Effects of metoprolol on cardiomyocyte apoptosis and caspase-12 activation after coronary microembolization in rats

AIM: To investigate the effects of metoprolol on cardiomyocyte apoptosis and caspase-12 activation after coronary microembolization in rats. METHODS: 30 rats were randomized to sham-operated group (S group), coronary microembolization group (CME group) and metoprolol group. Coronary microembolization models were produced by injection of 42 μm microspheres (3000/0.1mL) into the left ventricle during 10 seconds ascending aorta occlusion in rats. The S groups were injected saline instead. Intravenous metoprolol was infused into the rats assigned to the metoprolol groups.Cardiomyocyte apoptosis was detected with in TUNEL staining. The activation of caspase-12 was measured by Western blotting analysis. Left ventricular ejection fraction (LVEF) was assessed by transthoracic two-dimensional echocardiography. RESULTS: ① LVEF was significantly decreased in CME group compared to S group (P<0.05). No statistical difference between the metoprolol group and CME group was observed. ②Compared with S group, the apoptosis rate of cardiomyocytes and the levels of activated caspase-12 proteins in CME group were significantly increased (all P<0.05). Compared with CME group, the apoptosis rate of cardiomyocyte and the levels of activated caspase-12 proteins in metoprolol group were significantly decreased (all P<0.05). CONCLUSION: Metoprolol inhibits the apoptosis of cardiomyocytes and the activation of caspase-12 after coronary microembolization.     

Changes of coronary flow reserve and myocardial blood flow after coronary microembolization

AIM:To investigate the changes of coronary flow reserve (CFR) and myocardial blood flow (MBF) after coronary microembolization (CME).METHODS:The left anterior descending coronary artery of 12 pigs was embolized by injection of 42 μm microspheres with a total of 120 000.Study was divided as acute study (base, 2 h and 6 h) and chronic study (base and 1 week).CFR was measured using Doppler wire.Regional myocardial blood flow (MBF) was detected using colored microspheres.Serum endothelin-1(ET-1) was determined by ELISA.RESULTS:CFR decreased significantly after CME at acute phase (2.10±0.60 at baseline, 1.40±0.10 at 2 h and 1.10±0.10 at 6 h, 2 h and 6 h compared with base, P<0.01, respectively).At chronic phase, CFR was 2.03±0.43 at base and 1.58±0.22 at 1 week after CME.No changes were found for MBF at acute and chronic study.Serum ET-1 only elevated at 6 h after CME.CONCLUSION:CFR decreases with time at acute phase after CME and resumes 1 week later.Changes of CFR correlate with changes of endothelial function.Changes of CFR and MBF are mismatched after CME.     

Captopril exerts myocardial protective effect in coronary microembolization rats by inhibiting oxidative stress injury and alleviating inflammatory response

AIM: To investigate the effects of captopril (CAP) on oxidative stress injury and inflammatory response induced by coronary microembolization (CME) and its related molecular mechanisms. METHODS: The rat model of CME was established by clamping the rat artery and injecting blood microemboli. The rats were divided into control group, CME group and CME+CAP group, with 6 rats in each group. The myocardial tissues of each group were collected. The changes of myocardial structure and the degree of inflammatory response were analyzed by HE staining. Cardiomyocyte apoptosis was detected by TUNEL staining. The fluorescence intensity of cleaved caspase-3 was detected by immunofluorescence obervation. The protein levels of cleaved caspase-3 and Bax were determined by Western blot. The activity of superoxide dismutase (SOD) and catalase was measured by ELISA. The production of reactive oxygen species (ROS) was detected by DHE fluorescence staining. RESULTS: CAP significantly reduced the myocardial structural changes (P<0.05), inflammatory cell infiltration (P<0.01), number of apoptotic cardiomyocytes (P<0.01), the protein levels of cleaved caspase-3 and Bax (P<0.01), and ROS production levels (P<0.01), but promoted the activity of antioxidant markers SOD and catalase (P<0.01) in the CME rats.CONCLUSION: CAP attenuates CME-induced myocardial injury by resisting oxidative stress and alleviating inflammatory response.     

