Oxidative stress and liver toxicity in rats and human hepatoma cell line induced by pentachlorophenol and its major metabolite tetrachlorohydroquinone

Continuous exposure to bisphenol S increases the accumulation of endogenous metabolic toxicants by obstructing the glucuronic acid pathway

Uridine diphosphate glucuronic acid (UDPGA) is an essential substrate in the glucuronidation of exogenous and endogenous lipophilic compounds via the liver glucuronic acid pathway, and its synthesis depends on glucose and energy in the body. Bisphenol S (BPS), as a lipophilic environmental pollutant, has been widely utilized in the manufacturing of daily necessities. The biological effect of BPS in interference with liver energy metabolism might affect UDPGA synthesis and the excretion of lipophilic compounds, but this was not clearly revealed. Here, female zebrafish that were exposed to BPS for 35 days exhibited a significant decrease in UDPGA in the liver with significant accumulation of exogenous BPS and endogenous bilirubin in the body. One vital reason may be that the exposure to BPS for 35 days promoted the lipid formation through PPARg signaling and reduced energy levels in the liver, resulting in the decreased raw materials for UDPGA production in glucuronic acid pathway. Meanwhile, transcriptome analysis showed that BPS inhibited the mRNA expression levels of genes related to the glucuronic acid pathway. The accumulation of endogenous and exogenous lipophilic compounds can trigger a variety of toxicological effect. Thus, weakened liver detoxification might be the primary cause of the toxicological effects of lipophilic pollutants.

A comprehensive review of chlorophenols: Fate, toxicology and its treatment

Chlorophenols represent one of the most abundant families of toxic pollutants emerging from various industrial manufacturing units. The toxicity of these chloroderivatives is proportional to the number and position of chlorine atoms on the benzene ring. In the aquatic environment, these pollutants accumulate in the tissues of living organisms, primarily in fishes, inducing mortality at an early embryonic stage. Contemplating the behaviour of such xenobiotics and their prevalence in different environmental components, it is crucial to understand the methods used to remove/degrade the chlorophenol from contaminated environment. The current review describes the different treatment methods and their mechanism towards the degradation of these pollutants. Both abiotic and biotic methods are investigated for the removal of chlorophenols. Chlorophenols are either degraded through photochemical reactions in the natural environment, or microbes, the most diverse communities on earth, perform various metabolic functions to detoxify the environment. Biological treatment is a slow process because of the more complex and stable structure of pollutants. Advanced Oxidation Processes are effective in degrading such organics with enhanced rate and efficiency. Based on their ability to generate hydroxyl radicals, source of energy, catalyst type, etc., different processes such as sonication, ozonation, photocatalysis, and Fenton's process are discussed for the treatment or remediation efficiency towards the degradation of chlorophenols. The review entails both advantages and limitations of treatment methods. The study also focuses on reclamation of chlorophenol-contaminated sites. Different remediation methods are discussed to restore the degraded ecosystem back in its natural condition.

Pentachlorophenol-induced hemotoxicity diminishes antioxidant potential and oxidizes proteins, thiols, and lipids in rat blood: An in vivo study

Pentachlorophenol (PCP) is an excessively used wood preservative and pesticide, which has resulted in human exposure raising concerns about its potential toxic effects. This study is designed to evaluate the hemotoxicity of PCP in adult rats. Wistar rats were orally administered PCP (25-150 mg/kg bw) for five days while untreated (control) rats received corn oil. Animals were sacrificed, blood was taken and fractionated into plasma and red blood cells (RBC). PCP administration increased methemoglobin formation but decreased methemoglobin reductase activity. Significantly increased hydrogen peroxide level indicates initiation of oxidative stress condition in blood. PCP increased the oxidation of thiols, proteins and lipids, lowered glutathione levels, and compromised the antioxidant status of RBC in treated rats. Enzymes of the pathways of glucose breakdown, glycolysis and phosphogluconate pathway, were inhibited. Markers of liver damage were increased in the plasma of PCP-treated rats suggesting hepatotoxicity. This was confirmed by histopathological analysis of stained liver sections. Activity of xanthine oxidase, a reactive oxygen species (ROS) generating pro-oxidant enzyme, was increased. These hematological changes could be a result of the increased generation of ROS or direct chemical transformation by transient reaction species. These results show that PCP induces redox imbalance, diminishes antioxidant potential, inhibits metabolic pathways, and oxidizes cellular components in rat blood. This study suggests an elaborated possible molecular mechanism of PCP toxicity, and similar compounds so that methods can be devised to minimize its damaging effect.

Variability, determinants, and associations with oxidative stress biomarkers of pentachlorophenol among Chinese pregnant women: A longitudinal study

Pentachlorophenol (PCP) is ubiquitous and moderately persistent in the environment, and it is an identified human carcinogen. Previous animal experiments indicate that toxic mechanisms of PCP include oxidative stress. However, no epidemiological study has reported the association between PCP exposure and oxidative stress; such association in pregnant women, a vulnerable population, is of particular interest. This study aimed to characterize PCP concentrations in 2304 urine samples from 768 pregnant women, explore its determinants, and evaluate the associations between PCP exposure and three oxidative stress biomarkers across three trimesters. The median concentrations of PCP (100% detected) in the first, second, and third trimester were 0.61, 0.59, and 0.48 ng/mL, respectively, with a significant decrease trend. The intraclass correlation coefficient of specific gravity (SG)-adjusted PCP was 0.26, indicating high variability for PCP across the three trimesters. PCP concentrations were significantly higher in older, pre-pregnancy overweight, multiparous, high-income, and employed women during pregnancy. Urinary PCP was markedly lower in samples collected during spring compared to other seasons. Linear mixed effect models for repeated measures revealed that ln-transformed SG-adjusted PCP was significantly associated with increased 8-hydroxy-2'-deoxyguanosine (8-OHdG; percent change [%Δ] caused by each interquartile range increase of PCP: 46.2, 95% confidence interval [CI]: 40.2, 52.5) and 8-hydroxyguanosine (8-OHG;%Δ [95% CI]: 44.8 [40.1, 49.8]), but the positive association with 4-hydroxy2-nonenal-mercapturic acid (HNE-MA) was not significant. PCP was also positively associated with increased 8-OHdG and 8-OHG in each trimester using general linear models, and its associations with HNE-MA were only significant at T1 (%Δ [95% CI]: 19.1 [1.05, 40.3]) and T2 (%Δ [95% CI]: 12.6 [0.32, 26.3]). Our findings provide valuable information about PCP exposure characteristics during pregnancy and the potential effects of PCP exposure on oxidative stress in pregnant women.

