Increase In Manganese Superoxide Dismutase Research Articles

Alcohol increases tumor necrosis factor α and decreases nuclear factor‐κb to activate hepatic apoptosis in genetically obese mice†

Both obesity and alcohol can cause oxidative stress, cytokine induction, and steatohepatitis. To determine the consequences of their combination, we compared the hepatic effects of moderate ethanol binges in lean and obese ob/ob mice. Mice received water or ethanol (2.5 g/kg) by gastric intubation daily for 4 days, and were killed 2 hours after the last administration. Some obese mice also received pentoxifylline, an inhibitor of tumor necrosis factor-alpha (TNF-alpha) production, before each ethanol administration. In lean mice, these moderate ethanol doses did not increase plasma TNF-alpha and hepatic caspase-3 activity, but triggered some apoptotic hepatocytes. Naive ob/ob mice had a few necrotic and apoptotic hepatocytes, but exhibited little oxidative stress, possibly because of adaptive increases in manganese superoxide dismutase, heat shock protein 70 (Hsp70), mitochondrial cytochrome c, and mitochondrial DNA. Alcohol administration to ob/ob mice did not increase oxidative stress despite increased CYP2E1, but increased plasma TNF-alpha, further increased Hsp70, and profoundly decreased p65 nuclear factor kappaB (NF-kappaB) protein and DNA-binding activity in nuclear extracts. Caspase-3 was activated, and more apoptotic hepatocytes were found in intoxicated obese mice than naive obese mice. In intoxicated obese mice, pentoxifylline fully prevented the increase in plasma TNF-alpha the decrease in nuclear NF-kappaB activity, and the increase in hepatic caspase-3, and it also decreased hepatic triglycerides. In conclusion, obese mice develop adaptations that may limit oxidative stress. Moderate ethanol intoxication does not increase oxidative stress in obese mice, but increases TNF-alpha and also decreases nuclear NF-kappaB activity, thus unleashing the apoptotic effects of TNF-alpha.

The protective roles of nitric oxide and superoxide dismutase in adriamycin-induced cardiotoxicity

Treatment with adriamycin (ADR) is associated with cardiotoxicity mediated through the generation of superoxide (O2*-). Because nitric oxide (*NO) reacts with O2*-, generating peroxynitrite, we hypothesized that decreased *NO production would lead to protection in acute cardiac injury. We investigated the role of decreased *NO levels in exacerbation of ADR-induced cardiotoxicity in vivo using iNOS (-/-) mice. Pathology, biochemical injury markers, and cardiac function were used to assess ADR-induced cardiac injury. Ultrastructural analysis demonstrated that iNOS (-/-) mice exhibited extensive cytoplasmic swelling and degeneration of mitochondria when compared to wildtype mice following treatment with ADR. Mice lacking iNOS exhibited a decrease in resting indices of cardiac function as well as an impairment in the positive inotropic actions of isoproterenol following treatment with ADR compared to nTg mice. Cardiac troponin, creatine phosphokinase, and lactate dehydrogenase levels were significantly increased after treatment in iNOS (-/-) mice as compared to controls and wildtype mice. These results indicate that a lack of *NO production by iNOS caused significantly enhanced cardiac injury. However, when iNOS (-/-) mice were crossed with manganese superoxide dismutase (MnSOD)-overexpressing animals, mitochondrial injury was ameliorated to the level of the wild type. These findings suggest that reduction of *NO levels mediated by ADR treatment leads to increased cardiac mitochondrial injury that can be attenuated by a compensatory increase in MnSOD.

β-Sitosterol modulates antioxidant enzyme response in RAW 264.7 macrophages

Uncontrolled production of reactive oxygen species contributes to the pathogenesis of diseases such as cancer and cardiovascular disorders. Olive oil exerts remarkable preventive effects on the development of these diseases, which may be due to the action of various components of the olive oil. In fact, several findings suggest that minor components, like phytosterols such as β-sitosterol, are responsible, at least in part, for these beneficial effects. Our results show that β-sitosterol reverts the impairment of the glutathione/oxidized glutathione ratio induced by phorbol esters in RAW 264.7 macrophage cultures. These data can be correlated with the increase in manganese superoxide dismutase and glutathione peroxidase activities and the decrease in catalase activity. We also demonstrate that the effects of β-sitosterol on antioxidant enzymes depend on the estrogen/phosphatidylinositol 3-kinase pathway.

