Reperfusion-induced Injury Research Articles

Remote ischaemic conditioning: building evidence of efficacy

This editorial refers to ‘Improved long-term clinical outcomes in patients with ST-elevation myocardial infarction undergoing remote ischaemic conditioning as an adjunct to primary percutaneous coronary intervention’, by A.D. Sloth et al . doi:10.1093/eurheartj/eht369 Rapid restoration of coronary blood flow through primary percutaneous intervention (PPCI) remains the gold standard management of acute ST-elevation myocardial infarction (STEMI). As the availability of primary interventional facilities has improved, door to balloon times have fallen and this has been rewarded with concomitant reductions in mortality and morbidity.1 The question remains, however, even with PPCI and the associated evolution of optimized medical therapy, of whether we doing absolutely everything to preserve the jeopardized myocardium. In the face of improved clinical outcomes, it may be difficult to envisage where any further improvement might come from. Rapid recanalization/reperfusion of an occluded epicardial artery is a paradoxical phenomenon due to its association with reperfusion-induced injury. Reperfusion is indispensable for reviving the myocardium at risk of necrosis, but the reintroduction of oxygen leads to the generation of damaging reactive oxygen species, whereas re-energization of the processes necessary to maintain cellular ion homeostasis leads to rapid intracellular alkalization, which, combined with intracellular and mitochondrial calcium overload, represent the ‘perfect storm’ for initiation of cell death signalling cascades.2 The extension of the myocardial infarct by reperfusion is not necessarily inevitable. An intervention known as ischaemic conditioning was recognized in animal models as early as 19863 and is capable of reducing infarct size in these models by up to 50%.4 Ischaemic conditioning, whereby brief, repetitive, non-injurious ischaemia, before (pre-conditioning), during …

Editorial (Thematic Issues: Pharmacological Mechanisms and Interventions in Ischemia/ Reperfusion-Induced Injury)

Editorial (Thematic Issues: Pharmacological Mechanisms and Interventions in Ischemia/ Reperfusion-Induced Injury)

The effects of preoperative immunosuppressive therapy on ischemia and reperfusion (I/R) injury in healthy rats

Warm-ischemia-induced injuries might be encountered during renal transplants from cadavers and healthy donors. Toll-like receptors (TLR) in ischemia-reperfusion (I/R) injury are one of the indicators of intracellular injury pathways. The intensity of ischemic injury is directly proportionate to high TLR levels. To minimize the I/R injury, we investigated TLR2 and TLR4 levels on rats, which were pretreated with tacrolimus (FK506) before I/R. Eight Wistar albino rats in the study group were administered .01 mg/kg intramuscular tacrolimus. Administration to the study group was performed 24 and 1 h before warm ischemia. Eight rats in the control group were injected with 0.1 c.c. of distilled water. Blood samples were collected from the tail veins of all the rats on the first, second and third days. Expression levels of TLR2 and TLR4 genes were analyzed using the polymerase chain reaction method, to determine any significant difference between the control and study groups on the days when blood was taken. TLR2 (p = 0.045) and TLR4 (p = 0.022) levels in the study group were found to be statistically, and significantly, lower than those in the control group, on the second day following warm-ischemia- and reperfusion-induced injury. Administration of immunosuppressive drugs to healthy donor rats led to a statistically significant reduction in the expression levels of TLR2 and TLR4 in the early period. In light of the data obtained by this study, we hypothesize that a preoperative therapy on donors might have a role in preventing I/R injury.

