mRNA Levels Of Antioxidant Enzymes Research Articles

Effect of dietary bovine lactoferrin on lipid peroxidation and activities, and mRNA levels of antioxidant enzymes of piglets

Effect of dietary bovine lactoferrin on lipid peroxidation and activities, and mRNA levels of antioxidant enzymes of piglets

Standardized Hypericum perforatum reduces oxidative stress and increases gene expression of antioxidant enzymes on rotenone-exposed rats

Since oxidative stress is implicated in the pathophysiology of dementia and depression, this study was designed to investigate the pro-oxidant activity of rotenone, the protective role of standardized extract of Hypericum perforatum (SHP), as well as the mRNA levels of antioxidant enzymes, in brain homogenates of rats following exposure to rotenone and SHP extract. Quercetin in liposomes, one active constituent, was tested in the same experimental conditions to serve as a positive control. The animals received pretreatment with SHP (4 mg/kg) or quercetin liposomes (25 and 100 mg/kg) 60 min before of rotenone injection (2 mg/kg). All treatments were given intraperitoneally in a volume of 0.5 ml/kg body weight, for 45 days. Rotenone treatment increased activities of superoxide dismutase (SOD), glutathione peroxidase (GPx) and levels of malondialdehyde (MDA). The content of reduced glutathione (GSH) was decreased due to chronic rotenone treatment. Rotenone significantly induced the gene expression of CuZnSOD, MnSOD; CAT and GPx in brain. In contrast, SHP extract exerted an antioxidant action which was related with a decreased of MnSOD activity and mRNA levels of some antioxidant enzymes evaluated. Liposomal quercetin treatment resulted in a significant preservation of the activities of antioxidant enzymes and a decreased in the mRNA levels of these antioxidant enzymes. One possible mechanism of action of SHP extract may be related to quercetin in protecting neurons from oxidative damage. Therefore standardized extract of H. perforatum could be a better alternative for depressed elderly patients with degenerative disorder exhibiting elevated oxidative stress status.

Effect of hormonal manipulation on mRNA expression of antioxidant enzymes in the rat testis.

We evaluated the effects of ethane dimethane sulfonate, an agent that selectively destroys Leydig cells, and hypophysectomy on CuZn superoxide dismutase, catalase and glutathione peroxidase mRNA levels in the testis. A total of 18, 60-day-old adult rats were injected with ethane dimethane sulfonate (75 mg./kg.). After 3, 7, 14, 21, 30 and 50 days, respectively, the animals were sacrificed and the testes were harvested for RNA extraction. The 12 vehicle injected control rats were sacrificed at 0, 7, 21 and 50 days, respectively. Six 60-day-old hypophysectomized adult rats were sacrificed at age 66 days and the testes were harvested for RNA extraction. Antioxidant enzyme mRNA expression was assessed by Northern blot analysis using P labeled DNA probes derived from known cDNA sequences for superoxide dismutase, PHGPX (phospholipid hydroperoxide glutathione peroxidase) and catalase. Hypophysectomy and ethane dimethane sulfonate treatment resulted in a significant reduction in testis weight compared with controls. Compared with vehicle injected controls PHGPX mRNA levels were reduced by 50% in the testes of ethane dimethane sulfonate treated rats 21 days after injection (p <0.05). Likewise testicular catalase mRNA levels were also reduced 21 and 30 days after injection by 55% and 50%, respectively (p <0.05). The 0.8 kb superoxide dismutase mRNA transcript levels were increased 30 and 50 days after injection by 80% and 60%, respectively (p <0.05). In hypophysectomized rats testicular PHGPX mRNA levels were increased 3-fold compared with age matched controls (p <0.05). This study demonstrates that testicular antioxidant enzyme mRNA levels are altered in response to pituitary hormone and/or androgen deficiency.

