Oxidative modification of tropomyosin and myocardial dysfunction following coronary microembolization.

AIMS: We addressed a potential mechanism of myocardial dysfunction following coronary microembolization at the level of myofibrillar proteins. METHODS AND RESULTS: Anaesthetized pigs underwent intracoronary infusion of microspheres. After 6 h, the microembolized areas (MEA) had decreased systolic wall thickening to 38 +/- 7% of baseline and a 2.62 +/- 0.40-fold increase in the formation of disulphide cross-bridges (DCB) in tropomyosin relative to that in remote areas. The impairment in contractile function correlated inversely with DCB formation (r = -0.68; P = 0.015) and was associated with increased TNF-alpha content. DCB formation was reflected by increased tropomyosin immunoreactivity and abolished in vitro by dithiothreitol. Ascorbic acid prevented contractile dysfunction as well as increased DCB and TNF-alpha. In anaesthetized dogs, 8 h after intracoronary microspheres infusion, contractile function was reduced to 8+/-10% of baseline and DCB in MEA was 1.48+/-0.12 higher than that in remote areas. In conscious dogs, 6 days after intracoronary microspheres infusion, myocardial function had returned to baseline and DCB was no longer different between remote and MEA. Again contractile function correlated inversely with DCB formation (r = -0.83; P = 0.005). CONCLUSION: Myofibrillar protein oxidation may represent a mechanistic link between inflammation and contractile dysfunction following coronary microembolization.     

Bidirectional role of tumor necrosis factor-alpha in coronary microembolization: progressive contractile dysfunction versus delayed protection against infarction

In patients with unstable angina, plaque rupture and coronary microembolization (ME) can precede complete coronary artery occlusion and impending infarction. ME-induced microinfarcts initiate an inflammatory reaction with increased tumor necrosis factor-alpha (TNF-alpha) expression, resulting in progressive contractile dysfunction. However, TNF-alpha is not only a negative inotrope but can also protect the myocardium against infarction. In anesthetized pigs, we studied whether ME protects against infarction when TNF-alpha expression is increased. ME (group1; n=7) was induced by intracoronary infusion of microspheres (42 microm; 3000 per mL/min inflow). Controls (group 2; n=8) received saline. Groups 3 and 4 (n=4 each) were pretreated with ovine TNF-alpha antibodies (25 mg/kg body weight) 30 minutes before ME or placebo, respectively. Ischemia (90 minutes) was induced 6 hours after ME when TNF-alpha was increased (66+/-21 pg/g wet weight; mean+/-SEM) or after placebo (TNF-alpha, 21+/-10 pg/g; P<0.05). Infarct size (percentage area at risk) was determined after 2 hours of reperfusion (triphenyl tetrazolium chloride staining). ME decreased systolic wall thickening progressively over 6 hours (group 1 versus group 2, 65+/-4% versus 90+/-1%; percentage of baseline; P<0.05). TNF-alpha antibodies attenuated the progressive decrease in systolic wall thickening following ME (group 3, 77+/-5% of baseline; P<0.05 versus group 1) with no effect in controls (group 4; 90+/-8% of baseline). With ME, infarct size was decreased to 18+/-4% versus 33+/-4% in group 2 (P<0.05). The infarct size reduction was abolished by TNF-alpha antibodies (group 3 versus group 4, 29+/-3% versus 35+/-5%). In ME, TNF-alpha is responsible for both progressive contractile dysfunction and delayed protection against infarction.     

阿托伐他汀对冠状动脉微栓塞后心肌炎症的影响

目的 探讨阿托伐他汀干预治疗对冠状动脉微栓塞（CME）后心肌炎症的影响.方法 48只清洁级雄性SD大鼠经左心室内注射自体微血栓,同时短暂夹闭主动脉,建立大鼠CME模型后,随机分为未治疗组及阿托伐他汀（Atrovastatin）干预组,于术后7 d处死.HE染色观察梗死心肌,免疫组织化学染色及Western blot检测肿瘤坏死因子α（TNF-α）、白介素6（IL-6）及细胞间黏附因子1（ICAM-1）等炎症因子在心肌中表达的变化.结果 阿托伐他汀可轻度减少梗死面积,显著抑制CME后心肌中白细胞浸润及TNF-α、IL-6、ICAM-1 蛋白表达（P均〈0.05）.结论 阿托伐他汀能显著抑制CME后心肌炎症反应.     