Mild pentachlorophenol-mediated uncoupling of mitochondria depletes ATP but does not cause an oxidized redox state or dopaminergic neurodegeneration in Caenorhabditis elegans

Aims

Mitochondrial dysfunction is implicated in several diseases, including neurological disorders such as Parkinson's disease. However, there is uncertainty about which of the many mechanisms by which mitochondrial function can be disrupted may lead to neurodegeneration. Pentachlorophenol (PCP) is an organic pollutant reported to cause mitochondrial dysfunction including oxidative stress and mitochondrial uncoupling. We investigated the effects of PCP exposure in Caenorhabditis elegans, including effects on mitochondria and dopaminergic neurons. We hypothesized that mild mitochondrial uncoupling by PCP would impair bioenergetics while decreasing oxidative stress, and therefore would not cause dopaminergic neurodegeneration.

Results

A 48-hour developmental exposure to PCP causing mild growth delay (∼10 % decrease in growth during 48 h, covering all larval stages) reduced whole-organism ATP content > 50 %, and spare respiratory capacity ∼ 30 %. Proton leak was also markedly increased. These findings suggest a main toxic mechanism of mitochondrial uncoupling rather than oxidative stress, which was further supported by a concomitant shift toward a more reduced cellular redox state measured at the whole organism level. However, exposure to PCP did not cause dopaminergic neurodegeneration, nor did it sensitize animals to a neurotoxic challenge with 6-hydroxydopamine. Whole-organism uptake and PCP metabolism measurements revealed low overall uptake of PCP in our experimental conditions (50 μM PCP in the liquid exposure medium resulted in organismal concentrations of < 0.25 μM), and no measurable production of the oxidative metabolites tetra-1,4-benzoquinone and tetrachloro-p-hydroquinone.

Innovation

This study provides new insights into the mechanistic interplay between mitochondrial uncoupling, oxidative stress, and neurodegeneration in C. elegans. These findings support the premise of mild uncoupling-mediated neuroprotection, but are inconsistent with proposed broad "mitochondrial dysfunction"-mediated neurodegeneration models, and highlight the utility of the C. elegans model for studying mitochondrial and neurotoxicity.

Conclusions

Developmental exposure to pentachlorophenol causes gross toxicological effects (growth delay and arrest) at high levels. At a lower level of exposure, still causing mild growth delay, we observed mitochondrial dysfunction including uncoupling and decreased ATP levels. However, this was associated with a more-reduced cellular redox tone and did not exacerbate dopaminergic neurotoxicity of 6-hydroxydopamine, instead trending toward protection. These findings may be informative of efforts to define nuanced mitochondrial dysfunction-related adverse outcome pathways that will differ depending on the form of initial mitochondrial toxicity.

Pentachlorophenol mediated regulation of DAMPs and inflammation: In vitro study

Pentachlorophenol (PCP) was once widely employed organochlorine pesticide and wood preservative in United States. Due to its toxicity, the U.S. Environmental Protection Agency classified it as a restricted-use pesticide and established as a liver carcinogen. Earlier reports have indicated increased production of inflammatory mediators like IL-1β and TNF-α by immune cells, including NK cells, lymphocytes, or monocytes, on PCP exposure. Yet, there is little to no knowledge regarding the molecular mechanisms affected by acute and chronic exposure to PCP in humans. Considering this, we examined PCP-induced inflammation and downstream signaling in-(a) human lung adenocarcinoma cells (A549) with type II alveolar epithelial characteristics; and (b) human liver carcinoma cells (HepG2). We treated A549 and HepG2 cells with 1 μM and 10 μM of PCP for 24 h duration. We observed a significant induction of cytokine/chemokine production (IL-1β, IL-6, TNF-α, IL-8, CCL2, and CCL5) in PCP-treated- HepG2 and A549 cells. The mRNA expression analyses showed upregulated levels of danger associated molecular patterns (DAMPs)-HMGB1 and heat shock protein 70 (Hsp70); and TLR-4 receptor in PCP-challenged cells. Increased expression of transcription factors-NF-kB and STAT3 provide further insights into PCP-induced molecular mechanisms. Interestingly, antibody mediated blocking of DAMPs abrogated PCP-mediated transcriptional induction of cytokines/chemokines and transcription factors in HepG2 and A549 cells. Overall, our findings demonstrate important role of DAMPs in PCP-induced inflammatory responses.

Detecting and Quantifying Polyhaloaromatic Environmental Pollutants by Chemiluminescence-Based Analytical Method

Polyhaloaromatic compounds (XAr) are ubiquitous and recalcitrant in the environment. They are potentially carcinogenic to organisms and may induce serious risks to the ecosystem, raising increasing public concern. Therefore, it is important to detect and quantify these ubiquitous XAr in the environment, and to monitor their degradation kinetics during the treatment of these recalcitrant pollutants. We have previously found that unprecedented intrinsic chemiluminescence (CL) can be produced by a haloquinones/H₂O₂ system, a newly-found ^●OH-generating system different from the classic Fenton system. Recently, we found that the degradation of priority pollutant pentachlorophenol by the classic Fe(II)-Fenton system could produce intrinsic CL, which was mainly dependent on the generation of chloroquinone intermediates. Analogous effects were observed for all nineteen chlorophenols, other halophenols and several classes of XAr, and a novel, rapid and sensitive CL-based analytical method was developed to detect these XAr and monitor their degradation kinetics. Interestingly, for those XAr with halohydroxyl quinoid structure, a Co(II)-mediated Fenton-like system could induce a stronger CL emission and higher degradation, probably due to site-specific generation of highly-effective ^●OH. These findings may have broad chemical and environmental implications for future studies, which would be helpful for developing new analytical methods and technologies to investigate those ubiquitous XAr.

Modulation and Protection Effects of Antioxidant Compounds against Oxidant Induced Developmental Toxicity in Zebrafish

The antioxidant effect of compounds is regularly evaluated by in vitro assays that do not have the capability to predict in vivo protective activity or to determine their underlying mechanisms of action. The aim of this study was to develop an experimental system to evaluate the in vivo protective effects of different antioxidant compounds, based on the zebrafish embryo test. Zebrafish embryos were exposed to tert-butyl hydroperoxide (tBOOH), tetrachlorohydroquinone (TCHQ) and lipopolysaccharides from Escherichia coli (LPS), chemicals that are known inducers of oxidative stress in zebrafish. The developmental toxic effects (lethality or dysmorphogenesis) induced by these chemicals were modulated with n-acetyl l-cysteine and Nω-nitro l-arginine methyl ester hydrochloride, dimethyl maleate and dl-buthionine sulfoximine in order to validate the oxidant mechanism of oxidative stress inducers. The oxidant effects of tBOOH, TCHQ, and LPS were confirmed by the determination of significant differences in the comparison between the concentration–response curves of the oxidative stress inducers and of the modulators of antioxidant status. This concept was also applied to the study of the effects of well-known antioxidants, such as vitamin E, quercetin, and lipoic acid. Our results confirm the zebrafish model as an in vivo useful tool to test the protective effects of antioxidant compounds.

Dual-emissive dye@MOF composite for ratiometric detection and discrimination of two isomers of tetrachlorobenzenediol

A dye@MOF composite was screened out for the ratiometric fluorescent detection and discrimination of the two isomers of tetrachlorobenzenediol.

