Relationship between the carbon skeleton length of ketonic solvents and potentiation of chloroform-induced hepatotoxicity in rats

Response of earthworm coelomocytes and catalase to pentanone and hexanone: a revelation of the toxicity of conventional solvents at the cellular and molecular level

Organic solvents like 2-pentanone and 2-hexanone which are widely used in industrial production make up a large proportion of the source of chemical pollution. What is worrisome is that the cellular and molecular toxicity of 2-pentanone and 2-hexanone has not been reported yet. Based on this, earthworms and catalase (CAT) were chosen as target receptors for the toxicity studies. The cytotoxicity of 2-pentanone and 2-hexanone was revealed by measuring the multiple intracellular indicators of oxidative stress. At the molecular level, changes in the structure and function of CAT were characterized in vitro by the spectroscopy and molecular docking. The results show that 2-pentanone and 2-hexanone that induced the accumulation of reactive oxygen species can eventually reduce coelomocytes viability, accompanying by the regular changes of antioxidant activity and lipid peroxidation level. In addition, the exposure of 2-pentanone and 2-hexanone can shrink the backbone structure of CAT, quench the fluorescence, and misfold the secondary structure. The decrease in enzyme activity should be attributed to the structural changes induced by surface binding. This study discussed the toxicological effects and mechanisms of conventional solvents at the cellular and molecular level, which creatively proposed a joint research method.

Organism and molecular-level responses of superoxide dismutase interaction with 2-pentanone

2-Pentanone is an excellent organic solvent and extractant, which is widely used in industrial production. 2-Pentanone is harmful to soil organisms when it enters the soil. However, current studies have not clarified the response of the antioxidant enzyme superoxide dismutase (SOD) to 2-Pentanone and its mechanism. In this study, the response of earthworm antioxidant enzyme SOD to 2-Pentanone and its molecular mechanism was investigated at organism molecular levels. The results showed that the SOD activity of earthworms under 2-Pentanone stress was significantly inhibited, and the inability of superoxide anion radicals (·O₂^-) to be scavenged in time might be one of the reasons for the increase of lipid peroxidation. Under 2-Pentanone exposure conditions, catalase (CAT), an antioxidant enzyme closely related to SOD, and the total antioxidant capacity (T-AOC) of earthworms were activated to resist oxidative damage. On the other hand, the observation of earthworm microstructure provided evidence of a direct risk of 2-Pentanone on earthworm body wall tissues. Molecular-level assays have shown that 2-pentanone altered the secondary structure of SOD, which further led to the loosening of the SOD backbone structure and the extension of the polypeptide chain. On the other hand, 2-pentanone quenched the endogenous fluorescence of SOD in the form of static quenching and formed the 2-pentanone/SOD complex. Molecular simulation results suggested that 2-pentanone tended to bind on the surface of SOD rather than close to the active site, and it is speculated that the alteration of SOD structure is the key reason for the change in its activity. This study enriches the toxicological data of 2-Pentanone on soil organisms, thus responding to the current concerns about its ecological risk.

Effect of commercial or depurinized milk on rat liver growth-regulatory kinases, nuclear factor-kappa B, and endonuclease in experimental hyperuricemia: comparison with allopurinol therapy

Hyperuricemia is a biochemical hallmark of gout, renal urate lithiasis, and inherited purine disorders, and may be a result of enormous ATP breakdown or purine release as a result of cardiovascular disease, hypertension, kidney disease, eclampsia, obesity, metabolic syndrome, psoriasis, tumor lysis syndrome, or intense physical training. The beneficial role of dairy products on hyperuricemia management and prevention is well documented in the literature. The primary aim of our experimental study was to examine the effect of milk dietary regimen (commercial 1.5% fat UHT milk or patented depurinized milk) compared with allopurinol therapy on experimental hyperuricemia induced by oxonic acid in rats. Principal component analysis was applied on a data set consisting of 11 variables for 8 different experimental groups. Among the 11 parameters measured (plasma uric acid and the liver parameters NFκB-p65, Akt kinase/phospho-Akt kinase, ERK kinase/phospho-ERK kinase, IRAK kinase/phospho IRAK kinase, p38/phospho-p38, and DNase), Akt/phospho Akt and ERK/phospho-ERK signaling were extracted as the most discriminating. We also compared the content of various potentially toxic compounds (sulfur compounds, ketones, aldehydes, alcohols, esters, carboxylic acids, and phthalates) in untreated commercial milk and depurinized milk. Of all the compounds investigated in this study that were observed in commercial milk (24 volatile organic compounds and 4 phthalates), 6 volatile organic compounds were not detected in depurinized milk. For almost all of the other compounds, significant decreases in concentration were observed in depurinized milk compared with commercial milk. In conclusion, a depurinized milk diet may be recommended in nutritional treatment of primary and secondary hyperuricemia to avoid uric acid and other volatile, potentially toxic compounds that may slow down liver regeneration and may induce chronic liver diseases.

