Free radicals and inflammation: superoxide-dependent activation of a neutrophil chemotactic factor in plasma

Prevention of influenza-induced lung injury in mice overexpressing extracellular superoxide dismutase

Reactive oxygen and nitrogen species such as superoxide and nitric oxide are released into the extracellular spaces by inflammatory and airway epithelial cells. These molecules may exacerbate lung injury after influenza virus pneumonia. We hypothesized that enhanced expression of extracellular superoxide dismutase (EC SOD) in mouse airways would attenuate the pathological effects of influenza pneumonia. We compared the pathogenic effects of a nonlethal primary infection with mouse-adapted Hong Kong influenza A/68 virus in transgenic (TG) EC SOD mice versus non-TG (wild-type) littermates. Compared with wild-type mice, EC SOD TG mice showed less lung injury and inflammation as measured by significant blunting of interferon-gamma induction, reduced cell count and total protein in bronchoalveolar lavage fluid, reduced levels of lung nitrite/nitrate nitrotyrosine, and markedly reduced lung pathology. These results demonstrate that enhancing EC SOD in the conducting and distal airways of the lung minimizes influenza-induced lung injury by both ameliorating inflammation and attenuating oxidative stress.

Beneficial effects of tempol, a membrane-permeable radical scavenger, on the multiple organ failure induced by zymosan in the rat

BACKGROUND AND METHODS

We investigated the effects of tempol, a membrane-permeable radical scavenger, on the multiple organ failure (MOF) caused by zymosan in the rat. Zymosan (500 mg/kg, suspended in saline solution, ip) enhances formation of reactive oxygen species, which contribute to the pathophysiology of MOF. After zymosan or saline administration, animals were monitored for 12 days.

RESULTS

Treatment of rats with tempol (10, 30, or 100 mg/kg ip, 1 and 6 hrs after zymosan) attenuated the peritoneal exudation and the migration of polymorphonuclear cells caused by zymosan in a dose-dependent fashion. Tempol also attenuated the lung, liver, and intestinal injury (histology) as well as the increase in the concentrations of myeloperoxidase and malondialdehyde caused by zymosan in the lung, liver, and intestine. Immunohistochemical analysis for nitrotyrosine and for poly(adenosine 5'-diphosphate-ribose)synthetase demonstrated a positive staining in lung, liver, and intestine from zymosan-treated rats. The degree of staining for nitrotyrosine and for poly(adenosine 5'-diphosphate-ribose) synthetase was markedly reduced in tissue sections obtained from zymosan-treated rats that had received tempol (100 mg/kg ip). Furthermore, treatment of rats with tempol significantly reduced the following: a) the formation of peroxynitrite, b) the DNA damage, c) the impairment in mitochondrial respiration, and d) the decrease in the cellular concentration of oxidized nicotinamide adenine dinucleotide observed in macrophages harvested from the peritoneal cavity of rats treated with zymosan.

CONCLUSION

This study provides the first evidence that tempol, a small molecule that permeates biological membranes and scavenges reactive oxygen species, attenuates the degree of MOF associated with zymosan-induced peritonitis in the rat.

Modulation of myocardial SOD and iNOS during ischemia-reperfusion by antisense directed at ACE mRNA

Renin-angiotensin system (RAS) is involved in the regulation of superoxide dismutase (SOD) and nitric oxide (NO) equilibrium, and its modulation protects hearts from ischemic dysfunction. We examined the effect of a new antisense-oligodeoxynucleotides (AS-ODNs) directed at ACE mRNA on SOD and iNOS expression during myocardial ischemia. Sprague-Dawley rats were treated with saline, AS-ODNs, or inverted-ODNs (IN-ODNs), given with liposome DOTAP/DOPE. Hearts were excised and subjected to 25 min of ischemia followed by 30 min of reperfusion. Ischemia-reperfusion in saline-treated hearts resulted in a decrease in the expression of SOD and an increase in the expression of inducible NOS (iNOS) genes concurrently with myocardial dysfunction. AS-ODNs, but not IN-ODNs, protected hearts against functional deterioration, and upregulated SOD expression and inhibited the expression of iNOS. ACE protein expression was decreased in the rat hearts of the AS-ODNs-treated group, but not in the IN-ODNs group. Thus manipulation of RAS with AS-ODNs directed at ACE mRNA can ameliorate cardiac dysfunction and modulate expression of SOD and iNOS at genomic level.

Purification and characterization of iron superoxide dismutase and copper-zinc superoxide dismutase from Acanthamoeba castellanii

Two superoxide dismutases (SOD I and SOD II) were purified from Acanthamoeba castellanii and characterized for several biochemical properties. Analysis of the primary structure and inhibition studies revealed that SOD I is iron SOD (Fe-SOD), with a molecular mass of 50 kDa, and SOD II is copper-zinc SOD (Cu,Zn-SOD), with a molecular mass of 38 kDa. Both enzymes have a homodimeric structure consisting of 2 identical subunits, each with a molecular mass of 26 and 19 kDa for SOD I and SOD II, respectively. The isoelectric points of SOD I and SOD II were 6.4 and 3.5, respectively, and there were no isoenzyme forms detected. Both enzymes show a broad optimal pH of 7.0-11.0. Because no differences were observed in the apparent molecular weight of SOD I after addition of the reducing agent 2-mercaptoethanol, the subunits do not appear to be linked covalently by disulfide bonds. However, the subunits of SOD II were covalently linked by intra- and interdisulfide bonds. Western blot analyses showed that the 2 enzymes have different antigenicity. Both enzymes occur as cytoplasmic and detergent-extractable fractions. These enzymes may be potential virulence factors of A. castellanii by acting both as antioxidants and antiinflammatory agents. These enzymes may be attractive targets for chemotherapy and immunodiagnosis of acanthamoebiasis.

Elevated oxidative stress in skin of B6C3F1 mice affects dermal exposure to metal working fluid

Metal working fluids (MWFs) are widely used in industry for metal cutting, drilling, shaping, lubricating, and milling. Potential for dermal exposure to MWFs exists for a large number of men and women via aerosols and splashing during the machining operations. It has been reported earlier that occupational exposure to MWFs causes allergic and irritant contact dermatitis. Previously, we showed that dermal exposure of female and male B6C3F1 mice to 5% MWFs for 3 months resulted in accumulation of mast cells and elevation of histamine in the skin. Topical exposure to MWF also resulted in elevated oxidative stress in the liver of both sexes and the testes in males. The goal of this study was to evaluate the interaction between oxidative stress in the skin and topical application of MWF. Oxidative stress in skin ofB6C3F1 mice of both sexes was generated by intradermal injection ofthe hydrogen peroxide (H2O2) -producing enzyme, glucose oxidase with polyethylene glycol (GOD+PEG). In mice given GOD+PEG, topical treatment with MWF (200 microl, 30%, for 1, 3, or 7 days) resulted in a mixed inflammatory cell response, accumulation of peroxidative products, and reduction of GSH content in the skin. Such changes were not observed with MWF treatment alone. These data indicate that oxidative stress can enhance dermal inflammation caused by occupational exposure to MWF.

