Myocardial Ischemia-reperfusion Model Research Articles

Comment on "Comparison of Electroacupuncture in Restrained and Unrestrained Rat Models".

Comment on "Comparison of Electroacupuncture in Restrained and Unrestrained Rat Models".

Effects of Ang Ⅱ perfusion on transmural heterogeneous of Cx43 in acute myocardial ischemia reperfusion.

To observe the effects of angiotensin Ⅱ(Ang Ⅱ) perfusion on transmural heterogeneity of Cx43 expression in the rabbit model with acute myocardial ischemia reperfusion (MIR), and investigate the role of rennin-angiotensin system in malignant ventricular arrhythmia induced by MIR. Twenty rabbits were randomly divided into MIR group (n=10) and Ang Ⅱ group (n=10). MIR model was produced with traditional ligation and opening of the anterior descending coronary artery in all animal. The hearts invitro in the MIR group and the Ang Ⅱ group were perfused with simply improved Tyrode's solution and containing Ang Ⅱ Tyrode's solution respectively. 90% monophasic action potential repolarization duration, transmural dispersion of repolarization, Cx43 protein (Cx43-pro) and mRNA (Cx43-Cq) expression in subepicardial, midmyocardial and subendocardial myocardium were measured in both groups. The greatest differences of Cx43-pro and Cx43-Cq among three myocardial layers were calculated and shown with ΔCx43-pro and ΔCx43-Cq respectively. After Ang Ⅱ perfusion, 90% monophasic action potential repolarization duration among three myocardial layer were significantly prolonged (P<0.05 and P<0.01), and transmural dispersion of repolarization also significantly increased compared with the MIR group (P<0.05). Compare with the MIR group, three myocardial Cx43-pro and Cx43-Cq expression in the Ang Ⅱ group were significantly decreased (P<0.05 and P<0.01), but ΔCx43-pro and ΔCx43-Cq were significant increased. Renin-angiotensin system increases transmural heterogeneity of Cx43 expression in the rabbit model with MIR by Ang Ⅱ, and enlarge transmural dispersion of repolarization among three myocardial layers of left ventricular which induces malignant ventricular arrhythmia.

An intact small animal model of myocardial ischemia-reperfusion: Characterization of metabolic changes by hyperpolarized 13C MR spectroscopy.

Hyperpolarized carbon-13 magnetic resonance spectroscopy ((13)C MRS) enables the sensitive and noninvasive assessment of the metabolic changes occurring during myocardial ischemia-reperfusion. Ischemia-reperfusion models using hyperpolarized (13)C MRS are established in heart preparations ex vivo and in large animals in vivo, but an in vivo model in small animals would be advantageous to allow the study of reperfusion metabolism with neuroendocrine and inflammatory responses intact with the option to perform a greater number of experiments. A novel intact rat model of ischemia-reperfusion is presented that incorporates hyperpolarized (13)C MRS to characterize reperfusion metabolism. Typically, in an in vivo model, a tissue input function (TIF) is required to account for apparent changes in the metabolism of injected hyperpolarized [1-(13)C]pyruvate resulting from changes in perfusion. Whereas the measurement of a TIF by metabolic imaging is particularly challenging in small animals, the ratios of downstream metabolites can be used as an alternative. The ratio of [(13)C]bicarbonate:[1-(13)C]lactate (RatioBic/Lac) measured within 1-2 min after coronary release decreased vs. baseline in ischemic rats (n = 10, 15-min occlusion, controls: n = 10; P = 0.017 for interaction, 2-way ANOVA). The decrease in oxidative pyruvate metabolism [RatioBic/Lac(Ischemia)/RatioBic/Lac(Baseline)] modestly correlated with area at risk (r = 0.66; P = 0.002). Hyperpolarized (13)C MRS was also used to examine alanine production during ischemia, which is observed in ex vivo models, but no significant change was noted; metrics incorporating [1-(13)C]alanine did not substantially improve the discrimination of ischemic-reperfused myocardium from nonischemic myocardium. This intact rat model, which mimics the human situation of reperfused myocardial infarction, could be highly valuable for the testing of new drugs to treat reperfusion injury, thereby facilitating translational research.

