Impacts of glutathione peroxidase-1 knockout on the protection by injected selenium against the pro-oxidant-induced liver aponecrosis and signaling in selenium-deficient mice

Regorafenib activates oxidative stress by inhibiting SELENOS and potentiates oxaliplatin-induced cell death in colon cancer cells

Colorectal cancer (CRC) is the third most common cancer, and is one of the leading causes of cancer-related death worldwide. At the time of diagnosis, about 20% of patients with CRC present metastatic disease. Regorafenib, an oral multi-kinase inhibitor, has been demonstrated the efficacy and tolerability in patients with metastatic CRC. Oxaliplatin is a frontline treatment regimen for CRC, and combination treatments with oxaliplatin and other chemotherapeutic agents exert superior therapeutic effects. However, side effects and drug resistance limited their further clinical application. Here, we found that combined treatment with regorafenib and oxaliplatin synergistically enhanced anti-tumor activities in CRC by activating reactive oxygen species (ROS) mediated endoplasmic reticulum (ER) stress, C-Jun-amino-terminal kinase (JNK) and p38 signaling pathways. Regorafenib promoted ROS production by suppressing the expression of selenoprotein S (SELENOS). Knocking down SELENOS sensitized ROS-mediated anti-tumor effects of regorafenib in CRC cells. Furthermore, mouse xenograft models demonstrated that synergistic anti-tumor effects of combined treatment with regorafenib and oxaliplatin. This study provided solid experimental evidences for the combined treatment with regorafenib and oxaliplatin in CRC.

Selenoprotein S silencing triggers mouse hepatoma cells apoptosis and necrosis involving in intracellular calcium imbalance and ROS-mPTP-ATP

Selenoprotein S (SelenoS) is one of the cellular endoplasmic reticulum (ER) and membrane located selenoproteins, and it has the main functions of anti-oxidation, anti-apoptosis and anti-ER stress. To investigate the effect of SelenoS silencing on mouse hepatoma cell death and the intracellular biological function of SelenoS, we knocked down SelenoS in Hepa1-6 cells, and detected ER stress, intracellular calcium homeostasis, mitochondrial dynamics, apoptosis and necrosis. To further explore whether reactive oxygen species (ROS) has an effect on apoptosis and necrosis under SelenoS silencing, we used NAC (2.5 mM) to pretreat cells, and detected ΔΨm, ATP, and apoptosis and necrosis rates. SelenoS silencing broke the intracellular calcium homeostasis, induced mitochondrial dynamic disorder, ROS accumulation, loss of ΔΨm and ATP, and triggered apoptosis and necrosis in mouse hepatoma cells. The clearance of ROS alleviated the loss of ΔΨm and ATP caused by silencing of SelenoS, reduced cell necrosis and increased apoptosis. However, SelenoS silencing did not cause ER stress in Hepa1-6 cells. These results indicate that SelenoS silencing triggers mouse hepatoma cells apoptosis and necrosis through affecting intracellular calcium homeostasis and ROS-mPTP-ATP participates in cell death transformation from apoptosis to necrosis to rise damage.

Interplay between autophagy and apoptosis in selenium deficient cardiomyocytes in chicken

Dietary selenium (Se) deficiency can cause heart dysfunction, however the exact mechanism remains unclear. To understand this mechanism, 180day-old chicks, divided into two groups, C (control group) and L (low Se group), were fed with either a Se-sufficient (0.23mg/kg) or Se-deficient (0.033mg/kg) diets for 25days, respectively. Heart tissues and blood samples were collected. In L group, the activities of serum creatine kinase (CK) and creatine kinase-myoglobin (CK-MB) increased and typical ultrastructural apoptotic features were observed. Se deficiency up-regulated the mRNA levels of Cysteinyl aspartate specific proteinase 3 (Caspase-3), Cysteinyl aspartate specific proteinase 8 (Caspase-8), Cysteinyl aspartate specific proteinase 9 (Caspase-9), B cell lymphoma/leukemia 2 (Bcl-2), Bcl-2 Associated X Protein (Bax), (P<0.05), whereas, the mRNA levels of Microtubuleassociated protein light chains 3-1 (LC3-1), Autophagy associated gene 5 (ATG-5), Mammalian target of rapamycin (mTOR), Dynein and Becline-1 were down-regulated (P<0.05). Noticeably, Microtubuleassociated protein light chains 3-2 (LC3-2) mRNA level increased (P<0.05) by 20%. Western blot results showed that Se deficiency decreased the expression of Becline-1 and LC3-1 protein, however, the expression of Bax, Caspase-3 and Cysteinyl aspartate specific proteinase 12 (Caspase-12) increased at protein levels. The present study revealed that Se deficiency induced apoptosis while inhibited autophagy in chicken cardiomyocytes through Bax/Bcl-2 inhibition and caspases-mediated cleavage of Becline-1. Moreover, correlation analysis illustrates that apoptosis and autophagy might function contradictorily. Altogether we conclude that Se deficient chicken cardiomyocytes experienced apoptosis rather than autophagy which is considered to be more pro-survival.

Role of Hydrogen Sulfide on Autophagy in Liver Injuries Induced by Selenium Deficiency in Chickens

Selenium (Se) is an indispensable trace mineral that was associated with liver injuries in animal models. Hydrogen sulfide (H₂S) is involved in many liver diseases, and autophagy can maintain liver homeostasis with a stress stimulation. However, little is known about the correlation between H₂S and autophagy in the liver injury chicken models induced by Se deficiency. In this study, we aimed to investigate the correlation between H₂S and autophagy in the liver injury chicken models. We randomly divided 120 1-day-old chickens into two equal groups. The control group was fed with complete food with a Se content of 0.15 mg/kg, and the Se-deficiency group (lab group) was fed with a Se-deficient diet with a Se content of 0.033 mg/kg. When the time comes to 15, 25, and 35 days, the chickens were sacrificed (20 each). The liver tissues were gathered and examined for pathological observations, the mRNA and protein levels of H₂S synthases (CSE, CBS, and 3-MST) and the mRNA and protein levels of autophagy-related genes. The results showed that the expression of CSE, CBS, and 3-MST and H₂S production were higher in the lab group than in the control group. Swellings, fractures, and vacuolizations were visible in the mitochondria cristae in the livers of the lab group and autophagosomes were found as well. In addition, the expression of autophagy-related genes (ATG5, LC3-I, LC3-II, Beclin1, and Dynein) was higher in the lab group than in the control group (p < 0.05) while TOR decreased significantly in the lab group (p < 0.05). The results showed that H₂S and autophagy were involved in the liver injury chicken models, and H₂S was correlated with autophagy.