Glutathione oxidation and PTPase inhibition by hydrogen peroxide in Caco-2 cell monolayer

The role of H(2)O(2) and protein thiol oxidation in oxidative stress-induced epithelial paracellular permeability was investigated in Caco-2 cell monolayers. Treatment with a H(2)O(2) generating system (xanthine oxidase + xanthine) or H(2)O(2) (20 microM) increased the paracellular permeability. Xanthine oxidase-induced permeability was potentiated by superoxide dismutase and prevented by catalase. H(2)O(2)-induced permeability was prevented by ferrous sulfate and potentiated by deferoxamine and 1,10-phenanthroline. GSH, N-acetyl-L-cysteine, dithiothreitol, mercaptosuccinate, and diethylmaleate inhibited H(2)O(2)-induced permeability, but it was potentiated by 1,3-bis(2-chloroethyl)-1-nitrosourea. H(2)O(2) reduced cellular GSH and protein thiols and increased GSSG. H(2)O(2)-mediated reduction of GSH-to-GSSG ratio was prevented by ferrous sulfate, GSH, N-acetyl-L-cysteine, diethylmaleate, and mercaptosuccinate and potentiated by 1,10-phenanthroline and 1, 3-bis(2-chloroethyl)-1-nitrosourea. Incubation of soluble fraction of cells with GSSG reduced protein tyrosine phosphatase (PTPase) activity, which was prevented by coincubation with GSH. PTPase activity was also lower in H(2)O(2)-treated cells. This study indicates that H(2)O(2), but not O(2)(-). or.OH, increases paracellular permeability of Caco-2 cell monolayer by a mechanism that involves oxidation of GSH and inhibition of PTPases.

Oxidative stress after moderate to extensive burning in humans

Lipid peroxidation products, lipid antioxidants, and hematologic and blood chemistry changes were evaluated in plasma of patients after acute burning injury involving 10% (n=8), 20% (n=8), and 40% (n=5) of total body surface area (TBSA), 24 h after burning (baseline) up to 30 days after. Markedly increased plasma levels of malondialdehyde (MDA) were observed at baseline in all patients, according to the extent of the injury, then the values declined progressively. However, levels of MDA remained above normal up to 30 days even in less injured patients. On the other hand, the plasma level of conjugated diene lipid hydroperoxides was only slightly higher than control at the baseline, then dropped under the control value in all patients. Cholesterol showed a marked fall at baseline, followed by a rapidly progressive decrease, indicating a massive loss of circulating lipids by the acute thermal injury. Because of such an extensive and rapidly spreading oxidative degradation of lipids, decomposition of conjugated diene hydroperoxides, produced in early stages of the peroxidation process, occurs, so these compounds cannot be a suitable index to value lipid oxidation in burned patients. Aldehydic products of lipid peroxidation act as endotoxins, causing damage to various tissues and organs. Damage to liver and decrease of erythrocyte survival were assessed by increased plasma levels of asparate and alanine transaminases, within 7-15 days after injury, and by a decreased number of red blood cells, which remained under the normal value at 30 days. A marked decrease of lipid antioxidants, beta-carotene, vitamin A and vitamin E was observed at baseline. The level of beta-carotene remained low in all patients at the end of the 30-day observation. A complete recovery of vitamin A did not occur at 30 days post-burn, even in the patients with 10% of burned TBSA. Plasma levels of vitamin E decreased significantly in 1-7 days after burn in all patients, but these levels increased thereafter, with almost total recovery at 30 days. These data show evidence of a marked, long-lasting oxidant/antioxidant imbalance in burned patients, in accordance with the severity of the injury, which is also reflected as systemic oxidant stress.

A threshold concept for cancer therapy

Oxygen free radicals have been implicated in many disease processes, including aging and carcinogenesis, and have been associated with a variety of complications resulting from the treatment of cancer. As a result, the treatment of free radical-induced disease with antioxidants or free radical scavengers has become an important therapeutic modality. Ironically, these same oxygen free radicals also play a critical role in anti-cancer therapies. The use of antioxidants such as superoxide dismutase (SOD), in this setting, has been found to decrease the efficacy of anti-tumor therapies, which depend on free radical generation for their action. In addition, increased antioxidant activity can often be utilized by the tumor cell to favor increased growth. Therefore, the appropriate application of oxygen free radicals and antioxidants seems to be critically important in designing proper strategies for both prevention and treatment of malignant disorders. This review will summarize free radical and antioxidant regimens that have been employed to date, examine some of the problems associated with these regimens, introduce the 'threshold concept' explaining the dual effects of oxygen free radicals and antioxidants, and discuss a novel hypothesis regarding therapy that could potentially improve outcome in cancer patients.

The evolution of free radicals and oxidative stress

The superoxide free radical has come to occupy an amazingly central role in a wide variety of diseases. Our metabolic focus on aerobic energy metabolism in all cell types, coupled with some chemical peculiarities of the oxygen molecule itself, contribute to the phenomenon. Superoxide is not, as we once thought, just a toxic but unavoidable byproduct of oxygen metabolism. Rather it appears to be a carefully regulated metabolite capable of signaling and communicating important information to the cell's genetic machinery. Redox regulation of gene expression by superoxide and other related oxidants and antioxidants is beginning to unfold as a vital mechanism in health and disease.

Is the endogenous peroxyl-radical scavenging capacity of plasma protective in systemic inflammatory disorders in humans?

Systemic inflammatory response syndrome (SIRS) in humans is associated with heightened intravascular oxidative stress. The clinical significance of plasma endogenous antioxidative capability in SIRS remains undetermined. Time-sequence changes of plasma total radical-trapping antioxidant parameter (TRAP) and its components were measured in 135 patients with various clinical conditions leading to SIRS. The results were correlated with clinical parameters. Plasma TRAP significantly depressed upon diagnosis of SIRS (SIRS vs. healthy subjects (n = 50), 605.7 +/- 20.4 vs. 803.4 +/- 30.8 microM Trolox equivalent, p <.001). In survivors (n = 86), TRAP declined further during the course of SIRS, followed by a mild recovery at the end of follow-up. General linear mixed model analysis revealed that uric acid, vitamin C, vitamin E and unidentified antioxidants contributed to most of the changes in TRAP (each factor p <.001). In nonsurvivors (n = 49), TRAP increased steadily until death, and the increase was predominantly the result of the increased contribution of bilirubin (p <.01). Higher TRAP levels were not correlated with diminished blood oxidants formation (r = -0.13, p.05), lower intensity of lipid peroxidation (r = 0.261, p <.05) or lesser disease severity of SIRS. The results do not support the hypothesis that the endogenous peroxyl radical scavenging ability of plasma plays a protective role in the course of SIRS.

Influence of tolrestat on the defective leukocyte-endothelial interaction in experimental diabetes

One of the most devastating secondary complications of diabetes is the blunted inflammatory response that becomes evident even in the very early stages of poorly controlled diabetes mellitus. While the etiology of this diminished response is not clearly understood, it has been linked to a decrease in the respiratory burst of neutrophils, as well as a decrease in microvessel response to inflammatory mediators and defective leukocyte-endothelial interactions. Using video microscopy to visualize vessels of the internal spermatic fascia, we have characterized leukocyte-endothelial interactions in alloxan-induced diabetic and in galactosemic rats by quantitating the number of leukocytes rolling along the venular endothelium and the number of leukocytes sticking to the vascular wall after topical application of zymosan-activated plasma or leukotriene B(4) (1 ng/ml), as well as after the application of a local irritant stimulus (carrageenan, 100 microg). We observed that while 33 days of alloxan-induced diabetes or 7 days of galactosemia had no effect on total or differential leukocyte counts and on the wall shear rate, both treatments significantly (P<0.001) reduced the number of leukocytes rolling along the venular endothelium by about 70% and the number of adhered leukocytes in postcapillary venules by 60%. These effects were not observed in diabetic and galactosemic animals treated with an aldose reductase inhibitor. The results suggest that impaired leukocyte-endothelial cell interactions are a consequence of an enhanced flux through the polyol pathway.