Scutellarin's Cardiovascular Endothelium Protective Mechanism: Important Role of PKG-Iα.

Scutellarin (SCU), a flavonoid glycoside compound, has been successfully used in clinic for treatment of ischemic diseases in China. In this report, we checked the effects of SCU on endothelium dysfunction (ED) of coronary artery (CA) against myocardial ischemia reperfusion (MIR) injury in vivo. The involvement of PKG-Iα was further studied using cultured endothelial cells subjected to hypoxia reoxygenation (HR) injury in vitro. In rat MIR model, SCU (45 and 90 mg/kg, iv) significantly reduced ischemic size and restored the endothelium-dependent vasodilation of isolated CA rings. PKG inhibitor Rp-8-Br-cGMP (50 μg/kg, iv) could ameliorate the protective effects of SCU. Increase in phosphorylation of vasodilator-stimulated phosphoprotein (VASP), a main substrate of PKG, at Ser 239 was observed in both heart tissue and serum of SCU-treated animals. In cultured human cardiac microvascular endothelial cells (HCMECs), SCU (1 and 10 μM) dose-dependently protected cell viability and increased the mRNA and protein level of PKG-Iα against HR injury. The activity of PKG was also increased by SCU treatment. The activation of PKG–1α was then studied using targeted proteomic analysis (MRM-MS) checking the phosphorylation state of the autophosphorylation domain (aa42-94). Significant decrease in phosphorylation of PKG-Iα at Ser50, Ser72, Ser89 was induced by HR injury while SCU treatment significantly increased the phosphorylation of PKG-Iα, not only at Ser50, Ser72 and Ser89, but also at Ser44 and Thr58 (two novel phosphorylation domains). Our results demonstrate PKG-Iα might play an important role in the protective effects of SCU on ED against MIR injury.

Design, Synthesis, and Cardioprotective Effects of N-Mercapto-Based Hydrogen Sulfide Donors.

Hydrogen sulfide (H2S) is a signaling molecule which plays regulatory roles in many physiological and/or pathological processes. Therefore, regulation of H2S levels could have great potential therapeutic value. In this work, we report the design, synthesis, and evaluation of a class of N-mercapto (N-SH)-based H2S donors. Thirty-three donors were synthesized and tested. Our results indicated that controllable H2S release from these donors could be achieved upon structural modifications. Selected donors (NSHD-1, NSHD-2, and NSHD-6) were tested in cellular models of oxidative damage and showed significant cytoprotective effects. Moreover, NSHD-1 and NSHD-2 were also found to exhibit potent protective effects in a murine model of myocardial ischemia reperfusion (MI/R) injury.

Evaluation of effect of adenosine triphosphate postconditioning on myocardial ischemia reperfusion injury in rabbits using ultrasound speckle tracking imaging

Objective To evaluate the effect of adenosine triphosphate postconditioning on myocardial ischemia reperfusion injury in rabbits by ultrasound speckle tracking imaging(STI). Methods Forty-two healthy rabbits were randomly divided into three groups averagely: ischemia-reperfusion(IR) group, ischemia postconditioning(IPost) group, ATP-pharmacological postconditioning(PPost) group. The model of myocardial ischemia reperfusion was established. Echocardiography examinations were conducted before the coronary artery ligatured, after 45 min later and at the end of reperfusion. Pathological examinations were applied to detect the change of which two rabbits randomly selected from each group after the coronary artery ligatured 45 minutes later and the rests after reperfusion of 120 min. Results ①Ischemic and infarct changes could find in the six rabbits which were sacrificed after the coronary artery ligatured 45 minutes later. The same changes also could be found in the three groups after reperfusion, and the damage in IR group was the most significant. ②After block of coronary artery, left ventricular ejection fraction(LVEF) decreased in all groups (P<0.05) and STI index decreased in all groups (P<0.01). ③After reperfusion of 120 min later, global longitudinal systolic strain rate(GLSrsys), global longitudinal systolic strain(GLSsys) increased in IPost group and GLSrsys increased in ATP-PPost group, and longitudinal systolic strain rate(SrLsys), longitudinal diastolic strain rate(SrLd), longitudinal systolic strain(SLsys) increased both in IPost group and ATP-PPost group(P<0.05 or P<0.01). Compared in groups, GLSsys, SrLsys, SLsys in IPost group and ATP-PPost group all higher than those in IR group (P<0.05). Conclusions STI can evaluate exactly the global and regional myocardial function of rabbit myocardial infarct-reperfusion model and local index is better than overall index. STI can also detect correctly the protect effects on myocardial reperfusion injury of ATP. Key words: Echocardiography; Myocardial ischemia; Reperfusion injury; Postconditioning; Adenosine; Speckle tracking imaging