Hepatoprotective effects of the n-butanol extract from Perralderia coronopifolia Coss. against PCP-induced toxicity in Wistar albino rats

In the present study, in vivo antioxidant properties of the n-butanol extract obtained from aerial parts of Perralderia coronopifolia were investigated in term of its hepatoprotective effect of female Wistar albino rats (n, 36; average age, 48 ± 5 days; weighing 150 ± 18 g) against PCP (pentachlorphenol)-induced toxicity. PCP (20 mg/kg b.w.) and plant extract (50 mg/kg b.w.) were administered daily by gavages for 2 weeks. Vitamin E (100 mg/kg b.w.) was given intraperitoneally as a positive control. Lipid peroxidation (LPO) levels, reduced glutathione (GSH) levels, and glutathione peroxidase (GPx) activities were evaluated in liver homogenates. While, aspartate aminotransferase (AST), alanine aminotransferase (ALT), cholesterol, and triglyceride parameters were analyzed in serums. The liver fragments were observed using light microscopy. Experimental results exhibited that PCP-treated group has a significant increase in the liver lipid peroxidation (LPO) levels of animals while decreased in plant extract-treated group. In addition, PCP caused significant decreases in glutathione peroxidase (GPx) activities and reduced glutathione (GSH) levels. Moreover, PCP induced hepatotoxicity by increasing serum transaminase enzymes, cholesterol, and triglyceride levels. While, these levels were restored to control value in animals treated with plant extract. The regularized levels of LPO, GSH, cholesterol, triglyceride, transaminase enzymes, and GPx activities revealed the antioxidant properties of the extract plant as well as of the vitamin E. The histological study showed the hepatoprotective effect of our extracts against PCP-induced acute intoxication, protecting the hepatic architecture and decreasing the functional and structural alterations of the liver. The plant extract had high antioxidant potential and completely prevented the toxic effect of PCP on the above of liver and serum parameters.

Pentachlorophenol-induced cytotoxicity in human erythrocytes: enhanced generation of ROS and RNS, lowered antioxidant power, inhibition of glucose metabolism, and morphological changes

Pentachlorophenol (PCP) is a class 2B human carcinogen that is used as an insecticide, herbicide, and wood preservative. PCP is rapidly absorbed and enters the blood where it can interact with erythrocytes. We have examined the effect of PCP on human erythrocytes. Treatment of erythrocytes with PCP increased the intracellular generation of reactive oxygen and nitrogen species. It also increased lipid and protein oxidation accompanied by decrease in glutathione levels and total sulfhydryl content. The activities of all major antioxidant enzymes were altered. The antioxidant power was significantly impaired resulting in lower free radical quenching and metal reducing ability of the PCP-treated cells. PCP exposure also inhibited the activities of enzymes of glycolysis and pentose phosphate shunt, the two pathways of glucose metabolism in erythrocytes. Heme degradation was enhanced leading to the release of free iron. Incubation of erythrocytes with PCP caused significant cell lysis suggesting plasma membrane damage which was also evident from inhibition of bound enzymes. Scanning electron microscopy of erythrocytes confirmed these biochemical results and showed that PCP treatment converted the normal biconcave discoids to echinocytes and other irregularly shaped cells. Thus, PCP induces oxidative and nitrosative stress in erythrocytes, alters the enzymatic and nonenzymatic antioxidant defense systems, inhibits glucose metabolism, and causes significant modifications in cellular morphology.

Hepatoprotective effects of vitamin E against hexachlorobenzene-induced hepatotoxicity and oxidative stress in rats: histological, biochimical and antioxidant status changes

The protective effects of α-Tocopherol (vitamin E) on liver injury induced by hexachlorobenzene (HCB) were investigated in adult male rats of Wistar strain. Animals were randomly divided into six groups of eight rats each. Group 1 and 2 have received HCB, dissolved in olive oil, at a dose of 4 mg or 16 mg/kg b.w., respectively. Group 3 and 4 were treated by the same doses of HCB (4 mg and 16 mg/kg b.w.) after 1 h of pretreatment with α-tocopherol at a dose of 100 mg kg^-1 b.w. The other two groups served as controls; which received either olive oil only, a solvent of HCB, or α-tocopherol. A significant increase in hepatic lipid peroxidation (LPO) and GSH activity were observed following HCB administration. The activities of antioxidant enzymes like superoxide dismutase and catalase were significantly decreased while glutathione peroxidase was significantly increased following HCB administration. Similarly, a significant increase in plasma levels of various marker enzymes [aminotransferase (aspartate aminotransférase (AST) and alanine aminotransferase (ALT)), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH)] and a decrease of total protein level were observed. Pretreatment with vitamin E of HCB treated rats ameliorated all biochemical parameters to near normal values. Liver histological study confirmed biochemical parameters and the beneficial role of vitamin E.

Pentachlorophenol, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzo furans in surface soil surrounding pentachlorophenol-treated utility poles on the Kenai National Wildlife Refuge, Alaska USA

Composite surface soil samples were collected at 0, 25, and 50 cm from the base of 12 utility poles on the Kenai National Wildlife Refuge in Alaska, to assess the extent to which pentachlorophenol, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzo furans may have leached from pentachlorophenol-treated poles. Six pairs of utility poles were included, consisting of an "old" pole manufactured in 1959 or 1963, a "new" pole manufactured within the past 20 years, and a suitable background soil sample from the same vicinity. Old poles had greater concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) equivalents (TEQs) near the pole base and at 25 cm than "new" poles did. For all 12 poles combined, the mean pentachlorophenol levels in soil were 1810, 157, and 17.8 ppm dry weight (d.w.) near the pole bases, at 25 and 50 cm from the poles, respectively, while the mean total TEQ levels in soil were 15,200, 5170, and 1510 parts per trillion d.w. at those distances. Surface soil levels of pentachlorophenol and TCDD-TEQs exceeded both human health and ecological risk-based screening levels. The design and results of this study were similar to another project in Montreal, Quebec in Canada. Together the results are cause for concern, indicating that millions of similarly treated utility poles in North America may be point sources of pentachlorophenol and dioxins/furans to soil.

