Effect of glutathione peroxidase activity on lipid peroxidation in biological membranes

Effects of diphenhydramine on crayfish cytochrome P450 activity and antioxidant defence mechanisms: First evidence of CYP2C- and CYP3A-like activity in marbled crayfish

Growing evidence has reported that diphenhydramine (DPH), an ionisable antihistamine, is widely present in surface waters across the world. Relative to vertebrates studied, its impact on invertebrates, particularly concerning cytochrome P450 (CYP) metabolism and oxidative stress, remains poorly understood. In this study, we aimed to investigate the effects of 2, 20, and 200 µg/L DPH on marbled crayfish (Procambarus virginalis) after 96-h exposure. Specifically, we assessed CYP activity, antioxidant enzyme responses, and acetylcholinesterase (AChE) activity in gills, muscle, and hepatopancreas. The crayfish CYP metabolised fluorogenic CYP-metabolic substrates of 7-benzyloxy-4-trifluoromethylcoumarin (BFC) and dibenzylfluorescein (DBF), which evidenced the activity of CYP2C and CYP3A isoforms, well known in mammalian detoxification metabolism. Both BFC and DBF dealkylations showed a positive correlation with each other but were negatively correlated to water and haemolymph DPH concentrations. Exposure to 200 µg/L DPH elicited an apparent inhibition trend, albeit not significant, in BFC- and DBF-transformation activities in crayfish. Other tested 7-benzyloxyresorufin and 7-pentoxyresorufin substrates were poorly metabolised, suggesting their relatively low activity or the lack of mammalian-like CYP1A and CYP2B isoforms in marbled crayfish. The significant modulation of antioxidant enzymes was demonstrated in gills and hepatopancreas. The exposure to DPH did not alter the activity of AChE. Integrated biomarker response version 2 showed the highest cumulative effect of DPH exposure on gills, implying that gill tissue is the most reliable matrix for evaluating DPH toxicity. Activities of glutathione peroxidase and glutathione-S-transferase were the most deviated determinants among the investigated biomarkers, providing insights into the DPH toxicity in crayfish. This study brought the first insight into utilising the fluorogenically active substrates BFC and DBF to demonstrate the CYP involvement in the detoxification metabolism in marbled crayfish. Further, our results provided information on valuable antioxidant defence mechanisms and biomarker responses for a future DPH toxicity assessment in aquatic organisms.

Development of a New Aggregation Method to Remove Nanoplastics from the Ocean: Proof of Concept Using Mussel Exposure Tests

The overproduction and mismanagement of plastics has led to the accumulation of these materials in the environment, particularly in the marine ecosystem. Once in the environment, plastics break down and can acquire microscopic or even nanoscopic sizes. Given their sizes, microplastics (MPs) and nanoplastics (NPs) are hard to detect and remove from the aquatic environment, eventually interacting with marine organisms. This research mainly aimed to achieve the aggregation of micro- and nanoplastics (MNPs) to ease their removal from the marine environment. To this end, the size and stability of polystyrene (PS) MNPs were measured in synthetic seawater with the different components of the technology (ionic liquid and chitosan). The MPs were purchased in their plain form, while the NPs displayed amines on their surface (PS NP-NH2). The results showed that this technology promoted a significant aggregation of the PS NP-NH2, whereas, for the PS MPs, no conclusive results were found, indicating that the surface charge plays an essential role in the MNP aggregation process. Moreover, to investigate the toxicological potential of MNPs, a mussel species (M. galloprovincialis) was exposed to different concentrations of MPs and NPs, separately, with and without the technology. In this context, mussels were sampled after 7, 14, and 21 days of exposure, and the gills and digestive glands were collected for analysis of oxidative stress biomarkers and histological observations. In general, the results indicate that MNPs trigger the production of reactive oxygen species (ROS) in mussels and induce oxidative stress, making gills the most affected organ. Yet, when the technology was applied in moderate concentrations, NPs showed adverse effects in mussels. The histological analysis showed no evidence of MNPs in the gill's tissues.

Boron Facilitates Amelioration of Hepatic Injury by the Osmolyte Glycine and Resolves Injury by Improving the Tissue Redox Homeostasis

Background: Glycine is a conditional non-essential amino acid in human and other mammals. It is abundant in the liver and is known for a wide spectrum of characteristics including the antioxidant, antiinflammatory, immunomodulatory, and cryoprotective effects. The amino acid is a naturally occurring osmolyte compatible with protein surface interactions and has been reported in literature as a potent therapeutic immuno-nutrient for liver diseases such as alcoholic liver disease. Oral glycine administration protects ethanol-induced liver injury, improves serum and tissue lipid profile, and alleviates hepatic injury in various conditions. In recent years, sodium salt of boron (borax) has been reported for its beneficial effects on cellular stress, including the effects on cell survival, immunity, and tissue redox state. Incidentally both glycine and boron prevent apoptosis and promote cell survival under stress. Objective: This study investigates the beneficial effect of borax on liver protection by glycine. Methods: Briefly, liver toxicity was induced in rats by a single intraperitoneal injection of thioacetamide (400 mg/kg b. wt.). Results: Significant changes in oxidative stress and liver function test parameters, the molybdenum Fe-S flavin hydroxylase activity, nitric oxide and tissue histopathology were observed in thioacetamide treated positive control group. The changes were ameliorated both by glycine as well as borax, but the combinatorial treatment yielded a better response indicating the impact of boron supplementation on glycine mediated protection of liver injury in experimental animal model. Conclusions: The study has clinical implications as the hepatotoxicity caused by thioacetamide mimics features of hepatitis C infection in human.

Epstein-Barr virus infection controls the concentration of the intracellular antioxidant glutathione by upregulation of the glutamate transporter EAAT3 in tumor cells

Epstein-Barr virus or human herpesvirus 4 (EBV/HHV-4) is an omnipresent oncovirus etiologically associated with various B-cell lymphomas and epithelial cancers. The malignant transformation associated with the persistent expression of viral proteins often deregulates the host cellular machinery and EBV infection is coupled to elevated levels of reactive oxygen species. Here, we investigated the role that the glutamate transporter EAAT3 plays in regulating the antioxidant system as a protective mechanism of EBV-infected cells against the virus-induced oxidative stress. Our study demonstrated that the expression of EAAT3 was upregulated and localized to the plasma membrane in EBV latently infected and de novo EBV-infected cells. EAAT3 was regulated by the transcription factor NFAT5 in the infected cells. Membrane localized EAAT3 was found to be involved in the transportation of glutamate from the extracellular space into the cell, as EAAT3 and NFAT5 inhibitors markedly reduced the levels of intracellular glutamate levels in EBV latently infected cells. Additionally, our data demonstrated a notable decrease in the intracellular glutathione levels following treatment with an EAAT3 inhibitor. Collectively, our results suggest that upregulation of the glutamate transporter EAAT3 is an adaptation of EBV-infected cells to maintain cellular redox homeostasis against the virus-induced oxidative stress, and that this cellular balance could be therapeutically destroyed by targeting EAAT3 to impede EBV-associated cancers.

