High Levels Of Antioxidant Enzymes Research Articles

A novel antioxidant peptide, purified from Bacillus amyloliquefaciens, showed strong antioxidant potential via Nrf-2 mediated heme oxygenase-1 expression

A novel antioxidant peptide YD1 (∼1.0kDa), purified from the strain Bacillus amyloliquefaciens CBSYD1, displayed activity in several in vitro assays and was also efficient against Gram-positive, Gram-negative as well as multidrug-resistant (MDR) bacteria. Strain growth was adapted to bile-salt conditions where a clear halos-zone was observed in a bile-salt plate assay and was viable in different digestive track conditions. YD1 treatment on RAW 264.7 cells increased the transcriptional and translational activities of NF-E2-related factor-2 (Nrf-2) through the enhanced levels of heme oxygenase-1 (HO-1). Furthermore, the YD1-treated group showed higher levels of antioxidant enzymes compared to the oxidative stress group. YD1 demonstrated a strong antioxidant activity by decreasing nitric oxide (NO) and reactive oxygen species (ROS) in RAW 264.7 cells. This study suggests that YD1 and the strain could be a natural antioxidant and a probiotic candidate respectively.

P 204 - Differences in antioxidant enzymes in tumour tissue and non-tumour adjacent tissue in colorectal cancer patients at different stages (III and IV)

Colorectal Cancer (CRC) is one of the leading causes of death by cancer worldwide; its high mortality rate is mainly attributable to metastases. Oxidative stress has been classically related to cancer due to the harmful effects of free radicals, both in their onset and in their evolution. Recent studies have revealed the influence of non-tumour adjacent tissue on the progression and metastasis of CRC. Based on this, we have studied the protein levels of antioxidant enzymes by western blot comparing samples of non-tumour adjacent tissue and tumour tissue of CRC patients in advanced stages (III and IV). In the results obtained, higher levels of antioxidant enzymes have been observed in the tumour tissue than in the non-tumour adjacent tissue, although these differences are shortened in stage IV, due to the fact that stage IV patients present a significant increase in levels of antioxidant enzymes in non-tumour adjacent tissue. In addition, higher levels of antioxidant enzymes have been observed in the non-tumour adjacent tissue of patients in IV stage than in III This study emphasizes the importance of non-tumour adjacent tissue as a prognostic factor in the evolution of CRC cancer patients.

Antioxidative enzyme activities in maize genotypes grown under saline water irrigation

Plants with high levels of antioxidant enzymes have been reported to have greater tolerance to this oxidative damage caused by salinity. Role of antioxidative enzyme activity in salt stress and screening maize hybrids for salinity tolerance was investigated in this study. A pot culture experiment was conducted to evaluate six maize hybrids (CO 6, CO 7, CO 8, CO 10, NK 6240 and 900M gold) for their tolerance to saline water irrigation. The maize hybrids were irrigated with saline water having a natural EC of 0.06, 3.2, 4.8, 6.2 and 8.9 dSm -1 for 30 days and replicated thrice in a FCRD. The antioxidant activities such as catalase (CAT), peroxidase (POX) and superoxy dismutase (SOD) were measured in maize hybrids grown under saline water irrigation besides recording and dry matter production (DMP) and growth attributes. CO 6 and CO 7 were identified as saline tolerant maize hybrids based on their antioxidant enzyme activities and DMP. However CO 8 has been observed as a salt sensitive maize hybrid as it showed lesser enzyme activities and DMP. The order of tolerance exists among the maize hybrids to irrigation water salinity were: CO 6 > CO 7 > NK6240 > 900M gold > CO 10 > CO8. Antioxidant enzyme activities and dry matter production were found to be useful traits for identifying salinity tolerance in maize hybrids at seedling stage.

Depletion of the Third Complement Component Ameliorates Age-Dependent Oxidative Stress and Positively Modulates Autophagic Activity in Aged Retinas in a Mouse Model.