Celastrol protects kidney against ischemia–reperfusion-induced injury in rats

BackgroundIschemia–reperfusion (IR) causes various damages in renal tissues, which is exacerbated by hypoxia-induced excessive inflammation and deteriorates the prognosis of patients after kidney surgery. Celastrol is a potent inflammation inhibitor that has little toxicity. In this report, we investigated whether celastrol protects against IR-induced renal injury in rats. Materials and methodsRenal IR injury was induced by occlusion of the bilateral renal pedicles for 45 min followed by reperfusion for 6 h. Celastrol or vehicle solution was intraperitoneally injected 30 min before renal ischemia, respectively. Renal histology, function, and pro-inflammatory cytokines and mediators were assessed. The effect of celastrol on nuclear translocation of nuclear factor kappa B (NF-κB) was also measured. ResultsCelastrol significantly suppressed elevation of the renal function markers and the lipid peroxidation level, alleviated renal tubular damage, and decreased the levels of tumor necrosis factor-α, interleukin-1β, and monocyte chemotactic protein-1 (MCP-1) messenger RNA in kidney caused by IR. Moreover, celastrol prevented IR-induced expression of pro-inflammatory mediators, which was associated with suppression of nuclear translocation of NF-κB subunit p65. ConclusionsCelastrol ameliorated the acute kidney injury caused by IR, which was associated with inhibiting local NF-κB activation and inflammation. Our findings suggest that celastrol could be useful for preventing IR-induced renal injury.

A novel bioactivity of andrographolide from Andrographis paniculata on cerebral ischemia/reperfusion-induced brain injury through induction of cerebral endothelial cell apoptosis

Context: Andrographolide, extracted from the leaves of Andrographis paniculata (Burm. f.) Nees (Acanthaceae), is a labdane diterpene lactone. It is widely reported to possess anti-inflammatory and antitumorigenic activities. Cerebral endothelial cells (CECs) play a crucial role in supporting the integrity and the function of the blood–brain barrier (BBB). However, no data are available concerning the effects of andrographolide in CECs. The aim of this study was to examine the detailed mechanisms of andrographolide on CECs.Objective: This study investigated a novel bioactivity of andrographolide on cerebral ischemia/reperfusion-induced brain injury.Materials and methods: CECs were treated with andrographolide (20–100 µΜ) for the indicated times (0–24 h). After the reactions, cell survival rate and cytotoxicity were tested by the MTT assay and the lactate dehydrogenase (LDH) test, respectively. Western blotting was used to detect caspase-3 expression. In addition, analysis of cell cycle and apoptosis using PI staining and annexin V-FITC/PI labeling, respectively, was performed by flow cytometry. We also investigated the effect of andrographolide on middle cerebral artery occlusion (MCAO)/reperfusion-induced brain injury in a rat model.Results: In the present study, we found that andrographolide (50–100 µΜ) markedly inhibited CEC growth according to an MTT assay and caused CEC damage according to a LDH test. Our data also revealed that andrographolide (50 µM) induced CEC apoptosis and caspase-3 activation as respectively detected by PI/annexin-V double staining and western blotting. Moreover, andrographolide arrested the CEC cell cycle at the G0/G1 phase by PI staining. In addition, andrographolide (5 mg/kg) caused deterioration of MCAO/reperfusion-induced brain injury in a rat model.Conclusions: These data suggest that andrographolide may disrupt BBB integrity, thereby deteriorating MCAO/reperfusion-induced brain injury, which are, in part, associated with its capacity to arrest cell-cycle and induce CEC apoptosis.

Cardioprotective potential of Allium humile leaves extract

The present study has been designed to investigate the efficacy of various extracts of Allium humile leaves to limit ischaemia and reperfusion-induced myocardial injury in wister albino rats. Various extracts of Allium humile leaves were prepared viz. Pet.ether, chloroform, acetone and methanol. These extracts evaluated for cardioprotective effect. Isolated perfused rat heart was subjected to global ischaemia for 30 min. followed by reperfusion for 120 min. Coronary effluent was analysed for LDH and CK-MB release to assess the degree of cardiac injury. Myocardial infarct size was estimated macroscopically using TTC staining by volume method. The present study demonstrates that methanolic extract of Allium humile leaves significantly prevented myocardial infarct size and markedly reduced LDH and CK-MB release in coronary effluent at dose level of 100 mg/kg body weight as compared with that of standard ramipril (1 mg/kg body weight). These results suggest that cardioprotective effect of methanolic extract of Allium humile was found significant (p < 0.05) as compared to vehicle control group.

