Biochemical effects of chloral hydrate on male rats following 7-day drinking water exposure

Associations of exposure to disinfection by-products with blood coagulation parameters among women: Results from the Tongji reproductive and environmental (TREE) study

BACKGROUND

Experimental studies have shown that disinfection byproducts (DBPs) induce coagulotoxicity, but human evidence is scarce.

OBJECTIVE

This study aimed to explore the relationships of DBP exposures with blood coagulation parameters.

METHODS

Among 858 women from the Tongji Reproductive and Environmental (TREE) study, urinary dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) were detected as internal biomarkers of DBP exposures. We measured activated partial thromboplastin time (APTT), fibrinogen (Fbg), international normalized ratio (INR), prothrombin time (PT), and thrombin time (TT) as blood coagulation parameters. Multivariable linear regression models were utilized to estimate the relationships between urinary DCAA and TCAA and blood coagulation parameters. The effect modifications by demographic and lifestyle characteristics were further explored.

RESULTS

Elevated tertiles of urinary DCAA concentrations were associated with increased PT and INR (11.29%, 95% CI: 1.66%, 20.92% and 0.99%, 95% CI: 0.08%, 1.90% for the third vs. first tertile, respectively; both P for trends < 0.05). Stratification analysis showed that the positive associations were only observed among younger (< 30 years), leaner (body mass index < 24.0 kg/m2), and non-passive smoking women. Moreover, elevated tertiles of urinary TCAA concentrations in positive associations with PT and INR were observed among younger women (17.89%, 95% CI: 2.50%, 33.29% and 1.82%, 95% CI: 0.34%, 3.30% for the third vs. first tertile, respectively; both P for trends < 0.05) but not among older women (both P for interactions < 0.05).

CONCLUSION

Higher levels of urinary DCAA and TCAA are associated with prolonged clotting time among women.

Aldehyde dehydrogenase inhibitors: a comprehensive review of the pharmacology, mechanism of action, substrate specificity, and clinical application

Aldehyde dehydrogenases (ALDHs) belong to a superfamily of enzymes that play a key role in the metabolism of aldehydes of both endogenous and exogenous derivation. The human ALDH superfamily comprises 19 isozymes that possess important physiological and toxicological functions. The ALDH1A subfamily plays a pivotal role in embryogenesis and development by mediating retinoic acid signaling. ALDH2, as a key enzyme that oxidizes acetaldehyde, is crucial for alcohol metabolism. ALDH1A1 and ALDH3A1 are lens and corneal crystallins, which are essential elements of the cellular defense mechanism against ultraviolet radiation-induced damage in ocular tissues. Many ALDH isozymes are important in oxidizing reactive aldehydes derived from lipid peroxidation and thereby help maintain cellular homeostasis. Increased expression and activity of ALDH isozymes have been reported in various human cancers and are associated with cancer relapse. As a direct consequence of their significant physiological and toxicological roles, inhibitors of the ALDH enzymes have been developed to treat human diseases. This review summarizes known ALDH inhibitors, their mechanisms of action, isozyme selectivity, potency, and clinical uses. The purpose of this review is to 1) establish the current status of pharmacological inhibition of the ALDHs, 2) provide a rationale for the continued development of ALDH isozyme-selective inhibitors, and 3) identify the challenges and potential therapeutic rewards associated with the creation of such agents.

Evaluation of neurotoxic and immunotoxic effects of trichloroacetic acid on rats

This study was carried out to investigate the neurotoxic and immunotoxic effects of trichloroacetic acid (TCA) on rats at subchronic exposure. The neurotoxic effects of TCA were evaluated by measuring the activities of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Biomarkers selected for immunotoxic monitoring were the activities of adenosine deaminase (ADA) and myeloperoxidase (MPO) in various tissues of rats exposed to 2000 parts per million (ppm) dosage of TCA for 52 days. Results showed that the administrations of TCA decreased BChE activities in heart and lungs tissue of the rats treated with TCA. With regard to the immunotoxic effects, ADA activity significantly decreased in the heart, lungs and spleen whereas MPO activity increased after subchronic exposure with 2000 ppm dosage in all of the tissues except for heart tissue of rats compared with controls. The observations presented led us to conclude that the administration of TCA at subchronic was decreased BChE and ADA activities whereas increased MPO activity in various tissues of rats. This may reflect the potential role of these parameters as useful biomarkers for toxicity of TCA.

Evaluation of the role of peroxisome proliferator-activated receptor alpha (PPARalpha) in mouse liver tumor induction by trichloroethylene and metabolites

Trichloroethylene (TCE) is an industrial solvent and a widespread environmental contaminant. Induction of liver cancer in mice by TCE is thought to be mediated by two metabolites, dichloroacetate (DCA) and trichloroacetate (TCA), both of which are themselves mouse liver carcinogens. TCE, TCA, and DCA are relatively weak peroxisome proliferators (PP), a group of rodent hepatocarcinogens that activate a nuclear receptor, PP-activated receptor alpha (PPARalpha. The objective of this review is to assess the weight of evidence (WOE) that PPARalpha is or is not mechanistically involved in mouse liver tumor induction by TCE and metabolites. Based on similarities of TCE and TCA to typical PP, including dose-response characteristics showing PPARalpha-dependent responses coincident with liver tumor induction and abolishment of TCE and TCA effects in PPARalpha-null mice, the WOE supports the hypothesis that PPARalpha plays a dominant role in TCE- and TCA-induced hepatocarcinogenesis. Data indicates that the MOA for DCA tumor induction is PPARalpha-independent. Uncertainties remain regarding the genesis of the TCE-induced tumors. In contrast to the TCA-induced tumors, which have molecular features similar to those induced by typical PP, there is evidence, albeit weak, that TCE tumors arise by a mode of action (MOA) different from that of TCA tumors, based largely on dissimilarities in molecular markers found in TCE versus TCA-induced tumors. In summary, the WOE indicates that TCA-induced liver tumors arise by a PPARalpha-dependent MOA. Although the TCE MOA is likely dominated by a PPARalpha-dependent contribution from TCA, the contribution of a PPARalpha-independent MOA from DCA cannot be ruled out.