Nuclear cardiac myosin light chain 2 modulates NADPH oxidase 2 expression in myocardium: a novel function beyond muscle contraction

Recent studies demonstrated that NADPH oxidase 2 (NOX2) expression in myocardium after ischemia-reperfusion (IR) is significantly upregulated. However, the underlying mechanisms remain unknown. This study aims to determine if nuclear cardiac myosin light chain 2 (MYL2), a well-known regulatory subunit of myosin, functions as a transcription factor to promote NOX2 expression following myocardial IR in a phosphorylation-dependent manner. We examined the phosphorylation status of nuclear MYL2 (p-MYL2) in a rat model of myocardial IR (left main coronary artery subjected to 1 h ligation and 3 h reperfusion) injury, which showed IR injury and upregulated NOX2 expression as expected, accompanied by elevated H₂O₂ and nuclear p-MYL2 levels; these effects were attenuated by inhibition of myosin light chain kinase (MLCK). Next, we explored the functional relationship of nuclear p-MYL2 with NOX2 expression in H9c2 cell model of hypoxia-reoxygenation (HR) injury. In agreement with our in vivo findings, HR treatment increased apoptosis, NOX2 expression, nuclear p-MYL2 and H₂O₂ levels, and the increases were ameliorated by inhibition of MLCK or knockdown of MYL2. Finally, molecular biology techniques including co-immunoprecipitation (Co-IP), chromatin immunoprecipitation (ChIP), DNA pull-down and luciferase reporter gene assay were utilized to decipher the molecular mechanisms. We found that nuclear p-MYL2 binds to the consensus sequence AGCTCC in NOX2 gene promoter, interacts with RNA polymerase II and transcription factor IIB to form a transcription preinitiation complex, and thus activates NOX2 gene transcription. Our results demonstrate that nuclear MYL2 plays an important role in IR injury by transcriptionally upregulating NOX2 expression to enhance oxidative stress in a phosphorylation-dependent manner.

A novel function of nuclear nonmuscle myosin regulatory light chain in promotion of xanthine oxidase transcription after myocardial ischemia/reperfusion

Nuclear myosin regulates gene transcription and this novel function might be modulated through phosphorylation of the myosin regulatory light chain (p-MLC20). Nonmuscle MLC20 (nmMLC20) is also present in the nuclei of cardiomyocytes and a potential nmMLC20 binding sequence has been identified in the promoter of the xanthine oxidase (XO) gene. Thus, we investigated its function in the regulation of XO transcription after myocardial ischemia/reperfusion (IR). In a rat model of myocardial IR and a cardiomyocyte model of hypoxia/reoxygenation (HR) injury, the cardiac or cell injury, myosin light chain kinase (MLCK) content, XO expression and activity, XO-derived products, and level of nuclear p-nmMLC20 were detected. Coimmunoprecipitation (co-IP), chromatin immunoprecipitation, DNA pull-down, and luciferase reporter gene assays were used to decipher the molecular mechanisms through which nmMLC20 promotes XO expression. IR or HR treatment dramatically elevated nuclear p-nmMLC20 level, accompanied by increased XO expression, activity, and products (H2O2 and uric acid), as well as the IR or HR injury; these effects were ameliorated by inhibition of MLCK or knockdown of nmMLC20. Our findings from these experiments demonstrated that nuclear p-nmMLC20 binds to the consensus sequence GTCGCC in the XO gene promoter, interacts with RNA polymerase II and transcription factor IIB to form a transcription preinitiation complex, and hence activates XO gene transcription. These results suggest that nuclear p-nmMLC20 plays an important role in IR/HR injury by transcriptionally upregulating XO gene expression to increase oxidative stress in myocardium. Our findings demonstrate nuclear nmMLC20 as a potential new therapeutic target to combat cardiac IR injury.

