Superoxide Dismutase Derivative Research Articles

Superoxide dismutase transcellular shuttle constructed from dendritic MOF and charge reversible protein derivatives.

The development of molecular biology has led to the identification of protein-based therapeutics as an intriguing approach for the treatment of a wide range of diseases. To manufacture transcellular protein delivery shuttles, we attempted charge reversal chemistry on native proteins [e.g., superoxide dismutase (SOD): an enzyme capable of scavenging detrimental reactive oxygen species] by the selective conversion of the positively charged amino residues of native SOD to conjugated negatively charged citraconic moieties, eliciting overall negatively charged polyelectrolytes for the subsequent electrostatic self-assembly with cationic metal-organic framework (MOF) derivatives into protein delivery systems. Please note that the charge conversion was reversible, restoring the original amino groups in intracellular acidic endosome compartments (pH 5), which afforded facile charge reversible functions to reclaim the active SOD in the cell interior. In particular, the strategic manufacture of dendritic MOF supramolecular architectures as transcellular shuttles for the aforementioned charge-reversible SOD derivatives is noteworthy. The MOF was surface-functionalized with several polycationic segments, thus contributing to the hyper-charged architecture for the easy accommodation of the negatively charged SOD derivatives. Consequently, the SOD derivatives managed to internalize into cells by hitchhiking via endocytosis of the positively charged MOF. Once they resided in the acidic endosomes, the charge reversal of the SOD derivatives could occur smoothly and result in reduced interactions between the charged-reversed SOD and MOF, leading to the release of active SOD. Simultaneously, the dendritic MOF due to protein release presented a highly positive-charged architecture to provoke endosome membrane disruption, consequently spurring the translocation of SOD to the cytosol for the execution of its enzymatic activities. Herein, the intracellular ROS level of the activated macrophages was validated to be markedly suppressed by our proposed transcellular SOD shuttles, thereby indicating their wide availability to diverse functional proteins for biomedical applications.

Augmented inhibitory effect of superoxide dismutase on superoxide anion release from macrophages by chemical modification with polysaccharide and attenuation effects on radiation-induced inflammatory cytokine expression in vitro

To improve the ability of superoxide dismutase (SOD) to suppress reactive oxygen species (ROS)-mediated injury, chemically modified derivatives of SOD with N,N,N-trimethyl chitosan chloride (TMC) and heparin, cationized SOD (TMC-SOD), and anionized SOD (heparin-SOD) were designed and prepared. In this study, the inhibitory effect of TMC-SOD and heparin-SOD on superoxide anion release from macrophages was studied in vitro. Both TMC-SOD and heparin-SOD exhibited excellent inhibitory effects on superoxide anion release from macrophages, and the effects of TMC-SOD surpassed those of native SOD and heparin-SOD. The effects of TMC-SOD and heparin-SOD on inflammatory cytokine expression in vitro were also evaluated. The results showed that both TMC-SOD and heparin-SOD could significantly lower the levels of transforming growth factor-β1 (TGF-β1) and interleukine-1β (IL-1β) expressed by irradiated 3T3 fibroblasts. These results demonstrated that cationic polysaccharide or anionic polysaccharide SOD derivatives might be useful in the prevention and treatment of ROS-mediated inflammatory diseases. This study also demonstrated that chemical modification of SOD, especially cationization, greatly enhanced SOD’s intracellular delivery and, consequently, produced a significant protective effect against ROS-mediated injury.

The suppressive effect of gelatin-conjugated superoxide dismutase on disease development and severity of collagen-induced arthritis in mice.

We studied the effect of superoxide dismutase (SOD) on murine collagen-induced arthritis (CIA), an animal model of human rheumatoid arthritis (RA). Among SOD derivatives studied, only gelatin-SOD conjugate which has prolonged half life in vivo was effective to suppress the development of CIA, while native SOD or gelatin carrier alone was ineffective. Interestingly, pyran polymer-conjugated SOD which also has a long half life showed no suppressive effect on the disease. No significant effect on immune response against type II collagen (CII) was found in any of the experimental groups. In addition, induction of suppressor cells was not detected in spleen or lymph node cells of the gelatin-SOD-treated group. Therefore, these results suggest that oxygen radicals may have an important role in the effector phase of the immune response to manifest this chronic autoimmune polyarthritis. Thus, the use of appropriate antioxidants for the treatment of human RA may be rationalized.

