Article

Polychlorinated-biphenyl-induced oxidative stress and cytotoxicity can be mitigated by antioxidants after exposure

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Abstract

PCBs and PCB metabolites have been suggested to cause cytotoxicity by inducing oxidative stress, but the effectiveness of antioxidant intervention after exposure has not been established. Exponentially growing MCF-10A human breast and RWPE-1 human prostate epithelial cells continuously exposed for 5 days to 3 microM PCBs [Aroclor 1254 (Aroclor), PCB153, and the 2-(4-chlorophenyl)-1,4-benzoquinone metabolite of PCB3 (4ClBQ)] were found to exhibit growth inhibition and clonogenic cell killing, with 4ClBQ having the most pronounced effects. These PCBs were also found to increase steady-state levels of intracellular O(2)(*-) and H(2)O(2) (as determined by dihydroethidium, MitoSOX red, and 5-(and 6)-carboxy-2',7'-dichlorodihydrofluorescein diacetate oxidation). These PCBs also caused 1.5- to 5.0-fold increases in MnSOD activity in MCF-10A cells and 2.5- to 5-fold increases in CuZnSOD activity in RWPE-1 cells. Measurement of MitoSOX red oxidation with confocal microscopy coupled with colocalization of MitoTracker green in MCF-10A and RWPE-1 cells supported the hypothesis that PCBs caused increased steady-state levels of O(2)(*-) in mitochondria. Finally, treatment with either N-acetylcysteine (NAC) or the combination of polyethylene glycol (PEG)-conjugated CuZnSOD and PEG-catalase added 1 h after PCBs significantly protected these cells from PCB toxicity. These results support the hypothesis that exposure of exponentially growing human breast and prostate epithelial cells to PCBs causes increased steady-state levels of intracellular O(2)(*-) and H(2)O(2), induction of MnSOD or CuZnSOD activity, and clonogenic cell killing that could be inhibited by a clinically relevant thiol antioxidant, NAC, as well as by catalase and superoxide dismutase after PCB exposure.

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... Studies from the past ten years strongly suggest that PCBs and PCB metabolites, such as 4-chlorobenzoquinone and 4OH-PCB11, induce mitochondrial reactive oxygen species (ROS) and oxidative stress in cultured cells and mice [8][9][10][11][12]. In Zhu et al. (2009), we showed that exposure to PCBs and PCB metabolites increased the activity of MnSOD, the major mitochondrial enzyme responsible for removing O 2 • - [12]. ...
... Studies from the past ten years strongly suggest that PCBs and PCB metabolites, such as 4-chlorobenzoquinone and 4OH-PCB11, induce mitochondrial reactive oxygen species (ROS) and oxidative stress in cultured cells and mice [8][9][10][11][12]. In Zhu et al. (2009), we showed that exposure to PCBs and PCB metabolites increased the activity of MnSOD, the major mitochondrial enzyme responsible for removing O 2 • - [12]. Interestingly, this increase in MnSOD activity was not accompanied by an increase in MnSOD immunoreactive protein, suggesting that MnSOD was regulated post-translationally. Further, SIRT3, as the major deacetylase in mitochondria, is capable of affecting MnSOD by deacetylating its critical lysines to regulate its activity [13][14][15]. ...
... The mean fluorescence intensity (MFI) of 10,000 cells was analyzed and corrected for autofluorescence from unlabeled cells. The MFI data were presented in arbitrary units for Mitosox, and the ratio of red/green fluorescence was plotted for JC-1 [12,24]. ...
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Although the production of polychlorinated biphenyls (PCBs) is prohibited, the inadvertent production of certain lower-chlorinated PCB congeners still threatens human health. We and others have identified 3,3’-dichlorobiphenyl (PCB11) and its metabolite, 3,3’-dichlorobiphenyl-4-ol (4OH-PCB11), in human blood, and there is a correlation between exposure to this metabolite and mitochondrial oxidative stress in mammalian cells. Here, we evaluated the downstream effects of 4OH-PCB11 on mitochondrial metabolism and function in the presence and absence of functional Sirtuin 3 (SIRT3), a mitochondrial fidelity protein that protects redox homeostasis. A 24 h exposure to 3 μM 4OH-PCB11 significantly decreased the cellular growth and mitochondrial membrane potential of SIRT3-knockout mouse embryonic fibroblasts (MEFs). Only wild-type cells demonstrated an increase in Manganese superoxide dismutase (MnSOD) activity in response to 4OH-PCB11–induced oxidative injury. This suggests the presence of a SIRT3-mediated post-translational modification to MnSOD, which was impaired in SIRT3-knockout MEFs, which counters the PCB insult. We found that 4OH-PCB11 increased mitochondrial respiration and endogenous fatty-acid oxidation-associated oxygen consumption in SIRT3-knockout MEFs; this appeared to occur because the cells exhausted their reserve respiratory capacity. To determine whether these changes in mitochondrial respiration were accompanied by similar changes in the regulation of fatty acid metabolism, we performed quantitative real-time polymerase chain reaction (qRT-PCR) after a 24 h treatment with 4OH-PCB11. In SIRT3-knockout MEFs, 4OH-PCB11 significantly increased the expression of ten genes controlling fatty acid biosynthesis, metabolism, and transport. When we overexpressed MnSOD in these cells, the expression of six of these genes returned to the baseline level, suggesting that the protective role of SIRT3 against 4OH-PCB11 is partially governed by MnSOD activity.
... Using electron paramagnetic resonance spectrometry, a previous study has demonstrated the formation of a semiquinone radical in 4-ClBQ treated MCF-10A human mammary epithelial cells, which correlated with an increase in hydrogen peroxide levels and toxicity (Venkatesha et al., 2008). 4-ClBQ treatment has also been shown to increase cellular ROS levels causing toxicity in human keratinocytes, and breast and prostate epithelial cells (Xiao et al., 2014(Xiao et al., , 2013Zhu et al., 2009). This study investigates whether PGC-1a regulates 4-ClBQ induced oxidative stress and toxicity by modulating antioxidant gene expression. ...
... A clonogenic cell survival assay was used to measure toxicity (Xiao et al., 2013;Zhu et al., 2009). Untreated control and 24 h of 4-ClBQ treated cells were replated using appropriate dilutions designed to plate single cell. ...
... Cellular ROS levels were determined by measuring the oxidation of MitoSOX Red following a published protocol (Xiao et al., 2013;Zhu et al., 2009). Control and 4-ClBQ treated cells were incubated with 2 lM MitoSOX Red at 37°C for 20 min. ...
... The proposed mechanism suggests that PCBs cause an increase in steady-state levels of reactive oxygen species (ROS) in cells and tissues of the reproductive system. It is wellknown that elevated ROS levels can play a role in causing oxidative stress and damage to vital cellular components, leading to mutations, carcinogenesis, cell death, and hereditary diseases [15]. ...
... ROS level was measured using the DCFH fluorescence reaction. Both PCBs at the tested concentration (75 µM) induced significant (p < 0.05) ROS formation in ovarian cells (Figure 3), which is consistent with our previous studies [10,11], as well as with the results of other studies [15,31]. Thus, reducing intracellular ROS levels could be an effective strategy to prevent PCB-induced cytotoxicity. ...
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Polychlorinated biphenyls (PCBs) can induce neurotoxicity, immunotoxicity, reproductive toxicity, genotoxicity, and carcinogenicity (IARC group 1 Carcinogens). Scientific data suggest that resveratrol possesses the ability to attenuate ortho-PCB-induced toxicity. Recently, a novel ferrocene-containing triacyl derivative of resveratrol (RF) was synthesized and in this study, its potential to protect CHO-K1 cells from selected PCB congeners (75 µM) was evaluated. Cell viability/proliferation was observed by Trypan Blue (TB), Neutral Red (NR), Kenacid Blue (KB), and MTT bioassays, ROS formation by fluorescent probes, and the extent of apoptosis by flow cytometry. All applied bioassays confirmed that RF (2.5–100 μM) remarkably improves viability in PCB 153-treated cells with an increase in cell survival almost up to control levels. This effect was not determined after PCB 77 exposure, although ROS formation was decreased at RF ≥ 50 µM. Apoptosis was significant (p < 0.05) for both congeners. In PCB 77-treated cells, RF did not suppress the induction of cell death. The intended protective effect of RF was evident when cells were treated with PCB 153, and this correlates with results obtained for cell viability. Compared to resveratrol, the novel RF showed promising results in terms of improved biological activity and cell protection against PCB 153 toxicity at all concentrations tested.
... Reproductive tissues are one of the target sites of the PCB toxic effects and reproductive failure has been associated with PCB exposure (Fernández-González et al. 2015;Karwacka et al. 2019). Numerous studies propose many specific, critical underlying mechanisms of PCB-mediated reproductive dysfunction at the cellular level (on ovarian cells (Murati et al. 2015), on Leydig cell steroidogenesis (Thangavelu et al. 2018), on human mammary and prostate epithelial cells (Zhu et al. 2009), etc.), but only a few hydroperoxide. Data are presented as mean ± SEM. ...
... Guida et al. (2015) also showed that resveratrol blocked non-dioxin-like PCB 95-induced neuronal cell death by activating the SIRT1/c-Jun/REST (sirtuin 1/c-Jun/RE1-silencing transcription factor) pathway. Zhu et al. (2009) found that antioxidant intervention after PCB exposure (PCB 153, Aroclor 1254) significantly protected breast and prostate cells from toxicity. However, it is important to highlight the synergistic inhibitory effect of resveratrol and dioxin-like congener on cell viability (Fig. 3a-d) which may be the subject of future research. ...
Article
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Polychlorinated biphenyls (PCBs) can induce chronic oxidative stress, inflammation, and cell death, leading to coronary heart disease, endothelial dysfunction, neurotoxicity, cancer, obesity, type 2 diabetes, reproductive dysfunction, etc. The aim of this study was to investigate possible protective effect of resveratrol (2.5–20 μM) in ovarian cells exposed to PCBs. An emphasis was on identifying mechanisms of resveratrol action upon distinct structure of the individual PCB congener—planar dioxin-like PCB 77 and non-planar di-ortho-substituted PCB 153. Multiple toxicity endpoint analysis was performed. Cell viability/proliferation was assessed by Trypan Blue exclusion method, Neutral Red, Kenacid Blue, and MTT bioassays. The level of oxidative stress was measured by fluorescent probes, and flow cytometry was applied to evaluate the mode of cell death. Resveratrol applied alone did not affect cell proliferation and viability in doses up to 20 µM, although significant antioxidative activity was observed. Toxic effects of ortho-PCB 153 (cytotoxicity, oxidative stress, and cell death) were mitigated by resveratrol. On the contrary pre-incubation with resveratrol did not result in cell viability protection when planar PCB 77 was applied. This indicates that resveratrol efficacy may be linked to specific structure of the individual congener, suggesting nutritional modulation of environmental insults caused by ortho-PCBs. We point out the importance of resveratrol dosage considering that synergistic cytotoxic effect with both PCB congeners is observed at concentrations ≥ 10 μM. Graphical Abstract
... While studies reporting oxidative stress following PCB exposure at the cellular level are numerous, the focus was set here on studies that investigated changes at the mitochondrial level, which are far more limited in number. Nonetheless, exposure to PCB3-benzoquinones (Xiao et al., 2016;Zhu et al., 2009) (in vitro), PCB153 (Zhu et al., 2009) (in vitro) or Aroclor 1254 Lee and Opanashuk, 2004;Zhu et al., 2009) (in vivo and in vitro) increased mitochondrial ROS production, and altered the expression of other oxidative stress markers (e.g., reduction in superoxide dismutase enzymes, and increase in oxidized lipids (Table 1). ...
... While studies reporting oxidative stress following PCB exposure at the cellular level are numerous, the focus was set here on studies that investigated changes at the mitochondrial level, which are far more limited in number. Nonetheless, exposure to PCB3-benzoquinones (Xiao et al., 2016;Zhu et al., 2009) (in vitro), PCB153 (Zhu et al., 2009) (in vitro) or Aroclor 1254 Lee and Opanashuk, 2004;Zhu et al., 2009) (in vivo and in vitro) increased mitochondrial ROS production, and altered the expression of other oxidative stress markers (e.g., reduction in superoxide dismutase enzymes, and increase in oxidized lipids (Table 1). ...
Chapter
Polychlorinated biphenyls (PCBs) are a family of 209 anthropogenic compounds that are highly hydrophobic and persist in the environment. They have been associated with various toxic effects in organisms. At the cellular level, PCB exposure was linked to an increase in oxidative stress. Mitochondria are one of the main sources of intracellular reactive oxygen species and, thus, a major target for PCB toxicity. In the last 50 years, our understanding of toxic effects of PCBs toward the mitochondria improved. Overall, studies showed that interactions of PCB congeners with mitochondrial function depend on structural features. Especially, non-planar PCBs, i.e., ortho-substituted congeners, appear more potent for inducing toxicity to the mitochondrion. A variety of effects has been reported following exposure to PCBs; they can alter the structure of mitochondria, including membrane integrity, inhibit proper function of the respiratory chain, affect calcium storage, and dysregulate apoptosis mechanisms in vivo and in vitro. While specific interactions with cellular targets were identified along the respiratory chain, the majority of the research strongly indicates that loss of mitochondrial function is subsequent to a non-specific increase in ion permeability following integration of PCBs within the lipid bilayer and disruption of membrane integrity. Altogether, toxic effects of PCBs on mitochondria appear central to oxidative stress generation and to the development of associated negative health outcomes described in the literature, such as neurotoxicity, reprotoxicity, metabolic alterations, and cancer.
... age (aOR = 1.94; 95% CI: 1.12-3. 34 have a protective effect. [6][7][8][9][10][11] Other studies have also confirmed occupation of parents as a possible causative factor for the development of CHDs. ...
... [29][30][31][32][33] Other endocrine disrupting chemicals, for example polychlorinated organic compounds, induce oxidative stress, which may also interfere with the intrauterine development of the heart. [34][35][36] The fetus is usually exposed to these chemicals through the placental cord. 37 However, phthalates may also enter the amniotic fluid directly, as these compounds are water-soluble. ...
