Beneficial effect of raxofelast, an hydrophilic vitamin E analogue, in the rat heart after ischemia and reperfusion injury

Importance of internal mammary artery perfusion in cardiac ischemia and reperfusion

Purpose: Our purpose was to investigate the changes in antioxidant defense systems due to internal mammary artery (IMA) perfusion during coronary artery bypass graft (CABG) operations in which proximal anastomoses were completed under partial bypass with the aid of a side-biting clamp.

Material and Method: Twenty-five patients to be studied were divided into two groups according to the criterion of whether during proximal anastomoses left internal mammary artery (LIMA) perfusion was applied ( n = 15, LIMA group) or not ( n = 10, non-LIMA group). The erythrocyte catalase (CAT), superoxide dismutase (SOD), serum lipid peroxidation (LPO) products and whole blood reduced glutathione (GSH) levels were measured in the blood samples taken from the coronary sinus before cardiopulmonary bypass (CPB) (t1), before declamping (t2), at the 5th min after declamping (t3), at the 5th (t4) and 15th (t5) min after removing the side-biting clamp.

Results: While erythrocyte CAT enzyme activity decreases in both groups after the basal measurements, no significant difference was detected between the groups. Although the GSH levels did not differ at t1, t2 and t3, they were found to be higher in the LIMA group at t4 ( p = 0.006) and t5 ( p = 0.021). The erythrocyte SOD enzyme activity decreased after the basal measurements in both groups, but this reduction was less in the LIMA group at t4 ( p= 0.034) and t5 ( p = 0.018) compared to the other group. LPO products rose in both groups when reperfusion started after declamping. The levels of LPO products were significantly higher at t4 and t5 in the non-LIMA group than the other group ( p = 0.011 and p = 0.008).

Conclusion: If proximal anastomoses of coronary grafts are completed under partial bypass, permitting LIMA perfusion during this procedure will be beneficial to antioxidant defense systems.

Exosomes in mesenchymal stem cells, a new therapeutic strategy for cardiovascular diseases?

Cardiovascular diseases (CVDs) are still a major cause of people deaths worldwide, and mesenchymal stem cells (MSCs) transplantation holds great promise due to its capacity to differentiate into cardiovascular cells and secrete protective cytokines, which presents an important mechanism of MSCs therapy for CVDs. Although the capability of MSCs to differentiate into cardiomyocytes (CMCs), endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) has been well recognized in massive previous experiments both in vitro and in vivo, low survival rate of transplanted MSCs in recipient hearts suggests that therapeutic effects of MSCs transplantation might be also correlated with other underlying mechanisms. Notably, recent studies uncovered that MSCs were able to secret cholesterol-rich, phospholipid exosomes which were enriched with microRNAs (miRNAs). The released exosomes from MSCs acted on hearts and vessels, and then exerted anti-apoptosis, cardiac regeneration, anti-cardiac remodeling, anti-inflammatory effects, neovascularization and anti-vascular remodeling, which are considered as novel molecular mechanisms of therapeutic potential of MSCs transplantation. Here we summarized recent advances about the role of exosomes in MSCs therapy for CVDs, and discussed exosomes as a novel approach in the treatment of CVDs in the future.

Mitochondrial dysfunction and biogenesis: do ICU patients die from mitochondrial failure?

Mitochondrial functions include production of energy, activation of programmed cell death, and a number of cell specific tasks, e.g., cell signaling, control of Ca²⁺ metabolism, and synthesis of a number of important biomolecules. As proper mitochondrial function is critical for normal performance and survival of cells, mitochondrial dysfunction often leads to pathological conditions resulting in various human diseases. Recently mitochondrial dysfunction has been linked to multiple organ failure (MOF) often leading to the death of critical care patients. However, there are two main reasons why this insight did not generate an adequate resonance in clinical settings. First, most data regarding mitochondrial dysfunction in organs susceptible to failure in critical care diseases (liver, kidney, heart, lung, intestine, brain) were collected using animal models. Second, there is no clear therapeutic strategy how acquired mitochondrial dysfunction can be improved. Only the benefit of such therapies will confirm the critical role of mitochondrial dysfunction in clinical settings. Here we summarized data on mitochondrial dysfunction obtained in diverse experimental systems, which are related to conditions seen in intensive care unit (ICU) patients. Particular attention is given to mechanisms that cause cell death and organ dysfunction and to prospective therapeutic strategies, directed to recover mitochondrial function. Collectively the data discussed in this review suggest that appropriate diagnosis and specific treatment of mitochondrial dysfunction in ICU patients may significantly improve the clinical outcome.