SOD derivatives prevent metastatic tumor growth aggravated by tumor removal

Although surgical removal is the most aggressive strategy to treat removable tumors, it sometimes aggravates tumor growth in metastatic sites. Because surgical procedures generate reactive oxygen species (ROS), known promoters of tumor metastasis and growth, we examined whether the growth of micrometastasis is inhibited by superoxide dismutase (SOD) derivatives after surgical removal of tumors in mice. Murine melanoma B16-BL6 cells were inoculated into the footpad to establish spontaneous pulmonary metastasis. The removal of the footpad tumor significantly (P < 0.05) increased the level of plasma lipoperoxides and the number of tumor cells in the lung. An intravenous injection of SOD or its pegylated-SOD derivative significantly (P < 0.05) inhibited the peroxidation and metastatic tumor growth. It also extended the survival period of mice undergoing removal of the footpad tumor. These findings indicate that the removal of tumor produces ROS, which then aggravates the growth of tumor cells in micrometastases. SOD derivatives can effectively prevent this metastatic tumor growth by detoxifying ROS.

Extracellular oxidative damage of vascular walls and their protection using antioxidant enzymes

Reactive oxygen species damage blood vessel walls in both initial and subsequent stages of vascular pathology. Oxidative stress contributes to the atherogenic modification of low-density lipoproteins, the development of lipid streaks on the luminal surface, the disturbance of the glycocalyx, and the ulceration and rupture of atherosclerotic plaques. Such a broad spectrum of damaging activity implies the need for both intra-and extracellular protection of vascular walls, which can be realized by the combined use of gene therapy and exogenous biological antioxidants. Recent in vivo studies have shown that modified superoxide dismutase (SOD) and catalase as well as extracellular SOD (an enzyme that employs the specificity of glycosaminoglycan-protein interactions) can be effectively used as antioxidants. Covalent binding of SOD to catalase via the vascular wall glycosaminoglycan (chondroitin sulfate) leads to the formation of a bienzyme conjugate, which exhibits more pronounced antithrombotic activity in vivo in comparison to several other SOD and catalase derivatives. These results point to the importance of the attachment of bioantioxidants to the vascular wall and the conjugation of SOD and catalase activities on this surface. Extracellular bioantioxidants have good prospects for the development of highly effective protectors of vascular walls against oxidative damage in the framework of complex therapy of cardiovascular injury.

Внеклеточное оксидативное поражение сосудистой стенки и её ферментная антиоксидантная защита

Reactive oxygen species damage the blood vessel walls in both the initial and subsequent stages of vascular pathology. The oxidative stress contributes to the atherogenic modification of low-density lipoproteins, the development of lipid streaks on the luminal surface, the disturbance of glycocalyx, and the ulceration and rupture of atherosclerotic plaques. Such a broad range of damaging activity implies the need for both intra- and extracellular protection of vascular walls, which can be realized by a combined use of gene therapy and exogenous biological antioxidants. Recent in vivo studies have shown that modified superoxide dismutase (SOD) and catalase as well as extracellular SOD (an enzyme that employs the specificity of glycosaminoglycan - protein interactions) can be effectively used as antioxidant protectors. Covalent binding of SOD to catalase via the vascular wall glycosaminoglycan (chondroitin sulfate) leads to the formation of a bienzyme conjugate, which exhibits more pronounced antithrombotic activity in vivo in comparison to several other SOD and catalase derivatives. These results point to the importance of the attachment of bioantioxidants to the vascular wall and the conjugation of SOD and catalase activities on this surface. Extracellular bioantioxidants have good prospects for the development of highly effective protectors of vascular walls against oxidative damage in the framework of a complex therapy of cardiovascular injury.

Prevention of inflammation-mediated acquisition of metastatic properties of benign mouse fibrosarcoma cells by administration of an orally available superoxide dismutase