Mitochondrial redox state regulates transcription of the nuclear-encoded mitochondrial protein manganese superoxide dismutase: a proposed adaptive response to mitochondrial redox imbalance

Overexpression of human manganese superoxide dismutase (MnSOD) in mouse NIH/3T3 cells using an inducible retroviral system led to alterations in the mitochondrial redox state since levels of reactive oxygen species rapidly increased after induction of human MnSOD ( Antioxid. Redox Signal. 6:489–500; 2004). Alterations in exogenous human MnSOD led to large increases in levels of endogenous mouse MnSOD ( sod2) and thioredoxin 2 ( txn2) mRNAs, but smaller increases in MnSOD and thioredoxin 2 protein expression. Tight regulation of mitochondrial protein levels seems to be necessary for optimal cellular function, since mitochondrial antioxidant protein levels did not increase to the same extent as antioxidant protein mRNA levels. We hypothesize that these changes in antioxidant proteins are adaptations to the altered mitochondrial redox state elicited by MnSOD overexpression. The mitochondrial-specific antioxidant MitoQ reversed cell growth inhibition, and greatly decreased levels of endogenous sod2 and txn2 transcripts following induction of exogenous MnSOD. Elevated levels of mouse sod2 transcripts resulted from transcriptional activation of the endogenous sod2 gene since actinomycin D prevented transcription of this gene. Therefore, the mitochondrial redox state appears to modulate a nuclear-driven biochemical event, i.e., transcriptional activation of a nuclear gene encoding a protein targeted to mitochondria.

Cytochromecrelease from mitochondria in the aging heart: a possible mechanism for apoptosis with age

There is a loss of myocytes in the aging heart due to necrosis and apoptosis. Oxidative stress, an apoptosis-inducing signal, may also increase in the aging heart. Cytosol and mitochondria isolated from the left and right ventricle of the hearts of 6-, 16-, and 24-mo-old male Fischer 344 rats were used to measure key markers of apoptosis and to assess oxidative stress. Cytosolic cytochrome c content was significantly elevated in the 16- and 24-mo-old animals compared with the 6-mo-old animals. Furthermore, Bcl-2, an antiapoptotic protein, showed a strong tendency to decrease with age, whereas Bax, a proapoptotic protein, remained unchanged. Apoptotic protease-activating factor 1 levels and caspase-3 activities were not different among the three age groups. Indicative of the chronic oxidative stress with age, heart mitochondria from old animals showed increases in manganese superoxide dismutase and glutathione peroxidase activity and increases in lipid peroxidation. This is the first study to report cytochrome c release from the mitochondria and alterations in Bcl-2 with age in vivo, providing a potential mechanism for the increase in apoptosis seen in the aging heart.

Protein Kinase C and Changes In Manganese Superoxide Dismutase Gene Expression In Cultured Glial Cells

1. To study the role of protein kinase C (PKC) in the increase in manganese superoxide dismutase (Mn-SOD) gene expression following transient hypoxia in glial cells, we examined the mRNA levels of Mn-SOD using northern blot analysis. 2. The Mn-SOD mRNA levels were markedly increased after exposure to nitrogen gas for 5 min. 3. Pretreatment with chelerythrine or GF109203x, inhibitors of PKC, attenuated the increase in Mn-SOD mRNA following hypoxia in a concentration-dependent manner. 4. Incubation with phorbol 12-myristate 13-acetate, the PKC activator, enhanced the increase in Mn-SOD gene expression in response to transient hypoxia. 5. The results suggest that hypoxia increases Mn-SOD gene expression in cultured glial cells mainly through activation of a PKC pathway.