Coronary microembolization induced myocardial contractile dysfunction through a p38 mapk pathway

Background Cathepsin S and its endogenous inhibitor cystatin C are implicated in the pathogenesis of atherosclerosis,especially in the plaque destabilization and rupture leading to acute coronary syndrome.However, whether circulating cathepsin S and cystatin C also change in association with coronary plaque morphology is unknown yet. Methods Sprague-Dawley rats were randomly divided into three groups;Sham group,CME group and SB203580 group (n=10 per group).CME rats were produced by injection of 42μm microspheres into the left ventricle with occlusion of the ascending aorta.SB203580,a p38 MAPK inhibitor,was injected into femoral vein after finishing the injection of microspheres in SB203580 group.Left ventricular Ejection Fraction was determined by echocardiography.The level of phosphorylated and total P38 MAPK in myocardium was assessed by Western Blot.Results Left ventricular(LV) Ejection Fraction was depressed at 3 hours and until up to 12 hours in CME group.The increased p38 MAPK activation was observed in CME group.The administration of SB203580 partly inhibited the p38 MAPK activity and preserved cardiac contractile function.Conclusions p38 MAPK is significantly activated by CME and the inhibition of p38 MAPK can partly preserve cardiac contractile function.     

阿托伐他汀对冠状动脉微栓塞后非梗死区心肌炎症的影响

目的：探讨阿托伐他汀干预治疗对冠状动脉微栓塞（CME）后非梗死区心肌炎症的影响。方法：给清洁级雄性新西兰兔选择性经左前降支（LAD）注入微栓子颗粒悬液建立CME模型,将36只新西兰兔随机分为CME组（模型组）、阿托伐他汀（atrovastatin）干预组及对照组,每组12只（n=12）。于术后7d处死,取左心室乳头段心肌经HE染色后,观察梗死心肌并检测梗死面积。用ELISA法及RT-PCR检测肿瘤坏死因子α（TNF-α）、白介素6（IL一6）及其基因在非梗死区（右室）心肌中的表达。结果：前降支动脉微栓塞后,非梗死区右室心肌中白细胞浸润明显增多,TNF-α、IL-6蛋白及其基因的表达显著增强。与未处理组相比,阿托伐他汀可显著抑制CME后右室心肌中白细胞浸润及TNF-α、IL-6蛋白及其基因的表达（均P〈0．01）。结论：冠脉微栓塞后,炎症反应的激活不仅局限于梗死灶,且累及非梗死区心肌。阿托伐他汀可显著抑制CME后非梗死区心肌炎症反应。     

阿托伐他汀对冠状动脉微栓塞后非梗死区心肌炎症的影响

目的:探讨阿托伐他汀干预治疗对冠状动脉微栓塞（CME）后非梗死区心肌炎症的影响。方法: 给清洁级雄性新西兰兔选择性经左前降支(LAD)注入微栓子颗粒悬液建立CME模型,将36只新西兰兔随机分为CME组（模型组）、阿托伐他汀（atrovastatin）干预组及对照组,每组12只(n=12)。于术后7 d处死,取左心室乳头段心肌经HE染色后,观察梗死心肌并检测梗死面积。用ELISA法及RT-PCR检测肿瘤坏死因子α（TNF-α）、白介素6（IL-6）及其基因在非梗死区（右室）心肌中的表达。结果: 前降支动脉微栓塞后,非梗死区右室心肌中白细胞浸润明显增多,TNF-α、IL-6蛋白及其基因的表达显著增强。与未处理组相比,阿托伐他汀可显著抑制CME后右室心肌中白细胞浸润及TNF-α、IL-6蛋白及其基因的表达(均P<0.01)。结论: 冠脉微栓塞后,炎症反应的激活不仅局限于梗死灶,且累及非梗死区心肌。阿托伐他汀可显著抑制CME后非梗死区心肌炎症反应。     

Experimental model of chronic global left ventricular dysfunction secondary to left coronary microembolization

