Lazaroid U74500A as an additive to University of Wisconsin solution for pulmonary grafts in the rat transplant model

Reperfusion Injury

The restoration of blood flow to ischemic tissues causes additional damage, which is termed reperfusion injury. All tissues are susceptible to reperfusion injury, but this susceptibility varies between tissues. Reperfusion has wide clinical relevance. It influences the outcome of patients after myocardial infarction, stroke, organ transplantation, and cardiovascular surgery. Advances in the treatment of reperfusion injury have created an opportunity for plastic surgeons to apply these treatments to flaps and reimplanted tissues. The main putative mechanisms identified in animal models involve leukocyte-endothelium interactions, reactive oxygen species, and the complement system. However, it has become evident that these fundamental biological systems are controlled by many interrelated pathways. Attempts to bypass this complexity have led to a search for the early "upstream" initiating events, rather than the "downstream" cascading events. This contrasts with current clinical efforts that are directed toward hypothermia, intraarterial flushing, and preconditioning. This article outlines the molecular and cellular events that occur during reperfusion injury and then reviews the efforts that have been made to exploit this knowledge for clinical advantage.

Protective effect of lipophilic antioxidants on phorbol-induced acute lung injury in rats

OBJECTIVE

To determine whether the lipophilic antioxidant U-74389G can ameliorate the acute lung injury induced by phorbol myristate acetate (PMA) in our isolated lung model in rats, and to compare its activity with the intracellular enzymes superoxide dismutase (SOD) or catalase.

DESIGN

Randomized, controlled study.

SETTING

Animal-care facility procedure room.

SUBJECTS

Forty-two adult male Sprague-Dawley rats each weighing 250-350 g.

INTERVENTIONS

Typical acute lung injury was induced successfully by PMA during 60 mins of observation. PMA (2 microg/kg) elicited a significant increase in microvascular permeability (measured by using the capillary filtration coefficient Kfc), lung weight gain, the lung weight/body weight ratio, pulmonary arterial pressure, and the protein concentration of the bronchoalveolar lavage fluid.

MEASUREMENTS AND MAIN RESULTS

Pretreatment with 1 mg of U-74389G significantly attenuated the acute lung injury induced by PMA, all parameters having decreased significantly (p <.001). The protective effect of U-74389G was dose dependent, but SOD (6,000 U/kg) or catalase (50,000 U/kg) exhibited no protective effect.

CONCLUSIONS

U-74389G significantly ameliorates acute lung injury induced by PMA in rats.

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.

RU486-induced growth inhibition of human endometrial cells

OBJECTIVE

To determine the direct action of RU486 on endometrial cell proliferation and to differentiate whether the antioxidant or the antiprogesterone property of RU486 is predominately responsible for its effect on cell growth.

DESIGN

In vitro study comparing the effects of RU486 (antiprogesterone and antioxidant), reduced RU486 (antioxidant), ZK112,993 (antiprogesterone), and lazaroid U74,500A (antioxidant) on endometrial cell growth. The human endometrial cell line EM42 was used in transient transfection assays to confirm the relative antiprogesterone potency of the various compounds.

SETTING

Academic medical center

PATIENT(S)

Women presenting with pelvic pain or infertility and diagnosed with endometriosis at time of surgery or women desiring tubal ligation with a normal pelvis (controls).

INTERVENTION(S)

Endometrial cell cultures were treated with RU486, reduced RU486, lazaroid U74,500A, and ZK112,993.

MAIN OUTCOME MEASURE(S)

Tritiated thymidine incorporation was used to assess cell growth. Inhibition of progesterone induction of transiently transfected reporter plasmids was used to measure antiprogesterone activity of compounds studied.

