Model Of Myocardial Reperfusion Injury Research Articles

Protective effect and mechanism of different proportions of “Danggui-Kushen” herb pair on ischemic heart disease

This study aims to investigate the protective effect and mechanism of “Danggui-Kushen” herb pair (DKHP) on ischemic heart disease (IHD). The rat model of myocardial reperfusion injury (MIRI) was established by ligation of the left anterior descending coronary artery. Rats were randomly divided into seven groups and administered orally for 7 days: control group, IHD group, DKHP1:1 group, DKHP1:2 group, DKHP2:1 group, DKHP1:3 group, DKHP3:1 group, the dosage was 2.7 g/kg. Measure electrocardiogram (ECG), myocardial infarction and injury assessment, Hematoxylin and eosin (HE) staining to evaluate myocardial injury and the protective effect of DKHP. Lactate dehydrogenase (LDH), Reactive oxygen species (ROS), IL-1β and IL-6 kit detection, immunohistochemical analysis, establishment of H9c2 cardiomyocyte hypoxia (Hypoxia) model, DKHP pretreatment for 3 h, MTT method to detect cell survival rate, cell immunofluorescence to observe NF- The expression of TLR-4, NF-κB, p-NF-κB, IKβα, p-IKβα, HIF-1α, VEGF and other genes and proteins were detected by κB nuclear translocation, mitochondrial membrane potential measurement, Western blot and Polymerase Chain Reaction (PCR). Compared with the model group, DKHP can reduce the size of myocardial infarction, reduce the levels of factors such as LDH, ROS, IL-1β and IL-6, and improve the cell survival rate; Compared with the model group, DKHP can inhibit the nuclear transfer of NF-κB and reduce mitochondrial damage; the results of immunohistochemical analysis, PCR and Western blot showed that compared with the model group, DKHP can reduce TLR-4, p-NF-κB, Expression levels of p-IKβα, HIF-1α, VEGF and other proteins. Reveal that DKHP may play a protective role in ischemic heart disease by reducing inflammation and oxidative stress damage. DKHP may have protective effect on ischemic heart disease, and its mechanism may be through reducing inflammatory response and oxidative stress damage to achieve this protective effect.

Imatinib attenuates reperfusion injury in a rat model of acute myocardial infarction

Following an acute myocardial infarction, reperfusion of an occluded coronary artery is often accompanied by microvascular injury, leading to worse long-term prognosis. Experimental studies have revealed the potential of tyrosine-kinase inhibitor imatinib to reduce vascular leakage in various organs. Here, we examined the potential of imatinib to attenuate microvascular injury in a rat model of myocardial reperfusion injury. Isolated male Wistar rat hearts (n = 20) in a Langendorff system and male Wistar rats (n = 37) in an in vivo model were randomly assigned to imatinib or placebo and subjected to ischaemia and reperfusion. Evans-blue/Thioflavin-S/TTC staining and Cardiac Magnetic Resonance Imaging were performed to assess the extent of reperfusion injury. Subsequently, in vivo hearts were perfused ex vivo with a vascular leakage tracer and fluorescence and electron microscopy were performed. In isolated rat hearts, imatinib reduced global infarct size, improved end-diastolic pressure, and improved rate pressure product recovery compared to placebo. In vivo, imatinib reduced no-reflow and infarct size with no difference between imatinib and placebo for global cardiac function. In addition, imatinib showed lower vascular resistance, higher coronary flow, and less microvascular leakage in the affected myocardium. At the ultrastructural level, imatinib showed higher preserved microvascular integrity compared to placebo. We provide evidence that low-dose imatinib can reduce microvascular injury and accompanying myocardial infarct size in a rat model of acute myocardial infarction. These data warrant future work to examine the potential of imatinib to reduce reperfusion injury in patients with acute myocardial infarction.

Effect of Endometrial Stem Cell-derived Cytokine Cocktail on a Mouse Model of Myocardial Reperfusion Injury.

