Effect of brief regional ischemia followed by reperfusion with or without superoxide dismutase and catalase administration on myocardial sarcoplasmic reticulum and contractile function

The effect of reperfusion with and without free radical scavengers on sarcoplasmic reticulum and contractile function was examined in a canine model of 15-minute coronary artery occlusion followed by reperfusion. Dogs were reperfused with (n = 13) or without (n = 16) superoxide dismutase and catalase or were killed at 15 minutes of ischemia (n = 17). Superoxide dismutase and catalase were administered as a bolus (20,000 and 12,500 U/kg, respectively) beginning 1.25 minutes before reperfusion followed by infusion of 16,000 and 12,500 U/kg/hr, respectively. Sarcoplasmic reticulum function was evaluated from the rate of calcium uptake of unfractionated subepicardial, subendocardial, and transmural homogenates determined with and without ruthenium red to close the calcium release channel. Mechanical function was evaluated by means of sonomicrometry. Fifteen minutes of ischemia significantly (p less than 0.05) depressed the sarcoplasmic reticulum calcium uptake rate only in the subendocardium (from 25 +/- 2 to 14 +/- 1 nmol/min/mg without ruthenium red and from 60 +/- 3 to 49 +/- 3 nmol/min/mg with ruthenium red). Reperfusion with or without superoxide dismutase and catalase restored homogenate calcium uptake rates to normal, although severe contractile dysfunction persisted. This indicates that damage to the sarcoplasmic reticulum may not be the major cause of postreperfusion contractile dysfunction. Ischemia-reperfusion caused a decrease in systolic shortening from 19 +/- 2% to 1 +/- 2% with and from 18 +/- 1% to 4 +/- 1% without free radical scavengers (p = NS between groups). Thus administration of superoxide dismutase and catalase beginning shortly before reperfusion had no effect on postreperfusion contractile dysfunction or sarcoplasmic reticulum function.     

Lack of significant effects of superoxide dismutase and catalase on development of reperfusion arrhythmias

Summary It has been reported that agents having the ability to scavenge oxygen-derived free radicals reduce the severity of ventricular arrhythmias that occur after brief coronary occlusion and reperfusion. Superoxide dismutase plus catalase (SOD + CAT) or placebo was administered in a blinded randomized fashion prior to coronary occlusion in rats (n = 25 each group) undergoing a 5-min left coronary occlusion followed by 15 min of reperfusion. During reperfusion, ventricular tachycardia (VT) developed in 96 % of animals in both groups. Reperfusion ventricular fibrillation (VF) developed in 60 % of the placebo group vs 56 % in the SOD + CAT group (p =1.0). Irreversible VF occurred in 40 of the placebo group vs 20 % in the SOD + CAT group (p = 0.22). Atrioventricular block occurred in 12 % of placebo and 4 % of SOD + CAT animals (p = 0.61).There were no significant differences between groups in duration of VT (85 ± 15 s (mean ± SEM) placebo vs 81 ± 14 s SOD + CAT, p = 0.81), total duration of VT plus VF (391 ± 76 s placebo vs 256 ± 64 SOD + CAT, p = 0.45) or numbers of single ventricular ectopic beats (65 ± 15 placebo vs 97 ± 18 SOD + CAT, p = 0.18). Heart rate at reperfusion was slightly higher in control than SOD + CAT animals (340 ± 33 vs 319 ± 32, p = 0.02). Risk zone size, determined by Monastral blue injection, was equal in both groups (34 ± 2 % of ventricular mass). The occurrence of reperfusion VF in this model could not be predicted by heart rate at reperfusion (331 ± 33 VF animals vs 328 ± 36 no VF, p = 0.77), or by risk zone size (34 ± 2 %, VF and no VF groups).Treatment with SOD + CAT did not reduce the overall incidence or duration of reperfusion arrhythmias in this model, though such treatment was associated with a non-significant trend toward less irreversibility of VF.Supported in part by National Institutes of Health SCOR HL-26215, Bethesda, Maryland 660     

