Cytotoxicity and genotoxicity evaluation of chloroform using Vicia faba roots

Chloroform is a widely used industrial chemical that can also pollute the environment. The aims of this study were to examine the potential cytotoxicity and genotoxicity of chloroform on plant cells, using the Vicia faba bioassay. Chloroform was evaluated at concentrations of 0.1, 0.5, 1, 2, and 5 mg·L-1. The following parameters were analyzed: the mitotic index (MI), micronucleus (MN) frequency, chromosomal aberration (CA) frequency, and malondialdehyde (MDA) content. The results showed that exposure to increasing concentrations of chloroform caused a decrease in MI and an increase in the frequency of MN in Vicia faba root tip cells, relative to their controls. Moreover, various types of CA, including C-mitosis, fragments, bridges, laggard chromosomes, and multipolar mitosis, were observed in the treated cells. The frequency of MN was positively correlated with the frequency of CA in exposure to 0.1-1 mg·L-1 chloroform. Furthermore, chloroform exposure induced membrane lipid peroxidation damage in the Vicia faba radicle, and a linear correlation was observed between the MDA content and the frequency of MN or CA. These findings indicated that chloroform exposure can result in oxidative stress, cytotoxicity, and genotoxicity in plant cells.

Physiological and biochemical responses of Mediterranean green crab, Carcinus aestuarii, to different environmental stressors: Evaluation of hemocyte toxicity and its possible effects on immune response

Effects of natural stressors such as copper (Cu²⁺), temperature, hypoxia, chloroform and adrenaline on physiological and biochemical responses were investigated in the Mediterranean green crab Carcinus aestuarii from tidal shallow waters of Narta Lagoon, Albania. For this purpose, hemolymph glucose levels, total and differential hemocyte count, in normal and eye-stalked individuals, exposed to above mentioned stressors like, were assessed. In addition, lysosomal membrane stability was evaluated as biomarker of hemocyte toxicity, with possible implications on crab immune response. Hemolymph glucose levels were significantly increased in all treatment groups with 1.25-to 3.5-fold above baseline levels of 37.8 ± 2.7 mgdL^-1. Response times were being manifested within 30-120 min following exposure and recovery happened within 2 h of restoration of pretreatment conditions. Total hemocyte count (THC) and differential hemocyte count (DCH) showed a significant decrease for all stressors, except for copper, were an increase of semi-granular hemocyte fraction were recorded. Meanwhile, significant reduction of neutral red retention time (NRRT), in both eyestalk-ablated and exposed animals, were recorded, indicated the loss of hemocyte lysosomal membrane integrity. The responsiveness of hemolymph blood levels to all stressors, the decrease in total hemocyte count, as well as the loss of lysosomal membrane integrity demonstrated that exposure to environmentally realistic stressors placed a heavy metabolic load on C. aestuarii, modulating their immune competence and overall physiological wellness. Overall, results suggest that monitoring cellular and biochemical parameters like hemolymph glucose titres, TCH, DHC and NRRT, may be useful and sensitive means of evaluating the crustacean's ability to cope with the wide variety of environmental stressors through modulation of the immune parameters.

Co-expression network analysis of lncRNAs and mRNAs in rat liver tissue reveals the complex interactions in response to pathogenic cytotoxicity

Liver is one of the most vital organs to maintain homeostasis because of its peculiar detoxification functionalities to detoxify chemicals and metabolize drugs and toxins. Due to its crucial functions, the liver is also prone to various diseases, i.e., hepatitis, cirrhosis and hepatoma, etc. Additionally, long non-coding RNAs (lncRNAs) has emerged as key regulators which are found to play important roles in transcription, splicing, translation, replication, chromatin shaping and post translational modification of proteins in living cells. However, the underlying mechanisms of biological processes mediated by lncRNA remain unclear. Here, with the aim of disclosing potential lncRNAs implicated in the biological processes in liver in response to cytotoxicity, we performed a co-expression network analysis based on the transcriptome data of the damaged liver tissue of Rattus norvegicus induced by three cytotoxic compounds (carbon tetrachloride, chloroform and thioacetamide). Our analysis unveils that many biological processes and pathways were collectively affected by the three cytotoxic compounds, including drug metabolism, oxidation-reduction process, oxidative stress, glucuronidation, liver development and flavonoid biosynthetic process, etc. Also, our network analysis has identified several highly conserved lncRNA-mRNA interactions participating in those correlated processes and pathways, implying their potential roles in response to the induced cytotoxicity in liver. Our study provides new insights into lncRNA-mRNA regulatory mechanisms in response to pathogenic cytotoxic damaging in liver and facilitates the development of lncRNA-oriented therapies for hepatic diseases in the future.

Environmental risk appraisement of disinfection by-products (DBPs) in plant model system: Allium cepa

The organic toxicants formed in chlorinated water cause potential harm to human beings, and it is extensively concentrated all over the world. Various disinfection by-products (DBPs) occur in chlorinated water are genotoxic and carcinogenic. The toxicity is major concern for chlorinated DBPs which has been present more in potable water. The purpose of the work was to evaluate genotoxic properties of DBPs in Allium cepa as a plant model system. The chromosomal aberration and DNA laddering assays were performed to examine the genotoxic effect of trichloroacetic acid (TCAA), trichloromethane (TCM), and tribromomethane (TBM) in a plant system with distinct concentrations, using ethyl methanesulfonate (EMS) as positive control and tap water as negative control. In Allium cepa root growth inhibition test, the inhibition was concentration dependent, and EC₅₀ values for trichloroacetic acid (TCAA), trichloromethane (TCM), and tribromomethane (TBM) were 100 mg/L, 160 mg/L, and 120 mg/L respectively. In the chromosome aberration assay, root tip cells were investigated after 120 h exposure. The bridge formation, sticky chromosomes, vagrant chromosomes, fragmented chromosome, c-anaphase, and multipolarity chromosomal aberrations were seen in anaphase-telophase cells. It was noticed that with enhanced concentrations of DBPs, the total chromosomal aberrations were more frequent. The DNA damage was analyzed in roots of Allium cepa exposed with DBPs (TCAA, TCM, TBM) by DNA laddering. The biochemical assays such as lipid peroxidation, H₂O₂ content, ascorbate peroxidase, guaiacol peroxidase, and catalase were concentration dependent. The DNA interaction studies were performed to examine binding mode of TCAA, TCM, and TBM with DNAs. The DNA interaction was evaluated by spectrophotometric and spectrofluorometric studies which revealed that TCAA, TCM, and TBM might interact with Calf thymus DNA (CT- DNA) by non-traditional intercalation manner.

Toxicological aspects of trihalomethanes: a systematic review

Chlorine is considered the most used chemical agent for water disinfection worldwide. However, water chlorination can lead to by-product generation which can be toxic to humans. The present study aimed to perform a systematic review on the toxicity of trihalomethanes (THMs) through bioindicators of cytotoxicity, genotoxicity, and mutagenicity. The results showed that studies on the effects of THMs on DNA are a current research concern for evaluating the toxicity of the pure compounds and real samples involving several types including water for recreational use, reused water, and drinking water. THMs deleterious effects have been assessed using several biosystems, where the Ames test along with experimental animal models were the most cited. A wide range of THM concentrations have been tested. Nevertheless, DNA damage was demonstrated, highlighting the potential human health risk. Among the studied THMs, chloroform presented a different action mechanism when compared with brominated THMs, with the former being cytotoxic while brominated THMs (bromodichloromethane, bromoform, and dibromochloromethane) were cytotoxic, genotoxic, and mutagenic. The described evidence in this research highlights the relevance of this topic as a human health issue. Nevertheless, research aimed to represent THMs current exposure conditions in a more accurate way would be needed to understand the real impact on human health.

Ames and random amplified polymorphic DNA tests for the validation of the mutagenic and/or genotoxic potential of the drinking water disinfection by-products chloroform and bromoform

Chloroform and Bromoform are two abundant trihalomethanes found in Algerian drinking water. The investigation of the mutagenic hazard of these disinfection by-products was studied by Ames test as prokaryotic bioassay to show their mutagenic effects. For this, Salmonella typhimurium TA98 and TA100 strains were employed. Both chloroform and bromoform showed a direct mutagenic effect since the number of revertant colonies gradually increase in dose-dependent manner with all concentrations tested with the two bacterial strains and these were both in the absence and presence of S9 metabolic activation. The genotoxic hazard was also studied by random amplified polymorphic DNA test on the root cells of Allium cepa as eukaryotic bioassay. DNA extracted from the roots of the onion were incubated at different concentrations of chloroform and bromoform and then amplified by polymerase chain reaction. This was based on demonstrating a major effect of disappearance of bands compared to roots incubated in the negative control (distilled water). The results showed that these two compounds affected genomic DNA by breaks although by mutations.

