Effects of different ages on ventricular remodeling after ischemic heart failure in mice

AIM: To observe ventricular remodeling induced by ischemic heart failure in the mice at different ages.METHODS: Three-month-old (young group, n=50) and 18-month-old (old group, n=50) male C57BL/6J mice were selected in the study. Forty mice underwent ligation of left coronary artery with certain infarct size, and 10 were sham-operated for control. Echocardiography was performed after 8 weeks of infarction. All mice were killed and the hearts were collected for examinations. Masson trichrome staining was used to detect myocardial fibrosis. The expression of type I and type Ⅲ collagens was measured by the method of immunohistochemistry.RESULTS: The incidences of cardiac rupture (18% vs 10%, P<0.05) and heart failure (22% vs 10%, P<0.05) were significantly higher in aged mice than those in young mice. The degrees of left ventricular dilation, contractile dysfunction and heart rate were significantly higher in aged mice than those in young mice (P<0.05). The left ventricular mass index, collagen volume fraction, the expression of type I collagen and ratio of type Ⅰ/Ⅲ collagens were significantly increased in aged mice as compared with young mice (P<0.05).CONCLUSION: After heart failure, aged mice show abnormal collagen distribution, and suffer from worse cardiac functions and more serious ventricular remodeling.     

Effects of spironolactone on atrial structural remodeling in rabbit model of chronic atrial fibrillation

AIM: To evaluate the effects and potential mechanism of spironolactone (SP) on atrial structural remodeling in rabbit model of chronic atrial fibrillation (AF). METHODS: The sternotomy was performed and the pacing electrodes were fixed to the left atria of New Zealand white rabbits. The animals were randomly divided into 3 groups. The rabbits were subjected to rapid atrial pacing (RAP) for 3 weeks in RAP group (intragastric administration with placebo) and RAP+SP group (intragastric administration with spironolactone at 20 mg·kg^-1·d^-1), respectively. The rabbits in sham group did not receive RAP and drugs. Before and after RAP, the structure and function of the atria were evaluated and AF inducibility was tested. After RAP, the atrial fibrosis was evaluated, and the expression levels of collagen I, collagen Ⅲ, matrix metalloproteinase (MMP)-2 and MMP-9 were determined. RESULTS: After 3 weeks of RAP, compared with sham group, obvious left atrial enlargement and dysfunction were observed in RAP group and RAP+SP group, but those had no significant differences in these 2 groups. Sustained AF was induced in 7, 5, and 0 rabbits in RAP group, RAP+SP group, and sham group, respectively. Compared with sham group, atrial interstitial fibrosis and the protein expression levels of collagen Ⅰ, collagen Ⅲ, MMP-2 and MMP-9 were all significantly increased in RAP group and RAP+SP group(P<0.05). Compared with RAP group, the the above indexes were all decreased in RAP+SP group(P<0.05). CONCLUSION: Spironolactone suppresses the atrial interstitial fibrosis and collagen expression, thus preventing atrial structural remodeling in rabbit model of chronic AF. The effect of spironolactone on reducing atrial MMP-2 and MMP-9 levels may be the potential mechanism.     

Correlation between myocardial interstitial collagen remodeling and changes in hemodynamics in rats with myocardial infarction

AIM: To study the relationship between cardiac extracellular matrix remodeling and cardiac function after myocardial infarction. METHODS: We observed sequential changes in collagen contents and collagen Ⅰ/Ⅲ ratios in infarct zone (IZ) and non-infarct zone (NIZ) and their relationship to the parameters of left ventricular systolic and diastolic function in the rat model of myocardial infarction induced by ligation of left main coronary artery. RESULTS: Collagen conteants in IZ and NIZ after 3d of myocardial infarction were significantly higher than those in sham group at corresponding time (P<0.05, P<0.01). Collagen Ⅰ/Ⅲ ratio in IZ decreased on day 3, significantly increased after 7 d (P<0.01). Collagen Ⅰ/Ⅲ ratio in NIZ increased significantly afte14 d. Correlated analysis between collagen contents in IZ or NIZ and collagen type Ⅰ/Ⅲ ratio and maximal ascending velocity (+p'_max) or maximal descending velocity of the left ventricular pressure (-p'_max) was performed and the negative correlation between collagen contents in NIZ and +P'_max (r=-0.589, P>0.05) and -P'_max (r=-0.788, P<0.01) was found. Collagen content in IZ positively correlated to the +P'_max (r=0.70, P<0.50), but not to -P'_max (r=-0.29, P>0.05). Collagen type Ⅰ/Ⅲ ratios in NIZ correlated negatively to the +P'_max (r=-0.504, P>0.05) and -P'_max (r=-0.545, P>0.05), but there were no relationship between collagen type Ⅰ/Ⅲ ratios in IZ and +P'_max or -P'_max in IZ. CONCLUSION: Collagen deposition in IZ after myocardial infarction was of benefit to improvement of systolic function. Collagen deposition in NIZ was harmful to systolic and diastolic function.     