Article
The etiology of congenital heart diseases is not fully understood yet, however, endocrine disrupting chemicals may have a causative role in their development. The purpose of our study was to examine the association between congenital heart diseases and periconceptional parental occupational exposure to endocrine disrupting chemicals. In our Hungarian population‐based case‐control study, we examined 2263 live born cases with any congenital heart disease and 6789 matched controls selected between years 1997 to 2002. Occupational exposure was assessed with a job‐exposure matrix developed for endocrine disrupting chemicals. Conditional multiple logistic regression analyses were performed to test associations between parental occupational exposure to endocrine disrupting chemicals and congenital heart diseases of the offspring as a whole and by congenital heart disease subtypes. The prevalence of exposure to endocrine disrupting chemicals was 4.5% for both case and control mothers and 19.1% and 19.4% for case and control fathers, respectively. We found a positive association between paternal pesticide (adjusted odds ratio = 1.66, 95% confidence interval: 1.03‐2.69) and alkylphenolic compound exposure (adjusted odds ratio = 1.95, 95% confidence interval: 1.30‐2.93) and the development of patent ductus arteriosus in the offspring. Alkylphenolic compound exposure occurred among painters, famers, and those working in the food service industry, while pesticide exposure occurred predominantly among farm workers. We identified that certain occupations may increase the occurrence of certain congenital heart disease phenotypes in the offspring. By paying closer attention to those working in these areas, antenatal detection rates of congenital heart diseases may be improved.
... In mouse Leydig cells testosterone synthesis was stimulated and cell viability was decreased (Johansson, 1989). Human breast and prostate epithelial cells treated with PCBs and PCB metabolites exhibited inhibition of cell growth as well as clonogenic cell killing (Zhu et al., 2009). Loss of cell viability and apoptosis induction were observed in ovary cells after treatment with 10e100 mM PCB 77 (Murati et al., 2015). ...
... Oxidative stress caused by an imbalance in the redox state of the cell, either by overproduction of ROS or by dysfunction of the antioxidant systems, leads to cell injury, mutagenesis, carcinogenesis and cell death. Even 3 mM PCBs [Aroclor 1254, PCB 153, and 4ClBQ -metabolite of PCB3] daily for 5 days were found to increase steady-state levels of intracellular O 2 $À and H 2 O 2 in MCF-10A and RWPE-1 cells (Zhu et al., 2009). This study was conducted to examine the influence of selected antioxidant e vitamin E on PCBs' promoted oxidative stress and cytotoxicity in ovary cells. ...
Article
The aim of this study was to evaluate protective effects of vitamin E (50 -150 μM) in ovary cells upon cytotoxic effects induced by two structurally distinct PCB congeners - planar „dioxin-like" PCB 77 and non-planar di-ortho-substituted PCB 153 with an emphasis on identifying differences in the mechanism of vitamin E action depending on the structure of congeners. Application of three bioassays confirmed that PCBs decrease ovarian cell proliferation with slightly profound effects of PCB 77. PCB - induced ROS production and lipid peroxidation were significant for both congeners with also more noticeable effect for PCB 77. Vitamin E pre-incubation has improved viability of cells, reduced ROS formation and lipid peroxidation induced by PCBs' treatment. Preincubation with vitamin E was more effective when cells where treated with non-planar PCB 153. Altogether, vitamin E action was protective, congener specific and more effective when ovary cells were exposed to ortho-substituted PCB congener.
... 2,3 It has been increasingly recognized that reactive oxygen species (ROS) (i.e., superoxide, hydrogen peroxide, hydroxyl radical) induce metabolic oxidative stress and may play an important role in cytotoxicity, genotoxicity and carcinogenesis. [4][5][6] Recent studies suggest that malignant cells have higher steady-state levels of ROS than normal tissue cells. 4,7 The excess ROS can react with a broad range of biomolecules including lipids, protein and DNA to form other radicals or cytotoxic byproducts, which could further contribute to carcinogenesis. ...
... MFI data was then normalized to control for each group at each respective time point, as indicated. 5,14 Western blot analysis Protein (40 μg) was resolved on 12% SDS-PAGE and electroblotted into nitrocellulose membranes (Bio Rad, Hercules, CA, USA). The membrane was incubated with monoclonal antibody diluted at 1:1,000 in 5% non-fat dry milk for 1 h at room temperature. ...
Article
Reactive oxygen species (ROS) contribute to adult tumorigenesis; however, their roles in pediatric solid tumors are unknown. Here, we sought to define the steady-state ROS levels in neuroblastoma and to examine whether aggressive cellular behavior, which may predict treatment failure, is regulated by ROS. Neuroblastoma sections were assessed for 4-hydroxynonenal (4-HNE), a marker of intracellular lipid peroxidation and a byproduct of increased levels of ROS. Human neuroblastoma cell lines, MYCN-amplified BE(2)-C and MYCN-nonamplified SK-N-SH, were examined in our study. Superoxide and hydroperoxide oxidation products were detected by staining for dihydroethidium (DHE) and 5, 6-carboxy-2', 7'-dichlorodihydrofluorescein diacetate (CDCFH2), using the oxidation-insensitive analog CDCF as a negative control. Cells were treated with N-acetylcysteine (NAC; 10 mmol/L) daily for 5 days and analyzed. Greater expression of 4-HNE was observed in undifferentiated tumor sections as compared with the more differentiated tumors. Interestingly, increased levels of ROS were detected in MYCN-amplified BE(2)-C cells. Moreover, gastrin-releasing peptide receptor-induced ROS production stimulated upregulation of the hypoxia inducible factor (HIF)-1α/vascular endothelial growth factor (VEGF) pathway and an increase in cell growth. Antioxidant NAC decreased HIF-1α/VEGF expression and inhibited BE(2)-C cell growth. We report a novel observation that shifting the redox balance toward greater ROS levels results in a more aggressive neuroblastoma phenotype. Our data suggest that ROS play a critical role in refractory neuroblastoma. Copyright © 2015 Elsevier Inc. All rights reserved.
... Assessment of ROS generation by fluorescence microscopy DHE staining slightly modified from the method of Zhu et al. [44] was used to detect the in vivo ROS production microscopically in the early life stages of microinjected zebrafish. Briefly, 60 embryos (72 hpf) microinjected with nrf2a-eGFP were exposed to PCB126 (0 (control; 0.01% DMSO), 25, 50, 100, or 200 μg/L PCB126 or 30 mM NAC þ200 μg/L PCB126 with NAC added 24 h before PCB126 exposure; n ¼ 10/treatment). ...
... In addition, pretreatment with NAC 24 h before exposure to PCB126 alleviated most of the toxic changes in tissues and ROS generation. This is in agreement with a previous study that demonstrated that treatment with NAC and other antioxidants significantly protects human breast cells from PCB toxicity, which may be associated with ROS production [44]. In vitro studies of human white blood cells also confirmed that PCB exposure induces ROS formation [63]. ...
Article
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Dioxin-like 3,3',4,4',5-pentachlorobiphenyl (PCB126) is one of the most potent and widespread environmental pollutants. Although PCB126-induced toxicity is related to aryl hydrocarbon receptor (AHR) pathway, there is still no study that has constructed an in vivo visual model to clarify the role of the NRF2/ARE signaling pathway in oxidative stress mechanism of PCB126-induced toxicity. In the present study, an in vivo zebrafish model of nrf2a fused to enhanced green fluorescent protein (nrf2a-eGFP) was constructed. The zebrafish embryos microinjected with nrf2a-eGFP [72h post-fertilization (hpf)] were exposed to different concentrations of PCB126 [0, 25, 50, 100, 200μg/L], and 30mMN-acetylcysteine (NAC)+200μg/L PCB126. After 72h exposure, PCB126 significantly increased the malformation rates and induced the eGFP expression in a dose-dependent manner in several zebrafish tissue types. The distribution of eGFP fluorescence coincided with developmental deformity sites. NAC pre-treatment effectively counteracted PCB126 induced developmental toxicity including heart rate, pericardial edema and body length. Highest PCB126 dose 200μg/L produced marked apoptosis in the eye, gill and trunk detected by the terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL) assay. At 48 and 72h exposure, 200μg/L PCB126 affected glutathione metabolism as evidenced by decreased glutathione (GSH) and increased glutathione disulfide (GSSG) concentrations, indicative of oxidative stress. These effects were also counteracted by NAC pre-treatment. Furthermore, the Nrf2-regulated genes gclc, gpx, gstp1 and hmox1 were significantly induced at 24, 48 and 72h at the highest PCB126 exposures but not in the NAC pretreated group. In addition, a significant increase in ROS generation was detected in zebrafish larvae at 72h PCB126 exposure, which might offer a link for future mechanistic studies. Collectively, these data suggest that PCB126 induced developmental toxicity and apoptosis in nrf2a-eGFP injected zebrafish model are due to oxidative stress mediated by disruption to glutathione metabolism and changes in Nrf2-regulated gene expression. Copyright © 2015. Published by Elsevier Inc.
... The excessive production of reactive oxygen species is a major feature during cerebral I/R injury, which usually leads to oxidative damage and cerebral dysfunction (14,15) . MDA and SOD are closely related to oxidative stress (16)(17)(18)(19) . In this study, the expression level of MDA was significantly increased after cerebral I/R, indicating that cerebral I/R injury in rats results in oxidative stress. ...
Article
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Total flavonoids in Premna fulva Craib (TFPFC) are a kind of flavonoid compound synthesized via photosynthesis extracted from Premna fulva Craib, which possess a strong anti-oxidative effect. Cerebral Ischemia-Reperfusion refers to the body's damage mainly caused by oxidative stress. This study aims to investigate the alleviating effect of TFPFC on brain neurological impairment and its influences on Nuclear factor E2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) expressions in rats with Ischemia-Reperfusion. The rat model of Ischemia-Reperfusion was established, and rats were treated with TFPFC or normal saline. At 24 h after reperfusion, the neurological score, volume of cerebral infarction and cerebral water content were analyzed in different groups. The influences of TFPFC treatment on the proliferative activity and apoptosis of oxygen and glucose deprivation/reoxygenation (OGD/R) neural stem cells were detected via methyl thiazolyl tetrazolium (MTT) assay and flow cytometry. Moreover, the malondialdehyde (MDA) level and superoxide dismutase (SOD) activity were measured to evaluate the oxidative stress effect. The influences of TFPFC treatment on the protein and messenger ribonucleic acid (mRNA) expressions of Nrf2 and HO-1 were analyzed using reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting. The TFPFC treatment alleviated the neurological impairment in rats after Ischemia-Reperfusion and reduced the volume of cerebral infarction and cerebral edema status in rats with Ischemia-Reperfusion. TFPFC increased the proliferative activity of OGD/R neural stem cells and decreased damage and apoptosis. In addition, the TFPFC treatment reduced the MDA level, improved the SOD activity, and up-regulated the protein and mRNA expressions of Nrf2 and HO-1. The TFPFC treatment may improve oxidative damage and protect the nervous system through the up-regulation of expressions of transcription factors Nrf2 and HO-1.
... Notably, the researchers looked into PCB metabolites; PCB29-pQ outlines latent metabolic processes, and particularly focuses its attention on the quinones (recorded as organic pollutants with carcinogenic characteristics and genotoxicity), causing reactive oxygen species (ROS) formation [221][222][223][224][225][226]. Song, Li, et al. (2015) pointed to the level of complexity through biochemical relations, namely the fact that PCB29-pQ promotes S-phase cell proliferation by suppressing cyclins A/D1/E, cyclin-dependent kinases (CDK 2/4/6), and cell division cycle 25A (CDC25A), increasing p21/p27 protein expression. ...
Article
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Micro‐ and nanoplatics have been already reported to be potential carcinogenic/mutagenic substances that might cause DNA damage, leading to carcinogenesis. Thus, the effects of micro‐ and nanoplastics exposure on human health are currently being investigated extensively to establish clear relationships between those substances and health consequences. So far, it has been observed that there exists a definite correlation between exposure to micro‐ and nanoplastic particles and the onset of several cancers. Therefore, we have conducted research using PubMed, Web of Science, and Scopus databases, searching for all the research papers devoted to cancers that could be potentially related to the subject of exposure to nano‐ and microplastics. Ultimately, in this paper, we have discussed several cancers, including hepatocellular carcinoma, pancreatic cancer, pancreatic ductal adenocarcinoma, biliary tract cancer, and some endocrinerelated cancers.
... This technique measures oxidation of dihydroethidium (DHE) (Thermo Fisher Scientific, Waltham, MA, #D11347) to its fluorescent product as a surrogate marker for superoxide [50,51]. Frozen pancreas tissue slides (thickness 6 μm) or islets cultures were used. ...
Article
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Cystic fibrosis-related diabetes (CFRD) is one the most common comorbidities in cystic fibrosis (CF). Pancreatic oxidative stress has been postulated in the pathogenesis of CFRD, but no studies have been done to show an association. The main obstacle is the lack of suitable animal models and no immediate availability of pancreas tissue in humans. In the CF porcine model, we found increased pancreatic total glutathione (GSH), glutathione disulfide (GSSG), 3-nitrotyrosine- and 4-hydroxynonenal-modified proteins, and decreased copper zinc superoxide dismutase (CuZnSOD) activity, all indicative of oxidative stress. CF pig pancreas demonstrated increased DHE oxidation (as a surrogate marker of superoxide) in situ compared to non-CF and this was inhibited by a SOD-mimetic (GC4401). Catalase and glutathione peroxidase activities were not different between CF and non-CF pancreas. Isolated CF pig islets had significantly increased DHE oxidation, peroxide production, reduced insulin secretion in response to high glucose and diminished secretory index compared to non-CF islets. Acute treatment with apocynin or an SOD mimetic failed to restore insulin secretion. These results are consistent with the hypothesis that CF pig pancreas is under significant oxidative stress as a result of increased O2●− and peroxides combined with reduced antioxidant defenses against reactive oxygen species (ROS). We speculate that insulin secretory defects in CF may be due to oxidative stress.
... After labeling, cells were washed with DBPS and kept on ice. Sample images were acquired using EVOS fluorescence microscope (531/40 nm Excitation; 593/40 nm Emission and 482/25 nm Excitation; 524/24 nm Emission filters) and analyzed using ImageJ software [69,98]. ...
