Effect of PPARδ activation on expression of MMP-9 and fibronectin in infarcted myocardium

AIM:To investigate the effect of peroxisome proliferator-activated receptor δ (PPARδ) activation with dietary GW610742X on the expression of matrix metalloproteinase-9 (MMP-9) and fibronectin (FN) in infarcted and remodeling myocardium. METHODS: Wistar rats were divided into 4 groups: control group, sham group, myocardial infarction (MI) group and MI+GW610742X (GW) group. The left coronary artery was ligated to establish the MI model. PPARδ activator GW610742X (100 mg·kg^-1·d^-1) was given to the rats in GW group. At the 3rd month of the procedure, the expression of PPARδ, MMP-9 and FN at mRNA and protein levels in the left ventricular free wall(LVFW) of the heart from each group was identified and the distribution of FN was detected by immunofluorescence. RESULTS: After 3 months following the procedure, obvious necrosis and fibrosis in LVFW were observed in MI group. The expression of PPARδ in MI group was higher than that in control, sham and GW groups (P<0.01), and PPARδ expression in GW group was lower than that in control and sham group (P<0.05). In MI and GW groups, the expression of MMP-9 was higher while the expression of FN was lower than those in control and sham group (P<0.05 or P<0.01). In GW group, the expression of MMP-9 was lower (P<0.05) while the expression of FN was higher (P<0.01) than those in MI group. Meanwhile, the expression of MMP-9 and FN in sham group was similar to those in control group (P>0.05). CONCLUSION: MMP-9 is upregulated and FN is downregulated in infarcted myocardium during the remodeling process. Activation of PPARδ inhibits the upregulation of MMP-9 and degradation of FN, thus ameliorating the myocardial remodeling.     

Effect of angelica on myocardial fibrosis post myocardial infarction in rats

AIM: To investigate 1) the role of transforming growth factor-β₁ (TGF-β₁) and macrophage infiltration during the development of myocardial fibrosis (MF) in rats after myocardial infarction (MI);and 2) mechanisms of MF post-MI and the inhibitory effect of angelica.METHODS: Sprague-Dawley (SD) rats were subjected to MI by ligating the left anterior descending coronary artery.The animals were randomly divided into three groups: sham, MI and MI+angelica.After 24 hours of ligation, rats received angelica (20 mL·kg^-1·d^-1, ip) or saline.Left ventricular hemodynamics were measured and rats were killed at week 1, week 2 and week 4, respectively.Collagen content, macrophage infiltration and TGF-β₁ expression were examined in the non-infarcted area.RESULTS: ① In MI group, the numbers of macrophage and TGF-β₁ expression were significantly upregulated compared to sham at week 1 post-MI and remained elevated at week 4 (P<0.01).Angelica significantly decreased macrophage infiltration and TGF-β₁ expression (P<0.01 vs MI).② Collagen content was increased significantly in MI group compared to sham at week 2 and week 4 (P<0.01), and decreased in MI+angelica group (P<0.05 vs MI).③ Cardiac function was markedly decreased post-MI in MI group (P<0.01), and improved at week 4 in MI+angelica group (P<0.05).CONCLUSION: In MF post-MI, angelica may have an antifibrotic effect by decreasing macrophage infiltration and TGF-β₁ expression, by which reactive myocardial fibrosis is reduced, and cardiac function is improved.     

Effect of atorvastatin on ventricular remodeling in spontaneous hypertension rats