Weakly tumorigenic and nonmetastatic QR-32 cells derived from a fibrosarcoma in C57BL6 mouse are converted to malignant cells once they have grown after being coimplanted with a gelatine sponge which induces inflammation. We administered a newly developed peroral superoxide dismutase (SOD), oxykine, and as control vehicle, gliadin and saline, starting 2 days before the coimplantation and continued daily throughout the experiment. In the oxykine group, tumour incidence was lower (41%) than in the gliadin or saline group (83 and 79%, respectively). The inhibitory effect of oxykine was lost when an individual component of oxykine was administered, that is, SOD alone and gliadin alone. The effect was also abolished when administered by intraperitoneal route. When perfused in situ with nitroblue tetrazolium, an indicator of superoxide formation, the tumour masses from gliadin and saline groups displayed intense formazan deposition, whereas, those from oxykine group had less deposition. Enzymatic activity of SOD was also increased in oxykine group. Arising tumour cells in gliadin and saline groups acquired metastatic phenotype, but those in oxykine group showed reduced metastatic ability. These results suggested that the orally active SOD derivative prevented tumour progression promoted by inflammation, which is thought to be through scavenging inflammatory cell-derived superoxide anion.

Improved anti-oxidant activity of superoxide dismutase by direct chemical modification

Chemically modified derivatives of superoxide dismutase (SOD), i.e., cationized (Cat-SOD) and mannosylated SOD (Man-SOD), were designed to improve an ability of SOD to suppress reactive oxygen species (ROS)-mediated injury in the alveolar epithelium. To evaluate their effectiveness, an in vitro model of paraquat poisoning was developed with primary cultured rabbit alveolar type II cells. Despite a 5.6-fold higher cellular association than native SOD, Man-SOD did not protect cell injury due to paraquat following evaluation by MTT assay. In contrast, Cat-SOD exhibited a 140-fold higher cellular association than native SOD and greatly suppressed paraquat-induced cell injury, as well as lipid peroxidation. Incubation with 300 U/ml Cat-SOD for 2 h increased intracellular SOD activity 5.3-fold. The increase in intracellular SOD activity was significantly inhibited in the presence of cytochalasin B, an endocytosis inhibitor. Internalization of Cat-SOD was also confirmed by confocal laser scanning fluorescein microscopy. In addition, the protective effect of Cat-SOD against paraquat-induced cell injury was completely abolished by the presence of cytochalasin B. In conclusion, this study demonstrated that cationization of SOD greatly enhances its intracellular delivery and, as a consequence, produces a significant protective effect against ROS-mediated injury of the alveolar epithelium.

Targeting Superoxide Dismutase to Renal Proximal Tubule Cells Inhibits Mitochondrial Injury and Renal Dysfunction Induced by Cisplatin

We recently reported the synthesis of a cationic superoxide dismutase (SOD) derivative (AH-SOD) that rapidly and selectively accumulates in and around proximal tubule cells and effectively dismutes superoxide radicals in situ. The present study revealed that administration of cis-diamminedichloroplatinum(II)-elicited oxidative stress in renal mitochondria, decreased the renal expression of Bcl-x, released cytochrome c from mitochondria to cytosol, and induced apoptosis and renal dysfunction by a mechanism that was inhibited by AH-SOD. These results suggest that targeting SOD to proximal tubule cells protects renal function and permits the administration of fairly high doses of nephrotoxic anticancer agents, such as cisplatin, without causing renal injury.

Granulocyte-colony stimulating factor enhances anti-tumour effect of hyperthermia

The combined effect of granulocyte-colony stimulating factor (GCSF) and hyperthermia in the treatment of experimental tumours was studied to examine the possible involvement of activated granulocytes in the antitumour effect of hyperthermia. Two weeks after transplantation of SCC VII cells (1 x 105) into the instep of the left leg of C3H/HeJ male mice, the mice were given subcutaneous injections of GCSF (0.2mg/kg) for 4 days. On day 4, hyperthermia was applied locally at 43 C for 40min. Hyperthermia inhibited the tumour growth, and this effect was enhanced by pre-treating the animals with GCSF. The numbers of circulating neutrophils in control and GCSF-treated mice were 2728 +/- 517/mul and 3124 +/- 194/mul, respectively ( p = 0.53). Hyperthermia increased the number of neutrophils to 4409 +/- 700/mul ( p < 0.05). Hyperthermia combined with GCSF significantly increased the number of netrophils to 5479 +/- 691/mul ( p < 0.01). Chemiluminescence analysis using L-012 revealed that GCSF enhanced the generation of reactive oxygen species by about 10-fold. Glutathione contents in tumours 24h after hyperthermia decreased by about 50% in both the hyperthermia groups with or without GCSF, as compared to those in the control. The GCSF-enhanced anti-tumour activity of hyperthermia was markedly inhibited by administration of a long-acting superoxide dismutase derivative (SM-SOD). These results suggest that GCSF activates the ability to generate active oxygen species by neutrophils and, thereby, enhances the anti-tumour effect of hyperthermia.