The effects of erdosteine, N-acetylcysteine and vitamin E on nicotine-induced apoptosis of cardiac cells

This study was conducted to investigate the frequency of apoptosis in rat cardiomyocytes after intratraperitoneal nicotine injection, in order to examine the roles of inflammatory markers [myeloperoxidase (MPO) and tumor necrosis factor alpha (TNF-alpha)] in nicotine-induced cardiac damage and to determine the protective effects of three known antioxidant agents (N-acetylcysteine (NAC), erdosteine and vitamin E) on nicotine toxicity in the heart. Female Wistar rats were divided into seven groups, each composed of nine rats: two negative control groups, two positive control groups, one erdosteine-treated group (500 mg kg(-1)), one NAC-treated group (500 mg kg(-1)) and one vitamin E-treated group (500 mg kg(-1)). Nicotine was intraperitoneally injected at a dosage of 0.6 mg kg(-1) for 21 days. Following nicotine injection, the antioxidants were administered orally; treatment was continued until the rats were killed. Heart tissue samples were stained with hematoxylin-eosin for histopathological assessments. Apoptosis level in cardiomyocytes was determined by using TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick endlabelling) method. Staining of cytoplasmic TNF-alpha in cardiomyocytes and heart MPO activity were evaluated by immunohistochemistry. The treatments with erdosteine, NAC and vitamin E significantly reduced the rate of nicotine-induced cardiomyocyte apoptosis. The effect of vitamin E on apoptosis regulation was weaker than the effects of erdosteine and NAC. Erdosteine, NAC and vitamin E significantly reduced the increases in the local production of TNF-alpha and heart MPO activity. This findings suggest that the effects of erdosteine and NAC on apoptosis regulation are stronger than that of vitamin E.

Acute administration of vitamin E triggers preconditioning via K(ATP) channels and cyclic-GMP without inhibiting lipid peroxidation

Vitamin E (VitE) is considered an antioxidant agent. One or more brief periods of ischemia (isc), followed by short reperfusion (rep), increase the tolerance of the heart to a subsequent prolonged ischemia, a phenomenon known as ischemic preconditioning (PC). Mitochondrial KATP channels (mitoKATP), cyclic-GMP (cGMP), and free radicals are involved in the mechanism of PC, whereas some antioxidants abolish this benefit. The purpose of this study was to evaluate the effect of VitE on infarct size, PC, and the oxidative status in vivo. Male rabbits were divided into seven groups and were subjected to myocardial ischemia (isc) and reperfusion (rep) with the following interventions: (1) control (no intervention); (2) E150 (iv VitE at a dose of 150 mg/kg for 75 min, starting 40 min before index isc and lasting through 5 min of rep); (3) E300 (iv VitE 300 mg/kg as previously described); (4) PC (two cycles of 5 min isc and 10 min rep), (5) combined E150-PC; and (6) combined E300-PC. In the last two groups VitE was given 40 min before index ischemia. Blood samples were taken for malondialdehyde (MDA) and conjugated dienes (CDs) measurement. In a second series of experiments heart tissue samples were taken at the time of long ischemia for MDA and CD determination and for cGMP assay. In order to test whether combined treatment with VitE (as the E150 group) and the mitoKATP blocker 5-hydroxydecanoic acid (5-HD) changes the infarct size, an additional group was assessed in the first series of experiments. Tissue VitE concentration was evaluated in myocardium. VitE at both doses reduced the infarct size (19.7 +/- 2.8% for E150 and 18.8 +/- 4.9% for E300 vs 47.4 +/- 2.6% in control, P < 0.05) without attenuating the effect of PC (10.2 +/- 3.1% for E150-PC, 12.4 +/- 2.2% for E300-PC, vs 13.5 +/- 3.3% for PC). Combined VitE and 5-HD treatment abrogates this benefit (37.4 +/- 6.5%, P < 0.05 vs E150 and NS vs control). VitE increases intracellular cGMP and CDs levels (P < 0.05 vs control) to the same extent as PC (P < 0.05 vs control), with no effect on MDA (P = NS between all the groups). Peripheral markers of oxidative stress are increased during reperfusion in all groups (P < 0.05 vs baseline). Overall, VitE limits infarct size via mitoKATP and cGMP, while preserving the benefit of ischemic PC.

