Antioxidant enzyme complex of tissues of the bivalve Mytilus galloprovincialis Lam. under normal and oxidative-stress conditions: a review

The results of studies of tissue specifics of the enzymatic antioxidant complex of the bivalve Mytilus galloprovincialis Lam. are summarized. It is shown that the highest oxidative load is experienced by gills. The antioxidant complex of gills largely depends on environmental conditions than on the mollusk's state, which allows this tissue to be used for ecological diagnostics. A decrease in the content of carotenoids in tissue s suppressed the activities of the key enzymes of antiradical defense-superoxide dismutase (SOD) and catalase-and is accompanied by a decrease in the reduced glutathione (GSH) pool. The state of the antioxidant complex of molluscan tissues under conditions of natural (spawning) and artificial (exposure to a cationic surfactant) oxidative stress was studied.     

State of the antioxidant enzyme complex in tissues of the Black Sea mollusc <Emphasis Type="Italic">Mytilus galloprovincialis</Emphasis> under natural oxidative stress

The state of the antioxidant (AO) system (AOS) and the content of products of lipid peroxidation (LPO) in hepatopancreas, gill, and foot of the Black Sea mollusc Mytilus galloprovincialis Lam. were studied in norm and under conditions of natural oxidative stress (spawning). It has been established that under conditions of spawning, the AO-protection of hepatopancreas cells is predominantly oriented to inactivation of high concentrations of peroxide compounds with participation of glutathione peroxidase and catalase. In the foot tissue, on the contrary, the main role in AO-processes is played by enzymatic inhibition of superoxide anion radical with aid of superoxide dismutase. The highest level of oxidative stress in the spawning state is revealed in the mollusc gill, which is indicated by the maximal increase of the content of TBA (thiobarbituric acid)-active products.     

Antioxidant response of the bivalve Pinna nobilis colonised by invasive red macroalgae Lophocladia lallemandii

Invasive species represent a risk to natural ecosystems and a biodiversity hazard. The present work aims to determine the antioxidant enzyme response – superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX), the phase II detoxifying enzyme – glutathione S-transferase (GST) – and markers of oxidative damage – thioredoxin reductase (TR) and malondialdehyde (MDA) – in gills and digestive gland of Pinna nobilis and to study the antioxidant response effects in the bivalve colonised by the invasive macroalgae Lophocladia lallemandii. Colonised specimens were collected in a control area without L. lallemandii and another area completely colonised by L. lallemandii. All enzyme activities were found to be present in gills and digestive gland, with some tissue differences. CAT and SOD activities were higher in gills than digestive gland, whereas GST activity and MDA levels were higher in digestive gland. The presence of L. lallemandii induced a significant increase in the activities of antioxidant enzymes in both gills and digestive gland, except for CAT activity in gills. GST and TR activities were also increased in both tissues, as well as the MDA concentration. We can conclude that the presence of L. lallemandii colonising P. nobilis induces a biological stress and oxidative damage to the fan mussel.     

The effects of selenium on oxidative stress biomarkers in the freshwater characid fish matrinxã, Brycon cephalus (Günther, 1869) exposed to organophosphate insecticide Folisuper 600 BR (methyl parathion)

Methyl parathion (MP), an organophosphate widely applied in agriculture and aquaculture, induces oxidative stress due to free radical generation and changes in the antioxidant defense system. The antioxidant roles of selenium (Se) were evaluated in Brycon cephalus exposed to 2 mg L(-1) of Folisuper 600 BR (MP commercial formulation - MPc, 600 g L(-1)) for 96 h. Catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), glutathione S-transferase (GST), reduced glutathione (GSH) and lipid peroxidation (LPO) levels in the gills, white muscle and liver were evaluated in fish fed on diets containing 0 or 1.5 mg Se kg(-1) for 8 weeks. In fish treated with a Se-free diet, the MPc exposure increased SOD and CAT activities in all tissues. However, the GPx activity decreased in white muscle and gills whereas no alterations were observed in the liver. MPc also increased GST activity in all tissues with a concurrent decrease in GSH levels. LPO values increased in white muscle and gills and did not change in liver after MPc exposure. A Se-supplemented diet reversed these findings, preventing increases in LPO levels and concurrent decreases in GPx activity in gills and white muscle. Similarly, GSH levels were maintained in all tissue after MPc exposure. These results suggest that dietary Se supplementation protects cells against MPc-induced oxidative stress.     

