A simultaneous visualization of the antioxidant enzymes glutathione peroxidase and catalase on polyacrylamide gels

Alterations in certain immunological parameters in the skin mucus of the carp, Cirrhinus mrigala, infected with the bacteria, Edwardsiella tarda

The bacterial fish pathogen Edwardsiella tarda causes heavy stock mortality, severely hampering fish production, resulting in great economic loss to the farming industry. The first biological barriers that confer immune protection against pathogen entry are the fish mucosal surfaces. The present study was undertaken to investigate the influence of E. tarda on certain enzymatic and non-enzymatic parameters in the skin mucous secretions of the fish Cirrhinus mrigala using spectrophotometry and zymography. Fish were randomly divided into three groups: control, vehicle control, and infected. A sublethal dose of E. tarda (2.2 × 106 CFU/fish) suspended in 50 μL of PBS was injected intra-peritoneally at 0 day (d). Subsequently, mucus samples were collected at 2 d, 4 d, 6 d and 8 d post-infection. The activities of lysozyme (LYZ), protease (PROT), alkaline phosphatase (ALP), acid phosphatase (ACP), catalase (CAT), peroxidase (PER), superoxide dismutase (SOD), and glutathione S-transferase (GST) decreased significantly in the skin mucus of the challenged fish, indicating the suppressed immune system and decreased antioxidant capacity of C. mrigala to E. tarda infection. Lipid peroxidation (LPO) and total nitrate-nitrite were significantly higher at several time points post-infection, suggesting that physiological functions have been impaired following pathogen challenge. The present findings could be relevant for fish aquaculture and underline the importance of skin mucus not only for assessing fish immune status but also for identifying early warning signals of disease caused by pathogens.

In Vitro and In Vivo Antimicrobial Activity of an Oxidative Stress-Mediated Bicyclic Menaquinone Biosynthesis Inhibitor against MRSA

Menaquinone (MK) is an essential component in the oxidative phosphorylation pathway of Gram-positive bacteria. Drugs targeting enzymes involved in MK biosynthesis can prevent electron transfer, which leads to ATP starvation and thereby death of microorganisms. Previously, we reported a series of MenA inhibitors and demonstrated their antimicrobial activity against Gram-positive bacteria, including Methicillin-resistant Staphylococcus aureus (MRSA) and mycobacteria. These inhibitors were developed by mimicking demethylmenaquinone, a product of MenA enzymatic reaction in MK biosynthesis. In this study, compound NM4, MK biosynthesis inhibitor, inhibited the formation of MRSA biofilm and it was screened against 1952 transposon mutants to elucidate mechanisms of action; however, no resistant mutants were found. Also, compound NM4 induced the production of reactive oxygen species (ROS) by blocking electron transfer in the oxidative phosphorylation pathway as observed by MRSA growth recovery using various ROS scavengers. An oxygen consumption assay also showed that NM4 blocks the oxygen consumption by MRSA, but the addition of menaquinone (MK) restores growth of MRSA. The NM4-treated MRSA induced the expression of catalase by more than 25%, as quantified by the native gel. A pulmonary murine model exhibited that NM4 significantly reduced bacterial lung load in mice without toxicity. An NM4-resistant USA300 strain was developed to attempt to identify the targets participating in the mechanism of resistance. Our results support that respiration and oxidative phosphorylation are potential targets for developing antimicrobial agents against MRSA. Altogether, our findings suggest the potential use of MK biosynthesis inhibitors as an effective antimicrobial agent against MRSA.

Morin mitigates cadmium-induced testicular impairment by stimulating testosterone secretion and germ cell proliferation in mice

Cadmium (Cd) is one of the heavy metal pollutants present in the environment due to human intervention. It is well known that Cd causes toxicological effects on various organs, including the testes. Morin hydrate is a plant-derived bioflavonoid with antioxidant, anti-inflammatory, and anti-stress properties. Thus, the question can be raised as to whether Morin has an effect on Cd-intoxication-induced testicular impairment. Therefore, the aim of this study was to investigate the role of Morin on Cd-mediated disruption of testicular activity. Mice were divided into three groups: group 1 served as the control group, group 2 was given Cd (10 mg/kg) orally for 35 days, and group 3 was given Cd and Morin hydrate (100 mg/kg) for 35 days. To validate the in vivo findings, an in vitro study on testicular explants was also performed. The results of the in vivo study showed that Cd-intoxicated mice had testicular disorganization, reduced circulating testosterone levels, decreased sperm density, and elevated oxidative stress and sperm abnormality. The expression of the germ cell proliferation marker, germ cell nuclear acidic protein (GCNA), and adipocytokine visfatin were also downregulated. It was observed that Morin hydrate upregulated testicular visfatin and GCNA expression in Cd-intoxicated mice, along with improvement in circulating testosterone, testicular histology, and sperm parameters. Furthermore, the in vitro study showed that Cd-mediated downregulation of testicular visfatin and GCNA expression, along with the suppressed secretion of testosterone from testicular explants, was normalized by Morin treatment, whereas visfatin expression was not. Overall, these data indicate that environmental cadmium exposure impairs testicular activity through downregulation of visfatin and GCNA expression, and Morin might play a protective role against Cd-induced testicular toxicity.

Thioredoxin overexpression in mitochondria showed minimum effects on aging and age-related diseases in male C57BL/6 mice

Objective:

In this study, the effects of overexpression of thioredoxin 2 (Trx2) on aging and age-related diseases were examined using Trx2 transgenic mice [Tg(TXN2]^+/0]. Because our previous studies demonstrated that thioredoxin (Trx) overexpression in the cytosol (Trx1) did not extend maximum lifespan, this study was conducted to test if increased Trx2 expression in mitochondria shows beneficial effects on aging and age-related pathology.

Methods:

Trx2 transgenic mice were generated using a fragment of the human genome containing the TXN2 gene. Effects of Trx2 overexpression on survival, age-related pathology, oxidative stress, and redox-sensitive signaling pathways were examined in male Tg(TXN2)^+/0 mice.

Results:

Trx2 levels were significantly higher (approximately 1.6- to 5-fold) in all of the tissues we examined in Tg(TXN2)^+/0 mice compared to wild-type (WT) littermates, and the expression levels were maintained during aging (up to 22-24 months old). Trx2 overexpression did not alter the levels of Trx1, glutaredoxin, glutathione, or other major antioxidant enzymes. Overexpression of Trx2 was associated with reduced reactive oxygen species (ROS) production from mitochondria and lower isoprostane levels compared to WT mice. When we conducted the survival study, male Tg(TXN2)^+/0 mice showed a slight extension (approximately 8-9%] of mean, median, and 10th percentile lifespans; however, the survival curve was not significantly different from WT mice. Cross-sectional pathological analysis (22-24 months old) showed that Tg(TXN2)^+/0 mice had a slightly higher severity of lymphoma; however, tumor burden, disease burden, and severity of glomerulonephritis and inflammation were similar to WT mice. Trx2 overexpression was also associated with higher c-Jun and c-Fos levels; however, mTOR activity and levels of NFκB p65 and p50 were similar to WT littermates.

Conclusions:

Our findings suggest that the increased levels of Trx2 in mitochondria over the lifespan in Tg(TXN2)^+/0 mice showed a slight life-extending effect, reduced ROS production from mitochondria and oxidative damage to lipids, but showed no significant effects on aging and age-related diseases.

