Inhibition of lipid peroxidation with the lazaroid U74500A attenuates ischemia-reperfusion injury in a canine orthotopic heart transplantation model

A guide to ferroptosis, the biological rust of cellular membranes

Unprotected iron can rust due to oxygen exposure. Similarly, in our body, oxidative stress can kill cells in an iron-dependent manner, which can give rise to devastating diseases. This type of cell death is referred to as ferroptosis. Generally, ferroptosis is defined as an iron-catalyzed form of regulated necrosis that occurs through excessive peroxidation of polyunsaturated fatty acids within cellular membranes. This review summarizes how ferroptosis is executed by a rather primitive biochemical process, under tight regulation of lipid, iron, and redox metabolic processes. An overview is given of major classes of ferroptosis inducers and inhibitors, and how to detect ferroptosis. Finally, its detrimental role in disease is briefly discussed.

Heart Transplantation From Brain Dead Donors: A Systematic Review of Animal Models

Despite advances in mechanical circulatory devices and pharmacologic therapies, heart transplantation (HTx) is the definitive and most effective therapy for an important proportion of qualifying patients with end-stage heart failure. However, the demand for donor hearts significantly outweighs the supply. Hearts are sourced from donors following brain death, which exposes donor hearts to substantial pathophysiological perturbations that can influence heart transplant success and recipient survival. Although significant advances in recipient selection, donor and HTx recipient management, immunosuppression, and pretransplant mechanical circulatory support have been achieved, primary graft dysfunction after cardiac transplantation continues to be an important cause of morbidity and mortality. Animal models, when appropriate, can guide/inform medical practice, and fill gaps in knowledge that are unattainable in clinical settings. Consequently, we performed a systematic review of existing animal models that incorporate donor brain death and subsequent HTx and assessed studies for scientific rigor and clinical relevance. Following literature screening via the U.S National Library of Medicine bibliographic database (MEDLINE) and Embase, 29 studies were assessed. Analysis of included studies identified marked heterogeneity in animal models of donor brain death coupled to HTx, with few research groups worldwide identified as utilizing these models. General reporting of important determinants of heart transplant success was mixed, and assessment of posttransplant cardiac function was limited to an invasive technique (pressure-volume analysis), which is limitedly applied in clinical settings. This review highlights translational challenges between available animal models and clinical heart transplant settings that are potentially hindering advancement of this field of investigation.

Effects of different steroid treatment on reperfusion-associated production of reactive oxygen species and arrhythmias during coronary surgery

BACKGROUND

During conventional cardiac surgery ischemia and reperfusion may cause excessive production of reactive oxygen species leading to tissue damage including early arrhythmias. We therefore assessed the kinetics of markers of radical stress including oxidized and reduced glutathione (GSSG/GSH), oxidized proteins (PCG) and malondialdehyde (MDA), and tested the hypothesis that different steroid treatments inhibit these markers and early reperfusion-associated supraventricular and ventricular extrasystolic beats.

METHODS

In a randomized, controlled, blinded, prospective trial 36 patients received a preoperative infusion of methylprednisolone (MP, 15 mg kg-1, n = 12), tirilazad mesylate (TM, 10 mg kg-1, n = 12) or placebo (PL, NaCl, n = 12). Coronary sinus and arterial blood was drawn at baseline and 2, 5, 15, 30, 60 and 240 min after aortic declamping. Holter-ECG analysis was used to identify arrhythmias.

RESULTS

Cardiac GSSG release occurred very early (< 15 min) and was not significantly attenuated by either drug treatment. Cardiac PCG production showed biphasic increases, lasted > 4 h and was significantly reduced only by TM. Cardiac MDA release was short (< 30 min) and significantly reduced by MP and TM. Neither treatment had a significant influence on the early occurrence of ventricular or supraventricular arrhythmias. The number of patients needing cardioversions or defibrillations also were not different.