Intracoronary infusion of superoxide dismutase and reperfusion injury in the pig heart

Summary The effects of an intracoronary infusion of superoxide dismutase on infarct size were studied in 16 pigs submitted to a 48-min coronary occlusion of the mid left anterior descending coronary artery followed by reperfusion for 24 h. Areas at risk marked with fluoresccine and infarct sizes calculated with triphenyl tetrazolium chloride staining 24 h after the occlusion were similar in the five control animals with coronary reperfusion alone, in the five animals with an intracoronary infusion of lactate Ringer initiated 3 min before reperfusion and maintained for 33 min and in the six animals with superoxide dismutase added to the solution of lactate Ringer and infused at a rate of 2500 units/min. The ratios infarct size/area at risk were respectively 0.50±0.10, 0.63±0.10 and 0.65±0.04 in the three study groups (NS). The extent of intramyocardial hemorrhage, evaluated by morphometric analysis was also similar 0.90±0.29×10⁶, 0.70±0.14 and 1.62±0.42 red blood cells/mm³ of tissue (NS). The superoxide dismutase infusion, however, resulted in significantly fewer early reperfusion arrhythmias which involved 23±15 s of each minute electrocardiographic recording in the superoxide dismutase group, compared to 37±13 s in the lactate Ringer group and 45±14 s in the control group (p=0.004). The lack of an effect of intracoronary infusion of superoxide dismutase on infarct size suggests that in this experimental model, extracellular superoxide radicals generated during early reperfusion have no major role on myocardial cell necrosis and microvascular damage. Reperfusion arrhythmias were, however, reduced.Partially supported by a grant PA 86/0389 from the Comisión Interministerial de Ciencia y Tecnología (CICYT), grant 1/86 from the Sección de Cardiopatía isquemica de la Sociedad Española de Cardiología and grant 17/88 of the Convenio Madrid-Quebec.     

Effect of superoxide dismutase plus catalase on myocardial infarct size in rabbits

A previous study by the authors showed that myocardial infarct size in the rabbit, measured after 45 mins of ischemia and 3 h of reperfusion, could be limited by administration of superoxide dismutase (SOD) plus catalase. The present study examined whether this infarct size limitation is sustained for the following three days. Under anesthesia, a coronary branch of the Japanese white rabbit was occluded for 45 mins and then reperfused. Three days after surgery, the heart was excised and the volume of myocardium supplied by the occluded coronary branch (ischemic zone size) was assessed with fluorescent particles and the infarct size was estimated by hematoxylin and eosin and with Mallory's staining. The SOD plus catalase group (n = 14) received 15,000 units/kg of SOD plus 50,000 units/kg of catalase in saline over 90 mins, starting 15 mins before the coronary occlusion. Saline was infused in the control group (n = 15). Three rabbits in the control group and three in the SOD plus catalase group died of ventricular fibrillation during the ischemic period. Three control and two SOD plus catalase rabbits were excluded because the ischemic zone was ambiguous. The percentage of the ischemic zone which was infarcted was 59.4 +/- 6.9% (mean +/- SE) in the control group (n = 9) and 49.4 +/- 5.1% in the SOD plus catalase group (n = 9). These were not statistically different. Ischemic zone size and hemodynamic parameters were similar in the two groups. These findings suggest that SOD plus catalase may serve only to delay rather than prevent myocardial infarction.     

Protection against pulmonary oxygen toxicity in rats by the intratracheal administration of liposome-encapsulated superoxide dismutase or catalase

To test the feasibility of using liposomes to deliver therapeutic agents to the lungs, the effect of liposome-encapsulated superoxide dismutase (SOD) or catalase on pulmonary oxygen toxicity was studied in rats. The SOD or catalase was encapsulated in negatively changed multilamellar liposomes and administered directly into the trachea of adult rats, which were subsequently exposed to hyperoxia (greater than 95% O2). Response to hyperoxia was examined by studying lung SOD and catalase activities, survival rates, and lung morphology. Rats receiving liposome-encapsulated SOD or catalase showed increased levels of enzyme activities in the lung homogenates compared with those in the control groups after 24 to 72 h of hyperoxic exposure. Elevated enzyme levels in the lungs of rats treated with liposome-encapsulated SOD or catalase were accompanied by a significant improvement in survival rates after 72 h of hyperoxic exposure and less lung injury than in the other control groups.     

