Doses Of Trichloroethylene Research Articles

Histone demethylase KDM4A mediating macrophage polarization: A potential mechanism of trichloroethylene induced liver injury.

Trichloroethylene (TCE) is a commonly used organic solvent in industry. Our previous studies have found that TCE can cause liver injury accompanied by macrophage polarization, but the specific mechanism is unclear. The epigenetic regulation of macrophage polarization is mainly focused on histone modification. Histone lysine demethylase 4A (KDM4A) is involved in the activation of macrophages. In this study, we used a mouse model we investigated the role of KDM4A in the livers of TCE-drinking mice and found that the expression of KDM4A, M1-type polarization indicators, and related inflammatory factors in the livers of TCE-drinking mice. In the study, BALB/c mice were randomly divided into four groups: 2.5 mg/mL TCE dose group and 5.0 mg/mL TCE dose group, the vehicle control group, and the blank control group. We found that TCE triggered M1 polarization of mouse macrophages, characterized by the expression of CD11c and robust production of inflammatory cytokines. Notably, exposure to TCE resulted in markedly increased expression of KDM4A in macrophages. Functionally, the increased expression of KDM4A significantly impaired the expression of H3K9me3 and H3K9me2 and increased the expression of H3K9me1. In addition, KDM4A potentially represents a novel epigenetic modulator, with its upregulation connected to β-catenin activation, a signal critical for the pro-inflammatory activation of macrophages. Furthermore, KDM4A inhibitor JIB-04 treatment resulted in a decrease in β-catenin expression and prevented TCE-induced M1 polarization and the expression of the pro-inflammatory cytokines TNF-α and IL-1β. These results suggest that the association of KDM4A and Wnt/β-catenin cooperatively establishes the activation and polarization of macrophages and global changes in H3K9me3/me2/me1. Our findings identify KDM4A as an essential regulator of the polarization of macrophages and the expression of inflammatory cytokines, which might serve as a potential target for preventing and treating liver injury caused by TCE.

Effects of Trichloroethylene on p53 and Bcl-2 Expression, Chromosome Loss and Catalase Activity Inhibition in Human

Trichloroethylene (TCE) is a common organic solvent that has been widely used in industrial applications.TCE is highly lipophilic and readily absorbed into the circulation following oral, dermal or inhalationexposure. The purpose of this study is to examine the alterations of p53 and Bcl-2 expression, chromosomeloss and catalase activity inhibition after treatment with TCE. Human lymphocytes were cultured withvarious doses of TCE for 24 h. Quantitative RT-PCR (qRT-PCR) technique, chromosome culture techniqueand catalase activity assay were performed in human lymphocyte cultures. The results of Quantitative RTPCR (qRT-PCR) analysis showed up-regulated expression in the experimental groups comparison with thecontrol groups of p53 gene [0.016 mM/L (1.4-fold) and Bcl-2 gene [0.008 mM/L (1.4-fold) and 0.016mM/L (1.6-fold)]. Loss of chromosome 8 and 22 were observed. Catalase activity was reduced whenTCE concentration increased (p<0.05). It is indicated that TCE effects on p53 and Bcl-2 gene expression,chromosome loss and catalase activity inhibition. These effects may lead to the onset of cancer in the future.

Trichloroethylene injures rat liver and elevates the level of peroxisomal bifunctional enzyme (Ehhadh)

Trichloroethylene (TCE) is a common industrial solvent and an occupational toxicant. TCE exposure can cause severe hepatotoxicity, but its mode of action is poorly understood. Many studies have shown TCE-induced liver damage in mice, while few have examined the effects of TCE in rats. To explore the effects of TCE in Sprague–Dawley (SD) rats and the potential mechanisms in TCE-induced hepatocytotoxicity. The liver index and activities of liver damage marker enzymes (ALT, AST and ALP) in rat serum were elevated along with the increase in TCE dose, while the levels of total proteins and albumin in serum were reduced. The results suggest that TCE is hepatotoxic in rats. 2D-DIGE electrophoresis showed that the levels of 66 liver proteins in TCE-treated rats were abnormally altered (39 up-regulated and 27 down-regulated). In these proteins, six enzymes were related to liver damage and carcinogenesis as indicated by bioinformatics analysis, and Western blot analysis confirmed the alterations of three of them, i.e., aldehyde dehydrogenase 2 (Aldh2), glutathione S-transferase Mu 1 (Gstm1) and peroxisomal bifunctional enzyme (PBE, also named as Ehhadh). PBE was the only protein elevated in a dose dependent manner. Whether PBE can be a biomarker of TCE hepatotoxicity needs to be further studied. These findings indicate that TCE induces liver injury in rats.

