Lazaroid U-74389G for 48-hour canine liver preservation

The Effects of Ascorbic Acid and U-74389G on Renal Ischemia-Reperfusion Injury in a Rat Model

BACKGROUND/AIM

U-74389G and ascorbic acid protect the cells from oxidation. This study aimed to depict their role in ischemia-reperfusion injury in a renal rat model.

MATERIALS AND METHODS

Sixty Wistars rats were randomized into six groups of 10 animals each. Group A Ischemia 30 min, reperfusion 60 min; Group B Ischemia 30 min, reperfusion 120 min; Group C Ischemia 30 min, ascorbic acid administration, reperfusion 60 min; Group D Ischemia 30 min, ascorbic acid administration, reperfusion 120 min; Group E Ischemia 30 min, U-74389G administration, reperfusion 60 min; Group F Ischemia 30 min, U-74389G administration, reperfusion 120 min. We then collected tissue and blood samples.

RESULTS

Histology and the significantly decreased malondialdehyde and tumor necrosis factor-α levels indicated that ascorbic acid was superior to U-74389G, at pre-defined time intervals.

CONCLUSION

Ascorbic acid and U-74389G ameliorated renal damage induced by ischemia-reperfusion injury, suggesting a therapeutic effect.

Lazaroid U-74389G in liver ischemia-reperfusion injury: A swine model

Reactive oxygen species have a key role in liver ischemia-reperfusion (I/R) injury. In the present study, the effect of the anti-oxidant compound lazaroid U-74389G in preventing liver I/R injury was investigated in a swine model. Ischemia was produced by portal vein occlusion. Two sets of experiments were performed, each with two groups (n=7 per group). In the first group, the potential protective effect of an intracaval injection of U-74389G after a 30-min ischemia, followed by a 60-min reperfusion period was assessed (biopsies at 0, 15, 30 and 90 min experimental time). In the second set, the effect of intracaval U-74389G injection after 30 min of ischemia, followed by a longer reperfusion period of 120 min was determined (biopsies at 0, 15, 30 and 150 min experimental time). Liver malondialdehyde, hepatocyte vacuolation-degeneration, venous congestion, inflammatory cell infiltration, sinus congestion-dilation and Chiu score of intestinal damage were determined at up to 150 min of reperfusion. In the second set of experiments, the Chiu score of intestinal damage was improved by the administration of U-74389G (3.17±0.40 vs. 4.33±0.21; P=0.030). However, in the two sets of experiments, the liver inflammatory reaction was more pronounced in the U-74389G groups (P=0.017 for the first set, P=0.021 for the second set). No significant effect of U-74389G on any other parameters was detected. In conclusion, intestinal damage due to portal venous congestion and reflow appears to be mitigated by the lazaroid U-74389G; however, intracaval administration of U-74389G does not appear to exert any protective effects against liver I/R-induced inflammation.

Experimental Hemorrhagic Shock Protocol in Swine Models: The Effects of 21-Aminosteroid on the Small Intestine

Background

The protective potential of lazaroids has been reported in previous studies on ischemia/reperfusion and induced hemorrhagic shock protocols.

Objectives

The present study is the first experimental protocol on the effects of the antioxidant factor U-74389G on the small intestine of swine models in a hemorrhagic shock protocol and resuscitation with 3 different types of fluids.

Methods

The study included 49 Landrace breed swine that were divided into groups of 7 each. Hemorrhage was provoked 45 minutes after starting the surgical protocol (0 minutes), followed by resuscitation starting 30 minutes after haemorrhage ceased by using 3 different fluids. Three groups (Group A, resuscitation using blood; Group B, resuscitation with Ringer’s lactate solution; and Group C, resuscitation with hypertonic saline solution) underwent resuscitation with fluid alone, and another 3 groups (named A', B,' and C') were administered lazaroid U-74389G in addition to fluid. Control Group S underwent all the surgical procedures without hemorrhagic shock. Vital signs, complete blood count, and biochemical markers were analyzed, and tissue samples of the small intestine were collected from all animals. Further, malondialdehyde, tumor necrosis factor-α, and levels of inflammation in the tissue sample were measured.