Evidence for a reversible oxygen radical-mediated component of reperfusion injury: reduction by recombinant human superoxide dismutase administered at the time of reflow

It has been suggested that the beneficial effects of reperfusing ischemic myocardium might be in part reversed by the occurrence of "reperfusion injury." One possible mechanism could be the generation of oxygen free radicals. Superoxide dismutase enzymatically scavenges superoxide radicals by dismutation to hydrogen peroxide. This study tested the hypothesis that administration of recombinant human superoxide dismutase (h-SOD) at the time of reflow after a period of prolonged global ischemia would result in improved recovery of myocardial metabolism and function by preventing or reducing a potentially harmful component of reperfusion. We also sought to determine whether catalase, an enzymatic scavenger of hydrogen peroxide, was a necessary addition for optimal benefit. Langendorff perfused rabbit hearts were subjected to 30 min of normothermic (37 degrees C) total global ischemia. At the moment of reperfusion, 12 control hearts received a 10 ml bolus of normal perfusate followed by 15 min of reperfusion with normal perfusate (group I), 12 hearts received 60,000 IU of h-SOD as a bolus followed by a continuous infusion of 100 IU/ml for 15 min (group II), and 12 hearts received 60,000 IU of h-SOD and 60,000 IU of catalase as a bolus followed by 100 IU/ml of both enzymes for 15 min (group III). Myocardial ATP and phosphocreatine (PCr) content and intracellular pH during ischemia and reperfusion were continuously monitored with 31P nuclear magnetic resonance (NMR) spectroscopy. During 30 min of normothermic global ischemia intracellular pH dropped from 7.11-7.18 to 5.58-5.80 in all three groups of hearts. Likewise myocardial PCr content fell rapidly to 7% to 8% and ATP fell more slowly to 29% to 36% of preischemic control content. After 45 min of reperfusion PCr recovered to 65 +/- 5% of control in untreated (group I) hearts compared with 89 +/- 8% in h-SOD-treated (group II) hearts (p less than .01 vs group I) and with 83 +/- 6% of control in h-SOD/catalase-treated (group III) hearts (p less than .05 vs group I). Recovery of isovolumic left ventricular developed pressure was 68 +/- 5% of control in h-SOD-treated (group II) hearts and 66 +/- 6% of control in h-SOD/catalase-treated (group III) hearts after 45 min of reflow, compared with 48 +/- 6% of control in untreated (group I) hearts (p less than .005 for groups II and III vs group I). The NMR data confirmed equal depletion of ATP and PCr content in all three groups of hearts.(ABSTRACT TRUNCATED AT 400 WORDS)     

Combined adenosine and lidocaine administration limits myocardial reperfusion injury