Specific induction of metallothionein synthesis by mitochondrial oxidative stress

Metallothionein (MT), a sulfhydryl-rich protein, may be increased by administration of a variety of agents, including metals, cytokines and oxidative stress agents. Mitochondria are a major source of reactive oxygen species, but antioxidant systems against mitochondrial free radicals are not fully understood. In this study, we examined the induction of MT synthesis by administration of mitochondrial-specific reactive oxygen generators such as antimycin A (AA), an electron transfer inhibitor, and 2,4-dinitrophenol (DNP), an uncoupling agent. Subcutaneous administration of AA to mice significantly increased the hepatic MT concentration in a dose- and time-dependent manner. AA slightly elevated glutathione peroxidase (GSHPx) activity, but the rate of increase in GSHPx (1.3-fold) was smaller than that in MT (11.8-fold). Other antioxidants such as catalase, manganese-superoxide dismutase (Mn-SOD), copper/zinc-superoxide dismutase (Cu/Zn-SOD) and GSHPx were not activated by AA treatment. Moreover, administration of DNP induced the synthesis of MT in the liver. Although DNP slightly elevated Mn-SOD activity, the rate of increase in Mn-SOD (1.3-fold) was smaller than that in MT (3.7-fold). Other antioxidants such as catalase, Cu/Zn-SOD and GSHPx were not activated by DNP treatment. These data suggest that MT plays a major role in protection against oxidative stress induced in mitochondria.

Effects of oxygen concentrations on human fibroblasts treated with Fe3+-NTA

Free radicals derived from the reaction of iron and oxygen are thought to be one of the causes of tissue injury. In order to identify whether oxygen concentrations are an important factor in iron-mediated damage to cells, cytotoxic effects of Fe(3+)-NTA on human fibroblasts (KMST-6 line) were studied under the conditions of 1% and 20% oxygen concentrations in an incubator. A comparison of the effects of Fe(3+)-NTA on cells cultured in 1% and 20% oxygen environments showed that the following features were more prominent under the usual culture concentrations of 20% oxygen: i) cytotoxicity, ii) increase in intracellular reactive oxygen species, iii) increase in H(2)O(2) production in the cells, and iv) formation of 8-hydroxydeoxyguanosine. To elucidate the roles of endogenous antioxidants, the levels of manganese superoxide dismutase (MnSOD) and catalase were measured by Western blotting. The increase in MnSOD in the presence of Fe(3+)-NTA was greater under the condition of 20% O(2) than under the condition of 1% O(2). The expression of catalase was significantly up-regulated at 20% O(2). However, when the cells were treated with Fe(3+)-NTA, the expression of catalase was markedly down-regulated under the condition of 20% O(2). Hydroxyl radical scavengers such as vitamin E, dimethyl-sulfoxide (DMSO) and mannitol reduced endogenous ROS generation and alleviated the cytotoxic effects of iron. On the other hand, superoxide dismutase (SOD), vitamin C and catalase did not show any protective effects against Fe(3+)-NTA. These findings suggest that enhanced cytotoxic effects of Fe(3+)-NTA at 20% O(2 )are due to endogenously produced hydroxyl radicals.

The activity of antioxidant enzymes and the content of uncoupling protein-1 in the brown adipose tissue of hypothyroid rats: comparison with effects of iopanoic acid

The activity of antioxidant enzymes, copper-zinc superoxide dismutase (CuZnSOD), manganese superoxide dismutase (MnSOD) and catalase (CAT), as well as that of the mitochondrial FAD-dependent a-glycerophosphate dehydrogenase (a-GPD) in the rat interscapular brown adipose tissue (IBAT) were studied after the treatment with methimazole (MMI) for three weeks or with iopanoic acid (IOP) for five days. Besides, the mitochondrial concentration of uncoupling protein-1 (UCP-1) and the activity of catecholamine degrading enzyme monoamine oxidase (MAO) in the IBAT as well as the activity of the catecholamine synthesizing enzyme, dopamine b-hydroxylase (DBH) in rat serum were examined. Judging by the significantly enhanced level of serum DBH, which is an index of sympathetic activity, and that of IBAT MAO, the increase in MnSOD and CAT activities in the IBAT of hypothyroid (MMI-treated) rats seems to be due to elevated activity of sympathetic nervous system (SNS). However, CuZnSOD activity is not affected by SNS. On the contrary, IOP, which is a potent inhibitor of T4 deiodination into T3 producing "local" hypothyroidism, did not change either SNS activity or activities of IBAT antioxidant enzyme. However, both treatments significantly decreased IBAT UCP-1 content and a-GPD activity suggesting that the optimal T3 concentration in the IBAT is necessary for maintaining basal levels of these key mitochondrial parameters.