Changes in the antioxidant metabolism in the embryonic development of the common South American toad Bufo arenarum: differential responses to pesticide in early embryos and autonomous-feeding larvae

Amphibians may be critically challenged by aquatic contaminants during their embryonic development. Many classes of compounds, including organophosphorus pesticides, are able to cause oxidative stress that affects the delicate cellular redox balance regulating tissue modeling. We determined the progression of antioxidant defenses during the embryonic development of the South American common toad, Bufo arenarum. Superoxide dismutase (SOD) and catalase (CAT) activities were high in the unfertilized eggs, and remained constant during the first stages of development. SOD showed a significant increase when the gills were completely active and opercular folds began to form. Reductase (GR) activity was low in the oocytes and increased significantly when gills and mouth were entirely developed and the embryos presented a higher exposure to pro-oxidant conditions suggesting an environmental control. Reduced glutathione (GSH) content was also initially low, and rose continuously pointing out an increasing participation of GSH-related enzymes in the control of oxidative stress. GSH peroxidases and GSH-S-transferases showed relatively high and constant activities, probably related to lipid peroxide control. B. arenarum embryos have plenty of yolk platelets containing lipids, which provide the energy and are actively transferred to the newly synthesized membranes during the early embryonic development. Exposure to the pro-oxidant pesticide malathion during 48 h did not significantly affect the activity of antioxidant enzymes in early embryos, but decreased the activities of CAT, GR, and the pool of GSH in larvae. Previous work indicated that lipid peroxide levels were kept low in malathion-exposed larvae, thus we conclude that oxidative stress is overcome by the antioxidant defenses. The increase in the antioxidant metabolism observed in the posthatching phase of development of B. arenarum embryo, thus constitutes a defense against natural and human-generated pro-oxidants present in the aquatic environment.     

Lipid peroxidation and antioxidant defence enzyme activity in multiple sclerosis

Changes of state of lipid peroxidation and activity of antioxidant defence enzymes katalase, superoxide dismutase, glutathione peroxidase and glutathione reductase - in the brain and liver tissue of guinea-pig in conditions of different stages of experimental autoimmune encephalomyelitis (EAE; 11th, 21st, 27th day after inoculation) and in blood of multiple sclerosis (MS) patients with different types, degrees of severity and length of disease and blood level of reduced glutathione have been investigated. We have found, that the development of oxidative stress in animal organism during the disease development is progressive and intensive lipid peroxide oxidation without compensation by antioxidant mechanisms have been shown in the late period (27th day) of the experiment. In MS conditions this state was accompanied with high activity of demyelination process, severe degree of neuronal injury and length of disease above 5 years. In addition reduced glutathione level was increased in many patient groups: remitting type, light (II) degree of severity and among the patients with strongly disturbed neurological functions and long course of the disease. The obtained data allow us to suppose that the development of oxidative stress under demyelination conditions is a result of strong metabolic disorders and decrease of antioxidant defence in the patients during the disease development. The necessity of individual approaches for antioxidant therapy of patients with MS is discussed.     

Adrenaline induces mitochondrial biogenesis in rat liver

We studied the effects of adrenaline administration and depletion (induced by reserpine) on rat liver oxidative metabolism. We showed that adrenaline increases, and reserpine decreases aerobic capacity (inferred by cytochrome oxidase activity) in tissue modifying the hepatic content of mitochondrial proteins without changing mitochondrial aerobic capacity. The changes in tissue cytochrome oxidase activity, which agreed with the expression levels of factors involved in mitochondrial biogenesis, such as PGC-1, NRF-1, and NRF-2, were associated with similar changes in tissue and mitochondrial State 3 respiration. Adrenaline and reserpine induced extensive lipid and protein oxidative damage in tissue and mitochondria. The increase in H₂O₂ release by respiring mitochondria and the decrease in the activities of the antioxidant enzymes glutathione peroxidase and reductase contributed to the reserpine effect on oxidative damage. The adrenaline effect is more difficult to explain, since the hormone increased the antioxidant enzyme activities but, in respiring mitochondria, increased ROS release rate in the presence of succinate and decreased it in the presence of pyruvate/malate. These opposite changes were due to the increased content of the autoxidizable electron carrier located at complex III and decreased content of that located at complex I. Our data suggest that adrenaline can be involved in the mitochondrial population adaptation which verify in conditions in which an increased body energy expenditure verify such as cold exposure.     

