Increased oxidative stress and antioxidant expression in mouse keratinocytes following exposure to paraquat

Environmental pro-oxidants induce altered envelope protein profiles in human keratinocytes

Cornified envelopes (CEs) of human epidermis ordinarily consist of transglutaminase-mediated cross-linked proteins and are essential for skin barrier function. However, in addition to enzyme-mediated isopeptide bonding, protein cross-linking could also arise from oxidative damage. Our group recently demonstrated abnormal incorporation of cellular proteins into CEs by pro-oxidants in woodsmoke. In this study, we focused on 2,3-dimethoxy-1,4-naphthoquinone (DMNQ), mesquite liquid smoke (MLS), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), to further understand the mechanisms through which environmental pro-oxidants induce CE formation and alter the CE proteome. CEs induced by the ionophore X537A were used for comparison. Similar to X537A, DMNQ- and MLS-induced CE formation was associated with membrane permeabilization. However, since DMNQ is non-adduct forming, its CEs were similar in protein profile to those from X537A. By contrast, MLS, rich in reactive carbonyls that can form protein adducts, caused a dramatic change in the CE proteome. TCDD-CEs were found to contain many CE precursors, such as small proline-rich proteins and late cornified envelope proteins, encoded by the epidermal differentiation complex. Since expression of these proteins is mediated by the aryl hydrocarbon receptor (AhR), and its well-known downstream protein, CYP1A1, was exclusively present in the TCDD group, we suggest that TCDD alters the CE proteome through persistent AhR activation. This study demonstrates the potential of environmental pro-oxidants to alter the epidermal CE proteome and indicates that the cellular redox state has an important role in CE formation.

Nilotinib alleviates paraquat-induced hepatic and pulmonary injury in rats via the Nrf2/Nf-kB axis

BACKGROUND

Paraquat (PQ, 1,1'-dimethyl-4-4'-bipyridinium dichloride) is a highly toxic quaternary ammonium herbicide widely used in agriculture. It exerts its toxic effects mainly as a result of its redox cycle via the production of superoxide anions in organisms, leading to an imbalance in the redox state of the cell causing oxidative damage and finally cell death. The aim of this study was to estimate the beneficial protective role of nilotinib (NIL) on PQ-induced hepatic and pulmonary toxicity in rats.

METHODS

Male wistar rats were randomly divided into four groups, namely control, PQ (15 mg/kg), PQ plus NIL (5 mg/kg) and PQ plus NIL (10 mg/kg). NIL (5 and 10 mg/kg/day) was taken by oral syringe for five days followed by a single intra-peritoneal administration of PQ (15 mg/kg) on sixth day.

RESULTS

Pretreatment with NIL relieved the histological damage in liver and lung tissues and improved hepatic biochemical markers. It significantly (p < 0.05) reduced serum levels of ALT, AST, ALP, Y-GT and total bilirubin while increased that of albumin. Meanwhile, NIL significantly (p < 0.05) reduced oxidative stress markers via reduction of malondialdhyde (MDA) and elevation of glutathione (GSH) contents in liver and lung tissues. In addition, it significantly (p < 0.05) decreased the inflammation by reducing hepatic and pulmonary tumor necrosis factor alpha (TNF-α) and nuclear transcription factor kappa B (NF-KB/p65) contents. Nilotinib also down-regulated apoptosis by reducing cysteinyl aspartate-specific proteinase-3 (caspase-3). Furthermore, it upregulated the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and microtubule-associated protein 1A/1B-light chain 3 II (LC3II) in liver and lung tissues.

SIGNIFICANCE

NIL suppressed PQ-induced inflammation, oxidative stress and apoptosis in liver and lung tissues by modulating Nrf2/Nf-kB axis.

Microsomal glutathione transferase 1 in cancer and the regulation of ferroptosis

Microsomal glutathione transferase 1 (MGST1) is a member of the MAPEG family (membrane associated proteins in eicosanoid and glutathione metabolism), defined according to enzymatic activities, sequence motifs, and structural properties. MGST1 is a homotrimer which can bind three molecules of glutathione (GSH), with one modified to a thiolate anion displaying one-third-of-sites-reactivity. MGST1 has both glutathione transferase and peroxidase activities. Each is based on stabilizing the GSH thiolate in the same active site. MGST1 is abundant in the liver and displays a broad subcellular distribution with high levels in endoplasmic reticulum and mitochondrial membranes, consistent with a physiological role in protection from reactive electrophilic intermediates and oxidative stress. In this review paper, we particularly focus on recent advances made in understanding MGST1 activation, induction, broad subcellular distribution, and the role of MGST1 in apoptosis, ferroptosis, cancer progression, and therapeutic responses.

Method for Determining the Body's Level of Protection According to Oxidant Status in Assessing the Influence of Industrial Risk Factors on Health

This work aims at improving the quality of health assessments, specifically under the influence of occupational risk factors. For this purpose, additional informative indicators are utilized in prognostic and diagnostic models. The models are used to characterize the level of body protection based on oxidative status. A quantitative method is proposed to assess the body's level of protection by means of the levels of lipid peroxidation and antioxidant activity, which characterize the body's oxidative status. A mechanism is developed for integrating the proposed method into prognostic and diagnostic decision rules. The developed rules are in the form of mathematical models used to synthesize hybrid fuzzy decision rules, which are then used to quantify the level of body protection (LBP) against external risk factors, based on the use of protection level functions in terms of lipid peroxidation and antioxidant activity. A mechanism for embedding LBP into predictive and diagnostic decision rules has been proposed. The proposed method is used to predict the occurrence and development of coronary heart disease in railroad locomotive drivers. It was found that to improve the predicting and diagnosing of diseases caused by external pathogenic factors, quantitative assessments of LBP, determined by oxidative status, can be implemented. It has been established that the use of the protection level indicator in predictive decision rules makes it possible to increase the efficiency of the prediction while simultaneously increasing its accuracy.

Isorhapontigenin Modulates SOX9/TOLLIP Expression to Attenuate Cell Apoptosis and Oxidative Stress in Paraquat-Induced Acute Kidney Injury

Paraquat (PQ) is a widely used herbicide but can be lethal to humans. The kidney is vital for PQ elimination; therefore, explorations for therapeutic approaches for PQ-induced acute kidney injury (AKI) are of great significance. Here, the effects of a natural bioactive polyphenol isorhapontigenin (ISO) on PQ-AKI were investigated. In vitro experiments carried out in PQ-intoxicated rat renal tubular epithelial cells (NRK-52E) showed that ISO treatment inhibited PQ-induced cell apoptosis and oxidative stress, which was evidenced by the decreased proapoptotic proteins [cleaved caspase 3/9 and poly (ADP-ribose) polymerase (PARP)], the reduced oxidative stress indicators [reactive oxygen species (ROS), malondialdehyde (MDA), and lactate dehydrogenase (LDH) leakage], and the increased antioxidants [superoxide dismutase (SOD), nuclear factor E2-related factor 2 (NRF2), and oxygenase-1 (HO-1)]. Furthermore, 50 mg/kg ISO pretreatment before PQ administration significantly attenuated PQ-AKI in rats, as manifested by the improved renal tubule damage, the reduced serum and urine markers of kidney injury, and the inhibited cell apoptosis and oxidative stress in the renal cortex. Furthermore, expression of sex-determining region Y box 9 (SOX9) and Toll-interacting protein (TOLLIP) in NRK-52E cells and the renal cortex was significantly upregulated after ISO treatment. Overexpression of SOX9 increased TOLLIP transcription and attenuated PQ-induced apoptosis and oxidative stress, whereas knockdown of SOX9 impaired the protective effects of ISO on NRK-52E cells against PQ toxicity. In conclusion, the present study demonstrated that ISO modulated SOX9/TOLLIP expression to attenuate cell apoptosis and oxidative stress in PQ-AKI, suggesting the potential of ISO in treating PQ-poisoned patients.