Impact of Cu, Zn-Superoxide Dismutase and Se-Dependent Glutathione Peroxidase-1 Knockouts on Acetaminophen-Induced Cell Death and Related Signaling in Murine Liver

There is increasing evidence showing dual functions of antioxidant enzymes in coping with reactive oxygen species (ROS) versus reactive nitrogen species (RNS). The objective of this study was to compare the impacts of knockout of Cu, Zn-superoxide dismutase (SOD1) and Se-dependent glutathione peroxidase-1 (GPX1) on cell death and related signaling mediated by acetaminophen (APAP), a RNS inducer in liver. Two groups of young adult knockout mice (SOD1−-/– and GPX1−-/–), along with their wild types (WT), were killed 5 hrs after an ip injection of saline or APAP (300 mg/kg body wt). While the WT mice showed more hepatic necrosis and DNA breakage than the GPX1−-/– mice, the SOD1−-/– mice had essentially no positive response compared with their saline-injected controls. The APAP treatment activated liver c-jun N-terminal kinase (JNK) in the WT and GPX1−-/– mice, but not in the SOD1−-/– mice. The APAP-induced changes in other cell death-related signal proteins such as p21, caspase-3, and poly(ADP-ribose) polymerase (PARP) also were obviated in the SOD1−-/– mice. In conclusion, knockout of GPX1 did not potentiate APAP-induced cell death and related signaling, whereas the SOD1 null blocked APAP-induced hepatic JNK phosphorylation and cell death.

Paradoxical Roles of Antioxidant Enzymes: Basic Mechanisms and Health Implications

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated from aerobic metabolism, as a result of accidental electron leakage as well as regulated enzymatic processes. Because ROS/RNS can induce oxidative injury and act in redox signaling, enzymes metabolizing them will inherently promote either health or disease, depending on the physiological context. It is thus misleading to consider conventionally called antioxidant enzymes to be largely, if not exclusively, health protective. Because such a notion is nonetheless common, we herein attempt to rationalize why this simplistic view should be avoided. First we give an updated summary of physiological phenotypes triggered in mouse models of overexpression or knockout of major antioxidant enzymes. Subsequently, we focus on a series of striking cases that demonstrate "paradoxical" outcomes, i.e., increased fitness upon deletion of antioxidant enzymes or disease triggered by their overexpression. We elaborate mechanisms by which these phenotypes are mediated via chemical, biological, and metabolic interactions of the antioxidant enzymes with their substrates, downstream events, and cellular context. Furthermore, we propose that novel treatments of antioxidant enzyme-related human diseases may be enabled by deliberate targeting of dual roles of the pertaining enzymes. We also discuss the potential of "antioxidant" nutrients and phytochemicals, via regulating the expression or function of antioxidant enzymes, in preventing, treating, or aggravating chronic diseases. We conclude that "paradoxical" roles of antioxidant enzymes in physiology, health, and disease derive from sophisticated molecular mechanisms of redox biology and metabolic homeostasis. Simply viewing antioxidant enzymes as always being beneficial is not only conceptually misleading but also clinically hazardous if such notions underpin medical treatment protocols based on modulation of redox pathways.

The role of nitric oxide and autophagy in liver injuries induced by selenium deficiency in chickens

Selenium (Se) is recognized as a necessary trace mineral in animal diets, including those of birds.

Effect of maternal morphine sulfate exposure on neuronal plasticity of dentate gyrus in Balb/c mice offspring

This study carried out to evaluate the effects of maternal morphine exposure during gestational and lactation period on the neuronal cells of dentate gyrus in 18 and 32 days Balb/c mice offspring. In this experimental study 10 female mice were randomly allocated into cases and controls. In experimental group, animals were received morphine sulfate 10 mg/kg/body weight intraperitoneally during 7 days before mating, gestational period (GD0-21), 18 and 32 days after delivery. The control animals were received an equivalent volume normal saline. Cerebrum of six infant for each group were removed and stained with cresyl violet and monoclonal anti-neuronal nuclei (NeuN) antibody. Quantitative computer-assisted morphometric study was done on dentate gyrus of hippocampus. In the P18 mice, the numbers of granular cells in dentate gyrus medial blade and dentate gyrus lateral blade significantly reduced from 171.45 +/- 4.2 and 174.51 +/- 3.1 cells in control group to 153.32 +/- 2.8 and 151.23 +/- 3.2 cells in 10000 microm2 area of granular layer in treated group (p < 0.001). In P32 mice the numbers of granular cells in mb and lb of dentate gyrus significantly decreased from 155.31 +/- 4.1 and 153.77 +/- 3.4 in control group to 138.33 +/- 4.5 and 135.13 +/- 4.3 in treated group, respectively (p < 0.001). The granular layer thickness in mb and lb area of dentate gyrus significantly reduced in treated mice in compared to controls in P18 and P32 mice (p < 0.05). This study revealed that morphine administration before, during pregnancy and lactation period causes neuronal cells loss of dentate gyrus in 18 and 32 days old infant mice.

Effect of oxygen free radicals and nitric oxide on apoptosis of immune organ induced by selenium deficiency in chickens

Selenium is an essential element with antioxidant roles in immune regulation, but there is little understanding of how Se acts in apoptosis in the immune organs of birds. The aim of study was to evaluate the influence of Se deficiency on oxygen free radicals, NO and apoptosis in immune organ of chickens. 160 1-day-old chickens were randomly assigned to two groups of 80 each and were fed on a low-Se diet (0.032 mg/kg Se) or a control diet (0.282 mg/kg Se), respectively. OFR production in blood was determined on days 30, 45, 60 and 75, respectively. The iNOS-NO system activity in immune organ (thymus, spleen, bursa of fabricius) was identified by NO content and NOS activity assay on days 30, 45, 60 and 75, respectively. Apoptosis was measured by DNA ladder analysis, ultrastructural observations, TdT-mediated dUTP nick end labeling TUNEL assay and flow cytometric analysis of apoptotic DNA. The transcription of factor-associated suicide, caspase-3 mRNA was tested by fluorescence quantitative PCR. The results showed that OFR production, NO and inducible NO synthases (iNOS) activity in the low-Se group were significantly increased (p < 0.05) than in the control group. In addition, apoptosis was observed in chicken immune organ in the low-Se group. The degree and the number of apoptotic cells rose in a time-dependent manner. The expression of Fas and caspase-3 mRNA increased (p < 0.05) than in the control group. It indicated that the oxidative stress and NO played a causative role in the apoptosis of immune tissues induced by selenium deficiency.