Gene expression changes in blood RNA after swimming in a chlorinated pool

Exposure to disinfection by-products (DBP) such as trihalomethanes (THM) in swimming pools has been linked to adverse health effects in humans, but their biological mechanisms are unclear. We evaluated short-term changes in blood gene expression of adult recreational swimmers after swimming in a chlorinated pool. Volunteers swam 40min in an indoor chlorinated pool. Blood samples were drawn and four THM (chloroform, bromodichloromethane, dibromochloromethane and bromoform) were measured in exhaled breath before and after swimming. Intensity of physical activity was measured as metabolic equivalents (METs). Gene expression in whole blood mRNA was evaluated using IlluminaHumanHT-12v3 Expression-BeadChip. Linear mixed models were used to evaluate the relationship between gene expression changes and THM exposure. Thirty-seven before-after pairs were analyzed. The median increase from baseline to after swimming were: 0.7 to 2.3 for MET, and 1.4 to 7.1μg/m³ for exhaled total THM (sum of the four THM). Exhaled THM increased on average 0.94μg/m³ per 1 MET. While 1643 probes were differentially expressed post-exposure. Of them, 189 were also associated with exhaled levels of individual/total THM or MET after False Discovery Rate. The observed associations with the exhaled THM were low to moderate (Log-fold change range: -0.17 to 0.15). In conclusion, we identified short-term gene expression changes associated with swimming in a pool that were minor in magnitude and their biological meaning was unspecific. The high collinearity between exhaled THM levels and intensity of physical activity precluded mutually adjusted models with both covariates. These exploratory results should be validated in future studies.

Synergistic mitotoxicity of chloromethanes and fullerene C60 nanoaggregates in Daphnia magna midgut epithelial cells

Adsorption of non-polar compounds by suspended fullerene nanoaggregates (nC₆₀) may enhance their toxicity and affect the fate, transformation, and transport of non-polar compounds in the environment. The potential of stable fullerene nanoaggregates as contaminant carriers in aqueous systems and the influence of chloromethanes (trichloromethane and dichloromethane) were studied on the midgut epithelial cells of Daphnia magna by light and electron microscopy. The size and shape of fullerene nanoaggregates were observed and measured using dynamic light scattering, transmission electron microscopy, and low vacuum scanning electron microscopy. The nC₆₀ in suspension appeared as a bulk of aggregates of irregular shape with a surface consisting of small clumps 20-30 nm in diameter. The presence of nC₆₀ aggregates was confirmed in midgut lumen and epithelial cells of D. magna. After in vivo acute exposure to chloromethane, light and electron microscopy revealed an extensive cytoplasmic vacuolization with disruption and loss of specific structures of D. magna midgut epithelium (mitochondria, endoplasmic reticulum, microvilli, peritrophic membrane) and increased appearance of necrotic cells. The degree of observed changes depended on the type of treatment: trichloromethane (TCM) induced the most notable changes, whereas fullerene nanoaggregates alone had no negative effects. Transmission electron microscopy also indicated increased lysosomal degradation and severe peroxidative damages of enterocyte mitochondria following combined exposure to chloromethane and fullerene nanoaggregates. In conclusion, the adsorption of chloromethane by fullerene nanoaggregates enhances their toxicity and induces peroxidative mitochondrial damage in midgut enterocytes.

Effect of trihalomethanes (chloroform and bromoform) on human haematological count

With the increasing concerns about the harmful effects of disinfection products, the process of chlorination is becoming questionable. Bromoform and chloroform are among the most frequently occurring disinfection by-products. Haematological parameters are an important indicator of human well-being which is why the prime objective of the current study was to conduct a dose-response assessment to investigate the effects of trihalomethanes on human haematological count. Blood samples of healthy subjects were exposed to different concentrations (10, 30 and 50 μg/mL) of chloroform and bromoform in vitro to analyse how these compounds affected the haematological count with increasing dose concentrations. Headspace gas chromatography analysis was also conducted on samples to assess the difference between measured and spiked values of doses. The results indicated that the damage caused by bromoform was statistically more significant as compared to chloroform. Haemoglobin (HGB) and mean corpuscular haemoglobin concentration levels lowered as they were significantly affected (p < 0.05) by bromoform at all administered doses. It also significantly damaged platelet level at doses of 30 (p < 0.05) and 50 μg/mL (p < 0.01). Conversely, the damage caused by chloroform was statistically less significant (p > 0.05).

[Genetically determined lipid metabolism disorders due to oral intake of technogenic hyperchlorination products]

The study covered genetically determined lipid metabolism disorders due to oral intake of technogenic hyperchlorination drinkable water products. Findings are that overweight and obese children in a main group appeared to have serum chloroform level 2.3 times higher than that in a reference group. In oral intake of hyperchlorination drinkable water products, the study revealed main genes having polymorphism associated with endocrine disorders: overweight and obesity--APOE, PPARG, HTR2A, characterizing antioxidant system state--SOD2 and detoxication--SULTA. Polymorphism of candidate genes HTR2A and SOD2 was characterized by increased occurrence of mutant homo-- and heterozygous genotype, relative risk of pathologic allele presence in population exceeded the refrence group values. Probability of increased serum serotonin and lower Cu/Zn in children with mutant homozygous genotype HTR2A and SOD2 is 1.2-1.3 times higher than in those with heterozygous and normal homozygous genotypes.

The occurrence of disinfection by-products in municipal drinking water in China's Pearl River Delta and a multipathway cancer risk assessment

Disinfection byproducts were measured in the finished drinking water from ten water treatment plants in three Chinese cities - Guangzhou, Foshan and Zhuhai. A total of 155 water samples were collected in 2011 and 2012. The median (range) of trihalomethane (THM) and haloacetic acid (HAA) levels were 17.7 (0.7-62.7) μg/L and 8.6 (0.3-81.3) μg/L, respectively. Chloroform, dichloroacetic acid and trichloroacetic acid were the dominant species observed in Guangzhou and Foshan water, while brominated THMs predominated in water from Zhuhai. Haloacetonitriles, haloketones, chloral hydrate and trichloronitromethane were usually detected at levels ranging from unquantifiable (<0.2μg/L) to 12.2μg/L (choral hydrate). THMs and HAAs showed clear seasonal variations with the total concentrations higher in winter than in summer. Correlations among DBP levels varied, with the strongest linear correlation observed between chloroform and chloral hydrate levels (R(2)=0.77). The risk of cancer from ingestion, inhalation and dermal contact exposure to THMs was estimated. CHCl2Br contributed the highest percentage of the cancer risk from ingestion pathway and CHCl3 contributed the highest of cancer risk from inhalation pathway.

Reaction of benzophenone UV filters in the presence of aqueous chlorine: kinetics and chloroform formation

The transformation of two benzophenone UV filters (Oxybenzone and Dioxybenzone) was examined over the pH range 6-11 in the presence of excess aqueous chlorine. Under these conditions, both UV filters were rapidly transformed by aqueous chlorine just above circumneutral pH while transformation rates were significantly lower near the extremes of the pH range investigated. Observed first-order rate coefficients (k(obs)) were obtained at each pH for aqueous chlorine concentrations ranging from 10 to 75 μM. The k(obs) were used to determine the apparent second-order rate coefficient (k(app)) at each pH investigated as well as determine the reaction order of aqueous chlorine with each UV filter. The reaction of aqueous chlorine with either UV filter was found to be an overall second-order reaction, first-order with respect to each reactant. Assuming elemental stoichiometry described the reaction between aqueous chlorine and each UV filter, models were developed to determine intrinsic rate coefficients (k(int)) from the k(app) as a function of pH for both UV filters. The rate coefficients for the reaction of HOCl with 3-methoxyphenol moieties of oxybenzone (OXY) and dioxybenzone (DiOXY) were k(1,OxY) = 306 ± 81 M⁻¹s⁻¹ and k(1,DiOxY) = 154 ± 76 M⁻¹s⁻¹, respectively. The k(int) for the reaction of aqueous chlorine with the 3-methoxyphenolate forms were orders of magnitude greater than the un-ionized species, k(2,OxY) = 1.03(±0.52) × 10⁶ M⁻¹s⁻¹ and k(2_1,DiOxY) = 4.14(±0.68) × 10⁵ M⁻¹s⁻¹. Also, k(int) for the reaction of aqueous chlorine with the DiOXY ortho-substituted phenolate moiety was k(2_2,DiOxY) = 2.17(±0.30) × 10³ M⁻¹s⁻¹. Finally, chloroform formation potential for OXY and DiOXY was assessed over the pH range 6-10. While chloroform formation decreased as pH increased for OXY, chloroform formation increased as pH increased from 6 to 10 for DiOXY. Ultimate molar yields of chloroform per mole of UV filter were pH dependent; however, chloroform to UV filter molar yields at pH 8 were 0.221 CHCl₃/OXY and 0.212 CHCl₃/DiOXY.