Dexamethasone mediated downregulation of PGC-1α and visfatin regulates testosterone synthesis and antioxidant system in mouse testis

Dexamethasone, a synthetic glucocorticoid has been used as an immunosuppressive and anti-inflammatory and affects reproduction. It has been suggested that testicular steroidogenesis involves PGC-1α and visfatin as key regulators. Previous studies have shown that dexamethasone down-regulates PGC-1α and visfatin expression in muscle and mammary epithelial cells respectively. However, the effect of dexamethasone on testicular visfatin and PGC-1α expressions has not been investigated. The aims of the present study were to investigate the effect of dexamethasone, on the expression of PGC-1α, visfatin and antioxidant enzymes activities in mouse testis. The results of the present study showed that dexamethasone treatment significantly decreased the expression of visfatin and PGC-1α in mice testis, along with significant decreased in testicular antioxidant enzymes activates. Further, dexamethasone treatment also significantly increased the testicular lipid peroxidation and decreased testosterone synthesis. The dexamethasone induced changes in PGC-1α and visfatin in the testis were significantly correlated with changes in serum testosterone concentrations and antioxidant enzymes activities. Thus, dexamethasone induced testicular toxicity may involve the PGC-1α and visfatin as important molecules to exhibit its effects.

Estrogen and progesterone dependent expression of visfatin/NAMPT regulates proliferation and apoptosis in mice uterus during estrous cycle

Visfatin is an adipokine which has an endocrine effect on reproductive functions and regulates ovarian steroidogenesis. There is scant information about the expression, regulation, and functions of visfatin in the mammalian uterus. The present study examined expression and localization of visfatin in the mouse uterus at various stages of the natural estrous cycle, effects of estrogen and progesterone on localization and expression of visfatin in the ovariectomised mouse uterus and effect of visfatin inhibition by a specific inhibitor, FK866 on proliferation and apoptosis in the uterus. Western blot analysis of visfatin showed high expression in proestrus and metestrus while it declined in estrus and diestrus. Immulocalization study also showed strong immunostaining in the cells of endometrium, myometrium, luminal and glandular epithelium during proestrus and metestrus that estrus and diestrus. The uterine visfatin expression closely related to the increased estrogen levels in proestrus and suppressed when progesterone rose to a high level in diestrus. The treatment with estrogen to ovariectomised mice up-regulates visfatin, PCNA, and active caspase3 whereas progesterone up-regulates PCNA and down-regulates visfatin and active caspase3 expression in mouse uterus. The co-treatment with estrogen and progesterone up-regulates visfatin and down-regulates PCNA and active caspase3. In vitro study showed endogenous visfatin inhibition by FK866 increased expression of PCNA and BCL2 increased catalase activity while FK866 treatment decreased expression of active caspase3 and BAX with decreased SOD and GPx activity. BrdU labeling showed that inhibition of visfatin modulates the uterine proliferation. This study showed that expression of visfatin protein is steroid dependent in mouse uterus which is involved in the regulation of proliferation and apoptosis via modulating antioxidant system in the uterus of mice during the reproductive cycle.

Continuous overexpression of thioredoxin 1 enhances cancer development and does not extend maximum lifespan in male C57BL/6 mice

We examined the effects of continuous overexpression of thioredoxin (Trx) 1 on aging in Trx1 transgenic mice [Tg(TXN)^+/0]. This study was conducted to test whether increased thioredoxin expression over the lifespan in mice would alter aging and age-related pathology because our previous study demonstrated that Tg(act-TXN)^+/0 mice had no significant maximum life extension, possibly due to the use of actin as a promoter, which may have resulted in loss of Trx1 overexpression during aging. To test this hypothesis, we generated new Trx1 transgenic mice using a fragment of the human genome containing the TXN gene with an endogenous promoter to ensure continuous overexpression of Trx1 throughout the lifespan. Universal overexpression of Trx1 was observed, and Trx1 overexpression was maintained during aging (up to 22–24 months old) in the Tg(TXN)^+/0 mice. The levels of Trx1 are significantly higher (approximately 4 to 31 fold) in all of the tissues examined in the Tg(TXN)^+/0 mice compared to the wild-type (WT) littermates. The overexpression of Trx1 did not cause any changes in the levels of Trx2, glutaredoxin, glutathione, or other major antioxidant enzymes. The survival study demonstrated that male Tg(TXN)^+/0 mice slightly extended the earlier part of the lifespan compared to WT littermates, but no significant life extension was observed over the lifespan. The cross-sectional pathological analysis (22–25 months old) showed that Tg(TXN)^+/0 mice had a significantly higher severity of lymphoma and more tumor burden than WT mice, which was associated with the suppression of the apoptosis signal-regulating kinase 1 (ASK1) pathway. Our findings suggest that the increased levels of Trx1 over the lifespan in Tg(TXN)^+/0 mice showed some beneficial effects (slight extension of lifespan) in the earlier part of life but had no significant effects on median or maximum lifespans, and increased Trx1 levels enhanced tumor development in old mice.

Thioredoxin overexpression in both the cytosol and mitochondria accelerates age-related disease and shortens lifespan in male C57BL/6 mice

To investigate the role of increased levels of thioredoxin (Trx) in both the cytosol (Trx1) and mitochondria (Trx2) on aging, we have conducted a study to examine survival and age-related diseases using male mice overexpressing Trx1 and Trx2 (TXNTg × TXN2Tg). Our study demonstrated that the upregulation of Trx in both the cytosol and mitochondria in male TXNTg × TXN2Tg C57BL/6 mice resulted in a significantly shorter lifespan compared to wild-type (WT) mice. Cross-sectional pathology data showed a slightly higher incidence of neoplastic diseases in TXNTg × TXN2Tg mice than WT mice. The incidence of lymphoma, a major neoplastic disease in C57BL/6 mice, was slightly higher in TXNTg × TXN2Tg mice than in WT mice, and more importantly, the severity of lymphoma was significantly higher in TXNTg × TXN2Tg mice compared to WT mice. Furthermore, the total number of histopathological changes in the whole body (disease burden) was significantly higher in TXNTg × TXN2Tg mice compared to WT mice. Therefore, our study suggests that overexpression of Trx in both the cytosol and mitochondria resulted in deleterious effects on aging and accelerated the development of age-related diseases, especially cancer, in male C57BL/6 mice.

Role of aloin in the modulation of certain immune parameters in skin mucus of an Indian major carp, Labeo rohita

Enhancement of immune system seems to be the most promising method of preventing fish diseases. Several herbal products have immunostimulant properties, and are environmental friendly, economical and can act against a broad spectrum of pathogens. Present study was designed with an aim to evaluate the role of aloin, extracted from a herb Aloe barbadensis, in the modulation of certain immune parameters in an Indian major carp, Labeo rohita. Fishes were divided into control, vehicle control and aloin treated groups. Experiments were conducted for 7 days and fishes from the three groups were analyzed at 2d, 4d, 6d and 8d. The results demonstrated that at different intervals, L. rohita administered with aloin showed a significant increase in the activity of enzymes - lysozyme, protease, carboxylesterase, alkaline phosphatase, acid phosphatase, catalase and peroxidase, and non-enzymatic factors hemagglutinin and alternate complement compared with that of the controls. Thus, it can be concluded that administration of aloin is beneficial in enhancing the immune response and hence it can be used as potent immunostimulant in aquaculture.

Carnitine-mediated antioxidant enzyme activity and Bcl2 expression involves peroxisome proliferator-activated receptor-γ coactivator-1α in mouse testis

The protective effects of carnitine have been attributed to inhibition of apoptosis, alleviating oxidative stress and DNA repair mechanism by decreasing oxidative radicles. Carnitine also increases mitochondrial biogenesis via peroxisome proliferator-activated receptor-γ coactivator-1α (PGC1α). The role of carnitine in testicular PGC1α expression has not been documented. We hypothesised that the effects of carnitine as an antioxidant, inhibitor of apoptosis and controller of steroidogenesis in mouse testis may involve PGC1α as a regulator. The present study was designed to evaluate the localisation of PGC1α and the effects of carnitine treatment on the expression of PGC1α, Bcl2 and antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx)) in mouse testis and serum testosterone concentrations. PGC1α was primarily immunolocalised to the Leydig cells and primary spermatocytes. Western blot analysis showed that carnitine (50 mg kg–1 and 100 mg kg–1 for 7 days) significantly increased PGC1α and Bcl2 expression in the testis in a dose-dependent manner. In addition, carnitine treatment significantly increased antioxidant enzyme (CAT, SOD and GPx) levels. The carnitine-induced changes in PGC1α in the testis were significantly correlated with changes in serum testosterone concentrations, as well as with changes in Bcl2 expression and antioxidant enzyme activity in the testis, as evaluated by electrophoresis. Therefore, the results of the present study suggest that carnitine treatment of mice increases PGC1α levels in the testis, which may, in turn, regulate steroidogenesis by increasing expression of Bcl2 and antioxidant enzymes.

