X-ray irradiation increases sensitivity of myocardium to ischemia/reperfusion injury in rats

AIM：To observe the sensitivity of myocardium to ischemia/reperfusion (I/R) injury in the rats with chest radiotherapy. METHODS：The radiation-induced heart disease model was established by local 20 Gy of X-ray irradiation in the chest. Male Wistar rats (n=42) were randomly divided into 6 groups:sham trauma group, trauma group, sham trauma+sham operation group, sham trauma +I/R group, trauma+sham operation group and trauma+I/R group. The rats were subjected to 30 min of ischemia and 1 h of reperfusion 2 week after trauma. The left ventricular developed pressure (LVDP) and ±dp/dtmax were recorded by BL-410 biological signal recording and analysis system. The serum cardiac troponin I (cTnI) and creatine kinase isoenzyme (CK-MB) were measured by ELISA. The myocardial infarct size was determined by nitroblue tetrazolium(NBT) staining method and BI2000 image analysis software. RESULTS：Compared with sham trauma+I/R group, significant decreases in LVDP and ±dp/dtmax were observed in trauma+I/R group (P<0.01) with significant increases in the infarct size and the concentrations of cTnI and CK-MB (P<0.01). CONCLUSION:Chest X-ray irradiation increases the sensitivity of myocardium to I/R injury in rats.     

Protection of Glycyl-L-Glutamine against myocardial ischemia-reperfusion injury in the isolated rat heart

AIM: To study the protection of Glycyl-L-Glutamine(Gly-Gln) against myocardial ischemia/reperfusion(I/R) injury in the isolated rat heart.METHODS: A model of myocardial ischemia-reperfusion injury was established with a Langendorff apparatus. Thirty male SD rats were randomly divided into four groups: control group, Gly-Gln group, I/R group and I/R+Gly-Gln group. Both I/R and I/R+Gly-Gln group were pre-perfused for 30 min, followed by 20 min ischemia and 40 min reperfusion. During reperfusion I/R+Gly-Gln group was perfused with Gly-Gln perfusate. Control group was kept perfused for 90 min. Gly-Gln group Gly-Gln perfusate was also kept perfused for 90 min. The left ventricular end-diastolic pressure(LVEDP), left ventricular developed pressure (LVDP), ±dp/dtmax, heart rate (HR), monophasic action potentials(MAP) was measured during perfusion. The coronary effluent fluid was collected at different certain times. The activities of lactic dehydrogenase (LDH) and creatine kinase(CK) were determined.RESULTS: The isolated rat heart function decreased severely after 20 min ischemia and 40 min reperfusion(I/R): the LVEDP increased and the LVDP, ±dp/dtmax decreased. But the LVEDP decreased and the LVDP, ±dp/dtmax increased in I/R+Gly-Gln group compared with I/R group. Moreover, the activities of LDH and CK in the coronary effluent fluid decreased remarkably in I/R+Gly-Gln group compared with I/R group.CONCLUSION: Gly-Gln can play a protective role against myocardial I/R injury in isolated rat hearts via maintaining the left ventricular function and decreasing the release of LDH and CK.     

Protective effect of aFGF delivery by ultrasound-targeted microbubble destruction on left ventricular function in diabetic cardiomyopathy rats

AIM：To observe the protective effect of delivery of acidic fibroblast growth factor (aFGF) to myocardium by ultrasound-targeted microbubble destruction (UTMD) on left ventricular function in diabetic cardiomyopathy (DCM) rats and to investigate the possible mechanisms. METHODS：Twenty-four rats were intraperitoneally injected with streptozocin to induce DCM and were randomly divided into DCM group and aFGF treatment group. Twelve healthy rats served as normal controls. The rats in aFGF treatment group were infused with SonoVue-aFGF mixed fluid through tail vein and UTMD was simultaneously performed. Four weeks after intervention, all rats underwent cardiac catheterization to mea-sure left ventricular end-systolic pressure (LVESP), left ventricular end-diastolic pressure (LVEDP) and the maximal increase/decrease rate of left ventricular pressure (LV±dp/dtmax). The microvessel density (MVD) of rat myocardial tissues was measured by immunohistochemical staining for CD31. The myocardial collagen volume fraction (CVF) was determined by improved Masson staining. The apoptotic index (AI) was detected by TUNEL method. RESULTS：Four weeks after intervention, the LVESP and LV±dp/dtmax in aFGF treatment group were significantly increased compared with DCM group (P<0.01), while the LVEDP in aFGF treatment group was significantly lower than that in DCM group (P<0.01). The MVD in aFGF treatment group was significantly increased compared with DCM group (P<0.01), but the CVF and AI in aFGF treatment group were significantly lower than those in DCM group (P<0.01). CONCLUSION: Delivery of aFGF to diabetic myocardium by UTMD could improve the left ventricular function of DCM rats and may be a new feasible therapeutic method for DCM.     