Pathophysiology of ischaemia-reperfusion injury

Reperfusion of ischaemic tissues is often associated with microvascular dysfunction that is manifested as impaired endothelium-dependent dilation in arterioles, enhanced fluid filtration and leukocyte plugging in capillaries, and the trafficking of leukocytes and plasma protein extravasation in postcapillary venules. Activated endothelial cells in all segments of the microcirculation produce more oxygen radicals, but less nitric oxide, in the initial period following reperfusion. The resulting imbalance between superoxide and nitric oxide in endothelial cells leads to the production and release of inflammatory mediators (e.g. platelet-activating factor, tumour necrosis factor) and enhances the biosynthesis of adhesion molecules that mediate leukocyte-endothelial cell adhesion. Some of the known risk factors for cardiovascular disease (hypercholesterolaemia, hypertension, and diabetes) appear to exaggerate many of the microvascular alterations elicited by ischaemia and reperfusion (I/R). The inflammatory mediators released as a consequence of reperfusion also appear to activate endothelial cells in remote organs that are not exposed to the initial ischaemic insult. This distant response to I/R can result in leukocyte-dependent microvascular injury that is characteristic of the multiple organ dysfunction syndrome. Adaptational responses to I/R injury have been demonstrated that allow for protection of briefly ischaemic tissues against the harmful effects of subsequent, prolonged ischaemia, a phenomenon called ischaemic preconditioning. There are two temporally and mechanistically distinct types of protection afforded by this adaptational response, i.e. acute and delayed preconditioning. The factors (e.g. protein kinase C activation) that initiate the acute and delayed preconditioning responses appear to be similar; however the protective effects of acute preconditioning are protein synthesis-independent, while the effects of delayed preconditioning require protein synthesis. The published literature in this field of investigation suggests that there are several potential targets for therapeutic intervention against I/R-induced microvascular injury.

Superoxide dismutase activity in children with chronic liver diseases

BACKGROUND/AIMS

Liver disease in infancy has multiple etiologies. As reactive oxygen intermediates are involved in several types of tissue damage, we have investigated whether different forms of liver disease in infancy are associated with increased free radical generation, using an indirect approach in which superoxide dismutase (a free radical scavenger) activity is determined in the liver tissue.

METHODS

A total of 48 liver biopsies performed at diagnosis were evaluated retrospectively. Nine infants had biliary atresia, eight Alagille syndrome, seven alantitrypsin deficiency and 12 cryptogenic hepatitis. As controls we studied 12 biopsies with normal histology obtained from seven children with portal vein thrombosis and five children who underwent biopsy for management reason but had no liver disease. Superoxide dismutase activity in liver biopsy specimens was measured using the cytochrome C method by spectrophotometry and expressed as U SOD/mg protein.

RESULTS

Superoxide dismutase activity was significantly increased in biliary atresia (1.25 +/- 0.56 U SOD/mg protein, p<0.0001) and Alagille syndrome (1.31 +/- 0.56 U SOD/mg protein, p<0.0001) as compared with al-antitrypsin deficiency (0.75 +/- 0.3 U SOD/mg protein), neonatal hepatitis (0.72 +/- 0.37 U. SOD/mg protein) and normal controls (0.4 +/- 0.7 U. SOD/mg protein). The highest level of SOD activity was found, however, in control children with portal vein thrombosis (2.09 +/- 0.96 U SOD/mg protein; p<0.0001 as compared to the other groups).

CONCLUSION

Superoxide dismutase, a key enzyme in free radical protection, is increased significantly in the liver tissue of infants with cholestatic liver disease due to bile duct damage and in children with portal vein thrombosis, suggesting that products of free radical reactions are involved in the pathogenesis of these disorders.

N-acetylcysteine and ambroxol inhibit endotoxin-induced phagocyte accumulation in rat lungs

We have investigated whether pretreatment with N-acetylcysteine (NAC) and/or ambroxol (Amb), drugs known as reactive oxygen species (ROS) scavengers, would minimize lipopolysaccharide (LPS)-induced leucocyte accumulation in rat lung microvasculature and protect lungs from damage and the effect of these drugs on chemotactic peptide (fMLP)-induced chemiluminescence of human polymorphonuclear leukocytes (PMNs). Animals were injected ip with NAC (27.6 mg/kg, n=8), ambroxol (70 mg/kg, n=8), combination NAC+ambroxol (n=8), or 1 ml buffer alone (n=8), once a day for 3 consecutive days. Then animals were injected with LPS (17 mg/kg), and killed 3 h later. In each of another four groups eight rats were used as a control, and received the same drug treatment but LPS was replaced with 0.9% NaCl. PMNs and macrophages (Ms) were counted in histologic slides of lung tissue. Using computer image analysis we measured the area of alveolar profiles. Luminol-enhanced chemiluminescence was measured in PMNs suspensions obtained from healthy volunteers. Chemiluminescence intensity was measured in resting and fMLP-stimulated cells, and compared between cells incubated with Amb, NAC or distilled water. We observed significant differences in the number of PMNs and Ms, alveolar profile area between control and LPS-treated animals (P<0.01). PMNs and Ms were numerous in lungs of LPS-administered animals (PMNs: Median (M)=137.5 per 6 high power fields range (r)=54.0; Ms: M=123.0 r=11.0), less numerous in ambroxol-treated group (PMNs: M=101.5 r=32.0 and Ms:53.5 r=36.0), not abundant in NAC (PMNs:M=56.0 r=28.0 and Ms:M=20.5 r=13.0) and in NAC+ambroxol treated rats (PMNs:M=53.5 r=21.0 and Ms:M=29.0 r=9.0), and rare in LPS+drugs-untreated control group (PMNs:M=40.5 r=19.0 and Ms:M=18.5 r=15.0). Chemiluminescence assay revealed that 100 micro;M ambroxol stimulated fMLP-induced PMNs chemiluminescence and NAC of the same concentration had no significant effect.

CONCLUSION

In our experiment we showed that pretreatment with NAC and ambroxol may inhibit phagocyte influx to rat lung and may protect it from damage. We also revealed that NAC at dose 27.6 mg/kg has stronger protective properties than ambroxol at dose 70 mg/kg and this may result from enhancing effect of ambroxol on fMLP-provoked PMNs chemiluminescence.

Oxidative stress during selenium deficiency in seedlings of Trigonella foenum-graecum and mitigation by mimosine. Part I. Hydroperoxide metabolism

Oxidative stress during selenium (Se) deficiency in the seedlings of Trigonella foenum-graecum grown for 72 h was investigated and the response to supplemented levels of Se (0.5-1 ppm) and mimosine (0.05-1 mM) was evaluated. Beneficial effects of Se was maximal at 0.75 ppm. Mimosine, a toxic amino acid, was also found to be beneficial to the growth of the seedlings exposed up to 0.2 mM. When compared to the stressed seedlings, mitochondrial oxygen uptake from seedlings of Se (0.75 ppm) group and mimosine (0.2 mM) group exhibited threefold enhancement in state 3 respiration rate and a controlled state 4 rate, with respiratory control ratios of 5-8. Upon supplementation at the optimal levels, superoxide dismutase (SOD) activities were enhanced fourfold with Se and eightfold with mimosine in the mitochondria. The soluble activity in mimosine groups increased twofold, but only by 75% in Se groups. Peroxidase activity registered a significant increase by threefold in mitochondria and fourfold in soluble fraction in both Se and mimosine groups. Exposure to Se or mimosine exhibited a differential response in the mitochondrial catalase and ascorbate peroxidase (Asc-Px) activities. In the Se groups, both catalase and Asc-Px in mitochondria decreased by 50-60%, which was contrasted by 60% increase in Asc-Px activity and 40% in catalase activity in mimosine groups. Supplementation with either Se or mimosine evoked similar responses of increases with respect to soluble catalase by twofold to threefold and Asc-Px by 90%. The results of the present study reveal (1) the prevalence of oxidative stress in T. foenum-graecum during Se deficiency, (2) enhanced mitochondrial functional efficiency mediated by Se and mimosine independently, and (3) an antioxidative role for mimosine during Se deficiency. The study demonstrates for the first time that mimosine, a naturally occurring toxic amino acid, could be a beneficial growth factor in concentrations between 0.1 and 0.2 mM.