Increased Levels of Catalase and Cathepsin V/L2 but Decreased TIMP-1 in Keratoconus Corneas: Evidence that Oxidative Stress Plays a Role in This Disorder

The mRNA levels of antioxidant enzymes, matrix metalloproteinases, cathepsin V/L2, and tissue inhibitor of matrix metalloproteinases (TIMPs) were determined in keratoconus and normal corneas. Protein levels or enzyme activities were analyzed when RNA levels were different. A total of 25 physiologic (normal) and 32 keratoconus corneas were studied. mRNAs were analyzed by semiquantitative reverse transcription-polymerase chain reaction and Southern blot analysis. Proteins were assessed by immunohistochemistry and/or Western blot analysis. Catalase activity was measured in corneal extracts. Antioxidant enzymes examined were catalase, superoxide dismutase (SOD)-1, SOD3, glutathione reductase, glutathione S-transferase and aldehyde dehydrogenase 3A1. Degradative enzymes examined were cathepsin V/L2 and matrix metalloproteinase (MMP)-1, -2, -7, -9, and -14. Tissue inhibitor of matrix metalloproteinase (TIMP)-1, -2, and -3 were also examined. Keratoconus corneas exhibited a 2.2-fold increase of catalase mRNA level (P < 0.01) and 1.8-fold of enzyme activity (P < 0.03); a 1.5-fold increase of cathepsin V/L2 mRNA (P < 0.03) and abnormal protein distribution; and a 1.8-fold decrease of TIMP-1 mRNA (P < 0.05) and 2.8-fold decrease of protein (P < 0.0001) compared with normal (physiologic) corneas. RNA levels for other antioxidant and degradative enzymes were similar between normal and keratoconus corneas. Keratoconus corneas have elevated levels of cathepsins V/L2, -B, and -G, which can stimulate hydrogen peroxide production, which, in turn, can upregulate catalase, an antioxidant enzyme. In addition, decreased TIMP-1 and increased cathepsin V/L2 levels may play a role in the matrix degradation that is a hallmark of keratoconus corneas. The findings support the hypothesis that keratoconus corneas undergo oxidative stress and tissue degradation.

Pro-oxidant activity of aluminum in the rat hippocampus: gene expression of antioxidant enzymes after melatonin administration

Aluminum (Al)-induced pro-oxidant activity and the protective role of exogenous melatonin, as well as the mRNA levels of some antioxidant enzymes, were determined in the hippocampi of rats following administration of Al and/or melatonin. Two groups of male rats were intraperitoneally injected with Al (as Al lactate) or melatonin only, at doses of 7 and 10 mg/kg/day, respectively, for 11 weeks. During this period, a third group of animals received Al (7 mg/kg/day) plus melatonin (10 mg/kg/day). At the end of the treatment, hippocampus was removed and processed to examine the following oxidative stress markers: glutathione transferase (GST), reduced glutathione (GSH), oxidized glutathione (GSSG), superoxide dismutase (SOD), glutathione reductase (GR), glutathione peroxidase (GPx), catalase (CAT), thiobarbituric acid reactive substances (TBARS), as well as protein content. Gene expression of Cu–ZnSOD, MnSOD, GPx, and CAT was evaluated by real-time RT-PCR. On the other hand, Al, Fe, Mn, Cu, and Zn concentrations in hippocampus were also determined. The results show that Al exposure promotes oxidative stress in the rat hippocampus, with an increase in Al concentrations. The biochemical changes observed in this tissue indicate that Al acts as pro-oxidant agent, while melatonin exerts antioxidant action by increasing the mRNA levels of the antioxidant enzymes evaluated. The protective effects of melatonin, together with its low toxicity and its capacity to increase mRNA levels of antioxidant enzymes, suggest that this hormone might be administered as a potential supplement in the treatment of neurological disorders in which oxidative stress is involved.