The aim of the study was to investigate the influence of complement component C3 global depletion on the biological structure and function of the aged retina. In vivo morphology (OCT), electrophysiological function (ERG), and the expression of selected oxidative stress-, apoptosis-, and autophagy-related proteins were assessed in retinas of 12-month-old C3-deficient and WT mice. Moreover, global gene expression in retinas was analyzed by RNA arrays. We found that the absence of active C3 was associated with (1) alleviation of the age-dependent decrease in retinal thickness and gradual deterioration of retinal bioelectrical function, (2) significantly higher levels of antioxidant enzymes (catalase and glutathione reductase) and the antiapoptotic survivin and Mcl-1/Bak dimer, (3) lower expression of the cellular oxidative stress marker—4HNE—and decreased activity of proapoptotic caspase-3, (4) ameliorated retinal autophagic activity with localization of ubiquitinated protein conjugates commonly along the retinal pigment epithelium (RPE) layer, and (5) significantly increased expression of several gene sets associated with maintenance of the physiological functions of the neural retina. Our findings shed light on mechanisms of age-related retinal alterations by identifying C3 as a potential therapeutic target for retinal aging.

Effects of alpha lipoic acid on motor function and antioxidant enzyme activity of nerve tissue after sciatic nerve crush injury in rats.

Background: Alpha lipoic acid (ALA) that is a strong antioxidant drug is tried for both protection and treatment of various diseases of central and peripheral nervous systems. Material and Methods: Protective effects of ALA on crush type peripheral nerve injury were evaluated. 28 Sprague-Dawley rats were divided into four groups: In Group 1, sciatic nerve was only explored. Sciatic nerve crush injury was performed after serum physiologic injection intraperitoneally in Group 2, and after ALA injection in Groups 3 and 4. In all subjects, Sciatic Functional Index (SFI) was calculated. All subjects were sacrificed 1 hour after injury in first three groups, and 48 hours after in Group 4. Nerve samples were taken. Superoxide dismutase, catalase and glutathione peroxidase activities were measured in nerve tissue. Results: Administration of ALA before injury provided significantly better SFI values and higher levels of antioxidant enzymes than control group. These effects were significantly prominent 48 hours after injury. Conclusion: ALA that was given before crush type peripheral nerve injury provided to decrease damage of the nerve. Specific mechanisms of this effect must be clarified and must be shown that it is whether effective when it is given after injury or not.

Proteomic response of oat leaves to long-term salinity stress.

Salinity adversely affects plant growth and production. Oat is a moderately salt-tolerant crop and can contribute to improving saline soil. The physiological and molecular responses of the oat plant to long-term salinity were studied. After a 16-day salt treatment (150mmolL-1NaCl in Hoagland's solution), photosynthetic rate, maximum photosystem II photochemical efficiency, and actual efficiency of photosystem II decreased. The activities of superoxide dismutase, peroxidase, and catalase significantly increased. We also investigated the protein profiles of oat leaves in response to salinity and detected 30 reproducible protein spots by two-dimensional gel electrophoresis that were differentially abundant. Specifically, one protein was up-regulated and 29 proteins were down-regulated compared with the control. These 29 proteins were identified using MALDI-TOF mass spectrometry, and 19 corresponding genes were further investigated by quantitative real-time PCR. These proteins were involved in four types of biological processes: photosynthesis, carbohydrate metabolism and energy, protein biosynthesis, and folding and detoxification. This study indicates that the lower levels of Calvin cycle-related proteins, 50S ribosomal protein L10 and adenosine-triphosphate regulation-related proteins, and the high levels of antioxidant enzymes play important roles in the response of oat to long-term salinity stress.

Differences in photosynthetic syndromes of four halophytic marsh grasses in Pakistan.