Oxidative stress in the development, maintenance and resolution of paclitaxel-induced painful neuropathy

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ROS levels assessed in peripheral and central sensory neurons following paclitaxel.

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Increased ROS levels seen in non-peptidergic neurons prior to paclitaxel-induced pain.

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Elevated ROS levels in spinal neurons, but not microglia/astrocytes, after paclitaxel.

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Assayed activity of main antioxidant enzymes during paclitaxel-evoked pain timecourse.

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Inadequate antioxidant response suggests elevated ROS sustains paclitaxel-evoked pain.

Paclitaxel is a first-line chemotherapeutic with the major dose-limiting side effect of painful neuropathy. Previous preclinical studies indicate mitochondrial dysfunction and oxidative stress are associated with this disorder; however no direct assessment of reactive oxygen species (ROS) levels and antioxidant enzyme activity in sensory neurons following paclitaxel has been undertaken. As expected, repeated low doses of systemic paclitaxel in rats induced long-lasting pain behaviour with a delayed onset, akin to the clinical scenario. To elucidate the role of ROS in the development and maintenance of paclitaxel-induced painful neuropathy, we have assessed ROS and antioxidant enzyme activity levels in the nociceptive system in vivo at three key behavioural time-points; prior to pain onset (day 7), peak pain severity and pain resolution. In isolated dorsal root ganglia (DRG) neurons, ROS levels were unchanged following paclitaxel-exposure in vitro or in vivo. ROS levels were further assessed in DRG and spinal cord in vivo following intrathecal MitoTracker®RedCM-H₂XRos administration in paclitaxel-/vehicle-treated rats. ROS levels were increased at day 7, specifically in non-peptidergic DRG neurons. In the spinal cord, neuronally-derived ROS was increased at day 7, yet ROS levels in microglia and astrocytes were unaltered. In DRG, CuZnSOD and glutathione peroxidase (GPx) activity were increased at day 7 and peak pain time-points, respectively. In peripheral sensory nerves, CuZnSOD activity was increased at day 7, and at peak pain, MnSOD, CuZnSOD and GPx activity were increased. Catalase activity was unaltered in DRG and saphenous nerves. These data suggest that neuronally-derived mitochondrial ROS, accompanied with an inadequate endogenous antioxidant enzyme response, are contributory factors in paclitaxel-induced painful neuropathy.

UVB irradiation severely induces systemic tissue injury by augmenting oxidative load in a tropical rodent: efficacy of melatonin as an antioxidant

Tropical animals are regularly exposed to solar UV radiation. The generation and accumulation of free radicals as a result of UVB incidence causes tissue damage. In the present study we report that the irradiation of Funambulus pennanti by 1.5 J/cm(2) of UVB caused significant oxidative damage to the spleen. The systemic immunity suffered collateral damage as depicted by results of total leukocyte count (TLC) while an increase in the thiobarbituric acid reactive substances (TBARS) and decline in the activities of enzymes superoxide dismutase (SOD), Glutathione peroxidase (GSH-Px) and Catalase (CAT) denoted oxidative tissue damage. Melatonin the indole-amine with known antioxidative properties when administered subcutaneously (s.c 100 μg/100 gm body weight), before the UVB irradiation recovered the damages caused by UVB radiation in the spleen. The action of melatonin was direct and might have involved its membrane receptor (MT1) as well as nuclear receptor (RORα) indicating the fact that the mode of action of melatonin in ameliorating UVB radiation induced free radical load may be receptor mediated. Our study hence reports for the first time that UVB radiation incurred oxidative damage to the spleen and suppressed the normal tissue functions. This UVB mitigated oxidative stress was recovered by the free radical scavenging and anti-apoptotic functions of melatonin when administered prior to UVB irradiation.

CoCl2-induced biochemical hypoxia down regulates activities and expression of super oxide dismutase and catalase in cerebral cortex of mice

Hypoxia-induced oxidative stress is one of the major hallmark reasons underlying brain dysfunction. In the present manuscript, we have used CoCl2-induced hypoxic mice to investigate alterations in the activities of chief antioxidative stress enzymes- superoxide dismutase (SOD) and catalase (CAT) and expression of their genes Sod1 and Cat in the cerebral cortex as this model has not been routinely used for carrying out such study. Hypoxia mimetic mice model was accordingly developed by oral CoCl2 administration to mice and validated by analyzing alterations in the expression of the hypoxia inducible factor gene Hif-1α and its immediate responsive genes. Our Western blot data demonstrated that a dose of 40 mg/kg BW of CoCl2 was able to generate hypoxia like condition in mice in which Hif-1α and its immediate responsive genes-glutamate transporter-1 (Slc2a1) and erythropoietin (Epo) expression were up regulated. Our in-gel assay data indicated that SOD and CAT activities significantly declined and it was associated with significant down regulation of Sod1 and Epo expression as evident from our semi quantitative RT-PCR and Western blot data, which might be correlated with up regulation of Hif-1α expression in the cerebral cortex of the CoCl2-treated hypoxic mice. Our findings suggest that CoCl2-induced hypoxic mouse model is useful for studying alterations in the anti oxidative enzymes and biochemical/molecular/neurobiological analysis of hypoxia-induced alterations in brain function.

Hepatoprotective effects of apple polyphenol extract on aluminum-induced liver oxidative stress in the rat

This study was undertaken to determine the effectiveness of apple (Ralls) polyphenol extract (APE) in modulating aluminum chloride (AlCl3) induced hepatotoxicity in rats. The rats were distributed among 4 groups and fed different diets with or without AlCl3(171.8 mg Al·kg−1·day−1) and APE (200 mg·kg−1·day−1) for 10 weeks. The activities of superoxide dismutase and catalase as well as the levels of glutathione and ATP synthesis were decreased by comparison with the control, while the activities of transaminases in serum, the levels of Al, and ATP hydrolysis were increased significantly in the liver of the Al-treated group. Furthermore, abnormal changes in the histological structure of the liver were observed in the Al-treated group. However, these toxic effects of Al were significantly reduced when the rats were fed diets supplemented with APE. This suggests that APE plays a role in the reduction of the toxic effects from Al in rats.

Superoxide Enhances the Antitumor Combination of AdMnSOD Plus BCNU in Breast Cancer

Overexpression of manganese superoxide dismutase (MnSOD) can sensitize a variety of cancer cell lines to many anticancer drugs. Recent work has shown that cancer cells can be sensitized to cell killing by raising peroxide levels through increased manganese superoxide dismutase (MnSOD) when combined with inhibition of peroxide removal. Here we utilize the mechanistic property of one such anticancer drug, BCNU, which inhibits glutathione reductase (GR), compromising the glutathione peroxidase system thereby inhibiting peroxide removal. The purpose of this study was to determine if anticancer modalities known to produce superoxide radicals can increase the antitumor effect of MnSOD overexpression when combined with BCNU. To enhance MnSOD, an adenoviral construct containing the cDNA for MnSOD (AdMnSOD) was introduced into human breast cancer cell line, ZR-75-1. AdMnSOD infection alone did not alter cell killing, however when GR was inhibited with either BCNU or siRNA, cytotoxicity increased. Futhermore, when the AdMnSOD + BCNU treatment was combined with agents that enhance steady-state levels of superoxide (TNF-α, antimycin, adriamycin, photosensitizers, and ionizing radiation), both cell cytotoxicity and intracellular peroxide levels increased. These results suggest that the anticancer effect of AdMnSOD combined with BCNU can be enhanced by agents that increase generation of superoxide.