Antioxidant defenses in TNF-treated MCF-7 cells: selective increase in MnSOD

Oxidative stress has been implicated in the mechanism of tumor necrosis factor-α (TNF)-induced apoptosis, raising a question about the status of antioxidant defenses in TNF-sensitive cells. Antioxidant defenses were examined in MCF-7 cells after treatment with TNF. Cell morphology and DNA fragmentation assays were used to confirm increased apoptosis as a result of TNF treatment. The expression and activity of antioxidant defenses were assessed using Northern blot hybridization analyses and biochemical assays, respectively. Five- and ten-fold increases in manganese superoxide dismutase (MnSOD) mRNA were measured after one and five days of TNF treatment, respectively. The expression of copper,zinc superoxide dismutase, catalase or thioredoxin was not altered. An approximate five-fold increase in MnSOD activity followed the change in gene expression, but no difference in the activity of catalase or glutathione peroxidase was seen. Thus, increased MnSOD activity was not accompanied by an increase in other antioxidant defenses and in particular, H 2O 2-scavenging enzymes. MnSOD has previously been shown to afford protection against TNF-mediated cytotoxicity. The observed lack of increased peroxidase activity is consistent with mitochondrially-generated superoxide anion radical contributing to the mechanism of TNF-induced apoptosis.

INCREASE OF MnSOD EXPRESSION AND DECREASE OF JNK ACTIVITY DETERMINE THE TNF SENSITIVITY INbcl2-TRANSFECTED L929 CELLS

To investigate the protection mechanism of Bcl-2 against tumour necrosis factor (TNF)-mediated cell death, thebcl2gene was transfected into the L929 cells and stably expressed. Two clones having different sensitivity amongbcl2-transfected L929 clones had been isolated, and termed clone R1 and R2. It was observed that activation of manganese superoxide dismutase (MnSOD) and suppression of Jun kinase of clone R1 and R2 were correlated with protection from TNF cytotoxicity. Upon treatment with TNF, clone R1 and R2 were more resistant than control L929 cells against TNF cytotoxicity and the protective effect of clone R1 was stronger than clone R2. However, in case of TNF plus actinomycin D treatment, clone R1 was still resistant against TNF cytotoxicity, whereas clone R2 became more sensitive than control L929 cells. The JNK activities of clone R1 and R2 were suppressed upon TNF treatment and in case of TNF plus actinomycin D treatment, clone R2 showed a marked increase in JNK activities and had higher activity than control L929 cells. The specific activities of MnSOD of clone R1 and R2 upon TNF treatment were 70U/ml and 33U/ml, respectively, while the MnSOD activity was not detectable in control L929 cells. When TNF and actinomycin D were treated simultaneously, MnSOD activity was not detectable in control L929 cells andbcl2-transfected L929 cells (clone R1, R2). Consistent with these results, both clone R1 and R2 showed higher levels of MnSOD mRNA expression than control L929 cells after TNF treatment. These data suggest that suppression of Jun kinase and increase of MnSOD may be involved in inhibitory action of Bcl-2 against TNF, and the balance between MnSOD and JNK signalling pathway may be an important factor for the protection ofbcl2-transfected L929 cells from TNF cytotoxicity.

Generation of reactive oxygen species by human mesothelioma cells.