Salt-tolerant grasses of warm sub-tropical ecosystems differ in their distribution patterns with respect to salinity and moisture regimes. Experiments were conducted on CO2 fixation and light harvesting processes of four halophytic C4 grasses grown under different levels of salinity (0, 200 and 400mM NaCl) under ambient environmental conditions. Two species were from a high saline coastal marsh (Aeluropus lagopoides and Sporobolus tremulus) and two were from a moderate saline sub-coastal draw-down tidal marsh (Paspalum paspalodes and Paspalidium geminatum). Analyses of the carbon isotope ratios of leaf biomass in plants indicated that carbon assimilation was occurring by C4 photosynthesis in all species during growth under varying levels of salinity. In the coastal species, with increasing salinity, there was a parallel decrease in rates of CO2 fixation (A), transpiration (E) and stomatal conductance (g s), with no effect on water use efficiency (WUE). These species were adapted for photoprotection by an increase in the Mehler reaction with an increase in activity of PSII/CO2 fixed accompanied by high levels of antioxidant enzymes, superoxide dismutase and ascorbate peroxidase. The sub-coastal species P. paspalodes and P. geminatum had high levels of carotenoid pigments and non-photochemical quenching by the xanthophyll cycle.

Effect of trans-chalcone on atheroma plaque formation, liver fibrosis and adiponectin gene expression in cholesterol-fed NMRI mice

Trans-chalcone is the precursor molecule to flavonoids and possesses antioxidant and anti-inflammatory properties. This study aimed to evaluate the effects of trans-chalcone on atheroma plaque formation and the relevant biochemical parameters in high cholesterol diet (HCD)-fed NMRI mice. Fifty male NMRI mice were divided into 5 groups (n=10 per group): control (received a normal diet); HCD (received an additional 2% cholesterol for 18 weeks); sham (received a HCD for 12 weeks and were then shifted to a normal diet and trans-chalcone vehicle (sunflower oil) for 6 weeks), and two experimental groups (received a HCD for 12 weeks and were then shifted to a normal diet and either 12mg/kg or 24mg/kg trans-chalcone for 6 weeks). After 12 weeks, HCD-induced atheroma plaques were observed by hematoxylin and eosin staining of aortic sections. At the end of experiment, the following factors had significantly increased in the HCD group: body weight, insulin resistance, and serum levels of triglycerides, total-cholesterol, glucose, insulin, leptin, liver enzymes (AST and ALT), malondialdehyde and direct bilirubin. The serum levels of high-density lipoprotein cholesterol, adiponectin, superoxide dismutase, and glutathione had considerably decreased. Histologic analysis of liver sections indicated hepatic fibrosis and steatosis. Treatment by both doses of trans-chalcone, particularly the 24mg/kg dose, significantly attenuated these alterations. Administration of trans-chalcone improved the consequences of atheroma plaque formation and liver fibrosis via increased expression of adiponectin, generation of higher levels of antioxidant enzymes, as well as modulation of serum leptin and lipid profiles.

The inherent high vulnerability of dopaminergic neurons toward mitochondrial toxins may contribute to the etiology of Parkinson′s disease

Although the exact mechanism(s) of the degeneration of dopaminergic neurons in Parkinson's disease (PD) is not well understood, mitochondrial dysfunction is proposed to play a central role. This proposal is strongly strengthened by the findings that compromised mitochondrial functions and/or exposure to mitochondrial toxins such as rotenone, paraquat, or MPTP causes degeneration of the midbrain dopaminergic system and manifest symptoms similar to Parkinson's disease in primates and rodents (Goldman, 2014). In fact, the specific dopaminergic toxin MPTP is one of the most commonly used models in the mechanistic studies of environmental factors associated with the etiology of PD, particularly due to the availability of direct and unequivocal clinical and biochemical evidence from human and primate subjects. Several decades of intense studies in many laboratories have led to the proposition of a general mechanism for the specific dopaminergic toxicity of MPTP (Przedborski and Jackson-Lewis, 1998). The salient features of this mechanism are (a) lipophilic pro-toxin, MPTP, freely crosses the blood-brain barrier and enters the brain; (b) in glial cells monoamine oxidase-B converts it to the toxic metabolite MPP+; (c) the polar MPP+ is extruded into the extracellular space through organic cation transporter-3; (d) presynaptic dopamine transporter (DAT) takes it up specifically into dopaminergic neurons; (e) in dopaminergic neurons, MPP+ accumulates in the synaptic vesicles and/or mitochondria; (f) mitochondrial MPP+ inhibits the mitochondrial complex-I of the electron transport chain, leading to cellular ATP depletion and excessive reactive oxygen species (ROS) production causing apoptotic cell death (Lotharius and O’Malley, 2000; Storch et al., 2004). Although this mechanism is generally well accepted, numerous recent studies seriously challenge the central dogma of this proposal that the specific dopaminergic toxicity of MPP+ is primarily due to the specific uptake into dopaminergic neurons through presynaptic DAT.

