PDCB does not promote CNS autoimmunity in the context of genetic susceptibility but worsens its outcome.

BACKGROUND: Para-dichlorobenzene (PDCB) is an aromatic hydrocarbon contained in mothballs that is potentially neurotoxic. A potential pathogenic role of PDCB in MS pathogenesis has been suggested. METHODS: To determine the ability of chronic PDCB ingestion to induce CNS autoimmunity in a genetically susceptible mammalian species, naive myelin oligodendrocyte glycoprotein peptide (MOGp)35-55 T cell receptor (TCR) transgenic mice (2D2) on the C57Bl/6 background were orally gavaged once daily with corn oil control, 125 mg/kg PDCB, or 250 mg/kg PDCB for 45 days. The incidence of spontaneous EAE is increased in this mouse strain. RESULTS: Both PDCB treatment groups showed the same spontaneous incidence of EAE, an earlier disease onset, and a slight decrease in survival for 125 mg/kg PDCB mice compared to control mice. We were unable to detect any PDCB, or its metabolites 2,5-dichlorophenol, 2,5-dicholormethylsulfide, and 2,5-dichloromethylsulfone in the brain and spinal cord of control mice. In contrast, PDCB was readily detectable in both compartments in mice who received PDCB via oral gavage, with concentrations being significantly higher in the brain (p < 0.01). Levels of the metabolites 2,5-dichlorophenol and 2,5-dichloromethylsulfone were also significantly higher in brains compared to spinal cords. CONCLUSION: Our study refutes the hypothesis that PDCB or its metabolites trigger spontaneous T cell-mediated CNS autoimmunity in the setting of genetic susceptibility. A slight increase in mortality with PDCB exposure may be due systemic toxicity of hydrocarbons.

Organochlorine pesticides accumulation and breast cancer: A hospital-based case-control study.

The aim of this study is to detect the accumulation status of organochlorine pesticides in breast cancer patients and to explore the relationship between organochlorine pesticides contamination and breast cancer development. We conducted a hospital-based case-control study in 56 patients with breast cancer and 46 patients with benign breast disease. We detected the accumulation level of several organochlorine pesticides products (ß-hexachlorocyclohexane, γ-hexachlorocyclohexane, polychlorinated biphenyls-28, polychlorinated biphenyls-52, pentachlorothioanisole, and pp'-dichlorodiphenyldichloroethane) in breast adipose tissues of all 102 patients using gas chromatography. Thereafter, we examined the expression status of estrogen receptor, progesterone receptor, human epidermal growth factor receptor-2 (HER2), and Ki-67 in 56 breast cancer cases by immunohistochemistry. In addition, we analyzed the risk of breast cancer in those patients with organochlorine pesticides contamination using a logistic regression model. Our data showed that breast cancer patients suffered high accumulation levels of pp'-dichlorodiphenyldichloroethane and polychlorinated biphenyls-52. However, the concentrations of pp'-dichlorodiphenyldichloroethane and polychlorinated biphenyls-52 were not related to clinicopathologic parameters of breast cancer. Further logistic regression analysis showed polychlorinated biphenyls-52 and pp'-dichlorodiphenyldichloroethane were risk factors for breast cancer. Our results provide new evidence on etiology of breast cancer.

The metabolite 3,4,3',4'-tetrachloroazobenzene (TCAB) exerts a higher ecotoxicity than the parent compounds 3,4-dichloroaniline (3,4-DCA) and propanil.

3,4,3',4'-tetrachloroazobenzene (TCAB) is not commercially manufactured but formed as an unwanted by-product in the manufacturing of 3,4-dichloroaniline (3,4-DCA) or metabolized from the degradation of chloranilide herbicides, like propanil. While a considerable amount of research has been done concerning the toxicological and ecotoxicological effects of propanil and 3,4-DCA, limited information is available on TCAB. Our study examined the toxicity of TCAB in comparison to its parent compounds propanil and 3,4-DCA, using a battery of bioassays including in vitro with aryl hydrocarbon receptor (AhR) mediated activity by the 7-ethoxyresorufin-O-deethylase (EROD) assay and micro-EROD, endocrine-disrupting activity with chemically activated luciferase gene expression (CALUX) as well as in vivo with fish embryo toxicity (FET) assays with Danio rerio. Moreover, the quantitative structure activity response (QSAR) concepts were applied to simulate the binding affinity of TCAB to certain human receptors. It was shown that TCAB has a strong binding affinity to the AhR in EROD and micro-EROD induction assay, with the toxic equivalency factor (TEF) of 8.7×10(-4) and 1.2×10(-5), respectively. TCAB presented to be a weak endocrine disrupting compound with a value of estradiol equivalence factor (EEF) of 6.4×10(-9) and dihydrotestosterone equivalency factor (DEF) of 1.1×10(-10). No acute lethal effects of TCAB were discovered in FET test after 96h of exposure. Major sub-lethal effects detected were heart oedema, yolk malformation, as well as absence of blood flow and tail deformation. QSAR modelling suggested an elevated risk to environment, particularly with respect to binding to the AhR. An adverse effect potentially triggering ERß, mineralocorticoid, glucocorticoid and progesterone receptor activities might be expected. Altogether, the results obtained suggest that TCAB exerts a higher toxicity than both propanil and 3,4-DCA. This should be considered when assessing the impact of these compounds for the environment and also for regulatory decisions.