Prediction of rodent carcinogenic potential of naturally occurring chemicals in the human diet using high-throughput QSAR predictive modeling

Consistent with the U.S. Food and Drug Administration (FDA) Critical Path Initiative, predictive toxicology software programs employing quantitative structure-activity relationship (QSAR) models are currently under evaluation for regulatory risk assessment and scientific decision support for highly sensitive endpoints such as carcinogenicity, mutagenicity and reproductive toxicity. At the FDA's Center for Food Safety and Applied Nutrition's Office of Food Additive Safety and the Center for Drug Evaluation and Research's Informatics and Computational Safety Analysis Staff (ICSAS), the use of computational SAR tools for both qualitative and quantitative risk assessment applications are being developed and evaluated. One tool of current interest is MDL-QSAR predictive discriminant analysis modeling of rodent carcinogenicity, which has been previously evaluated for pharmaceutical applications by the FDA ICSAS. The study described in this paper aims to evaluate the utility of this software to estimate the carcinogenic potential of small, organic, naturally occurring chemicals found in the human diet. In addition, a group of 19 known synthetic dietary constituents that were positive in rodent carcinogenicity studies served as a control group. In the test group of naturally occurring chemicals, 101 were found to be suitable for predictive modeling using this software's discriminant analysis modeling approach. Predictions performed on these compounds were compared to published experimental evidence of each compound's carcinogenic potential. Experimental evidence included relevant toxicological studies such as rodent cancer bioassays, rodent anti-carcinogenicity studies, genotoxic studies, and the presence of chemical structural alerts. Statistical indices of predictive performance were calculated to assess the utility of the predictive modeling method. Results revealed good predictive performance using this software's rodent carcinogenicity module of over 1200 chemicals, comprised primarily of pharmaceutical, industrial and some natural products developed under an FDA-MDL cooperative research and development agreement (CRADA). The predictive performance for this group of dietary natural products and the control group was 97% sensitivity and 80% concordance. Specificity was marginal at 53%. This study finds that the in silico QSAR analysis employing this software's rodent carcinogenicity database is capable of identifying the rodent carcinogenic potential of naturally occurring organic molecules found in the human diet with a high degree of sensitivity. It is the first study to demonstrate successful QSAR predictive modeling of naturally occurring carcinogens found in the human diet using an external validation test. Further test validation of this software and expansion of the training data set for dietary chemicals will help to support the future use of such QSAR methods for screening and prioritizing the risk of dietary chemicals when actual animal data are inadequate, equivocal, or absent.

Chlorinated methanes and liver injury: highlights of the past 50 years

The chlorinated methanes, particularly carbon tetrachloride and chloroform, are classic models of liver injury and have developed into important experimental hepatoxicants over the past 50 years. Hepatocellular steatosis and necrosis are features of the acute lesion. Mitochondria and the endoplasmic reticulum as target sites are discussed. The sympathetic nervous system, hepatic hemodynamic alterations, and role of free radicals and biotransformation are considered. With carbon tetrachloride, lipid peroxidation and covalent binding to hepatic constituents have been dominant themes over the years. Potentiation of chlorinated methane-induced liver injury by alcohols, aliphatic ketones, ketogenic compounds, and the pesticide chlordecone is discussed. A search for explanations for the potentiation phenomenon has led to the discovery of the role of tissue repair in the overall outcome of liver injury. Some final thoughts about future research are also presented.

Toxicokinetics of organic solvents: a review of modifying factors

This article reviews, with an emphasis on human experimental data, factors known or suspected to cause changes in the toxicokinetics of organic solvents. Such changes in the toxicokinetic pattern alters the relation between external exposure and target dose and thus may explain some of the observed individual variability in susceptibility to toxic effects. Factors shown to modify the uptake, distribution, biotransformation, or excretion of solvent include physical activity (work load), body composition, age, sex, genetic polymorphism of the biotransformation, ethnicity, diet, smoking, drug treatment, and coexposure to ethanol and other solvents. A better understanding of modifying factors is needed for several reasons. First, it may help in identifying important potential confounders and eliminating negligible ones. Second, the risk assessment process may be improved if different sources of variability between external exposures and target doses can be quantitatively assessed. Third, biological exposure monitoring may be also improved for the same reason.