AIM：To explore the effect of atorvastatin on cardiac remodeling in spontaneous hypertension rats (SHR).METHODS：Twelve spontaneous hypertension rats were divided randomly into two groups：group of atorvastatin (atorvastatin 50 mg·kg^-1·d^-1) and group of SHR (0.5% mucilage of arabic gum,10 mL·kg^-1·d^-1).Additionally,six male Wistar-Kyoto rats (0.5% mucilage of arabic gum,10 mL·kg^-1·d^-1) were selected as control group.Systolic blood pressure was assessed with the tail-cuff method.After six weeks,entire heart,and left ventricle were weighed.The left ventricular weight index was calculated and myocardial hydroxyproline and collagen protein concentration were measured.The serum high sensitivity CRP (hs-CRP) was measured by nephelometry.The localization of vascular cell adhesion molecule (VCAM) in myocardium was investigated by immunohistochemistry assays.The level of NF-κB mRNA expression was detected with in situ hybridization.Ultrastructure in cardiac muscle was also observed under transmission electron microscope.RESULTS：The expression of myocardial VCAM and NF-κB in SHR group was stronger than that in WHY group.Compared with SHR group,entire heart weight,left ventricular weight,left ventricular weight index,serum hs-CRP,myocardial hydroxyproline and collagen protein concentration was decreased,the expression of myocardial VCAM and NF-κB in SHR group was weaker than that in atorvastatin treatment group.The myocardial pathological change such as incomplete karyotheca in cardiac muscle cells,no clear of transverse striation and the mess in myofibril alignment,and hyperplasy in interstitial collagen fibre were observed in SHR group and these changes were improved in atorvastatin treatment group.CONCLUSION：The cardiac remodeling in SHR is improved by atorvastatin.The molecular mechanism may be related to its down-regulating the expression of VCAM protein and NF-κB and inhibiting myocardial chronic inflammation.     

Effects of angiotensionⅡon metalloproteinases and matrix in hypertrophied myocardium from infarcted rats

AIM: To investigate the roles of angiotensionⅡ (AngⅡ) receptors (AT₁, AT₂) antagonists on matrix metalloproteinases (MMPs) and extracellular matrix (ECM) system in septal myocardium from infarcted rats.METHODS: The model of rat myocardium infarction (MI) was established by permanent ligation of the left coronary artery. The treatments of the AT₁ receptor antagonist valsartan (10 mg·kg^-1·d^-1) or AT₂ receptor antagonist PD123319 (30 mg·kg^-1·d^-1) were started 7 days prior to surgery. On day 14 after MI, protein levels of MMP-2, 3, 9, fibronectin (FN), tenascin-C (TN-C) in interventricular septum (IS) were determined. The distributions of FN and TN-C were also determined by immunofluorescence.RESULTS: Pathological changes of IS on day 14 after MI showed typical myocardial hypertrophy. Protein expressions of MMP-2, 3, 9 and TN-C of IS in banding group were higher than those in sham-operation group (P<0.01). The expressions of TIMP-1 and FN were lower than those in sham-operation group (P<0.01). Protein expressions of MMP-2, 3, 9 and TN-C in valsartan group were obviously lower than those in banding and PD123319 groups (P<0.01). TIMP-1 and FN protein expressions in valsartan group were higher than those in banding and PD123319 groups (P<0.01). No difference between banding and PD123319 groups was observed (P>0.05).CONCLUSION: AngⅡis involved in myocardium remodeling in infarcted rats, which is mediated via AT₁ receptor to degrade matrix by MMPs. The heart protection of AT₁ receptor antagonists may relate to inhibition of MMPs.     

Protective effects of tongxinluo,carvedilol and valsartan on microvascular endothelial function and integrity after late reperfused AMI in rabbits