Melatonin reduces lipid peroxidation and tissue edema in cerulein-induced acute pancreatitis in rats

Since oxygen free radicals and lipid peroxidation have been implicated in the pathogenesis of an early stage of acute pancreatitis, we examined whether melatonin, a recently discovered free-radical scavenger, could attenuate pancreatic injury in Sprague-Dawley rats with cerulein-induced pancreatitis. Acute pancreatitis was induced by four intraperitoneal injections of cerulein (50 microg/kg body wt) given at 1-hr intervals. Thirty minutes after the last cerulein injection, the rats were killed and the degree of pancreatic edema, the level of lipid peroxidation in the pancreas, and serum amylase activity were increased significantly. Pretreatment with melatonin (10 or 50 mg/kg body wt) 30 min before each cerulein injection resulted in a significant reduction in pancreatic edema and the levels of lipid peroxidation. Serum amylase activity, however, was not significantly influenced by either dose of melatonin. Moreover, we found that cerulein administration was associated with stomach edema as well as high levels of lipid peroxidation in the stomach and small intestine, which were also reduced by melatonin. Melatonin's protective effects in cerulein-treated rats presumably relate to its radical scavenging ability and to other antioxidative processes induced by melatonin.

Protection by vitamin B2 against oxidant-mediated acute lung injury

The effect of vitamin B2 (riboflavin) on oxidant-mediated acute lung injury has been examined in three different rat models. Pulmonary injury was induced by intravenous injection of cobra venom factor (CVF), by the intrapulmonary deposition of IgG immune complexes, or by hind limb ischemia-reperfusion. In each of the three models, injury was characterized by increases in vascular permeability (leakage of 125I-labeled bovine serum albumin), alveolar hemorrhage (extravasation of 51Cr-labeled rat erythrocytes), and neutrophil accumulation (myeloperoxidase activity). Intraperitoneal administration of riboflavin at a dose of 6 micromoles/kg body weight reduced vascular leakage by 56% in the CVF model, by 31% in the immune complex model, and by 53% in the lung injury model following ischemia-reperfusion of the hind limbs. Similar treatment reduced hemorrhage by 76%, 51%, and 70% in the three models of lung injury. In the CVF model, riboflavin was also shown to decrease products of lipid peroxidation (conjugated dienes) in lungs (by 45%) and in plasma (by 74%). Neutrophil accumulation in the lungs was not influenced by riboflavin administration in any of the three models. The studies demonstrate that riboflavin can mount a significant protection against oxidant-mediated inflammatory organ injury.

Reperfusion injury: experimental evidence and clinical implications

Postischemic reperfusion may profoundly alter cardiac function. Principal mediators of this phenomenon are oxygen radicals and neutrophils. Upon reflow, oxygen radicals are generated in large amounts, overwhelming cellular defenses and inducing oxidative tissue damage; biochemical markers of oxygen radical formation and attack can be found in postischemic myocardium. Reintroduction of neutrophils in postischemic tissues is accompanied by their activation, with release of lytic enzymes that directly induce tissue damage and proinflammatory mediators that amplify the local inflammatory reaction. Neutrophils may also plug capillaries, mechanically blocking flow. Oxidants can also modulate various events, ultimately leading to tissue injury, such as nitric oxide formation, platelet-activating factor metabolism, tissue factor synthesis, and exposure of adhesion molecules. In the clinical setting, important consequences of postischemic reperfusion are reversible contractile dysfunction ("stunning"), which is mostly caused by oxygen radical attack, and impairment to flow at the microvascular level ("no-reflow") secondary to neutrophil plugging and vasoconstriction.

Free radical activity, antioxidant enzyme, and glutathione changes with muscle stretch injury in rabbits

The present study investigated changes in rate of free radical production, antioxidant enzyme activity, and glutathione status immediately after and 24 h after acute muscle stretch injury in 18 male New Zealand White rabbits. There was no change in free radical production in injured muscles, compared with noninjured controls, immediately after injury (time 0; P = 0.782). However, at 24 h postinjury, there was a 25% increase in free radical production in the injured muscles. Overall, there was an interaction (time and treatment) effect (P = 0.005) for free radical production. Antioxidant enzyme activity demonstrated a treatment (injured vs. control) and interaction effect for both glutathione peroxidase (P = 0.015) and glutathione reductase (P = 0.041). There was no evidence of lipid peroxidation damage, as measured by muscle malondialdehyde content. An interaction effect occurred for both reduced glutathione (P = 0.008) and total glutathione (P = 0.015). Morphological analysis (hematoxylin and eosin staining) showed significant polymorphonuclear cell infiltration of the damaged region at 24 h postinjury. We conclude that acute mechanical muscle stretch injury results in increased free radical production within 24 h after injury. Antioxidant enzyme and glutathione systems also appear to be affected during this early postinjury period.

Inhibition of oxidant-induced barrier disruption and protein tyrosine phosphorylation in Caco-2 cell monolayers by epidermal growth factor

The effect of epidermal growth factor (EGF) on the H202-induced increase in paracellular permeability in Caco-2 and T-84 cell monolayers was evaluated to examine the role of EGF in intestinal mucosal protection from oxidative stress. Oxidative stress was induced by exposing cell monolayers to H2O2 or a mixture of xanthine oxidase + xanthine (XO + X). Paracellular permeability was assessed by measuring transepithelial electrical resistance (TER), sodium chloride dilution potential, and unidirectional flux of [3H]mannitol. H2O2 (0.1 to 5.0 mM) reduced TER and dilution potential and increased mannitol flux. Administration of EGF delayed H2O2 and XO + X-induced changes in TER, dilution potential, and [3H]mannitol flux. This protective effect of apically or basally administered EGF was concentration-related, with A50 (95% confidence limits) values of 2.1 (1.17 to 4.34) and 6.0 (4.37 to 8.34) nM, respectively. The EGF-mediated protection was prevented by treatment of cell monolayers with genistein (10 microM), a tyrosine kinase inhibitor. H2O2 and XO + X also induced tyrosine phosphorylation of a number of proteins in Caco-2 and T-84 cell monolayers. EGF treatment inhibited the oxidant-induced tyrosine phosphorylation of proteins, particularly those with a molecular mass of 110-220 kDa. Treatment of Caco-2 cells with anti-transforming growth factor-alpha antibodies potentiated the H2O2-induced changes in TER, dilution potential, and mannitol flux. These studies demonstrated that an EGF receptor-mediated mechanism delays oxidant-induced disruption of the epithelial barrier function, possibly by suppressing the oxidant-induced tyrosine phosphorylation of proteins.