Structure-toxicity relationship of monoketones: in vitro effects on beta-adrenergic receptor binding and Na(+)-K(+)-ATPase activity in mouse synaptosomes

The structure-toxicity relationship of monoketones, a class of organic solvents widely used in industry, was investigated with respect to their in vitro effects on synaptosomal membrane proteins. The toxic parameters used were Na(+)-K(+)-adenosine triphosphatase (Na(+)-K(+)-ATPase), a well-known marker enzyme often used as a membrane toxicity model, and 3H-dihydroalprenolol (3H-DHA)-labeled beta-adrenergic receptor binding that has been shown to be vulnerable to solvent-induced changes in membrane fluidity. In vitro treatments with 12 kinds of monoketones (carbon chain length from 3-10) dose-dependently inhibited both 3H-DHA binding to mouse synaptosomes and Na(+)-K(+)-ATPase activity. The potency of inhibition (IC50) for both the two parameters was linearly related to n-octanol/water partition coefficient and synaptosome/buffer partition coefficient of the test compounds. Additions of monoketones did not significantly alter the number of 3H-DHA binding sites but markedly decreased their affinity. In each monoketone, the IC50 values for 3H-DHA binding and Na(+)-K(+)-ATPase activity were generally within the same range. The anisotropy of fluorescence probe 1,6-diphenyl-1,3,5-hexatriene-labeled synaptosomal membranes was dose-dependently decreased by the monoketones, implying increased membrane fluidity. These results indicate that increasing lipophilicity of monoketones results in increased solvent penetration of synaptic membrane preparations, leading to conformational changes in membrane structure and increased ability to inhibit both neuroreceptor binding and enzyme activity. The present data confirm the importance of the lipid micro-environment of membranes in maintaining the normal functions of membrane-bound proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Dichloroacetic acid and trichloroacetic acid increase chloroform toxicity

Dichloro- and trichloroacetic acids (DCA and TCA) and chloroform are formed during chlorination disinfection of drinking water. The effects of DCA and TCA treatment on CHCl3 toxicity were assessed in these studies. Male and female rats were gavaged with DCA or TCA (0.92 and 2.45 mmol/kg administered 3 times over 24 h). Three hours after the last dose CHCl3 was injected ip (0.75 mg/kg). Male rats experienced some weight loss (15%) and slight increases of ALT and BUN, but there were no effects of either DCA or TCA on any of these responses. In females, CHCl3 increased plasma ALT and this response was greater (up to threefold) in the DCA group, compared to saline controls. Similarly, BUN was increased by CHCl3 and this was more severe (up to threefold) in both the DCA and TCA pretreated groups. These results show that CHCl3 toxicity is increased by DCA and TCA, and this effect is gender-specific, occurring only in females. DCA increases both liver and kidney toxicity, whereas TCA affects only kidney toxicity.

Developmental toxicology of industrial alcohols: a summary of 13 alcohols administered by inhalation to rats

The developmental toxicology of 13 industrial alcohols (methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, tertiary-butanol, 1-pentanol, 1-hexanol, 2-ethyl-1-hexanol, 1-octanol, 1-nonanol, and 1-decanol), and the behavioral teratogenicity of 4 of these alcohols, were assessed in a series of experiments. The results of individual alcohols have been published previously, but the present paper summarizes the results in view of structure-activity relationships among these alcohols. The alcohols were administered by inhalation for 7 hours per day (6 hours/day for 1-decanol) on gestation days 1-19 to groups of approximately 15 pregnant Sprague-Dawley rats. For developmental toxicology evaluations, dams were sacrificed on gestation day 20. Fetuses were serially removed, weighed, sexed, and examined for external malformations. The frequency of visceral malformations and variations was determined in one-half of the fetuses, and the frequency of skeletal deviations was determined in the other half. Behavioral teratology endpoints were investigated in groups of 15 pregnant rats exposed to one of four alcohols (ethanol, 1-propanol, 1-butanol, and tertiary-butanol) and also involved groups of 18 male rats which were exposed to the same concentrations of each alcohol for 6 weeks, and then mated to untreated females. In the behavioral teratology evaluations, all litters were culled to eight pups and fostered to unexposed mothers. Offspring were tested from days 10-90 on a series of behavioral tests designed to evaluate neuromotor integrity, activity levels, learning, and memory. Additionally, brains were removed from 10 offspring per group at 21 days of age, and were dissected into cerebrum, cerebellum, brainstem, and midbrain; these samples were assayed for steady-state levels of protein and the neurotransmitters acetylcholine, dopamine, norepinephrine, 5-hydroxytryptamine (serotonin), substance P, B-endorphin, and met-enkephalin. Congenital malformations were noted for methanol, 1-propanol, isopropanol, and 1-butanol, but only at concentrations in excess of 5000 ppm. These concentrations also produced toxicity in the maternal animals; thus, there was little evidence of selective developmental toxicity among the alcohols. Although sporadic behavioral and neurochemical deviations were detected, no consistent pattern of effects was seen for any of the alcohols we tested. It should be noted that alcohols with chain lengths longer than the butyl series could not be generated as vapors at sufficiently high concentrations to produce observable toxicity in the maternal animals. This limits the generality of these findings to the possible developmental effects of these alcohols when taken through other routes of exposure.(ABSTRACT TRUNCATED AT 400 WORDS)