A white paper on Phospholipid Hydroperoxide Glutathione Peroxidase (GPx4) forty years later

The purification of a protein inhibiting lipid peroxidation led to the discovery of the selenoperoxidase GPx4 forty years ago. Thus, the evidence of the enzymatic activity was reached after identifying the biological effect and unambiguously defined the relationship between the biological function and the enzymatic activity. In the syllogism where GPx4 inhibits lipid peroxidation and its inhibition is lethal, cell death is operated by lipid peroxidation. Based on this rationale, this form of cell death emerged as regulated iron-enforced oxygen toxicity and was named ferroptosis in 2012. In the last decades, we learned that reduction of lipid hydroperoxides is indispensable and, in cooperation with prooxidant systems, controls the critical steady state of lipid peroxidation. This concept defined the GPx4 reaction as both the target for possible anti-cancer therapy and if insufficient, as cause of degenerative diseases. We know the reaction mechanism, but the details of the interaction at the membrane cytosol interface are still poorly defined. We know the gene structure, but the knowledge about expression control is still limited. The same holds true for post-transcriptional modifications. Reverse genetics indicate that GPx4 has a role in inflammation, immunity, and differentiation, but the observations emerging from these studies need a more specifically addressed biochemical evidence. Finally, the role of GPx4 in spermatogenesis disclosed an area unconnected to lipid peroxidation. In its mitochondrial and nuclear form, the peroxidase catalyzes the oxidation of protein thiols in two specific aspects of sperm maturation: stabilization of the mid-piece and chromatin compaction. Thus, although available evidence converges to the notion that GPx4 activity is vital due to the inhibition of lipid peroxidation, it is reasonable to foresee other unknown aspects of the GPx4 reaction to be disclosed.

Elasmobranchs as bioindicators of pollution in the marine environment

Bioindicator species are increasingly valuable in environmental pollution monitoring, and elasmobranch species include many suitable candidates for that role. By measuring contaminants and employing biomarkers of effect in relevant elasmobranch species, scientists may gain important insights about the impacts of pollution in marine ecosystems. This review compiles biomarkers applied in elasmobranchs to assess the effect of pollutants (e.g., metals, persistent organic pollutants, and plastics), and the environmental changes induced by anthropogenic activities (e.g., shifts in marine temperature, pH, and oxygenation). Over 30 biomarkers measured in more than 12 species were examined, including biotransformation biomarkers (e.g., cytochrome P450 1A), oxidative stress-related biomarkers (e.g., superoxide anion, lipid peroxidation, catalase, and vitamins), stress proteins (e.g., heat shock protein 70), reproductive and endocrine biomarkers (e.g., vitellogenin), osmoregulation biomarkers (e.g., trimethylamine N-oxide, Na⁺/K⁺-ATPase, and plasma ions), energetic and neurotoxic biomarkers (e.g., lactate dehydrogenase, lactate, and cholinesterases), and histopathological and morphologic biomarkers (e.g., tissue lesions and gross indices).

Aging and Light Stress Result in Overlapping and Unique Gene Expression Changes in Photoreceptors

Advanced age is one of the leading risk factors for vision loss and eye disease. Photoreceptors are the primary sensory neurons of the eye. The extended photoreceptor cell lifespan, in addition to its high metabolic needs due to phototransduction, makes it critical for these neurons to continually respond to the stresses associated with aging by mounting an appropriate gene expression response. Here, we sought to untangle the more general neuronal age-dependent transcriptional signature of photoreceptors with that induced by light stress. To do this, we aged flies or exposed them to various durations of blue light, followed by photoreceptor nuclei-specific transcriptome profiling. Using this approach, we identified genes that are both common and uniquely regulated by aging and light induced stress. Whereas both age and blue light induce expression of DNA repair genes and a neuronal-specific signature of death, both conditions result in downregulation of phototransduction. Interestingly, blue light uniquely induced genes that directly counteract the overactivation of the phototransduction signaling cascade. Lastly, unique gene expression changes in aging photoreceptors included the downregulation of genes involved in membrane potential homeostasis and mitochondrial function, as well as the upregulation of immune response genes. We propose that light stress contributes to the aging transcriptome of photoreceptors, but that there are also other environmental or intrinsic factors involved in age-associated photoreceptor gene expression signatures.

Effects of Simulated Heat Wave on Oxidative Physiology and Immunity in Asian Yellow Pond Turtle (Mauremys mutica)

Global warming has led to an increase in the frequency, duration, and intensity of heat waves in the summer, which can cause frequent and acute heat stress on ectotherms. Thus, determining how ectothermic animals respond to heat waves has been attracting growing interest among ecologists. However, the physiological and biochemical responses to heat waves in reptiles, especially aquatic reptiles, are still poorly understood. The current study investigated the oxidant physiology, immunity, and expression levels of heat shock proteins (HSP) mRNA after exposure to a simulated heat wave (1 week, 35 ± 4°C), followed by a recovery period (1 week, 28 ± 4°C) in juvenile Asian yellow pond turtle (Mauremys mutica), a widely farmed aquatic turtle in East Asia. The contents of malondialdehyde (MDA) in the liver and muscle were not significantly affected by the heat wave or recovery. Of all antioxidant enzymes, only the activity of glutathione peroxidase (GSH-Px) in muscles increased after heat wave, while the total superoxide dismutase (T-SOD), catalase activity (CAT), and total antioxidant capacity (T-AOC) did not change during the study. The organo-somatic index for the liver and spleen of M. mutica decreased after the heat wave but increased to the initial level after recovery. In contrast, plasma lysozyme activity and serum complement C4 levels increased after the heat wave, returning to the control level after recovery. In addition, heat waves did not alter the relative expression of HSP60, HSP70, and HSP90 mRNA in the liver. Eventually, heat wave slightly increased the IBR/n index. Therefore, our results suggested that heat waves did not lead to oxidative damage to lipids in M. mutica, but deleteriously affected the turtles’ immune organs. Meanwhile, the constitutive levels of most antioxidative enzyme activities, HSPs and enhanced blood immune functions might protect the turtles from the threat of heat waves under the current climate scenarios.