Effects of chronic and subtoxic chlorobenzenes on adrenocorticotrophic hormone release.

Many environmental chemicals and pesticides have been found to alter neuroendocrine communication in exposed biological objects. The environmental loads have primary and secondary effects that can alter the homeostatic regulation potential. Since it is difficult to avoid human exposition, a potentially important area of research to develop in vivo and in vitro experimental models. In this context, the primary aim of this study was to demonstrate the effects of chlorobenzenes on adrenocorticotrophic hormone (ACTH) release. In our experimental study, male Wistar rats were exposed to 0.1, 1.0 and 10 µg/b.w. (body weight)kg of 1,2,4- trichlorobenzene and hexachlorobenzene (ClB) mix via gastric tube for 30, 60 or 90 days. At the endpoints of the experiment blood samples were taken and animals were decapitated. Primary, monolayer adenohypophysis cell cultures were prepared by enzymatic and mechanical digestion. The ACTH hormone content in serum and supernatant media was measured by immuno-chemiluminescence assay. The Mg(2+)-dependent ATPase activity was determined by modified method of Martin and Dotty. Significant differences were detected in the hormone release between the control and treated groups. The hormone release was enhanced characteristically in exposed groups depending upon the dose and duration of exposure. The Mg(2+)-ATPase activity enhanced after chronic and subtoxic ClB exposition. Light microscopy revealed that the adenohypophysis seemed to be more abundant. Results indicate that Wistar rats exposed to subtoxic ClB have direct and indirect effects on hypothalamus-hypophysis-adrenal axis.

Mutation spectra of Kras and Tp53 in urethral and lung neoplasms in B6C3F1 mice treated with 3,3',4,4'-tetrachloroazobenzene.

3,3',4,4'-tetrachloroazobenzene (TCAB) is a contaminant formed during manufacture of various herbicide compounds. A recent National Toxicology Program study showed B6C3F1 mice exposed to TCAB developed a treatment-related increase in lung carcinomas in the high-dose group, and urethral carcinomas, an extremely rare lesion in rodents, in all dose groups. As the potential for environmental exposure to TCAB is widespread, and the mechanisms of urethral carcinogenesis are unknown, TCAB-induced urethral and pulmonary tumors were evaluated for alterations in critical human cancer genes, Kras and Tp53. Uroplakin III, CK20, and CK7 immunohistochemistry was performed to confirm the urothelial origin of urethral tumors. TCAB-induced urethral carcinomas harbored transforming point mutations in K-ras (38%) and Tp53 (63%), and 71% displayed nuclear TP53 expression, consistent with formation of mutant protein. Transition mutations accounted for 88% of Tp53 mutations in urethral carcinomas, suggesting that TCAB or its metabolites target guanine or cytosine bases and that these mutations are involved in urethral carcinogenesis. Pulmonary carcinomas in TCAB-exposed animals harbored similar rates of Tp53 (55%) and Kras (36%) mutations as urethral carcinomas, suggesting that TCAB may induce mutations at multiple sites by a common mechanism. In conclusion, TCAB is carcinogenic at multiple sites in male and female B6C3F1 mice through mechanisms involving Tp53 and Kras mutation.

Yusho patients show increased serum IL-17, IL-23, IL-1ß, and TNFα levels more than 40 years after accidental polychlorinated biphenyl poisoning.

The Yusho poisoning incident, caused by rice oil contaminated with polychlorinated biphenyls (PCBs), polychlorinated quarterphenyls (PCQs), and polychlorinated dibenzofurans (PCDFs) generated by heat-denatured PCBs, occurred in 1968 in western Japan. Although severe symptoms are rarely observed today, the levels of PCBs and PCDFs in the sera of Yusho patients remain high. The aryl hydrocarbon receptor (AhR), which also acts as a dioxin receptor, is a transcriptional regulator that mediates dioxin toxicity. Recent studies show that dioxin mediates its immune toxic effects via AhR and that AhR activation induces dysregulation of interleukin (IL)-17- producing T (TH17) cells. This study therefore hypothesized that Yusho patients would show dysregulated TH17 cell-mediated immune responses. To validate the hypothesis, levels of IL-17 and IL-22, each secreted by TH17 cells, along with IL-1ß and IL-23 were measured in serum samples from 40 Yusho patients and 40 age-matched controls. Levels of tumor necrosis factor (TNF)-α potentially secreted by TH17 cell-stimulated neutrophils and macrophages were also measured. The results indicated that serum IL-17 levels, as well as those of IL-1ß, IL-23, and TNFα, were significantly higher in Yusho patients than in controls. In contrast, serum IL-22 levels were significantly lower in the Yusho patients. These results suggest that Yusho patients have dysregulated TH17 cell-mediated immune responses that may be linked to inflammation.