Article
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Space is a high-stress environment. One major risk factor for the astronauts when they leave the Earth’s magnetic field is exposure to ionizing radiation from galactic cosmic rays (GCR). Several adverse changes occur in mammalian anatomy and physiology in space, including bone loss. In this study, we assessed the effects of simplified GCR exposure on skeletal health in vivo. Three months following exposure to 0.5 Gy total body simulated GCR, blood, bone marrow and tissue were collected from 9 months old male mice. The key findings from our cell and tissue analysis are (1) GCR induced femoral trabecular bone loss in adult mice but had no effect on spinal trabecular bone. (2) GCR increased circulating osteoclast differentiation markers and osteoclast formation but did not alter new bone formation or osteoblast differentiation. (3) Steady-state levels of mitochondrial reactive oxygen species, mitochondrial and non-mitochondrial respiration were increased without any changes in mitochondrial mass in pre-osteoclasts after GCR exposure. (4) Alterations in substrate utilization following GCR exposure in pre-osteoclasts suggested a metabolic rewiring of mitochondria. Taken together, targeting radiation-mediated mitochondrial metabolic reprogramming of osteoclasts could be speculated as a viable therapeutic strategy for space travel induced bone loss.
... , and H 2 O 2 and downregulation of antioxidant defense agents like superoxide dismutase (SOD), glutathione (GSH), glutathione S-transferase (GST) and catalase (CAT) have been reported (Jaishankar et al., 2014). PCBs and its metabolites are known to induce oxidative stress by the upsurge in ROS (H 2 O 2 and O 2 -) thereby causing cell injury and death (Zhu et al., 2009). MPTP is neurotoxic to various tissues like cortical brain tissue, striatum, and especially to dopaminergic neurons in the substantia nigra of the brain. ...
... , and H 2 O 2 and downregulation of antioxidant defense agents like superoxide dismutase (SOD), glutathione (GSH), glutathione S-transferase (GST) and catalase (CAT) have been reported (Jaishankar et al., 2014). PCBs and its metabolites are known to induce oxidative stress by the upsurge in ROS (H 2 O 2 and O 2 -) thereby causing cell injury and death (Zhu et al., 2009). MPTP is neurotoxic to various tissues like cortical brain tissue, striatum, and especially to dopaminergic neurons in the substantia nigra of the brain. ...
Article
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Memory impairment (MI) is one of the predominant criteria generally used to identify schizophrenia, dementia and amnesia that are associated with neurodegenerative disorders by evaluating patient’s cognitive symptoms. To date, there is no available treatment that can completely mitigate MI. Currently, there is a trend in recent investigations towards symptomatic therapy approaches using a variety of natural compounds. Mangiferin is one of them that have been investigated extensively. Mangiferin is a naturally occurring potent glucoxilxanthone and is mainly isolated from the Mangifera indica (Mango) plant. This review is aimed at providing a comprehensive overview on the efficacy of mangiferin on MI, based on in-vivo animal studies. After screening through articles identified from Scopus and PubMed based on the inclusion and exclusion criteria, a total of 11 articles between 2009 and 2019 were included. The minimum and maximum dose of mangiferin were 10 and 200 mg/kg respectively and administered over the period of 12–154 days. The results of 11 articles showed that mangiferin effectively improved spatial recognition, episodic aversive events, short- and long-term memories primarily occurring via its antioxidant and anti-inflammatory effects. The outcomes of the review revealed that mangiferin improves memory and cognitive impairment in different animal models, indicating that it has potential preventive and therapeutic roles in MI.
... Many endocrine disrupting chemicals have an estrogenic effect and may lead to impaired semen quality (Jeng 2014), disrupted oocyte maturation (Gregoraszczuk and Ptak 2013), or fetal epigenomic changes (Bommarito et al. 2017). Polychlorinated compounds can induce oxidative stress (Zhu et al. 2009), which has also been associated with CHDs (Wu et al. 2016). Pesticides have a more complex effect, they not only disrupt the endocrine system but also interfere with the proper function of the immune system and neurodevelopment, moreover, they are carcinogenic as well (Kalliora et al. 2018). ...
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Purpose Our study aimed to explore the effect of parental occupational exposure to endocrine disrupting chemicals (EDCs) on the development of congenital heart diseases (CHDs) in the offspring, and to compare job-exposure matrix (JEM)-assessed and self-reported occupational exposures with each other. Methods Live-born infants born in 2007–2008 were selected from the population-based Hungarian Case–Control Surveillance of Congenital Abnormalities Study. 577 cases with any CHDs were compared to 1731 matched controls. Parental periconceptional occupational exposure to EDCs was assessed by a JEM and by questionnaire-based self-reporting of parents. Multivariate conditional logistic regression analyses were conducted to explore associations between parental occupational exposure to EDCs and the entire spectrum of CHDs and by CHD subtypes in the offspring. Kappa statistics were also performed to determine the consistency among JEM-assessed and self-reported occupational exposure of parents. Results JEM-assessed paternal exposure to polychlorinated organic substances, phthalates, biphenolic compounds, and solvents were significantly associated with the entire spectrum of CHDs. Ventricular septal defects were significantly associated with paternal self-reported exposure to pesticides, while atrial septal defects were significantly associated to paternal JEM-assessed phthalate exposure. Paternal solvent exposure was significantly associated with atrial septal defects and right ventricle outflow tract obstructions. JEM-assessed and self-reported exposures to pesticides, heavy metals, and solvents exhibited poor agreement for mothers and slight agreement for fathers. Conclusion Even though parental occupational exposure to EDCs seems to have a minor impact on the occurrence of CHDs, the results of biological and environmental monitoring should be taken into consideration as well.
... Interestingly, exposure to dioxin-like PCBs or to Aroclor 1260, a PCB mixture containing dioxin-and non-dioxin-like PCBs, has been linked to increased oxidative stress in different cell types or tissues and to abnormal mitochondrial function, such as increased uncoupling respiration, decreased mitochondrial respiration, and decreased activity of electron transport chain complexes (Ebner and Braselton 1987;Ramadass et al. 2003;Hennig et al. 2007;Aly and Domènech 2009;Zhu et al. 2009;Lu et al. 2010;Shen et al. 2011;Newsome et al. 2014;Zhong et al. 2015;Cocco et al. 2015;Ounnas et al. 2016). Coplanar PCBs, in the same way as dioxins, act through aryl hydrocarbon receptor (AhR) (Zhou et al. 2010). ...
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In the past few years, polychlorinated biphenyls (PCBs), a class of environmental pollutants, have been associated with metabolism dysregulation. Muscle is one of the key regulators of metabolism because of its mass and its important role in terms of glucose consumption and glucose storage. It has been shown that muscle alterations, such as oxidative stress and mitochondrial dysfunction, contribute significantly to the development of metabolic diseases. No study has yet investigated the toxicological effect of PCBs on muscle mitochondrial function and oxidative stress in vivo. The aim of this study was to assess the effect of PCB126 in vivo exposure (single dose of 1.05 μmol/kg) on muscle mitochondrial function and oxidative stress in rats. PCB126-treated rats showed a marked increase in Cyp1a1 mRNA levels in skeletal muscles in association with a 40% reduction in state 3 oxygen consumption rate measured with complex I substrates in permeabilized muscle fibers. Furthermore, PCB126 exposure altered the expression of some enzymes involved in ROS detoxification such as catalase and glutaredoxin 2. Our results highlight for the first time a toxic effect of coplanar PCBs on skeletal muscle mitochondrial function and oxidative stress. This suggests that acute PCB exposure, by affecting muscle metabolism, could contribute to the development of metabolic disorders. Studies are needed to determine if lower-level but longer-term PCB exposure exhibits the same effect.
... However, studies have shown that PCBs are linked to neurotoxicity (Xia, 2009), reproductive toxicity (Oskam et al., 2005), hepatotoxicity (Liu et al., 2014), immunotoxicity (Danis et al., 2006) and even tumor promotion (Bunaciu et al., 2007). Although commercial production of PCBs was banned in North America in 1977 (Zhu et al., 2009) due to their hazardous effects, trace concentrations (up to several 100 μg kg −1 ) of PCBs can still be found in animals, such as fish (Cocco et al., 2011), posing a risk to ecological and human health via food ingestion. ...
Article
Polychlorinated biphenyls (PCBs) are persistent organic pollutants (POPs) that have neurotoxicity, reproductive toxicity, hepatotoxicity and immunotoxicity in both animals and humans. Few studies have focused on the changes to endogenous glycerophospholipid metabolism caused by PCB153. To evaluate the relationships between exposure to PCB153 and specific endogenous glycerophospholipid metabolism, an ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method was implemented in this study. Twenty-two endogenous glycerophospholipids in PC12 cells were analyzed after exposure to PCB153 at dosages of 0.05 μg mL−1, 0.5 μg mL−1 or 20 μg mL−1 for 120 h. PC(14:0/14:0), PE(16:0/18:1), PE(16:0/18:2), PS(18:0/18:1) and PI(16:0/18:1) were identified as potential biomarkers under the rules of t-test (P) value < 0.05 and variable importance at projection (VIP) value > 1. It was also found that the alterations at 0.05 μg mL−1 and 20 μg mL−1 PCB153 were similar at 120 h, while 0.5 μg mL−1 PCB153 presented an opposite trend. Additionally, significant upregulation of PC, PE and PS with the same fatty acid chains of 18:0/18:2 was found after exposure to 0.05 μg mL−1 and 20 μg mL−1 PCB153 at 120 h. This study revealed that PCB153 exposure modulated 22 endogenous glycerophospholipids in PC12 cells and provided the basis for the further study of PCB153 on the effects of glycerophospholipids on PC12 cells.
... Because is a CB are pollutant with potentially persistent immunological and neurological efects [86,87]. It has also been reported that CB can increase the production of ROS and cytotoxicity [88]. The neurological and immunological abnormalities as well as oxidative stress due to CB exposure have also been observed in autistic children [89][90][91]. ...
... It has been reported that PCB153 caused an increase of steady state levels of intracellular O 2 .− and H 2 O 2 in cells in vitro and an adaptive increase in MnSOD and Cu-ZnSOD activity (Zhu et al., 2009). ...
Article
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Polychlorinated biphenyls (PCB) exposure at low chronic levels is a significant public health concern. Animal and epidemiological studies indicate that low PCB body burden may cause neurotoxicity and be a risk factor for neurodegenerative diseases. In the current study, we measured the ability of two non-dioxin like PCBs, 2,2',4,4',5,5'-hexachlorobiphenyl (PCB153) and 2,2'3,5',6-pentachlorobiphenyl (PCB95), to alter dopamine (DA) levels and metabolism using the dopaminergic PC12 cell line. Our hypothesis is that treatment of PC12 cells with non-toxic concentrations of PCB153 or PCB95 for 12 and 24h will have different effects due to different congener structures. Levels of DA and of 3,4-dihydroxyphenylacetaldehyde (DOPAL), 3, 4-dihyroxylphenylethanol (DOPET), and 3,4-dihyroxylphenylacetic acid (DOPAC) metabolite, gene expression of the dopamine synthesis enzyme tyrosine hydroxylase (TH) and the vesicular monoamine transporter (VMAT2), and gene expression of the anti-oxidant enzymes Cu/Zn and Mn superoxide oxidase (Cu/ZnSOD, MnSOD), glutathione peroxidase (GPx) and catalase were determined. PCB153 decreased intracellular and extracellular levels of DA after 12h exposure and this was consistent with an increase in DA metabolites. After 24h, the level of DA in medium increased compared to the control. In contrast, PCB95 exposure increased the intracellular DA level and decreased DA in medium consistent with a down-regulation of VMAT2 expression at 12h. After 24h exposure, PCB95 increased DA levels in media. Expression of TH mRNA increased slightly following 12h but not at 24h exposure. MnSOD mRNA increased up to 6-7 fold and Cu/ZnSOD increased less than two-fold after treatment with both congeners. Catalase expression was up-regulated following 24h exposure to PCB153 and PCB95, but GPx expression was down-regulated after 12h exposure to PCB95 only. These results suggest that PCB153 and PCB95 are neurotoxic and affect DA turnover with structure-dependent differences between these two congeners.
... Cells use γ-H2A.X in response to a wider range of DNA damage, including oxidative damage and the formation of DNA adducts (Audebert et al., 2010;Watters et al., 2009;Zhou et al., 2006). PCB 153 has been shown to form DNA adducts (Jeong et al., 2008) and increase the production of reactive oxygen species (ROS), which can lead to oxidative DNA damage (Zhu et al., 2009). Additionally, PCB 153 has been shown to induce the activation of NADPH oxidase, a major source of ROS within cells (Choi et al., 2010). ...
Article
Background: Polychlorinated biphenyls (PCBs) are persistent organic pollutants that adversely affect human health. PCBs bio-accumulate in organisms important for human consumption. PCBs accumulation in the body leads to activation of the transcription factor NF-κB, a major driver of inflammation. Despite dietary exposure being one of the main routes of exposure to PCBs, the gut has been widely ignored when studying the effects of PCBs. Objectives: We investigated the effects of PCB 153 on the intestine and addressed whether PCB 153 affected intestinal permeability or inflammation and the mechanism by which this occurred. Methods: Mice were orally exposed to PCB 153 and gut permeability was assessed. Intestinal epithelial cells (IECs) were collected and evaluated for evidence of genotoxicity and inflammation. A human IEC line (SW480) was used to examine the direct effects of PCB 153 on epithelial function. NF-кB activation was measured using a reporter assay, DNA damage was assessed, and cytokine expression was ascertained with real-time PCR. Results: Mice orally exposed to PCB 153 had an increase in intestinal permeability and inflammatory cytokine expression in their IECs; inhibition of NF-кB ameliorated both these effects. This inflammation was associated with genotoxic damage and NF-кB activation. Exposure of SW480 cells to PCB 153 led to similar effects as seen in vivo. We found that activation of the ATM/NEMO pathway by genotoxic stress was upstream of NF-kB activation. Conclusions: These results demonstrate that oral exposure to PCB 153 is genotoxic to IECs and induces downstream inflammation and barrier dysfunction in the intestinal epithelium.
... Educations of the oxidative pressure response in water organisms have been projected as a basis of significant material that could be secondhand as gears to control the excellence of the environment 2 . Cellular antioxidant enzymes respond to augmented ROS stages with unalike planes of magnitude 3 and their goings-on alteration below the inspiration of periodic rhythmicity 4 , revision to low ecological temperatures 5 and site-specific conservation impac 6 . Modifications in antioxidant enzyme activities can afford valuable statistics for characteristic sandwiched between different groups of plants conferring to the indigenous fundamental conservational scene and biological factors 7 . ...