Low selenium diet alters cell cycle phase, apoptotic population and modifies oxidative stress markers of spleens in broilers

The purpose of this 42-day study was to investigate the effects of low selenium (Se) on histopathological changes of spleen, cell cycle and apoptosis of splenocytes, and oxidative status of the spleen. One hundred twenty 1-day-old avian broilers were randomly divided into two groups of 60 each and were fed on a low Se diet (0.0342 mg/kg Se) or a control diet (0.2 mg/kg Se), respectively. The weight and relative weight of the spleen were significantly decreased in the low Se group when compared with those of the control group. Histopathologically, splenic lesions in low-Se chicken were characterized by lymphocyte depletion and congestion of red pulp. As measured by flow cytometry, splenocytes in G(0)/G(1) phase were significantly increased, while splenocytes in S phase and G(2) + M phase were obviously decreased in the low Se group. The percentage of apoptotic splenocytes was greatly increased in the low Se group when compared with that of control group. At the same time, the occurrence frequencies of apoptotic splenocytes was markedly increased in the low Se group with the appearance of condensed nucleus ultrastructurally. Oxidative stress in the spleens of the low Se group was evidenced by decrease in glutathione peroxidase and catalase activities and increase in malondialdehyde contents. The results showed that low Se diet intake caused increased apoptosis, arrested cell cycle, and obvious oxidative stress, which provided a possible pathway for the injured structure and immune function of the spleen in chickens.

Purkinje cells loss in off spring due to maternal morphine sulfate exposure: a morphometric study

The toxic effects of morphine sulfate in the adult cerebral cortex and one-day neonatal cerebellum have been studied. This study was carried out to evaluate the effect of maternal morphine exposure during gestational and lactation period on the Purkinje cells and cerebellar cortical layer in 18- and 32-day-old mice offspring. Thirty female mice were randomly allocated into cases and controls. In cases, animals received morphine sulfate (10 mg/kg/body weight intraperitoneally) during the 7 days before mating, gestational day (GD 0-21) 18 or 32. The controls received an equivalent volume of saline. The cerebellum of six infants for each group was removed and each was stained with cresyl violet. Quantitative computer-assisted morphometric study was done on cerebellar cortex. The linear Purkinje cell density in both experimental groups (postnatal day [P]18, 23.40±0.5; P32, 23.45±1.4) were significantly reduced in comparison with the control groups (P18, 28.70±0.9; P32, 28.95±0.4) (P<0.05). Purkinje cell area, perimeter and diameter at apex and depth of simple lobules in the experimental groups were significantly reduced compared to the controls (P<0.05). The thickness of the Purkinje layer of the cerebellar cortex was significantly reduced in morphine treated groups (P<0.05). This study reveals that morphine administration before pregnancy, during pregnancy and during the lactation period causes Purkinje cells loss and Purkinje cell size reduction in 18- and 32-day-old infant mice.

Selenium and its' role in the maintenance of genomic stability

Selenium (Se) is an essential micronutrient for humans, acting as a component of the unusual amino acids, selenocysteine (Se-Cys) and selenomethionine (Se-Met). Where Se levels are low, the cell cannot synthesise selenoproteins, although some selenoproteins and some tissues are prioritised over others. Characterised functions of known selenoproteins, include selenium transport (selenoprotein P), antioxidant/redox properties (glutathione peroxidases (GPxs), thioredoxin reductases and selenoprotein P) and anti-inflammatory properties (selenoprotein S and GPx4). Various forms of Se are consumed as part of a normal diet, or as a dietary supplement. Supplementation of tissue culture media, animal or human diets with moderate levels of certain Se compounds may protect against the formation of DNA adducts, DNA or chromosome breakage, and chromosome gain or loss. Protective effects have also been shown on mitochondrial DNA, and on telomere length and function. Some of the effects of Se compounds on gene expression may relate to modulation of DNA methylation or inhibition of histone deacetylation. Despite a large number of positive effects of selenium and selenoproteins in various model systems, there have now been some human clinical trials that have shown adverse effects of Se supplementation, according to various endpoints. Too much Se is as harmful as too little, with animal models showing a "U"-shaped efficacy curve. Current recommended daily allowances differ among countries, but are generally based on the amount of Se necessary to saturate GPx enzymes. However, increasing evidence suggests that other enzymes may be more important than GPx for Se action, that optimal levels may depend upon the form of Se being ingested, and vary according to genotype. New paradigms, possibly involving nutrigenomic tools, will be necessary to optimise the forms and levels of Se desirable for maximum protection of genomic stability in all humans.

Low dietary selenium induce increased apoptotic thymic cells and alter peripheral blood T cell subsets in chicken

The purpose of this 42-day study was to investigate the effects of low selenium (Se) on immune function by determining histopathological changes of thymus, apoptosis of thymic cells, and subpopulation of peripheral blood T cells. One hundred twenty 1-day-old avian broilers were randomly assigned to two groups of 60 each and were fed on a low Se diet (0.0342 mg/kg Se) or a control diet (0.2 mg/kg Se), respectively. The relative weight of thymus was significantly decreased in low Se group from 21 days of age in time-dependent manner when compared with that of control group. Histopathologically, lymphopenia in the cortex and medulla of thymus was observed in low Se group. In comparison with those of control group, the percentage of Annexin-V positive cells was increased, and the percentages of CD3(+) and CD3(+)CD8(+) T cells of the peripheral blood were decreased in low Se group, as measured by flow cytometry. These data suggested that low dietary Se induced histological lesions of thymus, increased apoptosis of thymic cells, and decreased T cell subsets. The cellular immune function was finally impaired in broilers.

The cell cycle arrest and apoptosis of bursa of Fabricius induced by low selenium in chickens

The purpose of this 42-day study was to investigate the effects of low selenium (Se) on immune function by determining cell cycle and apoptosis of bursa of Fabricius. One hundred twenty 1-day-old avian broilers were randomly assigned to two groups of 60 each and were fed on a low Se diet (0.0342 mg/kg Se) or a control diet (0.2 mg/kg Se), respectively. The relative weight of bursa was significantly decreased in low Se group from 28 days of age in time-dependent manner when compared with that of control group. Cell cycle analysis by flow cytometry showed that low Se caused an increase in G₀G₁ phase cells that corresponded to a decrease in S phase cells in bursa of Fabricius. Ultrastructurally, mitochondria injury and increased apoptotic cells with condensed nuclei were observed. Low Se increased the percentage of Annexin V-positive cells, as measured by flow cytometry, in comparison with that of control group. These data suggested that low Se diet restrained the development of bursa of Fabricius by cell cycle arrest and apoptosis.