2.45 GHz microwave irradiation-induced oxidative stress affects implantation or pregnancy in mice, Mus musculus

The present experiment was designed to study the 2.45 GHz low-level microwave (MW) irradiation-induced stress response and its effect on implantation or pregnancy in female mice. Twelve-week-old mice were exposed to MW radiation (continuous wave for 2 h/day for 45 days, frequency 2.45 GHz, power density=0.033549 mW/cm(2), and specific absorption rate=0.023023 W/kg). At the end of a total of 45 days of exposure, mice were sacrificed, implantation sites were monitored, blood was processed to study stress parameters (hemoglobin, RBC and WBC count, and neutrophil/lymphocyte (N/L) ratio), the brain was processed for comet assay, and plasma was used for nitric oxide (NO), progesterone and estradiol estimation. Reactive oxygen species (ROS) and the activities of ROS-scavenging enzymes- superoxide dismutase, catalase, and glutathione peroxidase-were determined in the liver, kidney and ovary. We observed that implantation sites were affected significantly in MW-irradiated mice as compared to control. Further, in addition to a significant increase in ROS, hemoglobin (p<0.001), RBC and WBC counts (p<0.001), N/L ratio (p<0.01), DNA damage (p<0.001) in brain cells, and plasma estradiol concentration (p<0.05), a significant decrease was observed in NO level (p<0.05) and antioxidant enzyme activities of MW-exposed mice. Our findings led us to conclude that a low level of MW irradiation-induced oxidative stress not only suppresses implantation, but it may also lead to deformity of the embryo in case pregnancy continues. We also suggest that MW radiation-induced oxidative stress by increasing ROS production in the body may lead to DNA strand breakage in the brain cells and implantation failure/resorption or abnormal pregnancy in mice.

In vivo protective effect of dietary curcumin in fish Anabas testudineus (Bloch)

The present study describes, for the first time, the protective effect of natural curcumin in vivo in a lower vertebrate, a teleost, Anabas testudineus (Bloch). Two doses of curcumin 0.5 and 1% were supplemented in the 40% protein feed and fed to fish for the periods, 2 and 8 weeks. The antioxidant status, protein content, and the tissue structure in experimental fish were examined after the short-term and long-term feeding. In all the curcumin fed groups, the lipid peroxidation product, thiobarbituric acid reactive substances content either decreased or unaffected. The glutathione content increased while the antioxidant enzyme activity pattern varied with time and dose. The histological analysis also confirmed the safety of curcumin retaining the normal arrangement of hepatocytes, hepatopancreas, macrophage-melanocyte centers in Anabas. The improved antioxidant status and protein content suggest a favorable effect for curcumin in cultured fish.

Thioredoxin 1 overexpression extends mainly the earlier part of life span in mice

We examined the effects of increased levels of thioredoxin 1 (Trx1) on resistance to oxidative stress and aging in transgenic mice overexpressing Trx1 [Tg(TRX1)(+/0)]. The Tg(TRX1)(+/0) mice showed significantly higher Trx1 protein levels in all the tissues examined compared with the wild-type littermates. Oxidative damage to proteins and levels of lipid peroxidation were significantly lower in the livers of Tg(TRX1)(+/0) mice compared with wild-type littermates. The survival study demonstrated that male Tg(TRX1)(+/0) mice significantly extended the earlier part of life span compared with wild-type littermates, but no significant life extension was observed in females. Neither male nor female Tg(TRX1)(+/0) mice showed changes in maximum life span. Our findings suggested that the increased levels of Trx1 in the Tg(TRX1)(+/0) mice were correlated to increased resistance to oxidative stress, which could be beneficial in the earlier part of life span but not the maximum life span in the C57BL/6 mice.

Administration of rat acute-phase protein α(2)-macroglobulin before total-body irradiation initiates cytoprotective mechanisms in the liver

Previously, we showed that administration of the acute-phase protein α(2)-macroglobulin (α(2)M) to rats before total-body irradiation with 6.7 Gy (LD(50/30)) of X-rays provides the same level of radioprotection as amifostine. Here, we compare the cytoprotective effects of α(2)M and amifostine on rat liver. The potential of the liver to replenish cells destroyed by ionizing radiation was assessed by immunoblot analysis with antibody to proliferating cell nuclear antigen (PCNA). After irradiation, in unprotected rats PCNA decreased 6-fold from the basal level. In rats pretreated with either α(2)M or amifostine, PCNA was increased throughout a 4 week follow-up period, indicating that hepatocyte proliferation was unaffected. Since PCNA is an important component of the repair machinery, its increased expression was accompanied by significantly lower DNA damage in α(2)M- and amifostine-treated rats. At 2 weeks after irradiation, the Comet assay revealed a 15-fold increase in DNA damage in unprotected rats, while in α(2)M- and amifostine-treated rats we observed 3- and 4-fold rise in damage, respectively. The improved protection to DNA damage was supported by elevated activity of the antioxidant systems. Compared to untreated rats, pretreatments with α(2)M and amifostine led to similar increases in levels of the inflammatory cytokine IL-6 and the redox-sensitive transcription factor NFκB, promoting upregulation of MnSOD, the major component of the cell's antioxidant axis, and subsequent increases in Mn/CuZnSOD and catalase enzymatic activities. The results show that α(2)M induces protein factors whose interplay underlies radioprotection and support the idea that α(2)M is the central effector of natural radioprotection in the rat.

Oxidative stress in mouse liver caused by dietary amino acid deprivation: protective effect of methionine

The aim of this work was to evaluate the effects of a diet depleted of amino acids (protein-free diet, or PFD), as well as the supplementation with methionine (PFD+Met), on the antioxidant status of the female mouse liver. With this purpose, cytosolic protein spots from two-dimensional non-equilibrium pH gel electrophoresis were identified by several procedures, such as mass spectrometry, Western blot, gel matching and enzymatic activity. PFD decreased the contents of catalase (CAT), peroxiredoxin I (Prx-I), and glutathione peroxidase (GPx) by 67%, 37% and 45%, respectively. Gene expression analyses showed that PFD caused a decrease in CAT (-20%) and GPx (-30%) mRNA levels but did not change that of Prx-I. It was also found that, when compared to a normal diet, PFD increased the liver contents of both reactive oxygen species (+50%) and oxidized protein (+88%) and decreased that of glutathione (-45%). Supplementation of PFD with Met prevented these latter effects to varying degrees, whereas CAT, Prx-I and GPx mRNA levels resulted unmodified. Present results suggest that dietary amino acid deprivation deranges the liver antioxidant defences, and this can be, in part, overcome by supplementation with Met.

Metabolic oxidative stress induced by a combination of 2-DG and 6-AN enhances radiation damage selectively in malignant cells via non-coordinated expression of antioxidant enzymes

Our earlier studies have shown that simultaneous inhibition of glycolysis and pentose phosphate pathway using 2-deoxy-d-glucose (2-DG, an inhibitor of glycolysis) and 6-aminonicotinamide (6-AN, an inhibitor of pentose phosphate pathway) lead to metabolic oxidative stress (MOS), resulting in radiosensitization in malignant cells. Present study was carried out to investigate the effects of 2-DG and 6-AN on intricately regulated endogenous antioxidant defense against MOS during radiosensitization by this combination. Two human tumor cell lines {Head and Neck Squamous carcinoma (KB) and Glioma (BMG-1)} and one non-malignantly transformed cell line (human embryonic kidney, HEK) were used in this study. The presence of 2-DG and 6-AN (added just before irradiation) for 4h, significantly decreased the clonogenicity and metabolic viability of KB and BMG-1 cell lines, while no significant change was seen in HEK cells. Accumulation of ROS was observed only in malignant cell lines, which displayed a compromised redox status evident from enhanced NADP(+)/NADPH and GSSG/GSH ratios and a concomitant decrease in glutathione reductase level and activity at 24h following treatment. The levels and activities of Cu, Zn-SOD and Mn-SOD increased with MOS and were accompanied by a decreased GPx and unaltered catalase activity and level. These results suggest that non-coordinated expression of antioxidant defense, besides compromised redox status, led to selective radiosensitization in the malignant cells.