Free radical involvement in hypertrophic scar formation

Hypertrophic scarring following thermal injury has become a major problem in Hong Kong. There is evidence that immunological and biochemical changes are associated with thermal injury, including pyridinoline crosslinks which are present in large quantities in hypertrophic scar, but the primary cause of hypertrophic scar formation still remains to be established. It has been reported that free radicals are assosciated with the formation of pyridinoline. In this study, attempts have been made to elucidate the involvement of free radicals in hypertrophic scar formation after thermal injury by determining the concentrations of Complement, free iron and pyridinoline crosslinks in collagen fibres. The results showed that the Complement activation product, C3d, was increased in the first week (i.e., day 7) postburn, indicating an acute inflammatory response. Free radicals, reported to be associated with the formation of pyridinoline crosslinks, and free iron content, were also found to have higher concentration in hypertrophic scar than in normal skin. The data suggest the involvement of free radical in hypertrophic scar formation. The observed increase in serum C3d concentration in about the first week indicates an acute inflammatory response to thermal injury. Both C3d and free iron concentrations (in vitro) are found higher in hypertrophic scar than in normal skin may suggest their roles in the generation of free radicals.

Direct evidence of caeruloplasmin antioxidant properties

The chain-breaking antioxidant potential of caeruloplasmin and bovine serum albumin (BSA) has been investigated in comparison with other well-established antioxidants. Their Oxygen Radical Absorbing Capacity (ORAC), was measured by using beta-phycocyanin (beta-PC) as a fluorescent indicator protein, 2,2'-azobis (2-amidinopropane) hydrochloride (AAPH) as a peroxyl radical generator and the water soluble vitamin E analogue, Trolox, as a reference standard. The relative peroxyl absorbing capacities/mole for Trolox, caeruloplasmin, heat-denatured caeruloplasmin (hCP), catalase, bovine serum albumin (BSA), superoxide dismutase (SOD), and deferoxamine were 1; 2.6; 3.3; 3.7; 1.2; 0.1; 0.2, respectively. Caeruloplasmin was far more effective as a peroxyl radical scavenger than SOD, deferoxamine and BSA, but slightly less effective than catalase. The peroxyl radical absorbing capacity of caeruloplasmin was enhanced by heat-denaturation of the protein. Electron paramagnetic resonance (EPR) spectroscopy using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin-trap, was applied in order to measure the scavenger abilities of caeruloplasmin on superoxide radical and hydroxyl radical production and the concentration required to inhibit by 50% oxygen free radical formation (IC50) was determined. The IC50 values of caeruloplasmin, hCP, and BSA for the superoxide radical were 12, 2, 260 microM and for the hydroxyl radical 15, 2, 200 microM. These results show that caeruloplasmin is an effective chain-breaking antioxidant for a variety of radicals, independently of its catalytic ferroxidase activity.

Resistance of filarial nematode parasites to oxidative stress

All filariae examined to date express a comprehensive repertoire of both cytoplasmic and secreted anti-oxidant enzymes, although significant differences exist between species and life-cycle stages. Adult Brugia malayi, Dirofilaria immitis and Onchocerca volvulus secrete CuZn superoxide dismutases, and the former two species also secrete a selenocysteine-independent glutathione peroxidase. This enzyme has been localised to the cuticular matrix of B. malayi, and the preferential reduction of fatty acid- and phospholipid hydroperoxides suggests that it may protect cuticular membranes from oxidative damage rather than directly metabolise hydrogen peroxide. Adult O. volvulus may compensate for an apparent deficiency in expression of this enzyme via a secreted variant of glutathione S-transferase. Recent studies have identified a highly expressed family of enzymes collectively termed peroxiredoxins, which most probably play an essential role in reduction of hydroperoxides. Data from cDNA cloning exercises indicate that all filarial species examined thus far express at least two peroxiredoxin variants which have been localised to diverse tissues. In-vitro studies have shown that B. malayi are particularly resistant to oxidative stress, and that the parasites do not rely solely on enzymatic mechanisms of defence. Cuticular lipids are relatively resistant to lipid peroxidation due to the low unsaturation indices of the constituent fatty acyl residues, but complete protection is afforded by the presence of alpha-tocopherol, presumably assimilated from host extracellular fluids. Brugia malayi are also relatively resistant to nitric oxide-mediated toxicity, and this may be due in part to incomplete dependence on aerobic metabolism. Little is known of potential mechanisms for detoxification of nitric oxide derivatives and adaptive responses to oxidative stress in general, and these represent goals for future research.

Glutathione peroxidase mimics prevent TNFalpha- and neutrophil-induced endothelial alterations

Based on the assumption that glutathione peroxidase (GPx) activity might be limiting in preventing peroxide-induced impairment of endothelial regulatory functions, we studied the effect of a series of new selenium-containing GPx mimics on endothelial cells exposed to an inflammatory stress. The two compounds that have the highest GPx activity, BXT-51072 and BXT-51077, were shown to be the most efficient inhibitors of leukocyte recruitment by human umbilical vein endothelial cells (HUVEC), upon incubation with neutrophils (10-fold excess over HUVEC) and with 1 ng/ml TNF-alpha for 1 or 3.5 h. When HUVEC were pre- and cotreated with 10 microM of either compound, neutrophil adhesion and endothelial alteration were markedly inhibited, as assessed by immunoassays of myeloperoxidase and von Willebrand factor, respectively. These two GPx mimics were also found to be the most efficient inhibitors of the TNFalpha-induced endothelial expression of P- and E-selectin and of the TNFalpha- or interleukin1-induced endothelial release of interleukin-8. Our results demonstrate that GPx mimics such as BXT-51072 behave as potent antagonists of TNF-alpha and interleukin-1 through the downregulation of endothelial proinflammatory responses.

Oxidative stress: an important phenomenon with pathogenetic significance in the progression of acute pancreatitis

BACKGROUND

Reactive oxygen species and related oxidative damage have been implicated in the initiation of acute pancreatitis. Changes in these parameters during disease progression merit further investigation.

AIMS

To evaluate changes and the clinical relevance of superoxide radicals, endogenous antioxidants, and lipid peroxidation during the course of acute pancreatitis.

PATIENTS AND METHODS

Superoxide radicals (measured as lucigenin amplified chemiluminescence), ascorbic acid, dehydroascorbic acid, alpha tocopherol, and lipid peroxidation (measured as thiobarbiturate reactive substances) were analysed in blood samples from 56 healthy subjects, 30 patients with mild acute pancreatitis, and 23 patients with severe acute pancreatitis. The association with grades of disease severity was analysed. Measurements were repeated one and two weeks after onset of pancreatitis.

RESULTS

In the blood from patients with acute pancreatitis, there were increased levels of the superoxide radical as well as lipid peroxides. There was notable depletion of ascorbic acid and an increased fraction of dehydroascorbic acid. Changes in alpha tocopherol were not great except in one case with poor prognosis. Differences between severe and mild acute pancreatitis were significant (p < 0.01). Variable but significant correlations with disease severity scores were found for most of these markers. The normalisation of these indexes postdated clinical recovery one or two weeks after onset of disease.

CONCLUSIONS

Heightened oxidative stress appears early in the course of acute pancreatitis and lasts longer than the clinical manifestations. The dependence of disease severity on the imbalance between oxidants and natural defences suggests that oxidative stress may have a pivotal role in the progression of pancreatitis and may provide a target for treatment.