CONCLUSIONS

The results indicate that cardiac production of reactive oxygen species occurs after reperfusion in humans and is not inhibited by steroid treatment. Steroid treatment effectively reduces lipid peroxidation during cardiac surgery but has no influence on arrhythmias.

Lazaroid (U74389G)-supplemented cardioplegia: results of a double-blind, randomized, controlled trial in a porcine model of orthotopic heart transplantation

BACKGROUND

U74389G (16-desmethyl tirilazad), a 21-aminosteroid or "lazaroid," inhibits lipid peroxidation, which is an important element of ischemia-reperfusion injury. The aim of this study was to determine whether the addition of U74389G to the cardioplegic preservation solution could improve early cardiac allograft function.

METHODS

A porcine model of donor brain death and orthotopic cardiac transplantation was used. Hearts were arrested and preserved for 6 hours in an aspartate-enriched extracellular cardioplegia that had been supplemented with either U74389G and its carrier (n = 7) or the carrier alone (n = 9). Epicardial sonomicrometry and transmyocardial micromanometry were used to obtain pressure-volume loops before and after transplantation. Left ventricular wall volume was measured by volume displacement.

RESULTS

A higher proportion of U74389G-treated hearts were weaned successfully from cardiopulmonary bypass, but this difference did not achieve statistical significance (86% [6 of 7] vs 56% [5 of 9]; p = 0.308). In the hearts that were weaned successfully, preservation of left ventricular contractility, as judged by the pre-load recruitable stroke work relationship, was significantly better in the U74389G-treated hearts (p = 0.0271). In contrast, left ventricular compliance, as judged by the end-diastolic pressure-volume relationship, was significantly better preserved in the control group (p < 0.0001). U74389G-treated hearts developed less myocardial edema, as judged by the post-transplant left ventricular wall volume/baseline steady-state epicardial end-diastolic volume ratio (64 +/- 9% vs 76 +/- 11%; p = 0.045).

CONCLUSIONS

The benefit obtained from U74389G-supplemented cardioplegic preservation solution was marginal for hearts stored for 6 hours. After longer ischemic times, the benefit may be clearer.

Cardioprotective effect of ischemic preconditioning on global myocardial ischemia in a sheep right heart bypass model

OBJECTIVES

Ischemic preconditioning has been used to induce the myocardium to adapt to ischemic stress preceded by short periods of ischemia and reperfusion. We used a sheep right heart bypass model with a conductance catheter to assess the cardioprotective effect of ischemic preconditioning on 30-minute normothermic global myocardial ischemia.

METHODS

Ischemic preconditioning was conducted in 6 sheep in 35-minute aortic cross-clampings interspersed with 5 minutes of reperfusion during cardiopulmonary bypass, with 6 sheep as time-matched controls. Global myocardial ischemia was subsequently achieved in 30-minute aortic cross-clamping with left ventricular unloading during normothermic cardiopulmonary bypass. Weaning from cardiopulmonary bypass was conducted 40 minutes after reperfusion. Before ischemia and 40, 70, and 100 minutes after reperfusion, left ventricular pressure-volume loops were measured using a conductance catheter during right heart bypass preparation. Left ventricular contractility, diastolic function, and mechanical efficiency were then evaluated. Right heart bypass was instituted to control the preload and to decompress the right ventricle completely, thereby eliminating parallel conductance variation.

RESULTS

No differences in the studied parameters were seen between ischemic-preconditioning and control groups before ischemia. Left ventricular contractility, diastolic function, and mechanical efficiency in the ischemic-preconditioning group were significantly superior to those in the control group after reperfusion.

CONCLUSIONS

Ischemic preconditioning attenuates postischemic myocardial dysfunction in a sheep model using 30-minute unloaded normothermic global myocardial ischemia. Ischemic preconditioning would thus be clinically significant when the ischemic damage is severe.

Effect of phosphodiesterase III inhibitor on contractility, afterload, and vascular capacitance during right heart bypass preparation

OBJECTIVES

Phosphodiesterase III inhibitors, which have both positive inotropic and vasodilatory effects, occasionally cause hypotension due to afterload reduction and possibly due to preload reduction caused by the increase in vascular capacitance.