Results

In Group S-A-A' and Group S-C-C', the analysis did not show statistically significant differences in the percentage changes of histopathology, malondialdehyde, and tumor necrosis factor-α through time. In Group S-B-B', the malondialdehyde levels in the small intestine were reduced in both the B and B' groups, without lazaroid (Group B) (P = 0.038) and lazaroid (Group B') (P = 0.011), compared with Group S (control), but the group without lazaroid (Group B) had greater reduction in malondialdehyde levels than the group treated with lazaroid (Group B'). With regard to the biochemistry results, 24% reduction was observed for alkaline phosphatase (P = 0.022) in Group A' treated with lazaroid compared with that in the untreated group. Lastly, for the complete blood count parameters, a 14% reduction in white blood cells was observed in Group B', which was treated with lazaroid in all phases (P = 0.015) (absolute value = 6.23) compared with Group B (absolute value = 13.74).

Conclusions

Despite few initial findings of this study suggesting that administration of lazaroid U-74389G may have some potential in attenuation of the effects of hemorrhagic shock in the small intestine of swine models, no differences remained after correction for multiple comparisons was made. Therefore, further research is required to investigate this result thoroughly.

Pretreatment with mangafodipir improves liver graft tolerance to ischemia/reperfusion injury in rat

Ischemia/reperfusion injury occurring during liver transplantation is mainly due to the generation of reactive oxygen species (ROS) upon revascularization. Thus, delivery of antioxidant enzymes might reduce the deleterious effects of ROS and improve liver graft initial function. Mangafodipir trisodium (MnDPDP), a contrast agent currently used in magnetic resonance imaging of the liver, has been shown to be endowed with powerful antioxidant properties. We hypothesized that MnDPDP could have a protective effect against liver ischemia reperfusion injury when administrated to the donor prior to harvesting. Livers from Sprague Dawley rats pretreated or not with MnDPDP were harvested and subsequently preserved for 24 h in Celsior® solution at 4°C. Organs were then perfused ex vivo for 120 min at 37°C with Krebs Henseleit solution. In MnDPDP (5 µmol/kg) group, we observed that ATP content was significantly higher at the end of the cold preservation period relative to untreated group. After reperfusion, livers from MnDPDP-treated rats showed better tissue integrity, less hepatocellular and endothelial cell injury. This was accompanied by larger amounts of bile production and higher ATP recovery as compared to untreated livers. The protective effect of MnDPDP was associated with a significant decrease of lipid peroxidation, mitochondrial damage, and apoptosis. Interestingly, MnDPDP-pretreated livers exhibited activation of Nfr2 and HIF-1α pathways resulting in a higher catalase and HO-1 activities. MnDPDP also increased total nitric oxide (NO) production which derived from higher expression of constitutive NO synthase and lower expression of inducible NO synthase. In conclusion, our results show that donor pretreatment with MnDPDP protects the rat liver graft from cold ischemia/reperfusion injury and demonstrate for the first time the potential interest of this molecule in the field of organ preservation. Since MnDPDP is safely used in liver imaging, this preservation strategy holds great promise for translation to clinical liver transplantation.

The use of a supercooling refrigerator improves the preservation of organ grafts

Current medical transplantation confronts major problems such as the shortage of donors and geographical restrictions that inhibit efficient utilization of finite donor organs within their storage lives. To overcome these issues, expanding organ preservation time has become a major concern. We investigated whether a strategy which best preserves organ grafts can be achieved by the use of a newly developed refrigerating chamber, which is capable of establishing a supercooled and unfrozen state stably by generating an electrostatic field in its inside. When adult rat organs such as heart, liver, and kidneys were stored in the supercooled conditions, the levels of major biochemical markers leaked from the preserved organs were significantly lower than in the ordinary hypothermic storage. No apparent tissue damages were observed histologically after the supercooled preservation. Our results suggest that the use of this supercooling refrigerator improves organ preservation and may provide an innovative technique for human organ transplantation.