[Population-related peculiarities of molecular stress-responsive systems of bivalve mollusk under the effect of tetrazine pesticide].

Tetrazine pesticides are widely used for the treatment of crops in most EU countries and USA. However, data about the effect of environmentally realistic concentrations of biocides on the molecular stress response system in non-target organisms are absent. The aim of our study was the comparison of adaptive capability of bivalve mollusk Anodonta cygnea from two populations under the effects of commercial pesticide Apollo in terms of biochemical parameters of the digestive gland. The differences between parameters of oxidative stress and glutathione transferase activity in specimens of control groups from clean (I group) and polluted (B group) areas have been shown. Under the effect of Apollo, the level of protein carbonyls and microsomal oxidation processes increased, and the level of metallothioneins and oxyradical formation decreased in the specimens from both populations. However, the treatment provoked the activation of antioxidant processes in the I group and their inhibition in B group. Potentially the injury of cellular thiols, glutathione and metallothioneins, seems to be key point of tetrazine pesticides toxicity.

Endocrine-mediated effects of two benzene related compounds, 1-chloro-4-(chloromethyl)benzene and 1,3-diethyl benzene, based on subacute oral toxicity studies using rats.

The purpose of this study was to investigate the endocrine-mediated effects of the benzene-related compounds with reference to Organization for Economic Co-operation and Development (OECD) Test Guideline No. 407. Rats were orally gavaged with 0, 10, 50, and 250 mg/kg/day of 1-chloro-4-(chloromethyl)benzene, and 0, 25, 150, and 1000 mg/kg/day of 1,3-diethyl benzene for at least 28 days, beginning at 8 weeks of age. Thyroid dysfunction was observed in rats given the 1,3-diethyl benzene. Serum T4 values increased in all groups of male rats and in the 1000 mg/kg group of female rats, and TSH values also increased in the 1000 mg/kg groups of both sexes after 28 days' administration. Decreased T3 values were observed in the 1000 mg/kg group of female rats after 28 days' administration, and hormone values increased in the 1000 mg/kg groups of both sexes after the 14-day recovery period. In addition, thyroid weight increased in the 1000 mg/kg groups and thyroid follicular cell hyperplasia was detected in one male rat from the 1000 mg/kg group after 28 days' administration. Endocrine-mediated effects, including thyroid dysfunction were not observed in any groups of rats treated with 1-chloro-4-(chloromethyl)benzene. Our results indicated that endocrine-mediated effects such as thyroid dysfunction were associated with some benzene-related compounds.

Immunohistochemical features of 3,3',4,4'-tetrachloroazobenzene-induced rat gingival lesions.

Gingival lesions of squamous hyperplasia, cystic keratinizing hyperplasia (CKH), and squamous cell carcinoma (SCC) can be induced in rats treated by chronic gavage with 10-100 mg/kg 3,3',4,4'-tetrachloroazobenzene. We evaluated gingival squamous hyperplasia (GSH), CKH, and SCC for the immunohistochemical pattern of expression of carcinogenesis-associated markers. The 3 types of lesions and controls were stained with proliferation markers (proliferating cell nuclear antigen [PCNA] and cyclin-D1), tumor-suppressor markers (ß-catenin and mammary serine protease inhibitor [maspin]) and stroma-related markers (α-smooth muscle actin [SMA] and osteonectin/SPARC). The lesions had common immunohistochemical characteristics that differed in their expression patterns among the various diagnoses. PCNA and cyclin-D1 expression was higher in GSH, CKH, and SCC than in controls. The normal membranous expression of ß-catenin was lower in GSH, and almost absent in CKH and SCC. Maspin expression was similar in GSH and controls, whereas both CKH and SCC showed decreased expression. SMA and/or osteonectin/SPARC were seen in stromal cells in CKH and SCC. Collectively, there appears to be a progression from hyperplastic and cystic lesions toward malignancy based on the morphological changes, supported by the expression of carcinogenesis-associated proteins. The exact sequence of events leading to SCC remains to be defined in a time-dependent manner.

Differential acute toxicity of tetrachlorobenzene isomers to oligochaetes in soil and water: application of the critical body residue concept.