Altered Redox State in Whole Blood Cells from Patients with Mild Cognitive Impairment and Alzheimer's Disease

Oxidative stress plays an essential and early role in the pathophysiology of Alzheimer's disease (AD). Alterations in the redox state in AD and in mild cognitive impairment (MCI) patients appear in the brain and at peripheral level. Given that it is easier to study the latter, most of the research has been focused on plasma. However, the analysis of redox parameters in whole blood cells (including erythrocytes and leukocytes) has not really been investigated. Moreover, the association of these parameters with Mini-Mental State Examination (MMSE) clinical scores, has scarcely been studied. Therefore, the aim of the present work was to analyze several redox markers in whole blood cells from male and female MCI and AD patients. Antioxidant (superoxide dismutase, catalase (CAT), glutathione peroxidase (GPx), and reductase (GR) activities, and reduced glutathione (GSH) concentration) together with oxidant parameters (oxidized glutathione (GSSG) and thiobarbituric acid-reactive substances (TBARS)) were investigated using MCI and AD (10 women and 10 men in each group) and their age-matched control groups (15 women and 15 men). The results show an altered redox state in whole blood cells from AD patients (higher CAT, GSSG/GSH, TBARS and lower GPx, GR, GSH). Some of these redox parameters are already affected in MCI patients (higher TBARS and lower GPx and GR activities) in both sexes and, consequently, they could be used as markers of prodromal AD. Since GR, GSH, GSSG, and GSSG/GSH were found to be associated with MMSE scores, they seem to be useful clinically to monitor cognitive decline in AD progression.

Potential of environmental concentrations of the musks galaxolide and tonalide to induce oxidative stress and genotoxicity in the marine environment

Polycyclic musk compounds have been identified in environmental matrices (water, sediment and air) and in biological tissues in the last decade, yet only minimal attention has been paid to their chronic toxicity in the marine environment. In the present research, the clams Ruditapes philippinarum were exposed to 0.005, 0.05, 0.5, 5 and 50 μg/L of the fragrances Galaxolide® (HHCB) and Tonalide® (AHTN) for 21 days. A battery of biomarkers related with xenobiotics biotransformation (EROD and GST), oxidative stress (GPx, GR and LPO) and genotoxicity (DNA damage) were measured in digestive gland tissues. HHCB and AHTN significantly (p < 0.05) induced EROD and GST enzymatic activities at environmental concentrations. Both fragrances also induced GPx activity. All concentrations of both compounds induced an increase of LPO and DNA damage on day 21. Although these substances have been reported as not acutely toxic, this study shows that they might induce oxidative stress and genotoxicity in marine organisms.

Assessment of the cerebellar neurotoxic effects of nicotine in prenatal alcohol exposure in rats

The adverse effects of prenatal nicotine and alcohol exposure on human reproductive outcomes are a major scientific and public health concern. In the United States, substantial percentage of women (20-25%) of childbearing age currently smoke cigarettes and consume alcohol, and only a small percentage of these individuals quit after learning of their pregnancy. However, there are very few scientific reports on the effect of nicotine in prenatal alcohol exposure on the cerebellum of the offspring. Therefore, this study was conducted to investigate the cerebellar neurotoxic effects of nicotine in a rodent model of Fetal Alcohol Spectrum Disorder (FASD). In this study, we evaluated the behavioral changes, biochemical markers of oxidative stress and apoptosis, mitochondrial functions and the molecular mechanisms associated with nicotine in prenatal alcohol exposure on the cerebellum. Prenatal nicotine and alcohol exposure induced oxidative stress, did not affect the mitochondrial functions, increased the monoamine oxidase activity, increased caspase expression and decreased ILK, PSD-95 and GLUR1 expression without affecting the GSK-3β. Thus, our current study of prenatal alcohol and nicotine exposure on cerebellar neurotoxicity may lead to new scientific perceptions and novel and suitable therapeutic actions in the future.

Antioxidant properties of coenzyme Q10-pretreated mouse pre-antral follicles derived from vitrified ovaries

AIM

This study evaluated the antioxidant status of pre-antral follicles derived from vitrified ovaries pretreated with coenzyme Q10 (CoQ10).

METHODS

Mouse pre-antral follicles derived from fresh and vitrified warmed ovarian tissue were cultured with or without CoQ10 (50 μmol/L). Follicular growth, total antioxidant capacity (TAC), malondialdehyde (MDA) level, and superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT) activity during cultivation were assessed.

RESULTS

The growth rate of the fresh pre-antral follicles was higher compared with the vitrified groups, especially in the CoQ10-treated than non-treated groups. MDA increased while TAC decreased at 96 h of the cultivation period. TAC was higher while MDA was lower in the fresh pre-antral follicles than in the vitrified groups. These rates were higher in the CoQ10-treated than non-treated groups. The vitrified and fresh CoQ10-pretreated groups had significantly higher SOD, GPX, and CAT activity compared with the CoQ10 non-treated groups.

CONCLUSION

CoQ10-supplemented maturation medium can increase antioxidant enzyme activity and decrease lipid peroxidation in cultured pre-antral follicles derived from fresh and vitrified mouse ovaries.

Rho GTPases, oxidation, and cell redox control

While numerous studies support regulation of Ras GTPases by reactive oxygen and nitrogen species, the Rho subfamily has received considerably less attention. Over the last few years, increasing evidence is emerging that supports the redox sensitivity of Rho GTPases. Moreover, as Rho GTPases regulate the cellular redox state by controlling enzymes that generate and convert reactive oxygen and nitrogen species, redox feedback loops likely exist. Here, we provide an overview of cellular oxidants, Rho GTPases, and their inter-dependence.

In vivo antioxidant activity of deacetylasperulosidic Acid in noni

Deacetylasperulosidic acid (DAA) is a major phytochemical constituent of Morinda citrifolia (noni) fruit. Noni juice has demonstrated antioxidant activity in vivo and in human trials. To evaluate the role of DAA in this antioxidant activity, Wistar rats were fed 0 (control group), 15, 30, or 60 mg/kg body weight per day for 7 days. Afterwards, serum malondialdehyde concentration and superoxide dismutase and glutathione peroxidase activities were measured and compared among groups. A dose-dependent reduction in malondialdehyde was evident as well as a dose-dependent increase in superoxide dismutase activity. DAA ingestion did not influence serum glutathione peroxidase activity. These results suggest that DAA contributes to the antioxidant activity of noni juice by increasing superoxide dismutase activity. The fact that malondialdehyde concentrations declined with increased DAA dose, despite the lack of glutathione peroxidase-inducing activity, suggests that DAA may also increase catalase activity. It has been previously reported that noni juice increases catalase activity in vivo but additional research is required to confirm the effect of DAA on catalase. Even so, the current findings do explain a possible mechanism of action for the antioxidant properties of noni juice that have been observed in human clinical trials.

Neuroprotective effects of the 17β-estradiol against ethanol-induced neurotoxicity and oxidative stress in the developing male rat cerebellum: biochemical, histological and behavioral changes

During particular periods of central nervous system (CNS) development, exposure to ethanol can decrease regional brain growth and can result in selective loss of neurons. Unfortunately, there are few effective means of attenuating damage in the immature brain. In this study, the possible antioxidant and neuroprotective properties of 17β-estradiol against ethanol-induced neurotoxicity was investigated. 17β-estradiol (600 μg/kg) was injected subcutaneously in postnatal day (PD) 4 and 5, 30 min prior to intraperitoneal injection of ethanol (6g/kg) in rat pups. Ninety minutes after injection of ethanol, the activities of several antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (Gpx) in vermis of cerebellum were assayed. Thiobarbituric acid reactive substance (TBARS) levels were also measured as a marker of lipid peroxidation. Behavioral studies, including rotarod and locomotor activity tests were performed in PD 21-23 and histological study was performed after completion of behavioral measurements in postnatal day 23. The results of the present work demonstrated that ethanol could induce lipid peroxidation, increase TBARS levels and decrease glutathione peroxidase levels in pup cerebellum. We also observed that ethanol impaired performance on the rotarod and locomotor activities of rat pups. However, treatment with 17β-estradiol significantly attenuated motoric impairment, the lipid peroxidation process and restored the levels of antioxidants. Histological analysis also indicated that ethanol could decrease vermis Purkinje cell count and 17β-estradiol prevented this toxic effect. These results suggest that ethanol may induce lipid peroxidation in the rat pups cerebellum while treatment with 17β-estradiol improves motor deficits by protecting the cerebellum against ethanol toxicity.