Evaluation of the Potential Protective Effect of 21-Aminosteroid U-74389G on Liver Injury Induced by Reduced and Prolonged Partial Hepatic Ischaemia Reperfusion in Rats

The protective effect of the 21-aminosteroid U-74389G was studied in an experimental model of partial ischaemia reperfusion liver injury. Previous studies have proven the remarkable potency of 21-aminosteroids to prevent oxidant-induced cell injury in vitro and in vivo. However, the capability of these compounds to limit oxidative injury in clinical trials has been considered to be less certain. The potential protective effect exerted by U-74389G on reduced and prolonged models of ischaemia reperfusion liver injury was studied in male rats subjected to 75 min. of segmentary hepatic ischaemia followed by 1 or 24 hr of reperfusion. Liver injury was evaluated by measuring serum levels of liver enzymes and by histopathological studies. The oxidative status of liver cells was measured by evaluating the levels of liver lipid peroxidation products such as malondialdehyde and the levels of reduced glutathione. Our results lead us to think that treatment with U-74389G (6 mg/kg) does not bring about any protective effect neither in the levels of transaminases nor in the percentage of hepatocellular necrosis and cellular infiltration observed in any reperfusion-period groups. In fact and in contrast with our expectations, U-74389G seemed to increase enzyme release. Furthermore, at the dose used, this 21-aminosteroid is not capable of inhibiting the lipoperoxidation processes, although it induced an important increase of GSH levels at any time-period of reperfusion. This last finding seem to suggest that U-74389G could increase the resistance to oxidant-induced liver tissue damage. However, our results show that, at the dose used, this compound did not exert any protective effect on liver tissue, thus explaining, at least partially, the absence of beneficial effects on the part of these compounds in clinical trials carried out to limit organ injury in transplants.

Trends in organ preservation

Organ preservation aims to provide a viable graft with primary function post-transplant. The current basis of preservation for transplantation is static cold storage using specific preservation solutions which minimise cellular swelling and membrane pump activity, thus maintaining cellular ATP levels. The current organ shortage and consequent expansion of donor criteria places even greater reliance on minimising graft injury during preservation. This review focuses on current and future advances in preservation technology. The key areas of advance are additives to preservation solutions, alternatives/adjuncts to preservation solutions including perfluorocarbons. A major area of advance is in the modulation of organs during the storage period. This may be achieved by biochemical additives or genetic manipulation. Machine perfusion technology is improving, and this is discussed together with the recent concept of warm (normothermic) perfusion as an alternative means of preservation. The authors provide an overview over the current methods of organ preservation. Cold storage, effective in the short-term is insufficient for marginal organs, does not allow assessment of viability markers, and provokes ischaemic injury. Potential strategies for minimising ischaemic injury include additives to preservation solutions; the two-layer method with perfluorcarbons and UW solution-at present limited to pancreas preservation; organ modulation; organ preconditioning and genetic modification of organs. In particular, the authors illuminate the potential in a reappraisal of the concept of normothermic perfusion.

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.

Improvement of ischaemia-reperfusion injury by lazaroid U74389G in rat lung transplantation model

The effect of lazaroid 74389G on ischaemia-perfusion injury in a rat lung transplantation model was investigated using three administration methods. In all groups, the University of Wisconsin (UW) solution was used as a flush and preservation solution at 4 degrees C, and lungs were stored for 12 h. Group I rats (controls) were not given any lazaroid treatment. In group II, lazaroid U74389G was added to the UW solution (100 micromol/l). In group III, lazaroid (10 mg/kg) was intravenously injected in the donors 30 min before lung ischaemia. Group IV received lazaroid treatment by the combined methods of groups II and III. In all the experimental groups (II-IV), recipient rats were given lazaroid (6 mg/kg) intravenously 30 min before reperfusion. Lazaroid improved the gas exchange function (groups II, III and IV), reduced the tissue lipid peroxides (group II) and ameliorated histologic lung damage (group II). The results thus seemed to be better in group II than in groups III and IV.