The acute, lethal potency of the 1,2,3,4-, 1,2,4,5- and 1,2,3,5-tetrachlorobenzene isomers was compared in the terrestrial and aquatic oligochaetes Eisenia andrei and Tubifex tubifex. 1,2,4,5-TeCB was neither lethal, nor produced any perceptible adverse effects, at lipid normalized concentrations predicted to be lethal according to the well-established critical body residue concept. If a narcotic is defined as a substance capable of inducing narcosis, rather than a substance displaying certain physical or chemical properties (e.g., log K(ow)), then we do not believe these findings challenge the critical body residue because by the former definition, 1,2,4,5-tetrachlorobenzene is not a narcotic.

Differential accumulation of HCBz and PeCBz in porcine ovarian follicles and their opposing actions on steroid secretion and CYP11, CYP17, 17ß-HSD and CYP19 protein expression. A tissue culture approach.

In the current study, we determined in vitro accumulation of hexachlorobenzene (HCBz) and pentachlorobenzene (PeCBz) in porcine ovarian follicles, the effect on steroidogenesis and the expression of enzymes responsible for steroid synthesis. Sixty percent of the HCBz and almost 100% of the PeCBz that was added to the culture medium accumulated in ovarian tissue, and only 1% of each was found in the medium. An inhibitory HCBz effect and stimulatory PeCBz effect on testosterone and estradiol secretion were noted. Immunoblot analyses showed an inhibitory effect of HCBz on CYP17, 17ß-HSD and CYP19, a stimulatory effect of PeCBz on CYP17 and CYP19 and no effect on 17ß-HSD protein expression. In conclusion, the greater exposure to an estrogenic action of PeCBz than anti-estrogenic HCBz would be a consequence of the preferential accumulation of PeCBz in the ovarian follicles. As one of the mechanisms of action, we propose modulation of steroidogenic enzymes expression.

Chlorinated benzenes cause concomitantly oxidative stress and induction of apoptotic markers in lung epithelial cells (A549) at nonacute toxic concentrations.

In industrialized countries, people spend more time indoors and are therefore increasingly exposed to volatile organic compounds that are emitted at working places and from consumer products, paintings, and furniture, with chlorobenzene (CB) and 1,2-dichlorobenzene (DCB) being representatives of the halogenated arenes. To unravel the molecular effects of low concentrations typical for indoor and occupational exposure, we exposed human lung epithelial cells to CB and DCB and analyzed the effects on the proteome level by 2-D DIGE, where 860 protein spots were detected. A set of 25 and 30 proteins were found to be significantly altered due to exposure to environmentally relevant concentrations of 10(-2) g/m(3) of CB or 10(-3) g/m(3) of DCB (2.2 and 0.17 ppm), respectively. The most enriched pathways were cell death signaling, oxidative stress response, protein quality control, and metabolism. The involvement of oxidative stress was validated by ROS measurement. Among the regulated proteins, 28, for example, voltage-dependent anion-selective channel protein 2, PDCD6IP protein, heat shock protein beta-1, proliferating cell nuclear antigen, nucleophosmin, seryl-tRNA synthetase, prohibitin, and protein arginine N-methyltransferase 1, could be correlated with the molecular pathway of cell death signaling. Caspase 3 activation by cleavage was confirmed for both CB and DCB by immunoblotting. Treatment with CB or DCB also caused differential protein phosphorylation, for example, at the proteins HNRNP C1/C2, serine-threonine receptor associated protein, and transaldolase 1. Compared to previous results, where cells were exposed to styrene, for the chlorinated aromatic substances besides oxidative stress, apoptosis was found as the predominant cellular response mechanism.

Health risk assessment of exposure to selected volatile organic compounds emitted from an integrated iron and steel plant.

Workplace air samples from sintering, cokemaking, and hot and cold forming processes in the integrated iron and steel industry were analyzed to determine their volatile organic compound (VOC) concentration. Sixteen VOC species including three paraffins (cyclohexane, n-hexane, methylcyclohexane), five chlorinated VOC species (trichloroethylene, 1,1,1-trichloroethane, tetrachloroethylene, chlorobenzene, 1,4-dichlorobenzene), and eight aromatics (benzene, ethylbenzene, styrene, toluene, m,p-xylene, o-xylene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene) were selected to measure their noncancer risk for workers. Concentrations of toluene, xylene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, dichlorobenzene, and trichloroethylene were high in all four processes. Carbon tetrachloride and tetrachloroethylene concentrations were high in the hot and cold forming processes. The noncancer risk followed the increasing order: cokemaking > sintering > hot forming > cold forming. 1,2,4-trimethylbenzene and 1,3,5-trimethylbenzene contributed 44% to 65% and 13% to 20% of noncancer risk, respectively, for the four processes. Benzene accounted for a high portion of the noncancer risk in cokemaking. The hazard index (HI: 17-108) of the average VOC concentrations suggests that health risks can be reduced by improving workplace air quality and protecting workers.