Acute toxicity of 3,3',4,4',5-pentachlorobiphenyl (PCB 126) in male Sprague-Dawley rats: effects on hepatic oxidative stress, glutathione and metals status

Although polychlorinated biphenyl (PCBs) production, and new uses for PCBs, was halted in the 1970s in the United States, PCBs continue to be used in closed systems and persist in the environment, accumulating in fatty tissues. PCBs are efficacious inducers of drug metabolism and may increase oxidative events and alter many other biochemical and morphologic parameters within cells and tissues. The goal of the present study was to evaluate the effects of a single, very low dose of PCB 126 (3,3',4,4',5-pentachlorobiphenyl), a coplanar, dioxin-like PCB congener and aryl hydrocarbon receptor (AhR) agonist, on redox status, metals homeostasis, antioxidant enzymes, and cellular morphology. To examine these parameters, male Sprague-Dawley rats were fed a purified AIN-93 basal diet containing 0.2 ppm selenium for two weeks, then administered a single i.p. injection of corn oil (5 ml/kg body weight) or 1µmol PCB 126/kg body weight (326µg/kg body weight) in corn oil. Rats were maintained on the diet for an additional two weeks before being euthanized. This dose of PCB 126 did not alter feed intake or growth, but significantly increased liver weight (42%) and hepatic microsomal cytochrome P-450 (CYP1A) enzyme activities (10-40-fold increase). Hepatic zinc, selenium, and glutathione levels were significantly decreased 15%, 30%, and 20%, respectively, by PCB 126. These changes were accompanied by a 60% decrease in selenium-dependent glutathione peroxidase activity. In contrast, hepatic copper levels were increased 40% by PCB 126. PCB 126-induced pathology was characterized by hepatocellular hypertrophy and mild steatosis in the liver and a mild decrease in cortical T-cells in the thymus. This controlled study in rats fed a purified diet shows that even a single, very low dose of PCB 126 that did not alter feed intake or growth, significantly perturbed redox and metals homeostasis and antioxidant and enzyme levels in rodent liver.

Selenium and vitamin E increases polymorphonuclear cell phagocytosis and antioxidant levels during acute mastitis in riverine buffaloes

Antioxidant, antiinflammatory and phagocytic activities were studied in milk polymorphonuclear cells (PMNs) isolated from healthy buffaloes (group I) and during clinical mastitis with the treatment of Enrofloxacin alone (group II) and combined treatment with Enrofloxacin and Vitamin E plus selenium (group III). On days 0,3, 8 and 15 the milk Somatic cell count (SCC) were significantly higher in mastitic milk than in milk obtained from healthy buffaloes. In group II SCC decreased significantly on day 3 and day 8, however in group III reduction in SCC was observed on day 3, day 8 and day 15 (P < 0.05). The antiinflammatory activity was evaluated by determining nitrite plus nitrate (NOx) production in the milk PMNs before treatment and on day 8. NOx activity was significantly higher in mastitic milk than from healthy controls, both before and after treatment (P < 0.05). In group II and group III the activity decreased significantly on day 8 (P < 0.05). The Glutathione peroxidase (GSH-Px) activity was estimated in the milk polymorphonuclear cell (PMNs) supernatant. GSH-Px activity was significantly lower in mastitic buffaloes than in healthy controls, both before and after treatment (P < 0.05). In group II levels did not change in response to treatment, whereas in group III levels had increased significantly on day 8 (P < 0.05). The phagocytic activity (PA) (percentage of neutrophil that had phagocytosed 1-6 bacteria) and phagocytic index (PI) (average number of bacteria/ leukocytes counted in 100 cells) of the milk PMNs was significantly lower in mastitic buffaloes (P < 0.05). In group II the PA and PI did not change in response to treatment, whereas in group III both the parameters had increased significantly on day 8 (P < 0.05). The results of the present experiment indicated enhancement of antioxidative and cellular defense and reduction of somatic cell count in the mastitic animals treated with Enrofloxacin and Vitamin E plus Selenium as compared to the Enrofloxacin treatment alone. Hence Vitamin E plus selenium therapy may be added along with the antibiotics for effective amelioration of intramammary infection in buffaloes.

Impaired Cu/Zn-SOD activity contributes to increased oxidative damage in APP transgenic mice

Oxidative stress plays an important role in the pathogenesis of Alzheimer's disease. To determine which mechanisms cause the origin of oxidative damage, we analyzed enzymatic antioxidant defense (Cu/Zn-superoxide dismutase Cu/Zn-SOD, glutathione peroxidase GPx and glutathione reductase GR) and lipid peroxidation products malondialdehyde MDA and 4-hydroxynonenal HNE in two different APP transgenic mouse models at 3-4 and 12-15 months of age. No changes in any parameter were observed in brains from PDGF-APP695(SDL) mice, which have low levels of Abeta and no plaque load. In contrast, Thy1-APP751(SL) mice show high Abeta accumulation with aging and plaques from an age of 6 months. In brains of these mice, HNE levels were increased at 3 months (female transgenic mice) and at 12 months (both gender), that is, before and after plaque deposition, and the activity of Cu/Zn-SOD was reduced. Interestingly, beta-amyloidogenic cleavage of APP was increased in female Thy1-APP751(SL) mice, which also showed increased HNE levels with simultaneously reduced Cu/Zn-SOD activity earlier than male Thy1-APP751(SL) mice. Our results demonstrate that impaired Cu/Zn-SOD activity contributes to oxidative damage in Thy1-APP751(SL) transgenic mice, and these findings are closely linked to increased beta-amyloidogenic cleavage of APP.