A novel hydroxyl radical scavenger, nicaraven, protects the liver from warm ischemia and reperfusion injury

BACKGROUND

Reactive oxygen species have been considered to be involved in liver injury at the procurement, preservation, and transplantation from donors without beating hearts. A novel hydroxyl radical scavenger, nicaraven with hydrophilic and lipophilic properties, infiltrates both intracellular and extracellular spaces where it effectively scavenges reactive oxygen species. Protection by nicaraven against ischemia and reperfusion damage of the brain, heart, and kidneys has been shown. The effect of this agent on the liver remains unclear.

METHODS

Two-hour total hepatic vascular exclusion was used. Eighteen beagle dogs were randomly assigned to 2 groups: 12 animals were not treated (group I) and 6 were treated with nicaraven (group II). Nicaraven was administered intravenously (2mg/kg/min) for 60 minutes before ischemia and for 3 hours, starting 30 minutes before reperfusion.

RESULTS

Two-week survival rates were 25% in group I and 100% in group II (P <.01). Nicaraven inhibited lipid peroxidation in the liver, improved hepatic and systemic hemodynamics and energy metabolism, and suppressed liver enzyme release, endothelin-1 elevation in hepatic venous blood, histologic damage, and neutrophil infiltration into the liver.

CONCLUSIONS

Nicaraven exerted hepatic protection against warm ischemia and reperfusion injury. This may indicate nicaraven as a potential candidate to attenuate liver injury from warm ischemia and preservation in transplantation from donors without beating hearts.

Effect of the 21-aminosteroid on nuclear factor-kappa B activation of Kupffer cells in endotoxin shock

BACKGROUND

The 21-aminosteroid (U-74389G) is a nonglucocorticoid steroid that was synthesized to inhibit lipid peroxidation without the glucocorticoid activity. We recently demonstrated that the 21-aminosteroid administered to endotoxin shock mice reduces liver injury and improves the survival rate of mice through inhibition of nuclear factor-kappa B activation in the liver. The study was undertaken to determine whether the 21-aminosteroid could suppress pro-inflammatory gene up-regulation through inhibition of nuclear factor-kappa B activation in Kupffer cells.

METHODS

Kupffer cells were isolated from rats by collagenase perfusion followed by pronase digestion. After a lipopolysaccharide addition, each assay was performed for tumor necrosis factor-alpha, interleukin-6, tumor necrosis factor-alpha messenger RNA, nuclear factor-kappa B, and I kappa B proteins.

RESULTS

After the lipopolysaccharide addition, Kupffer cells released both tumor necrosis factor-alpha and interleukin-6. The 21-aminosteroid treatment suppressed the release of tumor necrosis factor-alpha in a dose-dependent manner. The 21-aminosteroid also inhibited the increase of tumor necrosis factor-alpha messenger RNA expression and nuclear factor-kappa B activation in Kupffer cells 1 hour and 30 minutes, respectively, after lipopolysaccharide addition. Furthermore, the 21-aminosteroid treatment suppressed the degradation of I kappa B proteins in lipopolysaccharide-stimulated Kupffer cells.

CONCLUSIONS

These results suggest that the 21-aminosteroid inhibits release of the tumor necrosis factor-alpha and interleukin-6 from lipopolysaccharide-stimulated Kupffer cells by inhibiting nuclear factor-kappa B activation. This is accomplished by inhibiting I kappa B degradation in endotoxin shock and this may prove useful for the treatment of endotoxin shock.