The endogenous compound adenosine may play a role in limiting myocardial ischemia-reperfusion injury through its ability to cause vasodilation, modulate cardiac adrenergic responses, inhibit neutrophil function, or modulate energy supply and demand of the myocardium. The local anesthetic lidocaine has been shown to be protective against myocardial ischemia-reperfusion injury, although its mechanism of action remains unresolved. We hypothesized that administration of exogenous adenosine during reperfusion would limit the size of the infarct that results from a period of ischemia and reperfusion only when the animals are treated with lidocaine. Male, mongrel dogs (13.0-20.0 kg) were anesthetized (30 mg/kg i.v. sodium pentobarbital), and a left thoracotomy was performed. The left circumflex coronary artery (LCx) was isolated and instrumented with an electromagnetic flow probe, a 25-gauge nonobstructing intracoronary catheter, and a critical stenosis. The dogs were allocated randomly to one of four groups: 1) control, n = 13, (saline), 2) adenosine, n = 13, (0.15 mg/kg/ml/min i.c. for the first hour of reperfusion), 3) lidocaine, n = 9, (2.0 mg/kg i.v. given immediately before coronary artery occlusion and just before reperfusion), or 4) adenosine plus lidocaine, n = 11. The LCx was occluded for 90 minutes and reperfused for 6 hours. Regional myocardial blood flow (RMBF) was determined (n = 6 per group) at 80 minutes of occlusion and at 45 minutes of reperfusion with radiolabeled microspheres. RMBF determinations revealed an increase in blood flow to the inner two thirds of the myocardium at 45 minutes of reperfusion only in the presence of the combined treatment. Adenosine treatment alone or lidocaine treatment alone did not affect RMBF. Quantification of infarct size (triphenyltetrazolium method) expressed as a percent of the area at risk revealed a significant limitation of infarct size only in the group treated with both adenosine and lidocaine: control, 47.8 +/- 6.6%; adenosine, 45.0 +/- 3.2%; lidocaine, 46.9 +/- 6.0%; and adenosine and lidocaine, 20.8 +/- 5.6%. Statistical analyses were performed with two-way analysis of variance to account for the two individual drug treatments. The findings show that intracoronary administration of exogenous adenosine, at the dose used, is only effective at limiting myocardial infarct size when administered to lidocaine-treated animals.     

Effects of reperfusion and superoxide dismutase on myocardial infarct size in a closed chest pig model.

OBJECTIVE: The aim was to study the effects on myocardial infarct size of reperfusion alone or of CuZn superoxide dismutase (SOD) as an adjunct to reperfusion. METHODS: Occlusion was induced in closed chest, pentobarbitone anaesthetised, mechanically ventilated pigs by injection of a 2 mm ball into a preselected coronary artery. Reperfusion was achieved by retraction of the ball via an attached filament. Twenty nine placebo treated and 25 SOD treated animals were subjected to 30 (n = 21), 60 (n = 21), and 90 (n = 12) min of coronary occlusion followed by reperfusion to 24 h; a control group of 24 pigs was subjected to a sustained occlusion for 24 h. Infarct size was assessed by tetrazolium staining and plasma creatine kinase (CK), aspartate aminotransferase (ASAT), and lactate dehydrogenase (LD). In the CuZn SOD group, 200 mg bovine CuZn SOD was given as a bolus intravenously immediately before reperfusion followed by a continuous infusion (100 mg) for 60 min. The size of the ischaemic myocardium at risk was measured from post mortem autoradiograms. RESULTS: Infarct size as percent of myocardium at risk was 46.0(SD 15.5)%, 80.1(9.9)%, and 88.9(5.0)% respectively in placebo animals with 30, 60, and 90 min occlusion, and 94.2(5.1)% in pigs with 24 h sustained occlusion. Compared to 24 h sustained occlusion, limitation of infarct size by reperfusion was only demonstrated in the 30 (p less than 0.001) and 60 min groups (p less than 0.001). Plasma values of CK, ASAT, and LD at 90 min post-reperfusion correlated closely with infarct size as assessed by tetrazolium staining and were related to occlusion duration. No myocardial salvage, as assessed by plasma ASAT, CK, or LD, was shown in the SOD treated groups. CONCLUSIONS: Early reperfusion resulted in myocardial salvage as assessed by tetrazolium staining and peak ASAT, CK, and LD at 90 min after the reperfusion. No limitation of infarct size by SOD could be demonstrated from analyses of plasma CK, ASAT, or LD.     