The modulating effect of coat color mutations on the generation and neutralization of reactive oxygen species in the Аmerican mink (Neovison vison) as a model

The influence of gene mutations encoding coat color on parameters of reactive oxygen species (RO S) generation and neutralization in six organs of the mink (Neovison vison) was evaluated. The study was conducted with standard dark brown (+/+), monorecessive royal pastel (b/b) and silver-blue (р/р), and direcessive sapphire (a/a р/р) mutant minks. It was found that the functioning of both RO S generation and neutralization systems was genotypespecific. The direcessive sapphire (a/a р/р) combination induced high levels of antioxidant enzymes’ activities as well as of thiobarbituric acid-reactive products (TBА-RPs), characterizing lipid peroxidation level. In heart tissue, coat color mutations exerted modulating effects on both RO S generation and the level of low-molecular-weight antioxidants. The royal pastel (b/b) genotype showed the highest level of RO S generation, and the sapphire (a/a р/р), the lowest (statistically significant difference from standard). Coat color mutations modulate the dintensity of RO S generation and neutralization in lung tissue. On the one hand, royal pastel (b/b) in comparison with standard dark brown (+/+) decreases the total level of RO S generation, and on the other hand, it increases the level of generation of superoxide anion-radicals. Cluster analysis, presented in a combined dendrogram, showed that royal pastel (b/b) and sapphire (a/a р/р) minks, the farthest from standard (+/+), had the greatest modulating effects. It is reasonable to suggest that such effects contributed to the genetic plasticity of American mink in the course of colonization of North America and then during mink introduction in Northern Eurasia and South America.

Copper-induced adaptation, oxidative stress and its tolerance in Aspergillus niger UCP1261

Background: The effects of exposure to copper, during growth, on the production of biomass, total protein, catalase, glutathione-S transferase, glutathione peroxidase, peroxidase, polyphosphate, acid and alkaline phosphatases, ultrastructure and the ability to remove this metal from Aspergillus niger , obtained from caatinga soil, were evaluated. Results: All parameters tested were influenced by the concentration of metal in the culture medium. The presence of metal induced high levels of antioxidant enzymes, including lipid peroxidation, thereby revealing the appearance of an oxidative stress response. The variation in polyphosphate levels indicates the participation of the polymer in response to stress induced by copper. The activities of the phosphatases were positively influenced by growing them in the presence of copper. Ultrastructure changes in the cell surface, electron density, thickness, and septation were visualized by exposing cells to increasingly larger concentrations of metal. The isolate was able to remove the agent from the growth medium, while maintaining its physiological functions. The metal removed from the cultures exposed to 0.5 mM, 1 mM and 2 mM copper exhibited percentages of removal equivalent to 75.78%, 66.04% and 33.51%. Conclusions: The results indicate that the isolate was able to grow in high concentrations of copper, activates mechanisms for adaptation and tolerance in the presence of metal, and is highly efficient at removing the agent. Such data are fundamental if a better understanding is to be reached of the cellular and molecular abilities of native isolates, which can be used to develop bioprocesses in environmental and industrial areas.