Comparative analysis of metabolism of trichloroethylene and tetrachloroethylene among mouse tissues and strains

Trichloroethylene (TCE) and tetrachloroethylene (PCE) are structurally similar chemicals that are metabolized through oxidation and glutathione conjugation pathways. Both chemicals have been shown to elicit liver and kidney toxicity in rodents and humans; however, TCE has been studied much more extensively in terms of both metabolism and toxicity. Despite their qualitative similarities, quantitative comparison of tissue- and strain-specific metabolism of TCE and PCE has not been performed. To fill this gap, we conducted a comparative toxicokinetic study where equimolar single oral doses of TCE (800 mg/kg) or PCE (1000 mg/kg) were administered to male mice of C57BL/6J, B6C3F1/J, and NZW/LacJ strains. Samples of liver, kidney, serum, brain, and lung were obtained for up to 36 h after dosing. For each tissue, concentrations of parent compounds, as well as their oxidative and glutathione conjugation metabolites were measured and concentration-time profiles constructed. A multi-compartment toxicokinetic model was developed to quantitatively compare TCE and PCE metabolism. As expected, the flux through oxidation metabolism pathway predominated over that through conjugation across all mouse strains examined, it is 1,200–3,800 fold higher for TCE and 26–34 fold higher for PCE. However, the flux through glutathione conjugation, albeit a minor metabolic pathway, was 21-fold higher for PCE as compared to TCE. The degree of inter-strain variability was greatest for oxidative metabolites in TCE-treated and for glutathione conjugation metabolites in PCE-treated mice. This study provides critical data for quantitative comparisons of TCE and PCE metabolism, and may explain the differences in organ-specific toxicity between these structurally similar chemicals.

Developmental neurotoxic effects of a low dose of TCE on a 3-D neurosphere system.

Trichloroethylene (TCE) is one of the industrial toxic byproducts that now persist in the air, soil, and water. Several studies have already illustrated the toxic effect of high doses of TCE on the biological functions of several organs. This study aims to highlight the toxic impact of a low dose of TCE (1 μmol/L) on the development of rat neural stem cells (NSCs). The subventricular zones (SVZ) of rat pup's brains were collected and minced, and the harvested cells were cultured in the presence of neural growth factors B27/N2 to develop neurospheres. The cells were then exposed to a dose of 1 μmol/L TCE for 1 or 2 weeks. The outcomes indicated a remarkable inhibitory effect of TCE on the differentiation capacity of NSCs, which was confirmed by down-regulation of the astrocyte marker GFAP The inhibitory effect of TCE on the proliferation of NSCs was identified by the reductions in neurosphere diameter, Ki67 expression, and cell cycle arrest at the G1/S phase. Immunolabelling with annexin V indicated the proapoptotic effect of TCE exposure. PCR results revealed a TCE-mediated suppression of the expression of the antioxidant enzyme SOD1. This paper illustrates, for the first time, a detailed examination of the toxic effects of an environmentally low dose of TCE on NCSs at the transcriptional, translational, and functional levels.

A single dose of trichloroethylene given during development does not substantially alter markers of neuroinflammation in brains of adult mice

Trichloroethylene (TCE) is a widespread environmental contaminant associated with developmental immunotoxicity and neurotoxicity. Previous studies have shown that MRL+/+ mice exposed to TCE from gestation through early-life demonstrate robust increases in inflammatory markers in peripheral CD4+ T-cells, as well as glutathione depletion and increased oxidative stress in cerebellum-associated with alterations in behavior. Since increased oxidative stress is associated with neuroinflammation, we hypothesized that neuroinflammatory markers could be altered relative to unexposed mice. MRL+/+ mice were given 0.5 mg/ml of TCE in vehicle or vehicle (water with 1% Alkamuls EL-620) from conception through early adulthood via drinking water to dams and then directly to post-weaning offspring. Animals were euthanized at 49 days of age and levels of pro- and anti-inflammatory cytokines, density of T-cell staining, and micro-glial morphology were evaluated in brains to begin to ascertain a neuroinflammatory profile. Levels of IL-6 were decreased in female animals and while not statistically significant, and levels of IL-10 were higher in brains of exposed male and female animals. Supportive of this observation, although not statistically significant, the number of ameboid microglia was higher in exposed relative to unexposed animals. This overall profile suggests the emergence of an anti-inflammatory/neuroprotective phenotype in exposed animals, possibly as a compensatory response to neuroinflammation that is known to be induced by developmental exposure to TCE.