Changes of cytokine and collagen in the myocardial remodeling after acute myocardial infarction in rats

AIM:To clarify the relationship between the cytokine and collagen in myocardial remodeling after acute myocardial infarction (MI) in rats. METHODS:In MI group, Wistar rats were undergone acute myocardial infarction by ligation of the anterior descending coronary artery. Sham operation was made in rats as control. The mRNA expression of collagen and cytokines such as TNF-α and TGF-β1 in infract and non-infarct region of left myocardium were detected by RT-PCR at different time point (3 d, 1 and 4 weeks). RESULTS:Collagen type Ⅰ and Ⅲ elevated as well as the TNF-α and TGF-β1 in the MI group at 3th day. Expression of collagen type Ⅰ and Ⅲ were higher in the infarct region than that in the non-infarct region even at 4 weeks. TNF-α and TGF-β1 peaked at 1 week and declined gradually to the baseline, which was still higher than those in control group (P<0.01). Correlation analysis revealed that expressions of TNF-α and TGF-β1 were positively correlated with the collagen type Ⅰand Ⅲ (P<0.01). CONCLUSION:Cytokines participate in the myocardial remodeling after MI. Interfering with expression of cytokines may be the potentially preventative method in the myocardial remodeling.     

Effect of atorvastatin on cardiac function and HGF/c-Met signaling pathway after acute myocardial infarction in diabetic rats

AIM: To investigate the effect of atorvastatin on myocardial apoptosis, ventricular remodeling and cardiac function after acute myocardial infarction (AMI) in diabetic rats, and to explore whether the effect is mediated by hepatocyte growth factor (HGF)/c-Met signaling pathway. METHODS: Diabetes in 70 male SD rats was induced by intraperitoneal injection of streptozotocin (STZ, 65 mg/kg). After 8 weeks, AMI was induced by the ligation of the left anterior descending coronary artery in the diabetic rats, and 32 surviving rats were divided into AMI group (n=16) and AMI＋atorvastatin group (n=16, 20 mg·kg-1·d-1) at random. The similar surgical procedure was completed in sham group (n=11) without coronary ligation. Atorvastatin was given daily by gavage from the first day after AMI. Two weeks later, the cardiac function, pathological changes of myocardial tissues, myocardial apoptosis, and the expression of HGF and c-Met were compared among groups. RESULTS: AMI significantly reduced cardiac function, increased collagen volume fraction (CVF) and myocardial apoptotic index, and up-regulated the expression of HGF and c-Met at mRNA and protein levels in AMI control group (P<0.05). The cardiac function was improved, and CVF and myocardial apoptotic index were reduced by the treatment with atorvastatin, which also up-regulated the expression of HGF and c-Met (P<0.05). CONCLUSION: Atorvastatin significantly attenuates myocardial apoptosis and cardiac remodeling, and improves cardiac function after AMI in diabetic rats by further enhancing the activation of HGF/c-Met pathway.     