Trihalomethanes in Lisbon indoor swimming pools: occurrence, determining factors, and health risk classification

Characterization of water quality from indoor swimming pools, using chorine-based disinfection techniques, was performed during a 6-mo period to study the occurrence, distribution, and concentration factors of trihalomethanes (THM). Several parameters such as levels of water THM, water and air chloroform, water bromodichloromethane (BDCM), water dibromochloromethane (DBCM), water bromoform (BF), free residual chlorine (FrCl), pH, water and air temperature, and permanganate water oxidizability (PWO) were determined in each pool during that period. Chloroform (CF(W)) was the THM detected at higher concentrations in all pools, followed by BDCM, DBCM, and BF detected at 99, 34, and 6% of the samples, respectively. Water THM concentrations ranged from 10.1 to 155 μg/L, with 6.5% of the samples presenting values above 100 μg/L (parametric value established in Portuguese law DL 306/2007). In this study, air chloroform (CF(Air)) concentrations ranged from 45 to 373 μg/m³ with 24% of the samples presenting values above 136 μg/m³ (considered high exposure value). Several significant correlations were observed between total THM and other parameters, namely, CF(W), CF(Air), FrCl, water temperature (T(W)), and PWO. These correlations indicate that FrCl, T(W) and PWO are parameters that influence THM formation. The exposure criterion established for water THM enabled the inclusion of 67% of Lisbon pools in the high exposure group, which reinforces the need for an improvement in pool water quality.

Mass spectrometry-based quantification of myocardial protein adducts with acrolein in an in vivo model of oxidative stress

Acrolein (ACR) exposure leads to the formation of protein-ACR adducts. Protein modification by ACR has been associated with various chronic diseases including cardiovascular and neurodegenerative diseases. Here, we report an analytical strategy that enables the quantification of Michael-type protein adducts of ACR in mitochondrial proteome samples using liquid chromatography in combination with tandem mass spectrometry and selected ion monitoring (LC-MS/MS SRM) analysis. Our approach combines site-specific identification and relative quantification at the peptide level of protein-ACR adducts in relation to the unmodified protein thiol pool. Treatment of 3-month-old rats with CCl(4) , an established in vivo model of acute oxidative stress, resulted in significant increases in the ratios of distinct ACR-adducted peptides to the corresponding unmodified thiol-peptides obtained from proteins that were isolated from cardiac mitochondria. The mitochondrial proteins that were found adducted by ACR were malate dehydrogenase, NADH dehydrogenase [ubiquinone] flavoprotein 1, cytochrome c oxidase subunit VIb isoform 1, ATP synthase d chain, and ADP/ATP translocase 1. The findings indicate that protein modification by ACR has potential value as an index of mitochondrial oxidative stress.

A Bayesian approach to probabilistic ecological risk assessment: risk comparison of nine toxic substances in Tokyo surface waters

BACKGROUND, AIM, AND SCOPE

Quantitative risk comparison of toxic substances is necessary to decide which substances should be prioritized to achieve effective risk management. This study compared the ecological risk among nine major toxic substances (ammonia, bisphenol-A, chloroform, copper, hexavalent chromium, lead, manganese, nickel, and zinc) in Tokyo surface waters by adopting an integrated risk analysis procedure using Bayesian statistics.

METHODS

Species sensitivity distributions of these substances were derived by using four Bayesian models. Environmental concentration distributions were derived by a hierarchical Bayesian model that explicitly considered the differences between within-site and between-site variations in environmental concentrations. Medians and confidence intervals of the expected potentially affected fraction (EPAF) of species were then computed by the Monte Carlo method.

RESULTS

The estimated EPAF values suggested that risk from nickel was highest and risk from zinc and ammonia were also high relative to other substances. The risk from copper was highest if bioavailability was not considered, although toxicity correction by a biotic ligand model greatly reduced the estimated risk. The risk from manganese was highest if a conservative risk index estimate (90% upper EPAF confidence limit) was selected.

CONCLUSION

It is suggested that zinc is not a predominant risk factor in Tokyo surface waters and strategic efforts are required to reduce the total ecological risk from multiple substances. The presented risk analysis procedure using EPAF and Bayesian statistics is expected to advance methodologies and practices in quantitative ecological risk comparison.

Effect of classic methanogenic inhibitors on the quantity and diversity of archaeal community and the reductive homoacetogenic activity during the process of anaerobic sludge digestion

In this study, the microbial response of anaerobic sludge digestion to the addition of two classic methanogenic inhibitors (chloroform, 2-bromoethanesulfonate) was investigated. Both the toxicants showed their effectiveness on CH(4) production, whereas the hydrogen responses and acetate accumulations were elicited to different extent. Terminal restriction fragment length polymorphism analyses in combination with clone library showed that both toxicants inhibited not only methanogenic activity but the structure of methanogenic communities. The acetoclastic Methanosaetaceae was more sensitive than hydrogenotrophic Methanobacteriales and Methanomicrobiales. Interestingly, as reflected by the favorable thermodynamic condition and the increase of formyltetrahydrofolate synthetase (fhs) gene copy numbers, reductive homoacetogenesis from H(2)/CO(2) was also stimulated by selective inhibition of methanogenesis with 2-bromoethanesulfonate (BES).

Cancer risk disparities between hispanic and non-hispanic white populations: the role of exposure to indoor air pollution

BACKGROUND

Hispanics are the fastest growing minority group in the United States; however, minimal information is available on their cancer risks from exposures to hazardous air pollutants (HAPs) and how these risks compare to risks to non-Hispanic whites.

METHODS

We estimated the personal exposure and cancer risk of Hispanic and white adults who participated in the Relationships of Indoor, Outdoor, and Personal Air (RIOPA) study. We evaluated 12 of the sampled volatile organic compounds and carbonyls and identified the HAPs of most concern and their possible sources. Furthermore, we examined sociodemographic factors and building characteristics.

RESULTS

Cumulative cancer risks (CCRs) estimated for Hispanics (median = 519 x 10(-6), 90th percentile = 3,968 x 10(-6)) and for whites (median = 443 x 10(-6), 90th percentile = 751 x 10(-6)) were much greater than the U.S. Environmental Protection Agency (EPA) benchmark of 10(-6). Cumulative risks were dominated by formaldehyde and p-dichlorobenzene (p-DCB) and, to a lesser extent, by acetaldehyde, chloroform, and benzene. Exposure to all of these compounds except benzene was primarily due to indoor residential sources. Hispanics had statistically higher CCRs than did whites (p </= 0.05) because of differences in exposure to p-DCB, chloroform, and benzene. Formaldehyde was the largest contributor to CCR for 69% of Hispanics and 88% of whites. Cancer risks for pollutants emitted indoors increased in houses with lower ventilation rates.

CONCLUSIONS

Hispanics appear to be disproportionately affected by certain HAPs from indoor and outdoor sources. Policies that aim to reduce risk from exposure to HAPs for the entire population and population subgroups should consider indoor air pollution.

[Carcinogenic hazard of chloroform and other drinking water chlorination by-products]

The paper presents the results of studying the carcinogenic effect of chloroform and its combination with carbon tetrachloride, 1,2-dichloroethane, trichloroethylene during chronic oral administration to F1(CBAxC57Bl6) mice. There is a relationship between the manifestation of carcinogenesis to the dose of chloroform and a combination of chemicals, as well as its enhancement upon exposure to the combination as compared with acute administration of chloroform. Exposure to a combination of substances at the level of their maximum permissible concentrations does not affect carcinogenesis. The possible mechanisms of the specific features of carcinogenesis in this experiment are discussed.

Computational toxicology of chloroform: reverse dosimetry using Bayesian inference, Markov chain Monte Carlo simulation, and human biomonitoring data

BACKGROUND

One problem of interpreting population-based biomonitoring data is the reconstruction of corresponding external exposure in cases where no such data are available.

OBJECTIVES

We demonstrate the use of a computational framework that integrates physiologically based pharmacokinetic (PBPK) modeling, Bayesian inference, and Markov chain Monte Carlo simulation to obtain a population estimate of environmental chloroform source concentrations consistent with human biomonitoring data. The biomonitoring data consist of chloroform blood concentrations measured as part of the Third National Health and Nutrition Examination Survey (NHANES III), and for which no corresponding exposure data were collected.

METHODS

We used a combined PBPK and shower exposure model to consider several routes and sources of exposure: ingestion of tap water, inhalation of ambient household air, and inhalation and dermal absorption while showering. We determined posterior distributions for chloroform concentration in tap water and ambient household air using U.S. Environmental Protection Agency Total Exposure Assessment Methodology (TEAM) data as prior distributions for the Bayesian analysis.

RESULTS

Posterior distributions for exposure indicate that 95% of the population represented by the NHANES III data had likely chloroform exposures < or = 67 microg/L [corrected] in tap water and < or = 0.02 microg/L in ambient household air.

CONCLUSIONS

Our results demonstrate the application of computer simulation to aid in the interpretation of human biomonitoring data in the context of the exposure-health evaluation-risk assessment continuum. These results should be considered as a demonstration of the method and can be improved with the addition of more detailed data.