Acupuncture and oxidative stress.

The current special issue is the 2014 issue which includes 7 interesting papers. As one of the modalities of traditional oriental medicine, acupuncture has been widely used to treat many disorders and diseases including chronic pain, stroke, and insomnia as well as depression, while its mechanisms remain unclear. Enhanced production of reactive oxygen species causes oxidative stress leading to damage in lipids, proteins, and nucleic acids. Recent experimental studies have demonstrated that acupuncture could attenuate oxidative stress, which seems possible to explore the physiological antioxidative mechanism of acupuncture in various diseases. This special issue contains 7 papers, of which 5 articles study the antioxidative mechanism of acupuncture in some diseases by animal models. These studies suggested that acupuncture may result from antioxidation, anti-inflammation, and antiapoptosis effects in several kinds of diseases. Among these, one study is related to the effect of laser acupuncture on memory impairment, oxidative stress status, and the functions of both cholinergic and dopaminergic systems in hippocampus of animal model of Parkinson's disease. One study explores whether electroacupuncture reduces myocardial ischemia-reperfusion (I/R) injury and inflammatory responses through inhibiting early growth response (Egr)-1 expression via the extracellular signal-regulated protein kinase-1 and kinase-2 (ERK1/2) pathway in a mouse model of myocardial ischemia reperfusion. Besides, one study compares the effects of antioxidant interventions on the electrical potential difference between acupoints along the stomach meridian on human. This paper suggests a possible underlying mechanism of acupuncture involving superoxide removal. One study focuses on the emerging links between acupuncture and redox modulation in vascular dementia, Alzheimer's vascular dementia, Parkinson's disease and hypertension, which represents an important step forward in the research of acupuncture antioxidative effect. We are excited to explore the studies on the specific oxidative stress biomarkers and redox signaling cascades using oxidative stress-related assessments techniques should be particularly useful in generating new hypotheses to enhance our understanding of the mechanism of antioxidative effects of acupuncture. Cun-Zhi Liu Shu-Feng Zhou Sergio-Botelho Guimaraes William Chi-shing Cho Guang-Xia Shi

Experimental study on the protective effect of salvia miltiorrhiza on myocardial lsehemia reperfusion Injury in rats

Objective To observe the protective effect of Salvia miltiorrhiza on myocardial ischemia reperfu-sion injury in rats.Methods 150 healthy male rats were randomly divided into 5 groups：sham operation group,model group,Radix Salviae Miltiorrhizae in high dose group（100mg/kg）,middle dose group（30mg/kg）,low dose group （10mg/kg）.Salvia miltiorrhiza group were administered orally preoperatively,once a day.On 3 consecutive days. Sham operation group and model group were treated with equal volume of saline.The coronary artery ligation rat for 30min,then sonza coronary artery for 180 min to make the model of myocardial ischemia reperfusion injury.Make determination of myocardial infarct size;make determination of serum creatine kinase （ CK ） , lactate dehydrogenase （ LDH） .Results In the model group compared with the sham operation group,myocardial infarction and serum CK and LDH activity significantly increased（t =14.382,21.460,all P〈0.05）,made up of the myocardial ischemia reperfusion injury in rats model.The different doses of Danshen group can significantly reduce the myocardial ischemia reperfusion injury in rats about the range of myocardial infarction and decrease serum CK , there were significant＆amp;nbsp;differences compared with the model group （t=7.426,6.891,11.274,all P〈0.05）.Different doses of Danshen group can significantly reduce serum LDH, there were significant differences compared with the model group （ t =22.436,10.843,16.252,all P〈0.05）.Conclusion Salvia miltiorrhiza has oxidative stress on myocardial ischemia reperfusion in rats,which has protective effect of Salvia miltiorrhiza on myocardial ischemia reperfusion injury in rats. Key words: Salvia miltiorrhiza; Myocardial ischemia reperfusion injury; Protective effect; Pharmacological experiment