METHODS

Six open-chest adult mongrel dogs were used to compare the effects on left ventricular contractility, afterload, and vascular capacitance of the phosphodiesterase III inhibitor, olprinone, with those of dobutamine using a right-heart-bypass model. Contractility and afterload were evaluated by the left ventricular pressure-volume relations with the use of a conductance catheter to derive the end-systolic elastance (Ees) and the effective arterial elastance (Ea). Vascular capacitance change was evaluated by reservoir volume change under a constant bypass flow (80 ml/kg per minute).

RESULTS

Ees increased significantly both with dobutamine (7.6 +/- 2.8 to 14.3 +/- 4.8 mmHg/ml, p < 0.05) and with olprinone (7.6 +/- 2.9 to 11.5 +/- 4.2 mmHg/ml, p < 0.05). Ea did not change with dobutamine (14.4 +/- 3.5 to 14.5 +/- 3.6 mmHg/ml, p = 0.9), whereas it decreased with olprinone (14.0 +/- 4.1 to 11.4 +/- 3.8 mmHg/ml, p = 0.093). Reservoir volume increased after the infusion of dobutamine (-94.0 +/- 39.8 ml), and decreased after the infusion of olprinone (-114.0 +/- 62.3 ml). The difference was statistically significant (p = 0.007). The reservoir volume change indicated that vascular capacitance decreased with dobutamine, and increased with olprinone.

CONCLUSIONS

Pre- and afterload reduction of olprinone combined with the positive inotropic effect are useful in treating congestive heart failure and managing low cardiac output syndrome after cardiac surgery.

Influence of cyclic variation of right ventricular volume on left ventricular mechanical parameters measured with conductance catheter

The conductance catheter is widely used for the continuous measurement of the left ventricular (LV) pressure-volume loops. Cyclical change of the right ventricular (RV) volume may alter the parallel conductance volume, thereby affecting the LV mechanical parameters. Using 8 open-chest adult mongrel dogs, multiple LV pressure-volume loops were obtained by 2 methods: first with a vena cava occlusion (VCO) method, which involved RV volume alteration, and second with a right-heart-bypass (RHB) preparation, which decompressed the right ventricle completely. The slope of the end-systolic pressure-volume relation (Ees), the end-systolic volume associated with the end-systolic pressure of 100 mmHg (V100,es), stiffness constant (beta), and the end-diastolic volume associated with the end-diastolic pressure of 9 mmHg (V9,ed) were calculated from each loop. There was minimal influence from RV volume alteration on systolic-phase indices [Ees (VCO method, 6.37 +/- 1.91 mmHg/ml; RHB preparation, 6.60 +/- 1.66mmHg/ml; p=0.356), and V100,es (VCO method, 18.4 +/- 9.3ml; RHB preparation, 17.8 +/- 9.0 ml; p=0.681)], but there was a significant influence on diastolic-phase indices [beta (VCO method, 0.0599 +/- 0.0152; RHB preparation, 0.0839 +/- 0.0150; p=0.007), and V9,ed (VCO method, 35.6 +/- 11.3 ml; RHB preparation, 31.9 +/- 12.3 ml; p=0.001)]. The increase in the RV volume in the diastolic phase increased the parallel conductance volume, causing overestimation of the LV diastolic volume measured by the conductance catheter.

Effect of a neutrophil elastase inhibitor (ONO-5046 Na) on ischemia/reperfusion injury using the left-sided heterotopic canine heart transplantation model

BACKGROUND

Ischemia/reperfusion injury is a major cause of transplanted heart dysfunction. Several reports have demonstrated that polymorphonuclear neutrophil (PMN) elastase derived from the activated neutrophils might play an important role in this injury. Herein, we investigated the protective effects of PMN elastase inhibitor (ONO-5046 Na) on ischemia/reperfusion injury using a left-sided canine heterotopic heart transplantation model.