Reduction in experimental infarct size by recombinant human superoxide dismutase: insights into the pathophysiology of reperfusion injury

To determine the importance of reperfusion injury and the ability of the free-radical scavenger recombinant human superoxide dismutase (h-SOD) to prevent it, open-chest dogs underwent 90 min of proximal circumflex coronary artery occlusion, and only at the moment of reperfusion received either h-SOD (400,000 IU bolus into the left atrium followed by a 300,000 IU iv infusion over 1 hr) or saline. After 48 hr the surviving animals were killed and measurements were made of the risk region (by postmortem angiography) and infarct size (by gross pathology). All measurements were made by investigators blinded to treatment given, and the code was broken only at the end of the study. Hemodynamic variables and collateral flow during ischemia were similar in the two groups. Infarct size in control animals (n = 8) averaged 22.4 +/- 3.1% of the left ventricle and 52.2 +/- 7.1% of the risk region, compared with 13.3 +/- 0.8% of the left ventricle and 33.6 +/- 2.1% of the risk region in h-SOD-treated dogs (n = 8) (p less than .05). Infarcts in treated animals were not only smaller, but also exhibited a distinctive "patchiness," suggesting protection along vascular distributions. Furthermore, analysis of the relationship between infarct size and collateral flow measured during ischemia in the two groups indicated that protection by h-SOD was greatest in animals with the lowest collateral flows. This study supports the concept that reperfusion of ischemic myocardium results in a separate component of cell damage, presumably linked to the generation of oxygen free radicals on reflow. Since the h-SOD preventable reperfusion component of injury was most pronounced in hearts with the most severe ischemia, scavenging of oxygen radicals at the time of reflow may offer a novel and particularly promising therapeutic approach for the protection of ischemic myocardium.     

Failure of superoxide dismutase and catalase to alter size of infarction in conscious dogs after 3 hours of occlusion followed by reperfusion

Superoxide dismutase (SOD) and catalase (CAT), enzymes that degrade superoxide anion and hydrogen peroxide, respectively, reduce size of infarction in anesthetized, open-chest dogs subjected to coronary occlusion followed by reperfusion. To evaluate potential protective effects of these enzymes in conscious animals, three groups of dogs were instrumented at sterile surgery with a hydraulic occluder on the left circumflex (LCX) coronary artery, sonomicrometers to measure regional wall thickness, and catheters to monitor arterial and left ventricular pressures. Ten to 14 days after surgery, the animals were sedated with morphine sulfate (0.5 mg/kg). The LCX artery was occluded for 3 hr by inflation of the hydraulic cuff. Infusions of SOD (n = 7), CAT (n = 6), or saline (control group, n = 7) were begun 15 min before reperfusion and lasted for 45 min of reperfusion. The doses of SOD and CAT were 5 mg/kg, dissolved in 60 ml of saline, and infused at a rate of 1 ml/min. Myocardial blood flow was measured with tracer-labeled microspheres (15 micron diameter) before occlusion, after 5 to 10 min of occlusion, after 150 min of occlusion, and 5 to 10 min after reperfusion. Size of infarction was measured 24 hr later by dual-perfusion staining with Evans blue and triphenyl tetrazolium. Size of infarction (expressed as a percentage of area at risk) did not differ significantly among the three groups: control, 32 +/- 17% (mean +/- SD); SOD, 38 +/- 17%; CAT, 27 +/- 17%. Hemodynamic parameters and myocardial blood flows (measured before infusion of any agents) were not significantly different among the three groups. Serum SOD levels in SOD-treated dogs were 19 +/- 2 micrograms/ml at the onset of reperfusion and 29 +/- 3 micrograms/ml at the end of the infusion. Blood assays collected after infusion showed a monoexponential decay of SOD levels with a half-life of 22 +/- 6 min. We conclude that myocardial protection by SOD or CAT is model dependent. In conscious dogs subjected to 3 hr of coronary occlusion followed by reperfusion, SOD and CAT failed to alter size of infarction.     