A model of chronic left ventricular dysfunction characterized by left ventricular dilation, elevated filling pressures and histologic changes has been lacking. In this study the use of coronary microsphere embolization-induced ischemia was explored as a method of producing chronic left ventricular dysfunction. Acute ischemic left ventricular dysfunction was induced in 13 mongrel dogs with 50 microns plastic microspheres until the peak positive first derivative of left ventricular pressure (dP/dt) decreased by 25% and the left ventricular end-diastolic pressure increased to greater than or equal to 12 mm Hg. After 8 weeks of observation, hemodynamic and echocardiographic variables were measured in each dog. Acute left ventricular dysfunction resulted in a dilated left ventricle with systolic dysfunction (area ejection fraction 24 +/- 6% vs. 57 +/- 9% initially, p less than 0.01) and elevated left ventricular filling pressures. Isovolumetric relaxation was prolonged and the peak rapid filling/atrial filling velocity and integral ratios were reduced. Eight weeks after embolization, there was an increased left ventricular size (end-diastolic area 15.1 +/- 2.1 cm2 at 8 weeks vs. 13.5 +/- 1.4 cm2 early after microsphere injection, p less than 0.05), unchanged end-systolic area, improved area ejection fraction and increased left ventricular mass. Left ventricular end-diastolic pressure increased and, despite continued abnormal relaxation, the peak rapid filling/atrial filling velocity and integral ratios increased to above baseline values, demonstrating a "restrictive" pattern. Gross and histologic examination revealed diffuse, patchy scarring associated with perivascular fibrosis. Thus, coronary microsphere embolization resulted in a model of chronic moderate left ventricular systolic dysfunction and abnormal diastolic function characterized by a "restrictive" filling pattern.     

Reduced myocardial blood flow resulting from dynamic changes in coronary artery stenosis

To evaluate the interaction of coronary vasomotor tone and stenosis, we studied the effects of ergonovine and adenosine on partially obstructed coronary arteries in 6 closed chest dogs. Coronary stenosis was created by partially inflating a balloon catheter with a distal lumen in the left anterior descending or circumflex coronary artery. Stenotic resistance was calculated as the mean pressure gradient across the stenosis divided by the mean blood flow measured with 15 micron radioactive microspheres. Coronary artery vasoconstriction, induced by ergonovine (0.6 mg i.v.), caused a small, but nonsignificant, increase in stenotic resistance (1.42 ± 0.25 to 2.68 ± 0.64 mm Hg/ml per min) and had no effect on myocardial blood flow. Coronary arteriolar dilation induced by adenosine increased stenotic resistance (1.52 ± 0.25 to 9.01 ± 2.49 mm Hg/ml per min, P < 0.05) and the pressure gradient across the stenosis (18.8 ± 3.0 to 41.3 ± 7.5 mm Hg, P < 0.05). Adenosine increased myocardial blood flow from 0.52 ± 0.05 ml/min per g to 1.43 ± 0.20 ml/min per g (P < 0.05) in the regions supplied by unstenosed arteries, while in the region perfused by the stenosed artery blood flow fell from 0.51 ± 0.06 to 0.29 ± 0.13 ml/min per g (P < 0.05), with the endocardium most severely affected (0.55 ± 0.04 ml/min per g to 0.26 ± 0.09 ml/min per g, P < 0.05).Thus changes in severity of stenosis produced by altered coronary pressure and flow can influence blood flow to the myocardium. Such dynamic changes in coronary artery stenosis may be important in the pathogenesis of angina and myocardial infarction.     

尼可地尔调控半胱氨酸天冬氨酸蛋白酶3对猪冠状动脉微栓塞后心肌凋亡的影响

目的探讨尼可地尔调控半胱氨酸天冬氨酸蛋白酶3(caspase-3)对猪冠状动脉微栓塞(CME)后心肌凋亡的影响。方法选择12周龄健康小型猪15只,随机分为假手术组、CME组、尼可地尔组,每组5只。模型建立后12 h采用心脏超声检测心功能,TUNEL染色检测心肌细胞凋亡,Western blot检测活化caspase-3表达水平。结果与假手术组比较,CME组左心室舒张末期内径(LVEDD)明显升高,CME组和尼可地尔组LVEF、左心室短轴缩短率(LVFS)及心输出量(CO)明显降低(P 0. 05);与CME组比较,尼可地尔组LVEF、LVFS及CO明显升高,LVEDD明显降低(P 0. 05)。与假手术组比较,CME组肌钙蛋白Ⅰ明显升高[(0. 325±0. 128) ng/ml vs (0. 058±0. 028)ng/ml,P 0. 05];与CME组比较,尼可地尔组肌钙蛋白Ⅰ明显降低[(0. 156±0. 089) ng/ml vs (0. 325±0. 128) ng/ml,P 0. 05]。与假手术组比较,CME组心肌细胞凋亡指数和活化caspase-3表达明显升高(P 0. 05);与CME组比较,尼可地尔组心肌细胞凋亡指数和活化caspase-3表达明显降低(P 0. 05)。结论尼可地尔能够通过调控caspase-3降低猪CME后心肌凋亡。     