Antioxidant defenses and oxidative stress parameters in tissues of mud crab (Scylla serrata) with reference to changing salinity

The effects of salinity (10, 17 and 35 ppt) on O₂ consumption, CO₂ release and NH₃ excretion by crabs and oxidative stress parameters and antioxidant defenses of its tissues were reported. An increase in salinity caused a decrease in O₂ consumption and CO₂ release and an increase in ammonia excretion by crabs. Lipid peroxidation, protein carbonyl, H₂O₂ levels and total antioxidant capacity of the tissues elevated significantly at 35 ppt salinity except in abdominal muscle where H₂O₂ content was low. Ascorbic acid content of tissues was higher at 17 ppt salinity than at 10 and 35 ppt salinities. With increasing salinity, a gradual decrease in SOD, an increase in catalase, no change in GPx and a decrease followed by an increase in GR activities were recorded for abdominal muscle. While for hepatopancreas, an increase followed by a decrease in SOD and catalase, decrease in GPx and GR activities were noticed with increasing salinity. In the case of gills, a decrease followed by an increase in SOD, a decrease in catalase and GPx and an increase in GR activities were noted when the salinity increased from 10 ppt to 35 ppt. These results suggest that salinity modulation of oxidative stress and antioxidant defenses in Scylla serrata is tissue specific.     

Antioxidant levels from different Antarctic fish caught around South Georgia Island and Shag Rocks

Antarctic fish have been isolated for over several million years in an environment with a very low and constant temperature and high oxygen concentration. In such conditions the oxidative stress might be an important factor affecting their metabolic adaptive strategies. Activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), vitamin E levels and total antioxidant capacity (TRAP) were measured in liver, gill, heart and muscle homogenates of red-blooded (Nototheniidae) and white-blooded (Channichthyidae) Antarctic fish. SOD activity was also measured in blood samples. Gill SOD activity was threefold higher in channichthyids than in nototheniids while CAT and GPx were significantly higher in the gills of channichthyids. The increased SOD activity of channichthyids probably reflects the large PO₂ gradient across their gills. The H₂O₂ produced seems to be preferentially eliminated by diffusion, according to the low levels of CAT and GPx found in the gills of these species. In contrast, blood SOD was about fivefold higher in the latter group, which possesses erythrocytes and thus a much higher oxygen-carrying capacity. CAT activity was always higher in nototheniids except in muscle. However, vitamin E did not show clear differences between families except for the pattern observed in muscle. The higher content of vitamin E in this tissue shown in channichthyids is related to the higher volume density of mitochondria reported for this group, since vitamin E is responsible for preventing membrane lipid peroxidation. Accordingly, TRAP (representative of hydrosoluble antioxidant capacity) was also higher in muscle of channichthyids. This is probably related to the role of ascorbic (a hydrosoluble compound) acid in regenerating vitamin E. Accepted: 4 September 1999     

Adipose tissue proadipogenic redox changes in obesity

The role of inflammation and oxidative stress in the development of obesity and associated metabolic disorders is under debate. We investigated the redox metabolism in a non-diabetic obesity model, i.e. 11-week-old obese Zucker rats. Antioxidant enzyme activities, lipophilic antioxidant (alpha-tocopherol, coenzymes Q) and hydrophilic antioxidant (glutathione, vitamin C) contents and their redox state (% oxidized form), were studied in inguinal white fat and compared with blood and liver. The adipose tissues of obese animals showed a specific higher content of hydrophilic molecules in a lower redox state than those of lean animals, which were associated with lower lipophilic molecule content and lipid peroxidation. Conversely and as expected, glutathione content decreased and its redox state increased in adipose tissues of rats subjected to lipopolysaccharide-induced systemic oxidative stress. In these in vivo models, oxidative stress and obesity thus had opposite effects on adipose tissue redox state. Moreover, the increase in glutathione content and the decrease of its redox state by antioxidant treatment promoted in vitro the accumulation of triglycerides in preadipocytes. Taken together and contrary to the emergent view, our results suggest that obesity is associated with an intracellular reduced redox state that promotes on its own the development of a deleterious proadipogenic process.     