Histopathological and biochemical changes of morphine sulphate administration on the cerebellum of albino rats

In this study the long-term effects of morphine sulphate treatment (MST) on histopathological and biochemical changes in the cerebellum was assessed in albino rats. Normal saline (5ml) was given orally as placebo in the control group (n=25). Morphine groups received morphine orally at a dose level of 5mg/kg body weight day after day for 10, 20 and 30 days (n=25/group). Light microscopy revealed that the molecular layer showed vacuolation. The Purkinje cells lost their specific shaped appearance, decreased in size and numbers. The granular cells highly degenerated. Electron microscopy revealed fragmentation of the cisterns of the both types of endoplasmic reticulum, resulted in a progressive depletion of total protein contents as well as general carbohydrates in all treated groups as supported by histochemical observation. Obvious destruction of mitochondrial inner membrane and cristae mediate cell death. Also, abnormal nucleus with deformed perforated nuclear membrane and deformation of the plasma membrane with degeneration of the synapses could interpreted as a sign of necrosis. Biochemical analysis revealed that dopamine (DA) and norepinephrine (NE) were significantly decreased in four brain areas (cortex striatum, thalamus/hypothalamus, and cerebellum). In contrast, serotonin (5-HT) level was increased in these brain regions; with an exception of 5-HT on day 10 and neurotransmitter levels in the pons were unaffected. The quantitative analysis showed a significant decrease (P<0.05) in the diameter of Purkinje cells and in the thickness of both molecular and granular layers treated groups. Morphine sulphate induces may be a cell death or necrosis in the rat cerebellum and modulating neurotransmitter system. Our findings pointed out the risk of increased cerebellum damage due to long-term of morphine use.

The hepatic microcirculation: mechanistic contributions and therapeutic targets in liver injury and repair

The complex functions of the liver in biosynthesis, metabolism, clearance, and host defense are tightly dependent on an adequate microcirculation. To guarantee hepatic homeostasis, this requires not only a sufficient nutritive perfusion and oxygen supply, but also a balanced vasomotor control and an appropriate cell-cell communication. Deteriorations of the hepatic homeostasis, as observed in ischemia/reperfusion, cold preservation and transplantation, septic organ failure, and hepatic resection-induced hyperperfusion, are associated with a high morbidity and mortality. During the last two decades, experimental studies have demonstrated that microcirculatory disorders are determinants for organ failure in these disease states. Disorders include 1) a dysregulation of the vasomotor control with a deterioration of the endothelin-nitric oxide balance, an arterial and sinusoidal constriction, and a shutdown of the microcirculation as well as 2) an overwhelming inflammatory response with microvascular leukocyte accumulation, platelet adherence, and Kupffer cell activation. Within the sequelae of events, proinflammatory mediators, such as reactive oxygen species and tumor necrosis factor-alpha, are the key players, causing the microvascular dysfunction and perfusion failure. This review covers the morphological and functional characterization of the hepatic microcirculation, the mechanistic contributions in surgical disease states, and the therapeutic targets to attenuate tissue injury and organ dysfunction. It also indicates future directions to translate the knowledge achieved from experimental studies into clinical practice. By this, the use of the recently introduced techniques to monitor the hepatic microcirculation in humans, such as near-infrared spectroscopy or orthogonal polarized spectral imaging, may allow an early initiation of treatment, which should benefit the final outcome of these critically ill patients.

In vitro effects of selenium deficiency on West Nile virus replication and cytopathogenicity

Background

Selenium (Se) deficiency plays an important role in viral pathogenesis. To understand the effects of Se deficiency on West Nile virus (WNV) infection, we analyzed cytopathogenicity, apoptosis and viral replication kinetics, using a newly developed Se-deficient cell culture system.

Results

Both Vero and SK-N-SH cells grown in Se-deficient media exhibited a gradual loss of glutathione peroxidase (GPx1) activity without any significant effect on cell growth and viability. In SK-N-SH cells, Se deficiency had no effect on the expression of key antioxidant enzymes, including manganese- and copper-zinc superoxide dismutase (MnSOD and CuZnSOD), catalase and inducible nitric oxide synthase, whereas Vero cells demonstrated a significant increase in the expression of MnSOD and an overall increase in oxidative stress (OS) at day 7 post-induction of Se deficiency. At 2 days after infection with WNV, CPE and cell death were significantly higher in WNV-infected Se-deficient Vero cells, compared to WNV-infected control cells. Furthermore, WNV-induced apoptosis was significantly heightened in Se-deficient cells and was contributed by loss of mitochondrial membrane potential and increased caspase activity. However, no significant difference was found in WNV copy numbers between control, Se-adequate and Se-deficient cell cultures.

Conclusion

Overall results demonstrate that the in vitro Se-deficient model can be used to study responses of WNV to this essential nutrient. Although Se deficiency has no in vitro effect on WNV replication kinetics, adequate Se is presumably critical to protect WNV-infected cells against virus-induced cell death.

Combination of selenium and three naturally occurring antioxidants administration protects D-galactosamine-induced liver injury in rats

D-Galactosamine (D-GaIN) is a highly selective hepatotoxin that causes liver injury similar to human viral hepatitis via depletion of uridine nucleotides, which subsequently diminishes synthesis of RNA and proteins. The aim of this study was to investigate the role of selenium, ascorbic acid, beta-carotene, and alpha-tocopherol on D-GaIN-induced liver injury of rats by morphological and immunohistochemical means. In this study, Sprague-Dawley female rats were divided into four groups. Group I consists of rats injected physiologic saline solution intraperitoneally. Group II consists of rats given selenium (0.2 mg/kg per day), ascorbic acid (100 mg/kg per day), beta-carotene (15 mg/kg per day), and alpha-tocopherol (100 mg/kg per day) for 3 days via gavage method. Group III consists of the single dose of D-GaIN (500 mg/kg)-injected animals. Group IV are the D-GaIN-injected animals given the same antioxidant combination. In situ terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate nick-end labeling (TUNEL) assay was applied to determine apoptosis for paraffin sections of the liver samples. Moreover, caspase-3 and proliferating cell nuclear antigen antibody were applied for paraffin sections. In the group given D-GaIN, apoptotic cells with TUNEL assays and caspase-3 activity, which are liver injury markers induced by D-GaIN, the hepatocyte proliferation with cell proliferation assay increased. However, selenium and other three antioxidants combination clearly suppressed an increase in apoptotic cells with TUNEL assay and caspase-3 activity. In addition, it suppressed D-GaIN-induced cell proliferation in the liver. As a result, these results indicate that selenium and three naturally occurring antioxidants shows a protective effect against liver injury induced by D-GaIN. These results suggest that supplementation with the combination of selenium, ascorbic acid, beta-carotene, and alpha-tocopherol may help prevent the development of liver injury.