Difficulty of mode of action determination for trichloroethylene: An example of complex interactions of metabolites and other chemical exposures

The mode(s) of action (MOA) of a pollutant for adverse health effects may be dependent on the mixture of metabolites resulting from exposure to a single agent and may also be affected by coexposure to pollutants that have similar targets or affected pathways. Trichloroethylene (TCE) can be an useful example for illustration of the complexity coexposure can present to elucidation of the MOA of an agent. TCE exposure has been associated with increased risk of liver and kidney cancer in both laboratory animal and epidemiologic studies. There are a number of TCE metabolites that could play a role in the induction of these effects. Coexposures of other chemicals with TCE typically occurs as a result of environmental cocontamination that include its own metabolites, such as trichloroacetic acid, dichloroacetic acid, and other pollutants with similar metabolites such as perchloroethylene. Behaviors such as alcohol consumption can also potentially modify TCE toxicity through similar MOAs. The U.S. Environmental Protection Agency (EPA)'s 2001 draft TCE risk assessment, Trichloroethylene (TCE) Health Risk Assessment: Synthesis and Characterization, concluded that it was difficult to determine which of the metabolites of TCE may be responsible for these effects, what key events in their hypothesized MOAs are involved, and the relevance of some of the hypothesized MOAs to humans. Since the publication of U.S. EPA's draft TCE assessment, several studies have been conducted to understand the effects of coexposures to TCE. They cover both pharmacodynamic and pharmacokinetic considerations. This article highlights some of the recently published scientific literature on toxicological interactions between TCE, its metabolites, and other coexposures, including solvents, haloacetates, and ethanol. These studies give insight into both the potential MOAs of TCE exposure itself and putative modulators of TCE toxicity, and illustrate the difficulties encountered in determining the MOAs and modulators of toxicity for pollutants with such complex metabolism and coexposures.

Cancer risk assessment from exposure to trihalomethanes in tap water and swimming pool water

We investigated the concentration of trihalomethanes (THMs) in tap water and swimming pool water in the area of the Nakhon Pathom Municipality during the period April 2005-March 2006. The concentrations of total THMs, chloroform, bromodichloromethane, dibromochloromethane and bromoform in tap water were 12.70-41.74, 6.72-29.19, 1.12-11.75, 0.63-3.55 and 0.08-3.40 microg/L, respectively, whereas those in swimming pool water were 26.15-65.09, 9.50-36.97, 8.90-18.01, 5.19-22.78 and ND-6.56 microg/L, respectively. It implied that the concentration of THMs in swimming pool water was higher than those in tap water, particularly, brominated-THMs. Both tap water and swimming pool water contained concentrations of total THMs below the standards of the World Health Organization (WHO), European Union (EU) and the United States Environmental Protection Agency (USEPA) phase I, but 1 out of 60 tap water samples and 60 out of 72 swimming pool water samples contained those over the Standard of the USEPA phase II. From the two cases of cancer risk assessment including Case I Non-Swimmer and Case II Swimmer, assessment of cancer risk of non-swimmers from exposure to THMs at the highest and the average concentrations was 4.43 x 10(-5) and 2.19 x 10(-5), respectively, which can be classified as acceptable risk according to the Standard of USEPA. Assessment of cancer risk of swimmers from exposure to THMs at the highest and the average concentrations was 1.47 x 10(-3) and 7.99 x 10(-4), respectively, which can be classified as unacceptable risk and needs to be improved. Risk of THMs exposure from swimming was 93.9%-94.2% of the total risk. Cancer risk of THMs concluded from various routes in descending order was: skin exposure while swimming, gastro-intestinal exposure from tap water intake, and skin exposure to tap water and gastro-intestinal exposure while swimming. Cancer risk from skin exposure while swimming was 94.18% of the total cancer risk.

One-day dietary restriction changes hepatic metabolism and potentiates the hepatotoxicity of carbon tetrachloride and chloroform in rats

Although dietary restriction (DR) is common in modern society, research about hepatic metabolism and the hepatotoxicity induced by DR has been conducted less intensively than that induced by fasting. In the present study, we fed male Wistar rats at five levels of food intake for one day, including conventional feeding (60 kcal), three of DR (45, 30, and 15 kcal), and fasting (0 kcal), and observed the metabolic changes of hepatic cytochrome P450 2E1(CYP2E1) and the hepatotoxicity of chloroform (CHCl(3)) and carbon tetrachloride (CCl(4)). The CYP2E1 content was significantly increased in 15 kcal-food and fasting groups. The hepatic glutathione (GSH) content, which protects the liver from hepatotoxic agents, was depleted in 15 kcal-food and fasting groups. After the challenge by CHCl(3) and CCl(4), the activities of aspartate aminotransferase and alanine aminotransferase, marker enzymes for liver damage, were elevated remarkably at all food groups. Moreover, their activities increased significantly in DR groups, in comparison to the corresponding 60 kcal-food group. After the challenge, the hepatic GSH content was also depleted significantly in 15 kcal-food and fasting groups. CHCl(3) was cleared by hepatic metabolism about 8-10 times faster than that of CCl(4). Similarly, the areas under the blood concentration-time curve of CCl(4) was as much as twice that of the corresponding CHCl(3). In conclusion, when food was restricted to less than half of conventional amount, hepatic metabolism was affected and the hepatotoxicity induced by CCl(4) or CHCl(3) was augmented by, at least in part, CYP2E1 induction and GSH depletion.

Bayesian estimation of pharmacokinetic and pharmacodynamic parameters in a mode-of-action-based cancer risk assessment for chloroform

Chloroform is a carcinogen in rodents and its carcinogenicity is secondary to events associated with cytotoxicity and regenerative cell proliferation. In this study, a physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) model that links the processes of chloroform metabolism, reparable cell damage, cell death, and regenerative cellular proliferation was developed to support a new cancer dose-response assessment for chloroform. Model parameters were estimated using Markov Chain Monte Carlo (MCMC) analysis in a two-step approach: (1) metabolism parameters for male and female mice and rats were estimated against available closed chamber gas uptake data; and (2) PD parameters for each of the four rodent groups were estimated from hepatic and renal labeling index data following inhalation exposures. Subsequently, the resulting rodent PD parameters together with literature values for human age-dependent physiological and metabolism parameters were used to scale up the rodent model to a human model. The human model was used to predict exposure conditions under which chloroform-mediated cytolethality is expected to occur in liver and kidney of adults and children. Using the human model, inhalation Reference Concentrations (RfCs) and oral Reference Doses (RfDs) were derived using an uncertainty factor of 10. Based on liver and kidney dose metrics, the respective RfCs were 0.9 and 0.09 ppm; and the respective RfDs were 0.4 and 3 mg/kg/day.

Mechanisms of chloroform-induced hepatotoxicity: oxidative stress and mitochondrial permeability transition in freshly isolated mouse hepatocytes

The role of mitochondrial permeability transition (MPT) and oxidative stress in chloroform toxicity was determined in freshly isolated female B6C3F1 mouse hepatocytes. Incubation of chloroform (12 mM) with hepatocytes resulted in cell death (alanine aminotransferase release and propidium iodide fluorescence). Chloroform had volatilized from the incubation and glutathione was depleted by 1 h; however, toxicity was not significantly different between control and chloroform-incubated cells. Hepatocytes were washed and reincubated in fresh media at 1 h. Subsequent reincubation of chloroform-treated hepatocytes resulted in significant toxicity at 3-5 h. Inclusion of the MPT inhibitor cyclosporine A or the antioxidant N-acetylcysteine (NAC) in the reincubation media at 1 h prevented toxicity. Confocal microscopy studies with the dye calcein AM indicated MPT that was blocked by cyclosporine A or NAC. Fluorescence microscopy studies utilizing JC-1 indicated loss of mitochondrial membrane potential, which was also blocked by cyclosporine A or NAC. Dichlorofluorescein fluorescence increased during the reincubation phase, indicating increased oxidative stress, and the increase was blocked by cyclosporine A. Since oxidative stress may occur by peroxynitrite, its role in toxicity was examined. Either of the nitric oxide synthase inhibitors N(G)-methyl-L-arginine (L-NMMA) and 7-nitroindazole (7-NI) at 1 h blocked toxicity. Western blot analysis of hepatocytes for 3-nitrotyrosine in proteins, a biomarker of peroxynitrite, indicated one major nitrated protein at 81 kD. Nitration of this protein was inhibited by cyclosporine A, L-NMMA, 7-NI, or NAC. The data indicate that chloroform-induced cell death occurs in two phases: a metabolic phase characterized by glutathione depletion, and an oxidative phase characterized by MPT and protein nitration.

Biocompatibility of gutta-percha solvents using in vitro mammalian test-system

OBJECTIVES

Taking into consideration that DNA damage and cellular death play important roles during carcinogenesis, the purpose of the present study was to evaluate in vitro genotoxic or cytotoxic effects of chloroform and eucalyptol by single cell gel (comet) assay and trypan blue exclusion test, respectively.

STUDY DESIGN

Chloroform and eucalyptol were exposed to Chinese hamster ovary cells in culture directly for 3 hours at 37 degrees C at final concentrations ranging from 1.25 to 10 microL/mL. The negative control group was treated with vehicle control (phosphate-buffered solution), and the positive control group was treated with methyl metasulfonate (MMS, at 1 microg/mL concentration). All data were analyzed by the Kruskal-Wallis nonparametric test followed by the Dunn test.