Sa1934 Importance of Thromboxane A2/Prostacyclin Balance in Pathogenic Mechanism of Ischemia/ Reperfusion-Induced Gastric Injury in Mice

Sa1934 Importance of Thromboxane A2/Prostacyclin Balance in Pathogenic Mechanism of Ischemia/ Reperfusion-Induced Gastric Injury in Mice

The effect of mesenchymal stem cell therapy on ischemia–reperfusion-induced injury of the rat pancreas

The effect of mesenchymal stem cell therapy on ischemia–reperfusion-induced injury of the rat pancreas

Pharmacological activation of mitochondrial BKCa channels protects isolated cardiomyocytes against simulated reperfusion-induced injury

The aim of this study was to find out whether opening of mitochondrial large-conductance Ca(2+)-activated potassium channels (BK(Ca)) protects cardiomyocytes against injury caused by simulated ischemia and reperfusion. This study also aimed to determine whether the protective mechanism involves signaling by reactive oxygen species (ROS) and phosphatidylinositol-3-kinase (PI3K). We used isolated ventricular myocytes, which are believed to contain no functional BK(Ca) channels in the sarcolemma. Cells were isolated from the left ventricles of adult male Wistar rats and subjected to 25-min metabolic inhibition with NaCN and 2-deoxyglucose followed by 30-min re-energization. NS11021 (0.1 μmol/L), a novel BK(Ca) channel opener, or hydrogen peroxide (2 μmol/L) added at re-energization, increased cell survival (the number of rod-shaped cells) and markedly reduced the release of lactate dehydrogenase (LDH). These cytoprotective effects of NS11021 were completely abolished by paxilline, a BK(Ca) inhibitor, or tempol, an antioxidant, but not by wortmannin, an inhibitor of PI3K. NS11021 slightly but significantly increased the fluorescence signal in 2'7'-dichlorodihydrofluorescein diacetate (DCF-DA)-loaded myocytes, indicating an increased ROS formation. The NS11021-induced ROS formation was abolished by paxilline or tempol. NS13558 (0.1 μmol/L), an inactive structural analogue of NS11021, affected neither cell survival/LDH release nor DCF-DA fluorescence. These results suggest that pharmacological activation of mitochondrial BK(Ca) channels effectively protects isolated cardiomyocytes against injury associated with simulated reperfusion. The mechanism for this form of protection requires ROS signaling, but not the activation of the PI3K pathway.

Remote ischemic postconditioning enhances cell retention in the myocardium after intravenous administration of bone marrow mesenchymal stromal cells

Efficacy of intravenous administration of mesenchymal stromal cells (MSCs) for myocardial infarction (MI) is limited by low cell retention in the damaged myocardium. Previous studies indicated that remote ischemic conditioning could protect against ischemia–reperfusion-induced injury by release of various cytokines including stromal cell derived factor-1 alpha (SDF-1α). However, whether remote ischemic postconditioning (RIPostC) can also enhance the retention of infused cells in the myocardium by activating MSC homing is unclear. In this study, RIPostC was induced with 4cycles of 5min occlusion and reperfusion of the abdominal aorta in female Sprague–Dawley (SD) rats which underwent ligation of the coronary artery 1week previously. Cytokine levels in serum and myocardium were evaluated by enzyme-linked immunosorbent assay (ELISA) at 1, 6, 24 and 48h after RIPostC. Then, a total of 4×106 male MSCs were infused intravenously at 24h after RIPostC. The number of survived cells in the myocardium was evaluated by real-time polymerase chain reaction analysis for Y chromosome and the heart function was evaluated by echocardiography at 1month after cell infusion. Furthermore, 10μg/kg rabbit anti-rat CXCR4 polyclonal antibody was injected intraperitoneally to prove the role of SDF-1α for RIPostC. RIPostC induced an increase in SDF-1α in serum at 1h and enhanced SDF-1α transcription and protein synthesis in the myocardium at 24h after the procedure. 1month after cell transplantation, RIPostC significantly increased MSC myocardial retention by 79.1±12.3% and thereby contributed to enhanced cardiac function in comparison with cell transplantation without RIPostC. Furthermore, blockade with a CXCR4-specific antibody after RIPostC markedly attenuated the enhancement of therapeutic efficacy. We conclude that RIPostC activated SDF-1α expression and enhanced retention of the infused MSCs in the injured myocardium. Priming of the heart with RIPostC might be a novel adjunctive approach for intravenous cell delivery.