Selenium deficiency activates mouse liver Nrf2-ARE but vitamin E deficiency does not

Selenium (Se) and vitamin E are antioxidant micronutrients. Se functions through selenoproteins and vitamin E reacts with oxidizing molecules in membranes. The relationship of these micronutrients with the Nrf2-antioxidant response element (ARE) pathway was investigated using ARE-reporter mice and Nrf2-/- mice. Weanling males were fed Se-deficient (0 Se), vitamin E-deficient (0 E), or control diet for 16 or 22 weeks. The ARE reporter was elevated 450-fold in 0 Se liver but was not elevated in 0 E liver. Antioxidant enzymes induced by Nrf2-ARE (glutathione S-transferase (GST), NAD(P)H quinone oxidoreductase (NQOR), and heme oxygenase-1 (HO-1)) were elevated in 0 Se livers but not in 0 E livers. Deletion of Nrf2 had varying effects on the inductions, with GST induction being abolished by it but induction of NQOR and HO-1 still occurring. Thus, Se deficiency, but not vitamin E deficiency, induces a number of enzymes that protect against oxidative stress and modify xenobiotic metabolism through Nrf2-ARE and other stress-response pathways. We conclude that Se deficiency causes cytosolic oxidative stress but that vitamin E deficiency does not. This suggests that the oxidant defense mechanisms in which these antioxidant nutrients function are independent of one another.

Metabolic regulation and function of glutathione peroxidase-1

Glutathione peroxidase-1 (GPX1) represents the first identified mammalian selenoprotein, and our understanding in the metabolic regulation and function of this abundant selenoenzyme has greatly advanced during the past decade. Selenocysteine insertion sequence-associating factors, adenosine, and Abl and Arg tyrosine kinases are potent, Se-independent regulators of GPX1 gene, protein, and activity. Overwhelming evidences have been generated using the GPX1 knockout and transgenic mice for the in vivo protective role of GPX1 in coping with oxidative injury and death mediated by reactive oxygen species. However, GPX1 exerts an intriguing dual role in reactive nitrogen species (RNS)-related oxidative stress. Strikingly, knockout of GPX1 rendered mice resistant to toxicities of drugs including acetaminophen and kainic acid, known as RNS inducers. Intracellular and tissue levels of GPX1 activity affect apoptotic signaling pathway, protein kinase phosphorylation, and oxidant-mediated activation of NFkappaB. Data are accumulating to link alteration or abnormality of GPX1 expression to etiology of cancer, cardiovascular disease, neurodegeneration, autoimmune disease, and diabetes. Future research should focus on the mechanism of GPX1 in the pathogeneses and potential applications of GPX1 manipulation in the treatment of these disorders.

Differential effects of paraquat on oxidative stress parameters and polyamine levels in two freshwater invertebrates

Paraquat is still a widely used herbicide in several countries. Its toxic action on plants occurs through a one-electron reduction interfering with the photosynthesis process. By a similar reaction, the herbicide may induce peroxidation processes in non-target animal species. Furthermore, paraquat may interfere with the cellular transport of polyamines. The aim of this work was to investigate some aspects related to paraquat-induction of oxidative stress (lipoperoxidation, enzymatic activities of catalase and superoxide dismutase) and also the levels of polyamines (putrescine, spermidine and spermine) in two species of freshwater invertebrates, the oligochaete Lumbriculus variegatus and the gastropod Biomphalaria glabrata. The results showed that both organisms elicited differential responses. In addition, the data suggested that polyamines may play an important role against lipoperoxidation processes.

From selenium to selenoproteins: synthesis, identity, and their role in human health

The requirement of the trace element selenium for life and its beneficial role in human health has been known for several decades. This is attributed to low molecular weight selenium compounds, as well as to its presence within at least 25 proteins, named selenoproteins, in the form of the amino acid selenocysteine (Sec). Incorporation of Sec into selenoproteins employs a unique mechanism that involves decoding of the UGA codon. This process requires multiple features such as the selenocysteine insertion sequence (SECIS) element and several protein factors including a specific elongation factor EFSec and the SECIS binding protein 2, SBP2. The function of most selenoproteins is currently unknown; however, thioredoxin reductases (TrxR), glutathione peroxidases (GPx) and thyroid hormone deiodinases (DIO) are well characterised selenoproteins involved in redox regulation of intracellular signalling, redox homeostasis and thyroid hormone metabolism. Recent evidence points to a role for selenium compounds as well as selenoproteins in the prevention of some forms of cancer. A number of clinical trials are either underway or being planned to examine the effects of selenium on cancer incidence. In this review we describe some of the recent progress in our understanding of the mechanism of selenoprotein synthesis, the role of selenoproteins in human health and disease and the therapeutic potential of some of these proteins.

The functional haplotype of peptidylarginine deiminase IV (S55G, A82V and A112G) associated with susceptibility to rheumatoid arthritis dominates apoptosis of acute T leukemia Jurkat cells

Peptidylarginine deiminase IV (PADI4) posttranslationally converts peptidylarginine to citrulline. It plays an essential role in immune cell differentiation and apoptosis. A haplotype of single-nucleotide polymorphisms (SNPs) in PADI4 is functionally relevant as a rheumatoid arthritis (RA) gene. It could increase enzyme activity leading to raised levels of citrullinated protein and stimulating autoantibody. Previously, our study showed that inducible PADI4 causes haematopoietic cell death. Herein, we further investigate whether RA risk PADI4 haplotype (SNP PADI4; S55G, A82V and A112G) and the increase of its enzymatic activity induce apoptosis. In the tetracycline (Tet)-On Jurkat T cells, ionomycin (Ion) only treatment didn't induce apoptosis however it promoted inducible PADI4-decreased cell viability and -enhanced apoptosis. Through in vitro and in vivo PADI enzyme activity assay, we demonstrated that PADI4 enzyme activity of SNP PADI4 was higher than RA non-risk PADI4 haplotype (WT PADI4). The effect of SNP PADI4-induced apoptosis was superior to WT PADI4. In addition, both Ion and SNP PADI4 synergistically provoked apoptosis were compared with both Ion and WT PADI4. Concurrently, in the conditionally inducible SNP PADI4 cells of Ion treatment-induced apoptosis, not only the expression of Bcl-xL was down-regulated and Bax up-regulated, but also cytochrome c was released from mitochondria to cytoplasm in significant amounts. Western blotting data showed the increase in apoptosomal caspase activation during programmed cell death in the inducible SNP PADI4 cells subsequent to Ion treatment. These data demonstrated that both SNP PADI4 increasing their enzyme activity could enhance apoptosis through the mitochondrial pathway and further provide a conceivable explanation in the pathogenesis of RA following the upregulation of PADI4 activity in its SNPs.