Spontaneous coronary dissection resulting in acute myocardial infarction: Successful treatment with primary angioplasty

Spontaneous coronary dissection is an unusual cause of acute myocardial infarction for which the optimal therapy has not been established. We report the case of a 63-year-old man with acute lateral wall myocardial infarction resulting from spontaneous dissection of the major diagonal branch of the left anterior descending artery in whom acute and long-term patency was restored by primary PTCA. © 1996 Wiley-Liss, Inc.     

Relation of coronary microvascular dysfunction in hypertrophic cardiomyopathy to contractile dysfunction independent from myocardial injury

We studied the spatial relations among hyperemic myocardial blood flow (hMBF), contractile function, and morphologic tissue alterations in 19 patients with hypertrophic cardiomyopathy (HC). All patients were studied with oxygen-15 water positron emission tomography during rest and adenosine administration to assess myocardial perfusion. Cardiovascular magnetic resonance was performed to derive delayed contrast-enhanced images and to calculate contractile function (E(cc)) with tissue tagging. Eleven healthy subjects underwent similar positron emission tomographic and cardiovascular magnetic resonance scanning protocols and served as a control group. In the HC group, hMBF averaged 2.46 ± 0.91 ml/min/g and mean E(cc) was -14.7 ± 3.4%, which were decreased compared to the control group (3.97 ± 1.48 ml/min/g and -17.7 ± 3.2%, respectively, p <0.001 for the 2 comparisons). Delayed contrast enhancement (DCE) was present only in patients with HC, averaging 6.2 ± 10.3% of left ventricular mass. In the HC group, E(cc) and DCE in the septum (-13.7 ± 3.6% and 10.2 ± 13.6%) significantly differed from the lateral wall (-16.0 ± 2.8% and 2.4 ± 5.9%, p <0.001 for the 2 comparisons). In general, hMBF and E(cc) were decreased in segments displaying DCE compared to nonenhanced segments (p <0.001 for the comparisons). In the HC group, univariate analysis revealed relations of hMBF to E(cc) (r = -0.45, p <0.001) and DCE (r = -0.31, p <0.001). Multivariate analysis revealed that E(cc) was independently related to hMBF (beta -0.37, p <0.001) and DCE (beta 0.28, p <0.001). In conclusion, in HC hMBF is impaired and related to contractile function independent from presence of DCE. When present, DCE reflected a progressed disease state as characterized by an increased perfusion deficit and contractile dysfunction.     

Edema resulting from experimental filariasis

Domestic cats and patas monkeys were infected with Brugia malayi so that the worms localized in the regional lymphatics of the hind legs. Reaction to the filarial parasites resulted in visible local edema in cats and disruption of normal lymph flow in the monkeys. Edematous tissue was examined grossly and by light and electron microscopy. Lymph flow patterns were examined by direct observation following injection of lymph staining dye and reflection of the skin, by X-ray following injection of radio-opaque contrast media, and by lymphscintigraphy after subcutaneous injection of radioisotopes. Clinical edema occurred in cats but not in monkeys. However, disruption of normal lymph flow in monkeys infected with Brugia could be demonstrated by lymphscintigraphy.     