Developmental and Hepatic Gene Expression Changes in Chicken Embryos Exposed to p-Tert-Butylphenyl Diphenyl Phosphate and Isopropylphenyl Phosphate via Egg Injection

Organophosphate flame retardants (OPFRs) are used in a variety of products such as clear coats, resins, and plastics; however, research into their toxicological effects is limited. p-Tert-butylphenyl diphenyl phosphate (BPDP) and isopropylphenyl phosphate (IPPP) are two OPFRs that were prioritized for whole-animal toxicological studies based on observed effects in cultured avian hepatocytes in a previous study. The present study investigates the toxicity of BPDP and IPPP in chicken embryos at different developmental stages by evaluating morphological and gene expression endpoints. Chicken eggs were exposed via air cell injection to 0-250 μg/g (nominal) of either compound and then artificially incubated. At day 11 (midincubation), liver samples were collected for mRNA expression analysis; and at day 20 (1 day prehatch), morphological measurements and liver samples for transcriptomic evaluation were collected. At 250 μg/g, gallbladder size was significantly reduced for both compounds, head/bill length and tarsus length were significantly decreased, and liver somatic index was significantly increased following IPPP exposure only. No effects on mortality were observed up to the highest administered concentration for either chemical. Using a ToxChip polymerase chain reaction array, we report significant differences in hepatic gene expression for both compounds and time points; the most pronounced transcriptomic effects occurred at midincubation. Genes related to xenobiotic metabolism, bile acid/cholesterol regulation, and oxidative stress were significantly dysregulated. Given these changes observed throughout avian embryonic development, further research into the long-term effects of BPDP and IPPP are warranted, especially as they pertain to liver cholestasis. Environ Toxicol Chem 2022;41:739-747. © 2021 Her Majesty the Queen in Right of Canada. Environmental Toxicology and Chemistry © 2021 SETAC. Reproduced with the permission of the Minister of Environment and Climate Change Canada.

Gallic acid exerts anti-inflammatory, anti-oxidative stress, and nephroprotective effects against paraquat-induced renal injury in male rats

Paraquat (PRQ) is a toxic chemical compound that is very noxious to animals and humans. Gallic acid is a phenolic compound that has antioxidant properties. In this study, we evaluated the ameliorative effect of gallic acid against PRQ-induced renal injury and oxidative stress. In this research, the rats were segregated into six groups. Group 1 is the control group; group 2 received paraquat only; group 3 received gallic acid only; and groups 4, 5, and 6 received paraquat plus gallic acid at doses of 25, 50, and 100 mg/kg bw respectively. Findings of this work displayed that the renal contents of the vitamin C, superoxide dismutase (SOD), and catalase (CAT) significantly reduced and the levels of the serum protein carbonyl, creatinine, serum glutamate pyruvate transaminase (sGPT), urea, serum glutamate oxaloacetate transaminase (sGOT), uric acid, MDA, serum IL-1β, and the kidney IL-1β gene expression were remarkably increased in the group receiving PRQ only compared with that in the control group. On the other hand, treatment with gallic acid after exposure to PRQ led to a significant elevation in renal vitamin C, SOD, and CAT levels plus a remarkable decrease in the serum protein carbonyl, creatinine, sGPT, urea, sGOT, uric acid, MDA, IL-1β, and renal gene expression of IL-1β in comparison with the PRQ-only-treated rats. Histological changes were also ameliorated by gallic acid administration. The data approve that gallic acid diminished the deleterious effects of PRQ exposure. In this regard, our results indicated that the administration of gallic acid could alleviate the noxious effects of PRQ on the antioxidant defense system and renal tissue.

Survival Mechanisms and Xenobiotic Susceptibility of Keratinocytes Exposed to Metal-Derived Nanoparticles

Metal-derived nanoparticles (Mt-NPs) are increasingly used in cosmetology due to their ultraviolet shielding (titanium dioxide [TiO₂]), antioxidant (cerium dioxide [CeO₂]), and biocidal (silver [Ag]) properties. In the absence of overt toxicity (i.e., cell death), Mt-NPs are considered safe for cosmetic applications. However, there is little understanding about the mechanisms involved in the survival of keratinocytes exposed to subtoxic levels of Mt-NPs. Human keratinocytes (HaCaT) were exposed subacutely to subtoxic concentrations (≤30 μg/mL, 48-72 h) of rutile (r) TiO₂ (cylindrical), CeO₂ (cubic) and Ag (spherical) with a core/hydrodynamic size of <50/<100 nm and >98% purity. Mt-NP uptake was indirectly quantified by changes in the light side scatter, where the kinetics (time/dose-response) suggested that the three types of Mt-NPs were similarly uptaken by keratinocytes. rTiO₂ and CeO₂, but not Ag-NPs, increased autophagy, whose inhibition prompted cell death. No increase in the steady-state levels of reactive oxygen species (ROS) was induced by exposure to any of the Mt-NPs tested. Interestingly, intracellular Ag-NP aggregates observed an increased far-red autofluorescence (≥740 nm em), which has been ascribed to their binding to thiol molecules such as glutathione (GSH). Accordingly, inhibition of GSH synthesis, but not the impairment of oxidized GSH recycling, sensitized keratinocytes to Ag-NPs suggesting that GSH homeostasis, and its direct scavenging of Ag-NPs, but not ROS, is essential for keratinocyte survival upon exposure to Ag-NP. rTiO₂ and Ag, but not CeO₂-NPs, compromised metabolic flux (glycolysis and respiration), but ATP levels were unaltered. Finally, we also observed that exposure to Mt-NPs sensitized keratinocytes to non-UV xenobiotic exposure (arsenite and paraquat). Our results demonstrate the differential contribution of autophagy and GSH homeostasis to the survival of human keratinocytes exposed to subtoxic concentrations of Mt-NPs and highlight the increased susceptibility of keratinocytes exposed to Mt-NPs to a second xenobiotic insult.

Synthetically modified methoxsalen for enhanced cytotoxicity in light and dark reactions

Linear furocoumarins, also known as psoralens, are clinically useful photo-activated pharmaceuticals employed to address hyperproliferative skin diseases. Seven diverse cytotoxic pharmacophores have been synthetically attached to 8-methoxypsoralen via a 5-amino functionality. The resulting unique set of compounds was evaluated for dark and light toxicity against PAM212 keratinocytes in culture.

Rapid and sensitive surface-enhanced Raman spectroscopy (SERS) method combined with gold nanoparticles for determination of paraquat in apple juice

BACKGROUND

Paraquat, a highly efficient herbicide, is widely used in agricultural practices throughout the world. However, paraquat residues in food pose a threat to human health. In order to develop a rapid and sensitive method, surface-enhanced Raman spectroscopy (SERS) coupled with gold nanoparticles was applied to analysis of paraquat in apple juice.

RESULTS

Natural organic compounds (sugars and organic acids) in apple juice interfered with SERS measurement. Sample preparation was needed. Paraquat could be detected at concentrations as low as 0.02 and 0.1 µg mL^{- 1} with the weak cation-exchange solid-phase extraction (WCX-SPE) method and dilution method for sample preparation, respectively. For quantitative analysis, the R2 cv of the partial least-squares regression model with the dilution method (0.939) was not as good as with the WCX-SPE method (0.984), but the dilution method is much less costly, simpler and time saving. Satisfactory recovery values were obtained ranging from 94.73% to 114.81%, with the exception of 56.55% for the lowest concentration.