Induction of cytochromes P450IIE1 and P450IIB1 by secondary ketones and the role of P450IIE1 in chloroform metabolism

It has been shown previously that the potentiation of chloroform-induced hepatotoxicity by linear secondary ketones increases with the carbon-chain length. The present work examines the possibility that this potentiation is due to the induction of P450IIE1. The metabolism of chloroform, as measured using headspace gas chromatography, in the presence of microsomes from acetone-treated rats was elevated threefold compared to controls. Inclusion of monoclonal antibody against P450IIE1 inhibited the metabolism by 81%. Alternate substrates of P450IIE1 were also inhibitory. Chloroform metabolism was observed using purified, reconstituted P450IIE1 plus cytochrome b5, but was not detected using P450IIB1. The inductive effect of 18-hr oral pretreatment (15 mmol/kg body wt) with each of three secondary ketones on two isozymes of rat liver microsomal cytochrome P450, P450IIE1, and P450IIB1 was studied. The content of total microsomal P450 and NADPH-dependent cytochrome c reductase, the rates of oxidation of N-nitrosodimethylamine, benzphetamine, and pentoxyresorufin, as well as levels of immunoreactive protein for both of the isozymes were elevated by the pretreatments in the rank order of acetone less than or equal to 2-butanone less than 2-hexanone, in agreement with other trends noted by previous investigators. The results provide further evidence for the role of P450IIE1 induction in the potentiation phenomenon.

Lipid composition of liver microsomes from rats treated with acetone

The metabolism of certain compounds by rat hepatic microsomal preparations obtained from acetone-treated rats is greater than that measured in microsomes obtained from control rats. Since the lipid composition of membranes can significantly influence metabolism catalyzed by membrane-bound enzymes, studies were conducted in order to determine whether acetone-induced alterations in microsomal metabolism are associated with changes in the lipid composition of these membranes. Phospholipid and cholesterol concentrations were measured in extracts of rat liver microsomes obtained from rats treated with acetone, sodium phenobarbital, or vehicle. Acetone treatment did not alter the phospholipid and cholesterol content of the microsomes, whereas sodium phenobarbital (positive control) caused a significant decrease in cholesterol content/mg microsomal protein. These data indicate that acetone-induced alterations in microsomal metabolism may not be attributed to changes in the phospholipid and cholesterol content of the microsomes.

Dose-response relationships in ketone-induced potentiation of chloroform hepato- and nephrotoxicity

Chloroform (CHCl3)-induced hepato- and nephrotoxicity was evaluated in male, Fischer 344 rats pretreated with various dosages (1.0 to 15.0 mmol/kg, po) of acetone (Ac), 2-butanone (Bu), 2-pentanone (Pn), 2-hexanone (Hx), or 2-heptanone (Hp). The CHCl3 challenge dosage (0.5 ml/kg, ip) produced slight centrilobular hydropic degeneration and patchy degeneration and necrosis in the proximal tubules of corn oil-pretreated rats. Each of the ketones studied produced a dose-related potentiation of CHCl3 liver and kidney injury. CHCl3 produced extensive tubular and centrilobular necrosis when administered to ketone-pretreated rats. The relationship between ketone dosage and the magnitude of the potentiated response was nonlinear. Maximum potentiation of CHCl3 toxicity occurred in the dosage range of 5.0 to 10.0 mmol ketone/kg. Ketone dosages greater than 10.0 mmol/kg were associated with a reduction in the degree of CHCl3 injury. At the lowest ketone dosage (1.0 mmol/kg), potentiating capacity appeared to be related to ketone carbon skeleton length. No differences in potentiating capacity were discernable between the ketones at dosages of 5.0 to 10.0 mmol/kg. Thus, whether or not there is a relationship with carbon chain length and potentiation depends upon the dosage of the ketone.