Protective effects of antioxidant raxofelast in alcohol-induced liver disease in mice

We investigated the effect of raxofelast on lipid peroxidation inhibition in mice exposed to chronic ethanol. Female C57BL/6 mice were fed a modified Lieber-DeCarli liquid ethanol (ETOH) or control diet (sham ETOH) for up to 14 days. Animals were assigned to receive either raxofelast (20 mg/kg/day i.p.) or its vehicle (DMSO:NaCl 0.9% 1:1, v:v; 1 ml/kg i.p.). Serum alanine aminotransferase (ALT), plasma and liver triglyceride levels, hepatic malondialdehyde (MDA), reduced glutathione (GSH) concentrations, liver gene expression of Toll-like receptor-4 (TLR-4), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) and intercellular adhesion molecule-1 (ICAM-1) were studied at the end of the study. A histological evaluation of liver damage was also carried out. Raxofelast, an analog of vitamin E, blunted the increased hepatic nuclear factor-kappaB activity, reduced serum ALT, plasma and liver triglycerides, lowered hepatic MDA levels, prevented liver GSH depletion and decreased TLR-4, TNF-alpha, IL-6 and ICAM-1 hepatic gene expression. Furthermore raxofelast ameliorated liver damage. Our results suggest that raxofelast blunts the inflammatory cascade and organ damage during chronic ethanol exposure.

Depletion of antioxidants is associated with no-reflow phenomenon in acute myocardial infarction

BACKGROUND

No-reflow phenomenon is observed in approximately one-third of patients after percutaneous coronary intervention (PCI) for acute myocardial infarction (AMI), and is associated with poor functional and clinical outcomes. On the other hand, the formation of free radicals in vasculature exerts deleterious effects on coronary microcirculation.

HYPOTHESIS

We hypothesized that redox state in coronary circulation may play a crucial role in no-reflow phenomenon in AMI.

METHODS

Consecutive 26 patients with first AMI who underwent primary PCI < 24 h after onset were enrolled. Before PCI, blood samples were obtained from coronary sinus to measure plasma or serum antioxidative vitamins (vitamin C, vitamin E, and beta-carotene) and antioxidative enzymes (extracellular glutathione peroxidase [GPX], superoxide dismutase, and catalase). After PCI, the corrected Thrombolysis In Myocardial Infarction (TIMI) frame count (CTFC) was measured in the target vessel. Patients with TIMI < or = 2 flow despite an optimal PCI result were designated as no-reflow group (Group NR, n = 6) and the others as reflow group (Group R, n = 20).

RESULTS

Levels of vitamin C, vitamin E, and GPX before PCI were significantly lower in Group NR than in Group R. The CTFC correlated inversely with levels of vitamin C, vitamin E, and GPX (p < 0.05).

CONCLUSIONS

Depletion of antioxidants is associated with no-reflow phenomenon in AMI. These findings strongly suggest that the redox state in coronary circulation plays an important role in the pathogenesis of no-reflow phenomenon.