Objective To study the effect of endometrial stem cells (EnSCs) derived cytokine cocktail (EdCC) on myocardial ischemic reperfusion injury (I/R) in a mouse model. Methods EdCC was concentrated from the culture medium of EnSCs with Millipore ultra-filtration technology and was administrated to a myocardial I/R mouse models through tail vein injection. The infarct area was determined by TTC/Evans Blue staining. The apoptotic cells were counted by TUNEL assay and the protein level of cleaved caspase 3 was evaluated by Western blotting. Results The EdCC extraction efficiency was (222.4±29.3) Μg/10(6) cells in every 24 h,but the protein gradually degraded under-80 ℃ storage. As compared with I/R group,100 Μg fresh EdCC decreased infarct area (P=0.001),reduced apoptotic nuclei in the infarct border (P=0.019),and inhibited cleaved caspase 3 expression (P=0.002). Increasing EdCC dosage did not further reduce the infarct area. The myocardial protective effect of EdCC diminished after 90 days' storage under-80 ℃. Conclusion EdCC reduces myocardial I/R injury through protecting cardiomyocytes from apoptosis within 30 days storage under-80 ℃.

Abstract 12337: Platelet-neutrophil Complex Infiltration is Regulated by Serotonin in a Mouse Model of Myocardial Reperfusion Injury

Background: Myocardial reperfusion injury leads to platelet neutrophil complex (PNCs) migration into cardiac tissue, which promotes post-infarction necrosis. Local serotonin levels are elevated during ischemia and platelet serotonin promotes recruitment of inflammatory cells. Tryptophan hydroxylase-1-deficient mice (Tph1-/-) lack peripheral serotonin and show attenuated inflammatory response. We evaluated PNC infiltration after myocardial ischemia reperfusion (I/R) in the absence of peripheral serotonin. Methods: C57Bl/6 (WT) and Tph1-/- mice underwent coronary artery ligation to induce myocardial infarction. Reperfusion was allowed after 30min, heart function determined by echocardiography after 24h. Hearts were excised to evaluate infarct size. PNC content was determined by flow cytometry and histology. The function of healthy WT and Tph1-/- hearts was analyzed in an ex vivo working heart model and compared to global flow/no flow/flow. Cardiomyocytes were isolated from healthy WT and Tph1-/- mice and their survival following different in vitro challenges was assessed over 48h. Results: Infarct size was 37±9% in Tph1-/- and 53±13% area at risk in WT mice (p<0.01). Fractional shortening in echocardiography was better in Tph1-/- mice (49±4% vs. 41±6%, p<0.05), whereas cardiac power after no flow in the ex vivo working heart assay was similar (33±4 vs. 31±3mW/gHW). Isolated cardiomyocytes of Tph1-/- and WT mice showed similar survival after 48h (11.5% vs. 8.8%). These data indicate that contractility and cardiomyocyte function were independent of serotonin in this setting. Histology displayed a reduced number of PNCs in Tph1-/- hearts (7±3) compared to WT (16±3/350μm2, p<0.01). This was confirmed by flow cytometry of homogenized heart tissue (4±2 vs. 13±1%leukocytes, p<0.05) and blood samples (24±8 vs. 41±15%leukocytes; p<0.05). Conclusion: Lack of peripheral, i.e. platelet serotonin did not influence the function of isolated hearts or cardiomyocytes in vitro. However, PNC formation and infiltration was reduced in the absence of serotonin, resulting in attenuated reperfusion injury in vivo. Serotonin appears to account for up to 30% of myocardial reperfusion injury by promoting PNC formation.

Imaging of Receptors for Advanced Glycation End Products in Experimental Myocardial Ischemia and Reperfusion Injury