Oxidative stress and vascular permeability in steroid-induced osteonecrosis model

We focused on the role of oxidative stress in the pathogenesis of steroid-induced osteonecrosis (ON) and the possibility of preventing this condition by antioxidant administration. Methylprednisolone 4 mg/kg was injected only once into Japanese white rabbits. The involvement of oxidative stress and the presence/absence of bone circulatory impairment were investigated in groups of 10 rabbits killed at 3, 5, and 14 days each and in 10 rabbits administered the antioxidant glutathione. Reduced blood glutathione and lipid peroxide levels were determined biochemically, and the presence/absence of advanced glycation end-product expression was determined immunohistochemically. Vascular permeability in bone was confirmed by finding albumin leakage into the stroma. These blood biochemical and immunohistochemical studies clarified that the oxidative stress in this model developed 3-5 days after steroid administration. Elevated vascular permeability was observed in the 5- and 14-day groups. Hence, circulatory disturbance in bone was noted 5 days after steroid administration, coinciding with the onset of oxidative stress. The rate of ON development, which was 70% in the steroid-alone 14-day group, was significantly reduced to 0% in the steroid + antioxidant group. These results suggest the involvement of oxidative stress and vascular permeability in this steroid-induced ON model and the possibility of its prevention by suppression of oxidative stress.

Effect of vitamin E on glutathione-dependent enzymes

Reactive oxygen species and various electrophiles are involved in the etiology of diseases varying from cancer to cardiovascular and pulmonary disorders. The human body is protected against damaging effects of these compounds by a wide variety of systems. An important line of defense is formed by antioxidants. Vitamin E (consisting of various forms of tocopherols and tocotrienols) is an important fat-soluble, chain-breaking antioxidant. Besides working as an antioxidant, this compound possesses other functions with possible physiological relevance. The glutathione-dependent enzymes form another line of defense. Two important enzymes in this class are the free radical reductase and glutathione S-transferases (GSTs). The GSTs are a family of phase II detoxification enzymes. They can catalyze glutathione conjugation with various electrophiles. In most cases the electrophiles are detoxified by this conjugation, but in some cases the electrophiles are activated. Antioxidants do not act in isolation but form an intricate network. It is, for instance, known that vitamin E, together with glutathione (GSH) and a membrane-bound heat labile GSH-dependent factor, presumably an enzyme, can prevent damaging effects of reactive oxygen species on polyunsaturated fatty acids in biomembranes (lipid peroxidation). This manuscript reviews the interaction between the two defense systems, vitamin E and glutathione-dependent enzymes. On the simplest level, antioxidants such as vitamin E have protective effects on glutathione-dependent enzymes; however, we will see that reality is somewhat more complicated.

A comparison of hepatoprotective activities of aminoguanidine and N-acetylcysteine in rat against the toxic damage induced by azathioprine

Azathioprine (AZA) is an important drug used in the therapy of autoimmune system disorders. It induces hepatotoxicity that restricts its use. The rationale behind this study was the proven efficacy of N-acetylcysteine (NAC; a replenisher of sulfhydryls) and reports on the antioxidant potential of aminoguanidine (AG; an iNOS inhibitor), that might be useful to protect against the toxic implications of AZA. AG (100 mg/kg; i.p.) or NAC (100 mg/kg; i.p.) were administered to the Wistar male rats for 7 days and after that AZA (15 mg/kg, i.p.) was given as a single dose. This caused an increase in the activity of hepatic aminotransferases (AST and ALT) in the serum 24 h after AZA treatment. AZA (7.5 or 15 mg/kg, i.p.) also caused an increase in rat liver lipid peroxides and a lowering of reduced glutathione (GSH) contents. In the other part of experiment, protective effects of AG and NAC were observed on AZA induced hepatotoxicity. NAC significantly protected against the toxic effects produced by AZA. Pretreatment with NAC prevented any change in the activities of both the aminotransferases after AZA. This pretreatment also resulted in a significant decline in the contents of lipid peroxides and a significant elevation in GSH level was evident after AZA treatment. In the group with AG pretreatment the activities of AST and ALT did not increase significantly after AZA when compared to control. However, the lipid peroxides and GSH levels did not have any significant difference when compared to AZA group. These observations also indicate that the improvement in the GSH levels by NAC is the most significant protective mechanism rather than any other mechanistic profile. The protective effect of AG against the enzyme leakage seems to be through the liver cell membrane permeability restoration and is independent of any effects on liver GSH contents.

Review article: oxidative stress as a pathogenic factor in inflammatory bowel disease--radicals or ridiculous?

Virtually all inflammatory mediators investigated to date seem to be dysregulated in the inflamed intestinal mucosa of patients with inflammatory bowel disease. However, which of these are actually involved in the initiation and perpetuation of intestinal tissue damage is still not fully understood. Amongst these mediators are the reactive oxygen metabolites, produced in large amounts by the massively infiltrating leucocytes. These reactive oxygen metabolites are believed to constitute a major tissue-destructive force and may contribute significantly to the pathogenesis of inflammatory bowel disease. This paper provides a concise overview of reactive oxygen metabolite biochemistry, the types of cell and tissue damage potentially inflicted by them, and the endogenous antioxidants which should prevent these harmful effects. An up-to-date summary of the available human experimental data suggests that reactive oxygen metabolite-mediated injury is important in both the primary and downstream secondary pathophysiological mechanisms underlying intestinal inflammation. Nonetheless, how the individual components of the mucosal antioxidant enzymatic cascade respond to inflammatory conditions is a neglected area of research. This particular aspect of intestinal mucosal oxidative stress therefore merits further study, in order to provide a sound, scientific basis for the design of antioxidant-directed treatment strategies for inflammatory bowel disease patients.

Influences of supplementary dietary tungsten on methionine metabolism in rabbits fed a low-cholesterol plus methionine diet

Hyperhomocysteinemia results from an impaired methionine metabolism. Sulfite oxidase, which is an important enzyme in methionine metabolism, contains molybdenum. In contrast, tungsten has a molybdenum-antagonistic effect. Thus, we hypothesized that dietary tungsten may decrease plasma homocysteine levels and influence methionine metabolism. Male New Zealand White rabbits (n=15) were fed a low-cholesterol basal diet and then placed on three different diets: 0.1% cholesterol (Chol), Chol plus 1% methionine (Met), and Chol plus Met plus 0.1% tungsten (W). The animals received these diets for 20 weeks. Biochemical tests of blood and urine were performed. Plasma homocysteine levels were significantly lower in the Chol+Met+W group than in the Chol+Met group. Plasma levels of total cholesterol, triglyceride, lipid peroxide, and urinary 24-h taurine concentrations were higher in the Chol + Met + W group than in the Chol + Met group. In comparison, concentrations of 2, 3-diphosphoglycerate (2, 3-DPG), reduced glutathione (GSH) in erythrocytes, and urinary 24-h SO4(2) were lower in the Chol+Met+W group than in the Chol+Met group. From these results, tungsten could be expected to exhibit an antiatherogenic effect. Conversely, it may have effects on atherogenic factors. Thus, tungsten may play a number of roles in the methionine metabolism.

