Interaction between 1,2-dichloroethane and tetraethylthiuram disulfide (disulfiram). II. Hepatotoxic manifestations with possible mechanism of action

Roles of CYP2e1 in 1,2-dichloroethane-induced liver damage in mice

The aim of this study was to explore the roles of cytochrome P450 2E1 (CYP2E1) in 1,2-dichloroethane (1,2-DCE)-induced liver damage. Two parts were included in this study: first, effect of 1,2-DCE on microsomal expression of CYP2E1, and second, potential of an inhibitor of CYP2E1 to reduce 1,2-DCE-induced liver damage. In part one, mice were exposed to 0, 0.225, 0.45, or 0.9 g/m³ 1,2-DCE for 10 days, 3.5 h per day through static inhalation. In part two, mice were divided into blank control, solvent control, inhibitor control, 1,2-DCE-poisoned group, and low or high intervention group. In part one, compared to the control, serum alanine aminotransferase (ALT) activities and hepatic malondialdehyde (MDA) levels in 0.9 g/m³ 1,2-DCE group, and microsomal CYP2E1 protein expression and activity in both 0.45 and 0.9 g/m³ 1,2-DCE groups increased significantly; conversely, hepatic nonprotein sulfhydryl (NPSH) levels in both 0.45 and 0.9 g/m³ 1,2-DCE groups and hepatic SOD activities in 0.9 g/m³ 1,2-DCE group decreased significantly. In part two, microsomal CYP2E1 protein expression and activity decreased significantly in both low and high intervention groups compared to 1,2-DCE-poisoned group. Along with the changes of CYP2E1, hepatic MDA levels and serum ALT activities decreased; conversely, hepatic NPSH levels and SOD activities increased significantly in high intervention group. Taken together, our results suggested that 1,2-DCE could enhance CYP2E1 protein expression and enzymatic activity, which could cause oxidative damage in liver, serving as an important mechanism underlying 1,2-DCE-induced liver damage. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1430-1438, 2016.

Distribution of blood and tissue concentrations in rats by inhalation exposure to 1,2-dichloroethane

The compound 1,2-dichloroethane (DCE) is a ubiquitous environmental contaminant. The primary route of exposure of humans to DCE is inhalation of its vapor. The present investigation was undertaken to determine the distribution and accumulation of DCE in the blood, lung, liver, brain, kidney and abdominal fat of rats during and after inhalation exposure. Male rats were exposed to 160 ppm (v/v) of DCE vapor for 360 min and the concentrations of DCE in the blood and tissues during the inhalation exposure period and after the end of the exposure period were measured. DCE accumulation in the abdominal fat was much greater than that in the blood and other tissues. The information we obtained in this study is useful basic data pertaining to the pharmacokinetics of DCE and DCE-mediated carcinogenicity: Our results suggest that one of the factors involved in the induction of peritoneal tumors in rats exposed to DCE vapor by inhalation is DCE accumulation in the abdominal fat.

Carcinogenicity and Chronic Toxicity in Rats and Mice Exposed by Inhalation to 1,2‐Dichloroethane for Two Years

Carcinogenicity and chronic toxicity of 1,2-dichloroethane (DCE) were examined by inhalation exposure of groups of 50 F344 rats and 50 BDF1 mice of both sexes to DCE vapor or clean air as control for 6 h/d, 5 d/wk and 104 wk. The rats were exposed to 10, 40 or 160 ppm (v/v) DCE, while the mice were exposed to 10, 30 or 90 ppm. The 2-yr exposure to DCE produced a dose-dependent increase in incidences of benign and malignant tumors, including subcutaneous fibroma, mammary gland fibroadenoma and peritoneal mesothelioma in male rats; subcutaneous fibroma and mammary gland adenoma, fibroadenoma and adenocarcinoma in female rats; and bronchiolo-alveolar adenoma and carcinoma, endometrial stromal polyp, mammary gland adenocarcinoma and hepatocellular adenoma in female mice. No exposure-related change in the incidence of non-neoplastic lesions or in any hematological, blood biochemical or urinary parameter occurred in any DCE-exposed rat or mouse group. The types of tumors and their target organs found in this study were consistent with those observed in rats and mice administered DCE by gavage in a NCI study. Selection of the exposure concentrations was considered appropriate with reference to the maximum tolerated dose for the highest doses and an occupational exposure limit of DCE for the lowest dose. The present findings suggest that those carcinogenic responses be primarily considered for standard setting of occupational and environmental exposure to DCE.