Malignant mesothelioma cells contain elevated levels of manganese superoxide dismutase (MnSOD) and are highly resistant to oxidants compared to non-malignant mesothelial cells. Since the level of cellular free radicals may be important for cell survival, we hypothesized that the increase of MnSOD in the mitochondria of mesothelioma cells may alter the free radical levels of these organelles. First, MnSOD activity was compared to the activities of two constitutive mitochondrial enzymes; MnSOD activity was 20 times higher in the mesothelioma cells than in the mesothelial cells, whereas the activities of citrate synthase and cytochrome c oxidase did not differ significantly in the two cell lines. This indicates that the activity of MnSOD per mitochondrion was increased in the mesothelioma cells. Superoxide production was assayed in the isolated mitochondria of these cells using lucigenin chemiluminescence. Mitochondrial superoxide levels were significantly lower (72%) in the mesothelioma cells compared to the mesothelial cells. Oxidant production in intact cells, assayed by fluorimetry using 2′,7′-dichlorodihydrofluorescein as a fluorescent probe, did not differ significantly between these cells. We conclude that mitochondrial superoxide levels are lower in mesothelioma cells compared to nonmalignant mesothelial cells, and that this difference may be explained by higher MnSOD activity in the mitochondria of these cells. Oxidant production was not different in these cells, which may be due to the previously observed increase in H2O2-scavenging mechanisms of mesothelioma cells. © 1999 Cancer Research Campaign

Transient increase of manganese-superoxide dismutase in remote brain areas after focal photothrombotic cortical lesion.

Free radicals including superoxide are responsible for postlesional cytotoxicity. In contrast to the constitutive CuZn-superoxide dismutases (SODs), manganese-superoxide dismutase (Mn-SOD) is inducible and has the potential to protect neurons by its superoxide dismutating activity. Therefore, we studied the presence and the regional changes in Mn-SOD within the brain after focal cortical ischemia. Focal cortical photothrombotic lesions were produced in the hindlimb region of rat brains. Animals were anesthetized and transcardially perfused with Zamboni's fixative. Mn-SOD was immunohistochemically localized using an antiserum against rat-Mn-SOD. Changes in Mn-SOD immunoreactivity were quantified by image analysis. Focal photothrombosis caused a perilesional increase in Mn-SOD after 24 hours, followed by a further significant increase at 48 hours in perilesional cortex, ipsilateral corpus callosum, hippocampus, and thalamus, as well as in a homotopic cortical area within the nonlesioned hemisphere. At day 2, Mn-SOD was present in neurons and astrocytes. Up to day 7, Mn-SOD increased in the entire ipsilateral and contralateral cortex but remained higher elevated in the ipsilateral hippocampus and thalamus. Thereafter, Mn-SOD decreased globally but remained elevated in some cortical neurons up to day 60. The early transient increase of Mn-SOD in distinct brain regions, which are functionally connected via afferents and efferents, suggests that these regions are affected by the injury. It suggests that Mn-SOD protects the cells in these regions from superoxide-induced damage and therefore may limit the retrograde and anterograde spread of neurotoxicity.

COCAINE-INDUCED INCREASE OF Mn-SOD IN ADULT RAT LIVER CELLS

Cultured adult rat liver cells (non-induced) were exposed to two different concentrations (2 μg/ml and 4 μg/ml) of cocaine-HCl for 1–3 hours. Cocaine-treated rat liver cells showed a significant increase in manganese superoxide dismutase (Mn-SOD) activity with time. Coinciding the rise in Mn-SOD activity was the Mn-SOD mRNA transcript, which also demonstrated a time-dependent elevation in its level (p < 0.005). At the end of 1 and 3 hr. of cocaine exposure, the increase in Mn-SOD activity was 23% (p < 0.05) and 39% (p < 0.005), respectively. In contrast, activities of catalase (CAT) and glutathione peroxidase (GSH-px) were significantly diminished. Induction of Mn-SOD mRNA by cocaine (4 μg/ml) was inhibited by actinomycin D (4 μM), revealing that the up regulation of Mn-SOD involved transcriptional activation. The increase in Mn-SOD was accompanied by a decrease in liver cell integrity, indicated by increased lactate dehydrogenase (LDH) release by rat liver cells. These results suggest that antioxidant enzymes may play a critical role in cocaine-induced liver injury.

Cocaine-induced peroxidative stress in rat liver: antioxidant enzymes and mitochondria.