RESULT(S)

RU486 reduced cell growth in a dose-dependent fashion of the endometrial cell lines EM42 and RL95-2 and of endometrial and endometriosis cells from primary culture. After being reduced, RU486 lost most of its antiprogesterone activity but retained its antiproliferative properties. ZK112,993 was similar in potency to RU486 as a progesterone antagonist but did not significantly modify endometrial cell growth. Lazaroid U74,500A was devoid of antiprogesterone activity but was shown to be a potent antiproliferative agent.

CONCLUSION(S)

RU486 has a direct inhibitory effect on human endometrial cell growth. This activity appears to be at least partly mediated through its antioxidant property.

Cold storage induces time-dependent F2-isoprostane formation in renal tubular cells and rat kidneys

BACKGROUND

Previous findings suggest a possible role for free radicals in cold-storage-associated tissue injury. Because free radical-induced lipid peroxidation catalyzes the cyclooxygenase-independent formation of vasoconstrictive F2-isoprostanes, the hypothesis that isoprostanes are produced during cold storage was tested in this study.

METHODS

Total isoprostanes (free and esterified) in renal tubular epithelial (LLC-PK1) cells or whole kidneys, subjected to cold storage, were quantitated employing the gas chromatographic-mass spectroscopic method. LLC-PK1 cells were stored at 4 degrees C in a University of Wisconsin (UW) solution for 0, 24, 48, and 72 hours or 48 hours with desferrioxamine (DFO) or the lazaroid compound 2-methyl aminochroman (2-MAC). In the rat model, kidneys were perfused and stored for 48 hours in the UW solution with or without added DFO or 2-MAC.

RESULTS

Isoprostanes in LLC-PK1 cells increased by fivefold following 24 hours of cold storage (36 +/- 2 pg/well to 185 +/- 6, mean +/- SE, following 24 hours of cold storage, P < 0.0001), and the levels continued to increase significantly at 48 and 72 hours. DFO and 2-MAC caused significant suppression of isoprostane formation. Cold storage of the kidneys in UW solution for 48 hours was accompanied by an eightfold increase in isoprostanes compared with control kidneys not subjected to cold storage (25.0 +/- 3.0 vs. 2.9 +/- 0.1 ng/g, P < 0.0001). The addition of 2-MAC or DFO to the UW solution was associated with a near complete suppression of 48-hour cold-induced isoprostane formation.

CONCLUSION

Our findings provide evidence for the formation of large quantities of antioxidant-suppressible isoprostanes in kidney cells and whole kidney during cold-preservation. Based on this, it is hypothesized that (a) isoprostanes, which are potent renal vasoconstrictors, may contribute to immediate post-transplant vasoconstriction and dysfunction in kidneys subjected to extended cold storage, and that (b) the addition of 2-MAC or DFO to a UW solution in such circumstances may attenuate these alterations partly by suppressing isoprostane formation.

Early alterations of lung injury following acute smoke exposure and 21-aminosteroid treatment

In a simulated fire-related smoke exposure protocol, New Zealand white rabbits were utilized to investigate the potential effects of the 21-aminosteroid (lazaroid) analog U75412E on the early events of acute lung injury. Inhalation of a total of 1.6 mg/kg U75412E aerosolized at a rate of 1.53 mg/min at 0.5 hr after smoke exposure significantly attenuated the extent of lung injury at 1 hr, as evidenced by decreased bronchoalveolar lavage (BAL) concentration of total protein, 6-keto-prostaglandin F1-alpha, and blood gas defect. Histopathologic examination demonstrated that the lazaroid significantly attenuated smoke-induced lung injury as evidenced by a decrease in wet lung/body weight ratio, necrosis, and sloughing of airway epithelial cells. Electron microscopy showed that the lazaroid decreased smoke-induced interstitial edema and the vacuolization of alveolar type II epithelium (21.6 +/- 9.7 vs 8.5 +/- 3.6 vacuoled blebs/cell, smoke only vs smoke + lazaroid). However, U75412E did not attenuate smoke-induced changes in BAL concentration of tumor necrosis factor-alpha, total cell count, and granulocyte percentage. These observations suggest that U75412E may exert its action through cooperative mechanisms, such as the modulation of arachidonic acid metabolism, in addition to its characterized antioxidative effects.