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Abstract Objectives: Two freshwater snails Bellamya bengalensis and Lymnaea acuminata from Malangaon reservoir of Dhule district (Maharashtra, India) were examined to study biomarkers of oxidative stress with the investigation of antioxidant enzyme activities. Methods: The experimental snail species were collected seasonally and acclimatized in the laboratory. Their digestive glands were used to study the activities of oxidative biomarker enzymes like Lipid PerOxidation (LPO), Glutathione-S-Transferase (GST), reduced glutathione (GSH), SuperOxide Dismutase (SOD), CATalase (CAT) and Glutathione Peroxidase (GPx). All investigations were carried out on double beam spectrophotometer (Elico BL 200). Findings: It was observed that, LPO level in B. bengalensis was 0.63, 0.55and 0.60(nmol of MDA formed/mg protein) while in L.acuminata0.74, 0.67 and 0.70 respectively in summer, monsoon and winter seasons. GST activity was 23.41,15.73 and 19.61 in B. engalensis while 26.29, 18.34and 22.29in L.acuminata. Level of GSH was 0.083, 0.117and 0.094 (μM/g wet tissue) in B. bengalensis while in L.acuminata it was 0.018, 0.056 and 0.026 (μM/g wet tissue) in three seasons. The level of SOD was 20.87, 24.83 and 23.33 (U/mg of protein) in B. bengalensis while in L. acuminata it was 18.32, 22.35 and 20.73 in three seasons. Level of CAT was 9.23, 13.20, and 11.56 (U/mg of protein) in B. bengalensis while in L.acuminata it was 7.02, 10.53 and 8.86 (U/mg of protein) respectively during three seasons. GPx movement was 6.57, 8.50and 7.48 (mg of GSH utilized/min/mg protein) in B. bengalensis. It was 5.05, 8.07and 7.04 (mg of GSH utilized/min/mg protein) in L.acuminata respectively in three seasons. The obtained data also showed the lowest levels of LPO and activities of GST and uppermost doings of SOD, CAT, and GPx and uppermost heights of GSH in two snail types in rainy period than summer and winter period. This designates that in summer, the snails were under more conservation stress than winter and rainy periods. Application: It was decided that changes in antioxidant enzymes and LPO and GST activity can be used as tool in ecological nursing packages.
... Regarding endometrial cancer, molecular epidemiological studies have shown how the activity of superoxide dismutase (SOD) would be lower in the endometrial cancer tissue than in the normal endometrium [43,44] and PCBs have been recently showed to activate the enzymatic activity of SOD 1 in endometrial cancer cells [45] as shown in a previous study where PCBs enhanced the activity of SOD both in MCF-10A human breast cells and RWPE-1 human prostate epithelial cells [46]. ...
Article
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Background: Although exposure to endocrine disruptor compounds (EDCs) has been suggested as a contributing factor to a range of women’s health disorders including infertility, polycystic ovaries and the early onset of puberty, considerable challenges remain in attributing cause and effect on gynaecological cancer. Until recently, there were relatively few epidemiological studies examining the relationship between EDCs and endometrial cancer, however, in the last years the number of these studies has increased. Methods: A systematic MEDLINE (PubMed) search was performed and relevant articles published in the last 23 years (from 1992 to 2016) were selected. Results: Human studies and animal experiments are confirming a carcinogenic effect due to the EDC exposure and its carcinogenesis process result to be complex, multifactorial and long standing, thus, it is extremely difficult to obtain the epidemiological proof of a carcinogenic effect of EDCs for the high number of confusing factors. Conclusions: The carcinogenic effects of endocrine disruptors are plausible, although additional studies are needed to clarify their mechanisms and responsible entities. Neverthless, to reduce endocrine disruptors (ED) exposure is mandatory to implement necessary measures to limit exposure, particularly during those periods of life most vulnerable to the impact of oncogenic environmental causes, such as embryonic period and puberty.
... After an entry into the alive body, they move into fat tissues and accumulate there. Then, these persistent organic contaminants produce quite a lot of free radicals, particularly lipid peroxidation (3,5,6). ...
Article
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Polychlorinated biphenyls (PCBs) are chlorinated organic compounds and well known carcinogenic and toxic pollutants. Currently, their detection and degradation to products with less risk are among environmental and health priorities. Passing 2,2′,4,4′,5,5′-Hexachlorobiphenyl (PCB-153) through the armchair single-walled carbon nanotubes (SWCNTs) (8, 8) and (10, 10) was investigated by Modified Neglect of Diatomic Overlap in the semi-empirical method. The analysis of results suggests that there are meaningful changes in the middle of the tubes. Based on the obtained evidence, the nanotubes have substantial potential to interact with the PCB-153 molecule effectively. The results show that the increased diameter in the armchair SWCNTs improves the detection and degradation potential of the tube to PCBs. According to the calculated thermodynamic parameters, the diameter of nano-structures is an effective factor in PCBs removal efficiency, as it could be helpful to make a more sensitive PCB nano-sensor.
... To determine the role of oxidative stress in the killing of MM cells by 2-DG and/or 10-TPP treatments, specific wells were pretreated with PEG-catalase to scavenge H 2 O 2 [30,77]. PEGcatalase significantly protected MM.1S and OPM-2 cells from 2-DG and/or 10-TPP-induced apoptotic death (Fig 6C). ...
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Therapeutic advances have markedly prolonged overall survival in multiple myeloma (MM) but the disease currently remains incurable. In a panel of MM cell lines (MM.1S, OPM-2, H929, and U266), using CD138 immunophenotyping, side population staining, and stem cell-related gene expression, we demonstrate the presence of stem-like tumor cells. Hypoxic culture conditions further increased CD138low stem-like cells with upregulated expression of OCT4 and NANOG. Compared to MM cells, these stem-like cells maintained lower steady-state pro-oxidant levels with increased uptake of the fluorescent deoxyglucose analog. In primary human MM samples, increased glycolytic gene expression correlated with poorer overall and event-free survival outcomes. Notably, stem-like cells showed increased mitochondrial mass, rhodamine 123 accumulation, and orthodox mitochondrial configuration while more condensed mitochondria were noted in the CD138high cells. Glycolytic inhibitor 2-deoxyglucose (2-DG) induced ER stress as detected by qPCR (BiP, ATF4) and immunoblotting (BiP, CHOP) and increased dihydroethidium probe oxidation both CD138low and CD138high cells. Treatment with a mitochondrial-targeting agent decyl-triphenylphosphonium (10-TPP) increased intracellular steady-state pro-oxidant levels in stem-like and mature MM cells. Furthermore, 10-TPP mediated increases in mitochondrial oxidant production were suppressed by ectopic expression of manganese superoxide dismutase. Relative to 2-DG or 10-TPP alone, 2-DG plus 10-TPP combination showed increased caspase 3 activation in MM cells with minimal toxicity to the normal hematopoietic progenitor cells. Notably, treatment with polyethylene glycol conjugated catalase significantly reduced 2-DG and/or 10-TPP-induced apoptosis of MM cells. Also, the combination of 2-DG with 10-TPP decreased clonogenic survival of MM cells. Taken together, this study provides a novel strategy of metabolic oxidative stress-induced cytotoxicity of MM cells via 2-DG and 10-TPP combination therapy.
... 39 PCB-induced oxidative stress and cytotoxicity in cell lines can be mitigated by NAC. 40 In cell cultures, quercetin blocks the inflammatory induced by PCBs. 41 ...
Article
The incidence of diabetes has increased 7 to 10-fold in the past 50 y. Although increased sugar consumption, obesity, and lack of exercise certainly contribute, the effect of environmental toxins may be far greater. The data are so compelling that some researchers now label these toxins as diabetogens. This editorial summarizes the research showing which toxins are the worst offenders, how they disrupt blood sugar control, where they come from, how to assess body load, and strategies for detoxification and excretion.
... Exposure to PCBs has been associated with dramatic adverse effects in many species (e.g., eggshell thinning in birds of prey; Wiemeyer and Porter, 1970;Ross, 2004;Frye et al., 2011). Several studies have shown that increased OS may be an additional mechanism underlying the negative effects of PCBs on the organism (e.g., Oakley et al., 1996;Zhu et al., 2009). One important mechanism of action of PCBs is the binding capacity of some "dioxin-like" congers, such as PCBs 77 and 126, with the aryl hydrocarbon receptor (AhR), activating the enzyme cytochrome P450 1A subfamily (Hennig et al., ...
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The capacity to communicate effectively with other individuals plays a critical role in the daily life of an individual and can have important fitness consequences. Animals rely on a number of visual and non-visual signals, whose production brings costs to the individual. The theory of honest signaling states that these costs are higher for low than for high-quality individuals, which prevents cheating and makes signals, such as skin and plumage coloration, indicators of individual's quality or condition. The condition-dependent nature of signals makes them ideally suited as indicators of environmental quality, implying that signal production might be affected by contaminants. In this mini-review article, we have made the point that oxidative stress (OS) is one overlooked mechanism linking exposure to contaminants to signaling because (i) many contaminants can influence the individual's oxidative balance, and (ii) generation of both visual and non-visual signals is sensitive to OS. To this end, we have provided the first comprehensive review on the way both non-organic (heavy metals, especially mercury) and organic [persistent organic pollutants (POPs)] contaminants may influence either OS or sexual signaling. We have also paid special attention to emerging classes of pollutants like brominated flame-retardants (BFRs) and perfluoroalkoxy alkanes (PFAs) in order to stimulate research in this area. We have finally provided suggestions and warnings for future work on the links among OS, sexual signaling, and contaminant exposure.
... Since PCBs have been reported to increase intracellular ROS content [50,51], we evaluated whether PCBs-mediated changes of ROS intervene in the regulation of pituitary cells apoptosis. As shown in Fig 7A, the ROS levels did not change when cells were exposed to individual PCBs, either alone or in combination with vitamin C, a ROS production inhibitor. ...
Article
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Polychlorinated biphenyls (PCBs) can disrupt the endocrine function, promote neoplasms and regulate apoptosis in some tissues; however, it is unknown whether PCBs can affect the apoptosis of pituitary cells. The study evaluated the effect of PCBs on the apoptosis of normal pituitary cells and the underlying mechanisms. Primary cell cultures obtained from mouse pituitary glands were exposed to Aroclor 1254 or selected dioxin-like (PCB 77, PCB 126) or non-dioxin-like (PCB 153, PCB 180) congeners. Apoptosis was evaluated by Annexin V staining, DNA fragmentation, and TUNEL assay. Both the expression and activity of caspases were analyzed. Selective thyroid hormone receptor (TR) or aryl-hydrocarbon receptor (AhR) or CYP1A1 antagonist were used to explore the mechanisms underlying PCBs action. Our results showed that Aroclor 1254 induced the apoptosis of pituitary cells as well as the final caspase-3 level and activity through the extrinsic pathway, as shown by the increased caspase-8 level and activity. On the other hand, the intrinsic pathway evaluated by measuring caspase-9 expression was silent. The selected non-dioxin-like congeners either increased (PCB 180) or reduced (PCB 153) pituitary cell apoptosis, affecting the extrinsic pathway (PCB 180), or both the extrinsic and intrinsic pathways (PCB 153), respectively. In contrast, the dioxin-like congeners (PCB 77 and PCB 126) did not affect apoptosis. The anti-apoptotic phenotype of PCB 153 was counteracted by a TR or a CYP1A1 antagonist, whereas the pro-apoptotic effect of PCB 180 was counteracted by an AhR antagonist. The induced apoptosis of Aroclor 1254 or PCB 180 was associated with a reduction of cell proliferation, whereas the decreased apoptosis due to PCB 153 increased cell proliferation by 30%. In conclusion, our data suggest that non-dioxin-like PCBs may modulate apoptosis and the proliferation rate of pituitary cells that have either pro- or anti-apoptotic effects depending on the specific congeners. However, the impact of PCBs on the process of pituitary tumorigenesis remains to be elucidated.
... In addition, the release of cytochrome c into the cytoplasm activates caspase-dependent apoptosis (Spierings et al. 2005). PCB3 quinone was reported to increase oxidative stress in the mitochondria of human cells in culture and to inhibit the mitochondrial electron chain; PCB29 quinone caused an increase in mitochondrial oxidative stress, a transfer of cytochrome c from the mitochondria into the cytoplasm and induced caspase-dependent apoptosis (Xiao et al. 2013(Xiao et al. , 2014Xu et al. 2014Xu et al. , 2015Zhu et al. 2009). These reports suggest that cytochrome c may play a crucial role in PCB quinone toxicity. ...
Article
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Polychlorinated biphenyls (PCBs) are a group of 209 individual congeners widely used as industrial chemicals. PCBs are found as by-products in dye and paint manufacture and are legacy, ubiquitous, and persistent as human and environmental contaminants. PCBs with fewer chlorine atoms may be metabolized to hydroxy- and dihydroxy-metabolites and further oxidized to quinoid metabolites both in vitro and in vivo. Specifically, quinoid metabolites may form adducts on nucleophilic sites within cells. We hypothesized that the PCB-quinones covalently bind to cytochrome c and, thereby, cause defects in the function of cytochrome c. In this study, synthetic PCB quinones, 2-(4'-chlorophenyl)-1,4-benzoquinone (PCB3-pQ), 4-4'-chlorophenyl)-1,2-benzoquinone (PCB3-oQ), 2-(3', 5'-dichlorophenyl)-1,4-benzoquinone, 2-(3',4', 5'-trichlorophenyl)-1,4-benzoquinone, and 2-(4'-chlorophenyl)-3,6-dichloro-1,4-benzoquinone, were incubated with cytochrome c, and adducts were detected by liquid chromatography-mass spectrometry (LC-MS) and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI TOF). Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was employed to separate the adducted proteins, while trypsin digestion and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were applied to identify the amino acid binding sites on cytochrome c. Conformation change of cytochrome c after binding with PCB3-pQ was investigated by SYBYL-X simulation and cytochrome c function was examined. We found that more than one molecule of PCB-quinone may bind to one molecule of cytochrome c. Lysine and glutamic acid were identified as the predominant binding sites. Software simulation showed conformation changes of adducted cytochrome c. Additionally, cross-linking of cytochrome c was observed on the SDS-PAGE gel. Cytochrome c was found to lose its function as electron acceptor after incubation with PCB quinones. These data provide evidence that the covalent binding of PCB quinone metabolites to cytochrome c may be included among the toxic effects of PCBs.