Effect of Shenshuguanxin granula on coronary circulation in rats with myocardial infarction

AIM：To explore the effect of traditional Chinese medicine Shenshuguanxin granula on coronary circulation in a rat model of myocardial infarction (MI). METHODS：SD rats (n=50, SPF grade) were randomly divided into 5 groups (n=10):sham group, MI group, and high-dose, middle-dose and low-dose Shenshuguanxin granula treatment groups. The rat MI model was established by ligation of the coronary artery. The cardiac markers, small and medium-sized blood vessels ［microvessel count (MVC) value］ in the infarct zone, and platelet endothelial cell adhesion mo-lecule 1 (PECAM-1) and vascular endothelial growth factor (VEGF) expression in the infarct border zone were measured. RESULTS：After 4 weeks of coronary artery ligation, the significant increases in MVC in the infarct zone, and the expression of PECAM-1 and VEGF in the infarct border zone were detected compared with sham group (P<0.05). The differences of cardiac markers between MI group and other groups were insignificant (P>0.05). CONCLUSION:Shenshuguanxin granula improves coronary circulation in the rats with myocardial infarction by increasing the expression of PECAM-1 and VEGF, and promoting small and medium-sized angiogenesis.     

Changes in plasma neurotension level of patients with coronary heart disease and its clinical significance

AIM: To investigate the plasma neurotensin(NT) concentration in patients with coronary heart disease: acute myocardial infarction(AMI),unstable angina(UA),stable angina pectoris(SAP), old myocardial infarction (OMI), and to study the relationship between the plasma NT level and the myocardial ischemia . METHODS:The plasma NT concentration of 30 patients with AMI,32 pat ients with UA,35 patients with SAP,31 pat ients with OMI and 32 normal controls were determined by radioimmunoassay(RIA). RESULTS: The plasma NT level in patients with AMI(24 h),in patients with UA when angina attacked is significantly higher than that of healthy controls. The plasma NT level in patients with SAP, in patients with OMI is not significantly different from that of healthy controls. The NT level of patients with UA when angina attacked is significantly higher than that after 2 weeks treatment (P＜0.01). The NT level of AMI patients rose from early period and reached peak value at 24 h .It began to decline at 48h,and restored to normal level at 72h. CONCLUSION: When acute myocardial ischemia occured in patients with coronary heart disease, the plasma NT level was elevated. This suggests NT may have participated in the pathophysiological course of myocardial ischemia.     

Expression of melusin in myocardial tissues with different degrees of coronary atherosclerosis

AIM: To observe the pathological changes of myocardial tissues with different degrees of coronary atherosclerotic lesions, and to detect the level of melusin in myocardial tissue for exploring the role of melusin in the deve-lopment of coronary heart disease. METHODS: The cases of coronary heart disease were confirmed by autopsy and histopathological examination, and were classified into 3 groups: coronary atherosclerotic stable plaques (B group); atherosclerotic unstable plaques without thrombosis, plaque rupture, plaque hemorrhage and other secondary changes (C group); atherosclerotic unstable plaques with any of the secondary changes mentioned above (D group). The control group (A group) had no lesion of coronary artery. The coronary and myocardial tissues were collected separately, and routine HE staining of paraffin sections was performed to observe the histological structure of myocardium. The expression of melusin was detected by immunohistochemical staining, Western blot and real-time PCR. Logistic regression analysis was used to analyze the relationship between melusin expression changes and the development of coronary heart disease. RESULTS: Compared with A group, human cardiac myocytes showed pathological changes such as hypertrophy, atrophy, necrosis and adipose tissue infiltration in the other 3 groups. The expression of melusin in C and D groups was significantly lower than that in control group, while the expression of melusin was increased in B group (P<0.05). The expression of melusin in myocardial tissues was negatively correlated with the development of coronary heart disease (OR=0.3; 95% CI: 0.2~0.4; P<0.01). CONCLUSION: Melusin in human myocardial tissue may be a protective factor of heart in coronary heart disease. It plays an important role in the development of coronary heart disease.     