Beneficial effects of hyperosmotic perfusion in the myocardium after ischemia/reperfusion injury in isolated rat hearts

A simple method to reduce the ischemia/reperfusion injury that can accompany cardiac surgery would have great clinical value. This study was to investigate the effect of hyperosmotic perfusion on ischemia/reperfusion injury in isolated perfused rat hearts. Forty male Sprague-Dawley rats were randomly divided either to have their isolated hearts perfused with normal osmotic buffer or buffer made hyperosmotic by addition of glucose. Hearts were then subjected to 30 min ischemia followed by 30 min reperfusion. Coronary flow, time to ischemic arrest, reperfusion arrhythmia, and ventricular function were recorded. Creatine phosphokinase leakage into the coronary artery, and myocardial content and activity of superoxide dismutase and catalase were also examined. Rat hearts with hyperosmotic perfusion showed higher coronary flow, a prolonged time to ischemic arrest (10.60 vs. 5.63 min, P<0.005), a lower reperfusion arrthythmia score (3.2 vs. 5.3, P<0.001), better ventricular function, and less creatine phosphokinase leakage (340.1 vs. 861.9, P<0.001) than normal osmotic controls. Myocardial catalase content and activity were increased significantly (1435 vs. 917 U/g wet weight, P<0.001) in hearts perfused with hyperosmotic solution in comparison to the normal osmotic controls. Pretreatment with hyperosmotic perfusion in normal rat hearts, which is attributed partly to the increased antioxidative activity, could provide beneficial effects from ischemia and reperfusion-induced injury by increasing coronary flow, and decreasing reperfusion arrhythmia.

Reduction of Infarct Size in Patients with Acute ST Elevation Myocardial Infarction by Postconditioning during Percutaneous Coronary Intervention : A Meta Analysis

BACKGROUND: Following an acute coronary artery occlusion, timely myocardial reperfusion by primary percutaneous coronary intervention (PCI) is the recommended therapy, but restoring blood flow can induce reperfusion injury. Myocardial postconditioning (POC), defined as a sequence of intermittent interruptions of coronary blood flow applied at the onset of reperfusion after a period of sustained ischemia, has been shown to attenuate infarct size and reperfusion injury in patients with acute myocardial infarction undergoing PCI. METHODS: This is a meta-analysis of the available data from randomized trials on the effects of postconditioning on infarct size, as measured by single-photon emission computed tomography (SPECT) in ST elevation myocardial infarction (STEMI) patients who underwent PCI . RESULTS: Four randomized control trial studies were identified, comprising 244 patients with STEMI undergoing PCI with or without postconditioning. No adverse events occurred in the postconditioning group. Pooled analysis of all studies demonstrated a significant reduction in infarct size with postconditioning relative to standard care (standard mean difference -0.82, 95% CI -1.10 to -0.55; p=0.00005) as measured by SPECT. CONCLUSION: Postconditioning is a safe and feasible strategy that may reduce the infarct size in patients with STEMI and confer cardioprotection in the clinical setting.