Protection by superoxide dismutase from myocardial dysfunction and attenuation of vasodilator reserve after coronary occlusion and reperfusion in dog

Previous studies indicate impairment of coronary arterial ring relaxation and loss of coronary vasodilator reserve after coronary artery occlusion and reperfusion. These changes are mediated in part through loss of endothelium-derived relaxing factor (EDRF) and/or myocardial neutrophil accumulation. To examine if superoxide dismutase (SOD), a scavenger of superoxide radicals, would modify the diminished coronary vasodilator reserve after temporary coronary occlusion in the intact animal, open-chest mongrel dogs were subjected to 1 hour of circumflex (Cx) coronary artery occlusion followed by 1 hour of reperfusion and treated with saline or SOD. Before Cx occlusion, coronary blood flow increased, and vascular resistance decreased (both p less than 0.01) in response to EDRF-dependent vasodilator acetylcholine as well as EDRF-independent vasodilator nitroglycerin. After Cx reperfusion, resting Cx coronary blood flow and vascular resistance were similar to the preocclusion values. In the saline-treated animals, there was evidence of myocardial dysfunction, which was measured by segmental shortening (-6 +/- 2% vs. 10 +/- 2%). Furthermore, increase in Cx coronary blood flow and reduction in vascular resistance in response to both vasodilators were significantly (p less than 0.01) impaired; these occurrences suggested loss of coronary vasodilator reserve. Myocardial histology showed extensive capillary plugging by neutrophils in the Cx-supplied myocardium. Myocardial myeloperoxidase activity, an index of neutrophil infiltration, was also increased in the Cx compared with the left anterior descending coronary artery region (p less than 0.02). Treatment of dogs with SOD, started at the end of Cx occlusion and continued during reperfusion, exerted significant (p less than 0.01) protective effect against reperfusion-induced attenuation of coronary vasodilator reserve in response to both acetylcholine and nitroglycerin. Loss of myocardial function (segmental shortening 5 +/- 1% vs. 10 +/- 1%) was less than in the saline-treated animals (p less than 0.01). Cx region-myocardial neutrophil accumulation and myeloperoxidase activity were also less (p less than 0.02) in the SOD-treated than in the saline-treated dogs. These observations suggest that coronary reperfusion impairs coronary vasodilator reserve in intact dogs. This impairment can be modified by treatment of animals with SOD before reperfusion. Capillary plugging by neutrophils may contribute to the altered coronary vasodilator reserve observed in the immediate postreperfusion period, and SOD modifies this reperfusion-induced impairment.     

Extracellular superoxide dismutase attenuates lung injury after hemorrhage.

Reperfusion of the lung after hemorrhage generates free radicals such as superoxide (O(2)(.)) that may injure the lung; however, the relative importance of intracellular versus extracellular free radicals is unclear. The superoxide dismutases (SOD) are the primary enzymatic method to reduce superoxide. We examined whether lung-specific overexpression of extracellular superoxide dismutase (EC-SOD) would attenuate hemorrhage-induced lung injury. Wild-type mice and mice overexpressing the human EC-SOD gene with a lung-specific promoter were hemorrhaged by removing 30% of blood volume. After hemorrhage, the lung wet to dry weight ratios increased from 5.4 +/- 0.11 in unmanipulated control mice to 6.3 +/- 0.16 in wild-type mice, but to only 5.60 +/- 0.17 in the EC-SOD transgenic mice (p < 0.05 compared with hemorrhaged wild-type). Hemorrhage-induced lipid peroxidation, as assessed by lung F(2) isoprostanes, was lower in the EC-SOD transgenic mice (3.4 +/- 0.3 microg/lung) compared with wild-type mice (1.9 +/- 0.2 microg/lung; p < 0.05). Compared with wild-type, EC-SOD transgenic mice had attenuated the hemorrhage-induced increase in both pulmonary nuclear factor kappa B (NK-kappaB) activation (relative absorbance 1.1 +/- 0.2 for EC-SOD transgenic versus 2.5 +/- 0.1 for wild-type; p < 0.05) and myeloperoxidase activity (5.1 +/- 0.87 units/g for EC-SOD transgenic versus 11.3 +/- 1.8 units/g for wild-type; p < 0.01). Thus, overexpression of pulmonary EC-SOD in the mouse lung attenuates lung injury after hemorrhage.     