Endoplasmic reticulum stress is involved in 2,4-dichlorophenol-induced hepatotoxicity

2,4-Dichlorophenol (2,4-DCP) is an environmental pollutant exhibiting a wide spectrum of toxic effects. We investigated the toxic effects and potential mechanisms underlying 2,4-DCP-induced hepatotoxicity. In vitro, 2,4-DCP caused hepatotoxicity manifested by a decrease in cell viability and inhibition of colony formation. Bip and CHOP expression was up-regulated at the mRNA and protein levels. Moreover, 2,4-DCP induced eIF2α phosphorylation and Xbp1 mRNA splicing, indicating that endoplasmic reticulum (ER) stress was activated after exposure of HL7702 cells to 2,4-DCP for 12 hr. Furthermore, the mitochondrial membrane potential collapsed and apoptosis was triggered after exposure to 2,4-DCP for 24 hr. In vivo, 2,4-DCP caused histological changes in the liver, and dramatically elevated the serum alanine transaminase (ALT) and aspartate aminotransferase (AST) levels of mice. ER stress was also triggered in the liver of mice on days 1 and 3. The ER stress inhibitor TUDCA could partly relieve the liver damage, as indicated by the restoration of serum ALT and AST levels. Taken together, our results demonstrated that ER stress may serve as an early warning mechanism against 2,4-DCP-induced hepatotoxicity, and severe ER stress may lead to apoptosis.

Effects of pentachlorophenol on the detoxification system in white-rumped munia (Lonchura striata)

Pentachlorophenol (PCP), a priority pollutant due to its persistence and high toxicity, has been used worldwide as a pesticide and biocide. To understand the adverse effects of PCP, adult male white-rumped munias (Lonchura striata) were orally administrated commercial PCP mixed with corn oil at dosages of 0, 0.05, 0.5, and 5mg/(kg·day) for 42day. Gas chromatography-mass spectrometry (GC-MS) analysis found that PCP was preferentially accumulated in the kidney rather than in the liver and muscle in all exposure groups. To examine the function of CYP1A in pollutant metabolism, we isolated two full-length cDNA fragments (designated as CYP1A4 and CYP1A5) from L. striata liver using reverse transcription-polymerase chain reaction and rapid amplification of cDNA ends. PCP induced the expression of CYP1A5, although no obvious change was observed in CYP1A4 expression. Furthermore, PCP significantly elevated the activities of ethoxyresorufin O-deethylase and methoxyresorufin O-demethylase and decreased the activity of benzyloxy-trifluoromethyl-coumarin, with no significant responses observed in benzyloxyresorufin O-debenzylase. PCP induced significant changes in antioxidant enzyme (superoxide dismutase and catalase) activities and malondialdehyde content, but decreased glutathione peroxidase (GSH-Px) and glutathione S-transferase activities and GSH content in the liver of L. striata. The present study demonstrated that PCP had hepatic toxic effects by affecting CYP1As and anti-oxidative status.

Ecotoxicogenomic approaches for understanding molecular mechanisms of environmental chemical toxicity using aquatic invertebrate, Daphnia model organism

Due to the rapid advent in genomics technologies and attention to ecological risk assessment, the term “ecotoxicogenomics” has recently emerged to describe integration of omics studies (i.e., transcriptomics, proteomics, metabolomics, and epigenomics) into ecotoxicological fields. Ecotoxicogenomics is defined as study of an entire set of genes or proteins expression in ecological organisms to provide insight on environmental toxicity, offering benefit in ecological risk assessment. Indeed, Daphnia is a model species to study aquatic environmental toxicity designated in the Organization for Economic Co-operation and Development’s toxicity test guideline and to investigate expression patterns using ecotoxicology-oriented genomics tools. Our main purpose is to demonstrate the potential utility of gene expression profiling in ecotoxicology by identifying novel biomarkers and relevant modes of toxicity in Daphnia magna. These approaches enable us to address adverse phenotypic outcomes linked to particular gene function(s) and mechanistic understanding of aquatic ecotoxicology as well as exploration of useful biomarkers. Furthermore, key challenges that currently face aquatic ecotoxicology (e.g., predicting toxicant responses among a broad spectrum of phytogenetic groups, predicting impact of temporal exposure on toxicant responses) necessitate the parallel use of other model organisms, both aquatic and terrestrial. By investigating gene expression profiling in an environmentally important organism, this provides viable support for the utility of ecotoxicogenomics.

ROS-triggered signaling pathways involved in the cytotoxicity and tumor promotion effects of pentachlorophenol and tetrachlorohydroquinone

Free radical-triggered tissue damage is believed to play an essential role in a variety of human diseases. Pentachlorophenol (PCP) is applied as a pesticide worldwide in both industries and homes. It is used extensively as a biocide and wood preservative. Tetrachlorohydroquinone (TCHQ) was proved as a major toxic metabolite of PCP, contributing the release of free radicals during PCP metabolism. PCP has been proposed as a tumor promoter; however, only limited knowledge is available regarding the mechanisms of tumor promotion induced by PCP and its metabolite, TCHQ. A growing amount of literature suggests that a link between reactive oxygen species (ROS) and tumor promotion could exist. Herein, we summarize the findings regarding the ROS-triggered signaling pathways involved in the cytotoxicity and tumor promotion effects of PCP and TCHQ. Some of the notable findings demonstrated that TCHQ can induce DNA lesions and glutathione depletion in mammalian cells; meanwhile, oxidative stress and apoptosis/necrosis can be found both in vivo and in vitro. Interestingly, PCP and TCHQ were proved as mild tumor promoters in two-stage tumorigenesis models, in which the possible mechanism could be through ROS generation and changed Bcl-2 gene expression. We also found significant effects of antioxidants in attenuating the oxidative stress, cyto- and genotoxicity, and apoptosis/necrosis induced by PCP and/or TCHQ. In addition, mitogen-activated protein kinase (MAPK) activation is involved in PCP/TCHQ-triggered cytotoxicity, as evidenced by the finding that higher doses of TCHQ could lead to necrosis of freshly isolated splenocytes through the production of a large amount of ROS and sustained ERK activation. These results could explain partly the underlying molecular mechanisms contributing to the tumorigenesis induced by PCP. However, the detailed mechanisms of free radicals in triggering PCP/TCHQ-mediated tumor promotion and toxicity are still not completely resolved and need to be investigated further.

Transcriptional changes induced by in vivo exposure to pentachlorophenol (PCP) in Chironomus riparius (Diptera) aquatic larvae

Pentachlorophenol (PCP) has been extensively used worldwide as a pesticide and biocide and is frequently detected in the aquatic environment. In the present work, the toxicity of PCP was investigated in Chironomus riparius aquatic larvae. The effects following short- and long-term exposures were evaluated at the molecular level by analyzing changes in the transcriptional profile of different endocrine genes, as well as in genes involved in the stress response and detoxification. Interestingly, although no differences were found after 12- and 24-h treatments, at 96-h exposures PCP was able to induce significant increases in transcripts from the ecdysone receptor gene (EcR), the early ecdysone-inducible E74 gene, the estrogen-related receptor gene (ERR), the Hsp70 gene and the CYP4G gene. In contrast, the Hsp27 gene appeared to be downregulated, while the ultraspiracle gene (usp) (insect ortholog of the retinoid X receptor) was not altered in any of the conditions assayed. Moreover, Glutathione-S-Transferase (GST) activity was not affected. The results obtained show the ability of PCP to modulate transcription of different biomarker genes from important cellular metabolic activities, which could be useful in genomic approaches to monitoring. In particular, the significant upregulation of hormonal genes represents the first evidence at the genomic level of the potential endocrine disruptive effects of PCP on aquatic invertebrates.