Resistance of Cultured Human Skin Fibroblasts from Old and Young Donors to Oxidative Stress and Their Glutathione Peroxidase Activity

Background: It has been suggested that oxidative stress is involved in the aging process and that the resistance of animals to oxidative stress may decrease with advancing aging. However, there are only a limited number of reports of studies on the relationship between aging and resistance to oxidative stress. Objective: The aim of this work is to examine the relationship between the resistance of human skin fibroblasts to oxidative stress and donor age, and the relevance of antioxidant enzyme activities to this resistance. Methods: Percent cell survival was determined by the trypan blue exclusion test and the neutral red method. Superoxide dismutase activity was assayed by the method of Oyanagi, catalase activity by the method of Aebi, and glutathione peroxidase activity by the method of Flohé and Günzler. Reduced glutathione concentration was measured by the method of Griffith. Antioxidant enzyme mRNA levels were estimated by reverse transcription polymerase chain reactions (RT-PCR). Results: The percent survivals of cultured human skin fibroblasts, derived from young and old donors (referred to as young and old cells, respectively), under oxidative stress from hydrogen peroxide, linoleic acid hydroperoxide, or ultraviolet light B were examined. Old cells were more resistant to such oxidative stress than young cells. The activity of glutathione peroxidase was higher by 46.1% in old cells than in young cells, although there was no difference between their relative glutathione peroxidase mRNA levels. Further, there was no difference between their activities of copper/zinc superoxide dismutase, manganese superoxide dismutase, or catalase. However, the relative mRNA levels of copper/zinc superoxide dismutase and manganese superoxide dismutase were lower by 13.9 and 20.9% in old cells than in young cells, respectively, while there was no difference between the levels of catalase. Conclusions: These results suggest that old cells are more resistant to oxidative stress than young cells, presumably because of an increase in cellular glutathione peroxidase activity.

Aorta of ApoE-deficient mice responds to atherogenic stimuli by a prelesional increase and subsequent decrease in the expression of antioxidant enzymes.

Oxidative stress has been implicated in the development of atherosclerotic lesions. We evaluated the relationship between extent of atherosclerotic lesion formation and vascular expression of pro- and antioxidant enzymes in apoE-deficient mice. On normal chow, these mice showed elevated serum cholesterol levels (7.5- to 9.5-fold), and age-dependent, spontaneous development of all stages of atherosclerotic lesions, starting at the age of 12 weeks. RNA was extracted from the aortic arch and descending aorta, and mRNA expression of pro- and antioxidant enzymes was measured with real-time PCR. Local infiltration of monocytes/macrophages, reflected by increased vascular expression of CD68 mRNA (>10-fold), indicated that the arch was more susceptible than the descending aorta. The expression of catalase-1 and various isoforms of superoxide dismutase, glutathione peroxidase, and glutathione S-transferase alpha was significantly increased in the aortic arch, but not in the descending aorta, in the period preceding lesion formation (age 6 to 12 weeks). These expression levels were 1.5 to 5 times higher than in age-matched wild-type animals. Remarkably, there was an inverse relationship between extent of lesion formation and the mRNA levels of antioxidant enzymes, most of which started to decline after 12 weeks, as lesions developed. In contrast, inducible nitric oxide synthase expression increased 4-fold in the aortic arch over the course of the disease. Our results suggest that the arterial wall responds to increased serum levels of atherogenic lipoproteins by stimulating expression of antioxidant enzymes. The observed co-ordinate decline in expression of many of these protective systems may greatly accelerate the development of atherosclerosis.

Dietary orotic acid affects antioxidant enzyme mRNA levels and oxidative damage to lipids and proteins in rat liver

We investigated the effects of the dietary addition of orotic acid on liver antioxidant enzymes, mRNA levels of these enzymes, and peroxidative products by comparing casein with soy protein as the source of dietary protein. Rats fed the casein diet accumulated more liver lipids than those fed the soy protein diet when orotic acid was added. The addition of orotic acid lowered both the activity of liver Cu, Zn-superoxide dismutase and the level of Cu, Zn-superoxide dismutase mRNA. The addition of orotic acid led to a significant increase in the contents of conjugated dienes and protein carbonyls in the liver. In addition, dietary soy protein protected the increase in the levels of lipids and proteins peroxide induced by orotic acid. The addition of orotic acid to the casein diet increased the activities of both serum ornithine carbamoyltransferase and alanine aminotransferase. Thus, liver damage might result from the increased superoxide anion due to the decrease in the activity of hepatic superoxide dismutase, as well as increase in the production of hepatic peroxidative products in rats fed the casein diet with orotic acid.