CuZn superoxide dismutase, Mn superoxide dismutase, catalase and glutathione peroxidase in lymphocytes and erythrocytes in insulin-dependent diabetic children

CuZn superoxide dismutase, Mn superoxide dismutase, catalase and glutathione peroxidase activities in lymphocytes and erythrocytes were studied in 9 children with insulin-dependent diabetes mellitus (IDDM) as well as in 21 healthy children. The mean erythrocyte CuZn superoxide dismutase and glutathione peroxidase were statistically significantly lower in the IDDM group compared with the controls although almost all IDDM results fell within the mean +/- 2 SD limits of the controls. The small differences found can hardly be assigned biological significance. Erythrocyte catalase as well as lymphocyte CuZn superoxide dismutase and Mn superoxide dismutase did not differ from the controls.     

Effects of hemorrhagic shock and retransfusion on catalase and superoxide dismutase activities in rabbits.

The effects of hemorrhagic shock and retransfusion on the activities of two endogenous antioxidant enzymes, catalase and superoxide dismutase, were studied in male New Zealand white rabbits. Following instrumentation and stabilization, blood was withdrawn to reduce mean arterial pressure to 35 mmHg (SHOCK). After 60 min of shock, the warmed autologous blood was infused and the animals were allowed to recover for an additional 30 min (RETRANS). CONTROL animals were instrumented but not bled or transfused. A 60 min period of hemorrhagic shock had no significant effect on tissue or plasma activities of catalase or superoxide dismutase. However, transfusion following hemorrhagic shock resulted in an increase in catalase activity of nearly two-fold in the liver and five-fold in the small intestine. In contrast, superoxide dismutase activity remained unchanged after retransfusion in other tissues and in plasma. These results indicate that superoxide dismutase and catalase activities may be preserved or even induced following transfusion for hemorrhagic shock.     

Evidence against the "early protection-delayed death" hypothesis of superoxide dismutase therapy in experimental myocardial infarction. Polyethylene glycol-superoxide dismutase plus catalase does not limit myocardial infarct size in dogs

We previously found that superoxide dismutase (SOD) did not limit myocardial infarct size after 40 or 90 minutes of ischemia and 4 days of reperfusion in dogs. Because some other studies have shown limitation of infarct size after shorter periods of reperfusion, we postulated that our negative results might be due to late reperfusion injury mediated by superoxide anions produced after excretion of SOD. To test this "early protection-delayed death" hypothesis, we have examined whether SOD, conjugated to polyethylene glycol (PEG-SOD) to prolong its circulating half-life, limited myocardial infarct size. The circumflex artery was occluded for 90 minutes followed by 4 days of reperfusion. PEG-SOD (total dose, 10,000 units/kg) and catalase (55,000 units/kg) were given during the 30 minutes before reperfusion. Plasma SOD levels in the treated group were 330 +/- 20 units/ml at the onset of reperfusion and 140 +/- 10 units/ml on day 4 (circulating half-life, 75 +/- 5 hours) versus 5 +/- 1 units/ml in controls. Histological infarct size was 37.1 +/- 4.2% of the area at risk in the treated group (n = 11) versus 44.5 +/- 6.2% in controls (n = 10) (p = NS). Infarct size and collateral blood flow were inversely related in controls; PEG-SOD and catalase did not shift this regression (p = NS by analysis of covariance). Thus, infarct size was not limited when measured after 4 days of reperfusion, even though plasma SOD exceeded 100 units/ml throughout this reperfusion period.(ABSTRACT TRUNCATED AT 250 WORDS)     

Polymorphisms and functional activity in superoxide dismutase and catalase genes in smokers with COPD.