Effects of environmental anoxia and different periods of reoxygenation on oxidative balance in gills of the estuarine crab Chasmagnathus granulata

We investigated the effects of anoxia (8 h) and different periods of reoxygenation (20 and 40 min) on the oxidative balance in anterior and posterior gills of the crab Chasmagnathus granulata. Enzyme activity of catalase and GST was increased in the gills of the animals submitted to anoxia, and SOD activity was decreased. These enzymes returned approximately to control levels during the anoxia recovery time. These results demonstrated enzyme activities change with variations in environmental oxygen levels. The posterior gills showed a higher antioxidant enzyme activity than anterior gills. In the gills, there were no changes in the non-enzymatic antioxidant system (TRAP) during anoxia. On the other hand, during anoxia recovery, an increase of TRAP in both gills was observed. Anoxia does not change lipid peroxidation (TBARS) in the gills. During anoxia recuperation, an increase in levels of TBARS was observed. Thus the results demonstrate that C. granulata has a similar strategy of preparation for oxidative stress as observed in other intertidal species, enabling the crabs to survive in an environment with extreme variations in physical and chemical characteristics, such as salt marshes.     

Effect of cadmium on antioxidant enzyme activities and lipid peroxidation in the gills of the clam Ruditapes decussatus

Metals are known to influence the oxidative status of marine organisms, and antioxidant enzymes have been often proposed as biomarkers of effect. The clam Ruditapes decussatus is a well-known metal bioindicator. In this species cadmium (Cd) induces metallothionein (MT) synthesis only after 7 days of exposure. Before MT synthesis is induced, the other mechanisms capable of handling the excess of Cd are unknown. In order to identify some of these mechanisms, variations in antioxidant systems (superoxide dismutase, catalase, selenium-dependent glutathione peroxidase and non-selenium-dependent glutathione peroxidase), malondialdehyde (MDA) and MT were studied in the gills of R. decussatus exposed to different Cd concentrations (4, 40 and 100 gl^-1) for 28 days. These parameters, together with total proteins and Cd concentrations, were measured in the gills of the clams over different periods of exposure. Results indicate that Cd accumulation increased linearly in the gills of R. decussatus with the increase in Cd concentration. This increase induces an imbalance in the oxygen metabolism during the first days of Cd exposure. An increase in cytosolic superoxide dismutase (SOD) activity and a decrease in mitochondrial SOD activity was observed at the same time as or after a decrease in cytosolic and mitochondrial catalase activity and of selenium-dependent and non-selenium-dependent glutathione peroxidase activity. After 14 days of exposure, Cd no longer affect these enzymes but there was elevation of other cellular activities, such as MDA and MT production. MT bound excess Cd present in the cell. These variations in these parameters suggest their potential use as biomarkers of effects such as oxidative stress resulting from Cd contamination in molluscs.     

Effect of cadmium on antioxidant enzyme activities and lipid peroxidation in the gills of the clam Ruditapes decussatus

Metals are known to influence the oxidative status of marine organisms, and antioxidant enzymes have been often proposed as biomarkers of effect. The clam Ruditapes decussatus is a well-known metal bioindicator. In this species cadmium (Cd) induces metallothionein (MT) synthesis only after 7 days of exposure. Before MT synthesis is induced, the other mechanisms capable of handling the excess of Cd are unknown. In order to identify some of these mechanisms, variations in antioxidant systems (superoxide dismutase, catalase, selenium-dependent glutathione peroxidase and non-selenium-dependent glutathione peroxidase), malondialdehyde (MDA) and MT were studied in the gills of R. decussatus exposed to different Cd concentrations (4, 40 and 100 gl^-1) for 28 days. These parameters, together with total proteins and Cd concentrations, were measured in the gills of the clams over different periods of exposure. Results indicate that Cd accumulation increased linearly in the gills of R. decussatus with the increase in Cd concentration. This increase induces an imbalance in the oxygen metabolism during the first days of Cd exposure. An increase in cytosolic superoxide dismutase (SOD) activity and a decrease in mitochondrial SOD activity was observed at the same time as or after a decrease in cytosolic and mitochondrial catalase activity and of selenium-dependent and non-selenium-dependent glutathione peroxidase activity. After 14 days of exposure, Cd no longer affect these enzymes but there was elevation of other cellular activities, such as MDA and MT production. MT bound excess Cd present in the cell. These variations in these parameters suggest their potential use as biomarkers of effects such as oxidative stress resulting from Cd contamination in molluscs.     