Disruption of cardiogenesis in human embryonic stem cells exposed to trichloroethylene.

Trichloroethylene (TCE) is ubiquitous in our living environment, and prenatal exposure to TCE is reported to cause congenital heart disease in humans. Although multiple studies have been performed using animal models, they have limited value in predicting effects on humans due to the unknown species-specific toxicological effects. To test whether exposure to low doses of TCE induces developmental toxicity in humans, we investigated the effect of TCE on human embryonic stem cells (hESCs) and cardiomyocytes (derived from the hESCs). In the current study, hESCs cardiac differentiation was achieved by using differentiation medium consisting of StemPro-34. We examined the effects of TCE on cell viability by cell growth assay and cardiac inhibition by analysis of spontaneously beating cluster. The expression levels of genes associated with cardiac differentiation and Ca2+ channel pathways were measured by immunofluorescence and qPCR. The overall data indicated the following: (1) significant cardiac inhibition, which was characterized by decreased beating clusters and beating rates, following treatment with low doses of TCE; (2) significant up-regulation of the Nkx2.5/Hand1 gene in cardiac progenitors and down regulation of the Mhc-7/cTnT gene in cardiac cells; and (3) significant interference with Ca2+ channel pathways in cardiomyocytes, which contributes to the adverse effect of TCE on cardiac differentiation during early embryo development. Our results confirmed the involvement of Ca2+ turnover network in TCE cardiotoxicity as reported in animal models, while the inhibition effect of TCE on the transition of cardiac progenitors to cardiomyocytes is unique to hESCs, indicating a species-specific effect of TCE on heart development. This study provides new insight into TCE biology in humans, which may help explain the development of congenital heart defects after TCE exposure. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1372-1380, 2016.

The Relationship between the Occupational Exposure of Trichloroethylene and Kidney Cancer.

Trichloroethylene (TCE) has been widely used as a degreasing agent in many manufacturing industries. Recently, the International Agency for Research on Cancer presented “sufficient evidence” for the causal relationship between TCE and kidney cancer. The aim of this study was to review the epidemiologic evidences regarding the relationship between TCE exposure and kidney cancer in Korean work environments. The results from the cohort studies were inconsistent, but according to the meta-analysis and case–control studies, an increased risk for kidney cancer was present in the exposure group and the dose–response relationship could be identified using various measures of exposure. In Korea, TCE is a commonly used chemical for cleaning or degreasing processes by various manufacturers; average exposure levels of TCE vary widely. When occupational physicians evaluate work-relatedness kidney cancers, they must consider past exposure levels, which could be very high (>100 ppm in some cases) and associated with jobs, such as plating, cleaning, or degreasing. The exposure levels at a manual job could be higher than an automated job. The peak level of TCE could also be considered an important exposure-related variable due to the possibility of carcinogenesis associated with high TCE doses. This review could be a comprehensive reference for assessing work-related TCE exposure and kidney cancer in Korea.

Metabolic changes and DNA hypomethylation in cerebellum are associated with behavioral alterations in mice exposed to trichloroethylene postnatally

Previous studies demonstrated that low-level postnatal and early life exposure to the environmental contaminant, trichloroethylene (TCE), in the drinking water of MRL+/+ mice altered glutathione redox homeostasis and increased biomarkers of oxidative stress indicating a more oxidized state. Plasma metabolites along the interrelated transmethylation pathway were also altered indicating impaired methylation capacity. Here we extend these findings to further characterize the impact of TCE exposure in mice exposed to water only or two doses of TCE in the drinking water (0, 2, and 28mg/kg/day) postnatally from birth until 6weeks of age on redox homeostasis and biomarkers of oxidative stress in the cerebellum. In addition, pathway intermediates involved in methyl metabolism and global DNA methylation patterns were examined in cerebellar tissue. Because the cerebellum is functionally important for coordinating motor activity, including exploratory and social approach behaviors, these parameters were evaluated in the present study. Mice exposed to 28mg/kg/day TCE exhibited increased locomotor activity over time as compared with control mice. In the novel object exploration test, these mice were more likely to enter the zone with the novel object as compared to control mice. Similar results were obtained in a second test when an unfamiliar mouse was introduced into the testing arena. The results show for the first time that postnatal exposure to TCE causes key metabolic changes in the cerebellum that may contribute to global DNA methylation deficits and behavioral alterations in TCE-exposed mice.