Cytotoxic effects exerted by pentachlorophenol by targeting nodal pro-survival signaling pathways in human pancreatic cancer cells

Pancreatic adenocarcinoma is one of the deadliest human solid tumors in the developed countries characterized by high resistance toward chemotherapeutic treatment. We have previously shown that silencing of the pro-survival protein kinase CK2 by RNA interference contributes to enhance the cytotoxicity of the chemotherapeutic agent 2′,2′-difluoro 2′-deoxycytidine (gemcitabine). Initial experiments showed that pentachlorophenol (PCP) inhibits CK2 and induces cell death in human pancreatic cancer cell lines. We report here evidence that exposure of this type of cells to PCP induces caspase-mediated apoptosis, inhibition of the lysosome cysteine protease cathepsin B and mitochondrial membrane depolarization. Beside cellular inhibition of CK2, the analysis of signaling pathways deregulated in pancreatic cancer cells revealed that PCP causes decreased phosphorylation levels of NF-κB/p65, suppresses its nuclear translocation and leads to activation of JNK-mediated stress response. Surprisingly, exposure to PCP results in increased phosphorylation levels of AKT at the canonical S473 and T308 activation sites supporting previous data showing that AKT phosphorylation is not predictive of tumor cell response to treatment. Taken together, our study provides novel insights into the effects induced by the exposure of pancreatic cancer cells to chlorinated aromatic compounds posing the basis for more advanced studies in vivo.

Luminescent threat: toxicity of light stick attractors used in pelagic fishery

Light sticks (LS) are sources of chemiluminescence commonly used in pelagic fishery, where hundreds are discarded and reach the shores. Residents from fishing villages report an improper use of LS contents on the skin. Given the scarce information regarding LS toxicity, the effects of LS solutions in cell cultures were evaluated herein. Loss of viability, cell cycle changes and DNA fragmentation were observed in HepG2 cell line and skin fibroblasts. A non-cytotoxic LS concentration increased the occurrence of the mutagenic lesion 1,N(6)-εdAdo in HepG2 DNA by three-fold. Additionally, in vitro incubations of spent LS contents with DNA generated dGuo-LS adducts, whose structure elucidation revealed the presence of a reactive chlorinated product. In conclusion, the LS contents were found to be highly cyto- and genotoxic. Our data indicate an urgent need for LS waste management guidelines and for adequate information regarding toxic outcomes that may arise from human exposure.

Tetrachlorobenzoquinone induces acute liver injury, up-regulates HO-1 and NQO1 expression in mice model: the protective role of chlorogenic acid

Tetrachlorobenzoquinone (TCBQ) is an active metabolite of pentachlorophenol (PCP). Although PCP has been investigated extensively, there are only a few reports describing the toxicity effect of TCBQ, and no report regarding TCBQ-induced liver injury in vivo. In the current study, we aimed to examine the acute hepatic toxicity of TCBQ in the mice model. Chlorogenic acid (CGA) exhibits promising antioxidant activity in the past studies, thus, the second aim of this study was to evaluate the protective effect of CGA on TCBQ-induced liver injury. Our results indicated TCBQ-intoxication caused marked liver cell necrosis and inflammation but not apoptosis, and this damage was alleviated by CGA treatment. Meantime, TCBQ-intoxication enhanced serum ALT, AST activities, TBIL content, hepatic oxidative stress and lipid peroxidation, decreased GSH content and inhibited the activities of antioxidant enzymes. Western blot and immunohistochemical analysis showed that TCBQ marked up-regulated HO-1 and NQO1 expression. On the other hand, pretreatment of CGA reduced TCBQ-induced liver damage remarkably. Taking together, these results revealed that TCBQ has strong hepatic toxic effect, and at least a part of this effect is initiated by free radical and relieved with CGA administration.

The pentachlorophenol metabolite tetrachlorohydroquinone induces massive ROS and prolonged p-ERK expression in splenocytes, leading to inhibition of apoptosis and necrotic cell death

Pentachlorophenol (PCP) has been used extensively as a biocide and a wood preservative and has been reported to be immunosuppressive in rodents and humans. Tetrachlorohydroquinone (TCHQ) is a major metabolite of PCP. TCHQ has been identified as the main cause of PCP-induced genotoxicity due to reactive oxidant stress (ROS). However, the precise mechanisms associated with the immunotoxic effects of PCP and TCHQ remain unclear. The aim of this study was to examine the effects of PCP and TCHQ on the induction of ROS and injury to primary mouse splenocytes. Our results shown that TCHQ was more toxic than PCP and that a high dose of TCHQ led to necrotic cell death of the splenocytes through induction of massive and sudden ROS and prolonged ROS-triggered ERK activation. Inhibition of ROS production by N-acetyl-cysteine (NAC) partially restored the mitochondrial membrane potential, inhibited ERK activity, elevated caspase-3 activity and PARP cleavage, and, eventually, switched the TCHQ-induced necrosis to apoptosis. We suggest that prolonged ERK activation is essential for TCHQ-induced necrosis, and that ROS play a pivotal role in the different TCHQ-induced cell death mechanisms.

Effects of multigenerational exposures of D. magna to environmentally relevant concentrations of pentachlorophenol

The re-emergence of schistosomiasis has given rise to ubiquitous concentrations of the primary control agent pentachlorophenol (PCP) in the environment, especially in the surface waters of China. In this study, the effects of environmentally relevant concentrations of PCP, namely, 0.0002, 0.002, 0.02, 0.2, and 2 μmol/L on survival, age at first reproduction, fecundity, length of mothers, and number of molts of Daphnia magna were studied over three generations. The survival of D. magna exposed to 2 μmol/L was significantly affected in the three generations. Toxic effects were enhanced in later generations. Age at first reproduction of F1 and F2 D. magna was significantly slower than that of the controls. The total number of offspring per female exposed to concentrations of 0.002 μmol/L or greater was less (23.5 to 67.6, 9.4 to 73.7, and 3.6 to 83.7%) than that of the controls in the F0, F1, and F2 generations, respectively. The body length of mothers significantly decreased (4.7 to 6.8, 9.6 to 15.1, and 13.3 to 23.2%) after exposure to 0.002 μmol/L or greater than those of unexposed individuals in the F0, F1, and F2 generations, respectively. Dose-response relationships between concentrations of PCP and length and number of molts of D. magna were observed in the F0 to F2 generations. PCP concentrations on the surface waters of China caused adverse effects to D. magna, which increased over successive generations. Significant effects were observed in the third generation. The multigenerational studies were more sensitive than the single-generation experiments. Thus, multigenerational exposure may be more predictive of chronic exposure under field conditions.