This study investigated how the cocaine-induced lipid peroxidation affected liver antioxidant enzymes and mitochondria. Acute cocaine (40 mg/kg) injection produced a significant, time-dependent increase in manganese-superoxide dismutase (Mn/SOD) activity and cellular thiobarbuturic acid reactive substances (TBARS), but activities of glutathione peroxidase and catalase were reduced significantly. These changes coincided with increased production of reactive oxygen species by mitochondria and decreased cellular ATP and glutathione. Binge cocaine (25 mg/kg; 5 injections in 3 days) significantly increased TBARS and conjugated dienes, but decreased ATP and glutathione. Accumulation of TBARS and reduction of glutathione was seen in mitochondria. Activities and mRNA of Mn/SOD and copper-zinc-superoxide dismutase were significantly elevated, but mRNA and activities of glutathione peroxidase and catalase were decreased in cocaine-treated rats. Cocaine (binge model) produced scattered liver necrosis (20%) and compromised cell integrity. This is the first report demonstrating cocaine-induced liver necrosis in rats. Pretreatment (acute model) with dimethylaminoethyl-2,2-diphenylvalerate, inhibitor of cocaine bioactivation, curtailed in part the generation of reactive oxygen species by mitochondrial fraction. Dimethylaminoethyl-2,2-diphenylvalerate also prevented the increase of TBARS and Mn/SOD. The results suggest that elevated levels of Mn/SOD and copper-zinc-superoxide dismutase, without a concomitant increase in glutathione peroxidase, catalase and glutathione s-transferase, may have contributed to cocaine-induced cellular and mitochondrial peroxidative stress. Reactive metabolites of cocaine N-oxidative metabolism may be responsible for the cocaine-induced oxidative stress and liver necrosis.

Differential Regulation of Manganese Superoxide Dismutase Activity by Alcohol and TNF in Human Hepatoma Cells

Increasing evidence implicates free radical processes in the pathogenesis of ethanol-induced liver injury. One of the antioxidant defense systems in mammalian cells is the mitochondrial enzyme manganese superoxide dismutase (MnSOD). MnSOD activity is increased by agents that cause oxidative stress. One such agent is the cytokine tumor necrosis factor-α (TNF). Increased serum/tissue TNF levels have been observed in alcoholic liver disease, and TNF has been postulated to play a role in ethanol-induced liver injury. Substantial evidence suggests that ethanol itself can cause oxidative stress. In order to investigate the mechanism of the cellular adaptive response to ethanol-induced oxidative stress, the effects of short-term ethanol exposure on MnSOD RNA, protein, and activity were determined in a human hepatoma cell line (HepG2). We found that exposure to ethanol (25 mMconcentration) for 72 h increased the protein level and enzyme activity of MnSOD. However, examination of the mRNA levels of the enzyme showed no corresponding increase. Long-term administration of ethanol (10 weeks) did not significantly increase MnSOD protein and MnSOD activity. MnSOD activity was significantly increased by TNF. Thus it appears that both TNF and ethanol are capable of increasing MnSOD activity presumably via enhanced oxidative stress. However, unlike TNF, acute ethanol administration increases the activity of MnSOD without increasing MnSOD mRNA. The increase in MnSOD after a short-term dose of ethanol is diminished with repeated ethanol administrations. These findings are compatible with the view that chronic exposure to ethanol suppresses the cellular adaptive response to oxidative stress. If this adaptive response of MnSOD is lessened, it may have implica tions in the increased toxicity due to prolonged ethanol exposure.

Elevated cerebrospinal fluid levels of manganese superoxide dismutase in bacterial meningitis

We examined the mechanism of increase of manganese superoxide dismutase (Mn SOD) in the cerebrospinal fluid (CSF) in bacterial meningitis (BM). The elevated levels of Mn SOD in the CSF in BM, measured with an enzyme immunoassay method, were more prominent than those in aseptic meningitis (AM) and encephalitis (EN). In AM and EN Mn SOD levels well correlated with levels of neuron-specific enolase and S-100b protein, which are markers of damages to nervous tissues, but did not with any of them in BM. CSF concentrations of tumor necrosis factor-α (TNF-α) and interleukin-1α (IL-1α) were higher in BM than in AM and EN. From the serial measurements in BM, the peak values of these cytokines chronologically preceded or corresponded to those of Mn SOD. Immunohistochemically, a large number of the glial cells were stained for Mn SOD in the cerebral cortex from a patient with BM. By contrast, in the normal cerebral cortex, the glial cells were negative for Mn SOD staining. These results suggest that the marked increase of Mn SOD in the CSF in BM may be related to the increase of such cytokines as TNF-α and IL-1α and that these cytokines may play a role in the induction of Mn SOD in nervous tissues.