... As such, pre-treatment with antioxidants is anticipated to suppress ROS-mediated activation of AhR-signaling in 4-ClBQ treated cells. Pre-treatment with antioxidants (NAC; superoxide dismutase and catalase) has been shown to suppress 4-ClBQ induced increase in ROS levels and toxicity in HaCaT, and human mammary and prostate epithelial cells (Venkatesha et al., 2008;Xiao et al., 2013;Zhu et al., 2009). Pre-treatment with NAC significantly suppressed 4-ClBQ-induced increase in CYP1A1 mRNA expression ( Fig. 6A and B). ...
Article
Aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that plays a critical role in metabolism, cell proliferation, development, carcinogenesis, and xenobiotic response. In general, dioxin-like polychlorinated biphenyls (PCBs) exhibit a ligand-dependent activation of AhR-signaling. Results from this study show that a quinone-derivative (1-(4-Chlorophenyl)-benzo-2,5-quinone; 4-ClBQ) of a non-dioxin like PCB (PCB3) also activates AhR-signaling. Treatments of HaCaT human keratinocytes with 4-ClBQ and dioxin-like PCB126 significantly increased AhR-target gene expression, CYP1A1 mRNA and protein levels. 4-ClBQ-induced increase CYP1A1 expression was associated with an increase in the nuclear translocation of AhR protein as well as an increase in the luciferase-reporter activity of a human CYP1A1 xenobiotic response element (XRE). 6,2',4'-trimethoxyflavone (TMF), a well-characterized AhR-ligand antagonist significantly suppressed PCB126-induced increase in CYP1A1 expression, while the same treatment did not suppress 4-ClBQ-induced increase in CYP1A1 expression. However, siRNA-mediated down-regulation of AhR significantly inhibited 4-ClBQ-induced increase in CYP1A1 expression, suggesting that AhR mediates 4-ClBQ-induced increase in CYP1A1 expression. Interestingly, treatment with the antioxidant N-acetyl-L-cysteine significantly suppressed 4-ClBQ-induced increase in CYP1A1 expression. Furthermore, CYP1A1 expression also increased in cells treated with hydrogen peroxide. These results demonstrate that a ligand-independent and oxidative stress dependent pathway activates AhR-signaling in 4-ClBQ treated HaCaT cells. Because AhR signaling is believed to mediate xenobiotics response, our results may provide a mechanistic rationale for the use of antioxidants as effective countermeasure to environmental pollutant-induced adverse health effects. Copyright © 2015. Published by Elsevier Ireland Ltd.
Article
Exposure to toxic chemicals, such as plasticizers, alkylphenol compounds, and polychlorinated biphenyls (PCBs), has increased due to environmental contamination. PCBs, categorized as persistent organic pollutants (POPs), are lipophilic chemicals commonly used in lubricants, cutting oils, and electrical insulators. PCBs may have detrimental effects on hormone-producing glands, potentially contributing to male infertility. Thus, the objective of this study was to provide a comprehensive overview of the adverse effects of PCBs on the male reproductive system. Searches of three electronic databases were performed using MESH terms and 32 studies were included. Although the exact mechanism of action for PCBs remains unclear, several PCBs are regarded as potential endocrine disruptors due to their ability to interact with hormone signaling pathways. PCBs have been found to disrupt physiological functions by mimicking endogenous hormones as agonists or antagonists, altering patterns of hormone synthesis, hormone receptor affinities or numbers, and modulating enzymes involved in hormone secretion. These reports highlight the pleiotropic nature of PCB function and the susceptibility of the reproductive system. Endocrine-disrupting PCBs can mimic, alter, or block hormonal responses, inhibiting natural signaling to the testes and epididymis via various mechanisms such as binding to sex hormone-binding globulin and androgen-binding protein or blocking cell surface receptors. Furthermore, PCBs can alter the hormonal environment in the prostate or seminal vesicles by changing the affinity of androgens for their receptors. The testicles and genital organs may be susceptible to various estrogenic effects, leading to changes in the quality or quantity of their secretions and the volume of semen.
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Ferulic acid (FA) is a naturally occurring phenolic compound commonly found in the plant Ferula communis. This study aims to investigate the hepatoprotective effect of FA and its derivatives (methyl ferulic acid and trans-ferulic acid) against oxidative stress and inflammation-related hepatotoxicity due to toxicants based on the results of different non-clinical and preclinical tests. For this, data was collected from different reliable electronic databases such as PubMed, Google Scholar, and ScienceDirect, etc. The results of this investigation demonstrated that FA and its derivatives have potent hepatoprotective effects against oxidative stress and inflammation-related damage. The findings also revealed that these protective effects are due to the antioxidant and anti-inflammatory effects of the chemical compound. FA and its analogues significantly inhibit free radical generation and hinder the effects of proinflammatory markers and inflammatory enzymes, resulting in diminished cytotoxic and apoptotic hepatocyte death. The compounds also prevent intracellular lipid accumulation and provide protective effects.
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Pesticides are now a risk to the environment and public health. Monocrotophos (MCP) is known to cause organ toxicity and impart degenerative effects at cellular levels. N-acetylcysteine (NAC) is a natural antioxidant having various prophylactic properties. Male Wistar rats were given NAC (200 mg/kg b.wt), MCP (0.9 mg/kg b.wt) and NAC followed by MCP; intragastrically for 28 consecutive days. Regulation of MnSOD, UCP-2 and cytochrome c was analyzed by western blotting and polymerase chain reaction. Histology, electron microscopy and weight parameters were evaluated in the liver. MCP exposure significantly decreased body weight gain, relative liver weight, and structural changes. Altered MnSOD protein expression, decreased transcription of UCP-2 and MnSOD, and released cytochrome c indicated that oxidative stress is involved in MCP exposure. Treatment of NAC to MCP-exposed rats normalized the weight and structural changes, restored MnSOD and UCP-2 levels and prevented the release of cytochrome c. The present study suggests that the regulation of UCP-2, MnSOD and cytochrome c is involved in NAC efficacy against MCP toxicity. These findings illustrate that NAC can serve as a potential therapeutic agent for toxicity and oxidative stress in mammals.
Article
Titanium dioxide nanoparticles (n-TiO2) and polychlorinated biphenyls (PCBs) can be present in the food of fish, leading to intestinal exposure uptake, and accumulation in inner organs. This study examined combination effects of n-TiO2 and PCB77 in in vitro models of the fish intestinal epithelium and liver, i.e., RTgut-GC cell cultures grown in ThinCertsTM and RTL-W1 cell cultures grown in standard tissue culture plates. Mass spectrometry and microscopy techniques were used to obtain information on nanoparticle translocation across the intestinal barrier model. In addition, the substances’ effect on intestinal barrier permeability, cell viability, expression of dioxin – and antioxidant response element -controlled genes, and induction of cytochrome P450 1a (Cyp1a)-dependent ethoxyresorufin-O-deethylase (EROD) activity were assessed. TiO2 nanoparticles were taken up by RTgut-GC cells and detected in the bottom compartment of the intestinal epithelial barrier model. It was not possible to conclude definitively if n-TiO2 translocation occurred via transcytosis or paracellular migration but observations of nanoparticles in the lateral space between adjacent epithelial cells were rare. PCB77 (1 and 10 µM, 24 h) did not affect barrier permeability, i.e., n-TiO2 translocation is probably not facilitated in case of co-exposure. Furthermore, previous and simultaneous exposure to n-TiO2 (1 and 10 mg/L, 24 h) did not have any influence on PCB77-induced Cyp1a mRNA and enzyme activity levels in RTL-W1 cells. Furthermore, there were no significant differences in expression of antioxidant response element-controlled genes comparing control, single substance, and mixture treatments, not even following long-term exposure (0.01-1 mg/L n-TiO2 + 1 nM PCB77, 4 weeks). While an underestimation of the effects of n-TiO2 and PCB77 cannot be fully excluded as concentration losses due to sorption to cell culture plastics were not measured, the results suggest that the test substances probably have a low potential to exhibit combination effects on the assessed endpoints when co-existing in fish tissues.
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Exposure to environmental toxicants is prevalent, hazardous and linked to varied detrimental health outcomes and disease. Polychlorinated biphenyls (PCBs), a class of hazardous organic chlorines once widely used for industrial purposes, are associated with neurodegenerative disease and oxidative stress in both in vitro and in vivo models. Here, we investigated the impact of Aroclor 1254, a commercially available PCB mixture, on primary murine astrocytes to determine the response to this once ubiquitously used toxicant on the most numerous cells of the central nervous system (CNS). Astrocytes are a critical component of homeostasis throughout the CNS, including at the blood-brain barrier, where they serve as the primary defense against xenobiotics entering the CNS, and at the synapse, where they are closely coupled to neurons through several metabolic pathways. We hypothesized that PCBs cause astrocytic oxidative stress and related dysfunction including altered metabolism. We exposed primary murine cortical astrocytes to PCBs and report an increased expression of antioxidant genes (Prdx1, Gsta2, Gfap, Amigo2) in response to oxidative stress. Our data show increased ATP production and spare respiratory capacity in astrocytes exposed to 10 μM (∼ 3 ppm) of PCBs. This dose also causes an increase in glucose uptake that is not seen at a higher dose (50 μM) suggesting that, at a lower dose, astrocytes are able to engage compensatory mechanisms to promote survival. Together, these data suggest that exposure to polychlorinated biphenyls impact astrocytic metabolism, which is important to consider both in the context of human health and disease and in cell culture and animal models.
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Polychlorinated biphenyls (PCBs) are notorious persistent organic pollutants that were banned in the last century. However, PCBs are still remained ubiquitous in the ecosystem due to their persistence and bio-accumulative potency that against environmental and biological degradation. Albeit there is no longer the permission of commercial production of PCBs, they were continuously released into global biota via illegal disposal of e-waste or as byproducts of industrial supplies. Role of oxidative stress are often implicated in PCBs’ toxicology. PCBs, especially coplanar ones, have high affinity toward aryl hydrocarbon receptor (AhR) and inducing CYP1A1 that was considered a source of oxidative stress. Although commercial PCBs and coplanar individual PCBs, e.g. PCB 77 and 126, induced oxidative stresses have been extensively investigated, however, PCB metabolites-induced oxidative stress were paid less attention. PCBs can undergo phase I metabolism which metabolize parent PCBs into hydroquinone/semiquinone/quinone metabolites as a futile redox cycle, and producing downstream reactive oxygen species (ROS) as byproducts; PCBs can also undergo phase II metabolism yielding methylsulfonyl metabolites that deplete glutathione and such. PCB metabolites induce oxidative stress generally via direct producing of ROS, or indirect scavenge antioxidant and inhibit antioxidant enzymes, and disturb cellular redox balance. This review aims to provide critical summary of PCBs metabolism, PCBs parents and daughter metabolites-induced oxidative stress. We especially focused on the connection between parent PCBs and downstream metabolites, to encourage research associated with PCB metabolites induced oxidative stress.
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Environmental chemicals, particularly organochlorinated contaminants (OCs), are associated with a ranged of adverse health effects, including impairment of the immune system and antiviral immunity. Influenza A virus (IAV) is an infectious disease of major global public health concern and exposure to OCs can increase the susceptibility, morbidity, and mortality to disease. It is however unclear how pollutants are interacting and affecting the outcome of viral infections at the cellular level. In this study, we investigated the effects of a mixture of environmentally relevant OCs on IAV infectivity upon in vitro exposure in Madin Darby Canine Kidney (MDCK) cells and human lung epithelial cells (A549). Exposure to OCs reduced IAV infectivity in MDCK and A549 cells during both short (18-24h) and long-term (72h) infections at 0.05 and 0.5ppm, and effects were more pronounced in cells co-treated with OCs and IAV than pre-treated with OCs prior to IAV (p<0.001). Pre-treatment of host cells with OCs did not affect IAV cell surface attachment or entry. Visualization of IAV by transmission electron microscopy revealed increased envelope deformations and fewer intact virions during OC exposure. Taken together, our results suggest that disruption of IAV infection upon in vitro exposure to OCs was not due to host-cell effects influencing viral attachment and entry, but perhaps mediated by direct effects on viral particles or cellular processes involved in host-virus interactions. In vitro infectivity studies such as ours can shed light on the complex processes underlying host-pathogen-pollutant interactions.
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It is a safe and environmentally-friendly method to exploit natural gas hydrates (“hydrate”) by using flue gas (mainly including CO2 and N2) from electric power plants. So far, however, its energy consumption and energy efficiency has not been investigated thoroughly. In this paper, the process to exploit hydrates from flue gas was established. Firstly, flue gas is injected into hydrate reservoirs after it is pressurized. The hydrates in reservoirs partially experience thermal decomposition while the rest is replaced with flue gas, so CH4CO2N2 mixture is formed. Secondly, the concentrated CH4CO2 mixture is got after N2 is separated and removed by using membrane component. And thirdly, the CH4CO2 mixture is delivered to the original electric power plant. This process was simulated by using the software Aspen Plus to analyze the production/injection ratio in the process of flue gas replacement under different injection pressures, the methane replacement ratio, and the energy consumption and energy efficiency in the whole process. It is indicated that the energy in the process of hydrate exploitation from flue gas is mainly consumed at the pressurized injection stage, and the injection pressure increase correspondingly results in the increase of energy consumption at pressurization and membrane separation stages, and to some extent improves the recovery ratio of pressure energy. Besides, when the injection pressure is 5–16 MPa, the production/injection ratio in the process of flue gas replacement is 0.03–0.26, the methane replacement ratio is 19.9–56.2%, the unit energy consumption in the whole process is 2.15–1.05 (kW·h)/kgCH4, and the energy return on investment (EROI) is 7.2–14.7. It is concluded that the energy efficiency of hydrate exploitation from flue gas can be effectively improved by increasing the injection pressure in the range of 5–10 MPa.