Donor treatment with the lazeroid U74389G reduces ischemia-reperfusion injury in a rat lung transplant model

BACKGROUND

Antioxidant treatment with lazeroids has proven beneficial for the amelioration of reperfusion injury in experimental lung transplantation. This study compares the effect of donor versus recipient treatment on immediate postoperative graft function.

METHODS

A model of acute double-lung transplantation in rats was used to assess graft function. Transplanted controls after 2 (group I) and 16 hours of ischemia (group II) were compared to a recipient (group III; 16-hour ischemia) and a donor treatment group (group IV; 16-hour ischemia) using the lazeroid U74389G (6 mg/kg). Serial assessment of alveolar-arterial oxygen difference, dynamic lung compliance, airway and pulmonary vascular resistance was obtained during a 2-hour reperfusion period. Final analysis included survival, weight gain, and histologic examination.

RESULTS

Graft function was significantly better after 2 hours of ischemia than in any of the three 16-hour ischemia groups (II, III, IV). After 16 hours of ischemia, donor treatment provided superior graft function with respect to dynamic lung compliance, airway resistance, and alveolar-arterial oxygen difference when compared with groups II and III. The pulmonary vascular resistance was significantly higher in group III when compared with groups II and IV. Graft weight increase reflecting edema was highest in groups III (104%) and II (98%).

CONCLUSIONS

After prolonged ischemia only donor treatment with the lazeroid U74389G was able to significantly reduce ischemia-reperfusion-related graft dysfunction.

PGE1, dexamethasone, U-74389G, or Bt2-cAMP as an additive to promote protection by UW solution in I/R injury

A method to reduce ischemia-reperfusion (I/R) injury can be an important criterion to improve the preservation solution. Although University of Wisconsin solution (UW) works as a lung preservation solution, its attenuation effect on I/R injury has not been investigated. We attempted to determine whether, by adding various protective agents, modified UW solutions will enhance the I/R attenuation by UW. We examined the I/R injury in an isolated rat lung model. Various solutions, e.g., physiological salt solution (PSS), UW, and modified UW solutions containing various protective agents such as prostaglandin E1, dexamethasone, U-74389G, or dibutyryl adenosine 3',5'-cyclic monophosphate were perfused individually to evaluate the I/R injury. Isolated rat lung experiments, with ischemia for 45 min, then reperfusion for 60 min, were conducted in a closed circulating system. Hemodynamic changes, lung weight gain (LWG), capillary filtration coefficient (Kfc), protein content of lavage fluid, concentration of cytokines, and lung histopathology were analyzed. Results showed that the acute I/R lung injury with immediate permeability pulmonary edema was associated with an increase in tumor necrosis factor-alpha (TNF-alpha) production. A significant correlation existed between TNF-alpha and Kfc (r = 0.8, P < 0.0001) and TNF-alpha and LWG (r = 0. 9, P < 0.0001), indicating that TNF-alpha is an important cytokine modulating early I/R injury. Significantly lower levels of Kfc, LWG, TNF-alpha, and protein concentration of lung lavage (P < 0.05) were found in the UW-perfused group than in the control group perfused with PSS. Modified UW promoted the protective effect of UW to further decrease Kfc, LWG, and TNF-alpha (P < 0.05). Histopathological observations also substantiated this evidence. In the UW+U-74389G group, bronchial alveolar lavage fluid contained lowest protein concentration. We conclude that the UW solution attenuates I/R injury of rat lung and that the modified UW solutions further enhance the effect of UW in reducing I/R injury. Among modified solutions, UW+U-74389G is the best. Further investigation of the improved effects of the modified UW solutions would be beneficial in lung transplantation.