Biochemical basis of sodium valproate hepatotoxicity and renal tubular disorder: time dependence of peroxidative injury

Mice fed with sodium valproate for 7, 14 and 21 days were evaluated for hepatotoxicity and renal tubular disorder. The drug was administered as an aqueous solution with an increasing concentration up to five days gradually reaching up to 0.71% w/v, which persisted throughout the study period. Mice fed with sodium valproate for 7, 14 and 21 days showed, marked hepatic injury and renal tubular disorder, evidenced by increased levels of malondialdehyde as a measure of lipid peroxidation. Administration of sodium valproate affected the glutathione contents both in liver and kidney tissue at all the three time points. However, this reduction in glutathione concentration was more pronounced in kidney when compared to control group. These results support the hypothesis that lipid peroxidation mediates the effect of sodium valproate on liver and kidney. Furthermore, the valproate induced toxicity is time related and the increase in lipid peroxide levels and depletion of glutathione occur time dependent even if the dose is clinically appropriate.

Glutathione-dependent factors and inhibition of rat liver microsomal lipid peroxidation

The effects of reduced glutathione (GSH) and glutathione disulfide (GSSG) on lipid peroxidation were investigated in rat liver microsomes containing deficient or adequate amounts of alpha-tocopherol (alpha-TH). Rates of formation of thiobarbituric acid reactive substances (TBARS) as well as rates of consumption of alpha-TH and O2 were decreased by GSH and were more pronounced in the NADPH-dependent assay system than in the ascorbate-dependent system. The GSH-dependent inhibition of lipid peroxidation was potentiated by GSSG in the NADPH-dependent assay system, but it had no effect in the nonenzymatic system. Diphenyliodonium chloride, an inhibitor of NADPH cytochrome P-450 reductase, completely prevented lipid peroxidation in the NADPH-dependent assay system whereas it had no effect on the ascorbate-dependent system. This is further evidenced by the fact that purified rat liver microsomal NADPH cytochrome P-450 reductase (EC 1.6.2.4) was inhibited approximately 24% and 52% by 5 mM GSH and 5 mM GSH + 2.5 mM GSSG, respectively. Glutathione disulfide alone had no effect on reductase activity. Similarly, other disulfides such as cystine, cystamine and lipoic acid were without effect on reductase activity. These results clearly delineate different mechanisms underlying the combined effects of GSH and GSSG on microsomal lipid peroxidation in rat liver. One mechanism involves recycling of microsomal alpha-TH by GSH during oxidative stress via a labile protein, ostensibly associated with "free radical reductase" activity. A second glutathione-dependent mechanism appears to be mediated through the inhibition of NADPH cytochrome P-450 reductase. The enhanced inhibition by GSH + GSSG of microsomal lipid peroxidation in the NADPH-dependent assay system suggests suppression of the initiation phase at the level of NADPH cytochrome P-450 reductase which is independent of microsomal alpha-TH.

Studies on the effects of monosodium glutamate on hepatic microsomal lipid peroxidation, calcium, ascorbic acid and glutathione and its dependent enzymes in adult male mice

Daily administration of monosodium glutamate (MSG) to adult male mice subcutaneously, for 6 days, at dose levels of 4 and 8 mg/g body weight, significantly increased lipid peroxidation in the hepatic microsomes, as seen 31 days after the last injection. A highly significant increase was observed in the level of hepatic calcium and ascorbic acid. The glutathione (GSH) content was significantly decreased but the activities of glutathione dependent enzymes like GR, GPX, GSTs were found to be significantly increased. These observations suggested that MSG at dose levels above 4 mg/g body weight induced oxidative stress in hepatic microsomes. Attempts to maintain the redox state of the cell are suggested by increase in the ascorbic acid content and the activities of glutathione dependent enzymes.

Reduction of intracellular glutathione levels produces sustained arterial narrowing

OBJECTIVE

Although lipid peroxidation and alterations in endogenous antioxidants have been hypothesized to contribute to cerebral vasospasm after subarachnoid hemorrhage, there has been no direct evidence demonstrating the relationship between oxidative stress and delayed arterial narrowing. To elaborate the role of the endogenous intracellular antioxidant and electron exchanger glutathione (GSH) in cerebral vasospasm, rat femoral arteries were treated with perivascular application of I-buthionine-(SR)-sulfoximine (BSO), which inhibits the synthesis of GSH.

METHODS

To determine the dose-response relationship, BSO at doses of 10 to 100 mg/ml, in platelet-rich plasma, was applied for 7 days to rat femoral arteries in vivo. Vessels were then perfusion-fixed for morphometric analysis of luminal cross-sectional area. To determine the time course of arterial narrowing, BSO (75 mg/ml) was applied to femoral arteries for 1, 3, 7, or 21 days before histological analysis, as described above. With rats treated with 50 to 100 mg/ml BSO, exogenous GSH (100 mg/kg) was administered, by intraperitoneal injection, daily for 7 days. To demonstrate the mechanism of BSO effects in smooth muscle cells (SMCs), cultured rat aortic SMCs were treated with 1 mmol/l BSO for 24 hours and assayed for intracellular levels of GSH and two products of lipid peroxidation, malondialdehyde and 4-hydroxyalkenal.

RESULTS

Compared with control arteries treated with platelet-rich plasma alone, perivascularly administered BSO applied for periods of 1 to 21 days produced sustained and reversible narrowing of rat femoral arteries with a time course, severity, and histological appearance analogous to those observed after perivascular application of whole blood. BSO-induced arterial narrowing was dose-dependent, with 60% reductions in the luminal cross-sectional area being noted at 75 and 100 mg/ml (P < 0.005). Systemic administration of exogenous GSH slightly inhibited the effect of BSO on arterial narrowing, although the inhibition was not statistically significant. Cultured rat aortic SMCs exposed to BSO for 24 hours showed a 70% decrease in intracellular GSH levels (P = 0.03); levels of two products of lipid peroxidation, malondialdehyde and 4-hydroxyalkenal, were increased by 25% (P = 0.24) and 38% (P = 0.09), respectively.

CONCLUSION

These data support the hypothesis that diminished intracellular levels of GSH may produce delayed chronic arterial narrowing after subarachnoid hemorrhage. The specific mechanism by which GSH levels modulate vasoconstriction remains uncertain but may involve endogenous antioxidant capacity in SMCs.

Protein-energy malnutrition and oxidative injury in growing rats

1. Weaning rats were fed ad libitum isocaloric diets containing 5% and 20% casein based proteins. 5% protein diet was protein deficient diet. Pair fed rats with the 5% protein group were maintained simultaneously on 20% protein diet but the amount restricted to the amount taken up by PEM group. 2. Glutathione, antioxidative enzymes, lipid peroxidation and histopathological studies in liver and only glutathione and antioxidative enzymes in blood were carried out. 3. Rats fed the 5% protein diet developed a severe protein energy malnutrition (PEM) whereas those on pair-fed diet developed mild to moderate PEM. 4. Glutathione related thiols superoxide dismutase, glutathione peroxidase, catalase and glutathione-Stransferase with (1 Chloro 2,4-dinitro benzene (CDNB) substrate) were decreased in liver with concomitant increase of lipid peroxidation in severe PEM. In blood glutathione, glutathione peroxidase and catalase were decreased while superoxide dismutase was increased in severe PEM group. 5. Mild to moderate PEM (pair-fed group) also resulted in similar changes in liver except glutathione peroxidase, lipid peroxidation in liver and superoxide dismutase in blood. 6. Hepatic injury was detectable only in the severe PEM group. 7. Oxidative-stress and hepatic injury occurred in severe PEM and to a lesser degree in mild to moderate PEM.