Modulation of growth, antioxidant system in seedling of mustard under different levels of Nickel in adaptive response to metal resistant bacteria

Plant growth is hindered by high concentration of metals in soil by disturbing various physiological processes. However, some bacteria with plant growth promoting features have been recognized to alleviate stress in plants even under elevated levels of metal concentration. The two bacterium NWM 71 and NWM 103, identified as Pseudomonas sp. and Bacillus sp. respectively were found to be resistant to the toxic effects of nickel (Ni2+) and were identified with plant growth promoting features. Both the strains showed the production of indole acetic acid (IAA) and solubilisation of phosphate. Brassica juncea (mustard) was used as a test plant to identify the plant growth promoting activity of the selected strains of bacteria. The growth was positively influenced by the inoculation of both the strains. The tests for the measurement of chlorophyll contents and antioxidative activity were carried out to determine the level of stress in plants. High levels of Ni decreased the growth and chlorophyll content, however, significant increase in the antioxidant activity was recorded along the treatment. Inoculation of both the selected strains of bacteria increased the shoot and root biomass of mustard grown in both unspiked and spiked soil. This positive influence on growth can be attributed to the solubilisation of phosphate and production of IAA. Furthermore the observed high levels of antioxidant enzymes led to decrease in the toxic effects of Ni. This led to enhanced growth and chlorophyll content which in turn might have enhanced the photosynthetic capacity of the plants.

Synthesis and localization of L-lactate oxidase in yeasts Yarrowia lipolytica

Conditions for L-lactate oxidase synthesis by the yeast Yarrowia lipolytica were investigated. The enzyme was found to be synthesized during growth on L-lactate in the exponential growth phase. L-lactate oxidase synthesis was also observed on glucose after adaptation to stress conditions (oxidative or thermal stress) during the stationary growth phase after glucose consumption. The cells grown on L-lactate exhibited high levels of antioxidant enzymes (catalase, superoxide dismutase, glucose-6-phosphate dehydrogenase, and glutathione reductase), which exceeded those of glucose-grown cells. Ultrastructurally, L-lactate-grown cells and the cells grown on glucose and adapted to various stress conditions were also found to be similar, with increased mitochondria, elevated number and size of peroxisomes, and formation of lipid and polyphosphate inclusions. In order to determine the intracellular localization of L-lactate oxidase, the cells were disintegrated by the lytic enzyme complex from Helix pomatia. Centrifugation of the homogenate in Percoll gradient resulted in the isolation of purified fractions of the native mitochondria and peroxisomes. L-lactate oxidase was shown to be localized in peroxisomes.

Cellular levels of oxidative stress affect the response of cervical cancer cells to chemotherapeutic agents.

Treatment of advanced and relapsed cervical cancer is frequently ineffective, due in large part to chemoresistance. To examine the pathways responsible, we employed the cervical carcinoma-derived SiHa and CaSki cells as cellular models of resistance and sensitivity, respectively, to treatment with chemotherapeutic agents, doxorubicin, and cisplatin. We compared the proteomic profiles of SiHa and CaSki cells and identified pathways with the potential to contribute to the differential response. We then extended these findings by comparing the expression level of genes involved in reactive oxygen species (ROS) metabolism through the use of a RT-PCR array. The analyses demonstrated that the resistant SiHa cells expressed higher levels of antioxidant enzymes. Decreasing or increasing oxidative stress led to protection or sensitization, respectively, in both cell lines, supporting the idea that cellular levels of oxidative stress affect responsiveness to treatment. Interestingly, doxorubicin and cisplatin induced different profiles of ROS, and these differences appear to contribute to the sensitivity to treatment displayed by cervical cancer cells. Overall, our findings demonstrate that cervical cancer cells display variable profiles with respect to their redox-generating and -adaptive systems, and that these different profiles have the potential to contribute to their responses to treatments with chemotherapy.