Antiproliferative mechanisms of raxofelast (IRFI-016) in H2O2-stimulated rat aortic smooth muscle cells

Reactive oxygen species-mediated cellular injury is involved in the pathogenesis of many diseases, including those affecting the cardiovascular system, such as myocardial ischemia-reperfusion injury, inflammation, and atheroscleosis. Raxofelast (IRFI-016; (+/-)-5-acetoxy-2, 3-dihydro-4, 6, 7-trimethyl-2-benzofuran-acetic acid) was designed with the aim of maximizing the antioxidant potency of phenols chemically related to vitamin E. The antioxidant activity of raxofelast has been convincingly demonstrated in several in vitro studies and in various models of ischemia-reperfusion injury. In this study, the antiproliferative effects of raxofelast were investigated to determine whether transduction signals and protooncogenes are affected in H(2)O(2)-stimulated rat aortic smooth muscle cells. In a tetrazolium-based colorimetric assay, the proliferation of rat aortic smooth muscle cells was increased by 3-fold in 0.1% fetal bovine serum/Dulbecco's modified Eagle's medium (DMEM) containing 500 microM H(2)O(2), indicating that exogenous 500 microM H(2)O(2) was a growth stimulator of rat aortic smooth muscle cells. Exogenous H(2)O(2) significantly activated extracellular signal-regulated kinases (ERKs) activity within 30 min and raxofelast inhibited the ERKs activation dose dependently in 500 microM H(2)O(2)-stimulated rat aortic smooth muscle cells (IC(50): 200 microM). Raxofelast reduced the intracellular reactive oxygen species generated by exogenous H(2)O(2) in a dose-dependent manner. In 500 microM H(2)O(2)-stimulated rat aortic smooth muscle cells, raxofelast dramatically attenuated the activation of mitogen-activating protein kinase (MAPK)/ERK kinase 1, 2 (MEK1,2) and protein kinase C (PKC) without affecting Ras expression. Induction of c-myc mRNA was significantly reduced dose dependently up to 100 microM by raxofelast in concentrations. These data indicate that the antiproliferative effects of raxofelast in H(2)O(2)-stimulated rat aortic smooth muscle cells may involve the suppression of intracellular reactive oxygen species formation and the inhibition of ERKs by inactivation through PKC and MEK1,2 and down-regulation of c-myc expression, regardless of Ras activation.

Melatonin does not prevent the protection of ischemic preconditioning in vivo despite its antioxidant effect against oxidative stress

Free radicals are involved in the protective mechanism of preconditioning (PC), whereas antioxidant compounds abolish this benefit. Melatonin is a hormone with antioxidant properties. The aim of our study was to evaluate the effect of melatonin on infarct size in ischemic preconditioning in vivo. We randomly divided 33 male rabbits into four groups and subjected them to 30 min of myocardial ischemia and 3 h of reperfusion with the following prior interventions: (i) no intervention, (ii) iv melatonin at a total dose of 50 mg/kg, (iii) PC with two cycles of 5 min ischemia and 10 min reperfusion, and (iv) combined melatonin and PC. In a second series of experiments, another antioxidant agent N-acetylcysteine (NAC) was used in a control and in a PC group. Myocardial infarct size was determined and blood samples were drawn at different time points for the determination of lipid peroxidation products, total superoxide dismutase (SOD) activity, and (1)H-NMR spectra to evaluate the changes in the metabolic profile. Melatonin showed no effect on myocardial infarct size in the group of sustained ischemia (42.9 +/- 3.6% vs 47.4 +/- 4.9%) and it did not attenuate the reduction of myocardial infarct size in the PC group (13.6 +/- 2.4% vs 14.0 +/- 1.7%). A similar effect was found in NAC-treated groups (44.8 +/- 3.4% vs 14.3 +/- 1.3%). Lipid peroxidation product levels were significantly elevated in the control and PC groups, whereas melatonin decreased them in both groups. The SOD activity was enhanced in the PC group compared to controls; melatonin kept SOD activity unchanged during ischemia/reperfusion and enhanced its activity when it was combined with PC. Melatonin did not change the metabolic profile of the control and PC groups. Melatonin does not prevent the beneficial effect of ischemic PC on infarct size despite its antioxidant properties.