Chapter
Autism spectrum disorders (ASDs) are behaviorally defined neurodevelopmental disorders. The increased prevalence of oxidative stress in autism has been demonstrated by analyzing markers of oxidative damage (lipid peroxidation and protein and DNA oxidation), glutathione redox/antioxidant capacity, antioxidant enzymes, antioxidant proteins, methionine metabolism, and nitric oxide. Many environmental factors such as heavy metals, maternal drugs (valproic acid, thalidomide), and endocrine-disrupting chemicals (e.g., bisphenol A, polychlorinated biphenyls, polybrominated diphenyl ethers, and phthalates) can induce or increase vulnerability to oxidative stress and have been suggested to be involved in the pathophysiology of ASDs. A few studies have also suggested involvement of genes involved in oxidative/nitrosative stress in autism. Here, we review evidence of increased oxidative damage coupled with reduced antioxidant defense, genetic susceptibility to oxidative/nitrosative stress, and impact of environmental agents in autism.
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The Muli area is the only region where gas hydrates have been found in the mid-latitude permafrost regions of the world. The use of geophysical method and certain geophysical parameters have a strong predominance in identifying gas hydrates and optimizing the effective gas hydrate detection methods in hard rock permafrost areas. Since 2009, a series of tests has been performed in the Muli area, including seismic reflection and electromagnetic methods, and integrated geophysical well logging. The results show the presence of three types of gas hydrate reservoir, namely sandstone pore, mudstone fracture, and shale fracture types, with each showing a different well logging response. The gas hydrate reservoirs in the Muli area are characterized by high frequency and weak amplitude on the two-dimensional seismic profiles, and high horizontal resistivity on the electrical sections. The geophysical characteristics are complex, particularly as a result of the specific environments of gas hydrate reservoirs. These characteristics can be used to estimate the type and distribution of the gas hydrate reservoir, and to improve gas recovery rates by directing preliminary exploration.
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The Endocrine Society's first Scientific Statement in 2009 provided a wake-up call to the scientific community abouthow environmental endocrine-disrupting chemicals (EDCs) affect health and disease. Five years later, a substantially larger body of literature has solidified our understanding of plausible mechanisms underlying EDC actions and how exposures in animals and humans-especially during development-may lay the foundations for disease later in life. At this point in history, we have much stronger knowledge about how EDCs alter gene-environment interactions via physiological, cellular, molecular, andepigeneticchanges, therebyproducingeffects inexposedindividuals as well as theirdescendants. Causal links between exposure and manifestation of disease are substantiated by experimental animal models and are consistent with correlative epidemiological data in humans. There are several caveats because differences in how experimental animal work is conducted can lead to difficulties in drawing broad conclusions, and we must continue to be cautious about inferring causality in humans. In this second Scientific Statement, we reviewed the literature on a subset of topics for which the translational evidence is strongest: 1) obesity and diabetes; 2) female reproduction; 3) male reproduction; 4) hormone-sensitive cancers in females; 5) prostate; 6) thyroid; and 7) neurodevelopment and neuroendocrine systems. Our inclusion criteria for studies were those conducted predominantly in the past 5 years deemed to be of high quality based on appropriate negative and positive control groups or populations, adequate sample size and experimental design, and mammalian animal studies with exposure levels in arange that was relevant to humans. We also focused on studies using the developmental origins of health and disease model. No report was excluded based on a positive or negative effect of the EDC exposure. The bulk of the results across the board strengthen the evidence for endocrine health-related actions of EDCs. Based on this much more complete understanding of the endocrine principles by which EDCs act, including nonmonotonic dose-responses, low-dose effects, and developmental vulnerability, these findings canbemuchbetter translated tohumanhealth. Armedwith this information, researchers, physicians, andother healthcare providers can guide regulators and policymakers as they make responsible decisions.
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Polychlorinated biphenyls (PCBs) are organic chemicals that were traditionally produced and widely used in industry as mixtures and are presently formed as byproducts of pigment and dye manufacturing. They are known to persist and bioaccumulate in the environment. Some have been shown to induce liver cancer in rodents. Although the mechanism of the toxicity of PCBs is unknown, it has been shown that they increase oxidative stress, including lipid peroxidation. We hypothesized that oxidative stress-induced DNA damage could be a contributor for PCB carcinogenesis and analyzed several DNA adducts in female Sprague-Dawley rats exposed to 3,3',4,4',5-pentachlorobiphenyl (PCB 126), 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153), and a binary mixture (PCB 126 + 153) for 14, 31, and 53 wks. Eight adducts were measured to profile oxidative DNA lesions, including 8-oxo-deoxyguanosine (8-oxo-dG), 1,N(6)-ethenodeoxyadenosine (1,N(6)-εdA), N(2),3-ethenoguanine (N(2),3-εG), 1,N(2)-ethenodeoxyguanosine (1,N(2)-εdG), as well as malondialdehyde (M1dG), acrolein (AcrdG), crotonaldehyde (CrdG), and 4-hydroxynonenal-derived dG adducts (HNEdG) by LC-MS/MS analysis. Statistically significant increases were observed for 8-oxo-dG and 1,N(6)-εdA concentrations in hepatic DNA of female rats exposed to the binary mixture (1000 ng/kg/day + 1000 μg/kg/day) but not in rats exposed to PCB 126 (1000 ng/kg/day) or PCB 153 (1000 μg/kg/day) for 14 and 31 wks. However, exposure to PCB 126 (1000 ng/kg/day) for 53 wks significantly increased 8-oxo-dG, 1,N(6)-εdA, AcrdG, and M1dG. Exposure to PCB 153 (1000 μg/kg/day) for 53 wks increased 8-oxo-dG, and 1,N(6)-εdA. Exposure to the binary mixture for 53 wks increased 8-oxo-dG, 1,N(6)-εdA, AcrdG, 1,N(2)-εdG, and N(2),3-εG significantly above control groups. Increased hepatic oxidative DNA adducts following exposure to PCB 126, PCB 153, or the binary mixture shows that an increase in DNA damage may play an important role in hepatic toxicity and carcinogenesis in female Sprague-Dawley rats.
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Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants present in dietary fats. Most studies evaluating PCB effects have been conducted with a single compound or a mixture of PCBs given as a single acute dose. The purpose of this study was to evaluate in vivo PCB toxicity in a realistic model of exposure: a low daily dose of PCBs (twice the tolerable daily intake (TDI)), chronically administered (8 weeks) to rats in contaminated goat milk. Liver and brain PCB toxicities were investigated by evaluating oxidative stress status and mitochondrial function. PCB toxicity in the liver was also estimated by transaminase enzymatic activity. This study shows that even at low doses, chronic PCB exposure resulted in a statistically significant reduction of mitochondrial function in liver and brain. In the liver, oxygen consumption in the condition of adenosine triphosphate (ATP) production (state 3) decreased by 22-29% (p < 0.01), according to the respiratory substrates. In the brain, respiratory chain complexes II and III were reduced by 24% and 39%, respectively (p < 0.005). The exposed rats presented higher lipid peroxidation status (+20%, p < 0.05) and transaminase activity (+30%, p < 0.05) in the blood. Thus, our study showed that exposure of rats to a daily realistic dose of PCBs (twice the TDI in a food complex mixture of environmental origin) resulted in multiple disruptions in the liver and brain.
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Critical components of the Qinghai-Tibet Plateau natural-gas hydrate (NGH) petroleum system has been examined in this study. The results demonstrate that the Kaixinling-Wuli permafrost region contains viable prospects for gas hydrate exploration within favorable temperature and pressure stability conditions. In the study area, the average annual temperature of ground surface is -4.2°C, the thickness of permafrost ranges from 40 - 150 m (average 84 m), and the geothermal gradient beneath the permafrost is between 1.54°C/100 m and 2.67°C/100 m (average 2.03°C/100 m). The thickness of the methane-gas hydrate stability zone (GHSZ) is approximately 240-450 m. The Upper Permian Nayixiong Formation is dominated by braided delta and shallow shelf facies under mostly reducing conditions. The potential swamp deposited source rocks have a high total organic carbon (TOC) content that features a mixture of kerogen types II or III and an average vitrinite reflectance (Ro) of 2.04%. Overall, the thick sedimentary column in this region, its abundance of organic matter and its high thermal maturity suggest that the Nayixiong Formation source rocks has a high gas-generation potential. An effective fault-fracture-pore system also provide migration channels for deeper gas and also act as a reservoir for vein-type gas hydrate occurrences. The Kaixinling-Wuli area, when compared to other regions in the Qinghai-Tibet Plateau, exhibits greater gas hydrate petroleum system exploration potential as a result of the favorable temperature/pressure stability conditions and effective gas and gas-hydrate migration-storage system.
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Polychlorinated biphenyl (PCBs) are high resistant pollutants which cause adverse health effects in recent years. The accumulation of these toxic compounds in the food chain lead to oxidative stress in various ecosystems. Detection, absorption, and elimination of them are an environmental priority. Passing of PCB-153 through the armchair single walled carbon nanotube (SWNT) (8,8) were investigated by MNDO in semi-empirical quantum method. Calculated electrical and thermodynamic properties show a sudden change in the middle of the tube which may act as a trap for the studied pollutant. The results indicated the nanotube has considerable ability to interact with PCB-153 and cause its degradation. According to calculated thermodynamic parameters through the molecular modeling, it is expected that single wall carbon nanotube is a candidate in remediation of PCBs as well as in gas sensor devices for detection of them. The median tube is a place for trapping pollutants.
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Polychlorinated biphenyls (PCBs) are a group of persistent organic pollutants, the toxic behaviors and mechanisms of PCBs individual and congener have been extensively investigated. However, there only has limited information regarding to their metabolites. In our previous studies, we have shown a synthetic PCBs metabolite, PCB29-pQ causes oxidative damage with the evidences of cytotoxicity, genotoxicity and mitochondrial-driven intrinsic apoptosis. Here, we investigate the effect of PCB29-pQ on DNA damage checkpoint activation, cell cycle arrest and death receptor-related extrinsic apoptosis in human liver hepatocellular carcinoma HepG2 cells. Our results illustrated that PCB29-pQ increased S-phase cell population by down-regulating cyclins A/D1/E, cyclin-dependent kinases (CDK 2/4/6) and cell division cycle 25A (CDC25A) and up-regulating p21/p27 protein expression. PCB29-pQ also induced apoptosis via the up-regulation of Fas/FasL and activation of caspase 8/3. Moreover, p53 played a pivotal role in PCB29-pQ-induced cell cycle arrest and apoptosis via the activation of ATM/Chk2 and ATR/Chk1 checkpoints. Cell cycle arrest and apoptotic cell death were attenuated by the pretreatment with antioxidant N-acetyl-cysteine (NAC). Taking together, these results demonstrate that PCB29-pQ-induced oxidative stress and promotes p53-dependent DNA damage checkpoint activation, S-phase cycle arrest and extrinsic apoptosis in HepG2 cells.
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Headspace gases from cores are sampled in the gas hydrate drilling well DK-8 in the Qilian Mountain permafrost. Gas components and carbon isotopes of methane from headspace gas samples are analyzed. The geochemical features of the headspace gases along the well profile are compared with occurrences of gas hydrate, and with the distribution of faults or fractures. Their geochemical significance is finally pointed out in gas hydrate occurrences and hydrocarbon migration. Results show high levels of hydrocarbon concentrations in the headspace gases at depths of 149–167 m, 228–299 m, 321–337 m and 360–380 m. Visible gas hydrate and its associated anomalies occur at 149–167 m and 228–299 m; the occurrence of high gas concentrations in core headspace gases was correlated to gas hydrate occurrences and their associated anomalies, especially in the shallow layers. Gas compositions, gas ratios of C1/ΣC1–5, C1/(C2 + C3), iC4/nC4, and iC5/nC5, and carbon isotopic compositions of methane (δ13C1, PDB‰) indicate that the headspace gases are mainly thermogenic, partly mixed with biodegraded thermogenic sources with small amounts derived from microbial sources. Faults or fracture zones are identified at intervals of 149–167 m, 228–299 m, 321–337 m, and near 360–380 m; significantly higher gas concentrations and lower dryness ratio were found in the headspace gases within the fault or fracture zones compared with areas above these zones. In the shallow zones, low dryness ratios were observed in headspace gases in zones where gas hydrate and faults or fracture zones were found, suggesting that faults or fracture zones serve as migration paths for gases in the deep layers and provide accumulation space for gas hydrate in the shallow layers of the Qilian Mountain permafrost.
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Survival curves of normal human cells from a variety of tissues exposed to varying doses of x-irradiation have been constructed, which permit definition of the intrinsic radiation sensitivity of the reproductive power of each cell type. The mean lethal dose of x-irradiation for all the cells employed, including those from normal and cancerous organs, those exhibiting diploid and polyploid chromosome number; those from embryonic and adult tissues, including recently isolated cells and cultures which had been maintained in vitro for many years, and cells exhibiting either epithelioid or fibroblastic morphology, was found to be contained between the limits of 50 to 150 r. Other similarities in the pattern of radiation effects, such as giant formation and abortive colonial growth, in these cells and that of the HeLa S3, previously studied, confirm the hypothesis that the pattern of reaction to x-irradiation previously elucidated, is representatative, at least in over-all outline, for a large variety of human cells. While the radiation survival curves of various human cells are similar in the gross, small but important characterizing differences have been found. All epithelioid cells so far studied are approximately 2-hit, and more radioresistant than the fibroblast-like cells whose survival data correspond to a mean lethal dose of around 60 r, and which so far can be fitted by either 1-hit or 2-hit curves. The earlier prediction that the major radiobiologic damage to mammalian cells is lodged in the genetic apparatus was confirmed by the demonstration of high frequency of mutants among the survivors of doses of 500 to 900 r. All the data on the x-radiosensitivity of these cells can be explained on the basis of a defect resulting from primary damage localized in one or more chromosomes. These considerations afford a convincing explanation of several aspects of the mammalian radiation syndrome.