Abstract 17443: Inhibition of the Calcineurin Interaction Site on TRPV1 Reduces Myocardial Infarct Size in Rats

Introduction: With recent public concerns of opioid overuse, misuse and addiction along with the heightened FDA restrictions on opioid prescribing, non-opioid cardiac-safe pain therapeutics for those with cardiovascular disease is needed. The transient receptor potential vanilloid 1 (TRPV1), a mediator of heat, pain and noxious stimuli, mediates nociception. While blocking TRPV1 reduces pain, the finding preconditioning-induced cardioprotection is lost in TRPV1 knockout mice or by TRPV1 inhibition indicates a dual role for TRPV1 both in protection from cardiac injury and in pain signaling. Hypothesis: We tested whether a peptide corresponding to a calcineurin interaction site on TRPV1 could separate the functions of TRPV1 by reducing myocardial injury while providing pain control. Methods: The peptide was synthesized using a Liberty peptide synthesizer and conjugated to TAT for intracellular entry. Male Sprague-Dawley rats 8 weeks of age were used for both isolated heart and in vivo studies consisting of 30 minutes of ischemia followed by reperfusion. Infarct size was assessed by triphenyltetrazolium staining. Results: Testing the peptide using a calcineurin activity assay kit in vitro showed the peptide inhibited calcineurin activity vs. TAT control (0.46±0.03* vs. 0.77±0.02, nmol phosphate, n=3/group, *P&lt;0.05). Further, peptide treatment of isolated hearts (1μM, infused over 10 minutes prior to ischemia) reduced infarct size and creatine phosphokinase (CPK) release when compared to TAT-treated hearts (Infarct size: 19±3%* vs. 53±4%, %infarct/left ventricle; CPK: 69±22* vs. 459±132, n=6/group, *P&lt;0.01). In an in vivo myocardial ischemia-reperfusion model, the peptide (1mg/kg), given subcutaneously to the abdominal skin prior to ischemia, reduced infarct size compared to control (50±2*% vs. 66±1%, *P&lt;0.001). Initial evidence also suggests that the peptide provides analgesia in pain models. Conclusions: Our results suggest a peptide blocking the calcineurin interaction site of TRPV1 reduces myocardial infarct size. Therefore, disrupting specific protein-protein interactions between calcineurin and TRPV1 may provide a novel strategy to design non-opioid therapeutics for cardioprotection, while also providing pain relief.

Effective inhibition of cardiomyocyte apoptosis through the combination of trimetazidine and N-acetylcysteine in a rat model of myocardial ischemia and reperfusion injury