The aim of this study was to image expression of receptor for advanced glycation end products (RAGE) in a mouse model of myocardial reperfusion injury. RAGE and its ligands are implicated in the pathogenesis of ischemia/reperfusion injury and infarction. We hypothesized that RAGE-directed quantitative imaging of myocardial uptake of technetium-99m ((99m)Tc)-anti-RAGE F(ab')(2) in a mouse model of myocardial ischemic injury can detect RAGE expression and show quantitative differences between early (18 to 20 h) and later times (48 h) after reperfusion. Twenty-five wild-type (WT) mice underwent left anterior descending coronary artery occlusion for 30 min. Mice were injected with 19.98 ± 1.78 MBq of (99m)Tc anti-RAGE F(ab')(2) at 2 time points after reperfusion (at 18 to 20 h [n = 8] and at 48 h [n = 12]) and 5 h later with 6.14 ± 2.0 MBq of thallium-201 ((201)Tl). Five WT mice were injected with nonspecific F(ab')(2) and (201)Tl 18 to 20 h after reperfusion. Six WT mice underwent sham operation without coronary intervention. After injection with (201)Tl, all mice immediately underwent dual isotope single-photon emission computed tomography/computed tomography. At completion of imaging, hearts were counted and sectioned. The uptake of (99m)Tc-anti-RAGE F(ab')(2) in the ischemic zone from the scans as mean percentage injected dose was significantly greater at 18 to 20 h (5.7 ± 2.1 × 10(-3)%) as compared with at 48 h (1.4 ± 1.1 × 10(-3)%; p < 0.001) after reperfusion. Disease and antibody controls showed no focal uptake in the infarct. Gamma well counting of the myocardium supported the quantitative scan data. By immunohistochemical staining there was greater caspase-3 and RAGE staining at 18 to 20 h versus at 48 h (p = 0.04 and p = 0.01, respectively). On dual immunofluorescence, RAGE colocalized mainly with injured cardiomyocytes undergoing apoptosis. RAGE expression in myocardial ischemic injury can be imaged in vivo using a novel (99m)Tc-anti-RAGE F(ab')(2). RAGE plays a role in several cardiovascular diseases and is a potential target for clinical imaging.

Oxidant-induced cardiomyocyte injury: Identification of the cytoprotective effect of a dopamine 1 receptor agonist using a cell-based high-throughput assay

Myocyte injury due to myocardial reperfusion injury plays a crucial role in the pathogenesis of acute myocardial infarction even after successful coronary revascularization. Identification of compounds that reduce reperfusion-associated myocyte death is important. Therefore, we developed an in vitro model of myocardial reperfusion injury in H9c2 rat cardiomyocytes and applied a cell-based high-throughput approach to screen a standard library of pharmacologically active compounds (LOPAC) in order to identify drugs with cardioprotective effects. Oxidative stress was induced with hydrogen peroxide (H2O2) treatment, which resulted in approximately 50% reduction in cell viability. Test compounds were added at a 3-microM final concentration as a pretreatment or in a delayed fashion (30 min after the peroxide challenge in order to imitate pharmacological treatment following angioplasty). Cells were cultured for 3 or 24 h. Viability was quantitated with the methylthiazolyldiphenyl-tetrazolium bromide method. Cytotoxicity and cytoprotection were also evaluated by measuring the lactate dehydrogenase activity in the cell culture supernatant. The screening identified a number of compounds with cytoprotective action, including molecules that are known to interfere with components of DNA repair and cell cycle progression, e.g. poly(ADP-ribose) polymerase (PARP) inhibitors, topoisomerase inhibitors, and cyclin dependent kinase inhibitors, or reduce energy consumption by interfering with cardiac myofilament function. A number of dopamine D1 receptor agonists also provided significant cytoprotection at 3 h, but only three of them showed a similar effect at 24 h: chloro- and bromo-APB and chloro-PB hydrobromide. Chloro-APB hydrobromide significantly reduced peroxide-induced PARP activation in the myocytes independently of its action on dopamine D1 receptors, but lacked PARP inhibitor capacity in a cell-free PARP assay system. In conclusion, the pattern of cytoprotective drugs identified in the current assay supports the overall validity of our model system. The findings demonstrate that cytoprotective agents, including novel indirect inhibitors of cellular PARP activation can be identified with the method, chloro-APB hydrobromide being one such compound. The current experimental setting can be employed for cell-based high-throughput screening of various compound libraries.

Mechanism of cGMP-mediated protection in a cellular model of myocardial reperfusion injury