Experimental research on cardiac fibrosis induced by recombinant mouse interleukin-11 in mice

AIM To observe the effect of recombinant mouse interleukin-11 （rmIL-11）injected subcutaneously into mice on heart structure and function and to determine its pro-fibrotic effect. METHODS C57BL/6 mice were randomly divided into experimental group and control group.The mice in experimental group were injected subcutaneously with recombinant mouse IL-11 at the dose of 100 μg·kg^-1·d^-1 for 3 consecutive weeks, while the control group were given equal volume of normal saline in the same way. After the experiment was finished, the parameters of heart function were measured by echocardiography.The heart weight was weighed and the cardiac weight index (CWI) was calculated. HE staining and Masson's trichrome staining were performed to observe the pathological changes and the extent of myocardial fibrosis in mouse myocardia respectively, and the cardiac collagen volume fraction (CVF) was calculated. The expression levels of extracellular matrix proteins in the myocardial tissues of mice, including type Ⅰ collagen, type Ⅲ collagen and fibronectin, were determined by Western blot. RESULTS Left ventricular ejection fraction and left ventricular fraction shortening in experimental group were obviously lower than those in control group (P<0.01), however left ventricular end-diastolic diamension and left ventricular end systolic dimension were significantly higher than those in control group (P<0.05).Compared with control group, the CWI was increased (P<0.01), the myocardial arrangement was disorder, the necrosis of cardiac myocytes was increased, and excessive deposition of collagen was observed in the myocardial tissues in experimental group. Correspondingly, the CVF and protein levels of type Ⅰ collagen, type Ⅲ collagen and fibronectin in the left ventricle in experimental group were increased significantly (P<0.05). CONCLUSION Injection of rmIL-11 into the mice subcutaneously induces fibrogenesis in the heart, which implies that IL-11 is likely a novel pro-fibrotic factor.     

Effects of fluvastatin on the left ventricular function,MHC gene expression and collagen remodeling after myocardial infarction

AIM: To observe the effects of fluvastatin (FV) on the left ventricular (LV) function, MHC mRNA and collagen remodeling of non-infarcted area after acute myocardial infarction (AMI). METHODS: Six hours after ligating left coronary artery, survivors of AMI female SD rats were randomly assigned to: ①AMI control; ②FV; ③sham-operated groups. After 8 weeks of therapy, the LV function, hemodynamics, expression of non-infarcted myocardial MHC mRNA, collagen volume fraction (CVF) and the ratio of type Ⅰ/Ⅲ collagen of non-infarcted area were assessed. RESULTS: Compared with sham-operated group, E wave, E wave deceleration, E/A ratio, LV end diastolic pressure (LVEDP), β MHC mRNA, CVF and the ratio of type Ⅰ/Ⅲ collagen were all significantly increased in AMI group, while fractional shortening (FS), ejection fraction (EF), mean arterial pressure (MAP) and α MHC mRNA were all significantly decreased. In comparison with AMI group, E wave, E wave deceleration, E/A, LVEDP, β MHC mRNA, CVF and the ratio of type Ⅰ/Ⅲ collagen were all significantly decreased, while FS, EF, MAP and α MHC mRNA were all significantly increased in FV group. CONCLUSION: FV improves the LV function after AMI and has beneficial effects on reversing LV myocardial pathologic switching of MHC isoform and collagen remodeling.     

Effects of Ginkgo biloba extract on myocardial TGF-β1 and collagen expression and interstitial fibrosis in type I diabetic cardiomyopathy rats

