalloproteinases (MMPs) are an endogenous family of enzymes which contribute to matrix remodeling in several disease states. The goal of this report is to summarize recent findings regarding the myocardial MMP system and the relation to matrix remodeling in the failing heart. In both experimental and clinical forms of dilated cardiomyopathy (DCM), increased expression of certain species of myocardial MMPs have been demonstrated. Specifically, increased myocardial levels of the gelatinase, MMP-9 has been identified in both ischemic and non-ischemic forms of human DCM. In addition, stromelysin or MMP-3 increased by over four-fold in DCM. The increased levels of MMP-3 in DCM may have particular importance since this MMP degrades a wide range of extracellular proteins and can activate other MMPs. In normal human LV myocardium, the membrane type 1 MMP (MT1-MMP) was detected. These MT-MMPs may provide important sites for local MMP activation within the myocardium. In a pacing model of LV failure, MMP expression and activity increased early and were temporally associated with LV myocardial matrix remodeling. Using a broad-spectrum pharmacological MMP inhibitor in this pacing model, the degree of LV dilation was attenuated and associated with an improvement in LV pump function. Thus, increased LV myocardial MMP expression and activity are contributory factors in the LV remodeling process in cardiomyopathic disease states. Regulation of myocardial MMP expression and activity may be an important therapeutic target for controlling myocardial matrix remodeling in the setting of developing heart failure.     

Heart failure in pressure overload hypertrophy. The relative roles of ventricular remodeling and myocardial dysfunction

OBJECTIVES: We sought to explore the relative contributions of ventricular remodeling and myocardial dysfunction to heart failure in pressure overload hypertrophy (POH). BACKGROUND: The mechanism that underlies heart failure in POH is adverse left ventricular (LV) chamber remodeling or decreased myocardial function, or a combination of these. METHODS: Twenty weeks after suprarenal aortic banding in rats, animals with POH were classified as those with heart failure (POH-HF) or those with no heart failure (POH-NHF). The LV chamber and myocardial systolic and diastolic functions were determined from in vivo and ex vivo experiments. RESULTS: The LV mass was similar in both POH groups. Chamber remodeling in the POH-HF group was characterized by marked LV enlargement with a normal relative wall thickness (eccentric remodeling), whereas remodeling in the POH-NHF group was characterized by a normal chamber size and increased relative wall thickness (concentric remodeling). The LV systolic function, as determined in vivo from the end-systolic pressure-diameter relationship and ex vivo from the pressure-volume relationship, was lower in the POH-HF group than in the POH-NHF and sham-operated control groups. In contrast, myocardial function was similar in both POH groups, as determined in vivo from the stress-midwall fractional shortening relationship and myocardial systolic stiffness, and ex vivo from the slope of the LV systolic stress-strain relationship. The diastolic chamber stiffness constant was lower in the POH-HF group than in the POH-NHF group, but the myocardial stiffness constant was similar in the two POH groups. CONCLUSIONS: The two POH groups differed primarily in their remodeling process, which led to a chronically compensated state in one group and to heart failure in the other. Hence, heart failure in POH is more closely related to deleterious LV remodeling than to depressed myocardial function.     

Effect of ramipril and furosemide treatment on interstitial remodeling in post-infarction heart failure rat hearts

Extracellular matrix (ECM) remodeling and increased matrix metalloproteinase (MMP) expression and activity have been observed to be relevant in the development of heart failure (HF). We examined the effects of ramipril alone or with furosemide on ECM in a heart failure model. HF was induced by occlusion of the left coronary artery in spontaneously hypertensive rats (SHR). Rats were assigned to placebo (n=9), ramipril 1 mg/kg/day (n=11), furosemide 2 x 2 mg/kg/day (n=7) or both (1 mg/kg/day + 2 x 2 mg/kg/day n=8). LV-function, collagen content, MMP/TIMP (tissue inhibitor of matrix metalloproteinases) protein- and mRNA-expression were examined in non-infarcted LV tissue. MMP-2/TIMP-4 ratio was increased in HF. Ramipril reduced MMP-2 expression (active form), collagen type I mRNA expression and content and increased TIMP-4 levels associated with decreased left ventricular end diastolic pressure (LVEDP), mortality rate and increased LV pressure (LVP). Combination therapy with furosemide is less efficient with regard to collagen content and MMP-2 (active form) reduction but did not worsen beneficial effects of ramipril on LV function and mortality rate. Furosemide alone had no effect on MMP-2 (active form) expression, collagen content, LV function and mortality rate. Prevention of LV dilatation by ramipril was associated with decreased gelatinolytic activity and increased MMP-inhibition in heart failure SHR. Furthermore, ramipril reduced fibrosis by enhanced interstitial collagenase expression. Furosemide did not show the beneficial effects of ramipril on ECM remodeling but did not worsen LV function. Positive effects of furosemide treatment alone on LV remodeling and function were not observed.