Role of neutrophils in indomethacin-induced gastric mucosal lesions in rats

Nonsteroidal anti-inflammatory drugs (NSAIDs) cause clinically important gastric damage by several mechanisms. In order to evaluate the role of neutrophil infiltration in lesion formation, tissue myeloperoxidase activities were assessed in different gastric layers of the stomach both in rats with normal neutrophil levels and in neutropenic rats. Sprague-Dawley rats were treated either with indomethacin (Indo; 25 mg/kg, s.c.) or the vehicle. A group of rats were made neutropenic by administration of methotrexate (MTX; 2.5 mg/kg i.p.) once a day for 3 days. The stomachs were removed for the determination of lesion index, glutathione, lipid peroxide levels, protein oxidation and tissue myeloperoxidase activities. MTX treatment appeared to reduce neutrophil infiltration significantly while producing insignificant effects on eosinophils and macrophages. Indo administration caused multiple gastric lesions and treatment with MTX significantly reduced lesion index. In rats treated with Indo, neither glutathione nor LP levels showed any significant changes but the protein oxidation was significantly higher than that of other groups. The MPO level of gastric mucosa was increased in Indo-treated rats and reversed by MTX pretreatment. The results of the present study indicate that neutrophil infiltration in the gastric mucosa of rats may be involved in the pathogenesis of NSAID-induced gastric mucosal injury, but no correlation was found between lesion formation and protein oxidation in the gastric mucosa.

Protective effect of selenium on hemoglobin mediated lipid peroxidation in vivo

The toxicity of hemoglobin (Hb) solutions is related, at least in part, to the generation of oxygen free radicals with consequent induction of lipid peroxidation. The present study was designed to examine whether selenium (Se) may prevent the oxidative damage observed after Hb administration. Three groups of rats were compared; (I) the negative control group receiving autotransfusion; (II) the positive control group with replacement of 40% total blood volume (TBV) with modified bovine Hb solution; and (III) the experimental group which received dietary supplemented selenium (Na2SeO3) in daily doses of 5 micrograms.kg body wt-1 in drinking water, 4 days before and 3 days after administration of Hb solution in the same volume as in group II. Three days after Hb injection, all animals were sacrificed. Oxidative stress was determined by measuring conjugated dienes (CD) and thiobarbituric acid reactants (MDA) in homogenates of the perfused liver, heart, lungs, kidney, brain and plasma. Additionally, the 45k x g supernatants of the organs homogenates and plasma were assayed for the antioxidant enzymes activity: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and the intracellular level of reduced glutathione (GSH). Also, a measurement of nonprotein bound intracellular free iron (Fe) and tissue Se concentrations was performed. Simultaneously, injury dysfunction of vital organs was assessed by the measurement of plasma LDH, SGPT, creatinine, blood PaO2 and by histopathological studies. Results indicate that the exchange transfusion with Hb solution introduced significant increases in CD and MDA formation, particularly in the liver and heart tissues, and in plasma. While the values of the SOD and CAT in the liver and heart tissue were generally altered, the SOD/CAT ratio was also increased. After the Hb injection, activity of GSH-Px remained unchanged and was associated with significant depletion of GSH. The plasma levels of SGPT and LDH were increased, but the creatinine and PaO2 was similar to that of the control and corresponded with histopathological findings. The liver and heart intracellular free Fe was found to be higher than that of control. Treatment with Se was very effective in the prevention of oxidative damage introduced by Hb. Full protection from MDA formation was noted in liver tissue (p < 0.001). Also, plasma levels of MDA, SGPT and LDH were significantly decreased and appeared similar to that of the control group (I). Treatment with Se increased liver (p < 0.05) and plasma (p < 0.1) level of GSH-Px.(ABSTRACT TRUNCATED AT 400 WORDS)

Importance of Se-glutathione peroxidase, catalase, and Cu/Zn-SOD for cell survival against oxidative stress

Eukaryotic cells have to constantly cope with highly reactive oxygen-derived free radicals. Their defense against these free radicals is achieved by natural antioxidant molecules but also by antioxidant enzymes. In this paper, we review some of the data comparing the efficiency of three different antioxidant enzymes: Cu/Zn-superoxide dismutase (Cu/Zn-SOD), catalase, and selenium-glutathione peroxidase. We perform our comparison on one experimental model (human fibroblasts) where the activities of these three antioxidant enzymes have been modulated inside the cells, and the repercussion of these changes was investigated in different conditions. We also focus our attention on the protecting role of selenium-glutathione peroxidase, because this enzyme is very rarely studied due to the difficulties linked to its biochemical properties. These studies evidenced that all three antioxidant enzymes give protection for the cells. They show a high efficiency for selenium-glutathione peroxidase and emphasize the fact that each enzyme has a specific as well as an irreplaceable function. They are all necessary for the survival of the cell even in normal conditions. In addition, these three enzymes act in a cooperative or synergistic way to ensure a global cell protection. However, optimal protection is achieved only when an appropriate balance between the activities of these enzymes is maintained. Interpretation of the deleterious effects of free radicals has to be analyzed not only as a function of the amount of free radicals produced but also relative to the efficiency and to the activities of these enzymatic and chemical antioxidant systems. The threshold of protection can indeed vary dramatically as a function of the level of activity of these enzymes.

The influence of vitamin E and selenium on lipid peroxidation and aldehyde dehydrogenase activity in rat liver and tissue

Malondialdehyde (MDA) production and cytosolic aldehyde dehydrogenase (ALDH) response were examined in rat liver tissues after feeding different levels of dietary vitamin E and/or selenium and polyunsaturated fat for 12-38 wk. MDA production was significantly increased by vitamin E deficiency or by high levels of polyunsaturated fat intake, but not by selenium deficiency. The activity of cytosolic ALDH increased upon increased production of MDA after 12-16 wk of feeding the lipid peroxidation-inducing diets. However, ALDH activity was suppressed after 38 wk of feeding the vitamin E-deficient diet. The results indicate that the hepatic cytosolic ALDH may be involved in the metabolism of MDA during a relatively short-term increase in in vivo lipid peroxidation, but that ALDH activity becomes suppressed after more severe in vivo lipid peroxidation has been produced. Hepatic and plasma alpha-tocopherol levels and lipid peroxidation products were measured for the various dietary groups.