Inhaled nitric oxide at the time of harvest improves early lung allograft function

BACKGROUND

Inhalation of nitric oxide (NO) has been shown to have beneficial effects on a variety of acute lung injuries, including lung allograft reperfusion injury. The purpose of the present study was to investigate the effects of inhaled NO at the time of harvest on function of canine left lung allografts after transplantation.

METHODS

Ten dogs underwent left lung allotransplantation. Donor lungs were flushed with modified Euro-Collins solution and stored for 21 hours at 1 degree C. Immediately after transplantation, the contralateral main pulmonary artery and bronchus were ligated to assess isolated allograft function. Hemodynamics and arterial blood gases (inspired oxygen fraction, 1.0) were assessed intermittently for 6 hours prior to sacrifice. Allograft myeloperoxidase activity and wet to dry weight ratio were assessed. Donor animals were divided into two groups. Group I animals (n = 5) received no NO. In group II (n = 5), donors received inhaled NO (60 ppm) at the time of harvest.

RESULTS

Pulmonary vascular resistance decreased to 79.6% of baseline because of inhalation of 60 ppm NO in group II donor animals. Thiobarbituric acid-reactive materials were reduced during the storage period in group II, a finding suggesting less oxidant injury during storage in donor lungs treated with NO. Throughout the 6-hour assessment, oxygenation in group II was superior to that in group I (p < 0.05). At 360 minutes of assessment, mean arterial oxygen tension in groups I and II was 88.9 +/- 11.4 mm Hg and 169.1 +/- 33.0 mm Hg, respectively. Myeloperoxidase activity was significantly decreased in group II (p < 0.05), data indicating reduced neutrophil sequestration. Wet to dry weight ratio was significantly lower in group II.

CONCLUSIONS

These data suggest that inhaled NO at the time of harvest improves early function of preserved lung allografts by attenuating oxidant injury during storage and subsequent neutrophil sequestration.

Renoprotective effects of the 21-aminosteroid U74389G in ischemia-reperfusion injury and cold storage preservation

Free radical mediated lipid peroxidation (LPO) has been implicated in the pathogenesis of ischemic-reperfusion injury (IRI). To address the renoprotective effect(s) of LPO inhibition, the efficacy of the 21 aminosteroid U74389G was evaluated in three IRI models. In Model 1 51 unilateral nephrectomized rats that underwent 60 min of warm ischemia followed by a 72-hr reperfusion interval were treated with the test vehicle only, or 3, 6, or 12 mg/kg of U74389G intravenously, 5 min pre- or postischemia. In Model 2 Sprague-Dawley rats underwent sham operation (n=9), or 45 min of warm ischemia and 10 min of reperfusion with U74389G (6 mg/kg; n=10) or test vehicle only (n=10) administered intravenously over 10 min beginning 5 min prior to clamp release. After reperfusion, LPO was determined by assay of snap frozen tissue for thiobarbituric acid (TBA) concentrations (nmol/g tissue weight). In Model 3 domestic lean maid pigs (14-18 kg) underwent left nephrectomy with 30 min of warm ischemia, Collins C-4 flush, and 24 hr of cold storage preservation. Heterotopic autotransplantation and immediate contralateral nephrectomy was then performed in Group A-nonischemic controls (n=4), Group B-ischemic controls (n=5), and Group C-U74389G (6 mg/kg) administered preischemia and at autotransplantation (n=5). In Model 1 maximal renoprotection was demonstrated with the 6 mg/kg dose of U74389G administered after ischemia (ischemic control 72-hr serum creatinine (Cr) = 8.01+/-1.1 mg% vs. 3.32+/-0.96 mg%; ischemic control creatinine clearance = 0.069+/-0.03 ml/min vs. 0.206+/-0.04 ml/min; P<0.05). In Model 2 TBA levels were significantly lower in U74389G treated animals (88.5+/-10.0 vs. ischemic controls = 296.8+/-81.4; P=0.02). In Model 3 graft survivals were 100%, 0%, and 60% respectively. Peak Cr and BUN (mg%) were significantly greater in Group C vs. Group A, (Group A Cr = 8.59+/-0.63 vs. Group C = 12.8+/-1.01; Group A BUN = 64.1+/-2.73 vs. Group C = 104.9+/-12.21)--however, by day 10, thee were no significant differences in renal function: (Group A Cr = 2.15+/-0.3 vs. Group C = 2.10+/-0.06; Group A BUN = 27.0+/-6.0 vs. Group C = 31.1+/-6.4). These results support the beneficial effects of LPO inhibitors in models of ischemia-reperfusion, as well as preservation/transplantation, and suggest that this renoprotection correlates with decreased membrane lipid peroxidation.