Objective: Apoptosis is the early and predominant form of cell death in infarcted myocardia. The aim of the study was to investigate the effects of trimetazidine (TMZ) and N-acetylcysteine (NAC), used alone or in combination, on oxidative stress, infarct size, and ischemia-reperfusion (IR)-induced cardiomyocyte apoptosis in a rat model of myocardial IR. Methods and results: Myocardial IR was established by ligating an area under the left main coronary artery for 30 min followed by 3 h of reperfusion. Saline (1 ml/kg), NAC (50, 150 mg/kg), or TMZ (3, 5 mg/kg) was intravenously injected during the middle of the ischemic period. At the end of the reperfusion, blood samples were collected from the animals to measure serum M30 and M65 levels, which are markers of cell death, the S100b level, which is a marker of inflammation, and the malondialdehyde (MDA) level, which is a marker of oxidative stress. The infarct size was evaluated as the ratio of the infarct area to the risk area. Apoptotic activation was assessed by caspase-3 immunostaining and a TUNEL assay. TMZ and NAC, either alone or in combination, significantly reduced serum MDA levels, infarct area and apoptotic activity compared to those observed in saline group. Interestingly, the infarct area was more smaller in TMZ (3 and 5 mg/kg) injected groups (9.72 ± 1.3% and 9.96 ± 2.3%) than those observed in NAC (50 and 150 mg/kg) (16.1 ± 2.5% and 19.1 ± 2.14%) or TMZ (5 mg/kg)- NAC (150 mg/kg) combination groups (16.9 ± 1.6%). However, the apoptotic activity was reduced more significantly in the combination of TMZ (5 mg/kg)-NAC (50 mg/kg) compared to TMZ-only group. Neither TMZ or NAC treatments nor the combination of the drugs significantly affected serum M30, M65 and S100B levels. Conclusion: Intravenous NAC and TMZ administration decreased oxidative stress, infarct area and apoptotic activity in a rat model of IR. Although the combination treatment was more effective in reducing the apoptotic activity than either treatment groups alone, TMZ treatment was more successful in reducing the infarct area than NAC or combination treatments. Present results suggest that, in addition to mechanical attempts to secure myocardial reperfusion, the use of TMZ and NAC may help to reduce IR injury.

GW25-e0520 Cardioprotective effect of sCR1 on myocardial ischemia-reperfusion injury in Rats

The aim of this study was to investigate the effects of soluble complement receptor 1 (sCR1) on rat models of myocardial I/R, explore its potential mechanisms of cardioprotection. Myocardial ischemia-reperfusion model was built, randomly assigned to sham operation group (SOG) and ischemia

GW25-e3233 Effects and mechanisms of Nicorandil anatomic no reflow after myocardial ischemia/reperfusion in rats

To establish the model of myocardial ischemia-reperfusion, to investigate effects and mechanisms of nicorandil and adenosine anatomic no reflow and ventricular remodeling after acute myocardial ischemia reperfusion in rats. To Investigate the pharmacological effects and the safety between nicorandil

The protective effect of microRNA-320 on left ventricular remodeling after myocardial ischemia-reperfusion injury in the rat model.

The primary objective of this study investigated the role of microRNA-320 (miR-320) on left ventricular remodeling in the rat model of myocardial ischemia-reperfusion (I/R) injury, and we intended to explore the myocardial mechanism of miR-320-mediated myocardium protection. We collected 120 male Wistar rats (240–280 g) in this study and then randomly divided them into three groups: (1) sham surgery group (sham group: n = 40); (2) ischemia-reperfusion model group (I/R group: n = 40); and (3) I/R model with antagomir-320 group (I/R + antagomir-320 group: n = 40). Value changes of heart function in transesophageal echocardiography were recorded at various time points (day 1, day 3, day 7, day 15 and day 30) after surgery in each group. Myocardial sections were stained with hematoxylin and eosin (H&E) and examined with optical microscope. The degree of myocardial fibrosis was assessed by Sirius Red staining. Terminal dUTP nick end-labeling (TUNEL) and qRT-PCR methods were used to measure the apoptosis rate and to determine the miR-320 expression levels in myocardial tissues. Transesophageal echocardiography showed that the values of left ventricular ejection fraction (LVEF), left ventricular fractional shortening (LVFS), left ventricular systolic pressure (LVSP) and ±dp/dtmax in the I/R group were obviously lower than those in the sham group, while the left ventricular end-diastolic pressure (LVEDP) value was higher than that in the sham group. The values of LVEF, LVFS, LVSP and ±dp/dtmax showed a gradual decrease in the I/R group, while the LVEDP value showed an up tendency along with the extension of reperfusion time. The H&E staining revealed that rat myocardial tissue in the I/R group presented extensive myocardial damage; for the I/R + antagomir-320 group, however, the degree of damage in myocardial cells was obviously better than that of the I/R group. The Sirius Red staining results showed that the degree of myocardial fibrosis in the I/R group was more severe along with the extension of the time of reperfusion. For the I/R + antagomir-320 group, the degree of myocardial fibrosis was less severe than that in the I/R group. Tissues samples in both the sham and I/R + antagomir-320 groups showed a lower apoptosis rate compared to I/R group. The qRT-PCR results indicated that miR-320 expression in the I/R group was significantly higher than that in both the sham and I/R + antagomir-320 groups. The expression level of miR-320 is significantly up-regulated in the rat model of myocardial I/R injury, and it may be implicated in the prevention of myocardial I/R injury-triggered left ventricular remodeling.