METHODS

We used 10 pairs of adult beagle dogs. The donor heart was transplanted heterotopically into the left thoracic cavity of the recipient without cardiopulmonary bypass. A bolus of ONO-5046 Na (10 mg/kg) was introduced intravenously to 5 recipients (group II) at 15 minutes before reperfusion and was followed by continuous infusion (10 mg/kg per hour) for 180 minutes. Five dogs (group I) did not receive ONO-5046 Na and thus served as a control. After reperfusion, we evaluated transplanted heart function and obtained blood samples from the coronary sinus over a 360-minute period.

RESULTS

E(max) and pre-load recruitable stroke work in group II showed significantly better recovery than group I. Blood levels of PMN elastase, creatine kinase MB, lactate and inflammatory cytokines (tumor necrosis factor-alpha, interleukin-6, interleukin-8) were significantly lower in group II. Depletion of myocardial concentration of adenosine triphosphate at 120 minutes after reperfusion and myocardial water content was significantly lower in group II.

CONCLUSIONS

ONO-5046 Na, which inhibits PMN elastase, could reduce ischemia/reperfusion injury in heart transplantation. These results indicate that clinical application of ONO-5046 Na should be considered.

A leukocyte depleting filter reduces endothelial cell dysfunction and improves transplanted canine heart function

BACKGROUND

To date leukocytes have been known to play a major role in reperfusion injury and have directed attention to leukocyte-endothelium interaction. This study was designed to investigate how much graft viability and the coronary microcirculatory function could be preserved by leukocyte depletion (LD) in a model of orthotopic cardiac transplantation.

METHODS

The heart in 10 beagle dogs was arrested by introducing a 4 degrees C St. Thomas' cardioplegic solution. They were harvested, immersed in the cold saline for 3 hours, and then orthotopically transplanted. Five recipients underwent LD (LD group) at reperfusion with the use of a Pall BC1B leukocyte depleting filter inserted into the cardiopulmonary bypass (CPB) circuit. The other 5 dogs without filtration served as a control group.

RESULTS

Leukocytes were about 80% filtrated and neutrophils were also 85% filtrated during the first 30 minutes of reperfusion in the LD group. A high level of adenosine triphosphate was maintained after transplantation in the LD group. The polymorphonuclear elastase level was significantly lower in the LD group. The cardiac function assessed by the slopes of the end-systolic pressure volume relation after transplantation was significantly higher in the LD group than in the control group (p < 0.05). The coronary vascular resistance responses to acetylcholine and nitroglycerin after transplantation were preserved significantly better in the LD group than in the control group (p < 0.05).

CONCLUSIONS

These results suggest that a leukocyte depleting filter placed in the CPB circuit would prevent leukocyte-mediated endothelial cell injury, improve microcirculation of the myocardium, and lead to excellent graft function.

Bidirectional Glenn procedure improves the mechanical efficiency of a total cavopulmonary connection in high-risk fontan candidates

BACKGROUND

A total cavopulmonary connection (TCPC) is a widely performed surgical procedure for Fontan candidates. High-risk candidates who have undergone the bidirectional Glenn procedure (BDG) before TCPC have shown good results. The exact mechanism of this procedure, however, is still poorly understood. We hypothesized that a volume reduction with BDG improved ventricular contractility, thereby optimizing mechanical efficiency after TCPC.