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

BACKGROUND

The lazaroid U74500A is a 21-aminosteroid that inhibits lipid peroxidation and attenuates ischemia-reperfusion injury. We examined the effect of U74500A on heart preservation with the use of a clinically relevant canine orthotopic heart transplantation model.

METHODS AND RESULTS

Six donor dogs (group L) were pretreated intravenously with U74500A (10 mg/kg), and the dogs without pretreatment served as a control (group C, n = 6). The donor heart was preserved in cold University of Wisconsin solution for 24 hours. The heart was then transplanted orthotopically. Myocardial biopsy was performed to measure the adenosine triphosphate level at the end of ischemia. Before reperfusion, recipients in group L received another dose of U74500A (10 mg/kg) intravenously. After 3 hours of reperfusion, left ventricular function was evaluated by left ventricular pressure-volume relations with the use of a Millar catheter and conductance catheter, thereby deriving the slope of the end-systolic pressure-volume relation, the slope of the stroke work-- end-diastolic volume relation, and the slope of the maximum dP/dt--end-diastolic volume relation. At the same time, serum creatine kinase MB isoenzyme and lipid peroxide levels were measured. The slopes of the end-systolic pressure-volume relation, the stroke work--end-diastolic volume relation, and the maximum dP/dt--end-diastolic volume relation for group L were significantly higher than those for group C. The adenosine triphosphate levels for group L were significantly higher than those for group C. Serum creatine kinase MB isoenzyme and lipid peroxide levels for group L were significantly lower than those for group C.

CONCLUSIONS

Inhibition of lipid peroxidation by the administration of U74500A was effective for 24-hour canine cardiac preservation. These results indicate that U74500A is a promising agent for heart allograft preservation.

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

Lazaroids have been reported to attenuate preservation and reperfusion injury. In this study, we examined whether lazaroids can improve the outcome after 48-hr canine liver preservation and transplantation. Adult female beagle dogs were randomized into 4 dosage groups (5 animals each). Lazaroid U-74389G was intravenously administered at a dose of 0 mg/kg, 6 mg/kg, 10 mg/kg, or 15 mg/kg to donors 30 min before harvesting and also to recipients 30 min before revascularization. Control animals (0 mg/kg) were given the lazaroid vehicle. The liver grafts were orthotopically transplanted after 48 hr of hypothermic preservation in UW solution. Lazaroid treatment significantly improved outcome after transplantation. Five-day animal survival increased from 0% in the control to 60% in the 6 mg/kg group, 100% in the 10 mg/kg group, and 80% in the 15 mg/kg group. Lazaroid protected the hepatocytes from damage during preservation, and enhanced energy charge and hepatic blood flow after reperfusion. Histological alterations were significantly less severe in the lazaroid-treated groups. The area of necrotic hepatocytes decreased from 43.7 +/- 17.7 in the control to 13.5 +/- 3.0 in the lazaroid 10 mg/kg group. These results indicate that lazaroid U-74389G has potential for improvement of clinical liver preservation.