Acute oxidative stress is associated with cell proliferation in the mouse liver

Oxidative stress is known to produce tissue injury and to activate various signaling pathways. To investigate the molecular events linked to acute oxidative stress in mouse liver, we injected a toxic dose of paraquat. Liver necrosis was first observed, followed by histological marks of cell proliferation. Concomitantly, activation of the MAP kinase pathway and increased levels of the anti-apoptotic protein Bcl-XL were observed. Gene expression profiles revealed that the differentially expressed genes were potentially involved in cell proliferation. These data suggest that paraquat-induced acute oxidative stress triggers the activation of regeneration-related events in the liver.

Selenoprotein deficiency accelerates prostate carcinogenesis in a transgenic model

Considerable animal and human data have indicated that selenium is effective in reducing the incidence of several different types of cancer, including that of the prostate. However, the mechanism by which selenium inhibits carcinogenesis remains unknown. One possibility is that dietary selenium influences the levels of selenium-containing proteins, or selenoproteins. Selenoproteins contain selenium in the form of selenocysteine and perform a variety of cellular functions, including antioxidant defense. To determine whether the levels of selenoproteins can influence carcinogenesis independent of selenium intake, a unique mouse model was developed by breeding two transgenic animals: mice with reduced selenoprotein levels because of the expression of an altered selenocysteine-tRNA (i6A-) and mice that develop prostate cancer because of the targeted expression of the SV40 large T and small t oncogenes to that organ [C3(1)/Tag]. The resulting bigenic animals (i6A-/Tag) and control WT/Tag mice were assessed for the presence, degree, and progression of prostatic epithelial hyperplasia and nuclear atypia. The selenoprotein-deficient mice exhibited accelerated development of lesions associated with prostate cancer progression, implicating selenoproteins in cancer risk and development and raising the possibility that selenium prevents cancer by modulating the levels of these selenoproteins.

Low concentrations of paraquat induces early activation of extracellular signal-regulated kinase 1/2, protein kinase B, and c-Jun N-terminal kinase 1/2 pathways: role of c-Jun N-terminal kinase in paraquat-induced cell death

Paraquat is a herbicide with a potential risk to induce parkinsonism due to its demonstrated neurotoxicity and its strong structural similarity to 1-methyl-4-phenylpyridinium (MPP(+)), a well-known neurotoxin which causes a clinical syndrome similar to Parkinson's disease (PD). However, at present very little is known about the signaling pathways activated by paraquat in any cell system. In this study, we have investigated the effect of paraquat on extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun N-terminal kinase (JNK), and protein kinase B (PKB) activation in E18 cells. Low concentrations of paraquat stimulated very early increases in ERK1/2, JNK1/2, and PKB phosphorylation. The phosphatidylinositol 3-kinase (PI-3K) inhibitors wortmannin and LY 294002 (2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one) inhibited early paraquat-induced increases in PKB phosphorylation. Furthermore, early paraquat-mediated increases in ERK1/2 activation were sensitive to the mitogen-activated protein kinase kinase 1 (MEK1) inhibitor PD 98059 (2'-amino-3'-methoxyflavone), whereas JNK1/2 responses were blocked by the JNK1/2 inhibitor SP 600125 (anthra[1-9-cd]pyrazol-6(2H)-one). Pretreatment with wortmannin, LY 294002, or PD 98059 had no effect on paraquat cell death in E18 cells. In contrast, SP 600125 significantly decreased paraquat-induced cell death in E18 cells. In conclusion, we have shown that low concentrations of paraquat stimulate robust very early increases in ERK1/2, JNK1/2, and PKB phosphorylation in E18 cells. Furthermore, the data presented clearly suggest that inhibition of the JNK1/2 pathway protects E18 cells from paraquat-induced cell death and support the fact that inhibition of early activation of JNK1/2 can constitute a potential strategy in PD treatment.

Reduced antioxidant level and increased oxidative damage in intact liver lobes during ischaemia-reperfusion

AIM: To determine whether increased blood flow of the liver can cause oxidative stress and hepatocyte damage, and to elaborate methods suitable for measuring the antioxidant defence during hepatic surgery on rat model.

METHODS: In nembutal narcosis, the left lateral and the medial lobes of the liver were clipped for 45 min to make the total blood supply flow through the other lobes. Total antioxidant status, glutathione peroxidase and superoxide dysmutase activity, as well as the concentrations of diene conjugates and free sulphydril groups, H-donating ability and reducing power of the liver samples were determined. Chemiluminescent intensity of the liver was also measured. Metal ions (Al, Ca, Cu, Fe, Mg, Mn, Zn) and P and S concentrations of the liver were determined with an inductively coupled plasma optical emission spectrometer and Se content was measured by cathodic stripping voltammetry.

RESULTS: Glutathione peroxidase and superoxide dysmutase activities of the liver decreased significantly in the hyperemia group compared to those observed in the sham operated group. The level of total antioxidant status was also significantly lower in the hyperemia group. H-donating ability, reducing power and free sulphydril group concentration showed the same tendency. A significant correlation (P<0.05) was found between the changes in non-specific antioxidant activities. This pointed to simultaneous activity of the antioxidant defence system. Al, Cu, Mn, Zn, and S were lower in the hyperemia group than in the sham operated group when the levels of Ca, Fe, Mg, Se and P ions were higher during hyperemia.

CONCLUSION: Oxidative stress is one of the main factors for the injury of intact liver lobes during ischaemia-reperfusion.