AIM:To study the effects of Ginkgo biloba extract (EGB) on myocardial TGF-β1 and collagen expression and interstitial fibrosis in type I diabetic cardiomyopathy rats. METHODS:Thirty male SD rats were randomly divided into normal control group (CON), diabetes mellitus group (DM) and EGB treatment group (EGB). Streptozocin was intraperitoneally injected into the animals in the latter 2 groups to induce type I diabetic rat model. The rats in EGB group were intraperitoneally injected with EGB. At the end of the 12th week, the body weight of each rat and its left ventri-cular weight, blood glucose, glycosylated hemoglobin and serum insulin concentration were measured. The left ventricular end-diastolic volume (LVEDV), the left ventricular end-systolic volume (LVESV), the left ventricular ejection fraction (LVEF) and the stroke volume (SV) were determined by echocardiography. The content of collagen in left ventricular myocardium, and the expression of transforming growth factor β1 (TGF-β1), procollagen type I and collagen type III were assayed by Sirius red staining, immunohistochemical staining and RT-PCR, respectively. Left ventricular myocardial cells of the neonatal SD rats were isolated and cultured in vitro with low-glucose culture medium (LG group), high-glucose culture medium (HG group) or high-glucose culture medium plus EGB (HG+EGB group). The mRNA levels of TGF-β1, procollagen type I and collagen type III were detected by RT-PCR. RESULTS:Compared with CON group, blood glucose, glycosylated hemoglobin, left ventricular weight index, the content of collagen, and the expression of TGF-β1, procollagen type I and collagen type III in left ventricular myocardial tissues of DM group were significantly increased, while the levels of blood insulin, LVEDV and SV were significantly decreased. However, compared with DM group, blood glucose, glycosylated hemoglobin, left ventricule weight index, the content of collagen, and the expression levels of TGF-β1, procollagen type I and collagen type III in the left ventricular myocardial tissues of EGB-treated rats were significantly decreased, while the levels of blood insulin, LVEDV and SV were significantly increased. Compared with LG group, the mRNA expression levels of TGF-β1, procollagen type I and collagen type III were significantly increased. However, compared with HG group, the mRNA expression levels of TGF-β1, procollagen type I and collagen type III were significantly decreased after treated with EGB. CONCLUSION: EGB retards the process of myocardial fibrosis and improves the cardiac functions in type I diabetic cardiomyopathy rats by down-regulating the expression of TGF-β1, reducing the synthesis and deposition of collagen type I and collagen type III.     

Effects of soluble transforming growth factor-β type Ⅱ receptor on cardiac functions after myocardial infarction in rats

AIM: To observe the effects of soluble transforming growth factor-β type Ⅱ receptor (sTGFβRⅡ) on cardiac functions after myocardial infarction (MI) in rats. METHODS: MI was induced in Sprague-Dawley (SD) rats by ligating the left anterior descending coronary artery. The rats surviving to the third day after MI were included in the study and randomly divided into MI group, pAd-sTGFβRⅡ group (transfected with recombinant adenovirus vector expressing the extracellular domain gene of TGF-βRⅡ), vector group and sham group. Four weeks later, the heart rate (HR), left ventricular end-diastolic dimension (LVEDD), left ventricular end-systolic dimension (LVESD) and ejection fraction (EF) were evaluated by echocardiograms. The expression of sTGFβRⅡ in myocardial tissues was observed under fluorescence microscope by frozen sectioning, and the expression of typeⅠ and Ⅲ collagens was observed by Sirius red-saturated picric acid staining. The expression of matrix metalloproteinase 9 (MMP-9) at mRNA and protein levels was determined by RT-PCR and immunohistochemical method. The activity of MMP-9 was assayed by gelatin zymography. RESULTS: Compared with sham group, HR, LVEDD, LVESD, typeⅠ and Ⅲ collagen, mRNA and protein of MMP-9, and the activity of MMP-9 increased significantly (P<0.01), and EF decreased (P<0.01) in MI group and vector group. Compared with MI group, EF was increased (P<0.01), but HR, LVEDD, LVESD, typeⅠ and Ⅲ collagen, mRNA and protein expression of MMP-9 and the activity of MMP-9 decreased significantly (P<0.01) in pAd-sTGFβRⅡ group, and all the parameters above were still higher than those in sham group. CONCLUSION: sTGFβRⅡ intervention improves the cardiac functions after MI by inhibiting TGF-β-mediated MMP-9 expression.     

Effect of hydrogen sulfide on myocardial fibrosis and PPARγ and NF-κB expression in rat model of diabetes

AIM: To explore the effects of hydrogen sulfide (H₂S) on the myocardial fibrosis in a rat model of diabetes and its mechanism.METHODS: Single intraperitoneal injection of streptozotocin (STZ) was utilized to establish a rat model of diabetes. Sodium hydrosulfide was used as an exogenous donor of hydrogen sulfide. Male SD rats were randomly divided into control group, STZ group, STZ+H₂S group and H₂S group. Eight weeks later, HE and VG staining methods were used to observe the collagen distribution and collagen volume fraction was measured by image analysis. The expression levels of type I collagen, PPARγ and NF-κB in the cardiac tissues were determined by Western blotting.RESULTS: Compared with control group, collagen distribution and the expression levels of type I collagen and NF-κB in the cardiac tissues were markedly increased (P<0.05), while PPARγ was significantly decreased in STZ group (P<0.05), but these indexes were reversed significantly in STZ+H₂S group (P<0.05). The expression levels of type I collagen, PPARγ and NF-κB had no significant difference between H₂S group and control group.CONCLUSION: Hydrogen sulfide attenuates cardiac fibrosis in diabetic rats, and its mechanism may be related to PPARγ-NF-κB signaling pathway.     