Dietary vitamin-E modulates antioxidant defence system in giant freshwater prawn, Macrobrachium rosenbergii

The objectives of the present study were to determine the effect of supplementary vitamin-E (200, 400 and 600 mg/kg feed) on lipid peroxidation (LPX) and antioxidant defence system in gills and hepatopancreas of the freshwater prawn, Macrobrachium rosenbergii. Results indicated that vitamin-E inhibited LPX in the hepatopancreas in a comparatively lower dose than gills. Superoxide dismutase (SOD) activity was decreased significantly in gills in response to all the three supplemented diet, but in hepatopancreas decrease was observed only in response to higher doses of vitamin-E (400 and 600 mg/kg feed). Catalase (CAT) activity was reduced significantly only in gills but not in hepatopancreas. While glutathione peroxidase (GPX) activity was significantly elevated in the hepatopancreas by vitamin-E, its activity remains unaltered in gills. On the contrary, glutathione reductase (GR) activity was decreased in gills but that of hepatopancreas was constant. Glutathione (GSH) content of both gills and hepatopancreas was substantially elevated in the vitamin-E supplemented prawns. Although the ascorbic acid (ASA) content of gills was unchanged by vitamin-E, its level elevated significantly in hepatopancreas. Thus the findings of the present investigation suggest that dietary vitamin-E is capable of reducing LPX level and can modulate antioxidant defence system in gills and hepatopancreas, nevertheless, the response is highly tissue specific. It is further observed that highest dose of vitamin-E (600 mg/kg feed) could not render much additional protection in both the tissues.     

Complex trade-offs in the pigeon (Columba livia): egg antioxidant capacity and female serum oxidative status in relation to diet quality

Despite the great deal of ecological research interest in modulators of offspring quality and consequences of reproduction on female status, we still know little about the relationships among diet quality, antioxidant capacity of egg components (yolk and albumen) and oxidative status of female birds. In this study, I compared the egg quality (egg size, albumen and yolk antioxidant capacity) and serum oxidative status (oxidative damage, total serum antioxidant capacity, and serum thiols) of female pigeons (Columba livia) fed with foods of different quality (standard quality and decreased quality). I also analysed the patterns of covariation among egg and female traits. The study focussed on the first clutch laid by the female in the breeding season and on the short-term effects of a decrease in diet quality. The treatment did not affect the egg volume, the lipophilic and hydrophilic components of antioxidant capacity (lipOXY and hydrOXY, respectively) or the antioxidant capacity of the albumen (albumOXY). However, females fed a higher quality diet were fatter and had marginally higher values of serum hydroperoxides (oxidative damage) than females fed a lower quality diet. Moreover, females that showed an increase in yolk hydrOXY and serum hydroperoxides also showed a decrease in yolk lipOXY, albumOXY and serum antioxidant capacity. These results show that the female’s oxidative status can be correlated with the antioxidant content of her eggs, but the nature of these correlations is complex, depending on the molecular component measured. The results also suggest that in the pigeon the deposition of hydrophilic and lipophilic antioxidants in the egg may trade off against each other.     

Bystrow’s Paradox – gills,fossils, and the fish‐to‐tetrapod transition

Schoch, R.R. and Witzmann, F. 2011. Bystrow’s Paradox – gills, fossils, and the fish‐to‐tetrapod transition. —Acta Zoologica (Stockholm) 92 : 251–265. The issue of which breathing mechanism was used by the earliest tetrapods is still unsolved. Recent discoveries of stem tetrapods suggest the presence of internal gills and fish‐like underwater breathing. The same osteological features were used by Bystrow to infer a salamander‐like breathing through external gills in temnospondyl amphibians. This apparent contradiction – here called Bystrow’s Paradox – is resolved by reviewing the primary fossil evidence and the anatomy of the two gill types in extant taxa. Rather unexpectedly, we find that internal gills were present in a range of early crown tetrapods (temnospondyls), based on the anatomy of gill lamellae and location of branchial arteries on the ventral side of gill arch elements (ceratobranchials). Although it remains to be clarified which components are homologous in external and internal gills, both gill types are likely to have been present in Palaeozoic tetrapods – internal gills in aquatic adults of some taxa, and external gills in the larvae of these taxa and in larvae of numerous forms with terrestrial adults, which resorbed the external gills after the larval phase. Future developmental studies will hopefully clarify which mechanistic pathways are involved in gill formation and how these might have evolved.     