Raxofelast, a hydrophilic vitamin E-like antioxidant, reduces testicular ischemia-reperfusion injury

Testis torsion is a surgical emergency that lead to permanent gonad damage. The damage has been ascribed to mechanisms of ischemia-reperfusion similar to other tissues. The mechanisms involved are different, but the lipid peroxidation of plasma membrane, caused by reactive oxygen species (ROS), generated particularly during reperfusion, is one of the most accredited. In the present study, we aimed to evaluate the effects of raxofelast, a vitamin E-like antioxidant with potent action and no systemic toxicity, on lipid peroxidation and histopathology in both testes after unilateral testicular torsion and detorsion. Adult male Wistar rats were subjected to total occlusion (3 h) of the left testis followed by 4 hours of reperfusion (TI/R). Sham testicular ischemia-reperfusion rats (SHAM TI/R) were used as controls. The animals were then randomized to receive either vehicle (1 ml/kg/i.p. of a dimetylsulphoxide/NaCl 0.9% 1:10 v/v solution, injected either 15 min before detorsion and 15 min after detorsion) or raxofelast (20 mg/kg i.p. 15 min before detorsion and 15 min after detorsion). Conjugated dienes (CD) levels, an index of lipid peroxidation, and testis histopathology were evaluated. Testicular ischemia reperfusion (TI/R) in untreated rats produced high testicular levels of CD (3.6+/-0.3 DeltaABS/g protein on the left side and 2.5+/-0.2 DeltaABS/g protein on the right side). Furthermore, histological examination revealed marked damage to the testis interstitium with severe haemorrhage and edema. The administration of raxofelast lowered CD levels (2.8+/-0.2 DeltaABS/g protein on the left side and 1.9+/-0.1 DeltaABS/g protein in the right side) and significantly reduced histological damage. These data suggest that the hydrophilic vitamin E-like antioxidants are good candidates for designing a novel therapeutic strategy to halt the oxidative stress that follows acute testis torsion.

Relationships between hemodynamic parameters and myocardial energy and antioxidant status in heart transplantation

The relationships between high-energy phosphate levels, oxidative insult and mechanical function represent a key point in heart transplantation and related post-ischemic functional recovery. We evaluated myocardial purine compounds and glutathione antioxidant defence mechanism during 19 heart transplant operations. Heart biopsies were taken before harvesting on beating heart (t1), at the end of cold static preservation (t2) and 30 min after implantation and reperfusion (t3); perchloric extracts of the tissue were analyzed by capillary electrophoresis (CE). Correlation analyses were performed with hemodynamic parameters evaluated 90 min after aortic declamping (T90), 6 h following admission in intensive care unit (T6A) and 1 d post-operation (D1). We evidenced that AMP levels measured at T1 negatively correlate with both cardiac index (CI) and oxygen delivery index (DO2I) evaluated at T6A, respectively. The same behavior was evident plotting IMP levels measured at T3 with CI and DO2I evaluated at D1. After t2 the nucleotide/(nucleoside + base) ratio was in positive correlation with hemodynamic parameters at T6A. Energy charge and GSH/GSSG ratio measured before harvesting were in positive correlation with DO2I evaluated at T90. The present research shows that despite the complexity of the high-energy phosphate metabolism and that of the events associated to a clinical heart transplantation, there are some parameters that, besides reflecting the degree of myocardial preservation, also represents predictive parameters for the following organ functional recovery. It also suggests that heart preservation strategies should carefully take into account the sub-optimal nature of the donor heart at the time of procurement, through a broad spectrum of purine compound and glutathione antioxidant system measurements.

Protective effect of a novel antioxidant non-steroidal anti-inflammatory agent (compound IA) on intestinal viability after acute mesenteric ischemia and reperfusion

Reactive oxygen species play an important role in the basic pathophysiology of ischemia-reperfusion injury. We investigated whether the administration of a novel non-steroidal anti-inflammatory compound with antioxidant properties, the compound [5-(2-amino-ethylamino)-1-phenyl-2-pentanone] (compound IA), has a beneficial effect on the repair process of the intestinal mucosa after transient mesenteric ischemia in a randomized blind trial. Six groups of rats were subjected to a model of 60 min of intestinal ischemia that was produced by occluding the superior mesenteric artery. At the end of ischemia, compound IA was administered intravenously and the clamp was removed allowing reperfusion. At 60 min after reperfusion, animals were sacrificed and a 10 cm section of terminal ileum was resected. The outcome was evaluated by histopathologic assessment, measurement of polymorphonuclear leukocytes and the extent of lipid peroxidation measuring the small intestine tissue malondialdehyde. After 1 h of reperfusion, the mucosal damage was less in IA-treated rats compared with the control group. Moreover, the number of polymorphonuclear leukocytes in intestinal mucosa was significantly lower in IA group. Compound IA resulted in a statistically significant reduction of the concentration of small intestine tissue malondialdehyde, compared to those of controls. Administration of compound IA decreased the mucosal damage in rats that were subjected to 60 min of ischemia followed by 60 min of reperfusion. The mechanism of compound IA action is considered to be mediated via its potent antioxidant, free radical scavenging activities and inhibition of polymorphonuclear leukocytes infiltration.