Regulation and actions of activin A and follistatin in myocardial ischaemia–reperfusion injury

Activin A, a member of the transforming growth factor-β superfamily, is stimulated early in inflammation via the Toll-like receptor (TLR) 4 signalling pathway, which is also activated in myocardial ischaemia–reperfusion. Neutralising activin A by treatment with the activin-binding protein, follistatin, reduces inflammation and mortality in several disease models. This study assesses the regulation of activin A and follistatin in a murine myocardial ischaemia–reperfusion model and determines whether exogenous follistatin treatment is protective against injury. Myocardial activin A and follistatin protein levels were elevated following 30min of ischaemia and 2h of reperfusion in wild-type mice. Activin A, but not follistatin, gene expression was also up-regulated. Serum activin A did not change significantly, but serum follistatin decreased. These responses to ischaemia–reperfusion were absent in TLR4−/− mice. Pre-treatment with follistatin significantly reduced ischaemia–reperfusion induced myocardial infarction. In mouse neonatal cardiomyocyte cultures, activin A exacerbated, while follistatin reduced, cellular injury after 3h of hypoxia and 2h of re-oxygenation. Neither activin A nor follistatin affected hypoxia-reoxygenation induced reactive oxygen species production by these cells. However, activin A reduced cardiomyocyte mitochondrial membrane potential, and follistatin treatment ameliorated the effect of hypoxia-reoxygenation on cardiomyocyte mitochondrial membrane potential. Taken together, these data indicate that myocardial ischaemia–reperfusion, through activation of TLR4 signalling, stimulates local production of activin A, which damages cardiomyocytes independently of increased reactive oxygen species. Blocking activin action by exogenous follistatin reduces this damage.

Dual effects of tumor necrosis factor alpha on myocardial injury following prolonged hypoperfusion of the heart

Objective: To examine the dose response of TNFα in an ex vivo rat model of myocardial ischemia reperfusion. Methods and Results: Seventy-two rat hearts were mounted on Langendorff apparatus and perfused with oxygenated Krebs-Henseleit solutions. Ischemia was induced by reducing the perfusate flow rate. During reperfusion, incremental doses of recombinant TNFα were infused as a part of perfusate. TNFα was blocked with monoclonal TNFα antibody. Myocardial function was measured by dP/dT and relaxation time (IVRT). Cellular injury was assessed by released myoglobin and tissue concentration of malondialdehyde activity of the heart homogenates. Baseline +dP/dT was 1645 ± 125 mmHg/sec, –dP/dT was 945 ± 73 mmHg/sec and IVRT was 65 ± 5 msec. At the conclusion of reperfusion period, lower doses of TNFα increased +dP/dT and lowered IVRT. In contrast, the higher doses of TNFα decreased +dP/dT and prolonged IVRT. Pretreating the hearts with monoclonal TNFα antibody completely abolished the effects of TNFα on myocardial contractility and relaxation comparable to ischemia controls. Conclusion: Low dose TNFα improved myocardial function and decreased resultant cellular injury while high dose TNFα decreased myocardial function and increased myocardial injury following ischemia and reperfusion.