Prevention of ongoing lipid peroxidation by wound excision and superoxide dismutase treatment in the burned rat

To determine if wound excision and superoxide dismutase (SOD) treatment prevent ongoing lipid peroxidation after burn injury, the plasma, kidney, and lung lipid peroxide (LPO) levels in 25% total body surface area (TBSA) burned rats was studied. The animals were given intraperitoneal bovine copper-, zinc-SOD ( Cu Zn -SOD ) (50,000 U/kg dissolved in saline) or saline immediately after burns and were operated by wound debridement and allograft 2 hours after the burn. We measured LPO levels of 6-hour postburn plasma and tissues by the thiobarbituric acid (TBA) method, and measured the manganese SOD (Mn-SOD) by an enzyme-linked immunosorbent assay. Wound excision alone prevented the increase of plasma LPO levels but could not prevent the increase in tissues. The combination of wound excision and Cu Zn -SOD treatment markedly inhibited the increase in both plasma and tissue LPO levels after the burn, but did not prevent the increase in Mn-SOD. Wound excision in conjunction with SOD-treatment might be therapeutic in the management of severe burns.

Lung manganese superoxide dismutase increases during cytokine-mediated protection against pulmonary oxygen toxicity in rats.

Parenteral injection of the cytokines interleukin-1 and tumor necrosis factor, or of endotoxin (lipopolysaccharide), protects rats against lethal pulmonary oxygen toxicity. To determine the potential importance of manganese superoxide dismutase (MnSOD) in this model, we measured MnSOD mRNA and activity in lung. In addition, we confirmed that increases in activities were related to changes in MnSOD protein, which was measured using an enzyme-linked immunosorbentassay (ELISA) technique. After cytokine or endotoxin administration, increases in lung MnSOD mRNA occurred promptly (4 h), with or without hyperoxic exposure. In parallel, lung MnSOD protein and activity were increased after 24 h, and protein levels remained elevated after 52 h. MnSOD activity and protein levels were closely correlated. Neither lung copper-zinc superoxide dismutase (CuZnSOD) mRNA nor activity increased following administration of cytokines. Small increases in CuZnSOD mRNA, which did not exceed those in beta-actin mRNA, occurred early (4 h) after endotoxin, but CuZnSOD activity was unchanged. Immunohistochemistry was used to demonstrate in which cell types the increase in MnSOD protein occurred after cytokine or endotoxin administration. In agreement with ELISA findings, immunoreactive MnSOD appeared to be increased in lung parenchyma, but not in lung neutrophils, 24 h after cytokine or endotoxin treatment. MnSOD was heavily concentrated in alveolar type II cells. However, the numbers of surfactant protein D-positive (type II) cells in lung sections did not appear to be increased after treatment with cytokines or endotoxin. We conclude that early and sustained increases in endogenous MnSOD, but not CuZnSOD or other antioxidant enzymes, are associated with protection of rat lungs against hyperoxic damage by cytokines or endotoxin.

Suppressive effect of interleukin-1 on pulmonary cytochrome P450 and superoxide anion production

Interleukin-1 has been shown to prolong the survival of rats exposed to lethal concentrations of oxygen. This oxygen tolerance has been attributed by some workers to an increase of manganese superoxide dismutase. We report here that the administration of interleukin-1 to male adult rats results in (i) significant decrease of pulmonary cytochrome P450 at 24 and 72 hours, (ii) decrease of P450 IIB1 mRNA at 24 and 72 hours and (iii) significant decrease of superoxide anion generation from pulmonary microsomes isolated from treated rats. To the best of our knowledge, this is the first report to demonstrate these effects of interleukin-1 on pulmonary P450 and its oxidase activity ( O − 2 generation). On the basis of these results and several earlier reports in which various P450 depressants have been shown to depress superoxide production from microsomes and to prolong the lives of rodents in hyperoxia, we conclude that oxygen tolerance induced by interleukin-1 administration is likewise mediated, at least in part, by reduced generation of superoxide anion from cytochrome P450 monooxygenase system.