Identification of toxicity variations in a stream affected by industrial effluents using Daphnia magna and Ulva pertusa

A comprehensive toxicity monitoring study from August to October 2011 using Daphnia magna and Ulva pertusa was conducted to identify the cause of toxicity in a stream receiving industrial effluents (IEs) from a textile and leather products manufacturing complex. Acute toxicity toward both species was observed consistently in IE, which influenced toxicity of downstream (DS) water. A toxicity identification evaluation (TIE) confirmed that both Cu and Zn were key toxicants in the IE, and that the calculated toxicity based on Cu and Zn concentrations well simulated the variation in the observed toxicity (r2=0.9216 and 0.7256 for D. magna and U. pertusa, respectively). In particular, U. pertusa was sensitive enough to detect acute toxicity in DS and was useful to identify Zn as a key toxicant. Activities of catalase, superoxide dismutase, glutathione peroxidase, glutathione S-transferase, and malondialdehyde were induced significantly in D. magna, although acute toxicity was not observed. In addition, higher levels of antioxidant enzymes were expressed in DS than upstream waters, likely due to the Cu and Zn from IE. Overall, TIE procedures with a battery of bioassays were effective for identifying the cause of lethal and sub-lethal toxicity in effluent and stream water.

Ciliate Nassula sp. grazing on a microcystin-producing cyanobacterium (Planktothrix agardhii): impact on cell growth and in the microcystin fractions

The proliferation of microcystins (MCs)-producing cyanobacteria (MCs) can have detrimental effects on the food chain in aquatic environments. Until recently, few studies had focused on the fate of MCs in exposed organisms, such as primary consumers of cyanobacteria. In this study, we investigate the impact of an MC-producing strain of the cyanobacterium Planktothrix agardhii on the growth and physiology of a Nassula sp. ciliate isolated from a non-toxic cyanobacterial bloom. We show that this Nassula sp. strain was able to consume and grow while feeding exclusively on an MC-producing cyanobacterium over a prolonged period of time (8 months). In short-term exposure experiments (8 days), ciliates consuming an MC-producing cyanobacterial strain displayed slower growth rate and higher levels of antioxidant enzymes than ciliates feeding on two non-MC-producing strains. Three high-performance methods (LC/MS, LC/MS–MS and ELISA) were used to quantify the free and bound MCs in the culture medium and in the cells. We show that ciliate grazing led to a marked decrease in free MCs (methanol extractable) in cells, the MCs were therefore no longer found in the surrounding culture medium. These findings suggest that MCs may have undergone redistribution (free vs bound MCs) or chemical degradation within the ciliates.

Caveolin-1 Inhibits Expression of Antioxidant Enzymes through Direct Interaction with Nuclear Erythroid 2 p45-related Factor-2 (Nrf2)

The Nrf2 (nuclear erythroid 2 p45-related factor-2) signaling pathway is known to play a pivotal role in a variety of oxidative stress-related human disorders. It has been reported recently that the plasma membrane resident protein caveolin-1 (Cav-1) can regulate expression of certain antioxidant enzymes and involves in the pathogenesis of oxidative lung injury, but the detailed molecular mechanisms remain incompletely understood. Here, we demonstrated that Cav-1 inhibited the expression of antioxidant enzymes through direct interaction with Nrf2 and subsequent suppression of its transcriptional activity in lung epithelial Beas-2B cells. Cav-1 deficiency cells exhibited higher levels of antioxidant enzymes and were more resistant to oxidative stress induced cytotoxicity, whereas overexpression of Cav-1 suppressed the induction of these enzymes and further augmented the oxidative cell death. Cav-1 constitutively interacted with Nrf2 in both cytosol and nucleus. Stimulation of 4-hydroxynonenol increased the Cav-1-Nrf2 interaction in cytosol but disrupted their association in the nucleus. Knockdown of Cav-1 also disassociated the interaction between Nrf2 and its cytoplasmic inhibitor Keap1 (Kelch-like ECH-associated protein 1) and increased the Nrf2 transcription activity. Mutation of the resembling Cav-1 binding motif on Nrf2 effectively attenuated their interaction, which exhibited higher transcription activity and induced higher levels of antioxidant enzymes relative to the wild-type control. Altogether, these studies clearly demonstrate that Cav-1 inhibits cellular antioxidant capacity through direct interaction with Nrf2 and subsequent suppression of its activity, thereby implicating in certain oxidative stress-related human pathologies.