AIM:To compare the protective effects of tongxinluo, a Chinese medicine, and carvedilol and valsartan on myocardium microvascular endothelial function and integrity after late reperfusion of acute myocardial infarction (AMI) in rabbits. METHODS:Forty-eight rabbits were randomly assigned to the following groups:(1) sham operated rabbits;(2) ischemia-reperfusion (I-R) controls;(3) tongxinluo (1.0 g·kg^-1·d^-1);(4) carvedilol (5 mg·kg^-1·d^-1);(5) valsartan (10 mg·kg^-1·d^-1) and (6) ticlopidine + aspirine (30 and 20 mg·kg^-1·d^-1, respectively) groups. After 3 d of drug treatment, the left coronary artery in the rabbit was ligated for 2 h and loosed subsequently for another 2 h. The serum levels of nitric oxide (NO₂^-/NO₃^-) and endothelin (ET) at baseline before AMI, 2 h after both AMI and reperfusion were examined. Also, the number of circulating endothelial cells (CEC), MI size and percentage myocardium focal bleeding incidence were determined 2 h after reperfusion. RESULTS:(1) The baseline level of NO₂^-/NO₃^- was significantly higher in tongxinluo group than that in other groups (all P<0.01), whereas the content of ET was not significantly different among the groups. 2 h after both AMI and reperfusion, NO₂^-/NO₃^- was significantly reduced (P<0.05, P<0.01) and ET was significantly increased in each group as compared with their baseline (P<0.05, P<0.01). Yet among the groups, NO₂^-/NO₃^- was still significantly higher and ET was significantly lower in tongxinluo-treated group than that in the other groups (P<0.05, P<0.01). (2) CEC number was significantly increased in I-R controls as compared with sham group (P<0.01), and was significantly reduced in the tongxinluo-treated groups as compared with I-R controls (P<0.05). (3) MI size was significantly reduced in the four treatment groups as compared with I-R controls (all P<0.01). (4) The percentage of myocardium focal bleeding incidence was significantly lower in tongxinluo and valsartan-treated groups than that in I-R controls (P<0.05, P<0.01). CONCLUSION:Tongxinluo as well as valsartan effectively protectsmyocardium endothelial function and integrity during AMI and late reperfusion,with the effects of tongxinluo being superior.     

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.     

Effects of Tongxinluo on connexin 43 remodeling and ventricular arrhythmia after myocardial infarction in rats

AIM: To determine the effects of Tongxinluo(TXL) on connexin 43(Cx43) remodeling and ventricular arrhythmia(VA) after myocardial infarction(MI) in rats. METHODS: Male SD rats were randomly divided into sham-operated(sham) group(n=25) and operation group(n=75). The left anterior descending(LAD) was ligated in operated group, while the rats in sham group only underwent pericardiotomy. The rats in operation group which survived for 3 d after operation were randomly assigned to TXL group and MI group. The rats in TXL group was administrated with TXL(2 g·kg^-1·d^-1, intragastric administration) for 4 weeks, while normal saline was applied to the rats in sham group and MI group. The levels of interleukin-1β(IL-1β) and endothelin-1(ET-1) in the tissue from the border zone were measured by ELISA after treatment. The distribution and the mRNA and protein expression of Cx43 were detected by immunohistochemical staining, RT-PCR and Western blotting, respectively. The burst pacing was used to induce ventricular arrhythmia(VA). RESULTS: Compared with sham group, the levels of IL-1β and ET-1 and the incidence of VA were significantly increased, while the mRNA and protein expression of Cx43 was markedly reduced with irregular distribution in MI group(P<0.05). Compared with MI group, the levels of IL-1β and ET-1 and the incidence of VA were significantly reduced, while the expression of Cx43 at mRNA and protein levels was markedly increased with augmented linear distribution in the myocardial cell intercalated disc in TXL group(P<0.05). CONCLUSION: TXL reduces the incidence of VA after MI via inhibiting the Cx43 remodeling.     

Inhibitory effects of right cervical sympathetic trunk transection on inflammatory response after acute myocardial infarction in rats and its influence on HMGB1/TLR4/NF-κB signaling pathway