Improvement of vascular hyporesponsiveness in rats with sepsis by protein C activator from Agkistrodon acutusvenom

AIM:To investigate the effects of protein C activator (PCA) from Agkistrondon acutusvenom (AAV) on the tension of thoracic aorta rings isolated from the rats with sepsis. METHODS:The model of sepsis was established by intraperitoneal injection of lipopolysaccharide (LPS). SD rats were randomly divided to 6 groups (n=6): sham group, LPS group, PCA intervention group (LPS+PCA, PCA at doses of 0.1 mg/kg, 0.3 mg/kg and 0.6 mg/kg) and LPS+ polymyxin B (at dose of 0.2 mg/kg) group. Using perfusion experiment in vitro, the tension of the aortic rings was measured by biological signal analytical system. RESULTS:The values of MABP, HR, LVDP and ±dp/dtmax were significantly lower in LPS group than those in sham group and LPS+PCA groups. Compared with sham group, the relaxation response to acetylcholine (ACh) and the contractile response of aorta rings induced by phenylephrine (Phe) were significantly decreased in LPS group, which were increased significantly in PCA intervention group (especially at dose of 0.6 mg/kg) compared with LPS group. The dose-response curve of aorta contraction with denuded endothelium induced by Phe shifted down significantly in LPS group compared with sham group, and no significant difference between LPS group and PCA intervention group was observed. Also no statistical difference was found in non-endothelium dependent relaxation of aortic rings induced by sodium nitroprusside among the groups. Pretreatment of N-nitro-L-arginine methl ester and methylene blue increased the contraction amplitude of aortic rings induced by Phe. CONCLUSION: PCA from AAV effectively reverses the hypoergia of the vessels in rats with sepsis through protecting vascular endothelium, the mechanism of which may be mediated by inhibiting NO-GC-cGMP signal transduction pathway.     

Expression of angiogenic factors in myocardial tissue of diabetic rats

AIM：To observe the expression of angiogenesis factors in the myocardial tissue of streptozotocin-induced diabetic rats. METHODS：The diabetic rat model was induced by intraperitoneal injection of streptozotocin. After 12 weeks, the cardiac function was measured by MPA cardiac function analysis system. The myocardial collagen volume fraction (CVF) was assessed by Masson staining. The capillary vessels was quantified as the ratio of capillary to myocyte (C/M) using CD31 immunostaining. The expression levels of vascular endothelial growth factor (VEGF), angiopoietin (Ang)-1, endostatin and Ang-2 were observed by Western blotting. RESULTS：Compared with normal control group, the left ventricular end-diastolic pressure (LVEDP) was evidently increased (P<0.01), but left ventricular pressure rise maximum rate (+dp／dtmax), left ventricular pressure decrease maximum rate (-dp／dtmax) and the ratio of capillary/myocyte (C/M) were significantly decreased (P<0.05). The CVF and the expression level of endostatin were significantly increased, whereas the expression levels of VEGF and Ang-1 evidently decreased (both P<0.05) in diabetic rats. However, no marked difference in the expression of Ang-2 between the 2 groups was observed (P>0.05). CONCLUSION：Imbalances between the angiogenic factors (VEGF and Ang-1) and anti-angiogenic factors (endostatin) may play an important role in the pathogenesis of diabetic cardiomyopathy.     

Effect of valsartan on calcium channel current and sodium-calcium exchanger current in heart failure rats