Exercise modulates antioxidant enzyme gene expression in rat myocardium and liver.

Our previous studies have shown that exercise caused changes in the tissue activities of the antioxidant enzymes glutathione peroxidase, superoxide dismutase, and catalase in spontaneously hypertensive (SH) and Wistar-Kyoto (WKY) rats. To determine whether the changes observed were due to changes in mRNA levels of the enzymes, levels of tissue mRNA were determined by quantitative RNase protection assay. Comparisons of tissue enzyme activities and mRNA levels in sedentary and exercised animals showed that, in some cases (e.g., glutathione peroxidase in SH and WKY myocardium), parallel changes in enzyme activity and mRNA levels occurred, whereas in other cases (e.g., catalase in SH and WKY liver), nonparallel changes were found. Exercise of hypertensive rats altered antioxidant enzyme mRNA levels to those seen in normotensive animals in some, but not all, cases. The results suggest that transcriptional control over changes in exercise-related antioxidant enzyme activities is operative in some cases, although in other cases posttranscriptional regulatory mechanisms may exist.

Antihypertensive drug therapy and antioxidant enzyme mRNA levels in spontaneously hypertensive (SHR) rats

Previous studies have shown that chronic treatment of SHR (spontaneously hypertensive) rats with the antihypertensive drugs captopril, hydralazine and terazosin results in changes in the specific activities of the antioxidant enzymes glutathione peroxidase, catalase and Cu/Zn superoxide dismutase in liver and myocardium. In order to determine if these changes were caused by alterations in the levels of the mRNAs for these enzymes, the tissue levels of the antioxidant enzyme mRNAs have been measured. In myocardium, all three drug treatments increased Cu/Zn superoxide dismutase mRNA but decreased glutathione peroxidase mRNA levels, and in liver, all three drugs changed glutathione peroxidase mRNA levels. In comparison to untreated SHR animals, the levels of all three mRNAs were altered in the myocardium, but not in the liver, of normotensive WKY rats. Comparisons of mRNA levels with tissue enzyme specific activities suggest that tissue antioxidant enzyme expression is, in most cases, regulated by antihypertensive drugs through transcriptional control mechanisms.

Modulation of rat antioxidant enzyme mRNA levels by antihypertensive drugs

Previous studies have shown that treatment of SHR (spontaneously hypertensive) rats with the antihypertensive drugs captopril, hydralazine and terazosin results in changes in the specific activities of the antioxidant enzymes glutathione peroxidase, catalase and CuiZn superoxide dismutase in liver and myocardium. In order to determine if these changes were caused by alterations in the levels of the mRNAs for these enzymes, the tissue levels of the antioxidant enzyme mRNAs were measured by a quantitative ribonuclease protection assay procedure. In myocardium, all three drug treatments significantly increased CuiZn superoxide dismutase mRNA but decreased glutathione peroxidase mRNA levels, and hydralazine and terazosin decreased myocardial catalase mRNA levels. In liver, all three drugs changed glutathione peroxidase mRNA levels, whereas only captopril treatment changed the CuiZn superoxide dismutase mRNA level, and none of the drug treatments affected catalase mRNA levels. With the exceptions of the effects of captopril and hydralazine on liver CuiZn superoxide dismutase and catalase mRNA levels respectively, the data for the mRNA levels paralleled previously reported changes for tissue enzyme specific activities, suggesting that these changes are. in most cases, caused by changes in the levels of the mRNAs for the enzymes.

Effects of aging and food restriction on the antioxidant enzyme activity of rat livers.