AIM: To observe the effects of transection of right cervical sympathetic trunk (TCST) on inflammatory response and expression of high mobility group box 1 (HMGB1) and TLR4/NF-κB signaling pathway in the rats after acute myocardial infarction (AMI). METHODS: AMI model was established by ligation of left anterior descending coronary artery in SD rats, then the model rats were randomly divided into MI group and MI+TCST group. MI+TCST model was performed by transection of right cervical sympathetic trunk after left anterior descending coronary artery ligation. The rats in MI group and MI+TCST group were divided into 1, 3, 7, 14 and 28 d subgroups, and another sham operation group threading without ligation, with 8 rats in above each group. After modeling for 4 weeks, the cardiac function was measured by echocardiography. All rats were killed to harvest the hearts for mesuring cardiac hypertrophy index. The myocardial tissue close to infarction was observed with HE staining. The relative mRNA expression levels of HMGB1, tumor necrosis factor α(TNF-α) and interleukin (IL)-6 at different time points were detected by real-time PCR. The protein expression of HMGB1 and TLR4 at different time points after AMI was determined by Western blot. The effect of transection of right cervical sympathetic trunk on the expressions of HMGB1 and TLR4/NF-κB signaling pathway was also analyzed.RESULTS: Compared with the MI group, left ventricular ejection fraction (LVEF) and left ventricular shorterning fraction (LVFS) were significantly higher (P<0.05), left ventricular end-diastole dimension (LVEDd), left ventricular end-systole dimension (LVESd) and cardiac hypertrophy index were significantly lower (P<0.05), and the mRNA levels of HMGB1, TNF-α and IL-6 decreased significantly in MI+TCST group (P<0.05). Western blot results revealed that the protein expression level of HMGB1 increased in the infarct border zone at 3 d, and reached its peak at 7 d, then gradually decreased, and at 28 d after MI in MI group was still significantly higher than that in sham group (P<0.05). The protein expression of TLR4 was consistent with that of HMGB1. Transection of right cervical sympathetic trunk reduced protein expression of HMGB1 and TLR4/NF-κB signaling pathway-related proteins (P<0.05).CONCLUSION: Transection of right cervical sympathetic trunk improves ventricular remodeling and maintaining cardiac function. The mechanism may be related to inhibiting HMGB1/TLR4/NF-κB signaling pathway to reduce inflammatory response.     

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.     

Effects of celecoxib on cardiac myocyte apoptosis after myocardial infarction

AIM: To investigate the effects of celecoxib, a selective cyclooxygenase-2 inhibitor, on antioxidative capability and apoptosis of cardiac myocytes after myocardial infarction. METHODS: 24 New Zealand rabbits were divided into three groups randomly (8 in each group): sham-operated group (sham group), myocardial infarction group (MI group), celecoxib group (Cele group, 10 mg kg^-1·d^-1, qd, with the drugs gastric gavage for six weeks). The NO concentration, total antioxidative capability (T-AOC), the activity of constitutive nitric oxide synthase (cNOS) and inducible NOS (iNOS) in cardiac tissue homogenate, adjacent to the infracted area, were detected. The pathological changes were observed by light microscope and electron microscopy. The expressions of Bcl-2 and Bax protein in myocytes were observed using immunohistochemistry, and the degree of apoptosis were examined by TUNEL. RESULTS: Cardiac tissue in MI group presented interstitial edema, fibroplastic proliferation, inflammatory cellular infiltration, and vacuolar degeneration in cardiac myocytes. The results of electron microscopy showed that myocytes presented more changes caused by ischemic injury: widened interspace of myofibril, disordered myofibrillae, focal lysis of myofilament, ectasia of sarcoplasmic reticulum. In Cele group, the pathological changes were light, the NO^-₂/ NO^-₃ concentration, the activity of iNOS were lower (P<0.05), while the activity of cNOS and T-AOC were higher (P<0.05) than those in MI group. The expression rate of Bcl-2 protein in Cele group was higher than that in MI group, while the Bax was lower (P<0.01). The number of apoptotic myocytes was lower than that in MI group (P<0.01).CONCLUSION: Celecoxib decreases the number of apoptotic cardiomyocytes and increases the antioxidative capability after myocardial infarction.     

Effects of crocetin on the apoptosis and the changes of its related regulating proteins caspase-3 and Bcl-2 induced by H2O2 in myocardial cells

AIM: To observe the effect of crocetin on the apoptosis and the changes of its related regulating proteins caspase-3 and Bcl-2 expression induced by hydrogen peroxide (H₂O₂) in cultured cardiomyocytes. METHODS: Changes of cellular morphology were detected under microscope. Apoptosis rates of the cells were analyzed by PI staining with flow cytometry. Expressions of caspase-3 and Bcl-2 proteins in the cells were determined by immunofluorescence with flow cytometry. RESULTS: In the concentrations used, more severe morphological changes with higher apoptosis rate of the cultured myocardial cells were seen in each H₂O₂ group than that in control group. When treated with 1×10-4 mol·L^－1 H₂O₂, the caspase-3 was increased and Bcl-2 protein decreased remarkably in the cells. But each dosage of crocetin, especially the highest one (5×10^－5 mol·L^－1, P<005 compared with 5×10^－7 mol·L^－1 group), seemed efficient in maintaining the cell morphology, reducing the cell apoptosis rate and improving the changes in caspase-3 and Bcl-2 protein expression in the cells exposed to 1×10^－4 mol·L^－1 H₂O₂. CONCLUSION: Crocetin obviously inhibits the apoptosis induced by H₂O₂ in the cultured myocardial cells. The mechanisms may involve the balance of the functions of the apoptosis-related regulating proteins, caspase-3 and Bcl-2 protein.     