Prostaglandin E1 protects heart after myocardial infarction by inhibiting endoplasmic reticulum stress in rats

AIM To investigate the effect of prostaglandin E1 (PGE1) on heart after myocardial infarction (MI) in rats and its related molecular mechanism. METHODS Fifty male SD rats were divided into sham group, model group and model+PGE1 group. The MI rat model was established by ligation of left anterior descending coronary artery. Cardiac function in the rats was detected by echocardiogaphy. The myocardial histomorphologic changes were evaluated by HE and Masson staining. The MI area was measured by TTC staining. The cardiomyocyte death was detected by TUNEL staining. The protein levels of endoplasmic reticulum stress (ERS)-related factors glucose-regulated protein 78 (GRP78), C/EBP homologous protein (CHOP) and caspase-12, and apoptosis-related factors Bcl-2, Bax and cleaved caspase-3 were determined by immunofluorescence staining and Western blot. RESULTS Compared with sham group, the cardiac function in model group was decreased, with significant myocardial pathological changes. The MI area was enlarged, and the death of cardiomyocytes was promoted. The protein levels of GRP78, CHOP, caspase-12, Bax and cleaved caspase-3 in the myocardial tissues were significantly increased, while Bcl-2 was decreased (P<0.01). Compared with model group, the cardiac function in model+PGE1 group was significantly improved, and the myocardial pathological damage was significantlty attenuated. The MI area and myocardial cell death were significantly reduced. The protein levels of GRP78, CHOP, caspase-12, Bax and cleaved caspase-3 in the myocardial tissues were significantly decreased, while Bcl-2 was increased (P<0.01). CONCLUSION PGE1 reduces collagen deposition and inflammation, and improves cardiac function by reducing ERS level, thus protecting cardiomyocytes from MI damage.     

Effects of short-chain acyl-CoA dehydrogenase on collagen expression and proliferation of rat cardiac fibroblasts

AIM: To investigate the effect of short-chain acyl-CoA dehydrogenase (SCAD) on collagen expression and proliferation of rat cardiac fibroblasts and to explore the relationship between SCAD and cardiac fibrosis. METHODS: The model of proliferation and collagen expression of rat cardiac fibroblasts induced by angiotensin II was established. After treatment with siRNA-1186, the expression of SCAD at mRNA and protein levels, fatty acids beta oxidation rate, ATP, the enzyme activity of SCAD and free fatty acids in the rat cardiac fibroblasts were determined. RESULTS: The mRNA and protein expression of SCAD was decreased in the rat cardiac fibroblasts induced by angiotensin II compared with the control cells, and the expression of collagen I and collagen III was significantly upregulated. Compared with negative control group, SCAD expression and activity, fatty acid beta-oxidation rate and ATP significantly decreased in siRNA-1186 group, but the content of free fatty acids were obviously increased in the rat cardiac fibroblasts, and the expression of collagen I and collagen III was significantly up-regulated. CONCLUSION: The expression and synthesis disorder of collagen may be triggered by down-regulation of SCAD. SCAD may be a promising therapeutic target for myocardial fibrosis.     