AIM: To determine the effects of valsartan on calcium channel and sodium-calcium exchanger current in isolated ventricular myocytes of congestive heart failure (CHF) rats. METHODS: Eight weeks after coronary ligation, the rats with heart failure were confirmed by measuring the hemodynamic parameters and divided randomly into the group treating with valsartan (CHF-T, 20 mg/kg) and placebo (CHF-C). Sham-operated group rats served as negative controls (PS). Twelve weeks later, 6 rats were selected randomly for the study of ion channel. Single ventricular myocytes of rats were isolated by enzymatic dissociation. The whole-cell patch-clamp recording technique was used to record calcium channel current and sodium-calcium exchanger current. RESULTS: (1) In the hemodynamic variables, HR and blood pressure were not significantly different in three groups. Compared CHF-C with PS group, LVEDP and Cm increased, LVSP and ±dp/dtmax decreased (P<005). Compared CHF-T group with CHF-C group, LVEDP and Cm decreased, LVSP and ±dp/dtmax increased (P<005). (2) Calcium channel current in CHF-C decreased significantly (P<005). Calcium channel current in CHF-T group was larger significantly than that in CHF-C group (P<005). (3) The activation, inactivation and recovery curves were not altered in 3 groups (P>005). (4) Na+-Ca2+ exchanger current in CHF-C group increased significantly. Na+-Ca2+ exchanger current in CHF-T group was smaller significantly than that in CHF-C group. However, CHF-T group and PS group were not significantly different. CONCLUSION: Administration of valsartan is effective in preventing from cardiac function deterioration, increases calcium channel current and decreases Na+-Ca2+ exchanger current in ventricular myocytes of heat failure rats.     

Ischemic preconditioning relieves the ischemia/reperfusion injury of neurons in hippocampus by inhibiting the expression of p53

AIM: To examine whether ischemic preconditioning (IPC) can protect against apoptosis in CA1 subfield of hippocampus following reperfusion of a lethal ischemia in rats and explore the role of IPC by inhibiting the expression of p53 in this process. METHODS: Wistar rats were used in the experiment. A global ischemia/reperfusion model was induced by 4-vessel occlusion. The rats were divided into the following three groups randomly: (1) ischemic preconditioning group (IPC group); (2) ischemia/reperfusion group (IR group); (3) control group. The histopathological changes, the percentage of apoptosis and the expression of p53 gene in CA1 region of rat hippocampus were examined by HE staining, FCM, RT-PCR and immunohistochemistry techniques. RESULTS: The neuronal density of CA1 region in IPC group ［(217±9)/0.72 mm²］ was significantly higher than that in IR group ［(29±5)/0.72 mm², P<0.01］. The percentage of apoptotic neurons in IPC group (2.07%±0.21%) was lower than that in IR group (4.26%±0.08%), P<0.01. Compared with IR group, the expression of p53 gene in IPC group was significantly weakened. CONCLUSION: Ischemic preconditioning protects the ischemic neurons in CA1 region of rat hippocampus by inhibiting the expression of p53 gene.     

Brain damage of cerebral ischemia/reperfusion and expression of TGF-β1 mRNA in diabetic rats

AIM:To observe the difference of cerebral inj ury following ischemia/reperfusion and mR-NA expression of TGF-β₁ between diabetic and non-diabetic rats.METHODS:At first,Wistar rats weredivided i nto two groups,non-diabetes and diabetes,and then two groups followed by sham,middle cerebralartery occlusion(MCAO) 2h and reperfusion 24 h after MCAO 2 h respectively.TGF-β₁ mRNA expressionwas measured by semi-quantitative reverse transcri ption polymerase chain reaction(RT-PCR);Cerebraldamage was eval uated by histopathology.RESULTS:In the same condition of ischemia or ischemia/reperfu-sion,inj uried area enlarged in DMgroups;The expressionlevel of TGF-β₁ mRNA increased at the ti me of 2h after MCAOi n non-diabetic group and diabetic group,especialy significantly in non-diabetic group withMCAO 2 h,and decreased at the time of reperfusion 24 h after MCAO 2 h,but still higher than that in theshamgroup.CONCLUSION:Diabetes mellitus exacerbated brain lesion following ischemia/repefusion,in-creased TGF-β₁ mRNA expresion after MCAO may be an anti-injury reaction,and anti-injury abilityis de-creased under diabetic condition.     

Effects of 11, 12-EET and ischemic preconditioning on phosphorylated ERK and p38 MAPK during ischemia and reperfusion in rat myocardium