The effect of lazaroid (U74500A), a novel inhibitor of lipid peroxidation, on 24-hour heart preservation. A study based on a working model using cross-circulated blood-perfused rabbit hearts

Lazaroid, an inhibitor of iron-mediated lipid peroxidation, has been shown to reduce free radical-mediated injury after ischemia and reperfusion. We thus examined the efficacy of pretreatment with lazaroid (U74500A) in enhancing functional recovery after 24-hr heart preservation. An isolated rabbit heart model perfused with the blood from a support rabbit was used. Before preservation, either U74500A (4 mg/kg, group L; n = 6) or solvent (group S; n = 7) was given to the donor rabbit. After 24-hr preservation with UW solution at 0 degrees C, all hearts were perfused with cross-circulated blood for 60 min with the Langendorff mode followed by 40 min of the working mode. In group S, ventricular fibrillation (Vf) after reperfusion was observed in all hearts, whereas no Vf was observed in the U74500A-pretreated group. In group L, the serum creatine phosphokinase; its isozyme, troponin-T; and serum lipid peroxide levels after 10 min of reperfusion were all significantly (P < 0.05) lower than those in group S. The Frank-Starling curve (indicating the left atrial pressure-aortic flow relationship) showed a significant left and upward shift in group L compared with that in group S (P < 0.0001). The heart pretreated with U74500A showed less ischemia-reperfusion injury, better ventricular function, and a lower lipid peroxide level. We thus conclude that the inhibition of lipid peroxidation with lazaroid appears to offer some potential benefits for long-term heart preservation.

Donor lazaroid pretreatment improves viability of livers harvested from non-heart-beating rats

BACKGROUND

Lazaroids are potent inhibitors of lipid peroxidation. Whether the compounds can benefit the liver procured from non-heart-beating donors (NHBDs) is unknown.

METHODS

Donor rats were pretreated with lazaroid U74006F (4.5 mg/kg) 1 hour before cardiac arrest, and transplantation was performed in the rats with donor cardiac arrest from 0 to 60, 100, 120, 140, and 160 minutes as lazaroid pretreated groups. The same number of liver transplantations were done in each paired control group without donor lazaroid pretreatment. Recipient survival rates, bile secretion, serum enzymes, and a lidocaine metabolism test were analyzed.

RESULTS

Donor lazaroid pretreatment significantly increased recipient 3-day survival rates in groups with 60, 100, and 120 minutes of warm ischemia and 7-day survival with 60 minutes of warm ischemia. Also, the pretreatment increased bile secretion and reduced serum aspartate aminotransferase and lactate dehydrogenase levels in the lazaroid-pretreated groups.

CONCLUSIONS

Donor U74006F pretreatment improves viability of livers procured from NHBDs.

Free radical-mediated vascular injury in lungs preserved at moderate hypothermia

BACKGROUND

Early allograft dysfunction remains a frequently encountered problem in clinical lung transplantation. Lung ischemia-reperfusion injury is associated with increased vascular permeability, which may be due in part to oxygen (O2) free radicals. However, it is not clear whether O2 free radicals are produced during ischemia under storage conditions in clinical lung transplantation.

METHODS

Using an isolated ex vivo rabbit lung model, we studied the effects of preservation temperature on pulmonary capillary filtration coefficient (Kf) and lipid peroxidation in rabbit lungs inflated with 100% O2 after preservation with or without the O2 free radical scavenger dimethylthiourea. New Zealand white rabbits weighing 2.7 to 3.1 kg were intubated and ventilated with room air or 100% O2 (tidal volume = 25 mL). After heparinization and sternotomy, the pulmonary artery was flushed with low-potassium-dextran-1% glucose solution (200 mL). The heart-lung block was excised, submerged, and stored for 24 hours at 1 degree or 10 degrees C. After 24-hour preservation, the heart-lung block was suspended from a strain-gauge force transducer and ventilated with room air. The pulmonary artery cannula was connected to a reservoir of hetastarch solution. The lungs were flushed briefly with the hetastarch solution, and the reservoir was raised sequentially at 8-minute intervals to achieve 1.0 to 1.5 mm Hg increments in pulmonary artery pressure. Lung weight gain, airway pressure, pulmonary artery pressure, and left atrial pressure were measured continuously. The slope of steady-state lung weight gain was used to determine Kf (g.min-1.cm H2O-1 x 100 g-1 wet weight).