Effects of trichloroethylene on hepatotoxicity in cytochrome 2E1-silenced hepatocytes

To prepare cytochrome (CYP)2E1-silenced hepatocytes by lentivirus-mediated RNA interference technology and to investigate the hepatotoxicity of trichloroethylene (TCE) in CYP2E1-silenced hepatocytes. Short hairpin RNA fragments were designed and synthesized and were then ligated into the lentiviral vector; single colonies were screened; the plasmid was extracted after PCR and sequence identification and then transferred into L02 hepatocytes; the CYP2E1-silenced hepatocytes were selected; real-time quantitative PCR and Western blot were used to evaluate the interference effects. The obtained CYP2E1-silenced hepatocytes, as well as normal L02 hepatocytes, were treated with TCE (0, 0.25, 0.50, 1.00, 2.00, and 4.00 mmol/L). The cell viability and half maximal inhibitory concentration (IC50) of TCE were measured; the apoptotic rate of cells was measured by flow cytometry; the mRNA expression levels of apoptosis genes and oncogenes were measured by real-time quantitative PCR. The IC50s of TCE for L02 hepatocytes and CYP2E1-silenced hepatocytes were 15.1 mmol/L and 23.6 mmol/L, respectively. The apoptotic rate increased as the dose of TCE rose in the two types of cells; the CYP2E1-silenced hepatocytes hada significantly lower apoptotic rate than L02 hepatocytes when they were exposed to 2.0 and 4.0 mmol/L TCE (P < 0.05 or P < 0.01). The mRNA expression level of bcl-2 (anti-apoptosis gene) in CYP2E1-silenced hepatocytes was 15% ∼ 60% higher than that in L02 hepatocytes (P < 0.01), while the mRNA expression levels of caspase-3 and caspase-9 (apoptosis genes) in CYP2E1-silenced hepatocytes were 30% ∼ 60% lower than those in L02 hepatocytes (P < 0.01). The mRNA expression level of p53 (cancer suppressor gene) in CYP2E1-silenced hepatocytes was 81 - 278% higher than that in L02 hepatocytes (P < 0.01), while the mRNA expression levels of c-fos and k-ras (oncogenes) in CYP2E1-silenced hepatocytes were 20-68% lower than those in L02 hepatocytes (P < 0.01). CYP2E1-silenced cells can be successfully prepared by lentivirus-mediated RNA interference technology. Silencing CYP2E1 gene can reduce the hepatotoxicity of TCE and inhibit the expression of some apoptosis genes and oncogenes, suggesting that CYP2E1 gene plays an important role in TCE metabolism and is related to the hepatotoxicity of TCE.

Trichloroethylene-induced formic aciduria: Effect of dose, sex and strain of rat

The industrial solvent trichloroethylene (TCE) has been reported to increase the excretion of formic acid in the urine of male Fischer 344 (F-344) rats following large oral doses. We have examined the dose–response relationship for formic aciduria in male and female Fischer 344 rats, the effect of some known metabolites of TCE and examined the response in male Wistar rats to help understand its relevance to renal toxicity. We report that doses of TCE as low as 8mg/kg for 3 days to both male and female F344 rats produced formic aciduria. The formic aciduria was time-dependent being more marked after 3 doses compared to one dose in male F344 rats and to a lesser extent in female F344 rats. TCE administration to male Wistar rats produced less formic aciduria than in male F344 rats, indicating a strain difference in response. As TCE is primarily metabolised by cytochrome P450 2E1, Wistar rats were administered inducers of cytochrome P450 2E1 followed by TCE, this increased formic acid excretion to a concentration similar to that observed in male F344 rats, indicating a role for P450. Administration of the major metabolites of TCE, trichloroethanol and trichloroacetic acid to male F344 rats also produced a marked and sustained formic aciduria, while the metabolite of TCE formed via glutathione conjugation had no effect on formic acid excretion. The mechanism whereby this response occurs is currently not understood, but the formic acid excreted is not a metabolite of TCE, but appears to be due to interference with the metabolic utilisation of formate by a down stream metabolite of TCE. Over the three days of the studies no histopathological evidence of kidney toxicity was observed in F344 rats given TCE, indicating that the perturbation of formate metabolism does not lead to acute renal injury.