Overexpression of human GPX1 modifies Bax to Bcl-2 apoptotic ratio in human endothelial cells

As they scavenge reactive oxygen species, antioxidants were studied for their ability to interfere with apoptotic processes. However, their mechanisms of action remain unclear. In this study, we measured the expression of two Bcl-2 family members, Bax and Bcl-2, in a human endothelial like cell-line overexpressing the organic hydroperoxide-scavenging enzyme glutathione peroxidase (GPX1), in the absence of any apoptotic/oxidant stimulus. ECV304 were stably transfected with the GPX1 cDNA and used for quantification of Bax (pro-apoptotic) and Bcl-2 (antiapoptotic) mRNA and protein levels, by quantitative RT-PCR and Western-blot. We found that, compared to control cells, cells from a clone showing a 13.2 fold increase in GPX1 activity had unchanged mRNA or protein Bcl-2 levels but expressed 42.6% and 46.1% less Bax mRNA and Bax protein respectively. Subsequently to Bax decrease, the Bax/Bcl-2 ratio, reflecting the apoptotic state of the cells, was also lower in cells overexpressing GPX1. Noticeably, the mRNA and the protein level of the cell-cycle protein p53, known to activate Bax expression, was unchanged. Our study showed that overexpressing an antioxidant gene such as GPX1 in endothelial cells is able to change the basal mRNA and protein Bax levels without affecting those of p53 and Bcl-2. This phenomenon could be useful to antiatherogenic therapies which use antioxidants with the aim of protecting the vascular wall against oxidative stress injury.

Effects of gpx4 haploid insufficiency on GPx4 activity, selenium concentration, and paraquat-induced protein oxidation in murine tissues

Selenium-dependent glutathione peroxidase-4 (GPx4) catalyzes the reduction of phospholipid hydroperoxides. Because a full gpx4 knockout is embryonic lethal, we examined the effect of deletion of one copy of gpx4 on the activities of three selenoperoxidases (GPx1, GPx3, and GPx4), selenium concentrations, and pro-oxidant-induced protein oxidation in various tissues of mice. A total of 32 gpx4 hemizygous (GPx4+/-) and wild-type (WT) mice (8- to 10-weeks old; 16 males and 16 females) were fed a selenium-adequate diet and given an intraperitoneal injection of paraquat (PQ; 24 mg/kg body wt) or phosphate-buffered saline (PBS). All mice were euthanized 4 hrs after injection to collect tissues for analyses. In PBS-treated mice, GPx4 activities in lung, liver, kidney, and testes of GPx4+/- mice were 24-39% lower (P < 0.05) than in WT mice. Among PQ-treated mice, only testis GPx4 activity in GPx4+/- mice was significantly lower (54% P < 0.05) than WT mice. Selenium concentration in testes, but not in other tissues, was reduced (34% P < 0.05) in GPx4+/- mice compared with WT mice, irrespective of treatment. Tissue GPx1 activities and plasma GPx3 and alanine aminotransferase (ALT) activities were unaffected by PQ treatment or gpx4 hemizygosity. Total protein carbonyl was elevated (73% P < 0.05) by PQ only in lung, and this effect of PQ was independent of genotypes. In conclusion, gpx4 haploid insufficiency reduced GPx4 activities and/or selenium concentrations, but had no effect on pro-oxidant-induced protein oxidation in various tissues of mice.

New roles for an old selenoenzyme: evidence from glutathione peroxidase-1 null and overexpressing mice

Cellular glutathione peroxidase-1 (GPX1) is the first identified and the most abundant selenoprotein in mammals. Although GPX1 has been widely considered to be a major antioxidant enzyme, there has been no direct evidence for such role in vivo until GPX1 transgenic and null mice became available 10 y ago. Using these new models, we demonstrated that GPX1 protects against oxidative stress mediated by reactive oxygen species (ROS), and the physiologic importance of this protection varies with insult level and body Se status. Full expression of GPX1 is needed, and overexpression of GPX1 is beneficial for Se-adequate mice to defend against severe oxidative stress. This function of GPX1 is associated with attenuating the prooxidant-induced oxidation of NADPH, NADH, lipid, and protein in various tissues. In Se-deficient mice, a minute amount of GPX1 activity (4% of adequate levels) protects against hepatic aponecrosis induced by mild oxidative stress. In contrast, knockout of GPX1 renders mice and their hepatocytes resistant to oxidative stress related to reactive nitrogen species (RNS). More intriguingly, mice overexpressing GPX1 develop insulin resistance and obesity, accompanied by a downregulation of insulin-mediated phosphorylations of insulin receptor and Akt protein. In conclusion, GPX1 seems to play contrasting roles in coping with ROS vs. RNS, and its metabolic functions extend beyond redox regulation.

Molecular chemoprevention by selenium: a genomic approach

Basic research and clinical chemoprevention trials support the protective role of selenium in cancer prevention but the mechanisms based on the molecular level remain to be fully defined. This mini-review focuses only on the elucidation of the molecular mechanisms of cancer prevention by selenium using the genomics approach; target organs discussed here are breast, prostate, colon and lung. The results described here support the utility of microarray technology in delineating the molecular mechanisms of cancer prevention by selenium. These results are based on studies employing human and rodent cell lines and tissues from animal models ranging from normal to frank cancer. The dose and the form of selenium are determining factors in cancer chemoprevention. The results of the microarray analysis reviewed here indicate that selenium, independent of its form and the target organ examined, alters several genes in a manner that can account for cancer prevention. Selenium can up regulate genes related to phase II detoxification enzymes, certain selenium-binding proteins and select apoptotic genes, while down regulating those related to phase I activating enzymes and cell proliferation. Independent of tissue type, selenium arrests cells in G1 phase of cell cycle, inhibits CYCLIN A, CYCLIN D1, CDC25A, CDK4, PCNA and E2F gene expressions while induces the expressions of P19, P21, P53, GST, SOD, NQO1, GADD153 and certain CASPASES. In addition to those described above, genes such as OPN, which is mainly involved in metastasis and recently reported to be down regulated by selenium, should be considered as potential molecular marker in clinical chemoprevention trials. Collectively, literature data indicate that some of these genes that were altered by selenium are also involved in the development of human cancers described in this review. It appears that androgen receptor status may influence the effect of selenium on gene expression profile in prostate cancer; whether estrogen receptor may influence the effect of selenium on gene expression in breast cancer requires further studies. Knowledge from gene array data in combination with proteomics approaches, using homogenous population of cell types with the aid of laser capture microdissection, may provide an individualized dimension of information on cancer risk and potential targets for its prevention. The molecular (genetic) biomarkers presented in this review will provide the foundation for future studies of the chemopreventive properties of structurally varied selenium compounds.