毛云芝菌菌丝体化学成分在运动保健中的作用

通过小鼠毛细血管通透性和血小板聚集功能试验表明,毛云芝菌菌丝体的有效成分能够疏通血管、改善脏器血液微循环,增加运动血液供给;体外抗氧化性能试验表明,毛云芝菌菌丝体的有效成分对氧自由基有很好的清除效果,有显著的运动保健作用。     

Agkistrodon halys venom PCA improves hemorheology in rats with coronary artery microthrombosis

AIM: To explore the effect of protein C activator (PCA) from Wannan Agkistrodon halys venom on hemorheology in the rats with coronary artery microthrombosis(CAM). METHODS: Fifty SD rats were randomly divided into sham operation group, CAM group, low dose (0.5 mg/kg), medium dose (2 mg/kg ) and high dose (8 mg/kg) of PCA treatment groups. The model of CAM was induced by injecting sodium laurate at dose of 1.0 mg/kg with the concentration of 10 g/L from aortic root to left ventricle. Thrombelastogram was obtained by thromboelastography instrument system. The content of endothelin-1(ET-1) and P-selectin, and the activity of creatine kinase-MB (CK-MB),lactate dehydrogenase (LDH) and aspartate aminotransferase (AST) in plasma were determined by ELISA. The protein expression of myocardial P-selectin and TNF-α was detected by Western blotting. The structural changes of the myocardial cells and interstitial tissues were observed under microscope. RESULTS: Compared with CAM group, clotting time and clot formation time significantly prolonged in high-dose PCA group. The alpha angle, maximum amplitude, coagulation index, and the levels of ET-1, P-selectin, CK-MB, LDH and AST in plasma were decreased. The protein expression levels of P-selectin and TNF-α in myocardial tissues were down-regulated (P<0.05). Cardiac histological observation showed that coronary microthrombi in medium-dose and high-dose PCA groups were not found. CONCLUSION: Agkistrodon halys venom PCA inhibits the formation of coronary microthrombi, down-regulates the expression of P-selectin and TNF-α, improves the abnormal hemorheology after microthrombi, and effectively protects myocardial cells.     

Protective effects of basic fibroblast growth factor (bFGF) against to myocardial ischemia in rats

AIM: To study the protective effects of basic fibroblast growth factor (bFGF) on myocardial ischemia in rats and their underlying mechanism. METHODS: A rat myocardial ischemic injury model was established by left coronary artery ligation. The rats were killed at 2 h, 4 h, 8 h after coronary artery occlusion. The samples of blood and myocardium were collected for observing the expression of Bcl-2 and Bax in myocardial cells and the changes of superoxide dismutase (SOD) or myocardial enzymes. RESULTS: The amount of Bcl-2 protein expression of myocardial cells in ischemia + bFGF group was significantly higher than that in ischemia+saline group (P＜0.01) at 2 h, 4 h after coronary artery occlusion. However, the change of Bax protein expression was reversed (P＜0.05). The activity of SOD in ischemia+bFGF group was higher than that in ischemia+saline group, and the changes of LDH, CK-MB and α-HBDH in ischemia+bFGF group were reversed (P＜0.05) in serum. CONCLUSION: bFGF has protective roles against myocardial ischemia in rats.     

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.     