AIM: In order to study the relationship between the ERK and p38 MAPK activation and the protection of 11, 12-epoxyeicosatrienoic acid (11, 12-EET) and ischemia preconditioning (IP), the effects of 11, 12-EET and ischemic preconditioning on phosphorylated ERK and p38 MAPK during ischemia and reperfusion in rat myocardium were examined. METHODS: The rat heart was subjected to ischemia for 5 min by ligating the left anterior descending coronary artery followed by reperfusion for 5 min (two times) to undergo ischemia preconditioning. The rats were divided into 5 groups: (1) control; (2) sham group; (3) ischemia/reperfusion (I/R) group, in which the rat heart suffered from 60 min ischemia followed by 30 min reperfusion; (4) IP plus I/R group; (5) EET plus I/R group, in which 6.28×10^-8 mol/L 11, 12-EET was injected intravenously 20 min before I/R. The heart function was examined, and phosphorylated ERK and p38 MAPK were detected by Western blot. RESULTS: At 30 min reperfusion, +dp/dt_max, -dp/dt_max and LVDP decreased significantly in I/R group compared with sham group, IP plus I/R group and EET plus I/R group; Phosphorylated ERK1/2 level was higher in I/R group than sham group, but was lower in I/R group than IP plus I/R group and EET plus I/R group; Phosphorylated p38 MAPK level was lower in control, sham, IP plus I/R and EET plus I/R group than I/R group. CONCLUSION: 11,12-EET protects rat heart against ischemia/reperfusion injury, the mechanism may be related to activation of ERK1/2 and inhibition of p38 MAPK.     

Effect of β3-adrenoceptor activation on ventricle fibrillation threshold and effective refractory period in rats with heart failure

AIM: To observe the effect of β₃-adrenoceptor (AR) on ventricle fibrillation threshold (VFT) and effective refractory period (ERP) in rats with heart failure.METHODS: Rats were randomized into control group and heart failure group. The expression of β₃- AR mRNA was detected with RT-PCR. The VFT, ERP, left ventricle end-systolic pressure(LVESP)，left ventricle end-diastolic pressure(LVEDP), +dp/dtmax and -dp/dtmax were measured at the same time with administration of BRL37344 (β₃-AR agonist).RESULTS: ① Both the expression of β₃-AR mRNA and the proportion (β₃/β₁+β₂+β₃) were increased in failure rats comparied with those in control rats (0.028 vs 0.011 and 5.4% vs 1.2%, P<0.05). ② ERP was longer in rats with heart failure than that in control group (70.5 ms±5.5 ms vs 59.5 ms±6.4 ms, P<0.05). No difference in ERP in rats with heart failure was observed before and after administration of BRL37344 (73.0 ms±4.8 ms vs 70.5 ms±5.5 ms, P>0.05). ③ VFT was lower in rats with heart failure than that in control group (10.9 mV±0.8 mV vs 30.5 mV±1.3 mV, P<0.05) and decreased obviously in rats with heart failure after administration of BRL37344 (7.1 mV±0.6 mV vs 10.9 mV±0.8 mV, P<0.05). The decrease in VFT correlated with the effect of LVESP, +dp/dtmax, -dp/dtmax with BRL37344 and the expression of β₃-AR mRNA (correlation coefficient: 0.788, 0.708, 0.759, 0.787; P<0.05). CONCLUSION: The expression of β₃-AR mRNA in left ventricle is obviously increased in rats with heart failure. The activation of β₃-AR has no effect on ERP but can decrease VFT which correlates with the effect of β₃-AR on LVESP, +dp/dtmax, -dp/dtmax and the expression of β₃-AR mRNA.     

Effects of ischemic preconditioning on hepatocyte apoptosis induced by hepatic ischemia-reperfusion in cirrhotic rats

AIM:To investigate the protective effect of ischemic preconditioning (IPC) on hepatic ischemia-reperfusion(I/R) injury in cirrhotic rats and its possible mechanism. METHODS:Hepatic I/R was induced by Pringle maneuver. The cirrhotic rats were randomized into three groups: Group A: before 30 min of ischemia, a short period of 5 min ischemia and 5 min reperfusion were given; Group B: before 30 min of ischemia, a short period of 10 min ischemia and 10 min of reperfusion were given; Group C: 30 min ischemia only. The serum alanine transferase (ALT), hepatic Fas-mRNA, caspase-3 activity and hepatocyte apoptosis were analyzed. RESULTS:The 7-day survival rate in the group A and B were 100%, respectively. However, it was only 62.5% in the group C. After 6 h of reperfusion, the ALT levels in both group A and B were significantly lower than that of in group C, P＜0.01. The ALT level of group A was also lower than that of group B, P＜0.01. The hepatic Fas-mRNA expression, caspase-3 activity and apoptotic hepatocyte in group A were significantly lower than those of in group C, P＜0.01. CONCLUSIONS:IPC has significant protective effect against hepatic I/R injury. An IPC with 5 min of ischemia and 5 min of reperfusion has the maximal protective effect. The protective mechanism of IPC against hepatic I/R injury is via down-regulation of Fas-mRNA expression, inhibiting caspase-3 activity and subsequently inhibiting hepatocyte apoptosis.     