CONCLUSION

This work showed that SERS combined with gold nanoparticles could determine paraquat in apple juice. As a simple, rapid and ultrasensitive method, it has great practical potential for detection of other contaminants in a variety of foods. © 2018 Society of Chemical Industry.

Sulfur mustard triggers oxidative stress through glutathione depletion and altered expression of glutathione-related enzymes in human airways

CONTEXT

Sulfur mustard (SM) is a lipophilic and reactive chemical compound that targets human airway system.

OBJECTIVE

Glutathione (GSH) depletion, oxidative stress (OS) status, and changes in expression of GSH-dependent antioxidant enzymes were considered in human mustard lungs.

MATERIALS AND METHODS

Lung biopsies and bronchoalveolar lavage (BAL) were collected from non-exposed (n = 10) individuals and SM-exposed patients (n = 12). Alterations in expression of GSH-dependent enzymes were studied using RT² Profiler™ PCR array. OS was evaluated by determining BAL fluid levels of total antioxidant capacity (TAC), malondialdehyde (MDA), and GSH.

RESULTS

Mean TAC (0.142 ± 0.027 µmol/l) and GSH (4.98 ± 1.02 nmol/l) in BAL fluids of control group was significantly higher (p < .05) than those in SM-exposed patients (TAC = 0.095 ± 0.018 µmol/l and GSH= 3.09 ± 1.02 nmol/l), while MDA level in BAL fluids of these patients (0.71 ± 0.06 nmol/l) was significantly (p = .001) higher than that in controls (0.49 ± 0.048 nmol/l). Glutathione peroxidases (GPXs), glutathione-s-transferases (GSTs), and glutathione synthetase (GSS) enzymes were overexpressed in mustard lung biopsies, while glutathione reductase (GSR) was significantly downregulated (14.95-fold).

CONCLUSIONS

GSH depletion induced by GSR downregulation may be a major mechanism of SM toxicity on human lung. Despite overexpression of GSTs and GPXs genes, GSH depletion may decline the productivity of these enzymes and total antioxidants capacity, which is associated with OS.

Metabolic and Growth Rate Alterations in Lymphoblastic Cell Lines Discriminate Between Down Syndrome and Alzheimer's Disease

BACKGROUND

Deficits in mitochondrial function and oxidative stress play pivotal roles in Down syndrome (DS) and Alzheimer's disease (AD) and these alterations in mitochondria occur systemically in both conditions.

OBJECTIVE

We hypothesized that peripheral cells of elder subjects with DS exhibit disease-specific and dementia-specific metabolic features. To test this, we performed a comprehensive analysis of energy metabolism in lymphoblastic-cell-lines (LCLs) derived from subjects belonging to four groups: DS-with-dementia (DSAD), DS-without-dementia (DS), sporadic AD, and age-matched controls.

METHODS

LCLs were studied under regular or minimal feeding regimes with galactose or glucose as primary carbohydrate sources. We assessed metabolism under glycolysis or oxidative phosphorylation by quantifying cell viability, oxidative stress, ATP levels, mitochondrial membrane potential (MMP), mitochondrial calcium uptake, and autophagy.

RESULTS

DS and DSAD LCLs showed slower growth rates under minimal feeding. DS LCLs mainly dependent on mitochondrial respiration exhibited significantly slower growth and higher levels of oxidative stress compared to other groups. While ATP levels (under mitochondrial inhibitors) and mitochondrial calcium uptake were significantly reduced in DSAD and AD cells, MMP was decreased in DS, DSAD, and AD LCLs. Finally, DS LCLs showed markedly reduced levels of the autophagy marker LC3-II, underscoring the close association between metabolic dysfunction and impaired autophagy in DS.

CONCLUSION

There are significant mitochondrial functional changes in LCLs derived from DS, DSAD, and AD patients. Several parameters analyzed were consistently different between DS, DSAD, and AD lines suggesting that metabolic indicators between LCL groups may be utilized as biomarkers of disease progression and/or treatment outcomes.

Paraquat Induces Peripheral Myelin Disruption and Locomotor Defects: Crosstalk with LXR and Wnt Pathways

AIMS

Paraquat (PQT), a redox-active herbicide, is a free radical-producing molecule, causing damage particularly to the nervous system; thus, it is employed as an animal model for Parkinson's disease. However, its impact on peripheral nerve demyelination is still unknown. Our aim is to decipher the influence of PQT-induced reactive oxygen species (ROS) production on peripheral myelin.

RESULTS

We report that PQT provokes severe locomotor and sensory defects in mice. PQT elicited an oxidative stress in the nerve, resulting in an increase of lipid peroxidation and protein carbonylation, despite the induction of nuclear factor erythroid 2-related factor 2 (Nrf2)-dependent antioxidant defenses. We observed a dramatic disorganization of myelin sheaths in the sciatic nerves, dysregulation of myelin gene expression, and aggregation of myelin proteins, a hallmark of demyelination. PQT altered myelin gene expression via liver X receptor (LXR) signaling, a negative regulator of peripheral myelin gene expression through its dialog with the Wnt/β-catenin pathway. PQT prevented β-catenin binding on myelin gene promoters, resulting in the inhibition of Wnt/β-catenin-dependent myelin gene expression. Wnt pathway activation by LiCl dampened the deleterious effects of PQT. LiCl blocked PQT-induced oxidative stress and reduced Schwann cell death. LiCl+PQT-treated mice had normal sensorimotor behaviors and a usual nerve structure.

INNOVATION

We reveal that PQT damages the sciatic nerve by generating an oxidative stress, dysregulating LXR and Wnt/β-catenin pathways. The activation of Wnt signaling by LiCl reduced the deleterious effects of PQT on the nerve.

CONCLUSION

We demonstrate that PQT instigates peripheral nerve demyelinating neuropathies by enhancing ROS production and deregulating LXR and Wnt pathways. Stimulating Wnt pathway could be a therapeutic strategy for neuropathy treatment. Antioxid. Redox Signal. 27, 168-183.

Autophagy deficient keratinocytes display increased DNA damage, senescence and aberrant lipid composition after oxidative stress in vitro and in vivo

Autophagy allows cells fundamental adaptations to metabolic needs and to stress. Using autophagic bulk degradation cells can clear crosslinked macromolecules and damaged organelles that arise under redox stress. Accumulation of such debris results in cellular dysfunction and is observed in aged tissue and senescent cells. Conversely, promising anti-aging strategies aim at inhibiting the mTOR pathway and thereby activating autophagy, to counteract aging associated damage. We have inactivated autophagy related 7 (Atg7), an essential autophagy gene, in murine keratinocytes (KC) and have found in an earlier study that this resulted in increased baseline oxidative stress and reduced capacity to degrade crosslinked proteins after oxidative ultraviolet stress. To investigate whether autophagy deficiency would promote cellular aging, we studied how Atg7 deficient (KO) and Atg7 bearing cells (WT) would respond to stress induced by paraquat (PQ), an oxidant drug commonly used to induce cellular senescence. Atg7 deficient KC displayed increased prostanoid signaling and a pro- mitotic gene expression signature as compared to the WT. After exposure to PQ, both WT and KO cells showed an inflammatory and stress-related transcriptomic response. However, the Atg7 deficient cells additionally showed drastic DNA damage- and cell cycle arrest signaling. Indeed, DNA fragmentation and -oxidation were strongly increased in the stressed Atg7 deficient cells upon PQ stress but also after oxidizing ultraviolet A irradiation. Damage associated phosphorylated histone H2AX (γH2AX) foci were increased in the nuclei, whereas expression of the nuclear lamina protein lamin B1 was strongly decreased. Similarly, in both, PQ treated mouse tail skin explants and in UVA irradiated mouse tail skin, we found a strong increase in γH2AX positive nuclei within the basal layer of Atg7 deficient epidermis. Atg7 deficiency significantly affected expression of lipid metabolic genes. Therefore we performed lipid profiling of keratinocytes which demonstrated a major dysregulation of cellular lipid metabolism. We found accumulation of autophagy agonisitic free fatty acids, whereas triglyceride levels were strongly decreased. Together, our data show that in absence of Atg7/autophagy the resistance of keratinocytes to intrinsic and environmental oxidative stress was severely impaired and resulted in DNA damage, cell cycle arrest and a disturbed lipid phenotype, all typical for premature cell aging.