METHODS AND RESULTS

We measured percent normal systemic ventricular end-diastolic volume (%N-EDV), contractility (end-systolic elastance; E(es)), afterload (effective arterial elastance; E(a)), and mechanical efficiency (ventriculoarterial coupling; E(a)/E(es)) on the basis of the cardiac catheterization data before and after TCPC. Eighteen patients who underwent staged TCPC after BDG (staged group) were compared with 29 patients who underwent primary TCPC (primary group). E(es) and E(a) were approximated as follows: E(es)=mean arterial pressure/minimal ventricular volume, and E(a)=maximal ventricular pressure/(maximal ventricular volume-minimal ventricular volume), and E(a)/E(es) was then calculated. The ventricular volume was normalized with the body surface area. A canine experimental model with conductance catheter was used to validate the accuracy of this approximation of E(es) and E(a). %N-EDV decreased after TCPC in both groups. In the staged group, a smaller ventricular volume resulted in better contractility (E(es)). Although afterload (E(a)) increased in both groups, the increment of E(a) was smaller in the staged group. These changes resulted in an improvement of E(a)/E(es) in the staged group, whereas E(a)/E(es) increased in the primary group.

CONCLUSIONS

The volume reduction of BDG preceding TCPC allows for any afterload mismatch to be corrected, thereby improving ventricular energetics after TCPC.

Small oxidative changes in atherogenic LDL concentrations irreversibly regulate adhesiveness of human endothelial cells: effect of the lazaroid U74500A

The adherence of monocytes to the endothelium is an early event in atherogenesis which is modulated by low density lipoproteins (LDL). We analyzed the effect of atherogenic LDL levels (180 mg cholesterol/dl, for 24 h) with minimal oxidative modifications (thiobarbituric-acid-reactive-substances (TBARS) concentration between 1.2+/-0.1 and 2.5+/-0.3 nmol of malonaldehyde bis-diethyl acetal (MDA) per mg protein) on human umbilical vein endothelial cell (HUVEC) adhesive properties. We used native LDL (n-LDL), and LDL exposed to spontaneous oxidation without antioxidants (mox-LDL) or with 20 micromol/l of the antioxidant butylated hydroxytoluene (BHT-LDL) or 10 micromol/l U74500A (U74500A-LDL), a scavenger of free radicals. Thiobarbituric-acid-reactive-substances (TBARS) levels were significantly higher in mox-LDL (2.5+/-0.3 nmol MDA/mg protein) than in BHT-LDL (1.6+/-0.2), U74500A-LDL (1.2+/-0.1) or in n-LDL (1.3+/-0.1). mox-LDL induced the greatest adhesion of U937 cells to HUVEC (103+/-9% over controls) followed by BHT-LDL (75+/-10%), U74500A-LDL (36+/-9%) and n-LDL (35+/-3%). The lazaroid U74500A efficiently protected U74500A-LDL against oxidative damage and prevented endothelial adhesiveness associated with this LDL modification, inducing adhesion effects similar to those of n-LDL. However, U74500A could not reverse the adhesion induced by previously oxidized LDL (mox-LDL). LDL did not induce the expression of the intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) or E-selectin, but it produced a downregulation of endothelial nitric oxide synthase (NOS III) mRNA levels. Thus, adhesiveness of human endothelial cells (EC) exposed to atherogenic concentrations of LDL is closely modulated by minimal changes in LDL oxidative state, and could be related to a downregulation of NOS III.

Nitroglycerin as a nitric oxide donor accelerates lipid peroxidation but preserves ventricular function in a canine model of orthotopic heart transplantation

BACKGROUND

Nitric oxide has cardioprotective effects through several mechanisms. However, nitric oxide may have deleterious effects in the presence of superoxide because it is converted to peroxynitrite, which then initiates lipid peroxidation. Using a canine model of orthotopic heart transplantation, we examined whether adding an organic nitric oxide donor, nitroglycerin, to preservation solution elicits lipid peroxidation after reperfusion and causes deleterious effects on coronary endothelial function and left ventricular function.