Study of platelet aggregations in patients with coronary heart disease and the effect of ticlopidine treatment

AIM: To investigate the platelet aggregations in patients with coronary heart disease(CHD) and the effect of ticlopidine treatment. METHODS: Platelet aggregations induced by adenosine diphosphate(ADP), epinephrine(EPI), collagen(Coll), arachidonic acid(ACA) in CHD group before and after ticlopidine treatment were measured by turbidity assay. RESULTS: Maximum ratios of platelet aggregations (max%) induced by ADP, EPI in CHD group (0.78±0.23, 0.86±0.25) were significantly higher than that of control group (0.65±0.19, 0.73±0.21, P＜0.05). After the treatment with ticlopidine, they were lowered obviously (0.68±0.18, P＜0.05;0.75±0.20, P＜0.05). There were no difference in max% induced by Coll and ACA between two groups and there were no significantly changes of max% induced by Coll and ACA by ticlopidine in CHD group. CONCLUSION: The platelet aggregations were increased in patients with coronary heart disease and could be inhibited by ticlopidine.     

Association between platelet membrane glycoprotein IIb polymorphism and coronary heart disease in Han people

AIM: To investigate the genotype distributions of HPA-3 in Han people from Beijing and Hebei province, and to study the association of the platelet glycoprotein IIb polymorphism with coronary heart disease (CHD).METHODS: Two hundred and twelve patients with coronary heart disease and 106 healthy controls were enrolled in this case-control study. The number of occlusive coronary artery was performed in all subjects. The genotypes of HPA-3 were determined by TaqMan probe technology. RESULTS: In CHD patients (older than 45 years) carriers of HPA-3b were over- represented compared with healthy controls (P<0.05). The prevalence of HPA-3 genetic variants had no difference in CHD patients of different numbers of occlusive coronary artery. Results were statistically evaluated with Binary Logistic regression, which showed the HPA-3 polymorphism was associated with an increased risk for CHD(OR: 2.105).CONCLUSION: The HPA-3 polymorphism of GP IIb is the risk factor of CHD in Han people, especially in patients older than 45 years.     

Endogenous basic fibroblst growth factor is a protective factor against myocardial ischemia/reperfusion injury of rats

AIM: To observe the role of exogenous and endogenous basic fibroblst growth factor (bFGF) on myocardial ischemia/reperfusion(I/R) injury of rats.METHODS:bFGF and bFGF antiserum were applied to rat isolated I/R heart. Myocardial function, coronary effluent volume,protein and myoglobin content as well as LDH activity in coronary effluent fluid, myocardial calcium, MDA and ATP concentration as well as PKC, MAPK activity were measured. RESULTS:Compared with control, myocardial function in I/R group significantly decreased. Protein, myoglobin content and LDH activity in coronary effluent liquid as well as myocardial MDA and calcium content increased, while myocardial ATP concentration decreased(all P＜0.01). Compared with I/R group, ±LV dp/dt_max in bFGF group increased by 43% and 26%, respectively. LVEDP decreased by 40%. HRr/HRi and B/A augmented by 42% and 20%, respectively. Protein and myoglobin content as well as LDH activity lowered by 29%,30％ (all P＜0.01) and 33％ (P＜0.05) respectively. Myocardial MDA and calcium content decreased by 44% and 35%, respectively, while myocardial ATP level as well as PKC and MAPK activity increased by 34%,41％ and 10% (all P＜0.01), respectively. In bFGF antiserum group, ±LV dp/dt_max were 35% and 38% lower than those in I/R group. LVEDP increased by 93%. HRr/HRi and B/A decreased by 36% and 45%, respectively. Protein and myoglobin content as well as LDH activity augmented by 54%,96％ (all P＜0.01) and 34％ (P＜0.05) respectively. Myocardial MDA and calcium content increased by 24% and 50%, respectively, while myocardial ATP level as well as PKC and MAPK activity lowered by 28%,21％ and 8% (all P＜0.01), respectively. CONCLUSION:Endogenous bFGF is a protective factor against myocardial ischemia/reperfusion injury of rats.     