Specific carotenoid pigments in the diet and a bit of oxidative stress in the recipe for producing red carotenoid-based signals

Colorful ornaments have been the focus of sexual selection studies since the work of Darwin. Yellow to red coloration is often produced by carotenoid pigments. Different hypotheses have been formulated to explain the evolution of these traits as signals of individual quality. Many of these hypotheses involve the existence of a signal production cost. The carotenoids necessary for signaling can only be obtained from food. In this line, carotenoid-based signals could reveal an individual’s capacity to find sufficient dietary pigments. However, the ingested carotenoids are often yellow and became transformed by the organism to produce pigments of more intense color (red ketocarotenoids). Biotransformation should involve oxidation reactions, although the exact mechanism is poorly known. We tested the hypothesis that carotenoid biotransformation could be costly because a certain level of oxidative stress is required to correctly perform the conversion. The carotenoid-based signals could thus reveal the efficiency of the owner in successfully managing this challenge. In a bird with ketocarotenoid-based ornaments (the red-legged partridge; Alectoris rufa), the availability of different carotenoids in the diet (i.e. astaxanthin, zeaxanthin and lutein) and oxidative stress were manipulated. The carotenoid composition was analyzed and quantified in the ornaments, blood, liver and fat. A number of oxidative stress biomarkers were also measured in the same tissues. First, we found that color and pigment levels in the ornaments depended on food levels of those carotenoids used as substrates in biotransformation. Second, we found that birds exposed to mild levels of a free radical generator (diquat) developed redder bills and deposited higher amounts of ketocarotenoids (astaxanthin) in ornaments. Moreover, the same diquat-exposed birds also showed a weaker resistance to hemolysis when their erythrocytes were exposed to free radicals, with females also enduring higher oxidative damage in plasma lipids. Thus, higher color production would be linked to higher oxidative stress, supporting the biotransformation hypothesis. The recent discovery of an avian oxygenase enzyme involved in converting yellow to red carotenoids may support our results. Nonetheless, the effect could also depend on the abundance of specific substrate carotenoids in the diet. Birds fed with proportionally higher levels of zeaxanthin showed the reddest ornaments with the highest astaxanthin concentrations. Moreover, these birds tended to show the strongest diquat-mediated effect. Therefore, in the evolution of carotenoid-based sexual signals, a biotransformation cost derived from maintaining a well-adjusted redox machinery could coexist with a cost linked to carotenoid acquisition and allocation (i.e. a resource allocation trade-off).

Periodic Exposure of Keratinocytes to Cold Physical Plasma: An In Vitro Model for Redox-Related Diseases of the Skin

Oxidative stress illustrates an imbalance between radical formation and removal. Frequent redox stress is critically involved in many human pathologies including cancer, psoriasis, and chronic wounds. However, reactive species pursue a dual role being involved in signaling on the one hand and oxidative damage on the other. Using a HaCaT keratinocyte cell culture model, we investigated redox regulation and inflammation to periodic, low-dose oxidative stress after two, six, eight, ten, and twelve weeks. Chronic redox stress was generated by recurrent incubation with cold physical plasma-treated cell culture medium. Using transcriptome microarray technology, we identified both acute ROS-stress responses as well as numerous adaptions after several weeks of redox challenge. We determined a differential expression (2-fold, FDR < 0.01, p < 0.05) of 260 genes that function in inflammation and redox homeostasis, such as cytokines (e.g., IL-6, IL-8, and IL-10), growth factors (e.g., CSF2, FGF, and IGF-2), and antioxidant enzymes (e.g., HMOX, NQO1, GPX, and PRDX). Apoptotic signaling was affected rather modestly, especially in p53 downstream targets (e.g., BCL2, BBC3, and GADD45). Strikingly, the cell-protective heat shock protein HSP27 was strongly upregulated (p < 0.001). These results suggested cellular adaptions to frequent redox stress and may help to better understand the inflammatory responses in redox-related diseases.

Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: the challenge ahead

Low-dose exposures to common environmental chemicals that are deemed safe individually may be combining to instigate carcinogenesis, thereby contributing to the incidence of cancer. This risk may be overlooked by current regulatory practices and needs to be vigorously investigated.

Lifestyle factors are responsible for a considerable portion of cancer incidence worldwide, but credible estimates from the World Health Organization and the International Agency for Research on Cancer (IARC) suggest that the fraction of cancers attributable to toxic environmental exposures is between 7% and 19%. To explore the hypothesis that low-dose exposures to mixtures of chemicals in the environment may be combining to contribute to environmental carcinogenesis, we reviewed 11 hallmark phenotypes of cancer, multiple priority target sites for disruption in each area and prototypical chemical disruptors for all targets, this included dose-response characterizations, evidence of low-dose effects and cross-hallmark effects for all targets and chemicals. In total, 85 examples of chemicals were reviewed for actions on key pathways/mechanisms related to carcinogenesis. Only 15% (13/85) were found to have evidence of a dose-response threshold, whereas 59% (50/85) exerted low-dose effects. No dose-response information was found for the remaining 26% (22/85). Our analysis suggests that the cumulative effects of individual (non-carcinogenic) chemicals acting on different pathways, and a variety of related systems, organs, tissues and cells could plausibly conspire to produce carcinogenic synergies. Additional basic research on carcinogenesis and research focused on low-dose effects of chemical mixtures needs to be rigorously pursued before the merits of this hypothesis can be further advanced. However, the structure of the World Health Organization International Programme on Chemical Safety ‘Mode of Action’ framework should be revisited as it has inherent weaknesses that are not fully aligned with our current understanding of cancer biology.

The effect of environmental chemicals on the tumor microenvironment

Potentially carcinogenic compounds may cause cancer through direct DNA damage or through indirect cellular or physiological effects. To study possible carcinogens, the fields of endocrinology, genetics, epigenetics, medicine, environmental health, toxicology, pharmacology and oncology must be considered. Disruptive chemicals may also contribute to multiple stages of tumor development through effects on the tumor microenvironment. In turn, the tumor microenvironment consists of a complex interaction among blood vessels that feed the tumor, the extracellular matrix that provides structural and biochemical support, signaling molecules that send messages and soluble factors such as cytokines. The tumor microenvironment also consists of many host cellular effectors including multipotent stromal cells/mesenchymal stem cells, fibroblasts, endothelial cell precursors, antigen-presenting cells, lymphocytes and innate immune cells. Carcinogens can influence the tumor microenvironment through effects on epithelial cells, the most common origin of cancer, as well as on stromal cells, extracellular matrix components and immune cells. Here, we review how environmental exposures can perturb the tumor microenvironment. We suggest a role for disrupting chemicals such as nickel chloride, Bisphenol A, butyltins, methylmercury and paraquat as well as more traditional carcinogens, such as radiation, and pharmaceuticals, such as diabetes medications, in the disruption of the tumor microenvironment. Further studies interrogating the role of chemicals and their mixtures in dose-dependent effects on the tumor microenvironment could have important general mechanistic implications for the etiology and prevention of tumorigenesis.