Dihydrolipoic acid--a universal antioxidant both in the membrane and in the aqueous phase. Reduction of peroxyl, ascorbyl and chromanoxyl radicals

Thioctic (lipoic) acid is used as a therapeutic agent in a variety of diseases in which enhanced free radical peroxidation of membrane phospholipids has been shown to be a characteristic feature. It was suggested that the antioxidant properties of thioctic acid and its reduced form, dihydrolipoic acid, are at least in part responsible for the therapeutic potential. The reported results on the antioxidant efficiency of thioctic and dihydrolipoic acids obtained in oxidation models with complex multicomponent initiation systems are controversial. In the present work we used relatively simple oxidation systems to study the antioxidant effects of dihydrolipoic and thioctic acids based on their interactions with: (1) peroxyl radicals which are essential for the initiation of lipid peroxidation, (2) chromanoxyl radicals of vitamin E, and (3) ascorbyl radicals of vitamin C, the two major lipid- and water-soluble antioxidants, respectively. We demonstrated that: (1) dihydrolipoic acid (but not thioctic acid) was an efficient direct scavenger of peroxyl radicals generated in the aqueous phase by the water-soluble azoinitiator 2,2'-azobis(2-amidinopropane)-dihydrochloride, and in liposomes or in microsomal membranes by the lipid-soluble azoinitiator 2,2'-azobis(2,4-dimethylvaleronitrile); (2) both dihydrolipoic acid and thioctic acid did not interact directly with chromanoxyl radicals of vitamin E (or its synthetic homologues) generated in liposomes or in the membranes by three different ways: UV-irradiation, peroxyl radicals of 2,2'-azobis(2,4-dimethylvaleronitrile), or peroxyl radicals of linolenic acid formed by the lipoxygenase-catalyzed oxidation; and (3) dihydrolipoic acid (but not thioctic acid) reduced ascorbyl radicals (and dehydroascorbate) generated in the course of ascorbate oxidation by chromanoxyl radicals. This interaction resulted in ascorbate-mediated dihydrolipoic acid-dependent reduction of the vitamin E chromanoxyl radicals, i.e. vitamin E recycling. We conclude that dihydrolipoic acid may act as a strong direct chain-breaking antioxidant and may enhance the antioxidant potency of other antioxidants (ascorbate and vitamin E) in both the aqueous and the hydrophobic membraneous phases.

The role of lipid peroxidation in the nephrotoxicity of cisplatin

The possible role of lipid peroxidation in the nephrotoxicity of the antitumour drug cisplatin was studied in vitro. In contrast to Adriamycin, cisplatin did not induce lipid peroxidation in rat kidney microsomes containing a NADPH-generating system. Pretreatment of rat kidney microsomes with cisplatin did not reduce the activity of a microsomal glutathione (GSH)-dependent protective factor against lipid peroxidation induced by Fe(2+)-ascorbate. However, pretreatment of rat kidney microsomes with 0.1 mM N-ethyl maleimide (NEM) did reduce this GSH-dependent protection. Cisplatin also did not reduce the activity of a cytosolic GSH-dependent protective factor against Fe(2+)-ascorbate-induced lipid peroxidation. The results of our experiments indicate that, in contrast to Adriamycin, cisplatin does not induce lipid peroxidation in vitro in various test systems. It also does not destroy microsomal and cytosolic GSH-dependent protective factors against lipid peroxidation.

Research note: antioxidant activity of Japanese quail liver cytosol in the absence and presence of reduced glutathione

The antioxidant activity of Japanese quail liver cytosol was assessed in the presence of .1, 1.0, or 10.0 mM reduced glutathione (GSH) using an in vitro assay system that utilized quail liver microsomes as the lipid substrate. The formation of malonaldehyde (MA), an indicator of lipid peroxidation, was reduced (P less than .01) by 1.0 and 10.0 mM GSH, even in the absence of cytosolic protein. Cytosolic protein at a level of 1 mg/mL of assay medium did not further reduce MA formation at any of the GSH concentrations tested. Increasing the cytosolic protein concentration to 6 mg/mL decreased (P less than .01) MA formation, even in the absence of added GSH.

Stability of sonicated aqueous suspensions of phospholipids under air

The stability of phospholipids in liposomal aqueous suspension against oxidative degradation in air was investigated using spectrophotometric indices, glutathione peroxidase reactivity and thin layer chromatography. Zwitterionic phospholipid was found to be susceptible to degradation via oxidation of polyunsaturated hydrocarbon chains and ester hydrolysis, producing oxidized lysophosphatide and free fatty acid derivatives. These products were characterized as hydroperoxides based on their reactivity with the selenium-dependent glutathione peroxidase isolated from human erythrocytes. Lecithin in Tris buffer was more resistant to hydrolysis than in water. The sonication of 8.0 mM of soybean phosphatidylcholine (SB-PC) suspension in 0.1 M Tris (pH 7.5) in the presence of air produced relatively high concentration of conjugated diene hydroperoxide, but a small amount of hydrolyzed products. Anionic phospholipids, such as egg-phosphatidylglycerol (egg-PG), demonstrated higher resistance to air oxidation than the zwitterionic lecithin, but its oxidation was promoted by sonication.

Effect of exposure of various oxidants on rat liver and intestinal microsomes--a comparative study

Rat liver and intestinal microsomes were exposed to various free radical generating systems and their effect were assessed by studying different parameters such as formation of malonaldehyde (MDA) and conjugated diene, arachidonic acid depletion and alteration in protein thiol groups and tocopherol levels. These studies revealed that liver being highly vulnerable tissue showed all the effects of free radical attack whereas intestinal microsomes were resistant to most oxidants except iron independent generation of free radicals using 2-2'-azobis (2-amidinopropane) dihydrochloride (ABAP). Intestinal microsomes were found to contain considerable amount of non-esterified fatty acids in total lipid fraction as compared to liver microsomes and iron-fatty acid complex may be incapable of participating in peroxidation. In vitro measurement of hydroxyl radical generation showed that intestinal microsomes were incapable of generating these active species. These results suggest that iron dependent free radical mediated lipid peroxidation might not occur in intestinal epithelial cells.

Association of antioxidant systems in the protection of human fibroblasts against oxygen derived free radicals

The protection of human diploid fibroblasts against high oxygen tension was investigated using various combinations of the three major antioxidant enzymes: superoxide dismutase, catalase and glutathione peroxidase. alpha-Tocopherol, a well-known hydrophobic antioxidant, was also tested in combination with the different enzymes. Microinjection of solutions containing different combinations of the three enzymes was compared with the injection of each single enzyme. We observed that the protections given by catalase or superoxide dismutase on the one hand, and by glutathione peroxidase on the other hand, were additive. Surprisingly, the combinations of catalase and superoxide dismutase were less effective than catalase alone and was even toxic at low SOD concentrations. Addition of alpha-tocopherol following the injection of any of the three enzymes was highly beneficial, but the strongest synergistic effect was obtained with glutathione peroxidase. These results stress the importance of membrane protection by alpha-tocopherol and indirectly by glutathione peroxidase. They also showed that any injection leading to the decrease in the O2.- or H2O2 concentration combined with one of these two protectors is very beneficial for the cells probably by decreasing the OH concentration. This is also proven by the very good protective effect obtained with desferrioxamine.