Effects of the 21-aminosteroid U74389G in a model of chronic myocardial infarction in the rat

21-Aminosteroids are a group of new synthetic compounds developed as antiperoxidants. Although several studies have demonstrated their cardioprotective properties in acute ischemic models, none has assessed their long-term benefits after chronic myocardial infarction. In this investigation, we examined the cardioprotective effects of U74389G, a novel 21-aminosteroid, in a model of chronic myocardial infarction in the rat. After permanent ligation of the proximal branch of the left coronary artery, the experimental animals were treated daily by gavage with U74389G (10 mg/kg) for 21 days. After the study period, harvested hearts were perfused ex vivo and submitted to cold cardioplegia with 90-min global ischemia and 30-min reperfusion (surgical stress). Myocardial function and coronary endothelial (bradykinin, 1 microM) and smooth muscle (sodium nitroprusside, 1 microM) reactivity were assessed before and after exposure to the surgical stress. Percentage infarct size of the left ventricle was computed as the ratio of infarct area (mg)/total left ventricle (mg) x 100. During or immediately after surgery, there were eight deaths, which were considered technical failures. No further deaths occurred during the follow-up period (21 days). Compared with vehicle-treated rats, long-term administration of U74389G elicited a significant reduction of infarct size (percentage of left ventricle, 9 +/- 5% in the U74389G-treated group vs. 32 +/- 5% in the vehicle-treated group; p < 0.01). Ex vivo heart-perfusion studies showed no significant difference in baseline coronary flow, left ventricular developed pressure, and heart rate between normal and chronic infarcted hearts treated with the vehicle or with U74389G. However, a reduced endothelium-dependent coronary dilator response was observed in infarcted hearts from vehicle-treated controls but not in those from U74389G-treated rats. When cardioplegia and global myocardial ischemia/reperfusion were added, most of the benefits from U74389G were lost. These results indicate that 21-aminosteroids can reverse oxygen-derived free radicals and lipid peroxidation-induced myocardial and coronary dysfunction associated with chronic myocardial infarction. However, additive protective measures are required when an acute ischemic stress is superimposed.

The effect of Lazaroid U-74389G on extended liver resection with ischemia in dogs

BACKGROUND

In liver surgery, total clamping of the portal triad (Pringle's procedure) is commonly used, and it sometimes causes liver failure. This study was designed to evaluate the effect of Lazaroid U-74389G (LAZ-G), which inhibits iron-dependent lipid peroxidation, on ischemia-reperfusion injury during liver resection in dogs.

METHODS

The experiment animals were divided into 2 groups. The control group was subjected to 60 minutes of warm ischemia by partial inflow occlusion. The LAZ-G-treated group received LAZ-G before ischemia and then underwent liver ischemia. After reperfusion, the nonischemic lobes were resected, and the remnant liver function was evaluated.

RESULTS

The LAZ-G-treated group showed a significantly improved animal survival rate. Biochemical analysis and morphologic evaluation by electron microscopy suggest that LAZ-G pretreatment protects both hepatic parenchymal cells and sinusoidal endothelial cells from ischemia-reperfusion injury. Expression of IL-1 beta messenger RNA in hepatic venous blood was measured by a reverse transcriptase-polymerase chain reaction; it was shown to be inhibited in the LAZ-G-treated group after reperfusion. This suggests that LAZ-G decreases the activation of proinflammatory cytokine expression.

CONCLUSIONS

Lazaroid U-74389G ameliorates ischemia-reperfusion injury caused by Pringle's procedure during extensive liver resection. This agent may therefore be clinically applicable for extended liver surgery involving vascular isolation.

Donor and recipient treatment with the Lazaroid U-74006F do not improve post-transplant lung function in swine

OBJECTIVE

U-74006F is the only Lazaroid which is currently in clinical use. A number of experimental studies demonstrate that Lazaroids reduce ischemia/reperfusion injury in various organ systems. We evaluated the effect of U-74006F on reperfusion injury in a large animal model of lung allo-transplantation.