Efeito protetor do per-condicionamento isquêmico remoto nas lesões da síndrome de isquemia e reperfusão renal em ratos

To evaluate the protective effect of remote ischemic per-conditioning in ischemia and reperfusion-induced renal injury. Fifteen rats (Rattus norvegicus) were randomized into three groups (n = 5): Group Normality (GN), Control Ischemia and Reperfusion (GIR) and Group remote ischemic per-conditioning (GPER). With the exception of the GN group, all others underwent renal ischemia for 30 minutes. In group GPER we performed the ischemic remote per-conditioning, consisting of three cycles of ischemia and reperfusion applied every five minutes during the ischemic period, to the left hindlimb of the rats by means of a tourniquet. To quantify the lesions we measured serum levels of creatinine and urea, as well as analyzed renal histopathology. The GPER group presented with better levels of urea (83.74 ± 14.58%) and creatinine (0.72 ± 26.14%) when compared to GIR group, approaching the GN group. Histopathologically, the lower levels of medullary congestion and hydropic degeneration were found in group GPER. The remote ischemic per-conditioning had a significant protective effect on renal ischemia and reperfusion.

Pleiotropic Effects of Simvastatin Are Associated With Mitigation of Apoptotic Component of Cell Death Upon Lethal Myocardial Reperfusion-Induced Injury

Although statins exert non-lipid cardioprotective effects, their influence on cell death is not fully elucidated. For this purpose, we investigated whether simvastatin treatment (S, 10 mg/kg, 5 days) is capable of mitigating ischemia/reperfusion-induced (IR) apoptosis in the isolated rat hearts, which was examined using immunoblotting analysis. In addition, the content of signal transducer and activator of transcription 3 (STAT3) and its active form, phosphorylated STAT3 (pSTAT3-Thr(705)), was analyzed. Simvastatin induced neither variations in the plasma lipid levels nor alterations in the baseline content of analysed proteins with the exception of upregulation of cytochrome C. Furthermore, simvastatin significantly increased the baseline levels of pSTAT3 in contrast to the control group. In the IR hearts, simvastatin reduced the expression of Bax and non-cleaved caspase-3. In these hearts, phosphorylation of STAT3 did not differ in comparison to the non-treated IR group, however total STAT3 content was slightly increased. The improved recovery of left ventricular developed pressure co-existed with the increased Bcl-2/Bax ratio. In conclusion, pleiotropic action of statins may ameliorate viability of cardiomyocytes by favouring the expression of anti-apoptotic Bcl-2 and downregulating the pro-apoptotic markers; however STAT3 does not seem to be a dominant regulator of this anti-apoptotic action of simvastatin.

Protective effects of Chinese herbal medicine Naoshuantong on neurovascular unit in rats with cerebral ischemia/reperfusion injury

To investigate the protective effects of Naoshuantong, a compound traditional Chinese herbal medicine, on the main components of neurovascular unit in rats with cerebral ischemia/reperfusion injury. A total of 30 male Sprague-Dawley rats were randomly divided into sham-operated, ischemia/reperfusion, and ischemia/reperfusion plus Naoshuantong groups. The cerebral ischemia was induced by 1.5 h of middle cerebral artery occlusion, followed by unlocking the thread to induce reperfusion injury. After 24 h of reperfusion, neurological functional deficits were assessed, apoptosis of main components of neurovascular unit was determined by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling combined with neuronal nuclei antigen, glial fibrillary acidic protein or CD31 immunofluorescence double staining. Naoshuantong significantly reduced neurological functional deficits, and reduced neuron, astrocyte and vascular endothelium cell apoptosis induced by ischemia/reperfusion injury in the border zone of ischemic cortex. Naoshuantong is effective in protecting the neurovascular unit including neurons, astrocytes and vascular endothelium cells against cerebral ischemia/reperfusion-induced apoptosis.

A novel CB2 agonist, COR167, potently protects rat brain cortical slices against OGD and reperfusion injury