Enhanced cytotoxicity of pentachlorophenol by perfluorooctane sulfonate or perfluorooctanoic acid in HepG2 cells

Chlorinated phenols and perfluoroalkyl acids (PFAAs) are two kinds of pollutants which are widely present in the environment. Considering liver is the primary toxic target organ for these two groups of chemicals, it is interesting to evaluate the possible joint effects of them on liver. In this work, the combined toxicity of pentachlorophenol (PCP) and perfluorooctane sulfonate (PFOS) or perfluorooctanoic acid (PFOA) were investigated using HepG2 cells. The results indicated that PFOS and PFOA could strengthen PCP's hepatotoxicity. Further studies showed that rather than intensify the oxidative stress or promote the biotransformation of PCP, PFOS (or PFOA) might lead to strengthening of the oxidative phosphorylation uncoupling of PCP. By measuring the intracellular PCP concentration and the cell membrane properties, it was suggested that PFOS and PFOA could disrupt the plasma membrane and increase the membrane permeability. Thus, more cellular accessibility of PCP was induced when they were co-exposed to PCP and PFOS (or PFOA), leading to increased cytotoxicity. Further research is warranted to better understand the combined toxicity of PFAAs and other environmental pollutants.

Lack of nrf2 results in progression of proliferative lesions to neoplasms induced by long-term exposure to non-genotoxic hepatocarcinogens involving oxidative stress

To explore the role of oxidative stress in chemical carcinogenesis driven by non-genotoxic mechanisms, nrf2-deficient (nrf2(-/-)) and nrf2-wild-type (nrf2(+/+)) mice were exposed to pentachlorophenol (PCP) at concentrations of 600 or 1200 ppm for 60 weeks, or piperonyl butoxide (PBO) at concentrations of 3000 or 6000 ppm in the diet for 52 weeks, respectively. Additional studies were performed to examine 8-hydroxydeoxyguanosine (8-OHdG) levels in liver DNA and hepatotoxicological parameters in serum following 8 weeks of exposure of each group to PBO at the same doses as in the long-term study. Exposure to 600 ppm PCP caused cholangiofibrosis (CF) only in nrf2(-/-) mice, while 1200 ppm PCP induced CF in both genotypes. Moreover, cholangiocarcinomas were found with significant incidence only in nrf2(-/-) mice treated with 1200 ppm PCP. Short-term exposure to 6000 ppm PBO caused significant elevation of 8-OHdG levels in both genotypes, while exposure to 3000 ppm caused a significant increase in 8-OHdG only in nrf2(-/-) mice. There were no inter-genotype changes in the incidences of regenerative hepatocellular hyperplasia (RHH) following long-term exposure to PBO. However, the incidence and multiplicity of hepatocellular adenomas, especially those observed in RHH, were much higher in nrf2-/- mice treated with 6000 ppm PBO than in nrf2+/+ mice treated with 6000 ppm PBO. Therefore, oxidative stress generated through PCP or PBO metabolism may promote the proliferation and progression of preneoplastic lesions to neoplasms.

Toxicological profile of chlorophenols and their derivatives in the environment: the public health perspective

Chlorophenol compounds and their derivatives are ubiquitous contaminants in the environment. These compounds are used as intermediates in manufacturing agricultural chemicals, pharmaceuticals, biocides, and dyes. Chlorophenols gets into the environment from a variety of sources such as industrial waste, pesticides, and insecticides, or by degradation of complex chlorinated hydrocarbons. Thermal and chemical degradation of chlorophenols leads to the formation of harmful substances which constitute public health problems. These compounds may cause histopathological alterations, genotoxicity, mutagenicity, and carcinogenicity amongst other abnormalities in humans and animals. Furthermore, the recalcitrant nature of chlorophenolic compounds to degradation constitutes an environmental nuisance, and a good understanding of the fate and transport of these compounds and their derivatives is needed for a clearer view of the associated risks and mechanisms of pathogenicity to humans and animals. This review looks at chlorophenols and their derivatives, explores current research on their effects on public health, and proffers measures for mitigation.

Short-term assessment of toxicological aspects, oxidative and inflammatory response to dietary melon superoxide dismutase in rats

The protective effects of SODB, a gastro-resistant encapsulated melon superoxide dismutase, on haematological and biochemical parameters and inflammatory and oxidative status, were evaluated in the blood and liver tissue. The study consisted in a 28-day experiment on rats supplemented with three doses (10, 40 and 160USOD/day) of SODB-M, SODB-D or SODB-S, different depending on the nature of the coating (palm oil, shellac or gum Arabic respectively). No mortality, abnormal clinical signs, behavioural changes or macroscopic findings were observed whatever the groups. Haematological parameters (total red blood cell count, haemoglobin content, haematocrit, red cell indices, white blood cell count and platelets count) were not modified in SODB treated-groups. No marked change was recorded in biochemical parameters (plasma urea, creatinine, lipids, electrolytes, bilirubin, transaminases and gamma-glutamyl transferase). The liver endogenous antioxidant enzymes (copper/zinc and manganese superoxide dismutase) expressions were significantly increased in the rats receiving the highest dose of SODB (160USOD/day) whatever the coating. Moreover, interleukin-6, a marker of inflammation, was significantly decreased in these high dose-treated-groups. The present study indicates that dietary supplementation of SODB on rats has no harmful side effects and could be beneficial especially at high doses.

Mortality of US pentachlorophenol production workers through 2005

A cohort of 2122 US pentachlorophenol (PCP) production workers from four plants in the National Institute for Occupational Safety and Health Dioxin Registry was exposed to PCP and to polychlorinated dibenzo-p-dioxin and dibenzofuran contaminants of PCP production. A subcohort of 720 was also exposed to 2,3,7,8-tetrachlorodibenzodioxin, a contaminant of trichlorophenol (TCP) while using TCP or a TCP derivative. PCP and several production contaminants have been implicated as animal carcinogens. A priori hypotheses were that the cohort would have elevated standardized mortality ratios (SMRs) for aplastic anemia, soft-tissue sarcoma, and non-Hodgkin lymphoma, as suggested by human studies, and for leukemia and liver, adrenal, thyroid, and parathyroid cancer, as suggested by animal studies. From 1940 to 2005 1165 deaths occurred with an overall SMR of 1.01 [95% confidence limits (CI), 0.95-1.07]. Overall cancer mortality (326 deaths, SMR 1.17, CI 1.05-1.31) was in statistically significant excess. There were excess deaths for trachea, bronchus and lung cancers (126 deaths, SMR 1.36, CI 1.13-1.62), non-Hodgkin lymphoma (17 deaths, SMR 1.77, CI 1.03-2.84), chronic obstructive pulmonary disease (63 deaths, SMR 1.38, CI 1.06-1.77), and medical complications (5 deaths, SMR 3.52, CI 1.14-8.22). In race- and sex-specific analyses, white males had increased non-Hodgkin lymphoma mortality (17 deaths, SMR 1.98, CI 1.15-3.17) and males of other races had increased leukemia mortality (four deaths, SMR 4.57, CI 1.25-11.7). The excess of cancers of a priori interest, non-Hodgkin lymphoma and leukemia, provide some support for the carcinogenicity of PCP, however, further studies with more detailed exposure assessment are needed.