Efficacy of treatment with glycosaminoglycans on experimental collagen-induced arthritis in rats

To evaluate the antioxidant activity of the glycosaminoglycans hyaluronic acid (HYA) and chondroitin-4-sulphate (C4S), we used a rat model of collagen-induced arthritis (CIA). Arthritis was induced in Lewis rats by multiple intradermal injections of 250 microl of emulsion containing bovine type II collagen in complete Freund's adjuvant at the base of the tail and into three to five other sites on the back. Rats were challenged again with the same antigen preparation 7 days later. Disease developed about 11 days after the second immunization. The effects of treatment in the rats were monitored by biochemical parameters and by macroscopic and histological evaluations in blood, synovial tissue and articular cartilage. Arthritis produced the following symptoms: severe periarticular erythema, edema and inflammation in the hindpaws; membrane peroxidation in the cartilage of the joints; endogenous antioxidant wasting; high tumour necrosis factor-alpha (TNF-alpha) plasma levels; and synovial neutrophil accumulation. Treatment with HYA and C4S, starting at the onset of arthritis for 10 days, limited the erosive action of the disease in the articular joints of knee and paw, reduced lipid peroxidation, restored the endogenous antioxidants reduced glutathione (GSH) and superoxide dismutase, decreased plasma TNF-alpha levels, and limited synovial neutrophil infiltration. These data confirm that erosive destruction of the joint cartilage in CIA is due at least in part to free radicals released by activated neutrophils and produced by other biochemical pathways. The beneficial effects obtained with the treatment suggest that HYA and C4S could be considered natural endogenous macromolecules to limit erosive damage in CIA or as a useful tool with which to study the involvement of free radicals in rheumatoid arthritis.

Cardiac surgery: myocardial energy balance, antioxidant status and endothelial function after ischemia-reperfusion

Myocardial and endothelial damage is still a widely debated problem during the ischemia-reperfusion sequence in heart surgery. We evaluated myocardial purine metabolites, antioxidant defense mechanisms, oxidative status and endothelial dysfunction markers in 14 patients undergoing coronary artery by-pass graft (CABG). Heart biopsies were taken before aortic cross-clamping (t1), before clamp removal (t2) and 30 min after reperfusion (t3); perchloric extracts of the tissue were analyzed for glutathione, NAD, nucleotide nucleoside and base content by capillary electrophoresis (CE). In plasma samples from the coronary sinus we evaluated: nitrate and nitrite concentrations by CE, plasma glutathione peroxidase (plGPx) by ELISA, endothelin-1 (ET-1) by RIA and reactive oxygen metabolites (ROM) by colorimetric assay. During the ischemic period (t2) we observed a reduction in cellular NAD and GSH levels, as well as nitrate, nitrite and plGPx. ATP and GTP levels decreased and their catabolic products AMP, GMP, IMP, adenosine, inosine and hypoxanthine accumulated. The energy charge, ATP/ADP ratio, and nucleotide/(nucleoside + base) ratios decreased. At t3, levels of plasma ET-1 increased and monophosphate nucleotides tended to return to basal values. The energy charge did not increase but the nucleotide/(nucleoside + nucleobase) ratio recovered to some extent. Levels of nitrates plus nitrites continued to decrease. No significant variation in ROM levels was observed. Our data indicate that oxidative stress and endothelial damage are major events during CABG, overwhelming the scavenging capacity of the myocyte and preventing restoration of the normal energy balance for 30 min after reperfusion. The AMP deaminase pathway leading to IMP production is active during ischemia and adenosine is not the main compound derived from ATP break-down in the human heart. The possible role of extracorporeal circulation is also discussed.