Correlation analysis between visualization of hemorrheologic changes and platelet function in patients with acute coronary syndrome after percutaneous coronary intervention

AIM:To intuitionally observe the characteristics of blood rheology in the patients with acute coronary syndrome (ACS) after percutaneous coronary intervention (PCI) for 1 year to 3 years by micro-channel array flow analyzer (MC-FAN) combined with other platelet function indexes, and to explore the correlations between the test results of MC-FAN and platelet function. METHODS:This study brought 74 patients with ACS after PCI for 1 year to 3 years into test group, and 21 healthy subjects were enrolled as normal group. The levels of platelet aggregation test (PAgT), platelet adhesiveness test (PAdT), P-selectin, platelet-derived growth factor BB (PDGF-BB) and von Willebrand factor (vWF) were detected. MC-FAN HR300 was used to detect the transiting time (MC-FAN TT) of the blood passing through the model body capillaries. The differences of the test results between the 2 groups were compared, and the correlations between the results of MC-FAN and platelet function in the patients with ACS after PCI were also explored. RESULTS:Compared with normal group, the MC-FAN TT in test group was prolonged (P<0.01), the ability of erythrocyte deformation was weakened, and the leukocyte attaching the vascular wall and platelet adhesion and aggregation relatively increased. The levels of PAgT, PAdT, P-selectin and PDGF-BB in test group were all higher than those in normal group (P<0.01). No difference of vWF between the 2 groups was observed. The intergroup correlation analysis showed that there were correlations between MC-FAN TT and platelet function, in which 10 μL MC-FAN TT and 30 μL MC-FAN TT had the most significant correlation with P-selectin (r=0601, P<0.01; r=0334, P<0.01), 60 μL MC-FAN TT had the most significant correlation with PAgT (r=0527, P<0.01), and 100 μL MC-FAN TT had the most significant correlation with PAdT (r=0. 815, P<0.05). CONCLUSION:The visualization of hemorrheologic changes and platelet function in the patients with ACS after PCI are abnormal.There are correlations between MC-FAN TT and platelet function.The results of MC-FAN can objectively evaluate the blood rheology of the patients, and provide the reference for clinical treatment.     

Effects of diltiazem on platelet activation and cytosolic calcium during percutaneous transluminal coronary angioplasty

AIM: To evaluate effects of diltiazem on platelet hyperreactivity in situations associated with endothelial injury and their possible relationship to cytosolic calcium concentration. METHODS: Blood samples were collected at 7 time points from 35 patients undergoing percutaneous transluminal coronary angioplasty (PTCA) who received combined diltiazem and aspirin/ticlopidine therapy or aspirin/ticlopidine therapy alone. Platelet expression of glycoprotein Ⅱb/Ⅲa and cytosolic calcium concentration were measured, respectively, by whole blood flow cytometry and fluorospectrophotometry. The effects of diltiazem of different concentrations on expression of glycoprotein Ⅱb/Ⅲa were also studied in vitro in blood samples from patients with chronic stable angina. RESULTS: Of the two treatments, aspirin/ticlopidine therapy did not prevent an acute increase of expression of glycoprotein Ⅱb/Ⅲa 5 minutes and 10 minutes after first inflation and 10 minutes after PTCA, whereas combined diltiazem and aspirin/ticlopidine therapy had a significant inhibitory effect. In the group receiving aspirin/ticlopidine therapy, there was a short-term elevation of platelet i immediately following PTCA which was significantly reduced by diltiazem treatment. Expression of glycoprotein Ⅱb/Ⅲa was significantly inhibited in vitro by diltiazem in the concentration of 200 μg/L or higher, but not 50 μg/L. CONCLUSIONS: Combined diltiazem and aspirin/ticlopidine therapy significantly inhibited platelet activation that continued in the presence of conventional aspirin/ticlopidine treatment. Antiplatelet effects of diltiazem were probably a consequence of reduction of platelet i and may only be achieved in higher than therapeutic concentrations.     