Effect of tea polyphenols on the contractile function of the papillary muscles of right ventricle in diabetic rats

AIM: To investigate the effect of tea polyphenols (TP) on the contractile function of the papillary muscles of right ventricle in the sixth and eighth week diabetic rats and the control rats. METHODS: Rats were induced to diabetic by an intravenous injection of alloxan. The papillary muscles of right ventricle in the sixth and eighth week diabetic rats were segregated and superfused with oxygenated Tyrode's solution. The contractile function and functional change under the electric stimulation state was recorded and compared between diabetic group and control group. RESULTS: 1/2 diastole interval elongation (P<0.05) and the depression of +dT/dtmax (P<0.01) and -dT/dtmax (P<0.05) of the papillary muscles of right ventricle were showed in the 6th week diabetic rats, while further damages, such as tension addition (P<0.01), 1/2 diastole interval elongation (P<0.01) and the depression of +dT/dtmax (P<0.01) and -dT/dtmax (P<0.01) in 8th week diabetic rats were also observed. TP at certain concentrations (15-120 mg/L) did not produce any effect on the 8th week diabetic rat's papillary muscle, but the positive muscle strength has been showed in the control rats and the sixth week diabetic rats. CONCLUSIONS: TP produces the positive muscle strength in the early diabetic cardiomyopathy, but has no beneficial effect on serious impaired diabetic myocardium.     

Role of mitochondrial calcium uniporter in hypoxic preconditioning

AIM: To investigate the role of mitochondrial calcium uniporter (MCU) in the cardioprotection by hypoxic preconditioning (HPC) and its relationship to mitochondrial permeability transition pore (MPTP). METHODS: Intraventricular balloon technique was employed to measure the left ventricular developed pressure (LVDP), the maximum rise/fall rate of left ventricular pressure (±dp/dtmax), and the left ventricular end-diastolic pressure (LVEDP) in Langendorff isolated rat heart. The hypoxia was achieved by ligation of left anterior coronary artery for 30 min followed by release of ligation for 120 min as reoxygenation. Hypoxic preconditioning was set as two episodes of 5 min global hypoxia and 5 min reoxygenation. RESULTS: Both HPC and treatment with ruthenium red (5 μmol/L) during the first 10 min reoxygenation improved recovery of LVDP, ±dp/dtmax and decreased LVEDP, which was associated with reduced infarct size and lactate dyhydrogenase release. These protective effects were attenuated by treatment with spermine (20 μmol/L) during the first 10 min reoxygenation. Administration of cyclosporin A (0.2 μmol/L) during the last 5 min of hypoxia period and first 15 min of reoxygenation period reduced the injury effect by spermine. CONCLUSION: These results indicate that inhibition of MCU is involved in the cardioprotection of HPC via inhibiting MPTP.     

Effects of volatile anesthetics on rat heart ischemia-reperfusion injury in vitro

AIM: To investigate the effect of volatile anesthetics on function,metabolism,ATPase activity and free radicals in isolated ischemia /reperfusion (I/R) rat hearts.METHODS: 136 SD rats were anesthetized with pentobarbital and randomly divided into six groups and 17 sub-groups (n=8),according to the given drug.In a normal thermal isolated Langendorff rat heart model,four volatile anesthetics in 1.5 MAC concentration were given before global ischemia 25 min and during reperfusion 30 min.Coronary flow (CF),LVEDP,left ventricular developed pressure (LVDP),±dp/dt were monitored at 15 min of equilibrium,15 min of drug treatment,the end of reperfusion.Myocardial adenosine triphosphate (ATP),malodialdehyde (MDA),activity of Ca2＋-ATPase and Na＋-K＋-ATPase,and superoxide dismutase (SOD) were determined at 15 min of equilibrium,15 min of drug treatment or absence,10 min global ischemia and the end of reperfusion.RESULTS: CF and LVEDP were increased significantly after exposured to volatile anesthetics 15 min,and LVDP,+dp/dtmax were significantly decreased.However,LVDP and +dp/dtmax were increased at the end of reperfusion in the treated groups.HR in halothane and isoflurane groups was decreased before ischemia and after reperfusion.The myocardial ATP content was significantly increased before and after ischemia in the treated groups.At the end of reperfusion,the activity of SOD was significantly higher and myocardial MDA content was significantly lower in the treated groups than those in control group.The activity of Ca2＋-ATPase,compared with the control group,was markedly decreased before ischemia in halothane,enflurane and isoflurane group.Nonetheless,the activity of Ca2＋-ATPase was clearly increased in the treated groups during ischemia and at the end of reperfusion.The activity of Na＋-K＋-ATPase was only enhanced in halothane group at the end of reperfusion among groups.CONCLUSION: The volatile anesthetics depress myocardial systolic function.There are markedly protective effects against myocardial I/R injury.Meanwhile,the volatile anesthetics improve the recovery of function and metabolism,and increase CF and the activity of Ca2＋-ATPase and Na＋-K＋-ATPase in rats.     