Reperfusion injury of the myocardium is characterised by development of cardiomyocyte hypercontracture. Previous studies have shown that cGMP-mediated stimuli protect against reperfusion injury, but the cellular mechanism is still unknown. To simulate ischemia/reperfusion, adult rat cardiomyocytes were incubated anoxically (pH(o) 6.4) and then reoxygenated (pH(o) 7.4). Cytosolic calcium [Ca(2+)](i) (fura-2 ratio), pH(i) (BCECF ratio), cell length, and phospholamban phosphorylation were analysed. Under simulated ischemia cardiomyocytes develop [Ca(2+)](i) overload. When reoxygenated they rapidly undergo hypercontracture, triggered by oscillations of [Ca(2+)](i). We investigated whether cGMP-mediated stimuli can modulate [Ca(2+)](i) or pH(i) recovery and whether this contributes to their protective effect. Membrane-permeable cGMP analogues, 8-bromo-cGMP (1 mmol/L) or 8-pCPT-cGMP (10 micrommol/L), or a receptor-mediated activator of particulate guanylyl cyclase, urodilatin (1 micromol/L), were applied. The investigated stimuli protect against reoxygenation-induced hypercontracture (cell length as percent of end-ischemic length; control: 68+/-1.6; 8-bromo-cGMP: 88+/-1.5*; 8-pCPT-cGMP: 84+/-2.9*; urodilatin: 87+/-1.1*; n=24; *p<0.05). Recovery from [Ca(2+)](i) overload after 2 min reoxygenation [fura-2 ratio (a.u.); control: 1.43+/-0.15; 8-bromo-cGMP: 1.86+/-0.15*; 8-pCPT-cGMP: 1.92+/-0.19*; urodilatin: 1.93+/-0.24*; n=25; *p<0.05] was accelerated, and the frequency of [Ca(2+)](i) oscillations (min(-1)) was significantly reduced (control: 49+/-5.0 min(-1); 8-bromo-cGMP: 18+/-3.5* min(-1); 8-pCPT-cGMP: 18+/-4.5* min(-1); urodilatin: 16+/-4.1* min(-1); n=24; *p<0.05). cGMP-mediated stimuli increased sarcoplasmic Ca(2+) sequestration (caffeine-releasable Ca(2+) pool: 2-3 fold increase vs. control). Inhibition of sarcoplasmic Ca(2+)-ATPase (SERCA) by thapsigargin (150 nmol/L) or of protein kinase G with KT-5823 (1 micromol/L) abolished the effect of these stimuli on [Ca(2+)](i) recovery. The investigated stimuli significantly enhanced phospholamban phosphorylation. We conclude that cGMP-dependent signals activate SERCA via a protein kinase G-dependent phosphorylation of phospholamban. The increase in SERCA activity seems to reduce peak [Ca(2+)](i) and [Ca(2+)](i) oscillation during reoxygenation and to attenuate the excessive activation of the contractile machinery that otherwise leads to the development of hypercontracture.

Proteasome inhibition ablates activation of NF-kappa B in myocardial reperfusion and reduces reperfusion injury.

Both acute coronary occlusion and reperfusion of an infarct-related artery lead to significant myocardial cell death. Recent evidence has been presented that activation of the transcription factor nuclear factor-kappaB (NF-kappaB) plays a critical role in reperfusion injury. NF-kappaB is usually bound to its inhibitor, IkappaB, and classic activation of NF-kappaB occurs when the 20S proteasome degrades IkappaB that has been phosphorylated and ubiquitinated. In this study, activation of NF-kappaB was inhibited by systemic administration of a 20S proteasome inhibitor (PS-519) in a porcine model of myocardial reperfusion injury. The experimental protocol induced myocardial ischemia in the distribution of the left anterior descending coronary artery for 1 h with subsequent reperfusion for 3 h. A single systemic treatment with PS-519 reduced 20S proteasome activity; blocked activation of NF-kappaB induced by reperfusion; reduced creatine kinase, creatine kinase-muscle-brain fraction, and troponin I release from the myocardium; preserved regional myocardial function measured by segmental shortening; significantly reduced the size of myocardial infarction; and exhibited no acute toxicity. These data show that myocardial reperfusion injury can be inhibited by using proteasome inhibitors, which likely function through the inhibition of NF-kappaB activation.

Leukocyte and endothelial cell adhesion molecules in a chronic murine model of myocardial reperfusion injury.