Interleukin-8 (IL-8) and monocyte chemotactic and activating factor (MCAF/MCP-1), chemokines essentially involved in inflammatory and immune reactions

Leukocyte infiltration is a hallmark of inflammation. Knowledge on molecular mechanisms of leukocyte infiltration has advanced rapidly due to the recent elucidation of structures and functions of adhesion molecules and chemokines. Since the discovery of interleukin-8 (IL-8), a prototype of CXC chemokines, in 1987 and monocyte chemotactic and activating factor/monocyte chemoattractant protein-1 (MCAF/MCP-1), a prototype of chemotactic cytokines (CC) chemokines, in 1989, more than 30 members of chemokines have been identified so far. Evidence is accumulating that these chemokines exert overlapping but distinct actions on specific types of leukocytes in vitro through interacting with their specific G-protein-coupled receptors with seven transmembrane domains. However, redundancy at receptor levels has frequently hindered the clarification on the precise physiological or pathophysiological roles of chemokines. Here, we describe the pathophysiological roles of IL-8 and MCAF/MCP-1 in several animal models of neutrophil- and macrophage-mediated inflammation, respectively, by focusing on our recent work using neutralizing antibodies to these chemokines. We discuss further potential roles of these chemokines in T-lymphocyte-mediated immune responses.

Application of various antioxidants in the treatment of influenza

We determined the effect of the antioxidants superoxide dismutase, desferrioxamine and allopurinol on the survival of male CBA mice infected intranasally with 2-5 LD50 lung influenza virus A/Aichi/2/68. Survival for at least 20 days was observed for 45% of the mice that received 1000 U/day superoxide dismutase prepared from red blood cells on days 5, 6, 7 and 8 after infection, and 75% survival was observed for mice that received the same dose on days 4, 5, 6, 7 and 8. Desferrioxamine, 25 mg/kg per day and 100 mg/kg per day injected subcutaneously, resulted in survival rates of 5 and 0%, respectively, compared to 10% survival observed for saline-injected controls. Allopurinol at doses of 5 to 50 mg/kg per day had no effect on mouse survival. These data demonstrate the efficacy of superoxide dismutase for the protection of mice against hemorrhagic lung edema. The ineffectiveness of allopurinol suggests that the xanthine oxidase system does not play a major role in hemorrhage or lung edema and that caution is necessary when desferrioxamine is administered during an acute inflammatory process accompanied by erythrocyte lysis.

Identification of a neutrophil chemotactic factor from Tritrichomonas foetus as superoxide dismutase

Antibodies to a neutrophil chemotactic factor from Tritrichomonas foetus were used to screen a T. foetus cDNA expression library in lambda gt11. All positive clones were identified as homologs of iron-containing superoxide dismutase (SOD). Native gel electrophoresis showed that the antibodies indeed recognized T. foetus antigens with SOD activity. Two SOD genes were found in T. foetus, and cloned and sequenced as parts of larger genomic segments of 3844 and 4089 base pairs. Transcription initiated between the first and second methionine codons of each genomic open reading frame, generating mRNAs with 5' untranslated regions of 11-15 bases, and encoding proteins of 195 amino acids. The two SOD coding sequences lacked obvious introns. They were 79% identical at both the nucleotide and amino acid levels. Both SOD genes were inserted into a eukaryotic expression vector and stably expressed in mammalian cells; both proteins were recognized by the antibodies, and both assumed a cytosolic, extranuclear distribution in these cells. Histidine-tagged forms of both T. foetus SODs were expressed in E. coli and after purification, found to have neutrophil chemotactic activity similar to the non-recombinant factor purified from T. foetus. Identification of this neutrophil chemotactic factor as SOD provides additional insight into the host-parasite interaction.

Enhanced anti-inflammatory effects of Cu, Zn-superoxide dismutase delivered by genetically modified skin fibroblasts in vitro and in vivo

PURPOSE

The purpose of this work was to evaluate the anti-inflammatory effects of secretable human Cu, Zn-superoxide dismutase (hSOD) delivered by genetically modified skin fibroblasts in vitro and in vivo.

METHODS

Rat skin fibroblasts were transfected with pRc/CMV-ILSOD including secretable SOD-coding cDNA. The effects of host and transformants on oxidative stress in vitro models using the xanthine/xanthine oxidase (X/XO) system were examined to study the paracrine SOD action. The anti-inflammatory effects by transplantation of host and transformants were evaluated in an acute inflammation model, carrageenin-induced paw edema, in rats.

RESULTS

The transformants (ILSOD cells) secreted SOD protein into the extracellular space, and the extracellular SOD activity in ILSOD cells cultures was significantly increased compared with that in host cell cultures. ILSOD cells diminished the cytotoxic activity by X/XO in a paracrine fashion. These protective effects of ILSOD cells against X/XO-induced cytotoxicity correlated well with the decrease in lipid peroxidation in the damaged cells. The in vivo study showed that transplantation of ILSOD cell suspensions into the hind paw in rats inhibited carrageenin-induced paw edema for at least 7 days, and the degree and the durability of these inhibitory effects were dependent on the number of ILSOD cells transplanted. These inhibitory effects of ILSOD cell suspensions were reduced by co-administration of antiserum for hSOD. Furthermore, the healing of paw edema caused by carrageenin was markedly enhanced by transplantation of ILSOD cells into the edemics hind paw.

CONCLUSIONS

The findings suggested that genetically modified skin fibroblasts are a suitable delivery system for obtaining an efficient and continuous supply of SOD to the target site, and this strategy may be a useful drug delivery system for therapeutic proteins.

Inducible macrophage apoptosis following sepsis is mediated by cysteine protease activation and nitric oxide release

Recent studies indicate that polymicrobial sepsis can markedly increase inducible macrophage Ao (nonnecrotic cellular suicide) and that this is associated with decreased M phi function. In vitro studies suggest that M phi Ao can be induced by IL-1 beta via interleukin-1 beta-converting enzyme (ICE, a cysteine protease), prostanoids, or reactive oxygen/nitrogen. However, the mechanism(s) underlying this process in septic M phi remains unknown. To determine this, male C3H/HeN mice were subjected to sepsis (cecal ligation and puncture, CLP) or sham-operation. Twenty-four hours thereafter, M phi were isolated from the peritoneum (PM phi) and liver (LM phi). Macrophage monolayers were treated with LPS (10 micrograms/ml) alone (Cont) or in the presence of iodoacetamide (Iodo, 5 mM), N-methylmalamide (meth, 5 mM), ibuprophen (Ibu, 40 micrograms/ml), N-methyl-L-arginine (LNMA, 0.4 mM), or superoxide dismutase (SOD, 60,000 U/ml) for 24 hr. The extent of Ao was determined using an enzyme-linked immunosorbent cell-death assay, which detects the presence of cytoplasmic oligonucleosomes measured as optical density. The results indicate that both PM phi and LM phi from septic animals exhibit increased Ao over cells from sham animals. However, only the nonspecific cysteine protease inhibitors (Iodo and meth) and the NO inhibitor LNMA blocked septic mouse M phi Ao. Furthermore, only PM phi from CLP mice treated with Iodo, but not LNMA or IBU, showed an improved capacity to release IL-6. We conclude that increased M phi Ao seen during sepsis appears to be mediated by both ICE-like cysteine protease activation and NO release but the level/mechanism of action of these inhibitors differs.

A trial of antioxidants N-acetylcysteine and procysteine in ARDS. The Antioxidant in ARDS Study Group

OBJECTIVE

To determine the levels of glutathione and cysteine in patients with ARDS and examine the effect of treatment with N-acetylcysteine (NAC) and L-2-oxothiazolidine-4-carboxylate (Procysteine; Clintec Technologies Inc; Chicago [OTZ]) on these levels and on common physiologic abnormalities, and organ dysfunction associated with ARDS.

DESIGN

Randomized, double-blind, placebo-controlled, prospective clinical trial.

SETTING

ICUs in five clinical centers in the United States and Canada.

PATIENTS

Patients meeting a predetermined definition of ARDS and requiring mechanical ventilation.

INTERVENTION

Standard care for ARDS and I.V. infusion, every 8 h for 10 days, of one of the following: NAC (70 mg/kg, n=14), OTZ (63 mg/kg, n=17), or placebo (n=15).