Changes of adiponectin and adiponectin receptor 1 in diabetic rats of different courses during myocardial ischemic preconditioning

AIM: To investigate the different effects of adiponectin (APN) and adiponectin receptor 1 (Ad-R1) on myocardial ischemia-reperfusion (IR) injury and ischemic preconditioning (IPC) in different course of diabetic rats in vitro. METHODS: The rat models of type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) were successfully established using streptozotocin and high-fat diet plus streptozotocin, respectively. These rats were divided into 2 groups:4 weeks and 8 weeks. The model of isolated cardiac perfusion was established by Langendorff method. Each group was further divided into control (Con) group, IR group and IPC group. The activity of lactate dehydrogenase (LDH) and creatine kinase (CK) in coronary effluent was detected. The serum and myocardial levels of APN were determined by ELISA. The expression of Ad-R1 in the myocardial tissues was detected by Western blot. The area of myocardial infarction was detected, and the ultrastructure of ventricular papillary muscle was observed by transmission electron microscopy. RESULTS: Compared with the corresponding IR group, the activity of LDH and CK in the IPC group at 4 weeks was significantly decreased (P<0.01), and the area of myocardial infarction was significantly reduced. However, no significant difference of each index in DM groups at 8 weeks was observed. Serum APN level was decreased in diabetic rats, especially in T2DM rats (P<0.05). The levels of APN and Ad-R1 in myocardium of normal rats had no difference among Con, IR and IPC groups. The level of APN in myocardium of T1DM rats had no difference in all subgroups, while the expression of Ad-R1 in myocardial tissue of IR group was significantly increased as compared with Con group (P<0.01) and IPC group (P<0.01) both at 4 and 8 weeks. In T2DM rats, the levels of APN in myocardium both at 4 and 8 weeks were decreased in IR group compared with Con group (P<0.05). The level of APN in IR group at 4 weeks was significantly decreased compared with IPC group, but had no significant difference at 8 weeks. The expression of Ad-R1 in myocardial tissue of IR group was significantly increased compared with Con group (P<0.05) both at 4 and 8 weeks. The level of Ad-R1 in IR group at 4 weeks was significantly increased compared with IPC group (P<0.05), but had no significant difference at 8 weeks. CONCLUSION: The protective effect of IPC exists in diabetic rats at 4 weeks, whereas it disappears at 8 weeks. APN and Ad-R1 in myocardium were probably involved in the protective effect of IPC on T2DM rats.     

Effects of lipoteichoic acid-induced delayed preconditioning on cardioplegic arrest/reperfusion injury in donor rat heart

AIM: To study the potential effects of lipoteichoic acid (LTA)-induced delayed preconditioning (PC) on cardioplegic arrest/reperfusion injury in donor rat heart. METHODS: The rats were pretreated with LTA (1 mg/kg, ip) 24 h before the experiment, and the isolated hearts were subjected to arrested by cardioplegic solution and stored in Eurocollin's solution for 4 h by the Langendorff method, and to evaluate the changes of cardiac function at the reperfusion for 30 min and 60 min, to measure the amounts of MB isoenzyme of creatine kinase (CK-MB), lactate dehydrogenase (LDH) and total nitric oxide (NO) oxidation products in the coronary effluent, and to detect myocardial apoptosis on tissue samples of left ventricle at the end of reperfusion by TUNEL staining. RESULTS: Pretreated with LTA significantly improved the recovery of cardiac function with a significant increase in coronary flow (CF), left ventricular developed pressure (LVDP), maximal rate of left ventricular developed pressure (+dp/dtmax), and minimal rate of left ventricular decline pressure (-dp/dtmax) at 30 min and 60 min of reperfusion (all P<0.01), reduced CK-MB (P<0.01) and LDH (P<0.01) release and raised the concentrations of NO2-/NO3- in coronary effluent. In addition, LTA pretreatment obviously decreased myocardial apoptosis in left ventricle at the end of reperfusion (P<0.01). The protective effects were abrogated by pretreatment of the rats with L-nitroarginine methyl eater (L-NAME, 10 mg/kg, ip). CONCLUSION: LTA pretreatment significantly improves cardiac function after cardioplegic arrest/reperfusion injury in donor heart of rats, and endogenous NO plays an essential role as an effector of delayed PC induced by LTA.     