RESULTS

The results showed that both gutta-percha solvents were cytotoxic at concentrations of 2.5, 5, and 10 microL/mL (P < .05). On the other hand, both solvents did not induce DNA breakage at 1.25 microL/mL concentration.

CONCLUSIONS

These results suggest that both chloroform or eucalyptol are strong cytotoxicants, but they may not be a factor that increases the level of DNA lesions in mammalian cells.

The phytotoxic effect of C(1)/C(2)-halocarbons and trichloroacetic acid on the steppe plant Artemisia lerchiana

Artemisia lerchiana is a wormwood species of the Central Asian steppe regions, where it completely cover whole areas. For the first time it was possible to show through field experiments that C(1)/C(2) halocarbons (VCHCs), such as chloroform (CHL), tetrachloroethene (PER) and hexachloroethane (HEX), can be taken up by test plants of the species A. lerchiana via the soil/root pathway and metabolised inter alia into trichloroacetic acid (TCA) under semi-aride conditions. At the same time, chlorophyll a fluorescence measurements carried out on the test plants revealed a phytotoxic influence on plant vitality (max. decline in vitality of 52% with application of CHL) and less efficient energy flows in the photosynthesis mechanism of the A. lerchiana test plants. The authors examine possible links between the simultaneous appearance of VCHCs and additional drought stress in the acceleration of desertification processes.

Enhancement of renal carcinogenicity by combined inhalation and oral exposures to chloroform in male rats

Chloroform, ubiquitously present in indoor and outdoor air, drinking water, and some foodstuffs, enters the human body by inhalation, oral and dermal routes of exposure. In order to provide bioassay data for risk assessment of humans exposed to chloroform by multiple routes, effects of combined inhalation and oral exposures to chloroform on carcinogenicity and chronic toxicity in male F344 rats were examined. A group of 50 male rats was exposed by inhalation to 0 (clean air), 25, 50, or 100 ppm (v/v) of chloroform vapor-containing air for 6 h/d and 5 d/wk during a 104 w period, and each inhalation group was given chloroform-formulated drinking water (1000 ppm w/w) or vehicle water for 104 wk, ad libitum. Renal-cell adenomas and carcinomas and atypical renal-tubule hyperplasias were increased in the combined inhalation and oral exposure groups, but not in the oral- or inhalation-alone groups. Incidences of cytoplasmic basophilia and dilated tubular lumens in the kidney, as well as incidence of positive urinary glucose, were markedly increased by the combined exposures, compared with those after single-route exposures. It was concluded that combined inhalation and oral exposures markedly enhanced carcinogenicity and chronic toxicity in the proximal tubule of male rat kidneys, suggesting that carcinogenic and toxic effects of the combined exposures on the kidneys were greater than the ones that would be expected under an assumption that the two effects of single route exposures through inhalation and drinking were additive.

Subchronic chloroform priming protects mice from a subsequently administered lethal dose of chloroform

Protection offered by pre-exposure priming with a small dose of a toxicant against the toxic and lethal effects of a subsequently administered high dose of the same toxicant is autoprotection. Although autoprotection has been extensively studied with diverse toxicants in acute exposure regimen, not much is known about autoprotection after priming with repeated exposure. The objective of this study was to investigate this concept following repeated exposure to a common water contaminant, chloroform. Swiss Webster (SW) mice, exposed continuously to either vehicle (5% Emulphor, unprimed) or chloroform (150 mg/kg/day po, primed) for 30 days, were challenged with a normally lethal dose of chloroform (750 mg chloroform/kg po) 24 h after the last exposure. As expected, 90% of the unprimed mice died between 48 and 96 h after administration of the lethal dose in contrast to 100% survival of mice primed with chloroform. Time course studies indicated lower hepato- and nephrotoxicity in primed mice as compared to unprimed mice. Hepatic CYP2E1, glutathione levels (GSH), and covalent binding of (14)C-chloroform-derived radiolabel did not differ between livers of unprimed and primed mice after lethal dose exposure, indicating that protection in liver is neither due to decreased bioactivation nor increased detoxification. Kidney GSH and glutathione reductase activity were upregulated, with a concomitant reduction in oxidized glutathione in the primed mice following lethal dose challenge, leading to decreased renal covalent binding of (14)C-chloroform-derived radiolabel, in the absence of any change in CYP2E1 levels. Buthionine sulfoximine (BSO) intervention led to 70% mortality in primed mice challenged with lethal dose. These data suggest that higher detoxification may play a role in the lower initiation of kidney injury observed in primed mice. Exposure of primed mice to a lethal dose of chloroform led to 40% lower chloroform levels (AUC(15-360 min)) in the systemic circulation. Exhalation of (14)C-chloroform was unchanged in primed as compared to unprimed mice (AUC(1-6 h)). Urinary excretion of (14)C-chloroform was higher in primed mice after administration of the lethal dose. However, neither slightly higher urinary elimination nor unchanged expiration can account for the difference in systemic levels of chloroform. Liver and kidney regeneration was inhibited by the lethal dose in unprimed mice leading to progressive injury, organ failure, and 90% mortality. In contrast, sustained and highly stimulated compensatory hepato- and nephrogenic repair prevented the progression of injury resulting in 100% survival of primed mice challenged with the lethal dose. These findings affirm the critical role of tissue regeneration and favorable detoxification (only in kidney) of the lethal dose of chloroform in subchronic chloroform priming-induced autoprotection.

In vitro modulation of HERG channels by organochlorine solvent trichlormethane as potential explanation for proarrhythmic effects of chloroform

Acute chloroform intoxication can cause depression of the central nervous system and may lead to death from lethal arrhythmias or respiratory arrest. Thus, the organic solvent is no longer in clinical use as an anaesthetic, but still plays a role in cases of suicide, homicide or inhalation for psychotropic effects. Several cases of lethal arrhythmia after intoxication with chloroform have been described. Pharmacological inhibition of cardiac "human ether-à-go-go-related gene" (HERG) potassium channels is linked to proarrhythmic effects of cardiac and noncardiac drugs. To further investigate the electrophysiological basis of the arrhythmogenic potential of chloroform, we analysed inhibitory effects of chloroform on cloned HERG potassium channels, heterologously expressed in Xenopus oocytes and in Human Embryonic Kidney (HEK 293) cells using the double-electrode voltage-clamp technique and the whole-cell patch-clamp technique, respectively. In HEK cells, chloroform blocked HERG tail currents with an IC(50) of 4.97mM. Biophysical properties were further investigated in the Xenopus oocyte expression system. Onset and wash-out of block was fast and inhibition was completely reversible. Chloroform did not alter channel activation, however, direct channel inactivation was accelerated significantly. Steady-state-inactivation of HERG was not affected. Chloroform dependent block of HERG channels was voltage dependent with a decrease of inhibition at more positive membrane potentials. No frequency-dependence of block could be observed. In summary, chloroform blocked HERG potassium channels probably in a toxicologically relevant concentration. These findings contribute to the pathophysiology of proarrhythmic effects in acute chloroform intoxication.

Inhaled chemicals may enhance allergic airway inflammation in ovalbumin-sensitised mice

Occupational allergy and asthma is a challenging issue in the developing countries. Chemicals inhaled in the workplaces may act not only as allergens but also as immune response modifiers, contributing to asthma exacerbation. In this study, we tested the adjuvant effect of 20 ppm chloroform, 10 ppm 1,1-dichloroethylene, and 100 ppm styrene in mice. Female BALB/c mice were sensitised to ovalbumin (OVA) without using alum. During the OVA-sensitisation period, these mice were exposed by inhalation to the chemicals studied for 6h/day for four consecutive days. After two OVA-intratracheal challenges, a mild Th2 immune response was observed in the OVA-exposed groups. This response was characterised by a mild increase in serum specific IgE level, in local Th2 cytokine production, and in lung inflammatory reaction. Exposure to styrene or chloroform alone slightly increased Th2 cytokine production by lung-draining lymph node cells cultured with concanavaline A, except for the IL-4 level in the chloroform exposure group, which decreased. On the other hand, exposure to 1,1-dichloroethylene alone markedly increased the Th2 cytokine levels compared to those observed in the groups exposed to OVA alone. In the combined OVA+chemical-treated groups, styrene potentiated IL-4, -5 and -13 production efficiently (approximately two, four and three times higher, respectively), resulting in an increase in the total IgE levels and inflammatory reaction. On the other hand, the enhanced IgE levels and the exacerbation of the inflammatory response by 1,1-dichloroethylene or chloroform were associated with only minor changes in local cytokine levels. These findings suggest that exposure to chemicals through inhalation may aggravate the allergic lung inflammation. And this, depending on the chemical exposure conditions, may result from the synergistic effect of chemicals and allergen on local Th2 cytokine production.