METHODS

Two different treatment modalities were evaluated and compared with corresponding control groups. Unilateral left lung transplantation was performed in 21 weight-matched pigs (24-31 kg). Donor lungs were flushed with 1.51 cold (1 degrees C) LPD solution and preserved for 20 h. In group I (n = 5), donor animals were pretreated with U-74006F (10 mg/ kg i.v.) 20 min before harvest. In addition U-74006F was added to the flush solution (10 mg/l). In group III (n = 6), the Lazaroid was given to the donor before flush and to the recipient before reperfusion (3 mg/kg i.v.). Group II and IV (n = 5) served as control. One hour after reperfusion, the recipient contralateral right pulmonary artery and bronchus were ligated to assess graft function only. Extravascular lung water index (EVLWI), mean pulmonary artery pressure, cardiac output, and gas exchange were assessed during a 5 h observation period. Lipid peroxidation (TBARS) and neutrophil migration (MPO activity) were measured at the end of the assessment in lung allograft tissue.

RESULTS

A significant change of TBARS concentration was shown in group III (group III 78.7+/-4.6 pmol/g vs. group IV 120.8+/-7.2 pmol/g (P = 0.0065) normal lung tissue 41.3+/-4.2 pmol/g). MPO activity was reduced in group III 3.74+/-0.25 deltaOD/mg per min vs. group IV 4.97+/-0.26 deltaOD/mg per min (P = 0.027), normal lung tissue 1.04+/-0.27 deltaOD/mg per min). Pulmonary hemodynamics and gas exchange after reperfusion did not differ between groups. In group I and III, a tendency towards a reduced EVLWI was noted.

CONCLUSION

We conclude that combined treatment of donor and recipient with U-74006F reduces free radical mediated injury in the allograft. However, this intervention did not result in a significant reduction of post-transplant lung edema or improvement of pulmonary hemodynamics. Donor pretreatment alone did not improve lung allograft reperfusion injury. These results indicate that the benefit of U-74006F is too small to consider clinical application in lung transplantation.

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.

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.

Natural antioxidants enhance and prolong the oxyradical/no-related suppression by dexamethasone of ischemic and histamine paw edema in mice

Dexamethasone (0.1 mg/kg, s.c.) suppressed 2, 22, 12, 6, and 4% of ischemic paw edema of mice at 1, 3, 6, 18, and 40 h. Various antioxidants when given with 0.1 mg/kg Dex enhanced and prolonged the suppression. For example, 30 mg/kg of tannic acid induced suppression of 6, 52, 59, 42 and 27%, whereas no increase of Dex suppression at 1 h was observed with any of the antioxidants tested. The prolonging effect of antioxidants may be due to the change of glucocorticoid (GC) receptor signaling under new redox state, because oxyradicals modified the suppression, whereas nitric oxide (NO) showed no effect on Dex suppression enhanced by antioxidants. ED30 (mg/kg, i.p.) at 6 h after Dex was: morin (0.02) > alpha-tocopherol (0.03) > tannic acid (0.12) > rutin (0.2) = bilirubin (0.2) > beta-carotene (0.3) >> quercetin (6) > melatonin (8) > ascorbic acid (12), whereas none of the antioxidants alone afforded more than 10% suppression even at 30 mg/kg. Similar Dex plus antioxidant actions were observed in histamine paw edema. Clinical trials of nontoxic natural antioxidants might be successful when coinjected with low dose of GC which shows very little side effects.

Lazaroid U-74500A for warm ischemia and reperfusion injury of the canine small intestine

BACKGROUND

Although lazaroids have been shown to protect various organs from ischemia/reperfusion injury, results obtained in the small intestine have been conflicting.

STUDY DESIGN

The canine small intestine was made totally ischemic for 2 hours by occluding the superior mesenteric artery and the superior mesenteric vein with interruption of the mesenteric collateral vessels. A lazaroid compound, U74500A, or a citrate vehicle was given intravenously to each of the six animals for 30 minutes before intestinal ischemia. Intestinal tissue blood flow, lipid peroxidation, neutrophil infiltration, adenine nucleotides and their catabolites, and histologic changes after reperfusion were determined.