Effects of exposure to sublethal propiconazole on the antioxidant defense system and Na+-K+-ATPase activity in brain of rainbow trout, Oncorhynchus mykiss

Propiconazole (PCZ), a triazole fungicide, is widely present in the aquatic environment, but little is known regarding its chronic toxicity in the fish brain. This study assessed the effects of long-term exposure to PCZ on the antioxidant defense system and Na(+)-K(+)-ATPase activity of rainbow trout brain. Fish were exposed to sublethal concentrations of PCZ (0.2, 50, and 500 microg/l) for 7, 20, and 30 days, respectively. Oxidative stress indices (reactive oxygen species, lipid peroxidation, and carbonyl protein) and antioxidant parameters (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and reduced glutathione) were measured, as well as Na(+)-K(+)-ATPase activity. Adaptive responses to PCZ-induced stress were observed at 7 days. With prolonged exposure, significantly higher levels of oxidative indices were indicative of oxidative stress, as also were the significant inhibition of antioxidant enzyme activity and reduced glutathione content. Na(+)-K(+)-ATPase activity was significantly inhibited after prolonged exposure. Chemometrics of all parameters by principal component analysis, enabled the separation of sampled individuals into four groups with 93.39% of total accumulated variance. A low level of oxidative stress can induce the adaptive responses of the antioxidant defense system, while prolonged exposure to PCZ may lead to serious oxidative damage in fish brain. We suggest that selected biochemical markers in fish brain could be used as potential biomarkers for monitoring residual fungicides present in the aquatic environments.

Inducibility of metallothionein biosynthesis in the whole soft tissue of zebra mussels Dreissena polymorpha exposed to cadmium, copper, and pentachlorophenol

Freshwater mussels Dreissena polymorpha (Pallas, 1771) were exposed to the elevated concentrations of Cd (10, 50, 100, and 500 microg/L), Cu (10, 30, 50, and 80 microg/L), and an organochlorinated pesticide, pentachlorophenol (PCP) (1, 10, and 100 microg/L). Induced synthesis of biomarker metallothionein (MT) and changes in concentrations of cytosolic Cd, Cu, and Zn in the whole soft tissue of mussels were monitored after a 7-day laboratory exposure to the contaminants. A clear dose-dependent elevation in the MT concentration was observed after exposure to Cd at doses of 10-100 microg/L, and this increase of MT content was accompanied with a linear increase of cytosolic Cd. Cd concentration of 500 microg/L caused no additional increase of MT and Cd in mussel cytosol, suggesting possible toxic effects due to exceeding cellular inducible/defense capacity. Cu exposure resulted with variable changes in MT concentrations, with no clear linear relationship between MT and Cu concentrations in water, although a progressive dose-dependent accumulation of Cu in the soluble fraction of mussel tissues was recorded. A decrease of cytosolic Zn was evident at higher exposure concentrations of both metals used. PCP in concentrations applied was unable to induce MT synthesis, but the higher concentrations of PCP influenced the cytosolic metal concentrations. In conclusion, the results obtained confirm the specificity of MT induction in D. polymorpha as an biological response on metal stimulation, especially by cadmium, being more closely correlated to MT than copper within the ecologically relevant concentration range. The strong induction potential of cadmium as well as an absence of MT induction following exposure to PCP as an organic chemical contaminant are supporting evidences for usage of zebra mussel MT as a specific biomarker of Cd exposure in biomonitoring programs.

Induction of oxidative stress and apoptosis by pentachlorophenol in primary cultures of Carassius carassius hepatocytes

Pentachlorophenol (PCP) is a highly toxic contaminant of chlorophenols. Due to its slow and incomplete biodegradation, it can be found in surface, groundwater and in soils. To investigate the role of intracellular calcium and reactive oxygen species in apoptosis induced by PCP in cultured hepatocytes, the primary hepatocytes of Carassius carassius were incubated with different concentrations of PCP at 25 degrees C for 8 h in vitro. Apoptosis was detected by DNA laddering, caspase activation and flow cytometry. The results demonstrated that apoptosis was involved in the cytotoxic effect of PCP, and that PCP-induced apoptosis occurred in a dose-dependent manner. In addition, the induction of apoptosis by PCP was accompanied with Ca2+, Mg2+-ATPase activity decline, intracellular Ca2+ elevation, generation of intracellular reactive oxygen species (ROS), mitochondrial membrane potential (DeltaPsi(m)) disruption and ATP depletion. Concomitantly, there were dose-dependent increases in lipid peroxidation production (MDA) and decreases in glutathione (GSH). These investigations suggest that PCP-induces apoptosis in the cultured hepatocytes by affecting multiple targets, and suggest that [Ca2+]i increase and ROS generation may be involved in apoptosis induction by PCP.

Pentachlorophenol decreases ATP levels in human natural killer cells

Pentachlorophenol (PCP) is used as a wood preservative and is found in human blood and urine. PCP causes significant decreases in the tumor-killing (lytic) function of human natural killer (NK) cells, a critical immune defense. The current study examined the association between decreased lytic function and decreased ATP levels, as well as the ability of antioxidants (vitamin E and reduced glutathione) to prevent PCP-induced decreases in either ATP levels or lytic function. Exposure of NK cells to 10 microm PCP decreased ATP levels by 15% at 24 h, and exposure to 5 microm PCP decreased ATP levels by 32% at 48 h. No effects were seen with 0.5 microm at 48 h or with 5 microm at 24 h. However, 10 microm PCP decreased lytic function by 69% at 24 h and 5 microm decreased it by 90% at 48 h. Even 0.5 microm PCP decreased lytic function by 46% at 48 h. None of these effects were prevented by pretreatment with 1 mm vitamin E or reduced glutathione.

2-Chlorophenol induced hydroxyl radical production in mitochondria in Carassius auratus and oxidative stress--an electron paramagnetic resonance study

In our previous study, electron paramagnetic resonance (EPR) evidence of reactive oxygen species (ROS) production in Carassius auratus following 2-chlorophenol (2-CP) administration was provided. To further investigate the potential pathway of ROS production, liver mitochondria of C. auratus was isolated and incubated with 2-CP for 30 min. An EPR analysis indicated ROS was produced, and intensities of ROS increased with increasing concentrations of 2-CP. The ROS was then assigned OH by comparing with Fenton reaction. Either catalase or superoxide dismutase, extinguished OH completely in the mitochondria mixture. These facts suggested that O2(.-) and H2O2 contributed to the formation of OH in mitochondria in C. auratus stressed by 2-CP. Combining previous references and our own data, it is reasonable to suggest that 2-CP is first oxidized by H2O2 present in vivo to form phenoxyl radical under the catalytic action of cellular peroxidase (1); phenoxyl radical oxidizes mitochondria NADH to NAD in the presence of NADH (2); NAD reacts with oxygen in vivo to produce O2(.-) (3); O2(.-) is spontaneously dismutated by SOD to form H2O2 and O2, which creates a renewable supply of H2O2 as the initiators of the chain reactions until NADH is consumed (4); simultaneously with reaction (4), O2(.-) reacts with H2O2 to form OH radical via the Haber-Weiss reaction (5). A strong negative correlation (r=-0.9278, p<0.01) between glutathione (GSH) pool and OH production was observed after fish were i.p. injected with 2-CP (250 mg kg(-1)), indicating the depletion of GSH caused by OH.