Synthesis of Superoxide Dismutase Derivative That Specifically Accumulates in Renal Proximal Tubule Cells

Protection of tissues from oxygen toxicity is one of the major prerequisites to aerobic life. Since a wide variety of xenobiotics with prooxidant activity is excreted by the kidney, renal tubule cells should be protected from hazardous oxygen species. Because intravenously injected Cu/Zn-type superoxide dismutase (SOD) is rapidly excreted in the urine in its intact form, effective dismutation of superoxide radicals cannot be achieved in vivo by intravenously administered SOD. To scavenge superoxide radicals and inhibit their toxic effects in and around renal tubule cells, a hexamethylene–diamine (AH)-conjugated SOD (AH–SOD) was synthesized. When injected intravenously into the rat, 125I-labeled AH–SOD disappeared from the circulation with a half-life of 3 min and accumulated in the kidney. After 30 min of administration, more than 80% of the radioactivity derived from AH–SOD was found to localize in the kidney without being excreted in the urine. Immunohistochemical examination revealed that, 60 min after administration, the major part of AH–SOD localized in renal proximal tubule cells. Kinetic analysis using right-side-out-oriented renal brush border vesicles revealed that AH–SOD bound to their membrane surface by some mechanism which was inhibited by AH but not by heparin and albumin. These results indicated that AH–SOD rapidly underwent renal glomerular filtration, bound to apical plasma membranes of proximal tubule cells, and localized in these cells for a fairly long time without being excreted in the urine. Thus, AH–SOD might permit studies on the role of superoxide radicals in and around renal proximal tubule cells.

Preventive Effects of Superoxide Dismutase Derivatives Modified with Monosaccharides on Reperfusion Injury in Rat Liver Transplantation

Background.Superoxide dismutase (SOD) derivatives modified with monosaccharides such as mannosylated SOD (Man-SOD) and galactosylated SOD (Gal-SOD) are taken up by parenchymal and nonparenchymal cells of the liver, respectively, via receptor-mediated endocytosis. We examined the preventive effects of Man- or Gal-SOD on cold ischemia–reperfusion injury in orthotopic liver transplantation (OLT) in rats.Methods.Male Lewis rats underwent OLT. Native SOD and modified SOD with mannose (Man-SOD) or galactose (Gal-SOD) were intravenously given just prior to reperfusion of the grafted liver.Results.After OLT, no significant changes in serum levels of aspartate aminotransferase or lactate dehydrogenase were evident among rats, with or without various types of SOD. However, tissue levels of Na+,K+-ATPase, an indicator of tissue viability, were significantly higher in rats treated with Man- and Gal-SODs compared with that in untreated OLT rats. When comparisons were made between Gal-SOD and Man-SOD, higher levels of Na+,K+-ATPase were evident in rats treated with Gal-SOD. Elevations of tissue levels of lipid peroxides were significantly inhibited by modified SODs. The survival rates of rats following OLT after prolonged cold preservation correlated with results of graft viability.Conclusions.SOD derivatives, particularly Gal-SOD, have protective effects on cold ischemia–reperfusion injury during OLT in rats.

Pharmacokinetics and targeted delivery of proteins and genes

The effectiveness of various approaches for controlling in vivo disposition of proteins and genes was compared based on pharmacokinetic analysis. The potential of introduction of galactose or mannose residues aiming at receptor-mediated endocytosis, succinylation to be recognized by a scavenger receptor, and cationization for universal electrostatic interaction were characterized using model proteins. Corresponding to the results, a superior therapeutic effect was shown with derivatives of superoxide dismutase against hepatic and renal ischemia/reperfusion injury. A similar approach was adopted for plasmid DNA and oligonucleotide and their rapid degradation in the blood pool and preferential uptake by the liver after intravenous injection were characterized by pharmacokinetic analysis. The effects of incorporation into cationic liposomes and conjugation with macromolecules on their in vivo distribution were also elucidated.

Superoxide dismutase derivative prevents oxidative damage in liver and kidney of rats induced by exhausting exercise.

