Time dependence of chloroform-induced metabolic alterations in the liver and kidney of B6C3F1 mice

Micronuclei in bone marrow and liver in relation to hepatic metabolism and antioxidant response due to coexposure to chloroform, dichloromethane, and toluene in the rat model

Genotoxicity in cells may occur in different ways, direct interaction, production of electrophilic metabolites, and secondary genotoxicity via oxidative stress. Chloroform, dichloromethane, and toluene are primarily metabolized in liver by CYP2E1, producing reactive electrophilic metabolites, and may also produce oxidative stress via the uncoupled CYP2E1 catalytic cycle. Additionally, GSTT1 also participates in dichloromethane activation. Despite the oxidative metabolism of these compounds and the production of oxidative adducts, their genotoxicity in the bone marrow micronucleus test is unclear. The objective of this work was to analyze whether the oxidative metabolism induced by the coexposure to these compounds would account for increased micronucleus frequency. We used an approach including the analysis of phase I, phase II, and antioxidant enzymes, oxidative stress biomarkers, and micronuclei in bone marrow (MNPCE) and hepatocytes (MNHEP). Rats were administered different doses of an artificial mixture of CLF/DCM/TOL, under two regimes. After one administration MNPCE frequency increased in correlation with induced GSTT1 activity and no oxidative stress occurred. Conversely, after three-day treatments oxidative stress was observed, without genotoxicity. The effects observed indicate that MNPCE by the coexposure to these VOCs could be increased via inducing the activity of metabolism enzymes.

Nanoscale hepatoprotective herbal decoction attenuates hepatic stellate cell activity and chloroform-induced liver damage in mice

BACKGROUND

San-Huang-Xie-Xin-Tang (SHXXT) decoction, a traditional Chinese medicine containing Rhei rhizome, Coptidis rhizome, and Scutellariae radix, is widely used in hepatoprotective therapy. However, preparation of the decoction requires addition of boiling water that causes loss of numerous effective components.

METHODS

To improve the bioavailability of the decoction, nanoscale SHXXT was developed. Chloroform-induced liver injury and hepatic stellate cell activity in mice were used to demonstrate the hepatoprotective characteristics of nanoscale SHXXT decoction.

RESULTS

Liver/body weight ratio and serum aspartate and alanine aminotranferase levels were recovered by the nanoscale SHXXT. TIMP-1 gene expression was inhibited and MMP-2 gene expression was accelerated in activated hepatic stellate cells.

CONCLUSION

Nanoscale SHXXT decoction prepared in room temperature water could have preserved hepatoprotective ability. The results of this study indicate that nanoscale SHXXT could be extracted easily. The simple preparation of this herbal decoction is more convenient and energy-efficient.

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.

Not only training but also exposure to chlorinated compounds generates a response to oxidative stimuli in swimmers

Relations between exposure to chlorinated compounds and biological markers of response to oxidative stimuli were investigated in swimmers, taking into account the effect of training. Twenty-two male swimmers aged 15-25 years were surveyed twice. Prevalence of irritant symptoms and asthma and number of hours of training were reported. Exposure to nitrogen trichloride (NCl3) and blood response to oxidative stimuli [catalase, superoxide dismutase (Cu2+/Zn2+ SOD), glutathione peroxidase (GSH-Px) activities and ceruloplasmin, ferritin and total antioxidant concentrations] were measured. Univariate analyses were completed by multivariate analyses. High prevalences of irritant symptoms and asthma were found. Multivariate analysis confirmed the results of the univariate analyses and showed that Cu2+/Zn2+ SOD activity was increased by exposure and by training (P = 0.01, P = 0.0001, respectively). Erythrocyte GSH-Px was decreased, whereas plasma GSH-Px was increased by exposure (P = 0.002, P = 0.002). No other association was found. Higher irritant symptoms and increases in the activities of erythrocyte Cu2+/Zn2+ SOD and of plasma GSH-Px with exposure support the hypothesis that the production of reactive oxygen species is not only related to training but also to exposure to chlorinated compounds. Other athletes tend to have respiratory problems such as asthma, but the exposure to chlorinated compounds may increase the respiratory disease among swimmers.

Correlation of a specific mitochondrial phospholipid-phosgene adduct with chloroform acute toxicity

The dose and time dependence of formation of a specific adduct between mitochondrial phospholipid and phosgene have been determined in the liver of Sprague-Dawley (SD) rats as well as in the liver and kidney of B6C3F1 mice after dosing with chloroform. Rats were induced with phenobarbital or non-induced. Determination of tissue glutathione (GSH) and of serum markers of hepatotoxicity and nephrotoxicity was also carried out. With dose-dependence experiments, a strong correlation between the formation of the specific phospholipid adduct, GSH depletion and organ toxicity could be evidenced in all the organs studied. With non-induced SD rats, no such effects could be induced up to a dose of 740 mg/kg. Time-course studies with B6C3F1 mice indicated that the specific adduct formation took place at very early times after chloroform dosing and was concurrent with GSH depletion. The adduct formed during even transient GSH depletion (residual level: 30% of control) and persisted after restoration of GSH levels. Following a chloroform dose at the hepatotoxicity threshold (150 mg/kg), the elimination of the adduct in the liver occurred within 24 h and correlated with the recovery of ALT, which was slightly increased (12 times) after treatment. Following a moderately nephrotoxic dose (60 mg/kg), the renal adduct persisted longer than 48 h, when a 100% increase in blood urea nitrogen and a 40% increase in serum creatinine indicated the onset of organ damage. The formation of the adduct in the liver mitochondria of B6C3F1 mice was associated with the decrease of phosphatidyl-ethanolamine (PE), in line with previous results in rat liver indicating that the adduct results from the reaction of phosgene with PE. The adduct levels implicated the reaction of phosgene with about 50% PE molecules in the liver mitochondrial membrane of phenobarbital-induced SD rats and of about 10% PE molecules of the inner mitochondrial membrane of the liver of B6C3F1 mice. The association of this adduct with the toxic effects of chloroform makes it a very good candidate as the primary critical alteration in the sequence of events leading to cell death caused by chloroform.