MAIN RESULTS

Both antioxidants effectively repleted RBC glutathione gradually over the 10-day treatment period (47% and 49% increases from baseline values for NAC and OTZ, respectively). There was no difference in mortality among groups (placebo, 40%; NAC, 36%; OTZ, 35%). However, the number of days of acute lung injury was decreased and there was also a significant increase in cardiac index in both treatment groups (NAC/OTZ [+]14%; placebo [-]6%).

CONCLUSIONS

Our findings suggest that repletion of glutathione may safely be accomplished with NAC or OTZ in patients with acute lung injury/ARDS. Such treatment may shorten the duration of acute lung injury, but larger studies are needed to confirm this.

Exercise and oxidative stress: Sources of free radicals and their impact on antioxidant systems

Strenuous exercise is characterized by increased oxygen consumption and the disturbance between intracellular pro-oxidant and antioxidant homeostasis. At lease three biochemical pathways (i.e., mitochondrial electron transport chain, xanthine oxidase, and polymorphoneutrophil) have been identified as potential sources of intracellular free radical generation during exercise. These deleterious reactive oxygen species pose a serious threat to the cellular antioxidant defense system, such as diminished reserves of antioxidant vitamins and glutathione. However, enzymatic and non-enzymatic antioxidants have demonstrated great versitility and adaptability in response to acute and chronic exercise. The delicate balance between pro-oxidants and antioxidants suggests that supplementation with antioxidants may be desirable for physically active individuals under certain physiological conditions by providing a larger protective margin.

The role of oxygen free radicals in occupational and environmental lung diseases

Oxygen free radicals and their metabolites, collectively described as reactive oxygen species (ROS), have been implicated in the pathogenesis of many diseases. The pulmonary system is particularly vulnerable to ROS-induced injury because of its continuous exposure to toxic pollutants from a wide variety of sources in the ambient air. Additionally, lungs are exposed systemically to ROS generated from xenobiotic compounds and endogenous sources. This review describes the sources of endogenous and exogenous ROS generation in the lung. Special emphasis is given to major sources of ROS in occupational and environmental exposures to asbestos, crystalline silica, coal, chromium, herbicides, bleomycin, and cigarette smoke. ROS-induced lung injury at different target levels may contribute to similar patterns of cell injury and alterations at the molecular level by initiation, propagation, and autocatalytic chain reactions. Intracellular signalling, activation and inactivation of enzymes, stimulation, secretion, and release of proinflammatory cytokines, chemokines, and nuclear factor activation and alterations are also common events. Understanding the interactions of these intricate mechanistic events is important in the prevention and amelioration of lung injury that results from acute and chronic exposures to toxins in ambient air.

Effects of oren-gedoku-to and unsei-in, Chinese traditional medicines, on interleukin-8 and superoxide dismutase in rats

This study was conducted to elucidate the mechanisms of action of two Chinese traditional drugs, Oren-gedoku-to and Unsei-in, which have been used for many years in the treatment of inflammatory disorders. In rats with acetic acid-induced inflammation, both drugs reduced interleukin-8 concentrations in the serum. Neither drug significantly affected superoxide dismutase activity in the serum, although Unsei-in increased superoxide dismutase activity in liver after 1 month of administration. Oren-gedoku-to showed no significant effect on liver superoxide dismutase activity. It was considered that these medicines exert their anti-inflammatory effects mainly on the early stages of inflammation, wherein increased capillary permeability and migration of leucocytes occur.

Superoxide dismutase activity in Helicobacter pylori-positive antral gastritis in children

Reactive oxygen metabolites have been implicated in gastric mucosal injuries. Superoxide dismutase, a scavenger of superoxide radical, is a key enzyme in gastric mucosal protection against several damaging factors. This study was aimed at investigating the relationship of superoxide dismutase activity to Helicobacter pylori-induced antral gastritis in children. Two groups of 11 children each, one positive and the other negative for Helicobacter pylori, were studied. Biopsies from the antrum and corpus were obtained for evaluation of Helicobacter pylori by CLOtest and histology as well as for superoxide dismutase activity (cytochrome c method). Erythrocytic and serum superoxide dismutase levels were determined as well. Superoxide dismutase activity was significantly higher only in the antrum of children with Helicobacter pylori-induced antral gastritis. There was no significant difference in superoxide dismutase activity in the corpus, erythrocytes, or serum of both groups. These findings may suggest a pathogenic relationship between the presence of Helicobacter pylori and oxygen radicals in inducing antral mucosal injury.

Manganese-based superoxide dismutase mimetics inhibit neutrophil infiltration in vivo

In a previous study (Hardy et al. (1994) J. Biol. Chem. 269, 18535-18540), we observed that the manganese-based superoxide dismutase mimetic Mn(II)-dichloro(1,4,7,10,13-pentaazacyclopentadecane) (MnPAM) inhibited neutrophil-mediated cell injury in vitro. We have extended these studies with the low molecular weight superoxide dismutase mimic to evaluate the role of superoxide in neutrophil-mediated tissue injury in vivo. In a dose-dependent manner, MnPAM inhibited colonic tissue injury and neutrophil accumulation into the colonic tissue induced by the intracolonic instillation of dilute aqueous acetic acid in mice. Tissue injury was assessed by visual and histological analysis. Neutrophil infiltration was determined by tissue myeloperoxidase activity and confirmed by histological analysis. Two novel Mn(II) dichloro complexes of the carbon-substituted macrocycles 2-methyl-1,4,7,10,13-pentaazacyclopentadecane (MnMAM) and 2-(2-methylpropyl)-1,4,7,10,13-pentaazacyclopentadecane (MnBAM) effectively catalyzed the dismutation of superoxide with catalytic rate constants (kcat) of 3. 31 x 10(7) M-1 s-1 and 1.91 x 10(7) M-1 s-1, respectively, as determined by stopped-flow kinetic analysis at pH 8.1 and 21 degrees C. The superoxide dismutase mimetics MnMAM and MnBAM also attenuated dilute aqueous acetic acid-induced tissue injury and neutrophil infiltration into colonic tissue; however, two Mn(II) complexes that had little or no detectable SOD activity (kcat </= 0.1 x 10(7) M-1 s-1), specifically the Mn(II) dichloro complexes of 1,4,7,10,13-pentaazacyclohexadecane and 1,4,7,11,14-pentaazacycloheptadecane, failed to inhibit the colonic tissue injury or infiltration of neutrophils in mice treated intracolonically with dilute aqueous acetic acid. These results are consistent with a proinflammatory role for superoxide in the mediation of neutrophil infiltration in vivo.

Glutathione-dependent modulation of exhausting exercise-induced changes in neutrophil function of rats

Reduced glutathione (GSH) plays a central role in maintaining an effective synergism between various physiological and exogenous antioxidants. We tested the effects of GSH and N-acetylcysteine (NAC, a pro-GSH clinical drug), intraperitoneal (i.p.) supplementation and GSH deficiency on exercise-induced leucocyte margination and neutrophil oxidative burst activity. GSH, NAC (1g.kg-1) or placebo saline was i.p. injected (one or eight times) to male rats (n > or = seven per group). The GSH-deficient rats were prepared by i.p. injections of L-buthionine-[SR]-sulphoximine (BSO, 6 mmol.l-1.kg-1) twice daily for 4 days. Exercised animals were subjected to treadmill run to exhaustion. Exhausting treadmill exercise significantly decreased peripheral blood leucocyte count in the controls (P < 0.001). Such exercise-associated leucocyte margination was prevented by GSH supplementation. Peripheral blood neutrophil counts were significantly higher (P < 0.02) in the GSH-supplemented groups compared to the placebo control groups. Exercise-induced increase in peripheral blood neutrophil oxidative burst activity as measured by luminol-enhanced chemiluminescence per volume of blood tended to be higher in the GSH-supplemented group (P < 0.10), and lower in the GSH-deficient rats (P < 0.02). In these experiments, for the first time we have shown that GSH supplementation can induce neutrophil mobilization and decrease exercise-induced leucocyte margination, and that exogenous and endogenous GSH can regulate exercise-induced stimulation of the neutrophil oxidative burst.