Effects of combination treatment with perindopril and losartan on left ventricular remodeling and cardiac function in patients with myocardial infarction

AIM: Inhibiting the renin-angiotensin-aldosterone system prevents left ventricular (LV) remodeling after myocardial infarction (MI). This study was designed to assess the effects of a combination of perindopril and losartan on LV remodeling, cardiac function and serum procollagen type Ⅲ aminoterminal peptide (PⅢNP) levels in patients with acute MI.METHODS: Patients with anterior MI were divided into 3 groups: MI+perindopril, MI+losartan, and MI+perindopril+losartan. After successful intervention therapy, perindopril 2-4 mg/d or losartan potassium 25-50 mg/d or combination of the both were administered. All patients took aspirin, clopidogrel and statins, while some of the patients were treated with beta-blockers, nitrate and a platelet glycoprotein IIb/Ⅲa receptor antagonist. Three months later, LV dimensions and LV ejection fraction (LVEF) were measured by ultrasonography. Plasma brain natriuretic peptide (BNP), serum C-reactive protein (CRP) and PⅢNP levels were evaluated with ELISA or RIA.RESULTS: Baseline characteristics of the 3 groups were the same. All patients showed decreased CRP, increased BNP and PⅢNP levels, and LV dilation and dysfunction after treatment for three months. Compared with the 2 single therapy groups, patients in the combination group showed significantly lower CRP, BNP and PⅢNP levels, less LV dilation and higher LVEF. Serum PⅢNP level was positively correlated with CRP level and LV end-diastolic volume index(r=0.597 and r=0.543, respectively,both P<0.01), and negatively correlated with LVEF(r=-0.565, P<0.01).CONCLUSION: For patients with AMI, combination of perindopril and losartan significantly inhibited LV remodeling and improved LV function. Inhibition of myocardial interstitial fibrosis might be part of the mechanism.     

Effect of bFGF on promoting angiogenesis in infarct area and improving myocardial fibrosis in mouse myocardial infarction model

AIM: To investigate the protective effect of basic fibroblast growth factor (bFGF) on the heart of mice with myocardial infarction and its mechanism. METHODS: The model of myocardial infarction was established by the ligation of left anterior descending artery of C57/B6 mice (8~12 weeks old) after lateral thoracotomy. The mice were divided into sham operation group, myocardial infarction group and bFGF administration group. bFGF at 0.5 μg was intraperitoneally injected on alternate days after myocardial infarction for 7 d. Cardiac Doppler ultrasonography was used to detect cardiac function after myocardial infarction for 28 d, and left ventricular end-diastolic diameter, left ventricular end-systolic diameter, left ventricular ejection fraction and left ventricular shortening fraction (LVFS) were used to evaluate cardiac function. After myocardial infarction for 28 d, the mice were sacrificed and the hearts were collected for preparing pathological sections. The degrees of myocardial fibrosis and angiogenesis in the myocardial infarction area were observed. Western blot was used to detect the indicators of angiogenesis. RESULTS: The results of Masson staining showed that bFGF administration significantly reduced myocardial fibrosis at 28 d after myocardial infarction. Cardiac ultrasound data showed that cardiac functions in myocardial infarction group were poorer than those in sham group, and bFGF administration significantly improved cardiac functions. Immunofluorescence staining showed that neovascularization in myocardial infarction area of bFGF administration group was more than that in myocardial infarction group. The results of Western blot showed that bFGF activated AKT/HIF-1α/VEGF signaling pathway. CONCLUSION: Intraperitoneal injection of bFGF reduces myocardial fibrosis and improves cardiac function in myocardial infarction mice. bFGF may promote angiogenesis by activating AKT/HIF-1α/VEGF signaling pathway.     

Role of carvedilol on energy metabolic reversion and remodeling of pressure overload-induced left ventricular hypertrophy in rats