Natural antioxidant betanin protects rats from paraquat-induced acute lung injury interstitial pneumonia

The effect of betanin on a rat paraquat-induced acute lung injury (ALI) model was investigated. Paraquat was injected intraperitoneally at a single dose of 20 mg/kg body weight, and betanin (25 and 100 mg/kg/d) was orally administered 3 days before and 2 days after paraquat administration. Rats were sacrificed 24 hours after the last betanin dosage, and lung tissue and bronchoalveolar lavage fluid (BALF) were collected. In rats treated only with paraquat, extensive lung injury characteristic of ALI was observed, including histological changes, elevation of lung : body weight ratio, increased lung permeability, increased lung neutrophilia infiltration, increased malondialdehyde (MDA) and myeloperoxidase (MPO) activity, reduced superoxide dismutase (SOD) activity, reduced claudin-4 and zonula occluden-1 protein levels, increased BALF interleukin (IL-1) and tumor necrosis factor (TNF)-α levels, reduced BALF IL-10 levels, and increased lung nuclear factor kappa (NF-κB) activity. In rats treated with betanin, paraquat-induced ALI was attenuated in a dose-dependent manner. In conclusion, our results indicate that betanin attenuates paraquat-induced ALI possibly via antioxidant and anti-inflammatory mechanisms. Thus, the potential for using betanin as an auxilliary therapy for ALI should be explored further.

Betanin attenuates oxidative stress and inflammatory reaction in kidney of paraquat-treated rat

The effects of natural pigment betanin on oxidative stress and inflammation in kidney of paraquat-treated rat were investigated. Paraquat was injected intraperitoneally into rats to induce renal damage. The rats were randomly divided into four groups: a control group, a paraquat group, and two paraquat groups that were treated with betanin at 25 and 100 mg/kg/d three days before and two days after paraquat administration. Treatment with betanin alleviated the paraquat-incurred acute kidney injury, evidenced by histological improvement, reduced serum and urine markers for kidney injury. Betanin antagonized the paraquat-induced inflammation, indicated by reduced expression of inducible nitric oxide synthase and cyclooxygenase, blunted activation of nuclear factor kappa B, and diminished lysosomal protease activities. Betanin also decreased oxidative stress elicited by paraquat. In conclusion, betanin may have a protective effect against paraquat-induced acute kidney damage. The mechanisms of the protection appear to be the inhibition of oxidative stress and inflammation.

Betanin attenuates paraquat-induced liver toxicity through a mitochondrial pathway

We attempted to determine whether betanin (from natural pigments) that has anti-oxidant properties would be protective against paraquat-induced liver injury in Sprague-Dawley rats. Paraquat was injected intraperitoneally into rats to induce liver toxicity. The rats were randomly divided into four groups: a control group, a paraquat group, and two groups that received betanin at doses of 25 and 100mg/kg/day three days before and two days after they were administered paraquat. We evaluated liver histopathology, serum liver enzymatic activities, oxidative stress, cytochrome P450 (CYP) 3A2 mRNA expression, and mitochondrial damage. The rats that were injected with paraquat incurred liver injury, evidenced by histological changes and elevated serum aspartate aminotransferase and alanine aminotransferase levels; paraquat also led to oxidative stress, an increase of cytochrome P450 3A2 mRNA expression, and mitochondrial damage, indicated by mitochondrial membrane swelling, reduced mitochondrial cytochrome C, and apoptosis-inducing factor protein levels. Pathological damage and all of the above mentioned markers were lesser in the animals treated with betanin than in those who received paraquat alone. Betanin had a protective effect against paraquat-induced liver damage in rats. The mechanism of the protection appears to be the inhibition of CYP 3A2 expression and protection of mitochondria.

Potent antioxidative and UVB protective effect of water extract of Eclipta prostrata L

Oxidative stress, including Ultraviolet (UV) irradiation-induced skin damage, is involved in numerous diseases. This study demonstrates that water extract of Eclipta prostrata L. (WEP) has a potent effect in scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH), superoxide radicals, and chelating ferrous ion, exhibiting IC₅₀ values of 0.23 mg/mL, 0.48 mg/mL, and 1.25 mg/mL, respectively. The WEP total phenol content was 176.45 mg gallic acid equivalents (GAE)/g sample. Chlorogenic acid, a component of the plant's active ingredients, was determined by HPLC and antioxidative assay. However, no caffeic acid, stigmasterol, or wedelolactone was present in WEP. WEP absorbs both UVA and UVB irradiation, and furthermore, the extract shows a dose-dependent response in the protection of HaCaT human keratinocytes and mouse fibroblasts 3T3 cells against UVB-induced cytotoxicity, which may result from a synergistic effect between chlorogenic acid and other active components present in WEP.

Regulation of keratinocyte expression of stress proteins and antioxidants by the electrophilic nitrofatty acids 9- and 10-nitrooleic acid

Nitric oxide and various by-products including nitrite contribute to tissue injury by forming novel intermediates via redox-mediated nitration reactions. Nitration of unsaturated fatty acids generates electrophilic nitrofatty acids such as 9-nitrooleic acid (9-NO) and 10-nitrooleic acid (10-NO), which are known to initiate intracellular signaling pathways. In these studies, we characterized nitrofatty acid-induced signaling and stress protein expression in mouse keratinocytes. Treatment of keratinocytes with 5-25μM 9-NO or 10-NO for 6h upregulated mRNA expression of heat shock proteins (hsp's) 27 and 70; primary antioxidants heme oxygenase-1 (HO-1) and catalase; secondary antioxidants glutathione S-transferase (GST) A1/2, GSTA3, and GSTA4; and Cox-2, a key enzyme in prostaglandin biosynthesis. The greatest responses were evident with HO-1, hsp27, and hsp70. In keratinocytes, 9-NO activated JNK and p38 MAP kinases. JNK inhibition suppressed 9-NO-induced HO-1, hsp27, and hsp70 mRNA and protein expression, whereas p38 MAP kinase inhibition suppressed HO-1. In contrast, inhibition of constitutive expression of Erk1/2 suppressed only hsp70, indicating that 9-NO modulates expression of stress proteins by distinct mechanisms. 9-NO and 10-NO also upregulated expression of caveolin-1, the major structural component of caveolae. Western blot analysis of caveolar membrane fractions isolated by sucrose density centrifugation revealed that HO-1, hsp27, and hsp70 were localized within caveolae after nitrofatty acid treatment of keratinocytes, suggesting a link between induction of stress response proteins and caveolin-1 expression. These data indicate that nitrofatty acids are effective signaling molecules in keratinocytes. Moreover, caveolae seem to be important in the localization of stress proteins in response to nitrofatty acids.