English

Alterations in antioxidant enzymes and lipid peroxidation was studied in 90 Wistar albino rats exposed to cycads and fed with Nigerian-like and western-like diets supplemented with folic acid. The animals were divided into three diet classes of 30 animals each. One group was fed with a wholly compounded Nigerian-like diet (NLD) which was low in protein and high in carbohydrate and fiber. Another group was fed with a western like diet (WLD) which was high in protein and fat, while the third group of animals was fed with a normal diet which served as the control class. The animals of each class were further divided into three subgroups of ten rats each. In each subclass, one group received the diet alone; another group received the diet and cycads, while the third group received the diet and folic acid. Low levels of catalase, feed intake and faecal output was observed with experimental animals fed NLD as compared to WLD and normal diet (ND) fed animals. High levels of antioxidant enzymes: super oxide dismutase, catalase and glutathione reductase as well as low levels of lipid peroxidation was observed with the addition of folic acid to the diets of experimental rats. These results suggest the role of folic acid in diet and colon carcinogenesis. Key words: Antioxidant enzymes, cycads, diets, folic acid, lipid peroxidation.

Survival in extreme environments – on the current knowledge of adaptations in tardigrades

Tardigrades are microscopic animals found worldwide in aquatic as well as terrestrial ecosystems. They belong to the invertebrate superclade Ecdysozoa, as do the two major invertebrate model organisms: Caenorhabditis elegans and Drosophila melanogaster. We present a brief description of the tardigrades and highlight species that are currently used as models for physiological and molecular investigations. Tardigrades are uniquely adapted to a range of environmental extremes. Cryptobiosis, currently referred to as a reversible ametabolic state induced by e.g. desiccation, is common especially among limno-terrestrial species. It has been shown that the entry and exit of cryptobiosis may involve synthesis of bioprotectants in the form of selective carbohydrates and proteins as well as high levels of antioxidant enzymes and other free radical scavengers. However, at present a general scheme of mechanisms explaining this phenomenon is lacking. Importantly, recent research has shown that tardigrades even in their active states may be extremely tolerant to environmental stress, handling extreme levels of ionizing radiation, large fluctuation in external salinity and avoiding freezing by supercooling to below -20 °C, presumably relying on efficient DNA repair mechanisms and osmoregulation. This review summarizes the current knowledge on adaptations found among tardigrades, and presents new data on tardigrade cell numbers and osmoregulation.

Antioxidant defences role during post anoxic recovery in bivalve mollusc Scapharca inaequivalvis

Euryoxic organisms are able to withstand hypoxic conditions until the restoration of normal O2 levels, when the re-introduction of oxygen causes a decisive burst in reactive oxygen species (ROS). The consequent oxidative damage is countered by defence systems constituted by antioxidant enzymes, such as SOD, CAT, Se-GPx and G6PDH. Specimens of Scapharca inaequivalvis were exposed to anoxia for 3, 6 and 24 hours and subsequent reoxygenation for 1, 3, 5 and 24 hours. It has been investigated SOD, CAT, Se-GPx and G6PDH activity and MnSOD and CuZnSOD expression in the digestive gland. The results showed SODs activity to be high during both anoxia and reoxygenation. CAT and Se-GPx increase significantly overall during recovery. Only CuZnSOD expression was greater after 6 and 24 hours of anoxia. The presence of high levels of antioxidant enzymes during anozia suggests that the response of S. inaequivalvis is typical of euryoxic animals and represents an interesting model for studying the processes of ischaemia/reperfusion in mammals.