METHODS AND RESULTS

The donor heart was preserved for 24 hours in cold University of Wisconsin solution with nitroglycerin (0.1 mg/mL) supplementation (group NTG, n = 8) or in standard University of Wisconsin solution (group C, n = 8). After reperfusion, changes of coronary resistance were measured during the infusion of acetylcholine (0.1 mg/min) and of sodium nitroprusside (1 mg/min), and percent coronary relaxation was calculated. Left ventricular function was evaluated by pressure-volume relations with the use of a conductance catheter, thereby deriving the slopes of end-systolic pressure-volume relation, stroke work-end-diastolic volume relation, and maximum rate of change of left ventricular pressure-end-diastolic volume relation. Serum lipid peroxide level was measured. Percent coronary relaxation was similar for the 2 groups. The slopes of end-systolic pressure-volume relation, stroke work-end-diastolic volume relation, and maximum rate of change of left ventricular pressure-end-diastolic volume relation in group NTG were significantly higher than those in group C. On the other side, serum lipid peroxide level in group NTG was significantly higher than that in group C.

CONCLUSIONS

Nitroglycerin may have detrimental effects evidenced by the increase in lipid peroxidation, which implied peroxynitrite formation. However, the overall effect of nitroglycerin was cardioprotective. Although the exact mechanism is yet to be clarified, the superb cardioprotective effect of nitroglycerin overwhelms the exaggeration of lipid peroxidation.

Cardioprotective effects of Lazaroid U-74389G on ischemia-reperfusion injury in canine hearts

BACKGROUND

Lazaroid, an inhibitor of iron-mediated lipid peroxidation, has been shown to reduce free radical-mediated injury after ischemia and reperfusion. The effect of Lazaroid U-74389G was investigated on ischemia-reperfusion injury of the heart through preservation and transplantation (Tx) in dogs.

METHODS

Eleven pairs of adult mongrel dogs weighing 8.5 to 12 kg formed the recipient-donor combinations. Following electromechanical arrest of the heart using cardioplegia, the coronary vascular beds were washed out with a cold University of Wisconsin solution followed by 12-hour preservation and orthotopic Tx. Experimental animals were divided into 2 groups; 6 pairs formed the control group, and 5 formed the Lazaroid-treated group in which Lazaroid U-74389G at 10 mg/kg was administered intravenously 30 minutes before reperfusion of the heart. The cardiac function including cardiac output, left ventricular (LV) pressure, and LV dp/dt was assessed 2 hours after Tx by comparing it with the recovery rates (%) from cardiac function of donor dogs. Each transplanted heart was harvested for histological study.

RESULTS

The recovery of cardiac function after Tx was significantly better in the Lazaroid-treated group than in the control group. Histologically, myocardial damage, evaluated by both light and transmission electron microscopy, was less evident in the Lazaroid-treated group than in the control group.

CONCLUSION

Early cardiac function following Tx was significantly better and histological damage was less in the Lazaroid-treated group than in the control group, suggesting that Lazaroid U-74389G is effective in preventing ischemia-reperfusion injury after preservation and Tx.

Excellent recovery after prolonged heart storage by preservation with coronary oxygen persufflation: orthotopic pig heart transplantations after 14-hr storage

BACKGROUND

Improvement of heart preservation is still the greatest challenge in preservation research. The unchanged severe restriction of acceptable storage periods of heart grafts since the beginning of clinical heart transplantation indicates that technical innovations are necessary if a substantial improvement is to be achieved.

METHODS

Here, we present the results of hypothermic preservation using the innovative technique of coronary oxygen persufflation (COP). COP simply adds gaseous oxygen to hypothermic graft storage and requires only a "valve guard" for reversible closure of the aortic valve. Fourteen-hr preservation was followed by orthotopic transplantation and evaluations of functional as well as metabolic recovery. Mature pig hearts, a model with restricted preservation tolerance similar to the human heart, were used to guarantee the clinical relevance of this study.

RESULTS

After 14-hr hypothermic storage, COP-preserved hearts were able to recover within 2 hr of cardiopulmonary bypass to a steady cardiovascular function without mechanical or pharmacologic support. The left ventricular pressure amplitude of mHTK-COP-preserved hearts as well as energy charge potential recovered to pregrafting values and the ventricular power output to 66%. Hearts simply stored in University of Wisconsin (UW), modified Bretschneider's histidine-tryptophan-ketoglurate (mHTK), or Euro-Flush with glutathione (EFG) solution had only limited recovery, with significantly lower ventricular power output of 18%, 29% or 30% of pregrafting controls on average.