RESULTS

Twenty-four-hour lung preservation at both 1 degree and 10 degrees C increased Kf. A similar increase in Kf was observed in lungs stored at 1 degree C while inflated with 100% O2. However, a significant increase in Kf was observed when lungs inflated with 100% O2 were stored at 10 degrees C. This increase in Kf was ameliorated by dimethylthiourea. Thiobarbituric acid-reactive substance levels were increased in lungs stored at 10 degrees C while inflated with 100% O2. This finding was eliminated by dimethylthiourea.

CONCLUSIONS

These results indicate that free radical injury occurs during the ischemic phase when lungs are stored at moderate hypothermia while inflated with 100% O2.

Lazaroid pretreatment preserves gas exchange in endotoxin-treated dogs

PURPOSE

The lazaroids are a new class of potent free-radical scavengers. We tested whether U-74389G, a lazaroid, could attenuate some of the adverse cardiopulmonary effects of sepsis.

METHODS

Dogs were randomized to receive either 10 mg/kg U-74389G (n = 10), or a saline control (n = 11). After baseline measurements of hemodynamics and gas exchange, they were then randomized to receive either 0.2 mg/kg endotoxin or a saline infusion. Measurements of hemodynamics and gas exchange were repeated. The study was concluded 70 minutes after endotoxin infusion and the lungs were then removed for histologic evaluation.

RESULTS

In endotoxin-treated control animals, PO2 decreased (278 +/- 123 mm Hg to 67 +/- 13 mm Hg, P < .05) and intrapulmonary shunt increased (12.9% +/- 1.1% to 28.2% +/- 11.4%, P < .05) after endotoxin. Pretreatment with U-74389G attenuated the decrease in PO2 (476 +/- 61 mm Hg to 226 +/- 143) and the increase in intrapulmonary shunt (12.6% +/- 6.1% to 14.3% +/- 6.8%) observed after endotoxin. The extent of lung injury and systemic hemodynamics were similar between control or U-74389G-treated dogs.

CONCLUSIONS

A free-radical-scavenger can attenuate the gas exchange defect commonly associated with endotoxin but it does not improve the derangement of systemic hemodynamics.

Tirilazad mesylate protects stored erythrocytes against osmotic fragility

The hypoosmotic lysis curve of freshly collected human erythrocytes is consistent with a single Gaussian error function with a mean of 46.5 +/- 0.25 mM NaCl and a standard deviation of 5.0 +/- 0.4 mM NaCl. After extended storage of RBCs under standard blood bank conditions the lysis curve conforms to the sum of two error functions instead of a possible shift in the mean and a broadening of a single error function. Thus, two distinct sub-populations with different fragilities are present instead of a single, broadly distributed population. One population is identical to the freshly collected erythrocytes, whereas the other population consists of osmotically fragile cells. The rate of generation of the new, osmotically fragile, population of cells was used to probe the hypothesis that lipid peroxidation is responsible for the induction of membrane fragility. If it is so, then the antioxidant, tirilazad mesylate (U-74,006f), should protect against this degradation of stored erythrocytes. We found that tirilazad mesylate, at 17 microM (1.5 mol% with respect to membrane lecithin), retards significantly the formation of the osmotically fragile RBCs. Concomitantly, the concentration of free hemoglobin which accumulates during storage is markedly reduced by the drug. Since the presence of the drug also decreases the amount of F2-isoprostanes formed during the storage period, an antioxidant mechanism must be operative. These results demonstrate that tirilazad mesylate significantly decreases the number of fragile erythrocytes formed during storage in the blood bank.