Protective effects of total saponins of panax notoginseng on myocardial hypertrophy and fibrosis induced by isoproterenol in rats

AIM: To investigate the protective effects of total saponins of panax notoginseng (PNS) on myocardial hypertrophy and fibrosis induced by isoproterenol (ISO) in rats.METHODS: Myocardial hypertrophy and fibrosis model of rats were induced by injection of ISO (5 mg·kg^-1·d^-1,sc) for 7 days.From day 2,the rats were administered with PNS at dose of 25 and 50 mg·kg^-1·d^-1,ip for 14 days,the control and ISO model group were received saline injection.Then,the heart-weight (HW),left ventricular weight (LVW),the ratio of HW/BW and LVW/BW (LVI) were measured;the hydroxyproline and malondialdehyde (MDA) and angiotensin (AngII) content of left ventricle.The level of nitric oxide (NO),nitric oxide synthase (NOS),superoxide disrnutase (SOD) and glutathione peroxidase (GSH-Px) activities in left ventricle were determined by spectrophotemetry and radioimmunoassay,respectively.RESULTS: Compared with NS control group,the ratio of HW/BW,LVW/BW and the content of hydroxyproline,AngII,MDA and iNOS activity in the left ventricle were significantly increased.The cNOS,SOD,GSH-Px activities and NO content were obriously decreased in the ISO model group.After treatment with PNS,the left ventricular NO content,cNOS,SOD and GSH-Px activities were markedly higher than those in ISO model group.The content of MDA,AngII and iNOS activities and the ratio of HW/BW,LVI were significantly lower than those in ISO model group.CONCLUSION: PNS reverses the myocardial hypertrophy and fibrosis induced by isoproterenol in rats.This effect may be related to eliminating the oxygen free radicals and raising NO level.     

Effect of fluvastatin on left ventricular remodeling after myocardial infarction in rats

AIM: To clarify the protective effect of long-term administration of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor fluvastatin on ventricular remodeling after myocardial infarction (MI) in rats and its mechanisms. METHODS: Myocardial infarction were established by ligated left coronary anterior artery in SD rats, 24 hours after the operation, the survival rats were treated by gavage fluvastatin (20 mg·kg^-1·d^-1) or distilled water for 8 weeks. Doppler echocardiography, homodynamic and cardiac histomorphometry were used to assess the ventricular remodeling and cardiac function. The plasma levels of total cholesterol (Tch), creatinine (Cr), glutamic-oxal (o) acetic transaminase (AST), lipid peroxidation (LPO), glutathione perioxidase (GSH-PX), nitrogen monoxide (NO₂^-/NO₃^-) were detected. RESULTS: The Tch, Cr and AST were not significant difference in groups. Left ventricular end-diastole pressure, right relative weight, left ventricular posterior wall thickness, collagen volume fraction and the lung weight were decreased in AMI+fluvastatin group compared to AMI group (P＜0.05, P<0.01); The levels of LPO, NO₂^-+NO₃^- in plasma and LPO in myocardium decreased, but plasma GSH-PX level increased in AMI+fluvastatin group (P＜0.05). CONCLUSION: Fluvastatin ameliorates the ventricular structural remodeling in a rat model of infarction, and delays the development of heart failure. The anti-oxidation mechanism of fluvastatin may take part in this process.     