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Polychlorinated biphenyls are a group of industrial chemicals that are widely distributed in the environment. Since these compounds occur as mixtures, studies of their possible interactive effects are important. In order to determine whether an interaction of 2,5,2',5'-tetrachlorobiphenyl (TCB) with 3,4,3',4'-TCB occurs during multistage hepatocarcinogenesis in vivo, like that previously observed in lymphocytes in vitro (L. M. Sargent et al., Mutat. Res., 224: 79-88, 1989), we exposed rats to a single initiating dose of diethylnitrosamine (DEN), 10 mg/kg after a 70% partial hepatectomy, and subsequently to 0.1 ppm 3,4,3',4'-TCB and/or 10 ppm 2,5,2',5'-TCB in the diet for 1 year. Administration of each of the TCBs alone after DEN initiation resulted in a low incidence of chromosomal damage in hepatocytes; but when the two were given together after DEN initiation, there was a more than additive effect on this parameter at both 7 and 12 months which was highly significant. Administration of the TCBs alone or in combination in the absence of DEN initiation also resulted in chromosomal damage, approaching that seen in livers of animals initiated with DEN when sacrificed at 12 months. In animals receiving 0.05% phenobarbital for a 12-month period after initiation with DEN, a significant degree of chromosomal breakage and fragment formation occurred both in hepatocytes expressing the ectoenzyme gamma-glutamyltranspeptidase (GGT) and in those that were GGT negative. However, the GGT-negative cells showed a significantly lower incidence of chromosomal damage than the GGT-positive hepatocytes. Exposure to phenobarbital for 7 months after DEN initiation resulted in no significant chromosomal damage in hepatocytes, whether GGT positive or GGT negative. Some degree of specificity in chromosomal alterations was seen in hepatocytes of animals initiated with DEN and promoted either with a combination of TCBs or with phenobarbital. The most frequent alterations seen were a trisomy of chromosome 1 or of its long arm and a monosomy of chromosome 3 or its short arm. Some chromosome 7 aberrations were also seen. The highest frequency of specific aberrations occurred in hepatocytes from rats that also bore hepatocellular carcinomas, suggestive of the hypothesis that genes involved in the development of hepatic carcinoma may reside in chromosome 1 and/or 3 of the rat.
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Toxic aldehydes, such as 4-hydroxy-2-nonenal (4HNE) and 2-nonenal (2NE), formed during lipid peroxidation have been isolated and implicated in the cytotoxic effects of oxidative stress. We have investigated the cytotoxicity and metabolism of 4HNE and 2NE in control (HA-1) cells and in two H2O2-resistant Chinese hamster fibroblast cell lines. The H2O2-resistant cells were found to be significantly more resistant than HA-1 cells to the cytotoxicity of 4HNE, as determined by clonogenic cell survival (dose-modifying factors at 10% isosurvival of 2.0-3.0). The H2O2-resistant cells demonstrated a significant 2-3-fold increase in the amount of 4HNE removed (mol/cell) from culture media containing 72 microM-4HNE when compared with HA-1 cells. The enhanced ability of H2O2-resistant cells to metabolize 4HNE was abolished by heating the cells at 100 degrees C for 45 min. Similar results were obtained with 2NE. Total glutathione and glutathione transferase activity, believed to be involved in cellular detoxification of 4HNE, were found to be significantly increased (2-3-fold) in the resistant cells when compared with the HA-1 cells. These results show that cell lines adapted and/or selected in a highly peroxidative environment are also resistant to the cytotoxicity of aldehydes formed during lipid peroxidation. This resistance appears to be related to increased cellular metabolism of these aldehydes, possibly through the glutathione transferase system. These findings suggest that the formation of aldehydes due to lipid peroxidation may contribute significantly to the mechanisms of oxidant-induced injury and the selective pressure exerted by H2O2-mediated cytotoxicity in culture.
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During the course of measuring superoxide dismutase (SOD) activity in rat breast tissue, interferences in the nitroblue tetrazolium (NBT) and cytochrome c assay systems were noted. These interferences inhibit accurate measurement of SOD activity in breast tissues, necessitating the development of a new NBT-based assay that includes compounds capable of inhibiting tissue specific interferences. The most effective compounds were metal chelators that were also electron transport chain inhibitors. Bathocuproine sulfonate (BCS) was the most effective of these compounds. The inclusion of BCS in the NBT assay system was shown to make the accurate measurement of SOD activity in tissues with interferences possible.
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Activation of apoptosis is associated with generation of reactive oxygen species. The present research shows that superoxide is produced by mitochondria isolated from apoptotic cells due to a switch from the normal 4-electron reduction of O2 to a 1-electron reduction when cytochromec is released from mitochondria. Bcl-2, a protein that protects against apoptosis and blocks cytochrome c release, prevents superoxide production when it is overexpressed. The switch in electron transfer provides a mechanism for redox signaling that is concomitant with cytochrome c-dependent activation of caspases. The block of cytochrome c release provides a mechanism for the apparent antioxidant function of Bcl-2.
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Chronic exposure (>200 days) of HA1 fibroblasts to increasing concentrations of H2O2 or O2 results in the development of a stable oxidative stress-resistant phenotype characterized by increased cellular antioxidant levels, particularly catalase (D. R. Spitz et al, Arch. Biochem. Biophys., 279: 249-260, 1990; D. R. Spitz et al., Arch. Biochem. Biophys., 292: 221-227, 1992; S. J. Sullivan et al., Am. J. Physiol. (Lung Cell. Mol. Physiol.), 262: L748-L756, 1992). Acutely stressed cells failed to develop a stably resistant phenotype or increased catalase activity, suggesting that chronic exposure is required for the development of this phenotype. This study investigates the mechanism underlying increased catalase activity in the H2O2- and O2-resistant cell lines. In H2O2- and O2-resistant cells, catalase activity was found to be 20-30-fold higher than that in the parental HA1 cells and correlated with increased immunoreactive catalase protein and steady-state catalase mRNA levels. Resistant cell lines also demonstrated a 4-6-fold increase in catalase gene copy number by Southern blot analysis, which is indicative of gene amplification. Chromosome banding and in situ hybridization studies identified a single amplified catalase gene site located on a rearranged chromosome with banding similarities to Z-4 in the hamster fibroblast karyotype. Simultaneous in situ hybridization with a Z-4-specific adenine phosphoribosyltransferase (APRT) gene revealed that the amplified catalase genes were located proximate to APRT on the same chromosome in all resistant cells. In contrast, HA1 cells contained only single copies of the catalase gene that were not located on APRT-containing chromosomes, indicating that amplification is associated with a chromosomal rearrangement possibly involving Z-4. The fact that chronic exposure of HA1 cells to either HO2 or 95% O2 resulted in gene amplification suggests that gene amplification represents a generalized response to oxidative stress, contributing to the development of resistant phenotypes. These results support the hypothesis that chronic exposure to endogenous metabolic or exogenous environmental oxidative stress represents an important factor contributing to gene amplification and genomic instability.
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Non-phagocytic NAD(P)H oxidases have been implicated as major sources of reactive oxygen species in blood vessels. These oxidases can be activated by cytokines, thereby generating O⨪2, which is subsequently converted to H2O2 and other oxidant species. The oxidants, in turn, act as important second messengers in cell signaling cascades. We hypothesized that reactive oxygen species, themselves, can activate the non-phagocytic NAD(P)H oxidases in vascular cells to induce oxidant production and, consequently, cellular injury. The current report demonstrates that exogenous exposure of non-phagocytic cell types of vascular origin (smooth muscle cells and fibroblasts) to H2O2 activates these cell types to produce O⨪2 via an NAD(P)H oxidase. The ensuing endogenous production of O⨪2 contributes significantly to vascular cell injury following exposure to H2O2. These results suggest the existence of a feed-forward mechanism, whereby reactive oxygen species such as H2O2 can activate NAD(P)H oxidases in non-phagocytic cells to produce additional oxidant species, thereby amplifying the vascular injury process. Moreover, these findings implicate the non-phagocytic NAD(P)H oxidase as a novel therapeutic target for the amelioration of the biological effects of chronic oxidant stress.
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Tissue culture strains of cells from four different normal human tissues—liver, conjunctiva, kidney, and appendix—have been grown by the plating procedure previously developed for the HeLa strain of cervical carcinoma cells. This technique results in colony formation from isolated single cells, in a manner completely analogous to the plating of bacteria in semisolid nutrient media. Clonal cell strains have been isolated from each cell type. All behaved exactly alike in all properties studied except that some differences in plating efficiency were displayed in some of the growth media employed. The cells from normal human tissues resembled the HeLa S3 carcinomatous cell in the following properties:— (a) Single cells displayed a plating efficiency close to 100 per cent in an appropriate medium. (b) They all grew as an epithelial sheet on glass, the cells being closely packed and polygonal in shape. (c) They had mean generation times of 20 to 23 hours in the nutrient media employed, (d) The mitotic frequency was constant, and therefore the duration of mitosis was the same for all the strains studied, (e) The incidence of multinuclearity and giant formation was very low and similar in both types of cells. (f) Both classes of cells had the same total volume, and the same nuclear cross-sectional area. (g) Both also showed a tendency to spread more in the presence of human serum (concentration of 20 per cent or more) than in porcine serum. However, this differential morphological response was much more marked in the HeLa cell than in those from normal tissues. The only difference noted in the behavior of these two groups of cells lay in the tendency of the cells from normal tissues always to exhibit a greater cross-sectional area when spread on glass than the HeLa cell in the same medium. The frequency of occurrence of different types of multinuclearity in the HeLa cell and cells from normal tissues has been measured. The data suggest that multinuclearity depends on two factors: a necessary, predisposing state in the cell, and a random, independent event causing the appearance of an additional nucleus in such a prepared cell.
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Understanding the cell biology of many proteins requires knowledge of their in vivo topological distribution. Here we describe a new fluorescence-based technique, fluorescence protease protection (FPP), for investigating the topology of proteins and for localizing protein subpopulations within the complex environment of the living cell. In the FPP assay, adapted from biochemical protease protection assays, GFP fusion proteins are used as noninvasive tools to obtain details of protein topology and localization within living cells in a rapid and straightforward manner. To demonstrate the broad applicability of FPP, we used the technique to define the topology of proteins localized to a wide range of organelles including the endoplasmic reticulum (ER), Golgi apparatus, mitochondria, peroxisomes and autophagosomes. The success of the FPP assay in characterizing the topology of the tested proteins within their appropriate compartments suggests this technique has wide applicability in studying protein topology and localization within the cell.
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Residents of Anniston, Alabama were highly exposed to PCBs released from a nearby manufacturing plant from the 1950s or earlier into the 1970s. Exposures probably declined during the 1980s and 1990s following reductions in releases and declined even further in the late 1990s following remediation steps and increased awareness of residents. In 1995, congener-specific serum PCB analysis of 24 residents revealed a high proportion of octa- and nonachlorobiphenyls, reflecting and documenting the high exposure early in life. Additional serum samples were drawn in September, 2000 from 12 residents spanning age, gender and exposure group. More sensitive analysis of these samples confirmed the aged residue pattern and permitted further interpretations. The most important implications include the following: 1) Increased proportions of octa- and nonachlorobiphenyls indicated that some serum residues levels had been >1,000 ppb in the past; 2) Detectable levels of episodic congeners in some residents indicated that they were being currently exposed, most likely to airborne PCBs; 3) Children removed from recent exposures had decreased levels consistent with dilution of perinatal residues by growth, while body weight reduction correlated with an increased current concentration in an adult resident 4) One child had a high serum residue level, possibly reflecting both high perinatal exposure and modest recent exposure;.
Article
Polychlorinated biphenyls, or PCBs, were widely used in various industrial applications for their insulating and fire retardant properties, In the 1960s, PCBs were found in soil and water, and research confirmed that some PCB congeners degrade very slowly in the environment and can build up in the food chain, Two widespread poisoning episodes in Japan and Taiwan were initially attributed to the consumption of rice bran oil contaminated with PCBs, Although subsequent analysis suggested that toxic thermal degradation products of PCBs in the oil, rather than the PCBs, were responsible for the observed health effects, commercial production of PCBs in the United States was discontinued in 1979. Several regulatory and advisory agencies have categorized PCBs as animal carcinogens; however, studies of workers exposed to high doses of PCBs over long periods of time have not demonstrated an increased cancer risk, In fact, the only health effects that could be attributed to PCBs were skin and eye irritation. Recent studies of the possible effects of prenatal exposure to PCBs on neurodevelopment in infants and children have been criticized for methodological deficiencies, There is no conclusive evidence that PCB levels in the general population are causing intellectual deterioration in children exposed in utero. Some investigators have also suggested that PCBs and other chemicals in the environment can interfere with the body's endocrine system, leading to infertility, certain types of cancer, and other hormone-related disorders. Evidence for estrogenic effects of environmental PCBs remains weak and circumstantial, The following actions are recommended: development of innovative, cost-effective remediation techniques, particularly for sites that are difficult to remediate (e.g., river sediments); and scientifically based improvements to risk assessment, to reduce the considerable uncertainty associated with PCB exposure and health effects in humans. (C) 1997 Academic Press.
Article
Survival curves of normal human cells from a variety of tissues exposed to varying doses of x-irradiation have been constructed, which permit definition of the intrinsic radiation sensitivity of the reproductive power of each cell type. The mean lethal dose of x-irradiation for all the cells employed, including those from normal and cancerous organs, those exhibiting diploid and polyploid chromosome number; those from embryonic and adult tissues, including recently isolated cells and cultures which had been maintained in vitro for many years, and cells exhibiting either epithelioid or fibroblastic morphology, was found to be contained between the limits of 50 to 150 r. Other similarities in the pattern of radiation effects, such as giant formation and abortive colonial growth, in these cells and that of the HeLa S3, previously studied, confirm the hypothesis that the pattern of reaction to x-irradiation previously elucidated, is representatative, at least in over-all outline, for a large variety of human cells. While the radiation survival curves of various human cells are similar in the gross, small but important characterizing differences have been found. All epithelioid cells so far studied are approximately 2-hit, and more radioresistant than the fibroblast-like cells whose survival data correspond to a mean lethal dose of around 60 r, and which so far can be fitted by either 1-hit or 2-hit curves. The earlier prediction that the major radiobiologic damage to mammalian cells is lodged in the genetic apparatus was confirmed by the demonstration of high frequency of mutants among the survivors of doses of 500 to 900 r. All the data on the x-radiosensitivity of these cells can be explained on the basis of a defect resulting from primary damage localized in one or more chromosomes. These considerations afford a convincing explanation of several aspects of the mammalian radiation syndrome.