Humoral and cell-mediated autoimmunity in allergy to Aspergillus fumigatus

A cDNA encoding an allergenic protein was isolated from an Aspergillus fumigatus (A. fumigatus) cDNA library displayed on the surface of filamentous phage. Serum immunoglobulin E (IgE) from A. fumigatus-sensitized individuals was used to enrich phage-expressing gene products binding to IgE. One of the cDNAs encoded a 26.7-kD protein that was identified as a manganese superoxide dismutase (MnSOD) sharing 51.5% identity and 67.2% homology to the corresponding human enzyme. Both human and A. fumigatus MnSOD coding sequences were expressed in Escherichia coli as [His]6-tagged fusion proteins and purified by Ni(2+)-chelate affinity chromatography. The two recombinant MnSODs were both recognized by IgE antibodies from subjects allergic to the A. fumigatus MnSOD and elicited specific immediate type allergic skin reactions in these individuals. Moreover, both human and A. fumigatus MnSOD induced proliferation in peripheral blood mononuclear cells of A. fumigatus-allergic subjects who showed specific IgE responses and reacted in skin tests to MnSOD. These observations provide evidence for autoreactivity to the human MnSOD in allergic persons sensitized to an environmental allergen from A. fumigatus who share a high degree of sequence homology to the corresponding human enzyme.

Aprotinin prevents the development of the trauma-induced multiple organ failure in a chronic sheep model

Trauma-induced multiple organ failure in sheep was prevented by aprotinin therapy. Multiple organ failure was induced in 16 female merino sheep by initial haemorrhagic shock and intramedullary femoral nailing (day 0), and 12 hourly injections of 0.75 micrograms/kg Escherichia coli endotoxin +0.7 ml/kg zymosan-activated plasma (days 1-5). In addition, the aprotinin group (n = 6) received simultaneous injections of 5 mg/kg (35 695 KIU/kg) aprotinin, whereas ten animals did not receive aprotinin and served as the control group (n = 10). Organ functions were monitored for a total of 11 days by measuring haemodynamic, cardio-respiratory and biochemical quantities of blood, urine and epithelial lining fluid. During the subsequent eleven day period, aprotinin induced a significant (p < 0.05) reduction of the pathological changes (development of multiple organ failure) seen in the control group. Thus, aprotinin prevented an alteration of cardiac function (cardiac index for control/aprotinin groups at day 1: 6.5/6.2, and at day 10: 10.47/7.0 1/min x m2), an impairment of lung function (mean pulmonary arterial pressure at day 1: 2.26/1.86, and at day 10: 3.83/2.13 kPa; epithelial lining fluid/plasma ratio of albumin concentrations as a direct marker of lung capillary permeability damage at day 0: 0.18/0.16, and at day 10: 0.45/0.15), a deterioration of liver function (plasma sorbitol dehydrogenase at day 0: 7.9/7.6, and at day 10: 29.6/7.4 U/1), but not of renal function (creatinine clearance at day 1: 91.4/66.1, and at day 10: 53.1/59.2 ml/min). Urinary aprotinin excretion increased up to day 3, then decreased rapidly despite further aprotinin administration. As a non-specific marker of cell damage, plasma lactate dehydrogenase indicated an aprotinin-induced organ protection (day 0: 501/409, and at day 10: 719/329 U/1). The neutrophil count and the measured chemiluminescence of neutrophils from the blood and epithelial lining fluid showed that aprotinin reduced the in vivo neutrophil activation, the alveolar neutrophil invasion, the production of inflammatory mediators, and the production of reactive oxygen metabolites during the passage of the capillary-interstitial-alveolar space by neutrophils.

Mice lacking extracellular superoxide dismutase are more sensitive to hyperoxia

Extracellular superoxide dismutase (EC-SOD; superoxide:superoxide oxidoreductase, EC 1.15.1.1) is a secreted Cu- and Zn-containing tetrameric glycoprotein, the bulk of which is bound to heparan sulfate proteoglycans in the interstitium of tissues. To test the function of EC-SOD in vivo, mice carrying a targeted disruption of the EC-SOD gene were generated. The EC-SOD null mutant mice develop normally and remain healthy until at least 14 months of age. No compensatory induction of other SOD isoenzymes or other antioxidant enzymes was observed. When stressed by exposure to > 99% oxygen, the EC-SOD null mutant mice display a considerable reduction in survival time compared to wild-type mice and an earlier onset of severe lung edema. These findings suggest that while under normal physiological conditions other antioxidant systems may substitute for the loss of EC-SOD; when the animal is stressed these systems are unable to provide adequate protection.

Role of neutrophils in myocardial ischemia and reperfusion

In the intact organism, ischemic myocardial injury initiates an acute inflammatory response in which polymorphonuclear leukocytes (PMNs) are major participants. Evidence indicates that the interplaying inflammatory reactions are augmented by reperfusion and that accumulating PMNs can contribute to myocardial damage, eg, by release of oxygen-derived free radicals, proteases, and leukotrienes. In experimental models, interventions aimed at PMN inhibition can exert cardioprotective effects, and some of these strategies raise hope for future clinical applications. A greater understanding of the mechanisms involved in PMN-mediated myocardial damage is necessary for designing a rational approach to reduce the putative detrimental effects of PMNs without antagonizing their favorable consequences in tissue healing.

Polarized Caco-2 cells. Effect of reactive oxygen metabolites on enterocyte barrier function

Reactive oxygen metabolites are implicated in gastrointestinal disease and enterocyte injury associated with ischemia-reperfusion, bacterial translocation, inflammatory bowel disease, and necrotizing enterocolitis. The ileal-like, human colon carcinoma cell line, Caco-2, was used to investigate oxidative damage. After challenging Caco-2 cells with reactive oxygen metabolites, the permeability, viability, and energy charge of Caco-2 cells were assessed. Permeability was determined by transepithelial electrical potential and flux of small molecules. Viability was determined by release of 51Cr. Cell energy was evaluated by determining adenylate energy charge. The source of reactive oxygen metabolites, with the exception of menadione, did not affect viability of Caco-2 cells; cell permeability was increased. The increased varied with the source and location of the reactive oxygen metabolite. There was no change in energy charge. This study suggests that reactive oxygen metabolites could cause enterocyte damage and that the source of the reactive oxygen metabolite is an important variable in determining the extent of damage. Antioxidants might prevent injury.

Xanthine oxidase contributes to lung leak in rats subjected to skin burn

We found that rats subjected to thermal skin injury (skin burn) had increased serum xanthine oxidase (XO) activities, increased serum complement activation (decreased serum CH50 levels), increased erythrocyte (RBC) fragility, increased lung neutrophil accumulation, and increased lung leak compared to sham-treated rats. Treatment of rats with allopurinol (an XO inhibitor) not only decreased serum XO activity, but also decreased complement activation, RBC fragility, lung neutrophil accumulation, and lung leak abnormalities in rats subjected to skin burn. We conclude that XO may contribute to acute lung injury and a number of events associated with the development of acute lung leak following skin burn.