Aging decreases expression and activity of glutathione peroxidase-1 in human endothelial progenitor cells

The mechanisms underlying effects of aging on functions of pro-angiogenic endothelial progenitor cells (EPCs) are poorly understood. Previous studies demonstrated that human EPCs express high levels of antioxidant enzymes as compared to mature endothelial cells. Here, we hypothesized that aging impairs antioxidant capacity of EPCs. So called "early EPCs" derived from cultured blood mononuclear cells were obtained from healthy young (average=24 years old) and old (average=72 years old) subjects. In EPCs of old subjects, the levels of glutathione peroxidase-1 (GPX1) protein and enzymatic activity were significantly reduced. The serum selenium levels in young and old subjects were not significantly different. Increasing selenium concentration in the cell culture also did not affect the protein levels of GPX1, suggesting the reduced GPX1 in old subject's EPCs is selenium independent. Expressions of catalase, Mn-superoxide dismutase (MnSOD), and CuZnSOD were not affected by aging. EPCs of old subjects were more sensitive to oxidative stress induced by H(2)O(2) as compared with EPCs of young subjects, suggesting that impairment of GPX1 during aging may contribute to low survival ability of EPCs in response to oxidative stress. The results indicate that GPX1 may represent a potential therapeutic target for enhancement of regenerative capacity of EPCs in old subjects.

Curcumin analogue inhibits lipid peroxidation in a freshwater teleost, Anabas testudineus (Bloch)--an in vitro and in vivo study

The effect of a synthetic curcumin analogue (salicylcurcumin) on fish lipid peroxidation was investigated in both in vitro and in vivo conditions using a teleost model Anabas testudineus (Bloch). Curcumin analogue inhibited the formation of lipid peroxidation products and thiobarbituric acid reactive substances (TBARS) content at the three concentrations (10(-2) M, 10(-3) M and 10(-4) M) in vitro. TBARS content was reduced by 80% in the liver and 68% in brain by the higher concentration of salicylcurcumin. For in vivo study, salicylcurcumin (0.5%) was supplemented along with the basal feed for a period of 60 days. It produced a 60% reduction in liver TBARS content. The antioxidant enzyme superoxide dismutase (SOD) was stimulated, whereas catalase (CAT) and glutathione peroxidase (GPx) were inhibited. Glutathione (GSH) was reduced and glutathione reductase (GR) unchanged. Even though there was an increase in SOD activity, the CAT and GPx did not increase accordingly, maybe due to the direct scavenging of H(2)O(2) by salicylcurcumin. The protein content also increased in the curcumin-fed animals, indicating a positive growth-promoting effect. Therefore, it would be beneficial to supplement salicylcurcumin along with the aquaculture feed in order to help the fish to cope with adverse conditions in the environment. This would increase the survival rate, disease resistance and ultimately the growth rate.

Methoxychlor-induced alteration in the levels of HSP70 and clusterin is accompanied with oxidative stress in adult rat testis

Methoxychlor, an organochlorine pesticide, has been reported to induce abnormalities in male reproductive tract. However, the insight into the mechanisms of gonadal toxicity induced by methoxychlor is not well known. We investigated whether treatment with methoxychlor would alter the levels of stress proteins, heat shock proteins (HSP), and clusterin (CLU), and oxidative stress-related parameters in the testis of adult male rats. Animals were exposed to a single dose of methoxychlor (50 mg/kg body weight) orally and were terminated at various time points (0, 3, 6, 12, 24, and 72 h) using anesthetic ether. The levels of HSP70, CLU, and the activities of superoxide dismutase (SOD), catalase, and lipid peroxidation levels were evaluated in a 10% testis homogenate. A sequential reduction in the activities of catalase and SOD with concomitant increase in the levels of thiobarbituric acid reactive substance (TBARS) was observed. These changes elicited by methoxychlor were very significant between 6-12 h of posttreatment. Immunoblot analysis of HSP revealed the expression of HSP72, an inducible form of HSP, at certain time points (3-24 h) following exposure to methoxychlor. Similarly, the levels of secretory CLU (sCLU) were also found to be elevated between 3-24 h of treatment. The present data demonstrate methoxychlor-elicited increase in the levels of inducible HSP72 and sCLU, which could be a part of protective mechanism mounted to reduce cellular oxidative damage.

Enhancing the antitumor activity of adriamycin and ionizing radiation

Overexpression of manganese superoxide dismutase (MnSOD), when combined with certain chemicals that inhibit peroxide removal, increases cancer cell cytotoxicity. Elevating MnSOD levels in cells enhances the conversion of superoxide (O(2)(*-)) to hydrogen peroxide (H(2)O(2)), combined with inhibiting the removal of H(2)O(2), further increases H(2)O(2) levels, leading to increased cytotoxicity. We hypothesized that increasing endogenous O(2)(*-) production in cells that were pretreated with adenoviral MnSOD (AdMnSOD) plus 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) would lead to an increased level of intracellular H(2)O(2) accumulation and increased cell killing. The cytotoxic effects of Adriamycin or radiation, agents known to produce O(2)(*-), were determined in MDA-MB-231 breast cancer cells pretreated with AdMnSOD plus BCNU both in vitro and in vivo. In vitro, AdMnSOD plus BCNU sensitized cells to the cytotoxicity of Adriamycin or radiation. In vivo, AdMnSOD, BCNU, and Adriamycin or ionizing radiation inhibited tumor growth and prolonged survival. The results suggest that agents that produce O(2)(*-) in combination with AdMnSOD plus BCNU may represent a powerful new antitumor regimen against breast cancer.

Manganese superoxide dismutase modulates hypoxia-inducible factor-1 alpha induction via superoxide

Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that plays an important role in O(2) homeostasis. Numerous observations suggest that changes in reactive oxygen species affect HIF-1 alpha stabilization and HIF-1 alpha transcriptional activation in many cell types. The antioxidant enzyme manganese superoxide dismutase (MnSOD) modulates the cellular redox environment by converting superoxide (O(2)(*-)) to hydrogen peroxide and dioxygen. Previous results from our group have shown that overexpression of MnSOD in MCF-7 cells alters stabilization of HIF-1 alpha under hypoxic conditions; however, the underlying mechanism(s) is not known. Here, we tested the hypothesis that MnSOD regulates the expression of HIF-1 alpha by modulating the steady-state level of O(2)(*-). We found that decreasing MnSOD with small interfering RNA in MCF-7 cells resulted in (a) an associated increase in the hypoxic accumulation of HIF-1 alpha immunoreactive protein, (b) a significant increase in the levels of O(2)(*-) (P < 0.01), but (c) no significant change in the steady-state level of H(2)O(2). Removal of O(2)(*-) using spin traps (alpha-4-pyridyl-1-oxide-N-tert-butylnitrone and 5,5-dimethyl-1-pyrroline N-oxide) or the O(2)(*-) scavenger Tempol or an SOD mimic (AEOL10113) resulted in a decrease in HIF-1 alpha protein, consistent with the hypothesis that O(2)(*-) is an important molecular effector responsible for hypoxic stabilization of HIF-1 alpha. The evidence from both genetic and pharmaceutical manipulation is consistent with our hypothesis that O(2)(*-) can contribute to the stabilization of HIF-1 alpha.