The effects of aging and food restriction on the activities and mRNA levels of antioxidant enzymes in rat livers were examined. Rats were fed ad libitum every day (AL) or ad libitum on every other weekday (FR). At 30 months of age, the catalase and glutathione peroxidase activities were lower, whereas the thiobarbituric acid (TBA) value, an index of lipid peroxidation of the AL rats, was higher than that at younger ages. At 33 months of age, copper/zinc superoxide dismutase (CuZnSOD), catalase, and glutathione peroxidase activities increased, and the TBA value of the FR rats remained unchanged as compared with those at younger ages. Until old age, food restriction gave rather decreasing effects on antioxidant enzyme activities. Furthermore, antioxidant enzyme activities and the TBA values of the FR rats were higher at the end of a fasting period than those at the end of a feeding period.

Differential Effects in Vivo of Thyroid Hormone on the Expression of Surfactant Phospholipid, Surfactant Protein mRNA and Antioxidant Enzyme mRNA in Fetal Rat Lung

Antenatal administration of triiodo-L-thyronine (T3) to late gestation rats resulted in decreased lung antioxidant enzyme (AOE) activity but increased surfactant phospholipids. In fetal rat lung explant cultures, T3 decreased the expression of surfactant proteins (SP) A and B. There have been no reported studies of the simultaneous in vivo developmental influence of T3 on both pulmonary AOE and SP gene expression. We hypothesized that antenatal T3 treatment would cause differential regulation of surfactant phospholipid, SP, and AOE genes in the late gestation fetal rat. Timed pregnant rats received intramuscular injections of either T3 (7 mg/kg) or placebo on days 19 and 20 of gestation and fetuses were delivered on day 21. Fetal lung SP-A, SP-B, SP-C, and AOE mRNA levels were studied by Northern analysis. AOE mRNA levels were further quantitated by solution hybridization. Total lung phospholipids (TPL) and disaturated phosphatidylcholine (DSPC) content were quantitated by a phosphorus assay. T3 significantly increased TPL and DSPC content, and significantly decreased the expression of SP-A, SP-C, CuZnSOD, and catalase genes. Because of a crucial interplay of these factors for normal lung function at the time of birth, the molecular mechanisms by which these apparently opposing changes are accomplished warrant further investigation

In vivo protection by melatonin against delta-aminolevulinic acid-induced oxidative damage and its antioxidant effect on the activity of haem enzymes.

Accumulation of delta-aminolevulinic acid (ALA), as it occurs in acute intermittent porphyria, is a potential endogenous source of reactive oxygen species (ROS) which can then produce oxidative damage to cell structures and macromolecules. This in vivo study investigated whether melatonin could prevent the deleterious effects of ALA. Rats were injected i.p. for 2 weeks with ALA (40 mg/kg on alternate days) and/or with melatonin (50 microg/kg or 500 microg/kg daily). Administration of pharmacological doses of melatonin reduced and/or prevented ALA-induced lipid peroxidation (LPO) in both cerebral cortex and cerebellum, providing further evidence of melatonin's action as a ROS scavenger. Administration of pharmacological concentrations of melatonin to ALA-injected rats showed the protective properties of melatonin on the activities of both porphobilinogen-deaminase and delta-aminolevulinate dehydratase (ALA-D) in the cerebral cortex; the effect on ALA-D activity was unexpectedly high (at least 6-fold), indicating that, besides acting as a scavenger of hydroxyl radicals, melatonin may exert its protection on ALA-D through other mechanisms, such as increasing mRNA levels of antioxidant enzymes or/and inducing glutathione peroxidase activity. The possibility that changes in the expression of antioxidant enzymes could affect the expression of other proteins, even those not related to the cellular ROS homeostasis, should also not be discarded. The potential use of melatonin as an antioxidant and for its reactivating properties in the treatment of acute porphyrias is considered.

Modulation of endogenous antioxidant enzymes by nitric oxide in rat C6 glial cells.