In vitro evaluation of macrophage viability after incubation in orange oil, eucalyptol, and chloroform

OBJECTIVE

The aim of this study was to evaluate the cytotoxicity of orange oil, eucalyptol, and chloroform in a cell culture assay by using peritoneal macrophages from Swiss mice.

STUDY DESIGN

Control (Dulbecco's modified Eagle's medium [DMEM] plus 1.25% ethyl alcohol) and experimental (orange oil, eucalyptol, and chloroform) groups were studied. Solvents used were tested at 0.025% and 0.050% concentrations in DMEM plus 1.25% ethyl alcohol.

RESULTS

Orange oil, eucalyptol, and chloroform were all cytotoxic in comparison to the control group (P < .001). Orange oil showed the least cytotoxicity (P < .001). No significant differences were observed regarding cell viability when comparing the eucalyptol and chloroform groups (P < .05). There were significant differences in the cytotoxicity of eucalyptol and chloroform with an increase in concentration (P < .0001). Nevertheless, this difference was not significant in the orange oil group (P < .05).

CONCLUSION

Orange oil was less cytotoxic than eucalyptol and chloroform.

Adaptive tolerance in mice upon subchronic exposure to chloroform: Increased exhalation and target tissue regeneration

The aims of the present study were to characterize the subchronic toxicity of chloroform by measuring tissue injury, repair, and distribution of chloroform and to assess the reasons for the development of tolerance to subchronic chloroform toxicity. Male Swiss Webster (SW) mice were given three dose levels of chloroform (150, 225, and 300 mg/kg/day) by gavage in aqueous vehicle for 30 days. Liver and kidney injury were measured by plasma ALT and BUN, respectively, and by histopathology. Tissue regeneration was assessed by (3)H-thymidine incorporation into hepato- and nephro-nuclear DNA and by proliferating cell nuclear antigen staining. In addition, GSH and CYP2E1 in liver and kidney were assessed at selected time points. The levels of chloroform were measured in blood, liver, and kidney during the dosing regimen (1, 7, 14, and 30 days). Kidney injury was evident after 1 day with all three doses and sustained until 7 days followed by complete recovery. Mild to moderate liver injury was observed from 1 to 14 days with all three dose levels followed by gradual decrease. Significantly higher regenerative response was evident in liver and kidney at 7 days, but the response was robust in kidney, preventing progression of injury beyond first week of exposure. While the kidney regeneration reached basal levels by 21 days, moderate liver regeneration with two higher doses sustained through the end of the dosing regimen and 3 days after that. Following repeated exposure for 7, 14, and 30 days, the blood and tissue levels of chloroform were substantially lower with all three dose levels compared to the levels observed with single exposure. Increased exhalation of (14)C-chloroform after repeated exposures explains the decreased chloroform levels in circulation and tissues. These results suggest that toxicokinetics and toxicodynamics (tissue regeneration) contribute to the tolerance observed in SW mice to subchronic chloroform toxicity. Neither bioactivation nor detoxification appears to play a decisive role in the development of this tolerance.

In vitro cytotoxic and non-genotoxic effects of gutta-percha solvents on mouse lymphoma cells by single cell gel (comet) assay

Chloroform and eucalyptol are widely used in clinical dentistry as gutta-percha solvents. However, these compounds may represent a hazard to human health, especially by causing injury to genetic apparatus and/or inducing cellular death. In this study, the genotoxic and cytotoxic potentials associated with exposure to chloroform and eucalyptol were assessed on mouse lymphoma cells in vitro by the single cell gel (comet) assay and trypan blue exclusion test, respectively. Both gutta-percha solvents proved to be cytotoxic at the same levels in concentrations of 2.5, 5 and 10 muL/mL (p<0.05). On the other hand, neither of the solvents induced DNA breakage. Taken together, these results suggest that although both tested compounds (chloroform and eucalyptol) are strong cytotoxicants, it seems that they are not likely to increase the level of DNA damage on mammalian cells.

Resolution of liver fibrosis in chronic CCl4 administration in the rat after discontinuation of treatment: effect of silymarin, silibinin, colchicine and trimethylcolchicinic acid

The purpose of this work was to obtain a suitable model of fibrosis, in which spontaneous reversion was minimal, to study the ability of silymarin, silibinin, colchicine and trimethylcolchicinic acid (TMCA) to reverse it. Reversal of liver fibrosis was studied in male Wistar rats after one, two or three months of CCl(4) administration (0.4 g/kg intraperitoneally, three times per week), by discontinuation of the toxin for 2 months. Silymarin (50 mg/kg), silibinin (50 mg/kg), colchicine (10 microg/rat) and trimethylcolchicinic acid (100 microg/rat) were administered daily, by gavage, after 3 months of CCl(4) administration. Collagen content was determined by measuring hydroxyproline in liver samples; glycogen, was determined utilizing the anthrone reagent; Mallory's trichromic stains of liver sections were performed. The best scheme of treatment was obtained when CCl(4) was administered during three months (collagen increased 6 times). Discontinuation of the toxin for two months produced a significant but relative small reduction of fibrosis (collagen was still 4.5 times over control). Colchicine, TMCA, silymarin or silibinin treatment showed no significant fibrolitic effect. This scheme of treatment may be an excellent tool to study the ability of drugs to reverse fibrosis. The hepatoprotective properties of silymarin, silibinin, colchicine and trimethylcolchinic acid may be irrelevant to reverse established cirrhosis.

Dose-dependent liver regeneration in chloroform, trichloroethylene and allyl alcohol ternary mixture hepatotoxicity in rats

The present study was designed to examine the hypothesis that liver tissue repair induced after exposure to chloroform (CF) + trichloroethylene (TCE) + allyl alcohol (AA) ternary mixture (TM) is dose-dependent similar to that elicited by exposure to these compounds individually. Male Sprague Dawley (S-D) rats (250-300 g) were administered with fivefold dose range of CF (74-370 mg/kg, ip), and TCE (250-1250 mg/kg, ip) in corn oil and sevenfold dose range of AA (5-35 mg/kg, ip) in distilled water. Liver injury was assessed by plasma alanine amino transferase (ALT) activity and liver tissue repair was measured by (3) H-thymidine incorporation into hepatonuclear DNA. Blood and liver levels of parent compounds and two major metabolites of TCE [trichloroacetic acid (TCA) and trichloroethanol (TCOH)] were quantified by gas chromatography. Blood and liver CF and AA levels after TM were similar to CF alone or AA alone, respectively. However, the TCE levels in blood and liver were substantially decreased after TM in a dose-dependent fashion compared to TCE alone. Decreased plasma and liver TCE levels were consistent with decreased production of metabolites and elevated urinary excretion of TCE. The antagonistic interaction resulted in lower liver injury than the summation of injury caused by the individual components at all three-dose levels. On the other hand, tissue repair showed a dose-response leading to regression of injury. Although the liver injury was lower and progression was contained by timely tissue repair, 50% mortality occurred only with the high dose combination, which is several fold higher than environmental levels. The mortality could be due to the central nervous system toxicity. These findings suggest that exposure to TM results in lower initial liver injury owing to higher elimination of TCE, and the compensatory liver tissue repair stimulated in a dose-dependent manner mitigates progression of injury after exposure to TM.

Effects of betaine supplementation on hepatic metabolism of sulfur-containing amino acids in mice

BACKGROUND/AIMS

We previously reported that acute betaine treatment induced significant changes in the hepatic glutathione and cysteine levels in mice and rats. The present study was aimed to determine the effects of dietary betaine on the metabolism of sulfur-containing amino acids.

METHODS/RESULTS

Male mice were supplemented with betaine (1%) in drinking water for up to 3 weeks. Changes in hepatic levels of major sulfur amino acid metabolites and products were stabilized after 2 weeks of betaine supplementation. Betaine intake increased methionine, S-adenosylmethionine, and S-adenosylhomocysteine levels significantly, but homocysteine and cystathionine were reduced. Methionine adenosyltransferase activity was elevated to three-fold of control. Cysteine catabolism to taurine was inhibited as evidenced by a decrease in cysteine dioxygenase activity and taurine levels in liver and plasma. Despite the significant changes in the transsulfuration reactions, neither hepatic cysteine nor glutathione was altered. Betaine supplementation decreased the hepatotoxicity induced by chloroform (0.5 ml/kg, ip) significantly.

CONCLUSIONS

Betaine supplementation enhances recycling of homocysteine for the generation of methionine and S-adenosylmethionine while reducing its utilization for the synthesis of cystathionine and cysteine. However, the hepatic levels of cysteine or glutathione are not affected, most probably due to the depression of taurine generation from cysteine.