Halogenated acetaldehydes: analysis, stability and fate in drinking water

In our previous studies, chloral hydrate has been the only chlorinated acetaldehyde determined in drinking water because authentic standards of other related haloacetaldehydes were not available. Recently, standards of dichloroacetaldehyde, bromochloroacetaldehyde, dibromoacetaldehyde, bromodichloroacetaldehyde, chlorodibromoacetaldehyde, and tribromoacetaldehyde have become available commercially. They were obtained and verified for purity and stability using a dual-column GC-ECD system. Each commercial standard was found to contain small amounts of the other target haloacetaldehydes (HAs). The stability of the HAs stock solutions was solvent dependent: in acetone, the brominated species partially degraded to bromoacetone, while all target HAs were stable in MTBE for up to 8 months. The analytical parameters, required for the quantification of HAs in water, were determined and used to evaluate the stability of the HAs in water. Under the conditions of the sampling protocol (field pH adjustment to pH 4.5 and storage at 4 degrees C), the target HAs were stable in water for up to 14 days. However, at typical drinking water pH and temperature conditions, the stability varied with the HA species, pH, temperature and storage period. The trihalogenated acetaldehydes degraded, in part, to their corresponding trihalomethanes (THMs) at increasing pH and temperature. Most target HAs were detected in drinking water samples collected from various Canadian drinking water systems, and the speciation was dependent on water parameters (e.g. bromide concentration) and treatment processes. From the water samples analysed, chloral hydrate ranged between 7% and 51% of the total HAs (w/w). The weigh ratio of total HAs to total THMs (10-46%) indicated that HAs contributed significantly to the pool of DBPs in drinking water.

Subchronic toxicity of chloral hydrate on rats: a drinking water study

The subchronic toxicity of chloral hydrate, a disinfection byproduct, was studied in rats following 13 weeks of drinking water exposure. Male (262 +/- 10 g) and female (190 +/- 8 g) Sprague-Dawley rats, ten animals per group, were administered chloral hydrate via drinking water at 0.2, 2, 20 and 200 ppm. Control animals received distilled water only. Gross and microscopic examinations, serum chemistry, hematology, biochemical analysis, neurogenic amine analysis and serum trichloroacetic acid (TCA) analysis were performed at the end of the treatment period. Bronchoalveolar fluids were collected at necropsy and urine specimens were collected at weeks 2, 6 and 12 for biochemical analysis. No treatment-related changes in food and water intakes or body weight gains were observed. There were no significant changes in the weights of major organs. Except for a mild degree of vacuolation within the myelin sheath of the optic nerves in the highest dose males, there were no notable histological changes in the tissues examined. Statistically significant treatment-related effects were biochemical in nature, with the most pronounced being increased liver catalase activity in male rats starting at 2 ppm. Liver aldehyde dehydrogenase (ALDH) was significantly depressed, whereas liver aniline hydroxylase activity was significantly elevated in both males and females receiving the highest dose. A dose-related increase in serum TCA was detected in both males and females starting at 2 ppm. An in vitro study of liver ALDH confirmed that chloral hydrate was a potent inhibitor, with an IC(50) of 8 micro M, whereas TCA was weakly inhibitory and trichloroethanol was without effect. Analysis of brain biogenic amines was conducted on a limited number (n = 5) of male rats in the control and high dose groups, and no significant treatment-related changes were detected. Taking into account the effect on the myelin sheath of male rats and the effects on liver ALDH and aniline hydroxylase of both males and females at the highest dose level, the no-observed-effect level (NOEL) was determined to be 20 ppm or 1.89 mg kg(-1) day(-1) in males and 2.53 mg kg(-1) day(-1) in females. This NOEL is ca. 1000-fold higher than the highest concentration of chloral hydrate reported in the municipal water supply.

Chloral hydrate for progressive myoclonus epilepsy: a new look at an old drug

This study demonstrates that chloral hydrate can be used to control daytime myoclonic exacerbations. It reports on four patients with progressive myoclonus epilepsy--three with Unverricht-Lündborg disease (EPM1) and one with progressive external ophthalmoplegia (PEO)--all of whom were taking more than one antiepileptic drug. Response to the liquid formulation was faster than response to the capsule and was preferred by the patients. The unusual feature was less than expected sedation or development of tolerance even at daily doses above 500 mg administered for years. Because chloral hydrate helped to improve quality of life, it should be made available to patients with progressive myoclonus epilepsy as adjunctive therapy. Recent evidence of interactions with various excitatory and inhibitory amino acid neurotransmitter-operated ion channels as a mechanism of action may provide insight into altered neurotransmission in progressive myoclonus epilepsy.