Regulatory and structural differences in the Cu,Zn-superoxide dismutases of Salmonella enterica and their significance for virulence

Many of the most virulent strains of Salmonella enterica produce two distinct Cu,Zn-superoxide dismutases (SodCI and SodCII). The bacteriophage-encoded SodCI enzyme makes the greater contribution to Salmonella virulence. We have performed a detailed comparison of the functional, structural, and regulatory properties of the Salmonella SodC enzymes. Here we demonstrate that SodCI and SodCII differ with regard to specific activity, protease resistance, metal affinity, and peroxidative activity, with dimeric SodCI exhibiting superior stability and activity. In particular, monomeric SodCII is unable to retain its catalytic copper ion in the absence of zinc. We have also found that SodCI and SodCII are differentially affected by oxygen, zinc availability, and the transcriptional regulator FNR. SodCII is strongly down-regulated under anaerobic conditions and dependent on the high affinity ZnuABC zinc transport system, whereas SodCI accumulation in vitro and within macrophages is FNR-dependent. We have confirmed earlier findings that SodCII accumulation in intracellular Salmonella is negligible, whereas SodCI is strongly up-regulated in macrophages. Our observations demonstrate that differences in expression, activity, and stability help to account for the unique contribution of the bacteriophage-encoded SodCI enzyme to Salmonella virulence.

Increased oxidative stress created by adenoviral MnSOD or CuZnSOD plus BCNU (1,3-bis(2-chloroethyl)-1-nitrosourea) inhibits breast cancer cell growth

Superoxide dismutases (SODs) have been found to decrease tumor formation and angiogenesis. SOD gene therapy, as with many other gene transfer strategies, may not completely inhibit tumor growth on its own. Thus, concomitant therapies are necessary to completely control the spread of this disease. We hypothesized that intratumoral injection of AdSOD in combination with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) chemotherapy would synergistically inhibit breast cancer growth. Our data indicate that BCNU when combined with SOD overexpression increased oxidative stress as suggested by elevated glutathione disulfide (GSSG) production in one of three breast cancer cell lines tested, at least in part due to glutathione reductase (GR) inactivation. The increased oxidative stress caused by BCNU combined with adenovirally expressed SODs, manganese or copper zinc SOD, decreased growth and survival in the three cell lines tested in vitro, but had the largest effect in the MDA-MB231 cell line, which showed the largest amount of oxidative stress. Delivery of MnSOD and BCNU intratumorally completely inhibited MDA-MB231 xenograft growth and increased nude mouse survival in vivo. Intravenous (iv) BCNU, recapitulating clinical usage, and intratumoral AdMnSOD delivery, to provide tumor specificity, provided similar decreased growth and survival in our nude mouse model. This cancer therapy produced impressive results, suggesting the potential use of oxidative stress-induced growth inhibitory treatments for breast cancer patients.

Acute and Chronic Hyperammonemia Modulate Antioxidant Enzymes Differently in Cerebral Cortex and Cerebellum

Studies on acute hyperammonemic models suggest a role of oxidative stress in neuropathology of ammonia toxicity. Mostly, a low grade chronic type hyperammonemia (HA) prevails in patients with liver diseases and causes derangements mainly in cerebellum associated functions. To understand whether cerebellum responds differently than other brain regions to chronic type HA with respect to oxidative stress, this article compares active levels of all the antioxidant enzymes vis a vis extent of oxidative damage in cerebral cortex and cerebellum of rats with acute and chronic HA induced by intra-peritoneal injection of ammonium acetate (successive doses of 10 x 10(3) & 8 x 10(3) micromol/kg b.w. at 30 min interval for acute and 8 x 10(3) micromol/kg b.w. daily up to 3 days for chronic HA). As compared to the respective control sets, cerebral cortex of acute HA rats showed significant decline (P < 0.01-0.001) in the levels of superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx) but with no change in glutathione reductase (GR). In cerebellum of acute HA rats, SOD, catalase and GR though declined significantly, GPx level was found to be stable. Contrary to this, during chronic HA, levels of SOD, catalase and GPx increased significantly in cerebral cortex, however, with a significant decline in the levels of SOD and GPx in cerebellum. The results suggest that most of the antioxidant enzymes decline during acute HA in both the brain regions. However, chronic HA induces adaptive changes, with respect to the critical antioxidant enzymes, in cerebral cortex and renders cerebellum susceptible to the oxidative stress. This is supported by approximately 2- and 3-times increases in the level of lipid peroxidation in cerebellum during chronic and acute HA respectively, however, with no change in the cortex due to chronic HA.

Protective effect of silymarin on erythrocyte haemolysate against benzo(a)pyrene and exogenous reactive oxygen species (H2O2) induced oxidative stress

The present study was carried out to evaluate the in vitro antioxidant properties and protective effects of silymarin (milk thistle) in human erythrocyte haemolysates against benzo(a)pyrene [B(a)P], a potent carcinogenic chemical. Protective effect of silymarin was assessed in vitro by monitoring the antioxidant enzymes and malondialdehyde in three groups of haemolysates-(I) vehicle control (II) B(a)P incubated group and (III) B(a)P co incubated with silymarin. The effects of silymarin on lipid peroxidation (LPO) and antioxidant enzymes [superoxide dismutase; SOD, catalase; CAT, glutathione peroxidase; GPx, glutathione reductase; GR and glutathione-S-transferases; GST] were assessed on haemolysates. It was observed that specific activity of antioxidant enzymes were significantly decreased and the malondialdehyde levels were elevated when haemolysates were incubated with B(a)P. The protective effect of silymarin is elucidated by the significant reversal of the antioxidant enzymes and reduction in the levels of malondialdehyde. In addition, haemolysates were incubated with B(a)P for 45 min and the B(a)P metabolite, 3-hydroxy benzo(a)pyrene (3-OH-B(a)P) was detected using HPLC. An increased level of the metabolite was detected in group II. Whereas, when haemolysates were co-incubated with silymarin, the reactive metabolite 3-OH-B(a)P was not detectable which further confirms the protective role of silymarin. Generation of 3-OH-B(a)P in group II implicates the possibility of reactive oxygen species (O2- and H2O2) production in haemolysates during cytochrome P4501A1 (CYP1A1) mediated Phase-I-metabolism. Hence, we incubated the haemolysates with exogenous reactive oxygen species H2O2 and assessed the protective role of silymarin against H2O2. From the results of our study, it was suggested that silymarin possess substantial protective effect and free radical scavenging mechanism against environmental contaminants induced oxidative stress damages.

Silymarin Protection against Major Reactive Oxygen Species Released by Environmental Toxins: Exogenous H2O2Exposure in Erythrocytes

Silymarin is a polyphenolic plant flavonoid (a mixture of flavonoid isomers such as silibinin, isosilibinin, silidianin and silichristin) derived from Silymarin marianum that has anti-inflammatory, hepatoprotective and anticarcinogenic effects. Our earlier studies have shown that silymarin plays a protective role against the oxidative damage induced by environmental contaminants like benzo(a)pyrene in erythrocyte haemolysates. During the detoxification of these environmental contaminants, the major reactive oxygen species generated is hydrogen peroxide (H(2)O(2)). Because H(2)O(2 )can easily penetrate into the cell and cause damage to biomolecules, the protective role of silymarin was further assessed against this cytotoxic agent in vitro in erythrocyte haemolysates. The protective effect was monitored by assessing the levels of the antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione-s-transferase, glutathione peroxidase and malondialdehyde (LPO) in three groups: vehicle control, H(2)O(2)-exposed groups and drug co-incubation group (H(2)O(2) + silymarin). The protective effect of silymarin on the non-enzymic antioxidant glutathione and haemolysis, methaemoglobin content and protein carbonyl content were also assessed. It was observed that the activities of antioxidant enzymes and glutathione were reduced and the malondialdehyde levels were elevated after H(2)O(2 )exposure. There were also alterations in haemolysis, methaemoglobin content and protein carbonyl content, whereas after the administration of silymarin, the antioxidant enzyme activities reversed to near normal with reduced malondialdehyde content and normalized haemolysis, methaemoglobin content and protein carbonyl content. The results suggest that silymarin possesses substantial protective effect and free radical scavenging mechanism against exogenous H(2)O(2)-induced oxidative stress damages, hence, can be used as a protective drug against toxicity induced by environmental contaminants.