Increased oxidative stress has been implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). This study investigated the risk of COPD and the substitution of alanine 16 with valine (Ala16Val) polymorphism of manganese-superoxide dismutase (Mn-SOD) and the cytosine to thymidine transition of nucleotide -262 (-262C>T) polymorphism of the catalase gene, and the activity of erythrocyte SOD and catalase. The subjects were stable COPD patient ever smokers (n = 165) and healthy controls, matched for age and cigarette consumption. Genotyping of Mn-SOD at Ala16Val and the catalase gene at -262C>T was performed, and the functional activity of SOD and catalase in erythrocytes determined. There were no significant differences in the distribution of the different genotypes or allele frequencies between patients and controls for both the Mn-SOD and catalase genes. Among healthy controls or COPD patients, no differences were observed in erythrocyte SOD and catalase activity, irrespective of genotype. Significantly higher erythrocyte catalase activity was found in COPD patients than in healthy controls. The T/T catalase genotype and Ala/Ala Mn-SOD genotype were uncommon in the present Chinese population. The increase in erythrocyte catalase activity in Chinese patients with chronic obstructive pulmonary disease probably indicates dysfunction of the oxidant/antioxidant defence system, but it is unclear whether this increase is compensatory or a pathogenic factor.     

Cell multiplication of an ascites tumour in the presence of superoxide dismutase and catalase

Summary The anti-neoplastic activity of N-[N-(2-chloroethyl)-N-nitrosocarbamoyl(CNC)]-alanine, CNC-alanyl-alanine, CNC-alanine-methylamide and CNC-glycine-methylamide was examined in murine transplantable colon tumours (MAC). The methylamide derivatives were highly active against a solid adenocarcinoma (MAC 13) and an ascitic adenocarcinoma (MAC 15A). CNC-alanyl-alanine was also highly active against MAC 15A. Responses of the three latter agents against the ascitic tumour were better than for any previously tested drugs including the nitrosoureas but their eventual usefulness cannot be determined without further toxicological studies.This work was supported by the Turner/Whyte Watson Cancer Research Trust (Bradford) and was undertaken within the Screening and Pharmacology Group of the EORTC     

Effects of the superoxide radical scavenger superoxide dismutase,and of the hydroxyl radical scavenger mannitol,on reperfusion injury in isolated rabbit hearts

Summary Hydroxyl radical formation, secondary to superoxide radical generation, has been advocated as the actual mechanism of oxygen radical-mediated damage in biological systems. The present study was designed to compare the efficacy of administration of the hydroxyl radical scavenger mannitol vs. that of the superoxide radical scavenger superoxide dismutase (SOD) in reducing myocardial reperfusion injury, and to test whether combined treatment with both agents would confer better tissue protection compared with either intervention alone. Rabbit hearts perfused within a ³¹P nuclear magnetic resonance (³¹P-NMR) spectrometer were subjected to 30 minutes of total global ischemia at 37°C. At reflow, 12 hearts in each group received either (a) a bolus of standard perfusion buffer, followed by 45 minutes of reperfusion (controls); (b) the superoxide radical scavenger recombinant human SOD (h-SOD, as a 60,000 U bolus followed by a 100 U/ml infusion for 15 minutes); (c) the hydroxyl radical scavenger mannitol (50 mM bolus followed by 15 minutes of 50 mM infusion); or (d) a combination of both agents. All treated hearts were switched to standard buffer for the remaining 30 minutes of reperfusion. Treatment with h-SOD alone was associated with a significant improvement in the recovery of cardiac contractility and coronary flow, as well as of ATP content, compared to control hearts. In contrast, mannitol treatment resulted in a small, nonsignificant improvement in these parameters. The addition of mannitol to h-SOD did not result in further significant improvement of contractility and ATP recovery compared to h-SOD alone. These data demonstrate that under our experimental conditions significant protection against reperfusion injury can be achieved by the administration of h-SOD alone, without the need for additional hydroxyl radical scavenger therapy with mannitol. These results do not exclude that significant tissue protection may be achieved by different doses of mannitol or by other agents. However, they suggest that under definite experimental conditions prevention of hydroxyl radical formation, rather than attempts to minimize hydroxyl radical toxicity, might be a more efficient method to prevent oxygen radical-mediated reperfusion injury in isolated hearts.