Expression of endothelial and leukocyte cell adhesion molecules is a principal determinant of polymorphonuclear neutrophil (PMN) recruitment during inflammation. It has been demonstrated that pharmacological inhibition of these molecules can attenuate PMN influx and subsequent tissue injury. We determined the temporal expression of alpha-granule membrane protein-40 (P-selectin), endothelial leukocyte adhesion molecule 1 (E-selectin), and intercellular cell adhesion molecule 1 (ICAM-1) after coronary artery occlusion and up to 3 days of reperfusion. The expression of all of these cell adhesion molecules peaked around 24 h of reperfusion. We determined the extent to which these molecules contribute to PMN infiltration by utilizing mice deficient (-/-) in P-selectin, E-selectin, ICAM-1, and CD18. Each group underwent 30 min of in vivo, regional, left anterior descending (LAD) coronary artery ischemia and 24 h of reperfusion. PMN accumulation in the ischemic-reperfused (I/R) zone was assessed using histological techniques. Deficiencies of P-selectin, E-selectin, ICAM-1, or CD18 resulted in significant (P < 0.05) attenuation of PMN infiltration into the I/R myocardium (MI/R). In addition, P-selectin, E-selectin, ICAM-1, and CD18 -/- mice exhibited significantly (P < 0.05) smaller areas of necrosis after MI/R compared with wild-type mice. These data demonstrate that MI/R induces coronary vascular expression of P-selectin, E-selectin, and ICAM-1 in mice. Furthermore, genetic deficiency of P-selectin, E-selectin, ICAM-1, or CD18 attenuates PMN sequestration and myocardial injury after in vivo MI/R. We conclude that P-selectin, E-selectin, ICAM-1, and CD18 are involved in the pathogenesis of MI/R injury in mice.

Effect of dantrolene in an in vivo and in vitro model of myocardial reperfusion injury.

In skeletal muscle, dantrolene reduces free cytosolic calcium by inhibiting calcium release from the sarcoplasmic reticulum. A similar effect in ischemic-reperfused heart cells would protect myocardial tissue against reperfusion injury. We tested the hypothesis that dantrolene infusion during reperfusion protects the heart against reperfusion injury. Isovolumetric beating rat hearts were subjected to 30 min of ischemia followed by 60 min of reperfusion. Left ventricular (LV) developed pressure (LVDP) and creatine kinase release (CKR) were determined as indices of myocardial performance and cellular injury, respectively. In the treatment groups, dantrolene (25 (DAN25) or 100 (DAN100) micromol l(-1)) was infused during the first 15 min of reperfusion; control hearts received the respective concentration of the vehicle (mannitol (CON25, CON100), each group n=7). To investigate the effects of dantrolene on reperfusion injury in vivo, 18 chloralose-anesthetized rabbits were subjected to 30 min occlusion and 180 min reperfusion of a major coronary artery. LV pressure (LVP), cardiac output (CO), and infarct size were determined. During the last 5 min of ischemia, nine rabbits received 10 mg kg(-1) dantrolene intravenously (DAN). Another nine rabbits received the vehicle (dimethylsulfoxide) and served as controls (CON). In isolated rat hearts, there was no recovery of LVDP in any group. Total CKR during 1 h of reperfusion was 845+/-76 (CON100) and 550+/-81 U g(-1) dry mass (DAN100, P<0.05). In rabbits in vivo, hemodynamic baseline values were similar between groups (CON vs. DAN: LVP, 99+/-6 (mean+/-SEM) vs. 91+/-6mm Hg, P=0.29; CO, 252+/-26 vs. 275+/-23 ml min(-1), P= 0.53). During coronary artery occlusion, LVP and CO were reduced in both groups (CON: LVP, 89+/-3%; CO, 90+/-5% of baseline values) and LVP did not recover to baseline values during reperfusion (51+/-5% (CON) vs. 67+/-7% (DAN) of baseline, P=0.10). Infarct size was 41+/-4% of the area at risk in controls and 37+/-6% in dantrolene treated hearts (P=0.59). Dantrolene reduced CKR, indicating an attenuation of lethal cellular reperfusion injury in isolated rat hearts. However, in the rabbit in vivo, there was no effect on the extent of reperfusion injury after regional myocardial ischemia.

A single cell model of myocardial reperfusion injury: changes in intracellular Na+ and Ca2+ concentrations in guinea pig ventricular myocytes.