RESULTS

Lazaroid treatment attenuated decline of the mucosal and serosal blood flow after reperfusion. Accumulation of lipid peroxidation products and neutrophils in mucosal tissues was markedly inhibited by the treatment. Postischemic energy resynthesis was also augmented by lazaroid. Morphologically, mucosal architectures were better preserved with lazaroid treatment after reperfusion, and recovered to normal by postoperative day 3 in the treated group and by postoperative day 7 in control animals.

CONCLUSIONS

Lazaroids protect the canine small intestine from ischemia/reperfusion injury by inhibiting lipid peroxidation and neutrophil infiltration. Dogs are tolerant of 2-hour normothermic complete intestinal ischemia.

Nitric oxide synthase activity in renal ischemia-reperfusion injury in the rat: implications for renal transplantation

Cadaveric kidney transplants with delayed graft function have poorer graft survival by an unknown mechanism. Nitric oxide, produced by nitric oxide synthase (NOS), has a proven role in both recovery of ischemia and promotion of rejection. We therefore wished to study the patterns of NOS activity in a model of renal ischemia. The left renal pedicle of Fisher rats was occluded for 1 hr. Both kidneys were removed at various times and frozen. Renal NOS activity was measured by conversion of [3H]arginine to [3H]citrulline and the content of endothelial NOS isoenzyme (eNOS) was compared by Western blot. NOS activity increased significantly in the left ischemic kidney over the first 24 hr, from a control of 33.8 pmol/min/mg to 79.8 at 2 hr and 56.8 at 24 hr. NOS activity then dropped below baseline, returning to near normal levels at day 21. eNOS content was stimulated over the entire time course, consistent with the presence of an eNOS inhibitor. Oral treatment with the NOS substrate L-arginine at 5 g/L significantly hastened the return of serum creatinine to baseline, if simultaneous contralateral nephrectomy was performed. The lazaroid U74389G given perioperatively also improved renal function and hastened recovery of NOS activity. Because nitric oxide plays an important role in maintaining blood flow during recovery from renal ischemia, the observed decrease in NOS activity may be prevented by perioperative treatment with oral L-arginine and corticosteroids. In addition, U74389G may provide a clinically useful method of minimizing and/or shortening DGF, thereby improving graft function and survival.

Comparison of various lazaroid compounds for protection against ischemic liver injury

Lazaroids are a group of 21-aminosteroids that lack steroid action but have a potent cytoprotective effect by inhibiting iron-dependent lipid peroxidation. However, there have been conflicting reports on the effectiveness and potency of the various lazaroid compounds. In this study, we compared the effectiveness of three major lazaroids on warm liver ischemia in dogs using a 2-hr hepatic vascular exclusion model. The agents were given to the animals intravenously for 30 min before ischemia. The animals were divided into 5 groups: Control (n=10), no treatment; Group F (n=6), U-74006F (10 mg/kg); Group G (n=6), U-74389G (10 mg/kg); Group A1 (n=6), U-74500A (10 mg/kg); Group A2 (n=6), U-74500A (5 mg/kg). The effect of treatment was evaluated by two-week animal survival, hepatic tissue blood flow, liver function tests, blood and tissue biochemistry, and histological analyses. Animal survival in all treated groups was significantly improved compared with the control (83-100% versus 30%). Elevation of liver enzymes after reperfusion was markedly attenuated in treated groups, except for an early significant increase in Group G. Postreperfusion hepatic tissue blood flow was much higher in all treated animals (50% of the preischemic level vs. 25% in the control). Lazaroids, particularly U-74500A at 5 mg/kg (Group A2), suppressed adenine nucleotide degradation during ischemia and enhanced the resynthesis of high-energy phosphates after reperfusion. Although structural abnormalities in postreperfusion liver tissues were markedly ameliorated in all treated groups, Group A2 showed significantly less neutrophil infiltration. Liver injury from warm ischemia and reperfusion was attenuated with all lazaroid compounds, of which U-74500A at 5 mg/kg exhibited the most significant protective activity.