To prevent oxidative tissue damage induced by strenuous exercise in the liver and kidney superoxide dismutase derivative (SM-SOD), which circulated bound to albumin with a half-life of 6 h, was injected intraperitoneally into rats. Exhausting treadmill running caused a significant increase in the activities of xanthine oxidase (XO), and glutathione peroxidase (GPX) in addition to concentrations of thiobarbituric acid-reactive substances (TBARS) in hepatic tissue immediately after running. There was a definite increase in the immunoreactive content of mitochondrial superoxide dismutase (Mn-SOD) 1 day after the running. Meanwhile, the TBARS concentration in the kidney was markedly elevated 3 days after running. The activities of GPX, and catalase in the kidney increased significantly immediately and on days 1 and 3 following the test. The immunoreactive content of Mn-SOD also increased 1 day after running. The exercise induced no significant changes in immunoreactive Cu, Zn-SOD content in either tissue. The administration of SM-SOD provided effective protection against lipid peroxidation, and significantly attenuated the alterations in XO and all the anti-oxidant enzymes, measured. In summary, the present data would suggest that exhausting exercise may induce XO-derived oxidative damage in the liver, while the increase in lipid peroxidation in the kidney might be the result of washout-dependent accumulation of peroxidised metabolites. We found that the administration of SM-SOD provided excellent protection against exercise-induced oxidative stress in both liver and kidney.

Superoxide dismutase derivative reduces oxidative damage in skeletal muscle of rats during exhaustive exercise.

A superoxide dismutase derivative (SM-SOD) that circulates and is bound to albumin with a half-life of 6 h was injected intraperitoneally into rats before exhaustive treadmill running to study its antioxidant scavenging capacity in the plasma and soleus and tibialis muscles. The exercise induced a marked increase in xanthine oxidase activity in plasma and an increase in thiobarbituric acid-reactive substances in the plasma as well as in the soleus and tibialis muscles of nonadministered rats immediately after the exercise. The immunoreactive content and activity of both SOD isoenzymes (Cu,Zn-SOD and Mn-SOD) of the nonadministered rats increased in the soleus and tibialis muscles immediately after running. SM-SOD treatment definitely attenuated the degree of the increase in thiobarbituric acid-reactive substances and xanthine oxidase in all samples examined immediately after exercise. Glutathione peroxidase activity significantly increased in the soleus muscle of nonadministered rats 1 day after running, whereas catalase activity remained unchanged throughout the experimental period. These results suggest that a single bout of exhaustive exercise induces oxidative stress in skeletal muscle of rats and that this oxidative stress can be attenuated by exogenous SM-SOD.

Inhibition of puromycin-induced renal injury by a superoxide dismutase derivative with prolonged in vivo half-life.

To know the possible involvement of reactive oxygen species and the site(s) of their action in puromycin aminonucleoside (PAN)-induced renal injury, two types of superoxide dismutase (SOD) derivatives were synthesized: one (SM-SOD) circulates bound to albumin with a half-life of 6 h and the other (AH-SOD) linked with hexamethylenediamines rapidly undergoes glomerular filtration and accumulates in renal proximal tubule cells without being excreted in urine. When injected intravenously to the rat, PAN induced a marked proteinuria, increased plasma levels of cholesterol and triglyceride, and suppressed the growth of animals. Intravenously administered SM-SOD significantly inhibited such changes induced by PAN. However, native SOD which rapidly undergoes urinary excretion failed to inhibit the renal injury caused by PAN. Though AH-SOD markedly accumulated in renal proximal tubule cells, it also failed to inhibit the renal injury. These results suggested that superoxide and/or its hazardous metabolite(s) in and around the renal glomerulus, but not in tubule cells, may play critical roles in the pathogenesis of PAN-induced renal injury.

ドラッグデリバリーの空間的・時間的制御 生物の分子局在化機構と酵素分子設計

Reactive oxygen species have been postulated to underlie the pathogenesis of various diseases. Since these species rapidly react with various molecules, they should be scavenged appropriately at their site of generation. Superoxide dismutase (SOD) and related antioxidants have been expected to protect tissues from oxygen toxicity. However, because of their unfavorable pharmacokinetic properties, they often failed to inhibit oxidative tissue injury. In case of Cu/Zn-SOD, it disappeared from the circulation with a half-life of 5 min and underwent urinary excretion. Hence, intravenously administered SOD failes to dismutate superoxide radicals in vivo. The present work describes the chemical and genetic methods for targeting SOD to the site of generation and/or pathologic action of superoxide radical. Some SOD derivatives (SM-SOD, FA-SOD) reversibly bind to endogenous albumin thereby remain in the circulation with a half-life of 6 hr. Other derivatives (GSL-SOD, MAN-SOD, AH-SOD) selectively accumulate in hepatocytes, reticuloendothelial cells of liver, spleen and other tissues and renal proximal tubule cells, respectively. The fusion SOD (HB-SOD) preferentially binds to vascular endothelial cells thereby dismutates superoxide radicals in and around vascular walls. Pathophysiological role of superoxide and related free radicals, such as nitric oxide, were studied using these site-directed SODs.