AIM: To study changes of medium chain acyl-CoA dehydrogenase (MCAD), muscle carnitine palmitoyltransferase I (M-CPT-I) and colligin mRNA/protein expression, to elucidate molecular mechanism of the recapitulation of fetal energy metabolism and ventricular remodeling and the effects of carvedilol during the development of pressure overload-induced left ventricular hypertrophy in rats. METHODS: Male Wistar rats of hypertrophy induced by constriction of abdominal aorta （CAA） were randomized into 2 groups (n=12, each group): 4-week group (CAA4 weeks group) and 12-week carvedilol intervention group (CAR group). Additional rats (n=12) underwent abdominal cavity incision without ligation to serve as age-matched sham operated controls (SH). Hemodynamics, ventricular remodeling parameters and free fatty acid （FFA） both in blood serum and myocardium were measured. RT-PCR analysis of the expression of mRNA of M-CPT-I, MCAD and collagen binding protein (colligin) were investigated. The protein expression of colligin was analyzed by Western blotting in the experimental animals and sham operation.RESULTS: LVM/BW and MAP in CAA group were increased more significantly than in sham group. There were progressive increases in FAA both in blood serum and myocardium in CAA group than in sham group, accompanied with downregulation of gene expressions of M-CPT-I and MCAD and colligin mRNA/ protein upregulation in LV in CAA group, while changes of all of these parameters in CAR group were attenuated.CONCLUSIONS: (1) The down-regulated expression of cardiac FAO enzyme genes (M-CPT-I and MCAD) in the hypertrophied heart may be responsible for “the recapitulation of fetal energy metabolism” during the development of pressure overload-induced left ventricular hypertrophy in rats. (2) Carvedilol attenuates the reversion of the metabolic gene expression back towards fetal type. (3) Carvedilol is effective in regressing the left ventricular remodeling by inhibiting colligin protein expression. A molecular mechanism by which carvedilol may confer cardioprotective effects in heart failure may be, in part, via preserving of the adult metabolic gene regulation and regressing left ventricular remodeling.     

Expression of MPO,MMP-2 and MMP-9 in atrial myocardium of rabbit atrial fibrillation model

ATM: To investigate the expression of myeloperoxidase (MPO), matrix metalloproteinase (MMP)-2 and MMP-9 in the atrial myocardium, and their potential effects on atrial structural remodeling in a rabbit atrial fibrillation (AF) model. METHODS: The sternotomy was performed and the pacing electrode was fixed to the left atria of 20 New Zealand white rabbits. The animals were randomly divided into 2 groups:rapid atrial pacing (RAP) group and sham group. The rabbits in RAP group were subjected to RAP for 3 weeks. The structure and function of the atria and ventricle were analyzed by echocardiography. Atrial burst stimulation was performed to test AF inducibility. The atrial fibrosis was evaluated by Masson trichrome-staining. The mRNA and protein levels of MPO, MMP-2 and MMP-9 were detected by RT-qPCR and Western blot. RESULTS: After 3 weeks of RAP, obvious left atrial enlargement and dysfunction were observed, but almost no change of left ventricular diameter and function was found in RAP group compared with sham group. AF inducibility, atrial interstitial fibrosis and the mRNA and protein levels of MPO, MMP-2 and MMP-9 were all significantly increased in RAP group compared with sham group. CONCLUSION: Obvious atrial structural remodeling is found in the rabbit AF model induced by sustained RAP, and the up-regulation of MPO, MMP-2 and MMP-9 may be the potential molecular mechanism of atrial structural remodeling.     

Cardiac collagen metabolism in murine viral heart diseases

AIM：To investigate the dynamic alteration of cardiac collagen metabolism in mice with acute,chronic myocarditis and dilated cardiomyopathy (DCM).METHODS：BALB/c mice infected with coxsackievirus B3 were used to establish animal models of acute,chronic myocarditis and dilated cardiomyopathy,while uninfected animals were also prepared and served as controls.After verification of models by histopathological methods and echocardiography,serum concentration of aminoterminal propeptide of type Ⅲ procollagen (PIIINP),aminoterminal propeptide of type Ⅰ procollagen (PINP) and carboxyterminal propeptide of type I procollagen (PICP) in each group of mice were detected by enzyme linked immunosorbent assay (ELISA).The expression of matrix metalloproteinase 1 (MMP-1) and its tissue inhibitor (TIMP-1) were determined by Western blotting analysis.The MMP-1 activity was also detected.RESULTS：Marked myocardial fibrosis was observed in all groups of CVB3-infected mice.Reparative fibrosis,promotion of synthesis and degradation of cardiac collagens were presented in heart tissue of acute myocarditis mice.Both reparative and reactive fibrosis,enhanced synthesis and lightened degradation of collagen were present in chronic myocarditis,while reactive fibrosis and excess collagen synthesis were confirmed in DCM.Expression and activity of MMP-1 was progressively decreased.TIMP-1 showed unchanged.The ratio of MMP-1/TIMP-1 was progressively descended.CONCLUSION：Collagen metabolism was special in different phase of viral heart diseases,which may play different roles in the progression and prognosis of these kinds of disease.     