Biophotonic imaging in HO-1.luc transgenic mice: real-time demonstration of gender-specific chloroform induced renal toxicity

The metabolism of luciferin in mice transgenic for luciferase (luc) produces light that may be detected trans vivo by an intensified CCD camera (biophotonics). Thus, the generation of transgenic promoter-luciferase animals for genes regulated by specific toxic processes, coupled with real-time evaluation of site-specific gene expression may provide novel, non-invasive biomarkers which are predictive of developing toxicity in vivo. As part of a programme to evaluate the potential of biophotonics for predictive toxicology we have conducted a series of studies in HO-1.luc transgenic mice. Male and female animals were treated with chloroform (200 mg/kg, p.o., daily for 5 days) and imaged 2 and 6 h after dosing. During a 2-day washout period, female animals were treated daily with testosterone prior to repeat administration of chloroform for a further 5 days. Comparison of the in vivo response of the luciferase reporter with markers of toxicity measured ex vivo (differential gene expression of adaptive antioxidant response genes, clinical chemistry and microscopic examination) confirms the gender-specific difference in chloroform renal toxicity in HO-1.luc transgenic mice and its reversal following androgenisation of females and correlates with the expression of the endogenous haem oxygenase-1 (HO-1) gene. These studies demonstrate the capacity of biophotonics for real-time site-specific gene expression, which may be predictive of developing toxicity.

Oxidative DNA damage from potassium bromate exposure in Long-Evans rats is not enhanced by a mixture of drinking water disinfection by-products

Public drinking water treated with chemical disinfectants contains a complex mixture of disinfection by-products (DBPs) for which the relative toxicity of the mixtures needs to be characterized to accurately assess risk. Potassium bromate (KBrO(3)) is a by-product from ozonation of high-bromide surface water for production of drinking water and is a rodent carcinogen that produces thyroid, mesothelial, and renal tumors. The proposed mechanism of KBrO(3) renal carcinogenesis involves the formation of 8-oxoguanine (8-oxoG), a promutagenic base lesion in DNA typically removed through base excision repair (BER). In this study, male Long-Evans rats were exposed via drinking water to carcinogenic concentrations of KBrO(3) (0.4 g/L), 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (0.07 g/L), chloroform (1.8 g/L), bromodichloromethane (0.7 g/L), or a mixture of all these chemicals at the same concentrations for 3 weeks. Half of one kidney was processed for microscopic examination, and the remaining kidney was frozen for isolation of genomic DNA. Levels of 8-oxoG were measured using HPLC with electrochemical detection in DNA samples incubated with formamidopyrimidine-DNA glycosylase. Aldehydic lesions (e.g. abasic sites) in DNA samples were quantitated using an aldehyde-reactive probe slot-blot assay. Treatment with KBrO(3) produced a measurable increase of 8-oxoG in the kidney, and this effect was greater than that produced by treatment with the DBP mixture. No other single chemical treatment caused measurable increases of 8-oxoG. The mixture effect on the amount of 8-oxoG observed in this study suggests an interaction between chemicals that reduced the generation of oxidative DNA damage. No increases in abasic sites were observed with treatment, but a decrease was apparent in the rats treated with the DBP mixture. These data are consistent with previous studies where chronic exposure to this chemical mixture in drinking water resulted in a less than additive carcinogenic response in Tsc2 mutant Long-Evans rats.

Chlorination disinfection by-products and pancreatic cancer risk

Chlorination disinfection by-products (CDBPs) are produced during the treatment of water with chlorine to remove bacterial contamination. CDBPs have been associated with an increased risk of bladder cancer. There is also some evidence that they may increase the risk of pancreatic cancer. We report results from a population-based case-control study of 486 incident cases of pancreatic cancer and 3,596 age- and sex-matched controls. Exposure to chlorination by-products was estimated by linking lifetime residential histories to two different databases containing information on CDBP levels in municipal water supplies. Logistic regression analysis found no evidence of increased pancreatic cancer risk at higher CDBP concentrations (all odds ratios < 1.3). Null findings were also obtained assuming a latency period for pancreatic cancer induction of 3, 8, or 13 years.

Cytotoxicity evaluation of gutta-percha solvents: Chloroform and GP-Solvent (limonene)

OBJECTIVE

The purpose of this study was to compare the cytotoxicity of 2 gutta-percha solvents, chloroform and GP-Solvent, on cell line L929.

STUDY DESIGN

2 gutta-percha solvents were diluted into the concentrations of 1:100, 1:400, and 1:800. The experiment was done in a 96-well tissue-culture plate. Cell viability of L929 was determined after each gutta-percha solvent was left in contact with MTT solution for 3 hours.

RESULTS

Both solvents proved toxic at the same levels of concentrations of 1:100 and 1:400 (P>.05). At the dilution of 1:800 the GP-Solvent seems to be more toxic than the chloroform (P < .05).

CONCLUSIONS

Within the limitation of this experiment, GP-Solvent was not less cytotoxic than chloroform to the target cells. Because in clinical procedures we use a higher concentration of solvent to dissolve gutta-percha for retreatment than that used in this study, the overflowing of liquefied gutta-percha, or solvent out of apical foramen, should be a cause for concern.

Reduced mitochondrial membrane potential and metabolism correspond to acute chloroform toxicity ofin vitro hepatocytes

Chloroform is a non-genotoxic compound that is present in drinking water and ambient air as a result of water chlorination but whose carcinogenic mechanism in humans is unknown. Chloroform targets the liver in humans, where cytochrome P-450-dependent biotransformation to phosgene results in mitochondrial damage and cell death. The purpose of this study is to investigate the relationship between cell death, loss of mitochondrial membrane potential (MMP) and reduction of metabolic rates for in vitro cultured mouse hepatocytes after acute exposure to two doses of chloroform. Immediately following a 2-h exposure, culture viabilities were 70% and 54% for concentrations of 7.0 and 8.8 mM, respectively, in contrast with 90.0% for controls. Interestingly, the viabilities of these cultures decreased further, to 6% and 12%, respectively, over the next 24-h period despite being placed in fresh, chloroform-free medium. Measurement of MMP for viable cells at the end of the exposure revealed a decrease in Rhodamine 123 uptake, which indicates a loss of MMP. Additionally, glucose consumption and lactate production rates were reduced during the 6-h period following the exposure. These results support the hypothesis that a subpopulation of cells at the end of an acute exposure may be activated for apoptosis, suggesting a role for apoptosis markers during risk assessment for chloroform.

Comparative Study of Different Silymarin Formulations: Formulation, Characterisation and In Vitro / In Vivo Evaluation

The aim of the present study was to study the synergistic hepatoprotective effect of silymarin with phospholipids when it is encaged in microspheres so as to passively target it to liver and to compare these silymarin formulations with silymarin solution. Various silymarin loaded lipid emulsions were formulated which include formulation A prepared with soyabean oil as an internal oily phase, soya lecithin as surfactant and tween 80 as cosurfactant; formulation B which was same as formulation A but was filtered through 0.45 micro membrane filter and finally steam sterilized for intravenous administration; formulation C containing soyabean oil as an internal oily phase, soya lecithin as surfactant, tween 80 and propylene glycol as cosurfactant/ cosolvent. These formulations were compared for their release profile with silymarin solution in propylene glycol, i.e. formulation D. In vivo evaluation was carried out using three models i.e. phenobarbitone induced sleep time in mice, biochemical estimation of SGOT and SGPT enzyme levels and histopathological examination of rat livers. Results revealed that there was significant reduction in sleep time in the mice treated with silymarin loaded lipid microspheres (both p.o. as well as i.v.) when compared with control and even with plain lipid microspheres and silymarin solution and significant reduction in enzyme levels in silymarin lipid microspheres treated group when compared with control, plain lipid microspheres as well as silymarin solution treated group. Histopathological studies also supported the results obtained from the other two models. A positive outcome of these studies gave an insight that if silymarin is coupled with phospholipid in such microparticulate delivery systems, hepatoprotective effect of drug molecules can be pronounced further by self targeting nature and synergistic action.

Bioactivation, toxicokinetics and acute effects of chloroform in Fisher 344 and Osborne Mendel male rats

Chloroform has been regarded as a renal carcinogen, based on results obtained with Osborne Mendel (OM) rats. Fisher 344 (F344) rats, considered representative of OM rats on the basis of comparable acute toxic effects, have been used in most of the studies aimed to elucidate the mechanisms of kidney tumour induction. In the present work, in vitro and in vivo chloroform bioactivation in the liver and kidney of F344 and OM rats has been reported, as well as additional toxicokinetics and acute toxicity information. Complete similarity of chloroform metabolism and toxicokinetics was evidenced in the two rat strains. Chloroform metabolism was fully saturated at the OM rat bioassay doses (90-180 mg kg(-1) body wt.), working at a maximal rate of 40-50 micro mol (14)CO(2) expired kg(-1) h(-1). No acute hepatotoxicity, nephrotoxicity or consequent cell proliferation was evidenced at 180 mg kg(-1) body wt. chloroform. In the rat liver, phosgene was confirmed as the major metabolite. Renal microsomes from both F344 and OM rats in vitro were unable to produce any oxidative metabolite; at variance, adducts due to oxidative and reductive metabolites were detected in vivo. Our results indicated the presence in the rat kidney of electrophilic metabolites other than phosgene, representing either oxidative metabolites formed elsewhere and sufficiently stable to be transported to the kidney or electrophilic metabolites secondary to the formation of reductive radicals. Therefore, the rat kidney represents a suitable model to study the toxicological effects, including genotoxicity, of chloroform metabolites in the absence of cytotoxic effects produced by phosgene formed in situ.