Cannabinoid CB2 receptor activation has been shown to have many pharmacological but not psychotropic effects. The aim of this study was to investigate the potential protection of brain tissues afforded by the novel substituted 4-quinolone-3-carboxylic acid derivative COR167, a selective CB2 agonist, toward ischemia and reperfusion-induced injury, as well as the mechanism of this potential effect.Rat brain cortical slices subjected to oxygen and glucose deprivation (OGD) followed by re-oxygenation were used. Cell damage was quantified by measuring at the end of the reperfusion phase the release into the artificial cerebrospinal fluid (ACSF) of lactate dehydrogenase (LDH), glutamate, IL-6 and TNF-α and by evaluating in tissue the lipid-peroxides (thiobarbituric acid-reactive substances, TBARS), the free, reduced glutathione content (GSH) and the water gain (TWG), taken as an index of cell swelling.COR167 (10nM or 100nM), added to ACSF during the entire reperfusion phase, markedly reduced LDH and glutamate release, as well as TWG. Lower (0.1–1nM) or higher concentrations (1000nM) were ineffective, suggesting thereby an hormetic behavior. COR167 at 10nM concentration markedly reverted in tissues TBARS increase and GSH decrease, while reducing IL-6 and TNF-α release into ACSF. COR167 effects on glutamate and LDH release were abrogated by the selective CB2 inverse-agonists COR170 (1nM) and AM630 (1μM) but not by the CB1 antagonist AM251 (1μM). COR170 as well as AM630 per se were able to revert TWG.The CB2 receptor agonist COR167 potently protected rat brain cortical slices against OGD and reperfusion injury, partly through CB2 receptors activation.

A20 is up‐regulated in primary mouse hepatocytes subjected to hypoxia and reperfusion

Hepatic ischemia reperfusion-induced injury is a major medical concern, and it is important to characterize the adaptive mechanisms of hepatocytes to hypoxia and reoxygenation to sustain liver function. In this study, we reported a proteomic analysis of ischemia reperfusion-induced global responses in primary hepatocytes. The primary hepatocytes were isolated from mice and exposed to oxygen to mimic ischemia reperfusion. Total proteins were extracted from the cells and analyzed by two-dimensional gel electrophoresis followed by matrix-assisted laser desorption time-of-flight mass spectrometry. Zinc finger protein A20, mercaptopyruvate sulfur transferase, apolipoprotein E precursor and carbamoyl-phosphate synthase mitochondrial precursor were identified as differentially expressed in differently exposed groups. Reverse transcriptase polymerase chain reaction and Western blot analysis validated that A20 was significantly up-regulated in the hepatocytes subjected to hypoxia and reperfusion. In addition, the expression of peroxisome proliferator-activated receptor α, an A20 target, was up-regulated in the hepatocytes subjected to hypoxia and reperfusion. Our results on A20 provide new insight into the mechanism underlying the adaptation of hepatocytes to hypoxia and reperfusion. Because of its role in the up-regulation of peroxisome proliferator-activated receptor α expression to protect hepatocytes from reperfusion-induced apoptosis, A20 is a potential target for the prevention and therapy of liver injury after ischemia reperfusion.

Recombinant adeno-associated virus serotyoe 9 with CaMEK gene transfected on myocardial cells leads to reduce I/R-induced apoptosis

Objective To determine whether recombinant adeno-associated virus serotyoe 9 with CaMEK gene transfected on myocardial cells leads to reduce I/R-induced apoptosis.Methods Establish an ischemic/reperfusion(I/R) model of myocardial cells in vitro and the cells were divided into four experimental groups:(1) control group;(2) I/R group;(3) I/R+rAAV9-CBA-CaMEK group;(4) I/R+rAAV9-CBACaMEK+PD98059 group,respectively.The P-ERK1/2 and the Caspase-3,Bax were quqntitated by Western blot.Results These data clearly demonstrate that AAV9-mediated CaMEK gene transfected lead to active ERK1/2 and reduce I/R-induced apoptosis notablely.Conclusion rAAV9-mediated CaMEK gene transfected on myocardial cells can reduce I/R-induced apoptosis. Key words: Recombinant adeno-associated virus serotype 9; CaMEK gene; Ischemia reperfusioninduced injury; Apoptosis

THE GLUCAGON-LIKE PEPTIDE-1 RECEPTOR AGONIST EXENATIDE IS SAFE AND MAY BE CARDIOPROTECTIVE IN ACUTE MYOCARDIAL INFARCTION: THE EXAMI PHASE L TRIAL