CONCLUSIONS

Fourteen-hr oxygenated pig heart preservation using COP results in optimal recovery. Storage preservation in solutions containing hyaluronidase (mHTK and EFG) results in higher recoveries as compared to UW solution, an effect that may support the excellent recovery after mHTK-COP preservation.

Lazaroid U74500A is superior to U74006F in preserving rabbit heart for 24 hours

BACKGROUND

Lazaroid, a series of 21-aminosteroids, has been shown to reduce free-radical-mediated injury after ischemia and reperfusion. Recent in vitro studies have demonstrated that, among the various compounds studied, the most efficient agent was U74500A. The question is whether these findings apply to the whole heart experiencing ischemia-reperfusion injury. In this study we compared the myocardial protective effects of U74006F, the only clinical candidate, and U74500A.

METHODS

An isolated rabbit heart preparation perfused with the blood from a support rabbit was used. All hearts were divided into three groups according to the administration of U74500A (4 mg/kg, group A; n = 7), U74006F (4 mg/kg, group F; n = 7), or solvent (group S; n = 7) to the donor rabbit before preservation. After 24 hours of preservation with University of Wisconsin solution at 0 degrees C, all hearts were perfused with cross-circulated blood for 60 minutes with the Langendorff mode followed by 40 minutes in the working mode.

RESULTS

After 10 minutes of reperfusion the serum lipid peroxide levels were significantly (p < 0.05) lower in group A (0.62+/-0.31 nmol/mL) than those in group S (2.1+/-1.3 nmol/mL) and group F (1.0+/-0.6 nmol/mL). The aortic flow rate at 10 mm Hg of left atrial pressure was significantly higher in group A (164+/-37 mL/min) than that of other groups (71+/-28 mL/min in group S and 97+/-28 mL/min in group F). There were no significant differences in high-energy phosphate levels after reperfusion among the three groups.

CONCLUSION

These data imply that U74500A inhibits lipid peroxidation and prevents ischemia-reperfusion injury more efficiently than U74006F.

Cardioprotective effects of pinacidil pretreatment and lazaroid (U74500A) preservation in isolated rat hearts after 12-hour hypothermic storage

BACKGROUND

Two important processes in the preservation of the function of donor hearts are the maintenance of ATP-sensitive potassium channel activity during myocardial ischemia and the scavenging of reactive oxygen species formed during reperfusion. The aim of this study was to compare the effect of three protocols on the preservation of hemodynamic function in isolated rat hearts after hypothermic storage. These protocols were: (1) pretreatment of the heart with a potassium channel opener (200 microM pinacidil); (2) storage of the heart in an aspartate-enriched extracellular cardioplegic solution containing the lazaroid antioxidant, U74500A (30 microM); and (3) a combination of protocols 1 and 2.

METHODS

Hearts from Wistar rats were perfused on a Langendorff apparatus. After stabilization in working mode, baseline measurements of heart rate, coronary and aortic flow, and cardiac output were performed. Hearts (n=6 in each group) were then randomized to protocols 1-3, untreated controls, or vehicle-treated controls. Hearts were stored in extracellular-based preservation solution for 12 hr at 2-3 degrees C, remounted on the perfusion apparatus, and stabilized as before; hemodynamic measurements were then repeated.

RESULTS

Recovery of hemodynamic function was enhanced by pinacidil pretreatment or incorporation of lazaroid in the storage solution, but the combination of these two treatments produced the best results.

CONCLUSIONS

Combined pharmacological activation of ATP-sensitive potassium channels before cardioplegia and the addition of U74500A to the preservation solution is associated with significantly enhanced hemodynamic function in the isolated rat heart after 12 hr of hypothermic storage. These data suggest a novel use for these agents in the transplantation context.