Protective role of lactobacilli in Shigella dysenteriae 1–induced diarrhea in rats

OBJECTIVE

Studies on lactic acid bacteria exemplify their use against various enteropathogens in vitro. Nevertheless, in vivo effects of Lactobacillus during Shigella infection have not been evaluated. The present study evaluated the effect of Lactobacillus rhamnosus and Lactobacillus acidophilus on neutrophil infiltration and lipid peroxidation during Shigella dysenteriae 1-induced diarrhea in rats.

METHODS

The rats were divided into eight groups (n = 6 in each group). Induced rats received single oral dose of S. dysenteriae (12 x 10(8) colony-forming units [cfu]/mL). Treated rats received L. rhamnosus (1 x 10(7) cfu/mL) or L. acidophilus (1 x 10(7) cfu/mL) orally for 4 d, alone or in combination, followed by Shigella administration. At the end of the experimental period, animals were sacrificed and the assay of the activity of alkaline phosphatase, myeloperoxidase, and antioxidants and the estimation of lipid peroxides were performed. Activity staining of superoxide dismutase and catalase was done in addition to gelatin zymography for matrix metalloproteinase (MMP; MMP-2 and MMP-9) activity. A portion of the intestinal tissue was fixed in 10% formalin for histologic studies.

RESULTS

Administration of S. dysenteriae 1 alone resulted in increased levels of myeloperoxidase, lipid peroxidation, alkaline phosphatase, and the expression of MMP-2 and MMP-9 with concomitant decrease in the antioxidant levels. Pretreatment with the combination of L. rhamnosus (1 x 10(7) cfu/mL) and L. acidophilus (1 x 10(7) cfu/mL) significantly attenuated these changes when compared with the diseased group. Histologic observations were in correlation with biochemical parameters.

CONCLUSION

Lactobacillus rhamnosus plus L. acidophilus offered better protection when compared with individual treatment with these strains during Shigella infection.

Overexpression of Akt converts radial growth melanoma to vertical growth melanoma

Melanoma is the cancer with the highest increase in incidence, and transformation of radial growth to vertical growth (i.e., noninvasive to invasive) melanoma is required for invasive disease and metastasis. We have previously shown that p42/p44 MAP kinase is activated in radial growth melanoma, suggesting that further signaling events are required for vertical growth melanoma. The molecular events that accompany this transformation are not well understood. Akt, a signaling molecule downstream of PI3K, was introduced into the radial growth WM35 melanoma in order to test whether Akt overexpression is sufficient to accomplish this transformation. Overexpression of Akt led to upregulation of VEGF, increased production of superoxide ROS, and the switch to a more pronounced glycolytic metabolism. Subcutaneous implantation of WM35 cells overexpressing Akt led to rapidly growing tumors in vivo, while vector control cells did not form tumors. We demonstrated that Akt was associated with malignant transformation of melanoma through at least 2 mechanisms. First, Akt may stabilize cells with extensive mitochondrial DNA mutation, which can generate ROS. Second, Akt can induce expression of the ROS-generating enzyme NOX4. Akt thus serves as a molecular switch that increases angiogenesis and the generation of superoxide, fostering more aggressive tumor behavior. Targeting Akt and ROS may be of therapeutic importance in treatment of advanced melanoma.

Enzymatic activity is necessary for the tumor-suppressive effects of MnSOD

The antioxidant protein manganese-containing superoxide dismutase (MnSOD) has been found to be a new type of tumor-suppressor protein. Overexpression of the cDNA for this gene in various types of cancer via plasmid transfection or adenovirus transduction leads to growth suppression both in vitro and in vivo. The growth-suppressive effect of MnSOD overexpression has been presumed to be due to the enzymatic activity of the MnSOD protein, but could be due to a number of other mechanisms, including a regulatory effect of the RNA or protein produced. To examine this question, we used site-directed mutagenesis to produce a mutant form of human MnSOD that has a leucine at amino acid 26 in the active site rather than the usual histidine. We demonstrate that plasmid transfection or adenoviral transduction of this mutant MnSOD cDNA leads to a large increase in immunoreactive MnSOD protein, but little or no increase in enzymatic activity. In contrast, overexpression of wild-type MnSOD leads to cells with both increased MnSOD protein and activity. Overexpression of wild-type, but not mutant, MnSOD leads to decreased plating efficiency and growth. These results clearly demonstrate that the tumor-suppressive effect of MnSOD protein is largely due to its enzymatic activity.

Protection effect of piper betel leaf extract against carbon tetrachloride-induced liver fibrosis in rats

Piper betel leaves (PBL) are used in Chinese folk medicine for the treatment of various disorders. PBL has the biological capabilities of detoxication, antioxidation, and antimutation. In this study, we evaluated the antihepatotoxic effect of PBL extract on the carbon tetrachloride (CCl(4))-induced liver injury in a rat model. Fibrosis and hepatic damage, as reveled by histology and the activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were induced in rats by an administration of CCl(4) (8%, 1 ml/kg body weight) thrice a week for 4 weeks. PBL extract significantly inhibited the elevated AST and ALT activities caused by CCl(4) intoxication. It also attenuated total glutathione S-transferase (GST) activity and GST alpha isoform activity, and on the other hand, enhanced superoxide dismutase (SOD) and catalase (CAT) activities. The histological examination showed the PBL extract protected liver from the damage induced by CCl(4) by decreasing alpha-smooth muscle actin (alpha-sma) expression, inducing active matrix metalloproteinase-2 (MMP2) expression though Ras/Erk pathway, and inhibiting TIMP2 level that consequently attenuated the fibrosis of liver. The data of this study support a chemopreventive potential of PBL against liver fibrosis.

Hypocatalasemic fibroblasts accumulate hydrogen peroxide and display age-associated pathologies

Human epidemiological studies point to an association of hypocatalasemia and an increased risk of age-related disease. Unfortunately, the cellular and molecular manifestations of hypocatalasemia are only poorly understood. In this analysis, we have extensively characterized hypocatalasemic human fibroblasts and report that they amass hydrogen peroxide and are oxidatively damaged. Protein and DNA alike are affected, as are functioning and biogenesis of peroxisomes - the subcellular organelles which normally house catalase. Despite these pathologies and their relative inability to grow, the cells do not appear to be intrinsically senescent. With the goal of restoring oxidative balance and perhaps reversing some of the accumulated damage to critical cellular components, we transduced hypocatalasemic fibroblasts with a form of catalase specifically designed to efficiently traffic to peroxisomes. We show the strategy is extremely effective, with dramatic reductions seen in cellular hydrogen peroxide levels. Future longitudinal studies aimed at examining the effects of a more continuous and long-term protein therapy may now commence.

Characterization of transgenic mice that overexpress both copper zinc superoxide dismutase and catalase

Transgenic mice overexpressing both Cu/ZnSOD and catalase [Tg(SOD1/CAT) +/o] were used to evaluate the effects of overexpression of both genes against oxidative stress. Characterization of these transgenic mice revealed that catalase or Cu/ZnSOD activities were two- to fourfold higher in the tissues of transgenic mice compared to wild-type mice, and the activities of the other major antioxidant enzymes were not altered in the tissues of the transgenic mice. The murine embryonic fibroblasts (MEFs) from the Tg(SOD1/CAT) +/o and MEFs overexpressing Cu/ZnSOD were more resistant to paraquat cytotoxicity, relative to wild-type MEFs. The MEFs from Tg(SOD1/CAT) +/o tended to be more resistant (up to 2.25-fold) to paraquat cytotoxicity than MEFs overexpressing either Cu/ZnSOD or catalase alone. MEFs from Tg(CAT) +/o and Tg(SOD1/CAT) +/o were equally as resistant to hydrogen peroxide cytotoxicity. However, there were no significant differences in whole animal survival against either paraquat or gamma-radiation.