Comparison of various lazaroid compounds for protection against ischemic liver injury

Lazaroids are a group of 21 -aminosteroids that lack steroid action but have a potent cytoprotective effect by inhibiting iron-dependent lipid peroxidation. However, there have been conflicting reports on the effectiveness and potency of the various lazaroid compounds. In this study, we compared the effectiveness of three major lazaroids on warm liver ischemia in dogs using a 2-hr hepatic vascular exclusion model. The agents were given to the animals intravenously for 30 min before ischemia. The animals were divided into 5 groups: Control (n=10), no treatment; Group F (n=6), U-74006F (10 mg/kg); Group G (n=6), U-74389G (10 mg/kg); Group A1 (n=6), U-74500A (10 mg/kg); Group A2 (n=6), U-74500A (5 mg/kg). The effect of treatment was evaluated by two-week animal survival, hepatic tissue blood flow, liver function tests, blood and tissue biochemistry, and histological analyses. Animal survival in all treated groups was significantly improved compared with the control (83–100% versus 30%). Elevation of liver enzymes after reperfusion was markedly attenuated in treated groups, except for an early significant increase in Group G. Postreperfusion hepatic tissue blood flow was much higher in all treated animals (50% of the preischemic level vs. 25% in the control). Lazaroids, particularly U-74500A at 5 mg/kg (Group A2), suppressed adenine nucleotide degradation during ischemia and enhanced the resynthe-sis of high-energy phosphates after reperfusion. Although structural abnormalities in postreperfusion liver tissues were markedly ameliorated in all treated groups, Group A2 showed significantly less neutrophil infiltration. Liver injury from warm ischemia and reperfusion was attenuated with all lazaroid compounds, of which U-74500A at 5 mg/kg exhibited the most significant protective activity.

Antioxidant lazaroid U-74006F improves renal function and reduces the expression of cytokines, inducible nitric oxide synthase, and MHC antigens in a syngeneic renal transplant model. Partial support for the response-to-injury hypothesis

In a recent study, antioxidant therapy at the time of renal transplantation in humans was associated with fewer rejection episodes and extended graft survival. A hypothesis generated by such studies and based on the response-to-injury model is that reducing the oxidative injury during transplantation may dampen certain cellular responses to injury that are important in triggering allograft rejection. To test whether ablation of oxidative injury would limit such responses, kidneys were transplanted between Wistar-Furth rats, with and without antioxidant 21-aminosteroid. 21-Aminosteroid was administered before kidney harvest and, again, before transplant reperfusion. The recipient's left kidneys, removed to accommodate the donor kidneys, were used as normal control. The removal of the right kidneys contralateral to the transplant were delayed to day 4 to provide interim renal support. The transplanted kidneys were harvested on day 7. Administration of 21-aminosteroid was associated with better graft function and reduced lipid peroxidation. Compared with the normal control kidneys, the kidneys transplanted with vehicle had higher cytokine mRNA levels (measured by reverse transcriptase-polymerase chain reaction) for interleukin 2, interleukin 6, tumor necrosis factor-alpha, and interferon-gamma. The levels for these cytokines were reduced in kidneys transplanted with 21-aminosteroid. An increase in inducible nitric oxide synthase mRNA in the transplanted kidney was inhibited by 21-aminosteroid, as were the increase in class I and II MHC antigens. The new finding, that a reduction in transplantation-related oxidative injury in a syngeneic model is accompanied by a reduction in the expression of cytokines, MHC antigens, and inducible nitric oxide synthase, provides partial support for the response-to-injury hypothesis in the setting of renal transplantation. The data also demonstrate for the first time the efficacy of 21-aminosteroid to reduce lipid peroxidation and renal injury in kidneys transplanted after cold preservation.