Effects of bilirubin on oxygen free radicals and caspase-3 in acute lung injury rats

AIM:To investigate the mechanisms by which bilirubin inhibits acute lung injury (ALI). METHODS:30 female Wistar rats were divided into normal group, ALI group and bilirubin treatment group. ALI was induced by intravenous injection of LPS. The contents of OH^-, H₂O₂ and O₂^· in the lung as well as the expression of caspase-3 in the lungs were investigated. RESULTS:(1) The contents of OH^-, H₂O₂ and O₂^· in the lung homogenate and the expression of caspase-3 in the lungs in ALI group increased compared with those in normal group (P<0.05). (2) The contents of OH^-, H₂O₂ and O₂^· in the lung homogenate and the expression of caspase-3 in the lungs in bilirubin treatment group increased compared with those in normal group, but decreased compared with those in ALI models (P<0.05). CONCLUSION:(1) Bilirubin was shown to be able to ameliorate apoptosis in ALI rats. (2) The increase in the contents of OH^-, H₂O₂, O₂^· in ALI group indicated the development of oxidative lung injury, which was ameliorated by bilirubin. (3) Expression of caspase-3 confirmed that the model made by LPS was associated with apoptosis, which was reduced by bilirubin.     

Effect of amiodarone and metoprolol on platelet activation,fibrinolytic activity and vasoactive mediators in acute myocardial infarction in rabbits

AIM:To explore the significance of platelet activation, fibrinolytic activity and the changes of vasoactive mediators in acute myocardial infarction in rabbits and the intervention of amiodarone and metoprolol.METHODS:Fifty New Zealand white rabbits were randomly assigned to five groups, ten for each. Group Ⅰ: sham group, group Ⅱ: acute myocardial infarction(AMI) group, group Ⅲ: AMI and lidocaine group, group Ⅳ: AMI and amiodarone group, group Ⅴ: AMI and metoprolol group.The middle point of left ventricular coronary artery was ligated (groupⅡ,Ⅲ, Ⅳ and Ⅴ ) or a sham ligation(group Ⅰ). Four hours later, blood was collected for measuring plasma concentration of TXB₂, 6-Keto-PGF_1α, ET, NO, plasma activity of t-Pa and PAI.After that, the heart was taken out to evaluate the infarction size(IS).RESULTS:Plasma concentration of TXB₂, ET, NO and plasma activity of PAI were significantly higher in groupⅡ,Ⅲ, Ⅳ and Ⅴ than those in group Ⅰ(P＜0.01), but the plasma concentration of 6-Keto-PGF_1α and plasma activity of t-Pa were remarkably lower in groupⅡ,Ⅲ, Ⅳ and Ⅴ than those in group Ⅰ(P＜0.01). There were no difference in plasma concentration of TXB₂, 6-Keto-PGF_1α, t-Pa activity and infarction size in group Ⅱ,Ⅲ and Ⅳ(P＞0.05).Compared to group Ⅱ, plasma concentration of ET, NO and PAI activity were significantly decresed (P＜0.01)in group Ⅳ. Plasma concentration of TXB₂, ET, NO and plasma activity of PAI were significantly lower in groupⅤ than those in group Ⅱ(P＜0.01). Conversely, plasma concentration of 6-Keto-PGF1 and plasma activity of t-Pa were remarkably higher in group Ⅴ than those in group Ⅱ(P＜0.01). The infarction size was remarkly decrease(P＜0.01)in group Ⅴ.CONCLUSIONS:Amiodarone inhibited PAI avtivity, decreased release of ET and NO in AMI in rabbits. Metoprolol inhibited platelet activation, improved fibrinolytic, decreased release of ET and NO, and reduced myocardial infarction size in AMI in rabbits; Lidocaine had no effect above.     

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 rhynchophylline on TGF-β1/Smad pathway for processing ventricular remodeling in spontaneously hypertensive rats