To understand the possible mechanism of nitric oxide (NO)-mediated cytotoxicity, we investigated the effect of NO on the endogenous antioxidant enzymes (AOEs) catalase, glutathione peroxidase (GPX), and CuZn- and Mn-superoxide dismutases (SODs) in rat C6 glial cells under conditions in which these cells expressed oligodendrocyte-like properties as evidenced by the expression of 2',3'-cyclic-nucleotide 3'-phosphohydrolase. The 24-h treatment with S-nitroso-N-acetylpenicillamine (SNAP), a NO donor, decreased the activities and the protein levels of catalase, GPX, and Mn-SOD in a dose-dependent manner. Alternatively, the activity and the protein level of CuZn-SOD were increased. 2-Phenyl-4,4, 5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO), a NO scavenger, blocked the effect of SNAP. Moreover, the treatment of C6 cells with sodium nitroprusside, another NO donor, or with a combination of lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma), which induce excessive production of NO, also significantly modulated the AOE activities in a manner similar to that seen with SNAP treatment. The compounds/enzymes that inhibit the production of NO (e.g., N-nitro-L-arginine methyl ester hydrochloride, arginase, and PTIO) blocked the effects of LPS and IFN-gamma on the activities of AOEs. Treatment with SNAP and a combination of LPS and IFN-gamma also modulated the mRNA levels of AOEs, parallel to the changes in their protein levels and activities, except for Mn-SOD where the combination of LPS and IFN-gamma markedly stimulated the mRNA expression. In spite of the stimulation of mRNA level, LPS and IFN-gamma significantly inhibited the activity of Mn-SOD within the first 24 h of incubation; however, Mn-SOD activity gradually increased with the increase in time of incubation. These results suggest that alterations in the status of AOEs by NO may be the basis of NO-induced cytotoxicity in disease states associated with excessive NO production.

Positive regulation of pulmonary antioxidant enzyme gene expression by prenatal thyrotropin releasing hormone plus dexamethasone treatment in premature rats exposed to hyperoxia.

Prenatal administration of thyrotropin releasing hormone (TRH) plus dexamethasone (DEX) to pregnant rats produces significantly depressed fetal lung antioxidant enzyme (AOE) activities and AOE mRNA levels in late gestation. Because of this negative regulation of AOE gene expression in the late fetal lung, we hypothesized that hormonally pretreated prematurely delivered rats might demonstrate inferior tolerance to prolonged hyperoxia. Litters of prenatal TRH+DEX-treated and sham-treated prematurely delivered rat pups (gestational d 21 of 22) were randomized to either > 95% O2 or room air for up to 14 d. The right lungs of 2- and 7-d exposure pups were assayed for AOE activities; the left lungs of the same pups were used to quantitate the concentrations of AOE mRNA by solution hybridization. The prenatal TRH+DEX-treated pups were able to induce adaptive lung AOE mRNA and activity responses to hyperoxia by 2 d of exposure; and by 7 d in O2 they showed greater increases in AOE mRNA concentrations and AOE activities in response to hyperoxic challenge compared with the sham-treated controls. Lung lipid surfactant measurements after hyperoxia were not affected by prenatal TRH+DEX treatment. In addition, TRH+DEX-pretreated premature rats did not show the hypothesized increased susceptibility to O2-induced lung damage and lethality, but, in fact, had slightly improved hyperoxic survival (d 3-7 of O2 exposure) compared with sham-treated controls. Exposure to hyperoxia significantly reduced serum triiodothyronine and thyroxine levels in the sham-control pups.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of type of dietary fat and ethanol on antioxidant enzyme mRNA induction in rat liver.

We carried out a study to relate the effect of the type of dietary fat and ethanol on antioxidant enzyme mRNA levels in liver in the intragastric feeding rat model. Different types of dietary fat were administered [saturated fat (SE), corn oil (CE) and fish oil (FE)] with ethanol to induce varying severities of liver injury. Ethanol-fed rats were pair-fed with dextrose-fed controls that received isocaloric amounts of dextrose. All animals were killed at 1 month and the following studies were carried out: evaluation of severity of pathologic liver injury, mRNA quantitation for catalase, glutathione peroxidase (GPx), and manganese superoxide dismutase (MnSOD), microsomal conjugated dienes, and hydrogen peroxide. SE animals had no liver injury, FE animals had severe liver injury, and CE animals had moderate liver injury. Ethanol induced GPx mRNA in all dietary groups, with the highest levels seen in the FE group. The pattern of catalase mRNA induction was similar to that of GPx mRNA. In contrast, MnSOD mRNA was decreased compared to controls in animals that developed pathologic liver injury, i.e., CE and FE groups. A positive correlation was seen between conjugated diene levels and GPx mRNA (r = 0.88, P < 0.01) and catalase mRNA. The similar slopes for the relationship between conjugated dienes and catalase in the fish oil and non-fish oil groups indicate that the same degree of lipid peroxidation increases catalase mRNA to a greater degree in fish oil-fed rats. A positive correlation was also seen between catalase mRNA and H2O2 (r = 0.95, P < 0.001).