Effects of ERK1/2 on pressure overload-induced cardiomyopathy and heart failure in mice

AIM: To explore the changes in extracellular regulated protein kinase (ERK1/2) in the hypertrophic myocardium induced by pressure overload at the different time courses and to determine the molecular mechanism in the myocardium from hypertrophy to heart failure. METHODS: C57/BL mice, aged 12 week old, were subjected to sham-operation (SH) or transversing aortic constriction (TAC) to establish left ventricular hypertrophy. Echocardiographic assessments, hemodynamic determination, organ weight measurement, morphological and histological examination were performed at 1, 4, 8, 12 and 16 weeks after surgery. Meanwhile mRNA levels of atrial natriuretic peptide (ANP), α-myosin heavy chain (α-MHC), bcl-2 and bax were measured by RT-PCR, and ERK1/2 levels were detected by Western blotting. The animals in SH group were performed the same tests then sacrificed at 16 weeks. RESULTS: (1) Compared to SH group, LVESd, LVEDd, Awsth, Awdth, Pwsth and Pwdth progressively increased after TAC. Meanwhile, ejection fraction (EF%) significantly decreased at 16th week (P<0.05). LVSP, dp/dtmax and dp/dtmin in TAC group were progressively increased after 4 weeks. From 8-12 weeks these parameters maintained stable and then sharply decreased at 16th week (all P<0.05). However, LVEDP was statistically increased at 8th week. These echocardiographic and hemodynamic changes indicated a development of LVH and eventually progressing towards to heart failure. (2) Histologically, cardiac collagen measured by percentage of Sirius red positive stained area and apoptosis index showed progressive increases from 4 to 16 weeks. (3) Compared to SH group, mRNA levels of ANP was time-dependently increased while α-MHC and Bcl-2 were time-dependently decreased. The ratio of Bcl-2 /Bax was decreased. Phosphorylation of ERK1/2 was increased at 4th week, then decreased with age of TAC (all P<0.05). CONCLUSION: Pressure-overload induced by TAC results in a development of LVH from early concentric hypertrophy to late eccentric hypertrophy, and eventually toward cardiac dysfunction or heart failure. Those changes are associated with increase in cell size and cardiac fibrosis. ERK1/2 signaling pathway may involve in the regulation of myocardial cell apoptosis in hypertrophic and failure heart.     

Xinshuaikang inhibits myocardial autophagy and MAPK/ERK1/2 signaling pathway in rats with chronic heart failure

AIM:To explore the effect of Xinshuaikang on myocardial autophagy in the rats with chronic heart failure and its relationship with the MAPK/ERK1/2 signaling pathway. METHODS:The rats were divided into sham group, model group (rat model of chronic heart failure was established by ligation of anterior descending branch of left coronary artery), low-, middle-, and high-dose Xinshuaikang treatment (TL, TM and TH) groups and captopril group (treated with captopril as positive control), with 12 in each group. Doppler echocardiography was used to evaluate the cardiac function. The morphological changes of the myocardium were observed by HE staining. TUNEL staining was used to detect cardiomyocyte apoptosis. The expression of microtubule-associated protein 1 light chain 3-Ⅱ (LC3-Ⅱ) in the myocardium was detected by immunofluorescence labeling. The protein levels of p-ERK, p-p38 MAPK, LC3-Ⅱ, beclin-1 and p62 in the myocardium were determined by Western blot. RESULTS:Compared with sham group, left ventricular end-diastolic dia-meter (LVEDD) and left ventricular end-systolic diameter (LVESD) in model group were increased, while left ventricular posterior wall thickness at end-diastole (LVPWTd), left ventricular posterior wall thickness at end-systole (LVPWTs), left ventricular ejection fraction (LVEF), cardiac output (CO), left ventricular diastolic pressure (LVDP), left ventricular systolic pressure (LVSP) and maximum rate of rise/decrease of left ventricular pressure (+dp/dt_max/-dp/dt_max) were decreased (P<0.05). The myocardial cells were deformed and necrotic, and the myocardial fibers were broken, with inflammatory cell infiltration. The apoptotic rate, the positive rate of LC3-Ⅱ, and the protein levels of p-ERK, p-p38 MAPK, LC3-Ⅱ/LC3-I and beclin-1 were increased, and the protein expression of p62 was decreased (P<0.05). Compared with model group, the levels of LVEDD and LVESD were decreased, LVPWTd, LVPWTs, LVEF, CO, LVSP, LVDP, +dp/dt_max and -dp/dt_max were increased in Xinshuaikang groups and captopril group (P<0.05). The morphological changes of myocardial cells were gradually returned to normal, and inflammatory cell infiltration, the apoptotic rate and the positive rate of LC3-Ⅱ were decreased. The protein levels of p-ERK, p-p38 MAPK, LC3-Ⅱ/LC3-I and beclin-1 were decreased, and the protein expression of p62 was increased (P<0.05). CONCLUSION:Xinshuaikang inhibits myocardial auto-phagy to play a role of cardiac protection in the rats with chronic heart failure, and its mechanism may be related to inhibition of MAPK/ERK1/2 signaling pathway.     