AIM: To investigate the effect of rhynchophylline (Rhy) on blood pressure, cardiac hypertrophy and myocardial fibrosis in spontaneously hypertensive rats (SHR). METHODS: Spontaneously hypertensive rats were randomly divided into model group, high dose (10 mg·kg^-1·d^-1) and low dose (2.5 mg·kg^-1·d^-1) group of rhynchophylline, captopril group (17.5 mg·kg^-1·d^-1). Wistar-Kyoto rats were used as normal control. Respectively, systolic blood pressure was measured by tail cuff every 2 weeks. After 10 weeks, heart weight index and left ventricular weight index were calculated. The myocardial hydroxyproline and plasma angiotensin Ⅱ were detected. Moreover, basic myocardial histopathological changes and myocardial collagen fibres were observed by HE staining and Masson staining, respectively. The protein expression of TGF-β₁ and Smad3 in the myocardium was measured by the methods of immunohistochemistry and Western blot. RESULTS: Compared with SHR model group, Rhy significantly reduced blood pressure (P<0.05), the levels of HYP in the myocardium (P<0.05) and the levels of AngⅡ in the plasma (P<0.01). The pathological damages of the myocardial tissues and collagen deposition were attenuated. The protein expression of TGF-β₁ and Smad3 was significantly reduced by the treatment with Rhy (P<0.01). CONCLUSION: Rhynchophylline reduces blood pressure and adjusts to improve ventricular remodeling of SHR. The mechanism may be involved in the TGF-β₁/Smad pathway and reducing AngⅡ content.     

Effects of catestatin on calcium handling abnormalities and ventricular arrhythmia after myocardial infarction in rats

AIM: To determine the effects of catestatin (CST) on calcium handling abnormalities and ventri-cular arrhythmia (VA) after myocardial infarction (MI) in rats. METHODS: The adult male SD rats (n=85) were randomly divided into sham group (n=20) and operation group (n=65). MI was induced by ligation of the left anterior descending coronary artery in operation group. The rats in sham group underwent pericardiotomy but without ligating the artery. The rats survived for 1 week after operation were randomly assigned to MI group and CST group. The rats in CST group was treated with CST (30 mg·kg^-1·d^-1, intraperitoneal administration) for 4 weeks, while saline was applied to the rats in sham group and MI group. The calcium imaging study was performed by loading isolated ventricular cardiomyocytes with Fura-2 AM. In the whole Langendorff-perfused hearts, the programmed electrical stimulation was used to induce action potential duration (APD) alternans and VA. The protein levels of ryanodine receptor 2 (RyR2), phosphorylated RyR2 (p-RyR2), calcium/calmodulin-dependent protein kinase II (CaMKII) and phosphorylated CaMKII (p-CAMKII) were determined by Western blot. RESULTS: Compared with sham group, the protein levels of p-RyR2 and p-CaMKII, the diastolic intracellular Ca²⁺ concentrations and the inducibility of VA were significantly increased, whereas the thresholds of Ca²⁺ transient (CaT) and APD alternans and the CaT amplitude were markedly decreased in MI group (P<0.01). Compared with MI group, the protein levels of p-RyR2 and p-CaMKII, the diastolic intracellular Ca²⁺ concentration and the inducibility of VA were significantly decreased, while the thresholds of CaT and APD alternans and the CaT amplitude were markedly increased in CST group (P<0.01). No significant difference of the protein expression of RyR2 and CaMKII among the 3 groups was observed (P>0.05). CONCLUSION: CST reduces the susceptibility to VA after MI via preventing calcium handling abnormalities.     

Expression of NADPH oxidase subunit p22phox in myocardial infarction rats

AIM: To determine the relevance of NADPH oxidase subunit p22hox and the expression of superoxide anion on ventricular remodeling in myocardial infarction (MI) rats. METHODS: MI of Sprague-Dawley rats were established by left anterior descenting coronary artery ligation. 8 weeks after MI, Doppler echocardiography, hemodynamic study and histomorphometry were performed to analyze the ventricular remodeling. The level of thiobarbituric acid reactive substance in plasma and myocardium were measured, and the distribution of superoxide anion was observed with laser scanning confocal microscope. The expression of p22phox mRNA and protein level was detected by RT-PCR and immunohistochemistry. RESULTS: The left ventricular remodeling was significant in MI rats, also the level of thiobarbituric acid reactive substance increased in the plasma and non-infarcted myocardium. The expressions of p22-phox mRNA and protein levels, and superoxide anion increased in infarcted and non-infarcted myocardium in MI rats. CONCLUSION: Our results suggest that the expression of NADPH oxidase and its derived superoxide anion may take part in left ventricular remodeling through oxidative stresss after MI.