Modulation of keratinocyte expression of antioxidants by 4-hydroxynonenal, a lipid peroxidation end product

4-Hydroxynonenal (4-HNE) is a lipid peroxidation end product generated in response to oxidative stress in the skin. Keratinocytes contain an array of antioxidant enzymes which protect against oxidative stress. In these studies, we characterized 4-HNE-induced changes in antioxidant expression in mouse keratinocytes. Treatment of primary mouse keratinocytes and PAM 212 keratinocytes with 4-HNE increased mRNA expression for heme oxygenase-1 (HO-1), catalase, NADPH:quinone oxidoreductase (NQO1) and glutathione S-transferase (GST) A1-2, GSTA3 and GSTA4. In both cell types, HO-1 was the most sensitive, increasing 86-98 fold within 6h. Further characterization of the effects of 4-HNE on HO-1 demonstrated concentration- and time-dependent increases in mRNA and protein expression which were maximum after 6h with 30 μM. 4-HNE stimulated keratinocyte Erk1/2, JNK and p38 MAP kinases, as well as PI3 kinase. Inhibition of these enzymes suppressed 4-HNE-induced HO-1 mRNA and protein expression. 4-HNE also activated Nrf2 by inducing its translocation to the nucleus. 4-HNE was markedly less effective in inducing HO-1 mRNA and protein in keratinocytes from Nrf2-/- mice, when compared to wild type mice, indicating that Nrf2 also regulates 4-HNE-induced signaling. Western blot analysis of caveolar membrane fractions isolated by sucrose density centrifugation demonstrated that 4-HNE-induced HO-1 is localized in keratinocyte caveolae. Treatment of the cells with methyl-β-cyclodextrin, which disrupts caveolar structure, suppressed 4-HNE-induced HO-1. These findings indicate that 4-HNE modulates expression of antioxidant enzymes in keratinocytes, and that this can occur by different mechanisms. Changes in expression of keratinocyte antioxidants may be important in protecting the skin from oxidative stress.

Docosahexaenoic and eicosapentaenoic acid supplementation does not exacerbate oxidative stress or intravascular haemolysis in homozygous sickle cell patients

We investigated whether or not Omega-3 long-chain polyunsaturated fatty acid (omega-3 LCPUFA) supplementation exacerbates oxidative stress in homozygous sickle cell patients aged 2 to 14 years. Depending on their age, they received between one and three omega-3 (277.8mg DHA and 39.0mg EPA/capsule) or placebo (high oleic acid sunflower seed oil) capsules for one year. Supplementation increased significantly the levels of the two fatty acids in red cell phosphatidylcholine and phosphatidylethanolamine (p<0.001). The patients who received omega-3 LCPUFA compared with their placebo-taking counterparts had a higher concentration of plasma vitamin E at one year (14.3±2.8 versus 12.3±2.8µmol/l; p<0.001). The two groups had comparable concentrations of the vitamin at six month intervention (10.8±2.2 versus 10.7±2.9µmol/l; p>0.05) and baseline (10.7±3.1 versus 10.7±2.8µmol/l; p>0.05). After six month of intervention, the patients on omega 3 fatty acids had lower GPx-1 (33.5±13.4 versus 46.6 ±17.6, p<0.01) and Cu/Zn-SOD (1070±600 versus 1470±690 p<0.05) activities than at baseline. GPx-1 (33.5±17.6IU/g Hb versus 43.7±13.2IU/g Hb; p<0.01) and Cu/Zn-SOD (1070±600IU/g Hb versus 1360±920IU/g Hb; p>0.05) activities were reduced in the omega 3 compared with the placebo at six month intervention. There was no difference in the activity of either of the enzymes between baseline and six month intervention in the placebo group (p>0.05). This study demonstrates; DHA and EPA supplementation, rather than exacerbating the inherent oxidative stress associated with the disease, seems to provide an antioxidant protection. Hence, it will be safe to provide omega-3 LCPUFA to sickle cell patients to help ameliorate vaso-occlusive and haemolytic crises and membrane fatty acid abnormality.

Antioxidant response and histopathological changes in brain tissue of pigeon exposed to avermectin

Avermectins (AVMs) are the active components of some insecticidal and nematicidal products used in agriculture and veterinary medicine for the prevention of parasitic diseases. Residues of AVM drugs or their metabolites in livestock feces have toxic effects on non-target aquatic and terrestrial organisms. In this study, oxidative stress responses and pathological changes on pigeon brain tissues and serum after subchronic exposure to AVM for 30, 60 and 90 days were investigated. The decrease in antioxidant enzyme (superoxide dismutase, SOD and glutathione peroxidase, GSH-Px) activities and increase in methane dicarboxylic aldehyde content in a dose-time-dependent manner in the brain and serum of pigeon were observed. The protein carbonyl content, an indicator of protein oxidation, and DNA-protein crosslink coefficient were significantly augmented with dose-time-dependent properties. The microscopic structures of the cerebrum, cerebellum and optic lobe altered obviously, the severity of which increased with the concentration of AVM and exposure time. The results imply that AVM could induce oxidative damage to the brain tissue and serum of pigeon. The information presented in this study is helpful to understand the mechanism of AVM-induced oxidative stress in birds.

Biochemical and molecular mechanisms of N-acetyl cysteine and silymarin-mediated protection against maneb- and paraquat-induced hepatotoxicity in rats

Oxidative stress is one of the major players in the pathogenesis of maneb (MB) and paraquat (PQ)-induced disorders. N-acetyl cysteine (NAC), a glutathione (GSH) precursor and silymarin (SIL), a naturally occurring antioxidant, encounter oxidative stress-mediated cellular damage. The present study was aimed to investigate the effects of NAC and SIL against MB and/or PQ-induced hepatotoxicity in rats. The levels of hepatotoxicity markers - alanine aminotransaminase (ALT), aspartate aminotransaminase (AST) and total bilirubin, histological changes, oxidative stress indices, phase I and phase II xenobiotic metabolizing enzymes - cytochrome P450 (CYP) and glutathione S-transferase (GST) and pro-inflammatory molecules - inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were measured in animals treated with MB and/or PQ in the presence or absence of NAC and SIL. MB and/or PQ augmented ALT, AST, total bilirubin, lipid peroxidation and nitrite contents and catalytic activities of superoxide dismutase and glutathione peroxidase however, the GSH content was attenuated. NAC and SIL restored the above-mentioned alterations towards basal levels but the restorations were more pronounced in SIL treated groups. Similarly, MB and/or PQ-mediated histopathological symptoms and changes in the catalytic activities/expressions of CYP1A2, CYP2E1, iNOS, TNF-α, and IL-1β were alleviated by NAC and SIL. Conversely, MB and/or PQ-induced GSTA4-4 expression/activity was further increased by NAC/SIL and glutathione reductase activity was also increased. The results obtained thus suggest that NAC and SIL protect MB and/or PQ-induced hepatotoxicity by reducing oxidative stress, inflammation and by modulating xenobitic metabolizing machinery and SIL seems to be more effective.

Reactive oxygen species regulated mitochondria-mediated apoptosis in PC12 cells exposed to chlorpyrifos

Reactive oxidative species (ROS) generated by environmental toxicants including pesticides could be one of the factors underlying the neuronal cell damage in neurodegenerative diseases. In this study we found that chlorpyrifos (CPF) induced apoptosis in dopaminergic neuronal components of PC12 cells as demonstrated by the activation of caspases and nuclear condensation. Furthermore, CPF also reduced the tyrosine hydroxylase-positive immunoreactivity in substantia nigra of the rat. In addition, CPF induced inhibition of mitochondrial complex I activity. Importantly, N-acetyl cysteine (NAC) treatment effectively blocked apoptosis via the caspase-9 and caspase-3 pathways while NAC attenuated the inhibition of mitochondrial complex I activity as well as the oxidative metabolism of dopamine (DA). These results demonstrated that CPF-induced apoptosis was involved in mitochondrial dysfunction through the production of ROS. In the response of cellular antioxidant systems to CPF, we found that CPF treatment increased HO-1 expression while the expression of CuZnSOD and MnSOD was reduced. In addition, we found that CPF treatment activated MAPK pathways, including ERK 1/2, the JNK, and the p38 MAP kinase in a time-dependent manner. NAC treatment abolished MAPK phosphorylation caused by CPF, indicating that ROS are upstream signals of MAPK. Interestingly, MAPK inhibitors abolished cytotoxicity and reduced ROS generation by CPF treatment. Our results demonstrate that CPF induced neuronal cell death in part through MAPK activation via ROS generation, suggesting its potential to generate oxidative stress via mitochondrial damage and its involvement in oxidative stress-related neurodegenerative disease.