Doxorubicin increases intracellular hydrogen peroxide in PC3 prostate cancer cells

We studied the effect of doxorubicin on the production of hydrogen peroxide by PC3 human prostate cancer cells, using a sensitive assay based on aminotriazole-mediated inhibition of catalase. PC3 cells exposed to increasing concentrations of doxorubicin had an increase in intracellular hydrogen peroxide that was concentration-dependent up to 1 microM doxorubicin. The apparent hydrogen peroxide concentration in the PC3 cells was 13 +/- 4 pM under basal steady-state conditions and increased to 51 +/- 13 pM after exposure to 1 microM doxorubicin for 30 min. The level of hydrogen peroxide in the medium as measured by Amplex Red did not increase as a result of doxorubicin treatment. PC3 cells overexpressing catalase were no more resistant to doxorubicin cytotoxicity as compared to non-transduced wild-type cells; therefore, the exact role of hydrogen peroxide in anthracycline cytotoxicity remains unproven. This study demonstrates that a specific oxidative event associated with the exposure of PC3 human prostate cancer cells to anthracyclines results in an increase in intracellular hydrogen peroxide.

Manganese superoxide dismutase suppresses hypoxic induction of hypoxia-inducible factor-1α and vascular endothelial growth factor

Hypoxia-inducible factor-1 (HIF-1) is a transcription factor that governs cellular responses to reduced O2 availability by mediating crucial homeostatic processes. HIF-1 is composed of an HIF-1alpha subunit and an HIF-1beta subunit. HIF-1alpha is degraded following enzyme-dependent hydroxylation of prolines of HIF-1alpha in the presence of molecular oxygen, Fe2+, alpha-ketoglutarate, and ascorbate. These cofactors contribute to the redox environment of cells. The antioxidant enzyme manganese superoxide dismutase (MnSOD) also modulates the cellular redox environment. Here we show that MnSOD suppressed hypoxic accumulation of HIF-1alpha protein in human breast carcinoma MCF-7 cells. This suppression was biphasic depending on MnSOD activity. At low levels of MnSOD activity, HIF-1alpha protein accumulated under hypoxic conditions. At moderate levels of MnSOD activity (two- to six-fold increase compared to parent cells), these accumulations were blocked. However, at higher levels of MnSOD activity (>6-fold increase), accumulation of HIF-1alpha protein was again observed. This biphasic modulation was observed under both 1 and 4% O2. Coexpression of mitochondrial hydrogen peroxide-removing proteins prevented the accumulation of HIF-1alpha protein in cells with high levels of MnSOD; this effect demonstrates that the restabilization of HIF-1alpha observed in high MnSOD overexpressors is probably due to hydrogen peroxide, most likely produced from MnSOD. Hypoxic induction of vascular endothelial growth factor (VEGF) protein was also suppressed by elevated MnSOD activity and its levels reflected HIF-1alpha protein levels. These observations demonstrated that HIF-1alpha accumulation and VEGF expression could be modulated by the antioxidant enzyme MnSOD.

Redox regulation of pancreatic cancer cell growth: role of glutathione peroxidase in the suppression of the malignant phenotype

Pancreatic cancer has low levels of antioxidant enzymes including manganese superoxide dismutase (MnSOD), which converts superoxide radical (O(2)(*-)) into hydrogen peroxide (H(2)O(2)), and glutathione peroxidase (GPx), which converts H(2)O(2) into water. Recent studies have demonstrated that overexpression of MnSOD has a tumor-suppressive effect in pancreatic cancer. However, GPx overexpression has been shown to reverse the tumor cell growth inhibition caused by MnSOD overexpression in other types of cancer. Our aims were to determine if overexpression of GPx alters in vitro pancreatic cancer cell behavior and if delivering the GPx gene directly to tumor xenografts alters growth and survival. In vitro, AdGPx slowed tumor growth by 39% and AdMnSOD slowed tumor growth by 35%. AdGPx also decreased plating efficiency and growth in soft agar. The combination of AdGPx and AdMnSOD had the greatest effect on tumor cell growth suppression with a 71% reduction in cell growth compared to controls. In vivo, either AdGPx or AdMnSOD alone slowed tumor growth by 51% and 54%, respectively, while the combination of AdGPx and AdMnSOD potentiated tumor growth suppression by 81% of controls and increased animal survival. GPx may be a tumor suppressor gene in pancreatic cancer. Delivery of the GPx gene alone or in combination with the MnSOD gene may prove beneficial for treatment of pancreatic cancer.

Transgenic mice overexpressing glutathione peroxidase 4 are protected against oxidative stress-induced apoptosis

Glutathione peroxidase 4 (Gpx4) is uniquely involved in the detoxification of oxidative damage to membrane lipids. Our previous studies showed that Gpx4 is essential for mouse survival and that Gpx4 deficiency makes cells vulnerable to oxidative injury. In the present study, we generated two lines of transgenic mice overexpressing Gpx4 (Tg(GPX4) mice) using a genomic clone containing the human GPX4 gene. Both lines of Tg-(GPX4) mice, Tg5 and Tg6, had elevated levels of Gpx4 (mRNA and protein) in all tissues investigated, and overexpression of Gpx4 did not cause alterations in activities of glutathione peroxidase 1, catalase, Cu/Zn superoxide dismutase, and manganese superoxide dismutase. The human GPX4 transgene rescued the lethal phenotype of null mutation of the mouse Gpx4 gene, indicating that the transgene can replace the essential role of mouse Gpx4 in mouse development. Cell death induced by t-butylhydroperoxide and diquat was significantly less in murine embryonic fibroblasts from Tg(GPX4) mice compared with wild type mice. Liver damage and lipid peroxidation induced by diquat were reduced significantly in Tg(GPX4) mice. In addition, diquat-induced apoptosis was decreased in Tg(GPX4) mice, as evidenced by attenuated caspase-3 activation and reduced cytochrome c release from mitochondria. These data demonstrate that Gpx4 plays a role in vivo in the mechanism of apoptosis induced by oxidative stress that most likely occurs through oxidative damage to mitochondrial phospholipids such as cardiolipin.

Human endothelial progenitor cells tolerate oxidative stress due to intrinsically high expression of manganese superoxide dismutase

OBJECTIVE

Endothelial progenitor cells (EPCs) display a unique aptitude to promote angiogenesis and restore endothelial function of injured vessels. How progenitor cells can execute a regenerative program in the unfavorable environment of injury/inflammation-induced oxidative stress is poorly understood. We hypothesized that EPCs are resistant to oxidative stress and that this resistance is due to high expression and activity of antioxidant enzymes.

METHODS AND RESULTS

EPCs outgrown from human blood of healthy subjects demonstrated a marked resistance to cytotoxic effect of LY83583 (an generator), tumor necrosis factor-alpha, and serum depletion. LY83583 inhibited in vitro tube formation by human umbilical vein endothelial cells (HUVECs) and human coronary artery endothelial cells (CAECs), but not by EPCs. Compared with HUVECs and CAECs, EPCs exhibited approximately 3- to 4-fold higher expression and activity of manganese superoxide dismutase (MnSOD), but not copper zinc superoxide dismutase (CuZnSOD) or catalase. The antioxidant profile in EPCs was associated with preservation of the mitochondrial network when exposed to LY83583. Moreover, cytotoxic effects of LY83583 on CAECs and HUVECs were reversed by adenoviral overexpression of MnSOD.

CONCLUSIONS

Human EPCs are resistant to oxidative stress. High intrinsic expression of MnSOD is a critical mechanism protecting EPCs against oxidative stress.