Liver toxicity due to 1,2-dichloropropane in the rat

The effect of 1,2-dichloropropane on rat liver was studied after short (5 days) and long term (4 weeks) i.p. administration. Animals were injected daily with 10-500 mg/kg body wt 1,2-dichloropropane and biochemical and histological changes of liver were investigated. Treatment was monitored by measuring urinary mercapturic acid excretion. A significant increase of mercapturate excretion was observed at all dose levels, with no further increase during the treatment; at lower doses a return to baseline values occurred within 48 h after the end of treatment. Mercapturate excretion at the end of weeks 2, 3 and 4 of treatment was significantly lower than that observed at the end of week 1. The liver reduced glutathione content was different after single or repeated injections. A dose-dependent decrease of liver reduced glutathione was observed after a single injection and a dose-dependent increase after 4 weeks. The liver biochemical pattern after 4 weeks of treatment (characterized by a decrease of cytochrome P-450 and by an increase of reduced glutathione and glutathione S-transferase activity) suggests a hyperplastic evolution of the liver cells, probably a repair mechanism induced by early depletion of reduced glutathione. Light microscopy confirms that the prevalent alterations are regenerative in type (atypical mitosis and hyperplastic nodules). Areas of focal necrosis are isolated, and trend to disappear after long term treatment.

Elemental alterations during the exposure of 1,2-dichloroethane (EDC), disulfiram (DSF), and EDC-DSF to male Sprague-Dawley rats

Trace elements participate in the organ specific impact of 1,2-dichloroethane (EDC) and Disulfiram (tetraethylthiuram disulfide; Antabuse (DSF] administered singly or together, on male Sprague-Dawley rats exposed by diet (AIN-76) to DSF (0 and 0.15% for 10 d before and during exposure to EDC) and by inhalation to EDC (0, 153, 304, 455 ppm (v/v); 7 h/d for 5 d/wk for 30 exposure days). Kidney, liver, spleen, and testes at exposure d 30 as well as progressive urine samples were examined for elemental content by simultaneous inductively coupled plasma atomic emission spectroscopy. Each compound singly or together produced EDC dose related (r greater than or equal to 0.8) changes in metal content in organs relative to controls. There were increases induced by EDC alone for P and Sr in the liver and decreases for Fe, Mg, and P in the spleen. EDC in DSF-exposed animals caused increases in Ca, Cu, Fe, Mn, and S and a decrease in K in the liver; increases in Ca, Cu, Fe, Mn, Mo, P, and S and a decrease of Zn in the testes; an increase in Fe and a decrease in K in the spleen; and an increase of P in the kidney. DSF alone increased Cu in the liver but decreased it in the testes and kidney; Pb was increased in the liver and kidney and Zn in the liver, spleen, and kidney; Al and Si were increased also in the liver, S in the spleen, and K in the kidney; Mn and Na were decreased in the kidney. The organs showing histopathology (the liver and testes) both showed increases in Ca, Cu, Fe, Mn, and S. Metals in urine characterized a "shock" impact of the initial exposure by initial excretion of Na and retention of most other elements. After steady state (greater than 12 d), EDC alone caused increases for Sr and Zn; for EDC-DSF, EDC also decreased Na in addition to the changes elicited by DSF alone (increases in S and Zn and a decrease for Cu). The results were interpreted from the perspective of the effects of metals on the glutathione detoxicative pathway, the concentration of free diethyldithiocarbamate in urine, and an interaction with bone. Mechanisms of action of EDC, DSF, and EDC-DSF must include consideration of trace elements in addition to organic intermediates, metabolites, and enzymes.

Ethanol decreases plasma sulphydryls in man: effect of disulfiram

Based on animal experiments, interactions of ethanol and its metabolites with sulphydryls have been implicated in the toxicity of ethanol, but acute effects of ethanol on sulphydryls have not been documented in man. Plasma free glutathione and cysteine were therefore measured following the administration of 0.2 g kg-1 ethanol to normal healthy volunteers and chronic alcoholics on disulfiram, where the effects of high concentrations of acetaldehyde can be observed. In both groups, plasma glutathione decreased shortly following ethanol, and a sustained decreased in glutathione was seen in the subjects on disulfiram. In patients on disulfiram, but not the healthy controls, plasma cysteine decreased significantly. The decrease in plasma cysteine was correlated to the rise in acetaldehyde, suggesting that cysteine, but not glutathione, forms an adduct with acetaldehyde in man. We conclude that even moderate doses of ethanol may disturb the sulphydryl homeostasis and could interfere with biologically important processes that depend on sulphydryl groups.