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.     

Effects of ischemic preconditioning on oxidative stress and mitochondrial function in young and old rat myocardium with ischemia/reperfusion

AIM: To study the protective effect of ischemia preconditioning (IPC) on ischemia/reperfusion (IR)-damaged myocardium in young and old rats. METHODS: Male Wistar rats aged at 3 months (young) and 20 months (old) were used to establish myocardial IPC model and IR model with the method of Langendorff heart perfusion. The rats were divided into young ischemia/reperfusion (YIR) group, young ischemic preconditioning (YPC) group, old ischemia/reperfusion (OIR) group and old ischemic preconditioning (OPC) group. Transmission electron microscopy was used to observe the ultrastructural changes of myocardial tissue and myocardial mitochondria. The myocardial infarction area was determined by TTC staining. The lactate dehydrogenase (LDH) content in coronary effluent fluid and the levels of superoxide dismutase (SOD) and malondialdehyde (MDA) in myocardial tissues were detected by the method of colorimetry. The levels of nitrated and carbonylated proteins in myocardial tissue were measured by ELISA. The myocardial cell apoptosis was analyzed by TUNEL assay. The mitochondrial respiratory function and mitochondrial permeability transition pore opening induced by calcium load were evaluated by oxygen electrode method. RESULTS: Compared with YIR group, the myocardial infarction area in YPC group was obviously smaller, SOD activity in myocardial tissues increased, LDH activity in coronary effluent fluid and the content of MDA decreased, and the levels of nitrated and carbonylated proteins in the cardiac tissues reduced. In YPC group, the mitochondrial membrane structure appeared intact, cristae of the mitochondria showed close arrangement, and the matrix was compressed under the electron microscope. Myocardial mitochondrial respiratory control rate, state Ⅲ oxygen consumption and the P/O ratio in YIR group all significantly increased, proton leak decreased, mitochondrial swelling induced by calcium distinctly reduced, and myocardial apoptosis rate declined. No significant difference of the above indexes between OIR group and OPC group was observed. Compared with YPC group, myocardial ultrastructural damage increased clearly, cardiac oxidative stress increased, mitochondrial respiratory function declined, and cell apoptosis and necrosis increased in OPC group. CONCLUSION: Ischemic preconditioning has protective effect against myocardial IR injury in young rat hearts, while old rat hearts were less sensitive to ischemic preconditioning, leading to bluntness of cardioprotection with IPC in aging hearts. This may be related to mitochondrial injury and severe cellular apoptosis caused by increase of cardiac oxidative stress levels in the aging ischemic preconditioning heart.     

Effect of diazoxide postconditioning on cardiac function and mitochondrial cardiolipin in isolated rat heart

AIM: To investigate the effect of diazoxide (D) postconditioning on Cardiac function and mitochondrial cardiolipin in isolated rat heart and to explore the protective effect of ATP sensitive potassium channel on diazo-xide postconditioning myocardium. METHODS: The myocardial ischemia/reperfusion injury model in isolated rat hearts was established by Langendorff apparatus. The isolated rat hearts were randomized into 4 groups (n=8): control group (control), myocardial ischemia/reperfusion injury group (I/R), diazoxide postconditioning group (I/R+D), 5- hydroxy decanoic acid (5-HD) plus diazoxide postconditioning group (I/R+5-HD+D). The hearts in each group were started with 20 min perfusion for equilibration. The hearts in control group perfused for 70 min; The hearts in I/R group was global ischemia for 40 min after ischemia reperfusion at 4 ℃ ST. Thomas cardioplegia, then reperfusion for 30 min; The hearts in I/R+D group were treated with diazoxide (50 μmol/L) in K-H perfusion for 5 min after global ischemia for 40 min, then reperfusion for 25 min; The hearts in I/R+5-HD+D group were treated with 5-HD (100 μmol/L) in K-H perfusion for 5 min before diazoxide postconditioning, then reperfusion for 20 min. The heart rate, coronary outflow volume, heart function, myocardial enzymes and myocardial mitochondrial cardiolipin at the end of perfusion in each group were determined. RESULTS: Compared with control group and I/R+D group, the heart rate, the concentration of heart phospholipid and the coronary outflow volume were reduced, the heart function was significantly impaired the contents of myocardial enzymes were increased in I/R group. However, no significant difference between I/R group and I/R+5-HD+D group was observed. CONCLUSION: The diazoxide postconditioning protects the myocardium by increasing mitochondrial cardiolipin content, reducing the release of myocardial enzymes, improving heart function and reducing myocardial reperfusion injury. The myocardial protective effect of diazoxide is completely blocked by 5- hydroxy decanoic acid.     