Low-Dose Trichloroethylene Alters Cytochrome P450-2C Subfamily Expression in the Developing Chick Heart

Trichloroethylene (TCE) is an organic solvent and common environmental contaminant. TCE exposure is associated with heart defects in humans and animal models. Primary metabolism of TCE in adult rodent models is by specific hepatic cytochrome P450 enzymes (Lash et al. in Environ Health Perspect 108:177-200, 2000). As association of TCE exposure with cardiac defects is in exposed embryos prior to normal liver development, we investigated metabolism of TCE in the early embryo. Developing chick embryos were dosed in ovo with environmentally relevant doses of TCE (8 and 800 ppb) and RNA was extracted from cardiac and extra-cardiac tissue (whole embryo without heart). Real-time PCR showed upregulation of CYP2H1 transcripts in response to TCE exposure in the heart. No detectable cytochrome expression was found in extra-cardiac tissue. As seen previously, the dose response was non-monotonic and 8 ppb elicited stronger upregulation than 800 ppb. Immunostaining for CYP2C subfamily expression confirmed protein expression and showed localization in both myocardium and endothelium. TCE exposure increased protein expression in both tissues. These data demonstrate that the earliest embryonic expression of phase I detoxification enzymes is in the developing heart. Expression of these CYPs is likely to be relevant to the susceptibility of the developing heart to environmental teratogens.

Altered expression of hepatic metabolic enzyme and apoptosis-related gene transcripts in human hepatocytes treated with trichloroethylene

Trichloroethylene (TCE) is a common organic solvent that has been widely used in industrial applications. Hundred cases of allergic reactions occurred after the workers were occupationally exposed to TCE in China in the past decade, but the underlying effector mechanisms of TCE remain unclear. The purpose of the present study is to examine the alteration of hepatic metabolic enzyme gene and apoptosis-related gene messenger RNA (mRNA) expression in L02 human hepatocytes (L02 cells) after treatment with TCE. L02 cells were cultured either with various doses of TCE (0.25, 0.5, 1.0 and 2.0 mmol/L) for 24 h or with a single dose of TCE (1.0 mmol/L) for different time intervals, whereas samples treated with dimethyl sulfoxide served as control. Quantitative real-time polymerase chain reaction analysis was performed to detect the mRNA expression of hepatic metabolic enzyme genes (CYP1A2, CYP3A4 and CYP2E1) and apoptosis-related genes (BAX and BAD). It was found that the transcript levels of hepatic metabolic enzyme genes and apoptosis genes including BAX and BAD were significantly increased after TCE treatment at various doses for 24 h when compared with controls. Additionally, when the cells were treated with a single dose of TCE (1.0 mmol/L) for different periods of time (3, 6, 12 and 24 h), the mRNA expression of these genes also increased significantly compared with control (p < 0.05 or p < 0.01). The conclusion of the study is that TCE could induce alteration of mRNA expression of hepatic metabolic enzyme genes and apoptosis genes, which might be implicated in the effector mechanisms of TCE cytotoxicity in vivo.

Postnatal exposure to trichloroethylene alters glutathione redox homeostasis, methylation potential, and neurotrophin expression in the mouse hippocampus

Previous studies have shown that continuous exposure throughout gestation until the juvenile period to environmentally relevant doses of trichloroethylene (TCE) in the drinking water of MRL+/+ mice promoted adverse behavior associated with glutathione depletion in the cerebellum indicating increased sensitivity to oxidative stress. The purpose of this study was to extend our findings and further characterize the impact of TCE exposure on redox homeostasis and biomarkers of oxidative stress in the hippocampus, a brain region prone to oxidative stress. Instead of a continuous exposure, the mice were exposed to water only or two environmentally relevant doses of TCE in the drinking water postnatally from birth until 6 weeks of age. Biomarkers of plasma metabolites in the transsulfuration pathway and the transmethylation pathway of the methionine cycle were also examined. Gene expression of neurotrophins was examined to investigate a possible relationship between oxidative stress, redox imbalance and neurotrophic factor expression with TCE exposure. Our results show that hippocampi isolated from male mice exposed to TCE showed altered glutathione redox homeostasis indicating a more oxidized state. Also observed was a significant, dose dependent increase in glutathione precursors. Plasma from the TCE treated mice showed alterations in metabolites in the transsulfuration and transmethylation pathways indicating redox imbalance and altered methylation capacity. 3-Nitrotyrosine, a biomarker of protein oxidative stress, was also significantly higher in plasma and hippocampus of TCE-exposed mice compared to controls. In contrast, expression of key neurotrophic factors in the hippocampus (BDNF, NGF, and NT-3) was significantly reduced compared to controls. Our results demonstrate that low-level postnatal and early life TCE exposure modulates neurotrophin gene expression in the mouse hippocampus and may provide a mechanism for TCE-mediated neurotoxicity.