Different characteristics of reactive oxygen species production by human keratinocyte cell line cells in response to allergens and irritants

Keratinocytes mount immune responses through the secretion of a variety of inflammatory cytokines, soluble proteins and reactive oxygen species (ROS). However, the role of ROS in keratinocytes in response to allergens and irritants has not yet been elucidated. In this study, we investigated the (i) ROS production; (ii) potential sites of ROS production; (iii) expression of cell surface molecules; (iv) secretion of cytokines; and (v) ROS-dependent protein carbonylation in chemical-treated human keratinocyte cell line (HaCaT) cells. Treatment of HaCaT cells with 2,4-dinitrochlorobenzene (DNCB) and benzalkonium chloride (BKC) increased ROS levels in a time- and dose-dependent manner, as determined with dichlorodihydrofluorescein diacetate (CM-H(2) DCFDA), without reducing cell viability. Potential sources of ROS production were evaluated with pretreatment of diphenylene iodonium (DPI), an inhibitor of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase; rotenone, an inhibitor of the mitochondrial electron transport chain complex or allopurinol, a xanthine oxidase inhibitor. The DNCB-induced ROS was related to both NADPH oxidase and mitochondrial electron transport chain complex. Conversely, BKC-induced ROS was related to NADPH oxidase only. Western blotting using an anti-DNP antibody revealed ROS-dependent protein carbonylation in response to DNCB but not BKC. Both DNCB and BKC increased the secretion of IL-1α from HaCaT cells; however, ROS production as well as other changes, except DNCB-induced secretion of IL-1α, was not inhibited by antioxidants. Although the role of ROS in keratinocytes in response to chemicals was inconclusive, our results suggest that the characteristics of ROS produced by keratinocytes in response to chemicals might differ.

Microsomal glutathione transferase 1: mechanism and functional roles

Microsomal glutathione transferase 1 (MGST1) belongs to a superfamily named MAPEG (membrane-associated proteins in eicosanoid and glutathione metabolism). This family is represented in all life forms, except archae. Of the six human members, three are specialized in the synthesis of leukotrienes and prostaglandin E, whereas the others (MGST1-3) have potential roles in drug metabolism. MGST1 has a well-established role in the conjugation of electrophiles and oxidative stress protection, whereas MGST2 and 3 have been less studied. Here, we review the recent advances regarding the structure, mechanism, and functional roles of MGST1. Emerging data show that the enzyme is overexpressed in certain tumors and support a role for the enzyme in protecting cells from cytostatic drugs.

Dopamine and paraquat enhance α-synuclein-induced alterations in membrane conductance

We have previously demonstrated that α-synuclein overexpression increases the membrane conductance of dopaminergic-like cells. Although α-synuclein is thought to play a central role in the pathogenesis of several neurodegenerative diseases including Parkinson's disease, multiple system atrophy, and diffuse Lewy body disease, the mechanism of action is not completely understood. In this study, we sought to determine whether multiple factors act together with α-synuclein to engender cell vulnerability through an augmentation of membrane conductance. In this article, we employed a cell model that mimics dopaminergic neurons coupled with α-synuclein overexpression and oxidative stressors. We demonstrate an enhancement of α-synuclein-induced toxicity in the presence of combined treatment with dopamine and paraquat, two molecules known to incite oxidative stress. In addition, we show that combined dopamine and paraquat treatment increases the expression of heme oxygenase-1, an antioxidant response protein. Finally, we demonstrate for the first time that combined treatment of dopaminergic cells with paraquat and dopamine enhances α-synuclein-induced leak channel properties resulting in increased membrane conductance. Importantly, these increases are most robust when both paraquat and dopamine are present suggesting the need for multiple oxidative insults to augment α-synuclein-induced disruption of membrane integrity.

Enzymatic cascade reactions inside polymeric nanocontainers: a means to combat oxidative stress

Oxidative stress, which is primarily due to an imbalance in reactive oxygen species, such as superoxide radicals, peroxynitrite, or hydrogen peroxide, represents a significant initiator in pathological conditions that range from arthritis to cancer. Herein we introduce the concept of enzymatic cascade reactions inside polymeric nanocontainers as an effective means to detect and combat superoxide radicals. By simultaneously encapsulating a set of enzymes that act in tandem inside the cavities of polymeric nanovesicles and by reconstituting channel proteins in their membranes, an efficient catalytic system was formed, as demonstrated by fluorescence correlation spectroscopy and fluorescence cross-correlation spectroscopy. Superoxide dismutase and lactoperoxidase were selected as a model to highlight the combination of enzymes. These were shown to participate in sequential reactions in situ in the nanovesicle cavity, transforming superoxide radicals to molecular oxygen and water and, therefore, mimicking their natural behavior. A channel protein, outer membrane protein F, facilitated the diffusion of lactoperoxidase substrate/products and dramatically increased the penetration of superoxide radicals through the polymer membrane, as established by activity assays. The system remained active after uptake by THP-1 cells, thus behaving as an artificial organelle and exemplifying an effective approach to enzyme therapy.

Heart tissue of harlequin (hq)/Big Blue mice has elevated reactive oxygen species without significant impact on the frequency and nature of point mutations in nuclear DNA

Age is a major risk factor for heart disease, and cardiac aging is characterized by elevated mitochondrial reactive oxygen species (ROS) with compromised mitochondrial and nuclear DNA integrity. To assess links between increased ROS levels and mutations, we examined in situ levels of ROS and cII mutation frequency, pattern and spectrum in the heart of harlequin (hq)/Big Blue mice. The hq mouse is a model of premature aging with mitochondrial dysfunction and increased risk of oxidative stress-induced heart disease with the means for in vivo mutation detection. The hq mutation produces a significant downregulation in the X-linked apoptosis-inducing factor gene (Aif) impairing both the antioxidant and oxidative phosphorylation functions of AIF. Brain and skin of hq disease mice have elevated frequencies of point mutations in nuclear DNA and histopathology characterized by cell loss. Reports of associated elevations in ROS in brain and skin have mixed results. Herein, heart in situ ROS levels were elevated in hq disease compared to AIF-proficient mice (p<0.0001) yet, mutation frequency and pattern were similar in hq disease, hq carrier and AIF-proficient mice. Heart cII mutations were also assessed 15 days following an acute exposure to an exogenous ROS inducer (10 mg paraquat/kg). Acute paraquat exposure with a short mutant manifestation period was insufficient to elevate mutation frequency or alter mutation pattern in the post-mitotic heart tissue of AIF-proficient mice. Paraquat induction of ROS requires mitochondrial complex I and thus is likely compromised in hq mice. Results of this preliminary survey and the context of recent literature suggest that determining causal links between AIF deficiency and the premature aging phenotypes of specific tissues is better addressed with assay of mitochondrial ROS and large-scale changes in mitochondrial DNA in specific cell types.