The effects of in utero and lactational exposure to chloroform on postnatal growth and glucose tolerance in male Wistar rats

Water chlorination results in the formation of trihalomethanes (THMs) including chloroform. In human stud-ies, fetal growth restriction has been associated with exposure to THMs during pregnancy and impaired fetal growth has been associated with an increased risk of type 2 diabetes. Therefore, the objective of this study was to determine the effect of in utero and lactational exposure to chloroform on birthweight and postnatal indicators of type 2 diabetes. Female Wistar rats were given chloroform (0 microg/L, 75 microg/L) in their drinking water for 2 wk prior to mating until parturition (in utero exposure only) or until weaning (in utero+lactational exposure). At postnatal d 1 (PND1) pups of dams exposed to chloroform had significantly higher serum glucose levels and lower insulin levels, but this effect was not due to b<FONT "Optima">-cell depletion in the neonatal pancreas. Glucose homeostasis in response to a glucose challenge was not changed by chloroform treatment. Chloroform exposure did not affect birthweight; however, offspring of dams exposed to chloroform had significantly impaired postnatal growth. Although fetal and neonatal exposure to chloroform did not elicit physiological changes associated with the onset of type 2 diabetes, there were physiological changes resulting in impaired postnatal growth.

[The influence of halogenorganic compounds on radiation induced damage of rat eye lens components]

In experiments with white rats the damages of eye lens components of the animals are investigated under combined action of halogenorganic compounds (chloroform and sodium trichloroacetate) and radiation (137Cs) in vivo. It was shown that the injection of these compounds into animals amplifies the radiation-induced oxidation of eye lens components. The effect is manifested in the increase in the content of chromophors with fluorescence in the visible range and products of lipid peroxidation, the decrease in the amount of reduced glutathione. The data support the increased risk of development of radiation-induced cataract in the conditions of tehnogenic pollution of the environment.

Liver necrosis and fulminant hepatic failure in rats: protection by oxyanionic form of tungsten

The hepatic lesion produced as a result of oxidative stress is of wide occurrence. In the present study, the effect of tungsten on liver necrosis and fulminant hepatic failure (FHF) has been studied in rats treated with various compounds known to produce oxidative stress. Supplementation of animals with sodium tungstate for 7 weeks before the induction of liver injury by chemicals including thioacetamide (TAA), carbon tetrachloride (CCl(4)), or chloroform (CHCl(3)) could protect progression of hepatic injury. Various biochemical changes associated with liver damage and oxidative stress were measured. Hepatic malondialdehyde content, endogenous tripeptide, and reduced glutathione were measured as oxidative stress markers. The activity of xanthine oxidase, which generates reactive oxygen species (ROS) as a by-product, was also determined and found to be perturbed. Tungsten supplementation to rats caused a significant decrease in lipid peroxidation and lowered the levels of the biochemical markers of hepatic lesions produced by TAA, CCl(4) (CCl(4)), or CHCl(3). Tungsten could also cause an increase in the survival rate in rats receiving lethal doses of TAA, CCl(4), or CHCl(3). The protective effect of tungsten, however, is suggested to be limited to the conditions where the hepatic lesion is reported to be due to the generation of ROS. The progression of liver injury produced by the compounds causing oxidative stress without initiating the generation of free radicals such as bromobenzene (BB), or acetaminophen (AAP), could not be inhibited by tungsten. The possible mechanism explaining the role of oxyanionic form of tungsten in free radical-induced hepatic lesions is discussed.

The short, tragic life of Robert M. Glover

Robert Mortimer Glover (1815-1859) was a contemporary of John Snow and James Young Simpson. Although he did not reach the standing of those two giants, his researches, writings and lectures were important contributions to the early development of British anaesthesia. Glover was the first to explore the physiological action of chloroform in the laboratory and to discover its anaesthetic effect in 1842. He helped Sir John Fife in Hannah Greener's autopsy in January 1848 and influenced Fife's conclusions on the cause of the young girl's death. His numerous and extensive articles reviewing the history, chemistry, pharmacology and clinical applications of various anaesthetics were widely read and quoted by his colleagues, including John Snow. While in Edinburgh and Newcastle, Glover was recognised as a remarkably astute physician, original researcher, prolific writer and enthusiastic lecturer with an enormous knowledge of medicine, the physical sciences, mathematics and philosophy. His brilliant career deteriorated after his arrival in London and, especially, after his return from the Crimea, although he continued to publish until the week before his death. The causes of his decline remain obscure. The last year of his life was ruined by his addiction to chloroform, to whose development he had contributed so much, and which killed him at the early age of 43.

Residual toxicity after biodegradation: interactions among benzene, toluene, and chloroform

A microbial enrichment originating from a pristine aquifer was found to aerobically biodegrade benzene and toluene, but not chloroform. This enrichment culture was used to study changes in pollutant toxicity as affected by biodegradative activity. Two assays for toxicity were used: (1) a 48-h acute toxicity test using the freshwater invertebrate Ceriodaphnia dubia and (2) microbial biodegradation activity as affected by the presence of mixed pollutants. At 20-ppm concentrations, toluene was significantly more toxic (99% mortality) to C. dubia than benzene (48% mortality) or chloroform (40% mortality). Also at 20-ppm concentrations, but before biodegradation, toluene was significantly more toxic (88% mortality) to C. dubia than benzene (33% mortality). After biodegradation of 98% of toluene and benzene, significant residual toxicity still remained in the bacterial supernatant: toluene-degraded supernatant caused 33% mortality in C. dubia and benzene-degraded supernatant caused 24% mortality. In the second toxicity assay, examining the effect of mixed pollutants on biodegradation activity, the presence of benzene slowed the biodegradation of toluene, but chloroform had no effect on either benzene or toluene biodegradation. Results indicate that significant toxicity remain after biodegradation and that halogenated aliphatic hydrocarbons may have little or no effect on aromatic hydrocarbon biodegradation at sites impacted by mixed pollutants.

Changes in cecal microbial metabolism of rats induced by individual and a mixture of drinking water disinfection by-products

Disinfection of drinking water has been one of the greatest public health successes. Numerous halogenated disinfection by-products (DBPs) occur and chronic ingestion has been associated with an increased risk for colorectal cancer in human populations. Because the intestinal microbiota can bioactivate xenobiotics, studies have been performed to examine the effects of individual DBPs on intestinal microbial metabolism. No studies have been conducted on a defined mixture of DBPs to determine if there is an enhancement of response to a mixture. Ten-week-old male Long-Evans rats were treated in their drinking water for 17 weeks with 0.4 g/l potassium bromate, 1.8 g/l chloroform, 0.7 g/l bromodichloromethane (BDCM), 0.07 g/l 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), or a mixture of the four chemicals or distilled water. Cecal nitroreductase (NR), azoreductase (AR), dechlorinase (DC), beta-glucuronidase (GLR), beta-galactosidase (GAL), and beta-glucosidase (GLU) were assayed. No change in GLU or GLR activity was detected after treatment. BDCM treatment reduced DC and GAL activities and elevated NR and AR activity. GAL, AR, and NR activities were significantly different after treatment with bromate, chloroform, BDCM, and MX, but not the mixture. DC activity after chloroform-, MX-, or BDCM-treatment was significantly below control levels. The present study shows that changes in intestinal microbial metabolism do occur after treatment with individual and a mixture of DBPs but the changes were not additive in the mixture group.

Mutagenicity of carbon tetrachloride and chloroform in Salmonella typhimurium TA98, TA100, TA1535, and TA1537, and Escherichia coli WP2uvrA/pKM101 and WP2/pKM101, using a gas exposure method

The volatile solvents carbon tetrachloride and chloroform are carcinogens that are often reported as nonmutagenic in bacterial mutagenicity assays. In this study, we evaluated the mutagenicity of these compounds in Salmonella typhimurium TA98, TA100, TA1535, and TA1537, and Escherichia coli WP2uvrA/pKM101 and WP2/pKM101, with and without S9 mix, using a gas exposure method. Tests were also conducted with a glutathione-supplemented S9 mix. Carbon tetrachloride was mutagenic in TA98 without S9 mix, and in WP2/pKM101 and WP2uvrA/pKM101 with and without S9 mix; carbon tetrachloride was not mutagenic in TA100, TA1535 or TA1537. Chloroform was mutagenic in WP2/pKM101, but only in the presence of glutathione-supplemented S9 mix. Chloroform was not mutagenic in TA98, TA100, TA1535, TA1537, or WP2uvrA/pKM101 with or without S9 mix, and was not mutagenic in TA98, TA100, TA1535, TA1537, or WP2uvrA/pKM101 in the presence of glutathione-supplemented S9 mix. The data indicate that carbon tetrachloride and chloroform are bacterial mutagens when adequate exposure conditions are employed and suggest that a genotoxic mode of action could contribute to the carcinogenicity of these compounds.