To investigate the contribution of the changes in intracellular Na+ and Ca2+ concentrations ([Na+]i and [Ca2+]i) to myocardial reperfusion injury, we made an ischemia/reperfusion model in intact guinea pig myocytes. Myocardial ischemia was simulated by the perfusion of metabolic inhibitors (3.3 mM amobarbital and 5 microM carbonyl cyanide m-chlorophenylhydrazone) with pH 6.6 and reperfusion was achieved by the washout of them with pH 7.4. [Na+]i increased from 7.9 +/- 2.0 to 14.0 +/- 3.4 mM (means +/- S.E., p < 0.01 ) during 7.5 min of simulated ischemia (SI) and increased further to 18.8 +/- 3.0 mM at 7.5 min after reperfusion. [Ca2+]i, expressed as the ratio of fluo 3 fluorescence intensity, increased to 133 +/- 8% (p < 0.01) during SI and gradually returned to the control level after reperfusion. Intracellular pH decreased from 7.53 +/- 0.04 to 6.31 +/- 0.04 (p < 0.01) and recovered quickly after reperfusion. Reperfusion with the acidic solution or the continuous perfusion of hexamethylene amiloride (2 microM) prevented the reperfusion-induced increase in [Na+]i. When the duration of SI was prolonged to 15 min, the cell response after reperfusion varied, 16 of 37 cells kept quiescent, 21 cells showed spontaneous Ca2+ waves, and 4 cells out of these 21 cells became hypercontracted. In quiescent cells, both [Na+]i and [Ca2+]i decreased immediately after reperfusion. In cells with Ca2+ waves, [Na+]i transiently increased further at the early phase of reperfusion, while [Ca2+]i declined. In hypercontracted cells, [Na+]i increased as much as in 'Ca2+ wave' cells, but [Ca2+]i increased extensively and both ion concentrations continued to increase. Reperfusion with the Ca2+-free solution prevented both the [Ca2+]i increase and morphological change. In the presence of ryanodine (10 microM), the increase in [Ca2+]i after reperfusion was augmented and some cells became hypercontracted. We concluded that (1) Na+/H+ exchange is active both during SI and reperfusion, resulting in the additional [Na+]i elevation on reperfusion, (2) the [Na+]i level after reperfusion and the following Ca2+ influx via Na+/Ca2+ exchange are crucial for reperfusion cell injury, and (3) the Ca2+ buffering capacity of sarcoplasmic reticulum would also contribute to the Ca2+ regulation and cell injury after reperfusion.

Lack of any additional benefit in combining aspirin with iloprost in a canine model of myocardial reperfusion injury.

The effects of iloprost infusion (100 ng/kg/min for 75 min) alone and in combination with aspirin (3 mg/kg IV bolus) were compared in a canine model of myocardial reperfusion injury. Regional ischemia of 40 min was produced by temporary occlusion of the left anterior descending coronary artery, after which the myocardium was reperfused for a period of 3 hours. Mean arterial pressure (MAP), heart rate (HR), left ventricular end diastolic pressure (LVEDP), positive (+) LVdP/dtmax and negative (-) LVdP/dtmax were monitored. Rate pressure product and (-) dP/dt/Pmax were also derived from the above. Myocardial tissue levels of adenosine triphosphate (ATP), creatine phosphate (CP), glycogen and lactate were estimated. Following reperfusion in the saline treated group, there was a significant fall in (i) MAP, (ii) (+) LVdP/dtmax and (iii) (-) LVdP/dtmax. LVEDP was corrected about 2 hours after reperfusion. Despite correction of lactate accumulation, ATP and glycogen were not restored although the CP store was replenished. The hemodynamic profiles in both iloprost and in combination treated groups were similar; (i) depressed MAP (particularly during iloprost infusion) without any significant change in HR (ii) no significant depression in (+) LVdP/dtmax (iii) depression in (-) LVdP/dtmax but not when corrected for lower Pmax and (iv) a significant reduction in the incidence of reperfusion arrhythmias. Similarly, in both the drug/s treated groups, ATP, CP and lactate were normalised although glycogen store was not restored. The results of this study indicate (i) cardioprotective effect of iloprost even when administered prior to reperfusion and (ii) no additional protective effect of combining iloprost and aspirin.