Toxicity of xenobiotics during sulfate, iron, and nitrate reduction in primary sewage sludge suspensions.

The effect and persistence of six organic xenobiotics was tested under sulfate-, iron-, and nitrate-reducing conditions in primary sewage sludge suspensions. The xenobiotics tested were acenaphthene, phenanthrene, di(2-ethylhexyl)phthalate (DEHP), 4-nonylphenol (4-NP), linear alkylbenzene sulfonate (LAS), and 1,2,4-trichlorobenzene (1,2,4-TCB) added to initial analytical concentrations of 54-117 mgL(-1). The suspensions were incubated at 30 degrees C for 15 weeks and rates of sulfate, iron, and nitrate reduction were estimated from the time course of hydrogen sulfide accumulation, Fe(II) accumulation, and nitrate depletion, respectively. Chemical analysis showed that the xenobiotics were persistent under the different electron acceptor regimes for the duration of the experiment. This was partly attributed to low bioavailability and microbial toxicity of the xenobiotics. Rates of anaerobic respiration in control suspensions (without added xenobiotics) showed a weekly reduction potential of 0.84 mM SO(4)(2-), 0.92 mM Fe(III), and 9.25 mM NO(3)(-). All three processes were completely inhibited by 1,2,4-TCB (54 mgL(-1)) whereas there was no significant (P<0.05) toxicity of phenanthrene (109 mgL(-1)) and DEHP (105 mgL(-1)). Sulfate reduction was inhibited completely by LAS (105 mgL(-1)), 76% by acenaphthene (54 mgL(-1)) and 57% by 4-NP (117 mgL(-1)), and likewise iron reduction was inhibited 62% by LAS and 55% by 4-NP (the latter though at P<0.10). Nitrate reduction was not significantly inhibited by acenaphthene and 4-NP and furthermore was resistant to LAS toxicity (105 mgL(-1)). Nitrate reduction also had the highest potential for mineralization of organic matter and thus was the most robust of the tested anaerobic processes in the sewage sludge suspensions.

Urethral carcinoma and hyperplasia in male and female B6C3F1 mice treated with 3,3',4,4'-tetrachloroazobenzene (TCAB).

B6C3F1 mice chronically exposed to 3,3',4,4'-tetrachloroazobenzene (TCAB), a contaminant of dichloroaniline-derived herbicides, developed a number of neoplastic and nonneoplastic lesions, including carcinoma of the urinary tract. Groups of fifty male and fifty female B6C3F1 mice were exposed by gavage to TCAB at dose levels of 0, 3, 10, and 30 mg/kg five days a week for two years. Control animals received corn oil:acetone (99:1) vehicle. Decreased survival of male mice in the mid-dose group and of male and female mice in the high-dose groups was related mainly to the occurrence of urethral transitional cell (urothelial) carcinoma and resulting urinary obstruction. Increased urethral transitional cell carcinomas were seen in all treated male groups in a dose-related manner as well as in the females treated with 30 mg/kg TCAB. Administration of TCAB was also associated with increased transitional cell hyperplasia of the urethra. Most nonneoplastic lesions of the urogenital tract were considered secondary to local invasion and urinary obstruction by the urethral transitional cell carcinomas. The mechanism of tumor induction is uncertain, but the high frequency of tumors in the proximal urethra of male mice suggests that the neoplasms result from the exposure of a susceptible population of urothelial cells to a carcinogenic metabolite of TCAB.

A Mechanism for the induction of renal tumours in male Fischer 344 rats by short-chain chlorinated paraffins.

Short-chain chlorinated paraffins (SCCPs) cause kidney tumours in male rats, but not in female rats or mice of either sex. Male rat-specific tumours also occur in rats dosed with a range of compounds including 1,4- dichlorobenzene (DCB) and d-limonene (DL). These compounds bind to a male rat-specific hepatic protein, alpha-2-urinary globulin (α2u), and form degradationresistant complexes in the kidney. The resulting accumulation of α2u causes cell death and sustained regenerative cell proliferation, which in turn leads to the formation of renal tumours. To investigate whether the SCCP, Chlorowax 500C (C500C), causes tumours via the accumulation of α2u male rats were orally dosed with either C500C (625 mg/kg of body weight), DCB (300 mg/kg of body weight), or DL (150 mg/kg of body weight) for 28 consecutive days. An increase in renal α2u and cell proliferation was observed in DCB- and DL-treated rats but not in C500C-treated rats. C500C caused peroxisome proliferation and a down-regulation of α2u synthesis in male rat liver. This down-regulation occurred at the transcriptional level. Since less α2u was produced in C500C-treated rats, there was less available for accumulation in the kidney hence a typical α2u nephropathy did not appear. However, the administration of a radiolabelled SCCP, [14C]polychlorotridecane (PCTD), to male rats demonstrated its binding to renal α2u. Thus, it is possible that SCCPs bind to α2u and cause a slow accumulation of the protein in the kidney followed by delayed onset of α2u nephropathy. As a consequence of these findings in the current experiments, while evidence exists implicating α2u-globulin in the molecular mechanism of action of the C500C, the classic profile of a α2u-globulin nephropathy seen with other chemicals such as DCB and DL was not reproduced during this experimental protocol.