Biodegradation of tri- and perchloroethylene in sewage waters and soils by a microbial consortium of compost and phototrophic bacteria

Compost and phototrophic bacteria are found to be able to degrade trichloroethylene (TCE) and perchloroethylene (PCE). With a TCE dose increase by more than 10 mg/kg, the TCE degradation decreases due to the toxic effect of this pollutant on microbial consortium activity. The addition of compost combined with a liquid culture of phototrophic bacteria (PTB) is experimentally proved to effectively decrease the TCE content in soil and water.

Gene expression profiling in the fetal cardiac tissue after folate and low‐dose trichloroethylene exposure

Previous studies show gene expression alterations in rat embryo hearts and cell lines that correspond to the cardio-teratogenic effects of trichloroethylene (TCE) in animal models. One potential mechanism of TCE teratogenicity may be through altered regulation of calcium homeostatic genes with a corresponding inhibition of cardiac function. It has been suggested that TCE may interfere with the folic acid/methylation pathway in liver and kidney and alter gene regulation by epigenetic mechanisms. According to this hypothesis, folate supplementation in the maternal diet should counteract TCE effects on gene expression in the embryonic heart. To identify transcriptional targets altered in the embryonic heart after exposure to TCE, and possible protective effects of folate, we used DNA microarray technology to profile gene expression in embryonic mouse hearts with maternal TCE exposure and dietary changes in maternal folate. Exposure to low doses of TCE (10 ppb) caused extensive alterations in transcripts encoding proteins involved in transport, ion channel, transcription, differentiation, cytoskeleton, cell cycle, and apoptosis. Exogenous folate did not offset the effects of TCE exposure on normal gene expression, and both high and low levels of folate produced additional significant changes in gene expression. A mechanism by which TCE induces a folate deficiency does not explain altered gene expression patterns in the embryonic mouse heart. The data further suggest that use of folate supplementation, in the presence of this toxin, may be detrimental and not protective of the developing embryo.

USE OF NATIVE PLANTS FOR REMEDIATION OF TRICHLOROETHYLENE: II. CONIFEROUS TREES

The phytoremediation of trichloroethylene (TCE) from contaminated groundwater has been extensively studied using the hybrid poplar tree (Populus spp.). Several metabolites of TCE have been identified in the tissue of poplar including trichloroethanol (TCEOH) and dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA). In addition to the use of hybrid poplar for the phytoremediation of TCE, it is important to screen native tree species that could be successful candidates for field use. This study involves a greenhouse-based comparison of four different native southeastern conifers to a hybrid poplar species for their potential to phytoremediate TCE through the analysis of various plant tissues for TCE and major TCE metabolites, as well as several growth parameters that are desirable for phytoremediation. Longleaf pine (Pinus palustris), Leyland cypress (X Cupressocyparis leylandii), two varieties of Loblolly pine (Pinus taeda), and hybrid poplar species H11-11 (Populus trichocarpa x deltoides) were examined for the concentration of TCE and its metabolites in their tissue following treatment with either a low (50 mg L−1) or high dose of TCE (150 mg L−1) for 2 mo. The amount of water taken up, change in height of the tree, TCE transpiration, and total fresh weight of various tissue types were also measured. All trees contained detectable levels of TCE in their root and stem tissue. TCEOH was found only in the tissue of longleaf pine, suggesting that TCE metabolism was occurring in this tree. TCAA was only detected in the leaves of hybrid poplar and piedmont loblolly pine. Conifers took up less water over the 2-mo treatment period than hybrid poplar and grew at a slower rate. However, phytoremediation field sites may benefit from the evergreen's ability to transpire water throughout the winter months.