[WITHDRAWN] Overexpression of superoxide dismutase or glutathione peroxidase protects against the paraquat + maneb-induced Parkinson disease phenotype

Oxidative stress has been implicated in the pathogenesis of Parkinson disease based on its role in the cascade of biochemical changes that lead to dopaminergic neuronal death. This study analyzed the role of oxidative stress as a mechanism of the dopaminergic neurotoxicity produced by the combined paraquat and maneb model of the Parkinson disease phenotype. Transgenic mice overexpressing either Cu,Zn superoxide dismutase or intracellular glutathione peroxidase and non-transgenic mice were exposed to saline, paraquat, or the combination of paraquat + maneb twice a week for 9 weeks. Non-transgenic mice chronically exposed to paraquat + maneb exhibited significant reductions in locomotor activity, levels of striatal dopamine and metabolites, and dopaminergic neurons in the substantia nigra pars compacta. In contrast, no corresponding effects were observed in either Cu,Zn superoxide dismutase or glutathione peroxidase transgenic mice. Similarly, the increase in levels of lipid hydroperoxides in the midbrain and striatum of paraquat + maneb-treated non-transgenic mice was not detected in either Cu,Zn superoxide dismutase or glutathione peroxidase transgenic mice. To begin to determine critical pathways of paraquat + maneb neurotoxicity, the functions of cell death-inducing and protective mechanisms were analyzed. Even a single injection of paraquat + maneb in the non-transgenic treated group modulated several key pro- and anti-apoptotic proteins, including Bax, Bad, Bcl-xL, and upstream stress-induced cascade. Collectively, these findings support the assertion that protective mechanisms against paraquat + maneb-induced neurodegeneration could involve modulation of the level of reactive oxygen species and alterations of the functions of specific signaling cascades.

Selective Rescue of Selenoprotein Expression in Mice Lacking a Highly Specialized Methyl Group in Selenocysteine tRNA

Selenocysteine (Sec) is the 21st amino acid in the genetic code. Its tRNA is variably methylated on the 2'-O-hydroxyl site of the ribosyl moiety at position 34 (Um34). Herein, we identified a role of Um34 in regulating the expression of some, but not all, selenoproteins. A strain of knock-out transgenic mice was generated, wherein the Sec tRNA gene was replaced with either wild type or mutant Sec tRNA transgenes. The mutant transgene yielded a tRNA that lacked two base modifications, N(6)-isopentenyladenosine at position 37 (i(6)A37) and Um34. Several selenoproteins, including glutathione peroxidases 1 and 3, SelR, and SelT, were not detected in mice rescued with the mutant transgene, whereas other selenoproteins, including thioredoxin reductases 1 and 3 and glutathione peroxidase 4, were expressed in normal or reduced levels. Northern blot analysis suggested that other selenoproteins (e.g. SelW) were also poorly expressed. This novel regulation of protein expression occurred at the level of translation and manifested a tissue-specific pattern. The available data suggest that the Um34 modification has greater influence than the i(6)A37 modification in regulating the expression of various mammalian selenoproteins and Um34 is required for synthesis of several members of this protein class. Many proteins that were poorly rescued appear to be involved in responses to stress, and their expression is also highly dependent on selenium in the diet. Furthermore, their mRNA levels are regulated by selenium and are subject to nonsense-mediated decay. Overall, this study described a novel mechanism of regulation of protein expression by tRNA modification that is in turn regulated by levels of the trace element, selenium.

Molecular targets for bioactive food components

Mounting evidence points to dietary habits as an important determinant of cancer risk and tumor behavior. Although the linkages with diet are intriguing, the literature is also laden with inconsistencies. The reasons for these inconsistencies are likely multi-factorial, but probably reflect variations in the ability of bioactive constituents to reach or affect critical molecular targets. Fluctuations in the foods consumed not only influence the intake of particular bioactive components, but may alter metabolism and potentially influence the sites of action of both essential and nonessential nutrients. Genetic polymorphisms are increasingly recognized as another factor that can alter the response to dietary components (nutritional transcriptomic effect) by influencing the absorption, metabolism, or sites of action. Likewise, variation in DNA methylation patterns and other epigenetic events that influence overall gene expression can be influenced by dietary intakes. Furthermore, variation in the ability of food components to increase or depress gene expression (nutrigenomic effect) may account for some of the observed inconsistencies in the response to dietary change. Because a host of food components are recognized to influence phosphorylation and other posttranslational events, it is also likely that these and other proteomic modifications account for at least part of the response and variation that is reported in the literature. Collectively, it is clear that bioactive food components can influence a number of key molecular events that are involved in health and disease resistance. As the era of molecular nutrition unfolds, a greater understanding of how these foods and components influence cancer will surely arise. Such information will be critical in the development of effective tailored strategies for reducing cancer burden. Just as important, however, is that as this information unfolds it is utilized within a responsible bioethical framework.

Oxidative stress is the master operator of drug and chemically-induced programmed and unprogrammed cell death: Implications of natural antioxidants in vivo

ROS, RNS, BRIs and ROS-RNS hybrids are produced during drug or chemical metabolism in vivo. These reactive species are instrumental to the culmination of cellular oxidative stress (OS). OS, once turned on, does not spare any vital intracellular macromolecule, such as glutathione, DNA, RNA, proteins, enzymes, lipids and ATP. Since concentration gradients of such components are very delicately balanced for normal cellular functioning, a gross perturbation leads to cell injury and cell death. Abundant evidence now suggests that intracellular antioxidants keep OS in check and maintain homeostasis. Our laboratory has focused on the role of OS in orchestrating various forms of cell death during drug and chemically-induced target organ toxicity and their counteraction by various natural or synthetic antioxidants in in vivo models. Despite complexity of the in vivo models, results show that metabolism of xenobiotics are invariably associated with different degrees of OS and natural antioxidants such as grape seed extract, bitter melon extract (Momordica charantia) and N-acetylcysteine (NAC) which were very effective in counteracting organ toxicities by minimizing events linked to OS (lipid peroxidation and total glutathione), and CAD-mediated DNA fragmentation. Phytoextract exposure rescued cells from toxic assaults, protected genomic integrity, and minimized apoptotic, necrotic and apocrotic (oncotic necrosis) cell deaths. Pre-exposure mode was more effective than post-exposure route. Overall scenario suggests that OS may have been the prime modulator of death and/or survival programs, whereas, antioxidants may have imparted a dual role in either erasing death signals or reviving survival signals, and a combination of antioxidants may be more beneficial than a single entity to influence a number of intracellular events operating simultaneously to neutralize chaotic toxicological consequences.