Morphological damages of a glyphosate-treated human keratinocyte cell line revealed by a micro- to nanoscale microscopic investigation

Among the molecules to which the human skin is exposed, glyphosate is used as an herbicide. Glyphosate has been shown to induce in vitro cutaneous cytotoxic effects, concomitant with oxidative disorders. In this following study, we focused on dynamic events of the loss of HaCaT cell integrity appearing after a glyphosate treatment. In these conditions, we showed that glyphosate is able to disrupt HaCaT cells and to induce intracellular oxidative cascade. In this aim, we optimized the conditions of cell treatment playing on exposure time (from 24 h to 30 min), which directly modify the cell viability profile (glyphosate 50% inhibition concentration from 28 to 53 mM) and allow to track cells along the treatment as an "induction and visualization" process. The combination of atomic force and fluorescence microscopic approaches offered opportunities to lead in parallel an investigation of the membrane surface and of the intracellular disorders, through cytoskeleton, nuclear, and oxidative stress marker targeting. The originality of our approach relies on monitoring all events derived from oxidative stress in process and performed by simultaneous cytotoxic induction and nanoscale cell visualization. We revealed a transition from spread and globular to elongated cell morphology, with a drastic cell size reduction, after a dose- and time-dependent glyphosate treatment; a redistribution of cell surface protrusions was also pointed out. All these membrane damages, added to observations of disorganized cytoskeleton, condensed chromatin, and overproduction of oxidative reactive species, lead us to conclude that glyphosate acts in induction of apoptotic process.

PML/RARA oxidation and arsenic binding initiate the antileukemia response of As2O3

As(2)O(3) cures acute promyelocytic leukemia (APL) by initiating PML/RARA oncoprotein degradation, through sumoylation of its PML moiety. However, how As(2)O(3) initiates PML sumoylation has remained largely unexplained. As(2)O(3) binds vicinal cysteines and increases reactive oxygen species (ROS) production. We demonstrate that upon As(2)O(3) exposure, PML undergoes ROS-initiated intermolecular disulfide formation and binds arsenic directly. Disulfide-linked PML or PML/RARA multimers form nuclear matrix-associated nuclear bodies (NBs), become sumoylated and are degraded. Hematopoietic progenitors transformed by an As(2)O(3)-binding PML/RARA mutant exhibit defective As(2)O(3) response. Conversely, nonarsenical oxidants elicit PML/RARA multimerization, NB-association, degradation, and leukemia response in vivo, but do not affect PLZF/RARA-driven APLs. Thus, PML oxidation regulates NB-biogenesis, while oxidation-enforced PML/RARA multimerization and direct arsenic-binding cooperate to enforce APL's exquisite As(2)O(3) sensitivity.

Induction of Cardiac Angptl4 by Dietary Fatty Acids Is Mediated by Peroxisome Proliferator-Activated Receptor β/δ and Protects Against Fatty Acid–Induced Oxidative Stress

Rationale : Although dietary fatty acids are a major fuel for the heart, little is known about the direct effects of dietary fatty acids on gene regulation in the intact heart.

Objective : To study the effect of dietary fatty acids on cardiac gene expression and explore the functional consequences.

Methods and Results : Oral administration of synthetic triglycerides composed of one single fatty acid altered cardiac expression of numerous genes, many of which are involved in the oxidative stress response. The gene most significantly and consistently upregulated by dietary fatty acids encoded Angiopoietin-like protein (Angptl)4, a circulating inhibitor of lipoprotein lipase expressed by cardiomyocytes. Induction of Angptl4 by the fatty acid linolenic acid was specifically abolished in peroxisome proliferator-activated receptor (PPAR)β/δ −/− and not PPARα −/− mice and was blunted on siRNA-mediated PPARβ/δ knockdown in cultured cardiomyocytes. Consistent with these data, linolenic acid stimulated binding of PPARβ/δ but not PPARα to the Angptl4 gene. Upregulation of Angptl4 resulted in decreased cardiac uptake of plasma triglyceride-derived fatty acids and decreased fatty acid-induced oxidative stress and lipid peroxidation. In contrast, Angptl4 deletion led to enhanced oxidative stress in the heart, both after an acute oral fat load and after prolonged high fat feeding.

Conclusions : Stimulation of cardiac Angptl4 gene expression by dietary fatty acids and via PPARβ/δ is part of a feedback mechanism aimed at protecting the heart against lipid overload and consequently fatty acid–induced oxidative stress.

Role of MAP kinases in regulating expression of antioxidants and inflammatory mediators in mouse keratinocytes following exposure to the half mustard, 2-chloroethyl ethyl sulfide

Dermal exposure to sulfur mustard causes inflammation and tissue injury. This is associated with changes in expression of antioxidants and eicosanoids which contribute to oxidative stress and toxicity. In the present studies we analyzed mechanisms regulating expression of these mediators using an in vitro skin construct model in which mouse keratinocytes were grown at an air-liquid interface and exposed directly to 2-chloroethyl ethyl sulfide (CEES), a model sulfur mustard vesicant. CEES (100-1000 microM) was found to cause marked increases in keratinocyte protein carbonyls, a marker of oxidative stress. This was correlated with increases in expression of Cu,Zn superoxide dismutase, catalase, thioredoxin reductase and the glutathione S-transferases, GSTA1-2, GSTP1 and mGST2. CEES also upregulated several enzymes important in the synthesis of prostaglandins and leukotrienes including cyclooxygenase-2 (COX-2), microsomal prostaglandin E synthase-2 (mPGES-2), prostaglandin D synthase (PGDS), 5-lipoxygenase (5-LOX), leukotriene A(4) (LTA(4)) hydrolase and leukotriene C(4) (LTC(4)) synthase. CEES readily activated keratinocyte JNK and p38 MAP kinases, signaling pathways which are known to regulate expression of antioxidants, as well as prostaglandin and leukotriene synthases. Inhibition of p38 MAP kinase suppressed CEES-induced expression of GSTA1-2, COX-2, mPGES-2, PGDS, 5-LOX, LTA(4) hydrolase and LTC(4) synthase, while JNK inhibition blocked PGDS and GSTP1. These data indicate that CEES modulates expression of antioxidants and enzymes producing inflammatory mediators by distinct mechanisms. Increases in antioxidants may be an adaptive process to limit tissue damage. Inhibiting the capacity of keratinocytes to generate eicosanoids may be important in limiting inflammation and protecting the skin from vesicant-induced oxidative stress and injury.

Basic properties and molecular mechanisms of exogenous chemical carcinogens

Exogenous chemical carcinogenesis is an extremely complex multifactorial process during which gene-environment interactions involving chronic exposure to exogenous chemical carcinogens (ECCs) and polymorphisms of cancer susceptibility genes add further complexity. We describe the properties and molecular mechanisms of ECCs that contribute to induce and generate cancer. A basic and specific property of many lipophilic organic ECCs including polycyclic aromatic hydrocarbons and polyhalogenated aromatic hydrocarbons is their ability to bioaccumulate in the adipose tissue from where they may be released in the blood circulation and target peripheral tissues for carcinogenesis. Many organic ECCs are procarcinogens and consequently need to be activated by the cytochrome P450 (CYP) system and/or other enzymes before they can adduct DNA and proteins. Because they contribute not only to the cocarcinogenic and promoting effects of many aromatic pollutants but also to their mutagenic effects, the aryl hydrocarbon receptor-activating and the inducible CYP systems are central to exogenous chemical carcinogenesis. Another basic property of ECCs is their ability to induce stable and bulky DNA adducts that cannot be simply repaired by the different repair systems. In addition, following ECC exposure, mutagenesis may also be caused indirectly by free-radical production and by epigenetic alterations. As a result of complex molecular interplays, direct and/or indirect mutagenesis may especially account for the carcinogenic effects of many exogenous metals and metalloids. Because of these molecular properties and action mechanisms, we conclude that ECCs could be major contributors to human cancer, with obviously great public health consequences.