An investigation of hormesis of trichloroethylene in L-02 liver cells by differential proteomic analysis

Hormesis is the dose-response pattern of the biological responses to toxic chemicals, characterized by low-dose stimulation and high-dose inhibition. Although it is known that some cell types exhibit an adaptive response to low levels of cytotoxic agents, its molecular mechanism is still unclear and it has yet to be established whether this is a universal phenomenon that occurs in all cell types in response to exposure to every chemical. Trichloroethylene (TCE) is an organic solvent widely used and is released into the atmosphere from industrial degreasing operations. Acute (short-term) and chronic (long-term) inhalation exposure to trichloroethylene can affect the human health. In order to elucidate a cell-survival adaptive response of L-02 liver cells exposed to low dose of TCE, CCK-8 assay was used to assess cytotoxicity, and examined the possible mechanisms of hormesis by proteomics technology. We found that exposure of L-02 liver cells to low level of TCE resulted in adaptation to further exposure to higher level, about 1,000 protein-spots were obtained by two-dimensional electrophoresis (2-DE) and five protein spots were identified by matrix-assisted laser desorption/ionization mass spectrometry and tandem mass spectrometry sequencing of tryptic peptides. Our results suggest that a relationship may exist between identified proteins and TCE-induced hormesis, which are very useful for further study of the mechanism and risk assessment of TCE.

Trichloroethylene Disrupts Cardiac Gene Expression and Calcium Homeostasis in Rat Myocytes

We have been investigating the molecular mechanisms by which trichloroethylene (TCE) might induce cardiac malformations in the embryonic heart. Previous results indicated that TCE disrupted expression of genes encoding proteins involved in regulation of intracellular Ca2+, [Ca2+](i), in cardiac cells, including ryanodine receptor isoform 2 (Ryr2), and sarcoendoplasmatic reticulum Ca2+ ATPase, Serca2a. These observations are important in light of the notion that altered cardiac contractility can produce morphological defects. The hypothesis tested in this study is that the TCE-induced changes in gene expression of Ca2+-associated proteins resulted in altered Ca2+ flux regulation. We used real-time PCR and digital imaging microscopy to characterize effects of various doses of TCE on gene expression and Ca2+ response to vasopressin (VP) in rat cardiac H9c2 myocytes. We observed a reduction in Serca2a and Ryr2 expression at 12 and 48 h after exposure to TCE. In addition, we found significant differences in Ca2+ response to VP in cells treated with TCE doses as low as 10 parts per billion. Taken all together, our data strongly indicate that exposure to TCE disrupts the ability of myocytes to regulate cellular Ca2+ fluxes. Perturbation of calcium signaling alters cardiac cell physiology and signal transduction and may hint to morphogenetic consequences in the context of heart development. These results point to a novel area of TCE biology and, if confirmed in vivo, may help to explain the apparent cardio-specific toxicity of TCE exposure in the rodent embryo.

In situ derivatization/solid‐phase microextraction coupled with gas chromatography/negative chemical ionization mass spectrometry for the determination of trichloroethylene metabolites in rat blood

An in situ derivatization solid-phase microextraction (SPME) method has been developed for the determination of the trichloroethylene (TCE) metabolites, trichloroacetic acid (TCA), dichloroacetic acid (DCA) and trichloroethanol (TCOH), in rat blood. The analytical procedure involves derivatization of TCA and DCA to their ethyl esters with acidic ethanol, headspace sampling using SPME, and gas chromatography/negative chemical ionization mass spectrometry (GC/NCI-MS) determination. Parameters affecting both derivatization efficiency and the headspace SPME procedure, such as the concentration of sulfuric acid, amount of ethanol, derivatization-extraction temperature and time, sample preheating time, agitator speed and desorption conditions, were optimized. The method showed good linearity over the range of 1-1000 ng/mL in rat blood for each metabolite with correlation coefficients (R(2)) higher than 0.99. The intra-day and inter-day precision and accuracy were less than 10%. The relative recoveries for all analytes were greater than 84%. Validation results demonstrated that selected ion monitoring of the (35)Cl and (37)Cl isotopes using NCI resulted in reliable and sensitive quantitation of all three TCE metabolites. This validated method was successfully applied to study the toxicokinetic behavior of TCE metabolites following a 1 mg/kg oral dose of TCE.