Preservation of myocardial energy status by bovine hemoglobin solutions during ischemia

Compared to murine and human hemoglobin, bovine hemoglobin has a less exothermic oxygen binding and delivers oxygen even at low temperatures. This property could improve oxygen availability for myocytes during hypothermic arrest of hearts. The aim of this study was to evaluate the advantage of using cardioplegic solutions enriched with bovine hemoglobin when storing rat hearts. Hearts excised from rats after perfusion with different cardioplegic solutions (Celsior, Celsior plus 4% human hemoglobin, Celsior plus 4% and 8% bovine hemoglobin) were compared. Biopsies were obtained from the beating hearts before cardioplegic infusion and during a 48 h period of cold storage. Adenosine triphosphate, its catabolites and markers of oxidative stress were measured as indices of preservation. The results show that bovine hemoglobin-enriched solutions highly improve adenosine triphosphate content, decreasing its catabolites; no significant changes in antioxidant status were evident. The statistically significant difference was evident up to 6 h of storage. Doubling the concentration of bovine hemoglobin produces only slight improvement. Alternative hemoglobins with different properties may improve and prolong heart storage. As bovine hemoglobin delivers oxygen even at low temperatures, it improves energy content and anabolic reactions, without decreasing oxidative stress.

The water-soluble vitamin E analogue Trolox protects against ischaemia/reperfusion damage in vitro and ex vivo. A comparison with vitamin E

We investigated the activities, both in vitro and ex vivo, of the water-soluble vitamin analogue Trolox in a model of isolated heart ischaemia-reperfusion and we compared them with those of alpha -tocopherol. Isolated rat hearts were perfused with Krebs-Henseleit solution. For in vitro experiments, the hearts were perfused with Trolox (20 micromol l (-1)) and were subsequently subjected to 20 min of global ischaemia and 40 min of post-ischaemic reperfusion. For ex vivo experiments, either Trolox or alpha -tocopherol (10 mg kg(-1) ) were administered by gastric gavage 60 min before excision of the heart. Various parameters of cardiac function were evaluated and oxidative damage was assessed by TBARS production. Trolox significantly enhanced cardiac recovery after ischaemia/reperfusion, both when it was perfused in vitro and after its oral administration. Vitamin E also favourably affected cardiac recovery but did so less effectively than Trolox. Further, the production of TBARS was significantly inhibited by Trolox, suggesting that its beneficial effects are due to its antioxidant activities. In conclusion, perfusion of isolated rat hearts with low concentrations of the water-soluble vitamin E analogue Trolox effectively enhances cardiac recovery after a 20 min ischaemic period and decreases reperfusion-induced oxidative damage. Interestingly, Trolox retains its activities after oral administration. Vitamin E, when administered per os, also increases functional recovery but does so less potently than Trolox. These differential effects are likely due to the scavenging, by Trolox, of reactive oxygen species generated in the water phase.

Beneficial effects of astringinin, a resveratrol analogue, on the ischemia and reperfusion damage in rat heart

Oxidative stress plays an important role in the pathogenesis of myocardial ischemia and infarction. Antioxidants might then be beneficial in the prevention of these diseases. Astringinin (3,3',4',5-tetrahydroxystilbene), a resveratrol (3,4',5-trihydroxystilbene) analogue with considerably higher antioxidative activity and free radical scavenging capacity, was introduced to examine its cardioprotective effects in ischemia or ischemia-reperfusion (I/R) rats. In the present study, the left main coronary artery was occluded by the following procedures: (i) 30 min occlusion, (ii) 5 min occlusion followed by 30 min reperfusion, and (iii) 4 h occlusion. Animals were infused with and without astringinin before coronary artery occlusion. Mortality, and the severity of ischemia- and I/R-induced arrhythmias were compared. Pretreatment of astringinin dramatically reduced the incidence and duration of ventricular tachycardia (VT) and ventricular fibrillation (VF) during either ischemia or I/R period. Astringinin at 2.5 x 10(-5) and 2.5 x 10(-4) g/kg completely prevented the mortality of animals during ischemia or I/R. During the same period, astringinin pretreatment also increased nitric oxide (NO) and decreased lactate dehydrogenase (LDH) levels in the carotid blood. In animals subjected to 4 h coronary occlusion, the cardiac infarct size (expressed as a percentage of occluded zone) was reduced from 44.4 + or - 4.1% to 19.1 + or - 2.4% by astringinin (2.5 x 10(-4) g/kg). We conclude that, astringinin is a potent antiarrhythmic agent with cardioprotective activity in ischemic and ischemic-reperfused rat heart. The beneficial effects of astringinin in the ischemic and ischemic-reperfused hearts may be correlated with its antioxidant activity and upregulation of NO production.