Effect of leonurine on expression of miR-1 in rats with myocardial fibrosis induced by isoproterenol

AIM: To investigate effect of leonurine on the expression of microRNA-1 (miR-1) in rats with myocardial fibrosis induced by isoproterenol (ISO). METHODS: SD rats (n=10) were used as normal control group, and 80 rats were given ISO by intraperitoneal injection daily for 2 weeks to establish the model of myocardial fibrosis. The model rats were randomly divided into 5 groups:model group, low-dose (7.5 mg·kg^-1·d^-1) leonurine group, middle-dose (15 mg·kg^-1·d^-1) leonurine group, high-dose (30 mg·kg^-1·d^-1) leonurine group and p38 mitogen-activated protein kinase (p38 MAPK) inhibitor (0.3 mg·kg^-1·d^-1) group. After the treatment for 2 weeks, the ultrastructure of left ventricular myocardial tissues was observed under electron microscope. Masson staining was used to detect collagen fibrosis, and the expression of collagen I and collagen Ⅲ was determined by the method of immunohistochemistry. The contents of endothelin-1 (ET-1) and angiotensin Ⅱ (Ang Ⅱ) were measured by ELISA. The expression of miR-1 and ET-1 mRNA was detected by real-time PCR, and the protein expression of p38 MAPK, β-myosin heavy chain (MHC) and α-MHC was determined by Western blot. RESULTS: Compared with model group, the ultrastructure of left ventricular myocardial tissues in high-dose leonurine group was attenuated, and the expression of miR-1 and the protein expression of α-MHC in left ventricular myocardial tissues of high-dose leonurine group were increased (P<0.05). Collagen volume fraction, collagen I, collagen Ⅲ, the ratio of collagen Ⅰ/collagen Ⅲ, the contents of ET-1 and Ang Ⅱ, the mRNA expression of ET-1, and the protein expression of p38 MAPK and β-MHC in high-dose leonurine group were lower than those in model group (P<0.05). CONCLUSION: Leonurine attenuates myocardial fibrosis in the rats induced by ISO, and it is potentially associated with affecting the expression of miR-1, and inhibiting ET-1/p38 MAPK signaling pathway.     

Effects of noninvasive delayed limb ischemic preconditioning on prognosis of myocardial infarction

AIM: To study the effects of noninvasive delayed limb ischemia preconditioning (NDLIP) on animal cardiac function, myocardial morphology and myocardial apoptosis after myocardial infarction (MI). METHODS: Healthy SD male rats[n=45, weighing (250±10) g] were randomly divided into 3 groups:MI group:the animal model of MI was established by surgical ligation of left anterior descending artery (LAD) after 2 weeks; NDLIP group:after the success of the MI animal model, NDLIP was carried out every other day until the 4th, 6th and 8th weeks; sham group:as the negative control group, the animals were taken heart LAD threading but no ligation. All rats were fed conventionally. At the end of the 4th, 6th and 8th weeks, all rats were made ventricular intubation, and then the hemodynamic parameters were recorded. The blood samples were withdrawn from the abdominal aorta and the serum was separated via centrifugation. The serum contents of Bcl-2 and Bax were measured by ELISA. Left ventricular anterior wall was homogenized. The mitochondrial respiratory chain complexes Ⅰ, Ⅱ, Ⅲ and Ⅳ in the myocardial tissues were detected by ELISA. RESULTS: At the end of the 4th, 6th and 8th weeks, compared with MI group, left ventricular systolic pressure in NDLIP group was significantly increased, while left ventricular end-diastolic pressure in NDLIP group was significantly decreased (both P<0.05). Mitochondrial respiratory chain complexesⅠ, Ⅱ, Ⅲ and Ⅳ in NDLIP group were significantly increased (P<0.05). The serum level of Bcl-2 in NDLIP group was significantly increased and Bax level was reduced remarkably (both P<0.01). CONCLUSION: NDLIP improves the hemodynamic indexes, promotes the mitochondrial respiratory function and inhibits cell apoptosis, thus improving the prognosis of MI.