Effect of ligustrazine on pulmonary arterial pressure and pulmonary arterial wall collagen of chronic hypoxic hypercapnic rats

AIM:To study the effect of ligustrazine on pulmonary hypertensive rats induced by hypoxic hypercapnia. METHODS:Thirty rats were randomly divided into three groups:control group(A),hypoxic hypercapnic group(B), hypoxic hypercapnia+ligustrazine(lig.) group(C). RESULTS: (1) Mean pulmonary arterial pressure(mPAP)of group B was significantly higher than that of group A and mPAP of group C was significantly lower than that of group B(P＜0.01),differences of mean carotid pressure(mCAP) were not significant among three groups (P＞0.05); (2)Electron microscopy and immunohistochemistry showed ligustrazine could inhibit the diposition of collagenous fiber(collagen typeⅠ)in pulmonary arterioles induced by hypoxic hypercapnia; (3) Plasma endothelin level of group C was significantly lower than that of group B (P＜0.01), serum (NO ₂^-/NO₃^-) of group C was significantly higher than that of group B (P＜0.01). CONCLUSION:Ligustrazine can inhibit pulmonary hypertension and the diposition of collagen type Ⅰ in pulmonary arterial wall induced by hypoxic hypercapnia.     

Effect of rosiglitazone on myocardial energy substrate utilization in type 2 diabetic rats

AIM: To study the effect of rosiglitazone (RSG) to improve insulin sensitivity on myocardial energy substrate utilization as well as the cardiac function in a rat model of type 2 diabetes mellitus. METHODS: Sprague-Dawley rats were conducted into three groups: chow-fed rats were fed with normal chow (12% of calories as fat); fat-fed/STZ rats were fed with high-fat diet (40% of calories as fat) for 4 weeks and then injected with streptozotocin 35 mg/kg intraperitoneal; fat-fed/STZ/RSG rats were fat-fed/STZ rats treated with rosiglitazone (3 mg·kg-1·d-1) for 2 weeks. A cannula connected to a passive transducer was inserted the heart for the measurement of the cardiac function including heart rate (HR), left ventricular end-diastolic pressure (EDP) and ±dp/dtmax. Then the isolated hearts were mounted onto a Langendorff perfusion apparatus to perfuse with Krebs-Henseleit buffer in the presence of 5 mmol/L glucose and 0.4 mmol/L ［3H］ labelled palmitate. Glucose uptake and ［3H2O］ collection were measured to evaluate the rate of carbohydrate and fatty acid oxidation. RESULTS: Compared with the chow-fed rats, fat-fed/STZ rats had a significantly depression of glucose uptake in the hearts ［(54.7±6.2 vs 69.0±5.7) μmol·g-1 dry weight, P<0.01］ after 30 min perfusion. The oxidation of glucose and palmitate were 18% and 82%, respectively. Paralleling the reduction was a change of EDP ［(14.3±1.8 vs 10.5±1.1) mmHg, P<0.05］ and -dp/dt ［(550±57 vs 650±42) mmHg/s, P<0.01］, indicating a impaired left ventricular diastolic function. In the hearts subjected to fat-fed/STZ group, rosiglitazone treated for 2 weeks resulted in a elevated level of glucose uptake ［(63.5±6.4 vs 54.7±6.2) μmol·g-1 dry weight, P<0.05］. A protective role of the ventricular function ［EDP decreased from （14.8±1.9） to （11.0±0.8） mmHg/s and -dp/dtmax increased from （558±60） to （629±51） mmHg/s, P<0.05］ were observed. CONCLUSIONS: Our study indicates that there is a depression of glucose oxidation and at increase in fatty acid oxidation in type 2 diabetic hearts. Elevation of insulin sensitivity using rosiglitazone increases the myocardial glucose metabolism and shows a benefitial result to heart functions.