Role of superoxide dismutase and nitric oxide on the interaction between brain and systemic circulation during brain ischemia

To elucidate the critical role of superoxide dismutase (SOD) and nitric oxide in brain injury and systemic circulation during brain ischemia, we performed bilateral carotid artery ligation (BCAL) on rats and evaluated the effects of N G-monomethyl- l-arginine ( l-NMMA) and a long-acting SOD derivative (SMA-SOD). After administration of l-NMMA, specific inhibitor against niric oxide synthase (NOS), most of BCAL rats died within 6 h while no BCAL rats without l-NMMA died at all. Administration of SMA-SOD exhibited no effect on the life span of BCAL rats. Magnetic resonance imaging (MRI) and microscopic analysis for the ischemic brain revealed that, although adminstration of l-NMMA showed no significant effect on the ischemic brain of BCAL rats, SMA-SOD effectively prevented the ischemic changes based on permeability edema in the frontal lobe. Measurement of changes in the blood flow of the ischemic brain revealed that administration of l-NMMA decreased the blood flow in the BCAL rats while no remarkable changes were seen after administration of SMA-SOD. Urinary secretion of NO 2 − NO 3 − , the metabolites of nitric oxide, was increased by challenging BCAL, and the presence of l-NMMA or SMA-SOD diminished this elevation. Blood pressure was increased by performing BCAL to rats, and administration of l-NMMA showed further elevetion of the blood pressure. On the contrary, administration of SMA-SOD decreased post-ischemic hypertension. These results suggest that SOD may play a protective role for brain ischemia by suppressing increased vascular permeability, while nitric oxide showed beneficial effect on the ischemic brain by increasing the blood flow in the ischemic brain.

32] In vivo determination of superoxide and vitamin C radicals using cytochrome c and superoxide dismutase derivatives

Publisher Summary Most of the reactive oxygen species rapidly react with various molecules and interfere with cellular functions. Based on experiments using antioxidant enzymes and scavengers for reactive oxygen species and free radicals, such as Cu/Zn-type superoxide dismutase (SOD), glutathione, ascorbic acid, and dimethyl sulfoxide (DMSO), critical roles of these reactive species in the pathogenesis of various diseases are presented in this chapter. However, these antioxidants react with a wide variety of compounds and are involved in various metabolic pathways. Thus, even if these scavengers inhibited tissue injury, the corresponding reactive oxygen species may not always be involved in their pathogenesis. To get direct evidence for the involvement of reactive oxygen species in the pathogenesis of various diseases, these species should be determined quantitatively in vivo. Cytochrome c (Cyt c) is used for determining superoxide radicals in vitro. Because Cyt c reacts not only with superoxide radicals but also with other compounds with reducing activity and serves as a substrate for cytochrome c-reductase and cytochrome c-oxidase, acetylated Cyt c (AC) is used for the detection of superoxide radicals, particularly in complex biological systems.

The effect of an SOD derivative (SM-SOD) administration in a burned rat model.

To determine whether superoxide radicals may influence the pathogenesis of burn injury, we investigated the effects of a long-acting, site-directed superoxide dismutase derivative (SM-SOD) on the rats subjected to burn shock. Anesthesized animals were injected intravenously with either 2 ml/kg of saline or SM-SOD (10 mg/kg; dissolved in saline). After 30 min they were subjected to full-thickness burns of about 40% of total body surface area. The 7-day survival rate was significantly higher in the SM-SOD-treated animals than in the untreated controls. Also, administration of SM-SOD markedly inhibited the increase in the levels of thiobarbituric acid reactive metabolites, such as lipid peroxides in the plasma, lung and kidney, and the decrease in plasma protein levels particularly at the early stage of burn injury. These findings suggested that superoxide radicals may play a critical role in the pathogenesis following thermal injury.