Toxicology and carcinogenesis studies of 3,3',4,4'-tetrachloroazobenzene (TCAB) (CAS No. 14047-09-7) in Harlan Sprague-Dawley rats and B6C3F1 mice (gavage studies).

3,3',4,4'-Tetrachloroazobenzene (TCAB) is not commercially manufactured but is formed as an unwanted by-product in the manufacture of 3,4-dichloroaniline and its herbicidal derivatives Propanil, Linuron, and Diuron. It occurs from the degradation of chloroanilide herbicides (acylanilides, phenylcarbamates, and phenylureas) in soil by peroxide-producing microorganisms; and is formed by the photolysis and biolysis of 3,4-dichloroaniline. Humans may be exposed to TCAB during the manufacture as well as the application of herbicides containing TCAB as a contaminant. TCAB was nominated by the United States Environmental Protection Agency for toxicity and carcinogenicity testing based on its structural and biological similarity to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and the potential for human exposure from the consumption of crops contaminated with 3,4-dichloroaniline-derived herbicides. Male and female Harlan Sprague-Dawley rats and B6C3F1 mice were administered TCAB (at least 97.8% pure) in corn oil:acetone (99:1) by gavage for 3 months (rats only) or 2 years. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female Harlan Sprague-Dawley rats were administered 0.1, 0.3, 1, 3, 10, 30, or 100 mg TCAB/kg body weight in corn oil:acetone (99:1) by gavage, 5 days a week, for 14 weeks; groups of 10 male and 10 female rats received the corn oil:acetone vehicle alone. Special study groups of 30 (dosed groups) or 6 (vehicle control group) female Harlan Sprague-Dawley rats were administered 0.1, 3, or 100 mg TCAB/kg body weight in corn oil:acetone (99:1) by gavage, 5 days a week, for 13 weeks; vehicle controls received the corn oil:acetone vehicle alone. All male and female rats survived to the end of the study. Terminal mean body weights of males were not significantly different from vehicle controls in any group. Terminal mean body weights of females administered 10 mg/kg or greater were significantly less than those of the vehicle controls. Mean body weight gains of all dosed groups of females were significantly less than those of the vehicle controls. The hematology results indicate that TCAB induced a microcytic normochromic responsive anemia in male Sprague-Dawley rats. Serum concentrations of total thyroxine (T4) and free T4 were significantly decreased in a dose-related manner in all dosed groups in both sexes compared to their respective vehicle controls; total triiodothyronine (T3) and thyroid stimulating hormone (TSH) concentrations were generally unaffected. There were no statistically significant differences in the BrdU labeling indices in the liver of males or females exposed to TCAB compared to their respective vehicle controls. Significant induction of hepatic 7-ethoxyresorufin-O-deethylase (EROD) and 7-pentoxyresorufin-O-deethylase activities was observed in all dosed groups of males and females. Significant induction of hepatic acetanilide-4-hydroxylase activity was observed in males exposed to 3 mg/kg or greater and all treated groups of females. EROD activities in the lung generally increased with increasing dose and were significantly greater in all treated groups of males and females compared to their respective vehicle controls. The highest concentrations of TCAB were observed in fat tissue with lower concentrations in the liver and lung. TCAB concentrations were significantly increased in a dose-dependent manner in all tissues from dosed groups relative to vehicle controls. At the end of the 3-month study, absolute and relative liver weights were significantly greater than those of the vehicle controls in all dosed groups of males and in females administered 10 mg/kg or greater. Absolute and relative lung weights were significantly greater in 100 mg/kg males and 3 mg/kg or greater females. Absolute and relative right kidney and spleen weights were generally significantly greater for all dosed groups of males. Absolute thymus weights of 10 mg/kg or greater males and absolute and relative thymus weights of 1 mg/kg or greater females were significantly less than those of the vehicle controls. In the liver, the incidences of midzonal to diffuse hepatocytic hypertrophy in males administered 1 mg/kg or greater and in females administered 10 mg/kg or greater were significantly greater than the vehicle control incidences. Hematopoietic cell proliferation occurred in most males administered 3 mg/kg or greater and most females administered 10 mg/kg or greater. The incidences of midzonal hepatocytic cytoplasmic fatty vacuolization were significantly increased in males administered 3 mg/kg or greater. In the lung, significantly increased incidences of bronchiolar metaplasia of the alveolar epithelium and interstitial mononuclear cell infiltration occurred in 10, 30, and 100 mg/kg males. The incidence of interstitial mononuclear cell infiltration was also significantly increased in 100 mg/kg females. Significantly increased incidences of hematopoietic cell proliferation of the spleen occurred in males administered 10 mg/kg or greater. The incidences of hemosiderin pigment of the spleen were significantly increased in 10 mg/kg or greater females. Atrophy in the thymus was significantly increased in all dosed groups of females, except the 0.1 mg/kg group, and in males administered 10 mg/kg or greater. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female Harlan Sprague-Dawley rats were administered 10, 30, or 100 mg TCAB/kg body weight in corn oil:acetone (99:1) by gavage, 5 days a week, for 2 years; groups of 50 male and 50 female rats received the corn oil:acetone vehicle alone. The survival of all dosed groups of males was significantly less than that of the vehicle controls. Mean body weights of 100 mg/kg males were less than those of the vehicle control group throughout the study. Mean body weights of 30 mg/kg males were 6% less than those of the vehicle control group after week 24, and those of 10 mg/kg males were 7% less than the vehicle control group after week 80. Mean body weights of 100 mg/kg females were less than those of the vehicle control group throughout the study, and those of 30 mg/kg females were 6% less than the vehicle control group after week 36. In the lung, the incidences of multiple cystic keratinizing epithelioma and single or multiple cystic keratinizing epithelioma (combined) in males and females were significantly increased in all dosed groups (except multiple epithelioma in 10 mg/kg females). Significantly increased incidences of pigmentation, alveolar epithelium squamous metaplasia (except 10 mg/kg females), and alveolar epithelium bronchiolar metaplasia occurred in all dosed groups of males and females. The incidences of histiocytic cellular infiltration in all dosed groups of males were significantly increased. In the liver, the incidences of cholangiocarcinoma (single or multiple) occurred in a positive trend in males and were significantly greater than that in the vehicle control group; the incidence in 100 mg/kg females was also increased. A significant dose-related increase in hepatic toxicity was observed in dosed rats and was characterized by increased incidences of numerous lesions including hepatocyte hypertrophy, centrilobular degeneration, hepatocellular necrosis, pigmentation, fatty change, bile duct hyperplasia, oval cell hyperplasia, nodular hyperplasia, hematopoietic cell proliferation, eosinophilic focus, mixed cell focus, multinucleated hepatocytes, bile duct cyst, toxic hepatopathy, and cholangiofibrosis. Significantly increased incidences of gingival squamous cell carcinoma within the oral mucosa occurred in 10 mg/kg males and 100 mg/kg males and females. The incidences of gingival squamous hyperplasia and cystic keratinizing hyperplasia in dosed groups of males and females were generally significantly increased. The incidences of follicular cell adenoma (single or multiple) of the thyroid gland in 30 and 100 mg/kg males were significantly greater than that in the vehicle control group. The incidences of follicular cell hypertrophy, follicular cell hyperplasia, and inflammation were significantly increased in 30 and 100 mg/kg males. Three incidences of single or multiple squamous cell papilloma of the forestomach occurred in 100 mg/kg females, and single incidences of squamous cell carcinoma of the forestomach occurred in 10 and 100 mg/kg females. Significantly increased incidences of epithelial hyperplasia occurred in all dosed groups of males and females. There were three incidences of malignant schwanomma in the thoracic cavity in 100 mg/kg males and a single incidence in 30 mg/kg males. In the adrenal cortex of 30 and 100 mg/kg females, there were slightly increased incidences of adenoma. In all dosed groups of males, the incidences of degeneration, cytoplasmic vacuolization, and hyperplasia of the zona fasciculata were significantly increased. Increased incidences and severities of necrosis occurred in 30 and 100 mg/kg males. Incidences of cytoplasmic vacuolation in 10 and 100 mg/kg females and hyperplasia of the zona fasciculata in 30 mg/kg females were significantly greater than those in the vehicle controls. Numerous nonneoplastic effects were seen in other organs including atrophy, acinar cytoplasmic vacuolization, and inflammation of the pancreas; blood vessel inflammation; lymphoid follicle atrophy and pigmentation of the spleen; pigmentation and atrophy of the mesenteric lymph node; germinal epithelial degeneration of the testes; and inflammation of the nose. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were administered 3, 10, or 30 mg TCAB/kg body weight in corn oil:acetone (99:1) by gavage, 5 days a week, for 2 years; groups of 50 male and 50 female rats received the corn oil:acetone vehicle alone. Survival of 10 and 30 mg/kg males and 30 mg/kg females was significantly less than that of vehicle controls. All 30 mg/kg males died before the end of the study. (ABSTRACT TRUNCATED)

Chlorobenzene induces oxidative stress in human lung epithelial cells in vitro.