Induction of hepatic antioxidants in freshwater catfish (Channa punctatus Bloch) is a biomarker of paper mill effluent exposure

Enzymatic and non-enzymatic antioxidants serve as an important biological defense against environmental oxidative stress. Information on antioxidant defense in fish is meager despite that fish are constantly exposed to a myriad of environmental stress including the oxidants. This study, therefore, assesses the activities of antioxidant enzymes viz., glutathione peroxidase, catalase and glutathione S-transferase and the non-enzymatic antioxidants viz., glutathione and metallothionein in various tissues of freshwater fish Channa punctatus (Bloch), in response to short-term and long-term exposures to paper mill effluent. The fish were exposed to the effluent at a concentration of 1.0% (v/v) for 15, 30, 60 and 90 days. The exposure caused a time-dependent increase in glutathione level (P < 0.001), activities of glutathione peroxidase (P < 0.05 to P < 0.001), glutathione S-transferase (P < 0.001) and a marginal initial decrease in catalase activity in the liver (P < 0.01 to P < 0.001). Metallothionein was induced in liver after 60 days of exposure. Two isoforms of metallothionein were detected. Catalase activity also increased 60 days afterwards. Antioxidant pattern was different in gill and kidney showing that liver was more resistant to oxidative damage as compared to gills and kidney. Our results demonstrate a pollutant-induced adaptive response in fish. In addition, levels of enzymatic and non-enzymatic tissue antioxidants may serve as surrogate markers of exposure to oxidant pollutants in fish.     

Oxidative stress and anti-oxidant metabolites in patients with hyperthyroidism: effect of treatment.

OBJECTIVE: Oxygen free radicals (OFR) play a role in the pathogenesis of tissue damage in many pathological conditions via the peroxidation of membrane phospholipids. Experimental studies showed an elevated oxidative stress during hyperthyroidism, which is reduced by treatment. Therapy per se might decrease oxidative stress. DESIGN: Fasting plasma levels of thiobarbituric acid reacting substances (TBARS), vitamin E and coenzyme Q10 were measured in 22 hyperthyroid patients, before treatment for their thyroid disease, after 13.9 [SD 9.2] weeks, when they achieved an euthyroid state on thyrostatic drugs, and again after 47.7 [21.0] weeks, off therapy. No patient presented additional risk factors for increased lipoperoxidation and/or increased OFR levels. Smokers were asked to abstain from smoking overnight. METHODS: All analytes were measured by HPLC. RESULTS: In hyperthyroidism, plasma levels of TBARS were increased, whereas vitamin E and coenzyme Q10 were reduced. Average levels of TBARS and antioxidant agents returned to normal in euthyroid patients, without differences in relation to stop of thyrostatic therapy. CONCLUSIONS: Our data confirm the presence of oxidative stress and decreased anti-oxidant metabolites in hyperthyroid patients, which are corrected in euthyroidism, without any influence of thyrostatic drugs per se. Nutritional support with antioxidant agents, which are defective during hyperthyroidism, is warranted.     

Effects of ozone oxidative preconditioning on TNF-alpha release and antioxidant-prooxidant intracellular balance in mice during endotoxic shock

Ozone oxidative preconditioning is a prophylactic approach, which favors the antioxidant-prooxidant balance for preservation of cell redox state by the increase of antioxidant endogenous systems in both in vivo and in vitro experimental models. Our aim is to analyze the effect of ozone oxidative preconditioning on serum TNF-alpha levels and as a modulator of oxidative stress on hepatic tissue in entodoxic shock model (mice treated with lipopolysaccharide (LPS)). Ozone/oxygen gaseous mixture which was administered intraperitoneally (0.2, 0.4, and 1.2 mg/kg) once daily for five days before LPS (0.1 mg/kg, intraperitoneal). TNF-alpha was measured by cytotoxicity on L-929 cells. Biochemical parameters such as thiobarbituric acid reactive substances (TBARS), enzymatic activity of catalase, glutathione peroxidase, and glutathione-S transferase were measured in hepatic tissue. One hour after LPS injection there was a significant increase in TNF-alpha levels in mouse serum. Ozone/oxygen gaseous mixture reduced serum TNF-alpha levels in a dose-dependent manner. Statistically significant decreases in TNF-alpha levels after LPS injection were observed in mice pretreated with ozone intraperitoneal applications at 0.2 (78%), 0.4 (98%), and 1.2 (99%). Also a significant increase in TBARS content was observed in the hepatic tissue of LPS-treated mice, whereas enzymatic activity of glutathion-S transferase and glutathione peroxidase was decreased. However in ozone-treated animals a significant decrease in TBARS content was appreciated as well as an increase in the activity of antioxidant enzymes. These results indicate that ozone oxidative preconditioning exerts inhibitory effects on TNF-alpha production and on the other hand it exerts influence on the antioxidant-prooxidant balance for preservation of cell redox state by the increase of endogenous antioxidant systems.