非选择性冠状动脉微栓塞对大鼠心肌细胞凋亡及左室功能的影响

目的:探讨非选择性冠状动脉微栓塞(CME)对大鼠心肌细胞凋亡及左室功能的影响.方法:采用雄性SD大鼠56只, 体重280～320 g.随机分为假手术组(Sham组,24只)和CME组(32只).CME组夹闭升主动脉同时自左室腔注入自体微血栓混悬液,Sham组则注入等容量的0.9%氯化钠溶液.术后3 d、7 d、14 d及28 d(每个时间点CME组8只,Sham组6只)采用苏木精-伊红染色观察心肌组织病理学改变,Real Time PCR(实时定量聚合酶链式反应)检测心肌细胞Bcl-2、Bax、Fas、Fas-L等凋亡调控基因mRNA的表达,采用Western blot蛋白印迹法检测Caspase3、Caspase9和裂解PARP蛋白的表达,TUNEL(脱氧核糖核苷酸末端转移酶介导的缺口末端标记法)测定凋亡细胞,应用有创血流动力学检测大鼠左心功能的变化.结果:①苏木精-伊红染色显示,CME术后可见心内膜下多中心小灶性心肌缺血、坏死伴白细胞浸润.②术后7 d,与Sham组相比较,CME组Bax、Fas及Fas-L mRNA的表达水平明显增高,Bcl-2/Bax的比值明显降低(0.18±0.04∶2.98±0.49 P<0.01);Caspase-3、Caspase-9及裂解PARP蛋白表达明显升高 (0.762±0.129∶0.133±0.027,0.295±0.023∶0.067±0.020,0.992±0.146∶0.386±0.074,均P<0.01).③术后7 d CME组凋亡指数较Sham组明显增高(17.2±1.9∶1.2±0.6, P<0.01).④LVSP及±dp/dtmax较Sham组明显降低(P<0.01).结论:CME早期即可通过改变凋亡调控基因的平衡,启动、激活Caspase级联反应,促进心肌细胞凋亡,降低左室功能.     

Effects of propranolol on myocardial damage resulting from coronary artery occlusion followed by reperfusion

To evaluate the effects of propranolol on myocardial metabolism after coronary reperfusion, serial measurements of myocardial creatine kinase (CK) and calcium (Ca) contents and CK and lactic acid (LA) concentrations in coronary sinus blood were carried out in 33 open-chest dogs. The left anterior descending coronary artery was occluded for 60 minutes and was then reopened. Twelve of the dogs were given propranolol before occlusion. Reperfusion for 30 minutes in dogs with and without propranolol pretreatment resulted in reduced myocardial CK in the ischemic region and rapidly elevated plasma CK and LA. However, when compared with the control group, the propranolol-treated group showed smaller changes in myocardial CK and plasma LA. Myocardial Ca in the ischemic region was significantly higher than that in the nonischemic region in the control group, but not in the propranolol-treated group. It was concluded that propranolol was protective against myocardial damage resulting from coronary occlusion followed by reperfusion.     

Effect of metoprolol on myocardial apoptosis and caspase-9 activation after coronary microembolization in rats

OBJECTIVE:

To explore the effect of metoprolol on myocardial apoptosis and caspase-9 activation after coronary microembolization (CME) in rats.

METHODS:

Forty rats were randomly divided into four groups (n=10 each): a sham operation (control) group, CME plus saline (CME) group, CME plus metoprolol (metoprolol) group and caspase-9 inhibitor Z-LEHD-FMK (ZLF) group. CME was induced by injecting 3000 polyethylene microspheres (42 μm diameter) into the left ventricle during a 10 s occlusion of the ascending aorta. Echocardiography, terminal deoxynucleotidyl transferase dUTP nick end labelling and Western blotting were used to evaluate cardiac function, apoptosis and activation of caspase-9/caspase-3, respectively, 6 h after CME.

RESULTS:

The echocardiographic parameters of left ventricular function were significantly decreased in the CME group compared with the control group (P<0.05); however, the metoprolol group and ZLF group showed significantly improved cardiac function compared with CME alone (P<0.05). Compared with the control group, the myocardial apoptosis rate and the levels of activated caspase-9 and -3 increased significantly in the CME group (P<0.05). Again, these effects were ameliorated by metoprolol and ZLF (P<0.05).

CONCLUSIONS:

The present study demonstrates that metoprolol and ZLF can protect the rat myocardium during CME by inhibiting apoptosis and improving cardiac function, likely by inhibiting apoptosis/ mitochondrial apoptotic pathway. These results suggest that antiapoptotic therapies may be useful in treating CME.