Transcriptome analysis reveals that multidrug efflux genes are upregulated to protect Pseudomonas aeruginosa from pentachlorophenol stress

Through chemical contamination of natural environments, microbial communities are exposed to many different types of chemical stressors; however, research on whole-genome responses to this contaminant stress is limited. This study examined the transcriptome response of a common soil bacterium, Pseudomonas aeruginosa, to the common environmental contaminant pentachlorophenol (PCP). Cells were grown in chemostats at a low growth rate to obtain substrate-limited, steady-state, balanced-growth conditions. The PCP stress was administered as a continuous increase in concentration, and samples taken over time were examined for physiological function changes with whole-cell acetate uptake rates (WAURs) and cell viability and for gene expression changes by Affymetrix GeneChip technology and real-time reverse transcriptase PCR. Cell viability, measured by heterotrophic plate counts, showed a moderately steady decrease after exposure to the stressor, but WAURs did not change in response to PCP. In contrast to the physiological data, the microarray data showed significant changes in the expression of several genes. In particular, genes coding for multidrug efflux pumps, including MexAB-OprM, were strongly upregulated. The upregulation of these efflux pumps protected the cells from the potentially toxic effects of PCP, allowing the physiological whole-cell function to remain constant.

Effects of hexachlorobenzene on antioxidant status of liver and brain of common carp (Cyprinus carpio)

Hexachlorobenzene (HCB)-induced oxidative damages have been published in rats while the effects have not yet been reported in fishes. Juvenile common carps (Cyprinus carpio) were exposed to waterborne HCB from 2 to 200 microg l-1 for 5, 10 or 20 days. Liver and brain were analyzed for various parameters of oxidative stress. There were no significant changes of glutathione (GSH) content and superoxide dismutase (SOD) activity in liver after 5 or 10 days exposure, whereas obvious drops were observed at higher concentrations after 20 days exposure. Significant decreases of GSH content and SOD activity in brain were found during all the exposure days. In brain, HCB also significantly elevated the contents of reactive oxygen species (ROS), thiobarbituric acid- reactive substances (TBARS, as an indicator of lipid peroxidation products), glutathione disulfide (GSSG), and activities of nitric oxide synthase (NOS), glutathione peroxidase (GPx), and glutathione reductase (GR), and inhibited activities of acetylcholinesterase (AchE) and glutathione S-transferase (GST). The results clearly demonstrated that environmentally possible level of HCB could result in oxidative stress in fish and brain was a sensitive target organ of HCB toxicity.

Clinical model for distinguishing nonalcoholic steatohepatitis from simple steatosis in patients with nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) encompasses both simple steatosis and nonalcoholic steatohepatitis (NASH). Differentiation of these two entities requires histopathologic evaluation. The aim of this study was to establish a reliable diagnostic model for differentiating steatosis from steatohepatitis utilizing both clinical characteristics and a panel of biochemical markers of lipid peroxidation and fibrosis. Eighty subjects with biopsy proven NAFLD were enrolled, 39 with simple steatosis and 41 with histopathologic evidence of NASH. Demographic and laboratory data to include serologic testing for 8-epi-PGF(2alpha), transforming growth factor-beta (TGF-beta), adiponectin, and hyaluronic acid (HA) were obtained and compared between the two groups. There were significant differences between the two groups with respect to age (P=0.004), female gender (P=0.024), aspartate aminotransferase (AST) (P=0.028), body mass index (BMI) (P=0.003), fasting insulin (0.018), AST/alanine aminotransferase (ALT) ratio (AAR) (P=0.017), quantitative insulin sensitivity check index (QUICKI) (P=0.002), and HA (P=0.029). A composite index for distinguishing steatosis from NASH was calculated by summing the risk factors of age >or=50 years, female gender, AST>or=45 IU/l, BMI >or=30 mg/kg2, AAR>or=0.80, and HA>or=55 microg/l, and its accuracy was determined by receiver operating characteristic (ROC) analysis to be 0.763 (95% CI: 0.650-0.876). The presence of three or more risk factors had a sensitivity, specificity, PPV, and NPV of 73.7%, 65.7%, 68.2%, and 71.4%, respectively. In addition, HA at a cutoff of 45.3 microg/l was a good predictor of advanced fibrosis. In conclusion, we propose a noninvasive screening model for distinguishing simple steatosis from NASH. Identifying patients at risk for NASH will allow clinicians to more accurately determine who may benefit from liver biopsy.

A crucial role of Nrf2 in in vivo defense against oxidative damage by an environmental pollutant, pentachlorophenol

Our goal was to elucidate roles of Nrf2 in in vivo defense against pentachlorophenol (PCP), an environmental pollutant and hepatocarcinogen in mice. We examined oxidative stress and cell proliferation, along with other hepatotoxicological parameters, in the livers of nrf2-deficient (wild:+/+, heterozygous:+/-, homozygous:-/-) animals fed PCP in their diet at doses of 0, 150, 300, 600, or 1200 ppm for 4 weeks. For measurement of methoxyresorufin-O-demethylase (CYP 1A2), NAD(P):quinone oxidoreductase 1 (NQO1), and UDP-glucuronosyltransferase (UDP-GT), an additional study was performed with all but the 150-ppm dose. Significant elevation of 8-hydroxydeoxyguanosine (8-OH-dG) levels in the liver DNA was observed only in -/- mice treated with PCP at 1200 ppm. Levels of thiobarbituric-acid-reactive substances (TBARS) were also raised significantly compared to those of the relevant +/+ mice. Bromodeoxyuridine labeling indices (BrdU-LIs) of hepatocytes in -/- mice were significantly higher at all doses than those in the relevant +/+ mice. Relative liver weights were unchanged in mice lacking Nrf2, whereas liver weight in +/+ and +/- mice was increased. Significant elevations of serum ALP activity, but not ALT and AST activity, occurred at 600 ppm and above in -/- mice compared to the relevant +/+ mice. Histopathologically, centrilobular hepatocyte necrosis was severe in the -/- mice that received 600 ppm. Although CYP 1A2 activity was elevated in all treated mice, increases in NQO1 levels and UDP-GT activities did not occur only in -/- mice. These data suggest that Nrf2 plays a key role in prevention of PCP-induced oxidative stress and cell proliferation.