.Reperfusion limits myocardial necrosis, however induces reperfusion injury leading to additional necrosis and apoptosis. Glucagon Like Peptide-1 (GLP-1), an incretin hormone, has anti-apoptotic properties and proved to be cardioprotective in experimental studies. This pilot study assessed the safety and feasibility of the GLP-1 receptor agonist exenatide in patients with acute MI undergoing primary PCI. Methods: Seventy-one non-diabetic patients with acute MI undergoing primary PCI were randomized to placebo or exenatide 5μg bolus administered in 30 minutes prior to PCI, followed by continuous infusion of 20μg/ 24 hours for 72 hours. Blood samples were obtained including enzymatic infarct size and glucose levels. Magnetic resonance imaging and echocardiography were conducted 3-5 days and 4 months post MI for measurements including infarct size, cardiac function and myocardial salvage index (MSI), a predictor for mortality and major adverse cardiac events. Results: Forty out of 71 randomized patients completed the full protocol. Exclusion was mainly due to angiographic criteria. Patient characteristics were well balanced between the groups. An equal amount of hypo- and hyperglycemic episodes (glucose 10 mmol/L) were observed in both groups. No deaths, CABG or re-infarction occurred during the 4-month follow-up. Although more patients in the exenatide group experienced nausea (58% v 20%, p = 0.015), no decrease or cessation of exenatide was required. Infarct size, cardiac function and MSI at 4 months did not differ signiicantly. However, a trend towards a higher MSI was seen in patients with TIMI 0 and 1 low receiving exenatide (0.65 ± 0.14 (n = 12) v 0.53 ± 0.17 (n = 11), p = 0.09). Conclusions: We demonstrated that administering exenatide in patients with acute MI undergoing primary PCI is feasible and safe. Although not powered for this analysis, Exami phase l seems to show a trend towards a higher MSI in the exenatide group. A large randomized placebo controlled study is required to assess the eficacy of exenatide on myocardial salvage.

A myocardial ischemia- and reperfusion-induced injury is mediated by reactive oxygen species released from blood platelets

In recent experimental studies, blood platelets have been found to exhibit some cardiodepressive effects in ischemic and reperfused guinea pig hearts independent of thrombus formation. These effects seemed to be mediated by reactive oxygen species (ROS). However, the source of these ROS – platelets or heart – remained still unknown. Isolated, buffer-perfused and pressure-volume work performing guinea pig hearts were exposed to a low-flow ischemia (1 ml/min) of 30 min duration and reperfused at a constant flow of 5 ml/min. Human thrombocytes were administered as 1 min bolus (20 000 thrombocytes/µl perfusion buffer) in the 15th min of ischemia or in the 1st or 5th min of reperfusion in the presence of thrombin (0.3 U/ml perfusion buffer). Recovery of external heart work (REHW) was expressed as ratio between postischemic and preischemic EHW in percent. Intracoronary platelet retention (RET) was quantified as percent of platelets applied. In a second set of experiments, thrombocytes were incubated with 10 µM of the irreversible NADPH oxidase blocker diphenyliodonium chloride and washed twice, thereafter, and administered according to the same protocol as described above. Hearts exposed to ischemia and reperfusion in the presence of thrombin but without application of platelets served as controls. Controls without application of platelets did not reveal a severe compromisation of myocardial function (REHW 85.5 ± 1%). However, addition of platelets during ischemia or in the 1st or 5th min of reperfusion led to a significant reduction of REHW as compared with controls (REHW 62.4 ± 6, 53.9 ± 3, 40.5 ± 3, respectively). Application of platelets pretreated with diphenyliodonium chloride did not reveal any cardiodepressive effects being significantly different from controls without platelet application. Moreover, treatment of platelets with diphenyliodonium chloride did not significantly decrease intracoronary platelet retention. In conclusion, these results demonstrate that cardiodepressive effects of human thrombocytes in ischemic and reperfused guinea pig hearts are mediated by ROS released from thrombocytes and not the heart.