Effects of tirofiban on no-reflow and activation of NF-κB after myocardial ischemia/reperfusion in rats

AIM: To investigate the effects of platelet glycoprotein Ⅱb/Ⅲa receptor inhibitor tirofiban on myocardial no-reflow and activation of NF-κB after acute ischemia/reperfusion in rats. METHODS: Male Wistar rats were randomized into sham operation group, control group and tirofiban treatment group. Control group and tirofiban group were subjected ischemia for 90 min by ligation of coronary artery after thoracotomy and subsequently reperfusion for 120 min to establish acute myocardial ischemia/reperfusion no-reflow models. Thioflavine S, Evans blue and triphenyltetra zolium chloride (TTC) staining were performed to evaluate the area of no-reflow (ANR), infracted area (IA) and risk area (RA) of the heart. Immunohistochemistry was used for semi-quantitative analysis of the expression of nuclear factor-κB p65 (NF-κB p65) protein in myocytes and arteriole. Activity of myeloperoxidase (MPO) and content of malondialdehyde (MDA) in risk area of the heart were detected by ultraviolet spectrophotometer. RESULTS: After 120 min for reperfusion, compared to sham group, the statistical differences of higher positive expression of NF-κB p65 in myocytes and arteriole, activity of MPO and content of MDA both in control and tirofiban group were observed. Compared to control group, lower positive expression of NF-κB p65 in myocyte and arteriole, activity of MPO and content of MDA in tirofiban group were found (P<0.05, P<0.01). A markedly reduced ANR and IA were observed in tirofiban group than those in control group (34.36%±6.04% vs 52.09%±6.89%, P<0.01; 80.41%±8.48% vs 90.13%±5.72%, P<0.05). CONCLUSION: After myocardial ischemia/reperfusion for 120 min, no-reflow phenomenon can be observed in rats. Tirofiban reduces the areas of anatomic no-reflow and infarction, inhibits the activation of NF-κB in myocyte and arteriole, and decreases the infiltration of neutrophils and release of oxygen free radicals.     

Impacts of connexin 43 degradation on conduction velocity during acute myocardial ischemia

AIM:To study the impacts of the myocardial connexin 43 degradation on conduction velocity during acute myocardial ischemia.METHODS: Studies were carried out in 16 dogs which were randomly divided into control group(n=4) and ischemia group(n=12). The acute myocardial ischemia was induced by ligation of the left anterior descending coronary artery. The conduction velocity of ischemic myocardium was determined. The content of Cx43 of the ischemic myocardium was examined by laser confocal microscopy with a double-label immunohistochemistry technique. RESULTS:(1)The Cx43 degraded rapidly during acute myocardial ischemia, and the conduction velocity of ischemic myocardium declined greatly; (2)The conduction velocity correlated positively with the Cx43 pixel density in each small region of ischemic myocardium; (3) The Cx43 pixel density decreased over 50% in the region which occuring permanent conduction block.CONCLUSION: These data suggest the degradation of Cx43 decreases the conduction velocity greatly during acute short time myocardial ischemia, and severe degradation of Cx43 would lead to permanent conduction block.