Capillary electrophoresis in the evaluation of ischemic injury: simultaneous determination of purine compounds and glutathione

An understanding of tissue energy metabolism and antioxidant status is of major interest in the field of organ preservation for transplantation. Nucleotide and glutathione are indicators of cell damage occurring during ischemia and reperfusion. A high performance capillary electrophoresis (HPCE) method with UV detection (185 nm) for the simultaneous analysis of intracellular free ribonucleotides, nucleosides, bases and glutathione (oxidized and reduced form) in myocardial tissues is described. The method does not involve thiol derivatization. The separations were carried out in an uncoated fused-silica capillary, 60 cm long, 52.5 cm to detector, 75 microm ID, with 20 mM Na-borate buffer, pH 10.00, at 20 kV voltage and reading at 185 nm. Injection was hydrostatic for 12 s and total analysis time was 20 min. The technique enables optimum separation of all the compounds examined and has a resolution similar to that of HPLC analysis, with the advantage of fast simultaneous measurement of cell nucleotide metabolism and redox state, not possible with HPLC.

Cardioprotective effects of N-hydroxyguanidine PR5 in myocardial ischaemia and reperfusion in rats

1. The potential for the N-hydroxyguanidine compound PR5 (N-(3, 4-dimethoxy-2-chlorobenzylideneamino)-N'-hydroxyguanidine) as a cardioprotective agent in heart ischaemia and reperfusion injury was investigated using rat models. 2. Administration of 1-10 mg kg-1 of PR5 5 min before 10 min of left coronary artery occlusion, followed by 20 min reperfusion, strongly inhibited reperfusion burst of arrhythmias and markedly improved the survival of the animals (e.g. ventricular fibrillation incidence 93 vs 43% (P<0.05); mortality 47 vs 0% (P<0.05), for controls and for 3 mg kg-1 of PR5, respectively). 3. Administration of 3 mg kg-1 of PR5 1 min before reperfusion to rats subjected to 10 min occlusion, 20 min reperfusion was most effective in reducing arrhythmias and decreasing mortality (43 vs 0%, P<0.05), but effects were also seen when PR5 was administered 0, 1 and 5 min after start of reperfusion. 4. Coronary occlusion/reperfusion (10 - 20 min) increased malondialdehyde (MDA) of rat hearts (0.88+/-0.13 for sham vs 1.45+/-0.12 nmol mg-1 protein for ischaemic; P<0.05). In rats where 3 mg kg-1 PR5 were administered 1 min before reperfusion the increase was attenuated (MDA being 1.04+/-0.12; P<0.05 vs ischaemic). 5. PR5 caused a substantial reduction of the infarction size in rats subjected to 180 min left coronary artery occlusion, followed by 120 min of reperfusion; the necrotic zone being 326+/-32 mg for controls vs 137+/-21 mg for animals treated with 3x3 mg kg-1 of PR5 (P<0.01). 6. PR5 reduced the elevation of the ST-segment of the ECGs, as well as caused pronounced attenuation of the rapid blood pressure drop seen at the start of reperfusion following coronary artery occlusion. 7 We conclude that the N-hydroxyguanidine PR5 provides remarkable protection against ischaemia and reperfusion induced myocardial necrosis and life-threatening arrhythmias. These effects of PR5 are discussed in relation to a recently discovered ability of N-hydroxyguanidines to function as electron acceptors at the xanthine oxidase enzyme.