Oxidative stress decreases antioxidant enzyme activities in reaggregation cultures of rat brain cells

The brain has been suggested to be especially sensitive to damage by reactive oxygen species. In this study, we examined the effects of hyperoxic conditions on the activities and mRNA levels of antioxidant enzymes in reaggregation cultures of rat forebrain cells. Cultures were exposed to 80% oxygen for 12–60 h starting on Days 17 and 33 in culture. Superoxide dismutase activities and mRNA levels were not affected by hyperoxia, whereas catalase activity was slightly decreased after 24 h in 80% oxygen at Day 17. Glutathione peroxidase activity was markedly decreased already after 12 h of hyperoxia, and decreased activities of glutathione reductase and glucose-6-phosphate dehydrogenase were also noted. The glutathione peroxidase mRNA levels were increased in hyperoxic cultures at Day 17 but not at Day 33. These results suggest that the enzymatic defense mechanisms against reactive oxygen species in the brain are rather weak and deteriorate during oxidative stress but that a potential for compensatory upregulation exists at least during the first postnatal weeks.

Dose-responsive increases in pulmonary fibrosis after inhalation of asbestos.

We focused here on steady-state mRNA levels of genes involved in antioxidant defense, i.e., manganese superoxide dismutase and copper-zinc superoxide dismutase, and in cell proliferation, i.e., ornithine decarboxylase, c-jun, and glyceraldehyde-3-phosphate-dehydrogenase in whole-lung homogenates from Fischer 344 rats at 3 h to 20 d after exposure to crocridolite asbestos. Changes in gene expression were correlated with histopathologic findings, total and differential cell counts in bronchoalveolar lavage, and levels of hydroxyproline in lung. Dosage-dependent increases in mRNA levels of antioxidant enzymes and proliferation-related genes were observed. Differential cell counts revealed a dose-related infiltration of neutrophils that preceded elevations in gene expression. Neutrophil infiltration into lung and focal lesions of fibrosis as well as increased levels of hydroxyproline were observed only at high concentrations of asbestos. These results indicate that high airborne concentrations of asbestos cause molecular changes in lung that may be related to antioxidant defense and the triggering of cell proliferation, a feature of asbestosis and lung cancer.

Effects of inhibition of catalase and superoxide dismutase activity on antioxidant enzyme mRNA levels

We examined the effects of inhibition of Cu,Zn superoxide dismutase (Cu,Zn SOD) and catalase (Cat) activities on the steady-state mRNA levels of the three major antioxidant enzymes [Cu,Zn SOD, Cat, and glutathione peroxidase (GP)] in human umbilical vein endothelial cells under normoxia and hyperoxia. Inhibition of Cat activity by aminotriazole was not associated with alteration of the other antioxidant enzymes or with potentiation of cell injury. On the other hand, inhibition of Cu,Zn SOD activity by N-N'-diethyl-dithiocarbamate (DDC) was associated with an increase in Cu,Zn SOD mRNA level and a decrease in Cat and GP mRNA level. The combination of DDC and hyperoxia treatments was associated with an additive effect on Cu,Zn SOD message. We propose that these coordinate mRNA changes might be an adaptation to the oxidative environment. This proposal supports the concept that the intracellular O2 metabolites themselves could be the signals that trigger the antioxidant enzymes gene expression.