Protective effect of the lazaroid U74006F in cold ischemia-reperfusion injury of the liver

Lipid peroxidation may play a major role in the loss of liver graft viability after prolonged cold ischemia and reperfusion injury. The lazaroid compound U74006F is a potent inhibitor of lipid peroxidation, and this study was designed to evaluate the efficacy of this compound in preventing cold ischemia-reperfusion damage in three different models: pig endothelial cells in culture, ex vivo isolated pig liver perfusion and orthotopic transplantation of syngeneic rat livers. The addition of U74006F to University of Wisconsin preservation solution significantly prolonged endothelial cell viability after 48 and 72 hr of cold ischemia and reoxygenation (p < 0.01). Donor pigs were injected with vehicle or U74006F (4.5 mg/kg) before liver harvest. After 24 hr of cold storage in University of Wisconsin solution, the livers were perfused with pig blood for 180 min in an isolation chamber. Measurements of liver function parameters, including AST, ALT, bile production, superoxide anion and phospholipase A2 release, were assessed every 60 min. Although bile production was similar in the U74006F-treated and control groups, significant decreases of AST and ALT levels (p < 0.01) in the perfusate of the livers from treated donors were observed. In addition, the U74006F group displayed significantly reduced release of superoxide anion and phospholipase A2 compared with these parameters in the untreated group (p < 0.05 and p < 0.01, respectively). In the last model, donor rats were treated with U74006F before harvest; the rat liver grafts were preserved in cold University of Wisconsin solution for 24 hr and then transplanted into recipient rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of in vitro lipid peroxidation by 21-aminosteroids. Evidence for differential mechanisms

In a previous report (Ryan and Petry, Arch Biochem Biophys 300: 699-704, 1993), the effects of two 21-aminosteroids (U-74500A and U-74006F) on the oxidation and reduction of iron in a buffer/organic solvent system were investigated. In those studies, U-74500A was found to be an efficient iron reductant and potential iron chelator, whereas U-74006F had little effect on iron redox chemistry. As an extension of those studies, we now report the effects of U-74006F and U-74500A on lipid peroxidation in systems that are dependent upon iron oxidation/reduction. In liposomes, U-74500A inhibited ADP:Fe(II)-dependent lipid peroxidation in a concentration-dependent manner, whereas U-74006F was minimally effective in this system. The mechanism of U-74500A-dependent inhibition probably involved interactions with iron, as iron oxidation was inhibited in the presence of this compound. No effects on iron oxidation were observed in the presence of U-74006F. Addition of Ferrozine to liposomal incubation mixtures indicated that at least two iron pools were present in samples containing U-74500A, one immediately bound by Ferrozine, and another that was bound more slowly. Furthermore, ADP:Fe(III)/ascorbate-dependent lipid peroxidation was blocked completely by U-74500A, presumably by formation of a redox inert complex upon reduction of the iron. U-74500A partially protected ADP:Fe(II) from oxidation by H2O2 and lipid hydroperoxides, indicating that the U-74500A:iron complex was stable in the presence of biologically relevant oxidants. U-74006F did not markedly affect iron oxidation or reduction when incorporated into phospholipid liposomes. In microsomal lipid peroxidation systems containing ADP:Fe(III) and NADPH, both U-74500A and U-74006F inhibited lipid peroxidation. U-74006F-dependent inhibition of microsomal lipid peroxidation was dependent on both NADPH and Fe(III). Further, it was enhanced when U-74006F was allowed to preincubate in this system prior to iron addition. Preincubation of U-74006F with microsomes, NADPH, and ADP:Fe(III) produced several metabolites detectable by HPLC. These results suggest that U-74500A inhibits lipid peroxidation by directly affecting iron redox chemistry, whereas U-74006F-mediated inhibition is enhanced by preincubation with a metabolically competent microsomal system.