Article
: Recently, glucose deprivation-induced oxidative stress has been shown to cause cytotoxicity, activation of signal transduction (i.e., ERK1, ERK2, JNK, and Lyn kinase), and increased expression of genes associated with malignancy (i.e., bFGF and c-Myc) in MCF-7/ADR human breast cancer cells. These results have led to the proposal that intracellular oxidation/reduction reactions involving hydroperoxides and thiols may provide a mechanistic link between metabolism, signal transduction, and gene expression in these human tumor cells. The current study shows that several other transformed human cell types appear to be more susceptible to glucose deprivation-induced cytotoxicity and oxidative stress than untransformed human cell types. In a matched pair of normal and SV40-transformed human fibroblasts the cytotoxic process is shown to be dependent upon ambient O2 concentration. A theoretical model to explain the results is presented and implications to unifying modern theories of cancer are discussed.
Article
Non-phagocytic NAD(P)H oxidases have been implicated as major sources of reactive oxygen species in blood vessels. These oxidases can be activated by cytokines, thereby generating O⨪2, which is subsequently converted to H2O2 and other oxidant species. The oxidants, in turn, act as important second messengers in cell signaling cascades. We hypothesized that reactive oxygen species, themselves, can activate the non-phagocytic NAD(P)H oxidases in vascular cells to induce oxidant production and, consequently, cellular injury. The current report demonstrates that exogenous exposure of non-phagocytic cell types of vascular origin (smooth muscle cells and fibroblasts) to H2O2 activates these cell types to produce O⨪2 via an NAD(P)H oxidase. The ensuing endogenous production of O⨪2 contributes significantly to vascular cell injury following exposure to H2O2. These results suggest the existence of a feed-forward mechanism, whereby reactive oxygen species such as H2O2 can activate NAD(P)H oxidases in non-phagocytic cells to produce additional oxidant species, thereby amplifying the vascular injury process. Moreover, these findings implicate the non-phagocytic NAD(P)H oxidase as a novel therapeutic target for the amelioration of the biological effects of chronic oxidant stress.
Article
Polychlorinated biphenyls (PCBs) are a group of industrial chemicals that are widely distributed in the environment. Because these compounds occur as mixtures, studies of their possible interactive effects are essential for an understanding of the mechanism of the toxicity of these mixtures. For the determination of a possible interaction of the effects in vivo of 2,5,2′,5′-tetrachlorobiphenyl (TCB) and 3,4,3′,4′-TCB, rats were exposed to a single dose of diethylnitrosamine (DEN) and subsequently to 0.1 p.p.m. 3,4,3′,4′-TCB and&sol;or 10 p.p.m. 2,5,2′,5′-TCB in the feed for 1 year. The two major targets of PCB toxicity, the liver and the peripheral blood, were examined after these treatments. TCB treatment after DEN exposure caused a predominance of increased placental glutathione S-transferase (PGST) and deficiencies of ATPase as preneoplastk markers in focal hepatic lesions. When 0.05&percnt; phenobarbital (PB) was administered after DEN exposure, the distribution of markers in altered hepatic foci (AHF) was essentially equal for increased PGST and 7-glutamvttranspeptidase (GGT) and for ATPase deficiency. Many of these AHF also exhibited increased P450 b&sol;e expression. Our results demonstrated that the two PCB congeners interacted in vivo to produce an increase in AHF that were PGST positive and ATPase negative. PGST-positive and ATPase-negative AHF correlated best with focal areas of P450 b&sol;e expression. The combination of the two PCBs caused a greater than additive decrease in the total number of lymphocytes and antibody-producing B-cells. Also the thymocyte-dependent T-helper cells isolated from the annuals receiving the combination of TCBs demonstrated a morphologically abnormal subpopulation. The results indicate that the interaction of 2,5,2′,5′-TCB and 3,4,3′,4′-TCB in vivo induced much greater toxicity and mutagenicity in peripheral lympyhocytes and hepatocytes than treatment with either congener alone.
Article
2-Methoxyestradiol (2-ME) is described as an inhibitor of the superoxide dismutase (SOD) enzyme activity. However, it attenuates PI3K/Akt pathway and induces radiosensitization in human tumor cells as well. Since the activation of catalytic subunit of DNA-protein kinase (DNA-PKcs) is partially regulated by Akt activity, in the present study we investigated whether 2-ME-induced radiosensitization is dependent on inhibition of Akt and DNA-PKcs activities or on SOD targeting. This study was performed using the lung carcinoma cell line A549. Ionizing radiation-induced SOD activity was analyzed by superoxide dismutase activity assay. Applying Western blotting, the pattern of radiation-induced SOD expression and activation of Akt as well as DNA-PKcs was analyzed. Colony formation assay and gammaH2AX foci assay were performed to measure radiosensitization and DNA-double strand break (DNA-DSB) repair. To downregulate SOD expression small interfering RNA (siRNA) was used. Irradiation with 4Gy stimulated SOD enzyme activity as early as 1min after radiation exposure. Expression of Cu/Zn-SOD (SOD1) as well as Mn-SOD (SOD2) was increased by single doses of 1-4Gy within 24-36h. 2-ME blocked radiation-induced SOD enzyme activity but not protein expression and enhanced radiation sensitivity. Pretreatment with 2-ME blocked IR-induced Akt as well as DNA-PKcs phosphorylation and impaired the repair of DNA-DSB. SiRNA targeting of SOD1 and SOD2 affected neither DNA-PKcs phosphorylation nor post-irradiation survival while inhibition of Akt by specific inhibitor abrogated 2-ME-induced radiosensitization. These results may indicate that 2-ME-induced radiosensitization is independent of SOD inhibition but mainly depends on inhibition of Akt and DNA-PKcs activities.
Article
Polychlorinated biphenyls (PCBs) are environmental chemical contaminants believed to adversely affect cellular processes. We investigated the hypothesis that PCB-induced changes in the levels of cellular reactive oxygen species (ROS) induce DNA damage resulting in cytotoxicity. Exponentially growing cultures of human nonmalignant breast epithelial cells (MCF10A) were incubated with PCBs for 3 days and assayed for cell number, ROS levels, DNA damage, and cytotoxicity. Exposure to 2,2',4,4',5,5'-hexachlorobiphenyl (PCB153) or 2-(4-chlorophenyl)benzo-1,4-quinone (4-Cl-BQ), a metabolite of 4-chlorobiphenyl (PCB3), significantly decreased cell number and MTS reduction and increased the percentage of cells with sub-G1 DNA content. Results from electron paramagnetic resonance (EPR) spectroscopy showed a 4-fold increase in the steady-state levels of ROS, which was suppressed in cells pretreated with catalase. EPR measurements in cells treated with 4-Cl-BQ detected the presence of a semiquinone radical, suggesting that the increased levels of ROS could be due to the redox cycling of 4-Cl-BQ. A dose-dependent increase in micronuclei frequency was observed in PCB-treated cells, consistent with an increase in histone 2AX phosphorylation. Treatment of cells with catalase blunted the PCB-induced increase in micronuclei frequency and H2AX phosphorylation that was consistent with an increase in cell survival. Our results demonstrate a PCB-induced increase in cellular levels of ROS causing DNA damage, resulting in cell killing.
Article
PCB residues are found in biota all over the world. A biologic magnification of PCBs has been demonstrated in the food chain: plankton-fish-fish eating birds. A world map of the PCBs residues in biota and some of their biologic effects are given in this study. The biologic effects of PCBs are varied and may generally be explained by the induction or inhibition of the activity of a large number of enzymes, which upsets quantitatively, normal biochemical processes. Harm to reproduction, growth, development, defense systems, tissues, and organs appeared in susceptible organisms as a result of such changes or as a chain reaction to heterostases. The adverse health effects, observed in persons occupationally exposed and in those accidentally poisoned, point to the risk for the general population of an ever-increasing environmental pollution by PCBs. There is need for an integrated approach, consisting of epidemiologic studies on high risk groups in the general population and in persons occupationally exposed, as well as periodic assessment of PCB residues in man, his food, and feed supplies.
Article
The comparative toxicity of polychlorinated biphenyl (PCB) and polybrominated biphenyl (PBB) in livers was studied in male Holtzman rats. Four-week-old animals were fed at dietary levels of 0, 5, 50, or 500 ppm for 5 weeks and then sacrificed. The mean liver-body weight ratios of the 50 and 500 ppm groups were increased. Histopathologic examination of the livers revealed fatty degenerative change associated with both compounds. This change was more marked at 500 than at 50 ppm. Various sized lamellar cytoplasmic inclusions were detected in livers of animals fed 500 ppm of either compound. However, the inclusions were more numerous in the PBB-treated rats. Several animals fed 50 ppm PBB had a few inclusions. In rats that received 500 ppm PBB, hypertrophic degenerative hepatocytes were present around the central veins. On the periphery of this change there were occasionally multinucleated hepatocytes. Electron microscopic examination at a dose level of 5 ppm in both the PCB and PBB groups showed a slight proliferation of smooth endoplasmic reticulum (SER), a moderate increase of lipid droplets and some liposomes, and a marked proliferation of Golgi condensing vesicles containing lipoprotein particles. A decreased number of mitochondria and lysosomes was also observed. At 50 ppm, similar but more marked ultrastructural alterations were seen. In addition, an increased number of branched and cup-shaped profiles of mitochondria and a decreased number of Golgi condensing vesicles containing lipoprotein particles were observed. Concentric membranous cytoplasmic whorls were encountered only in the 50 ppm PBB-treated rats. At 500 ppm the number of mitochondria decreased in both groups. There was also a marked increase in the number of SER and liposomes concomitant with a decreased number of Golgi condensing vesicles containing lipoprotein granules. Membranous whorls were also present in the 500 ppm groups.
Article
A protein determination method which involves the binding of Coomassie Brilliant Blue G-250 to protein is described. The binding of the dye to protein causes a shift in the absorption maximum of the dye from 465 to 595 nm, and it is the increase in absorption at 595 nm which is monitored. This assay is very reproducible and rapid with the dye binding process virtually complete in approximately 2 min with good color stability for 1 hr. There is little or no interference from cations such as sodium or potassium nor from carbohydrates such as sucrose. A small amount of color is developed in the presence of strongly alkaline buffering agents, but the assay may be run accurately by the use of proper buffer controls. The only components found to give excessive interfering color in the assay are relatively large amounts of detergents such as sodium dodecyl sulfate, Triton X-100, and commercial glassware detergents. Interference by small amounts of detergent may be eliminated by the use of proper controls.
Article
Besides being toxic, oxidants can induce pathophysiological effects in mammalian cells. For example they can stimulate rather than inhibit cell growth. Since oxidants are ubiquitous they may represent 'natural' tumour promoters. Our work with xanthine/xanthine-oxidase as an extracellular source of active oxygen (AO) and promotable (clone 41) and non-promotable (clone 30) mouse epidermal cells JB6 allows insights into the mechanism of action of oxidant promoters. We found that AO stimulated the growth only of promotable clone 41 after an initial period of moderate inhibition while it was strongly cytostatic for non-promotable clone 30. Active oxygen induced larger amounts of DNA-strand breaks and poly ADP-ribosylation of chromosomal proteins in non-promotable cells. In addition, AO was capable of inducing the growth- and differentiation-related proto-oncogenes c-fos and c-myc in promotable and non-promotable JB6 cells. We speculate that these genes can exert their functions only in the promotable clone 41 because the general cytostatic effects of AO are moderate. A possible explanation for the differences between these 2 clones was discovered when we compared the constitutive activities, protein concentrations and mRNA levels for the antioxidant enzymes catalase (CAT), Cu,Zn-superoxide dismutase (SOD) and glutathione-peroxidase (GPx). We found that CAT and SOD (but not GPx) levels were 2-3-fold higher in the promotable clone 41. We propose that promotable cells possess a superior antioxidant defence which protects them from excessive cytostatic effects of AO.
Article
Much evidence indicates that superoxide is generated from O2 in a cyanide-sensitive reaction involving a reduced component of complex III of the mitochondrial respiratory chain, particularly when antimycin A is present. Although it is generally believed that ubisemiquinone is the electron donor to O2, little experimental evidence supporting this view has been reported. Experiments with succinate as electron donor in the presence of antimycin A in intact rat heart mitochondria, which contain much superoxide dismutase but little catalase, showed that myxothiazol, which inhibits reduction of the Rieske iron-sulfur center, prevented formation of hydrogen peroxide, determined spectrophotometrically as the H2O2-peroxidase complex. Similarly, depletion of the mitochondria of their cytochrome c also inhibited formation of H2O2, which was restored by addition of cytochrome c. These observations indicate that factors preventing the formation of ubisemiquinone also prevent H2O2 formation. They also exclude ubiquinol, which remains reduced under these conditions, as the reductant of O2. Since cytochrome b also remains fully reduced when myxothiazol is added to succinate- and antimycin A-supplemented mitochondria, reduced cytochrome b may also be excluded as the reductant of O2. These observations, which are consistent with the Q-cycle reactions, by exclusion of other possibilities leave ubisemiquinone as the only reduced electron carrier in complex III capable of reducing O2 to O2-.
Article
The effects of the xenobiotics, i.e. butylated hydroxytoluene, beta-naphthoflavone, isosafrole, pregnenolone-16 alpha-carbonitrile, trans-stilbene oxide, 3-methylcholanthrene, phenobarbital, 3,3',4,4'-tetrachlorobiphenyl, 2,2',4,4',5,5'-hexachlorobiphenyl, on rat liver cytosolic glutathione transferase and glutathione peroxidase activities have been investigated. Although the glutathione transferase isozymes (measured by the specific substrates ethacrynic acid and delta 5-androstene-3,17-dione) which have been shown to possess peroxidase activity were significantly increased, little or no increase in peroxidase activity (toward cumene hydroperoxide, tert-butyl hydroperoxide or hydrogen peroxide) was observed. Likewise during a 16-day time course following the administration of Aroclor 1254 or fireMaster BP-6 (each 500 mg/kg, i.p.), potent induction of glutathione transferase activities was seen without any significant increases in peroxidase activities. In fact during the second week of the time course, there were significant decreases in selenium-dependent glutathione peroxidase activity (toward hydrogen peroxide). The inverse regulation of these activities, i.e. the depression of selenium-dependent glutathione peroxidase activity following sustained induction of glutathione transferases, may have direct implications for the toxicity of the polyhalogenated aromatic hydrocarbons.