Chlorobenzene is a volatile organic compound (VOC) that is widely used as a solvent, degreasing agent and chemical intermediate in many industrial settings. Occupational studies have shown that acute and chronic exposure to chlorobenzene can cause irritation of the mucosa of the upper respiratory tract and eyes. Using in vitro assays, we have shown in a previous study that human bronchial epithelial cells release inflammatory mediators such as the cytokine monocyte chemoattractant protein-1 (MCP-1) in response to chlorobenzene. This response is mediated through the NF-kappaB signaling pathway. Here, we investigated the effects of monochlorobenzene on human lung cells, with emphasis on potential alterations of the redox equilibrium to clarify whether the chlorobenzene-induced inflammatory response in lung epithelial cells is caused via an oxidative stress-dependent mechanism. We found that expression of cellular markers for oxidative stress, such as heme oxygenase 1 (HO-1), glutathione S-transferase pi1 (GSTP1), superoxide dismutase 1 (SOD1), prostaglandin-endoperoxide synthase 2 (PTGS2) and dual specificity phosphatase 1 (DUSP1), were elevated in the presence of monochlorobenzene. Likewise, intracellular reactive oxygen species (ROS) were increased in response to exposure. However, in the presence of the antioxidants N-(2-mercaptopropionyl)-glycine (MPG) or bucillamine, chlorobenzene-induced upregulation of marker proteins and release of the inflammatory mediator MCP-1 are suppressed. These results complement our previous findings and point to an oxidative stress-mediated inflammatory response following chlorobenzene exposure.

Lipid peroxidation and changes of trace elements in mice treated with paradichlorobenzene.

Paradichlorobenzene (pDCB) has been used as a space deodorant and moth repellant, as well as an intermediate in the chemical industry. Given its broad applications and high volatility, considerable concern exists regarding the adverse health effects of pDCB in the home and the workplace. In this study, changes in lipid peroxidation, antioxidants, and trace element levels in the liver and kidney of pDCB-treated mice were investigated to determine their roles in toxicity. Mice were orally gavaged once daily for seven consecutive days with pDCB (0 (corn oil control), 450, and 900 mg/kg). The level of malondialdehyde (MDA), an end product of lipid peroxidation, markedly increased in the high-dose pDCB group in both the liver and kidney compared with the control group. Changes in hepatic levels of reduced glutathione (GSH) in the pDCB groups were indistinguishable from the control group, while renal levels of reduced GSH in the high-dose pDCB group were significantly lowered in comparison to the control and the low-dose groups. Superoxide dismutase (SOD) activity in the liver of mice treated with pDCB showed a downward trend, whereas there was no consistent trend associated with changes in SOD activity in the kidney. Additionally, renal iron levels in the high-dose pDCB group were significantly decreased compared with the low-dose group and the controls, whereas hepatic iron content in the low-dose pDCB group was significantly lower compared with the controls. Selenium and zinc levels in the kidney were both significantly decreased in the high-dose pDCB group vs. the control and low-dose groups. There were no treatment-induced changes in copper levels in either the kidney or liver. However, a significant increase was found in the liver zinc/copper ratio in the high-dose pDCB group vs. the controls. In addition, blood zinc levels showed a downward trend with increased pDCB dosage. These results suggest that pDCB toxicity is mediated by oxidative damage and tissue-specific alterations in trace element levels both in the liver and the kidney of mice.

Responses of wheat seedlings to cadmium, mercury and trichlorobenzene stresses.

The molecular response of wheat (Triticum aestivum L., cv. Yangmai 13) seedlings to heavy metal (Cd, Hg) and 1,2,4-trichlorobenzene (TCB) stresses were examined by two-dimensional gel electrophoresis, image analysis, and peptide mass fingerprinting. The results showed inhibitions of root and shoot growth by Cd, Hg, and TCB. These stresses led to water deficit and lipid phosphorylation in the seedling which also promoted protein phophorylation in the leaves. Hg stress inhibited protein synthesis while Cd and TCB stresses induced or up-regulated more proteins in the leaves. Most of these induced proteins played important roles in the biochemical reactions involved in tolerance of wheat to Cd and TCB stresses. The primary functions of Cd- and TCB-induced proteins included methionine metabolism, Rubisco modification, protein phosphorylation regulation, protein configuration protection, H+ transmembrane transportation and also the synthesis of ethylene, defense substances and cell wall compounds.