Lack of Any Additional Benefit in Combining Aspirin with Iloprost in a Canine Model of Myocardial Reperfusion Injury

The effects of iloprost infusion (100ng/kg/min for 75 min) alone and in combination with aspirin (3mg/kg IV bolus) were compared in a canine model of myocardial reperfusion injury. Regional ischemia of 40 min was produced by temporary occlusion of the left anterior descending coronary artery, after which the myocardium was reperfused for a period of 3 hours. Mean arterial pressure (MAP), heart rate (HR), left ventricular end diastolic pressure (LVEDP), positive (+) LVdP/dt max and negative (−) LVdP/dt max were monitored. Rate pressure product and (−) dP/dt/P max were also derived from the above. Myocardial tissue levels of adenosine triphosphate (ATP), creatine phosphate (CP), glycogen and lactate were estimated. Following reperfusion in the saline treated group, there was a significant fall in (i) MAP, (ii) (+) LVdP/dt max and (iii) (−) LVdP/dt max. LVEDP was corrected about 2 hours after reperfusion. Despite correction of lactate accumulation, ATP and glycogen were not restored although the CP store was replenished. The hemodynamic profiles in both iloprost and in combination treated groups were similar; (i) depressed MAP (particularly during iloprost infusion) without any significant change in HR (ii) no significant depression in (+) LVdP/dt max (iii) depression in (−) LVdP/dt max but not when corrected for lower P max and (iv) a significant reduction in the incidence of reperfusion arrhythmias. Similarly, in both the drug/s treated groups, ATP, CP and lactate were normalised although glycogen store was not restored. The results of this study indicate (i) cardioprotective effect of iloprost even when administered prior to reperfusion and (ii) no additional protective effect of combining iloprost and aspirin.

Expression of sialyl Lewis(X) in rat heart with ischaemia/reperfusion and reduction of myocardial reperfusion injury by a monoclonal antibody against sialyl Lewis(X)

Neutrophils which infiltrate into the myocardial tissue subjected to ischaemia, followed by reperfusion, play a major role in myocardial reperfusion injury. It is known that early rolling attachment of neutrophils is mainly mediated by the selection family of cell-adhesion molecules and that this adhesion is then strengthened through the interaction of integrins and intercellular adhesion molecule-1. To investigate the role of sialyl Lewis(X) (SLe(X)), which is a ligand of all three members of the selections, in myocardial reperfusion injury, the expression of SLe(X) was examined in rat hearts subjected to 30 min of ischaemia followed by reperfusion. The effects were also analysed of in vivo administration of an anti-SLe(X) monoclonal antibody (MAb) on myocardial necrosis in a rat model of myocardial reperfusion injury. Reperfusion of ischaemic myocardial tissue resulted in enhanced expression of SLe(X) on the luminal surface of vascular endothelial cells (VECs), as well as cardiac myocytes. Furthermore, the in vivo administration of an anti-SLe(X) MAb significantly reduced the extent of the myocardial infarction developed after 30 min of ischaemia followed by 48 h of reperfusion. These findings indicate that SLe(X) plays a critical role in the development of myocardial reperfusion injury and offer a potentially useful immune therapy to protect against this injury.

923-1 Inhibition of Neutrophil Function by Lidocaine as a Mechanism for the Beneficial Effect to Reduce Myocardial Reperfusion Injury

We have recently shown that lidocaine (lido) significantly reduces infarct size in the rabbit model of Myocardial Reperfusion Injury (MRI). In that study rabbits (n = 22) underwent 30 mins of circumflex occlusion and 48 hrs of reperfusion and where randomized in a blinded fashion to receive lido (n = 11, 4 boluses of 10 mg/kg in the first 10 mins of ischemia) or saline (n = 11). Lido reduced infarct size by approximately 50% (p &lt; 0.01) of the area at risk. The present study further examines possible mechanisms for this beneficial effect. We studied the reperfused myocardium of both groups in a blinded fashion for histologic changes including the degree of neutrophil infiltration (PMN). hemorrhage (Hemo) and contraction bands (Band). Associated with the reduction on infarct size, lido inhibited the PMN infiltration and hemorrhage in these hearts. We next examined the effects of lido ex vivo on PMN activation by chemiluminescence in whole blood. A significant reduction in the chemiluminescence response to the chemoattractant FMLP was obtained with rabbit and human blood. Chemiluminescence results expressed as percent inhibition of FMLP response. Mean ± SEM: (i) The beneficial effect of lido on infarct size was associated with a significant reduction in the accumulation of PMNs in the reperfused rabbit myocardium. (ii) This beneficial effect may occur as a direct inhibitory effect of lido on PMNs. (iii) This effect of lido on infarct size may also occur in man as human cells respond similarly in vitro to equal doses of lidocaine. (iiii) Lidocaine may confound the interpretation of other interventions to reduce infarct size in animals and possibly in man.