Protective effects of CeO2 nanoparticles on the myocardial ischemia-reperfusion injury in rats

Objective To investigate the protective effects of cerium oxide (CeO2) nanoparticles on myocardial ischemia-reperfusion injury in rats.Methods Fifty male Sprague-Dawley rats were randomly divided into five groups:sham group,experimental group and three preconditioning groups with different particle diameter [1-10 nm group,10-25 nm group and 50 nm group (n =10 in each group)].The myocardial ischemia-reperfusion model was established successfully.The activities of superoxide dismutase (SOD) and glutathione (GSH)-Px,and the content of malondialdehyde (MDA) in myocardial tissue were determined.The morphology of myocardium was observed under a light microscope,and the apoptosis of myocardial cells was detected by using TdT-mediated dUTP nick end labeling (TUNEL) method.Results As compared with the Sham group,the activities of SOD and GSH-Px in experimental group were significantly decreased (P ＜ 0.05),while the content of MDA was increased (P ＜ 0.05).The activities of SOD and GSH-Px were increased and the content of MDA was decreased in the three different particle diameter groups as compared with the experimental group (P ＜ 0.05).The apoptosis of myocardial cells was significantly decreased in the three different particle diameter groups [(21.00 ± 3.90)％ for 1-10 nm group; (16.38 ± 3.59)％ for 10-25 nm group; and (24.20 ± 5.88)％ for 50 nm group] as compared the experimental group [(32.92 ± 7.46) ％] (P ＜ 0.05).Conclusion The CeO2 nanoparticles can protect the myocardium from ischemia-reperfusion injury by attenuating oxidative stress. Key words: CeO2 nanoparticles ; Myocardial ischemia; Reperfusion injury ; Cardioprotection

Effect of scutellarin on JAK/STAT pathway in myocardial ischemia reperfusion rats (LB561)

Animal studies have demonstrated that scutellarin (SCU) limits damage after myocardial ischemia injury. However, the underlying molecular mechanisms of SCU protecting against myocardial injury induced by ischemia reperfusion (IR) are not well known. This study examined whether SCU protects against myocardial IR injury in rats is mediated by the Janus kinase and signal transducer and activator of transcription (JAK/STAT) pathway. Protein expression of JAK2/STAT3 and phosphorylative products were assessed by Western blot and immunohistochemistry methods in myocardial tissue from myocardial IR rats pretreated with SCU (45 and 90 mg/kg, iv). Western blot and immunohistochemistry assays showed that myocardial IR injury caused significant increases of phosphorylated JAK2 (p‐JAK2) and phosphorylated STAT3 (p‐STATS) levels in the rat myocardial IR model. SCU (45 and 90 mg/kg, iv) significantly reduced ischemic size, and decreased histological p‐JAK2 and p‐STATS expression. SCU attenuates myocardial IR injury which involved in JAK/STAT signaling pathway.Grant Funding Source: Supported by grants from the National Natural Science Foundation of China (Nos. 30960450 and 81173110) and Yunnan Provincial Science and Technology Department (Nos. 2011FA022, 2012BC012, 2008CD054, and 2008ZC111M).

Effect and mechanism of salvianolic acid B on the myocardial ischemia-reperfusion injury in rats

ObjectiveTo investigate the effect of salvianolic acid B on rats with myocardial ischemia-reperfusion injury. MethodsSD rats were randomly divided into five groups (n=10 in each group): A sham operation group, B ischemic reperfusion group model group, C low dose salvianolic acid B group, D median dose salvianolic acid B group, E high dose salvianolic acid B group. One hour after establishment of the myocardial ischemia-reperfusion model, the concentration and the apoptotic index of the plasma level of myocardial enzymes (CTn I, CK-MB), SOD, MDA, NO, ET were measured. Heart tissues were obtained and micro-structural changes were observed. ResultsCompared the model group, the plasma CTn, CK-MB, MDA and ET contents were significantly increased, NO, T-SOD contents were decreased in the treatment group (group C, D, and E) (P<0.05); compared with group E, the plasma CTn I, CK-MB, MDA and ET levels were increased, the NO, T-SOD levels were decreased in groups C and D (P<0.05). Infarct size was significantly reduced, and the myocardial ultrastructural changes were improved significantly in treatment group. ConclusionsSalvianolic acid B has a significant protective effect on myocardial ischemia-reperfusion injury. It can alleviate oxidative stress, reduce calcium overload, improve endothelial function and so on.